Co-reporter:Wenqiang Zhao, Haoming Pang, and Xinglong Gong
Industrial & Engineering Chemistry Research August 9, 2017 Volume 56(Issue 31) pp:8857-8857
Publication Date(Web):July 21, 2017
DOI:10.1021/acs.iecr.7b01553
This work reported a novel magnetorheological plastomer doped with hard magnetic NdFeB particles (named as H-MRP). The dynamic properties of the H-MRP were systematically tested, and the mechanism of its unusual response to magnetic field was discussed. Unlike the MRP filled with soft magnetic particles (S-MRP), the storage modulus (G′) of H-MRPs kept growing by 20% when the magnetic field decreased, while that of S-MRPs decreased with decreasing of the magnetic field immediately without an obvious change. Under the magnetic field ranging from 0 to 1 T, there was a peak value in the rising stage of G′ at about 400 mT magnetic field, while that of S-MRPs changed monotonically. After an off–on progress of the magnetic field, the final G′ of H-MRPs increased by over 10%. A possible mechanism was proposed to study the microstructure dependent mechanical properties. It was found that the complex viscoelastic behavior originated from the large hysteresis characteristics of the H-MRPs.
Co-reporter:Li Ding, Shouhu Xuan, Jiabin Feng, Xinglong Gong
Composites Part A: Applied Science and Manufacturing 2017 Volume 100(Volume 100) pp:
Publication Date(Web):1 September 2017
DOI:10.1016/j.compositesa.2017.04.025
Here reports a lastex yarn-silver nanowires-magnetic polymer based magnetic-conductive composite fibre (MCF) prepared by a simple dropping-drying process. The magnetic-mechanic-electric coupling properties of the multifunctional fibre are systematically investigated. It’s found that the electrical resistance increases by 44% when the tensile strain reaches 8%. Meanwhile, the relative resistance meets a dramatically variation by applying the external magnetic field. For instance, a 1.5% relative resistance increment is achieved by bending the MCF to 44 deg under a 400 mT magnetic field, in which the magnetic induced force is equivalent to 15 mN. Afterwards, a potential mechanism is proposed to investigate the magnetic-mechanic-electric coupling behavior. The results show that the MCF can be applied both as strain sensors and magnetic field sensors. Furthermore, a magnetic-sensing on-off switch and a flexible gripper are subsequently developed, demonstrating that the MCF possesses high potential in the implement of intelligent soft sensors and actuators.
Co-reporter:L. Lu, T. Sun, K. Fezzaa, X.L. Gong, S.N. Luo
Materials Science and Engineering: A 2017 Volume 701(Volume 701) pp:
Publication Date(Web):31 July 2017
DOI:10.1016/j.msea.2017.06.073
Dynamic split Hopkinson pressure bar experiments with in situ synchrotron x-ray imaging and diffraction are conducted on a rolled magnesium alloy at high strain rates of ~5500 s−1. High speed multiscale measurements including stress–strain curves (macroscale), strain fields (mesoscale), and diffraction patterns (microscale) are obtained simultaneously, revealing strong anisotropy in deformation across different length scales. {101¯2} extension twinning induces homogenized strain fields and gives rise to rapid increase in strain hardening rate, while dislocation motion leads to inhomogeneous deformation and a decrease in strain hardening rate. During the early stage of plastic deformation, twinning is dominant in dynamic compression, while dislocation motion prevails in quasi-static loading, manifesting a strain-rate dependence of deformation.Graphical abstractDownload high-res image (210KB)Download full-size image
Co-reporter:Saisai Cao, Qian Chen, Yunpeng Wang, Shouhu Xuan, Wanquan Jiang, Xinglong Gong
Composites Part A: Applied Science and Manufacturing 2017 Volume 100(Volume 100) pp:
Publication Date(Web):1 September 2017
DOI:10.1016/j.compositesa.2017.04.015
To investigate the anti-impact mechanism, the mechanical property and energy absorption of the STF impregnated Kevlar (STF/Kevlar) fabric at high strain rate were conducted using a split Hopkinson pressure bar (SHPB) system. The volume fraction of STF, number of fabric specimens, and impact velocity highly affected the dynamic mechanical performance of the STF/Kevlar composite. The energy transfer rate decreased from 0.85 to 0.01 once the number of fabric specimens increased from 2 layers to 8 layers. The strain rate stiffening mechanism of the STF/Kevlar was analyzed. The Kevlar fabrics underwent four sections during the impact process. The STF was mainly worked in the slip and deformation section by enhancing the friction between fabric yarns and preventing the fabric yarns from slipping. Overall, this work demonstrated that the multilayer Kevlar fabrics impregnated with high volume fraction of STF were the optimal choice for soft body armor.
Co-reporter:Chenhui Xu, Yu Wang, Jie Wu, Shichao Song, Saisai Cao, Shouhu Xuan, Wanquan Jiang, Xinglong Gong
Composites Science and Technology 2017 Volume 153(Volume 153) pp:
Publication Date(Web):1 December 2017
DOI:10.1016/j.compscitech.2017.10.019
A soft sandwich structure consisting of two layer Kevlar face sheets and a silly putty (SP) core was fabricated. The storage modulus of SP, which was prepared by dispersing CaCO3 particles into polyborodimethylsiloxane, increased by two to three orders of magnitude with increasing of the shear frequency. The higher CaCO3 content resulted in better shear-hardening behavior, which further enhanced the anti-impact performance of the sandwich structure. When the impact velocity was below 110 m/s, all energy was dissipated by the sandwich structure and the maximum energy dissipation was 20.8 J, represented a 60% increment than the neat Kevlar. Importantly, under the same impact energy, the energy dissipation of the sandwich structure under ballistic impact was 63% higher than under low velocity impact, which must be due to the shear-hardening nature. The mechanism of the excellent protection performance was discussed. The sensitivity to loading rate and reliable energy dissipation of the soft sandwich structure widely broad its practical applications.
Co-reporter:Jiabin Feng, Shouhu Xuan, Li Ding, Xinglong Gong
Composites Part A: Applied Science and Manufacturing 2017 Volume 103(Volume 103) pp:
Publication Date(Web):1 December 2017
DOI:10.1016/j.compositesa.2017.09.004
This work reported a high performance flexible magnetically controllable actuator based on magnetoactive elastomer (MAE) and poly (vinylidene fluoride) (PVDF) composite film. The magnetic-mechanic-electric coupling properties of the actuator were systematically investigated by cyclical wrinkle, magnetic bending, and stretching test. The induced charge under a magnetic bending can reach as large as 158 pC even at small magnetic field of 100 mT with the bending angle up to almost 90° within 0.6 s. Moreover, a new model was proposed to theoretically reveal the intrinsic correspondence. The model matches well with the experimental results. Based on this kind of actuator, a magnetically controllable tentacle is developed, which could grasp, transport, and release object by switching the supplied current. Due to the real-time deformation feedback characteristics, this kind of actuators can find wide applications in actively controllable engineering, artificial robotics, and biomedicine.
Co-reporter:L. Lu, B.X. Bie, Q.H. Li, T. Sun, ... S.N. Luo
Acta Materialia 2017 Volume 132(Volume 132) pp:
Publication Date(Web):15 June 2017
DOI:10.1016/j.actamat.2017.04.065
In situ synchrotron x-ray imaging and diffraction are used to investigate deformation of a rolled magnesium alloy under uniaxial compression at room and elevated temperatures along two different directions. The loading axis (LA) is either perpendicular or parallel to the normal direction, and these two cases are referred to as LA⊥〈c〉 and LA∥〈c〉 loading, respectively. Multiscale measurements including stress–strain curves (macroscale), strain fields (mesoscale), and diffraction patterns (microscale) are obtained simultaneously. Due to initial texture, {101¯2} extension twinning is predominant in the LA⊥〈c〉 loading, while dislocation motion prevails in the LA∥〈c〉 loading. With increasing temperature, fewer {101¯2} extension twins are activated in the LA⊥〈c〉 samples, giving rise to reduced strain homogenization, while pyramidal 〈c+a〉 slip becomes readily activated, leading to more homogeneous deformation for the LA∥〈c〉 loading. The difference in the strain hardening rates is attributed to that in strain field homogenization for these two loading directions.Download high-res image (473KB)Download full-size image
Co-reporter:Lei Pei;Haoming Pang;Xiaohui Ruan;Shouhu Xuan
RSC Advances (2011-Present) 2017 vol. 7(Issue 14) pp:8142-8150
Publication Date(Web):2017/01/23
DOI:10.1039/C6RA28436A
A novel superparamagnetic magnetic fluid based on Fe3O4-immobilized-SiO2-nanospheres (MSiNPs) was developed. Both the experimental analyses and computational simulations were conducted to investigate its magnetorheology. In comparison to the pure Fe3O4 based magnetic fluid, the magnetorheological (MR) effect of the MSiNPs based magnetic fluid was about 25 times larger. To demonstrate the improving mechanical properties, a modified magnetic dipolar model was proposed to describe the magnetic interaction of two close magnetized particles. Moreover, the molecular dynamic simulations were carried out to understand the microstructure evolution under an applied magnetic field. The simulation results showed that chain-like and column-like particulate structures were formed in the stationary state and transferred into lamellar microstructures in the steady shear flow. Particle-level simulations were in good agreement with experimental data. The dramatic increase in MR effect of the MSiNPs based magnetic fluid originated from the intensity of the magnetic attractions and the size scale of the particulate structures.
Co-reporter:Zhiyuan Wang;Shouhu Xuan;Wanquan Jiang
RSC Advances (2011-Present) 2017 vol. 7(Issue 42) pp:25855-25860
Publication Date(Web):2017/05/15
DOI:10.1039/C7RA04236A
This work studied the normal stress of an ER fluid in compression mode through both experiment and simulation. The TiO2 based ER fluid was used to test the normal stress under different DC voltages and compressive speeds. The normal stress reached about tens of kPa and was affected by the applied voltage and compressive parameters. Then, a simulation model was presented to investigate the influencing factors on the normal stress. The computational normal stresses agreed well with the experimental results. Typically, the shear action was also found to be very important for the normal stress during the compression. When the shear rate is small, the shear action showed little effect on normal stress. When the shear rate exceeded a critical value, the normal stress oscillated within a certain range. At last, an ideal 2D simulation was conducted to investigate the relation between the mechanical property and the structure transformation.
Co-reporter:Sheng Wang;Shouhu Xuan;Mei Liu;Linfeng Bai;Shuaishuai Zhang;Min Sang;Wanquan Jiang
Soft Matter (2005-Present) 2017 vol. 13(Issue 13) pp:2483-2491
Publication Date(Web):2017/03/29
DOI:10.1039/C7SM00095B
A novel S-ST/MWCNT/Kevlar-based wearable electronic textile (WET) with enhanced safeguarding performance and force sensing ability was fabricated. Stab resistance performance tests under quasi-static and dynamic conditions show that the maximum resistance force and penetration impact energy for the WET are 18 N and 11.76 J, which represent a 90% and 50% increment with respect to the neat Kevlar, respectively. Dynamic impact resistance tests show that the WET absorbs all the impact energy. The maximum resistance force of the WET is 1052 N, which represents an improvement of about 190% with respect to neat Kevlar. With the incorporation of multi-walled carbon nanotubes (MWCNTs), the WET can achieve a stable electrical conductivity of ∼10−2 S m−1, and the conductivity is highly sensitive to external mechanic forces. Notably, the sensing fabric also exhibits an outstanding ability to detect and analyze external forces. In addition, it can be fixed at any position of the human body and exhibits an ideal monitoring performance. Because of its flexibility, high sensitivity to various types of deformations and excellent safeguarding performance, the WET has a strong potential for wearable monitoring devices that simultaneously provide body protection and monitor the movements of the human body under various conditions.
Co-reporter:Jie Wu;Qifan Yan;Shouhu Xuan
Microfluidics and Nanofluidics 2017 Volume 21( Issue 3) pp:
Publication Date(Web):2017 March
DOI:10.1007/s10404-017-1886-7
This paper reported an efficient method to size-selective separate magnetic nanospheres using a self-focusing microfluidic channel equipped with a permanent magnet. Under external magnetic field, the magnetophoresis force exerted on particles leads to size-dependent deflections from their laminar flow paths and results in effective particles separation. By adjusting the distance between magnet and main path of channel, we obtained two monodisperse nanosphere samples (Ca. 90 nm, Ca. 160 nm) from polydispersing particles solution whose diameters varied from 40 to 280 nm. Based on the magnetostatic and laminar flow models, numerical simulations were also used to predict and optimize the nanospheres migrations. Two thresholds of particles diameters were obtained by the simulations and diverse at each position of magnet. Therefore, appropriate position of the magnet could be determined at a certain particle sizes’ range when the flow rate of the two inlets remains unchanged.
Co-reporter:Tiantian Yin, Yu Wang, Linghui He, Xinglong Gong
Computational Materials Science 2017 Volume 138(Volume 138) pp:
Publication Date(Web):1 October 2017
DOI:10.1016/j.commatsci.2017.06.014
•The volume fractions of phases and then the mechanical properties of the matrix are analyzed.•The thermal deformation including the competition between thermal expansion and chemical shrinkage is investigated.•The matrix sustains tension circumferential stress after reaction activates due to the matrix shrinkage.•The significant tension stress increases rapidly with reaction progress to cause damage.•The damage evolves along the fiber/matrix interface with the reaction progress.Carbon/carbon composites are widely used in aerospace industry due to their excellent mechanical and thermal properties in high temperature. However, understanding of the mechanism for defects induced in the carbonization process of carbon/carbon composites is still inadequate. In this paper, a model is established to obtain the matrix properties and simulate the stress and damage evolution during the carbonization process of carbon/carbon composites. First, the phase evolution equations are used to gain the volume fractions of phases, and then the elastic modulus and Poisson ratio are obtained by a nested homogenization method. Then, the thermal deformation including the competition between thermal expansion and chemical shrinkage is discussed. The damage evolution in the matrix is incorporated through the progressive damage model. Finally, we perform the finite element simulation for the carbonization of the unidirectional fiber bundle reinforced carbon/carbon composites. The results show that matrix sustains compression circumferential stress before reaction start. After reaction activates, the circumferential stress turns to tension due to the matrix shrinkage, and the tension stress increases rapidly to cause damage. The damage evolves along the fiber/matrix interface with the temperature increasing. With damage accumulation, micro cracks may generate along the fiber/matrix interface, which is similar as the literature reported.Download high-res image (214KB)Download full-size image
Co-reporter:Jie Wu;Qifan Yan;Yiwen Cui;Shouhu Xuan
Microfluidics and Nanofluidics 2017 Volume 21( Issue 7) pp:119
Publication Date(Web):28 June 2017
DOI:10.1007/s10404-017-1954-z
Co-reporter:Mei Liu;Qian Chen;Sheng Wang;Linfeng Bai;Min Sang
Journal of Nanoparticle Research 2017 Volume 19( Issue 7) pp:234
Publication Date(Web):28 June 2017
DOI:10.1007/s11051-017-3911-x
We develop a modified method to improve the rheological performance of SiO2-based shear thickening fluid (STF). Directly adding surfactant into STF is the most common method to improve the rheological performance of SiO2-based STF. However, the final viscosity increases quickly with the increase of shear rate, which is against for the practical applications. In this work, SiO2 nanospheres are firstly modified by PVP K30 through an ethanol refluxing method and the modified SiO2 nanospheres are used to prepare PVP@SiO2-STF. Compared with the unmodified SiO2 based STF (SiO2-STF), the PVP@SiO2-STF presents an obvious increase of shear thickening (ST) effects and the maximum viscosity increases by 7 times and the critical shear rates decrease about 10 times approximately. A reasonable explanation is proposed to interpret the influence of the modification methods on the rheological properties of STF. This work provides a new way to control the shear thickening behavior and also contributes to understand the mechanism of ST effect, which has an important significance to develop controllable STF.
Co-reporter:Sheng Wang, Shouhu Xuan, Yunpeng Wang, Chenhui Xu, Ya Mao, Mei Liu, Linfeng Bai, Wanquan Jiang, and Xinglong Gong
ACS Applied Materials & Interfaces 2016 Volume 8(Issue 7) pp:4946
Publication Date(Web):February 2, 2016
DOI:10.1021/acsami.5b12083
A simple and scalable “dip and dry” method was developed for fabricating stretchable polyurethane sponge-based polymer composite with excellent shear stiffening effect, creep resisting and adhesion property. The stiffness of the composite was tunable, the storage modulus (G′) could automatically increase 3 orders of magnitude with the increasing of shear frequency, and the G′max could reach to as high as 1.55 MPa. Importantly, the composite with ideal damping capacity reduced the impact force by 2 orders of magnitude even under 26 cycles of consecutive dynamic impact loading with no obvious mechanical degradation. Moreover, an enhancing mechanism was proposed and it was found the “B–O cross bond” and the entanglement of polymer chains were attributed to the shear stiffening characteristic. Finally, the excellent adhesion ability and hydrophobicity guarantee the composite with reliable mechanical performance and longer lifespan.Keywords: adhesion; energy dissipation; hydrophobicity; shear stiffening; stretchable polyurethane sponge
Co-reporter:Yunpeng Wang, Sheng Wang, Chenhui Xu, Shouhu Xuan, Wanquan Jiang, Xinglong Gong
Composites Science and Technology 2016 Volume 127() pp:169-176
Publication Date(Web):28 April 2016
DOI:10.1016/j.compscitech.2016.03.009
The dynamic mechanical behavior of the magnetically responsive shear-stiffening gel (MSTG) was investigated by using a modified Split Hopkinson Pressure Bar (SHPB) system. It was found that the elastic modulus of the MSTG increased with increasing strain rate and magnetic field. The elastic modulus of the MSTG with 45 wt% carbonyl iron (CI) particles reached to 126.6 MPa at the strain rate of 7236 s−1, while it was merely 160 Pa without excitation. Under a 300 mT magnetic field, the elastic modulus also increased from 116.5 MPa (no magnetic field) to 255.5 MPa at the strain rate of 2900 s−1. The shear stiffening performance of the MSTG was stable and its maximum yield strain was 17.2%, which was very important for its practical application. The magnetically strengthened mechanisms of the high strain-rate-dependent mechanical properties were proposed. It was found that the enhanced shear-stiffening behavior was attributed to the phase transitions from viscous-liquid state to elastomeric state to glassy state under impact.
Co-reporter:Lin Ge, Xinglong Gong, Yu Wang, Shouhu Xuan
Composites Science and Technology 2016 Volume 135() pp:92-99
Publication Date(Web):27 October 2016
DOI:10.1016/j.compscitech.2016.09.015
Conductive magnetorheological elastomers (MREs) consisting of carbonyl iron particles (CIPs), polydimethylsiloxane matrix and carbon nanotube (CNT) covered polyurethane sponge (PUS) were developed. The CIPs were linearly orientated within the porous PUS and the magnetic saturation modulus of PUS-reinforced anisotropic MRE was 1.3 MPa when CIPs content was 70 wt%. This MRE presented typical magnetorheological (MR) effects and the shear storage modulus increased from 0.49 MPa to 0.64 MPa after reinforcing the anisotropic MRE with PUS. Owing to the presence of the CNTs on the PUS networks, the final MRE was conductive. The electrical resistance of the MRE increased with increasing tensile strain, ranging from 27.5 kΩ to 30.5 kΩ at various tensile rates (50, 100, 150, 200, 250 and 300 mm/min respectively). As a result, the smart MRE was effective in a flexible, sensitive and reversible strain sensor.
Co-reporter:Wei Cai, Xiaming Feng, Weizhao Hu, Ying Pan, Yuan Hu, and Xinglong Gong
Industrial & Engineering Chemistry Research 2016 Volume 55(Issue 40) pp:10681
Publication Date(Web):September 16, 2016
DOI:10.1021/acs.iecr.6b02579
Mass production of graphene was successfully achieved with a simple and environmentally friendly electrochemical exfoliation approach. The obtained graphene was noncovalently modified by ligninsulfonate and iron ion (Fe-lignin) to form the flame retardant functionalized graphene sheets (FGNS). Subsequently, FGNS was introduced to reduce fire hazards of thermoplastic polyurethane (TPU). The FGNS/TPU nanocomposites presented higher thermal conductivity, thermal stability, and flame retardancy than those of neat TPU. By adding 2.0 wt% FGNS, a significant reduction (62.8%) in peak heat release rate (pHRR) and high char yield (from 3.6 to 9.4 wt%) were observed. During the combustion, in situ formed char derived from catalysis action of Fe-lignin can protect the layer structure of graphene to further hinder the transfer of pyrolysis volatile with barrier effect. The simple exfoliation and effective functionalization of graphene shows a promising application prospect in polymer nanocomposites.
Co-reporter:L. Lu, C. Li, W.H. Wang, M.H. Zhu, X.L. Gong, S.N. Luo
Materials Science and Engineering: A 2016 Volume 651() pp:848-853
Publication Date(Web):10 January 2016
DOI:10.1016/j.msea.2015.11.040
We investigate dynamic fracture or spallation of a ternary bulk metallic glass, Zr50Cu40Al10, under high strain-rate (4–5×105 s−1) loading. Both incipient and full spall are achieved. Free-surface velocity histories and microstructure features of the recovered samples, such as necking, softening, microvoids, and rounded cups/cones, indicate exceptional ductility in deformation and fracture of this glass. Softening/necking is attributed to decreased glass transition temperature with increasing tension, and rounded cups/cones, to localized shear banding, void formation, and their interactions.
Co-reporter:Sheng Wang, Shouhu Xuan, Wanquan Jiang, Weifeng Jiang, Lixun Yan, Ya Mao, Mei Liu and Xinglong Gong
Journal of Materials Chemistry A 2015 vol. 3(Issue 39) pp:19790-19799
Publication Date(Web):12 Aug 2015
DOI:10.1039/C5TA06169E
A novel rate-dependent and self-healing conductive composite with a well-defined shear stiffening (S-ST) effect was facilely fabricated by dispersing multi-walled carbon nanotubes (MWCNTs) into a shear stiffening polymer matrix. The storage modulus (G′) of the multi-functional composite automatically increased 4 orders of magnitude when encountering external shear stimuli and the G′max was over 1 MPa, demonstrating an obvious shear stiffening effect and good safe-guarding performance. It was found that the electrical conductivity changed accordingly when shear stiffening occurred, therefore it can be applied as a force sensor during the attacking process. The rate-dependent piezoresistance effect of the composite was investigated. In quasi-static compression and high rate impact tests, different force signals can be obtained because of the negative and positive piezoresistivity effect. Self-healing tests indicated that the as-prepared composite can maintain its mechanical and electrical properties after destruction and healing treatments. Owing to the shear stiffening performance, the rate dependent conductive composite could both absorb impact energy and sense the attacking forces. Finally, a mechanism was proposed and it was believed that the glass transition induced by B–O interactions and the changes in the microstructure during the external action can be attributed to the S-ST performance and rate dependent electrical conductivity, respectively.
Co-reporter:Haoming Pang, Shouhu Xuan, Taixiang Liu and Xinglong Gong
Soft Matter 2015 vol. 11(Issue 34) pp:6893-6902
Publication Date(Web):27 Jul 2015
DOI:10.1039/C5SM00984G
In this work we reported a novel graphite doped conductive magnetorheological plastomer (GMRP) with magnetic field dependent electro-conductivity. The conductivity of the GMRPs increased by increasing the content of the graphite particles, while it decreased with the graphite size. When the graphite content reached 15 wt%, the conductivity of GMRPs is approximately 10000 times higher than the non-doped MRP. Because the iron particles in the GMRPs were magnetic, the conductivity of the GMRPs was magnetically sensitive. Upon applying a 780 mT magnetic field, the electric conductivity could increase about 1000 times larger than the one under zero magnetic field. A particle–particle resistance model was developed to investigate the influence of the magnetic field and graphite doping on the conductivity, and the fitting curve matched the experimental results very well. Finally, a magnetically controllable on–off switch based on GMRPs was proposed and its working mechanism was discussed.
Co-reporter:Ya Mao, Wanquan Jiang, Shouhu Xuan, Qunling Fang, Ken Cham-Fai Leung, Beng S. Ong, Sheng Wang and Xinglong Gong
Dalton Transactions 2015 vol. 44(Issue 20) pp:9538-9544
Publication Date(Web):08 Apr 2015
DOI:10.1039/C5DT00913H
A novel rod-like β-FeOOH@poly(dopamine)–Au–poly(dopamine) nanocomposite is developed for recyclable catalysis. Firstly, the rod-like β-FeOOH template was coated in situ by a layer of poly(dopamine) (PDA) to form a core/shell nanostructure. Then the negatively charged Au nanocatalysts were well-immobilized onto the periphery of the β-FeOOH@PDA nanorod. To protect the Au nanocrystals from leaching during the catalytic reactions, another PDA layer was coated onto the above particles to form a sandwich-like PDA–Au–PDA shell on the β-FeOOH rod core. The reduction of Rhodamine B (RhB) was introduced as a model reaction to evaluate the catalytic activity of the as-prepared nanocomposites. It was found that the catalytic rate sharply increased with an increasing amount of the nanocatalyst. Benefitting from the thin outer layer of PDA, the recyclability of the nanocatalyst dramatically increased. After five times of catalytic reaction, the activity was maintained as high as 98.3%, while the β-FeOOH@PDA–Au showed it to be retained at only 73.4%.
Co-reporter:Qianyun He;Shouhu Xuan;Wanquan Jiang
Journal of Materials Science 2015 Volume 50( Issue 18) pp:6041-6049
Publication Date(Web):2015 September
DOI:10.1007/s10853-015-9151-5
In this work, shear thickening (ST) performance of a novel suspension of porous silica nanoparticles was systematically studied. The porous silica nanoparticles which were synthesized by using CTAB as a pore-forming agent were dispersed into ethylene glycol to form shear thickening fluid (STF). Both the steady and oscillatory shear rheological properties of the STF were characterized. The STF showed distinct ST effects when the concentration of the porous nanoparticles was only 42.5 wt%. This value was much lower than the previously reported STF prepared by non-porous particles. The viscosity increased from 0.80 to 14.3 Pa s by increasing the shear rate from 0.1 to 49.4 s−1, while a noticeable overall downward trend with a high initial viscosity was found in the prepared suspension of non-porous silica. The results indicated that porous nature of the silica nanoparticles could remarkably influence the ST effect. A possible enhancing mechanism was proposed and it was found that the difference of macroscopic rheology behavior was mainly according to interfacial interaction between the porous silica nanoparticles. This work provided valuable information for understanding the relationship between the porous characteristics and ST behavior.
Co-reporter:Qifan Yan;Shouhu Xuan;Xiaohui Ruan;Jie Wu
Microfluidics and Nanofluidics 2015 Volume 19( Issue 6) pp:1377-1384
Publication Date(Web):2015 December
DOI:10.1007/s10404-015-1652-7
This paper reports the manipulation of ferrofluid droplets by using a microfluidic flow-focusing device equipped with a magnetic tweezer. Besides the traditional flow rate controlling method, the magnetic field also can be applied to control the size of the droplets. Two major effects in magnetic manipulation process: magnetoviscous effect and magnetic drag effect, were studied. Under a fixed flow rate (CP = 1 mL/h, DP = 0.2 mL/h), the average sizes of ferrofluid droplets were tunable from 135 to 95 μm by varying the magnetic field from 0 to 60 mT. Moreover, square wave magnetic field can be used to periodically generate droplets with different sizes. These results are helpful to understand the generation mechanism of the ferrofluid droplet and supply a novel method for manipulating droplets with a predetermined size and distribution.
Co-reporter:Sheng Wang, Wanquan Jiang, Weifeng Jiang, Fang Ye, Ya Mao, Shouhu Xuan and Xinglong Gong
Journal of Materials Chemistry A 2014 vol. 2(Issue 34) pp:7133-7140
Publication Date(Web):11 Jul 2014
DOI:10.1039/C4TC00903G
A novel multi-functional polymer composite (MPC) with both excellent shear stiffening (ST) performance and magnetorheological (MR) effect is prepared by dispersing magnetic particles into shear stiffening polymer matrix. Besides having the magnetically dependent mechanical properties (MR effects), this multi-functional MPC automatically changes its rheological behavior in response to external shear stimuli. The mechanical properties of this smart composite can be alternatively achieved by varying the particle's types and contents. Upon applying a shear stress with excitation frequency from 1 Hz to 100 Hz, the storage modulus (G′) of the MPC increases from 102 to 106 Pa, demonstrating an excellent ST effect. Interestingly, the ST effects of the MPC are also tunable by varying the external magnetic field, and the area of G′ could be greatly increased and precisely controlled. Based on the experimental results, a possible mechanism is proposed and discussed. It is believed that the “cross bonds” and the particle chains induced by the magnetic field are due to the excellent multi-functional stimulus-response properties.
Co-reporter:Wanquan Jiang, Fang Ye, Qianyun He, Xinglong Gong, Jiabin Feng, Lei Lu, Shouhu Xuan
Journal of Colloid and Interface Science 2014 Volume 413() pp:8-16
Publication Date(Web):1 January 2014
DOI:10.1016/j.jcis.2013.09.020
•A novel kind of shear thickening fluid (STF) of polymer nanoparticles was developed.•The particles’ structure dependent of the STF rheology was studied.•A possible mechanism for the shear thickening (ST) behavior was proposed.•The surface charges and hardness of the particles strongly affected the ST effects.A novel kind of shear thickening fluid (STF) was developed via dispersing poly(styrene–acrylic acid) (PS–AA) nanospheres into ethylene glycol (EG). By varying the structure characteristics of the PS–AA particles, STFs with different rheological properties can be obtained. Firstly, the influence of the styrene/acrylic acid ratio on the PS–AA nanospheres was investigated. It was found that the higher ratio often led to the better shear thickening (ST) effects and under the optimum condition the maximum viscosity of the STF could reach to 152 Pa s, while the ST effects decreased under further increasing the monomer ratio. Then, the divinyl benzene (DVB) was introduced to increase the cross-link density of the PS–AA. In comparison with the non-cross-link PS–AA nanospheres, the poly(styrene–acrylic acid–divinyl benzene) (PS–AA–DVB) based STFs exhibited much higher ST effects and the maximum viscosity was up to 385 Pa s when the DVB was only increased to 0.3%. In combination of the rheological properties and the structure characterization, a possible mechanism for the ST behavior was proposed and the influence of the particles’ characteristics on the mechanical performance of the PS–AA based STF was carefully analyzed.Graphical abstract
Co-reporter:Zhiman Bai, Lei Song, Yuan Hu, Xinglong Gong, Richard K.K. Yuen
Journal of Analytical and Applied Pyrolysis 2014 Volume 105() pp:317-326
Publication Date(Web):January 2014
DOI:10.1016/j.jaap.2013.11.019
•The star-shaped phosphorus-containing flame retardant was synthesized.•TRIPOD-DOPO can impart excellent flame retardant properties to UPR.•TRIPOD-DOPO acted in the gas and condensed phase at the same time.The phosphorus-containing star-shaped flame retardant (TRIPOD-DOPO) was synthesized, while the flame retardant unsaturated polyester resins (FR-UPRs) composites with various amounts of TRIPOD-DOPO were prepared. The thermogravimetric analysis (TGA) and oxygen index (OI) results showed that the incorporation of TRIPOD-DOPO improves the thermal stability and flame retardancy of UPR. The combustion properties of composites were evaluated by microscale combustion calorimeter (MCC), and the results indicated that TRIPOD-DOPO decreased the peak heat release rate (pHRR) and total heat release (THR) of UPR. Fourier transform infrared coupled with the thermogravimetric analyzer (TG–IR) revealed that UPR and TRIPOD-DOPO decomposed independently of each other. Flame inhibition was expected to occur in the gas phase. Under the air condition, TRIPOD-DOPO showed a more obviously condensed phase interaction increasing charring from the TG results. The SEM results showed that the residual char of composites were more compact and continuous, which could prevent mass and thermal transfer.
Co-reporter:Taixiang Liu, Xinglong Gong, Yangguang Xu and Shouhu Xuan
Soft Matter 2014 vol. 10(Issue 6) pp:813-818
Publication Date(Web):28 Nov 2013
DOI:10.1039/C3SM52865K
The magneto-induced stress and relative microstructure in a colloidal suspension of paramagnetic and superparamagnetic particles dispersed in a ferrofluid medium is studied using particle-level dynamics simulation. It shows that the stress perpendicular to the direction of an external uniaxial magnetic field can be strongly enhanced by increasing the ratio of paramagnetic particles to approaching that of superparamagnetic particles. The magnetic field-induced net-like or embedded chain-like microstructures formed by paramagnetic and superparamagnetic particles contribute to this stress enhancing effect.
Co-reporter:Yu Wang, Xinglong Gong, Jie Yang, and Shouhu Xuan
Industrial & Engineering Chemistry Research 2014 Volume 53(Issue 8) pp:3065
Publication Date(Web):February 5, 2014
DOI:10.1021/ie402395e
A novel method was developed to enhance the cyclic performance of magnetorheological elastomers (MREs) by incorporating silicon carbide (SiC) nanoparticles. Different amounts of SiC nanoparticles were doped into the MREs, and their dynamic properties were investigated. In comparison to the neat MREs, the duration performance of SiC doped MRE was obviously improved. After the same cyclic loading, the maximum storage modulus and the magneto-induced storage modulus of the 4 wt % SiC-doped-MRE were approximately 1.1 and 1.3 times larger than the nondoped MREs. The maximum storage modulus, the magneto-induced storage modulus, and the MR effect in MRE-4 were approximately 1.73, 2.10, and 1.65 times that in MRE-0, respectively, after the cyclic load of different strain amplitudes. The improving mechanism was studied, and it was found that incorporating SiC nanoparticles can affect the stress distribution surrounding the magnetized carbonyl iron (CI) particles in the prestructure process and, thus, can affect the microstructures of the MREs.
Co-reporter:Tiantian Yin, Zhongwei Zhang, Xiaofeng Li, Xiang Feng, Zhihai Feng, Yu Wang, Linghui He, Xinglong Gong
Computational Materials Science 2014 Volume 95() pp:35-40
Publication Date(Web):December 2014
DOI:10.1016/j.commatsci.2014.07.013
•Non-uniform temperature and pressure are involved in the ablation model.•Ablation behavior of carbon/carbon leading edge structure is investigated.•Non-uniform surface pressure plays a vital role in the ablation configuration.•The effect of altitude on the chemical ablation behavior are obtained.•The efficiency of oxidation protection by matrix modifiers is evaluated.Carbon/carbon composites usually work in complex thermo-chemical environments, surface recession is thus inevitable due to chemical ablation and further affects the system stability and safety. In this paper, a model for chemical ablation of the materials which accounts for the effects of non-uniform temperature and pressure is proposed. As an application, the surface recession of a carbon/carbon composites leading edge structure are simulated in detail. The results show that the non-uniform distributed pressure plays an important role in the final ablation configuration. The effects of altitude and oxidation protection on the chemical ablation are discussed as well.
Co-reporter:Yufeng Zhou, Wanquan Jiang, Shouhu Xuan, Xinglong Gong, Fang Ye, Sheng Wang and Qunling Fang
Journal of Materials Chemistry A 2013 vol. 1(Issue 10) pp:1414-1420
Publication Date(Web):08 Jan 2013
DOI:10.1039/C2TB00508E
Novel asymmetric hollow microspheres with polystyrene-ethylacrylate (PSt-EA) semi-spherical cores and porous hierarchical Ni-Silicate shells have been successfully fabricated by the combination of emulsifier-free polymerization, a modified Stöber method and an in situ hydrothermal conversion reaction. During the conversion of the PSt-EA@SiO2 core/shell microspheres to the asymmetric PSt-EA/Ni-Silicate composite, the spherical PSt-EA was melted within the hollow Ni-Silicate interior to form semi-microspheres. Upon further treating the asymmetric hollow microspheres by 500 °C calcination for 5 h, hierarchical Ni-Silicate hollow spheres were obtained. The BET area of the asymmetric hollow PSt-EA/Ni-Silicate microspheres was 58.9 m2 g−1 and the pore diameter was about 10–20 nm. The large porous nature of the products enable them be used as carriers for bio-molecules, and experiments indicated that the maximum adsorption ability of the asymmetric hollow microspheres could reach 8.2 μmol g−1 when the concentration of Cytochrome C was 200 mmol L¬1.
Co-reporter:Yangguang Xu, Xinglong Gong, Taixiang Liu and Shouhu Xuan
Soft Matter 2013 vol. 9(Issue 32) pp:7701-7709
Publication Date(Web):23 May 2013
DOI:10.1039/C3SM51072G
An impedance spectroscopy (IS) method is employed to investigate the magneto-induced microstructure mechanism of magnetorheological plastomers (MRP). The IS of MRP with two typical particle distributions (isotropic and anisotropic) are compared and an equivalent circuit model is proposed to analyze the different impedance responses. It is found that the IS of anisotropic MRP is quite sensitive to the magnetic field and the electron diffusion effect will be restricted in the presence of a magnetic field. Furthermore, the conduction behavior of MRP in the presence of a magnetic field reveals the existence of elasticity in the polymer matrix. The influence of particle chain direction on the conductivity of anisotropic MRP with different particle contents is also investigated. Based on the experimental results, an equivalent method is developed to quantitatively characterize the anisotropy of MRP. With this method, the microstructure-dependent conduction mechanism of MRP can be presented more clearly.
Co-reporter:Taixiang Liu, Xinglong Gong, Yangguang Xu, Shouhu Xuan and Wanquan Jiang
Soft Matter 2013 vol. 9(Issue 42) pp:10069-10080
Publication Date(Web):21 Aug 2013
DOI:10.1039/C3SM52130C
Magneto-induced microscopic particulate structures of magnetorheological plastomers (MRP) are investigated using particle-level dynamics simulation, as this is a basis for studying the macroscopic physical or mechanical properties of MRP. In the simulation, a modified magnetic dipolar interaction force model is proposed to describe the magnetic interaction of two close magnetized iron particles. Other microscopic analytical models of particle–particle and particle–matrix interactions are also constructed. The simulation results show that chain-like and column-like particulate structures are formed when MRP is placed into a steady uniform magnetic field. When MRP is subjected to a stepwise in-plane rotating magnetic field, the microstructure rearranges to form a layered structure parallel to the rotation plane. Moreover, some other patterns or complex magneto-induced rearrangeable microstructures can be achieved by spatially changing the external magnetic field. With the evolution of the microscopic particulate structure in every changing step of the external magnetic field, the microstructure dependent magnetic potential energy and stress state vary sharply at the beginning and then approach respective stable values gradually.
Co-reporter:Yanceng Fan, Xinglong Gong, Shouhu Xuan, Lijun Qin, and Xiaofeng Li
Industrial & Engineering Chemistry Research 2013 Volume 52(Issue 2) pp:771
Publication Date(Web):December 14, 2012
DOI:10.1021/ie302536e
The effect of cross-link density of the matrix on the controllable damping properties of magnetorheological elastomers (MREs) has been investigated. MRE samples with different cross-link densities and plasticizer contents were fabricated and their microstructures were observed using an environmental scanning electron microscope (SEM). The dynamic performances of these samples were measured using a modified dynamic mechanical analyzer (DMA). The experimental results indicated the magneto-induced change of loss factor was enhanced by decreasing the cross-link density. The plasticizer and the frequency markedly influenced the magneto-induced change of loss factor when the cross-link density of the matrix was low. In addition, by reducing cross-link density, the magneto-induced modulus and the relative MR effect increased. A mechanism for the magneto-induced change of loss factor was proposed and the analysis implied that the rearrangement of particles is an important influence on controlling the damping properties of MREs.
Co-reporter:Guojiang Liao, Xinglong Gong, and Shouhu Xuan
Industrial & Engineering Chemistry Research 2013 Volume 52(Issue 25) pp:8445
Publication Date(Web):May 30, 2013
DOI:10.1021/ie400864d
The dynamic compressive property of magnetorheological elastomer (MRE) under high strain rate was investigated using a modified split Hopkinson pressure bar system. Both the compressive properties in the pre-yield region and the post-yield region were studied. Experimental results show that the dynamic compressive property of MRE under high strain rate is related to the magnetic field and the strain rate. In the pre-yield region, with increasing magnetic field or strain rate, both the Young’s modulus and the yield stress increase. However, the yield strain decreases with increasing magnetic field or strain rate. A constitutive model consisting of hyperelasticity, viscoelasticity, and a magnetic part was proposed to describe the compressive property of MRE, and the model agrees well with the experimental results. In the post-yield region, the stress first decreases to a minimum value and then increases smoothly when the strain exceeds the yield strain, which is due to the change of the chainlike structures of iron particles in MRE.
Co-reporter:Dong Wang, Keqing Zhou, Wei Yang, Weiyi Xing, Yuan Hu, and Xinglong Gong
Industrial & Engineering Chemistry Research 2013 Volume 52(Issue 50) pp:17882
Publication Date(Web):November 28, 2013
DOI:10.1021/ie402441g
In this work, molybdenum disulfide (MoS2)–modified graphene (MoS2/GNS) hybrids were prepared by the hydrothermal method and characterized by X-ray diffraction (XRD), Laser Raman spectroscopy (LRS) and transmission electron microscope (TEM). The characterization results show layered molybdenum disulfide was deposited on the surface of graphene nanosheets (GNSs) and grahene oxide was reduced simultaneously. Thermogravimetric analysis results of MoS2, GNS and MoS2/GNS hybrids showed that incorporation of MoS2 increased the thermal oxidation resistance of the graphene evidently. Compared to pure epoxy resins (EP), the addition of MoS2/GNS hybrids into EP enhanced the onset thermal degradation temperature (Tonset) with an 53 °C increment under air atmosphere and an 18 °C increment under nitrogen atmosphere. The addition of MoS2/GNS hybrids endows excellent flame retardant properties to EP, confirmed by the dramatically reduced peak heat release rate value and total heat release value. Moreover, the addition of MoS2/GNS hybrids dramatically decreased the smoke products.
Co-reporter:Guojiang Liao, Xinglong Gong, Shouhu Xuan
Materials Letters 2013 Volume 106() pp:270-272
Publication Date(Web):1 September 2013
DOI:10.1016/j.matlet.2013.05.035
•The influence of shear deformation on the normal force of MRE was investigated.•Two opposite trends of normal force with increasing shear strain were first observed.•A microstructure based theory was proposed to explain the observed phenomenon.The influence of shear deformation on the normal force of magnetorheological elastomer was investigated. In quasi-static shear, the normal force decreases with increasing shear strain at low magnetic field, while increases with increasing shear strain when the magnetic field exceeds 452 mT. In oscillatory shear, the normal force shows similar trend. However, it decreases sharply when the strain amplitude exceeds 7%. A microstructure based theory was proposed to investigate this phenomenon. Under shearing, the elastic modulus decreases while the magnetic torque increases, which lead to the different trends of normal force at different magnetic fields. This mechanism agrees well with the experimental results.
Co-reporter:Lijun Qin;Zhongwei Zhang;Zhihai Feng;Xiaofeng Li
Journal of Materials Science 2013 Volume 48( Issue 9) pp:3454-3460
Publication Date(Web):2013 May
DOI:10.1007/s10853-013-7135-x
Carbon fiber reinforced carbon matrix composites (C/Cs), as important candidate aviation and aerospace materials, have good prospects for application in extreme environments. However, notch effects of C/Cs have not been studied adequately. In this work, the notch effects of 3D-C/C composites were investigated by the full-field measurement digital image correlation method. Six kinds of specimens with different notch patterns including one central hole, multi-holes, and double edge notches, were examined to analyze their mechanical properties. The tests were carried out on MTS 809 testing machine and the deformations of specimens were monitored by a CCD camera. Using the full-field measurement, both the local mechanical properties (stress concentration, shear damage, and fracture behavior) and the globe properties (notch sensitivity and tensile behavior) were studied. The results indicated that the fracture stress on the net cross section was constant and it was independent on the material heterogeneity, notch patterns, and notch depth.
Co-reporter:Gang Tang, Xin Wang, Rui Zhang, Wei Yang, Yuan Hu, Lei Song, Xinglong Gong
Composites Part A: Applied Science and Manufacturing 2013 Volume 54() pp:1-9
Publication Date(Web):November 2013
DOI:10.1016/j.compositesa.2013.07.001
This work developed flame retarded glass fiber reinforced polyamide 6 (FR-GFPA) composites with excellent mechanical properties, thermal stability and flame retardancy using a novel flame retardant, lanthanum hypophosphite (LaHP). The flame-retarded properties of FR-GFPA composites were characterized by limiting oxygen index, Underwriters Laboratories 94 testing and cone calorimeter test. FR-GFPA composite with 20 wt% LaHP reached V-0 rating and a high LOI value (27.5 vol%). The mechanical performance analysis showed that both the storage modulus and tensile strength increased and then decreased with the increase of LaHP loading. For FR-GFPA composite with 15 wt% LaHP loading, the storage modulus was 164% higher than that of glass fiber reinforced polyamide 6 (GFPA). Thermogravimetric analysis (TGA) and char residue characterization showed that the addition of LaHP can promote the formation of compact physical char barrier, reduce the mass loss rate and thus improve the flame retardancy of FR-GFPA composites.
Co-reporter:Chaoyang Guo;Shouhu Xuan;Lijun Qin;Qifan Yan
Rheologica Acta 2013 Volume 52( Issue 2) pp:165-176
Publication Date(Web):2013 February
DOI:10.1007/s00397-013-0678-6
This work is concerned with an experimental and theoretical study on compression properties of magnetorheological fluids under the nonuniform field. Experimental tests of unidirectional monotonic compression were firstly carried out under constant area operation using a commercial plate–plate magneto-rheometer where the magnetic field radial distribution was nonuniform. Normal forces increased with decreasing of the gap distance, and two regions were found through the normal force versus gap distance curves: elastic deformation and plastic flow. High normal forces could be obtained in the case of high magnetic field, high compression velocity, low initial gap distance, high volume fraction, and high medium viscosity. In the plastic flow region, the normal force with the gap distance could be fitted with a power law relation \(F_{\textrm {N}} \propto h^n\), and the index n was around well in the range (−3, −2). Taking nonuniform magnetic field into account, the theoretical modeling in the plastic flow was then developed to calculate the normal force under compression based on the continuum media theory. Compared to the uniform field, there existed a magnetic field gradient-induced normal force under nonuniform field. Considering the sealing and squeeze strengthening effect, the gap distance-dependent shear yield stress was proposed, and a good correspondence between the theoretical and experimental results was obtained.
Co-reporter:Jie Yang;Luhang Zong;Chao Peng ;Shouhu Xuan
Polymer Engineering & Science 2013 Volume 53( Issue 12) pp:2615-2623
Publication Date(Web):
DOI:10.1002/pen.23529
A novel silicon carbide (SiC)-strengthened magnetorheological elastomers (MREs) was developed to enhance its viscoelastic performance. The influences of the size and weight content of the SiC particles on the viscoelastic performance of the MREs were systematically studied. The shear storage modulus, damping property, and magnetorheological effects were analyzed to evaluate their dynamic properties. Under optimum condition, the initial storage modulus (G0) of the MRE-0.06-SiC-3 (SiC weight content 3.2 wt%, mean diameter 0.06 μm) is about 2.16 times larger than the MRE-0.06-SiC-0 (nondoped MRE), whereas the magnetorheological effect was almost kept constant. In addition, the damping properties of the as-prepared MREs which were obtained from the intrinsic damping, the magnetomechanical hysteresis, and the interface damping were also analyzed. These results provided a meaningful method for developing MREs with controllable storage modulus and damping capacity. POLYM. ENG. SCI., 53:2615–2623, 2013. © 2013 Society of Plastics Engineers
Co-reporter:Shouhu Xuan, Yanli Zhang, Yufeng Zhou, Wanquan Jiang and Xinglong Gong
Journal of Materials Chemistry A 2012 vol. 22(Issue 26) pp:13395-13400
Publication Date(Web):10 May 2012
DOI:10.1039/C2JM32375C
A novel black Plasticine™ was developed by dispersing iron microparticles into the paraffin wax–petroleum jelly composite matrix. Due to the presence of magnetic particles, this Plasticine™ exhibited magnetic-dependent mechanical properties and can be defined as a typical magnetorheological gel (MRG) material. The magnetic Plasticines™ were malleable and their mechanical properties were highly influenced by the iron contents. With increasing of the externally applied magnetic field, the shear storage modulus sharply increased. Under the optimum iron content, the magnetic induced modulus can be increased to as high as 4.23 MPa, whereas the relative magnetorheological effect was 305% and this value was higher than the reported magnetorheological elastomer (MRE). Interestingly, when the temperature reached a critical point, the magnetic Plasticine™ changed to a fluid like material which exhibited the typical characteristics of magnetorheological fluid (MRF). It was found the versatile magnetic Plasticine™ can seldom be transformed between the MRG and MRF without changing its dynamic properties.
Co-reporter:Chenlu Bao, Lei Song, Charles A. Wilkie, Bihe Yuan, Yuqiang Guo, Yuan Hu and Xinglong Gong
Journal of Materials Chemistry A 2012 vol. 22(Issue 32) pp:16399-16406
Publication Date(Web):13 Jun 2012
DOI:10.1039/C2JM32500D
Graphite oxide, graphene, ZrO2-loaded graphene and β-Ni(OH)2-loaded graphene (joint appellation: Gs) were prepared and incorporated into polystyrene so as to improve the fire safety properties of polystyrene. By the masterbatch-melt blending technique, Gs nanolayers were well dispersed and exfoliated in polystyrene as thin layers (thickness 0.7–2 nm). The fire safety properties were visibly improved, including an increased thermal degradation temperature (18 °C, PS/Ni–Gr-2), decreased peak heat release rate (40%, PS/Zr–Gr-2) and reduced CO concentration (54%, PS/Ni–Gr-2). The mechanism for the improved thermal stability and fire safety properties was investigated based on this study and previous works. The physical barrier effect of graphene, the interaction between graphene and polystyrene, and the synergistic effect of the metal compounds are the causes for the improvements.
Co-reporter:Shuang Hu, Lei Song, Haifeng Pan, Yuan Hu, Xinglong Gong
Journal of Analytical and Applied Pyrolysis 2012 Volume 97() pp:109-115
Publication Date(Web):September 2012
DOI:10.1016/j.jaap.2012.06.003
Functional materials prepared from natural resources arouse a great interest recently. Herein, a novel natural material based flame retardant chitosan phosphate acrylate (GPCS) containing phosphorus and acrylate structure has been prepared. Its effect on thermal properties and combustion behaviors of epoxy acrylate (EA) has been investigated. Microscale combustion calorimeter (MCC) data showed that GPCS reduced the peak heat release (PHRR) and total heat release (THR) of samples greatly, which meant that GPCS was efficient in reducing the flammability of EA. The results of thermogravimetric analysis (TGA) exhibited that GPCS improved the thermal stability of materials at high temperature. Investigation of real time Fourier transform infrared (RT-IR) and thermogravimetric analysis/infrared spectrometry (TGA-IR) revealed that GPCS promoted the formation of char and reduced the release of combustible gas. Thermomechanical properties data showed that the storage modulus of samples increased then decreased with increasing GPCS content while the glass transition temperature continued reduced.Highlights► A novel natural material based flame retardant chitosan phosphate acrylate (GPCS) has been prepared. ► We investigated the effect of GPCS on thermal and combustion properties of epoxy acrylate. ► The fire hazards of epoxy acrylate reduced greatly.
Co-reporter:Wanquan Jiang, Yufeng Zhou, Yanli Zhang, Shouhu Xuan and Xinglong Gong
Dalton Transactions 2012 vol. 41(Issue 15) pp:4594-4601
Publication Date(Web):22 Feb 2012
DOI:10.1039/C2DT12307J
Superparamagnetic Ag@Fe3O4 nanospheres with core–shell nanostructures have been prepared by a facile one-pot method. The diameter of the as-synthesized nanospheres was about 200 nm and the core sizes were between 50 and 100 nm. By varying the concentrations, particles with tunable core size and total size are successfully achieved. Time dependent experiments were constructed to investigate the synthesis mechanism, which indicated that the present method corresponded to an Ostwald ripening progress. The BET area of the core–shell nanospheres is about 22.6 m2/g and this result indicates that the product shows a porous character. The saturated magnetization of the superparamagnetic Ag@Fe3O4 nanospheres is 27.4 emu g−1 at room temperature, which enables them to be recycled from the solution by simply applying a small magnet. Due to the unique nanostructure, these particles show high performance in catalytic reduction of 4-nitrophenol and can be used as reusable nanocatalysts.
Co-reporter:Yangguang Xu, Xinglong Gong, Shouhu Xuan, Xiaofeng Li, Lijun Qin and Wanquan Jiang
Soft Matter 2012 vol. 8(Issue 32) pp:8483-8492
Publication Date(Web):05 Jul 2012
DOI:10.1039/C2SM25998B
The creep and recovery behaviors of magnetorheological plastomer (MRP) were systematically investigated to further understand its deformation mechanism under constant stress. The experimental results suggested that the time-dependent mechanical properties of MRP were highly dependent on the magnetic field and the magnetic-controllable mechanism was discussed. The influences of iron particle distribution and temperature on the creep and recovery behaviors in the absence and presence of a magnetic field were investigated, respectively. A great discrepancy was presented in creep curves for the isotropic and anisotropic MRP under an external magnetic field, which must be induced by the different particle assemblies. In addition, the creep strain of MRP tended to decrease with increasing temperature under a 930 mT magnetic field and this phenomenon was opposite to the results obtained without a magnetic field. Finally, a hypothesis was proposed to explain the temperature effect on the creep behaviors of MRP.
Co-reporter:Xinglong Gong, Chaoyang Guo, Shouhu Xuan, Taixiang Liu, Luhang Zong and Chao Peng
Soft Matter 2012 vol. 8(Issue 19) pp:5256-5261
Publication Date(Web):28 Mar 2012
DOI:10.1039/C2SM25341K
The normal forces of magnetorheological fluids were investigated by a commercial magneto-rheometer with plate–plate geometry. Based on the analysis, it was found that the oscillatory normal forces can be achieved both under steady shear and oscillatory shear. The oscillatory normal forces obtained under steady shear developed from the nonparallelism of the testing plates, while the oscillatory normal forces under oscillatory shear mainly arose from the microstructure revolution of magnetorheological fluids. Finally, a dynamic simulation was utilized to analyze this oscillatory shear normal force and the formation mechanism was discussed.
Co-reporter:Xinglong Gong, Yanceng Fan, Shouhu Xuan, Yangguang Xu, and Chao Peng
Industrial & Engineering Chemistry Research 2012 Volume 51(Issue 18) pp:6395-6403
Publication Date(Web):April 19, 2012
DOI:10.1021/ie300317b
A novel kind of magnetorheological elastomers (MREs) with controllable damping properties was developed in this study. Polycaprolactone (PCL) was selected as the temperature-controllable component in the cis-polybutadiene rubber (BR) based MREs. Several samples with different BR/PCL mass ratio matrixes were prepared. The dynamic performances of the samples, including loss factor, shear storage modulus, and loss modulus, were measured with a rheometer. Differential scanning calorimetry (DSC) analysis indicated that PCL is a phase change material and it can transform from a semicrystalline solid to a liquated soft material by increasing the surrounding temperature above the PCL melting point. Experimental results showed that the damping properties of the MREs can be controlled by varying the PCL weight ratio, the temperature, and the magnetic field. The controlling mechanism was proposed and the influence factors were analyzed. Last, it was also observed that the magneto-induced modulus and the MR effect of the MREs were changed remarkably by the added PCL under different temperatures.
Co-reporter:Guojiang Liao, Xinglong Gong, Shouhu Xuan, Chaoyang Guo, and Luhang Zong
Industrial & Engineering Chemistry Research 2012 Volume 51(Issue 8) pp:3322-3328
Publication Date(Web):January 30, 2012
DOI:10.1021/ie201976e
The magnetic-field-induced normal force of magnetorheological elastomer (MRE) under compression status is studied in this paper. The influence of monotonic loading of the magnetic field, particle distribution, temperature, and cyclic loading of the magnetic field are investigated. The experimental results show that the normal force increases with increasing magnetic field and precompression force. For aligned MRE, the change of the magnetic-field-induced normal force is larger than that of isotropic MRE due to the special chainlike structure. When the temperature increases, the maximum change of the magnetic-field-induced normal force first increases and then decreases, due to the interaction of iron particles and the decreasing of the saturation magnetization of the carbonyl iron particles. If the magnetic field is circularly applied on the MRE, the normal force during unloading is smaller than that during loading due to the stress relaxation.
Co-reporter:Wei Yang, Ningning Hong, Lei Song, Yuan Hu, Richard K. K. Yuen, and Xinglong Gong
Industrial & Engineering Chemistry Research 2012 Volume 51(Issue 24) pp:8253-8261
Publication Date(Web):June 4, 2012
DOI:10.1021/ie300176s
This work aims to develop glass-fiber reinforced poly(1,4-butylene terephthalate) (GRPBT) composites with enhanced mechanical, thermal stability, and flame retardancy properties using a novel compound, cerium hypophosphite (CHP). Mechanical performance studies showed that both the storage modulus and the tensile strength increased first and then decreased with increasing CHP content. For the GRPBT composite with 15 wt % of CHP, the storage modulus value at 30 °C was 3 times that of GRPBT. Thermogravimetric analysis (TGA) illustrated that low loading of CHP could improve the thermal stability of GRPBT composites. The volatilized esters measured by TGA coupled with FTIR (TGA-FTIR) in the decomposition of GRPBT with 20 wt % of CHP are decreased by about 69%. The combustion properties were evaluated by limiting oxygen index (LOI), Underwriters Laboratories 94 (UL 94), and cone calorimeter testing. For GRPBT containing 20 wt % of CHP, it achieved a V-0 classification with a high LOI (28.5%). Additionally, the peak heat release rate (PHRR) and total smoke production (TSP) were respectively reduced by around 76% and 45% as compared to the results obtained from GRPBT.
Co-reporter:Yu Jia, Zhimin Jiang, Jinping Peng, Xinglong Gong, Zhong Zhang
Composites Part A: Applied Science and Manufacturing 2012 Volume 43(Issue 9) pp:1561-1568
Publication Date(Web):September 2012
DOI:10.1016/j.compositesa.2012.04.011
Materials subject to cyclic stress can succumb to fatigue, causing failure at stress levels much lower than those in static loading cases. Herein we discussed the viscoelastic behaviors of polystyrene/multi-walled carbon nanotube (MWCNT) composites during short-term creep and recovery under tensile cyclic loading. Both unmodified and ozone oxidized MWCNTs were applied. It was found in general that the creep strain of thermoplastics dropped with decreasing temperature and stress, and with increasing content of carbon nanotubes. Moreover, with the increased cycle number, the creep strain reduced remarkably. This trend would be even more obvious at high levels of stress and temperature. Further mechanism analysis indicated the network-like structure formed by the molecule chains and nanotubes caused the reduction of the creep strain, the increasing of recovery ratio and the restriction on the mobility of amorphous molecule chains.
Co-reporter:ChaoYang Guo;ShouHu Xuan;YanLi Zhang
Korea-Australia Rheology Journal 2012 Volume 24( Issue 3) pp:171-180
Publication Date(Web):2012 September
DOI:10.1007/s13367-012-0021-2
In this work the normal force behavior of magnetorheological suspensions are systematically investigated. Four magnetorheological suspensions with different volume fractions (10%, 20%, 30%, and 40%) are prepared and both the static and dynamic normal forces of the samples are measured by using a commercial plate-plate magneto-rheometer under constant and sweeping magnetic field. A positive normal force will be generated when the applied magnetic field exceeds a critical value. The normal force firstly increases with the increasing of magnetic field strength and then reaches a saturation value. A magnetization model is utilized to represent this mechanism. The oscillatory dynamic normal forces with time are studied and their changes with shear rates are dependent on the volume fraction. Comparisons between static and dynamic normal forces show that the differences between them are dependent on the volume fraction and magnetic filed. The temperature effect on the normal force is studied and under high magnetic field the normal force would increase slightly with the increasing of temperature.
Co-reporter:Xinglong Gong;Chao Peng;Shouhu Xuan
Journal of Mechanical Science and Technology 2012 Volume 26( Issue 11) pp:3411-3422
Publication Date(Web):2012 November
DOI:10.1007/s12206-012-0857-x
This paper presents the design of a pendulum-like adaptive tuned vibration absorber (ATVA) and its application to a multi-mode system. The natural frequency of the pendulum-like ATVA can be adjusted in real time by adjusting its geometric parameters. The principle and the dynamic property of the ATVA are theoretically analyzed. Based on the analysis, a prototype of the ATVA is proposed and developed. Simulations are carried out to predict the effectiveness of the ATVA when applied to the multi-mode system. The simulated results are verified by experimental studies, which are conducted on a multi-mode platform that comprises mass, isolator, and a flexible base. The results indicate that the ATVA installed on an optimized location in the system can effectively reduce vibration over a broad frequency range and can perform better than a tuned vibration absorber.
Co-reporter:Lijun Qin, Zhongwei Zhang, Xiaofeng Li, Xiaoguang Yang, Zhihai Feng, Yang Wang, Hong Miao, Linghui He, Xinglong Gong
Composites Part A: Applied Science and Manufacturing 2012 Volume 43(Issue 2) pp:310-316
Publication Date(Web):February 2012
DOI:10.1016/j.compositesa.2011.11.006
In this work, the digital image correlation (DIC) technique was used as full-field measurement to analyze the shear properties of the 3D orthogonal woven C/C composites. Both the in-plane and the through-the-thickness specimens were tested and the macroscopic average strain was obtained. The composites were composed of lots of periodic units and the macroscopic average strain was dependent on these meso-structures. There were three regions within one unit, which showed different mesoscopic strain. The relationship between the shear test region and the macroscopic average strain was systematically studied. Finally, the accuracy of conventional strain-gauge rosette measurement was also discussed.
Co-reporter:Qunling Fang;Shouhu Xuan;Wanquan Jiang
Advanced Functional Materials 2011 Volume 21( Issue 10) pp:1902-1909
Publication Date(Web):
DOI:10.1002/adfm.201002191
Abstract
Yolk-like nano/microparticles with superparamagnetic iron oxide (SPIO) cores and hierarchical nickel silicate (NS) shells, designated yolk SPIO@NS, are fabricated by combining the versatile sol–gel process and the hydrothermal reaction, involving the coating of SPIO particles with SiO2 and transformation of the SiO2 shells into NS hollow spheres with hierarchical nanostructures. Various yolk/shell nanostructures with tunable NS shell thicknesses and SPIO core sizes are successfully prepared by controlling the experimental parameters. Au nanoparticles can be impregnated into the yolk-like microspheres in situ to form SPIO@NS/Au composite particles and the as-prepared magnetic nanocatalysts show good catalytic activity, using the catalytic reduction of RhB as a model reaction. This facile method can be extended to the synthesis of other encapsulated particles with yolk-like nanostructure.
Co-reporter:Shouhu Xuan, Yufeng Zhou, Huajian Xu, Wanquan Jiang, Ken Cham-Fai Leung and Xinglong Gong
Journal of Materials Chemistry A 2011 vol. 21(Issue 39) pp:15398-15404
Publication Date(Web):01 Sep 2011
DOI:10.1039/C1JM12798E
Here reported a facile approach to synthesize rattle type magnetic nanocomposite with a permeable Fe3O4 shell and noble metallic core. The core of yolk materials are controlled by varying the metallic ion precursor (such as K2PdCl4, AgNO3, KAuCl4, and Cu(NO3)2). The content of the metallic cores increases by increasing of the amount of the metallic salt. This one step method is based on an in situreduction and Ostwald ripening process. As-obtained particles show porous nature and superparamagnetic characteristic. Moreover, the as-prepared magnetic recyclable nanocatalyst manifests high activity when evaluated for their catalytic properties and they can be separated from the reaction system by using a magnet.
Co-reporter:Yangguang Xu, Xinglong Gong, Shouhu Xuan, Wei Zhang and Yanceng Fan
Soft Matter 2011 vol. 7(Issue 11) pp:5246-5254
Publication Date(Web):18 Apr 2011
DOI:10.1039/C1SM05301A
A novel high-performance magnetorheological material, named as magnetorheological plastomer (MRP), was developed by dispersing iron particles into a plastic polyurethane (PU) matrix. The dynamic properties (including storage modulus and loss factor) of the MRP material were systematically tested and the influences of the iron particle content and magnetic field were analyzed. It is found that the anisotropic MRP product with 80% iron particle weight fraction (A-MRP-80), shows a high dynamic property: the maximum magneto-induced storage modulus is 6.54 MPa; the relative MR effect reaches as high as 532%; the loss factor can be reduced to 0.03 by adjusting magnetic field. This kind of MRP shows a much higher magnetorheological performance than the previously reported magnetorhelogical elastomer (MRE). The mechanism for its high MR performance was proposed and the influence of the iron particle distribution and temperature on the dynamic properties were discussed.
Co-reporter:Wei Zhang, Xinglong Gong, Shouhu Xuan, and Wanquan Jiang
Industrial & Engineering Chemistry Research 2011 Volume 50(Issue 11) pp:6704-6712
Publication Date(Web):April 19, 2011
DOI:10.1021/ie200386x
Magnetorheological elastomers (MREs) are composed of magnetizable particles (iron particles) and a soft rubberlike matrix. Their mechanical properties, including modulus and damping capability, depend on both an external magnetic field and an environmental temperature. To systematically investigate thetemperature-dependent mechanical properties, six different kinds of MREs samples based on a mixed rubber matrices (cis-polybutadiene rubber and natural rubber) and their mass ratios of BR and NR were 100:0, 80:20, 60:40, 40:60, 20:80, and 0:100, were fabricated in this study. The steady-state and dynamic mechanical properties of the samples were measured under different conditions by using a rheometer. The results revealed that storage modulus (G′) and loss modulus (G′′) of samples, which contained only cis-polybutadiene rubber (BR), decreased linearly with the temperature increment. However, the modulus of sample which contained much natural rubber (NR) showed different characteristic, and the relationships between stress and strain also exhibited different characteristics with different rubber matrix. An improved constitutive equation was developed to model these properties under different magnetic fields and temperatures. The comparison between modeling predicting results with experimental data demonstrated that the model can well-predict the modulus of MRE in different conditions.
Co-reporter:W. Zhang, X. L. Gong, S. H. Xuan, and Y. G. Xu
Industrial & Engineering Chemistry Research 2010 Volume 49(Issue 24) pp:12471-12476
Publication Date(Web):November 9, 2010
DOI:10.1021/ie101904f
To improve mechanical performance of magnetorheological elastomers (MREs), two novel hybrid magnetorheological elastomers that were embedded with magnetorheological fluids (MRFs) and magnetorheological gels (MRGs) were fabricated. In this work, MRFs and MRGs were injected into different numbers of holes that were punched on MRE specimens regularly. The nonlinear mechanical properties of the as-prepared magnetorheological fluid-elastomers (MRFEs) and magnetorheological gel-elastomers (MRGEs) were investigated in the presence of external homogeneous magnetic fields. The modulus, loss factor, and hysteresis were evaluated with a modified dynamic mechanical analyzer (DMA) and vibrating sample magnetometer (VSM). Dependence of the rheological response on the volume fraction was also investigated. As the experimental results show, not only were the initial moduli of the two novel hybrid magnetorheological materials higher than those of both the MRFs and MRGs, but also their magnetorheological (MR) effects were better than those of MREs. The loss factors of the two new hybrids were different from those of traditional MREs. Moreover, their dynamic properties changed according to the different volume ratios of MRFs and MRGs injected into the MRE specimens. These results suggest that the two novel hybrid magnetorheological elastomers are improved systems with volume-fraction-dependent rheological responses and the mechanical properties of MREs can be improved by embedding them with MRFs and MRGs.
Co-reporter:Xueping Zhang, Wanquan Jiang, Xinglong Gong, Zhong Zhang
Journal of Alloys and Compounds 2010 Volume 508(Issue 2) pp:400-405
Publication Date(Web):22 October 2010
DOI:10.1016/j.jallcom.2010.08.070
A Fe3O4/Ag composite, with high efficiency in the degradation of rhodamine B was synthesized through a simple sonochemical method. These composites were obtained from sonication of Ag(NH3)2+ and (3-aminopropyl)triethoxysilane (APTES)-coated Fe3O4 nanoparticles solution at room temperature in ambient air for 1 h. A formation mechanism was proposed and discussed. This sonochemical method is attractive since it eliminated the use of any reductants, which is necessary to transform the Ag+ to the Ag0. In comparison to high temperature or high pressure experimental processes, this method is mild, inexpensive, green and efficient. The M–H hysteresis loop of these Fe3O4/Ag composite microspheres indicates that the composite spheres exhibit superparamagnetic characteristics at room temperature. Furthermore, these composites can be recycled six times by magnetic separation without major loss of activity. Thus, these Fe3O4/Ag composites can be served as effective and convenient recyclable catalysts for practical application.Research highlights▶ A Fe3O4/Ag composite, with high efficiency in the degradation of rhodamine B was synthesized through a simple sonochemical method. ▶ This sonochemical method is attractive since it eliminated the use of any reductant, which is needed to transform the Ag+ to the Ag0. Furthermore, the sonochemical preparation was accomplished at low temperature for short time. Compared with high temperature or high pressure experimental processes, it is found to be mild, inexpensive, green and efficient. ▶ Fe3O4/Ag composites exhibit excellent superparamagnetic characteristics. So Fe3O4/Ag catalyst can be rapidly gathered for recycling. ▶ Fe3O4/Ag composites can be recycled six times by magnetic separation without major loss of activity. It can be used as convenient and efficient recyclable catalysts. Moreover, this effective approach is expected to be used as attractive alternative to prepare other composites with tailored and unique properties.
Co-reporter:Bing Wei;Wanquan Jiang;Lijun Qin;Yanceng Fan
Journal of Applied Polymer Science 2010 Volume 118( Issue 5) pp:2765-2771
Publication Date(Web):
DOI:10.1002/app.32688
Abstract
Magnetorheological gels (MRGs) known as a new kind of magnetorheological material are composite gels containing magnetic particles suspended in polymer gels. In this study, a category of MR polymer gels based on polyurethane (PU) were prepared. The microstructures of these MRGs were observed with a digital microscope. Their rheological properties under both steady shear and oscillation testing were characterized by using a MR rheometer. The viscosity of the PU MRG decreased with the increment of NCO/OH ratio and increased with the increment of the weight concentration of carbonyl iron particles, molecular mass of poly propylene glycol, and applied magnetic field. The storage modulus increased gradually with the increment of applied magnetic field and weight concentration of carbonyl iron particles. The PU MRG exhibits high static shear yield stress (60.8 kPa, at 573 mT) and dynamic shear yield stress (83.9 kPa, at 573 mT) and wide variation range (static shear yield stress: 6–62 kPa, dynamic shear yield stress: 15–85 kPa). These advantages indicate that PU MRG is able to satisfy wide applications. In addition, both static and dynamic shear yield stresses of the MRG samples increase with the increment of molar mass of polypropylene glycol. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Co-reporter:Bing Wei;Wanquan Jiang
Journal of Applied Polymer Science 2010 Volume 116( Issue 2) pp:771-778
Publication Date(Web):
DOI:10.1002/app.31474
Abstract
Magnetorheological elastomers (MREs) are mainly composed of magnetizable particles and elastic polymer. The polymer matrix plays an important role in mechanical performances of MREs. In this study, the polyurethane (PU), which is synthesized by using toluene diisocyanate (TDI) and poly (propylene glycol) (PPG-220), is selected as a matrix because it has better degradation stability than natural rubber and higher mechanical stability than silicone rubber. Four different MRE samples were fabricated by adjusting the reaction molar ratio of TDI to PPG to change the property of PU matrix. Structural characterization of the PU matrix was described by Fourier transform infrared analysis. The microstructures of samples were observed by using an environmental scanning electron microscope. The mechanical performances of samples, including shear modulus, magnetorheological effect (MR) effect, loss factor, and glass transition temperature (Tg), were characterized with dynamic mechanical analyzer. The results show that the shear modulus, the relative magnetic residual shear modulus and glass transition temperatures of samples increase with the increment of toluene diisocyanate, while the relative MR effects and loss factors decrease steadily. The experimental results indicate that optimal molar ratio (TDI : PPG) is 3 : 1. The field-induced shear modulus of sample with molar ratio 3 : 1 is 4.9 MPa, and the relative MR effect is 121% under an external magnetic field of 800 mT at room temperature. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Co-reporter:Wanquan Jiang;Yingqiang Sun;Yulei Xu;Chao Peng
Rheologica Acta 2010 Volume 49( Issue 11-12) pp:1157-1163
Publication Date(Web):2010 December
DOI:10.1007/s00397-010-0486-1
The rheological behavior of polymethylmethacrylate (PMMA) particles suspensions in glycerine–water mixtures has been investigated by means of steady and dynamic rheometry in this work. The shear rheology of these suspensions demonstrates a strong shear thickening behavior. The variations of shear viscosity with the volume fraction and ratios of glycerine to water are discussed. The effect of volume fraction can be qualitatively explained using a clustering mechanism, which attributes the phenomena to the formation of temporary, hydrodynamic clusters. The influence of interactions between glycerine–water mixtures and PMMA particles on shear thickening is investigated by varying the ratio of glycerine to water. In addition, the reversible and thixotropic properties of suspensions of PMMA dispersed in glycerine–water (3:1) mixtures are also investigated, and the results demonstrate the excellent reversible and thixotropic properties of PMMA particle suspensions.
Co-reporter:Jianfeng Li, Xinglong Gong, Hong Zhu, Wanquan Jiang
Polymer Testing 2009 Volume 28(Issue 3) pp:331-337
Publication Date(Web):May 2009
DOI:10.1016/j.polymertesting.2009.01.008
In this paper, core-shell structured poly methyl methacrylate (PMMA) coated carbonyl iron (CI) particles were prepared to study the influence of particle coating on the dynamic properties of magnetorheological elastomers (MREs). The CI-PMMA composite particles were encapsulated via an emulsion polymerization method. Two MRE samples were prepared with CI-PMMA composite particles and CI particles, respectively. Their microstructure was observed by using a scanning electron microscope (SEM). Dynamic properties of these two samples under various strain and magnetic fields were measured with a dynamic mechanical analyzer (DMA). The experimental results indicate that the MRE sample with CI-PMMA composite particles has larger storage modulus, smaller loss factor and smaller Payne effect than that of the sample with only CI particles. The analysis indicates that the use of CI-PMMA particles would increase the bond strength between particles and matrix. These experimental results were also verified by the SEM images.
Co-reporter:Wanquan Jiang, Cuifeng Jiang, Zhen Cao, Xinglong Gong, Zhong Zhang
Journal of Physics and Chemistry of Solids 2009 Volume 70(3–4) pp:782-786
Publication Date(Web):March–April 2009
DOI:10.1016/j.jpcs.2009.03.014
Co-reporter:Wanquan Jiang;Chuanxia Jiang
Journal of Sol-Gel Science and Technology 2009 Volume 52( Issue 1) pp:8-14
Publication Date(Web):2009 October
DOI:10.1007/s10971-009-2011-5
In this paper, a novel nanoporous barium titanate (BaTiO3) crystalline powder was synthesized by using triblock poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO) based systems (P-123) as the soft template via a sol–gel method and their structure-dependent electro rheological property was studied. The pore diameter and specific surface area of BaTiO3 were precisely controlled by varing the calcined temperature. The chemical composition, structure and surface morphology of BaTiO3 were characterized by X-ray diffraction (XRD), thermo gravimetric analysis (TGA), and nitrogen adsorption–desorption method, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The result revealed that the pore volume and specific surface area of BaTiO3 decreased with the increment of calcined temperature. The electro rheological fluids (ERFs) were obtained by dispersing BaTiO3 crystallites in silicon oil and three kinds ERFs were fabricated by using three kinds of BaTiO3 which were prepared under different calcined temperature (550, 600 and 900 °C) as the precursors. The behaviors of the ERFs were evaluated via a rotational rheometer fixed with electric field generator. The results showed that electro rheological effect was related to the pore volume and specific surface area of BaTiO3. Due to the distinct advantage of sol–gel method for preparing nanoporous BaTiO3 without contamination of the materials, the markedly low current destiny of the ERFs was obtained. The yield stress of ERFs with large specific surface area of BaTiO3 reached the maximum of 3 kPa, which is higher than that of ERFs using traditional pure BaTiO3 crystallites (lower than 1 kPa).
Co-reporter:T.L. Sun, X.L. Gong, W.Q. Jiang, J.F. Li, Z.B. Xu, W.H. Li
Polymer Testing 2008 Volume 27(Issue 4) pp:520-526
Publication Date(Web):June 2008
DOI:10.1016/j.polymertesting.2008.02.008
Magnetorheological elastomers (MREs) are composed of magnetizable particles (iron particles) and a soft rubber-like matrix. Their mechanical properties, including modulus and damping capability, can be controlled by an external magnetic field. The damping properties of MREs, which play an important role in applications, depend mainly on particle content. This paper aims to investigate MRE's damping capabilities by studying two categories of cis-polybutadiene rubber-based MREs: isotropic and structured MREs. Both isotropic and structured MRE samples with various iron particle contents (60, 70, 80 and 85 wt%) were fabricated and their damping properties were measured by using a modified dynamic mechanical analyzer (DMA) and a universal testing machine. The results show that the loss factor in the glass transition region decreases with the increment of iron particle content. The loss factors of structured MREs are lower than those of isotropic MREs when the iron particle contents are the same. Furthermore, dynamic testing was conducted to study the effect of strain amplitude, frequency and magnetic field on the loss factor of MREs. In addition, the stress-softening experiments indicate that the ratio of remaining strain energy versus initial strain energy shows a decreasing trend with iron particle content and loading time.
Co-reporter:L. Chen, X.L. Gong, W.H. Li
Polymer Testing 2008 Volume 27(Issue 3) pp:340-345
Publication Date(Web):May 2008
DOI:10.1016/j.polymertesting.2007.12.003
Several magnetorheological elastomer (MRE) samples, with different weight percentages of carbon black, were fabricated under a constant magnetic field. Their microstructures were observed by using an environmental scanning electron microscope (SEM), and their mechanical performance including magnetorheological (MR) effect, damping ratio and tensile strength were measured with a dynamic mechanical analyzer (DMA) system and an electronic tensile machine. The experimental results demonstrate that carbon black plays a significant role in improving the mechanical performance of MR elastomers. Besides the merits of high MR effect and good tensile strength, the damping ratio of such materials is much reduced. This is expected to solve a big problem in the application of MR elastomers in practical devices, such as in adaptive tuned vibration absorbers.
Co-reporter:Yinling Wang;Yuan Hu;Wanquan Jiang;Peiqiang Zhang;Zuyao Chen
Journal of Applied Polymer Science 2007 Volume 103(Issue 5) pp:3143-3149
Publication Date(Web):19 DEC 2006
DOI:10.1002/app.24598
Magnetorheological (MR) elastomers, which are mainly composed of magnetic particles and elastic polymer, are a new kind of smart materials whose modulus can be controlled by changing the strength of magnetic fields. In this article, MR elastomers based on immiscible silicon rubber/polystyrene (SR/PS) blend matrix were fabricated successfully via cosolvent method and the MR effect, electric and mechanical properties, and the microstructures of the corresponding materials were studied. SEM studies showed that the dispersion of iron particles in blend matrix were different from that in single polymer, which could be further proved by the different electric conductivity. The MR effect of MR elastomers based on blend matrix varied with the different ratios of SR and PS, which was discussed in detail from the special dispersion of iron particles and of zero-modulus of MR elastomers. In addition, the MR elastomers based on SR/PS blend matrix had enhanced mechanical properties, which made them more hopeful to be applied in practice. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3143–3149, 2007
Co-reporter:Lingyun Hao, Xinglong Gong, Shouhu Xuan, Hong Zhang, Xiuqing Gong, Wanquan Jiang, Zuyao Chen
Applied Surface Science 2006 Volume 252(Issue 24) pp:8724-8733
Publication Date(Web):15 October 2006
DOI:10.1016/j.apsusc.2005.12.084
Abstract
SiO2@CdSe core-shell particles were fabricated by controllable deposition CdSe nanoparticles on silica colloidal spheres. Step-wise coating process was tracked by the TEM and XRD measurements. In addition, SiO2@CdSe/polypyrrole(PPy) multi-composite particles were synthesized based on the as-prepared SiO2@CdSe particles by cationic polymerization. The direct electrochemistry of myoglobin (Mb) could be performed by immobilizing Mb on the surface of SiO2@CdSe particles. Immobilized with Mb, SiO2@CdSe/PPy-Mb also displayed good bioelectrochemical activity. It confirmed the good biocompatible property of the materials with protein. CdSe hollow capsules were further obtained as the removal of the cores of SiO2@CdSe spheres. Hollow and porous character of CdSe sub-meter size capsules made them becoming hopeful candidates as drug carriers. Doxorubicin, a typical an antineoplastic drug, was introduced into the capsules. A good sustained drug release behavior of the loading capsules was discovered via performing a release test in the PBS buffer (pH 7.4) solution at 310 k. Furthermore, SiO2@CdSe/PPy could be converted to various smart hollow capsules via selectively removal of their relevant components.
Co-reporter:Yinling Wang, Yuan Hu, Lin Chen, Xinglong Gong, Wanquan Jiang, Peiqiang Zhang, Zuyao Chen
Polymer Testing 2006 Volume 25(Issue 2) pp:262-267
Publication Date(Web):April 2006
DOI:10.1016/j.polymertesting.2005.10.002
In this paper, we prepared MR elastomers containing carbonyl iron particles based on silicon rubber without using a magnetic field during curing by γ-ray radiation. The effects of interactions between iron particles and the matrix on the performance of MR elastomers based on silicon rubber, including MR effect and mechanical properties, were investigated. The rubber/magnetic particle interactions were controlled by the modification of the iron surface using different kinds of silane coupling agents and characterized by SEM and DSC. The results showed that tensile strength increased with the increased interaction. However, the MR effect had a certain relationship with the structure of silane coupling agents and this is discussed in detail in relation to the mechanism of the MR effect.
Co-reporter:Yinling Wang;Yuan Hu;Yinling Wang;Huaxia Deng;Peiqiang Zhang;Wanquan Jiang;Zuyao Chen
Polymer Engineering & Science 2006 Volume 46(Issue 3) pp:264-268
Publication Date(Web):27 JAN 2006
DOI:10.1002/pen.20462
Magnetorheological (MR) elastomers are a group of smart materials whose modulus can be controlled by the application of an external magnetic field. In this paper, MR elastomers based on isobutylene–isoprene rubber were prepared by the common manufacturing procedure of rubber and the corresponding MR effect, mechanical properties, and thermal stability were investigated. The results showed that MR effect varied with the volume content of iron particles and a maximum of 20% in MR effect was obtained at 15 vol% of iron particles. The relationship between MR effect and microstructure was discussed in detail. Mechanical tests showed that iron particles could improve the tensile strength and hardness. However, compared with carbon black with the same volume content, the reinforcing effect was far worse. TG analysis showed the thermal stability of isobutylene–isoprene rubber was improved by incorporation of iron particles. POLYM. ENG. SCI. 46:264–268, 2006. © 2006 Society of Plastics Engineers
Co-reporter:X.L. Gong, X.Z. Zhang, P.Q. Zhang
Polymer Testing 2005 Volume 24(Issue 5) pp:669-676
Publication Date(Web):August 2005
DOI:10.1016/j.polymertesting.2005.03.015
This paper presents a new method to fabricate isotropic magnetorheological (MR) elastomers under natural conditions. In the absence of a magnetic field, a variety of MR elastomer samples made of carbonyl iron particles, silicon rubber and silicone oil, were fabricated. Their dynamic viscoelastic properties were characterized by a measurement system developed by our group. Also, the microstructure of the samples was observed by a scanning electron microscope. The effects of iron particles and additives on the MR effect and the relationship between microstructure and mechanical properties were investigated. Furthermore, a simple self-assembled microstructure was proposed to explain the inherent magnetoviscoelasticity of MR elastomers prepared in the absence of a magnetic field. The analytical results of the model are in agreement with experimental data. The study is also expected to provide a good guide for designing and preparing new MR elastomers.
Co-reporter:Qian Chen, Mei Liu, Shouhu Xuan, Wanquan Jiang, Saisai Cao, Xinglong Gong
Materials & Design (5 May 2017) Volume 121() pp:92-100
Publication Date(Web):5 May 2017
DOI:10.1016/j.matdes.2017.02.056
•Carbon nanotube (CNT) particles enhance the shear thickening effect of conductive shear thickening fluid (C-STF).•The C-STF possesses unique electrical property due to the presence of CNT.•Resistance of C-STF critically decreases once accounting the unexpected shear and the decrements reached to as high as 90%.•The shear dependent impedance spectroscopies can describe the structure evolution during the shear thickening procedure.Conductive shear thickening fluid (C-STF) consisting of SiO2 particles, carbon nanotube (CNT) and ethyl glycol (EG) was developed. The shear thickening effect of C-STF was strengthened with the increasing CNT mass fraction. Different from the traditional shear thickening fluid (STF), the as-prepared C-STF showed unique electrical property due to presence of the conductive doping CNT. The initial resistance of C-STF varied from 94 kΩ to 18 kΩ at different CNT mass fractions (0.1 wt%, 0.2 wt%, 0.3 wt% and 0.4 wt%). Moreover, the resistance could be critically decreased once accounting the unexpected shear and the decrements reached to as high as 90%. Meanwhile, the shear dependent impedance spectroscopies at different shear rates were analyzed and an equivalent circuit model was proposed to investigate the microstructure dependent electrical property. This phenomenon not only gave much valuable information for understanding the detail shear thickening mechanism but also broadened their application in anti-impact sensor.Download high-res image (146KB)Download full-size image
Co-reporter:Xiaohui Ruan, Lei Pei, Shouhu Xuan, Qifan Yan, Xinglong Gong
Journal of Magnetism and Magnetic Materials (1 May 2017) Volume 429() pp:1-10
Publication Date(Web):1 May 2017
DOI:10.1016/j.jmmm.2017.01.003
•A superparamagnetic fluid based on Fe3O4 hollow nanospheres was investigated.•The stable magnetic fluid had a high yield stress even at low shear rate.•The shear stress of the hollow nanospheres is large.•A molecule dynamic simulation was conducted to analyze the shear stress.In this work, a superparamagnetic fluid based on Fe3O4 hollow nanospheres was developed and the influence of the particle structure on the rheological properties was investigated. The Fe3O4 hollow nanospheres which were prepared by using the hydrothermal method presented the superparamagnetic characteristic, and the magnetic fluid thereof showed well magnetorheological (MR) effect. The stable magnetic fluid had a high yield stress even at low shear rate and its maximal yield stress was dramatically influenced by the measurement gap. In comparison to the Fe3O4 nanoparticles based magnetic fluid (MF), the Fe3O4 hollow nanospheres based MF exhibited better MR effect and higher stability since the unique hollow nanostructure. The shear stress of the hollow nanospheres is about 1.85 times larger than the nanoparticles based MF because it formed stronger chains structure under applying a magnetic field. To further investigate the enhancing mechanism, a molecule dynamic simulation was conducted to analyze the shear stress and the structure evolution of the Fe3O4 hollow nanospheres based MF and the simulation matched well with the experimental results.
Co-reporter:Xiaohui Ruan, Lei Pei, Shouhu Xuan, Qifan Yan, Xinglong Gong
Journal of Magnetism and Magnetic Materials (1 May 2017) Volume 429() pp:1-10
Publication Date(Web):1 May 2017
DOI:10.1016/j.jmmm.2017.01.003
•A superparamagnetic fluid based on Fe3O4 hollow nanospheres was investigated.•The stable magnetic fluid had a high yield stress even at low shear rate.•The shear stress of the hollow nanospheres is large.•A molecule dynamic simulation was conducted to analyze the shear stress.In this work, a superparamagnetic fluid based on Fe3O4 hollow nanospheres was developed and the influence of the particle structure on the rheological properties was investigated. The Fe3O4 hollow nanospheres which were prepared by using the hydrothermal method presented the superparamagnetic characteristic, and the magnetic fluid thereof showed well magnetorheological (MR) effect. The stable magnetic fluid had a high yield stress even at low shear rate and its maximal yield stress was dramatically influenced by the measurement gap. In comparison to the Fe3O4 nanoparticles based magnetic fluid (MF), the Fe3O4 hollow nanospheres based MF exhibited better MR effect and higher stability since the unique hollow nanostructure. The shear stress of the hollow nanospheres is about 1.85 times larger than the nanoparticles based MF because it formed stronger chains structure under applying a magnetic field. To further investigate the enhancing mechanism, a molecule dynamic simulation was conducted to analyze the shear stress and the structure evolution of the Fe3O4 hollow nanospheres based MF and the simulation matched well with the experimental results.
Co-reporter:Kaihui Chen, Yu Wang, Shouhu Xuan, Xinglong Gong
Journal of Colloid and Interface Science (1 July 2017) Volume 497() pp:
Publication Date(Web):1 July 2017
DOI:10.1016/j.jcis.2017.03.038
To investigate the microstructural evolution dependency on the apparent viscosity in shear-thickening fluids (STFs), a hybrid mesoscale model combined with stochastic rotation dynamics (SRD) and molecular dynamics (MD) is used. Muller-Plathe reverse perturbation method is adopted to analyze the viscosities of STFs in a two-dimensional model. The characteristic of microstructural evolution of the colloidal suspensions under different shear rate is studied. The effect of diameter of colloidal particles and the phase volume fraction on the shear thickening behavior is investigated. Under low shear rate, the two-atom structure is formed, because of the strong particle attractions in adjacent layers. At higher shear rate, the synergetic pair structure extends to layered structure along flow direction because of the increasing hydrodynamics action. As the shear rate rises continuously, the layered structure rotates and collides with other particles, then turned to be individual particles under extension or curve string structure under compression. Finally, at the highest shear rate, the strings curve more severely and get into two-dimensional cluster. The apparent viscosity of the system changes from shear-thinning behavior to the shear-thickening behavior. This work presents valuable information for further understanding the shear thickening mechanism.
Co-reporter:Yufeng Zhou, Wanquan Jiang, Shouhu Xuan, Xinglong Gong, Fang Ye, Sheng Wang and Qunling Fang
Journal of Materials Chemistry A 2013 - vol. 1(Issue 10) pp:NaN1420-1420
Publication Date(Web):2013/01/08
DOI:10.1039/C2TB00508E
Novel asymmetric hollow microspheres with polystyrene-ethylacrylate (PSt-EA) semi-spherical cores and porous hierarchical Ni-Silicate shells have been successfully fabricated by the combination of emulsifier-free polymerization, a modified Stöber method and an in situ hydrothermal conversion reaction. During the conversion of the PSt-EA@SiO2 core/shell microspheres to the asymmetric PSt-EA/Ni-Silicate composite, the spherical PSt-EA was melted within the hollow Ni-Silicate interior to form semi-microspheres. Upon further treating the asymmetric hollow microspheres by 500 °C calcination for 5 h, hierarchical Ni-Silicate hollow spheres were obtained. The BET area of the asymmetric hollow PSt-EA/Ni-Silicate microspheres was 58.9 m2 g−1 and the pore diameter was about 10–20 nm. The large porous nature of the products enable them be used as carriers for bio-molecules, and experiments indicated that the maximum adsorption ability of the asymmetric hollow microspheres could reach 8.2 μmol g−1 when the concentration of Cytochrome C was 200 mmol L¬1.
Co-reporter:Shouhu Xuan, Yanli Zhang, Yufeng Zhou, Wanquan Jiang and Xinglong Gong
Journal of Materials Chemistry A 2012 - vol. 22(Issue 26) pp:NaN13400-13400
Publication Date(Web):2012/05/10
DOI:10.1039/C2JM32375C
A novel black Plasticine™ was developed by dispersing iron microparticles into the paraffin wax–petroleum jelly composite matrix. Due to the presence of magnetic particles, this Plasticine™ exhibited magnetic-dependent mechanical properties and can be defined as a typical magnetorheological gel (MRG) material. The magnetic Plasticines™ were malleable and their mechanical properties were highly influenced by the iron contents. With increasing of the externally applied magnetic field, the shear storage modulus sharply increased. Under the optimum iron content, the magnetic induced modulus can be increased to as high as 4.23 MPa, whereas the relative magnetorheological effect was 305% and this value was higher than the reported magnetorheological elastomer (MRE). Interestingly, when the temperature reached a critical point, the magnetic Plasticine™ changed to a fluid like material which exhibited the typical characteristics of magnetorheological fluid (MRF). It was found the versatile magnetic Plasticine™ can seldom be transformed between the MRG and MRF without changing its dynamic properties.
Co-reporter:Shouhu Xuan, Yufeng Zhou, Huajian Xu, Wanquan Jiang, Ken Cham-Fai Leung and Xinglong Gong
Journal of Materials Chemistry A 2011 - vol. 21(Issue 39) pp:NaN15404-15404
Publication Date(Web):2011/09/01
DOI:10.1039/C1JM12798E
Here reported a facile approach to synthesize rattle type magnetic nanocomposite with a permeable Fe3O4 shell and noble metallic core. The core of yolk materials are controlled by varying the metallic ion precursor (such as K2PdCl4, AgNO3, KAuCl4, and Cu(NO3)2). The content of the metallic cores increases by increasing of the amount of the metallic salt. This one step method is based on an in situreduction and Ostwald ripening process. As-obtained particles show porous nature and superparamagnetic characteristic. Moreover, the as-prepared magnetic recyclable nanocatalyst manifests high activity when evaluated for their catalytic properties and they can be separated from the reaction system by using a magnet.
Co-reporter:Chenlu Bao, Lei Song, Charles A. Wilkie, Bihe Yuan, Yuqiang Guo, Yuan Hu and Xinglong Gong
Journal of Materials Chemistry A 2012 - vol. 22(Issue 32) pp:NaN16406-16406
Publication Date(Web):2012/06/13
DOI:10.1039/C2JM32500D
Graphite oxide, graphene, ZrO2-loaded graphene and β-Ni(OH)2-loaded graphene (joint appellation: Gs) were prepared and incorporated into polystyrene so as to improve the fire safety properties of polystyrene. By the masterbatch-melt blending technique, Gs nanolayers were well dispersed and exfoliated in polystyrene as thin layers (thickness 0.7–2 nm). The fire safety properties were visibly improved, including an increased thermal degradation temperature (18 °C, PS/Ni–Gr-2), decreased peak heat release rate (40%, PS/Zr–Gr-2) and reduced CO concentration (54%, PS/Ni–Gr-2). The mechanism for the improved thermal stability and fire safety properties was investigated based on this study and previous works. The physical barrier effect of graphene, the interaction between graphene and polystyrene, and the synergistic effect of the metal compounds are the causes for the improvements.
Co-reporter:Sheng Wang, Wanquan Jiang, Weifeng Jiang, Fang Ye, Ya Mao, Shouhu Xuan and Xinglong Gong
Journal of Materials Chemistry A 2014 - vol. 2(Issue 34) pp:NaN7140-7140
Publication Date(Web):2014/07/11
DOI:10.1039/C4TC00903G
A novel multi-functional polymer composite (MPC) with both excellent shear stiffening (ST) performance and magnetorheological (MR) effect is prepared by dispersing magnetic particles into shear stiffening polymer matrix. Besides having the magnetically dependent mechanical properties (MR effects), this multi-functional MPC automatically changes its rheological behavior in response to external shear stimuli. The mechanical properties of this smart composite can be alternatively achieved by varying the particle's types and contents. Upon applying a shear stress with excitation frequency from 1 Hz to 100 Hz, the storage modulus (G′) of the MPC increases from 102 to 106 Pa, demonstrating an excellent ST effect. Interestingly, the ST effects of the MPC are also tunable by varying the external magnetic field, and the area of G′ could be greatly increased and precisely controlled. Based on the experimental results, a possible mechanism is proposed and discussed. It is believed that the “cross bonds” and the particle chains induced by the magnetic field are due to the excellent multi-functional stimulus-response properties.
Co-reporter:Wanquan Jiang, Yufeng Zhou, Yanli Zhang, Shouhu Xuan and Xinglong Gong
Dalton Transactions 2012 - vol. 41(Issue 15) pp:NaN4601-4601
Publication Date(Web):2012/02/22
DOI:10.1039/C2DT12307J
Superparamagnetic Ag@Fe3O4 nanospheres with core–shell nanostructures have been prepared by a facile one-pot method. The diameter of the as-synthesized nanospheres was about 200 nm and the core sizes were between 50 and 100 nm. By varying the concentrations, particles with tunable core size and total size are successfully achieved. Time dependent experiments were constructed to investigate the synthesis mechanism, which indicated that the present method corresponded to an Ostwald ripening progress. The BET area of the core–shell nanospheres is about 22.6 m2/g and this result indicates that the product shows a porous character. The saturated magnetization of the superparamagnetic Ag@Fe3O4 nanospheres is 27.4 emu g−1 at room temperature, which enables them to be recycled from the solution by simply applying a small magnet. Due to the unique nanostructure, these particles show high performance in catalytic reduction of 4-nitrophenol and can be used as reusable nanocatalysts.
Co-reporter:Sheng Wang, Shouhu Xuan, Wanquan Jiang, Weifeng Jiang, Lixun Yan, Ya Mao, Mei Liu and Xinglong Gong
Journal of Materials Chemistry A 2015 - vol. 3(Issue 39) pp:NaN19799-19799
Publication Date(Web):2015/08/12
DOI:10.1039/C5TA06169E
A novel rate-dependent and self-healing conductive composite with a well-defined shear stiffening (S-ST) effect was facilely fabricated by dispersing multi-walled carbon nanotubes (MWCNTs) into a shear stiffening polymer matrix. The storage modulus (G′) of the multi-functional composite automatically increased 4 orders of magnitude when encountering external shear stimuli and the G′max was over 1 MPa, demonstrating an obvious shear stiffening effect and good safe-guarding performance. It was found that the electrical conductivity changed accordingly when shear stiffening occurred, therefore it can be applied as a force sensor during the attacking process. The rate-dependent piezoresistance effect of the composite was investigated. In quasi-static compression and high rate impact tests, different force signals can be obtained because of the negative and positive piezoresistivity effect. Self-healing tests indicated that the as-prepared composite can maintain its mechanical and electrical properties after destruction and healing treatments. Owing to the shear stiffening performance, the rate dependent conductive composite could both absorb impact energy and sense the attacking forces. Finally, a mechanism was proposed and it was believed that the glass transition induced by B–O interactions and the changes in the microstructure during the external action can be attributed to the S-ST performance and rate dependent electrical conductivity, respectively.
Co-reporter:Ya Mao, Wanquan Jiang, Shouhu Xuan, Qunling Fang, Ken Cham-Fai Leung, Beng S. Ong, Sheng Wang and Xinglong Gong
Dalton Transactions 2015 - vol. 44(Issue 20) pp:NaN9544-9544
Publication Date(Web):2015/04/08
DOI:10.1039/C5DT00913H
A novel rod-like β-FeOOH@poly(dopamine)–Au–poly(dopamine) nanocomposite is developed for recyclable catalysis. Firstly, the rod-like β-FeOOH template was coated in situ by a layer of poly(dopamine) (PDA) to form a core/shell nanostructure. Then the negatively charged Au nanocatalysts were well-immobilized onto the periphery of the β-FeOOH@PDA nanorod. To protect the Au nanocrystals from leaching during the catalytic reactions, another PDA layer was coated onto the above particles to form a sandwich-like PDA–Au–PDA shell on the β-FeOOH rod core. The reduction of Rhodamine B (RhB) was introduced as a model reaction to evaluate the catalytic activity of the as-prepared nanocomposites. It was found that the catalytic rate sharply increased with an increasing amount of the nanocatalyst. Benefitting from the thin outer layer of PDA, the recyclability of the nanocatalyst dramatically increased. After five times of catalytic reaction, the activity was maintained as high as 98.3%, while the β-FeOOH@PDA–Au showed it to be retained at only 73.4%.
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![Benzaldehyde, 4,4',4''-[1,3,5-triazine-2,4,6-triyltris(oxy)]tris-](/data/chemimg/549400/3140-75-8_b.png)
