Co-reporter:Jing-Kai Qin, Wen-Zhu Shao, Cheng-Yan Xu, Yang Li, Dan-Dan Ren, Xiao-Guo Song, and Liang Zhen
ACS Applied Materials & Interfaces May 10, 2017 Volume 9(Issue 18) pp:15583-15583
Publication Date(Web):April 25, 2017
DOI:10.1021/acsami.7b02101
Substitutional doping of transition metal dichalcogenide two-dimensional materials has proven to be effective in tuning their intrinsic properties, such as band gap, transport characteristics, and magnetism. In this study, we realized substitutional doping of monolayer rhenium disulfide (ReS2) with Mo via chemical vapor deposition. Scanning transmission electron microscopy demonstrated that Mo atoms are successfully doped into ReS2 by substitutionally replacing Re atoms in the lattice. Electrical measurements revealed the degenerate p-type semiconductor behavior of Mo-doped ReS2 field effect transistors, in agreement with density functional theory calculations. The p–n diode device based on a doped ReS2 and ReS2 homojunction exhibited gate-tunable current rectification behaviors, and the maximum rectification ratio could reach up to 150 at Vd = −2/+2 V. The successful synthesis of p-type ReS2 in this study could largely promote its application in novel electronic and optoelectronic devices.Keywords: DFT calculations; homojunction; p−n diode; ReS2; substitutional doping;
Co-reporter:Na Chen, Jian-Tang Jiang, Cheng-Yan Xu, Yong Yuan, Yuan-Xun Gong, and Liang Zhen
ACS Applied Materials & Interfaces July 5, 2017 Volume 9(Issue 26) pp:21933-21933
Publication Date(Web):June 1, 2017
DOI:10.1021/acsami.7b03907
Ferromagnetic metal/alloy nanoparticles have attracted extensive interest for electromagnetic wave-absorbing applications. However, ferromagnetic nanoparticles are prone to oxidization and producing eddy currents, leading to the deterioration of electromagnetic properties. In this work, a simple and scalable liquid-phase reduction method was employed to synthesize uniform Co7Fe3 nanospheres with diameters ranging from 350 to 650 nm for high-performance microwave absorption application. Co7Fe3@SiO2 core–shell nanospheres with SiO2 shell thicknesses of 30 nm were then fabricated via a modified Stöber method. When tested as microwave absorbers, bare Co7Fe3 nanospheres with a diameter of 350 nm have a maximum reflection loss (RL) of 78.4 dB and an effective absorption with RL > 10 dB from 10 to 16.7 GHz at a small thickness of 1.59 mm. Co7Fe3@SiO2 nanospheres showed a significantly enhanced microwave absorption capability for an effective absorption bandwidth and a shift toward a lower frequency, which is ascribed to the protection of the SiO2 shell from direct contact among Co7Fe3 nanospheres, as well as improved crystallinity and decreased defects upon annealing. This work illustrates a simple and effective method to fabricate Co7Fe3 and Co7Fe3@SiO2 nanospheres as promising microwave absorbers, and the design concept can also be extended to other ferromagnetic alloy particles.Keywords: Co7Fe3 nanospheres; effective absorption bandwidth; liquid-phase reduction; microwave absorption; SiO2 coating;
Co-reporter:Jing Yu;Fei-Xiang Ma;Dr. Yue Du;Pan-Pan Wang; Cheng-Yan Xu; Liang Zhen
ChemElectroChem 2017 Volume 4(Issue 3) pp:594-600
Publication Date(Web):2017/03/01
DOI:10.1002/celc.201600652
AbstractNickel sulfides have been widely employed as high-performance electrocatalysts for the hydrogen evolution reaction (HER) with high activity and low cost, and their performance could be tremendously promoted by elaborate design. Herein, we report a simple solvothermal route for the in situ growth of a three-dimensional network structure of Sn-doped Ni3S2, assembled by using ultrathin nanosheets on Ni foam. The ultrathin nanosheets with thicknesses of approximately 5–9 nm could provide more exposed active edges and a shorter electron transfer path. The Sn-doped sample exhibited efficient and durable electrocatalytic HER activity both in acid and alkaline conditions, much better than that of undoped Ni3S2 nanorods. Nyquist plots indicated that the electrochemical impendence reduced with the introduction of elemental Sn, which was another critical factor for the enhanced catalytic performance.
Co-reporter:Shan-Shan Wang, Jian-Tang Jiang, Guo-Hua Fan, A.M. Panindre, ... Liang Zhen
Acta Materialia 2017 Volume 131(Volume 131) pp:
Publication Date(Web):1 June 2017
DOI:10.1016/j.actamat.2017.03.074
The surface microstructure and its evolution during long-term room-temperature storage were studied using transmission electron microscopy for an Al-Zn-Mg-Cu alloy processed by surface abrasion with grinding paper. An altered surface layer (ASL) with thickness of 0.4–0.8 μm was present on the alloy after abrasion. Ultrafine subgrains with width of about 50–120 nm and a high density of dislocations were observed in the ASL. The pre-existing aging-induced η′ and η precipitates dissolved during surface abrasion. During room-temperature aging, relatively pure Zn, Al2Cu and AlCu phases were observed to precipitate at the extreme surface and subgrain boundaries in the ASL. These phases are very unusual in that they are typically not formed in Al-Zn-Mg-Cu alloys. Mg was not found in these particles, as it remained dissolved in the solid solution of the ASL. Al2Cu and AlCu phases also precipitated at the grain boundaries in the underlying substrate right below the ASL, as far as 6 μm in depth from the extreme surface. Considerable growth and coarsening of these phases occurred during natural aging over a period of 42 months. The enhanced diffusion accelerated by vacancies, dislocations, and subgrain/grain boundaries was considered to be mainly responsible for the accelerated precipitation and growth of these atypical phases.Download high-res image (244KB)Download full-size image
Co-reporter:Jing-Kai Qin;Wen-Zhu Shao;Yang Li;Cheng-Yan Xu;Dan-Dan Ren;Xiao-Guo Song
RSC Advances (2011-Present) 2017 vol. 7(Issue 39) pp:24188-24194
Publication Date(Web):2017/05/03
DOI:10.1039/C7RA01748K
Rhenium disulfide (ReS2) has attracted scientists' attention for its unique physical properties and potential applications in high-efficiency photodetector devices. Although lots of works have been done to obtain high-quality ReS2 nanoflakes, in-plane uniform growth is still challenging due to its unique decoupling property between layers. In this work, we successfully realized the epitaxial growth of continuous monolayer ReS2 films on mica substrate by chemical vapour deposition (CVD). By prolonging the growth time, continuous multilayer ReS2 films can also be obtained. The growth mechanism of ReS2 films is proposed based on Stranski–Krastanov theory. Filed effect transistors (FETs) based on multilayer ReS2 films exhibit typical n-type semiconducting behaviour with a carrier density of 0.27 cm2 V−1 s−1 and ON/OFF ratio of about 4 × 103. The photoresponsivity of the phototransistor could reach up to 0.98 A W−1 with a light intensity of 0.56 mW cm−2, suggesting that ReS2 is a promising material for electronic and optoelectronic applications.
Co-reporter:Qing Chen;Penghao Xiao;Yi Pei;Yan Song;Cheng-Yan Xu;Graeme Henkelman
Journal of Materials Chemistry A 2017 vol. 5(Issue 32) pp:16722-16731
Publication Date(Web):2017/08/15
DOI:10.1039/C7TA03049E
Li2MnSiO4 is a promising high capacity cathode material due to the potential to extract two Li ions per formula unit. In practice, however, the use of Li2MnSiO4 is restricted by a low discharge capacity, which has been attributed to an irreversible structural change in the first charge cycle. In this work, we use density functional theory calculations to explore the details of this structural change, and our results reveal that the structural change during delithiation has two components. First, we find that the material undergoes a structural collapse upon partial delithiation, which is characterized by distortion of the MnO4 tetrahedron. Remarkably, while this transformation results in a disordered structure, our calculations show that it is reversible upon relithiation and that the transformation does not strongly impede Li de/intercalation. The calculated reversibility of the phase change is consistent with recent experimental X-ray diffraction measurements showing that peaks associated with the crystalline MnO4 order, which disappear upon delithiation, are restored upon lithiation. Additional experiments are conducted showing the reversibility of the material during cycling as a function of charging cutoff voltages. Second, we argue that, the irreversible structural degradation is primarily caused by oxygen evolution in the highly delithiated state; the oxygen deficient structure can only reincorporate half of the total Li when discharged to 1.5 V. Experimentally observed voltage profile shifts of Li2MnSiO4 during the first few cycles as well as the different electrochemical behavior exhibited by Li2FeSiO4 can be explained by this two-component structural change model.
Co-reporter:Shuang Yang;Cheng-Yan Xu;Bao-You Zhang
Journal of Materials Science: Materials in Electronics 2017 Volume 28( Issue 2) pp:1869-1876
Publication Date(Web):01 October 2016
DOI:10.1007/s10854-016-5738-0
Two-dimensional materials, such graphene and transition metal dichalcogenides with layered structures, and other non-layered materials, have found broad applications in optoelectronics, energy storage and photocatalysis, utilizing the unique properties arising from the two-dimensional characteristics. In this work, we report the solvothermal synthesis of uniform InOOH nanosheets with average length of c.a. 1.5 μm, width of c.a. 500 nm, and thickness of c.a. 60 nm. The obtained InOOH nanosheets are characterized by X-ray diffraction, scanning electron microscope and transmission electron microscope. The possible growth mechanism of the InOOH nanosheets was discussed. Photocatalytic and photoelectrochemical experiments indicated that the InOOH nanosheets present enhanced photocatalytic activity for the degradation of Rhodamine B under UV light irradiation, which can be ascribed to its high BET surface area as well as enhanced electron–hole separation originated from the two-dimensional morphological characteristics.
Co-reporter:Yang Li;Jing-Kai Qin;Cheng-Yan Xu;Jian Cao;Zhao-Yuan Sun;Lai-Peng Ma;Ping An Hu;Wencai Ren
Advanced Functional Materials 2016 Volume 26( Issue 24) pp:4319-4328
Publication Date(Web):
DOI:10.1002/adfm.201505412
Transition metal dichalcogenides van der Waals (vdWs) heterostructures present fascinating optical and electronic phenomena, and bear tremendous significance for electronic and optoelectronic applications. As the significant merits in vdWs heterostructures, the interlayer relaxation of excitons and interlayer coupling at the heterointerface reflect the dynamic behavior of charge transfer and the coupled electronic/structural characteristics, respectively, which may give rise to new physics induced by quantum coupling. In this work, upon tuning the photoluminescence (PL) properties of WSe2/graphene and WSe2/MoS2/graphene heterostructures by virtue of electric field, it is demonstrated that the interlayer relaxation of excitons at the heterointerface in WSe2/graphene, which is even stronger than that in MoS2/graphene and WSe2/MoS2 , plays a dominant role in PL tuning in WSe2/graphene, while the carrier population in WSe2 induced by electric field has a minor contribution. In addition, it is discovered that the interlayer coupling between monolayer WSe2 and graphene is enhanced under high electric field, which breaks the momentum conservation of first order Raman-allowed phonons in graphene, yielding the enhanced Raman scattering of defects in graphene. The interplay between electric field and vdWs heterostructures may provide versatile approaches to tune the intrinsic electronic and optical properties of the heterostructures.
Co-reporter:Yang Li;Cheng-Yan Xu;Jing-Kai Qin;Wei Feng;Jia-Ying Wang;Siqi Zhang;Lai-Peng Ma;Jian Cao;Ping An Hu;Wencai Ren
Advanced Functional Materials 2016 Volume 26( Issue 2) pp:293-302
Publication Date(Web):
DOI:10.1002/adfm.201503131
The behavior of excitons in van der Waals (vdWs) heterostructures depends on electron–electron interactions and charge transfer at the hetero-interface. However, what still remains to be unraveled is to which extent the carrier densities of both counterparts and the band alignment in the vdWs heterostructures determine the photoluminescence properties. Here, we systematically study the photoluminescence properties of monolayer MoS2/graphene heterostructures by modulating the carrier densities and contact barrier at the interface via electrochemical gating. It is shown that the PL intensities of excitons can be tuned by more than two orders of magnitude, and a blue-shift of the exciton peak of up to 40 meV is observed. By extracting the carrier density of MoS2 using an electric potential distribution model, and the Schottky barrier using first-principle calculations, we find that the controllable carrier density in MoS2 plays a dominant role in the PL tuning at negative gate bias, whereas the interlayer relaxation of excitons induced by the Schottky barrier has a major contribution at positive gate bias. This is further verified by controlling the tunneling barrier and screening field across MoS2 by inserting self-assembled monolayers (SAMs) at the interface. These findings will benefit to better understand the effect of many-body interactions and hetero-interfaces on the optical and optoelectronic properties in vdWs heterostructures.
Co-reporter:Pan-Pan Wang, Yan-Xin Yao, Cheng-Yan Xu, Long Wang, Wen He, Liang Zhen
Ceramics International 2016 Volume 42(Issue 13) pp:14595-14600
Publication Date(Web):October 2016
DOI:10.1016/j.ceramint.2016.06.075
Abstract
Self-standing V2O5 nanobelt electrode free of binders, conductive carbon or current collectors was successfully prepared via a simple one-step hydrothermal reaction. The length of V2O5 nanobelts was up to several hundreds micrometers and the thickness was around 40 nm. Ultralong nanobelts as building blocks and internal voids provide a robust mechanical flexibility and shortened ion/electron transport pathway. The self-standing electrode delivered an initial specific capacity of 127.4 mA h g−1 at a current density of 60 mA g−1 and exhibited excellent cycling stability with capacity retention up to 89.8% after 200 cycles. The outstanding cycling performance can be attributed to the excellent network stability, shortened Li-ion diffusion pathway and the high surface area between electrolyte/electrode interfaces.
Co-reporter:J.T. Jiang, Q.J. Tang, L. Yang, K. Zhang, S.J. Yuan, L. Zhen
Journal of Materials Processing Technology 2016 Volume 227() pp:110-116
Publication Date(Web):January 2016
DOI:10.1016/j.jmatprotec.2015.07.018
Excellent mechanical properties and satisfactory corrosion resistance were achieved in an Al–Zn–Mg–Cu alloy via non-isothermal ageing (NIA) treatment. The precipitation and age-strengthening were elucidated by combining the TEM observing, DSC analysis and the mechanical properties testing results. The corrosion resistance was evaluated based on the measured electrical conductivity. The effect of staring temperature (Ts) and the cooling rate (Rc) of the NIA processes on the properties was systematically investigated. The continuously decreasing temperature is found inhibit existing precipitates’ coarsening and also induces secondary precipitation. High Ts and low Rc bring about high conductivity and low hardness. Extra hardening together with a conductivity decrease occurs at the later stage of NIA processes due to the forming of fine secondary precipitates. High strength combined with high conductivity can be obtained by setting Ts at the 180–190 °C range and Rc at the 10–20 °C/h range. An optimized NIA process (cooled from 190 to 100 °C at 20 °C/h) provides higher strength and comparable SCC resistance within a halved processing time by looking the typical T74 ageing as a reference.
Co-reporter:Pan-Pan Wang, Cheng-Yan Xu, Wang-Da Li, Long Wang, Liang Zhen
Electrochimica Acta 2015 Volume 169() pp:440-446
Publication Date(Web):1 July 2015
DOI:10.1016/j.electacta.2015.04.084
The low temperature electrochemical behavior of β-LixV2O5 as cathode material was investigated by galvanostatic charge/discharge test and electrochemical impedance spectroscopy. The β-LixV2O5 cathode exhibited unusual high capacity retention ratio upon 100 cycles under subzero temperatures: 88.6% at −40 °C, 79.5% at −20 °C, and 82.3% at 0 °C while only 55.0% at room temperature. Electrochemical impedance spectroscopy results indicate that the charge-transfer resistance increases sharply and the lithium diffusion coefficient decreases gradually as temperature dropping to −40 °C. According to Randles plot and Arrhenius equation, the activation energies for charge-transfer and solid-state lithium diffusion at 20% state of charge are 43.28 and 47.96 kJ mol−1, respectively, suggesting that the electrochemical process dynamics of the β-LixV2O5 electrode is controlled by the sluggish charge-transfer kinetics as well as solid-state ionic diffusion.
Co-reporter:Ya-Bo Dong;Wen-Zhu Shao;Jian-Tang Jiang
Journal of Materials Engineering and Performance 2015 Volume 24( Issue 6) pp:2256-2265
Publication Date(Web):2015 June
DOI:10.1007/s11665-015-1505-2
In order to improve the balance of mechanical properties and residual stress, various quenching and aging treatments were applied to Al-Cu alloy forged plate. Residual stresses determined by the x-ray diffraction method and slitting method were compared. The surface residual stress measured by x-ray diffraction method was consistent with that measured by slitting method. The residual stress distribution of samples quenched in water with different temperatures (20, 60, 80, and 100 °C) was measured, and the results showed that the boiling water quenching results in a 91.4% reduction in residual stress magnitudes compared with cold water quenching (20 °C), but the tensile properties of samples quenched in boiling water were unacceptably low. Quenching in 80 °C water results in 75% reduction of residual stress, and the reduction of yield strength is 12.7%. The residual stress and yield strength level are considerable for the dimensional stability of aluminum alloy. Quenching samples into 30% polyalkylene glycol quenchants produced 52.2% reduction in the maximum compressive residual stress, and the reduction in yield strength is 19.7%. Moreover, the effects of uphill quenching and thermal-cold cycling on the residual stress were also investigated. Uphill quenching and thermal-cold cycling produced approximately 25-40% reduction in residual stress, while the effect on tensile properties is quite slight.
Co-reporter:Fei-Xiang Ma, Pan-Pan Wang, Cheng-Yan Xu, Jing Yu, Hai-Tao Fang and Liang Zhen
Journal of Materials Chemistry A 2014 vol. 2(Issue 45) pp:19330-19337
Publication Date(Web):30 Sep 2014
DOI:10.1039/C4TA03008G
Self-stacked CuFe2O4–Fe2O3 porous nanosheets were prepared via a facile polyol-mediated route followed by calcination. Because of its highly porous structures and good electrical and ion conductivity of the well-dispersed CuFe2O4 phase in the matrix, the hybrid material exhibits high specific capacity of 910 mA h g−1 at 0.5 C after 200 cycles, superior capacity retention (0.02% capacity loss per cycle) and good rate capability (417 mA h g−1 at 4 C) as a promising anode material for Li-ion batteries.
Co-reporter:Jing Yu, Cheng-Yan Xu, Fei-Xiang Ma, Sheng-Peng Hu, Yu-Wei Zhang, and Liang Zhen
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 24) pp:22370
Publication Date(Web):November 20, 2014
DOI:10.1021/am506396z
Graphene-like two-dimensional layered materials have attracted quite a lot of interest because of their sizable band gaps and potential applications. In this work, monodisperse tin disulfide (SnS2) nanosheets were successfully prepared by a simple solvothermal procedure in the presence of polyvinylpyrrolidone (PVP). Large PVP molecules absorbing on (001) facets of SnS2 would inhibit crystal growth along [001] orientation and protect the product from agglomeration. The obtained SnS2 nanosheets have diameters of ca. 0.8–1 μm and thicknesses of ca. 22 nm. Different experiment parameters were carried out to investigate the transformation of phase and morphology. The formation mechanism was proposed according to the time-dependent experiments. SnS2 nanosheets exhibit high photocatalytic H2 evolution activity of 1.06 mmol h–1 g–1 under simulated sunlight irradiation, much higher than that of SnS2 with different morphologies and P25-TiO2. Moreover, the as-obtained SnS2 nanosheets show excellent photoelectrochemical response performance in visible-light region.Keywords: nanosheets; photocatalytic hydrogen evolution; photoelectrochemical response; solvothermal; tin disulfide
Co-reporter:Sheng-Peng Hu, Cheng-Yan Xu, Fei-Xiang Ma, Lei Cao and Liang Zhen
Dalton Transactions 2014 vol. 43(Issue 22) pp:8439-8445
Publication Date(Web):24 Mar 2014
DOI:10.1039/C3DT53561D
We report the solvothermal synthesis of hierarchical structures of orthorhombic Sb2WO6 and their implementation as a visible-light-driven photocatalyst for the degradation of Rhodamine B. The obtained hierarchical structures constructed by tiny nanosheets are doughnut-like flat ellipsoids with concaves in the centres, and with typical sizes of 1.3 μm in length, 800 nm in width and 400 nm in thickness. The concave characteristics and sizes of Sb2WO6 hierarchical structures can be tuned by adjusting the volume ratio of EG–H2O. Time-dependent experiments reveal that the formation process of concave structures involves the aggregation of nanoparticles to form solid spheres, dissolution–recrystallization to form hierarchical structures subsequently, and an Ostwald ripening process to shape the desired concaves finally. Under visible-light irradiation, complete degradation of Rhodamine B is achieved within 180 min in the presence of Sb2WO6 hierarchical structures, which could be ascribed to the porous structures, high BET surface area (42.58 m2 g−1) and wide absorption in the visible-light region.
Co-reporter:Wenshou Wang, Liang Zhen, Wenzhu Shao and Zhonglin Chen
CrystEngComm 2014 vol. 16(Issue 13) pp:2598-2604
Publication Date(Web):08 Jan 2014
DOI:10.1039/C3CE42502A
A special structure, calcium molybdate (CaMoO4) notched microspheres, were prepared by a solution-phase rapid-injection-based route using only CaCl2, (NH4)6Mo7O24, and sodium dodecyl sulfate as reagents and ethylene glycol as a solvent. X-ray diffraction, scanning electron microscopy, transmission electronic microscopy and an X-ray energy dispersive spectrometer were used to characterize the obtained samples. The notched microspheres were uniform in size and shape, with each sphere containing one notch on its surface. The results show that the formation process of the CaMoO4 notched microspheres is due to a “two-step” growth process, in which CaSO4 nanorods are formed first and then CaMoO4 microspheres are grown on the surfaces of the CaSO4 nanorods. The reaction intermediate, the CaSO4 nanorods, acts as a self-template for the formation of “CaMoO4 sphere gripped CaSO4 nanorod” structures, and finally produce very special structures – CaMoO4 notched microspheres. The shape and size of the notched CaMoO4 samples can be tuned from ellipses to spheres with diameters in the range of 0.1–1 μm by controlling the reaction conditions.
Co-reporter:Wenshou Wang, Jianxun Cui, Panpan Wang, Liang Zhen, Wenzhu Shao and Zhonglin Chen
RSC Advances 2014 vol. 4(Issue 73) pp:38527-38534
Publication Date(Web):15 Aug 2014
DOI:10.1039/C4RA05472E
Three-dimensional (3D) CdMoO4 hierarchical structures constructed by single-crystalline nanoplates were prepared by a facile hydrothermal route. The obtained samples were systematically characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and UV-Vis spectrophotometry. The morphology modulation of the as-prepared products could be easily tuned by changing the concentration of reactants, reaction temperature, molybdenum source, pH value and reaction time. The formation process of CdMoO4 hierarchical structures was related to the two-step growth, in which CdMoO4 main nanoplates were formed first in the synthesis, followed by self-construction of small nanoplates on both side of the main nanoplates in a regular fashion. The photocatalytic activities of CdMoO4 hierarchical structures and nanoplates for degradation of Rhodamine B (RhB) under ultraviolet (UV) light irradiation were also evaluated. CdMoO4 hierarchical structures constructed by nanoplates have a higher photocatalytic activity toward photo-degradation of RhB than that of CdMoO4 nanoplates, mainly due to their unique morphology and high crystallinity.
Co-reporter:Hui-Jian Ye, Li Yang, Wen-Zhu Shao, Yang Li, Song-Bai Sun and Liang Zhen
RSC Advances 2014 vol. 4(Issue 26) pp:13525-13532
Publication Date(Web):23 Jan 2014
DOI:10.1039/C3RA47550F
The effect of electron irradiation on the crystal structure and dielectric properties of poly(vinylidene fluoride) (PVDF) films was investigated. X-ray diffraction (XRD) and differential scanning calorimetry (DSC) were employed to examine the degree of participation in PVDF and the relative fraction of electroactive phase as well as the thermal property of PVDF films. The results showed that both the exothermal peak temperature and the crystallinity of the irradiated film decreased with increasing doses. Huge damage on the morphology of spherulite was observed in irradiated films by atomic force microscopy (AFM). The results of fine structures in PVDF films characterized by X-ray absorption near edge structure (XANES) implied that the dominance of the oxidation reaction occurred during irradiation, and further induced destruction of the regular packed structure. The results indicate that the β-phase exhibits good anti-irradiation ability during the electron irradiation on PVDF film. Because a large portion of the electroactive phase is maintained and intermediate phases are produced in the irradiated PVDF sample, the irradiated film exhibits a relatively high dielectric constant (around 7.8 under 2200 kGy) with low loss.
Co-reporter:Sheng-Peng Hu, Cheng-Yan Xu, Wen-Shou Wang, Fei-Xiang Ma, Liang Zhen
Ceramics International 2014 Volume 40(Issue 8) pp:11689-11698
Publication Date(Web):September 2014
DOI:10.1016/j.ceramint.2014.03.179
We report a facile template-free solvothermal approach for the synthesis of Bi2WO6 hierarchical structures assembled by porous nanoplates, the unique morphology of which endows the sample with high photocatalytic activity under visible light irradiation. The synthesized Bi2WO6 hierarchical structures have diameters of ~1 μm, and consist of multiple crossed-plates in three-dimensional configuration. A possible three-stage formation mechanism was proposed for the construction of hierarchical structures, and Ostwald ripening was responsible for the formation of meso-pores. The as-prepared Bi2WO6 hierarchical structures exhibited high photocatalytic activity on the degradation of Rhodamine B under visible light irradiation, due to the larger specific surface area (20.4 m2 g−1), unique hierarchical structures with multiple-crossed porous layer and higher crystallinity. A comparison of photocatalytic performance between the hierarchical structures and other samples with different morphologies was performed. The main active species of Bi2WO6 hierarchical structures during a photocatalytic process were determined to be O2− and h+ radicals by dissolving different trapping agents.
Co-reporter:J.F. Chen, J.T. Jiang, L. Zhen, W.Z. Shao
Journal of Materials Processing Technology 2014 Volume 214(Issue 4) pp:775-783
Publication Date(Web):April 2014
DOI:10.1016/j.jmatprotec.2013.08.017
•Stress relaxation behavior in the simulated age-forming process of the Al–Zn–Mg–Cu alloy can be divided into three stages.•Activation energies are 132 kJ/mol, 119 kJ/mol and 91 kJ/mol, respectively, in different stages of the simulated aging-forming process.•Stress relaxation behavior in the simulated age-forming process is controlled by dislocation creep and Coble creep.•A threshold stress presents in the stress relaxation process of the Al–Zn–Mg–Cu alloy.The stress relaxation behavior of age-forming for an Al–Zn–Mg–Cu alloy was studied using a designed device that can simulate the age forming process. The mechanism of stress relaxation was also revealed through calculating thermal activation parameters and analyzing the microstructures. The results suggested that the stress relaxation behavior of the Al–Zn–Mg–Cu alloy in the simulated age-forming process can be divided into three stages according to the stress level. The three stages of stress relaxation are: (i) the initial high stress stage, (ii) the subsequent middle stress transition stage and (iii) the last low stress equilibrium stage, respectively. The deformation activation energies are 132 kJ/mol in the initial high stress stage, 119 kJ/mol in the subsequent middle stress transition stage and 91 kJ/mol in the last low stress equilibrium stage, respectively. The analysis of the thermal activation parameters and microstructures revealed that dislocation creep was the dominant deformation mechanism in the initial and subsequent stages of the stress relaxation; whereas diffusion creep is the mechanism in the last stage of the stress relaxation. Additionally, a special threshold stress phenomena was present in the stress relaxation of the age-forming process, which was scribed to the interaction between precipitation and dislocation in the Al–Zn–Mg–Cu alloy
Co-reporter:W.S. Wang, L. Zhen, W.Z. Shao, Z.L. Chen
Materials Letters 2014 Volume 131() pp:292-294
Publication Date(Web):15 September 2014
DOI:10.1016/j.matlet.2014.05.203
•CdMoO4 nanoplates were synthesized by a simple hydrothermal method.•CdMoO4 nanoplates have a single crystalline structure.•NaCl provides a suitable chemical environment to direct the growth of CdMoO4 nanoplates.Square-shaped CdMoO4 nanoplates with an average size of ~4 μm and thickness of ~200 nm have been successfully synthesized via a NaCl-assisted hydrothermal method without using any surfactants or templates. X-ray diffraction pattern, scanning electron microscopy, transmission electron microscopy and UV–vis diffuse reflectance spectroscopy were used to characterize the samples. The formation process of CdMoO4 nanoplates is related to NaCl, which provides a favorable chemical environment for the growth of nanoplates.
Co-reporter:J.T. Jiang, W.Q. Xiao, L. Yang, W.Z. Shao, S.J. Yuan, L. Zhen
Materials Science and Engineering: A 2014 Volume 605() pp:167-175
Publication Date(Web):27 May 2014
DOI:10.1016/j.msea.2014.03.023
A non-isothermal ageing (NIA) process was proposed for an Al–Zn–Mg–Cu alloy aiming to accommodate heating and/or cooling procedures in large components. The precipitation was investigated systematically via TEM observation and DSC analysis. The age-hardening and the conductivity variation were examined to evaluate the potential in the strength and the corrosion resistance, respectively. Double cantilever beams (DCB) experiments were carried out to evaluate the stress corrosion cracking (SCC) resistance. A secondary precipitation occurs during the cooling procedure of the NIA process, which leads to an increase in the precipitates number density and thus induces an extra hardening. The secondary precipitation also contributes to the increase of conductivity of the alloy in the most part of the cooling procedure, but leads to a slight decrease at the terminal stage. The alloy׳s resistance to SCC improves persistently as the NIA proceeds. The evolution in microchemistry in grain boundary and adjacent regions is supposed to contribute to the improvement of corrosion resistance. The current study suggests that the NIA process (40 °C→190 °C→100 °C, 20 °C/h) is capable of enduing higher mechanical performances and comparable corrosion resistance to Al–Zn–Mg–Cu alloys, as compared with that of the T74 condition, which can be technically significant for ageing treatment of large components.
Co-reporter:Shan-Shan Wang, Jian-Tang Jiang, Guo-Hua Fan, Li Yang, Sheng-Long Dai, G.S. Frankel, Liang Zhen
Materials Characterization 2014 98() pp: 18-25
Publication Date(Web):
DOI:10.1016/j.matchar.2014.10.009
Co-reporter:W.S. Wang, L. Zhen, C.Y. Xu, L. Yang, W.Z. Shao, Z.L. Chen
Materials Research Bulletin 2014 56() pp: 1-7
Publication Date(Web):
DOI:10.1016/j.materresbull.2014.04.015
Co-reporter:Wang-Da Li, Cheng-Yan Xu, Xiao-Liang Pan, Yu-Dong Huang and Liang Zhen
Journal of Materials Chemistry A 2013 vol. 1(Issue 17) pp:5361-5369
Publication Date(Web):21 Feb 2013
DOI:10.1039/C3TA01609A
LixV2O5 (x ∼ 0.42) nanorods, an overdoped β-phase vanadium oxide bronze with a rigid three-dimensional framework, have been fabricated for the first time via a simple two-step synthetic method. It is found that the δ-type structure of the as-prepared hydrated nanobelts through the hydrothermal route is converted into the tunnel β geometry upon annealing-induced dehydration. After annealing at 600 °C, the β-LixV2O5 nanorods exhibit the desired electrochemical properties: an initial gravimetric discharge capacity of 388.4 mA h g−1 (corresponding to an uptake of ca. 2.68 lithium per cell unit) and a specific energy density of 1039.6 W h kg−1 are achieved within a 2.0 V cut-off voltage at C/20, which decreased to 295.3 mA h g−1 (ca. 2.04 Li/V2O5) and 789.0 W h kg−1 after 50 cycles, respectively. The irreversible formation of ω-LixV2O5 for layered V2O5 cathodes upon deep lithiation is not presented during cell operation, and such improved structural reversibility is attributed to the highly retrievable host framework of the β-Li bronze, as well as further strain relaxation facilitated by the one-dimensional nanostructures. Based on the distinctive crystallographic structure and superior electrochemical properties, this β-lithium vanadium bronze has shown promising potential as a cathode material for secondary lithium-based batteries.
Co-reporter:Xiao-Liang Pan, Cheng-Yan Xu, Da Hong, Hai-Tao Fang, Liang Zhen
Electrochimica Acta 2013 Volume 87() pp:303-308
Publication Date(Web):1 January 2013
DOI:10.1016/j.electacta.2012.09.106
Well-dispersed LiMnPO4 plates with thickness of about 100 nm were synthesized by a facile hydrothermal method at 200 °C for 10 h. The crystalline structure, morphology and microstructure were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). The LiMnPO4 electrode exhibits high discharge capacity, good rate capability and high cycling stability. At a 0.05 C rate, the plates delivered a discharge capacity of 139.2 mA h g−1 at 25 °C and 158.7 mA h g−1 at 50 °C. At elevated temperature (50 °C), the plates showed an enhanced rate capability, achieving a discharge capacity of 147.6, 141.4, 133.6, 121.4, and 110.7 mA h g−1 at 0.1, 0.2, 0.5, 1, and 2 C, respectively. Moreover, the plates had good cycling stability, retaining 92% of the initial capacity at 25 °C and 91% at 50 °C over 50 cycles at 0.1 C. The excellent electrochemical performance of this material is attributed to its high specific surface area, large percentage of exposed (0 1 0) facets as well as small thickness along the [0 1 0] direction.Highlights► Well-dispersed LiMnPO4 plates with exposed (0 1 0) facets and thickness of about 100 nm were synthesized by a hydrothermal method. ► The LiMnPO4 plates exhibited a discharge capacity of 139.2 mA h g−1 at 25 °C and 158.7 mA h g−1 at 50 °C, both at a rate of 0.05 C. ► The LiMnPO4 plates showed good cycling stability, retaining 92% of the initial capacity at 0.1 C after 50 cycles.
Co-reporter:Cheng-Yan Xu, Jia Wu, Pei Zhang, Sheng-Peng Hu, Jian-Xun Cui, Zeng-Quan Wang, Yu-Dong Huang and Liang Zhen
CrystEngComm 2013 vol. 15(Issue 17) pp:3448-3454
Publication Date(Web):22 Feb 2013
DOI:10.1039/C3CE27092K
The molten salt synthesis of sodium titanate one-dimensional nanostructures at relatively low temperature (ca. 825 °C) was re-examined in detail to elucidate the roles of various experimental parameters. Two kinds of sodium titanate nanowires, i.e., Na2Ti3O7 and Na2Ti6O13, with almost the same diameters were obtained in the presence of excess sodium oxalate, which also played an important role in enhancing nanowires yield. High calcining temperature favours the formation of Na2Ti6O13-predominant product at high sodium content. The introducing of nonionic surfactant NP-9 not only improves the uniformity of nanowires, but also favours the formation of Na2Ti6O13 phase. The obtained Na2Ti3O7 and Na2Ti6O13 nanowires have good crystallinity and both grow along the [010] crystallographic directions. The synthesized Na2Ti6O13 nanowires exhibited good photocatalytic activity towards the degradation of methyl orange under ultraviolet light irradiation. A humidity sensor based on Na2Ti3O7 nanowires was fabricated and showed good sensing performance at room temperature.
Co-reporter:Sheng-Peng Hu, Cheng-Yan Xu, Liang Zhen
Materials Letters 2013 Volume 95() pp:117-120
Publication Date(Web):15 March 2013
DOI:10.1016/j.matlet.2012.12.058
Bi2WO6 hollow structures consisting of nanoparticles with diameters of 10–20 nm were synthesized by a facile and reproducible solvothermal method in the presence of ethylene glycol. The obtained Bi2WO6 hollow structures exhibit higher photocatalytic activity towards the degradation of Rhodamine B (RhB) under visible-light irradiation, up to 99% within 40 min, which was much higher than P25-TiO2. The enhanced photocatalytic performance could be attributed to their tiny building blocks as well as high BET surface areas (65.04 m2 g−1). The obtained Bi2WO6 hollow structures are chemically stable, and the efficiency remained almost the same after recycled five times, suggesting that Bi2WO6 hollow structures are promising visible-light photocatalyst for practical applications.Graphical abstractBi2WO6 hollow structures consisting of nanoparticles with diameters of 10–20 nm were synthesized by a facile and reproducible solvothermal method. The obtained Bi2WO6 hollow structures exhibit superior visible-light photocatalytic property than P25-TiO2 as well as high cycling performance.Highlights► Bi2WO6 hollow structures were synthesized by a simple and reproducible solvothermal route. ► Compared with P25-TiO2, Bi2WO6 hollow structures show excellent photocatalytic property, and the catalyst shows high cycle performance under visible light irradiation. ► The excellent photocatalytic properties are attributed to their large surface area and small building blocks.
Co-reporter:Hui-Jian Ye;Wen-Zhu Shao
Journal of Applied Polymer Science 2013 Volume 129( Issue 5) pp:2940-2949
Publication Date(Web):
DOI:10.1002/app.38949
Abstract
The transformation of α to β-phase in poly(vinylidene fluoride) (PVDF) induced by the addition of tetradecylphosphonic acid (TDPA)-BaTiO3 nanoparticles and subsequently the isothermal crystallization kinetics of pristine PVDF and its nanocomposites have been investigated. The result of infrared spectra showed that the relative crystalline fraction of β-phase was enhanced greatly after the introduction of TDPA–BaTiO3 nanoparticles, and reached the peak of 93% when the concentration of nanofillers was 20%. The interaction between TDPA–BaTiO3 nanoparticles and PVDF macromolecular chains induced the change of conformation from trans-gauche to all-trans crystal structure in PVDF segment. The isothermal crystallization of TDPA–BaTiO3/PVDF nanocomposites was carried out by the differential scanning calorimetry (DSC). The influence of TDPA–BaTiO3 nanoparticles concentration on crystallization rate, activate energy, melting enthalpy, and peak temperature were studied. The nanocomposite film loaded 20% TDPA–BaTiO3 nanoparticles exhibited the highest crystallization rate and activate energy, which decreased after loading more nanofillers in the host because of high volume fraction of nanoparticles leading to steric hindrance and further weakening the mobility of PVDF chains during the crystallization. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Co-reporter:Yang Li, Cheng-Yan Xu, PingAn Hu, and Liang Zhen
ACS Nano 2013 Volume 7(Issue 9) pp:7795
Publication Date(Web):August 16, 2013
DOI:10.1021/nn402682j
Carrier doping of MoS2 nanoflakes was achieved by functional self-assembled monolayers (SAMs) with different dipole moments. The effect of SAMs on the charge transfer between the substrates and MoS2 nanoflakes was studied by Raman spectroscopy, field-effect transistor (FET) measurements, and Kelvin probe microscope (KFM). Raman data and FET results verified that fluoroalkyltrichlorosilane-SAM with a large positive dipole moment, acting as hole donors, significantly reduced the intrinsic n-doping characteristic of MoS2 nanoflakes, while 3-(trimethoxysilyl)-1-propanamine-SAMs, acting as electron donors, enhanced the n-doping characteristic. The additional built-in electric field at the interface between SiO2 substrates and MoS2 nanoflakes induced by SAMs with molecular dipole moments determined the charge transfer process. KFM results clearly demonstrated the charge transfer between MoS2 and SAMs and the obvious interlayer screening effect of the pristine and SAM-modified MoS2 nanoflakes. However, the KFM results were not fully consistent with the Raman and FET results since the externally absorbed water molecules were shown to partially shield the actual surface potential measurement. By eliminating the contribution of the water molecules, the Fermi level of monolayer MoS2 could be estimated to modulate in a range of more than 0.45–0.47 eV. This work manifests that the work function of MoS2 nanoflakes can be significantly tuned by SAMs by virtue of affecting the electrostatic potential between the substrates and MoS2 nanoflakes.Keywords: charge transfer; Kelvin probe microscopy; MoS2 nanoflakes; self-assembled monolayer; surface potential
Co-reporter:S. Ding, C.Y. Xu, W.S. Wang, Y.D. Huang, L. Zhen
Materials Research Bulletin 2013 48(11) pp: 4565-4569
Publication Date(Web):
DOI:10.1016/j.materresbull.2013.07.014
Co-reporter:Hui-Jian Ye, Wen-Zhu Shao, Liang Zhen
Colloids and Surfaces A: Physicochemical and Engineering Aspects 2013 Volume 427() pp:19-25
Publication Date(Web):20 June 2013
DOI:10.1016/j.colsurfa.2013.02.068
•1-Tetradecylphosphonic acid (TDPA) with soft carbon chain was synthesized and used to functionalize the surface of BaTiO3 nanoparticles.•The dispersion of BaTiO3 nanoparticles in several kinds of solvents was improved after functionalization.•TDPA–BaTiO3/PVDF nanocomposite film presents good flexibility even at high volume fraction of 40 vol.%.•TDPA–BaTiO3/PVDF nanocomposite film exhibits high dielectric constant and low dielectric loss.Surface-functionalization of BaTiO3 nanoparticles and subsequent utilization of simple solution casting to yield the good compatible PVDF nanocomposites were investigated. 1-Tetradecylphosphonic acid (TDPA) was synthesized and then used to functionalize the surface of BaTiO3 nanoparticles. The prepared TDPA–BaTiO3 nanoparticles were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). These results indicated that the surface of nanoparticles was grafted successfully with such phosphonic acid. Also, the existing ligands of surface were examined, and the coverage onto surface of BaTiO3 nanoparticles evaluated by thermogravimetric analysis (TGA) was 25.1%. The dispersion of modified nanoparticles in ethanol and dichloromethane was significantly improved. Besides of good flexibility, PVDF nanocomposite film with volume fraction of 40 vol.% modified nanofillers exhibited high dielectric constant and low dielectric loss.
Co-reporter:Li-Shun Fu, Jian-Tang Jiang, Liang Zhen, Wen-Zhu Shao
Materials Science and Engineering: B 2013 Volume 178(Issue 4) pp:225-230
Publication Date(Web):1 March 2013
DOI:10.1016/j.mseb.2012.10.027
FeNi3/indium tin oxide (ITO) composite nanoparticles were synthesized by a self-catalyzed reduction method and a sol–gel process. The dependence of the content of ITO phase with the mole ratios of In:Sn of different sols was investigated. The relation between the electrical conductivity, infrared emissivity of FeNi3/ITO composite nanoparticles and the content of ITO phase was discussed. Electromagnetic wave absorption (EMA) performance of products was evaluated by using transmission line theory. It was found that EMA performance including the intensity and the location of effective band is significantly dependent on the content of ITO phase. The low infrared emissivity and superior EMA performance of FeNi3/ITO composite nanoparticles can be both achieved when the mole ratio of In:Sn in sol is 9:1.Highlights► Electrical conductivity and infrared emissivity can be controlled by ITO content. ► The infrared emissivity is the lowest when the mole ratio of In:Sn in sol is 9:1. ► The permittivity in microwave band can be controlled by the electrical conductivity. ► EMA performance is significantly influenced by the content of ITO phase. ► FeNi3/ITO composite particles are suitable for both infrared and radar camouflage.
Co-reporter:Xiao-Liang Pan, Cheng-Yan Xu and Liang Zhen
CrystEngComm 2012 vol. 14(Issue 20) pp:6412-6418
Publication Date(Web):22 May 2012
DOI:10.1039/C2CE25593F
Olivine-structured LiMnPO4 microspheres assembled by plates, wedges and prisms with different crystallographic orientations were synthesized via a facile hydrothermal route at 200 °C for 10 h. Na2S·9H2O was employed as a sole additive for controlling the phase, shape and crystallographic orientation of LiMnPO4 microspheres. The obtained product was characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). The possible formation mechanism was proposed based on time-dependent experiments. The electrochemical properties of carbon-coated LiMnPO4 samples with different assembly units were investigated. The synthesized LiMnPO4 microspheres assembled with plates exhibited higher discharge capacity, more stable cycling stability and better rate capability, which were attributed to the exposed (010) facets as well as small thickness along the [010] direction allowing for a fast Li+ ion diffusion rate and short diffusion length.
Co-reporter:Li-Shun Fu, Jian-Tang Jiang, Cheng-Yan Xu and Liang Zhen
CrystEngComm 2012 vol. 14(Issue 20) pp:6827-6832
Publication Date(Web):03 Jul 2012
DOI:10.1039/C2CE25836F
Fe microflakes with uniform size and well-defined shape were successfully synthesized by hydrogen-thermal reduction of α-Fe2O3 precursor microflakes. The hexagonal Fe microflakes have edge lengths of about 5 μm and thicknesses of about 500–1000 nm. The complex permittivity and permeability of Fe microflakes–paraffin composite were measured using a vector network analyzer in the 2–18 GHz frequency range. Remarkable dielectric relaxation, natural resonance and exchange resonance were observed in the complex permittivity and permeability spectrum. Electromagnetic wave absorption (EMA) performance of samples was evaluated by using transmission line theory. An excellent microwave absorption performance was obtained for a coating containing Fe microflakes as filler, in which the maximum reflection loss is −15.3 dB and effective EMA band (RL < −10 dB) covers the whole frequency range of 12.2–16.6 GHz.
Co-reporter:W.S. Wang, L. Zhen, C.Y. Xu, W.Z. Shao, Z.L. Chen
Journal of Alloys and Compounds 2012 Volume 529() pp:17-20
Publication Date(Web):15 July 2012
DOI:10.1016/j.jallcom.2012.03.058
Eu3+-doped CdMoO4 red phosphor was prepared by a simple aqueous solution process at room temperature. X-ray diffraction (XRD), scanning electron microscopy and transmission electron microscopy were used to characterize the phosphor. Emission and excitation spectra show that the phosphor exhibits a dominant red emission at 617 nm with excitation wavelength of 300 nm at room temperature. The red emission is visible to naked eye, indicating that CdMoO4 is a new promising host material for the rare-earth elements. This result may bring opportunity for the generation of rare-earth element doped complex metal oxides with low cost and gram scale production.Highlights► Eu3+-doped CdMoO4 red phosphor was synthesized by an aqueous solution route at room temperature. ► The photoluminescence properties of Eu3+-doped CdMoO4 red phosphor were investigated. ► The effect of different Eu3+-doped concentration on photoluminescence properties was studied.
Co-reporter:L.S. Fu, C.Y. Xu, W.S. Wang, J.T. Jiang, L. Zhen
Materials Letters 2012 Volume 81() pp:62-64
Publication Date(Web):15 August 2012
DOI:10.1016/j.matlet.2012.04.139
Well-dispersed nickel ferrite (NixFe1 − xFe2O4) colloidal spheres with uniform size and tunable composition were synthesized by a simple hydrothermal method. The changes of diameter, grain size, and magnetic properties of nickel ferrite colloidal spheres with the content of nickel element were investigated. The saturation magnetization of nickel ferrite can be tuned via changing the composition, which affects molecular magnetic moment and diameter of colloidal spheres. All nickel ferrite colloidal spheres prepared in this work show superparamagnetic behavior, and thus can be used to construct magnetically responsive photonic crystals. The color of aqueous solution containing Ni0.40Fe0.60Fe2O4 colloidal spheres changed from blue to brown with decreasing external magnetic field.Highlights► Superparamagnetic nickel ferrite spheres were synthesized by a hydrothermal method. ► The composition of nickel ferrite colloidal spheres can be tuned. ► The saturation magnetization of nickel ferrite spheres varies with the content of Ni. ► The color of colloidal spheres in solution changes with variation of magnetic field.
Co-reporter:J.T. Jiang, L. Zhen, C.Y. Xu, W.Z. Shao, Z.X. Zhou
Surface and Coatings Technology 2012 Volume 212() pp:14-19
Publication Date(Web):November 2012
DOI:10.1016/j.surfcoat.2012.08.065
Al18B4O33w/CoxFeyBz composite powders were prepared through electroless plating CoxFeyBz alloy coating onto the surface of Al18B4O33 whiskers. The microstructure evolution of the CoxFeyBz coating and the relevant variations in the properties of Al18B4O33w/CoxFeyBz composite powders were investigated. Amorphous or nano-crystalline CoxFeyBz coatings with Fe content of up to 80 at.% were obtained in a wide range of [Co2 +]/[Fe2 +] ratios. The presence of Fe2 + reduced the reaction efficiency because of flocculation and the resulted coverage effect. The morphology of the CoxFeyBz coatings changed slightly but crystallization occurred quickly after annealing at 400 °C. The electrical resistivity of the CoxFeyBz coatings decreased dramatically after annealing at 400 °C for less than 60 min, but was maintained at 10− 2 Ω·cm despite the further increase of the temperature. The high resistivity likely hindered the interface polarization; consequently, no dielectric relaxation was detected in the microwave band. The saturation magnetization of the CoxFeyBz coatings persistently increased as the heat treatment proceeded or as the temperature elevated, which contributes to the improvement of permeability. The difference in microstructure evolution and the variations in the properties of Al18B4O33w/CoxFeyBz were discussed, and the effects of composition were preliminarily identified.Highlights► Deposited CoFe coatings containing ~ 80 at.% of Fe on the surface of AlBO whiskers ► Tailored the microstructure and EM properties of CoFe coatings via heat-treatment ► Revealed the effect of the Fe/Co ratio on the microstructure and EM properties
Co-reporter:J.F. Chen, L. Zhen, J.T. Jiang, L. Yang, W.Z. Shao, B.Y. Zhang
Materials Science and Engineering: A 2012 Volume 539() pp:115-123
Publication Date(Web):30 March 2012
DOI:10.1016/j.msea.2012.01.067
The effects of age-forming on microstructures and mechanical properties of 7050 Al alloy were investigated in this work. The alloy was subjected to age-forming as well as stress-free ageing at 160 °C for 6, 12, 18 and 24 h, and its microstructures were characterized by electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). It was shown that creep might lead to grain elongation during age-forming, and the applied stress induces the coarsening of precipitates in 7050 Al alloy. The texture in the alloy was also influenced by age-forming. Consequently, the differences in microstructures result in differences in mechanical properties of age-forming versus traditional stress-free ageing. The ultimate tensile strength of age-formed samples were slightly lower than that of stress-free aged samples, while the yield strength of age-formed samples were apparently lower than that of stress-free aged samples. Specifically, the elongation of samples age-formed displays apparently decrease.Highlights► Age-forming leads to the grain elongation in 7050 alloy. ► Age-forming varies the texture components in 7050 alloy. ► Age-forming promotes precipitates growth and PFZ enlargement in 7050 alloy. ► Age-forming induces to descend apparently elongation in 7050 alloy. ► The effect of age-forming on microstructure and properties is discussed in-depth.
Co-reporter:Ning Xie, Wenzhu Shao, Lichao Feng, Liangxing Lv, and Liang Zhen
The Journal of Physical Chemistry C 2012 Volume 116(Issue 36) pp:19517-19525
Publication Date(Web):August 13, 2012
DOI:10.1021/jp3040242
To obtain a different backbone structure of conductors in disordered insulator/conductor composites, Cu2O/Cu composites were prepared using two methods, named the direct hot-pressing (DHP) method and the in-situ reduction hot-pressing (IRHP) method via hot-pressing Cu2O powders and branch-like or spherical Cu powders and hot-pressing Cu2O powders and carbon black (CB) nanoparticles to reduce Cu2O into Cu, respectively. The dc electrical conductivity tests show that the percolation threshold of the prepared Cu2O/Cu composites varies with various Cu structures. The lowest and the highest percolation thresholds were obtained in those with branch-like Cu and with CB nanoparticle-reduced Cu, respectively. The percolation structures of Cu were analyzed by fractal theory, and the binarized optical microscope images were used for the box-counting fractal dimension calculation. Near the percolation threshold, the fractal dimension increases with an increasing volume fraction of Cu in all prepared Cu2O/Cu composites. The backbone structure of the conductors was first characterized by the fractal dimension increasing rate with an increasing volume fraction of Cu. For the Cu2O/Cu composites prepared with the IRHP method, near the percolation threshold, the fractal dimension increases little with an increasing volume content of Cu; for those prepared with spherical Cu, the rate of increase is relatively higher, and for those prepared with branch-like Cu, the fractal dimension increase rate is the highest.
Co-reporter:Wen-Shou Wang, Liang Zhen, Cheng-Yan Xu and Wen-Zhu Shao
CrystEngComm 2011 vol. 13(Issue 2) pp:620-625
Publication Date(Web):27 Sep 2010
DOI:10.1039/C0CE00062K
Strontium sulfate (SrSO4) sisal-like hierarchical structures (SLHS) were successfully synthesized by using SrCrO4 nanowires in mother solution as precursor to react with Na2SO4 aqueous solution at room temperature. The SrSO4 SLHS have a uniform diameter of about 6 μm, which are composed of single-crystalline SrSO4 nanopyramids oriented radially to their centre. The nanopyramids, which grow along [010] direction, are about 300–500 nm and 20–50 nm for the roots and tips in diameter and 1–3 μm in length. The controlled experimental results indicate that the formation mechanism of the SrSO4 SLHS is related to the “two-step” growth process.
Co-reporter:Cheng-Yan Xu, Jia Wu, Liang-Xing Lv, Jian-Xun Cui, Zeng-Quan Wang, Yu-Dong Huang and Liang Zhen
CrystEngComm 2011 vol. 13(Issue 7) pp:2674-2677
Publication Date(Web):14 Feb 2011
DOI:10.1039/C0CE00625D
We presented, for the first time, the evidence of loop-by-loop self-coiling of a nanobelt to form single-crystal Na2Ti6O13 nanorings with diameters of several micrometres. The winding nanobelts, with thickness of about 15 nm and widths of 100–500 nm, grow along their [010] crystallographic directions, and coherently match at ±(200) crystallographic planes. The driving force of such a coherent match is suggested to be the minimization of local electrostatic energy introduced by the cations and anions. We also discussed the dependence of the nanoring's yield on the thickness of the nanobelts, which affects the elastic deformation energy and misfit energy of the rings.
Co-reporter:Yuan-Xun Gong, Liang Zhen, Jian-Tang Jiang, Cheng-Yan Xu, Wen-Shou Wang and Wen-Zhu Shao
CrystEngComm 2011 vol. 13(Issue 22) pp:6839-6844
Publication Date(Web):20 Sep 2011
DOI:10.1039/C1CE05397C
Fe–ferrite composite nanotubes were successfully prepared by thermal hydrogen reduction of α-FeOOH nanowires. The nanotubes have diameters of about 100 nm and lengths of tens of micrometres. The formation mechanism of Fe–ferrite composite nanotubes is discussed, and the non-equilibrium diffusion between hydrogen and oxygen was found to be responsible for the formation of the hollow interior structure. Because of the high shape anisotropy of the 1-D shape, the coercivity of composite nanotubes was higher than that of reported granular Fe–ferrite composite nanoparticles. Since the eddy current is effectively suppressed by the thin wall characteristic of nanotubes, the composite nanotubes exhibit higher permeability than that of the reported ferromagnetic metal nanowires. Due to the better impedance matching and higher dissipation efficiency, a superior microwave absorption performance was obtained in Fe–ferrite composite nanotubes, in which the maximum reflection loss is −18 dB and the effective absorption band (<−10 dB) covers the entire frequency band of 12.5–17.5 GHz.
Co-reporter:D.L. Zou, L. Zhen, C.Y. Xu, W.Z. Shao
Materials Characterization 2011 Volume 62(Issue 5) pp:496-502
Publication Date(Web):May 2011
DOI:10.1016/j.matchar.2011.03.003
Adiabatic shear bands in Mg alloy under ballistic impact at a velocity of 0.5 km·s−1 were characterized by means of optical microscope, scanning electron microscope, transmission electron microscope and indenter technique. The results show that adiabatic shear bands were formed around the impacted crater, and the deformed and transformed bands were distinguished by etching colors in metallographic observation. TEM observation shows that the deformed bands were composed of the elongated grains and high density dislocations, while the transformed bands composed of the ultrafine and equiaxed grains were confirmed. In initial stage, the severe localized plastic deformation led to the formation of elongated grains in the deformed bands. With localized strain increasing, the severe localized deformation assisted with the plastic temperature rising led to the severe deformation grains evolved into the ultrafine and equiaxed grains, while the deformed bands were developed into transformed bands. The formation of the ultrafine and equiaxed grains in the transformed bands should be attributed to the twinning-induced rotational dynamic recrystallization mechanism. High microhardness in the bands was obtained because of the strain hardening, grain refining and content concentration.Research Highlights► Deformed and transformed bands are found in Mg alloy under ballistic impact. ► The microstructures in the deformed and transformed bands are characterized. ► The evolution process of the microstructure in the bands is discussed.
Co-reporter:L.X. Lv, L. Zhen
Materials Science and Engineering: A 2011 528(22–23) pp: 6673-6679
Publication Date(Web):
DOI:10.1016/j.msea.2011.05.040
Co-reporter:D.L. Zou, L. Zhen, Y. Zhu, C.Y. Xu, W.Z. Shao, B.J. Pang
Materials & Design (1980-2015) 2010 Volume 31(Issue 8) pp:3708-3715
Publication Date(Web):September 2010
DOI:10.1016/j.matdes.2010.03.010
Co-reporter:Z.Y. Zhan, C.Y. Xu, L. Zhen, W.S. Wang, W.Z. Shao
Ceramics International 2010 Volume 36(Issue 2) pp:679-682
Publication Date(Web):March 2010
DOI:10.1016/j.ceramint.2009.11.007
Abstract
Single-crystalline potassium triniobate (KNb3O8) nanobelts with widths of 50 to several hundreds nanometers and length up to tens of microns were synthesized in a large-scale by a facile molten salt synthesis method. The phase of the as-prepared nanobelts was determined by X-ray diffraction, and the morphology and structure were characterized by scanning electron microscopy, transmission electron microscopy, and selected area electron diffraction. The band gap of KNb3O8 nanobelts was estimated to be about 3.45 eV from the onset of UV–vis diffuse reflectance spectrum. The obtained KNb3O8 nanobelts exhibited high photocatalytic efficiency for the degradation of methyl orange under UV irradiation.
Co-reporter:Huizhong Xu, Yaping Wang, Liang Zhen, Zhuo Wang
Journal of Alloys and Compounds 2010 Volume 504(Issue 1) pp:155-158
Publication Date(Web):13 August 2010
DOI:10.1016/j.jallcom.2010.05.076
Sr0.13Na0.37Bi0.50TiO3 thin films were prepared by metalorganic solution deposition, and annealed at temperatures from 550 to 700 °C for 1–15 min. The influence of annealing on the morphology, phase and ferroelectric properties was studied by scanning electron microscopy, X-ray diffraction and ferroelectric analyzer. The doping of Na0.50Bi0.50TiO3 films with Sr results in the existence of two phases, i. e., Na0.5Bi0.5TiO3-like (matrix) phase and BiTiO3-like (second) phase, the relative contents of which depend on the annealing conditions. With the increase of annealing temperature and prolongation of annealing time, the phase content of the BiTiO3-like second phase increases and a phenocryst structure was formed, which leads to the decrease of remnant polarization of Sr0.13Na0.37Bi0.50TiO3 thin films.
Co-reporter:Huizhong Xu, Liang Zhen, Yaping Wang, Zhuo Wang
Journal of Alloys and Compounds 2010 Volume 489(Issue 1) pp:136-139
Publication Date(Web):7 January 2010
DOI:10.1016/j.jallcom.2009.09.033
Ca0.18Na0.32Bi0.50TiO3 (CNBT) ferroelectric thin films were prepared by metalorganic solution deposition on silicon substrate and annealed at different temperatures. The morphology and structure of the films were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The crystal structure of Ca-doped Na0.50Bi0.50TiO3 films shows no obvious lattice distortion compared with that of un-doped one. The optimal heat treatment process for CNBT films were determined to be high-temperature drying at 400 °C for no less than 15 min followed by annealing at 600 °C for 5 min, which leads to the formation of compact films with uniform grains of 30–50 nm. Ferroelectric property measurement shows that the remanent polarization of CNBT films is 18 times higher than that of un-doped Na0.50Bi0.50TiO3 (NBT) thin films.
Co-reporter:J.N. An, C.Y. Xu, L. Zhen, Y.D. Huang
Ceramics International 2010 Volume 36(Issue 6) pp:1825-1829
Publication Date(Web):August 2010
DOI:10.1016/j.ceramint.2010.03.031
Abstract
Single-crystal K2V8O21 nanobelts were prepared from the reaction between V2O5 and KHSO4 under hydrothermal condition using no surfactant or template. The synthesized nanobelts were characterized by X-ray diffraction, X-ray photon-electron spectrometry, scanning electron microscopy, and transmission electron microscopy. The nanobelts are single-crystalline in nature, and have typical width of 100–500 nm, thickness of less than 100 nm and length up to a few tens of microns. The effects of solution concentration, reaction temperature and molar ratio of K and V on the morphology and phase component of the obtained products have been investigated. The possible formation mechanism was also discussed.
Co-reporter:Huizhong Xu, Liang Zhen, Changhong Yang, Zhuo Wang
Journal of Materials Science & Technology 2010 Volume 26(Issue 3) pp:206-210
Publication Date(Web):March 2010
DOI:10.1016/S1005-0302(10)60034-5
Co-reporter:X.J. Wei, J.T. Jiang, L. Zhen, Y.X. Gong, W.Z. Shao, C.Y. Xu
Materials Letters 2010 Volume 64(Issue 1) pp:57-60
Publication Date(Web):15 January 2010
DOI:10.1016/j.matlet.2009.10.005
Fe/SiO2 composite particles were synthesized by hydrogen reduction of Fe2O3/SiO2 precursor, which was prepared by sol–gel method. A reduction temperature higher than 600 °C is required for the complete conversion of Fe2O3 to Fe. Fe/SiO2 composite particles exhibit superior complex permittivity and permeability in the microwave band. A reflection loss higher than − 70 dB as well as a broad absorption band can be simultaneously obtained for Fe/SiO2-based coatings about 2 mm in thickness, suggesting that the Fe/SiO2 composite particles are a promising candidate for high performance electromagnetic absorption materials.
Co-reporter:D.L. Zou, L. Zhen, Y. Zhu, C.Y. Xu, W.Z. Shao, B.J. Pang
Materials Science and Engineering: A 2010 527(15) pp: 3323-3328
Publication Date(Web):
DOI:10.1016/j.msea.2010.02.037
Co-reporter:L. Zhen, D.L. Zou, C.Y. Xu, W.Z. Shao
Materials Science and Engineering: A 2010 527(21–22) pp: 5728-5733
Publication Date(Web):
DOI:10.1016/j.msea.2010.06.013
Co-reporter:Wen-Shou Wang, Liang Zhen, Cheng-Yan Xu, Jun-Zhou Chen and Wen-Zhu Shao
ACS Applied Materials & Interfaces 2009 Volume 1(Issue 4) pp:780
Publication Date(Web):April 1, 2009
DOI:10.1021/am8002044
Nearly monodispersive CaF2 hollow microspheres were synthesized by a facile aqueous solution route from the mixed aqueous solutions of CaCl2, Na2WO4, and NaF at room temperature. The as-prepared products were characterized by X-ray diffraction (XRD), scanning electron microscopy, transmission electron microscopy (TEM), high-resolution transmission electron microscopy, and N2 adsorption−desorption techniques. The CaF2 hollow microspheres have an average diameter of about 1.5 μm and a hollow interior of 0.5 μm. The shell is composed of numerous single-crystalline nanoparticles with diameter of about 20 nm. The morphologies and diameters of the CaF2 products are strongly dependent on the experimental parameters, such as the concentration of the aqueous NaF solution and the reaction temperature. The synthetic experiments indicate that the growth process of CaF2 hollow microspheres involves first the formation of CaWO4 solid microspheres and then the formation of CaF2 solid microspheres through the reaction between CaWO4 and F− ions controlled by the difference of the solubility product for CaWO4 and CaF2. Phenomenological elucidation based on TEM observations and XRD patterns of intermediate products at different precipitation stages indicates that the formation mechanism for the CaF2 hollow microspheres is related to the Ostwald ripening mechanism. N2 adsorption−desorption measurement shows that the CaF2 hollow microspheres possess a high Brunauer−Emmett−Teller surface area and porosity properties. The synthetic procedure is straightforward and represents a new example of the Ostwald ripening mechanism for the formation of inorganic hollow structures in an aqueous solution at room temperature.Keywords: calcium fluoride; chemical conversion; hollow microspheres; Ostwald ripening
Co-reporter:Wen-Shou Wang, Liang Zhen, Cheng-Yan Xu and Wen-Zhu Shao
Crystal Growth & Design 2009 Volume 9(Issue 3) pp:1558
Publication Date(Web):February 6, 2009
DOI:10.1021/cg801194j
In this paper, we report the first synthesis of homogeneous core−shell CdMoO4 microspheres on a large scale by a facile aqueous solution route with the assistance of sodium dodecyl sulfate (SDS) at room temperature. The as-synthesized product is characterized by X-ray diffraction pattern, scanning electron microscopy, transmission electron microscopy, high resolution transmission electron microscopy, UV−vis absorption spectroscopy, and photoluminescence spectroscopy. The core−shell microspheres have an average diameter of about 4 μm and the shell has a uniform thickness of about 200 nm. The shell is composed of single-crystalline nanoparticles 50 nm in size. The effect of various reaction conditions on the morphology and size of CdMoO4 products is investigated. The results show that different kinds of surfactants, the concentration of SDS, and reaction times are crucial factors for the formation of core−shell CdMoO4 microspheres. A possible three-step growth mechanism is presented for the formation of homogeneous core−shell CdMoO4 microspheres. The calcined core−shell CdMoO4 microspheres at 500 °C for 2 h exhibit an excellent photocatalytic activity in the degradation of rhodamine B (RhB) under UV light irradiation. The photodegradation of RhB fits the first-order kinetics with K of 0.048 and 0.013 min−1 for the calcined and uncalcined core−shell microspheres, respectively. Photoluminescence measurement shows a strong and broad blue emission peak of 354 nm for the core−shell CdMoO4 microspheres. The successful synthesis of core−shell CdMoO4 microspheres may provide some insight into the design of homogeneous core−shell structures of molybdates for potential applications in photocatalysts and optical devices.
Co-reporter:L. Zhen, C.Y. Xu, W.S. Wang, C.S. Lao, Q. Kuang
Applied Surface Science 2009 Volume 255(Issue 7) pp:4149-4152
Publication Date(Web):15 January 2009
DOI:10.1016/j.apsusc.2008.11.003
Abstract
Single-crystalline Na2Ti6O13 nanobelts were prepared on large-scale by molten salt synthesis at 825 °C for 3 h. The obtained nanobelts have typical width of less than 200 nm and thickness of 10–30 nm, and length up to 10 μm. The growth direction of the nanobelts was determined to be along [0 1 0]. Electrical transport property of an individual nanobelt was measured at room temperature and ambient atmosphere, and results showed that the nanobelts are semiconductor. Na2Ti6O13 nanobelts exhibited good photocatalytic efficiency for the degradation of RhB under UV irradiation.
Co-reporter:C.Y. Xu, L. Zhen, J.T. Jiang, C.S. Lao, L. Yang
Ceramics International 2009 Volume 35(Issue 8) pp:3021-3025
Publication Date(Web):December 2009
DOI:10.1016/j.ceramint.2009.04.007
Abstract
K2Nb8O21 microwires with diameters of several hundred nanometers and lengths up to tens of microns were prepared by molten salt synthesis, and characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The as-synthesized microwires have semiconductor characteristics with band gap Eg of about 3.1 eV, consistent with electrical transport measurement of single microwire, which gives a resistivity of about 0.46 Ω m at room temperature. Microwave dielectric property measurement at 2–18 GHz shows that K2Nb8O21 microwires have a relative low complex permittivity. A weak dielectric relaxation occurs in the 12–16 GHz band due to the free charges polarization on the interfaces between K2Nb8O21 microwires and the PVB matrix.
Co-reporter:X.Y. Sun, L. Zhen, C.Y. Xu, L.X. Lv, W.Z. Shao, X.D. Sun
Materials Letters 2009 Volume 63(Issue 1) pp:64-65
Publication Date(Web):15 January 2009
DOI:10.1016/j.matlet.2008.09.007
Local structure in a low-cobalt-type Fe–25Cr–12Co–1Si ferromagnetic alloy spinodal decomposed under an external magnetic field up to 120 kOe was investigated by Mössbauer spectrometry. The high magnetic field was found to significantly affect the local structure in the alloy formed at the early stage of phase decomposition. It was found that high magnetic field favors the acceleration of phase decomposition of ferromagnetic alloy at the early stage, resulting in the enhancement of average hyperfine field. The effect of high magnetic field on spinodal decomposition in ferromagnetic alloy was initially interpreted based on the free energy analyses.
Co-reporter:Junzhou Chen, Liang Zhen, Shoujie Yang, Wenzhu Shao, Shenglong Dai
Materials Science and Engineering: A 2009 500(1–2) pp: 34-42
Publication Date(Web):
DOI:10.1016/j.msea.2008.09.065
Co-reporter:J.T. Jiang, L. Zhen, L. Yang, W.Z. Shao, C.Y. Xu, Z.M. Chao
Surface and Coatings Technology 2009 203(16) pp: 2221-2228
Publication Date(Web):
DOI:10.1016/j.surfcoat.2009.02.009
Co-reporter:Liang Zhen, Junzhou Chen, Shoujie Yang, Wenzhou Shao, Shenglong Dai
Materials Science and Engineering: A 2009 Volume 504(1–2) pp:55-63
Publication Date(Web):25 March 2009
DOI:10.1016/j.msea.2008.10.055
The evolution of texture as well as microstructures in an AA 7055 aluminum alloy during cold rolling was investigated by optical microscope (OM), transmission electron microscope (TEM), electron back-scattered diffraction (EBSD) and X-ray diffraction. The results show that more microbands are formed in the center of the plate with the rolling reduction, while the spacing between two bands decreases. The angles between the microbands (MBs) and rolling direction (RD) are 29° and 24°, respectively, from 30 and 43% reductions. The texture analysis shows that the intensity of the rolling texture in the center of the plate, keeps on decreasing rapidly with the reduction, especially the brass (Bs) orientation. The Bs orientation tends to rotate towards the {0 0 1} 〈1 1 0〉 rotated cube orientation with the reduction. When the reduction is up to 43%, a strong new orientation, which deviates about 30° from the ideal position of {0 0 1} 〈1 1 0〉 rotated cube texture, is developed.
Co-reporter:Wen-Shou Wang, Liang Zhen, Cheng-Yan Xu, Li Yang and Wen-Zhu Shao
Crystal Growth & Design 2008 Volume 8(Issue 5) pp:1734
Publication Date(Web):April 1, 2008
DOI:10.1021/cg070564f
Novel SrCO3 architectures were prepared by a facile aqueous solution route at room temperature using SrCl2, Na2CrO4, and NaOH as the starting reaction reagents and distilled water as the solvent. The synthesized products were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, selected-area electron diffraction and high-resolution transmission electron microscopy. The SrCO3 architectures are in dandelion-like and flower-like morphologies with diameters of 5–10 µm and composed of numerous well-aligned single-crystalline nanorods of 20–40 nm in diameter and 1–2 µm in length. It is found that the morphology of the final products is strongly dependent on the experimental parameters, such as the concentration of aqueous NaOH solution and the reaction temperature. Various controlled synthetic experiments indicate that the growth process of SrCO3 architectures involves the growth of single-crystalline SrCrO4 nanowires, the formation of CO32− ions through the reaction between CO2 gas from air and aqueous NaOH solution, and finally the formation of SrCO3 architectures through the reaction between SrCrO4 and CO32− ions controlled by the difference of the solubility product. In addition, a “rod to dumbbell to sphere” mechanism is proposed for the formation of the SrCO3 architectures.
Co-reporter:J.T. Jiang, L. Zhen, B.Y. Zhang, W.Z. Shao, C.Y. Xu
Scripta Materialia 2008 Volume 59(Issue 9) pp:967-970
Publication Date(Web):November 2008
DOI:10.1016/j.scriptamat.2008.06.047
A significant improvement in electromagnetic wave absorbing performance is achieved in an Al18B4O33w/Co based coating through the heat treatment of Al18B4O33w/Co particles. The electromagnetic properties of the Al18B4O33w/Co composite particles clearly increase after heat treatment. A maximal reflection loss of 78.3 dB and a high-efficiency absorption band of 4 GHz was obtained with an improved coating about 2 mm thick. Additionally, the absorption band was found to be able to cover the 7–18 GHz band by adjusting the coating thickness.
Co-reporter:L. Zhen, W.S. Wang, C.Y. Xu, W.Z. Shao, M.M. Ye, Z.L. Chen
Scripta Materialia 2008 Volume 58(Issue 6) pp:461-464
Publication Date(Web):March 2008
DOI:10.1016/j.scriptamat.2007.10.038
CdMoO4 hollow microspheres 5 μm in diameter with an interior diameter of 1–1.5 μm were synthesized by a facile aqueous method at room temperature. The shell of the synthesized microspheres was composed of aligned nanorods 80–120 nm in diameter and up to 2 μm long. These microspheres exhibit excellent photocatalytic efficiency for the degradation of Rhodamine B under UV irradiation, which was thought to be associated with their hollow structures. The photoluminescence property of the hollow microspheres was also measured.
Co-reporter:Liang Zhen, Wen-Shou Wang, Cheng-Yan Xu, Wen-Zhu Shao, Lu-Chang Qin
Materials Letters 2008 Volume 62(10–11) pp:1740-1742
Publication Date(Web):15 April 2008
DOI:10.1016/j.matlet.2007.09.076
Single-crystalline CoWO4 nanorods with average diameter of 20 nm and lengths of 100 to 300 nm have been successfully synthesized by a hydrothermal method using only CoCl2 and Na2WO4 as reaction reagents and distilled water as solvents. The structure and morphology of the nanorods were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), selected-area electron diffraction (SAED) and high-resolution TEM (HRTEM). This facile method does not need any seed, catalyst, surfactant, or template, thus is promising for large-scale and low-cost production with high-quality.
Co-reporter:Wen-Shou Wang, Liang Zhen, Cheng-Yan Xu, Li Yang and Wen-Zhu Shao
The Journal of Physical Chemistry C 2008 Volume 112(Issue 49) pp:19390-19398
Publication Date(Web):November 12, 2008
DOI:10.1021/jp8074783
Nearly monodispersed CaWO4 hollow microspheres with controlled diameters were successfully prepared by a facile one-step hydrothermal method using CaCl2, Na2WO4, and sodium dodecyl sulfate (SDS) as the starting reaction reagents and distilled water as solvent. The crystal structure, morphology, macroporous and photoluminescence properties of the as-synthesized products are characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, selected-area electron diffraction, nitrogen adsorption−desorption isotherm technique, and fluorescence spectrometer. The hollow microspheres have an average diameter of 2.2 μm and hollow interior of 0.5−1 μm. The shell is consisting of numerous nanoparticles 45 nm in diameter. The effects of SDS amount, pH value, concentrations of reaction reagents, and reaction durations have been studied systematically. The results indicate that a certain SDS amount plays a key important role in the final formation of hollow microspheres. It is also found that the average diameters of the hollow spheres can also be tuned by increasing the SDS amount in the range of 0.2−1 g into the reaction system. Based on the detailed investigation on the influences of experimental parameters, the formation mechanism of the hollow interiors by a SDS-induced Ostwald ripening process is proposed for the CaWO4 hollow microspheres. The Brunauer−Emmett−Teller (BET) surface areas and pore volume of the CaWO4 hollow microspheres are 14.4 m2/g and 0.087 cm3/g, respectively. Furthermore, photoluminescence spectrum of the CaWO4 hollow microspheres reveals a strong and broadband from 350 to 450 nm with an emission peak at 413 nm originating from the WO42− groups. This Ostwald ripening process could open novel and efficient pathway for the preparation of ternary metal oxides with hollow interiors.
Co-reporter:Wen-Shou Wang ; Liang Zhen ; Cheng-Yan Xu ;Wen-Zhu Shao
The Journal of Physical Chemistry C 2008 Volume 112(Issue 37) pp:14360-14366
Publication Date(Web):August 26, 2008
DOI:10.1021/jp8046483
In this work we demonstrate that Cd(OH)2 hollow microspheres could be prepared in high yield by a facile aqueous solution route from the mixture of aqueous solutions of CdCl2, Na2MoO4, and NaOH at room temperature. The synthesized products are characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, selected-area electron diffraction, and the nitrogen adsorption−desorption isotherm technique. The Cd(OH)2 hollow microspheres have an average diameter of 3 μm and hollow interior of about 1.5 μm. The shell consists of numerous single-crystalline nanoplates with thickness of about 100 nm and sizes of 400−700 nm. The controlled synthetic experiments indicate that the growth process of Cd(OH)2 hollow microspheres involves first the formation of CdMoO4 solid microspheres and then the formation of Cd(OH)2 solid microspheres through the reaction between CdMoO4 and OH− ions controlled by the difference of solubility product for CdMoO4 and Cd(OH)2. The Ostwald ripening mechanism is proposed to account for the formation of Cd(OH)2 hollow microspheres on the basis of scanning electron microscopy observations of intermediate products at different precipitation stages. Furthermore, the Cd(OH)2 hollow microspheres can be easily converted to CdO semiconductors with similar morphology by calcining Cd(OH)2 in air at 350 °C for 4 h.
Co-reporter:N. Chen, J.T. Jiang, Y. Yuan, C. Liu, C.Y. Xu, L. Zhen
Journal of Magnetism and Magnetic Materials (1 January 2017) Volume 421() pp:368-376
Publication Date(Web):1 January 2017
DOI:10.1016/j.jmmm.2016.08.026
•An EABW up to 6.1 GHz was obtained in a thin coating using Co particle as fillers.•The electromagnetic properties can be tailored via annealing and filling ratio.•High filling ratio is favorable to excellent EMA performance.Cobalt microspheres with diameters of 1.5–3.5 µm were synthesized by a liquid phase reduction method. The effects of hydrogen annealing on microstructure evolution and electromagnetic properties of Co microspheres were investigated. The influence of filling ratio on the electromagnetic properties of specimens containing Co microspheres as fillers was also examined. The results indicated that the annealing leads to increase in Co microspheres' permittivity as the improved conductivity that developed during annealing contributes to enhanced dielectric relaxation. High filling ratio is found to be favorable for achieving high electromagnetic properties and thus higher electromagnetic absorbing performances, which is of technical significant for application in low frequency band. Coatings containing 30, 45 and 50 vol% Co particles as fillers present excellent EMA performance, even very thin thickness is applied. High electromagnetic wave absorbing efficiency of −10 dB was observed at thickness of 1.5 mm in C band and the electromagnetic wave absorption bandwidth reaches up to 6.3 GHz (6.7–13 GHz) when the filling volume is 45 vol%.
Co-reporter:Shuang Yang, Cheng-Yan Xu, Bao-You Zhang, Li Yang, Sheng-Peng Hu, Liang Zhen
Journal of Colloid and Interface Science (1 April 2017) Volume 491() pp:
Publication Date(Web):1 April 2017
DOI:10.1016/j.jcis.2016.12.028
Hierarchical structures assembled by two-dimensional (2D) nanosheets could inherit the characteristics of nanosheets and acquire additional advantages from the unique secondary architectures, which would have important influences on the photocatalytic properties of semiconductor nanomaterials. In this work, we successfully synthesized Ca(II) doped β-In2S3 hierarchical structures stacked by thin nanosheets by a simple solution chemical process. The effects of reaction temperature and Ca2+ concentration on the size and morphology of the products were systematically investigated. The photocatalytic applications of the β-In2S3 hierarchical structures were evaluated for hydrogen production and degradation of Rhodamine B (RhB) under visible light irradiation (λ > 420 nm). The β-In2S3 hierarchical structures showed promising activity towards photocatalytic hydrogen production (145.0 μmol g−1 h−1) and RhB solution (1 × 10−5 M) was completely degraded within 100 min under visible light irradiation.Ca(II) doped β-In2S3 hierarchical structures were synthesized through a facile hot-injection method. These β-In2S3 hierarchical structures exhibited enhanced hydrogen production and efficient degradation of organic dye under visible light irradiation.Download high-res image (107KB)Download full-size image
Co-reporter:Sheng-Peng Hu, Cheng-Yan Xu, Fei-Xiang Ma, Lei Cao and Liang Zhen
Dalton Transactions 2014 - vol. 43(Issue 22) pp:NaN8445-8445
Publication Date(Web):2014/03/24
DOI:10.1039/C3DT53561D
We report the solvothermal synthesis of hierarchical structures of orthorhombic Sb2WO6 and their implementation as a visible-light-driven photocatalyst for the degradation of Rhodamine B. The obtained hierarchical structures constructed by tiny nanosheets are doughnut-like flat ellipsoids with concaves in the centres, and with typical sizes of 1.3 μm in length, 800 nm in width and 400 nm in thickness. The concave characteristics and sizes of Sb2WO6 hierarchical structures can be tuned by adjusting the volume ratio of EG–H2O. Time-dependent experiments reveal that the formation process of concave structures involves the aggregation of nanoparticles to form solid spheres, dissolution–recrystallization to form hierarchical structures subsequently, and an Ostwald ripening process to shape the desired concaves finally. Under visible-light irradiation, complete degradation of Rhodamine B is achieved within 180 min in the presence of Sb2WO6 hierarchical structures, which could be ascribed to the porous structures, high BET surface area (42.58 m2 g−1) and wide absorption in the visible-light region.
Co-reporter:Wang-Da Li, Cheng-Yan Xu, Xiao-Liang Pan, Yu-Dong Huang and Liang Zhen
Journal of Materials Chemistry A 2013 - vol. 1(Issue 17) pp:NaN5369-5369
Publication Date(Web):2013/02/21
DOI:10.1039/C3TA01609A
LixV2O5 (x ∼ 0.42) nanorods, an overdoped β-phase vanadium oxide bronze with a rigid three-dimensional framework, have been fabricated for the first time via a simple two-step synthetic method. It is found that the δ-type structure of the as-prepared hydrated nanobelts through the hydrothermal route is converted into the tunnel β geometry upon annealing-induced dehydration. After annealing at 600 °C, the β-LixV2O5 nanorods exhibit the desired electrochemical properties: an initial gravimetric discharge capacity of 388.4 mA h g−1 (corresponding to an uptake of ca. 2.68 lithium per cell unit) and a specific energy density of 1039.6 W h kg−1 are achieved within a 2.0 V cut-off voltage at C/20, which decreased to 295.3 mA h g−1 (ca. 2.04 Li/V2O5) and 789.0 W h kg−1 after 50 cycles, respectively. The irreversible formation of ω-LixV2O5 for layered V2O5 cathodes upon deep lithiation is not presented during cell operation, and such improved structural reversibility is attributed to the highly retrievable host framework of the β-Li bronze, as well as further strain relaxation facilitated by the one-dimensional nanostructures. Based on the distinctive crystallographic structure and superior electrochemical properties, this β-lithium vanadium bronze has shown promising potential as a cathode material for secondary lithium-based batteries.
Co-reporter:Fei-Xiang Ma, Pan-Pan Wang, Cheng-Yan Xu, Jing Yu, Hai-Tao Fang and Liang Zhen
Journal of Materials Chemistry A 2014 - vol. 2(Issue 45) pp:NaN19337-19337
Publication Date(Web):2014/09/30
DOI:10.1039/C4TA03008G
Self-stacked CuFe2O4–Fe2O3 porous nanosheets were prepared via a facile polyol-mediated route followed by calcination. Because of its highly porous structures and good electrical and ion conductivity of the well-dispersed CuFe2O4 phase in the matrix, the hybrid material exhibits high specific capacity of 910 mA h g−1 at 0.5 C after 200 cycles, superior capacity retention (0.02% capacity loss per cycle) and good rate capability (417 mA h g−1 at 4 C) as a promising anode material for Li-ion batteries.
