Co-reporter:Xin Zhang;Jie-He Sui;Yong-Chao Lei
Acta Metallurgica Sinica (English Letters) 2017 Volume 30( Issue 12) pp:1231-1235
Publication Date(Web):22 June 2017
DOI:10.1007/s40195-017-0606-3
Nanocrystalline Ti54.5Ni45.5 thin film was prepared by magnetron sputtering followed by rapid thermal annealing. The film displayed martensite structure and (001) compound twin substructure, and the transformation temperatures Ms and As are 313 and 365 K, respectively. The reflectivity for the wavelength from 200 to 800 nm at 298 and 393 K was investigated, and the results showed that the optical reflectivity contrast between martensite and austensite at 780, 650, 514 and 405 nm was 105.64, 170.83, 112.22 and 149.92%, respectively, which were larger than those of other reported optical recording materials.
Co-reporter:Zhai-Ping Yang, Chang-Long Tan, Zhi-Yong Gao, Yuan Gao, Wei Cai
Thin Solid Films 2017 Volume 632(Volume 632) pp:
Publication Date(Web):30 June 2017
DOI:10.1016/j.tsf.2017.04.032
•Ferromagnetic Ni54.50Mn26.28Ga19.22 films were irradiated by protons with energy of 3 MeV.•Effect of irradiation on microstructural and magnetic properties was investigated.•Crystalline structure of the irradiated film remains the 7 M martensite structure.•Nanoscale amorphous zones could be produced under the action of irradiating protons.•Proton irradiation significantly affects the magnetic properties of the films.To explore the effect of proton irradiation on ferromagnetic Ni–Mn–Ga alloy, Ni54.5Mn26.3Ga19.2 thin films with the seven-layer modulated (7 M) martensite structure were prepared by magnetron sputtering and irradiated by protons with an energy of 3 MeV. The influence of proton irradiation on the microstructural and magnetic properties was investigated and discussed in detail. It is found that although nanoscale amorphous zones could be introduced by proton irradiation, the crystalline structure of the irradiated films retained the 7 M martensite structure according to X-ray diffraction and transmission electron microscopy results. Moreover, the broad diffraction peak at 2θ = 42.0° for the unirradiated films is split into two peaks at diffraction angles of about 41.5° and 42.2°, and the peak at 47.2° disappeared for the irradiated films. Regarding the magnetic properties, the irradiation-induced nanoscale amorphous defects may hinder the movement of magnetic domain walls, causing increases in the coercivity (Hc) and remanence (Mr). In addition, irradiation-enhanced thermal ordering will play a dominant role in improving the ordering of incompletely annealed films, ultimately resulting in slight increases in saturation magnetization (Ms) and the Curie temperature (Tc).
Co-reporter:Zhai-Ping Yang, Zhi-Yong Gao, Wei Cai
Materials Science and Engineering: B 2017 Volume 223(Volume 223) pp:
Publication Date(Web):1 September 2017
DOI:10.1016/j.mseb.2017.06.004
•Ni51.90Mn28.86Ga19.24 films were irradiated by 120 keV protons at different fluences.•Effect of proton irradiation on structural and magnetic property was investigated.•Crystal structure of martensite transforms from 7 M to NM in the irradiated zone.•Two endothermic and two exothermic peaks were observed under 2.0 × 1016 protons/cm2.•An extra shoulder was produced on the M-T curves of irradiated films.Ni51.90Mn28.86Ga19.24 alloy films were irradiated by 120 keV protons at different fluences to investigate the effect of irradiation on their crystal structure, phase-transition temperature, and magnetic properties. The results show not only that a nanoscale amorphous layer may have been induced on the surface, but also that non-modulated (NM) martensite was produced. Moreover, differential scanning calorimetry peaks of the martensitic and austenitic transition temperatures are shifted to higher temperatures after irradiation; in particular, two endothermic and two exothermic peaks were observed for a proton fluence of 2.0 × 1016/cm2. Further, the formation of NM martensite could produce an extra shoulder on the M–T curves of the irradiated films. Regarding the magnetic properties, a gradual decrease in the Curie temperature TC can be caused by irradiation at a higher proton fluence. The changes in the saturation magnetization Ms with the proton fluence seem to be related to the reduction in TC.Download high-res image (210KB)Download full-size image
Co-reporter:Shengyuan Peng;Jianhui Sun;Bo Cui;Xianfu Meng;Dandan Qin;Zihang Liu
Inorganic Chemistry Frontiers 2017 vol. 4(Issue 10) pp:1697-1703
Publication Date(Web):2017/10/10
DOI:10.1039/C7QI00304H
In the present work, p-type skutterudites La0.8Ti0.1Ga0.1Fe3CoSb12 composite with n-type Fe3Si nanoprecipitate was fabricated via an in situ method. Both thermoelectric and mechanical properties of La0.8Ti0.1Ga0.1Fe3CoSb12/xFe3Si composites were thoroughly investigated. With the introduction of homogeneously dispersed nanosized Fe3Si in the matrix, the power factor is almost unchanged due to the counteraction between the decreased electrical conductivity and the significantly enhanced Seebeck coefficient. Simultaneously, the total thermal conductivity was decreased for samples with Fe3Si nanoprecipitate because of the reduced electronic thermal conductivity. As a result, a ZT value of about 1.2 at 700 K has been achieved for La0.8Ti0.1Ga0.1Fe3CoSb12/0.1Fe3Si sample, whose ZT value was slightly enhanced in comparison with the Fe3Si-freeLa0.8Ti0.1Ga0.1Fe3CoSb12 sample. Furthermore, the indentation fracture toughness of La0.8Ti0.1Ga0.1Fe3CoSb12/0.1Fe3Si was improved by nearly 30% compared to the Fe3Si-free skutterudites.
Co-reporter:Xu Zhao;Hong-En Wang;Robert C. Massé;Jian Cao;Jiehe Sui;Jiangyu Li;Guozhong Cao
Journal of Materials Chemistry A 2017 vol. 5(Issue 16) pp:7394-7402
Publication Date(Web):2017/04/18
DOI:10.1039/C7TA01056G
There has been tremendous progress in development of nanomaterials for energy conversion and storage, with sodium-ion batteries (SIBs) attracting attention because of the high abundance of raw materials and low cost. However, inferior cycling stability, sluggish reaction kinetics, and poor reversibility hinder their practical applications. In the present study, Ni3S2/carbon nanocomposites with coherent nanostructures were successfully used as anodes in half- and full-cells. Outstanding cycling and rate performances are attributed to a synergistic effect between the Ni3S2 nanoparticles and interconnected carbon networks. The coherent porous framework effectively alleviated volume changes of Ni3S2, shortened the Na+ diffusion path, and accelerated electron transport and ionic diffusion during the electrochemical reaction. More importantly, conversion reaction products can be confined by the entangled carbon networks, leading to reversible redox reactions as demonstrated in ex situ XRD studies. The coherent Ni3S2/C nanocomposites demonstrated a highly reversible charge capacity of 453 and 430 mA h g−1 at a current density of 0.1 and 0.4 A g−1 over 100 cycles, respectively. At a current density of 2.0 A g−1, high rate capacities of 408 mA h g−1 can be attained over 200 cycles. The high performance of Na3V2(PO4)3/Ni3S2 full-cells enrich prospects for future practical applications.
Co-reporter:Jian Yao, Xiaohang Zheng, Wei Cai, Jiehe Sui
Journal of Alloys and Compounds 2016 Volume 661() pp:43-48
Publication Date(Web):15 March 2016
DOI:10.1016/j.jallcom.2015.11.191
•Ni55.2Mn24.7Ga19.9Gd0.2 thin film was deposited by DC magnetron sputtering.•Single phase structure of 7M martensite is formed in the annealed film.•Variants are (202) Ι type twin relationship with clear and straight boundaries.•Stable SME is observed in the annealed thin film above 200 °C.Nanocrystalline Ni55.2Mn24.7Ga19.9Gd0.2 high temperature shape memory thin films had been prepared by the DC magnetron sputtering followed by rapid thermal annealing (RTA). Surface morphology, crystal structure, martensitic transformation behavior and shape memory effect (SME) were systematically investigated. The results showed that as-deposited film displayed a coexistence of amorphous and nanocrystal, while the annealed film was a single phase of seven-layered modulated martensite structure with the grain size about 200–500 nm at room temperature. The annealed film showed one step reversible martensitic transformation with martensitic transformation start temperature of 283 °C. Adjacent lamellar variants exhibited a (202) type Ι twin relationship and well coherent interlamellar interfaces. The annealed Ni55.2Mn24.7Ga19.9Gd0.2 thin film displayed a stable SME above 200 °C, which could be used in high temperature field as micro-electro-mechanical-system (MEMS) devices.
Co-reporter:Z.Y. Yang, X.H. Zheng, W. Cai
Materials Science and Engineering: A 2016 Volume 655() pp:122-131
Publication Date(Web):8 February 2016
DOI:10.1016/j.msea.2015.12.049
The effects of thermomechanical treatment on microstructure, mechanical properties and shape memory effect of Ti–13V–3Al alloy were investigated. A dual-phase structure which consists of α phase and α″ martensite phase forms after thermomechanical treatment. As annealing temperature increases, the amount of α phase decreases and its morphology changes. Stress plateau decreases when annealing temperature increases and elongation shows the opposite trend. Ti–13V–3Al alloy annealed at 700 °C has the best comprehensive mechanical property. Recoverable strain first increases then decreases as annealing temperature increases. Ti–13V–3Al alloy annealed at 700 °C for 0.5 h displays a large fully recoverable strain of 7.5%. It is believed that small, uniformly distributed α phase benefits the shape memory effect. With the help of α phase, martensite variants become small. The variants are supposed to have a good mobility and that reduces the chance of introducing irrecoverable strain during tensile test. The microstructure evolution of Ti–13V–3Al alloy annealed at 700 °C during deformation was investigated. When the pre-strain is less than 7.5%, the recoverable martensite reorientation process contributes to the deformation. When the pre-strain exceeds 7.5%, the crossover of martensite plates leads to the deterioration of shape memory effect.
Co-reporter:Zihang Liu, Jing Shuai, Huiyuan Geng, Jun Mao, Yan Feng, Xu Zhao, Xianfu Meng, Ran He, Wei Cai, and Jiehe Sui
ACS Applied Materials & Interfaces 2015 Volume 7(Issue 41) pp:23047
Publication Date(Web):October 5, 2015
DOI:10.1021/acsami.5b06492
Microstructure has a critical influence on the mechanical and functional properties. For thermoelectric materials, deep understanding of the relationship of microstructure and thermoelectric properties will enable the rational optimization of the ZT value and efficiency. Herein, taking AgSbSe2 as an example, we first report a different role of alkaline-earth metal ions (Mg2+ and Ba2+) doping in the microstructure and thermoelectric properties of p-type AgSbSe2. For Mg doping, it monotonously increases the carrier concentration and then reduces the electrical resistivity, leading to a substantially enhanced power factor in comparison to those of other dopant elements (Bi3+, Pb2+, Zn2+, Na+, and Cd2+) in the AgSbSe2 system. Meanwhile, the lattice thermal conductivity is gradually suppressed by point defects scattering. In contrast, the electrical resistivity first decreases and then slightly rises with the increased Ba-doping concentrations due to the presence of BaSe3 nanoprecipitates, exhibiting a different variation tendency compared with the corresponding Mg-doped samples. More significantly, the total thermal conductivity is obviously reduced with the increased Ba-doping concentrations partially because of the strong scattering of medium and long wavelength phonons via the nanoprecipitates, consistent with the theoretical calculation and analysis. Collectively, ZT value ∼1 at 673 K and calculated leg efficiency ∼8.5% with Tc = 300 K and Th = 673 K are obtained for both AgSb0.98Mg0.02Se2 and AgSb0.98Ba0.02Se2 samples.Keywords: AgSbSe2; alkaline-earth metal ions (M2+) doping; leg efficiency; microstructure; nanoprecipitates; thermoelectric properties
Co-reporter:Xin Zhang, Jiehe Sui, Zheyi Yang, Xiaohang Zheng, Wei Cai
Materials Letters 2014 Volume 123() pp:250-253
Publication Date(Web):15 May 2014
DOI:10.1016/j.matlet.2014.02.088
Co-reporter:Xin Zhang, Jiehe Sui, Xiaohang Zheng, Zheyi Yang, Wei Cai
Materials Science and Engineering: A 2014 Volume 597() pp:178-182
Publication Date(Web):12 March 2014
DOI:10.1016/j.msea.2013.12.081
The influence of Gd content on the properties of Ni54Mn25Ga21−xGdx alloy was investigated. Proper Gd doping significantly enhanced the mechanical properties. Complete recovery was observed in Ni54Mn25Ga20.9Gd0.1 alloy after heating when the pre-strain is less than 10%, while further doping decreased such properties due to the Gd-rich phase formation.
Co-reporter:Qian Cheng, Jiehe Sui and Wei Cai
Nanoscale 2012 vol. 4(Issue 3) pp:779-784
Publication Date(Web):12 Dec 2011
DOI:10.1039/C1NR11365H
β-NaGdF4:Yb3+/Er3+ nanoparticles (NPs) codoped with Li+ ions were prepared for the first time via a thermal decomposition reaction of trifluoroacetates in oleylamine. The influence of site occupancy of Li+ on the upconversion emission of β-NaGdF4:Yb3+/Er3+ NPs was investigated in detail. The upconversion emission intensity was significantly enhanced by introducing different concentrations of Li+ ions. In contrast to lithium-free β-NaGdF4:Yb3+/Er3+, the green and red UC emission intensities of the NPs codoped with 7 mol% Li+ ions were enhanced by about 47 and 23 times, respectively. The luminescence enhancement should be attributed to the distortion of the local asymmetry around Er3+ ions. The mechanisms for the enhancement of upconversion emission were discussed. In addition, it was found in our research work that β-NaGdF4:Yb3+/Er3+ NPs exhibited paramagnetic features at room temperature and the magnetization was slightly increased by introducing Li+ ions.
Co-reporter:Maryam Amirian;Ali Nabipour Chakoli;Jie He Sui
Iranian Polymer Journal 2012 Volume 21( Issue 3) pp:165-174
Publication Date(Web):2012 March
DOI:10.1007/s13726-012-0014-5
The physical and mechanical properties of poly(l-lactide)/poly(ε-caprolactone) (PLLA/PCL) blends reinforced with multiwalled carbon nanotubes (MWCNTs) before and after in vitro degradation were investigated. Because of brittleness, PLLA needs to be plasticized by PCL as a soft polymer. The MWCNTs are used to balance the stiffness and the flexibility of PLLA/PCL blends. The results showed that with incremental increase in concentration of MWCNTs in composites, the agglomerate points of MWCNTs were increased. The physical and mechanical properties of prepared PLLA/PCL blends and MWCNT/PLLA/PCL nanocomposites were characterized. The X-ray diffraction analysis of the prepared blends and composites showed that MWCNTs, as heterogeneous nucleation points, increased the lamella size and therefore the crystallinity of PLLA/PCL. The mechanical strength of blends was decreased with incremental increase in PCL weight ratio. The mechanical behavior of composites showed large strain after yielding and high elastic strain characteristics. The tensile tests results showed that the tensile modulus and tensile strength are significantly increased with increasing the concentration of MWCNTs in composites, while, the elongation-at-break was decreased. The in vitro degradation rate of polymer blends in phosphate buffer solution (PBS) increased with higher weight ratio of PCL in the blend. The in vitro degradation rate of nanocomposites in PBS increased about 65% when the concentration of MWCNTs increased up to 3% (by weight). The results showed that the degradation kinetics of nanocomposites for scaffolds can be engineered by varying the contents of MWCNTs.
Co-reporter:Maryam Amirian;Ali Nabipour Chakoli;Jie He Sui
Polymer Bulletin 2012 Volume 68( Issue 6) pp:1747-1763
Publication Date(Web):2012 April
DOI:10.1007/s00289-012-0700-7
The poly(l-lactide) (PLLA) biocompatible and biodegradable polymer was reinforced with functionalized Multiwalled carbon nanotubes (MWCNTs) to overcome on insufficient mechanical properties of this polymer for high load bearing applications. To fully realize the potential of MWCNTs for this purpose, they have to be homogeneously dispersed in polymer matrix and have efficient load transfer across the MWCNTs/polymer interface. The pristine MWCNTs (pMWCNTs) were functionalized, at first, by Friedel–Crafts acylation, which introduced the aromatic amine groups on the sidewall of MWCNTs (MWCNT–NH2) without shortening or cutting of pMWCNTs. And then, the PLLA chains covalently grafted from the sidewall of MWCNT–NH2 by in situ ring-opening polymerization of l-lactide oligomers using stannous octanoate as the initiating system. The Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy spectra revealed that the PLLA chains grafted form the sidewall of MWCNTs strongly. The surface morphology of pristine and PLLA-grafted MWCNTs (MWCNT-g-PLLAs) was characterized by scanning electron microscopy and transmission electron microscopy. The tensile test of prepared composites of PLLA with various concentrations of MWCNT-g-PLLAs show a significant increment in tensile strength and elongation at failure of composites with increasing the concentration of MWCNT-g-PLLAs in composites. Also, it is found that the MWCNT-g-PLLAs increased the photoluminescence effect of PLLA and widened the luminescence region of PLLA.
Co-reporter:Wei Cai;Xue Feng;Jiehe Sui
Rare Metals 2012 Volume 31( Issue 1) pp:48-50
Publication Date(Web):2012 February
DOI:10.1007/s12598-012-0461-3
Carbon nanotube (CNT)-reinforced TiNi matrix composites were synthesized by spark plasma sintering (SPS) employing elemental powders. The phase structure, morphology and transformation behaviors were studied. It was found that thermoelastic martensitic transformation behaviors could be observed from the samples sintered above 800 °C even with a short sintering time (5 min), and the transformation temperatures gradually increased with increasing sintering temperature because of more Ti-rich TiNi phase formation. Although decreasing the sintering temperature and time to 700 °C and 5 min could not protect defective MWCNTs from reacting with Ti, still-perfect MWCNTs remained in the specimens sintered at 900 °C. This method is expected to supply a basis for preparing CNT-reinforced TiNi composites.
Co-reporter:Chang-Yan Cao, Wei Guo, Zhi-Min Cui, Wei-Guo Song and Wei Cai
Journal of Materials Chemistry A 2011 vol. 21(Issue 9) pp:3204-3209
Publication Date(Web):25 Jan 2011
DOI:10.1039/C0JM03749D
A rapid method based on an efficient gas/liquid interfacial microwave-assisted process has been developed to synthesize flowerlike NiO hollow nanosphere precursors, which were then transformed to NiO by simple calcinations. The wall of the sphere is composed of twisted NiO nanosheets that intercalated with each other. Such hollow structure is different from widely reported flowerlike nanostructures with solid cores. An Ostwald ripening mechanism was proposed for the formation of the hollow nanostructures. The products were characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, high-resolution TEM, energy-dispersive X-ray analysis, and N2adsorption-desorption methods. These flowerlike NiO hollow nanospheres have high surface area of 176 m2 g−1. Electrochemical properties show a high specific capacitance of 585 F g−1 at a discharge current of 5 A g−1 and excellent cycling stability, suggesting its promising potentials in supercapacitors.
Co-reporter:X.H. Tian, J.H. Sui, X. Zhang, X. Feng, W. Cai
Journal of Alloys and Compounds 2011 Volume 509(Issue 10) pp:4081-4083
Publication Date(Web):10 March 2011
DOI:10.1016/j.jallcom.2011.01.001
Martensitic transformation, mechanical property and magnetic-field-induced strain of Ni–Mn–Ga alloys obtained using the spark plasma sintering method have been investigated. The results show that the martensitic transformation of the sintered specimen is basically similar to that of conventional bulk alloys. The ductility of sintered Ni–Mn–Ga alloys is significantly enhanced compared to the specimen obtained by conventional melting technique. The highest fracture strain so far is reported. Moreover, magnetic-filed-induced strain in sintered Ni–Mn–Ga alloys has been studied for the first time.Research highlights▶ Ni–Mn–Ga shape memory alloys have been fabricated by the spark plasma sintering technique. ▶ The ductility of sintered Ni–Mn–Ga alloys is significantly enhanced compared to the specimen obtained by conventional melting technique. ▶ The highest fracture strain of 27% up to now has been reported. ▶ The magnetic-filed-induced strain in sintered Ni–Mn–Ga alloys has been studied for the first time.
Co-reporter:Zhiguo Li, Jiehe Sui, Xiaoli Li, and Wei Cai
Langmuir 2011 Volume 27(Issue 6) pp:2258-2264
Publication Date(Web):February 1, 2011
DOI:10.1021/la1043552
Quantum-sized CdS nanorods were synthesized by direct thermal decomposition of a single-source precursor in a monosurfactant system. The CdS nanorods were uniform, had high crystallinity, and exhibited strong quantum confinement effect. The nanorod growth was controlled by an oriented attachment mechanism, and the morphology was determined by the competition between dipole attraction and steric repulsion of nanodots. Increasing precursor concentration and prolonging reaction time were favorable for the formation of CdS nanorods.
Co-reporter:Guo-hua ZHANG, Jian-xin ZHANG, Bing-chao LI, Wei CAI
Progress in Natural Science: Materials International 2011 Volume 21(Issue 5) pp:380-385
Publication Date(Web):October 2011
DOI:10.1016/S1002-0071(12)60073-2
AbstractThis paper focuses on a typical automotive piston material to characterize its fractographic appearance after tensile rupture. The fracture of this heavily alloyed Al–Si alloy takes place in a brittle manner. The consecutive eutectic zone is found to break by debonding of Si platelets from the Al matrix or by fracturing of Si platelets. The various intermetallic particles break up complicatedly under the stress field of the propagating crack. The fracture tends to pass through or approach to the boundary between the eutectic Al matrix and Si platelets and there is a strong interaction between the propagating crack and the obstructing intermetallic compound. A tensile fracture mechanism in the heavily alloyed Al–Si alloy is elucidated.
Co-reporter:Ali Nabipour Chakoli;Jiehe Sui;Maryam Amirian
Journal of Polymer Research 2011 Volume 18( Issue 6) pp:1249-1259
Publication Date(Web):2011 November
DOI:10.1007/s10965-010-9527-9
Well-dispersed multiwall carbon nanotubes (MWCNTs) were prepared by grafting poly(L-lactide-co-ε-caprolactone) (PLACL) biodegradable copolymer onto the sidewall of hydroxylated MWCNTs using oligomeric L-lactide (LA) and ε-caprolactone (CL). After preparation of MWCNT/PLACL composites, the effect of functionalized MWCNTs on crystallinity of PLACL was investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and polarized light optical microscopy (POM). The surface functionalization effectively improved the dispersion and adhesion of MWCNTs which acted as reinforcing filler in the PLACL polymer matrix and hence improved the physical and thermomechanical properties of the nanocomposites. The glass transition temperature (Tg) and the crystallinity of nanocomposites decreased in comparison with those of neat PLACL when the concentration of functionalized MWCNTs in nanocomposites was 0.5 wt%. With further increment in concentration of functionalized MWCNTs, the Tg of composites increased until the Tg of neat PLACL, and also the crystallinity of composites increased. The functionalized MWCNTs have no significant effect on the melting point of nanocomposites. The MWCNTs acted as heterogeneous nucleation points and increased the lamella size and therefore the crystallinity of PLACL. Furthermore, the larger agglomerated clusters of both kinds of MWCNTs (i.e., MWCNT-grafted-PLACL and pristine MWCNTs) are more effective than small clusters as nucleation points for growing the spherulites.
Co-reporter:Zhijiang Wang, Lina Wu, Yulin Qi, Wei Cai, Zhaohua Jiang
Surface and Coatings Technology 2010 204(20) pp: 3315-3318
Publication Date(Web):
DOI:10.1016/j.surfcoat.2010.03.049
Co-reporter:Chang-Yan Cao;Chao-Qiu Chen;Wei Li; Wei-Guo Song; Wei Cai
ChemSusChem 2010 Volume 3( Issue 11) pp:1241-1244
Publication Date(Web):
DOI:10.1002/cssc.201000229
Co-reporter:Chang-Yan Cao, Zhi-Min Cui, Chao-Qiu Chen, Wei-Guo Song and Wei Cai
The Journal of Physical Chemistry C 2010 Volume 114(Issue 21) pp:9865-9870
Publication Date(Web):May 13, 2010
DOI:10.1021/jp101553x
Ceria hollow nanospheres composed of CeO2 nanocrystals were synthesized via a template-free and microwave-assisted aqueous hydrothermal method. This is a low-cost and environmentally benign method. The chemicals used are all environmentally benign materials (cerium nitrate, urea, and water). An Ostwald ripening mechanism coupled with a self-templated, self-assembly process, in which amorphous solid spheres are converted to crystalline nanocrystals and the latter self-assemble into hollow structures, was proposed for the formation of the hollow structures. The products were characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, high-resolution TEM, energy-dispersive X-ray analysis, X-ray photoelectron spectroscopy, and N2 adsorption−desorption methods. These ceria hollow nanospheres show an excellent adsorption capacity for heavy metal ions, for example, 22.4 mg g−1 for As(V) and 15.4 mg g−1 for Cr(VI). These values are significantly higher than reported data from other ceria nanostructures. These ceria hollow nanospheres are also excellent supports for gold nanoparticles, forming a Au/CeO2 composite catalyst. In CO oxidation, a 100% CO conversion was achieved at room temperature.
Co-reporter:Zhijiang Wang;Lina Wu
Chemistry - A European Journal 2010 Volume 16( Issue 5) pp:1459-1463
Publication Date(Web):
DOI:10.1002/chem.200902463
Co-reporter:Y.C. Lei, H.J. Zhao, W. Cai, L.X. Gao, X. An
Vacuum 2010 Volume 84(Issue 9) pp:1138-1141
Publication Date(Web):19 April 2010
DOI:10.1016/j.vacuum.2010.01.048
The Ti49Ni46.5Ce4.5 alloy thin film was prepared by direct current (DC) magnetron sputtering system for the first time. Crystallization kinetics, phase composition and the behaviors of martensitic transformation were studied. The results by X-ray diffraction (XRD) and differential scanning calorimeter (DSC) demonstrated that the primary second phase of TiNiCe alloy thin films was Ce2Ni7 phase, apparent activation energy was determined to be 510 kJ/mol at the continuous heating process, Avrami exponents for different isothermal temperature were in the range of 1.1–1.88 between 713 and 730 K, one-step martensitic transformation was observed in the crystallized Ti49Ni46.5Ce4.5 alloy thin films. The influence of thermal process on martensitic transformation temperature was investigated with non-isothermal and isothermal crystallization. The reason behind the transformation temperature change was also discussed.
Co-reporter:Feng Xue, Sui Jiehe, Feng Yan, Cai Wei
Materials Science and Engineering: A 2010 527(6) pp: 1586-1589
Publication Date(Web):
DOI:10.1016/j.msea.2009.12.003
Co-reporter:Ali Nabipour Chakoli, Jing Wan, Jiang Tao Feng, Maryam Amirian, Jie He Sui, Wei Cai
Applied Surface Science 2009 Volume 256(Issue 1) pp:170-177
Publication Date(Web):15 October 2009
DOI:10.1016/j.apsusc.2009.07.103
Abstract
Up to now, synthetic polymers and biomacromolecules have been grafted or assembled onto the convex surface of carbon nanotubes (CNTs) via covalent bonds or chemisorptions. In this research, poly(l-lactide-co-ɛ-caprolactone)-functionalized multiwalled carbon nanotubes (MWCNT-OH-g-PCLA)s are synthesized by in situ ring-opening copolymerization of l-lactide (LA) and ɛ-caprolactone (CL) using stannous octanoate and hydroxylated MWCNTs (MWCNT-OHs) as the initiating system. The pristine MWCNTs are modified to possess carboxyl groups and then hydroxyl groups. MWCNT-OHs are used as coinitiators to polymerize LA and CL by the surface-initiated ring-opening polymerization. The FT-IR spectra, SEM and TEM micrographs revealed that the PCLA grafted form the sidewall of MWCNTs strongly. The TGA analysis indicates that about 75 wt% of functionalized MWCNTs with PCLA belongs to grafted PCLA and the remaining 25 wt% to the initial MWCNT-OH.
Co-reporter:Z.Y. Gao, G.F. Dong, W. Cai, J.H. Sui, Y. Feng, X.H. Li
Journal of Alloys and Compounds 2009 Volume 481(1–2) pp:44-47
Publication Date(Web):29 July 2009
DOI:10.1016/j.jallcom.2009.03.105
The martensitic transformation behavior and mechanical properties were investigated in a Ti-doped Ni53Mn23.5Ga18.5Ti5 alloy aged at 873 K for different durations. It is shown that the volume fraction of the Ni3Ti phase increases and the Ni content in the matrix reduces with increasing aging time, resulting in the decrease of the martensitic transformation temperatures. The precipitation of Ni3Ti particles strengthens the matrix, resulting in the increasing in the fracture toughness. Fracture morphology observation shows the fracture type changing from intergranular brittleness fracture to a mixture of intergranular and transgranular ductile failure is responsible for the improved mechanical properties.
Co-reporter:Xiang Wu, Fengyu Qu, Guozhen Shen, Wei Cai
Journal of Alloys and Compounds 2009 Volume 482(1–2) pp:L32-L35
Publication Date(Web):12 August 2009
DOI:10.1016/j.jallcom.2009.04.070
Fishbone-like ZnS nanostructures have been successfully synthesized by using a simply thermal evaporation of ZnS powders using ITO glass as the deposition substrate. Scanning electron microscope (SEM) images indicated that as-grown ZnS nanostructures consisted of main spines with lengths of several micrometers and numerous secondary branches with widths of 50 to 100 nm and lengths of about 500 nm distributed on both sides of the spines. Transmission electron microscopy (TEM) and selected area electron diffraction (SAED) results reveal that both the spines and the branches grew along the [0 0 0 1] directions. A possible growth mechanism was proposed to explain the formation of complex nanostructures.
Co-reporter:Lili Liu, Wei Cai
Materials Letters 2009 Volume 63(Issue 20) pp:1656-1658
Publication Date(Web):15 August 2009
DOI:10.1016/j.matlet.2009.04.037
Co-reporter:Y. Feng, J.H. Sui, L. Chen, W. Cai
Materials Letters 2009 Volume 63(Issue 12) pp:965-968
Publication Date(Web):15 May 2009
DOI:10.1016/j.matlet.2009.01.035
In this paper, the phase transformation behaviors and structures of Ni50Mn28 + xGa22 − x (x = 0, 1, 2, 3) alloys and ribbons as well as the magnetic properties of ribbons are discussed. Rapidly quenching process decreases the degree of order and introduces some internal stress, which influences the martensitic transformation temperatures of the ribbons. The structures of the ribbons become 7 M modulated, which is different from the 5 M modulated martensite of the corresponding bulk materials. Higher annealing temperature and annealing under magnetic field are all in favor of the magnetization of the ribbons, and this is related to the enhancement of orientation perpendicular to the surface of the ribbons.
Co-reporter:L. Gao, J.H. Sui, W. Cai, Z.Y. Gao
Solid State Communications 2009 Volume 149(5–6) pp:257-260
Publication Date(Web):February 2009
DOI:10.1016/j.ssc.2008.10.030
Co-reporter:Zhijiang Wang, ;Jiehe Sui Dr.
ChemPhysChem 2009 Volume 10( Issue 12) pp:2012-2015
Publication Date(Web):
DOI:10.1002/cphc.200900067
Co-reporter:Y. Feng, J.H. Sui, Z.Y. Gao, J. Zhang, W. Cai
Materials Science and Engineering: A 2009 Volume 507(1–2) pp:174-178
Publication Date(Web):15 May 2009
DOI:10.1016/j.msea.2008.12.003
Ni–Mn–In alloys are doped by Fe in order to improve the ductility of this intermetallic. The phase transformation behavior, microstructures and mechanical properties of Ni50Mn34In16 − yFey (y = 0, 2, 3, 4, 5, 8) alloys are investigated in this paper. The phase transformation temperatures increase with the increase of Fe content, and some second phase particles appear both along the grain boundaries and inside the grains after being doped 5 at.% and 8 at.% Fe. The compressive strength and maximum compressive strain reach up to 1200 MPa and 15.8% for amounts higher than 8 at.% Fe. In addition, the fracture type changes from typical intergranular crack to transgranular crack gradually with the increase of Fe content.
Co-reporter:C. Liu, Z.Y. Gao, X. An, H.B. Wang, L.X. Gao, W. Cai
Applied Surface Science 2008 Volume 254(Issue 9) pp:2861-2865
Publication Date(Web):28 February 2008
DOI:10.1016/j.apsusc.2007.10.031
Abstract
In present paper, the off-stoichiometric Ni–Mn–Ga ferromagnetic shape memory alloy thin films are fabricated using radio frequency magnetron sputtering method. The compositions, microstructures and mechanical properties of the thin films are characterized by energy dispersive X-ray spectrum (EDAX), X-ray photoelectron spectroscopy (XPS), scanning electronic microscope (SEM), atomic force microscope (AFM) and nanoindentation test, respectively. The results show that there is a thinner layer of oxides consisting of NiO, Ga2O3 and an unspecified manganese oxidation (MnxOy) at the surface, whereas a small amount of MnO precipitates exist in internal layers of post-annealed Ni–Mn–Ga thin films. The hardness and elastic modulus decrease with increasing film thickness. Nanoindentation tests reveal that the hardness and elastic modulus of the films can be up to 5.5 and 155 GPa, respectively. The Ni–Mn–Ga thin films have remarkably improved the ductility of Ni–Mn–Ga ferromagnetic shape memory alloys bulk materials.
Co-reporter:G.F. Dong, W. Cai, Z.Y. Gao, J.H. Sui
Scripta Materialia 2008 Volume 58(Issue 8) pp:647-650
Publication Date(Web):April 2008
DOI:10.1016/j.scriptamat.2007.11.034
The effect of isothermal ageing on the microstructure, martensitic transformation and mechanical properties of Ni53Mn23.5Ga18.5Ti5 alloy has been investigated. The results show that Ni3Ti precipitates are observed in aged samples. The martensitic transformation temperature decreases remarkably with increased ageing time, while the martensitic structure of these alloys is five-layered martensite at room temperature. Additionally, Ti doping can significantly enhance the compressive strength and improve the ductility of Ni–Mn–Ga alloy with the appropriate ageing treatment.
Co-reporter:J. Zhang, W. Cai, Z.Y. Gao, J.H. Sui
Scripta Materialia 2008 Volume 58(Issue 9) pp:798-801
Publication Date(Web):May 2008
DOI:10.1016/j.scriptamat.2007.12.031
Microstructure and magnetic properties were investigated in Mn50+xNi25Ga25−x ferromagnetic shape memory alloys. Some Mn-rich precipitates were observed in polycrystalline samples after being annealed at 1073 K for 24 h, and 1123 K for 24 h is required for a single martensitic phase. The saturation magnetization substantially decreases with higher Mn content and higher annealing temperature at which no precipitates were found in a field up to 50 KOe.
Co-reporter:W. Cai, Y. Feng, J.H. Sui, Z.Y. Gao, G.F. Dong
Scripta Materialia 2008 Volume 58(Issue 10) pp:830-833
Publication Date(Web):May 2008
DOI:10.1016/j.scriptamat.2007.12.035
The microstructure and martensitic phase transformation behavior of the Ni50Mn36In14 melt-spun ribbons were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). The results show that fine crystal grains with preferential orientation have been obtained in the rapidly quenched ribbons, the martensitic transformation temperatures of the as-cast ribbon are low, and increased after heat treatments. The reason is clarified as the variation in degree of order and internal stress.
Co-reporter:X. L. Lu;W. Cai;Z. Y. Gao
Journal of Applied Polymer Science 2008 Volume 108( Issue 2) pp:
Publication Date(Web):
DOI:10.1002/app.27703
Abstract
A series of biodegradable poly(L-lactide-co-ϵ-caprolactone) (PCLA) copolymers with different chemical compositions are synthesized and characterized. The mechanical properties and shape-memory behaviors of PCLA copolymers are studied. The mechanical properties are significantly affected by the copolymer compositions. With the ϵ-caprolactone (ϵ-CL) content increasing, the tensile strength of copolymers decreases linearly and the elongation at break increases gradually. By means of adjusting the compositions, the copolymers exhibit excellent shape-memory effects with shape-recovery and shape-retention rate exceeding 95%. The effects of composition, deformation strain, and the stretching conditions on the recovery stress are also investigated systematically. A maximum recovery stress around 6.2 MPa can be obtained at stretching at Tg − 15°C to 200% deformation strain for the PCLA70 copolymer. The degradation results show that the copolymers with higher ϵ-CL content have faster degradation rates and shape-recovery rates, meanwhile, the recovery stress can maintain a relative high value after 30 days in vitro degradation. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Co-reporter:Y.C. Lei, W. Cai, X. An, L.X. Gao
Journal of Non-Crystalline Solids 2008 Volume 354(40–41) pp:4572-4576
Publication Date(Web):15 October 2008
DOI:10.1016/j.jnoncrysol.2008.06.004
The crystallization kinetics of amorphous thin TiNi films deposited on SiO2 (or NaCl)/Al foils substrates were investigated. A dramatic acceleration of the crystallization rate was observed for amorphous attached-substrate films. The acceleration originated from the presence of the thin film/middle-wafer interface which served as a two-dimensional nucleus for the growth of the crystalline phase. In the process of non-isothermal annealing by DSC, apparent activation energies for two kinds of underlying thin TiNi films were determined to be 352.96 and 403.69 kJ/mol, respectively, which was lower than those free-standing films studied in previous works. For the process of isothermal annealing, the crystallization kinetics parameters had remarked drop, reflected from the lower Avrami exponent n (the range of 1.35–2.11) and shorter incubation time τ (the range of 0.1–0.4 min) between 758 and 775 K.
Co-reporter:Wei Cai, Lili Liu
Materials Letters 2008 Volume 62(Issue 14) pp:2171-2173
Publication Date(Web):15 May 2008
DOI:10.1016/j.matlet.2007.11.042
In the present work, we report the excellent shape-memory behavior of Poly (glycerol–sebacate) (PGS) elastomer for the first time. It is found that the crosslinked, three-dimensional networks of the PGS acting as fixed phase and the amorphous phase of the PGS acting as reversible phase are the two necessary conditions for PGS with shape memory behavior. The response temperature of shape memory is dependent on the glass transition temperature of PGS. The PGS polymer developed has an excellent shape-memory effect, having a shape-memory ratio of above 99.5%.
Co-reporter:Xiang Wu, Jiehe Sui, Wei Cai, Fengyu Qu
Materials Chemistry and Physics 2008 Volume 112(Issue 2) pp:325-328
Publication Date(Web):1 December 2008
DOI:10.1016/j.matchemphys.2008.05.069
Novel dendritic SnO2 nanostructures were successfully synthesized through thermal evaporation of the mixture of ZnS and Sn powders. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and contact angle (CA) apparatus were used to characterize the crystal structure and wettability of as-synthesized product. The results show that each dendrite-like SnO2 nanostructures consists of several branches, and each branch possess lengths of several tens to hundreds nanometers. The whole dendrite covers several square micrometers. A possible growth mechanism based on growth condition was proposed to interpret the formation of dendritic SnO2 nanostructures. The synthesized dendritic SnO2 nanostructures might be used for fabricating novel sensor nanodevices.
Co-reporter:C.L. Tan, X.H. Tian, G.J. Ji, T.L. Gui, W. Cai
Solid State Communications 2008 Volume 147(1–2) pp:8-10
Publication Date(Web):July 2008
DOI:10.1016/j.ssc.2008.04.032
Elastic property and electronic structure of TiNiPt high-temperature shape memory alloys have been investigated by first-principles calculations using the pseudopotentials plane wave method. The effect of Pt content on the martensitic transformation temperature and transformation type is clarified based on the elastic constants of the B2 phases. It is found that high martensitic transformation temperature is due to a low shear resistance C′C′. Furthermore, the electronic structure mechanisms behind the elastic properties are discussed based on the density of states.
Co-reporter:Jiaqi Wan, Wei Cai, Jiangtao Feng, Xiangxi Meng and Enzhong Liu
Journal of Materials Chemistry A 2007 vol. 17(Issue 12) pp:1188-1192
Publication Date(Web):03 Jan 2007
DOI:10.1039/B615527H
Nearly monodisperse magnetite nanoparticles with sizes less than 10 nm have been successfully deposited on multi-walled carbon nanotubes (MWNTs) by in situ high-temperature decomposition of the precursor iron(III) acetylacetonate and MWNTs in polyol solution. The effects of the concentration of the iron precursor on the ultimate nanocomposites characteristics were investigated. XRD, TEM, HRTEM, EDS, and PPMS of Quantum Design were used to characterize the final products. It was found that the sizes of nanoparticles and their coverage density on MWNTs could be easily controlled by changing the concentration of the precursor and the weight radio to MWNTs. A possible formation mechanism of the magnetite–MWNT nanocomposites was suggested. It was concluded that the magnetite nanoparticles formation on MWNTs through an aggregation process of subparticles that is influenced strongly by the presence of polyols. Magnetic measurements showed that the nanocomposites are superparamagnetic at room temperature and the magnetization of the samples is strongly influenced by the reaction conditions. The resulting nanomaterials can be easily dispersed in water and can be manipulated by an external magnetic field. As-synthesized nanocomposites have high potential for applications in the fields of composites, wastewater treatment, sensors, and biomaterials.
Co-reporter:Wei Cai, Jiaqi Wan
Journal of Colloid and Interface Science 2007 Volume 305(Issue 2) pp:366-370
Publication Date(Web):15 January 2007
DOI:10.1016/j.jcis.2006.10.023
Magnetite nanoparticles have been successfully synthesized in liquid polyols at elevated temperature. Polyol solvent plays a crucial role in determining the morphology and colloidal stability of the resulting particles. The structure and morphology of the nanoparticles were studied using XRD, TEM, SAED, TGA and FTIR. The magnetic properties of the samples were measured using physical properties measurement system (PPMS) of Quantum Design. The results show that as-prepared magnetite nanoparticles are monodisperse, highly crystalline and superparamagnetic at room temperature. The nanoparticles can be easily dispersed in aqueous media and other polar solvents due to coated by a layer of hydrophilic polyol ligands in situ. This approach provides a facile route to prepare magnetite nanoparticles.Monodisperse water-soluble magnetite nanoparticles were synthesized by the one-pot decomposition of iron(III) acetylacetonate in triethylene glycol. As-prepared nanoparticles have nearly spherical shapes and narrow size distribution and can be well re-dispersed in water due to coated a layer of hydrophilic triethylene glycol on the surface of the particles in situ.
Co-reporter:Changlong Tan, Wei Cai, Xiaohua Tian
Scripta Materialia 2007 Volume 56(Issue 7) pp:625-628
Publication Date(Web):April 2007
DOI:10.1016/j.scriptamat.2006.12.024
The structural, electronic and elastic properties of NbRu alloy have been studied by the plane-wave pseudopotential method within the generalized gradient approximation. The crystal structure of the β′ phase is obtained for the first time. Our calculations show that the hybridization between Nb d and Ru d states is responsible for the phase stability of NbRu. In addition, it is found that the β to β′ martensitic transformation is closely related to the elastic properties.
Co-reporter:Wei Cai, Changlong Tan, Tao Shen, Xiaohua Tian
Journal of Alloys and Compounds 2007 Volume 438(1–2) pp:30-33
Publication Date(Web):12 July 2007
DOI:10.1016/j.jallcom.2006.08.013
The alloying effect on the martensitic transformation behavior of TiNi alloy is investigated for the first time from the elastic properties and electronic structure by the plane-wave pseudopotential method within the local density approximation. The elastic constants and density of states are calculated. The results show that the alloying effect on the martensitic transformation behavior of TiNi alloy is close related to its elastic properties. The Ti d density of states at Fermi level is mainly responsible for the B2 phase stability of TiNi alloy with the low addition of the third element. As for TiNiPd ternary alloy, the high martensitic transformation temperature stems from the stabilization of B19 phase TiNiPd by the high addition of Pd content.
Co-reporter:Wei Cai;Li Gao;Z. Y. Gao
Journal of Materials Science 2007 Volume 42( Issue 22) pp:9216-9220
Publication Date(Web):2007 November
DOI:10.1007/s10853-007-1893-2
A Heusler Ni50Mn29Ga16Gd5 alloy with a high transformation temperature has been obtained by substituting 5 at% Gd for Ga in a ternary Ni50Mn29Ga21 ferromagnetic shape memory alloy. The microstructure and phase transformations in the Ni50Mn29Ga16Gd5 alloy have been investigated by scanning electron microscopy, transmission electron microscopy, X-ray diffraction and differential scanning calorimetry. It is shown that the microstructure of the Ni50Mn29Ga16Gd5 alloy consists of matrix and hexagonal Gd (Ni,Mn)4Ga phase, which indicates a eutectic structure composed of these two phases. One-step thermoelastic martensitic transformation occurs in this quaternary alloy. Ni50Mn29Ga16Gd5 alloy exhibits a martensite transformation start temperature up to 524 K, approximately 200 K higher than that of Ni50Mn29Ga21 alloy. At room temperature, non-modulated martensite with twin substructure is observed in Ni50Mn29Ga16Gd5 alloy.
Co-reporter:J.H. Sui, Z.Y. Gao, W. Cai, Z.G. Zhang
Materials Science and Engineering: A 2007 Volumes 452–453() pp:518-523
Publication Date(Web):15 April 2007
DOI:10.1016/j.msea.2006.10.159
A dense and well-adhered diamond-like carbon (DLC) coating was prepared on NiTi alloys by plasma immersion ion implantation and deposition (PIIID). Electrochemical impedance spectroscopy and potentiodynamic polarization tests indicated the corrosion resistance of the NiTi alloys was markedly improved by DLC coating.
Co-reporter:J.H. Sui, W. Cai
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 2006 Volume 251(Issue 2) pp:402-406
Publication Date(Web):October 2006
DOI:10.1016/j.nimb.2006.06.028
ZrO2 films were fabricated by plasma immersion ion implantation and deposition (PIIID) on the polished NiTi alloys. The results obtained from X-ray diffraction (XRD) and scanning electronic microscopy (SEM) showed the dense and well adhered ZrO2 coating were successfully fabricated by PIIID. Pin-on-disc and scratch tests revealed the surface friction coefficient of NiTi alloys was decreased due to the ZrO2 coating and good adhesion strength between the coating and substrate was obtained, respectively. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) studies indicated a significantly larger increase of the coated sample in the corrosion resistance compared with the uncoated samples. The mechanism of the improvement in the corrosion resistance of NiTi alloys due to ZrO2 coating was clarified.
Co-reporter:W. Cai, X.L. Meng, L.C. Zhao
Current Opinion in Solid State and Materials Science 2005 Volume 9(Issue 6) pp:296-302
Publication Date(Web):December 2005
DOI:10.1016/j.cossms.2006.07.002
Recent developments in China on TiNi-based shape memory alloys (SMAs), including TiNi binary SMAs, TiNiNb wide hysteresis SMAs, TiNiCu narrow hysteresis SMAs, TiNiHf high temperature SMAs and TiNiRE SMAs were concisely reviewed. The damping characteristics and corresponding mechanisms of TiNi and TiNiNb alloys were described and discussed. Some surface modifications of TiNi binary alloys were employed to improve the corrosion resistance and the biocompatibility, which are very useful for the medical applications. Shape memory effect and mechanical properties of TiNiHf alloys were enhanced by aging Ni-rich TiNiHf alloys, while the Ms still remain enough high. The authors found that the addition of RE to TiNi alloys increases the phase transformation temperatures and even changes the transformation sequence. Fundamental research on the TiNi-based alloys is still in the ascendant, leading to increasingly extending of the applications.
Co-reporter:L. Gao, J.H. Sui, W. Cai, Z.Y. Gao
Solid State Communications (February 2009) Volume 149(5–6) pp:257-260
Publication Date(Web):1 February 2009
DOI:10.1016/j.ssc.2008.10.030
The precipitate phases and martensitic transformation behavior of polycrystalline Ni50Mn29Ga21−xDyx (x=0–5) ferromagnetic shape memory alloys are investigated. The results show that some Dy-rich precipitates are observed in higher Dy-addition alloys. The precipitates can be indexed to Dy(Ni,Mn)4Ga phase with a hexagonal CaCu5 type structure. When the content of Dy increases from 0.5 at.% to 2 at.%, Dy(Ni,Mn)4Ga phase distributes mainly along the grain boundaries, while a eutectic structure composed of the matrix and Dy(Ni,Mn)4Ga phase is observed with the further increase of Dy content. In addition, structural transition from 5M to 7M, and then to non-modulated T martensite appears with the increase of Dy content. It is found that substitution of Dy for Ga up to 5 at.%, one-step thermoelastic martensitic transformation can still be observed in this quaternary alloy. The Dy doping markedly increases the martensitic transformation temperature from 326 K to 512 K.
Co-reporter:Chang-Yan Cao, Wei Guo, Zhi-Min Cui, Wei-Guo Song and Wei Cai
Journal of Materials Chemistry A 2011 - vol. 21(Issue 9) pp:NaN3209-3209
Publication Date(Web):2011/01/25
DOI:10.1039/C0JM03749D
A rapid method based on an efficient gas/liquid interfacial microwave-assisted process has been developed to synthesize flowerlike NiO hollow nanosphere precursors, which were then transformed to NiO by simple calcinations. The wall of the sphere is composed of twisted NiO nanosheets that intercalated with each other. Such hollow structure is different from widely reported flowerlike nanostructures with solid cores. An Ostwald ripening mechanism was proposed for the formation of the hollow nanostructures. The products were characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, high-resolution TEM, energy-dispersive X-ray analysis, and N2adsorption-desorption methods. These flowerlike NiO hollow nanospheres have high surface area of 176 m2 g−1. Electrochemical properties show a high specific capacitance of 585 F g−1 at a discharge current of 5 A g−1 and excellent cycling stability, suggesting its promising potentials in supercapacitors.
Co-reporter:Jiaqi Wan, Wei Cai, Jiangtao Feng, Xiangxi Meng and Enzhong Liu
Journal of Materials Chemistry A 2007 - vol. 17(Issue 12) pp:NaN1192-1192
Publication Date(Web):2007/01/03
DOI:10.1039/B615527H
Nearly monodisperse magnetite nanoparticles with sizes less than 10 nm have been successfully deposited on multi-walled carbon nanotubes (MWNTs) by in situ high-temperature decomposition of the precursor iron(III) acetylacetonate and MWNTs in polyol solution. The effects of the concentration of the iron precursor on the ultimate nanocomposites characteristics were investigated. XRD, TEM, HRTEM, EDS, and PPMS of Quantum Design were used to characterize the final products. It was found that the sizes of nanoparticles and their coverage density on MWNTs could be easily controlled by changing the concentration of the precursor and the weight radio to MWNTs. A possible formation mechanism of the magnetite–MWNT nanocomposites was suggested. It was concluded that the magnetite nanoparticles formation on MWNTs through an aggregation process of subparticles that is influenced strongly by the presence of polyols. Magnetic measurements showed that the nanocomposites are superparamagnetic at room temperature and the magnetization of the samples is strongly influenced by the reaction conditions. The resulting nanomaterials can be easily dispersed in water and can be manipulated by an external magnetic field. As-synthesized nanocomposites have high potential for applications in the fields of composites, wastewater treatment, sensors, and biomaterials.
Co-reporter:Xu Zhao, Hong-En Wang, Robert C. Massé, Jian Cao, Jiehe Sui, Jiangyu Li, Wei Cai and Guozhong Cao
Journal of Materials Chemistry A 2017 - vol. 5(Issue 16) pp:NaN7402-7402
Publication Date(Web):2017/03/21
DOI:10.1039/C7TA01056G
There has been tremendous progress in development of nanomaterials for energy conversion and storage, with sodium-ion batteries (SIBs) attracting attention because of the high abundance of raw materials and low cost. However, inferior cycling stability, sluggish reaction kinetics, and poor reversibility hinder their practical applications. In the present study, Ni3S2/carbon nanocomposites with coherent nanostructures were successfully used as anodes in half- and full-cells. Outstanding cycling and rate performances are attributed to a synergistic effect between the Ni3S2 nanoparticles and interconnected carbon networks. The coherent porous framework effectively alleviated volume changes of Ni3S2, shortened the Na+ diffusion path, and accelerated electron transport and ionic diffusion during the electrochemical reaction. More importantly, conversion reaction products can be confined by the entangled carbon networks, leading to reversible redox reactions as demonstrated in ex situ XRD studies. The coherent Ni3S2/C nanocomposites demonstrated a highly reversible charge capacity of 453 and 430 mA h g−1 at a current density of 0.1 and 0.4 A g−1 over 100 cycles, respectively. At a current density of 2.0 A g−1, high rate capacities of 408 mA h g−1 can be attained over 200 cycles. The high performance of Na3V2(PO4)3/Ni3S2 full-cells enrich prospects for future practical applications.
