The transition-metal carbide cemented by metal has excellent combined properties. In this study, cermets were prepared by vacuum sintering from carbide-metal composite powders. The transition- metal oxides (Cr 2O3, Mo...
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The transition-metal carbide cemented by metal has excellent combined properties. In this study, cermets were prepared by vacuum sintering from carbide-metal composite powders. The transition- metal oxides (Cr 2O3, MoO3, V2O5, Nb 2O5 and TiO2), cementing-metal oxides (Co 3O4 and NiO), and carbon black were used as raw materials to pre-synthesize composite powders such as Cr3C2-Co, Mo2C-Co, VC-Co, NbC-Co and TiC-Ni, by a direct reduction and carburization process in vacuum. Results show that the participation of Co 3O4 and NiO as well as the vacuum circumstance were greatly propitious to the carburization of transition-metal oxides into carbides. The carbothermal condition was greatly improved by the direct reduction and carburization process.
A series of samples of hexagonal boron nitride-aluminum nitride (10-90, 15-85, 20-80, 25-75, 30-70wt.%) ceramic composites were prepared by spark plasma sintering in a nitrogen atmosphere at 1650°C-1800°C fo...
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A series of samples of hexagonal boron nitride-aluminum nitride (10-90, 15-85, 20-80, 25-75, 30-70wt.%) ceramic composites were prepared by spark plasma sintering in a nitrogen atmosphere at 1650°C-1800°C for 5min. Different amounts of CaF2 were added as sintering aids. The effects of CaF2 and sintering temperature on densification and dielectric properties were discussed. The addition of CaF2 enhances relative dielectric constant and loss tangent of the samples. The increase in sintering temperature promotes the densification and decreases the dielectric loss tangent. When being sintered at 1700°C, the relative density, dielectric constant and dielectric loss tangent of the sample with 15wt.%BN are 98.04%, 7.15 and 6.31×10-4 respectively.
Composite magnetic particles (CMPs) with carbonyl iron (CI) core and N-glucose ethylenediamine triacetic acid (GED3A) shell were prepared by an in-situ chelating reaction, where the CI surface was coated with GED3A. A...
Composite magnetic particles (CMPs) with carbonyl iron (CI) core and N-glucose ethylenediamine triacetic acid (GED3A) shell were prepared by an in-situ chelating reaction, where the CI surface was coated with GED3A. And novel kind of aqueous magnetorheological (MR) fluids were prepared with thus obtained CMPs. The properties of CMPs, including morphology, structure, and magnetic behaviours were characterized, and the magnetorheological properties of the MR fluids were analyzed via a strain-controlled rheometer. It was found that the MR fluids exhibited high shear stress and quick response rate to magnetic field. Furthermore, the dispersion stability and the anti-oxidation property were substantially improved as revealed by stability test.
Solvothermal synthesis has been explored to prepare Sb2Te3 material in the solvent of DMF. The effect of reaction temperature and time on the phase composition and micro-structure have also been studied. The structure...
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Solvothermal synthesis has been explored to prepare Sb2Te3 material in the solvent of DMF. The effect of reaction temperature and time on the phase composition and micro-structure have also been studied. The structure and morphologies of nano-powders were investigated by XRD, SEM, TEM, and EDS observations. The growth mechanism of Sb2Te3 crystal has been researched. The results indicate that the particle size of the powders significantly increase with the escales temperature and the increasing time. At the temperature of 180 degree and maintaining for 24 hours, Sb2Te3 powder of hexagonal crystal was yielded.
ZnO whiskers were grown by a simple vapor-phase approach by using microwave energy without any catalyst in a very short time. The result of the XRD indicates that the production structure was wurtzite. The SEM shows s...
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ZnO whiskers were grown by a simple vapor-phase approach by using microwave energy without any catalyst in a very short time. The result of the XRD indicates that the production structure was wurtzite. The SEM shows some are rod crystals, the other are tubes with 50 μm diameter and 500 μm length. The photoluminescence (PL) exhibits strong ultraviolet emission (wavelength is 360 nm) and blue emission (wavelength is 470 nm) at room temperature. Experiments indicate that the temperature gradient is very important for the ZnO whiskers growth by using vapor phase. The temperature gradient between conventional and microwave heating is different.
In this paper, we presented a novel route for fabricating Ti 3SiC2-based and Ti3AlC2-based solid solutions with mixed powders of TiC/Ti/Si/Al in different molar ratios. The phase compositions of these solid solutions ...
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In this paper, we presented a novel route for fabricating Ti 3SiC2-based and Ti3AlC2-based solid solutions with mixed powders of TiC/Ti/Si/Al in different molar ratios. The phase compositions of these solid solutions were studied by XRD and the stoichiometrics of these compounds were determined to be Ti 2.63Si0.87Al0.13C2 and Ti 2.76Al0.78Si0.22C2 by EDS. We also investigated the electronic properties and mechanical properties of these two ceramics. The results showed that the dopants were not only beneficial to the fabrication of Ti3SiC2 and Ti3AlC2 but also improved the properties of these two ceramics.
Ca(Al1/2Nb1/2)O3 (CAN) and Ca(Fe 1/2Nb1/2)O3 (CFN) were prepared by solid reaction route. With the sintering temperature increased, the Q15;f value of CAN changes from 7 200 to 17 500 GHz due to the changing of the...
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Ca(Al1/2Nb1/2)O3 (CAN) and Ca(Fe 1/2Nb1/2)O3 (CFN) were prepared by solid reaction route. With the sintering temperature increased, the Q×f value of CAN changes from 7 200 to 17 500 GHz due to the changing of the ordering degree, whereas, the dielectric constant and Q×f value of CFN decrease remarkably without structural changing. The reason of this phenomenon is that the difference in size of two B-site ions in CAN is larger than that in CFN. As a result, the ordering degree of CAN is more sensitive to the conditions of sample preparation, compared with CFN.
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