Low or zero thermal expansion porous ceramics are required for several applications. In this work near zero thermal expansion porous ceramics were fabricated by using SiC and ZrW2O8 as positive and negative thermal ex...
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Low or zero thermal expansion porous ceramics are required for several applications. In this work near zero thermal expansion porous ceramics were fabricated by using SiC and ZrW2O8 as positive and negative thermal expansion materials, respectively, bonded by soda lime glass. The mixture of SiC, ZrW2O8 and soda lime glass was sintered by Pulsed Electric Current Sintering (PECS, or sometimes called Spark Plasma Sintering, SPS) at 700°C. Sintered samples with ZrW2O 8 particle size smaller than 25 μm have high thermal expansion coefficient, because ZrW2O8 has the reaction with soda lime glass to form Na2ZrW3O12 during sintering process. The reaction between soda lime glass and ZrW2O8 is reduced by increasing particle size of ZrW2O8. Sintered sample with ZrW2O8 particle size 45-90 μm shows near zero thermal expansion.
Cross-linked polystyrene/glass fiber composites were fabricated using cross-linked polystyrene （CLPS） as matrix and E-glass fiber as the reinforcement. Surfaces of E-glass fibers were modified by vinyl triethoxysila...
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Cross-linked polystyrene/glass fiber composites were fabricated using cross-linked polystyrene （CLPS） as matrix and E-glass fiber as the reinforcement. Surfaces of E-glass fibers were modified by vinyl triethoxysilane （VTES）, vinyl trimethoxysilane （VTMS） and γ-methacryloylpropyl trimethoxysilane （MPS）. The treated glass fibers were analyzed by fourier transform infrared spectroscopy （FTIR）. Dynamic mechanical thermal analysis （DMTA） and thermo-gravimetric analysis （TGA） were employed to investigate the effect of glass fibers surface modification on viscoelastic behavior and thermal properties. The morphology of fracture surfaces of various composites was observed by scanning electron microscopy （SEM）. The results revealed that these coupling agents were connected to the surfaces of the fibers by chemical bonding. Dynamic mechanical properties as well as thermal stability of the composites were improved considerablely, but to varying degrees depending on the fiber modification. The diversities of improvement of properties were attributed to the different interfacial adhesion between CLPS matrix and the glass fibers.
Zinc oxide hexagonal tubular crystals were synthesized by direct microwave heating from ZnO powders within 5 min without any metal catalysts or transport agents. ZnO source materials were evaporated from the high-temp...
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Zinc oxide hexagonal tubular crystals were synthesized by direct microwave heating from ZnO powders within 5 min without any metal catalysts or transport agents. ZnO source materials were evaporated from the high-temperature zone in an enclosure, and crystals were grown on the self-source substrate in an appropriate condition. The ZnO vapor formed in the high-temperature zone can deposit and grow on the powders located in the low-temperature zone to form crystals. The scanning electron microscopy （SEM） reveals that these products are hexagonal tube crystals with 80 ~rn in diameter and 250 μm in length, having a well faceted end and side surface. A possible growth mechanism and the influence of reaction temperature on the formation of crystalline ZnO hexagonal tubes were presented. The photoluminescence （PL） exhibits strong ultraviolet emission at room temperature, indicating the potential applications in short-wave light-emitting photonic devices.
Nanocrystalline titanium dioxide powder was synthesized by in-flight oxidation of titanium dihydride （TiH2） powder in a thermal plasma jet. TiH2 powder was injected into the thermal plasma jet and allowed to react w...
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Nanocrystalline titanium dioxide powder was synthesized by in-flight oxidation of titanium dihydride （TiH2） powder in a thermal plasma jet. TiH2 powder was injected into the thermal plasma jet and allowed to react with oxygen injected downstream the jet. Characteriza- tion of the powder by various analytical tools indicated that the powder consisted of nano-sized titanium dioxide particles consisting predominantly of the anatase phase. It is suggested that the thermo-chemistry of the oxidation process contributes significantly to the formation of nano-sized titania. The large energy released during the oxidation process dissociates the TiO2 particles into TiO（g） and titanium vapour, which recombine downstream with oxygen and form nano particles of TiO2.
The B4C-ZrB2-SiC ternary composites with super hard and high toughness were obtained by arc melting in argon atmosphere. Microstructures were observed by SEM, and phase compositions were analyzed by XRD. The hardness ...
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The B4C-ZrB2-SiC ternary composites with super hard and high toughness were obtained by arc melting in argon atmosphere. Microstructures were observed by SEM, and phase compositions were analyzed by XRD. The hardness and fracture toughness of ternary composites are 28GPa and 4.5MPa-m1/2. The eutectic mole composition is 0.39B4C-0.25ZrB2-0.36SiC, and the eutectic lamellar microstructure is composed of B4C matrix with the lamellar ZrB2 and SiC grains.
Using steel slag and charcoal as raw materials, the steel slag/charcoal nano-/micro-composites with magnetic-resistance mixed loss mode were fabricated by a high-performance milling process, and then the composition, ...
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Using steel slag and charcoal as raw materials, the steel slag/charcoal nano-/micro-composites with magnetic-resistance mixed loss mode were fabricated by a high-performance milling process, and then the composition, phase structure, morphology, and electromagnetic (EM) characteristics of the products were characterized by XRD, EDS, SEM, and vector network analyzer, respectively. The results showed that EM characteristics of the products were strongly dependent on the content of the charcoal (WCharcoal). The real and imaginary parts of the permittivity of the steel slag/charcoal nano-/micro-composites significantly increased with the increasing WCharcoal. Among them, the steel slag/charcoal composites with WCharcoal=50wt% exhibited the best EM-wave absorption performance, with a maximum reflectivity value of -33.4dB, the effective bandwidth 15.2GHz(<-10dB) and 8.6 GHz (<-20 dB), respectively, which is a consequence of enhanced dielectric loss and a proper EM matching.
作者：
Fangjun XuGuangze TangXinxin MaSun MingrenLiqin WangKen YukimuraG.E.OzurSchool of Material Science & Engineering
Harbin Institute of Technology Harbin 150001 China National Key Laboratory of Science and Technology on Precision Hot Processing of Metals Harbin Institute of Technology Harbin 150001 China State Key Lab of Advanced Welding Production Technology Harbin Institute of Technology Harbin150001China School of Mechatronics Engineering Harbin Institute of Technology Harbin 150001 China School of Material Science & Engineering Harbin Institute of Technology Harbin 150001 China Institute of High Current Electronics 4 Academichesky Av. Tomsk 634055 Russia State Key Lab of Advanced Welding Production Technology
Harbin Institute of Technology Harbin150001China
In the present study, (1-x)(Sr_(0.88)Bi_(0.08))TiO_(3)-xBi(Mg_(0.5)Ti_(0.5))O_(3) (SBT-BMT) system was synthesized using conventional solid stateprocessing. X-ray diffraction (XRD) and SEM testings were employed to d...
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ISBN:
(纸本)9781457711626
In the present study, (1-x)(Sr_(0.88)Bi_(0.08))TiO_(3)-xBi(Mg_(0.5)Ti_(0.5))O_(3) (SBT-BMT) system was synthesized using conventional solid stateprocessing. X-ray diffraction (XRD) and SEM testings were employed to determine the phase constitution and microstructure of ceramics. SBT-BMT ceramics exhibited moderate dielectric permittivities ((epsilon)_(r)) (>1100 at RT) and low dielectric loss (0.07percent) over the temperature range from -20 to 200 deg C, with flat temperature coefficients of permittivity. In addition, SBT-BMT ceramics were observed to possess dielectric relaxation characteristics and energy densities, being on the order of 1.4 J/cm~(3) at 180 kV/cm was observed for the 0.8S_(0.88)B_(0.08)T-0.2BMT ceramics.
ZnO/SnO2 composite films were prepared on electro-conductive glass substrate by an electrophoretic deposition (EPD) method and were further characterized by SEM and XRD. The results showed that the optimum deposition ...
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ZnO/SnO2 composite films were prepared on electro-conductive glass substrate by an electrophoretic deposition (EPD) method and were further characterized by SEM and XRD. The results showed that the optimum deposition time for obtaining compact and uniform films is about 20min, and these films with 20 min deposition min showed the highest photocatalytic activity (0.016 min-1) for photocatalytic decolorization of Rhodamine-B aqueous solution. A hetero-junction structure composed of ZnO and SnO2 is formed and makes it easier for exitons to be separated and result in a higher activity. Moreover, the effects of calcination temperature on the photocatalytic activity of ZnO/SnO2 composite films were further investigated. The decoloring rate will be decreased as raising the calcination temperature, and at 300°C, the ZnO/SnO2 composite films showed the highest photocatalytic activity.
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