1wt% multiwalled carbon nanotube （MWNTs） reinforced alumina composites was sintered to full density by spark plasma sintering. And pure alumina and graphite/alumina composites were also prepared by the same way for ...
详细信息
1wt% multiwalled carbon nanotube （MWNTs） reinforced alumina composites was sintered to full density by spark plasma sintering. And pure alumina and graphite/alumina composites were also prepared by the same way for comparison. Indentation and single edge V-notched beam （SEVNB） toughness were measured respectively. The experimental results show that MWNTs could not improve toughness of alumina too much as that once expected. And SEVNB toughness was more valid than indentation toughness.
MgO thin films were deposited on Si（100） substrates by laser ablation under various substrate temperatures （Tsub）,expecting to provide a candidate buffer layer for the textured growth of functional perovskite oxid...
详细信息
MgO thin films were deposited on Si（100） substrates by laser ablation under various substrate temperatures （Tsub）,expecting to provide a candidate buffer layer for the textured growth of functional perovskite oxide films on Si *** effect of Tsub on the preferred orientation,crystallinity and surface morphology of the films was *** films in single-phase were obtained at 473-973 *** increasing Tsub,the preferred orientation of the films changed from （200） to （111）.The crystallinity and surface morphology was different too,depending on *** Tsub=673 K,the MgO film became uniform and smooth,exhibiting high crystallinity and a dense texture.
The effects of different sintering addictives on the preparation of CaF2 transparent ceramics were studied. Transparent CaF2 ceramics were fabricated by vacuum sintering and hot isostatic pressing （HIP） method, usin...
详细信息
The effects of different sintering addictives on the preparation of CaF2 transparent ceramics were studied. Transparent CaF2 ceramics were fabricated by vacuum sintering and hot isostatic pressing （HIP） method, using CaF2 nanopowders synthesized by chemical precipitation method as raw materials. The nanopowders and transparent ceramics were studied using X-ray diffraction, transmission electron microscopy （TEM）, scanning electron microscopy （SEM） and spectrophotometer. The experimental results indicated that the obtained nanopowders presented normal distribution with grain size about 30 nm; transmittance of CaF2 transparent ceramics was 39% and 26% at 1100 nm for LiF and NaF as sintering addictives, respectively, with corresponding mean grain size 188 μm and 44 μm. Loss of transmission could be attributed to the residual closed porosity. Sintering mechanism was liquid-phase sintering at pre-stage, then solid-phase sintering at later stage, as well as solid solution of lithium ions and sodium ions in the CaF2 lattice structure.
Various parameters in spark plasma sintering（SPS）,such as sintering temperature,holding time,heating rate,and pressure,were adopted to investigate their effects on the densification of pure SnO2 *** obtained experim...
详细信息
Various parameters in spark plasma sintering（SPS）,such as sintering temperature,holding time,heating rate,and pressure,were adopted to investigate their effects on the densification of pure SnO2 *** obtained experimental data show that the SPS process enhances *** high-density undoped SnO2 ceramics （96.6% of theoretical） was obtained at much lower temperature （1000℃）,within a much shorter time,compared to the conventional sintering *** high-density undoped SnO2 ceramics （96.6% of theoretical） were obtained by SPS,under the condition of temperature：1000℃,pressure：40MPa,heating-rate：200℃/min,and holding time：3min
Nanocomposites offer a promising approach to the incorporation of nanostructured constituents into bulk thermo- electric materials. The 0.7-at% Bi-doped Mg2Si nanocomposites are prepared by spark plasma sintering of t...
详细信息
Nanocomposites offer a promising approach to the incorporation of nanostructured constituents into bulk thermo- electric materials. The 0.7-at% Bi-doped Mg2Si nanocomposites are prepared by spark plasma sintering of the mixture of nanoscale and microsized 0.7-at% Bi-doped Mg2Si powders. Microstructure analysis shows that the bulk material is composed of nano- and micrograins. Although the nanograin hinders electrical conduction, the nanocomposite struc- ture is more helpful to reduce thermal conductivity and increase the Seebeck coefficient, hence improving thermoelectric performance. A dimensionless figure of merit of 0.8 is obtained for the 0.7-at% Bi-doped Mg2Si nanocomposite with 50-wt % nanopowder, which is about twice larger than that of the sample without nanopowder.
This thesis designs embedded control system for Consumable DE-GMAW, the system based on 32bits ARM7 microcontroller LPC2124 could real time collect and display welding parameters, and the system could control bypass a...
详细信息
This thesis designs embedded control system for Consumable DE-GMAW, the system based on 32bits ARM7 microcontroller LPC2124 could real time collect and display welding parameters, and the system could control bypass arc and metal current, ensure welding process stability. All modules of the system could perform serial communication based on RS-485 interface and Modbus protocol. This design has been simulated by the Proteus software, the system could output require PWM waveform in simulation process. Simulation result principally proves that design scenario of Consumable DE-GMAW embedded control system is practicable, and it can work well in simulation platform, lay the foundation for reality process control.
In this paper, Mo and Cu were welded together by diffusion welding with or without a Ni interlayer. SEM, EDS, EPMA, XRD were used to characterize the structure and the element distribution of the interface zone. The r...
详细信息
In this paper, Mo and Cu were welded together by diffusion welding with or without a Ni interlayer. SEM, EDS, EPMA, XRD were used to characterize the structure and the element distribution of the interface zone. The results showed that the Mo/Cu joint combined homogeneously by diffusion welding, the diffusion layer formed at the interface due to Mo atoms and Cu atoms inter-diffusion. There were some micro-voids on the copper side of the joint due to the role of kirkendall effect, and the voids reduced the performance of the joint. For the Mo/Ni/Cu joint, Mo/Ni and Ni/Cu interface were linked together, and the tensile strength of the Mo/Ni/Cu joint was higher than the Mo/Cu joint, because the added nickel eased the thermal stress of the joint. A solid solution was formed at the Mo/Ni interface where a joint brittle fracture took place.
The band structure of Mg2Si1−xSnx solid solutions with 0.250 ⩽ x ⩽ 0.875 is calculated using the first-principles pseudopotential method. It is found that the low-lying light and heavy conduction bands converge and th...
The band structure of Mg2Si1−xSnx solid solutions with 0.250 ⩽ x ⩽ 0.875 is calculated using the first-principles pseudopotential method. It is found that the low-lying light and heavy conduction bands converge and the effective mass reaches a maximum value near x = 0.625. Using the semiclassical Boltzmann transport theory and relaxation-time approximation, we find that the system with x = 0.625 exhibits both higher Seebeck coefficient and higher electrical conductivity than other solid solutions at intermediate temperatures. By fitting first-principles total energy calculations, a modified Morse potential is constructed, which is used to predicate the lattice thermal conductivity via equilibrium molecular dynamics simulations. Due to relatively higher power factor and lower thermal conductivity, the Mg2Si0.375Sn0.625 is found to exhibit enhanced thermoelectric performance at 800 K, and additional Sb doping is considered in order to make a better comparison with experiment results.
The effect of calcination temperatures on the active species of WO 3 /SiO 2 catalysts for propylene production from metathesis of ethylene and 2-butene was studied to elucidate the structure-reactivity *** influence o...
详细信息
The effect of calcination temperatures on the active species of WO 3 /SiO 2 catalysts for propylene production from metathesis of ethylene and 2-butene was studied to elucidate the structure-reactivity *** influence of calcination temperatures on catalyst physicochemical properties,relating to the active species,was summarized from an array of characterization *** has been found that the surface tetrahedral tungsten species with high metal support interaction were formed on the catalyst calcined at 550℃ as confirmed by Raman,UV-Vis and H 2-TPR spectra,respectively.
暂无评论