It is very difficult to prepare full-densified aluminum nitride-boron nitride （AIN/BN） composite ceramics with homogeneous microstructure and high thermal conductivity. Spark plasma sintering （SPS） was used to ful...
详细信息
It is very difficult to prepare full-densified aluminum nitride-boron nitride （AIN/BN） composite ceramics with homogeneous microstructure and high thermal conductivity. Spark plasma sintering （SPS） was used to fully densify the AIN/BN composites in this work. Microstructure, mechanical properties and thermal conductivity of the SPS sintered AIN/BN composites with 5-30 vol% BN were investigated. The results show that the microstructure of composites is fine and homogenous, and the AIN/BN composites exhibit high mechanical properties. To promote the growth of AIN grains and modify the distribution of grain boundary in AIN/BN composites, a heat treating methodology was introduced through gas pressure sintering （GPS）. This processing was significantly beneficial to enhancing the thermal conductivity of the specimen. The thermal conductivity of AIN/BN composites with 5-30 vol% BN reached 60 W/m K after the samples were treated by GPS.
Water transport in membrane plays an important role in PEM fuel cell performance. Therefore research on water transport in membrane is extremely essential. This article established a 3D single fuel cell model with ser...
详细信息
Water transport in membrane plays an important role in PEM fuel cell performance. Therefore research on water transport in membrane is extremely essential. This article established a 3D single fuel cell model with serpentine flow field. The influences of the operating temperature, membrane thickness, air stoichiometry, relative humidity, operating pressure and current density on the water content in membrane under low current density are studied, and then the influence of the above parameters on the performance of fuel cell is obtained. The results show that: As the temperature rises, the water content will increased and then lower. Reducing the proton exchange membrane thickness and air stoichiometry, increasing the relative humidity, pressure and current density operation, the water content in the membrane will increase, the conductivity will increase and thus will improve the performance of the fuel cell.
In order to investigate the influence of gas diffusion layer (GDL) structure on the drainage, electric and gas conductivity of proton exchange membrane fuel cell(PEMFC), such factors as electrochemical reaction, phase...
详细信息
In order to investigate the influence of gas diffusion layer (GDL) structure on the drainage, electric and gas conductivity of proton exchange membrane fuel cell(PEMFC), such factors as electrochemical reaction, phase change, transfer of water and oxygen, and water transfer in membrane are investigated, and GDL with spacing porosity in plane is also studied. Results show that the performance of PEMFC with GDL with spacing porosity is better than that of PEMFC with normal GDL. GDL with spacing porosity in plane can improve the transfer of liquid water and gas and then improve the performance of PEMFC.
Phase-based matching is a key technique for optical measurements using projected grating pattern analysis. The matching accuracy determines the final 3-D reconstruction accuracy. However, the reconstruction accuracy o...
详细信息
Phase-based matching is a key technique for optical measurements using projected grating pattern analysis. The matching accuracy determines the final 3-D reconstruction accuracy. However, the reconstruction accuracy of integer-pixel matching is relatively low. A sub-pixel matching algorithm was developed based on phase linear interpolation assuming a linear phase distribution between adjacent pixels. Simulation results indicate that the proposed sub-pixel matching algorithm improves the final 3-D reconstruction accuracy with high processing speed. Verification experiments show that the accuracy can reach 0.03 mm. A 3-D surface measurement system utilizing the sub-pixel matching algorithm can provide very high accuracy.
Based on the theory of photonic crystal and its characteristic, which was known as photonic band gap (PBG), the finite-difference time-domain (FDTD) method, including absorbing boundary condition and periodic boundary...
详细信息
Based on the theory of photonic crystal and its characteristic, which was known as photonic band gap (PBG), the finite-difference time-domain (FDTD) method, including absorbing boundary condition and periodic boundary condition, was used to simulate transmission characteristic of two-dimensional photonic crystal, which has periodic Al2O3 cylinder array structure. Incident wave was presumed as s-polarized wave. In two incident angles which were 0° and 30°, electric field, phase and transmissivity in the range of 1-30 μm were calculated. Numerical simulation results showed that PBG of photonic crystal existed in the range 12-18 μm (infrared waveband), and it may be used to develop infrared wave-guide.
A novel process was introduced in this paper for the diameter-controlling synthesis of carbon nanofibers (CNFs) in the ethanol flames. The carbon nanofibers were grown on a nanocrystalline Fe layer, which was electro-...
A novel process was introduced in this paper for the diameter-controlling synthesis of carbon nanofibers (CNFs) in the ethanol flames. The carbon nanofibers were grown on a nanocrystalline Fe layer, which was electro-deposited on a substrate using periodic reverse (P.R.) pulse plating. It was found that the quality of the plating nanocrystalline and the corresponding carbon nanofibers was related with two plating parameters: output pulse frequency ( f ) and duty cycle ( r ). In addition to that the straight and helical carbon nanofibers were selectively synthesized by addition of different additives in plating bath. In this paper, the base-growth mechanism of carbon nanofibers was clearly discussed.
Polycrystalline samples of Sm partially filled skutterudites SmyFexCo4-xSb12 were prepared by melting and Spark Plasma Sintering technique. The results of Rietveld refinement showed that the obtained SmyFexCo4-xSb12 s...
详细信息
Polycrystalline samples of Sm partially filled skutterudites SmyFexCo4-xSb12 were prepared by melting and Spark Plasma Sintering technique. The results of Rietveld refinement showed that the obtained SmyFexCo4-xSb12 samples possessed filled skutterudite structures. The thermal parameter （B） of Sm is larger than that of Sb, Fe, and Co, indicating that Sm ＂rattled＂ in Sb-icosahedron voids. The effects of filling atom Sm on thermoelectric properties of these compounds were investigated. With the increase of Sm filling fraction （y）, electrical conductivity decreased, Seebeck coefficient increased and had a maximum value when y was 0.38; thermal conductivity reduced and had a minimum value when y was 0. 32. At 750 K, the highest figure of merit of 0.68 was obtained for Sm0.32Fe1.47Co2.53Sb12.
作者：
CAO MingHe TIAN Wei LI MingFa SUN WenHua HU MingJi LIU HanXingState Key Laboratory of Advanced Technology for Materials Synthesis and Processing
Wuhan University of Technology Wuhan 430070 China State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of Technology Wuhan 430070 China State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of Technology Wuhan 430070 China State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of Technology Wuhan 430070 China State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of Technology Wuhan 430070 China State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of Technology Wuhan 430070 China
The NaNbO3 powders were synthesized and their crystal structure changes were analyzed by ultrahigh pressure up to 6 *** results indicate that the pure NaNbO3 powders can be synthesized at 300℃ under a pressure of 4 G...
详细信息
The NaNbO3 powders were synthesized and their crystal structure changes were analyzed by ultrahigh pressure up to 6 *** results indicate that the pure NaNbO3 powders can be synthesized at 300℃ under a pressure of 4 GPa, to sig- nificantly restrain the Na element volatilization compared with the traditional syn- thesis method. It is found that the crystal structure of synthesized NaNbO3 changes from low symmetry to high symmetry with the increase of the pressure.
The spores of Ganoderma lucidum were ground and broken to ultrafine particles by high speed centrifugal shearing（HSCS） pulverizer. The characteristics of Ganoderma lucidum spores were analyzed by scanning electron m...
详细信息
The spores of Ganoderma lucidum were ground and broken to ultrafine particles by high speed centrifugal shearing（HSCS） pulverizer. The characteristics of Ganoderma lucidum spores were analyzed by scanning electron microscope （SEM）, Fourier transform infrared spectrophotometry （FTIR）. Ultraviolet-visible pectrophotometer was used to determine the extraction ratio of aqueous solubility polysaccharide between the raw and broken spores. The immunological function on the mice before and after the breaking of spores wan investigated. The experimental results show that after being ground, the sporoderm-broken ratio reachs 100%, the original active ingredients of ganoderma lucidum spores do not change, and the extraction ratio of aqueous solubility polysaccharide is greatly increased by 40.08%. The broken spores show much higher immunological activity comparing with original spores of Ganoderma lucidum.
暂无评论