The synthesis of Ti3AlC2/TiB2 composites was studied by in-situ spark plasma sintering with different volume content of TiB2. Results indicated the bulk Ti3AlC2/TiB2 was fabricated by SPS, which soaked for 8 min under...
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The synthesis of Ti3AlC2/TiB2 composites was studied by in-situ spark plasma sintering with different volume content of TiB2. Results indicated the bulk Ti3AlC2/TiB2 was fabricated by SPS, which soaked for 8 min under a pressure of 30 MPa at 1250°C. The properties of composites was great increased with the addition of TiB2;the Vicker's hardness increased with addition of TiB2 content, the maximum value is 10.4 GPa. The maximum flexural strength and fracture toughness reached maximum value, which were 696 MPa and 6.6 MPa·m1/2 when the volume content of TiB2 was 10%.
Nafion/Silicon oxide composite membranes were produced via in situ sol-gel reaction of tetraethylorthosilicate （TEOS） in Nafion membranes. The physicochemical properties of the membranes were studied by FT-IR,TG-DSC...
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Nafion/Silicon oxide composite membranes were produced via in situ sol-gel reaction of tetraethylorthosilicate （TEOS） in Nafion membranes. The physicochemical properties of the membranes were studied by FT-IR,TG-DSC and tensile strength. The results show that the silicon oxide is compatible with the Nation membrane and the thermo stability of Nation/Silicon oxide composite membrane is higher than that of Nation membrane. Furthermore, the tensile strength of Nation/Silicon oxide composite membrane is similar to that of the Nation membrane. The proton conductivity of Nation/Silicon oxide composite membrane is higher than that of Nation membrane. When the Nation/Silicon oxide composite membrane was employed as an electrolyte in H2/O2 PEMFC, a higher current density value （1 000 mA/cm^2 at 0.38 V） than that of the Nafion1135 membrane （100 mA/cm^2 at 0.04 V） was obtained at 110 ℃.
Grid computing is an active field in high-availability computing. This paper focuses on the numerical calculation of two-dimensional frequency selective surface using the finite difference time domain (FDTD) method on...
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Grid computing is an active field in high-availability computing. This paper focuses on the numerical calculation of two-dimensional frequency selective surface using the finite difference time domain (FDTD) method on grid-enabled cluster. The result of experiment shows that the evaluation via the parallel FDTD is in good agreement with the result obtained via the traditional FDTD method. The parallel FDTD algorithm is correct and reasonable, which can be extended to other periodic structure and finite exciting sources.
A novel method was used to fabricate AIN coating on graphite substrate. This approach included two steps: firstly, the emulsion composed of BN and anhydrous ethanol was sprayed on the surface of the graphite substrate...
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A novel method was used to fabricate AIN coating on graphite substrate. This approach included two steps: firstly, the emulsion composed of BN and anhydrous ethanol was sprayed on the surface of the graphite substrate; secondly, AIN coating was formed through the in-situ reaction of Al with the sprayed BN. The reaction was investigated by thermogravimetric-differential thermal analysis (TG-DTA), and the phase composition in the synthetic process was characterized by X-ray diffraction (XRD). Scanning electronic microscopy (SEM) was used to observe the morphology, and electron probe microanalysis (EPMA) was used to observe the distribution of the elements. The experimental results show that the AIN coating is dense and bonded with graphite tightly.
Based on the electrochemical model, a simulation model has been developed with Matlab/Simulink. Steady-state analysis has been developed to evaluate how the temperature affect the voltage and output power of the fuel ...
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Based on the electrochemical model, a simulation model has been developed with Matlab/Simulink. Steady-state analysis has been developed to evaluate how the temperature affect the voltage and output power of the fuel cell. Dynamic analysis focus on the dynamic response of the output voltage, the output power, the consumed power, the efficiency and the internal resistance of a single PEMFC when the current of a PEMFC increase or decrease transiently. This simulation model also adapted to the simulation of PEMFC stack. The study is helpful for the optimization and control of PEMFC.
Buffer material plays an important role in the hypervelocity launching experiments. By using numerical calculations, the influence of TPX buffer material's thickness on high impedance tantalum flier plate's ve...
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Buffer material plays an important role in the hypervelocity launching experiments. By using numerical calculations, the influence of TPX buffer material's thickness on high impedance tantalum flier plate's velocity is analyzed, and the optimal thickness of buffer material is also evaluated. For thickness of 0.3 mm and 0.5 mm tantalum flier plate, the relative error of tantalum flier plate's center velocity is about 5%-6% at different thicknesses of the TPX buffer materials. In order to compare the influence of different buffer materials on tantalum flier plate's velocity, the two-dimensional results of tantalum flier plate's center velocity and pressure histories are calculated at the same thickness of TPX and Lexan buffer.
Ti2AlC bulk material was synthesized by hot pressing of mixture powders of TiC, Ti, Al and active carbon. The phase compositions of resultant product at different temperature were detected by X-ray diffractometer. The...
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Ti2AlC bulk material was synthesized by hot pressing of mixture powders of TiC, Ti, Al and active carbon. The phase compositions of resultant product at different temperature were detected by X-ray diffractometer. The microstructures of the samples were observed by SEM. Finally, the mechanical properties and thermal properties of the sample at 1400 ℃ were measured. The results show that high purity Ti2AlC material with little Ti3AlC2 can be synthesized by hot pressing 0.5TiC/1.5Ti/1.0Al/0.5C at 1 400 ℃. Ti2AlC exhibits high mechanical properties and metallic electrical properties. Its fracture toughness is 7.0 MPa·m1/2, its flexural strength is 384 MPa at room temperature, and its electrical conductivity is 2.56×106 Ω1·m-1 at room temperature.
Combustion synthesis of titanium diboride(TiB2) from titanium(Ti) and boron(B) powders was studied by theoretical calculation and experimental analysis. In high temperature range or in low temperature range, the calcu...
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Combustion synthesis of titanium diboride(TiB2) from titanium(Ti) and boron(B) powders was studied by theoretical calculation and experimental analysis. In high temperature range or in low temperature range, the calculated activation energies are 140KJ/mol or 355KJ/mol respectively, which is described by a change from dissolution-precipitation controlled process to diffusion-controlled process. With the increase of particle size of the raw materials, combustion temperature and propagating rate will both reduce. The propagating rate decreases with the addition of diluents. Further increase of diluents may result in a stop of the combustion wave halfway or even a failure of ignition.
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...
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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...
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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.
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