Sintering behavior, microstructure and microwave dielectric properties of Ba1+x(Mg1/3Nb2/3)O3 (-0.01 [less-than or equal to] x [less-than or equal to] 0.01) were investigated. An improvement of the degree of 1:2 order...
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Sintering behavior, microstructure and microwave dielectric properties of Ba1+x(Mg1/3Nb2/3)O3 (-0.01 [less-than or equal to] x [less-than or equal to] 0.01) were investigated. An improvement of the degree of 1:2 ordering and sinterability was found in Ba-deficient Ba(Mg1/3 Nb2/3)O3 because there existed Ba vacancies. Excessive Ba inhibits the sintering and the degree of 1:2 ordering. It was proposed that excessive Ba exist in grain boundary and inhibit the movement of grain boundary. Therefore, the sintering was restrained. Ba-deficiency had little effect on dielectric constant of Ba(Mg1/3Nb2/3)O3 ceramics. With Ba-deficiency increasing, Qf value decreased drastically.
In this paper the inflaming retarding effects of epoxy resins blended with basic magnesium carbonate [Mg(OH)2·4MgCO3·5H2O] were synthesized. When the add-on of basic magnesium carbonate reached 56.5%, the LO...
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In this paper the inflaming retarding effects of epoxy resins blended with basic magnesium carbonate [Mg(OH)2·4MgCO3·5H2O] were synthesized. When the add-on of basic magnesium carbonate reached 56.5%, the LOI of the epoxy resins increased to 29.7%. The flame retardant mechanisms of basic magnesium carbonate for epoxy resins was investigated by XRD, TG-DSC and SEM. Results showed that through the ways of diluting, cooling, isolating and their synergies, basic magnesium carbonate achieves the flame retarding target.
The laser cladding technique was used to form Ni3 (Si, Ti) composite coating reinforced by in-situ formation TiC particles on GH864 Ni-based alloy substrate. By means of SEM, EDAX and XRD, the effect of (Ti + C) addit...
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The laser cladding technique was used to form Ni3 (Si, Ti) composite coating reinforced by in-situ formation TiC particles on GH864 Ni-based alloy substrate. By means of SEM, EDAX and XRD, the effect of (Ti + C) addition on the microstructure and microhardness of the coating was investigated. The experimental results show that an excellent bonding between the coating and the substrate can be ensured by the strong metallurgical interface. The clad coating is very good and free from cracks and pores. The microstructure of the coating is mainly composed of Ni (Si), Ni3 (Si, Ti) and TiC. The average microhardness of the coating is improved in terms of addition quantity of TiC in coating structure. When the addition quantity of (Ti + C) is 20wt%, the microhardness of coating was up to 780Hv that is 2.4 times of the substrate.
The air plasma spray (APS) technology was used to prepare WC/NiCrAl and WC/NiCrBSi ceramic/metal composite wear preventive coating on cast iron substrate. The microstructure, microhardness, bond strength and slurry we...
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The air plasma spray (APS) technology was used to prepare WC/NiCrAl and WC/NiCrBSi ceramic/metal composite wear preventive coating on cast iron substrate. The microstructure, microhardness, bond strength and slurry wear preventive performance of coating was measured. The results revealed that all of the coating prepared by APS has good qualities. The coating with NiCrBSi as its combining metal is better than that with NiCrAl on wear preventive performance, and coating containing more WC is supreme than that containing less WC Finally, wear mechanics and the principle of the coating's wear preventive property was concluded.
Based on a high power CO2 laser beam passing by pyramid polygon mirror, the bioceramic coatings of gradient composition were fabricated on titanium alloy substrate (Ti-6A1-4V). The relations among laser processing par...
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Based on a high power CO2 laser beam passing by pyramid polygon mirror, the bioceramic coatings of gradient composition were fabricated on titanium alloy substrate (Ti-6A1-4V). The relations among laser processing parameters, microstructure and biocompatibility of the gradient bioceramic coatings were investigated. The results indicated that the contents of rare earth oxide additions had an immediate effect on the formation of bioactive phases. The gradient bioceramic coatings showed favorable biocompatibility in vivo after they were implanted into canine femur for 45, 90, and 180 days, respectively. The bioceramic coatings of Ca/P=1.4 and 0.6wt.% Y 2O3 totally combined with new bones merely implanted for 45 days. Furthermore, the MTT (Methyl Thiazolyl Tetrazolium) colorimetry results of cell proliferation demonstrated that the cell growth distinctly increased on the gradient bioceramic coatings by laser cladding compared with the un-treated titanium alloy substrate.
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.
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...
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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.
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.
The thermoelectric energy conversion efficiency of the thermoelectric generator devices not only depends on the figure of merit of the materials, but also on the temperature distribution in the device. However, each s...
The thermoelectric energy conversion efficiency of the thermoelectric generator devices not only depends on the figure of merit of the materials, but also on the temperature distribution in the device. However, each single thermoelectric material is only suitable for a narrow range of temperature and no single thermoelectric material is suitable for use over a very wide range of temperatures (∼300–800 K). Recently, the concept of integrating new thermoelectric materials into a segmented thermoelectric unicouple has been introduced. In the present paper, the thermal stresses of CoSb3/Bi2Te3 thermoelectric unicouple subjected to thermal cyclic loading are simulated by finite element method. The results show that the maximum thermal tensile stress would reach about 180 MPa or even higher because of the mismatch of the theromechanical properties of the CoSb3 and Bi2Te3. This means that the device cannot work as the tensile strength of CoSb3 is about 100 MPa. In order to improve the performance, the graded interlayers are inserted to reduce the thermal stresses. It is shown that the thermal stresses in the thermoelectric device with graded interlayers would reduce to about 100 MPa.
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