P-type Ba 8 Ga 16 Cd x Ge 30-x (x=0.95, 1.00, 1.05, 1.10) type-I clathrates with different Cd contents were synthesized by combining melt method with spark plasma sintering (SPS). The effects of Cd content on electri...
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P-type Ba 8 Ga 16 Cd x Ge 30-x (x=0.95, 1.00, 1.05, 1.10) type-I clathrates with different Cd contents were synthesized by combining melt method with spark plasma sintering (SPS). The effects of Cd content on electrical transport properties have been investigated. The results show that all samples exhibit p-type conduction. The Seebeck coefficient alpha and room temperature carrier mobility mu H decrease with the increasing Cd content. The electrical conductivity sigma and the room temperature carrier concentration N p increase with the increase of Cd content. In the low temperature range (T<150 K), the carrier scattering mechanism is mainly ionized impurity mechanism, and gradually changes to an acoustical mechanism with the rising temperature. The maximum power factor value of 0.35times10 -3 Wm -1 K -2 is obtained at 550 K for Ba 8 Ga 16 Cd 1.00 Ge 29.00 .
After combining the PVDF and BST powders with different particle sizes, the anti-voltage strengths of composites was tested. Although the concentrates of ceramic were all the same, their anti-voltage strengths were di...
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After combining the PVDF and BST powders with different particle sizes, the anti-voltage strengths of composites was tested. Although the concentrates of ceramic were all the same, their anti-voltage strengths were distinguished. The results showed that the bigger particles or less thickness of material could benefit to the anti-voltage strength and ultimately enhanced the energy storage density of composites. Moreover, the distribution of particle dimension also influenced the strengths of materials. Composite with homogeneous particles performed higher strength than that of composites with inhomogeneous particles.
Cubic Boron Nitride powder was heat treated in N2 or in vacuum at different temperatures and dwell time. Its phase composition and morphology were investigated by means of X-ray diffraction (XRD) and scanning electron...
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Cubic Boron Nitride powder was heat treated in N2 or in vacuum at different temperatures and dwell time. Its phase composition and morphology were investigated by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis. Results showed that the cubic Boron Nitride was transformed into hexagonal phase after heat treatment in N2 at 1350°C for 10 h, or in vacuum (pressure = 1-5 Pa) at 1550°C for 5 h, while no changes occurred in particle size and morphology.
A kind of gradient thermal and environmental barrier coating applied in internal combustion engine is brought forward to improve its reliability, emission and efficiency. The multi-layer plate and cylinder models are ...
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A kind of gradient thermal and environmental barrier coating applied in internal combustion engine is brought forward to improve its reliability, emission and efficiency. The multi-layer plate and cylinder models are established for the simulations of heat transfer and thermal stress in the coatings. Both the theoretical and the numerical analysis with multi-layer cylinder model with coating inside are carried out and compared. The results show good agreement.
Permittivity and anti-voltage ability commonly determined the energy storage density of material. Although composite could be molded easier than ceramic, its lower energy storage density prevented the material from ap...
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Permittivity and anti-voltage ability commonly determined the energy storage density of material. Although composite could be molded easier than ceramic, its lower energy storage density prevented the material from application since the polymer usually took on poor dielectric constant. In order to enhance the energy storage performance of composite, PAn was introduced to PVDF by emulsion polymerization. SEM of the co-polymers showed that they could construct continuous media till the concentrate of aniline reached 25% while polymerizing. The permittivity of polymer rose along with the concentrate increasing of aniline and pH falling value of retreating solution. The permittivity and anti-voltage strength of composite also charged correspondingly. As a consequence, the energy storage density innovated much higher than ever. The maximum energy storage density could approach 0.9185Johr/cc.
Diamond films were deposited by using CH4/A1-/H2 gas system and silicon (111) wafers as substrate in microwave plasma CVD (MPCVD) at low temperature about 350°C . The effects of the gas system and proportion, dif...
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Diamond films were deposited by using CH4/A1-/H2 gas system and silicon (111) wafers as substrate in microwave plasma CVD (MPCVD) at low temperature about 350°C . The effects of the gas system and proportion, different microwave power, and different pretreatment methods of substrate on the microstructure of diamond films were respectively discussed. The diamond film samples were investigated by X-ray-diffraction (XRD) and scanning electron microscopy (SEM). The results showed that diamond (111) peak of XRD patterns was very low because of non-diamond phase and defects. The SEM images showed that diamond films were stacked with regular ranged and about 200 nm ball-like diamond secondary nucleation particles. The diamond films are consisted of no well-faceted particles.
Dense SnO2 based ceramics are widely used. In this paper, 95SnO2-5MnO2 ceramics were prepared by pressureless sintering in air at different temperatures. Phase compositions and microstructures are examined by XRD, SEM...
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Dense SnO2 based ceramics are widely used. In this paper, 95SnO2-5MnO2 ceramics were prepared by pressureless sintering in air at different temperatures. Phase compositions and microstructures are examined by XRD, SEM and EDX, respectively. The SEM results show that different morphologies exist at the SnO2 grain boundary of ceramic, which compose of manganese oxidation, testified by EDX. The different manganese oxides phases, found by XRD, are the source of oxygen concentration at the grain boundary during heating and oxygen dissipation when cooling. However, solid solutions of Mn, Sn and O are not observed. The density of 95SnO2-5MnO2 ceramics decreases with increasing the sintering temperature, due to the evaporation of SnO and decreasing concentration of oxygen at grain boundary in the cooling process. Densification of the ceramic is promoted with inhibiting the decomposition of SnO2 by increasing oxygen concentration in the heating process, but it is limited by the dissipation of oxygen at the grain boundary in the cooling process.
The proton exchange membrane could be sufficiently hydrated when a proton exchange membrane fuel cell (PEMFC) operated normally. Based on Springer model, the equation of the distribution of water molecules number bond...
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The proton exchange membrane could be sufficiently hydrated when a proton exchange membrane fuel cell (PEMFC) operated normally. Based on Springer model, the equation of the distribution of water molecules number bonded with SO4 in the membrane was derived. Considering the effects of the membrane thickness, operating temperature and current density, the water transfer in the membrane was analyzed. Conclusions were drawn that the thinner the membrane can be more easily self-hydrated;the thinner the membrane was and the higher the current density was, the less the time was needed to hydrate the membrane;when the thickness was less than 15 μm and current density was higher than 0.6 A/cm2, the time was decreased drastically. The conclusions were helpful for PEMFC's design and operation.
Aluminosilicate refractory waste was used to prepare high performance ceramic ball grinding media with 75% Al2O3. The influence of milling time on the particle size of raw materials, the sintering temperature, and per...
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Aluminosilicate refractory waste was used to prepare high performance ceramic ball grinding media with 75% Al2O3. The influence of milling time on the particle size of raw materials, the sintering temperature, and performance of ceramic balls were studied. Results show that with increasing milling time the particle size of the raw materials decreased, resulting in a decrease of ceramic ball sintering temperature and an increase in wear resistance and volume density. The wear rate and volume density of balls prepared by milling the materials for 72 h were 0.01886 %/h and 3.374 g/cm 3, respectively.
A physical model for mobility degradation by interface-roughness scattering and Coulomb scattering is proposed for SiGe p-MOSFET with a high-k dielectric/SiO2 gate stack. Impacts of the two kinds of scatterings on mob...
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A physical model for mobility degradation by interface-roughness scattering and Coulomb scattering is proposed for SiGe p-MOSFET with a high-k dielectric/SiO2 gate stack. Impacts of the two kinds of scatterings on mobility degradation are investigated. Effects of interlayer （SiO2） thickness and permittivities of the high-k dielectric and interlayer on carrier mobility are also discussed. It is shown that a smooth interface between high-k dielectric and interlayer, as well as moderate permittivities of high-k dielectrics, is highly desired to improve carriers mobility while keeping alow equivalent oxide thickness. Simulated results agree reasonably with experimental data.
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