In this paper, the lower and upper bounds of Young's modulus and Poisson ratio are determined by the effective stress method and effective strain method from material mechanics. The effective heat flux method base...
详细信息
In this paper, the lower and upper bounds of Young's modulus and Poisson ratio are determined by the effective stress method and effective strain method from material mechanics. The effective heat flux method based on the hypothesis of equivalent temperature difference and the effective temperature difference method based on the hypothesis of equivalent heat flux are proposed, the lower and upper bounds of the thermal conductivity of ceramic/metal composite material are determined similarly. The result shows that the property values of ceramic/metal composites calculated from current theoretical property formulas are within the lower and upper bounds determined by the above methods.
A peptizing-hydrothermal method to prepare nanometer γ-AlOOH crystal powder with industrial Al(OH)3 as raw materials has been proposed in the present paper. The XRD and TEM results show the product is a pure γ type ...
详细信息
A peptizing-hydrothermal method to prepare nanometer γ-AlOOH crystal powder with industrial Al(OH)3 as raw materials has been proposed in the present paper. The XRD and TEM results show the product is a pure γ type nanometer A100H crystal powder with average grain diameter of 70nm. Laser grading analysis indicates the average grain diameters of the product in the solution are 66.52nm in water and 84.33nm in N,N-dimethylformamide, respectively without surface modification and dispersant. The experimental result indicated that polymer/inorganic nano-composite with high content of nanometer AlOOH presents inorganic characteristic of polymer. The wear rate of the alumina ceramic ball sintered at 1465°C from ceramic, which contains 98% alumina (wt), can be reduced up to 40% with addition of 3.5% nanometer AlOOH.
Four Coating schemes and two substrate materials are designed to evaluate the characteristics of the ceramic/metal gradient thermal barrier coating. The gradient coating is successfully prepared by plasma spray with s...
详细信息
Four Coating schemes and two substrate materials are designed to evaluate the characteristics of the ceramic/metal gradient thermal barrier coating. The gradient coating is successfully prepared by plasma spray with single torch and single feeder. The coating performance is evaluated by observing microstructure, measuring thermal shock resistance and thermal residual stress. The coating microstructure is observed by scanning electron microscope (SEM). Diffractive peaks for the gradient coating are got at different zone by X-ray spectroscopy (XRS). The thermal shock experiment shows that the thermal shock resistance property of the gradient coating is better than that of the non-gradient coating. The measurements of thermal residual stresses in different coating schemes are carried out by hole-drilling method, the results show that compressional stress presents on 1Cr18Ni9Ti substrate and tensile stress presents on 2Cr13 substrate.
The transient stress field analysis aims at the thermal and mechanical response of LPG vessel under pool fire surrounding environment. Finite element analysis method is used to calculate the stress field. Thermal boun...
详细信息
The transient stress field analysis aims at the thermal and mechanical response of LPG vessel under pool fire surrounding environment. Finite element analysis method is used to calculate the stress field. Thermal boundary conditions of LPG vessel are determined according to heat transfer theory and calculated by the software PLGS99. The results show that the maximum whole stress of the vessel appears near the highest surface where liquid can reach, the maximum thermal stress is much greater than the maximum mechanical stress and fluctuation of liquid surface is the main reason of high stress. The highest position of the LPG vessel which liquid can reach should be protected as it is the most dangerous place.
As one of the advanced functional inorganic power materials, nanometer ZnO has extensive application fields. The specific surface area is considered to be a big factors for its application. In this paper, the gas adso...
详细信息
As one of the advanced functional inorganic power materials, nanometer ZnO has extensive application fields. The specific surface area is considered to be a big factors for its application. In this paper, the gas adsorption method was adopted to measure ZnO specific surface area, and the influences of different testing conditions on the results were studied. It was found that optimal testing condition is that sample weight, degas temperature and degas time are 0.3-0.5g, 250°C, 2h respectively.
The method of single detector, direct contact and longitudinal wave were used in this research. Ultrasonic wave attenuation coefficient of nine WC-10 Co hardmetals samples were tested, while fracture toughness values ...
详细信息
The method of single detector, direct contact and longitudinal wave were used in this research. Ultrasonic wave attenuation coefficient of nine WC-10 Co hardmetals samples were tested, while fracture toughness values were obtained by indentation method. SEM was performed to observe the sections of the samples. Distributions of the WC grains were analyzed. Density, Vickers hardness and transverse rupture strength were also tested. The relationships among ultrasonic wave attenuation coefficient, mean grain size, fracture toughness, density, Vickers hardness and transverse rupture strength were studied. Results showed that with the decrease of the mean WC grain size, the ultrasonic wave attenuation coefficient and the fracture toughness value increased. However, ultrasonic wave attenuation coefficient had no direct relation with density, Vickers hardness and transverse rupture strength. It was concluded that ultrasonic wave attenuation coefficient could be used to evaluate the fracture toughness of WC-10 Co hardmetals, instead of destructive mechanical method.
(AgSbTe2)x(PbTe)1-x (x = 0.04-0.20) samples were prepared by slow-cool-from-melts and the influences of AgSbTes content on the microstructure and thermoelectric properties were investigated. Results indicated that pha...
详细信息
(AgSbTe2)x(PbTe)1-x (x = 0.04-0.20) samples were prepared by slow-cool-from-melts and the influences of AgSbTes content on the microstructure and thermoelectric properties were investigated. Results indicated that phase segregation occurs as x increases and the samples are characterized by a bi-phased material containing one main Pb-rich phase and another Ag-Sb-rich phase. As AgSbTe2 content increases, the thermal conductivity is depressed and the electrical properties decrease to some extent. The dimensionless of figure of merits (ZT) is greater for sample with a lower AgSbTe2 content.
In the present study, α-Si3N4 was prepared using MgO and Al2O3 as the sintering additives and spark plasma sintering (SPS) technique. The SPS sintering behaviour and mechanism have been discussed. The relationship be...
详细信息
In the present study, α-Si3N4 was prepared using MgO and Al2O3 as the sintering additives and spark plasma sintering (SPS) technique. The SPS sintering behaviour and mechanism have been discussed. The relationship between the content of sintering additives, sintering temperature, and relative densities of the samples have been analyzed. The phase composition was determined by XRD, the microstructures of the fracture surfaces were observed by SEM and the dielectric properties have been tested. The results suggest that when the sintering temperature is 1300-1500 °C, the content of sintering additives - 6-10%, the relative density of the sintered samples is 64-96%. When the sintering temperature reaches 1400 °C, the content of sintering additives 10%, the samples could be fully dense sintered (the relative density up to 95%) The sintering mechanism is liquid phase sintering. The electric permittivity of the sintered samples is 5-8 being in a close relationship with the relative density. The dielectric loss, influenced by the liquid phase, is less than 1 × 10-2.
Ce0.8Sm0.2O1.9(SDC) was synthesized by calcination of mixed solution method. XRD patterns showed that SDC powders calcined at 800°C had a cubic fluorite structure and the average grain size was between 1-3 μm. A...
详细信息
Ce0.8Sm0.2O1.9(SDC) was synthesized by calcination of mixed solution method. XRD patterns showed that SDC powders calcined at 800°C had a cubic fluorite structure and the average grain size was between 1-3 μm. After sintered for 4 h at 1450°C, the relative density was 91.9%. The conductivity of SDC solid electrolyte was 0.087 S·cm-1 at 800°C.
Single-phase n-type (AgIn)xPb1-2xTe compounds were synthesized using the melting reaction method. Influences of (AgIn) substituting for Pb on the constituent phases and thermoelectric properties of the (AgIn)xPb1-2xTe...
详细信息
Single-phase n-type (AgIn)xPb1-2xTe compounds were synthesized using the melting reaction method. Influences of (AgIn) substituting for Pb on the constituent phases and thermoelectric properties of the (AgIn)xPb1-2xTe(x=0.01-0.05) were investigated. Results indicate that single phase compound is obtained when the (AgIn) substitution fraction x&le0.04. However, the second phase (AgInTe2) was observed in the sample with x=0.05. The Seebeck coefficient increases gradually with the increasing of the (Agin) substitution fraction x, and the electrical conductivity of the compounds decreases with the increasing of x. Thermal conductivity decreases with the increasing of x. In all of the n-type (AgIn)xPb1-2xTe compounds, (AgIn)0.01Pb0.98Te compound has the greatest ZT value, reaching 1.1 at 800K.
暂无评论