Mo/SiO2 composites with different mass compositions were sintered by spark plasma sintering (SPS) technique. The mechanism of sintering and densifications were studied and the relationship between the distribution of ...
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Mo/SiO2 composites with different mass compositions were sintered by spark plasma sintering (SPS) technique. The mechanism of sintering and densifications were studied and the relationship between the distribution of Mo in composites and the electrical property was discussed. The result indicated that there was no reaction between Mo and SiO2;the composites are mechanically mixed instead. Partly softened SiO2 and the particles of Mo filling the hole facilitated the compact of Mo/SiO2 composites. When the mass composition of Mo was less than 35%, the particles of Mo dispersed individually in SiO2 and the composite was an insulator;when that exceeds 40%, the composite was a conductor due to the connection of the particles of Mo.
Ti2AlC bulk material was synthesized by hot pressing using elemental powder mixture of Ti, Al and active carbon. X-ray diffraction (XRD) in different temperature of hot pressing was used to determine the phase composi...
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Ti2AlC bulk material was synthesized by hot pressing using elemental powder mixture of Ti, Al and active carbon. X-ray diffraction (XRD) in different temperature of hot pressing was used to determine the phase composition and scanning electron microscope (SEM) was observed to investigate the microstructure of samples synthesized respectively. Results show that high purity Ti2AlC bulk material was synthesized by hot pressing elemental powder mixture of 2.0 Ti/1.0 Al/1.0 C at 1500 °C for 60 minutes, in which little TiC and Ti3AlC2 existed as secondary phases. According to the results of thermodynamics calculation, for Ti, Al and C system the most stable compound in thermodynamics was TiC. Moreover, the formation of Ti3AlC2 during the synthesizing progress of Ti2AlC was explained.
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...
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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 ...
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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...
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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.
Thermogravimetry (TG-DTA) was used to study the heat resistance characteristics and curing heat decomposition kinetics of ATPU/epoxy resin system. Results showed that the decomposition temperature of the cured ATPU-2/...
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Thermogravimetry (TG-DTA) was used to study the heat resistance characteristics and curing heat decomposition kinetics of ATPU/epoxy resin system. Results showed that the decomposition temperature of the cured ATPU-2/E-44 was higher than that of ATPU-1.5/E-44. The calculation results of decomposition reaction showed that the cured system of ATPU-2/E-44 had better heat resistance, the reaction decomposition active energy of ATPU-2/E-44 system was higher than that of ATPU-1.5/E-44.
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...
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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.
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...
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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.
Taking the running parameters of boiler drum in 8 typical working conditions as data of boundary conditions, the transient thermal stress, mechanical stress and total stress of a 300MW boiler drum is calculated by fin...
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Taking the running parameters of boiler drum in 8 typical working conditions as data of boundary conditions, the transient thermal stress, mechanical stress and total stress of a 300MW boiler drum is calculated by finite element method. The results show that when the vapor pressure is close to or higher than the normal working vapor pressure, the temperature difference on the boiler wall has little influence on the total stresses. The vapor pressure in boiler drum is the main influential factor to the total stresses, and there is a proportion relationship between them. With the relationship, the maximum stress in the drum can be calculated.
Nanocrystalline WC-Co composite powder and coated tungsten diamond by using vacuum vapor deposition were consolidated by the spark plasma sintering （SPS） process to prepare diamond-enhanced WC-Co cemented carbide co...
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Nanocrystalline WC-Co composite powder and coated tungsten diamond by using vacuum vapor deposition were consolidated by the spark plasma sintering （SPS） process to prepare diamond-enhanced WC-Co cemented carbide composite materials. The interface microstructures between coated tungsten diamond and WC-Co cemented carbide matrix were investigated by scanning electron microscopy （SEM） and energy dispersive X-ray spectroscopy （EDXS）. The results showed that there is a transitional layer between the diamond and the matrix, in which the carbon content is 62.97wt.%, and the content of cobalt in the transitional zone is 6.19wt.%; the content of cobalt in the WC-Co cemented carbide matrix is 6.07wt.%, in which the carbon content is 15.95wt.%, and the content of cobalt on the surface of diamond is 7.30wt.%, in which the carbon content is 80.38wt.%. The transitional zone prevents the carbon atom of the diamond from spreading to the matrix, in which the carbon content does coincide with the theoretical value of the raw nanocomposite powders, and the carbon content forms a graded distribution among the matrix, transitional zone, and the surface of diamond; after the 1280℃ SPS consolidated process the diamond still maintains a very good crystal shape, the coated tungsten on the surface of the diamond improves thermal stability of the diamond and increases the bonding strength of the interface between the diamond and the matrix.
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