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排序方式: 共有1713条查询结果,搜索用时 15 毫秒
61.
Yujie Wu Amit Bandyopadhyay Susmita Bose 《Materials Science and Engineering: A》2004,380(1-2):349-355
Magnesia–doped alumina and yttria–doped zirconia nano-powders were synthesized using sucrose as a chelating agent and template material from the aqueous solutions of aluminium nitrate, magnesium nitrate, ytrrium nitrate and zirconyl nitrate, respectively. Synthesis parameters were optimized with varying sucrose to metal ion ratio, calcinations time, and temperature to produce these nano-powders. As-synthesized powders were characterized by room temperature X-ray diffraction, BET surface area analyzer and transmission electron microscopy. Y2O3–ZrO2 nano-powders had particle size in the range of 80–200 nm with specific average surface area of 119 m2/g and for MgO–Al2O3 powders, particle sizes were 30–200 nm with the specific average surface area of 250 m2/g. Our results indicate that this synthesis method is a versatile one and can be applied to a variety of oxide-based materials to form nano-powders. Nano-powders were compacted uniaxially and densified in a muffle furnace. Sintered discs were used for hardness testing and density measurements, as well as for microstructural characterization. 相似文献
62.
Relationship between particle erosion and lamellar microstructure for plasma-sprayed alumina coatings 总被引:5,自引:0,他引:5
The lamellar structure determines mechanical properties of a thermal spray coating. A model for the erosion of thermally sprayed ceramic coatings resulting from the debonding of flattened ceramic particles is proposed based on the examination of the erosion mechanism. The relationship between erosion rate and microstructural parameters is established both experimentally and theoretically to reveal main lamellar structural parameters controlling erosion of thermally sprayed ceramic coating. The microstructural parameters include the mean bonding ratio between lamellae and thickness of the lamellae. The erosion rate of plasma-sprayed Al2O3 coatings was measured at impact angle of 90° under the fixed erosion test conditions. The correlation of theoretical model with the observed structural parameters and erosion data of alumina coatings was examined. It is revealed that the theoretical relationship agreed well with the observed relation. The results clearly revealed that the erosion of plasma-sprayed ceramic coating was inversely proportional to the mean lamellar bonding ratio. The influences of spray parameters on erosion effected mainly through their influences on the lamellar bonding. The erosion resistance of a thermally sprayed ceramic coating was controlled by coating fracture toughness. 相似文献
63.
V. Hiremath 《塑料、橡胶和复合材料》2016,45(5):199-206
Nanocomposites were synthesised by dispersing two different types of alumina nanoparticles in epoxy matrix by ultrasonication. Alumina nanoparticles of two shapes, rod and spherical were selected to investigate the effect of particle morphology on viscoelastic and flexural properties of nanocomposites. Specific surface area of both the selected nanoparticles was kept in the similar range. Good dispersion of nanoparticles was observed through transmission electron microscopy. The addition of nanoparticles in epoxy had significant enhancement in the viscoelastic properties and moderate improvement in flexural properties of composites. Composites having alumina nanorods showed higher improvement both in storage modulus as well as in flexural properties in comparison to composites having spherical alumina nanoparticles. Efficacy of Mori-Tanaka method was explored in modelling storage modulus of nanocomposites. Assorted size of alumina nanorods based on particle size distribution was used to model composites with nanorods to see the effect of size assortment on storage modulus. 相似文献
64.
65.
《Fusion Engineering and Design》2014,89(7-8):1309-1313
The experimental determination of mechanical and thermal properties of ceramic pebble beds, such as the lithium orthosilicate or lithium metatitanate, is a key issue in the framework of fusion power technology, for the reason that they are possible candidates in the design of breeder blankets.The paper deals with an experimental method for the evaluation of the thermal conductivity of ceramic pebble beds versus the temperature and compressive strain, based on a steady state heat flux through a material (alumina) of known conductivity. The alumina thermal conductivity is determined by means of the hot wire method. To assess the experimental method, a thermo-mechanical characterization of alumina pebble beds (a material largely available), having different diameters, considering a wide range of temperatures and compression forces has been carried out.Moreover preliminary tests have been performed on lithium orthosilicate and lithium metatitanate pebble beds. 相似文献
66.
Hossein Vojoudi Jahan B. Ghasemi Ahmadreza Hajihosseinloo Bahareh Bastan Alireza Badiei 《Advanced Powder Technology》2021,32(4):1060-1069
A hybrid nanocomposite of alumina and hematite was synthesized by ultrasonic spray pyrolysis technique. The study of microscopic images, mapping analysis, and XRD patterns revealed that the Al2O3 – Fe2O3 nanocomposite was composed of separated spherical particles with a thin layer ball-shaped structure that metal oxides are uniformly distributed in the wall of hollow sphere particles, led to a coherent and monotonous construction. A series of coefficients of equilibrium sorption of polycyclic aromatic hydrocarbons (PAHs) as hazardous materials were measured on the prepared composite material in a batch technique. The free or pure Al2O3 or Fe2O3 showed negligible removal efficiency for the mentioned analytes. The various significant variables, such as initial analyte concentration, solution pH, adsorbent dose, and contact time to remove analyte, were studied in the aqueous solutions. Adsorption data were modeled to Langmuir, Freundlich, and Temkin isotherms, and a good correlation found in the case of Langmuir isotherm and adsorption capacity for anthracene, phenanthrene, and naphthalene were 370, 333, and 322 mg g?1, respectively. Investigation of the kinetic models proved a pseudo-second-order, and the prepared adsorbent can be reused more than 7 times without a significant decrease of adsorption performance. 相似文献
67.
《Journal of the European Ceramic Society》2014,34(10):2453-2463
Different factors such as the way of incorporating the Y2O3 stabilizer, alumina addition and sintering temperature were assessed with the goal to improve the low temperature degradation (LTD) resistance of 3Y-TZP without compromising on the mechanical properties. The degradation of hydrothermally treated specimens was studied by X-ray diffraction, micro-Raman spectroscopy and scanning electron microscopy.Decreasing the sintering temperature decreased the LTD susceptibility of 3Y-TZPs but did not allow to obtain a LTD resistant 3Y-TZP with optimized mechanical properties. Alumina addition along with the use of Y2O3 stabilizer coated starting powder allowed to combine both an excellent toughness and LTD resistance, as compared to alumina-free and stabilizer co-precipitated powder based equivalents. Transmission electron microscopy revealed that the improved LTD resistance could be attributed to the segregation of Al3+ at the grain boundary and the heterogeneously distributed Y3+ stabilizer. 相似文献
68.
《Journal of the European Ceramic Society》2014,34(14):3373-3378
Particulate composites of the Al2O3–YAG system were produced by precipitation of the yttrium oxide precursor in the aluminium oxide suspension. The solid state reaction took place during thermal treatment of the resulting powder and led to the creation of the YAG phase. This method allowed fine and homogenously distributed YAG inclusions within the alumina matrix to be obtained. The performed investigations involved determining of the critical stress intensity factor (KIC), Vickers hardness and bending strength of the materials. The composites showed higher hardness (HV) than α-Al2O3. The presence of YAG inclusion in the amount higher than 7.5 vol.% improved also fracture toughness when compared to polycrystalline alumina. In the case of the material with the best mechanical properties measurements of subcritical cracking were conducted and the threshold value of KIC (KI0) was determined. 相似文献
69.
《Ceramics International》2016,42(7):8460-8466
Dense bulk alumina (Al2O3) has been prepared by explosive compaction and its microstructure has been investigated by optical microscopy, Raman spectroscopy, scanning electron microscopy and transmission electron microscopy. The average microhardness of the alumina compact is about 171 HV0.025. Ultra-thin alumina films with glassy (translucent) appearance formed during the explosive compaction process. Nanograin Al2O3 particles are covered by amorphous Al2O3 which help to achieve a dense microstructure by promoting interparticles bonding. Phase transformation from γ-Al2O3 to α-Al2O3 during the explosive compaction process has been confirmed. Formation of the alumina compact is due to the large cooling rate and the high pressure during the explosive compaction. 相似文献
70.
Laser machining of different diameter holes into alumina tiles is carried out. Temperature and stress fields are predicted by using the finite element code. Surface temperature and residual stress predictions are validated through the thermocouple data and X-ray diffraction measurements. Morphological changes in the cutting section are examined by incorporating optical and scanning electron microscopes. It is found that the predictions of surface temperature and the residual stress formed at the cut section agree well with the experimental findings. In general, cut sections are free from large asperities; however, local dross attachments at the kerf edge and crack network formation at the kerf surface are observed. 相似文献