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21.
《Ceramics International》2016,42(4):5291-5298
The effect of WC content on microstructure and mechanical properties of the TiC–Ni3Al system cermets was investigated. Ni3Al-bonded cermets showed a core–rim structure with carbide particle coupled with rim embedded in Ni3Al binder. With WC content increasing, TiC grains were refined and the white rim became complete and got thicker gradually. Interface between core and rim showed a completely coherent relationship. The rim enriched in W constituted an ideal coherence between hard phase and Ni3Al binder phase. With WC content increasing, the densification of cermets was enhanced, and hardness and TRS were increased firstly and then reduced, reaching peak values 90.9 HRA (HV30 15 GPa) and 1629 MPa, respectively in cermet N5 (25 wt% WC). Similarly, fracture toughness got a peak value (11.6 MPa m1/2), at the composition with 20 wt% WC. 相似文献
22.
针对高性能聚合物尼龙6材料的选择性激光烧结(SLS)工艺,研究了不同激光功率与扫描速度对成型件致密度的影响并进行了工艺优化。实验中激光功率10~50 W,扫描速度1 000~5 000 mm/s,其他工艺参数保持恒定。引入能量密度对激光功率与扫描速度的综合作用进行研究。结果表明:随着激光功率的增加或扫描速度的增大,制件的致密度呈现先增大后减小的趋势;随着能量密度的增加,制件的致密度呈现先增大后减小的趋势。在不同工艺参数下,获得制件的最大致密度为86.74%,此时激光功率为30 W,扫描速度为2 000mm/s,能量密度为0.043 J/mm^2。选定致密度为衡量指标,通过响应面回归分析模型建立了激光功率、扫描速度与致密度的优选工艺图谱,得到最优的工艺参数为激光功率45 W,扫描速度3 465 mm/s,此时预测的制件致密度为88.971%。 相似文献
23.
《Ceramics International》2020,46(2):2063-2071
Photocurable gray-colored Si3N4 ceramic slurry with high solid loading, suitable viscosity and high curing depth is critical to fabricate dense ceramic parts with complex shape and high surface precision by stereolithography technology. In the present study, Si3N4 ceramic slurry with suitable viscosity, high solid loading (45 vol %) and curing depth of 50 μm was prepared successfully when surface modifier KH560 (1 wt%) and dispersant Darvan (1 wt%) were used. The slurry exhibits the shear thinning behavior. Based on the Beer-Lambert formula, Dp (the attenuation length) and Ec (the critical energy dose) of Si3N4 ceramic slurry with solid loading of 45 vol % were derived as 0.032 mm and 0.177 mJ/mm2, respectively. Si3N4 ceramic green parts with complex shape and high surface precision were successfully fabricated by stereolithography technology. After optimizing the debinding and sintering process for green parts, dense Si3N4 ceramics with 3.28 g/cm3 sintering density were fabricated. The microhardness and fracture toughness of as-sintered Si3N4 ceramics are ~14.63 GPa and ~5.82 MPa m1/2, respectively, which are comparable to those of the samples by traditional dry-pressed and pressureless sintering technology. These results show that ceramic stereolithography technology could be promising to fabricate high performance ceramics, especially for gray-colored monolithic Si3N4 ceramics. 相似文献
24.
《Ceramics International》2020,46(9):13047-13053
Porous (Ba,Sr)(Co,Fe)O3-δ (BSCF) ceramics with high open porosity and good electrical conductivity was fabricated using Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF), which shows a high mixed ionic-electronic conductivity. In general, during the fabrication of porous ceramics by the sacrificial template method using pore former particles, closed pores are easily formed unless sufficient pore former particles are added. In this study, we have devised a method using the gelatinization-retrogradation phenomena of starch for producing a porous body with an excellent percolated pore network structure. By dispersing BSCF and starch in an aqueous slurry (0–50% by weight) and heating, gelatinization of the starch occurred and the starch particles adhered to each other. Furthermore, in order to retain the percolated structure, the water solvent was removed by freeze-drying without heating to obtain a dried green body. The sintering behavior of the porous BSCF bodies prepared under various conditions was characterized by microstructural observations and relative density measurements. By optimizing the process conditions of the gelatinization and retrogradation, a porous body having an open porosity of 48.3%, and with 99% of the total pores open, was obtained. The matrix was also well connected and showed a sufficiently high conductivity which was similar to the porous bodies made by the traditional sacrificial template method. 相似文献
25.
《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》1988,30(2):217-218
Fitting parameters for site energy difference expression of Miedema coordinates has been determined for Si. 相似文献
26.
Anode-supported planar solid oxide fuel cells (SOFCs) with an active area of 81 cm2 (9 cm × 9 cm) and nano-structured La0.6Sr0.4Co0.2Fe0.8O3−δ + Y2O3 stabilized ZrO2 (LSCF + YSZ) composite cathodes are successfully fabricated by tape casting, screen printing, co-firing and solution impregnation, and tested using H2 fuel and air oxidant at various flow rates. Maximum power densities of 437 and 473 mW cm−2 are achieved at 750 °C by loading 0.6 and 1.3 mg cm−2 of LSCF in the composite cathodes, respectively. The gas flow rates, particularly the air, have a significant effect on the cell performance. Cell performance degradation with time is also observed, which is considered to be associated with the growth and coalescence of the nanosized LSCF particles in the composite cathode. The use of the LSCF cathode in combination with YSZ electrolyte without a Gd-doped CeO2 (GDC) buffer layer is proved to be applicable in large cells, even though the thermal stability of the nanosized LSCF needs to be further improved. 相似文献
27.
采用阳极氧化法在有机介质中制备垂直排列的厚度达百微米的TiO2纳米管阵列,重点考察TiO2纳米管表面形貌特性的控制,以期从微观修饰角度来提高TiO2纳米管阵列膜的光电化学性能;在此基础上,考察不同处理条件下的TiO2纳米管阵列膜的光电化学特性。实验结果表明:采用无水乙醇作为超声液并结合二次蒸馏水进行漂洗能彻底清除纳米管表面聚集堵塞部分,得到清洁、规整有序的纳米管阵列表面,且不破坏纳米管阵列膜的最佳超声振动时间为20~30s。在对纳米管阵列的表面形貌特性进行控制后,采用一步阳极氧化法+无水乙醇超声制备的样品经500℃退火在全谱段的光转换效率达到1.48%,证实对纳米管阵列的表面形貌特性实施控制能有效提高其光电化学性能。 相似文献
28.
29.
Zr55Cu30Al10Ni5块体非晶合金(BMG)在过冷液态区内的单向压缩实验表明: 材料在过冷液态区内的形变行为强烈依赖于温度和变形速率. 随着应变速率的增加, 材料的流变特征由Newtonian流变转变为非Newtonian流变.利用扩展指数本构方程模型建立了非晶合金的流变应力、应变速率和温度的关系. 相似文献
30.
电视机透明支柱注射模设计 总被引:1,自引:3,他引:1
电视机透明支柱直径较大,为实心结构,外观要求高,采用常规工艺方法成型易出现缺陷。现提出一种新工艺,将塑件分为内芯和外层两部分,内芯采用透明PC材料,并预加热到一定温度,外层利用动态模温控制系统,在高温状态下注射成型。模具为两板式结构,1模2腔,模具动、定模部分各有1个大滑块;采用开放式浇口热流道与普通流道相结合的浇注系统,采用扇形浇口,生产的塑件满足设计要求。实践证明,这种镶嵌式注射模结构合理、操作方便,产品外观无缺陷,对超厚型塑件的注射成型具有一定的借鉴作用。 相似文献