共查询到19条相似文献,搜索用时 93 毫秒
1.
2.
尖晶石LiMn2O4表面包覆MgO及其性能 总被引:1,自引:0,他引:1
Mn^2 在电解液中的溶解是引起LiMn2O4正极材料性能恶化的重要原因。用沉淀法在LiMn2O4表面包覆一层Mg(OH)2,再进行热地理,制备由表面包覆MgO的LiMn2O4。用X光电子能谱、扫播电镜和X射线衍射对包覆前后的LiMn2O4的结构进行了表征。充放电测试结果表明.经表面修饰处理后LiMn2O4的循环及高温性能明显改善。研究结果表明表面修饰北理可以抑制正极材料和电解液之间的相互作用.是改善锂离子二次电池正极材料性能的有效途径。 相似文献
3.
通过差热分析(DTA)、X射线衍射分析(XRD)、扫描电子显微镜(SEM)研究了3种不同晶化温度对MgO-Al2O3-SiO2系微晶玻璃析晶性能、微观结构及抗弯强度的影响。研究结果表明,随着晶化温度逐步升高,晶粒尺寸逐步增大,抗弯强度逐渐增高。 相似文献
5.
ZnO-MgO-Al2O3陶瓷是一种复合烧结体,其主晶相为ZnO与ZnAl2O4,且均以晶粒存在。MgO能调节电阻温度系数,使之由负变为正。Al2O3能调节电阻率。慢的降温速度能提高线性及耐浪涌能量,降低电阻温度系数。 相似文献
6.
利用湿化学法制备了MgO/Eu2O3共掺Al2O3陶瓷, 研究了不同的MgO/Eu2O3掺杂量对Al2O3陶瓷物相组成、显微结构和微波介电性能的影响。结果表明: 适量的MgO/Eu2O3共掺有助于Al2O3的致密化和晶粒生长。在介电性能方面, MgO/Eu2O3共掺对Al2O3陶瓷的介电常数没有明显的影响, 但对介电损耗的影响显著。随着Eu2O3含量的增加, Al2O3陶瓷的Q×f值会呈现先增加后下降的变化趋势。0.05wt% MgO/0.10wt% Eu2O3共掺的样品在1590℃下保温4 h获得的微波介电性能最佳, εr~9.82, Q×f ~225, 225 GHz。Q×f值的这种变化可能与样品微观结构的变化相关。先是随着MgO/Eu2O3共掺量的增加, 晶粒尺寸不断增加, 晶界不断减少, 这有利于Q×f值的提高; 接着, 当MgO/Eu2O3共掺量进一步增加时, 晶粒尺寸不断下降, 晶界增多, 这会导致样品Q×f值的降低。另外, 应力和第二相也可能对Q×f值的变化产生影响。 相似文献
7.
8.
本文采用电熔刚玉、镁铝尖晶石、SiC、球状沥青和Si3N4为主要原料,借助XRD和EDAX分析技术,研究了Si3N4加入量对Al2O3-尖晶石-SiC-C质出铁沟浇注料常温物理性能和抗渣性能的影响。结果表明:随着Si3N4加入量的增加,浇注料的显气孔率变化不大,体积密度逐渐减小,1100℃及1500℃埋炭烧成后的抗折和耐压强度逐渐增大,当Si3N4加入量超过4%(质量分数,下同)时,浇注料的体积密度有所增大,抗折和耐压强度显著提高;浇注料在埋炭气氛下抗渣性能优良,氧化气氛下的侵蚀指数明显增大,且随着Si3N4加入量的增加,浇注料的侵蚀指数呈现出先增大后减小的趋势。本文对浇注料的性能变化进行了探讨。 相似文献
9.
采用脉冲激光沉积法制备了斜方相Sc2W3O12薄膜。利用X射线衍射仪(XRD)和场发射扫描电镜(FESEM)对Sc2W3O12靶材和Sc2W3O12薄膜组分、表面形貌和靶材断面形貌进行表征, 研究衬底温度与氧分压对薄膜制备的影响。采用变温XRD和热机械分析仪(TMA)分析了Sc2W3O12陶瓷靶材和薄膜的负热膨胀特性。实验结果表明: 经1000℃烧结6 h得到结构致密的斜方相Sc2W3O12陶瓷靶材, 其在室温到600℃的温度范围内平均热膨胀系数为-5.28×10-6 K-1。在室温到500℃衬底温度范围内脉冲激光沉积制备的Sc2W3O12薄膜均为非晶态, 随着衬底温度的升高, 薄膜表面光滑程度提高; 随着沉积氧压强增大, 表面平整性变差。非晶膜经1000℃退火处理7 min后得到斜方相Sc2W3O12多晶薄膜, 在室温到600℃温度区间内, Sc2W3O12薄膜的平均热膨胀系数为-7.17×10-6 K-1。 相似文献
10.
11.
12.
Al2-xYxW3O12的合成与热膨胀特性的研究 总被引:2,自引:0,他引:2
近零及负热膨胀材料有诸多的潜在应用领域,而具有负热膨胀效应的A2M3O12系列材料在较宽的温度范围,易于通过组份变化调整其热膨胀系数.本文首次使用共沉淀法合成了Al2-xYxw3O12(x=0~2)系列粉体材料.经X射线衍射分析证明Al2W3O12和Y2W3O12能完全固溶形成二元固溶体,采用PowderX软件对Al2-xYxW3O12的晶胞参数进行计算,结果表明室温下随着稀土钇(Y)含量的增加,晶体的晶胞参数与晶胞体积逐渐增加.高温X射线衍射结果表明,随着稀土钇(Y)含量的增加,Al2-xYxW3O12的本征热膨胀系数逐渐由正到负变化.热机械分析(TMA)压缩法测定其宏观热膨胀系数,发现通过调整材料的组成,可以将其热膨胀系数控制为一定的正值、负值或零.但是由于其结构的各向异性,多晶陶瓷内部存在的微裂纹使热膨胀曲线出现较大的滞后环. 相似文献
13.
14.
15.
采用传统熔体冷却法制备TiO_2掺杂量为0~1.8wt%的TiO_2/SiO_2-Al_2O_3-MgO系玻璃,探讨了不同TiO_2质量分数对玻璃体积密度、弯曲强度、压缩强度、压缩模量和结构稳定性的影响规律。结果发现:当TiO_2含量小于1.5wt%时,TiO_2/SiO_2-Al_2O_3-MgO系玻璃的光学带隙随着TiO_2含量的增加而减小、玻璃结构更加稳定,其体积密度、弯曲强度、压缩强度以及压缩模量均随着TiO_2含量的增加而上升;当TiO_2含量超过1.5wt%后,该玻璃体系的结构稳定性和力学性能均随着TiO_2含量增加而下降;当TiO_2的质量分数为1.5wt%时,玻璃的光学带隙达到最小值为3.75eV,各项力学性能达到最优,其弯曲强度为110.36 MPa、压缩强度为240.18 MPa、压缩模量为115.03GPa。适量TiO_2的掺杂,减少了玻璃网络结构中非桥氧的数量,使孤立的岛状网络单元重新聚合,从而显著提高了玻璃的结构稳定性和力学性能;但过量的TiO_2迫使TiO_2/SiO_2-Al_2O_3-MgO系玻璃结构中的桥氧键断裂生成非桥氧,由此显著降低了其结构稳定性和力学性能。 相似文献
16.
17.
In this study, Al2024 matrix composites reinforced with Al2O3 nanoparticle contents ranging from 1 to 5?wt% were produced via a new method called as flake powder metallurgy (FPM). The effect of flake size and Al2O3 nanoparticle content on the reinforcement distribution, microstructure, physical, and mechanical properties of the composites were studied. SEM analysis was performed to investigate the microstructure of metal matrix and the distribution of nanoparticles. The hot-pressed density increased with decreasing the matrix size. The hardness of the Al2024–Al2O3 nanocomposites fabricated by using fine matrix powders increased as compared to the Al2024–Al2O3 nanocomposites produced by using coarse matrix powders. It has been found that the FPM method proposed in this study revealed to be an effective method for the production of nanoparticle reinforced metal matrix composites. 相似文献
18.
Al–Cu matrix composites reinforced with diamond particles (Al–Cu/diamond composites) have been produced by a squeeze casting method. Cu content added to Al matrix was varied from 0 to 3.0 wt.% to detect the effect on thermal conductivity and thermal expansion behavior of the resultant Al–Cu/diamond composites. The measured thermal conductivity for the Al–Cu/diamond composites increased from 210 to 330 W/m/K with increasing Cu content from 0 to 3.0 wt.%. Accordingly, the coefficient of thermal expansion (CTE) was tailored from 13 × 10−6 to 6 × 10−6/K, which is compatible with the CTE of semiconductors in electronic packaging applications. The enhanced thermal conductivity and reduced coefficient of thermal expansion were ascribed to strong interface bonding in the Al–Cu/diamond composites. Cu addition has lowered the melting point and resulted in the formation of Al2Cu phase in Al matrix. This is the underlying mechanism responsible for the strengthening of Al–Cu/diamond interface. The results show that Cu alloying is an effective approach to promoting interface bonding between Al and diamond. 相似文献
19.
Luciana Prates Prisco Carl P. Romao Fernando Rizzo Mary Anne White Bojan A. Marinkovic 《Journal of Materials Science》2013,48(7):2986-2996
Orthorhombic Al2Mo3O12 was investigated as a model anisotropic phase to understand the influence of powder preparation routes and bulk microstructure (mean grain size) on the bulk coefficient of thermal expansion (CTE) and to compare it to the intrinsic CTE of powder samples. A co-precipitation route was used for the synthesis of pure single-phase nanopowders, while a polyvinyl alcohol-assisted sol–gel method was utilized for the synthesis of micron-sized powders. Sintered samples prepared from both powders exhibited different microstructures in terms of mean crystal sizes and porosity. Bulk samples obtained from nanopowders were highly porous and contained crystals of approximately 100-nm diameter, while the bulk pieces produced from the micron-sized powders were denser, contained crystals larger than 5 μm, and showed occasional intergranular and transgranular microcracks. Such different microstructures hugely impact the bulk CTE: the nanometric sample possesses a bulk CTE (0.9 × 10?6 °C?1, from 200 to 700 °C) closer to the instrinsic CTE (2.4 × 10?6 °C?1) than for the micrometric sample, which showed a negative CTE (?2.2 × 10?6 °C?1) from 200 to 620 °C, and an even more negative CTE above 620 °C (?35 × 10?6 °C?1). A finite element analysis showed that the local maximum thermal tensile stresses could be as high as 220 MPa when simulating a temperature drop of 700 °C as an example of thermal treatment following sintering. This tensile stress is expected to exceed the tensile strength of Al2Mo3O12, explaining the origin of microcracks in bulk samples prepared from the micron-sized powders. The thermal behavior of the microcracks leads to differences between the intrinsic and bulk thermal expansion; we show experimentally that such differences can be reduced by nanostructuring. 相似文献