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101.
熔铸-原位反应法生成α-Al2O3晶须的形貌及结晶方向 总被引:4,自引:0,他引:4
利用熔铸-原位反应法制备TiC/Al复合材料时,发现Ti-C-Al反应块表面存在大量的Al2O3晶须,晶须的形貌包括长而直的板状和串珠状,取决于反应进行时铝熔体的温度,当铝熔体温度低于900℃时,形成板状晶须,而当铝熔体温度高于900℃时,形成串珠状的晶须,其原因是由于较高的铝熔体温度加剧了TiC原位反应的放热,热起伏的结果致使部分α-Al2O3晶须异常长大,X射线衍射和透射电镜分析确认晶须为α-Al2O3,其形貌以直板状为主,电子衍射花样斑点显示其结晶方向为[0002]。 相似文献
102.
结合高效的动态格点搜索(DLS)算法与扰动操作(Perturbation Operation)提出一种新的改进方法(DLS-PO),用于确定团簇的最低能量结构。针对一个特定构型,DLS算法总能给出其对应搜索空间的最规则结构。然而,一次失败的DLS优化将消耗大量的运算资源。为此,采取原子移动和结构旋转的扰动操作成功地改变了构型,再结合后续的DLS操作,提高了优化效率。将该算法用于原子数高达309的Lennard-Jones团簇及100原子NP-B函数铝团簇的结构优化。优化结果显示相比于DLS算法,DLS-PO算法更为高效。 相似文献
103.
The reactivity of AlN powder with water in supernatants obtained from centrifuged Si3 N4 and SiC slurries was studied by monitoring the pH versus time. Various Si3 N4 and SiC powders were used, which were fabricated by different production routes and had surfaces oxidized to different degrees. The reactivity of the AlN powder in the supernatants was found to depend strongly on the concentration of dissolved silica in these slurries relative to the surface area of the AlN powder in the slurry. The hydrolysis of AlN did not occur if the concentration of dissolved silica, with respect to the AlN powder surface, was high enough (1 mg SiO2 /(m2 AlN powder)) to form a layer of aluminosilicates on the AlN powder surface. This assumption was verified by measuring the pH of more concentrated (31 vol%) Si3 N4 and SiC suspensions also including 5 wt% of AlN powder (with respect to the solids). 相似文献
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A method of electrical conductivity and an analysis of recovered explosion products are used to study interaction of aluminum
with detonation products of condensed high explosives. The electrical conductivity of HMX/Al and RDX/Al mixtures is inhomogeneous;
a region with the maximum electrical conductivity is adjacent to the detonation front, whereas the electrical conductivity
decreases with distance from the front. If the wave is incident onto a wall, the electrical resistance of the composite high
explosive increases, which indicates that the high-conducting zone disappears. The electrical conductivity, resistance of
the conducting zone, and the time of resistance growth are found as functions of the particle size of the additive. The results
obtained confirm the reaction of the metal additive with detonation products in a microsecond range of time. An analysis of
condensed explosion products shows that the reaction of aluminum with detonation products proceeds on the particle surface.
The amount of reacted aluminum and the oxide-layer thickness are estimated.
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Translated from Fizika Goreniya i Vzryva, Vol. 42, No. 1, pp. 120–129, Jnuary–February, 2006. 相似文献
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109.
Yinzhong Guo Vijay M. Mannari Pulin Patel John L. Massingill 《Journal of Coatings Technology and Research》2006,3(4):327-331
A series of soybean oil phosphate ester polyols (SOPEP) was prepared by reaction of fully epoxidized soybean oil with phosphoric
acid and simultanoeous hydrolysis in the presence of a polar solvent. The polyols were characterized by determination of acid
value, oxirane number, hydroxyl value, molecular weight (GPC), and FTIR spectra. These polyols with varying amounts of acid
phosphate groups could be self-emulsified to form aqueous dispersions after neutralization with organic base. These aqueous
dispersion showed varying degrees of stability and their appearance ranged from opaque dispersions to translucent to clear
solutions. Waterborne coating compositions were prepared using these aqueous dispersions as principal components and their
thermally cured film properties were studied. it was found that by careful selection and formulation, SOPEPs can be successfully
used for low-VOC waterborne coating formulations. SOPEPs with 3.5% phosphate ester content showed visibly superior corrosion
resistance properties. 相似文献
110.