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991.
利用等离子喷涂设备将Ti与羟基磷灰石(HA)的混合粉末喷射入水,采用扫描电子显微镜和X射线衍射仪研究了Ti HA入水颗粒的形态和相组成,结果表明,经等离子熔融喷射入水后,钛粒子的尺寸小于HA粒子,主要原因之一是HA内形成了空心结构,空心结构的形成是由于HA在熔融时生成气相P2O5和H2O,它们在颗粒内聚集形成气泡,入水Ti HA粒子主要是由晶相和非晶相HA,分角相磷酸三钙(TCP)和磷酸四钙(TTCP)以及Ti的化合物所组成,由于与Ti的混合,HA的分解加剧,而Ti与HA粒子的融合及元素的扩散在飞行过程中已经发生。 相似文献
992.
Mechanical milling behavior of Mo-Si-Fe powders was investigated u sing XRD, SEM and TEM techniques. The mixtures of elemental molybdenum (>99%), s ilicon (>99%) and iron (>98%) powders with a stoichiometry of Mo5-xFe xSi3 (x=0.5, 1, 2) were milled in a planetary mill for up to 195 h. For all three powder mixt ures, high-energy milling of 60h led to formation of the Mo(Fe, Si) supers aturated solid solution (Moss); and to a remarkable expansion of the solub ility of Fe, Si in molybdenum. The transformation of Moss to an amorphous phase was identified after longer time milling. In the milling process, the grain size of Mo (Fe, Si) decreased gradually and the internal stress increased linearly. After 40 h milling, the grain size was reduced to about 11 nm. SEM analysis of milled powders showed that the particle size increased initially with milling time. After 195 h milling, particles exhibited a spherical morphology and the particle size were reduced to about 100 nm. 相似文献
993.
994.
G. Antou G. Montavon F. Hlawka A. Cornet C. Coddet 《Journal of Thermal Spray Technology》2006,15(4):765-772
Complex multiscale pore network architecture characterized by multimodal pore size distribution and connectivity develops
during the manufacture of ceramic thermal spray coatings from intra- and interlamellar cracks generated when each lamella
spreads and solidifies to globular pores resulting from lamella stacking defects. This network significantly affects the coating
properties and their in-service behaviors. De Hoff stereological analysis permits quantification of the three-dimensional
(3D) distribution of spheroids (i.e., pores) from the determination of their two-dimensional (2D) distribution estimated by
image analysis when analyzing the coating structure from a polished plane. Electrochemical impedance spectroscopy electrochemically
examines a material surface by frequency variable current and potential and analyzes the complex impedance. When a coating
covers the material surface, the electrolyte percolates through the more or less connected pore network to locally passivate
the substrate. The resistive and capacitive characteristics of the equivalent electrical circuit will depend upon the connected
pore network architecture. Both protocols were implemented to quantify thermal spray coating structures. Al2O3-13TiO2 coatings were atmospherically plasma sprayed using several sets of power parameters, are current intensity, plasma gas total
flow rate, and plasma gas composition in order to determine their effects on pore network architecture. Particle characteristics
upon impact, especially their related dimensionless numbers, such as Reynolds, Weber, and Sommerfeld criteria, were also determined.
Analyses permitted identification of (a) the major effects of power parameters upon pore architecture and (b) the related
formation mechanisms.
This article was originally published inBuilding on 100 Years of Success, Proceedings of the 2006 International Thermal Spray Conference (Seattle, WA), May 15–18, 2006, B.R. Marple, M.M. Hyland, Y.-Ch. Lau, R.S. Lima, and J. Voyer, Ed., ASM International, Materials
Park, OH, 2006. 相似文献
995.
996.
997.
本文首先介绍了系统失效的分支-界限分析法,然后以空间桁架系统为例用分支-界限分析法进行了可靠性分析。系统失效的分支-界限分析法直观、明了,适合对实际工程中的复杂系统进行可靠性分析。 相似文献
998.
我国空军多架现役重型战斗机的结构损伤(裂纹)经用复合材料微波快速抢修技术修复。本文以此为例,详细推介了这一我国独创的快速抢修技术。 相似文献
999.
H. Fukanuma 《Journal of Thermal Spray Technology》1994,3(1):33-44
Thermal spray coatings have porosity; however, reasons for the production of porosity during the coating process are not known.
This paper proposes a physical and mathematical model for the production of porosity by considering deformation of a molten
particle during thermal spray coating processes. The theoretical model shows that the impinging velocity, the ambient gas
pressure, the particle diameter, and the molten material viscosity contribute to producing porosity. This paper also proposes
that there is a porosity distribution along the splat radius and that most of the porosity exists in the periphery of the
splat. Also, a flattening model proposed in this work agrees well with the results of Engel (Ref 1). 相似文献
1000.
铸铁件电弧冷焊熔合区白口组织的控制 总被引:3,自引:0,他引:3
进行了冷焊条件下控制铸铁件焊补区白口组织的试验.结果表明,采用Si-Ca-Al-Bi系合金粉层对焊补熔合区进行集中强石墨化孕育处理及焊前在缺陷表面形成Ni基合金粉末喷涂层,均可消除熔合区白口 相似文献