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441.
等离子熔射制备功能梯度涂层及其应用进展 总被引:3,自引:1,他引:3
介绍了功能梯度材料的概念及其应用前景,分析了几种功能梯度材料制备方法的优缺点,重点介绍等离子熔射制备功能梯度材料的工艺过程和应用进展。 相似文献
442.
XUE Weia b YAO Zhong-pinga JIANG Zhao-huaa * aDepartment of Applied Chemistry Harbin Institute of Technoogy Harbin China bHeilongjiang Provincial Institute of Measurement Verification Harbin China 《中国航空学报》2006,19(Z1)
Compound ceramics coatings on the Ti-6Al-4V alloy were prepared by the direct current micro-plasma oxidation (MPO) in NaAlO2 solution. The composition and morphology of the coatings were studied with the X-ray diffraction (XRD) and the scanning electron microscopy (SEM), respectively. Inductively coupled plasma atomic emission spectrometer technique was used to analyze the solution features of Ti-6Al-4V alloy in the process of preparation. The results reveal that Al2TiO5 forms in the coatings at the initial stages of MPO reaction, and its content changes rapidly with the reaction continuing: after 20 min, the ceramics coatings are composed of α-Al2O3, γ-Al2O3 and Al2TiO5, but after 40 min, its main composition is of α-Al2O3. The content of Ti in the solution will increase when the MPO time extends, and as will Al in the anode area until, after 30 min, it reaches the maximum and keeps constant from then on. Both substrata of Ti and Al in the electrolyte join the MPO reaction at the initial stage, where the formation of Al2TiO5 happens; but as the MPO reaction prolongs, more and more Al in the electrolyte will take part in the reaction, leading to the appearance of a large amount of Al2O3. 相似文献
443.
444.
Kelvin-Helmholtz Instability (KHI) is an MHD-scale instability that grows in a velocity shear layer such as the low-latitude
boundary layer of the magnetosphere. KHI is driven unstable when a velocity shear is strong enough to overcome the stabilization
effect of magnetic field. When the shear is significantly strong, vortices in the nonlinear stage of KHI is so rolled-up as
to situate magnetospheric plasma outward of the magnetosheath plasma and vice versa. The big question is if such highly rolled-up
vortices contribute significantly to the plasma transport across the boundary and to the filling of the plasma sheet by cool
magnetosheath component, which is observed under northward Interplanetary Magnetic Field (IMF) condition. Here we review our
recent results from two-fluid simulations of MHD-scale KHI with finite electron inertia taken into account. The results indicate
that there is coupling between the MHD-scale dynamics and electron-scale dynamics in the rolled-up stage of the vortices.
While the details differ depending on the initial magnetic geometry, the general conclusion is that there is significant modification
of the MHD-scale vortex flow pattern via coupling to the micro-physics. The kick-back from the parasitic micro-physics enhances
highly the potential for large-scale plasma mixing of the parent MHD-scale vortices, which is prohibited by definition in
ideal-MHD. We also review our recent 3-D MHD simulation results indicating that KHI vortex can indeed roll-up in the magnetotail-flank
situation despite the strong stabilization by the lobe magnetic field. These results encouraged us to search for evidence
of rolled-up vortices in the Cluster formation flying observations. As reviewed in this paper, a nice event was found during
northward IMF interval. This interval is when the plasma transport via large scale reconnection becomes less efficient. The
finding supports the argument that KHI is playing some role in transporting solar wind into the magnetosphere when the normal
mode of transport cannot dominate. 相似文献
445.
Distributions with excess numbers of superthermal particles are common in space environments. They are well modelled by the
isotropic kappa distribution, or, where magnetic effects are important, the kappa-Maxwellian. This paper presents a review
of some studies of electrostatic and electromagnetic waves in such plasmas, based on the associated generalized plasma dispersion
functions, Z
κ and Z
κM. In particular, the effects of low values of κ are considered, i.e. strongly accelerated distribution functions. Recently the full susceptibility tensor for oblique propagation of electromagnetic
waves in a kappa-Maxwellian magnetoplasma has been established and has been applied to the study of whistler waves. 相似文献
446.
447.
2Cr13钢的全方位离子注入与离子束增强沉积复合表面强化处理 总被引:4,自引:0,他引:4
对 2Cr13不锈钢表面进行了等离子体浸没离子注入(PIII)与离子束增强沉积(IBED)复合强化处理。对强化后的试样进行了俄歇电子能谱(AES)、X光电子能谱(XPS)分析及显微硬度、摩擦磨损和耐腐蚀性能测试。结果表明,处理后的试样表面层中含有强化相TiN和CrN;与基体相比,被处理试样的显微硬度显著增大,最大增幅达80 4%;摩擦系数降至 0 2~0 3,磨痕宽度最大减少了近 4倍;腐蚀电位最大提高了 5倍,腐蚀电流密度减少了 26倍。磨损中粘着现象大大减轻,耐磨耐蚀性能得到了显著改善。 相似文献
448.
等离子体流动控制作为一种新概念主动流动控制技术,其物理作用依据之一是“动力效应”。体积力作为表征“动力效应”的重要参数,对研究等离子体流动控制的原理具有重要意义。介绍了实验原理及系统的基本组成,对等离子体气动激励体积力进行了实验测量。结果表明:体积力的大小在mN量级;固定激励频率,激励电压增大时,体积力增大,且线性关系非常明显;固定激励电压,体积力受激励频率的影响不大。 相似文献
449.
450.
航空等离子体动力学与技术的发展 总被引:8,自引:1,他引:8
自20世纪60年代以来,美国、俄罗斯等发达国家开始研究等离子体的性能.近年来,以美国为首的西方国家在航空等离子体动力学与技术的研究取得了突破性的进展,国内相关研究也取得了一些进展和自主创新.本文主要介绍了空军工程大学等离子体动力学重点实验室的等离子体流动控制技术研究成果,主要包括改善飞行器气动性能和推进效能、等离子体冲... 相似文献