Magnetic Perovskite Superlattices Grown by Pulsed Laser Deposition

Magnetic multilayers of (SrRuO₃) _m (SrMnO₃) _n were grown artificially using the pulsed laser deposition technique on (001)-oriented SrTiO₃ substrates. The temperature and magnetic field dependent reisistivity of the superlattices consisting of ferromagnetic (FM) SrRuO₃ and antiferromagnetic (AFM) SrMnO₃ are studied as a function of the SrRuO₃ unit cells. We observed a pinned/biased moment instead of the biased field in the superlattices and we redefine the structure as AFM/FM(Pin)/FM(Free)/FM(Pin) units below a critical field.     

Comparison of Particle Size Distributions Measured Using Different Techniques

In this article, particle size distributions (PSDs) measured by different techniques, including image analysis (IA), laser diffraction (LD), ultrasonic attenuation spectroscopy (UAS), and focused-beam reflectance measurement (FBRM), are compared for spherical glass beads and nonspherical silica flakes. It is shown that particle shape strongly affects the results obtained by different techniques. For spheres, the PSDs obtained by IA, LD, and UAS agree well. There is no consistent result among different particle measurement techniques for nonspherical particles. The conversion between PSDs obtained by IA, LD, and UAS has been based on particle shape factors. Caution must be exercised when a measured chord length distribution (CLD) is used to indicate the PSD during a process because the CLD result obtained by FBRM is complex, depending not only on the PSD, but also on particle optical properties and shape.     

Study of incomplete transformations of near equiatomic TiNi shape memory alloys by DSC methods

The incomplete transformations of near equiatomic TiNi shape memory alloys were investigated by differential scanning calorimeter (DSC). The results showed that the incomplete transformation can induce multistage phase transformation in a sample showing R-phase transformation, when the turn back temperature located in a value between R_f and M_s, the heat flow detected upon following heating only shows one endothermic peak. With decreasing the turn back temperature to a temperature between M_s and M_f, two endothermic peaks (multistage phase transformation) can be observed upon the following heating. There were no incomplete transformation induced multistage phase transformations in a sample without R-phase transformation.     

Study of transformation behavior in a Ti–4.4 Ta–1.9 Nb alloy

An alloy of composition Ti–4.4 wt.% Ta–1.9 wt.% Nb is being developed as a structural material for corrosion applications, as titanium and its alloys possess excellent corrosion resistance in many oxidizing media. The primary physical metallurgy database for the Ti–4.4 wt.% Ta–1.9 wt.% Nb alloy is being presented for the first time. Determination of the β transus, M_s temperature and classification of the alloy have been carried out, employing a variety of microscopy techniques, X-ray diffraction (XRD), micro-hardness and differential scanning calorimetry (DSC). The β transition temperature or β transus determined using different experimental techniques was found to agree very well with evaluations based on empirical calculations. Based on chemistry and observed room temperature microstructure, the alloy has been classified as an + β titanium alloy. The high temperature β transforms to either ′ or + β by a martensitic or Widmanstatten transformation. The mechanisms of transformation of β under different conditions and characteristics of different types of have been studied and discussed in this paper.     

Advanced resonant ultrasound spectroscopy for measuring anisotropic elastic constants of thin films

This paper presents an advanced resonant ultrasound spectroscopy (RUS) method to determine the elastic constants C_ij of thin films. Polycrystalline thin films often exhibit elastic anisotropy between the film growth direction and the in‐plane direction, and they macroscopically show five independent elastic constants. Because all of the C_ij of a deposited thin film affect the mechanical resonance frequencies of the film/substrate layer specimen, measuring resonance frequencies enables one to determine the C_ij of the film with known density, dimensions and the C_ij of the substrate. Resonance frequencies have to be measured accurately because of low sensitivity of the C_ij of films to them. We achieved this by a piezoelectric tripod. Mode identification has to be made unambiguously. We made this measuring displacement–amplitude distributions on the resonated specimen surface by laser Doppler interferometry. We applied our technique to copper thin film and diamond thin film. They show elastic anisotropy and the C_ij smaller than bulk values of C_ij. Micromechanics calculations indicate the presence of incohesive bonded regions.     

大功率激光加工设备实时参数检测系统

阐述了利用分光器、衰减器和热电堆检测激光功率的原理和方法,该检测方法满足了系统实时参数检测和对测量精度优于5%的要求;介绍了利用隔离器抑制激光电源产生的强共模干扰对系统影响方法和系统嵌入式硬件设计的原理和系统软件功能。     

光纤传感器在机器人导航中的应用

简述了光纤传感器的工作原理,并测试了颜色对BF3RX光纤传感器测试位移的影响;利用该传感器这一特性在扫查机器人中进行导航,介绍了导航原理和导航算法,实验结果表明:利用该光纤传感器进行导航,具有较高的精度,完全可以满足超声波串列扫查的要求。     

激光强化处理参数对轧辊表面性能的影响

通过试验，研究了激光功率、光斑直径、扫描速度、搭接量和合金粉含量等激光处理工艺参数对轧辊表面性能的影响，结果表明，轧辊表面经激光淬火处理后。性能稳定，耐磨性和抗疲劳性均有所提高，达到了生产要求．     

可调脉宽YAG激光脱毛机研究

介绍了可调脉宽YAG激光脱毛机的工作原理，整机结构和关键技术指标。该机工作频率为1次／秒，脉宽可达40ms，单脉冲输出可达40J，能量密度达140J／cm^2，经初步临床实验，取得了较满意的结果。