Solid–state diffusion–controlled growth of the phases in the Au–Sn system

The solid state diffusion-controlled growth of the phases is studied for the Au–Sn system in the range of room temperature to 200 °C using bulk and electroplated diffusion couples. The number of product phases in the interdiffusion zone decreases with the decrease in annealing temperature. These phases grow with significantly high rates even at the room temperature. The growth rate of the AuSn₄ phase is observed to be higher in the case of electroplated diffusion couple because of the relatively small grains and hence high contribution of the grain boundary diffusion when compared to the bulk diffusion couple. The diffraction pattern analysis indicates the same equilibrium crystal structure of the phases in these two types of diffusion couples. The analysis in the AuSn₄ phase relating the estimated tracer diffusion coefficients with grain size, crystal structure, the homologous temperature of experiments and the concept of the sublattice diffusion mechanism in the intermetallic compounds indicate that Au diffuses mainly via the grain boundaries, whereas Sn diffuses via both the grain boundaries and the lattice.     

泄漏Lamb波在固井质量评价中的应用

轻质水泥在油气田固井中的广泛应用使得传统声阻抗测井方式难以准确地对固井水泥胶结质量作出评价。本文基于弯曲型Lamb波传播特征对层状介质胶结质量较为敏感的特点,首先对套管井建立合适的层状介质模型,计算了层状介质的平面波反射系数,从反射系数的角度探讨了在套管井内激发弯曲型Lamb波的条件。然后依据该条件并结合声波角谱理论计算了稳态有限宽脉冲束入射时在套管井内产生的弯曲型Lamb波泄漏波的时间波列信号。通过对泄漏波波列信号的分析,得到了弯曲型Lamb波与套管井水泥胶结质量间的关系。研究表明,入射声波在满足一定条件下可以在套管内激发弯曲型Lamb波,其传播时的衰减率与套管水泥胶结质量以及水泥的声学参数均相关,当水泥为轻质水泥或者普通水泥时,其衰减率随着套管水泥间水层厚度的增加而减小,当水泥为快水泥时,其衰减率随着水层厚度的减小而增加,但当水层厚度减为零即套管水泥胶结良好情况下,其衰减率转而变小。     

A micromechanical model for porous materials with a reinforced matrix

In this study a micromechanical model is proposed for ductile porous material whose matrix is reinforced by small inclusions. The solid phase is described by a pressure sensitive plastic model. Based on works of Maghous et al. [6], a macroscopic plastic criterion is firstly obtained by using a two-step homogenization procedure. The effect of porosity at the mesoscale and the influence of inclusions at the microscale are taken into account simultaneously by this criterion. With a non-associated plastic flow rule, the micro-macro model is applied to modeling of mechanical behavior of a cement paste. In particular, we have considered at the microscopic scale the formation of calcite grains by carbonation process in the solid matrix. The studied cement paste is then seen as a reinforced matrix–pore system. Comparisons between numerical results and experimental data show that the proposed model is able to capture the main features of the mechanical behavior of the studied material.     

水泥生料品质激光在线检测设备研制

水泥质量的优劣直接影响到建筑工程的安全,使用品质合格的水泥材料是保证工程结构质量的必要前提,因此快速检测水泥生料成份对于及时指导调整原料配比和保障水泥产品品质具有重要意义。传统的生料检测需要经过取样、制样、化验等环节,检测结果严重滞后于生产。我们通过产学研协同攻关,研制了一套基于激光诱导击穿光谱(laser-induced breakdown spectroscopy, LIBS)技术的水泥生料品质在线检测设备,该设备由LIBS光学检测系统和气动取送样系统两部分组成,实现了对水泥生产线上水泥生料品质的实时连续测量,避免了传统的取制样环节,从而大大缩短了化验时间,所测水泥生料成分的实时数据能够及时指导调整水泥原料的配比,保证水泥质量的合格。我们利用该LIBS水泥品质在线检测设备对水泥生产线上生料中的主成分Al₂O₃,CaO,Fe₂O₃,MgO和SiO₂进行了定量分析,利用全谱归一化和支持向量机(support vector machine,SVM)对水泥生料建立定标模型,对水泥生料中Al₂O₃,CaO,Fe₂O₃,MgO和SiO₂测量的最大误差分别是0.34%,0.35%,0.07%,0.14%和0.55%。现场实验结果表明,本水泥生料品质激光在线检测设备的测量结果与传统化验法的结果相吻合,测量精度与X射线荧光光谱法(XRF)相接近,从而证实了LIBS可以作为水泥在线检测的一种有前景的方法。     

Deformation behaviour in advanced heat resistant materials during slow strain rate testing at elevated temperature

In this study, slow strain rate tensile testing at elevated temperature is used to evaluate the influence of temperature and strain rate on deformation behaviour in two different austenitic alloys. One austenitic stainless steel (AISI 316L) and one nickel-base alloy (Alloy 617) have been investigated. Scanning electron microscopy related techniques as electron channelling contrast imaging and electron backscattering diffraction have been used to study the damage and fracture micromechanisms. For both alloys the dominante damage micromechanisms are slip bands and planar slip interacting with grain bounderies or precipitates causing strain concentrations. The dominante fracture micromechanism when using a slow strain rate at elevated temperature, is microcracks at grain bounderies due to grain boundery embrittlement caused by precipitates. The decrease in strain rate seems to have a small influence on dynamic strain ageing at 650°C.     

EB/UV treatment of protective coatings for porous materials

A method for improving surface properties of porous inorganic materials is presented. The method is particularly tailored to cement-based materials in order to obtain properties suitable for mechanical applications such as dies manufacturing, where hardness, abrasion resistance and low friction are requested. The coating system is based upon using two coatings of different characteristics. The underlying base coating layer is infiltrated in air on three different formulations of hardened cement composite. Two different bi-component resins, one relatively soft and the other relatively hard, were tested as underlying surface coating. The outer surface coating, based upon a bi-component resin characterized by high hardness, is added after hardening and curing of the first layer. Both coatings were chemically hardened and then cured with EB. UV curing is also suitable for the outer surface coating. An experimental campaign was carried out in order to evaluate the influence of radiation processing as curing treatment with reference to particular investigated materials. Hardness and resistance to peeling of coating systems have been measured and are presented.     

Some results on the proportional reversed hazards model

The proportional reversed hazards model consists in describing random failure times by a family {[F(x)]^θ, θ>0} of distribution functions, where F(x) is a baseline distribution function. We show various results on this model related to some topics in reliability theory, including ageing notions of random lifetimes, comparisons based on stochastic orders, and relative ageing of distributions.     

Colouring Agents for SBR Vulcanizates and Their Effects on Ageing and UV Radiation Resistance

Summary: Metal free and some metal-perylene polymers as well as some metal phthalocyanine polymers were incorporated into styrene butadiene rubber (SBR) compounds as colouring agents. The ageing and UV resistance of the vulcanizates obtained were studied in terms of their mechanical properties. The results obtained revealed that cobalt perylene and cobalt phthalocyanine polymers showed superior performance in SBR vulcanizates against thermal ageing and UV radiation. The optimum concentration of cobalt phthalocyanine polymer was found to be 1 phr (parts per hundred parts of rubber).     

基于LIBS技术的水泥粉末在线成分分析

在工业现场生产水泥的过程中，各种成分的含量直接影响着水泥的质量，因此如何快速准确地监测水泥中各个成分的含量意义重大。采用的实验方式为，将不经过任何预处理的水泥粉末直接放入位于二维移动平台上的物料盒中，通过激光诱导击穿光谱(LIBS)直接对水泥粉末表面的不同位置进行激发检测，对得到的光谱数据首先进行归一化和主成分分析等预处理操作，然后针对水泥中Ca, Si, Al, Fe, Mg五种元素，分别建立偏最小二乘(PLS)和支持向量回归(SVR)两种定量分析模型进行方法比较。此外，对比了粉末状水泥与压片式水泥两种测量方式的结果。实验结果表明，采用粉末状水泥直接测量的方式下，针对水泥样品元素浓度与所得到的光谱中特征线强度的关系，SVR方法比PLS方法更具优势，粉末状水泥直接测量的精度接近压片式测量的精度，说明LIBS技术对水泥粉末状样品直接在线测量具有可行性。