The use of macroscopic modelling of intermetallic phases in aluminium alloys in the study of ferricyanide accelerated chromate conversion coatings

Chromate conversion coatings are used on aluminium alloys, primarily for their renowned corrosion resistant properties. Although these coatings are in common industrial use, neither the protection mechanisms, nor the coating interation with the intermetallic precipitation phases are fully understood. Macroscopic models have been developed in order to represent the galvanic cells present in aluminium alloys due to the presence of such intermetallic particles. Particles modelled include CuAl₂, FeAl₃ and Cu₂FeAl₇, all know to be cathodic to the aluminium matrix. Variations in deposition, both in composition and thickness, are indicative of the mechanisms of deposition over each phase. Characterisation of the coating deposition was carried out using X-ray photoelectron spectroscopy, Rutherford backscattering spectroscopy, Auger electron spectroscopy, scanning electron microscopy with X-ray analysis. Depositional characteristics have been determined for each phase. The coating on the intermetallic phases is primarily Al oxide, and is significantly thinner than the coating on the matrix. This coating on the matrix consists mainly of a mixed Cr/Al oxide. The coating on the intermetallic phases was only one tenth the thickness of the matrix coating, and contained higher levels of Fe, Al and O. Matrix coating chemistry predominated with Cr, O, Fe and N, indicative of a chromate conversion coating. The mechanism for reduced rates of deposition over intermetallic phases was found to be affected by fluorine ion attack leading to intermetallic de-alloying and decomposition of Fe(CN)₆²⁻ accelerator into amide groups on the matrix.     

The many limits of mixed means

The sequences introduced by Carlson (1971) are variants of the Gauss arithmetic geometric sequences (which have been elegantly discussed by D. A. Cox (1984, 1985)). Given (complex)a ₀,b ₀ we define

Mo2C膜表面粗糙化规律的计算机模拟

引入晶粒边界修正,改进了Ｍｏ２Ｃ膜表面粗糙化物理模型,将ＤＴ２模型推广到包括有温度的情况对Ｍｏ２Ｃ膜表面形态进行计算机模拟并统计模拟图的高度分布,确定表面粗糙度随沉积时间和基底温度的变化规律,结果表明：引入晶粒边界修正大大促进了理论与实验结果的一致,Ｍｏ２Ｃ膜表面粗糙化属快速粗造化,粗造度随基底温度升高在而非线性地增大。     

激光光束传输因子M2的一些问题

本文讨论与M²因子有关的一些问题,指出在近轴近似条件下由光束的二阶强度矩定义的M²因子满足M²≥1,其中只有对基模高斯光束等式才成立.由光束的功率通量值定义的M²因子(M_pc²)有可能小于1,M_pc²的大小取决于所定义的光斑半径内包含的光功率的百分数.通过计算光场的二阶矩,我们获得了轴向相干叠加的高斯光束的M²因子的解析解.     

双金属团簇Cu12Fe吸附CO和H2的理论研究

基于第一性原理密度泛函理论(DFT)方法研究了Cu₁₂Fe团簇的结构稳定性、热力学稳定性和反应活性.计算得出正二十面体Fe原子核心团簇Ih-core比正二十面体Fe原子壳层团簇Ih-shell的热力学稳定性更强.通过分析吸附能讨论了CO和H₂在Ih-core团簇上的吸附构型.计算结果表明,Ih-core团簇以顶角Corner位吸附CO时吸附能最大,吸附模型最稳定,H₂吸附过程中发生了解离,两个氢原子均形成表面Facet位吸附构型.最后,通过分析前线轨道得到吸附过程的轨道信息.     

高功率可调谐连续NaCl：（F2^＋）H色心激光器

报道了掺硫和掺氧ＮａＣｌ：（Ｆ２＾＋）Ｈ色心激光器最新实验结果。最高输出功率分别达３Ｗ和４．８Ｗ。实验比较了掺硫及掺氧（Ｆ２＾＋）Ｈ心的热光稳定性。     

高温高压下SrB4O7：Eu2+玻璃的晶化

 利用X射线衍射和Eu²⁺发射光谱方法研究了非晶玻璃SrB₄O₇在高温高压下的晶化。结果表明：在5.0 GPa压力下，200 ℃仍为玻璃态，只有几个强度极低的小峰，表明有晶化的迹象；600 ℃时已基本晶化，但为SrB₄O₇正交相与SrB₄O₇高压立方相二相共存；当温度提高到1 000 ℃时，晶化成了近单相的与常压SrB₄O₇粉末晶体相同的正交结构。伴随晶化度的加强，Eu²⁺发射强度增强，与Ｘ射线衍射结果相一致。     

Cd3Al2Ge3O12:Mn2+锗酸盐石榴石光谱性质

本文报道室温下Cd₃Al₂Ge₃O₁₂:Mn²⁺(简称CAGG:Mn²⁺)锗酸盐石榴石的漫反射光谱、激发和发射光谱.在UV光激发下,在CAGG中Mn²⁺离子发射强黄光,这是基质到Mn²⁺离子无辐射能量传递的结果.Mn²⁺的黄发射带是由一个弱的红带和一个强的绿带所组成.讨论了这两个Mn²⁺发射带的起因.     

On the non-BoltzmannA-X emission in Na2 following laser excitation of theB state

A ¹Σ _u ⁺ -X ¹Σ _g ⁺ emission in Na₂ is observed following excitation ofB ¹π _u by various lines of an argon ion laser. The excitation energy ofB ¹π _u is collisionally transferred to the (2)¹Σ _g ⁺ which then radiatively populates theA ¹Σ _u ⁺ state. The Na vapour is contained in a stainless steel crossed heat pipe with Ar buffer gas and temperature around 600°C. For all laser lines except 4579 Å, the coarse features ofA-X emission are independent of the laser wavelength. However, at high resolution the finer differences between different laser line excitation are explained. Variousv′-v″ transitions in this emission are identified. Computer simulation is presented to help explain some features of this emission.     

原子吸收光度法测定钢铁及合金中的铌量

本法叙述了一氧化二氮－乙炔火焰原子吸收光度法测定铌量，用鞣酸沉淀分离和在盐酸－氢氟酸介质中加入增感剂三氯化铝，灵敏度１２μｇ／ｍＬ／１％吸收，检出限６．１μｇ／ｍＬ。