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Diffusion of rhenium in Poco graphite.

机译：Po在Poco石墨中的扩散。

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摘要

Diffusion is a major concern for materials operating at high temperatures. Graphite is under serious consideration as a potential material for the construction of the receiver-absorber-converter which will be used in the Integrated Solar Upper Stage (ISUS) solar-powered spacecraft. One of the anticipated problems is the loss of graphite through diffusion at high temperatures. Although the diffusion of rhenium in graphite is not well understood, rhenium has been proposed as a diffusion barrier for graphite to prevent excessive loss of the material.;A technique to study the diffusion of rhenium in graphite was developed based on the technique of Rutherford Backscattering Spectroscopy (RBS). The graphite samples used in this experiment were Poco graphite purchased from UnocalRTM. The samples coated with rhenium were given diffusion anneals at temperatures between 1373 K and 2273 K for various periods of time in a vacuum electron beam furnace. The diffusion profiles were determined by examining the energy distribution of backscattered helium ions. It was therefore necessary to convert the RBS spectra into concentration profiles. RUMP (Rutherford Universal Manipulation Program) is a commercially available computer program which is limited to thin films with thicknesses up to approximately 300 nm.;A new algorithm for interpreting RBS spectra was developed by comparing the calculated spectra with the experimental data, and better fits for the RBS data were obtained. The intrinsic diffusion coefficients were determined using the Matano method.;The diffusion constants for rhenium in graphite were found to range from 1.5 x 10-18 m2/s at 1373 K to 1.9 x 10-17 m2/s at 2273 K, whereas the diffusion constants for carbon in rhenium ranged from 2.7 x 10 -18 m2/s at 1373 K to 3.3 x 10-17 m2/s at 2273 K. Both Arrhenius plots of rhenium in graphite and carbon in rhenium clearly showed a change in the slope with temperature, indicating that there are two diffusion mechanisms involved. At lower temperatures, rhenium atoms diffuse along the open pores in the Poco graphite, whereas at temperatures above 2073 K, diffusion of rhenium. through the graphite lattice becomes the dominant mechanism. (Abstract shortened by UMI.).
机译：扩散是在高温下工作的材料的主要问题。石墨正被认真考虑作为接收器-吸收器-转换器的构造的潜在材料，该接收器-吸收器-转换器将用于集成太阳能高层（ISUS）太阳能航天器。预期的问题之一是石墨在高温下因扩散而损失。尽管人们对understood在石墨中的扩散还不甚了解，但人们提出了as作为石墨的扩散阻挡层，以防止材料的过度损失。；基于卢瑟福背散射技术，开发了一种研究study在石墨中扩散的技术。光谱（RBS）。本实验中使用的石墨样品是从UnocalRTM购买的Poco石墨。在真空电子束炉中，将涂有rh的样品在1373 K和2273 K之间的温度下进行不同时间的扩散退火。扩散曲线是通过检查反向散射氦离子的能量分布来确定的。因此，有必要将RBS光谱转换为浓度曲线。 RUMP（卢瑟福通用操纵程序）是一种市售的计算机程序，仅限于厚度最大为300 nm的薄膜;通过将计算的光谱与实验数据进行比较，开发了一种解释RBS光谱的新算法，并且拟合效果更好获得RBS数据。使用Matano方法确定本征扩散系数; found在石墨中的扩散常数范围为1373 K时的1.5 x 10-18 m2 / s到2273 K时的1.9 x 10-17 m2 / s carbon中碳的扩散常数范围从1373 K时的2.7 x 10 -18 m2 / s到2273 K时的3.3 x 10-17 m2 / s。石墨中的A和碳中的碳的Arrhenius图均清楚地表明斜率发生了变化随温度变化，表明涉及两种扩散机制。在较低的温度下，rh原子沿着Poco石墨中的开孔扩散，而在2073 K以上的温度下，diffusion的扩散。通过石墨晶格成为主导机理。 （摘要由UMI缩短。）。

著录项

  • 作者

    Li, Jinglong.;

  • 作者单位

    Auburn University.;

  • 授予单位 Auburn University.;
  • 学科 Materials science.
  • 学位 Ph.D.
  • 年度 2000
  • 页码 162 p.
  • 总页数 162
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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