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Sintering in Ceramics and Solid Oxide Fuel Cells

机译：陶瓷和固体氧化物燃料电池中的烧结

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摘要

Nature's propensity to minimize energy, and the change in energy with respect to position, drives diffusion. Diffusion is a means by which mass transport resulting in the bonding of the particles of a powder compact can be achieved without melting. This phenomenon occurs in powdered materials near their melting temperature, and is referred to as "sintering". Because of the extreme melting temperature of some materials, sintering might be the only practical means of processing. The complexity and subtlety of sintering ceramics motivated the evaluation of empirical data and existing sintering models.;This project examined polycrystalline cubic-zirconia sintering with and without transition-metal oxide additions that change sintering behavior. This study was undertaken to determine how sintering aids affect the driving force, and activation energy, the energy barrier that must be overcome in order for an atom or ion to diffuse, of the densification occurring during sintering. Examination of commercially-available cubic-zirconia powder sintering behavior was undertaken with dilatometry, which allows monitoring of the length change a material undergoes as it sinters, and with scanning electron microscopy, which facilitates the study of sintered-sample microstructure. MATLAB algorithms quantifying sintering results were developed.;Results from this work include proposed definitions of a 26-year-old undefined function of density factor in a well-accepted mathematical model of sintering. These findings suggest activation energy is not changing with density, as is suggested by recent published results. The first numerical integration of the studied sintering model has been performed. With these tools, a measure of the activation energy of densification of cubic-zirconia with and without the addition of cobalt-oxide as a sintering aid has been performed. The resulting MATLAB algorithms can be used in future sintering studies.;It is concluded that sintering enhancement achieved with cobalt-oxide addition comes from reduction in activation energy of densification of cubic-zirconia. Further, it is suggested that the activation energy of densification does not change with material density. This conclusion is supported by the sensitivity of the numerical integration of the aforementioned sintering model to changes in activation energy.
机译：自然界倾向于使能量最小化，以及能量相对于位置的变化，推动了扩散。扩散是一种可以实现导致粉末压块颗粒结合的质量传输而不会熔化的方法。这种现象在粉末状材料的熔化温度附近发生，被称为“烧结”。由于某些材料的极高熔化温度，烧结可能是唯一可行的加工方法。烧结陶瓷的复杂性和微妙性促使了对经验数据和现有烧结模型的评估。该项目研究了添加和不添加改变烧结行为的过渡金属氧化物的多晶立方氧化锆烧结。进行这项研究是为了确定烧结助剂如何影响烧结过程中致密化的驱动力和活化能，活化能是必须克服的能垒，以使原子或离子扩散。商业上可利用的立方氧化锆粉末的烧结行为是用膨胀计进行的，它可以监测材料在烧结过程中所经历的长度变化，而扫描电子显微镜则可以方便地研究烧结样品的微观结构。开发了用于量化烧结结果的MATLAB算法。该工作的结果包括在公认的烧结数学模型中对26岁的密度因子未定义函数的拟议定义。这些发现表明，活化能并没有随密度变化，正如最近发表的结果所表明的那样。已经完成了所研究烧结模型的第一次数值积分。使用这些工具，已经测量了添加和不添加氧化钴作为烧结助剂的立方氧化锆致密化的活化能。所得的MATLAB算法可用于未来的烧结研究。结论：添加氧化钴可提高烧结效率，是由于立方氧化锆致密化活化能的降低。此外，建议致密化的活化能不随材料密度而变化。前述烧结模型的数值积分对活化能变化的敏感性支持了这一结论。

著录项

  • 作者

    Hunt, Clay Dale.;

  • 作者单位

    Montana State University.;

  • 授予单位 Montana State University.;
  • 学科 Materials science.;Engineering.
  • 学位 Ph.D.
  • 年度 2017
  • 页码 360 p.
  • 总页数 360
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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