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Consolidation of amorphous oxide powders using spark plasma sintering.

机译：使用火花等离子体烧结固结无定形氧化物粉末。

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摘要

The objective of this study is to synthesize amorphous oxide powders and sinter the systems close to or at theoretical density for optical transparency while retaining the amorphous structure using the Spark Plasma Sintering (SPS) method. In addition, the parameters that govern the formation of these systems were investigated. The main powder processing techniques are sol-gel, flame-spaying and spherodizing.;The systems chosen for this study are alumina-rich rare earth oxides of alumina-lanthana (AL) and alumina-gadolinia (AG). These systems cannot be formed in bulk form by the melt method because of the extremely fast cooling rates needed to maintain the glassy phase. Sintering is an alternative method. Attempts were made by others to form or sinter these systems with little or no success. Amorphous powders of different processing methods and compositions were sintered using SPS at temperatures ranging from 840 to 900°C and pressures from 164 to 742 MPa. For the AL system, the highest transmittance which correlates to the highest relative density without crystallization was obtained with the parameters of 860°C, 742 MPa, and a 200C.min -1 ramp rate and a 4 min hold time for transmittance in the UV/Vis range of more than 40% at 650 nm. In the IR range, the transmittance was above 65%. At lower pressures, e.g. 164 MPA, increasing the hold time increased the transmittance of the sample. Likewise, the AG system showed higher transmittance with increased pressure. Densities of both systems increased with increasing temperature. However, above 880°C, the increase in densities was due to partial crystallization which resulted in the decrease of transmittance. The spherodization process resulted in the crystallization of some of the beads. The transmittance could be improved by removal of the crystallized beads since the amorphous phase sintered to high densities. The flame spray method resulted in nanometric particles which also sintered to high densities. The powders contained silica fibers from the collection process which causes scattering and a reduction of the transmittance. The fast heating rates and short sintering times of the SPS make it possible to sinter amorphous systems at higher temperatures compared to other sintering techniques without crystallization.
机译：这项研究的目的是合成无定形氧化物粉末，并通过火花等离子体烧结（SPS）方法烧结接近或达到理论密度的光学透明性体系，同时保留无定形结构。另外，研究了控制这些系统形成的参数。主要的粉末加工技术是溶胶-凝胶，火焰喷涂和球化。本研究选择的系统是氧化铝-氧化镧（AL）和氧化铝-氧化d（AG）的富含氧化铝的稀土氧化物。这些系统不能通过熔融法以散装形式形成，因为维持玻璃态需要极快的冷却速率。烧结是另一种方法。其他人试图建立或烧结这些系统的尝试很少或没有成功。使用SPS在840至900℃的温度和164至742 MPa的压力下烧结不同加工方法和组成的非晶态粉末。对于AL系统，通过860°C，742 MPa，200C.min -1的升温速率和4分钟的UV保持时间参数，获得了与最高相对密度而不结晶相关的最高透射率。 / Vis范围在650 nm时超过40％。在IR范围内，透射率高于65％。在较低的压力下164 MPA，增加保持时间会增加样品的透射率。同样，AG系统在压力增加时显示出更高的透射率。两个系统的密度都随温度的升高而增加。然而，在880℃以上，密度的增加归因于部分结晶，这导致透射率降低。球化过程导致一些珠粒结晶。由于非晶相被烧结成高密度，因此可以通过除去结晶珠来提高透射率。火焰喷射法产生纳米颗粒，该纳米颗粒也被烧结成高密度。这些粉末包含来自收集过程的二氧化硅纤维，这会引起散射并降低透射率。与没有结晶的其他烧结技术相比，SPS的快速加热速率和较短的烧结时间使其可以在更高的温度下烧结非晶体系。

著录项

  • 作者

    Fredrick, Daniela Marisa.;

  • 作者单位

    University of California, Davis.;

  • 授予单位 University of California, Davis.;
  • 学科 Engineering Materials Science.
  • 学位 Ph.D.
  • 年度 2009
  • 页码 100 p.
  • 总页数 100
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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