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首页> 外文学位 >Synthesis of Silicon Nitride and Silicon Carbide Nanocomposites through High Energy Milling of Waste Silica Fume for Structural Applications.
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Synthesis of Silicon Nitride and Silicon Carbide Nanocomposites through High Energy Milling of Waste Silica Fume for Structural Applications.

机译：通过高能磨碎废硅粉在结构应用中合成氮化硅和碳化硅纳米复合材料。

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摘要

Nanocomposites have been widely used in a multitude of applications in electronics and structural components because of their improved mechanical, electrical, and magnetic properties. Silicon nitride/Silicon carbide (Si 3N4/SiC) nanocomposites have been studied intensively for low and high temperature structural applications, such as turbine and automobile engine components, ball bearings, turbochargers, as well as energy applications due to their superior wear resistance, high temperature strength, high oxidation resistance and good creep resistance. Silica fume is the waste material produced during the manufacture of silicon and ferro-silicon alloys, and contains 94 to 97 wt.% SiO2. In the present dissertation, the feasibility of using waste silica fume as the raw material was investigated to synthesize (I) advanced nanocomposites of Si3N4/SiC, and (2) porous silicon carbide (SiC) for membrane applications. The processing approach used to convert the waste material to advanced ceramic materials was based on a novel process called, integrated mechanical and thermal activation process (IMTA) process.;In the first part of the dissertation, the effect of parameters such as carbothermic nitridation and reduction temperature and the graphite concentration in the starting silica fume plus graphite mixture, were explored to synthesize nanocomposite powders with tailored amounts of Si3N4 and SiC phases. An effective way to synthesize carbon-free Si3N 4/SiC composite powders was studied to provide a clear pathway and fundamental understanding of the reaction mechanisms. Si3N4/SiC nanocomposite powders were then sintered using two different approaches, based on liquid phase sintering and spark plasma sintering processes, with Al 2O3 and Y2O3 as the sintering aids. The nanocomposites were investigated for their densification behavior, microstructure, and mechanical properties. Si3N4/SiC nanocomposites thus obtained were found to possess superior mechanical properties at much lower costs.;The second part of the work has comprised of the successful fabrication of bilayered SiC membranes with a graded porosity, consisting of porous nano-SiC layer on the surface of a porous coarse-grained SiC support layer. The effect of different particle sizes of SiC in the support layers was systematically studied. Also, the effects of sintering temperature were investigated to control the pore size, particle size and overall density of the bi-layered SiC membrane.
机译：纳米复合材料由于其改善的机械，电和磁性能而被广泛用于电子和结构部件的众多应用中。氮化硅/碳化硅（Si 3N4 / SiC）纳米复合材料因其优异的耐磨性，高耐磨性而被广泛研究用于低温和高温结构应用，例如涡轮和汽车发动机部件，球轴承，涡轮增压器以及能源应用。高温强度，高抗氧化性和良好的抗蠕变性。硅粉是在硅和铁硅合金制造过程中产生的废料，并且包含94至97重量％的SiO2。本文研究了以废硅粉为原料合成（I）Si3N4 / SiC高级纳米复合材料和（2）用于膜应用的多孔碳化硅（SiC）的可行性。用于将废料转化为高级陶瓷材料的加工方法是基于一种称为机械和热活化集成工艺（IMTA）的新型工艺。在论文的第一部分中，碳热氮化和碳等参数的影响探索还原温度和起始硅粉加石墨混合物中的石墨浓度，以合成具有定制量的Si3N4和SiC相的纳米复合粉末。研究了合成无碳Si3N 4 / SiC复合粉末的有效途径，为反应机理提供了清晰的途径和基础知识。然后，基于液相烧结和火花等离子体烧结工艺，使用Al 2O3和Y2O3作为烧结助剂，使用两种不同的方法烧结Si3N4 / SiC纳米复合粉末。研究了纳米复合材料的致密化行为，微观结构和机械性能。发现由此获得的Si3N4 / SiC纳米复合材料具有优异的机械性能，而成本却低得多。;第二部分工作是成功制造出具有分级孔隙率的双层SiC膜，该膜由表面上的多孔纳米SiC层组成多孔粗晶SiC支撑层的结构。系统地研究了不同粒径的SiC在支撑层中的影响。另外，研究了烧结温度的影响以控制双层SiC膜的孔径，粒径和总密度。

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  • 作者

    Suri, Jyothi.;

  • 作者单位

    University of Connecticut.;

  • 授予单位 University of Connecticut.;
  • 学科 Engineering Materials Science.
  • 学位 Ph.D.
  • 年度 2012
  • 页码 160 p.
  • 总页数 160
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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