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Influence of the surface constitution on the as-sintered strength of Si_3N_4 micro specimens

机译：表面组成对Si_3N_4显微样品烧结强度的影响

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摘要

In order to study the significance of as-sintered surfaces for the strength of Si_3N_4 micro components, micro bending specimens with dimensions of 240 μm x 240 μm x 1400 μm were prepared from sintered reaction-bonded silicon nitride. The processing parameters sintering temperature and dwell time were varied, and two different types of powder bed were applied during sintering. The characteristic strength ó0 - determined by micro-3-point-bending tests - varied from about 500 to 1200 MPa. Strength values of about 1000 MPa and higher were observed when powder beds were applied which were newly prepared and doped with the sintering additives Y_2O_3, AI_2O_3, and MgO. In that case, the mass loss during sintering was negligible or even a small mass gain occurred. Samples sintered in used and undoped powder beds by contrast showed mass loss and an enrichment of the secondary phase YN-melilite (Y_2Si_3O_3N_4) at the surface; for these samples a0 was found to be restricted to about 500-700 MPa.Contrary to expectations, it was observed that the residual porosity - ranging from less than 1% up to 11% - does not act as a predominant strength-determining factor. Instead, the more or less pronounced formation of surface-near defects, due to the decomposition and volatilization of Si3 N4 during sintering, is considered to be decisive for the achievable strength. Mass loss and YN-melilite formation are indicators for defect creating reactions. Due to the increased surface-to-volume ratio of micro components, the affected surface zone in particular determines the overall mechanical properties.
机译：为了研究烧结后表面对于Si_3N_4微观组件强度的重要性，用烧结的反应结合氮化硅制备了尺寸为240μmx 240μmx 1400μm的微弯曲试样。改变了烧结温度和停留时间的加工参数，并且在烧结过程中使用了两种不同类型的粉末床。通过微三点弯曲试验确定的特征强度ó0在500到1200 MPa之间变化。当应用新制备的并掺有烧结添加剂Y_2O_3，Al_2O_3和MgO的粉末床时，观察到的强度值约为1000 MPa或更高。在这种情况下，烧结过程中的质量损失可以忽略不计，甚至出现很小的质量增加。相比之下，在用过的和未掺杂的粉末床中烧结的样品表现出质量损失，并且在表面富集了第二相YN沸石（Y_2Si_3O_3N_4）。对于这些样品，发现a0被限制在约500-700 MPa。与预期相反，观察到残余孔隙率（范围从小于1％到11％）不是主要的强度决定因素。相反，由于在烧结过程中Si 3 N 4的分解和挥发，或多或少明显地形成了近表面缺陷，这对可达到的强度起决定性作用。质量损失和YN-沸石的形成是缺陷产生反应的指标。由于微组件的表面积体积比增加，受影响的表面区域尤其决定了总体机械性能。

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  • 来源
    《Materials Science and Engineering》 |2011年第27期|p.7895-7900|共6页
  • 作者

    Marcus Miiller; Joachim R6gner; Werner Bauer; Regina Knitter;

  • 作者单位

    Karlsruhe Institute ofTechnology, Institute for Applied Materials, IAM-WPT, P.O. Box 3640, D-7602I Karlsruhe, Germany;

    Karlsruhe Institute ofTechnology, Institute for Applied Materials, IAM-WK, P.O. Box 6980, D-76049 Karlsruhe, Germany;

    Karlsruhe Institute ofTechnology, Institute for Applied Materials, IAM-WPT, P.O. Box 3640, D-7602I Karlsruhe, Germany;

    Karlsruhe Institute ofTechnology, Institute for Applied Materials, IAM-WPT, P.O. Box 3640, D-7602I Karlsruhe, Germany;

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  • 原文格式 PDF
  • 正文语种 eng
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  • 关键词

    Silicon nitride; Sintering; Micro-mechanical characterization;

    机译：氮化硅;烧结;微机械表征;

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