Viscous Slip along Grain Boundaries in Chlorine‐Doped Silicon Nitride
Viscous Slip along Grain Boundaries in Chlorine‐Doped Silicon Nitride
复制标题
掺氯氮化硅中的粘性滑移晶界
DOI：
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发表时间：
2005
期刊：
影响因子：
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通讯作者：
H. Kleebe
中科院分区：
文献类型：
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作者：
G. Pezzotti;K. Ota;H. Kleebe
研究了氯掺杂对氮化硅（Si{sub 3}N{sub 4}）多晶体滞弹性弛豫和扭转蠕变行为的影响。两个模型多晶体-一个未掺杂和其他掺杂的氯的小裂缝-进行了研究。它们的微观结构由等轴和良好的小面Si{sub 3}N{sub 4}晶粒组成，其边界由连续的纳米尺寸的二氧化硅（SiO{sub 2}）玻璃膜分隔。通过离子色谱法确定掺杂多晶中氯的实际存在，并认为其在晶界处富集。氯对晶间膜结构的影响，其特征在于通过高分辨电子显微镜。在剪切应力下的SiO{sub 2}晶界的微机械响应被监测到非常高的温度（即，{约} 2，000 C）的内部摩擦和扭转蠕变实验。氯掺杂剂是SiO{sub 2}玻璃的网络改性剂，也会导致晶界膜的加宽，其存在显著降低了残余玻璃的体积粘度。由于晶界化学的变化，氯掺杂材料的内摩擦曲线向较低的温度和扭转蠕变速率显着增加，相比，未掺杂的材料。根据themore> Si{sub 3}N{sub 4}多晶体的粘弹性模型，内耗数据作为两个单独分量的叠加而产生：（i）与沿沿着晶界的滞弹性滑移机制相关的弛豫峰和（ii）由不可逆扩散蠕变机制产生的背景分量。«少
The effect of chlorine doping on the anelastic-relaxation and torsional-creep behavior of a silicon nitride (Si{sub 3}N{sub 4}) polycrystalline body was studied. Two model polycrystals--one undoped and the other doped with a small fracture of chlorine--were investigated. Their microstructures consisted of equiaxed and well-faceted Si{sub 3}N{sub 4} grains whose boundaries were separated by a continuous, nanometer-sized film of silica (SiO{sub 2}) glass. The actual presence of chlorine in the doped polycrystal was ascertained by ion chromatography and is thought to be enriched at the grain boundaries. The effect o chlorine on the intergranular film structure was characterized by high-resolution electron microscopy. The micromechanical response of the SiO{sub 2} grain boundary under shear stress was monitored up to very high temperatures (i.e., {approximately}2,000 C) by internal-friction and torsional-creep experiments. The presence of the chlorine dopant, which is a network modifier of SiO{sub 2} glass that also causes a widening of the grain-boundary film, significantly lowered the bulk viscosity of the residual glass. As a consequence of the change in grain-boundary chemistry, the internal-friction curve of the chlorine-doped material shifted toward lower temperatures and the torsional-creep rate markedly increased, as compared to the undoped material. According to a viscoelastic model of themore » Si{sub 3}N{sub 4} polycrystal, the internal-friction data resulted as a superposition of two individual components: (i) a relaxation peak that is related to the anelastic slip mechanism along grain boundaries and (ii) a background component that results from an irreversible diffusional-creep mechanism.« less