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High-Strength and High-Toughness Porous Silicon Nitride for Structural Applications

机译：用于结构应用的高强度和高韧性多孔氮化硅

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In structural materials, pores are generally believed to deteriorate mechanical reliability. This study, however, demonstrates pores can cause improved or unique performance whenever the porous microstructure is carefully controlled. For examples, porous silicon nitrides where fibrous grains and plate-like pores in between are aligned (anisotropy in microstructure) exhibit high fracture energy as well as high fracture strength. The material of 14% porosity has fracture strength in excess of 1 GPa, when a stress is applied in the alignment direction. The fracture energy obtained by a chevron-notched beam technique was about 490 J/m{sup}2, which is 7 times larger than that of dense silicon nitride. High fracture toughness above 17 MPa m{sup}(1/2) as well as high strength above 1.5 GPa were attained in the porosity range below 5%. This high fracture energy is primarily attributable to grain "pullout" enhanced by the existence of pores around the aligned fibrous grains. They enhanced debonding between the interlocking fibrous grains, resulting in increase of numbers of the grains contributing to the toughening.
机译：在结构材料中，通常认为孔劣化机械可靠性。然而，这项研究表明孔隙可以在仔细控制多孔微观结构时引起改善或独特的性能。例如，在对准之间的纤维颗粒和板状孔的多孔硅氮化物（微结构中的各向异性）表现出高裂缝能量以及高裂缝强度。当在对准方向上施加应力时，14％孔隙率的孔隙率具有超过1GPa的断裂强度。通过字形缩小梁技术获得的断裂能量为约490J / m {sup} 2，其比致密氮化硅的7倍。高于1.5GPa的高于17MPa m {sup}（1/2）的高断裂韧性，孔隙率范围低于5％。这种高裂缝能量主要归因于谷物“拉出”通过围绕对齐的纤维颗粒的孔而增强。它们在互锁纤维颗粒之间增强了剥离，导致增加谷物的数量增加，这是有助于增韧的谷物。

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