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Decoupling grain growth from densification during sintering of oxide nanoparticles

机译:氧化物纳米颗粒烧结期间致密化去耦谷物生长

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摘要

When external pressure is exerted on oxide nanoparticles (NPs), they densify without exhibiting significant grain growth at temperatures lower than half their melting temperature. This type of densification behavior contradicts the usual sintering behavior observed during densification, which is inevitably accompanied by grain growth. It has been found that NPs of various oxides, including ZnO, CuO, TiO _(2) , SnO _(2) , Fe _(2) O _(3) , and BaTiO _(3) , show slight low-temperature densification (LTD) at temperatures much lower than half their melting temperature, even when an external pressure is not applied. Here we report that LTD is crucial for the densification of NPs during pressure sintering: without LTD, densification does not progress sufficiently even when a pressure as high as 2 GPa is applied. The phenomenon of LTD can be ascribed to surface and/or boundary diffusion in the NPs because of the low thermal activation energy of LTD as well as its sensitivity to changes in the NP surface morphology. It is likely that the decoupling of grain growth from densification in oxide NPs is related to LTD-assisted yield deformation, that is, the migration of surface atoms, which is not accompanied by significant lattice diffusion.
机译:当外部压力施加在氧化物纳米颗粒(NPS)上时,它们致密化而不在低于其熔化温度的温度下表现出显着的晶粒生长。这种类型的致密化行为与致密化期间观察到的通常烧结行为相矛盾,这不可避免地伴有谷物生长。已经发现各种氧化物的NPS,包括ZnO,CuO,TiO _(2),SnO _(2),Fe _(2)O _(3)和Batio _(3),显示出轻微的低温即使不施加外部压力,致密化(LTD)在低于其熔化温度的一半。在这里,我们报告了该LTD在压力烧结期间NPS的致密化至关重要:没有LTD,即使应用高达2GPa的压力,致密化也不会充分进展。 LTD的现象可以在NPS中归因于NPS中的表面和/或边界扩散,因为LTD热激活能量低以及对NP表面形态的变化的敏感性。从氧化物NPS致密化的晶粒生长的去耦可能与LTD辅助产率变形有关,即表面原子的迁移,其不伴随着显着的晶格扩散。

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