Design of Superplastic Ceramics

研究了采用分散的第二相制备超塑性陶瓷的最佳微观结构设计。晶间硅酸盐相和纳米分散晶体氧化物将被用于制造具有改进性能的陶瓷材料，通过超塑性变形形成形状。第二相的体积和分布以及它们的界面能和溶解度将成为多晶氧化物中与晶粒生长、晶界滑动和断裂有关的变量。实验分析技术将包括分析电子显微镜和阻抗谱，以及在室温和高温下的机械变形测试。这项研究的目标是了解如何在纳米尺度上使用化学上不同的分散剂来调整氧化物陶瓷的机械性能，从而使高度可变形的陶瓷可以在高温下形成净形状，同时在较低温度下保持优越的机械和电气性能。超塑性成形有可能制造出传统陶瓷加工技术难以达到的形状。然而，陶瓷的超塑性变形目前只可能在少数有限的陶瓷系统中保持细晶粒微观结构。此外，该工艺所需的极高温度和缓慢的应变速率限制了该技术的工业应用。本研究将侧重于优化微结构设计参数，从而降低超塑性成形的温度，提高变形速率，同时扩大可通过超塑性成形成形的陶瓷材料的范围，从而使该技术成为陶瓷净形状成形的更经济可行的方法。

The optimal microstructural design of superplastic ceramics using finely dispersed second phases will be studied. Intergranular silicate phases and nanodispersed crystalline oxides will be used to create ceramic materials with improved properties for shape forming via superplastic deformation. The volume and distribution of second phases and their interfacial energy and solubility will be variables analyzed with respect to grain growth, grain boundary sliding, and fracture in polycrystalline oxides. Experimental analysis techniques will include analytical electron microscopy and impedance spectroscopy as well as mechanical deformation tests both at room temperature and at high temperatures. The goal of this research is to understand how chemically dissimilar dispersants can be used at the nanoscale to tailor the mechanical properties of oxide ceramics, so that highly deformable ceramics can be net shape formed at high temperatures while retaining a superior mechanical and electrical performance at lower temperatures.Superplastic forming has the potential to allow the production of shapes not easily attained by conventional ceramic processing techniques. Superplastic deformation of ceramics currently, however, is currently possible only in a few limited ceramic systems that retain a fine grain microstructure. In addition, the extremely high temperatures required for this process and slow strain rates attained limit the industrial applications of this technique. This research will focus on optimizing the microstructural design parameters that will result in lower temperatures for superplastic forming and increased deformation rates while expanding the range of ceramic materials that can be shaped by superplastic forming, thus making this technique a more economically viable method for net shape forming of ceramics.