Mechanisms Governing the Enhanced Plasticity of Ceramics by a Modest Electric Field

非技术描述：陶瓷是一类重要的技术材料，用于绝缘体、燃料电池、燃气轮机和各种其他电子和结构部件。然而，陶瓷的加工通常在高温和低速下进行。已发现，施加适度的电场可提高处理速率，从而减少所需的处理时间或温度。这提供了显著降低所需能量和相关成本的潜力。因此，电场的使用为材料的处理提供了一种新的方法。拟议研究的目的是确定负责电场有益效果的原子机制，目的是优化条件。一个主要因素是存在于陶瓷材料中的电子空间电荷。 在该项目期间，将培训一名博士后学者和来自代表性不足群体的本科生。技术规格：在先前的工作中发现，在多晶氧化物MgO、Al 2 O3和ZrO 2（3 Y-TZP）的塑性变形期间施加电场使得流动应力显著降低。在3 Y-TZP的情况下，减少由三个组件组成：一个由于焦耳加热，一个快速可逆的组件，由于直接影响的领域上的塑性变形动力学和不可逆的，累积的组件，由于影响的微观结构上的字段。这些效应归因于离子传导、形成空位的能量减少和动态晶粒生长的延迟。与3 Y-TZP相比，MgO和Al 2 O3没有表现出相同的三个组分。理论分析表明，这三种成分与晶界处的空间电荷有关。因此，本研究的目的是确定的物理机制，负责减少流动应力的氧化物中发生的应用程序的电场，专注于溶质添加剂的价的作用：（a）在晶界的空间电荷和（B）相关的晶界结构，采用先进的高分辨率电子显微镜技术。为了获得与机制有关的时间常数的信息，正在研究电场频率的影响。

NON-TECHNICAL DESCRIPTION: Ceramics are an important class of technological materials being used in insulators, fuel cells, gas turbines and various other electronic and structural components. However, the processing of ceramics is usually performed at high temperatures and slow rates. It was discovered that the application of a modest electric field enhances the processing rate, thereby reducing the required processing time or temperature. This offers the potential of significantly reducing the required energy and related cost. Thus, the use of an electric field provides a novel approach to the processing of materials. The objective of the proposed research is to determine the atomic mechanisms responsible for the beneficial effect of an electric field with the aim of optimizing the conditions. A major factor is the electronic space charge which exists in ceramic materials. A post-doctoral scholar and undergraduate students from underrepresented groups will be trained during the course of this project. TECHNICAL DETAILS: It was discovered in prior work that the application of an electric field during the plastic deformation of the polycrystalline oxides MgO, Al2O3 and ZrO2(3Y-TZP) gave a significant reduction in flow stress. In the case of 3Y-TZP the reduction consisted of three components: one due to Joule heating, a rapid reversible component due to the direct effect of the field on the plastic deformation kinetics and an irreversible, cumulative component due to the effect of the field on the microstructure. These effects are attributed to ionic conduction, a reduction in the energy to form vacancies and a retardation of dynamic grain growth. In contrast to 3Y-TZP, MgO and Al2O3 did not exhibit the same three components. Theoretical considerations indicate that the three components are related to the space charge at the grain boundaries. Therefore, the objective of the research is to determine the physical mechanisms responsible for the reduction in flow stress in oxides which occurs with application of an electric field, with focus on the role of the valence of solute additions on: (a) the space charge at the grain boundaries and (b) the related grain boundary structure employing advanced high-resolution electron microscopy techniques. To obtain information on the time constants relating to the mechanisms, the influence of the electric field frequency is being investigated.