Flash Sintering of Multiphase Ceramics

传统上，由陶瓷粉末或粘土制造部件的工艺需要在高温下在炉中长时间（许多小时或数天）烧制（烧结），这是一种消耗大量能量的昂贵工艺。 一种被称为“快速烧结”的新工艺涉及直接通过工件运行电流，以使陶瓷致密化，并在几秒钟内生产出可用的部件。 最初的研究表明，许多类型的陶瓷都可以用这种方法烧制，但这些研究都集中在单相材料上，而实际应用往往需要由不同类型的陶瓷制成的多相材料。 该奖项支持基础研究，以调查多相陶瓷的每个组件的电气和热行为如何响应闪速烧结。 这项工作将导致对闪速烧结工艺的新理解，这将允许这些关键材料的更低成本，更高效率的加工和制造。将研究这些材料的加工和强度，以确保通过这种新工艺制造的部件与传统方法制造的部件相当或更好。 该项目的科学成果被整合到面向中小学生的视频模块中，以展示科学家和工程师正在研究如何在制造新材料的同时节省能源。陶瓷部件通常需要多相以提高机械强度、增强导热性和增加抗热震性。与花费大量能量加热样品和炉腔的常规烧结方法相比，可以使用具有流过样品的电流的高施加电场来在空气中并且在低得多的温度下在没有施加压力的情况下致密氧化物陶瓷。本研究计划将评估如何直接应用电场可用于闪速烧结多相陶瓷粉末压坯。 多组分氧化物系统与不同的电/离子和导热性的阶段被用来确定这些材料的性能在促进闪速烧结的作用。该信息用于创建组成设计参数，以通过引入次要相来优化闪速烧结。 快速烧结的多相陶瓷复合材料的机械性能相比，传统的烧结材料，以评估任何差异，通过电子显微镜的微观结构表征。

Traditionally, the process to make a components from ceramic powders or clays requires firing (sintering) in a furnace at high temperatures for a long time (many hours or days), a costly process that consumes a large amount of energy. A new process known as "flash sintering" involves running electrical current directly through the piece, to densify the ceramic and produce a usable component in a matter of seconds. Initial studies show that many types of ceramics can be fired this way, but these studies have focused on single phase materials, while practical applications often require multiple phases made of different types of ceramics. This award supports fundamental research to investigate how the electrical and thermal behavior of each component of a multi-phase ceramic responds to flash sintering. This work will lead to new understanding of the flash sintering process, which will allow for lower cost, higher efficiency processing and manufacture of these critical materials. The processing and the strength of these materials will be studied, to ensure that the components made by this new process are comparable to or better than those made by traditional methods. The scientific results of the project are integrated into video modules for outreach to elementary and middle school children, to demonstrate the ways that scientists and engineers are studying methods to save energy while making new materials. Multiple phases are often required for ceramic components in order to improve mechanical strength, enhance thermal conductivity, and increase thermal shock resistance. In contrast to conventional sintering approaches which expend significant energy heating the sample and furnace cavity, a high applied electric field with current flowing through the sample can be used to densify oxide ceramics in air and without applied pressure and at much lower temperatures. This research program will evaluate how the direct application of electric fields can be used to flash sinter multiphase ceramic powder compacts. Multicomponent oxide systems with phases of varying electrical/ionic and thermal conductivity are used to determine the role of these material properties in promoting flash sintering. This information is used to create compositional design parameters to optimize flash sintering via incorporation of minor phases. Mechanical properties of flash sintered multiphase ceramic composites are compared to conventional sintered materials to evaluate any differences, with microstructural characterization by electron microscopy.