I-Corps: Commercialization of a Decontamination Process for Powders for Transparent Ceramics

为了降低陶瓷粉末中不需要的杂质含量，开发了一种新的净化工艺并申请了专利。该工艺去除硫和氯等杂质，这些杂质在很大程度上被忽视，并且不能被商业上使用的传统净化工艺去除。因此，即使是市售的“超高纯度”粉末也经常含有大量的此类杂质。提出的净化工艺已成功应用于铝酸镁尖晶石（MgAl2O4），这是NASA和DOD在各种国防和航空航天应用中选择的材料，需要高透明度和高强度的材料。与目前用于此类应用的弹道玻璃相比，利用尖晶石可以在重量和厚度减半的情况下实现改进的弹道性能。这将在各种方面产生显著的有益影响，例如降低维护成本和增加组件的使用寿命，节约能源/燃料并增加可以利用尖晶石部件的车辆/航天器的有效载荷能力。所提出的专利工艺已成功地在实验室中使用，以始终如一地生产杂质含量足够低的粉末，用于进一步加工，而不管起始粉末中的杂质含量如何。相信该专利工艺将为尖晶石和其他陶瓷的大规模生产提供成本效益高、可扩展的解决方案，从而促进尖晶石的商业化。这将使大量服务于这个市场的工业制造商受益。这种新型的净化过程包括在超高真空中处理接收到的粉末，同时加热或不加热很长一段时间。该工艺不会改变粉末的物理特性，如为特定应用而优化的丝锥密度或粒度分布。利用加工过的粉末，在不添加任何烧结助剂的情况下，通过热压就可以在尖晶石样品中获得接近理论的密度和透明度。目前的加工策略包括使用烧结助剂来达到理论密度和透明度，这总是导致机械性能的退化，因为异常的晶粒生长。当前加工策略中的另一个加工步骤包括在高温下热压后热等静压步骤，以去除残余孔隙。虽然该步骤在零件中产生接近理论的透明度，但它会导致加工温度下的异常晶粒生长，并显着增加尖晶石零件的生产成本。该专利工艺可以潜在地避免这些复杂因素，但需要进一步评估以达到商业规模的有效性和可行性。

A novel purification process has been developed and patented to reduce unwanted impurity content in ceramic powders. This process removes impurities such as sulfur and chlorine which have largely been neglected and cannot be removed by traditional purification processes utilized commercially. As a result, even the 'ultra-high purity' powders that are commercially available often contain significant amount of such impurities. The proposed purification process has been successfully applied to magnesium aluminate spinel (MgAl2O4), a material of choice for NASA and DOD for various defense and aerospace applications for which highly transparent and high strength materials are required. In comparison to the ballistic glasses, which are currently utilized for such applications, an improved ballistic performance at half the weight and thickness can be potentially achieved utilizing spinel. This will have a significant beneficial effect in various ways such as reducing the cost of maintenance and increasing the life-time of the components, energy/fuel savings and increase payload capacity of vehicles/spacecraft where spinel parts can be utilized. The proposed patented process has been successfully utilized in laboratories to consistently produce powders with impurity content that is sufficiently low for further processing, irrespective of impurity content in the starting powder. It is believed that the patented process will invigorate the commercialization of spinel by providing a cost-effective, scalable solution for the mass production of large monolithic bodies of spinel and other ceramics. This would benefit a large number of industrial manufacturers serving this market.The novel purification process involves treating as received powders in ultra-high vacuum with or without concurrent heating for extended periods of time. The process does not modify the physical characteristics of the powders such as tap density or particle size distribution that are already optimized for specific applications. Utilizing the processed powders, it is possible to achieve near theoretical density and transparency in the spinel samples by hot-pressing only without the addition of any sintering aids. Current processing strategies involve use of sintering aids to achieve theoretical density and transparency that invariably lead to degradation of mechanical properties because of abnormal grain growth. Another processing step in the current processing strategies involves a post hot-pressing hot-isostatic pressing step at high temperatures to remove residual porosity. Although this step produces near theoretical transparency in the parts, it results in abnormal grain growth at the processing temperatures and significantly increases the production cost of the spinel parts significantly. The patented process can potentially avoid such complicating factors, but needs further evaluation to be efficient and viable at a commercial scale.