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

一种新的纯化工艺已经开发并获得专利，以减少陶瓷粉末中不需要的杂质含量。该工艺去除了硫和氯等杂质，这些杂质在很大程度上被忽视，并且不能通过商业上使用的传统纯化工艺去除。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。所提出的纯化工艺已成功应用于镁铝尖晶石（MgAl 2 O 4），这是NASA和DOD用于各种国防和航空航天应用的首选材料，这些应用需要高透明度和高强度材料。与目前用于此类应用的防弹玻璃相比，利用尖晶石可以在一半重量和厚度下潜在地实现改进的防弹性能。这将以各种方式产生显著的有益效果，例如降低维护成本和增加部件的寿命，节省能源/燃料，并增加可以使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在实验室中成功应用，无论起始粉末中的杂质含量如何，均可持续生产杂质含量足够低的粉末，以进行进一步加工。据信，该专利工艺将通过为尖晶石和其他陶瓷的大型单片体的大规模生产提供具有成本效益的可扩展解决方案来促进尖晶石的商业化。这将使大量服务于该市场的工业制造商受益。新的纯化工艺包括在超高真空中处理接收的粉末，同时加热或不加热延长时间。该工艺不会改变粉末的物理特性，如振实密度或粒度分布，这些特性已经针对特定应用进行了优化。利用处理过的粉末，可以仅通过热压而不添加任何烧结助剂来实现尖晶石样品的接近理论密度和透明度。目前的加工策略涉及使用烧结助剂来实现理论密度和透明度，这总是导致机械性能的退化，因为异常晶粒生长。当前加工策略中的另一加工步骤涉及在高温下的后热压热等静压步骤以去除残余孔隙。虽然该步骤在部件中产生接近理论的透明度，但其导致在加工温度下的异常晶粒生长，并显著增加尖晶石部件的生产成本。该专利工艺可能会避免这些复杂因素，但需要进一步评估才能在商业规模上有效和可行。

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.