This Small Business Innovation Research (SBIR) Phase II project addresses the need for breakthrough technologies in the production of ultrahigh temperature (UHT) ceramics, including nanograin structures, with improved performance-to-cost ratio. UHT ceramics are often challenging to densify. The development of UHT microwave assist technology (MAT) furnaces will dramatically improve the commercial applicability of UHT ceramic products through lower temperature densification and faster heating cycles. MAT, the combination of microwaves with radiant heat, is proven to enhance diffusion, leading to finer grained microstructures. This project will extend the use of MAT to temperatures above 1700 deg. C, into the range of sintering temperatures for UHT ceramics. A prototype UHT MAT furnace will be designed and built, capitalizing upon in-house MAT system design expertise and research results from Phase I. Proprietary MAT-modeling software will assist with optimizing furnace design and process efficiency. Selected UHT ceramics will be studied to demonstrate sintering with the prototype. Three current industrial UHT ceramic manufacturers, who expressed strong interest in using MAT for sintering products, will collaborate on the project.
The broader impact/commercial potential of this project includes performance enhancements at reduced processing costs, and growth in the use of ultrahigh temperature (UHT) ceramics. Expanded uptake of UHT ceramics will benefit a wide array of manufactured products in electronics, automotive, and aerospace applications. The process of sintering UHT ceramics is extremely energy-intensive. UHT microwave-assist technology (MAT) processing will reduce energy consumption and green house gas emissions by 50-80% for UHT ceramic production. This process may replace pressure-assisted methods, by combining MAT with techniques such as variable rate sintering. MAT may also decrease the use of sintering aids to improve erosion and wear resistance, and high-temperature strength. This faster process enables just-in-time manufacture and enhances competition with respect to foreign competitors. Finally, the UHT MAT furnace technology will lead to new and value-added products, through property improvements from finer grain sizes and cost reduction. This will position American manufacturers for new revenue opportunities and job growth.
This SBIR Phase II project developed the capability for ultra high temperature (UHT) microwave processing for ceramics through the design and building of a commercially scalable prototype. Ultrahigh temperature materials, processed above 1700 °C, are typically difficult to densify during sintering, requiring significant pressure, which limits product shape. An alternative approach is to use additives that enable sintering, but negatively impact properties. There is pull from industry to find solutions that enables faster, lower energy, near net shape production of UHT materials. The enhanced diffusion enabled by microwave heating offers a potential solution, which has already been proven for densification up to 1700 °C. This project raised Ceralink’s profile in UHT materials processing, creating a number of commercial relationships pertaining to sintering, brazing, and the quickly expanding sapphire crystal growth market. The project centered on a plan to design, build, and evaluate a novel UHT Microwave Assist Technology (UHT-MAT™) furnace. MAT™, branded by Ceralink, is the combination of microwave energy with a radiant heat source, such as heating elements. The project initially focused on sintering of ultrahigh temperature ceramics, including carbides, nitrides, and borides, as well as refractory metals. A major interest is in the possibility of creating compositions with fewer additives and therefore better properties, which are sinterable using the enhanced diffusion enabled by UHT-MAT™. During the project, a new UHT materials application was identified that is experiencing explosive market growth – sapphire crystals for touch screen applications. The goal of building and testing a UHT-MAT™ graphite furnace was achieved. MAT™ testing was performed despite challenges encountered along the way that limited the extent of studies performed within the project timeframe. The furnace was successfully tested with MAT™ up to 1800 °C, and minor modifications are underway to bring full MAT™ operation up to 2300 °C. Ceralink is continuing to move UHT-MAT™ forward with furnace upgrades and materials testing beyond Phase II. This is being accomplished through commercially supported efforts with Ceralink customers. Broader impacts of this project include benefits for science, engineering, and manufacturing through the newly available UHT-MAT™ technology (patent pending). The UHT-MAT™ system opens the door to development of new UHT ceramic compositions that enable pressureless sintering with fewer additives than currently required, leading to improved properties at lower cost. The project also supported STEM education through four Research Experiences for Undergraduates (REU), two Research Experiences for Teachers (RET), and two Research Assistantships for High School Students (RAHSS) supplements from NSF. Each of these educational supplements added to the overall project effort. The high school supplement had perhaps the most significant impact by encouraging one of the students to go to college for engineering, who would not have otherwise done so.
