Journal and Conference Papers


A Comparison of Hot-Pressing, Rate-Controlled Sintering, and Microwave Sintering of Magnesium Aluminate Spinel for Optical Applications (PDF, 1.8mb) - There are several crystalline materials that transmit electromagnetic radiation in the visible and IR portion of the spectrum, (from 0.4 microns to 5 microns). At this time, single-crystal sapphire, aluminum oxynitride (ALON), and Spinel show promise for applications, including advanced electromagnetic windows and transparent armor. These applications require materials with high strength, hardness, and the ability to withstand high temperatures. Because of lower processing temperatures and shorter processing times, it is reasonable to assume that Spinel should ultimately be less costly to produce than ALON or sapphire. Despite many attempts to commercialize Spinel, it is not available today as an optical material due to difficulties in reliably obtaining the desired transparency. To help develop a commercial source for transparent Spinel, the U.S. Army Research Laboratory (ARL) and Ceramic Composites Inc. of Annapolis have signed a Cooperative Research and Development Agreement (CRDA), on the "Development and Dual-Use Assessment of Transparent Spinel". The advent of commercially available, highly pure Spinel powders should lead to improvements in processing Spinel to transparency. This investigation compares the advantages and limitations of hot-pressing, microwave sintering, and rate-controlled sintering and compares the limited property data available from each of these fabrication techniques.

 

 

Hard Transparent Domes and Windows from Magnesium Aluminate Spinel (PDF, 0.2mb) - Transparent magnesium aluminate spinel is an attractive material for use in a wide range of optical applications including windows, domes, armor, and lenses, which require excellent transmission from the visible through to the mid IR. Theoretical transmission is very uniform and approaches 87% between 0.3 to 5 microns. Transmission characteristics rival that of ALON and sapphire in the mid-wave IR, making it especially attractive for the ever increasing performance requirements of current and next-generation IR imaging systems. Future designs in missile technology will require materials that can meet stringent performance demands in both optical and RF wavelengths. Loss characteristics for spinel are being investigated to meet those demands.

 

Technology Assessment and Transfer Inc. (TA&T), have established a 9000 ft^2 production facility for optical quality spinel based on the traditional hot-pressing followed by hot isostatic pressing (HIPing) route. Additionally, TA&T is developing pressureless sintering - a highly scalable, near net shape processing method based on traditional ceramic processing technology – to fabricate optical components. These two main processing approaches allow the widest variety of applications to be addressed using a range of optical components and configurations. The polycrystalline nature of spinel facilitates near net shape processing, which provides the potential to fabricate physically larger optical parts or larger quantities of parts at significantly lower costs compared to single crystal materials such as sapphire. Current research is focused at optimizing the processing parameters for both synthesis routes to maximize strength and transparency while minimizing the cost of fabrication.

 

 

Manufacturing Issues for Polycrystalline Transparent Spinel Domes (PDF, 0.4mb) - Magnesium aluminate spinel is a durable, broadband, electro-optical material that can be readily manufactured into transparent domes for multimode seeker applications. Technology Assessment & Transfer reports on the results of its research and development effort to resolve manufacturing issues with regard to transparent spinel domes. The specific areas of study have been cost, quality, and ability to scale up to full production. Alternative manufacturing approaches were evaluated and compared.

Ta&T news

TA&T Part of Team to Improve EMP Protection

The Defense Threat Reduction Agency (DTRA)/SCC announces the beginning of a Small Business Innovation Research (SBIR) contract with Instant Access Networks, LLC (IAN) and its subcontractors as of March 28, 2016 entitled, “Accelerating Society-wide EMP Protection of Critical Infrastructure and Micro-grids”. DTRA’s request for proposals (RFP) was an invitation to small businesses to participate in a commercial R&D program to create EMP protected micro grids for critical infrastructure needed both on and off military bases and other defense critical infrastructure.  The need was explained by DTRA as follows: “An electromagnetic (EM) attack (nuclear electromagnetic pulse [EMP] or non-nuclear EMP [e.g., high-power microwave, HPM]) has the potential to degrade or shut down portions of the electric power grid important to the DoD….  Restoring the commercial grid from the still functioning regions may not be possible or could take weeks or months.” 

 

A key task on this contract is to demonstrate how to accelerate the adoption of EMP-protected critical infrastructure and microgrids among civilian institutions that need to operate in island mode during a prolonged power outage.   These critical suppliers to military bases include water utilities, hospitals, and emergency communications.  The final report would include proposals for additional research in the improvement of component technologies that comprise an EMP-protected microgrid such as EMP shielding, energy generation, energy storage and energy savings technology.  Those improvements can lead to performance and cost advantages that could make these microgrids competitive with grid provided power in some areas of the country and more easily funded in every location.

 

IAN set its own goal to gather collaborators who will fund EMP protected microgrids for water utilities, hospitals and emergency operations centers so that they don’t have to find funds out of their capital budgets.  Fairfax Water, a subcontractor to IAN in this contract, is a great example because of its critical role to many defense critical infrastructure applications in the national capital region and because of the attractive electricity rates it enjoys.  Fairfax Water supplies Fort Belvoir and the surrounding areas with 163 million gallons of water per day.  Though Fairfax Water  lies outside the base, it is essential for base operations but likely to be vulnerable to  EMP because of its dependence on civilian power grids that are not protected from EMP even though the local utility in this instance is otherwise extremely reliable.  Protecting civilian infrastructure such as Fairfax Water is just as important as protecting the critical applications on the base.

 

IAN developed EMP-protected microgrids that included solar, wind and diesel power generation and control rooms independently tested to exceed military standards for EMP by 1000 fold.  IAN subcontractors include Technology Assessment and Transfer (TA&T), a materials science R&D firm that will provide technical assistance on electromagnetic shielding materials and components of energy storage systems; DC Fusion/ Power Analytics that will provide support for direct current microgrids and modeling software for the design and management of microgrids; Jaxon Engineering and Maintenance who will provide EMP testing support and EMP shielding manufacturing guidance; and Fairfax Water, who will provide water utility management guidance.

Corporate Headquarters

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Dr. Larry Fehrenbacher, President
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Sharon Fehrenbacher, CEO
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Research & Manufacturing Facilities

Advanced Ceramics & Coatings
3D Printing of Ceramics
Thermal Management

1110 Benfield Blvd., Suite Q
Millersville, MD 21108
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Spinel & Optical Ceramics
215 Najoles Road
Millersville, MD 21108

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Memberships and Certifications

U.S. Small Business Administration certified
Woman-Owned Small Business (WOSB)

Alliance Member of the National Center
for Defence Manufacturing and Machining

Member of the Electro-Optics Alliance