Date: Dec 15, 2009 Author: Joe Singleton Source: MDA (
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by Joe Singleton/jsingleton@nttc.edu
Nanoscopic composite materials developed for missile defense may soon provide a quick, inexpensive way for end users to improve the strength and performance of their systems, while reducing the weight and cost of aerospace, automotive, and biomedical components.
Advanced Powder Solutions, Inc. (APS; Mitchellville, MD), produces tailor-made, environmentally friendly composite foams made from micron-size ceramic or metal hollow spheres. These composites offer an inexpensive and lightweight alternative to heavier metal and polymer components such as automotive exhaust manifold systems and x-ray equipment used in hospitals.
The metal foam composites offer significant benefits over competing materials. APS's composite materials can be 20 to 30 percent lighter than beryllium and 60 percent lighter than aluminum—two materials generally considered lightweight in their own right. And although lighter, the company's composites offer similar tailor-made mechanical properties, as well as other multifunctional benefits.
APS composites typically are manufactured with a two- to four-week delivery time, depending on the complexity of the item designed. This compares with beryllium product manufacturers who have historically taken eight to ten months to produce similar items. Composite tools manufactured by APS cost on average 50 percent less than comparable components made with beryllium.
MDA funded APS through a 2006 SBIR Phase II contract to develop environmentally safe, ultra-lightweight, multifunctional materials capable of improving launch payload capability, while reducing costs of missile defense and space systems. APS teamed with Raytheon Missile Systems of Tucson, AZ, and Advanced Materials and Manufacturing Technologies, LLC, of Riverbank, CA, to further test and develop the technology.
Beyond missile defense, company officials have already spoken to automotive manufacturers and motor racing circuits, such as NASCAR and Formula One, about designing composite parts and engine materials. APS and automotive manufacturers have discussed the feasibility of using the tailor-made composite materials for the safe storage of hydrogen used in fuel-cell vehicles. Other than automotive applications, the company's materials have potential use in reducing weight in aircraft, building x-ray equipment for biomedicine, designing lightweight mirrors for optics, and developing materials used in spaceflight, such as on NASA's proposed Space Shuttle replacement—the Orion Crew Exploration Vehicle.
The appeal of APS's technology lies in its ability to meet specific properties of desired components through improved powders and processing. The company's manufacturing process begins with millions of microscopic hollow spheres that are between 0.5 micron and 200 microns in diameter, the size being dependent on the application and desired
final properties. Properties such as thermal expansion, thermal/electrical conductivity, modulus, tensile strength, ductility, and shielding capabilities can easily be modified. These hollow spheres—known throughout the materials industry as microspheres or microballoons—can be off-the-shelf ceramic spheres modified by APS, or they can be made to order by the company using other suitable materials. The APS composites are easily machined—like bulk aluminum—threaded, and joined together for these purposes.
Once the application requirements are specified, APS determines a hollow sphere's composition and size. A decision also is made to determine what matrix composition would most effectively bind the hollow spheres together and achieve the final desired properties. Typical matrix materials include aluminum, lithium, magnesium, nickel, rhenium, tantalum, titanium, and their alloys.
The hollow spheres are pressed together with the matrix powders. APS has used a variety of consolidation techniques, from laser processing to dynamic forging, to process the powders into the final shapes. The end result is a metal foam that is strong, durable, and near theoretical density, but still ultra lightweight (less than 2 grams per cubic centimeter).
APS's innovation lies in its ability to "microdesign" materials—mixing, matching, and fine-tuning the spheres and matrix formulas during the manufacturing process—to craft end products with known properties—such as specific modulus, density, and shielding.
The fact that APS can produce multifunctional materials with inherent shielding in its composite is unique, said one company official. Shielding is normally made by taking a piece of aluminum or other metal in need of protection, and depositing a shielding layer on the outside. APS can reduce the need for extra layers by manufacturing the protective layers into the composite. Tests conducted by the company and the government have shown that the composites can provide significant radiation shielding results at lower densities.
APS generally forms its metal foams into symmetrically shaped objects such as blocks or cones, depending on what kind of part is needed. Should a car manufacturer, for instance, need net-shaped parts, APS can also craft such objects from the powders using metal injection molding or other net-shaping processes. The majority of the market now is using material in bulk, and easily machining the blocks into parts.
The company continues to work with MDA, the U.S. Armed Forces, Raytheon, and other prime contractors to move its patent-pending products into the defense sector. APS officials continue to look for additional funding and applications needing lightweight, multifunctional materials. With the base materials at a Technical Readiness Level 6, the company is looking for additional funding sources. APS's continued focus on material characterization and qualification testing is to determine other application areas in which its technology may be used. According to APS, mass application of these materials could provide for high-tech job creation and reassertion of U.S. leadership in nanomaterials, as well as address the White House's call for energy independence.
