True to Foam

January 1, 2008
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Reticulated ceramic foam provides a versatile material form that can be engineered and tailored for specific applications.

Structure of reticulated foam showing the open cell structure and continuous ligaments.


Picture a structure formed by fibers or ligaments framing open cells. The structure is lightweight, permeable and shock resistant while retaining the properties of the parent material. Polymer foam, used for insulation, cushions and packaging materials, was perhaps the first manmade material to take advantage of the unique characteristics of cellular solids. Today, another type of foam-reticulated ceramic foam-is providing industry and the research community with a versatile material form that can be engineered with particular properties and tailored for specific applications.

Reticulated foams are low-density, permeable structures of open cells and continuous ligaments; microscopically, they are rather like 3-D mesh. In fact, it is the continuous nature of the ligaments that make the foam reticulated (reticulum being Latin for network).

High-Tech Applications

Reticulated foams offer a number of features that benefit research and design engineers across many industries. The interconnected lattice of continuous ligaments within the cellular structure provides greater strength than shorter fibers and also ensures uniform material characteristics throughout the structure. Other characteristics that offer additional benefits are discussed below.

High Strength-to-Weight Ratio
Reticulated foam is particularly useful in structural sandwich panel cores. The isotropic properties of the foam allow for a uniform response to impact, regardless of impact angle. The foams also add strength and structure when used as part of a 3-D network of reinforcing fibers in composites.

High Surface Area-to-Volume Ratio
Deposition of a high-cost catalyst, such as platinum or silver, onto the ligament surfaces of a reticulated foam allows contact of a gas or liquid with the catalyst over a vast surface area. This cost-effective technique is proving to be particularly valuable in the development of fuel cells. In addition, reticulated foam offers a large surface area in a compact and lightweight structure for use as a scaffold for biological growth in pollution control and other devices.

Conductive or Insulating
Depending on the material chosen, a reticulated foam can provide very low-bulk thermal or electrical conductivity, as well as insulation against high temperatures. In particular, vitreous carbon and silicon carbide reticulated foams can endure the same extreme temperatures as solid material, but at a fraction of the weight. These characteristics lend themselves to use in aerospace applications; heat exchangers; porous electrodes; and wherever an exceptionally efficient, lightweight conductor or insulator is required.

Low Flow Resistance
The uniform cell structure and rigid geometry of reticulated ceramic foam contribute to a low pressure drop for fluid flow. These characteristics are useful in filters, demisters, gas diffusers and mixers, as well as liquid and gas separators, among other applications.

Resistance to Fracture and Thermal Shock
Because the properties of the parent material extend throughout the foam in three dimensions, reticulated foam provides enhanced resistance to fractures and thermal shock. The continuous ligaments of the material deter crack propagation, since a crack encountering a continuous ligament (as opposed to a short fiber) is stopped from progressing through the structure.

Tailored Foams

Although “standard” reticulated ceramic foams are suitable for many high-tech applications, it is possible to tailor a foam’s properties during fabrication for a specific application by adjusting its material composition, pore size, density and ligament structure. In fact, perhaps the most exciting aspect of working with reticulated foams is the opportunity to explore and exploit their properties for use in any number of new and existing applications.

Strong and lightweight, compact with a high surface area, conductive or insulating-reticulated foams have much to offer researchers and innovative engineers working in a range of industries.

For more information about reticulated foams, contact Goodfellow Corp., 305 High Tech Dr., Oakdale, PA 15071; (800) 821-2870; e-mail everitt@goodfellow.com; or visit www.goodfellow.com.  

SIDEBAR: Standard Types of Reticulated Ceramic Foams

  • Silicon Carbide
  • Alumina
  • Vitreous Carbon
 

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