Special Coverage

Home

Coating Carbon Fibers With Platinum

Uniform coats are produced relatively inexpensively. A process for coating carbon fibers with platinum has been developed. The process may also be adaptable to coating carbon fibers with other noble and refractory metals, including rhenium and iridium. The coated carbon fibers would be used as ingredients of matrix/fiber composite materials that would resist oxidation at high temperatures. The metal coats would contribute to oxidation resistance by keeping atmospheric oxygen away from fibers when cracks form in the matrices.

Posted in: Materials, Briefs

Read More >>

Improved C/SiC Ceramic Composites Made Using PIP

These materials are expected to remain strong for longer times at high temperatures. Improved carbon-fiber- reinforced SiC ceramic-matrix composite (C/SiC CMC) materials, suitable for fabrication of thick-section structural components, are producible by use of a combination of raw materials and processing conditions different from such combinations used in the prior art. In comparison with prior C/SiC CMC materials, these materials have more nearly uniform density, less porosity, and greater strength. The majority of raw-material/processing-condition combinations used in the prior art involve the use of chemical vapor infiltration (CVI) for densifying the matrix.

Posted in: Briefs

Read More >>

Ultrahigh-Temperature Ceramics

Materials are being developed to withstand temperatures above 1,650 °C. Figure 1. Examples of UHTC Components areshown that have been tested in the NASA AmesArc Jet facility to evaluate the materialsresponse in a simulated reentry environment.The cone and wedge models are representativeof the scale and geometries anticipated for useon UHTC sharp leading-edge vehicles.Ultrahigh temperature ceramics (UHTCs) are a class of materials that include the diborides of metals such as hafnium and zirconium. The materials are of interest to NASA for their potential utility as sharp leading edges for hypersonic vehicles. Such an application requires that the materials be capable of operating at temperatures, often in excess of 2,000 °C. UHTCs are highly refractory and have high thermal conductivity, an advantage for this application. UHTCs are potentially applicable for other high- temperature processing applications, such as crucibles for molten-metal processing and high-temperature electrodes.

Posted in: Briefs, TSP

Read More >>

Rapid Fabrication of Carbide Matrix/Carbon Fiber Composites

Melt infiltration offers advantages over chemical vapor infiltration. Composites of zirconium carbide matrix material reinforced with carbon fibers can be fabricated relatively rapidly in a process that includes a melt infiltration step. Heretofore, these and other ceramic matrix composites have been made in a chemical vapor infiltration (CVI) process that takes months. The finished products of the CVI process are highly porous and cannot withstand temperatures above 3,000 °F (≈1,600 °C). In contrast, the melt-infiltration-based process takes only a few days, and the composite products are more nearly fully dense and have withstood temperatures as high as 4,350 °F (≈2,400 °C) in a highly oxidizing thrust chamber environment. Moreover, because the meltinfiltration- based process takes much less time, the finished products are expected to cost much less.

Posted in: Materials, Briefs

Read More >>

Coating Thermoelectric Devices To Suppress Sublimation

Thermoelectric materials are covered with adherent, chemically stable metal outer layers. A technique for suppressing sublimation of key elements from skutterudite compounds in advanced thermoelectric devices has been demonstrated. The essence of the technique is to cover what would otherwise be the exposed skutterudite surface of such a device with a thin, continuous film of a chemically and physically compatible metal. Although similar to other sublimation- suppression techniques, this technique has been specifically tailored for application to skutterudite antimonides.

Posted in: Briefs, TSP

Read More >>

Polyaniline Compounds for Protection Against Corrosion

Protective surface layers can be formulated and applied in various ways. Corrosion of iron and steel substrates can be inhibited by coating them with any of the wide variety of compounds denoted generally as polyanilines. A polyaniline suitable for this type of application can be in either an electrically conductive salt (doped) form or an electrically nonconductive base form. Typically, polyaniline is dissolved in an organic solvent and the resulting solution is applied to a substrate by spraying, dipping, or brushing. The solvent is then allowed to evaporate leaving the substrate coated with a solid film of polyaniline, typically 1 to 200µm thick.

Posted in: Materials, Briefs, TSP

Read More >>

Composite-Matrix Regenerators for Stirling Engines

One can exploit the properties of composites to reduce thermal and flow losses. A prototype Stirling-engine regenerator containing a matrix made of carbon-fiber-based composite materials has been developed. The concept underlying this development effort is one of exploiting the properties of composite materials (e.g., the anisotropy of thermal conductivity of carbon fibers and the tailorability of composite materials and structures) to reduce thermal and flow losses below those of previously developed regenerators containing metal matrices.

Posted in: Briefs, TSP

Read More >>

White Papers

Automated Inspection Lowers Solar Cell Costs
Sponsored by Teledyne DALSA
How Paper-based 3D Printing Works: The Technology and Advantages
Sponsored by Mcor Technologies
The Sun’s Surface in Stunning Detail
Sponsored by mikrotron
Back to Basics of Electrical Measurement
Sponsored by Keithley
External Power Supply Efficiency Regulation Introduction
Sponsored by mega electronics
Overcome Challenges of Your Highly Constrained PCB Designs
Sponsored by Mentor Graphics

White Papers Sponsored By: