Special Coverage

Home

Optical Characterization of Molecular Contaminant Films

A theoretical model is correlated with measured spectral transmittances and VUV exposures of spacecraft optics. Lyndon B. Johnson Space Center, Houston, Texas A semi-empirical method of optical characterization of thin contaminant films on surfaces of optical components has been conceived. The method was originally intended for application to films that become photochemically deposited on such optical components as science windows, lenses, prisms, thin-film radiators, and glass solar-cell covers aboard spacecraft and satellites in orbit. The method should also be applicable, with suitable modifications, to thin optical films (whether deposited deliberately or formed as contaminants) on optical components used on Earth in the computer microchip laser communications and thin-film industries.

Posted in: Tech Briefs, ptb catchall, Photonics, Briefs

Read More >>

Photonics West Exhibitor Preview

View these and other new products on display by exhibitors at Photonics West, January 23-25, in San Jose, CA. Visit Photonics Tech Briefs at Booth 435. Visit http://spie.org/Conferences/programs/07/pw/ for more information.

Posted in: Products

Read More >>

Card Provides PCI-Based Multi-Axis Motion Control

Performance Motion Devices (Lincoln, MA) offers the Prodigy™-PCI motion card for multi-axis motion control. Available in 1-, 2-, 3-, and 4-axis versions, the card provides trajectory generation, performance trace, on-the-fly changes, and commutation. Motor type can be software- selected on a per-axis basis, and includes DC brush, brushless DC, step, and microstepping. The card communicates via a PCI bus, CANbus, or serial port. Card features include S-curve, trapezoidal, velocity contouring, electronic gearing, and user-generated profile modes. The card accepts input parameters such as position, velocity, acceleration, and jerk from the host, and generates a corresponding trajectory.

Posted in: Products

Read More >>

Reactive Additives for Phenylethynyl-Containing Resins

Processability is improved. Phenylethynyl containing reactive additive (PERA) compounds and mixtures have been found to be useful for improving the processability of oligomers, polymers, cooligomers, and copolymers that contain phenylethynyl groups. The additives can be incorporated in different forms:

Posted in: Materials, Briefs

Read More >>

Multicomponent, Rare-Earth-Doped Thermal-Barrier Coatings

Thermal conductivities are reduced while maximum use temperatures are increased. Multicomponent, rare-earth-doped, perovskite-type thermal-barrier coating materials have been developed in an effort to obtain lower thermal conductivity, greater phase stability, and greater high-temperature capability, relative to those of the prior thermal-barrier coating material of choice, which is yttriapartially stabilized zirconia. As used here, “thermal-barrier coatings” (TBCs) denotes thin ceramic layers used to insulate air-cooled metallic components of heat engines (e.g., gas turbines) from hot gases. These layers are generally fabricated by plasma spraying or physical vapor deposition of the TBC materials onto the metal components.

Posted in: Materials, Briefs

Read More >>

Development of Carbon-Nanotube/Polymer Composites

A report presents a short discussion of one company’s effort to develop composites of carbon nanotubes in epoxy and other polymer matrices.

Posted in: Materials, Briefs

Read More >>

Modifications of a Composite-Material Combustion Chamber

Two short reports discuss modifications of a small, lightweight combustion chamber that comprises a carbon/carbon composite outer shell and an iridium/rhenium inner liner. The first report discusses chamber design modifications made as results of hot-fire tests and post-test characterization. The modifications were intended to serve a variety of purposes, including improving fabrication, reducing thermal-expansion mismatch stresses, increasing strength-to-weight ratios of some components, and improving cooling of some components. The second report discusses (1) the origin of stress in the mismatch between the thermal expansions of the Ir/Re liner and a niobium sleeve and flange attached to the carbon/carbon shell and (2) a modification intended to relieve the stress. The modification involves the redesign of an inlet connection to incorporate a compressible seal between the Ir/Re liner and the Nb flange. A nickel alloy was selected as the seal material on the basis of its thermal-expansion properties and its ability to withstand the anticipated stresses, including the greatest stresses caused by the high temperatures to be used in brazing during fabrication.

Posted in: Materials, Briefs

Read More >>