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Fabrication and testing of bonded metal-ceramic, glass-coated metal, and glass-coated ceramic bonded to metal composite electrodes for cesium bombardment ion thrusters
Reflection polarizers and analyzers for the extreme UV spectral region are discussed. The conditions for optimum polarization are presented, and the polarization characteristics of a number of metal coatings, including gold and some of the platinum metals, are given. The performance of three- and four-mirror polarizers, using these metal coatings, is discussed. The properties required of a polarization analyzer are presented, and the performance of single and three- and four-reflection analyzers are discussed in terms of the optical properties of coating materials that might be useful for analyzers.
Spacecraft potable water systems require a biocidal agent that effectively provides both immediate and residual disinfection over long periods of time. Ionic silver (Ag+) is a leading candidate for this application, but suffers from rapid concentration loss due interactions with the metal storage containers and tubing. In order to maintain biocidal efficacy in systems with long periods of dormancy and to reduce the required rate of Ag+ injection, it is necessary to develop alternative materials and coatings for certified metal alloys that significantly reduce the Ag+ loss. In this work, we investigate the performance of two unusual polymers, Teflon AF 2400 and parylene-AF4, as barrier coatings under immersion in 400 ppb Ag+. We show that 25 m-thick parylene-AF4 is a promising coating with Ag+ losses similar to PTFE. Key challenges with this material include maintenance of adhesion under long-term immersion and control of deposition during the internal coating of high-aspect ratio tubing. Solutions to these problems may including surface structuring of substrates for mechanical anchoring or an alternative parylene-C chemistry (with more stable adhesion), and dynamic spatio-temporal control of substrate temperature, respectively.
“Spacecraft potable water systems require a biocidal agent that effectively provides both immediate and residual disinfection over long periods of time. Ionic silver (Ag+) is a leading candidate for this application, but suffers from rapid concentration loss due to interactions with the metal storage containers and tubing. In order to maintain biocidal efficacy in systems with long periods of dormancy and to reduce the required rate of Ag+ injection, it is necessary to develop alternative materials and coatings for certified metal alloys that significantly reduce the Ag+loss.”1In this work, we continue our investigation of vapor-deposited parylene (AF4, and now C) polymers as conformal barrier coatings under long-term (ca. 1-year) immersion in ca. 400 ppb Ag+. The performanceof internal coatings in tubing/two-ferrule fitting systems is characterized. We report successful “aging” and high concentration Ag+pretreatment of parylene coatings for quantitative reduction of Ag+loss rates. In addition, we observe long-term blister-free adhesion of mechanically anchored parylene-AF4 on nano-structured Ti-6Al-4V alloy and chemically bonded parylene-C on 316L stainless steel. Finally, we report preliminary experiments with mechanical and chemical anchoring of laboratory-deposited parylene-C on 316L.
High temperature coating techniques for the oxidation protection of refractory metals and alloys, noting advantages of the pack cementation process
Techniques for monitoring changes in preparation of solar sail materials resulting from space radiation simulation, stressing (e.g., thermal, mechanical) and exposure to terrestrial environments are developed. The properties of interest are: metallic coating deterioration, polymeric film deterioration, interfacial debonding and possible metallic coating diffusion into the polymeric film. Four accelerated tests were devised to simulate the possible degradation processes mentioned above. These four tests are: a thermal shock test to simulate the wide variation of temperature expected in space (260 C to -100 C), a cyclic temperature test to stimulate the 6 minute temperature cycle anticipated in space, a mechanical vibration test to simulate mechanical bonding, folding and handling, and a humidity test to simulate terrestrial environment effects. The techniques for monitoring property changes are: visual and microscopic examination, ellipsometry, surface potential difference (SPD), photoelectron emission (PEE), and water contact angles.
The invention relates to coated metal powders and to dispersions of such powders in liquid vehicles forming screenable, sinterable pastes for use in forming electrodes on photovoltaic devices. The primary nickel or copper metal particles are provided with a carrier of lower melting sintering metals such as 1-20% by weight, of a non-oxidizing metal such as lead or tin. The powdered metal systems operate on the basis of fusing together by way of eutectic alloying. As the paste is heated during firing the organic binder is first vaporized. An eutectic of the base metal (copper) and coating (tin) forms at the intersections of the base metal grains. This eutectic dissolves the grains and as the temperature is raised above the eutectic temperature, more of the base metal is dissolved. While the temperature is held at the higher value, the much smaller amount of sintering metal disappears as the eutectic dissolves and diffuses into the base metal until the composition of the eutectic is so enriched with base metal that it no longer has the eutectic properties and it solidifies. In this high temperature solidification, the base metal grains became thoroughly alloyed together and will not separate at the eutectic temperature (a lower temperature than their solidification by diffusion).
The metal-semiconductor solar cell is a possible candidate for converting solar to electrical energy for terrestrial application. A method is given for obtaining optical parameters of practical antireflection coatings for the metal-semiconductor solar cell. This method utilizes the measured refractive index obtained from ellipsometry since the surface to be AR coated has a multilayer structure. Both the experimental results and theoretical calculation of optical parameters for Ta2O5 antireflection coatings on Au-GaAs and Au-GaAs(0.78)P(0.22) solar cells are presented for comparison.
Two general types of thermal radiators are being considered for lunar missions: coated metallic surfaces and Second Surface Mirrors. Metallic surfaces are coated with a specially formulated white paint that withstands the space environment and adheres well to aluminium, the most common metal used in space hardware. AZ-93 White Thermal Control Paint, developed for the space program, is an electrically conductive inorganic coating that offers thermal control for spacecraft. It is currently in use on satellite surfaces (Fig 1). This paint withstands exposure to atomic oxygen, charged particle radiation, and vacuum ultraviolet radiation form 118 nm to 170 nm while reflecting 84 to 85% of the incident solar radiation and emitting 89-93% of the internal heat generated inside the spacecraft.
A metallic coating is plasma sprayed onto a smooth surface of a metal alloy substitute or on a bond coating. An initial thin ceramic layer is low pressure sprayed onto the smooth surface of the substrate or bond coating. Another ceramic layer is atmospheric plasma sprayed onto the initial ceramic layer.
The cold plasma techniques for deposition of various types of protective coatings are reviewed. The main advantage of these techniques for deposition of ceramic films is the lower process temperature, which enables heat treating of the metal prior to deposition. In the field of surface hardening of steel, significant reduction of treatment time and energy consumption were obtained. A simple model for the plasma - surface reactions in a cold plasma system is presented, and the plasma deposition techniques are discussed in view of this model.
Cermet for nuclear fuel constructed by pressing metal coated ceramic particles in die at temperature to cause bonding of metal coatings, and tested for thermal stability
A method of compensating for or minimizing phase differences between orthogonal polarizations of light reflected from metallic mirrors at oblique incidence, as, for example, from weakly curved mirrors, is undergoing development. The method is intended to satisfy a need to maintain precise polarization phase relationships or minimum polarization differences needed for proper operation of telescopes and other scientific instruments that include single or multiple mirrors. The basic idea of the method is to optimally coat mirrors with thin engineered layers of materials that introduce phase differences that, as nearly precisely as possible, are opposite of the undesired phase differences arising in reflection with non-optimum coatings. Depending on the specific optical system, the method could involve any or all of the following elements: a) Optimization of a single coat on all the mirrors in the system. b) Optimization of a unique coat for each mirror such that the polarization phase effects of the coat on one mirror compensate, to an acceptably high degree over an acceptably wide wavelength range, for those of the coat on another mirror. c) Tapering the coat on each mirror. Optimization could involve the choice of a single dielectric coating material and its thickness, or design of a more complex coat consisting of multiple layers of different dielectric materials and possibly some metallic materials. Such designs and coatings are particularly significant and needed for obtaining very high quality of wavefront required in high-contrast imaging instruments such as the NASA Terrestrial Planet Finder Coronagraph.
John B. Schutt, a chemist at Goddard Space Flight Center, created a coating for spacecraft that could resist corrosion and withstand high heat. After retiring from NASA, Schutt used his expertise to create new formulations for Daytona Beach, Florida-based Adsil Corporation, which now manufactures a family of coatings to preserve various surfaces. Adsil has created 150 jobs due to the products.
Refractory metallic coatings of (W/0.6/ Re/0.4/)76B24 (WReB) have been deposited onto glass, quartz, and heat-treated AISI 52100 bearing steel substrates by dc magnetron sputtering. As-deposited WReB films are amorphous, as shown by their diffuse X-ray diffraction patterns; chemically homogeneous, according to secondary ion mass spectrometry (SIMS) analysis; and they exhibit a very high (approximately 1000 C) crystallization temperature. Adhesion strength of these coatings on heat-treated AISI 52100 steel is in excess of approximately 20,000 psi and they possess high microhardness (approximately 2400 HV50). Unlubricated wear resistance of such hard and adherent amorphous metallic coatings on AISI 52100 steel is studied using the pin-on-disc method under various loading conditions. Amorphous metallic WReB coatings, about 4 microns thick, exhibit an improvement of more than two and a half orders of magnitude in the unlubricated wear resistance over that of the uncoated AISI 52100 steel.
The present invention provides a new process to deposit well adhered ultra smooth diamond films on metals by adding nitrogen gas to the methane/hydrogen plasma created by a microwave discharge. Such diamond coating process is useful in tribological/wear resistant applications in bio-implants, machine tools, and magnetic recording industry.
Fast and economical process now available. New process applies rapidly solidified (RS) metal coatings to substrates. RS metals made directly from molten material. Have amorphous or microcrystalline structures and yield coatings having superior wear and corrosion resistance. Mixture of RS metal powder and peening particles sprayed from nozzle against surface coated. Powder and peening particles strike surface simultaneously, and impact bonds powder to surface as uniform coating. New process, which employs shot peening, is safe, fast, and inexpensive.
Metal-coated graphite fibers are being considered as a thermal conductivity enhancement filler material for molten salts in solar dynamic thermal energy storage systems. The successful metal coating chosen for this application must exhibit acceptable wettability and must be compatible with the molten salt environment. Contact angle values between molten lithium fluoride and several metal, metal fluoride, and metal oxide substrates have been determined at 892 C using a modification of the Wilhelmy plate technique. Reproducible contact angles with repeated exposure to the molten LiF indicated compatibility.