SEARCH · Engineering Papers

Results for “inert atmosphere”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 145 records · Page 8

All sources NASA NTRS DOE OSTI

NASA NTRS1981

Research on graphite reinforced glass matrix composites

A broad group of fibers and matrices were combined to create a wide range of composite properties. Primary material fabrication procedures were developed which readily permit the fabrication of flat plate and shaped composites. Composite mechanical properties were measured under a wide range of test conditions. Tensile, flexure mechanical fatigue, thermal fatigue, fracture toughness, and fatigue crack growth resistance were evaluated. Selected fiber-matrix combinations were shown to maintain their strength at up to 1300 K when tested in an inert atmosphere. Composite high temperature mechanical properties were shown to be limited primarily by the oxidation resistance of the graphite fibers. Composite thermal dimensional stability was measured and found to be excellent.

Prewo, K. M.↗

NASA NTRS1982

Conduit for Transferring Molten Silicon

Proposed three-part conduit transfers pure silicon between crucibles. Four-strip heater augments layers of insulation to prevent molten silicon from cooling and solidifying during transfer. Since melt is maintained at temperature relatively close to fusion point, to minimize quartz erosion, even relatively-minor heat losses precipitate solidification and terminate work in progress. Several crucibles may be fed through conduits from central crucible. Each would be contained in its own compartment under inert atmosphere.

Fiegl, G.↗

NASA NTRS1982

Preparation of perfluorinated 1,2,4-oxadiazoles

Fluorinated alkyl or alkylether 1,2,4 oxadiazole compounds are prepared by cyclizing the corresponding alkyl or alkylether imidoyl amidoximes in vacuo or in an inert atmosphere at a temperature within the range of 40 C to 100 C. for a period of 8 to 144 hours in the presence of an acid compound which can accept ammonia to form a salt. The imidoyl amidoximes usable in this process are either polymeric or nonpolymeric. The products, when polymeric, have excellent heat, chemical and solvent resistance.

Kratzer, R. H.↗

NASA NTRS1984

Process for producing tris s(n-methylamino) methylsilane

A method of producing tris (N-methylamine) methylsilane is described including the steps of forming and cooling a liquid solution of methylamine in an inert solvent and under an inert atmosphere at a temperature of about -30 C and slowly adding a quantity of methyltricholorosilane while maintaining said temperature. The reaction mixture is then heated for about 60 minutes at a temperature of about 40 C, followed by filtering the solid portion from the liquid portion. The liquid is distilled to remove the solvent, resulting in a high yield of tris (N-methylamine) methylsilane.

Clemons, J. M.↗

NASA NTRS1984

Microstructures and properties of rapidly solidified alloys

The microstructure and properties of rapidly solidified aluminum alloys were researched. The effects of powder and flake chemistry and morphology and alternative consolidation processing parameters are being conducted. Samples of the powders being utilized were obtained for comprehensive metallurgical characterization. Seven aluminum alloys in the form of thin foils were studied by a variety of techniques including optical metallography, scanning electron microscope, and transmission electron microscope. Details of the microstructural characteristics are presented along with a discussion of the solidification process. A better understanding of the microstructure of the rapidly solidified aluminum alloys prepared by a variety of techniques such as roller quenching, the vacuum atomized procedure, ultrasonically atomized in inert atmospheres, and atomized in flue gas was provided.

Shechtman, D.↗

NASA NTRS1985

Demonstrated results of welded and soldered interconnections

Solar cell modules with welded and soldered interconnections were constructed using a flexible substrate material. These modules were thermally cycled between approx. 80 deg C at rates 100 cycles/day to demonstrate survivability under simulated low Earth orbit (LEO) temperature conditions. The modules, cycled in an inert atmosphere, show durability for 36,000 cycles.

Hart, R. E., Jr.↗

NASA NTRS1988

Observations on the dynamics of electromagnetically levitated liquid metals and alloys at elevated temperatures

Electromagnetic levitation and heating of small (0.5 to 1.0 gm) samples of Cu, Ni, and Ni-base alloys were performed in inert atmospheres. These experiments were recorded by high-speed photography using both regular film and video methods. Initial studies revealed interesting dynamics of the droplets that included axisymmetric oscillation, rotation, and oscillation mode changes. An attempt is made to explain the behavior using available models.

Hansen, G. P.↗

NASA NTRS1991

Paramagnetic resonance and susceptibility of ilmenite, FeTiO3 crystal

Large high-purity single crystals of FeTiO3 with ilmenite structure have been grown from a stoichiometric melt of Fe2O3 and TiO2 under an inert atmosphere using the modified Czochralski technique. Susceptibility and X-band paramagnetic resonance studies have been performed. Susceptibility measurements indicate a Neel temperature of about 59 K. The paramagnetic resonance spectrum for magnetic field perpendicular to the crystal c axis consists of a portion of a single, very intense approximately Lorentzian absorption line with its peak at about 600 G and half width at half maximum almost 1200 G. The absorption extends to zero magnetic field. For magnetic field approximately parallel to the c axis, the paramagnetic absorption is much smaller and may be considered a superposition of two approximately Lorentzian line shapes. The magnetic resonance measurements indicate a weak temperature dependence and large angular anisotropy.

Mcdonald, P. F.↗

NASA NTRS1992

SOHO MAMA openable cover/vacuum seal mechanism

The requirements, design, and test results of an openable cover mechanism with a high-vacuum seal developed for the Multi-Anode Microchannel Array (MAMA) Detectors, aboard the Solar and Heliospheric Observatory (SOHO) spacecraft. The mechanism, tested in summer/fall of 1991, has completed 1000 test cycles in an inert atmosphere at room temperature and pressure. Measured mechanism performance included: vacuum seal less than 5 x 10 exp -10 torr-liter/second, 103 degree angular range of travel, 20-minute cycle time, and successful latching functions. An openable cover mechanism that provides a clean, high-vacuum seal is vital to the success of a MAMA Detector operating over a full wavelength coverage from 500 to 1600 A.

Wiens, Mitchell T.↗

NASA NTRS1992

Boron-carbon-silicon polymers and ceramic and a process for the production thereof

The present invention relates to a process for the production of an organoborosilicon preceramic polymer of the structure: wherein R 1 is selected from alkyl having from 1 to 10 carbon atoms or phenyl, and x is selected from 0, 1, 2 or 3; which is pyrolyzable to produce a refractory material comprising inorganic compounds of Si, C and B, which process comprises: contacting a silicon containing compound of the structure: (R 1 ) x --Si--(CH=CH 2 ) 4- x or (R 1 ) x Si--(C=CH) 4- x with a boron containing compound selected from H 3 B:BH 3 , H 3 B:NH 3 , BH 3 :N(R 2 ) 3 wherein R 2 is selected from methyl, ethyl, propyl, butyl or phenyl in an inert atmosphere at a temperature of between about 90° and 170° C. for between about 0.1 and 20 hr and recovering the prepolymer. The prepolymer is pyrolyzed to produce a ceramic article useful in high temperature (e.g., aerospace) or extreme environmental applications.

Salvatore Riccitiello↗

NASA NTRS1993

Using rapid infrared forming to control interfaces in titanium-matrix composites

Control of the fiber-matrix reaction during composite fabrication is commonly achieved by shortening the processing time, coating the reinforcement with relatively inert materials, or adding alloying elements to retard the reaction. To minimize the processing time, a rapid IR forming (RIF) technique for metal-matrix composite fabrication has been developed. Experiments have shown that the RIF technique is a quick, simple, and low-cost process to fabricate titanium-alloy matrix composites reinforced with either silicon carbide or carbon fibers. Due to short processing times (typically on the order of 1-2 minutes in an inert atmosphere for composites with up to eight-ply reinforcements), the interfacial reaction is limited and well controlled. Composites fabricated by this technique have mechanical properties that are comparable to (in several cases, superior to) those made with conventional diffusion-bonding techniques.

Warrier, Sunil G.↗

NASA NTRS1994

Static and Dynamic Friction Behavior of Candidate High Temperature Airframe Seal Materials

The following report describes a series of research tests to evaluate candidate high temperature materials for static to moderately dynamic hypersonic airframe seals. Pin-on-disk reciprocating sliding tests were conducted from 25 to 843 C in air and hydrogen containing inert atmospheres. Friction, both dynamic and static, was monitored and serves as the primary test measurement. In general, soft coatings lead to excessive static friction and temperature affected friction in air environments only.

Dellacorte, C.↗

NASA NTRS1994

Ultra high purity, dimensionally stable INVAR 36

An INVAR 36 material having long-term dimensional stability is produced by sintering a blend of powders of nickel and iron under pressure in an inert atmosphere to form an alloy containing less than 0.01 parts of carbon and less than 0.1 part aggregate and preferably 0.01 part individually of Mn, Si, P, S and Al impurities. The sintered alloy is heat treated and slowly and uniformly cooled to form a material having a coefficient of thermal expansion of less than 1 ppm/C and a temporal stability of less than 1 ppm/year.

Sokolowski, Witold M.↗

NASA NTRS1995

Welding Using Chilled-Inert-Gas Purging

Report describes study of fusion welding using chilled inert gas. Marked improvement shown in welding of aluminum using chilled helium gas. Chilling inert gas produces two additional benefits: 1) creation of ultradense inert atmosphere around welds; 2) chilled gas cools metal more quickly down to temperature at which metals not reactive.

Mcgee, William F.↗

NASA NTRS1995

Ultra high purity, dimensionally stable INVAR 36

Sokolowski, Witold M.↗

NASA NTRS1997

Lightweight Ceramic Composition of Carbon Silicon Oxygen and Boron

Lightweight, monolithic ceramics resistant to oxidation in air at high temperatures are made by impregnating a porous carbon preform with a sol which contains a mixture of tetraethoxysilane, dimethyldiethoxysilane and trimethyl borate. The sol is gelled and dried on the carbon preform to form a ceramic precursor. The precursor is pyrolyzed in an inert atmosphere to form the ceramic which is made of carbon, silicon, oxygen and boron. The carbon of the preform reacts with the dried gel during the pyrolysis to form a component of the resulting ceramic. The ceramic is of the same size, shape and form as the carbon precursor. Thus, using a porous, fibrous carbon precursor, such as a carbon felt, results in a porous, fibrous ceramic. Ceramics of the invention are useful as lightweight tiles for a reentry spacecraft.

Leiser, Daniel B.↗

NASA NTRS1999

Carbon-Carbon Piston Architectures

An improved structure for carbon-carbon composite piston architectures consists of replacing the knitted fiber, three-dimensional piston preform architecture described in U.S. Pat. No. 4.909,133 (Taylor et al.) with a two-dimensional lay-up or molding of carbon fiber fabric or tape. Initially. the carbon fabric or tape layers are prepregged with carbonaceous organic resins and/or pitches and are laid up or molded about a mandrel. to form a carbon-fiber reinforced organic-matrix composite part shaped like a "U" channel, a "T"-bar. or a combination of the two. The molded carbon-fiber reinforced organic-matrix composite part is then pyrolized in an inert atmosphere, to convert the organic matrix materials to carbon. At this point, cylindrical piston blanks are cored from the "U" channel, "T"-bar, or combination part. These blanks are then densified by reimpregnation with resins or pitches which are subsequently carbonized. Densification is also be accomplished by direct infiltration with carbon by vapor deposition processes. Once the desired density has been achieved, the piston billets are machined to final piston dimensions; coated with oxidation sealants; and/or coated with a catalyst. When compared to conventional steel or aluminum-alloy pistons, the use of carbon-carbon composite pistons reduces the overall weight of the engine; allows for operation at higher temperatures without a loss of strength; allows for quieter operation; reduces the heat loss; and reduces the level of hydrocarbon emissions.

Rivers, H. Kevin↗

NASA NTRS1999

Long-Term Cyclic Oxidation Behavior of Uncoated and Coated Re-108 and In-939 at 980 and 870 C

Very long-term cyclic oxidation behavior of Re-108 and ln-939 with and without a protective coating was evaluated at 980 and 870 C, respectively. Re-108 and ln-939 without a protective coating began to show rapid weight loss at 3000 h due to scale spallation, indicating the need for an oxidation protective coating for longer than thousands of hours of oxidative life. NiAl-base coatings of a vapor phase aluminide (VPA), a pack aluminide (CODEP), and a slurry paint aluminide (SERMALOY J) were applied on Re-108 and ln-939. VPA and CODEP on Re-108 and all three coatings on ln-939 showed excellent cyclic oxidation resistance out to 10000 hr. Coated alloys were annealed in an inert atmosphere to determine the loss of Al from the coating into the alloy substrate through diffusion. The Al loss from the coating through diffusion was twice as great as the Al loss through oxidation after 10000 h of cyclic exposure. Oxidation life of VPA-coated Re-108 was estimated by calculating the amount of Al initially available for protective oxidation and the amount of Al lost through oxidation and diffusion.

Lee, K. N.↗