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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.

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At least 775 records · Page 43
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

Pyrolysis of polymeric materials. I - Effect of chemical structure, temperature, heating rate, and air flow on char yield and toxicity

Various polymeric materials, including synthetic polymers and cellulosic materials, were evaluated at different temperatures, heating rates and air flow rates for thermophysical and toxicological responses. It is shown that char yields appeared to be a function of air access as much as of the chemical structure of the material. It is stated that the sensitivity of the apparent thermal stability of some materials to air access is so marked that thermogravimetric studies in oxygen-free atmospheres may be a consistently misleading approach to comparing synthetic polymers intended to increase fire safety. Toxicity also appeared to be a function of temperature and air access as much as of the chemical structure of the material. Toxicity of the gases evolved seemed to increase with increasing char yield for some polymers.

Hilado, C. J.↗
NASA NTRS1979

Pyrolysis of polymeric materials. II - Effect of chemical structure and temperature on char yield and flammability

Various polymeric materials were evaluated at different temperatures for relative flammability as defined by the HC value, a measure of the concentration of combustibles related to the concentration representing the lower limit of flammability. Flammability generally decreased with increasing char yield. This appears to support the hypothesis that increasing char yield decreases flammability by reducing the probability of reaching the lower flammable limits.

Hilado, C. J.↗
NASA NTRS1978

Relative toxicity of pyrolysis gases from materials - Effects of chemical composition and test conditions

Relative toxicity test data on 270 materials are presented, based on test procedures developed at the University of San Francisco. The effects of chemical composition, using data on 13 types of synthetic polymers and eight types of fabrics, are discussed. Selected materials were evaluated using nine test conditions with the USF method, and using methods developed at the FAA Civil Aeromedical Institute, Douglas Aircraft Company and San Jose State University.

Hilado, C. J.↗
NASA NTRS1979

Screening materials for toxicity of pyrolysis gases

The USF-NASA toxicity screening test method is primarily intended to indicate which materials are more toxic under specific test conditions, and not necessarily to explain why they are more toxic. Analysis of the test data obtained, however, in the light of the experience accumulated, can provide some insight into the mechanisms of toxicity and the importance of specific toxicants. The use of free-field movement offers both advantages and disadvantages relative to other behavioral paradigms, and the use of Swiss Webster mice offers both advantages and disadvantages relative to other species and strains.

Hilado, C. J.↗
NASA NTRS1981

Molten salt pyrolysis of latex

Latex-rich plants such as Guayule or extracts thereof are pyrolyzed in an inert nitrogen atmosphere inorganic salt melts such as a LiCl/KCl eutectic at a temperature of about 500 C. The yield is over 60% of a highly aromatic, combustible hydrocarbon oil suitable for use as a synthetic liquid fuel.

Bauman, A. J.↗
NASA NTRS1981

Silane pyrolysis in a free-space reactor

The Union Carbide process for producing silicon for photovoltaic applications proceeds via high purity silane as an intermediate. Decomposition of silane is accomplished in a freespace reactor which utilizes recirculating product hydrogen and silicon to transfer energy from a heated wall to an entering silane jet. Reaction occurs away from the wall, minimizing problems with wall deposition and contamination. A series of long duration and throughput tests has proven the feasibility of this concept. High purity powder can be produced at flows up to 4.5 kg/hr (10 lb/hr) in a 0.2 m (8 inch) diameter reactor with better than 99.99% conversion efficiency. This work is funded by DOE under JPL's Low Cost Solar Array (LSA) program.

Lay, J. R.↗
NASA NTRS1984

Combined Silane Pyrolysis and Silicon-Particle Melt

Melter directly coupled to pyrolyzer eliminates difficulties of transport. Proposed coupling of free-space silane pyrolyzer and melter without intervening steps produce molten silicon with no problems of fine-particle movement, storage, contamination in transport, or oxide formation.

Levin, H.↗
NASA NTRS1984

Highly photoconducting O2-doped CdS films deposited by spray pyrolysis

CdS films have been prepared by spraying in air solutions of thiourea with either cadmium chloride or cadmium acetate with varying mole ratio and substrate temperature, and subsequently heat treating in oxygen. Substrates included both bare glass or sapphire and transparent conducting oxide-coated sapphire for electrical measurements lateral and transverse to the CdS plane, respectively. Dark resistances of over 10 to the 14th ohms and light-to-dark conductivities of up to 10 to the 7th were obtained using uncoated substrates. The use of Cd(C2H3O2)2 in place of CdCl2 greatly increased the speed of response although with some sacrifice in photoconductivity. Deposition of CdS on ITO-coated surfaces led to greatly reduced dark resistances for the case of CdCl2, but not Cd(C2H3O2)2, presumably due to HCl reaction with the ITO coating in the course of spraying with the former. Ion microprobe analysis detected indium within the CdS films exhibiting low dark resistance. Measurements of the dark and light conductivities at temperatures down to 77 K are given as are the response times for unetched and HCl-etched surfaces.

Richards, D.↗
NASA NTRS1985

High-Purity Silicon Seeds for Silane Pyrolysis

Seed particles for fluidized-bed production of silicon made by new contamination-free, economical method. In new method, large particles of semiconductor-grade silicon fired at each other by high-speed streams of gas and thereby break up into particles of suitable size for fluidized bed. No foreign materials introduced, and leaching unnecessary. Method used to feed fluidized-bed reactor for continuous production of high-purity silicon.

Hsu, G. C.↗
NASA NTRS1984

A fluidized-bed reactor for silane pyrolysis

The silane decomposition in a fluidized bed reactor was studied. The process feasibility and operating windows were determined. Long duration tests were conducted and silicon purity was demonstrated. A high purity linear was installed in the fluid bed reactor; the FBR product was melted and single crystallized. Product purity improvements are noted.

Iya, S.↗
NASA NTRS1986

Use of laboratory simulated pyrolysis in tracing the history of sedimentary organic matter

Results from laboratory simulated pyrolyses experiments show that in addition to depth of burial, preservation of kerogen, and hence any morphologic structure in it, is also dependent on the mineral matrix with which it is associated. In the presence of clay minerals, and especially under dry conditions, extractable lipids released during kerogen decomposition are more rapidly destroyed than in the presence of calcite or chert matrices. The result is production of gas, polar bitumen and pyrobitumen and destruction of biomarkers. During such an early reorganization of the kerogen, the biomarker constituents can be destroyed, or unrecognizably altered. The above process of organic residues maturation appears to be inhibited in the presence of water and is significantly reduced where kerogen is hosted in limestones, dolomites or cherts. These minerals have been characteristically found to be the most reliable in yielding morphological fossils and small quantities of extractable bitumen in Archean and Proterozoic rocks. To understand the validity of chemical and morphological fossils, in the early geologic record, it will be necessary to understand the process of kerogen in sedimentary rocks. To test the role of various minerals on the preservation process, kerogen extracted from a variety of rocks has been heated together with montmorillonite, illite and calcite. The kinetics of the process has been monitored and the products quantitatively identified.

Kaplan, I. R.↗
NASA NTRS1990

Pyrolysis Products Of Dimethyldichlorosilane

Report describes experimental study of chemical reactions and chemical products of chemical-vapor deposition of silicon carbide from dimethyldichlorosilane. Topic important because it relates to current interest in lightweight refractory materials for use in advanced aircraft and spacecraft. Analyses showed that at temperature of 700 to 1,100 degrees C and contact time of about 1 minute, SiC forms by two chemical-reaction paths.

Cagliostro, D. E.↗
NASA NTRS1990

Analysis of the pyrolysis products of dimethyldichlorosilane in the chemical vapor deposition of silicon carbide in argon

A study of the products and reactions occurring during the chemical vapor deposition of silicon carbide from dimethyldichlorosilane in argon is presented. Reaction conditions were as follows: 700 to 1100 C, a contact time of about 1 min, and a pressure of 1 atm. At these conditions, the gases that formed were mainly methane, hydrogen, silicon tetrachloride, trichlorosilane, and methyltrichlorosilane. The silicon carbide solid that formed showed the presence of hydrogen and chloride as impurities, which might degrade the silicon carbide properties. These impurities were eliminated slowly, even at 1100 C, forming hydrogen, trichlorosilane, and silicon tetrachloride.

Cagliostro, Domenick E.↗
NASA NTRS1991

Chemical spray pyrolysis of Tl-Ba-Ca-Cu-O high-T(sub c) superconductors for high-field bitter magnets

The deposition of Tl-Ba-Ca-Cu-O thick films by spray pyrolyzing a Ba-Ca-Cu-O precursor film and diffusing thallium into the film to form the superconducting phase is examined. This approach was taken to reduce exposure to thallium and its health and safety hazards. The Tl-Ba-Ca-Cu-O system was selected because it has very attractive features which make it appealing to device and manufacturing engineering. Tl-Ba-Ca-Cu-O will accommodate a number of superconducting phases. This attribute makes it very forgiving to stoichiometric fluctuations in the bulk and film. It has excellent thermal and chemical stability, and appears to be relatively insensitive to chemical impurities. Oxygen is tightly bound into the systems, consequently there is no orthorhombic (conductor) to tetragonal (insulator) transition which would affect a component's lifetime. More significantly, the thallium based superconductors appear to have harder magnetic properties than the other high-Tc oxide ceramics. Estimates using magnetoresistance measurements indicate that at 77 K Tl2Ba2CaCu2O10 will have an upper critical field, H(sub c2) fo 26 Tesla for applied fields parallel to the c-axis and approximately 1000 Tesla for fields oriented in the a-b plane. Results to date have shown that superconducting films can be reproducibly deposited on 100 oriented MgO substrates. One film had a zero resistance temperature of 111.5 K. Furthermore, x ray diffraction analysis of the films showed preferential c-axis orientation parallel to the plane of the substrate. These results have now made it possible to consider the manufacture of a superconducting tape wire which can be configured into a topology useful for high-field magnet designs. The research which leads to the preparation of these films and plans for further development are reviewed.

Derochemont, L. Pierre↗