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At least 1,225 records · Page 68

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NASA NTRS1979

Extraterrestrial fiberglass production using solar energy

A conceptual design is presented for fiberglass production systems in both lunar and space environments. The raw material, of lunar origin, will be plagioclase concentrate, high silica content slag, and calcium oxide. Glass will be melted by solar energy. The multifurnace in the lunar plant and the spinning cylinder in the space plant are unique design features. Furnace design appears to be the most critical element in optimizing system performance. A conservative estimate of the total power generated by solar concentrators is 1880 kW; the mass of both plants is 120 tons. The systems will reproduce about 90 times their total mass in fiberglass in 1 year. A new design concept would be necessary if glass rods were produced in space.

Ho, D.↗

NASA NTRS1979

Laser Techniques in Photovoltaic Research

High-power laser pulses were used to replace the conventional high temperature furnace processing for the p-n junction formation step in high speed, low cost solar cell fabrication. Three different approaches to junction formation were tested: (1) laser annealing of ion-implanted Si in which laser radiation is used to remove the radiation damage and to recover the electrical activity in the implanted layer; (2) a process in which a thin film of dopant is first deposited on the substrate and then incorporated into the near-surface region by laser-induced diffusion; and (3) a process in which a heavily doped amorphous silicon layer is deposited on the Si substrate and epitaxially regrown from the melted substrate layer by laser radiation. All three methods were found to provide suitable candidates for high efficiency Si solar cells.

Young, R. T.↗

NASA NTRS1979

Extraterrestrial processing and manufacturing of large space systems, volume 2, chapters 7-14 and appendices

Production and support equipment specifications are described for the space manufacturing facility (SMF). Defined production equipment includes electromagnetic pumps for liquid metal, metal alloying furnaces, die casters, electron beam welders and cutters, glass forming for structural elements, and rolling. A cost analysis is presented which includes the development, the aquisition of all SMF elements, initial operating cost, maintenance and logistics cost, cost of terrestrial materials, and transportation cost for each major element. Computer program listings and outputs are appended.

Miller, R. H.↗

NASA NTRS1978

Properties of GaN grown on sapphire substrates

Epitaxial growth of GaN on sapphire substrates using an open-tube growth furnace has been carried out to study the effects of substrate orientation and transfer gas upon the properties of the layers. It has been found that for the (0001) substrates, surface appearance was virtually independent of carrier gas and of doping levels. For the (1(-1)02) substrates surface faceting was greatly reduced when He was used as a transfer gas as opposed to H2. Faceting was also reduced when the GaN was doped with Zn, and the best surfaces for the (1(-1)02) substrates were obtained in a Zn-doped run using He as the transfer gas. The best sample in terms of electrical properties for the (1(-1)02) substrate had a mobility greater than 400 sq cm/V per sec and a carrier concentration of about 10 to the 17th per cu cm. This sample was undoped and used He as the transfer gas. The best (0001) sample was also grown undoped with He as the transfer gas and had a mobility of 300 sq cm/V per sec and a carrier concentration of 1 x 10 to the 18th per cu cm.

Crouch, R. K.↗

NASA NTRS1979

Effects of compositional changes on the performance of a thermal barrier coating system

Systems consisting of Ni-base bond coatings containing about 16Cr, 6Al, and from 0.15 to 1.08Y (all in wt %) and zirconium oxide layers containing from 4.0 to 24.4Y2O3 were evaluated for suitability as thermal barrier systems for advanced aircraft gas turbine engine components. The evaluations were performed in a cyclic furnace between 990 and 280 C as well as between 1095 and 280 C on solid specimens; in a natural gas-oxygen torch rig between about 1200 and 100 C on solid specimens and up to 1580 C surface temperatures on air-cooled blades; and in a Mach 1.0 burner rig up to 1570 C surface temperatures on air-cooled blades. The data indicate that the best systems consist of combinations involving the Ni-16.4Cr-5.1Al-0.15Y and Ni-17.0Cr-5.4Al-0.35Y bond coatings and the 6.2Y2O3- and 7.9Y2O3- (all in wt %) stabilized zirconium oxide layers.

Stecura, S.↗

NASA NTRS1978

Shear rupture of a directionally solidified eutectic gamma/gamma-prime - alpha /Mo/ alloy

Directionally solidified gamma/gamma-prime - alpha (Mo) eutectic alloys are being evaluated for application as advanced aircraft engine turbine blades. Their excellent high-temperature strength is partly due to their directionally aligned microstructure. However, alloys with such directional structures may display low shear strength at 760 C, the operating temperature of advanced blade roots. The objective of this investigation was to determine the shear rupture strength of the gamma/gamma-prime - alpha eutectic alloy and possibly to improve it by microstructural and heat-treatment variations. Bars of gamma/gamma-prime - alpha alloy containing nominally 5.7% Al and 33.5% Mo by weight with balance Ni were directionally solidified at rates between 10 and 100 mm per hour. Materials were solidified in furnaces with thermal gradients at the liquid-solid interface of 250 or 100 C per cm. A limited number of longitudinal shear rupture tests were conducted at 760 C and 207 MPa in the as-solidified and in several heat-treated conditions. It was found that the shear rupture failures are partly transgranular and that resistance to failure is promoted by good fiber alignment and a matrix structure consisting mainly of gamma-prime. Well-aligned as-solidified specimens sustained the shear stress for an average of 81 hours, while cellular material failed in one hour or less.

Harf, F. H.↗

NASA NTRS1979

Spray combustion models - A review

Due to recent theoretical and experimental advances, modeling spray combustion can be contemplated as a means of supplementing traditional cut and try combustor development methods. This review describes spray models that are currently being developed and their validation. The review is limited to steady, turbulent two- and three-dimensional systems typified by furnaces and gas turbine combustors. Both locally homogeneous flow models, where the phases are assumed to be in kinematic and thermodynamic equilibrium at each point in the flow, and more complete two-phase flow models, which allow for finite rate processes between the phases, are considered.

Faeth, G. M.↗

NASA NTRS1979

Gravitational influences on the liquid-state homogenization and solidification of aluminum antimonide

Typical commercial or laboratory-prepared samples of polycrystalline AlSb contain microstructural inhomogeneities of Al- or Sb-rich phases in addition to the primary AlSb grains. The paper reports on gravitational influences, such as density-driven convection or sedimentation, that cause microscopic phase separation and nonequilibrium conditions to exist in earth-based melts of AlSb. A triple-cavity electric furnace is used to homogenize the multiphase AlSb samples in space and on earth. A comparative characterization of identically processed low- and one-gravity samples of commercial AlSb reveals major improvements in the homogeneity of the low-gravity homogenized material.

Ang, C.-Y.↗

NASA NTRS1978

Fractional crystallization of iron meteorites, an experimental study

Measurements of the distribution coefficients of various elements (Ni, Co, P, Pt, Ir, Ge, Cr, and Au) between solid and liquid phases were made for FeNi alloys. A high thermal gradient crystal growing furnace was employed in order to promote plane front solidification, rapid mixing in the liquid and a minimum of diffusion in the solid. Eight measurements of the nickel distribution coefficient gave an average value of 0.91 plus or minus 0.03 and this value was independent of the Ni concentration in the range 5.5 to 8.75 wt. % Ni. Equilibrium distribution coefficients were also calculated by correcting for the diffusion boundary layer present in the liquid. These values are within 20% of the measured distribution coefficient values. Except for Co and Ni, all the measured distribution coefficient values are closer to 1.0 than those calculated by Scott (1972) for the IIIAB irons. Using the experimental values and the calculated equilibrium values for ternary additions to FeNi melts, it appears that fractional crystallization processes will not explain the observed chemical variations in the major iron meteorite groups. Alternative explanations are suggested which also recognize the fact that cooling rates vary widely in several chemical groups.

Goldstein, J. I.↗

NASA NTRS1978

Evaluation of options for process sequences

A methodology is being developed to ease the comparative evaluation of competing options in the process sequence for the manufacture of photovoltaic solar energy utilization systems. This evaluation will largely involve process economic analyses but will place equal emphasis on other characteristics, including energy consumption and environmental effects of the process options. Early analyses have been performed for the energy consumption in the arc furnace reduction of SiO2, for the costs and energy consumption in CZ crystal pulling and various slicing processes, and for the total energy consumption of process sequence through the completed module.

Wolf, M.↗

NASA NTRS1978

The suppression of low-temperature intergranular brittleness in ferritic Fe-Mn alloys

A method for obtaining cryogenic toughness in an Fe-12Mn-0.2Ti alloy by a controlled cooling technique is presented. The intergranular fracture surface of the quenched alloy, using an AES, revealed no significant difference from that obtained by the bulk transgranular fracture surface, indicating the absence of large-scale grain boundary segregation during the austenitizing treatment. Attention is given to the step cooling method, using a furnace at temperatures of 100 to 120 C, followed by fast cooling to ambient temperature, which in turn produces a high-impact toughness without intergranular brittleness. It is concluded that the sources of brittle intergranular fracture in the alloy are both chemical, operating in martensitic structure, and nonchemical, active during quenching from the austenitizing treatment.

Hwang, S. K.↗

NASA NTRS1980

Progress in MOSFET double-layer metalization

Report describes one-year research effort in VLSL fabrication. Four activities are described: theoretical study of two-dimensional diffusion in SOS (silicon-on-sapphire); setup of sputtering system, furnaces, and photolithography equipment; experiments on double layer metal; and investigation of two-dimensional modeling of MOSFET's (metal-oxide-semiconductor field-effect transistors).

Gassaway, J. D.↗

NASA NTRS1980

An automated oxide and diffusion facility for IC's

Report discusses totally-automated oxidation and diffusion facility for fabricating IC's. Several innovations are demonstrated: process controller specifically designed for semiconductor processing; automatic loading system to accept wafers from air track, insert them in quartz carrier, and place carrier on paddle for insertion into furnace; automatic unloading of wafers back onto air track; and boron diffusion using diborane.

Kennedy, B. W.↗

NASA NTRS1981

Three story residence with solar heat--Manchester, New Hampshire

When heat lost through ducts is counted for accurate performance assessment, solar energy supplied 56 percent of building's space heating load. Average outdoor temperature was 53 degrees F; average indoor temperature was 69 degrees F. System operating modes included heating from solar collectors, storing heat, heating from storage, auxiliary heating with oil fired furnace, summer venting, and hot water preheating.

Source record↗

NASA NTRS1981

Solar heating for an observatory--Lincoln, Nebraska

Report describes solar-energy system for 50 seat observatory that provides 60 percent of space heating needs. System includes 9 flat-plate collectors, rock storage bin, blowers, controls, ducting, and auxiliary natural-gas furnace; it has five operation modes. Net energy savings were 11.31 million Btu for 12 months, or equivalent of 1.9 barrels of oil. Report appendixes list performance factor definitions, performance equations, and average area weather conditions.

Source record↗

NASA NTRS1981

Single-family-residence solar heating--Carlsbad, New Mexico

Solar-heating and hot-water system includes 408 square feet of flat-plate air collectors, rock storage bin, energy transport system, air-to-water heat exchanger, controls, and hot-water preheat tank. Hot-air oil furnace supplies auxiliary space heating, and electricity powers air-handler blower and hot water preheat pump. For 12 month period, system provided 43 percent of space-heating and 53 percent of hot-water energy; net energy savings were 23.072 million Btu.

Source record↗

NASA NTRS1981

Mobile glazing unit

Unit programs thermal cycle from 100 to 2,300 F for firing ceramic gglaze coatings on refractory surfaces in any attitude and position. Device includes control console, heater assembly, protective cover, and manipulator boom; boom places heater next to surface to be fired. Unit is industrially useful for in situ repair of ceramics and curing individual refractory blocks during furnace maintenance.

Holt, J. W.↗

NASA NTRS1979

Engineering evaluation of existing space hardware for utilization in small self-contained payloads

The NASA small self-contained payload program allows research and development experiments of less than 5 cu ft to be flown in the Orbiter payload bay on a space available basis. Materials processing equipment available from Apollo, Skylab, SPAR, and MEA that include such items as furnaces for metallurgical processing and crystal growth, apparatus for measuring crystallization processes, and electrophoretic separators for cell separation are being offered by NASA through this program. Eighteen items for the self-contained payload program were evaluated and many were found to be suitable.

Lovoi, P. A.↗