Electronic structure of disordered systems
Crystal lattice disordered systems, calculating electronic density of states by overlap integral transformation
Dy, K. S.↗
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Development of methods of producing large areas of silicon sheet by the slicing of silicon ingots using Inside-Diameter (I.D.) saws
Inside diametar wafering equipment, blades and processes were used to develop methods to produce large areas of silicon sheet. Modifications to a 16 inch STC automated saw included: programmable feed system, crystal rotating system, and STC dynatrack blade monitoring and control system. By controlling the plating operation and by grinding of the cutting edge, 16 inch ID blades with a cutting edge thickness of .22 mm can be produced. Crystal rotation mechanism was used to slice 100 mm diameter crystals with a 16 inch blade down to a thickness of .20 mm. Cutting rates with crystal rotation were generally slower than with standard plunge ID slicing techniques. Using programmed feeds and programmed rotation, maximum cutting rates were from 0.3 to 1.0 inches per minute.
Aharonyan, P.↗
Intermediate phases in the lanthanum- and neodymium-cobalt systems.
Crystal structures of intermediate phases in La-Co and Nd-Co systems by powder X ray diffraction technique
Raman, A.↗
Development of improved amorphous materials for laser systems
Crystallization calculations were performed in order to determine the possibility of forming a particular type of laser glass with the avoidance of devitrification in an outer space laboratory. It was demonstrated that under the homogenuous nucleating conditions obtainable in a zero gravity laboratory this laser glass may be easily quenched to a virtually crystal-free product. Experimental evidence is provided that use of this material as a host in a neodymium glass laser would result in more than a 10 percent increase in efficiency when compared to laser glass rods of a similar composition currently commercially available. Differential thermal analysis, thermal gradient oven, X-ray diffraction, and liquidus determination experiments were carried out to determine the basics of the crystallization behavior of the glass, and small-angle X-ray scattering and splat-cooling experiments were performed in order to provide additional evidence for the feasibility of producing this laser glass material, crystal free, in an outer space environment.
Neilson, G. F.↗
Investigation of the kinetics of crystallization of molten binary and ternary oxide systems Quarterly status report no. 4, Jun. 1 - Aug. 31, 1966
Investigation of glass formation by studies of molten binary and ternary oxide systems crystallization kinetics
TERNARY SYSTEM↗
Convection analysis on various crystal growth systems
Specific work done during an indicated contract period was reviewed. An extensive survey of crystal growth literature and related topics was accomplished during this time. Specific attention was given to those areas dealing with the effects of transport phenomena on crystal growth. Critical evaluations of growth techniques were made. Techniques studied included closed tube vapor growth, open reactor vapor growth, melt growth and solution growth.
Source record↗
Solar energy concentrator system for crystal growth and zone refining in space
The technological feasibility of using solar concentrators for crystal growth and zone refining in space has been performed. Previous studies of space-deployed solar concentrators were reviewed for their applicability to materials processing and a new state-of-the-art concentrator-receiver radiation analysis was developed. The radiation analysis is in the form of a general purpose computer program. It was concluded from this effort that the technology for fabricating, orbiting and deploying large solar concentrators has been developed. It was also concluded that the technological feasibility of space processing materials in the focal region of a solar concentrator depends primarily on two factors: (1) the ability of a solar concentrator to provide sufficient thermal energy for the process and (2) the ability of a solar concentrator to provide a thermal environment that is conductive to the processes of interest. The analysis indicate that solar concentrators can satisfactorily provide both of these factors.
Mcdermit, J. H.↗
Development of coated single-crystal superalloy systems for gas turbine applications
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Strangman, T. E.↗
Immiscible fluid: Heat of fusion heat storage system
Both heat and mass transfer in direct contact aqueous crystallizing systems were studied as part of a program desig- ned to evaluate the feasibility of direct contact heat transfer in phase change storage using aqueous salt system. Major research areas, discussed include (1) crystal growth velocity study on selected salts; (2) selection of salt solutions; (3) selection of immiscible fluids; (4) studies of heat transfer and system geometry; and (5) system demonstration.
Edie, D. D.↗
Evolution of major mineral compositions and trace element abundances during fractional crystallization of a model lunar composition
The evolution of major mineral compositions and trace element abundances during perfect fractional crystallization of a model lunar magma ocean was calculated. The minerals in the model lunar composition were olivine, orthopyroxene, clinopyroxene, and plagioclase. Lunar bulk composition data, major mineral/melt equilibria data, and trace element partition data were taken from published sources. The results show olivine beginning to crystallize at 1380 C. Approximately 50% of the system crystallizes as olivine. From 50 to 60% solidification, orthopyroxene crystallizes alone. During the final 40% solidification, Ca-rich clinopyroxene and plagioclase crystallize together. Various changes in composition of all these minerals are also noted during the process. Concomitant evolution of major element abundances in the melt is followed along with that of trace element abundances. Consequences of the results for constraints on some aspects of the composition of the lunar magma ocean and of the primitive moon are discussed.
Drake, M. J.↗
Programs for calculating cell parameters in electron and X-ray diffraction
Ten programs for calculating cell parameters from single crystal electron diffraction patterns are presented. Most of the programs, written for use with a programmable desk calculator, are also applicable to X-ray diffraction work. The programs can be used to calculate d-spacings from electron diffraction plate measurements, and to determine cell data (including interplanar angles and zone angles) for all crystal systems. A program for rhombohedral-hexagonal conversions and one for matching crystal data from standards with apparent crystal parameters found in diffraction patterns are included. Because they allow rapid determination of data not present in X-ray listings or elsewhere in the literature, the programs facilitate identification of unknowns.
Polkowski, G.↗
Influence of convection on free growth of dendrite crystals from solution
The free growth of dendrites in a uniformly supercooled solution was examined using cine photography with a Schlieren optical system. Crystals were grown in the bulk of the solution from a centrally located capillary tube, nucleated at the interface with a liquid nitrogen cooled wire. Crystals propagated along the tube, the slower growing orientations eliminated, and emerged at the tip, usually growing parallel to the tube direction. For both sodium sulfate decahydrate from its solution and ice from sodium chloride solution, growth rate and fineness of dendrites increased with supercooling. In sodium sulfate, upward convection of the less dense depleted solution occurs; downward convection was observed for the rejected, more concentrated sodium chloride solution. In both cases, there was a spatial and temporal delay in the release of the convective plume from the moving dendrite tip. The role of this convection on the growth characteristics and the production of secondary crystals is examined. A proposed low-g experiment to examine differences in growth rate, crystal texture, and secondary nucleation in a reduced convective regime where molecular diffusion is the dominant transfer process is discussed.
Hallett, J.↗
Development of Methods of Producing Large Areas of Silicon Sheet by the Slicing of Silicon Ingots Using Inside Diameter (I.D.) Saws
Methods of producing large areas of silicon sheets were developed by using inside diameter (I.D.) saws to slice silicon ingots. A 16 inch automated I.D. slicing machine was modified to accept programmable electric feed system, a crystal rotating system and a dyna-track blade monitoring and control system. The saw and accessories were used to slice 75 mm diameter single crystal silicon ingots while rotating them. The automated saw automatically recovered the wafers and loaded them into a cassette. The amount of material lost during slicing was reduced by using smaller blades than ones normally used to slice the wafers. Slicing runs on 100 mm diameter silicon is the next goal.
Aharonyan, P.↗
Development of methods of producing large areas of silicon sheet by the slicing of silicon ingots using Inside Diameter (I.D.) saws
Modifications to a 16 inch STC automated saw included: a programmable feed system; a crystal rotating system; and a STC dynatrack blade boring and control system. By controlling the plating operation and by grinding the cutting edge, 16 inch I.D. blades were produced with a cutting edge thickness of .22 mm. Crystal rotation mechanism was used to slice 100 mm diameter crystals with a 16 inch blade down to a thickness of .20 mm. Cutting rates with crystal rotation were generally slower than with standard plunge I.D. slicing techniques. Using programmed feeds and programmed rotation, maximum cutting rates were from 0.3 to 1.0 inches per minute.
Aharonyan, P.↗
Sr-isotopic constraints on the petrogenesis of Apollo 12 mare basalts
As part of a study of Apollo 12 basalts, crystallization ages and initial Sr-87/Sr-86 (I) were determined for pigeonite basalts 12039 and 12055 and ilmenite basalt 12051. Sr-86/Sr-87 measurements for a larger suite of whole rock and plagioclase samples were obtained, and it is found that I-values for olivine and pigeonite basalts are indistinguishable while I-values for ilmenite basalts are distinctly lower. A self-consistent model for the evolution of the Sr-isotopic composition and REE abundances suggests that basalt was formed by small (2-10%) degrees of melting of cumulate sources composed of varying proportions of olivine, orthopyroxene, and clinopyroxene. This model requires nonchondritic relative abundances of the REE in the parental liquid at the time of formation of the cumulate sources. The model also describes Sr-isotopic composition and REE abundances of Apollo 17 high-Ti basalts and Apollo 15 low-Ti basalts. A lunar 'scenario' involving open system crystallization of a magma ocean from the crust downward is proposed.
Nyquist, L. E.↗
Analysis and Evaluation of Processes and Equipment in Tasks 2 and 4 of the Low-cost Solar Array Project
The significant economic data for the current production multiblade wafering and inner diameter slicing processes were tabulated and compared to data on the experimental and projected multiblade slurry, STC ID diamond coated blade, multiwire slurry and crystal systems fixed abrasive multiwire slicing methods. Cost calculations were performed for current production processes and for 1982 and 1986 projected wafering techniques.
Goldman, H.↗
Absorption-interferometric technique for mapping temperature and concentration profiles during crystal growth from solution
Two-dimensional mapping of a solution's temperature and concentration profiles is possible in principle by pointwise combination of data from simultaneous absorption and interferometric images. Preliminary feasibility analysis and experiments indicate that adequate precision is attainable for selected solution crystallization systems.
Shlichta, P. J.↗
The control of float zone interfaces by the use of selected boundary conditions
The main goal of the float zone crystal growth project of NASA's Materials Processing in Space Program is to thoroughly understand the molten zone/freezing crystal system and all the mechanisms that govern this system. The surface boundary conditions required to give flat float zone solid melt interfaces were studied and computed. The results provide float zone furnace designers with better methods for controlling solid melt interface shapes and for computing thermal profiles and gradients. Documentation and a user's guide were provided for the computer software.
Foster, L. M.↗