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Description: A study was made of fiber-texture type of preferred orientation in extruded Al rods and brass sheeting. Experiments to purify Zr by the zone- melting techniques were studied. Several transformation products of the decomposition of the BETA eutectoid of the Ag--Zr system were identified. The tempering of the martensitic structure of a hypoeutectoid Ag-- Zr was studied. Metallurgical treatments for the recovery of U from spent stainless steel fuel elements were investigated. Physical properties and radiation stability of the Si-- SiC fuel element material were investigated. The development and fabrication of a uniform fuel-bearing sandwich plate were continued. Methods of welding stainless steel were studied. An evaluation study was made of brazing alloys on the basis of corrosion resistance, neutron economy, flow temperature, availability, and cost. (C.H.)
Date: August 31, 1955
Creator: Bridges, W.H. ed.
Partner: UNT Libraries Government Documents Department

Float zone silicon sheet growth. Quarterly report number 9, October 1--December 31, 1995

Description: This report discusses progress made in each of the following tasks: (1) heat pipe construction; (2) heat pipe heater and heat extraction system; (3) optical temperature monitoring system; (4) replenishment source development; (5) RF electrode assembly; (6) solid-liquid interface monitors; (7) ribbon seed preparation; and (8) overall systems assembly.
Date: February 1, 1996
Creator: Bleil, C.E.
Partner: UNT Libraries Government Documents Department

Mechanical properties of melt-derived erbium oxide

Description: Erbium oxide (Er{sub 2}O{sub 3}) is a rare earth oxide that is chemically and thermally stable and has a melting point of 2,430 C. There is relatively little information available regarding single crystal growth of erbia or the properties of erbia. In this study, erbia single crystals have been grown in a Xenon Optical Floating Zone Unit (XeOFZ) capable of melting materials at temperatures up to 3,000 C. Erbia was melt synthesized in the XeOFZ unit in a container less fashion, proving for little chance of contamination. Crystals were grown in compressed air and in reducing atmospheres. A recurring problem with melt synthesis of erbia is the appearance of flakes at the edges of the melt zone during growth; these flakes disrupt the growth process. The processing details and an initial survey of the physical properties of erbia single crystals is discussed.
Date: December 31, 1998
Creator: Neuman, A.D.; Blacic, M.J.; Platero, M.; Romero, R.S.; McClellan, K.J. & Petrovic, J.J.
Partner: UNT Libraries Government Documents Department

Generalization of internal centrifugal zone growth of metal-ceramic composites. Progress report, December 1, 1974--August 31, 1975

Description: Objectives are (1) to develop a model of Internal Centrifugal Zone Growth (ICZG) and (2) to use this model to improve present ICZG systems. During the present year, models were developed for finite samples heated by finite induction coils. These models enable calculation of two-dimensional temperature profiles in solid samples. Molten zone shapes can be calculated provided that simplified boundary conditions for the rf field are employed. Experiments to test these models were conducted here and at ORNL. The heating instability phenomenon was possibly observed but not quantified. (DLC)
Date: January 1, 1975
Creator: Sekerka, R. F.
Partner: UNT Libraries Government Documents Department

Synthesis and properties of erbium oxide single crystals

Description: Erbium oxide (Er{sub 2}O{sub 3}, erbia) is a highly stable cubic rare earth oxide with a high melting point of 2,430 C. Because of this, it may have potential applications where high temperature stability and corrosion resistance are required. However, relatively little is known about the properties of this oxide ceramic. The authors have employed a xenon optical floating zone unit with a temperature capability of 3,000 C to grow high quality single crystals of erbia. The conditions for single crystal growth of erbia have been established. The mechanical properties of erbia single crystals have been initially examined using microhardness indentation as a function of temperature.
Date: April 1, 1999
Creator: Petrovic, J.J.; Romero, R.S.; Mendoza, D.; Kukla, A.M.; Hoover, R.C. & McClellan, K.J.
Partner: UNT Libraries Government Documents Department

Float zone silicon sheet growth. Technical progress report: Quarterly report Number 11, April 1--June 30, 1996

Description: During this period continued attention has been paid to task number 8 as cited in the proposed statement of work. While the water cooling and power feed to the heaters and the primary and secondary electrodes have been completed and are functional, vacuum leaks developed during testing of the system. A multitude of stress induced pinhole vacuum leaks which seriously delayed the final system assembly have been corrected. As a result, task No. 8 and the relevant changes in tasks numbered 3, 4, 5, and 6 have occupied more than 90% of the time.
Date: September 1, 1996
Creator: Bleil, C.E.
Partner: UNT Libraries Government Documents Department

Czochralski growth of gallium indium antimonide alloy crystals

Description: Attempts were made to grow alloy crystals of Ga{sub 1{minus}x}In{sub x}Sb by the conventional Czochralski process. A transparent furnace was used, with hydrogen purging through the chamber during crystal growth. Single crystal seeds up to about 2 to 5 mole% InSb were grown from seeds of 1 to 2 mole% InSb, which were grown from essentially pure GaSb seeds of the [111] direction. Single crystals were grown with InSb rising from about 2 to 6 mole% at the seed ends to about 14 to 23 mole% InSb at the finish ends. A floating-crucible technique that had been effective in reducing segregation in doped crystals, was used to reduce segregation in Czochralski growth of alloy crystals of Ga{sub 1{minus}x}In{sub x}Sb. Crystals close to the targeted composition of 1 mole% InSb were grown. However, difficulties were encountered in reaching higher targeted InSb concentrations. Crystals about 2 mole% were grown when 4 mole% was targeted. It was observed that mixing occurred between the melts rendering the compositions of the melts; and, hence, the resultant crystal unpredictable. The higher density of the growth melt than that of the replenishing melt could have triggered thermosolutal convection to cause such mixing. It was also observed that the floating crucible stuck to the outer crucible when the liquidus temperature of the replenishing melt was significantly higher than that of the growth melt. The homogeneous Ga{sub 1{minus}x}In{sub x}Sb single crystals were grown successfully by a pressure-differential technique. By separating a quartz tube into an upper chamber for crystal growth and a lower chamber for replenishing. The melts were connected by a capillary tube to suppress mixing between them. A constant pressure differential was maintained between the chambers to keep the growth melt up in the growth chamber. The method was first tested with a low temperature alloy Bi{sub ...
Date: February 1, 1998
Creator: Tsaur, S.C.
Partner: UNT Libraries Government Documents Department

Float zone silicon sheet growth. Quarterly report number 10, January 1--March 31, 1996

Description: During this period special attention has been paid to task number 8 as cited in the proposed statement of work. While the water cooling and power feed to the heaters and the primary and secondary electrodes has been completed and are functional, vacuum leaks developed during testing of the system. A multitude of stress induced pinhole vacuum leaks have seriously delayed the final system assembly. Progress has been extremely slow since the system has been completely disassembled and reassembled several times with extensive leak testing. As a result, task No. 8 and the relevant changes in tasks numbered 3, 4, 5, and 6 have occupied more than 90% of the time. Task No. 8 is the overall system assembly. Tasks 3, 4, 5 and 6 pertain to the optical temperature monitoring system, replenishment source development RF electrode assembly, and solid-liquid interface monitors.
Date: May 1, 1996
Creator: Bleil, C.E.
Partner: UNT Libraries Government Documents Department


Description: High-pressure Bridgman (HPVB) and vertical zone melting (HPVZM) growth processes have been applied for the manufacturing of Cd{sub 1-x}Zn{sub x}Te (x = 0.04-0.2), CdSe and ZnSe crystal tapes with sizes up to 120 x 120 x 12 mm. The influences of the technological parameters describing the growth processes on the crystal quality and some selected material properties are discussed. The dependence of the inclusion (bubbles) content on the deviation from melt stoichiometry is determined. A method for growing plates with low content of inclusions is described. High-resistivity crystal tapes of undoped CdZnTe (10{sup 10} Ohm x cm), CdSe (10{sup 11} Ohm x cm) and ZnSe (>10{sup 11} Ohm x cm) were prepared. The possibility of tape growth on oriented seeds is shown for the example of CdSe. The primary differences between HPVB and HPVZM results are described. The main HPVZM advantage for II-VI compound crystal growth is the possibility of obtaining crystals with more stoichiometric composition or with a controlled deviation from stoichiometry. Hence, HPVZM is preferable for growing high-resistivity II-VI crystals with low inclusion content and possibly with better transport properties. Keywords for this report are: Crystal growth, shaped crystal growth, ZnSe, CdSe, CdZnTe, CZT, HPVB, Bridgman, HPVZM, zone melting, radiation detectors.
Date: July 7, 2002
Partner: UNT Libraries Government Documents Department

Advanced Materials and Processes for High Energy Resolution Room Temperature Gamma Ray Spectrometers

Description: A significant amount of progress has been achieved in the development of the novel vacuum distillation method described in the proposal. The process for the purification of Te was fully developed and characterized in a series of trials. The purification effect was confirmed with GDMS sample analysis and indicates the process yields very high purity Te metal. Results of this initial process study have been submitted for publication in the Proceedings of the SPIE and will be presented on August 28, 2007 at the SPIE Optics and Photonics 2007 conference in San Diego, CA. Concurrent to the development of the Te process, processes for the purification of Cd, Zn, and Mn have also progressed. The development of the processes for Cd and Zn are nearly complete, while the development of the process for Mn is still in its infancy. It is expected that a full characterization of the Cd process will be completed within the next quarter, followed by Zn. Parallel to those characterization studies, efforts will be made to further develop the Mn purification process. Zone melting work for Te and Cd has also been efforted as per the project work schedule. Initial trials have been completed and the processes developed. Characterization of the results will be completed within the first fiscal year. Finally, an apparatus for the zone refinement of Cd, Zn, and Mn has been constructed and initial trials are set to begin shortly.
Date: December 12, 2007
Creator: McGregor, Douglas S.
Partner: UNT Libraries Government Documents Department

Float zone silicon sheet growth. Quarterly report number 12, July 1--September 30, 1996

Description: During this period continued attention has been paid to task number 8 as cited in the proposed statement of work. The water cooling and power feed to the heaters and the primary and secondary electrodes have been completed and are functional and all vacuum leaks have been repaired. Progress in the final assembly (task number 8) and the relevant additions to tasks numbered 3, 4, 5, 6 and 7 have occupied more than 80% of the time. Preparations have also been made for the completion of the final report.
Date: December 31, 1996
Creator: Bleil, C.E.
Partner: UNT Libraries Government Documents Department

Float zone silicon sheet growth. Final report, September 23, 1993--December 31, 1996

Description: Energy Materials Research was organized in 1984. The specific objective of the company is to generate new concepts and to move targeted applications of newly developing technologies into commercial production. The initial technology described here is the outgrowth of a research program to develop concepts and techniques for low-cost energy production from renewable energy resources. The first major project implements an innovative process for the direct production of crystalline silicon sheet from a polycrystalline silicon source. The apparatus is designed to achieve this objective. Its primary goal is the efficient, low cost production of crystal silicon sheet of the highest quality silicon for the electronics industry. The objective of this phase of the project is to develop a laboratory processor that will produce single crystal ribbons or sheets of semiconductor quality silicon. A summary description of the overall process to be implemented is as follows: a single crystal seed in the form of a sheet is placed on a substrate in a non-reactive ambient and a carefully controlled thermal environment. The seed is heated to a stabilized temperature near the melting point in the zone designated for the crystal growth. A melt zone is developed. Melting is accomplished in the growth zone with a unique heating source which provides a very low thermal gradient in the pull direction but permits a high thermal gradient normal thereto. The sheet is pulled from the melt allowing crystallization to occur nearly normal to the pulling direction. The melt is replenished from a polycrystalline source heated by an ancillary RF power supply. Development of this process, unique to silicon sheet technology, provides several important benefits.
Date: April 1, 1997
Creator: Bleil, C.E.
Partner: UNT Libraries Government Documents Department

Processing yttrium-barium-copper oxide superconductor zero gravity using a double float zone surface

Description: The effects of processing YBa{sub 2}Cu{sub 3}O{sub x} (Y123) superconductor in the near-zero gravity (0g) environment provided by the NASA KC-135 airplane flying on parabolic trajectories were studied. A new sheet float zone furnace, designed for this study, enabled fast temperature ramps. Up to an 18-gram sample was processed with each parabola. Samples of Y123 were processed as bulk sheets, composites containing Ag and Pd, and films deposited on single crystal Si and MgO substrates. The 0g-processed samples were multi-phase yet retained a localized Y123 stoichiometry where a single ground-based (1g) oxygen anneal at temperatures of 800 C recovered nearly 100-volume percent superconducting Y123. The 1g processed control samples remained multi-phase after the same ground-based anneal with less than 45 volume percent as superconducting Y123. The superconducting transition temperature was 91 K for both 0g and 1g processed samples. A 29 wt.% Ag/Y123 composite had a transition temperature of 93 K. Melt texturing of bulk Y123 in 0g produced aligned grains about a factor of three larger than in analogous 1g samples. Transport critical current densities were at or below 18 A/cm{sup 2}, due to the formation of cracks caused by the rapid heating rates required by the short time at 0g. Y123 deposited on single crystal Si and MgO in 0g was 30 vol.% y123 without an anneal. A weak superconducting transition at 80 K on MgO showed that substrate interactions occurred.
Date: April 1, 1997
Creator: Pettit, D. R.; Peterson, D. E.; Kubat-Martin, K. A.; Petrovic, J. J.; Sheinberg, H.; Coulter, Y. et al.
Partner: UNT Libraries Government Documents Department

Zone refining of plutonium metal

Description: The purpose of this study was to investigate zone refining techniques for the purification of plutonium metal. The redistribution of 10 impurity elements from zone melting was examined. Four tantalum boats were loaded with plutonium impurity alloy, placed in a vacuum furnace, heated to 700{degrees}C, and held at temperature for one hour. Ten passes were made with each boat. Metallographic and chemical analyses performed on the plutonium rods showed that, after 10 passes, moderate movement of certain elements were achieved. Molten zone speeds of 1 or 2 inches per hour had no effect on impurity element movement. Likewise, the application of constant or variable power had no effect on impurity movement. The study implies that development of a zone refining process to purify plutonium is feasible. Development of a process will be hampered by two factors: (1) the effect on impurity element redistribution of the oxide layer formed on the exposed surface of the material is not understood, and (2) the tantalum container material is not inert in the presence of plutonium. Cold boat studies are planned, with higher temperature and vacuum levels, to determine the effect on these factors. 5 refs., 1 tab., 5 figs.
Date: May 1, 1997
Partner: UNT Libraries Government Documents Department

Silicon float-zone crystal growth as a tool for the study of defects and impurities

Description: Because of its ability to produce silicon crystals of exceptionally high purity and crystallographic perfection, the float-zone method lends itself to use as a tool for the controlled study of deliberately introduced defects and impurities in Si crystals and their effects on materials properties such as minority charge-carrier lifetime or photovoltaic conversion efficiency. Some examples of such studies are presented here. Defects the authors have studied include grain size, dislocations, swirl defects, and fast-cooling defects. Impurity studies have focused on H, N, Fe, and interactions between Fe and Ga. They used the bulk DC photoconductive decay lifetime characterization method and small diagnostic solar cell characterization techniques to assess material quality. The low defect and impurity concentrations obtainable by float zoning allow baseline lifetimes over 20 milliseconds and photovoltaic device efficiencies over 22%; therefore, small effects of impurities and defects can be detected easily.
Date: June 20, 2000
Creator: Ciszek, T. F. & Wang, T. H.
Partner: UNT Libraries Government Documents Department

Growth of high {Tc} superconducting fibers using a miniaturized laser-heated float zone process. Progress report, November 6, 1990--December 31, 1991

Description: This report summarizes the progress made on the project ``Growth of High {Tc} Superconducting Fibers Using a Miniaturized Laser-Heated Float Zone Process`` during the 14 month period from Nov. 6, 1990 to Dec. 31, 1991. The studies during this period focused primarily on phase diagram studies, phase relations in the calcium aluminate system and on Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8} (BSCCO). Some work was also done on the Advanced Fiber Growing Station. Because of the complicated phase relationships found in the incongruently melting BSCCO system, the incongruently melting CA{sub 3}Al{sub 2}O{sub 6} phase of the calcium oxide-aluminum oxide system was studied as a model material. The data obtained was in agreement with well known solidification theory. Fibers grown from calcium oxide rich sources contained calcium oxide nodules which transported from the melting source interface to the growth interface, while those grown from aluminum oxide rich sources contained continuous inclusions of a divorced eutectic. The melt compositions were also found to follow theoretical predictions. The agreement of this data with the phase diagram and solidification theory demonstrates that phase equilibrium information can be extracted from fiber growth experiments. BSCCO feed rods were made from 12 different compositions. Fibers were grown from these rods and the melts were abruptly quenched which preserves the as-grown 2212 fiber, a glassy frozen melt and the source. A future study of these sections will reveal the phase relationships that exist in the BSCCO system. Melt temperature gradients of 500--1,000 C/cm were measured near the interface in these experiments. During this reporting period, work continued on the mechanical components of the Advanced Fiber Growth Station.
Date: December 31, 1991
Creator: Feigelson, R.S.; Route, R.K. & DeMattei, R.C.
Partner: UNT Libraries Government Documents Department

Low-cost thin-film polycrystalline silicon solar cells. Quarterly project report No. 1, March 15, 1979-June 30, 1979

Description: The objective of this contract is to advance the thin film silicon solar cell technology developed at Southern Methodist University, Dallas, Texas, with a view toward achieving photovoltaic conversion efficiencies greater than 10% at a cost of $100 to $300/kWe. The technology developed at SMU consists of: (1) the purification of metallurgical silicon by acid extraction and phosphorus pentoxide treatment, (2) the preparation of metallurgical silicon substrates by the unidirectional solidification of the melt on graphite, (3) the deposition of a silicon p-n junction structure on metallurgical silicon substrates by the thermal reduction of trichlorosilane, and (4) the application of grid contacts and anti-reflection coatings. Major efforts during this period have been directed to the organization and planning of the overall technical approaches, particularly in regard to the preparation of metallurgical silicon substrates. The zone-melting technique has been selected for the preparation of substrates, and a moving-coil zone-melting apparatus has been designed and constructed. A chemical vapor deposition apparatus for the deposition of the active region of solar cell has also been designed and constructed. In addition, the purification of metalurgical silicon by acid-extraction has been investigated semi-quantitatively.
Date: July 1, 1979
Creator: Crownover, J D & van der Leeden, G A
Partner: UNT Libraries Government Documents Department

Pulsed CO sub 2 laser processing of thin ion-implanted silicon layers

Description: We show that extremely shallow ({approx lt} 800 {Angstrom}) melt depths can be easily obtained by irradiating a thin heavily doped silicon layer with a CO{sub 2} laser pulse. Since the absorption of the CO{sub 2} laser pulse is dominated by free-carrier transitions, the beam heating occurs primarily in the thin degenerately doped film. For CO{sub 2} pulse-energy densities exceeding a threshold value, surface melting occurs and the reflectivity of the incident laser pulse increases abruptly to about 90%. This large increase in the reflectivity acts like a switch to reflect almost all of the energy in the remainder of the pulse, thereby greatly reducing the amount of energy available to drive the melt front to deeper depths in the material. Transmission electron microscopy shows no extended defects in the near-surface region after laser irradiation, and van der Pauw electrical measurements verify that 100% of the implanted arsenic dopant is electrically active. 8 refs., 3 figs., 1 tab.
Date: January 1, 1988
Creator: James, R.B. (Sandia National Labs., Livermore, CA (United States)) & Christie, W.H. (Oak Ridge National Lab., TN (United States))
Partner: UNT Libraries Government Documents Department

Stress studies in EFG. Quarterly progress report, October 1-December 31, 1983

Description: Stress analysis at Harvard University has examined the implication of non-zero interface stresses on model predictions. Stress distributions at distances greater than about 1 mm from the interface are shown to be independent of the interface stress at high creep intensities, and the predictions based on zero initial stress can be used with confidence. Numerical models for growth dynamics developed at MIT are compared with experimental data on t-V relationships and on interface shape obtained from impurity redistribution in aluminum-doped 10 cm wide ribbon. Comparison of primary creep responses in FZ (floating zone) and CZ (Czochralski) silicon above 1200/sup 0/C using four-point bending indicates that oxygen has a significant influence on the creep rate. Both the strain rate and resulting dislocation densities generated in FZ silicon are an order of magnitude higher than for the CZ material at comparable applied stress levels. A fiber optics probe suitable for temperature measurement during sheet growth has been constructed and tested. Study of the feasibility of using laser interferometric techniques for residual stress measurements has continued at the University of Illinois. The method has been successfully applied to CZ silicon, and is being evaluated for use with EFG ribbon.
Date: February 15, 1984
Creator: Kalejs, J.P.
Partner: UNT Libraries Government Documents Department