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Tempered glass

Description: This document describes a demonstration for making tempered glass using minimal equipment. The demonstration is intended for a typical student of materials science, at the high school level or above. (JL)
Date: November 1, 1991
Creator: Bunnell, L.R.
Partner: UNT Libraries Government Documents Department

Fiberglass material specification II

Description: This report describes the requirements for composite parts to be furnished to Martin Marietta Energy Systems, Inc. Topics discussed include: Part Fabrication Requirements, Scope, and Applicable Documents.
Date: October 1, 1991
Creator: Frame, B.J. & Janke, C.J.
Partner: UNT Libraries Government Documents Department

Jet penetration in glass

Description: We describe a phenomenological model which accounts for the mechanical response of glass to intense impulsive loading. An important aspect of this response is the dilatancy accompanying fracture. We have also conducted a number of experiments with 38.1-mm diameter precision shaped charges to establish the performance against various targets and to allow evaluation of our model. At 3 charge diameters standoff, the data indicate that both virgin and damaged glass offer better (Bernoulli-scaled) resistance to penetration than either of 4340 steel, or 6061-T6 aluminum alloy. Time-resolved measurements indicate two distinct phases of jet penetration in glass: An initial hydrodynamic phase, and a second phase characterized by a slower penetration velocity. Our calculations show that at early time, a crater is formed around the jet and only the tip of the undisturbed jet interacts with the glass. At late time the glass has collapsed on the jet and degraded penetration continues via a disturbed and fragmented jet.
Date: May 1, 1991
Creator: Moran, B.; Glenn, L.A. & Kusubov, A.
Partner: UNT Libraries Government Documents Department

Model of amorphous-silicon-layer regrowth

Description: A new model which combines the heterogeneous nucleation and growth process for the mechanism of regrowth of amorphous silicon, in contact with a single crystal substrate, is presented. The model explains the effects of substrate orientation and impurity concentration on the kinetics of regrowth and also on the formation of twins during regrowth. The mechanism of redistribution of impurities and the formation of secondary defects during crystal regrowth are also discussed. A comparison of experimental results with the predictions of the model is also included.
Date: January 1, 1983
Creator: Ling, P.
Partner: UNT Libraries Government Documents Department

Effect of laser annealing on the redistribution of boron in ion implanted and boron deposited silicon

Description: Secondary ion mass analysis (SIMS) is used to investigate the effect of laser annealing on the distribution of boron in the surface region of (100) silicon. Pulsed laser annealing was carried out using the Q-switched output of a ruby laser (20 x 10/sup -9/ sec pulse duration time). Above a pulse threshold energy of approx. 1/J cm/sup -2/, substantial alteration of the as-implanted profile of B occurred. The as-implanted profile was very nearly Gaussian, but after annealing the profile was almost uniform from the surface down to a depth of approximately twice the projected range. Redistribution of B was found to be both pulse energy and pulse number dependent. The effect of laser annealing on a thin evaporation deposited layer of B on (100) silicon was also studied. In this case a monotomically decreasing profile which resembled a Gaussian peaked at the surface resulted. A possible explanation for the redistribution of B in the surface region of (100) silicon involves melting of the near surface region during laser irradiation.
Date: January 1, 1978
Creator: Christie, W.H. & White, C.W.
Partner: UNT Libraries Government Documents Department

Modeling of forced flow/thermal gradient chemical vapor infiltration

Description: The forced flow/thermal gradient chemical vapor infiltration process (FCVI) has proven to be a successful technique for fabrication of ceramic matrix composites. It is particularly attractive for thick components which cannot be fabricated using the conventional, isothermal method (ICVI). Although it offers processing times that are at least an order of magnitude shorter than ICVI, FCVI has not been used to fabricate parts of complex geometry and is perceived by some to be unsuitable for such components. The major concern Is that selection and control of the flow pattern and thermal profile for optimum infiltration can be a difficult and costly exercise. In order to reduce this effort, we are developing a computer model for FCVI that simulates the densification process for given component geometry, reactor configuration and operating parameters. Used by a process engineer, this model can dramatically reduce the experimental effort needed to obtain uniform densification. A one-dimensional process model, described in a previous interim report, has demonstrated good agreement with experimental results in predicting overall densification time and density uniformity during processing and the effect of various fiber architectures and operating parameters on these process issues. This model is fundamentally unsuitable for more complex geometries, however, and extension to two- and three-dimensions is necessary. This interim report summarizes our progress since the previous interim report toward development of a finite volume'' model for FCVI.
Date: September 1, 1992
Creator: Starr, T.L. & Smith, A.W. (Oak Ridge National Lab., TN (United States))
Partner: UNT Libraries Government Documents Department

90503 mock study. Period covered: October--December 1975

Description: Two billets were pressed from each of three lots of 90503 mock. One billet from each of these lots was pressed using dried powder. Samples were taken from each pressing charge just prior to pressing and volatile content measured. Each of these six billets were then machined into compression and tensile specimens. Additional compression specimens were machined from an existing hemispherical part made from one of these lots of material. Dimensional stability tests were conducted on parts from each billet and the hemisphere. Compression and tensile testing was conducted at 21 C and 49 C on specimens from each of the six billets. The small scale compression specimens from the hemisphere were also tested at these temperatures. The mechanical properties testing shows that the compression strain at rupture and the tensile rupture stress were significantly affected by the higher temperature. No apparent differences were seen between parts made from dried or normal powder.
Date: January 1, 1976
Creator: Crutchmer, J.A. & Johnson, H.D.
Partner: UNT Libraries Government Documents Department

Parylene coated microspheres: Operational parameters and round robin results

Description: Achieving less than 0.1 micrometer defect and close thickness tolerances with parylene coatings has proven a challenge. Los Alamos has investigated how some parameters of coater design and operation affect coating quality. Numerous coater configurations (home-built and commercial) are being used at our Laboratory and elsewhere. In an effort to evaluate the ability of these various types of units to meet desired tolerances, we ran a round robin evaluation involving six coating operations (US and UK). Each participant received an identical and precharacterized set of targets. Results of both the round robin and coater design/operation evaluation are presented.
Date: January 1, 1987
Creator: Williams, J.M. & Foreman, L.R.
Partner: UNT Libraries Government Documents Department

Dip coating of sol-gels

Description: Dip coating is the primary means of depositing sol-gel films for precision optical coatings. Sols are typically multicomponent systems consisting of an inorganic phase dispersed in a solvent mixture, with each component differing in volatility and surface tension. This, together with slow coating speeds (<1cm/s), makes analysis of the coating process complicated; unlike most high-speed coating methods, solvent evaporation, evolving rheology, and surface tension gradients alter significantly the fluid mechanics of the deposition stage. We set out to understand these phenomena with computer-aided predictions of the flow and species transport fields. The underlying theory involves mass, momentum, and species transport on a domain of unknown shape, with models and constitutive equations for vapor-liquid equilibria and surface tension. Due accounting is made for the unknown position of the free surface, which locates according to the capillary hydrodynamic forces and solvent loss by evaporation. Predictions of the effects of mass transfer, hydrodynamics, and surface tension gradients on final film thickness are compared with ellipsometry measurements of film thickness on a laboratory pilot coater. Although quantitative agreement is still lacking, both experiment and theory reveal that the film profile near the drying line takes on a parabolic shape. 2 refs., 2 figs.
Date: January 1, 1991
Creator: Schunk, P.R.; Hurd, A.J. & Brinker, C.J.
Partner: UNT Libraries Government Documents Department

Graphite-to-metal bonding techniques

Description: The results of various bonding methods to join graphite to different metals are reported. Graphite/metal bonds were tested for thermal flux limits and thermal flux cycling lifetimes. The most successful bond transferred a heat flux of 6.50 MW/m/sup 2/ in more than 500 thermal cycles. This bond was between pyrolytic graphite and copper with Ti-Cu-Sil as the bonding agent.
Date: November 1, 1977
Creator: Lindquist, L.O. & Mah, R.
Partner: UNT Libraries Government Documents Department

Prototype casting fabrication by stereolithography

Description: A new product development technology is emerging which could have a major impact on the investment casting industry. It's identified by several names, the most common of which is STEREOLITHOGRAPHY.'' This technology involves a three-dimensional printing process which will yield plastic parts (polymer models) from solid, surface, or wireframe CAD files. The concept links a CAD database to a process which guides a laser beam to solidify liquid photo-curable polymer into a programmed shaped. The process can produce models in far less time and at far less cost than can be done by other known (conventional) model producing methods. Parts that would normally require weeks or months to prototype with conventional processes can be produced in a matter of hours by Stereolithography. The Allied-Signal Inc., Kansas City Division, is engaged in a development project (funded by the Department of Energy) which is aimed at establishing this process as a practical, expedient, and cost-effective method fabricating prototype investment castings. The early phases of the project include procurement of a special designed test unit for several companies (Service Centers) involved in fabrication of models. These models are produced in various materials and used in experimental casting programs being conducted with four casting suppliers (two ferrous and two non-ferrous). This presentation will cover the objectives of the project and the results obtained up to this time. We will also briefly review future plans for the continuation of the project, until this new technology has been proven as a viable process for rapid development of investment castings.
Date: November 1, 1990
Creator: Cromwell, W.E.
Partner: UNT Libraries Government Documents Department

Bone formation: The rules for fabricating a composite ceramic

Description: Bone, teeth and shells are complex composite ceramics which are fabricated at low temperature by living organisms. The detailed understanding of this fabrication process is required if we are to attempt to mimic this low temperature assembly process. The guiding principles and major components are outlined with the intent of establishing non-vital fabrication schemes to form a complex composite ceramic consisting of an organix matrix inorganic crystalline phase. 19 refs.
Date: January 1, 1990
Creator: Caplan, A.I. (Case Western Reserve Univ., Cleveland, OH (USA))
Partner: UNT Libraries Government Documents Department

Low pressure chemical vapor deposition of polysilicon

Description: The low pressure chemical vapor deposition of polycrystalline silicon was studied to define the controlling process parameters and the requirements for commercial implementation. Silane and silane-nitrogen mixtures were utilized as source gases in a tubular reactor containing parallel disk substrates oriented with surface normals in the direction of flow. The results of the study showed that the deposition reaction is surface kinetic reaction controlled over the range of temperature studied, 600 to 700/sup 0/C, that the reaction is first order with respect to silane, and with an activation energy of 1.33 x 10/sup 5/ J/g mole. A gradient in temperature along the reactor tube is sufficient to compensate for reactant depletion and to produce a uniform deposition rate.
Date: August 1, 1977
Creator: Gieske, R.J.; McMullin, J.J. & Donaghey, L.F.
Partner: UNT Libraries Government Documents Department

Influence of substrate topography on the nucleation of diamond thin films

Description: Polycrystalline diamond films are of interest because of their unique materials properties. However, depositing films with the desired morphology is hindered by the difficulty in controlling the nucleation process. A popular method of enhancing the nucleation rate and density is to abrade the substrate with diamond powder before deposition. Although effective, this procedure is difficult to analyze since it may leave residual powder, may introduce damage, and may modify the surface topography. In order to separate these effects, we have studied the nucleation on chemically etched silicon substrates. Our results show that the majority of nucleation events occur on protruding surface features.
Date: January 1, 1991
Creator: Dennig, P.A. & Stevenson, D.A.
Partner: UNT Libraries Government Documents Department

Feasibility demonstration of consolidating porous beryllium/carbon structures. Final report

Description: A preliminary feasibility study was initiated to determine if porous beryllium structures could be fabricated by consolidating beryllium-coated microballoons into a rigid structure. The target specifications were to coat nominally 1-mm diameter microspheres with 0.5-mil beryllium coatings and then bond into a structure. Because of the very short time period, it was agreeable to use existing or quickly-available materials. The general approach was to apply coatings to carbon or quartz microspheres. Physical vapor deposition and ''snow-balling'' of fine beryllium powder were the two methods investigated. Once the particles were coated, HIP (pressure bonding) and pressureless sintering were to be investigated as methods for consolidating the microballoons. A low level of effort was to be spent to look at means of fabricating an all-carbon structure.
Date: November 11, 1977
Creator: Browning, M.J.; Hoover, G.E.; Mueller, J.J. & Hanes, H.D.
Partner: UNT Libraries Government Documents Department

Effect of thermal annealing in boron implanted, laser annealed silicon

Description: Electron microscopy and x-ray techniques have been used to investigate dislocation generation, precipitation of dopants and intrinsic defects, and the relaxation of unidirectional strains after thermal annealing of boron implanted, laser annealed silicon. It is shown that the number density of dislocations created near the interface after thermal annealing is small and therefore the unidirectional nature of the contraction in the dopes layer is essentially retained. A small number density of defect clusters (mostly vacancy dislocation loops, average size 20A) was also observed after thermal annealing at 1000/sup 0/C. Boron depth profile changes, as determined by secondary ion mass spectroscopy, indicated an increase in boron concentration near the surface in addition to the expected broadening of profiles after thermal annealing.
Date: December 1, 1978
Creator: Narayan, J.; Larson, B.C. & Christie, W.H.
Partner: UNT Libraries Government Documents Department

Ceramic-ceramic seals by microwave heating

Description: Several conclusions may be drawn from this work. First, less energy is required to form a glass-ceramic seal by microwave heating than by conventional heating. Second, less time is required to form the seal by microwave heating, and third, the seal composition is different, and the bonding is different. The micostructure of the seal formed by microwave heating reflects extensive diffusion of the glass constitients throughout the alumina substrate; and alumina throughout the seal glassy matrix. Fourth, higher heating rates are possible with microwave heating than with conventional heating. Last, the energy is coupled differently to the reactants using microwave heating, and thus the reaction kinetics may be different, as indicated by the vastly different microstructures obtained.
Date: January 1, 1984
Creator: Meek, T.T. & Blake, R.D.
Partner: UNT Libraries Government Documents Department

Effects of various polishing media and techniques on the surface finish and behavior of laser glasses

Description: The advance of high-power laser technology is dependent on the rate of advancement in laser glass forming and surface preparation. The threshold damage of glass surfaces continues to be a weak link in the overall advancement of laser technology. Methods were developed and used in the evaluation of existing glass surface preparation techniques. Modified procedures were evaluated to reduce surface contamination and subsurface defects. Polishing rates were monitored under controlled polishing conditions (purity, pH, particle size distribution, particle concentration, etc.). Future work at LLL for this ongoing investigation is described.
Date: November 7, 1978
Creator: Landingham, R.L.; Casey, A.W. & Lindahl, R.O.
Partner: UNT Libraries Government Documents Department

Application of dry-polishing techniques to water-soluble glass ceramics

Description: A dry polishing technique is presented for the preparation of glass ceramics for microstructural characterization. The technique is shown to be applicable to water soluble phosphate based glass ceramics and also to a non-water soluble zinc silicate glass ceramic. Microstructural characterization is performed primarily with composition backscattered electron imaging in the scanning electron microscopy. Some relief is observed on the polished surface utilizing topographical backscattered electron imaging.
Date: April 1, 1981
Creator: Healey, J.T. & McAllaster, M.E.
Partner: UNT Libraries Government Documents Department

Fabrication, classification, and characterization of tellurium powders

Description: Tellurium powder is used as a constituent in heat-producing, thermite-type reactions. In such reactions, long-term stability and reaction rate considerations require a compromise between surface area and particle size. To meet these requirements, a spherical powder was fabricated by atomizing liquid tellurium. In general, air classification techniques proved to be the most successful means of removing adherent fines from tellurium powders. Development of a minimum set of standard powder characterization techniques is outlined and applied to several spherical and irregular tellurium powders.
Date: January 1, 1977
Creator: German, R. M. & Ham, V.
Partner: UNT Libraries Government Documents Department

Joining of polymer composite materials

Description: Under ideal conditions load bearing structures would be designed without joints, thus eliminating a source of added weight, complexity and weakness. In reality the need for accessibility, repair, and inspectability, added to the size limitations imposed by the manufacturing process and transportation/assembly requirements mean that some minimum number of joints will be required in most structures. The designer generally has two methods for joining fiber composite materials, adhesive bonding and mechanical fastening. As the use of thermoplastic materials increases, a third joining technique -- welding -- will become more common. It is the purpose of this document to provide a review of the available sources pertinent to the design of joints in fiber composites. The primary emphasis is given to adhesive bonding and mechanical fastening with information coming from documentary sources as old as 1961 and as recent as 1989. A third, shorter section on composite welding is included in order to provide a relatively comprehensive treatment of the subject.
Date: November 1, 1990
Creator: Magness, F.H.
Partner: UNT Libraries Government Documents Department

Sintering maps for ceramic-filled-glass composites

Description: Ceramic-filled-glass (CFG) composites densify by viscous flow during final-stage, non-reactive, liquid-phase sintering (NLPS). The rate of densification is controlled by the viscosity of the CFG composite dispersion during sintering, which is determined by the concentration of ceramic filler in the composite, and the viscosity of the suspending glass medium. A mathematical expression has been developed that determines the critical filler concentration in a given viscosity glass at which high-density CFG composites will be produced in a given time during final-stage NLPS. This expression has been used to predict the effects of sintering time, pore size, and glass viscosity on critical filler concentration, and to construct final-stage sintering maps that provide guidelines for designing and processing high-density CFG composites. 12 refs., 2 figs.
Date: January 1, 1990
Creator: Ewsuk, K.G.
Partner: UNT Libraries Government Documents Department

Various unique vacuum holders. [For glassblowing]

Description: Glassblowers use vacuum holding devices to support a flat plate in the glassflowing lathe to seal onto the end of, or inside of, a glass cylinder. Glassblowing blowhose swivels tend to leak; a rotating union from the hydraulics industry is better. Various graphite holder designs are described.
Date: January 1, 1992
Creator: Gregar, J.S.
Partner: UNT Libraries Government Documents Department