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Metastable phase equilibria in co-deposited Ni sub 1-x Zr sub x thin films

Description: We determine the glass forming range (GFR) of co-deposited Ni{sub 1-x}Zr{sub x} (0 < x < 1) thin films by measuring their electrical resistance during in situ constant-heating-rate anneals. The measured GFR is continuous for 0.10 < x < 0.87. We calculate the GFR of Ni-Zr melts as a function of composition and cooling rate using homogeneous nucleation theory and a published CALPHAD-type thermodynamic modeling of the equilibrium phase diagram. Assuming that the main competition to the retention of the amorphous structure during the cooling of the liquid comes from the partitionless crystallization of the terminal solid solutions, we calculate that for dT/dt = 10{sup 12} K s{sup {minus}1}, the GFR extends to x = 0.05 and x = 0.96. Better agreement with the measured values is obtained assuming a lower effective'' cooling rate during the condensation of the films. 18 refs., 6 figs.
Date: January 1, 1991
Creator: Rubin, J.B. & Schwarz, R.B.
Partner: UNT Libraries Government Documents Department

Kinetics of solid-state reactions in Ni-Zr thin films

Description: We have studied the kinetic of the solid-state amorphizing reaction in thin film multilayers of Ni and Zr. Crystalline Ni and Zr films were deposited in ultra-high vacuum onto platinum resistance thermometer embedded in alumina. An electronic feedback circuit controls the temperature of the substrata by adjusting the power dissipated by the platinum resistors. We find that structural relaxation in the as-deposited Ni and Zr films affects the initial stages of the reaction. For long reaction times there is a discontinuous change in the reaction rate. The time to reach this transition increases with film thickness and depends exponentially on 1/T, with an apparent activation energy of 3 eV atom{sup {minus}1}. 25 refs., 9 figs.
Date: January 1, 1991
Creator: Schwarz, R.B. & Rubin, J.B.
Partner: UNT Libraries Government Documents Department

Elastic properties of amorphous thin films studied by Rayleigh waves

Description: Physical vapor deposition in ultra-high vacuum was used to co-deposit nickel and zirconium onto quartz single crystals and grow amorphous Ni{sub 1-x}Zr{sub x} (0.1 < x < 0.87) thin film. A high-resolution surface acoustic wave technique was developed for in situ measurement of film shear moduli. The modulus has narrow maxima at x = 0. 17, 0.22, 0.43, 0.5, 0.63, and 0.72, reflecting short-range ordering and formation of aggregates in amorphous phase. It is proposed that the aggregates correspond to polytetrahedral atom arrangements limited in size by geometrical frustration.
Date: August 1, 1993
Creator: Schwarz, R. B. & Rubin, J. B.
Partner: UNT Libraries Government Documents Department

A comparison of chilled DI water/ozone and CO{sub 2}-based supercritical fluids as replacements for photoresist-stripping solvents

Description: Part of the Hewlett Packard Components Group`s Product Stewardship program is the ongoing effort to investigate ways to eliminate or reduce as much as possible the use of chemical substances from manufacturing processes. Currently used techniques to remove hard-baked photoresists from semiconductor wafers require the use of inorganic chemicals or organic strippers and associated organic solvents. Environmental, health and safety, as well as cost considerations prompted the search for alternative, more environmentally-benign, and cost-effective solutions. Two promising, emerging technologies were selected for evaluation: the chilled DI water/ozone technique and supercritical fluids based on carbon dioxide (CO{sub 2}). Evaluating chilled DI water/ozone shows this process to be effective for positive photoresist removal, but may not be compatible with all metallization systems. Testing of a closed-loop CO{sub 2}-based supercritical CO{sub 2} Resist Remover, or SCORR, at Los Alamos, on behalf of Hewlett-packard, shows that this treatment process is effective in removing photoresists, and is fully compatible with commonly used metallization systems. In this paper, the authors present details on the testing programs conducted with both the chilled DI H{sub 2}O/ozone and SCORR treatment processes.
Date: October 1998
Creator: Rubin, J. B.; Davenhall, L. B.; Barton, J.; Taylor, C. M. V. & Tiefert, K.
Partner: UNT Libraries Government Documents Department

Supercritical-fluid carbon dioxide (SCCO{sub 2}) cleaning of nuclear weapon components

Description: Supercritical fluid carbon dioxide (SCCO{sub 2}) has been evaluated as a cleaning solvent for the cleaning of plutonium (Pu) metal parts. The results of the evaluation show that SCCO{sub 2} is an effective alternative to halogenated solvents that are conventionally used for removing organic and inorganic contaminants from the surface of these parts. The cleaning process was demonstrated at the laboratory scale for steel and uranium substrates and has been found to be compatible with Pu. The efficacy of this cleaning method is found to be dependent on process conditions of pressure, temperature, fluid-flow rate, as well as cleaning time. Process parameters of P > 2,500 psi, T > 40 C, and moderate fluid flow rates, produced good cleaning results in less than 10 minutes using a simple flow-through process configuration. Within the parameter range studied, cleaning efficiency generally improved with increasing process pressure and flow rate. SCCO{sub 2} cleaning is suitable for a variety of component cleaning tasks and is adaptable to precision cleaning requirements. The SCCO{sub 2} cleaning process is currently being developed for deployment for weapons production at LANL.
Date: May 1, 1998
Creator: Taylor, C. M. V.; Sivils, L.D. & Rubin, J.B.
Partner: UNT Libraries Government Documents Department

CO{sub 2}-based supercritical fluids as environmentally-friendly processing solvents

Description: The production of integrated circuits involves a number of discrete steps that utilize hazardous or regulated solvents. Environmental, safety and health considerations associated with these chemicals have prompted a search for alternative, more environmentally benign, solvent systems. An emerging technology for conventional solvent replacement is the use of supercritical fluids based on carbon dioxide (CO{sub 2}). Supercritical CO{sub 2} (SCCO{sub 2}) is an excellent choice for IC manufacturing processes since it is non-toxic, non-flammable, inexpensive, and is compatible with all substrate and metallizations systems. Also, conditions of temperature and pressure needed to achieve the supercritical state are easily achievable with existing process equipment. The authors first describe the general properties of supercritical fluids, with particular emphasis on their application as alternative solvents. Next, they review some of the work which has been published involving the use of supercritical fluids, and particularly CO{sub 2}, as they may be applied to the various steps of IC manufacture, including wafer cleaning, thin film deposition, etching, photoresist stripping, and waste treatment. Next, they describe the research work conducted at Los Alamos, on behalf of Hewlett-Packard, on the use of SCCO{sub 2} in a specific step of the IC manufacturing process: the stripping of hard-baked photoresist.
Date: March 1, 1999
Creator: Rubin, J.B.; Davenhall, L.B.; Taylor, C.M.V.; Pierce, T. & Tiefert, K.
Partner: UNT Libraries Government Documents Department

Extraction of hydrogenous material from cemented wasteforms by supercritical fluid carbonation

Description: We are conducting experiments on an innovative transformation concept, using a traditional immobilization technique, that may significantly reduce the volume of hazardous and/or radioactive waste requiring transport and long-term storage. The standard practice at LANL for the stabilization of radioactive salts and residues is to mix them with portland cement, which may include additives to enhance immobilization. Many of these wasteforms do not qualify for transportation or underground disposition, however, because they do not meet Department of Energy regulations for free liquids, decay heat, and/or head-space gases. The present treatment method alters the bulk properties of a cemented wasteform by greatly accelerating the natural cement-aging reactions, producing a chemically stable form having reduced levels of free liquids and organic compounds, as well as reduced porosity, permeability and pH. These structural and chemical changes should allow for greater actinide loading, as well as reduced mobility of the anions, cations, and radionuclides in aboveground and underground repositories.
Date: November 1, 1997
Creator: Rubin, J.B.; Carey, J.W. & Taylor, C.M.V.
Partner: UNT Libraries Government Documents Department

Enhancement of cemented waste forms by supercritical CO{sub 2} carbonation of standard portland cements

Description: We are conducting experiments on an innovative transformation concept, using a traditional immobilization technique, that may significantly reduce the volume of hazardous or radioactive waste requiring transport and long-term storage. The standard practice for the stabilization of radioactive salts and residues is to mix them with cements, which may include additives to enhance immobilization. Many of these wastes do not qualify for underground disposition, however, because they do not meet disposal requirements for free liquids, decay heat, head-space gas analysis, and/or leachability. The treatment method alters the bulk properties of a cemented waste form by greatly accelerating the natural cement-aging reactions, producing a chemically stable form having reduced free liquids, as well as reduced porosity, permeability and pH. These structural and chemical changes should allow for greater actinide loading, as well as the reduced mobility of the anions, cations, and radionuclides in aboveground and underground repositories. Simultaneously, the treatment process removes a majority of the hydrogenous material from the cement. The treatment method allows for on-line process monitoring of leachates and can be transported into the field. We will describe the general features of supercritical fluids, as well as the application of these fluids to the treatment of solid and semi-solid waste forms. some of the issues concerning the economic feasibility of industrial scale-up will be addressed, with particular attention to the engineering requirements for the establishment of on-site processing facilities. Finally, the initial results of physical property measurements made on portland cements before and after supercritical fluid processing will be presented.
Date: August 1, 1997
Creator: Rubin, J.B.; Carey, J. & Taylor, C.M.V.
Partner: UNT Libraries Government Documents Department

Radioactive wastes dispersed in stabilized ash cements

Description: One of the most widely-used methods for the solidification/stabilization of low-level radwaste is by incorporation into Type-I/II ordinary portland cement (OPC). Treating of OPC with supercritical fluid carbon dioxide (SCCO{sub 2}) has been shown to significantly increase the density, while simultaneously decreasing porosity. In addition, the process significantly reduces the hydrogenous content, reducing the likelihood of radiolytic decomposition reactions. This, in turn, permits increased actinide loadings with a concomitant reduction in disposable waste volume. In this article, the authors discuss the combined use of fly-ash-modified OPC and its treatment with SCCO{sub 2} to further enhance immobilization properties. They begin with a brief summary of current cement immobilization technology in order to delineate the areas of concern. Next, supercritical fluids are described, as they relate to these areas of concern. In the subsequent section, they present an outline of results on the application of SCCO{sub 2} to OPC, and its effectiveness in addressing these problem areas. Lastly, in the final section, they proffer their thoughts on why they believe, based on the OPC results, that the incorporation of fly ash into OPC, followed by supercritical fluid treatment, can produce highly efficient wasteforms.
Date: December 31, 1997
Creator: Rubin, J.B.; Taylor, C.M.V.; Sivils, L.D. & Carey, J.W.
Partner: UNT Libraries Government Documents Department

Next generation enhancement of cements by the addition of industrial wastes and subsequent treatment with supercritical CO{sub 2}

Description: The natural curing reactions which occur in a standard portland cement involve the formation of portlandite, Ca(OH){sub 2}, and calcium silicate hydrates, CSH. Over time, the cured cement abstracts carbon dioxide, CO{sub 2}, from the air, converting the portlandite and CSH to calcium carbonate, CaCO{sub 3}. It turns out, however, that this secondary conversion results in the blockage and/or closure of pores, drastically slowing the reaction rate with time. By exposing a portland cement to supercritical CO{sub 2} (SCCO{sub 2}), it is found that the carbonation reaction can be greatly accelerated. This acceleration is due to (1) the ability of the supercritical fluid to penetrate into the pores of the cement, providing continuous availability of fresh reactant, in hyper-stoichiometric concentrations; and (2) the solubility of the reaction product in the supercritical fluid, facilitating its removal. By accelerating the natural aging reactions, a chemically stable product is formed having reduced porosity, permeability and pH, while at the same time significantly enhancing the mechanical strength. The supercritical CO{sub 2} treatment process also removes a majority of the hydrogenous material from the cement, and sequesters large amounts of carbon dioxide, permanently removing it from the environment. The authors describe the general features of supercritical fluids, as well as the application of these fluids to the treatment of cements containing industrial waste. Some of the issues concerning the economic feasibility of industrial scale-up will be addressed. Finally, some initial results of physical property measurements made on portland cements before and after supercritical fluid CO{sub 2} treatment will be presented.
Date: September 1, 1997
Creator: Taylor, C.M.V.; Rubin, J.B.; Carey, J.W.; Jones, R. & Baglin, F.G.
Partner: UNT Libraries Government Documents Department

Carbon dioxide-based supercritical fluids as IC manufacturing solvents

Description: The production of integrated circuits (IC's) involves a number of discrete steps which utilize hazardous or regulated solvents and generate large waste streams. ES&amp;H considerations associated with these chemicals have prompted a search for alternative, more environmentally benign solvent systems. An emerging technology for conventional solvent replacement is the use of supercritical fluids based on carbon dioxide (CO{sub 2}). Research work, conducted at Los Alamos in conjunction with the Hewlett-Packard Company, has lead to the development of a CO{sub 2}-based supercritical fluid treatment system for the stripping of hard-baked photoresists. This treatment system, known as Supercritical CO{sub 2} Resist Remover, or CORR, uses a two-component solvent composed of a nonhazardous, non-regulated compound, dissolved in supercritical CO{sub 2}. The solvent/treatment system has been successfully tested on metallized Si wafers coated with negative and positive photoresist, the latter both before and after ion-implantation. A description of the experimental data will be presented. Based on the initial laboratory results, the project has progressed to the design and construction of prototype, single-wafer photoresist-stripping equipment. The integrated system involves a closed-loop, recirculating cycle which continuously cleans and regenerates the CO{sub 2}, recycles the dissolved solvent, and separates and concentrates the spent resist. The status of the current design and implementation strategy of a treatment system to existing IC fabrication facilities will be discussed. Additional remarks will be made on the use of a SCORR-type system for the cleaning of wafers prior to processing.
Date: May 11, 1999
Creator: Rubin, J.B.; Davenhall, L.B.; Taylor, C.M.V.; Sivils, L.D.; Pierce, T. & Tiefert, K.
Partner: UNT Libraries Government Documents Department