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Research on silicon-carbon alloys and interfaces. Final subcontract report, 15 February 1991--31 July 1994

Description: This report describes work performed to develop improved p-type wide-band-gap hydrogenated amorphous silicon-carbon alloy (a-Si{sub 1-x}C{sub x:}H) thin films and interfaces for the ``top junction`` in hydrogenated amorphous silicon (a-Si:H)-based p-i-n solar cells. We used direct current reactive magnetron sputtering to deposit undoped a-Si{sub 1-x}C{sub x}H films with a Tauc band gap E{sub g} of 1.90 eV, a sub-band-gap absorption of 0.4 (at 1.2 eV), an Urbach energy of 55 MeV, an ambipolar diffusion length of 100 nm, an air-mass-one photoconductivity of 10{sup {minus}6}/{Omega}-cm, and a dark conductivity of 8{times} 1O{sup {minus}11}/{Omega}-cm. p{sup +}a-Si{sub 1-x}C{sub x}:H films with a Tauc band gap of 1.85 eV have a dark conductivity of 8 {times} 10{sup {minus}6}/{Omega}-cm and thermal activation energy of 0.28 eV. We used in-situ spectroscopic ellipsometry and post-growth X-ray photoelectron spectroscopy to determine the relative roles of H and Si in the chemical reduction of SnO{sub 2} in the early stages of film growth. We used in-situ spectroscopic ellipsometry to show that a-Si:H can be transformed into {mu}c-Si:H in a subsurface region under appropriate growth conditions. We also determined substrate cleaning and ion bombardment conditions which improve the adhesion of a-Si{sub 1-x}C{sub x}:H films.
Date: July 1, 1995
Creator: Abelson, J. R.
Partner: UNT Libraries Government Documents Department

Effect of Small Amounts of B and C Additions on Glass Formation and Mechanical Properties of a Zr-Base Alloy

Description: The effect of B and C additions up to 0.4 at. % on glass formation and mechanical properties of a Zr-base alloy Vitreloy 105 was studied using various techniques. All alloys were prepared by arc melting and drop casting. Boron additions increase the glass forming ability by lowering T<sub>m</sub> and increasing T<sub>g</sub>. Carbon additions only lower T<sub>m</sub>, but do not affect T<sub>g</sub>. B and C additions occupy free space and do not harden the glass phase.
Date: November 30, 1998
Creator: Chen, N.G.; Liu, C.T. & Pike, L.M.
Partner: UNT Libraries Government Documents Department

Microstructure of depleted uranium under uniaxial strain conditions

Description: Uranium samples of two different purities were used for spall strength measurements. Samples of depleted uranium were taken from very high purity material (38 ppM carbon) and from material containing 280 ppM C. Experimental conditions were chosen to effectively arrest the microstructural damage at two places in the development to full spall separation. Samples were soft recovered and characterized with respect to the microstructure and the form of damage. This allowed determination of the dependence of spall mechanisms on stress level, stress state, and sample purity. This information is used in developing a model to predict the mode of fracture.
Date: September 1997
Creator: Zurek, A. K.; Embury, J. D.; Kelly, A.; Thissell, W. R.; Gustavsen, R. L.; Vorthman, J. E. et al.
Partner: UNT Libraries Government Documents Department

Microstructure and properties of IN SITU toughened silicon carbide

Description: A silicon carbide with a fracture toughness as high as 9.1 MPa.m1/2 has been developed by hot pressing b-SiC powder with aluminum, boron, and carbon additions (ABC-SiC). Central in this material development has been systematic transmission electron microscopy (TEM) and mechanical characterizations. In particular, atomic-resolution electron microscopy and nanoprobe composition quantification were combined in analyzing grain boundary structure and nanoscale structural features.
Date: May 1, 2003
Creator: De Jonghe, Lutgard C.; Ritchie, Robert O. & Zhang, Xiao Feng
Partner: UNT Libraries Government Documents Department


Description: A National Pollutant Discharge Elimination System (NPDES) Permit was issued to the Savannah River Site (SRS) by the South Carolina Department of Health and Environmental Control (SCDHEC) and became effective on December 1, 2003. The new permit contained revised limits for copper and zinc derived by adjusting the South Carolina aquatic life water quality standards in accordance with dissolved metals criteria. The new copper and zinc limits are very low and may not be met consistently at Outfall H-12. The outfall has periodically exceeded the new 6 {micro}g/l (0.006 mg/L) monthly average limit and the 8 {micro}g/l (0.008 mg/L) maximum limit for copper and recently has begun exceeding the 100 {micro}g/l (0.100 mg/L) limit for zinc. The compliance date for Outfall H-12 is November 1, 2008. A study was conducted on this outfall and other outfalls to evaluate possible alternatives for meeting the new permit limits (Shipman and Bugher 2004). The study team recommended construction of a peat bed for treatment of the Outfall H-12 effluent. This recommendation was repeated by a second alternatives study team in 2007 (WSRC 2007). A bench-scale laboratory study demonstrated the feasibility of peat-bed treatment for Outfall H-12 effluent, with the peat demonstrating excellent removal of copper (Nelson and Specht 2005). An additional study was performed in 2006 and early 2007 using vertical-flow peat columns to investigate the influence of water retention time (contact time) on the removal of copper and zinc from the water (Nelson 2007c). Analytical results indicated that copper removal was very high at each of the three retention times tested, ranging from 99.6% removal at five and three hours to 98.8% removal at one hour. Effluent copper levels from these studies were much lower than the new compliance limit for the outfall. Most divalent metals, including zinc, were removed to below ...
Date: October 22, 2007
Creator: Halverson, N; Ralph Nichols, R & Topher Berry, T
Partner: UNT Libraries Government Documents Department

Understanding the function and performance of carbon-enhanced lead-acid batteries : milestone report for the DOE Energy Storage Systems program (FY11 Quarter 1: October through December 2010).

Description: This report describes the status of research being performed under CRADA No. SC10/01771.00 (Lead/Carbon Functionality in VRLA Batteries) between Sandia National Laboratories and East Penn Manufacturing, conducted for the U.S. Department of Energy's Energy Storage Systems Program. The Quarter 1 Milestone was completed on time. The milestone entails conducting a thorough literature review to establish the current level of understanding of the mechanisms through which carbon additions to the negative active material improve valve-regulated lead-acid (VRLA) batteries. Most studies have entailed phenomenological research observing that the carbon additions prevent/reduce sulfation of the negative electrode; however, no understanding is available to provide insight into why certain carbons are successful while others are not. Impurities were implicated in one recent review of the electrochemical behavior of carbon additions. Four carbon samples have been received from East Penn Manufacturing and impurity contents have been analyzed. Carbon has been explored as an addition to lead-acid battery electrodes in a number of ways. Perhaps the most notable to date has been the hybrid 'Ultrabattery' developed by CSIRO where an asymmetric carbon-based electrochemical capacitor is combined with a lead-acid battery into a single cell, dramatically improving high-rate partial-state-of-charge (HRPSoC) operation. As illustrated below, the 'Ultrabattery' is a hybrid device constructed using a traditional lead-acid battery positive plate (i.e., PbO{sub 2}) and a negative electrode consisting of a carbon electrode in parallel with a lead-acid negative plate. This device exhibits a dramatically improved cycle life over traditional VRLA batteries, as well as increased charge power and charge acceptance. The 'Ultrabattery' has been produced successfully by both The Furukawa Battery Co. and East Penn Manufacturing. An example illustrating the dramatic improvement in cycle life of the Ultrabattery over a conventional VRLA battery is shown in the graph.
Date: May 1, 2011
Creator: Shane, R. (East Penn Manufacturing, Lyon Station, PA); Enos, David George & Hund, Thomas D.
Partner: UNT Libraries Government Documents Department

Estimate of the contribution of load transfer to the yield strength and hardness of a dual-phase steel

Description: The ratio of the average stresses in ferrite and martensite at yield of a dual-phase steel is calculated from a shear-lag model of load transfer, based on a shape parameter of the martensite particles. For a specific steel, a stress ratio of 2.2 is determined. This value is compared to the stress ratio obtained from hardness and microhardness determinations. The results qualitatively and tentatively support the strengthening role of load transfer in dual-phase steels.
Date: June 1, 1981
Creator: Gurland, J
Partner: UNT Libraries Government Documents Department

The influence of composition on environmental embrittlement of iron aluminides

Description: The effects of water vapor in air and hydrogen gas on the tensile and fatigue crack growth behavior of Fe{sub 3}Al alloys have been studied at room temperature. Fe-28a% Al-5a% Cr alloys to which either Zr alone or Zr and C have been added and tested in controlled humidity air environments as well as in 1.3 atm hydrogen or oxygen gas and in vacuum. As with other Fe{sub 3}Al alloys, oxygen produces the lowest crack growth rates as well as the highest critical stress intensities and tensile ductility in each of the alloys tested. However, while Zr lowers crack growth rates in the Paris regime, there is no apparent beneficial effect on crack growth thresholds. Hydrogen gas also produces unusual results. While crack growth rates are very high in hydrogen in the Paris regime for all alloys, hydrogen only lowers the crack growth threshold relative to air in ternary Fe-28Al-5Cr; it does not lower the threshold in the Zr-containing alloys. It was found that decreased test frequency leads to increased crack growth rates in a Zr-containing alloy which points to a moisture-induced embrittlement mechanism responsible for the higher crack growth rates in air. Fracture path tends to be insensitive to environment for each alloy.
Date: July 1, 1996
Creator: Alven, D. A. & Stoloff, N. S.
Partner: UNT Libraries Government Documents Department

Measurements of the diffusion of iron and carbon in single crystal NiAl using ion implantation and secondary ion mass spectrometry

Description: Classical diffusion measurements in intermetallic compounds are often complicated by low diffusivities or low solubilities of the elements of interest. Using secondary ion mass spectrometry for measurements over a relatively shallow spatial range may be used to solve the problem of low diffusivity. In order to simultaneously obtain measurements on important impurity elements with low solubilities, the authors have used ion implantation to supersaturate a narrow layer near the surface. Single crystal NiAl was implanted with either {sup 12}C or both {sup 56}Fe and {sup 12}C in order to investigate the measurement of substitutional (Fe) versus interstitial (C) tracer diffusion and the cross effect of both substitutional and interstitial diffusion. When C alone was implanted negligible diffusion was observed over the range of times and temperatures investigated. When both Fe and C were implanted together significantly enhanced diffusion of the C was observed, which is apparently associated with the movement of Fe. This supports one theory of dynamic strain aging in Fe alloys NiAl.
Date: December 31, 1998
Creator: Hanrahan, R.J. Jr.; Withrow, S.P. & Puga-Lambers, M.
Partner: UNT Libraries Government Documents Department

Processing and mechanical behavior of hypereutectoid steel wires

Description: Hypereutectoid steels have the potential for dramatically increasing the strength of wire used in tire cord and in other high strength wire applications. The basis for this possible breakthrough is the elimination of a brittle proeutectoid network that can form along grain boundaries if appropriate processing procedures and alloy additions are used. A review is made of work done by Japanese and other researchers on eutectoid and mildly hypereutectoid wires. A linear extrapolation of the tensile strength of fine wires predicts higher strengths at higher carbon contents. The influence of processing, alloy additions and carbon content in optimizing the strength, ductility and fracture behavior of hypereutectoid steels is presented. It is proposed that the tensile strength of pearlitic wires is dictated by the fracture strength of the carbide lamella at grain boundary locations in the carbide. Methods to improve the strength of carbide grain boundaries and to decrease the carbide plate thickness will contribute to enhancing the ultrahigh strength obtainable in hypereutectoid steel wires. 23 refs., 13 figs., 1 tab.
Date: June 25, 1996
Creator: Lesuer, D.R.; Syn, C.K.; Sherby, O.D. & Kim, D.K.
Partner: UNT Libraries Government Documents Department

Evaluation of the intrinsic and extrinsic fracture behavior of iron aluminides

Description: Iron aluminides have excellent corrosion resistance in high-temperature oxidizing-sulfidizing environments; however, there are problems at room and medium temperatures with hydrogen embrittlement as related to exposure to moisture. In this research, a coordinated computational modeling/experimental study of mechanisms related to environmental-assisted fracture behavior of selected iron aluminides has been undertaken. The modeling and the experimental work connect at the level of coordinated understanding of the mechanisms for hydrogen penetration and for loss of strength and susceptibility to fracture. The focus of the modeling component has been on the challenging question of accurately predicting the iron vacancy formation energy in Fe{sub 3}Al and the subsequent tendency, if present, for vacancy clustering. The authors have successfully performed, on an ab initio basis, the first calculation of the vacancy formation energy in Fe{sub 3}Al. These calculations include lattice relaxation effects which are quite large for one of the two types of iron sites. This has significant implications for vacancy clustering effects with consequences for hydrogen diffusion. Indeed, the ab-initio-based estimate of the divacancy binding energy indicates a likely tendency toward such clustering for iron vacancies on the sites with large lattice relaxation. The experimental work has focused on the relationship of the choice and concentration of additives to the improvement of resistance to hydrogen embrittlement and hence to the fracture behavior.
Date: July 27, 1998
Creator: Cooper, B.R. & Kang, B.S.
Partner: UNT Libraries Government Documents Department

Solidification modeling of Nb bearing superalloys

Description: The solidification behavior of experimental Ni base and Fe base superalloys containing Nb, Si, and C was studied using differential thermal analysis (DTA) and microstructural characterization techniques. The solidification reaction sequences responsible for microstructural development were found to be similar to those expected in the Ni-Nb-C ternary system, where the solute-rich interdendritic liquid exhibited two eutectic-type reactions at the terminal stages of solidification: L {yields} ({gamma} + NbC) and L {yields} ({gamma} + Laves). A pseudo ternary {gamma}-Nb-C approach was developed to provide a quantitative description of solidification behavior for these experimental alloys. Solute redistribution calculations in the model are based on a previous approach developed by Mehrabian and Flemings, with modifications made to account for the high diffusion rate of C in the solid. Solidification parameters for Nb and C were determined through DTA and electron probe microanalysis techniques and used as inputs to the model. Reasonable agreement is found between calculated volume fractions of the {gamma}/NbC and {gamma}/Laves constituents and those measured experimentally. The modeling results permit detailed descriptions of the relation between alloy composition and microstructural evolution during solidification.
Date: August 1, 1997
Creator: DuPont, J.N.; Marder, A.R. & Robino, C.V.
Partner: UNT Libraries Government Documents Department

The effects of zirconium and carbon on the hot cracking resistance of iron aluminides. Topical report

Description: Iron aluminides have been of interest for about 60 years because of their good high temperature strengths (below 600{degrees}C) and excellent oxidation and sulfidation resistance, as well as their relatively low cost and conservation of strategic elements. These advantageous properties have driven the development of iron aluminides as potential structural materials. However, the industrial application of iron aluminides has been inhibited because of a sharp reduction in strength at temperatures higher than 600{degrees}C and low ductility at ambient temperatures due to hydrogen embrittlement. Oak Ridge National Laboratory has shown in recent years that room temperature properties of alloys containing 28% Al (all compositions are in atomic percent unless otherwise noted) can be improved through thermomechanical processing and alloying. Iron aluminides must have good weldability if they are to be used as structural materials. A coarse fusion zone microstructure is formed when iron aluminides are welded, increasing their susceptibility to cold cracking in water vapor. A recent study at Colorado School of Mines has shown that refining the fusion zone microstructure by weld pool oscillation effectively reduces cold cracking. Weld pool inoculation has been shown to refine fusion zone microstructures, but coarse carbide distribution caused this approach to reducing cold cracking to be ineffective.
Date: February 1, 1998
Creator: Mulac, B.L.; Edwards, G.R. & David, S.A.
Partner: UNT Libraries Government Documents Department

Clean iron production and machining technology. Year 1 summary report, January 1--December 31, 1995

Description: The first phase of this project was conducted to develop a technique for evaluating the machinability of gray and ductile iron. That technique was then used to measure the machinability of a variety of irons and determine the processing factors that influenced and controlled machinability. The procedure developed to evaluate machinability involved drilling holes with a feed rate of 0.009 in/rev at various surface speeds. High speed steel drills were used so wear was observed more quickly. Microcarbides present in the irons were found to dominate the machinability. Pearlitic irons considered to have ``acceptable`` machinability (indicated either by tool life measured in the laboratory using high speed steel (HSS) drills or reports from commercial machine shops using other cutters) were found to contain from 8.9 to 10.5% by weight microscopic carbides. The tool wear rate increased when machining at higher surface speeds or machining irons containing higher weight percentage of microcarbides. All irons containing above 11.5% microcarbides consistently exhibited poor machinability. Tool wear results obtained using cubic boron nitride (CBN) cutters paralleled those obtained with HSS. Higher iron microcarbide concentrations produced faster tool wear. Experiments are now being formulated to explore methods of improving iron machinability. Future work will extend the study to ductile irons.
Date: March 5, 1996
Partner: UNT Libraries Government Documents Department

Metallic Recovery and Ferrous Melting Processes

Description: The effects of melting atmosphere and charge material type on the metallic and alloy recovery of ferrous charge materials were investigated in two sets of experiments (Tasks 1 and 2). In addition, thermodynamic studies were performed (Task 3) to determine the suitability of ladle treatment for the production of ductile iron using scrap charge materials high in manganese and sulfur. Task 1--In the first set of experiments, the charge materials investigated were thin steel scrap, thick steel scrap, cast iron scrap, and pig iron in the rusty and clean states. Melting atmospheres in this set of experiments were varied by melting with and without a furnace cover. In this study, it was found that neither covered melting nor melting clean (non-rusty) ferrous charge materials improved the metallic recovery over the recovery experienced with uncovered melting or rusty charge materials. However, the silicon and manganese recoveries were greater with covered melting and clean materials. Silicon and manganese in the molten iron react with oxygen dissolved in the iron from uncovered melting and oxidized iron (surface rust). Silica and manganese silicates are formed which float to the slag decreasing recoveries of silicon and manganese. Cast iron and pig iron had higher metallic recoveries than steel scrap. Carbon recovery was affected by the carbon content of the charge materials, and not by the melting conditions. Irons with higher silicon contents had higher silicon recovery than irons with lower silicon contents. Task 2--In the second set of experiments, briquetted turnings and borings were used to evaluate the effects of briquette cleanliness, carbon additions, and melting atmosphere on metallic and alloy recovery. The melting atmosphere in this set of experiments was varied by melting in air and with an argon atmosphere using the SPAL process. In this set of experiments, carbon additions to the briquettes ...
Date: May 30, 2004
Creator: Trueba, Luis
Partner: UNT Libraries Government Documents Department

Discussion: ''toughness variations during the tempering of a plain carbon martensitic steel'' by J. E. King, R. F. Smith and J. F. Knott. Retained austenite and transgranular tempered martensite embrittlement

Description: Discussion is presented to substantiate, clarify and reinterpret some of the results of the above authors for the existence and origin of tempered martensite embrittlement (TME) in relation to retained austenite, with reference to the experimental steels worked at LBL for the past several years.
Date: June 1, 1977
Creator: Rao, B.V.N. & Thomas, G.
Partner: UNT Libraries Government Documents Department


Description: The measurement of oxygen flux across nanocrystalline CeO{sub 2} cerium oxide thin films at intermediate temperature (650 to 800 C) is presented. Porous ceria support substrates were fabricated by sintering with carbon additions. The final dense film was deposited from an optimized sol-gel solution resulting in a mean grain size of 50 nm which displayed oxygen flux values of up to 0.014 {micro}mol/cm{sup 2}s over the oxygen partial pressure range from air to helium gas used in the measurement at 800 C. The oxygen flux characteristics confirm mixed ionic and electronic conductivity in nanocrystalline ceria films and demonstrate the role of size dependent materials properties as a design parameter in functional membranes for oxygen separation.
Date: September 27, 2010
Creator: Brinkman, K.
Partner: UNT Libraries Government Documents Department

Beam induced heating of ferrite magnets

Description: Alerted by impedance measurements of ferrite kicker magnets and by apparent beam induced pressure increase in the neighborhood of window frame kicker magnets, bench measurements of magnet heating have been done. They confirmed the necessity of interrupting the ferrite yoke. Another method, which can be applied for existing magnets, will be described. 1 ref., 4 figs.
Date: January 1, 1991
Creator: van Asselt, W.K. & Lee, Y.Y.
Partner: UNT Libraries Government Documents Department

Interaction of stress with the martensitic phase transition in A15 compounds

Description: Recently there has been a resurgence of interest in the effect of the martensitic phase transition which occurs in many A15 compounds on superconductivity and on elastic and anelastic behavior. Since in many practical applications, A15 compounds are subject to considerable stress and strain, it is of interest to examine the interaction of stress with the martensitic transition; this paper is an examination of the effects of stress predicted by a simple Landau model which successfully describes many features of the transition and the related temperature dependence of the elastic modulus (c/sub 11/-c/sub 12/)/2. The effect of stress on the temperature ranges of stability and metastability of various types of martensitic domain is discussed. The non-linearity of the stress-strain relation in a polycrystalline A15 is studied.
Date: January 1, 1981
Creator: Welch, D.O.
Partner: UNT Libraries Government Documents Department

Identification of some crystallographic features of martensite in steels by microdiffraction

Description: Considerable attention should be paid to the interpretation of electron diffraction, such as the understanding of the extra reflections and other effects in an SAD pattern obtained from lath martensite by making allowances for spatial resolution limitations in the SAD patterns. These difficulties can be overcome by utilizing the convergent beam electron diffraction (CBED) method which permits the use of different probe sizes to obtain crystallographic information from very small regions. Some crystallographic features of lath martensite in low and medium C steels have been identified and some others verified by using CBED.
Date: March 1, 1980
Creator: Sarikaya, M.; Rao, B.V.N. & Thomas, G.
Partner: UNT Libraries Government Documents Department

Electron microscopy studies of undoped and phosphorus doped Si:H and Si,C:H films

Description: Microstructure of undoped and phosphorus doped Si:H and Si,C:H films was analyzed by selected-area diffraction, conical dark-field imaging, energy-dispersive x-ray spectroscopy, and electron energy-loss spectroscopy in transmission electron microscopes. Thin films were synthesized by remote plasma-enhanced chemical vapor deposition and characterized in terms of degree of crystallinity. Distribution of phosphorus in Si:H and Si,C:H films, and of carbon in Si,C:H films was evaluated. Results indicate that (i) the microstructure of a film may be two phase, consisting of silicon microcrystallites in an amorphous matrix, (ii) phosphorus doping as well as the presence of carbon influences the degree of crystallinity by reducing the average size and volume fraction of microcrystallites, (iii) the presence of carbon and phosphorus doping completely suppresses the crystalline phase, (iv) phosphorus is distributed at approximately the same concentration in both the crystalline and amorphous phases of diphasic films, and (v) carbon is detected in the amorphous phase of the Si,C:H films.
Date: December 31, 1993
Creator: Chen, Y. L.; Wang, C.; Lucovsky, G.; Maher, D. M. & Bentley, J.
Partner: UNT Libraries Government Documents Department

Atomic level characterization of defects in microalloyed NiAl: An atom probe investigation

Description: Since mechanical behavior is largely controlled by the microstructure (particularly dislocations, substitutional solutes, and solute segregation to grain boundaries) atom probe field ion microscopy is well suited to studying such microstructural features. The atom probe has been used to explain changes in yield stress when NiAl is doped with B, C, Be, or Zr/Mo. It showed that the beneficial effect of B segregation is masked by formation of ultrafine, deleterious second-phase particles. Be occupied Al sites almost exclusively. Zr segregated to both grain boundaries and dislocations.
Date: June 1, 1994
Creator: Jayaram, R. & Miller, M. K.
Partner: UNT Libraries Government Documents Department