Field Errors in Hybrid Insertion Devices (open access)

Field Errors in Hybrid Insertion Devices

Hybrid magnet theory as applied to the error analyses usedin the design of Advanced Light Source (ALS) insertion devices isreviewed. Sources of field errors in hybrid insertion devices arediscussed.
Date: February 3, 1995
Creator: Schlueter, R.D.
System: The UNT Digital Library
Measurement of ultrashort pulses with a non-instantaneous nonlinearity (open access)

Measurement of ultrashort pulses with a non-instantaneous nonlinearity

We show how non-instantaneous nonlinearities can be used to characterize an ultrashort pulse in an extension of the Frequency-Resolved Optical Gating technique. We demonstrate this principle using the Raman effect in fused silica.
Date: February 1, 1995
Creator: DeLong, K. W.; Ladera, C. L.; Trebino, R.; Kohler, B. & Wilson, K. R.
System: The UNT Digital Library
Identifying, meeting, and assessing customer expectations (open access)

Identifying, meeting, and assessing customer expectations

Maintaining proficiency in carrying out mission goals is fundamental to the success of any organization. The definitive mission of the Waste Management and Remedial Action Division (WMRAD) of Oak Ridge National Laboratory (ORNL) is {open_quotes}to conduct waste management activities in a compliant, publicly acceptable, technically sound, and cost-efficient manner{close_quotes}. In order to effectively fulfill this mission, must meet or exceed several standards in respect to our customers. These include: (1) identifying current and future customer expectations; (2) managing our relationships with our customers; (3) ensuring our commitment to our customers; and (4) measuring our success m customer satisfaction. Our customers have a great variety of requirements and expectations. Many of these are in the form of local, state, and federal regulations and environmental standards. Others are brought to our attention through inquires made to the Department of Energy (DOE).Consumer surveys have proven to be effective tools which have been used to make improvements, enhance certain program elements, and identify beneficial areas in already existing programs. In addition, national working groups, technology transfer meetings, and manager/contractor`s meeting offer excellent opportunities to assess our activities.
Date: February 1, 1995
Creator: Danner, T. A.
System: The UNT Digital Library
Experimental determination of cluster geometrical structure (open access)

Experimental determination of cluster geometrical structure

Chemical probes have been developed to provide insight into the geometrical structure of isolated transition metal clusters. By determining as a function of cluster size the number of adsorbate molecules that saturate a cluster, and/or the binding energy of molecules to cluster surfaces, it is often possible to propose geometrical structures consistent with the experimental observations. The authors review recent studies of the reactions of cobalt, nickel, and copper clusters with ammonia, water, and nitrogen that provide structural information. It is found that small (between 50 and 150 atoms) cobalt, nickel, and copper clusters generally adopt icosahedral packing. However, for even smaller (less than 20 atoms) clusters, cobalt and nickel differ in their structure. The authors also see evidence for adsorbate-induced structural changes. These changes may allow the properties of materials fabricated from such clusters to be tailored to specific needs. A preliminary illustration of the dramatic effect that heteroatoms can have on metal cluster chemical properties is presented.
Date: February 1, 1995
Creator: Riley, S. J.
System: The UNT Digital Library
Optical determinations of energy-band dispersion curves in novel compound semiconductor materials (open access)

Optical determinations of energy-band dispersion curves in novel compound semiconductor materials

We present magnetoluminescence data which provides a quantitative measure of the energy-band dispersion curves of novel compound semiconductor optoelectronic materials. Data for a n-type strained-layer InGaAs/GaAs (quantum-well width {approximately} 8 nm) and a n-type 4.5-nm-wide GaAs/AlGaAs lattice-matched single-quantum well are presented. We find that the -conduction-bands are almost parabolic, with a mass of about 0.068m{sub 0} for InGaAs/GaAs and 0.085m{sub 0} for the GaAs/AlGaAs structure. The valence-bands are nonparabolic with wave vector dependent in-plane valence-band masses varying from about 0.1 m{sub 0} at zone center to about 0.3 m{sub 0} for 20 meV energies.
Date: February 1, 1995
Creator: Jones, E. D.
System: The UNT Digital Library
Micro manipulator motion control to counteract macro manipulator structural vibrations (open access)

Micro manipulator motion control to counteract macro manipulator structural vibrations

Inertial force damping control by micro manipulator modulation is proposed to suppress the vibrations of a micro/macro manipulator system. The proposed controller, developed using classical control theory, is added to the existing control system. The proposed controller uses real-time measurements of macro manipulator flexibility to adjust the motion of the micro manipulator to counteract structural vibrations. Experimental studies using an existing micro/macro flexible link manipulator testbed demonstrate the effectiveness of the proposed approach to suppression of vibrations in the macro/micro manipulator system using micro-manipulator-based inertial active damping control.
Date: February 1, 1995
Creator: Lew, J. Y.; Trudnowski, D. J.; Evans, M. S. & Bennett, D. W.
System: The UNT Digital Library
Phase correction in two-crystal optical parametric oscillators (open access)

Phase correction in two-crystal optical parametric oscillators

The effect of the pump, signal, and idler wave phases on three-wave nonlinear parametric mixing is investigated in a series of single-pass-gain experiments. Measurements are made with two angle-tuned KTP crystals in a 532 nm pumped, walkoff-compensated, optical parametric amplifier that is seeded by an 800 nm cw diode laser. In one of the measurements the second crystal is orientated to have its effective nonlinearity d{sub eff.} of opposite sign to that of the first crystal, so that all mixing that occurred in the first crystal is cancelled by the second when the phase mismatch {Delta}k{sub crystal 1} = {Delta}k{sub crystal 2} = 0. Efficient two-crystal amplification is subsequently restored by selecting the correct phase relationship for the three waves entering the crystal by inserting a dispersive plate between the crystals. The experimental results are explained in a straightforward manner with diagrams involving the three input wave polarizations. These results demonstrate that walkoff-compensated geometries require phase correction to achieve efficient mixing in the second crystal whenever the nonlinear interaction involves two extraordinary waves (e-waves). One practical application of this work may be lower oscillation thresholds and enhanced performance in walkoff-compensated optical parametric oscillators which use two e-waves.
Date: February 1, 1995
Creator: Armstron, D. J.; Alford, W. J.; Raymond, T. D. & Smith, A. V.
System: The UNT Digital Library
Poster session ELIPGRID-PC (open access)

Poster session ELIPGRID-PC

ELIPGRID-PC, a new personal computer program, has been developed to provide easy access to Singer`s ELIPGRID algorithm for hot-spot detection probabilities. Three features of the program are the ability to determine: (1) the grid size required for specified conditions, (2) the smallest hot spot that can be sampled with a given probability, and (3) the approximate grid size resulting from specified conditions and sampling cost. ELIPGRID-PC also provides probability of detection versus cost data for graphing with spreadsheets or graphics software. The program has been successfully tested using Singer`s published ELIPGRID results. An apparent error in the published ELIPGRID code has been uncovered and an appropriate modification incorporated into the new program.
Date: February 1, 1995
Creator: Davidson, J. R.
System: The UNT Digital Library
Three-dimensional visualization of reactive flows in complex geometries (open access)

Three-dimensional visualization of reactive flows in complex geometries

The visualization of fluid flows has become more challenging, as recent advancements in computational methods have increased the complexity and size of simulations. Our objective is to develop a flexible flow visualization tool for fluid simulations that include the full physics and geometrical complexities found in modeling practical combustion systems, such as internal combustion engines. The challenges to flow visualization come from: (1) the large simulation output, especially when using massively parallel computers; (2) the increasingly complex geometries that include moving surfaces such as pistons and valves; (3) the complex physical phenomena in realistic problems of fuel injection, combustion fronts, boundary flows, and large scale turbulence; and (4) the numerical complexity of indirect addressing of computational elements, variable mesh connectivity, distorted elements, and moving meshes. We have developed a visualization program that addresses these complexities. The program was developed as a post-processor to the KIVA family of codes for reactive flow simulations. Because of the complexity of the KIVA codes, the visualization program is very versatile and applicable to any code with meshes of arbitrary hexahedrons. No comparable commercial visualization package could be found. To visualize the fluid flow, we use mass-less tracer particles that follow the movement of the …
Date: February 1, 1995
Creator: Fairfield, M. S.
System: The UNT Digital Library
Small-scale AFBC-hot air gas turbine power cycle (open access)

Small-scale AFBC-hot air gas turbine power cycle

The Energy and Environmental Research Corporation (EER), the Ohio Agricultural Research and Development Center (OARDC), the Will-Burt Company (W-B) and the U.S. Department of Energy (DOE) have successfully developed and completed pilot plant tests on a small scale atmospheric fluidized bed combustion (AFBC) system. This system can be used to generate electricity, and/or hot water, steam. Following successful pilot plant operation, commercial demonstration will take place at Cedar Lane Farms (CLF), near Wooster, Ohio. The system demonstration will be completed by the end of 1995. The project is being funded through a cooperative effort between the DOE, EER, W-B, OARDC, CLF and the Ohio Coal Development Office (OCDO). The small scale AFBC, has no internal heat transfer surfaces in the fluid bed proper. Combining the combustor with a hot air gas turbine (HAGT) for electrical power generation, can give a relatively high overall system thermal efficiency. Using a novel method of recovering waste heat from the gas turbine, a gross heat rate of 13,500 Btu/kWhr ({approximately}25% efficiency) can be achieved for a small 1.5 MW, plant. A low technology industrial recuperation type gas turbine is used that operates with an inlet blade temperature of 1450{degrees}F and a compression ratio of …
Date: February 1, 1995
Creator: Ashworth, Robert C.; Keener, Harold M. & Hall, Arthur W.
System: The UNT Digital Library
Production of metal waste forms from spent fuel treatment (open access)

Production of metal waste forms from spent fuel treatment

Treatment of spent nuclear fuel at Argonne National Laboratory consists of a pyroprocessing scheme in which the development of suitable waste forms is being advanced. Of the two waste forms being proposed, metal and mineral, the production of the metal waste form utilizes induction melting to stabilize the waste product. Alloying of metallic nuclear materials by induction melting has long been an Argonne strength and thus, the transition to metallic waste processing seems compatible. A test program is being initiated to coalesce the production of the metal waste forms with current induction melting capabilities.
Date: February 1, 1995
Creator: Westphal, B. R.; Keiser, D. D.; Rigg, R. H. & Laug, D. V.
System: The UNT Digital Library
Development of the stored waste autonomous mobile inspector (SWAMI II) (open access)

Development of the stored waste autonomous mobile inspector (SWAMI II)

A mobile robot system called the Stored Waste Autonomous Mobile Inspector (SWAMI) is under development by the Savannah River Technology Center (SRTC) Robotics Group of Westinghouse Savannah River Company (WSRC) to perform mandated inspections of waste drums stored in warehouse facilities. The system will reduce personnel exposure to potential hazards and create accurate, high-quality documentation to ensure regulatory compliance and enhance waste management operations. Development work is coordinated among several Department of Energy (DOE), academic, and commercial entities in accordance with DOE`s technology transfer initiative. The prototype system, SWAMI I, was demonstrated at Savannah River Site (SRS) in November, 1993. SWAMI II is now under development for field trials at the Fernald site.
Date: February 1, 1995
Creator: Peterson, K. D. & Ward, C. R.
System: The UNT Digital Library
Pyrochemical processing of DOE spent nuclear fuel (open access)

Pyrochemical processing of DOE spent nuclear fuel

A compact, efficient method for conditioning spent nuclear fuel is under development. This method, known as pyrochemical processing, or {open_quotes}pyroprocessing,{close_quotes} provides a separation of fission products from the actinide elements present in spent fuel and further separates pure uranium from the transuranic elements. The process can facilitate the timely and environmentally-sound treatment of the highly diverse collection of spent fuel currently in the inventory of the United States Department of Energy (DOE). The pyroprocess utilizes elevated-temperature processes to prepare spent fuel for fission product separation; that separation is accomplished by a molten salt electrorefining step that provides efficient (>99.9%) separation of transuranics. The resultant waste forms from the pyroprocess, are stable under envisioned repository environment conditions and highly leach-resistant. Treatment of any spent fuel type produces a set of common high-level waste forms, one a mineral and the other a metal alloy, that can be readily qualified for repository disposal and avoid the substantial costs that would be associated with the qualification of the numerous spent fuel types included in the DOE inventory.
Date: February 1, 1995
Creator: Laidler, J. J.
System: The UNT Digital Library
White goods recycling in the United States: Economic and technical issues in recovering, reclaiming, and reusing nonmetallic materials (open access)

White goods recycling in the United States: Economic and technical issues in recovering, reclaiming, and reusing nonmetallic materials

Obsolete white goods (appliances such as refrigerators, freezers, washers, dryers, ranges, dishwashers, water heaters, dehumidifiers, and air conditioners) contain significant quantities of recyclable materials, but because of economic and environmental concerns, only limited quantities of these scrap materials are currently being recycled. Appliances are manufactured from a mix of materials, such as metals, polymers, foam, and fiberglass; metals represent more than 75% of the total weight. Appliance recycling is driven primarily by the value of the steel in the appliances. Over the last 15 years, however, the use of polymers in appliance manufacturing has increased substantially at the expense of metals. The shift in the materials composition of appliances may threaten the economics of the use of obsolete appliances as a source for scrap metals. To increase the recycling of white goods, cost-effective and environmentally acceptable technologies must be developed to separate, recover, reclaim, and reuse polymers from discarded appliances. Argonne National Laboratory is currently conducting research, with industry support, to develop cost-effective processes and methods for recovering and reclaiming acrylonitrile butadiene-styrene and High-density polystyrene from discarded appliances. This collaborative research focuses on developing a combination of mechanical/physical and chemical separation methods for recovering and reusing these high-value plastics. In …
Date: February 1, 1995
Creator: Karvelas, D. E.; Jody, B. J. & Daniels, E. J.
System: The UNT Digital Library
Vibration suppression of fixed-time jib crane maneuvers (open access)

Vibration suppression of fixed-time jib crane maneuvers

A jib crane consists of a pendulum-like end line attached to a rotatable jib. Within this general category of cranes there exist devices with multiple degrees of freedom including variable load-line length and variable jib length. These cranes are commonly used for construction and transportation applications. Point-to-point payload maneuvers using jib cranes are performed so as not to excite the spherical pendulum modes of their cable and payload assemblies. Typically, these pendulum modes, although time-varying, exhibit low frequencies. The resulting maneuvers are therefore performed slowly, contributing to high construction and transportation costs. The crane considered here consists of a spherical pendulum attached to a rigid jib. The other end of the jib is attached to a direct drive motor for generating rotational motion. A general approach is presented for determining the open-loop trajectories for the jib rotation for accomplishing fixed-time, point-to-point, residual oscillation free, symmetric maneuvers. These residual oscillation free trajectories purposely excite the pendulum modes in such a way that at the end of the maneuver the oscillatory degrees of freedom are quiescent. Simulation results are presented with experimental verification.
Date: February 1, 1995
Creator: Parker, G. G.; Petterson, B.; Dohrmann, C. R. & Robinett, R. D.
System: The UNT Digital Library
How technology is improving decision making for environmental restoration (open access)

How technology is improving decision making for environmental restoration

Environmental restoration, or the cleanup of contaminants from past activities, at its core depends on a series of decisions about the nature and extent of contamination, the risk to human health and the environment, and the potential effectiveness of remediation techniques and technologies to reduce the risk to acceptable levels. The effectiveness with which these decisions are made has significant impacts on the cost and duration of the cleanup efforts. The decisions must often be made on the basis of incomplete and uncertain data. Emerging environmental information and data acquisition technologies together with appropriate strategies to support decision making are beginning to change the way environmental restoration occurs in the United States. Past environmental restoration activities too often relied on prescriptive data collection activities to generate the information upon which decisions were to be made. Retrospective studies of such activities have shown that, while often data were gathered for the purpose of reducing the risk in decision making, little true reduction in risk was realized and large amounts of resources were consumed. Recent examination of the failures in the United States to achieve many complete cleanups despite the investment of large sums and time points to the inability to have …
Date: February 1, 1995
Creator: Ditmars, J.
System: The UNT Digital Library
Analysis of surfaces, films and multilayers by resonant laser ablation (open access)

Analysis of surfaces, films and multilayers by resonant laser ablation

In this manuscript we review briefly the history of Resonant Laser Ablation (RLA), and discuss some current ideas regarding sample preparation, laser parameters, and mechanisms. We also discuss current applications including spectral analysis of trace components, depth profiling of thin films and multilayer structures, and the use of RLA with the Ion Trap Mass Spectrometer (ITMS).
Date: February 1, 1995
Creator: Allen, T. M.; Smith, C. H.; Kelly, P. B.; Anderson, J. E.; Eiden, G. C.; Garrett, A. W. et al.
System: The UNT Digital Library
A review of the Melcor Accident Consequence Code System (MACCS): Capabilities and applications (open access)

A review of the Melcor Accident Consequence Code System (MACCS): Capabilities and applications

MACCS was developed at Sandia National Laboratories (SNL) under U.S. Nuclear Regulatory Commission (NRC) sponsorship to estimate the offsite consequences of potential severe accidents at nuclear power plants (NPPs). MACCS was publicly released in 1990. MACCS was developed to support the NRC`s probabilistic safety assessment (PSA) efforts. PSA techniques can provide a measure of the risk of reactor operation. PSAs are generally divided into three levels. Level one efforts identify potential plant damage states that lead to core damage and the associated probabilities, level two models damage progression and containment strength for establishing fission-product release categories, and level three efforts evaluate potential off-site consequences of radiological releases and the probabilities associated with the consequences. MACCS was designed as a tool for level three PSA analysis. MACCS performs probabilistic health and economic consequence assessments of hypothetical accidental releases of radioactive material from NPPs. MACCS includes models for atmospheric dispersion and transport, wet and dry deposition, the probabilistic treatment of meteorology, environmental transfer, countermeasure strategies, dosimetry, health effects, and economic impacts. The computer systems MACCS is designed to run on are the 386/486 PC, VAX/VMS, E3M RISC S/6000, Sun SPARC, and Cray UNICOS. This paper provides an overview of MACCS, reviews some …
Date: February 1, 1995
Creator: Young, M.
System: The UNT Digital Library
Comparison of several contemporary ionization/mass analyzer techniques for large components of complex fossil-derived materials (open access)

Comparison of several contemporary ionization/mass analyzer techniques for large components of complex fossil-derived materials

Coals and coal-derived samples provide a unique mixture for development and comparison of mass spectrometric techniques for high molecular weight analyses. The Argonne Premium Coal samples (APCS) are convenient for assessing classical and novel mass spectrometric techniques. Vacuum pyrolysis mass spectrometry of APCS 4 (Pittsburgh No. 8) has been reported. Alkyl-substituted aromatic compounds and hydroxy- and dihydroxy-substituted aromatic compounds were observed. Newer techniques such as laser desorption (LD), as well as in-beam techniques, such as desorption chemical ionization (DCI) and desorption electron ionization (DEI) are better suited to the studies of mixture characterization as presented by fossil fuels.
Date: February 1, 1995
Creator: Hunt, J. E. & Winans, R. E.
System: The UNT Digital Library
Measurements of the volatilities of solutes from aqueous solutions and their application to water/steam cycles (open access)

Measurements of the volatilities of solutes from aqueous solutions and their application to water/steam cycles

Partitioning of NaSO{sub 4} and NaHSO{sub 4} between the liquid and vapor phases was measured at 300, 325 and 350{degrees}C by sampling both phases from a static platinum-lined autoclave. Sample compositions were determined by ion chromatography and acidimetric titrations. The solutions were buffered with either acid or base so that the volatility of individual species was determined. The molal thermodynamic partitioning constants were calculated by taking into account the mean stoichiometric activity coefficient in the liquid phase and the hydrolysis equilibrium constants. The vapor phase species were assumed to be neutral molecules with unit activity coefficients. The strong temperature dependence of the partitioning constant was treated by the isocoulombic method to obtain a linear dependence of the logarithm of the partitioning constant versus reciprocal temperature in Kelvin. A model is described for predicting the composition of the condensate in the water/steam cycle of power plants using drum boilers. Equilibrium between liquid and steam is assumed in the drum during boiling, and in the low pressure turbine on steam condensation. The model is based on the measured partitioning constants of HCl, NH{sub 4}Cl, NaCl, NaOH, H{sub 2}SO{sub 4}, NaHSO{sub 4}, NaSO{sub 4} and NH{sub 3}, the hydrolysis of HSO{sub 4}{sup -} …
Date: February 1, 1995
Creator: Jensen, J. P.; Palmer, D. A. & Simonson, J. M.
System: The UNT Digital Library
Home radon monitor modeled after the common smoke detector (open access)

Home radon monitor modeled after the common smoke detector

The EPA has declared that five million or so of the nation`s 80 million homes may have indoor radon levels that pose an unacceptably high risk of lung cancer to occupants. They estimate that four times as many people die from radon-induced lung cancers as from fires in the home. Therefore the EPA has recommended that all homes be tested and that action be taken to reduce the radon concentration in homes that test above the 4 pCi/L level. The push to have homeowners voluntarily test for elevated radon levels has been only marginally successful. A reliable, inexpensive, and accurate in-home radon monitor designed along the same general lines as a home smoke detector might overcome much of the public reluctance to test homes for radon. Such a Home Radon Monitor (HRM) is under development at Los Alamos National Laboratory. To be acceptable to the public, HRMs should have the following characteristics in common with smoke detectors: low cost, small size, ease of installation and use, low maintenance, and high performance. Recent advances in Long-Range Alpha Detection technology are being used in the design of a HRM that should meet or exceed all these characteristics. A proof-of-principle HRM detector prototype …
Date: February 1, 1995
Creator: Bolton, R. D.; Arnone, G. J. & Johnson, J. P.
System: The UNT Digital Library
Bubble chamber spectroscopy for chemical analysis: A new concept (open access)

Bubble chamber spectroscopy for chemical analysis: A new concept

A new technique for the detection of trace concentrations of molecules in solution has been developed. This system utilizes the amplification characteristics of a bubble chamber in which energy deposition from laser absorption is monitored. In the experimental set-up, a trace quantity of solute is introduced into liquid propane that is contained in a small (10 ml) stainless steel cell at 120 psi. The propane is superheated by sudden reduction of the cell pressure. Before wall nucleated boiling occurs, target solute molecules are energized by a laser pulse. Absorption of pump laser energy results in the formation of nucleation centers which develop into bubbles and which in turn are detected by CCD camera. Preliminary experiments with crystal violet used as a test absorber have demonstrated detection sensitivity of 10 parts per trillion (ppt).
Date: February 1, 1995
Creator: Atencio, J. H.; Luo, Xin; McCreary, E. I.; McCown, A. W. & Sander, R. K.
System: The UNT Digital Library
Three-dimensional computer modeling of hydrogen injection and combustion (open access)

Three-dimensional computer modeling of hydrogen injection and combustion

The hydrodynamics of hydrogen gas injection into a fixed-volume combustion chamber is analyzed and simulated using KIVA-3, a three-dimensional, reactive flow computer code. Comparisons of the simulation results are made to data obtained at the Combustion Research Facility at Sandia National Laboratory-California (SNL-CA). Simulation of the gas injection problem is found to be of comparable difficulty as the liquid fuel injection in diesel engines. The primary challenge is the large change of length scale from the flow of gas in the orifice to the penetration in the combustion chamber. In the current experiments, the change of length scale is about 4,000. A reduction of the full problem is developed that reduces the change in length scale in the simulation to about 400, with a comparable improvement in computational times. Comparisons of the simulation to the experimental data shows good agreement in the penetration history and pressure rise in the combustion chamber. At late times the comparison is sensitive to the method of determination of the penetration in the simulations. In a comparison of the combustion modeling of methane and hydrogen, hydrogen combustion is more difficult to model, and currently available kinetic models fail to predict the observed autoignition delay at …
Date: February 1, 1995
Creator: Johnson, N. L.; Amsden, A. A.; Naber, J. D. & Siebers, D. L.
System: The UNT Digital Library
Synthesis and processing of Al{sub 2}O{sub 3}/Al composites by in situ reaction of aluminum and mullite (open access)

Synthesis and processing of Al{sub 2}O{sub 3}/Al composites by in situ reaction of aluminum and mullite

Al{sub 2}O{sub 3}/Al composites, were formed by reacting molten aluminum metal with dense mullite ceramic preforms. The composites produced by this reactive metal penetration process (RMP) have a two phase, interpenetrating microstructure in which both the ceramic and the metal are continuous in three dimensions. Scanning electron microscopy (SEM) micrographs of composites produced by RMP show a fine microstructure comprised of interlocked metal and ceramic phases, with a feature size of approximately 2 {mu}m. RMP is a relatively rapid process with metal penetration rates of nearly 5 mm/hour at 1100{degrees}C after a short incubation period. An activation energy of 92 kJ/mole was calculated from reaction rate data. Transmission electron microscopy (TEM) micrographs reveal that aluminum metal penetrates along the mullite grain boundaries before reaction with the mullite grains, indicating that diffusion along grain boundaries may be the rate limiting step for the reaction. Thermodynamic information, results of microstructure analyses, and kinetic data indicate that RMP proceeds in 4 stages: (1) Al melting and the formation of a thermodynamically stable metal/ceramic interface; (2) depletion of oxygen from the grain boundaries intersecting the ceramic/metal interface; (3) Al metal penetration into the ceramic preform along grain boundaries; and (4) Al reaction with and …
Date: February 1995
Creator: Fahrenholtz, W. G.; Ewsuk, K. G.; Loehman, R. E. & Tomsia, A. P.
System: The UNT Digital Library