SCIENTIFIC AND TECHNICAL AEROSPACE REPORTS
A Biweekly Publication of the National Aeronautics and Space Administration
VOLUME 43, ISSUE 25 - DECEMBER 16, 2005
23 CHEMISTRY AND MATERIALS (GENERAL)
Includes general research topics related to the composition, properties, structure, and use of chemical compounds and materials as they relate to aircraft, launch vehicles, and spacecraft.
For specific topics in chemistry and materials see categories 25 through 29.
For astrochemistry see category 90 Astrophysics.
20050240859 Lawrence Livermore National Lab., Livermore, CA USA
Including Dislocation Flux in a Continuum Crystal Plasticity Model to Produce Size Scale Effects
Escobedoo, J. P.; Field, D. P.; Leblanc, M. M.; Feb. 24, 2004; 22 pp.; In English Report No.(s): DE2005-15013904; UCRL-TR-202509; No Copyright; Avail.: Department of Energy Information Bridge
An experimental procedure is reported to perform shear tests on specimens held under moderately high hydrostatic pressures (on the order of 0 GPa). The mechanical behavior of materials subjected to such pressures, varies substantially from that observed at atmospheric pressure or even pressures typically attained during industrial processing. These differences must be incorporated into models such as the Steinberg-Guinan hardening model or discrete dislocation dynamics simulations. The goal of the proposed research is to develop and implement testing procedures that experimentally determine pressure-dependent dislocation mobilities in oriented single crystals of the BCC transition metals. These experiments will provide calibration data for models of materials subjected to extreme pressures and will assist in model validation. This paper reports the development of the experimental procedures. A thin foil of polycrystalline Ta was used to perform the initial experiments under hydrostatic pressures ranging from 2.1 to 4.2 GPa. Both yielding and hardening behavior are observed to be sensitive to the imposed pressure. NTIS
Body Centered Cubic Lattices; Shear Strength
20050240860 Lawrence Livermore National Lab., Livermore, CA USA
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Including Dislocation Flux in a Continuum Crystal Plasticity Model to Produce Size Scale Effects
Arsenlis, A.; Becker, R.; Parks, D. M.; Bulatov, V. V.; Jun. 13, 2004; 12 pp.; In English Report No.(s): DE2005-15013845; UCRL-PROC-202356; No Copyright; Avail.: National Technical Information Service (NTIS)
A novel model has been developed to capture size scale and gradient effects within the context of continuum crystal plasticity by explicitly incorporating details of dislocation transport, coupling dislocation transport to slip, evolving spatial distributions of dislocations consistent with the flux, and capturing the interactions among various dislocation populations. Dislocation flux and density are treated as nodal degrees of freedom in the finite element model, and they are determined as part of the global system of equations. The creation, annihilation and flux of dislocations between elements are related by transport equations. Crystallographic slip is coupled to the dislocation flux and the stress state. The resultant gradients in dislocation density and local lattice rotations are analyzed for geometrically necessary and statistically stored dislocation contents that contribute to strength and hardening. Grain boundaries are treated as surfaces where dislocation flux is restricted depending on the relative orientations of the neighboring grains. Numerical results show different behavior near free surfaces and non-deforming surfaces resulting from differing levels of dislocation transmission. Simulations also show development of dislocation pile-ups at grain boundaries and an increase in flow strength reminiscent of the Hall-Petch model. The dislocation patterns have a characteristic size independent of the numerical discretization. NTIS
Continuum Modeling; Continuums; Crystals; Plastic Properties; Scale Effect
20050240901 Lawrence Livermore National Lab., Livermore, CA USA
Chemical Kinetic Study of Toluene Oxidation Under Premixed and Nonpremixed Conditions
Pitz, W. J.; Seiser, R.; Boezzelli, J. W.; Seshadri, K.; Chen, C. J.; Dec. 22, 2003; 26 pp.; In English Report No.(s): DE2005-15013742; UCRL-CONF-201575; No Copyright; Avail.: Department of Energy Information Bridge
A study was performed to elucidate the chemical-kinetic mechanism of combustion of toluene. A detailed chemical-kinetic mechanism for toluene was improved by adding a more accurate description of the phenyl + O(sub 2) reaction channels, toluene decomposition reactions and the benzyl + O reaction. Results of the chemical kinetic mechanism are compared with experimental data obtained from premixed and nonpremixed systems. Under premixed conditions, predicted ignition delay times are compared with new experimental data obtained in shock tube. Also, calculated species concentration histories are compared to experimental flow reactor data from the literature. Under nonpremixed conditions, critical conditions of extinction and autoignition were measured in strained laminar flows in the counterflow configuration. Numerical calculations are performed using the chemical-kinetic mechanism at conditions corresponding to those in the experiments. Critical conditions of extinction and autoignition are predicted and compared with the experimental data. Comparisons between the model predictions and experimental results of ignition delay times in shock tube, and extinction and autoignition in nonpremixed systems show that the chemical-kinetic mechanism predicts that toluene/air is overall less reactive than observed in the experiments. For both premixed and nonpremixed systems, sensitivity analysis was used to identify the reaction rate constants that control the overall rate of oxidation in each of the systems considered. Under shock tube conditions, the reactions that influence ignition delay time are H + O(sub 2) chain branching, the toluene decomposition reaction to give an H atom, and the toluene + H abstraction reaction. The reactions that influence autoignition in nonpremixed systems involve the benzyl + HO(sub 2) reaction and the phenyl + O(sub 2) reaction. NTIS
Combustion; Oxidation; Premixing; Reaction Kinetics; Toluene
20050240905 Forest Products Lab., Madison, WI USA, Marcel Dekker, Inc., New York, USA
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Wood as an Adherend (Chapter 1 from Volume 7: Treatise on Adhesion and Adhesives)
River, B. H.; Vick, C. B.; Gillespie, R. H.; January 1991; 242 pp.; In English Report No.(s): PB2006-101057; No Copyright; Avail.: CASI: A11, Hardcopy
Wood is a porous, permeable, hygroscopic, orthotropic, biological composite material of extreme chemical diversity and physical intricacy.
Table 1.1 provides an overview of the many variables, including wood variables, that bear on the bonding and performance of wood in wood joints and wood-based materials.
Of particular note is the fact that wood properties vary between species, between trees within a species, and even within a tree.
Variability within a single species alone is enough to significantly challenge an adhesive to perform consistently and satisfactorily.
In this chapter, we have attempted to describe wood and to explore how this complex biological material interacts with adhesives to affect the bonding process and the quality of the bonded joint or material.
First, we will present a short review of the history connecting wood and adhesives. NTIS
Adhesion; Adhesive Bonding; Adhesives; Bonding; Wood
20050240946 Department of Energy, Washington, DC, USA
Energy Materials Coordinating Committee (EMaCC) Annual Technical Report, Fiscal Year 2003
Oct. 18, 2004; 200 pp.; In English Report No.(s): PB2006-101408; DOE/SC-0088; No Copyright; Avail.: CASI: A09, Hardcopy
The DOE Energy Materials Coordinating Committee (EMaCC) serves primarily to enhance coordination among the Department's materials programs and to further effective use of materials expertise within the Department. These functions are accomplished through the exchange of budgetary and planning information among program managers and through technical meetings/workshops on selected topics involving both DOE and major contractors. In addition, EMaCC assists in obtaining materials-related inputs for both intra-and interagency compilations. NTIS
Management Systems; Budgets
20050240948 Department of Energy, Washington, DC, USA
Energy Materials Coordinating Committee (EMaCC) Annual Technical Report, Fiscal Year 2002
Aug. 08, 2003; 226 pp.; In English Report No.(s): PB2006-101407; DOE/SC-0077; No Copyright; Avail.: CASI: A11, Hardcopy
The DOE Energy Materials Coordinating Committee (EMaCC) serves primarily to enhance coordination among the Department's materials programs and to further effective use of materials expertise within the Department. These functions are accomplished through the exchange of budgetary and planning information among program managers and through technical meetings/workshops on selected topics involving both DOE and major contractors. In addition, EMaCC assists in obtaining materials-related inputs for both intra-and interagency compilations. NTIS
Management Planning; Coordination
20050240949 Department of Energy, Washington, DC, USA
Energy Materials Coordinating Committee (EMaCC) Annual Technical Report, Fiscal Year 2001
Aug. 2002; 218 pp.; In English Report No.(s): PB2006-101406; DOE/SC-0061; No Copyright; Avail.: CASI: A10, Hardcopy
The DOE Energy Materials Coordinating Committee (EMaCC) serves primarily to enhance coordination among the Department's materials programs and to further effective use of materials expertise within the Department. These functions are accomplished through the exchange of budgetary and planning information among program managers and through technical meetings/workshops on selected topics involving both DOE and major contractors. In addition, EMaCC assists in obtaining materials-related inputs for both intra-and interagency compilations. NTIS
Coordination; Management Systems
20050240950 Department of Energy, Germantown, MD, USA
Energy Materials Coordinating Committee (EMaCC) Annual Technical Report, Fiscal Year 2000
Jul. 31, 2001; 234 pp.; In English Report No.(s): PB2006-101405; DOE/SC-0040; No Copyright; Avail.: CASI: A11, Hardcopy
The DOE Energy Materials Coordinating Committee (EMaCC) serves primarily to enhance coordination among the Department's materials programs and to further effective use of materials expertise within the Department. These functions are accomplished through the exchange of budgetary and planning information among program managers and through technical meetings/workshops on selected topics involving both DOE and major contractors. In addition, EMaCC assists in obtaining materials-related inputs for both intra-and interagency compilations. NTIS
Coordination; Management Methods
20050240961 Lawrence Livermore National Lab., Livermore, CA USA
Distributed Activation Energy Model of Thermodynamically Inhibited Nucleation and Growth Reactions and Its Application to the Phase Transition of HMX
Burnham, A. K.; Weese, R. K.; Weeks, B. L.; Jul. 20, 2004; 18 pp.; In English Report No.(s): DE2005-15014551; UCRL-CONF-203167; No Copyright; Avail.: Department of Energy Information Bridge
Detailed and global models are presented for thermodynamically inhibitednucleation-growth reactions and applied to the beta-delta Phase Transition of HMX (nitramine octahydro-1, 3,5,7-tetranitro-1,3,5,7-tetrazocine). The detailed model contains separate kinetic parameters for the nucleation process, including an activation energy distribution resulting from a distribution of defect energies, and for movement of the resulting reaction interface within a single particle. A thermodynamic inhibition term is added to both processes so that the rates go to zero at the transition temperature. The global model adds the thermodynamic inhibition term to the extended Prout-Tompkins nucleation-growth formalism for single particles or powders. Model parameters are calibrated from differential scanning calorimetry data. The activation energy for nucleation (333 kJ/mol) is substantially higher than that forgrowth (29.3 kJ/mol). Use of a small activation energy distribution ( approximately 400 J/mol) for the defects improves the fit to a powered sample for both the early and late stages of the transition. The effective overall activation energy for the global model (208.8 kJ/mol) is in between that of nucleation and growth. Comparison of the two models with experiment indicates the thermodynamic inhibition term is more important than the energy distribution feature for this transition.Based on the applicability of the Prout-Tompkins kinetics approach to a wide range of organic and inorganic materials, both models should have equally broad applicability for thermodynamically constrained reactions. NTIS
Activation Energy; HMX; Nucleation; Phase Transformations; Thermodynamics; Transition Temperature
20050240977 Lawrence Livermore National Lab., Livermore, CA USA
Hybrid Passive/Active Magnetic Bearing System
Hagler, L. B.; Jun. 11, 2004; 28 pp.; In English Report No.(s): DE2005-15014167; UCRL-TR-204664; No Copyright; Avail.: National Technical Information Service (NTIS)
No abstract available
Machining; Magnetic Bearings; Precision
20050242954 Texas Univ., Austin, TX, USA
Thermodynamics and Kinetics of Aqueous Piperazine with Potassium Carbonate for Carbon Dioxide Absorption
Topical Report, January 1, 2005-March 31, 2005 Cullinane, J. T.; Apr. 18, 2005; 400 pp.; In English Report No.(s): DE2005-839556; No Copyright; Avail.: Department of Energy Information Bridge
This work proposes an innovative blend of potassium carbonate (K2CO3) and piperazine (PZ) as a solvent for CO2 removal from combustion flue gas in an absorber/stripper. The equilibrium partial pressure and the rate of absorption of CO2 were measured in a wetted-wall column in 0.0 to 6.2 m K(sup +) and 0.6 to 3.6 m PZ at 25 to 110 C. The equilibrium speciation of the solution was determined by H-1 NMR under similar conditions. A rigorous thermodynamic model, based on electrolyte non-random two-liquid (ENRTL) theory, was developed to represent equilibrium behavior. A rate model was developed to describe the absorption rate by integration of eddy diffusivity theory with complex kinetics. Both models were used to explain behavior in terms of equilibrium constants, activity coefficients, and rate constants. The addition of potassium to the amine increases the concentration of CO3(sup 2-)/HCO3(sup -) in solution. NTIS
Aqueous Solutions; Carbon Dioxide; Carbonates; Electrolytes; Potassium; Thermodynamics; Kinematics
20050243169 Geological Survey, Reston, VA USA
The Stability of Chlorofluorocarbons (CFCs) in Ground-Water Samples Archived in Borosilicate Ampoules
Shapiro, StephanieD.; Busenberg, Eurybiades; Plummer, L. N.; Jan. 1, 2004; 37 pp.; In English Report No.(s): AD-A439685; No Copyright; Avail.: CASI: A03, Hardcopy
The U.S. Geological Survey (USGS) Chlorofluorocarbon (CFC) Laboratory in Reston, Va., has been measuring concentrations of CFCs in ground-water samples since 1989 to estimate the year that a water sample was recharged to a ground-water flow system. The water samples have been collected in flamesealed borosilicate ampoules. Typically for each site, three samples were analyzed within days to a few months after collection, and additional samples were archived for extended periods of time (up to four years). The stability of CFC concentrations in the archived water samples from the USGS CFC Laboratory was investigated by analyzing the CFC concentrations in archived water samples and comparing them with the CFC concentrations that were obtained soon after the samples were collected. The archived samples selected for analysis were chosen from sites with a wide variety of hydrogeologic and geochemical conditions. For CFC-11 and CFC-12 concentrations, approximately 14% and 10.5%, respectively, of the archived samples were statistically different (both higher and lower) from the concentrations obtained from analyses conducted soon after the sample collection. Most of the extraneous values were attributed to natural variability of CFC concentrations originally in the water discharged from wells, rather than to microbial degradation within the ampoule on storage. DTIC
Ampoules; Borosilicate Glass; Chlorofluorocarbons; Fluorohydrocarbons; Ground Water; Sampling; Stability
Source: NASA.
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