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At least 1,207 records · Page 67
All sourcesNASA NTRSDOE OSTI
DOE OSTI2012

Freezing in porous media: Phase behavior, dynamics and transport phenomena

This research was focused on developing the underlying framework for the mechanisms that control the nature of the solidification of a broad range of porous media. To encompass the scope of porous media under consideration we considered material ranging from a dilute colloidal suspension to a highly packed saturated host matrix with a known geometry. The basic physical processes that occur when the interstitial liquid phase solidifies revealed a host of surprises with a broad range of implications from geophysics to materials science and engineering. We now understand that ostensibly microscopic films of unfrozen liquid control both the equilibrium and transport properties of a highly packed saturated host matrix as well as a rather dilute colloidal suspension. However, our description of the effective medium behavior in these settings is rather different and this sets the stage for the future research based on our past results. Once the liquid phase of a saturated relatively densely packed material is frozen, there is a rich dynamical behavior of particles for example due to the directed motion driven by thermomolecular pressure gradients or the confined Brownian motion of the particles. In quite striking contrast, when one freezes a dilute suspension the behavior can be rather more like that of a binary alloy with the particles playing the role of a ``solute''. We probed such systems quantitatively by (i) using X ray photon correlation spectroscopy (XPCS) and Small Angle X-ray Scattering (SAXS) at the Advanced Photon Source at Argonne (ii) studying the Argonne cell in the laboratory using optical microscopy and imagery (because it is not directly visible while in the vacuum can). (3) analyzed the general transport phenomena within the framework of both irreversible thermodynamics and alloy solidification and (4) applied the results to the study of the redistribution of solid particles in a frozen interstitial material. This research has gone a long way towards establishing a quantitative foundation for a wide class of problems in environmental and technological settings.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2016

Iodine Adsorption by Ag-Aerogel under Prototypical Vessel Off-Gas Conditions

U.S. regulations will require the removal of 129 I from the off-gas streams of any used nuclear fuel (UNF) reprocessing plant prior to discharge of the off-gas to the environment. The required plant decontamination factor for iodine will vary based on fuel burnup, cooling time, and other factors but is very likely to be >1000 and could be as high as 8000. Multiple off-gas streams within a UNF reprocessing plant combine prior to environmental release, and each of these streams contains some amount of iodine. To achieve the decontamination factors (DFs) that are likely to be required by regulations, iodine removal from the vessel off-gas will be necessary. The vessel off-gas contains iodine at very dilute concentrations (ppb levels), and will also contain water vapor. Iodine species present are likely to include both elemental and organic iodides. There will also be solvent vapors and volatile radiolysis products. The United States has considered the use of silver-based sorbents for removal of iodine from UNF off-gas streams, but little is known about the behavior of those sorbents at very dilute iodine concentrations. The purpose of this study was to expose silver-functionalized silica aerogel (AgAerogel) to a prototypical vessel off-gas stream containing 40 ppb methyl iodide to obtain information about organic iodine capture by silver-sorbents at very low iodine concentrations. The design of this extended duration testing was such that information about the rate of adsorption, the penetration of the iodine species, and the overall system DF could be obtained. Results show that CH 3 I penetrates into a AgAerogel sorbent bed to a depth of 3.9 cm under prototypical vessel off-gas conditions. An iodine loading of 22 mg I/g AgAerogel was observed in the first 0.3 cm of the bed. Of the iodine delivered to the system, 48% could not be accounted for, and future efforts will investigate this concern. Direct calculation of the decontamination factor is not possible, as no iodine was observed to break through the sorbent beds. Continued studies on the adsorption of iodine from prototypical vessel off-gas streams by silver-based sorbents will attempt to resolve some of the questions raised here, both regarding mass balance and the effect of aging on iodine adsorption by AgAerogel from a dilute gas stream. Additionally, the adsorption of different iodine species, such as I 2 and C 12 H 25 I will be studied. Other variables that merit examination are the gas velocity of the test and the dependence of the observed results on the inlet iodine concentration. Finally, longer duration testing should be considered in an effort to determine the mass transfer zone associated with iodine adsorption by AgAerogel under prototypical vessel off-gas conditions. The estimation of mass transfer zone is required for any future industrial implementation.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2017

Tank 40 final sludge batch 9 chemical and fissile radionuclide characterization results

A sample of Sludge Batch (SB) 9 was pulled from Tank 40 in order to obtain radionuclide inventory analyses necessary for compliance with the Waste Acceptance Product Specifications (WAPS)i. The SB9 WAPS sample was also analyzed for chemical composition, including noble metals, and fissile constituents, and these results are reported here. These analyses along with the WAPS radionuclide analyses will help define the composition of the sludge in Tank 40 that is fed to the Defense Waste Processing Facility (DWPF) as SB9. At the Savannah River National Laboratory (SRNL), the 3-L Tank 40 SB9 sample was transferred from the shipping container into a 4-L high density polyethylene bottle and solids were allowed to settle. Supernate was then siphoned off and circulated through the shipping container to complete the transfer of the sample. Following thorough mixing of the 3-L sample, a 547 g sub-sample was removed. This sub-sample was then utilized for all subsequent slurry sample preparations. Eight separate aliquots of the slurry were digested, four with HNO3/HCl (aqua regiaii) in sealed Teflon® vessels and four with NaOH/Na2O2 (alkali or peroxide fusioniii) using Zr crucibles. Three Analytical Reference Glass – 1iv (ARG-1) standards were digested along with a blank for each preparation. Each aqua regia digestion and blank was diluted to 1:100 with deionized water and submitted to Analytical Development (AD) for inductively coupled plasma – atomic emission spectroscopy (ICP-AES) analysis, inductively coupled plasma – mass spectrometry (ICP-MS) analysis, atomic absorption spectroscopy (AA) for As and Se, and cold vapor atomic absorption spectroscopy (CV-AA) for Hg. Equivalent dilutions of the alkali fusion digestions and blank were submitted to AD for ICP-AES analysis. Tank 40 SB9 supernate was collected from a mixed slurry sample in the SRNL Shielded Cells and submitted to AD for ICP-AES, ion chromatography (IC), total base/free OH-/other base, total inorganic carbon/total organic carbon (TIC/TOC) analyses. Weighted dilutions of slurry were submitted for IC, TIC/TOC, and total base/free OH-/other base analyses. Activities for U-233, U-235, and Pu-239 were determined from the ICP-MS data for the aqua regia digestions of the SB9 WAPS slurry using the specific activity of each isotope. The Pu-241 value was determined from a Pu-238/-241 method developed by SRNL AD and previously described.v

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2018

Multiscale Modeling of Supercritical Combustion with Two-Level Simulation on Adaptive Beamlets

Supercritical carbon dioxide (sCO 2 ) direct-powered turbine technology is a promising choice for the next generation of high-efficiency and low-emissions fossil fuel power systems. Breakthrough improvements in the design and development of the sCO 2 oxy-combustion devices are hampered by the lack of high-fidelity simulation tools suitable for the supercritical highly-CO 2 diluted reactive flow environment. The critically missing capabilities in many commercial and research codes exist due to the unaccounted effects of many nonlinearities, and the small-scale complex processes which become prominent at supercritical conditions. The present approach aims to address many shortcomings of the currently used models by adopting and generalizing a multiscale modeling concept of the Two-Level Simulation (TLS). In the TLS, all small-scale flow fields are simulated explicitly, albeit on one-dimensional (1D) domains -- beamlets represented by a collection of line segments embedded in a three-dimensional (3D) computational domain. In this research, we laid theoretical groundwork needed for application of the developed approach to variable density turbulent reacting flows and to sCO 2 combustors, in particular. The small-scale governing equations on the beamlets were introduced and analyzed by drawing a comparison with the supercritical Direct Numerical Simulation (DNS) data sets to validate the TLS modeling assumptions. A series of the 2D DNS studies of premixed flame propagation in pipes, in a highly CO 2 -diluted environment, was performed in order to elucidate the effects of dilution on the laminar burning velocity, flame thickness, as well as on the dynamics and morphology of a corrugated flame front. The demonstrated approach could be applicable to high-fidelity modeling of other supercritical combustion devices including liquid rocket engines.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2018

Development and Validation of a Lagrangian Soot Model Considering Detailed Gas Phase Kinetics and Surface Chemistry (July 2018 Progress Report)

The role of Sandia National Laboratories to this project is to image in-cylinder soot and PAH under conditions where PAH and soot are on the threshold of formation due to dilution by excess nitrogen gas. The primary effect of dilution is to lower the combustion temperatures, and if sufficient dilution is provided, soot and/or PAH formation can be completely inhibited. Hence, these experimental data are useful for validation of CFD predictions of initial soot and PAH formation.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Dead-End Filtration and Crystalline Silicotitanate Cesium Ion Exchange with Hanford Tank Waste AW-102

The Direct Feed Low-Activity Waste (DFLAW) flowsheet provides for the initial production of immobilized low-activity waste (ILAW) by feeding low-activity waste (LAW) directly from tank farms to the Hanford Tank Waste Treatment and Immobilization Plant (WTP) LAW facility for immobilization. Prior to the transfer of feed to the WTP LAW facility, tank supernatant waste will be pretreated by the Tank Side Cesium Removal (TSCR) system to meet the WTP LAW waste acceptance criteria (<3.18E-5 Ci 137Cs/mole of Na). This pretreatment facility will filter the waste to remove suspended solids and remove cesium from the waste stream through ion exchange. Bench-scale filtration testing of 7.4 liters of diluted of AW-102 supernate was conducted using dead-end filtration in the hot cells of the Radiochemical Processing Laboratory at Pacific Northwest National Laboratory. A Mott 70-mm disc filter (media grade 5) was used to capture solids. The filter area was adjusted to 2.2 in2 to match the planned TSCR supernate process volume to surface area ratio. There was no indication of filter fouling and no recoverable solids were observed on the filter. Ion exchange testing with the filtered, diluted AW-102 supernatant was conducted using crystalline silicotitanate (CST) ion exchange media. The IONSIV R9140-B CST was provided by Honeywell UOP, LLC in 2018 (Lot number 8056202-999). The column testing operations were prototypic to the intended Low-Activity Waste Pretreatment System operations in a lead-lag column format, although on a small-scale basis with 10-mL CST beds. The feed was processed downflow through the lead column and then through the lag column at ~1.8 bed volumes per hour (BV/h). After 88.6 BVs of feed processing, the volume in the feed bottle dropped below the inlet tube and the lead column fluid headspace was displaced with air. Feed processing was suspended while a new column was prepared and installed into the lead position. A total of 450 BVs of diluted AW-102 feed were processed through the new lead column; only 4.3% Cs breakthrough was achieved. This volume of feed was insufficient to generate useful Cs loading information without extrapolation. A straight-line extrapolation was used to determine the 50% breakthrough of the lead column and contract limit breakthrough from the lag. The values were found to be 1200 BVs and 930 BVs, respectively.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2018

Aluminum Hydroxide Solubility in Sodium Hydroxide Solutions Containing Nitrite/Nitrate of Relevance to Hanford Tank Waste

The technical basis to support the One System River Protection Project Integrated Flowsheet assumption for diluting staged direct feed low-activity waste (DFLAW) from the Hanford waste tanks with raw river water must be assessed in light of the risk of aluminum hydroxide (gibbsite) precipitation prior to the subsequent transfer of tank contents into the low-activity waste pretreatment system (LAWPS) and/or the Tank Side Cesium Removal (TSCR) system from days to months after dilution. Aluminum solubility must be predicted as a function of the significant variables that influence gibbsite dissolution and precipitation. These variables include (i) other solution components that meaningfully affect the activity coefficient of either hydroxide or the aluminate ion, particularly nitrate and nitrite; and (ii) temperature. Based on a review of waste solubility data and the impact of dilution on solution stabilities with specific focus on aluminum hydroxide, data gaps associated with the impact of these variables on the prediction of gibbsite solubility with temperature were identified. An experimental program to aid in the prediction of gibbsite solubility in NaOH solutions containing a range of sodium nitrate and sodium nitrite concentrations up to the solubility limit at a range of temperatures has been conducted. The results of these investigations are summarized in this report.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2023

Packaging Capacity Calculation: Pu Oxide Packaging Options with the 2 Quart SAVY Container

This calculation supports programmatic efforts to Dilute and Dispose Pu. Metal is to be oxidized at LANL, then transported to SRS for dilution at SRS. Ultimately, the diluted oxide will be disposed of at the Waste Isolation Pilot Plant (WIPP). Currently 3013 containers are used to package the oxide, which are placed in to 9975 Type B shipping containers. The Oxide Packaging Technology Maturation Plan determined that a transition to the used of 2-qt SAVY containers placed in 9977 would increase efficiency in shipping and handling and increase programmatic flexibility. The 2-quart SAVY container meets DOE M 441.1 and TA-55 Documented Safety Analysis requirements for handling and storage of Pu oxide at LANL.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Operation, maintenance, and installation instructions for HLW thermal catalytic oxidizer/reducer (TCO)

The HLW TCO Units are a combination of four rectangular vessels; the Recuperative Heat Exchanger, Electric Heater, Selective Catalytic Oxidizer (SCO), and the Selective Catalytic Reducer (SCR). Each housing is simply a closed rectangular box with formed angle stiffeners welded to the outside perimeter. The housings are connected with process piping and sit on a skid. There is an external frame to support all major process piping and the Electric Heater. The process piping consists of a 14" inlet which enters the heat exchanger. Then the off-gas flows through 18" cross over piping which leads to the heater. Once the off-gas is heated, another section of 18" process piping leads the off-gas through the SCO and SCR. The off-gas then flows through the heat exchanger before exiting through 16" process piping which leads to the customer's piping. The other equipment associated with the HLW TCO is the Ammonia Dilution Skid. The dilution skid controls the ammonia injection into the off-gas. The dilution skid supports two process lines, a 2" line and a 1" line which carries process air and anhydrous ammonia respectively. Ammonia injection into the off-gas is required prior to entering the SCR to ensure the NOx reduction occurs through the SCR catalyst bank.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2012

SCR-TCP Installation and Operating Manual, 24590-CM-POA-MBT0-00002-01-00002_00C

The HLW TCO Units are a combination of four rectangular vessels; the Recuperative Heat Exchanger, Electric Heater, Selective Catalytic Oxidizer (SCO), and the Selective Catalytic Reducer (SCR). Each housing is simply a closed rectangular box with formed angle stiffeners welded to the outside perimeter. The housings are connected with process piping and sit on a skid. There is an external frame to support all major process piping and the Electric Heater. The process piping consists of a 14” inlet which enters the heat exchanger. Then the off-gas flows through 18” cross over piping which leads to the heater. Once the off-gas is heated, another section of 18” process piping leads the off-gas through the SCO and SCR. The off-gas then flows through the heat exchanger before exiting through 16” process piping which leads to the customer's piping. The other equipment associated with the HLW TCO is the Ammonia Dilution Skid. The dilution skid controls the ammonia injection into the off-gas. The dilution skid supports two process lines, a 2” line and a 1” line which carries process air and anhydrous ammonia respectively. Ammonia injection into the off-gas is required prior to entering the SCR to ensure the NOx reduction occurs through the SCR catalyst bank.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2021

An Experimental Kinetics Study of Isopropanol Pyrolysis and Oxidation behind Reflected Shock Waves

Isopropanol has potential as a future bio-derived fuel and is a promising substitute for ethanol in gasoline blends. Even so, little has been done in terms of high-temperature chemical kinetic speciation studies of this molecule. To this end, experiments were conducted in a shock tube using simultaneous CO and H2O laser absorption measurements. Water and CO formation during isopropanol pyrolysis was also examined at temperatures between 1127 and 2162 K at an average pressure of 1.42 atm. Species profiles were collected at temperatures between 1332 and 1728 K and at an average pressure of 1.26 atm for equivalence ratios of 0.5, 1.0, and 2.0 in highly diluted mixtures of 20% helium and 79.5% argon. Species profiles were also compared to four modern C3 alcohol mechanisms, including the impact of recent rate constant measurements. The Li et al. (2019) and Saggese et al. (2021) models both best predict CO and water production under pyrolysis conditions, while the AramcoMech 3.0 and Capriolo and Konnov models better predict the oxidation experimental profiles. Additionally, previous studies have collected ignition delay time (τign) data for isopropanol but are limited to low pressures in highly dilute mixtures. Therefore, real fuel–air experiments were conducted in a heated shock tube with isopropanol for stoichiometric and lean conditions at 10 and 25 atm between 942 and 1428 K. Comparisons to previous experimental results highlight the need for real fuel–air experiments and proper interpretation of shock-tube data. The AramcoMech 3.0 model over predicts τign values, while the Li et al. model severely under predicts τign. The models by Capriolo and Konnov and Saggese et al. show good agreement with experimental τign values. A sensitivity analysis using these two models highlights the underlying chemistry for isopropanol combustion at 25 atm. Additionally, modifying the Li et al. model with a recently measured reaction rate shows improvement in the model’s ability to predict CO and water profiles during dilute oxidation. Finally, a regression analysis was performed to quantify τign results from this study.

09 BIOMASS FUELS↗
DOE OSTI2024

Tomato Brown Rugose Fruit Virus Is Transmissible through a Greenhouse Hydroponic System but May Be Inactivated by Cold Plasma Ozone Treatment

Tomato brown rugose fruit virus (ToBRFV) is an emerging tobamovirus infecting tomatoes and peppers, resulting in a pandemic in recent years. In addition to its abilities of being seed-borne, transmitted mechanically and overcoming current resistance, we speculated other factors may also contribute to such catastrophic effect on tomato production in a hydroponic greenhouse. The objective of this study was to evaluate whether ToBRFV can be transmissible through recirculating hydroponic systems and, more importantly, search for an effective approach to contain its spread. We not only detected ToBRFV in the runoff water samples collected from three greenhouses but also determined the virus’ infectivity through a bioassay. We then conducted a water treatment using cold plasma ozone to assess its efficacy in inactivating ToBRFV. The results showed that, with a high concentration of ToBRFV (inoculum in 1:100 dilution), a prolonged exposure (72 min) to two higher ozone concentrations (0.6 mg/L and 1.0 mg/L) achieved partial effects. With a medium virus concentration (inoculum in 1:1000 dilution), an exposure to ozone for 48 min was sufficient to completely suppress the virus’ infectivity. However, with a low virus concentration (inoculum in 1:10,000 dilution), the virus was completely inactivated even with just a short ozone exposure (24 min). Future work will need to confirm the efficacy of the ozone treatment against ToBRFV as well as its impact on tomato plants in a hydroponic greenhouse.

Agriculture↗
DOE OSTI2018

On Presolar Stardust Grains from CO Classical Novae

About 30%–40% of classical novae produce dust 20–100 days after the outburst, but no presolar stardust grains from classical novae have been unambiguously identified yet. Although several studies claimed a nova paternity for certain grains, the measured and simulated isotopic ratios could only be reconciled, assuming that the grains condensed after the nova ejecta mixed with a much larger amount of close-to-solar matter. However, the source and mechanism of this potential post-explosion dilution of the ejecta remains a mystery. A major problem with previous studies is the small number of simulations performed and the implied poor exploration of the large nova parameter space. In this paper, we report the results of a different strategy, based on a Monte Carlo technique, that involves the random sampling over the most important nova model parameters: the white dwarf composition; the mixing of the outer white dwarf layers with the accreted material before the explosion; the peak temperature and density; the explosion timescales; and the possible dilution of the ejecta after the outburst. We discuss and take into account the systematic uncertainties for both the presolar grain measurements and the simulation results. Only those simulations that are consistent with all measured isotopic ratios of a given grain are accepted for further analysis. We also present the numerical results of the model parameters. Lastly, we identify 18 presolar grains with measured isotopic signatures consistent with a CO nova origin, without assuming any dilution of the ejecta. Among these, the grains G270_2, M11-334-2, G278, M11-347-4, M11-151-4, and Ag2_6 have the highest probability of a CO nova paternity.

nuclear reactions↗
DOE OSTI2026

Total Cost of Ownership Reduction Using Passive Pre-Chamber Ignition in Natural Gas Engines

Spark plug durability is a factor affecting the total cost of ownership (TCO) of spark-ignited natural gas engines, with some heavy-duty platforms requiring plug replacement after only 750 hours of operation. The high ignition energy demand under lean or diluted conditions accelerates electrode wear, shortening plug life and increasing maintenance frequency. This work evaluates passive pre-chamber (PC) ignition operating at lowered spark energies as a strategy to reduce spark energy requirements and extend plug durability, thereby lowering TCO. Experiments were conducted on a medium-duty Cummins 6.7L ISB engine at 1600 RPM and 50% load under varying exhaust gas recirculation (EGR) dilution levels (0–40%). Two passive pre-chambers with 1.1 mm and 1.6 mm nozzle diameters were compared with conventional spark ignition (SI). SI was operated with a fixed coil dwell of 4 ms (~90 mJ), while the PC configuration was tested across 2–4 ms dwell times (~30–90 mJ). Cylinder pressure analysis revealed that PC ignition sustained stable combustion at significantly lower spark energies than SI, with improved combustion stability at ~30 mJ compared with SI at ~90 mJ. The PC system also extended the dilution tolerance beyond that achievable with SI, while delivering up to ~2% higher indicated thermal efficiency and reducing the COV by nearly 90% at 30% EGR. A TCO analysis was conducted to assess the economic benefit of adopting a passive PC system operating at reduced spark energies compared to SI. It was found that adopting a passive PC system could reduce TCO by approximately $11,000 per engine over a five-year operational period, primarily due to fuel savings, extended spark plug life, and reduced maintenance frequency. These projections were weighed against the additional hardware cost of the pre-chamber, yielding a rapid estimated return on investment of ~300 operating hours. Therefore, this work motivates continued research and development of passive PC technology and its commercial adoption in natural gas engines used in transportation applications.

Dhotre, Akash [University of Minnesota]↗
NASA NTRS1972

Evaluation of the pulse-contour method of determining stroke volume in man.

The pulse-contour method for determining stroke volume has been employed as a continuous rapid method of monitoring the cardiovascular status of patients. Twenty-one patients with ischemic heart disease and 21 patients with mitral valve disease were subjected to a variety of hemodynamic interventions. The pulse-contour estimations, using three different formulas derived by Warner, Kouchoukos, and Herd, were compared with indicator-dilution outputs. A comparison of the results of the two methods for determining stroke volume yielded correlation coefficients ranging from 0.59 to 0.84. The better performing Warner formula yielded a coefficient of variation of about 20%. The type of hemodynamic interventions employed did not significantly affect the results using the pulse-contour method. Although the correlation of the pulse-contour and indicator-dilution stroke volumes is high, the coefficient of variation is such that small changes in stroke volume cannot be accurately assessed by the pulse-contour method. However, the simplicity and rapidity of this method compared to determination of cardiac output by Fick or indicator-dilution methods makes it a potentially useful adjunct for monitoring critically ill patients.

Alderman, E. L.↗
NASA NTRS1976

Spectral radiance measurements and calculated soot concentrations along the length of an experimental combustor

Radiometric data were obtained over a range of parametric test conditions at three positions along the length of an experimental combustor segment corresponding to the primary, intermediate, and dilution zones. The concentration of soot entrained in the combustion gases was calculated by a technique using spectral radiance measurements. Tests were conducted primarily with Jet A fuel, although limited data were taken with two fuels having higher aromatic content, diesel oil number 2 and a blend of 40 percent tetralin in Jet A fuel. Radiometric observation of the combustion gases indicated that the maximum total radiance peaked at the intermediate zone, which was located immediately upstream of the dilution holes. Soot concentrations calculated from optical measurements in the dilution zone compared favorably with those obtained by in situ gas sampling at the exhaust. The total radiance increased with the higher aromatic content fuels.

Norgren, C. T.↗
NASA NTRS1980

Muon spin rotation research program

Data from cyclotron experiments and room temperature studies of dilute iron alloys and iron crystals under strain were analyzed. The Fe(Mo) data indicate that the effect upon the contact hyperfine field in Fe due to the introduction of Mo is considerably less than that expected from pure dilution, and the muon (+) are attracted to the Mo impurity sites. There is a significant change in the interstitial magnetic field with Nb concentration. The Fe(Ti) data, for which precession could clearly be observed early only at 468K and above, show that the Ti impurities are attractive to muon (+), and the magnitude of B(hf) is reduced far beyond the amount expected from pure dilution. Changes in the intersitital magnetic field with the introduction of Cr, W, Ge, and Si are also discussed. When strained to the elastic limit, the interstitial magnetic field in Fe crystals is reduced by 33 gauss, and the relaxation rate of the precession signal increases by 47%.

Stronach, C. E.↗
NASA NTRS1984

Friction and wear of nickel in sulfuric acid

Experiments were conducted with elemental nickel sliding on aluminum oxide in aerated sulfuric acid in concentrations ranging from very dilute (10 -4 N, i.e., 5 ppm) to very concentrated (96 percent) acid. Load and reciprocating sliding speeds were kept constant. With the most dilute concentration (10 -4 N) no observable corrosion occurred in or outside the wear area. This was used as the base condition to determine the high contribution of corrosion to total wear loss at acid concentrations between 0.5 percent (0.1 N) and 75 percent. Corrosion reached a maximum rate of 100 millimeters per year at 30 percent acid. At the same time, general corrosion outside the wear area was very low, in agreement with published information. It is clear that friction and wear greatly accelerated corrosion in the wear area. At dilute concentrations of 0.001 and 0.01 N, corrosion in the wear area was low, and general corrosion outside was also low, but local outside regions in the direction of the wear motion experienced some enhanced corrosion, apparently due to fluid motion of the acid.

Rengstorff, G. W. P.↗