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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1995

Heterogeneous reactions of HNO3(g) + NaCl(s) yields HCl(g) + NaNO3(s) and N2O5(g) + NaCl(s) yields ClNO2(g) + NaNO3(s)

The heterogeneous reactions of HNO3(g) + NaCl(s) yields HCl(g) + NaNO3(s) (eq 1) and N2O5(g) + NaCl(s) yields ClNO2(g) + NaNO3(S) (eq 2) were investigated over the temperature range 223-296 K in a flow-tube reactor coupled to a quadrupole mass spectrometer. Either a chemical ionization mass spectrometer (CIMS) or an electron-impact ionization mass spectrometer (EIMS) was used to provide suitable detection sensitivity and selectivity. In order to mimic atmospheric conditions, partial pressures of HNO3 and N2O5 in the range 6 x 10(exp -8) - 2 x 10(exp -6) Torr were used. Granule sizes and surface roughness of the solid NaCl substrates were determined by using a scanning electron microscope. For dry NaCl substrates, decay rates of HNO3 were used to obtain gamma(1) = 0.013 +/- 0.004 (1sigma) at 296 K and > 0.008 at 223 K, respectively. The error quoted is the statistical error. After all corrections were made, the overall error, including systematic error, was estimated to be about a factor of 2. HCl was found to be the sole gas-phase product of reaction 1. The mechanism changed from heterogeneous reaction to predominantly physical adsorption when the reactor was cooled from 296 to 223 K. For reaction 2 using dry salts, gamma(2) was found to be less than 1.0 x 10(exp -4) at both 223 and 296 K. The gas-phase reaction product was identified as ClNO2 in previous studies using an infrared spectrometer. An enhancement in reaction probability was observed if water was not completely removed from salt surfaces, probably due to the reaction of N2O5(g) + H2O(s) yields 2HNO3(g). Our results are compared with previous literature values obtained using different experimental techniques and conditions. The implications of the present results for the enhancement of the hydrogen chloride column density in the lower stratosphere after the El Chichon volcanic eruption and for the chemistry of HCl and HNO3 in the marine troposphere are discussed.

Leu, Ming-Taun↗
NASA NTRS1995

Heterogeneous Reactions of HNO3(g) + NaCl(s) Yields HCL(g) + NaNO3(s) and N2O5(g) + NaCl(s) Yields ClNo2(g) + NaNO3(s)

The heterogeneous reactions of HNO3(g) + NaCl(s) Yields HCL(g) + NaNO3(s) and N2O5(g) + NaCl(s) Yields ClNo2(g) + NaNO3(s)were investigated over a temperature range of 223-296 K in a flow-tube reactor coupled to a quadrupole mass spectrometer. The implications for volcanic enhancement of the HCl and HNO3 column density in the lower stratosphere are discussed.

heterogeneous↗
DOE OSTI2020

Materials Data on NaNO3 by Materials Project

NaNO3 is Calcite structured and crystallizes in the trigonal R-3c space group. The structure is three-dimensional. Na1+ is bonded to six equivalent O2- atoms to form corner-sharing NaO6 octahedra. The corner-sharing octahedral tilt angles are 64°. All Na–O bond lengths are 2.45 Å. N5+ is bonded in a trigonal planar geometry to three equivalent O2- atoms. All N–O bond lengths are 1.27 Å. O2- is bonded in a trigonal planar geometry to two equivalent Na1+ and one N5+ atom.

36 MATERIALS SCIENCE↗
NASA NTRS1994

Heterogeneous Reaction of ClONO2(g) + NaCl(s) to Cl2(g) + NaNO3(s)

The heterogeneous reaction of ClON02 + NaCl yields Cl2 + NaNO3 (eq 1) was investigated over a temperature range 220-300 K in a flow-tube reactor interfaced with a differentially pumped quadrupole mass spectrometer. Partial pressures of ClON02 in the range 10(exp -8) - 10(exp -5) Torr were used. Granule sizes and surface roughness of the NaCl substrates were determined by using a scanning electron microscope, and in separate experiments, surface areas of the substrates were measured by using BET analysis of gas-adsorption isotherms. For dry NaCl substrates, both the decay rates of ClON02 and the growth rates Of C12 were used to obtain reaction probabilities, gamma(sub l) = (4.6 +/- 3.0) x 10(exp -3) at 296 K and (6.7 +/- 3.2) x 10(exp -1) at 225 K, after considering the internal surface area, The error bars represent 1 standard deviation. The Cl2 yield based on the ClONO2 reacted was measured to be 1.0 +/- 0.2. In order to mimic the conditions encountered in the lower stratosphere, the effect of water vapor pressures between 5 x 10(exp -5) and 3 x 10(exp -4) Torr on reaction 1 was also studied. With added H20, reaction probabilities, gamma = (4.1 +/- 2.1) x 10(exp -3) at 296 K and (4.7 +/- 2.9) x 10(exp -3) at 225 K, were obtained. A trace of HOCl, the reaction product from the ClON02 + H20 yield HOCl + HN03 reaction, was observed in addition to the C12 product from reaction 1. The implications of this result for the enhancement of hydrogen chloride in the stratosphere after the El Chichon volcanic eruption and for the marine troposphere are discussed.

Timonen, Raimo S.↗
DOE OSTI2020

Materials Data on Na3MoNO3 by Materials Project

Na3MoNO3 is Stannite-like structured and crystallizes in the orthorhombic Pmn2_1 space group. The structure is three-dimensional. there are two inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded to one N3- and three O2- atoms to form NaNO3 tetrahedra that share corners with four equivalent MoNO3 tetrahedra and corners with eight equivalent NaNO3 tetrahedra. The Na–N bond length is 2.39 Å. There are one shorter (2.37 Å) and two longer (2.39 Å) Na–O bond lengths. In the second Na1+ site, Na1+ is bonded to one N3- and three O2- atoms to form NaNO3 tetrahedra that share corners with four equivalent MoNO3 tetrahedra and corners with eight NaNO3 tetrahedra. The Na–N bond length is 2.36 Å. There are a spread of Na–O bond distances ranging from 2.32–2.35 Å. Mo6+ is bonded to one N3- and three O2- atoms to form MoNO3 tetrahedra that share corners with twelve NaNO3 tetrahedra. The Mo–N bond length is 1.75 Å. There is one shorter (1.86 Å) and two longer (1.87 Å) Mo–O bond length. N3- is bonded to three Na1+ and one Mo6+ atom to form NNa3Mo tetrahedra that share corners with twelve ONa3Mo tetrahedra. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded to three Na1+ and one Mo6+ atom to form distorted ONa3Mo tetrahedra that share corners with four equivalent NNa3Mo tetrahedra and corners with eight ONa3Mo tetrahedra. In the second O2- site, O2- is bonded to three Na1+ and one Mo6+ atom to form distorted ONa3Mo tetrahedra that share corners with four equivalent NNa3Mo tetrahedra and corners with eight equivalent ONa3Mo tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Reactions during conversion of simplified low-activity waste glass feeds

The mechanisms that affect the incorporation of 99Tc, a volatile radioactive component of concern, into glass melt during vitrification of low-activity waste (LAW) are being investigated to develop the method to increase the retention of 99Tc in glass waste form. Previous studies with simulated LAW glass feeds (slurry mixture of liquid waste and chemical/mineral additives) demonstrated that the early stage feed-to-glass conversion reactions below 800°C are critical for the Re (used as a nonradioactive surrogate of 99Tc) retention in glass. To examine the effect of feed composition on the feed-to-glass conversion reactions, simplified systems containing major LAW components (NaNO3 and NaOH) and representative additive components (SiO2 and H3BO3) were designed and tested. The ratio of H3BO3 to NaNO3 was varied in three-component system without NaOH and that of NaOH to NaNO3 was varied in the four-component system at a fixed H3BO3 to NaNO3 ratio. As a first step of testing with simplified feeds, this study applied thermal analyses and phase characterization of the reacting feeds, which were performed without the addition of Re, to investigate the evolution of salt phases during slurry drying process and upon heating of dried feeds.

Jin, Tongan↗
NASA NTRS2000

Effects of End-Wall Vibration on Oscillatory Thermocapillary Flow

Our previous float zone experiments 1,2 with NaNO3 revealed that steady thermocapillary flow (TC flow) can be balanced/offset by the controlled surface streaming flow (CSS flow), induced by end-wall vibration. In the current experiments, we are examining the effects of surface streaming flow on steadying/stabilizing oscillatory thermocapillary flow. To this effect, we have set up a controlled NaNO3 half-zone experiment, where the processing parameters like zone dimensions and temperature gradients scan be easily varied to achieve oscillatory TC flow. In the present paper, we discuss the thermal signature of the TC flow, and how it is affected by imposition of CSS flow. The results will also include a comparison of the microstructure of a NaNO3- BaNO3 eutectic, processed under oscillatory TC conditions, with and without imposed CSS flow.

Bhowmick, J.↗
DOE OSTI2020

Materials Data on Na4Al3Si3CNO13 by Materials Project

Na4Al3Si3CNO13 crystallizes in the orthorhombic Ccc2 space group. The structure is three-dimensional. there are two inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded to four O2- atoms to form distorted NaO4 tetrahedra that share a cornercorner with one NaO4 tetrahedra, corners with three AlO4 tetrahedra, and corners with three SiO4 tetrahedra. There are a spread of Na–O bond distances ranging from 2.36–2.50 Å. In the second Na1+ site, Na1+ is bonded to one N3- and three O2- atoms to form distorted NaNO3 tetrahedra that share a cornercorner with one NaNO3 tetrahedra, corners with three AlO4 tetrahedra, and corners with three SiO4 tetrahedra. The Na–N bond length is 2.48 Å. There are a spread of Na–O bond distances ranging from 2.36–2.39 Å. There are two inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with four NaO4 tetrahedra and corners with four SiO4 tetrahedra. There is one shorter (1.75 Å) and three longer (1.76 Å) Al–O bond length. In the second Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with four NaO4 tetrahedra and corners with four equivalent SiO4 tetrahedra. All Al–O bond lengths are 1.76 Å. There are two inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with four NaO4 tetrahedra and corners with four AlO4 tetrahedra. All Si–O bond lengths are 1.64 Å. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with four NaO4 tetrahedra and corners with four equivalent AlO4 tetrahedra. All Si–O bond lengths are 1.64 Å. C4+ is bonded in a linear geometry to one N3- and one O2- atom. The C–N bond length is 1.20 Å. The C–O bond length is 1.23 Å. N3- is bonded in a 3-coordinate geometry to two equivalent Na1+ and one C4+ atom. There are seven inequivalent O2- sites. In the first O2- site, O2- is bonded in a 3-coordinate geometry to one Na1+, one Al3+, and one Si4+ atom. In the second O2- site, O2- is bonded in a 3-coordinate geometry to one Na1+, one Al3+, and one Si4+ atom. In the third O2- site, O2- is bonded in a 3-coordinate geometry to two equivalent Na1+ and one C4+ atom. In the fourth O2- site, O2- is bonded in a 3-coordinate geometry to one Na1+, one Al3+, and one Si4+ atom. In the fifth O2- site, O2- is bonded in a 3-coordinate geometry to one Na1+, one Al3+, and one Si4+ atom. In the sixth O2- site, O2- is bonded in a 3-coordinate geometry to one Na1+, one Al3+, and one Si4+ atom. In the seventh O2- site, O2- is bonded in a 3-coordinate geometry to one Na1+, one Al3+, and one Si4+ atom.

36 MATERIALS SCIENCE↗
NASA NTRS2000

Utilizing Controlled Vibrations in a Microgravity Environment to Understand and Promote Microstructural Homogeneity During Float-Zone Crystal Growth

Our previous experiments with NaNO3 float-zones revealed that steady thermocapillary flow can be balanced/offset by the controlled surface streaming flow induced by end-wall vibration. In the current experiments we are examining the effects of streaming flow on steadying/stabilizing nonsteady thermocapillary flow in such zones. To this effect we have set up a controlled NaNO3 half-zone experiment, where the processing parameters, like zone dimensions and temperature gradients, can be easily varied to generate nonsteady thermocapillary flows. In the present paper we present preliminary results of our investigations into stabilizing such flows by employing end-wall vibration.

Anilkumar, A. V.↗
NASA NTRS2001

Utilizing Controlled Vibrations in a Microgravity Environment to Understand and Promote Microstructural Homogeneity During Floating-Zone Crystal Growth

Our previous experiments with NaNO3 float-zones revealed that steady thermocapillary flow can be balanced/offset by the controlled surface streaming flow induced by end-wall vibration. In the current experiments we are examining the effects of streaming flow on steadying/stabilizing nonsteady thermocapillary flow in such zones. To this effect we have set up a controlled NaNO3 half-zone experiment, where the processing parameters, like zone dimensions and temperature gradients, can be easily varied to generate nonsteady thermocapillary flows. In the present paper we present preliminary results of our investigations into stabilizing such flows by employing endwall vibration.

Anilkumar, A. V.↗
DOE OSTI2021

Nitrate and Nitrite Incompatibility with Hydroxide Ions in Concentrated NaOH Solutions: Implications for Hydroxide and Gibbsite Reactivity in Alkaline Nuclear Waste

Electrolyte solutions in alkaline nuclear waste contain aluminate, hydroxide, nitrate and nitrite with sodium as the predominant counterion. The salts of these ions are highly soluble, so the liquids are highly concentrated. This study found that there is a substantial incompatibility between the hydroxide and nitrate and/or nitrate ions. This was determined by the observations that adding just one molal of NaNO2 or NaNO3 to saturated NaOH solution precipitation of 12 moles of NaOH·H2O salt, whereas the common ion effect would have expected only about 1 mole to precipitate. Further analysis indicates that the presence of nitrate and nitrite drastically increases the reactivity of sodium hydroxide ions in solution, which likely influences the reactivity of other hydroxide-mediated reactions. This enhanced reactivity is likely because it disrupts large Na+-OH- ion networks because nitrate and nitrite do not fit in those ion networks similarly to how some ions cannot substitute into a foreign crystal lattice. In contrast, the aluminate ion did not have the same large incompatibility with hydroxide.

Nitrite, Nitrate, Aluminate, NaOH*H2O, Ion-aggrega↗
DOE OSTI2022

Corrosion resistance of high nickel alloys in solar salt at 600 °C for up to 4000 h

This study focuses on the time dependent performance of the corrosion resistance of IN625, H230 and 740H alloys in the solar salt (60 wt% NaNO3, 40 wt% KNO3, at 600 °C) for up to 4000 h. Alloy IN625 showed the lowest mass change with parabolic oxidation kinetics that tends to stabilize with exposure time. Both 740H and H230 alloys deviated from the parabolic oxidation behavior beyond the 3000 h of exposure. Alloy 740H showed the highest mass loss due to the nonuniform surface oxidation and the high chromium dissolution rate. Internal oxidation was noticed with Alloy H230 due to the high tungsten concentrations.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Plutonium Retention by Crystalline Silicotitanate under Hyperalkaline Conditions Relevant to Tank-Side Cesium-Removal at the Hanford Site

Crystalline silicotitanate (CST) is used in Hanford’s Tank-Side Cesium-Removal (TSCR) process to selectively remove Cs-137 from highly caustic, nitrate-rich tank supernatants. Recent testing with actual waste samples suggests that CST can also retain measurable plutonium (Pu), which could affect radiological classification and disposal pathways for spent CST. To quantify this behavior, Pu partitioning to CST was studied under Hanford-relevant conditions using batch-contact experiments in a representative simulant (2 M NaNO3, 0.7 M NaOH). Isotherm data were measured and distribution ratios calculated, with Cs+ uptake used as benchmark. Under low-carbonate conditions, Pu was retained strongly by CST in systems initially contacted with either PuO2 nanoparticles (Pu(IV)) or aqueous Pu(VI), with distribution ratios of ~2,200–3,700 mL/g, generally exceeding those for Cs+ (~400–1,000 mL/g). Increasing carbonate concentration strongly reduced PuO2 nanoparticle retention; at [Na2CO3] = 1 M, distribution ratios decreased by up to one order of magnitude to roughly 100–300 mL/g. Electron microscopy suggests that Pu retention involves a combination of mechanisms such as PuO2 NP aggregation induced by CST leachate components, and association with CST bead surfaces.

Neumann, J.↗
DOE OSTI2020

Materials Data on Na8NO3 by Materials Project

Na8NO3 is Fluorite-derived structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Na1+ is bonded to one N2- and three equivalent O2- atoms to form a mixture of edge and corner-sharing NaNO3 tetrahedra. The Na–N bond length is 2.47 Å. All Na–O bond lengths are 2.44 Å. N2- is bonded in a body-centered cubic geometry to eight equivalent Na1+ atoms. O2- is bonded in a body-centered cubic geometry to eight equivalent Na1+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Radiolytic Gas Generation and Pressure Buildup in a Closed System Containing Mo-99 Solution

This study measured radiolytic gas generation and pressure buildup in a sealed stainless-steel system containing alkaline Mo-99 solution with added sodium nitrate as a hydrogen suppressant. In each of two experiments, approximately 200 Ci of Mo-99 solution was transferred into a closed experimental vessel inside a hot cell, isolated, and monitored for pressure rise caused by gas generation during radioactive decay. After pressure buildup, headspace gas samples were collected and analyzed by mass spectrometry to determine hydrogen and oxygen concentrations. The purpose was to quantify the magnitude of pressure buildup in a closed system and to characterize the gas composition produced by radiolysis of the Mo-99 target solution under representative handling and storage conditions. The two experiments used similar total Mo-99 activity but differed in solution volume, headspace volume, and leak integrity. In the first experiment, 197.5 Ci of Mo-99 in 16.92 mL of solution was loaded into a vessel with a 31.1-mL headspace; a small leak was later identified, and the measured peak pressure of 46 psig was extrapolated to about 70 psig in the absence of leakage. The headspace gas from this experiment contained about 21.4% H2 and 63.4% O2, but the composition was influenced by preferential hydrogen loss through the leak. In the second experiment, 193 Ci of Mo-99 in 5.41 mL of solution with 0.46 g NaNO3 was loaded into a vessel with a larger 42.61 mL headspace, and no detectable leak was observed. This experiment reached a peak pressure of 38 psig, and the measured gas composition was approximately 28.2% H2 and 51.5% O2. Because the second experiment was leak-free, it is considered the more reliable indicator of the true pressure buildup and intrinsic radiolytic gas composition of the Mo-99 solution.

Chemerisov, Sergey D.↗
NASA NTRS1972

Electrochemical behavior of the boron anode in aqueous solutions

The electrochemical oxidation of p-type boron in 0.2 N NaNO3 solutions of pH 0.4 to 13.1 was studied by galvanostatic techniques. The capacitance of the electrode, Tafel slopes, and a limited analysis of reaction mechanisms are reported. The anodic dissolution in acid solution is a charge-transfer-limited one-electron reaction to form a monovalent species in the over-potential region of 0.25 to 0.70 V. The dissolution in basic solution is most probably a one-electron charge-transfer reaction from a monovalent to divalent species involving three hydroxyl ions. Open circuit potentials were mixed potentials, probably due to hydrogen formation at open circuit but not contributing to the electrochemical reaction at the applied overpotential. Exchange current, estimated by extrapolation of the Tafel line to the standard oxidation potential for the boron reaction, were of the order of 10 to the minus 6th power A/cm2 in acid solution and 10 to the minus 12th power A/cm2 in basic solution. The reaction order of the rate determining acidic and basic reactions was determined with regard to (H+) and (OH-). The level of illumination had no effect on the electrochemical behavior of the electrode.

Delduca, B. S.↗