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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on CrO3 by Materials Project

CrO3 crystallizes in the orthorhombic Ama2 space group. The structure is one-dimensional and consists of two CrO3 ribbons oriented in the (0, 0, 1) direction. Cr6+ is bonded to four O2- atoms to form corner-sharing CrO4 tetrahedra. There is two shorter (1.59 Å) and two longer (1.77 Å) Cr–O bond length. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one Cr6+ atom. In the second O2- site, O2- is bonded in a single-bond geometry to one Cr6+ atom. In the third O2- site, O2- is bonded in a bent 150 degrees geometry to two equivalent Cr6+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CrO3 by Materials Project

CrO3 crystallizes in the hexagonal P6_3/mmc space group. The structure is two-dimensional and consists of two CrO3 sheets oriented in the (0, 0, 1) direction. Cr6+ is bonded to five O2- atoms to form corner-sharing CrO5 trigonal bipyramids. There is two shorter (1.71 Å) and three longer (1.98 Å) Cr–O bond length. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one Cr6+ atom. In the second O2- site, O2- is bonded in a trigonal planar geometry to three equivalent Cr6+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CrO3 by Materials Project

CrO3 is alpha Rhenium trioxide structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Cr6+ is bonded to six equivalent O2- atoms to form corner-sharing CrO6 octahedra. The corner-sharing octahedral tilt angles are 0°. All Cr–O bond lengths are 1.83 Å. O2- is bonded in a linear geometry to two equivalent Cr6+ atoms.

36 MATERIALS SCIENCE↗
NASA NTRS1977

Volatile products from the interaction of KCl(g) with Cr2O3 and LaCrO3 in oxidizing environments

Cooled target collection techniques and high pressure mass spectrometric sampling were used to measure the relative rates of oxidative vaporization and to identify the volatile products emanating from samples of chromia and Mg-doped lanthanum chromite. The materials were exposed to partial pressures of KCl with and without H2O in one atmosphere of slowly flowing oxygen at elevated temperatures. Chromia and fresh samples of lanthanum chromite exhibited enhanced rates of oxidative vaporization upon exposure to these reactants. Mass spectrometric identification showed that the enhancements resulted from the heterogeneous formation of complex molecules of the type KCl sub 1,2,3 CrO3 and KOH sub l,2 CrO3. Lanthanum chromite that had undergone prolonged oxidative vaporization exhibited no enhanced oxidation upon exposure to the reactants.

Kohl, F. J.↗
DOE OSTI2020

Materials Data on VCrO3 by Materials Project

V(CrO3) is Ilmenite-like structured and crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are four inequivalent V3+ sites. In the first V3+ site, V3+ is bonded to six O2- atoms to form VO6 octahedra that share corners with two equivalent VO6 octahedra, corners with seven CrO6 octahedra, edges with three VO6 octahedra, and a faceface with one CrO6 octahedra. The corner-sharing octahedra tilt angles range from 46–60°. There are a spread of V–O bond distances ranging from 2.00–2.10 Å. In the second V3+ site, V3+ is bonded to six O2- atoms to form VO6 octahedra that share corners with two equivalent VO6 octahedra, corners with seven CrO6 octahedra, an edgeedge with one CrO6 octahedra, edges with two equivalent VO6 octahedra, and a faceface with one CrO6 octahedra. The corner-sharing octahedra tilt angles range from 47–61°. There are a spread of V–O bond distances ranging from 2.01–2.10 Å. In the third V3+ site, V3+ is bonded to six O2- atoms to form VO6 octahedra that share a cornercorner with one VO6 octahedra, corners with eight CrO6 octahedra, an edgeedge with one VO6 octahedra, edges with two equivalent CrO6 octahedra, and a faceface with one VO6 octahedra. The corner-sharing octahedra tilt angles range from 47–61°. There are a spread of V–O bond distances ranging from 2.00–2.10 Å. In the fourth V3+ site, V3+ is bonded to six O2- atoms to form VO6 octahedra that share corners with four equivalent CrO6 octahedra, corners with five VO6 octahedra, edges with three CrO6 octahedra, and a faceface with one VO6 octahedra. The corner-sharing octahedra tilt angles range from 47–61°. There are a spread of V–O bond distances ranging from 2.01–2.10 Å. There are four inequivalent Cr3+ sites. In the first Cr3+ site, Cr3+ is bonded to six O2- atoms to form CrO6 octahedra that share corners with two equivalent CrO6 octahedra, corners with seven VO6 octahedra, edges with three CrO6 octahedra, and a faceface with one VO6 octahedra. The corner-sharing octahedra tilt angles range from 46–61°. There are a spread of Cr–O bond distances ranging from 2.01–2.06 Å. In the second Cr3+ site, Cr3+ is bonded to six O2- atoms to form CrO6 octahedra that share corners with two equivalent CrO6 octahedra, corners with seven VO6 octahedra, an edgeedge with one VO6 octahedra, edges with two equivalent CrO6 octahedra, and a faceface with one VO6 octahedra. The corner-sharing octahedra tilt angles range from 47–61°. There are a spread of Cr–O bond distances ranging from 2.01–2.06 Å. In the third Cr3+ site, Cr3+ is bonded to six O2- atoms to form CrO6 octahedra that share corners with four equivalent VO6 octahedra, corners with five CrO6 octahedra, edges with three VO6 octahedra, and a faceface with one CrO6 octahedra. The corner-sharing octahedra tilt angles range from 46–61°. There are a spread of Cr–O bond distances ranging from 2.01–2.07 Å. In the fourth Cr3+ site, Cr3+ is bonded to six O2- atoms to form CrO6 octahedra that share a cornercorner with one CrO6 octahedra, corners with eight VO6 octahedra, an edgeedge with one CrO6 octahedra, edges with two equivalent VO6 octahedra, and a faceface with one CrO6 octahedra. The corner-sharing octahedra tilt angles range from 47–60°. There are a spread of Cr–O bond distances ranging from 2.01–2.07 Å. There are twelve inequivalent O2- sites. In the first O2- site, O2- is bonded to two V3+ and two Cr3+ atoms to form a mixture of distorted edge and corner-sharing OV2Cr2 trigonal pyramids. In the second O2- site, O2- is bonded to two V3+ and two Cr3+ atoms to form a mixture of distorted edge and corner-sharing OV2Cr2 trigonal pyramids. In the third O2- site, O2- is bonded to one V3+ and three Cr3+ atoms to form a mixture of distorted edge and corner-sharing OVCr3 trigonal pyramids. In the fourth O2- site, O2- is bonded to two V3+ and two Cr3+ atoms to form a mixture of distorted edge and corner-sharing OV2Cr2 trigonal pyramids. In the fifth O2- site, O2- is bonded to two V3+ and two Cr3+ atoms to form distorted OV2Cr2 trigonal pyramids that share corners with twelve OV2Cr2 trigonal pyramids and edges with four OV3Cr trigonal pyramids. In the sixth O2- site, O2- is bonded to two V3+ and two Cr3+ atoms to form distorted OV2Cr2 trigonal pyramids that share corners with twelve OV2Cr2 trigonal pyramids and edges with four OVCr3 trigonal pyramids. In the seventh O2- site, O2- is bonded to three V3+ and one Cr3+ atom to form a mixture of distorted edge and corner-sharing OV3Cr trigonal pyramids. In the eighth O2- site, O2- is bonded to one V3+ and three Cr3+ atoms to form a mixture of distorted edge and corner-sharing OVCr3 trigonal pyramids. In the ninth O2- site, O2- is bonded to two V3+ and two Cr3+ atoms to form distorted OV2Cr2 trigonal pyramids that share corners with twelve OV2Cr2 trigonal pyramids and edges with four OV3Cr trigonal pyramids. In the tenth O2- site, O2- is bonded to three V3+ and one Cr3+ atom to form a mixture of distorted edge and corner-sharing OV3Cr trigonal pyramids. In the eleventh O2- site, O2- is bonded to two V3+ and two Cr3+ atoms to form distorted OV2Cr2 trigonal pyramids that share corners with twelve OV2Cr2 trigonal pyramids and edges with four OV3Cr trigonal pyramids. In the twelfth O2- site, O2- is bonded to two V3+ and two Cr3+ atoms to form a mixture of distorted edge and corner-sharing OV2Cr2 trigonal pyramids.

36 MATERIALS SCIENCE↗
NASA NTRS1974

Oxidation behavior of TD-NiCr in a dynamic high temperature environment

The oxidation behavior of TD-NiCr has been studied in static and high-speed flowing air environments at 1100 and 1200 C. It has been found that the stable oxide morphologies formed on the specimens exposed to the static and dynamic environments were markedly different. The faceted crystal morphology characteristic of static oxidation was found to be unstable under high-temperature, high-speed flow conditions and was quickly replaced by a porous NiO 'mushroom' type structure. Also, it was found that the rate of formation of CrO3 from Cr2O3 was greatly enhanced by high gas velocity conditions. The stability of Cr2-O3 was found to be greatly improved by the presence of an outer NiO layer, even though the NiO layer was very porous. An oxidation model is proposed to explain the observed microstructures and overall oxidation behavior of TD-NiCr alloys.

Tenney, D. R.↗
NASA NTRS1974

Investigation of the oxidation behavior of dispersion stabilized alloys when exposed to a dynamic high temperature environment

The oxidation behavior of TD-NiCr and TD-NiCrAlY alloys have been studied at 2000 and 2200 F in static and high speed flowing air environments. The TD-NiCrAlY alloys preoxidized to produce an Al2O3 scale on the surface showed good oxidation resistance in both types of environments. The TD-NiCr alloy which had a Cr2O3 oxide scale after preoxidation was found to oxidize more than an order of magnitude faster under the dynamic test conditions than at comparable static test conditions. Although Cr2O3 normally provides good oxidation protection, it was rapidly lost due to formation of volatile CrO3 when exposed to the high speed air stream. The preferred oxide arrangement for the dynamic test consisted of an external layer of NiO with a porous mushroom type morphology, an intermediate duplex layer of NiO and Cr2O3, and a continuous inner layer of Cr2O3 in contact with the alloy substrate. An oxidation model has been developed to explain the observed microstructure and overall oxidation behavior of all alloys.

Tenney, D. R.↗
NASA NTRS1975

Dynamic oxidation behavior of TD-NiCr alloy with different surface pretreatments

Oxidation tests of TD-NiCr alloy with different surface pretreatments were conducted in a Mach-5 arc-jet at 1200 C and 0.002 lb/sec flowing air environment. The mechanisms responsible for the observed oxidation behavior are examined. The presence of atomic oxygen in the air stream plays a significant role in determining the oxidation characteristic of the alloy. The rate of Cr2O3 vaporization by formation of volatile CrO3 is greatly enhanced by the flowing conditions. The typical microstructure of oxides formed in the dynamic tests consists of an external layer of NiO with a porous mushroom-type morphology, an intermediate layer of NiO and Cr2O3 oxide mixture, and a continuous inner layer of Cr2O3 in contact with the Cr-depleted alloy substrate. Three basic processes underlying the formation of mushroom-type NiO are identified and discussed. The oxidation rate is determined by the rate of vaporization of NiO. Surface pretreatment has a significant effect on the oxidation behavior of the alloy in the early stage of oxidation, but becomes less important as exposure time increases. Mechanical polishing induces surface recrystallization, but promotes the concurrence of external growth of NiO and internal oxidation of the alloy in the dynamic atmosphere.

Young, C. T.↗
NASA NTRS1976

Reactions of chromium with gaseous NaCl in an oxygen environment

Target collection techniques and high pressure mass spectrometric sampling have been used to study the formation of volatile chromium-containing species in the reaction of Cr2O3 with O2 and NaCl gases. Experiments were performed at atmospheric pressure as a function of chromium temperature, oxygen pressure, and NaCl gas concentration. The major chromium-containing vapor species were found to be (NaCl)x CrO3 gas, with x = 1,2, and 3, which are products of heterogeneous reactions on the surface. The kinetics indicate first order dependence on oxygen and sodium chloride pressures.

Stearns, C. A.↗
NASA NTRS1983

Interatomic Auger transitions in maximal valent V and Cr compounds

The sensitivity of the intensities of the L(3)M(23)M(45) and L(3)M(45)M(45) Auger transitions toward the 3d character in the valence band has been demonstrated by using argon ion bombardment as a means of in situ reduction for the valence state of V and Cr in their maximal valent compounds. The selected V(5+) and Cr(6+) compounds were V2O5, NH4VO3, K2Cr2O7, K2CrO4, and CrO3. Auger and X-ray photoelectron spectra of fresh samples were obtained, and the samples were then subjected to ion bombardment of various durations. The subsequent spectra were recorded to monitor possible alterations due to the reduction of the cation valence state. The interatomic to intraatomic transitions of the Auger spectra transitions of the Auger spectra were observed dynamically and in situ. In particular, the intensity of the cation L(3)M(23)N(45) transitions was observed to increase dramatically with ion bombardment. The correlation between the interatomic Auger transition and covalency as well as the movements of the 3d electrons are discussed.

Yin, L. I.↗
NASA NTRS1984

Chemical mechanisms and reaction rates for the initiation of hot corrosion of IN-738

Sodium-sulfate-induced hot corrosion of preoxidized IN-738 was studied at 975 C with special emphasis placed on the processes occurring during the long induction period. Thermogravimetric tests were run for predetermined periods of time, and then one set of specimens was washed with water. Chemical analysis of the wash solutions yielded information about water soluble metal salts and residual sulfate. A second set of samples was cross sectioned dry and polished in a nonaqueous medium. Element distributions within the oxide scale were obtained from electron microprobe X-ray micrographs. Evolution of SO was monitored throughout the thermogravimetric tests. Kinetic rate studies were performed for several pertinent processes; appropriate rate constants were obtained from the following chemical reactions: Cr2O3 + 2 Na2SO4(1) + 3/2 O2 yields 2 Na2CrO4(1) + 2 SO3(g)n TiO2 + Na2SO4(1) yields Na2O(TiO2)n + SO3(g)n TiO2 + Na2CrO4(1) yields Na2O(TiO2)n + CrO3(g).

Fryburg, G. C.↗
NASA NTRS1988

Isotopic anomalies of Ne, Xe, and C in meteorites. I - Separation of carriers by density and chemical resistance

The carriers of presolar noble gases were studied by isotopically analyzing 19 separates from the Murray and Murchison C2 chondrites for Ne, Xe, C, and N. It is found that the carriers of Ne-E(H) and Xe-S are resistant to HCl, HF, boiling HClO4, and CrO3-H2SO4, and thus must be either diamond or some resistant carbide or oxide. The carrier of Ne-E(L) may be some form of amorphous carbon with delta C13 of about +340 percent. A new carbon component, C theta, found as 0.2-2-micron inclusions in Murchison spinel, is amorphous and contains little or no noble gas. A new heavy nitrogen component is found which has an abundance of about 1 ppm in the bulk meteorite, combusts at 450-500 C, and may be associated wtih isotopically normal carbon or with C-alpha.

Ming, Tang↗
NASA NTRS1991

Soil emissions of nitric oxide in a seasonally dry tropical forest of Mexico

Soil emissions of NO were measured at the Chamela Biological Station, Mexico, using soil covers and a field apparatus of NO detection based on CrO3 conversion of NO to NO2 and detection of NO2 by chemiluminescence with Luminol. Mean NO fluxes from forest soils ranged from 0.14 to 0.52 ng NO-N/sq cm/hr during the dry season and from 0.73 to 1.27 ng NO-N/sq cm/hr during the wet season. A fertilized floodplain pasture exhibited higher fluxes, but an unfertilized upland pasture, which represents the fastest growing land use in the region, had flux rates similar to the forest sites. Wetting experiments at the end of the dry season caused large pulses of NO flux, equaling 10 percent to 20 percent of the estimated annual NO emissions of 0.5-1.0 kg N/ha from the forest sites. Absence of a forest canopy during the dry season and the first wet season rain probably results in substantial NO(x) export from the forest system that may be important to regional atmospheric chemical processes. Wetting experiments during the wet season and a natural rain event had little or no stimulatory effect on NO flux rates.

Davidson, Eric A.↗
NASA NTRS1992

Visible luminescence from silicon wafers subjected to stain etches

Etching of Si in a variety of solutions is known to cause staining. These stain layers consist of porous material similar to that produced by anodic etching of Si in HF solutions. In this work, photoluminescence peaked in the red from stain-etched Si wafers of different dopant types, concentrations, and orientations produced in solutions of HF:HNO3:H2O was observed. Luminescence is also observed in stain films produced in solutions of NaNO2 in HF, but not in stain films produced in solutions of CrO3 in HF. The luminescence spectra are similar to those reported recently for porous Si films produced by anodic etching in HF solutions. However, stain films are much easier to produce, requiring no special equipment.

Fathauer, R. W.↗
NASA NTRS2003

Compatibility Testing of Polymeric Materials for the Urine Processor Assembly (UPA) of International Space Station (ISS)

In the International Space Station (ISS), astronauts will convert urine into potable water with the Urine Processor Assembly (UPA) by a distillation process. The urine is pre-treated, containing flush water and stabilizers. About 2.5% solids in the urine are concentrated up to 16% brine through distillation. Dynamic mechanical analysis (DMA) in the stress relaxation mode was primarily used to test 15 polymeric UPA materials for compatibility with the pre-treated and brine solutions. There were concerns that chromium trioxide (CrO3), a stabilizer not in the original pre-treat formulation for similar compatibility testing in 2000, could have an adverse effect on these polymers. DMA testing is partially complete for polymeric material samples immersed in the two solutions at room temperature for as long as 200 days. By comparing each material (conditioned and virgin), the stress relaxation modulus (E) was determined for short-term use and predicted for as long as a 10-year use in space. Such a delta E showed a decrease of as much as 79% for a Nylon material, but an increase as much as 454% for a polysulfone material, with increasing immersion time.

Wingard, Charles D.↗