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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Ca3V3(CoO6)2 by Materials Project

Ca3V3(CoO6)2 crystallizes in the cubic Ia-3d space group. The structure is three-dimensional. Ca2+ is bonded in a distorted body-centered cubic geometry to eight equivalent O2- atoms. There are four shorter (2.44 Å) and four longer (2.55 Å) Ca–O bond lengths. V+4.67+ is bonded to four equivalent O2- atoms to form VO4 tetrahedra that share corners with four equivalent CoO6 octahedra. The corner-sharing octahedral tilt angles are 50°. All V–O bond lengths are 1.76 Å. Co2+ is bonded to six equivalent O2- atoms to form CoO6 octahedra that share corners with six equivalent VO4 tetrahedra. All Co–O bond lengths are 2.12 Å. O2- is bonded in a 4-coordinate geometry to two equivalent Ca2+, one V+4.67+, and one Co2+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ca(CoP)2 by Materials Project

CaCo2P2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Ca2+ is bonded in a distorted body-centered cubic geometry to eight equivalent P3- atoms. All Ca–P bond lengths are 3.00 Å. Co2+ is bonded to four equivalent P3- atoms to form a mixture of corner and edge-sharing CoP4 tetrahedra. All Co–P bond lengths are 2.24 Å. P3- is bonded in a 9-coordinate geometry to four equivalent Ca2+, four equivalent Co2+, and one P3- atom. The P–P bond length is 2.51 Å.

36 MATERIALS SCIENCE↗
NASA NTRS1988

Air Revitalization Using Superoxides

Pellets made from powder mixtures of potassium superoxide, KO2, and calcium superoxide, Ca(O2)2, proven markedly superior to pellets of pure KO2 for adding O2 to and removing CO2 from atmospheric-pressure flow of humidified CO2 in He. Superoxides used extensively to supply O2 and scrub CO2 in variety of ambient-pressure life-support applications, including portable self-contained breathing apparatuses, spacecraft, and undersea submersible craft.

Wydeven, Theodore↗
NASA NTRS1984

Changes in the High-latitude Ocean as Possible Causes of Atmospheric CO2 Variations

Measurements on air enclosed in old polar ice have indicated that the atmospheric CO2 concentration was ca. 50 to 70 ppm lower in late glacial times than during the Holocene. Similar measurements performed on samples from a Greenland ice core, dating ca. 30,000 to 40,000 B.P., and have yielded evidence of several CO2 oscillations with an amplitude of ca. 50 ppm. Each change lasted on the order of a few centuries. A mechanism by which circulation changes in the high-latitude ocean could lead to rapid variations in atmospheric CO2 is proposed. In the Antarctic Ocean a slowing down of the vertical mixing would imply a smaller upward flux of sigma CO2 and nutrients. Assuming constant productivity, sigma CO2 and nutrients would be more completely used which would imply lower CO2 in these high-latitude surface waters. In areas with a warm surface, a slowing down of the circulation would not have a direct impact on CO2 because productivity would automatically decrease by the same factor as the upwelling rate of nutrients. Studies with a simple box model of the ocean-atmosphere system suggest that a suddent decrease by a factor of 2 of the water exchange between the surface and deep sea in high latitudes could lead to a CO2 decrease of ca. 40 to 50 ppm with a time constant of ca. 200 years. Deep-sea sediment studies indicate rapid changes in the high-latitude surface conditions of the North Atlantic and the Antarctic Oceans at the end of the last glaciation. Studies of carbon isotope ratios should help ascertain whether this proposed mechanism was indeed responsible for the CO2 variation.

Siegenthaler, U.↗
DOE OSTI2020

Materials Data on Ca(CoAs)2 by Materials Project

Ca(CoAs)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Ca2+ is bonded in a body-centered cubic geometry to eight equivalent As3- atoms. All Ca–As bond lengths are 3.16 Å. Co2+ is bonded to four equivalent As3- atoms to form a mixture of edge and corner-sharing CoAs4 tetrahedra. All Co–As bond lengths are 2.33 Å. As3- is bonded in a 9-coordinate geometry to four equivalent Ca2+, four equivalent Co2+, and one As3- atom. The As–As bond length is 2.80 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba2CaV2CoF14 by Materials Project

Ba2CaV2CoF14 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. Ba2+ is bonded in a 12-coordinate geometry to twelve F1- atoms. There are a spread of Ba–F bond distances ranging from 2.67–3.29 Å. Ca2+ is bonded in a 8-coordinate geometry to eight F1- atoms. There are a spread of Ca–F bond distances ranging from 2.25–2.62 Å. V3+ is bonded to six F1- atoms to form VF6 octahedra that share corners with two equivalent CoF6 octahedra. The corner-sharing octahedra tilt angles range from 49–53°. There are a spread of V–F bond distances ranging from 1.93–2.03 Å. Co2+ is bonded to six F1- atoms to form CoF6 octahedra that share corners with four equivalent VF6 octahedra. The corner-sharing octahedra tilt angles range from 49–53°. There are a spread of Co–F bond distances ranging from 2.02–2.17 Å. There are seven inequivalent F1- sites. In the first F1- site, F1- is bonded in a 2-coordinate geometry to two equivalent Ba2+, one Ca2+, and one V3+ atom. In the second F1- site, F1- is bonded in a distorted bent 120 degrees geometry to two equivalent Ba2+, one V3+, and one Co2+ atom. In the third F1- site, F1- is bonded in a 3-coordinate geometry to one Ba2+, one Ca2+, and one V3+ atom. In the fourth F1- site, F1- is bonded in a distorted single-bond geometry to three equivalent Ba2+ and one V3+ atom. In the fifth F1- site, F1- is bonded in a distorted trigonal planar geometry to one Ba2+, one Ca2+, and one Co2+ atom. In the sixth F1- site, F1- is bonded in a 1-coordinate geometry to two equivalent Ba2+, one Ca2+, and one V3+ atom. In the seventh F1- site, F1- is bonded in a 2-coordinate geometry to one Ba2+, one V3+, and one Co2+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba2CaFe2CoF14 by Materials Project

Ba2CaFe2CoF14 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. Ba2+ is bonded in a 12-coordinate geometry to twelve F1- atoms. There are a spread of Ba–F bond distances ranging from 2.69–3.27 Å. Ca2+ is bonded in a 8-coordinate geometry to eight F1- atoms. There are a spread of Ca–F bond distances ranging from 2.27–2.61 Å. Fe3+ is bonded to six F1- atoms to form FeF6 octahedra that share corners with two equivalent CoF6 octahedra. The corner-sharing octahedra tilt angles range from 49–55°. There are a spread of Fe–F bond distances ranging from 1.93–2.00 Å. Co2+ is bonded to six F1- atoms to form CoF6 octahedra that share corners with four equivalent FeF6 octahedra. The corner-sharing octahedra tilt angles range from 49–55°. There are a spread of Co–F bond distances ranging from 1.99–2.20 Å. There are seven inequivalent F1- sites. In the first F1- site, F1- is bonded in a distorted single-bond geometry to three equivalent Ba2+ and one Fe3+ atom. In the second F1- site, F1- is bonded in a 3-coordinate geometry to one Ba2+, one Ca2+, and one Co2+ atom. In the third F1- site, F1- is bonded in a 3-coordinate geometry to one Ba2+, one Ca2+, and one Fe3+ atom. In the fourth F1- site, F1- is bonded in a 1-coordinate geometry to two equivalent Ba2+, one Ca2+, and one Fe3+ atom. In the fifth F1- site, F1- is bonded in a 2-coordinate geometry to two equivalent Ba2+, one Fe3+, and one Co2+ atom. In the sixth F1- site, F1- is bonded in a distorted bent 120 degrees geometry to two equivalent Ba2+, one Ca2+, and one Fe3+ atom. In the seventh F1- site, F1- is bonded in a 2-coordinate geometry to one Ba2+, one Fe3+, and one Co2+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ca4ZnCo(Si2O7)2 by Materials Project

Ca4CoZn(Si2O7)2 crystallizes in the tetragonal P-4 space group. The structure is three-dimensional. Ca2+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Ca–O bond distances ranging from 2.40–2.74 Å. Co2+ is bonded to four equivalent O2- atoms to form CoO4 tetrahedra that share corners with four equivalent SiO4 tetrahedra. All Co–O bond lengths are 1.95 Å. Zn2+ is bonded to four equivalent O2- atoms to form ZnO4 tetrahedra that share corners with four equivalent SiO4 tetrahedra. All Zn–O bond lengths are 1.95 Å. Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one CoO4 tetrahedra, a cornercorner with one ZnO4 tetrahedra, and a cornercorner with one SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.62–1.69 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Ca2+ and two equivalent Si4+ atoms. In the second O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Ca2+, one Zn2+, and one Si4+ atom. In the third O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Ca2+, one Co2+, and one Si4+ atom. In the fourth O2- site, O2- is bonded in a 1-coordinate geometry to three equivalent Ca2+ and one Si4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ca2CoC(NO)2 by Materials Project

Ca2CoC(NO)2 crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. Ca2+ is bonded in a 8-coordinate geometry to four equivalent N3- and four equivalent O2- atoms. All Ca–N bond lengths are 2.82 Å. All Ca–O bond lengths are 2.47 Å. Co2+ is bonded in a square co-planar geometry to four equivalent O2- atoms. All Co–O bond lengths are 1.83 Å. C4+ is bonded in a linear geometry to two equivalent N3- atoms. Both C–N bond lengths are 1.25 Å. N3- is bonded in a distorted single-bond geometry to four equivalent Ca2+ and one C4+ atom. O2- is bonded to four equivalent Ca2+ and two equivalent Co2+ atoms to form a mixture of distorted corner, edge, and face-sharing OCa4Co2 octahedra. The corner-sharing octahedral tilt angles are 0°.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Integration of hydrophobic gas diffusion layers for zero-gap electrolyzers to enable highly energy-efficient CO 2 electrolysis to C 2 products

Electrochemical CO 2 reduction (eCO2R) is an attractive route for mitigating global CO 2 emissions while producing value-added chemicals. Ethylene is one product of eCO2R and is an essential industrial precursor with a global market of $230 billion. The large-scale implementation of C 2 H 4 -selective CO 2 electrolyzers remains challenging because of low energy efficiencies. In this work, we develop the design principles necessary for incorporating an expanded polytetrafluoroethylene (ePTFE) electrode into a zero-gap electrolyzer while simultaneously developing an integrated electrical front contact that reduces the ohmic resistances inherent to electrically insulating gas diffusion layers. By co-designing the catalyst layer, gas diffusion medium, and operating conditions for a zero-gap ePTFE gas diffusion electrode (GDE), we achieved a full-cell voltage of 2.5 V at 200 mA cm −2 at 25 cm 2 geometric area cell with Faradaic efficiencies of 48% for ethylene and 40% for ethanol. This work highlights strategies for developing a scalable, stable, and highly energy-efficient eCO2R for C 2 products.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1992

Chemical stability of high-temperature superconductors

A review of the available studies on the chemical stability of the high temperature superconductors (HTS) in various environments was made. The La(1.8)Ba(0.2)CuO4 HTS is unstable in the presence of H2O, CO2, and CO. The YBa2Cu3O(7-x) superconductor is highly susceptible to degradation in different environments, especially water. The La(2-x)Ba(x)CuO4 and Bi-Sr-Ca-Cu-O HTS are relatively less reactive than the YBa2Cu3O(7-x). Processing of YBa2Cu3O(7-x) HTS in purified oxygen, rather than in air, using high purity noncarbon containing starting materials is recommended. Exposure of this HTS to the ambient atmosphere should also be avoided at all stages during processing and storage. Devices and components made out of these oxide superconductors would have to be protected with an impermeable coating of a polymer, glass, or metal to avoid deterioration during use.

Bansal, Narottam P.↗
DOE OSTI2020

Materials Data on Ca2CuH6(CO2)6 by Materials Project

Ca2Cu(HCOO)6 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. Ca2+ is bonded to seven O2- atoms to form distorted CaO7 pentagonal bipyramids that share a cornercorner with one CuO6 octahedra and edges with two equivalent CaO7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 42°. There are a spread of Ca–O bond distances ranging from 2.30–2.65 Å. Cu2+ is bonded to six O2- atoms to form distorted CuO6 octahedra that share corners with two equivalent CaO7 pentagonal bipyramids and edges with two equivalent CuO6 octahedra. There are four shorter (2.01 Å) and two longer (2.56 Å) Cu–O bond lengths. There are three inequivalent C2+ sites. In the first C2+ site, C2+ is bonded in a trigonal planar geometry to one H1+ and two O2- atoms. The C–H bond length is 1.11 Å. There is one shorter (1.25 Å) and one longer (1.29 Å) C–O bond length. In the second C2+ site, C2+ is bonded in a trigonal planar geometry to one H1+ and two O2- atoms. The C–H bond length is 1.11 Å. There is one shorter (1.26 Å) and one longer (1.28 Å) C–O bond length. In the third C2+ site, C2+ is bonded in a trigonal planar geometry to one H1+ and two O2- atoms. The C–H bond length is 1.11 Å. There is one shorter (1.26 Å) and one longer (1.28 Å) C–O bond length. There are three inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one C2+ atom. In the second H1+ site, H1+ is bonded in a single-bond geometry to one C2+ atom. In the third H1+ site, H1+ is bonded in a single-bond geometry to one C2+ atom. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Ca2+ and one C2+ atom. In the second O2- site, O2- is bonded in a 2-coordinate geometry to one Ca2+, one Cu2+, and one C2+ atom. In the third O2- site, O2- is bonded in a 1-coordinate geometry to two equivalent Ca2+ and one C2+ atom. In the fourth O2- site, O2- is bonded in a distorted linear geometry to one Ca2+ and one C2+ atom. In the fifth O2- site, O2- is bonded in a 3-coordinate geometry to two equivalent Ca2+ and one C2+ atom. In the sixth O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent Cu2+ and one C2+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Biomolecular Films for Direct Air Capture of CO 2

Efficient utilization of CO 2 is amongst the most critical cost drivers in algal biomass production in open pond systems. CO 2 delivery costs represent approximately 20% of the final biomass selling price in algal mass cultivation systems. Technologies that enable direct air capture (DAC) of atmospheric CO 2 to decouple algae cultivation from CO 2 point sources thus present an opportunity to improve the economics and resource potential of algal biomass. Current DAC technologies typically employ amine- or caustic-based absorption, demanding significant water and/or energy inputs and incurring substantial capital expenditures. Conversely, bio-based approaches to DAC offer a means to bypass conventional technoeconomic and sustainability hurdles. We integrate recent advances in computational metabolic modeling, algal genetic engineering, algal cultivation, and algal biomass upgrading to enable directed localization and self-assembly of carbonic anhydrase molecular films to gas-liquid interfaces for enhanced CO 2 capture and conversion.

09 BIOMASS FUELS↗
NASA NTRS2013

The Origin of Carbon-bearing Volatiles in Surprise Valley Hot Springs in the Great Basin: Carbon Isotope aud Water Chemistry Characterizations

There are numerous hydrothermal fields within the Great Basin of North America, some of which have been exploited for geothermal resources. With methane and other carbon-bearing compounds being observed, in some cases with high concentrations, however, their origins and formation conditions remain unknown. Thus, studying hydrothermal springs in this area provides us an opportunity to expand our knowledge of subsurface (bio)chemical processes that generate organic compounds in hydrothermal systems, and aid in future development and exploration of potential energy resources as well. While isotope measurement has long been used for recognition of their origins, there are several secondary processes that may generate variations in isotopic compositions: oxidation, re-equilibration of methane and other alkanes with CO2, mixing with compounds of other sources, etc. Therefore, in addition to isotopic analysis, other evidence, including water chemistry and rock compositions, are necessary to identify volatile compounds of different sources. Surprise Valley Hot Springs (SVHS, 41º32'N, 120º5'W), located in a typical basin and range province valley in northeastern California, is a terrestrial hydrothermal spring system of the Great Basin. Previous geophysical studies indicated the presence of clay-rich volcanic and sedimentary rocks of Tertiary age beneath the lava flows in late Tertiary and Quaternary. Water and gas samples were collected for a variety of chemical and isotope composition analyses, including in-situ pH, alkalinity, conductivity, oxidation reduction potential (ORP), major and trace elements, and C and H isotope measurements. Fluids issuing from SVHS can be classified as Na-(Cl)-SO4 type, with the major cation and anion being Na+ and SO4 2-, respectively. Thermodynamic calculation using ORP and major element data indicated that sulfate is the most dominant sulfur species, which is consistent with anion analysis results. Aquifer temperatures at depth estimated by both dissolved SiO2 and Na-K-Ca geothermometers are in the range of 125.0 to 135.4 oC, and higher than the values measured at orifices (77.3 to 90.0 oC). CO2 and homologs of straight chain alkanes (C1-C5) were identified in gas samples. Carbon isotope values of alkanes increase with carbon numbers. The 13C fractionation between CO2 and dissolved inorganic carbon suggests they are out of carbon isotope equilibrium. The hypothesis regarding the formation of carbon-bearing compounds in SVHS may involve two processes: 1) Under high heat flow conditions which are caused by regional faulting and crustal extension, original high molecular weight organic compounds (kerogens) in clay-rich rocks decomposed to generate methane and other alkane homologs. 2) The SVHS area is associated with outflow structures, and distant from the heat source. Anaerobic oxidation of methane (AOM) with sulfate at shallow depth (< 90 oC) is suggested as being responsible for the generation of CO2 in SVHS.

Fu, Qi↗
NASA NTRS2013

The Origin of Carbon-bearing Volatiles in Surprise Valley Hot Springs in the Great Basin: Carbon Isotope and Water Chemistry Characterizations

There are numerous hydrothermal fields within the Great Basin of North America, some of which have been exploited for geothermal resources. With methane and other carbon-bearing compounds being observed, in some cases with high concentrations, however, their origins and formation conditions remain unknown. Thus, studying hydrothermal springs in this area provides us an opportunity to expand our knowledge of subsurface (bio)chemical processes that generate organic compounds in hydrothermal systems, and aid in future development and exploration of potential energy resources as well. While isotope measurement has long been used for recognition of their origins, there are several secondary processes that may generate variations in isotopic compositions: oxidation, re-equilibration of methane and other alkanes with CO2, mixing with compounds of other sources, etc. Therefore, in addition to isotopic analysis, other evidence, including water chemistry and rock compositions, are necessary to identify volatile compounds of different sources. Surprise Valley Hot Springs (SVHS, 41 deg 32'N, 120 deg 5'W), located in a typical basin and range province valley in northeastern California, is a terrestrial hydrothermal spring system of the Great Basin. Previous geophysical studies indicated the presence of clay-rich volcanic and sedimentary rocks of Tertiary age beneath the lava flows in late Tertiary and Quaternary. Water and gas samples were collected for a variety of chemical and isotope composition analyses, including in-situ pH, alkalinity, conductivity, oxidation reduction potential (ORP), major and trace elements, and C and H isotope measurements. Fluids issuing from SVHS can be classified as Na-(Cl)-SO4 type, with the major cation and anion being Na+ and SO4(2-), respectively. Thermodynamic calculation using ORP and major element data indicated that sulfate is the most dominant sulfur species, which is consistent with anion analysis results. Aquifer temperatures at depth estimated by both dissolved SiO2 and Na-K-Ca geothermometers are in the range of 125.0 to 135.4 C, and higher than the values measured at orifices (77.3 to 90.0 C). CO2 and homologs of straight chain alkanes (C1-C5) were identified in gas samples. Carbon isotope values of alkanes increase with carbon numbers. The C-13 fractionation between CO2 and dissolved inorganic carbon suggests they are out of carbon isotope equilibrium. The hypothesis regarding the formation of carbon-bearing compounds in SVHS may involve two processes: 1) Under high heat flow conditions which are caused by regional faulting and crustal extension, original high molecular weight organic compounds (kerogens) in clay-rich rocks decomposed to generate methane and other alkane homologs. 2) The SVHS area is associated with outflow structures, and distant from the heat source. Anaerobic oxidation of methane (AOM) with sulfate at shallow depth (< 90 C) is suggested as being responsible for the generation of CO2 in SVHS.

Fu, Qi↗
DOE OSTI2020

Materials Data on CaV4Co(CuO6)2 by Materials Project

CaCu2CoV4O12 crystallizes in the orthorhombic Immm space group. The structure is three-dimensional. Ca2+ is bonded to twelve O2- atoms to form CaO12 cuboctahedra that share faces with eight equivalent VO6 octahedra. There are a spread of Ca–O bond distances ranging from 2.58–2.63 Å. V+4.50+ is bonded to six O2- atoms to form VO6 octahedra that share corners with six equivalent VO6 octahedra and faces with two equivalent CaO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 37–39°. There is two shorter (1.94 Å) and four longer (1.97 Å) V–O bond length. Co2+ is bonded in a distorted square co-planar geometry to four equivalent O2- atoms. All Co–O bond lengths are 2.02 Å. There are two inequivalent Cu1+ sites. In the first Cu1+ site, Cu1+ is bonded in a square co-planar geometry to four equivalent O2- atoms. All Cu–O bond lengths are 1.97 Å. In the second Cu1+ site, Cu1+ is bonded in a square co-planar geometry to four equivalent O2- atoms. All Cu–O bond lengths are 1.98 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a 3-coordinate geometry to one Ca2+, two equivalent V+4.50+, and one Cu1+ atom. In the second O2- site, O2- is bonded in a 4-coordinate geometry to one Ca2+, two equivalent V+4.50+, and one Co2+ atom. In the third O2- site, O2- is bonded in a 3-coordinate geometry to one Ca2+, two equivalent V+4.50+, and one Cu1+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ca2CoWO6 by Materials Project

Ca2CoWO6 is Orthorhombic Perovskite-derived structured and crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are two inequivalent Ca2+ sites. In the first Ca2+ site, Ca2+ is bonded in a 11-coordinate geometry to eleven O2- atoms. There are a spread of Ca–O bond distances ranging from 2.45–3.10 Å. In the second Ca2+ site, Ca2+ is bonded in a 11-coordinate geometry to eleven O2- atoms. There are a spread of Ca–O bond distances ranging from 2.44–3.10 Å. W6+ is bonded to six O2- atoms to form WO6 octahedra that share corners with six equivalent CoO6 octahedra. The corner-sharing octahedra tilt angles range from 3–8°. There are a spread of W–O bond distances ranging from 1.92–1.97 Å. Co2+ is bonded to six O2- atoms to form CoO6 octahedra that share corners with six equivalent WO6 octahedra. The corner-sharing octahedra tilt angles range from 3–8°. There are a spread of Co–O bond distances ranging from 2.00–2.08 Å. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a 5-coordinate geometry to three Ca2+, one W6+, and one Co2+ atom. In the second O2- site, O2- is bonded in a 5-coordinate geometry to three Ca2+, one W6+, and one Co2+ atom. In the third O2- site, O2- is bonded in a 2-coordinate geometry to four Ca2+, one W6+, and one Co2+ atom. In the fourth O2- site, O2- is bonded in a 4-coordinate geometry to four Ca2+, one W6+, and one Co2+ atom. In the fifth O2- site, O2- is bonded in a 2-coordinate geometry to four Ca2+, one W6+, and one Co2+ atom. In the sixth O2- site, O2- is bonded in a 4-coordinate geometry to four Ca2+, one W6+, and one Co2+ atom.

36 MATERIALS SCIENCE↗
NASA NTRS1986

Utilization of ammonium as a nitrogen source: effects of ambient acidity on growth and nitrogen accumulation by soybean

Dry matter accumulation of plants utilizing NH4+ as the sole nitrogen source generally is less than that of plants receiving NO3- unless acidity of the root-zone is controlled at a pH of about 6.0. To test the hypothesis that the reduction in growth is a consequence of nitrogen stress within the plant in response to effects of increased acidity during uptake of NH4+ by roots, nonnodulated soybean plants (Glycine max [L.] Merr. cv Ransom) were grown for 24 days in flowing nutrient culture containing 1.0 millimolar NH4+ as the nitrogen source. Acidities of the culture solutions were controlled at pH 6.1, 5.1, and 4.1 +/- 0.1 by automatic additions of 0.01 N H2SO4 or Ca(OH)2. Plants were sampled at intervals of 3 to 4 days for determination of dry matter and nitrogen accumulation. Rates of NH4+ uptake per gram root dry weight were calculated from these data. Net CO2 exchange rates per unit leaf area were measured on attached leaves by infrared gas analysis. When acidity of the culture solution was increased from pH 6.1 to 5.1, dry matter and nitrogen accumulation were reduced by about 40% within 14 days. Net CO2 exchange rates per unit leaf area, however, were not affected, and the decreased growth was associated with a reduction in rates of appearance and expansion of new leaves. The uptake rates of NH4+ per gram root were about 25% lower throughout the 24 days at pH 5.1 than at 6.1. A further increase in solution acidity from pH 5.1 to 4.1 resulted in cessation of net dry matter production and appearance of new leaves within 10 days. Net CO2 exchange rates per unit leaf area declined rapidly until all viable leaves had abscised by 18 days. Uptake rates of NH4+, which were initially about 50% lower at pH 4.1 than at 6.1 continued to decline with time of exposure until net uptake ceased at 10 days. Since these responses also are characteristic of the sequence of responses that occur during onset and progression of a nitrogen stress, they corroborate our hypothesis.

NASA Discipline Number 61-10↗