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12 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Hot corrosion of Co-Cr, Co-Cr-Al, and Ni-Cr alloys in the temperature range of 700-750 deg C

The effect of SO3 pressure in the gas phase on the Na2SO4 induced hot corrosion of Co-Cr, Ni-Cr, and Co-Cr-Al alloys was studied in the temperature range 700 to 750 C. The degradation of the Co-Cr and Ni-Cr alloys was found to be associated with the formation of liquid mixed sulfates (CoSO4-Na2SO4 or NiSO4-Na2SO4) which provided a selective dissolution of the Co or Ni and a subsequent sulfidation oxidation mode of attack which prevented the maintenance of a protective Cr2O3 film. A clear mechanism was not developed for the degradation of Co-Cr-Al alloys. A pitting corrosion morphology was induced by a number of different mechanisms.

Chiang, K. T.↗
NASA NTRS1972

Mechanisms of oxidation in the Co-Cr system.

Oxidation has been studied both as a function of temperature in the range from 900 to 1300 C and of the partial pressure of oxygen in the range from 0.05 to 760 torr. In addition, microstructures of oxide scales have been studied and characterized in more detail utilizing metallographic and X-ray techniques combined with electron microprobe analysis. The parabolic rate constants in 1100 C and at 100 and 10 torr oxygen are presented in a graph as a function of chromium content. Three main different mechanisms of oxidation in the Co-Cr system have been identified. In two of these, the rate determining process controlling the oxidation is the solid state diffusion of cobalt through the oxide CoO. The rate controlling process governing the oxidation for the third mechanism is chromium diffusion in dichromium trioxide.

Kofstad, P. K.↗
NASA NTRS1983

Low temperature hot corrosion

The reaction of Co-Cr, Ni-Cr, Co-Cr-Al, and Ni-Cr-Al alloys with Na2SO4 in the presence of SO3 at temperatures between 700 and 750 C leads to the formation of liquid CoSO4-Na2SO4 or NiSO4-Na2SO4 deposits on the alloy surface. The formation of Cr2O3 and/or Al2O3 below this deposit results in a locally low P(O2) and a higher P(S2) and P(SO2). It is noted that these conditions can prevent protective oxide formation either by sulfide formation in the alloy, which localizes the Cr and/or Al in discrete particles, or by acid fluxing involving a reaction between Al2O3 or Cr2O3 and SO2 to form a salt-soluble species and subsequent reprecipitation as porous oxides in regions of higher P(O2). These processes may occur simultaneously, although a given alloy generally exhibits features of predominantly one type. Here, the Ni-Cr and Ni-Cr-Al alloys, and to some extent the Co-Cr alloys, exhibit features indicative of the sulfidation mechanism, whereas the morphology for the Co-Cr-Al alloy is more consistent with a predominant acid fluxing mechanism.

Chiang, K. T.↗
DOE OSTI2023

Toward Carbon Monoxide Methanation at Mild Conditions on Dual-Site Catalysts

The catalytic carbon monoxide (CO) methanation is an ideal model reaction for the fundamental understanding of catalysis on the gas–solid interface and is crucial for various industrial processes. However, the harsh operating conditions make the reaction unsustainable, and the limitations set by the scaling relations between the dissociation energy barrier and dissociative binding energy of CO further increase the difficulty in designing high-performance methanation catalysts operating under milder conditions. In this work, we proposed a theoretical strategy to circumvent the limitations elegantly and achieve both facile CO dissociation and C/O hydrogenation on the catalyst containing a confined dual site. The DFT-based microkinetic modeling (MKM) reveals that the designed Co-Cr 2 /G dual-site catalyst could provide 4–6 orders of magnitude higher turnover frequency for CH 4 production than the cobalt step sites. We believe that the proposed strategy in the current work will provide essential guidance for designing state-of-the-art methanation catalysts under mild conditions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Materials Data on CrCo3 by Materials Project

Co3Cr is Uranium Silicide structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Cr is bonded to twelve equivalent Co atoms to form CrCo12 cuboctahedra that share corners with twelve equivalent CrCo12 cuboctahedra, edges with twenty-four equivalent CoCr4Co8 cuboctahedra, faces with six equivalent CrCo12 cuboctahedra, and faces with twelve equivalent CoCr4Co8 cuboctahedra. All Cr–Co bond lengths are 2.46 Å. Co is bonded to four equivalent Cr and eight equivalent Co atoms to form CoCr4Co8 cuboctahedra that share corners with twelve equivalent CoCr4Co8 cuboctahedra, edges with eight equivalent CrCo12 cuboctahedra, edges with sixteen equivalent CoCr4Co8 cuboctahedra, faces with four equivalent CrCo12 cuboctahedra, and faces with fourteen equivalent CoCr4Co8 cuboctahedra. All Co–Co bond lengths are 2.46 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cr3Co by Materials Project

Cr3Co is beta Cu3Ti-like structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. there are three inequivalent Cr sites. In the first Cr site, Cr is bonded to eight Cr and four equivalent Co atoms to form CrCr8Co4 cuboctahedra that share corners with four equivalent CoCr12 cuboctahedra, corners with fourteen CrCr8Co4 cuboctahedra, edges with six equivalent CoCr12 cuboctahedra, edges with twelve CrCr8Co4 cuboctahedra, faces with four equivalent CoCr12 cuboctahedra, and faces with sixteen CrCr8Co4 cuboctahedra. There are a spread of Cr–Cr bond distances ranging from 2.50–2.57 Å. There are two shorter (2.52 Å) and two longer (2.54 Å) Cr–Co bond lengths. In the second Cr site, Cr is bonded to eight Cr and four equivalent Co atoms to form CrCr8Co4 cuboctahedra that share corners with four equivalent CoCr12 cuboctahedra, corners with fourteen CrCr8Co4 cuboctahedra, edges with six equivalent CoCr12 cuboctahedra, edges with twelve CrCr8Co4 cuboctahedra, faces with four equivalent CoCr12 cuboctahedra, and faces with sixteen CrCr8Co4 cuboctahedra. There are a spread of Cr–Cr bond distances ranging from 2.50–2.57 Å. There are two shorter (2.52 Å) and two longer (2.54 Å) Cr–Co bond lengths. In the third Cr site, Cr is bonded to eight Cr and four equivalent Co atoms to form CrCr8Co4 cuboctahedra that share corners with four equivalent CoCr12 cuboctahedra, corners with fourteen CrCr8Co4 cuboctahedra, edges with six equivalent CoCr12 cuboctahedra, edges with twelve CrCr8Co4 cuboctahedra, faces with four equivalent CoCr12 cuboctahedra, and faces with sixteen CrCr8Co4 cuboctahedra. There are two shorter (2.52 Å) and two longer (2.54 Å) Cr–Co bond lengths. Co is bonded to twelve Cr atoms to form CoCr12 cuboctahedra that share corners with six equivalent CoCr12 cuboctahedra, corners with twelve CrCr8Co4 cuboctahedra, edges with eighteen CrCr8Co4 cuboctahedra, faces with eight equivalent CoCr12 cuboctahedra, and faces with twelve CrCr8Co4 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CrCo3 by Materials Project

Co3Cr is beta Cu3Ti-like structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Cr is bonded to twelve Co atoms to form CrCo12 cuboctahedra that share corners with six equivalent CrCo12 cuboctahedra, corners with twelve CoCr4Co8 cuboctahedra, edges with eighteen CoCr4Co8 cuboctahedra, faces with eight equivalent CrCo12 cuboctahedra, and faces with twelve CoCr4Co8 cuboctahedra. There are six shorter (2.46 Å) and six longer (2.50 Å) Cr–Co bond lengths. There are three inequivalent Co sites. In the first Co site, Co is bonded to four equivalent Cr and eight Co atoms to form CoCr4Co8 cuboctahedra that share corners with four equivalent CrCo12 cuboctahedra, corners with fourteen CoCr4Co8 cuboctahedra, edges with six equivalent CrCo12 cuboctahedra, edges with twelve CoCr4Co8 cuboctahedra, faces with four equivalent CrCo12 cuboctahedra, and faces with sixteen CoCr4Co8 cuboctahedra. There are a spread of Co–Co bond distances ranging from 2.45–2.51 Å. In the second Co site, Co is bonded to four equivalent Cr and eight equivalent Co atoms to form CoCr4Co8 cuboctahedra that share corners with four equivalent CrCo12 cuboctahedra, corners with fourteen CoCr4Co8 cuboctahedra, edges with six equivalent CrCo12 cuboctahedra, edges with twelve equivalent CoCr4Co8 cuboctahedra, faces with four equivalent CrCo12 cuboctahedra, and faces with sixteen CoCr4Co8 cuboctahedra. In the third Co site, Co is bonded to four equivalent Cr and eight equivalent Co atoms to form CoCr4Co8 cuboctahedra that share corners with four equivalent CrCo12 cuboctahedra, corners with fourteen CoCr4Co8 cuboctahedra, edges with six equivalent CrCo12 cuboctahedra, edges with twelve equivalent CoCr4Co8 cuboctahedra, faces with four equivalent CrCo12 cuboctahedra, and faces with sixteen CoCr4Co8 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CrCo3 by Materials Project

Co3Cr crystallizes in the hexagonal P-6m2 space group. The structure is three-dimensional. Cr is bonded to six equivalent Cr and six equivalent Co atoms to form CrCr6Co6 cuboctahedra that share corners with six equivalent CrCr6Co6 cuboctahedra, corners with twelve equivalent CoCo12 cuboctahedra, edges with six equivalent CrCr6Co6 cuboctahedra, edges with twelve equivalent CoCr3Co9 cuboctahedra, faces with six equivalent CrCr6Co6 cuboctahedra, and faces with fourteen CoCo12 cuboctahedra. All Cr–Cr bond lengths are 2.50 Å. All Cr–Co bond lengths are 2.46 Å. There are two inequivalent Co sites. In the first Co site, Co is bonded to twelve Co atoms to form CoCo12 cuboctahedra that share corners with six equivalent CoCo12 cuboctahedra, corners with twelve equivalent CrCr6Co6 cuboctahedra, edges with eighteen CoCo12 cuboctahedra, faces with two equivalent CrCr6Co6 cuboctahedra, and faces with eighteen CoCo12 cuboctahedra. There are six shorter (2.47 Å) and six longer (2.50 Å) Co–Co bond lengths. In the second Co site, Co is bonded to three equivalent Cr and nine Co atoms to form CoCr3Co9 cuboctahedra that share corners with eighteen equivalent CoCr3Co9 cuboctahedra, edges with six equivalent CrCr6Co6 cuboctahedra, edges with twelve CoCo12 cuboctahedra, faces with six equivalent CrCr6Co6 cuboctahedra, and faces with fourteen CoCo12 cuboctahedra. All Co–Co bond lengths are 2.50 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cr3Co2 by Materials Project

Cr3Co2 crystallizes in the orthorhombic Cmm2 space group. The structure is three-dimensional. there are seven inequivalent Cr sites. In the first Cr site, Cr is bonded in a 10-coordinate geometry to eight Cr and seven Co atoms. There are a spread of Cr–Cr bond distances ranging from 2.39–2.89 Å. There are a spread of Cr–Co bond distances ranging from 2.57–2.84 Å. In the second Cr site, Cr is bonded in a 11-coordinate geometry to seven Cr and eight Co atoms. There are a spread of Cr–Cr bond distances ranging from 2.37–2.81 Å. There are a spread of Cr–Co bond distances ranging from 2.56–2.84 Å. In the third Cr site, Cr is bonded in a 7-coordinate geometry to six Cr and five Co atoms. There are a spread of Cr–Cr bond distances ranging from 2.29–2.81 Å. There are a spread of Cr–Co bond distances ranging from 2.41–2.67 Å. In the fourth Cr site, Cr is bonded in a 4-coordinate geometry to nine Cr and five Co atoms. There are a spread of Cr–Cr bond distances ranging from 2.33–2.74 Å. There are a spread of Cr–Co bond distances ranging from 2.42–2.70 Å. In the fifth Cr site, Cr is bonded in a 7-coordinate geometry to seven Cr and five Co atoms. Both Cr–Cr bond lengths are 2.25 Å. There are a spread of Cr–Co bond distances ranging from 2.49–2.53 Å. In the sixth Cr site, Cr is bonded in a 2-coordinate geometry to five Cr and seven Co atoms. There are a spread of Cr–Co bond distances ranging from 2.24–2.51 Å. In the seventh Cr site, Cr is bonded in a 7-coordinate geometry to seven Cr and five Co atoms. There are a spread of Cr–Co bond distances ranging from 2.48–2.53 Å. There are five inequivalent Co sites. In the first Co site, Co is bonded to nine Cr and three Co atoms to form a mixture of distorted edge, face, and corner-sharing CoCr9Co3 cuboctahedra. There are a spread of Co–Co bond distances ranging from 2.32–2.51 Å. In the second Co site, Co is bonded to nine Cr and three Co atoms to form a mixture of distorted edge, face, and corner-sharing CoCr9Co3 cuboctahedra. There are a spread of Co–Co bond distances ranging from 2.34–2.48 Å. In the third Co site, Co is bonded to six Cr and six Co atoms to form distorted CoCr6Co6 cuboctahedra that share corners with sixteen CoCr9Co3 cuboctahedra, edges with two equivalent CoCr6Co6 cuboctahedra, and faces with four equivalent CoCr9Co3 cuboctahedra. Both Co–Co bond lengths are 2.55 Å. In the fourth Co site, Co is bonded to eight Cr and four equivalent Co atoms to form CoCr8Co4 cuboctahedra that share corners with sixteen CoCr9Co3 cuboctahedra, edges with two equivalent CoCr8Co4 cuboctahedra, and faces with four equivalent CoCr9Co3 cuboctahedra. In the fifth Co site, Co is bonded in a distorted linear geometry to nine Cr and five Co atoms.

36 MATERIALS SCIENCE↗