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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on MoO5 by Materials Project

MoO5 crystallizes in the monoclinic P2/m space group. The structure is two-dimensional and consists of two water molecules and one MoO4 sheet oriented in the (0, 1, 0) direction. In the MoO4 sheet, Mo is bonded to six O atoms to form distorted corner-sharing MoO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are a spread of Mo–O bond distances ranging from 1.76–2.22 Å. There are four inequivalent O sites. In the first O site, O is bonded in a linear geometry to two equivalent Mo atoms. In the second O site, O is bonded in a linear geometry to two equivalent Mo atoms. In the third O site, O is bonded in a linear geometry to two equivalent Mo atoms. In the fourth O site, O is bonded in a single-bond geometry to one Mo atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mo2N2O7 by Materials Project

(MoO3)4N2(NO)2 crystallizes in the triclinic P-1 space group. The structure is zero-dimensional and consists of two ammonia molecules, two nitroxyl molecules, and one MoO3 cluster. In the MoO3 cluster, there are two inequivalent Mo6+ sites. In the first Mo6+ site, Mo6+ is bonded to four O2- atoms to form corner-sharing MoO4 tetrahedra. There are a spread of Mo–O bond distances ranging from 1.72–1.93 Å. In the second Mo6+ site, Mo6+ is bonded to four O2- atoms to form corner-sharing MoO4 tetrahedra. There are a spread of Mo–O bond distances ranging from 1.72–1.93 Å. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 150 degrees geometry to two Mo6+ atoms. In the second O2- site, O2- is bonded in a single-bond geometry to one Mo6+ atom. In the third O2- site, O2- is bonded in a single-bond geometry to one Mo6+ atom. In the fourth O2- site, O2- is bonded in a single-bond geometry to one Mo6+ atom. In the fifth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to two Mo6+ atoms. In the sixth O2- site, O2- is bonded in a single-bond geometry to one Mo6+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Fe(MoO5)2 by Materials Project

Fe(MoO5)2 crystallizes in the triclinic P-1 space group. The structure is one-dimensional and consists of one Fe(MoO5)2 ribbon oriented in the (0, 1, 0) direction. there are two inequivalent Mo sites. In the first Mo site, Mo is bonded to four O atoms to form MoO4 tetrahedra that share corners with two equivalent FeO6 octahedra. The corner-sharing octahedra tilt angles range from 13–33°. There are a spread of Mo–O bond distances ranging from 1.72–1.94 Å. In the second Mo site, Mo is bonded in a 5-coordinate geometry to five O atoms. There are a spread of Mo–O bond distances ranging from 1.70–2.15 Å. Fe is bonded to six O atoms to form distorted FeO6 octahedra that share corners with two equivalent MoO4 tetrahedra and an edgeedge with one FeO6 octahedra. There are a spread of Fe–O bond distances ranging from 1.85–2.21 Å. There are ten inequivalent O sites. In the first O site, O is bonded in a water-like geometry to two equivalent Fe atoms. In the second O site, O is bonded in a single-bond geometry to one Fe atom. In the third O site, O is bonded in a bent 150 degrees geometry to one Mo and one Fe atom. In the fourth O site, O is bonded in a single-bond geometry to one Mo atom. In the fifth O site, O is bonded in a linear geometry to one Mo and one Fe atom. In the sixth O site, O is bonded in a bent 150 degrees geometry to two Mo atoms. In the seventh O site, O is bonded in a 2-coordinate geometry to one Mo and one O atom. The O–O bond length is 1.37 Å. In the eighth O site, O is bonded in a distorted L-shaped geometry to one Mo and one O atom. In the ninth O site, O is bonded in a bent 150 degrees geometry to one Mo and one Fe atom. In the tenth O site, O is bonded in a single-bond geometry to one Mo atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on KLiMoO4 by Materials Project

LiKMoO4 crystallizes in the hexagonal P6_3mc space group. The structure is three-dimensional. K1+ is bonded in a trigonal planar geometry to three equivalent O2- atoms. All K–O bond lengths are 3.47 Å. Li1+ is bonded to four O2- atoms to form LiO4 tetrahedra that share corners with four equivalent MoO4 tetrahedra. There is three shorter (1.89 Å) and one longer (1.94 Å) Li–O bond length. Mo6+ is bonded to four O2- atoms to form MoO4 tetrahedra that share corners with four equivalent LiO4 tetrahedra. There is three shorter (1.79 Å) and one longer (1.80 Å) Mo–O bond length. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a linear geometry to three equivalent K1+, one Li1+, and one Mo6+ atom. In the second O2- site, O2- is bonded in a linear geometry to one Li1+ and one Mo6+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on SnMoH6(CO2)2 by Materials Project

MoSnH6(CO2)2 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Mo6+ is bonded to four O2- atoms to form MoO4 tetrahedra that share corners with four equivalent SnC2O4 octahedra. The corner-sharing octahedra tilt angles range from 0–31°. There are a spread of Mo–O bond distances ranging from 1.77–1.81 Å. Sn4+ is bonded to two C4- and four O2- atoms to form SnC2O4 octahedra that share corners with four equivalent MoO4 tetrahedra. There are one shorter (2.12 Å) and one longer (2.13 Å) Sn–C bond lengths. There are a spread of Sn–O bond distances ranging from 2.14–2.57 Å. There are two inequivalent C4- sites. In the first C4- site, C4- is bonded in a distorted trigonal non-coplanar geometry to one Sn4+ and three H1+ atoms. All C–H bond lengths are 1.09 Å. In the second C4- site, C4- is bonded in a distorted trigonal non-coplanar geometry to one Sn4+ and three H1+ atoms. There is two shorter (1.09 Å) and one longer (1.10 Å) C–H bond length. There are four inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one C4- atom. In the second H1+ site, H1+ is bonded in a single-bond geometry to one C4- atom. In the third H1+ site, H1+ is bonded in a single-bond geometry to one C4- atom. In the fourth H1+ site, H1+ is bonded in a single-bond geometry to one C4- atom. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 150 degrees geometry to one Mo6+ and one Sn4+ atom. In the second O2- site, O2- is bonded in a linear geometry to one Mo6+ and one Sn4+ atom. In the third O2- site, O2- is bonded in a distorted linear geometry to one Mo6+ and one Sn4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MoPb5O8 by Materials Project

Pb5O4(MoO4) crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are two inequivalent Mo6+ sites. In the first Mo6+ site, Mo6+ is bonded in a tetrahedral geometry to four O2- atoms. There are a spread of Mo–O bond distances ranging from 1.80–1.82 Å. In the second Mo6+ site, Mo6+ is bonded in a tetrahedral geometry to four O2- atoms. There are a spread of Mo–O bond distances ranging from 1.79–1.81 Å. There are ten inequivalent Pb2+ sites. In the first Pb2+ site, Pb2+ is bonded in a 5-coordinate geometry to five O2- atoms. There are a spread of Pb–O bond distances ranging from 2.24–3.00 Å. In the second Pb2+ site, Pb2+ is bonded in a 5-coordinate geometry to five O2- atoms. There are a spread of Pb–O bond distances ranging from 2.22–3.20 Å. In the third Pb2+ site, Pb2+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Pb–O bond distances ranging from 2.29–3.05 Å. In the fourth Pb2+ site, Pb2+ is bonded in a 3-coordinate geometry to three O2- atoms. All Pb–O bond lengths are 2.31 Å. In the fifth Pb2+ site, Pb2+ is bonded in a 5-coordinate geometry to five O2- atoms. There are a spread of Pb–O bond distances ranging from 2.35–2.92 Å. In the sixth Pb2+ site, Pb2+ is bonded in a 5-coordinate geometry to four O2- atoms. There are a spread of Pb–O bond distances ranging from 2.30–2.70 Å. In the seventh Pb2+ site, Pb2+ is bonded in a 5-coordinate geometry to five O2- atoms. There are a spread of Pb–O bond distances ranging from 2.28–2.97 Å. In the eighth Pb2+ site, Pb2+ is bonded in a 5-coordinate geometry to five O2- atoms. There are a spread of Pb–O bond distances ranging from 2.27–3.01 Å. In the ninth Pb2+ site, Pb2+ is bonded in a 5-coordinate geometry to four O2- atoms. There are a spread of Pb–O bond distances ranging from 2.36–2.46 Å. In the tenth Pb2+ site, Pb2+ is bonded in a 4-coordinate geometry to four O2- atoms. There are a spread of Pb–O bond distances ranging from 2.37–2.46 Å. There are sixteen inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Mo6+ and one Pb2+ atom. In the second O2- site, O2- is bonded in a distorted single-bond geometry to one Mo6+ and two Pb2+ atoms. In the third O2- site, O2- is bonded in a distorted trigonal planar geometry to three Pb2+ atoms. In the fourth O2- site, O2- is bonded in a single-bond geometry to one Mo6+ and two Pb2+ atoms. In the fifth O2- site, O2- is bonded in a distorted trigonal planar geometry to three Pb2+ atoms. In the sixth O2- site, O2- is bonded to four Pb2+ atoms to form a mixture of edge and corner-sharing OPb4 tetrahedra. In the seventh O2- site, O2- is bonded in a distorted single-bond geometry to one Mo6+ and three Pb2+ atoms. In the eighth O2- site, O2- is bonded in a distorted single-bond geometry to one Mo6+ and two Pb2+ atoms. In the ninth O2- site, O2- is bonded to four Pb2+ atoms to form a mixture of edge and corner-sharing OPb4 tetrahedra. In the tenth O2- site, O2- is bonded to four Pb2+ atoms to form a mixture of distorted edge and corner-sharing OPb4 tetrahedra. In the eleventh O2- site, O2- is bonded to four Pb2+ atoms to form a mixture of distorted edge and corner-sharing OPb4 tetrahedra. In the twelfth O2- site, O2- is bonded to four Pb2+ atoms to form a mixture of edge and corner-sharing OPb4 tetrahedra. In the thirteenth O2- site, O2- is bonded in a distorted single-bond geometry to one Mo6+ and two Pb2+ atoms. In the fourteenth O2- site, O2- is bonded in a 1-coordinate geometry to one Mo6+ and two Pb2+ atoms. In the fifteenth O2- site, O2- is bonded in a distorted single-bond geometry to one Mo6+ and two Pb2+ atoms. In the sixteenth O2- site, O2- is bonded to four Pb2+ atoms to form a mixture of edge and corner-sharing OPb4 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MoH17C5(NO)4 by Materials Project

(MoO4)4(N(CH3)4)2(CN3H6)4C4NH11C4NH9 crystallizes in the triclinic P1 space group. The structure is zero-dimensional and consists of four guanidinium molecules, four molybdenum;tetrahydrate molecules, one tetramethylammonium molecule, one tetramethylammonium molecule, and two tetramethylammonium molecules.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Gd6Mo10O39 by Materials Project

Gd6Mo10O39 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. there are three inequivalent Gd3+ sites. In the first Gd3+ site, Gd3+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Gd–O bond distances ranging from 2.21–2.52 Å. In the second Gd3+ site, Gd3+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Gd–O bond distances ranging from 2.28–2.62 Å. In the third Gd3+ site, Gd3+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Gd–O bond distances ranging from 2.31–2.56 Å. There are five inequivalent Mo6+ sites. In the first Mo6+ site, Mo6+ is bonded in a tetrahedral geometry to four O2- atoms. There are a spread of Mo–O bond distances ranging from 1.76–1.84 Å. In the second Mo6+ site, Mo6+ is bonded in a tetrahedral geometry to four O2- atoms. There are a spread of Mo–O bond distances ranging from 1.78–1.85 Å. In the third Mo6+ site, Mo6+ is bonded in a tetrahedral geometry to four O2- atoms. There are a spread of Mo–O bond distances ranging from 1.78–1.82 Å. In the fourth Mo6+ site, Mo6+ is bonded in a tetrahedral geometry to four O2- atoms. There are a spread of Mo–O bond distances ranging from 1.77–1.84 Å. In the fifth Mo6+ site, Mo6+ is bonded to four O2- atoms to form corner-sharing MoO4 tetrahedra. There is three shorter (1.76 Å) and one longer (1.91 Å) Mo–O bond length. There are twenty inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Gd3+ and one Mo6+ atom. In the second O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Gd3+ and one Mo6+ atom. In the third O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Gd3+ and one Mo6+ atom. In the fourth O2- site, O2- is bonded in a bent 150 degrees geometry to two equivalent Mo6+ atoms. In the fifth O2- site, O2- is bonded in a linear geometry to one Gd3+ and one Mo6+ atom. In the sixth O2- site, O2- is bonded in a bent 150 degrees geometry to one Gd3+ and one Mo6+ atom. In the seventh O2- site, O2- is bonded in a bent 150 degrees geometry to one Gd3+ and one Mo6+ atom. In the eighth O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Gd3+ and one Mo6+ atom. In the ninth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Gd3+ and one Mo6+ atom. In the tenth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Gd3+ and one Mo6+ atom. In the eleventh O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Gd3+ and one Mo6+ atom. In the twelfth O2- site, O2- is bonded in a 3-coordinate geometry to two Gd3+ and one Mo6+ atom. In the thirteenth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Gd3+ and one Mo6+ atom. In the fourteenth O2- site, O2- is bonded in a bent 150 degrees geometry to one Gd3+ and one Mo6+ atom. In the fifteenth O2- site, O2- is bonded in a bent 150 degrees geometry to one Gd3+ and one Mo6+ atom. In the sixteenth O2- site, O2- is bonded in a 1-coordinate geometry to two Gd3+ and one Mo6+ atom. In the seventeenth O2- site, O2- is bonded in a 2-coordinate geometry to one Gd3+ and one Mo6+ atom. In the eighteenth O2- site, O2- is bonded in a 2-coordinate geometry to one Gd3+ and one Mo6+ atom. In the nineteenth O2- site, O2- is bonded in a bent 150 degrees geometry to one Gd3+ and one Mo6+ atom. In the twentieth O2- site, O2- is bonded in a 3-coordinate geometry to two Gd3+ and one Mo6+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mo2O by Materials Project

MoOMo is Fluorite structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Mo is bonded to four equivalent O atoms to form a mixture of corner and edge-sharing MoO4 tetrahedra. All Mo–O bond lengths are 2.42 Å. O is bonded in a body-centered cubic geometry to eight equivalent Mo atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on NaMoC2NO9 by Materials Project

(NaMoC2O9)2N2 crystallizes in the monoclinic P2_1/c space group. The structure is two-dimensional and consists of four ammonia molecules and one NaMoC2O9 sheet oriented in the (0, 0, 1) direction. In the NaMoC2O9 sheet, Na1+ is bonded in a 5-coordinate geometry to six O2- atoms. There are a spread of Na–O bond distances ranging from 2.29–2.98 Å. Mo6+ is bonded to four O2- atoms to form corner-sharing MoO4 tetrahedra. There are a spread of Mo–O bond distances ranging from 1.73–1.95 Å. There are two inequivalent C4+ sites. In the first C4+ site, C4+ is bonded in a linear geometry to two O2- atoms. There is one shorter (1.17 Å) and one longer (1.18 Å) C–O bond length. In the second C4+ site, C4+ is bonded in a linear geometry to two O2- atoms. There is one shorter (1.17 Å) and one longer (1.18 Å) C–O bond length. There are nine inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one C4+ atom. In the second O2- site, O2- is bonded in a single-bond geometry to one Mo6+ atom. In the third O2- site, O2- is bonded in a linear geometry to one Na1+ and one Mo6+ atom. In the fourth O2- site, O2- is bonded in a bent 120 degrees geometry to two equivalent Mo6+ atoms. In the fifth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Na1+ and one O2- atom. The O–O bond length is 1.29 Å. In the sixth O2- site, O2- is bonded in a single-bond geometry to one C4+ atom. In the seventh O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Na1+ and one O2- atom. In the eighth O2- site, O2- is bonded in a distorted single-bond geometry to two equivalent Na1+ and one C4+ atom. In the ninth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Na1+ and one C4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CsThMo2ClO8 by Materials Project

CsTh(MoO4)2Cl crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. Cs1+ is bonded in a 9-coordinate geometry to five O2- and four equivalent Cl1- atoms. There are a spread of Cs–O bond distances ranging from 3.13–3.67 Å. There are a spread of Cs–Cl bond distances ranging from 3.53–3.71 Å. Th4+ is bonded in a 8-coordinate geometry to seven O2- and one Cl1- atom. There are a spread of Th–O bond distances ranging from 2.40–2.45 Å. The Th–Cl bond length is 2.84 Å. There are two inequivalent Mo6+ sites. In the first Mo6+ site, Mo6+ is bonded in a tetrahedral geometry to four O2- atoms. There are a spread of Mo–O bond distances ranging from 1.79–1.81 Å. In the second Mo6+ site, Mo6+ is bonded in a tetrahedral geometry to four O2- atoms. There are a spread of Mo–O bond distances ranging from 1.74–1.83 Å. There are eight inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Cs1+, one Th4+, one Mo6+, and one Cl1- atom. The O–Cl bond length is 3.19 Å. In the second O2- site, O2- is bonded in a 1-coordinate geometry to one Cs1+, one Th4+, one Mo6+, and one Cl1- atom. The O–Cl bond length is 3.44 Å. In the third O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Cs1+, one Th4+, one Mo6+, and two equivalent Cl1- atoms. There are one shorter (3.46 Å) and one longer (3.61 Å) O–Cl bond lengths. In the fourth O2- site, O2- is bonded in a 2-coordinate geometry to one Cs1+, one Th4+, one Mo6+, and one Cl1- atom. The O–Cl bond length is 3.17 Å. In the fifth O2- site, O2- is bonded in a single-bond geometry to one Cs1+, one Mo6+, and one Cl1- atom. The O–Cl bond length is 3.30 Å. In the sixth O2- site, O2- is bonded in a distorted linear geometry to one Th4+ and one Mo6+ atom. In the seventh O2- site, O2- is bonded in a distorted linear geometry to one Th4+ and one Mo6+ atom. In the eighth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Th4+ and one Mo6+ atom. Cl1- is bonded in a 1-coordinate geometry to four equivalent Cs1+, one Th4+, and six O2- atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cs3Mo2BrO7 by Materials Project

Cs3Mo2O7Br crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. there are two inequivalent Cs1+ sites. In the first Cs1+ site, Cs1+ is bonded in a 10-coordinate geometry to nine O2- and one Br1- atom. There are a spread of Cs–O bond distances ranging from 3.30–3.47 Å. The Cs–Br bond length is 3.46 Å. In the second Cs1+ site, Cs1+ is bonded in a 12-coordinate geometry to six O2- and three equivalent Br1- atoms. There are four shorter (3.35 Å) and two longer (3.36 Å) Cs–O bond lengths. There are two shorter (3.84 Å) and one longer (3.85 Å) Cs–Br bond lengths. Mo6+ is bonded to four O2- atoms to form corner-sharing MoO4 tetrahedra. There is three shorter (1.77 Å) and one longer (1.92 Å) Mo–O bond length. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a linear geometry to two equivalent Mo6+ atoms. In the second O2- site, O2- is bonded in a distorted single-bond geometry to four Cs1+ and one Mo6+ atom. In the third O2- site, O2- is bonded in a distorted single-bond geometry to four Cs1+ and one Mo6+ atom. Br1- is bonded to five Cs1+ atoms to form distorted corner-sharing BrCs5 trigonal bipyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Rb2BiMoPO8 by Materials Project

Rb2Bi(PO4)(MoO4) crystallizes in the orthorhombic Ibca space group. The structure is three-dimensional. Rb1+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Rb–O bond distances ranging from 2.88–3.30 Å. Mo6+ is bonded in a tetrahedral geometry to four O2- atoms. There is two shorter (1.79 Å) and two longer (1.82 Å) Mo–O bond length. Bi3+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Bi–O bond distances ranging from 2.40–2.63 Å. P5+ is bonded in a tetrahedral geometry to four O2- atoms. There is two shorter (1.55 Å) and two longer (1.57 Å) P–O bond length. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a 1-coordinate geometry to three equivalent Rb1+ and one Mo6+ atom. In the second O2- site, O2- is bonded in a distorted single-bond geometry to two equivalent Rb1+, one Bi3+, and one P5+ atom. In the third O2- site, O2- is bonded in a 1-coordinate geometry to two equivalent Rb1+, one Mo6+, and one Bi3+ atom. In the fourth O2- site, O2- is bonded in a distorted single-bond geometry to one Rb1+, two equivalent Bi3+, and one P5+ atom.

36 MATERIALS SCIENCE↗
NASA NTRS1977

Susceptibility to hot corrosion of four nickel-base superalloys, NASA-TRW VIA, B-1900, 713C and IN-738

The susceptibility to hot corrosion of four nickel-base, cast superalloys has been studied at 900 and 1000 C. The test consisted of coating alloy samples with known amounts of Na2SO4 and oxidizing the coated samples isothermally in 1 atmosphere of slowly flowing oxygen, the weight-gain being monitored on a sensitive recording microbalance. Susceptibility to hot corrosion decreased in the order of decreasing molybdenum content of the alloys. Preoxidation of samples before hot-corrosion testing markedly increased the induction period observed prior to the inception of hot corrosion for all alloys tested. X-ray diffraction analyses of the oxide scales were made. All samples that underwent hot corrosion showed the presence of a (Ni,Co)MoO4 layer near the alloy-oxide interface. Several specimens displayed resistance to hot corrosion and these showed NaTaO3 as a prominent feature in their oxide scale. Our results may be interpreted as indicating that molybdenum in an alloy is detrimental, with respect to hot corrosion, while tantalum is beneficial.

Stearns, C. A.↗
DOE OSTI2023

Elucidating the role of $\mathrm{Fe}$-$\mathrm{Mo}$ interactions in the metal oxide precursors for Fe promoted $\mathrm{Mo/ZSM}$-5 catalysts in non-oxidative methane dehydroaromatization

Literature shows that adding Fe as a separate phase to MoO 3 /ZSM-5 catalysts can improve benzene selectivity in methane dehydroaromatization (MDA), but only when added in small quantities, making it difficult to characterize the state of Fe in the catalyst and understand the role of Fe-Mo interactions on the catalytic properties. We explore how the nature of the Mo-Fe interactions in the catalyst precursor can influence the stability and product selectivity in MDA, by employing for the first time Fe 2 (MoO 4 ) 3 /ZSM-5 as a catalyst precursor in MDA. We have compared the activity of Fe 2 (MoO 4 ) 3 /ZSM-5 with monometallic MoO 3 /ZSM-5 and mixed MoO 3 + Fe 2 O 3 /ZSM-5 containing equivalent Mo and Fe loadings and found that Fe 2 (MoO 4 ) 3 /ZSM-5 shows higher benzene selectivity than the mixed MoO 3 + Fe 2 O 3 /ZSM-5 catalyst and exhibits higher stability in reaction compared to the monometallic MoO3/ZSM-5 catalyst. Structural characterization suggests that Fe 2 (MoO 4 ) 3 partially segregates to Fe 2 O 3 and amorphous MoO x during thermal pretreatment. The MoO x species migrate into the zeolite channels during pretreatment, while Fe oxides remain on the external surface of the zeolite. Gas adsorption/desorption techniques and density functional theory calculations demonstrate that the preexisting Fe 2 O 3 phases on the external surface of the zeolite in the mixed MoO 3 + Fe 2 O 3 /ZSM-5 precursor trap (MoO 3 ) 3 clusters preventing them from migrating into the zeolite channels during pretreatment, whereas gradual formation of amorphous MoOx together with the segregation of the Fe 2 O 3 phase when using the Fe 2 (MoO 4 ) 3 precursor diminishes trapping of (MoO 3 ) 3 and consequently enhances migration and anchoring of the MoO x species in the zeolite channels, boosting selectivity to benzene. Characterization of used catalysts suggests that the presence of Fe promotes formation of structured carbon nanofibers which reduce the rate of catalyst deactivation.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗