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At least 307 records · Page 17

Depth profiles of Mn-53 in lunar rocks and soils

Results of measurements of cosmic-ray-produced Mn-53 taken down the length of the Apollo 16 deep drill core are presented. They indicate that the lunar regolith has been unmixed, on a meter scale, for the past 5 million years at the location of this core. The data are in agreement with earlier Mn-53 measurements on the Apollo 15 drill core. Mn-53 activity profiles in 14310, 12002, and 14321 are compared to each other; all three rocks have probably been on the lunar surface long enough to saturate their solar cosmic-ray-produced Mn-53 (half-life = 3.7 m.y.) activity.

Imamura, M.↗

Chemical abundances in Hg-Mn stars

An abundance analysis has been conducted of 21 elements in 21 Hg-Mn, two Si-Cr, and six normal stars using model atmospheres and high-dispersion spectroscopy in the visible and UV. Manganese line strengths imply abundances that correlate well with stellar effective temperature. Within the studied sample of Hg-Mn stars there appears to be no correlation of abundances of any element with projected rotational velocity. Abundances in several Hg-Mn stars show patterns that are probably consistent with diffusion but difficult to reconcile with equilibrium nucleosynthesis. In general, no combination of gross stellar physical parameters is sufficient to characterize the patterns of line strengths observed in Hg-Mb Hg-Mn stars.

Heacox, W. D.↗

Eutectic equilibria in the quaternary system Fe-Cr-Mn-C

The constitution of the quaternary system, Fe-Cr-Mn-C and to a lesser extent of the quinary system, Fe-Cr-Mn-Al-C were examined for in situ composite alloy candidates. Multivariant eutectic compositions were determined from phase equilibria studies wherein M7C3 carbides (approximately 30% by volume) formed from the melt within gamma iron. An extended field of the hexagonal carbide, (Cr, Fe, Mn)7 C3, was found without undergoing transformation to the orthorhombic structure. Increasing stability for this carbide was found for higher ratios of Cr/Fe(+) Cr + Mn. Aluminum additions promoted a ferritic matrix while manganese favored the desired gamma austenitic matrix. In coexistence with the matrix phase, chromium enters preferentially the carbide phase while manganese distributes equally between the gamma matrix and the M7C3 carbide. The composition and lattice parameters of the carbide and matrix phases were determined to establish their respective stabilities.

Nowotny, H.↗

Cosmogenic Mn-53 in meteorites

The distributions of the Mn-53 contents in 106 nonantarctic and 112 antarctic chondrites were analyzed. A correlation analysis of these distributions showed that the correlation coefficient is a maximum r sub max = 0.75 plus or minus 0.03) when the histogram for antarctic chondrites is displaced by 40 plus or minus 8 dpm kg-1Fe towards lower Mn-53 contents. The distribution of Mn-53 saturated contents in nonantarctic ordinary chondrites was investigated as a function of their radiation age (T). It is found that the Mn-53 average content is higher by (21 plus or minus 9)% in H-chondrites with radiation age T approximately 12 Myr than in thse with T 12 Myr. This effect can be attributed to the fact that a considerable proportion of H-chondrites with T 12 Myr originates from a comet or from the objects of Chiron like, with the orbits more inclined to the ecliptic plane and/or more extended, which caused their irradiation by cosmic rays of higher intensity.

Alexeev, V. A.↗

Directional solidification of Bi-Mn alloys using an applied magnetic field

Off-eutectic compositions of Bi-Mn were directionally solidified in applied transverse magnetic fields up to 3 kG, to determine the effects on thermal and solutal convection. Plane front directional solidification of eutectic and near-eutectic Bi-Mn results in a two-phase rodlike morphology consisting of ferromagnetic MnBi rods in a Bi solid solution matrix. Compositions of either side of the eutectic were studied in growth orientations vertically up and down. Temperature gradient was monitored during growth by means of an in-situ thermocouple. For Bi-rich compositions, the magnetic field appeared to increase mixing as determined from thermal, morphological, chemical, and magnetic analyses. For Mn-rich compositions, morphological and chemical analyses suggest some reduction in mixing due to application of the magnetic force. The capability for carrying out directional solidification of Bi-Mn in high longitudinal magnetic fields was established.

Decarlo, J. L.↗

Iron-base superalloys - A phase analysis of the multicomponent system (Fe-Mn-Cr-Mo-Nb-Al-Si-C)

In the course of studies on the iron-rich multicomponent system Fe-Mn-Cr-Mo-Nb-Al-Si-C, work was concentrated on pertinent quinary and six-component combinations namely Fe-Mn-Al-Si-C, Fe-Cr-Al-Si-C and Fe-Mn-Cr-Al-Si-C which had been elaborated at 65, 72, and 80 wt pct Fe. Manganese acts as a strong stabilizer for the cementite carbide. Chromium seems to stabilize the iron aluminide Fe2Al5 which forms in a considerable amount within an alloy of nominal composition Fe(65)Mn(15)Cr(12)Al(5)Si(2)C(1) (percent by weight). Although the Mn3AlC carbide is, like Fe3AlC, a perovskite carbide, manganese does not appear to favor the formation of the perovskite carbide. Because of the relatively low sintering temperature (700 C), for al large portion of the samples equilibria conditions are not always reached.

Gupta, H.↗

V, Cr, and Mn in the earth, moon, EPB, and SPB and the origin of the moon - Experimental studies

The abundances of V, Cr, and Mn inferred for the mantles of the earth and moon decrease in that order and are similar in both mantles (but distinct from those in the mantles of the Eucrite Parent Body and Shergottite Parent Body), suggesting a common origin for the mantles of the earth and the moon. This hypothesis was investigated on the basis of a comparison between the depletions of V, Cr, and Mn in the mantles of the earth and the moon, and the metal/silicate partition coefficients of these elements at 1260 C and 1 bar pressure among a S-bearing metallic liquid, a silicate melt, and a FeNi alloy. It was found that the earth and the moon depletions of V, Cr, and Mn are not correlated with metal/silicate partition coefficients; the V and Cr partitioned into S-rich metallic liquids under reducing conditions more strongly than Mn, consistent with the relative volatilities of these elements. This indicates that the depletion patterns of these elements in the mantles of the earth and moon cannot be attributed primarily to terrestrial core formation.

Drake, Michael J.↗

Near Infrared Luminescence Properties of Mn(5+): Ca5(PO4)3F

We report a spectroscopic investigation of Mn(5+) doped Ca5(PO4)(sub 3)F or FAP. Mn(5+) doped crystals have recently attracted world wide attention for potential solid-state laser applications. Following optical excitation of Mn: FAP with the 600 nm output of a Nd: YAG OPO laser system, we observed a strong near infrared luminescence centered at around 1150 nm. The room temperature luminescence decay time was measured to be approximately 635 microseconds. We attribute the infrared luminescence to the(1)E yields (3)A2 transition of tetrahedrally coordinated Mn5+ ions located in a strong crystal field environment. Absorption, luminescence and lifetime data of Mn: FAP will be presented and discussed.

Davis, Valetta R.↗

Enstatite Meteorites and the Original Heterogeneity of Mn-53 Distribution in the Solar Nebula

We have shown earlier that the relative abundance of radiogenic Cr-53 in bulk ordinary chondrites (approximately 0.48 epsilon) is clearly different from that in the earth-moon system (0 epsilon). The SNC parent body (Mars) is characterized by an intermediate Cr-53 excess (approximately 0.23 epsilon). We have also shown that the Mn-Cr systematics of the howardite-eucrite-diogenite parent body (HED PB, the asteroid Vesta) is consistent with the chondritic Mn/Cr ratio in the bulk HED PB and that it has a Cr-53 excess of approximately 0.5 epsilon units which is within error the same as that of chondrites. It appears that the excesses of Cr-53 in these planets are a function of their present heliocentric distance. The study of some other meteorite classes (angrites, pallasites, primitive achondrites) has shown that their Mn-CR systematics is consistent with that of the ordinary chondrites. The observed gradient in the radiogenic Cr-53 abundances can be explained by a). an early volatility controlled radial Mn/Cr fractionation in the nebula or b). an original heterogeneity of Mn-53. The first assumption, however, requires the Mn/Cr ratios of the bulk Earth and Mars to be considerably lower than the inferred model Mn/Cr ratios for these two planets. For this reason, we suggested that the observed gradient is due to an original radial Mn-53 heterogeneity in the late nebula.

Lugmair, Guenter W.↗

Materials Data on Mn(ReO4)2 by Materials Project

Mn(ReO4)2 crystallizes in the trigonal P-3 space group. The structure is two-dimensional and consists of one Mn(ReO4)2 sheet oriented in the (0, 0, 1) direction. Re7+ is bonded to four O2- atoms to form ReO4 tetrahedra that share corners with three equivalent MnO6 octahedra. The corner-sharing octahedral tilt angles are 15°. There is one shorter (1.73 Å) and three longer (1.76 Å) Re–O bond length. Mn2+ is bonded to six equivalent O2- atoms to form MnO6 octahedra that share corners with six equivalent ReO4 tetrahedra. All Mn–O bond lengths are 2.16 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one Re7+ atom. In the second O2- site, O2- is bonded in a linear geometry to one Re7+ and one Mn2+ atom.

36 MATERIALS SCIENCE↗

Materials Data on Mn(PO3)4 by Materials Project

Mn(PO3)4 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are two inequivalent Mn4+ sites. In the first Mn4+ site, Mn4+ is bonded to six O2- atoms to form MnO6 octahedra that share corners with six PO4 tetrahedra. There are a spread of Mn–O bond distances ranging from 1.93–1.96 Å. In the second Mn4+ site, Mn4+ is bonded to six O2- atoms to form MnO6 octahedra that share corners with six PO4 tetrahedra. There are a spread of Mn–O bond distances ranging from 1.95–2.20 Å. There are four inequivalent P5+ sites. In the first P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share a cornercorner with one MnO6 octahedra and corners with two equivalent PO4 tetrahedra. The corner-sharing octahedral tilt angles are 50°. There are a spread of P–O bond distances ranging from 1.48–1.64 Å. In the second P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share a cornercorner with one MnO6 octahedra and corners with two equivalent PO4 tetrahedra. The corner-sharing octahedral tilt angles are 51°. There are a spread of P–O bond distances ranging from 1.48–1.63 Å. In the third P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two MnO6 octahedra and corners with two equivalent PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 29–47°. There are a spread of P–O bond distances ranging from 1.48–1.61 Å. In the fourth P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two MnO6 octahedra and corners with two equivalent PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 31–46°. There is two shorter (1.51 Å) and two longer (1.60 Å) P–O bond length. There are twelve inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one P5+ atom. In the second O2- site, O2- is bonded in a bent 150 degrees geometry to one Mn4+ and one P5+ atom. In the third O2- site, O2- is bonded in a bent 120 degrees geometry to one Mn4+ and one P5+ atom. In the fourth O2- site, O2- is bonded in a bent 120 degrees geometry to one Mn4+ and one P5+ atom. In the fifth O2- site, O2- is bonded in a bent 120 degrees geometry to two P5+ atoms. In the sixth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Mn4+ and one P5+ atom. In the seventh O2- site, O2- is bonded in a bent 150 degrees geometry to two P5+ atoms. In the eighth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to two P5+ atoms. In the ninth O2- site, O2- is bonded in a bent 120 degrees geometry to two P5+ atoms. In the tenth O2- site, O2- is bonded in a bent 150 degrees geometry to one Mn4+ and one P5+ atom. In the eleventh O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Mn4+ and one P5+ atom. In the twelfth O2- site, O2- is bonded in a single-bond geometry to one P5+ atom.

36 MATERIALS SCIENCE↗

Materials Data on Mn(HO)2 by Materials Project

Mn(OH)2 crystallizes in the monoclinic C2 space group. The structure is two-dimensional and consists of one Mn(OH)2 sheet oriented in the (0, 0, 1) direction. Mn2+ is bonded to six equivalent O2- atoms to form edge-sharing MnO6 octahedra. There are a spread of Mn–O bond distances ranging from 2.20–2.25 Å. H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.98 Å. O2- is bonded in a distorted single-bond geometry to three equivalent Mn2+ and one H1+ atom.

36 MATERIALS SCIENCE↗

Materials Data on Mn(ReO4)2 by Materials Project

Mn(ReO4)2 crystallizes in the trigonal P-3 space group. The structure is two-dimensional and consists of one Mn(ReO4)2 sheet oriented in the (0, 0, 1) direction. Re7+ is bonded to four O2- atoms to form ReO4 tetrahedra that share corners with three equivalent MnO6 octahedra. The corner-sharing octahedral tilt angles are 16°. There is one shorter (1.73 Å) and three longer (1.76 Å) Re–O bond length. Mn2+ is bonded to six equivalent O2- atoms to form MnO6 octahedra that share corners with six equivalent ReO4 tetrahedra. All Mn–O bond lengths are 2.16 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one Re7+ atom. In the second O2- site, O2- is bonded in a distorted linear geometry to one Re7+ and one Mn2+ atom.

36 MATERIALS SCIENCE↗

Materials Data on Mn(PO3)3 by Materials Project

Mn(PO3)3 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are two inequivalent Mn3+ sites. In the first Mn3+ site, Mn3+ is bonded in a 5-coordinate geometry to five O2- atoms. There are a spread of Mn–O bond distances ranging from 1.90–2.11 Å. In the second Mn3+ site, Mn3+ is bonded to six O2- atoms to form distorted MnO6 octahedra that share corners with six PO4 tetrahedra. There are a spread of Mn–O bond distances ranging from 1.92–2.53 Å. There are six inequivalent P5+ sites. In the first P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two equivalent MnO6 octahedra and corners with two PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 44–47°. There are a spread of P–O bond distances ranging from 1.51–1.59 Å. In the second P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share a cornercorner with one MnO6 octahedra and corners with two PO4 tetrahedra. The corner-sharing octahedral tilt angles are 57°. There are a spread of P–O bond distances ranging from 1.50–1.60 Å. In the third P5+ site, P5+ is bonded to four O2- atoms to form corner-sharing PO4 tetrahedra. There are a spread of P–O bond distances ranging from 1.45–1.66 Å. In the fourth P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share a cornercorner with one MnO6 octahedra and corners with two PO4 tetrahedra. The corner-sharing octahedral tilt angles are 45°. There are a spread of P–O bond distances ranging from 1.49–1.62 Å. In the fifth P5+ site, P5+ is bonded to four O2- atoms to form corner-sharing PO4 tetrahedra. There are a spread of P–O bond distances ranging from 1.46–1.65 Å. In the sixth P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two equivalent MnO6 octahedra and corners with two PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 23–50°. There are a spread of P–O bond distances ranging from 1.50–1.60 Å. There are eighteen inequivalent O2- sites. In the first O2- site, O2- is bonded in a 3-coordinate geometry to two Mn3+ and one P5+ atom. In the second O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two P5+ atoms. In the third O2- site, O2- is bonded in a bent 150 degrees geometry to one Mn3+ and one P5+ atom. In the fourth O2- site, O2- is bonded in a bent 120 degrees geometry to two P5+ atoms. In the fifth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to two P5+ atoms. In the sixth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Mn3+ and one P5+ atom. In the seventh O2- site, O2- is bonded in a 2-coordinate geometry to one Mn3+ and one P5+ atom. In the eighth O2- site, O2- is bonded in a single-bond geometry to one P5+ atom. In the ninth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Mn3+ and one P5+ atom. In the tenth O2- site, O2- is bonded in a bent 150 degrees geometry to one Mn3+ and one P5+ atom. In the eleventh O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Mn3+ and one P5+ atom. In the twelfth O2- site, O2- is bonded in a bent 120 degrees geometry to two P5+ atoms. In the thirteenth O2- site, O2- is bonded in a bent 150 degrees geometry to two P5+ atoms. In the fourteenth O2- site, O2- is bonded in a single-bond geometry to one P5+ atom. In the fifteenth O2- site, O2- is bonded in a bent 120 degrees geometry to one Mn3+ and one P5+ atom. In the sixteenth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Mn3+ and one P5+ atom. In the seventeenth O2- site, O2- is bonded in a bent 150 degrees geometry to two P5+ atoms. In the eighteenth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Mn3+ and one P5+ atom.

36 MATERIALS SCIENCE↗

Materials Data on Mn(CO3)2 by Materials Project

Mn(CO3)2 crystallizes in the monoclinic P2_1/c space group. The structure is two-dimensional and consists of one Mn(CO3)2 sheet oriented in the (1, 0, 0) direction. Mn4+ is bonded in an octahedral geometry to six O2- atoms. There are a spread of Mn–O bond distances ranging from 1.93–1.99 Å. C4+ is bonded in a trigonal planar geometry to three O2- atoms. There is one shorter (1.28 Å) and two longer (1.30 Å) C–O bond length. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in an L-shaped geometry to one Mn4+ and one C4+ atom. In the second O2- site, O2- is bonded in an L-shaped geometry to one Mn4+ and one C4+ atom. In the third O2- site, O2- is bonded in a bent 120 degrees geometry to one Mn4+ and one C4+ atom.

36 MATERIALS SCIENCE↗

Materials Data on Mn(CoO3)2 by Materials Project

Mn(CoO3)2 is trigonal omega-derived structured and crystallizes in the monoclinic C2/m space group. The structure is two-dimensional and consists of one Mn(CoO3)2 sheet oriented in the (2, 0, -1) direction. Mn7+ is bonded to six O2- atoms to form MnO6 octahedra that share edges with two equivalent MnO6 octahedra and edges with four equivalent CoO6 octahedra. There is four shorter (1.93 Å) and two longer (1.94 Å) Mn–O bond length. Co+2.50+ is bonded to six O2- atoms to form CoO6 octahedra that share edges with two equivalent MnO6 octahedra and edges with four equivalent CoO6 octahedra. There are a spread of Co–O bond distances ranging from 1.88–1.90 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to one Mn7+ and two equivalent Co+2.50+ atoms. In the second O2- site, O2- is bonded in a distorted T-shaped geometry to two equivalent Mn7+ and one Co+2.50+ atom. In the third O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to three equivalent Co+2.50+ atoms.

36 MATERIALS SCIENCE↗

Materials Data on Mn(IO3)2 by Materials Project

Mn(IO3)2 crystallizes in the orthorhombic Pbcn space group. The structure is one-dimensional and consists of two Mn(IO3)2 ribbons oriented in the (1, 0, 0) direction. Mn2+ is bonded to six O2- atoms to form edge-sharing MnO6 octahedra. There are a spread of Mn–O bond distances ranging from 2.18–2.27 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Mn2+ and one I5+ atom. The O–I bond length is 1.87 Å. In the second O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Mn2+ and one I5+ atom. The O–I bond length is 1.85 Å. In the third O2- site, O2- is bonded in a distorted single-bond geometry to one I5+ atom. The O–I bond length is 1.82 Å. I5+ is bonded in a 3-coordinate geometry to three O2- atoms.

36 MATERIALS SCIENCE↗

Materials Data on Mn(ZnN)2 by Materials Project

Mn(ZnN)2 crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are two inequivalent Mn2+ sites. In the first Mn2+ site, Mn2+ is bonded in a distorted trigonal planar geometry to three N3- atoms. There are a spread of Mn–N bond distances ranging from 1.87–1.97 Å. In the second Mn2+ site, Mn2+ is bonded in a distorted trigonal planar geometry to three N3- atoms. There is two shorter (1.87 Å) and one longer (1.96 Å) Mn–N bond length. There are four inequivalent Zn2+ sites. In the first Zn2+ site, Zn2+ is bonded in a trigonal non-coplanar geometry to three N3- atoms. There are two shorter (2.02 Å) and one longer (2.10 Å) Zn–N bond lengths. In the second Zn2+ site, Zn2+ is bonded in a trigonal non-coplanar geometry to three N3- atoms. There are two shorter (2.02 Å) and one longer (2.10 Å) Zn–N bond lengths. In the third Zn2+ site, Zn2+ is bonded to four N3- atoms to form a mixture of corner and edge-sharing ZnN4 trigonal pyramids. There are a spread of Zn–N bond distances ranging from 1.97–2.54 Å. In the fourth Zn2+ site, Zn2+ is bonded to four N3- atoms to form a mixture of corner and edge-sharing ZnN4 trigonal pyramids. There are a spread of Zn–N bond distances ranging from 1.97–2.55 Å. There are four inequivalent N3- sites. In the first N3- site, N3- is bonded in a 5-coordinate geometry to one Mn2+ and four Zn2+ atoms. In the second N3- site, N3- is bonded in a 5-coordinate geometry to one Mn2+ and four Zn2+ atoms. In the third N3- site, N3- is bonded to two Mn2+ and three Zn2+ atoms to form a mixture of corner and edge-sharing NMn2Zn3 trigonal bipyramids. In the fourth N3- site, N3- is bonded to two Mn2+ and three Zn2+ atoms to form a mixture of corner and edge-sharing NMn2Zn3 trigonal bipyramids.

36 MATERIALS SCIENCE↗