Etude structurale de la phase `Mn₈Si₂C'

Abstract

The crystal structure of the 'MnsSi2C' phase has been determined by single-crystal X-ray diffraction analysis. The lattice constants are a=6.4492 (5), b=6.5187 (7), c=9.944 (2) A, ~=84.709 (8), ,8= 99"588 (8), 7= 119.979 (8) ° and the space group is P1 with 32 atoms in the unit cell. The structure has been determined by direct methods and refined by full-matrix least-squares analysis to a final R of 0" 12, based on 2027 reflexions observed with the diffractometer. The 'MnsSi2C' phase is related to intermetallic complex phases such as Laves phases of the type MgZn2 and belongs to the family of cementite carbides. There are close similarities between the structural arrangement in the MnsSiC phase and 'MnsSi2C' phase but in the latter the presence of a square 'tile' signifies a mixed Mn-Si site. This structure allowed us to interpret the (Mnl_~,Mox)sSi2C and (Mn1_xFe~)aSizC solid solutions and their limits.

Mavlyanovite, Mn5Si3: a new mineral species from a lamproite diatreme, Chatkal Ridge, Uzbekistan

“…Before settling on a fully Mn-Si ordered structure model, we carried out trial refinements sequentially for Mn-Si mixed occupancy on Mn(1), Mn(2) and Si sites, even though synthetic Mn 5 Si 3 has no Mn-Si disorder. A mixed Mn-Si site occurs in the silicicarbide Mn 8 Si 2 C (Spinat et al, 1975). However, these refinements gave standard errors on site occupancies that were larger than the deviations from fully-ordered states, e.g.…”

“…Carbon also occurs in sixfold, trigonalprismatic coordination in silicicarbides (e.g. Spinat et al, 1975). Therefore, it seems probable that the residual electron density at the centre of the Mn(2) 6 octahedron corresponds to a small amount of carbon at this site, although it was not possible to refine a meaningful occupancy, due to correlation with U iso .…”

Structure, phase composition and magnetic properties of Fe–Si–C system due to mechanical activation of Fe–Si alloy in organic liquids

“…The data published point out to the existence of various metastable phases, for example, amorphous [3], bcc [8], orthorhombic [6,7,10], triclinic [2,13], hexagonal [1,11] and cubic ones with the structures of a-and b-Mn type [8]. For many years it had been presuming the existence of iron-silicon carbides; however, the mechanism of formation and the nature of such structural components are have not been understood completely so far.…”

“…The Fe-Si-C alloys are of interest for researchers because of their importance in manufacturing steels and cast-irons [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. The amorphous Fe-Si-C alloys are attractive due to their better mechanical strength, plasticity, corrosion stability and magnetic properties as compared to those of technical cast-iron.…”

Structure, phase composition and magnetic properties of mechanically alloyed and annealed quasibinary Fe(70)Si(x)C(30−x) alloys

“…The variety of metastable Fe-Si-C phases with different compositions and crystal structures [1][2][3][4][5][6][7][8][9][10][11][12][13][14], such as amorphous [2,13], bcc and cubic [3], orthorhombic [4][5][6], triclinic [7,8], and hexagonal [1,9,12] ones, which have been referred to in the literature, is just striking. Furthermore, the information on chemical composition of the compounds formed within this system, namely, Fe 3 SiC, Fe 4 SiC, Fe 10 Si 2 C 2 [10], Fe 10 Si 2 C 3 [1], Fe 8 Si 2 C [7,14], Fe 9 SiC 2 [9], is far from being unambiguous.…”