An occurrence of a fully-oxidized natural titanomaghemite in basalt

Abstract

Titanomaghemite occurs in a relatively fresh doleritic intrusion in an area of Precambrian gneiss in Minas Gerais, Brazil. It hosts exsolution lamellae of ilmenite and contains more than 90% of the iron in the ferric form. It is more resistant to weathering than the ilmenite and is inherited virtually unaltered by the resulting soils. Titanomaghemite, extracted as grains from a weathered rind of the rock, has lattice parameter a0 = 0.8348(3)nm and has a canted spin structure due to substitution of non-magnetic ions on tetrahedral and octahedral sites of the spinel structure. The average canting angle is 32 + 3 ~ and canting occurs predominantly on the octahedral iron sublattice. Its formula, based on microprobe analysis and M6ssbauer spectroscopy may be expressed as:

High-temperature erosion behaviour of plasma-sprayed NiCrBSi–graphite coatings

“…According to the earlier observations by Wang et al. that the graphite particles are pushed by solid/liquid phase during solidification towards segregation at certain places in the matrix [13,29-34].

Figure 1 SEM image of the erodent particle.

Figure 2 Cross-section of the NiCrBSi Coating.

Figure 3 EDS mapping of coating with 4 wt-% graphite.

Figure 4 EDS mapping of coating with 8 wt-% graphite.

…”

“…According to the earlier observations by Wang et al that the graphite particles are pushed by solid/liquid phase during solidification towards segregation at certain places in the matrix [13,[29][30][31][32][33][34].…”