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Nash, Barbara P.

Publications and source records attributed to Nash, Barbara P..

4 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Interaction of magnesia-carbon refractory with metallic iron under flash ironmaking conditions

The interaction of a magnesia-carbon refractory with iron under flash ironmaking conditions has been investigated in this work. Oxidation of carbon from the magnesia-carbon refractory took place and the formation of magnesiowustite (Mg x Fe 1-x O) solid solution occurred as a result of the interaction between magnesia (MgO) in the refractory with iron (Fe). A kinetics model for the growth of magnesiowustite (Mg x Fe 1-x O) was developed based on the counterdiffusion of Fe 2+ and Mg 2+ cations through it. Experiments were conducted with iron powder and magnesia-carbon refractory in the temperature range 1200–1400 °C under gas atmospheres relevant to flash ironmaking and analyses of reacted samples using SEM-EDX and EPMA techniques confirmed the formation of magnesiowustite (Mg x Fe 1-x O). Using the kinetics model and the composition profiles determined with EPMA, the values of interdiffusion coefficient ( D ¯ F e - M g ), averaged over the composition range, were calculated. The activation energy ( E a ) for the solid-state diffusion process was determined to be 377 kJ/mol.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Rowleyite, [Na(NH4,K)9Cl4][V25+,4+(P,As)O8]6·n[H2O,Na,NH4,K,Cl], a new mineral with a microporous framework structure

Rowleyite, [Na(NH 4 ,K) 9 Cl 4 ][V 2 5+,4+ (P,As)O 8 ] 6 •n[H 2 O,Na,NH 4 ,K,Cl], is a new mineral species from the Rowley mine, Maricopa County, Arizona, U.S.A. It was found in an unusual low-temperature, apparently post-mining suite of phases that include various vanadates, phosphates, oxalates, and chlorides, some containing NH 4 + . Other secondary minerals found in association with rowleyite are antipinite, fluorite, mimetite, mottramite, quartz, salammoniac, struvite, vanadinite, willemite, wulfenite, and several other potentially new minerals. Analyzed δ 13 C values for the antipinite in association with rowleyite are consistent with a bat guano source. Crystals of rowleyite are very dark brownish green (appearing black) truncated octahedra up to about 50 μm in diameter. The streak is brownish green, the luster is vitreous, very thin fragments are transparent. The Mohs hardness is about 2, the tenacity is brittle, fracture is irregular, there is no cleavage, and the measured density is 2.23(2) g/cm 3 . Rowleyite is optically isotropic with n = 1.715(5).

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗