Experimental investigation of the bonding of sulfur in highly reduced silicate glasses and melts

peer reviewe

Investigation on viscosity and non-isothermal crystallization behavior of P-bearing steelmaking slags with varying TiO2 content

The viscous flow and crystallization behavior of CaO-SiO2-MgO-Al2O3-FetO-P2O5-TiO2 steelmaking slags have been investigated over a wide range of temperatures under Ar (High purity, >99.999 pct) atmosphere, and the relationship between viscosity and structure was determined. The results indicated that the viscosity of the slags slightly decreased with increasing TiO2 content. The constructed nonisothermal continuous cooling transformation (CCT) diagrams revealed that the addition of TiO2 lowered the crystallization temperature. This can mainly be ascribed to that addition of TiO2 promotes the formation of [TiO6]-octahedra units and, consequently, the formation of MgFe2O4-Mg2TiO4 solid solution. Moreover, the decreasing viscosity has a significant effect on enhancing the diffusion of ion units, such as Ca2+ and [TiO4]-tetrahedra, from bulk melts to the crystal–melt interface. The crystallization of CaTiO3 and CaSiTiO5 was consequently accelerated, which can improve the phosphorus content in P-enriched phase (n2CaO·SiO2-3CaO·P2O5). Finally, the nonisothermal crystallization kinetics was characterized and the activation energy for the primary crystal growth was derived such that the activation energy increases from −265.93 to −185.41 KJ·mol−1 with the addition of TiO2 content, suggesting that TiO2 lowered the tendency for the slags to crystallize

Melting Experiments on a Yamato Chondrite

One-atmosphere melting experiments have been carried out on Yamato L6 chondrite 74354 at temperatures 1125°, 1200°and 1275℃ and at Po_2 (oxygen partial pressure) between (10)^ and (10)^ atm. The compositions of olivine, Ca-poor pyroxene, Fe-Ni metal and liquid have been determined as functions of temperature and Po_2; for example, the composition of olivine varies from Fo_ to Fo_ and that of metal varies from Fe_Ni_ to Fe_Ni_6 as Po_2 varies from (10)^ to (10)^ atm at 1125℃, and from Fo_ to Fo_ and from Fe_Ni_ to Fe_Ni_ respectively as temperature varies from 1125°to 1275℃ at (10)^ atm Po_2. Based on these experimental data, Po_2 for equilibration of this chondrite is estimated as about (10)^ atm. The compositions of liquids coexisting with olivine, Ca-poor pyroxene and Fe-Ni metal at Po_2 lower than (10)^ atm are within the compositional ranges of howardite and eucrite, suggesting that chondrites may have a genetical relationship with these basaltic achondrites

Premelting Effects In Minerals - An Experimental-Study

High-temperature calorimetry experiments show that the isobaric heat capacity (C(p)) of minerals increases in an anomalously rapid way when the melting point is approached. These premelting effects can begin a few hundred degrees below the melting point, and they should also be observed for other physical properties such as the thermal expansion, compressibility and sound velocities. Premelting could thus affect the properties of partially molten rocks. In this study, new evidence for diopside (CaMgSi2O6), pseudowollastonite (CaSiO3), anorthite (CaAl2Si2O8), akermanite (Ca2MgSi2O7), Na2SiO3, L2SiO3 and CaMgGeO4 olivine obtained by means of calorimetry, electron microscopy and vibrational spectroscopy, demonstrates that premelting represents unquenchable configurational changes within phases remaining crystalline up to the reported melting points. The enthalpy and entropy effects of premelting are consistent with cation disordering over the various crystallographic sites of the structures. More generally, such temperature-induced cation disordering could be at the roots of intrinsic anharmonicity in oxide and silicate compounds

Nitrogen solubility in molten metal and silicate at high pressure and temperature

International audienceNitrogen is the dominant gas in Earth atmosphere, but its behavior during the Earth' differentiation is poorly known. To aid in identifying the main reservoirs of nitrogen in the Earth, nitrogen solubility was determined experimentally in a mixture of molten CI-chondrite model composition and (Fe, Ni) metal alloy liquid. Experiments were performed in a laser-heated diamond-anvil cell at pressures to 18 GPa and temperatures to 2850 ± 200 K. Multi-anvil experiments were also performed at 5 and 10 GPa and 2390 ± 50 K. The nitrogen content increases with pressure in both metal and silicate reservoirs. It also increases with the iron content of the (Fe, Ni) alloy. Sieverts' formalism successfully describes the nitrogen solubility in metals up to 18 GPa. Henry's law applies to nitrogen-saturated silicate melts up to 4-5 GPa. Independently of these solubility models, it is shown that the partition coefficient of nitrogen between metal and silicate melts changes from almost 104 at ambient pressure to about 10-20 for pressures higher than 1 GPa. The pressure-dependence of the nitrogen partitioning can explain the recently suggested depletion of nitrogen relative to other volatiles in the bulk silicate Earth