Critical evaluation and optimization of the thermodynamic properties and phase diagrams of the MnO-TiO2, MgO-TiO2, FeO-TiO2, Ti2O3-TiO2, Na2O-TiO2, and K2O-TiO2 systems

All available thermodynamic and phase diagram data have been critically assessed for all phases in the MnO-TiO₂, MgO-TiO₂, FeO-TiO₂, Ti₂O₃-TiO₂, Na₂O-TiO₂, and K₂O-TiO₂ systems at 1 bar pressure from 298 K to above the liquidus temperatures. All reliable thermodynamic and phase diagram data have been simultaneously optimized to obtain, for each system, one set of model equations for the Gibbs energy of the liquid slag as a function of composition and temperature and equations for the Gibbs energies of all compounds as functions of temperature. The modified quasichemical model was used for the molten slag phases.     

Thermodynamic optimization of the systems PbO-SiO2, PbO-ZnO, ZnO-SiO2 and PbO-ZnO-SiO2

Liquidus-phase equilibrium data of the present authors for the PbO-ZnO-SiO₂ system, combined with phase equilibrium and thermodynamic data from the literature, were optimized to obtain a self-consistent set of parameters of thermodynamic models for all phases. The modified quasichemical model was used for the liquid slag phase. From these model parameters, the optimized ternary-phase diagram was back-calculated.     

Nitrogen solubility in CaO-SiO2, CaO-MgO-SiO2, and BaO-MgO-SiO2 melts

Nitrogen solubility in molten CaO-SiO₂, CaO-MgO-SiO₂, and BaO-MgO-SiO₂ silicate systems was measured as functions of nitrogen and oxygen partial pressures and composition at 1823 K. Experimental findings indicate that nitrogen exists as a free nitride ion or is associated with silicate networks, depending principally on the slag composition. A special analytical technique was developed to separately determine the two species. Its dissolution mechanism, which is similar to that for hydrogen, was proposed, being supported by the detection of a Si-N bond by infrared spectroscopy. Neither the content of free nor incorporated nitrogen was demonstrated to have a very good correlation with the CaO or SiO₂ activity in the melts, probably because the activity coefficient of nitrogen is affected by the slag composition. Formerly Graduate Student, Department of Metallurgy, The University of Tokyo.     

Determination of standard gibbs energies of formation of CaC2, SrC2, and BaC2

The standard Gibbs energies of formation of CaC₂, SrC₂, and BaC₂ were determined by an equilibration technique at temperatures ranging from 1223 to 1673 K, yielding the following results: Ca (l)+ 2C (s)= CaC₂\GDG\dg = -90,100(\+-500)- 11.0(\+-1.1)T [J/mol]Sr (l) + 2C (s) = SrC₂ (s)\GDG\dg = -104,000(\+-1000) - 8.04(\+-2.76)T [J/mol]BA (l) + 2C(s) = BaC₂ (s)\GDG\dg = -115,000(\+-1000) + 3.53 (\+-1.69)T [J/mol]     

Synthesis and biological activities of 2 beta-chloro-, 2 beta-fluoro-, and 2 beta-methoxy-1 alpha,25-dihydroxyvitamin D3

Using 1 alpha,2 alpha-oxido-cholesta-5,7-diene-3 beta,25-diol (2) as a starting material, the provitamins of calcitriol with an additional 2 beta-chloro-, 2 beta-fluoro-, and 2 beta-methoxy-substituent (3,4,5) are obtained by transdiaxial opening of the oxirane ring with nucleophiles. An efficient irradiation process is described and used for the synthesis of the 2 beta-substituted calcitriols NS2 (2 beta-Cl), NS6 (2 beta-F), and NS7 (2 beta-OCH3). The affinity of these three vitamin D3 derivatives to the vitamin D receptor (VDR) and was determined. These three A-ring derivatives of 1,25(OH)2D3 were further tested for their proliferation-inhibitory and anti-adipogenic activity and gene regulatoric activity in the vitamin D3-sensitive, murine, mesenchymal cell line C3H10T1/2. The VDR-affinity of the 2 beta-chloro derivative, NS2 (2 beta-Cl), was identical to 1,25(OH)2D3 and its vitamin D binding protein (DBP)-affinity was in the range of 1,25(OH)2D3. NS2 inhibited the proliferation of C3H10T1/2(BMP-4)-cells in the presence of fetal calf serum (FCS) 9 times, and, in the absence of FCS, 111 times lower, as compared with 1,25(OH)2D3. The ID50 dose of adipogenesis-inhibition of NS2 was 13 times higher than the ID50 dose of 1,25(OH)2D3. NS6 (2 beta-F) displayed a slightly higher affinity than 1,25(OH)2D3 to the VDR and DBP-affinity. The proliferation-inhibitory activity in the presence of FCS was 90 times higher, as compared with 1,25(OH)2D3. In the FCS-free proliferation assay NS6 displayed an inhibitory activity in the range of 1,25(OH)2D3. NS6 showed an 5 times higher potency to inhibit (pre)adipocyte-differentiation in C3H10T1/2(BMP-4)-cells than 1,25(OH)2D3. NS7 (2 beta-OCH3) showed the lowest VDR-affinity and the highest DBP-affinity of the tested substances, as compared with 1,25(OH)2D3 (11 times lower and 35 times higher respectively). Its proliferation-inhibitory activity in the FCS-free medium was 9 times and in the FCS-containing assay 67 times lower in comparison with 1,25(OH)2D3. A 1250 times higher NS7-dose was needed to reach the anti-adipogenic potency of 1,25(OH)2D3. All tested substances displayed a similar ability to activate a vitamin D responsive element-regulated reporter gene compared to 1,25(OH)2D3 (NS2 and NS6: 1.3 times higher activity; NS7: 1,4 times lower activity).     

A thermodynamic study of dephosphorization using BaO-BaF2, CaO-CaF2, and BaO-CaO-CaF2 systems

Phosphorus partition ratios between BaO-BaF₂ fluxes and copper-phosphorus alloys have been measured as a function of slag composition at 1400 °C. A molybdenum sleeve has been used to avoid contact between the slag and the crucible in order to prevent the absorption of slag by the graphite crucible. The effects of additions of BaO to the CaO-CaF₂ system have been investigated by measuring the phosphorus partition ratios between these fluxes and Fe-C_sat-P alloy as a function of slag composition at 1400 °C. Also, the activity of BaO as a function of slag composition at 1400 °C has been determined by equilibrating a silver-barium alloy with the BaO-CaO-CaF₂ fluxes and CO in a graphite crucible. The results indicate that phosphorus partition ratios with carbon-saturated iron, L_P, for the BaO-BaF₂ system are relatively high, going up to 400, even for oxygen partial pressure as low as 7.8 × 10⁻¹⁶ atm. The phosphate capacity and the activity coefficient of PO_2.5 for this system were calculated from the experimental results using the available thermodynamic data. No effects of barium oxide addition in lime-based fluxes were observed for BaO contents less than 40 pct. One of the reasons for this phenomenon is that BaO activity in a lime-based flux is very small for BaO content less than 46 pct. However, for high BaO contents, increases significantly, as does the activity of BaO. Formerly Research Associate, Department of Metallurgical Engineering and Materials Science, Carnegie Mellon University