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By Toguri JM

A solid electrolyte technique has been used to measure the activity of cobalt in liquid cobalt-gold alloys containing between 0.085 and 0.50 mole fraction of cobalt, and for temperatures from just above the liquidus to around 1550 K. The system exhibits positive deviation from ideality, both in the activities of cobalt and gold, and in the enthalpy and excess entropy of mixing. The results agree with previous measurements using a Knudsen cell - mass spectrometer technique, but differ from those reported for a gas equilibration method. The data have been used to calculate the activity coefficient of cobalt oxide in silica saturated iron silicate slags and to express the solubility of cobalt in such slags as a function of cobalt activity and oxygen pressure.

Jan 1, 1984

Thermodynamic properties of the solutions of hydrogen in metals and carbon in austenite were investigated and it is possible to predict the interstitial solubility in these systems over relatively wide ranges of temperature and solute activity. Monte Carlo methods were used to compute the arrangements of interstitial atoms on the tetrahedral sites in body centred cubic metals and the octahedral sites in face centred cubic metals. It was shown that the non-configurational entropies of solution of hydrogen in metals can be interpreted as being principally vibrational and on this basis the potential value of the isotopic solubility ratio theory in indicating the compositional variation of these non-configurational entropies was discussed. The need for future work along these lines is pointed out.

Jan 1, 1970

Cospidie (3CaO*2SiO2*CaFe2) is one of the most important compounds crystallized in mold flux films during casting in the continuous casting process of steel, The primary crystallization field of cuspidine has been experimentally developed in the CaO-SiO2-CaF2-SiF4 system. The cuspidine-NaF binary and cuspidine-CaF2-NaF ternary systems have been also experimentally determined to study effects of addition of NaF on the primary field of cuspidine. In order to discuss its thermodynamic stability the standard Gibbs energy of formation of cuspidine has been deterimed by an electromotive force methods using CaF2 as solid electrolyte and a transpiration method as follows: ^fG° (cuspidine) /kjmol-1 = 5198 + 0.825T (+12) (1313<T/K<1329): EMF method ^fG° (cuspidine) /kjmol-1 = 5178 + 0.813T (+8) (1221<T/K<1469): Transpiration method The chemical potential diagram and constituent activities for the CaO-SiO2-CaF2 System have been evaluated based on the obtained thermodynamic data.

Jan 1, 2003

Cuspidine (3CaO?2SiO2?CaF2) is one of the most important compounds crystallized in mold flux films during casting in the continuous casting process of steel. The primary crystallization field of cuspidine has been experimentally developed in the CaO-SiOrCaF2-SiF4 system. The cuspidine-NaF binary and cuspidine-CaF2-NaF ternary systems have been also experimentally determined to study effects of addition of NaF on the primary field of cuspidine. In order to discuss its thermodynamic stability the standard Gibbs energy of formation of cuspidine has been determined by an electromotive force method using CaF2 as solid electrolyte and a transpiration method as follows: The chemical potential diagram and constituent activities for the CaO-Si02-CaF2 system have been evaluated based on the obtained thermodynamic data.

Jan 1, 2003

Thermodynamics of Non-Cyanide Gold Solvents The present status of the raw material base in the gold industry requires specific ways to recover gold and silver from ores. Most gold is closely associated with sulfides which require flotation followed by pressure or bacterial oxidation. The next stages of processing usually require using expensive operations for the preparation of leaching. A lot of researchers want to find a new alternative solvent for the extraction of precious metals from these products. According to the authors, one of the best ways is to use sulfur-based solvents (thiosulfate, sulfite, and their various mixtures). Thermodynamics of gold and silver thiosulfate dilution are calculated for conditions: the concentration of Au - 200 mg/L, oxygen - 3.2 mg/L, thiosulfate - 79 mg/L, OH- - 170 mg/L. the general result is the possibility of process remains under standard conditions. (erAu = = 0.035 V, ?G298 = - 29.18 kJ/g-atom ??). Silver with thiosulfate forms two strong complexes: [AgS203]- and [Ag(S203)2]3-. ?G0 = -1027 kJ/mol. The complex [AgS203]- is less stable: ?G0 = 486 kJ/mol. It should be noted that despite the high stability of gold complexes, the sodium thiosulfate may decompose to sulfite and elemental sulfur during the process, especially when heating. Gold is slightly soluble in the sodium sulfite solution, however it forms the strong complex [Au(SO3)2]3-. Depending on the concentration of free S2O32-ions, silver with sodium sulfite forms three complexes: [AgSO3]-, [Ag(SO3)2]3- and [Ag(SO3)3]5-. The dissolution speed of gold in sodium sulfite solution may be in the same range as it is during cyanidation. In this case, a practical application of sulfite process can be also used, especially for the products containing free elemental sulfur. In conclusion, sulfite-thiosulfate gold lixiviants can be used for concentrates after pressure oxidation of the cakes.

Sep 13, 2010

By J. H. E. Jeffes, K. T. Jacob

Solid oxide galvanic cells, of the type: Pt,Ni-NiO | Solid electrolyte | O(metal),Cermet,Pt, were used to measure the activity coefficient of oxygen in liquid Cu at 1 100 and 1 300°C and in Pb at 1 100°C. Similar cells were used to study the activity coefficient of oxygen in the whole range of Cu + Pb alloys at 1 100°C and in Pb-rich alloys at 900 and 750°C. The results obtained are discussed in terms of proposed solution models. An equation based on the formation of 'species' of the form M(2)O in solutions of oxygen in binary alloys is shown to fit the experimental data

Dec 1, 1971

By Takaaki Ishikawa

The distribution equilibria of lead, zinc and copper between CaO-Si02-Ah03 melts and liquid copper were measured at 1623K under a controlled H2-C02 atmosphere. The distribution ratios were plotted against the oxygen partial pressure, and reasonable oxide forms dissolved in the melts were estimated from the slopes of the plots. The activity coefficients of zinc oxide (ZnO), lead oxide (PbO) and cuprous oxide (CuOQs) increased with increasing slag basicity, defined by Xcao /XSiO, The temperature dependence of the activity coefficients was also measured.

Jan 1, 2003

By Takaaki Ishikawa

The distribution equilibria of lead, zinc and copper between CaO-Si02-Ah03 melts and liquid copper were measured at 1623K under a controlled H2-C02 atmosphere. The distribution ratios were plotted against the oxygen partial pressure, and reasonable oxide forms dissolved in the melts were estimated from the slopes of the plots. The activity coefficients of zinc oxide (ZnO), lead oxide (PbO) and cuprous oxide (CuO0.5) increased with increasing slag basicity, defined by XCao/Xsio2 The temperature dependence of the activity coefficients was also measured.

Jan 1, 2003

By Mansoor Barati, Leili Tafaghodi Khajavi

"This study involves employing solvent refining as a purification process in which silicon recrystallization takes place from an iron-silicon melt. It is believed that iron will act as the impurity “getter” and purified silicon crystals will grow from the alloy melt, while the impurities are segregated to the liquid alloy. Phosphorous is a problematic impurity to remove since its segregation coefficient in pure silicon is relatively large. To assess the feasibility and efficiency of phosphorous removal through solvent refining, it is critical to study its equilibrium distribution between solid Si and the Fe–Si alloy phase.The distribution of phosphorous between solid silicon and iron-silicon melt at 1210-1310 °C was measured to evaluate the impurity removal potential of each alloy. Interaction parameter between phosphorous and iron was calculated by varying the concentration of phosphorous in silicon.IntroductionAmong various semiconductor materials for manufacture of solar cells, silicon accounts for over 90 percent of today's PV materials [1, 2].The major challenge in producing solar silicon that operates efficiently is to meet purity level requirement through a cost efficient route. Silicon solar cells can play a significant role in answering the world's need for energy if cost reductions can be achieved through manufacturing process. Considerable effort has been made to replace the expensive, complex vapor-phase purification by a simpler and less costly process. One of the refining approaches that have attracted wide research interests is producing low-cost solar grade silicon by purification of metallurgical grade silicon. Since metallurgical processes are selective in removing impurities, a combination of various purification processes can be used to reduce the impurity level in silicon. Considering different thermodynamic characteristics of impurities, each refining step is responsible for lowering specific impurities."

Jan 1, 2012

By Takahiro Miki

In order to use metallurgical grade silicon (MG-Si) as a starting material for solar cell, phosphorus has to be removed from silicon because phosphorus is a n-type dopant. On the other hand, silicon, ferrosilicon, and silicomanganese are widely used as deoxidizers in steel refining processes. Since most of the phosphorus introduced during the deoxidation process is brought into final products, it is important -to lower the phosphorus content of these alloys. Hence, thermodynamics of phosphorus in such metals is important for the evaluation of dephosphorization processes. In the present study, thermodynamic properties of phosphorus in molten Si-P alloys at 1723- 1848K and those of Si-Fe-P and Si-Mn-P alloys at 1723K have been determined by equilibrating respective metals in a controlled phosphorus partial pressure. The results are expressed as follows.

Jan 1, 1998

By Fumitaka Tsukihashi

Increasing amounts of steel scrap are being used as resources for steelmaking. Therefore, there has been a growing interest in the removal of harmful tramp elements such as antimony, zinc, tin, arsenic, bismuth, lead and copper from the molten steel. The problem that should be solved is the economic removal treatment of residual tramp elements in the steelmaking processes and the production of high quality steel by reducing the effect of the contaminated tramp elements and satisfying the environmental regulations. In this paper, the available thermodynamic data of the residual tramp elements in the molten steel arc summarized and the possibility of the removal of residual tramp elements from the molten steel is thermodynamically estimated.

Jan 1, 2003

By Fumitaka Tsukihashi

Increasing amounts of steel scrap are being used as resources for steelmaking. Therefore. there has been a growing interest in the removal of handful tramp elements such as antimony, zinc, tin, arsenic, bismuth, lead and copper from the molten steel. The problem that should be solved is the economic removal treatment of residual tramp elements in the steelmaking processes and the production of high quality steel by reducing the effect of the contaminated tramp clements and satisfying the environmental regulations. In this paper, the available thennodynamic data of the residual tramp elements in the molten steel are summarized and the possibility of the removal of residual tramp elements from the molten steel is thcnnodynamieally estimated.

Jan 1, 2003

By Jongmin Jeong, Jaehong Shin, Joo Hyun Park, Chul-Woo Nam, Kyung-Ho Park

Because sulfur and phosphorus are very harmful in steel products, there are increasing requirements for refining these elements from ferroalloys industries. Hence, in the present study, simultaneous desulfurization (de-S) and reducing dephosphorization (Rde-P) from silicomanganese (SiMn) alloy were investigated using metal-slag equilibration method under highly reducing condition at 1773 K. Experiments were carried out by equilibration between SiMn alloy and MnO-based slag in graphite crucible under p(O2) = 10−18 atm. Slag composition was designed by changing basicity (CaO/SiO2) and MnO content at fixed Al2O3 (=20%) and MgO (=5%) contents. De-S ratio increased with increasing basicity until C/S = 1.5 whereas Rde-P ratio was not significantly affected by slag basicity. This was because thermodynamic driving force of de-S reaction was greater than that of Rde-P reaction under present experimental conditions. The de-S and Rde-P ratios commonly increased with decreasing oxygen partial pressure.

Mar 1, 2017

By S. E. Olsen, K. Tang

Slag-metal and slag-metal-gas heterogeneous equilibria involving MnO-containing slags have been simulated using recently developed Mn-based alloy and IRSID oxide thermochemical databases. A large number of experimental equilibrium data have been used to verify the calculation results. The experimental slag-metal and slag-metal-gas equilibria in MnO-SiO2binary, MnO-SiO2-CaO and MnO-SiO2-Al2O3ternary, MnO-SiO2-CaO-Al2O3quaternary andMnO-SiO2-CaO-Al2O3-MgO higher-order system can be reproduced within experimental uncertainties. The influence of temperature, CO partial pressure and slag chemistry on the Mn-and Si-distribution equilibria have been quantitatively evaluated. This leads to a sound basis for optimizing the manganese ferroalloy production processes. Key words: MnO-containing slag, manganese ferroalloy, equilibrium simulation, thermochemical database

Jan 1, 2004

By Shahab Alizadeh, Ahmad Khodadadi Darban, Mehdi Mohseni, Mahmoud Abdollahy

This study probed the selective separation of lanthanum and yttrium in a nitrate medium in the presence of aluminum and calcium impurities using di-(2-ethylhexyl) phosphoric acid (D2EHPA). The factors studied in a central composite design (CCD) included extractant concentration, pH, concentration ratio of total impurities to rare earth elements, and interaction of these three factors. The extraction mechanism and types of extracted metal-containing species were delineated by the slope analysis method. The obtained thermodynamic data showed that lanthanum and yttrium extraction by the D2EHPA extractant was exothermic. The extraction of both rare earth elements was accompanied by an entropy reduction. The negative magnitude of ΔS in yttrium extraction reaction suggests stronger D2EHPA-Y(III) complexation relative to La(III). As entropy decreased and enthalpy increased, the extraction process became unspontaneous. Using the proposed flowsheet, lanthanum and yttrium products with > 90% purity were obtained.

Aug 10, 2021

By Chikabumi Yamauchi, Mitsuru Tanahashi, Toshiharu Fujisawa

"Thermodynamic properties of impurities in molten silicon are of prime importance in developing economical production methods of solar grade silicon. In the present research work, thermodynamic properties of boron, the most difficult element to remove from molten silicon, were measured by chemical equilibration techniques at 1723 and 1773 K. Activity coefficients and self-interaction parameters of boron in molten silicon were determined by equilibrating the melt with solid BN under controlled nitrogen partial pressures. Interaction parameters between boron and nitrogen in molten silicon were also determined by equilibrating the molten Si-B alloys with solid Si3N4• Based on the data obtained, the stability diagram of the Si-B-N system was established.IntroductionPhotovoltaic power generation using a silicon solar cell is expected to be the most promising energy source, because it is inexhaustible, cleaner and more safety than conventional energy sources, such as thermal or atomic power generation. At present, expensive off-grade silicon for semiconductor (SEG-Si) is used for a solar cell production. However, if a large-scale photovoltaic energy conversion using silicon solar cell comes into wide use in the near future, silicon will be sure to be in short supply for the cell. Therefore, a development of a new large scale process for solar grade silicon (SOG-Si) production is definitely necessary, which can remove contained impurities from silicon.Among the impurities contained in silicon, boron is one of the most difficult ones to remove by a zone melting or an unidirectional solidification, because its segregation coefficient in silicon is close to unity (0.8). In addition, boron behaves as a p-type silicon semiconductor dopant and, therefore, its content in SOG-Si must be severely controlled. Although some attempts to remove boron by various metallurgical methods have been carried out [I -4], quantitative analysis has not been made due to lack in the information on the thermodynamic properties of boron in molten silicon. From this view point, the activity of boron in molten silicon was determined in the present study by chemical equilibration techniques at 1723 and 1773 K."

Jan 1, 1998

By Jan Vrestal, Josef Tomiska, Pavel Broz

"Thermodynamic investigations on fcc solid ternary Fe-Ni-Cr alloys have been performed by means of the computer-aided Knudsen cell mass spectrometry. Ternary T.AP.-series (Thermodynamically adapted power series) are used for the algebraic representation of the thermodynamic excess properties. At 1650 K the molar excess Gibbs energy GE is negative over the whole field of stable fcc phase. The molar heat of mixing HE is exothermic in the predominant part of the fcc phase field. Only between the section with a constant ratio of mole fraction Xcr/XNi = 0.64 and the fcc phase field boundary the HE values are slightly endothermic. The results of this work can be used successfully for phase diagram calculations.IntroductionThermodynamic investigations on multicomponent alloy systems such as the Fe-Ni-Cr ternary system including the three binary boundary systems are very time-wasting and usually beset with considerable experimental difficulties. Additionally, the required experimental equipment is very expansive and the obtained results are not always satistying. Therefore it is understandable that many phase diagram calculations are based only on few experimental values of the molar excess free Gibbs energy GE. Consequently, Kundrat and Elliott [1] as well as Hillert and Qiu [2] used in their reassessments of the phase diagram of the Fe-Ni-Cr system thermodynamic data mainly assumed and/or optimized by means of various reasoning.Lee [3] reported recently, a revision of the used thermodynamic description of the Fe-Ni liquid phase is necessary to obtain a better agreement with the experimental data on the bcc/liquid or fcc/liquid tie lines and liquidus temperatures in the Fe-rich region of the Fe-Ni-Cr ternary system than in the previous assessments. This is 'in full agreement with mass spectrometric investigations of Fe-Ni alloys in the liquid and in the fcc solid phase, published earlier [4,5]. Indeed, phase diagram calculations based upon the molar excess free Gibbs energies GE obtained in these studies yield liquidus and solidus lines in excellent agreement with experimental phase diagram data [5]. Nevertheless, these experimental data have not been considered later on any more, not even in the revision by Lee [3]."

Jan 1, 1996

By Leiting Shen

The thermodynamics of tungsten ore decomposition in mineral acid and alkaline solutions were studied. The published thermodynamic data of tungsten minerals were collected and assessed. The Gibbs energies of CaWO4 (−1538.43 kJ/mol), FeWO4 (−1053.91 kJ/mol), MnWO4 (−1206.08 kJ/mol), H2WO4 (−1003.92 kJ/ mol), and Na2WO4 (−1455.58 kJ/mol, aq) at 25 °C were adopted in the calculation using HSC software. The results show that CaWO4 is decomposed more readily in Na2CO3 solution than in NaOH,while FeWO4 andMnWO4 aremore reactive inNaOH solutions. Froma thermodynamic point of view, tungsten ore decomposes easily in acid solutions despite most ΔGo T increasing slightly with temperature. Oxidizing Fe2+ to Fe3+ in acidic solutions facilitates decomposition of FeWO4, and the reaction of CaWO4 in H2SO4 solution occurs more easily than in other mineral acids, due to the formation of sparsely soluble CaSO4. The results fit well with the experimental data and industrial experience previously reported in the literature.

By Jiayan Li, Yi Tan, Yao Liu, Yaqiong Li, Shenrui Wu

"A metallurgical grade silicon (MG-Si) refining concept process was presented. Under vacuum conditions, silicon was selectively oxidized by high purity silicon dioxide to form gaseous silicon monoxide while impurities with low vapor pressure in MG-Si were rejected in residue; Then high purity silicon was obtained from the disproportionation of condensed silicon monoxide; and by-produced silicon dioxide was recycled for the oxidation step. Thermodynamics on boron rejection during the oxidation were studied in this work. In the temperature range of 1200-1800K, the saturated vapor pressure of boron, and the Gibbs free energy changes, the equilibrium partial pressures of silicon monoxide and boron oxides of potential reactions were calculated. And the effect of boron activity in MG-Si was also discussed. The results indicated that boron in MG-Si can be rejected during the oxidation and it showed the potential for the further development of the new refining process.IntroductionAs global energy consumption growing dramatically, higher prices of energy and global warming problem have attracted more and more attention [1]. As a clean and renewable energy industry, the photovoltaic (PV) industry converts solar energy to electricity using solar cell device and has a growth rate of about 30% in recent years. It has caused a shortage of silicon feedstock due to that about 90% of solar cells are made of crystalline silicon. And high energy consumption during the production of silicon material, i.e. solar grade silicon (SoG-Si), is main obstacle for its mass production."

Jan 1, 2012

By J. H. E. Jeffes, K. T. Jacob

The activity coefficients of oxygen in liquid Pb-Sn alloys have been measured between 550 and 1100°C by use of solid oxide galvanic cells: Pt, Ni-NiO | Zr02 Solid electrolyte | O (Pb + Sn), Cermet, Pt; and Pt, Fe-FeO | Zr02 Solid electrolyte | 0(Pb + Sn), Cermet, Pt. Alcock and Richardson's quasi-chemical equation, with the coordination number of atoms set to 2, is found to predict successfully the activity coefficients of oxygen in these alloys. The relative partial molar enthalpy and entropy of oxygen at 1 atom per cent in the alloys have been calculated from the variation of the activity coefficient with temperature. The addition of Sn to an unsaturated solution of O in Pb is shown to decrease significantly both the partial molar enthalpy and entropy of O. As the measurements were restricted to a narrow range between 750 and 1100°C in Pb-rich alloys, however, the pronounced variation of the partial molar enthalpy of O with temperature at constant alloy composition predicted by the quasi-chemical model could not be verified.

Dec 1, 1971