Ternary dissolution kinetics in the Fe-Ni-P system

The dissolution of (FeNi)₃P in the ternary Fe-Ni-P system has been studied by optical and electron microprobe techniques. Precipitates of (FeNi)₃P, initially in equilibrium with their ternary matrix (a at 750°C, y at 875°C), were examined after being partially dissolved by heating at 975°C. In addition, diffusion couples with starting compositions similar to the equilibrated ternary alloys were examined after also being heat treated at 975°C. Phosphide, (FeNi)₃P, dissolution in the α or γ phase is diffusion controlled at 975°C. The ternary dissolution paths observed in each of the diffusion couples are unique and the same as those observed in the comparable alloys. The dissolution rate of (FeNi)₃P is controlled by the diffusion rate of P in the α or y phases. The Ni interface compositions in (FeNi)₃P and α or γ and the dissolution path through the ternary are determined by the rate of dissolution and the major Ni ternary diffusion coefficients. It is possible to calculate both the dissolution path and rate for (FeNi)₃P by using the binary dissolution equations in combination with the Fe-Ni-P diagram and the major (ternary) diffusion coefficients. In addition, numerical solutions can be correctly calculated for diffusion controlled dissolution where impingement of overlapping gradients occurs.     

Ternary diffusion in the α and γ phases of the Fe-Ni-P system

Ternary diffusion coefficients have been determined in the α-bcc and γ-fcc phases of the Fe-Ni-P system and at four temperatures 1200, 1100, 1000, and 900°C. At 1100°C the ratio ofD _NiNi ^Fe /D _PP ^Fe in the α phase is 0.3 to 0.4 and the ratio of the cross coefficientD _PNi ^Fe /D _PP ^Fe is 0.03 to 0.05. m the γ phase the corresponding ratios are 0.01 to 0,02 and 0.0015 to 0.0025. The other cross coefficientD _NiP ^Fe could not be evaluated because of experimental uncertainties. Estimates of the ratioD _NiP ^Fe /D _NiNi ^Fe using the interaction parameter ε₁₂ are 0.004 to 0.01 in the α phase and 0.02 to 0.04 in the γ phase. The addition of P in both the α and γ phase increases the major ternary coefficients up to as much as a factor of ten at one temperature. This is consistent with the fact that P lowers the melting point of FeNi in the ternary system, up to 500°C. Isodiffusion coefficient contours obtained at 1100°C plot approximately parallel to the α and γ solidus boundaries and are similar in shape to the α and γ solidus boundaries as a function of temperature. Activation energies andD ₀ values were computed at selected compositions in both α and γ phases forD _PP ^Fe andD _NiNi ^Fe and are given below: Formerly Graduate Student, Department of Metallurgy and Materials Science, Lehigh University, Bethlehem, Pennsylvania     

Ternary system Mo-W-B

Conclusions The investigation has established the existence of the compounds MoB₁₂ and WB₁₂, and of a continuous series of (Mo, W)B₁₂ solid solutions. A projection of the liquidus surface onto the concentrationtriangle plane of the Mo-W-B system and an isothermal section of the system at 1100°C have been plotted.Translated from Poroshkovaya Metallurgiya, No. 7 (79), pp. 60–64, July, 1969.     

Ternary intermetallic compounds in the system Ni-Ti-Nb

Conclusions Four ternary intermetallic compounds -Ni₈₀Ti₅Nb₁₅, Ni₇₅Nb₅Ti₂₀, Ni₇₅Nb₁₃Ti₁₂ and Ni₅₆Ti₂₉Nb₁₅ -were dis-covered in the system Ni-Ti-Nb by the methods of x-ray diffraction analysis. Isothermal phase diagram sections at 1000 and 900C have been plotted.Translated from Poroshkovaya Metallurgiya, No. 8(44), pp. 61–69, August, 1966.     

The kinetics of the dissolution of chalcocite in alkaline cyanide solution

A kinetic study of the dissolution of chalcocite in an alkaline cyanide solution indicates that the reaction is first order with respect to surface area and free cyanide ion concentration, and inversely proportional to the sulfide ion concentration to approximately the 0.1 power. The experimental rate constant is approximately 7.5 × 10⁻⁵ (mole Cu¹⁺/ min) ([S⁻²]^0.1/[CN¹⁻]/cm²/l at 25°C. The activation energy of 2.5 kcal/mole indicates rate control by diffusion through a limiting boundary layer. The concentrations of the important ions in the cyanide solutions are obtained by solving the ionic equilibria and mass balance equations for the system.     

氮在钢液中溶解的热力学及动力学研究

为探索用氮气直接合金化的低成本氮微合金化钢冶炼技术,对某钢厂生产的3种钢在不同氮分压下气相吸氮过程中氮的溶解行为进行了研究,并用试验数据对所建立的钢液吸氮热力学和动力学模型进行了验证。模型计算结果和实测值吻合较好,试验结果表明:氮分压越大钢中氮的溶解度越大,Mo,Ni等元素对钢中氮含量有显著的影响;钢液吸氮和脱氮反应均为一级反应,吸氮平衡时间为25 min,脱氮平衡时间为40 min。     

Growth of intragranular ferrite in Fe-Ni-P alloys

Analytical electron microscopy (AEM) techniques were used to study the growth of intragranular ferrite in Fe-Ni-P alloys. The spatial resolution of the AEM was exploited to gather microchemical information regarding elemental redistribution at ferrite/austenite interfaces in order to determine the growth mechanism for intragranular ferrite. In this alloy system, the growth kinetics are dictated by the bulk diffusion of Ni in austenite. Full equilibrium occurs during intragranular ferrite growth with full partitioning of Ni and P between austenite and ferrite, and chemical equilibrium occurs at the α/γ interface in both phases. A numerical model to simulate ferrite growth was developed based on equilibrium growth considerations. The Ni concentrations and precipitate sizes predicted by the model agree well with those measured by AEM techniques in the experimental alloys. The computer model has been extended to predict the thermal histories of iron meteorites and their parent asteroidal bodies.     

Nucleation of intragranular ferrite in Fe-Ni-P alloys

The nucleation of intragranular ferrite from austenite in Fe-Ni-P alloys was investigated in order to understand the development of the Widmanstätten pattern in iron meteorites. Alloys containing 5 to 10 wt pct Ni and 0 to 1 wt pct P were used to simulate iron meteorite compositions. In the isothermal and controlled cooling experiments the reaction path γ → α+ γ serves only to nucleate ferrite along austenite grain boundaries. It is necessary for (FeNi)₃P to be present within y grains in order to nucleate intragranular ferrite. The reaction path γ → γ+ phosphide → α + γ + phosphide yields rod shaped ferrite nuclei that bear a near Kurdjumov-Sachs orientation relationship with the surrounding matrix. The precipitation of ferrite, both along grain boundaries and within the austenite grains, is suppressed in the absence of P.     

Modelling the influences of solid-state interdiffusion and dissolution on transient liquid phase sintering kinetics in a binary isomorphous system

A simple model was developed to predict the impact that solid-state interdiffusion and dissolution have on liquid formation and its duration during transient liquid phase sintering (TLPS). The model predicts that solid-state interdiffusion can dramatically reduce the amount of liquid initially formed during heating. This reduction is dependent on the heating rate and initial base metal particle size. In cases of sintering above the additive phase melting point, the model predicts that base metal dissolution increases liquid phase formation and that this additional melting reduces the base metal particle size. The model predicts that longer times are required to solidify isothermally the greater amounts of liquid formed at higher temperatures (because of dissolution). This agreed qualitatively with experimental results for a Ni-65 wt pct Cu TLPS mixture sintered at 1090 °C and 1140 °C. Quantitative comparisons between the model and experiment were good at 1140 °C; however, the rate of isothermal solidification was underestimated by the model for intermediate sintering times at 1085 °C.     

Mechanism and kinetics of sulfite-thiosulfate dissolution of gold

Dissolution mechanisms of noble metals in aqueous solutions of sodium thiosulfate, sodium sulfite, and their mixture under standard conditions (without heating the medium) in alkali and acidic media are described. The conditions of intensifying the dissolution process are evaluated. The reaction rates are investigated. Based on the obtained data, it is concluded that it is rational to apply the sulfite-thiosulfate solvents of noble metals to recover them from concentrates under the usual conditions.     

The kinetics of dissolution of chalcopyrite in ferric ion media

The kinetics of dissolution of chalcopyrite (CuFeS₂) in ferric chloride-hydrochloric acid and in ferric sulfate-sulfuric acid solutions have been investigated using the rotating disk technique. Over the temperature range 50 to 100?C, linear kinetics were observed in the chloride media while nonlinear kinetics were noted in the sulfate system. The apparent activation energy in the chloride system was about 11 kcal/mole. The rate increased with increasing ferric chloride concentrations but was insensitive to the concentrations of hydrochloric acid, the ferrous chloride reaction product and “inert? magnesium or lithium chlorides. Cupric chloride substantially accelerated the rate. Small amounts of sulfate in an otherwise all chloride system greatly reduce the chalcopyrite leaching rate; still larger amounts of sulfate make the system behave essentially like the slower-reacting ferric sulfate medium.     

The kinetics of dissolution of sphalerite in ferric chloride solution

The dissolution of sphalerite in acidic ferric chloride solution was investigated in the temperature range 320 to 360 K. Both sized particles from three sources and polished flat surfaces were used as samples. The effect of stirring rate, temperature, ferric and ferrous ion concentration, purity, and particle size on the dissolution rate were determined. During the initial stages of the process chemical reaction at the mineral surface is rate controlling while during the later stages diffusion through the product sulfur layer is rate controlling. Overall the process follows the mixed-control model embodying both chemical reaction and diffusion. The activation energy for the dissolution of sphalerite particles was found to be 46.9 kJ/mol.     

Studies on dissolution kinetics of dolime in electrothermal magnesium slag

The electrothermal process of magnesium metal production is a promising route, where large sized internally heated reactor is used for magnesium production resulting in less energy and labour intensive and high space-time yield process. However, the dissolution behavior of dolime in the electrothermal slag has been found critical for the process optimization. In this paper, the dissolution kinetics of the dolime in the slag was discussed. Quaternary slag (CaO-Al₂O₃-SiO₂-MgO) was prepared having basicity CaO/SiO₂ ≥ 1.8 and Al₂O₃/SiO₂ ≥ 0.26 for dolime dissolution studies by static hot dip method. Prior to the experiments, FactSage calculations were carried out varying temperatures and slag compositions. In the kinetic studies, dolime particles 10–15 mm size was added in slag melted at 1450, 1500 and 1550°C and samples were taken at various time intervals. The chemical analysis of slag sample was carried out to investigate the dissolution kinetics to establish the rate expression. The activation energy for the process was calculated for different models used in study and was found to be in the range of 130–270 kJ/mol. SEM analysis was done for surface analysis of reacted particles. This study would be helpful in optimizing the dolime charging rate during pilot scale trials for electrothermal magnesium production at CSIR-NML, Jamshedpur.     

The kinetics of dissolution of chalcopyrite in ferric ion media

The kinetics of dissolution of chalcopyrite (CuFeS₂) in ferric chloride-hydrochloric acid and in ferric sulfate-sulfuric acid solutions have been investigated using the rotating disk technique. Over the temperature range 50 to 100‡C, linear kinetics were observed in the chloride media while nonlinear kinetics were noted in the sulfate system. The apparent activation energy in the chloride system was about 11 kcal/mole. The rate increased with increasing ferric chloride concentrations but was insensitive to the concentrations of hydrochloric acid, the ferrous chloride reaction product and “inert≓ magnesium or lithium chlorides. Cupric chloride substantially accelerated the rate. Small amounts of sulfate in an otherwise all chloride system greatly reduce the chalcopyrite leaching rate; still larger amounts of sulfate make the system behave essentially like the slower-reacting ferric sulfate medium.     

Influence of oxalic acid on the dissolution kinetics of manganese oxide

The kinetics and electrochemical processes of the dissolution of manganese oxides with various oxidation states in sulfuric acid solutions containing oxalate ion additives is studied under variable conditions (concentration, pH, temperature). The parameters favoring a higher degree of the dissolution of manganese oxides in acidic media are determined. The optimal conditions are found for the dissolution of manganese oxides in acidic media in the presence of oxalate ions. The mechanism proposed for the dissolution of manganese oxides in sulfuric acid solutions containing oxalic acid is based on the results of kinetic and electrochemical studies. The steps of the dissolution mechanism are discussed.     

The kinetics of magnesium vapour dissolution into pig iron

Abstract

Magnesium injections are used extensively in the iron and steel industry for the production of ductile iron, and for the desulphurization of blast furnace pig iron. However, little is currently known about the kinetic mechanisms involved in either of these two cases. In the present work, a magnesium vaporizer was used to inject pure magnesium vapour into 60-kg pig iron melts (1250°C) at rates of between 0.7 and 12 gm/min for bubbling periods of 20 to 60 minutes. The efficiency of magnesium dissolution ranged between 20 and 80%. A mass transfer model, based on single bubbles, was used, to interpret the results. In addition, residual magnesium concentrations following holding times of up to 60 minutes after bubbling compared reasonably well with those predicted on the basis of theoretical evaporation rates.

Résumé

L'injection de magnésium est utilisée intensivement dans l'industrie siderurgique pour la production de fonte ductile et pour la désulfuration de la fonte en gueuse provenant du haut-fourneau. Cependant, il y a présentement peu dapos;informations sur les mécanismes de réactions impliqués dans l'un ou l'autre des deux cas. Dans ce présent travail, un va porisateur de magnésium a été utilise afin d'introduire la vapeur de magnésium pur dans un bain de 60 kg de fonte liquide à 1250°C, a des taux variant entre 0.7 et 12 gn/min pour des durées d'injection variant de 20 à 60 minutes. L'efficacité de la dissolution du magnésium dans la fonte liquide était comprise entre 20 et 80%.

Un modele de transfert de masse a été utilisé pour interpréter les résultats. Il est à noter que les concentrations résiduelles de magnésium correspondant à des temps de bouillonnement allant jusqu'à 60 minutes se comparent raisonnablement bien avec les valeurs prédites théoriquement à partir des taux d' évaporation du Mg.     

The kinetics of dissolution of enargite in acidified ferric sulphate solutions

Abstract

Over the temperature range 60° to 95°C, sintered discs of synthetic enargite (Cu₃AsS₄) were dissolved slowly in acidified ferric sulphate solutions, yielding both elemental and sulphate sulphur, together with soluble copper and arsenic. The dissolution kinetics were linear and this was interpreted as indicating rate control by a reaction occurring on the surface of this sulphosalt. The activation energy associated with this reaction was 13.3 kcal/mole. The rate of copper extraction increased according to the 0.55 power of the ferric sulphate concentration and the 0.20 power of the sulphuric acid concentration. The rate decreased in a complex manner with increasing strengths of the ferrous sulphate reaction product. Natural enargite dissolves like the synthetic sulphosalt and at approximately the same rate.

Résumé

A des températures variant entre 60°C et 95°C, des disques frittés d'énargite synthétique (Cu₃AsS₄) ont été dissous lentement dans des solutions acides de sulfate ferrique, pour produire du soufre élémentaire et sous forme de sulfate, ainsi que du cuivre et de l'arsenic soluble. Les cinétiques de dissolution suivent une loi linéaire, due à la réaction qui a lieu en surface de ce sulfosel et qui, semble-t-il, contrôlerait la dissolution. L'énergie d'activation associée à la réaction est de 13.3 kcal/mole. Le taux d'extraction du cuivre croît comme la puissance 0.55 de la concentration en sulfate ferrique et la puissance 0.20 de la concentration en acide sulfurique. La vitesse décroît de façon complexe lorsque augmente la concentration du produit de la réaction du sulfate ferreux. L'énargite naturelle se dissout de la même manière que le sulfosel synthétique, et à sensiblement la même vitesse.     

The kinetics of dissolution of covellite in acidified ferric sulphate solutions

Abstract

Pure synthetic CuS disks and high-grade natural covellite were dissolved in acidified ferric sulphate solutions in the temperature range 25 to 95°C. For both materials, the rates were relatively slow and increased during the initial stages of the dissolution, eventually becoming nearly linear. The activation energy, as determined from the initial dissolution rates of the synthetic covellite, was 17.8 ± 2.0 kcal/mole. Microscopic examination of both the natural and the synthetic sulphide revealed that the attack occurred preferentially in certain areas. It was felt that the progressive development of such pits was responsible for the gradual rate increase observed during the initial leaching stage. From 0 to 6° of the leached sulphur reported in the sulphate form. The rate of copper dissolution decreased sharply with increasing ferrous sulphate concentrations in the leaching medium. The rate varied directly with the ferric concentration for initial concentrations below 0.005 M Fe³⁺ but was insensitive to higher ferric strengths. Natural covellite dissolved at approximately the same rate and with essentially the same temperature dependence as the synthetic material. The rate controlling step for the dissolution of CuS was felt to be a chemical reaction occurring on the surface of the sulphide.

Résumé

Des disques de CuS synthétique pur et de la covelline naturelle de haute qualité ont été dissous dans des solutions acidifiées de sulfate ferrique entre 25 et 95°C. Pour les deux matériaux, les vitesses étaient relativement lentes et augmentaient durant la période initiale de dissolution, pour finalement devenir presque linéaires. L'énergie d'activation, déterminée à partir de la vitesse de dissolution initiale de la covelline synthétique était de 17.8 ± 2.0 kcal/mole. L'examen microscopique des sulfures naturel et synthétique a révélé que l'attaque se produit de préférence dans certaines régions. On pense que le développement progressif de telles piqûres etait responsable de l'accroissement graduel observé durant le lavage initial. Zéro à 6% du soufre dissous l' était sous forme de sulfate. La vitesse de dissolution du cuivre diminuait rapidement avec l'accroissement de concentration en sulfate ferreux dans la solution. La vitesse variait directement avec la concentration ferrique pour des concentrations initiales inférieures à 0.005 M Fe³⁺, et était insensible aux plus fortes concentrations ferriques. La covelline naturelle se dissolvait avec approximativement la même vitesse, et avec la meme dépendance de la température que le matériau synthétique. On pense que l' étape contrôlant la vitesse de dissolution du CuS est une réaction chimique se produisant à la surface du sulfure.