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By Katsuyoshi Tatenuma

"In order to mitigate the effect of global warming by preventing the accumulation of atmospheric CO2, a permanent fixation method of surplus CO2 as an insoluble mineral onto the sea bottom is proposed. As the proposed reduction method of atmospheric CO2, the concrete concept of this method is to form an insoluble carbonate mineral (CaCO3) by direct electrolysis of the seawater; Ca2++2HCO3 -+OH- ? ?CaCO3(insoluble)+CO3 2- (soluble)+H++H2O <not as coral reef reaction>, are directly disposed of itself onto the sea bottom. By this treatment, a concentration of carbonate is reduced in the section of superficial seawater, and therefore the absorption capacity of atmospheric CO2 increases depending upon the shift of chemical carbon equilibrium between the mass of superficial seawater and the atmosphere. As no additives are required, or no secondary waste are produced, the proposed method assuming as green-orientated, has possibility to resolve fundamentally the problem of global warming in a green orientate manner.IntroductionRecently, the amount of atmospheric CO2 has been exponentially increasing and it is a main greenhouse effect gas causing the global warming [1, 2]. The concentration of atmospheric CO2 has increased more than 30% (370ppm in 2001) during only last two centuries, therefore approximately 750 Gton-C of CO2 currently exist in the atmosphere, in which 180 Gton-C of CO2 are accounted for the increment during two centuries [1, 3, 4]. In order to avoid the progressive increase of CO2 global abundance, 3 Gton-C of the incrementing amount per year [4], have to be removed annually from the atmosphere."

Jan 1, 2008

By Suleyman Tekeli, Serdar Salman, Bulent Aktas

"The effect of La2O3 content up to 15 wt% on phase stability, sintering and microstructure of cubic zirconia (8YSZ) was investigated. XRD results showed that the specimens containing up to 15 wt% La2O3 were composed of only cubic structure. Also, the specimens doped up to 5 wt% La2O3 revealed no La2O3 peaks, indicating that La2O3 was completely solubilized in the cubic structure. However, when> 5 wt% La2O3 was added, the peak of La2Zr2O7 compound emerged, showing that the overdoped La2O3 was not solubilized in the 8YSZ matrix. The lattice parameter of the 8YSZ slightly decreased with the increasing La2O3 content up to 1 wt% but further increase in the La203 amount resulted in an increased lattice parameter. The comparison of grain size of the 8YSZ specimens with various La2O3 content showed that grain size slightly increased with the increasing La2O3 content up to 1 wt% but further increase in the La2O3 amount resulted in a decreased grain size.IntroductionAt atmospheric pressures, three polymorphic forms of Zr02 are stable at different temperatures i.e. monoclinic, tetragonal and cubic. A high-pressure orthorhombic form of Zr02 has also been reported[l]. The successful production of pure Zr02 bodies is not possible all the time due to the large volume expansion associated with the martensitic tetragonal-monoclinic transformation. This fact restricts the applications of zirconia, in spite of its excellent mechanical and thermal properties. However, the stabilization of the high temperature polymorphs at room temperature as stable phases is made possible by addition of suitable dopants. Fully stabilized cubic Zr02 and partially stabilized tetragonal Zr02 show interesting properties and are widely used as ionic conductors, coatings and gas sensors in solid oxide fuel cells and structural applications[2]. Most frequently used dopants include Y203, CaO, MgO and Ce02, although other oxides, such as those of rare earth elements, can also act as stabilizers of the high temperature structures. The incorporation of aliovalent cations to the lattice, forming substitutional solid solutions, allows to control the concentration of anionic vacancies in the structure. This aspect is particularly important in designing ionic conductors[3], and is also determinant in the stabilization process[ 4]. The process of stabilization with larger ionic radii dopants is rationalized by the crystal chemistry model[ 5], that describes the dopant cations as typical stabilizer when they have larger ionic size, lower charged state and higher ionicity than Zr4+ The ionic radius of Zr4+ is 0.84 Å and that for La3+ is 1.016 Å [6]."

Jan 1, 2012

By V. M. Paretsky

The basic work conducted by Prof. A.Yazawa has demonstrated that in order to ensure single- stage white metal production by autogenous smelting of copper sulfide raw materials, it is most favorable to use highly basic slags, in particular oxide systems CaO-FeO-Fe2O3-SiO2. The special studies have been conducted in the Gintsvetrnet Institute to investigate the composition and structure of slags produced on a semi-commercial scale when testing the KFP and FBP processes for white metal smelting. as well as the slag obtained in a full-scale KFP furnace at the Almalyk copper smelter. The investigations conducted have demonstrated why production of high-grade matte or white metal is associated with lower loss of copper in slag in a series: silicate slag I silicate-calcium slag I ferrite-calcium slag.

Jan 1, 2003

By Dhanesh Chandra

In this symposium, research in the area of energy conversion is presented. This symposium has special significance, as we honor three prominent scientists from hydrogen storage research and development field. In this symposium, the majority of papers presented by international scientists and engineers are in the area of hydrogen storage. Other energy conversion papers include magnetic materials, superconductors, and thermal energy storage materials. Recent developments in light-weight high gravimetric hydrogen density hydrides have led to potential use of hydrides for onboard automobile and other applications. This, of course, is significant from environmental concerns of CO2 and other emissions from the current use of carbon based fuels in automobiles. Thus, it is becoming increasingly important to switch to cleaner alternative fuels such as hydrogen [1]. The Challenge of Vehicular Hydrogen Storage as potential hydrogen energy carriers for vehicular applications, with a driving range of approximately 300 miles, require ~5-13 kg of hydrogen stored on-board. In the United States, Centers of Excellence have been established in metal hydrides, chemical hydrides, and carbon-based materials, and abundant scientific and industrial research is being carried on metal hydrides; only some of the current research from the Centers will be reported here. The European commission, Japan Institutions, and others also have numerous hydrogen storage programs in progress. Several international collaborations have also begun between IEA and IPHE scientists to accelerate the progress of development of practical hydrides. A summary of the abstracts is included in this overview.

Jan 1, 2006

By Kimio Itagaki

As a fundamental study for smelting the copper matte with high contents of arsenic and antimony in a strongly reducing condition, phase relations between the liquid matte and copper-rich alloy phases in the Cu-Fe-S-As or -Sb quaternary system and between the liquid matte and iron-rich alloy phases in the Cu-Fe-S-As or -Sb system saturated with carbon were determined at 1473 K by a quenching method. Activities of arsenic and antimony in these systems were also measured at 1473K by Knudsen cell-mass spectrometry. Furthermore, distribution ratios of silver, gold and platinum between the liquid matte and copper-rich or iron-rich alloy phases were determined in relation to the arsenic or antimony content in the systems. On the basis of these data, the elimination of arsenic and antimony from the matte to the iron-rich alloy (speiss) and the recovery of precious metals in reduction smelting of the copper matte were evaluated. It was suggested that the addition of pig iron to make a strongly reducing condition and form the iron-rich alloy, which is fluid at smelting temperatures, will be useful for fixing arsenic in the speiss.

Jan 1, 2006

By María Eugenia Castro, Silvia Galasso, Jorge Duca, Claudia Osuna, Ernesto Esparza

"We present a procedure for treatment of non-active solutions equivalent to the solutions obtained from dissolution of ionic exchange resins used in purification of a nuclear reactor primary cooling system containing Co, Ni, Cs and its isotropic varieties as main radioactivity source. Finally it is immobilized into a ferritic matrix by calcination which avoids its future leaching into environment.In order to achieve the objective of this treatment, a bivalent and a trivalent iron salt is added to the solution. Then, either a base or an acid is added, depending on the initial pH of the treated solution, with a Cs precipitating additive in order to reduce Co and Cs by precipitation, flocculation and adsorption. Controlling the amount of precipitating reactives it is possible to modify the activity/volume rate becoming a medium into a low radioactivity waste.The leaching test result applied over the ferritic sample is lower than the minimum limit established by law. Therefore, it can be kept safely in a interim storage."

Jan 1, 2008

By Alessandro Blasi, Massimo Morgana, Corradino Sposato, Pietro Garzone, Giuseppe Devincenzis

A comparison among (2-ethylhexyl)-mono (2-ethylhexyl) ester Phosphonic acid (P507), Secondary-octyl phenoxy acetic acid (CA-12) and Bis(2,4,4-trimethylpentyl) phosphinic acid (Cyanex272), in heavy rare earths separation via hydrometallurgical processes has been investigated. The separation coefficients, , were obtained and the extraction selectivity has been evaluated using a mixture of heavy rare earths from Samarium to Ytterbium. The experimental results indicated that P507 and Cyanex 272 display a greater affinity for heavier rare earths while CA12 proved to be more effective for the lighter rare earth metals.

Jan 1, 2014

By László I. Kiss, Verena Mackowiak, Alexandre Perron, Dominic Toulouse, Alicia Liedtke, Sándor Poncsák

"Bubbles play a very important role in different metallurgical applications like for example in electrowinning. During heterogeneous nucleation, the maximal size of the bubbles growing at the nucleation sites as well as the nucleation frequency is determined by the so-called detachment condition. Detachment occurs when the external forces acting on the bubble exceed the retaining forces along the solid-gas-liquid triple interface line. The phenomenon depends strongly on the shape and orientation of the solid surface and on the nature and strength of the external buoyancy and drag forces. In the present study the detachment conditions of bubbles from downward facing horizontal and inclined plates were studied experimentally under the effect of gravitational and hydrodynamic forces. The results show the deformation of the bubbles under the effect of the external forces and the detachment conditions as function of the bubble volume.IntroductionIn heterogeneous nucleation bubbles are generated at the so-called nucleation sites along the solid-liquid interfaces. They continue to grow there and after they reached a certain size they detach from the solid surface and leave the nucleation site. This scenario is well known both in boiling and electrolysis. During the growth period a stable equilibrium exists between the forces that retain the bubble at the nucleation site and the forces that try to remove it. This equilibrium evolves with the increasing volume of the bubble to the point when the detachment forces overcome the retaining forces.The life of a single bubble generated by heterogeneous nucleation can be divided into two periods separated by the detachment - or in other words by the departure - of the bubble: first the growth at the nucleation site and then the movement away. The knowledge of the detachment conditions makes possible the determination of the maximal volume of the bubble at the nucleation site that, in tum, makes possible the determination of the nucleation frequency. This is why so many researches have been directed toward the clarification of the details of the bubble detachment in the past decades. The equilibrium between the attaching and separating forces depend on the presence of body, surface and flow induced forces in the liquid, on the geometry and orientation of solid surface, on the properties of the solid-liquidgas system etc."

Jan 1, 2004

By A. V. Tarasov, V. M. Paretsky

"The knowledge of the true phase composition of the liquid slag is a very important problem, mastering of which grants the possibilities for the scientifically founded choosing of the decoppering method of the autogenous smelting slags. The investigation using different methods of the phase composition of the flash quenched autogenous copper melt's slags has shown, that the most effective method of the slags' decoppering during smelting with the white matte production is the flotation of the recrystallized slags. In this work the authors posed the problem to realize the slags quenching with the rates similar to those, which are used in the modem investigations devoted to the flash quenching of the ironcontaining alloys, with the subsequent study of the quenched samples using the Mossbauer spectroscopy methods in order to establish the connection between the liquid slag's structure and the metals losses with the slag."

Jan 1, 2000

By Jacques Magnaudet, Julie Cranga, Didier Huin, Pascal Gardin

"With the aim of controlling steel grade in steelmaking reactors, IRSID and IMFT are developing a numerical description of the evolution of bubbles in the vicinity of a liquid steel/ slag interface. The objective is to identify the main parameters affecting the hydrodynamics of the various phases. The goals of the present paper are:• To describe the numerical technique developed to predict the multi phase flow including bubbles, liquid metal and slag layer.• To analyze the influence of the absolute pressure on the bursting of bubbles in a RH degasser. Validation is given by comparison with results available in the literature. The major point concerns the distinct behaviors observed whether the pressure is low or high.• To study the influence of the properties of the slag layer (thickness, viscosity and interfacial tension) on the entrainment of liquid metal in the wake of the bubble and on the nature of the projections from the bath surface.IntroductionMost of secondary steelmaking processes use gas stirring for homogenization, removal of nonmetallic inclusions or decarburization under reduced pressure. The bursting of gas bubbles at the metal or slag layer surface produces a beneficial ejection of metal droplets in the low pressure atmosphere, provided that there is no violent projection, which may have detrimental effects on the process.Our objective is to develop a numerical tool to study the phenomena occurring in the vicinity of the bath surface, in particular bubble bursting under reduced pressure and entrainment of metal in the slag layer. In this paper we report the first conclusions of our study. In the first section we describe the numerical model used to describe the three-phase flow and the expansion of the gas bubbles under the effect of the ferrostatic pressure. The second section is devoted to the study of pressure effects on bubble rise and bursting. The third section reports some computational results about the rise of a gas bubble through the interface between the two liquids."

Jan 1, 2001

By M. Kobayashi, Y. Nishisu

"Fine multicomponent particles of yttrium and europium were synthesized through the precipitation from homogeneous solution, and the various characteristics related with the fluorescence were investigated. The morphology and the fluorescent characteristics of the synthesized particles were affected by ionic species in the stock solution. In the presence of sulfate ion, some parts of the precipitated particles were aggregated, and _the fluorescent characteristics were not good. On the other hand, in the presence of chloride ion or nitrate ion, the particles precipitated were almost monodispersed, and, the intensity of the fluorescent emission were strong after calcination. Further, these particles were also very attractive as the red phosphor in the mercury-free fluorescent systems.Introduction Eu doped Y oxide particles have been widely investigated for the application to the fluorescent lamps and displays: Recently, the fluorescent lamps are pointed as harmful electric equipments because of using mercury for excitation. Therefore, the use of the mercury in the fluorescent- system will be limited or prohibited worldwide in near future. Then, the development of the mercury-free fluorescent lamp is strongly required without delay. Inert gas such as neon and/or xenon seem to be applicable as new excitation element that replaces the mercury. However, in case xenon the excitation wavelength,' 146 and 172nm, is different from that of the mercury, 254nm, and then, the commercial phosphors which are used in the present fluorescent lamp system are not available. Therefore, the invention of the novel phosphors is essential for the development of the mercury-free fluorescent lamp. Further, the controls of the size and shape of the particles precipitated are also important, because the homogeneity of the size and the shape is very important for the fabrication of the layer of the phosphor particles. That is to say, the development of the phosphor particles with controlled components, size and shape is essential. The precise control of size and shape improves the packing density, and so, the screen performance of the lamp [1]. In addition, these phosphor particles should be also useful for the application of the flat-plane displays, for example, PDP, etc. [2,3]. In the present work, first, the particles including yttrium and europium for the precursor for red phosphor were prepared through precipitation from homogeneous solution. This process was precisely controlled for the control of the components, size and shape of the particles precipitated. Next, the particles precipitated were calcined, and then, their fluorescent properties were characterized. As a result, some of them showed the possibly available characteristics as the red phosphor for mercury-free fluorescent lamp system. These experimental results are presented in this paper."

Jan 1, 2000

By Toshiro Kuji, Masakazu Fujita, Tetsuji Saito

"The magnetic properties of the magnetic materials were deeply dependent on the microstructures. In this study, the novel technique to produce the desired microstructures in a controlled manner was proposed. The technique consisted of the production of the amorphous alloys and the control of the crystallization process. The technique was applied to improve the magnetic properties of Nd-Fe-B permanent magnets. The microstructural control of the magnets exhibited the excellently high energy-products of higher than 430 kJm-1. The relationship between the magnetic properties and the microstructures of the Nd-Fe-B permanent magnets was discussed.IntroductionThe intrinsic properties of the materials are basically determined by the properties of the constituent elements or the compounds. However, it is often noticed the difference between the observed properties and the theoretical values expected from the intrinsic properties of the materials. This indicates that the observed properties of the materials are determined not only by the properties of the constituent elements. In other words, the observed properties of the materials are also strongly dependent on the morphology of materials. This means that the microstructural control may creates a great improvement of the properties of materials.In Nd-Fe-B permanent magnets, the superiority arises from the uniaxial intermetallic Nd2Fe14B compound which has a large saturation magnetization and a high anisotropy field [1,2]. The magnetic properties of the Nd-Fe-B permanent magnets are dependent on the microstructure, that is, the size, shape and degree of the crystallographic alignment of the Nd2Fe14B phase. Currently, the Nd-Fe-B permanent magnets have been produced by either sintering or melt-spinning [3,4]. In the sintered magnets, alignment of the Nd2Fe14B phase is achieved by the prior green compaction of the crushed ingot powders in an applied magnetic field [3]. In the melt-spinning approach, alignment of the Nd2Fe14B phase is achieved by hot deformation [5]. Amorphous melt-spun ribbons are comminuted and then are consolidated into bulk form by hot pressing before hot deformation. As-hot-pressed magnets have randomly oriented Nd2Fe1~ grains [6]. Subsequent die upsetting of as-hot-pressed magnets gives rise to the crystallographic alignment of the Nd2Fe14B phase."

Jan 1, 1998

By J. T. I. Poijärvi

The smelter off-gas cleaning and the weak acid treatment at Outokumpu Harjavalta Metals Oy are presented and described in this paper. The smelter consists of the copper and nickel smelters and the acid plant of three separate acid plants two of which are double contact and one single plant and of one liquid sulphur dioxide plant. The preliminary cooling and flue dust separation of the smelter off....,gases from the copper ?and nickel flash smelting furnaces and converters? in the waste heat boilers and in the hot electrostatic precipitators are described. The final cooling and cleaning of the gases in the scrubbers at the sulphuric acid plant and the treatment of the weak acid in the vacuum and in the submerged combustion evaporators for the removal of impurities are presented as well as the treatment of the condensates from the evaporators. The attention is paid to the generation of sulphur trioxide in the smelter off-gas.and to the treatment of that in the weak acid bleed-off and to the utilization of the treated acid.

Jan 1, 1992

By J. T. I. Poijärvi

The smelter off-gas cleaning and the weak acid treatment at Outokumpu Harjavalta Metals Oy are presented and described in this paper. The smelter consists of the copper and nickel smelters and the acid plant of three separate acid plants two of which are double contact and one single plant and of one liquid sulphur dioxide plant. The preliminary cooling and flue dust separation of the smelter off-gases from the copper and nickel flash smelting furnaces and converters in the waste heat boilers and in the hot electrostatic precipitators are described. The final cooling and cleaning of the gases in the scrubbers at the sulphuric acid plant and the treatment of the weak acid in the vacuum and in the submerged combustion evaporators for the removal of impurities are pre¬sented as well as the treatment of the condensates from the evaporators. The attention is paid to the generation of sulphur trioxide in the smelter off-gas and to the treatment of that in the weak acid bleed-off and to the utilization of the treated acid.

Jan 1, 1992

By Roberto Parra

The wear and corrosion phenomena in the furnace lining of the ferrous and non ferrous pyrometallurgical processes are complex problems where chemical, interfacial and mechanical phenomena are presents. The characteristics of the processes determine the conditions to which these materials are submitted, where the thermal conditions reached during the operation is one of the most important parameter. Assuming that all the degradation phenomena are thermal activated, the rate of the different steps of the wear mechanism will depend on the thermal field in the lining. In view to apply the independent physicochemical knowledge of degradation mechanisms to the analysis and design of furnace lining the methodology of the Nodal Wear Model (NWM) was done. It combines the mathematical modelling of the heat transfer in the lining with the physicochemical control equation for the wear-corrosion phenomena. The NWM has been applied to different examples: theoretical analysis, laboratory scale test and industrial applications. We present in this paper the theoretical background of the model and two examples of applications: the sole of an electric furnace and the earth of a blast furnace.

Jan 1, 2006

By Masayuki Kudoh, Tohru Maruyama, Yohichi. Ito

When hypo-peritectic carbon steel is quenched during unidirectional solidification, the region of fine columnar grain is observed. It is classified into two coexisting phases. One is coexisting phases of liquid, delta and gamma in the upper part of the region, and the other is coexisting phases of delta and gamma in the lower part of the region. To form the coexisting part of the three phases means that solidification in this experiment proceeds in non-equilibrium state. The size of the narrow side of one fine columnar grain coincides with the arm spacing of a primary dendrite and this result is the same as the hyper-peritectic carbon steel. However, the boundary of the fine grain in the hypo-peritectic carbon steel is formed in different location from that of the hyper-peritectic carbon steel. The former is formed in the skeleton of the dendrite, while the latter is formed in the interspacing of the dendrite. The region of the fine grain changes suddenly to that of the coarse grain when the delta phase in the coexisting part of two phases disappears completely. Therefore, the delta phase in the hypo-peritectic carbon steel might prevent the growth of gamma grain. In order to recognize it, ferrite formers such as Mo, V and Ni are added in the sample. Then, the longitudinal length of the fine columnar grain extends in the sequence of the no addition, Mo, V and Nb.

Jan 1, 2000

By Zdzislaw Miczkowski

At KGHM Polska Miedz S.A, a direct flash smelting process is used for smelting of chalcocite concentrate for the production of blister copper. The paper presents a model of complex oxidation process of single concentrate grains smelted at KGHM. The description covers main chemical reactions, phenomena of heat and mass exchange inside the grains and between a grain and the surrounding space. In the model, two zones describing the course of process inside the grain were distinguished: ? The first one, which moves faster towards the centre of a grain, both organic and carbonate carbon are freed, The process takes place without the presence of oxygen and results in an increase of the temperature in the core of the particle. ?The second zone moves slower into the grain and the rate of the movement is determined by the presence of oxygen, In that zone the sulphur is eliminated and the oxidation of the organic compounds vapours moving from deeper layers of a grain takes place. Based on the results of laboratory tests, the coefficients that describe the oxygen transportation into the grain and decide the progress in the chemical reaction were determined, The paper contains the results of model calculations for single grains reacting in environment of various content of oxygen as well as the results of model calculations for the laboratory reactor system.

Jan 1, 2003

By Zdzistaw MiGzkowski

At KGHM Polska Miedi S.A. a direct flash smelting process is used for smelting of chalcocite concentrate for the production of blister copper. The paper presents a model of complex oxidation process of single concentrate grains smelted at KGHM. The description covers main chemical reactions, phenomena of heat and mass ex-change inside the grains and between a grain and the surrounding space. In the model, two zones describing the course of process inside the grain were distinguished: ? The first one, which moves faster towards the centre of a grain, both organic and carbonate carbon are freed. The process takes place without the presence of oxygen and results in an increase of the temperature in the core of the particle. ? The second zone moves slower into the grain and the rate of the movement is deter-mined by the presence of oxygen. In that zone the sulphur is eliminated and the oxidation of the organic compounds vapours moving from deeper layers of a grain takes place. Based on the results of laboratory tests, the coefficients that describe the oxygen transportation into the grain and decide the progress in the chemical reaction were determined. The paper contains the results of model calculations for single grains reacting in environment of various content of oxygen as well as the results of model calculations for the laboratory reactor system.

Jan 1, 2003

By Hirofumi Tai, Masafumi Morishita, Toshiya Miyake

"In order to prevent corner cracks on cast steel slab and bloom, solidification delay at the corners should be controlled at the proper level. For this purpose, controlling the heat flux from the molten steel to the solidified shell at corners is essential. In this paper, optimization of the submerged nozzle was studied based on flow and solidification analysis.First, for the slab caster, the submerged nozzle shape was optimized. The improved nozzle was tested in actual casting and completely succeeded in preventing corner cracks. It was clearly demonstrated that the solidification delay and the corner cracks were strongly affected by the spouting stream from the submerged nozzle.For the bloom caster, on the other hand, the setting angle of the nozzle was optimized. Numerical simulations demonstrated that the spouting stream from the nozzle causes solidification delay, impinging at the corners under electromagnetic stirring conditions. Optimization of the setting angle of the nozzle is a possible means to reduce the solidification delay at the corners for the bloom caster.Related to the numerical analysis of flow and solidification, the effect of the critical solid fraction at the tip of the dendrite structure on the solidification under electromagnetic stirring conditions was studied."

Jan 1, 1999

By Helfried Nafe

"For about a century thermodynamically absurd facts have been propagated in conjunction with the iron-carbon phase diagram. These facts concern fundamental relationships of chemical thermodynamics. Attention is turned here to the discussion of only one of the relevant aspects of the subject, i.e. the definition of the thermodynamic activity of the solute and its implications for the iron-carbon solution.IntroductionThe view on the iron-carbon solution is characterized by the assumption that the solute may appear in two different forms, i.e. graphite and cementite. Accordingly, two carbon solubilities are differentiated, on the one hand for graphite and, on the other hand, for cementite. As a consequence, two versions of the phase diagram exist simultaneously, the application of which depends on the prevailing conditions, (i) the so-called stable phase diagram with graphite as solute and (ii) the metastable one that is based on the cementite-in-iron solution. These diagrams are joined together in the double phase diagram that originates from Heyn [l ], with the first ideas mainly going back to Stansfield [2] and Charpy [3].Thermodynamically, the most inadequate implication of the Fe-C double phase diagram is that the carbon activity may take values larger than unity. With the standard state of the activity being that of the pure substance, i.e. the Raoultian one, such a value implies the nonsensical existence ofa state purer than pure. The explanation of this physical state, ifthere is any, vaguely refers to supersaturation and, in the wider sense, to the physico-chemical phenomenon of metastability. Other aspects of chemical thermodynamics are likewise involved. Therefore, the comprehensive investigation into the present subject requires more topics to be considered than only one separate issue. Not only should the criticism of the present view be in the focus but also the discussion of new ideas capable of reconciling the experimental facts, known about the F e-C system, with the fundaments of chemical thermodynamics. All this, however, cannot be provided here because of the limited space available. As a consequence, in what follows only a part of the whole problem is under scrutiny, i.e. the definition of the thermodynamic activity and its role for the interpretation ofrelevant experimental facts."

Jan 1, 2014