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By Laurentiu Nastac

"The importance of investigating solute redistribution during the unidirectional solidification of multi-component alloys is broadly discussed in the literature. A previously developed analytical model that was experimentally validated for Al-Cu, Sn- Bi and Fe-Si dilute binary alloy systems is used in this article to study in detail the solute redistribution, the liquid/solid interface stability based on an extended transient constitutional undercooling criterion and the size of the initial transient region during the unidirectional solidification of Ti-6-4 and Ti-17 alloys. A comparison between Ti-6-4 and Ti-17 alloy systems with respect to interface stability and the size of the initial transient region is also provided. The effective partition coefficients of the alloying elements in these alloys were determined based on specially designed experimental measurements.IntroductionThe importance of investigating solute redistribution during alloy solidification is broadly discussed in the literature [1-5]. One of the relevant applications of this study would be the mathematical modeling of equiaxed and columnar solidification of multicomponent alloys. This includes the instability of the solid/liquid interface. There are several mass and heat transfer processes that involve the calculation of solute redistribution during directional solidification such as industrial directional solidification processes, continuous casting, remelting processes, Czochralski crystal growth technique, floating zone techniques, etc."

Jan 1, 2012

By Juliana Gutiérrez-Paredes

Keywords: Slag, chromium oxide, recovery, stainless steel Experimental and theoretical work was performed to estimate the effect of slag basicity and amount of reducing agents on the reduction of chromium oxide from the slag which interacted with molten steel at 1600°C. The slag system contained CaO, MgO, SiO2, CaF2 and Cr2O3 together with Fe-alloys (Fe-Si and Fe-Si-Mg). The CaF2 and MgO contents in the slags were 10 mass % each; Cr2O3 was 25%. The amount of the ferroalloys ranged from 12.5 to 50 g per 100 g of slag. The (CaO+MgO)/SiO2 ratio was held at 1 and 2. The Cr yield was determined using both Fe-alloys as reducing agents. Some estimations were made to determine the theoretical effect of temperature, slag basicity, (CaO+MgO)/SiO2, and amount of reducing agents in the slag on the chromium recovery. The FACT (Facility for the Analysis of Chemical Thermodynamics) computational package is used to determine the equilibrium between the slag and molten steel.

Jan 1, 2005

By Shadia J. Ikhmayies

"Tin oxide (SnU2) thin films of thicknesses in the range 100-600 nm were prepared on glass substrates by vacuum evaporation at ambient temperature. The films were characterized by transmittance measurements, X-ray diffraction (XRD), scanning electron microscope (SEM) observations and energy dispersion X-ray analysis (EDAX). It is found that the films have high transmittance and non sharp absorption edges. XRD diffractograms showed that the films are amorphous and the SEM micrographs showed that the surfaces are smooth, uniform and well covered with the material. The EDAX analysis showed that the films are deficient in oxygen. Indirect optical bandgap energy and Urbach tailing in the bandgap was observed, and the width of the tail, which is related with disorder and localized states, was estimated.IntroductionTin oxide is an n-type wide bandgap semiconducting material with a direct bandgap energy of 4 eV and an indirect bandgap of 2.6 eV [1], where inherent oxygen vacancies act as an n-type dopant [2], Tin oxide thin films have been used for transparent electrodes in photoelectric conversion devices namely amorphous silicon solar cells, liquid crystal displays, gas discharge displays, etc. [3]. Perfectly amorphous thin SnO2 films show good electrical response to reducing gases in air and could, hence, be applied to construct semiconductor gas sensors where the metal oxide films function as a monograin-eqivalent active layer [4]. Amorphous SnU2 can also be used in extended gate field-effect transistors (EGFET) as a pH sensor, where the sensitive part is made of the SnO2/Al structure. This device can be used to detect and to quantify any kind of substance that can produce or consume protons, like an enzymatic reaction, therefore showing a large range of applications as biosensors [5].There are different methods to prepare SnO2 films, such as atomic layer deposition (ALD) [6], reactive magnetron sputtering [7], chemical vapor deposition [8, 9], dip coating [10], spray pyrolysis (SP) [3, 11-14], and evaporation [8], The thermal evaporation method was chosen to produce SnO2 thin films in this work because deposition by this technique does not present any compositional problems. In addition, it is a low temperature technique, which increases the probability of producing amorphous films. To increase this probability, the films were deposited at ambient temperature."

Jan 1, 2012

By Vasil Kopaleishvili

The bainitic Fe-C-Si alloys with optimum content of retained austenite serve as ?containers? for storing of hydrogen. Both the vacancies of fcc lattice and the possibility of forming hydrides of silicon and other alloying elements will be used. The idea is based on our scientific hypothesis. There is the silicon threshold (Si=0,50%) in "Fe-Si" system and Fe-C bainitic alloys, above which it causes self-organized phenomena: sudden increase of hydrogen solubility and amount of retained austenite in the alloy after ??ß transformation, formation of two supersaturated solid solutions <a??r>, "rejuvenation? and its reverse process. Rapprochement of iron atoms when Si=0,50%, causes appearance of new covalent forces where uncompensated electrons of 3d-subshell are involved and it provokes synergetic phenomena. They ?free? silicon atoms from the previous bonds. After that silicon itself becomes a getter of hydrogen using vacancies (14) of 3P2(6)d0(10) subshell and it results in sudden increase of hydrogen solubility in metal. Simultaneously sudden decrease of iron activity takes place. That in its turn ?releases? the carbon. Thus, its redistribution, controlling the bainitic transformation, is hastened. It stipulates for creation of ?brittle bainite" B[a(C,H)+?r(C,H)] after ??ß transformation. While weathering of metal, "rejuvenating", hydrogen diffuses in ?islets? of retained austenite and ?relaxed bainite? (B[(C)+?r(C,H+H)]) is obtained. When heating austenite ?(C,H) is obtained, and after cooling ?brittle bainite? is obtained, etc. Presented scientific hypothesis explains the available experimental facts ("rejuvenation? and its reverse process, graphitization, weldability, forming of flakes, reaching high strength, etc.) in a new manner, as well as, gives real opportunity for creating of new trends in many fields, e.g. iron based HAA. Provisional data having been obtained are encouraging.

Jan 1, 2006

By Sijun Li, Bingyu Zhang, Haitao Zhou, Zhendong Zhang, Guofei Si, Xianghua Liu

"Hot compression test of Nb microalloyed coiled tubing steel is performed on Gleeble3500 at 1123K—1373K and strain rate from 0.001 to 5s-1. It is found that flow softening occurs and the flow curves exhibit a peak with a characteristic of dynamic recrystallization (DRX) and change with temperature and strain rate significantly. The peak stress and peak strain are dependent on the Zener-Hollomon relationship with activation energy of 390 KJ/mol. On the basis of Avrami equation and the Zener-Hollomon parameter, it is obtained that the dynamic recrystallization kinetics equation with which the calculated and measured recrystallization fraction is very close. On the results of hot compression test, the Nb microalloyed coiled tubing steel is rolled by Thermo-Mechanical-Control-Processing (TMCP), and it is obtained that the yield strength and tensile strength of Nb microalloyed coiled tubing steel are 565MPa and 685MPa respectively, and the elongation percentage is 30.1%.IntroductionCoiled tubing is widely used in oil field for well logging, well completion, drilling, work over and other operation in various fields to solve a number of conventional operating techniques problem which are difficult resolved, and it plays a more and more important part in exploration and production at oil field. [1] It will improve the efficiency of exploration and exploitation, studying, developing and using coiled tubing technology. Therefore, the development of domestic coiled tubing materials and manufacturing technology are great significance. It is well known that Coiled tubing has relatively poor working conditions and complex force state. So, the coiled tubing needs satisfier a kind of high strength, high plasticity, and corrosion resistant under complex oil gas condition. As the coiled tubing technology developed, the level of the coiled tubing steel is from CT55 originally to CT90 and CT100, and the corresponding tensile strength is 483MPa-758MPa. [2, 3]"

Jan 1, 2012

By Han Yi

The coarse indium ingots produced by Shaoguan smelter contained a lot of impurities. In order to produce the high pure indium with the purity more than 99.99%, the appropriate refining processes were designed and the practice of combined application of Glycerin-KI process and electrolysis in Shaoguan smelter was introduced.

Jan 1, 2005

By Fernanda de Paula, Lázaro A. Rohen, Sérgio N. Monteiro, Rafael G. de Castro, Carlos Maurício. F. V, Maycon A. Gomes, Frederico M. Margem, Anna C. C. Neves

Synthetic fiber has been gradually replaced by natural fiber, such as lignocellulosic fiber. In comparison with synthetic fiber, natural fiber has shown economic and environmental advantages. The natural fiber presents interfacial characteristics with polymeric matrices that favor a high impact energy absorption by the composite structure. However, until now little has been evaluated about the hemp fiber incorporated in polymeric matrices. This study has the purpose of evaluate the impact resistance of this kind of epoxy matrix composite reinforced with different percentages of hemp fibers. The impact resistance has substantially increased the relative amount of hemp fiber incorporated as reinforcement in the composite. This performance was associated with the difficulty of rupture imposed by the fibers resulting from the interaction of hemp fiber / epoxy matrix that helps absorb the impact energy.

Jan 1, 2015

By Dieter Wanner

Off-gas cleaning from metallurgical? plants, requires in many cases very low dust contents which are, difficult to achieve with conventional scrubbers, even with high energy input. Lurgi has developed a scrubber which improves the separation of the fine dust by electrical charge prior to the scrubbing zone,, An Electrostatic Scrubber has been successfully installed for the off-gas cleaning from slag granulation after a waelz kiln achieving less than l mg/m3 in the clean gas.

Jan 1, 1992

By Carlos Eduardo Gomes de Souza, Luis G. S. Sobral, Paulo A. Medeiros da Silva, Selma G. F. Leite, Renata de B. Lima

"The use of mixed cultures of acidophilus microorganisms that act in different temperature ranges, aims at speeding up the digestion of chalcopyrite, highly refractory sulphide mineral, the major mineral in the flotation concentrate of Caraíba Mining Co., with an attractive processing cost. The concentrate under consideration contains mainly chalcopyrite (CuFeS2) and bornite (Cu5FeS4) with contents of, approximately, 70 and 30%, respectively. It was observed in this study, the performance of consortium of mesophiles, moderate and extreme thermophile microorganisms, in the oxidation of the aforementioned sulphides minerals, evaluating operational parameters such as pH of the leaching solution, the reaction temperature and redox potential, with consequent extraction of 80% of the concentrate copper content within 60 days of bioleaching. Such high copper extraction was achieved in column bioleaching tests.INTRODUCTIONThe solubilization of metals by the application of microorganisms from the mineral ores and the subsequent recovery of metals from solution are referred to as bioleaching (Rohwerder, T et al, 2003). This is an economical method for the recovery of metals from minerals; especially lowgrade ores, overburden, and waste from current mining operations which requires moderate capital investment with operating cost (Watling, 2006).Furthermore, bioleaching is generally more environmentally friendly than conventional metal recovery processes such as concentration and smelting. Those physicochemical metal extraction processes generate sulphur dioxide, a toxic emission that is increasingly the target of regulatory legislation (Stott et al., 2000; Olson et al., 2003). Bioleaching of chalcopyrite is the key industry target. The main problem hindering commercial application of chalcopyrite bioleaching is the slow dissolution rate (Fu et al, 2008).Dissolution of acid-soluble sulphide minerals such as sphalerite, and to a lesser extent chalcopyrite, occurs by a combination of ferric iron and proton attack via the polysulphide pathway (Rohwerder et al., 2003)."

Jan 1, 2008

By Eric Pirard

Theoretical studies carried out on shape analysis supply mathematical tools to analyze the influence of grain shapes on ore beneficiation. In the case of statistic images like those encountered in applied mineralogy parametrical and harmonical analysis methods are used. It is important that the shape parameters are adapted to the specific processes involved in ore beneficiation, while remaining easy to manipulate. The inertia parameters are considered in the scope of granulometric and gravimetric processes It appears that they are able to distinguish between the resulting products where very popular shape parameters are not. The measured statistics are analyzed through discriminant analysis procedures in order to estimate the importance of morphological differentiation and the aptitude of shape parameters to account for this.

Jan 1, 1989

By Dinabandhu Ghosh

The stability diagram of the ternary system Ti-C-O is drawn in the present work for four temperatures, 1473 K, 1573 K, 1673 K and 1873 K, showing the stability fields of TiC, Ti, TiO, Ti2O3 and TiO2. An analysis of the system reveals that it is not possible to produce Ti in a carbon-saturated system; instead, the stable product is TiC. However, Ti can be an equilibrium product in a carbon-unsaturated system at prohibitively low values of pCO and pCO2; for example, at 1873 K, these limiting values are: pCO = 10-6.76 atm and pCO2 = 10-13.36 atm, which, when exceeded, produce TiC and TiO respectively. The magnesiothermic reduction is examined through the stability diagram (log pO2 vs. 1/T) of the system Ti-Mg-O, drawn for a number of pMg values, presenting the pairwise stability fields such as Mg(l) + Ti(s), Mg(v) + Ti(s), MgO(s) + Ti(s), etc. The diagram shows that magnesium reduction of TiO to Ti is possible only at T < 1641 K with pMg = 1 atm and only at T < 1569 K with pMg = 0.5 atm. An experimental scheme for Mg vapor reduction of TiO2 is proposed in which an argon stream is passed over a Mg(liquid) evaporator at temperature T1 (say, 1234 K); the resulting Ar-Mg mixture at 1 atm is subsequently flown over a bed of TiO2 at temperature T2. A thermodynamic analysis establishes that complete reduction to Ti is possible and that the best results are obtained when T1 = T2.

Jan 1, 2006

By A. Cullaj

During a period of 15 years the metallurgical and chemical complex of Elbasan containing more than 15 principal plants, producing cast-iron, steel, coke, nickel carbonate, nickel, cobalt, chromium and other products, discharged into air, river water and soil an extensive amount of hazardous wastes containing high toxic substances. A monitoring study for the levels of heavy metals in soils nearby the former plant is carried out for the first time. Very high levels (total and extractable) of contaminants such as nickel, cobalt and chromium are found in samples taken from a relatively vast territory including the city of Elbasan, situated 8 kilometres far from the plant. The most polluted samples present a total content of 1211.8 ? 2949.6 mg/kg Ni, 97.0 ? 181.2 mg/kg Co and 1358.7 ? 4130 mg/kg Cr. These levels exceed several times the phytotoxic thresholds and present a potential hazard for the inhabitants. This study, as part of a bigger multinational project on solid decontamination, will also serve to the possible application of the new phytoremediation and phytoextraction technologies, being developed in parallel in this project.

Jan 1, 2006

By K. B. McTaggart, G. Owusu, P. J. Merrin

"This study was conducted at Hudson Bay Mining and Smelting's zinc electrowinning tankhouse to determine the effects of varying levels of antimony and continuous gelatin addition on current efficiency. The levels of antimony and gelatin were varied from 0.012 to 0.030 mg/l and 0 to 10 mg/ll2 • 31 respectively, based on neutral ZnS04 electrolyte. A non-linear mathematical model relating current efficiency with antimony and gelatin was produced. The optimum operating point for gelatin was 6.5 mg/l. On the other hand the current efficiency increased with decreasing antimony levels. An interaction term between gelatin and antimony is present but is not significant enough to improve the ability of the tankhouse to handle purification upsets in antimony. Individually, the current efficiency was linear (decreasing) with antimony, and parabolic with gelatin concentration. However, at low antimony concentrations stripping of the cathode sheet was difficult. IntroductionThe zinc electrowinning tankhouse at Hudson Bay Mining and Smelting was designed in the 1930's and consists of 120 rows with each row containing ten cells. This system cascades acid from cell to cell In a row, with neutral zinc sulphate solution added to each cell through manually controlled spigots. Animal glue additions are made manually three times per day by operations personnel. The problem with this type of cell design and operation is that feed solution flows and composition can vary from cell to cell and from row to row due to the large number of manual control points. A new system which reduces the number of manual control points was designed and tested to determine if improvement in control of cell conditions would affect current efficiency. This system mixes spent acid, neutral ZnS04 electrolyte and reagents (gelatin, antimony and strontium carbonate) in a separate mix tank, ensuring that all cells receive a uniform feed solution. Gelatin was used in the test system instead of animal glue (which is presently used) because of the poor solubility and supply of industrial animal glue. The study reported here is the first in a series of experiments designed to justify the need to modify the present cascading cell feed system (Figure 1) to the proposed feed system (figure 2)."

Jan 1, 1997

By Suzzann Nordwick

The metallurgical treatment of mercury-containing materials for precious or base metals recovery imposes many processing and environmental challenges. Mercury is usually present as elemental or cinnabar. Historically, mercury has been removed from mined ores pyrometallurgically by roasting, but hydrometallurgical methods have also been employed. For example, alkaline sodium sulfide solution acts as an universal solvent for most mercury compounds. While, most other metals are highly insoluble in this solution. This allows for a high degree of selective separation of mercury from other metals with the exception of tin, antimony and arsenic. Mercury leached with a solution of sodium hydroxide and sodium sulfide or sulfur can be re-covered by cementation or stabilized through sulfide precipitation. Hydrometallurgical technology for the pretreatment of mercury removal from gold, silver, and base metal ores using alkaline sulfide leaching will be discussed with a focus on alkaline sulfide leaching of mercury sulfide-containing materials.

Jan 1, 2003

By Okechukwu Anopuo, Gerhard Tober, Petra Maier

"In this study, an investigation on the microstructure of hot rolled steel S355J2+N was conducted to optimize process parameters of complex forming, which combines rolling and bending. The best sets of parameters are worked out based on homogeneous mechanical properties and microstructure within the varied deformation degree with maximum at <p = 1.14 on a 25 mm thick plates. Mechanical properties, especially of heavy plates, are strongly influenced by the local deformation degree, strain rate and temperature. Detailed microstructural analyses showed that the ferrite-pearlite band structure changes near the surface, while maintaining homogeneous microstructure within the deformed work piece. Surface decarburization was also observed and this leads to decrease in hardness. To minimize iron oxide formation which could lead to side cracking, reduction in exposure time to temperature was suggested. On the other hand, temperature reduction below a critical value would risk the accurate forming process.IntroductionThis work presents the preliminary results of research to develop a new complex deformation process of thick steel plates. Complexity is given because the forming process combines rolling to reduce thickness and profiling by bending. The work piece will experience a thickness reduction from 25mm to 8 mm and is double curved. To explain and understand forming of thick plates basics of sheet forming as well as massive forming need to be used. At the moment there is no forming process established to produce double curved plates including reducing thickness in one process step. Technologies nowadays consist of two process steps: flat rolling and pressing in shape. Due to good weldability and formability the final product will be made of steel S355J2+N. This low-carbon steel is well understood and has a low strengthening exponent, which is expected to keep the forming forces down. Reduction of thickness from 25 mm to 8 mm gives furthermore a high deformation degree. Thus, hot forming has to be applied. The determination of process parameters is the main aim of overall research project; temperatures above lOOO°C are expected. Flow curves in literature are given at various temperatures and strain rates [1]. However, experiments with data close to the industrial application are rarely found, especially at low strain rates and high deformation degrees. Pre-test were done by flat rolling, being aware that the influence of bending is eliminated. The microstructure evolution were characterised in relationship to material formability with special attention to grain size change and recrystallization. Representative samples should be selected from specific locations in the deformation zone according to the knowledge about the metal forming process [2]. Due to no further alloying elements in S355, no precipitation hardening is expected to take place during hot forming, which keeps the mechanisms simple and the concentration on the feasibility of the complex forming process is given."

Jan 1, 2012

By Keizo Uematsu, Kumiko Sanda, Nozomu Uchida

"Full understanding of mechanical properties is the most important assignment in ceramics. Establishment of defects-property relationship is crucial for fulfilling the assignment. This study reports detailed characteristics of defects and their relevance to the mechanical properties for alumina ceramics made through a typical industrial processing. Novel characterization methods were applied to evaluate their defects. A very simple direct correlation was successfully found between defects and properties in ceramics. This result is a great epoch in the field of ceramics. IntroductionThe ceramic materials are used in refractoriness, corrosion resistant materials and structural materials. The low fracture toughness and scatter of strength are very important problems in ceramics. The toughness of ceramics is lower than metal and polymer materials, and the allowed defect size is small. Very small internal defects (pore, crack, huge particle) can be a fracture origin in the brittle fracture. The characteristics of defects such as size, distribution and shape change markedly by process condition, which cause the scatter of strength. This study conducts quantitative evaluation and direct observation of the sizes, shape and a number of internal defects with a light microscope, and discusses the relationship for mechanical properties and defect sizes"

Jan 1, 2000

By Jan Yaozhong

The composition and the possible utilization of Ti bearing blast furnace from a titanomagnetite blast furnace smelter were studied. The slag contained about 20% Ti02 and trace Sc. The mineralogical analysis indicated that Ti in the slag is mainly as perovskite. By means of magnetite separation, the Ti containing phase could not be enriched. An effective hydrometallurgical approach was proposed with sulphuric acid leaching. The method proposed for processing the studied slag renders product Ti02 and SC203. Besides the recovery ofTiO2 and SC2O3&apos; the leaching process yields fine grained residues which can used as additives for making cement.

Jan 1, 1996

Off-gas cleaning from metallurgical plants requires? in many cases very low dust contents which are difficult to achieve with conventional scrubbers, even with high energy input. Lur.gi has developed a scrubber which improves the separation of the fine dust by electrical charge prior to. the scrubbing zone. An Electrostatic Scrubber has been successfully installed for the off-gas cleaning from slag&apos; granulation after a waelzkiln achieving less than 1 mg/m3 in the clean gas.

Jan 1, 1992

By D. J. Wang

Based on the thermodynamic arid kinectic aspects, the vaccum distillation processes for the separation and recovery of metals from wastes are analyzed. As to the separation criteria, The separation coefficient and equilibrium composition relation between vapor phase and liquid phase are the bases of recovery of metals by vacuum distillation, The vaporization rates and condensation mechanisms are also discussed. Some experimental results which deal with metals-containing wastes are described and the performances of a new kind of horizontal vacuum furnace are introduced, which demonstrate that , vacuum distillation may be a prospective technique for circulation and regeneration of some non-ferrous metals from industrial wastes.

Jan 1, 1996

By Ma Lijuan, Zhang Yubing, Wang Bo, Sun Huilan

The effect of lime ratio on phase composition and alumina leaching property of MgO-contained calcium aluminate clinker were investigated by analytical reagent, the XRD analysis of its mechanism was discussed. The results showed that: when the sintering temperature was 1350 ℃, C/A was 1.4, A/S was 1.3 and the content of MgO was 4%, the increase of the C/A promoted the formation of C12A7 and restrained the formation of Q-phase. The alumina-leaching ratio of the clinker (A/S was 1.3) was increased from 74.33% to 91.34% when the content of CaO was 5.21%.

Jan 1, 2015