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By T. Takahashi, K. Oyamada, Y. Miyata, T. Isoo

The carbonation reaction of steelmaking slag has been known for many years. However, the size of blocks manufactured from this by-product material has been limited due to the difficulty of achieving a uniform reaction throughout the block. Using newly developed conditions, large porous slag blocks (1.0 x 1.0 x 0.5 m) were produced by car¬bonation of steelmaking slag with the optimum amount of water and supplying CO2 deep into slag powder compacted in molds. The development of these blocks has great poten-tial to solve the problem of slag utilization, for example, by recycling slag in large car¬bonated blocks for artificial fish reefs and seaweed cultivation beds. This paper de¬scribes the carbonation reaction, the new process for producing large slag blocks, and the utilization of blocks in past and recent years.

Jan 1, 2004

By M. Reza Bateni, M. Zandrahimi, J. A. Szpunar

Titanium aluminides and nickel aluminides offer the potentials, as coating materials, for high temperature and aerospace applications. In this research, attempt has been made to develop Al-Ti and Ni-Al intermetallic compound coatings on the surface of Inconel 738. The coatings applied through pack cementation and simultaneous diffusion annealing processes. Scanning-electron microscopy (SEM), energy-dispersive X-ray spectrometry (EDAX) and grazing angle X-ray diffraction were used for evaluating of coating structure. It was demonstrated that the pack cementation technique could be used to develop TiAl3 and AlNi intermetallic compounds coating on Inconel 738 substrate. When pack cementation technique is based on a halide-activated pack with aluminum and titanium powders, the coating consists of TiAl3 intermetallic compound phase. Whereas, by pack aluminization of Inconel 738, the coating consists of AlNi intermetallic compound phase.

Jan 1, 2004

By Z. Mubarok

An overview of the problems encountered the electrorefining of copper anodes containing high levels of nickel and antimony is presented. Our investigations have been focusing on the passivation behaviour of the anodes with high contents of Ni, Sb, Sn, and Pb, the formations of kupferglimmer and floating slimes. The results of linear voltammetry, chronopotentiometry and electrolysis test revealed a noticeable lower resistance of the anodes to passivation in comparison to those with lower contents of Ni, Sb, Sn, and Pb. Anode containing kupferglimmer exhibited oxygen gas evolution during the passivation state. Scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) indicated that tin can replace and/or join antimony in the kupferglimmer structure. Under specified experimental conditions, floating slimes precipitations took place with high Ni, Sb, Sn, and Pb anodes prior to the end of one anode period.

Jan 1, 2007

By F. Golestani-Fard, A. A. Nourbakhsh

In this paper microstructural development of nitride-Bonded SIC refractories is reported in presence of Al203, Mg() and Urea additives .The samples were prepared by mixing, shaping and firing at 1400-1500°c in a controlled atmosphere furnace. Phase analysis, microscopic observation and mechanical evaluation were taken for microstructural investigations. The strength of samples doped with Al203 was first increased and then decreased at higher amount of Al2O3 additions. The addition of MgO decreased the strength while the urea showed an improving effect on strength. These phenomena could be attributed to microstructural evolution and mainly to liquid phase formation and grain morphology. It was found that the additives such as Al203, MO and urea could modify the microstructure in terms of phase formation and texture modification, which in terms influences the mechanical behavior.

Jan 1, 2004

By Zhitong Sui, Feng Zhang, Li Zhang, Tie Ou, Guangqiang Li

Researches on the recovery of iron, manganese and the removal of phosphorus from converter slag were reviewed. The carbon thermal reduction experiments were carried out by induction heating the mixture of converter slag and graphite powders at 1650°C and 1800°C in a graphite crucible. It was found that 62.7% of the phosphorus in converter slag was reduced into carbon saturated iron alloy, 32.8% of that was vaporized and only 4.5% of that remained in the final product. Totally 95.5% of the phosphorus in converter slag was removed. Almost all iron and manganese was reduced to form carbon saturated alloy. It was found that the free lime in converter slag can react with carbon to form calcium carbide at 1800°C. The main phases in the reduced converter slag are dicalcium silicate and tricalcium silicate with small amount of calcium carbide.

Jan 1, 2004

By M. Huang

Electrodeless conductivity was employed to investigate the feasibility of continuous on-line monitoring of the free acidity of sulphate and/or chloride solutions of Cu and other base metals from various hydrometallurgical processes. These solutions were measured with both commercial and experimental electrodeless conductivity sensors from 15 to 250°C. It was confirmed that hydrogen ion has the greatest impact on conductivity by carrying the bulk of the current because it is the most mobile ion. In combination with a solution speciation analysis the conductivity sensor can be calibrated to account for the contribution of Cu electrolytes as well other dissolved salts allowing fast and accurate on-line measurement of free acid. The sensor was tested at both lab and pilot scale with very good performance. The average difference between the measured and the titrated acid concentration was less than 5%, which is excellent for industrial applications.

Jan 1, 2007

By F. Romero

In the last four years, Compañia Minera Doña Ines de Collahuasi has been working in the application of advanced multivariate statistical techniques for the improvement of the metallurgical processes. In this paper the main conclusions for the application of multivariable analysis to the EW process are presented; including the identification of (target) process patterns according to throughput and quality criteria. Based on the process patterns, process variables hierarchies were identified by selecting the most influential ones, as well as to identify and isolate the root causes of pattern deviations and sub-standard operating conditions, cause-effect relationships were established, leading to the definition of process policies and controls to give early corrections to potential failures. The analysis was focused on cathode quality, specifically in its sulfur content, using an empirical model based on those variables that from a phenomenological and statistical stand point appeared to be the most influencing ones.

Jan 1, 2007

By L. W. F. Mackenzie

The influence of rolling temperature and annealing on the recrystallization and texture of magnesium AZ31 has been investigated. 100x125x6 mm AZ31 plate was cast in a permanent steel mould and then homogenized at 380°C. As-cast and homogenized microstructures were then characterized, and 35x30x6 mm specimens were machined from the homogenized material. Specimens were rolled up to 40% at temperatures between 25 and 350°C; selected specimens were subsequently annealed at 400°C. Following rolling, the microstructures were compared. The influence of rolling temperature on as-rolled texture has been demonstrated, and texture evolution has been evaluated following annealing. The recrystallization behavior has also been characterized. Optical microscopy, scanning electron microscopy and electron backscattered diffraction (EBSD) were used to characterize the microstructures of the alloys. X-ray texture analysis was used to investigate the texture in as-rolled and annealed specimens.

Jan 1, 2006

By Masatake Haruta

Gold can be deposited as nanoparticles on a variety of support materials by coprecipitation or deposition-precipitation of Au(OH)3, grafting of organo-gold complexes such as dimethyl-Au(III)-acetylacetonate, mixing of colloidal Au particles, and vacuum deposition. Owing to the moderate adsorption of at least one of reactants (for example, CO) on the edges and corners of Au nanoparticles and to the activation of the counter reactant (for example, O2) at the perimeter interface with the supports, supported Au nanoparticle catalysts exhibit unique and practically useful catalytic properties at relatively low temperature below 473K. They have already been commercially used for deodorizers in rest rooms in Japan and will find growing applications in indoor air quality control, pollutant emission control, production of hydrogen energy carrier, and innovations in chemical processes. Cluster science of Au may also open an exciting area of research showing some magic numbers for dramatic changes in reactivity.

Oct 1, 2003

By Roger Reed

It is well known that the performance and carbon emissions associated with the modern gas turbine engine depend critically upon the properties of the nickel-based superalloys, particularly those used in single crystal form. However, the design of all alloys in current use has been essentially empirical, or at best heavily reliant upon regression/neural network analysis of experimental datasets. In this paper, alloy design approaches [1] are described which are able to identify new alloy composition spaces which are worthy of experimental study. It is shown that a large amount of design data can be generated, which can be interpreted in different ways. Of course, the success of the approach depends heavily upon the accuracy of the underlying sub-models. Estimates of the creep resistance, cost, castability, density and oxidation resistance are made. It is demonstrated that these methods allow quantitative trade-offs to be made between the properties of interest.

Jan 1, 2010

By Julie Q. Shang

The electrokinetic (EK) technology for dewatering of two tailings from the uranium mines in Northern Saskatchewan is studied in bench scale experiments. The study includes four phases: 1. Characterization of two uranium mine tailings; 2. Assessment of voltage loss on the coated Ti anode and water interface. 3. EK cell test series to measure electrokinetic permeability (ke) of two tailings; 4. EK dewatering test series to study electrokinetic enhanced gravity dewatering on two tailings samples. The results have demonstrated that both tailings responded positively to the EK process. For the tailings containing gypsum, the EK dewatering should be a short term process (within one hour) with anode conditioning (pH adjustment). The tailings containing clay minerals responded well to EK dewatering, in which pH adjustment is optional and will further enhance the EK flow. Both tailings as tested have low hydraulic conductivity and are particularly suitable for EK dewatering and consolidation.

Aug 1, 2010

By T. Watanabe, M. Nakagawa, K. Kimapong

Ultrasonic wave was irradiated on metal surface in water to introduce compressive residual stress. The ultrasonic wave that was oscillated with 19.5 kHz ultrasonic transducer and amplified with a step type horn was irradiated. Slight plastic deformation occurred at the surface region of pure metal such as Cu and compressive residual stress was introduced. It seemed that the plastically deformed depth from the metal surface corresponded approximately to the depth of introduced residual stress. The higher compressive residual stress could be introduced into the surface of Cu-Zn brass and SUS304 stainless steel because work-hardening was simultaneously induced to those alloys. Furthermore, since martensitic transformation was induced by the plastic deformation in the case of SUS304, the compressive residual stress could be introduced more deeply into the surface region. The residual stress of SUS304 reached to the maximum value of 574 MPa by irradiating for 5min.

Jan 1, 2004

By F. Schulz

NA's primary smelter has continually increased its production output in the past decade, making it necessary to improve the lifetime of the casting moulds for copper anodes. The current throughput of more than 1,100,000 tonnes per year of copper concentrates amounts to an output of about 450,000 tonnes per year of anode copper at NA's Hamburg plant. The anodes are cast on a single casting wheel with 24 anode moulds. Besides the stable chemical analyses, the reproducible geometry of the anodes is an important precondition for the success of the subsequent electro-refining process. The anode moulds are subjected to thermally-induced alternating stress and side reactions with the melt. Typical signs of wear will be shown and discussed. Different processes to produce anode moulds will be introduced and the results in terms of their lifetime and the quality of the anodes themselves will be discussed. Finally an outlook is given on possible efficiency improvements.

Jan 1, 2007

By M. Kawahara, H. Sunayama

Oxidation rates of the cubic specimens, which were prepared by cutting the shaped magnesia-carbon bricks, were measured continuously with a thermo balance in the temperature range from 1273 to 1 823 K in N2-02 and Ar-02 mixed gas with 2.1 x 104 and 3.7x 102 Pa of oxygen partial pressure respectively. The effect of the graphite content, the maximum grain size of magnesia clinker and the oxygen concentration in the atmospheric gas on the oxidation rate for the MgO-C refractory has been investigated. The value of effective diffusion coefficient of O2, which diffuses through the porous decarburized layer, decreased with the decreasing of the porosity and the oxygen concentration in the external gas phase. It was speculated that the dense layer formed easily due to the high tortuosity of pores and the low recession speed of the carbon interface in the MgO-C bricks.

Jan 1, 2004

By K. Madi, E. Yeugo Fogaing, S. Forest, M. Boussuge, L. Massard, M. Huger, Gaultm C.

This study has been carried out owing to the French research program PROMETHEREF, which aims to improve the knowledge of thermal and mechanical properties of industrial refractories at high temperature. In this frame, this paper relates a collaborative study between Saint-Gobain CREE, R&D Centre for Saint-Gobain Ceramics & Plastics in Europe (Cavaillon), the Materials Center P.M. Fourt of Ecole des Mines de Paris (Evry) and the Research Group on Heterogeneous Materials (GEMH) of ENSCI (Limoges). Data collected at high temperatures by using different means (bending tests, ultrasonic measurements,...) allows the identification of the high temperature behavior of two fused cast materials, produced by Saint-Gobain group for the glass manufacturing industry. The results emphasize the importance of the transformation of zirconia and of the viscosity of the glassy intergranular phase on the mechanical behavior. Damage under the form of microcracking caused by thermal expansion mismatch between the phases is also observed during cooling down at low temperature, when the material is elastic.

Jan 1, 2004

By I. Takahashi

Recently, electronic devices have become smaller for some kinds of electronic devices, thermal dissipation and electrical conductivity of conventional Fe based alloy becomes insufficient. We selected the Cu-Fe based alloy CDA19400 and optimized the wire manufacturing process. Precipitates during aging treatment were observed by TEM. The size and distribution of the precipitates varied according to solution treatment temperature. With solution treatment at 950°C, the precipitates of y-Fe as fine as 10 nm were distributed dense in the copper matrix with coherency. For the solution treatment at 750°C, y-Fe of approximately 200 nm was observed. Comparing heat resistance of drawn wires, the material at 950°C treatment was superior. Electrical conductivity decreased from 63% IACS upon aging to 29% IACS by drawing. It is considered as particular phenomena for wires where materials are drawn with high reduction ratio. By the optimized manufacturing process, we successfully developed a new wire that has superior in strength, thermal conductivity, electrical conductivity, heat resistance and repeated bendability.

Jan 1, 2007

By M. Boussuge

Ceramics and refractories have many common constituents and consecutively exhibit several analogous properties. For example, concerning the thermomechanical properties this paper will focus on, the type of creep that can be observed in both materials is often the same (kinematic hardening). Changes in microstructure (phase transformation, dehydration, sintering, crystallisation,...), induced by heating and/or cooling, can also drastically modify the mechanical behaviour of ceramics and refractories. But the coarse granulates, the porosity and the impurities contained in industrial refractories may lead to specific responses of this material to thermal and/or mechanical loadings. In particular, some differences can be observed with technical ceramics in the main type of damage observed in service : diffuse damage in refractories (microcracking) and localised damage in ceramics (macrocracking). In this paper, the possibilities of transferring a part of knowledge from ceramics to refractories will be discussed, in the field of thermomechanical properties : experimental characterization techniques, mechanical behaviour models. Finally, some problems caused by scale effects and by the integration of thermomechanical properties of refractories in the numerical simulation of industrial structures will be evoked.

Jan 1, 2004

By James R. Yeager, Eric L. Hoffman, John R. Clark

"Abstract -This paper describes fire assaying and ‘high tech’ alternatives for gold analysis, including advantages and disadvantages of each method. These ‘high tech’ methods include INAA (instrumental neutron activation), aqua regia digestion/AA (atomic absorption), GFAA (graphite furnaceatomic absorption) or ICP/MS (inductively coupled plasma emission mass spectrometry) and a combination of cyanidation with AA, GFAA or ICP/MS methods.Fire assay remains the stalwart among analytical methods for gold but, even with its multiple analytical finishes, is not fool-proof for recovering 100% of the gold present. Consumers of assays should not blindly trust the assay results without consideration of quality control data. Laboratories can and do make mistakes. Some of these can be easily discovered if you do your own due diligence. All these measures should ensure that gold analysis values from successive campaigns and from different laboratories meet acceptable levels of accuracy and precision, and can be correlated together, particularly when they occur in neighboring holes. This is essential just as much for prospect evaluation as for project feasibility."

Jan 1, 1998

By Mary Jean Buchanan

The last twenty years have seen the advent of environmental concerns and sustainable development, and the industry has witnessed the rise of Environmental Management Systems and their registration through several international standardization systems such as EMAS and ISO 14001. Beyond EMS and ISO 14001, which new goal the mining industry should aim at. Life-cycle assessment (LCA), another tool from the Environmental Management System series, is also on the rise and currently the object of an international standard (ISO 14040:1997). Through LCA, it is possible to assess the environmental aspects and potential impacts associated with products and services, taking into account all the activities required for its fabrication, its use, its transportation and its disposal. How could LCA be applied to the mining industry ? Is the international market pressurizing on mining companies to supply an ?environmental ore?? What about the automobile industry and its use of LCA ? Will it influence the ferrous and non-ferrous metal industry, suppliers of raw materials ? This paper presents a review of possible applications of LCA for the mining industry as well as world trends.

May 1, 2001

By Masakazu Daté

Moisture effect has been studied for the CO oxidation over Au/TiO2, Au/Al2O3 and Au/SiO2, in the range of H2O concentration over four orders of magnitude. It has been found that the catalytic activity is generally enhanced by moisture in the reactant gas. The enhancement is as large as two orders of magnitude. Response to the moisture concentration, however, depends on the support oxide, indicating different contributions of the support to the reaction steps. The moisture effect is reversible and the activity is mainly determined by the amount of moisture absorbed by the catalyst. The apparent activation energies are not significantly influenced by moisture for Au/TiO2 and Au/Al2O3. On the contrary, non-uniform conversion curves versus temperature observed for Au/SiO2 are drastically changed, which indicates that the reaction over Au/SiO2 does not take place at low temperatures without moisture. The moisture effect may be probably attributed to the decomposition of carbonate species accumulated during the reaction, while the ?OH group might directly participate in the reaction pathways as a promoter.

Oct 1, 2003