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By Selda Ozkan

In this study, a combination of cathodic arc physical vapor deposition (PVD) and molten salt electrolysis methods were used to obtain ZrB2 layers on AISI 304 grade stainless steel surface. Prior to boriding, steel surface was coated with metallic zirconium via cathodic arc PVD method and then the zirconium coated steel was borided by molten salt electrolysis. Well adherent, dense, ZrB2 layers are formed on the substrates. The thickness of the ZrB2 layer showed dependence on the thickness of the metallic Zr coating layer and the time of boriding. During the boriding process the alloying elements of the substrate also took part in the coating structure depending on their diffusion characteristics.

Jan 1, 2010

By D. Death

The Tapping Camera Prototype (TCP) is an instrument being developed to record and analyse video of the molten metal stream entering a tapping crucible as it is tapped from an aluminium reduction cell. The development aims to provide potroom floor operators with continuous real time vision of the tapping process and provide an alert in the event of excessive bath contamination in the extracted metal stream. Longer term the system may provide sufficient data to enable control of the tapping process. The TCP mounts a wireless camera and periscope to view the molten metal stream via a peephole in the tapping crucible. Real time video is recorded to either digital video tape or computer disk for subsequent video analysis to quantify the bath material drawn into the tapping crucible with the molten aluminium. The images transmitted by the camera are available on a handheld LCD video screen. This work is an initiative of the CSIRO?s Light Metals Flagship.

Jan 1, 2006

By F. Kavicka

An original application of ANSYS simulated the forming of the temperature field of a massive casting from ductile cast-iron during the application various methods of its cooling using chills. The numerical model managed to optimize more than one method of cooling but, in addition to that, provided serious results for the successive model of structural and chemical heterogeneity, and so it also contributes to influencing the pouring structure. The file containing the acquired results from both models brings new and, simultaneously, remarkable findings of causal relationships between the structural and chemical heterogeneity and the local solidification time in any point of the casting. The determined relations therefore enable the prediction of the face density of the spheroids of graphite in dependence on the local solidification time. The calculated temperature field of 500x500x1000 mm casting of ductile cast-iron with various methods of cooling has successfully been compared with temperatures obtained experimentally. Acknowledgments. This analysis was conducted using a program devised within the framework of the GA CR projects (No.106/04/1334, No. 106/04/1006 and No. 106/04/094), of the COSTAPOMAT-OC526.10, MPO/FI-IM/021, EUREKA No.2716 COOP and KONTAKT 14/ 2005/06.

Jan 1, 2006

By Ailton da Silva Ferreira

Thermoset polymers, like the polyester, become harder with increasing temperature owing to molecular crosslink formation, which is a thermal benefit for composite matrix applications. Natural lignocellulosic fibers, however, have low thermal resistance and tend to degrade with increasing temperature. Therefore, the combination of a lignocellulosic fiber, as reinforcement, with a thermoset polymer, as the matrix, results in a composite material with complex thermal behavior. In the present work, a thermal analysis was conducted on polyester composites with different amounts of curaua fibers. Both TGA and DTG curves were analyzed to determine the effect of the curaua fiber on the thermal resistance of the composites. It was found that the curaua fiber sensibly affects the thermal behavior of the polyester matrix for fiber amounts above 10% in volume. This effect is associated with an increase in thermal degradation.

Jan 1, 2010

By Jinhui Li

Silver is a very important metal used in a wide range of applications. It is necessary to recovery of Ag from electronic wastes for increasing of Ag price and circumstance protection. For separating and recycling Ag from Ag-Cu composite materials, thermodynamic data of reaction is calculated and some experiments have been proceeded with Ag-Cu composite material scraps, time, temperature, nitric-sulfuric mixed acid volume ratio and the volume ration of mixed acid vs. water have been discussed. The results show that the optimization conditions is that nitric-sulfuric mixed acid volume ratio 5:95, volume ratio of mixed acid vs. water 10:1, temperature 55?, time 25min. In the conditions, Ag can be selectively leached from Cu-based composite material, Cu base is not eroded nearly.

Jan 1, 2009

By P. N. Anyalebechi

Keywords: Aluminum alloy 3004, Solidification rate, Homogenization, Second phase particles The effects of the fineness of as-solidified cast microstructure and temperature on the response of aluminum alloy 3004 to homogenization heat treatment (a.k.a. preheat) have been investigated. The study was conducted at 538oC and 595oC on directionally solidified laboratory-size ingots with a range of solidification rate of 0.10oC/s to 29.4oC/s. Optical and electron microscopy, quantitative image analysis, electrical conductivity, and electron probe microanalysis were used to quantify the effects of the homogenization heat treatment on the microstructure of aluminum alloy 3004. In general, increase in fineness of as-cast microstructure and homogenization temperature enhances the a-transformation reaction, dissolution of Mg2Si, elimination of dendritic microsegregation, and dispersoid formation. The homogenization heat treatment reduces the average size of second phase particles in castings solidified at <1oC/s. However, in castings solidified at above 1oC /s, homogenization causes the coarsening of the second phase particles. Mn in solid solution is independent of homogenization heat treatment temperature.

Jan 1, 2005

By Sutham Niyomwas

Keywords: Al2O3-SiCW, Ceramic Matrix Composite, Carbothermal Reduction, Kaolin The formations of Al2O3-SiCw composite have been obtained in situ by carbothermal reduction of a mixture of kaolin and activated carbon. The reaction temperature was controlled at between 1400°C to 1600°C. The synthesized products were mixtures of alumina and silicon carbide in the form of whiskers. The effects of milling time of precursors and reaction temperature are presented. XRD and SEM analyses indicate complete reaction of precursors to yield Al2O3-SiC as product powders, with the SiC having porous and whisker morphology.

Jan 1, 2005

By Jilai Xue

Industrial wastes containing 30-50 wt.% Al2O3 and 40-60 wt.% SiO2 may serve as an alternative resource for producing Al-Si alloys. Various raw materials such as used refractory materials from metallurgical furnaces, coal fly ash, andalusite residues, and so on were tested in laboratory to produce Al-Si alloys using carbon-thermal reduction process. A mixture of anthracite and petroleum coke was used as reducing agent. One of the most important operations was to prepare the briquettes made of different raw materials with varying contents of Al2O3 and SiO2. The effects of briquette property, A/S ratio (mass ratio of Al2O3 and SiO2), the amount of carbon reducing agent, on the reduction process and the resulting metals were investigated. The results are useful for development of an alternative technology for Al-Si alloy production, which has the potential application in recycling metals from industrial wastes containing Al2O3 and SiO2.

Jan 1, 2010

By Zengjie Wang

Kinetic study of hydrochloric acid leaching of Panzhihua ilmenite from China is presented. Both temperature and concentration of hydrochloric acid have significant effects on the rate process of Fe dissolution from ilmenite ore, while the ratio of liquid to solid has little effect on the Fe dissolution. The Fe dissolution is found to follow the spherical model f (??) =1-(1- ??)1/3 and the apparent activation energy is calculated as 47.21 KJ/mol, suggesting a chemical reaction controlled mechanism. The dissolving behaviors vary at different kinetic stages. At the beginning the amount of the dissolved Fe and Ti increased monotonically with leaching time, while about 15 minutes later the dissolved Ti in the form of TiOCl2 began hydrolyzed into TiO2 fines reunited on the ilmenite ore surface, as observed by SEM and EDS technique. For the unreacted ilmenite particles covered by a layer of hydrolyzed TiO2, the leaching seemed to be as a selective leaching of iron and because Ti dissolved from and hydrolyzed rapidly again into the unreacted ilmenite particles. The leaching process can be ended 4 hour later when almost of Fe has dissolved into the solution and TiO2 remains as solid residues. The effects of acid concentration and leaching temperature were also investigated.

Jan 1, 2009

By Zhou Wenbin

In this paper the mechanical properties of high carbon equivalent cast iron for automobile brake discs were analyzed through thermal analysis curves. Experiment results show that the mechanical properties have a strong correlation with thermal analysis curves and an effective way to predict the mechanical properties of high carbon equivalent cast iron was proposed based on the features of thermal analysis curves.

Jan 1, 2010

By Aline Maria dos Santos Teixeira

Serpentinite is an ultra basic and metamorphic rock consisting mainly of magnesium, calcium and silicon oxides. The rock under study is a host rock of chromite mine located in Andorinha, BA. The objective of this paper is to evaluate the rock&apos;s physical and chemical characteristics to be used as an additional fertilizer of acid soils. After comminution, rock samples were submitted to chemical analysis, XRD, SEM-EDS and TGA. Afterwards, particle size distribution was determined. Result analysis confirms that our rock consists mainly of dolomite, calcite and diopside. According to the result obtained, it can be said that the serpentinite rock has promising applications in agriculture for the correction and additional fertilization of acid soils. However, it is necessary to study the characteristics of the rock such as its dangers and toxicity as well as evaluate them according to the legislation for corrective acidity.

Jan 1, 2010

By S. Uddin

An integrated device has been developed to measure sedimentation potential, conductivity and pH simultaneously of particulate systems. Maxwell?s model was used to calculate volume fraction of solid from the conductivity data. In this approach, all system variables are known and zeta potential can be calculated from Smoluchowski?s equation. The technique is validated by comparing zeta potential vs. pH for alumina and silica suspensions with electrophoresis measurements. The technique was extended to mixed alumina/silica systems. Sufficient column height along with size difference between the two minerals allowed gravity fractionation during settling. Sedimentation potential measured over time identified the transition from one mineral to the next. Using XRD analysis the results supported the correlation between surface charge and sample composition. This is a step towards characterizing surface charge of mixed systems of interest in mineral processing.

Jan 1, 2010

By Daudi R. Waryoba

Keywords: Wire Drawing, OFHC Copper, Recrystallization, Orientation imaging Microscopy (OIM), Texture inhomogeneity Textural inhomogeneities have been investigated in oxygen free high conducting (OFHC) copper wire drawn at room temperature to a true strain of 2.31, and isothermally annealed at 250°C and 750°C for annealing times ranging from 10 s to 1 hr. Local orientations were mapped by means of orientation imaging microscopy (OIM). The microtexture of the drawn wires showed a strong <111> + weak <100> duplex fiber texture at the inner core, whereas the mid and surface regions had a comparatively weak texture. Annealing at 250°C resulted into a recrystallization which originated from the mid section, proceed towards the surface regions and ends in the inner core. Recrystallization resulted into a strong<100>+weak<111> duplex fiber texture. A similar textural inhomogeneity was observed during short annealing at 750°C. However, prolonged annealing gave rise to abnormal grain-growth that proceed from the inner core to the outer surfaces with a dominant <111> fiber component at the inner region and mixed components of <111>, <100>, and <112> at the outer surfaces.

Jan 1, 2005

By A. Krishnan

Keywords: Tantalum extraction, SOM Technology, inert anode, membrane stability The Solid Oxide Oxygen Ion conducting Membrane (SOM) technology offers great potential for environment friendly and energy efficient extraction of high-energy content metals. This work was performed to demonstrate the technical and commercial viability of the technology to produce tantalum metal directly from tantalum oxide and ore concentrates using a solid-oxide, oxygen-ion-conducting membrane (SOM). The process can be used to efficiently produce tantalum metal without expensive pre-processing of raw materials and without harmful by products. The work reported in this paper is: the proof that high purity tantalum metal can be produced, study of the electrochemical behavior of the cell and the method to increase membrane stability.

Jan 1, 2005

By Kymberley Worrell

The Cripple Creek and Victor Gold Mine was acquired by Newmont in August 2015. The high grade flotation mill project was commissioned in February 2014. The mill to date has been throughput limited due to mechanical and design issues. In order to create the most value from a throughput limited plant a campaign to provide timely ore characterization was undertaken. A diagnostic leach methodology was developed to determine gold associations by ore type. The resulting associations were then used to characterize feed blend; gold losses and optimize gold production. The diagnostic methodology is presented along with discussion on flotation implications.

By Theo Lehner

"The Boliden Rönnskär Smelter operates in the European Context of tight EH&S limits, with ever increasing regulations and tribulations. The near future promises to bring new burdens in the form of C02 trading, miners and pre-treaters increased appetite for a larger share of contained values, and changing compositions and competition in raw materials. On the other hand, European Smelters such as Rönnskär, Harjavalta have demonstrated an astonishing power of survival. This presentation lists and comments on current challenges but opportunities for increased survival power are also presented. One example of the latter is the ongoing investment into increased treatment capacity for e-scrap.UPDATE ON RÖNNSKÄR OPERATIONSThe Rönnskär Smelter has achieved 80 years of age with no signs of retirement. The smelter is most active in spite of its age! And it has undergone some face lift operations to maintain its attractiveness.Raw material, processing facilities and a market for the products are some essential prerequisites for a viable operation. To justify long term survival, economic terms such as return on investments and positive cash flow need to be considered. Below, we illustrate how the Rönnskär Smelter complies with these terms. To update the reader on current operations, our current flow sheet is depicted in Figure 1. The figure summarizes our current input and output."

Jan 1, 2012

By A. G. Merma

In this work, the electrocoagulation technique was studied in order to treat chemically stabilized concentrated oil-water emulsions. This study was mainly focused on the effects of operating parameters such as initial pH, current density, reaction time, electrode distance and inlet concentration on the separation of oil as measured by the chemical oxygen demand -1(COD) method. The synthetic emulsion was prepared from Shell - Talpa 30 oil (3g.L-1) and sodium dodecyl sulfate (1.0 g.L), having a Zeta potential around -70 mv at pH 8.7. The process was carried out in an electrocoagulation cell with a set of four parallel monopolar electrodes. This set consisted of two aluminum plate anodes and two 316L stainless steel plate cathodes. Kinetic curves showed that the electrocoagulation process exhibits three phases: (1) an initial phase, where the COD did not decrease because the solution had not reached the minimum amount of dissolved aluminum required to cause the break-up of the emulsion, (2) a reactive phase during which COD decreased due to possible agglomeration of the precipitates and (3) a steady-state phase where the COD did not change. The results showed that the period to reach the reactive phase decreased as the current density increased and the pH values decreased.

Jan 1, 2009

By Xi Zhang

A technique for fabricating free-standing, high-aspect-ratio porous and pillar-type Ni structures has been developed using wet Si processing. A wafer of (100) Si was initially etched in HF solution to form deep pores with micron-sized diameter. The aspect ratio can exceed 200. By introducing the as-etched Si into a defined aqueous Ni2+ solution, Ni deposits grew rapidly onto the sidewalls and replaced the Si. Long-time immersion allows the Si sidewalls to be completely converted and thus form a metallic Ni structure with high-aspect-ratio pores. It is known that close-packed submicron Si pillars can be formed by oxidizing and subsequent etching of the macropore sidewalls. Treated in the same Ni solution, high-aspect-ratio Ni pillars were correspondingly emerged by replicating the original pillar-type Si structure.

Jan 1, 2006

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 Qiang Zhang

Hybrid composites are fabricated by adding two reinforcements into matrix materials so that the expected excellent properties can be achieved through the combined advantages of short fibers, and different size particles (micron or submicron), which provide a high degree of design freedom. In this paper, hybrid preforms were produced with the different size reinforcement of the Al2O3 particles and short fibers. The Al-Si alloy-based hybrid composites were fabricated by preform-squeezing casting route. The structure and performance of composite materials were studied with the Transmission Electron Microscopy (TEM), and Scanning Electron Microscopy (SEM). The results show that the reinforcements, both particles and fibers, distribute homogeneously in the matrix materials, and the properties of composites are found to improve in comparison with the matrix Al-Si alloy.

Jan 1, 2009