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By Kan Song, Lin Liu, Hengzhi Fu, Jun Zhang, Haijun Su, Xiaojiao Jia

"Al2O3/YAG/ZrO2 eutectic in situ composite has been regarded as new generation of high temperature structural material due to its excellent performance even close to its melting point. The directionally solidified Al2O3/YAG/ZrO2 eutectic ceramics are prepared by recently developed Laser Floating Zone Melting (LFZM) apparatus in which a splitter mirror is used to obtain two beams with the same quality from one CO2 laser. With the two laser beams irradiate the sample from opposite directions, the sample is zone melted. The apparatus configuration and the solidification processing are described in detail. The solid/liquid interface morphology is studied and the mechanism of microstructure formation especially the characteristic of eutectic cellular is discussed. It is shown that YAG and ZrO2 phases play a leading role during the ternary eutectic growth. Meanwhile, the relationship between the solidification microstructure and the processing parameters are investigated.IntroductionAl2O3/YAG/ZrO2 ternary eutectic in situ composite, due to its excellent high temperature mechanical properties, is now considered to be a promising candidate material as a replacement of nickel based super alloy for new generation aero space engine turbine blade [1]. They exhibit flexural strength of 360-500 MPa from room temperature to 2073K in air atmosphere [2]. The compression creep strength at 1873K is 433MPa with the strain rate of 104/s [3]. However, because of the high melting point and complex physical properties, there remain still many difficulties for its application. One of the bottlenecks is the poor understanding of the relationship between microstructure and solidification conditions."

Jan 1, 2012

By Dieter Offenthaler

Catalysts used in petroleum industry often contain valuable amounts of PGMs. The typical recycling route for those materials is the pyrometallurgical one, but this treatment way offers limited flexibility with respect to small charge weights. A new process, combining a pyrometallurgical pre-treatment step of the ceramic carriers with a hydrometallurgical leaching procedure overcomes this disadvantage. It not only allows the economical treatment of even very small charge weights, but also gives the possibility to maximize the PGM yield by individually adapting the process to the different charge materials. Due to an ingenious process design, where all leaching agents and effluents are recycled in a closed loop and therefore no waste waters leave the process, process operation becomes very economical. However, the temperature-time-regime in the pyrometallurgical pre-treatment step is of major importance for the success of the whole process. Therefore various investigations have been done to identify how the different process variables in the pyrometallurgical pre-treatment influence the subsequent leaching procedure. It turned out, that the adjustment of the correct phase-modification in the ceramic carrier materials during the pyrometallurgical treatment is the key factor of this process step. Although it is a troublesome issue to exactly adjust the correct phase modifications, it is the prerequisite to take advantage of the benefits of this new process concept.

Jan 1, 2006

By Kenji Monden

"In order to obtain basic data for the development of highly thermally conductive composite materials, the thermal conductivity of a resin composite material with an Aluminum Nitride filler was assessed. Several different measurement techniques such as the xenon flash and the temperature wave thermometric analysis method were employed to gather data on these composites. An excellent match between theoretical and experimental data was achieved by employing a predictive expression that takes into account the effect of percolation on thermal conductivity.IntroductionA thermal solution composite is made by incorporating dense inorganic fillers with high thermal conductivity into a resin. Because the composite materials have high thermal conductivities, they have been used in electrical products that generate excessive thermal energy during operation, such as inverters, amplifiers and motor drivers. They function as electrically insulating and thermally conducting parts of the electric modules. As the uses of thermal solutions are expanded, composites of higher thermal conductivities will be required. The aim of this work was to investigate, evaluate, and try to predict the influence of key parameters on thermal conductivity and diffusivity. This was achieved by analyzing the effect of both volume fraction and shape of Aluminum Nitride ceramic fillers and measuring the thermal conductivity. In addition, the influence of percolation on thermal conductivity is considered. The thermal conductivity of the composites is discussed by employing a predictive equation using literature data of thermal conductivities for both the filler and resin. As well as thermal conductivity measurements the effect of volume fraction of the filler was also explored.ExperimentalSpecimen PreparationThe composite samples were prepared from silicone resin and Aluminum Nitride (AlN) fillers. The AlN fillers with an average particle size of 20 µm are shown in Figure 1. The mean diameters of the AlN particles used are given in Table I. For comparison the AlN fillers with an average particle size of 5 µm are shown in Figure 2. A planetary centrifugal mixer was used for simultaneously dispersing the components uniformly and de-aerating the mixture. After mixing, these materials were placed in a silicone rubber case and cured at 150 °C for 1 hour."

Jan 1, 2013

In accordance with the new concept described in the paper presented at the TMS annual meeting in 1989, 1 a new zinc cellhouse was constructed and successfully operated. The new concept was proposed in order to reduce energy requirements and to mechanize the electrode handling in the cellhouse. Major modifications involved the use of an electrode unit consistfog of assembled anodes and cathodes with frame bodies between each cathode and anode. The space between a cathode and an anode could be halved by this unit structure. In this paper actual operation data are summarized and discussed in comparison with the calculated figures.

Jan 1, 1990

By H. Bai, B. G. Thomas

"A three-dimensional finite difference model has been developed to study the liquid steel-argon bubble two-phase turbulent flow in continuous casting tundish nozzles. Experiments have been performed on a 0.4-scale water model to verify the computational model by comparing its prediction with velocity measurements using PIV (Particle Image Velocimetry) technology. The computational model was developed using CFX and then employed to investigate the effects of various casting process variables. A fast, simple inverse model to quantify relationships between those process variables was developed, based on interpolation of the numerical model results, using Bernoulli's Equation and advanced multivariable curve fitting methods. Predictions using this model compare well with plant measurements. The model has been applied to present trends and observations on the relationship between casting speed, tundish depth, slide gate opening, and argon gas injection rate. The results can also be used to predict .the theoretical steel flow rate through the nozzle, so that clogging conditions can be identified in the plant.IntroductionTundish nozzle geometry is one of the few variables that are both very influential on the casting process and relatively inexpensive to change. Designing an effective nozzle requires quantitative knowledge of the relationship between nozzle geometry and other process variables on the influential characteristics of the flow exiting the nozzle. This relationship depends on the flow pattern within the nozzle components. Most previous modeling studies of flow in the nozzle have focused on single-phase flow [1-4]. Argon injection into nozzle is an efficient and widely employed method to reduce nozzle clogging, even though the real working mechanism(s) are still not fully understood [5]. Argon injection may greatly affect the flow pattern in the nozzle, and subsequently in the mold. Therefore, two-phase flow modeling is needed to improve understanding of fluid flow in the nozzle."

Jan 1, 2000

By David Seymour

Newmont Gold Company (NGC) located in Northeastern Nevada has been processing carbonaceous and sulfide refractory gold ores through a chlorination circuit prior to cyanidation. A "Flash Chlorination" pilot plant was installed in 1987 in an effort to obtain higher chlorine utilization efficiency and increase gold extraction. The Flash Chlorination process oxidizes organic carbon and sulfide sulfur. It also deactivates preg-robbing carbon, making the ore amenable to cyanidation. Significant recovery improvements were observed using this new process. This scheme has also been instrumental in the processing of higher than normal grade ores at economic chlorine levels. The Flash Chlorination pilot plant has been successfully treating carbonaceous ore on a production scale since April 1988. This paper summarizes laboratory and pilot plant optimization test work, using conventional and statistical methods.

Jan 1, 1989

By I. Perus, M. Fazarinc, G. Kugler, M. Tercelj

"Ledeburitic tool steels are highly alloyed steels used for specific highly loaded applications but are characterized by low and variable hot workability. In this contribution the importance of selecting the right choice of some essential process parameters, i.e. casting temperature, solidification rate and soaking temperature, needed for improving the intrinsic hot deformability of ledeburitic tool steels, is studied. An inappropriate selection of casting temperature and cooling rate results in precipitation of unusual eutectic carbides that decreases the hot workability, whereas with the selection of appropriate soaking temperature the temperature range of safe hot working can be broadened. For each initial as-cast microstructure individually determined soaking temperature should be selected.IntroductionThe surface cracking during hot deformation of ledeburitic tool steels reduces mechanical properties and their industrial yield. These tool steels have high hardness, wear resistance and high tempering resistance on one hand, and high flow stresses and low hot deformability on the other. Decreased hot deformability of the tool steels is attributed to the type, size, shape, distribution, fraction of eutectic carbides and/or other phases, grain growth, etc. at upper limit while precipitation of secondary carbides and decreased recrystallization rate at lower limit of the safe hot deformation temperature range, [1-6].The occurrence of cracks on most exposed areas of workpiece are related to the areas where similar conditions related to upper and/or lower limit of temperature working range prevail, i.e. areas with accelerated cooling, areas with higher value of accumulated strains where also decreased recrystallization rate with simultaneously presence of higher tensile stresses takes place, furthermore areas of workpiece which are due to combustion conditions in furnace heated to higher temperatures, etc. Thus the areas, where combination of previously mentioned conditions prevails, are more exposed to cracking. This additionally requires that hot deformability of ledeburitic tool steel should be considered as a complex problem. Publications in the literature with regards to hot deformability of tool steels are predominately of a partial nature thus all reasons for unexpected occurrence of cracks are not sufficiently explained in available literature so far. Furthermore modern practice proves that previous processing parameters significantly influence the hot deformability and thus this cannot be considered as a constant value. During heating, soaking and hot deformation various processes take place: decay (decomposition) of carbides, formation of new carbides, dissolution of carbides and of alloying elements, etc. Thus depending on variation of process parameters and chemical composition, that consequently influences the processes related to carbides, shifting of decreased deformability at both limits of temperature working range to higher and/or to lower temperatures can occur, [1-14]."

Jan 1, 2012

By Mathilde Guilpain

A wide variety of plants are able to extract nickel (Ni) from soils and accumulate this metal in their foliage. Hydrometallurgical processes have been developed to recover Ni in the form of metal or salts, starting from the plant A. murale. They include: (1) a combustion step, to obtain ash containing 15–20% Ni; (2) a leaching step; and (3) purification. That whole flowsheet has been thoroughly investigated, and the processes scaled up to the pilot scale. Another strategy is presented here, consisting of recovering Ni without burning the plant. Ni can be extracted from the dry plant by water leaching, but the leachate is a multi-element solution from which Ni has to be separated. Selective precipitation of Ni hydroxide is not possible since Ni is bound to organic ligands. In this work, the plant leachate is processed by adsorption on the chelating resin DOWEXTM M4195. The results showed that Ni was selectively retained whereas the other main cations were not. Nickel could be recovered at the elution step. This methodology needs to be further investigated but these initial results are very encouraging and open the possibility of Ni recovery by agromining.

By Raymond E. Healy

Circuit samples from the HBMS concentrator were assayed for l5elements, and image analysis was done to determine the modal quantities, grain size distributions and liberations of the minerals. Material balancing was done on these data to determine distributions of the minerals in each concentrator stream. The ore was mined during the waning phase of mining and is diluted with backfilled copper smelter slag. The mill feed grades 1.0 wt% Cu and 1.8 wt% Zn. The slag silicate phases contain approximately 1.5 wt% Cu and 6.5 wt% Zn; therefore the Cu and Zn head grades due to chalcopyrite and sphalerite, are only 0.9 wt% Cu and 1.2 wt% Zn, respectively. The recovery of Cu in the Cu-concentrate (Cu-conc.) is only 77.5 %, whereas that of chalcopyrite is 89.2 %. Similarly, the recovery of Zn in the Zn-concentrate (Zn-conc.) is only 40.2 %, whereas that of sphalerite is 71.0 %. The slag accounts for approximately 60 % of the Cu, and 85 % of the Zn in the tailings. The main loss of chalcopyrite is as unliberated grains to the tailings, and the main loss of sphalerite is as free grains to the Cu-concentrate and as unliberated grains to the Cu-concentrate and tailings. Approximately 85 % of the chalcopyrite and sphalerite lost to the tailings. accounting for 8 % and 10 % of the respective minerals in the concentrator feed, occur as middling and sub-middling grains. Extremely fine regrinding would be required to liberate these minerals.

Jan 1, 1989

By M. M. Swan

A stratiform gold occurrence of Precambrian age located 20 miles southeast of Prescott, Arizona, within the Agua Fria Mining District, displays chemical, mineralogical, structural and lithological patterns indicative of a distal, exhalative volcanogenic environment. Metavolcanic and metasedimentary rocks of the Proterozoic Yavapai Series (1775-1820 m.y.) host the mineralization and are'characterized by greenschist grade metamorphism, steeply-plunging penetrative folds and steeply-dipping schistosity. Mineralization is confined to a 100m thick stratigraphic section that is comprised of a series of thin auriferous massive sulfide beds and intercalated schist .containing disseminated sulfides. The mineralization extends more than 4km along strike. Coincident with, and largely confined to the mineralized strata, are anomalous amounts of As, Sb, Cu, Pb, Zn and Ag and associated silicification, sericitization and carbonatization. This exhalative mineralized system is interpreted to have been deposited in a paleo topographic low on the distal flank of a submarine rhyolite dome and to represent the final episode of a Precambrian volcanic cycle.

Jan 1, 1981

By Vince Newberry

Alcan Rolled Products at Oswego, New York, commissioned Recycle II during May of 1995. Recycle II is an advanced technology UBC recycling facility designed to meet the most stringent environmental standards enforced to date in the United States, particularly with respect to NO, and particulate emissions. This paper addresses the exacting requirements and strategies of Alcan's Recycle II project andThorpe Technologies' design considerations and solutions for the supply of environmentally favorable melting furnace and delacquering systems. The furnaces are equipped with low NOx regenerative burners and furnace pressure and hearth gas flow controls designed specifically for processing the hearth gases through baghouses. The delacquering system is a new generation Apros concurrent flow unit designed for low NOx emissions.

Jan 1, 1995

By Milorad Cirkovic

Kinetics of copper concentrate oxidation in roasting processes in a fluidized bed reactor has been studied at temperatures between 600°C and 720°C using particles of 0.038 to 2.5 mm in average size. The analysis of composition of samples has been done by chemical methods. Phase composition has been determined by Siemens X-ray equipment with Cu anticathode and Ni filters at a voltage of 40 kV and a current of 18 mA. The content of sulphur has decreased from 33.23 to 19.02 mass percent with the increase of temperature, but the content of Fe304 has increased from 0.15 to 17.14 mass percent. The new mechanism of copper concentrate oxidation in a fluidized bed reactor is proposed in this study. It has been shown from the mathematical model that the velocity of oxidation of copper concentrate between 600°C and 720°C is virtually controlled by the rate of diffusion of 02 through the layer of reaction product.

Jan 1, 1999

By Claire A. Chanenchuk

Catalytic Extraction Processing (CEP), a technology commercialized by Molten Metal Technology, Inc., a US.-based company, can convert industrial, household, and government wastes into commercial resources. CEP is an innovative elemental recycling technology that uses a molten metal bath to completely dissociate hazardous or toxic components of a feed and convert them to valuable products. The catalytic action of the molten metal bath converts the feed to its elemental constituents and the reducing atmosphere prevents the formation of any dangerous byproducts (NOx, SOx, dioxins, furans, etc.). Selective reactant addition allows engineering of valuable products from otherwise unexploited resources. Synthesis gas is generated from hydrocarbon feeds, ferro-alloys from metallic wastes, and ceramics from select inorganic species. Commercial-scale processing of multiple wastes and waste surrogates has been carried out at a destruction and removal efficiency exceeding 99.9999 wt.%, validating theoretical predictions. Unlike conventional hazardous waste treatment technologies, CEP offers resource recovery, minimal byproduct generation, and the potential for closed-loop recycling.

Jan 1, 1994

By Hideo Nakae, Hideki Yamaura, Toshiaki Kimura

"In 1968 J. N. Reding et al. suggested processes for fabricating composites. According to their patent, decompression atmosphere, which occurs during the reaction between magnesium and oxygen and/or nitrogen in the closed system, causes the spontaneous infiltration of melt into narrow spaces such as ceramic preforms. However, they did not report the proof of this phenomenon or the industrial manufacturing method. Therefore, this research measured the pressure change among SiC particles surrounding molten aluminum. As a result, the pressure reduction during the Mg reaction was identified. Moreover, the existence of Mg3N2, which improves the wettability between Al alloy melt and SiC particles on the interface, was observed on the surface of particles. Applying these two phenomena, a new process for the manufacturing of cast discontinuously reinforced aluminum composites (DRA) was developed. This new method is expected to produce DRA without additional pressure.IntroductionWith the increasing demands for light-weight materials in the automotive and aerospace industry in recent years, ceramic particulate reinforced aluminum matrix composites called DRA (Discontinuously Reinforced Aluminum Composite) have been receiving significant attention because of its lightness, superior abrasion resistance, high heat conductivity and low thermal expansion [1-3]. Consequently, DRA was considered for electronic parts such as heat-sinks or a base for power semiconductors, and began to be applied for automotive parts including brake drums, discs, cylinder liners, pistons and so on [4- 6]. However, high machining cost is one of the significant barriers to widespread use ofDRA. One solution to this problem is the adoption of cast DRA that can be produce to near-net shape, reducing machining cost."

Jan 1, 2000

By Xu Weimin

The existing copper electrorefining tankhouse of Jinchuan Nonferrous Metals Complex (JNC) was commissioned in 1986 for refining blister copper anodes. Blister copper is produced by reverberating chalcocite separated from converter high grade nickel-copper matter by means of flotation. Special chemical analysis of the anodes shows, a composition of 93.02 - 95.72 % copper, 3.0 - 4.96 % nickel and 0.5 - 1.23 % sulfur. The wide range of composition makes the electrorefining process fairly different from others throughout the world. The initial nickel content of 20 ppm and sulfur 40 ppm or more in copper cathodes are reduced to 8.5 ppm and 11 ppm respectively. Since 1986 the tankhouse has undergone significant evolutionary modifications and implementations to ameliorate cathodes quality desirably. The important fact is that the N-additive was utilized through many studies and pilot and field trials successfully. While our primary purpose is to improve chemical quality of the cathodes, tankhouse capacity is increased considerably and the process is perfected satisfactorily. The tankhouse is described with special emphasis on JINCHUAN PROCESS. The upgrading of our product by the utilization of the N-additive is highlighted. The other aspects of the tankhouse including spent electrolyte treatment and by product nickel sulfate manufacturing are briefed as well. Key words: JINCHUAN PROCESS, anode, cathode, electrolyte, electrorefining, N-additive.

Jan 1, 1993

By Jae-Chun Lee, Jinki Jeong, Manis Kumar Jha, Divika Gupta, Pankaj Kumar Choubey

Rare metal indium (In) is mostly used as electroluminescent material in liquid crystal displays (LCD) monitors. Present paper describes leaching studies for the recovery of In from waste LCD monitors in presence of different other impurities. The leaching studies showed that more than 85% of In was leached out using 20% sulfuric acid at 60oC in mixing time 30 min at fixed pulp density 25 g/L. The solution could be purified using SX/IX and from the pure solution metal/ salt could be produced by evaporation, precipitation, electrolysis, crystallization processes.

Jan 1, 2014

By C. T. Yavuz

Higher environmental standards have made the removal of arsenic from water an important problem for environmental engineering. Iron oxide is a particularly interesting sorbent to consider for this application. Its magnetic properties allow relatively routine dispersal and recovery of the adsorbent into and from groundwater or industrial processing facilities; in addition, iron oxide has strong and specific interactions with both As(III) and As(V). Finally, this material can be produced with nanoscale dimensions which enhance both its capacity and removal. The objective of this study was to evaluate the potential arsenic adsorption by nanoscale iron oxides, specifically magnetite (Fe3O4) nanoparticles. We focused on the effect of magnetite particle size on the adsorption and desorption behavior of As(III) and As(V). The results show that the nanoparticle size has a dramatic effect on the adsorption and desorption of arsenic. As particle size is decreased from 300 nm to 12 nm the adsorption capacities for both As(III) and As(V) increase nearly 1000 times. Interestingly, this increase is more than expected from simple considerations of surface area and suggest that nanoscale iron oxide materials sorb arsenic through different means than bulk systems. The desorption process however, exhibits some hysteresis with the effect becoming more pronounced with small nanoparticles. This hysteresis most likely results from a higher arsenic affinity for magnetite nanoparticles. This work suggests that magnetite nanocrystals and magnetic separations offer a promising method for arsenic removal.

Jan 1, 2006

By Guoqiang Lv, Xi Yang, Wenhui Ma

Cast multicrystalline silicon ingots are widely used in photovoltaic manufacturing. A key issue to achieve high solar cell efficiencies is to attain an optimized temperature field during directional solidification (DS) process. This paper reports numerical investigation of multicrystalline silicon (mc-Si) ingot production using two major types of DS furnace. Specific examination is made on thermal distribution, interface shape and stress field. Evaluation is performed for the applicability of thermal system design to reduce thermal stress, improve crystal quality and enhance energy efficiency. The effects of procedure parameters and geometric configuration on temperature distribution are discussed as well to provide the viable solutions for systems optimization.

Jan 1, 2015

By K. B. Shedd

Questions regarding possible adverse health effects from exposure to zeolites arose when the inhabitants of two villages in Turkey were found to have high incidences of mesothelioma, a disease generally identified with exposure to asbestos. No asbestos deposits are known in the area, but some fibrous zeolites have been found. Further investigations have resulted in conflicting opinions as to whether fibrous zeolites are related to the high incidence of mesothelioma in Turkey. The U.S. Department of the Interior, Bureau of Mines examined the habits of domestic zeolites by scanning and transmission electron microscopy. Only erionite and mordenite particles possessed acicular to fibrous habits. With the exception of a rarely occurring woolly erionite sample, the fibrous zeolites were not dimensionally equivalent to asbestos.

Jan 1, 1982

By Oleg I. Platonov

Method of high-temperature reduction of oxygen-bearing sulfurous gas has been developed at Copper Plant (CP) of MMC ?Norilsk Nickel? Trans-Polar Division (PD) with the aim of producing elemental sulfur from Vanyukov furnace? off-gas. Non-explosive reduction technology of oxygen-bearing sulfurous gas by methane utilized at Copper Plant has been designed to separate the processes of gas heating and sulfur dioxide reduction based on different kinetic of the reactions oxygen fixing and SO2 reduction. First, natural gas promptly reacts with oxygen contained in the process gas to heat a gas mixture up to the temperature of sulfur dioxide reduction (1200C). Then isothermal reduction takes place within 1 sec. Combustion chamber (pre-chamber) design developed based on the above principles is presented. Practical experience of the two reduction reactors operation at CP since 1996 proves high efficiency of the developed reduction process. The volume efficiency rises dramatically thanks to the fact that both fuel and reducing agent are fed into the reactor volume in the form of high-speed turbulent jets providing an intensive mixing of the reacting gases. On condition of equal internal volume of the reactors, the developed process offers higher efficiency of reagent interaction resulting in sulfur conversion exceeding 90%, as compared to the equilibrium one.

Jan 1, 2006