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By Kazuya Kitatani, Gen Sasaki, Naoto Ohta, Hideharu Fukunaga, Makoto Yoshida, Jin Pan, Kenya Nagahisa, Toshihiro Ishikawa

"A sintered SiC (Tyranno-SA) fiber-reinforced MAS glass matrix composite was fabricated by using a slurry infiltration method and hot-pressing. The microstructure and mechanical properties were investigated: To prepare the preform, the MAS glass slurry including a dispersing agent was infiltrated into a bundle of the fibers. The preform was then hot-pressed under the conditions of 1473 K, 30 MPa, 3.6 ksec. A unidirectionally-reinforced oxide matrix composite with 50% Vf. of the fiber and a density of 2.84 g/cm3 was obtained. As the mechanical properties at room temperature, the three-point flexural strength- and quasi-static adsorbed energy were 500 MPa arid 6,000 J/m2, respectively. Without graphite or an h-BN pre-coating on the surface of the fiber, pull-out and bridging of the fibers from the matrix was found, and this leads to a high value of the adsorbed energy. By TEM observation, nano-scale crystalline products were found between the fibers and the glass matrix. The push-out test reveals that this layer causes the appropriate debonding of the interface during the fracture process of the composite.Introduction It is known that the CFCCs (continuous-fiber-reinforced ceramic matrix composites) are characterized by their non-linear fracture behavior, which is' hardly found in monolithic ceramic materials. It is inevitable for the CFCCs to exhibit a large fracture toughness so 'that debonding of the fiber/matrix interface; pull-out and bridging of the fibers then' occurs during the fracture process. This series of fracture behavior is known as the so-called ""the mechanism of toughening of the CFCCs"". Thus, different from the MMCs in which strong interfacial bonding is necessary, the interfacial strength of the CFCCs has to be controlled. As techniques for controlling the interfacial strength, it is also known that both a CVD-graphite coating and an h-BN coating are effective to induce the mechanism of toughening[1,2]. In the case, of the Si-C-O or Si-Ti-C-O fibers/glass or crystalline oxide matrix composites, it is reported that the formation of the in-situ graphite layer, which is also effective to increase the fracture toughness of the CFCCs, is often found during the fabrication process such as hot-pressing. The lower the crystallinity of the Si-C-O fibers, the higher is the tendency to form the in-situ graphite layer as found by the chemical reaction between the fibers and the glass matrices[3-12]. On the-other hand crystallized stoichiometric 'SiC fibers are attractive for high temperature service because of the higher phase stability compared to the Si¬C-O or Si-Ti-C-O fibers. However, in the previous, studies, the mechanical properties and the interfacial chemical reaction of the crystallized SiC fibers / glass matrix Composites have still been unknown. In this study, a polycrystalline 'sintered SiC fiber-reinforced MAS glass composite was fabricated. The mechanical properties and microstructure were then investigated. The slurry infiltration technique followed by hot-pressing was used to prepare the composites. The formation of the in-situ graphite layer and the relationship between microstructure and mechanical properties at room temperature were examined by the TEM observation of the fiber/matrix interface."

Jan 1, 2000

By K. Sanjay

Factorial optimisation technique has been used to develop regression equations at different time intervals for extraction of manganese from precipitated manganese oxide/hydroxide in sulphuric acid using charcoal as the reductant. The three parameters chosen for a 23 full factorial design were : acid concentration, amount of carbon and temperature. The regression equations were used to predict >> 90% extractions as well as kinetic data.

Jan 1, 1996

By J. Pérez

A lead smelter slag with high copper, lead, arsenic and silver contents was treated at laboratory scale for arsenic removal. The slag was first leached at atmospberic pressure with sulfuric acid and oxygen. According to arsenic contents leaching of most of the arsenic was achieved in either one or two stages, producing a lead-silver rich residue and a solution high in copper and arsenic concentrations. Alternative routes were considered to treat the resulting solution. Firstly, solvent extraction of arsenic with a mixture of TBP and 2-etbyl-bexanol was tested and extractions of over 95 percent of arsenic were achieved. Secondly, a copper arsenate precipitation treatment was done to eliminate arsenic and copper from solution.

Jan 1, 1996

By A. Ohno

"A new near net shape casting process, OHNO Continuous Casting (OCC), has been recently developed. In this process, molten metal is fed into a heated mold maintained at a temperature above the solidification temperature of the metal being cast. Solidification begins from the central core of the casting rather than the wall of the mold. With the heated mold, the formation of crystals on the mold wall is prevented and solidification occurs out of contact with the mold surface. This produces near net shaped products with smooth, mirror-like surfaces and unidirectional grain structures free from cavities, porosity and segregation. Any crystals formed at the beginning of solidification decrease in number as solidification progresses and eventually a single crystal product is obtained. This process is applicable to any metal alloys, converting them into new materials with superior properties and quality.IntroductionAs a result of growing technical demands for more advanced and diversified materials, the OHNO Continuous Casting (OCC) technology has found many new applications in industry. Considerable interest in the process has been shown in Japan and other countries because of its distinct ability to:produce a single crystal, (1)produce a remarkably clean cast surface without a witness mark,provide extremely good ductility,and reduce casting defects and segregation.This paper provides an overview of the principle of the OCC process and describes the remarkable characteristics of the material produced by this method."

Jan 1, 1988

By Kevin L. Purdy

The Process Technology Center of Phelps Dodge Mining Company (PDMC) .operates several test facilities in support of PDMC's hydrometallurgical operations. Installations for small leach columns, 15 cm. to 60 cm. (6 in. to 24 in.) in diameter, and large leach columns, 1.8 m. (6 ft.) in diameter, are complemented by a test facility for SX/EW operations. The history of and reasons for the development of these facilities: are described and original standard equipment is discussed. A primary goal in constructing these facilities was achieving a high degree of flexibility to allow for testing of new equipment and new leaching and SX/EW technologies as they are developed. Along with this challenge, construction of a filly integrated SX/EW test facility on a small scale brought its own set of challenges.

Jan 1, 1999

By Kimberly Conner-Mills

Due to increasingly stringent worldwide environmental regulations for gaseous, aqueous and solid waste emissions, conventional smelting technology cannot effectively process arsenic containing materials. Many globally significant copper properties have copper sulfide mineralogy that has a high arsenic content present as enargite with significant contained precious metals. As global copper, silver and gold demand increases while significant world resources decrease, treatment of sulfide orebodies with enargite is becoming increasingly important. Methods to selectively dissolve and fix arsenic, leaving behind clean copper and precious metals-bearing concentrates could effectively treat these ores.

By C. H. Bucknam

A review of phase analysis methods used to characterize refractory gold ores is presented. Updating of assay methods using database technology, on-line instrument interfacing and response surface modeling is highlighted. The use of assay results to classify ores for metallurgical purposes is demonstrated.

Jan 1, 1987

By Michael Sheedy

Sulfuric acid is widely used as an electrolyte for the electrorefming and electrowinning or metals. Impurities in this electrolyte are controlled by continuously bleeding solution from the tank house. In addition to the contaminant these bleed streams contain high levels of sulfuric acid and the metal being recovered. Subsequent treatment of these bleed streams often requires neutralization which generates large volumes of solid waste. Absorption resin technology employing a novel ion exchange technique known as Recoflo® allows the separation of the mineral acid from dissolved metal salts. The recovered acid is suitable for recycle back to the electrolyte circuit. The metal salt and other contaminants leave the process free .of the sulfuric acid. In this process, known commercially as the APU®, ion exchange resin is used to sorb sulfuric acid while excluding the metal salts. The purified acid is then removed by washing the resin with water. The process has been extensively used for the recovery of waste pickling acids in the steel industry and anodizing solutions in the aluminum industry. In the mining and metallurgical industries the process has been successfully evaluated for the separation of excess sulfuric acid from copper electrolytes, the removal of magnesium and manganese contaminants from zinc electrolytes, and nickel and copper from copper electrolytes. A full scale installation on a copper refinery bleed stream at Palconbridge's Kidd Creek plant in Timmins, Ontario has now been operating successfully for more than 1 year while pilot field trials have been successfully completed on other applications.

Jan 1, 1997

By Anne Kvithydl

Printed circuited boards contain considerable quantities of valuable metal, while also containing many environmental pollutants making them unsuitable for landfill. In this study the decomposition of common plastics used in printed circuit boards were studied. Polytetrafluoroethylene (PTFE), polyvinyl chloride (PVC) and polyethylene (PE) were heated in both CO, and argon atmospheres using a thermo-gravimetric furnace (TG) coupled to a mass spectrometer (MS). Soda ash Na,C03 and baking soda NaHC03 were used as reactants. The degradation temperatures and evolved gases are presented for single plastics and mixtures. Mixed plastics are shown to behave as a sum of the individual plastics. The mass loss temperature is the same in CO, and argon. However, less residue is formed when heated in CO,.

Jan 1, 2008

By M. Vondersaar, B. Bulnes

Quemetco, Inc.,. as a subsidiary of RSR Corporation, operates one of RSR's three secondary lead smelters in the City of Industry, California, next to a residential area within Los Angeles County. The Reverberatory furnace serves as the main reactor for melting lead grid and paste recovered by the battery crushing system. Feed material is introduced via screw conveyor after drying in an upstream rotary kiln. Slag produced by the Reverb flows directly to an electric arc furnace. Products from this one-pass furnace system consist of soft lead bullion from the reverb, hard lead bullion from the arc furnace, and a non-hazardous slag from the arc furnace. Furnace bullion is processed into finished product in a six-kettle refinery. An overview ·of plant operations is presented. Where applicable, references will be made to changes that have taken place during the last decade.

Jan 1, 2000

By T. Feldmann

Despite the ubiquity of applications for germanium, there is a lack of practically useful solubility data in acidic solutions. Previous studies were done at ambient temperature and only for commonly used acids (H2SO4, HCl). Hence, an investigation of the solubility of GeO2 in different acids was undertaken. Several inorganic and organic acids were studied in the concentration range of 1–11 mol/L and at 23, 40, and 60 °C. In the case of H2SO4 and HCl previous data was confirmed. Lower acidity resulted in a higher solubility for Ge at all tested temperatures. Tests done at 40 and 60 °C and low to moderate acidity levels, gave slightly increased solubility values at higher temperatures compared to 23 °C. This wasn’t the case at higher acidity levels, i.e., the solubility curves at different temperatures converge at high acidity. Lastly, a relationship of water activity and GeO2 solubility in different acid media was established.

By Truan-Sheng Lui, Li-Hui Chen, Fei-Yi Hung, Cheng-Yi Chen

"This research used the austempering heat treatment on the SCM435 thin specimen with a type of double loop and obtained the Cr-Mo bainite structure, and then we could further investigate the mechanical properties of SCM435 bainite structure. Experimental data showed the stability of the mechanical properties of specimen with austempering temperature 830°C for 25 minutes was better than that of 15 minutes. The size of austenite grain affected the strength of thin specimen. After austempering at 830°C-25minutes and salt bath at 290°C, the stability of UTS was better than that of salt bath at 310°C and 330°C. The average hardness of all specimens was about more than HRA70. The specimen with austempering at 830°C-25minutes and salt bath at 290°C-30minutes had bigger grain size of austenite and retained y, it also had higher hardness and strength toughness. So, its stability was improved for tensile strength comparing with traditional tempered martensite process.IntroductionSCM435 is a Cr-Mo steel with high strength and high hardness properties, and it has been widely used in machine parts, shafts, gears and strength screw products [1-3]. However, this system often has lower reliability due to the brittleness of high-temperature tempering and quenching inequality. Considering the austempering heat treatment can obtain the uniform bainite structure to improve the temper brittleness, and the austempering heat treatment is a continuous process that it also has efficiency and uniformity. For the thin plate specimens, the mechanical properties of the bainite structure are better than traditional martempering structures."

Jan 1, 2013

By C. Lupi

The electrorefining of primary copper is a well known technology: in this work copper scrap was directly processed in the same way. he copper and copper alloy scrap was previously pressed by means of a 20 tons apparatus in order to avoid pyrometallurgical operations. The samples obtained in this manner showed a good compactness so that they were used as anodes in the electrorefining tests. The tests were carried out on anodes made by copper scrap, copper alloy scrap and a mixture of the two. The electrorefining tests were performed at both 303 and 333 K, in a perspex cell having a volume of 500 ml using a current density of 250 A/m2. The cathode used was always a sheet of pure copper and the electrolyte composition was 40-50 g/l Cu as CuS04 and 150-200 g/l H2SO4. Current efficiency in the range of 92-97% and specific energy consumption ranging from 0.14- 0.20 kWg of copper were reached in all the tests. The refined copper deposits were analyzed by AAS to verify their purity and observed by SEM to highlight their morphology.

Jan 1, 1998

By Guy Xueyi

The environmental impact assessment of the Imperial Smelting Process for metallic zinc and lead production in Shaoguan Smelter, China, was carried out by the life cycle assessment method. The detailed inventory analysis of the Input/Output in the process during 1998-2000 was conducted and the allocation was done among the main products of zinc, lead and sulfuric acid, according to the system expansion and substitution principle, The environmental impacts were assessed by using the following five Eco-indicators: Gross Energy Requirement (GER), Global Warming Potential (GWP), Acidification Potential (AP), Heavy Metal Toxicity' (HMT) and Solid Waste Burden (SWB). The results from this study are useful to address the environmental situation of the technology practice in this smelter, and provide a scientific basis for the further improvement.

Jan 1, 2003

By Felipe Daroch, Maria C. Ruiz, Rafael Padilla

Copper concentrates with high arsenic contents must be pretreated before conventional smelting to prevent environmental pollution with arsenic compounds. In this work, experimental results concerning the selective removal of arsenic and antimony from copper concentrates are presented. The process consists of an alkaline digestion using concentrated NaHS-NaOH solutions to transform the arsenic and antimony sulfides into soluble compounds. A water leaching follows the digestion to dissolve the arsenic and antimony, leaving clean copper sulfide solid residues. The laboratory scale tests were carried out using a copper–arsenic concentrate with 15.05% As and 1.42% Sb. The results showed that the most important digestion variables were temperature and concentrations of NaHS and NaOH. Over 97% of arsenic and 92% of antimony could be removed in 10 min of digestion using 8.9 M NaOH and 100% excess of NaHS at 80 °C. The subsequent water leaching was performed at 80°C for 20 min.

Jan 1, 2015

By Guo Xueyi

The environmental impact assessment of the Imperial Smelting Process for metallic zinc and lead production in Shaoguan Smelter, China, was carried out by the life cycle assessment method. The detailed inventory analysis of the Input/Output in the process during 1998-2000 was conducted and the allocation was done among the main products of zinc, lead and sulfuric acid, according to the system expansion and substitution principle, The environmental impacts were assessed by using the following five Eco-indicators: Gross Energy Requirement (GER), Global Warming Potential (GWP), Acidification Potential (AP), Heavy Metal Toxicity (HMT) and Solid Waste Burden (SWB). The results from this study are useful to address the environmental situation of the technology practice in this smelter, and provide a scientific basis for the further improvement.

Jan 1, 2003

By William Brinkman, Mark Jolly, Nasim Soleimanian, Karl Dearn, Oliver Brinkman

"Glass manufacturing is a heat intensive process. There is a direct correlation between the batch distribution techniques and the furnace energy consumption, productivity, and quality of the glass manufactured. All four major segments (float, container, fibre, and specialty glasses) would benefit from using an optimised batch distribution technique where possible. Oscillating batch chargers (OBC) have been in use since the early 70s, despite their superior batch shape, coverage, and in turn positive effects on the energy consumption and productivity of the furnace they are almost exclusively used in container glass manufacturing. The OBC’s main difference compared with other charging methods is its ability to directly influence the batch initial velocity. This paper reports on results achieved in CFD models (GFM) used to study effect of the machine on the overall energy consumption in the doghouse and the melt space.IntroductionGlass manufacturing can be divided to four major segments float glass, container glass, fiberglass, and specialty glasses. The financial cost of manufacture, its impact on the environment, lack of standardisation and mounting pressure imposed by the authorities for reduction in emissions means that the industry and its suppliers are utilising CFD modelling in order to tackle these challenges. The need for high temperature to create and maintain the viscous flow, homogenisation of the glass melt, and maintenance of the process to allow continuous output of glass of the right quality are the contributors to the energy intensive activities that are involved in continuous glass manufacturing. This in turn has resulted in design of large container glass furnaces which have high energy consumption, low specific performance, and high CO2 emissions where the most efficient furnaces in the container glass sector have a specific primary energy consumption of 3.8 GJ /tonne of glass at a level of 50% cullet in the batch making even very small improvements in efficiency by operation optimisation a value adding activity [1-14].The theoretical calculated energy required to melt glass is 2 to 3 times less than the energy actually used to melt glass as a result of glass melt passing a zone 5 to 8 times before leaving the tank.[8]. This causes contamination as the result of mixing between the completely molten glass free from bubbles returning to the batch area where there is freshly molten non-homogeneous glass, still containing very large numbers of bubbles and un-molten batch. At high temperature some components are dissolved rather than melted. Given that an un-molten batch is a good thermal insulator, it can be transported a long way into the furnace, increasing the need for homogenization which also increases the glass residence time of glass melt. This is why large unbroken strings of batch should be avoided, as should an overall blanket without gaps."

Jan 1, 2014

By J. B. Wiskel, H. Henein

"A study was conducted to establish the effective heat transfer coefficient for a single molten droplet moving in a gaseous medium. Towards this objective, a series of quench experiments were performed on molten droplets of AA6061 aluminum generated with the Impulse Atomization technique (IAP). IAP is a single fluid atomization process capable of producing powders with a predictable mean particle size and a relatively tight standard deviation under controlled atmospheric conditions. Microstructure analysis of the atomized powder was used to establish the extent of pre-quench solidification. A mathematical model was then employed to correlate the Ranz-Marshall and Whitaker equations with the observed particle cooling behaviour. These equations were found to provide a reasonable estimation of the heat transfer conditions only when the variation in gas thermophysical properties across the boundary layer was accounted for in the model. This model formulation of droplet heat transfer has important implications with regards to active sprays and atomization processing operations IntroductionAn understanding of droplet cooling is important in atomization powder production. It is well understood that dendrite arm spacing is inversely proportional to cooling rate during solidificationl1l. Through modification of the heat transfer conditions during metal atomization, the microstructure of a powder maybe tailored to the end user. However, owing to the complexity of gas flow it is difficult to determine a heat transfer coefficient for a moving droplet. This difficulty is further compounded when complex jets and/or streams and their interactions are considered. To provide a base for these more complicated types of analyzes, two approaches have been employed to calculate the effective heat transfer conditions for a single droplet. In one approach, Megardis [ZJ developed a numerical model to investigate the heat transfer process of a free falling droplet undergoing laminar convective cooling. The effective heat transfer coefficient as a function of angular position was determined by numerically solving the fluid and energy equations for the system."

Jan 1, 1999

By Mark R. Jolly, Jean-Christophe Gebelin, Aleksander Cendrowicz

"Injection of wax patterns is the first stage of the multi-stage process of investment casting. The quality of the final casting and its dimensional accuracy is highly dependent on this stage of the process. Pattern waxes used in the industry behave in a complex visco-elastic-plastic manner. The modelling of such material behaviour is therefore not simple.In this paper a number of configurations of die will be shown in which the injection of the wax has been carried out for a range of processing conditions. Some of the dies are transparent and the movements of wax front observed can be compared with those predicted by simulation. Surface defects in final components will also be shown and compared with the location predicted by simulation software. Some discussion will be presented on the limitations of the software used and the time-scales achieved for practical use as a design tool within the foundry environment. IntroductionThis paper presents the research activities carried out at the University of Birmingham on the modelling and prediction of the behaviour of industrial investment casting waxes during the injection of wax patterns. These research activities are done in the context of a more global study of the fundamental aspects of the investment casting process, the FOCAST project. Regarding the wax injection process, the aim of the project is to achieve a better understanding of the key factors that will lead to better castings. The filling of the die during the injection has been studied. Some other phenomena such as shrinkage/warpage or creep under residual stresses are also studied, but not presented here. Two commercial investment casting waxes have been characterised in order to model their behaviour and predict mould filling and subsequent defects.This paper will present the models that have been used in our work, the simulation packages used, the experiments carried out to validate the modelling and exhibit the defects due to bad filling, and finally the numerical simulation results."

Jan 1, 2001

By Larry G. Twidwell

The removal of dissolved arsenic from mine waste waters utilizing a lime/phosphate precipitation technique has been studied on a laboratory scale at Montana Tech of The University of Montana and on a pilot scale at MSE Technology Applications as a wastewater treatment process potentially capable of removing dissolved arsenic to <50 µg/L. Arsenic bearing lime and lime/phosphate slurries were subjected to laboratory extended-time air-sparged aging for over four years. The lime slurries released their arsenic back into solution in a relatively short period of time, whereas the lime/phosphate slurries showed limited release of arsenic. The developed process has been pilot scale tested by MSE-TA for the EPA Mine Waste Technology Program on three waters, ASARCO smelter blowdown water, ASARCO thickener overflow water, and Mineral Hill Mine groundwater. The laboratory study results will be presented and discussed in this presentation. The pilot scale results will be presented and discussed in a companion presentation. Stability, Aging, Apatite, Johnbaumite

Jan 1, 2005