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By Katsuyoshi Kondoh

The synthesis processing of Mg2Si or Mg2SiIMgO at lower temperature from the elemental magnesium alloy powder/chips and Si or SiO2 powder mixture was established via the repeated plastic working (RPW) based on Powder Metallurgy (PIM) process. RPW is much effective on the mechanical breakage of MgO surface films, which prevent from the solid-state reaction between Mg and Si powder. The solid-state synthesized Mg2Si particle of 200nm-2um is extremely fine, compared to that via the conventional casting process, causing the coarse one of 50-100um. This is because of not coarsening during the solid-state synthesis of Mg2Si. By using in-situ fonning process of Mg2Si via RPW and pre-heating before hot working such as extrusion and forging, the magnesium composite material with Mg2Si or Mg2Si/MgO dispersions was developed in employing Si or SiO2 particles, respectively. For example, when employing AZ31 chips as raw materials of the matrix, it has low density of 1.85g/cm3 and extremely superior mechanical properties, such as tensile strength over 350MPa with 5-10% elongation and Young's modulus of 47-50GPa, to the conventional Mg-Al-Zn alloys. The Mg composite alloy wires and pipes were produced via the hot extrusion process in the manufacturing plant, and also showed excellent mechanical properties.

Jan 1, 2003

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 Chang Wei, Zhigan Deng, Yizhao WANG, Cunxiong Li, Gang Fan, Xingbin Li

During the process of hematite precipitation, the transformation of Na jarosite convert into hematite has been studied in a batch reactor at different temperatures, ranging from 170°C to 200°C with 3h of the retention time in the presence of 30g/L Fe ( ) and 4g/L Na+. The composition of precipitation was seriously depended on the temperature, at 170°C hematite and sodium jarosite are the reaction products of iron precipitate, with an increasing in reaction temperature the sodium, sulfur content in precipitated decreased and sulfur mainly exist in forms of SO4 2-, and when temperature over 200°C hematite was the only phase in product. An increasing temperature was not only beneficial to iron precipitation, also conducive to jarosite conversion to form high quality hematite precipitate.

Jan 1, 2016

By W. B. Carter, A. T. Hunt, G. W. Book

"Combustion Chemical Vapor Deposition (CCVDSM ), an open air, flame assisted CVD process, is under development. The CCVD process produces non-line-of-sight, epitaxial deposition. Materials deposited include YBa2Cu3Ox' Y2BaCuOx, BaTiO3, Y2FesOI2, ZrO2, yttria stabilized ZrO2 (YSZ), partially (yttria) stabilized ZrO2 (PSZ), and amorphous silica. Two modifications of the CCVD process are being studied. Liquid fuel CCVD deposition, involves the combustion of an organic solvent that contains dissolved reagents carrying the desired coating cations. Gaseous fuel CCVD deposition uses a flammable gas as fuel. A non-flammable solution containing dissolved reagents is either aspirated into the flame or mixed with the fuel gas as an aerosol prior to its combustion. Substrates to be coated are held near the flames' ends.IntroductionThin films and coatings can be deposited using a wide variety of techniques including chemical vapor deposition (CVD). CVD is ""a materials synthesis process whereby constituents of the vapor phase react chemically near or on a substrate surface to form a solid product.""lIn conventional CVD processing, gases carrying coating constituents flow into a reaction vessel where deposition occurs onto a heated substrate. The deposition process is often conducted at reduced pressure. Both cold and hot wall reaction chambers are used. Heat can be provided by a resistance furnace, rf induction, or high-intensity radiation lamps. Plasma, microwave, photo, laser, RF, and electron-enhanced CVD processes have been developed. The necessity of using a reaction vessel limits the substrate size and affects coating economics. Although most CVD depositions are performed as batch processes, continuous deposition can be accomplished with the use of appropriate hardware.The chemical vapor deposition of thin, dense oxide films has been accomplished in the open atmosphere with a flame assisted process. The process is called combustion chemical vapor deposition (CCVDSM).2 Two modifications of the CCVD process have been developed. The liquid fuel CCVD process involves the combustion of an organic solvent in which reagents (containing the coating cations) are dissolved. The gaseous fuel CCVD process uses a flammable gas as fuel. In this modification, a non-flammable solution containing dissolved reagents is either aspirated into the flame or mixed with the fuel gas as an aerosol of small droplets prior to its combustion. Substrates to be coated are held near the flames' ends."

Jan 1, 1994

By Guo Chen, Jin Chen, Jinhui Peng

In this study, the influences of the green evaluation variables on the characterization of microwave shaft furnaces were systematically investigated. These variables include: resource consumption, environment impact, production cost, processing time and quality of microwave shaft furnaces. A greenness evaluation index, evaluation system and evaluation model of microwave shaft furnaces were established. The analytic hierarchy process and fuzzy comprehensive evaluation were applied to the evaluation process. Resource consumption and environment impact had a statistically significant effect on the green evaluation of microwave shaft furnaces. The results indicated that green evaluation techniques can be applied effectively and efficiently to the process manufacturing of microwave shaft furnaces.

Jan 1, 2015

By W. G. Davenport

This chapter extends our mathematical description of flash smelting to -nitrogen in the flash furnace blast. As in chapters 4 and 5, the discussion is limited to auto thermal smelting (no hydrocarbon combustion). Hydrocarbon combustion is introduced in Chapter 9. Outokumpu flash furnace blast is a mixture of air and industrial oxygen. Most of its N2 originates in the air portion of the blast. A small portion originates as an impurity in the industrial oxygen. The nitrogen entering a flash furnace must always be heated from its input temperature, 298 K in this chapter, to its off gas temperature, -1500 K. Energy must be supplied for this purpose. With auto thermal smelting, the energy is-provided by oxidizing extra Fe-and S.

Jan 1, 2001

By Kanchan Mondal

"Methanol, lower hydrocarbons, CO, and HCOOH formation have been by the reduction of CO2 with H2. Un-catalyzed electro-reduction requires a significant overvoltage. An alternate route has been conceptualized. Production of hydrogen from water can be achieved by chemical oxidation of a metal in water followed by oxidation of the hydronium ion by the released electrons to form hydrogen radical. It is hypothesized that circumventing the problem of the formation of hydrogen molecule is essential while having the hydrogen radical to react with CO2 forming methanol, etc. This may be possible by a bimetallic catalyst acting as a galvanic couple, wherein one metal acts as the electron donor for the production of hydrogen radical while the other acts as a catalyst for the reduction of CO2. This may enhance the reaction rates. The current concept circumvents the need for an external electric field unlike the electrochemical process.IntroductionUtilization of carbon dioxide as a raw material, not only as carbon sources but also as useful chemical feedstock is a more holistic approach to reduce air pollution by flue gases (1-3). Several methods have been proposed to maintain the concentration of atmospheric CO2 or to reduce and recycle it. One of these is the chemical fixations using catalysts. The conversion of CO2 to methanol by hydrogenation over copper containing catalysts is one of the most widely studied subjects in this area. The limitation in this reaction is the low conversion of CO2."

Jan 1, 2008

By M. del C. Ruiz

The extraction of Nb and Ta from a columbo-tantalite of San Luis, Argentina, is being studied by using a pressure reactor and HF as leaching agent. The reagents and products have been characterized by several techniques such as scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDXS), X-ray fluorescence (XRF), X-ray difracction (XRD), surface area (BET) and size particle analysis. Experimental results have shown that the extraction of niobium and tantalum increases with increasing temperature, reaction time and acid concentration. For particle size between +80 and -355 mesh no significant changes are detected. It is also slightly affected by the stimng speed. XRD analysis of the residues did not show formation of new crystalline structures.

Jan 1, 1999

By Y. Y. Sheng

Plume flows created by gas injection into liquid metals have been studied extensively, however the dynamics of bubbles within the plume have not received adequate attention, particularly for large, irregular bubbles, characteristic of the processing of liquid metals. The present model uses a combined Eulerian-Lagrangian approach in which an estimated void fraction distribution is used to calculate the liquid flow field with a conventional Eulerian scheme. The trajectories of bubbles are then computed in a Lagrangian manner using the estimated flow field, and experimentally measured information on bubble drag coefficients', lateral migration due to lateral lift forces and interaction with turbulent eddies, and variation in bubble size due to break-up. Turbulence in the two-phase zone is modeled with a modified k-e model with extra source terms to account for the second phase which have been recently determined by the present authors. The computed void fraction and turbulent liquid flow field distributions are in good agreement with experimental measurements.

Jan 1, 1993

By Jose Luis Lopez Mendez

In May 1992, MEXICANA DE CANANEA, S.A. DE C.V. finalized the life of its Reverberatory Furnace which lasted 16 years. This created the need to prepare the Smelter for the next campaign.

Jan 1, 1994

By Gunnar Eriksson

Computer simulation has become an everyday practice in thennodynamic and materials research. Advanced thennochemical algorithms take into account heat transfer effects and salient reaction kinetics when applied for process models. In particular, the combination of mass transfer or overall reaction rates with multi-component Gibbs energy minimisation provides an effective tool for simulation of industrial thennochemical processes and processing of materials. In this work the combination of rate factors with the Gibbs energy technique was studied by using the novel program ChemSheet, which operates through Microsoft's Excel® spreadsheets. Such processes as, for example, CVD of pure silicon production, titania pigment manufacturing, vapour pressure of Mercury in amalgams (in Hg-Iamp manufacturing) and melting behaviour of low-temperature alloys have been modelled. Provided that the thennochemical data is available simulations can be performed with any thennodynamic system. The calculation can be performed as an affinity study without a particular reactor model or with a specific reactor scheme.

Jan 1, 2001

By Seung-Chul Lee

Transparent conducting tin(1V) oxide thin films have been studies and developed for the electrode materials of solar cell substrate. Fabrication of tin oxide thin films by sol-gel method is process development of lower cost photovoltaic solar cell system. The research is focused on the establishment of process condition and development of precursor. The precursor solution was made of tin isopropoxide dissolved in isopropyl alcohol. The hydrolysis rate was controlled by addition of triethanolamine. Dip and spin coating technique were applied to coat tin oxide on borosilicate glass. The resistivity of the thin film was lower than 0.18-cm and the transmittance is higher than 90% in a visible range.

Jan 1, 1999

By Keith Rozenburg, Ivar Reimanis, Jesus Chapa

"Experiments in conjunction with finite element analysis (FEA) are used to better predict crack propagation in ductile/brittle graded composites. Cu/W graded composites were fabricated by stacking discrete layers of powders and hot pressing. Crack propagation was studied by loading a notched beam in four point bending and examining the subsequent crack deflection. The notch was placed within a particular composition of material, oriented in a direction perpendicular to the gradient direction. Elastic and plastic mismatch between different constituents in the graded composite induce shifts in the phase angle of loading, thereby causing the crack to deflect. FEA indicates that thermal residual stress has a negligible ""influence on the crack path. The combined FEA and experimental results suggest that elastic mismatch is the single most important material property-related factor in controlling crack deflection.IntroductionMany 'applications would benefit or may even require materials whose performance or functionality must vary spatially. While the concept of functionally graded materials has existed for nearly one hundred years, it is only within the last fifteen years, that research efforts have focused on generic issues in processing, properties and performance of functionally graded materials. This generic research effort has brought together scientists and engineers from traditionally different disciplines to address common issues with graded composites. The current work focuses on issues in structural joining. A wide variety of applications require some type of joining between dissimilar materials. Examples include thermal barrier coatings for turbine engines, wear resistant coatings for tools, ceramic engine parts, and microeiectronic devices, as well as many traditional applications involving metallic welding. The joints may either be discrete, involving a single interface, or they may· be spatially graded in composition. Extensive theoretical and experimental information exists on discrete bimaterial and trimaterial joints, but relatively little exists for graded joints or composites"

Jan 1, 2000

By Y. Maeda

Non-ferrous smelting furnaces generally lnstal1 a gas cooling system for treatment of waste gas containing S02. From the point of view of corrosion resistance and recovery of waste heat, the high pressure boiler system Is the best way to cool gas, however this system requires high Initial investment and relatively higher operating costs. Because the feasibility of this boiler system greatly depends on the smelting process and scale, other lower temperature systems, e.g. water-cooled Jacket system, are more suitable If the smelting process does not produce enough steam nor generate enough electricity to compensate operating cost. In addition, the water-cooled Jacket system Is simple in structure and easy to operate. For those reasons, it is applied widely. A new smelting furnace. was planned tin our factory and It was necessary to install waste gas cooling equipment. In our case, a water-cooled Jacket system was mo11e feasible because of the low gas volume and high dust content. H was also expected to operate without maintenance for ten years. On the other hand, some leakage problems with the water-cool1ed Jacket had been experienced In the past. That is because S02 in the waste gas changed into sulfuric acid which corroded the Jacket material, As the first step, several data from actual usage were reviewed to throw light on the corrosion process, and an appropriate procedure to determine the operating temperature of cooling water was obtained. For the basis of this study, a water-cooled Jacket system was newly designed and tested for three months in a pilot plant. After this system's performance was confirmed, It was installed In a new furnace as a commercial pl.ant. After one year of operation, the initial thickness of carbon steel Jacket remains almost the same.

Jan 1, 1992

By Li Yuhai

Kinetics of non-isothermal precipitate process and crystal growth of perovskite (CaO ? Ti02) phase in CaO-TiOz-Si02-AlP3-MgO system were studied. The experimental results show that the relative volume fraction can be described by the equation given by K. Matusita et at. and the experiential expression of average crystal radius was obtained. The particle coarsening in non-isothermal process has important effects on the crystal growth of perovskite phase.

Jan 1, 2000

By Richard D. Hagni

Reflected light microscopic examination of particles from laboratory experimental copper flash furnaces operated under varied furnace conditions shows that the particles exhibit a wide range in mineral compositions and mineral abundances that correlate with partial pressure of oxygen and concentrate/oxygen ratio. Chalcopyrite, bornite, and digenite are more abundant under low oxygen conditions. With increasing oxygen, metallic copper, delafossite and cuprite become increasingly abundant. The extent of particle agglomeration during flight varies with the furnace. Those products from the larger furnaces exhibit the greater degree of agglomeration. Significant particle fragmentation also is evidenced by cracking and brecciation of some particles.

Jan 1, 1991

By Marcelo R. Esquivel

A MmNi5 alloy is synthesized by a combination of mechanical milling and low temperature heating processes. Synthesis time is 40 h for powders milled in a low energy ball mill at room temperature. A reduction in milling time is obtained if massive sample is mechanically milled at shorter times (2 h to 10 h) and heated at temperatures lower (600 ºC) than the usual temperatures used in equilibrium methods (>800 ºC). The alloy formation is detected even at a combination of temperatures as low as 200 ºC and milling times as short as 5 h. The temporal evolution of mechanical milling process was followed by both X-ray diffraction (XRD) and scanning electron microscopy (SEM) to detect the main stages of milling. Four stages were detected: Initial, Intermediate, Final and Completion. These stages were correlated to an enhancement of the synthesis method by combination of times of milling shorter than 10 h and temperatures of heating lower than 600 ºC.

Jan 1, 2006

By Akihide Nagao

The behavior of impurity hydrogen that is contained in starting material or picked up during processing has been little investigated up to now. The hydrogen microprint technique is applied to determine the microscopic location of impurity hydrogen during deformation in aluminum without hydrogen charging. Three kinds of pure aluminum of 99.99% are prepared, in which hydrogen content is varied by changing the atmosphere when they are melted and heat-treated. After rolling, tensile specimens with a gage size of 4 x 4 rnm and 0.5 mm in thickness are stamped out from these three kinds of aluminum sheets. These specimens are covered with a liquid nuclear emulsion of silver bromide crystals, stretched by 5,10 and 15 percent plastic strain or fractured, developed and fixed. SEM micrographs reveal a number of silver particles on the slip lines and on the grain boundaries. Also shown is that the more hydrogen present in the specimen, the more silver grains appear on the slip limes and on the grain boundaries. Consequently, it is concluded that impurity hydrogen is transported to the surface with gliding dislocations during deformation.

Jan 1, 1998

By JiaPeng Xu, Brian Lo, Uday B. Pal, Yihong Jiang, Soumendra N. Basu

"The Solid-Oxide Oxygen-Ion-Conducting Membrane (SOM) electrolysis process has been successfully tested on a laboratory scale, producing silicon directly from silica in a cost-effective and environmentally friendly way. A yttria-stabilized zirconia (YSZ) tube, closed at one end was employed to separate the molten salt containing dissolved silica from a liquid metal anode placed inside the YSZ tube. When the applied electric potential between the liquid tin cathode in the molten salt and the anode exceeds the dissociation potential of silica, oxygen ions are pumped out of the molten salt through the YSZ membrane and oxidized at the anode while the silicon cations in the flux are reduced to silicon at the liquid tin cathode. The presence of high-purity silicon crystals on the surface of liquid tin cathode was confirmed by scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS). Silicon crystals were extracted from tin cathode by chemical etching.IntroductionPhotovoltaics (PV) generate electrical power by using solar cells, and dramatically reduce the emissions of greenhouse gases (GHG). Through 2006 to 2011, it grew the fastest of all renewable technologies with operating capacity increasing an average of 58% annually [l]. However, the cost of manufacturing solar-grade silicon (SoG-Si) for high-efficiency solar energy production represents a major barrier to achieving the industrial goal for solar power of $1/Wp (watt at peak exposure) which would enable widespread grid parity. The current contract price of silicon to PV manufacturers is $50-$60/kg, with the spot market in 2007-2008 showing prices as high as $300/kg [2]. This makes the development of low cost and environmentally friendly manufacturing of high purity silicon very important."

Jan 1, 2013

By Ann M. Hagni

Reflected Light Microscopy (RLM) And Scanning Electron Microscopic-Energy Dispersive Spectroscopic Analysis (SEM-EDS) Study Of Electric Arc Furnace (EAF) Dusts Have Shown That Their Mineralogy Is Complex And Varied. The Particles Are Largely Spherical, And Can Be Seen In RLM Sections To Be Composed Of Franklinite, And Zincite, But They Show Significant Solid Solution With Each Other And May Contain Small Amounts Of Chromium. These Crystalline Phases Occur As Crystals And Skeletal Growths Within Ca-Fe-Si Glass. Because Chlorine Is A Deleterious Constituent In Recovered Zinc Products From EAF Dusts, Special Attention Has Been Given To Chlorine-Bearing Phases, And They Include Hydrophylite (Cacl2), Lime (Cao), And Organic Phases. Pyrohydrolysis-Treated EAF Dusts With Silica (Si02), Tungstite (W03), Alumina (A1203), And Bunsenite (Nio) Additives Contain Franklinite, Scheelite (Cawo4), Willemite (Zn2SiO4), And Hematite (Fe2O3)

Jan 1, 1992