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By Anne Kvithyld

Silicon solar cells, that convert the energy of sunlight into electric energy, are attractive sources of energy. In the production line wafers of solar cells are sliced from a multicrystaline ingot solidified unidirectionally. Recycling scrap from top and sides of such ingots is addressed. SiC and Si3N4 inclusions are a major problem. Scrap from Scan Wafer ASA is melted in a high vacuum furnace at around 1500ºC. The filters, from commercial producers, are C and SiC with 10, 20 and 30 ppi. Characterisation of inclusions before and after filtration, and in the filter itself, is performed by microscopy. Dissolution of silicon in acid and counting of the un-dissolved inclusions is also carried out. In the filter Si3N4 needles and SiC inclusions were identified. The amount of these inclusions in the filtered silicon is much less than in the input. In conclusion, filtration using SiC and C filters in vacuum system in argon atmosphere removes SiC and Si3N4 inclusions from solar cell scrap. Flow of metal through the filters is not a problem. These results are promising with scale-up to industrial application in mind.

Jan 1, 2006

By Bowen Li, Canhua Li, Mingsheng He

Steelmaking slag is a by-product in considerable volume and a valuable material for various applications. In general, steelmaking slag is an alkaline compound of CaO, Fe2O3, and SiO2. However, its characteristics varies depending on the feedstocks, steelmaking process and cooling method of the slag. To utilize this by-product effectively, this study investigated the characteristics of steelmaking slags taken from Wuhan Iron & Steel Co. Ltd. The results showed that the slags mainly consist of the oxides of calcium, iron, and silicon, with low contents of magnesia, alumina, and manganese oxide with a feature of high alkalinity and lime saturation factor. The major mineral phases include belite, calcium ferrite, calcium hydroxide, wustite, quartz, and small amount of elite. Thermogravimetric analysis indicated the weight loss from ambient temperature to 800 °C is 8% in total. Melting test showed the glass transition temperature is between 1300 and 1350 °C, flow temperature is about 1400 °C. The slag samples investigated in this study can be considered as a typical glass-ceramic composite.

Mar 1, 2018

By J. D. Budai, D. H. Lowndes, D. P. Norton, D. K. Christen, B. C. Chakoumakos, J. R. Thompson, B. C. Sales

"Artificially-layered structures, consisting of (Sr,Ba,Ca)CuO2 layers in the tetragonal, ""infinite layer"" crystal structure, have been grown by pulsed-laser deposition. Superlattice chemical modulation is observed for structures with SrCuO2 and (Sr,Ca)CuO2 layers as thin as a single unit cell (~3.4 Å). In addition, novel thin film superconductors were formed by using the constraint of epitaxy to stabilize SrCuO2/BaCuO2 superlattices in the infinite layer structure. Using this approach, two new structural families, Ba2Srn-1CUn+l O2n+2+ d) and Ba4Srn-1CUn+3O2n+6+ d, have been synthesized which superconduct at temperatures as high as 70 K. These results represent not only the synthesis of new structural families of superconductors, but also demonstrate that pulsed-laser deposition and epitaxial stabilization can be effectively used to engineer artificially-layered thin-film materials.Advances in the understanding of epitaxial thin-film growth of the cuprates have heightened interest in creating artificially layered superconductors.(1-3) The layered structure of the copper oxide superconductors opens the possibility of forming novel materials by carefully controlling the epitaxial growth of sub-units of the crystal structures. Thin-film growth methods offer unique opportunities for the atomic engineering of new high-temperature superconducting (HTSc) materials through the ability to form artificially layered crystal structures.(4,S) Moreover, the surfaces of single-crystal substrates provide an ""atomic template"" that can be used to stabilize epitaxial films in metastable crystal structures.An important development in forming new HTSc compounds by artificially-layered epitaxy has been the epitaxial growth of (Sr,Ca)CuO2 films in the so-called infinite layer structure.(6-17) This material, which can be considered the parent compound of all of the copper oxide superconductors, has a relatively simple, layered structure consisting of CUO2 planes separated by planes of alkaline earth elements.(18) Bulk synthesis of (Sr,Ca)CuO2 with the tetragonal, infinite layer structure generally requires the use of high pressure and high temperature bulk processing techniques.(19-24) However, recent experiments show that this metastable compound can be epitaxially stabilized at less than atmospheric pressure, resulting in the growth of tetragonal (Sr,Ca)CuO2 single crystal thin films of the infinite layer defect perovskite structure by pulsed-laser deposition (PLD) over a wide range of growth conditions.(6-17)"

Jan 1, 1994

By Onuralp Yücel, Mehmet Bugdayc, Murat Alkan

"In this study, iron based alloys (Fe-Mo, Fe-Cr-Ni, etc.) were produced by using aluminothermic methods starting from Mill Scales obtained continuous casting processes. Mill scales are an oxidised layer of steel alloys containing iron oxide, which includes + 2, + 3 values, on the surface of slabs and billets occurring during annealing in heating furnace at integrated iron and steel milling plant, and continuous casting unit. In the metallothermic experiments, different ratios of starting mixtures and addition of the oxide powders (Alz03, Si02, CaO, MgO) were examined, and their effects on the metal recovery and alloy compositions were carried out. The samples were characterized by using chemical analysis (AAS), XRD, XRF and SEM/EDS techniques.IntroductionSelf Propagating High Temperature Synthesis process (SHS) has many favour compared to the furnace applications, such as low energy requirement, low cost, very short processing time and simple operation, [l, 2]. In a SHS process, the ignition starts the combustion and propagates throughout the reactant mixture yielding the desired product. However, the disadvantages of the process such as inhomogeneous or unreacted products due to undesirable reaction rates needs to be overcome by changing some parameters such as ignition temperature, particle size, additive, atmosphere etc. [3, 4]. Mill scale is a layer of iron oxide which forms on ferrous materials cooling after being processed in hot rolling or continuous casting plants. Mill scale contains iron (II) and iron (III) oxides, which result in a 70% total iron content in oxide form. Not being able to reuse this material will prevent the raw material entering the production plant from being fully utilized [5]. This study aimed to produce Fe-based alloys via SHS (Self Propagating High Temperature Synthesis) metallurgy which is attractive process technique regarding fast and low-cost production ability of cast alloys by using high metallic iron content by reducing continuous casting mill scale."

Jan 1, 2013

By Sergio N. Monteiro

Jute fabric obtained from discarded sackcloth is a promising low cost and post-used material being considered as reinforcement of polymeric matrix composites. In particular, the combination of this fabric with a recycled plastic constitutes an environmentally correct composite with both economical and environmental advantages. The present work investigates the toughness of recycled polyethylene composites reinforced with up to 40 wt% of post-used jute fabric extracted from discarded sackcloth. Standard Izod notched specimens were impact tested and the results showed an increase in toughness with the amount of jute fabric. Observation of the composite fracture by SEM revealed that the fabric weave, in spite of damages caused by the previous use of the sackcloth, act as an effective obstacle to crack propagation.

Jan 1, 2009

By Timo Kankaanpää

Keywords: Solvent extraction, dispersion, phase separation, CFD The liquid-liquid dispersion phases are separated by gravity in a solvent extraction settler. This separation step is made more effective by picket fences. The picket fence geometry and its physical placement have a significant effect on the separation process, because the purpose of a fence is to smoothen and control organic-aqueous dispersion flow in the first part of the settler and achieve a deep and dense dispersion layer in the front end of the settler resulting in a clean phase separation. In this study, physical phenomena in the solvent extraction process and phase separation in a solvent extraction settler with and without picket fences have been examined using a commercial CFX software package. It can be concluded that the used CFD-approach proved to be a complementary tool for optimizing and designing the solvent extraction settler.

Jan 1, 2005

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

The effect of rare earth element Y (0-2.0at.%) on the microstructure of TiAl alloys at the as cast and rapidly solidified conditions has been investigated. The results show that the addition of Y greatly refined the microstructure of TiAl alloys at both conditions. The refinement is more significantly with higher Y content. The refinement of Y in the cast alloys is attributed to that the strip-shaped Y-rich phase locating on the grain boundaries impedes the grain growth during solidification. In the rapidly solidified alloys, Y-rich phase dispersing uniformly as spherical particles in the matrix acts as heterogeneous nucleation sites which increases the nucleation rate of ??phase during the ????phase transformation, and produces a refined initial microstructure during solidification. Higher cooling rate restricts the grain growth during subsequent cooling.

Jan 1, 2010

By W. Zhao

Several years ago, Reddy and Blander presented upriori model for calculating the sulfide capacity of binary silicate melts. It is modified now to apply to CaO-AlO 1.5 melts at different temperatures and compositions. Our predictions are in very good agreement with the available experimental data. From a comparison of binary calcium aluminate and calcium silicate systems, higher sulfide capacities are obtained in aluminate systems. The sulfur can be removed from hot metal more effectively by adding aluminate melts.

Jan 1, 1995

By John R. FitzPatrick

The separation and purification of uranium from either nitric acid or hydrochloric acid media tan be accomplished by using either solvent extraction or ion-exchange. Over the past two years at Los Alamos, emerging programs are focused on recapturing the expertise required to do limited, small-quantity processing of enriched uranium. During this period of time, we have been investigating ion-exchange as a method for extraction/purification of uranium from acidic media. In addition, waste stream polishing is associated with this effort in order to achieve more complete removal of the uranium prior to recycle of the acid. Extraction chromatography has been demonstrated' to further polish the uranium from both nitric and hydrochloric acid media thus allowing for a more complete recovery of the actinide material and creation of less waste during the processing steps. We will discuss contact experiments for evaluation of eleven different resins for uranium removal from nitric acid, the evaluation (again by contact experiments) of uranium elution from the ion-exchange media by various chemicals, and small-scale experiments for the removal of 235U from nitric acid. Larger-scale (100-gram) flow experiments using depleted uranium, were done after the small-scale evaluation Of the selected resin. A discussion is also included concerning the shortcomings of the contact experiments and how the flow experiments were modified in order to overcome these problems. We will also discuss the application of ion-exchange for some specific process needs at Los Alamos Contact experiments were used to evaluate some commercially available solvent-impregnated resins in addition to evaluation of several resins of this type synthesized in our laboratory. These experiments' involved both nitric and hydrochloric acid media. The data from these experiments will be used to determine the column size and' amount of resin required to polish the waste stream produced by the ion-exchange process described above. Small-scale flow experiments will be described and data given on the mass balances achieved using this two step process. Future work for evaluation of new ion-exchange and solvent-impregnated resins as well as the search for new eluants will be discussed. Other future experiments for both processes, including large-scale experiments, will be discussed in detail.

Jan 1, 1996

By Chang Wei, Zhigan Deng, Minting Li, Cunxiong Li, Gang Fan, Xingbin Li

Molybdenum and nickel in black shale ore exists as amorphous sulfides which has highly active, and easily oxide to sulfuric acid and sulfate at low temperature in the presence of excess oxygen. Take advantage of the characteristic to leach molybdenum and nickel from black shale. Oxidation, conversion and dissolution behavior of amorphous colloidal molybdenum and nickel sulfide in pressure leaching process was studied. The effects of stirring speed, temperature, concentration of sulphuric acid, oxygen process and mineral granularity on molybdenum and nickel leaching were investigated. The results showed that dissolution rate increased with increasing temperature and stirring speed, but decreased with increasing concentration of sulphuric acid. And dissolution of molybdenum and nickel from ore only need oxygen without any other reagent.

Mar 1, 2017

By Alexander A. Knminskii

Polymorphism of BaR2F8 compounds is analyzed, and some peculiarities of obtaining monoclinic low-temperature (3-BaR2F8 crystals (R=Y, Ho-Yb) and orthorhombic high¬temperature a-ßaR2F8 crystals (R=Yb, Lu) by the Bridgman-Stockbarger growth technique are discussed. We pay a special attention to BaYb2F8:Er3+ crystals, which are able to generate both 2:µm SE using the new four-level operating scheme (4F9/2?4I11/2 laser channel) and 2- and 3-µm SE by means of the cascade scheme (4F92?+4I11/2?+4I31/2). This 2-µm generation of Er3+ ions has an advantage over similar SE of Ho3+ and Tm3+ ions (especially under diode laser pumping), that is important in designing the medicine and ecology laser. We report on orthorhombic BaR2F8 crystals with the ordered structure, a new crystalline materials for generating Ln3+ ions. The growth conditions are determined and orthorhombic BaLu2F8 crystals of several cm3 in volume doped with Ce3+, Nd3+, Ho3+, Er3+, and Tm3+ ions are obtained for the first time. Spectroscopic and laser characteristics of these crystals are discussed for Nd3+-and Era+-doped samples serving as representative examples. In particular, low-threshold stimulated emission was excited in 4F3/2?+4I11/2 channel of Nd3+ ions in the BaLu2F8. Room-temperature generation was obtained also at -1.317 µm wavelength for Nd3+ and at ~2.8 µm (several lines) for Era+ ions in this new laser crystalline host with a threshold of about 20 J.

Jan 1, 1997

By H. Y. Sohn, M. Pérez-Tello, P. J. Smith, K. M. Riihilahti

A three-dimensional computer model for the Kennecott-Outokumpu flash converting process for copper matte is presented. The model incorporates the transport of momentum, heat and mass, and reaction kinetics between the gas and particles in a particle-laden turbulent gas jet. The k-E model is used to describe gas-phase turbulence in an Eulerian framework. The particlephase is treated from a Lagrangian viewpoint which is coupled to the gas phase through the source terms in the Eulerian gas-phase governing equations. Matte particles were represented as Cu2S·yFeSx. Based on experimental observation, the oxidation products were assumed to be Cu2O, CuO, Fe3O4, and SO2. A reaction mechanism involving the external mass transfer of oxygen to the particle surface and diffusion of the oxygen through the oxide layers of CuzO/Fe304 and CuO/Fe3O4 is proposed. Predictions of the mathematical model were compared with the experimental data collected in a large laboratory furnace. A reasonable agreement between the model predictions and the measurements was obtained in terms of fractional conversion of the oxidation reactions and of sulfur remaining in the reacted particles. The simulation of an industrial flash converting furnace was also performed. Higher oxidation rates, more even distribution of particles, and thus a more efficient use of the reactor volume are predicted with a burner having a distributor cone, than with a single-entry burner.

Jan 1, 1999

By Xueming Lv, Xuewei Lv, Jie Qiu, Lunwei Wang

Non-isothermal multiple scanning rate analysis method was used to analyse the solid-state reduction of nickel laterite by carbon. According to the TG curves, the activation energies were calculated and the most probable mechanism functions were determined by the Malek method. The results show that the process can be divided into three stages according to the reaction degree (a): 0–40%, 40–70%, 70–100%, respectively. In the stage of 0 a 0.40, the most probable mechanism function fits the chemical reaction order function. In the stage of 0.40 a 0.70 and 0.70 a 1.0, the process may not be exactly described by one mechanism function.

Mar 1, 2017

By S. Stoyanov, M. Cross

"Silicon components containing transistor circuitry are at the heart of electronic products such as computers, mobile phones, etc. These components are connected to printed circuit boards (PCB's) using solder material that acts as the conductor for both electricity and heat. During the lifetime of a product it will undergo many thermal cycles where the chip becomes hot during product operation and then cools when the product is switched off. At the product design stage engineers undertake thermo-mechanical simulations to predict the thermal stress in the solder joints due to this thermal cycle and to ensure that the stress magnitude will not result in early fatigue-type failure. The design engineer's aim is to identify component parameters which ensure that the solder will survive beyond a certain number of thermal cycles.The aim of integrating computational mechanics and optimization tools together is to speed up dramatically the design process. From viewpoint of a design engineer in the electronics manufacturing sector, these tools can be used to quickly estimate key design parameters (i.e. material properties, product dimensions, etc) that will guarantee the required product performance. In this paper a modeling approach coupling computational mechanics techniques with numerical optimization is presented and demonstrated. The integrated modeling framework is obtained by coupling the multi-physics framework - PHYSICA - with the design optimisation tool- VisuaLDOC. Thermo-mechanical simulations are presented that predict the creep strains in solder material. Different numerical optimization procedures: Direct and Response Surface based optimization plus Design of Experiments, are tested as a part of this modeling framework."

Jan 1, 2001

By Chang Wei, Zhigan Deng, Minting Li, Cunxiong Li, Gang Fan, Xingbin Li

Iron precipitation occupies a vital position in the metallurgy industry, especially for treating iron-bearing sphalerite in hydrometallurgical processes. This paper emphasizes techniques for removing iron from high-iron sphalerite via hematite precipitation, and describes the results of research performed to examine ferrous oxydrolysis and precipitation. The behavior and mechanism of conversion between the iron phase and hematite residue at elevated temperature under pressure is ascertained by investigating the dissolving characteristic and thermodynamics stable area of hematite at sulfate system. The results show hematite precipitation went through the process of crystallization, dissolve, oxidation and precipitation of ferrous sulfate, and the overall iron precipitation was determined to be controlled by the rate of ferric sulphate hydrolysis rather than the oxidation of ferrous sulphate or the re-dissolution of ferrous sulphate crystals, or the transformation of basic ferric sulphate.

Mar 1, 2018

By Donald R. Sadoway

"Molten salt electrolysis is a proven technology for the extraction of metals -- all· the world's primary aluminum is produced in this manner. The unique properties of molten salts also make them excellent media in which to treat a variety of forms of waste. Of special note in this regard is electrolysis in molten oxides, a concept put forward by the author, initially as a ""clean technology"" for producing primary metal. However, in the context of waste treatment, electrolysis in molten oxides is a process offering the prospect of changing the-valence of dissolved heavy metals while making pure oxygen gas as the main by-product. Laboratory tests conducted at a temperature of 1550°C on chromate sludge dissolved in an melt composed of Al2O3, SiO2; CaO, and MgO have confirmed electrochemical production of oxygen on a carbon-free anode. IntroductionMolten salt electrolysis is the electrolytic decomposition of a compound dissolved in an ionic melt. The prime example of this process can be found in the production of aluminum. The compound, alumina (Al2O3)' derived from the mineral bauxite, is dissolved in an ionic melt comprising a multicomponent solution of cryolite (Na3AlF6)' aluminum fluoride (AlF3)' and calcium fluoride (CaF2,). The products of electrolysis are molten aluminum and carbon dioxide, the latter due to the attendant consumption of the carbon anode. Primary aluminum is produced in a reactor known as the Hall cell.' Alternatively, the compound undergoing electrolytic decomposition can be derived from waste. Processing in molten salts, with their capacity to dissolve materials to very high concentrations compared to those attainable in aqueous solutions, can be rather advantageous. High solubilities lead to high limiting current densities, and this, in tum, results in high productivities: For a primer on molten salt electrolysis and a review of the basic literature in the field of molten salts the reader is directed to an earlier publication of the author (1)."

Jan 1, 1996

By N. V. . Panishev

The Bakal (South Ural, Russia) deposit of iron ore bearing iron carbonate (siderite) with the capacity of more than 1 billion tones belongs to the MMK. This ore cannot be fully processed via blast furnace technology because of high content of MgO. According to the investigations carried out in the USA and Japan in 1999-2004 the ITmk3 (Ironmaking Technology mark three) RHF technology is a breakthrough in Ironmaking. Four iron ore types (hematite, magnetite, high and low Al2O3/SiO2) were tested. Reduction, melting and slag removal can be achieved in just 10 min. The main objective of the investigation is to establish optimum operation conditions for the production of iron nuggets from iron carbonate bearing ore via the ITmk3 by means of the lab scale testing. Samples of iron ore and carbon reductant were chemically and physically analyzed. Green pellets were processed via a lab tube furnace to simulate RHF conditions. The nuggets and slag were chemically analyzed. This preliminary test work provides valuable information which may be used for large-scale testing in a commercially sized RHF.

Jan 1, 2010

By Jilai Xue, Jun Zhu, Baisong Li

"TiB2-C/C Function Gradient Materials (FGM) is used in cathode materials to improve aluminum wettability and melt penetration in aluminum electrolysis. In this investigation, FGM was tested for use as part of the cathode materials, where a 10 mm thick TiB2-rich layer was on the top as an Al-wettable surface, the TiB2-C layers in the middle as a gradient layer and the carbon on the bottom as a base. Electrical resistances ofFGM were determined in the temperature range of25- 9600C in argon atmosphere. The results show that the present of TiB2-C gradient layer can reduce the open porosity and the electrical resistance of the cathodes materials at elevated temperatures. The cathode samples after aluminum electrolysis usually demonstrates an increase in electrical resistance, but the application of FGM layer can compensate such an increase for certain extend due to less variation in porosity and lower the level of melts penetration.IntroductionCarbon is still used for aluminum reduction cathodes dominantly, but it has a poor wetting properties by liquid aluminum and the anode-cathode distance has to be kept about 4-5cm with an additional 1.3-2.0 V voltage drop [l]. TiB2 has better wettability by liquid aluminum with higher electrical conductivity and stronger chemical resistance to the electrolyte attack. And the wettability ofTiB2-C composites cathode on liquid aluminum can be also improved, while liquid aluminum can completely wet the cathode surface ifTiB2 content exceeds 27% [2-4]. However, during the process of TiB2-C composites cathodes preparation and aluminum electrolysis, the deformation by temperature variation or sodium penetration are great disparity between TiB2 and carbon due to their physical properties difference. This will accelerate the cathodes cracking and deterioration."

Jan 1, 2013

By Andreas Siegmund

Cast or rolled lead anodes employed in zinc electrowinning typically contain between 0.5?1.0% silver to decrease the overall corrosion rate. The production of cast lead-silver or lead-silver-calcium anodes often results in the formation of numerous holes, voids or laps in the anode surface that can initiate internal corrosion in localized areas. In rolled anodes the presence of internal porosity is significantly reduced, thus resulting in extended service life. The obtained grain structure of cast or rolled Pb-Ag anodes, however, requires a relatively long period of time to form a stable protective PbO2/MnO2 layer that can evolve oxygen without excessive lead contamination of the cathode. Therefore, these anodes are often mechanically, chemically or electrochemically conditioned prior to being placed in the electrowinning process. RSR Technologies has developed an improved anode for zinc electrowinning. The anode consists of a rolled Pb-Ag-Ca-alloy with controlled surface grain structure. The preferred calcium and silver content of the alloy is 0.05?0.08 % and 0.3?0.4%, respectively. Since May 2001, industrial-scale tests have been carried out at two zinc refineries in North America in industrial electrowinning cells. The controlled grain structure of these anodes allows forming an adherent protective oxide coating within a short period of several days when placed in an electrowinning cell without the necessity of being preconditioned. Anode sludge growth is evenly distributed. The anodes stay dimensionally stable and no short-circuits have been observed. Consequently, low corrosion rates and improved current efficiencies have been achieved.

Jan 1, 2003