Search Documents

By S. Eck

In previous work the influence of the casting speed on the flow field and the shape of the solidification front in an industrial 0.82 x 0.25 x 0.8 m³ bronze caster had been investigated. Both numerical and experimental model represented 1:1 the real caster geometry. A comparison of the results of both numerical and experimental models for the flow during the casting process showed a good agreement in the qualitative velocity fields (flow direction and vortex formation). This work represents a parameter study of the numerical model with variations of the turbulence conditions at the inlet in order to clarify their influence on the flow field in the caster. In order to find the best boundary condition at the inlet, the numerical calculations for water have been compared with the measured flow fields in the water model. The new boundary conditions were then applied to the numerical model of the bronze casting process.

Jan 1, 2009

By Gabrielle Gaustad

For aluminum, substitution of primary with secondary resources decreases energy consumption; this energy advantage creates a strong economic incentive to recycle. Several authors have raised concerns that the current sinks for secondary materials may soon be saturated, impeding subsequent expansion of recycling. This work combines dynamic material flow analysis with optimal batch planning models to quantify the significance and drivers of these pending limits under several scenarios, and thereby explore potential opportunities to increase recycling. An aluminum recycling system case was developed that includes containers and packaging, automotive, and construction products and scraps. The impacts on aggregate scrap utilization and materials cost are explored in the context of changing alloy demand and lifetime. Insights drawn from this specific case study could be applied to multi-stakeholder, systemic models.

Jan 1, 2010

By Junfeng Shen

Geosynthetic clay liner (GCL) is a kind of waterproofing material used widely in engineering. The waterproof mechanism is understood in terms of bentonite particles becoming a water-obstructcolloid layer after they absorb water and swell. The swell stress, however, has not been determined directly till now. In our experiment, the swell stresses of the GCL under saturated and water absorbing conditions are measured directly using a custom-made instrument. The results show that (1) the instrument designed by the authors performed satisfactorily and the test results are reproducible; and, (2) The trend line of swell stress variation with time can be divided into three segments. The first segment is characterized by a quick increase of the swell force in the first 0?50 hours. The swell stress increases by 7.00×10-4?1.00×10-3 Mpa / hour. The second segment shows a slow increase of the swell stress during the 50?1730 hours. The swell force increases by 7.54×10-6?2.02×10-5Mpa / hour. The third segment is characterized by little variation in the swell stress after 1730 hours. In this segment, the average value of the swell stress measurements is 0.0719Mpa and the maximum value is 0.0729Mpa. It is suggested that the swell stress is mainly raised by water entering the pores among montmorillonite particles and the interstitial layers in individual montmorillonite crystals, leading to an increase in volume and manifested as a stress on the surrounding materials.

Jan 1, 2006

By Elsa Olivetti

Life cycle assessment (LCA) is used increasingly as a tool to provide quantitative metrics of environmental impact and inform early stage materials selection decisions. One common challenge in LCA stems from allocation of burden when multiple adjacent products share some of the same processes. A critical example of this is the partitioning of benefit or burden at product disposition in open-loop recycling scenarios. This work reviews the challenge of allocation and investigates the various methods proposed for allocating end-of-life (EOL) burden. Specifically this work examines whether these methods lead to different results and explores the trends in allocation method bias for or against particular materials classes.

Jan 1, 2010

By Eleazar Salinas R., Miguel Perez L., J. Cesar Juarez T., Martin Reyes P., Eduardo Cerecedo S., Isauro Rivera L., Francisco Patino C., Juan Hernández A.

"A complete characterization of burrows from Mining district of Pachuca - Real del Monte, in Hidalgo state Mexico, was done. These kind of residues had not been formally characterized, founding an average chemical composition of 70.43 % wt. of Si02, 7.032 % wt. of Ah03, 2.69 % wt. of Fe20 3, 0.70 % wt. of Mn, 3.98 % wt. ofK20, 3.34 % wt. of CaO, 2.50 % wt. ofNa20, 1.01 % wt. of MgO, 0.26 % wt. of Ti02, 0.04 % wt. of Zn, 0.026 % wt. of Pb, 56 g/ton of Ag and 0.6 g/ton of Au; In the same way, the residues present as majority mineralogical phases the following: Quartz, Berlinite, Orthoclase, Feldspar, Anorthoclase and Calcite. By the other hand, joint with the big volume that present these residues and the chemical and mineralogical characteristics, these materials or sub - products can be used for production of ceramics, into mixes forming some materials for architecture (bricks, blocks, and tiles), refractory bricks, in the production of cement and to get some metallic values such as gold and silver involved in these residues.IntroductionActually the mining residues in Hidalgo State, Mexico are the result of more tan 500 years of mining, leading so a great volume of deposits, which we can classify in different types, among the most communes we have: Acid Mining Waters, Waters of solid transport and elements in the form of radicals, deposits of abandoned minerals without processing, and mining wastes of processed minerals known as burrows or dumps, being these the most abundant in the Hidalgo State [1-4].Form the metallurgical point of view, it is known that a characterization study if fundamental to find the viability of reuse of these kind of residues, leading so an additional use and the opportunity of get an alternative use into several industrial processes, due to its contents of oxides of silicon, iron, aluminum, calcium, sodium and potassium, principally, besides of its mineralogy and distribution of chemical elements into its primary and secondary phases [ 1-2, 5- 6]."

Jan 1, 2011

By Chuanfu Zhang, Liwei Liang, Yanxin Wu, Jinliang Wang

"According to the reaction shaft operation characteristics during the flash smelting process, 15 groups of slag samples containing high Fe3O4 were prepared by some chemical reagents, and then the slag viscosities were measured using a RTW-10 type synthetic test instrument for melt physical property by the rotating cylinder method. The effects of Fe/SiO2 ratio (mFe/mSiO2), Fe3O4 content (wFe3O4), Cu2o), MgO content (WMgO) and Cao content (wCaO) on the slag viscosity were also studied. Results show that slag viscosity is decreased with the increase of temperature, mFe/mSiO2, wCu2o, wMgO and wCao, and with the decrease of wFe3O4, under the range of slag contents: mFe/mSiO2 1.36~1.78, wFe3O4 17.83%~21.18%, wCu2o 3.51%~8.34%m wNgI 2.21%~6.57%m w/caI 6.22%~9.387% and temperature range if 1250 o/c~1450 oC. Only wFe3O4m and w/caO have great influence on the slag viscosity when temperatures as high as 1400 oC. Only wFe3O4 and wCaO have great influence on the slag viscosity when temperatures as high as 1400 oC or so. To form a freeze slag with higher viscosity inside the reaction shaft, wFe3O4 should be more than 20% and wCaO should be less then 6%.IntroductionSince its appearance in 1949, Outokumpu flash smelting technology has making continuous innovation and has become the most competitive intensified smelting technology [1], widely considered to be the standard clean smelting process [2]. At present, flash smelting technology is adopted to newly build or reconstruct most of the world's copper or nickel smelting enterprise [3]. Reaction shaft is the most important part of the flash smelting furnace. During the flash smelting process, reaction shaft must be able to withstand the following harsh conditions at the same time: 1) high temperature varying from 1400 °C to 1500 °C. 2) strong oxidative atmosphere containing 50% - 80% oxygen. 3) solid particles and melt with speed up to l00 m/s. 4) high acidic or basic slag with strong chemical corrosiveness. 5) smelting gas containing 50% - 80% SO2. 6) matte with strong dissolution."

Jan 1, 2012

By Arthur E. Morris

Process modeling software is used extensively in process engineering, but there is a notable lack of affordable software for educational uses. This paper describes two educationally oriented software programs for thermochemical modeling of processes involving metals, minerals, and ceramic materials. Both programs run as Excel@ spreadsheet files. The first is FREED, a thermodynamic database program containing datafiles for 2500 species. It contains the entire U. S. Bureau of Mines and most of the U. S. Geological Survey database, plus data for scores of other species drawn from various sources. Several modules are available for manipulating and viewing the data. The second program is THERBAL, for making thermodynamic calculations using FREED data. Equilibrium calculations can be made for systems with non-ideal solutions, for a specified set of pressure, temperature, and input amounts of reactants. An optional heat balance is also calculated. The results are displayed as tables or charts in Excel worksheets. Examples of the use of THERBAL will be given for the reforming of natural gas for DRI production, DRI production, and EAF steelmaking. Some observations will be made on its use in the classroom. The development of FREED and THERBAL was initially carried out at the Department of Metallurgical Engineering, University of Missouri - Rolla as part of a project to preserve and enhance the Bureau of Mines database. The current versions were developed privately by the authors.

Jan 1, 2002

By Shadia J. Ikhmayies

Nanocrystalline CdS:In thin films with particle size in the range (3-36 nm) were produced by the spray pyrolysis technique on glass substrates. The films were characterized by investigating their X-ray diffractograms (XRD), scanning electron microscope images (SEM), transmittance curves and photoluminescence (PL) spectra. The size of the nanocrystallites was estimated from XRD difractograms and then from the hyperbolic band model and the bandgap energies of the nano- particles, which were calculated from the positions of the minima in the first derivative curve of the absorbance. Fine-structured PL spectra confirmed the nanocrystalline nature of the films.

Jan 1, 2010

By Jewel A. G. Gomes

Green rust (GR) are layered Fe(II)-Fe(III) double hydroxides, having a pyroaurite-type structure consisting of positively charged hydroxide layers and hydrated ions in interlayers. This special feature of GR is very efficient for wastewater treatment as the pollutants are easily taken in or exchanged with the anions in the interlayers. It can be simply and cost-effectively produced by electrocoagulation (EC). Chicken processing plant (CPP) produces large amount of wastewater containing variety of readily biodegradable organic compounds, fats, and proteins. The possible re-use of properly treated CPP wastewater would be economic and environment friendly. In this study, we present our work on treatment of CPP wastewater using EC, specifically for the removal of COD. Analysis of the EC-treated water for reuse in the same plant is discussed considering the U.S.EPA regulations. Two types of EC-reactors were used for this purpose. To better understand the treatment mechanism, EC-floc was also characterized using XRD and SEM-EDS.

Jan 1, 2010

The mineralogy of the platinum group metals is fairly complex, and it is therefore not surprising that the different minerals have variable responses to metallurgical processes, in particular, flotation and leaching. The PLATSOL® leach process was developed to extract simultaneously base metals, gold and platinum group metals from various materials. Extensive research has indicated that most PGM?s were amenable to the PLATSOL process, with the notable exception of cooperite PtS. Further work showed that a thermal pretreatment at 500-700ºC transformed the structure of the cooperite and similar refractory minerals (Pt,Pd)S into Pt metal and Pt-Pd alloys that responded well to the PLATSOL® process. Examples are presented of the mineralogy of PGM concentrates as produced, in the residue from the PLATSOL® leach and after thermal pretreatment.

Jan 1, 2006

By Jian Zhang

From the standpoint of quality, surface cracks normally pose more of a problem than internal cracks. Hypo-peritectic (HP) steel grades are well known for their proneness to surface longitudinal cracking (SLC) during continuous casting. This study analyzed the influences of chemical composition, technique parameter and secondary cooling on the surface longitudinal cracks. Based on the optimized the first and secondary cooling zone water distribution in the process of continuous casting, low cooling water distribution at solidification initial stages and uniform cooling at secondary cooling zone were suggested, which can be used to effectively control the surface longitudinal cracks.

Jan 1, 2010

By Shadia J. Ikhmayies

The SnO2/CdS/CdTe thin film solar cells were fabricated on glass substrates by using the spray pyrolysis (SP) technique for the deposition of the SnO2 and CdS layers and vacuum evaporation for the CdTe layer. The transmittance curves were used to investigate the interdiffusion in the two interfacial regions SnO2/CdS and CdS/CdTe by taking the first derivative of the absorbance as a function of wavelength. The appearance of new bandgaps around the bandgaps of SnO2:F, CdS:In and CdTe layers is a strong evidence on the interdiffusion in the two interfacial regions and/or the formation of quantum dots.

Jan 1, 2010

By Denise Crocce Romano Espinosa

The recycling of waste of electric and electronic equipment (WEEE) is one of the main modern challenges. Among the variety of WEEE, batteries can be set apart due to their composition and their growing demand along with portable devices. The objective of this work is to characterize the thermal behavior of a sample of mixed types of batteries using a thermobalance (TGA). The results of tests showed that Cd evaporated up to 800ºC, Zn evaporation occurred mainly above 900ºC and manganese oxides were pre-reduced to MnO at temperatures above 900ºC.

Jan 1, 2009

By Yunnen Chen

In the present study, waste materials like pine sawdust and spent grains were investigated to assess their potential for removal of cobalt ion from water by the process of biosorption. The effects of solution pH, reaction time and initial concentration were studied in batch experiments. The removal efficiency of Co(? ) by spent grains was higher than that of pine sawdust. The initial removal was rapid and equilibrium was established in less than 90 min. Equilibrium data all agreed well with both Langmuir and Freundlich isotherm models for the two metal-biomass sorption processes. Good correlation coefficients were obtained for the pseudo second-order kinetic model. Pine sawdust and spent grains were shown to be promising biosorbents for Co(? ) removal from aqueous solutions.

Jan 1, 2010

By Elisa Alonso

Manufacturing firms that rely on finite resources have a stake in ensuring sustainable materials use. Higher material prices and uncertain material supply, consequences associated with scarcity, can be damaging to firms. Firms have a number of options to improve material sustainability including dematerialization, material substitution and recycling. However, these options require technological capability, capital investments and supply-chain infrastructure; firms may decide to make such investments only if material prices increase. Once decisions are made, the barriers and delays to implementing changes may harm firms. The impact of not reacting to changes in material supply on firms was examined for the case of different platinum-using industries. It was found that taking action is particularly important for firms when limited material availability leads to volatile market conditions. Industries can benefit especially if they ensure process flexibility and have options for changing their material use patterns.

Jan 1, 2010

By M. T. Baquera

A comparison of microstructures associated with W single-crystal ([001], [011], [111]) rods prior to deformation (as grown), and after quasi-static compression (at a strain rate of ~1/s) by transmission electron microscopy (TEM) shows several orders of magnitude difference in dislocation density. Dislocation substructures were not significantly different amongst the deformed sample orientations. In contrast, [001] W rods penetrated into steel targets, at impact velocities of ~1.3 km/s, exhibited heavy dislocation densities and dynamic recrystallization as very distinct microstructural regimes accommodating the penetration process. Twinning on {112} also occurred as a precursor to, or remnant of, these microstructures near the projectile head. These results suggest that deformation accommodating the extreme strains and strain rates associated with the penetration of a single-crystal rod into a metal target is not adequately represented by conventional deformation

Jan 1, 2006

By N. Krishna

The utilization of Electrochemical Impedance Spectroscopy (EIS) in conjunction with Atomic Force Microscopy (AFM) is a powerful surface characterization technique to study the role of sulfur formation during acidic oxidation of chalcopyrite. It has been established that the chalcopyrite dissolution kinetics is controlled by the formation of passive sulfur layer during leaching. The objective of the study was to characterize the intermediate sulfur layer formation at different oxidation conditions in acidic solution. The chalcopyrite samples were subjected to anodic oxidation and the oxidation process was analyzed using impedance spectroscopy. The sulfur growth on the chalcopyrite surface during oxidation was further analyzed using Atomic Force Microscope for sulfur roughness and grain size, peak height and sulfur growth.

Jan 1, 1999

By R. Fragoudakis

AISI 4130 steel is a medium carbon Cr-Mo steel used in automotive, aeronautic and other general-purpose industries. In this study, 4130 steel fatigue specimens were carburized at 927oC to enhance the carbon content in the steel, raising it from approximately 0.30% (non-carburized) to 0.90% (carburized, oil quenched and tempered). Rotating bending fatigue tests were performed on the R. R. Moore Rotating Beam Fatigue Testing System, in order to determine the high cycle fatigue (HCF) life of 4130 steel and plot the corresponding S-N diagrams. A comparison of the results of carburized and non-carburized specimens shows that carburizing of steel: a) increases the surface hardness and b) improves the fatigue strength of the steel by at least two orders of magnitude.

Jan 1, 2010

By Y. Zhoa

The surface morphology of materials is of fundamental importance to many surface related applications, such as wetting, friction, reflection, drag, and adhesion. Various approaches for micro/nano patterning atop polymer surfaces have been proposed in recent years. However, a cost effective technique is still highly in demand. In this paper, we demonstrate a novel but rather simple and generic approach for surface micro/nano patterning using shape memory polymers (SMPs). Different types of novel patterns are realized and their 3-D surface features are quantitatively analyzed by a PLµ Confocal imaging profiler.

Jan 1, 2010

By Jinhui Li

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

Jan 1, 2009