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By Ramona Prillhofer

Salt slag is a waste product produced by the recycling of aluminum. In most European countries (e.g. Austria, Germany) the landfill disposal of this waste is forbidden because the slag contains soluble salts and these represent a potential source of pollution to the surface and groundwater. Additionally, consisting metal and some compounds in the salt slag can react with water and resulting from this, noxious gases are generated. The recovery of useful materials from these wastes is accordingly both environmentally necessary and economically feasible. This study describes a complete recycling-process for the salt slag, which includes a leaching-cristallization-process to obtain the oxidic residue, a pyrometallurgical-step to clear the oxidic residue and finally an extensive characterization of the achieved products. Due to the increasing price of raw materials, the utilization of the oxidic residue into commercial products has been investigated and application possibilities will be discussed.

Jan 1, 2009

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 Jiann-Yang Hwang

Microwave heating has been proved an effective method to rapidly heat iron oxide. This offers an opportunity to apply microwave heating in the steelmaking process. The reduction reaction of iron oxide is traditionally achieved at high temperature with reducing gases such as H2 and CO generated from various sources, including coke, coal, and natural gas. This study investigates the differences in iron oxide reduction using conventional and microwave heating under H2 and CO atmospheres. A special microwave thermal gravimetric device was designed and built to facilitate the investigation. With this device, iron oxides can be heated by electric resistance heating, microwave heating, or a combination of methods. The incoming CO and/or H2 also can be preheated to simulate a potential utilization of recovered heat. The iron oxide weight and temperature can be monitored during an entire reduction period. A series of reduction experiments have been conducted. The results are presented and discussed.

Jan 1, 2006

By Tian Sugui

By direct aging treated, creep properties measurement and microstructure observation, the influences of the direct aging treatment on the creep behaviors of Hot Continuous Rolled GH4169 superalloy are investigated. Results show that the creep resistance of Hot Continuous Rolled GH4169 superalloy may be obviously improved by directly aged treatment. Under the applied stress of 700MPa at 660, the creep lifetime of the alloy is enhanced to 126h from 60h. During hot continuous rolling, the deformation features of the alloy are the twinning and the double orientations slipping of the dislocation activated within the twinning regions. After direct aging treated, the alloy displays a smaller grain size, and the finer g² phase is dispersedly precipitated in the matrix of the alloy, which is thought to be a main reason of enhancing creep lifetime of the alloy.

Jan 1, 2010

By Taegong Ryu

A thermal plasma process was used to synthesize nanosized tungsten carbide -cobalt composite powder, in which ammonium paratungstate and cobalt oxide were reacted with a gas mixture containing CH4, H2 and Ar. The reduction and carburization of vaporized precursors produced nanosized tungsten carbide (WC1-x) - cobalt composite powder, which sometimes contained small amounts of W2C and/or W phase. The effects of gas composition, plasma torch power, and the flow rate of plasma gas on the product composition and grain size were investigated. The grain size of synthesized tungsten carbide powder was less than 20 nm. The synthesized composite powders were also subjected to a hydrogen heat treatment to fully carburize WC1-x, W2C, and W phases to the WC phase as well as to remove excess carbon in the product. Finally nanosized WC-Co composite powder of grain size less than 50 nm was obtained.

Jan 1, 2009

By Ludovic Charpentier

Production of metallic wires directly from liquid jets would avoid drawbacks of extrusion (space needed, damaging, cost?) and enable recycling. But liquid jets tend to break, due to capillary instabilities, unless a solid layer (coating or start of solidification) surrounds it. We recently developed a process to produce tin wires, cooled by water flow parallel to the jet. Superficial oxidization of tin produces a glass coating around the jet. Studies showed the length of wires increased when increasing speed of tin jets, and that water average speed should be the closest possible to the jet one to have smooth fibers. Producing 1 mm diameter wires is possible. The length of wires is limited by the experimental setup, which does not provide possibilities to coil the wire. Most of other metals do not generate glass-like oxides. The lack of coatings makes it necessary to reduce the capillary instabilities to obtain fibers.

Jan 1, 2006

By A. Gibson

Most methods for the treatment of scrap printed circuit boards do not reclaim the components in working order as the boards are either fed to a copper smelter, to recover the valuable elements, or, simply landfilled. This work reports the dissolution of the solder in fluoroboric acid containing Ti4+ ions which was particularly selective for solder, allowing the components to be recovered. The solder was subsequently electrowon from the leachant. The boards were then shredded and the copper dissolved in ammonium sulfate and, then treated via solvent extraction to give an electrolyte suitable for electrowinning. The remainder of the metals were dissolved aqua regia, silver remained unattacked by the aqua regia, palladium precipitated as Pd(NH4)Cl6 in the presence of zinc and nickel, the gold was removed by solvent extraction and precipitated as nanoparticles. The aqua regia was then diluted and the zinc and nickel separated by solvent extraction.

Jan 1, 2009

By Varadajan Seshadri

Keywords: torpedo car, kinetics, physical modeling A 1:6 torpedo car physical model was built to assess the optimum refining conditions for pig iron desulfurization in the torpedo car considering the industrial parameters used in the steel plant CSBM (Companhia Siderurgica Belgo-Mineira, João Monlevade, MG, Brazil). The refining practice in this plant is through injection of a CaO-CaF2-Mg powder in the pig iron melt. Similarity between the model and prototype were established through Froude and turbulent Reynolds criteria. Mixing times were evaluated by pulse tracer addition and the kinetics of metal/slag interactions were assessed from experiments investigating iodine transfer from kerosene to water. The influence of parameters such as level of metal, gas flow rate, lance penetration, lance orientation were also evaluated.

Jan 1, 2005

By Sadegh Firoozi

Experiments measuring the kinetics of oxidation and making visual observations of the oxidation of approximately 6 g static lead baths containing arsenic, antimony and tin were conducted in the temperature range from 500 to 600 oC. A range of repeatable behaviours were observed, notably: the formation of a coherent, solid oxide layers on pure lead and lead-tin alloys; the formation of liquid oxide droplets during the initial oxidation of lead-arsenic and lead-antimony alloys and the eventual formation of a complete oxide layer covering the entire free surface of these alloys. Thermogravimetric measurements revealed that the rate of oxygen uptake was strongly influenced by the form of oxides being generated at the melt/gas interface. Compared to the rates of oxidation of pure lead, arsenic increased the rate of oxygen uptake throughout the temperature range via the formation of liquid oxidation products. The presence of antimony resulted in a moderate increase in the rate of oxygen uptake as compared to arsenic. Tin was effective in lowering the rate of oxidation even in the presence of arsenic because the oxidation product was always a coherent layer that acted as a physical barrier to oxygen transport to the underlying alloy.

Jan 1, 2006

By M. Bilal Khan

Thermal stress relief by means of a typical heat treatment cycle (660oC for one hr) is compared with the one achieved through vibratory stress relief at resonant and multiple resonant frequencies for the D-406 HSLA material. Our analysis of the data is based on the microhardness profiles measured for the entire length of scales, namely, base metal, heat affected zone (HAZ) and the weld bead itself. The profiles obtained using the two techniques mimic each other, for an equivalent 70% stress relief level. The data are further qualified by impact testing wherein the zone of interest is projected in the retention groove to provide impact by the pendulum striker in the Charpy mode. Higher equivalent energy absorption in the treated specimens confirms the efficacy of the vibratory method. The present work rectifies earlier anomaly where heat treatment has been reported at 310oC for the same material.

Jan 1, 2009

By Sergio N. Monteiro

Polymeric matrix composites with dispersed hard particles are being as wear resistant tools in industrial polishing operations. In the present work, the microstructure of epoxy composites with different amounts of embedded diamond particles, up to 30 wt.%, was investigated for the effect on fracture characteristics. It was found that the introduction of diamond particles promoted an increase the porosity of the epoxy matrix. Moreover, the particle morphology associated with a non-uniform distribution within the matrix was responsible for the nucleation of cracks that caused rupture of the composites.

Jan 1, 2006

By A. J. Sideris

It is known that Mg can act as a catalyst/solvent in the high pressure high temperature diamond synthesis. However, above pressure levels of the order of 7 GPa, and temperatures from 1700 ? 1800oC, it was not possible yet to use Mg for the industrial production of diamond. A possible alternative is the use of MgNi based alloys. However, owing to the great Mg reactivity, it was consider, so far, a difficult task to deal with such alloys. The present work presents successful results regarding the production of MgNi alloys, with different composition, at high pressure conditions. The behavior of the alloys and their microstructural characterization is analyzed.

Jan 1, 2006

A molten metal granulator was designed and fabricated at the U.S. Dept. of Energy, Albany Research Center, for granulation of precious metal-bearing alloys and slags. The system was designed to safely granulate a metal alloy at a temperature of up to 1,600°C at a rate of roughly 50 kg of alloy per minute. The primary water jet was supplied by a 18.6-kW, 600 liter per minute pump which provided approximately 600 kg of water per minute through the primary jet. Two 3.7-kW, 150 liter per minute auxiliary pumps provided additional wash water to wet the granulation trough through 4 secondary jets, which were placed at either side of the primary jet. The water supply was closed-loop, including a 37,850-liter supply tank and 22,710-liter recovery tank. Magnetic separators and particulate filters were included for collection of the finest fraction of the granulation product, which cleaned the water sufficiently for continuous recycle.

Jan 1, 2006

By Jeremy Gregory

The disposal of end-of-life electronics is an issue receiving increasing scrutiny. This paper evaluates several alternatives for recycling cathode ray tubes (CRTs) within monitors and televisions. The primary recycling options for the glass, reuse in new CRTs or as a smelter flux, are examined from economic and environmental standpoints. The economics are modeled using a cost model that includes dependencies on processing costs, transportation logistics, and incoming material composition. The environmental consequences are modeled using life cycle assessment methodologies to determine the energy embodied in each processing alternative. Results map out preferred processing alternatives across a range of technological and operational conditions. The results indicate that economic costs and environmental consequences are heavily impacted by transportation. The preferred destination of CRT glass for a recycler is highly dependent on the proximity of the consumer to the recycler, although it is generally economically advantageous for the recycler to extensively dismantle the CRTs.

Jan 1, 2006

By A. L. D. Skury

In the synthesis of diamond, the precursor graphite must present a degree of crystallinity to assure optimum yield and quality for the transformed crystals. X-ray diffraction, SEM and TEM analyses were carried out to investigate the structural and morphologic transformations produced in natural graphite by high pressure-high temperature treatment. The present study had as its objective to characterize the morphological and structural changes suffered by a natural graphite that was subjected to high pressure and high temperature treatments in the region of diamond thermodynamic stability. The results indicate that the material that constitutes the gasket, for the deformable capsule, could act as catalyst in the graphite recrystallization process.

Jan 1, 2006

By Lifeng Zhang

The transport of fluid, heat ,and particles (bubbles and solid inclusions) in flowing molten steel is investigated in steel refining ladles, the continuous casting tundish, continuous casting mold and strand, and steel ingot casting processes. The two-equation k-?? model is used to simulate the turbulence. Multiphase fluid flow is numerically simulated with a Lagrangian-Eulerian approach, an Eularian-Eulerian approach and the Volume Of Fluid (VOF) method. The simulation can predict inclusion trajectories, inclusion removal fraction, free surface waves and other phenomena, which can be used to optimize these important metallurgical operations.

Jan 1, 2006

By Nobuaki Sato

For the recovery of uranium from spent nuclear fuel, sulfide reprocessing process, which consists of voloxidation, selective sulfurization, and magnetic separation or selective dissolution steps, are proposed. In this paper selective sulfurization of rare-earth oxides in the presence of uranium oxides was studied by thermogravimetry and X-ray diffractometry. In case of the mixture with UO2, the rare earth oxides R2O3 (R=Nd, Eu, etc.) were preferentially sulfurized by CS2 formingoxysulfides and sulfides, while UO2 remained at temperatures lower than 500 °C. When R2O3was mixed with U3O8, first, the reduction of U3O8 to UO2 occurred at low temperatures followed by the sulfurization of R2O3. The separation of rare earth elements from UO2 in suspensionsolution by the use of permanent magnet was examined. The advantage of the proposed process was also discussed by compared with current process.

Jan 1, 2006

By Esher Hsu

Keywords: Recycling, Consumer Battery, Fee rates On November 11, 1999, all types of spent consumer batteries are proclaimed to be collected in Taiwan. Under current recycling system, all producers and importers of consumer batteries have to pay a collection/recycling fee to the Recycling Management Fund (RMF) of EPA based upon the rate approved by EPA. Collectors and recycling plants receive subsidies from RMF according to the collected and treated amounts audited by an independent auditing organization. Collected spent consumer batteries only reached 923 tons in 2002 equivalent to 10% of the total quantity sold at the same year. How to increase the collection efficiency of used batteries becomes an important issue for EPA in Taiwan. The objective of this study is to explore current recycling system of spent consumer battery in increasing collection efficiency. Results provide some suggestions to Taiwan EPA regarding recycling route, recycling system, recycling rates, and recycling subsidies.

Jan 1, 2005

By Pengfu Tan

A thermodynamic model has been developed to predict the distribution behaviors of Cu, Fe, S, O, Pb, Zn, As, and heat balance in a lead blast furnace. The modeling results have been validated by the plant data of a lead smelter in Asia. The model can be used to predict for any set of controllable process parameters such as feed composition, smelting temperature, degree of oxygen enrichment and volume of oxygen-enriched air. The effects of the blast air, industrial oxygen, and coke charge on the distributions of Cu, Fe, S, O, Pb, Zn, As, and heat balance, and on the lead loss in slag have been presented and discussed.

Jan 1, 2005

By WU Jian-hui

Keywords: metallic material, precursor synthesis, precipitation, nickel, fibrillar powder The composition and morphology of the precursor of fibrillar nanocrystalline nickel powder prepared by oxalate precipitation are characterized by XRD,IR and SEM analysis, and the effects of temperature, nickel concentration, pH, surfactant and drying process on the morphology and the dispersion of the precursor are investigated. By the experiment results, the fibrillar precursor is a complicated nickel salt. The precursor prepared in the of 60~70°C,0.6~0.8 mol/L nickel ion, pH=8.4~8.6 and with addition of PVP surfactant is well dispersive and in fiber form. The powder dried by azeotropic distillation is dispersive.

Jan 1, 2005