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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 Chen Song

Keywords: Co3O4, Cobalt Compounds, Morphology, Urea, Homogeneous Precipitation Depending on experimental condition, precipitation from cobalt nitrate and chloride solution in the presence of urea yield dispersed cobalt compounds with different chemical compositions and morphologies. The effects of concentration of cobalt solution and urea, agitation, on precipitation morphology were investigated experimentally. Generally in closed systems the particles are identified as cobalt (II) basic carbonate with needle type shape. In open system, spherical and plate-like precipitations of cobalt (II) basic cyanate are formed. The chemical formula of cobalt compounds was confirmed. They are CoII,III(OH)0.83(CO3)0.49 Ay?0.14 H2O (in tightly-capped reactor: A stands for NO3?, Cl?; y[A]molecular weight < 12.9) and CoII,III(OH)0.83(NCO)XAy?0.14 H2O. (in open reactor A stands for: NO3?, Cl?; 42 x + y[A]molecular weight < 44.82). The main reason was that the primary particles had different chemical compositions for the effects of the different kinds of anions and stoichio-chemical compositions of the primary particles. The effect degree of the anions depended on the co-existing anion radius in the reaction solution. According DTA-TG analysis of the cobalt compounds, the latter particles transform to Co3O4 powders on calcining. The shape of the Co3O4 particle with porous character has inheritance with precipitation. In this paper, it concludes that the particle formed by the principle of nucleation-aggregation in aqueous solution. The process of aggregation has played an important role in formation of particles. During calcination, the aggregation would be destroyed partly.

Jan 1, 2005

By Qingwei Wang

Heavy metal-containing wastewater from hydrometallurgical processes of lead-zinc was treated by biologics in a 200 m3/h industrial scale experiment. The result shows that Zn concentration declined from 50.28 mg/L~240.81 mg/L to 0.21 mg/L~1.98 mg/L, Pb from 1.00 mg/L~13.47 mg/L to 0.083 mg/L~0.71 mg/L, Cu from 0.24 mg/L~2.38 mg/L to 0.059 mg/L~0.40 mg/L, Cd from 2.12 mg/L~23.47 mg/L to 0.011 mg/L~0.071 mg/L and As from 0.50 mg/L~6.00 mg/L to 0.005 mg/L~0.10 mg/L. The concentrations of the above heavy metals in the treated water were lower than that in Integrated Wastewater Discharge Standard (GB8978~1996) in China. Furthermore, the treated wastewater was recycled and reused in smelter plant. Zinc content in hydrolytic sludge reached up to 34.04%, which indicates that this sludge can be used to recover valuable metals.

Jan 1, 2010

By Denise Cristina Oliveira Nascimento

Environmental considerations in addition to technical, economical and societal benefits are increasingly promoting the substitution of natural fibers for glass fiber in polymer matrix composites. However, natural fibers are heterogeneous in their dimensions, specially the cross section, which plays an important role in their mechanical strength. It has been found that the equivalent diameter of fibers such as sisal, ramie, pineapple and curaua correlates to different levels of tensile resistance. Piassava is a promising stiff natural fiber for composite reinforcement. In this work, a statistical analysis of tensile strength of piassava fibers using the Weibull methodology was performed. An attempt to correlate the fiber strength, obtained in tensile tests, with the diameter, precisely measured by means of a profile projector, was carried out. The results revealed an inverse dependence between the piassava fiber diameter and corresponding tensile strength. Fracture tip observation by SEM suggested a possible mechanism that could justify this inverse correlation.

Jan 1, 2010

By M. E. Huckman

In this paper, we review the equations needed to construct an ion exchange column model. These models contain three major components: 1) a differential material balance around the colunm, 2) a differential material balance around an ion exchange particle, and 3) a constitutive equation for diffusive flux We then examine the ability of a fairly simple mathematical model to predict ion exchange column experimental data. This model contains the traditional absorption theory equations and is used to predict the behavior of a column filled with a hydrous crystalline silico-titanate and which is removing trace amounts of Cs+ from a high pH, complex electrolyte solution. Finally, we propose replacing Fick&apos;s law with the Nernst-Planck equation as the constitutive equation for diffusive flux We use a Nernst-Planck type model to predict batch experimental data, then evaluate it by comparing it&apos;s ability to predict experimental data to that of a more traditional Fick&apos;s law type model? The data from this comparison suggests that the Nemst-Planck type model yields better results.

Jan 1, 1996

By M. E. Alam

In the present study, 1.1 volume percent of nano size copper was incorporated into pure tin using hybrid microwave sintering assisted powder metallurgy route. Microwave sintered samples were extruded both at room temperature and at 230 °C. Microstructural characterization studies were conducted on the extruded samples to investigate the distribution characteristics of secondary phase and grain morphology. Room temperature tensile test results revealed that hot extruded Sn-Cu samples exhibited higher strengths (~ 41%, in case of 0.2% yield strength and ~ 38%, in case of ultimate tensile strength) and ductility (~ 15%) when compared to room temperature extruded samples. On the contrary, the tensile properties of pure tin remained independent of extrusion temperature. An attempt is made in this study to correlate the effect of extrusion temperature on the microstructural evolution and tensile properties of Sn-Cu solder.

Jan 1, 2009

By Chen-Ming Kuo, Esher Hsu

Energy recovery of livestock waste can not only reduce waste pollution but also generate renewable energy and further create economic bene fits. Currently, most of livestock waste in Taiwan is treated as waste without efficiently recycled. This paper aims to explore and evaluate the energy recovery of livestock waste in Taiwan and further provide policy suggestions. Study results show that small farming scale of livestock industry in Taiwan leads to a lower efficiency of biogas energy recovery. Besides, the environment with relative low price of electricity and high invest cost for power generation plant is hard to provide incentive for implementation of energy recovery which has further caused difficulty on policy promotion for renewable energy recovery of livestock waste in Taiwan. Policy reform with increasing FITs and differentiated purchasing rate for biogas power is suggested to stimulate energy recycling of livestock waste in Taiwan.

Mar 1, 2017

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 NRMR Bhargava

With the increasing use of lead-free solder alloys, low melting point alloy is often required due to the heat- sensitive parts or substrates in modern electronic devices. For such demand of low melting point, the nanostructure lead- free solder alloy, having excellent metallurgical characteristics and a melting point of <215oC, were developed by mechanical attrition of conventional lead free solder alloys (Sn-Ag-Cu, Sn-Ag and Sn-Cu). The decrease in melting point due to nanosize effect was calculated theoretically as function of particle size and the theoretical results were compared with experimental values measured by differential scanning calorimetry. The newly developed alloys have eutectic composition of Sn-3.5Ag-0.7Cu, Sn-3.5Ag and Sn-0.7Cu and the melting point depression found to be 5.10C, 4.10C and 6.20C when the bulk alloys reduced to 80 nm, 92nm and 96nm sizes respectively.

Jan 1, 2009

By P. A. Rusin

Many manganiferous silver deposits remain undeveloped because standard chemical extraction methods yield poor recoveries or are &apos; environmentally unacceptable. Biotreatment of such ore deposits in our laboratory resulted in manganese and silver recoveries of greater than 90%. Ore and sediment samples were collected from mining sites in Colorado and Arizona. Portions of samples were incubated in a semi-solid mineral salts medium amended with 20 mM glucose mid manganese dioxide (Mn medium). The cultures were incubated at 3(fC until manganese reduction was detected by a .color change fr:om .black to clear. Bacteria from these cultures were purified on Tryptic Soy Agar and individual isolates were retested for Mn reduction by an agar overlay method. Bacteria were identified according to Bergefs Manual ?of Systematic . Bacteriology. Most of the Mn-reducing bacteria are Bacillus species. Bacterial manganese reduction kinetic experiments were performed in 52 ml mineral salts broth supplemented with manganiferous silver ore instead of manganese dioiide. These cultures were incubated with agitation for 16 d. Aliquots were removed periodically and analyzed for solubilized manganese by atoniic absorption (AA). Cyanide (1,0 M) Vias added to the remaining ore-medium mixture for a 24 h bottle roll. The supernatant was analyzed for soluble silver by AA. Similar experiments were conducted on a larger scale using 15% pulp density. After bfotreatment of the ore, standard bottle rolls were performed. The pregnant solutions and the residues were analyzed for manganese and silver?using AA or fire assay as appropriate. In sterile. controls-which received no biotreatment, manganese and silver recoveries were 0.3% and 10% respectively; During biotreatment, total manganese solubilizatiori was as high as 99.8%. The reduced manganese could . be stripped from ?the growth medium using hydrometallurgical techniques. Silver recovery vaned from 70% to 92.5%. Microbial treatment of refractory mangairlferous ores can result in high recoveries of manganese and silver. Retention time varies depending upon the relative concentrations of manganese, silver, and other metals in the ore with only two days required in some cases, The biotreatment of ore is environmentally&apos; acceptable while the use. of chemicals such as sulfur dioxide is less so.

Jan 1, 1991

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 Akihide Hosokawa

The void growth and coalescence in model materials involving a pre-existing three dimensional void array (i.e. multiple layers of a void array) was studied by X-ray computed tomography (XCT) coupled with in situ tensile deformation. To reduce the recording time, a new technique called fast tomography was employed. The model materials used in this paper were fabricated by the combination of an ultra-short pulsed laser machining system and a diffusion bonding technique, and two different types of arrays were prepared namely, FCC 1 and FCC 2 type array. This methodology allowed the authors to capture the entire process of growth and coalescence events of a void array embedded in the metal matrix. The failures in the both materials involved internal necking and shear localization. One of the highlights of this paper is that the plastic strain at the onset of void coalescence was measured for each model material. These values are in fact the adequate values to be compared with the coalescence strain predicted by existing void coalescence models such as the Brown and Embury model, the Thomason model and the Pardoen and Hutchinson model. The comparison suggested that the Brown and Embury model underestimated the coalescence in neither of the current model materials, while the Thomason model and the Pardoen and Hutchinson model showed a quite good agreement with the result for FCC 1 material. On the other hand the result from FCC 2 material agreed with none of the models probably due to the geometry of the void array that is not compatible with the existing models.

Jan 1, 2010

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 J. W. Bridge

Triaxial compression tests at various confining pressures and temperatures, as well as tangent modulus tests using ultrasonic waves, were conducted for wax-coated granular composite materials. The material used is a surface for Thoroughbred horse racing. The purpose of these tests is to examine how track shear strength and tangent modulus at a range of loads respond to changing temperatures. Previous work has shown that a wide range of operational temperatures are experienced which have been reproduced in the lab. Using differential scanning calorimetry, it is confirmed that these operational temperatures correspond to distinct thermal transition regions for the wax that is used to coat the sand in these surfaces. Preliminary results show that both shear strength and tangent modulus are sensitive to temperature changes with maximum strength and modulus correlating with major DSC wax transition regions.

Jan 1, 2010

By Kwong. Kyei-Sing

Gasification is a process that converts a carbon feedstock into synthesis gas (CO+H2). Slagging gasifiers operate at high temperature and pressure and in a corrosive-wear environment from the slag. Cr2O3-based refractory linings are used to protect the steel vessel that comprises the gasifier from the aggressive gasification environment. Increasing service life of the gasifier is one of the keys for wide spread development of this technology. In support of the goals, research on the gasifier atmosphere, the slag chemistry, the interaction of Cr2O3 refractory with different feedstock mixtures (e.g., coal and petcoke) were characterized by post mortem analysis of bricks from service in gasifiers and thermodynamics simulation of the environment. Examples demonstrating how thermodynamic calculations can explain the post mortem results and make predictions of material interactions will be given. Attention is placed on the possibility of Cr+6 in different feedstock mixtures and operating conditions.

Jan 1, 2010

By Sergio Neves Monteiro

The efficiency by which an applied load is transmitted through the composite structure depends on the strength of the interface between the matrix and the second phase. In fiber reinforced composites, the interfacial shear stress plays a major role in the composite capacity to support the applied load. This interfacial stress can be obtained by means of pullout tests using the fiber embedded to a certain length in a socket of the matrix material. In the present work, pullout tests were performed to evaluate the interfacial shear stress of ramie, a relatively strong natural fiber, reinforcing polyester matrix composites. The general result permitted to calculate a critical length for the ramie fiber embedded in polyester resin. From this critical length, the value of the interfacial shear stress was calculated. An interpretation of this result together with SEM observation displayed a relatively weak bond between the ramie fiber and the polyester matrix.

Jan 1, 2010

02, NaCI03, H202, Na0CI and Ce+4 have been examined as oxidants in an alkaline carbonate system for uranium in in situ leaching. The South Texas and New Mexico ores contained up to 2.6 meqJg of reducing compounds which consume oxidants in the leading operation. Leaching rates did not increase linearly with the oxidation potential of the oxidants. A mild oxidant can be used to maximize uranium oxidation selectively and oxidant efficiency. 02 can oxidize most of the uranium mineral with an adequate rate and high oxidant efficiency.

Jan 1, 1990

By P. J. Mackey

Over the course of Dr. Robertson’s career, the ferrous and non-ferrous plants have seen enormous changes in technology and increases in plant capacity, essentially amounting to a “technological revolution”. In iron and steel, the “mega” blast furnace of some 6,000 m3 working volume is now standard (~10,000 tonnes (mt) of pig iron/day). Similar huge changes in process technology and plant size have occurred in the non-ferrous industry. As an example, the fuelfired reverberatory furnace, once the mainstay of the copper industry, has disappeared - replaced by large capacity flash and bath smelting technologies. The energy consumption per unit mass of metal produced has also been reduced considerably. Our understanding of the thermodynamics and mechanisms of metallurgical reactions, a field to which Dr. Robertson has significantly contributed, has made great strides. This paper reviews these changes with particular reference to the copper smelting industry, providing also comments on expected future trends.

Jan 1, 2014

By C. E. M. Meskers

Electronic and Electric Equipment contains a range of components made of a wide variation of metals, plastics and other substances. Up to 60 elements can be found in complex electronic equipment: base metals, precious metals and special metals in circuit boards and batteries. Because of its amount WEEE represents a considerable metal resource with a higher special and precious metal content than found in ores. The Umicore integrated smelter and refinery recovers and supplies back to the market 17 different metals from EEE. Pre-treated materials enter state of the art, material and energy efficient metallurgical processes for environmentally sound recovery of metals and treatment of off gasses and hazardous substances. The organics in the feed function as reducing agent and alternative energy source during smelting for precious metal recovery. Lithium-ion batteries are treated using a dedicated process. As a result the environmental footprint of metals produced from EEE is much smaller than primary production.

Jan 1, 2009

By Hiroyuki T. Takeshita

Ca-Ni based alloys were investigated on structures, hydrogenation properties and the effect of additive elements on hydrogenation properties. CaNi, samples were decomposed to form a new hydride with a CsCl-type structure on the constituent metal atoms at high temperatures such as 673K in a hydrogen atmosphere. The candidate of the third element which was added to stabilize the original compound was investigated by using the Miedema&apos;s semi- empirical model and, as a result, Pd was chosen. The hydrogenation of CaPd was conducted with a Sieverts&apos; type apparatus and the synthesis of Ca-Ni-Pd ternary alloys was performed by high frequency heating.

Jan 1, 2002