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By J. Gartelmann, B. Zaslavsky, Y. Vojta, D. J. Chaiko, W. Mego, A. N. Rollins

"Aqueous biphasic extraction (ABE) processes offer the potential for low-cost, highly selective separations. This countercurrent extraction technique involves selective partitioning of either dissolved solutes or ultrafine particulates between two immiscible aqueous phases. The extraction systems that we have studied are generated by combining an aqueous salt solution with an aqueous polymer solution.We have examined a wide range of applications for ABE, including the treatment of solid and liquid nuclear wastes, decontamination of soils, and processing of mineral ores. We have also conducted fundamental studies of solution microstructure using small angle neutron scattering (SANS). In this chapter we review the physicochemical fundamentals of aqueous biphase formation and discuss the development and scaleup of ABE processes for environmental remediation.IntroductionAqueous biphasic extraction (ABE) is a highly adaptable separation technique that can be used in a wide range of applications. We have been evaluating various types of ABE systems for possible applications in the treatment of solid radioactive wastes (1,2), liquid nuclear wastes (3,4), and contaminated soils (5-7), and in the removal of organics from aqueous salt solutions (8). We have also conducted fundamental studies of the solution microstructure of ABE systems using small angle neutron scattering (SANS) (9).The extraction systems are generated by combining an aqueous salt solution and an aqueous polymer solution. This produces two distinct liquid layers that are as immiscible as oil and water, yet each liquid layer contains at least 70 to 80 wt % water. The biphasic systems that we have been working with consist of immiscible polyethylene glycol (PEG) and salt solutions. Some inorganic salts that promote biphase formation with PEG solutions include the sodium/potassium salts of sulfate, carbonate, phosphate, and hydroxide (10)."

Jan 1, 1996

By Forsén. O.

In this ?paper practical solidification of anodes containing nickel, arsenic, antimony and bismuth is compared with the equilibrium? diagrams and kinetic ?factors. In order to clarify the distribution of the impurity elements in the anode the structures were studied after the solidification and also after the electrolysis of anodes. This examination was carried out with optical microscope, scanning electron microscope and electrochemical measurements. All the nickel is remaining metallic in the copper matrix during the solidification and therefore nickel is dissolved in the electrolysis at all oxygen contents, when the nickel content is 0.25 wt-% or less in the anode. The practical .solidification mechanism of the anodes, when the nickel content exceeds 0.25 wt-%, proceeds by the crystallization of nickel oxides. In oxygen containing copper anodes nickel oxide is verified to crystallize together with antimony in certain conditions and to form a micaceous compound (3Cu2O?4NiO?Sb2O5), which may build up a very harmful floating slime in the electrolyte. Arsenic is strongly enriched along the phase boundaries in oxygen free copper anodes. An intermetallic compound Cu3As is formed when the amount of arsenic in the anode. exceeds 0.7 wt-%. This compound is more noble than the copper matrix. This means 'that a selective dissolution of copper-arsenic compounds takes place. The copper matrix dissolves more strongly than the grain boundaries. The solidification structures of oxygen free bismuth containing copper anodes show clearly the influence of bismuth. Thin bismuth films which are less .noble than the metallic copper matrix, are formed during the solid1ficatton process. As a result of this the?grain boundaries are dissolved faster than the copper matrix.

Jan 1, 1987

By Francis C. Furman

Microscopic evidence indicates that the high sinterability of certain commercial dolomites is tied to specific dolomite textural characteristics. This study encompasses detailed characterization of the unprocessed dolomite and sintering doloma results. The chemical and mineralogical compositions, insoluble residue, chemistry homogeneity, crystal size, primary carbonate texture, secondary dolomite texture, deformation structure, porosity type, porosity, and density of the raw dolomite were observed. These characteristics are compared with sintering trials of <74um powder-compacts samples in which holding times were varied. The evolution of the dolomite characteristics are reviewed and related to the final sintered doloma characteristics. The critical characteristics of a single-stage sintering brick dolomite are the following: 1) primary oolitic texture, 2) dolomite purity, 3) dolomite stoichiometry 4) minimal impurities, less than 1 weight {%} Fe2O3 Al2O3 and SiO2, 5) chemical homogeneity, 6) high density, 7) very low porosity, S) very coarse homogeneous crystallinity, 9) nonplanar dolomite texture, 10) abundant strain related slip microdeformation structures, 11) minimal subsequent alteration. Even with grinding to <74um the nonplanar dolomite texture and slip deformation still have a major effect on doloma sintered density. The three newly identified characteristics of single-stage sintered refractory brick dolomite are their primary oolitic texture, secondary nonplanar texture and abundance of stress related microdeformation structures. The primary oolitic texture reflects a homogeneous pure carbonate with respect to chemistry and crystal size secondary nonplanar texture produces crystals with large surface area to volume ratio. Stress related slip deformation moves CO, groups in to the same site of another CO, group but different orientation which is very unstable. All of these characteristics may facilitate the formation of higher density dolorna sinters.

Jan 1, 1995

By S. Saptharishi

Selenium, which is a 6A group element of the periodic table, constitutes about 7x10-5 % of the earth?s crust. Even though selenium is a dispersed element with respect to its commercial exploitation, it is capable of forming number of minerals and nearly forty selenium minerals have been identified, out of which the copper ores are the richest sources of selenium. Electronics industries and glass industries are the major consumers of selenium, while pharma grade selenium used as micronutrient for humans and animals. Various methods have been developed to recover selenium as a by-product from copper anode slime during copper refining. Selenium being amphoteric in nature, it is soluble in both acid and alkali. While acid roast process is widely used, considerable work has been carried out in Russia for recovering selenium through alkali route. This paper enlightens the process developed at Central Research and Development Laboratory, for recovering selenium from decopperised slime through alkali pressure leaching. The decopperised slime is pressure leached with alkali under oxidizing conditions by which almost all the selenium present is converted to alkali selenate, which is easily separable from the rest of the decopperised slime. The solution so obtained is neutralized, during which, most of the impurities are precipitated out. Then selenium is precipitated in its elemental form upon purging sulphur-di-oxide under warm acidic medium. The purity of the selenium obtained by this process is higher than that of the selenium from acid roast process. Moreover selenium can be crystallized as sodium selenate and it can be marketed. The acidic content of the effluent is recovered and it is recycled back to the process. The sodium content of the effluent is converted into high purity sodium sulphate, which is marketable. The hazardous waste containing arsenic is precipitated as its sulphide and can be disposed off as landfill.

Jan 1, 2006

By Zhao Guangwen, Wu Tan, Qiuzhan Tian, Duan Shuzhen

"A thorough study of lost currents in bipolar cells has been made for the development of the great potential of bipolar cells in energy saving. A proper equivalent circuit for bipolar cells has been found, and mathematic methods for computing lost currents at all kinds of polarization have been developed.At linear polarization, the lost currents can be computed by solving either a tridiagonal matrix or an ordinary differential equation of second order. This kind of values can be used to evaluate the minimal lost currents at given conditions. At other kinds of polarization, the lost currents can be computed by the same methods as above if the necessary experiments of measuring the cell voltages of every electrolytic compartment have been made. This kind of values can be used to design bipolar cells at practical conditions.Extensive experiments have been made to evaluate the effects of electrode polarization, emf of galvanic cell for the formation of electrolyzed substance, gaseous products, geometric dimensions of electrolytic cells, special resistance of electrolyte used, and the total and ordinal number of electrolytic compartments on lost currents. It is the first time to make such a systematic research by experiments in the world. Experiments showed that theoretic models were in good agreement with measured data. Experiments also showed that D.C. energy consumption of 0.45 kwh/kg of Pb for lead electrolysis from molten chlorides could be achieved in a cell with 7 bipolar electrodes.IntroductionIt is very promising to apply bipolar electrolytic cells to electrolysis of aluminum, magnesium, lead, zinc and perchlorinates for their great potential of energy saving for example, bipolar cells had been used in the production of magnesium and saved more than 30% of energy, being one of the three main techniques of energy saving in the production of titanium sponge (1)."

Jan 1, 1988

By R. J. Dippenaar, W. H. Van Niekerk

"An injectable lime-based desulphurization reagent for the treatment of liquid iron was developed. Firstly, selected lime based slags containing small quantities of CaF2 to increase fluidity, and Na20 to increase the basicity, have been evaluated on laboratory scale from a thermodynamic point of view. Subsequently, pilot plant and full scale industrial injection trials were conducted. It was found that lime-based slags, containing Na20 and CaF2, are able to desulphurize liquid iron efficiently. By the injection of a lime based reagent consisting of 60% lime, 25% soda ash and 15% fluorspar at a rate of 7 kg reagent/ton hot metal, the sulphur level in the metal (115kg) was reduced from 0,07% to 0,01 % within 5 minutes. The lime-based reagent developed in this study was successfully injected, both from a metallurgical and from a pneumatic point of view, on an industrial scale. The mathematical model utilised in this study, can be used successfully to predict the course and extent of desulphurization by lime-based slags. IntroductionMainly due to environmental difficulties encountered with pure soda ash, dry slag formation with CaC2 and high cost when Mg are used as desulphurizers, much incentive exists for the development of an inexpensive, environmentally friendlier desulphurization reagent. As a first step in the development of such a reagent, selected lime based slags containing small quantities of CaF2 to increase fluidity, and Na2O to increase the basicity, have been evaluated on laboratory scale from a thermodynamic point of view. This was followed by pilot plant injection experiments in which the kinetics of the relevant desulphurization reactions were evaluated. Finally, full scale industrial trials were conducted. All three phases of the investigation will be discussed with the major emphasis being placed on the kinetic study."

Jan 1, 1996

By Anjan Kumari, B. K. Soni, Manis Kumar Jha, A. Vidyadhar, Vinod Kumar

"In the present paper, recovery of valuable metals from the poly-cracked ash obtained by pyrolysis of discarded PCBs has been studied following physical beneficiation and a hydrometallurgical process alternate to smelting. The ash is subjected to comminution for the separation of metallic components from non-metallic fractions by scrubbing, tabling and froth flotation which enriched the metal in the concentrate -97% which was further screened to separate high and low metal concentrate. The finer fraction containing -12% metallic value was leached in acidic solution. Almost all (Cu, Pb, Fe, etc) were leached in 4M HN03 at 90°C in 75 min at a pulp density 100 g/L. The characterization of both ash and residues were made by XRD, EPMA, EDS, etc. to validate the experimental results. The metals from the leach liquor could be recovered/separated using solvent extraction techniques which can further be processed to get pure metal salts/ sheets.IntroductionPrinted circuit boards (PCBs) are an essential component of electrical and electronic equipments (EEEs) as it plays an important role during operation of these devices. The world market of PCBs has reached nearly $60 billion in 2012, with 1.7 percent real growth over 2011 [1]. The diverse technology-driven global market is expected to grow at an average annual rate of 5% by 2014 [2]. The waste EEEs are generated due to replacement of obsolete equipments with modem ones and thus their demand is also increasing rapidly [3]. The discarded e-wastes are being piled up as landfills which affect the environment and cause health threats to living organisms, if not disposed of properly. These e-wastes contain metals some of which are precious, few are hazardous and others as valuable."

Jan 1, 2014

By Y. Kumagai, F. A. Souza

"Electroless plating process has been used in many fields such as automobile and electronic industries. Solutions used in these processes must be disposed or treated. Commonly, in these solutions metal ions, organic materials and others chemicals are in very high concentration. It is very difficult to keep the environmental regulations for disposal of these materials, and the cost of the plating process becomes higher.The objective of this study was to investigate the recovery of components of those baths in order to decrease the cost of the plating process as well as to meet the environmental regulation.In this study the recovery metal ions, sulfate ions, phosphite ions and organic compounds were investigated. Organic compounds used in electroless plating solutions are the organic acids. In this work the solvent extraction of the most used organic acids included citric, lactic, succinic, tartaric and malic was studied. The solvent phase considered in these studies was ethyl acetate.About 95% of the metal ion was recovered by chemical plating onto mica powder. The hypophosphite remained is oxidized to phosphite and with the sulfate ion, both are recovered as calcium salts by selective precipitation in pH 7 and 2 respectively. Organic acids were recovered by solvent extraction using ethyl acetate as solvent phase and the best results were for lactic acid and succinic acid.Along with this study, was developed the analytical parameters to perform wastewater analysis by using Ion Chromatography, High Performance Liquid Chromatography (HPLC), Fourrier Transform Infrared Spectroscopy (FTIR). Ion chromatography was used to perform analysis of sulfate and phosphite ions in liquid matrix, HPLC was used to perform analysis of organic acids in liquid matrix and FTIR was used for characterization of the solids obtained in the recovery processes."

Jan 1, 1997

By Jose Hector Figueroa P.

Mexicana de Cananea, S.A de C.V. is a major copper producer mining a large deposit of the disseminated porphyry type considered one of the largest copper resources of the world with 2.7 billion tons of 0.60% copper for the mill plus 4.1 billion tons of averaging 0.26% copper for leaching. Mining of low grade sulfide leach ore, has been an important part of the overall production of the open pit mine which started in 1944. Before this time all the mining in Cananea was by underground methods. The leaching process in Cananea began on the 1920&apos;s with in situ operations in the underground mine and small dumps up to the 1950&apos;s. Large scale leaching operations began in 1960 and the copper solutions produced were treated in precipitation plants until 1,980 when the first SX/EW Plant was put in operation in Cananea. Leaching action is essentially ferric-bacterial, with no fiesh acid added to the leaching solutions. Traditionally, 5540% copper extraction is recovered fiom ROM, 70- 120 meter high leach dumps in 80 months of leaching. Cananea has successfully improved copper recoveries by implementing several actions that include: 1. Stripping of old dumps. 2. Leaching of old dumps through slotted casing. 3. Crushing conveying leach ore to minus 8 inch and stacking it in 30 meter lifts. As result of these actions, copper recovery has been increased&apos; to about 70% of total copper with actions 1 and 2 and up to 85% in half the time by crushing-conveying the leach ore, based on the same solubility index of the run-of-mine ore. This paper describes the above actions that were implemented to enhance the leaching recoveries from. sulfide leach dumps and the economics of such actions.

Jan 1, 1999

By Matthew D. Andriese, Jiann-Yang Hwang, Zhiwei Peng

"It has been demonstrated that metallic-bearing minerals are physically liberated from host rock when exposed to microwave (MW) energy. The metallic minerals are iron sulfides and spinel oxide minerals contained in peridotite rock. Experimental evidence has shown ore particles readily couple with MW energy at 2.45 GHz, 1000 W resulting in rapid heating. Thermal stresses are generated by highly absorbing metallic-bearing minerals resulting in cracking and embrittlement of ore particles that assists in crushing and grinding processes. The liberated metallic-bearing minerals are shown to report to coarser size fractions as a result of MW exposure.IntroductionComminution of ore material during beneficiation is a large energy expenditure for the mineral processing industry. Crushing and grinding operations alone consume 50-70% amount of energy used in mineral processing [1]. Size reduction becomes increasingly difficult with decreasing particle size making grinding the most energy-intensive step of comminution. The aim of comminution is to maximize liberation of economically valuable minerals from the host rock [2]. Overall, the less material that needs to be handled, then grinded, to create a useful product for hydro/pyro metallurgical processes will achieve the greatest reduction of energy.Much of the scientific interest for use of microwave (MW) energy in mineral processing has been for improved hydro/pyro metallurgical techniques [3-6]. Early authors have employed MW energy for improved grinding of ore particles but most conclude the energy savings do not justify the energy input [7-9]. The effectiveness of MW assisted grinding is dependent on the ore mineralogy and the absorptive properties of minerals contained within it. Ore containing magnetic minerals should prove successful with MW assisted breakage from highly absorptive properties."

Jan 1, 2012

By Guan-zhou Qiu, Shui-shi Liu, Yu-feng Guo, Tao Jiang

"The preparation of high-quality synthetic ruitle from electric furnace titanium slag was systematically investigated by activation roasting followed by acid leaching process. The results showed that impurities such as Ca and Mg in titanium slag can be effectively removed and TiO2 grade of the product was markedly improved by the process. High-quality synthetic rutile containing 88.54% TiO2, 0.42% (CaO+MgO) was obtained under the conditions that roasted with 7.5%(wt) H3PO4 at 1000 oC for 2h, followed by two-stage leaching in boiling dilute sulfuric acid for 2h. Mechanism studies showed that anosovite solid solution and silicate minerals were reacted with phosphoric acid in the roasting process. As a result, titanium components in titanium slag turned into rutile (TiO2) and impurities were transformed into acid-soluble phosphate and quartz.IntroductionWith the gradual depletion of natural rutile and the rapid development of titanium industry in China, the natural rutile reserves cannot satisfy the requirement for production of titanium pigment and titanium sponge. Ilmenite is, therefore, becoming main raw material for titanium industry. However, because of its low TiO2 grade, it generally requires preconcentration to titanium-rich material such as titanium slag or synthetic rutile [1-3].Ilmenite resources are extremely rich in Pan-xi area of China, which account for 90.54% of total ilmenite reserves in China [4]. The titanium slag produced by electric smelting of ilmenite concentrate has high contents of Ca and Mg, and is not suitable as a raw material for chloride process and titanium sponge production. Therefore, upgrading titanium slag to prepare raw material suitable for chloride process and titanium sponge production has important significance for the development of China's titanium industry."

Jan 1, 2011

By L. Lü, M. O. Lai

"Mechanical alloying is a dry, high energy ball milling process which has been used to synthesize metallic powders in the solid state. The present study use this technique to synthesize Cu-base shape memory alloy powder from commercial Cu70Zn30, Cu86Zn14 and element AI powders. The evolution and formation of shape memory alloy powder were monitored using X-ray diffraction and microscopy. It was observed that shape memory alloy powder started to form after 1.8 ks of mechanical alloying. ? phase was clearly detected after 3.6 ks of mechanical alloying. The intensity of X-ray diffraction of the y phase increased when mechanical alloying duration was prolonged indicating an increase in the amount of y phase. Microstructure observation showed different stages of formation of alloyed powders: welding between powders and formation of layered structure, deformation and fracturing of layered structure, and finally the formation of alloyed powders.IntroductionMechanical alloying (MA) is a process used for producing powders with controlled and extremely fine microstructure. It was original developed in 1966 (1) to produce aNi-based superalloy combining oxide dispersion strengthening with gamma prime precipitation hardening. In recent years this technique has been used in producing a wide range of materials including intermetallic compounds (2, 3), amorphous materials (4-6) and other materials (7-9). In MA, a blend of powders is subjected to highly energetic compressive collision. The powder panicles are welded and fractured during ball milling. Therefore, it is essential that at least one of powders should be ductile to act as combiner. It has however been found that brittle components without soft element can also be mechanically alloyed (10), even ceramic powders (11).The present work aims to study the mechanism of formation of shape memory alloy powder during MA."

Jan 1, 1994

By K. Murayama, M. Kawakami, T. Takenaka, S. Yokoyama

"Cokes play an important role of spacer in blast furnace. However, they degenerate during Boudouard reaction. Blast furnace cokes are reacted with pure C02 at I 072 to 1673 K. Reaction rate was obtained by the weight change of spherical specimen. The specimen after reaction was examined by microscopic observation. The reaction rate increased with temperature and was expressed by two Arrhenius type lines. The activation energy was 126 KJ/mol at higher temperature than 13 73 K and 202 KJ/mol at lower temperature range. At the higher temperature range, the reaction proceeded from the surface leaving unreacted core, whereas homogeneously whole inside at lower temperature. The porosity increased from the center to surface at higher temperature, whereas it was almost constant at lower temperature.IntroductionThe cokes have the function of fuel, reductant and spacer to keep gas and liquid flow in the blast furnace. Thus, the reaction mechanism of coke with several gas and the strength after the reaction should be important factor to control the blast furnace operation. The reaction mechanism of coke with C02 has been studied extensively. The rate equations were derived by Gadsby[ I], Ergun[2] and Turkdogan and Vinters[3]. They were compared and discussed by Kobayashi and Omori [ 4]. Effect of crystallization degree on the reaction rate was examined by Kashiwaya and Ishii[5]. Catalytic enhancement effect of ash componets have been clarified by Kashiwaya et. al. [6]. Although degradation of coke in blast furnace has been examined recently[7], however, the degradation of coke after the reaction with C02 has not been well clarified yet. In the present work, the metallurgical coke specimen was heated in N2 and C02 and the reaction mechanism and degradation behavior after the reaction was investigated."

Jan 1, 2000

By Hongbo Zhu, Kun Yang, Jingyan Jia, Jinhui Peng, Libo Zhang, Yi Xia

"Titanium dioxide is broadly considered as the most potential useful photocatalytic material. In this work, titanium dioxide was synthetized by microwave solid-state method and characterized by thermogravimetry-differential scanning calorimetry (TG-DSC), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The result demonstrates that through microwave solid-state synthesis, we can obtain uniform size and anatase TiO2 photocatalyst, with the precursor being Ti(C2O4)2·2H2O. And its degradation kinetic parameter of MO can reach to 0.21232.IntroductionSince Fujishima and Honda found the photovoltaic property of titanium dioxide TiO2 [l], it has been widely used in the field of pollutant degradation, virus killer and environment protection [2-5]. Compared to other semiconductors, TiO2 has the advantage of low toxicity/cost, chemical stability, excellent photocatalytic activity, and long lifetime of electron/hole pairs, thus it is considered to be a most potential useful photocatalyst material [ 6]. Solid-state synthesis of oxide nanoparticle is a new method developed in recent years, which not only overcomes the shortcomings of easily aggregation existing in traditional hydrometallurgical process, but also fully demonstrates the unique technologic advantages of without solvents, high yield, easy control, less environmental pollution in solid-state reaction [7-11]. Researches show that the new method of microwave synthesis shows a lot of advantages such as fast reaction rate, efficient, high purity of product, uniform morphology, energy-efficient, and nonpolluting [12-15].In this work, we associated microwave heating and solid-state synthesis to prepare TiO2 photocatalyst material. Its photocatalytic activity was studied in the degradation of MO queous solution. Meanwhile, the formation process as well as the crystal structure and morphology of the synthesized powders were characterized by means of chermogravimetrydifferential scanning calorimetry (TG-DSC), X-ray diffractometry (XRD) and scanning electron microscopy (SEM) techniques."

Jan 1, 2014

By Kazue Moriya

At the 1980 TMS-AIME world symposium, Dr. Davey mentioned that the traditional lead blast furnace is now being challenged by direct smelting processes. In the copper smelting field both the blast furnace and reverberatory furnace are also disappearing in favour of direct smelting processes such as Outokumpu flash smelting, Mitsubishi continuous smelting, Noranda furnace, Inco furnace and so on. Those new processes all have the following in common: (1) High degree of mechanization (2) Metallurgical reactions carried out in closed vessels (3) Application of oxygen and/or oxygen enriched air (4) Minimization of handling materials and gaseous volume (5) Minimum energy requirements (6) Removal of workers from near the furnace (7) Reduction of emissions of harmful gas to meet environmental regulations. (8) Improvement to the work place environment to avoid occupational hygiene hazards. Direct and continuous smelting of powdered concentrate in one vessel was a romance of the metallurgist since early times. However as mentioned above, in the copper field this objective is being achieved in practice. The industry however can&apos;t deny that the serious and severe regulation of environmental pollution in every country was the prime motive for the modernization of smelters. In early days, to meet regulations, it was anticipated that many economic difficulties such as higher capital and energy costs and extravagant use of resources and waste disposal would be the result. "Turn a misfortune into a blessing" is an old saying which reveals the current thinking and reacent developments in the nonferrous industries. In the last ten years in the lead smelting field, about two decades later than copper, commercial scale smelting using new furnance technology has started. The KIVCET process and QSL process, which is flash smelting and bath smelting respectively, are becoming major competitors. They will be sure to upgrade their processes to remain economically and environmentally viable in the comming decade.

Jan 1, 1990

By K. Morsi, S. K. Kassegne, A. El-Desouky, K. S. Moon

"Current Activated Tip-based Sintering (CATS) is a new process for the powder-based fabrication of macro, micro and possibly nano-scale features and shapes. This new and unique process enables selective sintering of powders by localizing electrically activated sintering conditions through a stationary or moving electrically conducting tip. We present preliminary experimental results on the effect of tip size in the CA TS process as well as the effect of initial powder particle size on the sintering behavior of nickel powder.IntroductionSpark Plasma Sintering (SPS) has been the center of attention of numerous researchers due its noticeable advantages over conventional sintering techniques such as rapid heating rates, lower sintering temperature and shorter holding times. Research on SPS has been applied on a wide variety of materials such as pure metals [ 1], ceramics [2], composites [3], nano-materials [ 4], biomaterials [ 5], shape memory alloys [ 6] and many other material systems. However, it has been mostly limited to bulk materials with simple shapes with a few exceptions ofresearch efforts where the effect of electric current was combined with metal forming processes such as spark plasma extrusion [7,8] and electric rolling of powders[9]. In this paper a novel process (Current-Activated Tip-Based Sintering (CATS)) is discussed where electric current and pressure are applied simultaneously through a small conducting tip (stationary or moving) over a conducting powder compact. This process has the potential advantages of sintering complex geometries with minimum energy requirements as unconventionally high current densities can be achieved due to the small contact area between the tip and the powder compact. Furthermore, by controlling the tip size, it can be possible to sinter features on the macro-, micro- and even nanoscales."

Jan 1, 2011

By Wenjie Zhu

Hexavalent chromium is a widespread environmental contaminant. An Achromobacter sp. strain nominated Ch1 can reduce soluble and toxic chromate to insoluble and non toxic Cr(III) in aerobic cultures, and no Cr(VI) decrease was observed in anaerobic cultures. In contrast with other Cr(VI) reducing microorganisms, Ch1 showed higher Cr(VI) reduction at high pH. Reduction performed under alkaline conditions at pH 7 to 11, and the optimal pH was 10. During the reduction, pH decrease was observed may caused by production of acidic metabolic byproducts from aerobic respiration. In the present study, the ability of Achromobacter sp. Ch1 to reduce Cr(VI) during growth was evaluated with lactate as an electron donor. In NB medium, Ch1 reduced 100% of 24mM of Cr(VI) in 35h, but only 73% of 30mM of Cr(VI) after 48h of inoculation. Reduction was inhibited by metal ions like Ag+, Cu2+, Zn2+, slightly inhibited by Mn2+, and not affected by Mg2+. Results revealed that reduction rate of Cr(VI) also increased with the increasing of concentrations of lactate, and complete reduction was achieved at the concentrations above 40 mM. HPLC analysis demonstrated Cr(VI) reduction was associated with the consumption of lactate. There was a large quantity of dark blue sediment generated in the culture during Cr(VI) reduction by Ch1. Energy dispersive X-ray (EDX) analysis showed that the major element composed the formed sediment was chromium presented as Cr(OH)3 precipitate. The features characterizing Cr(VI) reduction by Achromobacter sp. Ch1 are high Cr(VI) concentrations and high pH.

Jan 1, 2006

By Alice Barreto Bevitori, Felipe Perissé Duarte Lopes, Denise Cristina Oliveira Nascimento, Sergio Neves Monteiro, Isabela Leão Amaral da Silva

"The piassava fiber is one of the most rigid natural lignocellulosic fibers, which has since the last decade been investigated as possible reinforcement for polymeric composites. In the present work, the tensile properties of polyester composites reinforced with piassava fibers with thinner diameters were investigated. Composites with volume fractions up to 30% of continuous and aligned piassava fibers were tensile tested at room temperature to evaluate the ultimate strength, elastic modulus and total strain. For each volume fraction, individually separated fibers with the smaller diameters were tested. The results indicated that the tensile properties tend to improve with increasing volume fraction of the thinner piassava fibers. The role played by the fiber/matrix interaction was analyzed by scanning electron microscopy.IntroductionA significant change in the transportation sectors mainly the aerospace and automotive, occurred last century with the introduction of stronger and lighter materials. The most relevant example was the polymer composite reinforced with synthetic fiber. They are nowadays replacing conventional materials such as the aluminum alloys in airplane body owing to superior specific strength. in recent years, however, environmental problems in a global scale are imposing a reversion in the use of synthetic fiber specially the glass fiber. In spite of its higher specific strength, this fiber and its polymer composites can neither be recycled nor incinerated in a thermal plant to generate electricity [1]. Moreover, the fabrication, processing and transportation of a glass fiber composite are associated with C02emission, the major responsible for global warming [2].A possible substitute for glass fiber without the above-mentioned environmental problems, could be a natural fiber. In fact, natural fibers obtained from cellulose-rich plants, also called lignocellulosic fiber, are already being used in several engineering fields, particularly the automobile industry [3-6]. Figure 1 illustrates an automobile and its many components made of lignocellulosic fiber composite [7]."

Jan 1, 2011

By Gopalakrishna B. Prabhu, David L. Bourell

"Three mol% Yttria-Stabilized Tetragonal Zirconia (YSTZ) was prepared by a sol-gel synthesis technique using zirconium tetrachloride and hydrated yttrium chloride precursors. After drying and annealing at 823K, the particle size was in the range 10 to 20 nm. The zirconia powder was sintered using a uniaxial hot press at an applied stress of 20 to 40 MPa. One hour, isothermal sintering was performed in air after initial heating at 50K/min. Theoretical density was obtained at densification temperatures above 1498K. After sintering, grain coarsening characteristics were studied using constant heating rate anneals followed by quenching, based on a model for grain coarsening in a linear heating rate cycle. The microstructural change was studied using SEM and TEM and the phases were determined using x-ray diffraction.IntroductionThe ability to sinter nanocrystalline materials to full density several hundred degrees below the normal sintering temperatures is one reason for their current interest. [1-5] Yttria Stabilized Tetragonal Zirconia (YSTZ) of grain size of about 300 nm has exhibited superplasticity, with elongations as large as 800%.[6-7] Fine grain size is critical for superplasticity. Retention of the fine grain size during sintering of nanocrystalline powder is important if a material is to exhibit superplasticity or to exhibit physical or mechanical properties associated with the ultra fine structure. This paper investigates the sintering behavior and the grain coarsening characteristics ofnanocrystalline YSTZ.Techniques for synthesizing nanocrystalline materials have been studied in great detail earlier. [8-12] The techniques used to synthesize nanocrystalline zirconia include alkoxide synthesis [9], the chloride method [11], the peroxide method [13] and the acetone-toluene method. [13] In this paper the method used in the synthesis of zirconia is the chloride technique. With this precipitation technique, either zirconium chloride or oxychloride and a corresponding yttrium salt or even pure yttria are used."

Jan 1, 1994

By Metehan Erdogan, Ishak Karakaya, Fuat Erden

"Mg-Ni system draws attention due to the promising hydrogen storage properties of Mg2Ni. The proposed method involves the use of NiO and MgCl2 in an electrochemical cell to from Mg-Ni intermetallics directly. The electrodeoxidation of NiO was followed by combination of Mg and Ni in molten salt electrolytes. The products were characterized by XRD analysis and SEM examinations. The quantitative results from Rigaku supported by Rietveld Refinement method conducted by Maud showed that more than 50 percent of the input Ni was converted to Mg-Ni intermetallics.INTRODUCTIONIt is well known that fossil fuels are the most common energy producing materials throughout the last century although, they are not renewable and their usage cause critical environmental problems [1, 2]. Hydrogen, on the other hand, is known as a clean, renewable energy carrier and instead of fossil fuels; usage of hydrogen for energy production will be the benefit of mankind. However, there are problems that hinder more common usage of hydrogen such as hydrogen storage [3]. Mg2Ni is known as Mg based hydrogen storage material with high hydrogen storage capacity [3-6]. Common Mg2Ni production methods are; mechanical alloying [8-11], vacuum induction melting [12, 13], vacuum arc melting [14], combustion synthesis [15], melt spinning [16], repetitive rolling [17] and isothermal evaporation casting [18] were also used. However, in all of these, pure Mg and Ni are required to be produced previously. Therefore, difficulties arise during handling, preparation and combination of Mg and Ni due to highly reactive nature of especially magnesium (i.e. oxidation of Mg) [11, 17, 19, 20]. Although hydrogen desorption dynamics can be significantly improved with usage of nanostructured Mg2Ni [7], it is difficult and it requires very long processing durations to produce nanostructured Mg2Ni by above processes."

Jan 1, 2014