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By Esperidiana A. B. Moura, Célio H. Wataya, Roberta A. Lima, Rene R. Oliveira

Biodegradable starch/copolyesters/silica nanocomposite films were prepared by melt extrusion, using a twin screw extruder machine and blown extrusion process. The influence of the silica nanoparticle addition on mechanical and thermal properties of nanocomposite films was investigated by tensile tests; X-rays diffraction (XRD), differential scanning calorimetry (DSC) and Scanning electron microscopy (SEM) analysis and the correlation between properties was discussed. The results showed that incorporation of 2 % (wt %) of SiO2 nanoparticle in the blend matrix of PBAT/Starch, resulted in a gain of mechanical properties of blend.

Jan 1, 2015

By Dai Yongnian

The methods of treating zinc crust and its development in the last hundred years are compared and reviewed. There are better effects from normal pressure metallurgy turned into vacuum metallurgy. The traditional methods dezinc only. But we must consider that delead on further step. From lab tests to industrial scale experiment are researched. The first step-dezinc, second-delead, crude ,metal of, zinc, lead and silver are produced, The flowsheet of treating zinc crust are simplified, material consumption reduced, work condition improved, environment protect mended. This method is pointed out that its application can be expanded.

Jan 1, 1992

By I. B. Scorzelli

The aim of this paper is to make a detailed mineralogical characterization of a typical brazilian xenotime and zircon from the Pitinga Mine using SEMIEDS techniques, On the other hand, superficial pretreatments with HCI, HN03 and HF were done to evaluate the modifications on surface compositions and the morphology of the particles for flotation purposes, The studies showed that both xenotime and zircon present very small inclusions of thorite; zircon is strongly metamictizated given rise to malacon. The HF pretreatment deeply affected the morphology of the particles as well as the surface properties in relation to flotation.

Jan 1, 1996

By Rubén J. Sánchez Rodriguez, Carlos M. Fontes Vieira, Carlos E. Gomes Ribeiro

Ornamental compound stone are produced by industry for decades, however, few published studies describe these materials. Brazil has many deposits of stone wastes and a big potential to produce these materials. This work aims to evaluate the chemical resistance of ornamental compound stones produced with marble waste and unsaturated polyester. An adaptation of Annex H of ABNT NBR 13818:97 standard, with reagents commonly used in household products, was used. The results were compared with those obtained for natural stone used in composite production.

Jan 1, 2015

By Itsuki Uehara, Hiroyuki T. Takeshita, Tetsuo Sakai, Nobuhiro Kuriyama, Hideaki Tanaka

"AB5 type hydrogen storage alloys (A: rare earths, B: transition metals) are extensively applied to a negative electrode of a nickel metal hydride (Ni-MH) rechargeable battery for portable electric equipments, electric vehicles, hybrid vehicles etc. Performance of a hydrogen storage alloy electrode is affected by various factors, microstructure and surface composition of the alloy and structure of the electrode as well as composition of the alloy. Control of those factors enables us to commercialize the Ni-MH battery in various field.IntroductionA Nickel-metal hydride (Ni-MH) battery has been extensively developed because of (1) good compatibility with a nickel cadmium (Ni-Cd) battery, (2) high energy density (1.5-2 times higher per unit volume than a Ni-Cd battery) and high dischargeability, and (3) low environmental pollution. The charge/ discharge reactions can be written as [l, 2,3]:(+) Ni(OH)2+OH- = NiOOH+H2O+e· (E=+0.490V NHE),(-) l/6LaNi5+H2O+e-· = 1/6LaNi5H6+OH- (E=-0.828V NHE),where E° is a standard potential of an electrode vs. normal hydrogen electrode (NHE). Because of the above advantages of a Ni-MH battery, the battery have been widely used as a power source of portable computers, cellular phones, electric vehicles (Toyota ""LAV4L EV"", Honda ""EV Plus"" etc.) etc. Some hybride vehicles (Toyota ""Prius"" and Honda ""INSIGHT"") and fuel cell vhehicles (Toyota ""FCEV"") are power-assisted by a high-power Ni-MH battery. In 1999, the production of Ni-MH batteries reached 870 million cells in Japan. Most of commercialized NiMH batteries are incorporated with rare-earth-based AB5-type hydrogen storage alloy as a negative_ electrode. The production of rare-earth-based alloy is estimated to be approximately 8000 tons.The battery performances of the Ni-MH battery, for example, capacity, durability (cycle life), dischargeability (kinetics) and selfdischarge, ate closely related to the metal hydride· (MH) electrode, especially, the hydrogen storage alloy in the electrode. Substitution of alloy components, heat treatment, and surface treatment in order to change surface and bulk structure of hydrogen storage alloys have been examined by us and many reseachers in order to improve the performances of MH electrodes. This paper is a review of our and their efforts to improve performances of MH electrodes."

Jan 1, 2000

By Shekhar Bhansali, Shyam Aravamudhan

"This paper reports on the design and simulation results of a silicon bulk-micromachined diaphragm-type piezoresistive pressure sensor capable of operating linearly over a wide dynamic range (0-1000 meters of water). The piezoresistor elements of the sensor are arranged in a wheat stone bridge configuration to achieve a higher output response. Simulation results (output voltage and sensitivity analysis) obtained using coupled MemPZR-MemMech module of the CoventorWare2003 Finite Element tool are presented. The effect of diaphragm size, diaphragm thickness and thickness of the piezos on output sensitivity were analyzed and optimized to get a linear response over the wide dynamic range.IntroductionThe physical and biological processes in the ocean are critically influenced by ocean parameters (pressure, salinity and temperature). Thus there is a need to develop inexpensive and reliable sensors to continuously measure large volumes of sea-space over long time spans. A key component in any such system will be a pressure/depth sensor. This sensor is routinely employed in marine applications such as wave and tide gauges, tsunami detection, platform leveling etc. More significantly, pressure measurement is needed for depth determination. Depth sensors are vital for remote operated vehicles (ROVs), profiling instruments and towed arrays.Several techniques have been routinely used in the past to measure pressure in the marine environment [1-3]. In general, the pressure sensor design is based on a flexible membrane as the spring element for the sensing pressure [4]. The deflection of the membrane, induced by the applied pressure, is converted into an electrical output through a component that is sensitive to diaphragm deflection (capacitive coupling) or associated stresses (piezoresistors, strain gauges). The temperature compensated pressure measurement can be readily converted to depth using"

Jan 1, 2004

By I. Hilerio

Chromium Nitride (CrN) thin films were deposited on AISI steel 316 substrates by means of the reactive magnetron sputtering method. CrN films were produced under two different conditions. In the first one, the substrate was heated by a DC source. For the second coating a negative substrate bias voltage was applied. X ray diffraction, quantitative energy dispersion and scanning electron microscope were employed to characterize the two different phases, their chemical composition as well as their microstructure. In addition, a microhardness test was carried out. The results show that a better phase formation of CrN thin films was achieved when a heating source was present (first case). Both coatings presented homogeneous surface. Their compositions show differences even when the gases flowing are the same in composition. Regarding to the hardness test results, there can be found a higher value when using a heating source.

Jan 1, 2009

By Chao Du, Xiaohui Ning, Hongmin Zhu, Qiuyu Wang, Shuqiang Jiao

"TiCxOl-x solid solutions were synthesized by sintering a mixture of titanium carbide and titanium monoxide at 1600 °C. The corresponding structures and morphologies of the TiCxOl-x solid solutions were characterized by XRD and SEM. A series of tests has been performed on the electrochemical dissolution behavior of TiCxOl-x solid solutions in NaCl-KCl molten salt. The influences of synthesis time and electrokinetic parameters on the anodic dissolution behavior were also investigated. The results showed that TiCxOl-x solid solutions can dissolve as Tin+ into alkali chloride melt. Titanium ion species dissolved from TiCxOl-x solid solutions changes between Ti2+ and Ti3+ depending on the applied potential. The tail gas on the anode was monitored by a mass spectrometer. It was found the synthesis time significantly affects the components of the anodic gas.IntroductionTitanium and titanium alloys have been desired greatly because of their many uses. The critical factor that restricts the range of uses for Ti is its high cost of extraction. The primary titanium metal, sponge titanium, is still produced industrially worldwide by a process invented by Dr. Kroll in the 1940s[1] •Since the early 1970s, the research focus of the titanium industry has been directed towards developing a continuous process to produce high purity titanium at low cost. [2-10] Of the many alternative methods that have previously been investigated, the electrolytic process has been considered a promising method for titanium metallurgy [4-10]. Recently, several electrolysis and related methods such as the PFC-Cambridge process[11-15], calciothermic reduction[16-18], USTB [19,20] and MER[21] process were extensively investigated.The USTB process is a new approach where the pure titanium can be directly obtained by the electrolysis with an anode of titanium oxycarbide in molten salts[19, 20]. The titanium oxycarbide was produced by carbothermal reduction of titanium dioxide under vacuum at a temperature"

Jan 1, 2011

By Yuanbo Zhang, Zhixiong You, FENG ZHOU, Guanghui Li, Zhengwei Yu, Zhiwei Peng

Reduction disintegration of sinter significantly affects the coke consumption and productivity of blast furnace smelting. As we know, the reduction disintegration index (RDI+3.15) of sinter obtained from titanomagnetite concentrate is relatively worse than those from ordinary iron ores. In this study, the effect of sintering parameters, mainly involving coke breeze dosage and basicity on sintering indexes was investigated using titanomagnetite concentrate as raw material in an experimental-scale pot. Subsequently, RDI+3.15 of the sinter was detected according to the Chinese standard of GB/T13242-91. The results show that RDI+3.15 rises with the increase of coke breeze dosage, while it decreases with increasing basicity from 0.5 to 2.0 and then increases in the basicity range of 2.0-3.0. Finally, the microstructure of sinter before and after reduction was studied. And the mechanism of reduction disintegration was preliminary revealed by analyzing the morphologies and distributions of minerals in the sinter.

Jan 1, 2015

By Nobuhiro Shinihara, Makio Naito, Keizo Uematsu, Tadashi Horta, Hiroya Abe, Masataro Okumiya

"A significant variation of strength was noted in silicon nitride ceramics made through the powder compaction processing with minor processing changes. The relevance of the fracture strength to the microstructure was examined in these ceramics. In the examination of microstructure, the ceramics were made into thinned specimens, and their internal structures were observed with an optical microscope in the transmission mode. This technique can distinguish a difference in microstructure associated with the minor processing changes. The strength of all ceramics examined in this experiment was qualitatively correlated with the -pore size distribution in the specimens. Clearly, the elimination of these detrimental defects will enhance the reliability of ceramics.IntroductionIn ceramics made through powder processing, a variation of properties is often encountered [l ,2]. This brings a major problem on producing reliable and cost-effective ceramics. The variation is often ascribed to the changes in the characteristics of defects. However, there is no clear evidence f\)r this explanation due to the lack of an adequate tool for identifying the defects determining the properties. Details of the origin of the variation have still been poorly understood.A new technique is very promising for clarifying the origin of the variation [3,4]. This has very high potential in detecting minor differences in structure for .engineering ceramics. With this technique, ceramics are made transparent with its thinning down to about 50 µ m and their internal structures are observed with various types of optical microscopes in the transmission mode. The characteristics of the defects determined through this approach were found to be directly related to the strength of the ceramics [4-6].The objective of this study is to clarify the ongm of fracture strength of silicon nitride ceramics. This material is representative of high performance ceramics, and the origin is of great practical interest. For this study, silicon nitride ceramics with minor changes in processing condition were prepared. Specific feature focused in this study is the difference of large pore structure determined with the new technique and its relevance to the strength of the silicon nitride ceramics."

Jan 1, 2000

By Zhihong Liu

In recent years, the removal of arsenic from different types of high arsenic containing materials produced in nonferrous metallurgical processes have been experimentally studied in the complex materials processing research group from Central South University. These materials include arsenic and antimony bearing flue dust, arsenic sulfide residue and arsenate bearing flue dust. The separation of arsenic from other valuable metals was carried out hydrometallurgically; for each type of arsenic bearing material, different processes have been employed individually to remove the arsenic effectively. In this paper, the flowsheets and typical experimental results have been summarized.

By Tengfei Qi, Liqiang Fan, Huiqing Tang

A new method to process the oolitic high phosphorus iron ore for phosphorus removal has been proposed in this research. It is an integration of direct reduction and melting separation with carbon-containing pellets prepared using biomass char. Experiments of direct reduction were preceded using a tubular furnace and three parameters were investigated and they were reduction temperature, biomass char adding ratio(molar ratio of carbon to oxygen） and atmosphere. Results show that the optimum condition is of reduction temperature is 1373 K, biomass adding ratio 0.9, PCO2/PCO 1.0 and reduction time 15~25 min. Under this condition, the reduced briquettes with a metallization of 75.0~80.0 % and a residual carbon content of 0.69~0.11 wt% could be obtained. Subsequent melting separation experiments were conducted using a Si-Mo high temperature furnace. Results show metal with phosphorus content of about 0.4 mass% could be obtained from the reduced sample.

Jan 1, 2015

By Motohiro Horiguchi, Kazuo Ichii, Toshio Oishi

"As a fundamental study to prepare copper-based alloys with rare earths (RE: La, Gd, Nd, Ce and Y) without any inclusions, the solubility of rare earth in liquid copper was experimentally determined. Liquid copper alloys were equilibrated with carbon and rare earth carbide in a graphite crucible in an argon atmosphere at 1523-1873 K.Solubilities of rare earth in liquid copper were determined by approaching the equilibrium values from both the lower and the ·higher concentrations than those expected· in the preliminary experiments. They were expressed as a function of temperature. Carbon in Cu-RE alloy was also analyzed and thermodynamically discussed.IntroductionOver the past several years, the demand for highly conductive and high strength copper-based alloys, such as Cu-Cr, Cu-Zr and Cu-Cr-Zr for use in electronic materials has increased.1 -7 These alloying elements are very reactive and easily oxidized to form oxide inclusions during melting. To avoid the oxide inclusions, it may be effective to utilize the strong reducing power of carbon in conditions under which no carbides form.In this study, to provide fundamental data for producing Cu-RE( rare earth) alloys without any inclusions, the solubility of rare earth in liquid copper in equilibrium with .carbon .was determined and discussed on the basis of the experimental results and the thermodynamic data.ExperimentalSample preparation for equilibrium experimentsOxygen-free copper (99.99%), lanthanum (99.9%), gadolinium (99.9%), neodymium (99.9%), cerium (99.9%) and yttrium (99.9%), and their oxides were used as starting materials.Each rare earth carbide was prepared by mixing rare earth oxide with carbon, which is a little more than the stoichiometric composition, pressing it into a tablet form and sintering at about 2000.K for 20 ks in a vacuum furnace using a graphite crucible. Powder X-ray analysis showed that only the carbon and rare earth carbide (REC2) was present in each sample.Cu-RE mother alloys (5-20 mass % RE) were prepared beforehand by mixing metallic rare earth with oxygen-free copper, and melting in an electric arc furnace."

Jan 1, 2000

By M. M. Swan

A stratiform gold occurrence of Precambrian age located 20 miles southeast of Prescott, Arizona, within the Agua Fria Mining District, displays chemical, mineralogical, structural and lithological patterns indicative of a distal, exhalative volcanogenic environment. Metavolcanic and metasedimentary rocks of the Proterozoic Yavapai Series (1775-1820 m.y.) host the mineralization and are'characterized by greenschist grade metamorphism, steeply-plunging penetrative folds and steeply-dipping schistosity. Mineralization is confined to a 100m thick stratigraphic section that is comprised of a series of thin auriferous massive sulfide beds and intercalated schist .containing disseminated sulfides. The mineralization extends more than 4km along strike. Coincident with, and largely confined to the mineralized strata, are anomalous amounts of As, Sb, Cu, Pb, Zn and Ag and associated silicification, sericitization and carbonatization. This exhalative mineralized system is interpreted to have been deposited in a paleo topographic low on the distal flank of a submarine rhyolite dome and to represent the final episode of a Precambrian volcanic cycle.

Jan 1, 1981

By Andriy Burbelko, Daniel Gurgul, Wojciech Kapturkiewicz, Marcin Gómy

"The mathematical model of the globular eutectic solidification in 2D was designed. The proposed model is based on the Cellular Automaton Finite Differences (CA-FD) calculation method. The model has been used for studies of the primary austenite and of globular eutectic grains growth during the ductile iron solidification in the thin wall casting. The model mentioned above takes into account, among other things, non-uniform temperature distribution in the casting wall cross-section, kinetics of the austenite and graphite grains nucleation, solute diffusion and non-equilibrium nature of the interphase boundary migration.Some aspects of stochastic nature of the solidification processes are taken into account. The results of the CA solidification modeling have been shown, that differences between cooling curves obtained in the same conditions of the casting solidification may be a result of the stochastic nature of the grain nucleation.The results of modeling were compared with the experimental microstructure. The model is well worked for thin walled ductile iron casting, for fast solidification process.IntroductionNodular graphite cast iron, also known as ductile iron (DI), has major applications in critical engineering parts due to its mechanical properties and castability. The mechanical and physical properties of this material depend on the shape and number of the graphite grains andmicrostructure of the metallic matrix.Solidification of DI was a subject of many computer modeling programs described in literature [ 1-5], in which the stationary conditions of carbon diffusion in austenite is pre-assumed. Recently, a tendency for production of thin-walled castings has been observed [ 6-8]. In this technology, the process of the fast solidification may be very far from equilibrium and steadystate conditions [9].The purpose of the present work is a two-dimension model development for simulation of the DI structure formation during the solidification in the condition of non steady-state temperature and diffusion fields in the thin-wall casting.Model of process The CA-FD is one of the known methods of the simulation ofmicrostructure formation during the solidification [ 10, 11]. In the CA microstructure modeling the outer grain shape is the result of the simulation and does not superimposed beforehand. The model development for a onephase microstructure evolution is a subject of the numerous researches [12 -23]. Model of the eutectic solidification of DI in the uniform temperature field and superimposed cooling rate is known [24]."

Jan 1, 2013

By Ricardo Melamed

Metallic mercury has been extensively used for gold recovery. Although the solubility and mobility of metallic mercury is low, this metal can undergo many transformations, leading to mercury contamination in humans. The complexity of Hg chemistry in the environment reflects its different possible oxidation states and species, with different physical-chemical properties. The interaction of Hg in the terrestrial system, as well as in the aquatic environment, is important to understand the mercury cycle. This paper reports data on the adsorption of Hg onto an Oxisol soil. Results show that the interaction of Hg(II) at the soil-solution interface depends strongly on ligand concentration in solution, which can affect Hg mobility. The presence of the chloride anion in solution increases the mobility of Hg(II) through the soil, due to a relative lower affmity of mercury chloride at the oxide surface. In the absence of chloride, Hg(II) form strong complexes with the surface, and its adsorption behaviour is similar to the adsorption of other hydrolizable cations.

Jan 1, 1996

By M. Krishna, Jayagopal Uchi1, Shanta Sastry, B. M. Satish

"A well-considered composite of ZA-27 reinforced with weight percentage 0, 2, 4, and 6% of alwninite particulate has been made by compocasting technique. The elastic properties of ZA- 27 /alwniniute particulate composite were determined by using U1M. The results showed that the modulus of elasticity and UTS of the composite gradually increases with increase in the wt.% of reinforcement. However, the overall ductility decreased monotonically with an increase in reinforcement. The results of these tests· as well as the predictions of several model~ for composite strengthening available in the literature were compared with experimental results. The data observed from Young's modulus by measurements studies were compared with theoretical results predicted by Eshelby model.IntroductionMetal matrix composites (MMCs) have received increasing attention in _the recent decades as engineering materials. The introduction of a ceramic reinforcement into a metal matrix produces a composite material resulting in an attractive combination of physical and mechanical properties that cannot be obtained with monolithic alloys. Particulate reinf9rced MMCs among the discontinuously reinforced MMCs have attracted quite a lot of attention both in the industrial sectors and the academic communities. There is an increasing need for knowledge about the processing techniques and mechanical behavior of particulate MMCs in view of their production getting enhanced and their commercial applications becoming wider [I]. Interest in particulate reinforced MMCs is mainly due to easy availability of particles and economical processing techniqu"

Jan 1, 2000

By D. P. Cook, Jr. Jones, J. W. Evans

"It is well understood that the flow of liquid metal in the mold region of the caster can have a notable effect on the overall solidification behavior in aluminum casting. Previously our group has characterized the flow in this region in a water model, using particle imaging velocimetry. The flow is significantly effected by the specifics of the metal delivery system, i.e. size, geometry, used during the cast. Recently, a time-averaged 3D numerical model of the nozzle, combo bag and sump region has been developed and its validity has been tested against experimental data. Cases were run for different sized combo bags as well as bags that have been blocked. The results show satisfactory agreement between the physical and mathematical models.IntroductionFluid flow in the head of an electromagnetic (EM) and direct chill (DC) ingots has been shown to effect many important operational parameters in casting such as superheat removal, macrosegregation, and hot cracking. In most cases, the momentum from the nozzle is diverted through a delivery system, termed a bag, before entering the mold region. The specific geometries of the bags vary widely from operator to operator suggesting that there is still some question as to the optimum design. Several studies [1-4] have been carried out to understand the influence of the bag design on the solidification behavior in aluminum casters. However, few studies have included numerical prediction with experimental verification. Unfortunately, many simulations performed today still do not accurately account for flow in such devices.Recently, a significant amount of research into the flow resulting from the metal delivery systems has been performed [5-8]. The thrust of this research has been characterizing the flow patterns by a measurement technique called particle imaging velocimetry. The data suggest that the method of delivering the liquid metal into the mold region has a significant effect on the nature of the flow. With a detailed set of quantitative data from a water model, a numerical model can be built and tested to ensure a proper description of the flow field. The computational model used in these simulations is designed to represent a laboratory scale model of a caster in which ""combo"" bags were simulated. Such bags are mostly of a densely woven glass fiber material with low permeability to aluminum. ""Windows"", of a more open weave, permit aluminum to flow from the bag, see Fig. I. Two different sized combo bags were modeled, each subject to two different outflow window configurations. Furthermore, experimental measurements [9] were used to validate the model results."

Jan 1, 1999

By T. Mutoh

Tellurium in raw slime has recently been recovered as copper telluride in Onahama Smelter & Refinery. The slime is decopperized with sulfuric acid solution in conventional leaching tanks. The pregnant leach solution containing 45 g/l of copper and 1 g/l of tellurium is introduced to a copper telluride recovering reactor. The tail solution from the reactor containing less than 20 mg/l of tellurium is recycled directly to circulation tanks of copper electrolysis. The impurities of the product copper telluride is kept below 1% without any purification.

Jan 1, 1990

By Henrique Kahn

The Anitapolis alkaline massif in southern Brazil underlies a sub circular area of 6 km2. Bore-hole data show a concentric rock distribution, with mafic rocks in the central part and felsic rocks in the border zone. The rocks are covered by talus and weathered material, 30 m thick on average, and very inhomogeneous in composition. Phosphate mineralization associated mainly with two levels of the weathering mantle and with fresh rocks. A preliminary ore-type classification was based on distribution of apatite, feldspar, vermiculite, biotite-phiogopite, calcite, pyroxene, amphibole and analcime, determined by semiquantitative diffraction method. Technological tests performed on eluvial ore samples from three adits resulted in a subdivision of ore-types based on the difference in behavior due to mineral characteristics during mineral pr

Jan 1, 1991