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By Sergio N. Monteiro, Artur C. Pereira, Foluke S. de Assis

Jute fibers are among the lignocellulosic with great potential for use in polymer composites. In this work, polyester matrix composites incorporated jute fabric were investigated for their flexural behavior. Specimens with up to 30% in volume of jute fabric were bend-tested until rupture. The results showed an increase in both the composite mechanical strength, principally to a polyester composite reinforced with 30% in volume of jute fabric. A fractograph analysis by SEM disclosed a moderate adhesion mechanism between the jute fabric and the polyester matrix. This mechanism is apparently responsible for the improved performance of the composites.

Mar 1, 2018

By D. J. Wang

Based on the thermodynamic arid kinectic aspects, the vaccum distillation processes for the separation and recovery of metals from wastes are analyzed. As to the separation criteria, The separation coefficient and equilibrium composition relation between vapor phase and liquid phase are the bases of recovery of metals by vacuum distillation, The vaporization rates and condensation mechanisms are also discussed. Some experimental results which deal with metals-containing wastes are described and the performances of a new kind of horizontal vacuum furnace are introduced, which demonstrate that , vacuum distillation may be a prospective technique for circulation and regeneration of some non-ferrous metals from industrial wastes.

Jan 1, 1996

By Suzzann Nordwick

The metallurgical treatment of mercury-containing materials for precious or base metals recovery imposes many processing and environmental challenges. Mercury is usually present as elemental or cinnabar. Historically, mercury has been removed from mined ores pyrometallurgically by roasting, but hydrometallurgical methods have also been employed. For example, alkaline sodium sulfide solution acts as an universal solvent for most mercury compounds. While, most other metals are highly insoluble in this solution. This allows for a high degree of selective separation of mercury from other metals with the exception of tin, antimony and arsenic. Mercury leached with a solution of sodium hydroxide and sodium sulfide or sulfur can be re-covered by cementation or stabilized through sulfide precipitation. Hydrometallurgical technology for the pretreatment of mercury removal from gold, silver, and base metal ores using alkaline sulfide leaching will be discussed with a focus on alkaline sulfide leaching of mercury sulfide-containing materials.

Jan 1, 2003

By Mariana H. Staia

The present communication reports the results obtained by applying different concentration methods, at laboratory level, to the black sands from Estado Bolivar, Venezuela, with the aim of obtaining an adequate ilmenitic concentrate for the subsequent chlorination process. Sizing analysis was performed and plasma emission spectroscopy method was used to determine the chemical composition. It was found that from the two hydrogravimetric methods used, the Humphrey spirals is much more effective than Wilfley tables, leading to a 85% recovery. The most convenient particle size group for these concentration methods was the one corresponding to ASTM 40-140 mesh. When magnetic concentration was applied to the concentrate, obtained as a product from Humphrey spiral, a recovery of ilmenite more than 90% was obtained in the first step. It has been shown that the ore would respond to the separation techniques employed, giving individual minerals: ilmenite, zircon and silica as concentration products.

Jan 1, 1995

By Yongzhong Xiao, Tiejun Chun, Jian Pan, Zhen He, Deqing Zhu

"In this paper, the reduction kinetics of low grade hematite ore was calculated. Mineralogy shows that the ROM (run of mine) ore is of low grade hematite ore type, assaying 27.2 wt% Fetotal and with main valuable minerals of hematite. The reduction kinetics shows that the reduction reaction rates of pellets with additive and without additive are all controlled by diffusion through the product layer. The calculated apparent activation energy of pellets with 12 wt% complex additive is 8.55 KJ/mol, dropping 62.23% compared to that of pellets without additive.IntroductionWith the rapid development of iron and steel industry in China, there has been a soaring demand for iron ores in the past decade. The imports of iron ores have increased from 148 million ton in 2003 to 620 million ton in 2010[1]. Therefore, large quantities of low grade iron resources are necessary to utilize in China at the moment. During the past years, extensive research has been carried out on the low grade hematite ores [2-6], such as reverse floatation, gravity separation, high-gradient magnetic separation and direct reduction-magnetic separation. Direct reduction-magnetic separation is an innovation way to treat the low grade hematite [7]. However, the research of reduction kinetics of low grade hematite is few. Some research about the reduction kinetics of reducing iron oxides by CO was studied [8]. The results indicated that the apparent activation energy is 8.0-28 KJ/mol when the reducing reaction is controlled by internal diffusion. The apparent activation energy is 50-75 KJ/mol when the reducing reaction is controlled by chemical reaction. In this paper, the reduction kinetics of pellets was also been studied."

Jan 1, 2012

By Fernanda de Paula, Lázaro A. Rohen, Sérgio N. Monteiro, Rafael G. de Castro, Carlos Maurício. F. V, Maycon A. Gomes, Frederico M. Margem, Anna C. C. Neves

Synthetic fiber has been gradually replaced by natural fiber, such as lignocellulosic fiber. In comparison with synthetic fiber, natural fiber has shown economic and environmental advantages. The natural fiber presents interfacial characteristics with polymeric matrices that favor a high impact energy absorption by the composite structure. However, until now little has been evaluated about the hemp fiber incorporated in polymeric matrices. This study has the purpose of evaluate the impact resistance of this kind of epoxy matrix composite reinforced with different percentages of hemp fibers. The impact resistance has substantially increased the relative amount of hemp fiber incorporated as reinforcement in the composite. This performance was associated with the difficulty of rupture imposed by the fibers resulting from the interaction of hemp fiber / epoxy matrix that helps absorb the impact energy.

Jan 1, 2015

By Xuewei Lv

An intelligent recognition and quantification system for the micrographs iron ore sinter was developed in the current paper. The average distribution parameters in a gray histogram of minerals by a Gaussian gray distribution model were obtained. The feature curves of the gray histogram of two minerals were achieved by combining the two density functions. The feature indexes, such as the number and position of the peaks and the valleys of two minerals in different ratios, were quantified by differentiating the distribution functions. This algorithm is able to extract the feature of the minerals adequately and accurately for recognizing the composition and phases of the minerals intelligently.

Jan 1, 2009

By Fabio J. Esper, Wildor T. Hennies, Guillermo R. Martín-Cortés, Francisco R. Valenzuela-Díaz, Antonio J. Santana de Araujo, Maria G. Silva Valenzuela

Seeking to replace carbon-black as filler of rubber in the production of vulcanized goods, researchers from University of São Paulo have studied different materials types as minerals, vegetal or wastes agricultural and industry. Results of rubber composites filled with MA1 a waste of mineral treatment provided by Esper Industries are presented. MA1 was characterized through X-ray diffraction; Thermal analysis; Scanning Electronic Microscopy; and others laboratory methods. The composite and shaped masses were evaluated by these methods plus their mechanical properties such as tensile strength, elongation at break and hardness. Exceptional results were obtained in the mechanical properties evaluated, better than those obtained with the traditional carbon-black. Seeing the kind of material used as filler, it can conclude that the environmental benefit is present, as well as economic development, giving credibility to the use of these alternative material in replacement carbon black.

Jan 1, 2015

By Xiangru Chen, Qijie Zhai, Haicheng Li, Chao Yang, Zhang Wei

The Nb-rich phase generated by the addition of trace amounts of Nb(<0.1wt%) \ and the effects of different content of Nb on the morphology and distribution of graphite in ductile iron were studied in this paper. The results showed that when the content of niobium less than 0.1wt%, the two-dimensional morphology of Nb-rich phase existed in microalloyed ductile iron were mainly regular pattern such as square, triangle, polygon etc. Besides, Nb-rich phase in large size distributed in the matrix with a certain distance from graphite. With the increasing amount of niobium, the dispersion degree of graphite diameter, average diameter and roundness increased slightly, and the number of graphite decreased slightly.

Jan 1, 2015

By D. M. Fermino, C. G. Bastos Andrade, M. G. Fernandes, F. R. Valenzuela-Diaz

Treatments with high concentration solution of inorganic acid at temperatures under boiling point are a usual method for clay minerals structure modification. For many industrial uses bentonites must be cleared of impurities. In the present paper, a sample of Brazilian bentonite from Vitoria da Conquista, Bahia was modified by mild acid attack using hydrochloric acid under moderate conditions (90 °C, reaction times of 1, 6, 12, 18 and 24 h in close reactor, concentration of the aqueous solution of hydrochloric acid 1.5 M, acid solution/clay ratio of 1 g/10 mL). The attacked samples were characterized by CEC, XRF, SEM, EDS and Stereomicroscopy. The purpose of these attacks is to reduce the concentration of impurities with minimal damage in clay minerals structure. The modified bentonite presented good results and tends to be a good economic and environmental alternative to manufacturing products with high added value such as polymer/clay nanocomposites, cosmetics and medicines.

Mar 1, 2017

By Mingming Zhang, Udaya Bhaskar Kodukula, Marcelo Andrade

The physical and chemical properties of sinter feed are important factors that determine the productivity and quality of sinter product. In this study the feasibility of treating sinter feed by high pressure grinding rolls (HPGR) is investigated for selective cracks generation exploiting weak zones along grain boundaries of poor quality iron ores without generating much fines. The pre-treated sinter feed was characterized for size distribution, surface area, contact angle, and SEM analyses. The characterization results indicated that surface area of the pre-treated sinter feed sample increased about 20%. Pot-grate sintering tests results also indicated improvement on cold permeability, sintering yield and productivity, sinter Tumbler index, and low temperature degradation index (LTD) after HPGR pre-treatment.

Mar 1, 2018

By Noboru Masuko, Sachiko Ono

"The structure and composition of anodic films formed on aluminum in a borate solution have been investigated by using TEM and SIMS with respect to the effect of current density and electrolyte temperature. The film is composed of a boron-containing outer layer and a boron-free inner layer with disc-like crystals present at the interface. The thickness of the film formed at constant current density up to an identical voltage, decreases with increasing current density. The thickness increases remarkably with elevated temperature. The transport number of Al3+ estimated from the thickness ratio .of the cuter to the inner layers is 0.4 when the film is formed at the current density of 20 Am-2 at 60°C. It increases slightly with increasing current density and decreases significantly with increasing temperature. Content of boron in the outer layer increases 1.5 times when current density .increases 10 times. These changes in film structure and composition with electrolysis conditions must have a significant role in the determination of electric properties of anodic alumina films as a capacitor material.IntroductionThe growth of anodic alumina film in ·a neutral electrolyte proceeds at both film/electrolyte and film/substrate interfaces giving a duplex structure. The oxide layer formed at the former interface includes electrolyte anions while a-pure alumina layer is formed at the latter interface. The thickness ratios of each layer respectively represent transport numbers of Al3+ and 0 2 - (1). The film thickness and the incorporated anion content as well as transport numbers of both ions must affect the dielectric properties of the film as a capacitor material. However, the correlation between film structure and electrolytic conditions is not fully understood (2). For the further clarification of anodic film growth mechanism, more detailed characterization of anodic films in relation to electrolytic conditions is advantageous. In the present paper, therefore, the effect of current density and electrolyte temperature on the microstructure and composition of anodic barrier films formed in a neutral borate solution was studied. The films were characterized by direct observation using transmission electron microscopy (TEM) and depth profiles of constituent elements obtained by secondary ion mass spectroscopy (SIMS)."

Jan 1, 2000

By Naixiang Feng, Shaohu Tao, Zhihui Wang, Yuezhong Di

"A novel vacuum aluminothermic reduction lithium process was developed in present work which used lithium carbonate, alumina and calcium oxide as raw material. The process mainly contained three steps. The first step is that LiA102 clinker is prepared in ambient environment, then metal lithium is vacuum extracted from LiAl02 clinker with aluminum power as reducing agent, and the last step is that alumina is leached from the reduction residue with a mixture of sodium hydroxide and sodium carbonate. The results show that the lithium reduction ratio can be over 95% under the conditions of reduction temperature 1423K, reduction time 3h, and aluminum excess 20%. The main components of reduction residue are CaO· Al203 and 12Ca0·7Alz03. The alumina leaching rate of calcium aluminate in residue is over 80%. High-whiteness aluminum hydroxide can be obtained by carbonation precipitation of the reduction slag leaching solution.IntroductionWith a density about half of water, lithium is with the lowest density of all solids, mere 0.5 g/cm3 at 20 °C [l]. Lithium is widely used in aerospace, aviation, nuclear-generated power and electric battery industry. Nowadays, over 90 % of the world's primary lithium is produced by molten salt electrolysis [2-4]. But the development of molten salt electrolysis will be effected by some factors: cost, environment, and so on. Vacuum thermal reduction may be used extensively in future because of its low-energy consumption, high-purity and short-cycle."

Jan 1, 2013

By Shan He, Qiang Wang, Xuling Chen, Min Gan, Lishun Yuan, Xiaohui Fan

"The sintering properties of vanadium-titanium magnetite concentrate(VTC) was studied in this paper. Through the optimizing the sintering process of VTC, the suitable granulation moisture and coke proportion were determined. The sintering velocity decreased from 23.05 mm/min to 18.22 mm/min. With the increase of VTC proportion from 0 to 46%, the specific productivity and tumbler index were respectively decreased from 1.55 t/(m2·h) to 1.21 t/(m2·h), and 62.93% to 57.73%. The temperature of liquid phase formations of mixtures increased, the amount of liquid lowered, and the content and sharp of sintering mineral gradually changed with the increase of VTC ,these lead that sinter quality became worse.IntroductionIn recent years, the steel industry of China is developing rapidly. And the steel production was 627 million tons in 2010. At present, the resources of vanadium-titanium magnetite concentrate(VTC) was about 14.4% of the total national iron reserves of China[1]. VTC has been used as sintering material by Magang, Chenggang and Pangang. The amount of VTC in Pangang is maximum. However, there exist many problems in VTC sintering, which involve in high specific productivity, bad sintering tumbler strength and high energy consumption[2~5]. That’s why the proportion of VTC is limited in sintering.The high quality of iron ore resources is worse in China. Therefore, it’s necessary to study the properties of VTC sintering, and to find out the reason how the VTC ratio affect the sinter performance. Purpose and significance of the research is to get high-quality sinter with the proportion of VTC greatly raised."

Jan 1, 2012

By Takashi Nakamura

Dismantling and detachment of parts from e-scrap are essential and involve higher cost techniques in pretreatment processes for physical separation. New techniques are desired for effective recycling of minor rare metals, therefore, we are trying to develop new detachment processes such as a new break down process. The principal of this new process is an electrical disintegration by electric pulse. E-scrap is broken down by high voltage electric pulses in water. IC chips and LSI can be detached from printed circuit boards under proper conditions. Ta- capacitors are also broken down to plastic parts and Ta sinter with lead wire. This is very useful in terms of pretreatment for e-scrap recycling. Also in the case of metallurgical production, with its intrinsic potential of smelting, extraction, enrichment and separation methods, play an important role in the context of minor rare metals.

Jan 1, 2015

By Hans Jürgen Maier, Gregory Gerstein, Florian Nürnberger

Microstructural analysis to support the development of material models provides valuable information to design complex forming operations. Damage models such as e.g. by Gurson consider spherical voids only. However, investigations of bcc steels by scanning electron microscopy reveal that voids exhibit an ellipsoidal shape with progressing deformation. The material’s weakening in the Gurson model is taken into account by the void volume fraction. Therefore, a three-dimensional characterization of the void shape offers important data for modelling. Thus, information on the anisotropy of the process of void evolution and accordingly, about the anisotropy of the deformation process is provided. Application of the information regarding the void shape anisotropy within the Gurson model is discussed.

Jan 1, 2016

By Takaaki Ishikawa

The distribution equilibria of lead, zinc and copper between CaO-Si02-Ah03 melts and liquid copper were measured at 1623K under a controlled H2-C02 atmosphere. The distribution ratios were plotted against the oxygen partial pressure, and reasonable oxide forms dissolved in the melts were estimated from the slopes of the plots. The activity coefficients of zinc oxide (ZnO), lead oxide (PbO) and cuprous oxide (CuOQs) increased with increasing slag basicity, defined by Xcao /XSiO, The temperature dependence of the activity coefficients was also measured.

Jan 1, 2003

By Toshiaki Tsuru, Takeshi Ohgai, Hisaaki Fukushima, Shigeo Kobayashi, Tetsuya Akiyama

"Electrodeposition behavior of Zn-Cr alloys from the methanol baths was investigated. In the methanol baths of low Cr3+ concentration, Cr (III) compound was incorporated in the deposits and no lusfrous Zn-Cr alloys was deposited. However, Cr was existed as metallic state in the deposits obtained from the baths of higher Cr3+ concentration. With an increase in water content in the baths, the chemical state of Cr in the deposits changed from metallic to trivalent state. Under the condition that metallic Cr can be electrodeposited, Zn deposition was significantly polarized to the potential of Cr deposition.INTRODUCTIONAn attention has been paid to Zn-Cr alloy plated steel sheet because of its excellent properties for body panels of automobile and electrical appliances [1]-[4]. This plating process can be operated using the sulfate solutions containing Cr3+ ion [1] - [6].In decorative single Cr plating, on the other hand, many attempts have been made to electroplate Cr from trivalent electrolytes, which is motived by environmental deficiencies of the presently used hexavalent process [7]. [8]. However, it has been reported that in the aqueous solutions the behavior of the electroreduction of 0 3+ is atypical due to the complicated nature of the chemistry and electrochemistry of cr3+ species [9]-[11]. Even in Zn-Cr alloy plating, it is difficult to codeposit metallic Cr with Zn in simple sulfate electrolytes [l]-[4], [12]. Therefore, it can be expected that the electrodeposition behaviors of Zn-Cr alloys as well as Cr are significantly changed when the electrodeposition is conducted in non-aqueous plating solutions.In this study, the electrodeposition of Zn-Cr alloy was conducted from methanol solutions to clarify the electroreduction mechanism of Cr3·-Cr0 in the alloy deposition process."

Jan 1, 2000

By W. L. Cornell

Bulk sulfide concentrate produced from Missouri Pb ore concentrator tailings must be reground to liberate sulfide values for subsequent sepa-ration. Studies to determine grinding parameters for optimum liberation were carried out using optical microscopy coupled with image analysis. The major sulfide phases present in the ground mineral particulates are marca-site, pyrite, sphalerite, galena, chalcopyrite, siegenite. and bravoite. Results showed that the base metal minerals were liberated by grinding to 74 micrometers (200 mesh), but the siegenite and bravoite required grinding to 20 micrometers or less to achieve liberation. Both the experimental method and results are presented.

Jan 1, 1987

By R. Y. Wan, S. L. Chryssoulis

"Gold associations were established in a·biooxidized, chlorinated CIL residue assaying 0.02 oz Ault and in a biooxidized thiosulfate leach residue assaying 0.01 oz Au/t. A detailed mineralogical study involved: assays of screened fractions; light microscopy; ion probe microanalysis to quantify 'invisible' gold in sulfide minerals; proton probe microanalysis to detect and quantify preg-robbed gold. In the CIL residue, most of the gold is preg-robbed (71 %). In the thiosulfate leach residue, gold occurs mainly as submicroscopic disseminations in microcrystalline quartz (chert). In both residues, the 'invisible' gold in pyrite accounts for a minor fraction of the gold assay. Quantitative determination of the gold occurrence in the two residue samples established conclusively that gold adsorption on carbonaceous matter in the thiosulfate leach is of minor importance.Acknowledgement: published with permission of Newmont Gold Company."

Jan 1, 1997