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By Marcos V. F. Fonseca, Djalma Souza, Luiz G. X. Borges, Sergio Monteiro, Caroline G. de Oliveira, Ygor M. de Moraes, Janine F. de Deus, Frederico M. Margem

Recently, the natural fibers have been studied as alternative reinforcement material to the use of synthetic fibers. Aiming to improve the properties of natural fibers composites, it is investigated the use of natural fibers fabrics, since they provide multidirectional reinforcement and enables the introduction of a larger fiber volume fraction. In this work, it was investigated the tensile behavior of the epoxy matrix composites reinforced with different volumefractions offabric made of Ramie, a highly resistant lignocellulosic fiber. The specimens were made by pressing the fabric with liquid resin to guarantee total impregnation, and then cutting the fabric in the mold format. Finally ,the fabric layers were placed into the mold with the liquid resin and catalyst. They were cured for 24 h and tested. The results revealed an increase in the tensile strength and almost no effect in the elastic modulus with the increase of fabric volume fraction.

Mar 1, 2017

A rotating-discelectrode system was used to evaluate the electrochemical behaviour of Eu(III) during its reduction in NaCl solutions. The solution pH and NaCl concentration have a great effect on the reduction kinetics. The thermodynamic modelling study also revealed that Eu(III) exists in various forms in NaCl solutions. At a low concentration of NaCl, the predominant species is the free Eu3+. Other Eu-chloro complexes become more predominant when the NaCl concentration increases.

Jan 1, 1992

By G. G. Krishna Murthy

Several experiments were conducted to determine the rates of heat transfer coefficients of CaO-SiO2-A1203-FeO slags at temperatures in the range 1623-1823 K The experimental technique involved measuring heating rates of a solid specimen, sub¬merged in slag phase, using a temperature probe made of Pt\ 10%Rh-Pt. Effect of %FeO (3-10%), %FeS (0.1-0.68%), %P205 (0.2-3.0%), %MgO(5-6%), and %MnO (0.96-3.84%) present in the slag on overall heat transfer coefficient, U, of slags was investigated. Simple first order heat balance equation in combination with experimental plots rising temperature of solid specimen versus time were employed to determine the values of U. The values of U determined in the present investigation were present in the range of 70-260 cal/Ks.m2. The value of U increased with increasing the slag temperature. The values of U were not effected by increased amounts of sulfur in the slag phase. The increased concentrations of MgO, FeO, MnO, and P205 in the slag phase decreased the values of U. On the other hand, the increased amounts of Fe2O3 in the slag phase increased the value of U. Comparison of the results, obtained using the slag bath stirred by argon injection, with those determined without any stirring indicated that both radiative and conductive heat transfer mechanisms are important even at high temperatures.

Jan 1, 1993

By M. X. Huang, Y. Z. Li

The titanium diboride (TiB2)-reinforced steel composite, designed for automotive applications, exhibits a combination of high isotropic Young’s modulus and low density as compared to existing advanced high strength steels (AHSS). The steel-based composite is produced by in situ precipitation of TiB2 particles during eutectic solidification followed by hot rolling, and its microstructure displays a homogeneous distribution of both large primary TiB2 and small eutectic TiB2 particles in the ferrite matrix. Instead of interfacial debonding, particle cracking is the primary mode of damage, revealing very high interfacial strength. To investigate the intrinsic interfacial strength, a hybrid method combining both nanoindentation and finite element analysis (FEA) was used. A micron-sized sample containing a single crystal TiB2 attached to the ferrite matrix was fabricated by focused iron beam (FIB), and was compressed using nanoindentation with a flat indentation tip. By combining the compression and FEA results, the interfacial strength was therefore determined.

Mar 1, 2017

By Lijun Lu, Honghui Fang

This article carried out the experimental study on using desulfurization ash in steel slag composite material. This was done by investigating the desulfurization ash content in formula one and formula two samples on the influence of setting time and strength of mortar. Through this study the following conclusions were reached for formula one: (1) a setting time of more than 10 hours is required, (2) a dosage of desulfurization ash of 1 ~ 2% is optimal, where flexural strength is reduced by 10% ~ 23% and compressive strength reduced by 5.7% ~ 16.4%. The conclusions of formula two were: (1) when the dosage of desulfurization ash is within 5%, the setting time is within 10 hours; (2) when the dosage of desulfurization ash is 1 ~ 2%, the flexural strength is increased by 5 ~ 7% and the compressive strength is reduced by 1 ~ 2%. The results show that the formula two is better.

Jan 1, 2015

By G. L. Pedroti

With the development of industrial processes and the consequent emergence of numerous products that quickly become necessities, industrial activity has acquired an essential character today. Although its importance is unquestionable, industrial activity is responsible for generating quite a large number of residues, with different shapes and characteristics. It has been observed, in particular the grits (Kraft process in the cellulose industry) and the residue from the processing of granite. And, given the importance of Portland cement as a building material, its vast employment and waste properties that resemble components of the clinker, it was decided to produce cementitious compounds from these industrial wastes. The residues were subjected to mineralogical, chemical, physical and morphological. And, the mixing ratio between the residues in the 70% and 30% grits residue granite was sintered at 1250 ° C furnaces to burn threshold of 6 hours forming new compounds observing tri-calcium aluminate and di-calcium silicate that are compounds found in portland cement.

Jan 1, 2015

By Huimin Lu, Liyuan Zhao, Zhijiang Gao

The aluminum matrix composite reinforced by graphene was successfully fabricated using high pressure torsion (HPT). With only 0.5wt% graphene, the grain size was reduced to 100nm while that of pure Al was about 500nm. The hardness of the composite increased from the center (64HV) to the edge (120HV) of the sample. Moreover, the tensile strength of this composite reached 197MPa, while that of pure Al was 157MPa. The enhancement in mechanical properties was induced by grain refinement, load transfer from the matrix to the reinforcement and dislocations piled up at the grain boundaries.

Jan 1, 2015

By C. W. Won

a-etchant solution is the waste material obtained during the etching by ammoniacal solution of printed circuits for PCs. This material contains a substantial amount of copper (13-14%) but is usually discarded after neutralization. In this work, copper recovery from such solutions by electrowinning or cementation using iron scrap was tested. For each method, the effects of temperature, solution pH, initial copper-ion concentration, and reaction time were investigated to obtain optimal conditions for copper recovery.

Jan 1, 1993

By K. A. Brunk

Newmont's research, operations, history and experience with pre-treatment of preg-robbing carbonaceous ores are described, with emphasis on the chemistry, physics and kinetics of chlorine treatment. Present operations, control strategy and projected changes are also described, including a summary of the adsorption of chlorine into pulps and off-gas scrubbing. Conditions of chlorination have been optimized by the use of Eh-pH diagrams of the gold-chlorine-water system, and have resulted in significant increases in gold recoveries and decreases in chlorine consumptions.

Jan 1, 1987

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 Yuan-bo Zhang, Gui-hong Han, Yan-fang Huang, Tao Jiang, Guang-hui Li

"Under isothermal conditions, the reduction behavior of oxidized pellets balled with bentonite was investigated with CO-CO2gas mixers in the temperature range from 900°C to 1100°C. The whole reduction of oxidized pellets was followed up by means of weight-loss technique. And the swelling index of pellets was examined by visualizing physical changes of pellet in a horizontal tube furnace. The results present that the reduction rate of oxidized pellets is increased with the increase of reduction temperature. While the swelling index is firstly increased and then decreased with the increase of reduction time and reduction extent, which can be ascribed to the disruptive stresses induced during the transformation of hematite to magnetite. The maximum swelling index is gradually increased with the increase of reduction temperature and CO content.IntroductionWith the rapidly development of iron and steel industry, direct reduction iron has been considered as one kind of high quality burdens in electric furnace steelmaking [1]. At present, ""Two-step"" coal-based direct reduction process, which employs oxidized pellets as raw materials, has been used in industrial production [2]. The reduction behavior of iron ore oxidized pellets has been becoming one of the most frequently studied topics in extractive metallurgy[3]. The heat and mass transfer in direct reduction processes results in a series of stepwise reduction reaction (hematite--magnetite--wustite--iron), accompany with the volumetric swelling of pellets[4]. A lot of literatures have been reported on the reduction model of ferrous oxides and swelling behavior of pellets. A. A. El-Geassy K, et.al [5-7] revealed that the reduction process was controlled by chemical reaction at early stage by employing pure Fe203 as raw materials and CO as reduction gas. Chen Y [8] made research on the reduction kinetics of porous oxidized pellets and obtained the rate constant and activation energy of at different reduction stage. In addition, the swelling and disintegration of iron ore pellets was affected by chemical composition of pellet and reducing parameters, which have been studied by numerous investigators [3,9, 1O]."

Jan 1, 2013

By Fumito Tanaka

The Mitsubishi process is the sole pyrometallurgical process for the continuous production of blister copper from copper concentrates and has been successfully operated around the world. The development of calcium ferrite slag (CaO-FeOx-Cu20), the so-called "C-slag", has enabled continuous converting from matte to blister copper in the commercial scale operations. Commercial interests in the slag led to many papers over the CaO-FeOx slag. However, CU2O- bearing slag has not been studied well due to experimental difficulties. The authors have quantified the thermodynamic properties ofthe CaO-FeOx-Cu2O system. The results have been utilized to analyze various issues related to the converting furnace, such as the magnetite precipitation from the slag or from blister copper and to develop better controlling criteria for the continuous converting operation.

Jan 1, 2003

By Xudong Liu, Ganghua Fu, Yufeng Guo, Wei Chen, Yujia Tan, Tao Jiang

Willemite is usually found in high-silicon oxide zinc ore and zinc metallurgical secondary resources but without effective extraction method yet. In this study, zinc was extracted from willemite by sodium salt roasting and ammonia-leaching process based on the idea of zinc phase reconstruction. The effects of Na2CO3 dosage, roasting temperature and roasting time on phase transformation and zinc leaching rate were studied, respectively. The results show that Zn2SiO4 was transformed into ZnO or Na2ZnSiO4 during roasting process. After roasting at 800 °C for 2.5 h at ratio of n(Na2CO3)/n(Zn2SiO4) = 2.5:1, willemite was thoroughly transformed into ZnO. The zinc leaching rate of the roasted sample was 97.62% in NH4Cl–NH3–H2O leaching system, which increased by 91.57% compared with zinc leaching rate of 6.05% when willemite was directly leached in NH4Cl–NH3–H2O system.

Mar 1, 2017

By R. E. Brewer

Pilot scale flotation tests were conducted with a l?ft-diam column at the Barrick Resources (USA) Mercur mine, Tooele County, UT, to scavenge unleached (0.01 to 0.018 oz/st) gold values from the tailings of a carbon-in-leach (CIL) circuit. The optimal recovery was 35 pct of the unamenable-to-leaching gold, at a grade of 0.353 ounces of gold per short ton, using a mixture of dithiophosphate, xanthate, and diesel fuel as a collector. This was achieved by floating approximately 1.6 wt pet of the CIL tailings. The gold values are believed to be contained in arsenic-bearing minerals, attrited carbon, and carbonaceous material in the ore. Redox potentials were measured with a gold electrode during the conditioning stage prior to flotation. The correlation between flotation recovery and redox potential values could be used to control reagent additions. Treatment of a previously leached and weathered tailings material, averaging about 0.055 ounces of gold per short ton, was also investigated. The tailings were first water leached at approximately 60? C, and the water-leached tailings, containing approximately 0.03 ounces of gold per short ton, were then fed to the column flotation unit. The effects of pH' and sodium sulfide addition on gold flotation recovery and redox potentials were examined. Maximum gold flotation recovery, 36 pct, was achieved at pH 8,5 with a sodium sulfide addition of 0.18 Ib/st. Overall gold recovery by leaching and flotation was in the range of 70 to 80 pet.

Jan 1, 1989

By John J. Friel

Digital imaging systems are particularly useful in microscopy, because they make it possible to extract information not readily accessible by manual methods and to display that information clearly. Computer-aided imaging systems analyze, process and compare images, and of these, image analysis is most useful in materials science. Image analysis quantifies the microstructure by making measurements on the entire field or by measuring the size and shape of features individually. Even true surface area can be calculated. Modem image analyzers make thousands of measurements in seconds, leaving the investigator to interpret the data and relate them to process and material properties. Image processing, which may be necessary to prepare an image for analysis, includes everything from simple contrast transforms and kernel filters to complicated processes such as grain boundary reconstruction using artificial intelligence. An example of image comparison is point-by-point screening of X-ray maps of different elements to extract phases. In all of these operations, the computer makes a large number of measurements in seconds and returns information that could not be realistically obtained by manual methods.

Jan 1, 1992

By B. J. Beaudry

The effect of various levels of purity of the rare earth fluorides and the calcium reductant used to prepare rare earth metals were determined. Metals which have low melting points such as La, Ce, Pr and Nd are not purified by distillation or sublimation. Impurities in the reactants remain as contaminants in these metals. Gd, Tb, Y and Lu which have slightly higher vapor pressures at their melting points than the first four metals are usually distilled to remove the Ta or W impurity introduced by the crucible and are purified slightly with respect to 0 and N by distillation. Rare earth metals that have high vapor pressures such as Sc, Dy, Ho and Er can be purified with respect to 0, N, C, as well as Ta or W by sublimation. The most volatile rare earth metals Sm, Eu, Tm and Yb are readily purified by sublimation and are usually prepared by a reduction-distillation process directly from the oxide. The importance of each step of the processes in determining the final purity of the individual rare earth metals is discussed.

Jan 1, 1989

By Gaifeng Xue, Lei Zhang, Xia Liu, Lina Wang, Pu Liu, Benquan Fu

"Experiments were conducted to investigate the behavior of the integrated process with a three-dimensional electrode reactor combined with Fenton process for coking wastewater treatment. Effects of initial pH value, reaction time, H20 2 dosage, Fe2+ dosage on Total organic carbon (f OC) removal rate were investigated. The kinetics of degradation of TOC from coking wastewater by three-dimensional fluid bed electrode reactor combined with Fenton process was also studied. Experimental results shows that three-dimensional fluid bed electrode reactor combined with Fenton process had better synergic effect, average 17.4% TOC removal rate was improved within an hour. It was found that TOC degradation in coking wastewater followed a pseudo-first-order reaction kinetic model. The optimum degradation efficiencies of TOC were up to 60% as pH3.4, 3.5 mM ofFe2+ andl.2-1.8ml/L H20 2 in 90min reaction period. Furthermore, the integrated process showed a rapid reaction performance at a low temperature within a short reaction time and remained high efficiencies for TOC removal. Overall, the integrated process was proved feasible for coking wastewater treatment in practical applications.IntroductionCoking wastewater is generated from coal coking, coal gas purification, and by-product recovery processes of coking, which is composed of phenolic compounds, heterocyclic compounds, polycyclic aromatic hydrocarbons, ammonia, cyanide, polycyclic nitrogen-containing aromatics, acyclic compounds, etc. Most of these constituents are refractory, poor biodegradability, toxic and carcinogenic['-31. Currently, coking wastewater is usually treated by different forms of A/O biological nitrogen removal process as the primary treatment process, but the aforementioned processes are not efficient enough to meet the requirements from the National Discharge Standard in China (GB13456-1992). According to the continuous requirement on improving environmental protection for coking industry (revised 2008), increasing wastewater utilization ratio and reducing discharge of effluent in the coke industry has to be implemented for cleaner production and sustainable development. Therefore, advanced technologies need to be developed to treat coking wastewater and reutilize the product as industrial cooling water, which would be one of the best choices to achieve zero discharge of wastewater and reduce water consumption per ton of steel [4-51 . In this study, three-dimensional fluidized bed electrode reactor combined with Fenton process was adopted to advanced treatment of coking wastewater, and the effects of operating conditions, including H2O 2 dosage, Fe2+ dosage, initial pH, and reaction time on TOC removal rate, were investigated. Meantime, study of kinetics of reaction was estimated."

Jan 1, 2013

By Aïda Espinola

Decontamination of synthetic solutions containing cadmium ions using coconut fibers in natura was investigated in laboratory scale. Cadmium ions, a serious pollutant of water ways, where it is detrimental to the environment, may be absorbed by fish and mollusk used as food, which will, eventually, poison humans; these ions are usually present in minero-metallurgical and electroplating industrial effluents. Usually employed for the aqueous effluents treatment are chemical precipitation, adsorption and electrolytic processes. Precipitation is not effective for cadmium removal, because of the high KpS of the cadmium hydroxide, which requires high pH; only sulfide would be efficient in cases of very small amounts. Some vegetal refuses have shown to be practical for absorption processes of several metallic ions. We have applied coconut (Cocos nucifera) shells, which are extremely abundant over most of the extensive Brazilian coast, in the removal of cadmium: it has been verified, in our laboratory, that the surface of the fiber of this coconut is rich in chemical compounds which are active scavengers for Cd2+. For the optimization of the process, hydrosoluble components existing on the surface of the fiber, which may be deleterious, were previously washed out by water, and variables, such as the pH and the proportion of mass of fiber to volume of solution, were adjusted. As much as 99% of the initial contaminant metallic ion has been eliminated, resulting a solution to be discarded which contains ca. 0.1 ppm; this attends to the maximum impurity legally admitted by the environmental control agency of Rio de Janeiro, FEEMA, for cadmium ions in aqueous effluents to be disposed in rivers and in the Guanabara Bay area.

Jan 1, 1998

By Donna M. Noel

Bacterial strains have been cultivated from solids previously exposed to cyanide that will tolerate 300 ppm sodium cyanide under anaerobic conditions. In selected solid samples, these bacteria have been shown to reduce the level of cyanide from approximately 300 ppm to essentially zero in about 50 days under anaerobic conditions. Various media were investigated, and the nutrients providing maximal growth were ?established .. Degradation of cyanide in sterilized solids was determined for comparison with degradation obtained in bioactive solids. All experiments were conducted at ambient temperature and initial pH of approximately 10.5.

Jan 1, 1991

By M. Drozd

Multi-use pad operators require an efficient and economic method to destroy cyanide in their process residues so new material can be stored on the pad and leached. Operators of the dedicated or single-use pads require an effective cyanide destruction method for pad closure. Cyanide destruction can be accomplished by utilizing oxidants such as hydrogen peroxide or calcium hypochlorite, or by utilizing ferrous sulfate which sequesters the cyanide in strong acid dissociable complex. Ferrous sulfate can be the preferred method of cyanide destruction because it is a less costly chemical, reaction rates are almost immediate and unlike oxidants, it can penetrate the total depth of a pile without being destroyed by side reactions. Literature indicates that the (Fe(CN)6)-4 com~lex is produced slowly but it appears that complexes such as Fe(CN)4(H20)2-or Fe(CN)4(OH)2)-4, are formed quickly and should have no U.V. sensitifity, unlike (Fe(CN)6)-4. Stoichiometry of the testwork indicates that Fe«CN)4(OH)2)-4 complex may be the species formed. The usage of ferrous sulfate has the advantage of being able to bring ~ level down that divalent metal ions such as Cu++, Cd++, Hg++, Pb++ and Zn will form insoluble complexes and precipitate from solutions does not destroy weak acid dissolvable complexes and can leave a heavy metal problem behind after cyanide destruction.

Jan 1, 1990