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By Shadia J. Ikhmayies

In this work the equilibrium temperature-composition phase diagrams of the Si-O2 system were calculated using Thermo-Calc software in the temperature range 500–3000 K. Constituents of stable phases were obtained, and the amounts of certain phases where investigated with the variations in the composition of oxygen and temperature. It is found that quartz with silicon represent a stable phase in the temperature range 500–1150 K, while tridymite with silicon represent a stable phase in the temperature range 1150–1700 K. A liquid phase is found besides tridymite in the temperature range 1700–1750 K, and a stable phase of cristobalite with liquid appears in the temperature range 1750–2000. The maximum amounts of quartz, tridymite, and cristobalite are found at oxygen mole percent of 67.7%.

Mar 1, 2017

By Vineet Kumar Yadav, Akshay Dvivedi, Pradeep Kumar

Near-dry electric discharge machining (EDM) is a process variant of EDM, which uses two-phase flow of liquid and gas as dielectric medium. This article reports the results of an investigation pertaining to the drilling of holes on high speed steel (T2 grade) by a rotary tool near-dry EDM. The One-Factor-At-a-Time (OFAT) approach was used for experimentation. The effects of process parameters, viz. tool rotation speed, peak current, pulse duration, gas pressure and liquid flow rate on material removal rate (MRR) and overcut were investigated. The dielectric medium used was a mixture of glycerin-air. The experimental results reveal that rotation of the tool electrode along with high pressure of two-phase dielectric medium contribute in an effective flushing of inter electrode gap (IEG). Further, in rotary tool near-dry EDM process, higher values of current can be used. This improves process economics in terms of MRR. The MRR measured with rotary tool near-dry EDM was three to four times higher in comparison with conventional EDM. Additionally, appreciable surface quality was achieved.

Mar 1, 2017

By S. Jolivet, A. Klöfverskjöld, P. Latostenmaa, B. P. Wilson, M. Lundström, P. Halli

Doré slag is secondary product of copper electrore fining anode slime treatment. The slag consists mainly of different slag formers, such as borax and silica based minerals together with soda and traces of sealing materials. However, Doré slag also contains metals present in the anode slime, such as Ag, Cu, Bi, Sb and Te. At some plants, slag cleaning has been conducted utilizing conventional grinding and flotation circuits in order to enrich the content of precious metals in the slag [1]. Nevertheless, the routine consideration of the slag as a secondary raw material has so far not been adopted on an industrial scale. The current study presents the preliminary results of the nitric acid and chloride leaching of antimony from Doré slag. Chemical and mineralogical analyses (SEM-EDS, AAS, XRD) were performed for the raw material, leaching residue, and leaching solution in order to ascertain the metal recovery and kinetics during leaching.

Mar 1, 2017

By Ze-Qiang Xie, Bai-hui Wang, Feng Chen, Ling-zhi Yang, Yu-feng Guo

In this paper, based on the big data in steelmaking process, equation about the relationship between steel composition (especially the oxygen content) and the element yield is established by using mathematical analysis method to analyze the factors influencing yield. Meanwhile, combining the alloy yield data-base that were established based on self-learning of historical data and computer technology in steelmaking process, a method of yield prediction of alloy elements is studied. To provide support for this method, alloying elements yield prediction software is developed to realize the rapid and intuitive site operation guidance, and to realize the precise control of dosage of alloy material.

Mar 1, 2017

By T. Thriveni, Ch. Ramakrishna, Ahn Ji Whan

Numerous reports and researches address the various environmental issues about the municipal solid waste incineration waste management of heavy metals and other particulate matters with the range of 10–2.5. Although in many developing and industrialization countries land fill with the disposal of municipal solid waste, open incineration has become a common practice. Bottom ash contains heavy metals including particulate matters. The investigation of size distribution for the heavy metals and particulate matters in the bottom ash is essential. However, ultra-fine particle size and heavy metal stabilization are the most important requirements for ecofriendly by products. There are wide variety commercial technologies available for monitoring PM 10, PM 2.5 and ultra-fine particles. In this paper, we reported the studies on physical and chemical characteristics of municipal solid waste incineration (MSWI) bottom ash containing particulate matter whose particulate sizes are lower than PM10, PM2.5 and heavy metal stabilization method by carbonation were investigated.

Mar 1, 2017

By Isadora Dias Perez, Denise C. Romano Espinosa, Flávia P. Cianga Silvas, Jorge A. Soares Tenório, Mónica M. Jiménez Correa

In view of the rising generation of wastewater containing metals, sustainable and clean techniques to recover them are being researched. This study investigated the adsorption of aluminum, cobalt, chromium, copper, iron (III), magnesium, manganese, nickel and zinc presents in a synthetic ef fluent by chelating ion exchange resin Dowex XUS43605. The resin was tested in columns experiments and was analyzed the flow rate (0.45, 0.66 and 1.11 BV/h), at pH 1.5 and 20 °C. After loading the column, the elution experiments occurred with 1 M of H2SO4 and 4 M of NH4O. The concentration of the metals in solution was obtained by X-ray fluorescence spectrometry energy dispersive (EDX). The results showed that the breakthrough experimental curves demonstrated that the main metals (aluminum, cobalt, manganese and zinc) were immediately broken through just after the initiation of the feeding, while the breakthrough of copper began later. Therefore, the study showed that the chelating resin could be used to treat contaminated effluents with metals.

Mar 1, 2017

By James Bennett, Jinichiro Nakano, Anna Nakano

Efficiency of the chemical looping combustion technology is adversely influenced by surface properties of oxygen carrier materials during oxidation–reduction process changes at elevated temperatures. In this work, natural hematite (Fe2O3) and alumina (Al2O3) supported Cu-spinel (CuFe2O4) oxygen carrier particles were isothermally exposed to redox gas cycles (air and 10 vol% CO–90 vol% Ar) at approximately 800 °C and studied using a high temperature confocal scanning laser microscope for real time alterations in surface morphology, roughness, and particle volume. 3D topological scans from each cyclic gas exposure indicated hematite particles exhibited noticeable volume expansion in reduction and shrinkage in oxidation, corresponding to respective phase transformations. Materials surface changes during the redox gas cycles are discussed.

Mar 1, 2017

By Yasuhiro Konishi, Norizoh Saitoh, Toshiyuki Nomura

This paper describes a new recycling method, based upon biotechnology, in order to extract platinum group metals (PGMs) from post-consumer products. The metal ion-reducing bacterium Shewanella algae was found to exhibit the ability to reduce and deposit PGMs. An integrated bioprocess using Shewanella bacteria to selectively recover Pd, Pt, and Rh from aqua regia leachates of spent automotive catalysts is demonstrated.

Mar 1, 2017

By Wei Han, Zhenwei Liu, Jianhong Yang, Qingwei Qin, Tiejun Chen, Zili Huang

The preparation of industrial ammonium molybdate from molybdenum concentrate was conducted according to the process of roasting—leaching—purification—precipitation—crystallization. The optimum technological conditions were determined: the roasting temperature was 680 degrees C, the roasting time was 2.5 h; in the leaching process the alkali excess coefficient was 1.2, the reaction temperature was 80 degrees C, the liquid-solid ratio was 3:1, the leaching time was 3 h; the amount of (NH4)2S added into the solution was 1.1 times of the theoretical amount, the temperature was 80-85 degrees C, and the terminal pH was 8.5-9 in the purification process; the density of the solution was 1.4-1.6 g/mL, the pH was 1.5-2 in the precipitation process; temperature of dissolution was controlled at 80-90 degrees C. The recovery of the preparation of ammonium molybdate can reach 85.18%.

Mar 1, 2017

By K. Morita, S. Ueda, Y. Matsuki

Tellurium has mainly been used as an alloying element for resulfurized free-machining steel. It globularizes MnS inclusions and improves both machinability and mechanical properties of such steel. This effect is quite sensitive to tellurium concentration.Therefore,its incorporation should be controlled accurately during the secondary refining process, using the thermodynamic properties of tellurium in molten iron. In the present study, Wagner’s interaction parameters of various elements on tellurium were experimentally evaluated by vapor-liquid equilibration, and the vapor pressure of tellurium was controlled using the transpiration method. The values obtained were compared with those of oxygen and sulfur, and they were found to be correlated with the standard Gibbs energy of formation of the corresponding oxides, sulfides, and tellurides.The results indicate that the relations described here could provide estimates of interaction parameters that have not been experimentally determined thus far by using available thermodynamic quantities.

Mar 1, 2017

By Mingming Zhang, Marcelo W. Andrade

The evolution of microstructure and mineral phases in iron ore sinters have been investigated by scanning electron microscope and QEMSCAN (Quantitative Evaluation of Minerals by Scanning Electron Microscopy). It was found that MgO, basicity and Al2O3 content play an important role in the formation of mineral phases and microstructure in sinter. The low Al2O3 (<2.0 wt%), medium MgO (2.0–2.5 wt%) and high basicity (>3.0) sinter showed higher low temperature degradation index (LTD) due to the presence of silico ferrites of calcium and aluminium (SFCA), and magnetite phase, and lower pore phase as compared to low basicity iron ore sinter.

Mar 1, 2017

By Lucas de A. Pontes, Lázaro A. Rohen, F. V. Carlos Maurício, Janaina da Silva Vieira, Sergio Monteiro, Dhyemila de P. Mantovani, Frederico M. Margem, Anna C. C. Neves

The lower density of the lignocellulosic fibers such as the hemp fibers and the other natural ones is one of the characteristics that allow the scientists to obtain high levels of specific properties that when compared to the properties of ordinary reinforcements gives to the hemp fibers an advantage as a material with an expressive potential in the mechanical properties area. Then, the aim of this present work is to characterize the relative density of the hemp fiber related to the water using the pycnometry technique. This technique uses the pycnometer and it is divided in two steps. In the first step the correction factor and the moisture content of the fresh hemp fiber specimen and in the other step some weightings were done such as the dry specimen (g), empty pycnometer (g), pycnometer + water (g) and pycnometer + water + specimen (g) using a digital balance with a precision scale of 0.001 g of the bran INNERSCAN. Based on these measurement and calculations using some formulations already established in previous studies, the relative density of the hemp fiber found was around 1.393 g/cm3 and the moisture content around 7.1%.

Mar 1, 2017

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 Ping Long, Peipei Liu, Xinlin Ren, Yunke Wang, Bin Yang, Jian Wu, Wenli Zhang

In this research, ICP-AES was used for determining ten impurity elements (Fe, Pb, Ca, Mg, Cu, Zn, Al, As, Sb, and Bi)in tin concentrate and smelting products, such as crude tin and slag. Samples were dissolved by hydrochloric acid and nitric acid. Determination conditions were investigated in detail. Influences of matrix and coexisting elements were eliminated by selecting proper analysis spectral lines. Under the optimum conditions, the correlation coefficient of cali- bration curves were higher than 0.999. The detection limits of these ten impurities were in the range between 0.0009 to 0.0621 lg/ml. Relative standard deviation (RSD) values were lower than 6.0%, and the recoveries of standard addition were between 85 and 109%. The proposed method was demonstrated to be reliable by comparingwithstandardanalysismethodsandcertifiedvaluesofstandardsample. It could be applied for determining impurity elements in tin concentrate and smelting products successfully.

Mar 1, 2017

By Xiao Hong, Zhang Wenqiang, Gao Bing

The characteristics of top charging coke (coke 1) and stamp charging coke (coke2) were investigated. The weight loss ratios of two kinds of cokes with and without alkalis were measured after reacting with CO under the temperature of 2 900, 1000, 1100 and 1200 °C respectively. The microstructures of original cokes were observed by SEM. The experiment results show that, with no addition of alkali, the weight loss ratios of coke 1 and coke 2 were nearly the same under the temperature of 900 and 1000 °C. While the weight loss ratio of coke 2 was much larger than coke 1 under the temperature of 1200 °C. With alkali-rich, the weight loss ratio of the two cokes was almost the same at 1100–1200 °C.

Mar 1, 2017

By Jorge D. Vier, Raúl B. Rebak, Alicia E. Ares, Natalia S. Zadorozne

Recent worldwide demand has driven nickel and molybdenum prices to record high values. Alloys containing significant amounts of nickel and molybde- num, such as the austenitic and duplex grades, have experienced significant price increases and some spot shortages have resulted in some regions. With low or no nickel content and reasonable molybdenum content, super-ferritic stainless steels are now proving to be the most cost effective corrosion resistant materials. The electrochemical behavior APMT® (Fe–21Cr–5Al–3Mo–0.04C) and 4C54® (Fe–26.5Cr–0.8Mn–0.5Si) super-ferritic stainless steel in NaCl solutions has been studied using open circuit potential measurements, potentiodynamic polarization curves, and electrochemical impedance spectroscopy. The aim is to compare the behavior of these materials with austenitic stainless steel alloy 316 (Fe–18Cr–10Ni– 2.5Mo). The results indicate that the APMT alloy presents a better performance than the AISI 316 stainless steel, while 4C54® does not, especially at anodic potentials. The good behavior of APMT® may be attributed to Al and Mo content in its composition.

Mar 1, 2017

By Xiaolong Lin, Yuanbo Zhang, Jiann-Yang Hwang, Guanghui Li, Hongjin Zhang, Jiaxing Yan, Zhiwei Peng, Tao Jiang

The pollution caused by the spent printed circuit boards (PCBs) is currently a concern of researchers and environmental managers due to its large quantity and exceptionally complex properties. This study characterized printed circuit boards (PCBs) from discarded computers using a number of characterization techniques, including chemical analysis, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), granulometric analysis and scanning electron microscopy (SEM).The PCBs contain approximately 50 wt% metals, 25 wt% glass fibers and 25 wt% polymers. The principal metals include copper, calcium, tin, aluminum, zinc and lead. They are still wrapped by brominated epoxy resin after the PCBs are preliminarily crushed. As precious metals, such as gold and silver, are barely found in the PCBs, copper and tin are the main metallic elements of recycling value which warrants extra attention.

Mar 1, 2017

By Chang Wei, Zhigan Deng, Minting Li, Cunxiong Li, Gang Fan, Xingbin Li

Molybdenum and nickel in black shale ore exists as amorphous sulfides which has highly active, and easily oxide to sulfuric acid and sulfate at low temperature in the presence of excess oxygen. Take advantage of the characteristic to leach molybdenum and nickel from black shale. Oxidation, conversion and dissolution behavior of amorphous colloidal molybdenum and nickel sulfide in pressure leaching process was studied. The effects of stirring speed, temperature, concentration of sulphuric acid, oxygen process and mineral granularity on molybdenum and nickel leaching were investigated. The results showed that dissolution rate increased with increasing temperature and stirring speed, but decreased with increasing concentration of sulphuric acid. And dissolution of molybdenum and nickel from ore only need oxygen without any other reagent.

Mar 1, 2017

By Jinsheng Wang, Wei Lv, Xuewei Lv, Pingsheng Lai, Jie Dang

The isothermal reduction kinetics of vanadium titanium magnetite sintering ore was investigated by thermo-gravimetric analysis at a temperature range of 1123–1223 K under 30% CO + 70% N2 gas mixtures. The apparent activation energy of reduction was calculated by iso-conversional method and its value is 36.7 kJ/mol. The model function describing the reduction mechanism was discussed by Sharp analysis and the results revealed that the reduction process is controlled first by random nucleation and nucleus growth mechanism (RNNGM) as reduction degree is lower than 0.5, followed by the mixed influence of RNNGM and phase boundary reaction when reduction degree is higher than 0.5.

Mar 1, 2017

By S. K. Shaha, A. Gryguc, S. B. Behravesh, B. Williams, M. Wells, H. Jahed

Warm forging to near final product geometry shows promising benefits in terms of microstructure refinement and texture modification. In the present study, Semi-closed die forging was performed on extruded AZ80 magnesium alloy at a forging temperature of 400 °C and various forging ram speeds. Compression tests were performed to investigate the influence of forging at various deformation rates on the performance of extruded AZ80 magnesium alloy. The microstructural analysis showed that the extruded AZ80 possesses a grain structure typical in wrought magnesium alloys, with sharp basal texture. In contrast, the forged samples had a recrystallized microstructures and a spatially varying textures and crystal orientations resulting from the complex flow behaviour within the closed die forging. Furthermore, once forged, a significant increase in the material isotropy, homogeneity as well as failure elongation were observed. An increase in UCS of 9% was observed in the forging direction, while the UCS in the extrusion direction was similar to that before forging. The changes in UCS can be attributed to both the refined grain microstructure and crystal reorientation. Successful microstructure recrystallization occurs for strain rates which traverse several orders of magnitude, and in general, UCS isotropy increases with increasing strain rate. It is believed that forging cause’s grain refinement and texture modification which act to enhance the mechanical performance (UCS, fracture strain and superficial hardness) for the forging conditions investigated in this study.

Mar 1, 2017