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By Lin Zhu, Zheng Wei, Meng Li, Xueli Cao, Hanying Wen, Guodong Shi, Lei Yu, Wen-xin Tang, Tao Li

Low energy electron microscopy and photoemission electron microscopy (LEEM/PEEM), as powerful in-situ surface-sensitive electron microscopy, find wide applications in surface physics, chemistry and catalysis. The high reflectivity of incident low-energy electrons (0–100 eV), allows it to image the surface structures in the topmost few atomic layers within less than one second, while the sample can be heated up to 1200 °C in real time which is potentially very useful in metallurgy and materials fields. A unique three-prism aberration correction (ac-) LEEM was commissioned successfully in Chongqing University, with a lateral resolution below 2 nm. A multiple gas source in the ac-LEEM system was installed as well, which allowed us to observe chemical reactions of nanoscale mineral powders on metallic substrates. In this paper, the latest results on the applications of this three-prism ac-LEEM on oxidation and reduction processes on copper and iron polycrystalline surfaces are demonstrated.

Mar 1, 2018

By Vahid Javaheri, David Porter, Tun Tun Nyo

A field emission scanning electron microscope equipped with EBSD has been employed to evaluate the role of 0.013 wt% Nb on the evolution of the microstructure and texture of a novel thermomechanically processed low-alloy, medium-carbon steel. Specimens were subjected to hot-rolling with a total reduction of 80%, four passes in the recrystallization regime and four passes below the non-recrystallization temperature. Immediately after rolling, the strips were quenched to 420 °C and subsequently cooled slowly in a furnace to simulate strip coiling with transformation of austenite to bainite. The results showed that Nb microalloying results in a finer microstructure with a sharper texture when compared to an identical steel but without Nb. In addition, analysis of the retained austenite texture indicated that the main bcc texture components are the product transformed brass and copper components in the parent austenite.

Mar 1, 2018

By Isadora Dias Perez, Monica M. Jimenez Correa, Jorge A. Soares Tenorio, Denise Crocce Romano Espinosa

The generation of mining waste has been the subject of environmental, economic and social concern. Alternative and sustainable methods of recycling metals technologies are desired. The present work focuses on the application of the ion exchange technique for the extraction of metals contained in a lateritic nickel mining effluent. The Purolite S950 chelating resin was used in the present work because it has the ability to adsorb transition metals present in an acidic solution. The experiments were carried out in a batch varying the pH in the range of 0.5–2.0. 1 g of resin was placed in contact with 50 mL of solution and stirred for 120 min at a speed of 200 rpm and temperature at 25 °C. The results demonstrated that the affinity of the resin varied with pH. The adsorbed metals were only copper, manganese, magnesium and zinc. The most extracted metal was copper, corresponding to 37%, when the solution was conditioned at pH 2.0.

Mar 1, 2018

By Zhi Yang, Ahmad Ghahreman, Farzaneh Sadri

Impurity removal is a very important stage of the hydrometallurgical treatment of rare earth elements (REE) processing circuit, which is performed after water leaching of the acid baked REE concentrate. Lime neutralization has a high efficiency in removal of impurities and is the preferred process due to its economic advantage; however, the process has its own problems, such as the production of large volumes of gypsum and co-precipitation of REE with gypsum, i.e. REE loss. This work deals with the effect of several additives (cetryltrimethylammonium bromide (CTAB), polyvinylsulfonic acid (PVS) and polyacrylic acid (PAA)) on the uptake of REE by gypsum from synthesized acidic solutions. The main purpose of this study is to investigate the changes in the crystalline morphology of gypsum precipitated by the addition of crystal habit modifiers and to determine the crystal changes’ effects on the uptake of REE by gypsum. In this regard, different concentrations (0.2, 2 and 5 g L−1) of above-mentioned additives were studied at room temperature.

Mar 1, 2018

By Yuanbo Zhang, Zijian Su, Bingbing Liu, Guanghui Li, Manman Lu, Tao Jiang

Acid wastewater containing toxic metal ions has become increasingly important global environmental concern and lead (Pb) is one of the prime toxic heavy metal ions. Humic acid (HA), a kind of natural organic matter, has been proventohaveagreatadsorptioncapacityformetalcations(Pb2+,Cu2+,etc.).Our previous study has verified that HA has excellent adsorbing ability on vanadium titanium-bearing magnetite(VTM) particles. In this study, VTM-HA complex magneticparticles werepreparedfor removing Pb(II)fromacidwastewater,which could be easily recycled by magnetic separation. The effects of pH value, ionic strength and VTM-HA concentration on the removal ratio of Pb(II) were deter- mined by isothermal adsorption tests. The results indicated that Pb(II) adsorption was subject topHand ionic strength. When initial Pb(II) concentration is 100 mg/ L, the residual concentration and removal ratio of Pb(II) reach 0.17 mg/L and 99.83%, respectively, which are much lower than the discharge standard. (cid:1) (cid:1)

Mar 1, 2018

By S. N. Monteiro, J. Alexandre, N. Cerqueira, B. C. Mendes, A. R. G. Azevedo, G. C. Xavier

Brazilian civil construction generates a huge amount of waste in different stages of construction, mainly due to the work methodology used in construction sites. The objective of this work is to study the inclusion of the residual of the civil construction in the sand mass in 0, 10 and 20%, with mortars used to cover masonry. For this study, the beneficiation of the material in crusher was obtained so that it obtained granulometry similar to sand and the most recurrent technological tests in mortars for this purpose, as the mechanical resistance (compression and flexion), water absorption and determination of the coefficient of Capillarity beyond the index of consistency, according to Brazilian norms, that define parameters of execution the technological tests. The results showed that the mortars after the incorporation presented value within the norm except the consistency and capillarity to the 20% that presented problems of fluidity and durability, hindering its use.

Mar 1, 2018

By Tarek M. Hatem, Salah M. Bedair, Khaled H. Khafagy

Our understanding for intrinsic stresses and defects evolution in photovoltaic devices has became an essential part of new developments. In particular, Multi-Junction Photovoltaic (MJ-PV) modules depend on multi-layer structures that may suffer high dislocation-densities as a result of high lattice and thermal expansion coefficient mismatch. These defects limit the performance, reliability, and lifetime of PV devices. In the current study, a three-dimensional multiple-slip crystal-plasticity model and specialized finite-element formulations are used to investigate InGaN growth on Si substrates. The formulation is based on accounting for thermal and intrinsic stresses as a result of different processing conditions and microstructures. Furthermore, the formulation was used to investigate a recently developed technique, Embedded Void Approach (EVA), which can be used to address both the high density of defects and the cracking/bowing of InGaN growth on Si. The current work lays the groundwork for more extensive use of silicon in MJ-PV devices.

Mar 1, 2018

By Oscar Restrepo, Juan C. Nino, Henry A. Colorado

New and extraordinary physical-chemical properties of materials at nanoscale open up new applications for the building and infrastructure industry such as structural reinforcements, electronic properties and energy harvesting. Therefore the issues and risks associated with the manufacturing of nanomaterials are now of big concern due to the large volumes and typical processing involved in this industry. This paper presents a discussion and selected applications of nanotechnology in the construction and building materials: from metals and alloys, clay and minerals, ceramics, cement and concrete, asphalt, wood and composites, to finishing systems and some of the most used characterization techniques. Besides the progress in some areas, nanotechnology is just emerging in this field, with many challenges and opportunities, problems unsolved and business opportunities. A discussion regarding the potential health issues and risks of using nanomaterials for workers and the potential environment effects is included as well. New images and diagrams are presented and discussed.

Mar 1, 2018

By Z. Jing, L. Qihou, C. Jun, L. Hui, Z. Yumeng

Three phases of Bi2O3 were first synthesized by extraction-stripping precipitation and post decomposition from BiCl3 leaching solution. The as-prepared Bi2O3 were characterized by X-ray powder diffraction (XRD), Fourier transform infrared spectra (FT-IR), scanning and transmission electron microscopy (SEM, TEM), UV-vis diffuse reflectance spectroscopy (UV-vis DRS), Brunauer-Emmett-Teller (BET) and X-ray photoelectron spectroscopy (XPS). The photocatalytic performances of the oxides were investigated by decomposing rhodamine B (RB) under visible irradiation. It shows that the Bi2O3 with different crystal structures and morphology were obtained under different decomposition temperature. The band gaps of as-prepared samples were 2.36, 2.41, and 2.78 eV for b-Bi2O3, a-Bi2O3, and d-Bi2O3, respectively, and the photocatalytic activities followed the order: b-Bi2O3 > a-Bi2O3 > d-Bi2O3, which was in good accordance with the photoluminescence spectra measurement results. The b-Bi2O3 exhibited the best photocatalytic performance which can effectively degrade 99.23% RB within 240 min.

Mar 1, 2018

By Afonso Garcez de Azevedo, Anna Carolina Lopes Rabello, Renan Tavares Vicente, Sergio Neves Monteiro, Amanda Maia Ferreira dos Santos

Civil construction is a sector of extreme impact in the Brazilian economy, with construction and demolition waste (RCD) having an extreme impact on the amount of urban solid waste. In this research it was proposed to propose a way of using these residues in the construction of concrete artifacts for structural use. Concrete specimens with sand substitution by RCD were produced in different percentages as a way to contribute to reduce,recycle and reuse thi large amount of waste from the construction industry. The objective of this work was to study the mechanical properties of structural concrete with total and partial replacement (25, 50, 75 and 100%) in sand mass. The results of the compression test indicate good quality for concretes with mass substitution of up to 75% per RCD.

Mar 1, 2018

By B. Manoj

Coal is a mineral and is extensively used as a solid fuel in developing nationsand hasa sizeable share inthe global fossil fuel reserve. Utilization of this resource generates excess spoil and large volume of low grade waste to the environment. In recent years there have been serious research on enhancing its value and exploring the utility of this carbonaceous material to novel carbon materials.

Mar 1, 2018

By Beatryz Mendes, Leonardo Pedroti, Afonso Azevedo, José Maria Carvalho

The dregs is a waste from the cellulose production, and its reuse is an effective way to reduce environmental impacts. Researches have already been done to incorporate it into building materials. The present work aimed at incorporating dregs in the production of mortar to replace hydrated lime. The methodology adopted was the Simplex network with ten sampling points, varying the amount of cement, sand, and dregs. Each mix was submitted to flexural strength, compressive strength, apparent mass density and water absorption by capillarity tests. The results were analyzed by the software Minitab, obtaining the influence of each component in the mixture. The best results were observed in mixes with a higher proportion of cement and less of residue when it was analyzed the flexural and compressive strengths. Larger rates of apparent mass density and water absorption were noticed with a greater amount of dregs. The experimental design also allowed the obtainment of mixture ratios from predetermined values of the tested properties and indicated that the addition of dregs in mortar could be an alternative to civil construction.

Mar 1, 2018

By Bart Blanpain, Muxing Guo, Bin Yang, Fei Wang

An experimental investigation of the precipitation behavior of the Dy2O3 containing slag during cooling was carried out in this work. The slag with composition 45 wt% SiO2—49 wt% CaO—6 wt% Dy2O3 was equilibrated at 1673, 1773 and 1873 K for 24 h in an argon atmosphere, and then quenched in water to determine the phase relations. The composition and microstructure of the equilibrated phases of the systems were determined by EPMA/WDS. The precipitation behavior of the REEs containing phases during cooling was studied by using an in-situ confocal scanning laser microscope (CLSM) observation technique combined with an infrared imaging furnace heating (IIF). Data resulting from this work aims to support further investigation on separation of rare earths from metallurgical slags.

Mar 1, 2018

By Liuyin Shi, Kang Liu, Fengqi Zhao, Yan Song, Zhiping Yang, Xing Fan

Due to the high energy consumption, long technical process, low usage rate of vanadium during the traditional smelting vanadium steel process, a new method for decarburization by CO2 to directly smelt vanadium-containing steel in blast furnace was proposed. In this paper, the thermodynamics of CO2 decarburization in molten iron process was calculated out by FactSage. The thermodynamic calculations indicated that in standard state, the transformation temperature of C and V was 1357 °C; the oxidation order of element was Si, C, V, Mn and S when using CO2 as oxidant. The experiment of blowing CO2 temperature showed that decarburization reaction temperature was 1550 °C, carbon content could be decreased to 0.676%, the decarburization rate was 88%. There was no effect on vanadium content in molten iron during the decarburization process, vanadium content was 0.323%, which meets the request of vanadium mould steel.

Mar 1, 2018

By Min-Min Lin, Bing Xie, Hong-Yi Li, Yang Yang

After precipitation of ammonium vanadates from vanadium-containing leaching liquor, vanadium (V(V)) and chromium (Cr(VI)) exist in the waste water in form of vanadate ions and chromate ions. In order to efficiently extract and recover V(V) and Cr(VI) from waste water, an environment-friendly method based on anion exchange was investigated in batch tests using macroporous weak base resin Dex-V. The adsorption conditions optimizes in detail, including the effect of pH, initial metal concentration, resin volume, contact time and temperature. The ion-exchange adsorption process for both V(V) and Cr(VI) showed maximum capacity at pH 3.0 for an initial concentration of 100 mg L−1, and reached equilibrium after about 40 min of contact at 298 K. The maximum adsorption ratio under the optimum conditions for V(V) and Cr(VI) was 98.98 and 99.87%, respectively. Result shows that the established method is a promising alternative for simultaneous extraction of vanadium and chromium.

Mar 1, 2018

By Xiang Zhang, Junjie Liu, Zhibo Tong, Langsha Shao, Guojun Ma

The aqueous mineral carbonation process that leaching alkaline earth metals from industrial residues by ammonium salt and carbonation thereafter is one of the potential technologies for CO2 sequestration. In this paper, the effect of particle size of waste slag on the leaching rate of metals under a microwave field and effect of microwave irradiation on the carbonation process were investigated. It was found that the initial leaching ratio of Ca decline seriously with the particle size of EAF slag increasing, and the Ca leaching ratio is relatively low during 120 min leaching. The lower leaching ratio of Ca with large particle size is due to the existence of a silica product layer produced on the surface of calcium silicates. Moreover, due to the microwave irradiation, the leaching ratio of calcium and the crystallization rate of calcium carbonate increase, though the particle size and distribution range of calcium carbonate reduce.

Mar 1, 2018

By Ritayan Chatterjee, P. K. Mukhopadhyay, Surajit Biswas, Dinabandhu Ghosh, Sandeep Agarwal

An Indian magnetite ore from the Nagaland region was characterized by powder X-ray diffraction, spectroscopies (ultraviolet-visible and Raman), high temperature magnetization and thermal analysis. A Rietveld refinement of the diffraction data revealed that the principal phase present in the sample is magnetite with partial substitution of Fe with Mg (mainly) and Cr, leading to the chemical formula of MgCr0.2Fe1.8O4. The UV-visible spectra of the sample in MeCN solution showed three distinct peaks. The lower region bands are due to metal-oxygen charge transitions and the other band is for d-d transition of iron. Raman spectral study at room temperature gave four characteristics bands of magnetite. The sample underwent a magnetic transition at high temperature and the thermomagnetization curve shows hysteresis during cooling cycle which indicates the possibility of first order structural transition at high temperature. The thermal property of the concentrate was studied by differential scanning calorimetric technique.

Mar 1, 2018

By Yuanbo Zhang, Zijian Su, Bingbing Liu, Guanghui Li, Jicheng Liu, Manman Lu, Tao Jiang

Blast furnace slag (BFS), one kind of typical solid waste in the steel industry, was used as structural materials to synthesize NaNO3/BFS composite phase change materials (C-PCMs) by mixing and sintering method. NaNO3 in the composites functioned as phase change materials (PCMs) and BFS as structural skeleton to maintain a stable external form. In this study, the prepared C-PCMs could remain in the solid state without salt leakage even if operating temperature exceeded the melting temperature of NaNO3. The composition and structure of BFS and the prepared composites were characterized by XRD, FTIR, SEM and TG-DSC analyses. The results showed that NaNO3 was well incorporated in the pores of BFS. The melting temperature and latent heat of the final composites were 300.5 °C and 65.53 J/g, respectively. The product also had good thermal storage performance and durability even after 100 thermal cycles. The energy density of the product was calculated as high as 468.03 J/g for an temperature range of 50–400 °C.

Mar 1, 2018

By Naiyang Ma

Along with fast growth of EAF steelmaking, better ways of treating EAF dust have been continuously pursued for better environmental protection and better economic benefits. In this contribution, various ways of collecting EAF dust in EAF off-gas cleaning systems are reviewed, and generation of dust and concentration of zinc in the dust from various collecting devices are examined. Accordingly, recycling of EAF dust through source separation is discussed.

Mar 1, 2018

By Camille Fleuriault

Continuous development of lead recycling technologies has driven the increasing contribution of secondary lead in battery manufacturing over the years. This review presents and compares the different technologies available for pyrometallurgical processing of secondary lead materials. Smelting is most often achieved in reverberatory, blast, rotary or electric arc furnaces, using single or two stage routes. Thermal re fining is the most common technique used for the production of lead and its alloys. Some improvements in battery breaking technologies and emission control have also specifically contributed to improve the performance of the smelting and refining units. Recycling lead is facing the challenge of increasing production while meeting more and more stringent regulations. This review will also include an analysis of the current secondary lead market as well as an economic outlook for the years to come in regards to rapidly changing environmental standards.

Mar 1, 2018