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By Xuemei Zheng, Aiyuan Ma, Jing Li, Jinhui Peng, Shaohua Yin, Libo Zhang

Zinc recovery from zinc oxide flue dust (ZOFD) by ultrasound enhanced neutral leaching process was investigated. In this study, the effects of leaching temperature, liquid/solid ratio, leaching time and ultrasound power were studied, and the conventional leaching experiments were also performed. The experimental results showed that the leaching time was greatly shortened and the leaching rate of zinc was effectively improved by the assistance of ultrasound. The optimum conditions of ultrasound-assisted leaching were determined as leaching time 20 min, temperature 35℃, and the liquid/solid ratio of 5. Under these conditions, the leaching rate of zinc was close to 80% as the ultrasound power of 540W, which was increased by 7% or so, in comparison with that of conventional leaching process.

Jan 1, 2015

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 Chengyi Ding, Yangyang Xie, Xuewei Lv, Senwei Xuan, Chenguang Bai, Kai Tang, Gang Li

Dicalcium ferrite (2CaOFe2O3, C2F) is one of the most significant bonding phase of fluxed sinters. Reduction of C2F was investigated via thermal kinetics analysis. The isothermal reduction behavior of C2F by 30% H2 and 70% N2 at 1123 K (850 °C), 1173 K (900 °C), and 1223 K (950 °C) were discussed by thermogravimetric analysis in this paper. The results revealed that the C2F reduction was typical one-step reaction. The apparent activation energy of the C2F reduction was 27.40 kJ/mol. The rate-determining steps of the C2F reduction were the first inner gas diffusion, then the inner gas diffusion and interface chemical reaction mixed controlling. The ln-ln analysis implied that the C2F reduction was described by the Avrami–Erofeev (A-E) equation, thus appeared as a 2D A-E equation kinetics reaction.

Mar 1, 2018

By S. Gupta, M. Fuka

This paper reports for the first time the synthesis of deintercalated MoAlB particulates which belongs to a family of novel ternary borides called MAB phases by selected etching of Al from these particulates by treating them with a solution of LiF and HCl. The FESEM analysis showed that these particulates hada stacked 2D-particles like morphology reminiscent of multilayered MXenes, but unlike MXenes, the 2D layers were interconnected with anisotropic porosity between them with an average length and width of pores being 257 ± 126 nm and 35 ± 10 nm, respectively. The EDS analysis of particulates showed that a typical particulate had a chemistry of (Mo Al )B{O F } which indicate partial 0.67 0.33 0.19 0.02 deintercalation of Al from the particulates. These novel particulates were also referred to as MABenes due to their microstructural similarity with multilayered MXenes.

Mar 1, 2018

By Chengyi Ding, Xuewei Lv, Senwei Xuan, Chenguang Bai, Kai Tang, Gang Li, Yang Xu

Perovskite easily forms during sintering of vanadium titanium magnetite (VTM) and is unfavorable for the following blast furnace. Steelmaking can concomitantly produce a great quantity of oxidized scale composed mainly of FeO and Fe3O4. Calcium ferrite (CaOFe2O3, CF) can be formed by oxidized scale with lime in air atmosphere and then added to the VTM during sintering. X-ray diffraction (XRD) results indicated that perovskite is not generated at low temperature but only when the temperature increases to 1473 K in the CF–TiO2 system. Therefore, VTM sintering can be performed with a low-temperature process with doping of CF. Perovskite formation is mainly divided into two steps. First, CF melts and produces CaO. TiO2 and CaO then combine to produce perovskite. This paper also discussed the reaction mechanism of CaO–Fe2O3–TiO2 ternary system to compare the generation routes of perovskite.

Mar 1, 2018

By Rikiya Kamezawa, Rudiono, Manabu Takeuchi

"Schottky type solar cells based on phthalocyanine (Pc) thin films were fabricated, and their photovoltaic performance was investigated in various ambient atmospheres. Most of cells prepared in this study showed a good rectification and photovoltaic effects in the visible wavelength region. The introduction ofN02 gas into the measuring chamber was confirmed to increase the current both in dark and under light illumination. However, chemical reaction between the Al electrode and N02 formed some oxide and deteriorated the Schottky barrier, resulting in an increase in cell resistivity. SF 6 gas also showed similar effects on the cell performance.IntroductionPhthalocyanine is one of the typical organic semiconductors, which shows high photoconductive sensitivity in the visible to infrared region. Today, several kinds of metal phthalocyanines are used in electrophotographic photoreceptors. In addition, application of phthalocyanines to solar cells have also been trying by many workers [1, 2]. Many efforts have been made for improving performance of phthalocyanine solar cells by modification of device structure [3, 4], doping by dye or pigment [5, 6] and incorporation of metal clusters [7]. It is known that electrical conductivity in phthalocyanine is increased by adsorption ofNO2 [8, 9]. We tried to improve photovoltaic performance ofphthalocyanine solar cell by adsorption ofNO2. This paper describes the influence of N02 adsorption on the photovoltaic behavior of phthalocyanine solar cells."

Jan 1, 2000

By T. V. Jayaraman, D. Das, B. Mallesham, A. R. James

The PNN-PZT xPb(Ni0.3Nb0.67)03-(1-x)Pb(Zr0.31 Ti0 69)03 (0.2=x=0.6) based relaxor-ferroelectric material was synthesized by colurnbite precursor (NiNb206) method via conventional solid state reaction. Homogeneous mixture of required oxides and precursor was calcined at 850°C for 4 hrs to obtain phase pure perovskite. Pellets of PNN-PZT ceramics were sintered at 1100oC for 4 hrs. Phase pure perovskite structure was confirmed by the X-ray diffraction analysis. From the X-ray diffraction analysis it is also confirmed that there is a structural transformation from the rhombohedral to tetragonal with increase in PZT content and existence of morphotrophic phase boundary (MPB) at x = 0.5 composition. The morphology and microstructure of the sintered pellets were observed using the scanning electron microscope. P-E loop measurement shows the high remnant polarization (19.12 µC/cm2) and low coercive field (6.89 kV/cm) at MPB compared to all other compositions. The electromechanical planar coupling coefficient (kp) was measured through the resonance and anti-resonance method using the LCR meter. The piezoelectric strain coefficient (d33) measured directly using the d33-meter. At x = 0.5 composition the highest value of d33 = 398 pC/N is obtained.

Jan 1, 2012

By A. J. Williams, T. N. Croft, M. Cross

"The computational modelling of extrusion and forging processes is now well established. In this work a novel approach is described which utilises finite volume methods on unstructured meshes. This technique can be used to solve simultaneously for fluid flow, heat transfer and non-linear solid mechanics and their interactions. The approach involves the solution of free surface non-Newtonian fluid flow equations in an Eulerian context to track the behaviour of the workpiece and its extrusion/forging, and the solution of the solid mechanics equations in the Lagrangian context to predict the deformation/stress behaviour of the die. Some preliminary examples of this approach will be discussed.IntroductionThe computational modelling of extrusion and forging processes is now well established. Within the last 20 years the finite element method has become the most commonly used technique to simulate metal forming processes [1]-[4]. The Lagrangian and Eulerian type of formulation have been the two major approaches to this problem.Lagrangian methods are efficient and suitable for handling non-linear problems in which small strains prevail, boundary conditions do not change with the course of deformation, and where mesh distortion is not a critical factor in the analysis. Unfortunately, the above points are essential to any accurate metal forming analysis. The problems of mesh distortion and element entanglement pose a serious drawback on the use of such methods. Some automatic remeshing techniques have been developed for Lagrangian finite element analyses of metal forming problems [5]-[7]. However, these methods are not robust and efficient enough to remedy the mesh distortion problems in general. An alternative is to update the mesh manually but this is not always possible, and even when it is feasible it involves major interaction by the user. In addition, remeshing is usually applied to the whole domain which is not necessary and increases CPU time. The complexities associated with remeshing also affect the ability to parallelise the code."

Jan 1, 2001

By S. K. Das, A. J. Gesing

This paper provides an overview of North American markets for magnesium and aluminum alloys along with life cycle material flow diagrams. Additionally, we review the production processes of magnesium and its alloys from various magnesium-bearing raw materials, including scrap. The main focus of the paper is on the collection, recycling and processing of post- and pre-consumer metal scrap containing magnesium. We discuss the latest status and economic analysis of RE-12™, a scrap-based process for recovering magnesium from aluminum alloys and its potential application to can sheet, automotive (body and closure sheets) and aluminum foundry markets.

Mar 1, 2017

By G. Richards

The Trail smelter of Teck Metals Ltd. produces about 90,000 tonnes of lead per year through two stages of refining following KIVCETTM smelting. Bullion from the KIVCET furnace is first treated in a pyro-refining plant in preparation for Betts electrorefining which makes 99.99% pure lead. Pyro-refining consists of number of integrated unit operations to remove primarily copper, arsenic, antimony and tin. The operation of this plant to meet the specifications for electrorefining requires attention to bullion management and selective use of reagents. The processes used for pyro-refining are reviewed in terms of chemistry and control.

By G. Johnston, J. Greenly, R. G. Buchheit, D. C. McIntyre, R. Muenchausen, D. J. Rej, R W. Stinnett

"Rapid thermal treatment of materials using high energy, high flux, pulsed ion beams can produce modified surface layers with unique microstrutures and properties. High energy ions loose their energy during the slowing down process in the workpiece and thus deposit their energy continuously over a depth of a few microns. The deposition of energy can lead to melting and in some causes ablation of the heated layer. Because the pulse duration of the ion beams is typically only 50-200 ns, steep thermal gradients generated during heating facilitate rapid cooling (107K/sec-108K/sec) of the treated layer by thermal diffusion into the underlying material. Rapid heating and cooling of materials can generate surface layers with non-equilibrium amorphous or nano-crystalline microstructures that exhibit increased hardness, wear resistance, and corrosion resistance. Pulsed ion beam treatment can also lead to surface smoothening or can be used to mix thin « 1 11m thick) coatings into underlying substrates. Pulsed ion beams can be generated using existing ""flashover"" ion source technology which is capable of producing single shot, mixed C, H, and O ion beams with beam cross sections of approximately 100 cm2 and energy fluxes up to 100 J/ cm2. Recent advances in repetitive high energy pulsed power technology and development of magnetically confined anode plasma ion sources have facilitated the development of ion beam systems that generate single species beams that pulse continuously at 120 shots/second. These capabilities will allow rapid treatment of large surface area workpieces at low cost.IntroductionThe rapid solidification of liquid materials can create unique materials and material microstructures that often have properties that can lead to enhanced performance. Rapid solidification processing of the surfaces of materials using continuous and pulsed laser beams (laser glazing) has been explored for over 20 years (1-5). Advances in high energy, pulsed electron and ion beam technologies over the past decade have provided rapid thermal treatment techniques that may be less expensive to impliment than laser surface treatment for many surface modification applications (6). High energy pulsed ion beams have recently been used to harden aluminum(7), copper(8) and tool steel surfaces (6,9), increase corrosion resistance of Al alloys (6), mix coatings into underlying substrates (10), and create amorphous films (11,12)."

Jan 1, 1994

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

By Zongliang Zhang

Electrowinning is a significant step in metal extraction processes. Because the nature of electrowinning is to reduce metal from its oxidized state, substantial energy consumption accompanies it. Electrowinning processes of different metals have much in common—the deposition of the metal on the cathode and the counter-reaction on the anode. An advanced model was developed that can be applied to a variety of metal electrowinning processes. A model for specific metals can be readily obtained by modifying parameters such as potential, kinetics, and side reactions in the model. The model incorporates mass transfer, gas-liquid flow, electrochemistry, and deposition, making it a comprehensive electrowinning model. The model is applied to copper, nickel, and zinc and verified with the experimental results. In addition, the parameter settings and results of different metals were compared, showing that this model has great versatility and accuracy, thereby making it an efficient and effective research tool.

By Hideki Yamamoto, Shigeno Matsumoto, Junji Shibata

"Some fundamental studies were carried out in order to produce composite powders comprising of two or three metal oxides ~y using liquid-liquid extraction and to develop the control technology of the particle size. The combination of samarium and cobalt was selected as the two component composite powders. Both stripping and crystallization occurred at the same time by emulsifying the organic phase loading the two metals extracted with Versatic Acid 10 and the aqueous solution containing oxalic acid. The effect of aqueous pH, oxalic acid concentration and agitation speed was examined on some properties such as crystallization percent, particle size and shape of each metal oxide powders obtained in this process. The analysis by using EDX showed that the two metal oxides were distributed uniformly.IntroductionComposite metal and metal oxide powders with high purity are indispensable as industrial materials in the fields of electrical engineering, electronics and metallurgy. It is difficult to mix metal powders or metal oxide powders uniformly for the production of alloy powders. If insoluble metal salts are allowed to collect as crystallization products in the crystallization-stripping process, the conventional melting and crushing process can be avoided. After mixing of the organic phase containing metals in fixed composition, fine metal and metal oxide powders of alloy composition are produced by using a crystallization-stripping method. Versatic Acid 10 and D2EHPA, both acidic extractants, were chosen in this experiment, and the metal oxide powders were produced by using oxalic acid as a crystallization reagent. Mixed metal oxalates containing samarium and cobalt were precipitated from the mixed organic phase containing these metals. Furthermore, the physical properties of the powders, such as particle size, shape and thermal decomposition, were measured in order to evaluate them for industrial purposes."

Jan 1, 2000

By W. K. Rankin

Achieving continued economic growth with social equity within the natural limits of the Earth's eco-systems is the major issue facing the world today. The material and energy needs of the world cannot be met with the current ways of addressing this issue. The need for metals, an important class of materials, will continue into the future because their unique properties make substitution by other materials impossible in many applications and this need will continue to be met from primary metal production and recycling. However, the recycling rate will increase and the usage pattern of metals will change to reflect the environmental impact of their production and use. Pyrometallurgy has an important role in meeting the metal needs of the future since some metals can only be produced pyrometallurgically; the energy required to produce some metals pyrometallurgically is significantly less than by other methods; most metals are most efficiently recycled pyrometallurgically; and the release of harmful and toxic elements into the biosphere can sometimes best be controlled through pyrometallurgical processing. The development of strategies for pyrometallurgical processing for the future lies in the recognition that sustainable development calls for large step improvements in value delivered per unit of environmental impact over the entire supply chain. Pyrometallurgists can respond to this challenge by contributing to reducing the environmental impact of meeting metal needs using three broad strategies: "end-of-pipe" approaches to convert emissions into benign materials for storage or disposal; flowsheet redesign to limit or eliminate emission production; and improved recycling technologies. A number of examples are discussed to illustrate how the sustainability driver is already influencing the technological development of pyrometallurgical processes, and how these will develop further as the sustainability driver strengthens.

Jan 1, 2003

Smelter operating and environmental requirements demand high on-stream time (high reliability) from the primary smelter sulfur retention device - the sulfuric acid plant. The key to reliable smelter sulfuric acid plant operation is the gas cooling and cleaning system. Problems in the gas cleaning system cause corrosion, plugging, equipment failure, etc - plant down time, in the contact section of the plant. The last fifteen years have seen major changes in gas cleaning system design to the current standard of brick lined venturi scrubber, packed gas cooling tower with plate type liquor coolers and lead or plastic tube precipitators. The current-design offers improved impurity scrubbing along with increased reliability. In addition, a number of alternate gas cleaning systems have been offered. Chematics LAB System: Monsanto DuPont Dynawave System; Lurgi venturi scrubber with lead star gas cooler. This paper will review the design and operating advantages, disadvantages, and risk of the standard gas cleaning system and compare it to the alternate systems.

Jan 1, 1992

By Laurentiu Nastac

"Two advanced control solidification technologies were studied in this article to improve the quality of the cast ingots as well as to control the solidification structure evolution during the plasma arc melting (PAM) processing of Ti-6-4 ingots: (i) electromagnetic stirring (EMS), and (ii) ultrasonic treatment (UST). The developed EMS modeling approach is based on the numerical solution of Maxwell's equations, fluid flow, and heat transfer equations, and mesoscopic modeling of the grain structure. The UST analysis tool is capable to model acoustic streaming and cavitation. It is used in this work to study ingot solidification under the presence of ultrasound. Predictions of the macrostructure, GET formation and primary dendrite arm spacing for PAM Ti-6-4 ingots processed with and without EMS or UST were discussed.1. IntroductionTitanium (Ti) alloys are melted, refined and cast into ingots through plasma arc cold hearth melting (PAM), electron beam cold hearth melting (EBM) and vacuum arc remelting (VAR) for jet engine applications. Process modeling has become a viable tool to optimize the PAM, EBM, and VAR processes. A comprehensive modeling approach to simulate ingot solidification phenomena in primary melting and secondary remelting processes of Ti alloys would include models for macroscopic mass transfer, heat transfer, fluid flow, acoustic, electromagnetic and species transport. The approach should also include microscopic models to predict the evolution of grain structure in solidifying ingots in conjunction with electromagnetic stirring (EMS) and ultrasonic stirring (UST)."

Jan 1, 2012

By John Gordon

Rare earth elements (REE) required in modern technological products are found in shale rocks above and below coal seams. Often during the process of mining coal, shale rock adjacent to the seam inadvertently is removed then diverted to landfill sites. Ecologically sound and potentially economic methods of extracting the REEs from these landfills are proposed. Methods include utilizing geomemembrane barrier beneath the landfill site, ion exchanging with moderate pH, slightly acidic, sodium chloride solutions. Sodium hydroxide is utilized to precipitate the REE-hydroxides subsequently converted to REE-chlorides with suitable amount of hydrochloric acid. All acid and base streams are co-produced with efficient membrane/electrolysis technology. Concentrated-REE chlorides are transported tocentralized solventextraction facilities for isolation and purification. Solvent extraction processes also employ the methodology of using co-produced acid/base streams. This paper details minimization of environmental impacts and maximizing economics to produce valuable REEs while increasing the economics of coal mining.

Mar 1, 2018

By Mikiya Tanaka, Hirokazu Narita, Takeshi Ogata

There is an increasing attention to recover dilute rare earth elements (REEs) from acidic solutions in order to meet their demands and stabilize their supply chain. Adsorption is suitable for recovering target metal ions when their concentrations are low. Many adsorbents for REEs have been studied; nevertheless, there are no adsorbents in practical use. We have developed adsorbents consisting of silica gel particles modified with diglycolamic acid groups. The adsorbent has the ability to selectively adsorb RE ions from solutions containing high concentrations of base metal ions in a low pH region, and the adsorption capacities of the adsorbent for the heavy REEs were higher than those for the light ones. Moreover, this adsorbent meets the requirements for a practical adsorbent, such as high durability, easy desorption, and high adsorption rate. We therefore conclude that the adsorbent can contribute the production of heavy REEs from underutilized resources.

Mar 1, 2017

By Guihong Han, Wei Wang, Chaolei Lv, Yongsheng Zhang

Silica aerogels are promising in many applications because of their excellent properties. However, the real applications of pure silica aerogels are limited because of their fragile network structure. We have prepared silica aerogel composites using humic acid as a composite material for improving the performance of silica aerogels and valorization of humic acid. The silica hydrogel composite was prepared using sodium silicate as a precursor and humic acid as a composite material by acid-base catalysis and sol-gel method. The hydrogel was followed by freeze-drying to obtain composite aerogel. The microstructures, specific surface area, and functional groups of silica and composite aerogel were characterized using scanning electron microscope (SEM), brunauer-emmett-teller (BET) and fourier transform infrared spectrometer (FTIR). The results demonstrated that the specific surface area of the silica composite aerogel was 307 m2/g under the condition of pH at 6, the mass ratio of silicon to humic acid (HA) at 3.82 and the molar ratio of N, N-dimethylformamide (DMF) to silicon at 0.9. X-ray diffraction (XRD) showed that the silica (composite) aerogels were amorphous. Thermogravimetric analysis (TGA) revealed that the silica aerogels lost weight from 150 to 250 °C and humic acid decomposed between 350 and 500 °C, and then the mass of the sample remained stable.

Mar 1, 2018