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By Yasuhiko Ito

"This talk is concentrated on the topics of compound film formation on the substrate electrode by interdiffusion of substrate element and electrochemically deposited species and/or by direct electrochemical implantation of the component element of the film into the substrate. As a typical example, electrochemical implantation of nitrogen atom into Ti metal to form TiN surface film is described. Another example is the formation of various kinds of intermetallic compound films including Ni2Y, Ni2Dy and Pd3 Y by the electrochemical implantation of lanthanoid elements into transition metal electrodes. By combining these two methods, Sm-Fe-N ternary material film also could be formed. The principle and application of the ""electrochemical implantation"" are discussed in detail.IntroductionGenerally speaking, surface film formation by molten salt electrochemical process can be divided into the following three categories:(i) single element film formation on the electrode by electrodeposition,(ii) compound film formation on the electrode by electrocodepostion of more than two elements, and(iii) compound film formation on the substrate electrode by interdiffusion of substrate element and electrochemically deposited species and/or by direct electrochemical implantation of the component element of the film into the substrate.This talk is .concentrated on the topics of category (iii), especially on the electrochemical implantation. Typical example can be seen in the electrochemical implantation of nitrogen atom into Ti metal to form TiN surface film. Another example is the formation of various kinds of intermetallic compound films including Ni2 Y, Ni2Dy and Pd3 Y by the electrochemical implantation of lanthanoid elements into transition metal electrodes. By combining these two methods, Sm-Fe-N ternary material film also could be formed. The principle and application of the ""electrochemical implantation"" are discussed in detail with examples above as well as other experimental results also obtained very recently in the author's laboratory."

Jan 1, 2000

By Liu Zhonghua

Hydrogen reduction of cobalt sulfide (Co9S8) was experimentally investigated in the temperature range 813-1053 K. The results revealed that the reaction kinetics can be described by the shrinking core mod¬el in chemical control regime at low temperatures, it is of first order with respect to hydrogen concentration, and the reaction activation energy is 67.4 kJ/mol. The SEM second electron images of the samples before and after experiments showed that the swelling of the sample above 973 K is due to the formation of metallic cobalt whiskers.

Jan 1, 1992

By Wilson Acchar

The accelerated growth of urbanization processes and current environmental concerns brought to light the existing enormous quantity of construction and demolition waste (C&DW). Considering the frequent lack of adequate landfill areas available for the disposal of these materials, their use in the manufacture of ceramic products has been attracting a growing interest from researchers and is becoming common practice, with the consequent relief in public administration concerns for the C&DW appropriate management. This work describes the study of clay-based products added with C&DW collected directly from the construction industry. Samples containing up to 50 wt.% C&DW were uniaxially pressed and sintered in air in an electric furnace (950-1150 °C, 1 hour). Sintered test pieces were characterized by X-ray diffraction, apparent density, open porosity and flexural strength. The results showed that up to 50 wt.% C&DW can be added to the clay material, with no degradation in the final product properties.

Jan 1, 2009

By Chenhui Liu, Hong-ying Xia, Bingguo Liu, Wei Li, Jinhui Peng, Libo Zhang

"Dielectric property is an important limiting factor in the development of microwave processing of minerals and ores. In this study, we used an open-ended coaxial sensor method to measure the complex permittivity of an ilmenite concentrate (41%TiC>2) and microwave absorption properties from room temperature to 100°C. The results show that the dielectric constant, loss factor and loss tangent increase with temperature rising at 2.45GHz. Microwave absorption properties of this ore are highly dependent on temperature and frequency. Ilmenite concentrate can be used as raw materials to prepare wideband microwave absorbing material. The research will be helpful in explaining the thermal running of microwave dielectric heating the ilmenite concentrate.IntroductionAs the sources of high-grade titanic mineral are decreasing worldwide, the utilization of low-grade minerals such as ilmenite has attracted more attention [1,2]. Because Panzhihua ilmenite has complex minerals and high contents of MgO, CaO, S1O2 , it is difficult to upgrade the ilmenite to titanium-rich slag and farther produce synthetic rutile and titanium dioxide pigment [3]. Therefore, it is desirable to develop new technology for processing ilmenite ore [4]."

Jan 1, 2012

By Zhao Guangwen, Wu Tan, Qiuzhan Tian, Duan Shuzhen

"A thorough study of lost currents in bipolar cells has been made for the development of the great potential of bipolar cells in energy saving. A proper equivalent circuit for bipolar cells has been found, and mathematic methods for computing lost currents at all kinds of polarization have been developed.At linear polarization, the lost currents can be computed by solving either a tridiagonal matrix or an ordinary differential equation of second order. This kind of values can be used to evaluate the minimal lost currents at given conditions. At other kinds of polarization, the lost currents can be computed by the same methods as above if the necessary experiments of measuring the cell voltages of every electrolytic compartment have been made. This kind of values can be used to design bipolar cells at practical conditions.Extensive experiments have been made to evaluate the effects of electrode polarization, emf of galvanic cell for the formation of electrolyzed substance, gaseous products, geometric dimensions of electrolytic cells, special resistance of electrolyte used, and the total and ordinal number of electrolytic compartments on lost currents. It is the first time to make such a systematic research by experiments in the world. Experiments showed that theoretic models were in good agreement with measured data. Experiments also showed that D.C. energy consumption of 0.45 kwh/kg of Pb for lead electrolysis from molten chlorides could be achieved in a cell with 7 bipolar electrodes.IntroductionIt is very promising to apply bipolar electrolytic cells to electrolysis of aluminum, magnesium, lead, zinc and perchlorinates for their great potential of energy saving for example, bipolar cells had been used in the production of magnesium and saved more than 30% of energy, being one of the three main techniques of energy saving in the production of titanium sponge (1)."

Jan 1, 1988

By Shigeru Ueda, Shin-ya Kitamura, Shohei Koizumi, Xu Gao

Steelmaking slag was confirmed to be a useful fertilizer for paddy growth as it efficiently supplies Ca and Si to soil water. In addition, supplement of Fe from slag fertilizer has been expected to suppress the H2S generation in paddy soil, especially for the degraded paddy soil. However, on the basis of our previous research, the Fe dissolution ability changed with slag brands, and even some brands could dissolve Fe under paddy soil pH, the supplying ability were not high. To improve Fe dissolution, we found that among various kinds of Fe-rich mineralogical phases in slag, the CaO–SiO2–FeO glassy phase showed highest water solubility of Fe. Because the CaO–SiO2–FeO glassy phase was a quenched molten phase, its dissolution behavior may depend on chemical composition, and this is important for controlling slag composition to produce fertilizer which can easily release Fe. Therefore, in this research, the CaO–SiO2–FeO glassy phase of various CaO/SiO2 ratio, Fe2+/T–Fe ratios, and FeO contents were synthesized, and the dissolution behaviors of Fe as well as other cations from these synthetic glassy phases into an aqueous solution at pH of 5 were investigated. The result showed that the dissolution ratio of Fe increased significantly by increasing Fe2+/T–Fe ratio. An increase in FeO content of glassy phase also increased the dissolution of Fe. In addition, the Fe dissolution ratio showed a local maximum with increasing CaO/SiO2 ratio.

Mar 1, 2017

By Axel Hoppe

Although Tantalum is not usually regarded as a precious metal, its pricing structure is very similar to that of Silver. Different from precious metals, Tantalum has only industrial applications and its use is about 1000 metric tons per year. The intrinsic value of Tantalum already in .the past was a driving force for its recycling. Based on these facts the Tantalum industry world-wide is approaching the closed-loop concept of its recycling. A detailed material flow of Tantalum processing as well as recovery of residues and used products will be discussed.

Jan 1, 1995

By Toshitaka Ota, Hisao Suzuki, Minoru Takahashi

"Perovskite-type lead zinc niobate (PZN) exhibits excellent electrical properties such as high dielectric constant, high electrostrictive coefficient and superior piezoelectricity. Therefore, PZN ceramics are very promising for high performance electronic devices. However, perovskite phase PZN is not stable under the ambient atmosphere. Accordingly, it is very difficult to prepare single-phase perovskite PZN ceramics. In this study, A-site cation of lead was partially substituted for barium to stabilize the perovskite phase of the PZN (Ba-doped PZN) powder. In addition, molecular design of an alkoxide precursor was controlled for a low-temperature processing. As a result, molecular design to suppress the lead-volatilization during calcination was preferred for a low-temperature processing. Processing temperature for a single-phase perovskite was depended on the amount of barium dopant. Doping of20 mole% of barium resulted in the single phase perovskite at 900 °C. The temperature for the single phase perovskite of Ba-doped PZN powder, which depended upon the amount of Ba-doping, was lower than that of the powder prepared by the atmosphere controlled conventional powder processing at least by 150 °C.IntroductionFerroelectric thin films and powders with perovskite structure are of renewed interest for micro-electronic applications, including ferroelectric random access memory (FRAM), dynamic random access memory (DRAM), and thin-layer capacitors integrated onto a silicon wafer [1-3]. In addition, recent advancement in micro-machine requires a high performance micro-actuator [4]. A perovskite type relaxor of Pb(Zn113 Nb213)03 is one of the promising materials for a high performance capacitor and microactuator because of their high permittivity and electrostrictive coefficient [5]. Therefore, this paper focuses on the low temperature processing of Ba-doped PZN powders.Chemical solution deposition (CSD) from molecular-designed alkoxide precursor solution is one of the most promising techniques for processing high-performance powders and thin films because it offers precise control of compositions on a molecular scale as well as a low processing temperature [6]. However, chemical solution deposition of perovskite type PZN powders and ceramics are very difficult because of the formation of stable pyrochlore phases. Therefore in the past, PZN powders and single crystal have been prepared by the hydrothermal method or flux method as well as the partial substitution method of a A-site cation [7-10]. In this study, a suitable molecular design for a preparation of perovskite type Ba-doped PZN powders with a chemical solution deposition process is investigated as well as the effect of A-site cation substitution. Chemical solution deposition from molecular-designed alkoxide precursor solution is expected to decrease the amount of a A-site substitution and/or a crystallization temperature for a single phase perovskite. This paper describes ""the relation between molecular-design and processing temperatures for a single-phase perovskite of Ba-doped PZN powders in comparison with the conventional oxides mixing method."

Jan 1, 2000

By M. M. Monte

A method for removing metallic mercury from contaminated tailing, using the flotation process, is described. In order to define some relevant parameters for the mercury flotation system, microflotation and electrophoretic mobility tests were carried out on (pure) metallic mercury in the presence of several surfactants. Based on the results obtained from fundamental studies a series of bench scale flotation experiments with mercury containing tailings from two wetland sites in Brasil were done. The results of microflotation tests with mercury showed that by using cetyl trimethyl ammonium bromide, an increase in mercury flotability is observed in the acid pH range, whereas in the presence of potassium oleate the highest mercury flotability was found in the alkaline pH region. The mercury flotability using potassium amyl xanthate was improved by the addition at sodium dithionate as an activator. The bench scale flotation tests with contaminated tailings from Poconé (brazilian wetland site) showed a recovery of 70% when sodium dithionate was used as activator and potassium amyl xanthate as collector. The resulting coefficient of separation is around 60%. However, the results of the flotation experiments with fine fractions from amalgamation tailings from Peixoto de Azevedo (brazilian wetland site) showed a low mercury recovery (32%).The results from this work suggest that since in the Poconé site tailings, the metallic mercury is not completely associated to the finer particles, the flotation process to recover the metallic mercury seems very promisor.

Jan 1, 1996

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

By Laszlo Kadar, J. D. Lavers

"In the continuous casting of aluminum killed steel, the tundish nozzle often experiences clogging problems. Water model studies have shown that the clogging problem is dependent on the flow pattern in the nozzle entry region. In particular, the flow can separate at the entrance to the nozzle, leading to the development of a recirculation region. Although a nozzle can be designed such that no recirculation develops, even a small misalignment from the vertical positioning of the nozzle may render the design ineffective.To reduce the possibility of nozzle clogging, the recirculation zone must be reduced or eliminated. This may be achieved by moving the fluid downwards or raising the turbulence level in the separation region. In the case of a tundish nozzle, it is proposed that this can be achieved by using electromagnetic forces.To generate the required electromagnetic force, two systems are considered. The first is based on injecting a DC current; the second by using electromagnetic induction. Both methods are described in this paper. Order of magnitude calculations are provided to illustrate that both methods are essentially feasible. The performance of each method in terms of modifying the turbulent flow characteristics in the nozzle entry region is then examined using a numerical model. It is shown that both methods can greatly reduce the recirculation zone. A cylindrical nozzle was chosen for the model studies since it represents a worst case situation.On the basis of the model studies, it can be concluded that whereas both of the proposed methods have the potential to reduce the troublesome recirculation zone, the induction method appears to be simpler in terms of practical implementation."

Jan 1, 1999

By Seref Sonmez, Onuralp Yücel, Kagan Benzeşik

The aim of this study is processing of domestic molybdenum concentrate to produce technical grade molybdenum trioxide may be the starting material for the production of various molybdenum products. In order to determine the optimum parameters for the total oxidizing roasting process of molybdenite concentrate to produce MoO3 and purify the MoO3 product by removing the copper content; first, MoS2 was roasted by controlling reaction temperature and duration in a chamber type furnace. The highest Mo concentration rate was obtained as 56.6 wt% of Mo at 650 °C for the roasting duration of 45 min. Secondly, roasted product was leached with H2SO4 to remove copper. Leaching conditions were optimized by investigating the effects of different H2SO4 concentrations and S/L ratios. The minimum copper content was obtained as 0.13 wt% at leach residue. The raw materials and the products were characterized by using AAS (atomic absorption spectrometry) and XRD (X-Ray Diffraction) techniques.

Mar 1, 2017

By Neal Schwartz, Robert De Saro, Richard Rosenthal, Ed Kear

"A Stack Melter has been installed and is currently operating at Lexington Die Casting. The Stack Melter consists of a 1 meter (3 foot) diameter refractory tube, 2 meters (7 feet) high. Specification ingots are continuously fed to the top of the melter and piled to nearly the top. A burner fires through the scrap which melts the lower portion and preheats the upper portion. As the lower portion is melted, it is drawn out and the upper preheated scrap falls to a lower level where it in tum melts. The molten metal is fed to one of two holding furnaces for eventual delivery to a casting machine.The Stack Melter's energy use is approximately 2900 joules/g (1,250 Btu/lbm), resulting in an overall energy savings of about 58%. This energy savings is brought about primarily because the flue gases preheat the scrap and the flue gas temperature is dropped to well under 528°C (1000°F)."

Jan 1, 2000

By Tianjiao Luo

The electroless copper plating process for continuous carbon fiber using CuSO4?5H2O as the main salt and formaldehyde as reducing agent was experimentally studied, including the effects of pH values and concentration of chelating agents, stabilizing agents and reducing agent on the electroless plating process. The surface morphology and the composition of coating were investigated by means of Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS), and deposited the coating thickness was measured by way of dissolution. The results indicated that the pretreatment of carbon fiber before plating was so important. This pretreatment could prevent the formation of the black cores, furthermore, it could form many active absorption cores with Ag as the center on the carbon fiber surface. Used the optimized parameters in this process, which led to a stable solution for plating, a homogeneous copper coating was conducted with the carbon fiber plated with favorable mechanical performance and high adhesion strength.

Jan 1, 2006

By Takayuki Ichikawa

Hydrogen storage properties of ballmilled mixtures composed of the hydrogenated nano-structured carbon (CnanoHx) and lithium hydride (LiH) were examined by thermal and optical spectroscopic analyses. LiH needs higher temperature than 600°C for hydrogen desorption even under vacuum condition, while CnanoHx, which was mechanochemically synthesized from graphite powder by ballmilling under hydrogen atmosphere, reveals hydrogen and hydrocarbons desorption in wide temperature range from 300 to 800°C. Nevertheless, the composite of CnanoHxand LiH prepared by ballmilling desorbs hydrogen in relatively lower temperature range from 150 to 450°C. These phenomena indicate that the thermally liberated hydrocarbon radicals immediately react with LiH and release hydrogen instead of hydrocarbons emission, because CnanoHx contains hydrocarbon groups at the edge of nano-meter sized graphenes, which are recognized as IR active C-H stretching mode, and LiH is well-known as an ionic crystal. Furthermore, it is of interest that a nanostructural feature persists in this composite even after annealing at 350°C, which shows excellent cycle properties as hydrogen storage media.

Jan 1, 2006

By Jay. M. Khodadadi, Josef Štetina, František Kavicka

"With the aid of the proper original numerical model of solidification the instruction for preparation of input parameters for numerical simulation of technological processes, with change of the phase or structure, will be presented. A method of calculation analysis of influence of therrpophysical properties of materials entering the system of casting-mould-cores environment, and also of boundary conditions on the required simulation accuracy will be suggested. For the cast material, the influence of heat .conductivity, specific heat capacity, density and latent heat of phase transformation also has been analysed. For metallic or non-metallic moulding material"" the influence of the see main parameters has been analysed and, furthermore, their combination, influence of thermal conductivity, and of heat storage. The order of influence of all quoted parameters of a casting and moulding material was established. For example heat conductivity in the liquid state is on the last place. From the boundary conditions the -most important influence on the total solidification time and · on the mechanism of forming of temperature field has the ·boundary condition on the casting mould boundary, then follows the boundary condition on the level of a molten metal. The negligible influence has the boundary condition on the mould frame and on the bottom.IntroductionThe original and universal mathematical model of solidification, cooling and heating has been set up and checked, in order to be capable of analysing a one- to three-dimensional steady or unsteady temperature field of the casting-mould-environment system and, namely, of the system as a whole or its arbitrary parts, during any industrial technological process whose individual processes could be solidification, cooling, heating, refrigeration and others, in any sequence or singly. The model enables the simulation of traditional and also non-traditional technologies of casting in foundries, metallurgical plants, forging operations, heat treatment processes, etc. If solidification is not the matter, the metal part of the system need not be called the casting but a component, a block, a forging and the like."

Jan 1, 2000

By Olga Frank-Kamenetskaya

The experimental results of study of atmospheric corrosion processes on Saint-Petersburg bronze monuments surface, received in situ and by means of simulating experiments, have been discussed. Influence of the time factor on corrosion film (patina) mineral composition has been analyzed. Direct dependence between patina mineral composition and environmental conditions has been proved. The sequence of patina phases crystallization has been established. Effect of the chemical composition and heterogeneity of artistic bronze and also monument surface structure on the rate of corrosion process has been regarded. The time variations of mass of the crystallized in the hydrochloric acid vapor phases have been investigated. The kinetic laws of their development at the initial stage of formation, indicating simple (non chain) reactions, have been revealed.

Jan 1, 2006

By Beatryz C. Mendes, Henrique de Paula Santos, Kléos M. L. Cesar, Eduardo Antônio G. Marques, Maurício Paulo F. Fontes, Rita de Cássia S. S. Alvarenga

Inadequate discard of industrial solid waste is a risk to human health and to the environment. Aiming at softening environmental damage caused by deposition on soil of an ink residue, from washing of printers used in carton box packages, it is intended to incorporate this residue into soil-cement bricks. The residue has other use potentialities such as in screeds, pavement parts, fertilizer, paints, etc. However, to explore these potentialities it is fundamental to assess the risks that the several forms of use of this residue can cause. For such, in this work the chemical analysis of the residue was performed in order to know its main chemical compounds, in addition to its characteristics of leaching and solubilization. The chemical composition assay showed traces of some heavy metals such as Pb, Cd, Cr, Zn, Al and Cu, although the residue-generating company uses ink labeled as heavy metals free. Among the elements analyzed in leaching and solubilization, some had concentration above the limit allowed by The Brazilian Codes. This code is based on CFR—Title 40—Protection of Environment—Part 260–265—Harzardous waste management. Therefore, it is suggested that the residue has a limited use to avoid contamination of ground water.

Mar 1, 2017

By Toshihide Takenaka

The management of radioactivated stainless steel from a terminated nuclear reactor will become an important subject in the near future. The separation of the elements in stainless steel should be effective to reduce the management labor. In this study, the separation of the elements in stainless steel by an electrorefining tcchnique was investigated in an aqueous solution. The electrochemical reactions of the elements in stainless steel werc studied by voltammetry and potentio-static electrolysis was carried out. A stainless steel anode was dissolved electro-chcmically with good anodic current etliciency in a chloride solution. The residue, where Ni was concentrated, was found on the anode after electrolysis. The electrodeposit in a stainless steel cathode consisted mainly of Fe and Cr and the Ni content in it was less than 0.5wt% under suitable condition. It is concluded that an electrorefining technique is effective for the separation of the elements in stainless steel.

Jan 1, 2003

By Jorge A. S. Tenorio, Pedro F. A. Prado, Denise C. R. Espinosa

There is an increasing challenge of waste management regarding the growth of photovoltaic (PV) technology. Often overlooked by its environmental benefits of greenhouse gas emission reduction, PV technology contain metals that are highly hazardous for the environment. Amorphous silicon (a-Si) PV modules employ indium-tin-oxide as transparent conductive oxide and given the high price of indium its recovery could be advantageous from an economic perspective as well. Leaching of indium was predicted by comparing the Pourbaix diagram with the values of oxidoreduction potential and pH measured on a phosphoric acid solution. The a-Si panel was subjected to thermal treatment to remove the proprietary, protective coating and allow leaching to occur. Then, indium could be leached by phosphoric acid in a jacketed reactor, reaching a concentration of 55 ppm (67% leaching rate) with a 0.2 g/mL of a-Si panel to aqueous solution ratio. The leaching of indium with phosphoric acid is novel and could open doors for many other recycling routes for solar panels.

Mar 1, 2018