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1.
The depletion of high grade ores and accumulation of huge quantities of metallic scrap and metallurgical wastes have generated significant interest in their processing. In this paper, both pyrometallurgical, as well as hydrometal-lurgical, methods for metal recovery from scrap and wastes (viz., slag, dusts, aqueous effluents, sludge and residues) are reviewed. Scrap recycling and the processing of metallurgical wastes will pollute the environment to a lesser extent and consume less energy compared to the primary metal production. Reprocessing metallurgical waste (viz., slag, red mud, etc.) serves a social objective and ensures raw materials conservation. Research trends reveal that hydrometallurgy may play a dominant role in the waste treatment. Recently developed processes like continuous ion exchange and fluidized bed electrolysis may be used in the future for recovering metals from dilute solutions.  相似文献   

2.
Germanium products are well suited for many advanced materials applications—lens blanks for infrared optics, dioxide for electronic and catalyst use, “intrinsic” metal for radiation detectors, and electronic grade tetrachloride for optical fibers. Before undertaking these applications, however, the germanium must first be recovered. This article reviews the germanium extraction and refining techniques of the late 1950’s and early 60’s, as practiced by American Metal Climax (now AMAX), and compares the practices with the more recent developments presented in current technical literature. Overall, there have been no major changes in the process chemistry of germanium extraction and refining in the period surveyed. Significant changes have, however, taken place in the engineering of process plants for producing semiconductor grade germanium. The use of zone refining for final purification of germanium metal to semiconductor grade is still required and will probably continue for some time. Finally, considerably more thermodynamic data is available for predicting the optimal germanium recovery conditions from smelter fumes than existed twenty years ago. As a result, less experimental work should be required to optimize recovery.  相似文献   

3.
As part of its effort to devise suitable technology for processing low-grade domestic materials and recycling wastes, the U.S. Bureau of Mines has evaluated the feasibility of smelting a chromite concentrate derived from residues generated by the processing of nickel and cobalt from domestic later-ites. The product sought was a high-carbon ferrochromium suitable for stainless- and alloy-steel production. The concentrate was blended with re-ductants and fluxing constituents and was smelted under submerged arc conditions in a laboratory-scale, single-phase ac electric arc furnace. The results revealed that metallurgical-grade coke provides the best quality product. High-carbon ferrochromium, which met ASTM specifications except for phosphorus and sulfur, was obtained. Agglomeration of the charge materials was not required.  相似文献   

4.
The inhibiting effect of Gatifloxacin drug (1-cyclopropyl-6-fluoro-1,4-dihydro-8-methoxy-7-(3-methyl-1-piperazinyl)-4-oxo-3-quinolinecarboxylic acid sesquihydrate) on carbon steel corrosion in 1.0M HCl solution was studied using weight loss, galvanostatic polarization and electrochemical impedance spectroscopy (EIS) methods. The inhibition efficiency was found to increase with increasing the concentration of the inhibitor and deceased with increasing the temperature. The polarization studies showed that drug compound acted as a mixed-type inhibitor. The inhibiting effect of this compound was interpreted in view of its adsorption on the metal surface. The adsorption of this compound was found to obey Langmuir adsorption isotherm. The possibility of chemisorption through a complex formation between metal ions and the inhibitor chelating centers was also discussed depending on the results derived from UV-visible spectrophotometric measurements as well as conductometric titration.  相似文献   

5.
Ultrasonic degassing of liquid metals has been studied over the last years, but it has been limited to laboratorial scale experiments of low volumes of melt. In this work, the combined effect of acoustic cavitation with metal agitation induced by the mechanical vibration of the ultrasonic radiator itself was studied, using a specially designed low frequency mechanical vibrator coupled to the ultrasonic degassing unit. Liquid motion in water was characterized by high speed digital Photron—FastCam APX RS video camera and Laser Doppler Anemometry to select the most favorable US and mechanical vibrator frequencies to induce suitable water stirring. Selected parameters were used to degas 10 L of AlSi9Cu3(Fe) alloy. A suitable piezoelectric sensor was used to measure sound pressure at different distances from the sonotrode to identify the zone of higher acoustic activity. Results have shown that melt stirring significantly improves US degassing efficiency (since it is possible to achieve almost the aluminum alloy theoretical density after 3 min processing time) which contributed to increase the tensile properties of the alloy.  相似文献   

6.
The electrochemical, spectroscopic and microscopic analyses of cytochrome c and its immobilization on bare glassy carbon (GC) and platinum (Pt) electrodes were performed. Cytochrome c interaction was examined by studying cyanide and arsenic as model compounds for these types of behavior. Subtractively normalized interfacial Fourier transform infrared (SNIFTIR) spectroscopy, fluorescence and electrochemical methods, Fourier transform infrared (FTIR) spectroscopy and atomic force microscopy (AFM) were used to characterize the protein in the immobilized state and to confirm that the protein was not denatured upon binding to the pre-treated bare GC and Pt electrodes. The spherical morphology of the immobilized protein, which is typical of native cytochrome c, was observed using AFM. The protein binding was monitored as a decrease in peak currents (by CV) for the immobilized protein. Under analysis was also a decrease in emission intensities by fluorescence in solution, by the FTIR and SNIFTIR spectroscopies. Fluorescence and AFM proved the existence of the binding process between the protein and the analytes. This behavior was confirmed by the FTIR and SNIFTIR spectroscopies, which gave evidence that the binding event took place at the amino acids side chain of the protein.  相似文献   

7.
Spent color bleach-fix solution (CBFS), a product of photographic processing operations, is a potential source of silver. Of the extraction reactors used in recovering this silver, the rotating cylindrical electrode (RCE) has an advantage in that it provides improved mass transfer with an extended effective surface area. In addition, the application of a potentiostatic technique allows the silver deposition reaction to take place preferentially, without the formation of silver sulfide. The process consists of prior physical treatment, subsequent chemical reduction of the ferric-EDTA (ethylene diamine tetra-acetic acid) complex present in the CBFS with sodium dithionite (monitored by measuring the redox potential of Fe3+/Fe2+ couple), followed by electrodeposition of silver in a divided cell using a cation exchange membrane. The combined procedure results in increased current efficiency and reduced electrolysis time.  相似文献   

8.
During electroplating operations, metal-rich sludges are generated which have been classified as hazardous by the U.S. Environmental Protection Agency (EPA). Despite a regulatory situation which sometimes hampers rather than assists recycling efforts, these plating wastes, designated F006, can be viewed as a natural resource if properly handled. Specifically, F006 wastes can be effectively treated using hydro-and/or pyrometallurgical techniques to recover such metals as copper, nickel, zinc, chrome, lead and tin. To do this, however, a number of procedural obstacles must be conquered, including more thoughtful management of the waste stream by electroplaters and the exercise of greater caution by the EPA to make sure that regulations do not discourage recyclers from handling materials classified as hazardous.  相似文献   

9.
The aim of this work was to characterize the structure and electrochemical behavior of a silicon-doped diamond-like carbon (DLC) film deposited by hollow cathode plasma immersion ion process (HCPIIP) on a cylinder liner for heavy duty diesel engine. The film structure was characterized by scanning electron microscopy, x-ray diffraction, and Raman spectroscopy. Nanoindentation tests were performed to evaluate the film hardness and Young’s modulus. Monitoring of the open circuit potential with time, electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization measurements was performed in a solution consisting of 0.25 wt.% NaCl + 5.0 wt.% H2SO4 at room temperature. The results showed that the film has an amorphous nature consisting of a mixture of sp3 and sp2-like carbon bonds with an I D/I G ratio of 0.87. Nanoindentation tests showed that the H/E ratio of the DLC film was 0.102. EIS measurements indicated that the impedance values were higher for the DLC-coated material. Potentiodynamic polarization curves revealed that the corrosion current density was almost three times lower for the coated alloy. The HCPIIP process was considered successful to enhance the surface properties of the cylinder liner.  相似文献   

10.
This work reports an efficient reactor, i.e., oxygen-rich side blow furnace (OSBF), for high-lead slag reduction. An OSBF with a cross-sectional area of 8.4 m2 was applied in an industrial-scale test and the results were compared with those from a traditional high-lead slag reduction reactor, i.e., blast furnace (BF), with which an additional electric heating fore well (EHFW) was connected for slag cleaning. By using the OSBF, Pb and Cu recoveries were raised by 1.07% and 7.99% compared with those from the traditional BF+EHFW, respectively. The optimal slag type for recovering metal values in the OSBF was also analyzed. Within the range of Fe/SiO2 = 1.56–1.87 and CaO/SiO2 = 0.8–1.05, lower Pb and Cu contents of the slag can be achieved with Fe/SiO2 = 1.65–1.75 and CaO/SiO2 = 1.0.  相似文献   

11.
There are a number of two-phase alloys which are technologically important. These include α-β titanium alloys and two-phase steels. Modeling of deformation of such alloys, however, is a difficult task for the simple reason that a number of factors have to be considered simultaneously. Whenever a metal consisting of more than one-phase with different stress-strain behavior is subjected to stress, neither the stresses nor the strains are constant. The softer phase deforms more than the harder phase. The actual stress and strain distributions depend on the morphology of phases. Therefore, the simple law of mixtures rule is inadequate to study stress/strain behavior in these two phase materials. The Finite Element Method (FEM), which has been successfully used for stress analysis, appears to be a viable tool for studying stress-strain behavior of two-phase materials. Some of the predictions of FEM were corroborated by experiment. With some improvements in computer programs dealing with FEM, this method can be applied for various problems of stress-strain and fracture behavior in two-phase materials.  相似文献   

12.
A study of several engineering alloys implanted at ultrahigh current densities has revealed that the process induces no change in the bulk microsctructure of the materials. Even though temperatures induced during processing exceed the transformation (tempering and annealing) temperatures, there is insufficient time for nucleation and growth reactions to occur during the temperature excursion associated with typical implantation dose and energy conditions. Substantially lower costs should accompany the shorter duration ultrahigh current density implantation process. Auger electron spectrographs reveal a substantially extended nitrogen range over those observed at low current densities (four-fold increase). This enhanced range appears to be due to radiation enhanced diffusion effects. Deeper penetration could lead to more durable surface layers.  相似文献   

13.
A computational approach, which targets on the prediction of SiC recession caused by SiO2 scale volatility under combustion environments, was developed in this study. In this approach, thermodynamic calculation was integrated with a gaseous-diffusion model to calculate the fluxes of volatile species, such as SiO(g), Si(OH)4(g), SiO(OH)2(g), and SiO(OH)(g), produced by the reaction of SiO2 scale with the combustion air. The resulted weight loss of SiC was then calculated under a variety of combustion environments. The benefit of using environmental barrier coating (EBC) in the protection of SiC from recession was demonstrated by the calculation. It is shown that the weight loss of SiC-based ceramics could be significantly reduced when EBCs, such as mullite (Al6Si2O13 or written as 3Al2O3·2SiO2) or SrAS2 (SrO·Al2O3·2SiO2), are used. The effects of combustion conditions, such as temperature and total pressure, on the volatility of SiO2 scale were also discussed.  相似文献   

14.
Rare earth (lanthanide metals) addiiions to continuously cast steel are particularly advantageous because of their ability to refine as-cast structures, reduce segregation and increase hot ductility at temperatures just below that of solidification. The complete shape control of sulfides in steels containing Rare Earth Metals (REM), whether continuously cast or ingot cast, is primarily responsible for improvements in ductility related mechanical properties, weldability, fatigue resistance and resistance to hydrogen damage. Complete sulfide shape control can be obtained with REM additions at sulfur levels as high as.020%. The greatest improvements, however, are obtained with REM additions to low sulfur steels. However, to achieve full operational advantages afforded by REM, nozzle blockage problems must be circumvented. Water model studies indicate a possible solution.  相似文献   

15.
Several advances in materials technology have resulted from the operation of the Savannah River nuclear materials production facility in Aiken, South Carolina. Among the research contributions of the Savannah River Site (SRS) to materials science and engineering are a greater understanding of stress-corrosion cracking and hydrogen embrittlement, and the development of technologies utilizing nuclear sources for heat and radiation. These advances arose from the technologies developed at SRS for the production, separation and packaging of nuclear materials.  相似文献   

16.
Electroless Ni-Co-P coating and Ni-Co-P-SiO2 nanocomposites were successfully applied on AZ91D magnesium alloy via environmentally friendly cerium-lanthanum-permanganate treatment and their properties were compared with traditionally binary Ni-P coating. The prepared coatings were analyzed using scanning electron microscopy, x-ray diffraction, and energy dispersive x-ray spectroscopy. Moreover, the corrosion behavior of the coatings in 3.5 wt.% NaCl was evaluated by two electrochemical methods. It is found that the Ni-Co-P coating possesses more uniform and compact structure and better corrosion protection characteristics in comparison with the Ni-P coating. The plating rate of Ni-Co-P bath is relatively lower than the Ni-P bath, but it significantly increases after addition of SiO2 nanoparticles more probably due to adsorption of silica nanoparticles on alloy surface. The corrosion resistance of Ni-Co-P-SiO2 composite coatings was superior with respect to Ni-P and Ni-Co-P coatings due to formation of thick and compact coating with tortuous grain boundaries.  相似文献   

17.
Sorption conditions (on hyper-cross-linked polystyrene) have been developed for six phenylcarboxylic acids (PCA), which are biomarkers of sepsis, from aqueous standard test solutions and conditions of elution of these acids for subsequent derivatization and analysis by gas chromatography-mass spectrometry (GC-MS). The conditions facilitate detection of PCA in solution at the level (and below) of content of these compounds in blood serum of normal patients. Group extraction of different in polarity required acids from aqueous solutions has been performed selectively with regard to cholesterol adopted as peculiar marker of high boiling interfering compounds. Application of the developed experimental procedure will make it possible to increase significantly the rate of express analysis for diagnostics of sepsis at early stages of development.  相似文献   

18.
Thermal spray processes have been widely used to minimize losses caused by wear mechanisms. Sprayed deposits using conventional wire and powder materials have been long solving tribological problems in engineering equipment. More recently, the option for new different technologies and consumables like nanostructured powder materials and nanocomposite cored wires have expanded the possibilities for technical solutions. Cored wire technology allows the use of compositions that cannot be drawn into wire form like carbides in metallic matrix and high-temperature materials, thus, intensifying the use of spraying processes with low operating cost to demanding wear and corrosion applications. The objective of this work was to study the mechanical characteristics and wear performance of coatings obtained by Flame, Wire Arc, and HVOF spraying using selected nanostructured WC10Co4Cr, WC12Co, and Fe-based 140 MXC powder and wire materials. Abrasive wear performance of the coatings was determinate following the ASTM G-65 standard. Based on the results, a higher abrasive wear resistance was found for the HVOF-sprayed WC10Co4Cr nanostructured coating.  相似文献   

19.
A review of the energy innovations for the electric arc furnace (EAF) steelmaking route is discussed. Preheating of scrap using vertical and horizontal shafts that have been commercially successful in lowering the energy consumption to as much as 90 kWh/t reaching almost the operational limit to heating input scrap materials into the EAF is discussed. Bucket-type and twin-shell preheaters have also shown to be effective in lowering the overall power consumption by 60 kWh/t, but these have been less effective than the vertical shaft-type preheaters. Beyond the scrap preheating technologies, the utilization of waste heat of the slags from the laboratory scale to the pilot scale has shown possible implementation of a granulation and subsequent heat exchange with forced air for energy recovery from the hot slags. Novel techniques to increase metal recovery have shown that laboratory-scale testing of localized Fe concentration into the primary spinel crystals was possible allowing the separation of an Fe-rich crystal from an Fe-depleted amorphous phase. A possible future process for converting the thermal energy of the CO/CO2 off-gases from the EAF into chemical energy was introduced.  相似文献   

20.
In the present work iron oxide nanoparticles have been synthesized by alkaline solvo thermal method using anhydrous ferric chloride, sodium hydroxide, polyethylene glycol and cetyl trimethyl ammonium bromide and characterized by X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Field Emission Scanning Electron Microscopy (FESEM), Energy-dispersive X-ray Spectroscopy (EDX) and Thermal Gravimetric Analysis (TGA). XRD indicated that the product is a mixture of different phases of iron oxide viz. gamma-Fe2O3 (maghemite, tetragonal), Fe2O3 (maghemite, cubic), Fe3O4 (magnetite, cubic) and ?-Fe2O3(epsilon iron oxide). FESEM studies indicated that size of the particles is observed in the range of about 19.8 nm to 48 nm. EDX spectral analysis reveals the presence of carbon, oxygen, iron in the synthesized nanoparticles. The FTIR spectra indicated absorption bands due to O-H stretching, C-O bending, N-H stretching and bending, C-H stretching and Fe-O stretching vibrations. TGA curve represented weight loss of around 3.0446 % in the sample at temperature of about 180°C due to the elimination of the water molecules absorbed by the nanoparticles from the atmosphere.  相似文献   

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