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By L Mariani, G. Mendoza-Suarez

In this investigation, TiH2 powders were coated with copper and nickel by electroless plating to delay hydrogen evolution. Copper-coated samples were found to have a mixed acicular (2D growth) and cauliflower (3D growth) morphology whereas the nickel-coated samples had a cauliflower morphology. Examinations of the coated powder cross-sections revealed that the coating thickness ranges from 0.2 µm to 4 µm. Uncoated areas on the powder surface and coating flakes unattached to TiH2 particles suggest poor adhesion between the coating and the substrate. The phase transformation undergone by the TiH2 during dehydrogenation was studied in samples taken at intermediary points in the heating cycles and examined by XRD. The findings reveal that as the powder is heated from room temperature to 800°C, it changes from TiH1.971 to Tiu and to aTi. Differential Thermal Analysis (DTA) was performed to study the effects of the coatings on the temperature of hydrogen release. It was found that increasing the number of plating iterations, and therefore the thickness of the coating, creates a significant shift in the temperature of gas release.

Jan 1, 2006

Silver has the highest electrical conductivity of all metals and consequently this property is an attractive feature which makes it a leading candidate for use in electronic devices. The research conducted was focused primarily on the development of a process for obtaining a deposited silver-coating onto alumina, for applications related to electrical-conducting devices and, ancillarily, catalysts. Alumina balls and plane substrates were utilized for the investigation. The coating process employed an aqueous arnmoniacal silver-nitrate electrolytes with a formaldehyde solution as the reductant. Modifying additives - an activator which would be expected to promote good deposition-characteristics onto the (dielectric) substrate and an inhibitor which would obviate homogeneous reduction (precipitation) of silver was observed when the activator-containing silver-electrolyte reductant constituents were combined. However, the silver-electrolyte/reductant system with inhibitor could be employed (at 80°C) to achieve a viable (subject to future research optimization) coating on alumina. The influence of the processing temperature on the deposition process was delineated during the course of the research. The morphology of the deposited-silver on the alumina balls was assessed by SEM imaging. A tape-peel test was employed, with the plane substrates, to semi-quantitatively characterize the adhesion to the alumina.

Jan 1, 1998

By M. Dadvand, G. Kipuros, A. Dadvand

"The ability to codeposit fillers within a nickel matrix has led to the production of a new generation of cermet coatings with properties useful for various applications. Hexagonal boron nitride (hBN) is a ceramic-type particulate matter with thermal conductivity, thermal stability, inertness, and lubricity properties that allow it to be codeposited. In this paper, a method was developed for modifying hBN surfaces to allow them to be uniformly dispersed in water-based solutions such as an electroless nickel plating bath. hBN surface modification improved wear performance of the electroless plated cermet due to enhanced interaction between the particulate and nickel matrix. RÉSUMÉ La capacité à effectuer un dépôt simultané de charges dans une matrice nickel a abouti à la production d’une nouvelle génération de revêtements cermet (une combinaison de céramique et de métal) dotés de propriétés très utiles pour diverses applications. Le nitrure de bore hexagonal (h-BN) est une matière particulaire de type céramique utilisée pour ses excellentes conductivité et stabilité thermiques, son inertie ainsi que son caractère lubrifiant, qui permettent son dépôt simultané. Cet article explore une méthode mise au point pour modifier les surfaces du h-BN de manière à ce qu’elles se répandent uniformément dans des solutions aqueuses telles qu’un bain de dépôt autocatalytique de nickel. La modification des surfaces du h-BN a amélioré la résistance à l’usure du placage autocatalytique du cermet en raison d’une interaction accrue entre la matière particulaire et la matrice nickel.INTRODUCTION Electroless nickel alloy coatings can be used for many applications; however, the need for improved tribological properties such as higher wear resistance and better lubricity has increased interest in incorporating particulates (fillers) into the nickel matrix by codepositing the particulates with nickel during the plating process. The selection of the particulate type depends on the desired properties (Sahoo & Das, 2011; Sudagar, Lian, & Sha, 2013). In terms of tribological applications, electroless nickel-based composites are categorized mainly into lubricating and wear-resistant composite coatings depending on the type of particles incorporated. The electroless nickel-phosphorus (Ni-P) composite coatings are composed of codeposited solid lubricants such as polytetrafluoroethylene (PTFE), graphite, WS2, MoS2, and hexagonal boron nitride (hBN) and, compared to nanocomposite electroless Ni-P coatings, they demonstrate a lower coefficient of friction. On the other hand, the nickel-phosphorus wear-resistant composite coatings are composed of hard particles such as silicon carbide (SiC), aluminum oxide (Al2O3), boron carbide (B4C), silicon nitride (Si3N4), diamond, tungsten carbide (WC), and zirconium oxide (ZrO2) and, compared to nanocomposite electroless Ni-P coatings, they have higher hardness and better wear resistance (Sahoo & Das, 2011; Sudagar et al., 2013; Parucker, Klein, Binder, Ristow, & Binder, 2014; Chakarova, Georgieva, Petrova, Dobreva, & Stoychev, 2016)."

Jan 1, 2018

By Gregor Mori

Niobium electrolysis has been performed in a NaCl-KCl-NaF-NbCls electrolyte. By means of electrolytic .refining the average valency of the niobium ions was determined as well as the crystallization behaviour. In electrowinning runs the influence of the main parameters such as temperature, RF (mole ratio F/Nb), chemical prereduction, niobium content of the melt and current density has been determined with respect to low specific energy consumption and high purity of the deposit.

Jan 1, 1995

By Zhihe Dou, Yu Fang, Zimu Zhang, Yan Liu, Xiaoli Jiang Dianhua Zhang, Guanting Liu

"With the idea of “waste control by waste itself”, we come up with the crafts of using waste calcium carbide to mineralize CO2 in electrolytic aluminum waste gas, design and make out “Venturi gas-liquid-solid three stage reactor”, do experiments under the system of CO2-Ca(OH)2, investigate the influence on gas absorption by pH meter; investigate the influence on diameter distribution , rise velocity of bubble and local gas hold-up by dual conductivity probes; investigated the absorption of CO2 in every stage reactor under different initial proportion of CO2 by intelligent gas measurement system. The results showed that the reactor can fully absorb the CO2 in waste gas, and it has largely shorten the time of absorption and improve the CO2 utilization compared with the single stage reactor.The residual proportion of CO2 in the gas is below 0.08% through the absorption of three stage reactor,which show that absorption is extremely improved.IntroductionCarbide slag is a kind of polluting hydrolysis reaction byproducts in producing carbide in wet reactor, and it is mainly comprised by Ca(OH)2, It's estimated that there are about million tons carbide slag are piled up per year. Carbide slag is a kind of industrial wastes that hard to deal with ,which are treated by land filled in the past. It would not only occupy a lot of land, but also lead to secondary pollution [1].CO2 is the main greenhouse gas by now. In 2010, global CO2 emission has reached 33.5 billion tons, while China has now become the world's second largest emitter of CO2, emissions accounting for about one-seventh of the world [2].As the experts estimates, the greenhouse gas emission of whole nonferrous metal industry may over 0.6 billion tons per year, while CO2 emission of electrolytic aluminum is 0.334 billion tons per year [3]. So it is necessary and pressing to discover the reusing CO2 of electrolytic aluminum. With the idea of “waste control by waste itself”, we came up with the crafts of using carbide slag to mineralize the CO2 in electrolytic aluminum waste gas, which was experimented on the counterflow-three stage-venturi reactor,and studied the local gas holdup, residual concentration of CO2 and the volumetric transfer coefficient in the reactor."

Jan 1, 2014

By W. E. Mitchell

ELECTROLYTIC, production of cadmium at the Great Falls plant started in the first part of the year 1925. Prior to that time, an experi¬mental unit had been in operation for a few months during the year . 1922. At present the plant is the largest producer of cadmium, not only in the United States but in the world. Electrolytic cadmium is characterized by its very low content of impurities. The main impurities, which are lead, copper, zinc, and iron, do not aggregate more than 0.05 per cent., leaving a cadmium content better than 99.95 per cent. The consumption of cadmium has increased rapidly since the war, with the growing use in the plating industry. Cadmium plating has come into prominence because of its connection with the automobile and radio industries. As a protective coating, a deposit of, cadmium is superior to zinc. Cadmium is also used extensively in alloys. Important among these is the alloy with copper used in telephone and trolley wire. In proportion of 0.5 to 1.2 per cent., cadmium adds materially to the strength and wearing qualities. Practically all commercial zinc concentrates contain a small amount of cadmium. In the electrolytic zinc process, the cadmium that is dissolved in the regular leaching operation is removed from solution with metallic zinc, generally added in the form of zinc dust. This precipitate also contains the copper taken into solution and the excess of zinc dust, which is required in order to insure a complete removal of all impurities. The precipitate is treated by a separate process to recover the copper, cadmium and excess zinc. In order to make the metals more soluble and to render insoluble such impurities as iron, arsenic and antimony, the precipitate is roasted. The roasting is carried out in gas-fired McDougall furnaces, with a roasting temperature of about 700° C.

Jan 1, 1930

As the Mount Morgan electrolytic chlorine plant is the first of its kind installed in Australia, and as the details of this method of producing chlorine have, up to the present time, been kept more or less secret all over the world, the author trusts that this paper may fill a gap in the technical literature of the subject.When an electric current is passed through a strong solution of sodium chloride the following reaction takes place -2 NaCl + 2 H 20 = 2 NaOH + C1 2 + H 2 Chlorine gas is liberated at the anode or entering pole of the current, while caustic soda and hydrogen are formed at the cathode or leaving pole of the current. If the two electrodes be simply immersed in a vessel containing salt and the current be turned on, there will be no result save slight smell of escaping chlorine gas. The passage of the current will have certainly split up the salt water according to the above equation, but as the products would be in juxtaposition they would immediately reunite, and the electrical energy would have been spent without any beneficial result having been obtained. Therefore, the all-important problem in designing an electrolytic chlorine cell is the finding of some effective means of isolating from each other the chlorine and caustic: soda as soon as liberated from the...

Jan 1, 1911

By W. K. Tolley

The U.S. Bureau of Mines (USBM) is currently investigating the electrochemistry of mineral flotation. A significant need in this area is greater reliability of sensors. The USBM is testing electrolytic methods to clean and condition redox-sensing electrodes to improve the reliability and extend the service life of these instruments in the harsh physical and chemical environment of mineral processing slurries. A novel method for removing scale from fouled electrodes has been developed that includes anodic polarization to 1.2 V versus the Ag/AgCl reference potential, followed by brief potentiodynamic conditioning. Laboratory results show that this technique removes calcarious deposits from gold sensing electrodes and returns the electrode to useful service within approximately 10 min. Mechanical abrasion to remove the scale is thereby avoided.

Jan 1, 1994

By Jackson Jenkins

The second survey of world copper SXEW plants has been completed. Solvent extraction and electrowinning data published in 1996 has been updated and leach data from seventeen plants is now included. The following pages list the results of the thirty- two plants that responded to the survey. Selected information is summarized in graphical form.

Jan 1, 1999

By K. Koyama

As a study to establish a new energy-saving copper recycling process, the copper deposition at a cathode and oxidation of copper(I) at an anode from ammoniacal alkaline solutions containing Cu(I) or Cu(II) were investigated in order to examine the feasibility of electrolysis in this solution.. The current efficiencies were greater than 95% in the current density range of 200 to 1000 A m-2. The current efficiency decreased with the increasing Cu(II) concentration and temperature. In the batch-type electrolysis at the anode, during the initial stage, the current efficiencies were 100%, and the anode potentials ranged from 0 to 0.15V vs. SHE at a current density of 100 A m-2. During the subsequent stage, the current efficiency decreased with time, and the anode potential was around 1.35V vs. SHE where oxygen evolution at the anode surface was observed. As a result, the present electrolytic method can be the core technology in the said copper recycling process.

Jan 1, 2007

World copper electrowinning tankhouse plant practices have been surveyed. This survey is a supplement to previous surveys that have been carried out in 1995, 1999, 2001, 2002 and 2003. On a world basis, process technology trends include the further installation of automated electrode handling systems including permanent cathode systems, automated cathode handling machines, fully automatic cranes and polymer concrete cells. Designs also have included larger electrode sizes and higher electrolyte flows and current densities. Overall these trends have further resulted in optimized tank house productivities and improved electrowon cathode purity. Most greenfield copper electrowinning projects are occurring in South America and Central Africa.

Jan 1, 2007

By W. G. Davenport

A survey of world copper refining tankhouse .practices has been carried out. This paper compiles the results and examines changes in operating practices .since the similar 1987, 1991 and 1995 surveys. Continuing trends are the installation of ISA Process and Kidd Process stainless steel cathode technology, polymer concrete cells, anode preparation machines and automatic cranes. Instrumentation and automatic control are increasing, particularly for addition agent optimization; solvent extraction .and ion exchange techniques are being increasingly applied for electrolyte purification. The overall consequences of these changes have been 'improved cathode purities and enhanced tankhouse productivities.

Jan 1, 1999

By M. Moats

World copper refining tankhouse practices have been surveyed. This survey is a supplement to previous surveys that have been carried out in the 1987, 1991, 1995, 1999, 2001 and 2003. On a world basis, process technology trends include the further installation of automated electrode handling systems including permanent cathode systems, automatic anode preparation and cathode handling machines, section switches, fully automatic cranes and polymer concrete cells. General plant process control has increased with more automation of material handling in the copper refining tankhouse. The general trend for most greenfield copper refining projects remains in eastern Asia.

Jan 1, 2007

By John H. Schloen

"The object of this paper is to review electrolytic copper refining as it was in 1954(1), as it is now in 1984, and to comment on the many improvements which have been made in the last thirty years.In 1954, and even in 1984, the ASTM specification B 115 for cathode copper was 99.90% minimum copper plus silver content and 100% minimum electrical conductivity, IACS standard. However, to meet competition and to satisfy the requirements of the fabricators and the electrical industry, the electrolytic refinery must supply a product of 99.95% to 99.96% minimum copper content, and 101fJlo minimum electrical conductivity.The range of cathode impurities reported by 20 major copper refineries in 1954 are given in Table I.The much more rigid British Specification, DD 78, for high-purity cathode copper, specifies individual elements, as well as groups of elements, as shown in Table 2.The Svenska test has been replaced by a similar procedure which uses 2.r mm diameter wire. The ISO test is the one listed in the DD 78 specification. In Table 3, corresponding values for the Svenska and ISO test s are given for various wire bar coppers."

Jan 1, 1986

By John H. Schloen

Copper refineries are constantly looking for methods to upgrade their plants to reduce refining costs and to improve the purity of their electrolytic cathodes at the same time that the purity of the anodes they refine is being lowered by the rehabilitation of reverberatory furnace smelters to one of the direct smelting processes. The comments given below are based on the answers to the questionnaire returned bf the 36 copper refineries that represent 66% of the western world s refining capacity. Eleven refineries employ some form of uniform weight anade casting, e.g., Outokumpu, Contilanode, Mitsubishi, Lurgi, or Hazelett. This type of anode casting presents the best possibility for improving cathode purity. The cathode press of Phelps Dadge can improve current efficiencies and cathode quality. The press is used on first-run cathodes, after 48-60 hours, on half-cells at a time without interruption of the cell current. One refinery interrupts current for sever.al hours to allow the anode slime to settle before the, cathode pressing. The cathode press is now used at eight refineries. Apart from periodic reverse current (PRC), it is not expected that current densities will be increased. Thirty refineries, using direct current, average 231 amps/M, with a low of 178 and a high of 350. Five refineries use PRC at an average of 338 amps/M, with a low of 290 and a high of 380. Current efficiencies are good at an average of 94%, with a low of 88% and a high of 99% for the 34 refineries that reported. It must be remembered that the cycle efficiency with PRC is about 93%., so that the effective current efficiency with PRC would be only .94 X .93 or 87% However, PRC should be considered seriously for refinery expansions because it can save about 25% on capital costs.

Jan 1, 1987

By David Kellogg

THE electrodeposition of iron has been practiced for many years. The earlier work along this line was directed toward the preparation of pure metal, but later applications were the production of thin adherent coatings as used in the electrotyping of Russian banknotes in 1860. A historical discussion of this subject, however, would require too much space and would be inconclusive. Much has been written on the subject but no two experimenters use the same methods or materials. During the war, the British army repair, shops developed a method for building up worn parts of automotive machinery, aero engines, etc., using the cold surfate . bath and low-current density method.1 The method has been used successfully in commercial work for the production of about 6000 repaired parts, therefore experiments along the same lines have since been made at the Westinghouse research laboratory. The apparatus used was essentially that described in the article mentioned except that the current -used for cleaning was obtained from a 3/4-kw. 60-volt, house-lighting generator, direct connected to a 2-h.p., 870-r.p.m., 440-volt, three-phase, type CS induction motor; while the plating current was taken from the storage batteries at any desired voltage. The anodes were made from 0.036 in. (0.9 mm.) Armco iron made into cylinders 5 in. (127 mm.) long by 8 in. (203 mm.) in diameter with a disk of 1/8 -in. (3.17 mm.) micarta, having a 2 in. hole in the center fitted at each end of the cylinder for stirring. The anodes were hung on a wooden rocker frame driven by a wooden connecting I rod directly connected to a small reducing gear, such as is sold by most of the apparatus supply firms; 3 gal. stoneware crocks were used as containers. The solution used by Thomas, 75 gm. of the crystallized ferrous ammonium sulfate per liter, was tried, using the current density recommended by him; namely, 0.33 amp. per sq. dm. Under these conditions the deposit on a ½ -in.

Jan 2, 1922

By Basant L. Tiwari

An electrolytic process, based on a three-layer concentration cell, to extract magnesium from commercial aluminum alloy scrap has been examined. The process was repeatedly tested at 1025 K with two cells of d1fferent sizes, 0.6 kg and 5 kg feed aluminum, to have a better understanding of the opera ting parameters and evaluate the scale-up potential. In both cells, the magnesium content of the scrap was selectively reduced ?from 1. 1 to less than 0.1 wt.% at anodic current dens-Hy as high as 1. 1 A/cm2 with current efficiency exceeding 85%. Magnesium was recovered in the form of salt coated globules. Comparison of performances for the two cells suggests that the process can be scaled up. With further development, this process could become a viable alternative for demagging secondary aluminum.

Jan 1, 1985

The electrochemical dissolution of gold and other noble metals in hydrochloric acid using alternating current has been investigated. The experimental results show that this technique is efficient for dissolving pure noble metals and offers prospects for their extraction from wastes and poor ores.

Jan 1, 1992

Develop technology for preparing thick corrosion-resistant coatings and electroforms of iron-chromium-nickel alloys. Approach To reduce the United States' dependence upon foreign sources for supplies of strategic and critical metals such as chromium, cobalt, and nickel, new technology must be devised to conserve these valuable commodities. One approach being investigated by the Bureau of Mines is the use of a modified-aqueous-electrodeposition method to prepare thick (-25 µm), complex alloy coatings (e.g., stainless steel composition) with properties similar to the commercial alloys. An alloy coating on a low-alloy steel or carbon steel substrate would require significantly less strategic and critical metals than those contained in an equivalent mass of the commercial alloy. Coatings applied to appropriate mandrel materials make possible the preparation of intricately-shaped alloy electroforms (near-net-shape parts). As a result, the loss of valuable metals associated with machining finished products would be minimized.

Jan 1, 1986

By Robert Pike

THE first authentic description of an iron bath for the deposition of iron is probably that of Bottger in 1846, who used a bath containing ferrous sulfate and ammonium chloride. In 1861, Kramer deposited iron from ferrous chloride solution. Electrolytic iron was produced in 1.869 by Bietz, who used it for making some magnetic tests. In the same year, Klein is said to have worked out his process. Jacobi1 in 1869 described the results obtained in electroplating with iron on copper for making dies and plates for bank notes, by Klein's process. A letter from Klein to Jacobi describes the bath more fully. It consisted of FeSO4 + (NH4)2S04. Lenz2 described ?some properties of electrolytically precipitated iron. He used Klein's bath, FeSO4 + MgSO4 + MgCO3, to neutralize and obtained fine-grained and hard iron. His conclusions were as follows: 1. Electrolytic iron and copper contain gases, notably hydrogen. 2. The volume of gas absorbed by iron varies within wide limits, but it is easy for iron to take up very considerable quantities of gas. 3. The absorption of gas is principally in the first formed layers of iron. 4. When iron is heated, gas begins to come off below 100°, principally hydrogen. 5. Heated to redness, reduced iron oxidizes in water, in part at least at the expense of the oxygen of the water, decomposing it and setting free hydrogen, which is partly or wholly absorbed. Siemens,3 in 1889, was the first to propose a general process embodying a step for leaching a sulfide mineral with ferric chloride or sulfate and a step for regenerating the leach and depositing iron on a cathode in a diaphragm cell. So far as is known, Siemens did not carry out his patent

Jan 1, 1930