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By Yuri Oliveira Lima, Vitor Furlan de Oliveira, Adriano Gomes de Freitas, Ricardo Borges dos Santos, Luis Alberto Martinez Riascos

O presente trabalho, resultante da parceria público-privada entre a empresa Zeppelin Systems Latin America e a Universidade Federal do ABC, tem por objetivo validar o desempenho em termos de taxa de transporte e consumo energético de um vaso de pressão não convencional, o equipamento atua como alimentador de sólidos industrial para transporte pneumático, desenvolvido para operação de transporte de materiais em fase densa. Calcário é usado como material de deslocamento durante os ensaios no Centro de Testes da empresa, foi verificado que o novo injetor pressurizado tem menores dimensões e complexidade de operação, e possui taxa de transporte e consumo específico efetivo equiparáveis às versões de vasos de pressão convencional.

Aug 1, 2019

By H. Fukuyama

The wetting behavior of single crystalline MgO by fayalite-type slag melts has been studied by the sessile drop technique incorporated with high temperature X-ray radiography. The experiments were performed under oxygen partial pressures of 10-6 and 10-4 Pa at 1473 K. Mass ratios of iron to silica, Fe/Si~, in the slag employed were 1.4 and 2.0. To investigate the interfacial reaction, experiments using high density MgO crucibles were also conducted. The reactions at the interfaces were examined by Electron Probe Microanalysis. The contact angles between the slag melts and the MgO substrates were found to be relatively low, ranging from 30 to 10 degrees. The surface tension of the slag was 0.4 N/m for a slag of Fe/Si02 = 2.0. Two phases, magnesiowiistite and olivine, were observed at the interface. Interdiffusivity in magnesiowiistite solid solution was determined as a function of iron oxide content. Phase relations between magnesiowilstite and olivine, and the growth rates of both phases, are also discussed

Jan 1, 1996

By L. Morin, S. Mortazavi, K. Volchek, A. Demers, A. Di Feo

The objective of this paper was to investigate the possibility of reducing process (fresh) water and increasing recycled water (thickener tank overflow water). As part of the investigation, rougher flotation tests were done with the two water types and a mixture of the two (50%/50%). The effect of recycled water on the grade-recovery response and rougher recoveries was investigated. When thickener tank overflow was used (50% and 100%), the nickel+copper grade versus nickel recovery decreased. The decrease in the grade-recovery was due to higher pyrrhotite recovery. Also, there were no effects on nickel and copper recoveries, which was confirmed using multivariate statistical analysis at the 95% significance level. Keywords: Flotation, nickel, copper, water recycling, multivariate statistical analysis, MANOVA, reverse osmosis

Jan 1, 2020

According to the previous research, it is found that the thickness of cover is mostly less than 100 m for highwall mining system. However, for most of the Chinese surface coal mines, the mining depth is over 150 m; on the other hand, the shovel-truck is the most common mining technology. As a result, a lot of residual coal will be remained around end-walls. Considering these facts, the calculated methodology of highwall mining system under thick cover is presented in this paper. Meanwhile, numerical simulation of highwall mining system under thick cover was carried out. The outcome shows that the calculated methodology for pillar stability of highwall mining system under thick cover presented in this paper is acceptable. In other words, the highwall mining system is feasible to extract the residual coal around end-walls in Chinese surface coal mines. Thus, not only coal recovery ratio can be improved, but also can increase the production life of surface coal mines in China.

Jan 1, 2012

By M. E. Smith

Waste rock dumps, tailings impoundments and spent leach heaps are common features at mine sites. Many of these waste disposal facilities contain sulfide-rich minerals, which generate acid mine drainage (AMD) when they oxidize. Control of AMD can be achieved by removing one or more of the three essential components in the acid-generating process (sulfides, air, or water). One AMD prevention measure is to cap the waste with an engineered cover system to minimize the infiltration of water and diffusion of air into the system. Possible cover designs include: ? Earthen ?store-and-release? covers (also known as evapotranspiration (ET) or water balance covers), including capillary barriers. These covers require climate conditions where there is both modest to little rainfall and significantly greater evapotranspiration than precipitation, both annually and seasonally. ? Low-permeability compacted clay liners (CCLs) employing fine-grained soils typically compacted at wet of optimum water content. ? Geosynthetic composite covers, comprised of a geomembrane liner placed over and in direct contact with either a CCL or a geosynthetic clay liner (GCL). These systems have been commonly used for base liners for leach pads as well as covers and base liners at municipal solid waste (MSW) landfills in the US for more than 20 years. Comparisons of these different cover systems, both in terms of performance and cost, are presented later in this paper. First, however, a review of the typical mine closure approaches, and the possible rationale behind them, is warranted.

Feb 27, 2013

By AIME AIME

TWENTY-TWO sections and all four of the divisions sent delegates to the annual meeting. They became so interested in the wide ranging dis6ussion of old and yet ever-new problems of Institute affairs that three instead of two sessions scheduled were necessary. Monday morning the meeting assembled with President Bassett presiding in the absence of President-elect Tally, who had been called to Baltimore by the serious illness of a brother. Thursday morning Vice-president Turner presided until Mr. Tally appeared after which the latter guided the sessions. Since reports from all of the active sections save one had been mimeographed and sent in advance to the delegates, detailed reports from each were dispensed with. The discussions dealt largely with membership problems, both local and national, with financing, speakers and programs, visits from national officers, and the conduct of the annual meeting. Many interesting and constructive suggestions were made and will be reported back to the sections by the delegates.

Jan 1, 1931

By Oliver W. Keener

This paper describing the methods and costs of mining at the Hartley-Grantham mine of the Century Zinc Co. in the Tri-State Lead and Zinc district is one of a series being prepared by the United States Bureau of Mines can mining practices, methods, and costs in the various mining districts of the United States. LOCATION, HISTORY, AND GEOLOGY The Hartley-Grantham Mine is located just outside the city limits of Baxter Springs, Kans., as shown in Figure 1. A plan of the mine is given in Figure 2, and Figure is a cross section through A - A of Figure 2.

Jan 1, 1930

By J. W. Walkiewicz

The Bureau of Mines investigated alloys containing mischmetal (MM), cobalt, copper, magnesium, and iron for use in permanent magnets in place of the scarce samarium-cobalt alloys. The magnetic properties of MM-Co, MM-Co-Cu, MM-Co-Cu-Mg, and MM-Co-Cu-Fe-Mg alloys were evaluated. Magnets were fabricated by powder metallurgy consisting of arc-melting the metals, crushing and grinding the resultant alloys, alining and compacting the powder, and sintering the compacts. Magnetic values of MHc = 4.7 kOe, BHc = 4.07 kOe, Br = 6.81 kG, and (BH)max = 10.0 MGOe were obtained with a MM-Co alloy containing 36±0.5 wt-pct MM. By substituting copper and magnesium for part of the cobalt, the values for MHc and BHc were increased to 29.0 kOe and 5.89 kOe, respectively. This intrinsic coercivity value exceeded that of Sm-Co alloy obtained in our laboratory. The addition of iron to MM-Co-Cu-Mg alloys resulted in an increase of Br to 6.90 kG and (BH)max to 10.3 MGOe. Copper and magnesium contents of these alloys were optimized to obtain maximum values of MHc.

Jan 1, 1981

By M. Tadie, J. Wiese, K. Corin

The use of potential control in the flotation of ores has been applied in a variety of operations and presents an opportunity for improvement of selectivity and recovery of valuable minerals. Although it is possible to vary the redox potential (Eh) using chemical additives such as sodium hypochlorite or hydrogen peroxide this is more commonly done by varying the pH and dissolved oxygen (DO) concentration. The present study involves an investigation into the effect of varying dissolved oxygen concentration, ionic strength (IS) and pH on the flotation response with the aim of application to a South African lead-zinc ore. In all cases the Eh is measured as a function of the different DO, IS and pH values. The main objective was to achieve selective flotation of galena from sphalerite. The first part of the work was micro-flotation tests conducted on single minerals with galena used as the basis for effect of the factors studied on redox potential and ultimately recovery. The DO was varied by alternating between the use of air and nitrogen as the gas source to the micro-flotation cell. PH was varied between pH 9.2 and pH 11.8 using sodium hydroxide. In the first part of this study a factorial design approach was used to determine the interactive effects of the variables tested, viz. DO, ionic strength and pH, on the Eh and on the recovery. Redox potential was measured using a combination electrode made up of platinum wire and Ag/AgCl reference combination. Recoveries indicated that pH had the most significant effect on recovery and Eh. The influence of redox potential on recovery was found to be of relevance to the condition of high dissolved oxygen concentration and less so at low dissolved oxygen concentrations. It was also noted that that the combined interaction between ionic strength and dissolved oxygen concentration had a positive effect on recoveries, however this was not so with Eh. The chemistry of the ions in solution was observed to play a dominant role on the recovery due to changes in solubility arising to pH modification. The longer term objective of this work is to determine the optimal Eh conditions for the separation of galena from sphalerite.

Jan 1, 2016

By Zervoudis J

Limitations of current touch-up solders for galvanised steel include coating thickness control problems and poor corrosion and abrasion resistance as well as health and environmental concerns due to toxic constituents such as lead. This paper reports on progress in ILZRO-sponsored research to develop an improved touch-up solder. Encouraging results were achieved in torch soldering trials with experimental zinc-tin-based alloys. Mouldability and coating thickness control were achieved over a practical working temperature range in which the solders consisted of a viscous mixture of solid primary zinc phase particles in a liquid zinc-tin eutectic matrix. The mouldability was dependent on the microstructure of the solder sticks, and optimum structures could be obtained through control of casting solidification rates and by the addition of small amounts of copper. Hardness, abrasion resistance, adhesion and corrosion tests on experimental Zn- (40 - 50 per cent) Sn-I per cent Cu also showed improved performance over lead-tin-zinc solders and compared the effects of tin content within this range. Atmospheric corrosion testing and optimisation of alloy composition and methods of solder stick production are continuing.

Jan 1, 1993

By A. Basçetin

Equipment selection in mining engineering is one of the most important decisions that affects the mine design, production planning and economic parameters in open pit and underground mining. Mine planning engineers generally use their intuition and experiences in decision making. Mostly, linguistic variables (the weather is raining, soil is wet, etc.) come into question and decision-makers may not know how these variables are computed. Since the advent of the fuzzy set theory, these uncertainties are easily interpreted in the decision-making process. The development of computer technology and programming of colloquial language with expert systems have considerably reduced decision-makers? burden. This paper reviews the development of a computer programme software called EQS (EQuipment Selection) that automates equipment selection in mining engineering using fuzzy set theory. The EQS with an introduction of the concepts and theories of multiple attribute decision-making, the fuzzy set theory, and EQS applications to mining industry problems with case studies are presented

Jan 1, 2006

By Ho Jung Heo

The proper control of slag composition is a dominant factor affecting yield of iron as well as dephosphorization efficiency in an electric arc furnace (EAF) operation. Moreover, thermophysical properties of slags such as viscosity are strongly affected by the changes in slag composition. Slag foaming, which is also a function of viscosity, is directly connected with the yield of iron and thus optimum slag chemistry are highly required in view of thermodynamics and physical properties. Therefore, we analyzed the slag composition in commercial melt shop (70 ton EAF) with the aim of higher yield of iron as well as higher dephosphorization during EAF process.

By Kirk W. McCabe

RokLok binder is a two-component polyurethane system consisting of a polymeric isocyanate (Component A) and a polyol resin (Component B). The two chemicals are mixed and injected into the mine rock under pressure. The initial low viscosity enables the RokLok material to permeate many of the smallest fractures. About 3-5 minutes after injection, the reacting material begins to expand in the fractures; the reaction is completed after 1-2 hours, and the material sets to a mechanically strong binder which adheres tightly to the rock. The consolidated rack provides resistance to any further f movement w thin the strata. The RokLok binder injection system is fast becoming an important engineering tool for coping with adverse underground geological conditions. Two case histories discussed in this paper, a longwall mining problem and an entry-roof problem, demonstrate the effectiveness of using the RokLok binder system to help solve complex ground-control problems in a cost-effective manner.

Jan 1, 1981

By R. V. Lundquist, H. Leitch

The solubility characteristics of three calcium aluminates , 12Ca0 · 7A120½ 3Ca0 A1203 , and 4Ca0 A12 03 Fe2O3 , were determined in water and in solutions of NaOH and Na₂ CO₂ to more clearly define their role in relation to the recovery of aluminum by the lime sinter and the lime - soda sinter processes . The calcium aluminates were prepared by sintering stoichiometric mixtures of CaCO3 , Al2O3 3H20, and Fe 0 at 1,375 ° C. The rates and extent of aluminum extractions were determined . The aluminum extractions from the aluminates were dependent on the presence of carbonate ions in the leach solutions , temperature , time , leach solution composition , and solid - liquid ratio of the slurry . The aluminum extracted from the calcium aluminates in water and in NaOH solutions varied from 4.6 to 22.9 percent . Virtually , complete extraction could generally be obtained for 12Ca0.7A120 and 4Ca0.A12 03 • Fe₂ 03 ; in one instance it was obtained for 3Ca0.A1203 , when an excess of carbonate ions was present over that required for the conversion of all of the calcium in the aluminates into CaCO3 . In some cases of poor aluminum recoveries , extractions could be improved by regrinding and releaching the solid residues .

Jan 1, 1964

By Edwin T. Myskowski, Alfred H. Hesse

THE development by the U. S. Bureau of Mines of a process for purifying manganese by electrolysis has stimulated interest in manganese alloys. While recent publications have shown some alloys of manganese and copper to possess rather unusual properties, none have included information on tensile properties, which have an important bearing on the usefulness of the alloys. Manganese-copper alloys can be heat-treated, since the single phases that exist at high temperatures may be retained by quenching. According to Persson,1 when quenched alloys containing from about 30 to nearly 100 per cent manganese are reheated, alpha manganese is precipitated (Fig. I). Calculations based on Persson's X-ray data indicate that this decomposition is accompanied by a change in volume of as much as 5 per cent. The reason that this large volume change has not been noted probably is the slow rate at which equilibrium is reached by these alloys. In an investigation on hardening by cold-work and heat-treatment, Dean and Anderson' found that quenched alloys increase in hardness with manganese content and that high-manganese alloys harden very slowly with cold-work, while high-copper alloys harden much more rapidly. Heat-treatment has little effect on manganese-copper alloys containing less than 40 per cent Mn, and affects those alloys containing more than 40 per cent in accordance with their manganese content and heat-treating temperature. Dean and Anderson4 also found that cold-work increased electrical resistance of alloys containing from 50 to 80 per cent Mn, and that heat-treatment of alloys containing from 40 to 96 per cent Mn altered the electrical resistance considerably. Dean, Anderson and Potter5 have shown that the high vibration damping capacity that characterizes manganese-copper alloys containing 40 to 90 per cent Mn is affected by cold-work and heat-treatments. Highest vibration damping capacity at low stresses was obtained by heating for 2 hr. at 450°C. (842°F.) after quenching from solution temperatures. Preparation of Alloys.-The alloys for these tests were melted in a 17-lb. basic-lined high-frequency induction furnace using electrolytic manganese, grade A ingot copper and a 70-30 Cu-Mn master alloy (69.80 per cent Cu, 0.12 Fe, 0.04 Si, 0.006 S, 0.07 C, balance Mn). The manganese was heated slowly to expel excess dissolved gases and melted before the addition of copper. No fluxes or covers were used. The melts were cast in tapered iron molds and the ingots were reduced 90 per cent when forged to ½ -in. rounds. These rods were given 2-hr. solution treatments at temperatures that depended upon the composition (Table I). Tensile Tests.-The tensile specimens, 0.313-in. diameter (1.25-in. gauge length), which were enclosed in evacuated Pyrex

Jan 1, 1942

By Alfred H. Hesse, Edwin T. Myskowski

The development by the U. S. Bureau of Mines of a process for purifying manganese by electrolysis has stimulated interest in manganese alloys. While recent publications have shown some alloys of manganese and copper to possess rather unusual properties, none have included information on tensile properties, which have an important bearing on the usefulness of the alloys. Manganese-copper alloys can be heat-treated, since the single phases that exist at high temperatures may be retained by quenching. According to Persson,1 when quenched alloys containing from about 30 to nearly IOO per cent manganese are reheated, alpha manganese is precipitated (Fig. I). Calculations based on Persson's X-ray data indicate that this decomposi-tion is accompanied by a change in volume of as much as ; per cent. The reason that this large volume change has not been noted probably is the slow rate at which equilibrium is reached by these alloys. In an investigation on hardening by cold-work and heat-treatment, Dean and Anderson3 found that quenched alloys increase in hardness with manganese content and that high-manganese alloys harden very slowly with cold-work, while high-copper alloys harden much more rapidly. Heat-treatment has little effect on manganese-copper alloys containing less than 40 per cent Mn, and affects those alloys containing more than 40 per cent in accordance with their manganese content and heat-treating temperature. Dean and Anderson4 also found that cold-work increased electrical resistance of alloys containing from 50 to 80 per cent Mn, and that heat-treatment of alloys containing from 40 to 96 per cent Mn altered the electrical resistance considerably. Dean, Anderson and Potter6 have shown that the high vibration damping capacity that characterizes manganese-copper alloys containing 40 to go per cent Mn is affected by cold-work and heat-treatments. Highest vibration damping capacity at low stresses was obtained by heating for 2 hr. at 450°C. (842°F.) after quenching from solution temperatures. Preparalion of Alloys.—The alloys for these tests were melted in a 17-lb. basic-lined high-frequency induction furnace using electrolytic manganese, grade A ingot copper and a 70-30 CU-Mn master alloy (69.80 per cent Cu, 0.12 Fe, 0.04 Si, 0.006 S, 0.07 C, balance Mn). The manganese was heated slowly to expel excess dissolved gases and melted before the addition of copper. No fluxes or covers were used. The melts were cast in tapered iron molds and the ingots were reduced go per cent when forged to 1/2-in. rounds. These rods were given 2-hr. solution treatments at temperatures that depended upon the composition (Table I). Tensile Tests.—The tensile specimens, 0.313-in. diameter (1.25-in. gauge length),

Jan 1, 1942

By Edwin T. Myskowski, Alfred H. Hesse

THE development by the U. S. Bureau of Mines of a process for purifying manganese by electrolysis has stimulated interest in manganese alloys. While recent publications have shown some alloys of manganese and copper to possess rather unusual properties, none have included information on tensile properties, which have an important bearing on the usefulness of the alloys. Manganese-copper alloys can be heat-treated, since the single phases that exist at high temperatures may be retained by quenching. According to Persson,1 when quenched alloys containing from about 30 to nearly i00 per cent manganese are reheated, alpha manganese is precipitated (Fig. I). Calculations based on Persson's X-ray data indicate that this decomposi¬tion is accompanied by a change in volume of as much as S per cent. The reason that this large volume change has not been noted probably is the slow rate at which equilibrium is reached by these alloys. In an investigation on hardening by cold-work and heat-treatment, Dean and Anderson3 found that quenched alloys increase in hardness with manganese content and that high-manganese alloys harden very slowly with cold-work, while high-copper alloys harden much more rapidly. Heat-treatment has little effect on manganese-copper alloys containing less than 40 per cent Mn, and affects those alloys containing more than 40 per cent in accordance with their manganese content and heat-treating temperature. Dean and Anderson4 also found that cold-work increased electrical resistance of alloys containing from 50 to 80 per cent Mn, and that heat-treatment of alloys containing from 40 to 96 per cent Mn altered the electrical resistance considerably. Dean, Anderson and Potters have shown that the high vibration damping capacity that characterizes manganese-copper alloys containing 40 to g0 per cent Mn. is affected by cold-work and heat-treatments. Highest vibration damping capacity at low stresses was obtained by heating for 2 hr. at 450°C. (842°F.) after quenching from solution temperatures. Preparation of Alloys.-The alloys for these tests were melted in a 17-lb. basic-lined high-frequency induction furnace using electrolytic manganese, grade A ingot copper and a 70-30 Cu-Mn master alloy (69.80 per cent Cu, 0.12 Fe, 0.04 Si, 0.006 S, 0.07 C, balance Mn). The manganese was heated slowly to expel excess dissolved gases and melted before the addition of copper. No fluxes or covers were used. The melts were cast in tapered iron molds and the ingots were reduced go per cent when forged to ½ in. rounds. These rods were given 2-hr. solution treatments at temperatures that depended upon the composition (Table I). Tensile Tests.-The tensile specimens, 0.313-in. diameter (1.25-in. gauge length), which were enclosed in evacuated Pyrex

Jan 1, 1942

By Edwin T. Myskowski, Alfred H. Hesse

The development by the U. S. Bureau of Mines of a process for purifying manganese by electrolysis has stimulated interest in manganese alloys. While recent publications have shown some alloys of manganese and copper to possess rather unusual properties, none have included information on tensile properties, which have an important bearing on the usefulness of the alloys. Manganese-copper alloys can be heat-treated, since the single phases that exist at high temperatures may be retained by quenching. According to Persson,1 when quenched alloys containing from about 30 to nearly IOO per cent manganese are reheated, alpha manganese is precipitated (Fig. I). Calculations based on Persson's X-ray data indicate that this decomposi-tion is accompanied by a change in volume of as much as ; per cent. The reason that this large volume change has not been noted probably is the slow rate at which equilibrium is reached by these alloys. In an investigation on hardening by cold-work and heat-treatment, Dean and Anderson3 found that quenched alloys increase in hardness with manganese content and that high-manganese alloys harden very slowly with cold-work, while high-copper alloys harden much more rapidly. Heat-treatment has little effect on manganese-copper alloys containing less than 40 per cent Mn, and affects those alloys containing more than 40 per cent in accordance with their manganese content and heat-treating temperature. Dean and Anderson4 also found that cold-work increased electrical resistance of alloys containing from 50 to 80 per cent Mn, and that heat-treatment of alloys containing from 40 to 96 per cent Mn altered the electrical resistance considerably. Dean, Anderson and Potter6 have shown that the high vibration damping capacity that characterizes manganese-copper alloys containing 40 to go per cent Mn is affected by cold-work and heat-treatments. Highest vibration damping capacity at low stresses was obtained by heating for 2 hr. at 450°C. (842°F.) after quenching from solution temperatures. Preparalion of Alloys.—The alloys for these tests were melted in a 17-lb. basic-lined high-frequency induction furnace using electrolytic manganese, grade A ingot copper and a 70-30 CU-Mn master alloy (69.80 per cent Cu, 0.12 Fe, 0.04 Si, 0.006 S, 0.07 C, balance Mn). The manganese was heated slowly to expel excess dissolved gases and melted before the addition of copper. No fluxes or covers were used. The melts were cast in tapered iron molds and the ingots were reduced go per cent when forged to 1/2-in. rounds. These rods were given 2-hr. solution treatments at temperatures that depended upon the composition (Table I). Tensile Tests.—The tensile specimens, 0.313-in. diameter (1.25-in. gauge length),

Jan 1, 1942

By P. Nyul, S. Caplan, M. F. Lamorte, T. Gonda

Therrnal resistance is measured on GaAs laser diodes in the temperature range 77" to 300°K. These data show that typically the thermal resistance increases fifteen times from 77 to 300°K. The increase is attributed to the decrease in thermal conductivity of Gds. Nornzalized thermal-resistance experimental and calculated from published thermal-conductivity data) values are compared and good agreement shown. In many practical applications, it is desirable to obtain high average power output from laser diodes. Average power output is determined in large measure by the external efficiency and thermal resistance of the diode.'-3 The average input power with which a laser diode may be pumped is dependent on the thermal resistance. Thermal resistance has been studied over the temperature range from 77" to 300°K which is usually of interest in practical applications. This correspondence presents data on thermal resistance for GaAs laser diodes and compares them to values calculated from thermal-conductivity data. Junction heating arises from three distinct components: 1) joule heating, 2) nonradiative recombinations, and 3) reabsorption of radiation. In high-threshold lasers, joule heating predominates.4 Typically, the nonradiative recombination is not negligible and contributes significantly to junction heating. The loss caused by reabsorption may be of the order of the joule-heating loss.' The fabrication and the geometry of laser diodes have been described in other publications.5 The data presented were obtained from diodes which were fabricated from the same region of a wafer to minimize differences. Fig. 1 shows four types of heat sinks employed in this study. In types 1 and 2, the laser cavities are alloyed; pressure contacts are employed in types 3 and 4, and indium is plated on the inside faces to improve the intimacy of contact between the diode and the heat sink. The thermal resistance R is defined by the following relationship: where AT is the junction-temperature rise above the heat-sink temperature for the diode power dissipation Pd. For measurement of thermal resistance, a direct current is passed through the junction, in the range from 1 to 50 pct of threshold. The diode is placed in the laser mode by superimposing a current pulse of low-duty cycle on the direct current.3 Junction-temperature rise is obtained from the time-resolved laser spectrum at the leading edge of the current pulse.' Typically, the laser line shift is 2.5A per OK. The resolution employed in these experiments is 0.5A; therefore, the accuracy in the temperature measurement is 0.2K. Typically, the temperature rise is 2" to 20°K. The power dissipation is the difference between the dc power input, and the radiation power exiting the diode. The measurement accuracy is less than 1

Jan 1, 1968

By A. W. Bryson, S. P. Fox, S. A. Godorr

"This work is an extension of a previous investigation on the development of surface roughness during electrodeposition of copper. A comprehensive model based on diffusion and migration in a force field together with surface diffusion and sticking probabilities is used to generate profiles which are compared to those produced experimentally. The roughness is characterized by using the technique of fractal geometry which is shown to describe both qualitatively and 9uantitatively the development of surface morphology during electrodeposition.The work is extended to the deposition of copper in the presence of various concentrations of thiourea. The development of roughness is observed experimentally on the edge of a thin copper disc mounted between two glass plates. This enables photographs to be taken at various stages during growth. The surface outline is digitized using an image analyzer which enables the fractal dimension to be determined as growth proceeds. As expected, the presence of thiourea at low concentrations produces a fractal dimension which is closer to unity (i.e. the surface becomes smoother).IntroductionThe development of surface morphology during electrodeposition has far-reaching implications for copper plating in the electrowinning and electrorefining processes. Short circuits as the cathode surface grows unevenly require operator intervention in a dangerous environment and imply processing delays, and the inclusion of electrolyte in small gaps in the plated cathode have implications in downstream processing of the cathode. Higher current densities are obviously desirable, as they result in greater production rates, but as shown by Ettel et. al.(l), Harvey et. al.(2), Cook (3), and Harvey et. al.(4), it is not possible to operate near the projected economically optimum conditions because the electrodeposition of copper from sulphate and acid solutions is a mass transfer controlled process. It has been shown (Ettel et. al.(l), Harvey et. al.(2)) that the closer a system operates to mass transfer limiting conditions, the poorer the resulting cathode quality. One solution is to use agitation techniques to increase the limiting current density. Another is to add surface active additives to the electrolyte which has been shown by Ettel et. al.(l), Harveyet. al.(2) and Afifi et. a1.(5) to allow higher rates of production without decreasing cathode quality. The second proposed solution is of interest in this work, since there is very little knowledge of the conditions under which these additives operate effectively, and little fundamental understanding of the mechanism by which they operate. The current work seeks to contribute to this field by correlating a simulation model with experimental results to describe the development of surface morphology in the electrodeposition process."

Jan 1, 1997