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By Zhongning Shi, Ramana G. Reddy

"By cyclic voltammetry and potentiostat electrodeposition using Potentiostat/Galvanstat, electrochemical behavior on Ag electrode in electrolyte 0.2M NaOH+0.01MPb(NO3)2-0.01M TeO2 -0.01M TlNO3 solution were also carried out at 298K. The processes of electrodeposition of Tl2Te3 and PbTl4Te3, a thermoelectric material, are reported along with analysis of the composition of the obtained deposits. The results showed that two different underlying processes are occurring depending on deposition potential. One process involves the reduction of TeO3 2- and Tl+ to Tl2Te3 in a potential interval of -0.70V < E < - 0.89V (vs. Hg/HgO). A second process at more negative reduction potentials involves reduction of TeO3 2-, Pb2+ and Tl+ to PbTl4Te3 in a potential interval of -1.02V < E < - 1.19V. The crystalline Tl2Te3 and PbTl2Te3 were deposited electrochemically on Ag substrates at -0.84V and -1.10V respectively. Thermoelectric (TE) material can form a temperature gradient across the material to make electric voltage, which is popular in waste heat utilization and recovery industry. Lead telluride, PbTe, is a small band gap semiconductor of 0.32eV at 300K. PbTe can change its n-type semiconductors with Pb-rich to p-type semiconductors with Te-rich[1]. And it is one of the best TE materials used in thermoelectric generators working between 500K and 600K, or even at a higher temperature of 800K.Three facto,rs play a role in the performance of a thermoelectric material: electrical conductivity (s), thermal conductivity(?), and the Seebeck coefficient (S). These can be combined with absolute temperature (T) to give a figure of merit (ZT) for the material, ZT = s2sT/?. By increasing the electrical conductivity and decreasing the thermal conductivity, which can enhance the ZT value, many efforts, such as alloying with other elements and making the materials nano-sized, have been done to improve its properties recently. Hsu et al. reported that the ZT value of Cubic AgPbmSbTe2+m is increased to 2.2 by doping Ag-Sb to PbTe.[2]."

Jan 1, 2011

By William A. Fuchs

A study of carbonaceous ore at the Santa Fe mine (Corona Gold Inc.) shows that there is no quantitative relationship between organic carbon content and preg rob, although much of this material preg robs. However, there is a relation between K20 and preg rob. Preg rob generally occurs only in those samples with greater than 2% K20. X-ray diffraction and chemical . studies show that the critical factor is the illite content of mixed (possibly interstratified) illite-smectite. Apparently illite, at a certain threshold, "geo-activates" the carbon. The potential for easily monitoring preg rob using a gamma ray spectrometer is discussed.

Jan 1, 1990

By Kimio Itagaki

The distribution ratios of Ag, Pb, As, Sb and Bi for the Cu2S-FeS or Ni3S2-FeS matte / FeOx SiO2, FeOx-SiO2-CaO or FeOx-CaO slag equilibration in a MgO crucible were determined experimentally at 1523~1573K under controlled partial pressures of S2 and O2 at given PSO2 of 10.1, 50.7 and 101.3 kPa (0.1, 0.5 and 1 atm) and be observed dependency of distribution ratio on the matte grade, SO2 pressure and slag basicity were analyzed on the basis of thermodynamics,

Jan 1, 2003

By Kimio Ilagaki

The distribution ratios of Ag, Pb, As, Sb and Bi for the Cu2S-FeS or Ni3S2-FeS matte I FeOx-SiOl, FeOx-Si02-CaO or FeOx-CaO slag equilibration in a MgO crucible were determined experimentally at 1523 ~1573K under controlled partial pressures of S2 and 02 at given PS02 of 10.1,50.7 and 101.3 kPa(O.I, 0.5 and I atm), and the observed dependency of distribution ratio on the matte grade, S02 pressure and slag basicity were analyzed on the basis of thermodynamics.

Jan 1, 2003

By W. Dresler

Design details of a 100 kVA DC electric-arc reduction furnace are described. The furnace is equipped with a 610 mm (24 inch) diameter graphite crucible hearth. A 76 mm (3 inch) diameter top graphite electrode is used as a cathode. The current passes through the bottom of the crucible and is carried to a bottom plate (the anode) by conductive magnesia carbon bricks. The furnace can be operated up to a maximum of 120 V, 1800 A, and presently 100 kW. The start-up operating experiences and metallurgical results of one reduction test with a Montana chromite containing 38% Cr2O3 are discussed.

Jan 1, 1994

By Jinsheng Wang, Wei Lv, Xuewei Lv, Pingsheng Lai, Jie Dang

The isothermal reduction kinetics of vanadium titanium magnetite sintering ore was investigated by thermo-gravimetric analysis at a temperature range of 1123–1223 K under 30% CO + 70% N2 gas mixtures. The apparent activation energy of reduction was calculated by iso-conversional method and its value is 36.7 kJ/mol. The model function describing the reduction mechanism was discussed by Sharp analysis and the results revealed that the reduction process is controlled first by random nucleation and nucleus growth mechanism (RNNGM) as reduction degree is lower than 0.5, followed by the mixed influence of RNNGM and phase boundary reaction when reduction degree is higher than 0.5.

Mar 1, 2017

By F. Robert Hubbard

IMCO Recycling Inc. has developed a new, patented technology for the production of fertilizer, K-SOIL?, as a by-product of its aluminum recycling operations. This new technology can substitute for conventional technology which now results in a saltcake residue that is placed in &apos;landfills. Four years of research and development work by IMCO culminated in a U. S. patent issued April 5, 1994. As part of the technology development effort, IMCO engaged the services of a nationally renowned research organization and a prominent university. These two organizations have conducted in-depth agronomy studies In the laboratory, greenhouse, and the field. Results have shown K-SOIL? to be performance equivalent, on a nutrient content basis, to conventional potash fertilizer. The first field applications on commercial farms were made in the spring of 1994. K-SOIL? is a potassium-bearIng, granular solid which may find use in fertilizer blends, direct application, and other forms of fertilizer products. The overall benefit of this new technology is to create a useful by-product rather than generate a useless residue and, thereby, reduce or eliminate the amount of salt cake now placed in landfills. As such, It is a significant, step toward IMCO&apos;s ultimate goal of complete recycle.

Jan 1, 1995

By Muhammad A. Imam, Ramana G. Reddy

This study provides a reasonable evaluation of the Mg-B binary system. Magnesium and Boron (Mg-B) alloys were investigated to determine their thermodynamic properties employing solid state electrochemical cells based on CaF2 electrolyte represented as –Pt; Ar= MgþCaMgF4 f gCaF2 k kf½Mg B alloy þ CaMgF4 g=Ar; Pt+ Investigations were performed over the temperature range of 773–873 K to measure the electromotive force (EMF), which was used to derive the partial Gibbs Free energies of the alloys in the composition range of XB = 0.07 to 0.95. The activities of Mg were also calculated from partial Gibbs Free energies. The activities of Mg in MgB2, MgB4, and MgB7 were expressed as a function of temperature respectively, ln aMg = 4.27–9.32 × 103/T, ln aMg = −7.54 + 6.67×103/T, and ln aMg = 4.93–19.57 × 103/T, where T is the temperature in K. From this expression, the activity of Mg for these intermediate phases can be extrapolated at a higher temperature to get the accurate phase boundaries for the Mg-B system.

Mar 1, 2017

By K. Osseo-Asare

Rate laws for the hydrogen reduction of metal ions are typically of the form: [r = -d[M(II)]/dt = k[M(II)]xPy2H] where k is an apparent rate constant, [M(II)] and PH2 represent dissolved metal concentration and hydrogen pressure respectively, while x = 0 - 1 and y = 0.5 - 2. Half-order dependences have been reported for some M(II)/H2 systems; however, no satisfactory explanations have been offered. In an effort to bridge this gap in our understanding, the published precipitation rate data (for M(II) = Cu(II), Ni(II), and Co(II)) are reviewed (with emphasis on the reported reaction orders) and compared with the corresponding but limited electrochemical polarization data. Based on the available literature on the electrochemical kinetics of the M/M(II) and H2/H+ systems it is demonstrated theoretically that, under certain conditions (e.g., in the presence of electron-conducting solids), the rate of the M(II)/H2 reaction can be expressed as: [-d[M2+]/dt = k[M2+]2/1P2/12H] It is concluded that electrochemical processes probably play an important role in the hydrogen reduction of metal ions, especially for systems that involve heterogeneous catalysis.

Jan 1, 2003

By Shunhong Huang

To improve understanding the effect of heavy metal chromium on soil biota, laboratory incubation experiment was carried out in the soils contaminated artificially with five concentrations of chromate (50, 250, 500, 1000 and 2000 mg kg_1 soil) over time (35 days). The population and diversity of bacteria, fungi and actinomycetes in soils were measured as indicators of soil microbial processes in the disturbances mentioned above. Incubation experiment results elucidated that the population and diversity of microorganisms decreased with increasing Cr (VI) concentration. Furthermore, various microorganisms showed different sensitivity to total Cr contamination. The sensitivity of microbial population to chromium contamination was in the order: actinomycetes >bacteria>fungi. The resulted implied that the microorganism can be used as an indicator of chromium contamination.

Jan 1, 2008

By Pratheesh George

Solid state galvanic cell with CaF2 as the electrolyte was employed for determining the thermodynamic properties of Nb-Al binary alloys in the temperature range of 973-1073 K. The activities and activity coefficients of Al in NbAl3 were determined. The experimental procedure and the design and construction of the experimental setup have been also explained in detail. Aluminum activity in NbAl3 increased with increase in temperature and shows a strong negative deviation from ideality. The activities of aluminum in NbAl3 were determined to be 0.0165 and 0.0289 at 973 and 1073 K respectively. The stability of NbAl3 has been compared with other available intermetallic systems.

Jan 1, 2006

By Ray D. Peterson

The hydrothermal enrichment of chalcopyrite by CuSO, occurs in the absence of oxidizing or reducing reagants. Kinetics of the enrichment process were determined under autoclave conditions in the temperature range of 398°K (125°C) to 473°K (200°C). Covellite (CuS) formed first, followed by digenite (Cu,,,S), with rejection of iron to the solution. The kinetics have been explained by a model which includes diffusion during the first stage formation of covellite followed by surface reaction rate control when digenite be. The effects of particle size, temperature, pH, and cupric and ferrous ion concentrations on the leaching kinetics were examined. Additions of ferrous ion to solution markedly increased the rate of reaction.

Jan 1, 1994

By Leszek Hoser

Polycrystalline oxide superconductors that have the perovskite structure, that are oxygen deficient, and that have compositions based. on the so-called. 1-2-3 (YBa2Cu3O7) compound, were investigated.. The materials exhibit a high critical transition to superconductivity at temperatures near 90oK. It was determined that maintaining the oxygen content within the correct range in connection with an appropriate amount of CU ions in the crystal lattice leads to high-critical temperature (Tc:) superconducting properties. High-Tc: superconductors with a critical temperature in the range of 100°K were developed. Further investigations, based. on the theoretical examinations of the origin of superconductivity, have been performed and are discussed..

Jan 1, 1989

By B. Balamurugan, D. J. Sellmyer, J. E. Shield, G. C. Hadjipanayis, Damien Le Ror, R. Skomski

"Rare-earth transition-metal (R-TM) alloys show superior permanent magnetic properties in the bulk, but the synthesis and application ofR-TM nanoparticles remains a challenge due to the requirement of high-temperature annealing above about 800 °C for alloy formation and subsequent crystalline ordering. Here we report a single-step method to produce highly ordered R-TM nanoparticles such as YCO5 and SmCO5, without high-temperature thermal annealing by employing a cluster-deposition system, and we investigate their structural and magnetic properties. Nanoparticles of size = 10 nm are monodispersed (s /d ~ 0.15) and have Hc values at T = 300 K of 8.0 and 4.5 kOe for YC05 and SmC05, respectively. Alignment of the easy axes is performed via a field applied to the clusters before deposition. These processing steps are highly desirable to create and assemble R-TM nanoparticle composites for future permanentmagnet applications.IntroductionMagnetic nanoparticles with high magnetocrystalline anisotropies (Ki > 1 MJ/m3) are required for permanent-magnet, recording-media, and other significant applications [1-3]. In this regard, bulk rare-earth transition metal alloys (R-TM) especially RC05 (R = Y and Sm) crystallized in the hexagonal CaCu5-type structure have shown a large Ki = 5 MJ/m3 (YC05) and 22 MJ/m3 (SmCo5) along with an appreciable saturation-magnetic polarization (Js, > 10 kG) and high curie temperatures (Tc > 1000 K) [2]. The challenges in controlling the size, sizedistribution, phase purity and crystalline ordering, however, limit the research on RCo5 nanoparticles [4,5]. The conventional arc-melting technique requires high-temperature annealing for alloy formation and subsequent crystalline ordering, which causes excess growth and thus results in nanocrystalline powders of particles sizes larger than 30 nm [6, 7]. Low-temperature wet-chemical techniques yield SmC05 nanoparticles of sizes smaller than 20 nm [5], but the control of phase purity is challenging due to the presence of surfactants and formation of other secondary phases [8]."

Jan 1, 2012

By Koji Matsubara, Yoshiaki Iguchi, Shoji Hayashi

Iron ore particles of a limonite iron ore were reduced completely with H2 at 1023K to 1273K in a fluidized bed. Then, at 973K, the formed iron was exposed to HrH2S mixtures (sulfur activity, as=0.5) for 3.6ks and carbidized with CO-H2-H2S· mixtures at 0.1 MPa. During the carbidization, the particles of about 150mg were sampled at every 600s interval. The sampled particles were analyzed by XRD and chemical analysis for C and S to evaluate the content of Fe3C, Fe5C2, Fe and free carbon. The reaction extent is defined as fo=Xfc3C +xFc5c2; x is the molar fraction of Fe in Fe3C. The carbidization curves can be fitted very well to -ln(l-f0)=g(pb T)t; g(p; T) is the carbidization rate, i.e. the carburization rate on the pore surface of reduced iron. The rate is found to be nearly proportional to the specific surface area of reduced iron, a P 0 , which decreases with increasing the reduction temperature. The value of a P 0 does not change by the carbidization and the stability of the iron carbide product in the atmosphere increases with the temperature.

Jan 1, 2000

By Gang Qi

The solubility of nitrogen in pure molybdenum was measured over the temperature range 2173 to 2473 K and up to one atmosphere (101 kPa) of nitrogen gas pressure. Both thermochemical and kinetic aspects of this phenomenon were considered in this study. The solution of nitrogen in molybdenum may be expressed by the reaction 1/2N2(g) = {N} (Mo,s), for which the standard Gibbs energy is given by the expression {A}G° = 78,500 + 27.36T Joules/g atom N. The formation of molybdenum nitrides, specifically Mo2N, was considered. Attention was also focused on the mechanism of nitrogen solution in molybdenum. Estimates of the diffusivity of nitrogen atoms in solid molybdenum were derived from the kinetic data.

Jan 1, 1991

By Marcelo B. Mourão

An experimental investigation was carried out to -study the rates of reduction of pellets containing iron oxides by carbon dissolved in liquid iron, at temperatures ranging from 1720 K to 1973 K. Several different pellet types were employed; the materials used in the pellet&apos;s manufacture were pure hematite, two kinds of commercial iron ores, and mixtures hematite/silica and hematite/lime: Reaction times were determined employing the constant volume pressure increase technique (CVPI). It has been observed that the reaction rate increases as the temperature and the pellet&apos;s specific surface area increases. The reaction rate is also affected by the oxide type: pellets made from commercial ores or from mixtures hematite/silica or hematite/lime show reaction rates lower than those made from pure hematite.

Jan 1, 1996

By W. G. Davenport

This chapter extends our mathematical description of flash smelting to -nitrogen in the flash furnace blast. As in chapters 4 and 5, the discussion is limited to auto thermal smelting (no hydrocarbon combustion). Hydrocarbon combustion is introduced in Chapter 9. Outokumpu flash furnace blast is a mixture of air and industrial oxygen. Most of its N2 originates in the air portion of the blast. A small portion originates as an impurity in the industrial oxygen. The nitrogen entering a flash furnace must always be heated from its input temperature, 298 K in this chapter, to its off gas temperature, -1500 K. Energy must be supplied for this purpose. With auto thermal smelting, the energy is-provided by oxidizing extra Fe-and S.

Jan 1, 2001

By Zhongning Shi, Ramana G. Reddy, Min Li, Zhaowen Wang

Electrodeposition of cobalt from cobalt tetrafluoroborate (Co(BF4)2) was investigated using 1- butyl-3-methylimidazolium tetrafluoroborate (BMIMBF4) ionic liquid. The experiments were conducted at 353 K. Chronoamperometry experiments confirm that the electrodeposition of cobalt on tungsten electrode proceeds via three-dimensional instantaneous nucleation with diffusion-controlled growth process. The average diffusion coefficient of Co(II) was found to be 7.5 × 10-8 cm2s-1 at 353 K, which is in good agreement with the estimated value from cyclic voltammetry. The electrochemical deposit was characterized using SEM-EDS and XRD methods. The SEM image shows formation of a dense and compact deposit at - 0.75 V. The EDS and XRD analysis confirm that the obtained deposit is pure cobalt metal.

Jan 1, 2015

The viscosity of high magnesium content FeO-Fe3O4-SiO2-CaO-MgO slags at nickel flash smelting conditions was investigated using a commercial rotational viscometer. The studied parameters were compositions of slag and temperature. The viscosity of these slags was measured as a function of CaO, MgO, SiO2, FeO. Fe3O4 and Fe/SiO2 in temperature range from 1473K to 1723K. These slags contained 5.81 to 10.59 pct MgO, 0 to 10.37 pct CaO, 28.21 to 36.21 pct SiO2, 39.40 to 55.42 pct Fe and 1.1 to 1.5 Fe/SiO2.

Jan 1, 1999