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1.
Krzysztof Pacławski Krzysztof Fitzner 《Metallurgical and Materials Transactions B》2004,35(6):1071-1085
In this article, the effect of different kinetic parameters such as pH, temperature, gold, and reductant concentrations on
the rate of Au reduction from aqueous chloride solutions by NaHSO3 is investigated. On the basis of available experimental data, the possible mechanism of [AuCl4]− reduction by sulfur(IV) is also assumed. The suggested mechanism yields the rate equation for reduction of [AuCl4]−, which is given in the form
, with respective rate constants given in the text. 相似文献
2.
A. D. Kulkarni 《Metallurgical and Materials Transactions B》1973,4(7):1713-1721
Oxygen activities in liquid Cu−O and Cu−Fe−O alloys were measured in the temperature range 1100° to 1300°C by the solid oxide
electrolyte emf method with mixtures of Ni−NiO and Co−CoO as reference electrodes. The Cu−O and Cu−Fe−O alloys were analyzed
for iron and/or oxygen content. The activity coefficient of oxygen at infinite dilution in liquid copper was found to be 0.115,
0.195, and 0.286 at 1100°, 1200°, and 1300°C, respectively. The results are compared with previous investigations on the Cu−O
system. Based on this comparison, the best equation for the free energy of solution has been suggested. The standard free
energy of formation of CoO(s) has been calculated at the experimental temperatures. In the liquid Cu−Fe−O system at 1200°C, a minima in oxygen solubility
is reached at 1.1 at. pct Fe in the alloy. The value of interaction coefficient,
, is −565 at 1200°C. Iron activities in the liquid Cu−Fe alloys have been calculated at 1100° and 1200°C, and a strong positive
deviation from ideality is observed. Results of this study were combined with literature data at 1550°C to obtain the values
of
and
at infinite dilution in liquid copper.
A. D. KULKARNI, formerly with Chase Brass and Copper Co., Cleveland, Ohio 相似文献
3.
4.
Victor T. Witusiewicz Ferdinand Sommer 《Metallurgical and Materials Transactions B》2000,31(2):277-284
The partial (Δ
and the integral (ΔH) enthalpies of mixing of liquid Ni-Zr and Cu-Ni-Zr alloys have been determined by high-temperature isoperibolic calorimetry
at 1565 ± 5 K. The heat capacity (C
p) of liquid Ni26Zr74 has been measured by adiabatic calorimetry (C
p=53.5±2.2 J mol−1 K−1 at 1261±15 K). The integral enthalpy of mixing changes with composition from a small positive (Cu-Ni, ΔH (x
Ni=0.50, T=1473 to 1750 K)=2.9 kJ mol−1) to a moderate negative (Cu-Zr; ΔH(x
Zr=0.46, T=1485 K)=−16.2 kJ mol−1) and a high negative value (Ni-Zr; ΔH(x
Zr=0.37, T=1565 K)=−45.8 kJ mol−1). Regression analysis of new data, together with the literature data for liquid Ni-Zr alloys, results in the following relationships
in kJ mol−1 (standard states: Cu (1), Ni (1), and Zr (1)):for Ni-Zr (1281≤T≤2270 K),
for Cu-Ni-Zr (T=1565±5 K),
相似文献
5.
Nikhil Dhawan M. Sadegh Safarzadeh Mustafa Birinci 《Russian Journal of Non-Ferrous Metals》2011,52(3):209-216
The dissolution kinetics of smithsonite ore in hydrochloric acid solution has been investigated. As such, the effects of particle
size (−180 + 150, −250 + 180, −320 + 250, −450 + 320 μm), reaction temperature (25, 30, 35, 40, and 45°C), solid to liquid
ratio (25, 50, 100, and 150 g/L) and hydrochloric acid concentration (0.25, 0.5, 1, and 1.5 M) on the dissolution rate of
zinc were determined. The experimental data conformed well to the shrinking core model, and the dissolution rate was found
to be controlled by surface chemical reaction. From the leaching kinetics analysis it can be demonstrated that hydrochloric
acid can easily and readily dissolve zinc present in the smithsonite ore, without any filtration problems. The activation
energy of the process was calculated as 59.58 kJ/mol. The order of the reaction with respect to HCl concentration, solid to
liquid ratio, and particle size were found to be 0.70, −0.76 and −0.95, respectively. The optimum leaching conditions determined
for the smithsonite concentrate in this work were found to be 1.5 M HCl, 45°C, −180 + 150 μm, and 25 g/L solid to liquid (S/L)
ratio at 500 rpm, which correspond to more than 95% zinc extraction. The rate of the reaction based on shrinking core model
can be expressed by a semi-empirical equation as:
$1 - \left( {1 - X} \right)^{{1 \mathord{\left/
{\vphantom {1 3}} \right.
\kern-\nulldelimiterspace} 3}} = k_0 \left[ {HCl} \right]^{0.70} \left( {\frac{S}
{L}} \right)^{ - 0.76} r_0^{ - 0.95} \exp \left( {\frac{{ - 59.58}}
{{RT}}} \right)t.$1 - \left( {1 - X} \right)^{{1 \mathord{\left/
{\vphantom {1 3}} \right.
\kern-\nulldelimiterspace} 3}} = k_0 \left[ {HCl} \right]^{0.70} \left( {\frac{S}
{L}} \right)^{ - 0.76} r_0^{ - 0.95} \exp \left( {\frac{{ - 59.58}}
{{RT}}} \right)t. 相似文献
6.
Marco A. Gimenes Herenilton P. Oliveira 《Metallurgical and Materials Transactions B》2001,32(6):1007-1013
In this work, a systematic study of the reaction between xenotime, chlorine, and carbon has been performed. The kinetics of
carbochlorination of xenotime raw material (rare-earth elements in phosphate form, REPO4) has been studied over a temperature range from 600 °C to 950 °C. The influences of temperature, partial pressure of chlorine,
carbon content, and particle size on the rate of conversion of xenotime to RECl3 were investigated. The results showed that the process follows the unreacted core-shrinking model with formation of a porous
product layer. Powder X-ray diffraction (XRD) corroborated this model, showing clearly the patterns related to the formation
of yttrium oxychloride (YOCl), indicating that the reaction mechanism involves the presence of an intermediate step before
the formation of lanthanide chloride. A global rate equation which includes these parameters has been developed:
7.
L. E. Eary 《Metallurgical and Materials Transactions B》1985,16(2):181-186
Hydrogen peroxide decomposition in acidic solutions is catalyzed by the free ferric ion, Fe3+. The following rate law for this reaction is determined by the initial rate method in solutions similar to those used for
acidicin situ uranium leaching:
wherek = 4.3 × 10−3 s°1 at 25 °C. From 25° to 50 °C, the activation energy is 85.6 kJ/mol. The decomposition of hydrogen peroxide proceeds by a particular
redox reaction sequence that depends on the ratio of the concentrations of hydrogen peroxide to free ferric ion. The rate
law determined here is consistent with the form derived from the redox sequence for the case where the ratio of hydrogen peroxide
to free ferric ion concentration is greater than 1.0. The magnitude of the rate constant indicates that the decomposition
of hydrogen peroxide may cause rapid loss of this oxidant in leaching solutions containing ferric ion.
Formerly a Graduate Student with the Department of Geochemistry and Mineralogy, Pennsylvania State University, 相似文献
8.
The dissolution equilibrium of calcium vapor in liquid iron was carried out at 1873 K in a two-temperature zone furnace using
a vapor-liquid equilibration method. A sealed Mo reaction chamber and a self-made CaO crucible were used in this study. The
thermodynamic parameters obtained are as follows.
For reaction Ca (g)=[Ca],
9.
Thermodynamic behavior of nickel in CaO-SiO<Subscript>2</Subscript>-Fe<Subscript>t</Subscript>O slag
Sang Hoon Lee Seok Min Moon Dong Joon Min Joo Hyun Park 《Metallurgical and Materials Transactions B》2002,33(1):55-59
The distribution ratio of nickel between Ag-Ni alloy and CaO-SiO2-Fe
t
O slag at high temperatures was measured to clarify the dissolution mechanism of nickel in this melt. Also, the nickel oxide
capacity was suggested and was compared to phosphate and sulfide capacities. The dissolution mechanism of nickel into the
CaO-SiO2-Fe
t
O slags could be described by the following equation from the effect of oxygen potential and slag basicity on nickel dissolution
behavior:
10.
Krzysztof Pacławski Krzysztof Fitzner 《Metallurgical and Materials Transactions B》2006,37(5):703-714
In this article, the effect of different kinetic parameters, namely, temperature, pH, and reductant concentration, on the
rate of Au(III) reduction from aqueous chloride solutions by H2O2 was investigated. The possible mechanism of complex [Au(OH)4]− ion reduction by hydrogen dioxide is also discussed and the model mechanism based on experimental data is postulated. On
the basis of the suggested mechanism, the rate equation for Au precipitation is given in the form
, in which respective rate constants k
1, k
3, and k
5 were determined experimentally and are given in the text. 相似文献
11.
Silicon-oxygen equilibria in an Fe-0.003 ~ 27 mass pct Si alloy in equilibrium with the CaO-SiO2 slags were studied in the temperature range of 1823 to 1923 K using a lime crucible. At the same time, nitrogen distribution
ratios, LN, between slag and metal were measured, and from these results and the reported values for activities of SiO2, nitride capacities,
, defined by (mass pct N).
were evaluated. It was found that the values for LN decreased, whereas those for
increased with an increase in temperature. Activities of SiO2 were determined using the values for LN and
obtained in previous gas-slag experiments. These values were compared with the previous results. 相似文献
12.
Hiroyasu Fujiwara Eiji Ichise Masahiro Kitou Takayuki Matsui 《Metallurgical and Materials Transactions B》1997,28(2):243-250
The distribution of iron between Fe
x
O-dilute CaO+Al2O3+Fe
x
O fluxes and Pt+Fe alloys, as well as the redox equilibrium of iron ions in these fluxes, was experimentally investigated
in pressure-controlled CO2/CO gas at 1873 K.
Total iron content in flux (pct Fe
T
) and the ratio of (pct Fe2+) to (pct Fe
T
) in fluxes with constant
can be related to the activity of iron, α
Fe, and the partial pressure of oxygen, a
Fe, using the following equation:
13.
14.
Qiyong Han Xiaodong Zhang Dong Chen Pengfei Wang 《Metallurgical and Materials Transactions B》1988,19(3):617-622
The equilibrium Ca3P2(s) = 3[Ca] + 2[P] was studied at 1600 ° by equilibrating liquid iron, saturated with Ca3P2, and contained in a TiN crucible, with Ca vapor. The source of Ca was liquid Ca contained in an Mo crucible, and the vapor
pressure of Ca was varied by varying the position of the Mo crucible in the temperature gradient of a vertical tube furnace.
A least-squares analysis of the data gave
and
. The simultaneous equilibria CaO(s) = [Ca] + [O] and CaS(s) = [Ca] + [S] were studied at 1600 ° by equilibrating liquid iron, contained in a pressed and sintered CaO-CaS crucible with
Ca vapor. The advantage of this technique is that two equilibrium constants,K
cas andK
cao, and two interaction coefficients,
and
can be determined from one set of experiments. It was determined that, at 1600 °,K
cas = 5.9 × 10−8
K
cao = 5.5 × 10−9,
, and
.
Formerly Graduate Students 相似文献
15.
Hiroyasu Fujiwara Eiji Ichise Masahiro Kitou Takayuki Matsui 《Metallurgical and Materials Transactions B》1999,30(3):419-427
In order to determine the ferrous and ferric ion capacities: 3
16.
Interdiffusion coefficients in Nb2C and NbC1−x were measured using bulk diffusion couples in the temperature range from 1400 °C to 1700 °C. Marker experiments were used
to show that carbon is the only component undergoing significant diffusion in both carbides. Carbon concentrations were measured
by difference using electron probe microanalysis, and interdiffusion coefficients were taken from Boltzmann-Matano analyses
of the resulting concentration profiles. This analysis clearly showed that, in NbC1−x, interdiffusion coefficient varies with carbon concentration, and is expressed by
17.
Various theoretical dendrite and cell spacing formulas have been tested against experimental data obtained in unsteady- and
steady-state heat flow conditions. An iterative assessment strategy satisfactorily overcomes the circumstances that certain
constitutive parameters are inadequately established and/or highly variable and that many of the data sets, in terms of gradients,
velocities, and/or cooling rates, are unreliable. The accessed unsteady- and steady-state observations on near-terminal binary
alloys for primary and secondary spacings were first examined within conventional power law representations, the deduced exponents
and confidence limits for each alloy being tabularly recorded. Through this analysis, it became clear that to achieve predictive
generality the many constitutive parameters must be included in a rational way, this being achievable only through extant
or new theoretical formulations. However, in the case of primary spacings, all formulas, including our own, failed within
the unsteady heat flow algorithm while performing adequately within their steady-state context. An earlier untested, heuristically
derived steady-state formula after modification,
18.
Hongsheng Xu Chang Wei Cunxiong Li Zhigan Deng Minting Li Xingbin Li 《Metallurgical and Materials Transactions B》2014,45(5):1622-1633
The dissolution kinetics of hemimorphite with low sulfuric acid solution was investigated at high temperature. The dissolution rate of zinc was obtained as a function of dissolution time under the experimental conditions where the effects of sulfuric acid concentration, temperature, and particle size were studied. The results showed that zinc extraction increased with an increase in temperature and sulfuric acid concentration and with a decrease in particle size. A mathematical model able to describe the process kinetics was developed from the shrinking core model, considering the change of the sulfuric acid concentration during dissolution. It was found that the dissolution process followed a shrinking core model with “ash” layer diffusion as the main rate-controlling step. This finding was supported with a linear relationship between the apparent rate constant and the reciprocal of squared particle radius. The reaction order with respect to sulfuric acid concentration was determined to be 0.7993. The apparent activation energy for the dissolution process was determined to be 44.9 kJ/mol in the temperature range of 373 K to 413 K (100 °C to 140 °C). Based on the shrinking core model, the following equation was established: $$ 1.21\ln \left( {1 - 0.83x} \right) - \left[ {1.02\ln \frac{{0.35 + \left( {1 - x} \right)^{{{2 \mathord{\left/ {\vphantom {2 3}} \right. \kern-0pt} 3}}} - 0.59\left( {1 - x} \right)^{{{1 \mathord{\left/ {\vphantom {1 3}} \right. \kern-0pt} 3}}} }}{{0.35 + \left( {1 - x} \right)^{{{2 \mathord{\left/ {\vphantom {2 3}} \right. \kern-0pt} 3}}} + 1.18\left( {1 - x} \right)^{{{1 \mathord{\left/ {\vphantom {1 3}} \right. \kern-0pt} 3}}} }} + 3.52\arctan \left( {1.96\left( {1 - x} \right)^{{{1 \mathord{\left/ {\vphantom {1 3}} \right. \kern-0pt} 3}}} - 0.58} \right)} \right] + 2.06 = 42,192.59{\text{e}}^{{ - \frac{44,900}{{{\text{R}}T}}}} t. $$ 相似文献
19.
Interaction parameters for Mn-based alloys were evaluated using both carbon solubility and activity data for species in binary
and ternary manganese alloys. The parameters at 1400 °C are the following
20.
E. W. Dewing 《Metallurgical and Materials Transactions B》1970,1(8):2211-2215
The theory of the solid-electrolyte cells
is given, and it is shown that cryolite itself with Ca2+ in solid solution is a suitable Na+-ion conductor. Experimental electromotive forces for the ranges 570° to 725°C and 570° to 670°C, r − 18,960 cal with a standard
deviation of ±36 cal (based on a third-law calculation). For 5NaF(s) + 3AlF3(s) = Na5Al3F14(s), ΔG° = −38,560 − 7.081T with a standard deviation of ±130 cal. Combination of these results with recent values for Al
+ 3/2 F2 = A1F3 and for 6NaF + Al = Na3AlF6 + 3Na gives ΔH°f298(Na3AlF6) = −792,400 cal and ΔH°f298(NaF) = −137,530 cal. The latter is in excellent agreement with the most recent critical assessment. 相似文献
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