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1.
Yasuhiro Awakura Hiroshi Hiai Hiroshi Majima Shuichiro Hirono 《Metallurgical and Materials Transactions B》1989,20(3):337-343
With the aim of developing a process for continuous electrolytic reduction of uranyl sulfate, the effects of temperature and
HF concentration on the electrolytic reduction were investigated using both a rectangular cell and a bipolar cell. Some tests
on the semicontinuous-type elec-trolytic reduction of U(VI) and the continuous monitoring of U(VI) in a catholyte were carried
out to examine the feasibility of a process for continuous electrolytic reduction. The reduction rate and current efficiency
of the electrolysis were increased with increasing temperature up to 333 K, due to an increase in the diffusion coefficient
of uranyl sulfate. The presence of a small amount of HF in the catholyte improved the polarization characteristics of the
electrolysis. The precipitation of uranous sulfate occurring in electrolysis above 323 K was eliminated by the addition of
HF of 2.3 g dm-3. However, the addition of the excess amount of HF causes the precipitation of UF4 on the cathode surface during electrolysis. Increase in electric current was not effective in the semicontinuous electrolytic
reduction of U(VI) for catholytes with high reduction ratios, and a catholyte with a composition of around 50 pct reduction
ratio is pref-erable for continuous operation. The concentration of U(VI) in a catholyte can be monitored continuously either
in the absence or in the presence of HF by using a device consisting of three small electrodes.
Formerly Graduate Student in the Department of Metallurgy, Kyoto University
Formerly Director, Mining and Ore Processing Division, Ningyo-toge Works, PNC Japan 相似文献
2.
Hiroshi Majima Yasuhiro Awakura Shuichiro Hirono 《Metallurgical and Materials Transactions B》1986,17(1):41-50
In order to examine the applicability of the electrolytic reduction process of U(VI) (originally developed for the chloride
system by PNC) to the sulfate solution system, a fundamental study was made. In this study, the concentrations of various
chemical species in the catholytes were calculated at 298 K at various percentages of uranium reduction, taking the chloro-complex
and sulfato-complex formation reactions of uranium into consideration. The polarization characteristics of the electrolytic
reduction of uranyl chloride and uranyl sulfate were determined, using titanium and platinum cathodes, respectively, at 303
± 1 K. In conjunction with this process, the electrical conductivity of the catholyte, the electrical resistivity of the cation
exchange membrane, and the diffusion coefficient of uranyl sulfate were also determined. 相似文献
3.
Hiroshi Majima Yasuhiro Awakura Koji Sato Shuichiro Hirono 《Metallurgical and Materials Transactions B》1986,17(1):69-76
The electrolytic reduction of U(VI) was investigated to improve the batch type electrolytic reduction of uranyl sulfate. For
this purpose, theoretical considerations were made on the time variation of reduction rate and of current efficiency. A monitoring
device consisting of two titanium electrodes and one platinum electrode was developed to determine the reduction ratio and
to detect the end point of the reduction of U(VI). The monitoring device worked well for these purposes. The reduction rate
in a batch type electrolytic reduction of U(VI) at constant current was larger than theoretically expected. This phenomenon
was attributed to the increase in the mass transfer rate of U(VI) species toward the cathode due to the disturbance of the
concentration boundary layer by hydrogen gas evolved from the cathode surface. The deterioration of titanium cathode experienced
in an operating plant was investigated, and was found to be caused by platinum plating onto the titanium cathode surface during
the operation. The deteriorated cathode could be restored by immersing it in a hot aqua regia or a mixture of hydrofluoric
acid and phosphoric acid for a few minutes. 相似文献
4.
Yasuhiro Awakura Masami Aoki Atsushi Tsuchiya Hiroshi Majima 《Metallurgical and Materials Transactions B》1989,20(5):555-565
The diffusion coefficients of NiCl2, ZnCl2, and CdCl2 in the aqueous solution systems of MC12 and MC12-HC1 were measured at 298 K using a diaphragm-cell method. The data are listed as a function of molar concentrations of MC12 at the HC1 concentrations of 0, 0.1, 0.5, 1.0, and 2.0 mol dm-3. It was found that the concentration dependencies of the diffusion coefficients for these metal chlorides in single-electrolyte
solutions differed from each other. This could be explained in terms of changes in the mean activity coefficients of chloride
and in the viscosities of those solutions. The diffusion coefficient of metal chloride in MC12-HC1 solution was greatly affected by the HC1 concentration; however, the behavior of the diffusion coefficients varied, depending
on the kind of chloride involved. In NiCl2-HCl solutions, an increase in HC1 con-centration caused a decrease in the diffusion coefficient value, while in ZnCl2-HCl solutions, the addition of 2 mol dm-3 HC1 caused an increase in the diffusion coefficient of ZnCl2. These phenomena are quite different from those of the sulfate systems reported in our previous work. It was also demonstrated
that the concentration dependency of the diffusion coefficients of MC12 in aqueous MC12-HC1 solutions could be attributed to the diffusion potential as well as the changes in the mean activity coefficient and
viscosity.
Masami Aoki, formerly Graduate Student, Department of Met-allurgy, Kyoto University. 相似文献
5.
Yasuhiro Awakura Toshiya Doi Hiroshi Majima 《Metallurgical and Materials Transactions B》1988,19(1):5-12
The diffusion coefficients of CuSO4, ZnSO4, and NiSO4 in the aqueous solution systems of MSO4 and MSO4-H2SO4 were measured at 298 K using a diaphragm-cell method, and are listed as a function of molar concentrations of MSO4 and H2SO4. It was found that the concentration dependencies of the diffusion coefficients for CuSO4, ZnSO4, and NiSO4 in each single metal sulfate solution are very similar. The presence of H2SO4 generally causes a less significant concentration dependency of the diffusion coefficients of MSO4. The concentration dependencies of the diffusion coefficients of CuSO4 in aqueous solutions of CuSO4 and CuSO4-H2SO4 are attributed to the changes in the mean activity coefficient of CuSO4 and the viscosity of the solutions.
formerly Graduate Student, Department of Metallurgy, Kyoto University, Kyoto, Japan 相似文献
6.
Hiroshi Majima Yasuhiro Awakura Koji Sato Shuichiro Hirono 《Metallurgical and Materials Transactions B》1987,18(1):49-57
Speciation models for aqueous solutions of UO2SO4−U(SO4)2−H2SO4−HF and UO2Cl2−UCl4−HCl−HF were proposed based on chemical reaction equilibria, mass balances, charge balance, and stoichiometry of UF4(s). The equilibrium concentrations of uranium and fluoride species in these solutions were calculated at 298 K, and are of
relevance to the electrolytic reduction of U(VI), followed by the precipitation of UF4(s). In these calculations, the reduction ratios of U(VI) were set at 25, 50, 75, and 100 pct. In the sulfate system the stable
domains of U4+, U(SO4)
n
4−2n
, UF
n
4−n
, and UF4(s) as U(IV) species and UO
2
2+
, UO2(SO4)
n
2−2n
, and UO2F
n
2−n
, as U(VI) species are strongly dependent on theC
T(F)/C
T(U(IV)) value. On the other hand, the stable domains of U4+ UCl3+, UF
n
/4−n
, and UF4(s) as U(IV) species and UO
2
2+
, UO2Cl+, and UO2F
n
2−n
as U(VI) species are also strongly affected by theC
T(F)/C
T(U(IV)) ratio in the chloride system. The initiation and precipitation of UF4(s) in both the sulfate and chloride systems are a function of the reduction ratio of U(VI). The higher the reduction ratio,
the lower theC
T(F)/C
T(U(IV)) values required. Compared to the chloride system, UF4(s) precipitation in the sulfate system starts at a lower value ofC
T(F)/C
T(U(IV)). The addition of an excess amount of HF does not cause the dissolution of UF4(s) precipitates because HF is a weak acid.
KOJI SATO, formerly Graduate Student, Department of Metallurgy, Kyoto University, Kyoto, Japan 相似文献
7.
The effect of the W(VI) and Mo(VI) ions on the electrical conductivity of ammonium hydroxide solutions (7 mol/L) is studied in the tungsten or molybdenum concentration range 0.1–0.5 mol/L and the temperature range 20–60°C. The electrical conductivities of the solutions are shown to depend linearly on the solution temperature and the metal concentration, and the coefficients of linear regression equations are calculated. The temperature coefficients of the electrical conductivities of the solutions are determined. 相似文献
8.
《Acta Metallurgica》1988,36(3):767-774
The results of a study of solubility and bulk diffusion of 110Ag and 63Ni in lead, lead-silver and lead-nickel solid solutions in the temperature range 220 to 88°C are reported. Owing to the low solubility of silver and nickel in lead, Pick's solution corresponding to the boundary condition of a constant concentration of solute at the surface has been used. Depth-profile concentration analysis of 110Ag and 63Ni suggests a fundamental difference between the diffusion mechanisms of silver and nickel. Since silver penetration profiles in pure lead give diffusion coefficients independent of the penetration depth and silver concentration, it is suggested that slight decrease of silver diffusivity in lead-silver solid solutions (which remain within experimental error) have no significance. This implies that the interstitial silver atoms do not associate significantly with each other to form Ag-Ag dimers. In contrast, different behaviors of 63Ni depth profile concentration in pure lead and saturated PbNi solid solutions agree with a strong Ni-Ni interaction leading to the formation of less mobile dimers near the surface in pure lead. The model proposed by Decker to describe the diminution of gold diffusivity in PbAu solid solutions yields H = 9500 cal/mol and S = 0.9 k for the binding enthalpy and entropy of Ni-Ni substitutional dimers. 相似文献
9.
A method is described by which the diffusion coefficients of electrically charged micelles can be determined using micellar electrokinetic chromatography (MEKC). The determination is based on a theory for the dispersion, at low electric field strengths, of analytes that are solubilized by only the micellar phase. The dispersion is represented by contributions from instrumental sources and from longitudinal diffusion. The latter depends on the micellar diffusion coefficient. The theory is used to determine the micellar diffusion coefficients of the surfactant sodium dodecyl sulfate in three solutions having different surfactant concentrations. These diffusion coefficients compare very favorably with those determined by diffusion-ordered two-dimensional NMR spectroscopy. An argument is presented justifying that the diffusion coefficients determined by MEKC are self-diffusion coefficients. 相似文献
10.
E. E. Maltseva A. A. Blokhin Yu. V. Murashkin M. A. Mikhaylenko 《Russian Journal of Non-Ferrous Metals》2017,58(5):463-469
The possibility of the additional purification of ammonia rhenium desorbates with respect to molybdenum in the course of the sorption recovery of rhenium from Mo-containing solutions with the help of Purolite A170 and Purolite A172 weak base anion-exchange resins is considered. The pH-dependence of sorption of Re(VII) and Mo(VI) on these anion-exchange resins is investigated in static conditions with the 1 M (NH4)2SO4 background in the solution. It is shown that the range of pH, in which anion-exchange resins retain the ability to sorb Re(VII), is also spread to a weakly basic region. A substantial decrease in the adsorption of Re(VII) starts already with an increase in pH above 7.5. The capacity of anion-exchange resins with respect to Mo(VI) starts to decrease noticeably with an increase in pH of solutions above 5.0, and molybdenum almost ceases to sorb by both anion-exchange resins upon reaching pH ~ 7.0. In order to decrease the Mo(VI) content in rhenium desorbates with the sorption recovery of Re(VII) from Mo-containing solutions on weak base anion-exchange resins, the following flowsheet is suggested. Initially, the main amount of sorbed Mo(VI) is desorbed by contacting the saturated anion-exchange resin with the ammonium sulfate solution upon mixture stirring and holding constant pH of the solution in limits of 7.0–7.5 due to the addition of dosed amounts of ammonia solution. Then anion-exchange resin is separated from the ammonium sulfate solution containing Mo(VI), washed with water, and Re(VII) is desorbed by ammonium solution in dynamic conditions. The verification of the proposed method for the resins saturated by sorption from the model solution of the composition, g/L, 98 H2SO4, 4 Mo(VI), and 0.5 Re(VII) showed the occurrence of desorption of no less than 90% sorbed molybdenum during the treatment of anion-exchange resins with ammonium sulfate solution. Herewith, concentration ratio Re(VII) : Mo(VI) in ammoniacal rhenium desorbates when using A170 anion-exchange resin increases 11-fold and when using A172 anion-exchange resin, it increases 20-fold compared with that attained without the additional washing of Mo(VI). Losses of Re(VII) with the Mo-containing desorbate (reversible) do not exceed 5.2% of the amount of sorbed Re(VII). 相似文献
11.
Hiroshi Majima Yasuhiro Awakura Takumi Mishima 《Metallurgical and Materials Transactions B》1985,16(1):23-30
The reactions of hematite in aqueous hydrochloric acid, perchloric acid, and sulfuric acid solutions with or without the addition
of common or uncommon salts were studied using monosized particulates in a well-stirred reactor and dilute solid concentration
to obtain fundamental details of the reaction kinetics. The experimental rate data suggest that the entire leaching reaction
is controlled by a chemical process. The leaching rate of hematite was seen to be first order with respect to hydrogen ion
activity, a(H+), in hydrochloric acid or perchloric acid solutions, with or without the addition of common salts, while the rate was of
a half order in sulfuric acid solutions with or without the addition of sodium sulfate. A theoretical analysis showed that
the anions next to the surface in the double layer were chloride ion and perchlorate ion in hydrochloric acid and perchloric
acid solutions, respectively, and sulfate ion in sulfuric acid solutions, with or without the addition of sodium sulfate.
The fact that the leaching rates of hematite were quite different in various acids having identical α(H+ values indicates the importance of anion adsorption. The dependency of the leaching rate upon α(H+) appeared to be controlled by adsorbed anions next to the surface in the double layer.
TAKUMI MISHIMA, formerly Graduate Student, Kyoto University 相似文献
12.
采用生物聚合硫酸铁絮凝剂对低浓度含铀废水进行絮凝试验研究,考察U(VI)溶液pH、絮凝剂投加量以及U(VI)初始浓度对絮凝效果的影响。结果表明,反应最佳pH范围在5~7,反应平衡时间为5 min,其絮凝过程符合Lagergren准二级反应动力学模型。含铀废水经生物聚合硫酸铁絮凝处理过后,残余铀浓度低于《铀加工与燃料制造设施辐射防护规定》(EJ 1056-2005)中的排放限值(0.05 mg/L)。 相似文献
13.
Shigeru Suzuki Shuichiro Hirono Yasuhiro Awakura Hiroshi Majima 《Metallurgical and Materials Transactions B》1990,21(5):839-844
To provide important thermodynamic data for use in uranium hydrometallurgy, solubilities of uranous sulfate were determined
as a function of free acid concentration and temperature. Two sets of experiments were performed in this study. One set was
the precipitation experiments of uranous sulfate crystals, in which concentrated uranous sulfate solution was mixed with sulfuric
acid solution of suitable concentration. The other set was the dissolution experiments of uranous sulfate crystals in aqueous
sulfuric acid solutions. It is noteworthy that good agreement exists between the solubilities determined by the two methods.
At elevated temperatures, say, 363 K, the presence of free sulfuric acid is required to avoid precipitation of uranous hydroxide
resulting from the hydrolysis of uranous sulfate. Generally speaking, however, an increase in free sulfuric acid concentration
results in a slight decrease in uranous sulfate solubility. The elevation of solution temperature causes a decrease in solubility
of uranous sulfate. It should be noted that the solid uranous sulfates equilibrated with saturated solutions at 298 K were
U(SO4)2 2H2O in dilute sulfuric acid solution and U(SO4)2 4H2O in concentrated sulfuric acid solution, while those at 333 K and 363 K were mainly U(SO4)2 4H2O.
Formerly Director, Mining and Ore Processing Division, Ningyo-toge Works, Power Reactor and Nuclear Fuel Development Corporation,
is Director, Ningyo-toge Nuclear Service Company, Tomata-gun, Okayama Prefecture 708-06, Japan. 相似文献
14.
Soluble uranyl ion [UO2(2+), U(VI)] is a kidney poison. Uranyl ion accumulates in bone, and the high specific activity uranium isotopes induce bone cancer. Although sought since the 1940's, no multidentate ligand was identified, until now, that efficiently and stably binds U(VI) at physiological pH, promotes its excretion, and reduces deposits in kidneys and bone. Ten multidentate ligands patterned after natural siderophores and composed of sulfocatechol [CAM(S)], carboxy-catechol [CAM(C)], or hydroxypyridinone [Me-3,2-HOPO] metal-binding units have been tested for in vivo chelation of U(VI). Ligands were injected intraperitoneally (i.p.) into mice 3 min after intravenous (i.v.) injection of 233U or (232+235)U as UO2Cl2 [ligand-to-metal molar ratio 75 to 92]. Regardless of backbone structure, denticity, or binding unit, all 10 ligands significantly reduced kidney U(VI) compared with controls or with mice given CaNa3-DTPA, and four CAM(S) or CAM(C) ligands also significantly reduced skeleton U(VI). Several ligands removed U(VI) from kidneys, when injected at 1 or 24 h. Injected at molar ratios > or = 300, 5-LIO(Me-3,2-HOPO) and TREN-(Me-3,2-HOPO) reduced kidney U(VI) to about 10% of control. Given orally to fasted mice at molar ratios > or = 300, those ligands significantly reduced kidney U(VI). In mice injected i.v. with 0.42 micromol kg(-1) of 235U and given 100 micromol kg(-1) of one of those Me-3,2-HOPO ligands i.p. daily for 10 d starting at 1 h after the U(VI)) loss of kidney U(VI) was greatly accelerated, and the kidneys of treated mice showed no microscopic evidence of renal injury. Crystals of uranyl chelates with linear tetradentate ligands containing bidentate Me-3,2-HOPO groups demonstrate a 1:1 structure. Considering low toxicity, effectiveness, and reasonable cost, the structurally simple linear tetradentate ligands based on the 5-LI backbone (diaminopentane) offer the most promising approach to a clinically acceptable therapeutic agent for U(VI). Work is in progress to identify the most suitable CAM or HOPO binding unit(s). 相似文献
15.
《Canadian Metallurgical Quarterly》2013,52(4):315-318
AbstractInterdiffusion was studied in copper (rich)-chromium solid solutions in the composition range approximately 0.2 to 0.8 at% Cr and in the temperature range 852°C – 1050°C. Diffusion couples consisted of cylindrical sections of OFHC copper electroplated with pure chromium. The concentration profiles of the diffusion couples were determined using an electron probe micro analyzer, and the diffusion coefficients were determined by fitting the error function solution of the diffusion equation to the experimental curves. The Arrhenius plot of the diffusion coefficients obtained for five different temperatures gives 48.4 ± 1.2 kcal/mole and 1.11?0.44+0.78 cm2/sec for the activation energy (ED) and frequency factor (Do) respectively (where the limits given are standard deviations for a 99 per cent confidence level), and approximate published chromium tracer diffusion and copper self diffusion results. Résumé Les auteurs ont étudié l'interdiffusion dans des solutions solides, riches en cuivre et con tenant environ 0.2 à 0.8% atomique de chrome, pour une gamme de temp;amp;#x00E9;ratures de 852 agrave; 1050°c. Les couples de diffusion étaient des sections cylindriques de cuivre OFHC électroplaqués avec du chrome pur. Les profils de concentration des couples ont été mesurés par microsonde électronique et les coefficients de diffusion ont été déterminés en lissant les courbes expérimentales grâce à la solution de la fonction erreur pour l'équation de diffusion. La courbe déArrhenius des coefficients de diffusion obtenus à cinq températures différentes donne une énergie d'activation (ED) de 48.4 ± 1.2 kcal/mole et un facteur de fréquence (Do) de 1.11 ?0.44+0.78 cm2/sec. (oú les limites indiquées sont les déviations standards pour un niveau de con fiance de 99%). Ces valeurs sont approximativement égales à celles publiées pour la diffusion de traceur de chrome et pour l'autodiffusion du cuivre. 相似文献
16.
Thermodynamic data for distribution coefficients and maximum loading are reported for cupric ion extraction by LIX 64N solution in xylene. The influence of ionic strength and chloride concentration in aqueous phase on distribution coefficients and measured pH is given and interpreted. The comparison of chloride and sulfate aqueous solutions shows that if extraction seems higher in chloride solution at the same measured pH, it is of the same order of magnitude at the same true concentration of H+ and it is higher in sulfate solution at the same apparent concentration of acid. 相似文献
17.
Hiroshi Majima Ernest Peters Yasuhiro Awakura Sung Kook Park 《Metallurgical and Materials Transactions B》1987,18(1):41-47
The electrical conductivities of the aqueous solution system of H2SO4-MSO4 (involving ZnSO4, MgSO4, Na2SO4, and (NH4)2SO4), reported by Tozawaet al., were examined in terms of a (H2O) and H+ ion concentration. The equations to compute the concentrations of various species in aqueous sulfuric acid solutions containing
metal sulfates were derived for a typical example of the H2SO4−ZnSO4−MgSO4−(Na2SO4)−H2O system. It was found that the H+ ion concentrations in concentrated sulfuric acid solutions corresponding to practical zinc electrowinning solutions are very
high and remain almost constant with or without the addition of metal sulfates. The addition of metal sulfates to aqueous
sulfuric acid solution causes a decrease in electrical conductivity, and this phenomenon is attributed to a decrease in water
activity, which reflects a decrease in the amount of free water. The relationship between conductivity and water activity
at a constant H+ ion concentration is independent of the kind of sulfates added. On the other hand, any increase in H+ ion concentration results in an increase in electrical conductivity. A novel method for the prediction of electrical conductivity
of acidic sulfate solution is proposed that uses the calculated data of water activity and the calculated H+ ion concentration. Also, the authors examined an extension of the Robinson-Bower equation to calculate water activity in
quarternary solutions based on molarity instead of molality, and found that such calculated values are in satisfactory agreement
with those determined experimentally by a transpiration method. 相似文献
18.
Stylianos Sifniades Theodore Largman Allen A. Tunick Fred W. Koff 《Hydrometallurgy》1981,7(3):201-212
U(VI) was transported at 23 ± 1°C from 5–6 M phosphoric acid solutions through liquid membranes of kerosene solutions of di(2-ethylhexyl) phosphoric acid and trioctyl phosphine oxide (D2EHPA/TOPO) supported on porous polytetrafluoroethylene to a solution of phosphoric acid of equal or greater molarity containing ferrous ion as a reducing agent. The ferrous ion could be omitted when the higher molarity acid was used. The uranium flux was proportional to the U(VI) concentration. The overall resistivity of the membranes to uranium flux had a diffusional component that was proportional to the membrane thickness and an interfacial component that resulted from rate-limiting uranium complexation/decomplexation kinetics. The interfacial component accounted for over 80% of the resistivity of a membrane 75 μm thick. Increasing the temperature to 60°C only slightly diminished the interfacial resistivity. A theoretical model was constructed that accommodated data obtained from uranium transport through the membranes and through quiescent layers of phosphoric acid and D2EHPA/TOPO in kerosene. The average uranium flux from simulated solutions of wet-process phosphoric acid at 90% uranium transfer was estimated to be 1.3 × 10?11 mol cm?2 sec?1, or 0.09 lb ft?2 yr?1. The flux was judged to be too low for supported liquid membranes to be competitive with liquid/liquid extraction for recovery of uranium from wet-process phosphoric acid. 相似文献
19.
Yasuhiro Awakura Tetsuji Hirato Akihiko Kagawa Yoshiyasu Yamada Hiroshi Majima 《Metallurgical and Materials Transactions B》1991,22(5):569-574
The kinetics of malachite dissolution in aqueous ethylenediaminetetraacetate (EDTA) solution has been investigated in the
temperature range of 298 to 318 K. The dissolution rate of malachite determined under the present set of experimental conditions
was found to be independent of agitation speed. The dissolution rate increased with increasing EDTA concentration, but leveled
off at higher concentrations. At constant EDTA concentration, an increase in dissolution rate was detected at higher temperatures.
A dissolution mechanism involving Langmuir-type EDTA adsorption was proposed, in which the dissolution rate of malachite is
controlled by the removal of Cu(II)-EDTA complex from the malachite lattice. The proposed mechanism can explain the dependency
of the dissolution rate on EDTA concentration. The activation energies determined at pHs 5, 7.5, and 10 were found to be 51.4,
50.2, and 57.5 kJ mol−1, respectively. The calculated enthalpy changes of EDTA adsorption equilibrium were −43.2, −35.2, and −45.0 kJ mol−1 for pHs 5, 7.5, and 10, respectively. These values are in agreement with the proposed mechanism.
Formerly Graduate Student, Department of Metallurgy, Kyoto University, is
Formerly Professor, is Professor Emeritus, Department of Metallurgy, Kyoto University. 相似文献
20.
Diffusion of silicon in aluminum 总被引:1,自引:0,他引:1
Shin-ichiro Fujikawa Ken-ichi Hirano Yoshiaki Fukushima 《Metallurgical and Materials Transactions A》1978,9(12):1811-1815
Interdiffusion coefficients in Al-Si alloys were determined by Matano’s method in the tem-perature range from 753 to 893 K
with the couple consisting of pure aluminum and an Al-Si alloy. Temperature dependence of the impurity diffusion coefficients
of Si in Al, obtained by extrapolation of the concentration dependence of the interdiffusion coeffi-cient to zero mole fraction
of Si, is given by the following equation: DSi/Al = (2.02+0.97
-0.66 × 10-4 exp [-(136 ±3) kJ mol-1/RT] m2/s. p ] The Kirkendall marker was found to move toward the Si-rich side, indicating that the Si atom diffuses faster than
the Al atom in Al-Si alloys. From the interdiffusion coeffi-cient and the marker shift, the intrinsic diffusion coefficients
were calculated.
The difference in the activation energies (ΔQ) between the impurity diffusion of Si in Al and the self-diffusion of Al was
estimated by means of the asymptotic oscillating po-tential and the Le Claire theory. The calculated value of ΔQ is in fair
agreement with the experimental value. The vacancy-solute binding energy for Si in Al was also dis-cussed based on the diffusion
data.
formerly Undergraduate Student, Tohoku University 相似文献