Cu-C and Al-Cu-C phase diagrams and thermodynamic properties of c in the alloys from 1550 °C to 2300 °C

The Cu-C and Al-Cu-C phase diagrams were determined at 1550 °C to 2300 °C by chemical and X-ray diffraction analyses of alloys saturated with carbon within sealed graphite crucibles. Isothermal sections for the ternary system were determined at intervals of 150 °C over the range of temperatures investigated. The univariant points in atomic percent on the 1700 °C, 1850 °C, and 2000 °C isotherms are 70.7Al-28.9Cu-0.4C, 74.4Al-24.0Cu-1.6C, and 78.3Al-17.0Cu-4.7C, respectively, as determined by metallographic examination of rapidly cooled alloys. Graphite and Al₄C₃ (decomposition temperature 2156 °C) were the only solid phases observed at these temperatures. The excess partial Gibbs energy for dissolved carbon in the liquid Al-Cu-C solutions in equilibrium with C, as calculated from the experimental solubilities, isˉ G _c ^e = - RT lnx =y ²[176,860 - 55.42T - (224,200 - 110.84T)x] +z ²[237,000 - 48.61T] +yz[320,510 - 36.77T + (30,180 + 35.10T)z + (51,570 - 74.13T)yz + (246,400 - 88.04T)yz ² - 60,000], J/g atom where R is the gas constant,T is the temperature in K, andx, y, andz are the atomic fractions of C, Al, and Cu, respectively. The equation also is a good approximation for liquid solutions in equilibrium with A1₄C₃.     

Phase Selection in Undercooled Ni-3.3 Wt Pct B Alloy Melt

The change of eutectic solidification mode in undercooled Ni-3.3 wt pct B melt was studied by fluxing and cyclic superheating. The eutectic structure is mainly controlled by the undercooling for eutectic solidification, ΔT ₂, instead of ΔT ₁, the undercooling for primary solidification. At a small ?T ₂ [e.g., 56 K (56 °C)], the stable eutectic reaction (L → Ni₃B + Ni) occurs and the eutectic morphology consists of lamellar and anomalous eutectic; whereas at a larger ?T ₂ [≥140 K (140 °C)], the metastable eutectic reaction (L → Ni₂₃B₆ + Ni) occurs and the eutectic morphology consists of matrix, network boundary, and two kinds of dot phases. Further analysis declares that the regularly distributed dot phases with larger size come from the metastable eutectic transformation and are identified as α-Ni structure, whereas the irregularly distributed ones with smaller size are a product of the metastable decomposition and tend to have a similar structure to α-Ni as it grows. Calculation of the classical nucleation theory shows that the competitive nucleation between Ni₂₃B₆ and Ni₃B leads to a critical undercooling, ΔT ₂ ^* [125 K < ΔT ₂ ^* < 157 K (125 °C < ?T ₂ ^* < 157 °C)], for the metastable/stable eutectic formation.     

Peculiarities of helium porosity formation in the surface layer of the structural materials used for the first wall of fusion reactor

Transmission electron microscopy is used to study the formation of helium porosity in the nearsurface layer of ferritic–martensitic steels and vanadium irradiated by 40-keV He⁺ ions at a temperature of 923 K up to fluence of 5 × 10²⁰ He⁺/m² and, then, by 7.5-MeV Ni²⁺ ions at 923 K up to dose of 100 dpa. Large gas bubbles are found to form in the zone with the maximum concentration of radiation vacancies during He⁺ ion irradiation. Moreover, small bubbles form in some grains at the depths that are larger than the He+ ion range in the irradiated material. Sequential irradiation by He⁺ and Ni²⁺ ions leads to the nucleation of helium bubbles at still larger depths due to helium atom transport via recoil and/or ion mixing. The precipitation hardening of the steels by Y₂O₃ oxide nanoparticles is found to suppress helium swelling substantially.     

Oxygen permeability of calcia-stabilized zirconia

Oxygen permeability of commercial calcia-stabilized zirconia has been measured at 1673 to 1823 K by the following cell; O₂ ZrO₂(CaO) N₂ - O₂ (P’tO₂ = 1 atm) solid electrolyte (P″O₂ = 0.39 - 10^10-3 atm). Oxygen permeability of calcia-stabilized zirconia is proportional to (1 - P″O₂ ^1/4). From the permeability measurement, the conduction properties of the electrolyte were log σ-_? ^b+ = 0.28- 5100/T and logP_b+ =-0.87 + 15,400/T where σ-_? ^b+ is the þ-@#@ type electronic conductivity at P_{O 2} = 1 atm, and P_b+ is the oxygen activity at which the þ-@#@ type electronic conductivity and the ionic conductivity are equal.     

Chemical equilibrium studies on the copper-sulfuric acid-kelex 100-xylene system

A thermodynamic equilibrium model is developed for the distribution of copper between the phases for the system copper-sulfuric acid-xylene-/3-alkenyl 8-hydroxyquinoline. Chemical equilibrium data were obtained for the range of experimental parameters of [Cu] _{aq, i} ^T (0.005 to 0.02 mol/dm³), [S]^T (0.05 to 0.2 mol/dm³), extractant (0.02 to 0.06 mol/dm³), and temperature (20 to 50 ?C). The nonlinear regression analysis best fit model is ln(Dαo/γCusu++) = 3.83 + 642(1/T - 1/308) +2 ln([HR]/[H⁺]γ_H ⁺) whereD is the distribution coefficient, α_o is the reciprocal of the degree of formation of copper ion, and γ refers to activity coefficients of ionic species. The analysis of the data considers the aqueous phase ionic equilibria and a technique to estimate the impurities present in the reagent. The results indicate that the enthalpy of the reaction and the entropy change are -5338 J/mol and 14.5 J/mol · K, respectively. Also, the stoichiometric coefficient of two, determined for the extractant with cupric ion, is in agreement with other investigators.     

Substitution Recovery of Gold from Copper-Ethylenediamine-Thiosulfate Leaching Solution with Copper Power

The substitution method of recovering gold from thiosulfate-ethylenediamine (en)-Cu²⁺ leaching solution using copper powder was studied. The effects of reaction time, stirring speed, pH, thiosulfate concentration, en/Cu²⁺ molar ratio, Cu/Au⁺ mass ratio, and temperature on gold recovery were systematically examined. The experimental results showed that reaction time, stirring speed, thiosulfate concentration, en/Cu²⁺ molar ratio, Cu/Au⁺ mass ratio, and temperature have a significant influence on the recovery rate of gold, whereas the pH has little effect. A high gold recovery rate of 95.38% was achieved in 0.2 mol/L thiosulfate at 40°C after 40 min with a stirring speed of 400 rpm, pH of 11, en/Cu²⁺ molar ratio of 6, and Cu/Au⁺ mass ratio of 150. A kinetic study revealed that the reduction of gold-thiosulfate complex ions (Au(S₂O₃) ₂ ^3- ) on the surface of copper powder follows a first-order kinetics model with an apparent activation energy of 39.82 kJ/mol.     

Determination of thermodynamic interaction parameters in solid V-Ti alloys using the mass spectrometer

The Knudsen effusion method was combined with a mass spectrometer sensing technique in order to measure thermodynamic quantities of solid solution alloys of V-Ti binary system. The technique makes use of the regular solution model in order to treat the vaporization data in terms of ion current ratios obtained from the mass spectrometer. Within the experimental temperature range of 1500° to 1725°C and the composition range of 0.10 <N _Ti<0.90, the activity of titanium in the bcc (β) phase relative to pure titanium for the binary alloy is:RT lna _Ti=RT lnN _Ti+N _V ² (1.82±0.13) kcal per g-atom while the activity of vanadium is:RT lna _V=RT lnN _V+N _Ti ² (1.82±0.13) kcal per g-atom. The experimental result on the pairwise interaction parameter agrees well with the theoretically calculated value.     

Adsorption of gold on activated carbon in bromide solutions

Adsorption of gold on activated carbon from gold bromide solutions was examined as a function of pH, particle size, amount of carbon, initial gold bromide concentration, bromine concentration, temperature, and various cations and anions. The pH did not have any effect on gold adsorption below pH = 6. Above pH = 6, pH had a dramatically negative effect. The adsorption occurred according to a first-order reaction-rate model. The reaction-rate constant was proportional to the inverse of carbon particle radius, the amount of carbon, and independent of the initial gold concentration. Temperature had very little effect on the rate of gold adsorption. Cations (Cu²⁺, Fe³⁺, Ca²⁺, Mg²⁺, and Na⁺) and anions (SO ₄ ² , Cl^-, Br^-) did not have any effect on gold adsorption. Free bromine had a very negative effect on gold uptake. Gold bromide is very stable and stays in this form on the carbon surface. Contrary to this, gold chloride is unstable, and elemental gold precipitates on the carbon surface. Loading capacity of carbon depended on the presence of free bromine. In the presence of free bromine, it was further dependent on temperature (increased with increasing temperature). AtT = 25 °C, gold loading was 27 to 64 kg Au/t carbon. In bromine-free solutions, gold loading was 174 to 315 kg Au/t carbon.     

Lead and nickel distribution in the Cup-PbO-SiO2 and the Cup-NiO-SiO2 Systems equilibrated with liquid copper

The distribution of lead and of nickel between molten copper and a ternary cuprous oxide-metal oxide-silica saturated slag was measured at 1498 K. The results are correlated using ion fractions, calculated either according to Temkin’s method, or as electrically equivalent ion fractions. The simpler method suggested by Temkin correlates slightly better than the other giving the following relations between the ionic concentration quotients and impurity concentration in the metal: logN _Pb ⁺⁺/N ² _Cu ⁺ = logX _Pb + 2.40 ± 0.05, valid up toX _Pb = 0.003 logN _Ni ⁺⁺/N ² _Cu ⁺ = 0.44 logX _Pb + 0.15 ± 0.07, valid up toX _Ni = 0.004. In the nickel systems, an Ni rich phase, identified as NiO, separates from the metal at X_Ni = 0.04 (0.4 wt pct). A tentative phase diagram of the Cu₂O-NiO-SiO₂ system at 1498 K is presented. The data found in this investigation explain why the impurities Pb or Ni cannot be practically reduced to low levels by oxidation. This results from the large amounts of copper that are oxidized in going to low impurity levels. Use of a two-slag refining process is shown to cut slag losses of copper to less than half those encountered with a single slag operation.     

Kinetics and mechanism of the conversion of covellite (CuS) to digenite (Cu1.8S)

Rates of conversion of covellite (CuS) to digenite (Cu_1.*S) in N₂ and various partial pressures of O₂ have been studied in the temperature range 260° to 400°C. The reaction is first order with respect to O₂ concentration in N₂?O₂ mixtures at 1 atm. The experimental activation energy for the conversion of CuS to Cu_1.8S is 23±3 kcal. In a nitrogen atmosphere, the conversion proceeds at a slower rate but with the same activation energy and leads to the formation of elemental sulfur instead of SO₂. An externally added small amount of iron powder (0.6 pct) increased the rate of conversion, but had no effect on the apparent activation energy. The rate-controlling reaction in the conversion mechanism is postulated to be Cu_1.8S→1.8Cu⁺+1.8e ^?+S at the Cu_1.8S/gas interface. Reduction of CuS by copper(I) ions and electrons occurs by a rapid reaction, 0.8 Cu⁺+0.8e ^?+CuS→Cu_1.8S at the CuS/Cu_1.8S interface, which steadily contracts with time.     

Equilibrium formation and thermodynamic properties of gaseous silicon monosulfide

The formation of gaseous silicon monosulfide according to the reaction 1/2 SiS_2(s + 1/2 Si_(s) = SiS_(g) has been studied by the Knudsen effusion-gravimetric technique over the temperature range 863 to 1161 K. The equilibrium SiS pressure may be expressed by the equation logP _SiS(atm) = 7.205 -12,600T ⁻¹+ 0.4677 logT -4.508 × 10⁻⁴ T + 29.88T ^−1/2 The experimental free energy of the reaction may be represented by the two-term expression ΔF _{863-1161 K} ⁰ = 54,270 -38.34T Combination of these results and recent experimental data provide the standard free energy of formation of gaseous silicon monosulfide as expressed by ΔF _{863-1686 K} ⁰ = 12,740 -19.18T Si_{(s )} + 1/2 S_2(g) = SiS_(g) ΔF _{1686-2953 K} ⁰ = 640 -12.02T Si_(l) + 1/2 S_2(g) = SiS_(g)     

The extraction of nickel from ammoniacal media and its separation from copper,cobalt and zinc using hydroxyoxime extractants I. SME-529

Nickel extraction from ammoniacal media, containing, initially, 0.03 mol dm^?3 of nickel, by 10% v/v Shell metal extractant 529 in MSB 210 or Shellsol A, has been studied as a function of pH, counter anions (nitrate or sulphate), ammonium salt concentration, temperature (10 to 50°C), and the presence of copper, cobalt and zinc. The extraction of copper as a function of pH was studied in the presence of nickel. The pH for maximum nickel extraction decreased from 8.2 to 7.4 as the ammonium sulphate concentration increased from 0.1 to 3.4 mol dm^?3. Nickel extraction was lower from sulphate than from nitrate media and with Shellsol A, and at higher temperature. The enthalpy and entropy of extraction were negative. The presence of copper, cobalt and zinc decreased nickel extraction. Separation factors between copper and nickel are reported as a function of pH and indicate that initial removal of copper is desirable.From a consideration of the equilibrium, the extraction of nickel (with MSB 210 diluent) at 25°C could be expressed by the equation:

$\text{log}\text{D}{}_{\mathrm{<mtext>Ni</mtext>}}\text{= ?9.25 +}\text{log}\text{α}{}_0\text{+ 2}\text{log}\text{(C}{}_{\mathrm{HR}}\text{?2[}\text{Ni}\text{]}{}_{\mathrm{<mtext>org</mtext>}}\text{) + 2}\text{pH}$

where D_Ni represents nickel distribution coefficient, C_HR the total extractant concentration, [Ni]_org the organic nickel concentration (both in mol dm^?3) and α₀, the fraction of uncomplexed nickel in the aqueous phase calculated from the overall stability constants of Ni(NH₃)_i²⁺ complexes and the formation constant of NiSO₄ ion pairs.The limiting slope of ?1 for long D_Ni versus log [NH₃]_free plots indicated an average co-ordination number of 3 for nickel by ammonia in the aqueous phase.The uptake of SO₄^2?, NO₃^? and water by the organic phase was negligible. The uptake of ammonia was dependent upon pH and the ammonia content of the aqueous phase, and was negligible in the absence of metal.     

The effect of heat treatment on corrosion behaviour of Ni–P–3 gr/lit Cu nano-composite coating

In this investigation, the effect of heat treatment on corrosion behaviour of Ni–P–Cu nano-composite coating was studied. Initially, an Ni–P–(3?g?l^?1) Cu nano-composite coating was produced under the bath condition of pH?=?4.5–5, RPM?=?400. The coatings were then heat treated at 400°C for 1?h. Scanning electron microscope (SEM), electron dispersive spectroscopy (EDS) and X-ray diffraction (XRD) techniques were employed to analyse the coating characteristics. As well, corrosion resistance of the coatings in a solution of 1?M HCl was explored by potentiodynamic polarisation and electrochemical impedance spectroscopy (EIS). Results show that heat treatment for 1?h at 400°C crystallised the Ni–P–Cu coating and changed the amorphous morphology of the coating. This crystallisation also decreased corrosion resistance mainly due to P content reduction of the nano-composite coating. Finally, heat treatment reduced the P content of the coating as it formed different phases such as Cu₃P, Ni₈P₃, Ni₅P₂ and CuP₂.     

Electrode processes at the glass carbon/LiCl-CuCl-CuCl2 melt interface

The kinetics of the electrode processes occurring at the glass carbon/LiCl-CuCl-CuCl₂ $\left( {N_{CuCl - CuCl_2 } = 0 - 7.5 mol \% } \right)$ melt interface is studied by the coulostatic method, single current pulse chronopotentiometry, and stationary voltammetry at a temperature of 950 K and the atmospheric pressure of chlorine over a melt. The exchange current densities in the molten mixtures are determined by the coulostatic method. These data are used to calculate the transfer coefficient (?? = 0.54 ± 0.06) and the rate constant of the electrode reaction Cu²⁺ + e ^? ai Cu⁺ (k _S = 0.26 ± 0.02 cm/s). The results of stationary voltammetry in the cathode potential region reveal pronounced limiting currents up to the precipitation of metallic copper on an electrode. The experimental data obtained by chronopotentiometry are used to find the transition times for various current densities over the entire concentration range under study. The dependences plotted in the i??^1/2 = f(i) coordinates suggest the presence of a chemical homogeneous reaction preceding the electrode process. The total value of the rate constants of the forward and back reactions is estimated to be ??2. The copper mono- and dichloride concentrations are determined in the concentration range under study.     

Aqueous Oxidation of Iron Monosulfide (FeS) by Molecular Oxygen

Aqueous oxidation of iron monosulfide (FeS) by oxygen at initial pH between 2.5 and 5 was investigated in a closed system at different temperatures (25, 35, and 40°C). It was found that the rate of aqueous oxidation of FeS increases when initial [H⁺] and temperature increase. The reaction order with respect to [H⁺] was 0.16 ± 0.02 at 25°C. The activation energy was found to be 23 ± 5 kJ mol^–1 at initial pH 2.5. This value suggests that aqueous oxidation of FeS by oxygen is controlled by a mixed regime of diffusion and surface reaction control. FTIR analysis of the initial and reacted FeS samples has shown that during the aqueous oxidation of FeS by O₂ a sulfur-rich layer is formed on the mineral surface. The experimental results indicate that the protons adsorb on the mineral surface and catalyze Fe²⁺ release into solution (by Couloumbic repulsion) and S(-II) oxidation to higher oxidation states.     

Tunable Curie temperature and magnetocaloric effect of FeCrMoCBYNi bulk metallic glass with different crystallized phases

The investigation on Curie temperature and magnetocaloric effect of the FeCrMoCBYNi bulk metallic glass(BMG) with different crystallized phases was carried out by XRD,TEM and PPMS. The experimental results show that the Curie temperature(T_c) of Fe_(45)Cr_(15)Mo_(14)C_(15)B_6 Y_2 Ni_3 BMG with different annealing condition reaches a highest value of 95 K. The value of magnetic entropy change △S_M(T) of Sample 3 reaches a maxima of 0.48 J/(kg·K) at Tc temperature, which result from the interaction among the precipitated phases of(Fe,Cr)_(23)(C,B)_6, Fe_3 Mo_3 C and residual amorphous phase. Based on the experiment results, it can be obtained that the Curie temperature, magnetocaloric effect can reach their optimal value at low temperature, when the content of amorphous phase and precipitated phases type run up to certain value. The magnetic properties of Sample 1 with full amorphous phase and Sample 4 with full crystalline phase will both decrease.     

The acid-base behavior of zinc sulfate electrolytes: The temperature effect

The pH of both synthetic zinc sulfate solutions of various compositions and commercial zinc plant electrolytes was measured over a range of temperatures. A model for the solution thermodynamics has been developed to predict the solution speciation, temperature, and concentration effects on the pH. It was found from both the thermodynamic predictions and the pH measurements that the pH of zinc sulfate electrolytes, in the absence of free acid, drops with increasing temperature. The pH-temperature behavior was largely dominated by zinc hydrolysis. The pH of zinc sulfate electrolytes with small amounts of free acid both increased and then decreased in the temperature range of interest. This was explained by taking into account the additional effects of bisulfate/sulfate equilibrium and/or ZnSO₄ ion pairing on the overall pH behavior. Based on the correlation between the model and pH measurements, it is evident that the dinuclear species Zn₂(OH)³⁺ exists at a much higher concentration than Zn(OH)⁺ ions and dominates the pH-temperature behavior of the solution. Speciation and the acid/base composition of a ZnSO₄ solution, against pH at 100 °C, were also predicted. The pH-temperature behavior of zinc plant electrolytes from Kidd creek (Falconbridge Limited, Timmins, Canada) and CEZinc (Noranda Limited, Valleyfield, Canada) was measured by saturating the electrolytes with ZnO at 100 °C and then allowing the solutions to cool. The pH first increased slightly and then dropped from a maximum pH of 4.2. By including species involving Al³⁺, Mg²⁺, Mn²⁺, and Na⁺ in the zinc plant electrolytes in the solution model calculation, model predictions of the pH-temperature were again correlated with the pH-temperature measurements on zinc plant electrolytes.     

Reduction kinetics of Ni(OH)2 to nickel powder preparation under hydrothermal conditions

The reduction kinetics from Ni(OH)₂ to fine Ni metal powder under hydrothermal and H₂ pressure conditions using anthraquinon as an activator were investigated. The reduction ratio increased with temperature up to 225 °C. The H₂ molecule was activated by anthraquinone. This activated hydrogen acts as a reduction reagent from Ni²⁺ to Ni⁰. The process may proceed by heterogeneous reaction of Ni²⁺ ion and solid anthraquinon as follows: (1) anthraquinon is hydrated, (2) Ni²⁺ ion is absorbed on anthraquinon hydride, and (3) this complex decomposes to Ni⁰ powder, anthraquinon, and H₂O. The particle size of nickel powder obtained increased with increasing temperature and with decreasing pH. The average particle size was about 350 nm. The reduction kinetics were in good agreement with a core model equation with surface reaction, that is, 1 − (1 −x)^1/3 =kt, wherex is a reaction ratio andt is reaction time. Arrhenius plots showed two slopes with activation energies 65.9 kJ/mol at higher temperature and 377.2 kJ/mol at lower one. This result shows that the hydration of anthraquinon and adsorption of Ni²⁺ ion onto anthraquinon hydride and decomposition to Ni metal and anthraquinone proceed by consecutive reactions and rate determining steps change in each temperature range.     

Kinetics of dissolution of synthetic heazlewoodite (Ni3S2) in nitric acid solutions

The dissolution rate of heazlewoodite in nitric acid solution has been determined. The effects of nitric acid concentration, temperature, particle size, stirring intensity and addition of Cu²⁺ ions have been investigated. Solid residues after leaching were examined by SEM, X-ray diffraction and chemical analysis. In the solutions containing less than 2.0 M HNO₃, dissolution was observed to be completely inhibited after 30 min leaching time, and the rate of hydrogen sulphide production was faster than its oxidation to S⁰ and HSO₄^?. In 3 M HNO₃, an abrupt increase in dissolution rate of Ni₃S₂ was found. Two different regions of the dissolution of heazlewoodite were observed below and above 50°C. At temperatures below 50°C, the dissolution rate was very slow, even in 3.0 M HNO₃ solution, and H₂S gas was evolved. Above 50°C, the dissolution rate rapidly increased. Over the temperature interval 60–90°C in 3.0 M HNO₃ dissolution followed a linear rate law, and the activation energy was found to be 42.1 kJ mol^?1. Most of the oxidized sulphide ion was found in the solution as sulphate. The leaching rate was independent of stirring speed. The rate-controlling step of the Ni₃S₂ dissolution is the oxidation of hydrogen sulphide to elemental sulphur or sulphate ions on the Ni₃S₂ surface. Addition of small amounts of Cu²⁺ ions to the nitric acid acted as catalyst for the dissolution of Ni₃S₂. Bubbling air through the leach suspension increased the dissolution rate of Ni₃S₂ in solutions containing less than 2.0 M HNO₃.     

酶催化分光荧光法测定环境水中痕量铬(Ⅵ)

铬（Ⅳ）对血红蛋白模拟酶催化荧光体系具有强烈的猝灭作用, 据此建立了一种酶催化分光荧光法测定铬（Ⅳ）的新方法。研究了溶液酸度、L-酪氨酸浓度、血红蛋白浓度、H₂O₂浓度及反应时间等因素对体系的影响。在pH10.4的NH₃·H₂O-NH₄Cl缓冲溶液中, 当L-酪氨酸、血红蛋白和H₂O₂的浓度分别为1.4×10^-4mol/L、1.0×10^-6mol/L和3.5×10^-5mol/L时, 测定铬（Ⅳ）的线性范围为2.0×10^-6～1.0×10^-4mol/L, 检出限为1.1×10^-8mol/L。1000倍NO₃^-、SO₄^2-、Na⁺、K⁺、Cl^-、Br^-, 300倍PO₄^3-、Al³⁺、NH₄⁺, 50倍Mn²⁺、Mg²⁺、Fe²⁺、Cu²⁺, 1倍Fe³⁺对铬（Ⅳ）的测定没有干扰。干扰较大的Fe³⁺, 可加入过量的柠檬酸掩蔽。对浓度为4.8×10^-5mol/L的铬（Ⅳ）进行11次平行测定, 其相对标准偏差为2.8%。该法已成功地应用于环境水样中铬（Ⅳ）含量的测定。