采用TRPO从过氧化氢溶液中萃取钼和钨的数学模型和反应机理（英文）

为了解利用三烷基氧化膦(TRPO)从过氧化氢溶液中萃取钼和钨的化学行为,采用斜率法、拉曼和红外光谱研究钼和钨的萃取反应机理。通过建立数学模型,获得钼或钨的萃取分配比(D_Mo或D_W)关于平衡pH值、TRPO浓度和温度等变量的经验公式,并进一步在H⁺-W-Mo-H₂O₂溶液中验证经验公式的可靠性。结果表明:经验公式计算的D_Mo或D_W和实验值吻合度良好。实验条件下,20℃时钼和钨的萃取平衡常数分别为K_Mo^app=8.51×10³(0.74≤pH_e≤1.70)、K_Mo^app=99.89×10³(1.7e≤4.62)和K_W^app=2.65×10³(0.92e&l...     

Corrosion resistance of tantalum base alloys. Elimination of hydrogen embrittlement in tantalum by substitutional alloying

The corrosion behaviour of substitutional Ta–Mo, Ta–W, Ta–Nb, Ta–Hf, Ta–Zr, Ta–Re, Ta–Ni, Ta–V, Ta–W–Mo, Ta–W–Nb, Ta–W–Hf and Ta–W–Re alloys has been investigated in various corrosive media, i.e. (1) concentrated sulfuric acid at 250°C and 200°C, (2) boiling hydrochloric acid of azeotropic composition, (3) concentrated hydrochloric acid at 150°C under pressure, (4) HF-containing solutions and (5)0.5% H₂SO₄ at room temperature (anodisation). In highly corrosive media such as concentrated H₂SO₄ at 250°C and concentrated HCl at 150°C tantalum is hydrogen embrittled, probably by stress induced precipitation of β-hydride. Both corrosion rate and hydrogen embrittlement in concentrated H₂SO₄ at 250°C are strongly influenced by alloying elements. Small alloying additions of either Mo or Re decrease the corrosion rate and the hydrogen embrittlement, while Hf has the opposite effect. Hydrogen embrittlement in concentrated H₂SO₄ at 250°C is completely eliminated by alloying Ta with 1 to 3 at % Mo (0.5 to 1.5 wt % Mo). These results can be explained in terms of the oxygen deficiency of the Ta₂O₅ film and the electronic structure of these alloys.     

Solvent extraction of molybdenum blue from alkaline leaching solution of the Ni-Mo ore

Molybdenum in the Ni-Mo ore was leached by air oxidation in an alkaline solution. Due to the high concentrations of SO₄²⁻, S₂O₃²⁻, SO₃²⁻ and AsO₄³⁻ in the solution, it was difficult to efficiently extract Mo by chemical precipitation or ion exchange process. So the extraction of Mo from the solution with the mixture of tertiary amine (N-235) and secondary caprylic alcohol dissolved in kerosene was investigated. The effects of several process parameters such as extractant concentration, feed solution pH, O/A ratio, temperature of extraction, and contact time were studied. Results proved that the extraction efficiency of Mo was 99.4% at pH 3, time 2 min and O/A ratio 1:4 with 15 v% N-235. Stripping of Mo with a 15 m% ammonia solution was essentially completed (99.9%) in a single stage at an O/A ratio of 3. Comparison of the chemical oxygen demand (COD) concentration of the feed solution (12,400 mg/L) and raffinate (8600 mg/L) indicated that the separation of Mo and reductive substances, such as S₂O₃²⁻ and SO₃²⁻, was achieved after solvent extraction. The Mo concentration in the strip liquor obtained in a single stage can be increased by contacting a new loaded organic phase. After repeated stripping, the concentration of Mo, As, P, W and V in the strip liquor were 125.82 g/L, 15.63 g/L, 0.73 g/L, 0.09 g/L, and 0.074 g/L respectively.     

Extracting Cu,Co, and Fe from white alloy with HCl by adding H<Subscript>2</Subscript>O<Subscript>2</Subscript>

White alloy, mainly containing Cu, Co, and Fe, has been successfully decomposed in HCl solution by adding H₂O₂. This process is discussed in this paper. Through exploratory experiments, hydrochloric acid and H₂O₂ solution were confirmed as the leaching system of white alloy and through a series of condition experiments the effect of HCl concentration, H₂O₂ addition amount, reaction temperature, reaction time, particle size, and liquid-solid ratio of the extraction are studied. The optimal leaching conditions are 5 mol/L HCl concentration, 1.85 mL H₂O₂/g white alloy H₂O₂ addition, 70°C reaction temperature, 90 min. reaction time, 100 mesh particle size, and a 5/1 liquidsolid ratio. With these conditions the extraction of Cu and Co exceeds 99.5%, and the extraction of Fe can reach 98.5%. The results show the addition of H₂O₂ and the introduction of Cl⁻ are very important factors to improve the extraction of metal.     

Evaporation of Cr2O3 in Atmospheres Containing H2O

Stainless steels in atmospheres containing H₂O form a Cr₂O₃ scale in the early stage of oxidation. However, the Cr₂O₃ scale gradually degrades with time. In order to determine the effect of H₂O on the deterioration of a Cr₂O₃ scale, the evaporation behavior of Cr₂O₃ in N₂–O₂–H₂O atmospheres was investigated. The rate of mass loss in an N₂–O₂–H₂O atmosphere was found to be one order of magnitude higher than the rates in N₂–O₂ and N₂–H₂O atmospheres, indicating that deterioration of the Cr₂O₃ scale is likely to occur in mixed atmospheres of oxygen and water vapor. Volatilization of Cr₂O₃ is probably based on the following reactions: 1/2Cr₂O₃(s)+3/4O₂(g)+H₂O(g)=CrO₂(OH)₂(g). However, it is also speculated that the reaction, Cr₂O₃(s)+2/3O₂(g)=2CrO₃(g), affects the evaporation of Cr₂O₃ at temperatures higher than 1323 K. The evaporation rate of Cr₂O₃ is roughly comparable to the growth rate of the Cr₂O₃ scale. Therefore, a Cr₂O₃ scale can be degraded by the evaporation of Cr₂O₃.     

Removal of vanadium from ammonium molybdate solution by ion exchange

The separation techniques of vanadium and molybdenum were summarized, and a new method of removal V(Ⅴ) from Mo(Ⅵ) by adsorption with chelate resin was presented. Nine kinds of chelate resins were used to investigate the adsorbent capability of V(Ⅴ) in ammonium molybdate solution with static method. The test results show that DDAS, CUW and CW-2 resins can easily adsorb V(Ⅴ) in ammonium molybdate solution, but hardly adsorb Mo(Ⅵ). The dynamic experimental results show more than 99.5% of V(Ⅴ) can be adsorbed, and the adsorption rate of Mo(Ⅵ) is less than 0.27% at 294-296 K for 60 min at pH 7.42-8.02. The mass ratio of V to Mo decreases to l/5 0000 in the effluent from 1/255 in the initial solution. The loaded resin can be desorbed by 5% NH3·H2O solution, and the vanadium desorption rate can reach 99.6%. The max concentration of vanadium in desorbed solution can reach 20 g/L, while the concentration of molybdenum is less than 0.8 g/L.     

Oxidation of 310 steel in H2O/O2 mixtures at 600 °C: the effect of water-vapour-enhanced chromium evaporation

The oxidation of type 310 stainless steel was investigated at 600 °C in the presence of O₂ and O₂+10% and 40% H₂O. The effect of gas velocity was studied. The oxidized samples were investigated by grazing angle X-ray diffraction, SEM/EDX and SAM. The addition of H₂O to O₂ resulted in a change of oxidation behaviour. A strong dependence on flow rate was observed in O₂/H₂O mixtures. At low flow rates a thin (30-50 nm) protective α-(Cr,Fe)₂O₃ formed, the outer part being depleted in chromium. When the flow rate was increased beyond a critical value the protective oxide failed. Under these conditions ?5 μm thick α-Fe₂O₃/(Cr,Fe)₃O₄, oxide islands formed on the part of the surface corresponding to the centre of the alloy grains. The effect of water vapour is attributed to the water-vapour-assisted evaporation of chromium from the oxide, in the form of a chromium oxide hydroxide, probably CrO₂(OH)₂. The oxidation behaviour is rationalized using a qualitative mechanism proposed previously and parallels that of the 304L alloy.     

Extraction of Molybdenum from Molybdenite Concentrates with Hydrometallurgical Processing

Molybdenite concentrates are usually treated by roasting, but low-concentration SO₂ pollution is an associated problem. A hydrometallurgical process with pressure oxidation leaching (POX) and solvent extraction (SX) was developed in recent years. During POX, the oxidation of molybdenum (Mo) is above 98%. More than 95% of the rhenium (Re) and 15% to 20% of the Mo are leached into solution. The sulfur in the concentrate is converted to H₂SO₄, which results in high acidity of the solution. SX was used to recover the Re and Mo from the solution. The extraction of Re and Mo were above 98%. The loaded organic reagent is stripped with ammonia. More than 98% of the Mo can be stripped from the organic phase. Compared with the roasting process, the total recovery of Mo increased from 93% to 97% and that of Re from 60% to 90% when POX and SX are utilized.     

Fabrication of Ta<Subscript>2</Subscript>O<Subscript>5</Subscript> Dispersion-Strengthened Mo-Si-B Alloy by Powder Metallurgical Method

In this study, we investigate the effect of oxide dispersion strengthening on mechanical properties by dispersion of nano-sized Ta₂O₅ particles in Mo-Si-B alloy. A Mo-Si-B core-shell powder consisting of two intermetallic compounds of Mo₅SiB₂ and Mo₃Si as the core and nano-sized Mo solid solution surrounding intermetallic compounds was fabricated by chemical vapor transport. And Mo-Si-B core-shell powder with uniformly dispersed nano-sized Ta₂O₅ particles on the surface of a Mo solid solution shell was produced by a wet blending process with TaCl₅ solution and heat treatment. Then, pressureless sintering was performed at 1400°C for 3 h under a H₂ atmosphere. The hardness and fracture toughness of the Ta₂O₅-dispersed Mo-Si-B alloy were measured using Vickers hardness and 3-point bending tests, respectively. The Vickers hardness and fracture toughness of the fabricated Mo-Si-B-Ta₂O₅ alloy were more improved than that of the Mo-Si-B alloy fabricated using core-shell powder with no addition of Ta₂O₅ particles (Mo-Si-B alloy: 353 Hv, 13.5 MPa·√m, Mo-Si-B-Ta₂O₅ alloy: 509 Hv, 15.1 MPa·√m).     

从沉钨钼后液中制备高纯铼酸铵

利用沉钨钼后液首先经氯化钾沉淀反应得到铼酸钾,其次采用离子交换法将铼酸钾溶液转为高铼酸溶液,最后经氨水中和-浓缩结晶-重结晶得到高纯铼酸铵。结果表明:向沉钨钼后液中加入KCl固体再浓缩析出KReO₄白色晶体,其主要杂质Na、Ca、Fe、Cl含量均小于1.00%,特别是W、Mo含量均小于0.10%,且Re结晶率可达94.92%～98.38%。采用动态法脱K,选用C160(H⁺型)树脂,当KReO₄溶液pH为中性,料液流速控制在2BVs·h^-1时,C160树脂对K⁺穿透容量和饱和容量分别为117.87和128.39g·L^-1,且树脂利用率达到91.81%;所得纯HReO₄溶液中K、Na、Ca、Fe、W、Mo、Mg浓度均降至0.50 mg·L^-1以下。通过添加优级纯氨水中和HReO₄溶液,控制终点pH为7～8,再经浓缩结晶+1次重结晶,所得铼酸铵纯度达到99.99%以上,其SEM形貌为树枝状。     

On the resistance of duplex steel to stress corrosion cracking

The paper gives the results of tests carried out into the stress corrosion cracking in duplex stainless steel (Type 02Cr22Ni5Mo3N, W.Nr. 1.4462); this grade is characterized by high resistance to intergranular corrosion, while resistance to stress corrosion cracking may be impaired by temperature and mode of loading. This behaviour requires special attention. The tests included testing in 35% MgCl₂ solution under constant load at 120°C, the drop evaporation test using a 0.1 mol · 1^? NaCl solution and the slow strain rate test in 35% MgCl₂ solution at 120°C.     

Oxidation of hydrocarbon films and metal materials in oxygen-containing low temperature plasma

Glow discharge in oxygen-containing gases (air, a mixture of O₂/N₂, N₂O) was used for selective removal of amorphous hydrocarbon (a-C:H) films predeposited on stainless steel, W, and Mo. The gasification rate of films was maximal in N₂O. H₂, H₂O, CO, and CO₂ were plasmolysis products. Thin (3?C30 nm) oxide layers, the thicknesses of which depended on the location of samples relative to plasma, formed on the metal after removal of the film.     

Synthesis and characterization of W-Cu nanopowders by a wet-chemical method

A wet-chemical process was employed to prepare W-Cu nanopowders. Precursors containing some tungstates were obtained by adding precipitants into a complex solution containing ammonium metatungstate and copper nitrate, afterwards spray-drying the complex solutions. The precursor powders were then calcined and hydrogen-reduced to convert into W-Cu powders. Phase constitution and morphology of the precursors, the calcined powders, as well as the reduced powders were characterized. Relations between the ratio of W to Cu in the complex solutions and the phase constitution of the calcined precursors were investigated. The effects of the reduction temperature and H₂ flow rate on the hydrogen reduction kinetics and the crystallite size of the W-Cu powder were also studied. It was shown that the wet-chemical process produces W-Cu powders with nanosized particles of about 100 nm. The composition of the calcined precursors varies with the ratio of W to Cu in the complex solution, and only CuWO₄ was found in the calcined precursors when the ratio of W to Cu is 74:26(wt.%). The reduction temperature and H₂ flow rate have a great influence on the hydrogen-reduction process and the crystallite size of the resulting W-Cu powders.     

The high-temperature corrosion behavior of Fe-Mo-Al alloys in H2/H2O/H2S mixed-gas environments

The corrosion behavior of 11 Fe-Mo-Al ternary alloys was studied over the temperature range 700–980°C in H₂/H₂O/H₂S mixed-gas environments. With the exception of Fe-10Mo-7Al, for which breakaway kinetics were observed at higher temperatures, all alloys followed the parabolic rate law, despite two-stage kinetics which were observed in some cases. A kinetics inversion was observed for alloys containing 7 wt.% Al between 700–800°C. The corrosion rates of Fe-20Mo and Fe-30Mo were found to be reduced by five orders of magnitude at all temperatures by the addition of 9.1 or higher wt.% aluminum. The scales formed on low-Al alloys (5 wt.% Al) were duplex, consisting of an outer layer of iron sulfide (with some dissolved Al) and a complex inner of Al_0.55Mo₂S₄, FeMo₂S₄, Fe_1.25Mo₆S_7.7, FeS, and uncorroded FeAl and Fe₃Mo₂. Platinum markers were always located at the interface between the inner and outer scales for the low-Al alloys, indicating that outer-scale growth was due mainly to outward diffusion of cations (Fe and Al), while the inner scale was formed primarily by the inward flux of sulfur anions. Alloys having intermediate Al contents (7 wt.%) formed scales that consisted of FeS and Al₂O₃. The amount of Al₂O₃ increased with increasing reaction temperature. The high-Al-content alloys (9.1 and 10 wt.%) formed only Al₂O₃ which was responsible for the reduction of the corrosion rates.     

Synthesis of nanocrystalline molybdenum powder by hydrogen reduction of industrial grade MoO3

In the present work, ultrafine metal Mo powder with a high purity was successfully prepared by one step direct reduction of MoO₃ vapor with H₂ at 1323 K. MoO₃ vapor was generated by the evaporation of industrial grade MoO₃, which is much cheaper than pure MoO₃. It is found that increasing H₂ concentration is beneficial for the reduction of MoO₃ to metal Mo, as well as for the decrease of particle size of Mo particles. The results obtained at a low H₂ concentration show that the mixture of hexagonal platelet-shaped MoO₂ single crystalline and Mo polycrystalline can be obtained. The present method provides a simple approach to prepare nanocrystalline Mo powder.     

Controlled crystallite orientation in ZnO nanorods prepared by chemical bath deposition: Effect of H2O2

ZnO nanorods with controlled crystallite orientation are grown on glass substrate by chemical bath deposition (CBD) method via hydrogen peroxide (H₂O₂) route. The crystallite orientation in the film is successfully controlled by varying content of H₂O₂ in the bath solution. The crystallites became increasingly oriented as content of H₂O₂ in the bath solution increased, resulting in the formation of vertically aligned ZnO nanorods. The possible growth mechanism for the vertically aligned ZnO nanorods is proposed. The influence of content of H₂O₂ in the bath solution on structural, surface morphological, electrical and optical properties is studied and reported.     

H2V3O8 single-crystal nanobelts: Hydrothermal preparation and formation mechanism

The formation mechanism of highly pure H₂V₃O₈ single-crystal nanobelts is clarified in a hydrothermal synthesis process with a specially designed precursor solution containing V⁵⁺ and V⁴⁺ in a fixed ratio of 2/1. This specially designed precursor solution provides an additional merit for the rapid fabrication of highly pure H₂V₃O₈ nanobelts through a simple hydrothermal route. During the hydrothermal synthesis process, V⁵⁺ species initially reacts with some V⁴⁺ to form a metastable, whisker-like V₁₀O₂₄ · nH₂O (n < 12). The V⁵⁺ species dissolved from the whisker-like V₁₀O₂₄ · nH₂O reacts continuously with residual V⁴⁺ ions in the precursor solution to form seeds of H₂V₃O₈ single-crystals. The anisotropic growth of H₂V₃O₈ single-crystal nanobelts with length > 10 μm and width between 50 and 150 nm occurs with prolonging the hydrothermal time. Finally, highly pure H₂V₃O₈ single-crystal nanobelts are obtained when the hydrothermal time reaches 4 h. The textures of vanadium oxides prepared at different hydrothermal times are systematically compared through X-ray diffraction, transmission electron microscopic and X-ray photoelectron spectroscopic analyses to clarify the synthesis mechanism of H₂V₃O₈ single-crystal nanobelts.     

Synthesis of LiNi1/3CO1/3Mn1/3O2 cathode material via oxalate precursor

Using oxalic acid and stoichiometrically mixed solution of NiCl2, CoCl2, and MnCl2 as starting materials, the triple oxalate precursor of nickel, cobalt, and manganese was synthesized by liquid-phase co-precipitation method. And then the LiNi1/3Co1/3Mn1/3O2 cathode materials for Li-ion battery were prepared from the precursor and LiOH-H2O by solid-state reaction. The precursor and LiNi1/3Co1/3Mn1/3O2 were characterized by chemical analysis, XRD, EDX, SEM and TG-DTA. The results show that the composition of precursor is Ni1/3Co1/3Mn1/3C2O4·2H2O. The product LiNi1/3Co1/3Mn1/3O2, in which nickel, cobalt and manganese are uniformly distributed, is well crystallized with a-NaFeO2 layered structure. Sintering temperature has a remarkable influence on the electrochemical performance of obtained samples. LiNi1/3Co1/3Mn1/3O2 synthesized at 900 ℃ has the best electrochemical properties. At 0.1C rate, its first specific discharge capacity is 159.7 mA·h/g in the voltage range of 2.75-4.30 V and 196.9 mA·h/g in the voltage range of 2.75-4.50 V; at 2C rate, its specific discharge capacity is 121.8 mA·h/g and still 119.7 mA·h/g after 40 cycles. The capacity retention ratio is 98.27%.     

Complexation extraction of scheelite and transformation behaviour of tungsten-containing phase using H2SO4 solution with H2C2O4 as complexing agent

The extraction of tungsten from scheelite was carried out using a sulfuric acid solution with oxalic acid as the chelating agent. Tungsten was obtained in the form of highly soluble hydrogen aqua oxalato tungstate (H₂[WO₃(C₂O₄)·H₂O]) during the leaching process, while calcium remained in the residue as calcium sulfate dihydrate (CaSO₄·2H₂O). About 99.2% of the tungsten was leached at 70 °C, 1.5 mol/L sulfuric acid, 1 mol/L oxalic acid, a liquid/solid ratio of 25:1 (mL/g), an oxalic acid to sulfuric acid molar ratio of 1:1, a stirring speed of 300 r/min and a leaching time of 2 h. H₂[WO₃(C₂O₄)·H₂O] was thermally decomposed into tungstic acid (H₂WO₄), and tungsten trioxide (WO₃) was directly produced by calcining H₂WO₄ at 700 °C for 2 h. The surface chemical reaction was determined to be the controlling step during tungsten leaching, and the apparent activation energy was calculated to be 51.43 kJ/mol.     

The high temperature oxidation of 11% chromium steel: Part II – Influence of flow rate

The oxidation of type X20 CrMoV 11 1 steel at 600°C in the presence of dry O₂ and O₂ + 10 or 40% H₂O was investigated. The flow rate was varied between 0.25 to 10.0 cm/s. Exposure time was 168 hours. The oxidized samples were investigated gravimetrically and by a number of surface analytical techniques including grazing angle SEM/EDX, GDOES and XRD. Oxidation is strongly influenced by pH₂O and flow rate. In O₂ + H₂O environment at 600°C, the protective Cr‐rich α‐(Cr,Fe)₂O₃ oxide loses chromium by vaporization of CrO₂(OH)₂. When chromium loss is limited (e. g., in 10% H₂O and in 40% H₂O at low flow rates) the supply of chromium from the alloy compensates for chromium vaporization and the oxide retains its protective properties, resulting in slow oxidation. In 40/60 H₂O/O₂ and high flow rates chromium evaporation becomes so rapid that the protective properties of the oxide are lost and a thick duplex (Fe₂O₃/Fe₂CrO₄) scale develops.