Papers by Keyword: Molybdenum

Abstract: Characterization of microstructure of silicide coatings obtained during diffusion process of pack cementation type was showed in this article. The basic materials were pure Mo sheet and TZM molybdenum alloys as well. The coatings were deposited in out of pack process with three different times of exposure. The temperature of deposition process was constant. In first step the phases compositions of coatings was described by XRD analysis. In each cases the MoSi₂ phase was obtained on top surface of the coatings. The morphology of the coatings was very similar as well. All types of coatings were characterized by network of cracks on top surface of the coatings. There was no influence of depositions time on phases constituent and coatings topography. LM and SEM analysis revealed that internal coatings morphology was very similar in all cases. Basic differences was related to the thickness of coatings. All coatings were good quality without deep cracks. Microstructure was a columnar-like type without pores and voids.

Abstract: Ultrapure water (UPW) is widely used for rinsing wafers and diluting chemicals in semiconductor manufacturing processes. The quality of UPW is severely controlled, but the generation of hydrogen peroxide (H₂O₂) as a impurity is inevitable due to the ultraviolet irradiation in a UPW production system (Figure 1). In our survey, it is revealed that the concentration of H₂O₂ in UPW reaches to 10~40 μg/L level. Considering the situation, we have developed a palladium-loaded monolithic anion exchange resin (Pd-M) as a catalyst that is able to remove H₂O₂ from UPW down to below 1 μg/L at an extremely high flow rate (space velocity SV = 6,000 h^-1), with no detectable elution of impurities [1, 2]. Furthermore, we have found that the dissolution rate of copper which is easy to be corroded oxidatively in CO₂-dissolved water (CO₂ UPW) [3] can be decreased to one-third by removal of H₂O₂ from CO₂ UPW using Pd-M catalyst [4]. In this study, we present the effects of H₂O₂ removal from UPW and diluted hydrofluoric acid (DHF) on the surfaces of copper, molybdenum and silicon.

Abstract: The paper presents experimental results on influence of tungsten, molybdenum nanopowders and aluminum oxyhydroxide phase introduced into the molten pool on the corrosion resistance of welded joints. It was shown that the nature of nanopowders significantly impacts intercrystalline corrosion of the welding joint.

Abstract: A solution containing tungsten and molybdenum was acidified using hydrochloric acid, and the ability of several commercial ion exchange resins to separate tungsten and molybdenum was evaluated. The results from the acidification test indicate that when the pH of the solution is adjusted to 7.0, WO₄^2- is polymerized into HW₆O₂₁^5-, while MoO₄^2- is not. The test results of resins selection show that the D213 resin and the D308 resin are superior to other resins in separating low concentrations of tungsten and molybdenum, whereas the D201 resin and the D309 resin are suitable for separating high concentrations of tungsten and molybdenum. The results from the column test indicate that weak-base anion exchange resins are better than strong-base anion exchange resins for both low and high concentrations of tungsten and molybdenum.

Abstract: A new fluorescent reagent, 2-hydroxy-1-naphthaldehydene-p-aminotoluene, was synthesized. The fluorescent reaction of this reagent with molybdenum was studied. Based on this chelation, a highly sensitive spectrofluorimetric method was developed for determination of trace amounts of molybdenum in a water-ethanol medium at pH 6.8. Under these conditions, the Mo-HNA complex has excitation and emission maxima at 300 and 380 nm, respectively. The linear range of the method is 0-2μg/L and the detection limit is 0.62μg/L. Interference of other ions was studied. It is necessary to remove the interfering cations through cation exchange. The procedure can be carried out easily and affords good precision and accuracy. This method has been successfully applied to the determination of molybdenum in pig liver and mussels.

Abstract: Based on the analysis of the properties of spent catalyst, extract vanadium and molybdenum from spent catalyst by roasting alkaline leaching. Sodium carbonate was leaching agent. The effects of roasting temperature, roasting time, the concentration of sodium carbonate and the number of leaching times on the leaching rate of vanadium and molybdenum were studied. Roasting temperature of 650°C, roasting time of 3h, the concentration of sodium carbonate of 50g/L and once counter-current leaching, under this condition, the leaching of vanadium is 83% and the leaching of molybdenum is 93%.Roasting alkaline leaching has good effect on extracting vanadium and molybdenum from spent catalyst.

Abstract: Steel alloyed by nickel, chromium and molybdenum reach according to normative standards (EN) yield point about 900 MPa and contraction about 25% after heat treatment. Authors of this paper noticeably increase the strength properties of that steel without changes in plastic properties with using of electroslug remelting refining technology (ESR). Subject of research are forgings of very large mass and dimensions. The forgings are used in special armament technology as (tank gun barrels). Very negative influence on mechanical properties of final product has content of nanodimensioned impurities.

Abstract: This paper describescrack-less electrical discharge machining (EDM) of molybdenum (Mo) with titanium (Ti) electrode. Mo is often machined by EDM because of its high hardness. However, a molybdenum carbide (MoC and Mo₂C) layer with high hardness and brittleness is formed by EDM in kerosene oil. Moreover, Mo becomes recrystallizationembrittlement at high temperature. Therefore, many cracks occurred in the EDMed surface. On the other hand, the addition of Ti rises recrystallization temperature and improves high temperature strength of Mo.In order to decrease the cracks in the machined surface, Mo was machined by EDM with a Ti electrode in deionized water. In the case of the positive electrode polarity, many cracks occurred in the base material and recast layer. The cracks in the base material might generate by crystal grain boundary embrittlement. In contrast, the EDMed surface indicated crack-less on the negative electrode polarity. To clarify the causes of crack-less surface on negative electrode polarity, componential analysis of EDMed surface was carried out. The component ratio of Ti on the negative electrode polarity was higher than that on the positive. In addition, the recast layer was composed by Mo-Ti solid solution.

Abstract: According to physicochemical property of molybdenum, the application of molybdenum is elaborated from three aspects that are molybdenum element, molybdenum alloys and molybdenum compound; The distribution of nature resource of molybdenum at abroad and home and the source of recoverable resources are summarized; the production method of ammonium molybdate is introduced which are oxidation roasting and wet oxidation, and the extracting method of molybdenum is introduced which is reduction method; the development tendency of molybdenum is pointed out.

Abstract: In this paper, we test proximity gettering layers obtained by carbon or silicon implantation for their efficiency in molybdenum and tungsten gettering. DLTS was used to measure the impurity concentration in the solid solution and so to evaluate gettering efficiency. It was found that carbon implantation is effective in capturing these impurities, whereas silicon implantation is not. Extended defects seem not to play an important role in gettering these impurities. In addition, gettering was found to be most effective at high impurity concentration.