Molybdenum Deposition Research Articles

On the Morphology and Optical Properties of Molybdenum Disulfide Nanostructures from a Monomolecular Layer to a Fractal-Like Substructure

The impact of layer thickness on the morphology and optical properties of MoS2 nanostructures, including monomolecular layers, formed by the carrier-gas-assisted transport of sulfur vapor to the hot zone of a reactor containing metallic molybdenum and subsequent deposition on mica (muscovite) substrates is investigated. Molybdenum disulfide nanostructures of different thicknesses grown at different temperatures of gas-transport synthesis are studied by atomic-force microscopy, optical absorption spectroscopy, and Raman spectroscopy. It is found that synthesis at temperatures of 525–600°C makes it possible to obtain monomolecular MoS2 layers containing trigonal domains and featuring direct-gap optical transitions at 1.84 eV with the formation of excitons at room temperature. Fractal-type MoS2 substructures are obtained for the first time. The frequencies of intralayer and interlayer vibrational modes $$E_{{2g}}^{1}$$ and A1g, respectively, in their Raman spectra (377.5 and 403.8 cm–1, respectively) differ both from the corresponding values for a monomolecular layer and the known frequencies for bulk samples. The frequency of the $$E_{{2g}}^{1}$$ intralayer mode in these samples (377.5 cm–1) is the lowest of all previously reported.

Physics affecting heavy impurity migration in tokamaks: Benchmarking test-ion code ASCOT against TEXTOR tracer experiment

Abstract Erosion, transport and deposition of wall impurities are major concerns in future magnetic fusion devices, both from the perspective of the fusion plasma and the machine wall. An extensive study on molybdenum transport and deposition performed in the TEXTOR tokamak yielded a detailed deposition map that is ideal for benchmark deposition studies. A qualitative benchmark is attempted in this article with the ASCOT code. We set up a full 3D model of the TEXTOR tokamak and studied the influence of different physical mechanisms and their strengths on molybdenum deposition patterns on the simulated plasma-facing components: atomic processes, Coulomb collisions, scrape-off layer (SOL) profiles, source distribution, marker starting energy, radial electric field strength, SOL flow and toroidal plasma rotation. The outcome comprises 13 simulations, each with 100,000 markers. The findings are: • Toroidal plasma movement, either within the LCFS or as SOL flow, is negligible. • SOL profile and marker starting energy have modest impact on deposition. • Source distribution has a large impact in combination with radial electric field profiles. • The E ⇀ × B ⇀ drift has the highest impact on the deposition profiles.

Direct Energy Deposition - Laser Additive Manufacturing of Titanium-Molybdenum alloy: Parametric studies, microstructure and mechanical properties

In this novel research, the Direct Energy Deposition - Laser Additive Manufacturing (DED-LAM) process is used for deposition of β-type Titanium Molybdenum (Ti-15Mo) biomedical alloy. A major challenge in the successful deposition of an alloy powder on the substrate by the DED-LAM process is the formation of a strong metallurgical bond with minimum track dilution. Targeting a crack-free and dense multi-layer deposition, a detailed investigation of the effect of three key process parameters on the track geometry characteristics is conducted. The response surface methodology (RSM) experimental design technique and ANOVA based quadratic regression modeling are employed to relate the process parameters with track geometric characteristics. The statistical analysis results show that minimum track dilution is achieved at maximum laser power and minimum scan speed and powder feed rate. Further, microstructural characterization is carried out to analyse the porosity, elemental composition and phase constituents. Microhardness of 385 ± 8 HV and elastic modulus of 73 ± 1.5 GPa are achieved for the Ti-15Mo deposits at the optimum parameter settings. This study establishes a methodology towards successful deployment of the DED-LAM process for potential fabrication of Ti-15Mo alloy biomedical implants.

A Comparative Study of MO Films Deposited on AISI 310 and Alumina Surface Using Anodic Vacuum Arc

The Surface of Alumina and Stainless Steel was considered for thin film deposition of molybdenum by using Anodic Vacuum Arc. The evaporation was carried out at 0.07 mbar pressure and at a welding current of 60 Amperes where the temperature reached beyond 2500˚C and a thin layer of molybdenum was coated on the substrates. The corrosion rate, surface morphology, crystallite size and lattice strain were calculated by using Electrochemical Analyzer, Scanning Electron Microscope and X-Ray Diffraction respectively.

Cooperative light irradiation and in-situ produced H2O2 for efficient tungsten and molybdenum deposition in microbial electrolysis cells

Tungsten (W) and molybdenum (Mo) deposition from ore dressing wastewater is a promising process for recovery of W and Mo with simultaneous ore dressing wastewater treatment, but suffers from consumption of large amount of extraction agent and energy, and generation of excess secondary polluted sludge. Here we reported light irradiation and in-situ produced H2O2 cooperatively enhanced W and Mo deposition in microbial electrolysis cells (MECs), achieving deposition of 81.5 ± 1.7% (W) and 97.2 ± 2.4% (Mo) with a Coulombic efficiency (CE) of 82.5 ± 1.5%. Only 52.0 ± 1.4% (W), 75.7 ± 2.1% (Mo) and 38.6 ± 1.4% (CE) were observed in the controls in the absence of both in-situ produced H2O2 and light irradiation, 62.4 ± 2.2% (W), 84.1 ± 1.5% (Mo) and 51.3 ± 1.7% (CE) with light irradiation only, and 57.6 ± 1.6% (W), 81.7 ± 1.7% (Mo) and 71.6 ± 0.8% (CE) with in-situ produced H2O2 only. A shift from the in-situ produced H2O2 at a period of 2.5 h to the absence of this species for another 2.5 h further improved W (98.1%) and Mo (100%) deposition. These results provide a sustainable and environmentally benign approach for efficient W and Mo recovery. The evidence of influence factors including light irradiation, in-situ produced H2O2, shift from in-situ produced H2O2 to the absence of this species, and applied voltage can contribute to improving understanding of and optimizing W and Mo deposition in MECs.

Preferable utilization of in-situ produced H2O2 rather than externally added for efficient deposition of tungsten and molybdenum in microbial fuel cells

In-situ H2O2 production at the cathode in microbial fuel cells (MFCs) has been well documented to be useful for removal of recalcitrant pollutants based on its reductive and oxidative characteristics. However, the advantages of in-situ produced H2O2, rather than using an exogenous source of this chemical has not been previously examined for removal and cathodic deposition of metals. Greater percentages of W and Mo were deposited on the cathodes of MFCs with in-situ produced H2O2 compared to that achieved with chemical addition to the solution through either intermittent multiple-time or one-time modes. A high oxygen supply with in-situ produced H2O2 reached deposition of 67.2±3.1% of W and 86.4±1.9% of Mo, and a coulombic efficiency of 66.4%±3.1%, which were 2.4, 1.3 and 3.1 times, respectively as those in the no oxygen control. These metals removals were appreciably higher than the maximum achieved with chemical H2O2 of 80mg/L externally added through either intermittent multiple-time or one-time modes for W deposition, although there was a negligible difference for Mo deposition. More acidic pHs and a lower external resistance were favorable for W and Mo deposition. This study provides a new approach for efficient W and Mo deposition, where in-situ produced H2O2 resulted in more complete metal removal than that obtained with an externally intermittent multiple-time or one-time added source of this oxidizer.

Surface composition and structure of divertor tiles following the JET tokamak operation with the ITER-like wall

Samples extracted from several divertor tiles following the 2011–2012 operation of JET with the ITER-Like wall were analyzed using ion beam analysis methods, x-ray fluorescence spectroscopy, scanning electron microscopy with energy dispersive spectroscopy analysis and x-ray diffraction. The emphasis was on the determination of light species and on material mixing including compound formation on the bottom and the outer divertor tiles. Deposition of deuterium, beryllium, carbon, nitrogen, oxygen, iron, chromium, nickel and molybdenum has been detected on all studied tiles. The thickest deposition, of around 4 µm, was measured on the bottom of the outer divertor, whereas the other surfaces (inner bottom and vertical outer) the co-deposits were around 1 µm. x-ray diffraction measurements have revealed the formation of the compound W2C on all specimens.

Effect of plasma molybdenized buffer layer on adhesive properties of TiN film coated on Ti6Al4V alloy

Effect of molybdenized buffer layer on adhesion strength of TiN film on Ti6Al4V alloy was investigated. The buffer layer composed of a dense molybdenum deposition layer, a rapid drop zone and a slow fall zone was prepared using double glow plasma surface alloying technique. Scratch tests and low energy repeated impact tests were adopted to comparatively evaluate the duplex treated layers and the single TiN samples. The results show that the critical load was increased from 62N for the single TiN film to over 100N for the duplex treated layer. The volume of impact pit, formed in impact tests, of the single TiN samples is 9.15×106μm3, and about 1.5 times than that of the duplex treated samples. The Leeb hardness values reveal that about 70% impact energy was transferred to the single TiN samples to generate permanent deformation, while that was only about 47% for the duplex treated samples. The mechanism of improving adhesion strength is attributed to synergistic effect due to an inverted-S shape elastic modulus distribution produced by the molybdenized layer.

Near infrared organic photodetector utilizing a double electron blocking layer.

A near infrared organic photodiode (OPD) utilizing a double electron blocking layer (EBL) fabricated by the sequential deposition of molybdenum (VI) oxide (MoO3) and poly(3,4ethylenedioxythiophene):poly(styrene-sulfonate) (PEDOT:PSS) is reported. The double EBL improves the on/off current ratio of OPD up to 1.36 x 104 at -1V, which is one order of magnitude higher than PEDOT:PSS single EBL (2.45 x 103) and three orders of magnitude higher than that of MoO3 single EBL (7.86). The detectivity at near infrared (800 nm) at -1V is 4.90 x 1011 Jones, which is 2.83 times higher than the PEDOT:PSS single EBL and 2 magnitudes higher compared to the MoO3 single EBL.

Influence of plasma molybdenizing and shot-peening on fretting damage behavior of titanium alloy

Effect of plasma molybdenizing and shot-peening on fretting wear and fretting fatigue behaviors of Ti6Al4V alloy was investigated. The plasma molybdenized layer composed of a dense molybdenum deposition layer and a Mo–Ti solid–solution layer can increase surface hardness by 2.8 times and cause its volume loss by fretting wear to decrease to 1/14 compared with that of the substrate. Plasma molybdenized treatment results in a significant decrease in resistance of the substrate to fretting fatigue. It is ascribed that the molybdenized layer with high hardness yields a low toughness, and its high surface roughness leads to a micro-notched effect. However, proper combination plasma molybdenizing and subsequent shot-peening may enhance the simultaneous fretting fatigue and fretting wear resistance of Ti6Al4V significantly, which can decrease the fretting wear volume loss to 1/27, and may increase the fretting fatigue life by more than 69 times. A synergistic improvement in fretting fatigue of the titanium alloy by combining surface alloying with shot-peening can be achieved. The results indicate that a beneficial residual compressive stress distribution, high surface hardness with suitable hardness gradient distribution, good apparent toughness, relatively low surface roughness, and excellent surface integrity are achieved.

Molybdeno-Aluminizing of Powder Metallurgy and Wrought Ti and Ti-6Al-4V alloys by Pack Cementation process

Wear and high temperature oxidation resistance of some titanium-based alloys needs to be enhanced, and this can be effectively accomplished by surface treatment. Molybdenizing is a surface treatment where molybdenum is introduced into the surface of titanium alloys causing the formation of wear-resistant surface layers containing molybdenum, while aluminizing of titanium-based alloys has been reported to improve their high temperature oxidation properties. Whereas pack cementation and other surface modification methods have been used for molybdenizing or aluminizing of wrought and/or cast pure titanium and titanium alloys, such surface treatments have not been reported on titanium alloys produced by powder metallurgy (PM). Also a critical understanding of the process parameters for simultaneous one step molybdeno-aluminizing of titanium alloys by pack cementation and the predominant mechanism for this process have not been reported. The current research work describes the surface modification of titanium and Ti-6Al-4V prepared by PM by molybdeno-aluminizing and analyzes thermodynamic aspects of the deposition process. Similar coatings are also deposited to wrought Ti-6Al-4V and compared. Characterization of the coatings was carried out using scanning electron microscopy and x-ray diffraction. For both titanium and Ti-6Al-4V, the use of a powder pack containing ammonium chloride as activator leads to the deposition of molybdenum and aluminium into the surface but also introduces nitrogen causing the formation of a thin titanium nitride layer. In addition, various titanium aluminides and mixed titanium aluminium nitrides are formed. The appropriate conditions for molybdeno-aluminizing as well as the phases expected to be formed were successfully determined by thermodynamic equilibrium calculations.

Characterisation of surface layers formed on plasma-facing components in controlled fusion devices: Role of heavy ion elastic recoil detection

Wall components retrieved from the TEXTOR tokamak after tracer experiments with nitrogen-15 and molybdenum hexafluoride (MoF6) injection were studied to determine deposition patterns and, by this, to conclude on material migration. Toroidal limiter tiles made of carbon fibre composites and fine grain graphite were examined using time-of-flight heavy ion elastic recoil detection analysis. Molybdenum deposition patterns indicated migration based on erosion and prompt re-deposition. Nitrogen-15 was trapped together with the deposited molybdenum. Some information on the depth distribution of species in the top 400 nm layer of the limiters was obtained; however surface roughness of the samples strongly limited resolution. In the case of molybdenum, the largest concentration was found in the 100 nm outermost layer, whereas fluorine and nitrogen-15 displayed more irregular profiles. Other species, besides deuterium fuel and carbon-12, were also identified: boron-10 and boron-11 originating from boronisations, carbon-13 from earlier tracer experiments, nitrogen-14 from plasma edge cooling and metals eroded from the Inconel wall.

U–Pb geochronology of the syn-orogenic Knaben molybdenum deposits, Sveconorwegian Orogen, Norway

AbstractPaired isotope dilution – thermal ionization mass spectrometry (ID-TIMS) and secondary ion mass spectrometry (SIMS) zircon U–Pb data elucidate geochronological relations in the historically important Knaben molybdenum mining district, Sveconorwegian Orogen, south Norway. This polyphase district providedc. 8.5 Mt of ore with a grade of 0.2%. It consists of mineralized quartz veins, silica-rich gneiss, pegmatites and aplites associated with a heterogeneous, locally sulphide-bearing, amphibolites facies gneiss called Knaben Gneiss, and hosted in a regional-scale monotonous, commonly weakly foliated, granitic gneiss. An augen gneiss at the Knaben I deposit yields a 1257±6 Ma magmatic zircon age, dating the pre-Sveconorwegian protolith of the Knaben Gneiss. Mineralized and non-mineralized granitic gneiss samples at the Knaben II and Kvina deposits contain some 1488–1164 Ma inherited zircon and yield consistent intrusion ages of 1032±4, 1034±6 and 1036±6 Ma. This age links magmatism in the district to the regional 1050–1020 Ma Sirdal I-type granite suite, corresponding to voluminous crustal melting during the Sveconorwegian orogeny. A high-U, low-Th/U zircon rim is present in all samples. It defines several age clusters between 1039±6 and 1009±7 Ma, peaking atc. 1016 Ma and overlapping with a monazite age of 1013±5 Ma. The rim records protracted hydrothermal activity, which started during the main magmatic event and outlasted it. This process was coeval with regional high-grade Sveconorwegian metamorphism. Molybdenum deposition probably started during this event when silica-rich mineralizing fluids or hydrous magmas were released from granite magma batches. An analogy between the Knaben district and shallow, short-lived porphyry Mo deposits is inappropriate.

Geology, fluid inclusions and sulphur isotopes of the Zhifang Mo deposit in Qinling Orogen, central China: a case study of orogenic‐type Mo deposits

The East Qinling region in central China, hosting several tens of Mesozoic magmatic‐hydrothermal Mo deposits, is one of the largest molybdenum belts in the world. The Zhifang Mo deposit is hosted in volcanic rocks of the Xiong'er Group in the Waifangshan area, Qinling Orogen. Previous studies variously correlated the mineralization in this deposit with Yanshanian magmatism or Palaeo‐Mesoproterozoic volcanic‐hydrothermal events. The orebodies are associated with quartz veins and controlled by subsidiary faults of the Machaoying Fault. The ore‐forming process can be divided into the early, middle and late stages and is characterized by quartz‐pyrite, quartz‐polymetallic sulphide and quartz‐carbonate veins, respectively. The early‐stage quartz is structurally deformed, suggesting a compressional tectonic regime; the middle‐stage sulphides fill the fractures of the early‐stage assemblages and show no deformation, suggesting a tensional setting; the late‐stage veins mostly infill the open‐space fissures. Three types of fluid inclusions (FIs) are identified at the Zhifang deposit: H2O‐NaCl (W‐type), CO2‐rich (C‐type) and daughter mineral‐bearing inclusions (S‐type). Fluid inclusions of early‐stage quartz homogenize between 380 and 470 °C, with salinities ranging from 0.4 to 9.6 wt.% NaCl equiv., whereas the late‐stage calcite contains only the W‐type FIs with homogenization temperatures of lower than 240 °C, and salinities of 0.4–8.7 wt.% NaCl equiv. This indicates that the ore fluid system evolved from CO2‐rich, probably metamorphic hydrothermal to CO2‐poor, meteoric fluid. All three types of FIs can be observed in the middle‐stage quartz, and even in the microscopic domain of a crystal, suggesting that this heterogeneous association was trapped from a boiling fluid system. These FIs homogenized at temperatures ranging from 250 to 360 °C and display two salinity clusters of <18.5 and 29.1–29.9 wt.% NaCl equiv. These results suggest that metal precipitation resulted from fluid boiling. The estimated trapping pressures of FIs range from 101 to 285 MPa, suggesting an alternating lithostatic–hydrostatic fluid system, which was controlled by a fault‐valve at the depth of 10 km. The δ34S values of ore minerals from the Zhifang Mo deposit show a range between −11.8‰ and 6.0‰, with a bimodal distribution. The early‐stage pyrite has a positive δ34S value of 6.0‰ that is similar to the host rocks of the Xiong'er Group and the Taihua Supergroup, suggesting that the wall rocks contributed much of the sulphur to the early‐stage pyrite during fluid–rock interaction. However, the δ34S values of the middle‐stage sulphides have negative mean and restricted range from −11.8‰ to −4.5‰. The widespread rutile grains coexisting with molybdenite in the middle‐stage correlate the negative δ34S values with relatively oxidized fluids. We consider phase separation as an efficient mechanism for ore‐fluid oxidation and molybdenum deposition based on fluid inclusions and sulphur isotope data. Geological, fluid inclusion and sulphur isotope data of the Zhifang Mo deposit suggest that the Mo mineralization is unrelated to the Yanshanian magmatism or the Palaeo‐Mesoproterozoic volcanic‐hydrothermal event. Here we propose that the Zhifang Mo deposit may be considered as an orogenic mineral system, with its formation in an active continental margin related to the northward subduction of the Mian‐Lue oceanic plate during the Triassic. Copyright © 2014 John Wiley & Sons, Ltd.

Growing process and reaction mechanism of electroless Ni–Mo–P film on SiO2 substrate

The diffusion barrier Ni–Mo–P film for Cu interconnects was prepared on SiO2/Si substrate using electroless method. The surface morphology and composition during the formation process of electroless Ni–Mo–P film were investigated through analyzing samples of different deposition time. Induced nucleation, induced co-deposition, and self-induced growth mechanisms involved in electroless process were confirmed by field-emission scanning electron microscopy (FE-SEM), energy dispersive spectrometry and atomic force microscopy (AFM). Firstly, the preceding palladium particles as catalysts induce the nucleation of nickel. Secondly, the nickel particles induce the deposition of molybdenum and phosphorus, which attributes to induced co-deposition. Thirdly, former deposited Ni–Mo–P induces deposition of the latter Ni–Mo–P particles. Moreover, the reaction mechanism was proposed with the oxydate of PO3−4.

Investigation of electrochemical co-deposition of zinc and molybdenum from citrate solutions

The co-deposition of molybdenum with zinc from citrate electrolytes was studied. Cyclic voltammetry with rotating disc electrode experiments and potentiostatic deposition in coulostatic conditions were carried out in order to analyse the mechanism of electrodeposition of molybdenum with zinc. The results of voltammetric studies indicate Zn and Mo interaction during the electrodeposition process. The electrodeposits were characterised by wavelength dispersive X-ray fluorescence (WDXRF), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Possibility of Zn–Mo alloy layers electrodeposition from citrate solutions was confirmed. The molybdenum content in metallic components (Zn–Mo alloy/compound or Mo) on the surface of deposit was close to 70% of the total molybdenum amount. The mechanism of the co-deposition of molybdenum with zinc has been proposed. It was found that the reaction of molybdenum deposition is limited by the presence of adsorbed Zn(I)-citrate ions, which are formed in the outer-sphere charge transfer mechanism. Further reduction processes are related to the formation of adsorbed mixed Zn(I)–Mo(VI)–citrate complexes, then reduced to metallic molybdenum and metallic zinc during a complicated, multi-stage process.

The deposition of smooth metallic molybdenum from aqueous electrolytes containing molybdate ions

This paper details the electrodeposition of metallic molybdenum from an aqueous electrolyte containing molybdate ions. The deposition is performed in an acetate bath that contains a high (up to 10 M) concentration of acetate. The molybdenum deposits are thick (up to 20 μm), adherent and were characterized by XRD and XPS analysis. The deposition is inefficient, with most of the current (up to 99%) used in the electrolysis of water to generate hydrogen. The effect of acetate concentration, pH, additives and current on the deposition efficiency and physical properties of the molybdenum deposit were investigated and optimized to obtain smooth, adherent coatings.

Kinetics of Ni–Mo electrodeposition from Ni-rich citrate baths

The kinetics of Ni–Mo alloy electrodeposition on steel substrates from an aqueous citrate–ammonia complex baths has been investigated by means of steady-state polarisation measurements in a system with a rotating disc electrode (RDE). Partial current densities for discharge of Ni(II) and Mo(VI) ions and hydrogen evolution as a function of molybdate concentration in the bath, cathode potentials and the rate of mass transport were determined. It has been shown that – under all investigated conditions – Ni–Mo alloy deposition is more favourable than pure nickel and the cathodic process is strongly influenced by the Mo(VI) content in the solution. The Ni(II) electroreduction rate initially increases, as the cathode potential shifts towards more negative values and the concentration of molybdate grows in the solution. However, for the highest examined MoO 4 2 − content, a considerable decrease in the rate of the process is subsequently observed at certain limit potentials, the values of which depend on molybdate concentration and hydrodynamic conditions. This effect, related to the formation of intermediate molybdenum oxides (characterised by very low overvoltage for hydrogen evolution), becomes less pronounced when the RDE rotation speed is increased. Hydrogen evolution is strongly associated with molybdenum deposition. An increase of the molybdate ions concentration in the bath, as well as an increase in the rate of mass transport, leads to an increase in Mo content in deposits and to the reduction of current efficiency. The Ni–Mo coatings electrodeposited from the designed bath (with the current efficiency of about 70%) containing about 30 wt.% Mo, are characterised by a shiny-grey appearance and good adhesion to the steel substrate. They are characterised by column growth and amorphous microstructure with randomly distributed nanocrystallites of the MoNi 4 intermetallic phase.

Physical–chemical and catalytic properties of deposited MoO3 and V2O5

Abstract The deposition of molybdenum and vanadium oxides onto fumed silica, titania, and alumina as supports through dry milling has been carried out. The structure of prepared compositions has been investigated by means of XRD, DTA–TG, FTIR, and UV–Vis spectroscopy, nitrogen adsorption. The deposited crystal phases are sufficiently uniformly distributed on support surface. The supported oxides are subjected to dispersion in process of milling to the state of oligomeric or isolated species. Milled bulk and deposited MoO3 (first of all, on alumina) possesses improved catalytic performance in process of epoxidation of 1-octene. Vanadium pentoxide also has higher activity in this process.

Effect of Additives on Structure and Corrosion Resistance of Molybdate Conversion Coatings Deposited on AZ31B Mg Alloy

Molybdate conversion coatings were prepared on AZ31B Mg alloy in a molybdate based solution with additives of sodium fluoride (NaF) or lanthanum nitrate (La(NO3)3). The effects of F- and La3+ additives on the morphology and on the corrosion resistance of the molybdate coatings were investigated by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and potentiodynamic polarization analysis. The results revealed that these additives could accelerate the deposition of molybdenum on the surface of AZ31B magnesium alloy. It can be seen that the composite conversion coatings consist of many spherical particles. It is also found that the corrosion resistance is greatly improved after molybdate treatment. The films formed in F- additive solution showed lower corrosion current density than in La3+ additive solution.