Effect Of Mo Addition Research Articles

Effect of Mo additions on microstructure and tensile behavior of a Co–Al–W–Ta–B alloy at room temperature

Phase constitutions, microstructures and room-temperature tensile behavior of Mo-doped Co–9Al–(9 − x)W–2Ta–0.02B–xMo alloys (where x = 0, 2, 4, 6, 9 at.%) are investigated. After aging treatment, the microstructure is composed of γ matrix and nanoscale cuboidal γ′ precipitates, with Mo contents of 0–4 at.%; however, a needle-like cellular κ-Co3Mo phase is additionally found in the γ′/γ microstructure, with Mo contents of 6–9 at.%. The pure γ′/γ microstructure exhibits better room-temperature tensile strength and elongation than the γ/γ′/κ microstructure.

ZrCuAlMo大块非晶的制备及热稳定性研究

(Zr₄₇Cu₄₄Al₉)_100-xMo_x(<italic>x</italic>=0, 1, 2, 3) metallic glass alloys were prepared by copper mould casting. The effect of Mo addition on the glass-forming ability (GFA) and thermal stability was investigated by using X-ray diffraction (XRD), and differential scanning calorimetry (DSC). The maximum diameter of glassy rods is increased from 4 mm for the base alloy to 6 mm for the (Zr₄₇Cu₄₄Al₉)₉₈Mo₂ alloy without detectable crystallinity, and 8 mm sample owns very low diffraction peak. Due to suppression of the formation and growth of the primary CuZr phase, properly adding Mo enhances the GFA of the base alloy. The characteristic temperature apparent activation energy was calculated by the Kissinger equation. The activation energies of glass transition (<italic>E</italic>_g), crystallization (<italic>E</italic>_x) and peak crystallization (<italic>E</italic>_p) are 278.57 kJ mol?1, 392.46 kJ mol^-1 and 376.97 kJ mol^-1, respectively. Compared with the base alloy, 2% Mo addition can not only improve the glass forming ability, but also increase the thermal stability. The possible mechanisms were also discussed.

Effect of Mo addition on the microstructure and wear resistance of in situ TiC/Al composite

In this work, Mo was investigated as an additive for in situ preparation of TiC/Al composite using a casting route assisted by self-propagating high-temperature synthesis (SHS). Experimental results show Mo improves the wettability between TiC phase and aluminium melt due to the formation of a Mo-rich shell around the formed TiC particles, which is a kind of good modificator. Compared with the composite without added Mo, 1.0 wt.% Mo addition developed finer matrix structure, significant refinement of TiC particles and more uniform distribution of TiC particles in the matrix. Meanwhile, both wear and tensile properties of TiC/Al composite were improved with 1.0 wt.% Mo addition and then deteriorated with the further increase of Mo content due to the formation of fragile phase Al 5Mo.

Development of high Zr-containing Ti-based alloys with low Young's modulus for use in removable implants

This research focuses on the development of new titanium (Ti) alloys with a low Young's modulus for use in removable implants. In this study, Ti-30Zr alloy was selected as the base alloy, and the effect of Mo addition on the microstructures, Young's moduli, and tensile properties of Ti-30Zr-(0–8 wt.% Mo) alloys was investigated in this study to assess the mechanical compatibility of these alloys for biomedical applications. Further, the cytocompatibility of a part of the designed alloys was examined. The experimental results indicate that both the microstructures and the mechanical properties of the designed alloys are strongly affected by the Mo contents. The Ti-30Zr-(6, 7 wt.%) Mo alloys, located near the boundary of (β + ω)/β with a metastable structure, show a good combination of a low Young's modulus, high tensile strength, fairly large elongation. In addition, Ti–30Zr–7Mo alloy is highly cytocompatible.

Mo microalloying effect on the glass-forming ability, magnetic, mechanical and corrosion properties of (Fe 0.76Si 0.096B 0.084P 0.06)100 -xMo x bulk glassy alloys

The effect of Mo addition on the glass-forming ability (GFA), magnetic properties, mechanical properties and corrosion resistance of (Fe 0.76Si 0.096B 0.084P 0.06) 100− x Mo x ( x = 0, 2, 4 and 6 at.%) bulk glassy alloys (BGAs) with high Fe contents was investigated. The 2 at.% Mo addition makes the alloy composition approach towards a eutectic point, which could result in an increase in the GFA. The BGA rod with diameters up to 3.5 mm was produced by copper mold casting. These BGAs exhibit a rather high saturation magnetization of 0.98–1.51 T and lower coercive force of 1.7–2.1 A/m. A significant improvement in corrosion resistance was observed with microalloying Mo element in 1 N H 2SO 4 solution. Furthermore, these Fe-based BGAs show super-high strength of ∼3.3 GPa and Young's modulus of 200 GPa.

Effect of Mo addition on microstructure and vacuum arc characteristics of CuCr50 alloy

The work functions of Cu, Cr, Mo and CrMo were calculated utilizing the first principle. The effect of Mo addition on the microstructure of CuCr50 alloy was characterized by a scanning electron microscope, and the arc motion characteristic was recorded and investigated by a digital high-speed video camera. The calculated results show that the selectivity of breakdown is closely related to the work function of close-packed plane. The experimental results show that Mo addition can strengthen Cr phase, the first breakdown transfers from Cr phase to Cu phase, and the cathode spots present the characteristics of division and deviation, thus avoiding concentrated erosion. In addition, the chopping current is reduced and the breakdown strength is enhanced as well.

Effects of mo addition on intergranular cracking behavior of 2.25CrW (P23) weld metal at elevated temperatures

A P23 weld metal showed a severe intergranular cracking at elevated temperatures. This reaction results from the strong segregation of impurities at the grain boundary carbide interfaces and the decrease in the bulk content of W which arises from the partitioning of W into carbides. Meanwhile, the other P23Mo weld metal containing 0.5 wt.% Mo showed a considerable ductility under the same conditions. The primary reasons for this result are the intrinsic grain boundary strengthening effect of Mo and the suppression of both the Fe2W Laves phase formation and the partitioning of W into carbides.

Lean duplex stainless steels – The role of molybdenum addition on pitting corrosion of concrete reinforcements

The use of stainless steels as concrete reinforcement is becoming increasingly popular in coastal and marine constructions in order to prevent corrosion induced by chloride ions penetrating into the concrete. In these highly aggressive situations, the lean duplex stainless steels have been extensively employed due to their high mechanical and corrosion resistances. However, the influence of Mo addition on pitting corrosion resistance of these steels is not clearly understood in alkaline chloride conditions even if this element is widely associated to an increasing corrosion resistance in acidic and neutral environments. Therefore, understanding Mo mechanism on corrosion resistance in alkaline media is hence of major importance to the setting of optimized alloy composition. The present work aims to study the effect of Mo addition on pitting corrosion properties of lean duplex stainless steels in alkaline environments (concrete). The results are discussed with respect to the influence of Mo addition on pitting potential for two industrial duplex alloys (1.4362 and 1.4462) in several aggressive media mainly in synthetic, chlorinated and carbonated solution simulating concrete pore environments (pH10 solution with carbonates and chlorides ions). In order to establish the real role of Mo addition on lean duplex corrosion and passivation properties, the corrosion behaviors of two specific laboratory lean duplex alloys, which the only difference between then is the amount of Mo (0 and 3% wt. Mo), are also studied. Furthermore, scanning electronic microscopy (SEM) was used to verify which phase of duplex microstructure (ferritic or austenitic) is mostly susceptible to the pit nucleation in these corrosion conditions as the role of Mo is probably different to each simple phase.

Enhanced flux pinning and formation ofBa4Y2CuMoOy in top-seeded meltgrowth processed YBa2Cu3O7 − d superconductors with Mo additions

The effect of Mo addition (0–10 wt%) on the superconductivity of top-seeded melt growth (TSMG)processed YBa2Cu3O7 − y (Y123) superconductors was studied. The low level Mo addition (≤1 wt%) led to a small decrease of the superconducting transition temperature (Tc) and increase of the critical current density (Jc).The Jc improvement induced by the low level Mo additions appeared as a peak effectat the intermediated magnetic fields and peak position shift to the lowermagnetic fields with increasing Mo content. The enhanced flux pinning causedby Mo additions seems to be attributed to the partial Cu substitution by Mo,YBa2(Cu1 − xMox)3O7 − d. The high level Mo additions (2–10 wt%), however, led to a largeJc decrease and broad superconducting transition due to the formation of low-Tc phases and the increased volume of the non-superconducting Mo-containing phase. Thesecond particle phase formed by the high level Mo additions was identified asBa4Y2CuMoOy (Mo4211) by x-ray diffraction (XRD) and scanning electron microscopy energy dispersivex-ray (SEM EDX) analysis.

Effect of Mo addition on the electrocatalytic activity of Pt–Sn–Mo/C for direct ethanol fuel cells

Carbon-supported Pt–Sn–Mo electrocatalysts have been synthesized by a polyol reduction method and characterized for ethanol electro-oxidation reaction (EOR). While the percent loading of the synthesized nanoparticles on the carbon support is higher than 35%, energy dispersive spectroscopy (EDS) reveals that the Mo contents in the nanoparticle catalysts are lower than the nominal value, indicating incomplete reduction of the Mo precursor. X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) analyses reveal that the Sn and Mo exist as oxide phases at the surface layers of the nanoparticles and the degree of alloying is very low. The electrochemical properties of the electrocatalysts have been evaluated by cyclic voltammetry (CV) and chronoamperometry. The catalytic activity for EOR decreases in the order PtSnMo 0.6/C > PtSnMo 0.4/C > PtSn/C. Single cell direct ethanol fuel cell (DEFC) tests also confirm that the PtSnMo 0.6/C anode catalyst exhibit better performance than the PtSn/C anode catalyst. An analysis of the electrochemical data suggests that the incorporation of Mo to Pt–Sn enhances further the catalytic activity for EOR.

Fe-Mo Catalysts with High Resistance to Carbon Deposition During Fischer–Tropsch Synthesis

Effects of Mo addition on the Fischer–Tropsch synthesis (FTS) performance of precipitated Fe and FeCu catalysts were tested at 280 °C, 1.5 MPa, H2/CO = 2.0, 2,000 h−1. Reaction results in fixed-bed reactor indicate that Mo addition stabilizes the selectivity to higher molecular-weight hydrocarbons of Fe and FeCu catalysts. Carbonaceous species over the spent catalysts were studied by Mossbauer effect spectroscopy (MES) and temperature-programmed hydrogenation (TPH). It is found that Mo addition inhibits the carbon deposition on iron catalysts surface during the FTS reaction and thus probably protects the active sites for producing heavy hydrocarbons. Mo addition inhibits the carbon deposition on iron catalysts surface during the Fischer–Tropsch synthesis and thus protects the sites for production of heavy hydrocarbons and stabilizes the selectivity to higher molecular-weight hydrocarbons (C5 +).

Effects of Mo additions on the glass-forming ability and magnetic properties of bulk amorphous Fe-C-Si-B-P-Mo alloys

Glass formation, mechanical and magnetic properties of the Fe76−xC7.0Si3.3B5.0P8.7Mox (x=0, 1 at.%, 3 at.% and 5 at.%) alloys prepared using an industrial Fe-P master alloy have been studied. With the substitution of Mo for Fe, glass-forming ability (GFA) was significantly enhanced and fully amorphous rods with a diameter of up to 5 mm were produced in the alloy with 3% Mo. The Mo-containing amorphous alloys also exhibited high fracture strength of 3635–3881 MPa and excellent magnetic properties including a high saturation magnetization of 1.10–1.41 T, a high Curie temperature and a low coercive force. The unique combination of high GFA, high fracture strength and excellent magnetic properties make the newly developed bulk metallic glasses viable for practical engineering applications.

Influence of Mo addition on dielectric properties of AlN ceramic matrix composites

AlN-Mo composite ceramics were prepared by spark plasma sintering (SPS) with CaF2 as sintering aids. Effect of Mo addition on the thermal conductivity and dielectric properties of the composite ceramics had been studied. The results show that the room temperature thermal conductivity increases with increasing the content of Mo, and the value begins to decrease slightly when the Mo concentration exceeds 20 vol. %. Analyses indicate that the key factors to dielectric properties are the metal phase concentration and the microstructure of Mo particles. 1 vol. % Ni has been added into the composite ceramics to change the distribution of the Mo phase. The elongated shape particles which link with each other have a tendency to acquire rounded forms which are thermodynamically more stable. Consequently, the dielectric constant and loss of the composite ceramics could be adjusted and the material becomes an electrical conductor in the case of Mo volume fraction of more than 23%. Furthermore, the dielectric properties could be improved to a large extent by transforming the microstructure of the metal particles when the concentration of Mo is fixed.

Effect of Mo addition on precipitated Fe catalysts for Fischer–Tropsch synthesis

Effects of Mo addition on the performance of precipitated Fe catalysts for Fischer–Tropsch synthesis (FTS) were studied in a slurry reactor at 280 °C, 1.5 MPa, 2000 h −1, and syngas H 2/CO = 1.2. The catalysts were characterized by N 2 adsorption, H 2 or CO temperature programmed reduction (TPR), NH 3 temperature programmed desorption (TPD), X-ray diffraction (XRD), and Mössbauer effect spectroscopy (MES). It was found that there is a strong interaction between Fe and Mo, which inhibited the reduction and carburization of Fe catalyst. The surface acidity of the catalysts was also found to increase with addition of molybdenum. In the FTS process, Mo addition decreased the FTS activity of Fe catalyst, markedly enhanced C 12 + hydrocarbon selectivity, while suppressed C 2–C 8 hydrocarbon selectivity as validated by non-ASF product distribution curves.

Formation and mechanical behavior of (Fe0.5Ni0.5)80−xMoxB20 (x = 0–8) amorphous alloys

Glass forming ability, thermal stability and mechanical behavior of (Fe0.5Ni0.5)80−xMoxB20 (x=0, 2, 4, 6, 8) amorphous alloys were studied by XRD, TEM, SEM, DSC, tensile test, microhardness test and tearing test. The effects of Mo addition on glass formation, strength and ductility of (Fe0.5Ni0.5)80−xMoxB20 amorphous alloys were discussed. The substitution of Mo for Fe and Ni simultaneously causes improvement in glass forming ability and thermal stability, and changes the crystallization process. The tensile fracture strength of amorphous alloy depends on both hardness and ductility; the alloy with high hardness and good ductility simultaneously also has a high tensile fracture strength. The (Fe0.5Ni0.5)78Mo2B20 amorphous alloy exhibits good glass forming ability and the highest tensile fracture strength among (Fe0.5Ni0.5)80−xMoxB20 alloys. Micro-plastic deformation occurred in ductile and brittle amorphous alloys that both show viscous flow characteristics. The mechanical behavior of (Fe0.5Ni0.5)80−xMoxB20 amorphous alloys is related to the average outer shell electron concentration of metal atoms.

Formation of bulk metallic glasses in the Fe–M–Y–B (M = transition metal) system

In this work, quaternary Fe 72− x M x Y 6B 22 (M = Ni, Co and Mo) bulk metallic glasses (BMGs) have been developed. It is found that a fully amorphous Fe 68Mo 4Y 6B 22 cylindrical rod with 6.5 mm in diameter can be prepared by copper mold injection. These alloys have a high glass transition temperature of about 900 K with high fracture strengths up to about 3 GPa although they are still brittle. Magnetic measurements reveal that they are ferromagnetic at ambient temperature with low coercive force of about 2 A/m, saturation magnetization of about 0.7 T and effective permeability of about 7000 at 100 kHz. The newly developed Fe-based quaternary alloys exhibit excellent combination properties: superior glass forming ability (GFA), high glass transition temperature, and soft magnetic properties, which could have potential applications in electronic industries. Furthermore, the effect of Mo addition on GFA in the Fe–Y–B BMG system has been discussed compared with those of Ni and Co additions.

Effect of Mo addition on the microstructure and mechanical properties of ultra-fine grade TiC–TiN–WC–Mo2C–Co cermets

Abstract Effect of Mo addition on the microstructure and mechanical properties of ultra-fine grade TiC–TiN–WC–Mo2C–Co cermets was studied in this work. Mechanical properties such as transverse rupture strength, fracture toughness and hardness were also measured. Results show that the microstructure exists in black core/grey rim structure and white core/grey rim structure, and the microstructure has an obvious trend to become finer with the increase of molybdenum content. When the added Mo exceeds 10%, ultra-fine TiC-based cermet with an average particle size of less than 0.5 μm is obtained, because of the formation of a Mo-rich rim and the improvement of the wettability between ceramic phase and metallic phase. The transverse rupture strength increases with the increase of Mo content, and the maximum values of the hardness and the fracture toughness were found with 10 wt% and 5 wt% Mo addition, respectively.

Mo−Fe Catalysts Supported on Activated Carbon for Synthesis of Liquid Fuels by the Fischer−Tropsch Process: Effect of Mo Addition on Reducibility, Activity, and Hydrocarbon Selectivity

The effects of Mo loading (0−12 wt %) on the properties of activated-carbon- (AC-) supported Fe−Cu−K catalysts and their performance for Fischer−Tropsch synthesis are studied. Physicochemical properties studied include particle size, reducibility, and dispersion, and catalytic properties include activity, selectivity, and stability. Catalysts were characterized by N2 adsorption, energy-dispersive spectroscopy, X-ray diffraction (XRD), H2 temperature-programmed reduction (TPR), and CO chemisorption. Catalyst performance was studied at 310−320 °C, 2.2 MPa, 3 Nl/g-cat/h, and H2/CO = 0.9. Reaction results in a fixed-bed reactor show that addition of 6% Mo into the Fe−Cu−K/AC catalyst improves catalyst stability without sacrificing activity, but activity is suppressed dramatically on a 12% Mo-loaded catalyst. Detectable hydrocarbons of C1 to C34 are produced on the Fe−Cu−K/AC catalysts with or without Mo. However, the addition of Mo results in the production of more CH4 and less C5+ hydrocarbons. The Mo promot...

Effects of Process Parameters and Substrate Structures on Growth of Single-Walled Carbon Nanotubes by Catalytic Decomposition of Ethanol

Single-walled carbon nanotubes (SWNTs) were prepared by ethanol chemical vapor deposition (CVD), using Co and Mo as metal catalysts deposited on Si/SiO2 substrates with and without an Al underlayer. The effects of Mo addition, catalyst particle size and the Al underlayer were discussed on the basis of the results of scanning electron microscopy (SEM), atomic force microscopy (AFM) and Raman measurement. In substrates with Si/SiO2/Co/Mo structures, a Co layer with a thickness of 1 nm produced smaller catalyst particles and SWNTs with a thinner diameter and at a higher yield than a Co layer with a thickness of 2 nm. The addition of Mo to Co films in substrates was shown to have the effect of suppressing Co aggregation and keeping catalyst particles small, even with high-temperature CVD growth. It was also found that the introduction of an Al underlayer promoted SWNT growth because of the formation of Al2O3 clusters after heat treatment.

Effect of Mo addition on transformation behavior of (α 2 + γ) based Ti–Al alloys

The structural and microstructural characterizations of four alloys with nominal compositions of Ti–42Al–2Mo, Ti–42Al–6Mo, Ti–40Al–2Mo, and Ti–40Al–6Mo have been studied. The 2 at.% Mo as cast alloys comprise of (α 2 + γ) phases whereas those of 6 at.% Mo show (B2 + γ) phases. The solution treatment at 1300 and 1400 °C for 1 h followed by water quenching of these alloys have shown composition specific phase transformation characteristics. The formation of the B2 phase during heat treatment has been discussed and structural model based on statistical occupancy to explain (1 0 0) peak will be presented. The change in the nature of bonding of the B2 phases in Ti–Al–M (M = Mo, Nb, V) alloys have been highlighted.