Mixture Of MoO3 Research Articles

ChemInform Abstract: The Double Molybdate Rb2Ba(MoO4)2: Synthesis, Crystal Structure, Optical, Thermal, Vibrational Properties, and Electronic Structure.

AbstractSingle crystals of Rb2Ba(MoO4)2 are grown from a 5:2:2 molar mixture of MoO3, Rb2CO3, and BaCO3 (Pt crucible, 1.

Effect of Al2O3 and Cu on the microstructure and oxidation properties of Mo5Si3 composite

Al2O3/Mo5Si3 and Al2O3/Mo5Si3–Cu composites were successfully synthesized via a ball-milled mixture of MoO3, Mo, Si and Al powders and consolidated by hot pressing. The microstructure and oxidation properties of the composites were investigated. Results show that Al2O3/Mo5Si3 and Al2O3/Mo5Si3–Cu composite powders were obtained after 10h of milling. At 600°C, the addition of Al2O3 and Cu in the Mo5Si3 could effectively restrain its pest oxidation. At 1200°C, the corresponding oxidation rate constants of the composites are almost an order of magnitude lower than the Mo5Si3 alloy. The composites have better oxidation resistance than the Mo5Si3 alloy.

ChemInform Abstract: Structural and Magnetic Characterization of the Novel Spin Frustrated Double Perovskite Sr2ScMoO6.

AbstractThe title compound is prepared by solid state reaction of a stoichiometric mixture of MoO3, SrCO3, and Sc2O3.

Molybdenum/graphene – Based catalyst for hydrogen evolution reaction synthesized by a rapid photothermal method

Catalysis of the hydrogen evolution reaction (HER) is important in the development of an energy economy based on clean hydrogen gas. In this work, we report a new catalyst material for the generation of hydrogen via hydronium reduction. The new material, which consists of MoO 2 , sulfur, and graphene, was prepared by co-reduction of molybdenum salt and graphite oxide in air in the presence of focused solar radiation. The potential utility of this material for HER catalysis was evaluated by cyclic and linear-sweep voltammograms and compared against a Pt/C commercial catalyst. The MoO 2 /graphene hybrid nanocomposite exhibits a Tafel slope of 47 mV/dec and hydrogen evolution at a potential only ∼120 mV more negative than the standard Pt/Carbon catalyst at 10 mA/cm 2 current density. The hydrogen gas generated by the catalytic material was measured using gas chromatography. The simple synthesis and low overpotential suggests that this hybrid composite has potential as an HER catalyst. • A mixture of MoO 2 , sulfur and graphene has been prepared with natural sunlight. • XRD, SEM, EDX and FTIR validate material composition. • The high material surface area is advantageous for HER processes. • The material has favorable overpotential and Tafel slope values for catalysis. • The stability, activity, and green synthesis are favorable for clean energy.

The Development of Pseudocapacitive Molybdenum Oxynitride Electrodes for Supercapacitors

Mo oxynitride was developed as pseudocapacitive electrode material for supercapacitors. A thin film Mo oxynitride was produced by first electrodeposition of Mo oxide on a Ti substrate followed by a low-temperature (400 oC) heat treatment in N2 environment. XPS analyses showed that the surface of the Mo oxynitride film was composed of a mixture of MoO3, MoO2 and less than 20 at.% Mo2N. However, the electrochemical behavior of the Mo oxynitride film was significantly different from that of Mo oxide but much similar to the behavior of pure Mo2N, a known pseudocapacitive material. The cycle life and stability of the Mo oxynitride were much improved over the Mo oxide. A two-electrode symmetric cell using the developed Mo oxynitride electrodes was demonstrated and showed high rate performance. An asymmetric cell using a Mo oxynitride as negative electrode and a carbon as positive electrode was also established and showed an extended voltage window and, thus, an increased energy density.

Synthesis and characterization of massive molybdenum carbides and supported carbide-containing catalysts Mo2C/C prepared through mechanical activation

Procedures for the synthesis of massive molybdenum carbide by the mechanical activation of a mixture of MoO3, commercial carbon, and Zn in air and the synthesis of the supported carbide-containing catalyst Mo2C/C by the mechanical activation of commercial carbon impregnated with a 16% aqueous solution of ammonium paramolybdate in an inert atmosphere were developed for the first time. With the use of a set of physicochemical methods, the metal contents, particle sizes, specific surface areas, and phase compositions of the mechanically activated composites were determined. The structure of the carbide-containing supported catalyst was studied by electron microscopy, and its acidic properties were studied by the temperature-programmed desorption of ammonia; catalytic tests in the model reactions of dibenzothiophene (DBT) and alkane aromatization were performed. It was found that the Mo2C/C catalyst exhibited high activity in these reactions: the conversion of DBT at a contact time of 3–6 h was 80–85%. The conversion of n-heptane at a contact time of 2 h was 31.2%, and 100% toluene was the reaction product. An increase in the contact time to 6 h led to a decrease in the conversion of n-heptane to 1.3%, and to 47% C6-C7 cycloalkanes were present in the reaction products. The results of this work are indicative of the high catalytic activity of the Mo2C/C catalyst obtained by mechanical activation.

Porous acicular mullite obtained by controlled oxidation of waste molybdenum disilicide

Porous acicular mullite was fabricated by using waste MoSi2 heating element and Al2O3. Careful calcination of the pulverized heating element led to the formation of a mixture of MoO3 and amorphous SiO2. This mixture was employed as both SiO2 precursor and pore former. The oxidation of MoSi2 and mullite formation were studied. The effect of fabrication temperature on phase composition, porosity, grain morphology, and compressive strength of sintered mullite was examined. Pure mullite with porosity of more than 60% and compressive strength of ∼20MPa was obtained at temperature as low as 1300°C. The microstructure consisted of elongated, rectangular, prism-like grains which are known to be effective in filtration of diesel engine exhaust. The increase in sintering temperature caused the change of grain morphology and reduction in compressive strength.

Synthesis of nano-structure molybdenum disilicide from primary mixture of MoO3 + Si + Al through mechanochemical reactions

The formation of nanocrystalline molybdenum disilicide intermetallic compound from the primary mixture of MoO3+Si+Al by mechanochemical synthesis (MS) method via mechanical milling was investigated. The mechanochemical processes were designed based on thermodynamic calculations and with the aim of studying the effects of changing the Al amount of the primary mixture. An MSR (mechanically induced self-propagating reaction) process was done using a high-energy planetary ball mill. The experiments were optimized to increase the amount of low temperature α-MoSi2 phase and convert the unstable β-MoSi2 phase to the stable α-MoSi2 phase. With the aid of XRD (X-ray diffraction) experiments, phases and their microstructure were analyzed. EDX (energy dispersive X-ray) experiments were carried out in order to investigate the composition of the products and TEM (transmission electron microscopy) was used to study powder particles. The crystallite size and the particle size of the obtained α-MoSi2 phase were around 18.2 and 179nm, respectively. The mass fraction of each obtained phase was determined employing the semi-quantitative analysis of X-ray diffraction patterns.

Bis(butane-1,4-diammonium) di-μ-oxido-bis[trifluoridooxidomolybdate(V)] monohydrate

The title compound, (C4H14N2)2[Mo2O4F6]·H2O, was obtained by solvothermal reaction at 443 K for 72 h from a mixture of MoO3, HF, 1,4-diamino­butane (dab), water and ethyl­ene glycol. The structure consists of [Mo2O4F6]4− anionic dimers containing strongly distorted MoO3F3 octa­hedra (with twofold symmetry), diprotonated dab cations and water mol­ecules (twofold symmetry) in the ratio 1:2:1. The cohesion of the three-dimensional structure is ensured through N—H⋯O, N—H⋯F and O—H⋯F inter­actions.

MECHANOCHEMICAL REDUCTION OF MoO3 POWDER BY Al AND Si TO SYNTHESIZE NANOCRYSTALLINE MoSi2

In this study, mechanical alloying was used to produce MoSi 2 powder directly from molybdenum trioxide. Mixture of MoO 3, Si and Al powders were exposed to high mechanical activation in a planetary ball mill. The ball to powder mass ratio was constant at 33:1 and the rotation speed (cup speed) was 290 rpm during the milling operations. Phase compositions and structural evolutions during milling were investigated by X-ray diffraction analysis. The morphology of the mechanically alloyed powders was evaluated with scanning electron microscope (SEM). From XRD results, it was observed that within 3 hours of milling, MoO 3 was completely reduced and a MoSi 2- Al 2 O 3 composite powder was produced. Further milling resulted in transformation of β- MoSi 2 phase to α- MoSi 2. Mean crystallite sizes in product phases in the sample milled for 30 hours calculated by Scherer method using XRD patterns were found to be less than 100 nm.

Preparation of MoSi2–Al2O3 nano-composite via MASHS route

In this study, MoSi2–Al2O3 nano-composite powder was prepared by mechanical alloying. Mixture of MoO3, Si and Al powders was exposed to high energy ball milling. Phase compositions and structural evolutions during milling were investigated by X-ray diffraction (XRD) analysis. The morphology of the milled powders was evaluated by scanning electron microscope (SEM). Within short milling times [15, 25 and 60minutes in ball to powder weight ratios (BPR) of 35:1, 20:1 and 10:1, respectively], a combustion process occurred within the milling powder and the process mechanism was characterized to be mechanically activated self-propagating high-temperature synthesis (MASHS) type. From XRD results it was found that during the combustion process, MoO3 was completely reduced with Al and the resulting Mo reacted with Si to produce molybdenum disilicide and eventually a MoSi2–Al2O3 nano-composite powder formed within a short period of time. Further milling resulted in reduced mean crystallite sizes and increased lattice micro strain in the product phases. After 30hours of milling in BPR of 35:1, the mean crystallite sizes were found to be 10, 9 and 11nm for Al2O3, α-MoSi2 and β-MoSi2, respectively. Also, effect of stearic acid addition as a Process Control Agent (PCA) was studied and the results showed that its usage postpones the reaction initiation and reduces mean crystallite sizes.

ChemInform Abstract: Cobalt—Zinc Molybdates as New Blue Pigments Involving Co2+ in Distorted Trigonal Bipyramids and Octahedra.

AbstractZn1‐xCoxMoO4 (x < 0.3) powders are prepared by solid state reaction of stoichiometric mixtures of MoO3, Co3O4, and ZnO (alumina crucible, 700 °C, 20 h and 800 °C, 10 h).

Mechanochemical Reduction of MoO<sub>3</sub> Powder by Silicone to Synthesize Nanocrystalline MoSi<sub>2</sub>

Molybdenum disiliside is known as a ceramic material with attractive properties for high temperature structural applications. In this study, mechanical alloying was used to produce MoSi2 powder directly from molybdenum oxide. Mixture of MoO3 and Si powders with commercial purity were exposed to high mechanical activation in a planetary ball mill. The ball to powder mass ratio was selected to be constant at 33:1 and the rotation speed (cup speed) was 600 rpm during the milling operations. Crystallite sizes and structural evolutions during milling were investigated by Xray diffraction analysis. The morphology of the mechanically alloyed powders was evaluated with scanning electron microscope (SEM). From XRD results, it was observed that within 6 hours of milling MoO3 was reduced and fully converted to MoO2. After 17 hours of milling MoO2 also began to reduce and peaks of MoSi2 (both and phases) and Mo were detected. Further milling resulted in a gradual decrease in MoO2 peak intensities because of its continuous reduction. Peaks of MoO2 were also broadened due to refinement of MoO2 crystallite sizes. Scherrer and Williamson-Hall methods using XRD patterns were employed to calculate the mean crystallite size. Calculations indicated that in the sample ball milled for 50 hours, MoSi2 crystallite sizes were less than 100 nm.

ChemInform Abstract: Investigation of the First‐Order Phase Transition in the Co1‐xMgxMoO4 Solid Solution and Discussion of the Associated Thermochromic Behavior.

AbstractPure β‐Co1‐xMgxMoO4 (0 ≤ x ≤ 1) solid solutions are prepared by solid state reactions of stoichiometric mixtures of MoO3, Co3O4, and MgO (alumina crucible, 700 °C, 20 h).

Interplay between phase formation mechanisms and magnetism in the Sr2FeMoO6–δ metal‐oxide compound

AbstractDouble perovskites with the structural formula A2BB′O6±δ, especially the strontium ferromolybdate Sr2FeMoO6–δ, have attracted a lot of attention due to their unique magnetic and electrical properties and a possible application in spintronic devices. However, a strict correlation between the functional characteristics of Sr2FeMoO6–δ and its synthesis technology has been lacking up to date. Thus, we have studied in the present work the crystallization kinetics of Sr2FeMoO6–δ using reagents with different pre‐history as well as the structural and magnetic properties of the obtained compounds. Differences in the crystallization kinetics as well as higher magnetic inhomogeneity of Sr2FeMoO6–δ synthesised from a mixture of MoO3, Fe2O3, SrCO3 in comparison with the compound synthesised from the SrFeO2.5 and SrMoO4–y precursors have been found and interpreted. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

New composite films based on MoO3−x nanowires aligned in a liquid single crystal elastomer matrix

In this study, we report the preparation, structure characterization, and application of new MoO3−x nanowires, promising candidates for lithium intercalation, hydrogen sensing, and smart windows due to their photochromic property. These nanowires are a mixture of MoO3 and conductive Mo5O14 phase and have been used to prepare composite films based on liquid single crystal elastomers (LSCE). The structure, morphology, and thermomechanic behavior of these films are discussed. In particular, we show that the particular combination of molybdenum-based nanowires and LSCEs allows for doping of liquid single crystal elastomers, preserving the pristine mechanical and optical properties of the host matrix.

MoO3 nanoparticles dispersed uniformly in carbon matrix: a high capacity composite anode for Li-ion batteries

A MoO3–carbon nanocomposite was synthesized from a mixture of MoO3 and graphite by a controlled ball milling procedure. The as-prepared product consists of nanosized MoO3 particles (2–180 nm) homogeneously distributed in carbon matrix. The nanocomposite acts as a high capacity anode material for lithium-ion batteries and exhibits good cyclic behavior. Its initial capacity exceeds the theoretical capacity of 745 mA h g−1 in a mixture of MoO3 and graphite (1 : 1 by weight), and the stable capacity of 700 mA h g−1 (94% of the theoretical capacity) is still retained after 120 cycles. The electrode performance is linked with the unique nanoarchitecture of the composite and is compared with the performance of MoO3-based anode materials reported in the literature previously (nanoparticles, ball milled powders, and carbon-coated nanobelts). The high value of capacity and good cyclic stability of MoO3–carbon nanocomposite are attractive in respect to those of the reported MoO3 electrodes.

ChemInform Abstract: Polar Hexagonal Tungsten Oxide (HTO) Materials: (1) Synthesis, Characterization, Functional Properties, and Structure—Property Relationships in A2(MoO3)3(SeO3) (A: Rb+ and Tl+) and (2) Classification, Structural Distortions, and Second‐Harmonic Generating Properties of Known Polar HTOs.

AbstractCrystals of the title compounds are prepared from mixtures of MoO3, A2CO3 (A: Rb, Tl), SeO2, and H2O (autoclave, 230 °C, 3 d, 50% and 80% yields for the Rb and Tl compounds, respectively).

Preparation and Tribological Properties of MoS2 Nanosheets

AbstractMoS2 nanosheets were successfully synthesized by a micro‐domain reaction method, employing a ball‐milled mixture of MoO3 and S as starting materials. The obtained MoS2 nanosheets are monodisperse, and the length and width are about 100 and 10 nm, respectively. Furthermore, the tribological performances of the as‐obtained MoS2 nanosheets were studied and possible optimized mechanisms were also proposed.

Crystallization of amorphous Si thin films by the reaction of MoO 3/Al nanoengineered thermite

In this work, we investigated a new crystallization method for amorphous silicon (a-Si) using a mixture of nano-energetic materials: molybdenum oxide and aluminum (MoO 3/Al). The purpose of using nano-energetic materials is to improve the performance of a-Si films with a self-propagating exothermic reaction over a period of microseconds without any substrate damage. The mixture of MoO 3/Al nanopowders was used for a thermite reaction for crystallization of a-Si thin films. Characterization results showed that a-Si thin films were successfully crystallized to poly-Si as evidenced by a Raman peak near 519 cm − 1 . The crystalline volume fraction of poly-Si after the nanoengineered thermite reaction was about 94.7% and poly-Si grains was uniformly distributed with an average grain size of around 40–50 nm. These results indicate that high quality poly-Si thin films were successfully prepared on the substrate.