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In this work, we propose a heterostructure composed of multilayer twisted black phosphorous (BP) and α-phase molybdenum trioxide (α-MoO3) since the twist angles among BP layers may result in exotic phenomena. We theoretically investigate the impact of the primary physical parameters on the Goos–Hänchen (GH) and Imbert–Fedorov (IF) shifts in or near the reststrahlen bands, including the twisted angle, carrier density, and layer numbers of the twisted BP film. The optimal twisted BP/α-MoO3 heterostructure is selected for the different crystalline structure of α-MoO3, where the maximum of GH-shifts can achieve 11704.5 λ 0 (λ 0 is the vacuum wavelength), resulting in a direct measurement. On the other hand, the IF-shift caused by the anisotropy of the twisted BP layer is increased at 1892.1 λ 0. Based on the tunable GH- and IF-shifts, information processing through two or four separate channels for barcode encryption is constructed and examined. The outcomes can serve as a guide for using GH- and IF-shift in optical encoder design. [ABSTRACT FROM AUTHOR]

Molybdenum (Mo) is a strategic metal for the manufacture of aerospace equipment, satellite components, and vehicle armor. Thus, understanding its behaviors under harsh conditions like shock compression is crucial for its practical utilization. Through molecular dynamic simulations, we have explored the mechanical responses and microstructural evolutions of nano-polycrystalline (NPC) Mo under different shock intensities, with grain sizes ranging from 5 to 33 nm. Our study reveals that grain size considerably influences the Hugoniot data and waveform of NPC Mo. NPC Mo with a smaller grain size exhibits higher compressibility and lower Hugoniot shear stress. As the grain size increases, the presence of a double-wave structure becomes more pronounced. Additionally, with the increase in shock intensity, there is a reduction in the shock front width. Significantly, when the shock stress ranges from approximately 60 to 100 GPa, twinning structures are detected in samples with grain sizes ranging from 10 to 33 nm. Moreover, the elevated temperature behind the shock wave further promotes detwinning reactions. When the shock stresses exceed 100 GPa, twinning–detwinning as well as amorphization-recrystallization become the predominant deformation mechanisms, almost unaffected by grain size. As the shock stress exceeds 250 GPa, the atoms in the samples become completely disordered. These findings provide new insights into the mechanical responses as well as the microstructural evolutions of NPC Mo under shock compression. [ABSTRACT FROM AUTHOR]

We present the ab initio thermoelastic properties of body-centered cubic molybdenum under extreme conditions obtained within the quasi-harmonic approximation including both the vibrational and electronic thermal excitation contributions to the free energy. The quasi-harmonic temperature-dependent elastic constants are calculated and compared with existing experiments and with the quasi-static approximation. We find that the quasi-harmonic approximation allows for a much better interpretation of the experimental data, confirming the trend found previously in other metals. Using the Voigt–Reuss–Hill average, we predict the compressional and shear sound velocities of polycrystalline molybdenum as a function of pressure for several temperatures, which might be accessible in experiments. [ABSTRACT FROM AUTHOR]

The surface properties of nickel-based alloys with different alloying compositions against aggressively corrosive species were systematically evaluated by using the segregated and non-segregated models designed through first-principles calculations. The presence of typical VIB alloying elements such as chromium (Cr), molybdenum (Mo), and tungsten (W) elements near the nickel surface was identified to significantly enhance the surface adsorption of water molecules (H2O) and their decomposed products (OH, O, and H). The doping patterns and surface electronic structures were found to determine the adsorption diversity of these substances. Consequently, adsorbates containing oxygen were likely to induce the segregation tendencies of these selected alloying elements from the deep area of nickel toward the top-most surface layer (TSL). The electrode potential shifts of the surface Ni atom in the designed alloying systems, compared to the bare Ni (111) surface, were further calculated to identify the beneficial electrochemical performance of alloy surfaces in the absence/presence of various adsorbates. In vacuum, the locations of these alloying elements in the near-surface layers would more increase the electrode potential shifts, thereby delaying the dissolution of Ni atoms from metal substrates. Nevertheless, the presence of adsorbates led to notably negative electrode potential shifts for the Ni (111) surface, among which the decomposed products (hydroxyl and oxygen) were of the most passive effects on corrosion behavior of nickel. The detrimental effects of these adsorbates on surface stability would be effectively alleviated with the aid of atomic VIB alloying elements of nickel-based alloys, especially W segregation to the TSL regardless of the pH in aqueous environments. [ABSTRACT FROM AUTHOR]

By electric transport measurements on high-purity bulk molybdenum single crystals at helium-temperature, it is shown that when approaching the ideal metallic crystal structure, there are deviations from Ohm's law that can exceed 30% even at low current densities ≅ 3 A / m m 2. This is due to the intrinsic circular magnetic field of the measuring current in the range of B ≅ 1 mT , which generates a magnetoresistance according to the two-band conduction model. With increasing lattice vibrations and/or crystal defects, this inherent uncertainty finally reduces to immeasurably small values. Finally, Ohm's law for a nearly ideal lattice structure can be strictly exact only in the theoretical limiting case of an infinite lattice plane, because then the magnetic fields of all electrons of the current compensate to zero. [ABSTRACT FROM AUTHOR]

Since the form of the exact functional in density functional theory is unknown, we must rely on density functional approximations (DFAs). In the past, very promising results have been reported by combining semi-local DFAs with exact, i.e. Hartree–Fock, exchange. However, the spin-state energy ordering and the predictions of global minima structures are particularly sensitive to the choice of the hybrid functional and to the amount of exact exchange. This has been already qualitatively described for single conformations, reactions, and a limited number of conformations. Here, we have analyzed the mixing of exact exchange in exchange functionals for a set of several hundred isomers of the transition metal carbide, Mo4C2. The analysis of the calculated energies and charges using PBE0-type functional with varying amounts of exact exchange yields the following insights: (1) The sensitivity of spin-energy splitting is strongly correlated with the amount of exact exchange mixing. (2) Spin contamination is exacerbated when correlation is omitted from the exchange-correlation functional. (3) There is not one ideal value for the exact exchange mixing which can be used to parametrize or choose among the functionals. Calculated energies and electronic structures are influenced by exact exchange at a different magnitude within a given distribution; therefore, to extend the application range of hybrid functionals to the full periodic table the spin-energy splitting energies should be investigated. [ABSTRACT FROM AUTHOR]

Since the form of the exact functional in density functional theory is unknown, we must rely on density functional approximations (DFAs). In the past, very promising results have been reported by combining semi-local DFAs with exact, i.e. Hartree–Fock, exchange. However, the spin-state energy ordering and the predictions of global minima structures are particularly sensitive to the choice of the hybrid functional and to the amount of exact exchange. This has been already qualitatively described for single conformations, reactions, and a limited number of conformations. Here, we have analyzed the mixing of exact exchange in exchange functionals for a set of several hundred isomers of the transition metal carbide, Mo4C2. The analysis of the calculated energies and charges using PBE0-type functional with varying amounts of exact exchange yields the following insights: (1) The sensitivity of spin-energy splitting is strongly correlated with the amount of exact exchange mixing. (2) Spin contamination is exacerbated when correlation is omitted from the exchange-correlation functional. (3) There is not one ideal value for the exact exchange mixing which can be used to parametrize or choose among the functionals. Calculated energies and electronic structures are influenced by exact exchange at a different magnitude within a given distribution; therefore, to extend the application range of hybrid functionals to the full periodic table the spin-energy splitting energies should be investigated. [ABSTRACT FROM AUTHOR]

As a function of the capillary die geometry for fibers (φ: 1 mm) and rods (φ: 3 mm), the bubble distribution and size have been studied. It is discussed how the pulling rate and the capillary die design impact the bubble propagation during sapphire crystallization from molybdenum crucibles using the micro-pulling down (μ-PD) technique. At a low pulling rate (v = 0.25 mm min−1), for both fibers and rods, the crystallization interface is flat, the bubble concentration is low, and they are regularly distributed in the periphery of the crystals. [ABSTRACT FROM AUTHOR]

Sustainable separation and purification strategies for transition metal molybdenum, enlisted as a critical mineral owing to its vast industrial applications and limited natural resources, from secondary resources are of paramount importance. Directed towards this aim, this is the first report of direct, mineral acid-free Mo recovery from solid matrices by supercritical carbon dioxide extraction using alpha benzoin oxime (ABO) and pentadecafluoro-n-octanoic acid (HPFOA) as complexing agents. Efficient (>90%) Mo recovery was achieved under optimised conditions (323 K, 200 atm, in situ complexation mode) by eliminating any high-temperature treatment and harsh acid/base leaching steps. Additionally, high removal efficiencies were obtained for other metal ions, namely, U (>91%) from the U–Mo blend matrix relevant to fission moly applications and V (∼100%), Al (>88%), and Ni (>91%) from the simulated spent catalyst matrix. Further insight into the Mo-complex in the SC CO2 extract was obtained by UV-vis spectrophotometry, FTIR and electrometric investigations. Mo oxalate precipitation from a compact SC CO2 extract was also demonstrated. This study, therefore, addresses the challenge of developing a simple, efficient and selective method for the recovery of Mo from various solid matrices. [ABSTRACT FROM AUTHOR]

Highly-dispersed Pt nanoclusters supported onto MoB is developed through microwave approach with various solvent to regulate the catalytic performance. The synthesized electrocatalyst Pt/MoB-M exhibits excellent electrocatalytic performance towards HER with low overpotential (13 mV at 10 mA cm−2), small Tafel slope (24 mV dec−1), and high mass activity (10.06 A/mgPt at 50 mV). [Display omitted] The interaction between metal nanoclusters and the carrier can enhance the electron transfer rate to optimize the hydrogen evolution reaction (HER) performance, but the common synthesis approaches often lead to metal particle agglomeration, and then blocking active sites. Herein, highly-dispersed Pt nanoclusters supported onto molybdenum boride (MoB) is developed through microwave approach with various solvent to regulate the catalytic performance. The synthesized electrocatalyst with the addition of methanol (Pt/MoB-M) exhibits excellent electrocatalytic performance towards HER with low overpotential (13 mV at 10 mA cm−2), small Tafel slope (24 mV dec−1), and high mass activity (10.06 A/mg Pt at 50 mV). This work presents a novel approach to prepare highly-efficient electrocatalysts for renewable energy-related applications of non-carbon supported low loading of precious metals. [ABSTRACT FROM AUTHOR]

Hydrogen is considered a promising alternative to conventional fossil fuels, as it can be easily produced from renewable energy sources. While electrocatalytic water splitting can achieve near-unity faradaic efficiency in producing hydrogen from water, the widespread implementation of large-scale water electrolysis is hindered by reliance on costly platinum group metal-based electrocatalysts. Here, we report on the rational design of Molybdenum-containing SiCN composites (Mo–SiCN) through an active-filler controlled pyrolysis (AFCOP) strategy. Our investigation into the composite's microstructural evolution revealed the formation of a Mo4.8Si3C0.6 Nowotny phase at a relatively low temperature of 1000 °C. After optimization, the resulting catalyst demonstrated a Tafel slope below 95 mV dec−1 and an overpotential near 575 mV at a normalized current density of 1 mA μF−1. As a proof of concept, the AFCOP strategy was employed to engineer a crack-free Mo–SiCN micropattern, enabling the miniaturization of a Pt-free electrochemical water splitting (EWS) reactor. Produced via soft lithography, the Mo–SiCN pattern exhibits feature sizes ranging from 10 to 200 μm, with near-net-shape replication and a Young's modulus of ≈60 GPa. [ABSTRACT FROM AUTHOR]

Bismuth vanadate (BiVO4) is a promising photoanode material for photoelectrochemical (PEC) water oxidation. However, its performance is greatly hindered by poor bulk and interfacial charge transfer. Herein, to address this issue, iron doped vanadyl phosphate (Fe:VOPO4) was grafted on molybdenum doped BiVO4 (Mo:BiVO4) for significantly enhancing charge transfer and oxygen evolution kinetics simultaneously. Consequently, the resultant Fe:VOPO4/Mo:BVO4 photoanode exhibits a remarkable photocurrent density of 6.59 mA cm-2 at 1.23 V versus the reversible hydrogen electrode (VRHE) under AM 1.5G illumination, over approximately 5.5 times as high as that of pristine BiVO4. Systematic studies have demonstrated that the hopping activation energy of small polarons is significantly reduced due to the Mo doping, resulting in accelerated bulk charge transfer. More importantly, the deposition of Fe:VOPO4 promotes the interfacial charge transfer between Mo:BiVO4 and Fe:VOPO4 via the construction of V-O-V and P-O bonds, in addition to facilitating water splitting kinetics. This work provides a general strategy for optimizing charge transfer process, especially at the interface between photoanodes and cocatalysts. [ABSTRACT FROM AUTHOR]

Background Due to the ability of metal ions to cross the blood–brain barrier, there has been interest in analyzing cerebrospinal fluid (CSF) for trace element concentrations to investigate possible correlations with neurodegenerative diseases. In this study, Sarstedt polypropylene CSF collection tubes were analyzed to determine the contamination levels of aluminum, titanium, chromium, manganese, cobalt, nickel, molybdenum, gadolinium, vanadium, arsenic, cadmium, mercury, lead, thallium, selenium, copper, zinc, and iron. Methods Sarstedt polypropylene CSF collection tubes from 2 separate lots (n = 10 per lot) were filled with a 2 mL aliquot of a CSF pool with known element concentrations. After 24 hours of leaching at room temperature, all 18 elements were analyzed via inductively coupled plasma mass spectrometry (ICP-MS). Results were subtracted from the initial pool concentration to determine contamination levels. Results No detectable contamination above the assay limit of detection was found in 11 analytes. Molybdenum and selenium contamination was measured in all tubes, and aluminum, titanium, manganese, thallium, and zinc had minimal levels of sporadic detectable contamination in 25% or fewer of the tubes tested. Conclusions Sarstedt polypropylene CSF tubes are an acceptable collection tube for the analysis of most assessed metals in CSF. [ABSTRACT FROM AUTHOR]