Large Molybdenum Research Articles

An expanded plasma jet assisted technique for very high-rate synthesis of 2D α-MoO3 nanomaterials, with surface oxygen vacancies and robust induced ferromagnetism

This article reports a novel, clean and energy-efficient thermal-plasma assisted synthesis technique, for very high rate production of defective, ferromagnetic, 2D stoichiometric molybdenum-oxide, maximum up to 750 g/h, but without compromising with the sizes of the nanomaterials or their state of aggregation. A collimated, laminar beam of plasma with large cross-section and uniform profile is produced as the jet expands supersonically into a vacuum chamber that engulfs a large molybdenum target plate and heat it up in a controlled manner. The surface of the target is rapidly oxidized into a sublimating vapour, from which nanometric metal-oxides are nucleated through gas phase condensation process. Surface oxygen-defects are introduced into the product, but even without employing an additional step of defect-engineering, which endowed them with robust room-temperature ferromagnetic properties (maximum saturation magnetization = 1.84 emu/g) and easy dispersibility in aqueous solutions. It is further demonstrated that the as-synthesized, phase-pure α-MoO3 sample with hierarchical morphology can adsorb cationic methylene blue (MB) dyes from an aqueous solution at 94.1 % in 30 min, and the corresponding maximum adsorption capacity is 1045.9 mg/g. The ferromagnetic nanoadsorbents may be separated from wastewater with a simple lab scale magnetic field, to reduce secondary pollution and for reuse of the adsorbents.

Direct liquid injection pulsed-pressure MOCVD of large area MoS2 on Si/SiO2.

Large-scale, high-quality growth of transition metal dichalcogenides (TMD) of controlled thickness is paramount for many applications in opto- and microelectronics. This paper describes the direct growth of well-controlled large area molybdenum disulfide (MoS2) on Si/SiO2 substrates by direct liquid injection pulsed-pressure metal-organic chemical vapor deposition (DLI-PP-MOCVD) using low-toxicity precursors. It is shown that control of the deposited thickness can be achieved by carefully tuning the amount of molybdenum precursor evaporated and that continuous layers are routinely obtained. Homogeneity and reproducibility have also been examined, as well as the average size of the grains. When targeting monolayer thickness, the MoS2 showed near stoichiometry (S/Mo = 1.93-1.95), low roughness and high photoluminescence (PL) quantum yield, equivalent to exfoliated monolayers and CVD MoS2 grown on the same substrates.

The Impacts of Molybdenum Exploration on Cd and Zn Contents in Surface Water: Evidence from a Molybdenum Mine in the Xiaoqinling Mountains

In order to study the impact of molybdenum ore development in a large molybdenum mining area in the Xiaoqinling Mountains on the water and sediment quality of the Wenyu stream, surface water, sediment, and surrounding rock samples were collected, and the Cd and Zn contents were analyzed. The pollution status and ecological risk degree of river water and sediment samples in the Wenyu stream watershed were evaluated using the single element pollution index method, geoaccumulation index method, Hakanson potential ecological risk assessment method, potentially toxic elements (PTEs) health risk assessment, and PTEs pollution comprehensive index method. Finally, the impact of mining development on the contents of Cd and Zn in the Wenyu stream were discussed, and the sources of pollution were identified. The study revealed that the levels of Cd and Zn in 23 water samples collected from the primary channel of the Wenyu stream were markedly higher compared to the unaffected contrast area. Similarly, the concentrations of Cd and Zn in the 17 sediment samples were significantly elevated compared to the average values in the reference area. These findings indicated that The Wenyu stream was heavily impacted by the molybdenum mining activities, resulting in a high ecological risk associated with the sediment in the primary channel. Acid mine drainage in the mining area, sediment release activities, and atmospheric dust fall are considered to be the main sources of PTEs polluting the Wenyu stream watershed. Relevant personnel should complete a thorough river water quality investigation and perform ecological environment restoration so as to ensure sustainable economic development.

The Impact of Molybdenum Mining on Cd Pollution along Wenyu Stream in Qinling Mountains, Northwest China

Mining has brought many environmental problems to the surrounding soil, water, and air, with toxic elements contaminating surface water, threatening ecological balance and human health. This study selected the Wenyu watershed downstream from a large molybdenum mine in the Qinling Mountains as the study area, aiming to explore the impact of molybdenum mining on surface water quality. The content characteristics of Cd, Pb, Cu, Cr and Hg in surface water, sediment, and rock samples were analyzed by field sampling and chemical testing. The results showed only obvious Cd pollution. The pollution status and ecological risk level of surface water and sediment samples in the Wenyu Stream watershed were evaluated using the single pollution index method, geo-accumulation index method, and Hakanson potential ecological risk assessment method. Finally, the sources of Cd pollution and the impact of mining on Cd distribution in the Wenyu Stream were comprehensively discussed. The research results showed that Cd content in the Wenyu Stream was significantly affected by mining activity and the coefficient of variation of Cd content reached 99.44%. Among 22 surface water samples, 21 samples met the Class II water standard, indicating a clean overall water quality of the Wenyu Stream, and only one sample exceeded the Class II water standard with a mild pollution level. All 15 sediment samples were polluted to varying degrees and the most severely polluted sample had reached a moderate to strong pollution level. Most of the samples were at a moderate pollution level. The potential ecological hazard indexes of Cd content were at medium to very strong risk level, indicating that the overall sediment in the main ditch of the Wenyu Stream was under a strong ecological risk level. The main sources of Cd pollution, including acid mine drainage, regional geological background, sediment release, and atmospheric dry and wet deposition, were discussed.

Petrogenesis and Mo(W) mineralization of deep porphyritic granites in the Laowan ore field, Eastern Qinling, Central China

The Laowan ore field of the Tongbai district is a crucial metallogenic belt within Eastern Qinling, including super large gold (Au) and large molybdenum (Mo) deposits. However, the Au and Mo metallogenic relationship and tectonic setting are still disputed. Petrology, geochemistry, and geochronology were conducted on the 3000 m scientific drilling hole, ZKE1012, south of the Laowan ore field. A concealed porphyritic granite with Mo mineralization was observed at a depth of 1717 m. The concealed porphyry comprises K-feldspar, plagioclase, quartz, biotite and minor magnetite, ilmenite, rutile, apatite, and zircon. Molybdenite, scheelite, pyrite, and chalcopyrite are immersed in the rock as veinlet-dissemination, showing typical porphyry mineralization characteristics. Zircon U–Pb data define that the deep rock was formed at 131.0 ± 2.1 and 133.2 ± 1.0 Ma, consistent with the molybdenite Re–Os age (130 Ma), indicating that the Mo mineralization was related to the porphyry. The rocks are characterized by high silica (SiO2 = 70.5–76.8 wt%), high alkali (Na2O + K2O = 8.55–9.25 wt%), and metaluminous to weakly peraluminous (A/CNK = 0.99–1.09). They are enriched with large ion lithophile elements (Rb, Y, Th, Ce, Sm, and Zr), depleted in Nb, Ba, and Sr, and show negligible Eu anomalies. The deep porphyries belong to I-type granite, and their zircon εHf(t) values are from − 11.2 to − 5.7. Therefore, the concealed porphyritic granite and its mineralization are the product of partial melting of the basements, mixing minor mantle materials caused by the subduction of the Paleo–Pacific Plate to Eurasia in the Early Cretaceous.

Fe-decorated hierarchical molybdenum carbide for direct conversion of CO2 into ethylene: Tailoring activity and stability

In the past few years, the production of olefins from various resources, particularly from carbon-rich sources, such as crude oil, natural gas, coal, and biomass, has received considerable attention. This study presented the production of light olefins by conducting CO2 hydrogenation through modified Fischer–Tropsch synthesis (M-FTS) by employing a Fe-decorated large surface molybdenum carbide catalyst. A novel strategy was adopted for the synthesis of large surface mesoporous molybdenum carbide by using a hard template. A theoretical loading limit of Fe nanoparticles, calculated using density functional theory, was decorated over β-Mo2C through simple wetness impregnation. The trans isomers of Fe-doped β-Mo2C exhibited higher symmetry and were energetically slightly more stable for the hydrogenation of CO2 into light olefins than the cis isomers. Under the optimized condition, Fe(0.5)-Mo2C showed 7.3% CO2 conversion with 79.4% C2= olefins.

Zircon Hf[sbnd]O isotope and magma oxidation state evidence for the origin of Early Cretaceous granitoids and porphyry Mo mineralization in the Tongbai-Hong'an-Dabie orogens, Eastern China

The Tongbai-Hong'an-Dabie orogens constitute the east segment of the Qinling-Dabie orogenic belt, which host several large molybdenum deposits, with a proven reserve of over 8 million tons metal Mo. In this study, we present an integrated study of in situ zircon UPb dating and HfO isotopes, in combination with magma oxidation state estimation for the Early Cretaceous granitoids in the Tongbai-Hong'an-Dabie regions. These granitoids can be divided into three groups on the basis of zircon UPb ages, including early-stage ore-related granitoids from Mushan, Xiaofan and Wangwan deposits (143–136 Ma), ore-barren granites (136–130 Ma), and late-stage ore-related granitoids from Qian'echong, Bao'anzhai, Tangjiaping and Shapinggou deposits (130–110 Ma). Early-stage ore-barren granitoids have the lowest average εHf(t) and δ18O values of −27.1 ± 1.6 and 4.25 ± 0.63‰ as well as the oldest two-stage Hf model ages (TDM2) of ~2.8 Ga, which are roughly comparable with the inferred Dabie lower crust, indicating that they were mainly derived from the partial melting of the lower crust. Ore-forming granitoids in two stages show similar two-stage Hf model ages from 2.2 to 2.3 Ga which differ from any inferred layer of crusts, while they exhibit different zircon HfO isotope and oxygen fugacity evolutionary trends. Granitoids display decreasing average εHf(t) and δ18O values from −17.1 ± 1.9 to −27.1 ± 1.6, and 5.71 ± 0.50‰ to 4.25 ± 0.63‰, and increasing average logƒO2 values from −17.4 ± 4.5 to −6.7 ± 3.8 with a decrease in age from 143 to 130 Ma. In addition, relict zircon cores with Paleoproterozic and Archean ages were observed with εHf(t) and δ18O values analogous to those of the Kongling Complex. These characteristics suggest that the early-stage granitoids were possibly produced by the remelting of the subducted lower crust mixed with the Kongling Complex, with the involvement of reducing Mo-rich black shales in the Yangtze Block that seemingly account for the lower oxygen fugacity of ore-forming granitoids with younger two-stage Hf model ages and lead to the formation of those early-stage Mo deposits. As the increasing contributions of the lower crust in the magma source, the metallogenic gap developed from 136 to 130 Ma in the Tongbai-Hong'an-Dabie orogens. Zircon HfO isotopic compositions of ore-related granitoids increase simultaneously up to −14.2 ± 4.3 and 5.82 ± 0.33‰ respectively at a lower slope after 130 Ma. Part of zircon δ18O values is slightly higher than 6.5‰, implying the involvement of supercrustal materials. Meanwhile, magma oxygen fugacity exhibits an abrupt drop at ca. 130 Ma in the Qian'echong deposit with the lowest average logƒO2 value (−19.3 ± 4.5) and Ce4+/Ce3+ ratios (1–138), then rises quickly up to a maximum average logƒO2 value of −7.3 ± 2.3. As such, these granitoids were likely generated by mixing of a blended crustal magma, derived from the lower crust and supercrustal materials, and the mantle-derived component which also contributes to the late-stage Mo mineralization. We propose that not only the highly oxidized magma but also the continuous change of oxygen fugacity in the deep magma chamber may have positive effects on the formation of porphyry Mo deposits. Given the significant geochemical change at ca. 130 Ma instead of 125 Ma, we agree that the intensive magmatism and mineralization in the Tongbai-Hong'an-Dabie orogens are closely associated with the delamination of the thickened lower crust of the Yangtze Block, which caused the asthenosphere upwelling that provided the heat source and led to partial melting of overlaying lower crust.

An experimental investigation into the partition of Mo between aqueous fluids and felsic melts: Implications for the genesis of porphyry Mo ore deposits

Abstract Most of the world’s large molybdenum (Mo) deposits are genetically related to magmas that underwent significant fractional crystallization and fluid exsolution, and the residual silicate melts are commonly peralkaline. To understand the relationship between melt compositions and the genesis of porphyry Mo mineralization, the partition coefficients of molybdenum (DMo) between fluid and felsic melt were determined at 850 °C, 900 °C, and 100 MPa with various values of A/NK [molar Al2O3/ (Na2O + K2O) in the melt] under an oxygen fugacity around the Ni–NiO (NNO) buffer. The results show that DMo decreases from 4.23 to 0.4 with increasing A/NK from 0.75 to 1.36 in the carbon dioxide series (fluid composed of X CO 2 = 0.096 [molar CO2/(CO2 + H2O)] and 17.5 wt% NaCl). A similar trend was observed in pure water, with A/NK varying from 0.72 to 1.23, DMo decreases from 0.54 to 0.15. Significantly, DMo in peralkaline melt is consistently higher than that in peraluminous melt, even with the same NBO/T (the ratio of non-bridge oxygen and tetrahedron ion). Our study therefore reveals that Mo is easily distributed into fluids that exsolved from peralkaline magmas. This finding explains why highly fractionated magmas are critical for porphyry Mo mineralization.

Spatial-temporal analysis and background value determination of molybdenum concentration in basins with high molybdenum geochemical background - A case study of the upper Yi River basin

The environmental background value of the river section is important. It can be used to evaluate the effect of pollution control of the upstream of that river section, analyze the trend of environmental pollution, and assist the government to make decisions. Yi river is the main tributary of the Yellow River. In the headwaters of the Yi river, there are two very large molybdenum mines with a history of mining and smelting of many years. This area is also a region with a high molybdenum geochemical background.Using the collected regional molybdenum geochemical map, historical monitoring data, sampling data, remote sensing image, and spatial information of mineral enterprises, we found two reasons of why the molybdenum concentration is unusual in the basin. The first reason is the area is a high molybdenum region. The second reason is that the inherent solubility of molybdenum in the soil is changed due to human engineering activities. In this paper, we did a linear fitting on the soil samples and water samples collected from the natural areas and areas affected by human mining activities, and established a leaching model. By comparing the leaching capability of molybdenum in the soil of different areas, we found that the molybdenum release capability in areas affected by human mining was much higher than that in natural areas.Finally, this paper proposed a method to analyze the contribution rate of molybdenum concentration of this river section, using a combination of the leaching model and the D8 algorithm. The experimental results showed that the contribution rate of natural factors and human influence factors at the exit section of Yi River was 81.38% and 18.62% respectively. The background molybdenum concentration in this section was 0.16 mg/L.

Direct Conversion of CO <sub>2</sub> into Ethylene Over Fe-Decorated Hierarchical Molybdenum Carbide: Tailoring Activity and Stability

In the past few years, the production olefin from various resources, particularly from carbon-rich sources, such as crude oil, natural gas, coal, and biomass, has received considerable attention. This study presented the production of light olefins by conducting CO2 hydrogenation through reverse water-gas shift and modified Fischer–Tropsch synthesis by employing a Fe-decorated large surface molybdenum carbide catalyst. A novel strategy was adopted for the synthesis of large surface mesoporous molybdenum carbide by using a hard template. A theoretical loading limit of Fe nanoparticles, calculated using density functional theory, was decorated over β-Mo2C through simple wetness impregnation. The trans isomers of Fe-doped β-Mo2C exhibited higher symmetry and were energetically slightly more stable for the hydrogenation of CO2 into light olefins than the cis isomers. Under the optimized condition, Fe(0.5)-Mo2C showed 7.3% CO2 conversion with 79.4% C2= olefins.

Tl0.6Mo3S5, an original large tunnel-like molybdenum sulfide with Mo zigzag chains and disordered Tl cations

A novel family of tunnel-like molybdenum sulfide is presented. Strongly disordered Tl cations residing in the large tunnels influence significantly the thermal transport.

Electrochemistry of complex molecular and biomolecular scale entities

Structural mapping of intermediate size and large molecules and biomolecules at ultra-high resolution using single-crystal electrodes and in situ scanning tunnelling microscopy continues to disclose surprising findings. In situ scanning tunnelling spectroscopy has also recently disclosed new electrochemical conductivity features at the level of the single molecule. We overview briefly elements of this development over the last few years, with focus on three recent discoveries: (1) a new packing mode of a core monolayer target thiol, the amino acid cysteine (Cys) on Au(100)-electrodes, quite different from Cys packing on Au(111)- and Au(110)-electrodes; (2) transition of a core ferrocene in situ scanning tunnelling spectroscopy probe from stochastic single-molecule to macroscopic behaviour, a concept at the heart of nanoscience; and (3) unexpected behaviour of the large molybdenum enzyme sulfite oxidase, when going from macroscopic to single-molecule electrochemistry. We compare these studies with other recent discoveries of single-molecule protein conductivity and molecular scale inorganic nanostructures.

High Thermoelectric Power Factor of Poly(3-hexylthiophene) through In-Plane Alignment and Doping with a Molybdenum Dithiolene Complex.

We report a record thermoelectric power factor of up to 160 μW m–1 K–2 for the conjugated polymer poly(3-hexylthiophene) (P3HT). This result is achieved through the combination of high-temperature rubbing of thin films together with the use of a large molybdenum dithiolene p-dopant with a high electron affinity. Comparison of the UV–vis–NIR spectra of the chemically doped samples to electrochemically oxidized material reveals an oxidation level of 10%, i.e., one polaron for every 10 repeat units. The high power factor arises due to an increase in the charge-carrier mobility and hence electrical conductivity along the rubbing direction. We conclude that P3HT, with its facile synthesis and outstanding processability, should not be ruled out as a potential thermoelectric material.

Large Area Deposition of MoSe2 on Paper as a Flexible Near-Infrared Photodetector

This letter demonstrates the fabrication of large area molybdenum diselenide (MoSe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) nanoflowers using a simple, cost-effective hydrothermal synthesis followed by vacuum filtration deposition on cellulose paper as a near-infrared region (NIR) light photodetector. An increase in the photocurrent was observed upon increasing intensity of NIR illumination, which could be attributed to the increased number of photogenerated excitons. The fabricated photodetector under the 780 nm wavelength illumination responded to the responsivity and external quantum efficiency (EQE) of the fabricated photodetector of 9.73 mA/W and 0.015%, respectively. Furthermore, even for an arbitrary bending, the fabricated device exhibits a negligible change in the responsivity and EQE, which display the robustness of the fabricated device. Successful fabrication of MoSe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /paper-based flexible, cost-effective, and environment-friendly NIR photodetector holds tremendous applications in future optoelectronic devices.

Formation of Molybdenum Blues Particles via the Reduction of Molybdate Solutions with Hydroquinone

Dispersions of molybdenum blues have been synthesized by reducing a molybdate with hydroquinone in an acidic medium. Spectrophotometry and photon-correlation spectroscopy have been employed to study the formation regularities of molybdenum blues particles (large molybdenum oxide clusters) under the conditions of varied reductant/molybdate ratio and dispersion medium pH.

Formation of Molybdenum Blue Particles via the Reduction of a Molybdate Solution with Glucose

Molybdenum blue dispersions are synthesized via the reduction of molybdate with glucose in an acidic medium. Spectrophotometry and photon correlation spectroscopy show that, depending on the reducing agent/molybdate ratio and the pH value, both colored complex Mo compounds and dispersed phase particles (large molybdenum oxide clusters) can form. It is shown that particles form in the 1.4–2.2 range of the dispersion medium’s pH and ceases 21 days after synthesis (at room temperature).

THE DIVERSE ORIGINS OF NEUTRON-CAPTURE ELEMENTS IN THE METAL-POOR STAR HD 94028: POSSIBLE DETECTION OF PRODUCTS OF i-PROCESS NUCLEOSYNTHESIS*

ABSTRACT We present a detailed analysis of the composition and nucleosynthetic origins of the heavy elements in the metal-poor ([Fe/H] = −1.62 ± 0.09) star HD 94028. Previous studies revealed that this star is mildly enhanced in elements produced by the slow neutron-capture process (s process; e.g., [Pb/Fe] = +0.79 ± 0.32) and rapid neutron-capture process (r process; e.g., [Eu/Fe] = +0.22 ± 0.12), including unusually large molybdenum ([Mo/Fe] = +0.97 ± 0.16) and ruthenium ([Ru/Fe] = +0.69 ± 0.17) enhancements. However, this star is not enhanced in carbon ([C/Fe] = −0.06 ± 0.19). We analyze an archival near-ultraviolet spectrum of HD 94028, collected using the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope, and other archival optical spectra collected from ground-based telescopes. We report abundances or upper limits derived from 64 species of 56 elements. We compare these observations with s-process yields from low-metallicity AGB evolution and nucleosynthesis models. No combination of s- and r-process patterns can adequately reproduce the observed abundances, including the super-solar [As/Ge] ratio (+0.99 ± 0.23) and the enhanced [Mo/Fe] and [Ru/Fe] ratios. We can fit these features when including an additional contribution from the intermediate neutron-capture process (i process), which perhaps operated through the ingestion of H in He-burning convective regions in massive stars, super-AGB stars, or low-mass AGB stars. Currently, only the i process appears capable of consistently producing the super-solar [As/Ge] ratios and ratios among neighboring heavy elements found in HD 94028. Other metal-poor stars also show enhanced [As/Ge] ratios, hinting that operation of the i process may have been common in the early Galaxy.

Flexible integrated circuits and multifunctional electronics based on single atomic layers of MoS2 and graphene

Two-dimensional materials, such as graphene and its analogues, have been investigated by numerous researchers for high performance flexible and conformal electronic systems, because they offer the ultimate level of thickness scaling, atomically smooth surfaces and high crystalline quality. Here, we use layer-by-layer transfer of large area molybdenum disulphide (MoS2) and graphene grown by chemical vapor deposition (CVD) to demonstrate electronics on flexible polyimide (PI) substrates. On the same PI substrate, we are able to simultaneously fabricate MoS2 based logic, non-volatile memory cells with graphene floating gates, photo-detectors and MoS2 transistors with tunable source and drain contacts. We are also able to demonstrate that these flexible heterostructure devices have very high electronic performance, comparable to four point measurements taken on SiO2 substrates, with on/off ratios >107 and field effect mobilities as high as 16.4 cm2 V−1 s−1. Additionally, the heterojunctions show high optoelectronic sensitivity and were operated as photodetectors with responsivities over 30 A W−1. Through local gating of the individual graphene/MoS2 contacts, we are able to tune the contact resistance over the range of 322–1210 Ω mm for each contact, by modulating the graphene work function. This leads to devices with tunable and multifunctional performance that can be implemented in a conformable platform.

Some Pertinent Features of Mo‐Mineralized Granitoids in the Circum‐Pacific Region

AbstractPetrological characteristics of granitic rocks related to the world large molybdenum deposits are studied. The granitoids are evaluated by Fe2O3+TiO2‐FeO+MnO‐MgO diagrams, and found to all plot to the magnetite‐series field. They are all high silica and high‐K series, but not A‐type, except for the Climax‐type porphyries and some others in the Colorado mineral belt. By‐product molybdenum contained in porphyry copper deposits, lower grade but huge tonnage, occurs with calc‐alkaline I‐type magnetite‐series granodiorite and monzogranite.Felsic intrusive rocks of the Climax mine are A‐type and are exceptionally high in trace elements such as F and Rb, which are generally enriched with W and Sn‐related granitoids that originated in crustal source rocks. The by‐product molybdenites in porphyry copper deposits appear to originate in adakitic granodiorite or monzogranite, having deep origins with the subducted slab or thickened juvenile mafic lower crust. Therefore, there is no single magma type but the magnetite series, which concentrates a large volume of molybdenum in the ore deposits.

Annular Phased Array Dynamic Focusing Method for Large Target Ultrasonic Testing

A novel method called dynamic focusing immersed ultrasonic testing (DFIUT) is proposed which utilizes an annular phased array ultrasonic transducer (APAUT) and one of the distinguished advantages is dynamic focusing. The proposed DFIUT is aimed at solving the focus deviation problem in the detection of large targets. The design methodology of APAUT and implementation of DFIUT method are presented in this paper. Furthermore, an annular phased array immersed ultrasonic testing (APAIUT) system is also set up. An experiment over the large molybdenum target using the DFIUT is conducted to verify the effectiveness of the proposed method.