Form Of MoS2 Research Articles

Thermodynamic analysis of decomposing Bi2S3 in acidic system and its application in treatment of molybdenite-bismuthinite mixed ore

Through thermodynamic calculations, the E-pH diagrams of the Bi-S-H2O and Bi-S-Cl-H2O systems at 298 K were plotted, the dominant regions of the components in the system and their changes with pH were clarified, and the mechanism and thermodynamic conditions for the decomposition of Bi2S3 in acidic systems were clarified. The key to the decomposition of Bi2S3 in acidic systems was based on the coordination of Cl− and Bi3+. The formation of BiCl4− can promote the decomposition of Bi2S3 in acidic systems, based on this characteristic, HCl was used to achieve efficient leaching of bismuth in molybdenite-bismuthinite mixed ore. Under the optimized conditions of hydrochloric acid concentration of 6 mol/L, liquid-to-solid ratio of 5:1, temperature of 95 °C, stirring speed of 400 rpm, and time of 300 min, the leaching efficiency of bismuth reached 97.64 %, and the bismuth content in the leaching residue was 0.93 %, while molybdenum remained in the form of MoS2 in the residue, The efficient separation of molybdenum and bismuth has been achieved, providing a new process to solve the traditional separation of molybdenite-bismuthinite mixed ores.

Extraction of Molybdenum Compounds from Solid Carbon-Containing Hydroconversion Residue of Heavy Oil Raw Materials

The results of a study of the extraction of molybdenum compounds introduced into hydroconversion heavy petroleum feedstock as part of a catalyst precursor are presented. A solid phase insoluble in an organic solvent, a Mo-containing concentrate, is isolated from the vacuum hydroconversion residue by filtration. According to X-ray powder diffraction, molybdenum in the concentrate is almost completely contained in the form of MoS2, which is transferred by hydrometallurgical method to the solution of the initial molybdenum precursor. It has been shown that the most effective solvent for isolating molybdenum concentrate from the hydroconversion residue is toluene. When a mixed aqueous solution of nitric and sulfuric acids acts on an isolated concentrate, depending on the ratio of components and solution flow rate (multiplicity) as well as temperature and processing time, a high degree (~99%) of molybdenum compound extraction into the solution is achieved.

Self-Limiting Layer Synthesis of Transition Metal Dichalcogenides.

This work reports the self-limiting synthesis of an atomically thin, two dimensional transition metal dichalcogenides (2D TMDCs) in the form of MoS2. The layer controllability and large area uniformity essential for electronic and optical device applications is achieved through atomic layer deposition in what is named self-limiting layer synthesis (SLS); a process in which the number of layers is determined by temperature rather than process cycles due to the chemically inactive nature of 2D MoS2. Through spectroscopic and microscopic investigation it is demonstrated that SLS is capable of producing MoS2 with a wafer-scale (~10 cm) layer-number uniformity of more than 90%, which when used as the active layer in a top-gated field-effect transistor, produces an on/off ratio as high as 108. This process is also shown to be applicable to WSe2, with a PN diode fabricated from a MoS2/WSe2 heterostructure exhibiting gate-tunable rectifying characteristics.

A generic tight-binding model for monolayer, bilayer and bulk MoS2

Molybdenum disulfide (MoS2) is a layered semiconductor which has become very important recently as an emerging electronic device material. Being an intrinsic semiconductor the two-dimensional MoS2 has major advantages as the channel material in field-effect transistors. In this work we determine the electronic structures of MoS2 with the highly accurate screened hybrid functional within the density functional theory (DFT) including the spin-orbit coupling. Using the DFT electronic structures as target, we have developed a single generic tight-binding (TB) model that accurately produces the electronic structures for three different forms of MoS2 - bulk, bilayer and monolayer. Our TB model is based on the Slater-Koster method with non-orthogonal sp3d5 orbitals, nearest-neighbor interactions and spin-orbit coupling. The TB model is useful for atomistic modeling of quantum transport in MoS2 based electronic devices.

Microstructure of sintered ND–Fe–Ga–B magnets with Mo and MoS2 addition

The effect of Mo and MoS2 additions on the magnetic and microstructure properties has been investigated in Nd–Fe–Ga–B sintered magnets. Coercivity can be increased by both the additions, but the MoS2 addition provides the larger increase per Mo atom for up to 0.6at.% Mo. Microstructure investigation reveals a new amorphous intergranular Ga rich phase. This phase forms a thin layer in the grain boundaries and leads to a wetting behavior of the grain boundary phase, therefore increasing the coercivity. Molybdenum addition in the form of MoS2 is found to modify the Nd2Fe14B phase, rather than form new minority phases, and the coercivity enhancement of the magnet is due to the increased anisotropy field of the hard magnetic phase.

XPS characterization of carbon nanotube supported CoMo hydrodesulfurization catalysts

AbstractIn this paper, the effect of catalytic support and sulfiding method on the chemical state of supported Co‐MO catalysts is studied by XPS. After sulfidation with in‐situ method, the majority of molybdenum in CNT supported CoMo catalyst is transferred to a species with a formal chemical state Mo(IV) in MoS2 phase, and the rest to Mo(V) which consists of Mo coordinated both to O and S, such as MoO2S22‐‐ and MoO3S2‐−. In case of CoMo/γ‐Al2O3 catalyst sulfided with in‐situ method, a fraction of molybdenum is transferred to formal state Moo in the form of MoS2, but there is still a mount of unreduced Mo(VI) phase which is difficult to be sulfided. In CoMo/CNT catalytic system sulfided with ex‐situ method, Mo(IV) in the form of MoS2 is detected along with a portion of unreduced Mo(VI) phase, suggesting that not all the Mo phases are reduced and sulfided by ex‐situ method. As for CoMo/γ‐Al2O3, a portion of molybdenum is sulfided to intermediate reduced state Mo(V) which consists of Mo coordinated both to O and S. such as MoO2S2–2 and MoO3S2–, in addition, there is still a fraction of unreduced Mo(VI) phase. XPS analyses results suggest that CNT support facilitates the reduction and sulfidation of active species to a large extent, and that alumina support strongly interacts with active species, hereby producing a fraction of phase which resists complete sulfiding. Catalytic measurements of catalysts in the HDS of dibenzothiophene (DBT) show that CoMo/CNT catalysts are of higher HDS activity and selectivity than CoMo/γ‐A2O3 catalyst, which is in good relation with the sulfiding behavior of the corresponding catalyst.

A C/MoS2mixed-layer phase (MoSC) occurring in metalliferous black shales from southern China, and new data on jordisite

A new phase composed mainly of Mo, S, and C and referred to herein as MoSC occurs widely in organic-rich, metalliferous Cambrian black shales in south China. MoSC, which has previously been referred to as jordisite, has been studied by scanning electron microscopy (SEM), electron microprobe analysis (EMPA), transmission electron microscopy (TEM), powder X-ray diffraction, (XRD), extended X-ray absorption fine structure (EXAFS), and catalytic activity. TEM data show MoSC to have a layered structure, with packets resembling molybdenite and graphite-like carbon that average five layers in thickness. Analytical data are consistent with an idealized formula of Mo3S6C10 but it commonly contains 1–3 wt% each of Fe, Ni, and As so that its composition may be better approximated by the formula (Mo,Fe,Ni)3(S,As)6C10. Selected area electron diffraction (SAED) patterns show a small number of broad, inhomogeneous rings corresponding to randomly oriented layers arranged in subspherical cells. A single broad, weak peak corresponds to a 10–11 A layer spacing in powder XRD diffraction patterns. Pseudomorphism after fossil bacteria implies an origin by replacement of sedimentary organic material. In its chemical properties and structure, MoSC resembles synthetic compounds used as catalysts for hydrodesulfurization (HDS) in the petrochemical industry. The large surface-to-volume ratio for MoSC may be an important factor in its relatively strong HDS catalytic activity. Cotype samples of jordisite from Germany, previously thought to be amorphous MoS2, were also studied by SEM and TEM. Jordisite occurs as sequences of a few curved layers that form sub-spherical units, with an appearance remarkably like that of MoSC. However, the layer spacing is ~6 A, like that of molybdenite. The ratio of Mo:S is ~1:2, and no carbon was detected, although it coexists with kerogen. Jordisite is thus confirmed to be a form of MoS2, but because powder diffraction-like SAED patterns were obtained, it is not amorphous.

The influence of the structure of molybdenum disulphide on its reactivity

The equilibrium in the system Mo-MoS2-H2S-H2 was studied between 569.4 and 1 276.8 K. The equilibrium gaseous mixture was analyzed by an iodometric method, the solid phase was studied by X-ray powder diffraction. The structure of MoS2 changed in the course of measurements from a “poorly crystalline” form at lower temperatures to a “well crystalline” one with a small number of stacking faults at higher temperatures. The poorly crystalline form is more reactive than the well crystalline one. For the formation of the well crystalline form of MoS2 a Gibbs-energy equation, ΔG0 (J mol-1) = -390 100 + 176.7T, was derived. It is in excellent agreement with the equation derived from the data obtained by fluorine calorimetry.