Molybdenum disulfide is an inorganic compound composed of molybdenum and sulfur. Its chemical formula is MoS2.
Intercalation is the reversible inclusion or insertion of a molecule into layered materials with layered structures. Examples are found in graphite and transition metal dichalcogenides.
Molybdenum trioxide describes a family of inorganic compounds with the formula MoO3(H2O)n where n = 0, 1, 2. The anhydrous compound is produced on the largest scale of any molybdenum compound since it is the main intermediate produced when molybdenum ores are purified. The anhydrous oxide is a precursor to molybdenum metal, an important alloying agent. It is also an important industrial catalyst. It is a yellow solid, although impure samples can appear blue or green.
A chalcogenide is a chemical compound consisting of at least one chalcogen anion and at least one more electropositive element. Although all group 16 elements of the periodic table are defined as chalcogens, the term chalcogenide is more commonly reserved for sulfides, selenides, tellurides, and polonides, rather than oxides. Many metal ores exist as chalcogenides. Photoconductive chalcogenide glasses are used in xerography. Some pigments and catalysts are also based on chalcogenides. The metal dichalcogenide MoS2 is a common solid lubricant.
In chemistry, stacking refers to superposition of molecules or atomic sheets owing to attractive interactions between these molecules or sheets.
Tungsten disulfide is an inorganic chemical compound composed of tungsten and sulfur with the chemical formula WS2. This compound is part of the group of materials called the transition metal dichalcogenides. It occurs naturally as the rare mineral tungstenite. This material is a component of certain catalysts used for hydrodesulfurization and hydrodenitrification.
Tantalum(IV) sulfide is an inorganic compound with the formula TaS2. It is a layered compound with three-coordinate sulfide centres and trigonal prismatic or octahedral metal centres. It is structurally similar to molybdenum disulfide MoS2, and numerous other transition metal dichalcogenides. Tantalum disulfide has three polymorphs 1T-TaS2, 2H-TaS2, and 3R-TaS2, representing trigonal, hexagonal, and rhombohedral respectively.
A tube furnace is an electric heating device used to conduct syntheses and purifications of inorganic compounds and occasionally in organic synthesis. One possible design consists of a cylindrical cavity surrounded by heating coils that are embedded in a thermally insulating matrix. Temperature can be controlled via feedback from a thermocouple. More elaborate tube furnaces have two (or more) heating zones useful for transport experiments. Some digital temperature controllers provide an RS-232 interface, and permit the operator to program segments for uses like ramping, soaking, sintering, and more. Advanced materials in the heating elements, such as molybdenum disilicide (MoSi2) offered in certain models can now produce working temperatures up to 1800 °C. This facilitates more sophisticated applications. Common material for the reaction tubes include alumina, Pyrex, and fused quartz, or in the case of corrosive materials molybdenum or tungsten tubes can be used.
Titanium disulfide is an inorganic compound with the formula TiS2. A golden yellow solid with high electrical conductivity, it belongs to a group of compounds called transition metal dichalcogenides, which consist of the stoichiometry ME2. TiS2 has been employed as a cathode material in rechargeable batteries.
Titanium diselenide (TiSe2) also known as titanium(IV) selenide, is an inorganic compound of titanium and selenium. In this material selenium is viewed as selenide (Se2−) which requires that titanium exists as Ti4+. Titanium diselenide is a member of metal dichalcogenides, compounds that consist of a metal and an element of the chalcogen column within the periodic table. Many exhibit properties of potential value in battery technology, such as intercalation and electrical conductivity, although most applications focus on the less toxic and lighter disulfides, e.g. TiS2.
Molybdenum diselenide is an inorganic compound of molybdenum and selenium. Its structure is similar to that of MoS
2. Compounds of this category are known as transition metal dichalcogenides, abbreviated TMDCs. These compounds, as the name suggests, are made up of a transition metals and elements of group 16 on the periodic table of the elements. Compared to MoS
2, MoSe
2 exhibits higher electrical conductivity.
Tungsten diselenide is an inorganic compound with the formula WSe2. The compound adopts a hexagonal crystalline structure similar to molybdenum disulfide. The tungsten atoms are covalently bonded to six selenium ligands in a trigonal prismatic coordination sphere while each selenium is bonded to three tungsten atoms in a pyramidal geometry. The tungsten–selenium bond has a length of 0.2526 nm, and the distance between selenium atoms is 0.334 nm. It is a well studied example of a layered material. The layers stack together via van der Waals interactions. WSe2 is a very stable semiconductor in the group-VI transition metal dichalcogenides.
Transition-metal dichalcogenide (TMD or TMDC) monolayers are atomically thin semiconductors of the type MX2, with M a transition-metal atom (Mo, W, etc.) and X a chalcogen atom (S, Se, or Te). One layer of M atoms is sandwiched between two layers of X atoms. They are part of the large family of so-called 2D materials, named so to emphasize their extraordinary thinness. For example, a MoS2 monolayer is only 6.5 Å thick. The key feature of these materials is the interaction of large atoms in the 2D structure as compared with first-row transition-metal dichalcogenides, e.g., WTe2 exhibits anomalous giant magnetoresistance and superconductivity.
Niobium diselenide or niobium(IV) selenide is a layered transition metal dichalcogenide with formula NbSe2. Niobium diselenide is a lubricant, and a superconductor at temperatures below 7.2 K that exhibit a charge density wave (CDW). NbSe2 crystallizes in several related forms, and can be mechanically exfoliated into monatomic layers, similar to other transition metal dichalcogenide monolayers. Monolayer NbSe2 exhibits very different properties from the bulk material, such as of Ising superconductivity, quantum metallic state, and strong enhancement of the CDW.
Hafnium disulfide is an inorganic compound of hafnium and sulfur. It is a layered dichalcogenide with the chemical formula is HfS2. A few atomic layers of this material can be exfoliated using the standard Scotch Tape technique (see graphene) and used for the fabrication of a field-effect transistor. High-yield synthesis of HfS2 has also been demonstrated using liquid phase exfoliation, resulting in the production of stable few-layer HfS2 flakes. Hafnium disulfide powder can be produced by reacting hydrogen sulfide and hafnium oxides at 500–1300 °C.
Rhenium disulfide is an inorganic compound of rhenium and sulfur with the formula ReS2. It has a layered structure where atoms are strongly bonded within each layer. The layers are held together by weak Van der Waals bonds, and can be easily peeled off from the bulk material.
Tantalum diselenide is a compound made with tantalum and selenium atoms, with chemical formula TaSe2, which belongs to the family of transition metal dichalcogenides. In contrast to molybdenum disulfide (MoS2) or rhenium disulfide (ReS2), tantalum diselenide does not occur spontaneously in nature, but it can be synthesized. Depending on the growth parameters, different types of crystal structures can be stabilized.
The +4 oxidation state dominates titanium chemistry, but compounds in the +3 oxidation state are also numerous. Commonly, titanium adopts an octahedral coordination geometry in its complexes, but tetrahedral TiCl4 is a notable exception. Because of its high oxidation state, titanium(IV) compounds exhibit a high degree of covalent bonding.
Hafnium compounds are compounds containing the element hafnium (Hf). Due to the lanthanide contraction, the ionic radius of hafnium(IV) (0.78 ångström) is almost the same as that of zirconium(IV) (0.79 angstroms). Consequently, compounds of hafnium(IV) and zirconium(IV) have very similar chemical and physical properties. Hafnium and zirconium tend to occur together in nature and the similarity of their ionic radii makes their chemical separation rather difficult. Hafnium tends to form inorganic compounds in the oxidation state of +4. Halogens react with it to form hafnium tetrahalides. At higher temperatures, hafnium reacts with oxygen, nitrogen, carbon, boron, sulfur, and silicon. Some compounds of hafnium in lower oxidation states are known.
Rhenium compounds are compounds formed by the transition metal rhenium (Re). Rhenium can form in many oxidation states, and compounds are known for every oxidation state from -3 to +7 except -2, although the oxidation states +7, +4, and +3 are the most common. Rhenium is most available commercially as salts of perrhenate, including sodium and ammonium perrhenates. These are white, water-soluble compounds. The tetrathioperrhenate anion [ReS4]− is possible.
