The present invention is directed to compositions comprising at least one layer or at least two layers, each layer comprising a substantially two-dimensional array of crystal cells, having first and second surfaces, each crystal cell having the empirical formula of M.sub.n+1X.sub.n, where M, X, and n are described in the specification, and devices incorporating these compositions.

The present invention discloses CrN thermoelectric material and its preparation method, which belongs to the field of thermoelectric materials. Here, we provide a study for thermoelectric properties, hardness, wear-resisting performance and thermal stability of CrN. These results show that CrN possesses excellent mechanical properties and thermal stability. The hardness of the bulk CrN sample is as high as 735.76 HV, which is far superior to most of thermoelectric materials. The thermogravimetric analysis test indicates that CrN remain stable at 873 K. Friction and wear test results demonstrate that the low friction coefficient (?0.42) and good wear resistance of CrN. The maximum ZT value of 0.104 is observed at 848 K. In this way, CrN may be a promising thermoelectric material in extreme environment application which requires both mechanical and thermoelectric properties. Such as collision avoidance systems and outerspace.

The present invention is directed to compositions comprising at least one layer or at least two layers, each layer comprising a substantially two-dimensional array of crystal cells, having first and second surfaces, each crystal cell having the empirical formula of M.sub.n+1X.sub.n, where M, X, and n are described in the specification, and devices incorporating these compositions.

A ceramic powder containing at least one of a nitride and a carbonitride of a metal element as a major component, the metal element being one or more elements selected from the group consisting of a group 4 element, a group 5 element and a group 6 element, the ceramic powder having particles having an average particle size of 5 m or less, and an oxygen content of 0.3% by mass or less.

The present invention is directed to crystalline solids having an empirical formula of M.sub.2A.sub.2X, wherein M is at least one Group IIIB, IVB, VB, or VIB metal, preferably Cr, Hf, Sc, Ti, Mo, Nb, Ta, V, Zr, or a combination thereof; wherein A is Al, Ga, Ge, In, Pb, or Sn, or a combination thereof; and each X is C.sub.xN.sub.y, where x+y=1. In some particular embodiments, the crystalline composition has a unit cell stoichiometry of Mo.sub.2Ga.sub.2C.

A composition having nanoparticles of a refractory-metal carbide or refractory-metal nitride and a carbonaceous matrix. The composition is not in the form of a powder. A composition comprising a metal component and an organic component. The metal component is nanoparticles or particles of a refractory metal or a refractory-metal compound capable of decomposing into refractory metal nanoparticles. The organic component is an organic compound having a char yield of at least 60% by weight or a thermoset made from the organic compound. A method of combining particles of a refractory metal or a refractory-metal compound capable of reacting or decomposing into refractory-metal nanoparticles with an organic compound having a char yield of at least 60% by weight to form a precursor mixture.

The present invention addresses the problem of providing a method for synthesizing hexagonal tungsten nitride by synthesizing hexagonal tungsten nitride as a main product, and of providing the hexagonal tungsten nitride. The problem is solved through use of a method for synthesizing hexagonal tungsten nitride comprising synthesizing hexagonal tungsten nitride by heating a starting material powder containing a tungsten halide and an alkali metal nitride and/or an alkaline earth metal nitride.

A composition having nanoparticles of a refractory-metal carbide or refractory-metal nitride and a carbonaceous matrix. The composition is not in the form of a powder. A composition comprising a metal component and an organic component. The metal component is nanoparticles or particles of a refractory metal or a refractory-metal compound capable of decomposing into refractory metal nanoparticles. The organic component is an organic compound having a char yield of at least 60% by weight or a thermoset made from the organic compound. A method of combining particles of a refractory metal or a refractory-metal compound capable of reacting or decomposing into refractory-metal nanoparticles with an organic compound having a char yield of at least 60% by weight to form a precursor mixture.

A catalytic composition from earth-abundant transition metal salts and biomass is disclosed. A calcined catalytic composition formed from soybean powder and ammonium molybdate is specifically exemplified herein. Methods for making the catalytic composition are disclosed as are electrodes for hydrogen evolution reactions comprising the catalytic composition.

Provided are methods of stabilizing MXene compositions using polyanionic salts so as to reduce the oxidation of the MXenes. Also provided are stabilized MXene compositions.