Niobium oxide particles which have a controlled crystal shape and exhibit excellent characteristics are provided. The niobium oxide particles include molybdenum. The niobium oxide particles preferably have a polyhedral, columnar or acicular shape. The MoO.sub.3 content (M.sub.1) measured by XRF analysis of the niobium oxide particles is preferably 0.1 to 40 mass % relative to the niobium oxide particles taken as 100 mass %. A method for producing the niobium oxide particles described above includes calcining a niobium compound in the presence of a molybdenum compound.

Provided is a molybdenum trioxide powder containing an aggregate of primary particles containing a crystal structure of molybdenum trioxide, the crystal structure containing crystals with an average crystallite size of 50 nm or less, a median diameter D.sub.50 of the primary particles being 2,000 nm or less determined by dynamic light scattering.

Provided is a molybdenum trioxide powder containing an aggregate of primary particles containing a crystal structure of molybdenum trioxide, the crystal structure containing crystals with an average crystallite size of 50 nm or less, a median diameter D.sub.50 of the primary particles being 2,000 nm or less determined by dynamic light scattering.

Provided is a method for preparing molybdenum oxide nanoparticles, including (a) preparing a precursor solution by dissolving a molybdenum salt in a first polar solvent, (b) generating an aerosol by applying ultrasonic waves to the precursor solution, and spraying the aerosol to a pre-heated reactor using a carrier gas, (c) obtaining molybdenum oxide micron-sized particles by pyrolyzing the aerosol, and (d) obtaining molybdenum oxide nanoparticles by dispersing the molybdenum oxide micron-sized particles in a second polar solvent and performing a solvothermal reduction reaction.

Provided is a method for preparing molybdenum oxide nanoparticles, including (a) preparing a precursor solution by dissolving a molybdenum salt in a first polar solvent, (b) generating an aerosol by applying ultrasonic waves to the precursor solution, and spraying the aerosol to a pre-heated reactor using a carrier gas, (c) obtaining molybdenum oxide micron-sized particles by pyrolyzing the aerosol, and (d) obtaining molybdenum oxide nanoparticles by dispersing the molybdenum oxide micron-sized particles in a second polar solvent and performing a solvothermal reduction reaction.

A compound represented by one of the formulae:

Ba.sub.aMo.sub.bO.sub.c(1),

MO.sub.dP.sub.eO.sub.f(2) or

Ba.sub.gMo.sub.hP.sub.iO.sub.j(3) wherein for formula (1) the ratio of a:b is greater than 1:1, wherein for formula (2) the ratio of d:e is from 1:100 to 0.45:1 or from 0.55:1 to 100:1, wherein for formula (3) the ratio of g:h is from 1:7 to 1:2 and the ratio of g:i is from 1:3 to 1:1, or the ratio of g:h is from 0.6:1 to 100:1 and the ratio of g:i is from 2.2:1 to 100:1, and wherein the molybdenum present within the compound is in the 4+ oxidation state.

A compound represented by one of the formulae:

Ba.sub.aMo.sub.bO.sub.c(1),

MO.sub.dP.sub.eO.sub.f(2) or

Ba.sub.gMo.sub.hP.sub.iO.sub.j(3) wherein for formula (1) the ratio of a:b is greater than 1:1, wherein for formula (2) the ratio of d:e is from 1:100 to 0.45:1 or from 0.55:1 to 100:1, wherein for formula (3) the ratio of g:h is from 1:7 to 1:2 and the ratio of g:i is from 1:3 to 1:1, or the ratio of g:h is from 0.6:1 to 100:1 and the ratio of g:i is from 2.2:1 to 100:1, and wherein the molybdenum present within the compound is in the 4+ oxidation state.

Disclosed is a method for clean metallurgy of molybdenum, including steps: 1) roasting molybdenite with calcium to obtain calcified molybdenum calcine, and leaching the calcified molybdenum calcine with an inorganic acid to obtain a molybdenum-containing inorganic acid leachate; 2) extracting molybdenum in the leachate with a cationic extractant to obtain an organic phase loaded with molybdyl cations and a raffinate; 3) using a hydrogen peroxide solution as a stripping agent to obtain a molybdenum stripping liquor; and 4) heating the molybdenum stripping liquor to dissociate peroxymolybdic acid therein so as to form a molybdic acid precipitate, and then calcining to obtain a molybdenum trioxide product. The method solves the problem of ammonia nitrogen wastewater production and can also be used for the enrichment and recovery of rhenium.

Disclosed is a method for clean metallurgy of molybdenum, including steps: 1) roasting molybdenite with calcium to obtain calcified molybdenum calcine, and leaching the calcified molybdenum calcine with an inorganic acid to obtain a molybdenum-containing inorganic acid leachate; 2) extracting molybdenum in the leachate with a cationic extractant to obtain an organic phase loaded with molybdyl cations and a raffinate; 3) using a hydrogen peroxide solution as a stripping agent to obtain a molybdenum stripping liquor; and 4) heating the molybdenum stripping liquor to dissociate peroxymolybdic acid therein so as to form a molybdic acid precipitate, and then calcining to obtain a molybdenum trioxide product. The method solves the problem of ammonia nitrogen wastewater production and can also be used for the enrichment and recovery of rhenium.

A group of reductive 2D materials (R2D) with extended reactive vacancies and a method for making the R2D with extended reactive vacancies are provided, especially the example of the reductive boron nitride (RBN). To create defects such as vacancies, boron nitride (BN) powders are milled at cryogenic temperatures. Vacancies are produced by milling, and the vacancies can be used to reduce various metal nanostructures on RBN. Due to the thermal stability of the RBN and the enhanced catalytic performance of metal nanostructures, RBN-metals can be used for different catalysts, including electrochemical catalysts and high temperature catalysts.