To obtain a composite ceramic powder composed of silicon nitride, β-Si3N4, zirconium dioxide ZrO2(monoclinic and tetragonal modifications), oxynitride silicon Si2N2O and iron (α-Fe) ne-synthesis is useful to nitrogen pressure of 2-20 MPa. Nitration mixture to when the nitrogen pressure up to 2 MPa in the combustion product contains iron silicides, which indicates a low degree of nitriding of ferrosilicon. Optimal nitrogen pressure of 4-6 MPa, because in this range there is a stable combustion with optimum speed at which there is the most complete conversion of the silicon nitride. When using pressures above 6 MPa product synthesis is a slightly sintered material in the form of granules, which can be used as a carrier for catalysts.
The method of self-propagating high temperature synthesis (SHS) has for several years used to obtain ceramic powder materials: silicon nitride, salanov, aluminum nitride, boron nitride and compositions on their basis with other refractory compounds (carbides, borides, oxides of metals and nonmetals), as well as for the direct synthesis of ceramic materials and products, such as Si2N2O-ZrO2-BN (the Engineer. The technologist. Work, 2002, No. 6 (18), pp.28-35).
synthesis of magnesium silicon nitride powder
When something like magnesium nitride forms, you have to supply all the energy needed to form the magnesium ions as well as breaking the nitrogen-nitrogen bonds and then forming N3- ions. All of these processes absorb energy.
and the white powder of boron nitride ..
SUBSTANCE: method consists in mixing aluminium and metal oxides powders in stoichiometric quantities and in carrying out aluminothermic reaction of interaction of said powders. As aluminium powder stabilised nano-dispersed aluminium powder with dimension of particles from 3 nm to 100 nm is used. As metal oxides powder nano-dispersed powders of metal oxides with dimensions of particles from 5 nm to 100 nm are used. Aluminothermic reaction is carried out at presence of initiator in the capacity of which stabilised nano-dispersed magnesium powder is used at the following ratio of components: (aluminium+metal oxide)/Mg=10/(1-10).
Evaluation of Thermal and Physical Properties of Magnesium Nitride ..
SUBSTANCE: for recovery there are chosen powdered silicon-bearing residues, including no less than 30% of silicon alloys, and alloys contains no less than 10% of silicon. Initial charge of powdered residues with grain size no more than 5.0 mm are dried with receiving of moisture content less than 0.2% and porosity from 30 till 80%. Dried charge is placed into the gaseous nitrogen atmosphere with oxygen concentration no more than 7.0 volume % under pressure from 0.2 till 20.0 MPa. It is implemented short-term local heating till the temperature of the beginning of exoergic chemical reaction of nitriding and oxidation. After lighting process proceed in mode of layerwise and volume combustion at the temperature 1500-2300°C. In the issue of burning major part of silicon transforms into nitride, oxynitride and/or carbide, and initial charge into sintered material, containing 30-80% of silicon, 7.0-39.0% nitrogen, 0.01-17.0 carbon and 0.01-7.0% oxygen. Sintered product allows compactness from 1.1 till 4.6 g/cm3.
Properties of Magnesium Nitride Powder: ..
1. A method of obtaining a composite ceramic powder based on silicon nitride and zirconium dioxide in the combustion mode in the atmosphere of nitrogen at high pressure, comprising mixing the components of the mixture consisting of nitridebased and ExecuteReader components, silicon nitride and ammonium halide, characterized in that as nitridebased and ExecuteReader components use pre-crushed to a particle size of >0.1 mm ferrosilicon and zircon concentrate in the amount of 40-50 wt.% and 20-50 wt.% accordingly, mixing them with silicon nitride and ammonium fluoride in the amount of 10-30 wt.% and 0.5 to 1.0 wt.% accordingly, locally initiate the combustion reaction at the nitrogen pressure of 2-20 MPa, toasteroven carried out in the mode volume of combustion at a nitrogen pressure of 0.1-10 MPa for 0.5-1.0 h, the cooled product is crushed to a particle size less 0,0 mm and subjected to magnetic separation, then handle 15-30%hydrochloric acid solution.