Method of making metal carbide and nitride powders

A process for forming a metal carbide power which comprises:

• reacting at least one metal oxide composition with a binder and a material capable of supplying said carbon to said reaction, or with a binder which is capable of supplying said carbon so as to produce granules having a controlled pore volume ranging from about 0.1 to 3 cm.sup.3 /g;
• subjecting said granules to a carbothermal reduction reaction at a temperature ranging between about 1300.degree. and 1600.degree. C. in a neutral atmosphere so as to form said metal carbide powder wherein said powder contains an excess of carbon;
• heating said powder so as to decarbonize said metal carbide until substantially all of said excess carbon is eliminated;
• and
• collecting said metal carbide powder in the form of articles or agglomerates, said metal carbide powder having a specific surface area of at least about 30 m.sup.2 /g.

A process for forming a metal nitride powder which comprises:

• mixing at least one metal oxide composition, selected from the group consisting of SiO.sub.2 Al.sub.2 O.sub.3, TiO.sub.2, ZrO.sub.2, HfO.sub.2 and B.sub.2 O.sub.3 and having a particle size between about 0.1-5 micrometers with a binder which has been coked at between about 350.degree.-500.degree. C., wherein said binder/metal oxide molar ratio is between about 2-60:1, said binder being a coal tar, a thermosetting resin or an organic, polymer at between ambient temperature and 200.degree. C. to produce a paste;
• extruding said paste;
• heating said extrudate to a temperature between about 50.degree.-250.degree. C. so as to dry said binder,
• forming granules from said extrudate having a pore volume ranging between about 0.1-3 cm.sup.3 /g;
• subjecting said granules to a carbothermal reduction reaction at a temperature between about 1300.degree.-1600.degree. C. in a nitrogen atmosphere or an atmosphere capable of releasing nitrogen, wherein the amount of nitrogen used ranges from about 2-10 times the stoichiometric requirement for the reaction so as to form agglomerates of a metal nitride powder wherein said powder contains an excess of carbon;
• grinding or screening said agglomerates so as to render the dimension of said powder more uniform in size and wherein the largest dimension of each of said granules ranges between about 1-30 mm;
• heating said uniformly dimensioned powder to a temperature between about 500.degree.-800.degree. C. until substantially all of said excess carbon is reacted with oxygen so as to form a carbon monoxide gas;
• controlling said gaseous carbon monoxide emission produced as a result of said decarbonization step;
• and
• collecting said metal nitride powder in the form of particles or agglomerates, said metal nitride powder having a specific source area of at least about 30 m.sup.2 /g.

A process for forming a metal carbide powder which comprises:

• mixing at least one metal oxide composition selected from the group consisting of Al.sub.2 O.sub.3, TiO.sub.2, ZrO.sub.3, HfO.sub.2 and B.sub.2 O.sub.3 and having a particle size between about 0.1-5 micrometers with a binder which has been coked at between about 350.degree.-500.degree. C., wherein said binder-metal oxide ratio is between about 2-60:1, said binder being a coal tar, a thermosetting resin or an organic polymer, at between ambient temperature and 200.degree. C. to produce a paste;
• extruding said paste;
• heating said extrudate to a temperature between about 50.degree.-250.degree. C. so as to dry said binder;
• forming granules from said extrudate having a pore volume ranging between about 0.1-3 cm.sup.3 /g.
• subjecting said granules to a carbothermal reduction reaction at a temperature between about 1300.degree.-1500.degree. C. in a neutral atmosphere so as to form agglomerates of a metal carbide powder wherein said powder contains an excess of carbon;
• grinding or screening said agglomerates so as to render the dimension of said powder more uniform in size and wherein the largest dimension of each of said granules ranges between 1-30 mm;
• heating said uniformly dimensioned powder to a temperature of between about 500.degree.-800.degree. C. until substantially all of said excess carbon is reacted with oxygen so as to from a carbon monoxide gas;
• controlling said gaseous carbon monoxide emissions produced as a result of said decarbonization step;
• and
• collecting said metal carbide powder in the form of particles or agglomerates, said metal carbide powder having a specific surface area of at least about 30 m.sup.2 /g.

A process for forming a silicon nitride powder which comprises:

• reacting a silicon oxide composition with a material capable of supplying carbon to said reaction to produce granules having a controlled pore volume ranging from about 0.1 to 3 cm.sup.3 /g;
• subjecting said granules to a carbothermal reduction reaction at a temperature ranging between about 1300.degree.-1600.degree. C. in an atmosphere which contains or is capable of releasing nitrogen to form a silicon nitride powder containing excess carbon;
• heating said powder until said excess carbon is substantially eliminated to produce a silicon nitride powder having a specific surface area of at least 30 m.sup.2 /g;
• and
• collecting said silicon nitride powder in the form of particles or agglomerates.

A process for forming an aluminum nitride powder which comprises:

• reacting an aluminum oxide composition with a material capable of supplying carbon to said reaction to produce granules having a controlled pore volume ranging form aobut 0.1 to 3 cm.sup.3 /g;
• subjecting said granules to a carbothermal reduction reaction at a temperature ranging between about 1300.degree.-1600.degree. C. in an atmosphere containing or capable of releasing nitrogen so as to form aluminum nitride powder containing excess carbon;
• heating said powder until said excess carbon is substantially eliminated to produce an aluminum nitride powder having a specific surface area of at least 30 m.sup.2 /g;
• and
• collecting said aluminum nitride powder in the form of particles or agglomerates.