Ceramic product and process
AssigneeW. R. Grace & Co.-Conn.
InventorChristian B. Lundsager
Life of this patent
Estimating the term…
Abstract
Porous ceramic greenware comprising finely divided ceramic filler, finely divided metal, and polyolefin controls shrinkage in fired shape. In a preferred embodiment the metal and ceramic filler are bound together with the clean burning polyolefin and a plasticizer. After molding the mixture into the final shape, the plasticizer is removed to introduce porosity into the shaped article. Next the article is heated to decompose the polyolefin which can exit as a gas through the pore openings. Finally, the article is fired to a high temperature to oxidize the metal to metal oxide which becomes sintered with the ceramic filler particles to form a sintered porous article where the oxidized metal bonds the filler particles together in the desired shape.
Claims38
Homogeneous precursor composition for forming a sintered porous ceramic article comprising
- (a) 5 to 90 wt. % of a finel divided solid metal capable of forming an oxide by heating in air and selected from the group consisting of Al, Zn, Fe, Cu, Si, Ti, Mg, Ba, Ta, U, Cr, Co, V, Mn, Ni, Sn, Zr, Th, Ge, T1, Pb, Mo, W, the rare earth metals and mixtures thereof,
- (b) 5 to 90 wt. % of a finely divided ceramic filler which is an oxide of a metal selected from the group listed in part (a), and
- (c) remainder of a particle binding effective amount of a nonaqueous polymer binder system which is capable of being removed when the composition is heated in the pressure of air or oxygen, said binder being present in at least 4% by weight of the composition and comprising a mixture of
- (1) a polymer which is capable of being oxidized away when the composition is heated and
- (2) a plasticizer for the polymer.
Homogeneous porous greenware composition consisting essentially of, in parts by weight:
- (a) 5 to 90 of a finely divided solid metal capable of forming an oxide by heating in air and selected from the group consisting of Al, Zn, Fe, Cu, Si, Ti, Mg, Ba, Ta, U, Cr, Co, V, Mn, Ni, Sn, Zr, Th, Ge, T1, Pb, Mo, W, the rare earth metals and mixtures thereof;
- (b) 5 to 90 of a finely divided ceramic filler which is an oxide of a metal selected from the group listed in part (a);
- and
- (c) 1 to 15 of a binder comprising a polymer which is capable of being oxidized away when the composition is heated, said binder previously having contained a plasticizer which has been essentially removed to create the porous greenware composition.
Sintered porous ceramic article consisting essentially of particles of ceramic filler having oxidized metal in the interstices thereof and bonding the filler particles, said article having been made from a mixture of metal particles selected from the group consisting of Al, Zn, Fe, Cu, Si, Ti, Mg, B, Ta, U, Cr, Co, v, Mn, Ni, Sn, Zr, Th, Ge, T1, Pb, Mo, W, the rare earth metals and mixtures thereof and ceramic filler particles which are oxides of metals selected from the group listed above and characterized by the substantial conversion of the metal particles over a period of time to form said oxidized metal with substantially no unoxidized metal remaining.
Process comprising firing greenware which is a porous homogeneous mixture consisting essentially of, in parts by weight:
- (a) 5 to 90 of a finely divided solid metal capable of forming an oxide by heating in air and selected from the group consisting of Al, Zn, Fe, Cu, Si, Ti, Mg, Ba, Ta, U, Cr, Co, V, Mn, Ni, Sn, Zr, Th, Ge, T1, Pb, Mo, W, the rare earth metals and mixtures thereof;
- (b) 5 to 90 of a finely divided ceramic filler which is an oxide of a metal selected from the group listed in part (a);
- and
- (c) 1 to 15 of a binder comprising a polymer which is capable of being oxidized away when the composition is heated, said binder previously having contained a plasticizer which has been essentially removed to create the porous greenware composition.
Process comprising:
- (1) forming a homogenous composition consisting essentially of:
- (a) 5 to 90 wt. % of a finely divided solid metal capable of forming an oxide by heating in air and selected from the group consisting of Al, Zn, Fe, Cu, Si, Ti, Mg, Ba, Ta, U, Cr, Co, V, Mn, Ni, Sn, Zr, Th, Ge, Tl, Pb, Mo, W, the rare earth metals and mixtures thereof,
- (b) 5 to 90 wt. % of a finely divided ceramic filler which is an oxide of a metal selected from the group listed in part (a),
- (c) 3 to 60 wt. % of a plasticizer, and
- (d) 1 to 15 wt. % of a polyolefin;
- (2) forming the composition of (1) into a desired shape;
- (3) removing most of the plasticizer from the shape thereby to form porous greenware;
- and
- (4) firing the greenware, thereby to remove polyolefin and any residual plasticizer, to sinter the ceramic filler, and to oxidize substantially all the metal.
Dependencies are inferred from the claim text.