Patent GB-940395-A (GB)
Title: Refractory materials
Inventor: HALL CLIFFORD
IPC: C04B35/65
Filed: 1961-01-27
Abstract: A refractory material is produced by forming an admixture of alumina or aluminous clay, with at least 10% of aluminium and a quantity of oxidizing agent for the aluminium which is less than that stoichiometrically necessary to oxidize all the aluminium, together with the minimum amount of bonding agent sufficient to impart shape-retaining properties to the admixture; the bonded mixture is then heated to initiate an exothermic reaction between the aluminium and the oxidizing agent, the character and quantity of the exothermically reacting ingredients being such as to cause the mixture to increase in temperature to at least 1400 DEG  C. The aluminium is in a state of subdivision such that it will pass a 60 mesh and at least 40% of it will pass a 200 mesh.  The aluminous clay preferably has an aluminium oxide content of 50% by weight at least and a coefficient of expansion of less than 4%. Suitable aluminous clays are molochite, chamotte and sillimanite.  The refractory component has a particle size wherein 45% will pass a 5 mesh but be retained on a 30 mesh, 10% will pass a 30 mesh and be retained on an 80 mesh and 45% will pass an 80 mesh.  The oxidizing agent is preferably a strongly oxidizing salt such as a nitrate or a chlorate. The composition may contain 2-5%, based on the weight of the whole admixture, of iron oxide or manganese oxide.  0.1-10% by weight of a fluoride may also be added. Bonding agents specified are aqueous gum arabic or sulphite lye. The composition exemplified comprises:-finely divided aluminium 25%, aluminium fluoride 4%, barium nitrate 10%, haematite 5%, gum arabic 3%, aluminous clay 53%.ALSO:A refractory material is produced by forming an admixture of alumina or aluminous clay, with at least 10% of aluminium and a quantity of oxidizing agent for the aluminium which is less than that stoichiometrically necessary to oxidize all the aluminium, together with the minimum amount of bonding agent sufficient to impart shape-retaining properties to the admixture; the bonded mixture is then heated to initiate an exothermic reaction between the aluminium and the oxidizing agent, the character and quantity of the exothermically reacting ingredients being such as to cause the mixture to increase in temperature to at least 1600 DEG  C. The aluminium is in a state of subdivision such that it will pass a 60-mesh and at least 40% of it will pass a 200 mesh.  The aluminous clay preferably has an aluminium oxide content of 50% by weight at least and a coefficient of expansion of less than 4%. Suitable aluminous clays are molochite, chamette and sillimanite. The refractory component has a particle size wherein 45% will pass a 5 mesh but be retained in a 30 mesh, 10% will pass a 30 mesh and be retained on an 80 mesh and 45% will pass an 80 mesh.  The oxidizing agent is preferably a strongly oxidizing salt such as a nitrate or a chlorate. The composition may contain 2-5%, based on the weight of the whole admixutre, of iron oxide or manganese oxide.  0.1-10% by weight of a fluoride may also be added. Bonding agents specified are aqueous gum arabic or sulphite lye. The composition exemplified comprises:-Finely divided aluminium 25%, aluminium fluoride 4%, barium nitrate 10%, haematite 5%, gum arabic 3% and aluminous clay 53%.