Abstract Fibres of alumina are prepared by introducing a gaseous mixture of a volatile aluminium compound vapour selected from aluminium halides and aluminium alcoholates having up to 3 carbon atoms, carbon dioxide and hydrogen into a reaction chamber heated to at least 1100 DEG C. at the inlet zone for the gaseous mixture, thereafter the gaseous mixture reacts during passage through the reaction chamber to form alumina at an absolute pressure of not more than 100 mm. of mercury and while simultaneously maintaining a temperature gradient in the reaction chamber up to approximately 1500 DEG C. along the direction of the gas flow at the exit of the reaction chamber, and finally depositing alumina fibres at the exit end of the chamber. In Example 1, hydrogen, carbon dioxide and vapours of aluminium chloride were preheated to 200 DEG C. and passed into a heated alumina tube 1180 DEG C. at the inlet and 1500 DEG C. at the exit. A vacuum pump was employed to maintain a pressure of 25-50 mm. of mercury, alumina fibres of average length 1 mm. were obtained after 10-15 minutes.
A PROCESS FOR ALUMINA FIBER PREPARATION COMPRISING (1) THE INTRODUCTION OF A GASEOUS MIXTURE OF A VOLATILE ALUMINUM COMPOUND, CARBON DIOXIDE AND HYDROGEN INTO A REACTION CHAMBER HEATED TO AT LEAST 1100*C. AT THE INLET ZONE FOR THE INTRODUCTION OF THE GASEOUS MIXTURE, (2) THEREAFTER REACTION THE GASEOUS MIXTURE DURING PASSING THROUGH THE REACTION CHAMBER TO FORM ALUMINA AT A REDUCED PRESSURE OF NOT MORE THAN 100 MM. OF MERCURY VACUUM AND WHILE SIMULTANEOUSLY MAINTAINING A TEMPERATURE GRADIENT IN THE REACTION CHAMBER ALONG THE DIRECTION OF THE GAS FLOW UP TO A TEMPERATURE OF APPROXIMATELY 1500* C. AT THE EXIT END OF THE REACTION CHAMBER, AND (3) FINALLY DEPOSITING THE ALUMINA REACTION PRODUCT OF (2) AT THE EXIT END OF THE REACTION CHAMBER IN THE FORM IF SINGLE CRYSTAL FIBERS OF HEXAGONAL STRUCTURE.
Claim 2
Dependent Claim
133 words
A PROCESS FOR ALUMINA FIBER PREPARATION COMPRISING (1) THE INTRODUCTION OF A GASEOUS MIXTURE OF A VOLATILE ALUMINUM COMPOUND, CARBON DIOXIDE AND HYDROGEN INTO A REACTION CHAMBER HEATED TO AT LEAST 1100*C. AT THE INLET ZONE FOR THE INTRODUCTION OF THE GASEOUS MIXTURE, (2) THEREAFTER REACTION THE GASEOUS MIXTURE DURING PASSING THROUGH THE REACTION CHAMBER TO FORM ALUMINA AT A REDUCED PRESSURE OF NOT MORE THAN 100 MM. OF MERCURY VACUUM AND WHILE SIMULTANEOUSLY MAINTAINING A TEMPERATURE GRADIENT IN THE REACTION CHAMBER ALONG THE DIRECTION OF THE GAS FLOW UP TO A TEMPERATURE OF APPROXIMATELY 1500* C. AT THE EXIT END OF THE REACTION CHAMBER, AND (3) FINALLY DEPOSITING THE ALUMINA REACTION PRODUCT OF (2) AT THE EXIT END OF THE REACTION CHAMBER IN THE FORM IF SINGLE CRYSTAL FIBERS OF HEXAGONAL STRUCTURE.