A method for making alumina fibres by co-extrusion of an alumina and starch paste

A method of producing alumina fibres has been developed. The process used a water-based alumina and rice starch paste. An initial feed-rod was made from a central cylindrical rod of alumina paste surrounded by a square shaped section of starch paste. This feed rod was subsequently extruded so that it is reduced in size by a determined ratio. The extrudate was cut into short lengths and re-assembled to the exact dimensions of the initial feed rod so that it contained many smaller alumina rods. This latter specimen was re-extruded and the steps repeated as many times as required to obtain a large amount of small diameter fibres. By selecting the die diameter and the number of extrusions the diameter of the fibres was easily controlled. Since all the fibres were in one easily handleable bunch, the bottleneck associated with sintering could be avoided. Hence an economic method of fibre production can be envisaged.