Alcatel

Philippe Oskeritsian

Jean-Florent Campion

Jean-Maxime Saugrain

Christelle Lavallade

Jean-Philippe Francois

Pierryle Jourdier

A process is described for making silica powder by a sol-gel process whereby an aqueous suspension is made of a silica-based raw material which includes particles containing chlorine, the pH of the suspension is adjusted to a value from 3 to 4.5 if necessary, the suspension is gelled, the gel obtained is dried and the dried gel is fractionated into silica granules. The silica-based raw material preferably includes particles containing chlorine having a specific surface area less than 80 m /g and less than 5 wt. % relative to the total quantity of particles containing chlorine of silica particles having a specific surface area from 150 m /g to 300 m /g. The use of such powder to manufacture an optical fiber preform is also described.

Process for making silica powder and use of such powder in the manufacture of an optical fiber preform

Silica granules made up of mutually agglomerated silica soot particles are treated by placing the granules in a crucible inside a furnace which contains an inert gas mixed with a chlorine-containing compound and in which the temperature lies in the range 1000&deg; C. to 1500&deg; C. According to the invention, a crucible is used that is made of porous graphite firstly to increase the surface area of the crucible through which the chlorine-containing compound diffuses. This gives rise to faster exchange between the granules and the gas for given partial pressure of the chlorine-containing compound, thereby improving purification. Secondly, the difference between the chemical natures of the silicas and the crucible make the two materials inert relative to each other so that the granules do not adhere to the walls of the crucible, thereby making it possible to recover the granules without having to apply any mechanical operation that might contaminate them.

Growing community of inventors

Rueil Malmaison, France

Philippe Oskeritsian