摘要:
The invention relates to a method of doping silica with fluorine. The method described comprises mixing a powder of silica granules with a solid fluorine compound, thermally decomposing the solid fluorine compound under an inert atmosphere, and densifying the granules to obtain dense grains of doped silica. It is preferable to use ammonium bifluoride. The invention is applicable to preparing high index silica glass, in particular for fabricating optical fiber preforms.
摘要:
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 m2/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 m2/g to 300 m2/g. The use of such powder to manufacture an optical fiber preform is also described.
摘要:
A method of manufacturing an optical fiber preform (3) comprising: forming at least one silica-based outer deposition layer (23) by depositing silica on a primary preform (24) constituted by a bar mainly comprising silica and including a silica-based outer peripheral portion (22), the method being characterized in that the viscosity of the outer deposition layer (23) is adjusted to be substantially identical to the viscosity of the outer peripheral portion (22) of the primary preform (24) by adding to the silica, over a substantial portion of the outer deposition layer (23), at least one compound selected from the group formed by the following compounds: CaF2, MgF2, AlF3, B2O3, and Al2O3.
摘要翻译:一种制造光纤预制件(3)的方法,包括:通过在主要包含二氧化硅的棒构成的初级预型件(24)上沉积二氧化硅,形成至少一个二氧化硅基外层沉积层(23),并且包括二氧化硅基外层 周边部分(22),其特征在于,通过将外部沉积层(23)的粘度调节至与初级预型件(24)的外周部分(22)的粘度基本相同, 二氧化硅,在外部沉积层(23)的大部分上,选自由以下化合物形成的基团中的至少一种化合物:CaF 2,MgF 2,AlF 3,B 2 O 3和Al 2 O 3。
摘要:
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° C. to 1500° 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.
摘要:
In the method, a suspension of silica particles in water is provided, the suspension is gelled, the resulting gel is dried under microwaves, the dried gel is fractioned into silica granules having a diameter lying in the range 10 .mu.m to 1000 .mu.m, having an apparent density of about 0.5 g/cm.sup.3 to 0.6 g/cm.sup.3, and a porosity of less than 20%, and the granules are screened in the range 100 .mu.m to 500 .mu.m. The suspension in water of silica particles is made by mixing silica soots having a size of less than 0.1 .mu.m and silica grains having a size greater than 1 .mu.m. Its maximum concentration in total weight is greater than that of a suspension of synthetic soots on their own, thereby making it possible to increase the production capacity of the method. Advantageously, the out-of-range granules rejected by the screening are recycled as silica grains for the aqueous suspension, thereby making it possible to increase the accumulated production efficiency of the method.
摘要翻译:在该方法中,提供二氧化硅颗粒在水中的悬浮液,悬浮液凝胶化,得到的凝胶在微波下干燥,将干燥的凝胶分级成直径在10〜1000μm的二氧化硅颗粒, 具有约0.5g / cm 3至0.6g / cm 3的表观密度和小于20%的孔隙率,并且将颗粒筛选在100μm至500μm的范围内。 二氧化硅颗粒的水悬浮液通过混合尺寸小于0.1μm的二氧化硅烟炱和尺寸大于1μm的二氧化硅颗粒来制备。 其总重量的最大浓度本身大于合成烟灰的悬浮液的最大浓度,从而可以提高该方法的生产能力。 有利地,通过筛选而排除的超出范围的颗粒作为水性悬浮液的二氧化硅颗粒再循环,从而可以提高该方法的累积生产效率。