Abstract: A method of making optical waveguides is disclosed in which, to fabricate a preform, glass forming pulverulent material is filled into a mold by means of one or more screw conveyors. The quantity of glass forming pulverulent material filled into the mold per unit of time is increased by passing a suitable gas through the apparatus. Thus, the quantity conveyed per unit of time can also be controlled by adjusting the gas pressure. By using a dry gas, the moisture content of the powder can be reduced.

Abstract: For fabricating porous bodies from a glass starting material, particularly in connection with the fabrication of an optical waveguide preform, it is proposed to fill powdery glass starting material under a pre-compaction into a compression mold, and to compress it thereafter. When the porous body to be formed is to have a varying composition in the radial direction, as is necessary with a view to step index optical fibers or optical waveguides having a graded index of the refractive-index profile, then differently composed powdery glass starting materials are filled one at a time, in adjacent coaxial areas, into the compression mold. This is effected with respect to each of the individual areas with the aid of a screw conveyor under a continuous, adjustable pressure and at an adjustable conveying speed.

Abstract: In order to facilitate a shape-keeping compression in a process of fabricating an elongated glass-body, particularly a preform for optical waveguides on the basis of SiO.sub.2 in which, from a powdery glass starting material a porous body is formed and sintered into a glass body, there is provided a process in which the filling of the powdery glass starting material into the compression mold is carried out by simultaneously effecting a precompaction and in which, following the fill-in operation, the pre-compacted powdery material is compressed to obtain the porous body. Steps and measures are proposed for stabilizing the flexible hose which is preferably used as a compression mold, in its shape during the fill-in process. For the filling-in of the material there is used a screw conveyor or an arrangement of several screw conveyors arranged coaxially or next to each other, in order to form a porous body having the desired radial material composition.

Abstract: The metal substrate of an electrophotographic member is provided with a selenium-tellurium alloy layer containing 5-30% tellurium, 10-5,000 ppm of a metallic element of the fifth main group, and 10-100 ppm of a halogen. A preferred embodiment contains 15% tellurium, 40 ppm arsenic, and 40 ppm chlorine. The addition of the metallic element of the fifth main group to the selenium-tellurium alloy results in a stabilization of charging potentials in multicycle operation.If the metal substrate is an aluminum drum, the electrophotographic member can be used as a copying drum in high-speed copiers.