Materials prepared as granulates, powders, fibers or other particles with small geometrical extensions play manifold roles in science, engineering and technology. Examples are basic studies of molecular adsorption, the employment of colloidal matter in catalysis or powder compaction in hot pressing and sintering processes. Also the possibility to include granulates or fibers into matrices as fillers or reinforcements is an important issue in the manufacturing of composite materials. Often the small particles are fragile due to their size, their composition or their geometry which makes their manipulation and modification an involved task.
The surface of the particles is of significant importance. It may have to be optimized in respect to surface energy and wettability to allow for good mixing and blending properties with solvents or carrier materials. Catalysts make use of the high surface to volume ratio of granulates and colloidal matter. Therefore surface modification often is decisive for activating several diverse classes of physio-chemical processes.
Physical Vapor Deposition (PVD) methods allow for the deposition of an extremely wide range of materials as single layers or complex multilayer systems. Unfortunately the line of sight characteristic of PVD processes makes it hard to coat particles if uniform exposure to the vapor beam is not guaranteed.
It is the aim of this project to design and optimize a container for fragile granular materials which shall be coated by means of PVD techniques. Metallic, oxidic and nitridic coatings in the thickness range from 1 ¿ 100 nm shall be deposited onto large quantities of hollow glass microspheres with diameters of 5 ¿ 70 µm and a wall thickness of 1 µm. The core feature is that the container design guarantees optimal exposure of the particles to the vapor beam while ensuring that the fragile objects are not destroyed by the movement necessary for intermixing. The goal of the project is to coat 1 litre of granulate within one deposition run.
The coated glass microspheres may have applications in gas storage, catalytic processes and anti- counterfeiting techniques. Common to all these topics is that there have to be sufficient amounts of coated microspheres to produce e. g. gas storage containers of sufficient size or to implement infrared reflective microspheres into mass products for anti counterfeiting purposes. Within the project this shall be established by the proposed high throughput PVD process.
