Advanced Materials and Surface Finishing Processes

Silicon carbide is abbreviated as SiC. It is one of the hardest known materials that is used for making cutting tools, sandpapers, and grinding wheels. SiC is an excellent thermal conductor that has oxidation resistance at very high temperatures. Due to these exceptional properties, it has found attention in the world of engineering. Lapping, grinding, abrasive grinding, and polishing are used normally for the surface finish of SiC.

Fused silica is the amorphous form of silicon dioxide that is used mainly in optical instruments like lenses, mirrors, metrology components, and parts of optoelectronic devices. As we know, there is a very high demand for the surface finish to aid the reflection, refraction, or transmittance of light. To fulfil this demand, abrasive powders have been used for surface finishing. Cerium oxide particles are used as abrasive powders. Moreover, Kemet has developed a polishing procedure that is very effective in obtaining a highly flat and pure fused silica surface.

As the name suggests, the compound is derived from alumina and silicon dioxide. It has a chemical formula of xAl₂O₃·ySiO₂·zH₂O. It has applications as a dyeing agent, filtering agent in pharmaceuticals, and raw material for the manufacturing of paper, cosmetics, and plastics. It is manufactured through precipitation on large scale followed by washing and drying. For materials manufactured with the addition of aluminium silicate, chemical mechanical processes are used for efficient surface finishing.

It is made by combining silica, alumina, and zirconia. This special blend is used for unidirectional solidification and single crystal growth. It has effective enamel and glazing properties. Its beads are used as grinding and polishing agents in the surface finishing techniques. Polishing methods are employed for the smoothness of silica zircon surfaces.

Alumina is a form of aluminium oxide (Al2O3) having a porous and granular structure. It is prepared at neutral pH and used mostly in the dry-activated form. It is mostly used in spark plugs, cutting tools, abrasion-resistant tools, tap washers, and monolithic refractories. Alumina is extracted from bauxite using two-step processes namely the digestion process that uses caustic soda for the separation of aluminium hydroxide and followed by calcination to remove water. To make parts from alumina powder, different manufacturing processes are used. It includes moulding, powder processing technology, and sintering techniques. After making the parts, different surface finishing operations are carried out. Kemet offers excellent surface finishing processes for alumina, most commonly used are polishing and grinding. A lapping process is also used before polishing for surface smoothness.

Aluminium nitride with a formula of AlN is famous for its very high thermal conductivity while being a good electrical insulator. AlN finds its applications in microwave devices, electronic packages, optoelectronics, heat spreaders, and electrical insulation for microdevices and lasers. It has a very good heat sinking property that makes its use excessive in the heat removal processes. Additive manufacturing processes are used for making these parts with a need for a surface finishing process that includes a highly precise lapping process and polishing technique. A highly precise lapping process can be obtained using Kemet lapping machines which can achieve up to 0.003 mm flatness results. With these methods, a very precise surface finish can be achieved.

Zirconia is the crystalline form of zirconium oxide. It exists in monoclinic crystal systems and is widely used in dental applications such as making dental crowns due to its excellent corrosion-resistant properties and high strength as compared to metals. The surface of zirconia parts can be treated by polishing, Kemet can be used to ensure the correct surface roughness value being obtained by the processes, inline with Surface finishing standards.

Solder and filler materials are used as brazing materials. These are fusible metal alloys that are used to join metal parts permanently. Brazing materials include alloys of tin, zirconium, lead, silver and indium. Acid core and rosin core are used for brazing metals. There is a need for the right surface finishing technique to save the brazed materials from oxidation. One of the commonly used processes is hot air surface leveling. Kemet also offers high-quality surface finishing processes for brazing materials such as dry electropolishing and centrifugal polishing. These processes remove micro-scratching and do not disturb the tolerances of given materials.

CVD SiC is used for the fabrication of fine and intricate parts. It also generates tiny holes with high precision. It also offers a very high thermal conductivity of 150 W/mK. CVD SiC is usually used for semiconductor processing applications, erosion resistance, and thermal shock resistance. Chemical etching is mostly used for surface finishing of CVD SiC. Liquid electropolishing can also be used for this purpose as it reduces the surface roughness to about 50%.