Chapter 27 Processes Used to Fabricate Ceramic Materials

Objectives Direct Bonding and Mechanical Attachment. Metallizing techniques to provide conductive pathways. Glass to glass and metal to glass bonds. Metal coatings. Refractory ceramic materials.

Direct Bonding Processes Metallizing is often used to provide a transmission path on ceramics for electrical current. Hermetic seals are painted on by hand or sprayed on to prevent movement of gases or liquids into or out of a product. Many medical products require hermetic seals. Glass to ceramic seals are used to bond unlike materials in products such as spark plugs and electronic components.

Fusion Sealing Many electronic products require pressure tight seals between metal and ceramic materials. The fusion sealing method uses special glass compositions to make direct glass to metal seals. The critical sealing temperature required must take into consideration the expansion and contraction requirements of both materials.

Laminating One of the most common glass products produced using lamination is the automobile windshield. A polyvinyl butyl plastic interlayer is placed between two pieces of curved glass and the sandwich is pressed together in an autoclave furnace to bond under heat and pressure. The vinyl layer holds the glass together and keeps the glass from shattering on impact.

Refractory Materials The most common material for making refractory products is clay. Refractory products are installed as linings for industrial furnaces or in similar high temperature environments. The metal casting industry is the largest user of refractory material.

Mechanical Attachment Process Mechanical attachment of one or more materials is often used when the product being manufactured may eventually need to be disassembled. An example is a unit that may need periodic servicing. It is important when working with ceramics not to apply too much pressure when joining parts together.

Summary Metallizing is often used to provide a transmission path on ceramics for electrical current. The fusion sealing method uses special glass compositions to make direct glass to metal seals. One of the most common glass products produced using lamination is the automobile windshield. Refractory products are installed as linings for industrial furnaces or in similar high temperature environments. Mechanical attachment of one or more materials is often used when the product being manufactured may eventually need to be disassembled.

Home Work 1. What keeps a glass windshield from shattering on impact? 2. Where is mechanical attachment often used?