All alumina bodies possess very good mechanical properties such as hardness and compressive strength. They also hold up well under harsh conditions such as acid corrosion, high wear areas, and sliding abrasion. They also possess very good electrical insulation properties and have very specific thermal conductive and thermal expansion rates.
- 92% Al2O3 Has very good electrical and mechanical properties and is metallized easily. The black body is used primarily for lids and when metallized and plated with gold has a very distinct appearance.
- 94% Al2O3 Possess very good electric and mechanical properties and is very easily metallized with the MoMn process.
- 96% Al2O3 This is our standard body and it has been formulized to meet with good success with just about anyone’s MoMn process. This body still possesses the same good mechanical and electric properties as the previous two alumina bodies.
- 99% Al2O3 This body is used extensively in the medical industry. Its finer grain allows it to be polished to achieve fine micron finishes making it the material of choice for pump manufacturers and it is used for wire/thread guides as well as for mechanical seals. Though it can be metallized it normally does not lend itself to that process due to its lack of glassy phase.
Glaze is generally considered to be a thin, glassy coating fired onto the surface of a ceramic form normally as a secondary process. Originally glaze was used to help prevent porosity on the outer surface of the fired ceramic body which would in turn prevent the surface from becoming dirty or collecting any metallic substances. With some materials, glaze is still used for the same reasons, but with most of the fully fired aluminas this is not the case. We believe that some of our customers are still using glaze because it has been specified on some type of government drawing or strictly for appearance sake.
Typically we have been supplying all high temperature glazes. These are glazes that will withstand the temperatures necessary for the metallizer to complete their process without deteriorating the glaze. They are normally good to temperatures around the range of 2600°F. A low temperature glaze can be applied to all of the alumina bodies and will normally sustain temperatures in the 1500°F to 1600°F range. As a general rule of thumb, we use the higher temperature glaze to be sure to cover the customer’s maximum temperature range.
There are three basic colors that we can produce that will still maintain their color integrity through the high temperature firing; they are purple, blue, and black. These three colors can be produced in ranges actually giving you a spectrum from a light pink to a dark purple and from a light blue to black. The reasons for using colored ceramics vary from needing to be able to recognize a white material such as yarn or thread passing over a purple alumina, or to have a contrast in color for visual purposes, or just for cosmetic reasons, e.g. the black alumina looks very rich when plated with gold.