Technical ceramics in 1920s: Alumina spark plugs

Scores compare Technical ceramics with the rest of the atlas on strength, heat, fire behaviour, insulation, workability and circularity. They are editorial, not certificates. Seven chapters follow. Fire and insulation claims name test families (Euroclass, ASTM E84, ISO 5660, KS F) rather than inventing a single safety number.

Technical ceramics (Al2O3, ZrO2, SiC, Si3N4…) is a family of grades whose density 3.2–6 g/cm³ class, heat band often >2000 °C, and fire letter A1. Technical ceramics is sold as grades, not as a single substance. Chemistry Al2O3, ZrO2, SiC, Si3N4…, density 3.2–6 g/cm³ class, heat band often >2000 °C.

Conductivity note: Al2O3 ~20–30; AlN higher; ZrO2 low. Insulation score 46/100 is relative to 32 entries — metals lose, VIPs and aerogels win. Fire letter in editorial use: A1. Do not equate A1 with “safe in a blaze” or E with “illegal”. Assemblies decide. Origin: 20th c. spark plugs / WWII carbides, Germany / US / Japan. The process chapter follows feedstock → conversion → forming → finish → install.