infusible

Infusible is an adjective used to describe a material that cannot be fused or melted by heating under specified conditions. In materials science, geology, and metallurgy, infusible materials resist forming a liquid phase at temperatures where many substances would melt, remaining solid or undergoing alternative changes such as decomposition or volatilization. The term is often applied to refractory ceramics and oxides, which maintain structure at very high temperatures and are valued for high-temperature applications such as crucibles, linings, and components exposed to reactive melts. By contrast, fusible materials form a liquid phase when heated and are used where melting or alloying is required.

The word derives from Latin infusibilis, meaning not pourable or not meltable, with downstream usage in French and English. The concept is context-dependent: a material described as infusible at one furnace temperature may still fuse, decompose, or volatilize at higher temperatures or in different atmospheric conditions. Consequently, infusibility is often tied to specific processing environments, such as oxidizing or reducing atmospheres, pressure, and the presence of fluxing agents.

In mineralogy, infusible components contribute to the refractory nature of rocks. In industry, infusible crucibles and linings are preferred for handling reactive melts and for maintaining chemical inertness under harsh conditions. However, no material is absolutely infusible under all possible conditions; the property is relative to temperature, pressure, and surrounding chemistry.

See also: fusible, refractory, crucible, melting point.