Tammann and Hüttig temperatures
The Tammann temperature (also spelled Tamman temperature) and the Hüttig temperature of a given material are approximations to the absolute temperatures at which atoms in a bulk crystal lattice (Tammann) or on the surface (Hüttig) of the solid material become sufficiently mobile to diffuse readily, and are consequently more chemically reactive and susceptible to recrystallization, agglomeration or sintering. These temperatures are equal to one-half (Tammann) or one-third (Hüttig) of the absolute temperature of the compound's melting point. The absolute temperatures are usually measured in Kelvin. Tammann and Hüttig temperatures are an important considerations for catalytic activity, segregation and sintering. The Tammann temperature is important for reactive compounds like explosives and fuel oxiders, such as potassium chlorate (, TTammann = 42 °C), potassium nitrate (, TTammann = 31 °C), and sodium nitrate (NaNO3, TTammann = 17 °C), which may unexpectedly react at much lower temperatures than their melting or decomposition temperatures. The bulk compounds should be contrasted with nanoparticles which exhibit melting-point depression, meaning that they have significantly lower melting points than the bulk material, and correspondingly lower Tammann and Hüttig temperatures. For instance, 2 nm gold nanoparticles melt at only about 327 °C, in contrast to 1065 °C for a