H4N

H₄N is a nitrogen-containing ceramic compound with an exceptionally low density, placing it in the family of lightweight refractory and structural ceramics. This material is primarily of research and developmental interest, with potential applications in aerospace thermal management, high-temperature insulation, and advanced composite reinforcement where ultra-low weight combined with ceramic stiffness is critical. Its unusual composition and density profile suggest exploration for applications requiring materials that combine low mass penalty with thermal or chemical stability, though industrial adoption remains limited compared to established ceramics like alumina or silicon carbide.