Concurrently, novel instruments for hydrothermal reaction sintering, hydrothermal hot pressing were developed and practiced by Japanese researchers for the production of oxide ceramics in between 70 and 80s [53]. In late 70s, pure metals, alloys and few ceramic compositions like NaCl, MgO, TiC, etc. were sintered at room temperature (RT) under high (e.g. 4 GPa) pressures [54,55].