The severe requirements of thermal reactors preclude the use of conventional ceramic materials. Special ceramics, such as recrystallized silicon carbide and reaction bonded silicon nitride, can be applied due to their superior thermal shock resistance and high temperature properties. Response time of reactors is critical and dictates thin-walled members with low heat capacities. Slip casting provides the means to achieve complex shapes while maintaining high strength; coatings with low emissivities and conductivities provide an additional barrier to heat loss. This combination provides a system which accomplishes the desired end result. Properties and shape capabilities will be discussed.Flame sprayed coatings are also discussed as thermal barriers on conventional metal alloy reactors. These coatings have the potential to extend the life of metals and reduce thermal transfer and subsequent heat loss.