ABSTRACT
This chapter discusses the effect of particle or grain size on the thermal, mechanical, electrical, magnetic, optical, and catalytic properties of nanomaterials. The electrical conductivity of the materials is the inverse of their electrical resistivity. The oxide-ion conductors are important functional materials used in fuel cells, oxygen pumps, oxygen sensors, water electrolysis, and oxygen-separating ceramic membrane. Melting point is the temperature when atoms, ions, or molecules of a crystalline material change their periodic ordered state to the disordered state. The elastic modulus of a material is proportional to the bond strength between atoms or molecules. The specific heat of a material is closely related to its vibrational and configurational entropy, which is significantly affected by the nearest-neighbor configurations. The high value of coefficient of thermal expansion for nanocrystalline materials has been attributed to the large fraction of grain boundaries, which have a considerably higher thermal expansion coefficient than that of the micrometer-sized crystallites.
