Isothermal reduction process and kinetic of nanomaterials in reducing atmosphere: A review

Abstract

The Isothermal reduction processes of nanomaterials received considerable attention because the reduction reaction considers one of the most important routes in the production of nanoally and magnetic nanomaterials. In view of this; thermal reduction processes of nano-size metal oxide or metal ferrite in reducing atmosphere has been reviewed. The rate and way of reduction reaction depend mainly on various parameters such as reduction temperature, flow rate and composition of reducing gas, preparation conditions, crystal size, morphology and composition of the reduced materials…etc. In all reduction process, the reduction rate increase with increasing reduction temperature, but a complete reduction process (100%) was limited and controlled. The literatures showed that; the reduction process can follow either by weight loss or conductivity techniques.The kinetic and activation energy of reduction process was also discussed in details. The reduction processes were controlled by various mechanisms and it was obtained that; single reduction process can proceed through more than one mechanism. The type of controlled mechanism depends on the values of apparent activation energy (Ea), these values were found to be affected by different parameters such as preparation and reduction temperature. The validity of controlling mechanism deduced from activation energy values was confirmed via different mathematical models.