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

•The thermal reduction processes of nano-size metal oxide or metal ferrite in reducing atmosphere has been reviewed.•The reduction process considers one of the most important routes in production of nanoally and magnetic nanomaterials.•The factors control and affect the rate and behavior of reduction reaction were discussed in details.•The kinetic, activation energy and the factor affect the reduction process were also discussed in details.

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.

Graphical abstractThe isothermal reduction process of nanosize metal oxide and metal ferrites is a significant step in metallurgical processes as applied to M-Fe-O systems and also in production of alloys in steel production. The measured values of activation energies (Ea) for reduction reaction were mainly depending on preparation and reduction temperature. The Ea values show direct proportional relationship with preparation and reduction temperatures.Download high-res image (181KB)Download full-size image