Kinetics of the crystallisation of Ni–Zn ferrite powders prepared by the hydrothermal method

Abstract

Recently published data on the precipitation of Ni-Zn ferrite powders prepared by the hydrothermal method have been analysed in a manner consistent with Avrami theory. The results indicate that the value of the time exponent is due to the growth of spherical particles in a solution which becomes progressively depleted of reactants. The analysis also indicates that the process can be considered to be one in which the particles all start growth from the initiation of the reaction.

Sintering behavior of Ni–Zn ferrite powders prepared by molten‐salt synthesis

“…Although increasing the calcination temperature can also improve the crystallinity to a certain extent, in the present case the mass transfer rate is low because the temperature is very low. Resultantly, the effect of increasing the calcination temperature from 400 to 550°C on the crystallinity of the obtained Ni 0.5 Zn 0.5 Fe 2 O 4 powders is not as significant as that of extending the holding time from 3 to 6 h. This observation is similar with the reports of Wang and Mancera et al 34,35 In their work, they investigated the crystallization of spinel Ni–Zn ferrite nanoparticles prepared by hydrothermal method, indicating that a long enough crystallization time (8 h) at a low temperature of 100 to 150°C would result in high crystallization fraction for Ni–Zn ferrites (close to 100%), but the same effect could not be achieved by increasing the temperature in a short crystallization time (just 2 h).…”

“…Although increasing the calcination temperature can also improve the crystallinity to a certain extent, in the present case the mass transfer rate is low because the temperature is very low. Resultantly, the effect of increasing the calcination temperature from 400 to 550°C on the crystallinity of the obtained Ni 0.5 Zn 0.5 Fe 2 O 4 powders is not as significant as that of extending the holding time from 3 to 6 h. This observation is similar with the reports of Wang and Mancera et al 34,35 In their work, they investigated the crystallization of spinel Ni-Zn ferrite nanoparticles prepared by hydrothermal method, indicating that a long enough crystallization time (8 h) at a low temperature of 100 to 150°C would result in high crystallization fraction for Ni-Zn ferrites (close to 100%), but the same effect could not be achieved behavior and the ceramic propert larly in the Sejnène region, northw the chemical composition, these c terized by high iron contents who of the ceramic materials is well k of fluxing agents as alkali and alk are necessary for low temperatur considered materials consist entir containing impurities, mostly ill iron, which serve as fluxing agen at low temperature [3][4][5][6] and appeare physical and mechanical propertie ramic materials. These materials can be used f they have appropriate chemical an tions composed of kaolinite and impurities including SiO 2 , CaO, F that are advantageous for its wor behavior, firing behavior, and qu ucts like mechanical strength and the suitability of these clayey ma products with low porosity and hig intended for applications for stone mentally important for the develo tor in Tunisia and the raw materi construction.…”