Study Of Preparation And Application Properties Of Spinel Ferrites Via Layered Double Hydroxide Precursors

Layered double hydroxides(LDHs) are a class of compounds with a lamellar structure with metal ions in the layers generally uniformly distributed at an atomic level. Therefore, in each microstructural unit of the layers, the chemical composition and structure are same, and thus homogenous spinel ferrites or mixtures of spinel ferrites and metal oxides can be obtained by calcining LDHs precursors. Making use of this special property of LDHs precursors, the thesis describes a systematic study mainly focusing on the preparation of porous spinel ferrite and metal oxide/ferrite magnetic composite materials, and their applications in enzyme immobilization and sterilization. The main results are as follows:1. Taking advantage of the controllable chemical composition of LDHs, potential sources of magnetic species and divalent metal cations with special properties have been incorporated into the layers. Well-crystallized NiZnFe-LDHs precursors have been prepared by the coprecipitation method. Synthesis parameters such as aging temperature, aging time, pH values and initial molar ratio have been investigated, and the optimal conditions for synthesis of NiZnFe-SO₄-LDHs have been determined. Other MZnFe-SO₄-LDHs (M=Mg, Co) and well-crystallized Mg (Fe²⁺) Fe³⁺-LDHs precursors have also been prepared by similar methods.2. By adjusting calcination conditions, mixtures of Ni_xZn_1-x]Fe₂O₄ spinel ferrites and ZnO phase could be formed on calcination of NiZnFe-SO₄LDHs precursors. After the removal of amphoteric ZnO with aqueous sodium hydroxide solution, porous ferrite magnetic materials could be obtained.