Synthesis Of Novel Ferrite Pigments And Its Application On Magnetic Inks

Magnetic ink is a kind of important special anti-forgery ink, with dark-color appearance, simple testing equipment, remarkable anti-counterfeiting. Spinel ferrite is the most common magnetic ink pigments. Preparation of high-performance ferrite pigments is the key to prepare magnetic ink. Herein, In this paper,spinel ferrite nanoparticles had been controlled fabricated via hydrothermal method. Then magnetic inks were prepared with homemade Fe₃O₄ nanoparticles as pigments. The contents are summarized as follows:(1) Flake and acicular Fe₃O₄ nanoparticles were successfully prepared by using NaAc as protective reagents with hydrothermal method at lower temperature, respectively. It has been found that morphology and size of final products prominently depended on concentration of NaOH, concentration of reaction and other additive agent. The possible formation mechanism for the Fe₃O₄ nanoparticles has also been proposed. The influence of both its morphology and size on the magnetic and microwave adsorption properties has been studied and revealed that saturation magnetization of acicular Fe₃O₄ nanoparticles was lower than flake Fe₃O₄ nanoparticles, both of them were magnetically soft material,and their microwave absorption properties were different .(2) MnZn ferrite nanoparticles were successfully prepared with hydrothermal method under conditions of 15 mmol FeSO4·7H2O, 3.75 mmol ZnCl2, 3.75 mmol MnCl2·4H2O, 10 mmol CH3COONa, 10 mmol C6H8O7·H2O, 10gNaOH, 80℃and reaction time 3.5 h. It has been found that morphology and size of final products strongly depended on reaction time, concentration of reaction and other surface active agents. The possible formation mechanism for the MnZn ferrite nanoparticles has also been proposed. Magnetic studies revealed that MnZn ferrite nanoparticles have low saturation magnetization of 44.79 emu/g, whick was lower than that of Fe₃O₄ nanoparticles. The microwave adsorption properties has been studied. Results revealed that absorption band were wide. The absorptivity which was lower than -3dB width was nearly 5.1 GHz. (3) Magnetic inks were prepared with homemade Fe₃O₄ nanoparticles as pigments. The printability and anti-counterfeiting effect has been studied via a lot of orthogonal test and printing performance testing. The influence of ink vehicle, pigment and additives on the magnetic inks has been studied, then decided the optimum formula of magnetic ink. Printing performance testing revealed that the range of the magnetic inks'viscosity was 10-80 Pa·s, and the range of the magnetic inks'tack was 4-13. Both of them conformed to the standard of offset printing ink, Rub Resistance , drying property and printability were excellent .