Study On The Preparation Of Cu-Cd@SiO₂ Bimetal Core-shell Nanoparticles

Nano core-shell structure material is a kind of special nano materials. It is usually used a nano particles as core and another kind of nanoparticles as shell. The core was coating by shell through chemical method or physical method. Nano silica materials have a wide range of applications in adsorption, biological and catalytic and other fields due to its high thermal stability, high specific surface area and surface modification. The core-shell structure catalyst has high stability, and can build confinement catalytic reaction space, reduce the mass transfer resistance, the coupling effect of strengthening the reaction process. So it is widely application in catalytic field. In this paper, through inverse microemulsion method preparation of Cu-Cd@SiO2 core-shell composite nanoparticles hope for applied in one step synthesis of DME.In chapter one of this paper,we mainly introduced several aspects of nano core-shell structure materials.(1) Core shell structural materials with some special properties compared with ordinary nano materials.(2) Core shell structure materials have a wide range of applications because of its excellent performance, such as core-shell structure materials in the catalysis field application.(3) Core-shell structure material preparation method has template method, st?ber method and inverse emulsion method and so on. Inverse emulsion method has obvious advantages in prepared of monodisperse nanoparticles. So this paper mainly used inverse emulsion method to prepare Cu-Cd@SiO2 core-shell structure particles.In chapter two of this paper, we mainly introduced the preparation of Cu-Cd@SiO2 particles in inverse emulsion system formed with liquid paraffin as solvent. Experiment is using Span-80 and Tween-80 as the emulsifier, the mixed solution of copper nitrate and cadmium chloride as water phase, TEOS as silicon source, hydrazine hydrate as reducing agent and ammonia as catalyst. This chapter uses two kinds of schemes to preparing Cu-Cd@SiO2 particle. Scheme 1 is adding hydrazine hydrate reduction of copper and cadmium ion as metal particles before the hydrolysis of TEOS. Scheme 2 is adding hydrazine hydrate reduction of metal complex ion as metal particles after the hydrolysis of TEOS. We observed the effects of different schemes and in the same scheme water-oil ratio and emulsifier content on the experimental results. And through the XRD, SEM, FTIR and TG-DSC were characterized to determine particle morphology and composition. The characterization results can be seen particles prepared by scheme 2 has better monodispersity. And we can see the particle size decreased when the emulsifier content increases in scheme 2. The core-shell structure nanoparticles size is between 40-80 nm when the water-oil ratio(volume of water phase and oil phase ratio) is 0.1 and the emulsifier content is 1.5g Span-80 and 0.5g Tween-80.In chapter third of this paper, we mainly introduced the preparation of Cu-Cd@SiO2 particles in inverse emulsion system formed with cyclohexane as solvent. We also observe the effects on the experimental results when change the water-oil ratio and emulsifier content. We used Triton X-100 as emulsifier, n-butanol as co-emulsifier, the mixed solution of copper nitrate and cadmium chloride as water phase. TEOS as silicon source, hydrazine hydrate as reducing agent and ammonia as catalyst. Through the SEM, FTIR and TG-DSC were characterized to determine particle morphology and composition. The characterization results can be seen the particle size decreased when the emulsifier content increases. When the water-oil ratio is 0.1 and the emulsifier content is 10 g Triton X-100, the core-shell structure nanoparticles size is between 60-80 nm, the particle have good monodispersity and microspheres with uniform particle size distribution.This paper was successfully prepared core-shell structure nanoparticles through the inverse emulsion method. The experimental results indicate that the main factors of the nano particles were the water-oil ratio and the emulsifier content and so on in the inverse emulsion method. We also observe the effect of the water-oil ratio and emulsifier content on the experimental results. The characterization results show that nanoparticles with smaller particle size and better dispersion when increasing the emulsifier content. And the nanoparticles size is increased when water-oil ratio increases.