Preparation Process And Performance Of Ultrafine Silver Powder And Its Derived Graphene Oxide Coated Silver Powder

Ultrafine silver powder has shown broad application in the fields of communications,electronics,and solar cell.Its size distribution,dispersion,and surface state have closely related to its performance.However,current domestic output and preparation process of ultrafine silver powder are far from the needs of the industry.Therefore,the preparation process of high-quality ultrafine silver powder with independent intellectual rights and stable production will play an important role in promoting the development of domestic photovoltaic industry.Due to the close dependence of ultrafine silver powder performance on the size distribution of particles,dispersion,and surface state,in this thesis,the preparation conditions that affect the size distribution,dispersibility,and surface state of silver powder coated graphene oxide(GO)were investigated in detail.On this basis,the mainfactors in large-scale production are studied,and the equipment and production flow closely related to particle size,distribution and morphology are designed.The main research contents are as follows:1.By introducing GO in the late stage of synthesising ultrafine silver powder by the liquid-phase reduction method,the relatively active surface interaction between the two materials in solution is used to obtain composite ultrafine silver powder with narrow size distribution,better dispersibility and higher conductivity.The structure and morphology of the obtained composite ultrafine silver powder were characterized by X-ray diffraction,Raman spectroscopy and scanning electron microscopy.The results showed that the ultrafine silver powder was with better dispersion and narrow size distribution.Furthermore,the interaction between GO and silver particles was explored using solids diffuse reflectance UV-vis spectra.Moreover,fixing the concentration of silver nitrate solution,with the increase of GO content,the conductivity of silver powder increased at first and then decreased.When the mass percentage content of GO is 2.5%,the contact between silver particles can be increased more effectively,the interfacial resistance of silver particles can be reduced,and the conductivity is higher.2.Based on the experimental conditions of extended amount for superfine silver powder:concentration of silver nitrate,quality percentage of gum arabic,feeding time of silver nitrate,reaction temperature,reaction time,stirring speed and drying methods were studied,the suitable conditions for preparing ultrafine silver powder at an extended amount were obtained.On this basis,a certain amount of GO was introduced in the late stage of synthesising silver particle.The structure and morphology of the obtained composite ultrafine silver powder were characterized by X-ray diffraction,Raman spectroscopy and scanning electron microscopy;the interaction between GO and silver particles was investigated by UV-vis spectroscopy;the tap density of the sample was 3.65 g/cm~3 based on the Ag particles with an average particle size of 1.5(?)m;the square resistance of the ultrafine silver powder tested by four-probe tester is 1.578 m?/?,which meets the main parameters required for the silver powder used in positive silver paste of photovoltaic cells.This research provides experimental and theoretical basises for further designing the production process of silver powder.3.Combined the existing equipment and process of preparing silver powder,the equipment and process conditions according to experimental conditions were optimized.In particular,a kettle equipped with a heating device is designed to save time for mixing.Double-layer transparent glass is adopted in the reactor for real-time observation of reaction conditions.The glass on the inner wall of the reactor is alkylated in order to avoid the silver mirror reaction.It is expected to increase the yield of silver powder and reduce the cost.The automatic lifting device above the reactor can adjust the stirring speed,which can make the stirring rod dip into different depths according to different systems and promote the reaction.At the bottom of the reactor,there is a pneumatic discharging valve which is alkylated in contact with the reaction mixture.The pneumatic discharging valve can prevent the ultra-fine silver particles from being blocked.At the same time,the silver particles easilyenter the next process without any blockage.The designed washing device is set with high pressure.The pressure of the nozzle can rotate 360°within 0-150 MPa to ensure the supply speed of water during washing and to thoroughly clean the inside of the washing tank after washing.The stirring device improves the washing efficiency of graphene oxide/ultra-fine silver particles.A vacuum device and an inclined roller were designed in the drying device.The graphene oxide/ultra-fine silver powder can be uniformly heated in the roller.In the vacuum state,the agglomeration of silver particles can be efficiently inhibitedduring drying,thereby the inherent nature of the particles can be maintained.This research provides a basis for obtaining better preparation device and process flow of graphene oxide/ultrafine silver powder.