Study On The Preparation Of Silver Nanomaterials And Nanocomposites By High-Gravity Technology

Electrodes are indispensable devices in electronic equipments,which can be divided into conductive electrodes,supercapacitor electrodes,primary cell electrodes,pH electrodes and so on.With the rapid development of intelligent instruments,wearable devices and flexible solar cells,there is an increasing demand for new flexible electrodes with high transparency and electrical conductivity.The commonly used transparent electrode materials are graphene,metal,metal oxides,conductive polymers,etc.Among them,silver nanomaterials exhibit excellent properties in electrical,optical and mechanical properties,which can be used to fabricate transparent electrode materials with excellent performance.However,there are still many problems to be solved in the preparation of silver nanomaterials,such as uncontrollable particle size,poor dispersion,and difficulty in scaling.Therefore,the research on the controllable preparation of silver nanomaterials and nanocomposites has become one of the hottest research fields at home and abroad.This paper aims to prepare silver nanomaterials and nanocomposites with uniform size and good dispersity by high-gravity technology.The effects of preparation conditions on the morphology,dispersibility and application properties of silver nanomaterials and nanocomposites are studied.The main contents and results are as follows.1.Silver nanowires?AgNWs?with high aspect ratio were controllably prepared by high-gravity technology combined with polyol reduction method.The optimal preparation conditions are as follows:the rotational speed of rotating packed bed?RPB?is 1500 rpm,the cycling time in RPB is 10 min,the reaction temperature in STR is 160?,the mass ratio of PVP to AgNO3 is 0.63,and the molar ratio of NaCl to NaBr is 2:1.The prepared AgNWs have an average diameter of 20 nm and an average length of 55 ?m.Moreover,the yield is up to 95%.In contrast,the length and yield of AgNWs prepared by using the traditional stirred tank reactor?STR?are significantly reduced.The average length is only 30 ?m and the yield is reduced to 91%.In addition,the macro-preparation of AgNWs is discussed.When the throughput is magnified 10 times,the yield of the STR process is decreased to 83%,and the average length of AgNWs is reduced to 25 ?m.In contrast,the yield and length of AgNWs prepared by the RPB process remain almost unchanged without scale-up effect.The size and uniformity of silver halide nanoparticles?AgHNPs?have a significant effect on the morphology of AgNWs.The AgHNPs produced by RPB process are smaller and more uniform than STR process,which are more easily dissociated into ethylene glycol to promote the growth of AgNWs.Therefore,both the the aspect ratio and yield of AgNWs prepared by RPB process are higher than that of the STR process.2.Flexible transparent conductive electrodes?FTCEs?were prepared by spin coating method with AgNWs.The effects of annealing temperature and concentration of AgNWs dispersion on the transmittance and sheet resistance?Rs?of FTCEs were studied.The prepared FTCEs have good stability with high transmittance and low Rs.When the transmittance of FTCE at 550 nm is 90.2%,the Rs is only 9.6 ?·sq^-1 and increases by only 19%after bending for 1000 times,which is significantly better than the reported ITO electrode.Compared with STR process,the visible light transmittance of FTCE prepared by RPB process is increased by 5%at the same Rs.In addition,the AgNW/bismuth tungsten bronze/polyvinyl butyral?AgNW/MTO/PVB?nanocomposites were prepared by coating method.AgNW/MTO/PVB nanocomposites have high visible transmittance and remarkable mid-infrared light reflection performance.When the transmittance at 550 nm is 65%,the reflectance at 25 ?m is above 60%.The excellent optical properties make AgNW/MTO/PVB nanocomposites have obvious heat preservation and insulation efficiency,which can save more than 16%of electrical energy for oven insulation.3.The water-phase monodisperse silver nanoparticles were prepared by high-gravity technology combined with in-situ surface modification.The optimal preparation process of silver nanoparticles is as follows:the rotational speed of RPB is 2000 rpm,the molar ratio of modifier to AgNO3 is 0.7,the molar ratio of NH3·H2O to AgNO3 is 1.0,the reaction temperature is 20?,the reaction time is 8 min,and the pH value is 10.0.The prepared silver nanoparticles have uniform size and good dispersion with an average diameter of 5.2 nm.The preferred formulation of silver ink is as follows:the content of silver nanoparticles is 30 wt%,the content of carboxymethylcellulose sodium is 0.3 wt%and the content of glycerin is 5 wt%.The resistivity of the prepared silver trace is only 7.5 × 10^-8 ?·m with good bending stability.Moreover,3M tape adhesion test shows that the silver trace also has good adhesion.When the mass ratio of water,organic solvent and silver nanoparticles in the silver microemulsion system is 80:60:1,the random conductive grid with uniform pore diameter is formed with the visible transmittance of 52.2%and sheet resistance of 4.1 ?·sq^-1.The structure-performance relationship of the conductive grid was also simulated by COMSOL Multiphysics simulation software.4.In-situ high-gravity reactive method was proposed to prepare silver/molybdenum disulfide/reduced graphene oxide?Ag/MoS₂/rGO?nanocomposites with rGO as substrates.The effects of different reaction conditions on the morphology and electrochemical properties of Ag/MoS₂/rGO nanocomposites were studied.The optimal preparation conditions of Ag/MoS₂/rGO nanocomposites prepared by RPB process?AMG-R?are as follows:the preferred reducing agent is glucose,the concentration of silver ions is 0.3 mmol·L^-1,the reaction temperature is 30?,and the pH is 11.The MoS₂ is flake-shaped with an average length of 85 nm and the silver is nanoparticulate with an average particle size of 5.5 nm.Both of them are uniformly distributed on rGO.However,the silver nanoparticles loaded on the Ag/MoS₂/rGO nanocomposites prepared by STR process?AMG-S?are unevenly distributed on rGO,and the average particle size is 9.7 nm with wide size distribution.Therefore,compared with AMG-S,AMG-R has higher specific capacitance and better cycle stability.When the scanning rate is 20 mV·s^-1,the specific capacitance of AMG-R nanocomposites is 540.6 F·g^-1 and decreased by 8.9%after 1000 cycles of continuous charge and discharge process.The specific capacitance of AMG-S nanocomposites is only 88.2%of AMG-R,and the specific capacitance is reduced by 10.3%after 1000 cycles.In addition,the composite of silver nanoparticles can significantly increase the specific capacitance of the nanomaterials.The specific capacitance of AMG-R is 84%higher than that of MoS₂/rGO nanocomposites.