Research On Ridge-loaded Microwave Processing Device And Silver Nanowire Transparent Electrode

From the birth of the world's first microwave oven in 1947 to the present,microwave energy has gradually entered people's lives as an efficient and clean heating energy source.Microwave energy was originally used to heat food.So far,it has been combined with chemical,textile,medical,and biological fields to generate a variety of emerging industries.However,the uniformity of microwave radiation is a factor that cannot be ignored when microwaves are used to research material modification,especially nanomaterial processing.Some experiments have shown that microwave annealing of silver nanowire transparent electrodes can improve conductivity of the film.Laboratory equipment retrofit with a microwave oven,but the problems of random field distribution and uncontrollable power of microwave oven seriously reduced the repeatability of experiment.Result in enormous difficulties in inductive and analysis results.In view of the above problems,a microwave nanomaterial processing device is designed and processed in this paper.The equipment uses the microwave reaction cavity based on ridge waveguide.By further optimizing the design,the online characterization and measurement functions of nanomaterials were achieved.Using the measured temperature,conductivity,and absorbed power conditions,the state of the material can be easily analyzed and fed back to the microwave source for timely adjustments.The optimized ridge waveguide cavity achieved S11 close to-30dB and reached a uniformity of more than 95%in a 1cm~2 area.The microwave source is composed of a solid-state source module and a self-made control device to achieve a power adjustable output at a stable frequency of 2.45GHz,with 0.1W adjustment accuracy at low power(<10W)and 5W adjustment accuracy at high power(>60W).Advance the research on microwave effect to precision,high efficiency and simple operation.In recent years,with the maturity of technologies such as wearable electronics and flexible screens,silver nanowire transparent electrodes have rewarded great attention and applications in the flexible conduction.However,the electron transmission rate of the nanowire junction is greatly obstructed by contact area of the wire junction,connection mode between the wires and the nanowire oxidation level.This article uses a self-designed microwave nanomaterial processing equipment for thermally annealing silver nanowire transparent electrodes,reducing the sheet resistance by up to 4 orders of magnitude.The best sample reduced the square resistance of the sample from1.62?10~5?/sq to 46?/sq at an optical transmittance of 93%(at 550 nm).The observation result of the scanning electron microscope confirmed that the nanowire junctions are welded under the action of microwaves.The welding principle is to generate a conductive current of varying size and direction inside the silver nanowire network through microwave radiation.Thermal energy generate due to ohmic losses at the junctions of the nanowires where electron transmission is impeded,and the local thermal effect reaches the temperature required for welding,making junctions more reliable connection.This method has selective heating and self-limiting,doesn't damage the substrate at appropriate power density,and keep original with prolonged microwave radiation.In order to further investigate the film formation quality of silver nanowires and the law of microwave needles welding,in this experiment,films with different thickness and uniformity were prepared by adjusting the spin-coating speed,spin-coating time and dispersion concentration.It was found that films were not welded had relatively high quality factors only at very poor transmittances(<70%).After microwave welding,the quality factor of films with high light transmittance(85%~94%)becomes better.In summary,microwave annealed silver nanowire transparent electrode is a low-temperature,efficient,highly controllable,and low-cost welding method.In addition,microwaves provide new strategies for other metal nanowire welding and nanodevice connection.Provide a method for microwave effect research from large size heating to miniaturization.