| With the development of social industrialization,the problem of water pollution has become more and more prominent.The application of nano materials for sewage purification plays an important role in the recycling of water resources.The research and production of high performance micro-nano materials become the key of materials engineering in the new era.Microwave chemistry is widely used in the synthesis of micro-nano materials because of its special dielectric heating mechanism and microwave effect.In order to solve the problem of how to use electromagnetic energy effectively in microwave chemical reaction,a microwave chemical reactor based on antenna radiation and heat pipe to realize synchronous cooling function is designed by theoretical calculation,simulation analysis and experimental tests.The details are as follows:The theory of microwave reactor and antenna was studied.The radiation structure of waveguide to coaxial antenna was designed by theoretical calculation,and the electromagnetic simulation was carried out by using HFSS.The transmission of microwave energy and the distribution of electric field intensity were analyzed under different parameters.The results show that the impedance matching can be affected by the step inner conductor and its axial misalignment compensation in the waveguide.A lower return loss can be achieved in the wide frequency band by optimizing the structure and position size.Through the simulation calculation,an arc antenna plate structure is designed,which can realize the central radiation in the cavity.The temperature test experiment shows that the field intensity distribution in the cavity of the antenna microwave reactor is reasonable and the uniformity of heating is improved.In the view of the problem that microwave radiation drops sharply after the stable temperature occuring in the microwave-assisted reaction,a heat pipe was added to the microwave reactor with antenna.The quality factor of the resonant cavity with adding the heat pipe was calculated by numerical simulation to determine the best evaporation section length in the cavity.The heat transfer characteristics of the heat pipe under different length of condensation section and microwave power were explored by experimental test.The speed of heating section and the microwave energy of temperature stable section were analyzed respectively.The results show that the change of the length of condensation section has a great influence on the heating rate of low power microwave resulting in parabola heating curve.The radiation energy of microwave reactor with cooling heat pipe in the stable temperature section can be obviously increased by optimizing the working parameters according to the heat transfer characteristicsNano ZnO was prepared by microwave hydrothermal method at atmospheric pressure in a microwave reactor with heat pipe or not.The effect of microwave energy change in the stable temperature section on the synthesis of ZnO was investigated.Different surfactants(sodium citrate and sodium oxalate)were added to modify Zn O on the basis of increasing microwave energy to explore its morphology and performance.The results show that with the increase of microwave energy during the stable temperature period,the morphology of ZnO nanoparticles is obviously inclined to nano-sheets structure,and the optical band gap of ZnO is sensitive to the change of microwave energy under high power.Under the same power,the photocatalytic degradation rate of ZnO prepared by increasing the microwave radiation energy increased significantly after 90 minutes.The zinc oxide prepared by sodium oxalate has excellent photocatalytic performance,and the degradation rate can reach over 99% within 120 minutesIn this study,the microwave reactor with antenna and the synchronous cooling functional microwave reactor with heat pipe are designed and developed,which can control the structure of nano ZnO and prepare nano ZnO with excellent performance,which has a broad application prospect. |
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