Radiation Synthesis And Application Of Manganese Oxides And Its Composite Materials

Manganese oxides have many kinds of species and complex structures,which have a wide range of applications in the fields of catalysts,adsorbents,batteries,and supercapacitors,etc.The common manganese oxides are MnO2,Mn2O3,Mn3O4,and so on.Many methods have been developed to synthesize manganese oxides with specific morphologies,especially the chemical method.Each method has its own advantages and disadvantages.Radiation method owns unique advantages in the synthesis of nanomaterials,but there are a few related studies having been reported compared with chemical method.From the perspective of radiation chemistry,potassium permanganate was reduced by reductive species generated by radiolysis of aqueous solution.And the synthesis of various manganese oxides was realized by controlling experimental conditions.The main research contents and experiemental results are as follows:1.The effect of the initial pH on the reduction products of potassium permanganate solution irradiated by gamma-ray was systematically studied.The experimental results show that the morphology of the products obtained by irradiation of potassium permanganate solution without tert-butanol at different initial pH is different.After adding tert-butanol,the product is MnO2 at initial pH≤<3 and pH≥11,however,when in the pH range from 5 to 10,the product is Mn3O4.The morphology of the products is greatly affected by pH and tert-butanol.The electrochemical properties of the three typical manganese oxides obtained under the tert-butanol-water system were investigated.The results show that the MnO2 prepared under strong acid or strong alkaline conditions has higher specific capacitance and better rate performance,while the manganese oxide prepared under neutral conditions has poor performance.This work provides a new method for the morphology regulation of manganese oxide by gamma-ray,and expands the application of radiation synthesis in the field of energy storage.2.The experimental conditions for the preparation of Mn3O4 by radiation method were explored,and the green synthesis of Mn3O4 was realized.The effect of reaction conditions on the synthesis of Mn3O4 were investigated including reaction atmosphere,absorbed dose,tert-butanol concentration,and potassium permanganate concentration.It was found that the content of MnOOH was strongly decreased by reducing the concentration of potassium permanganate,and high purity of Mn3O4 nanocrystals were obtained.According to the experimental results,the possible formation mechanism of Mn3O4 was proposed and the electrochemical properties of Mn3O4 were studied.The results show that the Mn3O4 nanocrystals prepared by radiation method have high specific capacitance and good rate performance.This method provides a new idea for the green synthesis of Mn3O4 nanocrystals.3.By adding TEOS to neutral solution of potassium permanganate,MnOx@SiO2 composite nanoparticles with a diameter of about 50 nm were prepared through one step by gamma ray radiation.The effects of absorbed dose rate,reaction atmosphere,and TEOS content on the formation of composite nanoparticles were investigated.According to the experimental results,the possible formation mechanism of composite nanoparticles was proposed.Since the obtained manganese oxide exhibits various valence states,it is expected to be applied in the field of degradation of organic dyes as Fenton-like reagent.This work provides a new method for the preparation of composite nanoparticles by radiation method,and expands the application of radiation synthesis in the field of oxidative degradation.