Investigation Of Modification Of Gadolinium Oxide And Preparation Of Gadolinium Oxide/Polyethylene Shielding Composites

With the development of nuclear energy, aviation and spaceflight, studies of the new shielding composites are becoming a hot spot. This new shielding materials have excellent mechanical properties and heat resistance. Rare earth oxide/polymer composites have attracted widespread attention recently. Rare earth-polymer composites are doped mainly by in the form of Rare earth oxide and small molecular compound. It is well known that, the surface of inorganic fillers is hydrophilic and the surface of polymer is hydrophobic. Therefore, there is little compatibility between the inorganic fillers and polymers. Inorganic fillers have a strong tendency to undergo agglomeration followed by insufficient dispersal in the polymer matrix, and then will cause the deterioration of mechanical properties. The particle surface modification and the particle-polymer interface are becoming important factors which are essential for the development and design of composite materials. The thesis consists of the following parts:(1)A brief description was given for the cause of filler modification and the preparation of new type shielding materials.(2)3-n-butyl-6-(1-decyl olefinic acid base)-4-cyclohexene diacid can be serve as surface modifiers and characterization:the surface of gadolinium oxide was coated by 3-n-butyl-6-(1-decyl olefinic acid base)-4-cyclohexene diacid. Thermogravimetric analysis shows that coated weight of the surface of inorganic particles with 3-n-butyl-6-(1-decyl olefinic acid base)-4-cyclohexene diacid is 10.3%. Study on the surface properties of the coated inorganic particles by IGC. The dispersive component of surface energy of 3-n-butyl-6-(1-decyl olefinic acid base)-4-cyclohexene diacid varied inversely and linearly with the temperature. With the temperature increasing, the surface force between the molecules is reduced. It leads to the material surface energy decrease. This phenomenon showed that trend of agglomeration of modified Gd2O3 using 3-n-butyl-6-(1-decyl olefinic acid base)-4-cyclohexene diacid was decreased and could increase dispersion in polymer materials.(3)The preparation of Gd2O3@PS core-shell particle and characterization:Gd2O3@PS was prepared by the way of chemical process, optimum reaction condition was studied, including temperature; concentration of sodium hydroxide aqueous solution; gadolinium hydroxide hydrate and KH570 feed ratio. The static contact angle shows that Gd2O3@PS can enhance hydrophobic properties. Value of thermogravimetric analysis is 67%.(4)The preparation of shielding composites and characterization:shielding composites with desired properties can be made by incorporating Gd2O3 fillers into a polymer matrix to suit various applications. Compared to Gd2O3/PE, the modification of Gd2O3/PE has better performance. Analysis of materials show that the mechanical properties are the best for 20% Gd2O3@PS; thermal stability of C22-Gd2O3/PE is best; 30% Gd2O 3@PS/PE has excellent shielding performance on 59.3keV.