Study On The Preparation And Surface Oxidation Behavior Of Uranium-silicon Compounds

Uranium has significant applications in key fields such as energy and security due to its physical and chemical properties.At the same time,uranium metal is a chemically active material with radiation that easily reacts with most environmental media.In engineering applications,corrosion problems of uranium must be considered to reduce material loss and prevent environmental pollution.Research on the corrosion protection of uranium metal has been carried out for many years.The method of surface modification of metal uranium has been developed rapidly for its promising application prospects in recent years.In the reported corrosion test or high temperature corrosive environment applications,metal silicide or siliconized metal surface shows strong stability.According to the existing research results,U-Si compounds may have valuable corrosion resistance with accurate control of composition and structure,but the research on corrosion resistance mechanism and corrosion products is still limited.In addition,the failure conditions of its corrosion resistance are not quite clear.Based on the above-mentioned background,this paper prepares uranium silicide samples by arc smelting,and also attempts to obtain uranium silicon modified layer by laser infiltration on the surface of metal uranium.This paper uses the main analytical equipment such as scanning electron microscope,X-ray diffractometer and X-ray photoelectron spectroscopy,combined with surficial morphology analysis,composition analysis and electronic structure analysis,to study the uranium silicide samples produced by arc melting and laser-siliconized modified.Full and in-depth analysis and discussion of various experimental phenomena and experimental results appearing in the experiment have been carried out,mainly in the following aspects:Three different silicon content uranium silicon compounds were prepared by arc melting method.X-ray diffractometry and X-ray photoelectron spectroscopy were used to analyze the phase and impurity state of different silicon-containing uranium silicon compounds.The analysis was carried out to determine the difference in surface oxidation behavior of uranium silicides with different silicon content using the deep sputtering function of X-ray photoelectron spectroscopy,and the identification of uranium silicide and its oxidation products was based on electronic structure.Uranium silicides with different silicon contents exhibit different oxidation behaviors.For samples with higher silicon content,Si participates more obviously in oxidation,when Si participates in oxidation,U no longer tends to be oxidized to a high valence state.The initial oxidation process of U3Si2 was investigated by in-situ XPS analysis.The results show that U and Si exhibit different oxidation behaviors when U3Si2 is initially oxidized,and U element oxidizes faster than Si element.Uranium silicide reacted with oxygen and formed uranium oxides quickly during initial oxidation.The oxidation product of U3Si2 is first uranium oxide and after enough oxygen exposure,the U 4f,Si 2s and valence bands show the same trend,uranium silicate might form.The percentage of oxide was obtained by the XPS peak fitting process,indicating that the percentage increase in oxide could be exponentially fitting.Further exploration of the preparation method was carried out,including laser scanning to obtain a uranium-silicon modified layer on the surface of the metal uranium workpiece,it was found that the surface modified sample showed a certain oxidation resistance.The surface morphology,oxidation state,composition and surface state of the sample placed in the air for a period of time were analyzed and studied.The results show that the surface of the sample is oxidized to form uranium oxide and silicon dioxide after being left in the air for a period of time.The internal transition layer that continues to be sputtered may be a certain U-Si-O ternary compound.The SiO2 and U-Si-0 ternary compounds formed by the oxidation of surface modified samples may contribute to the antioxidant properties.In addition,an attempt was made to modulate the state of the uranium silicon compound using a high-temperature annealing method,and it was found that the high temperature annealing can make a certain degree of modulation on the U:Si=3:1 sample and the U:Si=3:3 sample which crystal having a poor crystallization effect on the previous refining process.