| Tritium is an extremely important strategic resource for fusion reactors.However,it is also a radioactive waste in reactor waste water.There still is 1 million tons of low-concentration tritium-containing wastewater in Fukushima nuclear accident.The separation of three hydrogen isotopes,hydrogen,deuterium and tritium is the key to ensure the supply of tritium and the treatment of tritium-containing wastewater.How to design and prepare new materials to improve the efficiency of hydrogen isotope separation is one of the challenges currently facing.Traditional separation methods have the disadvantages of high energy consumption,many ancillary equipment and low separation factor.Recent experimental studies have shown that low-defect graphene is sub-atomic selective and can efficiently separate hydrogen isotopes in water;at the same time,a large number of theoretical studies have confirmed that microporous graphene prepared by introducing nanopores on the surface of graphene can achieve the sieving of molecules and ions with different sizes through the kinetic quantum sieving effect at low temperatures.This thesis will focus on the preparation of novel low-defect graphene and microporous graphene materials,which can be applied to the separation of hydrogen isotopes in water and gases,respectively.Firstly,the intercalation mechanism of anion and cation of inorganic salt in liquid phase exfoliation method was elucidated,and a novel liquid phase exfoliation method without stabilizer and ultrasonic assistance was developed,simplifying the preparation process of low defect graphene and avoiding the residual stabilizer which will influence the subsequent graphene device;subsequently,the High Intensity D-T Fusion Neutron Generator(HINEG),which can produce proton,deuterium and neutron is used to irradiate the low-defect single-layer graphene,and the proton irradiation is designed and manufactured.And a microporous graphene material was obtained and the damage effect of a proton beam with mA-grade current on graphene was studied.The main research results are summarized as follows:(1)It is proposed that co-intercalation with both anions and cations occurs during the intercalation process in the solution of inorganic salts.In this work,graphite powder was used as a precursor,and inorganic salts such as LiCl,KCl,and Li2SO4 were used as intercalation agents.Low-defect graphene was prepared through an environmentally friendly water-phase exfoliation system.Compared to LiCl,both KCl and Li2SO4 can signicantly enhance the exfoliation yields of graphene.Our results suggest that while the cation is a critical factor for improving the exfoliation yields,anions such as Cl-and SO42-also contribute to the exfoliation of graphene.Based on this experimental result,the mechanism of co-intercalation of cation and anion in intercalation process was proposed.The mechanism was verified by comparing the changes of chemical composition before and after ultrasonic cleaning,which provids a theoretical basis for optimizing the selection of intercalating agent.(2)A method for preparation of low-defect graphene with a surfactant-free aqueous system was developed.In this work,LiOH was used as an inorganic salt,and the low-defect graphene was prepared without surfactant.The lattice structure of the obtained graphene was intact and its size was 1-2 μm.The dispersion concentration in aqueous solution could reach 0.09.mg/mL.This method avoids the effect of surfactant residue’s on the performance of low defect graphene.By summarizing the experimental results and calculating the Gibbs free energy with the density functional theory(DFT),it was found that OH-was added to the edge of the low-defect graphene sheet during intercalation process which increases the affinity between graphene and water.Thus,stripped graphene can be stably dispersed in water without a stabilizer.In addition,the presence of OH-in the exfoliation system increases the electrostatic repulsion between the graphene sheets.This is also an important factor to promote dispersion of the graphene in water.(3)Based on the HINEG,a proton irradiation target plate for the preparation of microporous graphene was designed and manufactured.This work is based on the principle of preparing microporous graphene by particle irradiation,and a fixing method using pressure ring combined with the heat-conducting silver adhesive is designed,and several low-defect graphene irradiation samples(up to 8)can be tightly fixed on the rotating target plate.The developed proton irradiation target achieves vacuum sealing,water sealing,and sample fixing at a high-speed rotation of 1000 rpm,and can effectively control energy deposition caused by the continuous bombardment of 250 keV,mA-level proton beams.In the process,the proton fluence rate of each sample can be strictly kept consistent with the total fluence,which solves the problem,that fluence rate and the total fluence are difficult to control in past studies.It can be used for mass production of microporous graphene and is compatible with other film samples.(4)The microporous graphene was successfully prepared by the high intensity proton beam of HINEG.The effects of proton energy,fluence rate and total fluence on the damage of graphene structure were studied in this work.By comparing the defect of graphene after irradiation with proton beams with different fluence rates under the same magnitude of fluence,the fluence rate is an important factor affecting the structure and quantity of microporous graphene defects.The reason is that the increase of the fluence rate will inhibit the self-healing effect of graphene.In addition,it has been found that within a certain energy range,the smaller energy of incident protons,the greater the energy loss of protons in graphene,and the higher the radiation damage effect on graphene.And the defect density of pure copper substrate graphene after irradiation is lower than that of pure nickel substrate.The experimental results of the graphite damage effect are similar to graphene.Based on the liquid phase intercalation exfoliation,a low-defect graphene preparation method without surfactant and ultrasonic assistance has been developed,and the mechanism of the exfoliation has been studied to provide a clean production for low defect graphene.At the same time,the porous graphene was prepared by using a low-energy proton beam with mA level for the first time.The effects of proton energy,proton fluence and graphene substrate on the irradiation effect were studied.In order to proton irradiation,the generation mechanism of graphene micropores was studied.The low-defect graphene and porous graphene prepared in this paper can be used as a potential separation material to achieve efficient separation of hydrogen isotopes,it can be used as reference... |
