| The oxyfluoride transparent glass ceramics are new type of inorganic solidstate optical functional material,which are synthesized by the controlled crystallization during the heat treatment process,and are composed of both crystalline phase(fluoride)and glass phase(oxide).Because fluoride crystals have the advantages of low phonon energy and high doping concentration of transition metal ions,the oxyfluoride transparent glass ceramica are often used in various luminescent materials.In addition,in the process of secondary utilization of silicomanganese slag,Mn element mainly exists in silicoaluminate phase and can not be effectively utilized.To deal with the problem,this thesis proposes a new idea to prepare Mn:CaF2 transparent glass ceramics using silicomanganese slag as thermoluminescence dosimeter for the environmental radiation detection.Through melting the salg at hightemperature,Mn exists in the gap of glass network structure in the form of glass intermediate,and then Mn precipitates with CaF2 crystals in the form of solid solution during heat treatment,so as to increase the extrinsic defects and then improve the luminescence properties.Finally,the application problem of silicomanganese slag will be solved and its high value-added utilization is realized.In this thesis,the light transmission mechanism,crystallization mechanism,crystallization kinetics and glass structural stability,photoluminescence properties,thermoluminescence properties and luminescence mechanism of Mn:CaF2 transparent glass ceramics are systematically studied,which provides a theoretical basis and technical reference for the preparation and application of silicon manganese slag.Firstly,CaF2 transparent glass ceramics were prepared by high-temperature melting method with pure reagent raw materials.The heat treatment conditions were determined and the light transmission mechanism was analyzed.The products were successfully prepared between 630? and 710? for a period of 1-4 h;herein,the the CaF2 grain size was approximately 10-25 nm,and the average grain spacing is 5.64-25.74 nm.The conditions for the transparent glass ceramics to achieve transparency are not only the grain size that should meet the Rayleigh scattering law,but also related to the grain distribution,which directly affects the degree of light scattering caused by the crystal grains.When the temperature exceeds 730?,CaF2 grains appear cluster phenomenon,and the glow energy is consumed after multiple scattering,resulting in the phenomenon of impermeability;herein,the average grain spacing is far less than 5 nm.Secondly,the effects of CaF2 additions on the light transmittance and glass structure of CaF2 transparent glass ceramics were studied from the aspects of structural dynamics and structural stability,and the optimal CaF2 addition was determined.As the amount of CaF2 addition increases,the amount of non-bridging oxygen increases,the degree of glass polymerization decreases,the energy barrier to be overcome for crystallization decreases,and the crystallization ability increases.Only when the amount of CaF2 added is 27.4 wt.%,the crystallization activation energy and network structure polymerization degree of the sample just meet the energy barrier required to overcome the diffusion of Ca and F atoms,so that the single CaF2 crystal phase can be precipitated to achieve transparency.Moreover,the crystallization activation energy calculated by Kissinger model is 247.07 kJ·mol-1,and the mole fractions of bridging oxygen(Oo),non-bridging oxygen(O-)and free oxygen(O2-)are about 0.12,0.77 and 0.11,respectively.Thirdly,Mn:CaF2 transparent glass ceramics were prepared using silicomanganese slag.The heat treatment conditions and the maximum allowable addition of slag were determined,and the effects of heat treatment temperature and slag addition on optical properties were analyzed.It was found that the slag addition should not exceed 27.64 wt.%,while the heat treatment temperature was 650710?.With the increase of the amount of silicomanganese slag,the emission peak shifted toward longer wavelength,and the color of transparent glass ceramics changed from orange red to red.In addition,the valence state of Mn and its existing environment will affect the luminescence intensity.Through the analysis of the results of emission spectrum,with the increase of heat treatment temperature,the influence of the electronic transition of Mn2+ in glass phase(at 622 nm)and the electro1ic transition of Mn4+ in glass phase(at 689 nm)on the luminescence intensity increases.While the effect of the electronic transition(569 nm)of Mn2+in CaF2 crystal on the luminescence intensity decreases.Finally,the thermoluminescence properties and luminescence mechanism of Mn:CaF2 transparent glass ceramics used as radiation dosimeters were studied.It was found that the sample showed relatively good thermoluminescence properties when the heat treatment temperature was 710 ? and the slag addition was 19.28 wt.%,and the sample showed linear dose response characteristics between 50-500 Gy,and the absorbed radiation sensitivity was 364.22±0.11.Besides,the irradiated samples shall be stored in the dark for 40 days and annealed at 300 ? for 20 min to completely eliminate the residual electronic information in the trap.The thermoluminescence curve spectrum was fitted by CGCD method and Chen's peak method,and the trap parameters of the material were calculated.After the material was radiated,there were six traps with different depths,and their activation energies were 1.36,1.50,1.52,1.57,1.90 and 2.02 eV,respectively(CGCD method).The difference of activation energy calculated by the two methods is mostly within 5%;In addition,the luminescence curve of the material conforms to the second-order kinetic model.In this thesis,Mn:CaF2 transparent glass ceramics can be controllable prepared using silicomanganese slag as a new thermoluminescence dosimeter for the detection of environmental radiation dose.This provides a new idea for the high value-added utilization of silicomanganese slag. |
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