Effects Of Dopping CeO₂/TiO₂ And Irradiation On The Boro/Silicate Glass And Transparent Glass-ceramic

Developments in aerospace technology,nuclear medicine,nuclear power and green architecture put foreward increasingly rigorous requirements on glasses used in radioactive enviorment.Currently doping more radiation stabilizer CeO₂ deteriorates glass optical properties,while scanty introduction in addition to the incompatiblity with glass batch composition will in return impair the irradiation resistance.Moreover,the glass mechanical properties need to be further improved.Limited co-doping and microcrystallization to improve glasses' irradiation resistance and stability of optical,mechanical properties are proposed in this study.It is of much applicable worthiness and theoritical significance to study the effects of limited doping and rays radiation on the structure and performances of boro/silicate glass and transparent glass-ceramics in light of their wide applications and cost-effectiveness.In this study,silicate and borosilicate glasses were synthesized by melt quench method and the transparent glass-ceramics were prepared by isothermally crystallization.The structure and properties were characterized by means of FTIR,Raman spectrometry,spectrophotometry,XRD,DSC,nanoindentation and SEM.The effects of co-doping limited CeO₂/TiO₂ as well as ?-ray irradiation on the structure and properties of the as-prepared glasses and the glass-ceramics were investigated.The main contents and results are as follows:?1?Effects of doping CeO₂/TiO₂ on the structure and properties of glass SiO₂–Al₂O₃–Na₂O–K2O–CaO were investigated.The results show that polyvalent cerium acts as network modifier dominantly in presence of Ce3+ while titanium as a network intermediate tends to enhance network connectivity in the form of [TO4].Doping CeO₂ solely leads to network depolymerization,reducing bridging oxygens and narrowed Qn distribution and hence red shift of absorption edge as well as decrease in optical band gap,hardness and E-modulus but rise in fracture toughness.Doping TiO₂ singly or co-doping combined with CeO₂ favors enhancing polymerization of network,broadening Qn distribution and suppressing red shift of absorption edge compared to doping CeO₂ alone,and structural densification associated with interstitials filling may account for the increase of hardness and E-modulus at cost of the slight loss of toughness.The two opposite mechanism may synergistically affect the mechanical properties of silicate glasses co-doped with cerium and titanium.?2?Silicate transparent glass-ceramics containing CaF₂ nanocrystals were prepared through optimizing SiO₂–Al₂O₃–CaO–CaF₂ composition and the effects of doping CeO₂/TiO₂ on synthesis and properties of traparent glass-ceramics were investigated.The results reveal that CaF₂ and anorthite can successively crystallize out of glass matrix depending on composition and isothermal crystallization treatment temperature.Substitution of SiO₂ by CaO and/or CaF₂ may facilitate the precipitation of CaF₂ crystalline but suppress the crystallization of anorthite.Transparent Glass ceramic can be synthesized using glass with a molar ratio of SiO₂ to?CaO+CaF₂?approaching 1.3 through heat treatment below 700?.Doping CeO₂ solely leads to network depolymerization and partial conversion of [AlO₆] to [AlO₄] increasing the percolation floppy region that promotes CaF₂ crystallization.In case of co-doping CeO₂/TiO₂,Ti enters Si-O network in [TiO₄] improving network interconnectivity and suppressing CaF₂ crystallization.For a given dosage,substitution of CeO₂ by TiO₂ lessens red shift of absorption edge and increases the transparency of glass-ceramics.?3?Effects of doping CeO₂/TiO₂ on structure and properties of borosilicate glass SiO₂/B₂O₃/Al₂O₃/Na₂O/ZnO/Li₂O/CaF₂ was investigated and the results show that doping CeO₂ results in different structural states governed by varied structural parameter R based on revised Yun,Bray & Dell model.Doping solely CeO₂<1.5mol% allows conversion of [BO₃] to [BO₄] forming B–Si–O mixed tetrahedral structure with the enhanced Si?B?–O network in combination of static linkage between cerium ions and structural units playing the dominant role.The glass density,molar volume,hardness and E-modulus decrease but fracture toughness increase with increasing CeO₂ content.In case of doping 1.5mol%CeO₂,Si?B?–O network depolymerization coupled with close packing of interstitial ions become the major factors giving rise to non-bridging oxygen number,density and fracture toughness but reducing molar volume,hardness and E-modulus.1mol% CeO₂ is the critical point that marks the onset of glass structure and properties change.Co-doping CeO₂/TiO₂ with Ti in form of [TiO₄] reinforcing the network but hindering the formation of B–O–Si mixed tetrahedral leads to drop of molar volume but rise of hardness and E-modulus.Excessive TiO₂ as modifier filling interstitial space cause gradual decrease in glass hardness,E-modulus,molar volume but increase in density and fracture toughness?4?Effects of Doping CeO₂/TiO₂ on the synthesis and properties of borosilicate transparent glass-ceramics SiO₂/B₂O₃/Al₂O₃/Na₂O/ZnO/Li₂O/CaF₂ were investigated by virtue of percolation model.The results show that Glass transition temperature as well as the crystallization temperature decreases firstly and then increases with increasing CeO₂ content.Correspondingly,the size of precipitated CaF₂ crystals and the absorption coefficient of the glass ceramics are found to increase firstly and then decrease.The increase of CeO₂ relative concentration and elevation of treating temperature lead to red-shift of absorption edge and transparency deterioration of glass ceramics.For co-doping 0.5mol%CeO₂ with 1–2mol%TiO₂,Ti enhances the network in addition to the steric hindrance shrinking the percolation floppy region and thus suppressing CaF₂ crystallization,and substitution of CeO₂ by TiO₂ supresses the deteriorating transparency of glass and glass-ceramic.?5??-ray irradiation effect on silicate glass and transparent glass-ceramic was investigated.The results show that radiation results in bond rupture in network increasing non-bridging oxygen,red-shift of absorption edge,rising radiation-induced absorption coefficient?RIAC?,decrease in optical band gap and increase in Urbach energy,which tend to be stablilized with increasing ?-ray does.Doping CeO₂/TiO₂ significantly improves the irradiation stability of network and optical properties of glasses and glass-ceramics.Glass microcrystallization alleviates radiation induced structural disorder and augments stressed bonds in addition to inducing absorption bands due to hole-center and Fe²⁺.?6??-ray irradiation effect on borosilicate glass and transparent glass-ceramic was investigated.The results indicates that irradiation cause network depolymerization and conversion of [BO₄] to [BO₃] in glass and glass-ceramic.Doping CeO₂/TiO₂ markedly promotes the radiation stability of glass and glass-ceramic network,even under high does of ?-ray [BO₃],[AlO₆] can respectively transfer into [BO₄],[AlO₄] and more Si-O-Ti segments form enhancing the network.Doping CeO₂ singly or co-doping appropriate CeO₂/TiO₂ enable RIAC to drop remarkably and band gap and Urbach energy to stabilize.Rising TiO₂ content increases RIAC with band gap and Urbach energy varying significantly as function of does.Kinetic modeling analysis indicates that there exists a does-induced saturation effect for defects production and defect coloring occurs in two stages termed as ‘rapid' one and ‘slow' one that have impact on does-induced saturation for optical properties.