• Nuclear Engineering and Technology
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• v.55 no.7
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• pp.2366-2372
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• 2023

Are borate and silicate glasses suitable for working as shieling materials against fast neutrons? To correctly answer the above question, some silicate, and borate-based glasses were fabricated and irradiated with various doses of fast neutrons varied between 1.73 and 12.10 MGy. The color and hardness of the fabricated glasses were affected by the fast neutron fluence where the transparent glasses turned colored as well as the hardness of the fabricated glasses was decreased. The gamma-ray spectrometric analysis shows a high activity concentration produced in the barium borate glasses due to the formation of radioisotopes Ba-131 and Ba-133 reaches to 5.92E+05 Bq and 4.25E+03 Bq, respectively for sample Cd-5 Batch 3. Additionally, the gamma-ray spectrometric analysis for the sodium silicate glasses shows low activity concentrations emitted from isotopes formed due to the activation of Y₂O₃-associated impurities. These activities are low compared to that emitted by barium borate-based glasses.

• Journal of the Korean Ceramic Society
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• v.26 no.4
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• pp.521-531
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• 1989

The dependence of the chemical durability of simulated waste glasses containing the simplified waste similar to the SRP waste on compositions of host glasses, amounts of waste loading, and kinds of leachants has been investigated as a basic study on the waste immobilization through vitrification. The maximum limit of the amount of waste loading for glassforming with the host sodium borosilicate glasses selected in this study was 50wt%. The chemical durability of waste glasses whose host glass belonged to the immiscible composition region was much higher than that of waste glasses whose host glass belonged to the miscible composition region. The former waste glass showed lower chemical durability in deionized and silicate waters than in brine, while the latter glass showed the lowest chemical durability in deionized and silicate waters than in brine, while the latter glass showed the lowest chemical durability in silicate water. It was also observed that the total leaching rates in brine were noticeably small in comparison with those in other solutions. The composition of the host borosilicate glass which was suitable for the treatment of the waste through vitrification was found to be 25 Na2O-5B2O3-70SiO2(wt.%).

• Journal of the Korean Ceramic Society
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• v.40 no.8
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• pp.725-729
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• 2003

The fluorine doping along with heavy metal oxides remarkably raised the $^3$H$_4$ lifetime and the quantum efficiency in Tm$^{3+}$-doped silicate glasses. 29 mol% of fluorine substitution for oxygen in 70SiO$_2$-15Pbo-12ZnO-3KO$_{1}$2/ glass raised $^3$H$_4$ lifetime to 193 $mutextrm{s}$. Refractive indices were raised by heavy metal oxide substitution, but hardly changed by fluorine substitution. The fluorine doping changed the local structure around Tm$^{3+}$ions, then low energy vibrations related to fluorine are considered to largely reduce the multi-phonon relaxation rates in the oxyfluoride silicate glasses. The $^3$H$_4$ lifetimes and absorption and emission spectra of Tm$^{3+}$doped silicate and oxyfluoride silicate glasses are reported, and Judd-Ofelt calculation results are discussed in this paper.

• Journal of the Korean Ceramic Society
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• v.56 no.2
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• pp.167-172
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• 2019

Silicate glasses with varying SiO₂ and Na₂O contents were prepared and their viscous flow property at the elevated temperature was studied. When the glass powders were packed and sintered at 550℃ to examine their feasibility as a low sintering temperature glass frit, contrary to expectations, glasses with lower SiO₂ content than 60 mol% showed no vitrification after sintering. High temperature microscopy revealed the viscous flow change of the silicate glasses with varying temperature and duration time and also indicated that the viscous flow was limited at low SiO₂ content. X-ray diffraction (XRD) on the sintered samples and Raman spectroscopy were carried out to shed light on the compositional dependency of viscous flow of silicate glasses.

• Journal of the Mineralogical Society of Korea
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• v.18 no.1
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• pp.45-52
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• 2005

The recent development and advances in 2 dimensional solid-state NMR, particularly, triple quantum (3Q) MAS NMR yield much improved resolution compared with conventional 1 dimensional MAS NMR, allowing us to study the distributions of cations and anions in the non-crystalline silicate glasses and melts. Here, we present the recent progress made by 3QMAS NMR spectra of silicate glasses quenched from melts at pressures up to 10 GPa in a multi-anvil apparatus, revealing previously unknown details of structures of covalent oxide glasses and melts at high pressure.

• Journal of the Korean Ceramic Society
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• v.20 no.3
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• pp.250-254
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• 1983

The effects of the various amount of $CeO_2$ $MnO_2$ and $Fe_2O_3$ added to the high lead-silicate glasses on the X-ray induced coloration were studied. The light transmissions and chromaticities of the glasses before and after exposing to X-ray radiation were measured to investigate the effects by additivies. The results are as follows ; 1. High lead-silicate glass added $CeO_2$ or $MnO_2$ has a little effect on the transmission but has a considerable effect on the chromaticity. The chromaticies of 56.6wt% PbO content glasses were changed as 3-7 times as those of 28.3wt% PbO content glasses. 2. By the X-ray irradiation glasses containing 0.2-0.5wt% $CeO_2$ were changed the least in chromaticity that is the most effective in preventing the X-ray induced coloration. 3. By X-ray irradiation $MnO_2$ reduced the transmissions and showed purple coloration. 4. Transmission change amounts of the glasses added $CeO_2$ and $Fe_2O_3$ were less than those of the glasses added $CeO_2$ alone by X-ray irradiation.

• Journal of the Mineralogical Society of Korea
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• v.31 no.4
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• pp.295-306
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• 2018

Despite the utility of solid-state NMR, NMR studies of iron-bearing silicate glasses remain a challenge because the variations in the peak position and width with increasing iron content reflect both paramagnetic effect and iron-induced structural changes. Therefore, it is essential to elucidate the effect of temperature on the NMR signal for iron-bearing silicate glasses. Here, we report the $^{29}Si$ and $^{27}Al$ MAS NMR spectra for $(Mg_{0.95}Fe_{0.05})SiO_3$ and $Fe_2O_3$-bearing $CaAl_2Si_2O_8$ (anorthite) glasses with varying spinning speed to interpret the NMR spectra for iron-bearing silicate glasses. The increase in the spinning speed results in an increase in the sample temperature. The current NMR results allow us to understand the origins of the changes in NMR signal with increasing iron content and to provide information on the dipolar interaction between nuclear spins. The $^{29}Si$ NMR spectra for $(Mg_{0.95}Fe_{0.05})SiO_3$ glass and $^{27}Al$ NMR spectra for $Fe_2O_3$-bearing $CaAl_2Si_2O_8$ glasses show that the peak shape and position of iron-bearing glasses do not change with increasing spinning speed up to 30 kHz. These results suggest that the NMR signal in the Fe-bearing glasses may stem from the 'survived nuclear spins' beyond the cutoff radius from the Fe, not from the paramagnetic shift. Based on the current results, the observed apparent shifts toward lower frequency of Al peak for $Fe_2O_3$-bearing $CaAl_2Si_2O_8$ glasses with increasing $Fe_2O_3$ at all spinning speed (15 kHz to 30 kHz) indicate the increase in the fraction of ${Q^4}_{Al}$(nSi) with lower n (i.e., 1 or 2) with increasing $Fe_2O_3$ and the spatial proximity between Fe and ${Q^4}_{Al}$(nSi) with higher n (i.e., 3 or 4). The present results show that changes in the NMR signal for iron-bearing silicate glasses reflect the actual iron-induced structural changes. Thus, it is clear that the applications of solid-state NMR for iron-bearing silicate glasses hold strong promise for unraveling the atomic structure of natural silicate glasses.

• Journal of Welding and Joining
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• v.16 no.2
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• pp.122-128
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• 1998

This investigation was performed to collect fundamental informations concerning the behavior of glass solders on ceramic joining process. The wettability of glasses on two types of alumina was evaluated by sessile drop method. SiO$_2$-CaO-Al$_2$O$_3$system glasses were selected as solder glasses, and alumina that have different purities were used for substrate materials. It is indicated that contact angles of glasses on 99% purity of alumina substrate do not change as increasing time at elevated temperature, however the contact angles on the 92% purity of alumina substrate exhibit the strong time dependency. The time-dependent property on 92% alumina was due to the interlayer reactions occurred between the glass solder and impurities on the substrate.

• Journal of the Korean Ceramic Society
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• v.48 no.2
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• pp.117-120
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• 2011

In this study, the redox state of iron in sodium silicate glasses was varied by changing the melting conditions, such as the melting temperature and particle size of iron oxide. The oxidation states of the iron ion were determined by wet chemical analysis and UV-Vis spectroscopy methods. Iron commonly exists as an equilibrium mixture of ferrous ions, $Fe^{2+}$, and ferric ions $Fe^{3+}$. In this study, sodium silicate glasses containing nanoparticles of iron oxide (0.5% mol) were prepared at various temperatures. Increase of temperature led to the transformation of ferric ions to ferrous ions, and the intensity of the ferrous peak in 1050 nm increased. Nanoparticle iron oxide caused fewer ferrous ions to be formed and the $\frac{Fe^{2+}}{Fe^{3+}}$ equilibrium ratio compared to that with micro-oxide iron powder was lower.

• Journal of the Mineralogical Society of Korea
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• v.24 no.4
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• pp.301-312
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• 2011

The study on the atomic structure of iron-bearing silicate glasses has significant geological implications for both diverse igneous processes on Earth surface and ultra-low velocity zones at the core-mantle boundary. Here, we report experimental results on the effect of iron content on the atomic structure in iron-bearing alkali silicate glasses ($Na_2O-Fe_2O_3-SiO_2$ glasses, up to 16.07 wt% $Fe_2O_3$) using $^{29}Si$ and $^{17}O$ solid-state NMR spectroscopy. $^{29}Si$ spin-lattice ($T_1$) relaxation time for the glasses decreases with increasing iron content due to an enhanced interaction between nuclear spin and unpaired electron in iron. $^{29}Si$ MAS NMR spectra for the glasses show a decrease in signal intensity and an increase in peak width with increasing iron content. However, the heterogeneous peak broa-dening in $^{29}Si$ MAS NMR spectra suggests the heterogeneous distribution of $Q^n$ species around iron in iron-bearing silicate glasses. While nonbridging oxygen ($Na-O-Si$) and bridging oxygen (Si-O-Si) peaks are partially resolved in $^{17}O$ MAS NMR spectrum for iron-free silicate glass, it is difficult to distinguish the oxygen clusters in iron-bearing silicate glass. The Lorentzian peak shape for $^{29}Si$ and $^{17}O$ MAS NMR spectra may reflect life-time broadening due to spin-electron interaction. These results demonstrate that solid-state NMR can be an effective probe of the detailed structure in iron-bearing silicate glasses.