Properties Of Sodium Borosilicate Glasses Research Articles

Mechanical properties and structural evolution of sodium borosilicate glasses during uniaxial tension: Molecular dynamics simulation and experiments

The mechanical properties and structural evolution of sodium borosilicate glasses under the uniaxial tensile process were investigated through molecular dynamics simulation. The simulated properties of sodium borosilicate glasses were in good agreement with the experimental values. [BO3] and Na+ compensated [BO4] groups were generated in the glass network in low boron content, while [BO3] appeared with increasing boron oxide. The structure descriptor, Fnet synthesized the structure and energy information of the glass network which was positively correlated with Young's modulus. The strength has been diminished due to the decreased degree of polymerization of the glass network and the migration of Na+ cations. Simultaneously, the elastic deformation of sodium borosilicate glass arose from the motion of Na+ cations and alterations in the Si-O-Si bond angle. Moreover, the plastic deformation of sodium borosilicate glasses was attributed to the transition from [BO4] to [BO3] and the higher mobility of [BO3] than [BO4] and [SiO4].

Influence of sodium oxide substitution on structural and gamma-ray radiation shielding properties of sodium borosilicate glass

In this paper, borosilicate glasses with varying concentrations of sodium oxide were synthesized using the melt-quenching method. The amorphous nature of the glasses under investigation, with a composition of (20 + x)Na2O-(60-x)B2O3–20SiO2 (where x = 0, 3, 5, 7, 8, 10, 13, 15, 17, and 20 mol%), was confirmed through X-ray diffraction (XRD) analysis. Fourier-transform infrared (FT-IR) spectroscopy was employed to analyze the glasses and revealed an increase in the concentration of non-bridging oxygen atoms (NBO) with increasing amounts of Na2O. The N4 parameter, which represents the fraction of NBOs, was calculated and found to decrease from 74% to 52% as the concentration of Na2O increased. The density of the glasses increased from 2.391 g/cm3 to 2.744 g/cm3 when B2O3 was replaced with Na2O, while the molar volume decreased from 27.68 cm3/mol to 23.56 cm3/mol. Theoretically, theoretical calculations were performed using newly developed computer software called Phys-PSD to assess their shielding properties, including attenuation coefficients, half value layer, and buildup factors. The calculations were conducted in the energy range of 0.015–15 MeV. The results indicated that the synthesized glasses exhibited promising potential as radiation shields.

Effect of compression temperature on the structure and properties of hot compressed sodium borosilicate glasses from molecular dynamics simulations

Applying pressure during glass formation or annealing is an effective method to modify the properties of oxide glasses. The effect of compression temperature on the structure and properties of a sodium borosilicate glass has been investigated using molecular dynamics simulations. The connection between macroscopic properties (density and elastic moduli) and microscopic structures (short- and medium-range order) was investigated. Young’s modulus increased with the compression temperature and then reached a plateau at temperatures close to the glass transition temperature. The modulus increase was found to correlate linearly with glass density change. Correlations with structural changes, such as fraction of four-fold coordinated boron, oxygen triclusters, sodium ion coordination number and the Na–O and Na–Na distances were studied. The results suggest that the pressure-induced transformation from three-fold to four-fold coordinated boron was achieved through the formation of oxygen triclusters, which is different from the commonly observed mechanism involving nonbridging oxygen during the boron coordination change. In addition, the linear correlation between sodium coordination number and glass density suggests that change of sodium ion local environment and redistribution of sodium ions also play an important role in the property behaviour during pressure quenching of the glasses.

The effects of phosphorus pentoxide additions on the thermal, rheological, and structural properties of sodium borosilicate glass

This research has characterized the effects of P2O5 additions on the physical, chemical, thermal, rheological properties and the structure of SiO2-B2O3-Na2O glasses relevant to radioactive waste immobilization. Properties analysed include high-temperature viscosity, glass transition temperature (Tg) and structure. X-ray diffraction (XRD) confirmed a solubility limit of between 3.0 and 4.0 mol% P2O5 for the onset of crystallinity with formation of Na3PO4 and Na4P2O7 in annealed bulk glasses; and between 4.0 and 5.0 mol% P2O5 in unannealed (quenched) glasses. This difference in behaviour is attributed to the bulk glass annealing temperature being greater than Tg of phase-separated, phosphate-rich droplet phases present in the 4.0 mol% P2O5 glass, which promoted crystallization, where back scattered scanning electron microscopy (SEM) images suggested that phase separation had occurred as liquid-liquid phase separation, where there was evidence of a droplet like morphology in glasses containing between 4.0 and 6.0 molar % P2O5. However, the exact mechanism cannot be unequivocally confirmed as nucleation and growth based purely on phase morphology. Differential Thermal Analysis (DTA) and dilatometry showed modest increases in Tg with increasing P2O5 contents below the onset of crystallisation and a more substantial increase coinciding with the onset of crystallisation between 3.0 and 4.0 mol% P2O5. High-temperature viscosity measurements showed that increasing P2O5 contents led to increases in viscosity, with samples containing the highest P2O5 additions displaying non-Newtonian behaviour consistent with the presence of crystals in the melt at 950 °C. Raman difference spectra showed that the increase in P2O5 content resulted in characteristic peak intensities at 729 cm−1, 937 cm−1, 1000 cm−1, 1026 cm−1, 1109 cm−1 and 1445 cm−1 which were associated with phosphate species.

Thermal properties of sodium borosilicate glasses as a function of sulfur content

AbstractSulfur trioxide (SO3) additions, up to 3.0 mass%, were systematically investigated for effects on the physical properties of sodium borosilicate glass melted in air, with a sulfur‐free composition of 50SiO2–10Al2O3–12B2O3–21Na2O–7CaO (mass%). Solubility measurements, using electron microscopy chemical analysis, determined the maximum loading to be ~1.2 mass% SO3. It was found that measured sulfur (here as sulfate) additions up to 1.18 mass% increased the glass transition temperature by 3%, thermal diffusivity by 11%, heat capacity by 10%, and thermal conductivity by 20%, and decreased the mass density by 1%. Structural analysis, performed with Raman spectroscopy, indicated that the borosilicate network polymerized with sulfur additions up to 3.0 mass%, presumably due to Na2O being required to charge compensate the ionic additions, thus becoming unavailable to form non‐bridging oxygen in the silicate network. It is postulated that this increased cross‐linking of the borosilicate backbone led to a structure with higher dimensionality and average bond energy. This increased the mean free paths and vibration frequency of the phonons, which resulted in the observed increase in thermal properties.

Effect of the iron content on the structure and electrical properties of sodium borosilicate glasses: XRD, TEM, Mössbauer, FTIR and DIS spectroscopy study

The iron-bearing sodium borosilicate glasses with different contents of iron were prepared by the charge melting method and studied by XRD, TEM, FTIR, Mössbauer and Dynamic Impedance Spectroscopy techniques. An analysis and the transmittance spectra of two-phase sodium borosilicate glasses with different contents of iron oxide were carried out. A usage of the Mössbauer spectroscopy revealed differences between two-phase and porous glasses. In both cases Fe2+ and Fe3+ ions in octahedral and tetrahedral coordination were found, while in the two-phase glasses the significant contribution of magnetite was additionally detected. The activation energy associated with the relaxation processes determined from the electric modulus spectra was found to be in a range between 0.986 eV and 0.729 eV, which is close to the activation energy for dc conductivity. Two different conduction mechanisms were observed and their physical origin was explained. The hopping between two valence states of iron and the sodium ion conduction mechanism was additionally discussed.

Effects of energy deposition on mechanical properties of sodium borosilicate glass irradiated by three heavy ions: P, Kr, and Xe

Sodium borosilicate glasses are candidate materials for high-level radioactive waste vitrification; therefore, understanding the irradiation effects in model borosilicate glass is crucial. Effects of electronic energy deposition and nuclear energy deposition induced by the impact of heavy ions on the hardness and Young’s modulus of sodium borosilicate glass were investigated. The work concentrates on sodium borosilicate glasses, henceforth termed NBS1 (60.0% SiO2, 15.0% B2O3, and 25.0% Na2O in mol%). The NBS1 glasses were irradiated by P, Kr, and Xe ions with 0.3 MeV, 4 MeV, and 5 MeV, respectively. The hardness and Young’s modulus of ion-irradiated NBS1 glasses were measured by nanoindentation tests. The relationships between the evolution of the hardness, the change in the Young’s modulus of the NBS1 glasses, and the energy deposition were investigated. With the increase in the nuclear energy deposition, both the hardness and Young’s modulus of NBS1 glasses dropped exponentially and then saturated. Regardless of the ion species, the nuclear energy depositions required for the saturation of hardness and Young’s modulus were apparent at approximately 1.2 × 1020 keV/cm3 and 1.8 × 1020 keV/cm3, respectively. The dose dependency of the hardness and Young’s modulus of NBS1 glasses was consistent with previous studies by Peuget et al. Moreover, the electronic energy loss is less than 4 keV/nm, and the electronic energy deposition is less than 3.0 × 1022 keV/cm3 in this work. Therefore, the evolution of hardness and Young’s modulus could have been primarily induced by nuclear energy deposition.

Effects of system size and cooling rate on the structure and properties of sodium borosilicate glasses from molecular dynamics simulations.

Borosilicate glasses form an important glass forming system in both glass science and technologies. The structure and property changes of borosilicate glasses as a function of thermal history in terms of cooling rate during glass formation and simulation system sizes used in classical molecular dynamics (MD) simulation were investigated with recently developed composition dependent partial charge potentials. Short and medium range structural features such as boron coordination, Si and B Qn distributions, and ring size distributions were analyzed to elucidate the effects of cooling rate and simulation system size on these structure features and selected glass properties such as glass transition temperature, vibration density of states, and mechanical properties. Neutron structure factors, neutron broadened pair distribution functions, and vibrational density of states were calculated and compared with results from experiments as well as ab initio calculations to validate the structure models. The results clearly indicate that both cooling rate and system size play an important role on the structures of these glasses, mainly by affecting the 3B and 4B distributions and consequently properties of the glasses. It was also found that different structure features and properties converge at different sizes or cooling rates; thus convergence tests are needed in simulations of the borosilicate glasses depending on the targeted properties. The results also shed light on the complex thermal history dependence on structure and properties in borosilicate glasses and the protocols in MD simulations of these and other glass materials.

Effect of La2O3 addition on structural and electrical properties of sodium borosilicate glasses

Sodium borosilicate glasses doped with lanthanum oxide were prepared using conventional melt quench technique. The XRD study of the glasses were carried out to affirm the amorphous nature of glass. The glass transition temperature Tg and crystallization temperature Tc were determined from the DTA. It is observed that Tg increases with the addition of La2O3. This increase in Tg is supported by density results.. The conductivity of the prepared glasses were studied using impedance analyzer in the frequency interval 20 MHz–2 mHz and in the wide temperature range 423 K–673 K. The obtained data has been correlated with various other parameters like density, molar volume and glass transition temperature. Modulus formalism is introduced to study relaxation behavior of these glasses. The overlapping of data on single master curve indicates that conduction mechanism in these glasses is compositional dependent and temperature independent. There is a good correlation between physical and electrical properties.

Synthesis, electrical and magnetic properties of sodium borosilicate glasses containing Co-ferrites nanoparticles

Co-ferrites nanoparticles that have been prepared by the co-precipitation method were added to sodium borosilicate (Na2O–B2O3–SiO2) glass matrix by the solid solution method and they were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) and magnetization measurements. (XRD) revealed the formation of the Co-ferrite magnetic crystalline phase embedded in an amorphous matrix in all the samples. The investigated samples by (TEM) showed the formation of the cobalt ferrite nanoparticles with a spherical shape and highly monodispersed with an average size about 13nm. IR data revealed that the BO3 and BO4 are the main structural units of these samples network. IR spectra of the investigated samples showed the characteristic vibration bands of Co-ferrite. Composition and frequency dependent dielectric properties of the prepared samples were measured at room temperature in the frequency range 100–100kHz. The conductivity was found to increase with increasing cobalt ferrite content. The variations of conductivity and dielectric properties with frequency and composition were discussed. Magnetic hysteresis loops were traced at room temperature using VSM and values of saturation magnetization MS and coercive field HC were determined. The obtained results revealed that a ferrimagnetic behavior were observed and as Co-ferrite concentration increases the values of MS and HC increase from 2.84 to 8.79(emu/g) and from 88.4 to 736.3Oe, respectively.

Morphology and magnetic properties of ferriferous two-phase sodium borosilicate glasses.

This contribution is devoted to the study of morphology and magnetic properties of sodium borosilicate glasses with different concentrations (15, 20, and 25 wt.%) of α-Fe2O3 in an initial furnace charge. These glasses were prepared by a melt-quenching method. For all glasses a coexistence of drop-like and two-phase interpenetrative structures is observed. The most part of a drop structure is formed by self-assembling iron oxides particles. All types of glasses demonstrate the magnetic properties and can be used for preparation of porous magnetic matrices with nanometer through dendrite channel structure.

Direct Calculation of the Physical Properties of Sodium Borosilicate Glass from its Chemical Composition Using the Concept of Structural Units

The physical properties of sodium borosilicate glasses were calculated directly from their chemical compositions in the whole glass‐forming region. These properties included molar volume, refractive index, thermal expansion coefficient, elastic moduli, and glass transition temperature. The physical property values corresponding to the structural unit were estimated and then the calculation was carried out by accumulating the physical property values depending on the chemical composition of the glass. In the case of sodium borosilicate glass, the structural units are BO3/2, BO4/2Na, BO2/2ONa, BO1/2O2Na2, SiO4/2, SiO3/2ONa, SiO2/2O2Na2, and SiO1/2O3Na3. To conduct the calculation, the structural units’ physical property values were estimated by analyzing experimental data extracted from the database of glass properties, INTERGLAD. The calculated values were similar to the experimental data in the whole glass‐forming region. Furthermore, the calculation method provided, quantitatively, the structural units’ contributions to the glass’ physical properties. This study demonstrates that using the concept of structural units to calculate the physical properties of sodium borosilicate glass is a simple and powerful predictive tool.

Effect of BaO addition on the structural aspects and thermophysical properties of sodium borosilicate glasses

Sodium borosilicate glasses containing different amounts of BaO were prepared by a conventional melt quench method and characterized for their structural aspects by 29Si, 11B NMR and IR spectroscopy. From 29Si MAS NMR studies, it has been inferred that these glasses consist of Q 2 and Q 3 structural units of silicon and that the addition of BaO results in the marginal conversion of Q 3 to Q 2 structural units. There is no direct interaction between Ba 2+ ions and boron structural units, as revealed by the identical values of the relative concentration of BO 3 and BO 4 structural units and quadrupolar coupling constant values for the BO 3 structural units. The identical values of glass transition temperature and vibrational frequencies corresponding to Si–O–Si/Si–O–B and B–O linkages of all the samples further support this. As the borosilicate network is unaffected, the systematic increase in the values of thermal expansion coefficient with increase in BaO content has been attributed to the increase in the relative concentration of less rigid Ba–O linkages compared to the more rigid Si–O and B–O linkages in the glass. Such studies will be useful for the development of matrices for the management of nuclear waste generated during the reprocessing of the spent fuel from thoria based reactors.

Low-temperature heat capacity of sodium borosilicate glasses at temperatures from 13 K to 300 K

Thermodynamic properties of sodium borosilicate glasses {56.7 SiO2, (43.7 −x)B2O3,xNa2O} wherex= 14.4, 22.9, and 32.5, have been studied. The heat capacity was measured using an adiabatic calorimeter at temperatures between 13 K and 300 K. The thermodynamic functions were calculated from the smoothed values ofCp, m . The results differ from an additive model with pure glassy SiO2, B2O3, and crystalline Na2O as components. A model based on the assumption that the contribution of structural units of glasses to the heat capacity is equal to those of glasses with the same molecular formula is proposed.

Phase separation and physical properties of sodium borosilicate glasses with intermediate silica content

Microstructures of sodium borosilicate glasses with intermediate silica content, doped with CuO, were examined. Electron micrographs of heat-treated glasses show two randomly distributed phases. DC conductivity measurements indicate that alkali oxide is associated with B2O3. CuO is assumed to act as a network modifier in the borate matrix and does not affect the phase separation process. Optical absorption in the UV and visible regions was also examined. Phase separation causes a shift of the UV edge towards longer wavelengths, which is considered to be a result of light scattering on SiO2-rich particles produced by heat treatment.

Structural peculiarities of sodium borosilicate glasses in relation to chemical stability

1. Structural changes in porous glasses obtained from low-alkali sodium borosilicate glasses are found to be directly related to structural changes in the original glass, which depend on composition and heat treatment. 2. The structural transformations occurring in sodium borosilicate glasses consist in the formation of polar [B−(O2)4 Na+ groups, the association of these into borate complexes, changes in the number and dimensions of the complexes, the character of their distribution in the glass and the connections between them. 3. Many of the properties of sodium borosilicate glasses, and the complex nature of the dependence of these on the composition and heat treatment of the glass, are directly or indirectly related to these structural changes.