Ratio Of Non-bridging Oxygens Research Articles

Structural, linear and nonlinear optical properties of perovskite BaTiO3 tri-doped Er/Yb/Zn embedded in tellurium-zinc glass

Due to their excellent nonlinear optical characteristics, tellurium-zinc glass and perovskite structures have gained significant attention. In particular, perovskite-type BaTiO3 shows excellent potential for application in photonics devices. This study investigates structural, linear, and nonlinear optical properties of pure tellurium-zinc glass with embedded perovskites. Both glasses were prepared using the conventional melt-quenching method, and their structural modifications were analyzed through Raman spectroscopy. Optical absorption spectra revealed a redshift in the absorption edge, indicating a decrease in the band gap energy by the presence of the perovskite nanoparticles. When adding perovskite nanoparticles, Raman scattering results demonstrated decreased bridging and non-bridging oxygen ratio and structural changes. This suggests that the perovskite nanoparticles alter the local environment by affecting the Te-O- Zn2+ or Te=O bonds, resulting in a variation of the polarizability. Finally, the average nonlinear refractive for the glass containing perovskite nanoparticles is on the order of 0.3 × 10−18 m2 W−1 in the wavelength range of 580–990 nm, which is the same as of the pure glass. Thus, while the NP particles influence the arrangement of structural units and the linear optical response, their impact is not significant in the nonlinear refractive index. The observed modifications in structural and optical properties are relevant for advancing the use of perovskites in photonics.

Platinum solubility in silicate melts: The effects of sulfur (S2–), temperature, and melt composition

Platinum (Pt) solubility in silicate melt (SolPtSil) has been determined to understand its behavior in planetary magmas. However, the effect of sulfur (S) in the silicate melt on SolPtSil was paid little attention. Here we present experiments performed at 1–1.5 GPa, 1300–1700 °C, and oxygen fugacity (fO2) from IW−1.6 to IW+2.3 (IW denotes the iron–wüstite buffer) to determine SolPtSil for silicate melts with major element compositions corresponding to those of rhyolite, mid-ocean ridge basalt, high-FeO basalt, and Martian basalt. The results show that SolPtSil increases from ∼0.1 to 10 μg/g as the S content in silicate melt increases from nominally zero to ∼4000 μg/g, which indicates that Pt dissolves predominantly as Pt-sulfide species in S2–-bearing silicate melt. Our results also show that SolPtSil increases with increasing temperature and/or the silicate melt NBO/T (the ratio of non-bridging oxygens to tetrahedrally coordinated cations). Using our newly obtained SolPtSil and previous data, we developed an empirical model that describes SolPtSil as a multi-function of temperature, fO2, the silicate melt NBO/T, and the S2– content in silicate melt in the case at reducing conditions (fO2 < IW+3.5). The application of our empirical model to mantle partial melting suggests that Pt-rich alloys form only after sulfide liquid exhaustion because of the S-enhanced SolPtSil. We also applied our empirical model to predict the behavior of Pt during arc magmatic differentiation. The results agree with the observations that Pt-rich alloys formed before the saturation of sulfides in the oxidized Pual Ridge lavas. We suggest that the observed coexistence of Pt-bearing alloys and sulfide globules in oxidized arc magmas can be explained by an early formation of Pt-bearing alloys followed by a late formation of sulfide liquids. The strong effect of S2– on SolPtSil also implies that the oxidization of magmatic melts can lead to direct precipitation of Pt-bearing alloys due to the S2– to S6+ transformation, which can also be subsequently entrapped in the sulfide liquids formed later. Finally, our results show a strong effect of S2– in the silicate melt on lowering the metal–silicate melt partition coefficients of Pt, which should be considered when using Pt to trace planetary accretion and differentiation processes. Collectively, our study demonstrates an important role for S2– in controlling the behavior of Pt during planetary core–mantle–crust differentiation.

Mixed alkaline earth effect on the structure and elastic modulus of CaO–MgO–Al2O3–SiO2 glasses: A molecular dynamics simulation

The influence of mixed alkaline earth effect on the atomic structure and elastic modulus of the CaO–MgO–Al2O3–SiO2 glasses were studied by molecular dynamics simulation. The elastic modulus values obtained from the simulation of uniaxial tension and stiffness tensor methods showed the same trend with the change of composition, while the simulated results of the former were closer to the measured data. The variation trend of Qn species obtained by the simulation and Raman spectroscopy was consistent. Ca and Mg cations were more inclined to form non-bridging oxygen when the Ca/Mg ratio exceeded 1, which damaged the tetrahedral connection and further reduced the degree of network polymerization. The ratio of non-bridging oxygen to tetrahedrally coordinated cations (NBO/T) used to characterize the degree of polymerization was found to have a linear relationship with the elastic modulus. In addition, the local cluster of modifier atoms was beneficial to increase the elastic modulus values.

Apatite as a magma redox indicator and its application in metallogenic research

As an early crystallizing phase in the magma, apatite can accommodate a wide range of multivalent cations and has a capacity resistant to weathering and hydrothermal alteration. These features enable apatite to record the primary redox state of precursor magma. Here, we present new electron probe microanalysis (EPMA) and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) geochemical data on apatite and zircon grains from the epithermal gold ore-hosting Dahalajunshan Formation volcanics in the Tulasu basin (Western Tianshan Orogen, Central Asia). Calculated zircon Ce-/Ti-based oxybarometric results and sulfur content of apatite suggest that the parental magma of the volcanics was relatively oxidized. Furthermore, we compiled a regional apatite chemical dataset to assess whether other elements (Mn, V, Eu, Ce, As and Ga) in apatite can serve as a magma redox proxy. Negative correlation between apatite Mn and whole-rock MgO is evident, implying the control of magma fractionation on apatite Mn contents. Also, oxygen fugacity ( f O 2 ) calculated by Mn-in-apatite oxybarometer correlates strongly with magma fractionation, which indicates that fractional crystallization (instead of f O 2 ) controlled the Mn-uptake in apatite. The apatite As budget is sensitive to f O 2 variation but does not show any correlation with the ratio of nonbridging oxygens to tetrahedral cations (NBO/T), whole-rock SiO 2 , or aluminum saturation index. In contrast, apatite V and Ga contents correlate obviously with whole-rock SiO 2 and NBO/T but not f O 2 , and apatite Eu and Ce anomalies show no correlation with f O 2 . Therefore, we conclude that only the apatite As and S contents can reflect the magma redox state. The calculated f O 2 of the Dahalajunshan Formation volcanic rocks is ΔFMQ+0.53 ± 0.52 (based on the fayalite+magnetite+quartz buffer), which is markedly lower than those of typical porphyry Cu ore-forming magmas worldwide. Thus, from the perspective of magma f O 2 , regional magma is inferred to have little potential to form the porphyry Cu deposit. • Accurate f O 2 values by S-in-apatite show the potential to replace zircon oxybarometer. • S and As in apatite can record the magma f O 2 value, instead of Mn, V, Eu, Ce, and Ga. • Tectonic setting and porphyry Cu ore-forming potential were analyzed by magmatic f O 2 .

Correlating slag chemistry to setting and mechanical behaviors of alkali-activated slag

Aiming at uncovering the critical chemical parameters that govern the performance of alkali-activated slag (AAS), this work investigates the phase assemblage, microstructure, and setting and mechanical properties of AAS prepared using five different slags and two activators (sodium hydroxide or sodium carbonate). The results suggest that the ratio of non-bridging oxygens to tetrahedral cations (NBO/T) of slag structure is an appropriate reactivity indicator, correlating reasonably well with the mechanical performance of AAS at late ages. However, the NBO/T value of slag structure is relatively incompetent in indicating the setting performance of AAS, particularly for the sodium carbonate-activated system. The variability of slag chemistry has considerable impacts on the setting behaviors of AAS, but relatively insignificant effects on compressive strength, suggesting that the strength of AAS is dominated by activator and mixture proportioning parameters. Regardless of activator chemistry, the AAS with a higher amount of hydrotalcite formation tends to have higher compressive strength, implying the beneficial roles of hydrotalcite in microstructure densification and strength achievement.

Experimental determination of N2 solubility in silicate melts and implications for N2–Ar–CO2 fractionation in magmas

The solubility of nitrogen in magmatic melts is key for understanding the degassing of Earth’s interior and formation of Earth’s N-rich atmosphere. We performed high-pressure experiments to determine the solubility of nitrogen at N2-saturation in basaltic to granitic melts at pressures of 0.3–8 GPa, temperatures of 1200–1600 °C, and oxygen fugacities between the Fe–FeO and Ni–NiO oxygen buffers. The solubility and speciation of nitrogen in the quench silicate melts were quantified by Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), electron probe microanalyzer (EPMA), and Nano-scale secondary ion mass spectrometry (NanoSIMS). The results show that the predominant N-species in our silicate melts is N2, which dissolves physically by filling the interstitial sites of the silicate melt network. The measured N-solubilities in silicate melts (SN2melt) by using different approaches agree with each other, and they vary from 200 to 17,000 ppm by weight. The SN2melt increases with increasing pressure and/or decreasing silicate melt NBO/T (the ratio of non-bridging oxygens to tetrahedrally coordinated cations), but it is temperature-independent. Using our newly obtained SN2melt and previous SN2melt and SArmelt data, we develop an empirical model that describes the physical dissolution of N2 and Ar in silicate melts as a function of gas partial pressure and silicate melt composition, and this model can be used to predict SN2melt and SArmelt in magmatic melts of Earth’s mantle and crust. The comparison of our SN2melt data with previous SArmelt and SCO2melt data shows that the solubility in granitic melts is in the order of SArmelt >SCO2melt >SN2melt, but in basaltic melts it is in the order of SCO2melt >SArmelt > SN2melt. The lower SN2melt than SArmelt at Earth’s mantle and crustal conditions suggests N2–Ar fractionation during degassing of mid-ocean ridge basalts and arc magmas. Therefore, the N2/Ar ratios in degassed magmas may not fully represent those in their mantle source regions. The solubility-controlled, preferential degassing of N2 relative to CO2 in Earth’s oxidized shallow magma ocean, in conjunction with collision-induced atmospheric loss, can explain the superchondritic C/N ratio in the bulk silicate Earth. However, the two orders of magnitude higher N2/36Ar ratio in Earth’s mantle than in atmosphere could have resulted from preferential retention of reduced N-species in Earth’s reduced silicate magma ocean or preferential deep subduction of nitrogen.

SIMS oxygen isotope matrix effects in silicate glasses: Quantifying the role of chemical composition

Instrumental mass fractionation (IMF) associated with Secondary Ion Mass Spectrometry (SIMS) measurements of oxygen isotope compositions in silicate glasses was studied using a set of 27 synthesized glasses spanning a compositionally broad range of six major oxides: SiO2, TiO2, Al2O3, total FeO (FeOt), MgO and CaO. The impact of chemical composition on the IMF values was investigated using a Cameca 1280-HR during a single SIMS analytical session operated under constant instrumental conditions. The data measured were compared with the δ18O values obtained by laser fluorination gas source mass-spectrometry (LF). The offset between the δ18O(LF) and δ18O(SIMS) was found to reach up to 5‰. Our data document that SIMS oxygen isotope matrix effects in silicate glasses strongly depend on the chemical composition of silicate glasses, here the cation‑oxygen bond strength was found to have a strong influence on the IMF value. We tested a variety of models based on single oxide contents and various composition-dependent parameters, but none were fully satisfactory for predicting IMF. Neither mean atomic mass nor NBO/T (the ratio of non-bridging oxygens per tetrahedrally coordinated cation) show a strong correlation with the IMF values (R2 of 0.45 and 0.46, respectively). Among the single oxides, only the model based on the SiO2 content is useful for prediction of the IMF in silicate glasses, but this model has a large standard error (1σ = ± 0.90‰) and was also found to break down for glasses with high Na and K contents. We propose an empirical model based on the correlation of six major element oxides that shows a strong correlation with IMF (R2 = 0.98, 1σ = ± 0.40‰). This model describes the experimental data with uncertainties that are roughly a factor of two better than the correction methods proposed in earlier studies. We also investigated using the correlation between IMF and isotope I-18O index, which describes the correlation between atomic bond strength and relative oxygen isotope enrichment in silicate substances (R2 = 0.87). Although our efforts provide refinements to the SIMS determination of δ18O in natural silicate glasses, truly accurate IMF corrections will need further refinements related to the impact of alkali elements.

Electrical conductivity of melts: implications for conductivity anomalies in the Earth's mantle.

Magmatic liquids, including silicate and carbonate melts, are principal agents of mass and heat transfer in the Earth and terrestrial planets, and they play a crucial role in various geodynamic processes and in Earth's evolution. Electrical conductivity data of these melts elucidate the cause of electrical anomalies in Earth's interior and shed light on the melt structure. With the improvement in high-pressure experimental techniques and theoretical simulations, major progress has been made on this front in the past several decades. This review aims to summarize recent advances in experimental and theoretical studies on the electrical conductivity of silicate and carbonate melts of different compositions and volatile contents under high temperature and pressure. The electrical conductivity of silicate melts depends strongly on temperature, pressure, water content and the ratio of non-bridging oxygens to tetrahedral cations (NBO/T). By contrast, the electrical conductivity of carbonate melts exhibits a weak dependence on temperature and pressure due to their fully depolymerized structure. The electrical conductivity of carbonate melts is higher than that of silicate melts by at least two orders of magnitude. Water can increase electrical conductivity significantly and reduce the activation energy of silicate melts. Conversely, this effect is weak for carbonate melts. In addition, the replacement of alkali-earth elements (Ca2+ or Mg2+) with alkali elements causes a significant decrease in the electrical conductivity of carbonate melts. A distinct compensation trend is revealed for the electrical conductivity of silicate and carbonate melts under anhydrous and hydrous conditions. Several important applications of laboratory-based melt conductivity are introduced in order to understand the origin of high-conductivity anomalies in the Earth's mantle. Perspectives for future studies are also provided.

Correlation of Phase Composition, Structure, and Mechanical Properties of Natural Basalt Continuous Fibers

This paper presents a study of the influence of basalt rocks’ phase composition, acidity modulus, and structural parameter NBO/T on the tensile strength and elastic modulus of basalt continuous fibers (BCFs) derived from them. A series of BCF samples based on 14 different basalt deposits was obtained under equal conditions. The tensile strength and elastic modulus of the BCFs from different deposits vary in the ranges of 1495–3380 MPa and 58.2–78.7 GPa, respectively. Using the original method of quantitative phase analysis based on the Rietveld method, the phase compositions of the 14 deposits were defined. All deposits can be used to obtain BCFs. In the studied natural rocks, the main component is tectosilicates; the mass content of framework aluminosilicates is in the range of 16.5–3.3 mass percent. The second main component is inosilicates; the mass content of chain aluminosilicates is in the range of 6.0–58.0 mass percent. The correlations among phase composition, acidity modulus, ratio of non-bridging oxygens to tetrahedral cations, tensile strength, and elastic modulus of the BCFs from the 14 different basalt deposits were calculated. There were strong positive correlation between tectosilicate minerals mass content and elastic modulus [Pearson correlation coefficient (PCC) of 0.7] and strong negative correlation between content of chain and layered aluminosilicates and elastic modulus (PCC of − 0.74).

Effective Binary Diffusivity of Silica and Viscosity of Silicomanganese Slag in the Smelting of Comilog and Wessels Ores

Reduction of manganese and silicon oxides in smelting of silicomanganese causes significant changes in slag composition and properties, increasing the slag viscosity and decreasing diffusivities of slag components. These changes can have a strong effect on the kinetics of reduction reactions. This paper analyses effective binary diffusivity of silica and slag viscosity in the process of smelting of silicomanganese from Comilog and Wessels ores. Compositions of slag and metal phases and slag viscosity were calculated using FACTSage Version 7.2 at 1450-1600 oC. Comilog ore contained high concentration of alumina while Wessels ore had lower concentrations of Al2O3 and MnO and higher concentrations of FeO and CaO in comparison with Comilog ore. Silica effective binary diffusivity and slag viscosity were related to the ratio of non-bridging oxygens per tetrahedrally coordinated cations (NBO/T), which decreased in the process of oxides reduction. Changes in the slag composition and NBO/T ratio caused increase in the slag viscosity and decrease in the effective binary diffusivity of silica in the smelting of Comilog ore by more than an order in magnitude. In the smelting of Wessels ore, slag viscosity increased and silica effective binary diffusivity decreased by approximately 5-fold

Effect of melting time on volatility, OH in glass in microwave processing

ABSTRACT Glass comprising of SiO2-B2O3-Na2O-CaO-K2O is melted at 1523 K in the microwave (MW) and conventional heating. Evaporation loss was studied with varying melting time (30 min to 3 h). Assessment of B2O3, a more volatile component in the studied composition, is carried out by adopting wet chemical method like volumetric titrimetry. The rate of evaporation loss (of B2O3) is found ~ 20% less in MW heating. The density of glass increases slightly with increasing melting time. Chemical analysis for other volatile ingredient, K2O using ICP-AES suggests higher yield in glass signifying less loss of K2O in MW heating. A study adopting X-ray photoelectron spectroscopy (XPS) indicates that the ratio of nonbridging oxygen (NBO) to the total oxygen in glass increases with melting time. This signifies a higher loss of glass network former like B2O3. OH content in conventional glass decreases with increasing soaking time at melting temperature whereas it initially increases with time and reduces beyond 120 min of soaking at melting temperature in MW furnace. A significant reduction in energy consumption and time savings in MW heating has been recorded.

Changes of Effective Binary Diffusivity of Silica and Viscosity of Silicomanganese Slag in the Process of Reduction of MnO and SiO2

Reduction of manganese and silicon oxides in smelting of silicomanganese causes significant changes in slag composition and properties: decreasing the ratio of non-bridging oxygens per tetrahedrally coordinated cations (NBO/T), increasing the slag viscosity, and decreasing diffusivities of slag components. These changes can have a strong effect on the kinetics of reduction reactions. This paper analyses effective binary diffusivity of silica and slag viscosity in the process of smelting of silicomanganese from Comilog ore. Compositions of slag and metal phases and slag viscosity were calculated using FACTSage V.7.2 at 1723 K to 1873 K (1450 °C to 1600 °C). Silica effective binary diffusivity and slag viscosity were related to the NBO/T ratio which decreased in the process of MnO and SiO2 reduction from 3.18 (molten charge) to 0.97 at 1723 K (1450 °C), 0.486 at 1773 K (1500 °C), and 0.38 at 1823 K to 1873 K (1550 °C to 1600 °C). Changes in the slag composition and NBO/T ratio caused increase in the slag viscosity and decrease in the effective binary diffusivity of silica by more than an order in magnitude.

Structure characterizations of SnF2-WO3-B2O3-P2O5 glass with ultra low transition temperature

Tinfluride-tungsten-borophosphate (SnF2-WO3-B2O3-P2O5) (SWBP) glass was prepared for sealant material by the traditional melt-quenching method. Full characterization has been carried out by FTIR and Raman spectra, as well as by the XPS spectroscopies, concluding that the non-bridging oxygen existed extensivelyin network, the ratio of non-bridging oxygen (NBO) to bridging oxygen (BO) was 16:1, which was considered to be sign of a stable structure. Meanwhile, the Sn(IV) to Sn(II) was 7:3, and the FSn to FP was 7:3. The distinct structure lead to unique properties. Differential scanning calorimetry (DSC) of glass showed that the transition temperature was below 150 °C, and no crystalline points were found. Relative to chemical stability, the glass exhibited remarkable water durability and have a weight loss about 0.5 wt% in immersing measurements. In addition, proposed glass powder showed superior liquidity on metal substrate at 300 °C, which provides new ideas for the development of lower temperature and environmentally friendly of sealant materials.

Molecular Dynamics Simulation of the Structure and Properties of CaO-SiO2-CaF2 Slag Systems

As a fundamental slag system in metallurgical processes, the CaO-SiO2-CaF2 system, its properties, and related microstructures are of critical importance. The effect of the binary basicity and addition of CaF2 on the structure and viscosity of CaO-SiO2-CaF2 slag were investigated using molecular dynamics simulations and Fourier transform infrared spectrometry. The average bond lengths of Si-O, Ca-O, and O-O were 1.61, 2.31, and 2.61 A, respectively, and the coordinate number of Si remained constant. O-Si-O maintained an angle of 109.2, which was considered to be unaffected by the basicity changes. With increasing basicity, the network connectivity degrees Q3 and Q4 decreased, and the microstructure of the melt was significantly simpler. The effect of CaF2 on the depolymerization of the network structure was not obvious, and CaF2 acted mainly as a diluent. The calculations showed that the viscosity decreased upon setting up a ratio of nonbridging oxygen over tetrahedrally coordinated atoms (NBO/T). A good linear relationship was confirmed between the viscosity of the molten slag and the NBO/T.

A New Parameterization of Volcanic Ash Complex Refractive Index Based on NBO/T and SiO2 Content

AbstractRadiative transfer models used in remote sensing and hazard assessment of volcanic ash require knowledge of ash optical parameters. Here we characterize the bulk and glass compositions of a representative suite of volcanic ash samples with known complex refractive indices (n + ik, where n is the real part and k is the imaginary part). Using a linear regression model, we develop a new parameterization allowing the complex refractive index of volcanic ash to be estimated from ash SiO2 content or ratio of nonbridging oxygens to tetrahedrally coordinated cations (NBO/T). At visible wavelengths, n correlates better with bulk than with glass composition (both SiO2 and NBO/T), and k correlates better with SiO2 content than with NBO/T. Over a broader spectral range (0.4–19 μm), bulk correlates better than glass composition, and NBO/T generally correlates better than SiO2 content for both parts of the refractive index. In order to understand the impacts of our new parameterization on satellite retrievals, we compared Infrared Atmospheric Sounding Interferometer satellite (wavelengths 3.62–15.5 μm) mass loading retrievals using our new approach with retrievals that assumed a generic (Eyjafjallajökull) ash refractive index. There are significant differences in mass loading using our calculated indices specific to ash type rather than a generic index. Where mass loadings increase, there is often improvement in retrieval quality (corresponding to cost function decrease). This new parameterization of refractive index variation with ash composition will help to improve remote‐sensing retrievals for the rapid identification of ash and quantitative analysis of mass loadings from satellite data on operational timescales.

Influence of ionic radius of alkaline-earth metals in ion conducting 2(Ca, Sr, Ba)O[sbnd]2TiO2[sbnd]SiO2 glasses

We have studied the relationship between ionic conductivity and the ionic radius of A site in 2AO2TiO2SiO2 (ATSO; ACa, Sr and Ba) glasses. Electrical measurements were carried out in the frequency range 100 Hz ~ 30 MHz and temperature range 300–540 °C. Raman spectroscopy and differential thermal analysis measurements were also performed. The exponents of the Cole-Cole plot, power-law conductivity and modulus formalisms reveal the nature of ionic transport and the conductivity relaxation. Raman spectroscopic data of ATSO glasses clarify the modification of vibrational networks of silicate and titanate complexes by alkaline-earth metals (Ca, Sr and Ba). The ratio of non-bridging oxygens per tetrahedrally coordinated cations (NBO/T) in the 2CaO and 2SrO2TiO2SiO2 glasses decreases rapidly, suggesting polymerization of the silicate and titanate networks. The disorder of the glass matrix in 2BaO2TiO2SiO2 glass is greatly reduced with increasing non-bridging oxygens per NBO/T and decreasing interionic Coulomb interactions. The conduction mechanisms of dc and ac for all ATSO glasses are the same but the ions hop through a different fractal structured conduction pathway. The dimension of ionic conduction pathway decreases with increasing ionic radius of alkaline-earth metals in ATSO glasses.

Effects of doping SiO_2 on the defect’s change in B_2O_3-containing phosphate based laser glasses used for high energy UV lasers

The introduction of SiO2 affects the glass’s micro-structure and micro-defects as well as the corresponding optical and physical properties of the B2O3-containing multi-component phosphate glasses. The addition of SiO2 increases the transition temperature and causes shifts of the UV cut-off wavelength (λcut-off). The changes of λcut-off are closely related to the PO3-EC and PO4-EC defect centers that are associated with the Q2 tetrahedral in phosphate chains. The corresponding variations of Q2 units can also be found in the Raman, XPS, and 31P MAS-NMR spectra. With increasing the content of SiO2, the ratio of non-bridging oxygen (associated with Q2 units) is gradually decreased down to a critical level when SiO2/B2O3 ratio is 4/1.5, whereas the ratio of non-bridging oxygen increases when SiO2/B2O3 ratio is larger than 4/1.5, which suggests that the doping SiO2 can influence the concentration of PO3-EC and PO4-EC defects. Those results can be better obtained when the sample is exposed to gamma irradiation. As the SiO2 content increased gradually up to 4/1.5, the concentration of the PO3-EC defects declined, while the concentration of PO4-EC and the POHC defects increased when considering the irradiation dose, indicating that the addition of SiO2 can regulate the structure-related defects in phosphate based glasses.

Effect of gamma irradiation on X-ray absorption andphotoelectron spectroscopy of Nd-doped phosphate glass.

X-ray absorption near-edge structure (XANES) and X-ray photoelectron spectroscopy (XPS) of Nd-doped phosphate glasses have been studied before and after gamma irradiation. The intensity and the location of the white line peak of the L3-edge XANES of Nd are found to be dependent on the ratio O/Nd in the glass matrix. Gamma irradiation changes the elemental concentration of atoms in the glass matrix, which affects the peak intensity of the white line due to changes in the covalence of the chemical bonds with Nd atoms in the glass (structural changes). Sharpening of the Nd 3d5/2 peak profile in XPS spectra indicates a deficiency of oxygen in the glasses after gamma irradiation, which is supported by energy-dispersive X-ray spectroscopy measurements. The ratio of non-bridging oxygen to total oxygen in the glass after gamma radiation has been found to be correlated to the concentration of defects in the glass samples, which are responsible for its radiation resistance as well as for its coloration.

Fly ash as an assemblage of model Ca–Mg–Na-aluminosilicate glasses

Model Ca–Mg–Na-aluminosilicate glasses based on compositions found in a calcareous fly ash were synthesised and their reactivity assessed in NaOH solution and in Portland cement paste. It was found that the reactivity followed the same trend in both systems and that the reaction of the glasses in pastes was very similar to that of the components of similar composition in the real fly ash. This finding indicates that the reactivity of glass in cement can be directly linked to the chemical composition of the glass. Further, when the reactivity of the glasses was normalized to their surface area, it was found that there exists a strong correlation with the NBO/T, the ratio of non-bridging oxygens and tetrahedral ions in the glass.

Investigating the influence of Na+ and Sr2+ on the structure and solubility of SiO2-TiO2-CaO-Na2O/SrO bioactive glass.

This study was conducted to determine the influence that network modifiers, sodium (Na+) and strontium (Sr2+), have on the solubility of a SiO2-TiO2-CaO-Na2O/SrO bioactive glass. Glass characterization determined each composition had a similar structure, i.e. bridging to non-bridging oxygen ratio determined by X-ray photoelectron spectroscopy. Magic angle spinning nuclear magnetic resonance (MAS-NMR) confirmed structural similarities as each glass presented spectral shifts between -84 and -85 ppm. Differential thermal analysis and hardness testing revealed higher glass transition temperatures (Tg 591-760 °C) and hardness values (2.4-6.1 GPa) for the Sr2+ containing glasses. Additionally the Sr2+ (~250 mg/L) containing glasses displayed much lower ion release rates than the Na+ (~1,200 mg/L) containing glass analogues. With the reduction in ion release there was an associated reduction in solution pH. Cytotoxicity and cell adhesion studies were conducted using MC3T3 Osteoblasts. Each glass did not significantly reduce cell numbers and osteoblasts were found to adhere to each glass surface.