Number Of Non-bridging Oxygens Research Articles

Effect of replacing B2O3 with Dy2O3 on the structural, physical, and radiation shielding properties of sodium boroaluminate glass

AbstractIn this work, some transparent aluminum sodium borate-based glasses containing Dy2O3 have been prepared using the melt quenching method. The incorporation of Dy3+ ions in the glass network leads to increase and decrease the density and molar volume, respectively. The structural properties are investigated by XRD and FTIR spectroscopy. It is revealed that addition of Dy2O3 causes a conversion of boron coordination from BO4 to BO3, which indicates the increase in the number of non-bridging oxygen. Therefore, the optical band gap is found to decrease as the Dy3+ ions content increases. The temperature dependences of dielectric constant and AC conductivity are studied at different frequencies. The electric conductivity and dielectric parameters decrease with increasing Dy3+ content due to the decrease in Na+ ions mobility due to the blocking effect of Dy3+ cations in the glass network. The shielding factors have been evaluated for the prepared glasses with the help of Phy-X program. The maximum linear attenuation coefficient (LAC) is found at 0.284 MeV and varied between 0.125 and 0.140 cm−1. The results revealed that the incorporation of Dy2O3 into the glasses has a substantial effect on the Zeff.. The value of the Zeff for the D1 sample, which does not include any Dy2O3, stays relatively the same, ranging around 7.51. We found that the rate of reduction in Zeff was significantly high when the energy of the photons is smaller than 0.826 MeV. From the Zeff data, we found that the addition of Dy2O3 to the glasses improves both their capacity to absorb and their capability to scatter ionizing radiation.

Prediction of the ribbon length to determine the viscosity of ladle-refining powder containing CaF2 using inclined plane test and advanced mathematical model

ABSTRACT In the present research, the inclined plane test (IPT) and an author-developed advanced mathematical model were used to determine the viscosity of ladle-refining + CaF2 powder containing 3–10% CaF2 (LRC powder). The ladle slag powder is composed of such compounds as CaO, Al2O3, SiO2 containing percentages of CaF2 to make special changes to the chemical and physical properties of the compound. The procedure for determination of the viscosity obtained by IPT method was supported using a high-temperature viscometer. The results showed that the ribbon lengths of LRC powder obtained by using the IPT method were related to an Arrhenius relationship of viscosity. Furthermore, from the advanced mathematical relationships, it was found that there is a very close relationship between the oxygen-to-silicon molar ratio (O/Si), basic/acidic oxide molar ratio (B/A), the number of non-bridging oxygen per tetrahedrally-coordinated atoms (NBO/T), and the chemical compositions of LRC powder. Hence, the advanced mathematical relationships from the software output, and Statistical Package for the Social Sciences (SPSS), were used to determine the prediction model of the viscosity of LRC powder based on its chemical composition. This model had a very good correlation with the actual values obtained.

Nb5+-doped SrTiO3-based glass-ceramics: Insight into crystallisation kinetics, microstructure, and dielectric properties

Nb5+-doped SrTiO3-based glass-ceramics composed of SrO–B2O3–SiO2–TiO2 were modified by Nb2O5 doping and prepared via a melt-quenching process accompanied by controlled crystallisation. The effect of the Nb2O5 concentration on the crystallisation, microstructure, and dielectric properties of the glass-ceramics was investigated. Surface analysis conducted by XPS revealed that with the addition of Nb2O5, the number of non-bridging oxygens (NBO) decreased while the number of bridging oxygens (BO) increased, increasing the interconnection of the structural units. The crystallisation activation energies of the samples tended to decrease from 376.06 kJ/mol to 271.50 kJ/mol (Kissinger model), and the crystal growth modes changed from two-dimensional to three-dimensional (Avrami indexes n: 2.38–4.23) with increasing Nb2O5 concentration. The XRD, SEM, and EDS analyses showed that the addition of Nb5+ promoted the growth of crystals (0.44–1.35 μm). The dielectric properties show that an appropriate amount of Nb2O5 greatly improves the dielectric constant of the glass-ceramics. The dielectric constant of the glass-ceramic doped with 1.5 mol% Nb2O5 is 178.1 (300 K, 1 MHz), which is approximately 6.7 times higher than that of the undoped Nb2O5-doped glass-ceramics (26.5). The introduction of Nb2O5 reduced the activation energy of glass devitrification, promoted crystal development, and improved the dielectric properties of the glass-ceramics.

Analysis of radiation shielding, physical and optical qualities of various rare earth dopants on barium tellurite glasses: A comparative study

In the present study, the barium tellurite glasses with the compositions of 60TeO2– 20ZnO– 4BaF2-(16-x) BaCO3-xREEs2O3 (Rare Earth Elements) where x = 0, 1, and 2 of Tm2O3, Er2O3, and Ho2O3 in mol% have been studied via MCNPX simulation code in terms of radiation shielding, physical, and optical qualities. Seven various glasses coded as TeZnBB, TeZnBBTm1.0 (Tm1.0), TeZnBBEr1.0 (Er1.0), TeZnBBHo1.0 (Ho1.0), TeZnBBTm2.0 (Tm2.0), TeZnBBEr2.0 (Er2.0), and TeZnBBHo2.0 (Ho2.0) in this work. The radiation shielding features have been derived using BLL. In addition, N, VM, VS, ri, rp, and F are extracted analytically. The optical properties have been obtained using Tauc's Plot, Mott and Davis, and Lorentz –Lorentz equations. Findings show that the addition of various REEs to barium tellurite glasses improves the radiation shielding capacity of the base glass. Furthermore, the physical features of preferred glasses are enhanced remarkably and as a result, a tight glass structure is created. Moreover, M has small values near zero, showing a narrow bandgap in relevant optical glasses. Also, RLoss and ε increase which is owing to the increase in the number of Non-Bridging Oxygens and causes the locking up of the free movement of the electrons in preferred glasses.

Thermal, Structural, Morphological and Electrical Characterization of Cerium-Containing 45S5 for Metal Implant Coatings

Biomaterial coatings on dental implants are increasingly being used as a solution to the problems of rejection and implant loss. Bioglass® has been seen as a promising material for coating metal implants, increasing the integration rate and improving the bond between the bone and the implant. Multifunctional bioactive glasses can exhibit antibacterial, antitumor and antioxidant effects with the addition of therapeutic ions. The cerium ion has shown an antioxidant effect through mimicking mechanisms and by acting as a scavenger of reactive oxygen species (ROS), which is important for avoiding oxidative stress post-surgery. Furthermore, it is possible to store electrical charge on the bioglass surface, which potentiates osseointegration. In this work, glasses with various percentages of cerium oxide (0.25, 0.5, 1 and 2 mol%) were developed and structurally and electrically analyzed. It was verified that the cerium insertion did not modify the amorphous phase characteristic of the glass but showed an increase in the number of non-bridging oxygens (NBOs). This increase in NBOs did not modify the electrical conductivity in either the ac or dc regime. The similar permittivity values of the glasses also suggest that their storage ability is unchanged with the addition of CeO2. Concerning the impedance spectroscopy (IS) data, a decrease in resistance is visible with the addition of cerium oxide, suggesting a favorable behavior for applications as an antioxidant through the electro-Fenton reaction.

A comparative study on the physical and spectral (optical, EPR and FTIR) properties of NaF-CdO-B2O3 and KF-CdO-B2O3 glass systems doped with manganese ions

The glass systems with the composition xMF-(40-x) CdO-59.5B2O3, (M=Na, K and x= 5, 10, 15, 20, 25, 30 and 35 mol %) doped with 0.5 mol % of MnO2 were prepared using the melt quenching method. The glasses were analysed using XRD, UV-VIS, EPR and FTIR spectra. The optical band gap (Eg) values of the glass systems were observed to increase from 3.21 eV [NFCBM1] to 3.48 eV [NFCBM7] and 2.56eV [KFCBM1] to 3.31 eV [KFCBM7] with increase of NaF/KF concentration which may be due to decreasing of the number of non bridging oxygens. The (Δg) values suggest the presence of Mn2+ ions in octahedrally coordinated complex and the A values suggest that the bond between Mn2+ ions and its ligand filed is ionic. The BO4 atoms were increased in both NaF and KF containing glasses with increase in NaF/KF concentration.

Effect of Li+ ions on structural, optical and nano-crystallization behaviour of Na2O-CaO- P2O5-B2O3 glass system: Biomedical applications

Glassy system of composition xLi2O.3P2O5.21Na2O.26CaO.(50-x)B2O3 (x = 0, 1, 2, 3 and 4 mol%) was prepared by melt quench technique. X-ray diffraction, Infrared spectroscopy and Field emission scanning electron microscope with Energy dispersive spectroscopy were conducted to identify crystalline phase formation in glass powder and to study morphologies. The deconvoluted IR absorption spectra of synthesized samples, were analyzed to examine the structural rearrangements in the glass matrix before and after immersing in the phosphate solution. Optical band gap, Urbach energy and refractive index of the synthesized compositions were also obtained from the analysis of optical absorption spectra to examine the semiconducting behavior. The effects of the treatment in phosphate buffer solution for 12 days on crystallization & structural properties of these glasses were systematically investigated. The dependence of physical parameters on the glass composition suggested a variation in the number of non-bridging oxygen with Li2O content. Morphological and structural study alongside a possibility of hydroxyapatite formation suggests the biomedical applications of these materials.

Influence of manganese ions on physical and spectroscopic properties of mixed alkali-alkaline earth oxide borate glasses

In this paper the studies on xMO-10Li2O-10Na2O–10K2O-(70-x)B2O3 [M=Mg, Sr and Ba] [x = 2, 4, 6, 8 and 10 mol%] glasses doped with manganese ions are reported. The physical and spectroscopic properties were investigated to know about the influence of the alkaline ions. The density values of all the glasses were found to increase with increasing alkaline earth oxide content while the values of molar volume were decreasing. The UV–VIS spectra of these glasses have shown single broad band which was assigned to the 6A1 g(S) → 4T1 g (G) transition. The non-linear variation of the optical band gap with the increase of alkaline earth oxides suggests non-linear variation in the number of non-bridging oxygens. The EPR spectra demonstrated a predominant sextet hyperfine structure located around g = 2.0 which were ascribed to the octahedral symmetric octahedral Mn2+ ions. From the hyperfine splitting parameters (Aavg), it was noticed that the environment around Mn2+ ions is ionic. The number of spins participated in resonance (N) and magnetic susceptibility (χ) values were evaluated taking the high field g-values (g ≈ 2.0). It is interesting to note that, the observed zero field splitted (ZFS) values (D) are varying non-linearly with the glass compositions and their values were increasing with the substitution of alkaline earth ions from Mg to Ba. The FTIR spectra of the glasses were analyzed in the range 400–2200 cm–1 to investigate the structural changes in the glass network.

Investigation of structural and impedance spectroscopic properties of borate glasses with high Li+ concentration

Lithium borate glasses prepared by melt-quench technique have been studied with a view to ascertain their structural and electrical properties. FTIR analysis of the present samples reveals the absence of boroxol rings, presence of structural units of lithium formed with oxygen and increase in the number of Non-Bridging Oxygens (NBOs) in the glass system. The real and imaginary parts of dielectric constant increase with frequency and temperature arises due to interfacial ionic polarization. The non-exponential Kohlrausch-Williams-Watts (KWW) function has been found to follow by the imaginary part of electric modulus, thereby confirming its applicability. The fitting of data of ac conductivity as per Jonscher's universal power law indicates hoppable ion concentration dependent upon temperature and Li2O content. The analysis is further supported by the variations of ac-conductivity as well as the activation energy for dc conductivity. A decrease in impedance and increase in the space charge polarization is observed with increasing Li2O concentration. Further, the electrical behavior of samples has been investigated via an impedance equivalent circuit corresponding to the Nyquist plot.

Synthesis and characterization of [BaO-(10-x)ZrO2-TiO2-SiO2-xCrO3] type glass and glass ceramics

ABSTRACT Various glass compositions were prepared in a glassy system [25BaCO3-(10-x) ZrO2-20TiO2-45SiO2-xCrO3] (x = 0, 2, 4, and 6) using melt-quenching technique. XRD patterns of glass and glass ceramics showed amorphous and crystalline nature. Density of glass and glass ceramics decreased from 3.4553 to 3.4381 g/cm3 and 3.7485 to 3.1977 g/cm3 with increasing concentration of CrO3. DTA of the glasses revealed a shift in base line which suggests a change in specific heat and attributed to the glass transition temperature, Tg. FTIR and Raman spectroscopic analysis indicated that an increasing doping of CrO3 changes structural network by increasing number of nonbridging oxygens (NBO) within glassy matrix. These results revealed that bands toward low frequency side endorsed to the vibration of Ba2+ metal cation, bending vibration of Si-O-Si and bonding formation of ZrO2. Concentration of CrO3, changed the microsture significantly and hence, a denser, fully developed mixed morphology was noticed with spherical grains of ZrO2, irregular shape of bazirite (BaZr0.97Ti0.03Si3O9) phase and TiO2 grains. Glass ceramic sample BZTS6C971 CrO3 (x = 6) retains high value of dielectric constant, ~4555 due to space charge polarization. Hence, these glass ceramics might be useful for diverse applications such as in optical devices, electronic circuits, and multilayer ceramic capacitors.

Investigation of physical and spectroscopic properties of WO3 doped zinc-lithium-dysprosium borotellurite glasses

Abstract A set of WO3 doped zinc-lithium-dysprosium-borotellurite glasses in the compositions, (B2O3)0.2–(TeO2)0.3-x–(ZnO)0.28 –(Li2CO3)0.2 –(Dy2O3)0.02–(WO3)x; x = 0.02 to 0.12 (labeled as W1, W2, W3, W4, W5 and W6 respectively) have been synthesized. Amorphous nature of the samples has been confirmed and density measured. Molar volume, oxygen packing density and field strength were determined. Optical absorption spectra were recorded. Band gap values are found to increase with WO3 content up to 0.08 mol fractions and decreases for further amounts of WO3. Urbach energy behaved in the opposite fashion to that of band gap with WO3 content. These results are attributed to bonding defects and the number of non-bridging oxygen. Refractive index, molar refractivity, molar electronic polarizability, reflection loss, metallization ratio, oscillator strengths and Judd-Ofelt (J-O) intensity parameters have been determined. Based on the observed trends of JO intensity parameters, lasing ability of the glasses and their optical quality has been discussed. Photoluminescence (PL) spectra have been recorded and they exhibited three bands namely, 4F9/2 → 6H15/2 (blue), 6H13/2 (yellow) and 6H11/2 (red). The observed ratio of intensity of yellow to blue band inferred that asymmetry around rare earth ions decreases with increase of WO3 content. Using PL decay profiles, the lifetime (τexp) for yellow emission has been determined. Using the values of τexp and estimated radiative lifetime (τR), the quantum efficiency (η) has been determined and for 4F9/2 → 6H13/2 transition and, it is found to be in the range from 43% to 67% for the present glasses. Based on JO parameters, quantum efficiency and other radiative parameters, W4 glass is proposed for lasing in yellow region. For the first time, effect of WO3 on the optical properties of zinc-lithium-dysprosium-borotellurite glasses has been thoroughly investigated.

Effect of alkaline modifiers on the structural, optical and crystallization properties of niobium germanate glasses and glass-ceramics

Alkali niobium germanate glasses were prepared by melt-quenching in the ternary systems 75GeO2-15Nb2O5-10M2O with M = Li, Na, K, Rb and Cs. Thermal properties of these glasses and related glass-ceramics are strongly dependent on the alkaline modifier. Structural investigations by Raman allowed to determine that the alkali radius has an influence on the number of non-bridging oxygens and consequently on the average glass network connectivity. Raman spectra of sodium, potassium and rubidium germanate glass-ceramics exhibited slight changes when compared to the pristine glass and the new Raman features can be attributed to a 3D NbO6 network similar to orthorhombic niobium oxide. Characterization of the heat-treated glasses allowed to determine the crystalline phases precipitated in the samples and it has been shown that a single perovskite bronze-like phase of general formula M2Nb8O21 can be obtained in Na, K, and Rb-containing glasses. Luminescent properties of Eu3+-doped glasses pointed out a non-regular tendency where sodium-based glass seems to be the inflexion point of luminescent data with higher asymmetry around Eu3+ ions and higher quantum efficiency. In transparent glass-ceramics, the Eu3+ luminescent properties are clearly modified in the Na- and K-based samples with lower symmetry and quantum efficiency after heat-treatment. Such optical behavior is attributed to Eu3+ migration in the perovskite crystalline phase with highly distorted Eu3+ sites and shorter Eu3+-Eu3+ distances.

Effect of Li content in ion conductivity of lithium silicate glasses

We present the electrical and the phonon vibrational properties of Li2O–2SiO2 (LS12) and Li2O–SiO2 (LS11) glasses to exploit for lithium ion transport in the merits of solid electrolyte. Electrical impedance measurements are carried out in the frequency 100 Hz–30 MHz and temperature range 30–150 °C. Based on the theory of the modified fractional Rayleigh equation, we predict the number densities of the lithium ions in the lithium silicate glasses. As an increase in lithium content, the covalent interaction between the Li-cation and its local sites of network increases the number of the non-bridging oxygen (NBO) sites by the depolymerization of the silicate glass network. We find the fact that the number of NBOs in the LS11 glass increases a factor of two larger than the number of NBOs in the LS12 glass. A low conductivity of lithium oxide glasses is reflection of a long stay of the lithium ions in the NBO atoms. The partial Li+ ions in the lithium silicate glasses participate on the ac conduction through the NBO sites.

Structure of amorphous BaTiO3 by molecular dynamics simulations using a shell model

We studied the structure of amorphous BaTiO3 by molecular dynamics (MD) simulations. The local bonding units (LBUs) were mainly TiO6 in agreement with an X-ray absorption fine-structure (XAFS) study. An LBU was linked to its neighboring ones with their apexes, edges, and/or faces shared. The first peak of the Ti–Ti radial distribution function (g(r)) was located at ~ 3 Å with a trimodal distribution that results from the three linkage types, supporting extended X-ray absorption fine structure (EXAFS) experiments. If the number of Ba atoms around a Ti atom was larger than the average, the number of non-bridging oxygen (NBO; [1]O) atoms was larger around that Ti atom. In the opposite case, the number of tricluster oxygen (TO; [3]O) atoms was increased around it, and the number of edge or face-sharing linkages with the neighboring Ti atoms was also increased.

Effect of lithium addition on Te4+ emission in TeO2-Li2O glasses

Lithium tellurite glasses with xTeO2 + (100 − x)Li2O nominal composition, where x = 95, 90, 85, 80, 75 and 70 mol%, have been prepared to investigate the dependence of the Te4+ emission as a function of the lithium modifier. Optical and structural properties of the glasses were explored by using UV–Vis absorption, photoluminescence and photoluminescence excitation spectroscopies, photoluminescence lifetime and Raman spectroscopy. Besides, the influence of Li2O in the glass structure was verified by density, glass transition temperature, thermal stability, glass-forming tendency, optical band edge and the number of non-bridging oxygen. The results support there is a good correlation between the glass structure and the Te4+ center concentration: the Li2O content contributes to increase the Te4+ in the glass structure.

Ligand field and spectroscopic investigations of cobalt doped erbium–zinc borate glasses

The glasses of the composition [xCoO–(29.5 − x)Na2O–55B2O3–15ZnO–0.5Er2O3] (where x = 0, 0.3, 0.5, 1 and 3 mol%) have been prepared using melt quenching technique. The recorded UV/VIS/NIR absorption spectra have been studied and the resulting data was used for the ligand field theory analysis, from which the crystal field energy (10Dq), Racah parameters (B, C) and nephelauxetic ratio (β) were evaluated. The observed variations in the band gap and Urbach energy with CoO content have been discussed in relation with the glass structure. FT-IR spectra of the samples exhibit modes of vibration corresponding to the stretching of BO3 and BO4 unit. From IR studies, the number of non-bridging oxygens was increased, leading to loosen structure at higher CoO concentrations. The ESR spectra revealed that Co2+ ions are located both in distorted tetrahedral and octahedral sites.

Raman spectra and optical band gap in some PbO-ZnO-TeO2 glasses

The glasses PbO–ZnO–TeO2 were prepared with a classic melting method. The substitution of ZnO by PbO results in an increase in the density from 5.83 to 6.52 g/cm3 and in the refractive index from 2.19 to 2.25. In addition, the optical band gap and the glass-transition temperature decrease from 3.79 to 3.5 eV and from 314 to 281 °C, respectively. The estimated values of the non-linear refractive index from the optical band gap are comparable with the values typical for TeO2 based glasses. The Raman spectra indicate that the substitution of ZnO with PbO leads to a decrease in the density of Te–O–Te linkages while increasing both the density of Pb–O–Te linkages and also the number of non-bridging oxygen.

Unraveling the hidden Urbach edge and Cr6+ optical transitions in borate glasses

Two alkaline-borate glass systems of composition x Li2O · 0.2 Cr2O3 · (99.8–x) B2O3 (x = 20, 30 and 40 mol%) and y K2O · (20-y) Li2O · 0.2 Cr2O3 · 79.8 B2O3 (y = 5, 10, 15 and 20 mol%) were prepared by traditional melt-quenching technique. The tunability of their optical spectra, offered by different alkaline contents, allowed disentangling the absorption edge from the characteristic Cr6+ optical transitions. Specifically, the optical band gap is barely affected (3.55 ± 0.15 eV), whilst Cr6+/Cr3+ optical transitions undergo subtle intensity variation with the alkaline content. With increasing the alkaline content, or type, the crystal field strength (10 Dq) is increased, Racah parameters are decreased, and the ligand environment facilitates the crossover from weak into strong ligand field regimes. Electron spin resonance spectroscopy confirmed the existence and quantified the percentage of both Cr6+ (through charge transfer into Cr5+ O−) and Cr3+ oxidation states. Finally, the number of non-bridging oxygen, obtained from Infrared spectroscopy, is increased noticeably for both type and percentage of alkaline, while BO4 structural units increase with Li content and are barely affected for K-doped system.

UV–Vis-NIR spectroscopy, structural and thermal properties of novel oxyhalide tellurite glasses with composition TeO2-B2O3-SrCl2-LiF-Bi2O3 for optical application

Abstract The prepared glass samples within the composition (85-x) TeO2-xB2O3-5Bi2O3-5SrCl2-5LiF (TBBSL) with x = 0, 10, 20, 30, 40, 50 and 60 mol% were synthesized. The X-ray diffraction patterns (XRD) showed the amorphous nature of the system. The density (ρ), molar volume (vm) and oxygen packing density (OPD) have been measured and calculated. The Fourier Transform Infrared (FTIR) of TBBSL glasses showed the presence of TeO3, TeO4, BO3, BO4, LiF, SrO and BiO6. Also, FTIR spectra identified that the substitution of B2O3 with TeO2 in glass system led to convert the TeO4 to TeO3 and the formation of bridging structure Te-O-B with increasing the B2O3 mol%, consequently the BO4 units convert to BO3 and so the number of non-bridging oxygen (NBO) increases. The optical band gaps (Eopt), the Urbach energy (ΔE) and refractive index (n) have been calculated from optical absorption spectra. Thermal characterization was determined by using Differential Scanning Calorimetry (DSC) at different heating rates 10, 15, 20, 25 °C/min. The prepared glasses showed high thermal stability. High reflective index and higher thermal stability made the synthesized glass system is a suitable candidate for the large bulk glass and optical fiber production.

Improved glass bonding with plasma treatment

Bonding of automotive glass is generally performed with 1C PUR adhesive on a primed ceramic frit or naked glass surface. The aim of this research was to replace the chemistry of the primer with an atmospheric pressure plasma treatment (APPT) with compressed air for cleaning and activation directly before bonding. Characterization of the glass surface was performed with surface energy through contact angle, XPS, TOF-SIMS and adhesive peel bead test. The results show that APPT treatment can clean the surface, improve the wetting, improve the bonding but reduce the number of non bridging oxygen for the adhesive to bond to. The highest measured spot temperature of the glass during APPT was measured up to 270 °C, but the temperature was depending on process parameters. A reduction in non bridging oxygen was also seen during heating of the reference glass at 100 °C. A further reaction was seen when measured after a 550 °C heating. A modified APPT treatment with deionized water as precursor was used. The results show that the APPT with water does not lower the level of non bridging oxygen and the bonding was further improved.