Quaternary Glasses Research Articles

Testing stable isotope paleoaltimetry with Quaternary volcanic glasses from the Ecuadorian Andes

Testing stable isotope paleoaltimetry with Quaternary volcanic glasses from the Ecuadorian Andes

The effects of Cu2+ and La3+ doping on the sintering ability of sol-gel derived high silica bioglasses

This paper reports the hierarchical influence of co-doping copper and lanthanum in a sol–gel derived quaternary (Si, Ca, Na, P) bioactive glass on its sintering ability. The mutual effects of Cu & La on density, crystallisation and sinterability were investigated using Taguchi analysis. Thermal properties of bioglasses were assessed by DTA/TGA and dilatometry, while crystallisation phase evolution of was monitored by X–ray diffraction. Ten glass compositions were sintered at two temperatures (800 and 900 °C). The glass structure was analysed by MAS–NMR, the sintered density measured, and sintered microstructures observed by SEM/EDS. Results revealed that Cu promotes early densification, enhancing density at lower sintering temperatures. Oppositely, beneficial sintering effects of La might be observed at higher sintering temperatures (>1000 °C). These differences are induced by the distinct roles of doping elements on devitrification upon increasing their concentrations: crystallisation is promoted by Cu and is inhibited by La.

Investigations on frequency and temperature dependence of AC conductivity and dielectric parameters in Ge20Ga5Sb10S65 quaternary chalcogenide glass

Frequency and Temperature dependence of AC conductivity and dielectric parameters viz. dielectric constant, dielectric loss for multicomponent bulk Ge20Ga5Sb10S65 chalcogenide glass sample for the temperature range 313 K–373 K and 1kHz-1 MHz frequency regime has been investigated. The values of dielectric constant ε' and dielectric loss ε" for the sample prepared by the conventional melt-quenching method were found to decrease with frequency. The value of maximum barrier height calculated from the dielectric analysis according to Guintini equation is in agreement with theory of hopping across a potential barrier as proposed by Elliot for chalcogenide glasses. The increase in AC conductivity with frequency for the investigated sample confirms correlated barrier hopping (CBH)responsible for conduction mechanism. The density of localized states and ac activation energy were estimated for the present sample. This study of dielectric properties of quaternary Ge20Ga5Sb10S65 chalcogenide glass is useful for the determination of the structure and defects in these materials and thereby understanding the mechanism of conduction in the present sample.

Guidelines to adjust particle size distributions by wet comminution of a bioactive glass determined by Taguchi and multivariate analysis

A quaternary bioactive glass of high silica content was used as a model system for flexible design of powder characteristics obtained by ball milling. The dependence on milling time was used to demonstrate consistency with the expected correlation between comminution and cumulative kinetic energy of impacting balls. Additional experiments were based on Taguchi planning of simultaneous changes in milling time, balls-to-powder ratio and ethanol-to-powder ratio, with ethanol used as a process control agent (PCA) to prevent agglomeration and to seek greater flexibility in the design of powder distributions. Plausible physical mechanisms allowed us to obtain improved fitting by multivariate analysis, based on log-log scales. Normal distribution was found to be well-suited to describe the actual particle size distributions, which are very positively skewed. Weibull distributions provided good fitting, mainly by considering the three different contributions from particles in small, medium and large size ranges. These contributions are affected differently by ball milling parameters, as demonstrated by finer analysis. This yields suitable conditions for a flexible design of asymmetric powder size distributions (i.e. bimodal or skewed), in addition to a decrease in average particle size - both highly significant factors when designing glass-ceramic powders for robocasting and additive manufacturing.

Structural and Chemical Approach toward Understanding the Aqueous Corrosion of Sodium Aluminoborate Glasses

Despite an ongoing strenuous effort to understand the compositional and structural drivers controlling the chemical durability of oxide glasses, there is still no complete consensus on the basic mechanism of glass dissolution that applies to a wide composition space. One major reason for this problem is the structural complexity contained within the multicomponent silicate glasses chosen for glass corrosion studies. The nonsilicate network polyhedra present in these glasses interact with one another, often in unpredictable ways, by forming a variety of structural associations, for example, Al[IV]-B[III] and B[III]-B[IV], resulting in significant influence on both the structure of the glass network and related macroscopic properties. Likewise, the formation of a variety of next-neighbor linkages, as well as increasingly complex interactions involving Si and differently coordinated next-nearest neighbor cations, is very difficult to decipher experimentally. Consideration of these factors motivates instead a different strategy: that is, the study of a sequence of SiO2-free ternary or quaternary glass compositions, whose structures can be unambiguously determined and robustly linked to their corrosion properties. With this aim, the present study is focused on understanding the structural drivers governing the kinetics and mechanism of corrosion of ternary Na2O-Al2O3-B2O3 glasses (in water) over a broad composition space comprising compositions with distinct structural features. It has been shown that the addition of Al2O3 to binary sodium borate glasses decreases their corrosion rate in water and converts their dissolution behavior from congruent to incongruent leading to the formation of six-coordinated alumina, and higher concentration of four-coordinated boron (in comparison to pre-dissolution glasses) in post-dissolution glass samples. The drivers controlling the corrosion kinetics and mechanism in these glasses based on their underlying structure have been elucidated. Some open questions have been proposed which require an extensive analysis of surface chemistry of pre- and post-dissolution samples and will be investigated in our future work.

Effect of heat treatment on erbium-doped tellurite glass

Abstract Synthesis and characterization of quaternary erbium tellurite glass within the molar percentages of (75-x) TeO2 20ZnO 5Na2O-xEr2O3 where (0 ≤ x ≤ 2.5) were carried out. The optical properties were determined by recording the UV–Vis spectra in the range 200–800 nm which exhibited increasing the band gap with increasing Er2O3. The thermal characteristics of the glass were determined and showed higher thermal stability of the system suggesting its applicability for fiber drawing. The heat treatment was performed for the samples (0.5 and 2.5 mol %) of Er2O3 at different temperatures and times. Zn2 Te3O8, TeO2, ZnO, Er2TeO6, Er6Te5O19.2 and Er2O3 phases were identified, characterized and found to be in nanoscale. The annealing operation made the optical energy gap to decrease after the structure changes.

Towards a unifying mechanistic model for silicate glass corrosion

Borosilicate glasses are currently used for the immobilization of highly radioactive waste and are materials of choice for many biomedical and research industries. They are metastable materials that corrode in aqueous solutions, reflected by the formation of silica-rich surface alteration layers (SAL). Until now, there is no consensus in the scientific community about the reaction and transport mechanism(s) and the rate-limiting steps involved in the formation of SALs. Here we report the results of multi-isotope tracer (2H,18O,10B, 30Si, 44Ca) corrosion experiments that were performed with precorroded and pristine glass monoliths prepared from the six-component international simple glass and a quaternary aluminum borosilicate glass. Results of transmission electron microscopy and nanoscale analyses by secondary ion mass spectrometry reveal a nanometer-sharp interface between the SAL and the glass, where decoupling of isotope tracer occurs, while proton diffusion and ion exchange can be observed within the glass. We propose a unifying mechanistic model that accounts for all critical observations so far made on naturally and experimentally corroded glasses. It is based on an interface-coupled glass dissolution-silica precipitation reaction as the main SAL forming process. However, a diffusion-controlled ion exchange front may evolve in the glass ahead of the dissolution front if SAL formation at the reaction interface significantly slows down due to transport limitations.

High refractive index dispersion of compositionally optimized Ge-Ga-Sb-S sulfide glass for use as molded lens in the long-wavelength infrared range

In an effort to endow Ge-Sb-S sulfide glass with capability to transmit the long-wavelength infrared (LWIR) photons as well as to possess highly dispersive refractive indexes over the LWIR spectral range, we have compositionally adjusted ternary Ge-Sb-S glass prior to tuning quaternary Ge-X-Sb-S (X = Ga, Bi, In or Sn) glass. Among the constituent atoms of ternary Ge-Sb-S glass, Ge content turned out to exert the strongest influence not only on thermal and mechanical properties but also on infrared transmission edge. Specifically, glass transition temperature and Vickers hardness tended to be directly proportional to Ge content, but infrared transmission edge was blue-shifted upon increase of Ge content, simultaneously producing an additional multiphonon absorption peak at ~ 9 µm. As such, Ge-Sb-S glass containing Ge atoms less than ~ 15 at% was considered to feature applicability in LWIR range, which on the other hand suffers from relatively poor thermal and mechanical properties. In our experimental attempts on quaternary sulfide glasses performed to mitigate such deteriorations, presence of relatively small amount of Ga appeared to be most effective among the elements employed in this study as the fourth constituent. Moreover, only Ga atoms improved thermal stability with significantly increasing crystallization temperature. Quaternary Ge-Ga-Sb-S glass compositionally optimized in this study was then verified to be much more dispersive than typical Se-based chalcogenide glasses in the LWIR region.

New quaternary chalcogenide glasses with wide range IR transparency

Quaternary chalcogenide glasses based on sulphur and selenium Se80S18Tl2-xYbx (x = 0, 0.1, 0.2, 0.5 and 1) and Se65S10Ge15+xIn10-x (x = 0 and 5) were synthesized using the melt-quench technique. Formation of quaternary chalcogenide glasses was confirmed by Powder x-ray diffraction studies. Our differential scanning calorimetric studies on these glasses also are in good agreement with powder x-ray diffraction results. Thermo Gravimetric studies reveal the good thermal stability of these glasses. The IR transparency of Se80S18Tl1.5Yb0.5 extends throughout the range 3–25 μm and thus are good candidates for Infrared transmission applications.

Enhanced bioactivity of a rapidly-dried sol-gel derived quaternary bioglass

Novel quaternary (67Si-24Ca-10Na-8P) glass powders were successfully synthesised by sol-gel followed by two alternative drying schedules, conventional drying (CD) and an innovative fast drying (FD) process (200 times quicker). The glasses were thermally stabilised at 550 °C, and then characterised by different complementary techniques. The samples showed very similar silica network structures, with the FD one having slightly lower degree of polymerisation than the CD sample. This less polymerised, more open, network structure exhibited an improved bioactivity in simulated body fluid (SBF), probably also due to the apparent presence of poorly crystalline HAp in the stabilised glass powder. In contrast, the CD glass exhibited an unwanted secondary crystalline silica phase. Both glasses showed excellent biomineralisation upon immersion in SBF, being more pronounced in the case of FD with clear evidence of HAp formation after 4 h, while equivalent signs in the CD samples were only noticed after longer immersion periods between 8 h and 1 week.

The antibacterial, cytotoxic, and flexural properties of a composite resin containing a quaternary ammonium monomer

Statement of problemThe use of composite resin to restore teeth has increased substantially during the last decades. However, secondary caries and the fracture of restorations are the leading reasons for clinical restoration failure. Mechanically strong composite resins with caries-inhibition capabilities are needed. Although antibacterial dimethacrylate quaternary ammonium monomers have been synthesized, composite resin containing dimethacrylate quaternary ammonium monomers and glass fillers has rarely been reported. PurposeThe purpose of this in vitro study was to evaluate the possibility of the clinical use of an experimental composite resin containing urethane dimethacrylate quaternary ammonium compound (UDMQA-12) by investigating its antibacterial activity, cytotoxicity, flexural strength, and flexural modulus. Material and methodsAntibacterial activity against Streptococcus mutans was investigated by means of direct contact test. The antibacterial activity of specimens after water immersion and saliva treatment was also tested. These were compared with a commercially available composite resin, Z250, and a glass ionomer cement, Fuji VII. Effects of the eluent from the experimental composite resin on the metabolic activity of human dental pulp cells were quantified. Disks of 1 mm in thickness and 15 mm in diameter were used in the antibacterial and cytotoxic tests. Flexural strength and flexural modulus were measured with a 3-point bend test with bars of 2×2×25 mm. Three commercially available composite resins (Filtek Z250, G-aenial Anterior, and G-aenial Posterior) were used as controls in the flexural test. ResultsBacterial growth was inhibited on the experimental composite resin. After water immersion or saliva treatment, the experimental composite resin showed significant antibacterial effect compared with the conventional composite resin (P<.05). No significant difference was found in cytotoxicity between the experimental composite resin and the conventional composite resin (P＞.05), and a significantly higher cytotoxicity was shown by glass ionomer cement compared with the experimental composite resin and the conventional composite resin (P<.05). The conventional composite resin had the highest flexural strength and flexural modulus (P<.05), followed by the experimental composite resin, then G-ænial Posterior and G-ænial Anterior. ConclusionsThe antibacterial experimental composite resin was biocompatible and had mechanical properties similar to those of some commercially available composite resins. It might, therefore, be useful in preventing the occurrence of secondary caries.

Reactivity features of original sol-gel-derived 52S4 glass versus heat treatment temperature

This work is devoted to study the reactivity of the quaternary glass 52S4 (52% SiO2–30% CaO–14% Na2O–4% P2O5 (wt%)), synthesized by sol-gel process versus the treatment temperature. The dried gel was heat treated at 600 and 650 °C and soaked in simulated body fluid (SBF). XRD results confirm the amorphous character of glass treated at 600 °C even though the heat treatment at 650 °C induces Na2Ca2Si3O9 formation. After soaking in SBF, SEM and EDS results show the formation of carbonated hydroxyapatite (CHA) at the glass surface for both temperatures. For the glasses treated at 600 and 650 °C, two phenomena were observed: the glass dissolution in SBF and the CHA precipitation, but the reactivity kinetics of glass was different when temperature changes. For SGDG600, the CHA began to crystallize after 16 h. For SGDG650, a glass ceramic made of a glassy matrix and of Na2Ca2Si3O9, the crystallized carbonated HA was observed after 2 h. In addition, a new crystallization at the glass surface of Na2Ca2Si3O9 was observed after 15 days.

Influence of manganese doping on elastic and structural properties of silica borotellurite glass

The quaternary glass system tellurium dioxide, boron trioxide, silicon dioxide and manganese dioxide where x = 0.00 to 0.05 M fraction has been successfully prepared via conventional melt and quench-casting technique. The density was determined by Archimedes method with distilled water as buoyant liquid. The results showed that the density decreases and molar volume increases with respect to manganese concentration. FTIR spectral studies suggest that glass network is mainly built up of boron trioxide, tetrahedral boron, tellurium trioxide, trioxotellurate and silicon dioxide structural units. The ultrasonic velocities and elastic moduli were recorded using a pulse-echo method at frequency 5 MHz at room temperature. Some other physical properties such as Debye temperature, softening temperature, microhardness, Poisson's ratio, fugacity, fractal bond connectivity and Cauchy relation were determined. Results indicate that these parameters depend upon the composition of the glass system and the dopant concentration, MnO2 inside the glass system.

The influence of processing parameters on morphology and granulometry of a wet-milled sol-gel glass powder

A quaternary bioactive sol-gel glass of high silica content was heat treated at different temperatures, and then wet ball milled under different balls-to-powder ratios. A total of sixteen experiments were performed to study in detail the effects of both experimental variables on the structure, morphology, particle size distributions and nitrogen adsorption isotherms. The balls–to–powder ratio exerts a tremendous influence on the final particle size distribution of the powders, while its effects on the pore volume and morphology are minimal. These structural features are mostly governed by the changes in calcination temperature. Therefore, understanding the specific roles of each experimental parameter is of paramount importance towards achieving optimum powders with the desired properties. This work sheds light on the importance of using a suitable combination of these two parameters for tuning the morphology and the granulometry of the sol-gel derived bioactive glass powders.

A comprehensive study of electrical and optical properties of phosphate oxide-based glasses doped with Er2O3

In this study, the radiative parameters were acquired from the UV absorption spectra and the luminescence spectra of Er3+ ions doped Er2O3–Al2O3–Na2O–P2O5 glasses. The intensity of each absorption spectrum was utilized to deduce the radiative parameters and the parameters (Ω2, Ω4 and Ω6) of Judd–Ofelt theory. The FTIR and the elastic moduli of the quaternary glasses are also investigated. Analysis of the FTIR suggested that the presence of Er3+ ions created bridging oxygens and polymerized the local structure around atoms. This procedure manifested itself from decreasing the bond length of O–P and increasing the O/P ratio. The polymerization of the phosphate structure increased the ultrasonic velocity and the rigidity of the network. The electrical parameters of the phosphate glasses, such as the frequency and temperature dependence AC conductivity, dielectric loss and dielectric modulus were carried out. The Er3+ ions affected the carrier mobility by decreasing the electrical conductivity and increasing the activation energy. In addition, the frequency and temperature dependence of the dielectric modulus exhibited a Debye-type relaxation behavior.

Different property studies with network improvement of CdO doped alkali borate glass

Quaternary alkali borate glass matrix doped with CdO (0, 2, 4, 6, 8, 10 mol%) have been prepared by using conventional melting and quenching technique. For these glass systems structural properties were investigated by using X-ray diffraction, FE-SEM, EDS, FTIR and Raman spectroscopy characterization techniques. X-ray diffraction pattern and FE-SEM studies confirms the amorphous nature of prepared oxide glass. The optical absorption studies were done by using UV–Vis spectroscopy technique at room temperature. The physical parameters of all the glass samples were evaluated with respect to the composition, such as bulk density (ρ), average molar mass (M), molar volume (Vm), ionic concentration (N), interionic distance (ri). They exhibit the non-linearity supporting evidence for the borate glass network modification. Investigations of FTIR and Raman spectroscopy of prepared glass samples have been employed to confirm the role of oxides in the formation of glass network. These glasses are made up from converting [BO3] to [BO4] units without increasing the concentration of non-bridging oxygen. Experimental fraction of 4-coordinated boron atoms expressed by the parameter N4 was calculated and represented with the addition of concentration of CdO (mol%). The optical absorption studies revealed that the average refractive index (nav), optical band gap energy (Eg) nonlinearly increases. The electronic polarizability and optical basicity of the oxide ion (αO2−), as function of refractive index and optical band gap energy were also examined.

Investigations of radiation shielding using Monte Carlo method and elastic properties of PbO-SiO2-B2O3-Na2O glasses

Several physical parameters such as the packing density (PD), oxygen molar volume (OMV), oxygen packing density (OPD) and the elastic moduli of the quaternary glass system xPbO-(30-x)SiO2-46.67B2O3-23.33Na2O (x = 0, 5, 10 and 15 mol%) have been evaluated. The elastic moduli were computed according to Makishima-Mackenzie model and Rocherulle model. The values of these moduli have been compared to their experimental values. Moreover, different shielding parameters such as mass attenuation coefficients (MAC), half value layer (HVL), mean free path (MFP), effective atomic numbers (EAN), effective electron densities (EED) and buildup factors have been evaluated using the WinXcom program in the energy range 0.015–15 MeV for the quaternary studied glass system. The MAC values have been compared with MCNPX (version 2.6.0) Monte Carlo code. Besides, mass stopping power (MSP) for proton, alpha and electron as well as the removal cross section for fast neutron (∑R) have been calculated. The results observed that the composition has the highest value of PbO (15 mol %) showed excellent nuclear radiation shielding and elastic properties.

UV and electrical properties of TeO2-WO3-Li2O-Nb2O5/Sm2O3/Pr6O11/Er2O3 glasses

UV absorption spectra of quaternary tellurite glasses in the form TeO2-WO3-Li2O-Nb2O5/Sm2O3/Pr6O11/Er2O3 were measured in the range 200–850 nm. Optical energy gap EASFopt. (eV), EDASFopt. (eV), Urbach's energy Eu (eV), and refractive index (n) were calculated using both absorption spectrum fitting (ASF) and derivation of absorption spectrum fitting (DASF) methods. Room temperature electric measurements were carried out by using LCR Hi Tester Meter Bridge in the frequency range of 100 Hz-100 kHz. Dielectric constant, ε′, dielectric loss, ε″, and ac conductivity, σac, have been found. Results show that, in ASF method the optical energy gap values are in the range of 3.59 to 4.58 and 4.76 to 5.18 eV for indirect and indirect transition, respectively, while in DASf method, the optical energy gap values are in 5.14 to 5.30 eV. Refractive index values for glass systems are in the range of 2.06 to 2.25 and 1.973 to 2.254 for indirect and indirect transition, respectively in ASF method, while in DASF method it takes values from 1.95 to 1.97. Electrical data ε′, ε″ and σac of the present glasses were in the range 18,611.9 to 24,670.9 ± 0.25, 2070.4 to 2842.8 ± 0.15 at (100 Hz) and 4.50 to 6.26 ± 0.05 × 10−4 (Ω·cm)−1 (100 kHz), respectively.

Preparation of quaternary boro-phosphate multifunctional glasses and their structural, optical, switching and antibacterial properties

In this paper, the glass composition of (50-x)P2O5-xB2O3-30CuO-20Li2O (x = 0, 5, 10, 15, and 20 mol%) was prepared and the effect of P2O5 substitution by B2O3 on their structural, optical, switching, and antibacterial characteristics was studied. FT-IR spectra showed that an increase in the B2O3 content leads to gradual erosion of the phosphate characteristic bonds, and the emergence of borate-related ones by creating new linkages between phosphate chains through P–O–B bonds and formation of highly cross-linked P3-O-B4 linkages. The incorporation of boron up to 20 mol%, also leads to an overall increase in glass transition temperature together with a decrease in the molar volume which both, implied improvement of glass stability. Optical studies revealed that all glasses are almost transparent in the UV–Vis region with high band gap energy about 3.83 eV, which experiences a red-shift with increase in the B2O3 concentration to 15 mol%. By calculating the wavelength-dependent optical parameters, however, it was found that the present glass composition with highest concentration of B2O3 shows refractive index near one and very negligible extinction coefficient (and imaginary optical dielectric function) at the visible region. These results support the great potential of the mentioned glass composition as a window layer. The analysis of the high electric field measurements demonstrated a wide range reduction in switching threshold voltage as the B2O3 content increases. This hints at their potential application as electrical-induced sensors. The antibacterial activity of x = 0 and x = 5 glass compositions has been examined by zone of inhibition measurements and it was found that they have potential applications as antibacterial agent.

Synthesis and bioactivity assessment of high silica content quaternary glasses with Ca: P ratios of 1.5 and 1.67, made by a rapid sol-gel process.

Sol-gel glasses in quaternary silica-sodium-calcium-phosphorous systems have been synthesized using a rotary evaporator for rapid drying without ageing. This novel fast drying method drastically decreases the total drying and ageing time from several weeks to only 1 hour, thus overcoming a serious drawback in sol-gel preparation procedures for bioglasses. This work investigates the bioactivity behavior of two glasses synthesized by this fast method, with Ca:P ratios of 1.5, and 1.67. X-ray diffraction (XRD), Inductive coupled plasma, Fourier-transform infrared, and Raman spectroscopy were used to confirm the bioactivity of the synthesized powders. MAS-NMR was also used to assess the degree of silica polymerization. The composition with a higher Ca:P = 1.67 ratio showed better bioactivity in comparison to the one with Ca:P = 1.5, which exhibited little bio-response with up to 4 weeks of immersion in SBF (simulated body fluid). It was also found that an orbital agitation rate of 120 rpm favors the interfacial bio-mineralization reactions, promoting the formation of a crystalline hydroxyapatite (HAp) layer at the surface of the (Ca:P = 1.67) composition after 2 weeks immersion in SBF. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 510-520, 2018.