Pure Silica Glass Research Articles

Spray-dried ternary bioactive glass microspheres: Direct and indirect structural effects of copper-doping on acellular degradation behavior

Silicate-based bioactive glass nano/microspheres hold significant promise for bone substitution by facilitating osteointegration through the release of biologically active ions and the formation of a biomimetic apatite layer. Cu-doping enhances properties such as pro-angiogenic and antibacterial behavior. While sol-gel methods usually yield homogeneous spherical particles for pure silica or binary glasses, synthesizing poorly aggregated Cu-doped ternary glass nano/microparticles without a secondary CuO crystalline phase remains challenging. This article introduces an alternative method for fabricating Cu-doped ternary microparticles using sol-gel chemistry combined with spray-drying. The resulting microspheres exhibit well-defined, poorly aggregated particles with spherical shapes and diameters of a few microns. Copper primarily integrates into the microspheres as Cu0 nanoparticles and as Cu2+ within the amorphous network. This doping affects silica network connectivity, as calcium and phosphorus are preferentially distributed in the glass network (respectively as network modifiers and formers) or involved in amorphous calcium phosphate nano-domains depending on the doping rate. These differences affect the interaction with simulated body fluid. Network depolymerization, ion release (SiO44−, Ca2+, PO43−, Cu2+), and apatite nanocrystal layer formation are impacted, as well as copper release. The latter is mainly provided by the copper involved in the silica network and not from metal nanoparticles, most of which remain in the microspheres after interaction. This understanding holds promising implications for potential therapeutic applications, offering possibilities for both short-term and long-term delivery of a tunable copper dose. Statement of significanceA novel methodology, scalable to industrial levels, enables the synthesis of copper-doped ternary bioactive glass microparticles by combining spray-drying and sol-gel chemistry. It provides precise control over the copper percentage in microspheres. This study explores the influence of synthesis conditions on the copper environment, notably Cu0 and Cu2+ ratios, characterized by EPR spectroscopy, an aspect poorly described for copper-doped bioactive glass. Additionally, copper indirectly affects silica network connectivity and calcium/phosphorus distribution, as revealed by SSNMR. Multiscale characterization illustrates how these features impact acellular degradation in simulated body fluid, highlighting the therapeutic potential for customizable copper dosing to address short- and long-term needs.

Impact of Glass Free Volume on Femtosecond Laser-Written Nanograting Formation in Silica Glass.

In this study, we investigate the effects of densification through high pressure and temperature (up to 5 GPa, 1000 °C) in the making of nanogratings in pure silica glass, inscribed with femtosecond laser. The latter were monitored through retardance measurements using polarized optical microscopy, and their internal structure was observed under scanning electron microscopy. We reveal the difficulty in making nanogratings in densified silica glasses. Based on this observation, we propose that free volume may be a key precursor to initiate nanograting formation.

Reduction of injection molded silica glass defects and enhancement of glass quality via water debinding

Pure silica glass has been fabricated by the injection molding and sintering technique. The quality of the as-fabricated silica glass was improved via the water debinding process.

Temperature Dependence of the Thermo-Optic Coefficient of SiO2 Glass.

This paper presents a thorough analysis on the temperature dependence of the thermo-optic coefficient, dn/dT, of four bulk annealed pure-silica glass samples (type I-natural quartz: Infrasil 301; type II-quartz crystal powder: Heraeus Homosil; type III-synthetic vitreous silica: Corning 7980 and Suprasil 3001) from room temperature down to 0 K. The three/four term temperature dependent Sellmeier equations and respective coefficients were considered, which results from fitting to the raw data obtained by Leviton et al. The thermo-optic coefficient was extrapolated down to zero Kelvin. We have obtained dn/dT values ranging from 8.16 × 10-6 up to 8.53 × 10-6 for the four samples at 293 K and for a wavelength of 1.55 μm. For the Corning 7980 SiO2 glass, the thermo-optic coefficient decreases monotonically, from 8.74 × 10-6 down to 8.16 × 10-6, from the visible range up to the third telecommunication window, being almost constant above 1.3 μm. The Ghosh's model was revisited, and it was concluded that the thermal expansion coefficient only accounts for about 2% of the thermo-optic coefficient, and we have obtained an expression for the temperature behavior of the silica excitonic bandgap. Wemple's model was also analyzed where we have also considered the material dispersion in order to determine the coefficients and respective temperature dependences. The limitations of this model were also discussed.

No-Core optical fibers sensor for detecting hemoglobin concentration (HB) based on the Surface Plasmon resonance.

In this work, a fiber-optic biomedical sensor was manufactured to detect hemoglobin percentages in the blood. SPR-based coreless optical fibers were developed and implemented using single and multiple optical fibers. It was also used to calculate refractive indices and concentrations of hemoglobin in blood samples. An optical fiber, with a thickness of 40 nanometers, was deposited on gold metal for the sensing area to increase the sensitivity of the sensor. The optical fiber used in this work has a diameter of 125μm, no core, and is made up of a pure silica glass rod and an acrylate coating. The length of the fiber was 4cm removed buffer and the splicing process was done. It is found in practice that when the sensitive refractive index increases, the resonant wavelength increases due to the decrease in energy.

Hydroxylation and water-surface interaction for S-glass and silica glass using ReaxFF based molecular dynamics simulations

Hydrolysis at the water-glass interface significantly influences glass surface reactivity and adhesion characteristics. In glass fiber reinforced epoxy composite interphases, hydroxyls on the glass fiber surface reacts with silane coupling agents to form covalent bonds between the fiber and polymer matrix. In this study, the surface reactivity and hydrolysis reaction of silica glass and S-glass (Mg aluminosilicate glass with 65 % SiO2, 25 % Al2O3, and 10 % MgO in weight ratio) are simulated using ReaxFF molecular dynamics (MD) to investigate the formation of surface defects (i.e., under-coordinated atoms) and hydroxyls (number density, types and spatial distribution) at four surface annealing temperature conditions (300 K, 700 K, 1000 K and 1300 K). Our study showed that a higher areal number density of surface defects and hydroxyls formation occur at lower surface annealing temperature conditions. S-glass was predicted to have a lower number density of hydroxyls compared to pure silica glass. In addition, analysis on hydroxyl oxygen revealed the defects and oxide bond connected to Mg are responsible for hydrolysis in S-glass. RDF and hydroxyl categorization analysis revealed the S-glass could have closer proximity among hydroxyls despite the lower hydroxyl areal number density than silica glass. Lastly, silica glass showed more physisorbed water and surface energy, which agrees with previous studies. This surface hydrolysis and reactivity analysis study will guide the experiments to control the fiber coating process to tailor interphase in glass fiber-epoxy composites.

On the Formation of Nanogratings in Commercial Oxide Glasses by Femtosecond Laser Direct Writing.

Nanogratings (NGs) are self-assembled subwavelength and birefringent nanostructures created by femtosecond laser direct writing (FLDW) in glass, which are of high interest for photonics, sensing, five-dimensional (5D) optical data storage, or microfluidics applications. In this work, NG formation windows were investigated in nine commercial glasses and as a function of glass viscosity and chemical composition. The NG windows were studied in an energy—frequency laser parameter landscape and characterized by polarizing optical microscopy and scanning electron microscopy (SEM). Pure silica glass (Suprasil) exhibits the largest NG window, whereas alkali borosilicate glasses (7059 and BK7) present the smallest one. Moreover, the NG formation windows progressively reduced in the following order: ULE, GeO2, B33, AF32, and Eagle XG. The NG formation window in glasses was found to decrease with the increase of alkali and alkaline earth content and was correlated to the temperature dependence of the viscosity in these glasses. This work provides guidelines to the formation of NGs in commercial oxide glasses by FLDW.

A study of mechanical property and corrosion resistance of modified silica glass

In this study, alumina added silica glass was fabricated by rapid sintering synthesis. The alumina added samples consist of amorphous matrix phase and dispersed mixed phases including mullite and cristobalite. Dispersed strengthening phases do not induce cracks, instead, improve the overall mechanical properties. At the same time, alumina added sample maintains a similar good corrosion resistance compared with pure silica glass sample. This work provides a modification method to enhance the mechanical property of silica glass without damaging its corrosion resistance.

Bismuth-doped optical fiber from nanoporous glass with air cladding

The doping of nanoporous glass (PG) is a prospective technique for producing bismuth (Bi)-doped optical fibers. The refractive index of sintered PG is lower than pure silica glass because of PG high residual content of boron (2 to 3 at.%). This fact impedes the choice of fiber cladding for building a light-guiding structure. We have chosen the microstructured optical fiber with the core from Bi-doped nanoporous glass to overcome this problem. We have studied the glass composition and controlled the luminescent properties of bismuth active centers at each step of the fiber fabrication. The PG is suitable for the production of microstructured fibers.

Polarization-maintaining and radiation resistant optical fiber with germanosilicate elliptical core

This paper aims to consider fabrication of single-mode polarization-maintaining (PM) optical fibers with elliptical core, doped with 20 mol. % GeO2 and to study their optical properties and radiation resistance. The optical fiber preform was fabricated by chemical vapor deposition method. The low-oxygen central piece of the core in the preform was removed by high-temperature chemical gas-phase etching. The single-mode optical fibers 125 µm in diameter, with 65 µm thick polymer protection coating were drawn. The results of measurements of the optical properties at a wavelength of 1.3–1.55 μm confirmed that the highly-doped GeO2 optical fiber waveguides have a low optical loss and high radiation resistance owing to gas phase etching. Polarization-maintaining factor (h-parameter) of ≈ 8∙10-6 m−1 was achieved. As to the radiation resistance, our single-mode PM optical fiber with elliptical core appears to be quite competitive to the known PANDA PM optical fibers with a core made of pure silica glass.

Thermal Conductivity of Sodium Silicate Glasses and Melts: Contribution of Diffusive and Propagative Vibration Modes

The thermal conductivity of silicate melts and glasses is an important physical property for understanding the temperature distribution in high-temperature metallurgical processes; however, the mechanism of heat conduction in these non-crystalline materials remains unclear. Two types of vibration modes must be considered to understand the mechanism of heat conduction, namely, propagative and diffusive vibration modes. In the present study, we carefully derived the thermal conductivity of pure silica and sodium disilicate glasses and melts, and estimated the contribution of the diffusive vibration mode using a recently developed model. The results indicated that the diffusive vibration mode was not dominant in the silicate non-crystalline materials, whereas the propagative vibration mode (i.e., phonons) was dominant in the heat conduction of silicate glasses and melts, which is in contrast with borate glasses.

MCVD method for manufacturing polarization-maintaining and radiation resistant optical fiber with germanosilicate elliptical core

The aim of this work was to develop a fabrication process of single-mode polarization-maintaining germanosilicate optical fibers with elliptical core (GOFEC) doped with 20 mol % GeO2. The fiber preform was fabricated by MCVD method. The low-oxygen central piece of the core in the preform was removed by high-temperature chemical gas-phase etching. The influence of γ-radiation with a dose rate of 1 Gy/s on the optical losses in GOFEC at a wavelength of 1550 nm and at 25°C and −60°C were investigated. Their radiation resistance at −60°C is proved to surpass that of the existing analogous fibers. It has been found that the radiation-induced attenuation in such highly doped GeO2 single-mode fibers is higher than that in multimode fibers. In contrast to multimode fibers, radiation resistance in single-mode fibers depends on the material of the core and cladding. As to the radiation resistance, these GOFEC are comparable with the fiber of PANDA type with a pure silica glass core.

X-Ray And Phase Analysis Of Sio2 Glass

The formation of nanosized particles in pure silica glass irradiated in water in the reactor core with fast neutrons up to 1019 cm-2 and gamma radiation has been studied by optical spectroscopy and X-ray diffraction. Irradiation with neutrons leads to the destruction of the initial mesostructure of a - and β - quartz with dimensions of 1.7 and 1.2 nm and the formation of cristobalite and tridymite nanocrystallites with dimensions of 16 and 8 nm in displacement thermal peaks.

First-principles study of the surface of silica and sodium silicate glasses

We use \textit{ab initio} molecular dynamics simulations to investigate the properties of the dry surface of pure silica and sodium silicate glasses. The surface layers are defined based on the atomic distributions along the direction ($z-$direction) perpendicular to the surfaces. We show that these surfaces have a higher concentration of dangling bonds as well as two-membered (2M) rings than the bulk samples. Increasing concentration of Na$_2$O reduces the proportion of structural defects. From the vibrational density of states, one concludes that 2M rings have a unique vibrational signature at a frequency $\approx850$~cm$^{-1}$, compatible with experimental findings. We also find that, due to the presence of surfaces, the atomic vibration in the $z-$direction is softer than for the two other directions. The electronic density of states shows clear the differences between the surface and interior and we can attribute these to specific structural units. Finally, the analysis of the electron localization function allows to get insight on the influence of local structure and the presence of Na on the nature of chemical bonding in the glasses.

Effect of anionic substitution on the high temperature stability of polymer‐derived SiOC glasses

AbstractIn this study the high temperature stability (crystallization and decomposition) of two silicon oxycarbide glasses with a similar amount of free carbon (8.3 vs 9.6 wt%) but different content of Si‐C bonds (SiC0.22O1.57 vs SiC0.07O1.86) is presented. The two SiOC glasses are obtained from the same precursor (2 µm methyl‐silsesquioxane spheres) via pyrolysis at 1100°C in inert (Ar) or reactive (CO2) atmospheres. Further annealing in Ar flow at temperatures above 1100°C and up to 1500°C is performed and the samples are characterized by Fourier Transformed Infrared Spectroscopy (FT‐IR) and X‐ray diffraction (XRD). For comparison purposes the same precursor was annealed in air flow to obtain SiO2 and its high temperature evolution is also studied. Results suggest that the onset for the carbothermal reduction is not dependent on the amount of Si‐C bonds. Moreover, contrary to what is usually reported in the scientific literature, silica phase present in the SiOC glasses does not show, in the same experimental conditions, superior crystallization resistance compared to pure silica glass.

Hollow core optical fibres with comparable attenuation to silica fibres between 600 and 1100\u2009nm

For over 50 years, pure or doped silica glass optical fibres have been an unrivalled platform for the transmission of laser light and optical data at wavelengths from the visible to the near infra-red. Rayleigh scattering, arising from frozen-in density fluctuations in the glass, fundamentally limits the minimum attenuation of these fibres and hence restricts their application, especially at shorter wavelengths. Guiding light in hollow (air) core fibres offers a potential way to overcome this insurmountable attenuation limit set by the glass’s scattering, but requires reduction of all the other loss-inducing mechanisms. Here we report hollow core fibres, of nested antiresonant design, with losses comparable or lower than achievable in solid glass fibres around technologically relevant wavelengths of 660, 850, and 1060 nm. Their lower than Rayleigh scattering loss in an air-guiding structure offers the potential for advances in quantum communications, data transmission, and laser power delivery.

Modeling the effect of the addition of alumina on structural characteristics and tensile deformation response of aluminosilicate glasses

Aluminosilicate glasses, xAl2O3-(1-x)SiO2 with variable molar ratio 0 ≤ x ≤ 60%, were modeled by molecular dynamics (MD) in order to investigate the structural characteristics such as: coordination number and pair-angle distribution functions responsible for their mechanical performance. MD simulations showed that Si atoms coordinated to four O atoms are independently of the chemical composition. The number of O atoms coordinated to two decreased as the amount of Al2O3 is increased, while the opposite happened to O atoms coordinated to three. Al atoms coordinated to four O atoms were reduced as the amount of Al2O3 increases, whereas Al atoms coordinated to five O atoms were increased. Moreover, pair distribution function (PDF) study confirmed that the addition of Al2O3 causes densification of the aluminosilicate samples and, angle distribution function (ADF) corroborated PDF results and explained intermediate and long-range disorder structures of glasses. Assessment of the structural damage under uniaxial tension showed that aluminosilicate glasses are more capable of withstanding deformation without total structural failure than pure silica glasses.

Hugoniot states and optical response of soda lime glass shock compressed to 120 GPa

In contrast to relatively pure silica glass (fused silica—FS), commercial silica-rich glasses contain significant fractions of additional oxide components. In particular, soda-lime glass (SLG) consists of approximately 71% SiO2 by weight, which raises the question: what is the effect of additional cations on the shock compression response of silica-rich glasses? To address this question, plate impact experiments were conducted to determine the high-pressure Hugoniot states for shocked SLG (37 to 120 GPa) and compared with recently reported results on FS. Using laser interferometry, particle velocity profiles were measured at the impact surface and at the SLG/LiF window interface. In all experiments, the transmitted profiles show a single shock wave, with no features indicative of a phase transformation. The Hugoniot states determined from the wave profiles are described well using a linear shock velocity–particle velocity relation. Interferometry measurements (using 1550-nm wavelength laser) at the impact surface show that SLG is transparent when shocked to 55 GPa, transparent for tens of nanoseconds after impact between 55 and 81 GPa, and opaque beyond 81 GPa. From impact surface measurements, a linear relationship between the apparent and true particle velocity was observed, resulting in a linear relationship between the refractive index (at 1550 nm) and density. At 120 GPa, the SLG density is nearly twice its ambient value, indicating that SLG can achieve highly dense amorphous states. When compared to FS, shocked SLG is much less compressible and likely does not transform to a crystalline phase. A plausible explanation for this difference is suggested.

Broadband Radiative Cooling and Decoration for Passively Dissipated Portable Electronic Devices by Aperiodic Photonic Multilayers

AbstractBroadband radiative cooling and decoration for passively dissipated portable electronic devices by an aperiodic photonic multilayer structure is proposed theoretically. The designed optical structure can strongly emit in the infrared region from 6.9 to 40 µm within the blackbody radiation spectrum of electronic devices. Its emission spectrum exhibits good uniformity across different incident angles, enhancing the cooling performance. At an ambient temperature of 20 °C, the designed broadband radiative cooler can produce a net cooling power of 46.88 W m−2, 65.95% higher than pure silica of the same thickness. At a typical junction temperature of 90 °C allowed by the microprocessor die, the net cooling power reaches 239.55 W m−2, still with an 18.21% improvement over pure silica glass. In the visible regime, the designed structure displays a low uniformity in the reflection spectrum, producing an elegant color shift from the translucent gray color of normal direction to the silver and highly reflective look at a grazing angle. These results can be useful in future exterior and thermal designs of portable electronic devices.

Supercontinuum generation in nanostructured core gradient index fibers

We report on near-infrared supercontinuum generation in a submeter-long single-mode, nanostructured core fiber. The fiber core is composed of few thousand pure silica and germanium-doped silica glass nanorods with diameter of 200 nm each. The nanorods’ distribution is calculated based on the Maxwell–Garnett effective medium approach to mimic effective parabolic refractive index distribution in the fiber core. The standard stack-and-draw method was used to scale down the fiber structure and obtain subwavelength nanorods in the core. Size and distribution of individual nanorods are essential to determine modal and dispersion properties of the fiber without assistance of air holes in the fiber cladding. We study supercontinuum generation performance in this nanostructured core fiber pumping with low-cost microchip laser operating at 1550 nm with 1 ns pulse length and pulse energy of 0.4 µJ. A modulation instability-driven supercontinuum is generated in the fiber, covering a wavelength span of 1400–2300 nm. Due to possibility of dispersion engineering and all-solid structure the nanostructured fibers offer new possibilities for development of low-cost all-fiber supercontinuum light sources for the near-infrared range and cascaded ultrabroadband supercontinuum all-fiber systems.