Glass samples in the ternary NaPO3-MoO3-V2O5 system were prepared using the melt-quenching technique and structurally characterised by XRD, DSC, Raman and infrared spectroscopy. The system exhibited a wide glass-forming composition range, with observed Tg trends attributed to the formation of transition metal cluster structures and modifications in the phosphate network, leading to less connected Q1 and Q0 phosphate units within the glass matrix. Selected 70% transition metal-containing compositions were used to prepare their corresponding glass-ceramics. XRD analysis revealed the preferential crystallisation of vanadium-containing phases interconnected with phosphate tetrahedra, effectively replicating the local structural environment of their parent glass.
The colour coordinates on standard CIE 1931 chromaticity diagrams are presented for NCS (15 soda-15 lime-70 silica (mol%)) glasses, singly and doubly doped with the transition metals (Ti, V, Cr, Mn, Fe, Co, Ni and Cu) at low concentrations (<= 1 mol%) and with various rare earth dopants (Ce, Pr, Nd, Sm, Eu, Tb, Dy, Er, Ho). The colour coordinates were calculated from the transmission spectra in turn determined from measured glass absorption spectra. The colour coordinates of 232 glasses are reported, showing which colours can be made with common colouring dopants, and how their coordinates depend on: dopants, concentrations, sample thickness, melting conditions (oxidising electric furnace and reducing gas furnace) and concentrations of agents added to the batch as oxidising (NaNO3), reducing (C) and/or refining (Na2SO4) agents. Cu shows the greatest variability. The varying oxidation states of the dopants and their coordination are the main reasons for colour differences. The effect of the glass thickness in the colour appears because the absorption peaks can be very high and locate partly outside of the visible light range that changes the proportions of the spectrum that stimulate the three colour receptors in the eye.
The ability of bioactive glass/polymer and glass-ceramic/polymer composites to elicit bone bonding reactions, accompanied by degradability, when used as implants, without provoking adverse immune responses, makes them attractive biomaterials for bone regeneration. More efforts are being devoted to synthetic strategies to make the process cost-saving and more appealing for commercial production. Against this backdrop, we synthesised and studied the bioactivity of a bioactive glass-ceramic/polymer composite with the glass composition of SiO2-CaO-SrO-P2O5. A solution precipitation approach was used to obtain the bioactive-ceramic from sodium metasilicate (Na2SiO3.9H2O) as a low-cost silica alternative to alkoxysilane precursors, which was used afterwards as a filler phase in a starch-based matrix. An in vitro bioactivity experiment was conducted to determine the hydroxyapatite-inducing capacity of the samples in simulated body fluid for 7-14 days. Thereafter, the samples were characterised with scanning electron microscopy, energy dispersive x-ray analysis, x-ray diffractometry and Fourier transform infrared spectroscopy. Results obtained showed that the bioactive glass-ceramic composite exhibited superior morphological characteristics, higher bioactivity and degradability compared with the pristine sample. The strontium-based bioactive glass-ceramic/starch composite possesses promising characteristics that could make it a potential scaffold for bone regeneration. Hence, sodium metasilicate can be considered a viable and low-cost substitute for alkoxysilanes in the production of strontium-doped bioactive glass/polymer composites.
This paper is dedicated to the memory of B. L. Kheruka who was the Executive Chairman of Borosil Glass in India. Borosil marketed neutral glass pharmaceutical vials in India. In addition to this pioneering effort, Kheruka pursued newer glass products for the Indian market. His spirit is carried in this paper where we discuss newer, stronger yet lighter weight glass products and the technologies that could make them possible. Lightweight glass containers and laminated windows present market appeal in view of their contribution to sustainability. Among the technologies that could lead these markets are the thin glass thermal tempering, faster chemical strengthening, overlay glazing technologies, and superhard coatings. A whole new possibility is presented by the development of LionGlassTM under the guidance of one of the authors (JCM), which is a low melting glass system having chemical durability and mechanical properties at least as good as that of the traditional soda lime silicate glass.
A systematic study was conducted to investigate the sintering kinetics of BaO-CaO-Al2O3-SiO2 (BCAS) glass using a heating stage microscope. The analysis focused on densification behaviour, densification rate as a function of temperature and evaluation of the activation energy. Experimental results reveal that significant densification occurs within the temperature range of 800-900 degrees C, indicating that pore elimination and shrinkage are most effective in this regime due to viscous flow mechanisms. The densification rate increases sharply up to 860-885 degrees C, depending on the heating rate (5-40 degrees C/min), followed by a gradual decline at higher temperatures. Activation energy for densification, estimated using Chen's equation based on fixed levels of shrinkage, ranges between approximately 620 and 670 kJ/mol. It is observed that the activation energy increases with the extent of shrinkage, attributed to the increasingly dense glass structure and the transition of porosity from open to closed and isolated state. Conventional sintering experiments further corroborate the densification trends. The viscosity-temperature relationship was predicted by fitting data obtained from the heating stage microscope and mechanical dilatometer to the Vogel-Fulcher-Tammann (VFT) equation.
Silica optical fibres doped with rare-earths ions are key components of photonics devices like fibre lasers and fibre amplifiers operating in near-infrared spectral region. Since rare earths in silica glass cause clustering and phase separation, the silica glass matrix must be modified, e.g. by alumina. Since starting materials of such components are available only in solid state, conventional chemical vapour deposition methods (like the MCVD method) used for telecom fibre production and based on starting materials in gaseous (or liquid) state had to be modified. This paper deals with 'nanoparticle-doping' method by which high-quality thulium-doped and holmium-doped preforms for specialty optical fibre drawing can be prepared. An easy implementation of the nano-particle-doping method into established technologies belongs to its strong points. High dopant concentration up to 10 mol% of alumina and thousands of ppm of rare earths (and high alumina/rare-earth ratio up to 50/1) distributed homogeneously in preforms (fibres) in macro-, microand nano-scale can be achieved by the proposed way. Fibre lasers based on such fibres exhibited low threshold, high slope efficiency (up to 64% in case of thulium-doped fibre lasers and 80% in case of holmium-doped fibre lasers) and high output power (Watts in case of thulium-doped fibre lasers and tens of Watts in case of holmium-doped fibre lasers).
The present manuscript discusses the advanced heat reflective sun control coatings produced by large area magnetron sputtering. To develop such sun control heat reflective coatings, we have used five different glass substrates, such as float clear, bronze, blue, green, and dark gray. The target materials, which we used for the sun control coatings, belong to the Groups IV A and VI B of the periodic table, that is, silicon nitride (Si3N4), and chromium nitride (CrN). The deposition of such coatings on various glass substrates having a size of 2440 & times; 1220 mm was prepared and coated via large area magnetron sputtering under high vacuum conditions. The coated samples were analyzed by using various characterization techniques to evaluate their optical, thermal energy, mechanical, and morphology properties by UV-VIS-NIR spectrophotometer and field emission scanning electron microscopy (FESEM). The coated products have finally been found to be utilized for an application related to facade buildings toward sustainable solutions in the field of advanced engineering.
Samples of cemented magnesium turnings and Magnox alloy, simulating wasteforms that require re-work, have been thermally treated to produce largely glassy calcium magnesium aluminosilicate products. X-ray diffraction shows the presence of a variety of crystalline phases (MgxAl2-xO4 phases, akermanite-gehlenite phases and merwinite), as well as diffuse scattering characteristic of glassy material. Structural investigations using Raman spectroscopy show that the products contain amorphous aluminosilicate networks, with changes in the Q(2) and Q(1) species in the network with increasing metal content. These investigations also suggest a high number of [AlO4](-) tetrahedra are present in the network.
Density is a fundamental structural property of matter, and gas pycnometry provides an advantageous means for measuring the density of solids, especially powders. A report is given of an investigation of the use of a commercial constant volume gas pycnometer, with emphasis on the difficulties associated with small samples. Measurements were made on various numbers of high purity aluminium pellets, and on a series of barium tellurite glasses, with compositions from 10 to 25 mol% BaO. As the sample gets smaller, there is an increase in the statistical error, but more importantly the systematic error due to inadequate calibration becomes larger. We advocate the approach where calibration is performed using several standards of varying volume, and the calibration measurements are performed using exactly the same measurement procedure as for the samples of interest. The measurements on the aluminium pellets were used, with reference to the crystallographic density of aluminium, to refine the calibration of the pycnometer. The refined calibration was used to correct the glass density measurements, with notable improvement in the behaviour of the results and their consistency with results from the literature.
We discuss the viscosities, the Ising-like critical behaviour, and the boson peak of supercooled metallic liquids in terms of field-theoretical formulae with local gauge-invariability, which is developed from the Sethna-Sachdev-Nelson gaugeformula. The boson modes around the icosahedral clusters may be attributed to quasi-localised modes, which are created due to absorbing Nambu-Goldstone modes related to zero-modes of three-angle-freedoms of the icosahedral clusters. Furthermore, the present theoretical formula is compared with Elliott's unified model for the boson peak in network glasses. Also, new order parameters for supercooled liquids and glasses are introduced. An analysis from the point of view of the field-theoretical formula is given of experimental viscosity data for bulk metallic glass-forming liquids.
This article reviews our work on the structure of borate glasses conducted at the National Hellenic Research Foundation since 1985, in collaboration with numerous colleagues around the world. Both infrared and Raman spectroscopies were employed to study the borate structure, because these techniques provide complementary information due to differences in selection rules. Borate glasses containing modifier metal ions such as alkali, alkaline earth, rare earth, transition and post-transition metal ions,were prepared and studied to probe the evolution of the borate speciation with composition. B2O3 glass consists of neutral, planar [B & Oslash;(3)](0) triangles where & Oslash; is bridging oxygen, with ca.75% of them being arranged in planar hexagonal boroxol rings. At low metal oxide contents the [B & Oslash;(3)](0) species transform to negatively charged [B & Oslash;(4)](-) metaborate tetrahedra. The change in boron coordination is widely accepted as the basis of distinct differences in the composition dependence of properties between silicate and borate glasses. The latter exhibit non-monotonic variations in physical properties with metal oxide content, known as the borate anomaly. At higher modifier oxide contents, non-bridging oxygen atoms (O) are formed on metaborate triangles, [B & Oslash;O-2](-),and pyroborate species, [B & Oslash;O-2](2-), until finally orthoborate monomers, [BO3](3-), are generated and lead to the complete depolymerisation of the borate network. In highly modified glasses (invert glasses) the [BO3](3-) triangles may exist in equilibrium with isomeric orthoborate tetrahedra, [B & Oslash;O-2(2)](3-), the formation of which partially re-establishes the borate connectivity and leads to a second manifestation of the borate anomaly. It was discussed that the chemical reactions and equilibria between borate species are controlled by composition, the field strength of the modifier cation, the temperature and pressure, and the external dc electric field for electro-thermal poling. Change in borate speciation directly affects the complex environments (sites) of the metal ions in the glass matrix. This has important implications for physical properties like ionic transport and glass basicity, as these properties depend directly on the nature and spatial distribution of the sites hosting the modifier metal ions. In this context, far-infrared spectroscopy has been employed to probe metal ion-site interactions in glasses and the results are discussed in relation to those of molecular dynamics simulations on single and mixed alkali borate glasses.
The Tenth Borate Conference on Glass, Crystals, and Melts (Borate X) was held in July 2023 in Corning, NY and it honuored Efstratios “Stratos” Kamitsos. He is the leading advocate for the use of infrared and Raman spectroscopy in the study of glasses, with borate glasses having received considerably more attention than other glassy systems. For forty years he made essential discoveries of atomic‐level structure using these techniques in conjunction with other spectroscopies. Here, we review his personal life and present a selective, non‐comprehensive summary of his scientific accomplishments and his role as a teacher, mentor, and friend.
Over the past few decades, rare earth aluminate glasses have attracted widespread attention in different fields, owing to remarkable electric insulation performance, high refractive index and high transmittance. In this work, we firstly investigate the mixed rare earth effect by partial substitution of lanthanum for yttrium oxides in aluminate glasses by a contactless aerodynamic laser heated levitation technique. Different with previous reported mixed modifier glasses, the result of the aluminate glasses manifest a near‐linear trend in Vickers hardness with the rare earth substitution. Using Raman spectroscopies to insights into the structural these glasses, we demonstrate that the high crack resistance (CR) of aluminate glass is stronger correlation with the medium-range structure. In addition, we found the mixed rare earth effects on the glass transition temperatures, which show is stronger correlation with the medium-range structure order (peak width at half height of the lower-frequency region). In the aluminate glasses, the mixed rare earth have the Al–O and La–O bond distances diversity, which consequently increase the coefficient thermal expansion in aluminate melts. However, the isokom temperatures in aluminate melts exhibit a linear trend with composition.
The preparation, analysis and certification of a new certified glass reference material (CRM) for multi-element determination in soda–lime–silica glass is described. The CRM BAM-S006 is available in the form of discs (thickness: 5 mm, diameter: 40 mm) as well as in form of cullet. Certified properties are the mass fractions of 19 main, minor and trace elements. The certified values are based on the results of 18 laboratories which participated in the certification inter-laboratory comparison. The CRM is intended for establishing or checking the calibration of x-ray spectrometers for the analysis of samples of similar matrix composition as well as for wet chemical analysis.
The nature of the medium-range (MR) structure of glasses and other amorphous solids is still a maer of debate. On the other hand, the magnetism of ordinary insulating glasses devoid of magnetic species other than trace impurities has always been considered as made up of Larmor diamagnetism of the inner-shell electrons and the small Langevin paramagnetism of the outer-shell electrons of the atomic impurities. In this paper, evidence will be given that a novel type of paramagnetism is found in insulating glasses (notably in the multi-silicates) that is intrinsic to the glassy nature of the structure of these solids. This is revealed by the temperature, T, and magnetic field, H, dependence of the magnetisation M=M(T,H), once the Larmor and Langevin contributions are carefully subtracted out. The remaining, intrinsic part of the magnetisation displays a peculiar behaviour in all the samples that we have studied using a SQUID magnetometer. While the non-Larmor magnetisation of most solids made up of atomic-scale magnets typically saturates to a constant value at large H/T values, the glassy intrinsic part of M presents a broad peak at high H and small T that does not have a known theoretical explanation. Moreover, at moderate H, the intrinsic M presents some small unexplained oscillations in T that are to be found in all of the glassy materials studied. The explanation offered here is that the MR-structure of glasses should be thought of as made up of jam-packed solid-like cells, without crystallinity of the bulk, and liquid-like atomic species in the voids between the cells. A quantum-mechanical model that deals with effective quasi-particles tunnelling in a local three-welled potential describes rather well the atomic species adsorbed on the cell walls. The model can successfully reproduce the observed behaviour of the measured M(T,H) while the oscillations are thought to be associated with thermal rearrangements of elongated cells in the MR-structure. The size of the cells is typically in the tens of nm range for these glasses. The MR-structure advocated here has also been discovered in a glass specimen produced from melting the sol-gel paste of a barium aluminium silicate in a special graphite crucible. The resulting specimen shows, even to the naked eye, a distinct cellular MR-structure where the cells are indeed elongated, of mm size, and are separated by fluid-like regions.
Water diffusion in lead silicate melts has been measured at temperatures ranging from 800 to 1200°C for compositions containing 35 to 65 mol% PbO. The diffusivity of water increases with increasing PbO concentration and with experimental temperature, with values ranging from 1×10−6 to 5×10−5 cm2/s. Water diffusion was also measured at 1200°C for three series of sodium lead silicate melts. The diffusivity of water increases with decreasing SiO2 content. The results of this study are compared to those for water diffusivity in sodium silicate and soda lime silicate melts. The relation between water diffusivity and melt viscosity is considered for all four glass forming systems. It is demonstrated that the correlation between water diffusivity and melt viscosity only occurs for very limited ranges of temperature and melt composition. As has been found for many other systems, the glass transformation temperatures of the lead silicate and sodium lead silicate glasses decrease with increasing water concentration in the glass.
We have investigated the high frequency (1000–1300 cm−1) Raman spectroscopy envelope of vitreous silica (SiO2). The purpose of the study is to elucidate the multicomponent nature of the two bands in the high frequency envelope of v-SiO2. This is important as inferences about the nature of silicate glasses are often made based on fiing of these and other Raman bands. The high frequency envelope has two broad bands at 1065 and 1200 cm−1. These bands are commonly assigned to the T2 and A1 motions of an isolated SiO2 tetrahedron. However, we show that both broad bands are composite peaks each consisting of two individual peaks at 1054 and 1090 cm−1 (1065 cm−1), and 1181 and 1235 cm−1 (1200 cm−1), respectively. Furthermore, the assignment of the higher frequency band to an A1 symmetric stretch is unlikely given that polarised spectra indicate that the bands in the 1200 cm−1 envelope are highly depolarised.
This paper considers the density of sodium borate glass, 20Na(2)O.80B(2)O(3)(mol%), stabilised at various temperatures over the region from the glass transition point T-g=450 degrees C down to 390 degrees C. It was found that the density, which was measured after the glass sample air cooled to room temperature, increased with decreasing stabilisation temperature. Since the density stopped changing over the interval from 402 to 390 degrees & Scy;, it was assumed that the glass structure became as similar to that of the corresponding crystalline compound Na2O.4B(2)O(3) as was possible under the chosen experimental conditions. The structural changes that proceeded in stabilised glass with decreasing temperature are analysed quantitatively in terms of the short-range order and intermediate-range order in the glass structure. This analysis is based on the concept of the chemical structure, which enables both structural levels to be calculated. The concept applies to systems formed from oxides with different chemical natures, and it takes into account the set of crystalline compounds that form in a given system.
This study examined the influence of iron oxide incorporation on the durability of phosphate glasses with the following formula 50P(2)O(5)-3333K(2)O-(1111-x/2)CaO-(556-x/2)MgO-xFe(2)O(3) with 0 <= x <= 2 mol%. Indeed, the effects of adding iron on the glass structure, physicochemical properties, thermal properties, and especially, dissolution behaviours were investigated. The glasses were prepared using the classical melt quenching technique at 1000 degrees C. The characterisation was performed using differential thermal analysis, x-ray diffraction, density measurements, Raman spectroscopy and Fourier transform infrared spectroscopy. Dissolution behaviours were followed by measuring weight loss and pH. The substitution of calcium and magnesium for iron increased the characteristic temperatures (T-g, T-c, T-f) and reduced the molar volume, showing a more compact phosphate glasses network. Structural characterisation showed that the glass network is composed mainly of metaphosphate chains. The dissolution behaviours of the processed glasses revealed that the introduction of Fe2O3 to the phosphate glasses can improve the chemical durability due to the ionic crosslinking between the nonbridging oxygen atoms of the phosphate chains, which explains the changes in their physicochemical properties.
The aim of this work is to understand the main driving force of the crystallisation behaviour that occurs with the addition of P2O5 to a Na2O-B2O3-SiO(2)glass system with fixed component ratio. We apply P-31,B-11, Si-29 and Na-23 solid state NMR in combination with previously published x-ray diffraction (XRD) patterns and Rietveld analysis on the same samples to characterise the distribution of bridging and nonbridging oxygens in the glass matrices and the crystal compositions. We use the quantitative fractions of bridging and nonbridging oxygens per nucleus as obtained from the NMR experiments to characterise the oxygen partitioning between the nuclei. The strength of this analysis is that no information about the nature of the next nearest neighbours is necessary. Given the constant ([3]) B:([4]) B ratio (within signal-to-noise) our analysis shows that the oxygen requirements of P2O5, which depolymerises compared to its starting component, is met by the silica network, which in turn polymerises. Our estimates indicate that the depletion of nonbridging oxygens from the silica network initiates the crystal formation in the form of, first, Na3PO4 domains, and then Na4P2O7 crystals, consistent with phosphorus's highest cation field strengths between components.
