Glass samples in the ternary NaPO 3 –MoO 3 –V 2 O 5 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 T g trends attributed to the formation of transition metal cluster structures and modifications in the phosphate network, leading to less connected Q 1 and Q 0 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.
This study revisits structural connectivities and bonding preferences in alkali borosilicate and aluminoborosilicate glasses based on 25 years of research of the corresponding author, using a combination of infrared, Raman and, with various collaborators, also solid-state NMR spectroscopy. Three representative systems, low-alkali NBS2, high-alkali MBS1 with M=Li to Cs, and high-Al 2 O 3 NABS, were examined to assess the validity and extrapolation of the Dell–Bray–Yun–Xiao (DBYX) model. While the model accurately predicts the fraction of tetrahedral boron, [BO 4 ] – , across compositions, spectroscopic evidence reveals different connectivities for low R and high R values. NBS2 shows a shift from Si–O–B 4 to B–O–B linkages upon annealing, whereas MBS1 displays, as predicted, enhanced mixed bonds, including mixed-ring structures. The ring types, as well as packing density, depends on the modifier cation and its radius. In NABS, Al 2 O 3 wins the competition for Na 2 O for charge compensation, reducing [BO 4 ] – formation. High aluminium content (Al 2 O 3 >10 mol%) leads to fewer mixed Si–O–B 4 bonds. Fewer mixed bonds are also observed for borosilicate glasses with low alkali content, where often 1–2 mol% aluminium oxide are added to prevent phase separation. This review discusses how glass composition, modifier field strength, charge-compensation competition, geometric factors, and thermal history all influence network connectivity and structure–property relation-
A systematic investigation was conducted to evaluate the physical, microstructural and thermal properties of lithium aluminosilicate (LAS) glass-ceramics, with particular emphasis on the effect of MgO concentration on the coefficient of thermal expansion (CTE). Experimental results indicate that the glass to glass-ceramic transformation is accompanied by an approximately 3% volume shrinkage, resulting in an increased density of the glass-ceramic relative to the parent glass. X-ray diffraction analysis confirms the formation of (LiMg,Zn) 1.7 Al 2 O 4 Si 6 O 12 as the main crystalline phase, which is isostructural with the β-quartz solid solution (β-QSS). Transmission electron microscopy reveals uniformly distributed nanocrystals with a mean size of ˜15 nm embedded within the residual glassy matrix. Thermal expansion measurements show that glass-ceramics containing higher MgO exhibit lower CTE values compared to that with lower MgO content, attributed to an increased fraction of the β-QSS phase. Additionally, key thermal characteristic temperatures of the parent glass, including the softening point (T S ), sphere (T SP ), half-sphere (T HSP ), and onset of melting (T M ), were determined using a high temperature heating stage microscope. Such parameters provide valuable insights into the thermal behaviour and processing window of LAS glass-ceramics.
Moulds are critical components governing both thermal transfer and shape formation in glass container manufacture. This study employs finite element analysis to characterise temperature and stress fields in blow moulding moulds during processing. Results reveal a well-defined thermal gradient across the mould structure, with maximum temperatures at the inner cavity surface decreasing progressively outward. This thermal distribution correlates strongly with the mould's geometric design and wall thickness profile. Thermal analysis reveals significant stress localisation, particularly in the neck region, arising from the interplay of geometric constraints, wall thickness variations and thermal conditions. While quantitative results remain specific to the investigated configurations, the established relationships between these factors provide valuable guidance for moulds operating under similar thermomechanical constraints. Systematic consideration of these coupled phenomena in mould design demonstrates practical value through improved blowing stability, enhanced product quality and extended tool life. This work offers analytical approaches and physical understanding to support mould optimisation in industrial glass-working practice.
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 LionGlass™ 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.
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.
Foam glass or cellular glass, is a lightweight, porous glass material with a rigid structure. It is made by heating a mixture of powdered glass and one or more additives/ foaming agents and is used in different applications. From soil exchange and road construction (foam glass gravel), or being a high value add to cementitious binding products (foam glass granulate) to being a high end, dimensionally stable, block or plate for heat insulation (foam glass blocks). Many million tons of glass are recycled and reused in the world’s glass industry. The smaller fractions of the recycled glass have limited use and are often disposed off in landfills. As the starting material for foam glass is mainly a glass powder these fractions can be a perfect source. The presentation will show the path from waste glass recycling to a high end products showing the advantages manufacturing foam glass products. The requirements for the raw materials as well as foaming methods will be presented showing the advantages and disadvantaged of each method. The different production processes will be discussed and examples for the applications given.
The glass industry, one of the largest globally with production reaching 39·12 million tons in 2021 and a market value exceeding €28 billion, continues to face challenges related to high energy consumption, CO₂ emissions and competition from alternative materials. In this context, biomass ash and slag present a promising opportunity as an alternative raw material capable of driving significant progress towards decarbonising the glass industry. This study investigates processes and approaches to beneficiate ash and slag from gasification process to improve their suitability for industrial glass production. The biomass ashes and slag were characterised by x-ray fluorescence (XRF), x-ray diffraction (XRD), and Ultimate analysis (C,N,H,S) to determine ash composition. The results revealed that the ash samples contain 20–30% of carbon of the total ashes along with considerable amounts of chlorine, sulphur and heavy elements while slag samples were low in carbon, chlorine, sulphur and heavy elements. Both samples were then subjected to water leaching at 90°C, 75°C, 50°C and room temperatures for 1, 2 and 3 h, followed by analysis of leachates using ICP-MS, pH and conductivity measurements. XRF and ICP results confirm that the leaching process significantly reduced chlorine and sulphur levels, indicating high solubility and effective removal. Subsequent combustion of the samples reduced the carbon content from 20-30% to below 1% as confirmed via TGA and C,N,H,S analysis. Magnetic separation was employed to reduce iron levels and then the samples were sieved into respective size fractions, followed by incorporation into green soda–lime–silica (SLS) glass at a 5% substitution level using both raw and beneficiated ash and slag. The resulting glasses were then analysed and compared to benchmark green glass using XRF and UV-VIS analysis. The findings demonstrate that beneficiation route effectively removes impurities and inhomogeneity, offering a more resource-efficient and economically viable pathway aligned with circular economy for glass manufacturing.
Rare-earth-doped luminescent glasses, particularly lanthanide-activated materials, have garnered significant interest in modern luminescence research. This study investigates the luminescence features of Dy³⁺/Eu³⁺ co-activated multicomponent borosilicate glasses (10BaO–10ZnF₂–10K₂O–20SiO₂–(49−y)B₂O₃–1Eu₂O₃–yDy₂O₃, y=0·1, 0·25, 0·5, 0·75, 1 mol%), synthesized via the melt-quenching method. XRD analysis confirms the amorphous nature of the glasses. A comprehensive luminescence study – including photoluminescence excitation, emission, decay profiles, and colorimetric analysis – was conducted to explore energy transfer mechanisms. The spectral overlap between Eu³⁺ excitation (λem=612 nm) and Dy³⁺ emission (λexc=348 nm) bands in singly doped glasses suggests the presence of energy transfer in the co-doped multicomponent borosilicate glass. The increasing intensity of the ⁵D₀Æ⁷F₂ (Eu³⁺) emission under 348 and 392 nm excitation, correlating with Dy³⁺ concentration in Eu³⁺/Dy³⁺ co-activated multicomponent borosilicate glass, validates the predicted energy transfer pathways observed in the spectral overlap diagram. Decay profile analysis indicates a 42% energy transfer efficiency between the rare-earth ions in the prepared matrix. Additionally, a comparison of solar irradiance spectra with the photoluminescence characteristics of the prepared glasses was conducted to evaluate their potential as down-conversion materials for solar cells. The strong white and red emission characteristics of these glasses make them promising candidates for solid-state lighting and solar energy harvesting applications.
The digitalisation of engineered structures is being driven by the integration of advanced sensing and AI technology, enabling real-time monitoring, adaptive control, and autonomy of physical assets. Glass and photonic technologies, in particular optical fibre, are key in such development, as they offer robust sensing solutions that perform reliably in harsh environments, with minimal cabling intrusion. This paper reports a recently developed class of silica-based optical fibers, termed high-aspect-ratio-flat-fiber (HARFF). This optical fibre type, examples of which are shown in Figure 1, has been developed to enable new optical sensing capabilities, supporting higher-fidelity and more ubiquitous sensing systems for digitalization[1,2]. This new family of optical fibres are manufactured using stack-and-draw combined with laser-aided techniques to mitigate surface-tension related deformation of the preform, which can be common in traditional flame-based methods.
