Most of the advances in the current microelectronics industry derive from the experimental work involving semiconductor materials in the form of films (functioning as transistors, waveguides, sensors, etc.). The whole process considered various classes of materials (IV-IV-, III-V- and II-VI-based semiconductors) and it became possible only after their production and properties-control have been achieved. The same reasoning applies to the SiGe films in which new-intermediate (between those of Si and Ge) electronic-optical properties are expected to be mastered. Besides the Si-to-Ge relative composition, the final properties of the SiGe films are also susceptible to their atomic structure that, depending on the production-processing methods, can be amorphous, (nano-, micro-)crystalline, or a mixture of both. Motivated by these facts, the amorphous-to-crystalline transformation of Si1-xGex (with x ranging from 0 to 1) films was considered in detail in this work. The films were prepared by a standard (plasma-assisted) method and their main properties were investigated as a function of the Ge-to-Si relative composition and as influenced by different temperatures (of anneal and measurement). Raman scattering provided the structural information of the films, like the temperature at which the amorphous-to-crystalline transformation takes place as well as particulars of the lattice dynamics in the ∼ 80–1000 K range. Likewise, temperature-dependent optical transmission measurements yield the bandgap Egap of the amorphous-crystalline films, along with their Egap(T) behavior. Finally, the main aspects relating the composition, annealing-measurement conditions and structural-optical properties of the Si1-xGex films are presented and discussed envisaging future applications.
This work addresses structural and ionic transport properties of ion-exchanged borate glasses at temperatures below the glass transition, Tg. Analysis of the infrared reflectance spectra of the K-for-Na ion-exchanged glass 0.3Na2O-0.7B2O3 revealed short-range order structural changes, pointing towards the occurrence of alkali ion-induced sub-Tg structural relaxations of the borate structure leading to the establishment of suitable sites for the guest K ions. The conductivity spectra of the ion-exchanged glasses are dominated by two distinct dc responses before the dispersive regime. The low-frequency response is due to the development of a highly resistive ion-exchange layer where K and Na ions coexist, whereas the dynamics of Na ions in the core of the glass determine the high-frequency response. The structure and dynamics of the ion-exchange layer were shown to resemble those of the melt-quenched mixed K-Na borate glasses.
We present a theoretical study with focus on the transparency of silica glass (a-SiO2) in the ultraviolet light spectrum. All imperfections in the crystal structure can cause electronic subgap levels and thus increase the absorption of light. Therefore, we investigate a wide variety of defects and their respective electronic levels, like intrinsic point defects, defects connected to H2, O2 or H2O, and (inner) surfaces. Our calculations show that most subgap levels originating from stretched bonds, silane (SiH) or silanol (SiOH) groups concentrate in a range of 0–2 eV around the band edges. For an energy of ∼3.5 eV, like that of lasers in the controlled fusion ignition at the National Ignition Facility (NIF), these subgap levels do not cause absorption of such photons due to the large band gap ≥8 eV of a-SiO2. However, E’-centers (≡Si•), non bridging oxygen hole centers (NBOHC, ≡Si–O•) and peroxy linkages (POL, ≡Si–O–O–Si≡) may act as possible source of absorption. The addition of hydrogen can reduce the number of those defect levels in the middle of the band gap by shifting them to the band edges.
The High-energy Underwater Neutrino Telescope (HUNT) will deploy approximately 1200 underwater neutrino detector strings at depths of 1000m to 3000m. Carrying about 55,000 optical modules (OMs), these strings will form a three-dimensional observation array with an instrumented volume exceeding 30km3. Each OM mainly comprises a 20-inch photomultiplier tube, associated electronics, and a power supply system. The OM system’s long-term stability critically depends on the mechanical reliability and optical performance of its pressure-resistant glass sphere. HUNT therefore requires a sphere with a 23-inch outer diameter that can withstand 30MPa deep-sea hydrostatic pressure while maintaining optical transmittance of at least 85% from 380nm to 780nm. These combined requirements impose exceptional demands on sphere dimensions, structural strength, material quality, manufacturing precision, and broadband transparency under sustained deep-sea operating conditions. To the best of our knowledge, no commercial product currently satisfies all these specifications. To meet these requirements, stress simulations were first performed to determine the optimal wall thickness. The glass material and manufacturing process were subsequently developed in collaboration with a glass-instrument manufacturer, and prototype 23-inch pressure-resistant spheres were fabricated. The prototypes underwent comprehensive performance tests, including residual-stress measurement, dimensional inspection, optical-transmittance measurement, and pressure-resistance testing. Results show that the developed spheres possess highly stable mechanical and optical properties and satisfy the requirements of the present 2000 m prototype sea-trial campaign. Their successful development provides essential technical support for HUNT and offers potential applications in ocean observation and deep-sea engineering, including spherical housings for precision deep-sea instruments and deep-sea buoyancy modules.
In present work, Fe-based amorphous powders containing Al and Ti (Fe₈₅Al₁₃Ti₂, at%) were synthesized via mechanical alloying (MA) up to 100 h. Nanocrystalline phases formed at 60 h of milling following near-complete amorphization after 100 h MA with residual nanocrystalline inclusions detectable only by HRTEM. Consecutive consolidation via Spark plasma sintering (SPS) at varying sintering temperature from 550 °C to 1200 °C and holding time of 5–10 min, revealed phase formation during sintering. The increase in sintering temperature led to increase in particle bonding in the consolidated samples and consequently hardness from 2.0 ± 0.34 GPa for the sample sintered at 550 °C to 5.3 ± 0.09 GPa for the sample sintered at 1200 °C at 5 min holding time. Compression strength also increased from 104 MPa for the sample consolidated at 800 °C to approx. 1900 MPa consolidated at 1200 °C for 5 min. However, when the holding time increased from 5 min to 10 min at 1000 °C and 1200 °C compression strength decreased attributed to the coarsening phenomena. The fracture morphology changes from trans- granular brittle to ductile & mixed mode with increasing temperature due to improved interparticle bonding and coarsening phenomenon.
Calcium contamination is a critical limitation in the chemical tempering of glass, as even trace levels of Ca2+ can inhibit potassium–sodium ion exchange and degrade mechanical strengthening. This study systematically investigates the effects of Ca2+ contamination and regeneration strategies for KNO3 baths using oxide-based additives and waste-derived silica. Controlled experiments identify ≈5 ppm Ca2+ as a critical threshold at which ion exchange is effectively suppressed, yielding no measurable surface compressive stress (CS) or depth of layer (DOL), while lower concentrations cause progressive degradation. These findings are validated using industrial salt bath samples, confirming the high sensitivity of chemical tempering to ppm-level contamination. Regeneration experiments with alumina, silicic acid, and silica powders show that efficiency is governed by both chemical affinity toward Ca2+ and particle-size effects. Ca2+-induced blocking originates from interfacial accumulation, whereas regeneration proceeds via immobilization in the molten salt. Alumina exhibits the most stable regeneration behavior, while silicic acid is effective at low additions (0.1–0.5 wt%) but less efficient at higher levels. Silica-based regeneration strongly depends on particle size, with fine silica achieving performance comparable to alumina. Notably, waste-derived silica synthesized via alkali fusion matches or exceeds commercial materials, demonstrating its potential as a sustainable regeneration agent.
Borate-based glasses are attractive for bone regeneration due to their rapid dissolution and their ability to promote the formation of an apatite-like layer in physiological environments. However, a challenge associated with borate glasses is controlling boron ion (B) release, which is critical for maintaining biocompatibility and structural stability. In this study, a borate glass series based on 47B2O3-XSrO-17ZnO-11Ag2O-(25-X)CaO (wt%, X = 0, 1, 3, and 5) glasses were synthesized to investigate the influence of strontium oxide (SrO) on glass structure, thermal behaviour, and B release. X-ray diffraction (XRD) confirmed that all compositions were fully amorphous, and 11B magic angle spinning nuclear magnetic resonance (MAS-NMR) revealed no significant changes in B speciation with SrO incorporation. Differential scanning calorimetry (DSC) showed a progressive decrease in melting temperature with increasing SrO content, suggesting that SrO modifies the melt behavior of the borate glass system. However, the relatively constant Tg and Tc values across compositions indicate that overall thermal stability and network rigidity were not substantially altered. Immersion in phosphate-buffered saline for up to 60 days demonstrated that B release increased with immersion time, while only the highest SrO substitution (5 wt%) showed a statistically significant difference compared with the Sr-free control. These findings suggest that, within alkali-free borate glass systems, SrO acts as a secondary network modifier that modestly influences long-term B dissolution without substantially altering early-stage degradation behavior.
