Journal of Non-Crystalline Solids: X最新文献

Dynamic light scattering was performed to measure the structural relaxation in sodium and zinc phosphate glass-forming melts in the range from 50 mol% to 40 mol% P₂O₅ where long polymer-like chains of PO₄ tetrahedra are systematically shortened in length. The findings reveal compositional changes in the non-exponentiality of the relaxation as well as in the glass fragility, the latter of which exhibits anomalous differences between sodium and zinc.

Mesoporous phosphate bioactive glasses (MPBGs) are novel and attractive biomaterials for biomedical applications. Here we report the sol-gel processing of P₂O₅-CaO and P₂O₅-CaO-Li₂O MPBGs using Pluronic P123 as the surfactant. Our results showed that P123 could act as a crystallization inhibitor, thus extending the composition range of MPBGs. The concentration of CaO from 40 to 55 mol% in P₂O₅-CaO MPBGs did not affect the phosphate chain structure and mesoporous morphology. However, the specific surface area and pore volume were slightly enhanced with the increased CaO concentration. In ternary P₂O₅-CaO-Li₂O MPBGs, the increase in Li₂O concentration (from 5 to 20 mol%) did not alter the phosphate chain structure and mesoporous morphology. However, 20 mol% Li₂O incorporation induced crystallization. Binary and ternary MPBGs showed relatively low acellular bioactivity as indicated by the slow formation of hydroxyapatite in physiological fluids. Sol-gel processing is a feasible strategy for synthesizing P₂O₅-CaO and P₂O₅-CaO-Li₂O MPBGs.

Nickel and Cobalt ion containing silica based nanoglasses confined within mesoporous SBA-15 and mesoporous alumina templates were synthesized by sol-gel process. These nanocomposites were investigated to understand their microstructure, magnetization dynamics and magnetic memory effects near transition temperatures using state-of-the-art characterization techniques including XRD, TEM and SQUID. The temperature and frequency dependent dielectric properties and Nyquist plot were also investigated. The effect of transition ions and template on memory effect and relaxation dynamics of spin glass phase were explained with Scaling and Vogel-Fulcher laws. The mechanism accountable for the observed characteristics of these nanoconfined amorphous systems are explained systematically. The polarization mechanisms as a function of temperature and frequency were also investigated comprehensively. This study provides an advanced understanding of magnetization dynamics and dielectric property in nanoglass system which will be of fundamental and technological interest that will help to tune and fabricate advanced functional nano materials.

We report Raman spectra in the sub-anodic region after electro-thermal poling of the 46S4 bioglass and show a correlation between structural changes and the induced second harmonic generation (SHG). The Raman peak at ca. 625 cm⁻¹, due to the symmetric stretching-bending vibration of Si-O-Si bridges, was employed to quantify the poling-induced structural changes since its frequency ν_s(Si-O-Si) varies linearly with the silicate network connectivity, NC. Key results include the increase of network connectivity towards the anode after poling, with NC varying from 2.24 before poling to 2.37 at the anode after poling. SHG measurements showed the presence of an optically-inactive layer of 1.0 μm thick below the anode, followed by an optically-active layer where the SHG signal is maximized from about 1.5 to 4.0 μm. In this layer the NC takes intermediate values and reflects modest changes with respect to the pristine bioglass. The present findings suggest that the transport of electrons near the metal film anode is faster than the Na ion transport towards the cathode.

Alkali-borosilicate glasses 16M₂O–10B₂O₃–74SiO₂ were studied for M = Li to Cs. ¹¹B NMR showed 57% four-fold coordinated boron for Li, but 88 to 97% for M = Na to Cs. The fraction of neutral borate triangles decreases from Na to Cs. Vibrational spectroscopy shows significant non-bridging oxygen on silicate species for Li, decreasing to a low level from Na to Cs. The glass transition temperature is highest for M = Cs and correlates with increasing network connectivity. Sub-liquidus phase separation and homonuclear bonding was observed for M = Li, while M = Na to Cs show good linking of silicate with borate tetrahedra. Raman spectroscopy reveals a maximum of danburite rings for M = K, the glass with the highest packing density. Glasses doped with Ni₂O₃ changed color from yellow (Li) to purple (Na), to blue in samples of higher optical basicity (K, Rb, Cs). Tetrahedral Ni²⁺ likely coexists with trivalent nickel, Ni³⁺, in blue glasses, while higher coordinated Ni²⁺ prevails in the yellow Li-sample.

Synthesis and characterization of the optical properties of materials especially at a nanoscale, is considered as important tasks for the engineering of photonic devices and systems. In this paper we study the photoluminescence of new nanocomposite material consisting of arsenic sulfide doped in porous glasses and the effect of photoinduced structural transformations on it. The nanocomposite was obtained via chemical deposition method in which arsenic sulfide powder was dissolved in an amine solution and then clean pieces of porous glass were impregnated for 2 days in the solution. Strong photoluminescence signal was observed in the samples when excited with lasers with excitation wavelengths of 405 and 532 nm. Also, the effect of laser irradiation on the photoluminescence of the samples was studied using confocal microscope with two different operating lasers 405 and 514 nm. It was observed that laser irradiation influences photoluminescence differently depending on the irradiation wavelength.

We present comparison of spin-coated thin films prepared in traditional way from solution of dissolved bulk glass of particular ternary composition with films prepared from mixture of two separately dissolved binary bulk glasses targeting the same composition. The samples of five tie-line As-S-Se compositions ranging from As₃₃S₆₇ to As₃₃Se₆₇ were deposited in specular optical quality and thermal dependences of their optical properties, thickness, surface roughness, organic residual content, structure, and chemical resistance were studied. The deposited thin films were also structured by hot embossing at various temperatures to study the influence of source solution preparation on structuring process. Thin films prepared from solution mixtures show close physico-chemical properties to thin films prepared from solutions of corresponding bulk glasses.

The optimization of the oxide and fluoride content, crystallinity and rare earth ion concentration in oxyfluoride glass ceramics (GCs) are of great importance in obtaining high photoluminescence quantum yield (PLQY) for optical refrigeration applications. Presented herein are the important advancements in the development of a novel oxyfluoride GCS of the composition (SiO₂-Al₂O₃)_(100-a) (YLiF₄)_b: (YbF₃)_b (a = 35 and 40; in mol %, b = 1 and 2 mol%) with the corresponding parent glasses with an in-depth investigation on enhancing the optical performance for laser cooling. Depending on the oxide/fluoride (O/F) ratio and ytterbium content the internal quantum yield (iQY) varied between 70 and 99% in glass ceramics at several excitation wavelengths. The optical properties of GCs containing YLiF₄ and YF₃ nanocrystals obtained from the same initial composition (modulated by time and fusion temperature) were compared to find the optimal composition for optical refrigeration. Low fluorine content led to the generation of YLiF₄ as a major phase after ceramization and high fluorine content helped in the generation of the YF₃ phase. An increase in the radiative lifetime of YF₃ GCs compared to YLiF₄ GCs has been found to coincide with the enhancement of the PLQY, which is beneficial for laser cooling. The temperature change (ΔT) change measured using a fiber Bragg grating (FBG) in the glass and glass-ceramic samples with different pump wavelengths showed significant heat mitigation near ∼1030 nm. The observed enhanced PL intensity, iQY and lifetime after purification of YLiF₄ glasses imply that the purity of the material plays a paramount role in lowering the background absorption and enhancing the quantum yield. Looking ahead, we see a bright future for oxyfluoride GCs in applications requiring the ultimate levels of thermal, mechanical and optical performance, especially for the development of cryocooler devices, which are still technologically challenging and expensive. The usage of GCs will open up new possibilities in optical cooling technology, enabling cooling devices of any size and shape.