Journal of Non-Crystalline Solids: X最新文献

The purpose of this paper is to demonstrate the existence of a number of universal properties present in a wide variety of ionically conducting materials in the liquid, glassy and crystalline states. This remarkable finding deserves attention and explanation. Moreover these universal properties are at the same time anomalous. Progress in research and applications of ionic conductors is retarded without having given explanations or resolutions of these anomalous properties. Although the Coupling Model of the author have predictions that can explain these universal and anomalous properties of conductivity relaxation and ionic conductivity, it is highly desirable for other theories to participate in offering alternative explanations.

Hydrophobic coatings are widely employed in liquid-vapour phase change applications, offering advantageous control on condensation dynamics. However, they suffer from poor stability under harsh conditions and their durability is often neglected over thermal performance. Here, the global performance of a hybrid octyl-modified silica coating on aluminium was studied during saturated vapour condensation, in terms of thermal efficiency and durability. The coating successfully promoted dropwise condensation with heat transfer coefficients of ∼90 kW m⁻² K⁻¹, an average 9-fold increase with respect to filmwise condensation under similar heat flux conditions. Straightforward and reproducible tests were employed to separately evaluate the different factors influencing the coating's degradation, attempting to reproduce the conditions present in the apparatus used for the condensation experiments. The developed tests could successfully provide a rapid estimation of the coating's durability during a broad range of liquid-vapour phase change applications.

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.

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.

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.