Journal of Non-Crystalline Solids: X最新文献

Perovskite, particularly halide perovskite has drawn increasing attention in recent years because of its remarkable photoelectric properties. However, due to its susceptibility to environmental factors, its research and application have been hampered. Recently, perovskite nanocrystals (PNCs) have been precipitated inside glass by using thermal treatment or femtosecond laser irradiation, which results in unprecedented stability because they are protected by glass matrix. This article reviews the fundamental structure and properties of PNCs, the benefits of perovskite nanocrystals-glass composite structure, and the current state of research into the use of a femtosecond laser to induce PNCs in glass. We also discuss the recent progress in the use of perovskite nanocrystals-glass composite structure for stereo-holographic computing, micro-LEDs and optical storage.

Molecular dynamics simulations were used to evaluate the fracture strength of pre-stressed silica glass exposed to water molecules, with and without heating. The pre-stressed wet glasses had a strength enhancement of 5–7% in comparison to the original dry glasses. Heating the glasses while pre-stressed with included water resulted in an even greater strength enhancement. The glasses with a higher concentration of structural defects in the dry glass have an expected lower dry-glass strength in comparison to the glass with fewer defects. However, the weaker dry glass shows a greater strength enhancement after pre-stressed water exposure caused by the increase in the silanol concentration in the more defective glass that offsets the otherwise weakened glass. Increased silanol concentration has been shown to increase the expansion of silica glass, creating an increased compressive stress on the pre-stressed-wet glass relaxed to original dimensions, allowing for an increased strength enhancement.

Telluride glasses such as Ge-As-Te, Ge-Te, and As-Te are of much interest due to their extensive infrared transparency. The structure of these glasses has also been broadly investigated, but Raman studies are rare and current literature data shows a significant level of disagreements and discrepancies. Here we show that the source of this disparity is two-fold, first the low damage threshold of these glasses requires low photon energy and low power to obtain reliable spectra, and second the unusual surface oxidation of telluride glasses leads to strong Raman artefact in relatively short time. Overall, high resolution spectra of freshly polished glasses obtained at low power with a near infrared source reveal that only four main modes are required to consistently interpret all Raman spectral features. Analysis of these Raman spectra confirm the presence of large chemical disorder in Ge-As-Te and As-Te glasses, consistent with previously reported spectroscopic studies.

The oxygen speciation in (Na₂O)_x(GeO₂)_100-x glasses with 4 ≤ x ≤ 28 is studied using high-resolution ¹⁷O NMR spectroscopy at ultra-high field (35.2 T). The structure of glasses with x ≤ 18 consists of oxygen atoms bridging either two four-coordinated Ge^IV atoms (O⁴⁴) or a Ge^IV and another six-coordinated Ge^VI atom (O⁴⁶). The O⁴⁶: O⁴⁴ ratio monotonically increases with increasing Na₂O content in this composition range. Further addition of Na₂O results in a lowering of O⁴⁶ and in a concomitant rise in the concentration of non-bridging oxygen (NBO) atoms. The resulting compositional variation in the average coordination number of Ge atoms is associated with the non-monotonic evolution of density and the germanate anomaly in these glasses. On the other hand, increasing fictive temperature results in a net conversion of Ge^VI → Ge^IV + NBO in these glasses, which is argued to be a source of temperature dependent configurational entropy in germanate liquids.

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.