Journal of Non-Crystalline Solids: X最新文献

Glass surfaces play a critical role in several modern applications, and open questions remain as to how the bulk composition of a multicomponent glass informs its surface composition—particularly at the outermost monolayer. This has important implications for properties such as electrostatic charging, wetting, and adhesion. Here, we apply high-sensitivity low-energy ion scattering (HS-LEIS) to examine a systematic series of ternary CaO-Al₂O₃-SiO₂ glass compositions. Analyzed are fresh fracture surfaces created under high-vacuum conditions, giving rigorous attention to peak quantification details. Results indicate that the measured surface compositions are, within uncertainty, very close to analyzed bulk compositions. This finding runs contrary to many studies showing disagreement between surface and bulk composition in glass, and possible reasons are discussed. By providing an experimental foundation from relatively ideal fracture surfaces, these results pave the way for further studies on the outermost composition of realistic glass surfaces of commercial importance.

It has been a long-sought goal to explore the nature of amorphous formation. Investigate the role of interatomic potential can be a fascinating method to study this myth from bottom up. In this work, molecular dynamics is used to systematically study the glass forming processes of binary CuZr melts on both structural and dynamical evolutions. The strong repulsion between CuCu and the weak repulsion between ZrZr is found to determine the structural arrangement, and then affect the type, number and spatial correlation of clusters. The difference of melt dynamics is controlled by both the steep repulsion and the anharmonic attraction of potential. The increase of the anharmonic attraction in melts can also lead to a higher shear transformation zone density in the glass. Our findings provide deeper insights into the understanding of glass-forming processes and its connection to glassy performance controlled by interatomic potential.

This review is dedicated to recent advances in the study of bismuth-doped silica-based fibers, which are vital components for creating promising contemporary optical devices operating in the near IR region. The first part of the review summarizes features inherent to different types of bismuth active centers, such as photo- and thermally induced destruction and recovery, which are particularly of great interest with respect to the nature of luminescence in bismuth-doped fibers (BDFs). In addition, the review specifies the status and possible ways on how to improve the main characteristics of BDFs, moreover, the paper proposes the latest results regarding novel designs of BDFs and demonstrates recent progress in fiber lasers and amplifiers based on them, including bismuth lasers with record performance parameters, as well as compact and efficient broadband amplifiers. In conclusion, a short summary alongside with road-to-market perspectives of the developed active fibers are given.

PbS quantum dots (QDs) are appropriate for use in tunable optoelectronic devices such as optical amplifiers because of their large Bohr exciton radii (18 nm). Laser-assisted local heating around Ag NPs can provide an effective method for site selective precipitation and for controlling the size of QDs. Continuous wave (CW) laser irradiation has been applied on a Ag⁺-ion exchanged glass which lead to the precipitation of QDs PbS QDs of 5-nm diameter were precipitated after 3 min of CW laser illumination at 1.5 W. The PbS QDs showed a PL peak at λ ∼ 1490 nm, which shifted toward longer wavelength side as duration of Ag⁺ ion exchange and of laser illumination increased. This method was further applied to prepare a rod containing three sections with different diameters of PbS QDs to propose the possibility of developing broadband amplifiers to cover the 1.3–1.7 μm communication window using one glass fiber. Co²⁺ also absorbs 532 nm laser light and converts it to thermal energy that results in the precipitation of PbS QDs in the glass matrix. The emission peak of the QDs covers 1020 nm < λ < 1245 nm as laser power was increased from 6 to 7 W/cm². Temperature in the glass increased to ∼518 °C when it was illuminated at the intensity of 6 W/cm².

The process related to the formation of a multicomponent amorphous material during the reduction of α-Fe₂O₃ with the products of thermodestruction of WAS is studied using x-ray powder diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS). Because WAS contains sand and clay along with its bio-components, the thermal treatment of WAS is accompanied by the formation of amorphous carbon, SiO₂, Al₂O₃, and multicomponent alloys. At T = 1000 °C, under oxygen-deficient conditions, iron oxide was reduced according to the scheme: α-Fe₂O₃ → (amorphous phase)_{main part} + (Fe + Fe_0.94O)(crystalline)_{little part}. The main product of the Fe₂O₃ reduction is amorphous iron with a lamellar structure. Newly formed amorphous alloys form interlayers between the iron plates and 3D inclusions. Inclusions of C, SiO₂, and Al₂O₃ agglomerates are observed between the lamellar packs. This macrostructure of the material allows slow cooling of the 3D-samples while preserving the amorphous state of iron.

Glass structure remains puzzling to scientists, especially due to the challenges in characterizing their structural order beyond the first coordination shell, i.e., the so-called medium-range order. Structural method development is therefore needed to advance our understanding of, e.g., structure-property relations in these disordered materials. To this end, we here review the fundamentals, applications and perspectives of an interesting new approach, namely persistent homology, which is a type of topological data analysis. This method allows for the analysis of both ring- and void-type structures in materials without making any assumptions of the network structure. As discussed herein, it has recently been used to analyze atomic position data (as obtained from atomistic simulations or reverse Monte Carlo) of glasses, especially regarding their medium-range order structure. We also discuss the opportunities in coupling persistent homology analyses with machine learning calculations as well as the open questions and challenges that require further investigations.

We studied the short-range order and the atomic dynamics of stable and undercooled binary Zr₂Co alloy melts as well as their density and viscosity. The containerless processing technique of electrostatic levitation was used to achieve deep undercooling and to avoid contaminations. Static structure factors are determined by combining this technique with neutron and high energy X-ray diffraction. Co self-diffusion coefficients are measured by quasielastic neutron scattering. Our results reveal that the short-range order of the Zr₂Co melts closely resembles that previously observed for Zr₆₄Ni₃₆. We consider this as the origin of the very similar melt dynamics of these two alloys at same temperatures. On the other hand, the difference in the structure and dynamics when compared with those of Zr₂Cu and Zr₂Pd shows clearly that not only the atomic sizes, but also electronic properties or chemical bonding have an important influence on the melt properties of Zr-based glass forming melts.

PACS number(s): 61.20.−p, 61.25.Mv, 66.30.Fq, 61.05.F-, 61.05.cp