Corrosion of silicate glasses in aqueous environment is common and it impacts many physical and chemical properties of these materials that have wide ranges of industrial and technological applications. However, the corrosion mechanisms of silicate glasses remain relatively poorly understood due to complicated interfacial reactions and transport behaviors. Here, we have employed molecular dynamics simulations with the recently developed reactive force field to investigate the sodium silicate glass and water interfacial reactions. Simulations up to 3 nano-seconds at four different temperatures were performed to study the key processes at the glass−water interface. The simulation results reveal three-stage interfacial reactions: (i) in the near-surface region, water diffusion and subsequent reactions with the nonbridging oxygen to form silanol groups are the dominating reactions; (ii) in the near-bulk region, the main reaction is silanol reformation through proton transfer; (iii) in the subsurface region (between the above two), both reactions were observed. It was also found that water transports in sodium silicate glasses mainly through two mechanisms: molecular water diffusion and proton transfer, with the former dominating in near-surface region and the latter dominating in all other regions. Acceleration of reactions and deeper water penetration were observed for higher temperature simulations, but by-products were observed for temperatures higher than 500 K.

We propose the formation of silica glass with improved optical transport properties by compressing its melted phase with a hot isostatic pressure machine at high pressure and temperature. The lowest Rayleigh scattering loss was obtained for the glass held at 200 MPa and 2073 K for 4 h. The observed loss corresponds to 0.07 dB/Km at 1.55 μm, which is about half of the loss in conventional silica glass fiber. The decrease in the loss was well explained in terms of the decrease in the size of the sub-nanometer-sized structural voids observed by positron annihilation lifetime spectroscopy in silica glass. The achievement of high transparency and strong confinement of light represents a promising result for the development of future fiber-core media.

Energy release rate and fracture toughness of amorphous aluminum nanoparticles reinforced soda‐lime silica glass (SLSG) were measured by performing fracture simulations of a single‐notched specimen via molecular dynamics simulations. The simulation procedure was first applied to conventional oxide glasses and the accuracy was verified with comparing to experimental data. According to the fracture simulations on three models of SLSG/‐Al2O3 composite, it was found that the crack propagation in the composites is prevented through following remarkable phenomena; one is that a‐Al2O3 nanoparticles increase fracture surface area by disturbing crack propagation. The other is that the deformation of a‐Al2O3 nanoparticle dissipates energy through cracking. Moreover, one of the models shows us that the crack cannot propagate if the initial notch is generated inside a‐Al2O3 nanoparticle. Such strengthening is partly due to the fact that the strength of the interface between nanoparticle and SLSG matrix is comparable to that of SLSG matrix, implying that their interface does not reduce crack resistance of the oxide glass.

Calcium aluminosilicate (CAS) glass systems are industrially significant due to their favorable optical, mechanical, and thermal properties, as well as serving as a basis for many glasses in nuclear waste confinement and alkali-free display substrates. [1][2][3][4] The properties which make them industrially desirable are closely linked to their complex structure. In general, the glass system is comprised of network forming silica and alumina units, both ideally in tetrahedral arrangement with four bonded oxygens. Bonded oxygens which bridge to neighboring network formers are appropriately called bridging oxygens (BOs). An interesting feature of the CAS glass system occurs when varying the ratio, R, of [Al 2 O 3 ]/[CaO]. When R < 1 (i.e., percalcic regime), calcium cations act as charge compensators for the negatively charged (AlO 4/2 ) − tetrahedra. Excess calcium cations decrease network connectivity, resulting in non-bridging oxygens (NBOs). At R = 1, previous studies consider the network to be fully connected with no NBOs. 5 However, multiple studies have revealed that a finite concentration of NBOs exist at this ratio. 6,7 When R > 1 (i.e., peraluminous systems), the [AlO 4/2 ] − units are in excess, with insufficient calcium cations available for charge balancing. Two mechanisms have been proposed to compensate for the insufficient population of modifier cations: the formation of highly coordinated alumina (i.e., [5] Al and/or [6] Al), [8][9][10][11] or the formation of three-bonded oxygens (TBO), also known as triclusters. 12 While triclusters are present in crystalline polymorphs, 12,13 verification of triclusters in glassy systems has been limited spectroscopically, and hence molecular dynamics (MD) has been the primary

Interactions between metals and oxide glasses are indispensable owing to their ubiquitous usages ranging from microelectronics to industrial production processes. In this study, adhesion between metal copper and amorphous silica (a-SiO2) was investigated as a primitive metal/oxide interaction by using reactive molecular dynamics simulations. According to uniaxial and shear deformation simulations on copper/a-SiO2 layered models, we found that adhesion between a-SiO2 and crystalline or amorphous copper layers is very weak. Indeed, the interlayer is the breakable surface because the fracture stress is much less than the yield stress of the matrix oxide. Contrarily, since a sufficiently oxidized copper layer binds stronger to a-SiO2, the fracture surface varies from the copper/a-SiO2 interface to in-between the oxidized/crystalline copper layers. It is concluded from the simulations that the oxidization improves adhesion between metals and oxide glasses for bonding processes, whereas it causes defects or impurities in the manufacturing process, because the oxidized layer eventually remains on oxide glass substrates. In addition, fracture simulations of composite models composed of copper nanoparticles and a-SiO2 were also performed to examine the effect of the inclusions on crack propagation. Because a thickness of a few nanometers of an oxidized layer was observed at the surface of the copper particle that precipitated in soda-lime silica glass, by scanning transmission electron microscopy with electron energy-loss spectroscopy, we investigated the influence of the oxidized layer on the fracture. Accordingly, it was found that the oxidized nanoparticle avoids stress concentration at the crack tip and eventually prevents crack propagation, because oxidization induces ductility in the interlayer of the composite. In summary, the degree of oxidization on the metal surface is an influential factor to control adhesion at the metal/oxide glass interlayer as well as the mechanics of the composite materials.