Alkali Aluminosilicate Glasses Research Articles

Effects of P2O5 content on the structure, stress distribution and vickers hardness of Na2O-MgO-Al2O3-SiO2 glasses with chemical strengthening treatments

In this work, effects of P2O5 content on the structure, stress distribution and vickers hardness of alkali aluminosilicate glasses with different chemical strengthening treatments were investigated. The results showed that the addition of P2O5 increased the degree of polymerization for glass network. The coefficient of thermal expansion, glass transition temperature and density of the parent glasses were all decreased. Meanwhile, the molar volume of the samples increased. The chemical strengthening experiments revealed that increasing P2O5 content promoted the diffusion of K+ ions, which resulted in an increase in the depth of stress layer. However, surface compressive stress of the glasses decreased with P2O5 content increasing, mainly attributed to stress relaxation of the glass structure. After chemical strengthening treatments at 370 °C and 390 °C respectively, the vickers hardness of the glasses decreased with the increase of P2O5, while an opposite trend was observed at 410 °C.

Enhancing anti-reflective properties of electronic glass through two-step chemical etching

With the rapid growth of the electronic display industry, aluminosilicate glass has emerged as a replacement for traditional soda lime silica glass as the cover plate of various display devices because of its excellent physical and chemical properties. High transmittance and low reflectivity are the inevitable requirements of its application. However, few studies have been reported about the antireflection of aluminosilicate glass. In this study, a two-step etching method was employed to treat both sides of the alkali-aluminosilicate glass to obtain surface antireflection. Analytical methods such as EPMA, AFM, and UV spectrophotometry were utilized to evaluate the effect of the etching process and resultant surface microstructure on the optical properties of the glass. Furthermore, comparative research was conducted to distinguish the etching reaction differences between alkali-aluminosilicate glass and other glass compositions like soda-lime glass and high-boron-silicon glass. The results demonstrated that the controlled two-step etching process created a micro-porous surface structure, with a gradient refractive index. Subsequent to the secondary etching, the glass exhibits an impressive average transmittance of 98.88% within the visible light spectrum (380–780 nm). Moreover, identical etchant across different composition glasses leads to discernible differences in transmittance.

14‐3: Drop Resistance Optimization Through Post‐Hoc Analysis of Chemically Strengthened Glass

In the market of the mobile cover glass, the development of chemically strengthened glass is focused on the drop resistance improvement. The cover glass which protects the display panel is a typical brittle material that the micro cracks tends to be occurred underneath a glass surface by physical impacts. The micro cracks tends to be propagated by tensile stress and it is known as a general procedures on glass breakage. In purpose of the cover glass strength improvement, compressive stress is applied to the glass surface using chemical strengthening method by ion exchange. However, since the central area of the glass is relatively subjected to tensile stress, the glass is instantly broken when the propagated cracks are reached on the tensile stress exerted area. The glass specifications have been managed for maintaining the strength using parameters of compressive stress (CS), depth of compression (DOC), and central tension (CT). However, there was no method to judge the most effective factor for impact drop resistance. In order to solve this problem, we developed a machine learning program for cover glass that can predict the breakage height based on stress and mapped evaluation data based on the measured stress profile data and the actual drop breakage simulated evaluation. Especially, eXplainable AI (XAI) method is used to identify the effective factors on drop breakage height. And the test and measurement data were applied to various chemically strengthened glass for analysis.In this study, it was possible to predict the drop breakage height only by measuring the stress profile of chemically strengthened glass. The feature value of chemically strengthened that has the most effect on the drop breakage resistance on rough surfaces was identified to be stress value at 30um in the case of alkali aluminosilicate glass. And it was proved that the drop breakage height was improved by 25% only by increasing the compressive stress at 30um depth.

Influence of Al2O3/SiO2 ratio in multicomponent LNAS glasses and glass-ceramics on the crystallization behavior, microstructure and mechanical performance

Transparent glass-ceramics containing eucryptite and nepheline crystalline phases were prepared from alkali (Li, Na) aluminosilicate glasses with various mole substitutions of Al2O3 for SiO2. The relationships between glass network structure and crystallization behavior of Li2O–Na2O–Al2O3–SiO2 (LNAS) glasses were investigated. It was found that the crystallization of the eucryptite and nepheline in LNAS glasses significantly depended on the concentration of Al2O3. LNAS glasses with the addition of Al2O3 from 16 to 18 mol% exhibited increasing Q4 (mAl) structural units confirmed by NMR and Raman spectroscopy, which promoted the formation of eucryptite and nepheline crystalline phases. With the Al2O3 content increasing to 19–20 mol%, the formation of highly disordered (Li, Na)3PO4 phase which can serve as nucleation sites was inhibited and the crystallization mechanism of glass became surface crystallization. Glass-ceramics containing 18 mol% Al2O3 showed high transparency ∼84% at 550 nm. Moreover, the microhardness, elastic modulus and fracture toughness are 8.56 GPa, 95.7 GPa and 0.78 MPa m1/2 respectively. The transparent glass-ceramics with good mechanical properties show high potential in the applications of protective cover of displays.

Oxide Scale Sublimation Chemical Vapor Deposition for Controllable Growth of Monolayer MoS2 Crystals.

A newly developed oxide scale sublimation chemical vapor deposition (OSSCVD) technique for 2D MoS2 growth is reported. Gaseous MoO3 , which is supplied separately from H2 S, can be generated in situ by flowing O2 over Mo metal with oxidation and sublimation processes. In this method, particularly, controllably and abruptly modulating the supply of MoO3 is achievable by precisely tuning O2 flow. Having appropriate conditions, where the generation rate of MoO3 on the Mo metal surface is not larger than its sublimation rate, is critical to enable stable growth. Otherwise, MoS2 deposition can be caused by accumulated MoO3 on the metal surface, regardless of oxygen supply. Proof-of-concept experiments with varied process parameters are conducted, confirming OSSCVD enables MoS2 growth with significantly improved flexibility, controllability, and reproducibility relative to conventional powder-source CVD. By utilizing alkali-aluminosilicate glass, Dragontrail, as catalytic substrate, single-crystalline MoS2 triangular domains as large as 25µm are obtained, followed by a fully covered monolayer on Dragontrail in 25min. Substrate pretreatment by H2 S yields enlarged domain size and reduced domain density, owning to the extracted alkali metals from Dragontrail into the growth zone. The study opens new avenues for the controllable growth of high-quality MoS2 and other transition metal dichalcogenides.

Structure and properties of alkali aluminosilicate glasses and melts: Insights from deep learning

Aluminosilicate glasses and melts are of paramount importance for geo- and materials sciences. They include most magmas, and are used to produce a wide variety of everyday materials, from windows to smartphone displays. Despite this importance, no general model exists with which to predict the atomic structure, thermodynamic and viscous properties of aluminosilicate melts. To address this, we introduce a deep learning framework, ‘i-Melt’, which combines a deep artificial neural network with thermodynamic equations. It is trained to predict 18 different latent and observed properties of melts and glasses in the K2O-Na2O-Al2O3-SiO2 system, including configurational entropy, viscosity, optical refractive index, density, and Raman signals. Viscosity can be predicted in the 100–1015 log10 Pa·s range using five different theoretical frameworks (Adam-Gibbs, Free Volume, MYEGA, VFT, Avramov-Milchev), with a precision equal to, or better than, 0.4 log10 Pa·s on unseen data. Density and optical refractive index (through the Sellmeier equation) can be predicted with errors equal or lower than 0.02 and 0.006, respectively. Raman spectra for K2O-Na2O-Al2O3-SiO2 glasses are also predicted, with a relatively high mean error of ∼25% due to the limited data set available for training. Latent variables can also be predicted with good precisions. For example, the glass transition temperature, Tg, can be predicted to within 19 K, while the melt configurational entropy at the glass transition, Sconf(Tg), can be predicted to within 0.8 J mol−1 K−1.Applied to rhyolite compositions, i-Melt shows that the rheological threshold separating explosive and effusive eruptions correlates with an increase in the fraction of non-bridging oxygens in rhyolite melts as their alkali/Al ratio becomes larger than 1. Exploring further the effect of the K/(K + Na) ratio on the properties of alkali aluminosilicate melts with compositions varying along a simplified alkali magmatic series trend, we observe that K-rich melts have systematically different structures and higher viscosities compared to Na-rich melts. Combined with the effects of the K/(K + Na) ratio on other parameters, such as the solubility, solution mechanisms and speciation of volatile elements, this could ultimately influence the eruptive dynamics of volcanic systems emitting Na-rich or K-rich alkali magmas.

A comparative study on the effect of Zr, Sn, and Ti on the crystallization behavior of nepheline glass

In alkali aluminosilicate glasses, additions of 4+ cations like Zr and Ti are often added to promote crystallization. In this study, Zr, Ti, or Sn are progressively substituted for Si in nepheline (NaAlSiO4) glass to determine their impact on the crystallization behavior. For glasses homogeneous on quenching, up to NaAlZr0.075Si0.925O4, NaAlSn0.100Si0.900O4, and NaAlTi0.300Si0.700O4, respectively, crystallization temperatures were investigated by thermal analysis. A subset of compositions was subjected to additional thermal analysis, varying heating rate and particle size, to investigate the subtleties of crystallization behavior. Subsequent heat treatment of glass powders was performed to maximize crystallization, and glass-ceramic microstructure was assessed by optical microscopy and electron microprobe, while crystalline phases were determined by X-ray diffraction. In all cases the major crystalline phase was orthorhombic carnegieite, which accommodated Ti in its structure but not Zr or Sn, and excess 4+ cations formed MO2, i.e., brookite, baddeleyite, and cassiterite, respectively.

Understanding deposition temperature dependent photovoltaic characteristics of Cu(In,Ga)Se2 solar cells: A study with thermally stable alkali aluminosilicate glass substrates

During 3-stage thermal co-evaporation of Cu(In,Ga)Se2 (CIGSe), alkali aluminosilicate (AAS) glass has proven to be stable at process temperatures Tmax of up to 650 °C. This is considerably higher than the maximum endurable Tmax for soda-lime glass (SLG), which is in the range of 530–550 °C. As the Na-content of the AAS glass used here is comparable to that of SLG, growing CIGSe at elevated Tmax is expected to promote Na diffusion from the glass substrate through the Mo back contact (BC) into the absorber layer. An increased Na concentration in the CIGSe absorber would be expected to result in an improved device performance as it is mostly associated with an increased open-circuit voltage (Voc) and fill factor (FF). This paper discusses the influence of varying Tmax from 530 to 650 °C during the 2nd and the 3rd stage of the 3-stage process on the morphological, electrical, and photovoltaic performance of CIGSe solar cells. Upon raising Tmax from 530 to 650 °C, the short-circuit current density (Jsc) decreased due to bandgap (Eg) widening. Glow discharge optical emission spectrometry analysis reveals that the Na concentration in the absorber is gradually decreased when elevating Tmax. As will be seen, we attribute this in part to a densification of the Mo BC during the high temperature process. A maximum conversion efficiency (η) was realized at Tmax = 600 °C. An increased Voc at Tmax = 600 °C is due to the wider Eg and to an increased carrier concentration despite the fact that the Na concentration in the CIGSe thin film was low compared to lower Tmax. Admittance spectroscopy analysis is performed to access information on defect energy level and density in the finished devices. In the light of present findings, ways to further improve η at elevated Tmax are suggested.

Anomalously strong viscosity behavior in mixed oxy-sulfide Na4P2S7-xOx invert glasses

In this report, the first observations of the anomalously strong viscosity behavior in the melt quenched (MQ) invert mixed oxy-sulfide Na4P2S7-xOx, 0 ≤ x ≤ 5, (NaPSO) glass series. We find that these glasses even with 67 mole% modifier, Na2S, exhibit a calorimetric fragility index, mcal, as small as 29 compared to typical values of ~ 60 to 80 for alkali silicate glasses with > 50 mole% SiO2. We find that the calorimetric fragility of these glasses varies systematically with the extent of network forming bridging oxygens (BOs) in the glasses. The mcal values were converted to kinetic fragility (mvis) values and used with the measured Tgs to produce viscosity curves for the glasses using the Mauro-Yue-Ellison-Gupta-Allan (MYEGA) model. The viscosity of the glass with a minimum mcal value of x = 2.5 was then shown to exhibit a viscosity that was as strong as some alkali aluminosilicate glasses.In this report, the first observations have been made of anomalously strong viscosity behavior and correspondingly strong bulk glass formation and resistance to crystallization in a melt quenched (MQ) prepared series of invert, modifier content greater than the glass former content, mixed oxy-sulfide Na4P2S7-xOx, 0 ≤ x ≤ 5, (NaPSO) glasses. We find that these glasses even with 67 mole % modifier, Na2S, and only 33 mole% glass former P2S5-xOx, exhibit a calorimetric fragility index, mcal, as small as 29 compared to typical values of ~ 60 to 80 for alkali silicate glasses with > 50 mole% SiO2 and the theoretical minimum mcal of ~ 15. The mcal values were converted to kinetic viscosity fragility, mvis, values and used with the measured glass transition temperatures, Tgs, to produce viscosity curves for the glasses using the Mauro-Yue-Ellison-Gupta-Allan (MYEGA) model. The viscosity of the glass with a minimum mcal value of x = 2.5 was then shown to exhibit a viscosity that was as strong as, and for some compositions stronger than, the viscosity of alkali aluminosilicate glasses which have three dimensional network structures compared to the one dimensional chain structures observed in these MOS invert glasses. Consistent with these small values of fragility indices and therefore predicted higher viscosity above the glass transition temperature, Tg, in the supercooled liquid regime, these glasses are also particularly resistant to crystallization. For example, the x = 2.5 glass composition exhibits a crystallization temperature, TC, more than 150K above its Tg. We find that the calorimetric fragility of these glasses varies systematically with the extent of network forming bridging oxygens (BOs) in the glasses. The structural change caused by incrementally replacing sulfur with oxygen has been found to have consistent, large effects on the thermal properties.

Ab Initio Study of Hydrolysis Effects in Single and Ion-Exchanged Alkali Aluminosilicate Glasses

Hydrolysis in alkali-doped aluminosilicate glasses is one of the most complicated mechanisms in glass science. There remain many fundamental and unresolved issues with implications on their potential applications. Herein, we address this challenge by carrying out detailed calculations on the structure and properties of both anhydrate (dry) and hydrated alkali aluminosilicate glasses on carefully constructed models. Specifically, the Na-, (Na + K)- and K-doped aluminosilicate glasses with compositions (SiO2)0.6 (Al2O3)0.2 (Na2O)0.2-x (K2O)x (x = 0, 0.10 and 0.20) are simulated using ab initio molecular dynamics (AIMD). The local short- and intermediate-range order in these glasses are analyzed in terms of atomic pair distribution, coordination number, bond length and bond angle distributions to delineate the subtle variations due to different alkali size and hydrolysis. The electronic structure, interatomic bonding, mechanical and optical properties for these models are calculated and validated with available experimental data. We use the novel concept of total bond order density (TBOD), the quantum mechanically derived metric, to characterize the internal cohesion and strength in the simulated glasses. Detailed analysis of the hydrolysis mechanism enables us to provide information on the complex interplay of various participating elements and their interactions at the atomic level. Such detailed information provides new platform of knowledge which is crucial for understanding the issues related to glass corrosion and durability and ways and means for their special applications in commercial glass products. Both un-dissociated molecular water and dissociated water in the form of hydroxyl group exist in the hydrated models in the presence of alkali ions. For the first time, we observed the opposite mixed alkali effect in the Poisson's ratio for anhydrate and hydrated glasses.

Water in Alkali Aluminosilicate Glasses

To understand the influence of water and alkalis on aluminosilicate glasses, three polymerized glasses with varying ratios of Na/K were synthesized [(22. 5-x)Na2O-xK2O-22.5 Al2O3-55 SiO2 with x = 0, 7.5, and 11.25]. Subsequently, these glasses were hydrated (up to 8 wt% H2O) in an internally heated gas pressure vessel. The density of hydrous glasses linearly decreased with water content above 1 wt%, consistent with the partial molar volume of H2O of 12 cm3/mol. Near-infrared spectroscopy revealed that hydroxyl groups are the dominant species at water content of 5 wt%. The fraction of OH is particularly high in the pure Na-bearing glass compared to the mixed alkali glasses. 27Al magic angle spinning-NMR spectroscopy shows that aluminum is exclusively fourfold coordinated with some variations in the local geometry. It appears that the local structure around Al becomes more ordered with increasing K/Na ratio. The incorporation of H2O reinforces this effect. The differential thermal analysis of hydrous glasses shows a significant mass loss in the range of glass transition already during the first upscan, implying the high mobility of water in the glasses. This observation can be explained by the open structure of the aluminosilicate network and by the low dissociation enthalpy of H2O in the glasses (≈ 8 kJ/mol). The effect of the dissolved H2O on the glass transition temperature is less pronounced than for other aluminosilicate glasses, probably because of the large fraction of Al in the glasses.

The effect of individual elements of alkali aluminosilicate glass on scratch characteristics: A molecular dynamics study

Flaws on glass surfaces significantly reduce mechanical strength by concentrating applied stresses on their tips. Since these surface defects are formed by surface contact loading, such as scratching, it is crucial to enhance scratch resistance for high mechanical strength. In this regard, we investigate contributions of individual elements of alkali aluminosilicate glass (15Na2O∙5MgO∙11Al2O3∙69SiO2) to surface deformations during scratching by utilizing molecular dynamics simulations. It is found that the friction coefficient is inversely proportional to the amount of elastic deformation. Analyses of local atomic structure demonstrate that Mg and Al mainly contribute to the elastic response, whereas Na tends to heavily participate in plastic deformation. Chemical strengthening of glass further enhances the elastic behavior of Mg and Al and alters the characteristic of alkali elements from plastic to elastic participation. Atomic-level understanding of individual roles of glass elements is expected to contribute to developing advanced glasses with high surface damage resistance.

Position sensing of ultrashort pulsed laser-welded seams in glass by optical coherence tomography

Today's methods for the inspection of the position of weld seams in glass, which has a decisive effect on the strength and thus on the quality of the permanent bond, are costly and often carried out manually in a destructive manner. The present paper proposes the application of optical coherence tomography to determine the position of the weld seam by evaluation of the signals caused by the voids within weld seams. Blind welds of fused silica and alkali-aluminosilicate glass were investigated, and a method for data evaluation is presented. The method is predominantly suitable for glass that exhibits the formation of distinct voids during welding and provides an approach for online monitoring and control of glass welding processes.

Structural origins of the Mixed Alkali Effect in Alkali Aluminosilicate Glasses: Molecular Dynamics Study and its Assessment

The comprehension of the nonlinear effects provided by mixed alkali effect (MAE) in oxide glasses is useful to optimize glass compositions to achieve specific properties that depend on the mobility of ions, such as the chemical durability, glass transition temperature, viscosity and ionic conductivity. Although molecular dynamics (MD) simulations have already been applied to investigate the MAE on silicates, less effort has been devoted to study such phenomenon in mixed alkali aluminosilicate glasses where alkali cations can act both as modifiers, forming non-bridging oxygens and percolation channels, and as charge compensator of the AlO4− units present in the network. Moreover, the ionic conductivity has not been computed yet; thus, the accuracy of the atomistic simulations in reproducing the MAE on the property is still open to question. In this work, we have validated five major interatomic potentials for the classical MD simulations by modelling the structure, density, glass transition temperature and ionic conductivity for three aluminosilicate glasses, (25 − x)Na2O − x(K2O) − 10(Al2O3) − 65(SiO2) (x = 0, 12.5, 25). It was observed that only the core-shell (CS) polarizable force field well reproduces the experimentally measured MAE on Tg and the ionic conductivity as well as the higher conductivity of single sodium aluminosilicate glass at low temperature and the higher conductivity of single potassium aluminosilicate glass at high temperature. The MAE is related to the suppression of jump events of the alkaline ions between dissimilar sites in the percolation channels consisting of both sodium and potassium ions as in the case of alkaline silicates. The superior reproducibility of the CS potential is originated from the larger and the flexible ring structures due to the smaller Si-O-Si inter-tetrahedra angle, creating appropriate percolation channels for ion conductivity. We also report detailed assessments for using the potential models including the CS potential for investigating MAE on aluminosilicates.

Ionic self-diffusion of Na2O–Al2O3–SiO2 glasses from molecular dynamics simulations

The structure of alkali aluminosilicate glasses (NAS) as a function of the molar ratio of Al/Na (RAl/Na) were investigated by using classical molecular dynamics simulations and validated by comparing with the high energy X-ray diffraction experiments. General structural features, including the pair distribution functions, coordination number, Qn distribution, oxygen species and ring size distributions, were analyzed to elucidate the effects of Al content on the structure of the glasses. By inducing effective rings size as a new parameter, the RAl/Na dependence of the alkali ion diffusion ability below the glass transition temperature were analyzed on the basis of medium range structures instead of the calculated diffusion coefficient. The results suggest that the optimum aluminum content for NAS system exists at around RAl/Na = 1.2 not only with a high ionic self-diffusion but also with a good network connectivity, providing a theoretical guidance for the design and optimization of chemically strengthened glasses.

New interaction potentials for alkali and alkaline-earth aluminosilicate glasses.

We apply a recently developed optimization scheme to obtain effective potentials for alkali and alkaline-earth aluminosilicate glasses that contain lithium, sodium, potassium, or calcium as modifiers. As input data for the optimization, we used the radial distribution functions of the liquid at high temperature generated by means of ab initio molecular dynamics simulations and density and elastic modulus of glass at room temperature from experiments. The new interaction potentials are able to reproduce reliably the structure and various mechanical and vibrational properties over a wide range of compositions for binary silicates. We have tested these potentials for various ternary systems and find that they are transferable and can be mixed, thus allowing us to reproduce and predict the structure and properties of multicomponent glasses.

Composition – structure – property relationships in alkali aluminosilicate glasses: A combined experimental – computational approach towards designing functional glasses

A set of 12 glass compositions with distinct structural features have been designed over a broad composition space in the per-alkaline region of the Na2O – Al2O3 – SiO2 ternary system. As expected from a per-alkaline system, aluminum has been found to be tetrahedrally coordinated in all the glasses using 27Al magic angle spinning – nuclear magnetic resonance (MAS-NMR) spectroscopy and from structure models generated using molecular dynamic (MD) simulations. The physical properties of glasses, for example, density, coefficient of thermal expansion (CTE), glass transition, elastic moduli and Vickers hardness and brittleness have been measured experimentally and their trends have been explained based on the atomic structure of glasses, from both simulations and experiments. A reasonable agreement has been observed between the composition – structure – property relationship trends obtained experimentally when compared with those predicted by MD simulations. This demonstrates that MD simulation is a promising technique for predictive modeling and designing novel glass compositions for functional applications.

Effect of pressure on the short-range structure and speciation of carbon in alkali silicate and aluminosilicate glasses and melts at high pressure up to 8 GPa: 13C, 27Al, 17O and 29Si solid-state NMR study

Despite the pioneering efforts to explore the nature of carbon in carbon-bearing silicate melts under compression, experimental data for the speciation and the solubility of carbon in silicate melts above 4 GPa have not been reported. Here, we explore the speciation of carbon and pressure-induced changes in network structures of carbon-bearing silicate (Na2O-3SiO2, NS3) and sodium aluminosilicate (NaAlSi3O8, albite) glasses quenched from melts at high pressure up to 8 GPa using multi-nuclear solid-state NMR. The 27Al triple quantum (3Q) MAS NMR spectra for carbon-bearing albite melts revealed the pressure-induced increase in the topological disorder around 4 coordinated Al ([4]Al) without forming [5,6]Al. These structural changes are similar to those in volatile-free albite melts at high pressure, indicating that the addition of CO2 in silicate melts may not induce any additional increase in the topological disorder around Al at high pressure. 13C MAS NMR spectra for carbon-bearing albite melts show multiple carbonate species, including [4]Si(CO3)[4]Si, [4]Si(CO3)[4]Al, [4]Al(CO3)[4]Al, and free CO32–. The fraction of [4]Si(CO3)[4]Al increases with increasing pressure, while those of other bridging carbonate species decrease, indicating that the addition of CO2 may enhance mixing of Si and Al at high pressure. A noticeable change is not observed for 29Si NMR spectra for the carbon-bearing albite glasses with varying pressure at 1.5–6 GPa. These NMR results confirm that the densification mechanisms established for fluid-free, polymerized aluminosilicate melts can be applied to the carbon-bearing albite melts at high pressure.In contrast, the 29Si MAS NMR spectra for partially depolymerized, carbon-bearing NS3 glasses show that the fraction of [5,6]Si increases with increasing pressure at the expense of Q3 species ([4]Si species with one non-bridging oxygen as the nearest neighbor). The pressure-induced increase in topological disorder around Si is evident from an increase in peak width of [4]Si with pressure. 17O NMR spectrum shows that the fraction of Na⋯O[5]Si in carbon-bearing NS3 glasses is less than that of carbon-free NS3 glasses at 6 GPa potentially due to the formation of bridging carbonate species. While its presence is not evident from the 17O NMR spectrum primarily due to low carbon concentration, 13C MAS NMR results imply the formation of bridging carbonates, [4]Si(CO3)[4]Si, above 6 GPa. The spin-lattice relaxation time (T1) of CO2 in albite melts increases with increasing pressure from 42 s (at 1.5 GPa) to 149 s (at 6 GPa). Taking the pressure-induced change in T1 of carbon species into consideration, total carbon content in carbon-bearing albite melts increases with pressure from ∼1 wt% at 1.5 GPa to ∼4.1 wt% at 6 GPa. The results also reveal a noticeable drop in the peak intensity of free carbonates in carbon-bearing NS3 melts at 6 GPa, implying a potential non-linear change in the carbon solubility with pressure. The current results of carbon speciation in the silicate melts above 4 GPa provide an improved link among the atomic configurations around carbon species, their carbon contents, and isotope composition of carbon-bearing melts in the upper mantle.

In-situ microscopy of front and rear side ablation processes in alkali aluminosilicate glass using ultra short pulsed laser radiation

The visualization of the nonlinear absorption, the subsequent relaxation of excited states and the formation of defects enables the investigation of fundamental laser-material-interaction as well as the identification of process windows for micromachining of transparent materials with ultra short pulsed laser radiation. In this work, time resolved pump probe microscopy is applied to analyze the laser-material-interaction and to reduce damage inside the material during front- and rear side ablation of nonstrengthened Corning Gorilla glass. The experiments give an insight into the pulse duration dependence of the absorption zone, the influence of the surface geometry, in-volume damage and the formation of transient visible cracks.

Transverse pump-probe microscopy of moving breakdown, filamentation and self-organized absorption in alkali aluminosilicate glass using ultrashort pulse laser.

We present time and space resolved transverse pump-probe measurements of the free electron and defect generation induced by nonlinear absorption of ultra short pulsed laser radiation in unhardened Corning Gorilla glass. The applied setup exhibits a 100 fs probe pulse duration and an independent pump pulse duration up to 5 ps. Hence, our work comprises the absorption of ultra short pulsed laser radiation at a wavelength of 800 nm and pulse energies from 10 μJ to 50 μJ up to a delay of 6 ns. Our investigations reveal different absorption regimes like filamentation and moving breakdown as well as the formation of permanent modifications. Finally, the deposition of multiple pulses in the incubation regime is examined, observing a self-organizing absorption effect.