Surface Structure Of Glasses Research Articles

On the Relationship between Water Adsorption and Surface Chemistry in Soda-lime Silicate Glasses.

Understanding how the surface structure affects the bioactivity and degradation rate of the glass is one of the primary challenges in developing new bioactive materials. Here, classical and reactive molecular dynamics simulations are used to investigate the relationship between local surface chemistry and local adsorption energies of water on three soda-lime silicate glasses. The compositions of the glasses, (SiO2)65-x(CaO)35(Na2O)x with x=5, 10, and 15, were chosen for their bioactive properties. Analysis of the glass surface structure, compared to the bulk structure, showed that the surface is rich in modifiers and non-bridging oxygen atoms, which were correlated with local adsorption energies. The reactivity of the glasses is found to increase with higher Na2O content, attributed to elevated Na cations and undercoordinated species at the glass surfaces. The current work provides insights into the relationship between the surface structure, chemistry, and properties in these bioactive glasses and offers a step toward their rational design.

Combined experiments and atomistic simulations for understanding the effect of ZnO on the sodium silicate and sodium borosilicate glass network

Combined experiments and molecular dynamics (MD) simulations were performed over wide range of glass compositions to understand the improved durability of borosilicate glass with ZnO addition. A significant change in glass structure was monitored from short range and intermediate range order parameters. The MD results were found to be in good agreement with the experimental data for Young's Modulus, glass transition temperature, and leaching. Both experiments and MD simulations report the enhanced chemical durability of glass with ZnO addition. Low R (Na2O/B2O3) and high K (SiO2/B2O3) of ZnO doped sodium borosilicate (Zn–NBS) glass surface compared to bare NBS represents the more stable structure of glass surface for Zn–NBS than NBS. The enhanced chemical resistivity of Zn–NBS was established from the increasing activation energy for diffusion of Na ions. The combined experiments and MD simulations disclose many interesting microstructure and dynamics due to the presence of ZnO in the glass.

Effect of pH on the In Vitro Degradation of Borosilicate Bioactive Glass and Its Modulation by Direct Current Electric Field.

Controlled ion release and mineralization of bioactive glasses are essential to their applications in bone regeneration. Tuning the chemical composition and surface structure of glasses are the primary means of achieving this goal. However, most bioactive glasses exhibit a non-linear ion release behavior. Therefore, modifying the immersion environment of glasses through external stimuli becomes an approach. In this study, the ion release and mineralization properties of a borosilicate bioactive glass were investigated in the Tris buffer and K2HPO4 solutions with different pH. The glass had a faster ion release rate at a lower pH, but the overly acidic environment was detrimental to hydroxyapatite production. Using a direct current (DC) electric field as an external stimulus, the pH of the immersion solution could be modulated within a narrow range, thereby modulating ion release from the glass. As a result, significant increases in ion release were observed after three days, and the development of porous mineralization products on the glass surface after six days. This study demonstrates the effectiveness of the DC electric field in modulating the ion release of the bioactive glass in vitro and provides a potential way to regulate the degradation of the glass in vivo.

An analytical investigation on characterizing the properties of glass composition for crystalline silicon solar cells based on the digital microsystem measurement technology

As a significant component of silver paste, glass frit has a nonnegligible effect on crystalline silicon solar cells. The purpose of this research is to obtain an analysis method to explore the performance of glass frit for solar cells. The samples were measured by digital microscopic system, and the three-dimensional layered tinting model was established. Moreover, the longitudinal cutting was carried out. The data of cross section was analyzed to obtain the information of melt height, wetting base angle, and melting included angle, to further infer the relationship between thermal stability, fluidity, wettability with mathematical model of glass frit through theoretical derivation. The curve fitting method was introduced in detail and the law was summarized. Based on relationship of them, the melting characteristics of glass frit could be quantitatively tested. The vertical view and surface topography were measured by the digital microscope and found that the glass frit underwent shrinkage, softening, wetting, spreading, and equilibrium during sintering. Combined with the image, abundant information was detected from the macroscopic structure of glass surface. Meanwhile, the mechanism of spreading was explained. Finally, the screen-printing technology combined with the 3D microscopic view of the silver grid line proved that glass frit with satisfactory performance can effectively reduce the contact resistance of solar cells, improve the photovoltaic conversion efficiency, verify the feasibility and accuracy of the simulation method equally. This study not only enriches the understanding of glass frit for crystalline silicon solar cells, but also provides a theoretical guidance for the research and determination of its performance. • Digital microscope system was used to record the shape changes of glass samples and more wetting parameters. • This investigation used a combination of mathematical simulation and physical simulation. • The essence of the technology to characterize glass is to combine the fixed droplet technology with optical measurement.

Influence of structural change by heat treatment on the wettability of borosilicate glass

AbstractThe chemical composition and surface structure of glass affect its wettability and can thus lead to the formation of various functional surfaces. This study examined the influence of the structural changes induced by the heat treatment of sodium borosilicate glass on its wettability. Specifically, 15Na2O‐40B2O3‐45SiO2 glass was prepared through melt‐quenching. The obtained glass was subjected to heat treatment at 600°C for 3 h. The heat‐treated glass exhibited a higher hydrophilicity and surface free energy than the nontreated glass. The heat treatment led to a variation in the relative ratio associated with the boron coordination number and nonbridging oxygen. Therefore, the heat‐treatment‐induced changes in the glass structure considerably enhanced the wettability of the glass.

Synergetic effects of water and SO2 treatments on mechanical and mechanochemical properties of soda lime silicate glass

The synergetic effects of water and SO2 treatments on mechanical and mechanochemical wear properties of SLS glass were studied in this study. The results show that the nanomechanical properties (nanohardness and reduced modulus) as well as Vickers hardness and fracture toughness of treated SLS glass surface are increased, regardless of various treatment environments. After treated in dry SO2, the mechanochemical wear resistance of SLS glass in 40% RH becomes higher than pristine glass, but it doesnot change significantly in 70% RH. In contrast, after treated in wet SO2, the wear resistance of SLS glass in 40% RH decreases remarkably, and it shows much less wear resistance in 70% RH. This must be due to the change of glass surface structure and wear mechanism during the wear process. These results can provide deeper understanding of wear mechanism of glass and be helpful for operation process of functional and engineering glasses.

Lead-silicate glass surface sputtered by an argon cluster ion beam investigated by XPS

The conventional ion beam sputter-cleaning technique is frequently used for removing surface adsorbates and carbon contamination from air-exposed glass surfaces. Due to the ion-surface interaction, however, an altered near-surface layer is formed with a modified composition and modified bonding. In the present work, we first examine changes in surface composition and bonding due to X-ray and electron irradiation for both air-exposed and sputter-cleaned surfaces. Then we apply argon cluster ion beam sputtering, known as a very gentle technique with respect to the changes in surface chemistry, to air-exposed lead-silicate glass surfaces analyzed by high-energy resolved core-level photoelectron spectroscopy. It was found that (i) the surface contamination present on air-exposed lead-silicate glass surfaces has a qualitative influence on the results of an XPS analysis, and (ii) Ar cluster ion beam sputter-cleaning with mean energy per Ar atom in clusters of a few eV was successfully used to remove surface contamination from air-exposed lead-silicate glass with no substantial violation of the glass surface structure. This made it easier to reveal their intrinsic surface properties.

Hydrothermal reactions of soda lime silica glass – Revealing subsurface damage and alteration of mechanical properties and chemical structure of glass surfaces

Hydrothermal treatment provides a unique way to reveal subsurface damage of soda lime silica (SLS) float glass. During the hydrothermal treatment, the penetration of water, ion-exchange, and hydrolysis reaction can take place. These reactions are accelerated at locations where subsurface damage exists. Interestingly, the hydrothermally-treated glass surface exhibits higher fracture toughness, lower hardness, and less resistance to mechanochemical wear at high humidity compared to the pristine SLS float glass. These property changes can be explained by the leaching and polymerization of the silicate network and the chemical environment of hydrous species in the surface region of SLS glass.

Thermal Poling of Soda‐Lime Silica Glass with Nonblocking Electrodes—Part 1: Effects of Sodium Ion Migration and Water Ingress on Glass Surface Structure

It is generally well known that not only the sodium itself, but also the non‐bridging oxygen (NBO) sites associated with sodium ions are largely responsible for the surface reactivity of soda‐lime‐silica (SLS) glass. Thermal poling can modify the distribution of sodium in the subsurface region. In this work, a commercial SLS float glass was thermally poled using nonblocking electrodes in air. The Na+−depleted anode surface and the Na+−gradient cathode surface were characterized using a variety of methods to find the compositional, structural and morphological effects of thermal poling. Of particular significance is the use of nondestructive vibrational spectroscopy methods, which can lead to new and improved understanding of water interactions with sodium and its sites in the glass. It was found that during thermal poling, the Na+−depleted glass network on the anode side undergoes condensation reactions of NBO sites accompanied by the increase in concentrations of silanol (SiOH) groups and molecular water species. In contrast, silanol and water species do not increase and the silicate network change is negligible in the Na+−gradient cathode side. Vibrational sum frequency generation (SFG) spectroscopy analysis revealed the difference in distributions of hydrous species in the Na+−depleted and Na+−gradient surfaces. The structural information of the thermally‐poled surfaces provides critical insights needed to understand the mechanical and mechanochemical properties of the Na+−concentration modified SLS glass surfaces reported in the Part 2 companion paper.

Effect of physical aging on fracture behavior of Te2As3Se5 glass fibers

Fracture surface characteristics of Te2As3Se5 (TAS) glass fibers aged in light and in dark have been investigated respectively for understanding physical aging effect on their fracture behavior. The properties including tensile strength (σ), surface flaw depth (α), and mirror radii (rm) were measured by DY30 Adamel Lomarghy and SEM, respectively. Shape factor extracted by fitting of σ vs α confirms that fractures of fibers aged in dark for 4 months originate from their surface flaw, but it does not work for fibers aged in light for 4 months. However, mirror constants (=σrm1/2) of fracture surface for the TAS glass fibers aged in dark are in a good agreement with those aged in light. One possible reason is that the photoinduced effect changes the structure of glass surface during the physical aging.

Plasmonic molecules via glass annealing in hydrogen.

Growth of self-assembled metal nanoislands on the surface of silver ion-exchanged glasses via their thermal processing in hydrogen followed by out-diffusion of neutral silver is studied. The combination of thermal poling of the ion-exchanged glass with structured electrode and silver out-diffusion was used for simple formation of separated groups of several metal nanoislands presenting plasmonic molecules. The kinetics of nanoisland formation and temporal evolution of their size distribution on the surface of poled and unpoled glass are modeled.PACS78.67.Sc (nanoaggregates; nanocomposites); 81.16.Dn (self-assembly); 68.35.bj (surface structure of glasses); 64.60.Qb (Nucleation); 81.16.Nd (micro- and nanolithography)

The surface hydration of soda-lime glass and its potential for historic glass dating

More than three decades ago the idea of using ambient water diffusion on manufactured glasses as an archeological dating method was proposed for historic period artifacts. In this study, we use infrared spectroscopy (FTIR) and secondary ion mass spectrometry (SIMS) to model water diffusion into the surface of two soda-lime glasses that differ principally in the alumina and magnesium content. Lower temperature hydration experiments (60–140 °C) were conducted and the surface diffused water was measured by infrared absorption, transflectance, and reflectance spectroscopy to establish the diffusion coefficients and activation energies, and to investigate the change in glass surface structure with time at a constant temperature. SIMS was also used to document water diffusion within a sample recovered from a 19th century archeological slave quarters at Thomas Jefferson's Monticello plantation in Virginia, USA.

Antireflective surface structures in glass by self-assembly of SiO_2 nanoparticles and wet etching

We describe the fabrication of an antireflective surface structure with sub-wavelength dimensions on a glass surface using scalable low-cost techniques involving sol-gel coating, thermal annealing, and wet chemical etching. The glass surface structure consists of sand dune like protrusions with 250 nm periodicity and a maximum peak-to-valley height of 120 nm. The antireflective structure increases the transmission of the glass up to 0.9% at 700 nm, and the transmission remains enhanced over a wide spectral range and for a wide range of incident angles. Our measurements reveal a strong polarization dependence of the transmission change.

Light trapping scheme of ICP-RIE glass texturing by SF6/Ar plasma for high haze ratio

Inductive coupled plasma-reactive ion etching (ICP-RIE) offers an anisotropic texturing with superior surface structure of glass substrate. We report light trapping scheme of ICP-RIE glass texturing by SF6/Ar plasma. We observed that surface structure is an important factor to improve the diffused transmittance and haze ratio of textured glass. The presence of metal elements like Al, B, F and Na are responsible for low etching rate (22.66–27.33 nm/min) of textured glass. The total transmittance remains high whereas the diffused transmittance increased with the pattern size due to the variation of surface morphology of glass. Our textured glass substrates showed the high diffused transmittance and haze ratio in the visible-NIR wavelength region. The electrical properties of the ITO films are independent of glass surface structure that may be suitable for high performance of thin film solar cells.

Compositional dependence on the in vitro bioactivity of invert or conventional bioglasses in the Si‐Ca‐Na‐P system

The bioactivity of 34 invert or conventional glasses in the P-free and P-containing Si-Ca-Na system was evaluated by examining the in vitro Hydroxy Carbonate Apatite (HCA) formation time. The silica content in the glasses varies between 39.48 and 55 mol %. The surfaces of glasses after soaking in simulated body fluid at 37 degrees C were analyzed by Fourier transform infraRed spectroscopy and scanning electron microscopy coupled with energy dispersive spectroscopy. To understand the HCA formation mechanism, the modification of the glass surface structure was studied. The aim was to understand, in the Si-Ca-Na-P system, the function of each constituent on glass reactivity. It was noted that the bioactivity of Si-Ca-Na-P glasses depends on the P ratio. One of the P-free glasses is as bioactive as the Hench's Bioglass noted 45S5, because it needs 12 h to develop HCA as for Hench's one. In the quaternary system, some of the P-rich and Na, Si-poor glasses are more bioactive than 45S5 (6-10 h to obtain HCA). Two phosphorus effects were observed: the repolymerization of the silicate network and the formation of phosphate-modifier cation complexes.

산 에칭에 의한 BaO-B2O3-ZnO계 유리조성물의 용출 현상

For producing the fine ribs structure of plasma display panel, the metal ions of barrier materials during the etching process should be understood on the etching mechanism with etching conditions. Etching was done on bulk glasses of the BaO-B₂O₃-ZnO system with HNO₃ solution at 40℃. The surface structure of glasses and ion dissolution were analyzed by ICP (Inductive Coupled Plasma measurement). The structure and surface of the etched bulk glass were investigated by using scanning electron microscopy and nanoindenter. As a result, Ba (3 - 35 ppm/min) and Zn (2 - 27 ppm/min) ions as major components were leached in the solution and the leached layers were found to be phosphor-rich surface layers. A decrease of the bridge oxygen and relative increase of non bridge oxygen in the etched glass were found by X-ray photoelectron spectroscopy.

Chemical Exchange Between Volcanic Ash in Seawater: Abiotic Versus Biotic, Warm vs Cold

Volcanic glass is probably chemically the most reactive material that is deposited in the oceans, as aerosol, as suspended river load from volcanic terrain, or as part of the extrusive layer of the oceanic crust. The total volume of this material is large, probably on the order of about 10~6g/a, providing the potential of very large chemical fluxes. Recent studies have shown that microbial activity plays an important role in the dissolution of glass in the marine environment, through mediation of the dissolution process, and, presumably, utilization of components of the glass freed up during this process (e.g. Thorseth et al., 1995; Fumes et al., 1996, Giovarmoni et al., 1996; Staudigel et al., 1995). The interaction between biota and volcanic glass is likely an influence on local ecology as well as on the chemical mass balance between biosphere, hydrosphere and lithosphere. We carried out a series of experiments to explore further the role of colonizing microorganisms on the dissolution of glass. All experiments were done with natural populations of microbes from surface sea water at two temperatures, under the ambient light intensity in the laboratory and in the dark. Open system experiments were done with a constant supply of fresh seawater. The closed system apparatus included 501 seawater reservoirs and a FEP Teflon column setup with approximately 150 g of glass (Staudigel et al., 1997). A closed system with autoclaved components and seawater served as an abiotic control. More recent continuous flow experiments include approximately 300 g of glass and a continuous flow of 20 1 of fresh sand-filtered seawater per day. We carried out an experiment at 60 ~ C and compared this to an experiment at 16~ Run products were analysed for major and trace elements and for changes in glass surface structure and in microbial colonization by SEM. Microbial populations were characterized with a variety of metabolic tests. Closed-system sterile control experiments remained sterile for periods exceeding 450 days showing that these experimental conditions do not allow for microbial contamination. Biologically active experiments display a diverse population of microbes, including a series of algae including Si utilizers (diatoms) and algae with aragonitic exosceletons (halimeda). In cold experiments we identified several chemolithotrophs including a rod-shaped motile sulphur-oxidizer, probably Thiobacillus sp., and two strains of rod-shaped non-motile ammoniaoxidizers. Photoautotrophs, all cyanobacteria, include Spirulina, Phormidium, Anacystis, and a sheathed, filamentous strain that is probably either Anabaena or Nostoc. 60~ experiments displayed no significant thermophile activity for the first two months of its duration. However, after about g months we could identify a diverse population of thermophilic microorganisms, including heterotrophs, sulphuroxidizers, nitrite-oxidizers and ammonia-oxidizers. These results suggest that surface seawater has the means to transport thermophilic microbial life, even though in our experiments it took between two to eight months for them to appear. Overall these results suggests that surface seawater contains a sufficiently diverse environmental microbial population that can adjust to a wide range of conditions, and newly developed hydrothermal systems do not remain abiotic for a long time after initiation. Such processes are expected to occur not only in the mixing zone of

Influence of environment on surface of the ancient glasses

Investigations have produced significant advances in understanding glass surfaces and their environmental corrosion. This process acts as a destructive factor, due to inter-reactions between the glass surface and the surrounding environment. The main point of this paper is to analyse glass corrosion processes, mainly using ancient model glasses in different surroundings. The experiments were made for glasses with composition of the chosen ancient glasses. The tests were carried out in H 2O, 0.1M HCl, 20% H 2SO 4, 10% NaOH, 5% NaCl (in salt spray chamber) and H 2SO 4 with pH = 4 (in salt spray chamber). The results of this induced process were later analysed by X-ray diffraction, infrared Fourier transform spectroscopy, scanning electron microscopy observation and chemical analyses. Infrared spectra indicate that corrosion is connected mainly with the action of water, organic compounds and carbonates on the surface layer. Alkali react 100 times stronger than other media, destroying the surface silica gel layer. Destruction of Si-O-Si bonding pays a predominant role in the reaction between alkali and glass. The thickness of this layer is proportional to the time of reaction. Surface changes show the layer morphology, depending on the character of attacking media. Changes in chemistry and structure of glass surface, due to corrosion by chemicals, mentioned above, were studied. Time was a very important factor, having an important influence on the destructive process in all samples.

Effect of mechanical polishing on the surface structure of glasses studied by grazing angle neutron reflectometry

Grazing angle neutron reflectometry, optical and mechanical roughness profilometry techniques have been used to study the effects of the polishing operations on the surface of Borkron Schott glass (special borosilicate glass for neutron optics applications) as the polishing tool pressure P and the mean grain size of the polishing powder Φ. The neutron reflectivity investigations have shown that there is formation of a layer at the surface glass substrate. This layer is less dense than the bulk substrate and its thickness is around 60 Å. The optical and mechanical profilometry measurements have shown that both roughness and waviness decrease with P and Φ. All the experimental results show a good correlation between the neutron refractive index, the thickness and the roughness of the surface layer and the waviness of the glass surface with the two mechanical polishing parameters. The previous techniques have been completed by secondary ion mass spectroscopy and atomic force microscopy measurements.

Effect of adsorption on the surface structure of sodium alumino-silicate glasses: a molecular dynamics simulation

Classical molecular dynamics (MD) computer simulations were used to study adsorption of model metals onto sodium alumino-silicate glasses and the effect these adsorbates have on the surface structure of the glass substrates. Multibody potentials were used to describe the substrate-substrate interactions; Lennard-Jones potentials were used to describe the adsorbate-adsorbate and adsorbate-substrate interactions. Lennard-Jones parameters and adsorbate mass were chosen to model Pt as the adsorbate. The adsorbate atoms penetrated 5–6Å into the glass, with multilayer coverage eventually occurring during deposition. The substrate showed a slight compression of the surface due to the presence of the adsorbate film. There was also a pronounced shift to smaller bond angles in the distribution of siloxane bond angles at the bridging oxygen. This redistribution was predominantly caused by a compression of siloxane bonds in 5 and 6 membered rings, although there was a partial rearrangement of ring sizes. Finally, Na at the surface were displaced by the adsorbate atoms such that Na were observed in the adsorbate film and at the film/vacuum interface.