Morphology of silica and borosilicate glass fracture surfaces by atomic force microscopy

Fracture surfaces of Herasil (silica) and Duran (borosilicate) glass rods were examined with an atomic force microscope. Generally the roughness in the fracture surface increases with growing distance from the origin of fracture. The morphology displays a variety of features. In the smooth fracture mirror near the origin of fracture the surface consists of small hillocks ≈25 nm in diameter and ≤ 1 nm high. With growing distance these hillocks increase in size and height. In the mist zone bigger outcrops occur with steep flanks. Steps can also be discovered in the fracture surface. Parts of the surface are covered by ripples, which are proposed to result from a local melting of the glass near the crack tip during fracture

Atomic force microscope study of silicate glass fracture surfaces in air and in water environment

In the present work changes in the topography of less resistant K2O-CaO-SiO2 and more stable Na2O-CaO-Al2O3-SiO2 glasses were studied in-situ by using a high-resolution atomic force microscope (AFM) in contact mode. The images were taken in air and in water, using a special liquid cell in the latter case. Fresh fracture surfaces were prepared in the corresponding media and the samples were transferred immediately into the AFM. The freshly fractured K2O-containing glasses displayed an irregular ripple pattern in air with ripple diameters of (80 ± 20) nm, heights < 1.2 nm and root mean square (rms) roughnesses < 0.8 nm. With ongoing exposure time, these glasses form a gel layer, isolated droplets and larger drops which can even coalesce. Also partially crystalline secondary reaction products can be observed in the drops. The large drops themselves displayed topographies with a ripple pattern similar to that found on the gel layer-coated surfaces. The drops and the gel layers are soft and may be penetrated and moved by the scanning tip. The in-situ investigation of these glasses in water revealed topographies with a ripple pattern similar to freshly prepared surfaces. This pattern did not change with exposure time, obviously because the water in excess rinsed away possible reaction products. The more resistant Al2O3-containing glasses show a dissimilar behaviour. The ripple pattern on the fracture surfaces is smaller and does not change even after days. Due to the absence of capillary forces and lower van der Waals forces the ripple diameters are smaller in water than in air. Glasses with a high degree of network polymerization also show smaller ripples than glasses with more nonbridging oxygens

Twin-roller quenching of Bi2Sr2Ca2Cu3O10 melts

Melts of the target composition Bi2Sr2Ca2Cu3O10 were produced and quenched in a specially designed twin-roller device. Quenching rates were estimated to be between about 0.2 ∙ 10^6 and 2 ∙ 10^6 K ∙ s^-1. In all quenching experiments mainly three sample shapes resulted, thin slivers, fibers, and clusters of sticking droplets. Slivers and fibers proved to be glassy, whereas the bulk of the clusters was crystalline. The slivers showed surface features due to nonuniform solidification processes. Thus wavy regions could be found or the surfaces were layered because of a rupturing during quenching. It could further be shown that an AI2O3 content of the melts does have some influence on the glass formation

Study of surface changes on industrial glasses with AFM, FE-SEM, EDX, SNMS and LM : Part 2. Surface changes by water drop etching, annealing at atmosphere and flame treatment

One of the possible defects in sputter coating layers are cone shaped rods which originate from the float glass surface on the atmosphere side. The glass surface had been etched by wax-like corrosion droplets and holes were formed into the glass skin after washing. This results in inhomogeneity on the surface, which induces an inhomogenous deposition pattern of the material on the surface during the process of sputtering. In contrast, the tin bath side is shown to be an ideal coating surface without any inhomogen eity. In some eases however, it could not be bent above the glass transition temperature (Tg) in air due to formation of bloom patterns, which make the glass milky. Our studies revealed that phase separation is the ultimate cause of the observed bloom formation. In addition, sulphur flakes and needle-like nanocrystallites were detected on the tin bath side as well as hexagonal nanocrystallites on the atmosphere side of the annealed float glass. It was also found that flame treatment of borosilieate and lead crystal glasses induced two changes on the glass surfaces. These are precipitation of evaporation products and phase separation beneath the glass skin. The samples were studied by a combination of field emission scanning electron microscopy (FE-SEM) with different accelerating voltages and atomic force microscopy (AFM)

Weathering of tin oxide coated glass with low IR emissivity

The weathering of K-glass has been studied by measuring transmission and reflection in the visible (VIS), near infrared (NIR) and infrared (IR) wavelength ranges, by chemical depth profiling with secondary neutral mass spectrometry (SNMS) and by atomic force microscopy (AFM) imaging. K-glass is a commercial tin oxide coated glass with low IR emissivity. The SnO2:F-coated side has been exposed to atmospheric conditions for up to 32 weeks and for up to two years. It could be shown that the optical properties are only affected in the VIS range, but the visible contamination does not influence the high IR reflection. This means that the heat-insulating properties of window glazings with the K-glass coating on the surface do not degrade under atmospheric conditions. Chemical depth profiles did not reveal major changes, except for an increase in the signals of minor elements on the surface, namely sodium, carbon and silicon. AFM showed that after 32 weeks the deep valleys of the rather rough crystalline SnO2:F are partially filled up. The high transmission of new K-glass can be regained since contamination or corrosion products can be removed by washing. The coating itself is chemically stable

Fabrication of 3D microchannels for tissue engineering in photosensitive glass using NIR femtosecond laser radiation

The biocompatibility of photosensitive glasses allows various biomedical applications; one is the field of tissue engineering and more precisely microengineered tissue-on-a-chip platforms to study the tissue microenvironment and disease modelling. Three dimensional architectures of adapted components are required for modern materials. A photosensitive lithiumalumosilicate glass FS21 was investigated regarding the interaction with a Ti:Sapphire laser systemto build three dimensional buried channels inside the glass. Femtosecond laser radiation with a wavelength of 800 nm and pulse duration of 140 fs was used to modify the glass structure. Subsurface channel geometries were achieved by a subsequent thermal treatment and were formed into capillaries using wet chemical etching of the exposed and crystallised channels. Contrary to ultraviolet (UV) exposure, spectral optical investigations showed that fs laser exposure caused various radiation induced defects in the base glass coupled with the generation of photoelectrons for the photochemical modification of silver ions. We observed an outgassing of different species coming from raw materials of the original glass batch during the glass crystallisation process. Etch rate ratios differ between 1:25 and 1:45 and are dependent on: stoichiometric deviation between surface and bulk, crystal size and distribution and exchange of the etching agent in narrow capillaries

Study of surface changes on industrial glasses with AFM, FE-SEM, EDX, SNMS and LM : Part 1. Glass skin and corrosion

By combining different analytieal techniques, including modern high resolution imaging tools such as field emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM), new phenomena in the surface, near surface and bulk structure of various industrial glasses (without any cleaning process) have been diseovered. Investigations of soda-lime-silica container glass and lead silicate glass tubings exposed to atmospheric and to dried air are presented. The results of the first part of this paper can be explained with an SiO2 rich skin on the glass, which can protect the glass against the attack of external media. If the skin was mechanically injured, inhomogeneous corrosion products on pm scale grew around the injured site after exposure to humid air for times between days up to one year. Microchannels were formed through the injured site due to restricted ion exchange, followed by a local increase of the pH value and consequently the dissolution of the glass network. Finally some stress in the glass, yielded during manufacture, can be partially released and the cutting behaviour is improved. Faster cooling results in a thinner skin and the ions in the glass are able to migrate to the surface more easily when surrounded by some reactive media. Slower cooling results in thicker skin and wax-like droplets instead of erystallites are formed on the surface at a later stage in humid air. The wax-like droplets can etch the glass skin locally, followed by the growth of inhomogeneous corrosion products similar to the injury induced corrosion. If the fresh glass surface was hot-end treated, the quality of the adjacent coating layer depended strongly on the thickness of the skin

Multi-method characterization of soda-lime glass corrosion : Part 2. Corrosion in humidity Report of the International Commissionon Glass (ICG) Subcommittee of Technical Committee 19 "Glass Surface Diagnostics"

As-received and cleaned soda-lime glass surfaces corroded in high relative humidity of 95 % at a temperature of 60 °C for times up to one week are investigated by means of TOF-SIMS, SNMS, XPS, NRA, ERD, RBS, GIXR, AFM, SEM and optical microscopy. Distinct differences in the corrosion behavior are observed for as-received and cleaned glass surfaces. Changes in element concentration in the glass interface and in the topography of the glass surfaces are described for different exposure times in humidity. They are combined with variations in density of the modified surface layer. Cleaning before the corrosion treatment drastically reduces degradation; cleaning after the corrosion treatment can restore the surface