Comparative Atomic Force and Scanning Electron Microscopic Studies Disclosing Nanocrystallinity in Cordierite Glass-Ceramics : examples of Surface Modification

The atomic force microscopy (AFM), because of its unique features, can be used for a variety of applications and provides excellent research and development opportunities in the area of nanoscience and nanotechnology of glass and glass-ceramics. In this study, microscopic experiments have been carried out using both AFM and SEM on polished and etched as well as fracture cordierite glass-ceramic surfaces to unfold their comparative capabilities. Most importantly, it has been exhibited that the AFM is capable to ascertain single tiny crystallites originated at the beginning of crystallization of glasses before scanning electron microscope (SEM) or X-ray diffraction (XRD) detects them. AFM provides extraordinary two-dimensional (2D), three-dimensional (3D), and quick surface plot (QSP) formats of images with unobscured (since no coating is necessary) views of nanostructures rather than obscured (since conducting coating is essential for insulators such as glass and glass-ceramics) and only 2D microstructural profiles of SEM. Development of interatomic forces (extended up to tens to hundreds of angstorms from the sample surface) between the atoms of the very sharp tip (probe) and those of surface (sample) during measurement results in unprecedented resolution (similar to0.1 nm) of images in AFM. While SEM produces images (resolution similar to10 nm) based on secondary electron emission from the sample surface. By comparing the results with those of SEM experiments, the AFM is established as a simple and powerful technique for the characterization of nanostructures of glass-ceramics particularly of early stages of crystallization

Atomic force microscope study of the topography of float glasses and a model to explain the bloom effect

The topography and nanostructure of several technical borofloat and soda-lime-silicate float glasses were investigated by a high-resolution atomic force microscope (AFM). The irregular ripple pattern to be seen on as-received atmosphere and tin bath side surfaces had an average diameter of ≈ 60 nm, heights < 1 nm and root mean square (rms) roughnesses on (1 × 1) µm2 images of < 0.25 nm. Topographies obtained in the mirror region of fracture surfaces displayed a somewhat coarser nanostructure. It could further be assured that there are no specific differences between the interior and the edge of the float glass sample. Inhomogeneities like precipitates, crystals, phase separation or pores are not caused by the in-diffusion of tin into the float glass. After annealing the float glasses in air, several of them showed the already long known phenomenon of bloom, a greyish haze produced by a wrinkling of the tin bath glass surface. The borofloat glasses did not produce bloom under any condition. The same was true for the Fe2O3-rich green and blue glasses. Depending on sample dimensions and annealing conditions only the Fe2O3-poor clear float glasses developed a pronounced bloom effect. It is known that annealing of the glasses in air causes an oxidation of Sn2+ to Sn4+, which acts as a network former. This causes a change in glass properties near the surface. However, the precisely measured in-depth profiles of all relevant species in the nanometer and the micrometer regions of the float glasses showed that only in the ease of the Fe2O3-poor silicate float glasses a reversed Sn2+ diffusion from the interior to the surface is caused by the air annealing, forming a very high and steep tin (Sn4+) enrichment in a superficial layer with a thickness between 50 and 150 nm. In analogy to thin film technology a simplified model was developed and a free buckling length of ≈ 2.3 µm was estimated for the bloom surface, which is in reasonable agreement with the experimental finding. It was further shown that a sol-gel derived SiO2 coating of the bloom surface could enhance the optical transmission of the glass considerably

Experimental investigations of the internal friction of optical and technical glasses with a flexure pendulum equipment

Α special flexure pendulum equipment for investigation of the mechanical relaxation behaviour (internal friction) of glasses, glassceramics and other materials is presented. With the help of this apparatus it is possible to investigate the internal friction in the temperature ränge from room temperature until beyond Tg with a frequency of about 1 Hz. For analyzing the experimental results the shear behaviour of the investigated material is described in terms of a Maxwell body characterized by the rheological parameters Young's modulus and relaxation time. From the theoretical treatment of the bending problem for the experimental equipment calculation, formulae are obtained which connect the rheological parameters with the measured quantities period of oscillation and logarithmic decrement. Investigations of the internal friction of optical and technical glasses show weak effects in the ränge from room temperature until Tg and very strong damping peaks with different peak widths and maxima temperatures in the ränge beyond Tg. The syntheses and glass transformation ranges of the investigated glasses are very different. The activation energies of the hightemperature relaxation processes are obtained from the measured temperature dependences of relaxation times. These activation energies of the high-temperature relaxation process beyond Tg are smaller than the activation energies of viscosity determined by means of a bar elongation method

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

Mid-infrared laser absorption spectroscopy for process and emission control in the glass melting industry : Part 2. Difference frequency generation based MIR laser spectrometer for glass melting furnaces

Emerging techniques of mid-infrared absorption spectroscopy offer potentially great sensitivity and selectivity for combustion control and emission monitoring. Beeause of that, a differenee frequency based mid-infrared absorption spectrometer has been considered for application in the glass industry. Based on preliminary tests within laboratory conditions, a spectrometer which operates at wavelengths around 5 μm was applied to online monitoring of the atmosphere of a gas fired glass melting furnace. The CO concentration was measured in order to demonstrate the feasibility of a mid-infrared absorption spectrometer for process control in the glass industry. Α series of measurements was performed in situ as well as crossing the recuperator entry, resulting in general advice on the construction of a prototype device

Mid-infrared laser absorption spectroscopy for process and emission control in the glass melting industry : Part 1. Potentials

Laser spectroscopic diagnostics of combustion species at elevated temperature has shown considerable progress during the last years and decades. Particularly, techniques of mid-infrared absorption spectroscopy using fundamental rotational/vibrational transitions offer potentially great sensitivity and selectivity for combustion control. However, applications are still limited to mostly laboratoryscale investigations, which is mainly due to drawbacks of light sources and beam guidance materials. On the other band, many efforts are made to facilitate industrial application. In this context, the relevance of mid-infrared absorption spectroscopy for in situ monitoring of minor species in glass melting furnaces is obvious, too. The present paper gives a general review of available techniques and their impact on emission diagnostics in the glass industry, considering conventional as well as emerging light sources, detectors, peripheral devices and spectroscopic techniques

Bericht der Wissenschaftlergruppe der Arbeitsgruppe Benchmarking über Möglichkeiten zur Verbesserung der Beschäftigungschancen gering qualifizierter Arbeitnehmer

Die Teilnehmer am Bündnis für Arbeit, Ausbildung und Wettbewerbsfähigkeit haben der Arbeitsgruppe Benchmarking den Auftrag erteilt, Wege zur Erschließung neuer Beschäftigungsfelder und Ausbildungsmöglichkeiten für gering qualifizierte Arbeitnehmer unter Erprobung und Einsatz neuer Instrumente zu prüfen bzw. Optionen für eine Verbesserung der Erwerbschancen von Geringqualifizierten vorzulegen. "Die Wissenschaftlergruppe der Arbeitsgruppe Benchmarking ist einhellig zu der Auffassung gelangt, dass eine wirksame Verbesserung der Arbeitsmarktchancen gering qualifizierter Arbeitnehmer nur von einer dynamischen Entwicklung der Beschäftigung im Dienstleistungssektor, insbesondere bei den einfachen, niedrigproduktiven und zumeist personenbezogenen Dienstleistungen, zu erwarten ist. Zur Freisetzung einer neuen, anderen Ländern vergleichbaren Beschäftigungsdynamik in diesen Bereichen, in denen Geringqualifizierte am ehesten Arbeit finden können, bedarf es nach Ansicht der Wissenschaftlergruppe einer nachhaltigen Verbesserung der Angebotsbedingungen für Unternehmen des Dienstleistungssektors und einer Beschleunigung des Strukturwandels zugunsten von Beschäftigung im Dienstleistungsbereich." (IAB2

Multiplicity dependence of jet-like two-particle correlations in p-Pb collisions at sNN\sqrt{s_{NN}} = 5.02 TeV

Two-particle angular correlations between unidentified charged trigger and associated particles are measured by the ALICE detector in p-Pb collisions at a nucleon-nucleon centre-of-mass energy of 5.02 TeV. The transverse-momentum range 0.7 $< p_{\rm{T}, assoc} < p_{\rm{T}, trig} <$ 5.0 GeV/$c$ is examined, to include correlations induced by jets originating from low momen\-tum-transfer scatterings (minijets). The correlations expressed as associated yield per trigger particle are obtained in the pseudorapidity range $|\eta|<0.9$. The near-side long-range pseudorapidity correlations observed in high-multiplicity p-Pb collisions are subtracted from both near-side short-range and away-side correlations in order to remove the non-jet-like components. The yields in the jet-like peaks are found to be invariant with event multiplicity with the exception of events with low multiplicity. This invariance is consistent with the particles being produced via the incoherent fragmentation of multiple parton--parton scatterings, while the yield related to the previously observed ridge structures is not jet-related. The number of uncorrelated sources of particle production is found to increase linearly with multiplicity, suggesting no saturation of the number of multi-parton interactions even in the highest multiplicity p-Pb collisions. Further, the number scales in the intermediate multiplicity region with the number of binary nucleon-nucleon collisions estimated with a Glauber Monte-Carlo simulation.Comment: 23 pages, 6 captioned figures, 1 table, authors from page 17, published version, figures at http://aliceinfo.cern.ch/ArtSubmission/node/161