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Atomic force microscopy based Infrared spectroscopy (AFM-IR) is a quickly evolving technique that provides chemical analysis and compositional mapping with spatial resolution far below conventional optical diffraction limits. This is possible since the detection method is based on a very sharp AFM tip which starts to oscillate when the sample starts to thermally expand (the changed is caused by the absorption of IR wavelength) where the thermal expansion is related to the IR absorption. This presentation briefly described the application of that new technique from polymer characterization and utilization of AFM-IR in material research, up to life science applications.
An extraction of silica from natural sands of Bancar has been conducted by means of alkali fusion route using NaOH and mechanical alloying using planetary ball milling. The PANI/SiO2 Composite system has been coated in steel surfaces using spraying method. This study was designed to obtain PANI/SiO2 as an anti-corrosion coating material. The filler materials in the composite System consist of micro- and nano-SiO2. The structure of synthesized SiO2 be characterized using XRD and TEM. Corrosion of PANI/SiO2 composite has been tested using immersion method in synthetic geothermal atmosphere (Nord Deutsche Becken/NDB solution). The surface morphology after corrosion was observed by using SEM/EDX. XRD-Patterns and TEM show that the size of produced SiO2 is micro and nano. The size and composition of filler have influenced to surface degradation in geothermal atmosphere significantly. The addition of nano-SiO2 in the PANI matrix influenced corrosion resistance better than micro-SiO2 filler qualitatively. The nano-SiO2 has a high potential as an anti-corrosion material in geothermal atmosphere. The product of corrosion is mainly Fe2O3 and the corrosion process is identified as a pitting corrosion.
Partially crystalline glasses are predominantly used as solid oxide fuel cell (SOFC) sealants due to their superior long term durability. However, cracks caused by thermal cycling still remain a substantial bottleneck in developing durable SOFC sealants inasmuch as, in contrast to crystal free glasses, large crystal volume fractions can retard healing. Hence, the basic understanding of crack healing in glassy crystalline materials and the effects of micro structure are important for finding optimum micro structures for both, durability and crack healing.
For studying these effects, several model glass matrix composites (GMC), for which simultaneous crystal growth and crack healing can be excluded, have been synthesized. Sodium calcium silicate glass – zirconia GMC turned out to provide sufficiently homogeneous, dense and durable model GMC for our studies. The microstructure of this GMC shows large crystal free glassy regions embedded in network of finely dispersed ZrO2 nanoscale crystals. Whereas the glassy regions allow easy local crack healing, the network of dispersed crystals increases the effective viscosity on a global scale. This effect substantially retards crack broadening during later healing stages, which often ends up in large pores. Therefore, this type of microstructure seems to be an interesting candidate for crack healing optimized sealants.
Fundamental understanding of crack healing in glassy crystalline materials is very important for many applications, especially for sealing solid oxide fuel cells (SOFC) since cracks caused by sealing or thermal cycling still remain a substantial bottleneck in developing durable SOFC.
Previous studies on soda lime silicate glass [Sin14] showed that crack healing is driven by viscous flow and that healing progress is proportional to time t and inverse viscosity η. This finding would allow to present healing data of a given glass for different temperatures in a master curve healing progress versus t/η. Such master curves would be a helpful tool in understanding crack healing kinetics.
Against this background, crack healing in non-crystallizing sodium calcium silicate (NCS) and sodium borosilicate glasses (NBS) have been studied. Moreover, to evaluate the influence of micros structure in crystallized glass on crack healing process, glass matrix composites (GMC) where prepared out of NCS and zirconia as inert ceramic filler material mimicking a partially crystalline micro structure. Cracks were generated by Vickers indention and healed isothermally at different temperatures. Crack healing progress was monitored by optical and electron microscopy. Results show that the above mentioned proportionality actually applies for the studied glasses for which such a master curve could be obtained. In comparison to a non-crystallized glass, the effective viscosity of GMC is increased by rigid filler content. This effect substantially retards crack broadening during later healing stages, which often ends up in large pores. On the other hand, local viscous crack healing is still possible in larger glassy regions. This behavior seems to be very interesting for crack healing optimized sealants.
In this study, quasi-static material tests on unidirectional and multi-angle glass fiber reinforced epoxy laminates at ambient temperatures from -213 K to 353 K (-60 °C to +80 °C) are performed. In addition, neat resin is investigated under tension and compression loads at different temperatures. The coefficient of thermal expansion is determined for neat resin and unidirectional reinforced specimens. The dependence of the resin’s thermomechanical properties on the ambient temperature is shown. The point of damage onset at which first cracks appear within the matrix under quasi-static loading is investigated by means of optical grey scale analysis. The correlation between damage onset and effective matrix stress at different ambient temperatures is identified. An approach for the calculation of thermomechanical loads and the prediction of the damage onset by means of inverse calculations is presented. The impact of the strain blocking effect of the matrix is considered as well as residual thermal stresses due to curing and resin shrinkage.
Conventional approval requirements exclusively ask for minimum strength values, which have to be met. The probabilistic approach estimates how likely none of the comparatively manufactured units fails during operation.
Both questions are juxtaposed and compared here with respect to the load cycle tests. The influence of the sample sizes is discussed additionally.
Existing regulations and standards for the approval of composite cylinders in hydrogen service are currently based on deterministic criteria (ISO 11119-3, UN GTR No. 13). This paper provides a systematic analysis of the load cycle properties resulting from these regulations and standards. Their characteristics are compared with the probabilistic approach of the BAM. Based on Monte-Carlo simulations the available design range of all concepts is compared. In addition, the probability of acceptance for potentially unsafe design types is determined.
The application range of CPV (composite pressure vessels)
is multifaceted. But also the failure forms and the spectrum of measurement methods is manifold. On various, at BAM observed effects, it is shown why the micromechanical analysis of the composites is of such great interest for the prediction of aging effects of CPVs.
This presentation provides general data about BAM, the structure of department 3 and a short impression of the application of pressure vessels for hydrogen in stationary use, supply chain and onboard storage.
It guides to the actions of BAM as competent authority on this area and shows a lot different methods for testing operated at BAM. Based on this additional research has been detected as necessary for a competent tackling of the tasks as competent authority. After having mentioned several important research projects a figure is presented that compares the development of regulations with relevant re-actions of BAM. The outcome was a concept of a risk based definition of accepted failure rates in combination with probability-oriented safety assessment over entire service life.
The second aspect raised at INERIS is the issue of advising the BMVI concerning pressure vessels for hydrogen. Since the pressure is high for saving material consumption and weight there is still high interest in changing regulatory requirements. Therefor we developed an approach for the display of minimum requirements of regulations in diagrams (sample performance charts; SPC) and the probabilistic analysis for these deterministic requirements. This is done by Monte-Carlo simulation and the analysis of acceptance rate and survival rate of basic populations all over the SPC.
This finally provide same knowledge of non-approvable but safe ranges of parameters and even approvable but non-safe constellations. In addition, this analysis allows to optimise deterministic requirements in regulations to the intended level of safety for approved populations of pressure vessels, which is shown on the example of the GTR#13.