Assessing the Reliability of Single and Combined Diagnostic Tools for Testing the Mechanical Properties of Historic Masonry Structures

Diagnostics is an important and challenging task of the structural analysis and condition assessment of historic masonry structures. However the interpretation of the results of the measurements, especially for buildings made from brick and stone, is to be more subjective than that for concrete structures. Therefore improvement of the reliability of the used techniques and finding better correlations between the test results and the mechanical properties of masonry has proven to be of great importance. While several diagnostic procedures are commonly used in practice to test mechanical properties of masonry, e.g. Schmidt hammer test, analysis of drilled samples, penetration tests, etc. the results of these methods are considered reliable under laboratory conditions, several additional factors have to be taken into account in case of an in-situ application of these methods, that may largely affect the obtained results and conclusions. The results of the diagnostic procedures therefore need to be interpreted with a view to these environmental factors. The paper focuses on the practical use of several test methods for historic masonries via a real case study. The presented case study attempts to demonstrate benefits from the combined application of Pendulum Schmidt Hammer, moisture meter and scanning electron microscopy

Investigation of Façade Coatings Containing Algae-Prone Fillers

Algae are an evolutionary model of success and colonize all suitable ecological niches including building material surfaces that have favorable characteristics. In the last 25 years, building physics measures were developed to reduce water availability, especially on external thermal insulation composite systems. Investigations into the influence of coating formulations have so far primarily focused on binder systems, biocides and hygrothermal properties. Research on the algal susceptibility due to the fillers is not to be found, but these regularly constitute a large proportion of final coatings. The present work investigates the influence of magnesium-containing fillers in the process of algal colonization of free-weathered façade coatings and a defense-strategy by water-activated pigment composition

Imidazolium Ionic Liquids as Designer Solvents Confined in Silica Nanopores

Composite silica xerogels were prepared via acid catalysed sol–gel route using tetraethoxysilan (TEOS) as silica precursor, and 1-butyl-3-methylimidazolium tetrafluoroborate [BMIM][BF(4)] or 1-butyl-3-methylimidazolium chloride [BMIM][Cl] ionic liquids, used simultaneously as co-solvents, catalysts and pore templates, at various IL-to-silica ratios. Morphology of the xerogels prepared using the different IL templating agents were investigated using scanning electron microscopy (SEM), nitrogen sorption and small angle neutron scattering (SANS). The thermal behavior of the composites was analyzed by thermal gravimetry, whereas the compositions were checked by infrared spectroscopy and EDX. The differences in the morphology and thermal behavior of the composites due to the different IL additives were revealed

Characterization of the microstructure of tin-silver lead free solder

Reliability and lifetime are the two most relevant design considerations in the production of safety critical assemblies. For example in a modern automobile dozens of electronic assemblies are integrated in which thousands of solder joints are mounting the electronic components to the printed circuit boards. There exists no standardised and universal observation method for characterising the fine micro structure of such solder joints. Previously we have developed a new method for the quantitative characteriz ation of lead - free solder alloys and in present study the validity of the proposed method is demonstrated. M icrostructure of Sn - 3.5Ag lead free solder alloy was investigated by electrochemical impedance spectroscopy. Solder samples were solidified with dif ferent cooling rates in order to induce differences in the microstructure. M icrostructure of the ingots was revealed by selective electrochemical etching. Electrochemical impedance spectr a (EIS) were measured before and after the selective etching process. The complex impedance spectra contain information about microstructure of the solder alloys. Comparison and mode l ling of two EIS spectra allowed obtaining a characteristic parameter of surface structure of the etched specimens. The EIS measurements were c omplemented with small angle neutron scattering measurements and scanning electron microscopy , in order to correlate the EIS parameter with the magnitude of the interface of the β - Sn and Ag 3 Sn phases

Gelatin content governs hydration induced structural changes in silica-gelatin hybrid aerogels – Implications in drug delivery

Silica-gelatin hybrid aerogels of varying gelatin content (from 4 wt.% to 24 wt.%) can be conveniently impregnated with hydrophobic active agents (e.g. ibuprofen, ketoprofen) in supercritical CO2 and used as drug delivery systems. Contrast variation neutron scattering (SANS) experiments show the molecular level hybridization of the silica and the gelatin components of the aerogel carriers. The active agents are amorphous, and homogeneously dispersed in these porous, hybrid matrices. Importantly, both fast and retarded drug release can be achieved with silica-gelatin hybrid aerogels, and the kinetics of drug release is governed by the gelatin content of the carrier. In this paper, for the first time, a molecular level explanation is given for the strong correlation between the composition and the functionality of a family of aerogel based drug delivery systems. Characterization of the wet aerogels by SANS and by NMR diffusiometry, cryoporometry and relaxometry revealed that the different hydration mechanisms of the aerogels are responsible for the broad spectrum of release kinetics. Low-gelatin (4–11 wt.%) aerogels retain their open-porous structure in water, thus rapid matrix erosion dictates fast drug release from these carriers. In contrast to this, wet aerogels of high gelatin content (18–24 wt.%) show well pronounced hydrogel-like characteristics, and a wide gradual transition zone forms in the solid-liquid interface. The extensive swelling of the high-gelatin hybrid backbone results in the collapse of the open porous structure, that limits mass transport towards the release medium, resulting in slower, diffusion controlled drug release

Mechanistic Explanation for Differences Between Catalytic Activities of Dissolved and Aerogel Immobilized Cu(II) Cyclen

The copper(II) complex of 1,4,7,10-tetraazacyclododecane [Cu(II)-cyclen] was covalently immobilized in mesoporous silica aerogel. This immobilization significantly alters the catalytic activity of Cu(II)-cyclen when referenced to the dissolved complex in the oxidation of phenol by H2O2 in aqueous solution. In order to understand this phenomenon, the functionalized aerogel was characterized by scanning electron microscopy (SEM), N2 porosimetry, small angle neutron scattering (SANS), infrared spectroscopy (IR) and electron paramagnetic resonance spectroscopy (EPR). Aerogel morphology is typical of mesoporous silica aerogels, and the coordination mode of Cu(II) in the immobilized complex is well-related but not identical to solution phase Cu(II)-cyclen. The mechanisms of the catalytic reactions involving dissolved and immobilized Cu(II)-cyclen were explored by fine kinetic experiments using capillary electrophoresis (CE) and on-line UV–vis spectrophotometry. Hydroquinone, pyrocatechol and the related benzoquinones were identified as the main intermediates in both reaction systems. A detailed kinetic model is postulated based on global data fitting, which clearly highlights the mechanistic differences in the two systems. Interestingly, the activation of the catalyst by H2O2 is more effective in the case of the aerogel, but the total conversion of phenol is slower due to hindered mass transport compared to using dissolved Cu(II)-cyclen