Alexey Sidelev

meso-Tetraarylporpholactones as high pH sensors.

The ability of meso-tetra(pentafluorophenyl)porpholactone (T(F)PL) and its Pt(II) complex [meso-tetra(pentafluorophenyl)porpholactonato]Pt(II) (T(F)PLPt) to function as optical high pH sensors is described. Under strongly alkaline or high methoxide conditions, their UV-vis spectra undergo dramatic and reversible red-shifts. The dynamic range for the sensor T(F)PLPt in solution is from pH 11.5 to 13.2. Using (1)H, (19)F, and (13)C NMR, UV-vis and IR spectroscopy, mass spectrometry, and the use of model compounds, the molecular origin of this optical shift is deduced to be a nucleophilic attack of OH(-)/MeO(-) on the lactone carbonyl of the chromophore, representing a novel mechanism for porphyrin-based sensors. The sensing compound was solubilized with Cremophor EL for use in aqueous solutions and embedded in polymer matrixes for testing as optical fiber-based optodes and planar sheet optode materials.

Quantitative Assessment of Subsurface Oxidation in Coated Materials

AbstractA hybrid experimental-numerical method for the standoff and quantitative analysis of metal corrosion under protective coatings is proposed based on long-wave infrared broadband imaging. Thi...

Detection of Subsurface Metal Oxidation with Thermal Imaging

We introduce thermographic imaging as a non-destructive evaluation method for detection of hidden corrosion or delamination of coating on metals or other substrates. A hybrid experimental-numerical technique using long wave, broad band imaging for the standoff and quantitative analysis of the interface is introduced. Time lapsed measurements of surface temperature is carried out, followed by numerical simulation of the corresponding thermal signature. Results of damage detection using thermal imagery were compared with substrate wall thickness measured by a thickness gauge. It is concluded that imaging approach provides measures of metal loss, at levels less than the variations in the metal wall manufacturing tolerance, highlighting corroded areas which would otherwise be undetectable using sensors for measuring metal thickness.

Sensing Hygrothermal Processes in Calcium Silicate Hydrates

Two parameters are used to assess the maturity of fresh hydraulic cement during the curing process: temperature and water content. This chapter describes the preparation and the application of two optical fiber sensors for simultaneous measurement of temperature and moisture. The temperature sensor utilizes Europium beta diketonates, a luminescent complex with an emission signal that provides temperature data. The moisture sensor utilizes the intrinsic optical properties of the water molecule used for the quantitative measurement of the liquid phase moisture content. These probes were tested in fresh cement paste during the curing processes.

In Situ Analysis of Moisture in Cement Based Materials

An approach for the evaluation of moisture transport in porous media is introduced and demonstrated through measurement of capillary absorption and evaporative drying in cement mortar. The sensing method is based on the application of Near-Infrared spectroscopy, where the internal environment of the cement mortar is monitored by measurement the absorption peaks of the water molecule using light traveling through an optical fiber. The fibers were altered by replacing a short length of the fiber cladding with a porous membrane, allowing the propagating light to interact with the water in the surrounding pore space, registering the respective moisture content.

Monitoring the hysteresis effects in the strain-stress curve of carbon fiber reinforced laminates by FBG technology

In this paper, we present a study of detecting the hysteresis effect in strain-stress curve of carbon fiber reinforced materials by Fiber Bragg Grating technology. By calculating the dissipative energy density contoured by hysteresis loops, this method can be further applied in detecting the cracks and fatigue of carbon fiber reinforced laminates. In contrast to the traditional sensors, such FBG sensors have numerous merits, such as small size, immunity to Electromagnetic Interference and easy installation into the carbon fiber reinforced laminates. This method can also be extended into monitoring other materials which also exhibit hysteresis effects in their strain-stress curves.