Visualisation of environmental degradation in ceramic superconductors using digital speckle photography

Abstract

Differences in the environmental stability of Bi-2212 textured materials before and after annealing have been evaluated using digital speckle photography. This technique is able to provide information about the 2D evolution of the degradation processes by means of correlation coefficient reductions. The results indicate a faster degradation for as-grown samples. DSP detects this difference in very short times and allows determining the evolution of the process at any instant. The optical results were confirmed by analysing the differences in the samples microstructure and phase compositions by SEM-EDX, XRD and DRIFT techniques. All these techniques show that, in this material, environmental degradation process is associated with the chemical decomposition of the (Sr,Ca)CuO 2 phase.

Simple method for simultaneously measuring the magnitude and direction of 2D in-plane displacement in white-light speckle photography

“…Ten sets of different nominal feeds, i.e. 10,20,30,40,50,60,80,100,150 and 200 μm, are tackled repeatedly. For each set of nominal feed, 10 pairs of speckle images are recorded, and 10 measurement values of displacement can be obtained.…”

“…Since the classical work of Burch et al [8,9], SP has achieved significant developments in many application fields, such as engineering and materials science [5,[10][11][12], biomedicine [7,13] and geography and geology [14]. Numerous physical quantities, including in-plane displacement [15,16], in-plane rotation [15,17], out-of-plane displacement [18,19], angular displacement [20], surface tilt [21,22], velocity [23,24], angular velocity [25], vibration [6,17], stress [5,26], strain [27,28], temperature [4,29] and convection [30], can be evaluated with SP.…”

Application of digital speckle interferometry to visualize surface changes in metallic samples immersed in Cu(NO3)2 solutions

“…Optical techniques, due to their nondestructive character, have been applied to measure in situ changes in surfaces [1][2][3][4][5][6][7][8][9][10][11][12][13][14] as an alternative to traditional intrusive methods. Holographic techniques provide information about the evolution of the corrosion process in an aqueous solution by counting the number of fringes [3][4][5] or by monitoring the refractive index change in electrochemical reactions using an in-line recording setup.…”

Investigation of liquid immersed metallic surface corrosion processes using speckle interferometry

“…Optical techniques, due to their non-destructive character, have been applied to measure in situ changes in surfaces as an alternative to traditional intrusive methods [1][2][3][4][5][6][7][8][9][10] . Holographic techniques have been applied to measure the evolution of the corrosion process in an aqueous solution by counting the number of fringes [3][4] or the refraction index change in electrochemical reactions using an in-line recording setup [5][6][7] .…”

“…Digital Speckle Photography has been applied to measure the local surface changes in corrosion processes and to estimate the corrosion rate [8][9] . Speckle interferometry, using a twin-object-beam recording system, has been applied to the study of corrosion to obtain a global value of the corrosion rate 10 .…”