Stress microprobe

We will confine ourselves to those applications concerned with chemical analysis, although the Raman microprobe also enables the stress and strain imposed in a sample to be examined. Externally applied stress-induced changes in intramolecular distances of the lattice structures are reflected in changes in the Raman spectrum, so that the technique may be used, for example, to study the local stresses and strains in polymer fibre and ceramic fibre composite materials. 

The failure analysis can be done using a judicious combination of several methods such as visual examination, metallography, microscopy, electron microprobe, energy dispersive X-ray analysis, X-ray diffraction methods for determining residual stress in the sample, surface analytical techniques to determine the nature and composition of surface deposits and finite element analysis modeling. 

Raman photoluminescence piezospectroscopy of bone, teeth and artificial joint materials has been reviewed by Pezzotti (2005) with emphasis placed on confocal microprobe techniques. Characteristic Raman spectra were presented and quantitative assessments of their phase structure and stress dependence shown. Vibrational spectroscopy was used to study the microscopic stress response of cortical bone to external stress (with or without internal damages), to define microscopic stresses across the dentine - enamel junction of teeth under increasing external compressive masticatory load and to characterise the interactions between prosthetic implants and biological environment. Confocal spectroscopy allows acquisition of spatially resolved spectra and stress imaging with high spatial resolution (Green etal., 2003 Pezzotti, 2005 Munisso etal., 2008). 

Nishioka, T., Shinoda, Y., and Ohmachi, Y. Raman Microprobe Analysis of Stress in Ge and GaAs/Ge on Si02-Coated Si Substrates. J. Appl. Phys. 57(2) 276-281 (1985)... 

Under the action of mechanical stresses, the transformation of the tetragonal phase can proceed (a to c in Fig. 8.57). Such a process can occur at crack tips in materials in which the t-ZrOj has been retained below the equilibrium transformation temperature. Indeed, using a variety of techniques, such as transmission electron microscopy (TEM), x-ray diffraction and Raman microprobe analysis, it has been confirmed that some or all of the t-ZrOj can be transformed to the monoclinic phase in the vicinity of the fracture surface. Figure 8.59 shows microscopic evidence of a transformation zone around a crack. 

Kobayashi, K., Inoue, Y., Nishimura, T., Hirayama, M., Akasaka, Y., Kato, T. and Ibuki, S. (1990), Local-oxidation-induced stress measured by Raman microprobe spectroscopy, Journal of the Electrochemical Society 137, 1987-1998. 

Ag, Pb, and Cu Fiims. Evaporated Ag, Pb, andCu land patterns on ceramic substrates were tested in water-drop experiments under 10 volt bias as-evaporated, after being oxidized, "sulphized and exposed to HCI dilute solution to form metal chlorides. Five samples for each metal and surface condition were stressed. The reaction surface layers were < 50 nm thick and rather spotty (discontinuous) as determined by electron microprobe. The oxide and sulphide layers either halted migration or reduced its occurrence dramatically. It was obvious that dendrites, whenever they occurred, were associated with incomplete passivation and, in general, the surface treatment was very effective. 

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