This work presents an alternative for the determination of the torsion modulus, G, of polymers. These materials may be subjected to shear stresses in some structural applications; thereby, the knowledge of G is of great interest. For this purpose, a mechanical system featuring a simplified torsion pendulum version and a rotational motion sensor (RMS) coupled to it was used to establish an angular position as a function of time. The applied technique is considered non-destructive and makes it possible to obtain G without the Poisson’s ratio through an equation derived from mechanical spectroscopy and material strength. The main goal is to present and validate the employment of this method for polymers. Therefore, circular cross-sectional samples of extruded polytetrafluoroethylene (PTFE) were subjected to torsional stresses, in which a physical and quantitative explanation is given for the frequency and G curves as a function of the prefixed rotational inertia (I), length (L), and diameter (d). Differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) were also made to ensure the reliability of data. It is possible to establish an L/d ratio, which explains why G converges to a single value when the sample dimensions are different from each other. It was found that G is approximately 350 MPa for an L/d ratio equivalent to 10.64. Such a value is within limits found in the literature, opening the possibility of assessing other polymers.

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The discovery of the superconductivity of MgB2 was of great importance, because this material is one of the few known binary compounds and has one of the highest critical temperatures (39° K). As MgB2 is a granular compound, it is fundamentally important to understand the mechanisms of the interaction of the defects and the crystalline lattice, in addition to the eventual processes involving the grain boundaries that compose the material. In this sense, the mechanical spectroscopy measurements constitute a powerful tool for this study, because through them we can obtain important information about phase transitions, the behavior of interstitial or substitutional elements, dislocations, grain boundaries, diffusion, instabilities, and other imperfections of the lattice. For this paper, the samples were prepared using the PIT method and were characterized by density, X-ray diffraction, scanning electron microscopy, electric resistivity, magnetization, and mechanical spectroscopy. The samples were measured in their as-cast condition and after an ultra-high-vacuum heat treatment. The results showed complex spectra, in which were identified relaxation processes due to dislocation movement, interaction among interstitial elements and dislocations, auto-diffusion, and movement of grain boundaries. Some of these processes disappeared with the heat treatment.

Since the discovery of high-temperature superconductivity of cuprate oxides, it has been clear that it is strongly affected by the oxygen content, which is also a crucial factor to determine other physical properties of high Tc superconductors. Non-stoichiometric (interstitial) oxygen strongly influences the physical properties of various superconducting oxides, in particular by creating conducting holes. It is now ascertained that the amount of holes injected depends not only on the content of interstitial oxygen, but also on its ordering. Rearrangement of the oxygen ordering may occur even below room temperature due to the unusual high mobility of these atoms. This way, mechanical spectroscopy is one of the most adequate techniques for the study of the mobility (diffusion) of oxygen atoms. This technique allows the determination of the jump frequency of an atomic species precisely, regardless of the model or the different possible types of jumps. In order to evaluate the mobility and the effect of oxygen content on these oxides, ceramic samples we prepared and submitted to several oxygen removal cycles alternately with mechanical relaxation measurements. As for SBCO, it was assumed that the peak was due to O(1)-O(5) jumps of oxygen atoms at the chain terminals or in chain fragments in the orthorhombic phase. In the case of BSCCO, the results showed complex anelastic relaxation structures, which were attributed to interstitial oxygen atom jumps between two adjacent CuO planes.