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Mechanical characterisation techniques have been recently proposed, which use as main information source the geometry of the residual imprint left on metal surfaces by hardness or instrumented indentation tests. Relevant identification procedures have been developed but the problem has been investigated, so far, mainly from a methodological point of view, exploiting pseudo-experimental data. This contribution presents the results of a verification study based on the real deformation measurements, collected from tests performed at scales consistent with those of structural applications. It is shown that the recovered mechanical properties compare satisfactorily well with those resulting from traditional tensile tests.

In the present work we report an anelastic spectroscopy study of pure FeCO 3 (siderite) and of carbon steel samples covered by siderite films. Uncovered steel samples have also been investigated for reference. The siderite shows two relaxation processes below room temperature, at about 220 K and 140 K, while the covered steel sample displays only the peak at lower temperature. The presence of such a relaxation can be used to monitor the deposition of siderite.

This article summarizes the main results of an investigation about the corrosion detection in pipelines by infrared thermography, a non-destructive testing and evaluation technique that allows a reliable and fast analysis of large surfaces. The experimental work has been carried out in laboratory on a specimen that has been manufactured using a piece of a real pipeline system for oil transportation. Defects of different kinds have been artificially introduced in such a system to be tested by thermography. The objective is the detection and analysis of the presence of water in the pipeline jacketing system, that is the cause of the corrosion under insulation. Standards indicate thermography as a technique for the detection of this last phenomena, even though a precise procedure is not defined up today. This work aims at contributing in the specification of such a procedure.

Some ancient metallic art craft, utensils, silverware and weapons are externally undistinguishable from modern ones. Not only the general aspect and shape but also some uses have not changed through the ages. Moreover, when just some small pieces can be recovered from archaeological sites, the samples can not easily be ascribed to any known use and consequently identified. It is clear that mechanical processing has changed along history but frequently only a "microscopic" inspection can distinguish among different techniques. Some bronze samples have been collected from the Quarto d’Altino (Veneto) archaeological area in Italy (paleovenetian culture) and some model samples have been prepared by a modern artisan. The sample textures have been measured by X-ray Diffraction techniques. (111), (200) and (220) pole figures were used to calculate Orientation Distribution Functions and further recalculate pole figures and inverse pole figures. The results were compared with modern forging technology results. Textures are able to discern between hammering ancient techniques for sheet production and modern industrial rolling procedures. However, as it is demonstrated in the present work, forgery becomes difficult to detect if the goldsmith, properly warned, proceeds to erase the texture history with some hammering post-processing. The results of this contribution can offer to the archaeologists the opportunity to take into consideration the texture techniques in order to discuss the origin (culture) of the pieces and the characteristic mechanical process developed by the ancient artisan. Texture can also help the experts when discussing the originality of a certain piece keeping however in mind the cautions indicated in this publication.

The anelastic spectroscopy is a powerful method for studying the dynamics and geometry of defects and excitations carrying a local distortion. The vibrational stress affects the energy levels of the defects, which approach the dynamically perturbed thermal equilibrium, giving rise to dissipation of energy. The analysis of anelastic spectra provides the values of the defect jumping (or transition) rates and of the associated energy barriers. Furthermore, the application of the stress along different crystallographic directions gives indications on the symmetry of the relaxing defects. In this manner, important information on some hydrogenated complexes in semiconductors has been obtained. We report an overview of the more meaningful results in Si and III–V compound semiconductors.

Ultrasonic attenuation and velocity measurements were carried out in order to study the kinetics of water sorption process in hydrogels characterized by strong structural changes occurring in the material. Hydrogel, or gel contains water, can exist in two forms: a solid glassy phase when it is dry, a rubber phase in equilibrium with water. Scanning laser acoustic microscope (SLAM) technique has been used to monitor the change in the ultrasonic attenuation, during water sorption in crosslinked poly(hydroxyethylmethacrylate) and poly-vinyl alcohol (PVA) hydrogels of different thickness at the frequencies of 10 and 30 MHz. The pulse-echo technique has been applied to the measurement of the longitudinal velocity and ultrasonic attenuation and to monitor the advancement of the swollen–unswollen fronts. During the hydrogel water sorption a peak in the ultrasonic attenuation and a decrease in the longitudinal velocity have been detected. The increment in the ultrasonic attenuation has been analysed in terms of reflections from the swollen–unswollen boundary, microvoids scattering and absorption of the ultrasonic waves due to the glass to rubber transformation.

The elastic energy loss of InP has been measured between 1.9 and 450 K in the frequency range 1 to 16 kHz. In the InP samples displaying the semi-insulating state, obtained either by thermally treating at 950°C the undoped material or by doping with Fe, a well-developed thermally activated relaxation process appears at 300 K. The corresponding peak is described by a single-time Debye curve with an activation energy E=0.67 eV and a pre-exponential factor of the relaxation rate τ0−1=3×1014 s−1, indicating the presence of a species mobile at room temperature and constituted by atomic complexes. Instead, in the non-semi-insulating InP sample, the peak at 300 K is either absent or masked by the background. The possibility is discussed that the mechanism giving rise to the relaxation peak is due to hydrogen-related defects.

Venezia Tecnologie SpA (ENI Group), Via delle Industrie 39, I-30175 P. Marghera (VE), Italy~Received 2 December 1999!Elastic energy absorption measurements versus temperature on semiconducting, semi-insulating~SI!, andFe-doped InP are reported. A thermally activated relaxation process is found only in the SI state, which isidentified with the hopping of H atoms trapped at In vacancies. It is proposed that the presence of In vacanciesin InP prepared by the liquid encapsulated Czochralski method is due to the lowering of their energy by thesaturation of the P dangling bonds with H atoms dissolved from the capping liquid containing H

The time evolution of a GaAs(100) ‘epi-ready’ wafer exposed to air at normal conditions of pressure and temperature has been studied by means of Auger electron spectroscopy and argon-ion depth profiling. Our results show that the oxygen signal near the surface evolves during times as long as 5 months. The evolution of the oxygen signal is accompanied by the penetration of an oxidation front as the air exposure increases. This behavior is confirmed by means of different indicators obtained through the study of the low-energy Auger line-shape spectra.

Domain growth of bulk partially melted Nd1+xBa2−xCu3O7−δ in air was found to be severely limited by liquid-phase segregation and losses. The use of a reduced oxygen pressure greatly improved the stoichiometry control, leading to the formation of well-developed domains and enhanced superconducting properties. Direct nucleation of Nd1+xBa2−xCu3O7−δ from the liquid phase by dissolution of Nd2BaCuO5 and a spiral growth mechanism in three perpendicular directions of the platelets stacked in the domains, are suggested.

The importance of the distinction between 〈110〉 directions on the surface of (100)-oriented wafers for epitaxial growth and device fabrication is well known. The distinction is made by means of two flats. The traditional methods used for the accurate determination of flats location on ingots or wafers (with X-ray diffraction) or for the qualitative distinction between the flats (H2SO4 etchant) are compared with alternative procedures found in literature and/or developed in the present work: the use of dislocation-related etch pits (DREPs) revealed by the “Chu et al.” etchant and of the brightness and geometry of the faces on the cone of growth. Studies conducted on doped and undoped InP, by using optical and scanning electron microscopy, indicate that (i) concerning the cone of growth, the result differs from that typically used for GaAs and (ii) concerning the “Chu et al.” etchant, it originates well-defined pyramids with a rectangular base having its longer side parallel to the [0 11 ]-[011 ]axis on side A and rotated 90° on side B. It is suggested that DREPs can be used quantitatively for the control of flats location or for the determination of [0 11 ] and [0 1 1] directions on wafers without flats.

Large domains with platelets almost parallel to each other were obtained in bulk YBa2Cu3O7−δ by a single-step partial melting procedure. The mechanisms of nucleation and growth of platelets are discussed. The nucleation of peritectic material from the liquid phase is favoured by heterogeneities in the melt. Experimental evidence of spiral growth of the nuclei in the [0 0 1] direction is given. Furthermore, structures of growth, which could also be an indication of spiral growth in the [0 1 0]/[1 0 0] directions, are shown. The final morphology of the domains can be explained on the basis of the periodic bond chain (PBC) theory if the growth rates of flat (F) faces of the platelets are dominated by kinetic coefficients which differ between them. The morphology of the as-grown (0 0 1) surface is explained in the framework of the PBC theory with the shape of the steps of macrospirals governed by the transition from roughness to smoothness of the liquid-solid interface. An account of large step heights is given by the model of giant screw dislocations caused by an impurity-induced lattice-constant gradient. Even higher step heights are correlated to the presence of obstacles and lack of liquid phase.

For the design and optimisation of advanced materials, the possibility of reliably testing very small amounts of material or laboratory scale simple shape specimens is particularly interesting. To satisfy such requirements, this work presents a new procedure for mechanical testing of metal matrix composites. The method is essentially a diametral compression test of cylindrical specimens and represents an improvement of the ‘Brazilian’ test. The mechanisms leading to fracture of composites have been investigated via the mechanical behaviour of different metal matrix composites (A354–SiCp A354–A12O3 short fibres) and consideration given to the role of the major parameters involved (both test and material related). The results of the diametral compression test, in terms of rupture strength have been compared with those of conventional tensile tests and characterisation of the microstructure via light and electron microscopy has been carried out. Evaluation of the results led to the conclusion that th...

The high strength nickel alloys, and in particular Inconel type alloys, are extensively used in several applications, such as aeronautics and petroleum industry, thanks to the combination of their high mechanical properties and their thermal and chemical resistance. In particular Inconel 625 is already used in oil pipelines and pipelines of large thermal plants, and the possibility to replace high cost bulk Inconel parts with Inconel coated steel parts is of great interest. On this context the first topic to allow the use of coated parts instead of bulk Inconel is the capability to provide high corrosion and thermal resistance. The aim of this study is to investigate the capability of Coldspray in the deposition of high strength materials, such as hard nickel alloys, for corrosion protection, and to compare the corrosion behaviour of Coldspray coatings with commercial HVOF deposited coatings. Inconel 625 coatings were deposited by using CGT Kinetic3000 deposition system with nitrogen as carrier gas on AISI316L flat substrates. The coating thickness ranges between 0.3 and 1.0 mm. Different feedstock materials were used and the effect of powder size distribution on the growth capability, as well on coating microstructure and porosity, were evaluated. The corrosion behaviour of Coldspray coatings were studied by electrochemical potentiondynamic analysis and compared with the behaviour of commercially available coatings deposited by HVOF that could be considered as a high-quality benchmark. In particular, the effects of the different coating microstructures due to the different deposition processes were related with the corrosion resistance. Further development and key features are finally outlined in order to candidate the Coldspray as promising technology for the deposition of high-strength nickel alloys.

IR thermography is applied to detect hidden corrosion on carbon steel pipelines for oil transportation. The research is oriented to set up a robust technique to carry out in situ the early detection of corroded zones that may evolve either towards leakage or failure. The use of thermography associated with a transient thermal technique is investigated on 12.2 mm thick samples, machined to artificially create a reduction of wall thickness that simulates the effect of real corrosion in pipes. The extension and depth of the artificial defects is controlled by ultrasounds which represents the reference for the results obtained by thermography. Two approaches are proposed: the first is based on the processing of a single thermogram taken at the optimum time after a finite pulse heating of a large area of the external surface; the second technique is carried out by scanning the pipeline by means of a device composed of a linear lamp and a thermographic camera which move jointly over the surface to test. A suitable reconstruction provides a map of the tested surface with possible hot spots in correspondence with the corroded areas. The analysis of the thermal problem by Finite Element Method is used to optimize the experimental parameters. The experimental results demonstrate a detection capability starting from 15 % of wall thickness reduction. © 2011 SPIE.

A single-step partial melting procedure without temperature gradient on the sample was developed. The YBa2Cu3O7−δ platelets can be grown with their a–b planes almost parallel in the centimetre range. Morphological observations of regularly oriented macrospirals on the as-grown (001) surface suggest a screw dislocation growth mechanism along the c axis of the platelets.

The results of the development of two different technologies for the preparation of special surfaces for ready-to-use (‘epi-ready’) InP wafers are presented. The epi-ready state was studied by means of X-ray photoelectron spectroscopy. The quality of the substrates stored for 4–12 months was tested by growing an epilayer by metal-organic vapor phase epitaxy and by characterizing it with high-resolution X-ray diffraction and photoluminescence techniques. Evidence that one of our technologies could be adopted industrially is given.