Papers by Keyword: Laser Spectroscopy

Abstract: The chemical elements used in the binder system for the injection moulding of titanium metal powders will change the final composition when not adequately controlled. Excess levels of carbon, hydrogen, nitrogen and oxygen adversly effect the mechanical properties by embrittlement. Before sintering debinding is done to remove the maximum possible amount binder thereby ensuring residual carbon levels are minimal. Testing the mechanical properties of samples can acknowledge deficiencies in the final part however, identification of the nature of the deficiencies is not so simple.In this work titanium-based metal parts were made using the metal injection moulding process and the microstructure was inspected. The investigation used scanning electron microscopy imaging, electron dispersion spectroscopy point and area mapping, LECO trace analysis and X-ray diffraction elemental mapping. Following this samples were ground and polished before immersing their surfaces in an etching solution to further expose the microstructure. Although the data collected from debinding indicated the binder had been removed prior to sintering contamination was still evident. This result showed that the traditional means of reporting binder levels in proportion to part mass after debinding is inaccurate. Subsequently laser induced breakdown spectroscopy was trialed as a method by which to determine the binder levels for parts in the green, grey, brown and sintered form.Interstitial carbon is a known alpha stabiliser however excess carbon on particle surfaces may impinge on particle coalesence limiting density levels. Comparison of the part mass method of binder determination with the laser induced breakdown spectroscopy results showed that the mass determination method was more accurate for the green and grey parts but the laser induced breakdown spectroscopy results were able to detect the residual binder more accurately for brown and sintered parts.

Abstract: The surface layers resulting from prolonged exposure to the indoor environment and the bulk material of metal artifacts from the collection of National Museum in Gdansk are studied by means of spectroscopic techniques. The composition of the surface layers of the forged iron box lid covered with polychrome (XVI c.), and of the bronze female nude sculpture (antiquity) is obtained from the XRF and µ-Raman spectra. The elemental composition is confirmed by the LIP (Laser Induced Plasma) spectroscopic measurements. The quasi-nondestructive LIP technique applied for stratigraphic sampling performed with an accuracy of ca 2 µm across the multilayer surface coverage reveals such elements as C, Ba and Na in the uppermost layer. From coincidence of the XRF, Raman and LIP data the presence of surface contaminant CaCO₃, the corrosion product FeO(OH) and patina Cu₂ (OH)₃Cl are concluded. It is shown that the complementary spectroscopic analysis allows for the in-depth study of the environmental impact on historical objects and delivers indications for the appropriate strategy of the planned conservation activities. Moreover, from the data collected from the technologies applied in the past, origin, provenance and routing of the artifacts can be concluded.

Abstract: This article reviews laser-based analytical techniques, which find applications in the field of cultural heritage diagnostics, providing information about the chemical composition of materials, at the atomic or molecular level. Lasers are intense sources of light featuring unique characteristics that have been exploited in order to enhance the performance of certain spectroscopic techniques such as Raman or fluorescence spectroscopy, or even produce new schemes of analysis, including, for instance, non-linear or remote sensing spectroscopy as well as laser ablative sampling and excitation. In parallel, with advances in laser and detector technology, compact, mobile instrumentation is becoming available that permits broader use of such laser-based techniques for analysis of materials in works of art and archaeological findings.

Abstract: Recent observations of molecular positronium (Ps2) were based on a correlation between changes in positronium (Ps) lifetime spectra associated with the density of an incident positron beam and the population of a positronium (or positron) surface state. While the evidence for molecule formation is compelling it is nevertheless an indirect observation, and has not provided any information about the properties of Ps2 beyond its likely creation. Here we discuss the prospects for a direct observation via laser spectroscopy of a predicted 1S2P excited molecular state. Such a measurement would provide a direct and unambiguous signal of Ps2 formation and would also allow us to determine some properties of the molecule, namely the lifetime of the excited state and the 1S1S-1S2P energy interval.

Abstract: Archaeological ceramics Terra Sigillata manufactured in different production centres have been studied by “laser induced plasma spectroscopy” (LIPS). The aim of this work is to demonstrate the capability of LIPS for the classification of pottery shreds in function of their provenance. Characteristic emission spectra of different pottery groups were obtained and simple linear correlation methods were used for grouping samples. In addition, complementary scanning electron microscopy coupled with energy-dispersive X-ray spectrometry (SEM-EDX) analysis were performed to obtain morphological features and to confirm chemical results