K. Páleníková’s research while affiliated with Brno University of Technology and other places

The development of a remote laser-induced breakdown spectroscopy (LIBS) setup with an off-axis Newtonian collection optics, Galilean-based focusing telescope, and a 532 nm flattop laser beam source is presented. The device was tested at a 6 m distance on a slice of bone to simulate its possible use in the field, e.g., during archaeological excavations. It is shown that this setup is sufficiently sensitive to both major (P, Mg) and minor elements (Na, Zn, Sr). The measured quantities of Mg, Zn, and Sr correspond to the values obtained by reference laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) measurements within an approximately 20% range of uncertainty. A single point calibration was performed by use of a bone meal standard . The radial element distribution is almost invariable by use of LA-ICP-MS, whereas the LIBS measurement showed a strong dependence on the sample porosity. Based on these results, this remote LIBS setup with a relatively large ( 350 mm ) collecting mirror is capable of semiquantitative analysis at the level of units of mg kg − 1 .

It is well known that the collision of a high-velocity liquid mass with a solid generates short high-pressure transients which can cause serious damage to the surface and interior of the target material. To take advantage of this fact in the high-speed water jet technology, a special method of the generation of the high-speed pulsating water jet was developed recently and tested extensively under laboratory conditions. The method is based on the generation of acoustic waves by the action of the acoustic transducer on the pressure liquid and their transmission via pressure system to the nozzle. In this paper, results of investigation of the process of interaction of the pulsating jet and the aluminium sample are presented. Aluminium samples were exposed to pulsating jets generated under various operating conditions (such as operating pressure, stand-off distance and excitation amplitude of the acoustic generator). The effects of pulsating water jet impact on the aluminium surface were studied using methods of optical microscopy and image analysis. Topography of the surface created by the action of pulsating jet and characteristics of the surface were measured by the optical surface measuring system. Based on the analysis of obtained results, likely mechanism of the aluminium surface erosion and disintegration by the action of the pulsating water jet is discussed in the paper.

An acoustic signal was used for the internal standardization of laser-induced breakdown spectroscopy (LIBS) of a glazed wall tile. For the LIBS analyses, 1064 nm and 532 nm wavelengths of the Nd:YAG laser were utilized. The tile was depth profiled by a single-spot ablation from the glaze into the substrate. Some lines of major elements Si(I) 252.418, Si(I) 252.851, Al(I) 257.509, Cr(I) 295.368, Al(I) 309.271 nm and Ti(II) 334.904 nm were monitored. The decrease in the optical emissions during the ablation was successfully compensated for by normalization to the square power of the acoustic signal in the interval of 290-340 nm. This approach failed for the lines between 250-270 nm. The results were the same for both lasing wavelengths despite different irradiances. The acquired profiles are in good agreement with the reference X-ray fluorescence measurement. (C) 2008 Elsevier B.V. All rights reserved.

Cobalt-cemented hard metals present an example of samples with a complicated matrix consisting of components differing in chemical and physical properties and with extremely low volatility of all components. The purpose of this study was to compare particle formation of a set of real samples with similar matrices but different content of major components. The laser ablation process was studied using a Q-switched quintupled (213 nm) nanosecond Nd:YAG laser. Five samples of Co-cemented tungsten carbides, actually WC-TiC-(Ta,Nb)C-Co with a varied content of main constituents, were selected as representatives of a family of 15 miscellaneous tungsten carbide hard metal products. Physical and chemical properties vary over this specimen selection and therefore the effect on particle size formation and distribution was expected. The size distributions by number of ablated particles in different size ranges were measured using an optical aerosol spectrometer. The results proved the relationship between particle formation and sample composition. The structure of laser generated particles and the properties of ablation-craters were additionally studied by scanning electron microscopy (SEM). Spherical particles in the diameter range of 0.25-2 mu m and mu m-sized agglomerates composed of primary nano-particles were observed. The W and Co content in the aerosol particles was determined by energy dispersive X-ray spectroscopy (EDS). The volumes of ablation craters were measured by an optical profilometer. The laser ablation study of selected Co-cemented tungsten carbide hard metals indicates a similar total volume of formed particles with composition-dependent particle-size distributions.

We report on the development and implementation of analytical methodology for investigating elemental accumulation in different layers within plant leaves, with in-situ spatial resolution mapping, exploiting the technique of LIBS. The spectrochemical analysis of lead-doped leaf samples is demonstrated to develop a real time identification procedure in order to complement other analytical techniques not lending themselves for spatial resolution analysis. Our findings suggest that with elevated levels of Pb within the plants transportation and storage of some nutrition elements is changed.

Experimental study of the surface quality produced by abrasive waterjet (AWJ) on metallic materials has been performed. The surface roughness/waviness was quantitatively evaluated by using the contactless optical measurement. In order to characterize the cut surface qualities, a single-parameter criterion has been proposed. Based on root mean square (RMS) roughness evaluation of the worst cut surface zone, the dimensionless statistical parameter C can be calculated as a basic quantity for AWJ surface cut characterization. As it was approved, besides its dependency on depth of AWJ trace, the value of C-parameter for the specific material is noticeably related also to the traverse speed of the cutting head. Such a relationship can be potentially used for adjusting the cutting speed of the machining process. (C) 2007 Elsevier Ltd. All rights reserved.

The paper deals with results obtained by means of contactless optical shadow method and by commercial methods, namely by using an optical commercial profilometer MicroProf (FRT) and a contact profilometer HOMMEL TESTER T8000. The main emphasis is put on the analysis of results for defining the process of creation of a new surface generated by the stream of abrasive waterjet, including its geometric parameters and mechanisms of cutting tool-material interaction. New possibilities of the surface quality evaluation and optimizing the technological parameters selection of the cutting process appear.

In this study we report on the results of experiments devoted to the depth profile analysis of zinc-coated steel samples using the laser-induced breakdown spectroscopy (LIBS) technique. The dependence of zinc and iron emissions in three ablation atmospheres (air, argon, helium) was measured using the fundamental wavelength (1064 nm) of the Nd:YAG laser. The highest possible depth resolution was achieved by optimizing the experimental parameters, such as the delay time (which affects the tailing of the zinc emission signal), focusing conditions, energy delivered to the sample, and choice of buffer gases. Current research indicates that there is a constant need to optimize these parameters so that reliable depth-profiling analysis can be performed.

In this paper the influences of the technological conditions, i.e. the influences of the hydrogen flow rate and deposition time, on the values of the intrinsic mechanical stresses inside the diamond-like carbon (DLC) thin films prepared by plasma enhanced chemical vapor deposition onto silicon substrates are studied. These stresses are measured by two-beam interferometry and optical profilometry based on chromatic aberration through the measurements of deformations of the silicon substrates originating in consequence of the film stresses. It is shown that the influence of the deposition time (i.e. film thickness) on the film stress is relatively slight in contrast to the influence of the hydrogen flow rate on this quantity. It is namely shown that the film stresses are influenced by the hydrogen flow rate values in a pronounced way within the interval of interest, i.e. within the interval 1–7 sccm. Moreover, it is shown that the method of optical profilometry used can be competitive to the method of two-beam interferometry from the practical point of view.

Principle, parameters and selected applications of the optical profilometer MicroProf FRT (Fries Research & Technology GmbH) in determining surface quality are presented in this contribution.