Jiri Martan

University of West Bohemia · New Technologies - Research Centre

Pure W and W-Cr-Hf alloy which are prospective materials for nuclear fusion reactors, such as DEMO, were irradiated at room temperature with 5 MeV Au²⁺ ions with fluences between 4 × 10¹⁴ and 1.3 × 10¹⁶ ions.cm⁻² to generate various levels of lattice damage from about units up to tens of dpa. The distinct character of radiation damage accumulation,...

A unique combination of the ultrashort high-energy pulsed laser system with exceptional beam quality and a novel Diffractive Optical Element (DOE) enables simultaneous production of 2601 spots organized in the square-shaped 1 × 1 mm matrix in less than 0.01 ms. By adjusting the laser and processing parameters each spot can contain Laser Induced Per...

The electrolyte filling process of battery cells is one of the time-critical bottlenecks in cell production. Wetting is of particular importance here, since only completely wetted electrode sections are working. In order to accelerate and facilitate this process, the authors of this study developed a method to significantly increase the wettability...

Novel types of titanium oxidic surfaces were fabricated by a shifted Laser Surface Texturing of titanium in air, producing porous micro/nanostructured topography, and by a subsequent Nd:YAG laser-induced reactive deposition of Ti5Si3 titanium silicide in vacuum, coating this topography with scattered sub-micron particles of silicon monoxide. Both s...

Ultrashort pulse laser micromachining is affected by the heat accumulation resulting from the residual heat from previous laser pulses on the sample surface. Up to now, most of the works analysed the accumulation by numerical modelling. The present work focussed on development and application for the first time of a measurement system of heat accum...

A shifted laser surface texturing method (sLST) was developed for the improvement of the production speed of functional surface textures to enable their industrial applicability. This paper compares the shifted method to classic methods using a practical texturing example, with a focus on delivering the highest processing speed. The accuracy of the...

Plasma sprayed W-based coatings have the potential application as joining interlayers for the plasma-facing components of future fusion reactors. Particularly in the form of tungsten-steel functionally graded materials (FGMs), they would reduce the stress concentration between the W-based plasma-facing armor and steel-based construction. For mechan...

Laser surface texturing is a promising technology for future wide applications of functional surfaces with specific properties like hydrophobic, antibacterial, adhesive, self-cleaning, anticorrosion, light absorbing, low friction, etc. Great advancements have been made in this field in the last few years, but in most cases, it takes from minutes up...

A new measurement system was developed for time-resolved surface temperature measurement in nanosecond time scale. A study of surface temperatures reached by different parameters of laser marking and their correlation with resulting microstructure, phase composition and corrosion tests performed on marked samples is presented. The marking was done...

Laser scanning speed and high precision are two opposite parameters for effective laser surface texturing (LST) [1, 2]. Application of burst mode helps to increase the processing effectivity and speed, but precision control of laser pulses arriving becomes difficult task for micro-texturing. In this work, one possible solution for this dilemma is p...

In this paper, a new measurement system and a new approach in calculation for infrared (IR) radiation investigation in quasi-simultaneous transmission laser welding of plastics are presented. The measurement system is based on a MW/SWIR (medium-wave/short-wave IR) camera and optical filters narrowing the spectral region to SWIR. The measured signal...

Coatings deposited on a material surface are effective way of changing its surface properties. For increasing or decreasing radiation heat transfer, coatings with high or low emissivity are used. Measurement of spectral emissivity is a fundamental step to effective use of coatings for this application. Up to now the measurement methods are focused...

This article presents a new digital method, called Stamp method, for elimination of undesired noise data from a periodic IR signal. The Stamp method is a useful tool for statistical analysis of changes which appear in a noised input signal. One stamp is a statistical image of several consequence periods from a raw input signal. The Stamp method is...

Laser Surface Texturing (LST) is one of the perspective ways for creating of functional surfaces: low frictional, hydrophobic or hydrophilic, photonic structures, thermal spray substrates and so on. There are several methods for laser surface texturing of large areas, but they have some physical limitations, such as heat accumulation, plasma shield...

The paper deals with uncertainty analyses of the new laboratory method for the measurement of spectral emissivity of high-temperature coatings. These coatings are intended to increase heat transfer in various industrial applications. The experimental set-up of the method is shortly introduced. The method is innovative in the application of scanning...

The laser surface texturing (LST) technologies, based on creation of micro-pattern with pre-defined geometry can positively influence both the friction and wear of tribo-elements. In practice, the integration of LST technology is often limited due to its slowness. The new method, so called shifted laser surface texturing (sLST) with increased proce...

Příspěvek se zabývá možnostmi využití infračervené termografie pro kontrolu, dia-gnostiku a řízení procesu v technologiích laserového svařování. V příspěvku je představen proces laserového svařování a metody inspekce pomocí infračervené termografie. Mož-nosti využití infračervené termografie jsou demonstrovány na příkladech termovizní kontro-ly při...

Laser scanning processing of nickel-based superalloy AM1 surfaces by ultra-short pulses (10 ps) is introduced as a cleaning and deoxidation postprocess. The laser cleaning is investigated with two-directional surface scanning by a laser beam with several frequencies of pulse generation. The EDX elemental analyses of the laser cleaned AM1 surfaces w...

Acknowledgements The result was developed within the CENTEM project, reg. no. CZ.1.05/2.1.00/03.0088, co-funded by the ERDF as part of the Ministry of Education, Youth and Sports of the Czech Republic OP RDI program and in the follow-up sustainability stage, supported through CENTEM PLUS (LO1402) by financial means from the Ministry of Education, Y...

Abstract A new single-side flash method for thermal diffusivity determination is presented. The method is based on a laser-flash pulse excitation and infrared thermography non-contact temperature measurement of a thermal response of a studied object. Using this method, the both excitation and measurement at one side (front side) of the studied obje...

Laser surface texturing (LST) is one of the methods for obtaining surfaces with specific properties. In this paper the influence of initial surface state of sliding bearing steel on laser texturing of this material was studied. Initial surface with roughness R_a = 0.13 µm was used for providing shifted laser surface texturing (sLST) by ultrashort l...

A new non-contact laser heating method for the normal spectral emissivity measurements of high-temperature coatings is introduced. The method utilizes laser source in combination with scanning optics. General and specific requirements for the method development are discussed. Works on the development of the optimal heating strategy to ensure homoge...

We study the thermal, mechanical and electrical properties of B4C, BCN, ZrBC and ZrBCN ceramics prepared in the form of thin films by magnetron sputtering. We focus on the effect of Zr x (B4C)1-x sputter target composition, the N2+Ar discharge gas mixture composition, the deposition temperature and the annealing temperature after the deposition. Th...

Computer model of temperature distribution in the sample in high temperature spectral emissivity measurement method is introduced. Sensitivity analysis is performed using computer model to determine the effect of various measurement method parameters on the sample temperatures. The effects of measured and reference coating thicknesses, measured coa...

Measurement of thermal conductivity and volumetric specific heat of optically transparent thin films presents a challenge for optical-based measurement methods like pulsed photothermal radiometry. We present two approaches: (i) addition of an opaque optical layer to the surface and (ii) approximate correction of the mathematical model to incorporat...

Optical properties of materials have significant effect on laser processes. Laser beam interacts with a material as light and absorptivity of the material to this light determines the amount of heat that is coupled to the material. The other light is lost. Emissivity determines cooling effects during and after the process by radiation heat transfer...

A new experimental device for normal spectral emissivity measurements of coatings in the infrared spectral range from 1.38 μm to 26 μm and in the temperature range from 550 K to 1250 K is presented. A Fourier transform infrared spectrometer (FTIR) is used for the detection of sample and blackbody spectral radiation. Sample heating is achieved by a...

Two techniques of photothermal radiometry (PTR) in front face configuration were used to determine the thermal conductivity of thin nanocrystalline films. The first technique relies on using modulated laser beam as a heating source. The second is based on pulsed laser heating where the pulse can be assimilated to a Dirac function. In the two measur...

Cutting tools with coated inserts are widely used in high-speed cutting and in the cutting of hard-to-machine materials. The thermal properties of the coatings (or thin films) have a major impact on the cutting process and tool life. As there is a lack of data for high temperatures, we are presenting an experimental study of thermal conductivity an...

A study of temperature of a magnetron target was performed for the case of high power pulsed magnetron sputtering (HPPMS) of titanium thin films, using a water-cooled target and a hot target. Temporal evolution and spatial distribution of surface temperature were investigated. Temperature measurements were made by an infrared camera for target diam...

Infrared (IR) radiometry and time resolved reflectivity (TRR) methods can be used for investigation of laser pulse effects on materials in nanosecond time scale. The methods in combination are capable to quantify object temperature and detect phase transformations in the solid state, melting and plasma formation from vapour. Measurements with diffe...

A new arrangement of two-detector pulsed photothermal radiometry measurement system has been developed enabling temperature dependence measurement of thermal properties of thin films up to high temperatures. Only a few methods are available in this temperature range for thin films’ thermal properties investigation, but there is a need for their kno...

Nanosecond laser melting of silicon was investigated by infrared (IR) radiometry and time resolved reflectivity (TRR) methods. IR radiometry revealed interesting signal evolutions and their qualitative changes during different stages of the melting process. The observed signals represent melting front propagation, liquid phase overheating, and melt...

An optical system for fast IR radiometry designed for investigations of thin film thermal properties and pulsed laser melting was analyzed in this work. A methodology for determination of the view factor from calibration measurements was developed. The view factor (0.0255) of the optical system containing two paraboloid mirrors was determined exper...

Pulsed photothermal radiometry, a method developed in previous work for thin film thermal effusivity measurements, is now further developed for the determination of thin film thermal conductivity and volumetric specific heat. The present setup consists of a nanosecond laser source and two infrared IR detectors for temperature response measurement....

Interaction of nanosecond pulsed lasers with material was studied from thermal point of view using experimental techniques and theoretical approach of dimensional analysis. Experimental data of laser heating, melting and plasma formation on metallic samples and silicon, presented mainly in previous publication and partly in this paper, were used fo...

An optical system for fast IR radiometry designed for investigations of thin film thermal properties and pulsed laser melting was analyzed in this work. A methodology for determination of the view factor from calibration measurements was developed. The view factor (0.0255) of the optical system containing two paraboloid mirrors was determined exper...

Experimental system for nanosecond laser melting investigation was developed containing three independent noncontact methods: infrared radiometry, time-resolved reflectivity of He–Ne laser and sample surface reflected KrF heating laser pulse. The system was applied to the investigation of laser melting of Cu, Mo, Ni, Si, Sn, Ti, steel ČSN 15330 and...

Thermal conductivity and thermal interface resistance of tungsten thin films were investigated by means of pulsed photothermal radiometry. The experimental system based on a nanosecond pulsed laser and a high-speed IR photodetector is presented. Calibration of the IR detector is described. The thermal properties of the samples are identified by com...

A high number of papers were published on the simulation of laser/surface interaction at the level of nanosecond scale. Several assumptions on thermal properties data, laser spot homogeneity, were assumed for describing as well as possible the boundary conditions, the mathematical writing and finally the numerical or the analytical results. A few t...

An experimental system for investigation of thermal properties of thin films and material surfaces especially with high thermal conductivity was developed. This system is based on photothermal method using pulsed laser with nanosecond pulse duration in the UV range, and a high speed IR photodetector.Calibration of the experimental system, enabling...

Thermal barriers (TB) protect material against high temperatures and thermal shocks. The effect of various TB - substrate structures to their dynamic behaviour under the thermal shock is studied. The TB parameters such as number of individual layers, their thicknesses and porosities and thermal and mechanical properties of their materials have been...