Research Interests:
VEGA of the Ministry of Education, Science, Research and Sport of the Slovak Republic for financial support of project No. 1/0532/19, and to the SlovakResearch and Development Agency, contract No. APVV-17-0169.The most common cause of... more
VEGA of the Ministry of Education, Science, Research and Sport of the Slovak Republic for financial support of project No. 1/0532/19, and to the SlovakResearch and Development Agency, contract No. APVV-17-0169.The most common cause of mechanical failure of brushed electric motors is the damage to the commutator and brushes but in harsh environments also mechanical damage to the bearings occurs. One of the main grounds of bearing damage is an unsuitable lubricant, various microparticles entering the lubricant on grinding poor quality bearing parts or inclusions related to the mechanical wear of the commutator. We examined the foreign substances or particles in the grease (petroleum jelly) of the bearing by Energy Dispersive X-ray Spectroscopy (EDS) of the components of a used commutator and of a new one. After disassembling the bearing, we analysed the cage, balls, grease and inner ring of the bearing. The obtained results indicate that the undesirable properties of the studied beari...
Research Interests:
Research Interests:
Research Interests:
Research Interests:
The subjects of Raman and X-ray analyses were the beads from two necklaces found in ancient graves from the 11 and 12 centuries at the Castle of Devín. One of the necklaces (Fig. 1), consisting of 23 beads, was found in tomb 12/1980.... more
The subjects of Raman and X-ray analyses were the beads from two necklaces found in ancient graves from the 11 and 12 centuries at the Castle of Devín. One of the necklaces (Fig. 1), consisting of 23 beads, was found in tomb 12/1980. Inside the grave, an incomplete skeleton of a woman was found, oriented in the west – east direction. The skull, shoulder blades and lower limbs were preserved in good condition. The grave contained a rich inventory: a silver ear-ring at the left side of the skull, a necklace between the shoulder blades and a ring on the right side at the height of the right hand. The other necklace, consisting of six stones (Fig. 2), was found in grave 145/1985 in which, similarly like in the first grave, a woman’s skeleton was discovered. The stones were found below the mandible. All beads are drilled through axially. Results from systematic excavations performed between 1980 and 1987 were evaluated by Plachá and Divileková [1].
Research Interests:
Research Interests:
Research Interests:
Abstract Synthesis of carbon nanotubes on zeolite and montmorillonite is presented. Prior to synthesis, minerals were enriched by particles of iron. Synthesis of carbon nanotubes was performed by hot filament chemical vapour deposition... more
Abstract Synthesis of carbon nanotubes on zeolite and montmorillonite is presented. Prior to synthesis, minerals were enriched by particles of iron. Synthesis of carbon nanotubes was performed by hot filament chemical vapour deposition using methane as a source of carbon. A high density of carbon nanotubes was observed in the whole volume of zeolite and montmorillonite. Iron containing particles catalysing the formation and growth of carbon nanotubes were visualized at the ends of nanotubes by field-emission scanning electron microscopy in a combined mode of secondary and backscattered electrons. 57Fe Mossbauer spectroscopy was employed to find the oxidation state of iron in Fe-montmorillonite before the synthesis of nanotubes and in the structures of nanocomposites after the synthesis. The metallic particles in the structures of nanocomposites at the ends of carbon nanotubes are characterized by Mossbauer spectroscopy mainly as ferromagnetic cementite (Fe3C).
Research Interests:
Research Interests:
Research Interests:
The worldwide boom of biochar and pyrogenic carbonaceous material application as a potential soil additive has brought about not only agricultural benefits such as enhanced crop yield, nutrients supply (P), and soil organic carbon... more
The worldwide boom of biochar and pyrogenic carbonaceous material application as a potential soil additive has brought about not only agricultural benefits such as enhanced crop yield, nutrients supply (P), and soil organic carbon increase, but also, on the other hand, environmental risk of organic (polycyclic aromatic hydrocarbons (PAHs)) and potentially toxic element (PTE) penetration into arable soils. Therefore, our study assessed pyrogenic carbonaceous materials (PCM) produced from the P-rich feedstocks—chicken manure (CM) and bone meal (BM)—as promising and safe alternatives for inorganic P fertilizers. Pyrogenic materials produced in the process of slow pyrolysis at residence time 2 h, 400 and 500 °C, were characterized by determination of pH, electrical conductivity (EC), elemental analysis of total C, H, N, S scanning electron microscopy (SEM), total content of P, selected potentially toxic elements (PTEs), and available forms of PTEs and P by diethylenetriaminepentaacetic ...
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
This article summarizes the main topics related to the issue of particle size analysis. It provides a discussion of the term ’particle’ and briefly describes the advantages and disadvantages of the most important particle size analysis... more
This article summarizes the main topics related to the issue of particle size analysis. It provides a discussion of the term ’particle’ and briefly describes the advantages and disadvantages of the most important particle size analysis methods.
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Iron oxide nanoparticles were synthesized in microwave plasma torch at atmospheric pressure from the mixture of Ar/H2 and Fe(CO)5 in gas feed. Such prepared nanoparticles were used for carbon nanotube growth. Nanoparticles and carbon... more
Iron oxide nanoparticles were synthesized in microwave plasma torch at atmospheric pressure from the mixture of Ar/H2 and Fe(CO)5 in gas feed. Such prepared nanoparticles were used for carbon nanotube growth. Nanoparticles and carbon nanotubes were analyzed by scanning and transmission electron microscopy, Raman spectroscopy and x-ray powder diffraction.
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Raman spectroscopy is employed to characterize thin diamond and diamond-like carbon films deposited by hot filament chemical vapour deposition (HFCVD). A method is proposed and experimentally verified for a contact-less measurement of the... more
Raman spectroscopy is employed to characterize thin diamond and diamond-like carbon films deposited by hot filament chemical vapour deposition (HFCVD). A method is proposed and experimentally verified for a contact-less measurement of the actual substrate temperature by Raman spectroscopy.
Research Interests:
Similarities between the processes that occur during sputtering of monocrystalline Si by reactive O2+ primary ions and the interface SiO2/monocrystalline Si by noble gas ions (e.g., by Ar+) have motivated us to utilize the semiempirical... more
Similarities between the processes that occur during sputtering of monocrystalline Si by reactive O2+ primary ions and the interface SiO2/monocrystalline Si by noble gas ions (e.g., by Ar+) have motivated us to utilize the semiempirical model of P. C. Zalm and C. J. Vriezema [Nucl. Instrum. Methods B 67, 495 (1992)], modified later by M. Petravić, B. G. Svensson, and J. S. Williams [Appl. Phys. Lett. 62, 278 (1993)] to calculate the decay length λb, as defined by J. B. Clegg [Surf. Interface Anal. 10, 322 (1987)], at the SiO2/Si interface. The measured and calculated results agree remarkably well. Inconsistency observed to be larger than 100% for glancing incidence angles confirms limitations of this model that were admitted already by its authors.
Research Interests:
We report on the influence of 60Co gamma-radiation upon the properties of Cr-GaAs diode structures. Auger depth profiling proved that while a low dose of radiation made the transition region wider, higher doses caused its narrowing.... more
We report on the influence of 60Co gamma-radiation upon the properties of Cr-GaAs diode structures. Auger depth profiling proved that while a low dose of radiation made the transition region wider, higher doses caused its narrowing. Radiation treatment affected the Schottky barrier height and ideality factor favourably.
Research Interests:
Research Interests:
HF CVD (hot filament chemical vapour deposition) reaktor je technologické zariadenie, v ktorom sa na rôznych substrátoch syntetizujú uhlíkové nanorúr ky. Reaktor pracuje na princípe pyrolýzy metánu a vodíka. Substrát je umiestnený na... more
HF CVD (hot filament chemical vapour deposition) reaktor je technologické zariadenie, v ktorom sa na rôznych substrátoch syntetizujú uhlíkové nanorúr ky. Reaktor pracuje na princípe pyrolýzy metánu a vodíka. Substrát je umiestnený na molybdénovom držiaku niekoľko milimetrov pod žeravenými (2200 °C) volfrámovými vláknami a jeho teplota počas syntézy je optimalizovaná cca na 600 °C. Merania a regulácie teploty rotačného držiaku v priebehu syntézy sa vykonáva teplomerom s bezdrôtovým optickým prenosom dát. Počas prevádzky zariadenia sa v yskytol závažný probl é m, a to nestabilné napájanie, čo viedlo ku kolísaniu teploty v reaktore. To je dôvod, prečo bolo navrhnuté iné riešenie za použitia impulzného napájacieho zdroja. Merací reťazec bol zjednodušený od stránením mobilných kontaktov a izolačných zosilňovačov, ktoré po prehriatí pracovali ne s p r ávne a skresľovali údaje o teplote. Výsledkom tejto práce je návrh a rekonštrukcia obvodov napájajúcich merač teploty v HF CVD reaktore.HF ...
Research Interests:
Nanocomposites based on CNTs + zeolite and CNTs + montmorillonite were prepared by in-situ hot filament CVD technology. Silicates – zeolite and montmorillonite – were used in the synthesis as substrates for immobilizing the catalytic... more
Nanocomposites based on CNTs + zeolite and CNTs + montmorillonite were prepared by in-situ hot filament CVD technology. Silicates – zeolite and montmorillonite – were used in the synthesis as substrates for immobilizing the catalytic particles of iron ions. We studied the mechanisms of CNTs formation and growth on the catalytic particles, the influence of the type of the catalytic support upon the morphology, quality and structure of the final nanocomposite, especially of carbon nanotube bridges.
Research Interests:
In this work we briefly summarized results of extensive experiments focused on hybridization natural inorganic substrates by carbon nanotubes (CNTs). The kernel of the experiments is catalytic synthesis of CNTs on/into natural inorganic... more
In this work we briefly summarized results of extensive experiments focused on hybridization natural inorganic substrates by carbon nanotubes (CNTs). The kernel of the experiments is catalytic synthesis of CNTs on/into natural inorganic substrates involving two technological processes. The first one is incorporation of catalytically active metals into the structure of the substrates while the second one is in-situ synthesis of CNTs in a HF CVD reactor. The main objective of the experiments is to contribute to understanding the mechanism of the rise of new hybrid materials. Selection of the natural inorganic substances includes a group of minerals with similar chemical compositions but with markedly different morphologies as well as materials containing iron - colloid scraps after raw mineral mining. The main methods of characterizing the hybrids are Raman spectroscopy along with scanning and transmission electron microscopies.
Research Interests:
HF CVD (hot filament chemical vapour deposition) reactor is a technological apparatus in which carbon nanotubes are synthesized on various substrates. The reactor operates on the principle of pyrolysis of methane and hydrogen. The... more
HF CVD (hot filament chemical vapour deposition) reactor is a technological apparatus in which carbon nanotubes are synthesized on various substrates. The reactor operates on the principle of pyrolysis of methane and hydrogen. The substrate is placed on a molybdenum holder, several millimetres below hot (2200 °C) tungsten filaments and its temperature during synthesis is optimized to approximately 600 °C. Measurement and control of the temperature of the rotating holder during synthesis are carried out by a temperatur e gauge with wireless optical data transfer. During operation of the facility a severe drawback was encountered, namely instable supplying resulting in temperature fluctuations in the reactor. This is why another solution has been designed utilizing a swit ched mode power supply. The measurement string has been simplified by removing mobile contacts and isolation amplifiers that behaved incorrectly – when they became overheated – and distorted the data on temperature. ...
Research Interests:
The weathering of commercially available crystal glasses (PbO and BaO containing glasses) was investigated under conditions, in which relative humidity was about 53 % or 97 % and pollutant i.e. CO 2 or SO 2 concentrations were as in... more
The weathering of commercially available crystal glasses (PbO and BaO containing glasses) was investigated under conditions, in which relative humidity was about 53 % or 97 % and pollutant i.e. CO 2 or SO 2 concentrations were as in normal atmosphere or increased by approx. 1 vol.%. The influence of cyclic temperature changes on weathering of the glass samples was also investigated. After exposure surfaces of these glass samples were studied by means of optical microscopy, scanning electron microscopy with energy dispersive X-ray microanalyses and Raman spectroscopy. During the above experimental conditions of weathering, solid products formed on the glass surfaces. Their chemical composition and structure significantly depend on the type of crystal glass as well as on environmental composition used during weathering tests. It was found that larger solids or crystalline aggregates usually consist of various sulphates and carbonates (e.g. CaCO 3 , K 2 CO 3 , BaSO 4 , and K 2 SO 4 ).
Research Interests:
We are grateful to the scientific grant agency of the Ministry of Education, Science, Research and Sport of the Slovak Republic for financial support of project VEGA No. 1/0947/16.
Research Interests:
We continue in reconstruction of the temperature meter with optical transmission of temperature reading in the HF CVD reactor. The parasitic inductance causes degradation of the transformer. The issue is solved by including a... more
We continue in reconstruction of the temperature meter with optical transmission of temperature reading in the HF CVD reactor. The parasitic inductance causes degradation of the transformer. The issue is solved by including a non-dissipative snubber that recuperates the energy from the parasitic inductance back to the power supply and allows faster demagnetization, thereby improving the transfer of energy through the transformer to its secondary winding.
Research Interests:
Research Interests:
ABSTRACT We examined surface enhanced Raman maps of blue writing inks received from commercially available refills and deposited on a rigid silver-nanocrystalline diamond-silicon heterostructure. The heterostructure constituted an active... more
ABSTRACT We examined surface enhanced Raman maps of blue writing inks received from commercially available refills and deposited on a rigid silver-nanocrystalline diamond-silicon heterostructure. The heterostructure constituted an active substrate providing a possibility to write directly on the surface and to record Raman maps. Based on rich data containing several thousands of spectra we discriminated between the inks in spite of slight spectral differences. Such discrimination would not be reliable by analyzing single spectra since a number of surface effects contribute to the evolution of Raman bands. We also successfully distinguished the order in which the cross lines of the inks were deposited on the substrate. Raman spectra could not be obtained by conventional Raman spectroscopy; this is why surface-enhanced Raman spectroscopy had to be employed.
Research Interests:
Research Interests:
The topic of the submitted article is the issue of measuring the temperature in a hot filament chemical vapour deposition (HF CVD) reactor by a purpose-built electronic circuit. The topical objective is to optimize the substrate... more
The topic of the submitted article is the issue of measuring the temperature in a hot filament chemical vapour deposition (HF CVD) reactor by a purpose-built electronic circuit. The topical objective is to optimize the substrate temperature, one of the key technological parameters in the synthesis of carbon nanotubes. Design and construction of a functional thermometer and its calibration and, hereby, improved accuracy of temperature measurement is the main outcome of this experimental work.
Research Interests:
The floating gate technology is widely used as a memory element in digital circuits and as a novel memory element in analogue technology. In this work we prepare the basis for on-chip implementation of a Cellular Neural Network (CNN). For... more
The floating gate technology is widely used as a memory element in digital circuits and as a novel memory element in analogue technology. In this work we prepare the basis for on-chip implementation of a Cellular Neural Network (CNN). For this purpose we investigate the features of a pseudo-floating gate transistor introduced in [1]. After simulating the structure by T-CAD
Research Interests: Engineering, Electronic Engineering, Computer Science, Information Technology, Microelectronics, and 13 moreDigital Circuits, Doping, Design Tool, Cellular Neural Networks, Chip, SPICE, Transistor, Cadence, Cellular Neural Network, Floating Gate, Network on a Chip, Threshold Voltage, and Nonvolatile memory
ABSTRACT Diamond layers have been deposited by hot filament CVD on sapphire and glass substrates pre-treated by diamond grain seeding and by AC biasing. The quality of diamond layers has been evaluated by Raman spectroscopy. Diamond... more
ABSTRACT Diamond layers have been deposited by hot filament CVD on sapphire and glass substrates pre-treated by diamond grain seeding and by AC biasing. The quality of diamond layers has been evaluated by Raman spectroscopy. Diamond layers of different quality have been obtained as confirmed by detecting various Raman bands attributable to different forms of carbon.
Research Interests:
Research Interests:
Research Interests: Engineering, Materials Science, Technology, Nanocrystalline Material, Thin Film, and 15 morePhysical sciences, Nitrogen, Phase transition, Optical Properties, Sputtering, Grain size, Crystallinity, Magnetron Sputtering, Oxide, Room Temperature, Thin film deposition, Reactive Sputtering, Argon, Indium, and Indium tin oxide
Research Interests:
... [7] Y.-M. Lin, KA Jenkins, A. Valdes-Garcia, JP Small, DB Farmer, and P. Avouris, Nano Lett. 9, 422 (2009). [8] JS Moon, D. Curtis, M. Hu, D. Wong, C. McGuire, PM Campbell, G. Jernigan, JL Tedesco, B. VanMill, R. Myers-Ward, C. Eddy,... more
... [7] Y.-M. Lin, KA Jenkins, A. Valdes-Garcia, JP Small, DB Farmer, and P. Avouris, Nano Lett. 9, 422 (2009). [8] JS Moon, D. Curtis, M. Hu, D. Wong, C. McGuire, PM Campbell, G. Jernigan, JL Tedesco, B. VanMill, R. Myers-Ward, C. Eddy, Jr., and DK Gaskill, IEEE Electron. Dev. ...
Research Interests:
Research Interests:
ABSTRACT We carry on with the topic described in our previous paper [Microelectron. J. 32 (2001) 955] in which Raman spectroscopy was employed to study synthetic sapphire. On a sample of α-Al2O3 which had served as a cryostat window and... more
ABSTRACT We carry on with the topic described in our previous paper [Microelectron. J. 32 (2001) 955] in which Raman spectroscopy was employed to study synthetic sapphire. On a sample of α-Al2O3 which had served as a cryostat window and had been exposed to liquid nitrogen temperature for 2 years we measured three distinct types of Raman spectra in the wave number range 100–800 cm−1. On the edge of the sample, a Raman spectrum was measured similar to that of the γ-phase of Al2O3. With intention to confirm or to rule out potential conversion of phases under the effect of low temperature we have performed photoluminescence and X-ray diffraction (XRD) studies of the sample. Photoluminescence analysis has revealed a qualitative difference of the edge of the sample as compared with other spots of the sapphire disc. XRD has confirmed high crystallographic quality of the sapphire sample under study, nevertheless, we have not managed to resolve crystallographic modifications.