Ľubomír Čaplovič

Arsenic sulfide nanoparticles prepared by milling: properties, free-volume characterization, and anti-cancer effects

In this paper, nanosuspensions of three arsenic sulfide (As4S4) compounds, commercial synthetic arsenic(II) sulfide, and natural realgar and pararealgar minerals were prepared. Nanosuspensions were obtained by ultrafine wet milling in a circulation mill. The zeta potential and particle size distribution were measured for stability estimation. Structural changes were studied using Raman and Fourier transform infrared spectroscopic methods and positron annihilation lifetime method. The morphology of the prepared nanoparticles was determined using scanning and transmission electron microscopy. The anticancer effects were tested using flow cytometry and western blotting analysis. The average particle size in the individual samples varied from 137 to 153xa0nm. The effects of milling were associated with the formation of arsenic sulfide crystalline nanoparticles and the fragmentation of the corresponding free-volume entities. Consequently, an increase in the arsenic dissolution was observed. The anti-cancer effects of the nanosuspensions were verified on the human cancer H460 cell line, in which case DNA damage and greater numbers of apoptotic cells were observed.

Disk Laser Weld Brazing of AW5083 Aluminum Alloy with Titanium Grade 2

Disk laser weld brazing of dissimilar metals was carried out. Aluminum alloy 5083 and commercially pure titanium Grade 2 with the thickness of 2.0xa0mm were used as experimental materials. Butt weld brazed joints were produced under different welding parameters. The 5087 aluminum alloy filler wire with a diameter of 1.2xa0mm was used for joining dissimilar metals. The elimination of weld metal cracking was attained by offsetting the laser beam. When the offset was 0xa0mm, the intermixing of both metals was too high, thus producing higher amount of intermetallic compounds (IMCs). Higher amount of IMCs resulted in poorer mechanical properties of produced joints. Grain refinement in the fusion zone occurred especially due to the high cooling rates during laser beam joining. Reactions at the interface varied in the dependence of its location. Continuous thin IMC layer was observed directly at the titanium–weld metal interface. Microhardness of an IMC island in the weld metal reached up to 452.2 HV0.1. The XRD analysis confirmed the presence of tetragonal Al3Ti intermetallic compound. The highest tensile strength was recorded in the case when the laser beam offset of 300xa0μm from the joint centerline toward aluminum alloy was utilized.

Cryogenic Rotary Ultrasonic Machining of Titanium Alloys

Abstract Titanium alloys are utilized especially in applications that require a good combination of high strength, low mass and good corrosion resistance in aggressive environments. However, mechanical properties prejudge titanium alloys to hard machinability. Machining of titanium alloys is usually accompanied by cooling with liquids or gasses. One of the most effective cooling approaches is cooling by liquid nitrogen. Liquid nitrogen decreases temperature of tool, but also increases strength, hardness and brittleness of workpiece. One of the most suitable machining methods to machine hard and brittle materials is ultrasonic machining. In this article, rotary ultrasonic machining of titanium alloys under cryogenic conditions is analyzed.

IBA characterization of Ti-Si-C-N nanocomposite coatings

One of the new developing technologies for increasing hardness, wear resistance and lifetime of cutting tools are the Ti-Si-C-N nanocomposite coatings deposited by a LARC® method. To investigate the effect of the various coating deposition parameters on the coating properties, the Ti-Si-C-N layers were deposited on Ni2Cu backings. The nondestructive Ion Beam Analysis (IBA) was used for determination of elemental composition depth profiles of the prepared layers, so that samples can be further mechanically tested. By application of Rutherford Backscattering Spectrometry (RBS), Proton Induced X-ray Emission (PIXE), Elastic Recoil Detection Analysis (ERDA) and Nuclear Reaction Analysis (NRA) the concentration of Ti, Si, C, N and H was determined. The depth profiles of the individual elements in the surface area and in the layer interface with the backing material were also determined.One of the new developing technologies for increasing hardness, wear resistance and lifetime of cutting tools are the Ti-Si-C-N nanocomposite coatings deposited by a LARC® method. To investigate the effect of the various coating deposition parameters on the coating properties, the Ti-Si-C-N layers were deposited on Ni2Cu backings. The nondestructive Ion Beam Analysis (IBA) was used for determination of elemental composition depth profiles of the prepared layers, so that samples can be further mechanically tested. By application of Rutherford Backscattering Spectrometry (RBS), Proton Induced X-ray Emission (PIXE), Elastic Recoil Detection Analysis (ERDA) and Nuclear Reaction Analysis (NRA) the concentration of Ti, Si, C, N and H was determined. The depth profiles of the individual elements in the surface area and in the layer interface with the backing material were also determined.

Effect of Substrate Bias and Coating Thickness on the Properties of nc-AlCrN/a-Si x N y Hard Coating and Determination of Cutting Parameters

Nitride hard coatings Al25.5Cr21Si3.5N were deposited on WC-Co substrates with a different thickness and a negative substrate bias voltage by the LAteral Rotating Cathodes Arc technology. The nanoindentation tests were performed for analysis of AlCrSiN coatings in order to determine the most promising combination of parameters for subsequent machining. On the basis of results of nanohardness measurement and Ratio H/E*, which represents the resistance to plastic deformation and cracking, deposition conditions were selected for coating of turning cemented carbide inserts. For the evaluation of coating adhesion to substrate, Mercedes adhesion test was used. Chip forming tests and long-term tool life tests were performed for determination of cutting parameters (cutting speed, feed rate and depth of cut) for AlCrSiN coated cemented carbide inserts when machining austenitic stainless steel material.

Influence of Deposition Parameters on the Properties of Nanocomposite Coatings Prepared by Cathodic Arc Evaporation

The article deals with the influence of different deposition parameters on the selected properties of AlCrN/Si3N4 nanocomposite coatings. Bias voltage, cathodes currents and working gas pressure were changed during the deposition process. All coatings were deposited using Lateral Rotating Cathodes (LARC®) process that belongs to the group of cathodic arc evaporation PVD technologies. In comparison with the typical cathodic arc evaporation process which usually uses planar targets the LARC® process utilizes rotational cathodes that are positioned close to each other. Nanohardness, Youngs modulus, thickness and residual stresses were determinated in order to evaluate the influence of deposition parameters on these coatings properties

Nanohardness of DC Magnetron Sputtered W – C Coatings as a Function of Composition and Residual Stresses

The effects of residual stresses in thin W-C based coatings were investigated with the aim to find their influence on nanohardness and indentation modulus. Ten samples of W-C based coatings were deposited on microslide glass substrates using DC magnetron sputtering at the identical deposition parameters. Their thickness was in the range from 500 to 600 nm. The residual stresses in the coatings varied from 1.5 GPa up to 4.4 GPa. Increase of residual stress caused linear increase of HIT from 16 to 19.5 GPa. This increase was only the result of the compressive stresses. EIT of the studied coatings was not sensitive to residual stresses and corresponded to 185 GPa ± 15 GPa.

COMPARISON OF OXIDATION RESISTANCE OF TiAlN MONOLAYER COATING AND ITS nACo3 NANOSTRUCTURED VERSION

Abstract The contribution deals with comparison of oxidation resistance of classical TiAlN monolayer coating and its advanced high hard nanostructured and multilayered nACo3 version at elevated temperatures. Both coatings were deposited onto AISI M36 high speed steel using unique LAteral Rotating Cathodes process (LARC®). “In - situ” X-Ray diffraction analysis was employed for determination of the beginning of oxides creation and phase detection at different heating temperatures. Scanning electron microscopy fitted with EDX analysis was used for observation of fracture areas and measurements of coatings and oxide layers thicknesses as well. Determination of chemical composition of coatings surfaces and elemental linescans through the coatings and oxide layers were performed using EDX analysis. All measurements of these coatings were carried out not only before but also after the thermal annealing.

Evaluation of the Structure of Industrial Wastes

The aim of this paper is to evaluate the structure of wastes from non-ferrous metals. Wastes from the production of metals were selected namely waste from the production of aluminum - red mud and the waste from the production of nickel - black nickel mud. Morphology of samples was documented by scanning electron microscope, phase analysis using diffraction techniques and the content of elements was determined by EDX analysis. The influence of pretreatment of these wastes on the structure was also investigated.

Carbon Nanostructures Grown on Fe-Cr-Al Alloy

Carbon Nanostructures Grown on Fe-Cr-Al Alloy The morphology and nanostructure of carbon nanotubes (CNTs), synthesized directly on Fe-Cr-Al-based alloy substrate using an alcohol catalytic chemical vapour deposition method (ACCVD), were examined by transmission electron microscopy (TEM). The grown CNTs were entangled with chain-like, bamboo-like, and necklace-like morphologies. The CNT morphology was affected by the elemental composition of catalysts and local instability of deposition process. Straight and bended CNTs with bamboo-like nanostructure grew mainly on γ-Fe and Fe3C particles. The synthesis of necklace-like nanostructures was influenced by silicon oxide, and growth of chain-like nanostructures was supported by a catalysts consisting of Fe, Si, oxygen and trace of Cr. Most of nanotubes grew according to base growth mechanism.