Lukáš Voleský

TiO2 immobilised on biopolymer nanofibers for the removal of bisphenol A and diclofenac from water

Abstract Recently electrospinning has gained significant attention due to unique possibilities to produce novel natural nanofibers and fabrics with controllable pore structure. The present study focuses on the fabrication of electrospun fibres based on gum karaya (GK), a natural tree gum, with polyvinyl alcohol (PVA), and functionalization of the membrane with TiO2 nanoparticles with further methane plasma treatment. The GK/PVA/TiO2 membrane was analyzed with several techniques including: fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX), and water contact angle, in order to characterize its morphological and physicochemical properties. The GK/PVA/TiO2 membrane was further successfully used for the degradation (under UV irradiation) of bisphenol A and diclofenac from aqueous solution. It was also observed that the degradation kinetics of these compounds are faster in comparison to the UV treatment alone.

Impact Testing of H13 Tool Steel Processed with Use of Selective Laser Melting Technology

This paper deals with experimental determination of toughness, hardness and impact properties of AISI H13 (DIN 1.2344) tool steel which was manufactured using Selective Laser Melting (SLM) technology. The H13 is a chromium-based tool steel which is primarily used for hot working applications such as pressure casting moulds for automotive industry. Evaluation of toughness and impact properties are vital for reliable use of SLM-processed material, especially in the case of highly loaded structures. Mechanical tests were carried out on printed specimens, subjected to thermal treatment and proper data were evaluated. For better understanding of differences between conventionally produced and SLM-processed material, same mechanical tests were done even for hot-rolled H13 tool steel. SLM-printed material shows more brittle behaviour than conventionally made material. This is most probably caused by combination of H13 thermal properties and fast melting and solidification due to SLM processing.

Monitoring Changes in the Tribological Behaviour of CrCN Thin Layers with Different CH4/N2 Gas Ratios at Room and Elevated Temperatures

Totka Bakalova1, Nikolay Petkov2, Hristo Bahchedzhiev2, Pavel Kejzlar1, Lukáš Voleský1 1Faculty of Mechanical Engineering, Department of Material Science, Technical University of Liberec, Studentska 2, 461 17 Liberec, Czech Republic. E-mail: totka.bakalova@tul.cz, pavel.kejzlar@tul.cz, lukas.volesky@tul.cz 2Central Laboratory of Applied Physics, Bulgarian Academy of Sciences, 61, St. Peterburg Blvd. 4000 Plovdiv, Bulgaria. E-mail: petkovnik@gmail.com, hristo_bah@abv.bg

Steel Pile-Up Characterization by Atomic Force Microscopy

The Oliver–Pharr method has extensively been adopted for measuring hardness and Young’s modulus by indentation techniques. However, the method assumes that the contact periphery sinks in, which limits the applicability to the materials pile-up [1]. In this work, we characterize the pile-up (shape and height) in steel sheets with different mechanical properties and propose an improved methodology to calculate the real mechanical characteristics of steel sheets with significant pile-up. Pile-up correction of mechanical characteristics is based on ratio of pile-up height and contact depth. Pile-up height was measured by atomic force microscopy (AFM).

Possibilities of Usage of EBSD for Study of DC06 Steel Deformation

EBSD is an analytical technique, which uses diffraction of backscattered electrons on the sample’s crystal lattice to determine the crystal structure and orientation. Point-by-point mapping of crystal orientation and misorientation, calculation of sub-grain boundaries angles and statistical processing of grain data allow identifying and displaying elastically and plastically deformed zones, textures. Orientation mapping and pole-and inverse pole figures allow to identify preferred slip planes and texture, however misorientation reveals areas where higher stress concentration appears, dislocation arrays and internal defects.

Pre-treatment of polyethylene terephthalate by Grignard reagents for high quality polypyrrole coatings and for altering the hydrophobicity

Polypyrrole-coated polyethylene terephthalate is very attractive for various applications as electrically conductive fiber. This paper investigates the importance of polyester pre-treatment on the quality of the polypyrrole coating and its conductivity efficiency. The results showed nucleophilic pre-treatments by Grignard reagents resulting in the significantly higher surface quality and strongest adhesion of the polypyrrole coating to the polyester fibers compared to the other published methods. Moreover, several Grignard reagents were used for altering the hydrophobicity and morphology of the surface.

Selective Laser Melting Technology and Manufacturing of Accurate Thin Structures

This paper deals with finding the building parameters for manufacturing of fine structures with regard to their size precision and structural consistency. Practical use of these structures can be found in areas such as microelectronics, fine mechanics and automotive. Very fine structures with thickness lower than 0.3 mm are very hard to be manufactured due to the limitations of Selective Laser Melting (SLM) technology. These limitations lie in building parameters including mean size and shape of the powder particles, diameter of laser spot and scanning speed. Practical part of the work consists of printing the testing matrices from AlSi12 material with different building parameters for each element. Final products are then evaluated using scanning electron microscope in order to verify final size and structural properties of the specimens. Thanks to these tests, it was possible to find actual border of the technology for given type of powder. Structure with minimal thickness and sufficient strength was found to be 0.21 mm. Moreover, the method for finding parameters for manufacturing of fine structures is applicable for other types of materials.

Influence of Coating Process Parameters on the Mechanical and Tribological Properties of Thin Films

Titanium carbonitride (TiCN) thin films with differing C content were deposited by cathodic arc evaporation of pure Ti in a gas composite environment of N2 and C2H2. Scanning electron microscopy (SEM), scratch test, mechanical profilometer and “ball-on-disc” tribometer methods were used to characterize the surface, the coefficient of friction (CoF) of the TiCN thin films and the evaluated wear. An increase of the C2H2 fraction in the gas environment leads to a continuous increase in the deposition rate of the TiCN thin films, as well as an increase in the adhesion of the films to the substrate and the values of the CoF. Tribological test results (when tested against Si3N4 balls) show an increase in the friction coefficient of the TiCN from 0.08 to 0.32, with increasing carbon concentration in the film. The CoF decreases rapidly to 0.06 at a C content of 20.6 at.%, N 38.4 at.% and Ti 41.0 at.%.

The Impact of the Deposition Parameters on the Mechanical Properties of Thin Carbon Layers

The article describes the effect of the pressure in the chamber during the deposition of thin layers on the basic mechanical properties of thin layers based on carbon. Monitoring parameters are mainly nanohardness, coefficient of friction and adhesion between the layer and substrate. This parameters are observed using nanohardness tester and scratch tester. All observed layers had the same thickens of layers. Carbon layers generally have poor adhesion to the substrate. To improve the adhesion, is used the interlayer of titanium which is between the substrate and carbon layer. Carbon layers are mostly used for their very good sliding properties especially in cases where can not be used process fluids or where is necessary to reduce the friction between the two materials. The carbon layer can also be used in medicine (for their biocompatibility), for machine tools (for their hardness and abrasion resistance) or as barriers layers (for their high chemical resistance).

Biocompatibility of Surfaces of TiCN Thin Films

A series of titanium carbonitride (TiCN) films with differing C content were deposited by cathodic arc evaporation of pure Ti in a gas composite environment of N2 and C2H2. The increase of the C2H2 fraction in the gas environment leads to a continuous increase in the deposition rate of the TiCN thin films, as well as an increase in the adhesion of the films to the substrate. To evaluate the interaction of the material with the bacteria Escherichia coli CCM 3954 a method was used based on the ČSN EN ISO 56 0100 standard. The bacteria were inoculated in a liquid culture medium. It was observed that the monitored surfaces support the development of bacterial populations of E. coli depending on the type of TiCN thin films.