Pavel Kejzlar

In-situ development of highly photocatalytic multifunctional nanocomposites by ultrasonic acoustic method

Cotton-titania nanocomposites with multifunctional properties were synthesized through ultrasonic acoustic method (UAM). Ultrasonic irradiations were used as a potential tool to develop cotton-titania (CT) nanocomposites at low temperature in the presence of titanium tetrachloride and isopropanol. The synthesized samples were characterized by XRD, SEM, EDX and ICP-OES methods. Functional properties i.e. Ultraviolet protection factor (UPF), self-cleaning, washing durability, antimicrobial and tensile strength of the CT nanocomposites were evaluated by different methods. Central composite design and response surface methodology were employed to evaluate the effects of selected variables on responses. The results confirm the simultaneous formation and incorporation of anatase TiO2 with average crystallite size of 4nm on cotton fabric with excellent photocatalytic properties. The sustained self-cleaning efficiency of CT nanocomposites even after 30 home launderings indicates their excellent washing durability. Significant effects were obtained during statistical analysis for selected variables on the formation and incorporation of TiO2 nanoparticles (NPs) on cotton and photocatalytic properties of the CT nanocomposites.

Magnetic Poly(N-isopropylacrylamide) Nanocomposites: Effect of Preparation Method on Antibacterial Properties

The most challenging task in the preparation of magnetic poly(N-isopropylacrylamide) (Fe3O4-PNIPAAm) nanocomposites for bio-applications is to maximise their reactivity and stability. Emulsion polymerisation, in situ precipitation and physical addition were used to produce Fe3O4-PNIPAAm-1, Fe3O4-PNIPAAm-2 and Fe3O4-PNIPAAm-3, respectively. Their properties were characterised using scanning electron microscopy (morphology), zeta-potential (surface charge), thermogravimetric analysis (stability), vibrating sample magnetometry (magnetisation) and dynamic light scattering. Moreover, we investigated the antibacterial effect of each nanocomposite against Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus. Both Fe3O4-PNIPAAm-1 and Fe3O4-PNIPAAm-2 nanocomposites displayed high thermal stability, zeta potential and magnetisation values, suggesting stable colloidal systems. Overall, the presence of Fe3O4-PNIPAAm nanocomposites, even at lower concentrations, caused significant damage to both E. coli and S. aureus DNA and led to a decrease in cell viability. Fe3O4-PNIPAAm-1 displayed a stronger antimicrobial effect against both bacterial strains than Fe3O4-PNIPAAm-2 and Fe3O4-PNIPAAm-3. Staphylococcus aureus was more sensitive than E. coli to all three magnetic PNIPAAm nanocomposites.

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.

Different effects of nano-scale and micro-scale zero-valent iron particles on planktonic microorganisms from natural reservoir water

While nano-scale and micro-scale zero-valent iron (nZVI and mZVI) particles show high potential for remediation of polluted soil aquifers and elimination of cyanobacterial blooms, this has required their release into the environment. This study compares the impact of 100 mg L−1 of nZVI and mZVI on natural planktonic microorganisms from a reservoir, incubated in 1.5 L batches over 21 days. In addition to counting cyanobacterial and algal cell numbers, bacterial community structure was assessed using Ion Torrent sequencing and the number of cultivable bacteria determined using standard cultivation methods. Surprisingly, while mZVI had no significant effect on algal cell number, cyanobacteria numbers increased slightly after 14 days (P < 0.05). Algae were only marginally affected by nZVI after seven days (P < 0.05), while cyanobacteria numbers remained unaffected after 21 days. Total species richness and less common bacteria increased significantly when treated with mZVI (compared to nZVI). The abundance of Limnohabitans (Betaproteobacteria), Roseiflexus (Chloroflexi), hgcl_clade (Actinobacteria) and Comamonadaceae_unclassified (Betaproteobacteria) increased under nZVI treatment, while mZVI enhanced Opitutae_vadinHA64 (Verrucomicrobia) and the OPB35_soil_group (Verrucomicrobia). Interestingly, the number of cultivable bacteria increased significantly after three days in water with nZVI, and further still after seven days. nZVI shaped bacterial community both directly, through release of Fe(II)/Fe(III), and indirectly, through rapid oxygen consumption and establishment of reductive conditions. The strong physico-chemical changes caused by nZVI proved temporary; hence, it can be assumed that, under natural conditions in resilient reservoirs or lakes, microbial plankton would recover within days or weeks.

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

Cathodic Arc Deposition of TiCN Coatings - Influence of the C2H2/N2 Ratio on the Structure and Coating Properties

TiCN thin coatings with various different carbon contents were deposited using cathode arc evaporation of pure titanium in a mixture of N2 and C2H2gasses at a constant pressure of 1.5 Pa. The analyses show a transition from a stoichiometric to a non-stoichiometric coating structure with an increasing C2H2 content. Moreover, the increase in the acetylene in the gas mixture leads to a decrease in the crystal phase from pure polycrystalline to pure amorphous. Nanohardness changes from 30.4 to 4.4 GPa and the cohesive failure of the coatings is in the range of 61 - 72 N. The tribology is estimated by the Ball-on-Disc method and an Si3N4 ball as the counterpart. The measured coefficient of friction is in the range of 0.2 - 0.56.

The Analysis of Causes of Pressure Bottles Heads Destruction

The research deals with the cause of destruction of pressure bottles heads during ordinary operation. The scanning electron microscope (SEM) equipped with an energy dispersive detector (EDX) for local chemical analysis was used for material investigation. The analysis revealed selected oxidation penetrating deep into the material causing the loss of cohesion of phase boundaries leading to brittle fracture.

Fractographical Analysis of Screws Used for Truck Cab Holding

The research deals with determination of the breaking cause of the screws used to attach the truck cabins. Scanning electron and light optical microscopy were used for engineering investigation of the fracture cause. Fractographical and structural analysis revealed fatigue mechanism of the screw fracture with morphology corresponding to the combination of tensile and bending stresses. Based on the acquired results a structural adjustment was recommended to the customer.

The Use of Metallography for Examination of Causes of Surface Defects on Visual Parts

Many of currently manufactured components intended for automotive, must not only meet the requirements on functionality, but also considerable demands on the visual appearance. Parts are subjected to thorough inspection and suppliers are forced to deal with causes of a very slight visual defects. When examining the defects, it is necessary to use a whole range of advanced analytical methods and procedures previously used only for identification of the physical and chemical properties and structure of the material. This paper deals with several examples which have been solved. It focuses especially on the use of demanding metallographic sample preparation from components with surface defects, examining the defects on the cross-section using mainly microscopic techniques and determining the causes of their generation. These results then serve as a basis for modification of the technology and thus they are the tool for significant reduction of amount of NOK parts.

Application of Metallography in Solving of Manufacturing Defects of Galvanically Plated Polymers

Galvanic plating of polymeric structural parts is widely used in many industrial branches, e.g. in automotive. Minor errors in their manufacturing process are responsible for presence of surface defects. These defects, especially in the case of visual and decorative parts, are unacceptable. This paper demonstrates the usage of metallography to reveal and solve common problems in industrial production. Different types of galvanic plating defects on injection molded parts made of ABS, PC/ABS and PA manifest themselves by different ways.