Michał J. Woźniak

Arc Plasma Synthesis of (Fe-Nd-B) - Containing Carbon Encapsulates

The formation of novel carbon nanostructures containing Fe-Nd-B nanocrystallites is reported. Tests were performed in a DC arc plasma reactor under He atmosphere using (Fe-Nd-B)- filled anodes. The influence of the operational parameters pressure and anode composition on the product morphology was studied. The products were analyzed by HR TEM, MFM and magnetic measurements. Emission spectroscopy was performed to determine the temperature and C2 radical distribution in the arc.

Microstructure and nanomechanical properties of single stalks from diatom Didymosphenia geminata and their change due to adsorption of selected metal ions

We present topographical and nanomechanical characterization of single Didymosphenia geminata stalk. We compared the samples before and after adsorption of metal ions from freshwater samples. Transmission electron microscopy studies of single stalk cross‐sections have shown three distinct layers and an additional thin extra coat on the external layer (called “EL”). Using scanning electron microscopy and atomic force microscopy (AFM), we found that topography of single stalks after ionic adsorption differed significantly from topography of pristine stalks. AFM nanoindentation studies in ambient conditions yielded elastic moduli of 214 ± 170 MPa for pristine stalks and 294 ± 108 MPa for stalks after ionic adsorption. Statistical tests showed that those results were significantly different. We conducted only preliminary comparisons between ionic adsorption of several stalks in air and in water. While the stalks with ions were on average stiffer than the pristine stalks in air, they became more compliant than the pristine stalks in water. We also heated the stalks and detected EL softening at 50°C ± 15°C. AFM nanoindentation in air on the softened samples yielded elastic moduli of 26 ± 9 MPa for pristine samples and 43 ± 22 MPa for stalks with absorbed metal ions. Substantial decrease of the EL elastic moduli after heating was expected. Significantly different elastic moduli for the samples after ionic adsorption in both cases (i.e., for heated and nonheated samples), as well as behavior of the stalks immersed in water, point to permanent structural EL changes due to ions.

[Dental plaque as a biofilm - a risk in oral cavity and methods to prevent].

Bacteria living constantly in the oral cavity are in the form of a biofilm. The biofilm formed on a solid base such as the enamel of the teeth, fillings, restorations, orthodontic appliances or obturators is dental plaque. Disturbance of homeostasis of biofilm, excessive growth or increase in the number of acid-forming bacteria leads to the development of the most common diseases of the oral cavity, i.e. dental caries and periodontal disease. The presence of bacterial biofilm on the walls of the root canal or at the top of the root on an outer wall leads to complications and failure in endodontic treatment. The aim of the study was to present the latest information on the occurrence, development and the role of biofilm in the etiopathogenesis of oral diseases and its control. Based on the literature analyzed, it can be concluded that the biofilm, due to its complex structure and numerous mechanisms of bacteria adaptation, is an effective barrier against the traditional agents with antibacterial properties. There are now great hopes for nanotechnology as an innovative method for obtaining new structures of nanometric size and different properties than source materials. The use of antibacterial properties of nano-silver used in dentistry significantly reduces the metabolic activity and the number of colony forming bacteria and lactic acid production in the biofilm.

Catalytic Decomposition of Ethylene on Nanocrystalline Cobalt

Nanocrystalline cobalt was carburised with ethylene in the range 340– 500°C to obtain Co(C) nanocapsules. The carbon deposit was reduced by a flow of hydrogen in the range 500– 560°C. The reduction kinetics were studied using thermogravimetry, described by the equation: α = Α[1-exp(-kt)n]. The apparent activation energy of the reduction process of the carbon deposit was determined. After carburisation and reduction the samples were examined by XRD and HRTEM.

Fabrication, multi-scale characterization and in-vitro evaluation of porous hybrid bioactive glass polymer-coated scaffolds for bone tissue engineering

Bioactive glass-based scaffolds are commonly used in bone tissue engineering due to their biocompatibility, mechanical strength and adequate porous structure. However, their hydrophobicity and brittleness limits their practical application. In this study, to improve nanomechanical properties of such scaffolds, pure bioactive hybrid glass and two bioactive hybrid glass-polymer coated composites were fabricated. A complementary micro and nanoscale characterization techniques (SEM, AFM, μCT, FTIR, compressive test, goniometer) were implemented for detailed description of architecture and physicochemical properties of hybrid bioactive glass-based scaffolds with emphasis on nano-mechanics. The final step was in-vitro evaluation of three dimensional macroporous structures. Our findings show that after polymer addition, architecture, topography and surface properties of the scaffolds were changed and promoted favoured behaviour of the cells.

Structural and Magnetic Characterization of High Performance Die-Upset Forged Nd-Fe-B Magnets

Abstract The processing method of anisotropic Nd-Fe-B magnets, based on rapid solidification of a molten alloy, followed by hot pressing and die-upset forging is currently well established and commonly used for the processing of high performance magnets. In this method uniaxial stress, created in an isotropic, polycrystalline alloy, leads to texture formation with the crystallographic c axis, of the tetragonal structure in each grain, being parallel, to the deformation direction (DD). However, the mechanisms leading to the anisotropic structure and accompanying processes are still not fully understood. In this study the Fe 73.7 Nd 13.6 Co 6.6 Ga 0.6 B 5.5 alloy, after rapid solidification by melt spinning and hot pressing was subjected to die-upset forging with strains 30% and 65%, respectively. Systematic studies of the structure, microstructure and magnetic domain structure versus processing parameters were performed for this alloy, using magnetic measurements, transmission electron microscopy and atomic force microscopy.

Effect of sintering temperature on structure and properties of Al2O3/Ni-P composites with interpenetrating phases

An Al2O3/Ni-P composite was formed by hot pressing of alumina powder, coated with chemically plated nano Ni-P. The powders were consolidated at room temperature, 600 and 1000oC. The consolidated specimens were studied by SEM, TEM/HRTM, MFM (magnetic force microscopy) and tested or hardness. It was found that the fabrication method results in a structure of interpenetrating phases of high electric conductivity and that samples consolidated at room temperature and sintered at 600oC retain the nanometric grain size of the metallic phase. Hardness measurements are discussed in terms of the fabrication temperature and structure of the composites.