Michal Jambor, Otakar Bokůvka, František Nový, Libor Trško and Juraj Belan
Nickel base superalloys are hi-tech materials intended for high temperature applications. This property owns a complex microstructure formed by matrix of Ni and variety of precipitates. The type, form and the amount of these phases significantly affect the resulting properties of these alloys. At sufficiently long exposure to high temperatures, the transformation phase can occur, which can lead to degradation of properties of these alloys. A cyclic plastic deformation can accelerate these changes, and they could occur at significantly lower temperatures or in shorter time of exposure. The aim of this study is to describe phase transformation, which can occur by a cyclic plastic deformation at high temperatures in nickel base superalloy Inconel 718.
Barbara Lisiecka, Otakar Bokůvka, Tomasz Tański, Łukasz Krzemiński and Michal Jambor
Aim of this paper is to present the properties of carbon preforms for the production of biomorphic composites. Carbon samples were obtained through pyrolysis of paulownia wood, replicating the microstructure of the cellulosic precursor. Many characterization methods such as Raman Spectroscopy, light microscopy, hardness tests and pore size analyzer detection were used to investigate the microstructure of the product as well as the pore size of carbon samples. Obtained results showed that the parts of early or late wood template play an important role in the pore size, specific surface area and pore volume of the product. This review aims to be a comprehensive description of the development of carbon chars: from wood templates and their microstructure to potential applications of biomorphic materials.
František Nový, Otakar Bokůvka, Libor Trško and Michal Jambor
In this paper the authors introduce their own selected experimental results in the field of the investigation of fatigue resistance of structural steels. The experiments were carried out on the nine structural steels including high strength steels, DOMEX 700MC, HARDOX 400, HARDOX 450, 100Cr6 (UTS from 446 MPa to 2462 MPa) at high-frequency cyclic loading (f = 20 kHz, T = 20 ± 5 °C, R = -1) in the region of number cycles ranged from N ≈ 2×106 to N ≈ 2×109 cycles of loading. The continuous decrease of fatigue strength in dependence on the number of loading cycles was observed with the average value of ratio σa2×109/σa2×106 = 0.69.
Otakar Bokůvka, Michal Jambor, Libor Trško, František Nový and Barbara Lisiecka
In this paper, the authors publish their own experimental results of the examination of the different holes (milled, drilled and drilled + shot peened) on the fatigue lifetime of 20MnV6 steel. The experiments were carried out at low-frequency loading (f = 10 Hz, pulsating tension loading) in the region from N = 2×105 up to N = 2×106 cycles. The best fatigue properties were obtained in the parts with drilled + shot peened holes.
Adrian Głogowski, Zbigniew Marczyński, Michał Krzysztof Kołodziejczyk, Jerzy Jambor, Marta Kinga Stefan and Marian Mikołaj Zgoda
Introduction: Dietary supplements are a good way to supplement the deficiency of certain micronutrients and organic components (therapeutic agents) in human body. They are most often available in concentrated form as tablets, capsules, powder or liquid.
Objective: To investigate morphological parameters and the pharmaceutical availability of coated tablets – dietary supplements – that contain selected pharmacopeial titrated dry plant extracts.
Methods: Testing of the effective time of the tablet surface erosion was performed in model acceptor fluids using pharmacopeial methods in static (Erweka apparatus) and dynamic (unlimited diffusion method) conditions. Furthermore, morphological parameters of tablets (the original shape of an ellipse) as well as their hardness were determined.
Results: The effective erosion time was determined by conductometric method using carboxymethylcellulose sodium salt (NaCMC) contained in the tablet. The content of gum arabic and NaCMC in the tablet testifies that the granulate was produced using the “wet granulation” technique which resulted in high hardness of original, esthetic, elliptical tablets and in prolonged disintegration time (erosion).
Conclusions: The used excipients: gum arabic and NaCMC for the production of the tested tablets containing selected dry plant extracts result in their high hardness. The tested dietary supplements are characterized by esthetic design, original shape, and prolonged disintegration time which affects the pharmaceutical availability.
Elżbieta Nowak, Zbigniew Marczyński, Beata Skibska, Michał Jakub Nachajski, Jerzy Jambor and Marian Mikołaj Zgoda
Introduction: Common ivy (Hedera helix) is a plant used successfully in the treatment of various ailments. This is possible owing to the unique set of substances contained in it such as large amount of saponins, flavonoids, phenolic acids and phytosterols as well as polyacetylenes and coumarins. All these substances have been used in the production of cosmetic and medicinal preparations. Clinical trials on the efficacy and safety of dry ivy leaf extract have shown its high efficacy, comparable to synthetic medications, and better tolerance of herbal drugs.
Objective: Investigations were performed on model ivy leaf (Hedera helix) extracts which were created using a medium of diversified polarity ( εM). Measurements of viscosity and surface activity on phase boundary were performed. During preformulation studies attention was drawn to the possibility of micellar solubilization of cholesterol and selected structures of nonsteroidal anti-inflammatory drugs (NSAIDs) – ketoprofen.
Methods: Viscosity measurements of Extractum Hederae helicis e folium aqueous solutions and in 0.1 mol HCl were performed according to the Polish Standard with Ubbelohde dilution viscometer. The surface tension of aqueous solutions of Hederae helicis e folium extracts was determined according to the Polish Standard with stalagmometric method. Critical micellar concentration (cmc) was calculated. This enabled to evaluate the dependence RT×log cmc of the thermodynamic potential of micelle formation ( ). Results: It has been confirmed in the conducted comparative studies that aqueous solutions of Extr. Hederae helicis e folium created with maltodextrin as well as with SiO2 – maltodextrin result in micellar solubilization. The increase of granulometric size of cholesterol particle to Ø 1.60 mm decreased the amount of solubilized cholesterol but solubility preferences of the extracts were maintained.
Conclusions: Model extracts produced from Hederae helicis e folium with diversified polarity of the extraction medium (water – ethanol) are characterized by appropriate solubility of the components which results not only from the presence of chlorophyll and its derivatives in the extract but also from the technique used for spray drying of the extract.