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  • The Conference Report of Why R? Turkey 2022: The First R Conference with Call For Papers in Turkey
    • Mustafa Cavus
    • Olgun Aydin
    • Ozan Evkaya
    • Derya Turfan
    • Filiz Karadag
    • Ozancan Ozdemir
    • Ugur Dar
    • Deniz Bezer
    2022 Pełny tekst R Journal

    Why R? Turkey 2022 was a non-profit conference that aimed to bring Turkish R users together and encourage them to attend the R conferences. The targeted audience of the conference consisted of, data scientists, data analysts, and all R users from academia and industry. The three-day conference, which consisted of several events such as workshops, regular talks, lightning talks, short tutorials, and panels, was free of charge and fully online. This article describes the challenges and benefits, as well as providing an overview of the conference’s content and participants’ profile.

  • The content of biogenic amines in Rondo and Zweigelt wines and correlations between selected wine parameters
    • Anna Stój
    • Justyna Płotka-Wasylka
    • Vasil Simeonov
    • Magdalena Kapłan
    2022 Pełny tekst FOOD CHEMISTRY

    The purpose of this study was to evaluate the content of biogenic amines (BAs) in wines using dispersive liquid–liquid microextraction–gas chromatography–mass spectrometry (DLLME-GC–MS). An additional objective was to assess the correlations between selected parameters characterizing the samples such as the content of BAs, sugars, and organic acids, pH, and total acidity. Wines produced from the same grape variety in which alcoholic fermentation (AF) was carried out by different yeast strains and in which malolactic fermentation (MLF) was spontaneous, differed in the content of biogenic amines. The concentrations of putrescine, cadaverine and tryptamine were higher in the Rondo wines (237–405, 34.04–61.11, <LOD-12.456 µg/L, respectively) and Zweigelt wines (416–489, 72.67–88.43, <LOD-13.083 µg/L, respectively) subjected to spontaneous MLF than in the wines subjected to induced MLF. Chemometric analysis allowed us to determine correlations between selected wine parameters. The wine samples are well separated into two patterns depending on the grape variety. Despite the fact that information on BAs is not included in databases of wine composition, information on their concentration as well as knowledge of existing correlations between BAs and other wine parameters is crucial and may be useful for the food industry, health professionals and consumers.

  • The contribution of Hans von Wartenberg to the development of the Czochralski method
    • Wiesław Wojnowski
    • Antoni Konitz
    • Wojciech Wojnowski
    2022 Pełny tekst JOURNAL OF CRYSTAL GROWTH

    The contribution of Hans von Wartenberg to the development of the Czochralski Method for pulling single crystals is often overlooked. He was its earliest adopter, having introduced the use of seed crystals, and his detailed description of the method was the basis for its subsequent dissemination.

  • The Course and the Effects of Agricultural Biomass Pyrolysis in the Production of High-Calorific Biochar
    • Paweł Kazimierski
    • Katarzyna Januszewicz
    • Wojciech Godlewski
    • Aleksander Fijuk
    • Tomasz Suchocki
    • Patryk Chaja
    • Beata Barczak
    • Dariusz Kardaś
    2022 Pełny tekst Materials

    The thermal pyrolysis of agriculture biomass has been studied in a fixed-bed reactor, wherethe pyrolysis was conducted at a steady temperature of 800◦C. This work analyses the pyrolysisproducts of six agricultural wastes: pistachio husks, walnut husks, sunflower hulls, buckwheat husks,corncobs and coconut shells. The conducted research compared examples of large waste biomassstreams from different parts of the world as a potential source of renewable energy. Additionally, thekinetics of the reaction with the activation energy were analyzed and calculated for all raw materialsin pyrolysis process. Biochars are characterised by higher combustion heat in comparison to the rawmaterial samples. The average value of the heat of combustion increased due to pyrolysis processfrom 10 MJ/kg, with minimal value of 2.7 MJ/kg (corncob) and maximum of 13.0 MJ/kg for coconut,which is also characterised by the maximal absolute combustion heating value (32.3 MJ/kg). Theincrease in calorific values varied from 15% to 172% (with 54% reference for wood chips), whichindicates that charring is an effective method for increasing the energy concentration. The obtainedbiochar were compared with wood chips, which are widely used solid fuel of organic origin. Thestudied biomass-derived fuels are characterised by lower ash contribution than wood. An analogousobservation was made for the obtained biochars, whose ash contribution was lower than for thechips in terms of both unit-mass and unit-combustion-heat. The main advantage of this method isthe production of solid fuel from biomass, which increases the calorific value and bulk density ofbiochar in comparison to raw material.

  • The Development of a Conceptual Framework for Knowledge Sharing in Agile IT Projects
    • Rodrigo Oliveira de Castro
    • Cesar Sanin
    • Andrew Levula
    • Edward Szczerbicki
    2022 Pełny tekst CYBERNETICS AND SYSTEMS

    Organizations must adapt their resources to meet the challenges associated with changes in the work environment in order to remain competitive in the information era. Several research findings identify knowledge sharing as a means for an organization to improve its competitiveness. Knowledge sharing can be defined in a variety of ways, but it essentially refers to the exchange of knowledge from an information giver to an information receiver. This is a purposeful activity that adds value to the client organization, particularly in IT system that employs Agile methodology. For the scope of this paper, we are going to consider only Agile knowledge transfer in IT projects that occurs in two angles: business knowledge transfers from client to consultant; and IT technical knowledge transfers from consultant to client. However, when interdisciplinary teams are involved in Agile IT projects, the knowledge transfer mentioned before remains inefficient once the knowledge loss persists throughout the project life cycle. The conversion of conceptual knowledge, which only exists in the brains and minds of individuals, into explicit knowledge is essential for organizations to gain and maintain competitive advantages over its competitor. This study proposes an alternative conceptual framework to address conceptual knowledge transfer in IT projects that use Agile methodology.

  • The Digital Tissue and Cell Atlas and the Virtual Microscope
    • Jarosław Skokowski
    • Marika Bolcewicz
    • Kamila Jendernalik
    • Thierry Vanelslander
    • Jacek Gulczyński
    • Anna Lewandowska
    • Leszek Kalinowski
    2022 Pełny tekst

    With the cooperation of the CI TASK (Center of lnformatics Tri-Citry Academic Supercomputer and network) and the Gdańsk University of Technology, the Medical University of Gdańsk undertook the creation of the Digital Tissue and Cell Atlas and the Virtual Microscope for the needs of the Bridge of Data project. In the beginning, an extensive collection of histological and cytological slides was carefully selected and prepared by pathomorphology experts. After processing and digitising, the specimens were sent to servers of the TRYTON Supercomputer, where storing, searching for and scrolling through the images in the Virtual Microscope was made available. The collection consists of twenty thousand high definition images of human tissues and cells accompanied by structurised clinical metadata. Creating a digital atlas and a virtual microscope is an answer to modern education challenges that shape digital competence and are open to modern technologies. The main idea behind the creation of the information tools and digital image data repositories is using them for the purpose of education and as a basis for the creation of new methods of long-distance education. Those resources are shared under the terms of the open Creative Commons license (CC BY-SA), making it possible for teachers, students, and entrepreneurs to use the images safely and process content included in the presented materials without intellectual property infringement.

  • The Distribution of Glucosinolates in Different Phenotypes of Lepidium peruvianum and Their Role as Acetyl- and Butyrylcholinesterase Inhibitors—In Silico and In Vitro Studies
    • Dominik Tarabasz
    • Paweł Szczeblewski
    • Tomasz Laskowski
    • Wojciech Płaziński
    • Ewa Baranowska-Wójcik
    • Dominik Szwajgier
    • Wirginia Kukula-Koch
    • Henry O. Meissner
    2022 Pełny tekst INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES

    The aim of the study was to present the fingerprint of different Lepidium peruvianum tu- ber extracts showing glucosinolates-containing substances possibly playing an important role in preventinting dementia and other memory disorders. Different phenotypes of Lepidium peruvianum (Brassicaceae) tubers were analysed for their glucosinolate profile using a liquid chromatograph coupled with mass spectrometer (HPLC-ESI-QTOF-MS/MS platform). Qualitative analysis in 50% ethanolic extracts confirmed the presence of ten compounds: aliphatic, indolyl, and aromatic glucosi- nolates, with glucotropaeolin being the leading one, detected at levels between 0–1.57% depending on phenotype, size, processing, and collection site. The PCA analysis showed important variations in glucosinolate content between the samples and different ratios of the detected compounds. Applied in vitro activity tests confirmed inhibitory properties of extracts and single glucosinolates against acetylcholinesterase (AChE) (15.3–28.9% for the extracts and 55.95–57.60% for individual compounds) and butyrylcholinesterase (BuChE) (71.3–77.2% for the extracts and 36.2–39.9% for individual com- pounds). The molecular basis for the activity of glucosinolates was explained through molecular docking studies showing that the tested metabolites interacted with tryptophan and histidine residues of the enzymes, most likely blocking their active catalytic side. Based on the obtained results and described mechanism of action, it could be concluded that glucosinolates exhibit inhibitory properties against two cholinesterases present in the synaptic cleft, which indicates that selected phenotypes of L. peruvianum tubers cultivated under well-defined environmental and ecological conditions may present a valuable plant material to be considered for the development of therapeutic products with memory-stimulating properties.

  • The Dream of Black
    • Krzysztof Wróblewski
    2022

    The Dream of Black Wystawa Sen o czerni to projekt pedagogów Uniwersytetu w Ostrawie i Fundacji Wyspa Progress a właściwie ich studentów, którzy są również dzisiaj pedagogami. W wielu przypadkach jest to już drugie pokolenie studentów. The Dream of Black oferuje szerokie spektrum form artystycznych. Autorska próbka stanowiąca trzon projektu wystawy (gość: Viktor Frešo i inni artyści związani z Gdańską sceną artystyczną) to tylko wycinek całej sceny artystycznej Ostrawy i Gdańska. Widz będzie miał niewątpliwie również możliwość osobistej konfrontacji ze stereotypem postrzegania relacji miedzy centrum i peryferiami, które dziś postrzega się jako część europejskiego kontekstu sztuki całości wyróżniających się regionalnych centrów sztuki. Sny nie rodzą się i nie znikają, pochodzą z powietrza i z popiołów, nie kończą się błyskawicznie, ale stopniową erozją.1. Rzeczywistość pojawia się przed nami jako skupisko rozproszonych wydarzeń o wątpliwych syntezach i zgrupowaniach. Niewątpliwie rozmawialiśmy o niej nie raz, rozmawiamy o niej, lub możemy powiedzieć o niej, że jest ciemna. Czas i przestrzeń określają stosunki między ontologią tworzenia obrazów a jego reprezentacją. Kultura i filozofia Zachodu odsuwa znikanie, pustkę czy nicość na plan dalszy, jako coś, co związane jest z przemijaniem, niszczeniem, tak samo jak z ukrywaniem. Wbrew wszelkim faktom odzwierciedlenie tej nicości ma przecież swoje znaczenie. Post-konceptualny dyskurs wciąż prowadzi walkę z reprezentacją widzianego, idea przesuwa się do obszaru doświadczeń formalnych w dziele sztuki i stawia granice między obrazem realności a jego wewnętrznym odbiciem.(...) Tak, to czarna Ostrawa... Stocznia Gdańska Ostrawa, czy historycznie Stocznia Gdańska, miejsca które dziś już nie czują czerni i szukają swego charyzmatu w takich barwnych konotacjach, które są naprawdę bardzo kolorowe, są dosłownie kolorowymi gejzerami, ale i czarnym snem, który leży u podstaw tego myślenia o śnie i który, w pewnych okolicznościach może być postrzegany jako koszmar, jako coś przerażającego i uciążliwego, jest przede wszystkim żywą platformą aktualnego i współczesnego dążenia do racjonalnego opisu, a także sztucznej egzystencjalnej odpowiedzi mitologii pochodzenia. Kuratorzy: Tomáš Koudela, František Kowolowski, Piotr Mosur, Grzegorz Klaman

  • The Dynamics of Trade Relations between Ukraine and Romania: Modelling and Forecasting
    • Oleksandr Melnychenko
    • Valerii Matskul
    • Tetiana Osadcha
    2022 Pełny tekst Virtual Economics

    The article examines the monthly dynamics of exports, imports and balance of trade between Ukraine and Romania in the period from 2005 to 2021. Time series from 2015 to 2021 were used for modelling and forecasting (since the date the European Union–Ukraine Association Agreement took effect). Adequate models of the dynamics series of the Box-Jenkins methodology were built: additive models with seasonal component ARIMA (Autoregressive Integrated Moving Average) ARIMAS (or SARIMA) and Holt-Winters exponential smoothing with a dampened trend. Forecasting of exports, imports and trade balance for the fourth quarter of 2021 and first quarter of 2022 were completed. The forecast results showed a small relative error compared to the actual data. Thus, when forecasting the trade balance between countries using the Holt-Winters model, the relative prediction errors were: for October 2021 – 1.3%; for November 2021 – 2.6%; for December 2021 – 0.4%.

  • The Economic Legacy of Mega Sporting Events. The Impact of Hosting European Olympic Games on GDP Growth Through Infrastructure Development
    • Krystian Zawadzki
    2022 Pełny tekst Polish Journal of Sport and Tourism

    Introduction. The positive legacy of the Olympics is often cited by the International Olympic Committee and national or-ganizers. Some scholars, however, question an uncritical approach to an exclusively positive economic legacy. The aim of this study is to evaluate the impact of hosting the Olympics on infrastructure development, with a potential impact on economic growth in the form of Gross Domestic Product (GDP) in three phases of seven Olympic Games organised in Europe in recent years. Material and methods. The effect of a particular Olympic period on the GDP was analysed using a difference-in-differ-ence technique in which the difference between each of the analysed seven host countries’ GDPs and those of a reference set of countries was obtained. Each time, as part of the observation, an event time period was distinguished covering all three phases of the event: the preparatory phase, the event phase and the post-event phase. Results. For the Winter Olympic Games, no statistically significant positive results are observed in the long term, which may indicate a very limited importance of the economic legacy of these events for potential host countries. In the case of Summer Olympic Games, the positive impact of the organization of these events in the post-event phase is noticeable. Conclusions. The obtained results confirm the ambiguous impact of Olympic Games on the hosts’ economies and are in line with the attitude of many scholars to an uncritical approach to the only positive legacy of these events.

  • The effect of beech wood (Fagus sylvatica L.) steaming process on the colour change versus depth of tested wood layer
    • Aleksandra Konopka
    • Daniel Chuchała
    • Kazimierz Orłowski
    • Vilkovska Tatiana
    • Ivan Klement
    2022 Pełny tekst Wood Material Science & Engineering

    The results of experimental research on the colour changes of beech wood at different depths of the tested layer are presented. Beech wood (Fagus sylvatica L.) dried in a conventional kiln was tested. Half of the wood samples were steamed prior to the drying process. Colour changes were measured at various depths after the face milling process was used to remove the material to expose to the deeper surface. The colour changes were measured based on the three-axis CIELAB system, recommended by CIE (Comission Internationale de l'Eclairage) and according to ISO 11664-2 and ISO 11664-4 standards. As a result of the analysis, four parameters were determined: the colour changes (ΔE), the colour chroma (Cab), the hue angle (h) and the colour saturation (Sab). The performed experimental research revealed that the surface of steamed wood is more susceptible to colour change. A significant colour change in both steamed and dried wood occurs only up to a depth of about 2 mm.

  • The effect of boron concentration on the electrical, morphological and optical properties of boron-doped nanocrystalline diamond sheets: Tuning the diamond-on-graphene vertical junction
    • Michał Rycewicz
    • Adrian Nosek
    • Dong Hoon Shin
    • Mateusz Ficek
    • Josephus G. Buijnsters
    • Robert Bogdanowicz
    2022 Pełny tekst DIAMOND AND RELATED MATERIALS

    In this paper, the effect of boron doping on the electrical, morphological and structural properties of free-standing nanocrystalline diamond sheets (thickness ~ 1 μm) was investigated. For this purpose, we used diamond films delaminated from a mirror-polished tantalum substrate following a microwave plasma-assisted chemical vapor deposition process, each grown with a different [B]/[C] ratio (up to 20,000 ppm) in the gas phase. The developed boron-doped diamond (BDD) films are a promising semiconducting material for sensing and high-power electronic devices due to band gap engineering and thermal management feasibility. The increased boron concentration in the gas phase induces a decrease in the average grain size, consequently resulting in lower surface roughness. The BDD sheets grown with [B]/[C] of 20,000 ppm reveal the metallic conductivity while the lower doped samples show p-type semiconductor character. The charge transport at room temperature is dominated by the thermally activated nearest-neighbor hopping between boron acceptors through impurity band conduction. At low temperatures (<300 K), the Arrhenius plot shows a non-linear temperature dependence of the logarithmic conductance pointing towards a crossover towards variable range hopping. The activation energy at high temperatures obtained for lowly-doped sheets is smaller than for nanocrystalline diamond bonded to silicon, while for highly-doped material it is similar. Developed sheets were utilized to fabricate two types of diamond-on-graphene heterojunctions, where boron doping is the key factor for tuning the shape of the current-voltage characteristics. The graphene heterojunction with the low boron concentration diamond sheet resembles a Schottky junction behavior, while an almost Ohmic contact response is recorded with the highly doped BDD sheet of metallic conductivity. The free-standing diamond sheets allow for integration with temperature-sensitive interfaces (i.e. 2D materials or polymers) and pave the way towards flexible electronics devices.

  • The effect of cable duct diameter on the ampacity of high-voltage power cables
    • Filip Ratkowski
    • Michał Kołtun
    • Stanisław Czapp
    2022 Pełny tekst Przegląd Elektrotechniczny

    The ampacity of power cables depends, among others, on the conditions of heat dissipation from the cable to the environment. Cables are usually laid directly in the ground, but in some sections, they may be placed in ducts, which adversely affects the ampacity of the cable line. The paper presents heat transfer phenomena for cables installed in pipe-type ducts filled with air. The effect of cable duct diameter on this ampacity is discussed. The results of the theoretical analysis have been validated by calculations performed with CYMCAP software. The comparison of the ampacity for air-filled vs. water- or bentonite-filled ducts is also included. The analyses and comparisons have shown that with an appropriate dimension of the duct, the simplest filling (with air) allows to obtain the ampacity not lower than when water or bentonite is used.

  • The effect of external load on ultrasonic wave attenuation in steel bars under bending stresses
    • Adam Ścięgaj
    • Erwin Wojtczak
    • Magdalena Rucka
    2022 Pełny tekst ULTRASONICS

    The stress state in deformed solids has a significant impact on the attenuation of an ultrasonic wave propagating through the medium. Measuring a signal with certain attenuation characteristics can therefore provide useful diagnostic information about the stress state in the structure. In this work, basic principles behind a novel attenuation-based diagnostic framework are introduced. An experimental study on steel bars under three-point bending was carried out, and finite element analyses were used to numerically model the experiments. Obtained test results showed a strong correlation between the external load and the ultrasonic signal energy, which decreases with increasing load. A similar but positive correlation appeared between the level of attenuation of longitudinal ultrasonic wave signals and the external load, which allowed for efficient estimation of the mid-span bending moment. Upon proper calibration of testing equipment, the change in ultrasonic signal energy can therefore be used as an indicator of the external load level. As a result, this effect has potential applications in non-destructive structural health monitoring frameworks.

  • The effect of freeze-drying and storage on lysozyme activity, lactoferrin content, superoxide dismutase activity, total antioxidant capacity and fatty acid profile of freeze-dried human milk
    • Dorota Martysiak-Żurowska
    • Patrycja Rożek
    • Małgorzata Puta
    2022 Pełny tekst DRYING TECHNOLOGY

    Pooled human milk samples were freeze-dried and stored for 6 weeks at a temperature of 5 C and 25 C. Freeze-drying decreased the water content of milk by 86.5%, and the obtained lyophilizate was readily soluble in water. The freeze-drying process did not affect superoxide dismutase (SOD) activity, fatty acid (FA) profile or lactoferrin (LF) content, but it decreased total antioxidant capacity (TAC) of human milk by 22.1% and induced a minor increase in lysozyme (LZ) activity, by approximately 9.8%. Storage of freeze-dried milk did not show significant influence on TAC, LF, FA and LZ levels, while after six weeks of storage SOD activity decreased by around 27% relative to the level noted immediately after lyophilization. These findings and the remaining state of knowledge imply, that freeze-drying can be a useful method of human milk storage.

  • The Effect of Openings’ Size and Location on Selected Dynamical Properties of Typical Wood Frame Walls
    • Marcin Szczepański
    • Ahmed Manguri
    • Najmadeen Saeed
    • Daniel Chuchała
    2022 Pełny tekst Polymers

    The wooden frame constructions are now popular in many developed countries of the world. Many of these locations where such buildings are constructed are exposed to seismic and other shocks which are generated by human activities. This paper discusses the effect of the size and location of openings in the wooden frame walls under dynamic loadings. Natural frequencies of such frames with and without openings have been determined. Three 14 m high walls with different widths, including 3, 6, and 12 m, have been considered. Dynamic analysis has been made using finite element method structural analysis software Dlubal RFEM 5.17. The results show that the effect of the size and location of the openings on the natural frequency is significant. Numerically speaking, the relative change of the natural frequencies of a wall without and with an opening in a specific place could be up to 30%. In addition, the change of the natural frequency for the location of the openings is more sensitive than that to the sizes. Furthermore, the appropriate sizes and locations of openings of the wooden frame walls have been suggested. The appropriate size and place were found to be small openings in the top of the walls.

  • The effect of paleo-environment on hydrocarbon generation potential: Example from Vaca Muerta Formation, Neuquén Basin, Argentina
    • Aleksandra Małachowska
    • Grzegorz Lis
    • Maria Mastalerz
    • Fariborz Goodarzi
    • Hamed Sanei
    2022 JOURNAL OF PETROLEUM SCIENCE AND ENGINEERING

    A 137-m continuous core from the Jurassic-Early Cretaceous marine derived oil shale with the maturity Ro about 0.7 %, representing the oil window in the Vaca Muerta Formation, Neuquén Basin, Argentina, was examined using geological, mineralogical, petrographic, and geochemistry techniques. Three distinct intervals were identified within the core: the upper carbonate-rich section with intense bioturbation, indicating dysoxic to oxic conditions that resulted in poor organic matter preservation; a middle section with decreasing carbonate content, suboxic bottom conditions, and higher organic matter content; and a lower section with higher detrital input and low carbonate content, suboxic to anoxic water conditions, and enhanced preservation of organic matter. Based on the presence of indicator fossils and geochemical parameters, a general trend of increasing organic matter content with lower paleo-oxygen levels was observed. The proportion of solid bitumen within organic matter increases with decreasing oxygen content, suggesting that organic matter deposited in anoxic conditions is more prone to transformation and hydrocarbon generation. There is a negative impact of increasing paleo-oxygen levels on the quantity and quality of organic matter, represented by its potential to generate hydrocarbons.

  • The effect of shear deformations' rotary inertia on the vibrating response of multi-physic composite beam-like actuators
    • Mohammad Malikan
    • Victor Eremeev
    2022 Pełny tekst COMPOSITE STRUCTURES

    In consecutive studies on flexomagneticity (FM), this work investigates the flexomagnetic reaction of a vibrating squared multi-physic beam in finite dimensions. It is assumed that the bending and shear deformations cause rotary inertia. In the standard type of the Timoshenko beam the rotary inertia originated from shear deformations has been typically omitted. It means the rotary inertia resulting from shear deformation is a new concept considered here. Thus, the novelty in this work is that the effect of shear deformation's rotary inertia (SDRI) on the FM response will be considered in detail. When it comes to nanosize, the well-posed nonlocal elasticity assumption of Eringen can be worth choosing. In this study, the weak form of strain-driven nonlocal theory, which means differential form, is taken into hand for easiness. The procedure of solution will be in regard to the advantage of the Galerkin weighted residual technique based on an analytical flow for the meta beam located at simply-simply ends. Verifications of the mathematical model and solving steps come through macro and nanobeams concerning reputable literature. In pursuit of this step, several separate studies will show how SDRI and FM can influence each other. The observations give some new achievements in the series of studies on FM. It has been earned that the SDRI can directly impress the flexomagnetic feature of small-scale actuators.

  • The Effect of Sodium Tetrafluoroborate on the Properties of Conversion Coatings Formed on the AZ91D Magnesium Alloy by Plasma Electrolytic Oxidation
    • Lukasz Florczak
    • Ginter Nawrat
    • Kazimierz Darowicki
    • Jacek Ryl
    • Jan Sieniawski
    • Małgorzata Wierzbińska
    • Krzysztof Raga
    • Andrzej Sobkowiak
    2022 Pełny tekst Processes

    Magnesium and its alloys are widely used in many areas because of their light weight, excellent dimensional stability, and high strength-to-weight ratio. However, the material exhibits poor wear and corrosion resistance, which limits its use. Plasma electrolytic oxidation (PEO) is an effective surface modification method for producing ceramic oxide layers on Mg and their alloys. The influence of the additions of sodium tetrafluoroborate (NaBF4) and sodium fluoride (NaF) into alkaline-silicate electrolyte on the properties of the conversion layers formed in the magnesium AZ91D alloy has been investigated. Surface morphology and chemical composition were determined by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The anticorrosive properties of the layers were evaluated by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) methods in simulated body fluid (SBF). The presence of NaBF4 or NaF in the electrolyte increases the corrosion resistance of the protective layer. However, the best anticorrosive properties show the layers obtained in the presence of NaBF4. This is probably caused by the incorporation of boron and fluorine in the form of Mg (BF4)2 mainly in the barrier layer.

  • The effect of Sr and Mg substitutions on structure, mechanical properties and solubility of fluorapatite ceramics for biomedical applications
    • Mohammad Ghaemi
    • Sergiy Y. Sayenko
    • Volodymyr Shkuropatenko
    • Anna Zykova
    • Kateryna Ulybkina
    • Olena Bereznyak
    • Andrzej Krupa
    • Mirosław Sawczak
    2022 Pełny tekst Processing and Application of Ceramics

    Ionic substitutions play important role in the modifications of biological apatites. Recently, attention has been focused on the co-doping effects on the functional properties of apatite-based biomaterials. In this research work, the dense samples of fluorapatites, Ca10(PO4)6F2 and Ca8MgSr(PO4)6F2, were produced after sintering at 1250 °C for 6 h in air. Structural characterization carried out with XRD, IR, Raman and SEM, confirmed the formation of a dense and homogeneous structure with main fluorapatite and a small amount of Ca3(PO4)2 phase. The presented results also demonstrate the stability of structural and mechanical properties of fluorapatites after immersion tests in saline and buffer solutions. The durability of mechanical properties and biocompatibility of the Ca10(PO4)6F2 and Ca8MgSr(PO4)6F2 fluorapatites make these materials highly attractive for biomedical applications.