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Efektywność energetyczna systemów chłodniczych pracujących z dwutlenkiem węgla jako czynnikiem roboczym
- Paulina Boroń
- Blanka Jakubowska
2021 Pełny tekst Chłodnictwo : organ Naczelnej Organizacji Technicznej
Artykuł dotyczy zagadnienia efektywności energetycznej układów chłodniczych pracujących z dwutlenkiem węgla jako czynnikiem roboczym. W celu szczegółowego przeanalizowania potencjału zastosowania dwutlenku węgla, jako czynnika roboczego w urządzeniach chłodniczych, przeprowadzone zostały obliczenia dla kilku modeli układów chłodniczych. Do przeprowadzenia analizy wybrano trzy układy chłodnicze, tj. układ transkrytyczny, układ kaskadowy oraz typu booster. W ramach prowadzonej analizy zbadano i omówiono wpływ temperatury skraplania i parowania na efektywność energetyczną analizowanych układów.
Effect of annealing temperature on slurry erosion resistance of ferritic X10CrAlSi18 steel
- Marta Buszko
- Alicja Krella
- Artur Marchewicz
- Grzegorz Gajowiec
2021 TRIBOLOGY INTERNATIONAL
In the present work, the slurry erosion tests were carried out to investigate the influence of heat treatment on slurry erosion process of ferritic X10CrAlSi18 stainless steel using a slurry pot test rig. X10CrAlSi18 stainless steel was tested in as-received condition and after annealing at three different temperatures: 600°C, 800°C and 1000°C. Degradation of materials due to slurry erosion depends on many factors connected with fluid flow conditions, properties of target material and erodent characteristics. In this case, factors related to the properties of the eroded material such as microstructure, grain size, work hardening, hardness played an important role. The heat treatment decreased hardness of this steel and increased erosion resistance. Microstructure was one of the most important parameters influencing the slurry erosion process of tested materials. X10CrAlSi18 stainless steel after annealing at 600 °C with fine-grained microstructure and the deepest of work hardening layer obtained the best resistance to slurry erosion. Heat treatment contributed to approximately 55%, 23% and 41% decrease in mass loss compared to steel in as-received condition. After slurry erosion tests craters, fracture, ridges and flakes were observed on the eroded surface. Furthermore, to identify the dominant mechanism of erosion, the erosion efficiency parameter was used, η.
Effect of choline chloride based natural deep eutectic solvents on aqueous solubility and thermodynamic properties of acetaminophen
- Dorota Warmińska
- Bartosz Nowosielski
- Adrian Szewczyk
- Jakub Ruszkowski
- Magdalena Prokopowicz
2021 JOURNAL OF MOLECULAR LIQUIDS
In this work, natural deep eutectic solvents (NADESs) containing choline chloride as hydrogen bond acceptor and 1,2-propanediol, malic acid and tartaric acid as hydrogen bond donors have been synthesized and applied to enhance the aqueous solubility of model sparingly water-soluble drug – acetaminophen. The results indicate that the greatest impact on the solubility of acetaminophen have deep eutectic solvents based on 1,2-propanediol or malic acid and the solubility of acetaminophen increases with both the concentration of NADES and temperature. Among the Apelblat, λh (Buchowski-Ksiazczak), Yalkowsky and combined Jouyban–Acree and van ‘t Hoff models correlating the solubility data, the Apelblat model is more consistent with the experimental data. Moreover, densities and sound velocities of acetaminophen in aqueous NADESs were measured at T = (298.15–313.15) K and these data were used to derive the limiting apparent molar volumes and the apparent molar compressibilities of the transfer. The thermodynamic properties show that the hydrophilic-ionic and hydrophilic-hydrophilic interactions in solutions of acetaminophen are predominant and this effect is the strongest for acetaminophen in aqueous choline chloride:malic acid solution.
Effect of double thermal and electrochemical oxidation on titanium alloys for medical applications
- Agnieszka Ossowska
- Jean-marc Olive
- Andrzej Zieliński
- Andrzej Wojtowicz
2021 Pełny tekst APPLIED SURFACE SCIENCE
The research focuses on the development and characterization of innovative thin hybrid oxide coatings obtained in subsequent processes of thermal (TO) and electrochemical (EO) oxidation. Four different surface modifications were investigated and the microstructure was determined, the mechanical, chemical and biological properties of the Ti-13Nb-13Zr alloy were assessed using scanning electron microscopy, X-ray dispersion analysis, glow discharge emission spectroscopy, Raman spectroscopy, nanoindentation and corrosion resistance measurements. The composite layers were evaluated for antimicrobial activity, cytotoxicity bioassays and wettability tests were performed. The conducted studies of two-stage oxidation (TO + EO) have shown that it is possible to obtain layers with a different structure - crystalline and nanotubular. The formation of a nanotube layer on the surface of the crystalline layer is dependent on the thickness of the crystalline layer. The produced double titanium oxide coatings show high surface roughness, high corrosion resistance, are hydrophilic, slightly antibacterial, and not cytotoxic, which has a huge impact on the process of connecting the tissue with the implant.
Effect of excitation intensity on slope stability assessed by a simplified approach
- Aleksandra Korzec
- Robert Jankowski
2021 Pełny tekst Earthquakes and Structures
The paper concerns the selection of a design accelerograms used for the slope stability assessment under earthquake excitation. The aim is to experimentally verify the Arias Intensity as an indicator of the excitation threat to the slope stability. A simple dynamic system consisting of a rigid block on a rigid inclined plane subjected to horizontal excitation is adopted as a slope model. Strong ground motions recorded during earthquakes are reproduced on a shaking table. The permanent displacement of the block serves as a slope stability indicator. Original research stand allows us to analyse not only the relative displacement but also the acceleration time history of the block. The experiments demonstrate that the Arias Intensity of the accelerogram is a good indicator of excitation threat to the stability of the slope. The numerical analyses conducted using the experimentally verified extended Newmark’s method indicate that both the Arias Intensity and the peak velocity of the excitation are good indicators of the impact of dynamic excitation on the dam's stability. The selection can be refined using complementary information, which is the dominant frequency and duration of the strong motion phase of the excitation, respectively.
Effect of Functionalization of Reduced Graphene Oxide Coatings with Nitrogen and Sulfur Groups on Their Anti-Corrosion Properties
- Karolina Grajewska
- Jakub Karczewski
- Marek Lieder
2021 Pełny tekst Materials
Electrophoretic production of anticorrosion carbonaceous coatings on copper could be successfully performed by anodic oxidation of negatively charged graphene platelets suspended in an aqueous solution. The various platelets were synthesized by Hummer’s method followed by a hydrothermal reduction in the presence of NH4SCN which was expected to substitute some parts of graphene structure with nitrogen and sulfur groups. X-ray photoelectron spectroscopy analysis confirmed that the graphene precursors, as well as the coatings, contained typical nitrogen groups, such as pyridinic and pyrrolic, and sulfur groups, such as thiol, thiophene, or C-SO2 . However, due to oxidation during deposition, the qualitative and quantitative composition of the graphene coatings changed relative to the composition of the precursors. In particular, the concentration of nitrogen and sulfur dropped and some thiophene groups were oxidized to C-SO2 . Studies showed the functionalized coatings had a uniform, defect-free, hydrophobic, more adhesive surface than nonmodified films. The corrosion measurements demonstrated that these coatings had better protective properties than the ones without these heteroatoms. This behavior can be assigned to the catalytic activity of nitrogen towards oxidation of C-SO2 groups to C-SO3H with oxygen.
Effect of gas content in macropores on hydraulic fracturing in rocks using a fully coupled DEM/CFD approach
- Marek Krzaczek
- Michał Nitka
- Andrzej Tejchman-Konarzewski
2021 INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS
W pracy skupiono się na wpływie zawartości gazu w makroporach skał na proces szczelinowania hydraulicznego. Proces został zasymulowany przez połączenie metody elementów dyskretnych (DEM) z obliczeniową dynamiką płynów (CFD) w ramach dwuwymiarowych (2D) warunków izotermicznych. Mechaniczne zachowanie skały zostało zasymulowane za pomocą DEM, a CFD została wykorzystana do opisu zachowanie przepływu laminarnego, dwufazowego płynu szczelinującego (cieczy i gazu) we wcześniej istniejących i nowo powstałych szczelinach. Zmiany geometrii porów i pęknięć w matrycy skalnej zostały precyzyjnie odtworzone. W pełni sprzężone hydro-mechaniczne symulacje przeprowadzono na segmencie skalnym o uproszczonej mezostrukturze cząstek stałych pod wpływem odkształcenia płaskiego. Segment skalny zawierał jedno lub dwa gniazda wtryskowe. Wpływ początkowej zawartości fazy gazowej w makroporach na rozprzestrzenianie się szczelin hydraulicznych okreslono liczbowo dla różnych początkowych porowatości skał. Ponadto zbadano wpływ obecności różnych wcześniejszych nieciągłości w segmencie skalnym. Główne cechy pęknięcia segmentu skały w wyniku wtrysku płynu pod wysokim ciśnieniem zostały realistycznie odtworzone stosując proponowane podejście. Stwierdzono, że początkowa frakcja fazy gazowej w makroporach i istniejące wcześniej nieciągłości mają silny wpływ na przebieg szczelinowania hydraulicznego.
Effect of heat treatment on the diffusion intermixing and structure of the Cu thin ﬁlm on Si (111) substrate: a molecular dynamics simulation study
- Walery Pleczysty
- Ihor Shtablavyi
- Szymon Winczewski
- Kamil Rybacki
- B. Tsizh
- Stepan Mudry
- Jarosław Rybicki
2021 MOLECULAR SIMULATION
This work is devoted to the study of the diffusion process at the interface between copper films with a thickness of 2, 3, 4, 7 and 10 atomic monolayers and silicon substrate by molecular dynamics simulation method. For this purpose, the variation of the concentration of copper and silicon along the perpendicular direction to the interface was investigated. An analysis of the density profile along this direction made it possible to determine the melting point of the interface between copper and silicon. The atomic structure of the diffusion layer was compared with that of the bulk Cu3Si compound. Using the formalism pair correlation functions find partial coordination numbers distribution it was revealed the possibility of nucleation centres formation with the structure of the compound in the liquid state. This work will allow expanding knowledge about the process of atomic diffusion at the metal–semiconductor interface.
Effect of MAO coatings on cavitation erosion and tribological properties of 5056 and 7075 aluminum alloys
- Marek Szkodo
- Alicja Stanisławska
- Aleksandr Komarov
- Łukasz Bolewski
2021 Pełny tekst WEAR
Two ceramic coatings have been applied on 5056 and 7075 aluminum alloy by microarc oxidation (MAO) technology. The mass losses, surface morphologies and the phase constituents of the MAO coatings before and after cavitation tests were examined by means of digital scales, scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. In order to assess the impact of the mechanical properties of the surface layer on cavitation erosion resistance, hardness (H), reduced Young's modulus (E), surface elastic properties (Wel), surface toughness (KIC), structure continuity and resistance to delamination and cohesion forces were determined using nanoindentation and scratch tests. The results indicate that there is a correlation between cavitation erosion resistance and hardness, H/E ratio and surface elasticity.
Effect of pH on optical sensing with poly-L-lysine-modified nanodiamonds
- Maciej Jerzy Głowacki
- Monika Janik
- Mirosław Sawczak
- Anna Wcisło
- Paweł Niedziałkowski
- Mateusz Ficek
- Robert Bogdanowicz
2021
Nitrogen-vacancy (NV) centers are crystallographic defects which provide diamonds with unique physical properties. The centers are known for their intensive, time-stable fluorescence, and an electron spin, which exhibits long coherence time and may be manipulated using external stimuli. Nanodiamonds containing the NV centers are promising tools in biolabeling, biosensing, and drug delivery due to the aforementioned properties of the defects combined with a chemical inertness of a core and an easily functionalized surface of the diamond. Many biochemical reactions are pH-sensitive, therefore, in order to utilize the NV centers for monitoring of such processes, the pH-dependency of the properties of the nanodiamonds needs to be well-understood. Functionalization of the nanodiamonds’ surfaces with biological molecules undergoing pH-triggered changes of conformation, e.g. poly-L-lysine, could not only increase the particles’ biocompatibility and promote cell adhesion, but also possibly enhance pH-sensitivity. In the present study, an impact of pH on the fluorescence, a zeta potential, and a contact angle of the NV centers-containing nanodiamonds dispersed in liquid media is examined. The suspensions were made of commercially available, fluorescent diamond particles in an as-received, unmodified state, and after the poly-L-lysine had been attached to their surfaces via two different procedures – in aqueous, and anhydrous environment. Values of pH of dispersion media were specifically chosen to induce diverse conformation of the poly-L-lysine: from a fully relaxed conformation, through a state of being neither wholly extended, nor helical, to a complete α-helix conformation. The intensity of the photoluminescence emitted by the NV centers has been found to depend on the pH-triggered conformation of the poly-L-lysine attached to the surfaces of the nanodiamonds. The impact of the conformation of the poly-L-lysine on the electric charge of the nanoparticles has also been analyzed. This study confirms the potential of the nitrogen-vacancy centers for optical sensing of pH-triggered processes.
Effect of Pin Shape on Thermal History of Aluminum-Steel Friction Stir Welded Joint: Computational Fluid Dynamic Modeling and Validation
- Dmitry Olegovich Bokov
- Mohammed Abed Jawad
- Wanich Suksatan
- Mahmoud E. Abdullah
- Aleksandra Świerczyńska
- Dariusz Fydrych
- Hamed Aghajani Derazkola
2021 Pełny tekst Materials
This article studied the effects of pin angle on heat generation and temperature distribution during friction stir welding (FSW) of AA1100 aluminum alloy and St-14 low carbon steel. A validated computational fluid dynamics (CFD) model was implemented to simulate the FSW process. Scanning electron microscopy (SEM) was employed in order to investigate internal materials’ flow. Simulation results revealed that the mechanical work on the joint line increased with the pin angle and larger stir zone forms. The simulation results show that in the angled pin tool, more than 26% of the total heat is produced by the pin. Meanwhile, in other cases, the total heat produced by the pin was near 15% of the total generated heat. The thermo-mechanical cycle in the steel zone increased, and consequently, mechanical interlock between base metals increased. The simulation output demonstrated that the frictional heat generation with a tool without a pin angle is higher than an angled pin. The calculation result also shows that the maximum heat was generated on the steel side.
Effect of small quantities of potassium promoter and steam on the catalytic properties of nickel catalysts in dry/combined methane reforming
- Izabela Wysocka
- Aleksandra Mielewczyk-Gryń
- Marcin Łapiński
- Bartłomiej Cieślik
- Andrzej Rogala
2021 INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
Carbon dioxide and methane are two of the principal greenhouse gases. Reduction of their content in the atmosphere is currently the subject of much worldwide research. Dry and combined reforming of methane are effective methods of CO2 and CH4 utilization and production of synthesis gas (syngas) in chemical technology. Testing of catalysts that provide the desired H2/CO ratio and long operation time is one of the critical aspects of syngas production and the focus of much study. In this study, K-promoted Ni/MgAl2O4 catalysts prepared using a co-precipitation-impregnation method with different K/Ni ratios (range of 0–0.15) were examined in dry reforming of methane (DRM). The obtained catalysts were characterized using X-ray diffractometry (XRD), atomic emission spectrometry (MP-AES), Brunauer–Emmett–Teller (BET) specific surface area, BJH pore size distribution, TEM imaging, analysis of reducibility H2-TPR, infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Hammet basicity analysis, thermogravimetric analysis (TG) and elemental carbon-hydrogen-nitrogen analysis (CHN). Promotion of nickel catalysts with potassium led to changes in nickel distribution, metal-support interactions and deceleration of carbon deposition while enhancing sorption of carbon dioxide and reduction of nH2:CO to 0.5 for 0.7 K–Ni/MgAl2O4 catalyst. To obtain the required H2:CO ratio close to unity a study on the effect of steam in inlet stream was performed. It was found that maintaining inlet stream composition equal CH4:CO2:H2O = 1.0:1.0:0.1 obtained an H2:CO ratio close to unity.
Effect of surface on the flexomagnetic response of ferroic composite nanostructures; nonlinear bending analysis
- Mohammad Malikan
- Victor Eremeev
2021 Pełny tekst COMPOSITE STRUCTURES
Our analysis incorporates the geometrically nonlinear bending of the Euler-Bernoulli ferromagnetic nanobeam accounting for a size-dependent model through assuming surface effects. In the framework of the flexomagnetic phenomenon, the large deflections are investigated referring to von-Kármán nonlinearity. Employing the nonlocal effects of stress coupled to the gradient of strain generates a scale-dependent Hookean stress-strain scheme related to the small scale. Taking into account the supports of the nanobeam in two cases, that is, totally fixed and hinged, the deformations are predicted. A constant static lateral load is postulated uniformly along the length of the beam, which forces the deformation. As the analysis is based on the one-dimensional media, the electrodes are embedded so that they give off a transverse magnetic field creating a longitudinal force. The newly developed mathematical model is computed by means of the differential quadrature method together with the Newton-Raphson technique. The computational section discusses and reveals the numerical results in detail for the characteristics and parameters involved in the design of beam-like magnetic nanosensors. As shown later, the conducted research presents that there is a strong linkage between the surface effect and the flexomagneticity behavior of the bulk.
Effect of synthesis method parameters on properties and photoelectrocatalytic activity under solar irradiation of TiO2 nanotubes decorated with CdS quantum dots
- Aleksandra Pieczyńska
- Paweł Mazierski
- Wojciech Lisowski
- Tomasz Klimczuk
- Adriana Zaleska-Medynska
- Ewa Siedlecka
2021 Journal of Environmental Chemical Engineering
The growing research interest on photoelectrocatalysis has encouraged the search for new materials with high activity and the development of methods for their synthesis. The successive ionic layer adsorption and reaction (SILAR) method is an effective way to synthesize materials with photoelectrocatalytic (PEC) properties that are active under visible radiation. Therefore, studies on the impact of the parameters of the SILAR method on the properties and PEC activity of TiO2 nanotubes sensitized with CdS quantum dots (QDs) were conducted. PEC activity was determined based on the efficiency of ifosfamide (IF) degradation, which is currently one of the most commonly detectable anticancer drugs in aquatic environment. The highest IF PEC degradation rate (0.0184 min 1) and the highest TOC removal (48%) was achieved with the CdS-Ti/TiO2_NO3 _0.1M_3c_60s photoelectrode. Among the SILAR parameters, the highest impact on the PEC IF degradation efficiency had the concentration of the Cd precursor, as well as the number and time of the cycles. Our studies showed that CdS-Ti/TiO2 nanocomposites exhibited more than twice higher photocatalytic and PEC IF degradation efficiency than pristine Ti/TiO2 under UV–Vis irradiation. In addition, the PEC mechanism of IF degradation using pristine Ti/TiO2 and CdS-Ti/TiO2 was compared, from which it was concluded that the higher PEC activity of the nanocomposites is due to the greater contribution of h+ and the generation of other oxidants caused by the presence of CdS QDs. Based on the identified degradation products, a pathway for PEC IF degradation was also proposed.
Effect of Temperature and Nanoparticle Concentration on Free Convective Heat Transfer of Nanofluids
- Janusz Cieśliński
- Sławomir Smoleń
- Dorota Sawicka
2021 Pełny tekst ENERGIES
A theoretical analysis of the influence of temperature and nanoparticle concentration on free convection heat transfer from a horizontal tube immersed in an unbounded nanofluid was presented. The Nusselt (Nu) number and heat transfer coefficient were parameters of the intensity of the convective heat transfer. For free convection, the Nu number was a function of the Rayleigh (Ra) number and Prandtl (Pr) number. The Rayleigh (Ra) number and Prandtl (Pr) number were functions of the thermophysical properties of nanofluids. The thermophysical properties of nanofluids varied with temperature and nanoparticle concentration. Therefore, an analysis was conducted to evaluate the effects on the performance of nanofluids due to variations of thermal conductivity, viscosity, thermal expansion, density, and specific heat, which are functions of nanoparticle concentration and temperature. Water- and ethylene glycol (EG)-based nanofluids with dispersed alumina (Al2O3) nanoparticles at mass concentrations of 0.01%, 0.1%, and 1% were considered. Calculated Nu numbers and heat transfer coefficients were compared with experimental values taken from the published literature.
Effect of the Cavitation Generation Unit Structure on the Performance of an Advanced Hydrodynamic Cavitation Reactor for Process Intensifications
- Xun Sun
- Weibin You
- Xiaoxu Xuan
- Li Ji
- Xingtao Xu
- Guichao Wang
- Shan Zhao
- Grzegorz Boczkaj
- Joon Yong Yoon
- Songying Chen
2021 Pełny tekst CHEMICAL ENGINEERING JOURNAL
The advanced rotational hydrodynamic cavitation reactors (ARHCRs) that appeared recently have shown obvious advantages compared with conventional devices in process intensifications. In ARHCRs, the cavitation generation unit (CGU) located on the rotor and stator basically determines their performance. For the first time, the present study investigated the effect of the CGU structure on the performance of a representative ARHCR by utilizing computational fluid dynamics. The amount of generated cavitation and required torque of the axis for various shapes, diameters, interaction distances, heights, and inclination angles of the CGU were analyzed. The results indicate that the interaction-type ARHCR (cavitation is generated by stator-rotor interaction) was far superior to the non-interaction type one. In addition, the hemisphere-shaped CGU demonstrates the best performance compared with that with cone-cylinder, cone, and cylinder shapes. Moreover, by evaluating the effects of various geometrical factors, the hemisphere-shaped CGU with a diameter of 12 mm, interaction distance of 1 mm, height of 1 mm, and inclination angle of 10° achieved the highest performance. The reasons leading to different performance were elaborated in accordance with the flow and pressure field distributions, as well as the generated cavitation patterns. The findings of this work can strongly support the fundamental understanding, design, and application of ARHCRs for process intensifications.
Effect of the let-through energy of overcurrent protective devices on the temperature of conductors during short-circuits
- Stanisław Czapp
- Daniel Kowalak
2021 Pełny tekst Przegląd Elektrotechniczny
The scope of the verification of low-voltage systems covers the earth fault loop impedance measurement. This measurement is usually performed with the use of low-value current meters, which force a current many times lower than the one occurring during a real short-circuit. Therefore, the international standard recommends consideration of the increase of resistance of conductors with the increase of temperature, which may occur during short-circuits. This paper analyses the temperature rise of the conductors during short-circuits, taking into account the let-through energy of protection devices. The analysis has shown that in typical circuits the temperature rise of conductors is not significant.
Effect of Thermal Treatment and Erosion Aggressiveness on Resistance of S235JR Steel to Cavitation and Slurry
- Alicja Krella
- Dominika Zakrzewska
- Marta Buszko
- Artur Marchewicz
2021 Pełny tekst Materials
S235JR steel is used in many applications, but its resistance to the erosion processes has been poorly studied. To investigate this resistance, cavitation, and slurry erosion tests were conducted. These tests were carried out at different erosion intensities, i.e., different flow rates in the cavitation tunnel with a system of barricades and different rotational speeds in the slurry pot. The steel was tested as-received and after thermal treatment at 930 °C, which lowered the hardness of the steel. To better understand the degradation processes, in addition to mass loss measurements, surface roughness and hardness were measured. Along with increasing erosion intensity, the mass loss increased as well. However, the nature of the increase in mass loss, as well as the effect of steel hardness on this mass loss, was different for each of the erosion processes. In the cavitation erosion tests, the mass loss increased linearly with the increase in flow velocity, while in the slurry tests this relationship was polynomial, indicating a strong increase in mass losses with an increase in rotational speed. Cavitation erosion resulted in stronger and deeper strain hardening than slurry. Surface damage from cavitation erosion tests was mainly deep pits, voids, and cracks during the slurry tests, while flaking was the most significant damage.
Effect of TiO2 Concentration on Microstructure and Properties of Composite Cu–Sn–TiO2 Coatings Obtained by Electrodeposition
- Aliaksandr Kasach
- Dmitry Kharitonov
- Andrei Paspelau
- Jacek Ryl
- Denis Sergievich
- Ivan Zharskii
- Irina Kurilo
2021 Pełny tekst Materials
In this work, Cu–Sn–TiO2 composite coatings were electrochemically obtained from a sulfate bath containing 0–10 g/L of TiO2 nanoparticles. The effect of TiO2 particles on kinetics of cathodic electrodeposition has been studied by linear sweep voltammetry and chronopotentiometry. As compared to the Cu–Sn alloy, the Cu–Sn–TiO2 composite coatings show rougher surfaces with TiO2 agglomerates embedded in the metal matrix. The highest average amount of included TiO2 is 1.7 wt.%, in the case of the bath containing 5 g/L thereof. Composite coatings showed significantly improved antibacterial properties towards E. coli ATCC 8739 bacteria as compared to the Cu–Sn coatings of the same composition. Such improvement has been connected with the corrosion resistance of the composites studied by linear polarization and electrochemical impedance spectroscopy. In the bacterial media and 3% NaCl solutions, Cu–Sn–TiO2 composite coatings have lower corrosion resistance as compared to Cu–Sn alloys, which is caused by the nonuniformity of the surface.
Effect of urea and glycine betaine on the hydration sphere of model molecules for the surface features of proteins
- Marcin Stasiulewicz
- Aneta Panuszko
- Maciej Śmiechowski
- Piotr Bruździak
- Paweł Maszota
- Janusz Stangret
2021 JOURNAL OF MOLECULAR LIQUIDS
Water properties may significantly affect protein stability. Osmolytes are compounds that intrinsically affect water in many different ways and thus can influence proteins with this type of indirect mechanism. In this study, we characterize water properties in ternary solutions: model–water–osmolyte, with two model molecules: N-methylacetamide (NMA) and dimethyl sulfoxide (DMSO) and two osmolytes: glycine betaine (TMG)and urea. We focus primarily on the water affected simultaneously by two solutes and propose a new FTIR-based experimental approach to study their properties. Our findings, supported by DFT and AIMD calculations, indicate that TMG promotes hydration cage enhancement around both model molecules. However, direct model–TMG interactions are rare. Simultaneously, urea interacts with them directly, displacing water molecules and weakening the hydrogen bonds in overlapped hydration spheres. The latter behavior results from the cooperativity loss between hydrophobic and hydrophilic-type hydration exhibited by the model molecules in the absence of urea. Relating the obtained results to protein systems, in the case of both osmolytes, the potential mechanism of stabilization–destabilization of these biomolecules is enthalpy-driven