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    Wyświetlanie 1-4 z 4
    Tytuł:
    Review of possibilities of increasing the thickness of an anti-wear coating on piston rings by using specifically designed physical vapour deposition process
    Autorzy:
    Skorupa, P.
    Kaźmierczak, A.
    Błasiński, T.
    Borkowska, J.
    Krakowian, K.
    Łoza, Ł.
    Powiązania:
    https://bibliotekanauki.pl/articles/245017.pdf
    Data publikacji:
    2015
    Wydawca:
    Instytut Techniczny Wojsk Lotniczych
    Tematy:
    coatings
    anti-wear
    internal combustion engine
    PVD
    CVD
    thickness
    DLC
    Opis:
    The super-hard, anti-wear amorphic coatings based on carbon-like diamond (called DLC) show a promising direction in automotive industry, mainly in terms of decreasing friction coefficient in parts of internal combustion engine. However, the technology of producing DLC-coated parts, which is most often chemical vapour deposition (CVD) or physical vapour deposition (PVD) is proven to be still not perfect for achieving desired characteristics of the coating. The thickness of a coating is the main issue one should strive to improve, as the PVD methods produce films as thin as few micrometres. In such case, the coating is not only exposed to cracking, but also pitting is possible to happen. This is proven to be highly undesirable and unacceptable for this process. In addition, in case of thin films, the adhesion to the base is often too weak, despite the coating itself being extremely durable and hard. In this article, a theoretical ways to improve the process of coating are presented. The process itself is described, the achievable parameters are defined and the possible improvements are stated. The research made for the purpose of this article will be further exploited to design a process allowing creating the coating for testing of the best possible characteristics.
    Źródło:
    Journal of KONES; 2015, 22, 4; 281-286
    1231-4005
    2354-0133
    Pojawia się w:
    Journal of KONES
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    The impact of the energy state of the surface of friction pairs on the friction and wear in internal combustion engines
    Autorzy:
    Borkowska, J.
    Kaźmierczak, A.
    Krakowian, K.
    Cienciała, M.
    Skorupa, P.
    Łoza, Ł.
    Powiązania:
    https://bibliotekanauki.pl/articles/245015.pdf
    Data publikacji:
    2015
    Wydawca:
    Instytut Techniczny Wojsk Lotniczych
    Tematy:
    friction pairs
    top layer of surface
    sealing function
    piston ring
    cylinder sleeve
    combustion engine
    tangential force
    friction coefficient
    molecular structure
    bond
    tribology
    Opis:
    The elements creating a friction pairs are described to be very difficult in terms of defining all optimal parameters in an unequivocal way. The research on stability of friction pairs is focused on the surface and the top layer of surface in the parts concerned. The main goal is to find new design solutions and materials, thereby achieving one million kilometers of mileage to main repair in the case of internal combustion engines. The biggest structural difficulties are noticeable in friction pairs where it can be observed sliding and returning motion, which is also connected with sealing function. A typical example of such pair is piston ring – cylinder sleeve in piston – rings - cylinder unit in an internal combustion engine. Engineers are currently seeking an additional factor, which would enable gaining the reduction of tangential force by reducing the friction coefficient in elements of friction pair during operations. The surface free energy may be such factor - it results from molecular structure and nature of the bonds between the molecules present in the material. Components of surface free energy determine the tribological properties of the material, which is reflected in the stability of the units. Energy state of the surface, which is connected with chemistry and characteristics in the material, is the first step to consider about the impact on wearing in internal combustion engine. This is the main topic of this article.
    Źródło:
    Journal of KONES; 2015, 22, 4; 37-41
    1231-4005
    2354-0133
    Pojawia się w:
    Journal of KONES
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Various designs of the two-stroke engine heads with the valve flushed system
    Autorzy:
    Łoza, Ł.
    Kaźmierczak, A.
    Borkowska, J.
    Skorupa, P.
    Krakowian, K.
    Cienciała, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/242546.pdf
    Data publikacji:
    2015
    Wydawca:
    Instytut Techniczny Wojsk Lotniczych
    Tematy:
    engine
    two-stroke
    internal combustion
    valve flushed system
    piston-controlled cam
    high petrol consumption
    oil in the petrol
    toxic by-products
    loud noise
    uneven running
    low efficiency
    Opis:
    The two-stroke engines have never acquired the popularity of the four-stroke engines due to their inherent performance limitations. The tasks of many engineering teams were to find the basic causes, which resulted in the inferior performance of these engines. Today’s task is to build a two-stroke engine whose performance could match that of a four-stroke engine in areas of common use. The most typical performance problems of a two-stroke engine are high petrol consumption caused by low efficiency, toxic by-products of combustion being emitted into the atmosphere (caused by oil present in the petrol), and uneven and loud engine noise. The greatest challenge is to achieve a good chamber purge during one stroke in which the fresh fuel mixture flows through the piston-controlled inlet port while at the same time the fumes are being exhausted through the outlet port. This in contrast with the four-stroke engines where the intake and exhaust are each done with two separate strokes. From the energy point of view, the two-stroke engine is not efficient because a certain amount of fresh fuel is being wasted in the exhaust fumes. We propose to replace the piston-controlled cam with the valve-flushed system, which will cause the combustion process to become more efficient. The purpose of this paper is to present various designs of the engine heads and analyse their performance. The goal of this proposal is to choose the best combination of these engine heads in order to achieve the optimum overall engine performance.
    Źródło:
    Journal of KONES; 2015, 22, 4; 187-190
    1231-4005
    2354-0133
    Pojawia się w:
    Journal of KONES
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    On the nature of silver ions in complex media
    Autorzy:
    Loza, K.
    Diendorf, J.
    Sengstock, C.
    Koller, M.
    Epple, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/286036.pdf
    Data publikacji:
    2014
    Wydawca:
    Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Polskie Towarzystwo Biominerałów
    Tematy:
    silver ions
    biocides
    biomaterials
    Opis:
    Antimicrobial biocides are commonly used to present the growth of bacteria on surfaces and within materials. They are typically added in small quantities to many applications to prevent bacterial growth on the treated object. Silver is increasingly used in many applications due to the aim to replace organic chemical agents by inorganic additives. Examples of applications are bacteriostatic water filters for household use or swimming pool algaecides and numerous devices, ranging from consumer commodities like mobile phones, refrigerators, and clothes to medical devices like catheters, implant surfaces, and plasters. To meet the diversity of application types, many different forms of silver compounds have been developed to serve this market. In particular, there is little information on the types of transformations that silver nanoparticles will undoubtedly undergo in real, complex environments during long-term aging, and the impact of these transformations on their distribution in the environment, bioavailability, and toxicity potential. The biocidal action results from the interaction of silver ions with bacteria. The most potent compounds for a high silver release are soluble silver salts like silver nitrate or silver acetate. These are fully water soluble with a high silver ion release rate. Therefore they are often used as control in cell experiments to elucidate the biological effect of silver nanoparticles. However, in the case of free silver nanoparticles the interactions can be more complex and catalytic reactions on the particle surface which depend on the size and shape of the nanoparticles can render the system very complex. If AgNO3 is used as control, it is tacitly assumed, that the free silver ion concentration is the same as that in the added AgNO3. This obviously cannot be true because of the presence of a whole set of proteins, biomolecules and inorganic ions like Cl- and H2PO4- in the biological medium. These will react with the silver ions in one or the other way. We report on experiments on the behaviour of silver ions in biologically relevant concentrations in different media, from physiological salt solution over phosphate-buffered saline solution to cell culture media. For dissolution and immersion experiments PVP-coated silver nanoparticles were synthesized by reduction with glucose in the presence of PVP. The final silver concentration in all dispersions was determined by atomic absorption spectroscopy. The dissolution of silver nanoparticles was followed in long-term experiments out of a dialysis tube which was permeable only for silver ions. In case of immersion experiments, the nanoparticles and all precipitates were isolated by ultracentrifugation, redispersed in pure water and again subjected to ultracentrifugation. The particles were analyzed by scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray powder diffraction. The dissolution requires the presence of dissolved oxygen. If no oxygen is present, only a very small fraction of silver is dissolved, possibly by traces of oxygen in the experimental setup. An oxidizing agent like H2O2 clearly enhances the dissolution. The presence of NaCl, either in pure form or as PBS, strongly slows down the dissolution, probably due to silver chloride formation. Cysteine has a clearly inhibiting effect with almost no dissolution of the silver nanoparticles whereas glucose has a decelerating effect but leads to a similar final dissolved fraction. This suggests that cysteine adsorbs onto the silver nanoparticle surface with its thiol group and prevents the oxidation. In contrast, glucose slows down the dissolution, but clearly did not prevent the oxidation on a longer time scale. We have extended the studies by mixing silver nanoparticle dispersions with different media of increasingly biological nature. The solutions/dispersions were stirred for equilibration and then subjected to ultracentrifugation. All precipitates and nanoparticles were isolated by this way and then analyzed. The results show that both initially present silver ions and released silver ions are mainly precipitated as AgCl if chloride is present. Only in the absence of chloride, glucose is able to reduce Ag+ to Ag0. The initially present silver nanoparticles were recovered in all cases. Silver phosphate was not observed in any case, probably due to the moderate pH (around 7) at which phosphate is mostly protonated to hydrogen phosphate and dihydrogen phosphate. We can conclude that released silver ions precipitate mostly as AgCl in biological media, and that most cell culture studies where silver ions are used as control are in fact studying the effect of colloidal silver chloride on the cells. To prove this assumption, human mesenchymal stem cells (hMSC) were cultured in the presence of silver chloride nanoparticles (diameter 120 nm), and the viability of the cells was analyzed by fluorescence microscopy. In general, we clearly observed that pure silver nanoparticles have lower toxicity to hMSC compared to silver chloride nanoparticles with a comparable total silver dose. Silver acetate in the biological medium had a comparable toxicity to hMSC compared to silver chloride nanoparticles with the same total silver dose.
    Źródło:
    Engineering of Biomaterials; 2014, 17, no. 128-129; 80
    1429-7248
    Pojawia się w:
    Engineering of Biomaterials
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-4 z 4

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