Effect of Nanocrystalline Diamond Films Deflection on Wear Observed in Reciprocating Sliding Tests

The present study deals with the tribological behavior of nanocrystalline diamond (NCD) films. The diamond films were deposited by microwave plasma enhanced chemical vapor deposition (MPCVD) in methane/hydrogen/air plasma on the Si(100) substrates. The tribological properties were studied by reciprocal sliding tests against Si3N4 balls. The depth profiles and surface morphology of the wear scars were investigated by means of mechanical profilometry and scanning electron microscopy (SEM). Various adaptation processes occur between contacting surfaces including asperity polishing, formation of carbonaceous tribolayer and ripple patterns on the wear scar surfaces. The film deflection is the specific form of adaptation decreasing contact pressure and, therefore, the damage (including wear) of both counter bodies. The deflection of NCD films in sliding tests can be related with the effect of fatigue

Polishing of Black and White CVD Grown Polycrystalline Diamond Coatings

Microwave plasma CVD growth can produce black and white varieties of polycrystalline diamond (PCD), depending on their as-grown purity. These two types of PCDs have been polished by mechanical and chemo-mechanical polishing respectively. It has been observed that initial roughness of 2.21μm for white PCD can be brought down to 175 nm after 70 hours of combined polishing, whereas, 85 hours of combined polishing could bring down the high initial roughness of 11.2μm for black PCD down to 546 nm at the end. Although, the material that was removed during polishing was higher for the black variety of PCD but it had lower polishing rate of 4nm/hr than white PCD (13nm/hr) during chemo-mechanical polishing. Such differential polishing rate was due to harder top polished surface of the black diamond than the white diamond. The nanoindentation study on the polished PCD surfaces revealed that the black PCD has a final nanohardness of 32.58±1 GPa whereas the white variety PCD had a polished surface nanohardness of 28.5±2 GPa. More conversion of diamond surface into harder amorphous sp3 than softer graphite during polishing action may have resulted such slow rate of anisotropic polishing for black diamond than white diamond

Morphology of Diamond Layers Grown on Different Facets of Single Crystal Diamond Substrates by a Microwave Plasma CVD in CH4-H2-N2 Gas Mixtures

Epitaxial growth of diamond films on different facets of synthetic IIa-type single crystal (SC) high-pressure high temperature (HPHT) diamond substrate by a microwave plasma CVD in CH4-H2-N2 gas mixture with the high concentration (4%) of nitrogen is studied. A beveled SC diamond embraced with low-index {100}, {110}, {111}, {211}, and {311} faces was used as the substrate. Only the {100} face is found to sustain homoepitaxial growth at the present experimental parameters, while nanocrystalline diamond (NCD) films are produced on other planes. This observation is important for the choice of appropriate growth parameters, in particular, for the production of bi-layer or multilayer NCD-on-microcrystalline diamond (MCD) superhard coatings on tools when the deposition of continuous conformal NCD film on all facet is required. The development of the film morphology with growth time is examined with SEM. The structure of hillocks, with or without polycrystalline aggregates, that appear on {100} face is analyzed, and the stress field (up to 0.4 GPa) within the hillocks is evaluated based on high-resolution mapping of photoluminescence spectra of nitrogen-vacancy NV optical centers in the film

ORIGINS, ESTABLISHMENT AND TRADITION OF THE RESEARCH WORK IN LESGAFT NATIONAL STATE UNIVERSITY OF PHYSICAL EDUCATION, SPORT AND HEALTH

The article highlights the stages of formation, traditions and achievements of the research and pedagogical schools at Lesgaft University. The principle of teaching and research unity laid by the University founder Petr Lesgaft remains the base for modern scientific research and pedagogical activity at the University. The paper dwells on the perspectives of research within the cluster «Translational Medicine »

Improvement of ecological parameters of diesel engines work by application of catalysts

Objectives of the presented research are: o improvement of the environmental parameters of engines through decrease of detrimental substances concentration in exhaust, which occurs due to more complete combustion of fuel; o removal of carbon deposit from combustion chambers, injection jets and exhaust path; o preservation of the exhaust chamber design parameters and of the design condition for the fuel combustion; o stabilization of the engine operation under any load; o decrease of the engine cylinder-piston group parts deterioration by 70%; o decrease of fuel consumption amounting to 6%, 5÷7% increase of efficiency factor; o reduction of thermal and mechanical stresses and of deterioration rate of the cylinder- piston-group and crank-mechanism-group parts; o extension of the engine maintenance and repair cycle length accompanied by corresponding labour and cost reductions. Application area: trucks, public transport, passenger cars, rail-road diesel installations, river and ship power installations, self-contained diesel installations, quarry transport. Concentration of the additive is 0.01% volume, i.e. 100 ml per 1000 liters of fuel, neither physical nor chemical properties of fuel are changed. Additive "0010" decreases the harmful substances concentration in exhaust, as compared to the untreated fuel, by (percent): Smoke up to 90 Nitrogene oxides 12÷50 Carbon oxide 20÷85 Hydrocarbons 15÷65 Benz(a)pyrene 25÷40 Aldehydes 15÷60 Sulphur oxides up to 60 Aerosol up to 20 Oil mist up to 20 The State Committee of Russian Federation for Standardization issued the necessary permissions and certificates of approval for diesel fuels "DF EURO", technicals pecifications TY 0251-002-46978376-99

THE STATE OF LOCAL IMMUNITY OF THE ORAL CAVITY IN PERSONS WITH DISEASES OF MUCOUS MEMBRANE AND THE DIFFERENT DEGREE OF COLONIZATION OF THE STOMACH BY HELICOBACTER PYLORI BEFORE AND AFTER TREATMENT

The article presents the results of estimation of efficiency of complex treatment of diseases of the mucous membranes of the oral cavity in individuals with low, medium, high degrees of contamination of the stomach Helicobacter pylori structure of Helicobacter pylori-associated diseases of the mucous membranes of the oral cavity, assessment of the state of local immunity of oral cavity in this category of patients. The proposed scheme of general and local treatment of diseases of the mucous membranes of the oral cavity for these patients, the main stages of which should be: normalization of the microbial landscape of the mucous membranes of the oral cavity and mucous membranes of the gastrointestinal tract, restoration of acid-base balance of the oral cavity; prevention of reinfection of the mucous membranes of the oral cavity and gastrointestinal tract Helicobacter pylori

Industrial cleaning of fuel by means of porous polymeric materials

W swojej poprzedniej publikacji autorzy skupili się na problemie regeneracji olejów hydraulicznych metodą udoskonalonej filtracji [1]. Nie mniej ważnym zagadnieniem jest utrzymanie jakości paliw silnikowych na całej drodze dystrybucji od producenta do użytkownika. Główną przyczyną niskiej jakości paliwa jest naruszenie technologii produkcji, transportu i przechowywania paliwa, a nawet tankowania środków transportu i maszyn budowlanych. W Związku Radzieckim przypadki nieprzestrzegania wymagań stawianych jakości paliwa były nonsensem, ponieważ jego produkcja i realizacja znajdowała się pod państwową kontrolą. Wraz z przejściem do gospodarki wolnorynkowej możliwość produkcji i przechowywania paliw silnikowych uzyskały wszystkie chętne osoby fizyczne i podmioty gospodarcze [2]. Uciążliwym problemem jest zanieczyszczenie paliw przez związki smoliste, wodę, domieszki stałe i biozanieczyszczenia w procesie przechowywania, transportu i dystrybucji do hurtowni i stacji paliwowych [2]. Zanieczyszczenia działają w sposób skojarzony i nawzajem się nasilają, pogarszając jakość paliw w drodze do odbiorcy. Na przykład, występowanie wody sprzyja utlenianiu substancji ropopochodnych i rozwojowi w nich biozanieczyszczeń na granicy faz paliwo-woda. Obecność wilgoci zmniejsza wartość opałową paliwa i inicjuje korozję układu paliwowego, natomiast w obecności domieszek stałych obserwuje się zwiększone mechaniczne zużycie pomp paliwowych i wtryskiwaczy, zakleszczanie nurników i zatykanie dysz [3]. W niektórych układach paliwowych wilgoć powoduje zniszczenie filtru doczyszczania paliwa. Zanieczyszczenia stałe, zawierające w większości przyapadków metale w postaci produktów korozji, są katalizatorami utleniania, w trakcie którego powstają kwasy i różne związki smoliste i asfalteny. Z kolei kwasy powodują korozję zbiorników przewodów i armatury podczas przechowywania i przepompowania paliw, zwiększając w ten sposób ilość zanieczyszczeń stałych, a także sprzyjając tworzeniu warunków do polimeryzacji związków smolistych i powstawania statecznych układów koloidalnych. W wyniku działalności zanieczyszczeń biologicznych (grzybów i bakterii) zachodzi nie tylko gromadzenie szkodliwej biomasy, powodującej zakłócenia w pracy układu paliwowego, ale także utlenianie paliw z powstawaniem kwasów organicznych. Utrzymanie wysokiej jakości paliwa wymaga kompleksu środków przewidujących usunięcie wszystkich lub większości z wymienionych zanieczyszczeń. Tradycyjnie na szeroką skalę stosuje się tylko filtrację mechaniczną. Zastosowanie separatorów odśrodkowych w celu usunięcia wody i zanieczyszczeń stałych ograniczone jest z powodu złożoności i wysokich kosztów sprzętu, jak również jego skomplikowanej i pracochłonnej konserwacji i eksploatacji. Filtry koalescencyjne tracą sprawność w obecności znacznej ilości zanieczyszczeń mechanicznych. Natomiast odstojniki stosowane mogą być tylko jako środek do wstępnego oczyszczania paliwa.Longevity and reliability of work of engines in many respects are determined by the quality of used fuels. The presence of water, mechanical impurities, acids and biological pollution in oil leads to increased mechanical and corrosion wear as well as to failures of the engines. Using bad fuels is a serious environmental problem. This is caused both by possible environmental pollution and by huge quantity of used fuels. The problem of the complex cleaning of fuels can be solved most effectively by the use of porous polymeric compositions as the filtering material. Disadvantages of this material are non-uniformity of porous structure, and also infringement of form and size of a filtering element after regeneration with the subsequent drying. The new type of a filtering material has no such disadvantages. It is received by washing technology from reactionary mass away of water-soluble structural additives. This material is characterized by the uniform porous structure, possibility of obtaining the filtering elements of any form and sizes. It is obtained by the possibility to operate such characteristics as water absorption, size of pores, general porosity, strength, elasticity, etc. The material "APRISORB", created using this technology, not only effectively absorbs water and mechanical impurities but also continuously cleans itself from the accumulated water (Fig. 1, 2). Collecting efficiency was determined for dust quartz characterized with the specific surface area of 10500 sm2/g (Fig. 3). Depending on the type of the filtering element a pressure difference with the nominal charge was varied from 10.6 to 17.6 kPa, and the collecting efficiency from 77.0 to 99.8%. Researches showed that on the water-oil border were formed the steady colloidal structures. These systems contain a plenty of microorganisms and products of their vital activity. There were isolated cultures of microorganisms, including cultures of the simplest fungi and cultures of bacteria (Fig. 4). Among them are Pseudomonas aeruginosa, Cladosporium reinae and Candida. Specifically, these microorganisms participate in worsening of the quality of fuels. The filtration of oils polluted by microorganisms through the filter made of APRISORB, ensures effective clearing at a level of 99.4÷99.9%. The test results of new filters convincingly prove the perspectives of their use for cleaning of any fuels: from the stage of fuel manufacturing up to operation of cars and ships engines (Fig. 5-10)