Antibacterial properties of PMMA functionalized with CuFe2O4/Cu2O/CuO nanoparticles

We have prepared a composite thin coating by incorporation of CuFe2O4/Cu2O/CuO nanoparticles in polymethyl methacrylate (PMMA) matrix by using the solution casting method. The electrical explosion of two twisted wires (EETW) was used to obtain multicomponent CuFe2O4/Cu2O/CuO nanoparticles with an average particle size of 20–70 nm. The microscopic studies showed that the nanoparticles in the composite coatings are evenly distributed. However, nanoparticles are strongly agglomerated as the powder concentration in the coating increases to 5 wt.% and 10 wt.%, as the size of particle agglomerates increases to 50 and 100 µm, respectively. Therefore, nanoparticles were pre-treated with ultrasound when introduced into the PMMA matrix. The thermal stability of the composite coating does not change with the introduction of CuFe2O4/Cu2O/CuO nanoparticles in the amount of 5 wt.%. The inclusion of nanoparticles in the PMMA matrix significantly enhances its antibacterial activity. The addition of 5 wt.% nanoparticles inhibited the growth of E. coli by 100% and the growth of MRSA by 99.94% compared to pure PMMA already after 3 h of exposure of bacteria on the surface of the composites. This research provides an easy-to-manufacture and cost-efficient method for producing a uFe2O4/Cu2O/CuO/PMMA composite coating with a broad application as an antibacterial material

The low-temperature sol-gel synthesis of metal-oxide films on polymer substrates and the determination of their optical and dielectric properties

Photoactive, optically transparent heterostructures from silver nanowires and titanium dioxide were obtained by the sol-gel method on the surface of a polyethylene terephthalate film. The characteristics of optical transmission on the wavelength and those of dielectric permittivity, conductivity and dissipation on frequency in the range of 25–1,000,000 Hz were investigated

The effect of cultivation conditions on the growing processes of grape plants

One of alternative ways to maintain valuable genetic material is to develop optimal conditions for cultivation in an in vitro system. The goal was to evaluate the condition of plants based on changes in the shoot length indicator in order to explore the maintaining mode of the collection. We took the experimental samples from the “Vegetating collection of plants in vitro of promising varieties and clones of grapes”: 13 local Crimean varieties and 9 varieties of the Institute Magarach selection. Plant containing culture bottles were in the cold storage without internal lighting at 10-12°C for 6 months. The cultivation findings demonstrated that grape varieties differed in viability and intensity of morphogenesis. Moreover, after storage, they had a high regenerating ability of the buds

Glass micro balls based on glass domestic waste for road construction

The glass micro balls based on glass domestic waste for road construction were obtained. Glass micro balls will reduce the contamination of road marking and increase its light-reflective ability at night. Colorless and colored container glass, as well as lead crystal, was chosen as the starting material for producing glass micro balls. An electric arc plasmotron UPU-8M was used to produce glass micro balls. Pre-crushed fractionated glass together with plasma-forming gas – argon was fed to the powder feeder and from the feeder to the plasma burner. Under the influence of high plasma temperatures, about 9000-12000K, the particles were melted, followed by cooling in the outgoing flow of plasma-forming gases. Due to high-temperature plasma exposure, partial evaporation of alkaline oxides and lead oxide occurred. Glass micro balls were enriched with the oxides of silicon, aluminum and calcium. This helped to increase the acid and alkali resistance of glass micro balls. The micro hardness, density, and refractive index of glass micro balls were studied. It is shown that glass micro balls have an ideal spherical shape and are x-ray amorphous. Glass micro balls are recommended for use in road construction as a reflective element of road marking

Estimation of Damage Development and the TIME of Failure of Cutting Inserts Made of Hard Alloys and Superhard Composites by Chemography Methods

The results of theoretical and experimental studies aimed at identifying hidden defects in the structure of hard alloys and superhard composites used in the manufacture of cutting tools in order to control and predict gradual and sudden failures of cutting inserts.Damage control of cutting inserts is carried out by microscopic analysis. Deeper damage to the structure can be detected using the method of chemographic imaging. The proposed method is based on obtaining photographs of the oxidative reactions of materials of ultra-low concentrations occurring on the surface of solids under thermobaric loading.Before the moment of a sharp release of the energy of destruction, chemical processes of ultra-low concentrations are activated. Chemography allows to fix the zones where the incipient microcracks and microdefects are ready to actively develop, which can lead to the onset of macrodamage and failure to work.The chemographic image of the plate obtained as a result of the study is compared with the reference sample, as a result of which it is possible to assess the initial defect state of the material and predict the further period of the plate's operation.The criterion for the existing defects and imperfections in the structure is the change in the blackness index of the chemographic image, the minimum value of which indicates a minimum of structural defects and internal defects in the material under study.The results allow to propose a new method for controlling the surface of cutting plates, which can be easily implemented in any machine shop, which makes its application very promisin

Forming a Defective Surface Layer When Cutting Parts Made From Carbon-carbon and Carbon-polymeric Composites

We report results of theoretical and experimental research aimed at establishing the mechanisms for the formation of a defective layer at the machined surfaces made from carbon composite materials, specifically those from carbon-carbon and carbon-polymeric groups. Possessing a set of unique physical and mechanical properties, the latter are increasingly applied in aviation and space technologies. However, since the properties of a material are predetermined not only by the components applied but also by the processes to obtain products (laying of reinforcing fibers, orientation of threads), conducting mechanical tests of samples-witnesses is a compulsory stage in the operations performed.Based on the generalization of statistical and theoretical-analytical information, we have developed a model of the emergence and propagation of cracks in a quasi-fragile material, particularly the carbon-carbon and carbon-polymeric composites, caused by the action of a cutting wedge. It is shown that the stresses that occur in a surface layer predetermine the intensity of crack growth while a direction of microcracks propagation is due to the applied force load. Therefore, control over the direction of force action, as well as the application of certain technical means, including a hydroabrasive jet, could enable the localization of microcracks in small quantities at the surface of the formed edge.The established regularities in the formation of a defective layer at machining (including the hydroabrasive cutting) have made it possible to identify ways to improve the quality of a sample and to reduce the layer thickness to 0.05 mm. The derived dependences of the destruction zone parameters on the stresses that occur at cutting allowed us to obtain the rational sequence of machining transitions, at which the defective surface layer is the smallest.The results obtained provide a possibility to significantly increase the accuracy of mechanical tests of carbon composite materials, thereby reducing the variance in the measurements of controlled parameters by 30‒40 %.The results have been actually implemented industrailly, and are of interest for the further research aimed at the hybridization of processes, as well as the development of technologies based on a functional-oriented approach