Search

We describe an improvement to the photoacoustic method for determining diffusion coefficients of dyes in soft matter, such as agar hydrogels. The proposed method is based on the properties of thermal wave formed due to a heat transfer at the interface of the two media: the gel and polyethylene film. It is inherently simple, requires a small number of reagents and relatively fast, since samples are small. To assess the obtained results, we independently determined diffusion coefficients of the dyes using an optical image analysis method and found both sets of results to be in a good agreement. [ABSTRACT FROM AUTHOR]

Nanocellulose was made in the form of water gel using chemical and ultrasound treatments of the Miscanthus x giganteus plant. Properties both of nanogel and of its thin solid films deposited on glass, silicon and microcrystalline cellulose substrates were studied. Nondestructive methods (XRD, viscosymetry, scanning electron and optical microscopy, reflection and luminescence spectroscopy) were used to characterize studied materials. The results obtained allowed estimation of nanofibrils sizes both in water solutions and in the solid states. It was found that the aspect ratio for the nanofibrils (p = l/d, where l is the length and d – diameter) in the nanogel state decreases from 130 to 20, when temperature increases from 15 to 75 °C. The value of p for nanofibrils in solid films is in the range of 3–30. It was assumed that mentioned data are the result of aggregation of the nanofibrils in the solid state and under water nanocellulose gel cooling. The data about optical properties of the nanocellulose under study showed that optical reflection and photoluminescence methods are suitable, in principle, for characterization of nanocellulose made from Miscanthus x giganteus in the form of nanogel, too. [ABSTRACT FROM AUTHOR]

Bulk samples of pure polyvinyl chloride (PVC) and its composites with different content of methylene blue (MB) dye are prepared. The degree of crystallinity, dynamic elastic modulus E and shear modulus G (~1 MHz), photoluminescence (PL), temperature dependences of dielectric characteristics ε1, ε2, tgδ, electrical resistance R at different frequencies of alternating electric field are measured. As shown, the adding of a modifier (MB) with conjugated chromophores is accompanied by both the generation of linear conjugated systems (polyenes) in PVC and the destruction of monomer units. These processes are mechanisms for changing the mechanical, structural, optical, dielectric properties of PVC–MB composites caused by the peculiarities of the stack interaction between their conjugated components. [ABSTRACT FROM AUTHOR]

A method for the experimental determination of turbidity in thermoresponsive polymer solutions is presented. The method is based on measuring the intensity of light streams: weakened and backscattered from the sample, which is in the region of the volume phase transition. The turbidimeter developed by us, unlike industrial devices of this type, is equipped with a thermostat that allows to study the dependence of the solution turbidity on the temperature. The device operates automatically, the values of luminosity and temperature from digital sensors are processed by the microcontroller and transmitted via the RS-232 protocol to USB ports of a personal computer. The error of luminosity measurement does not exceed 0.1 lux, the temperature measurement accuracy is ± 0.1 °C. This article demonstrates an example of using the designed turbidimeter to study the first-order phase transition in an aqueous solution of hydroxypropylcellulose (2 wt. %) in the presence (absence) of NaCl ions. It is assumed that the sol-gel transition in the investigated solution is due to swelling of polymer coils and their subsequent aggregation. In our opinion, the displacement of the phase transition temperature is due to additional swelling of polymer coils owing to shielding of the electrostatic interaction of monomers in the presence of NaCl ions. It is shown that the intensity of backscattered light corresponds to the kinetics of the formation of the gel network, which makes it possible to establish the dimensions of formed aggregates in the network nodes. [ABSTRACT FROM AUTHOR]

Ukraine is an agricultural country with great agricultural potential for biogas production, which is the key to fertile soils and favorable climatic conditions for energy crops, including corn. The article analyzes the experience of using biogas in Ukraine and the world, its mechanism of production. The leader in biogas production in the world is the European Union in general and Germany in particular. The total number of biogas plants in Europe exceeds 11 thousand, of which 7.2 thousand in Germany. Installed biogas, which is released in the process of complex fermentation of organic waste, consists of a mixture of gases: methane - 55-75%, carbon dioxide - 23-33%, hydrogen sulfide - 7%. An important sector of renewable energy sources in biogas production is presented and the prospects for its use are determined. The energy dependence of our country on the volumes of imported natural gas is analyzed. The main aspects of biogas production are explored using renewable energy sources that are inexhaustible in our crane and the phased operation of the biogas plant is investigated. The real advantages of the need for biogas production and use in our country are outlined. Problems aimed at the development of alternative energy have been proved in order to detect environmental pollution. It has been established that in Ukraine the use of corn silage to improve the efficiency of biogas production at existing biogas stations has not been used so far. The problems of increasing the yield of corn plants have been proved not only by breeding and genetic methods, but also by cultivation technology. [ABSTRACT FROM AUTHOR]