Carbon-Carbon Composite Materials Based on Low Modulus Fabrics

Scientific research and the search for new technologies to increase the level of mechanical and high-temperature properties are ongoing. The article discusses the technology of using carbon materials, pyrolysis and impregnation with phenol-formaldehyde resins. It is shown that the proposed technology makes it possible to achieve a sufficient level of mechanical properties when using low-modulus carbon fabrics after pyrolytic treatment as a prepreg at a temperature treatment no higher than 900 K. Pillowcase and resole phenol-formaldehyde resins were used to impregnate the prepreg. The proposed technology also allows the introduction of alloying additives into the system to improve the properties. An example of the introduction of nitrogen into a composite by adding urotropine to a phenol-formaldehyde resin, which was used to impregnate the composite, is considered.

PRODUCTION TECHNOLOGY OF FRUIT-FILLED COTTAGE CHEESE FOR BABY FOOD OVER 6 MONTHS OF AGE

Currently, cottage cheese is one of the leading dairy products for infants’ nutrition. Today, the urgent task is to expand the range of sour-milk products by developing a technology for cottage cheese production with the addition of a fruit filler. The object of research is cottage cheese for the diet of children over six months. The cottage cheese is produced from whole milk subjected to high-temperature treatment with the use of starter microorganisms and with the addition of fruit filler “Banana”. The children’s curd recipe developed by the authors included the following raw materials and components: milk with the mass fraction of fat 3.4 %, skim milk with the mass fraction of fat 0.05 %, direct injection starter Flora C-170, fruit filler “Banana”. Production technology included the following stages: receiving and preparing raw materials, normalization of milk, homogenization, pasteurization and cooling of the normalized mixture, fermentation, ultrafiltration of curd clot, cooling and ripening of the product. The authors conducted laboratory studies of cottage cheese to assess the quality and safety of the resulting product. The products meet the requirements of GOST 32927-2014 for organoleptic indicators: taste and smell, appearance and consistency, colour. The products also meet the needs of the Technical Regulations of the Customs Union (TR CU) 033/2013 “On safety of milk and dairy products” in terms of microbiological and antibiotic content.

Seed Germination and Seedling Growth of Robinia pseudoacacia Depending on the Origin of Different Geographic Provenances

Black locust (Robinia pseudoacacia) is recognised as a forest species of interest due to its multiple uses. The management of forest genetic resources and their efficient conservation suffer from variations in traits and start with seed germination. The aim of the current study was to investigate the germination of seeds obtained from plus trees selected in eight Romanian provenances, as well as to investigate the influence of the origin upon plants’ growth and development. Two experiments were undertaken to test seed germination: one treatment involved water-soaked seeds and heat/cold treatment, while the other treatment was based on sulphuric acid, at different concentrations (50, 70, 90%). The results were correlated with the morphological analysis of the seeds. Satu-Mare had the lowest germination rate within both treatments. Sulphuric acid did not improve seed germination as much as the heat treatment. The highest germination rate occurred for the water and temperature treatment on seeds from Bihor provenance (68.2%). The most distant provenance was Bihor, in inverse correlation with Bistrița Năsăud and grouped separately within the hierarchical dendrogram of cluster analysis based on the analysed parameters of the provenances investigated. The results demonstrated that the genotypes and environmental heterogeneity of the seed origin within the provenances may finally result in different performances.

Stability of pyrolysis condensates during their high-temperature treatment

As part of a project dealing with the material use of waste plastics processed by pyrolysis, a method for the purification of primary pyrolysis gas at temperatures above the dew point of condensing components was proposed. In order to avoid the loss of liquid products, two procedures have been proposed to study this issue. The first procedure consists in separating the pyrolysis condensate from permanent gases and its subsequent evaporation and introduction into a high-temperature reactor where the purification takes place. The second procedure used the same equipment, but the pyrolyser was connected in series with a high temperature reactor by a heated tube. The function of the device is demonstrated on a pair of pure polymers, namely highdensity polyethylene and polypropylene. In practice, however, the device is used for testing waste plastics. The mass balance of liquid, gaseous and solid products of pyrolysis and subsequent vapour phase conduction through a high-tem-perature reactor was supplemented by data from chromatographic analysis. Experiments have shown that the separation of pyrolysis and subsequent evaporation of the condensate in an independent reactor causes the formation of an undesirable amount of fine aerosol (mist). Pyrolysis without any subsequent high-temperature step produced 85–90 % condensate. The inclusion of a separate high-temperature reactor reduced the yield of condensate to 44.5–47.5 %, at the expense of the above-mentioned mist. Its conver-sion back to liquid is difficult and makes the process inefficient for industry. In tests with the series-connected pyrolyser and the high-temperature reactor, the situation was significantly better. 68.5–73.5 % of condensate was obtained in this case. In addition to the formation of mist, the conduction of steam of condensing components through the high-temperature reactor also caused a slight change in the composition of the liquids obtained. There was a decrease in the proportion of C21–C29 hydrocarbons in products and, conversely, an increase in the concentration of C5–C15 hydrocarbons. Besides verifying a suitable approach to the high-temperature processing of pyrolysis products, the experiments showed that changing a single subparameter (in this case the separation of the two reactors) significantly altered the results of the experiments. During laboratory simulation of industrial processes, it is important not to approach simplifications, but to copy all conditions as much as possible.

Hydrothermal Synthesis of Ag Thin Films and Their SERS Application

In this article, a facile, one-step method for the formation of silver thin-film nanostructures on the surface of Al2O3 substrates using the hydrothermal method is proposed. The dependence of the SERS effect intensity of the formed films during the detection of methylene blue (MB) low concentrations on the synthesis conditions, additional temperature treatment, and laser radiation wavelength (532 and 780 nm) in comparison with similar dye films on commercial SERS substrates is shown. The detection limit of the analyte used for the indicated lasers is estimated. The effect of the synthesis temperature on the particle size, crystal structure, and microstructure features of the obtained thin films based on silver nanoparticles is demonstrated. Using spreading resistance microscopy, the interface between the substrate and Ag particles is studied, and the dependence of the size of the corresponding gap between them and the nature of microstructural defects on the parameters of hydrothermal treatment of reaction systems in the presence of Al2O3 substrates is shown. As a result of the study, the factors associated with the properties of the obtained SERS substrates and the parameters of recording the spectra, which affect the amplification factor of the spectral lines intensity of the analyte, are revealed.