Development of Porous Films Based on Polyanionic Cellulose to Form Functional Coatings

New porous films based on polyanionic cellulose with AlOOH nanoparticles have been developed. The morphology of the films has been studied by electron microscopy: the size of the formed pores is 1000-500 microns; the total surface porosity of the films is 30%. Using infrared microscopy, it was shown that during the formation of porous films, their chemical composition remains unchanged. Differential scanning calorimetry was used to determine the threshold for thermal destruction of porous films: 306 С. The possibility of using the obtained materials as antifriction coatings when filling the pores with solid lubricant MoS2 is considered. It is shown that for a steel sample protected by a porous coating with MoS2, the friction coefficient decreases by 50% compared to the friction coefficient for a steel surface under a load of up to 450 MPa.

New Way of Synthesis of Few-Layer Graphene Nanosheets by the Selfpropagating High-Temperature Synthesis Method From Bi-opolymers for Large-Scale Production - A Method of Utilization Waste From the Woodworking Industry for Clean Earth Tomorrow

For the first time, few-layer graphene (FLG) nanosheets were synthesized by the method of self-propagating high-temperature synthesis (SHS) from biopolymers (starch and lignin). We suggested that biopolymers (lignin, tree bark) and polysaccharides, in particular starch, could be an acceptable source of native cycles for the SHS process. The carbonization of biopolymers under the conditions of the SHS process was chosen as the basic method of synthesis. Chemical reactions, under the conditions of the SHS process, proceed according to a specific mechanism of nonsothermal branched-chain processes, which are characterized by the joint action of two fundamentally different process-accelerating factors - avalanche reproduction of active intermediate particles and self-heating. The method of obtaining FLG nanosheets included the thermal destruction of hydrocarbons in a mixture with an oxidizing agent. We used biopolymers as hydrocarbons and ammonium nitrate as an oxidizing agent. Thermal destruction was carried out in the mode of SHS, heating the mixture in a vessel at a speed of 20–30 oC/min to 150-200 oC and keeping at this temperature for 15–20 min with the discharge of excess gases into atmosphere. A combination of spectrometric research methods, supplemented by electron microscopy data, has shown that the particles of the carbonated product powder in their morphometric and physical parameters correspond to FLG nanosheets. An X-ray diffraction analysis of the indicated FLG nanosheets was carried out, which showed the absence of formations with a graphite crystal structure in the final material. The surface morphology was also studied and the features of the IR absorption of FLG nanosheets were analyzed. It is shown that the developed SHS method makes it possible to obtain FLG nanosheets with linear dimensions of tens of microns and a thickness of not more than 1-5 graphene layers (several graphene layers).

Еffect of graphene filler oxidation on the thermal destruction of epoxy-graphene composites

The participation of the electronic subsystem of graphene nanoparticles in heat transfer on the interfaphase surface with epoxy polymer, its participation in the thermodestruction processes of epoxy matrix and the concentration interval of the subsystem's influence on the thermal destruction of the polymer matrix are investigated. For such purpose, epoxy resin composites with oxidized and non-oxidized graphene nanoparticles have been used.The particles were obtained by electrochemical method and those are characterized by the same dispersion and analogical of defect spectra. The particles have the same crystal structure, however in composites with oxidized graphene, the participation of the electronic subsystem in thermophysical processes on the interfacial surface is blocked by the atomic layer of adsorbed oxygen. Сomposites of epoxy resin filled with the same particles of nonoxidized and oxidized nanoparticles in the filler content 0.0, 1.0, 2.0, and 5.0 wt%. The multilayered graphene particles were studied by X-ray diffraction analysis (XRD) and Raman spectroscopy (RS) methods. It was shown that the graphene particles are the 2D dimensional structures with about of 100 layers. Desorption curves of epoxy and its composites have been obtained using a programmable thermal desorption mass-spectroscopic (TDMS) technique for fragments with 15≤ m/z ≤108 and temperature interval 35 - 800 оС. The activation energy of desorption was determined from the Wigner-Polanyi equation as 35 - 150 kJ/mol, temperature and mass dependences of the quantity of desorbed atomic fragments have been calculated. It were established the graphene electron subsystem takes part in polymer structure thermodestruction for epoxy composites with nonoxidized graphene enhancing their heat resistance at graphene content С ≤ 1 wt%. With increasing filler content, the thermodestruction behavior in pristine epoxy and its composites with nonoxidized and oxidized graphene is analogical. The thermodestruction characterizes by the stepwise variations in the desorption intensity of atomic fragments. The electron subsystem of graphene particles does not participate in the heat resistance variations.

Studying the causes of destruction of steam superheater tubes in boiler equipment

Results of comprehensive studies of samples of prematurely destroyed 57×4 mm steam superheaer tubes of STBA 22 steel used in a boiler unit of Singburi Sugar Co, Ltd factory (Thailand) are presented. The tubes were manufactured at Interpipe Niko Tube Ltd. (Ukraine) according to JIS G 3462 Standard (Japan). They were destroyed in a short (~240 hrs) term of operation. The cause of premature destruction of tubes of the above steel grade and size assortment in the boiler unit has been established. Based on present-day investigation methods (metallography, X-ray diffraction, etc.), it was found that the tubes were operated with violation of fuel combustion conditions and heat-carrying agent circulation. Characteristic features of operation of damaged tubes include high thermal stresses from the side of the fire-chamber and limitation (or absence) of circulation of the heat-carrying agent (blockage in bends, drum heads, etc.). During operation, the tubes were also exposed to significant thermal vibration stresses (unstable combustion conditions). Prolonged overheating occurred at temperatures above 1000 °C because of violation of circulation of heat-carrying agent and unstable combustion mode. High thermal stresses at almost complete absence of a heat-carrying agent, uneven distribution of growing heat flows caused by violation of the combustion mode in the fire-chamber contributed to accelerated degradation of structure and thermal destruction of the tube metal. In a short term of operation (~240 hours), there was a significant change in the tube size (accelerated high-temperature creep) and complete recrystallization of metal structure throughout the entire wall thickness of the damaged tubes. It has been established that the accelerated degradation of metal microstructure in the destroyed tubes was associated with both overheating of the tube wall and the as-delivered metal structure non-recommended for operation at high temperatures and pressures. It was shown that it is necessary to adjust the heat treatment conditions for these tubes at Interpipe Niko Tube Ltd. The study results have made it possible to develop recommendations for eliminating violations of operating conditions and establishing control of actual heat flows in the most thermally loaded sections of the Singburi Sugar Co. Ltd factory’s steam boiler superheater. Taking into account peculiarities of the boiler equipment and its operating conditions, it was also recommended to use a more heat-resistant and refractory steel instead of the currently used material for manufacture of the steam superheater tubes. Keywords: boiler tube, steam superheater, damage, thermal destruction, structure degradation, combustion conditions, heat carrier circulation, overheating.

Nonoxidizing heating of chip‑powder dispersions of ferrous metals in hydrocarbon atmosphere

The process of inorganic and organic components temperature transformation of metal waste into solid and gaseous products in a continuous hot briquetting muffle furnace has been studied. The composition of the hydrocarbon atmosphere formed in the muffle under conditions of limited access to the oxidizer has been determined. It is shown that the thermal destruction of the coolant oil phase proceeds according to a complex mechanism of consecutive reactions, including polycondensation, polymerization, and deep compaction with a constant decrease in the hydrogen content and ends with the formation of a coke‑like carbon residue on the surface of metal particles and an air suspension of finely dispersed carbon particles (smoke). When it is heated to hot briquetting temperatures of 750–850 °C, chemically active dispersions of ferrous metals are protected from oxidation first by a hydrocarbon gas with a density of 9.0–13.5 kg/m3, then by a pyrocarbon coating with a thickness of 0.1–0.3 mm up to the completion of the processes of pressing and cooling the briquette.

Thermal analysis of building materials for decoration and INFRARED spectroscopy of gaseous products of their thermal destruction

В настоящей статье представлены результаты экспериментального исследования термической деструкции отделочных строительных материалов и идентификации продуктов их термического разложения. Исследование термической деструкции отделочных строительных материалов осуществлялось методом динамического термогравиметрического анализа, а идентификация продуктов термического разложения отделочных строительных материалов – методом инфракрасной спектроскопии. Термический анализ проводился на приборе синхронного термического анализа NETZSCH STA 449 F3 Jupiter, позволяющем фиксировать изменение массы и величин теплового потока от температуры. Нагрев образцов осуществлялся со скоростью 10℃/мин в атмосфере воздуха с расходом 100 мл/мин в интервале температур 25℃-650℃. Образующиеся при термической деструкции газообразные продукты анализировались на ИК-Фурье спектрометре «ФСМ 1201» с газовой кюветой ТГА 100 при длинах волн 600-4500 см-1. По результатам исследования получены ТГ, ДТГ и ДСК-кривые, характеризующие соответственно потерю массы образца, скорость потери массы и изменение величины теплового потока от температуры, а также ИК-спектры продуктов термической деструкции отделочных строительных материалов при различных температурах. Установлено, что отделочные строительные материалы при их термической деструкции образуют различные химические соединения, отдельные из которых представляют опасность для организма человека. This article presents the results of experimental research on thermal destruction of finishing building materials and a hazard assessment of the process. Thermal destruction of finishing materials was investigated by thermal analysis and the risk of the process was assessed by infrared spectroscopy of gaseous products resulting from thermal destruction. The thermal analysis was carried out by dynamic thermogravimetric analysis on the synchronous thermal analysis instrument NETZSCH STA 449 F3 Jupiter, which makes it possible to detect changes in mass and heat flow from temperature. The heating of the samples was carried out at a rate of 10 ℃/min in the atmosphere with a consumption of 100 ml/min. The gaseous products formed during thermal destruction were analyzed by infrared spectroscopy on IR-Fourier spectrometer «FSM 1201» with gas cell TGA 100 at wavelengths of 600-4500 cm-1. The results of the study led to the production of TG, TFG and DSK curves, describing respectively the loss of sample mass, the rate of mass loss and the change of heat flow from temperature as well as infrared spectra of products of thermal destruction of finishing building materials at various temperatures. It has been found that the finishing building materials, when thermally disrupted, form various chemical compounds, some of which are dangerous to the human body.

Magnetic Nanomaterials for Arterial Embolization and Hyperthermia of Parenchymal Organs Tumors: A Review

Magnetic hyperthermia (MH), proposed by R. K. Gilchrist in the middle of the last century as local hyperthermia, has nowadays become a recognized method for minimally invasive treatment of oncological diseases in combination with chemotherapy (ChT) and radiotherapy (RT). One type of MH is arterial embolization hyperthermia (AEH), intended for the presurgical treatment of primary inoperable and metastasized solid tumors of parenchymal organs. This method is based on hyperthermia after transcatheter arterial embolization of the tumor's vascular system with a mixture of magnetic particles and embolic agents. An important advantage of AEH lies in the double effect of embolotherapy, which blocks blood flow in the tumor, and MH, which eradicates cancer cells. Consequently, only the tumor undergoes thermal destruction. This review introduces the progress in the development of polymeric magnetic materials for application in AEH.

Determination of the Degree of Crystallinity of Poly(2-methyl-2-oxazoline)

A new method for purification of 2-methyl-2-oxazoline using citric acid was developed and living cationic ring-opening polymerization of 2-methyl-2-oxazoline was carried out. Polymerization was conducted in acetonitrile using benzyl chloride—boron trifluoride etherate initiating system. According to DSC data, the temperature range of melting of the crystalline phase of the resulting polymer was 95–180 °C. According to small-angle X-ray scattering and wide-angle X-ray diffraction data, the degree of crystallinity of the polymer was 12%. Upon cooling of the polymer melt, the polymer became amorphous. Using thermogravimetric analysis, it was found that the thermal destruction of poly(2-methyl-2-oxazoline) started above 209 °C.

Preparation of spheres based on NiO using cation with gel and macroporous structure

The article discusses the production of materials based on nickel oxide in the form of spherical granules ranging in size from 300 to 700 nm, by the method of thermal destruction of cation exchangers with gel (TOKEM-100)and macroporous (TOKEM-250) structures saturated with nickel (II) ions. Thermal analysis was used to establish the temperature regimes of annealing of Ni2+–ТОКЕМ-250 и Ni2+–ТОКЕМ-100 samples. The prepared materials were investigated by XRD and SEM. The use of TOKEM-100 cation exchanger makes it possible to obtain samples with spherical granules based on trigonal nickel (II) oxide, characterized by a sintered surface morphology. The use of TOKEM-250 cation exchanger leads to the formation of spheres based on NiO cubic modification with an inhomogeneous surface morphology.

Analysis of different factors on the features of thermal destruction of a fuel pin

The presented work studies the influence of various factors that affect the specific features of fuel pins melting. For this purpose, fuel pins with different geometries and energy release are considered. Numerical simulation of melting is carried out using a program module for calculating the destruction of fuel rods. Comparison with theoretical calculations is made. The analysis of the convergence of calculations with respect to the time step value and the number of calculated cells along the radius and height is carried out. As a result of work with the use of numerical methods, the characteristic times of destruction of fuel elements during an accident with a loss of coolant flow rate (an accident of the ULOF type) and the dependence of weight loss on time are obtained under various conditions.