Thermokinetic Parameters Research Articles

Detailed bioenergy investigation of Brazil biomass waste after biochemical process

The bagasse products generated after the extraction process have significant use in several industrial sectors however its application in the energy sector stands out, avoiding the use of fossil fuels. In this study an enzymatic process was applied through the Pleurotus sajor-caju fungus, for decomposition of the lignin present in the sugarcane bagasse, with the objective of improving the kinetic and bioenergetic parameters of this biomass. Detailed analyzes were carried out, such as kinetic, morphological, elementary and calorific, to verify its quality as biofuel. Values of Ea =31 kJ/mol to 65 kJ/mol, A = 1.4 105 s −1 to 3.0 105 s −1, ΔH = 26 kJ/mol to 60 kJ/mol, ΔG = 124 kJ/mol to 154 kJ/mol and ΔS = 150 J/mol to 157 J/mol for the conversion range (α) from 0.20 to 0.95, were obtained, with little variability in thermo-kinetic parameters. The HHV and fixed carbon values were 19.37 MJ/kg and 83.1%, respectively, demonstrating that this sugar cane residue has the potential to be used as a solid biofuel, after its use in the production of Pleurotus sajor-caju fungi, thus allowing to create more economic value in the sugar cane transformation chain.

The Application of Differential Scanning Calorimetry to Investigate Precipitation Behavior in Nickel-Base Superalloys Under Continuous Cooling and Heating Conditions

A suite of experimental tools and fast-acting, numerical-simulation techniques was used to quantify the precipitation behavior of three nickel-base superalloys: IN-100, LSHR, and 718. Experimental methods comprised differential scanning calorimetry (DSC) to establish the specific heat as a function of temperature and selected direct-resistance heating trials (using a Gleeble® machine) to obtain samples for microstructural analysis. For the DSC experiments, each alloy was cooled at a prescribed constant rate (between 5 and 20 K/min) after an initial soak/equilibration in the high-temperature, single-phase (supersolvus) temperature regime. On-heating DSC trials beginning at ambient temperature were also performed on alloy 718 in three different starting conditions: super-δ-solvus solution treated and water quenched (denoted as ST), solution treated and aged (STA), and solution treated and overaged (STOA). DSC results, revealing the thermal signatures associated with the kinetics of precipitation of γ′ (IN-100, LSHR) or γ′ and γ″ (718), were interpreted using a previously-developed fast-acting routine that treats concurrent nucleation, growth, coarsening, and dissolution. For these simulations, special attention was paid to various thermo-kinetic input parameters including equilibrium solvus-approach curves, bulk free energies of transformation, matrix-precipitate interface energies, and effective diffusivities. For the γ-γ′ superalloys (IN-100 and LSHR), estimates of precipitate volume fraction as a function of temperature from the specific-heat data revealed semi-quantitative agreement with simulation predictions. For the γ-γ′-γ″ superalloy (718), simulation predictions of precipitate volume fractions were converted to specific heat as a function of temperature and showed semi-quantitative agreement with the direct measurements.

Thermokinetic parameters of the primary coal tars destruction in the presence of catalysts and polymeric materials

The hydrogen-donor abilities of polymers and the activity of catalysts in the process of thermal destruction of the organic mass of primary coal tar (PCT) are studied by non-isothermal kinetics methods. PCT,magnetic microspheres, nickel-deposited chrysotilechrysotile and Fe3O4nanocatalysts were used as initial raw materials. Рolymers such as polyethylene (PE), polystyrene(PS) and polyethylene glycol (PEG) were selected as a hy-drogen donor. The phases Mg3[OH]4{Si2O5} and NiO were determined by X-ray phase analysis (XRD) in the obtained catalyst (nickel-deposited chrysotile), and the presence of highly dispersed nickel oxide particles on the surface and inside the nanotubes was shown by the transmission electron microscope (TEM). Nickel oxide particles of 8–11 nmand 30–37 nmwere evenly distributed on the surface and inside the chrysotile nanotubes. The kinetic parameters of the thermal destruction of a mixture of PCT, catalyst and polymer material were determined on the basis of thermogravimetric analysis using the integral method and the method for determin-ing the thermokinetic parameters by the inflection point on the thermogravimetric curve(TG). The change in the activation energy, rate constant and pre-exponential factor with an increase in the degree of destruction of the organic mass of the PCT is established. It was shown that the nature of polymers and catalysts significantly affects the value of the rate constant and the activation energy. The calculated activation energies of the thermal destruction of a mixture of coal tar with PS and PE in the presence of a catalyst (nickel-deposited chrysotile) by the first method are 47.6 kJ/mol and 40.4 kJ/mol, and by the second method are 47.3 kJ/mol and 86.5kJ/mol respectively.

Optimization for synthesized quinoline-based Cr3+, VO2+, Zn2+ and Pd2+complexes: DNA interaction, biological assay and in-silico treatments for verification

A novel momonuclear metal chelates were derived from Zn(II), Pd(II), VO(II) and Cr(III) ions with azomethine (BSQ) [BSQ = 4-Bromo-2-(quinolin-8-yliminomethyl)-phenol] ligand. The prepared compounds were subjected to different analytical and spectroscopic techniques as, IR, 1H NMR, UV–Vis, molar conductivity, magnetic moment and thermogravimetric analysis (TGA) to elucidate their structures. Accordingly, the most fitted geometry has been suggested for each complex. The ligand acts as a tri-dentate via NNO donors towards the metal ions inside octahedral geometry with Cr3+, square pyramidal with VO2+, tetrahedral with Zn2+ and square planner with Pd2+ ion. Thermo-kinetic parameters for the complexes have been determined and the values suggest the presence of ordered activated complexes. The reactivity of new compounds towards DNA was examined by different methods and the binding kinds seem to electrostatic, intercalation, or replacement. Also, in-vitro antimicrobial and anticancer potency of the compounds were evaluated. In addition, the therapeutic behavior of the complexes appeared promising towards breast cancer cells (MCF-7) in a concentration-dependent manner. Moreover, the redox potential of the newly synthesized compounds was evaluated and the results reflect suitability of Pd(II) complex in controlling the free radicals. Variable theoretical treatments were performed aiming to confirm the structural formulae as well as the biological assay results. A promising antimicrobial and anticancer behavior was recorded with Pd(II) complex (BSQPd) via in-vitro and in-silico ways.

Preparation and properties of hydrotalcite microcapsules for coal spontaneous combustion prevention

Microcapsule materials are a new type of composite fire-extinguishing material that show good effects in preventing the spontaneous combustion of coal. In this paper, polyethylene glycol 6000 (PEG6000) was selected as the wall material, and hydrotalcite (LDHs) was selected as the core material. Microencapsulated LDHs samples with different core-to-wall ratios were prepared by melting dispersion and condensation. Scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS), Fourier transform infrared spectroscopy (FTIR), thermogravimetry/differential scanning calorimetry (TG/DSC) and other experiments were used to characterize the surface morphology, dispersion, coating, pyrolysis and other characteristics of the microcapsules. On this basis, the microcapsules were mechanically mixed with a coal sample to prepare a chemically inhibited coal sample. Based on TG/DSC experiments, the effect of microcapsules with different core-to-wall ratios on the characteristics of coal spontaneous combustion was studied. Combined with thermokinetic parameters, the inhibition mechanism of the microcapsules with different core-to-wall ratios on coal spontaneous combustion was analyzed. The results showed that LDH-PEG6000 microcapsules were successfully prepared. The thermal reactivities and inhibition mechanism of microcapsules with different core-to-wall ratios were different, and the best effect was obtained when the core-to-wall ratio was 1:5. This microcapsule material can reduce the weight loss rate and heat release of coal, increase the critical temperature and maximum weight loss rate temperature by 8.8 °C and 33.6 °C, respectively, and increase the apparent activation energy of water evaporation and gas desorption stage by 13.42 kJ/mol and the thermal decomposition stage and combustion stage by 88.64 kJ/mol. Resistance microcapsules can effectively inhibit the coal spontaneous combustion reaction In addition, this research provides new ideas for solving the problem of coal spontaneous combustion in the goaf caused by the fully mechanized top coal caving technology and enriches the technical means of fire prevention.

Development of a Detailed Kinetic Model for the Oxidation of n-Butane in the Liquid Phase.

The chemistry underlying liquid-phase oxidation of organic compounds, the main cause of their aging, is characterized by a free-radical chain reaction mechanism. The rigorous simulation of these phenomena requires the use of detailed kinetic models that contain thousands of species and reactions. The development of such models for the liquid phase remains a challenge as solvent-dependent thermokinetic parameters have to be provided for all the species and reactions of the model. Therefore, accurate and high-throughput methods to generate these data are required. In this work, we propose new methods to generate these data, and we apply them for the development of a detailed chemical kinetic model for n-butane autoxidation, which is then validated against literature data. Our approach for model development is based on the work of Jalan et al. [J. Phys. Chem. B 2013, 117, 2955-2970] who used Gibbs free energies of solvation [ΔsolvG(T)] to correct the data of the gas-phase kinetic model. In our approach, an equation of state (EoS) is used to compute ΔsolvG as a function of temperature for all the chemical species in the mechanism. Currently, ΔsolvG(T) of free radicals cannot be computed with an EoS and it was calculated for their parent molecule (H-atom added on the radical site). Theoretical calculations with the implicit solvent model were performed to quantify the impact of this assumption and showed that it is acceptable for radicals in n-butane and probably in all n-alkanes. New rate rules were proposed for the most important reactions of the model, based on theoretical calculations and the literature data. The developed detailed kinetic model for n-butane autoxidation is the first proposed model in the literature and was validated against the experimental data from the literature. Simulations showed that the main autoxidation products, sec-butyl hydroperoxides and 2-butanol, are produced from H-abstractions from n-butane by sec-C4H9OO radicals and the C4H9OO + C4H9OO reaction, respectively. The uncertainty of the product ratio ("butanone + 2-butanol"/"2-butoxy + 2-butoxy") of the latter reaction remains high in the literature, and our simulations suggest a 1:1 ratio in n-butane solvent.

Oxy-fuel and air combustion performances and gas-to-ash products of aboveground and belowground biomass of Sedum alfredii Hance

The eco-friendly disposal choices of phytoremediation biomass still remain to be explored. This study characterized the combustions of Sedum alfredii Hance (SAH) in response to its aboveground (SAH-A) and belowground (SAH-B) parts, the oxy-fuel (CO2/O2) and air (N2/O2) atmospheres, temperature, and heating rate. The decomposition behaviors, gas-to-ash characteristics, thermo-kinetic parameters, and mineral transformations were quantified. In both atmospheres, the combustion performances were better for SAH-A than SAH-B at the same heating rate. In the range of 400.0–598.8 °C, the maximum mass loss rate of both samples obviously decreased and delayed with CO2 replacing N2 at the same oxygen concentration. The SAH-A and SAH-B combustions in both atmospheres emitted C- (CO2, CO, CH4, and small molecular organic substances) and N-containing (HCN and NH3) gases. In both atmospheres, the temperature dependency of the gas emissions remained the same. Both empirical indices and ternary phase diagrams indicated that both samples had a high deposition risk. Thermochemical equilibrium simulations were used to predict the slagging risk in response to ash mineral transformations. Our findings can provide new insights into the combustion dynamics of phytoremediation biomass and its effect on CO2 capture, utilization, and storage in mitigating climate change.

The study of the biotoxicity effect of alumina nanoparticle on soil microbes

Due to the unique properties, nanoparticles (NPs) have been widely used both in industrial products and individual life. However, with the huge benefits, NPs also possess potential toxicity to human health and ecosystem. Aluminum oxide NPs is so significant in industry that it occupies the second important position in US nanomaterials market. Aluminum oxide NPs belong to metal oxide nanoparticles which may have strong antimicrobial properties. As there is limited prior research on the toxicity of alumina NPs, the main goal of present research is to study the effects of alumina NPs on microorganisms in soils by combination methods of microcalorimetry and urease. Power-time curves and thermo-kinetic parameters (such as total heat evolution QT, growth rate constant k and maximum power output Pmax) were applied to evaluate the microbial community activities of the soil samples. A range of concentration of Aluminum oxide NPs gradient from 0 mg/L to 1000 mg/L was applied. The results showed that the concentration under 500 mg/L has negligible inhibitory effects on soil microorganisms while concentrations at 500mg/L and 1000 mg/L only have mild inhibition on microbes in soil. Urease experiments verified this result, therefore, it suggests that combination of microcalorimetry and urease may provide practical method for microorganism activity evaluating.

Thermal stability assessment of a completely incinerable ionic liquid system in presence of nitric acid – A calorimetric study

The thermal stability of a novel CHON (Carbon, Hydrogen, Oxygen and Nitrogen) based ionic liquid: Methyltrioctylammonium nitrate ([N1888] [NO3]), used for the separation of actinides and fission products was studied using an adiabatic calorimeter (in air ambience under heat-wait-search (HWS) mode) for the first time. The decomposition study of [N1888] [NO3] was accomplished in the presence and absence of nitric acid and a diglycolamide based extractant: N,N,N',N'-tetra(2-ethylhexyl) di-glycolamide (T2EHDGA) which is also incinerable in nature. The neat ionic liquid system showed stability up to 491 K followed by the self decomposition irrespective of the presence or absence of 0.1 M T2EHDGA. The thermal decomposition data on the nitric acid equilibrated ionic liquid phases were generated and were compared with that of ionic liquid – nitric acid biphase. A remarkable difference in the exothermic excursions and derived thermo-kinetic parameters corroborated the impact of nitric acid on the thermal stability of [N1888][NO3].

Green synthesis and microcalorimetric study of a novel N-alkylation Schiff base and its bismuth(III) complex

A new N-alkylation Schiff base [N2,N6-bis(2-hydroxy-3-methoxybenzyl)pyridine-2,6-dicarboxamide] was synthesized from o-vanillin and pyridine-2,6-dicarboxamide by a solid-phase microwave green synthesis without catalyst and solvent. A new bismuth(III) complex was prepared by reaction of the ligand with BiCl3. The ligand and its bismuth(III) complex were characterized by elemental analysis, spectral techniques (1HNMR, MS, FT-IR and UV), chemical analysis, thermogravimetric analysis and molar conductance. The compositions of the ligand and its bismuth(III) complex were (C23H23N3O6) and Bi(C23H21N3O6)Cl. Moreover, the antibacterial activity of the ligand and its bismuth(III) complex against S. pombe was evaluated by bio-microcalorimetry at 32 °C. The quantitative relationship between some thermokinetic parameters (k, tG and I) with the concentration (c) of the ligand and its bismuth(III) complex was investigated. The half inhibition concentrations (IC50) of the ligand and its bismuth(III) complex were obtained as 4.63 × 10–3 mol dm−3 and 2.10 × 10–3 mol dm−3, respectively. The results showed that the antibacterial activity of bismuth(III) complex was stronger than that of the ligand. Further, the action target of bismuth(III) complex on bovine serum albumin (BSA) was studied by the molecular docking simulation method, and we found that bismuth(III) complex bounded at in the hydrophobic cavity of the substructure domain IIB of BSA.

Spatial Variation of Thermokinetics and Associated Microstructural Evolution in Laser Surface Engineered IN718: Precursor to Additive Manufacturing

The spatial variation of thermokinetic parameters has a significant influence on solidification and microstructural aspects such as grain orientation, types and dimensions of the microstructural features, and crystallographic defects. In laser-based additive manufacturing, these factors are mainly dependent on the process parameters and have a wide implication on the microstructural aspects and, in turn, on the mechanical properties. In view of this, the current study focuses on the spatial variation on thermokinetic parameters such as cooling rate, thermal gradient (G), and solidification velocity (R) within the melt pool formed during laser processing of IN718. The continuous-wave Nd-YAG laser was employed at a laser fluence of 14.85, 19.10, and $$23.34\text { J/mm}^2$$ with varying power (700, 900, 1100 W) at a constant scanning speed of 100 mm/s. The finite element method-based multiphysics heat transfer model, coupled with the dynamic fluid flow, was developed to predict these parameters. The model was correlated with microstructural aspects such as melt pool dimensions, orientation of columnar grains, and secondary dendritic arm spacing. The cumulative diffusion length of Nb obtained via thermo-diffusion calculation during multiple heating/cooling cycles was enough to dissolve the fine intragranular plate-shaped $$\delta $$ precipitates in the heat-affected zone.The spatial variation of the G/R ratio recognized the transition of columnar to equiaxed solidification grains which was associated with the G/R ratio lower than $$10 \text {K s/mm}^2$$ in the top region ( $$\sim 25 \mu \text {m}$$ ) of the melt pool. In addition, the coupled solid mechanics model predicted the evolution of thermal stresses during solidification of the melt pool under a high thermal gradient, which marked the generation of high dislocation density in the solidified melt pool.

Quantitative Model for Reversibly Photoswitchable Sensors.

Composed of a reversibly photoswitchable unit allosterically linked to a sensing module, reversibly photoswitchable sensors (rs-sensors) represent a new and attractive strategy to quantitatively read-out analyte concentrations. However, their kinetic response to illumination is complex, and much attention is required from the design to the application steps. Here, we exploit a generic kinetic model of rs-sensors which enables us to point to key thermokinetic parameters, such as dissociation constants and kinetic rates for exchange toward the analyte, and cross-sections for photoswitching. The application of the model allows to evaluate the robustness of the analyzed parameters and to introduce a methodology for their reliable use. Model and methodology have been experimentally tested on a newly reported calcium sensor based on a reversibly photoswitchable green fluorescent protein allosterically linked to a calcium-sensing module integrating calmodulin and an RS20 peptide.

Structural, conformational and therapeutic studies on new thiazole complexes: drug-likeness and MOE-simulation assessments

A series of new complexes derived from Pd(II), Cu(II) and Fe(III) ions reacted with thiazole derivative (HL, CPTP) was prepared. Structures of all new compounds were characterized and confirmed using analytical and spectroscopic (IR, UV–Vis and 13C&1H NMR) techniques. All complexes have non-electrolytic nature based on molar conductance measurements. TGA was executed to confirm the presence of water molecules inside or outside the coordination sphere as well as the mono-nuclear feature of isolated complexes. Accordingly, thermo kinetic parameters were calculated for all decomposition steps. The obtained analytical data regarding complexation in solution, molar ratio and continuous variation methods suggest 1 M:1 L molar ratio. The oriented structures using advanced program assert on best distribution for coordinating sites (NH& NH2). Moreover, electrostatic potential map as well as iso-surface with array plot of ligand reflects high nucleophilic feature with reduced outer contour on two coordinating sites. In vitro antimicrobial, anticancer and antioxidant activities of ligand and its complexes were checked. All complexes exhibited superiority on free ligand in successful treatment, specifically CPTPPd complex. Drug-likeness as well as MOE-docking simulation outcomes indicates promising inhibitory feature of CPTPPd and CPTPCu complexes, in agreement with in vitro results.

Thermokinetics behaviour and parameters for spontaneous combustion of carbonised powders and oxidised powders from preparation of coal-based activated carbon

The spontaneous combustion of carbonised and oxidised powders has been long considered an intricate physicochemical process, and their combustion is often concealed and difficult to detect. The self-ignition characteristics and parameters of carbonised and oxidised powders were thus explored. The thermokinetic behaviours of carbonised and oxidised powders (303–1073 K) were assessed at four different heating rates (5.0, 10.0, 15.0, and 20.0 K min−1) through thermogravimetry–differential scanning calorimetry (TG–DSC). The variation of the thermogravimetric curve was obtained, and the apparent activation energy (Ea) of the carbonised and oxidised powders was calculated using the Kissinger–Akah–Sunose (KAS) and Flynn–Wall–Ozawa (FWO) methods. The LFA457 laser-flash apparatus was employed to measure thermophysical parameters of experimental samples. The results revealed that the TG–derivative thermogravimetry curve shifted towards high temperatures, and overall, the characteristic temperature increased as the heating rate increased (e.g. at heating rates of 5.0–20.0 K min−1, the critical temperatures were 329–349 and 332–356 K for carbonised and oxidised powders, respectively). The Ea values in the combustion stage obtained using the two calculation methods were similar. The Ea values of the carbonised powders were 148.64 (KAS) and 153.58 (FWO). The Ea values of the oxidised powders were 171.23 (KAS) and 175.68 kJ mol−1 (FWO). The specific heat capacity of carbonised powders was higher than that of oxidised powders, whereas the thermal diffusivity and thermal conductivity were lower than those of oxidised powders.

Study on Thermokinetic Parameters of Coal-oxygen Reaction Path with Constant Temperature Difference Guiding Method

ABSTRACT The low-temperature oxidation of coal includes processes such as coal-oxygen reactions and pyrolysis. As heat generated from coal-oxygen reaction is the fundamental driver of coal spontaneous combustion, the thermokinetic studies of coal spontaneous combustion should be focused on that. However, the pyrolysis path will impact the coal-oxygen reaction, resulting in limited capability of characterizing the t accurate hermokinetic parameters of coal-oxygen reaction process. Therefore, this paper proposed a new method to test the heat generation characteristics of coal-oxygen reaction path and the theoretical model of the method was established. The experimental results show that the method can achieve successful experiments within a short period of time, and exclude the impacts from heat absorption of water evaporation and pyrolysis, and well characterize the nature of coal spontaneous combustion. Meanwhile, the thermokinetic parameters such as heat generation rate and heat production can be obtained quickly and accurately. The coal-oxygen reaction path is divided into three stages by using the heat generation characteristics. By analyzing in-situ FTIR results, it is concluded that the gradual participation of different active groups is the main reason for the three stages. There are two main factors affecting the starting and heat generation of each stage, one is the activity of active groups which can participate in the initial reaction, and the other one is the number and activity of active groups that can participate in the reaction.

In English

Powders where the γ≈α-Al2O3-nano phases are the priority precursors for catalysts for heterogeneous catalysis with the maximum content of surface 5-coordinated Al centers for Pt attachment. Hydrogenated nano powders (~8 nm) of γ-, γ '-, θ-, κ-Al2O3 soluble in hydrochloric acid were obtained from the processing of aluminum boride powders with an icosahedral structure. Samples, which underwent a step-by-step and single heating of 50-100K heat treatment for 2 hours at temperatures of 570-1470K, were received in quantity of 34. The specific surface area of SВET, m2g-1 was measured by the thermal nitrogen desorption express method of gas chromatography through the GC-1 device. X-ray (phase and coherent), fluorescence and phase chemical-analytical evaluation of the samples were performed. The thermokinetic characteristics of the processes are calculated using the exponential Arrhenius law. Dimensional characteristics of crystallites (10.4-48 nm); specific surface area of powders (213-8.6 m2g-1, SВET); thermokinetic parameters of α-Al2O3 crystallite growth process (V α-Al2O3 - 1.44 10-3 - 6.67 10-3 nm s-1; E α-Al2O3 = 38.7±2.1kJ mol-1; A0 = 0.16±0.0 s-1 along the temperature line 1220-1470K were determined and calculated. The process of dehydration of two OH-groups occurs in the region 570-720K Ea H2O ↑ = 30.5 ± 0.5 kJ mol-1 A0 = 1.33±0.3 s-1. The last group of OH at temperatures of 820 -1070К and a rate of 2.13 10-4 - 4.93 10-4 mol s-1 Ea H2O ↑ = 13.2 ± 0.8 kJ mol-1 A0 = 16.9 ± 0.9 s-1. The activation energy of the phase transition is Ea., γ → α-Al2O3 = 23.9 ± 1.0 kJ mol-1 A0 = 2.01 ± 0.72 s-1 (770-970K) and Ea., γ → α-Al2O3 = 83.5 ± 0.8 kJ mol-1 A0 =(2,05±0,95) 103 s-1 (1070-1170K). It agrees well with the known heat of conversion Eа, γ→α-Al2O3 = 85 kJ mol-1. The TK of γ≈α-Al2O3-nano phases is at 1170K.

Substantiation of the choice of thermokinetic parameters of cooling of steel k76f to increase the hardness over the section of the rail head

Substantiation of the choice of thermokinetic parameters of cooling of steel k76f to increase the hardness over the section of the rail head

Application of Thermal Methods to Analyze the Properties of Coffee Silverskin and Oil Extracted from the Studied Roasting By-Product

The aim of the study was to characterize the thermal properties of coffee silverskin and fat extracted from the material by using differential scanning calorimetry, modulated differential scanning calorimetry and thermogravimetry/derivative thermogravimetry. Additionally, the thermokinetic parameters, oxidative stability and fatty acid composition of the extracted oil were defined. Thermal decomposition of the studied coffee roasting by-product under oxygen occurred in three defined stages. The most significant changes in weight were observed in the region of 200–500 °C and correspond to polysaccharide decomposition. These results are in agreement with the data obtained from the differential scanning calorimetry curve. On the curve course of silverskin, two main exothermic peaks can be observed with a maximum at 265 and 340 °C. These exothermic events represent the transitions of hemicellulose and cellulose. Fat extracted from silverskin turned out to be a source of polyunsaturated fatty acids with the recommended n-6 to n-3 ratio reaching the value 4:1. The studied fat was characterized by low oxidative stability. Considering the obtained results, it can be stated that thermal analysis can provide fast and reliable data concerning the composition and properties of coffee silverskin and coffee silverskin oil.

New cobalt(II) Schiff base complex: Synthesis, characterization, DFT calculation and antimicrobial activity

A new cobalt(II) Schiff-base complex [Co(L)2] was prepared by using equivalent molar of Schiff-base ligand [HL=(E)-N'-(2-hydroxy-3-methoxybenzylidene)isonicotinohydrazide] and CoCl2·6H2O. The structure of the complex was characterized by single-crystal X-ray diffraction, IR, ESI-MS, elemental analysis and DFT method. X-ray crystal structure analysis showed that the complex crystallized in space group Pbca, with two symmetry-independent molecules. The experimental vibrational bands(IR) have been discussed and assigned based on DFT calculations. The antibacterial activity of Schiff base and its complex against S. pombe were assessed by bio-microcalorimetry at 32 °C. Some thermokinetic parameters (k, Pmax,tG and Qtotal) were derived from the metabolic power–time curves, and their quantitative relationship with the concentration were analyzed. The half inhibition concentration (IC50) of Schiff base and its complex were calculated to be 1.18 × 10−2 mol L−1 and 1.07 × 10−3 mol L−1, respectively. The inhibition effect of the complex showed much stronger than that of Schiff base.

Хімічна і фізична неоднорідності та гази у великому сталевому зливку

For creation of the high-tech equipment that is used in energy, heavy engineering, chemistry and transport, the unique large-sized steel products are required. In the manufacture of such products, large forging ingots in the mass to 600 tons are used. However, an increase in the mass of the ingots leads to the formation of chemical and physical heterogeneity, enlargement and unfavorable distribution of non-metallic inclusions, of the development of segregation defects in them, which reduce the strength and exploitation characteristics of the metal. In this connection, the quality forgings and finished parts are not always meet the producing demands and the loss of metal, in the form of technological waste and rejects are reaching significant values. It is known that eccentric zonal segregation, especially it’s the most dangerous variety - cords, significantly reduce the quality and properties of products from large steel ingots. In connection with the continuous expansion of the production of large ingots, the problem of creating optimal technologies for their formation, which reduce or exclude the possibility of the formation of chemical heterogeneity and cords in steel during crystallization, it is currently important and relevant. In this paper it are presented the results of studies of the structure, gas distribution, physical and chemical heterogeneities in the cross section and height of an ingot in the mass of 140 tons, which was casted in vacuum from steel 25KHN3MFA. It is shown that depending on the temperature and time conditions of ingot hardening, among which the crystallization interval (due to the chemical composition of steels), cooling intensity in different volumes in height and cross section of ingot, temperature gradient before the crystallization front, solubility of alloying elements and gas content in the melt, etc. Based on this, when developing technology for large ingots to ensure their quality, optimal structure and properties should take into account not only their dimensions, but also the combination of these thermokinetic parameters on the crystallization process, dendritic structure formation, manifestations of liquation in different ingot volumes. Keywords: ingot, segregation strip and inclusions, dendrites, structure, oxygen, oxides, sulfides.