Thermogravimetric Analysis Methods Research Articles

Enhancing anti-carbonation properties of oil well cement slurry through nanoparticle and cellulose fiber synergy

The anti-carbonation property of oil well cement (OWC) is critical for sealing efficiency of wellbores under geological CO2 sequestration. However, gas migration through OWC around wellbores may lead to a deterioration and failure of the entire storage system. Developing carbon-resistant cement has been the emerging trend in the research community. Previous studies mainly focused on nanoparticles alone to enhance performance of OWC, and the purpose of the research is to explore the synergy of nanoparticles and cellulose fiber (CF) in enhancing engineering properties (e.g., carbonation resistance) of oil well cement slurry. The focus was on investigating compressive strength, permeability, pore structure, and carbonation depth associated with the micro-level texture in a CO2 corrosion environment using X-ray diffraction, Scanning Electron Microscopy, and thermogravimetric analysis methods. Four nanoparticles, namely, nano-SiO2 (NS), nano-TiO2 (NT), nano-Al2O3 (NA), and nano-CaCO3 (NC), were selected for the mixture design. Results indicated that the incorporation of 1∼2 % NPs into the OWC paste resulted in a notable decrease in portlandite and an increase in calcium silicate hydrates, thereby enhancing compressive strength and hydration process. In addition, the single admixture of CF could minimize the formation of cracks in the cement matrix and reduce the average carbonation depth by 54 %. More importantly, the synergy of CF and NP significantly improved the resistance of OWC to carbonation, and the OWC mixed with CF and NS displayed the highest carbonation resistance.

Synthesis, vibrational, thermal, topological, electronic, electrochemical stability and DFT studies of new DABCO based ionic liquids

The design of new ILs with different anions could provide interesting physico-chemical properties and for these reasons, the knowledge about the synthesis, the thermal, vibrational, topological, electronic, electrochemical properties and interaction between the selected cation-anion in these ILs are important subjects. Therefore, the understanding about these properties of these compounds is an important subject of study. In this work, we studied three ionic liquids based on the 1-decyl-1,4-diazabicyclo[2.2.2]octane, DABCO-cation, where the corresponding anions were [Br]-, [PF6]-, and [N(SO₂CF₃)₂]-. The syntheses of these bicyclic DABCO ionic liquids are based on an alkylation reaction of 1,4-diazabicyclo [2.2.2] octane and 1-bromodecanefollowed by anion exchange. The obtained ILs are characterized by 1H, 13C, 19F and 31P-NMR spectroscopy. Vibrational spectroscopy studies are conducted by infrared (FTIR/ATR) and Raman spectroscopy in the wavenumber range 600-4000 cm-1 and 45-3500 cm-1, respectively. Furthermore, the thermal stabilities were investigated using the thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) methods. Results indicate that the thermal stability follow the order [C10DABCO][Br]<[C10DABCO][PF6]<[C10DABCO][N(SO₂CF₃)₂]. Additionally, the structural parameters, electrostatic potential (ESP) maps, interaction energies, non-covalent interaction (NCI), atoms in molecule (AIM) analysis, natural bond orbital (NBO), frontier molecular orbital (FMO) analysis and Electrochemical window (ECW) are studied and analyzed by means of DFT calculations at the M06-2X-GD3/AUG–cc–pVDZ level of theory.

Thermal analysis of St. John's Wort wastes and biochars: A study of combustion characteristics and kinetics

St. John's wort, extensively utilized in industries such as food, medicine, and cosmetics, generates substantial biomass waste. Utilizing these wastes is crucial to reducing environmental harm and making an economic contribution. This study aimed to determine the potential of St. John's wort wastes and biochar forms produced from these wastes to be used as solid fuel. In this context, the combustion behavior of the biomass and biochar were determined by thermogravimetric analysis method. Additionally, the Kissenger-Akahira-Sunosa and Flynn-Wall-Ozawa techniques were used to compute the combustion activation energies of these samples. According to the analysis, biomass combustion commenced at approximately 250°C and occurred in two stages, whereas biochar combustion initiated at around 400°C and proceeded in a single stage. Furthermore, over 90% of the mass from both samples was observed to decompose during combustion, with average combustion activation energies ranging between 70.08 and 203.86 kJ/mol for biomass and biochar, respectively. These findings suggest that biomass exhibits more readily combustible characteristics compared to biochar but is less energy efficient. In conclusion, optimizing the biochar production process could enhance its energy efficiency and potentially narrow the performance gap between biomass and biochar. Additionally, further research into alternative methods or additives to improve the energy efficiency of biomass combustion is warranted.

Kinetic parameters of thermal decomposition of biofuels and its oil-containing composites

The kinetic features of the decomposition of fuel pellets formed from birch phloem and its composites with the addition of oil-containing waste (OCW) were studied by methods of thermogravimetric analysis carried out in various atmospheric conditions. The characteristic temperature ranges of thermal decomposition of the materials from which pellets are formed were identified, the rates of mass loss and activation energy at the main stages of thermal decomposition were evaluated, and the combustion indices of composite compositions were determined to identify the possibility of using such compositions as alternative fuels. By evaluation of activation energies for each stage of sample decomposition, the limiting influence of certain stages on the process of thermal destruction was established.

Investigation of the Effect of Temperature on the Biofuel Performance of Hydrochar Obtained from Kidney Bean Shell

In this study, hydrochar products were obtained from kidney bean shell (KBS) biomass at different temperatures using the hydrothermal carbonization (HTC) method. Hydrochar products were produced at three different temperatures (200, 220 and 240 C) and a holding time of 90 minutes. Biomass/water ratio was taken as 1:10. Analysis techniques such as Thermogravimetric analysis (TG), Ultimate analysis and Fourier Transform Infrared Spectroscopy (FTIR) were used in the characterization of raw materials and hydrochar products. In addition, the fuel properties (high heating value, energy yield and energy densification ratio) of raw KBS and hydrochar products were also investigated. As the HTC temperature increases, the high heating value of hydrochar products increases. Among hydrochar products, the highest high heating value belongs to the product obtained at 240 C. The combustion behavior of raw and hydrochar a product was examined using the thermogravimetric analysis method and combustion parameters (Ti, Tb and Tm) were determined. As a result, this study has shown that the hydrochar product produced from KBS by hydrothermal carbonization method can be used as a biofuel material.

Physical & mechanical properties of pervious concrete incorporating municipal solid waste incineration bottom ash

Municipal solid waste incineration bottom ash (BA) as a cementitious substitute in pervious concrete constitutes a viable strategy for waste recycling and carbon emission mitigation. Nonetheless, the resultant alterations in the cementitious matrix composition and the inter-aggregate macro-porous structure induced by BA incorporation still need to be explored, limiting a thorough understanding of the mechanical behavior and permeability. Macroscopic tests were employed to investigate the impact of BA and compaction densities on the physical and mechanical properties. The effects of BA on the hydration products were analyzed using X-ray diffraction (XRD) and thermogravimetric analysis (TG) methods. The results reveal that at a density of 2190 kg/m³, BA has minimal effect on the interconnected porosity and permeability. However, as the density increases, a higher BA substitution ratio leads to a narrowed pore distribution and a significant reduction in permeability. Furthermore, a power-function relationship exists between the compressive strength and dynamic modulus of elasticity. At a 15 % substitution ratio, a slight decrease in hydration products was observed, resulting in a minor reduction in compressive strength. Concurrently, a linear relationship was established between the proportion of tiny pores (less than two mm2) and the relative compressive strength. Considering both permeability and mechanical performance, pervious concrete with a density of 2310 kg/m3 and containing no more than 10 % BA meets the requirements of the CJJ/T135-2009 standard. These findings provide a scientific basis for the mix design of pervious concrete incorporating BA.

Synthesis, Structural Characterization, and Computational Studies of Novel Co(II) and Zn(II) Fluoroquinoline Complexes for Antibacterial and Antioxidant Activities.

Research into heterocyclic ligands has increased in popularity due to their versatile applications in the biomedical field. Quinoline derivatives with their transition metal complexes are popular scaffolding molecules in the ongoing pursuit of newer and more effective bioactive molecules. Subsequently, this work reports on the synthesis and possible biological application of new Zn(II) and Co(II) complexes with a bidentate quinoline derivative ligand (H2 L), [(H2 L):(E)-2-(((6-fluoro-2-((2-hydroxyethyl)amino)quinolin-3-yl)methylene)amino)ethanol]. The ligand and its metal complexes were structurally characterized by spectroscopic methods (1H NMR, 13C NMR, Fourier transform infrared (FTIR), UV-vis, fluorescence, and mass spectroscopy), as well as by thermogravimetric and elemental analysis methods. The spectroscopic findings were further supported by density functional theory (DFT) and time-dependent (TD)-DFT calculations. The biological application was examined by investigating the inhibitory action of the complexes against bacterial strains using diffusion and agar dilution methods, and their profiles against two Gram-positive and Gram-negative bacterial strains were supported by molecular docking analysis. To rationalize the in vitro activity and establish the possible mechanism of action, the interactions and binding affinity of the ligand and complexes were investigated against three different bacterial enzymes (Escherichia coli DNA gyrase (PDB ID 6f86), E. coli dihydrofolate reductase B (PDB ID: 7r6g), and Staphylococcus aureus tyrosyl-tRNA synthetase (PDB ID: 1JIJ)) using AutoDock with the standard protocol. The MIC value of 0.20 μg/mL for zinc complex against E. coli and associated binding affinities -7.2 and -9.9 kcal/mol with DNA gyrase (PDB ID 6f86) and dihydrofolate reductase B (PDB ID: 7r6g), as well as the MIC value of 2.4 μg/mL for cobalt(II) complex against Staphylococcus aureus and the associated binding affinity of -10.5 kcal/mol with tyrosyl-tRNA synthetase (PDB ID: 1JIJ), revealed that the complexes' inhibitory actions were strong and comparable with those of the standard drug in the experiments. In addition, the ability of the new quinoline-based complexes to scavenge 1,1-diphenyl-picrylhydrazyl radicals was investigated; the findings suggested that the complexes exhibit potent antioxidant activities, which may be of therapeutic significance.

Stepwise Multi-Temperature Thermogravimetric Analysis (SMT-TGA) for Rapid Alloy Development

AbstractA stepwise multi-temperature thermogravimetric analysis (SMT-TGA) method is a rapid and time- and material-efficient measurement procedure for oxidation kinetics over a wide range of temperatures. It is suitable for alloy design and material selection procedures. It involves subjecting a sample to a series of steps at increasing temperatures, followed by steps at decreasing temperatures to identify possible effects on the evolution of oxide layer microstructures on oxidation kinetics. This method has been tested for a wide range of metallic alloys in the present work, allowing for the mapping of possible ranges of parabolic oxidation kinetics of industrial alloys between 600 and 1300°C. Two examples of effects of thermal history have also been described in this publication.

Repercussion of fiber content on the mechanical, thermal, and thermomechanical properties of natural fibers reinforced thermoplastic composites for automotive application

Natural fibers are becoming very popular as a reinforcement in composite materials owing to their benefits, such as low-price, lightweight, availability, and environmental friendliness. In this study, abaca fiber-reinforced polypropylene (PP) and high-density polyethylene (HDPE) composites were created with the help of the injection molding method. Prior to composite fabrication, abaca fibers were chemically treated with a 5 wt% caustic soda (NaOH) solution to improve the bonding between the abaca fibers and the matrix and to enhance their properties. Scanning electron microscopy (SEM) was utilized to assess the fiber surface microstructures before as well as after the chemical treatment, along with the fractured surfaces of tensile specimens. The mechanical properties, such as tensile, bending, and impact strength, of abaca/PP and abaca/HDPE composites were evaluated and compared. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) methods were utilized to investigate the thermal behavior of composites. Also, the dynamic mechanical analysis (DMA) method was utilized to explore the thermomechanical properties of the fabricated composites. The outcomes of the experimental findings showed that abaca/PP composite with 10 and 20 wt% fibers is the best choice of material to be used in the automobile industry.

Sorption kinetics of salt-in-porous-matrix composites: The effect of expanded natural graphite on cooling power

Sorption heat transformers and thermal energy storage systems are emerging technologies that utilize and store low-grade waste heat for heating and cooling applications. The performance of sorption systems is not only affected by systems’ operating conditions, and overall systems’ design but also by sorption material or composite parameters such as thermal diffusivity, composition, and pore structure, among others. In this study, CaCl2-based salt-in-porous-matrix composites of different compositions and coating thicknesses were synthesized. During synthesis, salt to silica gel and polyvinyl alcohol to silica gel ratios were fixed and the thermal additive (expanded natural graphite) to silica gel ratio was varied with care from 0 to 0.26 (or 0 to 20.5 wt.%, additive to silica gel ratio). The thickness of samples varied from 2.3 to 8.3 ± 0.1 mm. The composites were characterized by a transient plane source (thermal conductivity and thermal diffusivity), nitrogen adsorption porosimetry (specific surface area and total pore volume), and thermogravimetric sorption analysis (water sorption equilibrium) methods. A custom-built gravimetric large pressure jump (G-LPJ) testbed was used to study water sorption kinetics (water uptake vs. time) for selected samples. The thermal conductivity and diffusivity of the studied composite samples have shown significant enhancements, e.g., 240% (0.11 W/(m·K) vs. 0.37 W/(m·K)) and 310% (0.21 mm2/s vs. 0.87 mm2/s), respectively, by adding 12.5 wt.% expanded natural graphite (additive to silica gel ratio is 0.14) as a thermally conductive additive (additive to silica gel ratio) because of thermal percolation effect. This ratio of expanded natural graphite to silica gel was found to be optimal for studied composition. The results indicate that sorption composites with higher thermal diffusivity offer notably higher specific cooling power and improved sorption kinetics, compared to the composites without expanded natural graphite of the same thickness (850 W/kg vs. 480 W/kg at 70% water conversion for samples with thickness of 5.3 mm).

Authentication of Mentha arvensis essential oil using attenuated total reflectance-Fourier transform infrared spectrophotometry coupled with chemometrics

Mentha arvensis essential oil is considered a product of high economic value that finds application in the food, pharmaceutical, and cosmetic industries. They are subjected to adulteration with synthetic chemicals and low-cost vegetable oils with higher boiling points. A rapid, non-destructive method using infrared spectroscopy has been investigated to authenticate Mentha arvensis Essential oils, helping to maintain their quality and trustworthiness for users who rely on them for their beneficial properties. Authentic samples of Mentha arvensis essential oil were obtained and analyzed using Attenuated Total Reflectance-Fourier Transform Infrared spectroscopy in the wavenumber range of 500–4000 cm−1. The resulting spectra were pre-processed with Multiplicative Scatter Correction. The initial investigation involved exploratory analysis using Principal Component Analysis, followed by discriminant analysis using Principal Component Analysis-Linear Discriminant Analysis, Partial Least Squares-Discriminant Analysis, and Soft Independent Modelling for Class Analogy. The classification models developed have a high accuracy of 100 % thus demonstrating higher efficiency in distinguishing different adulterants in Mentha arvensis essential oil with both high specificity and sensitivity. To assess the extent of adulteration in Mentha arvensis essential oil, Partial Least Squares Regression and Principal Component Regression were employed. The regression models were capable of identifying adulteration levels as low as 5 % in the essential oil thus enabling FTIR spectroscopy coupled with chemometrics to serve as a non-destructive method for identifying commonly used adulterants, potentially replacing traditionally used Chromatographic and Thermo-Gravimetric Analysis methods.

Synthesis of bilaterally thiadiazole substituted vic-dioxime ligands and investigation of their polymeric metal complexes

In this study, three novels substituted 1,3,4-thiadiazole-derived vic-dioxime ligands and their corresponding polymeric transition metal (Co2+and Ni2+) complexes were synthesized and their structural characterizations were performed. For this purpose, 4,4′-bis(chloroacetyldiphenyl) ether (OKS1) was obtained from the reaction of diphenyl ether with chloroacetyl chloride at a 1:2 molar ratio with the help of the Friedel-Crafts reaction. Our first starting oxime compound “2,2′-(oxybis(4,1-phenylene))bis(N‑hydroxy-2-oxoacetimidoyl) chloride (OKS2)” was obtained from the reaction of OKS1 with butyl nitrite at a 1:2 molar ratio under the catalysis of HCl gas. Then, our final starting vic-dioxime compound “2,2′-(oxybis(4,1-phenylene))bis(N‑hydroxy-2-(hydroxyimino) acetimidoyl) chloride (OKS3)” was obtained from the reaction of OKS2 with hydroxylamine hydrochloride in ethanol media at 40 °C. Then, our three original target vic-dioxime compounds (OKL1-OKL3) were synthesized from the reaction of substituted 2-amino-1,3,4-thiadiazole compounds with OKS3. Structural characterizations of all synthesized organic compounds were made using elemental analysis, FTIR, 1H and 13C NMR and mass spectroscopy methods. Target complexes were obtained from the reaction of all ligands with MCl2.nH2O (M: Co2+and Ni2+) salts, and their structures were elucidated using FTIR, magnetic susceptibility, thermogravimetric analysis, elemental analysis, and ICP-OES spectroscopy methods.

INVESTIGATION OF THE KINETICS OF THE COAL PYROLYSIS PROCESS

The study of the processes occurring in the temperature range of the main decomposition of the organic mass of coal (OMC) makes it possible to understand both the general patterns and the specifics of the decomposition of solid fuels. This temperature interval is used to calculate the kinetic parameters of the process, which carry important information both about the nature of the structural-chemical transformations and about the structure and direction of thermal destruction of OMC. In this article, to study the kinetics of pyrolysis of coal, the method of thermogravimetric analysis was used, in which heating of coal samples was carried out in ceramic crucibles in the temperature range of 25-900 °C at different heating rates (5-25 deg/min) in nitrogen and oxygen media. Coal from the Kenderlyk deposit was chosen as the object of study. Based on the constructed differential DTG curves (dependence of the sample mass change rate on time) at different heating rates, the kinetic parameters of pyrolysis of coal were calculated using the equations of non-isothermal formal kinetics. The effect of the rate and temperature of coal heating on the kinetic parameters of pyrolysis of coal has been studied. The main stages of OMC decomposition are revealed. It has been found that the heating rate of coal samples significantly affects the temperature and process rate corresponding to the main decomposition maxima on the differential DTG curves. The dependence between the kinetic parameters of pyrolysis of coal in the temperature range of the main decomposition of OMC on the rate and temperature of heating, as well as between the kinetic parameters at different stages of the main decomposition of coal, is analyzed.

THERMOGRAVIMETRIC ANALYSIS OF PULVERIZED RICE HUSK WASTE CATALYTIC COMBUSTION WITH NATURAL ZEOLIT

Rice husk is a type of agricultural waste that generated from rice production activities. The number continues to increase in line with the increasing food needs of the people in Indonesia. This study aims to determine the effect of the addition of natural zeolite as a catalyst and to determine the effect of natural zeolite mass percentage variation in the mixture on rice husk waste catalytic combustion by using the thermo gravimetric analysis method. The results of this study show that there is an effect of adding natural zeolite catalysts with the mass percentage of natural zeolite variations on the combustion characteristics and activation energy of each mixture. Increasing the mass percentage of natural zeolite catalysts can affect the reaction process become faster and minimize the effort required, but it was found that if the amount of natural zeolite catalyst is too much, it only adds to the heating load which causes slower reaction. The mixture of rice husks with 10% natural zeolite catalyst is the most optimal mixture because it has the lowest required activation energy value and the combustion reaction phases are achieved at a lower temperature than 5% and 15% mass percentage variations.

Research on the co-combustion characteristics and kinetics of rice husk hydrochar with anthracite

Co-combustion of anthracite and hydrochar derived from hydrothermal carbonization with process water recirculation was proposed as an effective way to achieve a transition to low-carbon energy in industries that rely heavily on coal combustion. In this study, thermogravimetric analysis and model-free methods were employed to investigate the co-combustion characteristics and kinetics of anthracite and hydrochar. The results demonstrate that the carbon content of hydrochar is lower than that of anthracite, but the volatile content is higher than that of anthracite, indicating that hydrochar has better combustion performance. There is a synergistic effect in the co-combustion reaction of hydrochar and anthracite. With the increase of the hydrochar addition ratio, the ignition and burnout temperatures of anthracite decrease gradually. With the increase of temperature rise rate, the combustion reaction is enhanced and the combustion performance of anthracite is improved under the fixed mixing ratio. According to the calculation of combustion activation energy by Flynn-Wall-Ozawa and Kissenger-Akahira-Sunose methods, the apparent activation energy of the mixed samples gradually decreases with the increase of combustion conversion rate. When the addition of hydrochar is 60 %, the average apparent activation energy of the mixed sample is the lowest, which is 66.51 kJ mol−1 and 54.62 kJ mol−1, respectively.

Silver Nanoparticles Decorated in In Situ Reduced Graphene Oxide Nanohybrids Improved Properties in Poly(vinylidene fluoride)/Poly(methyl methacrylate) Blends

In this paper, reduced graphene oxide decorated with silver nanoparticle (rGO-Ag) nanohybrids were prepared using an environmentally friendly approach and incorporated as reinforcement in poly(vinylidene fluoride)-poly(methyl methacrylate) blends via a melt mixing process. The microstructure of rGO-Ag nanohybrids and its effect on the microstructure, mechanical, thermal, and electrical properties of the PVDF/PMM/rGO-Ag was studied using Fourier transform infrared (FTIR), Raman spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), tensile, thermogravimetric analysis (TGA), and impedance spectroscopy methods. FTIR and TEM analysis confirmed that rGO-Ag successfully synthesized and Ag nanoparticles are located on the rGO surface. The tensile analysis demonstrated that incorporating 1 wt.% of rGO-Ag in PVDF/PMMA blend increases Young’s modulus and strength of nanocomposite up to 31% and 35%, respectively. The Halpin-Tsai model was also used for PVDF/PMMA/rGO-Ag nanocomposites, and the results confirmed that this model works well to predict the tensile modulus. Impedance spectroscopy analysis showed that the presence of rGO-Ag nanohybrids in PVDF/PMMA blend effectively enhanced the conductivity of PVDF/PMMA blend. TGA results demonstrated that the presence of rGO-Ag nanohybrids enhanced the thermal stability of nanocomposites and increased the degradation temperature of PVDF/PMMA/rGO-Ag nanocomposites in the range of 20°C compared to PVDF/PMMA blend.

Study on the Influence of Porous Gel on Coal Pyrolysis Performance Based on Experiments and Molecular Simulation

ABSTRACT Studying the kinetics of pyrolysis in pure coals and mixed coals (coals treated with porous gel) holds immense significance in effectively preventing and controlling the spontaneous combustion occurrences in coal. Firstly, porous gel materials were prepared based on physical mixing and chemical crosslinking reaction. Then, based on the thermogravimetric analysis method, the pyrolysis mechanism of porous gel in coal was studied using Flynn-Wall-Ozawa(FWO), Kissinger-Akahira-Sunose(KAS) and Coats Redfern models. Determine the mechanism of coal pyrolysis reaction using the Reaxx FF MD reaction mechanics model. Finally, the inhibition mechanism of porous gel on coal is analyzed through leading temperature rise experiment. The main reaction mechanisms of coal pyrolysis are the diffusion model in the low-conversion-rate range (D4), the R2 and R3 in the high-conversion-rate range, and the Avrami erofeev model (A2, A3). The molecular simulation results indicate that increasing the heating rate can accelerate the rate of coke cracking.

Functionalization of a liquid natural rubber by iron‐mediated radical chloro‐nitration and its thermal decomposition

AbstractThis study presents the functionalization of liquid natural rubber (LNR) by iron‐mediated radical chloro‐nitration over the LNR backbone, resulting in a chloro‐nitro compound of liquid natural rubber (Cl‐N‐LNR). The chloro‐nitration was prepared by a reaction of LNR with iron(III) nitrate nonahydrate and iron(III) chloride in an organic solvent. The structure of the obtained product was confirmed by using Fourier‐transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (1H NMR), and carbon‐13 nuclear magnetic resonance (13C NMR), which showed the existence of chloro‐nitro groups in the Cl‐N‐LNR chain. The degree of functionalization with a nitro group is 13.4% mol units of Cl‐N‐LNR. The thermal degradation was determined by the thermogravimetric analysis (TGA) method. As a result, the kinetic parameters for the degradation of Cl‐N‐LNR were calculated in the range from 40 to 330 °C. The half‐life of Cl‐N‐LNR was found to be about 33.0 years.

Reaction mechanism of micron-sized aluminum powders in O2 and CO2 gradually heated environment

The behavior of aluminum powders in specific oxidized environment is different from each other obviously. Thermal behaviors of micron-sized aluminum powders in different oxygenated and gradually heating environments were discussed in order to find out the oxidation mechanism. Particular attention is paid to the reaction mechanism of oxygen and carbon dioxide atmosphere. Thermogravimetric analysis and related characterization methods are used and the results demonstrated that under the certain condition, reaction process of micron-sized aluminum powders can be divided into four stages. General routes for the oxidation of micron-sized aluminum in general heating system are the same, however, itis different among the extent of reaction at the third stage in different kinds of oxidizing gas atmospheres. Gas phased products were detected during the main reaction stage under carbon dioxide by combining thermal analysis and mass spectrometry which contributes to the rupture of alumina shell and further reaction of micron-sized aluminum powders. Consequently, rapider and more complete reaction process was achieved. The increasing thickness of original alumina shell can restrict the reaction rate of aluminum powders harder at the same time.

EFFECT OF FILLING A POLYURETHANE MATRIX WITH KAOLIN ON DAMPING EFFICIENCY, MECHANICAL AND THERMAL PROPERTIES.

One of the ways to reduce the cost of a polymermaterial is to replace the weight part of its composition with a cheaper natural filler. In this work, the objects of study are polyurethane composites synthesized by the insitumethod, containing the mineralfiller kaolin from 10 to 40 mass parts. Filling with kaolin significantly lowers the price of polyurethane material, and its cost is reduced by almost 30 percent when the content of the filler is 40 mass parts. Morphological studies have shown that kaolin particles are uniformly dispersed in the poly­urethane matrix, but thereis a tendency for the iragglomerationas the filler concentration increases. Viscoelastic, mechanical, and thermal properties of polyurethane composites wer studied. The damping efficiency of polyurethane materials was estimated from the results of dynamic mechanical analysis. Itis found that the filler additions lightly decreases the effective damping temperature range of polyurethane composites, but their heat resistance and mechanical properties improve. The method of thermogravimetricanalysis was shown the presence of kaolin significantly changes the character of thermo-oxidative destruction of composites. The temperature interval of the intensive decomposition stage increases for filled systems and the temperature of the maximum rate of weight loss at the decomposition stage (Tmax) increases with increasing kaolin content. According to the results of mechanical studies, an increase in the kaolin content in polyurethanes leads to an increase in the storage modulus (E') and a significant decrease in the relative elongation (ε). Thus, filling with kaolin significantly reduces the cost of polyurethane composites and contributes to their expansion of functional properties due to increased heat resistance and improved mechanical characteristics.