Thermogravimetry Methods Research Articles

The effect of graphite nanoslabs on thermal oxidative destruction of polyethylene

The impact of graphite nanoslabs on thermal oxidation of polyethylene is studied via the methods of dynamic thermogravimetry and isothermal oxidation. Graphite nanoslabs are shown to exert an inhibiting effect on thermal oxidation of polyethylene, which leads to an increase in the induction period and in the oxygen-absorption rate. That there is an abnormal effect of the nanofiller content on the resistance to thermal oxidative destruction of composites, mainly for diffusion reasons, is established as well.

Research of ''water glass - graphite microparticles'' composite material by thermogravimetry method

Research of ''water glass - graphite microparticles'' composite material by thermogravimetry method

Thermal analysis of earlywood and latewood of larch (Larix gmelinii (Rupr.) Rupr.) found along the Polar tree line

This paper deals with the results of a study of the thermodestruction of the earlywood and latewood in the 1988–1998 growth rings of Gmelin larch (Larix gmelinii (Rupr.) Rupr.) trees growing along the polar tree line (70o52′53″N, 102°58′26″E, Taimyr Peninsula). The study used methods of thermogravimetry (TG/DTG) and differential scanning calorimetry (DSC). Thermogravimetric data obtained were analyzed by Ozawa–Flynn–Wall kinetic model. We determined macrokinetic parameters of thermodestruction. Earlywood and latewood showed no significant difference in cellulose/hemicellulose/lignin ratio, whereas they differed significantly in destruction average value of activation energy (197.55 and 55.90 kJ mol−1, respectively). Our analysis of the correlation of thermodestruction values with mean monthly air temperature and precipitation revealed that component composition of both earlywood and latewood was influenced more by the weather conditions at the beginning of the growing season (April–June). Air temperature had markable influence on the wood component composition during cell wall synthesis only in latewood, whereas precipitation influenced the composition in both latewood and earlywood. TG/DTG and DSC methods were found to be promising for developing information on biochemical composition of early and latewood tracheids in stems and for identifying the extent of the influence of climatic changes on cell wall synthesis.

POLYPHENOLS OF WOODY BARK – ORGANIC PRECURSORS TO PRODUCE ON THEIR BASIS OF POLYMER AEROGELS

New method for preparation of organic aerogels by sol-gel polymerization of formaldehyde with polyphenols (PFs), isolated from larch bark of and inner birch bark, was developed. The functional composition and properties of the original PFs were studied by thermogravimetry methods and FTIR- spectroscopy. It was found that larch polyphenol substances possess greater thermal stability in the temperature range 25-700 °C, while the process of thermal decomposition of birch bark polyphenols completes to 600 °C. It has been established that polyphenol larch compounds in their composition contain more aromatic structures and hydroxyl groups. The effect of the pH value of gelation solutions in the range of values from 4 to 12 on the porous structure of organic gels synthesized on the basis of polyphenols was studied. Porous structures and adsorption properties of polyphenol-formaldehyde organic gels were studied using BET method, scanning electron microscopy and sorption (methylene blue and gelatin). It is shown that an increase in pH contributes to the formation of a product with a more compacted texture. The electron microscopic images of polymer gels demonstrate a uniform granular texture with visible micro globules with an average particle size of ≈ 50-70 nm.

GETERONUCLEAR BIS(GALACTARATO)GERMINATES OF COBALT(ІІ), COPPER(ІІ), NICKEL(ІІ): SYNTHESIS, STRUCTURE AND CHEMICOPHYSICAL PROPERTIES

Heterometallic bic(galactarato)germanates of cobalt(ІІ), copper(ІІ) and nickel(ІІ) were synthesized for the first time and characterized with the method of elemental analyses, thermogravimetry and IR-spectroscopy.The IR-spectrum of the synthesized compounds showed the presence of nas(COO-) ~ 1600 сm-1, ns(COO-) ~ 1390 сm-1 and valence vibrations of the bond M-O ~ 530 сm-1. All this points on the deprotonation of carboxylic groups. The values of valence vibrations of carboxylate ions, the absence of narrow band ν(ОН) at 3600 сm-1 and presence of ν(Ge-O) at685 сm-1 allows us to conclude, that germanium coordination unit is formed by the bonding with oxygen atoms in hydroxyl groups and without any participation of ones in carboxylic groups. This statement is confirmed by the absence of hydroxyl ν(C-O) vibrations, which are specific for galactaric acid, and presence of alkoxyl n(С-О) vibrations. It was found that inner sphere of the synthesized compounds performs to be different-metal Ge4+–M2+ complex anion, the charge of which is neutralized by the hexa-aqua cation of 3d-meteal [М(Н2О)6][Ge(μ-HGala)2{М(H2O)2}2]·5H2O (HGala5- – galactaric acid anion, М – Сo2+, Ni2+, Cu2+). Their structure and chemical reaction is suggested to be next: GeCl4 + 2H6Gala + 3M(CH3COO)2 + 10NH4OH + 5H2O → [M(H2O)6][Ge(μ3-HGala)2{M(H2O)2}2]·5H2O + 6CH3COONH4 ++4NH4Cl

New amorphous nanophosphors obtained by evaporation of silicates and germanates REE

Abstract Amorphous nanophosphors have been produced by pulsed electron beam evaporation of bulk phosphors of rare earth elements (REE) silicates and germanates with oxyapatite structure activated with europium. The processes of crystallization of amorphous nanopowders (NP) have been studied by differential scanning calorimetry and thermogravimetry (40–1400°C) methods. A modification of the Raman and IR spectra of the samples was found when the particle size decreased from bulk to nanostate due to insignificant polymerization of Si(Ge)O4 tetrahedra. The spectral and luminescence characteristics of the bulk samples as well as nanoamorphous samples have been examined. It was established that Eu3+ forms two types of optical centers. Upon the transition of Sr2Gd8(SiO4)6O2:Eu3+ phosphor from bulk state to nanostate during laser excitation, the luminescence intensity of Eu3+ ions increases 10 times. Blue and white amorphous nanophosphors have been obtained for the first time by evaporation of Ca2M8(SiO4)6O2:Eu (M=Y, Gd) and Ca2La8(GeO4)O2:Eu phosphors. Radiation reduction of ions Eu3+→Eu2+ in electron beam has been presumably found.

Study on the mechanism of desulfurization and denitrification catalyzed by TiO2 in the combustion with biomass and coal

The effects of Ca/S molar ratio, catalyst type, catalyst dosage, temperature on desulfurization and denitrification efficiency were investigated in the coal-powder combustion with corn cobs as biomass. The thermal characteristics of Shanxi coal and corn cob blends with V-TiO2 were evaluated by thermogravimetric analyzer. The catalytic mechanisms of V-TiO2 on combustion, desulfurization and denitrification were discussed, suggesting that the mechanisms are in good agreement with the experimental data. The results show that the control parameters of the ideal desulfurization and denitrification efficiency should follow that the dosage of V-TiO2 catalyst is 8% with a Ca/S ratio of 2.3 at a treatment temperature 850 °C. Meanwhile, the combustion efficiency could be effectively improved with the mixture of corn cob and V-TiO2. The thermal characteristics of coal char and corn cob char blends with V-TiO2 were evaluated using thermogravimetric analysis and derivative thermogravimetry methods to discuss the heterogeneous NO reduction mechanisms. The results show that the biomass chars were more active than coal chars in reducing NO, and the specific surface area of the chars was increased with V-TiO2, which indicates that V-TiO2 exhibits significant influence on catalytic combustion, desulfurization and denitrification.

Calibrated quantitative thermogravimetric analysis for the determination of portlandite and calcite content in hydrated cementitious systems

Portlandite and calcite are compounds of interest regarding different processes related to microstructural and durability issues of cementitious materials, such as carbonation, pozzolanic action, and hydration degree. The quantification of their contents in cementitious systems is thus frequently required. Thermogravimetry (TG) measures the change in mass of a material (as a function of time) over a temperature range using a predetermined heating rate. The TG method can be applied with certain success to estimate portlandite and calcite contents in the hydrated cement system, considering the temperature range at which each compound decomposes and releases water or carbon dioxide, respectively. However, a mature hydrated cement paste contains hydrated calcium silicate, portlandite and calcite phases. The quantification procedure is therefore complicated because of the concurrent interference among them. The tangential method over the TG signal or the integral method over the derivative TG curve is usually used to discount water loss from hydrated calcium silicates over the temperature range at which portlandite and calcite decompose. However, by the use of TG consistent underestimation of portlandite content in hydrated cementitious systems is still described in the literature. Potential causes for this underestimation are analysed in this paper, and a calibration procedure by means of an internal standard is proposed. Cement paste and aggregate samples are analysed. Differences between TG quantifications of these pure samples and those diluted with low contents of internal standards are compared with the added amounts of internal standard. In that way, a calibration method of the device is applied for correction of the actual portlandite and calcite contents in the samples. For this purpose, both analytic quality calcite and freshly prepared portlandite were used as internal standards. The results show that improved quantifications can be achieved with this calibration. Also, calcite seems to be more suitable as internal standard than portlandite as the best outcome was obtained for the first case.

Influence of Nanosilica on Water-phase Transitions in Hygroscopic Systems

By low-temperature 1H NMR spectroscopy and thermogravimetry methods, the effect of hydrophobic (AM1) and hydrophilic (A-300) nanosilica on the process of evaporation and freezing water, linked to hygroscopic grape seed extract, biopreparation Enoxil (Ex), has been studied. It is shown that nanosilica modifies the character of binding water in composite systems. The total amount of water retained in the composite becomes substantially smaller than in pure biopreparation. This effect can be used to stabilize lyophilized biological tissues and cell cultures.

Oxygen isotope exchange, water uptake and electrical conductivity of Ca-doped lanthanum zirconate

Proton concentration of La1.9Ca0.1Zr2O7−α in H2O–O2 atmospheres has been measured by means of the method of high temperature thermogravimetry. The oxygen diffusion coefficient and the oxygen surface exchange coefficient have been measured for La1.9Ca0.1Zr2O7−α over the temperature range of 600–900°C using the oxygen isotope exchange method with gas phase equilibration. pO2-dependencies of the electrical conductivity have been determined in the temperature range 500–800°C and oxygen partial pressure range of 10−20<pO2<0.21atm in atmosphere saturated with water vapour at 25 °С (pН2О=0.03atm). Ionic conductivity has been divided into protonic and oxygen-ionic components. The influence of oxygen defect structure on the water uptake, oxygen diffusivity and electrical conductivity of La1.9Ca0.1Zr2O7−α has been discussed.

Fabrication and oxidation behavior of Al4SiC4 powders

AbstractAl4SiC4 powders with high purity were synthesized by heating the powder mixture of aluminum (Al), silicon (Si), and carbon (C) at 1800°C in argon. The microstructure is characterized as platelike single grain. Both the nonisothermal and isothermal oxidation behavior of Al4SiC4 was investigated at 800°C‐1500°C in air by means of thermogravimetry method. It is demonstrated that Al4SiC4 powder possesses good oxidation resistance up to 1200°C and is almost completely oxidized at 1400°C. At 800°C‐1100°C, the oxide scales consist of an Al2O3 outer layer and a transition layer. Al4SiC4 remains the main phase. At 1200°C, some spallation resulting from the increment of Al2O3 and the mismatch of thermal expansion coefficient between different product layers can be observed. Above 1300°C, the oxide layer is composed of two part, i.e., large‐scale Al2O3 crystals (outer layer) and mullite with less amount of SiO2 (inner layer). The oxidation behavior changes due to the different oxide products. For the reaction kinetics, a new kind of real physical picture model is adopted and obtains a good agreement with the experimental data. The apparent activation energy is calculated to be 176.9 kJ/mol (800°C‐1100°C) and 267.1 kJ/mol (1300°C‐1400°C).

Vaporization and deposition of cesium dimolybdate, Cs2Mo2O7

ABSTRACTVaporization and deposition of cesium dimolybdate (Cs2Mo2O7) in argon were studied by thermogravimetry and transpiration methods. From Raman spectra and electron probe microanalysis of deposits and inductively coupled plasma mass spectroscopy of the aqueous trap of the exhaust, it was judged that the Cs2Mo2O7 vaporizes as Cs2Mo2O7 (g). The effect of water addition on Raman spectral of Cs2Mo2O7 was also investigated. Comparing the high-temperature mass losses of Cs2Mo2O7 by thermogravimetry with that of Cs2MoO4, the equilibrium vapor pressure of Cs2Mo2O7 was estimated. The vapor pressure of Cs2Mo2O7 (l) in its liquid state was calculated to be: log10P (Cs2Mo2O7)(l) = (8.95 ± 0.07) − (1.03 ± 0.01) × 104 /T (T = 1273−1573 K). The enthalpy of vaporization of Cs2Mo2O7 (l) was estimated to be 197 ± 31 kJ·mol−1.

The study of forms of bonding marshmallow moisture with different composition by method of thermal analysis

Marshmallow is a sugar confectionary product with increased sugar content and energy value because of the significant content of carbohydrates, in particular sugar-sand. The main drawback of marshmallow is the rapid process of its drying during storage due to the crystallization of sucrose and the gradual removal of moisture from the product. A method for obtaining marshmallow without sugar on the basis of high-conversion glucose syrup. In the work, experimental studies were carried out to determine the content and ratio of free and bound forms of moisture in marshmallow on the basis of sugars and on the basis of high-conversion glucose syrup by Differential Scanning Calorimetry (DSC) and Thermogravimetry (TG). To study the patterns of thermal effects on the properties of marshmallow samples, the non-isothermal analysis method and the synchronous thermal analysis instrument (TG-DTA / DSC) of the STA 449 F3 Jupiter were used. In the process of thermal exposure, the samples decompose sugars and other organic compounds, as a result of which the sample weight decreases due to evaporation of moisture. The process of dehydration in a control sample of marshmallow using sugar occurs in a less wide temperature range than in a sample of marshmallow on the basis of high-conversion glucose syrup, which indicates a greater degree of moisture bonding in the developed sample. A quantitative evaluation of the forms of moisture bonding in the samples was carried out using the experimental curves obtained by the TG method. From the temperature curves, the endothermic effects were determined, which correspond to the release of moisture with different forms and energies. Substitution of sugar for treacle in the formula of marshmallow reduces the share of free moisture and increases the safety of the product without signs of staling.

Оценка антикоррозионных свойств тонких лент из двойных и тройных медных сплавов

Oxidation tendency of a series of binary copper-based and ternary copper-nickel-based alloys with additions of 3d-transition metals such as Cr, V and Fe has been studied. Oxidation resistance is estimated by the use of thermogravimetry method at the temperature of 700°С, which corresponds to the typical temperature of deposition of buffer and superconducting layers on metal substrates. It has been found that the tapes of binary alloys Cu-0.4%Cr, Cu–1.6%Fe and Cu–0.6%V containing dispersed particles of a second phase with a crystal lattice different from that of the matrix have an oxidation resistance reduced inversely proportional to the particle size. A tape of Cu–0.6%V alloy, in which vanadium particles have sizes as large as few microns has been found to possess an even less oxidation resistance than the copper tape, so it cannot be used for epitaxial deposition of functional layers at high temperatures. Textured tapes of binary alloys Cu–0.4%Cr and Cu–1.6%Fe have better anticorrosion properties at the temperature of 700°С than tapes of pure copper but worse than those of ternary copper-nickel-based alloy tapes. It has been shown that textured tapes of ternary copper-nickel-based alloys containing 30 to 40% Ni and 1–2 wt. % Fe, Cr or V have a FCC solid solution structure without inclusions. Cu–40%Ni–1.2%Cr and Cu–40%Ni–1.4%Fe alloy tapes, in addition to perfect cubic texture and high strength properties, have significantly better anticorrosion properties at temperature 700°С than the tapes of pure copper and other alloys studied. Thus, they can be recommended for a use as substrates for epitaxial deposition of buffer and superconducting layers at high temperatures.

Thermoanalytical Study and Purity Determination of Trospium Chloride and Tiemonium Methylsulphate

The thermal behavior of quaternary ammonium compounds; Trospium chloride and Tiemonium methylsulphate was investigated using different thermal techniques. The thermogravimetry method was used to study the thermal degradation and kinetic parameters; activation energy (Ea), frequency factor (A), and reaction order (n) of both drugs. The data revealed that the cited drugs followed first order kinetic behavior. The fragmentation pathway of both drugs with mass spectrometry was taken as example; to correlate the thermal decomposition with the resulted MS-EI. The melting point and purity were determined using DSC and Van’t Hoff equation for the studied drugs. The results were in agreement with the recommended pharmacopoeias.

ANALISIS TOTAL FENOL PADA BERBAGAI FORMULASI REBUSAN KULIT SALAK BALI SIBETAN KARANGASEM SEBAGAI MINUMAN FUNGSIONAL

Abstract&#x0D; Background: Snakefruit’s bark that only so far as waste, can be processed into a functional beverage is good for health. Snakefruit’s bark contains phenolic compounds which are natural antioxidants in fruits. Objective: The purpose of this study is to determine the total phenol levels and sensory value of stew salak bali sibetan karangasem’s bark in various formulations as functional beverage. Methods: Analysis of total used spectrophotometric method with Folin-Ciocalteu phenol reagent and gallic acid standard. It also performed the water content analysis used thermogravimetry method. Result: Salak Bali Sibetan’s bark have average water content 24.1872±0.036%wb. The results of total phenol analysis showed that 2, 10, 20, 30, 40 gram of Salak Bali’s bark with 200 ml water are: 10,84±0,587; 13,79±0,756; 12,19±0,205; 12,02±0,268; 10,57±0,389 mg/L GAE respectirely. Conclusions: The highest total phenol content is (10g/200ml) formulation, and also supported by a sensory test showed that a majority of panelist also prefer that formulation because has good colour, flavor and smell.&#x0D; &#x0D; Keywords : Salak Bali’s Sibetan bark, total phenol, Folin-Ciocalteu.

Synthesis and study of catalysts of electrochemical oxygen reduction reaction based on polymer complexes of nickel and cobalt with Schiff bases

The article presents the results of studies of new nanosize catalysts of electrochemical oxygen reduction reaction (ORR) obtained using the method of thermal decomposition of polymer complexes of nickel and cobalt with tetradentate (N2O2) Schiff bases. The catalysts are characterized using the methods of thermogravimetry, electrochemical quartz microgravimetry, scanning electron microscopy with X-ray microanalysis, XPS. The ORR process on electrodes modified by the above catalysts was studied using the voltammetry and rotating disk electrode techniques. The obtained catalysts manifested high specific activity per initial polymer mass (more than 600 mA/mg).

Chemical hydrogenation of La(Fe,Si) family of intermetallic compounds

In the present work, the chemical hydrogenation process of La(Fe,Si)13 compounds has been shown. It was found, that the La(Fe,Si) compound can be easily saturated with hydrogen by performing reaction with 0.6 M hydrochloric acid (HCl) for 2 h. After reaction, the heat treatment process is necessary to make hydrogenated powder homogenous. For the LaFe11.8Si1.2 micronized (<50 μm) and hydrogenated powder, the strength of the magnetocaloric effect was estimated by means of magnetocalorimetric measurements on plates consolidated with PVDF thermoplastic polymer. Magnetic entropy change was calculated by use of magnetization data acquired at magnetic fields with induction up to 2T. The adiabatic temperature change is equal to 3 K in magnetic field change 0–1.7T at 335 K, while magnetic entropy change is equal 13 J/kg*K at 2T. The structural homogeneity of initial and hydrogenated powders was validated by powder X-ray diffraction method. The amount of hydrogen in the hydrogenated compounds was evaluated using thermogravimetry method (4 H atoms per formula unit LaFe11.8Si1.2).

THE STUDY OF THERMAL PROCESSES IN FISH&amp;PLANT SEMI-PRODUCTS

The water-holding ability and forms of connection in fish&amp;plant semi-products were experimentally studied using derivatograph Q-1500 D by «МОМ» of Paulik-Paulik-Erdey system (Hungry). Using the methods of thermogravimetry methods in experimental samples was synchronously measured the temperature (Т), change of mass (TG), speed of temperature change (DTG) and change of thermal capacity (DТА). According to derivatograms the volume of the mass loss (Δm) and derivative change of DGT mass of the studied sample at correspondent temperature were determined. The thermal resistance of samples was assessed by the methods of thermogravimetry (by admissible mass loss that takes place at certain temperature) and differential-thermal analysis (by thermal effects that attend the chemical transformations of macromolecules, which intensity depends on temperature). According to the results of thermogravimetric and differential-thermal examination there was carried out the comparative characterization of the quantity of absorption- and capillary bound water in studied samples of fish&amp;plant semi-products and also determined the value of activation energy of water molecules at different temperatures of water removing. The dependence of DTG samples was divided in peaks using Gauss distribution. According to the analysis of DTG peaks the quantity of osmotic- and absorption-bound water was determined in the samples of minces, produced on the base of complex of raw and preliminary thermally processed muscular, connective and bone tissues of Azov goby (Neogobius melanostomus). The received results give a possibility to understand better the structural changes that take place in the process of drying of fish&amp;plant semi-products. They can be used for optimization of the process of drying of fish&amp;plant semi-products and prognostication of their technological behavior in the different food systems and at storage.

Thermal decomposition of Tatarstan Ashal’cha heavy crude oil and its SARA fractions

In this research, heavy crude oil from Ashal’cha field, Republic of Tatarstan, and its SARA (saturate, aromatic, resin and asphaltene) fractions were analyzed by differential scanning calorimetry (DSC) and thermogravimetry (TGA) methods. The experiments were performed at three different heating rates (10, 20, 30°C/min) for DSC and at single heating rate for TGA analysis, all under the air atmosphere. In DSC experiments, two main reaction regions were detected at each heating rate known as low and high temperature oxidation reactions. On the other hand, in TGA experiments, one main region was observed. For all the SARA fractions studied, highest heat of reaction was observed in lowest heating rate. The kinetic analysis of the crude oils and their fractions was also performed using ASTM E-698 and Arrhenius methods, respectively. Activation energy values of the crude oil sample and the fractions varied between 69.2 and 201.8kJ/mol in LTO region and 82.9–182.1kJ/mol in HTO regions, respectively. In Arrhenius method, the activation energy values were in the range of 33.1–108.9kJ/mol.