Stages Of Thermal Decomposition Research Articles

Chitosan from shrimp residues with a saturated solution of calcium chloride in methanol and water

Calcium chloride, methanol, and water in stoichiometric amounts were used for the extraction of chitosan from shrimp residues (Farfantepenaeus aztecus). Chitosan was characterized by FT-IR, TGA, XRD, SEM, elemental analysis, and 13C-NMR. The yield of chitosan with medium molecular mass was 65.90% (mass of extracted chitosan/mass of shrimp residues when the extraction was assisted with stirring at 60 °C for 20 min and ultrasound at 60 °C for 30 min. The extracted chitosan had a % DD of 64.06 and 65.87% (13C-NMR and FT-IR, respectively), thermal decomposition stage at 375 °C, porous on its surface, and calcite as the main mineral found. The experimental results revealed that the saturated solution of calcium chloride in methanol and water could be an alternative for the extraction of mineralized chitosan from shrimp residues with thermal stability and porosity.

Synthesis, Structural characterization, thermal, molecular modeling and biological studies of chalcone and Cr(III), Mn(II), Cu(II) Zn(II) and Cd(II) chelates

A number of new Cr(III), Mn(II), Cu(II) Zn(II) and Cd(II) chelates of (E)-3-(4-(dimethyl-amino)phenyl)-1-(pyridin-2-yl)prop-2-en-1-one were synthesized. The structures were elucidated by elemental and thermal analysis as well as spectral techniques (mass, IR, and electronic spectra) and magnetic measurements. The IR data suggested that the investigated chalcone acted as a bidentate ligand via the O and N atoms of the CO and CN groups, respectively. The spectral plus magnetic data revealed the formation of octahedral structures for all chelates while Cu(II) chelate has the square planar geometry. The kinetic and thermodynamic parameters of the thermal decomposition stages have been evaluated. Molecular orbital calculations have been performed to confirm the geometry of the isolated compounds. The in vitro antimicrobial activities of the chalcone and its metal chelates have been performed against some bacterial strains. The data indicated that all the metal chelates demonstrated a higher activity than the free chalcone. The anticancer activity of the mentioned metal chelates is evaluated against MCF7 cell. These compounds exhibited a moderate and weak activity against the tested cell line. The results were correlated with the experimental data.

Thermal performances and optical property of poly(L-lactic acid) under the influence of N,N'-dodecanedioic bis(3-phenylpropionic acid) dihydrazide as a crys­tal­lization promoter

Poly(L-lactic acid) (PLLA) as an important biodegradable polymer suffers from slow crystallization rate and poor heat resistance. An organic compound N,N’-dodecanedioic bis(3-phenylpropionic acid) dihydrazide (BHADD) was synthesized to evaluate its general influences on the physical properties of PLLA. The melt-crystallization process indicated that BHADD could serve as a heterogeneous nucleating agent for improving the crystallization of PLLA, and PLLA/1%BHADD exhibited the sharpest melt-crystallization peak located at the highest temperature, as well as an increase of cooling rate weakened the crystallization ability of BHADD-nucleated PLLA. And the final melting temperature also displayed the significant effect on the crystallization process of PLLA. For the cold-crystallization process, both BHADD concentration and heating rate affected the cold-crystallization behavior of PLLA/BHADD, the increasing of BHADD concentration caused the cold-crystallization peak to shift to the lower temperature; in contrast, a higher heating rate during heating leaded to the peak’s shift toward the higher temperature because of the thermal inertia. The melting behavior of PLLA/BHADD depended on the crystallization temperatures and heating rates, and the double melting peaks were attributed to the melting-recrystallization. Thermal decomposition experiment showed all PLLA/BHADD samples as the pure PLLA only exhibited one thermal decomposition stage, but PLLA/BHADD had a lower thermal stability than the pure PLLA. Additionally, the addition of BHADD seriously decreased the light transmittance of PLLA.

Kinetics Model Reconstruction for Multistep Overlapping Thermal Decomposition of Ammonium Perchlorate with and without the Copper Oxide Compound Catalyst

ABSTRACT The effects of copper oxide compound catalyst (Cu-O) on various stages of ammonium perchlorate (AP) thermal decomposition were investigated by TG. The results show that the thermal decomposition rate at the low-temperature section increases and the temperature at the maximum thermal decomposition rate (Tm ) appears at 571 K when the Cu-O catalyst was added. The Tm at the high-temperature section is reduced from 660 K to 606 K. The thermal decomposition activation energy (Ea ) of the whole process shows that the Ea of pure AP is significantly higher than that of AP+Cu-O when α > 0.25. According to the Gaussian peak-fit, the thermal decomposition of pure AP and AP+Cu-O can be divided into four stages. The Ea of each stage shows that the Cu-O catalyst has a significant catalytic effect on the first three stages of AP thermal decomposition, but has almost no catalytic effect on the fourth stage. According to the Coats-Redfern (CR) and masterplot method, the four stages of pure AP and AP+Cu-O are consistent with the n-order reaction F model and the Avrami-Eroféev (AE) model. Finally, the mechanism function reconstruction of four stages for pure AP and AP+Cu-O is completed by Arrhenius equation and kinetics compensation effect.

Experimental investigation on using ionic liquid to control spontaneous combustion of lignite

Coal spontaneous combustion (CSC) has become a safety topic and has been widely debated. This study investigated the inhibiting effect on CSC by using a series of novel ionic liquids (ILs) as chemical inhibitors. The microstructure and thermokinetic characters were observed and evaluated by Fourier transform infrared spectroscopy and synchronous thermal analyser. The results indicated that ILs could destroy reactive groups on relatively active coal surfaces, such as OH, aliphatic CH, and O-containing groups. However, as aromatic CH is the main chain of coal molecule, damaging it is difficult. Different anions and cations found in ILs exhibited different abilities for destroying the groups on the surface of coal molecules. The damage was caused by the properties of anions and cations by affecting the chain length, number of chains of the anion and cations, and electronegativity strength. The changes in microstructure increased the physical adsorption capacity of inhibitive coal samples during low-temperature oxidation, which changed the characteristic temperature points. In stages of water evaporation and desorption mass loss (stage 2) and the thermal decomposition (stage 3), the apparent activation energy of coal samples increased. The kinetic characteristics of the obstructed coal sample were predicted using the Flynn–Wall–Ozawa method. The development ability was delayed and the risk level was reduced of CSC in stages 2 and 3. Therefore, ILs should be utilised at relatively low-temperatures (<230.0 °C) to control CSC.

Thermal Studies of Iron (II) Schiff Base Complexes: New Precursors for Preparation of α-Fe2O3 Nanoparticles via Solid-State Thermal Decomposition

In this research study, four iron (II) complexes of tetradentate N2O2 Schiff base ligands with the general formula of Fe((MeO-bph)2 Am) (Am=1,2-ethyelenediamine (1), 1,3-propanediamine (2), 1,4-buanediamine (3) and 2,2-dimethyl-1,3-propanediamine (4) were synthesized and characterized using the elemental analysis (CHN) and FT-IR spectroscopy. Thermal properties and decomposition stages of all the complexes were evaluated. Finally, all complexes were decomposed at 600 °C for 3 h and the dark precipitates were characterized using the FT-IR, XRD and SEM. FT-IR and XRD results revealed that the precipitate were the pure phase of rhombohedral of magnetite (α-Fe2O3) nanoparticles. The SEM images showed that, the morphology of the precipitate was a relatively spherical shape and average diameter of 40-70 nm. The results of the thermogravimetric analysis the iron (II) complexes showed that the complexes 1–4 were stable until 140-200 °C. However, after that, all the complexes 1–4 decomposed in two stages at various temperatures.

Crystal growth, spectral, optical, thermal, luminescence and magnetic properties of blue light emitting diaquabis(hydrogenmalonato)cobalt(II)

The single crystals of diaquabis(hydrogenmalonato)cobalt(II) were synthesized and grown using the slow evaporation of solutions method. The structure of the compound was obtained through single crystal XRD analyses and it belongs to P21/c space group of monoclinic system. The UV-vis absorption spectrum exhibits two peaks at 216 nm and 259 nm in the UV region and one peak at 524 nm in the visible region. Photoluminescence studies revealed emission of intense blue radiation. The thermal stability and decomposition stages have been investigated by TGA-DTA analysis. The magnetic measurements exposed that the compound exhibits antiferromagnetic behavior at low temperature.

Kinetic study of the thermal decomposition of castor oil based polyurethane

Polyurethane is a class of polymer that presents as main feature the versatility in its physical and chemical properties. Knowing the kinetic parameters of the thermal degradation of these materials collaborates with the development of new applications. Therefore, this work had as objective to study of the kinetic parameters of the thermal decomposition of vegetable oil-based polyurethane (castor oil), through non - isothermal thermogravimetric method. The thermogravimetric curves of the samples showed two decomposition steps, and the kinetic parameters of each step were determined using the Flynn-Wall-Ozawa (FWO) method. The first stage of thermal decomposition presents characteristics of first-order reactions, the second stage of decomposition presented a behavior similar to that of the first stage until α equal to 0.4, in the conversion range between 0.4 and 0.9 a concave profile was observed, characteristic of complex processes, indicating parallel reactions and minimum lifetime of 1650 years old.

Restraining effect of nitrogen on coal oxidation in different stages: Non-isothermal TG-DSC and EPR research

Nitrogen is widely used to prevent the spontaneous combustion of coal in underground coal mines. A spontaneous combustion-prone coal seam was studied to investigate the restraining effect of nitrogen on coal oxidation in different oxidation stages, based on non-isothermal thermogravimetry-differential scanning calorimetry (TG-DSC) and electron paramagnetic resonance (EPR) experiments. We found that the key feature temperatures grow steadily with increasing nitrogen in the oxidation environment, resulting in longer oxidation stages. The most significant finding is that there is a stagnation of the inhibitory effect of nitrogen on coal oxidation in the range of 85.0–95.0% nitrogen in the slow and the rapid oxidation stages, owing to the competitive adsorption of coal by nitrogen and oxygen. However, the restraining effect cannot be reflected by the kinetic parameters of the coal before it reaches the thermal decomposition and combustion stage. Nitrogen can also affect free radical types and free radical concentrations during coal oxidation: the higher the concentration of nitrogen in the oxidation environment, the greater the number of free radical types and the lower the free radical concentration. This experimental study improves the understanding of the restraining effect of nitrogen on coal oxidation in different oxidation stages and provides an important reference for coal fire prevention in spontaneous combustion-prone coal seams.

Preparation and Characterization of Protein Bioplastics from Fish Waste Using Different Plasticizers

The objective of this study was to develop protein bioplastics from fish waste using different types of plasticizers; polyethylene glycol, triethylene glycol and glycerol. Fish protein powders (head, skin, scales, viscera) were prepared from sardine byproduct (SBP), mackerel fillet powder (MFP) and mackerel byproduct powder (MBP). Protein content was characterized using proximate analysis and amino acids was determine using amino acid analysis. SBP was transform into bioplastics by using extrusion and compression moulding. The properties were characterized using thermo gravimetric analysis (TGA) and mechanical testing. Protein content in byproduct (SBP and MBP) were reasonable at approximately 40-60%. TGA result showed two stages of thermal decomposition starting at 230 °C. Below 230 °C, it was believed that protein denaturation occurred, involve structural or conformational changes from native structure without alteration of amino acid sequence. Further heating after 230 °C showed massive weight loss that lead to degradation. Mechanical properties was majorly influenced by plasticizers which improved the elongation at break properties. Glycerol was found to be the most effective plasticizer among those studied here, possibly because of its characteristics such as low molecular weight, high solubility in water, and large protein miscibility. The results obtained in this study showed that plasticizer types and concentration significantly improve film properties and enhances their suitability for single used of agriculture applications.

Kinetics and Mechanism of Thermal Decomposition of 1-R-Substituted bis(1,1-Dinitromethyl-3-Nitro- 1,2,4-Triazole-5-yl)

Thermal decomposition kinetics of 1-substituted bis(1,1-dinitromethyl-3-Nitro-1,2,4-triazole- 5-yl) in solution of 1,3-dinitrobenzene is studied with manometric method under isothermal conditions. The limiting stage of thermal decomposition is homolytic break of C-NO2 bond in gem-dinitromethyl group; activation parameters of this stage are calculated. The reactivity of investigated compounds is analyzed. Correlation dependences between logarithm of rate constant, activation energy and steric constant of substituent R are obtained

Novel fullerene-based stabilizer for scavenging nitroxide radicals and its behavior during thermal decomposition of nitrocellulose

The safe storage of double-based propellants is becoming increasingly challenging due to the extreme storage environment and update of weapon system. Therefore, to obtain high performance stabilizers, a novel multifunctional fullerene derivative, 4,11,15,30-tetramethophenyl fullereno[1,2:2′,3′]dihydrobenzofuran (C60-DBTMP), was successfully designed and synthesized. The results of thermal stability indicated that the stability of C60-DBTMP is better than that of traditional stabilizers (DPA, C2, AKII), and still maintain good performance at high temperature. Further thermal analysis showed that C60-DBTMP interact with the decomposition products during the thermal decomposition of nitrocellulose, which changed the decomposition mechanism of nitrocellulose at the initial stage of thermal decomposition from self-accelerating catalytic model to non-autocatalytic reaction model. The stabilization mechanism was also investigated in detail, electron spin resonance (ESR) test showed that the nitroxide radicals scavenging efficiency of C60-DBTMP is 73.4%, and effectively inhibit the acidity change caused by the thermal decomposition of nitrocellulose. Our study demonstrated the potential application of this multifunctional fullerene derivative as a stabilizer for propellants and provided a new strategy for designing high-performance stabilizers.

Synthesis, spectroscopic, biological, and theoretical studies of new complexes from (E)‐3‐(2‐(5, 6‐ diphenyl‐1,2,4‐ triazin‐3‐ yl)hydrazono)butan‐2‐ one oxime

New mononuclear Fe (III), Cu (II), Ag (I), ZrO ( IV) and UO2(VI) complexes were synthesized by the reaction of metal ions with (E)‐3‐(2‐(5, 6‐ diphenyl‐1,2,4‐ triazin‐3‐ yl)hydrazono)butan‐2‐ one oxime. The structures of the metal complexes were characterized using analytical, spectral (infrared, electronic, 1H NMR, electron spin resonance (ESR), and mass), magnetic moment, molar conductance, thermal gravimetric analysis, and powder X‐ray diffraction (XRD) measurements. All complexes have octahedral geometries except the Cu (II) complex, which has square planar geometry, and the UO2(VI) complex, in which the coordination number is seven. The ligand acts as a (neutral, monoanionic or dianionic) tridentate with N2O coordinating sites: N‐azomethine, N‐triazine, and O‐oxime. Fluorescence spectral studies were carried out in solid state and in dimethylformamide (DMF). The kinetic parameters of the thermal decomposition stages were calculated using Coats–Redfern equations. The morphological structures of the ligand and some complexes were determined using XRD. The molecular orbital calculations were carried out for the ligand and metal complexes using the Hyperchem 7.52 program on the basis of the PM3 level. The antimicrobial activities of the ligand and its complexes were investigated towards the microorganisms S. aureus and B. subtilis as Gram‐positive bacteria, S. typhimurium and E. coli as Gram‐negative bacteria, C. albicans, and A. fumigatus. The ligand and its complexes showed antitumor activity against Hep G‐2 cell lines, where Cu (II) and Ag (I) complexes seem to be promising as they showed IC50 values that are lower than and comparable to that of the antitumor drug doxorubicin.

Kinetics of Lumefantrine Thermal Decomposition Employing Isoconversional Models and Artificial Neural Network

Thermal analysis can be used to determine shelf-life and kinetic parameters in pharmaceutical systems. This work investigates the kinetic of lumefantrine thermal decomposition, an antimalarial, using non-isothermal and isothermal experimental data. The non-isothermal conditions are analyzed applying Vyazovkin method, while isothermal conditions employ models fitting procedure and artificial neural network. Lumefantrine was characterized by powder X-ray diffraction and Fourier transform infrared spectroscopy. The initial stage of lumefantrine thermal decomposition, about 5% of conversion, corresponds to the loss of chlorine and hydroxyl, being correctly predicted by the neural network as a complex event. At room temperature, the D3 model is appropriate to describe the process, once the half-life time is 19 months, in agreement with manufacturer. Isoconversional model determined the activation energy along the whole process while isothermal methodology determined the global value considering the entire process. The results provide important information for the pharmaceutical industry to assay levels of acceptable lumefantrine contents.

Thermal Decomposition of Acidic Cobalt(II) Carboxylates with Unsaturated Dicarboxylic Anions

The thermal decomposition of acidic cobalt carboxylates (ACCs) with unsaturated carboxylic anions has been studied by TG/DTA in combination with DSC and mass spectrometry of gaseous thermolysis products. The temperature ranges of the main ACC thermal decomposition stages have been determined as (1) 50–225°С for dehydration (2) 210–450°C for dehydrated carboxylate polymerization, and (3) 370–500°C for decarboxylation. It has been concluded that the listed stages may superimpose on one another and occur simultaneously.

Spectral, HR-XRD, Thermal and Dielectric Studies on Mixed Solvent Grown DAST Single Crystals

The highly meritorious single crystal of DAST (4-N,N-dimethylamino-4’-N’-methylstilbazolium tosylate) was grown through solution growth technique. The grown single crystals crystalline perfection analysis was made by HRXRD studies. The dielectric constant (ε), dielectric loss (ε) of DAST crystal was studied at different temperatures. The thermal decomposition stages were examined by using thermogram of DAST crystal and also it was giving best description of kinetic changes. Dielectric character was studied to the DAST crystal. The dielectric character of DAST was too analyzed.

Study of pre-formulation and development of solid lipid nanoparticles containing perillyl alcohol

The aim of this work was to study the physicochemical characterization of lipid matrices composed of cetyl palmitate (CP)/perillyl alcohol (PA) and develop preliminary studies of SLN for potential application in cancer treatment. The pre-formulation was submitted to recrystallization process (heating–cooling) in a concentration of CP/AP (F1 1:0; F2 1:9; F3 1:3; and F4 1:1). The characterization showed TG presents a single stage of thermal decomposition for AP, F1, F2 and F3 and two stages for F4. DSC decrease of the onset temperature of CP before and after thermal decomposition in all samples indicates a reduction in crystallinity, and WAXD data confirmed DSC results, showing a reduction in the intensity of main diffraction peaks of the lipid mixtures and a presence of the amorphous portion in 2θ angles of 21.51° and 23.62°. Results showed the binary mixtures presented a amorphous portion facilitates AP incorporation in SLN satisfactory size, polydispersity index, zeta potential and morphology was obtained.

Analysis of thermodynamic characteristics of imidazolium-based ionic liquid on coal

To investigate the effects of ionic liquids (ILs) on the oxidative combustion characteristics of coal, the oxidation characteristics of ILs on coal, such as characteristic temperature, thermal mass loss rate, and oxidation kinetics characteristic parameters, were determined. The results the [BMIm][I]-treated coal samples increased cracking temperature (T1), maximum oxidization mass gain (T2), ignition temperature (T3), burnout temperature (T4), minimum thermal rate (Ta), maximum thermal energy (Tb), and maximum thermal rate (Tc) by 33.2, 29.3, 20.7, 42.8, 11.4, 23.0, and 27.9 °C, respectively. The increase mass ratio of coal samples treated with ILs increased and decreased at the water evaporation and thermal decomposition stages, respectively. The apparent activation energy (Ea) of coal samples treated with ILs increased, and the mechanism function also changed accordingly. These showed that the ILs improved the thermal stability of the coal samples in the stages of absorbing oxygen and increased mass, and the loss of combustion. The ILs caused damage to the molecular structure of the coal and ultimately effected changes in the combustion performance. In addition, the [BMIm][BF4] hardly weakens the inhibitory effectiveness of the coal sample over time; coal spontaneous combustion could be effectively inhibited.

Features of obtaining the catalyst for the synthesis of carbon nanotubes

In this paper, the features of obtaining a Co-Mo/Al2O3 catalyst to synthesize carbon nanotubes (CNTs) by thermal decomposition were studied. It was revealed that the duration of the pre-catalyst thermal decomposition stage in the process of developing a metal oxide system has a significant impact on its activity in the synthesis of carbon nanostructured materials by chemical vapor deposition (CVD). It was proved that an effective catalyst for CNTs synthesis can be obtained by through thermal decomposition of the pre – catalyst, without calcination of the metal oxide system. The use of the Co-Mo/Al2O3 catalyst, synthesized in such a way, in the CVD process makes it possible to reduce the cost of synthesized CNTs. Using scanning electron microscopy, it was shown that the size of the grains, and specific surface area of the formed Co-Mo/Al2O3 catalyst depend on the thermal treatment conditions of the pre-catalyst. Under the conditions for the implementation of the pre-catalyst thermal decomposition stage (temperature, volume, duration, etc.), it is possible to contro not only the characteristics of the resulting catalyst (specific surface area, efficiency), but also the characteristics of the CNTs (diameter, degree of defectiveness). In the course of experiments, the optimal modes of implementation of the method for obtaining the Co-Mo/Al2O3 catalyst allowed forming a system with a specific surface area of ~ 108 m2/g. The use of the resulting catalyst in the synthesis of nanostructured materials provides a high specific yield of multi-walled CNTs with a diameter of 8-20 nm and a degree of defectiveness of 0.97.

The heat treatment duration effect on the efficiency of a catalyst for carbon nanotubes synthesis

The present paper shows that the duration of the pre-catalyst heat treatment stage implementation for obtaining a metal oxide Co-Mo/Al2O3 catalyst through thermal decomposition has a significant impact on its effectiveness in the synthesis of carbon nanotubes (CNTs) via chemical vapor deposition (CVD). The size of active sites formed and the specific surface area of the Co-Mo/Al2O3 catalyst were found to depend on the pre-catalyst heat treatment conditions. It was experimentally proved that the characteristics of both the catalyst (specific surface area and efficiency) and the CNTs (diameter and degree of defectiveness) can be controlled by the mode parameters of the thermal decomposition stage. The research results confirm the possibility of obtaining an effective catalyst system without implementing the secondary heat treatment stage - calcination. Moreover, the use of the Co-Mo/Al2O3 catalyst, obtained according to this procedure, in the CVD process allows to reduce the cost of CNTs synthesized.