Activation Energy Of Decomposition Research Articles

Non-isothermal thermogravimetry as an accelerated tool for the shelf-life prediction of paracetamol formulations

In this work, non-isothermal thermogravimetric studies have been carried out on several paracetamol formulations with the aim to predict their shelf-lives under variable storage conditions. Specifically, paracetamol tablets of different brands have been investigated allowing to estimate their pharmaceutical quality by considering the specific drug stability. The proposed protocol is based on the kinetic study of thermogravimetric data by the combination of isoconversional procedures (Friedman and Kissinger-Akahira-Sunose (KAS) methods) and “Master plot” analysis. Accordingly, the kinetics of the paracetamol degradation is totally explored in terms of activation energy, pre-exponential factor and reaction mechanism of the drug decomposition. The obtained insights drive to simulate the decay time functions of paracetamol amount for the several pharmaceutical formulations. Interestingly, these simulations can be easily adapted to variable isothermal conditions providing the shelf-lives of the paracetamol tablets at different temperatures. The kinetic characteristics of the paracetamol degradation as well as the corresponding shelf-life values evidenced that the expiration date of the pharmaceutical products are significantly affected by the composition of the excipients. In conclusion, this work demonstrates that non-isothermal thermogravimetric analysis can be used as efficient and sensitive tool for the prediction of the shelf-lives of paracetamol formulations.

Macrocyclic tetra(azo-) and tetra(azoxyfurazan)s: Comparative study of decomposition and combustion with linear analogs

Thermal decomposition and combustion of macrocyclic tetra(azofurazan), TATF, and tetra(azoxyfurazan), TOATF, were studied using a number of complementary experimental techniques, namely thermogravimetry, differential scanning calorimetry, manometry, microthermocouple measurements in a combustion wave. Kinetic studies of polyazo- and azoxyfurazans have demonstrated that macrocycles, TATF and TOATF, have a different mechanism of thermal decomposition than their linear counterparts. While linear azo- and azoxyfurazans have relatively low activation energy (130–143 ​kJ·mol−1) of thermal decomposition, the activation energies for macrocyclic TATF and TOATF are 202–210 ​kJ·mol−1, which is close to the calculated breaking energy of the C-NN bond. The initial stage of decomposition of these macrocycles is the monomolecular cleavage of the C-NN bond, while linear azofurazan decomposes according to a concerted mechanism, loss N2 or N2O molecules. It was found that the condensed-phase chemistry determines the combustion mechanism of TOATF. Combustion instability is observed for TATF in the pressure range below 3 ​MPa. Both macrocyclic TATF and TOATF are relatively fast-burning energetic compounds, with burning rates exceeding the burning rates of the CL-20.

Doping hematite with bismuth to enhance its catalytic and oxidizing properties

• Doping Fe 2 O 3 with Bi can significantly enhance its intrinsic reactivity. • The catalytic decomposition mechanism of HMX has been studied. • The ignition delay time is greatly shortened with the increase of Bi amount. • A high ignition performance of Al/Bix-Fe 2 O 3 can be obtained. Bismuth-cation modulated hematite (Bi-Fe 2 O 3 ) was prepared by a one-step hydrothermal method and used as a catalyst for the thermolysis of energetic materials (EMs) and oxidant in an Al-based thermite. The effects of the amount of Bi doped Fe 2 O 3 on the catalytic property and thermite behavior were investigated using differential scanning calorimetry (DSC). Thermogravimetry–infrared spectroscopy-mass spectrometry (TG/IR/MS) was used to study the thermal decomposition gases of cyclotetramethylenetetranitramine (HMX) with or without catalyst. Bi-Fe 2 O 3 was found to reduce the initial thermal decomposition temperature and activation energy of HMX, and change the decomposition mechanism. In addition, the thermite reaction of Al/Bi-Fe 2 O 3 is exothermic and faster than that of undoped Al/Fe 2 O 3 , resulting in more rapid energy release. Al/Bi-Fe 2 O 3 also shows a shorter ignition delay time than Al/Fe 2 O 3 . This study demonstrates Al/Bi-Fe 2 O 3 as an efficient advanced combustion catalyst for solid propellants.

Eco-friendly rice husk pre-treatment for preparing biogenic silica: Gluconic acid and citric acid comparative study

Carboxylic acid leaching has been established eco-friendly pre-treatment method for producing biogenic silica (BSi) from rice husk. The most urgent issue is for carboxylic acid to promote new readily biodegradable acids and enhance carboxylic acid sustainability in BSi preparation. This research investigates gluconic acid (GA) applicability for biogenic silica preparation from rice husk compared with citric acid (CA). The results demonstrated that GA was preferable to CA on BSi recovery with 89.91% efficiency. Although GA leaching promoted slightly higher silica loss, the primary metal alkali impurities, such as K2O, Na2O, and Al2O3, were effectively removed at 92–93%, 89–93%, 95–97%, respectively. The combination effect of silica loss and high removal impurities resulted in lower rice husk thermal decomposition activation energy. The characteristics of BSi prepared by GA leaching were comparable with CA leaching, mainly mesoporous with 114.06 m2/g of specific surface area and 0.23 cm3/g of the pore volume. In addition, GA leaching was environmentally better than CA leaching, indicated by minor contribution to all environmental impact indices. The findings suggested that GA could be a potential replacement for prevalent carboxylic acids in BSi preparation.

Effects of graphene on thermal properties and thermal stability of polycarbonate/graphene nanocomposite

Polycarbonate (PC) /graphene nanocomposite was prepared using multilayer graphene (MLG) with loadings of 0.5, 1, and 3 wt% via melt mixing process. Morphological, structural, and thermal properties of the PC/MLG nanocomposites are investigated to look into the influence of MLG on the nanocomposite. A significant increase (∼6.4°C) in glass transition temperature is observed upon the addition of 3 wt% of MLG into the polycarbonate matrix. This increase in glass transition temperature may be due to the interaction between the MLG and polycarbonate polymer matrix. The specific heat capacity of pure PC and PC/MLG nanocomposites varies linearly with temperature below their glass transition. Upon the addition of MLGs, the overall thermal stability of PC/MLG nanocomposites increases with MLG loadings. A maximum increase about 29.23°C in Tonset of thermal decomposition is observed in PC/MLG nanocomposite having 3 wt% of MLG loading. The activation energy ( Ea) of thermal decomposition is also calculated by kinetic analysis of thermal decomposition of the PC/MLG nanocomposites using Horowitz–Metzger and Broido’s methods.

Utilization of waste tire powder for gaseous fuel generation via CO2 gasification using waste heat in converter vaporization cooling flue

This study proposes a novel approach to effectively solve the problems associated with reusing waste tires by injecting waste tire powder into the converter vaporization cooling flue (CVCF) to obtain gaseous fuels via CO2 gasification using high-temperature waste heat. The gasification behavior was investigated in a CO2 atmosphere using a thermogravimetry (TG)-mass spectrometry (MS) (TG-MS) system. A settling furnace was used to simulate CVCF to investigate the effects of gasification temperatures. The activation energy (E) was calculated using the Flynn-Wall-Ozaw (FWO) and Kissinger-Akahira- Sunose (KAS) methods. The main components in the gas phase were typically CO, CH4, H2, H2O, and C2H6 in a temperature range of 300°C–500 °C. The average activation energy of waste tire decomposition was 144.51 kJ/mol. The increase in temperature and decrease in particle size increased the amount of combustible gas and LHV value. The increase in the CO2/CO ratio decreased the content of residual coke from 12.62% to 11.98%. The lower heating values were determined to range between 8.75 and 10.27 MJ/Nm3. The research preliminarily confirmed the feasibility of injecting waste tire powders into the CVCF to generate gaseous fuels using waste heat via CO2 gasification.

Effects of 2CL-20/HMX cocrystals on the thermal decomposition behavior and combustion properties of polyether solid propellants

Herein, the effects of cocrystals of two nitroamine explosives, namely hexanitrohexaazaisowurtzitane (CL-20) and 1,3,5,7-tetranitro-1,3,5,7-tetrazoctane (HMX), which are denoted as CHC, on the combustion properties, heat release, and safety profiles of polyether solid propellants were systematically analyzed. The peak decomposition temperature of CHC was found to be 244.8 °C, which is lower than those of its component CL-20 and HMX. However, the thermal stability of CHC was similar to that of CL-20, and the thermal decomposition behavior of CHC was significantly different from that of a physical mixture of CL-20 and HMX. In addition, similar to CL-20, CHC was not completely decomposed upon heating, despite the decomposition activation energy of CHC (322.7 kJ·mol−1) being similar to that of HMX (322.4 kJ·mol−1). In contrast, the thermal decomposition behaviors of CHC-based propellants differed from those of solid propellants that were based on physical mixtures of CL-20 and HMX. During thermal decomposition, CHC did not decompose into CL-20 and HMX, and the heat released from the CHC-based propellants was more concentrated than that released from the other propellant mixture examined. Furthermore, the rate of combustion of CHC-based propellants fell between those of the CL-20- and HMX-based propellants at all the tested pressures. The pressure exponents of combustion rates of the examined CHC-based propellants were slightly lower than those of the CL-20- and HMX-based propellants, and the combustion rates and their corresponding pressure exponents decreased with a decrease in the CHC particle size. Moreover, the explosive heat of CHC-based propellant was between those of the CL-20-based and HMX-based propellants, and similar to that of a CL-20/HMX mixture-based propellant. Finally, the safety performance of CHC-based propellant was almost identical to that of the CL-20/HMX mixture.

Thermal Stability and Kinetics of Thermal Decomposition of Statistical Copolymers of N-Vinylpyrrolidone and Alkyl Methacrylates Synthesized via RAFT Polymerization

The thermal stability and the kinetics of thermal decomposition of statistical copolymers of N-vinylpyrrolidone (NVP) with the alkyl methacrylates, hexyl methacrylate (HMA) and stearyl methacrylate (SMA), were studied by Thermogravimetric Analysis (TGA) and Differential Thermogravimetry (DTG). Statistical copolymers of different compositions were studied, and their thermal decomposition behavior was compared to the corresponding homopolymers. The activation energies of the thermal decomposition were calculated using the Ozawa-Flynn-Wall, the Kissinger, and the Kissinger-Akahira-Sunose methodologies. The effects of the nature of the methacrylate monomer, the copolymer composition, and the rate of heating are discussed.

5‐(Chloromethyl)furfural production from glucose: A pioneer kinetic model development exploring the mechanism

AbstractConversion of glucose to 5‐(chloromethyl)furfural (CMF) is one of the well‐known high yield unit processes in lignocellulosic biomass valorization. A kinetic modeling study was not reported for the reaction, owing to the complexity in quantification of CMF. Herein we have successfully developed a rapid, sensitive, and specific HPLC method (reverse phase) to quantify the generated CMF (range: 10–650 μg/mL) in a dichloroethane solvent. The Box–Behnken design of experiment method employed for the statistical optimization. A kinetic model was developed based on the homogeneous first‐order kinetic model, and the results are in good agreement with the experiment data. The formation of CMF, 5‐(hydroxymethyl)furfural, formic acid, levulinic acid, and humins from glucose and HCl were modeled using a serial parallel reaction mechanism. The apparent activation energy (Ea) for glucose decomposition and CMF formation is 99 and 31 kJ/mol.

Evaluation of thermal hazards based on thermokinetic parameters of 2,4-dinitroanisole

ABSTRACT As a high-energy insensitive explosive which is expected to replace 2,4,6-trinitrotoluene (TNT), it is necessary to evaluate the thermal risk of 2,4-dinitroanisole (DNAN). In this article, the thermal performance of DNAN was tested using differential scanning calorimeter (DSC) and accelerating rate calorimeter (ARC). According to the test results, the decomposition activation energy (E), the pre-exponential constant (A), activation entropy (ΔS ≠), activation enthalpy (ΔH ≠), activation Gibbs free energy (ΔG ≠) at T P0 of the reaction and the critical temperature of thermal explosion (T b) were obtained. The kinetic model under adiabatic conditions was established. The thermal hazard assessment of DNAN was carried out according to the thermodynamic parameters, and the assessment results are of great significance to the application of DNAN.

Hydrogen storage properties of Mg-Li-Al composite system doped with Al2TiO5 catalyst for solid-state hydrogen storage

A systematic investigation was performed on the 4MgH2 + LiAlH4 destabilized system with the inclusion of 5 wt% Al2TiO5 that was prepared by a ball milling process, and the hydrogen sorption performances were studied for the first time. A great advancement of the onset dehydrogenation temperature and de/rehydrogenation kinetics of 4MgH2 + LiAlH4 composite was achieved by doping Al2TiO5 to the composite. For the first and second desorption stages, the 4MgH2 + LiAlH4 + 5 wt% Al2TiO5 composite began to liberate hydrogen at 85 °C and 230 °C. In comparison, the undoped system commenced to liberate hydrogen at 120 °C and 270 °C, which were 35 °C and 10 °C lower, respectively when contrasted with the undoped composite. For the rehydrogenation kinetics, about 1.9 wt% hydrogen was absorbed within 5 min for the 5 wt% Al2TiO5-doped 4MgH2 + LiAlH4 system, whereas the neat sample only absorbed about 1.2 wt% hydrogen under similar conditions. As for the dehydrogenation kinetics, 4MgH2 + LiAlH4 + 5 wt% Al2TiO5 composite desorbed 1.7 wt% hydrogen within 10 min of desorption, while the 4MgH2 + LiAlH4 system released 0.8 wt% hydrogen in the same time frame. The apparent activation energy for the MgH2-relevant decomposition decreased from 121 kJ/mol (4MgH2 + LiAlH4 system) to 102 kJ/mol, after 5 wt% Al2TiO5 was introduced into the destabilized system. The decline in particle size also enhance the hydrogen storage behaviors. The synergistic effect of Al2TiO5 on the hydrogen storage behavior of 4MgH2 + LiAlH4 sample is attributed to the formation of new species of TiH2, AlTi2 and LiTi2O4 after ball milling and heating process, which acted as a real catalyser in the 4MgH2 + LiAlH4 + 5 wt% Al2TiO5 destabilized system.

Strong yet tough, excellent thermal resistant and UV-Protective Polydopamine/Poly(vinyl alcohol) composites via hydrogen-bonding interaction

Strength and toughness are regarded to be mutually exclusive in polymeric materials. Herein, highly strong and tough polymeric materials, which simultaneously combined excellent heat resistance and UV-shielding function, were obtained by in-situ polymerization of dopamine in the presence of poly (vinyl alcohol) (PVA) solution based on hydrogen bonding interaction. Polydopamine (PDA)/PVA composites were prepared by a conventional solution-casting method. Strong hydrogen-bonding interaction between PDA and PVA was demonstrated by Fourier transform infrared (FT-IR) spectroscopy and rheological test. It is found that the addition of 2 wt% PDA has 42.6% and 104.9% increase in strength and toughness respectively compared with neat PVA. More importantly, the maximum thermal decomposition temperature of PDA-2 wt% composite was up to 389.0 °C with a remarkable increment of 79.4 °C. Accordingly, the decomposition activation energy of PDA-2 wt% composite was much larger than that of PVA. Additionally, unlike those fillers such as graphene and carbon nanotube, PDA-2 wt% composite was transparent in visible region but obviously blocked ultraviolet (UV) light. This work offers a simple and facile strategy to prepare strong, tough, thermal stable and UV-blocking polymeric materials, which will expand their applications in high-grade packaging and tissue engineering.

Synthesis and Properties of Hydrazine Picrate

Picric acid was reacted with liquid propellant anhydrous hydrazine to synthesize anhydrous hydrazine picrate. Its structure was characterized by elemental analysis, infrared spectrum analysis, nuclear magnetic resonance, and its thermal decomposition performance was analyzed by TG-DTG and DSC. The thermal decomposition of anhydrous hydrazine picrate was studied by using Kissinger method and its activation energy was calculated. The critical temperature of thermal explosion was calculated by using the characteristic data of non-isothermal DSC curve. The results shows that the thermal decomposition of anhydrous hydrazide is mainly between 179.8∼200.9°C, the decomposition process is exothermic reaction, the melting point is about 140°C, the non-isothermal kinetic equation is ln(β/T p 2 )=-17652 (1/T p)+28.009, the activation energy of thermal decomposition is E=146.76kJ/mol, pre-exponential factor lnA=30.34, and the critical temperature of thermal explosion T b=175.3°C. Anhydrous hydrazine picrate has the characteristics of simple synthesis, rapid reaction and good thermal stability. It provides a new way for the disposal and reuse of anhydrous hydrazine.

Processing End-of-Life Tube Lights for Recovery of Rare Earth Oxides

The investigation of secondary rare earth sources is attractive because of environmental concerns, economic benefits, and resource conservation. The present work investigates milling/mechanical activation, chemical and thermal (microwave) treatment for rare earth recovery from trichromatic phosphor of spent tubular lights. Ball milling prior to acid leaching of phosphor recovered 82% Y, 41% La, 33% Ce, 97% Eu, and 32% Tb. The activation energy for the thermal decomposition of the phosphor was determined as 498.9 kJ mol−1, 381.6 kJ mol−1, and 202.2 kJ mol−1 for Na2CO3, NaOH, and CaCl2, respectively. Mechanical activation with Na2CO3 reduced the decomposition temperature for microwave processing and yielded 99% Y, 97% La, 0.6% Ce, 99% Eu, and 80% Tb values. Direct leaching yielded 39 g Y-Eu oxide product; ball milling and the mechanical activation followed by acid leaching yielded 52 and 89 g of Y-Eu-La-Ce-Tb oxides, respectively, from the processing of 100 units of end-of-life tubular units.

Cu-MOF derived Cu/Cu2O/C nanocomposites for the efficient thermal decomposition of ammonium perchlorate

C-dispersed Cu/Cu2O/C nanocomposites were prepared using a simple one-step calcination of Cu-MOF. The morphology and the structure of the Cu/Cu2O/C nanocomposites were characterized using X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy. The thermal decomposition catalytic effect of the obtained nanocomposites on ammonium perchlorate (AP) was investigated using the differential thermal analysis (DTA), and the catalytic mechanism was analyzed. The results showed that Cu-MOF increased the pyrolysis peak temperature of AP to 382.51 ​°C. Cu/Cu2O/C calcined at different temperatures had better catalytic effect on AP than Cu-MOF, and Cu/Cu2O/C-350 had the best catalytic effect on AP, decreasing the decomposition peak temperature and activation energy of AP by 87.55 ​°C and 86.51 ​kJ ​mol−1, respectively. Results showed that the prepared Cu/Cu2O/C-350 nanocomposites were a promising catalyst for AP.

Studies on the Effect of Ageing on Thermal, Ballistic and Mechanical Properties of Advanced Energetic Propellants

AbstractIn order to study the ageing behaviour of advanced energetic propellants during storage and the effect of nitrate ester on the shelf life, accelerated ageing tests were conducted on two types of propellants based on nitrate esters, BTTN (as P‐1) and NG:BTTN (1 : 1) mixture (as P‐2). Mechanical and ballistic characterization of P‐1 and P‐2 propellants were carried out during storage at ambient (27 °C) and elevated temperature (40 °C and 55 °C). During ageing, tensile strength and Young‘s modulus of propellants are increasing and percentage elongation is decreasing due to depletion of nitrate ester from the locus. Also, there is a loss of stabilizer with time during ageing. Thermal decompositions of P‐1 and P‐2 were studied using differential thermal analysis at four heating rates (1 °C/min, 2 °C/min, 5 °C/min, and 10 °C/min) during ambient and accelerated ageing. Activation energies for thermal decomposition were calculated using Kissinger's and Ozawa's methods by assuming first‐order reaction kinetics for first stage decomposition in DSC studies of aged propellants. The shelf life of propellants was predicted based on the classical Arrhenius equation using zero‐order kinetics of degradation of the propellant mechanical property i. e. percentage elongation. With the 30 percentage elongation as the critical evaluation parameter, predicted shelf life at 25 °C is 23.97 years and 12.17 years for P‐1 and P‐2 respectively.

Optical Study on PVA/PEG Blend Doped with Nano-Silica

Transparent films of polyvinyl alcohol/polyethylene glycol (PVA/PEG) blend loaded with different nano-silica (SiO2) content were prepared by using solution casting. The effect of SiO2 nanoparticle loading on the optical properties of selected PVA/PEG blend ratio is studied in the spectral region 200–700 nm. The present study monitors the changes in the optical dispersion parameters such as band tail width, extinction coefficient, refractive index, and optical dielectric constant calculated as a function of nano-silica content. The results revealed that the obtained optical parameters were strongly affected by the SiO2 content in the blend films. Also, Cauchy model is used to fit the wavelength dependence of the refractive index of the composites. In addition, thermogravimetric analysis indicates the increase of thermal stability of the composites with respect to pure blend. The Coats and Redfern model is used to calculate activation energies for decomposition.

Thermal Stability of Ionic Liquids: Current Status and Prospects for Future Development

Ionic liquids (ILs) are the safest solvent in various high-temperature applications due to their non-flammable properties. In order to obtain their thermal stability properties, thermogravimetric analysis (TGA) is extensively used to analyze the kinetics of the thermal decomposition process. This review summarizes the different kinetics analysis methods and finds the isoconversional methods are superior to the Arrhenius methods in calculating the activation energy, and two tools—the compensation effect and master plots—are suggested for the calculation of the pre-exponential factor. With both parameters, the maximum operating temperature (MOT) can be calculated to predict the thermal stability in long-term runnings. The collection of thermal stability data of ILs with divergent cations and anions shows the structure of cations such as alkyl side chains, functional groups, and alkyl substituents will affect the thermal stability, but their influence is less than that of anions. To develop ILs with superior thermal stability, dicationic ILs (DILs) are recommended, and typically, [C4(MIM)2][NTf2]2 has a decomposition temperature as high as 468.1 °C. For the convenience of application, thermal stability on the decomposition temperature and thermal decomposition activation energy of 130 ILs are summarized at the end of this manuscript.

The effect of rGO-Fe2O3 nanocomposites with spherical, hollow and fusiform microstructures on the thermal decomposition of TKX-50

rGO-Fe2O3 nanocomposites with spherical, hollow and fusiform Fe2O3 (s, h and f) microstructures have been successfully fabricated using DMF as solvent via a facile solvothermal method. The morphologies and compositions of the as-synthesized rGO-Fe2O3 (s, h and f) nanocomposites were systematically studied using SEM, TEM, XRD, FTIR, RAMAN and XPS analysis. The rGO-Fe2O3 (s, h and f) nanocomposites were used to catalyze the thermal decomposition of energetic TKX-50 and the corresponding kinetic parameters were calculated using an isoconversional model. The catalytic performance of Fe2O3 (s, h and f) during the thermal decomposition of TKX-50 was significantly improved after being anchored onto the surface of graphene oxide. The as-synthesized rGO-Fe2O3 (h) and rGO-Fe2O3 (s) nanocomposites have an excellent effect toward reducing the temperature and apparent activation energy (Ea) for TKX-50 decomposition, respectively. The excellent catalytic performance of rGO-Fe2O3 (h) nanocomposite can be attributed to its external and internal surfaces, which provide more active sites for TKX-50 decomposition. In addition, the interactions formed between rGO and Fe2O3 have a positive effect toward reducing the Ea.

Preparation and evaluation of structural, optical, dielectric and thermal characteristics of unirradiated and irradiated polyurethane/magnesium silicate composites

Polyurethane filled with various amounts (5, 10, 15, and 20 wt%) of magnesium silicate was fabricated by the solution casting method. The structural and physical properties of PU due to the influence of adding magnesium silicate together with gamma irradiation were investigated. The structural properties of the prepared composites were investigated via X-ray diffraction (XRD) and scanning electron microscopy (SEM). The XRD analysis shows magnesium silicate formation in the PU matrix, which was further confirmed by the surface morphology images obtained by the SEM. Optical properties were characterized by ultraviolet–visible (UV–Vis) spectrophotometer. Refractive index dispersion was analyzed via the Wemple–Didomenico models. For both the unirradiated and irradiated composites, the ratio of carrier density to the effective mass, and the plasma frequency were calculated. Influences of magnesium silicate and gamma irradiation on these parameters as well as the dependence on the aforementioned additions were investigated. The dielectric investigation of the prepared composites reflected the increase of the dielectric constant, dielectric loss, and electrical conductivity with the addition of magnesium silicate and gamma irradiation, while it lowered with raising the applied frequency. The thermal stability of the prepared composites was investigated via thermogravimetric analysis. The thermal stability of all composites is significantly enhanced with the adding magnesium silicate and gamma irradiation. Kissinger model was applied to measure the activation energy of thermal decomposition and revealed the increasing trend of activation energy with the addition of the magnesium silicate and raising gamma absorbed dose. We believe that the outcomes of this work would provide a helpful contribution to the engineering of the components and the processes involved in the given structure presented.