Search Results (177)

Nitrocellulose (NC) is a long-established energetic polymer whose autocatalytic NO_x-driven degradation and conversion-dependent decomposition kinetics remain challenges for thin-film micro-ignition systems. This review examines NC as an energetic polymeric binder and film-forming matrix in selected nanothermite-containing formulations and micro-igniter architectures. It evaluates reported effects of formulation composition, stabilizers, nanothermite additives, deposition route, film architecture, and device geometry on thermal behavior, ignition response, safety, and storage-related limitations. Nitrogen content, molecular-weight information, crystallinity, and morphology are treated as formulation-specific characterization data rather than universal predictors of nanothermite performance. The review critically assesses Kissinger, Ozawa–Flynn–Wall, Kissinger–Akahira–Sunose, Friedman, advanced Vyazovkin, and distributed activation-energy-model approaches. Single-step kinetic models are generally inadequate for multistep, autocatalytic NC decomposition, whereas isoconversional methods provide more informative apparent activation-energy profiles when applied appropriately. Kinetic parameters obtained using different methods, sample forms, and heating programs should not be directly compared or used alone to predict ignition behavior. The review discusses stabilizers and NC-containing MICs, emphasizing formulation-specific thermal, ignition, processing, safety, and aging outcomes. In nanothermites, NC is usually a minor component functioning mainly as a binder, dispersing matrix, film-forming material, and ignition-coupling component. Full article

This study investigated the effect of replacing N₂ with CO₂ on the pyrolysis behavior, char structure evolution, and kinetics of Fushun (FS) and Changji (CJ) oil shales. Non-isothermal thermogravimetric experiments were conducted at 5, 10, 20, and 40 °C·min⁻¹ under N₂ and CO₂ atmospheres, and the resulting chars were characterized by FTIR, XPS, BET, and SEM. Kinetic parameters were evaluated using Friedman, FWO, KAS, Starink, and Vyazovkin iso-conversional methods. Both oil shales underwent three stages: moisture release, main organic-matter pyrolysis, and high-temperature mineral decomposition. Increasing the heating rate shifted T_s and T_max to higher temperatures and intensified volatile release. At 40 °C·min⁻¹, replacing N₂ with CO₂ increased T_s from 322.6 to 399.3 °C for FS and from 368.1 to 377.3 °C for CJ, while reducing the maximum mass-loss rates to 6.81 and 8.66%·min⁻¹, respectively. N₂ favored pore development, increasing the specific surface areas of FS and CJ chars to 14.1402 and 6.1464 m²·g⁻¹, whereas CO₂ caused pore blockage in FS char and reduced its surface area to 2.7783 m²·g⁻¹. XPS showed that CO₂ promoted the formation or preservation of oxygen-containing surface carbon, especially C=O and O–C=O groups. The E_α values first decreased and then increased with conversion and were generally lower in CO₂ than in N₂. The average activation-energy differences between the two atmospheres were 23.5 and 43.2 kJ·mol⁻¹ for FS and CJ, respectively. These results provide experimental and kinetic data for modeling primary oil shale pyrolysis and subsequent char combustion and gasification under CO₂-rich conditions. Full article

Algal cultivation has attracted significant attention due to CO₂ biocapture and potential for biofuel generation. Enormous generation of waste polymer often poses an environmental problem due to non-biodegradability. This study comprehensively analyses the thermal degradation characteristics of blue–green alga, Leptolyngbya subtilis JUCHE1 (LS) and waste textile polyester (WTP) and their mixtures (LS1P3 (1:3); LS1P1 (1:1); LS3P1 (3:1)) during co-pyrolysis. The interaction between LS and WTP during co-pyrolysis has been assessed through the verification of synergism using different blending ratio and through the comparison of the corresponding values of the Comprehensive Pyrolysis Index (CPI). The composite, LS1P3, exhibited the highest synergism and the maximum value of CPI. Isoconversional models (FWO, Starink, Bosewell and Tang) have been used to predict the activation energies (E_a). Thermodynamic parameters, namely, heat of reaction (ΔH), Gibbs free energy change (ΔG) and entropy change (ΔS), have also been determined for all. The average value of E_a for LS1P3 is also the lowest (96.015 kJ/mol) among all composites. The Master plot method identifies that there is a shift of reaction mechanism from phase boundary type (R2 and R3) for LS and WTP to a P2-type acceleratory reaction rate mechanism for LS1P3. The lowest average value of ΔH and the highest values of ΔG and ΔS for LS1P3 co-pyrolysis also support the least consumption of energy and the highest favorability under present conditions. The product yield distribution of co-pyrolysis in the isothermally operated conditions (450 °C) also establishes the superiority of LS1P3. Yields of pyro-oil and pyro-gas are the highest among all composites. The study ensures the future application prospects of co-pyrolysis of LS and WTP as a means for generation of energy resources (pyro-oil and pyro-gas) and chemicals (pyro-char). Full article

This study investigated the combustion behaviour of Hassawi rice straw (HRS) at industrially relevant high heating rates through a combination of detailed physicochemical characterisation and non-isothermal thermogravimetric analysis. The biomass was characterised for proximate and ultimate composition, lignocellulosic fibre fractions (Van Soest method), and surface functional groups (FTIR). Thermogravimetric combustion experiments were conducted at heating rates of 20, 40, 60, and 80 K min⁻¹ under oxidative conditions. The results demonstrate that HRS is a promising renewable solid biofuel, with high volatile matter content (72.48 wt%), moderate ash (10.27 wt%), and a higher heating value of 16.04 MJ kg⁻¹. Ultimate analysis revealed low nitrogen (0.67 wt%) and sulphur (0.31 wt%) levels, indicating low potential for NOx and SOx emissions. Thermal decomposition proceeded through three distinct stages, with the main devolatilisation phase occurring between 515 and 680 K due to the breakdown of hemicellulose and cellulose. Kinetic evaluation using six model-free isoconversional methods (FR, FWO, KAS, STK, K, and VY) together with the Coats–Redfern model-fitting approach yielded an average apparent activation energy of 139 kJ mol⁻¹, with the three-dimensional diffusion (D3) model providing the best fit mechanism to the experimental data. Thermodynamic analysis showed positive ΔH and ΔG values with predominantly negative ΔS, confirming the endothermic and non-spontaneous character of the process. These findings offer valuable kinetic and thermodynamic parameters for the design of efficient combustion systems utilising Hassawi rice straw as a sustainable biofuel in arid regions. Full article

The increasing generation of organic waste and the growing demand for sustainable solid fuels have intensified interest in hydrothermal carbonisation (HTC) as a pathway for biomass valorization within circular bioeconomy systems. HTC uses subcritical water to upgrade moist biomass into hydrochar with improved fuel properties and combustion behavior. This review correlates key HTC parameters, including temperature, residence time, pH, and the nature of feedstock, with the chemical evolution and thermal reactivity of different hydrochars. Data synthesis identifies a typical ‘kinetic optimization’ range between 180 and 220 °C for conventional lignocellulosic feedstocks. Within this thermal interval, activation energy (E_a) decreases from 180–260 kJ/mol for raw biomass to 70–180 kJ/mol for hydrochars, while the high heating value (HHV) reaches up to ~28 MJ/kg. The results further demonstrate that feedstock composition strongly influences combustion reactivity and kinetic behavior under similar HTC conditions. The integration of isoconversional methods with thermodynamic parameters (ΔH, ΔG, ΔS) confirms a transition toward more ordered and thermally stable carbon structures. Additionally, Criado’s master plots indicate a shift from diffusion-controlled to reaction-controlled combustion mechanisms with increasing HTC severity. These findings provide valuable insights into the optimizing of HTC conditions for balance energy densification and combustion reactivity, offering a comprehensive understanding to guide future hydrochar-based energy applications and scale-up studies. Full article

The effect of reversible addition–fragmentation chain transfer (RAFT) polymerization on the structure, morphology, and thermal degradation behavior of polypropylene glycol maleate–acrylic acid copolymers (p-PGM:AA) was investigated using 2-cyano-2-propyl dodecyl trithiocarbonate (CPDT) as the RAFT agent. Copolymers synthesized at different CPDT concentrations were characterized by ¹H/¹³C NMR spectroscopy, gel permeation chromatography (GPC), transmission electron microscopy (TEM), thermogravimetric analysis coupled with mass spectrometry (TG–MS), isoconversional kinetic methods, and density functional theory (DFT) calculations. ¹H NMR spectroscopy revealed a progressive decrease in the relative intensity of vinyl proton signals with increasing CPDT concentration, indicating enhanced conversion of unsaturated fragments during copolymerization. Alkaline hydrolysis followed by ¹H NMR and GPC analysis of the degradation products confirmed cleavage of polyester segments and yielded low-molecular-weight fragments with M_n = 1370 g mol⁻¹ and narrow dispersity (Đ = 1.035), providing additional information on the architecture of the vinyl-polymerized segments. Increasing CPDT concentration resulted in lower molecular weights and narrower molecular weight distributions of the soluble copolymer fractions. TEM analysis demonstrated broader domain size distributions and increased morphological heterogeneity in RAFT-modified samples, accompanied by an increase in swelling degree. Thermogravimetric analysis showed that RAFT-modified systems undergo multi-stage thermal degradation with the appearance of an additional low-temperature stage associated with thermolabile fragments. TG–MS revealed earlier evolution of CO₂ and oxygen-containing species and changes in the distribution of volatile products. DFT calculations indicated a decrease in the HOMO–LUMO energy gap and suggested the participation of RAFT-derived fragments in the energetic characteristics of decarboxylation processes. Isoconversional and nonlinear kinetic analyses demonstrated increased kinetic heterogeneity for branched copolymer s synthesized at elevated CPDT concentrations, whereas cross-linked systems exhibited more uniform degradation behavior. The combined experimental and theoretical results demonstrate that RAFT polymerization provides an effective route for tuning the macromolecular architecture, morphology, and thermal degradation pathways of p-PGM:AA copolymers. Full article

Background/Objectives: The thermal stability and degradation kinetics of β-lactam antibiotics are critical for understanding their behavior under processing and storage conditions. This study investigates the thermal decomposition of meropenem, ceftriaxone sodium, and cefazolin sodium in order to evaluate their kinetic parameters, assess the presence of the compensation effect, and determine isokinetic temperatures. Methods: Thermal analysis was performed using simultaneous TG/DTG/DSC measurements. Non-isothermal degradation experiments were conducted at four different heating rates. Kinetic parameters were evaluated using two isoconversional methods (Friedman and Flynn–Wall–Ozawa) and ASTM E698-based approach to obtain average activation energies. To determine the pre-exponential factor (A), the Coats–Redfern method was applied using multiple kinetic models. The resulting lnA—E_a pairs obtained from different models were used to construct lnA = f(E_a) correlations, enabling the evaluation of the compensation effect and calculation of isokinetic temperatures (T_iso). Results: All three β-lactam antibiotics exhibited consistent kinetic behavior across the applied models, with the F3 reaction model providing the best fit based on R² values. A clear linear relationship between lnA and E_a was observed, confirming the presence of an enthalpy–entropy compensation effect. However, significant differences in isokinetic temperatures were obtained indicating variability in kinetic compensation behavior among the studied compounds. Conclusions: The thermal degradation of the investigated β-lactam antibiotics follows a consistent kinetic framework, supported by isoconversional and model-fitting approaches. Nevertheless, the absence of a unique isokinetic temperature suggests differences in transition-state stabilization and enthalpy–entropy balance, likely driven by structural variations among the compounds. Full article

The use of hydrogen for smelting reduction ironmaking can effectively reduce the consumption of coke, as well as the CO₂ emission. However, the dynamic mechanism of this process is not clear. In this paper, isothermal thermogravimetric analysis (TGA) was used to study the reduction process of wustite by hydrogen at 1673–1773 K. Results show that wustite can be entirely reduced, and with the increase in temperature, the reduction reaction becomes more intense, and the time required for the entire reduction decreases. The hydrogen reduction of wustite at 1673–1773 K fits the Mampel power model: f(α) = 2α^1/2. When the reactants are molten and the products are solid, the apparent activation energy of the reduction process calculated by the iso-conversional method is 9.15 kJ·mol⁻¹. Molecular dynamics simulation results show that the adsorption of hydrogen molecule on FeO surface is spontaneous. With the increase in temperature, FeO substrate becomes more active, and hydrogen molecules move more violently. The average distance between a certain hydrogen atom and its neighboring atom was analyzed statistically. The increase in temperature will increase the average bond length of hydrogen molecules, reduce their bond energy, and facilitate the adsorption of hydrogen molecules on the FeO surface. Full article

Given the depletion of conventional oil and gas resources, oil shale represents a promising alternative source of hydrocarbons that can be recovered through pyrolysis. This study examines the thermal decomposition of raw oil shale from the Tarfaya deposit and its decarbonized concentrate, studied by thermogravimetric analysis at different heating rates (5, 10, 20 and 40 °C/min). Pretreatment with acetic acid enabled the selective removal of calcite, confirmed by elemental, XRF, and XRD analyses, which revealed a relative enrichment in silica and dolomite in the oil shale concentrate. Pyrolysis of the raw shale occurs primarily between 300 and 500 °C, with a conversion rate of approximately 30%. In contrast, for the oil shale concentrate, the pyrolysis process begins at a relatively low temperature, within a wider temperature range (260–520 °C). Kinetic analysis based on Flynn–Wall–Ozawa (FWO) and Kissinger–Akahira–Sunose (KAS) methods shows that at a conversion rate of 60%, the activation energy achieves 14.09 kJ/mol and 10.78 kJ/mol, respectively. The results indicate that the selective removal of calcite by acetic acid treatment facilitates kerogen pyrolysis by reducing mineral–organic interactions. Indeed, calcite dilutes the reactive organic fraction and can act as a physical barrier limiting heat and mass transfer within the oil shale. Its removal improves, on the one hand, the accessibility of kerogen to thermal cracking and promotes its decomposition, and on the other hand, reduces the amount of residue after pyrolysis. In addition, the kinetic analysis based on Criado master curves reveals changes in the reaction mechanism after decarbonation treatment depending on the heating rate (β). A shift from a two-dimensional Avrami–Erofeev model (A2) to a three-dimensional model (A3) was observed at a low heating rate (β = 5 °C/min), suggesting a change in nucleation and growth dynamics during kerogen decomposition. At high heating rates (10, 20 and 40 °C/min), the thermal decomposition of kerogen combines several reaction mechanisms depending on the temperature range considered. Full article

The present research article deals with the thermal degradation study of epoxy resins filled with hybrid nanostructured forms of carbon under oxidative conditions. In particular, the formulated polymer composites (denoted as HYB_0.1%_CNTs:GNs and HYB_0.5%_CNTs:GNs, respectively) consist of two kinds of fillers, namely multi-walled carbon nanotubes (CNTs) and graphene nanosheets (GNs), mixed together with two different total mass amounts: 0.1 and 0.5%. In both kinds of nanocomposites, three different CNT:GN mixing ratios were considered (5:1, 1:1, and 1:5, respectively), thus providing a total of six hybrid samples. The thermal behavior of these samples was studied by simultaneous thermogravimetry and differential thermal analysis (TG/DTA) under flowing air, and two processes took place in distinct temperature ranges. In each step, about 50% of mass loss is detected with an exothermic effect in the corresponding DTA curve, with the second one accompanied by an intense heat release. The kinetic analysis of the two-stage oxidative thermal degradation was investigated using a model-free isoconversional approach. A non-Arrhenian behavior of the temperature function k(T) was assumed, and lifetime prediction was estimated at temperatures close to those of the possible applications. Isoconversional analysis shows nearly constant activation energies for all composites except HYB_0.1%_5:1 (from 142 to 96 kJ·mol⁻¹), while lifetime predictions indicate that thermal stability increases with graphene content at 0.1% loading (HYB_0.1%_1:5) and with CNT content at 0.5% loading (HYB_0.5%_5:1), with uncertainties below 7%. Finally, because of the π–π bond interactions between the CNTs and the GNs dispersed in the epoxy resin matrix, an effective and remarkable electrical performance was found and a correlation with both electrical and morphological properties was established. In this regard, Tunneling Atomic Force Microscopy (TUNA) proved to be particularly powerful in allowing the simultaneous mapping of topography and localized conductive networks with exceptional sensitivity to nanofiller dispersion, such as CNTs and GNs. DC conductivity increased by up to nine orders of magnitude at 0.1 wt% hybrid loading (up to 3.73 × 10⁻⁴ S/m vs. 1.06 × 10⁻¹³ S/m for CNT-only), with nanoscale TUNA currents (−1.9 to 4.5 pA) mirroring macroscopic trends, while at 0.5 wt% all hybrids reached 10⁻² S/m, indicating reduced synergy once a fully developed conductive network is established. Full article

In this study, chemiluminescence (CL) is presented as a highly sensitive, mechanistically coupled method for investigating the thermo-oxidative aging of dammar resin, a triterpenoid natural resin of central relevance to conservation science. In contrast to conventional spectroscopic techniques, CL does not primarily reflect the accumulated oxidation state; instead, it selectively detects the formation and decomposition of reactive peroxide and hydroperoxide intermediates, thereby providing an early view of the oxidative reactivity of the material. Measurements performed under inert and oxidative atmospheres provide a clear distinction between pre-existing oxidative damage and ongoing autoxidation. Correlation with Fourier-transform infrared (FTIR) spectroscopy demonstrates that oxidized functional groups are not necessarily associated with high oxidative reactivity, underscoring the functional advantage of chemiluminescence for stability assessment. The combination of dynamic CL measurements with model-free isoconversional kinetics has been shown to reveal the pronounced dependence of effective activation energy on the extent of the reaction. This α-dependence confirms the multistep nature of dammar oxidation and highlights the limitations of classical Arrhenius models. Furthermore, chemiluminescence is an effective screening tool for evaluating stabilizers and synergistic additive combinations, providing a robust basis for kinetic modeling and evidence-based decision-making in conservation science. Full article

The subject concerns the determination of activation energy under dynamic conditions using two theoretical isothermal models, and subsequently experimental data, with reference to the α–T relationship matrix. In recent years, the Vyazovkin method, classified as one of the isoconversional variants, has gained the greatest recognition. Comparison was made between two isothermal models of the thermal dissociation of calcite, which in chronological terms are associated with a kinetic–nucleation reaction/process (the H-CL, as a kinetic model) and a kinetic–desorption reaction/process (the V, as a thermodynamic model). A comparison of numerical values, understood as the logarithm of the reaction/process rate with respect to temperature, shows correspondence in the temperature range up to the equilibrium temperature. The H-CL model is characterized by a strong dominance of the nucleation process relative to the chemical reaction, whereas the V model exhibits a certain type of balance resulting from the course of the chemical decomposition reaction combined with the transformation of a metastable oxide into a crystalline form. It was confirmed that both models describe the same phenomenon within the transformation process, which implies that for a constant conversion degree, the proportions of the chemical reaction and the physical process vary. Pointwise with increasing temperature, the H-CL model leads to a minimum activation energy E → 0, whereas the V model reaches a negative activation energy E < 0. In both cases, the apparent activation energy summed over the process is constant, and the assigned conversion degree, treated as isoconversional, remains fixed and corresponds to the assumed activation energy of the completed reaction/process. Several simple methods for its determination under dynamic/isoconversion conditions are used. Full article

This work contributes to advancing sustainable energy and waste management strategies by investigating the thermochemical conversion of food-based biomass through pyrolysis, highlighting the role of artificial intelligence (AI) in enhancing process modelling accuracy and optimization efficiency. The main objective is to explore the potential of underutilized biomass resources like spent coffee grounds (SCGs) and DSs (date seeds) for sustainable hydrogen production. Specifically, it aims to optimize the pyrolysis process while evaluating the performance of these resources both individually and as blends. Proximate, ultimate, fibre, TGA/DTG, kinetic, thermodynamic, and Py-Micro-GC analyses were conducted for pure DS, SCG, and blends (75% DS-25% SCG, 50%DS-50%SCG, 25%DS–75%SCG). Blend 3 offered superior hydrogen yield potential but had the highest activation energy (Ea: 313.24 kJ/mol), while Blend 1 exhibited the best activation energy value (Ea: 161.75 kJ/mol). The kinetic modelling based on isoconversional methods (KAS, FWO, and Friedman) identified KAS as the most accurate. These approaches work together to provide a detailed understanding of the pyrolysis process with a particular emphasis on the integration of artificial intelligence (AI). An LSTM model trained with lignocellulosic data predicted TGA curves with exceptional accuracy (R²: 0.9996–0.9998). Full article

This study presents a comparative thermal and kinetic analysis of three benzimidazole derivatives used in the pharmaceutical field: fenbendazole, mebendazole, and flubendazole. The investigations were carried out using thermoanalytical methods, including thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), in order to evaluate thermal stability, decomposition stages, and to calculate kinetic parameters. The obtained data were processed using isoconversional methods (Ozawa–Flynn–Wall, and Friedman) and non-parametric method (NPK) to determine activation energies and degradation mechanisms. The results revealed significant differences among the three compounds regarding their thermal stability and decomposition behavior, influenced by molecular structure and aromatic substituents. Furthermore, the comparative analysis provides valuable insights for optimizing technological processes, assessing stability in pharmaceutical formulations, and expanding research on the therapeutic potential of these compounds, including in oncological studies. Overall, the study contributes to a deeper understanding of the relationship between chemical structure and thermal stability in benzimidazole derivatives. Full article

In this study, thermogravimetric analysis was employed to investigate the non-isothermal combustion behavior and kinetic characteristics of poplar biomass under air and oxy-fuel (O₂/CO₂) atmospheres. The effects of heating rate and oxygen concentration on combustion performance, gaseous emissions, and kinetic parameters were systematically analyzed. Results show that poplar biomass combustion consists of four distinct stages: moisture evaporation, devolatilization with volatile oxidation, char and fixed carbon oxidation, and final burnout. Increasing the heating rate intensifies the combustion process, shifting characteristic temperatures to higher values and significantly enhancing the comprehensive combustion index. Compared with air combustion, oxy-fuel conditions reduce ignition temperature and the temperature corresponding to the maximum combustion rate, leading to an earlier ignition and a more concentrated reaction interval. Higher oxygen concentrations further improve overall combustion performance and promote more complete carbon conversion. Gas emission analysis indicates that oxy-fuel combustion effectively suppresses NO₂ and SO₂ formation, demonstrating notable emission-reduction potential. Kinetic analysis using the Kissinger–Akahira–Sunose and Flynn–Wall–Ozawa isoconversional methods shows that the activation energy varies with conversion degree and is generally higher under oxy-fuel atmospheres than in air. Overall, oxy-fuel combustion enhances biomass reactivity while achieving coordinated emission control through increased oxygen partial pressure and improved heat and mass transfer, supporting its practical application in biomass energy systems. Full article