Thermal Decomposition Process Research Articles

Co-pyrolysis of corn stalk and high-density polyethylene with emphasis on the fibrous tissue difference on thermal behavior and kinetics

The thermal properties of various corn stalk tissues (including stem, husk, ear, cob, and leaf), high-density polyethylene (HDPE), and their blends were investigated using thermogravimetric analysis under a nitrogen atmosphere. The results indicate that the thermal decomposition process of corn stalk tissue/HDPE mixtures is delayed with an increasing heating rate, regardless of the tissue type. Besides, the structural differences among various corn stalk tissues significantly influence their thermal behavior, product distribution, and co-pyrolysis kinetics with HDPE. Pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) was conducted to analyze the pyrolytic products of the blends with different corn stalk tissues, revealing that corn cob/HDPE blends produce a higher yield of valuable chemicals, such as the furan derivates and aromatic hydrocarbons. Kinetic analysis was further performed using Kissinger-Akahira-Sunose (KAS) and Flynn-Wall-Ozawa (FWO) methods to determine the activation energy for the reactions occurring during co-pyrolysis. The co-pyrolysis of corn cob/HDPE blend requires the least activation energy (149.3 kJ/mol) among five blends, which was ascribed to the high hemicellulose content in corn cob. Moreover, machine learning algorithms, including random forest (RF) and gradient boost regression tree (GBRT), were applied to predict mass loss in the corn fiber/HDPE blends, which showed RF possessed superior accuracy over GBRT. These findings suggest that isolating plant tissues during the feedstock pre-management could enhance the valorization performance of lignocellulose-waste plastic co-pyrolysis.

Study of the Thermal Decomposition Process of Explosive Mixtures Based on Hydrogen Peroxide

In this work, we have investigated the thermal features of hydrogen peroxide-based energetic materials formulations. Initial research has shown that both the auxiliary oxidiser (sodium nitrate, potassium nitrate or calcium nitrate) and sensitising agent (glass microspheres) have significant influence on the rate of hydrogen peroxide decay in such formulations. In terms of the thermal features of the tested energetic materials, a similar and significant influence of the auxiliary oxidising agent and sensitising agent choice was observed. We have established that the use of calcium nitrate as an auxiliary oxidising agent (at ambient temperature of approx 20 °C), which allows the formulations to maintain capacity to undergo detonation for longer under storage conditions, negatively impacts the qualitative characteristics of the mixture as an energetic material. The thermal effects accompanying chemical interaction are much smaller than mixtures containing potassium and sodium nitrates as additional oxidising agents. Another important conclusion is that glass microspheres as sensitising agents significantly impact the thermal decomposition processes of the investigated on-site mixed (OSM) energetic material (EM) samples, except for the mixture using calcium nitrate.

Pyrolysis characterization and mechanism studies of different structural plastics: A comparative study at optimal temperatures

Thermal conversion technology is an effective means to transform waste plastics into high-value-added products. This study explored the thermal decomposition characteristics and cracking mechanism of four different types of plastics (polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC), and polyethylene terephthalate (PET)) for thermal conversion technology. The findings revealed that PP exhibited the highest hydrogen yield, reaching 3.56 mmol/g at 510°C. PET's gas production was predominantly comprised of carbon monoxide and carbon dioxide. PVC gas products contained a significant amount of HCl, followed by hydrogen and methane. For solid products, the carbon yield followed the order PET > PVC > PS > PP, with the carbon content of PET accounting for 35.63% of the total products. PP and PS demonstrated higher oil yields for liquid products than PET and PVC. The oil yield of PP was 94.38%. Further analysis of the cracking mechanism found that during the thermal decomposition process, plastics underwent random fragmentation, leading to reactions such as β-scission, intramolecular and intermolecular hydrogen transfer, rearrangement, cyclization, etc., due to structural variations. This work provided foundational data for the thermal decomposition studies of different types of plastics.

Comprehensive revelation of the influence mechanism for the thermal decomposition of ammonium perchlorate by ammonium oxalate

Rate inhibitors for combustion are crucial to decrease the burning rate and prolong the working time of solid propellants. Ammonium oxalate (AO), the most frequently utilized and effective rate inhibitor in propellants, faces the challenge of an unclear influence mechanism regarding ammonium perchlorate (AP). Therefore, it is necessary to elucidate the influence mechanism of AO on the thermal decomposition of AP. This study fabricated AP/AO composites with varying AO content via wet milling, the structural, thermal decomposition processes and products of these composites were investigated. Additionally, the adsorption between AP and NH3 was simulated. The findings indicate that the inclusion of AO inhibits the low-temperature decomposition (LTD) of AP while enhancing its high-temperature decomposition (HTD). Furthermore, it was observed that the heat release of AP/AO composites was lower than that of AP. The Gibbs free energy (ΔG≠) of the AP/AO composites exceeded that of the AP at the LTD stage and was lower than that of AP at the HTD stage. Further study using molecular dynamics simulations revealed that as the increase of NH3 concentration, its adsorption on the AP surface intensifies during LTD, inhibiting the forward progress of the AP decomposition reaction. However, NH3 molecules desorbed from the AP surface and actively participated in gas-phase reactions with increasing temperature, thereby promoting the HTD of AP. This work is helpful to fully understanding the mechanism of AO in the process of the LTD and the HTD of AP but also contributes to the exploration of novel inhibitors and advances the development of low-burning rate solid propellants.

Thermal Decomposition of Core-Shell-Structured RDX@AlH3, HMX@AlH3, and CL-20@AlH3 Nanoparticles: Reactive Molecular Dynamics Simulations.

The reactive molecular dynamics method was employed to examine the thermal decomposition process of aluminized hydride (AlH3) containing explosive nanoparticles with a core-shell structure under high temperature. The core was composed of the explosives RDX, HMX, and CL-20, while the shell was composed of AlH3. It was demonstrated that the CL-20@AlH3 NPs decomposed at a faster rate than the other NPs, and elevated temperatures could accelerate the initial decomposition of the explosive molecules. The incorporation of aluminized hydride shells did not change the initial decomposition mechanism of the three explosives. The yields of the main products (NO, NO2, N2, H2O, H2, and CO2) were investigated. There was a large number of solid aluminized clusters produced during the decomposition, mainly AlmOn and AlmCn clusters, together with AlmNn clusters dispersed in the AlmOn clusters.

A functional fluorine (F)-containing oxidiser of nano-networked NH4CuF3 to improve the combustion efficiency of Al powder

Aluminium (Al) powder is the most common solid fuel component in metastable intermolecular composites (MICs). It is used in the field of propellants to provide energy for the flight of rockets and missiles. However, the passivation layer overlaying its surface hinders its energy release. Using fluorine (F)-containing oxidisers may etch the passivation layer, enabling Al to achieve a more direct redox process and improving its energy-release capacity. Herein, NH4CuF3, which has nano-network structure, was synthesised through the solvo-thermal method, and n-Al was filled into the nano-pore channels using a simple ultrasonic mixing method to form a new n-Al/NH4CuF3 MICs with excellent dispersion and interfacial contact. The thermal decomposition process of NH4CuF3 was investigated, and the results showed that NH4CuF3 could release hydrogen fluoride (HF) and ammonia (NH3) gaseous products. The passivation layer on the surface of the Al powder was etched by HF, and the abundance of gaseous products during the reaction of n-Al/NH4CuF3 Extended the combustion region. This can enhance air capture in the reaction system, minimise reaction sintering and aid in performing external work. Furthermore, n-Al/NH4CuF3 exhibits a lower onset reaction temperature, shorter ignition delay time and greater external work ability than n-Al/CuF2 and n-Al/CuO.

Cation reactivity inhibits perovskite degradation in efficient and stable solar modules.

Perovskite solar modules (PSMs) show outstanding power conversion efficiencies (PCEs), but long-term operational stability remains problematic. We show that incorporating N,N-dimethylmethyleneiminium chloride into the perovskite precursor solution formed dimethylammonium cation and that previously unobserved methyl tetrahydrotriazinium ([MTTZ]+) cation effectively improved perovskite film. The in situ formation of [MTTZ]+ cation increased the formation energy of iodine vacancies and enhanced the migration energy barrier of iodide and cesium ions, which suppressed nonradiative recombination, thermal decomposition, and phase segregation processes. The optimized PSMs achieved a record (certified) PCE of 23.2% with an aperture area of 27.2 cm2, with a stabilized PCE of 23.0%. The encapsulated PSM retained 87.0% of its initial PCE after ~1900 hours of maximum power point tracking at 85°C and 85% relative humidity under 1.0-sun illumination.

Syntheses, Structures, and Thermal Decomposition Kinetics of Two Silver/Copper‐Based Coordination Compounds with 1,2,4‐Triazole‐Containing Ligand

AbstractIn this work, two silver/copper‐based coordination compounds {[Ag(tty)]⋅NO3}n (1) and {[Cu2Cl2(tty)2(H2O)2]⋅Cl⋅NO3 ⋅ (H2O)2}n (2) (tty=1,2,4,5‐tetra(1H‐1,2,4‐triazol‐1‐yl))benzen), were synthesized using the different metal salts under the hydrothermal condition. Structural analyses show that compound 1 features tilted L‐shaped 1D Ag chains structure and compound 2 presents a 2D layer with free Cl−, NO3− and water molecules. The experimental results reveal that 1 displays considerably high thermal stability with the thermal decomposition temperature above 337 °C compared to compound 2, which further exemplifies that the framework structures may have a crucial effect on the resultant thermal stability. Additionally, the non‐isothermal kinetics parameters were evaluated at different heating rates by Kissinger's and Ozawa‐Doyle's methods. Importantly, the kinetic triplets (the apparent activation energy (Ea), the preexponential factor (logA) and the mechanism function (ƒ(α)) and the related thermodynamic parameters (the Gibbs energy of activation, ▵G≠, the enthalpy of activation, ▵H≠, and the entropy of activation, ▵S≠) of the thermal decomposition processes are discussed and calculated in detail.

Ignition and combustion properties of NGO coated AlH3

AlH3 is a highly promising additive for energetic materials and has gained considerable attention as a substitute fuel for aluminum in solid propellants. In order to improve its compatibility with energetic materials and oxidants, carbon coating materials are often used. Nitrated graphene oxide (NGO) was prepared and used as a surface modifier of α-AlH3 in our study. Various analytical techniques were utilized to examine its structure and morphology, including Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), particle size distribution (PSD) and X-ray diffraction (XRD). The oxidization, ignition characteristics, flame propagation behavior and heat of combustion of AlH3 and AlH3/NGO powder were investigated using differential thermal analysis (DTA), a laser igniter, a high-speed camera and an oxygen bomb calorimetry. Results show that NGO coating agent catalyzes the thermal decomposition and hydrogenation process of AlH3, and accelerates the oxidation process of AlH3. The addition of 4 % NGO decreases the oxidation activation energy of AlH3 by about 8.94 %. The laser ignition energy of AlH3/NGO is much lower than that of AlH3, and the ignition energy decreases linearly as NGO is added from 1 % to 10 %. The flame development process supports the good thermal conductivity assistance effect of an appropriate amount of NGO in the combustion process of AlH3 in air, which is consistent with the result of oxygen bomb test, indicating that the addition of NGO leads to an improvement in the combustion efficiency of AlH3.This may provide valuable insights for the development of new high-energy solid propellants.

Ultrasonic-Assisted Synthesis of Lead Citrate as Precursor for Preparation of Lead Oxide from Lead Sulfate

ABSTRACT In this study, an efficient method of lead recovery from lead sulfate in spent lead-acid batteries assisted by ultrasonic is developed using the citric acid–sodium citrate solution. Ultrasonic-assisted technology is employed to enhance the kinetics of lead sulfate leaching. Initially, the predominance area of the lead citrate complexes was analyzed. The study was conducted to evaluate the effect of ultrasonic-assisted technology on the kinetic behavior of lead sulfate within the citric acid–sodium citrate solution, thereby unveiling the differences between ultrasonic-assisted leaching and the non-ultrasonic-assisted leaching. Kinetic study indicated that the employment of ultrasonic-assisted technology could effectively reduce the apparent activation energy during the desulfurization process, decreasing the energy initially required from 43.27 kJ/mol to 35.15 kJ/mol. Furthermore, the ultrasonic-assisted leaching led to successful preparation of lead citrate precursor, characterized by a smaller particle size and larger specific surface area. Systematic investigations were performed on the thermal decomposition process of these precursors and the effects of calcination temperature and holding time on the properties of calcination products. It was revealed that pure porous lead oxide powder with a purity of 99.9% could be produced successfully under the conditions of calcination temperature at 350°C and holding time of 1 h. The research provides an innovative process for the efficient recovery of lead from spent lead acid batteries.

Step-by-step silicon carbide graphitisation process study in terms of time and temperature parameters

This work investigates the temperature and time as key parameters for graphene formation on the silicon carbide surface during the high thermal decomposition process. Measurements were performed using various experimental techniques under ultra-high vacuum conditions. The graphitisation process was divided into various stages, after which the surface chemical composition and atomic structures were analysed in detail. It has been shown that despite the known theory of graphitisation mechanism and initial condition for occurrence of this process, the application of different temperatures and heating times affect the quality and quantity of formed graphene layers. Applying a temperature too low or annealing the sample for a too short time led to an inefficient silicon sublimation process. On the other hand, too high temperature during flashing modifies the visibility of surface structures, which may be crucial for other investigations and potential applications of such systems.

X-ray spectromicroscopy of single NiO antiferromagnetic nanoparticles

The chemical and magnetic properties of NiO nanoparticles (NP) have been studied with single-particle sensitivity by means of synchrotron-based, polarization-dependent X-ray absorption spectroscopy using photoemission electron microscopy around the Ni L3,2 edges. Three samples of NP in a size range of 40-120 nm were synthesized by thermal decomposition and subsequent calcination processes. The analysis of the local X-ray absorption spectra of tens of individual NP indicates a strong dependence of their Ni oxidation state with the calcination protocol of each sample. Additional electron-microscopy-based images and spectra of a few individual NP as well as other standard macroscopic data are in very good agreement with these experimental findings. These results showcase the relevance of combining standard and advanced single-particle studies to gain further insight into the understanding and control of electronic and magnetic phenomena at the nanoscale.

Thermal Degradation Behavior of Thermally‐Oxidized Hydroxyl‐Terminated Polybutadiene (HTPB): An Assessment of Thermal Stability

AbstractThermal analysis was performed on different thermally oxidized hydroxyl‐terminated polybutadiene (HTPB) samples, varying in molecular weights, polydispersities, and viscosities. The HTPB sample was subjected to thermal ageing at 65 °C for 10 weeks and periodically withdrawn for thermal analysis. During thermal ageing, HTPB undergoes chain rearrangements that may include scission and subsequent crosslinking, leading to a higher average molecular weight and viscosity. Differential scanning calorimeter (DSC) and thermogravimetric analyses were performed on thermally oxidized HTPB samples under inert heating conditions to investigate their degradation behavior. The DSC results revealed no significant correlations between the glass transition (Tg) and the samples' molecular weight, viscosity, and polydispersity. In TGA, all HTPB samples showed a two‐step thermal decomposition process characterized by two distinct mass loss stages. Notably, the first stage exhibited a lower total mass loss and a considerably lower peak rate of mass loss than the second stage. The thermal stability of HTPB is significantly compromised by thermal‐oxidative degradation, leading to a pronounced decrease in the initial degradation temperature (TIDT) values, from 372 °C (pristine or 0 week) to 228 °C (10 weeks). Furthermore, we measured the energy of activation (Ea) and the pre‐exponential factor (A) from TGA data using the Coats–Redfern integral equation. Notably, we observed a slight but systematic increase in both Ea and A as the molecular weight of the aged samples increased.

Thermal decomposition behavior of ZrO2 barrier layer against Cr/Zr inter-diffusion under high temperature

The Cr/Zr inter-diffusion has been becoming a critical issue for Cr-coated Zr alloys as accident tolerant fuel (ATF) cladding. Here, ZrO2 barrier layers against Cr/Zr inter-diffusion were successfully fabricated between the Cr layer and Zry4 substrate. Thermal decomposition of ZrO2 is confirmed under high temperatures, and ZrO2 is transformed into oxygen-stabilized α-Zr (O), which is effective for mitigating the Cr/Zr inter-diffusion. In-situ transmission electron microscopy (TEM) results indicate that the ZrO2 thermal decomposition process becomes more obvious under 500 ℃. In addition, Cr/α-Zr (O) inter-diffusion leads to the thin Zr(Cr, Fe)2 interface layer due to the high stability of the α-Zr (O) phase.

An Investigation on the Thermal Degradation Kinetics of Wood-Polymer Composites Used in Interior Automobile Panels via Non-Isothermal Thermogravimetry

Wood plastic composites (WPCs) offer a promising alternative for various automotive components, combining the benefits of wood and polymers such as lightness, strength, and sustainability. However, determining decomposition kinetics is challenging due to the intricate composition of WPCs. Therefore, this research work focused to analyze the relationship between the thermal degradation of WPCs, the degradation atmosphere, and the kinetics. The kinetic parameters were evaluated by Coats and Redfern method based on a set of TGA experiments under variable atmospheres (inert and oxidative) using 10 ℃/min heating rate. Thermograms demonstrated significant differences in the thermal properties of WPC when subjected to oxidative and inert atmospheres, despite two conditions having the same number of thermal degradation zones. It has been suggested that the process of thermal decomposition of WPC contains three weight loss segments under inert and oxidative atmosphere according to the Gaussian multi-peak fitting function. The Coats-Redfern method showed multi-step chemical kinetics and more accurately characterizes the decomposition behavior of WPC, attributing to its multi-compositional properties. Proposed reaction schemes had regression coefficients higher than 0.9809 to obtain reaction order, activation energy and pre-exponential factor.

Extraction of Bio Oil from Jordanian Biomass Resources via Pyrolysis and its Antibacterial Effect

This study explores the potential of pyrolytic oil extracted from Jordanian biomass resources as an antibacterial agent. Pyrolysis, a transformative thermal decomposition process, offers a promising avenue for converting biomass into valuable products. Pyrolytic oil, derived from biomass via pyrolysis, presents a complex composition and inherent antibacterial properties, making it a candidate for addressing antibiotic resistance and promoting sustainable solutions. Five biomass feed stocks were subjected to pyrolysis and their product distributions were analyzed. Pyrolytic oil yields were investigated and antibacterial activities against four bacterial strains were evaluated using disc diffusion, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) assays. Results indicate varying levels of antibacterial activity among the biomass extracts, highlighting their potential as eco-friendly antibacterial agents.

Mechanistic insights into the pyrolysis of pine resin sludge based on experiments and ReaxFF-MD simulation: High-value bio-oil production, nitrogen conversion, kinetics and environmental risk assessment

Forestry and agro-industrial waste conversion into high-value chemicals and fuels is considered one of the hottest ongoing research and industrial topics toward sustainable development. As one of the forestry and agro-industrial waste, pine resin sludge (PRS) with amino acids, pine resin residues and their derivatives such as abietic acid and 4-Epidehydroabietal, have ecological toxicity and require environmentally friendly treatment. Herein, a thermal process of PRS that generates high-value biofuels while reducing environmental pollution was reported. The results of the experiment and simulation reveal that the N of bio-oil is the major evolution direction of N, and the nitrogenous gas product is mainly NH3, a useful synthesis gas. ReaxFF-MD simulations elucidated the migration and conversion mechanism of nitrogen in amino acids. The main products of amino acid pyrolysis are 3-oxo-2-Propenenitrile, 2,4-Cyclopentadien-1-ylidenemethanone and 4R)-4-amino-5,5-dihydroxypentanoic acid. PRS's thermal weightlessness was divided into three phases, and the average activation under non-isothermal conditions was calculated at 78.17, 85.68, 206.42 kJ/mol (thermal decomposition) and final 117.78, 149.31, 195.54 kJ/mol (thermal oxidation). Thermal decomposition and oxidation process followed Avrami-Erofeev model (n=2), three-dimensional diffusion model (n=3) and mampel power (n=1). PY-GC/MS analysis shows that pyrolysis at different temperatures recovered mainly 4-Epidehydroabietal (37.15–89.67 %) for potential use as the biosynthesis of dehydrofolate. The bio-oil from PRS pyrolysis shows an excellent yield (31.43 %) and a high calorific value (37.21 MJ/kg), which is comparable to biodiesel. This work focused on offering an appealing and instructive guide for the logical treatment of sludge from pine resin production.

Doping SrSnO3 perovskite with transition metals: Synthesis of double hydroxides, thermal decomposition, and pigment potential

The primary objective of this research is to explore the feasibility of synthesizing phase-pure perovskite SrSnO3 doped with transition metals and to evaluate the potential of these products as high-temperature inorganic pigments. The initial step in preparing perovskite powders with the general formula SrSn0.95M0.05O3-δ (M = Mn, Fe, Co, Ni) involved synthesizing SrSn0.95M0.05(OH)6 followed by its thermal decomposition. The thermal decomposition processes and the reaction pathway for perovskite formation were analyzed using thermal analysis and X-ray diffraction analysis. Single-phase products of beige SrSn0.95Fe0.05O3-δ and brown SrSn0.95Co0.05O3-δ were successfully obtained by calcining the precursors at 1,100 °C. In contrast, brown SrSn0.95Mn0.05O3-δ contained a phase impurity of SnO2 and doping with Ni ions resulted in a phase mixture of SrSnO3 and NiO. The pigment quality of the powders was assessed based on their color parameters, described using the CIE Lab system.

Pore structure regulation of nano-CdSnO3 based on particles adhesion and mass transfer for enhanced NO-sensing

CS-x (x = 1, 2, 4, 6) nanoparticles have been successfully prepared by simple hydrothermal method combined with calcination process, and the calcination time is adjusted to optimize micro-structure characterization for their enhanced NO-sensing. The techniques of XRD, Raman, SEM, TEM, TGA, DSC, BET, and XPS are used to study their phase structure, micro-morphology, thermal decomposition process and surface states, then the possible gas-sensitive mechanism is analyzed. Results show that the typical CS-2 sensor has the maximum response of 130–50 ppm NO at 90 ℃, the short response/recovery time of 40/45 s, and the low detection limit of 0.1 ppm (1.18). It also has the reliable NO selectivity against to other interfering gases, good repeatability and high stability. Its enhanced NO-sensing performance may be due to the optimization of pore structure by adjusting the calcination process based on particles adhesion and mass transfer, which increases the pore size and specific surface area that could provide the channel and active sites for gas diffusion and adsorption, thus further promoting the gas-sensing reaction. The experimental methods and ideas of pore structure regulation provide a new way for the design of high-performance sensitive materials.

Study on the cracking process of epoxy resin under oxygen and water atmosphere based on ReaxFF force field

Amino-cured epoxy resins are widely used in the electrical and electronic industry for their excellent properties. To investigate the mechanism of the effect of O2 and H2O on the pyrolysis behavior of epoxy resin, in this paper, the cross-linked structure of bisphenol A type epoxy resin cured by adducts of diethylenetriamine and butyl glycidyl ether is modeled based on the ReaxFF force field, and the thermal decomposition processes at different temperatures and gas atmospheres were simulated and the pathways of the small molecule products were clarified. The results show that epoxy resin will produce small molecule gas products, such as H2, CO, H2O, OH, CH2O, and free radicals, in the process of pyrolysis; the presence of amino groups also generates nitrogen-containing radicals, such as CN, CH2N, and C2H4N; as the reaction temperature increases, the rate of pyrolysis reaction will be accelerated. The same temperature in oxygen and water atmospheres can accelerate the breakage of epoxy resin main chain by promoting the breakage of carbon and oxygen bonds and, at the same time, promote the generation of small molecule gases, such as H2 and CO.