Variable Heating Rate Research Articles

Investigations on the effect of kaolin catalyst on the yield of various products obtained from pyrolysis of low-density polyethylene (LDPE) wastes and reaction kinetics.

The pyrolysis characteristics of low-density polyethylene (LDPE) wastes were investigated in a batch pyrolyzer in the temperature range of 550-650°C for a varying heating rate (5, 10, 15, 20, and 25°C/min) alone and using kaolin catalyst (10, 15, and 20% w/w). The yield distribution of various products under varying operating conditions was investigated, and the corresponding favourable conditions for maximum yield of pyrolytic oil (PO) were identified. The possible effect of the catalyst on pyrolysis kinetics was explored by extracting activation energies from the TGA experiments. The various model-free iso-conversion methods estimated the activation energy of 162-166kJ/mol during thermal degradation of LDPE, while it shifted to a lower range (138-145kJ/mol) on catalytic treatment. The catalytic pyrolysis with a 20% (by mass) catalyst in a batch pyrolyzer provided the maximum PO yield with the least solid residue at 600°C using a heating rate of 20°C/min, while the temperature of 600°C with 10% catalyst showed the least liquid product with more solid residue. The presence of a catalyst improved the oil quality with transparency and lower viscosity due to lighter hydrocarbons and higher aromatic content. The FTIR analysis detected various organic groups-alkanes, alkenes, cyclic, and aromatics in the oil. GC tests of gaseous products confirmed the gases like hydrogen, propane, butane, and propylene. The present study aims to provide technical know-how for the effective utilization of LDPE wastes towards clean energy sources and create a plastic-free green environment.

TEMPERATURE EFFECT ON THERMOLUMINESCENCE KINETIC PARAMETERS OF NANO-ALUMINA

This research explores the fundamental thermoluminescence characteristics of irradiated nano-α-alumina particles, investigating their response to varying heating rates. The study involves recording TL luminescence curves, revealing a distinct peak with a maximum at approximately 202°C. As dose levels increase, the peak consistently shifts towards lower temperatures, indicating adherence to non-first-order kinetics (b≠1). The crystallite size was calculated using XRD analysis and estimated as 40nm. To examine the impact of the heating rate on the TL glow curve and derive kinetic parameters for nano α-Al2O3, specimens were exposed to a 6 kGy dose. Subsequently, TL glow curves were documented over a temperature range from room temperature to 300°C, employing different heating rates (2, 4, 6, 8 and 12°C/s). The peak temperature of the glow peak shifts towards higher temperatures as the heating rate increases and the peak intensity continuously diminishes, aligning with TL theory. The observed decrease in TL glow peak intensity with escalating heating rates is attributed to thermal quenching, where quenching efficiency rises at higher temperatures. Normalizing maximum TL intensities to the lowest heating rate (2°C/s) reveals a substantial 22% decrease in peak intensity.

Pyrolysis of Khat waste vs. Coal: Experimental and Aspen plus analysis

This study explores the potential of Khat waste as a biofuel through a detailed analysis of its physical properties and pyrolytic behavior, employing both laboratory and simulation techniques. Biomass, including Khat waste, is a valuable renewable energy source with potential applications in reducing waste and CO2 emissions, especially in rural areas of developing countries like Ethiopia. The physical properties of the Khat waste were thoroughly examined, including moisture content, ash, volatile matter (VM), fixed carbon (FC), and elemental composition. The apparent density of the pyrolyzed khat waste was found to be 0.9688 g/cm³. The TGA results showed a moisture loss of 6.7 %, volatile matter of 4.7 %, fixed carbon of 6.78 %, and ash content of 5.55 %. Notably, Khat waste exhibited unique thermal behavior with a downward shift in TG curves above 220 °C. DTGA identified three decomposition peaks: moisture evaporation at 100 °C, hemicellulose breakdown at 210 °C, and cellulose degradation at higher temperatures. Fourier Transform Infrared Spectroscopy (FTIR) provided insights into the functional groups present in Khat waste, including alkene functional groups and O-H bonds, which are crucial for biofuel properties. Simulation using Aspen Plus software modeled the pyrolysis process, highlighting how varying heating rates affect volatile matter and fixed carbon content. Increasing heating rates decreased volatile matter and moisture but increased fixed carbon content. These findings offer valuable insights for optimizing Khat waste as a biofuel, emphasizing the need for tailored pyrolysis conditions to enhance biofuel production efficiency.

Thermoluminescence (TL) properties of Eu3+ incorporated with CaB4O7 phosphors prepared by solution-combustion process

The solution-combustion approach was used to create CaB4O7:Eu3+phosphors using Ba (NO3)2, Eu (NO3)3·5H2O, H3BO3, NH3(ON)H2, and NH4NO3 as source materials. We investigated the thermoluminescence (TL) characteristics of beta (β)-irradiated CaB4O7:Eu3+. When the TL intensity was evaluated at different dosages of β, it rose with the dose. Changes in peak temperature were observed because of the investigation of the effects of varying heating rates on TL glow curves. Moreover, the positions of the peak temperature and the TL intensity did not change when the same sample was measured again, suggesting that the sample was stable. Additionally, the study calculated several kinetic parameters, including activation energy (E), frequency factor (s), and geometrical factor (μg), for distinct TL glow curves. Through geometric analysis of TL glow peaks, the study determined activation energies and kinetic orders, enabling the calculation of the frequency factor. The findings highlight the suitability of the prepared phosphor for dosimetry and provide insights into trap characteristics crucial for continuous illumination at room temperature. The study also emphasises the importance of optimising trap depth for prolonged afterglow, shedding light on the interplay between trap energies and luminescence characteristics. These findings deepen our comprehension of phosphor behavior and open the door to better dosimetry applications.

Thermal slip and variable viscosity analysis on heat rate and magnetic flux through accelerating non-conducting wedge in the presence of induced magnetic field

The focus of present study is to incorporate the variable viscosity and temperature slip impact on heating rate and induced magnetic gradient along the moving non-conducting wedge under magnetic field. In industrial and engineering procedures, the impact of induced magnetization improves the efficiency of thermal systems to main the heating rates. The similarity transformations and stream functions are applied to reduce the governing equations into ordinary form. During this transformation, the pertinent parameters such as wedge parameter, moving parameter, Prandtl factor, viscosity parameter and temperature-slip parameter is obtained. These parameters play a prominent role on the physical values of fluid velocity, induced magnetic field and temperature distributions. The skin friction, Nusselt coefficient and induced magnetic gradient are incorporated through these parameters. The numerical values are executed by using the Keller box analysis with Newton–Raphson technique. It is depicted that the maximum slip in fluid velocity and temperature distribution is obtained for each values of thermal-slip parameter. It is noticed that maximum magnitude in induced magnetic field is reported for each wedge factor. The maximum velocity slip and temperature slip is observed for each choice of moving parameter. It is reported that the maximum variation in heating rate and induced magnetic gradient is obtained for magnetic force and viscosity parameter. The enhancing behavior of skin friction is observed for maximum values of Prandtl number.

Thermokinetic study of tannery sludge using combustion and pyrolysis process through non-isothermal thermogravimetric analysis

Sludge from the tannery is produced in enormous amount. This work has investigated the thermal analysis behaviour of the tannery sludge by use of the thermogravimetric analysis (TGA). The TGA experiments is carried out in both air and nitrogen environment at the varied heating rates of 5, 10, 20 and 40 °C/min from the temperature range of 30–900 °C. In the assessment of kinetic parameters, the model fitting (Combined kinetics) method was employed. It was investigated that thermal degradation of the tannery sludge sample occurred in three stages. Majorly the conversions were observed in stage II for both in air and nitrogen environment. The activation energy (Ea) value for the combustion is 165.9 kJ/mol while for the pyrolysis the Ea value is obtained as 65.2 kJ/mol from the conversion range between 0.2 and 0.8 which is a promising approximation supported by a strong R2 value of 0.9719 and 0.93 for combustion and pyrolysis respectively. It is estimated from the master plots that six ideal models A1/2, A1/3, A1/4, F3, F4 and D5 were probably in approximation with the linear fitted data for both air and nitrogen. Various thermodynamic parameters which include the ΔH, ΔG and ΔS are also complimented that indicates the formation of activated complex and non-spontaneity of the reaction. The detailed thermokinetic study of the tannery sludge in combustion and pyrolysis offers a novel approach to understanding how this waste material decomposes under different temperature conditions. This holistic perspective contributes valuable insights into waste management practices, environmental impacts, resource recovery, and process optimization within the leather industry. Furthermore, the optimization of leather production processes on a large scale can minimize waste generation and enhance energy efficiency, strengthening the competitiveness and sustainability of the leather industry.

Photoluminescence and beta-ray irradiation induced thermoluminescence of Er(III) doped tungstate double perovskite

A luminescent double perovskite Ca3WO6 doped with Er3+ was successfully synthesized via traditional solid-state reaction. Structural analysis was performed through X-ray diffraction (XRD) patterns utilizing Rietveld refinement. When excited at 380 nm, the Ca3WO6:Er3+ phosphors displayed green spectral emission, corresponds to 2H11/2, 4S3/2 to 4I15/2 transitions of Er3+. The influence of Er3+ concentrations on photoluminescence (PL) intensity and concentration quenching was discussed, ascribing multipolar interaction as a cause of intensity quenching. The temperature-dependent PL analysis revealed the phosphor's excellent thermal stability, retaining approximately 79.6 % of its PL intensity at 150 °C. Furthermore, the Ca3WO6:Er3+ phosphors exhibited high-quality thermoluminescence (TL) after beta irradiation. The impact of Er3+ concentrations and beta dose on TL intensity was investigated comprehensively. The reproducibility of the phosphor was checked after several TL readouts. The various heating rate (VHR) experiments were conducted to examine the effect of HR and to determine the trapping parameters.

Effects of heating rate and deposition cycle on the structural, optical, and photoelectrocatalytic properties of electrodeposited hematite films

In this research, electrodeposited hematite films were prepared at voltammetry deposition cycles of 60 and calcined at 550 °C in a furnace after ramping the temperature at the rates of 2 °C/min, 10 °C/min, 35 °C/min, and rapid heating of about 100 °C/min. Additional samples were fabricated at deposition cycles of 15, 30, and 80, and also calcined at 550⁰C at a heating rate of 10⁰C/min. The impact of heating rate and deposition cycle number variations on the structural, optical, and photoelectrocatalytic (PEC) properties of the hematite films were assessed. All the films' X-ray diffraction (XRD) measurements showed strong peaks at the lattice planes (104) and (110), verifying hematite's rhombohedral crystal structure. The films prepared at the heating rate of 10⁰C/min boosted the crystallization of the films by 47.2 % relative to the ones prepared at 2⁰C/min. An increase in the deposition cycle number resulted in increasing film thickness and the sample’s crystallization. An indirect bandgap of 1.94–2.1 eV was estimated for the samples, with the least value obtained for the films treated at the heating rate of 10⁰/min and deposition cycles of 60. The same samples also yielded the largest photocurrent density of 26.2 μA/cm2 at 1.23 V vs. reversible hydrogen electrode (RHE), while the photoanodes fabricated at 2 °C/min exhibited the lowest photo-activity. The enhanced photocurrent observed for the films has been associated with high crystallinity, improved photon absorption, reduced flatband potential, and increased charge separation at the film’s surface. This research underscores the importance of optimizing both the heating rate and deposition cycle numbers in the fabrication of electrodeposited photoelectrodes for PEC applications.

Thermal Decomposition of Bio-Based Plastic Materials.

This research delves into a detailed exploration of the thermal decomposition behavior of bio-based polymers, specifically thermoplastic starch (TPS) and polylactic acid (PLA), under varying heating rates in a nitrogen atmosphere. This study employs thermogravimetry (TG) to investigate, providing comprehensive insights into the thermal stability of these eco-friendly polymers. In particular, the TPS kinetic model is examined, encompassing the decomposition of three distinct fractions. In contrast, PLA exhibits a simplified kinetic behavior requiring only a fraction described by a zero-order model. The kinetic study involves a systematic investigation into the individual contributions of key components within TPS, including starch, glycerin, and polyvinyl alcohol (PVA). This detailed analysis contributes to a comprehensive understanding of the thermal degradation process of TPS and PLA, enabling the optimization of processing conditions and the prediction of material behavior across varying thermal environments. Furthermore, the incorporation of different starch sources and calcium carbonate additives in TPS enhances our understanding of the polymer's thermal stability, offering insights into potential applications in diverse industries.

Thermally stable luminescence and dosimetric features of Ho(III) activated tungstate double perovskite

Luminescent efficient tungstate double perovskites Ca3WO6 doped with Ho3+ were synthesized via the solid-state reaction at 1200 C°. The resulting phosphors were analyzed using Rietveld refinement of X-ray diffraction (XRD) data, confirming a monoclinic crystal structure with crystallite sizes ranging between 50 and 55 nm. Optical bandgap determination was facilitated by diffusion reflectance spectra (DRS). Fourier transform infrared (FTIR) studies were conducted to identify functional group vibrations. The optical excitation of the Ca3WO6:Ho3+ phosphors under different excitation conditions resulted in intense green photoluminescence (PL) emission at 545 nm, indicative of the 5F4–5I8 transition of Ho3+ ions. Thermal stability assessment of Ca3WO6:1 % Ho3+ phosphor under blue excitation (454 nm) revealed good thermally stable luminescence about 85.32 % at LED working temperature (150 °C). PL decay studies were conducted to analyze fluorescent behaviour, wherein by means of PL decay lifetime, the PL quantum efficiency of Ca3WO6:1 % Ho3+ phosphor is computed to be 91.1 %. The CIE color coordinates of the phosphors being investigated reside within the green spectral region, with a calculated color purity of 93.25 % observed for Ca3WO6:1%Ho3+. Furthermore, the phosphors under study exhibited high-quality thermoluminescence (TL) after beta irradiation. The detailed TL characterization conducted to assess dosimetric properties. The impact of Ho3+ concentrations and beta dose on TL intensity are two major aspects that have been investigated in detail. TL fading experiments were performed to determine dose storage capacity over a month after beta irradiation. Additionally, the various heating rate (VHR) experiments are conducted to determine the TL kinetic parameters. Besides, the glow curve deconvolution (GCD) for trap parameter determination is also applied, where the results obtained are comparable with the VHR results.

Slow pyrolysis of Agave americana L. fibers: Analysis of kinetics and thermodynamics using the coats-redfern method at different heating rates

This study employed thermogravimetric analysis (TGA) alongside the Coats-Redfern method (CRM) to investigate the thermal degradation's kinetics and thermodynamics of fibers extracted from the flower stalk of Agave americana (FSAA). We explored FSAA fibers' thermal behavior across varying heating rates (HRs) to elucidate complex reaction mechanisms and estimate critical parameters. TGA experiments at 5, 10, and 20 °C/min HRs reveal a multi-step breakdown process supported by solid coefficients of determination (R2 > 0.99). Activation energy values, ranging from 83.6 to 210.1 kJ/mol, vary with HR, providing insights into thermal decomposition kinetics. Thermodynamic parameters, including variations in entropy (ΔS), Gibb's free energy, and enthalpy, shed light on spontaneity and energy transfer during the process. Negative ΔS values suggested reduced disorder during thermal decomposition. This study represented a novel investigation into the thermal behavior of fibers extracted from the FSAA for the first time, using CRM in conjunction with TGA. Through comprehensive analysis, we elucidated the kinetics and thermodynamics of FSAA fiber degradation across various HRs. Our findings shed light on the intricate reaction mechanisms underlying FSAA fiber decomposition, providing valuable insights for potential applications in biofuel production and composite materials.

Unlocking biosolid pyrolysis: Towards tailored biochar with different surface properties

To develop a thorough understanding of the thermal decomposition process of biosolids and the qualities of biosolid-derived biochar, this study performs a thermogravimetric analysis (TGA) of biosolids and examines the properties of biosolid-derived biochar produced from varying temperatures of pyrolysis. The pyrolysis of biosolid is conducted under varying heating rates (10, 15, 20 and 25 °C/min) until reaching the maximum temperature of 900 °C. The kinetic triplet (kinetic model, activation energy, and frequency factor) at the corresponding conversion point is determined by analysing the TGA results of the biosolids. The thermal degradation of hydrated compounds shows activation energies ranging from 80 to 100 kJ/mol, whereas the thermal decomposition of organic matter in biosolids exhibits activation energies ranging from 120 to 497 kJ/mol. As the temperature increases, the thermal reactions transition from simple surface reactions with frequency factors below 109 s−1 to more complex reactions with frequency factors above 109 s−1. The distributed activation energy model (DAEM) is established using the approximated temperature function and the activation energy distribution functions. The DAEM shows the mean activation energies of 93–128 kJ/mol, 279–287 kJ/mol and 359–377 kJ/mol for activation energy distribution peaks. The standard deviations of the mean activation energies are 30–64 kJ/mol, 23–30 kJ/mol and 23–41 kJ/mol, respectively. As the pyrolysis temperature is raised from 700 °C to 900 °C, both the specific surface area and micropore volume of biosolid-derived biochar increase, from 48.25 m2/g to 65.74 m2/g and 0.0313 cm3/g to 0.0369 cm3/g, respectively. The findings of this study demonstrate biosolid pyrolysis kinetics, which is essential for establishing a pyrolysis facility for biosolid management and producing biosolid-derived biochar with varying qualities.

Modulated heating rate effect on optimizing sintered density and microstructure in CoCrFeMnNi high-entropy alloy fabricated through metal injection molding

The fabrication of high-entropy alloys (HEAs) using metal injection molding (MIM) represents a significant leap forward in the field of materials engineering, enabling the production of components with complex shapes while maintaining the unique mechanical properties of HEAs. This study investigates the effect of heating rate variations on the densification behavior in the equiatomic CoCrFeMnNi HEA, focused on microstructural analysis and densification behavior for each thermal schedule. By optimizing the sintering behavior with single and double-step heating rates, significant findings reveal that sintering under double-step heating rates leads to marked improvements in densification and microstructural uniformity. Microstructural analyses indicate that the modulated heating rates during sintering crucially affect the segregation of Cr and secondary phase formation. This research highlights the importance of sintering profiles in optimizing the microstructure and properties of HEAs processed through MIM, contributing valuable insights to a refined strategy for the improved microstructure and mechanical strength of HEAs in powder metallurgy.

A Study toward the Model Independence of Various Heating Rates Method in Thermoluminescence Glow Curve Analysis

This study analyzes thermoluminescence (TL) glow curves simulated in general order kinetics (GOK), one trap one recombination center (OTOR), and non‐interactive multi‐trap system (NMTS) models using various heating rates (VHR) method in linear heating scheme to extract the activation energy. A theoretical analysis to determine activation energy from TL curves using OTOR and NMTS models in an iterative manner, where the TL intensity is determined by using the Lambert‐W function, is proposed with its limitations. It is established that the activation energies in OTOR and NMTS models consist of the relevant GOK term and a respective correction term. Systematic analysis is carried out to study the improvement of the accuracy of activation energy derived from OTOR and NMTS model TL curves over the GOK model calculation. A quantitative analysis of the quasi‐equilibrium (QE) approximations is carried out for choosing appropriate system parameters. The validity of QE conditions are determined by studying variations of full width at half maximum as well as area under the curve as a function of heating rate. The present method is applied on some experimental data to estimate activation energies. This investigation reveals that the activation energy derived in VHR method has negligible dependence on the underlying theoretical models, i.e., the activation energy derived from GOK model calculation is significantly accurate for experimental scenario.

Synergistic co-pyrolysis of corn stover and refuse-derived fuel with microplastics: Kinetic and thermodynamic study

Biomass and refuse-derived fuel are prevalent constituents of municipal solid waste worldwide, exerting persistent pressures on environmental ecosystems. Consequently, there arises a critical necessity for their effective recycling and management. This study investigates the co-pyrolysis of corn stover (CS) and Refuse-Derived Fuel (RDF) in a 1:1 mass ratio through kinetic and thermodynamic analyses. Using a thermogravimetric analyzer and differential scanning calorimetry (DSC), the co-pyrolysis process is examined within a temperature range of 25–900 °C, under varying heating rates of 5, 10, and 20 °C/min in a nitrogen atmosphere. Kinetic analysis is conducted employing model-free methods, including Kissinger-Akahira-Sunose (KAS), Flynn-Wall-Ozawa (FWO), Starink, and Tang, with subsequent estimation of thermodynamic parameters such as enthalpy change (ΔH), entropy change (ΔS), and Gibbs free energy (ΔG). Additionally, mass and energy balances specific to the blended feedstock are calculated to evaluate future operational efficiency. The investigation reveals the higher heating values (HHV) of CS and RDF as 17.879 and 20.035 kJ/kg, respectively. Notably, the DTG and DSC curves indicate a positive interaction between CS and RDF's plastic component at temperatures exceeding 400 °C. Kinetic analysis yields average activation energies for CS, RDF, and the CS-RDF blend (1:1) as 202.26, 235.87, and 212.60 kJ/mol, respectively, suggesting a reduction in activation energy for the blend. In summary, these findings offer valuable insights into the co-pyrolysis of CS and RDF, thereby contributing to the optimization of co-pyrolysis as an effective waste-to-energy conversion process.

Kinetics of initial diffusion solidification during continuous heating in term of IN718 superalloy / 316LN steel TLP bonding system

In this work, the effect of heating rate on the solidification kinetics of the dissimilar transient liquid phase (TLP) bonding joint of IN718 superalloy / 316LN steel was investigated. It was determined that the initial diffusion solidification (IDS) during continuous heating, accompanied by the melting of interlayer, plays an important role on the formation of TLP bonding joint. The lower heating rate results in the more sufficient IDS and thus the shorter time needed for isothermal solidification. This overturns the conventional view that the solidification behavior in TLP bonding joints mainly occurs at the stage of isothermal holding. Additionally, the IDS process is modeled using diffusion-based concepts under varying heating rates. The proposed model is more applicable for the prediction of solidification time in TLP bonding joint than the classic models only on the consideration of isothermal solidification.

Thermal Decomposition and Combustion Analysis of Malaysian Peat Soil Samples Using Coats Redfern Model-free Method

This research investigates the thermal decomposition behaviour of Malaysian peat soil through thermogravimetric analysis at varying heating rates. The study aims to analyse the thermal kinetics of decomposition for distinct peat soil types under inert and oxidative atmospheres while considering the role of available oxygen. The investigation encompasses virgin and agricultural peat, employing a non-isothermal thermogravimetric analysis technique to evaluate thermal decomposition characteristics and compute kinetic parameters using the Coats Redfern model-free approach. The pyrolysis profiles reveal three primary stages: moisture evaporation (30–180°C), organic component decomposition (200–500°C), and mineral decomposition (600–800°C). Virgin peat experiences a 43% mass loss during pyrolysis, while agricultural peat shows a 46% mass loss, emphasising insights into thermal behaviour and consistent decomposition patterns across peat types. Combustion profiles exhibit three main stages: dehydration (30–180°C), oxidative pyrolysis transforming organic matter into volatiles and char (200–300°C), and subsequent char oxidation (300–500°C). The study determines average activation energy trends, measuring 14.87 kJ/mol for virgin peat and 5.37 kJ/mol for agricultural peat under an inert atmosphere, and 28.89 kJ/mol for virgin peat and 36.66 kJ/mol for agricultural peat under an oxidative atmosphere. The research introduces an innovative two-step reaction model elucidating peat thermal decomposition kinetics (excluding dehydration), including a discussion on the impact of oxygen availability on kinetic parameters. These findings essential peat fire smouldering modelling, contributing to peat combustion behaviour for effective strategies to reduce peat fire risks.

Theoretical understanding of defects-driven mechanoluminescence for Pr3+-doped NaNbO3/LiNbO3 heterojunctions

Mechanoluminescence (ML), which involves the emission of light under mechanical stimuli, shows great potential in various applications such as sensing, imaging, and energy harvesting. Current research suggests that the luminescence mechanism of ML is typically connected to specific defects present within the material. In this study, we focus on the investigation of ML defects in Pr3+-doped NaNbO3/LiNbO3 heterojunctions, employing a combination of experimental and theoretical approaches. Through experimental analysis, we confirmed the presence of the heterojunction and its influence on ML intensity, and the optimal doping ratio for the heterojunction in ML was established. Furthermore, we examined the influence of varying Pr3+ doping concentrations on ML behavior and a proof-of-concept was demonstrated using the X-rays charged heterostructural phosphor as a stress sensor for biological applications. The position and concentration of internal defects in the ML material were scrutinized through thermoluminescence tests employing the variable heating rate method and positron annihilation. Complementing the experimental findings, theoretical simulations were conducted to elucidate the underlying mechanisms responsible for the observed ML defects. Density functional theory calculations were employed to investigate the energy levels, charge transfer processes, and lattice distortions within the heterojunctions under mechanical stress. Theoretical predictions were compared and validated against the experimental results. The integration of experimental and theoretical approaches provides a comprehensive understanding of the ML behavior of Pr3+-doped NaNbO3/LiNbO3 heterojunctions. The insights gained from this research contribute to the development of novel ML materials and pave the way for their applications in next-generation sensing and energy conversion devices.

The thermal response of the ignition and combustion of high-energy material projectiles under the influence of heat

The thermal response of energetic materials involves processes of thermochemical mechanical coupling, which can lead to thermal damage in such materials both before and after ignition, thereby increasing ignition sensitivity and the level of danger. Many studies to date have either neglected or oversimplified the effects of thermal coupling, leading to significant discrepancies between simulated and experimental outcomes. This paper aims to examine the complex processes of ammunition ignition, combustion, and detonation. Employing finite element simulations in conjunction with Arrhenius dynamics and the ignition growth model theory under thermodynamic coupling analysis, it simulates the entire process from the thermal expansion of B explosive prior to ignition, through to combustion and detonation. It establishes the relationship between the damage and fracture state of the shell and the thermal response of the energetic material at varying heating rates. Findings indicate that the severity of the thermal response is determined by the balance between pressure accumulation and the loss of confinement leading to pressure release. Specifically, at heating rates below 0.25 K/min, the shell fractures before combustion of the energetic material; whereas, at rates exceeding 0.375 K/min, the shell fractures after combustion, significantly increasing the risk. The simulation outcomes of this study show strong correlation with experimental results reported in the literature, offering a valuable reference for simulating the ignition and combustion responses of ammunition with similar structural characteristics.

Detailed speciation of biomass pyrolysis products with a novel TGA-based methodology: the case-study of cellulose

Pyrolysis of waste biomass represents a key route for the circular economy and a promising solution for the generation of valuable chemicals and liquid biofuels. The complex multi-component and multi-phase nature of the process, however, poses a challenge in acquiring comprehensive experimental data on biomass devolatilization. These data are essential for refining kinetic schemes and optimizing technology. This work presents a novel experimental methodology suitable for the collection of kinetically relevant data on biomass devolatilization combined with a complete characterization of the product slate. This methodology consists of a thermogravimetric analyser employed to carry out pyrolysis experiments, useful for the accurate monitoring of mass loss dependencies at varying heating rate, for the control of reaction temperatures and for the suppression of secondary gas-phase reactions as well as of transfer limitations. Multiple analytical methodologies and sampling protocols were combined for product speciation – downstream online MS for gases and H2O, sorbing traps for integral offline GC–FID/MS measurement of heavy oxygenates, point vapour collection for instant GC–FID/MS analysis of light oxygenates – and allowed to independently determine the integral mass yield of each pyrolysis product, closing mass balances with very high accuracy. Experiments of cellulose pyrolysis at varying heating rate were carried out to tune and validate the methodology. Speciation protocols allowed to identify and individually quantify 31 species among pyrolysis products, including gases, condensable oxygenates, H2O and char. The comparison of experimental findings with predictions from a state-of-art lumped model has highlighted the significance of the present methodology in unravelling the kinetics governing both devolatilization and product distribution.