Thermochimica Acta最新文献

{"title":"Investigation of pyrolysis and combustion characteristics of chili straw waste with different O2/N2 ratios and heating rates","authors":"Pengyu Wei ,&nbsp;Guoyan Chen ,&nbsp;Fubiao Zhi ,&nbsp;Anchao Zhang ,&nbsp;Haoxin Deng ,&nbsp;Xiaoping Wen ,&nbsp;Fahui Wang ,&nbsp;Chenglong Yu","doi":"10.1016/j.tca.2024.179875","DOIUrl":"10.1016/j.tca.2024.179875","url":null,"abstract":"<div><div>To utilize chili straw waste (CSW) for energy production and generate higher-quality fuel, the pyrolysis characteristics of CSW under varying particle sizes and heating rates, as well as the effects of different O₂/N₂ ratios on its combustion characteristics, were investigated using Thermogravimetry-Mass Spectrometry (TG-MS). The gas production performance under three different conditions was also analyzed. Results indicated that the solid yield decreased as particle size increased, with the maximum weight loss rate of 77.79 % occurring at a particle size of 1.25∼1.60 mm. The highest relative pyrolysis rate was 0.77 %/K at a heating rate of 10 K/min, corresponding to a weight loss rate of 74.46 %. Increasing the proportion of oxygen in the atmosphere reduced both the ignition and burnout temperatures of CSW by 9.34 K and 51.89 K, respectively, shifting the Derivative Thermogravimetry (DTG) curve to a lower temperature range. Furthermore, an increase in the heating rate enhanced hydrogen production intensity during CSW pyrolysis, with the peak particle current of H₂ rising from 8.7 × 10⁻¹⁰ A to 1.2 × 10⁻⁹ A, representing a 0.38-fold increase when the heating rate was raised from 5 K/min to 40 K/min. A kinetic analysis of CSW pyrolysis using the Coats-Redfern (CR) and Achar methods revealed that activation energy (E_a) increases with particle size, indicating higher energy requirements due to heat transfer resistance. The Friedman, Kissinger-Akahira-Sunose (KAS), and Ozawa-Flynn-Wall (OFW) methods showed rising E_a with increasing conversion rates, corresponding to the decomposition of hemicellulose, cellulose, and lignin. In combustion, oxygen concentration significantly influences E_a, raising it for volatile matter and fixed carbon, and also increasing it for lignin at high temperatures. The CR and Achar models provided strong fits, confirming their reliability in describing CSW pyrolysis and combustion.</div></div>","PeriodicalId":23058,"journal":{"name":"Thermochimica Acta","volume":null,"pages":null},"PeriodicalIF":3.1,"publicationDate":"2024-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142434372","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Kinetic model of thermal decomposition of nitric acid solutions of hydrazine nitrate","authors":"Vera Kalistratova,&nbsp;Arseniy Obedkov,&nbsp;Elena Belova","doi":"10.1016/j.tca.2024.179876","DOIUrl":"10.1016/j.tca.2024.179876","url":null,"abstract":"<div><div>The kinetic parameters of thermal decomposition of an aqueous solution containing 0.029 mass fractions of hydrazine nitrate and 0.44 mass fractions of nitric acid have been determined: onset temperature and specific thermal effect of exothermic reactions, activation energy, pre-exponential factor, reaction rate and order. Based on the data obtained, a mathematical model of thermal decomposition of nitric acid solutions of hydrazine nitrate has been proposed. It has been found that thermolysis of the solution has a multi-stage nature and can be described by a system of 5 equations of 1st and 2nd order. A comparison of two approaches to creating a mathematical model has been carried out: based on adiabatic calorimetry and differential scanning calorimetry data.</div></div>","PeriodicalId":23058,"journal":{"name":"Thermochimica Acta","volume":null,"pages":null},"PeriodicalIF":3.1,"publicationDate":"2024-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142441389","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Sublimation rate of solid NaCl powders and evaporation rate of liquid NaCl upon heating in vacuum and air","authors":"Alexander M. Laptev ,&nbsp;Martin Bram","doi":"10.1016/j.tca.2024.179874","DOIUrl":"10.1016/j.tca.2024.179874","url":null,"abstract":"<div><div>The volatilization of sodium chloride (NaCl) is important for multiple applications, such as energy storage, manufacturing porous parts, and purification and recycling of composites. Until now, only limited information on this feature has been published. To expand the knowledge in this field, we investigated the sublimation and evaporation of two NaCl powders by thermal gravimetry in vacuum and air. The study has shown that the volatilization kinetics of powders with different shapes and sizes are identical. The volatilization of NaCl powders in vacuum occurs mainly by sublimation before melting. In contrast, the volatilization of NaCl in the air is preferentially caused by the evaporation of the melt. In a vacuum, the evaporation of NaCl powder after melting is significantly slower than the sublimation before melting, because of a drastic decrease in the volatilization area. The Hertz-Knudsen relation with an appropriate fitting coefficient satisfactorily describes the mass loss by volatilization in vacuum and air.</div></div>","PeriodicalId":23058,"journal":{"name":"Thermochimica Acta","volume":null,"pages":null},"PeriodicalIF":3.1,"publicationDate":"2024-10-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142441390","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Experimental determination of phase stability of the cubic L12 HfAl3-xZnx phase","authors":"S. Delsante ,&nbsp;G. Borzone ,&nbsp;N. Parodi ,&nbsp;S. Guerrucci","doi":"10.1016/j.tca.2024.179873","DOIUrl":"10.1016/j.tca.2024.179873","url":null,"abstract":"<div><div>The present study is devoted to the experimental investigation of homogeneity range and heat of formation (Δ_f<em>H°</em> at 300 K) of the cubic <em>L</em>1₂–HfAl_3-xZn_x solid solution. A high-temperature direct drop calorimeter has been employed to synthesize and simultaneously determine the Δ_f<em>H°</em> of several alloys along the HfZn₃–HfAl₃ section (25 at. % Hf) whereas X-Ray Powder Diffraction (XRPD) and Scanning Electron Microscopy (SEM) paired with an EDS (Energy Dispersive Spectrometer detector) have been employed to characterize the samples. The performed analysis confirmed that the ternary HfAl_3-xZn_x alloys were nearly single phase in the range 1 ≤ x ≤ 2.24 having the cubic <em>L</em>1₂ structure; this in turn helps establish the trend of <em>L</em>1₂ lattice parameter (at room temperature) with composition. Thanks to the interpolation of our experimental data, the following values of Δ_f<em>H</em>° (kJ/mol-atom at 300 K) for the <em>L</em>1₂–HfAl_3-xZn_x were determined: -37.1 ± 2.0 (HfAl_0.8Zn_2.2 corresponding to Hf₂₅Al₂₀Zn₅₅ at. %), -41.7 ± 2.0 (HfAl_1.2Zn_1.8 corresponding to Hf₂₅Al_30.0Zn_45.0 at. %), -45.1 ± 2.0 (HfAl_1.5Zn_1.5 corresponding to Hf₂₅Al_37.5Zn_37.5 at. %) and -48.5 ± 2.0 (HfAl_1.8Zn_1.2 corresponding to Hf₂₅Al_45.0Zn_30.0 at. %). For two pertinent binary intermetallic phases, the following Δ_f<em>H</em>° values (in kJ/mol-atom) at 300 K have been obtained: -31.8 ± 3.0 for HfZn₃ (unknown structure) and -37.0 ± 2.0 for HfAl₃ (tetragonal <em>DO</em>₂₃ – type structure).</div></div>","PeriodicalId":23058,"journal":{"name":"Thermochimica Acta","volume":null,"pages":null},"PeriodicalIF":3.1,"publicationDate":"2024-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142419194","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Kinetics of L-lactide bulk polymerization initiated with zirconium(IV) acetylacetonate studied by non-isothermal differential scanning calorimetry","authors":"Kirill T. Kalinin ,&nbsp;Dmitry R. Streltsov ,&nbsp;Petr V. Dmitryakov ,&nbsp;Nikita G. Sedush ,&nbsp;Sergei N. Chvalun","doi":"10.1016/j.tca.2024.179872","DOIUrl":"10.1016/j.tca.2024.179872","url":null,"abstract":"<div><div>The kinetics of L-lactide bulk polymerization initiated with a non-toxic initiator, zirconium(IV) acetylacetonate, was studied by non-isothermal differential scanning calorimetry. The polymerization kinetics was analyzed using a combination of isoconversional “model–free” and model–fitting methods. It was revealed that the model–free analysis results in an autocatalytic reaction model function. To provide a physical meaning for this effective reaction model, a model–fitting analysis with a two–step kinetic model taking into account irreversible initiation and reversible propagation reactions was applied. It was demonstrated, that even such simple multi–step kinetic model can explain the general features of the polymerization reaction revealed by the isoconversional analysis, i.e. a variation of the effective activation energy with a conversion degree and an autocatalytic character of the effective reaction model. The rate constants for the initiation, <span><math><msub><mi>k</mi><mi>i</mi></msub></math></span>, and propagation, <span><math><msub><mi>k</mi><mi>p</mi></msub></math></span>, reactions were evaluated. It was revealed that the values of <span><math><msub><mi>k</mi><mi>i</mi></msub></math></span> are about two decimal orders lower than that of <span><math><msub><mi>k</mi><mi>p</mi></msub></math></span> indicating slow initiation in the studied temperature range.</div></div>","PeriodicalId":23058,"journal":{"name":"Thermochimica Acta","volume":null,"pages":null},"PeriodicalIF":3.1,"publicationDate":"2024-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142419193","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Kinetics and mechanism of thermal and thermo-oxidative degradation for high-density polyethylene modified by fullerene and its derivative","authors":"Bingtao Wang ,&nbsp;Yanqun Pan ,&nbsp;Liping Zhao ,&nbsp;Juan Li ,&nbsp;Zhenghong Guo","doi":"10.1016/j.tca.2024.179871","DOIUrl":"10.1016/j.tca.2024.179871","url":null,"abstract":"<div><div>To investigate the effect of fullerene (C₆₀) and its iron compound (C₆₀-Fe) on the thermal and thermo-oxidative degradation mechanism of high-density polyethylene (HDPE), the Kissinger method, Flynn-Wall-Ozawa method and Coats-Redfern methods are used. The data of thermal and thermo-oxidative degradation are achieved through the thermogravimetric (TG) analysis, and the trapping free-radical ability and the dispersion of C₆₀ or C₆₀-Fe in matrix are characterized by the electron spin resonance (ESR) and transmission electron microscopy (TEM). C₆₀ and C₆₀-Fe improve effectively the thermal and thermo-oxidative stability of HDPE. In N₂, C₆₀ and C₆₀-Fe do not change the degradation mechanism of HDPE, and the degradation rate is determined by the random generation and growth of free-radicals. In air, C₆₀ changes the reaction order (<em>n</em>) of HDPE at the oxidation stage and the degradation mechanism at the random fracture. C₆₀-Fe changes the thermo-oxidative mechanism of HDPE due to the formation of cross-linked network.</div></div>","PeriodicalId":23058,"journal":{"name":"Thermochimica Acta","volume":null,"pages":null},"PeriodicalIF":3.1,"publicationDate":"2024-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142419192","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Pyrolysis kinetics and flame retardant enhancement of bio-based polyamide 56/6","authors":"Xiaoqi Zhang ,&nbsp;Haoyu Yang ,&nbsp;Yaxin Guo ,&nbsp;Jie Zhou ,&nbsp;Hao Liu ,&nbsp;Suqin He ,&nbsp;Miaoming Huang ,&nbsp;Wanlin Xu ,&nbsp;Chengshen Zhu ,&nbsp;Wentao Liu","doi":"10.1016/j.tca.2024.179869","DOIUrl":"10.1016/j.tca.2024.179869","url":null,"abstract":"<div><div>The development of polyamide materials with fire safety is of great importance at this stage. A novel nitrogen-phosphorus bisystem flame retardant (MC) with a multi-branched structure was synthesized and applied to a new bio-based polyamide 56/6 (PA56/6). Notably, at 8 wt% MC content, flame-retardant PA56/6@MC_8% (FRPA56/6@MC_8%) achieved an Limiting Oxygen Index (LOI) of 26.6% and a V-0 rating in UL-94 tests. Cone calorimetry results indicated that FRPA56/6@MC_8% exhibited a 22.9% reduction in total heat release (THR) and a 41.0% decrease in peak heat release rate (PHRR), underscoring the flame retardancy promotion by MC in PA56/6. The study further explored the pyrolysis kinetics and mechanisms of polyamide materials, offering insights crucial for flame-retardant modifications. Overall, the findings present an innovative strategy for enhancing the flame retardant properties of PA56/6, potentially applicable in automotive components and other pertinent fields.</div></div>","PeriodicalId":23058,"journal":{"name":"Thermochimica Acta","volume":null,"pages":null},"PeriodicalIF":3.1,"publicationDate":"2024-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142319992","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Flammability of Novolac epoxy cured with aromatic diamines","authors":"Mauro R.S. Silveira ,&nbsp;Vicente F. Moritz ,&nbsp;Carlos A. Ferreira ,&nbsp;Laurent Ferry ,&nbsp;José-Marie Lopez-Cuesta","doi":"10.1016/j.tca.2024.179870","DOIUrl":"10.1016/j.tca.2024.179870","url":null,"abstract":"<div><div>The modification of Novolac epoxy with the organophosphorus compound 9,10-dihydro-9-oxa-10-phosphaphenanthren-10-oxide (DOPO) to reduce flammability and its influence on curing reactions has been investigated. Three aromatic diamine curing agents were used, namely 4,4′-diaminodiphenylmethane (DDM), 4,4′-diaminodiphenylsulphone (DDS), and diethyltoluenediamine (DETDA). The thermal stability and dynamic-mechanical behaviour of the cured resin depend on interactions of the curing agent with DOPO. The onset degradation temperature decreased with increasing phosphorus content, indicating the influence of DOPO on thermal stability. The DDM 3 %P sample exhibited the highest glass transition (Tg) of 136 °C, while DDS-crosslinked simples displayed the highest Tg of 147 °C among all samples. An improvement in the reaction of Novolac epoxy to fire was achieved by incorporating DOPO compound, as indicated by cone calorimetry results, showing up to a 67 % reduction in the peak heat release rate (pHRR) and 53 % reduction in total heat release (THR) for DDM 3 %P. The modified samples containing DOPO presented a self-extinguishing performance, displaying a UL-94 V-0 rating and a limiting oxygen index (LOI) values reached a maximum of 37.1 % for DDM 3 %P, with less flame propagation than for neat Novolac epoxy.</div></div>","PeriodicalId":23058,"journal":{"name":"Thermochimica Acta","volume":null,"pages":null},"PeriodicalIF":3.1,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142312810","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Organic compounds as temperature calibrants for fast scanning calorimetry","authors":"Timur A. Mukhametzyanov ,&nbsp;Airat A. Notfullin ,&nbsp;Alisa A. Fatkhutdinova ,&nbsp;Christoph Schick","doi":"10.1016/j.tca.2024.179868","DOIUrl":"10.1016/j.tca.2024.179868","url":null,"abstract":"<div><p>Organic compounds can be used as temperature calibrants in fast scanning calorimetry. Their advantages include ease of surface cleaning of the calorimetric chip and good thermal contact with the chip surface. Among several compounds tested, benzoic acid was identified as a convenient and reliable calibrant for temperatures below approximately 130 °C. However, organic calibrants often exhibit unusual heating rate dependencies of the onset temperatures of melting. This phenomenon can be semi-quantitatively explained by considering different heat flows within the sensor. Notably, the thermal resistance between the heater and thermopile, often overlooked, introduces an additional time constant that can sometimes result in a negative apparent thermal lag. In addition, the onset temperatures are influenced by factors such as sample position, thickness, surface wetting, and spreading. These factors limit the accuracy of transition temperature determinations to approximately ±1 K below 130 °C and ±5 K up to 220 °C.</p></div>","PeriodicalId":23058,"journal":{"name":"Thermochimica Acta","volume":null,"pages":null},"PeriodicalIF":3.1,"publicationDate":"2024-09-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142240431","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Secondary crystallization of low-isotacticity polypropylene","authors":"Yoshitomo Furushima ,&nbsp;Akihiko Toda ,&nbsp;Kazuo Kimura ,&nbsp;Masaru Nakada ,&nbsp;Akihiro Masuda ,&nbsp;Kazuya Nakamura ,&nbsp;Hideaki Takahashi ,&nbsp;Toshiumi Tatsuki ,&nbsp;Kazuma Okada ,&nbsp;Masatoshi Ohkura","doi":"10.1016/j.tca.2024.179867","DOIUrl":"10.1016/j.tca.2024.179867","url":null,"abstract":"<div><p>This study aimed to clarify the secondary crystallization process of low-isotacticity polypropylene (LT-PP). LT-PP demonstrates an exceptionally low crystallization rate at room temperature, which is approximately 1/5000 lower than that of isotactic PP (iPP). During the secondary crystallization of LT-PP at 30 °C, the thickness of lamellar (c-axis) and a- and b-axes of crystallite size remained constant. In addition, no significant change was observed in the C<img>C-C bending vibration. It seems that the direction of the C<img>C-C molecular order is similar to the thickness direction. This vibration mode may be associated with changes in the thickness of the lamellae. To explain the log(<em>t</em>) dependence of crystallinity, the Seto–Frank model was employed.</p></div>","PeriodicalId":23058,"journal":{"name":"Thermochimica Acta","volume":null,"pages":null},"PeriodicalIF":3.1,"publicationDate":"2024-09-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142240429","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}