Journal of Thermal Analysis and Calorimetry

doi: 10.1007/s10973-023-12454-0pmid: N/A

Šesták, Jaroslav; Kočí, Václav; Černý, Robert; Kovařík, Tomáš

doi: 10.1007/s10973-023-12312-zpmid: N/A

The development of new materials called geopolymers is described, which at the turn of the nineties brought a new state of the art in material design through the so-called wet process resulting in a specific amorphous state. The classical configuration of glasses prepared by quenching is used for a joint appraisal and judgment. We can use the comparison and description of the known form of organic polymers with the so-called mers-structure. The formation involves a sol–gel polycondensation chemical reaction also known in the case of organic polymers. The formation is described using aluminosilicate oxide in IV-fold coordination with alkaline polysilicates to form polymeric Si–O–Al chains through amorphous to semi- and hypo-crystalline three-dimensional silico-aluminate structures. The revision of structural units and their interconnection is evaluated, and it turns out that the common factor of the multiparty description is the existence of bridging and non-bridging oxygen. The review provides a detailed overview of opinion while reminding that the historical origin of the field falls within the purview of the JTAC journal.

Frone, Adriana Nicoleta; Baciu, Dora Dominica; Popa, Marius Stelian; Nicolae, Cristian Andi; Gabor, Augusta Raluca; Raduly, Monica Florentina; Fierascu, Radu Claudiu; Panaitescu, Denis Mihaela

doi: 10.1007/s10973-023-12196-zpmid: N/A

Polysilsesquioxanes are extensively studied as durable and anti-adherent coatings for medical devices due to their superhydrophobic properties. However, their particular influence on the thermo-mechanical properties and biocompatibility of poly(lactic acid) (PLA)-based materials obtained by melt compounding is scarce. Herein, a facile and promising method to improve the performances of PLA for biomedical applications via the incorporation of different mass proportions of POSS nanoparticles with allyl-heptaisobutyl (AH-POSS) substituent through a melt-blending technique is proposed. The thermal, morpho-structural, mechanical properties at room (RT) and body temperatures (BT), and in vitro biocompatibility of the developed PLA/AH-POSS nanohybrids were investigated. AH-POSS nanoparticles were found to have simultaneous nucleation and plasticizing effects on the PLA nanohybrids, inducing enhanced thermal resistance and easy control of crystallinity while preserving PLA’s biocompatibility. An interesting effect of AH-POSS on the mechanical properties of PLA at body temperature was observed. These results indicate the considerable potential of the PLA/AH-POSS nanohybrids obtained by melt compounding in the fabrication of biomedical devices.

Kurajica, S.; Mandić, V.; Mužina, K.; Panžić, I.; Kralj, D.; Duplančić, M.; Ivković, I. K.

doi: 10.1007/s10973-023-12233-xpmid: N/A

Synthesis and properties of cerium aluminate catalyst were investigated. The catalyst was prepared via combustion synthesis involving aluminum and cerium nitrates and glycine in the presence of palladium chloride. The obtained material was investigated using X-ray diffraction, Fourier transformed infra-red spectroscopy, differential thermal and thermo-gravimetric analysis, N2 adsorption, Raman spectroscopy, scanning electron microscopy, energy dispersion X-ray spectroscopy and X-ray photoelectron spectroscopy. Catalytic activity was tested for the toluene oxidation process. The direct product of combustion synthesis was CeAlO3 which remained stable even after thermal treatment at 400 °C for 2 h in static air, while temperature treatment at 800 °C for 2 h resulted in the decomposition of CeAlO3 into CeO2 and γ-Al2O3. Both thermal treatment products had sponge-like microstructure, but relatively small specific surface areas. Nevertheless, CeO2 prepared at 800 °C was nanocrystalline. Palladium was present as oxide homogeneously dispersed throughout the catalyst. The prepared catalyst proved to be highly active for the toluene oxidation process.

Lázaro, David; Alonso, Alain; Lázaro, Mariano; Jiménez, Miguel Ángel; Alvear, Daniel

doi: 10.1007/s10973-023-12139-8pmid: N/A

Cone calorimeter is widely used to study fire behaviour of materials employing small size samples. This equipment allows obtaining parameters such as time to ignition (TTI), heat of combustion, mass loss rate (MLR), or heat release rate (HRR) under different heat fluxes. Some studies have considered a linear fitting between MLR and HRR peaks and the incident heat flux. In accordance with this hypothesis, the computer model Fire Dynamics Simulator (FDS) has included a simple model to extrapolate burning rate data collected from a cone calorimeter test to the heat feedback occurring during a simulation. Nevertheless, deviation in the prediction of the HRR peaks at 75 kW m−2 of approximately 39.3% and of 37.1% for the first and second peak, respectively, were found. Therefore, this work presents a correlation between the incident heat flux and the global HRR per unit area curve, testing up to five different cables and several heat fluxes. To do so, some modifications of the FDS correlation are performed to consider the effect of the flame heat flux in the decomposition of the cables. Once experimental data are acquired, a computational analysis is carried out using FDS to achieve the flame heat flux in the samples. Additionally, this flame heat flux has also been obtained from the literature. As a conclusion, the addition of the flame heat flux to the cone calorimeter incident heat flux provides better predictions than the linear fitting methodology defined in the FDS Guide. Furthermore, this correction is checked with: (1) the example included in FDS guide, decreasing the HRR peaks errors from around 38% to around 25%; and (2) to seven different cables from the literature, decreasing the HRR peaks relative errors, as average, from 14.2 to 9.5% approximately.

Król, Mariusz; Hajnyš, Jiří

doi: 10.1007/s10973-023-12330-xpmid: N/A

The Thermal-Derivative Analysis, or Computer-Aided Cooling Curve Analysis, is a commonly used method for determining the solidification parameters of metals and alloys. Knowledge of the enthalpy, kinetics and broad characteristics of the transformations taking place during the cooling of an alloy can be obtained with the proper configuration of analytical equipment and arrangement of test techniques. This work practically analyses the changes occurring in the Mg–4.5Li–1.5Al alloy as a result of the modification of the structure by the addition of TiB and Sr. The results indicate that adding grain refinements significantly affects the microstructure and thermal parameters of Mg–4.5Li–1.5Al alloy. The nucleation temperature and solidus temperature decrease with the addition of chemical reagents. Compressive strength improved due to the refinement of grain size. The results confirmed that thermal-derivative analysis is suitable for analysing changes in cast magnesium alloys.

Harabor, Novac-Adrian; Harabor, Ana; Rotaru, Petre; Palarie, Ion

doi: 10.1007/s10973-023-12380-1pmid: N/A

Most optical emission line intensities remain unchanged for a mercury HID plasma, exposed to coherent argon ion laser beam Innova 308 C (476.5 nm) in points far from electrodes. Small raise of Hg-546.08 nm line is due to photo-excitation of Ar+ ions, followed by excitation transfers through collision processes from excited (Ar+)* ions to Ar atoms, then from excited (Ar)* to Hg atoms. When the laser beam hits the electrode tip (photoelectric effect), the amount of electrons involved in plasma collisions increases: all characteristic emission spectral lines are intensifying. Electron temperature and concentration were also calculated. Differential Scanning Calorimetry performed in case of tungsten electrode with emissive material (Y2O3, BaCO3, CaCO3, WO3), linear and non-isothermally heated (0.17 K s-1) in flowing air, from 290.61 to 1603.72 K (platinum crucible), revealed both endothermic (CaCO3 and of BaCO3 decompositions) and exothermal (obtaining CaWO4, BaWO4 and Ba3WO6) processes. Thermogravimetry Analysis showed a mass decrease of 0.498%, in 290.61−505.15 K temperature range, due to water release. Oxidation of tungsten electrode causes a significant mass increase of 17.292% in 809.15−1183.15 K range. BaWO4, Ba3WO6 and WO3 sublimations gave a mass fall of 6.757% in 1513.15−1603.72 K range. No thermal effects were recorded on heating in argon atmosphere, from 446.15 to 1596.15 K, in alumina crucible.

Slaný, Michal; Kuzielová, Eva; Žemlička, Matúš; Matejdes, Marián; Struhárová, Alena; Palou, Martin T.

doi: 10.1007/s10973-023-12267-1pmid: N/A

In this paper, the composition and properties of two different activated calcinated clays were investigated under selected curing conditions. The tendency of metabentonite and metakaoline to form geopolymers and zeolites was investigated by FTIR spectroscopy, TGA and DSC techniques, PXRD, HT-PXRD, SEM, and BET-N2 adsorption analyses. The selection of the optimal sample compositions was done on a basis of preliminary results obtained from bentonite and kaolin clays activated at calcination temperatures (700, 750, 800 °C) with a holding time of 3 h in a combination with different NaOH concentrations (5, 10, 20 mass%). In a more detailed examination, the samples calcined at a temperature of 800 °C with different NaOH concentrations were studied. For metakaolin-based samples, dominant geopolymer formation was achieved using 5 mass% NaOH. The zeolite amount increased concomitantly with the concentration of the alkali activator, whereas zeolite A and zeolite P were determined as the predominant phases. For metabentonite-based samples, 10 mass% NaOH concentration was found to be optimal by the means of geopolymer formation. At higher alkaline activator concentrations, the presence of zeolitic phases faujasite and gobbinsite was confirmed. However, the determined degree of crystallinity was significantly lower than in the corresponding activated metakaolin samples. With a gradual increase in NaOH concentration, the specific surface area of the metabentonite-based samples increased reaching a value of 218.95 m2 g−1 promising for adsorption applications. The opposite effect was observed for the metakaolin-based samples, and this result is caused by the increased formation of zeolite phases and corresponding changes in their channel dimensions.

Li, Mi; Zhang, Dan; Jiang, Lin

doi: 10.1007/s10973-023-12379-8pmid: N/A

The combustion of wood materials is a complicated process involving multi-physics field coupling heat and mass transfer, with numerous intermediate volatiles from intricate sub-reactions. Both experimental and theoretical aspects of wood sample combustion were investigated in this work. Thermogravimetric analysis (TGA) experiments for Chinese fir wood sample with three different heating rates in a nitrogen atmosphere were carried out. The activation energies were calculated and analyzed. Additionally, bench-scale combustion experiments under the external radiation were conducted using a cone calorimeter. By incorporating appropriate assumptions and simplifying the complicated process, a one-dimension numerical model was developed to explore the micro-scale degradation kinetics and bench-scale combustion characteristics. A multi-scale comprehensive model addressing the pyrolysis and combustion processes was constructed in this study. Utilizing the thermophysical and kinetic parameters derived from the TGA test by employing a multi-parameter optimization algorithm, the combustion process, including variations in mass-loss rate (MLR) and heat release rate (HRR), was simulated. The model demonstrated strong predictive performance in MLR and HRR compared to the experimental data from bench-scale combustion. This research has implications for understanding solid fuel combustion mechanism and simulations.

Alonso, Alain; Lázaro, Mariano; Lázaro, David; Alvear, Daniel

doi: 10.1007/s10973-023-12258-2pmid: N/A

Polymers are widely employed in many areas, e.g. transport, packaging, electronic devices, etcetera. Among them, acrylonitrile–butadiene–styrene (ABS) is one of the most employed polymers due to its mechanical properties, its ease to mechanize and recyclability. Nevertheless, according to the fire properties, ABS behaviour is usually worse than other polymers, therefore, they have to be upgraded with flame retardant additives. To characterize the fire behaviour of a certain material is necessary to address several typology of tests, providing relevant properties such as thermal conductivity, flammability and heat released. However, researchers may not always be able to run all tests due to the lack of apparatus or samples. Therefore, it is necessary to seek bibliographic sources. As one might expect, for a given material, the property values should be similar, regardless of who performs the test. However, sometimes slightly different results are obtained, which may be due to different causes, such as differences in test set-up and in material composition/manufacture. These differences in properties may lead researcher to doubt which data to use. This paper presents the results of different types of tests using neat ABS polymer. Additionally, these results are compared with the data from literature, discussing the similarities/differences and offering a more comprehensive characterization of ABS. The laboratory techniques included in this work are: thermogravimetric analysis, differential scanning calorimetry, laser flash analysis, smoke density, cone calorimeter, fire propagation and flammability.