Search

The Journal of Thermal Analysis and Calorimetry (JTAC) expresses gratitude to its contributors and announces its success in 2023, achieving high impact factors and rankings in major scientometric indices. The journal published special issues and papers from international conferences, covering various fields including thermodynamics and materials science. The number of manuscripts submitted is expected to increase in 2024. The JTACC conference was successfully organized, bringing together participants from around the world. The journal plans to continue its excellence with a renewed editorial board and preparations for the next conference in 2025. The given text is a list of names and affiliations of researchers from various countries, representing diverse cultural backgrounds and perspectives. The purpose of this document is to provide information about the authors and their diverse backgrounds for research purposes. The publisher, Springer Nature, remains neutral and does not endorse any specific jurisdictional claims or institutional affiliations. [Extracted from the article]

This review discusses the development of the Derivatograph in the 1950s and the history of thermal analysis in Hungary. This device was the first commercial simultaneous thermogravimetry and differential thermal analysis (TG/DTA) instrument of the world. It initiated the development of thermal analysis and its application possibilities in a wide range during the second half of the last century. As a result, very strong thermoanalytical schools were established in Hungary, and the first thermoanalytical journal in the world, i.e., the Journal of Thermal Analysis was started in 1969, which is still a leading journal in the field, now under the title of Journal of Thermal Analysis and Calorimetry. In addition, several periodicals and books were published in thermal analysis in Hungary. In the paper, the most important Hungarian thermal analysis-related associations, events, acknowledgements and awards are also mentioned, together with names of major Hungarian researchers in this field. Presently, beside the internationally acknowledged research groups and the JTAC, the flagship of the Hungarian thermal analysis is the Journal of Thermal Analysis and Calorimetry Conference (JTACC) series. [ABSTRACT FROM AUTHOR]

In this paper, we combine the atomic layer deposition synthesis method of inverse opal with the hydrothermal growth of nanorods. From 460 nm polystyrene nanospheres opal crystals were produced using vertical deposition on Si wafers. The opal templates were covered with ZnO by atomic layer deposition. High temperature annealing was used to remove the polystyrene nanospheres to obtain the inverse opal structure. For the hydrothermal growth of ZnO nanorods, two production routes were analysed: hydrothermal reaction before and after the removal of the template. The two paths produced two distinct structures, one with plate like formations and one with nanorods, respectively. Also, the sample modified by the hydrothermal growth after the annealing showed slight differences in optical properties compared to the regular inverse opal. Morphology, composition and structure of the samples were explored using SEM, EDX and XRD. Optical properties were investigated with reflectance UV–Vis spectroscopy. Thermal stability of the polystyrene opal was determined using TG. [ABSTRACT FROM AUTHOR]

Over many years, great efforts have been made to develop new fluids for heat transfer applications. In this paper, the thermal conductivity (TC) and viscosity of SiO2–P25 TiO2 (SiO2–P25) hybrid nanofluids were investigated for different nanoparticle volume concentrations (0.5, 1.0 and 1.5 vol%) at five various temperatures (20, 30, 40, 50 and 60 °C). The mixture ratio (SiO2:P25) in all prepared hybrid nanofluids was 1:1. Besides, pure SiO2, P25 nanofluids were prepared with the same concentrations for comparison with the hybrid nanofluids. The base fluid used for the preparation of nanofluids was a mixture of deionized water and ethylene glycol at a ratio of 5:1. Before preparing the nanofluids, the nanoparticles were analyzed with energy-dispersive X-ray analysis, scanning electron microscope, X-ray powder diffraction, and Fourier transform infrared spectroscopy. The zeta potentials of the prepared nanofluids except SiO2 nanofluids were above 30 mV. These nanofluids were visually observed for stability in many days. The TC enhancement of the hybrid nanofluid was higher than the pure nanofluid. In particular, with 1.0 vol% concentration, the maximum enhancement of SiO2, P25 and SiO2–P25 nanofluids were 7.5%, 9.9% and 10.5%, respectively. The rheology of the nanofluids was Newtonian. The viscosity increment of SiO2, P25 and hybrid nanofluids were 19%, 32% and 24% with 0.5 vol% concentration. A new correlation was developed for the TC and dynamic viscosity of SiO2–P25 hybrid nanofluid. [ABSTRACT FROM AUTHOR]

Detailed vibrational (IR, Raman, far-IR) and thermal (TGA, TG–MS, DSC) analysis has been performed on di[κ1O,κ2O-carbonatotetraamminecobalt(III)] sulfate trihydrate, ([Co(NH3)4CO3]2SO4·3H2O (1). Its isothermic heating at 100 °C leads to formation of [Co(NH3)4CO3]2SO4 (compound 2). UV and IR studies showed that the distorted octahedral arrangement around cis-O2CoN4 core in compound 1 does not change during dehydration, which explains the reversible water loss and ability of compound 2 to rehydrate into compound 1. Compound 2 decomposes at ~ 240 °C in inert atmosphere giving final decomposition products, which are two modifications of nanosized metallic cobalt (hcp-15 nm, fcc-250 nm) and CoO (55 nm). The redox reaction results in N2 as an ammonia oxidation product. The decomposition intermediate is a cobalt(II) compound, Co2O1,14+δ(SO4)0.86 (δ = the oxygen surplus due to the presence of 2.8% of Co(III) ion). The same reaction in air atmosphere resulted in Co2O1.25+δ(SO4)0.75 (δ = the oxygen surplus due to the presence of 5.3% of Co(III) ion (compound 3a). Compound 3a is oxidized in air at 793 °C into Co3O4. The compound 3a exhibits catalytic activity in photodegradation in Congo red. The photodegradation process follows pseudo-first-order kinetic (kapp = 1.0 and 7.0. at pH = 3.4 and 5.25, respectively). [ABSTRACT FROM AUTHOR]

This study aims to describe the thermal decomposition of two solvatomorphs of decakis(dimethylammonium) dihydrogendodecatungstate ((Me2NH2)10H2W12O42·10H2O and 11 H2O) under inert and oxidizing atmospheres. Thermal studies have been done by TG-MS, TG-DSC-MS, XRD and IR methods in both synthetic air and helium atmospheres. The general characteristics of thermal decomposition are similar for both solvatomorphs. Minor differences could be observed in the resolution and shifting of the decomposition peak temperatures depending on the heating rate or atmosphere used. The first step of decomposition is endothermic in both atmospheres and involves 2 and 5 water molecule elimination with ~ 150 and ~ 120 °C peak temperatures for the decahydrate and undecahydrate, respectively. The elimination of further water and dimethylamine was observed with increasing the temperature, as well as the disruption of the lattice of compounds. Until 300 °C, these processes are endothermic in both atmospheres, and the further decomposition processes at higher temperatures are left endothermic in helium, but become exothermic in synthetic air atmosphere. In helium atmosphere, above 350 °C, a solid-phase quasi-intramolecular redox reaction takes place when the dimethylamine degradation products react with the W=O bonds with formation of oxidative coupling products of the organic fragments and reduced tungsten oxide with WO~2.93 composition. In synthetic air, above 350 °C, burning of organic fragments takes place, there are no oxidative coupling products and reduced tungsten oxide formation, and the end product of decomposition is monoclinic WO3. [ABSTRACT FROM AUTHOR]

In the literature data, several papers reported the synthesis by various chemical or physical methods of the SrCu2O2 (SCO) having possible applications in thermoelectric or completely electronic devices such as solar cells, liquid crystal displays and touch screen. A great challenge is represented by the formation of the pure SrCu2O2 (SCO), due to the high labiality of the Cu valence, depending on temperature. In the present paper, the thermal behavior of Sr–Cu–O gels obtained by sol–gel (SG) or microwave (MW)-assisted SG methods was studied in order to establish the appropriate thermal conditions for pure nanostructured SrCu2O2 preparation. As reagents, copper and strontium acetylacetonate in alcoholic media were used. The starting solutions were homogenized either by stirring for 2 h at room temperature or were exposed to MW for 5 min at 300 W and a frequency of 2.45 GHz. Both solutions were left to gel at room temperature. The obtained gels were investigated by scanning electron microscopy, Fourier-transform infrared spectroscopy, as well as by thermal analysis combined with evolved gas analysis (TG/DTA-MS) measurements in air, inert and reducing atmospheres. For both type of samples, a stepwise thermal decomposition of the gels was noticed in a large temperature range. In the case of samples obtained by microwave-assisted SG method, a higher number of thermal effects were registered assigned to a higher number of molecular species formed in the sample. The residues obtained by non-isothermal treatment up to 900 °C, of both type of samples, were investigated by X-ray diffraction. The results demonstrate the influence of the MW on the SG synthesis and on the thermal properties of the resulted gels. Based on the obtained results, the required thermal treatment of the gels in order to obtain convenient precursors powders for obtaining pure SrCu2O2 could be proposed. [ABSTRACT FROM AUTHOR]

Numerous researches to prepare and stabilize graphene-based nanofluids have been developed. [ABSTRACT FROM AUTHOR]

Graphene has attracted much attention from the science world because of its mechanical, thermal, and physical properties. Graphene nanofluid is well known for its easy synthesis, longer suspension stability, higher heat conductivity, lower erosion, corrosion, larger surface area/volume ratio, and lower demand for pumping power. This article is an audit of experimental outcome about the preparation and stability of graphene-based nanofluids. Numerous researches to prepare and stabilize graphene-based nanofluids have been developed, and it is indispensable to create a complete list of the approaches. This research work outlines the advancement on preparation and assessment methods and the techniques to enhance the stability of graphene nanofluids and outlook prospects. [ABSTRACT FROM AUTHOR]

Possible utilization of SRF (solid recovered fuel) in the energy industry is a widely investigated topic, because even though it is economically feasible, its complex reactions make a steady operation hard to maintain. SRF is prepared as a mixture of the well-combustible (but not recyclable) parts of municipal and industrial waste, which consists of mainly various papers, plastics and textiles with very different combustion characteristics. To describe the kinetics of a complex sample like this, the utilization of more advanced methods is recommended. In this work, genetic algorithm was used to fit four different reaction models to thermogravimetric data measured in oxidative atmosphere, and the results were compared. It was concluded that the tested distributed activation energy model and the simple and expanded nth-order models offer only a slightly better fitting value for this special sample, which promotes the usage of the simpler first-order model. [ABSTRACT FROM AUTHOR]

A new electrospinning process was developed for preparing TiO2 nanofibers using a water-soluble Ti-precursor, [bis(kappa1O-hydroxo)(bis(kappa2O,O′-lactato)titanium(IV)] commonly known as titanium(IV) bis (ammonium lactato) dihydroxide (TiBALDH). The importance of the study is justified by the fact that Ti-precursors used for electrospinning, sol–gel, hydrothermal and other fiber synthesis processes are mostly non-water soluble. Accordingly, anatase TiO2 nanofibers of diameter between 20 and 140 nm were synthesized by electrospinning and annealing. Polyvinylpyrrolidone (PVP) and different concentrations of TiBALDH were dissolved in a mixture of water, ethyl alcohol and acetic acid to optimize the electrospinning conditions. The thermal decomposition and fragmentation of PVP, TiBALDH and the fibers with 50% mass fraction of TiBALDH were studied by TGA-MS measurements. The fibers were then annealed at 1 °C min−1 until 600 °C. The TiO2 fibers were characterized using SEM–EDX, FTIR and XRD [ABSTRACT FROM AUTHOR]

A simple synthetic method was developed to prepare 4[Agpy2ClO4]·[Agpy4]ClO4 in a low-temperature decomposition process of [Agpy4]ClO4. A detailed IR, Raman and far-IR study including factor group analysis has been performed, and the assignation of bands is given. The compound decomposes quickly with a multistep ligand loss process with the formation of [Agpy2]ClO4 and AgClO4 intermediates and AgCl as an end product around ~ 85, ~ 350 and 450 °C, respectively. During the first decomposition step, a small fraction of the ligands is lost in a redox reaction: perchlorate oxidizes the pyridine, forming carbon, carbon dioxide, water and NO, while it itself is reduced into AgCl. In the next step, when AgClO4 forms after complete ligand loss and reacts with the carbon formed in the degradation of pyridine at lower temperatures and produces NO, CO2 and H2O. This reaction becomes possible because the AgCl formed in the redox reactions makes a eutectic melt with AgClO4 in situ, which is a favorable medium for the carbon oxidation reaction. AgCl is known to reduce the temperature of decomposition of AgClO4, in which process forms AgCl as well as O2 and so is an autocatalytic process. The loss and degradation of pyridine ligand are endothermic; the redox reactions including carbon oxidation and AgClO4 decomposition into AgCl and O2 are exothermic. The amount of absorbed/evolved heats corresponding to these processes was determined by DSC both under N2 and O2 atmospheres. [ABSTRACT FROM AUTHOR]

In this work, polyvinylpyrrolidone/titanium tetraisopropoxide (PVP/TTIP) composite nanofibers were prepared by electrospinning from alcoholic solutions. The morphology and the properties of the fibers were investigated by SEM, Raman spectroscopy, and XRD. The thermal properties and the evolved gases were studied in detail by TG/DTA-MS. The as-spun 800–900-nm-thick PVP/TTIP fibers were then, respectively, annealed in different atmospheres (air and nitrogen) and at different temperatures (550 °C, 900 °C) in order to obtain anatase and rutile TiO2 nanofibers. The investigation of the thermal properties was important before the preparation of the oxide nanofibers, because based on them the crystallinity and the composition of the TiO2 nanofibers could be controlled. Metal oxide nanofibers with a slightly smaller diameter, made up mostly by anatase TiO2, were successfully prepared when the annealing was done at 550 °C, while at 900 °C, rutile TiO2 fibers were obtained. If nitrogen atmosphere was applied, the nanofibers contained some carbon residue as well. [ABSTRACT FROM AUTHOR]

ZnO–SnO2 nanostructures are of great interest in practical applications such as optoelectronic devices, gas sensors and catalyst supports due to their excellent optoelectronic and highly sensitive gas sensing properties. In the present work, oxide powders of Sn, Sn/Zn = 1:1, Sn/Zn = 1:2 and Zn were synthesized by sol–gel method. Thermal behavior of the obtained gels was determined by thermogravimetry and differential thermal analysis coupled on-line with mass spectrometry (TG/DTA–MS) in air and nitrogen atmosphere. In air, endothermic effects due to the decomposition of the precursors and exothermic effects due to the oxidation of the organic part were observed. In the case of nitrogen atmosphere, only endothermic effects take place. The XRD and FTIR investigations have shown the same structure both for DTA resulted residues in air and for samples isothermally treated at 500 °C for 1 h. Based on the obtained results, the thermal treatment of the samples was established depending on their intended applications. In the experimental conditions used, the formation of ZnSnO3 was not confirmed. [ABSTRACT FROM AUTHOR]

In this study, the goal was to find lower temperature for separating the Zn and Fe content of ZnFe2O4 by sulfation reaction than previously achieved and to study the various reaction steps of sulfation. Hence, the reaction of ZnFe2O4 with Mohr's salt containing iron(II), i.e., (NH4)2Fe(SO4)2·6H2O, and ammonium iron alum containing Fe(III), i.e., NH4Fe(SO4)2·12H2O, was studied. At first, the thermal decomposition of precursor salts in air was studied by TG/DTA-MS to find the proper temperature for sulfation. Then ZnFe2SO4/precursor salt mixtures with ratios 1:2 and 1:5 were prepared and annealed at 400, 425 and 450 °C. The solubility of the products obtained at different annealing temperatures in water (e.g., ZnSO4, FeSO4, Fe2(SO4)3) and in HCl (Fe2O3, ZnO, Fex(OH)ySO4, Znv(OH)wSO4 basic sulfates) was studied. The morphology and structure of the starting materials was investigated by SEM, XRD and FTIR, the crystalline phases after each annealing and washing step were studied by XRD. The Fe in the starting materials and the products obtained at 425 °C was measured by Mössbauer. Based on the obtained results, it was demonstrated that the sulfation reaction with ammonium iron sulfates could be performed at lower temperatures than with iron sulfates. It was possible to detect the reaction intermediates and to obtain information about the reaction intermediates. With our sulfation reaction, depending on the reaction conditions, it is possible to obtain Fe2O3 as final product, but the Zn and Fe metals can be obtained also as sulfates. Our results open up further possibilities to recycle the ZnFe2O4 waste material. [ABSTRACT FROM AUTHOR]

Nitrogen-containing carbon aerogel was prepared from resorcinol-melamine-formaldehyde (R-M-F) polymer gel precursor. The polymer gel was supercritically dried with CO2, and the carbonization of the resulting polymer aerogel under nitrogen atmosphere at 900 °C yielded the carbon aerogel. The polymer and carbon aerogels were characterized with TG/DTA-MS, low-temperature nitrogen adsorption/desorption (− 196 °C), FTIR, Raman, powder XRD and SEM-EDX techniques. The thermal decomposition of the polymer aerogel had two major steps. The first step was at 150 °C, where the unreacted monomers and the residual solvent were released, and the second one at 300 °C, where the species belonging to the polymer network decomposition could be detected. The pyrolytic conversion of the polymer aerogel was successful, as 0.89 at.% nitrogen was retained in the carbon matrix. The nitrogen-doped carbon aerogel was amorphous and possessed a hierarchical porous structure. It had a significant specific surface area (890 m2 g−1) and pore volume (4.7 cm3 g−1). TG/DTA-MS measurement revealed that during storage in ambient conditions surface functional groups formed, which were released upon annealing. [ABSTRACT FROM AUTHOR]

In the continuation of our systematic research of pyrazole coordination compounds, complexes of Cu(II), Ni(II), Co(II) and Zn(II) with 4-nitro-3-pyrazolecarboxylic acid ligand (L) were synthesized in the reaction of warm ethanolic solutions of the ligand and CuCl2·2H2O, Ni(CH3COO)2, CoCl2·6H2O and Zn(CH3COO)2, mixed in the metal-to-ligand ratio of 1:2. As the compounds could not be obtained in the form suitable for single-crystal structure analysis, their bis(ligand) structures, ML2 (M = CuII, NiII, CoII and ZnII) were proposed on the basis of elemental analysis, IR spectrometry, conductometric and TG-MS measurements. The low conductivity of the compounds additionally supports the deprotonation of the ligand and the formation of neutral complexes. The solvent content was calculated using the thermogravimetric (TG) data. According to TG data, the copper(II) compound crystallizes with 8 while nickel(II) complex with 4 water molecules, CuL2·8H2O, NiL2·4H2O. Complexes of Co(II) and Zn(II) contain 1 and 1.5 water molecules. Despite the differences in solvation properties, the high similarity in the course of the decomposition refers to the similar coordination mode of the organic ligand. The crystal and molecular structures of HL·H2O and NH4[LHL] were determined by single-crystal X-ray structure analysis. Biological research based on determining the inhibition effect of commercial fungicide Cabrio top, ligand, and all newly synthesized complexes on Ph. viticola has been carried out using the phytosanitary method. [ABSTRACT FROM AUTHOR]

Two new zinc(II) coordination compounds have been synthesized by the reaction of diazine-ring containing Schiff bases di(2-pyridyl) ketone phthalazine-1-hydrazone (HzDPK) and di(2-pyridyl) ketone 3-chloropyridazine-6-hydrazone (HpDPK) with zinc(II) salts in acetonitrile in the presence of triethylamine. The crystal and molecular structures of the complexes and that of the ligand HpDPK were determined by single-crystal X-ray structure analysis. In both complexes, zinc atoms are situated in distorted octahedral environments, formed by two meridionally coordinated NNN tridentate, mono-deprotonated ligands. Since the applicability of the coordination compounds depends on their thermal properties, the thermal decomposition of the ligands and their complexes was followed by simultaneous TG-DSC measurements. The desolvation process of the complexes is rather slow as a consequence of a restricted diffusion through the lattice and finishes ~ 200 °C. The desolvated compounds are stable up to 340 °C. In order to follow the solvent evaporation and to have a better insight into the decomposition mechanism of the compounds coupled TG-MS measurements were carried out. [ABSTRACT FROM AUTHOR]

Synthesis of ammonium hydroxodisulfitoferriate(III), (diammonium catena-{bis(μ2-sulfito-κO,κO)-μ2-hydroxo-κ2O}ferrate(III) monohydrate) (NH4)2[Fe(OH)(SO3)2]·H2O (compound 1) and its thermal behavior is reported. The compound is stable in air. Its thermal decomposition proceeds without the expected quasi-intramolecular oxidation of sulfite ion with ferric ions. The disproportionation reaction of the ammonium sulfite, formed from the evolved NH3, SO2 and H2O in the main decomposition stage of 1, results in the formation of ammonium sulfate and ammonium sulfide. The ammonium sulfide is unstable at the decomposition temperature of 1 (150 °C) and transforms into NH3 and H2S which immediately forms elementary sulfur by reaction with SO2. The formation and decomposition of other intermediate compounds like (NH4)2SnOx (n = 2, x = 3 and n = 3, x = 6) results in the same decomposition products (S, SO2 and NH3). Two basic iron sulfates, formed in different ratios during synthesizing experiments performed under N2 or in the presence of air, have been detected as solid intermediates which contain ammonium ions. The final decomposition product was proved to be α-Fe2O3 (mineral name hematite). [ABSTRACT FROM AUTHOR]

To overcome the polyurethanes low heat resistance and obtain new PU-based materials, in continuation of our research in the synthesis of hybrid polymers, we report here the synthesis of metal-containing polyurethanes formed in the reaction of pyrazole-based coordination compounds [Cuampf(NO3)2MeOH]·MeOH and [CuampfCl2] where ampf denotes N,N′-bis(4-acetyl-5-methyl pyrazole-3-yl)formamidine ligand, and two isocyanates, 1,6-diisocyanatohexane (HDI) and Bayhydur 3100 (Bay, a hydrophilic linear polymer based on 1,6-diisocyanatohexane) using dibutyltin-dilaurate catalyst. The formed materials were characterized by FT-IR spectrometry and thermal methods. The formation of the new polymers, besides the corresponding FT-IR spectra, was proved by differential scanning calorimetry (DSC) determining their glass transition temperatures. The thermal decomposition of the materials was examined by simultaneous thermogravimetric (TG) and DSC measurement. For the evaluation of the decomposition mechanism, the data obtained by coupled TG-mass spectrometric (MS) measurements were used. The thermal stability of the hybrid materials based on HDI was found substantially higher than that of the pure 1,6-diisocyanatohexane and decomposition of hybrid materials was more complex, while in the reaction of the metal complexes with Bay the thermal properties of the obtained hybrid polymers were changed only slightly, referring to a small amount of incorporated complexes. [ABSTRACT FROM AUTHOR]

The improved Hummers’ synthesis of graphene oxide (GO) from graphite is investigated to monitor how the functional groups form during the synthesis steps. To achieve these, samples are taken after every preparation step and analyzed with TG–DTA/MS, FTIR, XRD and SEM–EDX techniques. It was found that the main characteristic mass loss step of GO was around 200 °C, where at first the carboxyl and lactone groups were released, and the evolution of sulfonyl groups followed them right away in a partially overlapping step. It became clear that in the as-prepared acidic GO sample the presence of H2SO4 originating from the reaction solution was still dominant. The functional groups were formed only after washing the as-prepared GO with HCl. The consecutive washing step with distilled water did not alter the functional groups or the thermal properties significantly; however, it made the GO structure more ordered. The reduction of the GO structure back to reduced GO resulted in the loss of the functional groups, and a graphitic material was obtained back. [ABSTRACT FROM AUTHOR]

Our study was directed to the analysis of the influence of various types of cements on the behaviour of concrete at high temperatures. In our experiments binary blended and ordinary Portland cements were involved: two Portland cements with different clinker compositions and Portland cements containing pozzolanic additives as replacement of clinkers. In the first part of the study we focused on the influence of cement types where cement paste specimens were investigated. Then, based on the results of cement paste specimens, concretes specimens were prepared with some selected types of cements. Most important observation of our experimental study was that the pozzolanic additives and their increased amount have a favourable effect on the heat resistance (fire resistance) properties of concrete. [ABSTRACT FROM AUTHOR]

Our study was directed to improve the residual flexural strength and the heat-resistant properties of concrete exposed to high temperatures using different fiber cocktail loadings including steel, polymer or cellulose fibers. At first the morphology and the thermal properties of the fibers and the fiber/cement composites were investigated by SEM and TG/DTA-MS. Then the influence of fiber type and amount on residual flexural strength was tested after cooling back from 150, 500 or 800 °C temperature loadings. By adding steel, cellulose and polymer (polypropylene) fibers to cement, improvements both in post-cracking residual flexural strength and in insensitivity against explosive spalling were reached. [ABSTRACT FROM AUTHOR]

Three complexes of general formula PtClR were synthesized, where R is the amine ligand with aromatic substituents. Coordination compounds [Pt( an) Cl] ( 1), [Pt( pa)Cl] ( 2) and [Pt( aph)Cl] ( 3), where an = 2-aminonaphthalene, pa = 2-aminopyrimidine, aph = 4-anilinophenol, were characterized by on-line coupled TG/DTA-MS, powder XRD and spectroscopic techniques (FTIR, ESI-MS and NMR), and tested against selected Gram(+) and Gram(-) bacteria. The thermal data show that all three compounds contain lattice or absorbed water, and the stability of the anhydrous compounds in nitrogen decreases in the order 2 > 1 > 3. Above 200 °C, the complexes loose characteristic fragments of their ligands. The spectroscopic data are in accordance with the thermal properties of the samples and prove their composition. The compounds are more effective inhibitors of Gram(+) than Gram(−) bacteria. [ABSTRACT FROM AUTHOR]

Concrete is a composite material that mainly consists of mineral aggregates bound by the matrix of hardened cement paste. Composition and microstructure of hardened cement paste have important influences on the properties of concrete exposed to high temperatures. An extensive experimental study was carried out to analyse the post-heating characteristics of concretes subjected to temperatures up to 800 °C. Major parameters of our study were the slag content of cement (0, 16, 25, 41 or 66 m%) and the value of maximum annealing temperature. Our results indicated that (1) the number and size of surface cracks as well as compressive strength decreased by the increasing slag content of cements due to elevated temperature; (2) the most intensive surface cracking was observed by using Portland cement without addition of slag. The increasing slag content of cement increased the relative post-heating compressive strength. Tendencies of surface cracking and reduction of compressive strength were in agreement, i.e. the more surface cracks, the more strength reduction. [ABSTRACT FROM AUTHOR]

The thermal behavior of ammonium molybdates, i.e., (NH)MoO·4HO ( 1) and (NH)MoO ( 2), was studied in inert (N) and oxidizing (air) atmospheres by TG/DTA-MS, XRD, FTIR and SEM. The thermal decomposition sequence of 2 had similarities to 1; however, there were significant differences as well. When both of them were annealed, NH and HO were released parallel, and in air the as-evolved NH was burnt partially into NO and NO. In both atmospheres, while 1 decomposed in four steps, the thermal decomposition of 2 involved 5 steps. In the case of 1, the intermediate products were (NH)MoO, (NH)MoO and h-MoO. In contrast, the decomposition intermediates of 2 were (NH)MoO, (NH)MoO, (NH)MoO and h-MoO. By both 1 and 2, the final product was dominated by o-MoO, accompanied with small amount of MoO in N, which was absent in air. Most decomposition steps were endothermic, except for the last step around 400 °C, where crystallization from the residual amorphous phase had an exothermic heat effect. In addition, the combustion of NH also changed the DTA curve into exothermic in some cases. The morphology of the final products was characterized by 1-5 μm sheet-like particles, except for annealing 2 in N, when 0.5- to 1-μm-thick and 5- to 10-μm-long needle-shaped particles were detected. [ABSTRACT FROM AUTHOR]

ZnO, Li doped, and Li, Ni co-doped ZnO powders to be later used as transparent conductive oxide thin film were prepared by heat treatment of gels obtained from alcoholic Zn(CHCOO)·2HO, LiNO·nHO and NiSO·6HO solutions with (CHCHOH)N as chelating agent. The properties of the powders and their thermal treatment were studied by thermogravimetric and differential thermal analysis (TG/DTA), differential scanning calorimetry, evolved gas analysis coupled with mass spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy coupled with energy-dispersive X-ray. The as-prepared gels consisted of submicron platelet-like particles and contained zinc acetate dihydrate and hydrozincite in different amount and with different preferred orientations. During annealing of the gels, zinc acetate decomposed between 110 and 350 °C with the release of CHCOOH, acetone and CO. The N content of the chelating agent was responsible for NH and NO evolution. The thermal behavior of the doped gels was similar, but there were also differences in the mass losses, amount of released gases. Based on TG/DTA data, ZnO powders were obtained from the gels by annealing both at 275 and 500 °C. After heating at 275 °C, the obtained powders consisted of spherical 1-2 micron grains of wurtzite. The inclusion of the dopants was successful according to EDX and cell parameter data. Thermal study of the powder annealed at 275 °C confirmed that they still contain some zinc acetate. In the case of the doped samples, the mass loss was smaller, since the Li and Ni dopants catalyzed the composition of zinc acetate during the previous annealing at 275 °C. After annealing the gels at 500 °C, stable undoped ZnO or doped ZnO particles were obtained. [ABSTRACT FROM AUTHOR]

The thermal decomposition of ammonium tetrathiotungstate (ATT), (NH)WS, was studied by SEM, FTIR, XRD, EDX and TG/DTA-MS. The decomposition of ATT involved three steps in inert atmosphere: (1) release of free water between 30 and 140 °C; (2) formation of an amorphous WS phase between 170 and 280 °C, from which (3) a slightly crystalline WS formed between 330 and 470 °C. As a difference compared to inert atmosphere, in air in the second step, the ATT decomposed into directly WS instead of WS. This WS phase was amorphous and still contained traces of ATT. Between 260 and 500 °C from the WS, monoclinic tungsten oxide crystallized in two steps: at 302 °C a slightly crystalline m-WO formed, which became more crystalline at 471 °C. During the investigation of the effect of the particle size, it was found that the thermal behaviour of ATT crystals was similar to ATT powder, with some shift in the decomposition temperature. The XRD results showed that the WS formed from the ATT powder in N had a higher level of crystallization, compared to the WS obtained from ATT crystals. [ABSTRACT FROM AUTHOR]

Novel copper containing epoxy polymers have been synthesized using copper(II) formamidine complex [Cu( ampf)Cl], ampf = N, N′-bis(4-acetyl-5-methylpyrazole-3-yl)formamidine, as curing agent for diglycidyl ether of bisphenol A-based epoxy resins (Araldite and its oligomer consisting of 3-4 monomer units). The curing reaction was performed at room temperature without catalyst. In order to prove the polymerization reaction, differential scanning calorimetry (DSC) was applied. Highly exothermic peaks around 150 °C refer to the polymerization, and according to DSC results, the epoxy resins above 200 °C were almost completely converted to the corresponding metal-containing polymer. The proposed structure of the hybrid polymers was confirmed by FT-IR analysis. Gel permeation chromatography analysis shows that the average molar masses of the polymers are in the range from 3,000 to 50,000 g mol. The low conductivities of the hybrid materials in tetrahydrofuran confirm the non-ionic structure of the new polymers in solution. The thermal stability and the decomposition mechanism of the components of the reaction mixture and the new polymers were studied by coupled TG/DTA-MS measurements. The thermal data were analysed also with the aim to obtain additional information about the composition of the synthesized materials. [ABSTRACT FROM AUTHOR]

The structure and morphology of ammonium metatungstate (AMT), (NH)[HWO]⋅4HO, and its thermal decomposition in air and nitrogen atmospheres were investigated by SEM, FTIR, XRD, and TG/DTA-MS. The cell parameters of the AMT sample were determined and refined with a full profile fit. The thermal decomposition of AMT involved several steps in inert atmosphere: (i) release of crystal water between 25 and 200 °C resulting in dehydrated AMT, (ii) formation of an amorphous phase between 200 and 380 °C, (iii) from which hexagonal WO formed between 380 and 500 °C, and (iv) which then transformed into the more stable m-WO between 500 and 600 °C. As a difference in air, the as-formed NH ignited with an exothermic heat effect, and nitrous oxides formed as combustion products. The thermal behavior of AMT was similar to ammonium paratungstate (APT), (NH)[HWO]⋅4HO, the only main difference being the lack of dry NH evolution between 170 and 240 °C in the case of AMT. [ABSTRACT FROM AUTHOR]

Monometallic complexes [Cudadb· yHO] ( 2) and [Nidadb· yHO] ( 3) and heterobimetallic complex [CuNidadb· yHO] ( 4) {where dadbH = 2,5-Diamino-3,6-dichloro-1,4-benzoquinone ( 1); y = 2-4; n = degree of polymerization} were characterized by elemental analysis, atomic absorption spectroscopy, infrared spectroscopy (FTIR) and powder X-ray diffraction. The thermal behaviour of the complexes was studied by thermal analysis (TG/DTA) under air as well as under helium atmospheres. The released gaseous products were investigated by evolved gas analysis performed by an online coupled mass spectrometer (TG/DTA-MS). Thermal degradation of 2 under helium atmosphere is distributed over five steps, whereas 3 and 4 exhibited only four degradation steps due to overlap of second and third degradation steps of into one major step. All the complexes exhibit three steps degradation under air. The complex 2 loses NH group in the second and HCl/Cl, CO groups simultaneously in third steps of decomposition under helium, whereas it loses NH and CO groups simultaneously in low temperature region of second step of degradation under air atmosphere as the loss of CO group is facilitated by air. EGA-MS under air and helium atmospheres shows that HCl, CO/CO and (CN) fragments are lost simultaneously at multiple steps, and not successively as predicted earlier. Rate of evolution of most evolved gases exhibits several maxima as a consequence of degradation followed by recombination reactions. Final residues under air and helium atmospheres correspond to the metal oxides and metals along with some carbonaceous matter. [ABSTRACT FROM AUTHOR]

This article demonstrates how important it is to find the optimal heating conditions when electrospun organic/inorganic composite fibers are annealed to get ceramic nanofibers in appropriate quality (crystal structure, composition, and morphology) and to avoid their disintegration. Polyvinylpyrrolidone [PVP, (CHNO)] and ammonium metatungstate [AMT, (NH)[HWO]· nHO] nanofibers were prepared by electrospinning aqueous solutions of PVP and AMT. The as-spun fibers and their annealing were characterized by TG/DTA-MS, XRD, SEM, Raman, and FTIR measurements. The 400-600 nm thick and tens of micrometer long PVP/AMT fibers decomposed thermally in air in four steps, and pure monoclinic WO nanofibers formed between 500 and 600 °C. When a too high heating rate and heating temperature (10 °C min, 600 °C) were used, the WO nanofibers completely disintegrated. At lower heating rate but too high temperature (1 °C min, 600 °C), the fibers broke into rods. If the heating rate was adequate, but the annealing temperature was too low (1 °C min, 500 °C), the nanofiber morphology was excellent, but the sample was less crystalline. When the optimal heating rate and temperature (1 °C min, 550 °C) were applied, WO nanofibers with excellent morphology (250 nm thick and tens of micrometer long nanofibers, which consisted of 20-80 nm particles) and crystallinity (monoclinic WO) were obtained. The FTIR and Raman measurements confirmed that with these heating parameters the organic matter was effectively removed from the nanofibers and monoclinic WO was present in a highly crystalline and ordered form. [ABSTRACT FROM AUTHOR]

This article discusses the formation and structure of ammonium tungsten bronzes, (NH4) xWO3− y. As analytical tools, TG/DTA-MS, XRD, SEM, Raman, XPS, and 1H-MAS NMR were used. The well-known α-hexagonal ammonium tungsten bronze (α-HATB, ICDD 42-0452) was thermally reduced and around 550 °C a hexagonal ammonium tungsten bronze formed, whose structure was similar to α-HATB, but the hexagonal channels were almost completely empty; thus, this phase was called reduced hexagonal (h-) WO3. In contrast with earlier considerations, it was found that the oxidation state of W atoms influenced at least as much the cell parameters of α-HATB and h-WO3, as the packing of the hexagonal channels. Between 600 and 650 °C reduced h-WO3 transformed into another ammonium tungsten bronze, whose structure was disputed in the literature. It was found that the structure of this phase—called β-HATB, (NH4)0.001WO2.79—was hexagonal. [ABSTRACT FROM AUTHOR]

This paper discusses the changes in the structure and thermal reduction of nanosize hexagonal ammonium tungsten bronze (HATB), (NH4)0.33−xWO3−y, which were caused by K+ ion exchange (doping) and studied by XRD, XPS, 1H-MAS NMR, FTIR, SEM and TG/DTA-MS. Comparison of the cell parameters of undoped and doped HATB revealed that both a and c cell parameters decreased after the ion exchange reaction, which showed that smaller K+ ions partly replaced the larger NH ions in the hexagonal channels of HATB. After the reaction, from the hexagonal channels less NH3 evolved, which also supported the incorporation of K+ ions into the hexagonal channels. [ABSTRACT FROM AUTHOR]

Inclusion complexes of Lippia sidoides essential oil and β-cyclodextrin were obtained by slurry method and its solid powdered form was prepared using spray drying. The influence of the spray drying, as well as the different essential oil:β-cyclodextrin ratio on the characteristics of the final product was investigated. With regard to the total oil retention 1:10 mass/mass ratio as optimal was found between the essential oil and β-cyclodextrin. Thermoanalytical techniques (TG, EGD, TG-MS) were used to support the formation of inclusion complex and to examine their physicochemical properties after accelerated storage conditions. It may be assumed that the thermal properties of the complexes were influenced not only by the different essential oil/ β-cyclodextrin ratio but also by the storage conditions. In the aspect of their thermal stabilities, complex prepared with 1:10 m/m ratio (essential oil:β-cyclodextrin) was the most stable one. [ABSTRACT FROM AUTHOR]

We studied the thermal stability of different hexagonal tungsten trioxide, h-WO3 samples, which were prepared either by annealing hexagonal ammonium tungsten bronze, (NH4)0.33−xWO3−y, or by soft chemical synthesis from Na2WO4. The structure and composition of the samples were studied by powder XRD, SEM-EDX, XPS and 1H-MAS NMR. The thermal properties were investigated by simultaneous TG/DTA, on-line evolved gas analysis (TG/DAT-MS), SEM and in situ powder XRD. The preparative routes influenced the thermal properties of h-WO3 samples, i.e. the course of water release, the exothermic collapse of the hexagonal framework and the phase transformations were all affected. [ABSTRACT FROM AUTHOR]

Thermal decomposition of ammonium paratungstate tetrahydrate, (NH4)10[H2W12O42]·4H2O has been followed by simultaneous TG/DTA and online evolved gas analysis (TG/DTA-MS) in flowing 10% H2/Ar directly up to 900°C. Solid intermediate products have been structurally evaluated by FTIR spectroscopy and powder X-ray diffraction (XRD). A previously unexplained exothermic heat effect has been detected at 700–750°C. On the basis of TG/DTA as well as H2O and NH3 evolution curves and XRD patterns, it has been assigned to the formation and crystallization heat of γ-tungsten-oxide (WO2.72/W18O49) from β-tungsten-oxide (WO2.9/W20O58) and residual ammonium tungsten bronze. [ABSTRACT FROM AUTHOR]

The thermotropic behaviour of the Synperonic A7-water (80%) system was investigated by different (SAXS, freeze-fracture, DSC) methods under the conditions of steady state and shear stress. It was found that above the melting point (about 55°C) lamellar structure exists at 80°C, which was interpreted as a consequence of phase separation. The phase separation is more extended if the sample was sheared. The shear process affects the thermotropic behaviour of the system drastically. Above the melting point the thermal treatment terminates the shear prehistory. The shear processes were executed in a shear cell constructed in two variants for small angle X-ray scattering and for freeze-fracture methods. [ABSTRACT FROM AUTHOR]

A ferronematic liquid crystal (FNLC) system containing 8CB (4-cyano-4'-[ n-octylbiphenyl]) and magnetite particles was prepared by using the two steps method. The magnetite particles were dispersed in the organic (liquid crystalline) media by using toluene. However, the toluene affected the thermotropic and structural behaviour of the pure basic (8CB) substance, drastically. The product was stable as no any sedimentation and coagulation has been observed during several weeks after the preparation. However, the distribution of magnetite particles was found not to be homogeneous in the nm size range. [ABSTRACT FROM AUTHOR]