Thermal behavior analysis of kaolinite–dimethylsulfoxide intercalation complex

The thermal behavior of kaolinite?Cdimethylsulfoxide intercalation complex was investigated by thermogravimetry (TG) and differential scanning calorimetry (DSC) analysis, X-ray diffraction (XRD) analysis, and Fourier-transform infrared (FT-IR) spectroscopic analysis. The samples gradually heated up to different temperatures were studied by XRD and FT-IR. The kaolinite?Cdimethylsulfoxide intercalation complex is stable below 130?°C. With the rise in the temperature, the relative intensity of the 1.124-nm peak gradually decreased and disappeared at 200?°C, however, the intensity of the 0.714?nm peak increased in the XRD patterns. In the infrared spectra, the appearance of methyl bands at 3018, 2934, 1428, and 1318?cm^?1 indicates the presence of intercalated dimethylsulfoxide, the intensities of these bands decreased with the temperature rising and remained until around 175?°C, which agree with the XRD and TG?CDSC data.     

TG–DSC–FTIR–MS study of gaseous compounds evolved during thermal decomposition of styrene-butadiene rubber

The thermal decomposition behavior of styrene-butadiene rubber was studied using a system equipped with thermogravimetric analysis, differential thermal analysis, Fourier transform infrared spectroscopy, and mass spectroscopy. Two different experiments were conducted. From these experiments, thermogravimetric analysis results indicated a mass loss of 58 % in the temperature range of ~290–480 °C and a mass loss of 39 % in the temperature range beyond 600 °C. Scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy confirmed the presence of oxides, even at 1,000 °C, accounting for the Zn, Mg, Al, Si, and Ca in the original sample.     

Comprehensive evolved gas analysis (EGA) of amorphous precursors for S-doped titania by in situ TG–FTIR and TG/DTA–MS in air: Part 2. Precursor from thiourea and titanium(IV)-n-butoxide

Thermal decomposition of an amorphous precursor for sulfur-doped titania (S:TiO₂) nanopowders, prepared by controlled sol–gel hydrolysis-condensation of titanium(IV) tetrabutoxide and thiourea in aqueous butanol, has been studied in situ up to 850 °C in flowing air by simultaneous thermogravimetric and differential thermal analysis coupled online with quadrupole mass spectrometer (TG/DTA–MS) and FTIR spectrometric gas cell (TG–FTIR) for analysis of gases and their evolution dynamics in order to explore and simulate thermal annealing processes of fabrication techniques aimed S:TiO₂ photocatalysts with photocatalytic activities under visible light.The studied S-doped precursor's decomposition course remembers to that of non-doped xerogel from Ti(IV)-n-butoxide, which seems to retard a considerable amount of organics in the solid phase even at high temperature, probably in polymeric forms, proven by evolution of CO₂ in several temperature regions of decomposition stages. The incorporation form of thiourea in the original xerogel seems to be chemically bounded, resulting lower decomposition temperature than that of pure thiourea, and producing evolution of carbonyl sulfide (COS) already between 120 and 190 °C. Nevertheless, evolution of SO₂, and that of CO₂ is also observed above 500 °C by both EGA detection methods. The latter observation implies that the blackish grey samples obtained even at 750 °C might be simultaneously S- and C-doped ones.     

Hyphenation of thermogravimetry and soft single photon ionization–ion trap mass spectrometry (TG–SPI–ITMS) for evolved gas analysis

Thermal processes are part of many industrial treatments; therefore, it is of great interest to gain more insight of these processes. Evolved gas analysis (EGA) is the most straightforward way to make chemical reactions in thermal processes accessible for on-line investigations. The sample matrix of evolved off gas e.g., from coffee roasting is a permanently changing and complex mixture of a multitude of substances that have to be analyzed simultaneously for real on-line investigations without any sample trapping or separation device. Therefore, a measurement system as an ion trap mass spectrometer (ITMS) with soft ionization is required with its tandem mass spectrometry capability to provide distinct substance identification unperturbed by the remaining matrix. The presented novel system setup is based on a thermogravimetric device (TG) to simulate the thermal treatment as in industrial processes combined with an ITMS with soft single photon ionization (SPI) to achieve the required substance information. Hence it is possible to gain single mass spectrometric information of expected substances for process control. More comprehensive than that are the two-dimensional MS data which are required for research and process development purposes though. The conducted analyses show that this novel setup is able to provide distinct substance identification in evolved gas of roast and ground coffee powder. To our knowledge, this is the first TG–SPI–ITMS setup with successful application in verifying the identity of different mass traces within a single run.     

Using TG–FTIR and TG–MS to study thermal degradation of metal hypophosphites

Three typical metal hypophosphite flame retardants La(H₂PO₂)₃·H₂O (LHP), Ce(H₂PO₂)₃·H₂O (CHP), and Al(H₂PO₂)₃ (AHP) were synthesized and characterized by Fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction, scanning electron microscopy, thermogravimetric analysis (TG), derivative thermogravimetric analysis, and differential thermal analysis. The thermal degradation products from the synthesized metal hypophosphites were also investigated using thermogravimetry coupled with Fourier transform infrared spectroscopy (TG–FTIR) and thermogravimetry coupled with mass spectrometry (TG–MS). The synthesized metal hypophosphites were also used as flame retardants for poly (1,4-butylene terephthalate) (PBT), and the combustion properties of flame-retarded PBT were evaluated using the limiting oxygen index and UL-94 tests. The results showed that the metal hypophosphites LHP, CHP, and AHP can be used as effective flame retardants for PBT, and these compounds can be obtained through a simple precipitation method. TG–FTIR and TG–MS results showed that the degradation process of AHP involves two steps, corresponding to the removal PH₃ reaction and the further dehydration reaction of the hydrogen phosphate aluminum. While LHP and CHP have three degradation steps, the additional step is due to that LHP and CHP which will loss the crystal water at lower temperature.     

TG–DTA, UV and FTIR spectroscopic studies of urea–thiourea mixed crystal

A mixed crystal of urea–thiourea was grown by slow evaporation of aqueous solution at room temperature. The bright and transparent crystals obtained were characterized by thermogravimetric–differential thermal analysis (TG–DTA), UV and FTIR spectroscopic analyses. A fitting decomposition pattern for the title compound was formulated on the TG curve which shows a two stage weight loss between 200 and 750 °C. In this temperature range DTA curve shows exothermic peaks supporting the formulated decomposition pattern. The UV and FTIR spectra show the characteristic absorption, vibration frequencies due to urea–thiourea mixed crystals. Detailed structural analysis of the compound is under progress.     

Thermal decomposition of RDX/AP by TG–DSC–MS–FTIR

The method of TG–DSC–MS–FTIR simultaneous analysis has been used to study the thermal decomposition mechanism of the RDX/AP (1/2) mixture. TG–DSC showed that there were two mass loss processes for thermal decomposition of RDX/AP. The first one was mainly ascribed to the thermal decomposition of RDX. Addition of AP to RDX causes decomposition to take place abruptly, after melting, resulting in a very sharp and strong peak at lower temperature. The apparent activation energies, calculated by model-free Friedman method, of this process were negative. The second mass loss process of RDX/AP was confirmed to be the thermal decomposition of AP, catalyzed by RDX. This process can be divided into three stages, which were an nth-order autocatalytic and two one-dimensional diffusion stages, respectively. There was a competition among the formation reactions of N₂O, HNCO, and HCl for the first stage and between NO₂ and N₂O for the later two stages. The production of N₂O dominated in the second stage, while NO₂ did in the third stage.     

TG–FTIR analysis of oxidation kinetics of some solid fuels under oxy-fuel conditions

A possible technology that can contribute reduction of carbon dioxide emission is oxy-fuel combustion of fossil fuels enabling to increase CO₂ concentration in the exhaust gas by carrying out the combustion process with oxygen and replacing air nitrogen with recycling combustion products to obtain a capture-ready CO₂ stream. The laboratory studies and pilot-scale experiments discussed during the last years have indicated that oxy-fuel combustion is a favorable option in retrofitting conventional coal firing. Estonian oil shale (OS) with its specific properties has never been studied as a fuel in oxy-fuel combustion, so, the aim of the present research was to compare thermo-oxidation of OS and some coal samples under air and oxy-fuel combustion conditions by means of thermal analysis methods. Experiments were carried out in Ar/O₂ and CO₂/O₂ atmospheres with two oil shale and two coal samples under dynamic heating conditions. FTIR analysis was applied to characterize evolved gases and emission dynamics. Kinetic parameters of oxidation were calculated using a model-free kinetic analysis approach based on differential iso-conversional methods. Comparison of the oxidation characteristics of the samples was given in both atmospheres and it was shown that the oxidation process proceeds under oxy-fuel conditions by all studied fuels with lower activation energies, however, it can last longer as the same temperatures are compared.     

Study on thermal degradation of cattlehide collagen fibers by simultaneous TG–MS–FTIR

Leather was useful materials since dawn of human history for excellent properties, but thermal degradation mechanism was not very clear yet. In this paper, much progress has been made in elucidating the thermal stability and thermal degradation mechanism by thermoanalytical study in argon. Thermogravimetric analysis simultaneously coupled with mass spectrometry and Fourier transform infrared spectrometry was employed to study the thermal degradation of cattlehide collagen fibers through in-depth analysis of the evolved gas. Thermogravimetry analyses carried out on sample, deprived from any residual catalyst and highlighted a two-step thermal degradation. New evidence demonstrates that the process during temperature range from 373 to 513 K was phase transformation. Photographs of polarizing microscope confirmed the conclusion. The decomposition of cattlehide collagen fibers starts at about 523 K. The cattlehide collagen fibers may undergo the process of melting, oxidation and decomposition. In decomposition, more than three steps take place. The mass spectra and Fourier transform infrared spectrometry stated clearly that double bond of carbon to oxygen, carbon to sulfur and carbon to nitrogen were destroyed firstly because the carbon dioxide, carbon monoxide and ammonia evolved simultaneously. The second peak of carbon monoxide in mass spectra indicated that some organic fragments were decomposed above 1073 K which confirmed that thermal degradation of leather is more than three steps.     

TG–FTIR analysis applied to the study of thermal behaviour of some edible mushrooms

The article is devoted to the study on the thermal behaviour of three species of edible mushrooms: Boletus edulis (foot and cap), Pleurotus ostreatus (foot and cap), Lactarius deterrimus (cap) by the TG–FTIR-coupled technique, in air, over the 30–900 °C temperature range. The analysis of the TG–DTG–DTA curves reveals the thermal degradation mechanism to be complex and specific to every species under the recording conditions applied. A similar degradation mechanism is noticed for the foot and cap of Pleurotus ostreatus in comparison with the Boletus edulis and Lactarius deterrimus species where the mechanisms are different. The TG–FTIR analysis, combustion heats and IR spectra of the starting samples also support these results. The initial degradation temperatures from TG–DTG indicate the temperature range where these species are thermally stable and their nutrient features maintained making them proper for food. The TG–FTIR analysis gives information on the gaseous species evolved by the thermal degradation bringing thus a contribution to the elucidation of the changes developing by processing the edible mushrooms (industrialization, conservation, culinary preparations, etc.) at temperatures above the initial degradation temperature. At the same time, the environmental impact, when the mushroom failed cultures are burned, is also important.     

Synergetic effect of poly(vinyl butyral) and calcium carbonate on thermal stability of poly(vinyl chloride) nanocomposites investigated by TG–FTIR–MS

In order to improve poly(vinyl chloride) (PVC) thermal stability, poly(vinyl butyral) (PVB) matrix and calcium carbonate nanoparticles were incorporated in plasticized PVC. Thermal properties of these composites were investigated by thermogravimetry analysis coupled with mass spectrometry and Fourier transform infrared spectroscopy (FTIR). This approach highlighted the efficiency of both PVB and CaCO₃ as HCl scavengers by postponing both the onset degradation temperature and the HCl release. Moreover, a synergetic effect was evidenced regarding the HCl release. Finally, kinetic parameters of the PVC first degradation stage, determined using the Flynn–Wall–Ozawa’s method, revealed a significant increase of the activation energy by incorporation of CaCO₃ in the presence or not of PVB.     

Synthesis and thermal decomposition of Cr–urea complex

In this work, Cr–urea complex ([Cr(NH₂CONH₂)₆](NO₃)₃) was synthesized by direct solid-state reaction of chromium nitrate and urea, and its thermal decomposition reaction was studied for the first time to explore the possibilities of using the complex as precursor to nanosized chromium oxide. The formation of [Cr(NH₂CONH₂)₆](NO₃)₃ is confirmed from infrared spectroscopy and elemental analysis. Thermogravimetric and differential thermal analysis of the compound show a three-stage thermal decomposition in the temperature range from 190 to 430 °C. The result of X-ray diffraction (XRD) shows that the [Cr(NH₂CONH₂)₆](NO₃)₃ decompose at ~300 °C into α-Cr₂O₃ nanopowder with an average crystallite size of 33 nm.     

CFD analysis of a TG–DSC apparatus

A ThermoGravimetric analyser with differential scanning calorimetry (TG–DSC) has been studied during the fusion of an indium sample using both an experimental procedure and a CFD simulation. To do so, a CAD model of the real device was built and meshed in detail, in order to take into account the small scale processes which occur inside the crucibles. Several theoretical models, some previously existing in the CFD software used and others developed ad hoc, were applied to simulate the whole facility. Therefore, realistic boundary conditions and a PID-based control system already developed for previous studies had to be used. The validation of the CFD model was done by comparing the outcome of the resulting simulation to the results obtained by experimental procedure in a case where natural convection is the main heat and mass transfer mechanism. This comparison was made for two different heating rates inside the furnace. Typical characteristics of phase change process inside a TG-DSC as thermal lag, onset temperature or heat flow exchange during the fusion could be analysed. As well, a more detailed approach to physical phenomena taking place inside the furnace could be done, since CFD simulations allow to obtain data which is not achievable experimentally. Besides, a valid CFD model for a TG-DSC could be later used in further CFD simulations.     

Kinetics of coal and char oxycombustion studied by TG–FTIR

Coal and char oxycombustion is a complex process because of very high reaction rate of oxygen with coals and chars carbon. Very important process during oxycombustion is diffusion of O₂ to surface of coal and char grain. This process can be minimized using small samples and high flow of the gas, but it is also dependent on temperature. For this reason, it is impossible to eliminate diffusion processes which cause significant impact on calculated kinetic parameters. This paper describes the results of thermogravimetric studies of oxycombustion process with evolved gas analysis by FTIR. Ultimate and proximate analysis of coal and char were made. Thermogravimetric experiments of coal and its char oxycombustion were conducted using five heating rates, namely 2.5, 5, 10, 20 and 40 K min^?1, and gas mixture composed of 20 % O₂ in CO₂. Activation energies of coal and char oxycombustion were calculated by isoconversional methods: integral Vyazovkin and differential Friedman. Activation energies for three ranges of heating rates were calculated. This paper shows influence of heating rate on calculated activation energy. The reason of this phenomenon is due to change of the mechanism of coal and char oxycombustion from the chemical kinetic control regime to mixed chemical kinetic–diffusion control regime.     

X‐ray diffraction,differential scanning calorimetry and evolved gas analysis of aged plutonium tetrafluoride (PuF4)

Journal of Radioanalytical and Nuclear Chemistry - A 30 year-old PuF4 sample consisting of brown powder (PuF4-b) and pink granules (PuF4-p) was analyzed. X-ray diffraction shows the bulk...     

Preparation and characterization of poly(urethane–urea) microcapsules containing limonene. Kinetic analysis

The synthesis of poly(urethane–urea) shells (PUU) using poly(ethylene glycols) of different molecular weights and methylene-bis(4-cyclohexylisocyanate) was performed for the microencapsulation of limonene, using a step-growth polymerization process. The obtained microcapsules were structurally characterized by dynamic light scattering, optical microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis. The results showed that the core–shell microcapsules had spherical shape, a mean diameter in between 10 and 20?µm, and characteristic urethane-urea bonds. Furthermore, the molecular weight of polyol influences the entrapment efficiency, which ranged from 38 to 55%. The release data were analyzed by applying the Korsmeyer–Peppas model.     

Study of effect of phosphate and uranium ions on the thermal properties of surfactant-modified natural red clay using TG–FTIR–MS techniques

Products of sorption of uranyl ions on HDTMA-red clay in the presence of phosphates were characterized by thermal analysis. It was established on the basis of DTG curves of the sorption products and FTIR spectra of the gaseous phase of sorption products decomposition that the thermal stability of the mineral increased when P(V) ions were sorbed along with U(VI) ions, i.e., the temperature of defragmentation/oxidation of surfactant increased when going from U(VI)–HDTMA-clay to U(VI)–P(V)–HDTMA-clay to P(V)–HDTMA-clay. The DSC curves of the sorption products showed that defragmentation/oxidation was an exothermic process and dehydration and dehydroxylation had an endothermic character. The investigated sorption system has practical importance, since an evident increase in U(VI) sorption over the entire pH range is observed when going from U(VI)–HDTMA-clay to U(VI)–P(V)–HDTMA-clay.