Synthesis,characterization, and thermal study of solid-state alkaline earth metal mandelates,except beryllium and radium

Characterization, thermal stability, and thermal decomposition of alkaline earth metal mandelates, M(C₆H₅CH(OH)CO₂)₂, (M = Mg(II), Ca(II), Sr(II), and Ba(II)), were investigated employing simultaneous thermogravimetry and differential thermal analysis or differential scanning calorimetry, (TG–DTA or TG–DSC), infrared spectroscopy (FTIR), complexometry, and TG–DSC coupled to FTIR. All the compounds were obtained in the anhydrous state and the thermal decomposition occurs in three steps. The final residue up to 585 °C (Mg), 720 °C (Ca), and 945 °C (Sr) is the respective oxide MgO, CaO, and SrO. For the barium compound the final residue up to 580 °C is BaCO₃, which is stable until 950 °C and above this temperature the TG curve shows the beginning of the thermal decomposition of the barium carbonate. The results also provide information concerning the thermal behavior and identification of gaseous products evolved during the thermal decomposition of these compounds.     

Effect of the thermal treatment conditions on the formation of zinc ferrite nanocomposite, ZnFe2O4, by sol–gel method

Zinc ferrite nanocomposite was synthesized via thermal decomposition of zinc acetate and iron nitrate at three different temperatures (350, 450, and 550 °C). The influence of the thermal decomposition of precursors on the formation zinc ferrites was studied by differential thermal gravimetry and thermogravimetry (TG). The TG curve shows two steps for the thermal decomposition with mass loss of 17.3 % at 78 °C and 63.3 % at 315 °C. The prepared zinc ferrites nanocomposite was characterized by X-ray diffraction and scanning electron microscopy. The X-ray diffractograms of ZnFe₂O₄ shows that a crystalline phase, spinel system is formed. SEM micrograph of the zinc ferrite nanocomposite indicates the formation of uniformly spherical 48-nm nanograins. The properties of the zinc ferrite phase were strongly dependent on their calcinations temperature and molar ratio of precursors.     

Effect of the antioxidants on the stability of poly(vinyl butyral) and kinetic analysis

The effect of several kinds of antioxidants on the stability of poly(vinyl butyral) (PVB) under air atmosphere is studied by thermogravimetry–differential scanning calorimetry method and kinetic analysis. After mixed with antioxidants, the thermal oxidative stability of PVB increases significantly, because the antioxidants could inhibit the oxidation of copolymer (stage I). The thermal oxidative stability increases in the following order: PVB < PVB/1010 < PVB/B215 < PVB/1098. However, the thermal oxidative degradation rate of PVB increases markedly after 320 °C, due to the loss of chemical activity for antioxidants gradually. The thermal stability of antioxidants increases in the following order: B215 < 1010 < 1098.     

Study of the thermal behavior of bicuíba oil (Virola bicuhyba)

Bicuíba belongs to the Virola bicuhyba (Schott ex Spreng.) Warb species, Miristicaceas (Myristicaceae) family, which is frequently found in the Atlantic Forest of South and Southeast Brazil. Extraction of the Bicuíba oil was carried out and characterized by gas chromatography. The composition of in nature of this oil indicates that there is a predominance of saturated fatty acids with ~35 % lauric acid and ~40 % myristic acid. Details concerning the thermal behavior were evaluated by thermogravimetry, differential thermal analysis, and differential scanning calorimetry under oxygen and nitrogen atmospheres, showing thermal stability between 208 and 210 °C, respectively. Additionally, the kinetic studies were evaluated from several heating rates with a sample mass of 5 and 20 mg in open crucibles. The obtained data were evaluated with the isoconversional method kinetic, where the values of activation energy (E _a/kJ mol^?1) were plotted in function of the conversion degree (α).     

Thermal stability of nanocrystalline ε-Fe2O3

Thermal behavior of highly crystalline ε-Fe₂O₃ nanoparticles of different apparent crystallite sizes was characterized using thermogravimetry, differential thermal analysis, and analysis of evolved gas by mass spectrometry. Phase composition of the samples was monitored ex situ by X-ray powder diffraction. The results show that the thermal stability of this metastable iron oxide polymorph decreases with increasing particle size. For the particle diameter of 19(2) nm, the transformation temperature was equal to 794(5) °C, while for 28(2) nm only 755(10) °C. Surface of the nanoparticles contained adsorbed water and carbon dioxide. Elimination of these species proceeds in two steps. Water is removed at temperatures below 200 °C and CO₂ in the temperature range between 200 and 450 °C.     

Thermal behavior of coffee oil (Robusta and Arabica species)

Coffee seeds are a source for obtaining oil which is used in the candy, soluble coffee, and cosmetics industries. The main purpose of this study was the investigation of the lipid profile and thermal behavior of the roasted and in nature coffee oil of Arabica and Robusta species, using thermogravimetry, differential thermal analysis, derivative thermogravimetry, differential scanning calorimetry (DSC), and modulated DSC. Details concerning the thermal decomposition as well as data of the kinetic parameters have been described here. The kinetic studies were evaluated from several heating rates with a sample mass of 10 mg in open crucible under nitrogen atmospheres. The obtained data were evaluated with the isoconversional kinetic method, where the values of activation energy (E _a/kJ mol^?1) were evaluated in function of the conversion degree (α). In addition, this oil was evaluated by modulated DSC from 25 to ?60 °C, where the transition phase behavior was verified.     

Catalytic effect analysis of metallic additives on light crude oil by TG and DSC tests

This research aimed at the investigation of the effect of different metallic additive on the combustion and kinetic behavior of crude oil. For this purpose, the thermal behavior of the oil-only and oil–metallic salts mixtures were studies by the thermogravimetry (TG)/derivative thermogravimetry and differential scanning calorimetry (DSC) on heating rate at 10 °C min^?1. The result shows that Dagang crude oil exhibited apparent low temperature oxidation (LTO), fuel deposition, and high temperature oxidation processes. With the addition of metallic salts, the LTO process has been shortened and samples added CuSO₄, CrCl₃·6H₂O, and AlCl₃·6H₂O achieved a much lower peak temperature than that of oil. Based on the Arrhenius model, metallic additives were proven to have obvious influence on the combustion activation energy. And, by comprehensive analysis of TG/DSC profile and activation energy, ZnSO₄ exhibited a positive influence on light crude oil combustion during the high pressure air injection process.     

Thermal analysis and Hot-stage Raman spectroscopy of the basic copper arsenate mineral

The thermal analysis of euchroite shows two mass loss steps in the temperature range 100–105 °C and 185–205 °C. These mass loss steps are attributed to dehydration and dehydroxylation of the mineral. Hot-stage Raman spectroscopy (HSRS) has been used to study the thermal stability of the mineral euchroite, a mineral involved in a complex set of equilibria between the copper hydroxy arsenates: euchroite Cu₂(AsO₄)(OH)·3H₂O → olivenite Cu₂(AsO₄)(OH) → strashimirite Cu₈(AsO₄)₄(OH)₄·5H₂O → arhbarite Cu₂Mg(AsO₄)(OH)₃. HSRS inolves the collection of Raman spectra as a function of the temperature. HSRS shows that the mineral euchroite decomposes between 125 and 175 °C with the loss of water. At 125 °C, Raman bands are observed at 858 cm^?1 assigned to the ν₁ AsO₄ ^3? symmetric stretching vibration and 801, 822, and 871 cm^?1 assigned to the ν₃ AsO₄ ^3? (A₁) antisymmetric stretching vibrations. A distinct band shift is observed upon heating to 275 °C. At 275 °C, the four Raman bands are resolved at 762, 810, 837, and 862 cm^?1. Further heating results in the diminution of the intensity in the Raman spectra, and this is attributed to sublimation of the arsenate mineral. HSRS is the most useful technique for studying the thermal stability of minerals, especially when only very small amounts of mineral are available.     

Study of the Thermal Stability Properties of Pyridoxine Using Thermogravimetric Analysis

The thermal decomposition behavior and kinetics of pyridoxine in nitrogen-only and air atmospheres were studied using thermogravimetry analysis (TGA). Kinetic interpretation of thermal analysis data for pyridoxine decomposition was carried out using Ozawa and ASTM E698 isoconversional methods. The activation energy of the decomposition process varied with the degree of decomposition and was different in the nitrogen and air atmospheres. At a 5% decomposition level, the activation energy and the pre-exponential factor were found to be 28.3 kcal mol^?1 and 1.2 × 10¹⁴ min^?1, respectively, in the nitrogen-only atmosphere. Thermal stability was determined by calculating the time for 5% of the pyridoxine vitamer to decompose at 25°C. The calculated shelf life for the pyridoxine vitamer obtained via TGA was surprisingly smaller in nitrogen (0.9 years) than in air (1.5 years). This is speculated to be the result of a more complex decomposition mechanism in air, involving thermo-oxidative decomposition in the presence of oxygen.     

Thermal stability of soil organic matter was affected by 23-yr maize and soybean continuous cultivation in northeast of China

Long-term continuous cropping affects the biochemical quality of soil organic matter (SOM), but whether the effects are relevant with their thermal stability is less clear. In northeast China, long-term continuous cropping occurred frequently owing to higher yield and economic interest requirement. To verify the thermal stability properties of SOM affected by the long-term continuous cropping, the study focused on 23-yr continuous cultivated maize and soybean plots, where the effect of cropping is likely to be detected. Bulk soils sampled in 1991 and 2014 were studied by thermogravimetry and differential scanning calorimetry (DSC). The results showed typical bimodal peaks in DSC curve in bulk Mollisols. A labile fraction peak was observed at 354–366 °C low-temperature zone and recalcitrant fraction one at high temperature of 430–438 °C. Energy density (J mg^?1 OM) was greater in soybean plots compared to maize plots; in contrast, long-term continuous maize cultivation also increased energy density, in reverse in soybean plots after 23-yr cultivation. The DSC-T₅₀, temperature at which half of energy release occurred, typically showed larger responses to long-term cultivation than crop species. Results obtained support the hypothesis of a potential link between long-term continuous cropping and the thermal stability of SOM, and a correlation with crop species.     

Thermal and spectroscopic characterization of nanostructured zirconia–scandia–dysprosia

Zirconia containing 10 mol% scandia and x mol% dysprosia (0 ≤ x ≤ 1.5) gels was synthesized by simultaneous precipitation at room temperature. The aim of this work is to verify the effect of dysprosium on the cubic phase stabilization of the zirconia–scandia solid electrolyte. The gel was characterized by thermogravimetry, differential scanning calorimetry, and differential thermal analyses. The thermally treated powders were analyzed by Fourier transform infrared spectroscopy, thermal analyses, and X-ray diffraction techniques. For comparison purpose, a commercial zirconia–10 mol% scandia powder was subjected to some characterization techniques. The infrared spectrum shows characteristic absorption bands due to residual material from the synthesis on the surface of the powder particles. Nanostructured powders were obtained after thermal treatments at 500 °C for 2 h. Infrared spectroscopy and X-ray diffraction results evidence the stabilization of the cubic phase in zirconia–scandia containing dysprosium. The thermal stability of the cubic phase during thermal cycling was ascertained by thermal analysis.     

Stability and physical structure tests of piperidyl and morpholinyl derivatives of diphenyl-diketo-pyrrolopyrroles (DPP)

Crystalline structure, thermo-oxidative and thermal stability of symmetrical and asymmetrical piperidyl and morpholinyl derivatives of both N-substituted and non-N-substituted butyl diphenyl-diketo-pyrrolopyrrole (DPP) pigments were studied using differential scanning calorimetry (DSC) and thermogravimetry (TG). Except for the asymmetrical morpholine DPP derivative, all the samples showed melting peaks which were relatively close to their degradation temperatures (from 260 to 430 °C). Using DSC, monotropic polymorphism was revealed in the symmetrical piperidyl-N-butyl-derivative which confirmed earlier observation about tendency of symmetrical N-alkyl DPP derivates to form several crystalline structures. TG carried out under nitrogen atmosphere served for distinguishing of evaporation/sublimation and degradation temperatures. Temperatures of evaporation/sublimation were typically 10–30 °C lower in comparison with temperatures of thermal degradation. The highest thermal (450 °C) and thermo-oxidative stability (around 360 °C) showed the DPP derivatives containing morpholine moieties with no alkyl substitution on NH-group of DPP core. The presence of the latter was found to be the most destabilizing factor. Piperidyl group showed more stabilizing effect due to its polar character and its influence on π–π intermolecular interactions of neighbouring phenyl groups. The highest stabilizing effect of morpholine moiety on DPP structure was explained based on the presence of polar oxygen atom in that group. The preparations of 3,6-di-(4-morpholinophenyl)-2,5-dihydro-pyrrolo[3,4-c]pyrrole-1,4-dione and 3-(phenyl)-6-(4-morpholinophenyl)-2,5-dihydropyrrolo[3,4-c]pyrrole-1,4-dione are reported.     

Synthesis and Characterization of a New Energetic Plasticizer: Acyl-Terminated GAP

A new energetic plasticizer, acyl-terminated glycidyl azide polymer (GAP), was synthesized through the reaction between 2,4,6-trinitrobenzoyl (TNB) chloride and GAP. The TNB-GAP structure was confirmed by FT-IR, UV-vis, ¹H NMR, and ¹³C NMR. The glass transition temperature (T _g ) of TNB-GAP was evaluated by differential scanning calorimetry (DSC), and the thermal stability of TNB-GAP was tested by thermogravimetric analysis (TGA). DSC traces showed that TNB-GAP had a T _g of ?46.01°C. TGA curves showed that the thermo-oxidative degradation of TNB-GAP in air was a two-step reaction, and the percentage of degraded TNB-GAP nearly reached 100% at 650°C. Exothermic decomposition reaction kinetic parameters of TNB-GAP were also studied using the non-isothermal DSC method. Results indicated that the values of apparent activation energy of TNB-GAP were 80.16 and 162.92 kJ/mol, and the values of the pre-exponential constant were 1.75 × 10¹⁰ and 1.22 × 10¹⁶.     

Measurement of thermo-oxidative stability of isotactic polypropylene by isothermal long-term differential thermal analysis

The thermo-oxidative stability of isotactic polypropylene with different antioxidant concentrations between 0% and 0·1% has been studied using isothermal long-term differential thermal analysis (ILDTA). In the temperature range from 90°C to 210°C the oxidation maximum times were measured up to 2000 h. The Arrhenius plot of the reaction maxima showed straight lines over the whole temperature range, which were not affected by the crystallite melting range. Thus, extrapolations from short-term experiments at elevated temperatures to long-term behaviour at lower temperatures are possible.Ageing tests in a circulating-air oven at 140°C showed that the loss of thermo-oxidative stability with increasing ageing time was nearly linear. So the state of thermo-oxidative deterioration of isotactic polypropylene can be estimated by measurement of residual life time in an ILDTA experiment.The end of the oven life of polypropylene coincided with the loss of mechanical properties which was confirmed by a long-term tensile test at 100°C and 120°C.     

Effect of acid-treated multi-walled carbon nanotubes on thermo-oxidative stability and degradation behavior of silicone rubber

The effect of acid-treated multi-walled carbon nanotubes (MWCNTs) on thermo-oxidative stability and degradation behavior of silicone rubber (SR) was evaluated. Raman microscopy, Fourier transformed infrared spectroscopy, X-ray photoelectron spectroscopy and thermogravimetric (TG) analysis were performed to characterize the surface states of MWCNTs samples. The results demonstrated that after acid treatment the nanodefects and surface oxygen-containing groups (mainly hydroxyl and carboxyl groups) were formed and the number of them was gradually increased by increasing the treatment time. Then these MWCNTs were embedded into SR matrix. Furthermore, the thermo-oxidative stability and degradation behavior of MWCNTs/SR composites were studied using thermogravimetric/infrared spectrometry (TG-IR). Thermo-oxidative stability test in air revealed that the degradation of SR, at relatively low temperature, was mainly due to the oxidation of Si-CH₃ side groups and the generation of free radicals. This behavior was hindered by the MWCNTs’ surface nanodefects and hydroxyl groups, as proved by TG-IR study which revealed that the amount of carbonyl compounds was reduced more than 60%, compared with that of neat SR. Therefore, acid treatment led a better thermo-oxidative stability of MWCNTs/SR. For 4hAT-MWCNTs/SR, with maximum hydroxyl groups on MWCNTs surface, the T_i (defined as the temperature for 5% mass loss) of it is increased by 34.8 °C compared to that of neat SR, and even increased by 18.5 °C compared with that of raw-MWCNTs/SR.     

Thermo-oxidative decomposition of biodiesel samples obtained from mixtures of beef tallow,soybean oil,and babassu oil

Biodiesel can be obtained from various fatty acid sources. Each raw material has a different chemical composition that leads to different properties. Owing to these properties, the mixture of different proportions of raw materials can lead to biodiesels with best features in relation to physicochemical parameters such as viscosity, oxidative stability and flow properties, generating a fuel whose characteristics meet the requirements of the current legislation of the Brazilian National Agency of Petroleum, Natural Gas and Biofuels (ANP). The objective of this study was to determine the physicochemical properties of biodiesel samples produced from mixtures of beef tallow, babassu oil, and soybean oil. The thermo-oxidative stability was evaluated using thermogravimetry (TG/DTG) and differential scanning calorimetry (DSC). The results showed that all samples were in accordance to the ANP specifications. The biodiesel obtained from a mixture containing 50% of babassu oil had lower values of pour point, cold filter plugging point, and freezing point. This biodiesel also showed a higher thermo-oxidative stability in synthetic air and in oxygen atmospheres.     

Interrelations between soil respiration and its thermal stability

Biological transformation of organic matter in soil is a crucial factor affecting the global carbon cycle. In order to understand these complex processes, soils must be investigated by a combination of various methods. This study compares the dynamics of biological mineralization of soil organic matter (SOM) determined via CO₂ evolution during an 80-day laboratory incubation with their thermo-oxidative stability determined by thermogravimetry (TG). Thirty-three soil samples, originating from a wide range of geological and vegetation conditions from various German national parks were studied. The results showed a correlation between the amount and rate of respired CO₂ and thermal mass losses of air-dried, conditioned soils occurring around 100?°C with linear coefficients of determination up to R ²?=?0.85. Further, correlation of soil respiration with thermal mass losses around 260?°C confirmed previous observations. The comparison of TG profiles from incubated and non-incubated soils underlined the importance of thermal mass losses in these two temperature intervals. Incubated soils had reduced thermal mass losses above 240?°C and conversely an increased mass loss at 100?C120?°C. Furthermore, the accurate determination of soil properties by TG such as soil organic carbon content was confirmed, and it was shown that it can be applied to a wider range of carbon contents as was previously thought. It was concluded that results of thermal analysis could be a helpful starting point for estimation of soil respiration and for development of methods revealing processes in soils.     

Evolved gas analysis of coal-derived pyrite/marcasite

The products evolved during the thermal decomposition of the coal-derived pyrite/marcasite were studied using simultaneous thermogravimetry coupled with Fourier-transform infrared spectroscopy and mass spectrometry (TG-FTIR–MS) technique. The main gases and volatile products released during the thermal decomposition of the coal-derived pyrite/marcasite are water (H₂O), carbon dioxide (CO₂), and sulfur dioxide (SO₂). The results showed that the evolved products obtained were mainly divided into two processes: (1) the main evolved product H₂O is mainly released at below 300 °C; (2) under the temperature of 450–650 °C, the main evolved products are SO₂ and small amount of CO₂. It is worth mentioning that SO₃ was not observed as a product as no peak was observed in the m/z = 80 curve. The chemical substance SO₂ is present as the main gaseous product in the thermal decomposition for the sample. The coal-derived pyrite/marcasite is different from mineral pyrite in thermal decomposition temperature. The mass spectrometric analysis results are in good agreement with the infrared spectroscopic analysis of the evolved gases. These results give the evidence on the thermal decomposition products and make all explanations have the sufficient evidence. Therefore, TG–MS–IR is a powerful tool for the investigation of gas evolution from the thermal decomposition of materials.     

Thermal decomposition and kinetics studies on the 2,2-dinitropropyl acrylate–styrene copolymer and 2,2-dinitropropyl acrylate–vinyl acetate copolymer

In the present work, kinetics of thermal decomposition of 2,2-dinitropropyl acrylate–styrene copolymer (DNPA/St) and 2,2-dinitropropyl acrylate–vinyl acetate copolymer (DNPA/VAc) was investigated by differential scanning calorimetry (DSC). The influence of the heating rate (5, 10, 15, and 20 °C min^?1) on the DSC behavior of the copolymer was verified. The results showed that, as the heating rate was increased, decomposition temperature of the copolymer was increased. Also, the kinetic parameters such as activation energy and frequency factor of the copolymer were obtained from the DSC data by the isoconversional methods proposed by Kissinger–Akahira–Sunose (KAS) and Flynn–Wall–Ozawa (FWO). Average activation energy obtained by KAS and FWO methods for the thermal decomposition reaction of DNPA/St and DNPA/VAc are 157.38 ± 0.27 and 147.67 ± 0.57 kJ mol^?1, respectively. The rate constants for thermal decomposition calculated from the activation parameters showed the structural dependency. The relative stability of two copolymers under 50 °C was in this order: DNPA/St > DNPA/VAc. The results of thermogravimetry (TG) analysis revealed that the main mass changes for DNPA/St and DNPA/VAc occurred in the temperature ranges of 200–270 °C. The DSC-FTIR analysis of DNPA/St indicates that the band intensity of nitro and other groups increased haphazardly from 230 °C due to thermal decomposition.     

Compatibility study between ibuprofen and excipients in their physical mixtures

The thermal techniques of analysis were used to assess the compatibility between ibuprofen (IB) and some excipients used in the development of extended released formulations. This study is a part of a systematic study undertaken to find and optimizes a general method of detecting the drug–excipient interactions, with the aim of predicting rapidly and assuring the long-term stability of pharmaceutical product and speeding up its marketing. The thermal properties of IB and its physical association as binary mixtures with some common excipients were evaluated by thermogravimetry/derivative thermogravimetry (TG/DTG) and differential scanning calorimetry. FT-IR spectroscopy and X-ray powder diffraction (XRPD) were used as complementary techniques to adequately implement and assist in interpretation of the thermal results. Based on their frequent use in preformulations nine different excipients: starch; microcrystalline cellulose (PH 101 and PH 102); colloidal silicon dioxide; lactose (monohydrate and anhydre); polyvinylpyrrolidone; magnesium stearate and talc were blended with IB. The samples were prepared by mixing the analyte and excipients in a proportion of 1:1 (w:w). The TG/DSC curves of the IB have shown a single stage of mass loss between 175 and 290 °C, respectively, an endothermic peak at 78.5 °C, which corresponds to the melting (literature T _m = 75–78 °C).