Thermogravimetry And Differential Thermal Analysis Research Articles

The status of zaratite: investigation of the type specimen from Cape Ortegal, Galicia, Spain

Three zaratite samples from Cape Ortegal (type locality, Spain), Texas, Lancaster County (Pennsylvania) and Heazlewood (Tasmania) were analyzed by electron-probe micro-analysis (EPMA), environmental scanning electron microscopy with energy-dispersive spectrometer (ESEM-EDS), X-ray diffraction (XRD), differential thermal analysis and thermogravimetry (DTA-TG), micro-Raman and Fourier-transform infrared spectrometry (FTIR). The empirical formulae calculated from EPMA exhibit different molar ratios (Ni/CO3, Ni/OH and H 2 O/Ni), showing that these three samples referred to as ‘zaratite’ are chemically distinct; they are actually close to either anhydrous zaratite (Ortegal), nullaginite (Tasmania) or gaspeite (Pennsylvania). The XRD patterns of the three samples only validate their low-crystallinity character with variable mineral inclusions. Raman and FTIR spectra confirm large similarities among the three samples, in line with the general chemical kinship of these nickel hydroxycarbonate (± hydrate) materials. Our data suggest that the natural nickel hydroxycarbonate materials, collectively referred to as ‘zaratite’ on the basis of colour, occurrence and poor crystallinity, are in fact so diverse in terms of Ni/C/H ratios that the ‘zaratite’ term should not deserve a species status and so remains highly questionable.

Niflumic Anion Intercalated Layered Double Hydroxides with Mechano-Induced and Solvent-Responsive Luminescence

Stimuli-responsive luminescent materials play an important role in fluorescent switches, optical storage devices and smart sensors. In this work, we report a mechano-induced and solvent stimuli-responsive luminescent change by the assembly of a typical aggregation-induced-emissive (AIE) molecule, niflumic acid (NFC), into the interlayer region of Zn–Al-layered double hydroxides (LDHs) with heptanesulfonate (HPS) as a cointercalation guest. The structure, chemical composition, and thermostability of the as-prepared NFC-HPS/LDHs composites were characterized by X-ray diffraction, elemental analysis, and thermogravimetry and differential thermal analysis (TG-DTA). Fluorescence spectra demonstrate that the sample with 5% NFC initial molar percentage, with respect to the interlayer guests, exhibits the optimal luminescent intensity. The NFC-HPS/LDH (5%) sample also exhibits the most obvious luminescent mechano-response with a 16 nm blue-shift and increase in the fluorescent intensity after grinding, while the ...

Synthesis and Electrochemical Properties of Co Doped MnO2 Framework with Nanofibrous Structure

Porous MnO2/Co composites with regular ellipse shape were synthesized through a facile hydrothermal‐decomposition method. Coembedded manganese oxalate precursors were firstly synthesized by a hydrothermal process. Then, Mn2O3/Co composites were obtained by a following precisely controlled decomposition process. After a further oxidation reaction, nanofibrous MnO2/Co composites were formed with well‐retained ellipse microframework inherited from precursors. X‐ray diffractometer (XRD), thermogravimetry and differential thermal analysis (TG‐DTA), field‐emission scanning electron microscope (FESEM), and energy dispersive spectroscope (EDS) were used to characterize the composition, structure, and morphology of all the samples. The electrochemical properties of MnO2/Co were studied using cyclic voltammetry and galvanostatic charge–discharge test in 1.0 mol/L Na2SO4 electrolyte. Doping of Co in an appropriate range can improve the electrochemical performance of MnO2.

Impact of mesoporous structure of acid-treated clay on nickel dispersion and carbon deposition for CO methanation

Nickel catalysts supported on different acid-treated clays were prepared by the impregnation method in order to investigate the effect of the pore structures of supports on the dispersion and the chemical states of nickel species, and thus on the carbon depositions resulted from the dissociation of the CO molecules adsorbed on different active nickel sites. The catalysts and supports were characterized by the X-ray diffraction (XRD), the transmittance electron microscopy (TEM), the H2 temperature-programmed reduction (H2-TPR), the nitrogen adsorption–desorption, and the thermogravimetry and differential thermal analysis (TG-DTA). The CO methanation performance of the catalyst was investigated at a temperature range from 300 °C to 500 °C. The results indicated that the dispersion and the states of the nickel species on the support were influenced strongly by the pore structures of the acid-treated clays, and only the mesopores composed by partly damaged clay layers were conducive to forming the active nickel species, and thus reducing the deposition of the inactive carbon and improving the stability of the catalyst. The carbon species deposited on different active sites was slightly different in the oxidative properties when it was oxidized in air. A fraction of aluminum in the clays was leached out by acid, which decreased the possibility of forming the spinel phase of nickel aluminate in the catalyst. The highly dispersed nickel species showed little relevance to the high activity of the catalyst, but it exhibited a strong relation to the nickel sites from the bulk nickel species.

Preparation of Phase‐Pure K0.5Na0.5NbO3 Fine Powders by a Solid‐State Reaction at 625°C from a Precursor Comprising Nb2O5 and K,Na Acetates

Phase‐pure K0.5Na0.5NbO3 (KNN) fine powders were synthesized via a solid‐state route from a homogeneous solid mixture. A colloidal dispersion comprising a mixed ethanol solution of potassium and sodium acetates and Nb2O5 fine particles was attrition milled and dried carefully to avoid water absorption. Two‐step calcination in air at 450°C and 625°C, each for 3 h, resulted in the phase‐pure KNN powders. The volume‐based median diameter of the final product was ca. 0.8 μm. Starting from the same precursors without dissolving the acetates, the phase‐pure KNN was never achieved even when the two calcination temperatures were increased to 550°C and 700°C, in spite of the same milling conditions. Key issues of eliminating second phases were (i) starting from a wet‐milled mixture with a single solution containing both of the A‐site species, and (ii) repeated wet milling of the reaction mixture to disintegrate reaction‐induced agglomerates. These enabled rapid nuclei growth from chemically interacted precursor prior to calcination, and short diffusion path due to repeated deagglomeration, excluding formation of off‐stoichiometric second phases. All these items were confirmed by different analytical tools, among others, thermo‐gravimetry and differential thermal analysis (TG‐DTA), particle size analyses, and XPS at various reaction stages. On the heating stage microscope, a shrinkage onset was observed at 850°C, that is, 150 K lower than that of conventionally prepared KNN, that is, via a solid‐state synthesis from carbonates by a two‐step calcination at 800°C and 750°C, for 4 h each. No second phase was observed after sintering up to 1100°C.

Phase Transformation and Morphology of Calcium Phosphate Prepared by Electrochemical Deposition Process Through Alkali Treatment and Calcination

The phase transformation and morphology of calcium phosphate prepared by the electrochemical deposition (ECD) process through alkali treatment and calcination have been characterized using X-ray diffraction (XRD), thermogravimetry and differential thermal analyses (TG/DTA), and scanning electron microscopy (SEM). At the ECD process, when the excess OH− was produced, the reaction of 10Ca2++6PO43−+2OH–→Ca10(PO4)6(OH)2 takes place on the Ti-6Al-4V and the HA is deposited. The XRD results reveal that the as-deposit was mostly composed of dicalcium phosphate dehydrate (Ca2H4P2O9; DCPD) and the minor phase of hydroxyapatite (Ca10(PO4)6(OH)2; HA). After NaOH treatment, all DCPD were converted to HA. Moreover, the content of HA phase increases with ECD potential. After being calcined at 673 K and 873 K (400 °C and 600 °C) for 4 hours, the phase of HA maintained the major phase for an alkali-treated deposited sample. After being calcined at 1073 K (800 °C) for 4 hours, some HA decomposed and caused the minor phases of β-tricalcium phosphate (β-Ca3(PO4)2; β-TCP), calcium pyrophosphate (Ca2P2O7; CPP), and calcium oxide (CaO) formation. The β-TCP becomes the major phase with residual HA and CaO after being calcined at 1273 K (1000 °C) for 4 hours. The crack forms due to the release of absorbed water from the interior to top surface of sample. For the as-alkali treatment samples, the microstructures were affected by ECD potentials; when the deposited samples after alkali treatment and calcined at 1073 K (800 °C) for 4 hours, the microstructure presents the need-like “preforming HA” (pre-HA) from the matrix of plate-like postforming HA (post-HA).

Thermal and spectroscopic studies on solid ibuprofen complexes of lighter trivalent lanthanides

Solid-state compounds of general formula Ln(L)3, in which L is ibuprofen and Ln stands for trivalent La, Ce, Pr, Nd, Sm and Eu, have been synthesized. Simultaneous thermogravimetry and differential thermal analysis (TG-DTA), X-ray powder diffractometry (DRX), complexometry, Fourier-transformed infrared spectroscopy (FTIR) and thermogravimetry coupled to Fourier-transformed infrared spectroscopy (TG-FTIR) were used to characterize these compounds. The results provided information concerning the chemical composition, dehydration, coordination modes of the ligands, crystallinity of the samples, thermal behavior and thermal decomposition of the compounds. The theoretical and experimental spectroscopic studies suggest that ibuprofen coordinates through the carboxylate group as a chelating ligand.

Effect of Surfactant on the Preparation of Nano-powder for Yb Doping Laser Transparent YAG Ceramic

AbstractYb:YAG transparent ceramic nano-powder was prepared by chemical co-precipitation method, with ammonium bicarbonate as the precipitant and polyethylene glycol as surfactant. The addition of polyethylene glycol can reduce the agglomeration and particle size of the prepared Yb:YAG powder. The morphology, thermal stability and phase structure of Yb:YAG nano-powder were charactered by scanning electron microscopy (SEM), thermogravimetry and differential thermal analysis (TG-DTA), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy. The results show that well-crystallized nano-powder was obtained by calcining the precursors at 900 °C for 3 h. The average particle size of Yb:YAG powder is about 100–200 nm. When the volume amount of polyethylene glycol is 2.0%, well-dispersed Yb:YAG powder with spherical particles of 100 nm diameter was obtained.

Nickel on a macro-mesoporous Al2O3@ZrO2 core/shell nanocomposite as a novel catalyst for CO methanation

A novel nickel catalyst supported on Al2O3@ZrO2 core/shell nanocomposites was prepared by the impregnation method. The core/shell nanocomposites were synthesized by depositing zirconium species on boehmite nanofibres. This contribution aims to study the effects of the pore structure of supports and the zirconia dispersed on the surface of the alumina nanofibres on the CO methanation. The catalysts and supports were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), H2 temperature-programmed reduction (H2-TPR), nitrogen adsorption–desorption, and thermogravimetry and differential thermal analysis (TG-DTA). The catalytic performance of the catalysts for CO methanation was investigated at a temperature range from 300 °C to 500 °C. The results of the characterization indicate that the metastable tetragonal zirconia could be stably and evenly dispersed on the surface of alumina nanofibres. The interlaced nanorods of the Al2O3@ZrO2 core/shell nanocomposites resulted in a macropore structure and the spaces between the zirconia nanoparticles dispersed on the alumina nanofibres formed most of the mesopores. Zirconia on the surface of the support promoted the dispersion and influenced the reduction states of the nickel species on the support, so it prevented the nickel species from sintering as well as from forming a spinel phase with alumina at high temperatures, and thus reduced the carbon deposition during the reaction. With the increase of the zirconia content in the catalyst, the catalytic performance for the CO methanation was enhanced. The Ni/Al2O3@ZrO2-15 exhibited the highest CO conversion and methane selectivity at 400 °C, but they decreased dramatically above or below 400 °C due to the temperature sensitivity of the catalyst. Ni/Al2O3@ZrO2-30 exhibited a high and constant rate of methane formation between 350 °C and 450 °C. The excellent catalytic performance of this catalyst is attributed to its reasonable pore structure and good dispersion of zirconia on the support. This catalyst has great potential to be further studied for the future industrial use.

The influence of structure order on the kinetics of dehydroxylation of kaolinite

Abstract The structural order of kaolinite is an important factor that shows a substantial effect on the processes which take place during the thermal treatment of kaolin. The influence of structural order on the dehydroxylation process was investigated by simultaneous thermogravimetry and differential thermal analysis (TG-DTA). The thermal analysis was performed on the samples with gradually decreasing structural order prepared by milling procedure. The apparent activation energy of dehydroxylation process decreases with decreasing structural order according to the exponential function. The extrapolation of experimental data leads to the estimation of apparent activation energy of 76.6 kJ mol −1 and of frequency factor of 0.12 × 10 4 s −1 related to completely disordered form of kaolinite, while the ordered form shows the apparent activation energy of 216.17 kJ mol −1 and the frequency factor of 9.26 × 10 4 s −1 . The relationships between features such as the infrared pattern of treated material, the degree of structural order and the apparent activation energy were established.

Nanocrystalline Cu0.5Zn0.5Fe2O4: Preparation and Kinetics of Thermal Decomposition of Precursor

Cu0.5Zn0.5Fe2O4 precursor was synthesized by solid-state reaction at low heat using CuSO4⋅5H2O, ZnSO4⋅7H2O, FeSO4⋅7H2O, and Na2CO3⋅10H2O as raw materials. The spinel Cu0.5Zn0.5Fe2O4 was obtained via calcining precursor above 600 ∘C. The precursor and its calcined products were characterized by thermogravimetry and differential thermal analyses (TG/DTA), Fourier transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectrometer (EDS), and vibrating sample magnetometer (VSM). The result showed that highly crystallization Cu0.5Zn0.5Fe2O4 was obtained when the precursor was calcined at 600 ∘C for 2 h. Magnetic characterization indicated that calcined products above 600 ∘C behaved with strong magnetic properties. The kinetics of the thermal decomposition of the precursor was studied using the TG technique. Based on the KAS equation, the values of the activation energy for the thermal decomposition of the precursor were determined.

Preparation, Characterization of Dawson-type Heteropoly Acid Cerium (III) Salt and Its Catalytic Performance on the Synthesis of n-Butyl Acetate

A novel cerium (III) salt of Dawson type tungstophosphoric acid (Ce2P2W18O62·16H2O) was prepared by doping cerous nitrate in H6P2W18O62·13H2O powder and characterized by thermogravimetry and differential thermal analyses (TG/DTA), Fourier transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), pyridine infrared spectroscopy (Py-IR) and scanning electron microscopy (SEM). Its catalytic activity was evaluated by the probe reaction of synthesis of n-butyl acetate with acetic acid and n-butanol. The effects of various parameters such as molar ratio of n-butanol to acetic acid, reaction temperature, reaction time, and catalyst amount have been studied by single factor experiment. The results show that Ce2P2W18O62·16H2O behaved as an excellent heterogeneous catalyst in the synthesis of n-butyl acetate. The optimum synthetic conditions were determined as follows : molar ratio of n-butanol to acetic acid at 2.0: 1.0, mass of the catalyst being 1.44% of the total reaction mixture, reaction temperature of 120 °C and reaction time of 150 min. Under above conditions, the conversion of acetic acid was above 97.8%. The selectivity of n-butyl acetate based on acetic acid was, in all cases, nearly 100%. The catalysts could be recycled and still exhibited high catalytic activity with 90.4% conversion after five cycles of reaction. It was found by means of TG-DTA and Py-IR that the catalyst deactivation was due to the adsorption of a complex of by-product on the active sites on catalysts surface or the catalyst loss in its separation from the products. Compared with using sulfuric acid as catalyst, the present procedure with Ce2P2W18O62·16H2O is a green productive technology due to simple process, higher yield, catalyst recycling and no corrosion for the production facilities.

Preparation YbFeO<sub>3</sub> by Microwave Assisted Method and its Visible-Light Photocatalytic Activity

Using Yb(NO3)3•6H2O and Fe(NO3)3•9H2O as raw material, the YbFeO3 nanoparticles were synthesized by microwave assisted method. The YbFeO3 nanoparticles were characterized by thermogravimetry and differential thermal analysis (TG-DTA), powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV-visible diffuse reflectance spectroscopy (DRS). It was found that the prepared YbFeO3 show an average grain size of 80 nm in diameter, and strong visible-light absorption with absorption onset of 608 nm, indicating a narrow optical band gap of 2.04eV. Consequently, the YbFeO3 nanoparticles show high photocatalytic activity for decomposition of methylene blue under visible-light irradiation.

Electron microscopy analyses and electrical properties of the layered Bi2WO6 phase

Abstract The bismuth tungstate Bi 2 WO 6 was synthesized using a classical coprecipitation method followed by a calcination process at different temperatures. The samples were characterized by X-ray diffraction, simultaneous thermogravimetry and differential thermal analysis (TGA/DTA), scanning and transmission electron microscopy (SEM, TEM) analyses. The Rietveld analysis and electron diffraction clearly confirmed the Pca 2 1 non centrosymmetric space group previously proposed for this phase. The layers Bi 2 O 2 2+ and WO 4 2− have been directly evidenced from the HRTEM images. The electrical properties of Bi 2 WO 6 compacted pellets systems were determined from electrical impedance spectrometry (EIS) and direct current (DC) analyses, under air and argon, between 350 and 700 °C. The direct current analyses showed that the conduction observed from EIS analyses was mainly ionic in this temperature range, with a small electronic contribution. Electrical change above the transition temperature of 660 °C is observed under air and argon atmospheres. The strong conductivity increase observed under argon is interpreted in terms of formation of additional oxygen vacancies coupled with electron conduction.

Synthesis and properties of BaCe1−xYxO3−δ–BaWO4 composite protonic conductors

Barium cerate doped by trivalent rare earth metal ions is a potentially huge component of materials for electrochemical industry due to its high protonic conductivity. However, the poor chemical stability especially in the presence of CO2, SO2 or H2O, resulting in decreasing the mechanical durability of obtained materials, limits their possible applications. The new approach towards stable ceramic protonic conductors with high electrical conductivity is presented. Thermal stability of yttrium doped (10 mol%) of BaCeO3 was enhanced by forming the composite material BaCe0.9Y0.1O3–BaWO4 (10 mol% of BaWO4). The synthesis was performed by solid-state reaction method. The detailed study of thermal decomposition of starting powders mixture was performed using thermogravimetry and differential thermal analysis (TG/DTA) techniques combined with Evolved Gas Analysis (EGA—mass spectrometry). Structure, phase composition and microstructure together with thermal stability of sintered materials were determined. The exposition tests were performed to characterise the stability of composites in carbon dioxide and water vapour-rich atmospheres. The samples were exposed to atmosphere containing CO2/H2O (7 % of CO2 in air, 100 % RH) at temperature of 25 °C for 300 h. Thermal analysis supplied with mass spectrometry was applied to analyse the materials after the test. The results of this experiment showed better chemical resistance of composite material—BaCe0.9Y0.1O3 with 10 mol% of BaWO4 compared to single phase material.

Coke deactivation of activated carbon-supported rubidium–potassium catalyst for C2F5I gas-phase synthesis

The coke formed on the Rb–K/AC catalysts during the synthesis of C2F5I by the reaction between C2HF5 and I2 was investigated using N2 adsorption–desorption, thermogravimetry and differential thermal analysis (TG-DTA), and X-ray photoelectron spectroscopy (XPS). The results indicated that the deactivation was mainly caused by the deposition of coke which induced micropore blockage and active sites coverage. The coke species on the Rb–K/AC catalysts surface included carbonaceous carbon and fluorocarbons with low F/C radio, and had different structures to that of graphite. Moreover, the deactivated catalyst was easily reactivated by burning out the coke formed on the catalyst by the addition of O2 at 150–350°C, and the reactivated catalyst exhibited catalytic activity almost as high as the fresh sample.

Synthesis, characterization and thermal behavior of solid state compounds of heavy trivalent lanthanide succinates

Solid-state Ln–L compounds, where Ln stands for heavy trivalent lanthanides or yttrium(III) (Tb–Lu, Y) and L is succinate, have been synthesized. Simultaneous thermogravimetry and differential thermal analysis (TG-DTA), differential scanning calorimetry (DSC), infrared spectroscopy, TG-DTA coupled to FTIR, elemental analysis, X-ray powder diffractometry and complexometry were used to characterize and study the thermal behavior of these compounds.For the terbium to thulium and yttrium compounds, the dehydration, as well the thermal decomposition of the anhydrous compound occurs in two consecutive steps, while ytterbium and lutetium the dehydration occurs in a single step. The results also led to information about the ligand's denticity, thermal stability and thermal decomposition of these compounds.

AP40 Bioactive Glass Ceramic by Sol-Gel Synthesis: <i>In Vitro</i> Dissolution and Cell-Mediated Bioresorption

In this work, the sol-gel synthesis of AP40 bioactive glass system was reported. The obtained powder was fully characterised in terms of microstructure, composition and thermal behaviour by X-ray diffraction (XRD) measurements, Fourier transform infrared (FT-IR) spectroscopy, thermogravimetry and differential thermal analysis (TG-DTA).In vitrodissolution tests were performed in order to assess the degradation behaviour of sol-gel derived AP40 samples thermally treated at different temperatures. Finally, preliminary results on cytocompatibility are reported, based on bioresorption activity of human peripheral blood monocytes differentiated into osteoclasts on sintered disks.

Effect of the Particle Size of Quartz Powder on the Synthesis and CO2 Absorption Properties of Li4SiO4 at High Temperature

Li4SiO4 was obtained by using quartz powder of different particle sizes (75–180 μm, 45–75 μm, 38–45 μm, and <38 μm) and Li2CO3 as raw materials through a solid-state reaction at 720 °C. X-ray diffraction (XRD), scanning electron microscopy (SEM), and differential thermal analysis and thermogravimetry (DTA/TG) were used to examine the sintering behavior and properties of the samples. The results indicated that when the particle size of the quartz powder decreased, the solid-state reaction performed more completely, the content of the Li4SiO4 phase increased, and the size of the grain agglomerates decreased gradually. The enhanced chemical reactivity of the quartz powder with Li2CO3 and the shortened diffusion distance as the quartz size decreases are helpful to the formation of the Li4SiO4 phase. The sorption analysis revealed that the samples synthesized using the quartz powder with smaller particle sizes experienced a more rapid absorption–desorption process with a higher absorption efficiency.

Electrical Properties of Semiconducting YBa2Cu3O7-x Thin Film for Uncooled Infrared Detectors

Uncooled pyroelectric infrared based on semiconducting YBa2Cu3O6+x (YBCO) thin films have been investigated. YBCO precursor solutions were prepared by sol-gel method and YBCO films were fabricated by the spin coating method and structural and electrical properties with variation of annealing temperature were studied. As a result of the differential thermal analysis and thermogravimetry (DTA-TG) analysis, endothermic peak was observed at around 750°C due to the formation of the tetragonal phase. The crystal structure of the YBCO film annealed at 750°C was polycrystalline tetragonal phase. The thickness of all the films was approximately 0.26∼0.31 μm and average grain size of the YBCO film sintered at 750°C was about 60 nm. Temperature resistance coefficient (TCR), responsivity and detectivity of the YBCO film sintered at 750°C were 3.7%/K at room temperature, 14.47 V/W and 7.23 × 106 cm Hz1/2/W, respectively.