Simultaneous Thermogravimetric Analysis Research Articles

Effect of nitro content on thermal stability and decomposition kinetics of nitro-HTPB

This paper has been utilizing the simultaneous thermogravimetric analysis and differential scanning calorimetry (TG–DSC) to investigate the thermal decomposition of nitro-HTPB as an energetic binder. Data on thermal stability along with the decomposition kinetics of energetic materials are required to better comprehend their decomposition mechanism and the hazards involved in their handling, storage and processing. The thermal behaviors of different nitro-HTPB samples with various nitro group contents were determined. Decomposition kinetic was investigated by evaluating the influence of DSC heating rate (10, 20, 30 and 40 °C min−1) on the behavior of a nitro-HTPB sample. The results as expected showed that the decomposition temperature of the nitro-HTPB decreases with the increase in the DSC heating rate, while thermal decomposition of the sample followed a first-order law. The kinetic and thermodynamic parameters of the nitro-HTPB decomposition under ambient pressure were obtained from the resulted DSC data via non-isothermal methods proposed by ASTM E698 and Flynn–Wall–Ozawa. Also, the critical temperature of the nitro-HTPB was estimated at about 181 °C.

Formation of the core–shell microstructure in lead-free Bi1/2Na1/2TiO3-SrTiO3 piezoceramics and its influence on the electromechanical properties

The Bi1/2Na1/2TiO3-based materials exhibit the largest electric-field-induced strains among lead-free piezoceramics and are considered as promising candidates for actuation applications. A typical representative of this group is (1-x)Bi1/2Na1/2TiO3-xSrTiO3, where its excellent electromechanical properties were recently related to the existence of a core–shell microstructure. Although the latter was also reported in other Bi1/2Na1/2TiO3-based ceramics, the formation mechanism remains unknown. In the present work we therefore first investigated the solid-state reaction occurring during calcination using simultaneous thermogravimetric analysis, X-ray diffraction, scanning and transmission electron microscopy. The reaction occurred in two steps, whereby the cores and shells had different formation reaction temperatures, which resulted in a metastable heterogeneous microstructure. Furthermore, a series of sintered samples with different relative densities, grain sizes, and core densities was prepared. Modifications of these microstructural parameters resulted in variation of the maximal strain by 17% and in the electric-field required to trigger the phase transitions by 38%.

Development of sintering-resistant CaO-based sorbent derived from eggshells and bauxite tailings for cyclic CO2 capture

Carbon dioxide, one of the major greenhouse gases, are believed to be a major contributor to global warming. As a consequence, it is imperative for us to control and remove CO2 emissions. The CaO, a kind of effective CO2 sorbent at high temperature, has attracted increasing attention due to some potential advantages. The main drawback in practical application is the deterioration of CO2 capture capacity following multiples cycles. In the present study, novel low-cost porous CaO-based sorbents with excellent CO2 absorption–desorption performance were synthesized using bauxite tailings (BTs) and eggshells as raw materials via solid-phase method. Effect of different BTs content on CO2 absorption–desorption properties was investigated. Phase composition and morphologies were analyzed by XRD and SEM, and CO2 absorption properties were investigated by the simultaneous thermogravimetric analyzer. The as-prepared CaO-based sorbent doped with 10 wt% BTs showed superior CO2 absorption stability during multiple absorption–desorption cycles, with being >55% conversion after 40 cycles. This improved CO2 absorption performance was attributed to the particular morphologies of the CaO-based sorbents. Additionally, during absorption–desorption cycles the occurrence of Ca12Al14O33 phase is considered to be responsible for the excellent CO2 absorption performance of CaO-based sorbents. In the meanwhile, the use of solid waste eggshell and BTs not only decreases the release of solid waste, but also moderates the greenhouse effect resulted from CO2.

THERMAL CARACTERIZATION OF SOYBEAN AND GRAPE SEED OIL-BASED POLYMERS: NEW SYNTHESIS PATHWAY FOLLOWING GREEN CHEMISTRY’S PRINCIPLES

Abstract This paper describes the synthesis of polymers from glycerol and vegetable oils as soybean and grape seed, synthesized following the principles of green chemistry. Simultaneous thermogravimetric analysis – differential thermal analysis (TG-DTA) and differential scanning calorimetry (DSC) were employed to evaluate the thermal decomposition, thermal stability, and oxidation, glass transition and crystallization processes. Hence it was possible to verify that they have glass transition near to room temperature. Therefore these polymers may be used as chemical slow release agents triggered by temperature and as thermal security tags. Trabalho SiAT 13 CARACTERIZACAO TERMICA DE POLIMEROS DE OLEO DE SOJA E UVA SINTETIZADO POR NOVA ROTA SINTETICA SEGUINDO PRINCIPIOS DA QUIMICA VERDE. Trabalho apresentado no VII SiAT – Simposio de Analise de Termica realizado no periodo de 19 a 21 de julho de 2015 em Bauru, na Faculdade de Ciencias – UNESP.

Preparation and Properties of Novel Quaternized Metal–Polymer Matrix Nanocomposites

A new class of PANI/Sn(II)SiO3/FCNTs nanocomposite was synthesized by mixing polyaniline into the gel of Sn(II)SiO3 followed by FCNTs (Polyaniline/Sn(II)SiO3/Functionalized Carbon nanotubes). The physico-chemical characterization was carried out by scanning electron microscope, XRD (X-ray Diffraction), FTIR (Fourier Transform Infrared Spectroscopy), ultraviolet–visible spectroscopy, and simultaneous thermogravimetric analysis studies. The ion-exchange capacity (1.2 meq/g) and distribution studies were also determined to understand the ion-exchange capabilities. The DC electrical conductivity studies revile it in the range of 3–5 × 10−3 S/cm. On the basis of distribution studies, ion-selective membrane electrode was designed for Hg(II). The analytical utility of this membrane was established by using it as an indicator electrode in electrometric titrations.

Staged reaction kinetics and characteristics of iron oxide direct reduction by carbon

Staged reduction kinetics and characteristics of iron oxide direct reduction by carbon were studied in this work. The characteristics were investigated by simultaneous thermogravimetric analysis, X-ray diffraction (XRD), and quadrupole mass spectrometry. The kinetics parameters of the reduction stages were obtained by isoconversional (model-free) methods. Three stages in the reduction are Fe2O3→Fe3O4, Fe3O4→FeO, and FeO→Fe, which start at 912 K, 1255 K, and 1397 K, respectively. The CO content in the evolved gas is lower than the CO2 content in the Fe2O3→Fe3O4 stage but is substantially greater than the CO2 contents in the Fe3O4→FeO and FeO→Fe stages, where gasification starts at approximately 1205 K. The activation energy (E) of the three stages are 126–309 kJ/mol, 628 kJ/mol, and 648 kJ/mol, respectively. The restrictive step of the total reduction is FeO→Fe. If the rate of the total reduction is to be improved, the rate of the FeO→Fe reduction should be improved first. The activation energy of the first stage is much lower than those of the latter two stages because of carbon gasification. Carbon gasification and Fe x O y reduction by CO, which are the restrictive step in the last two stages, require further study.

Phase formation of nano-sized metal aluminates using divalent cations (Mg, Co and Zn) by autoignition technique

The divalent metal aluminate spinels were synthesized by autoignition of gel systems containing metal (Al, Mg, Co and Zn) nitrates and glycine as a fuel. A mechanism for nanoparticle formation was proposed from dried gel autoignition to calcination. The simultaneous differential thermal and thermo-gravimetric analyses were applied to understand the nature of process. Independently, the polymeric matrixes exhibited typical self-propagating combustion behaviors at low temperatures, 220–275°C. The heat treatment was carried out on as-formed foamy materials to achieve the well crystallized spinels in nano-scale. The calcined products were characterized by X-ray diffraction, Brunauer–Emmett–Teller surface area measurements and transmission electron microscopy. Based on the resultant powders, the purity, crystallite size and specific surface area of spinels are directly related to cation type. The crystallized particles, having diameters smaller than 20nm, could be successfully synthesized through optimized process variables.

Conventional surfactant-doped poly (o-anisidine)/GO nanocomposites for benzaldehyde chemical sensor development

We report on the synthesis of conventional surfactant dodecylbenzenesulfonic acid-doped poly (o-anisidine)/graphene oxide composite (DPOMA/GO), a ortho-methoxy substituted derivative of anisidine, by in situ oxidative polymerization method. A mixture of Na2S2O8 in HCl was used as oxidant, while dodecylbenzenesulfonic acid was used as both dopant and surfactant. The physicochemical characterization was carried out using a field-emission scanning electron microscope and X-ray crystallography (XRD), Fourier transforms infrared, UV–Vis, and simultaneous thermo-gravimetric analysis study. Then, the DPOMA/GO nanocomposites were used to construct nonenzymatic sensors in practical with I–V technique, where the total analytical parameters were measured. The DPOMA/GO nanocomposites were deposited on flat silver electrode (AgE; surface area ~0.0216 cm2) to result in a sensor that has a fast response to selective benzaldehyde in buffer system. Features including sensitivity, detection limit, reproducibility, linear dynamic range, selectivity, and electrochemical performances were investigated in detail with the DPOMA/GO nanocomposites-fabricated AgE electrodes. The calibration plot is linear (r 2 0.9699) over the large concentration range (0.1 nM–0.1 mM). The sensitivity and detection limit are calculated as ~1.2277 µA cm−2 µM−2 and 0.03 nM (at a signal-to-noise ratio of 3), respectively.

Benefeciation of Derived Bovine Bone Waste Hydroxyapatite Obtained from Meatballs Sellers and its Characterization

In this study, bovine bone waste obtained from meatballs sellers was utilized as novel alternative bioresource of hydroxyapatite (HA). The femur bovine bone waste in bulk form was initially deproteinized using HCl and NaOH and then followed by calcination at 500 °C and 800 °C for 5 h to obtained HA powder. The thermal stability of HA powder was monitored using simultaneous thermogravimetric analysis (TG) and differential thermal analysis (DTA). The TG/DTA result shows that the combustion of the organic component of bone, especially of collagen occured at temperature range of 174-550 °C. The phase content, type of bond present, and morphology of calcined HA powder were conducted using x-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), and Scanning Electron Microscopy (SEM) respectively. The crystallinity of the HA sample shows increase with increasing of the temperature calcination. The characteristic of bands of HA and additionally peaks of carbonate ions were observed in the FTIR results and the morphologic characteristics of the HA particles shows the material is a homogeneous powder.

Synthesis and characterization of Mn-doped ZnO diluted magnetic semiconductors

In the present work undoped and Mn doped ZnO nanoparticles (ZnO:Mn), diluted magnetic semiconductors, were successfully synthesized by the sol–gel method at room temperature. The morphology of ZnO nanoparticles constituted by flower-like structures with hexagonal morphologies that changed significantly after the incorporation of Mn. Rietveld refinements results showed that Mn ions are successfully doped into ZnO matrix without altering its wurtzite phase. Meanwhile, Raman spectroscopy analyses confirm the wurtzite structure of undoped ZnO and ZnO:Mn nanoparticles. The lattice parameters increase with increasing Mn content due to the large ionic radius of Mn2+ compared to that of Zn2+. Electron spin resonance measurements were performed to gain information about oxidation state and site occupancy of the magnetic Mn ions in the ZnO lattice. Moreover, UV–vis absorption spectra have been utilized to calculate the optical band gap of the undoped ZnO and ZnO:Mn nanoparticles before and after different γ-irradiation doses. The band gap of ZnO:Mn (2%) is 2.62eV which is noticeably smaller than the 3.26eV of undoped ZnO. The thermal decomposition properties of the prepared nanoparticle samples were also studied using simultaneous Thermogravimetric analysis in temperature range from 30 to 500°C.

Effects of functional group modification on the thermal properties of nano-carbon clusters

In this paper, the thermal properties including thermal stability, thermal decomposition activation energy and the thermal enthalpy of nano-carbon clusters (NCCs, including fullerene[60](C60, with a diameter of 0.71 nm), multi-walled carbon nanotubes(MWCNTs, with a diameter of 10–30 nm and a length of 1–2 µm), single-walled carbon nanotubes (SWCNTs, with a diameter of ~2 nm and a length of 5–15 µm), ligands of NCC-based terpyridine (NCC-tpy), and NCC-based ruthenium complexes (NCC-tpyRuCl3) were systematically studied by method of simultaneous thermogravimetric and differential thermal analysis. The results show that the modification of NCCs with terpyridine leads to a decrease in the thermal stability and in the thermal decomposition activation energy (the thermal decomposition activation energy decreased from 174.4 for C60, 144.9 for MWCNTs and 161.2 kJ/mol for SWCNTs to 166.2 for C60-tpy, 119.7 for MWCNT-tpy and 85.0 kJ/mol for SWCNT-tpy). But the modification of NCCs with terpyridine results in an increase in the enthalpy change of NCC thermal decomposition reaction. The introduction of the metal ions through complexation further decreases the thermal stability and the thermal decomposition activation energy of NCC-tpyRuCl3 due to the catalytic oxidation of Ru(III) ions (the activation energy decreases to 124.1 for C60-tpyRuCl3, 106.4 for MWCNT-tpyRuCl3 and 41.2 kJ/mol for SWCNT-tpyRuCl3). The introduction of the metal ions also leads to a decrease in the enthalpy change of the thermal decomposition reaction.

DTA/TG study of CuO and MoO3 co-reduction by combined Mg/C reducers

The mechanism of copper (II) oxide and molybdenum (VI) oxide co-reduction by Mg + C mixture was investigated at non-isothermal conditions by carrying out simultaneous differential thermal (DTA) and thermogravimetric (TG) analyses combined with X-ray diffraction (XRD) analysis of intermediate and final products. The whole process was found to involve several phenomena: interaction between oxides with CuMoO4 salt formation, high-exothermic reactions occurring directly between metal oxides and magnesium, as well as low-exothermic carbothermal reactions. In order to better understand the complex nature of calorimetric and TG curves, the behaviour of each single reagent as well as that of binary, ternary and quaternary mixtures was studied at linear heating. It was revealed that the simultaneous reduction of Cu and Mo oxides proceeds more easily by carbon than by magnesium. Only due to the decisive role of carbon on the reaction pathway, the combined and complete reduction of oxides by Mg/C reducing mixture becomes possible at relatively low temperatures. The sequence of chemical reactions possibly occurring during the heating process on the basis of DTA/TG curves and XRD analyses results of quenched reaction products has been proposed.

Mechanical, dielectric and photoluminescence properties of alumina–mullite composite derived from natural Ganges clay

A highly dense mullite–alumina composite was developed utilizing external alumina and clay aggregates from the Ganges (India) bed in order to obtain a low-cost multifunctional composite. Thermal evaluation and phase formation were investigated by simultaneous differential thermal and thermo-gravimetric analysis, X-ray diffraction, Fourier transform infrared spectroscopy and field emission scanning electron microscopy. Both equiaxed and elongated whiskers of mullite were present along with alumina platelets. Mechanical characteristics of the mullite composites were measured in terms of relative density and Vicker's hardness and were found to be ~89% and ~4.5GPa at 1400°C. Dielectric constant of the composite was found to be ~18 at 1400°C which is higher than that of pure alumina or mullite. Structural defects and peculiar morphologies of the composite caused photoluminescence bands at around 310, 347, 436 and 460nm. Due to its remarkable density, Vicker's hardness, improved dielectric properties and prominent photoluminescence, the composite can be used as a multifunctional composite with structural, electrical and optical applications.

Thermal-Chemical Characteristics of Al–Cu Alloy Nanoparticles

This work investigated the oxidation, ignition, and thermal reactivity of alloy nanoparticles of aluminum and copper (nAlCu) using simultaneous thermogravimetric analysis (TGA) and differential scanning calorimeter (DSC) method. The microstructure of the particles was characterized with a scanning electron microscope (SEM) and transmission electron microscope (TEM), and the elemental composition of the particles before and after the oxidation was investigated with energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). The particles were heated from room temperature to 1200 °C under different heating rates from 2 to 30 K/min in the presence of air. The complete oxidation process of the nAlCu was characterized by two exothermic and two endothermic reactions, and the reaction paths up to 1200 °C were proposed. An early ignition of nAlCu, in the temperature around 565 °C, was found at heating rates ≥ 8 K/min. The eutectic melting temperature of nAlCu was identified at ∼546 °C, which played a critical role in the early ignition. The comparison of the reactivity with that of pure Al nanoparticles showed that the nAlCu was more reactive through alloying.

Enhancement of redox stability and electrical conductivity by doping various metals on ceria, Ce1−xMxO2−δ (M = Ni, Cu, Co, Mn, Ti, Zr)

Various metal oxide materials have been actively investigated to improve energy efficiency as exhaust-catalyst as well as electrodes in electrochemical devices such as fuel cells, ceramic sensors, photo-catalyst etc. Ceria-based materials are of great interest due to their wide applications; such as redox or oxygen storage promoter in automotive catalyst and solid state conductor in fuel cells. Here we report redox and electrical properties for Ce1−xMxO2−δ (M = Ni, Cu, Co, Mn, Ti, Zr) by X-ray diffraction (XRD) and simultaneous thermo-gravimetric analysis (TGA). Among various system, Ce1−xCuxO2−δ and Ce1−xNixO2−δ indicated relatively reversible redox behavior, although Cu2+ and Ni2+ had limited solid solubility in CeO2. The enhancement of oxygen carrier concentration and electrical conductivity as well as electrochemical activity in the ceria lattice by the introduction of small amounts transition metal cations have been considered in this study. Ce0.7Cu0.3O2−δ showed about 1015 μmol[O2]/g of oxygen storage capacity (OSC) with high redox stability at 700 °C. We also demonstrated that Ce0.9Ni0.1O2−δ was used as an anode of the YSZ electrolyte supported SOFC single cell; the maximum power density was 0.15 W/cm2 at 850 °C with hydrogen fuel.

Processing and characterization of pure cordierite and zirconia-doped cordierite ceramic composite by precipitation technique

Pure cordierite and cordierite–ZrO2 composite (5–20 wt%) ceramics for various stoichiometric compositions were synthesized from standard raw materials by a novel precipitation technique. The analytical techniques such as X-ray diffraction, simultaneous thermogravimetric and differential thermal analysis, Fourier transform infrared spectroscopy, scanning electron microscopy and bulk density were employed to evaluate the properties and microstructure. Results show that the ceramic composites consist of cordierite and zircon phases. The cordierite–zirconia (20 wt%) increased the fracture toughness value from 3.38 to 3.94 MPa, which is mainly due to martensitic transformation present in zirconia. The flexural strength of composite was found to increase from 126.46 to 297.62 MPa. The thermal expansion coefficients of cordierite and cordierite–zirconia (20 wt%) were 4.08 × 106 and 4.42 × 106 ∘C−1 which may be due to the addition of zirconia.

Role of mechanochemical milling in FeVO4 synthesis

Single phase, a FeVO4 triclinic crystalline structure was successfully synthesized by annealing the mechanochemically milled xV2O5·(1−x)α-Fe2O3 composites (x=0.5) at 550°C for 1h. X-ray powder diffraction (XRD), simultaneous differential scanning calorimetry and thermogravimetric analysis (DSC–TGA), Mössbauer spectroscopy, scanning electron microscopy (SEM), and optical diffuse reflectance spectroscopy were combined for a detailed study of the assisting role of the mechanochemical milling process. Mechanochemical milling homogeneously mixed the starting materials of α-Fe2O3 and V2O5 and substantially decreased their average grain sizes. The Mössbauer spectroscopy studies showed that the spectrum of the mechanochemically milled composites consisted of three sextets and one doublet, indicating the occurrence of V5+–Fe3+ ion substitutions in the corresponding α-Fe2O3 and V2O5 lattices, respectively. The partially V5+-substituted α-Fe2O3 phase and Fe3+-substituted V2O5 could be the important intermediate phases in the production of FeVO4 single phase. The synthesized FeVO4 phase had a slightly distorted nature with an unequal ratio in Fe3+ population in three inequivalent sites. Simultaneous DSC–TGA studies indicated that the synthesized FeVO4 is thermally stable up to 600°C. SEM images of the formed FeVO4 confirmed the wide particles size distribution range composed of nano-grains. Optical diffuse reflectance spectroscopy studies showed that the synthesized FeVO4 phase had semiconductor properties, with the band gap energy of ~2.44eV.

Phase behaviour and superionic phase transition in K3H(SeO4)2

The phase behaviour of K3H(SeO4)2 (TKHSe) above room temperature has been studied by differential scanning calorimetric (DSC), thermogravimetric analysis (TGA), simultaneous thermogravimetric and mass spectroscopy analysis (TG-MS), impedance spectroscopy (IS) and X-ray powder diffraction (XRD). Our results show that the previously claimed superionic phase transition in TKHSe at around 388 K (114.85 °C) is also the onset temperature of a slow thermal dehydration that occurs at reaction sites distributed over the surface of the crystal. That is, we propose that the TKHSe undergoes simultaneously a superionic phase transition and a decomposition process with a very slow reaction rate that is evident when the sample is pulverized to fine powder, both starting at the same temperature. As a matter of fact, we observe a decrease of the magnitude of the dc-conductivity on successive thermal runs in powdered sample attributed to sample decomposition that starts at the surface of the TKHSe grains, but the jump in conductivity is only a consequence of the order–disorder transition in the TKHSe phase that remains inside the grains.

Preparation and properties of novel sol-gel-derived quaternized poly(n-methyl pyrrole)/Sn(II)SiO3/CNT composites

A new class novel poly(n-methyl pyrrole)/nano-Sn(II)SiO3/CNT composite was synthesized using a sol-gel method. The sol of poly(n-methyl pyrrole) (PNMPy) was synthesized into the gel of Sn(II)SiO3 by ranging the mixing volume ratio concentration of inorganic reactant with the fixed mixing volume ratio, i.e., 1:1, of organic polymer followed by intercalating CNTs. The physicochemical characterization was carried out using a scanning electron microscope (SEM) and by XRD, Fourier transform infrared (FTIR), UV–Vis, and simultaneous thermogravimetric analysis (TGA) studies. Ion-exchange capacity, distribution studies were also carried out to understand the ion-exchange capabilities. Due to the presence of conducting polymer and functionalized carbon nanotubes (FCNTs), the dc electrical conductivity studies reveal it in highly semiconducting nature in the range of 2.5 × 10−3–4.3 × 10−3 S/cm. On the basis of distribution studies, it was found to be good selective for Cd2+, which is an important environmental pollutant. Due to the selective nature of the composite, an ion-selective membrane electrode was designed for the determination of Cd(ІІ) ions in solutions. The analytical utility of this membrane was established by employing it as an indicator electrode in electrometric titrations.

Qualitative and kinetic analysis of torrefaction of lignocellulosic biomass using DSC-TGA-FTIR

Torrefaction is a thermochemical conversion technique to improve the fuel properties of lignocellulosic biomass by treating at temperature 200 ℃-300 ℃ in the minimum oxygen environment for a reasonable residence time. In this study, thermal decomposition and thermal activities of miscanthus and wheat straw during the torrefaction at 200 ℃, 275 ℃, and 300 ℃ in a nitrogen environment for 45 minutes of residence time are analyzed in a simultaneous thermogravimetric analyzer (micro TGA) with a differential scanning calorimetry (DSC), and a macro-TGA. The output of the micro TGA is fed into the Fourier transform infrared spectrometry (FTIR) and qualitative analysis of the gaseous product is carried out. The composition of different gas products during the torrefaction of biomass are compared critically and kinetics were analyzed. It is found that the weight loss due to degradation of initial biomass in second stage (torrefaction process) is a much faster conversion process than the weight loss process in the first stage (drying process). The weight loss of biomass increases with increase in the residence time and torrefaction treatment temperatures. The yield after torrefaction is a solid bio-coal product. The torrefied product were less reactive and has nearly 25% better heating value than the raw biomass. Between the two feedstocks studied, torrefied miscanthus proved to be a more stable fuel than the torrefied wheat straw. The major gaseous components observed during torrefaction are water, carbon dioxide, carbon monoxide, 1,2-Dibromethylene.