Simultaneous Differential Thermal Analysis Research Articles

Oxidation of Micro-Sized Aluminium Particles: Hollow Alumina Spheres

Oxidized aluminium microparticles have recently been proposed for manufacturing new, environmentally-friendly, protective coatings on stainless-steels and Ni-base alloys. The oxidation mechanisms of spherical aluminium microparticles of an average particle size of 3.5 μm were studied. Accordingly, simultaneous differential thermal analysis–thermogravimetry tests were carried out in air at different temperatures, always above aluminium melting temperature. Scanning electron microscopy and XRD were also used for the interpretation of results. Weight gain and energy results were explained in terms of the different structural changes taking place in aluminium particles. Dehydroxylation process was identified. The transformation of amorphous alumina to γ-Al2O3 was numerically evaluated and the alumina phase transformation (γ-Al2O3→α-Al2O3) was also studied. The temperature ranges revealed the appearance of metastable phases (θ-Al2O3). Complete oxidation of particles can be obtained at 1,300 °C in <1 h, although this also takes place at lower temperatures if enough oxidation time is used. Activation energy of oxidation process at high temperature was also estimated, taking a value of 334 kJ/mol. High temperature oxidation causes the formation of hollow alumina spheres, without any aluminium left inside them.

Solid-state reaction synthesized Pd-doped tin oxide thick film sensor for detection of H2, CO, LPG and CH4

This paper deals with the synthesis of tin oxide (SnO2) nano-powders by a solid-state reaction technique. The synthesized powders have been characterized by simultaneous thermo gravimetric and differential thermal analysis (TG–DTA) and X-ray diffraction (XRD) techniques. Suitable calcination temperature is established by XRD and TG–DTA analysis. Thick film sensors have been developed from as-prepared undoped and palladium (Pd) doped (0.5 and 1 wt%) SnO2 powders using screen printing technology for the detection of various pollutant gases such as, hydrogen (H2), carbon monoxide (CO), liquefied petroleum gas (LPG) and methane (CH4). The surface of the thick film sensor has been characterized by field emission scanning electron microscopy (FESEM). The sensing characteristics of thick films have been studied from the aspect of crystallite size of sensing material and microstructure of the thick film surface. It is found that SnO2 doped with 1 % Pd exhibits the maximum sensitivity (79 %) towards CO gas along with fast response/recovery time (80 s, 197 s) and almost insensitive for H2, LPG and CH4.

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.

Study of Ion Diffusional Motion in Ionic Liquid-Based Polymer Electrolytes by Simultaneous Solid State NMR and DTA

Polymer electrolytes containing ionic liquid (IL), 2-methyl-1,3-dipropylimidazolium dihydrogenphosphate (MDPImH2PO4) have been studied by (1)H solid state NMR and differential thermal analysis (DTA) simultaneously by using a specially designed probe. To the best of our knowledge, this is the first report of its kind for IL based polymer electrolytes. The variation of NMR line width with temperature for the IL and polymer electrolytes shows line narrowing at the glass transition and melting temperature. The onset of long-range ion diffusional motion also takes place at these temperatures and is accompanied by a sudden increase in ionic conductivity value by 2-3 orders of magnitude. The presence of amorphous and crystalline phases in IL-based polymer electrolytes has been observed from X-ray diffraction (XRD) studies, and the amorphous phase is the high conducting phase in these polymer electrolytes. The IL-based polymer electrolytes have been observed to be thermally stable up to 200 °C. The results obtained from ion transport studies have also been supported by Fourier transform infrared (FTIR), XRD, and cyclic voltammetry (CV) studies.

Discharge Characteristics of Li-Mg-B Alloy/MnO2 Couples in Molten LiNO3-KNO3-Ca(NO3)2 Eutectic Electrolyte

High temperature battery cells using molten LiNO3-KNO3-Ca(NO3)2 eutectic electrolyte and Li-Mg-B alloy anodes have been evaluated with MnO2 as solid cathode material. Chemical-compatibility studies of these materials with the electrolyte are conducted using simultaneous differential thermal Analysis (DTA) and thermo gravimetric analysis (TGA). The cells are tested in single cells over a temperature range of 150°C–300°C at current densities from 10–30 mA/cm2. The results of those galvanostatic discharge characteristics are presented, and the merits of the system will be described.

Growth and Characterization of Electrospun LaMnO3 Nanofibers by Electrospinning Technique

The polycrystalline perovskite structure of LaMnO3 nanofibers was obtained by calcination of the PVA/[LaCl3+MnCl2+(NH4)2CO3] composite at 600°C with electrospinning technique. The decomposition and crystalline behavior of sample were examined by Thermogravimetric and Simultaneous Differential Thermal Analysis (TG-DTA). The crystal structure and phase formation were characterized by X-ray Diffraction (XRD). Scanning Electron Microscopy (SEM) was performed and the diameters of the LaMnO3 nanofibers were calculated to be 42 nm and 55 nm with different spinning intervals at 600°C. SEM analysis was also carried out to examine the fiber diameters and morphological properties.

Fullerene C60 and its Derivatives as Nanocomposites in Polymer Nanofibres

This work describes the application of oxo-derivatives of fullerene C60 and pristine fullerene as a nanocomposite in polymerous nanofibres. In this work we used oxo- fullerene derivative, of which preparation was presented by the authors of the State office for nuclear safety (Prague) on Nanocon 2009 and on Nanocon 2010 [1, 2]; there was presented its application in vivo as a radioprotective agens. With respect to wild spectrum of potential utilization of unique chemical, structural a electron properties of fullerene we investigate its another possible technical application as nanocomposite in polymer nanofibres. The nanocomposite polymer nanofibers were produced by needle-less electrospinning method. Polyvinyl alcohol, polyurethane a polyvinyl butharate were used as polymers. Thermal resistance of obtained nanofibres without and with nanocomposites was tested by simultaneous thermogravimetric analysis and differential thermal analysis (TGA/DTA). The retarding influence of fullerene and its derivative on the course of the thermal decomposition of nanofibres is discussed.

Mn–Zn nano-crystalline ferrites synthesized from spent Zn–C batteries using novel gelatin method

A novel recycling route using acid leaching, reduction and gelatin method was applied to recycle spent Zn–C batteries into more valuable magnetic nano-crystalline ferrites; Mn1−xZnxFe2O4 (with x=0.2–0.8). The cost of this recycling technology has economical advantages, which holds promising industrial application products. Dried gel thermal decomposition process was monitored by simultaneous differential thermal analysis–thermogravimetry–differential scanning calorimetry. Phase composition, morphological and magnetic properties of the as-prepared precursors were characterized using X-ray powder diffraction, transmission electron microscopy, Fourier transform infrared and vibrating sample magnetometer. Single-phase agglomerated cubic ferrites with crystal sizes in the range 21–41nm were detected. The obtained magnetization values are significantly lower than that of the bulk ferrite and showed a gradual increase with increasing Zn-substitution with an obvious decrease at x=0.6. On the other hand, a reverse trend was exhibited by coercivity. The effect of Zn-substitution on both structural and magnetic properties, paved the way to suggest proper cation distributions for the investigated system.

Thermoanalytical study of heavier trivalent lanthanides fumarates

Solid-state heavier lanthanides fumarates compounds have been synthesized, and the compounds were characterized by employing simultaneous thermogravimetry and differential thermal analysis (TG–DTA), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), TG coupled to FTIR, elemental analysis, and complexometry. On heating, the dehydration occurs in a single and two consecutive steps and the thermal decomposition of the anhydrous compounds occurs in consecutive and/or overlapping steps, with formation of the respective oxides: Tb4O7 and Ln2O3 (Ln=Dy to Lu). The results also led to information about composition, thermal behavior, and the type of coordination of the isolated compounds.

Structure, spectroscopic, thermal properties and catalytic activity of iron(III)-Schiff base complexes

Iron(III) complexes of the Schiff bases: [FeLCl3] (L=3-(1H-imidazole-1-yl)-N-[(1E)-1H-pyrrol-2-ylmethylene]propan-1-amine, L1; 3-(1H-imidazole-1-yl)-N-[(1E)-(3-methyl-2-thienyl) methylene]propan-1-amine, L2; 1-(3-{[(1E)-1H-pyrrol-ylmethylene] amino} propyl)pyrrolidin-2-one, L3; 1-(3-{[(1E)-2-furylmethylene]amino} propyl)pyrrolidin-2-one, L4 have been prepared and characterized by NMR, Mass, FTIR, UV–Vis spectroscopy, elemental analysis, conductance in non-aqueous solvent, and magnetic measurements. The analytical data showed that the Schiff bases act as tridentate ligands towards trivalent iron via azomethine, imidazole, pyrrole, pyrrolidin nitrogen, furan oxygen and thiophene sulfur. Thermal characterizations of the complexes have been studied in nitrogen atmosphere by simultaneous thermogravimetry and differential thermal analysis, TG-DTA. Two-step decompositions were observed until 800°C by TG-DTA, involving first release of water until 200°C. Finally, the organic portion of the complex was burnt out slowly accompanied by a sharp endothermic heat effect; meanwhile iron oxide is formed rapidly. The results suggested that the azomethines are tridentating chelates by N3, N2S and N2O donor atoms. A high spin octahedral geometry is assigned to the Iron(III) ion in all four complexes. It has been found that iron(III)-Schiff base complexes activate the epoxidation of cis-1, 2-diphenylethylene by NaOCl. The epoxide conversion cis-1, 2-diphenylethylene and the ratio of the cis:trans epoxides vary depending on the structure of the Schiff bases.

Kinetic investigation on thermal decomposition of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) nanoparticles

This is a study of the thermal decomposition of hexahydro-1,3,5-trinitro-1,3,5-triazine or cyclotrimethylenetrinitramine (RDX) nanoparticles by simultaneous thermo-gravimetry differential thermal analysis (TGA/DTA) and differential scanning calorimetry (DSC) under nonisothermal conditions, at various heating rates from 5 to 20°Cmin−1. The influence of particle size on the thermal decomposition was verified. The activation energy for the decomposition of each sample was calculated using the peak temperature shift method, proposed by Kissinger and Ozawa. A significant variation in varying particle observed the results size of RDX. The results showed that, as the particle size of RDX is increased the thermal decomposition temperature of RDX and its decomposition activation energy are enhanced. The values of activation energy obtained by the Kissinger and Ozawa methods for RDX samples with various particle sizes show that the activation energy for micron sized RDX is 1.5 times higher than that for nano-RDX.The values of ΔS#, ΔH# and ΔG# of decomposition reaction for each particle size were also computed. Base on the kinetic data, the relative sensitivity of RDX samples was found in the order: 180nm RDX>250nm RDX>300nm RDX>50μm RDX.

Liquid–liquid demixing and microstructure of Co–Cu–Zr alloys with low Zr content

Liquid–liquid phase separation and its effect on the microstructure has been investigated along the quasi-binary line (Co40Cu60)100−xZrx with x = 2, 4, 6, 9 and additionally for (Co50Cu50)94Zr6 and (Co60Cu40)94Zr6. The elemental distributions and the microstructures were analyzed by scanning electron microscopy and energy dispersive X-ray spectroscopy for samples that were (i) processed by thermal cycling in alumina crucibles at 10, 20 and 30 K/min with simultaneous differential thermal analysis, (ii) rapidly quenched by single-roller melt spinning and (iii) quenched after having been electromagnetically levitated at various temperatures. The metastable miscibility gap of the binary Co–Cu system with phase separation into Co- and Cu-rich liquids transforms into a stable miscibility gap for Zr contents 3 < x < 7.5 with separation into Co/Zr-rich and Cu-rich liquids. In contrast to the binary Co–Cu system where the Cu-rich liquid phase always surrounds the Co-rich phase, the Zr addition modifies the surface tension energies and/or wetting behavior in a peculiar way so that the Co/Zr-rich phase always encloses the Cu-rich liquid phase concerning the ternary Co–Cu–Zr system in that compositional range. The macrosegregation morphologies of the liquid phase separation that built up via Ostwald ripening, gravity-driven convection, collision, coalescence and wetting effects proceed on a very short time scale and even samples that have been prepared by rapid quenching techniques still exhibit phase separated regions in the micrometer regime.

A Crystallographic, Spectroscopic, Thermal, and DFT Investigation of Mixed Ligand Cu(II) Complexes of 2-benzoylbenzoate

Two mixed ligand complexes of copper(II)-2-benzoylbenzoate (bba) with pyridazine and 4-picoline, namely bis(2-benzoylben- zoate)di(pyridazine)copper(II) 1 and bis(2-benzoylbenzoate)bis(4-picoline)copper(II) 2, have been synthesized and characterized by X-ray crystallography. Complexes 1 and 2 crystallize in the monoclinic P21/c space groups. The calculated frequency shifts have shown that the participation of carboxylate groups in coordination to the metal centers in monodentate fashion (Δ(OCO) > 200 cm−1). The structural features of the complexes have been further studied by DFT/X3LYP extended hybrid functional. The thermal behavior of the complexes was studied by means of simultaneous thermogravimetry, differental thermogravimetry, and differential thermal analysis methods in a static air atmosphere.

A Study of Polyvinyl Butyryl Based Binder System in Titanium Based Metal Injection Moulding

Metal injection moulding (MIM) is an innovative injection moulding technique widely used to produce complex shaped components from feedstock composed of metal powders and thermosetting or thermoplastic binders. In MIM, binder selection and formulation are considered as critical processes since binder characteristics dictate the success of MIM. The purpose of this study is to determine the feasibility of polyvinyl butyryl (PVB) based binder system in Ti-6Al-4V(wt.%)/binder feedstock, as well as to understand the effects of key parameters, such as powder loading and mixing conditions on the rheological properties of a feedstock. In this study, PVB, polyethylene glycol (PEG), and stearic acid (SA) were chosen to formulate a multi-component binder system to prepare Ti-6Al-4V based feedstock with the aid of three types of mixers: a compounder, a modified mechanical mixer and a twin screw extruder. Further, morphological analysis was performed using optical microscopy and scanning electron microscopy. Thermal analysis was performed using simultaneous differential thermal analysis and thermogravimetric analysis. Results showed that binder formulation was reasonably successful with the aid of both mechanical mixer and a twin screw extruder under certain mixing conditions, and the critical powder loading was 68 vol.%, resulting in an optimum powder loading of 63 vol.% .

Dye-sensitized solar cells based on a single layer deposition of TiO2 from a new formulation paste and their photovoltaic performance

A new strategy for enhancing the efficiency and reducing the production cost of TiO2 solar cells by design of a new formulated TiO2 paste with tailored crystal structure and morphology is reported. The conventional three- or four-fold layer deposition process was eliminated and replaced by a single layer deposition of TiO2 compound. Different TiO2 pastes with various crystal structures, morphologies and crystallite sizes were prepared by an aqueous particulate sol–gel process. Based on simultaneous differential thermal (SDT) analysis the minimum annealing temperature to obtain organic-free TiO2 paste was determined at 400°C, being one of the lowest crystallization temperatures of TiO2 photoanode electrodes for solar cell application. Photovoltaic measurements showed that TiO2 solar cell with pure anatase crystal structure had higher power conversion efficiency (PCE) than that made of pure rutile-TiO2. However, the PCE of solar cells depends on the anatase to rutile weight ratio, reaching a maximum at a specific value due to the synergic effect between anatase and rutile TiO2 nanoparticles. Moreover, it was found that the PCE of solar cells made of crystalline TiO2 powders was much higher, increasing in the range 32–84% depending on anatase to rutile weight ratio, than that of prepared by amorphous powders. TiO2 solar cell with the morphology of mixtures of nanoparticles and microparticles had higher PCE than the solar cell with the same phase composition containing TiO2 nanoparticles due to the role of TiO2 microparticles as light scattering particles. The presented strategy would open up new insight into fabrication and structural design of low-cost TiO2 solar cells with high power conversion efficiency.

Effect of processing on the particle size of tin oxide nano-powders

Nano sized tin oxide powders have been syn- thesized via two different chemical routes namely solid- state and sol-gel route for the fabrication of tin oxide gas/ odors sensor. The synthesized powders have been charac- terized by simultaneous thermo gravimetric and differential thermal analysis (TG-DTA), powder X-ray diffraction (XRD), field emission scanning electron microscopy (FE- SEM) and Fourier transform infrared (FTIR) spectroscopy. The effect of synthesis routes have been investigated on particle size and morphology of tin oxide powders. Powder XRD patterns show that the synthesized powders have tetragonal (rutile) crystal structure. FESEM of formed thick films reveal that powder prepared by solid-state reaction route is less agglomerated as compared to the powder prepared by sol-gel route. XRD and FESEM indicate that there is the formation of tin oxide nanoparticles in the range of 15-50 nm. FTIR spectrums of synthesized pow- ders show Sn-O or Sn-O-Sn stretching modes and its lattice modes at 615 and 494 cm -1 .

Sol–gel preparation of pure and doped TiO2 films for the photocatalytic oxidation of ethanol in air

Stable sols of TiO2 were synthesized by a non-aqueous sol–gel process using titanium (IV) isopropoxide as precursor. The microstructure, optical and morphological properties of the films obtained by spin-coating from the sol, and annealed at different temperatures, were investigated using scanning electron microscopy, transmission electron microscopy, diffuse reflectance spectroscopy and ellipsometry. The crystalline structure of the films was characterized by X-ray diffraction and their photocatalytic activity was evaluated for the oxidation of ethanol in air. The influence of the calcination temperature, pre-heat treatment and the number of layers was studied. Simultaneous thermo-gravimetric and differential thermal analysis measurements were carried out to ascertain the thermal decomposition behavior of the precursors. In order to obtain a higher photoresponse in the visible region, a series of vanadium-, niobium- and tantalum-doped TiO2 catalysts was synthesized by the same sol–gel method. For V doping two different precursors, a vanadium alkoxide and V2O5, were used. The effect on the crystallization and photocatalytic activity of the doped TiO2 films was investigated. Furthermore, to identify the effective composition of the samples, they were characterized by X-ray photoelectron spectroscopy and the surface area of the powders was measured by N2 adsorption. The 10 wt.% doped catalysts exhibit high photocatalytic activity under visible light and among them the best performance was obtained for the sample containing Ta as dopant. The crystallite sizes are closely related to the photocatalytic activity.

Characterization of blue CoAl2O4 nano-pigment synthesized by ultrasonic hydrothermal method

Nano-sized CoAl2O4 pigments, which have received significant attention as a coloring agent in glaze and bulk tile compositions, were successfully synthesized by substituting mechanical stirring during hydrothermal process with ultrasonic irradiation. Difference in physicochemical and optical properties of the CoAl2O4 pigments prepared by an ultrasonic-assisted-hydrothermal method was characterized using simultaneous thermo-gravimetric and differential thermal analysis (TG–DTA), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), diffuse reflectance spectroscopy, CIELAB colorimetric analysis, and testing in ceramic glazes and bodies. The ultrasonic-assisted CoAl2O4 pigments present a narrow particle size distribution with vivid blue color, and better thermal stability, allowing their use for ceramic inks processed at high temperature. Application of ultrasonic irradiation during the hydrothermal process produces nano-sized powders with better physicochemical and optical properties.

Synthesis, thermal properties and spectroscopic study of solid mandelate of light trivalent lanthanides

Characterization, thermal stability and thermal decomposition of light trivalent lanthanide mandelates Ln(C6H5CH(OH)CO2)3·nH2O (Ln = La to Gd, except Pm) were investigated employing simultaneous thermogravimetry and differential thermal analysis (TG–DTA), differential scanning calorimetry (DSC), experimental and theoretical infrared spectroscopy, elemental analysis, X-ray diffractometry, complexometry and TG–DSC coupled to FTIR. The dehydration of the lanthanum, samarium, europium and gadolinium compounds occurs in a single step while for praseodymium and neodymium ones it occurs in two consecutive steps. The thermal decomposition of the anhydrous compounds occurs in three, four or five consecutive steps, with formation of the respective oxides CeO2, Pr6O11 and Ln2O3 (Ln = La, Nd to Gd) as final residues. The results also provide information concerning the composition, thermal behavior and gaseous products evolved during the thermal decomposition of these compounds. The theoretical and experimental spectroscopic data suggest the possible modes of coordination of the ligand with the lanthanum.

The phase diagram of KNO3–RbNO3

The phase diagram of the binary system KNO3–RbNO3 was studied using simultaneous direct and differential thermal analysis technique and differential scanning calorimetry. This system exhibits six invariants: a eutectic at 293 °C, four eutectoid reactions at 109, 157, 159, and 291 °C, respectively, and a peritectoid one at 288 °C.