Analytical Techniques Applied in Optimization of Electrophoretic Deposition of Thin Film YBCO Superconductors

 YBa₂Cu₃O _7−x (x = 0.1–0.2) compounds (YBCO) were produced by the oxalate coprecipitation and the solid state reaction methods. The powders obtained were used for the production of YBCO superconducting coatings on Pt/Si wafers, by the electrophoretic deposition technique. The optimum process conditions for the production of both powders and coatings were found by using a combination of modern analytical techniques. The thermal treatment of the samples was followed by thermogravimetry (TG) and differential scanning calorimetry (DSC). The optimization and characterization of the superconducting properties of the powders and coatings were achieved by X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), optical microscopy, magnetic susceptibility and electrical resistivity measurements.     

Pyrolysis and TG Analysis of Shivee Ovoo Coal from Mongolia

The coal sample of the Shivee Ovoo deposits has been non-isothermally pyrolysed in a thermogravimetric analyser to determine the influence of temperature, heating rate and purge gas employed on the thermal degradation of the sample. The heating rates investigated in the TG were 10–50 K min^–1 to final temperature of 1000°C. N₂or CO₂ were employed as well as type of purge gas on the process of thermal degradation of the coal sample. The coal was also investigated in a fixed bed reactor to determine the influence of temperature and heating rate of the pyrolysis on the yield of products and composition of the gases evolved. The main gases produced were H₂, CH₄, C₂H₂, C₂H₄, C₂H₆, C₃H₆ and C₃H₈ and also minor concentrations of other gases. This revised version was published online in August 2006 with corrections to the Cover Date.     

Determination of activation effect of Ca(OH)<Subscript>2</Subscript> upon the hydration of BFS and related heat by isothermal calorimeter

Isothermal conduction calorimetry, differential thermal analysis (DTA)–thermogravimetric analysis (TG) analysis, and SEM observations have proved the activation effect of Ca(OH)₂ released from the C₃S hydration upon blast furnace slag (BFS). Five sample mixtures of BFS and C₃S and two samples of pure BFS and C₃S were submitted to reaction with water inside the calorimeter at room temperature. The values of hydration heat were recorded up to 7 days. Samples were stored in humidity during 28 days and then were submitted to DTA–TG and SEM analysis. The effect of Ca(OH)₂ upon heat evolution of sample mixtures has been quantified and its influence upon the formation of new hydrates and microstructure of pastes was evidenced.     

Studies on Thermal Stability of Titanium Substituted Iron Molybdenum Spinel Oxide

The thermal stability of the solid solutions of Fe₂Mo_1–xTi_xO₄ for x=0.0 to 1.0 in air, had been investigated in the temperature range 303–1173 K using differential thermal analysis and thermogravimetry (DTA and TG). The products obtained by heating the sample in air, at different temperatures, have been characterized by X-ray diffraction and IR-studies. The results show that all the ferrite samples undergo surface oxidation during initial heating. On heating to 823 K, the samples undergo oxidation of the octahedral site cations only and forma cation deficient spinel phase. On further heating in air, the ferrites undergo complete oxidation. This revised version was published online in July 2006 with corrections to the Cover Date.     

Thermal characterization of a series of poly(vinylidenefluoride–chlorotrifluoroethylene–trifluoroethylene) terpolymer films

A number of solution-casted poly(vinylidenefluoride–chlorotrifluoroethylene–trifluoroethylene) [P(VDF–CTFE–TrFE)] terpolymer films with different CTFE content have been characterized by a series of thermal analysis techniques, including thermogravimetric analysis (TG), differential scanning calorimetry, dynamic mechanical analysis (DMA) and thermal mechanical analysis (TMA). The work intends to provide more comprehensive information about thermal behavior of these ferroelectric polymers. TG results suggest that the introduction of the CTFE units slightly decreases the thermal stability of the polymer due to the instability of C–Cl bond during heating. DMA detected a relatively weak α_a relaxation and a broad α_c relaxation in the samples of low CTFE content. These two relaxation processes completely mixed together in the sample with high CTFE content, revealing the crystalline structures in the polymer, become a more imperfect and diffuse state as CTFE units increasing. The polymer with less CTFE units possesses an enhanced stiffness due to its higher degree of crystallinity. A contraction process after a slight amount of thermal expansion upon heating is detected by TMA, due to the release of internal tensile strain/stress generated during solidification of the films. The higher crystallinity of the polymer film generated the greater strain/stress, leading to the larger degree of shrinkage. Also, the higher melting point of the polymer with less CTFE units allows the film soften at a higher temperature.     

Thermal behavior of loratadine

Simultaneous thermogravimetry (TG) and differential thermal analysis (DTA) techniques were used for the characterization the thermal degradation of loratadine, ethyl-4-(8-chloro-5,6-dihydro-11H-benzo[5,6]cyclohepta[1,2-b]pyridin-11-ylidine)-1-piperidinecarboxylate. TG analysis revealed that the thermal decomposition occurs in one step in the 200–400°C range in nitrogen atmosphere. DTA and DSC curves showed that loratadine melts before the decomposition and the decomposition products are volatile in nitrogen. In air the decomposition follows very similar profile up to 300°C, but two exothermic events are observed in the 170–680°C temperature range. Flynn–Wall–Ozawa method was used for the solid-state kinetic analysis of loratadine thermal decomposition. The calculated activation energy (E _a) was 91±1 kJ mol^–1 for α between 0.02 and 0.2, where the mass loss is mainly due to the decomposition than to the evaporation of the decomposition products.     

Thermal analysis of polyesters containing oxirane groups

The preliminary studies of the thermal behaviour of polyester obtained in polycondensation process of cyclohex-4-ene-1,2-dicarboxylic anhydride and ethylene glycol and its new epoxidized form have been performed. The thermal characterization of initial polyester and its completely oxidized form was done by using differential scanning calorimetry (DSC) and thermogravimetric analysis (TG). The non-isothermal DSC was applied to determine the influence of time and the temperature on the chemical modification of initial polyester using 38-40% solution of peracetic acid. On the basis of DSC profiles it has been found that the endothermic transition, due to the degradation process of initial polyester was characteristic feature under controlled heating program. The two characteristic transitions for the new epoxidized polyester, the exothermic peak corresponded to the thermal crosslinking of epoxidized polyester (322.8–336.4°C) and the endothermic decomposition peak of the cured material (363.8–388.9°C) were observed. The peak maximum temperatures (Tmax) and the heat of cross-linking reaction (ΔH_c) for epoxypolyester prepared at 20–60°C under 1–4 h were evaluated. The Tmax1 were almost independent from epoxidation conditions, while, the values of ΔH_c were dependent from conditions of synthesis. The ΔH_c values of this process decreased when time of oxidation increased. The highest values of ΔH_c at 40°C were obtained. Additionally, TG experiments confirmed two separated degradation steps of the new epoxidized polyester indicating the ester (370–380°C) and ether (450–460°C) bond breakdown.     

The interaction between TEOS and some polyols

Hybrid organic-inorganic materials, silica – polyols (ethylene-glycol – EG; 1,2 propane diol – 1,2PG; 1,3 propane diol – 1,3PG and glycerol – GL), were prepared by a sol-gel process starting from tetraethylorthosilicate (TEOS) and polyols, in acid catalysis. The resulting materials were studied by thermal analysis (in air and nitrogen), FTIR and solid state ²⁹Si-NMR spectroscopy. These techniques evidenced the presence of polyols in the silica matrix both hydrogen bounded and chemically bounded in the silica network. The thermal analysis proves to be the most appropriate technique to evidence the organic chains linked in the matrix network and to follow the thermal evolution of the gels to the SiO₂ matrix.     

Co-firing of biomass with coals

The combustion of coal and coal/fir (Abies bornmulleriana) wood blends at the proper ratio (20, 40, 50 wt%) was investigated with thermogravimetric analysis (TG). The influence of biomass blends on thermal and kinetic behavior of coal was studied under non-isothermal conditions. The activation energy of the samples was evaluated with the Ozawa–Flynn–Wall model which compares the combustion of these biowastes with coal under non-isothermal conditions. Our research found that blending influences activation energy of coal; moreover, activation energy related to 50 wt% blend was more similar to pure wood combustion than to coal combustion. Therefore, the activation energy profile shifted from 80.6 to 169.3 kJ/mol. The average reaction order of the samples ranged from 0.13 to 0.35.     

Thermal characterization of the intermediary products of the synthesis of Zn-substituted barium hexaferrite

The focus of this work is the use of thermal analyses and Fourier Transform Infrared Spectroscopy (FTIR) for characterization of the gel decomposition, resulting from the formation of Y-barium hexaferrite substituted by Zn ions (Zn-Y-barium hexaferrite). Samples with Ba₂Zn₂Fe₁₂O₂₂ composition were synthesized by the citrate auto-combustion method. During the TG experiments the highest mass loss was attributed to citrate decomposition owing to the self-combustion reaction, confirmed by the disappearance of –OH band, and the drastic decrease of –CO₂ ⁻and –NO₃ ⁻ bands. Zn substitution resulted in an X-band microwave absorber material.     

Preparation of nanoparticles of oxides by the citrate–nitrate process

This paper reports preparation of nanoparticles of oxides by the citrate–nitrate process and the effect of metal ions on the thermal decomposition characteristics of the corresponding citrate–nitrate gel precursors. In order to understand the effect of metal ions on the thermal decomposition characteristics of the precursors, we have prepared a series of single component oxides such as MO, where M = Zn, MO₂, where M = Sn, Ce, Zr, and M₂O₃ where M = Al, Fe, Bi. In all the cases the citrate to nitrate ratio was fixed at 0.3. In order to ascertain the decomposition characteristics of the gel samples, TG/DTA studies were performed on the dried gel samples. After complete physico-chemical characterization of the precursors and the calcined products, it could be concluded that the nature of decomposition of the precursors depends largely on the nature of the metal ions. Finally, the advantages of the citrate–nitrate process such as its high degree of reproducibility, its potential for large-scale production of nano-crystalline ceramic oxide powders and its lower cost could be established based on a series of experiments and examples.     

Investigation of the thermal properties of [Cd(hydet-en)2Pd(CN)4] AND [Zn(hydet-en)2Pd(CN)4] single crystals

Thermal properties of the single crystals have been investigated by thermogravimetry (TG) and differential scanning calorimetry (DSC) techniques. The thermodynamic parameters such as activation energy and enthalpy and thermal stability temperature of the samples were calculated from the differential thermal analysis (DTA) and TG data. The activation energies for first peak of DTA curves were found as 496.65 (for Cd–Pd) and 419.37 kJ mol^–1 (for Zn–Pd). For second peak, activation energies were calculated 116.56 (for Cd–Pd) and 173.96 kJ mol^–1 (for Zn–Pd). The thermal stability temperature values of the Cd–Pd and Zn–Pd compounds at 10°C min^–1 heating rate are determined as approximately 220.7 and 203°C, respectively. The TG results suggest that thermal stability of the Cd–Pd complex is higher than that of the Zn–Pd complex.     

Thermogravimetric investigation ofwastes from electrical and electronic equipment (WEEE)

Two components of electronic wastes (sample A – a mixture of three types of printed circuit boards, sample B – a mixture of electronic junctions with metal wires) were investigated using thermogravimetric analysis (TG). Thermogravimetric and derivative thermogravimetric data (TG and DTG) give information on the thermal stability of A and B samples and allows finding the correct conditions for their degradation using pyrolysis in an experimental system, built on the laboratory scale for utilization of hazardous wastes. X-ray fluorescence measurements prove that brominated flame retardant is present in sample A, whilst chlorinated flame retardant is a probable component of sample B. Preliminary liquid chromatography of oil products obtained as a result of thermal waste degradation shows that the hydrocarbons released during pyrolysis could be used as a fuel.     

Thermodynamic studies of (R)-BINOL-menthyl dicarbonates

The (R)-BINOL-menthyl dicarbonates, one of the most important compounds in catalytic asymmetric synthesis, was synthesized by a convenient method. The molar heat capacities C _p,m of the compound were measured over the temperature range from 80 to 378 K with a small sample automated adiabatic calorimeter. Thermodynamic functions [H _T–H _298.15] and [S _T–S _298.15] were derived in the above temperature range with a temperature interval of 5 K. The thermal stability of the substance was investigated by differential scanning calorimeter (DSC) and a thermogravimetric (TG) technique.     

Thermal characterization of indinavir sulfate using TG,DSC and DSC-photovisual

The object of the present work is to study the thermal characteristics of indinavir sulfate and to evaluate the quality of the raw materials. Indinavir A, B, C and reference samples were obtained from different suppliers and submitted to TG, DSC and DSC-photovisual analyses. TG/DTG curves indicated a desolvation and dehydration processes and were confirmed by DSC. According to the DSC curves the fusion took place at about 141–142°C for indinavir C and Reference sample B and about 146–149°C for the others. DSC-photovisual showed insoluble raw materials for indinavir C at 160°C. Indinavir sulfate is highly hygroscopic drug which requires attention during storage and manufacture by pharmaceutical industry.     

Rheology and MT-DSC studies of the flow properties of ethyl and methyl babassu biodiesel and blends

The synthesis of pigments from the system Ce_1−x O₂–M _x O (M = Cu, Co) was achieved via a polymeric precursors method, Pechini method. Differential scanning calorimetry (DSC) and thermogravimetry (TG) techniques were used to accurately characterize the distinct thermal events occurring during synthesis. The TG and DSC results revealed a series of decomposition temperatures due to different exothermal events, which were identified as H₂O elimination, organic compounds degradation, and phase formation. X-Ray diffraction patterns show the presence of pure cubic CeO₂ phase for the samples with low Cu and Co loading. A decrease of the specific surface area with increasing copper and cobalt content was observed. The UV–visible diffuse reflectance technique was employed to study the optical properties in the 200–800 nm range. Colorimetric coordinates L*, a*, b* were calculated for the pigment powders. The powders presented a variety of colors from yellow for pure CeO₂, to brown for the ones loaded with copper and gray for the ones with cobalt.     

Investigation on the thermal decomposition and flame retardancy of wood treated with a series of molybdates by TG–MS

A flame-retardant wood was prepared using a series of insoluble molybdates through the double bath technique. The flame retardancy of the wood samples was studied with the limiting oxygen index (LOI) method. The relationships between the flame-retardant performance and the thermal property of wood were studied by the thermogravimetry (TG), derivative thermogravimetry (DTG), differential thermal analysis (DTA), scanning electron microscopy (SEM), and the thermogravimetry–mass spectrometry (TG–MS) analysis methods. The results showed that the insoluble molybdates, which were precipitated into the wood by the double bath technique, can obviously improve the flame retardancy of wood. Similarly, the transition metal molybdates showed higher flame-retardant efficiency than the main group metal molybdates do, which probably due to the thermal barrier effect that Fe₂(MoO₄)₃ acts during the combustion of the samples. At the same time, Fe₂(MoO₄)₃ catalyzed the dehydration and carbonization reactions of wood, and caused an increase in the amount of char produced, and an improvement of the stability of the char residue. Moreover, the mass spectrometry results indicated that the excess transition metal ions speed up the deep decomposition of the char residue, and resulting in the smoldering of wood.     

Thermal degradation and smoke suspension of cotton cellulose modified with THPC and its lanthanide metal complexes

Complexes of cell–THPC–urea–ADP with transition metal ion Co²⁺ and lanthanide metal ions such as La³⁺, Ce⁴⁺, Nd³⁺ and Sm³⁺ have been prepared. The thermal behavior and smoke suspension of the samples are determined by TG, DTA, DTG and cone calorimetry. The activation energies for the second stage of thermal degradation have been obtained by following Broido equation. Experimental data show that for the complexes of cell–THPC–urea–ADP with the metal ions, the activation energies and thermal decomposition temperatures are higher than those of cell–THPC–urea–ADP, which shows these metal ions can increase the thermal stability of cell–THPC–urea–ADP. Moreover, these lanthanide metal ions can more increase thermal stability of samples than do the transition metal ion Co²⁺. The cone calorimetry data indicate that the lanthanide metal ions, similar to transition metal Co²⁺, greatly decrease the smoke, CO and CO₂ generation of cell–THPC–urea–ADP, which can be used as smoke suppressants.     

DSC investigation of nanocrystalline TiO<Subscript>2</Subscript> powder

The aim of the article is to investigate the influence of particle size on titanium dioxide phase transformations. Nanocrystalline titanium dioxide powder was obtained through a hydrothermal procedure in an aqueous media at high pressure (in the range 25–100 atm) and low temperature (≤200 °C). The as-prepared samples were characterized with respect to their composition by ICP (inductive coupled plasma), structure and morphology by XRD (X-ray diffraction), and TEM (transmission electron microscopy), thermal behavior by TG (thermogravimetry) coupled with DSC (differential scanning calorimetry). Thermal behavior of nanostructured TiO₂ was compared with three commercial TiO₂ samples. The sequence of brookite–anatase–rutile phase transformation in TiO₂ samples was investigated. The heat capacity of anatase and rutile in a large temperature range are reported.     

Emanation thermal analysis study of synthetic gibbsite

Emanation thermal analysis (ETA) was used for thermal characterization of microstructure changes taking place during heating of synthetic gibbsite sample in argon in the range of 25–1200°C. Microstructure development and the increase of the surface area under in-situ conditions of the sample heating were characterized. The increase of the radon release rate from 130–330°C monitored the increase of the surface area due to the dehydration of Al(OH)₃. During heating of the sample in the range 450–1080°C the ETA results characterized the annealing of surface and near surface structure irregularities of intermediate products of gibbsite heat treatment. The mathematical model for the evaluation of the ETA experimental results was proposed. From the comparison of the experimental ETA results with the model curves it followed that the model is suitable for the quantitative characterization of microstructure changes taking place on heating of gibbsite sample. This revised version was published online in July 2006 with corrections to the Cover Date.