TG-DTA Analysis Research Articles

Characterization of chemosynthetic H3PO4–Al2O3–2SiO2 geopolymers

Pure chemosynthetic Al2O3–2SiO2 powders fabricated by a sol–gel method exhibit high phosphoric acid-activated properties and high compressive strengths. The phosphoric acid-activated properties could be characterized by compressive strength. The phase structure evolution of synthetic powders and the resulting geopolymers were investigated by DTA-TG, XRD, FTIR and MAS NMR analysis. These results show that the phosphoric acid-activation region of the synthetic powders was in the range of 200–800°C, which was much lower than the temperature at which kaolinite was converted into metakaolinite. 31P MAS NMR analysis revealed that [PO4] tetrahedra were part of the geopolymer structure.

Textural characteristics, degree of protonation, water uptake and proton transport properties relationships in colloidal sol–gel derived micro- and mesoporous silica membranes

The effect of textural characteristics and the degree of surface protonation of the pore wall on water uptake and proton conductivity in micro- and mesoporous SiO2 membranes, prepared by colloidal sol–gel route, has been studied. For that, some aspects of the pore structure of the xerogels have been modified by the control of the size and the packing process of the nanoparticles in the sol. In addition, the modification of the pH before gelation changes the degree of the surface protonation of the pore wall for the resulting xerogels. Pore volume (Pv), pore size (Ps), and specific surface area (SSA) have been evaluated with nitrogen sorption techniques. Water content and water adsorption isotherms were calculated using data from DTA-TG analysis. In addition, proton conductivity was measured using impedance spectroscopy under controlled temperature and relative humidity (RH).At a given RH, membranes with the same water content showed differences in proton conductivity, then, water content is not the predominant variable controlling proton conductivity.For instance, at low and intermediate RH values (33 and 58%), the membranes with the highest proton conductivity were the membranes with the largest water contents, the smallest average pore sizes, and the highest specific surface area/pore volume (SSA/Pv) ratio. In particular, the membranes with the smallest average pore size (2.2 nm), i.e., the xerogels obtained from sols adjusted to pH 5.0 showed proton conductivity values of more than two orders of magnitude than those with the largest pore sizes. At high RH (75, 81, and 97%) the xerogels with the highest proton conductivity were the xerogels with the largest water content, the largest average pore sizes, the lowest SSA/Pv ratio, and the highest connectivity. Xerogels adjusted to pH 6.0 and 8.0 present all of those characteristics and both have the same water content at those RH; however, the membranes adjusted to pH 6.0 present the highest proton conductivity. That membrane has the highest degree of surface protonation and the highest connectivity value, if we compare both. It is clear that the features of the pore network influence the structure of the pore water that consequently affects the mobility of the protons. It seems that the SSA/Pv ratio, the average pore size, and the connectivity are the textural properties of these materials, within those studied in this work, having the most influence on proton conductivity. Furthermore, the degree of surface protonation of the pore wall seems to have also an important influence on proton conductivity, at least at high RH. The highest value of proton conductivity found was 2.01 × 10−2 Scm−1 at 80 °C and 81% RH and corresponds to the membrane prepared from the sol adjusted to pH 6.0. In addition, proton conductivity showed an Arrhenius-like dependence on temperature in all cases and according to the activation energy values, proton migration is dominated by the Grotthuss mechanism at low and intermediate RH. At high RH the vehicle mechanism also occurs for the xerogels adjusted to pH 6.0 and 8.0 according to the low activation energy values found (0.08–0.13 eV).

Formation of SrTiO3 in mechanically activated SrCO3–TiO2 system

In this study, mechanical activation process was used for intimate mixing as well as producing finely ground particles, increased surface area and improved chemical reactivity of milled materials for producing SrTiO3 from commercially pure strontium carbonate and TiO2 as a contributive process. Characterization of milled powder mixture by X-ray diffraction analysis showed that disappearing, decreasing and/or shifting of the patterns occurred with mechanical activation that means amorphization was taken place. Amorphization was also demonstrated by FT-IR analysis where shift of band centers as well as the decrement of transmittance related to CO3 was observed. Advantage of amorphization was established with high-temperature XRD analysis which showed 1300 °C was not enough for non-activated mixture to form SrTiO3, whereas structure only composed of SrTiO3 at 1000 °C for activated ones. The reason for this phenomenon was investigated by DTA-TG analysis, and it was based on energy accumulation originated from mechanical activation that corresponds to peak temperature shifting to the lower temperatures and CO2 liberation at mechanical activation step arising from local temperature rising at the vial during high-energy milling that was understood from peak temperature, and area decrement of endothermic peak corresponds to decomposition of SrCO3.

Ni and Ni-Co La0.8Sr0.2Ga0.8Mg0.2O3−δ infiltrated cells in H2and CH4/CO2 mixture

La0.8Sr0.2Ga0.8Mg0.2O3−δ(LSGM) based fuel cells infiltrated with different metal catalysts were fabricated and tested both in H2 and CH4/CO2mixture. Ni, Co, Ni-Cu, Ni-Co LSGM impregnated powders were investigated for the dry reforming of methane reaction (DRM) (CH4+CO2⇆2CO+2H2). The catalytic activity for CH4 and CO2 conversion followed the order Ni∼Ni-Co>Co>Ni-Cu. Both Ni and Ni-Co catalysts, investigated versus time (50h) on stream of CH4/CO2=1.5at 800°C, did not show any sign of deactivation indicating their stability toward coke deposition. Anyway, evidence of few carbon filaments was revealed by SEM micrographs and the carbon amount evaluated by TG-DTA analysis. Ni-LSGM and Ni-CoLSGM cells showed regarding electrochemical performance both in H2 and CH4/CO2 mixture in the 650–750°C temperature range. A discussion on the parallelism between catalytic and electrochemical performance is detailed.

Ion-exchange synthesis and improved Li insertion property of lithiated H2Ti12O25 as a negative electrode material for lithium-ion batteries

We successfully prepared the lithiated H2Ti12O25 sample by the H+/Li+ ion exchange synthetic technique in the molten LiNO3 at 270 °C using H2Ti12O25 as a starting compound. Chemical composition of the obtained lithiated H2Ti12O25 sample was determined to be H1.05Li0.35Ti12O25-δ having δ = 0.3 by ICP-AES and DTA-TG analyses. The H+/Li+ ion exchange was also confirmed by powder XRD, 1H-MAS NMR, and 7Li-MAS NMR measurements. Electrochemical Li insertion and extraction measurements revealed that the initial coulombic efficiency was improved from 88% in H2Ti12O25 to 93% in the lithiated H2Ti12O25 sample. In addition, superior capacity retention properties for the charge and discharge cycling performance and good charge rate capability of the present lithiated H2Ti12O25 were confirmed in the electrochemical measurements. Accordingly, the lithiated H2Ti12O25 is suggested to be one of the promising high-voltage and high-capacity oxide negative electrodes in advanced lithium-ion batteries.

Synthesis, crystal structure, spectroscopic and thermal analysis of hydrazinium hydrogen-3,5-pyrazoledicarboxylate monohydrate

A new hydrazinium(+1) salt of 3,5-pyrazoledicarboxylic acid (H2Pzdca) of formula, (N2H5)HPzdca·H2O (HPzdca is a hydrogen-3,5-pyrazoledicarboxylate anion), was prepared and characterized using elemental analysis, FT-IR spectroscopy, TG-DTA, and single-crystal X-ray diffraction analysis. The salt crystallized in the space group P21/c. The monoclinic unit cell of the title compound, N2H5 +·C5H4N2O4 −·H2O, is a molecular salt consisting of one mono-protonated hydrazine cation [hydrazinium(+1) cation], one singly deprotonated hydrogen-3,5-pyrazoledicarboxylate anion, and one solvent water molecule. The overall structure is a 3-D supramolecular network formed through extensive O–H…O and N–H…O hydrogen-bonding interactions. Although the H2Pzdca monohydrate exhibited a two-step (110 and 298 °C) decomposition, its salt had multiple-step decompositions. The free acid underwent only endothermic decomposition, while its hydrazinium salt underwent an endothermic decomposition, followed by sharp exothermic degradation to form a black residue as the end product.

Synthesis, growth, structural, optical, thermal and mechanical properties of an organic Urea maleic acid single crystals for nonlinear optical applications

A potential organic urea maleic acid (UMA) was synthesized and single crystals were grown at room temperature by slow evaporation and seed rotation methods. The grown crystal has been subjected to single crystal XRD analysis and found to have been crystallized in a noncentrosymmetric monoclinic crystal system with Cc as space group. The High resolution X-ray diffraction analysis revealed that the specimen is free from structural grain boundaries. The transparency of the grown crystal was confirmed by optical absorption and transmittance spectra with lower cut-off wavelength of 285nm. The microhardness test was carried out on different planes to study the load dependent hardness values. The dislocation density of the UMA crystal was estimated from the etching studies. The dielectric permittivity and dielectric loss of the grown crystal was carried out as a function of frequency for different temperatures along three crystallographic axes. Thermal properties of UMA crystals were studied by TG-DTA analysis and it is stable upto 112°C. The laser induced surface damage threshold of the grown crystal was measured using Nd: YAG laser. The birefringence of the crystal measured in the visible region was found to vary with the wavelength. The particle size dependent SHG of the sample was measured with different input energies by Kurtz's powder method using Nd:YAG laser.

Synthesis of TiO2 nanostructure membrane and influence of ZrO2 addition on microstructure, thermal stability and membrane properties

A technique for the synthesis of crystalline TiO2 nano-structured membranes by the sol–gel method is determined. Macroporous α-alumina support was used as substrate and intermediate layer was gained by coating and calcination of the colloidal titania sol on the mechanical support. The effect of several processing variables on particle size and sol stability of titania was studied. The influence of 20 mol% zirconia doping on microstructure, liquid permeability, thermal and mechanical stability of composite titania/zirconia membranes was investigated. The thermal and mechanical stability, phase transformation, surface morphology, pore size distribution and permeation of the defect-free titania–zirconia membrane were investigated using X-ray diffraction, atomic force microscopy, gas adsorption analyzer, TG–DTA analysis, scanning electron microscope, FTIR analysis and water permeation apparatus, respectively. It was shown that zirconia retards the phase transformation of anatase to rutile until at least 700 °C. The pore size decreases to 1.2 nm by addition of up to 20 mol% zirconia, while nitrogen sorption experiments shows that the porosity, BET surface area and pore connectivity increases.

Facile hydrothermal synthesis and structural, optical, and morphological investigations on PVP assisted Fe doped CuO nanocomposites

Fe doped copper oxide (CuO) nanocomposites have been synthesized by hydrothermal method. The synthesized products have been characterized by XRD spectrometer, FT-IR, UV–Visible, PL, SEM/EDS spectroscopy, Atomic Force Microscopy (AFM), and TG–DTA analysis, respectively. XRD patterns show that the particle sizes are 16, 18, 21, and 17nm, respectively for Fe (8, 10, 12, and 14%) doped CuO samples. FT-IR study confirms the presence of metal oxides within the wave number range 490 to 605cm−1. UV–Visible spectroscopy study shows the variation in direct band gaps and compared with XRD results. PL study reveals that the luminescence intensities of the as-synthesized samples increase with increasing doping material concentration due mainly to the increase of crystallinity. The porous aggregated nanocomposties, presence of Cu, Fe, and O elements have been confirmed by SEM /EDS analysis. AFM study confirms the formation cone shaped nanocomposites (10 nm), and are consistent with XRD results. Inorganic decomposition takes place in temperature range 276°C-362°C with an endothermic peak at 433°C indicates the formation of Fe (12%) doped CuO which was confirmed by TG–DTA analysis.

The Influence of “Small Molecules” on Crystallization of TiO2 Xerogels

The sol-gel method was used for preparation of sols and the precursor sols were prepared from a mixture of titanium(IV) tetra-isopropoxide, isopropanol, water, nitric acid and “small molecule” as stabilizing reagent. The acetylacetone and acetic acid were used as small molecules (“stabilizers”). Three TiO2 xerogels were studied by DTA–TG analysis in combination with the XRD analysis. The crystallization was determined by non-isothermal analysis. The values of activation energy of crystallization were calculated using Johnson-Mehl-Avrami model. For xerogel without “small molecules” and xerogel with acetic acid, the activation energy of anatase crystallization is E = (1.07 ± 0.02)·105 J.mol-1 and E = (0.78 ± 0.02)·105 J.mol-1, respectively. According to Avrami coefficient M ∼ 1 for both xerogels, the mechanism of crystallization is surface nucleation. There is no crystallization of anatase in xerogel with acetylacetone.

Investigation and Comparison of Optical and Raman Bands of Mechanically Synthesised MoO3 Nano Powders

MoO3 Nano powders were synthesized using mechanochemical assisted synthesis technique at different time intervals at room temperature. The structural properties were analyzed by Powder X-ray Diffraction technique (PXRD), which reveals the average crystalline size, strain, dislocation densities and phase structure. The surface morphology and chemical composition of the sample is revealed by Scanning Electron Microscope (SEM) images and Energy Dispersive X-ray Spectroscopy (EDS) Spectra. The fundamental vibrational modes and Raman modes are demonstrated by FT-IR spectroscopy and Raman Spectroscopy and are compared. X-ray diffraction data is well matched with JCPDS data and confirms the orthorhombic α- MoO3 phase structure of the Nano powders. The band-energy is calculated from the UV-Spectra. The thermal properties are studies from TGDTA analysis.

Experimental studies from FT-IR with TG-DTA analysis of ferrites

Experimental studies from FT-IR with TG-DTA analysis of ferrites

Crystallisation, thermal analysis and acetal protection activity of new layered Zn(ii) hybrid polymorphs

Two new polymorphic mononuclear complexes, with analogous structural formula (C6H9N2)2[Zn(H2O)6](SO4)2·2H2O, of zinc(II) templated by 2-amino-6-methylpyridinium ligand have been discovered. These polymorphic hybrid crystals, which differ only in terms of their crystal structures, were prepared in one-step synthesis under ambient conditions and investigated for their thermal and catalytic properties. Single-crystal X-ray diffraction of the obtained materials revealed that polymorphs 1 and 2 crystallise in the triclinic system, space group P. In an effort to further explore the form diversity of these compounds, the structural arrangements and intermolecular interactions such as hydrogen-bonding and π⋯π interactions are discussed from which supramolecular assembly was formed. Meanwhile, these new polymorphic forms can be described as the stacking of 3D layers where the interlayer distances are 13.23 and 12.59 A for 1 and 2, respectively. The thermal behaviour of the precursors checked by TG-DTA analysis for both zinc sulfate polymorphs and variable temperature powder X-ray diffraction (VT-PXRD) show successive intermediate crystalline anhydrous phases upon dehydration in 1. The catalytic activity of both polymorphic structures has been tested in the acetalisation reaction of aldehydes as a benchmark process. Interestingly, both complexes showed excellent activity with almost total conversion in many examples and using MeOH as solvent and as the unique source of acetalisation.

Experimental studies from FT-IR with TG-DTA analysis of ferrites

Mg0.40Mn0.60-xNixFe2O4 spinel nanoferrites were obtained by the co-precipitation method. The as-obtained powders were characterised by XRD analysis. All nanoferrite powders obtained from different organic precursors, after synthesising, were pure spinel phase, without secondary phases. TEM and AFM analyses confirmed that the average crystallite size, estimated from Scherrer equation, was the smallest for nanoferrites obtained from a mixture of the compounds and showing their particle size ranging from 20 nm to 50 nm. The prepared nanoferrites were characterised by Fourier transform-infrared spectroscopy (FT-IR), thermogravimetry (TG), differential thermal analysis (DTA) and derivative thermogravity (DTG). The results of these observations are described and discussed.

Sol–gel Derived Mixed Oxide Zirconia: Titania Green Heterogeneous Catalysts and Their Performance in Acridine Derivatives Synthesis

Various zirconia content in ZrO2–TiO2 mixed oxide catalysts (x = 5, 10, 20 ZrO2 wt%) were synthesized by cost-effective sol–gel process and characterized by different techniques, i.e. XRD diffraction patterns, TG–DTA analyses, FTIR spectroscopy, N2 adsorption/desorption measurements, and TEM microscope. The investigation of the acidic/basic properties was studied by means of FTIR spectroscopy using pyridine as an adsorbed molecule. Characterization estimates exhibit that the deposition by ZrO2 improves the surface properties of TiO2 structures and increase the TiO2 surface area up to 92 m2/g. TEM results affirmed the homogeneous distribution of ZrO2 particles on the surface of TiO2 of particle size in the range of 12–17 nm. The performance of the prepared zirconia–titania catalysts with different concentration ratios in acridine derivates synthesis from hydroxyl-benzaldehyde was studied. The results of catalytic test reveal that, the activity of ZrO2–TiO2 catalysts was significantly enhanced by depositing an optimum amount ratio of ZrO2 reach to 10 % to raise the yield to 95, 97 and 99 %. This can be attributed to the higher its surface area and its performance as basic site catalyst in the studied test.

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CaCO 3 as a filler has been used in the PVC. In this study, industrial waste was used instead of CaCO 3 and were investigated changes in the thermal properties. Used in cutting waste was emerged during the produced in GRP pipe production from wet cutting. PVC, GRP waste powder and process aids were mixtured then produced in extrusion system for polymer matrix composite production. Thirteen different weight (%5-%70) percentages of cutting waste as a filler were reinforced to PVC. CaCO 3 reinforced and pure PVC were produced in extrusion system to make comparison. All PVC samples were evaluated through DTA-TG analysis.

Structural, optical, thermal, photoconductivity, laser damage threshold and fluorescence analysis of an organic material: β-P-amino benzoic acid single crystal

β-P-amino benzoic acid, an organic single crystal was grown by slow evaporation technique. Single crystal X-ray diffraction studies show that the grown crystal has β-polymorph of P-amino benzoic acid [β-PABA] form and the lattice parameters are a=6.30Å, b=8.61Å, c=12.43Å α=γ=90° and β=100.20°. FTIR analysis confirms that bands at 1588cm−1, 1415cm−1 are assigned to ring skeletal vibrations of title compound. The molecular structure of the grown crystal has been identified by Nuclear Magnetic Resonance spectral study. The optical absorbance spectrum from 200 to 1100nm shows that there is an edge absorbance in UV region. Optical band gap of the crystal has been assessed from the absorbance spectrum. The thermal properties of crystals were evaluated from TG-DTA analysis, it exhibits that there is no weight loss up to 187°C. Laser damage threshold indicates that the grown crystal has no surface damage up to 35mJ. Photoconductivity and fluorescence spectral experiments are also carried out and the results are discussed.

Influence of TiO2 on the electrochemical performance of pasted type β-nickel hydroxide electrode in alkaline electrolyte

Nickel hydroxide was used as the positive electrode material in rechargeable alkaline batteries, which plays a significant role in the field of electric energy storage devices. β-nickel hydroxide (β-Ni(OH)2) was prepared from nickel sulphate solution using potassium hydroxide as a precipitating agent. Pure β-phase of nickel hydroxide was confirmed from XRD and FT-IR studies. The effects of TiO2 additive on the β-Ni(OH)2 electrode performance are examined. The structure and property of the TiO2 added β-Ni(OH)2 were characterized by XRD, TG-DTA and SEM analysis. A pasted–type electrode is prepared using nickel hydroxide powder as the main active material on a nickel sheet as a current collector. Cyclic voltammetry and electrochemical impedance spectroscopy studies were performed to evaluate the electrochemical performance of the β-Ni(OH)2 and TiO2 added β-Ni(OH)2 electrodes in 6 M KOH electrolyte. Anodic (Epa) and cathodic (Epc) peak potentials are found to decrease after the addition of TiO2 into β-Ni(OH)2 electrode material. Further, addition of TiO2 is found to enhance the reversibility of the electrode reaction and also increase the separation of the oxidation current peak of the active material from the oxygen evolution current. Compared with pure β-Ni(OH)2 electrode, TiO2 added β-Ni(OH)2 electrode is found to exhibit higher proton diffusion coefficient (D) and lower charge transfer resistance. These findings suggest that the TiO2 added β-Ni(OH)2 electrode possess improved electrochemical properties and thus can be recognized as a promising candidate for the battery electrode applications.

Preparation of activated carbons from peach stone by H4P2O7 activation and its application for the removal of Acid Red 18 and dye containing wastewater

ABSTRACTThe present study consists of the preparation of activated carbon from peach stone (PSAC) by H4P2O7 activation and its detailed characterization. The influence of different activants and various operational conditions including; soaking time, activation time, and activation temperature during PSAC preparation were systematically investigated. The chemical properties and morphology of prepared activated carbon was characterized by various analytical techniques (FTIR, SEM and EDX). TG-DTA analysis showed that the pore development of PSAC was significant at temperatures > 450°C. The prepared PSAC were utilized for the rapid removal and adsorption of Acid Red 18 (AR18) from aqueous solution that follows pseudo–second-order kinetics. The Langmuir isotherm model corresponded well with equilibrium data than the others, implying that the adsorption of AR18 onto prepared PSAC from the aqueous solutions proceeds by a monolayer formation. Thermodynamic investigations showed that the adsorption process is an exothermic and spontaneous process. During reusability studies, PSAC showed complete removal of AR18 upto seventh cycle increasing its practical applicability. Finally the prepared PSAC showed the best adsorptive capacity as compared to commercial AC for dye removal from actual industrial wastewater. This confers the possibility of applying PSAC economically viable option for the treatment of industrial wastewaters containing dye pollutants using suitable reactor.

Ageing of fired-clay ceramics: Comparative study of rehydroxylation processes in a kaolinitic raw material and moon-shaped ceramic idol from the Bronze Age

ABSTRACT Sources of raw materials and identification of the provenance of ancient ceramics as well as the estimation of the firing temperatures of ceramic findings are two principal problems archaeologists solve with material scientists. These two problems are closely interconnected. This paper is focused on the identification of clay mineral kaolinite in a ceramic body of archaeological ceramic idol in comparison with a reference kaolinitic raw material. Kaolinite identified in studied ceramic samples can be from a primary source or a product of rehydroxylation of metakaolinite of the ceramics. The rehydroxylation process is simulated here in laboratory conditions in an autoclave by modifications of standardized test methods. The rehydroxylation process was studied on a kaolinitic raw material and the acquired results were then applied to evaluate samples of a unique archaeological object from the Late Bronze Age — a moon-shaped ceramic idol, which was found at an archaeological site near Prague in the Czech Republic. XRF, XRD, TG-DTA, TG-DSC and IR analyses were used to study this process. XRD and TA proved the presence of the clay mineral kaolinite in its end parts. A small amount of kaolinite was also detected in the central part, but only by TA. It was proved that kaolinite in the end parts originated from raw material and that its presence in the central part was caused by the rehydroxylation of the metakaolinite. It was probably due to the use of the moon-shaped ceramic idol as an andiron in an open fireplace.