DTA Studies Research Articles

AErP2O7 (A = Rb, Cs) and HEuP2O7·3H2O: Crystal Structures, Vibrational Studies and Thermal Behaviours

New diphosphates AErP2O7, A = Rb (1), Cs (2), and HEuP2O7·3H2O (3) have been prepared via soft chemistry route from evaporation of aqueous solution. Their crystal structures have been solved by single crystal diffraction data. The compounds (1) and (2) crystallize in the monoclinic space group P21/c with the following unit cell dimensions: (1) a = 7.7248(4) A, b = 10.9342(6) A, c = 8.6716(3) A, β = 105.434(4)° and Z = 4; (2) a = 7.9192(4) A, b = 10.8606(4) A, c = 8.7684(5) A, β = 104.317(5)° and Z = 4. Compound (3) crystallises in the triclinic space group P − 1, with the unit cell parameters: a = 6.4036(5) A, b = 6.8753(6) A, c = 9.7964(8) A, α = 81.706(7)°, β = 80.218(7)°, γ = 88.381(7)°. Crystal structure of (1) and (2) consists of 3D open framework built from [ErO6] octahedra sharing corners with [P2O7] units, leading to the formation of channels running along c direction in which A+ [A = Rb(1), Cs(2)] ions are located. The compound (3), on the other hand, exhibits a lamellar structure, in which edge-sharing polyhedra of eightfold coordinated europium form chains along [010]. These chains are joined in turn to each others using diphosphates bridges. A network of O–H···O hydrogen bonds reinforces the cohesion of the structure of (3). The diphosphate groups in (1), (2) and (3) adopts an eclipsed configuration. IR and Raman spectra of the three new phosphates show usual signals related to the P2O7 diphosphate group and the water molecule. TG and DTA studies were carried out on crystals of (3). The data are correlated to the crystal structures ones. Edge-sharing [LnO8] polyhedra (here Ln is Eu) lead to ladder channels in the crystal structure of HEuP2O7·3H2O. These channels are linked through O–P–O bridges from the diphsophates groups and an intricate H-bonds network to build a lamellar structure. Crystal structure of AErP2O7, A is Rb or Cs consists of a three dimensional open framework, built from octa-coordinated Er which share corners with diphosphates groups. These channels run through the monoclinic cell along c, in which the nonovalent cations are located.

Effect of fillers based on calcium hydro hardening process of lime composites

The information about the laws of hardening of the lime-filled composites based on calcium hydro are given. According to DTA, chemical and physico-mechanical studies have established the chemical interaction of fillers based on calcium hydro with lime. The acceleration of hardening of lime composites and hardening of the structure of the lime composites is shown

Effect of Sr-doping on multiferroic properties of Bi0.8La0.2Fe0.9Mn0.1O3

The effect of Sr-doping on ferroelectricity and ferromagnetism at room temperature has been studied for Bi0.8La0.2Fe0.9Mn0.1O3 ceramic system. X-ray diffraction shows that a structural phase transition occurs from rhombohedral structure of BiFeO3 (space group R3c) to orthorhombic structure of Bi0.8La0.2FeO3 (space group C222). Substitutions of Sr-ions in Bi-site and Mn-ions in Fe-site do not induce any further structural change. Moreover, doping of Sr-ions plays a crucial role to obtain single phased samples. DTA and TGA studies show that both the magnetic transition temperature (TM) and the ferroelectric transition temperature (TC) decrease for Bi0.7Sr0.1La0.2Fe0.9Mn0.1O3. Sr-doping enhances the ferroelectric property by increasing the electric polarization. M–H measurement shows that Sr-ions partially destroy the spin cycloidal structure in it giving rise to weak ferromagnetism (nonlinearity) at room temperature.

Research on SUE DTA Model with Constant Demand Based on Probit Model

Logit model is among the most important model in SUE DTA study. A lot of work have been done based on Logit model. As the other very important SUE DTA model, Probit model has not been the focus of many researcher. This paper presents a SUE model based on Probit model, which aims at building up the Probit model with constant demand. The existence and uniqueness of the model is presented, Finally, a algorithm is given.

Synthesis, spectroscopic characterization, pH-metric and thermal behavior on Co(II) complexes formed with 4-(2-pyridyl)-3-thiosemicarbazide derivatives

Four new cobalt (II) complexes of some thiosemicarbazides have been synthesized and spectrochemically characterized. The thiosemicarbazides are prepared by the addition of 4-(2-pyridyl)-3-thiosemicarbazide to phenyl isothiocyanate (H 2PPS), benzoyl isothiocyanate (H 2PBO), phenyl isocyanate (H 2APO) and 2-pyridyl isothiocyanate (H 2PPY). The complexes are characterized by elemental analysis, spectral (IR, 1H NMR and UV–Vis), thermal and magnetic measurements. The studies revealed that structures of complexes are of two types octahedral and tetrahedral. The octahedral complexes are of H 2PPS, which acts as di-anionic tetradentate SSNN and H 2APO acts as mono-anionic tridentate NON. The tetrahedral complexes are of H 2PBO, which acts as di-anionic tridentate NSO and H 2PPY acts as mono-anionic bidentate NS. From the modelling studies, the bond length, bond angle, HOMO, LUMO and dipole moment had been calculated to confirm the geometry of the ligands and their investigated complexes. From TG and DTA studies kinetic parameters are determined using Coats–Redfern and Horowitz–Metzger methods. From pH metric studies at 298, 303 and 308 K and μ (0.1, 0.15 and 0.2) in 50% dioxane–water mixture the protonation constants of the ligands, the stepwise stability constants of the complexes and their thermodynamic parameters are calculated.

Spectroscopic, thermal and antitumor investigations of sulfasalazine drug in situ complexation with alkaline earth metal ions

The complexes of sulfasalazine (H 3Suz) with some of alkaline metals Mg(II), Ca(II), Sr(II) and Ba(II) have been investigated. Sulfasalazine complexes were synthesized and characterized by spectroscopic tools; infrared spectra, electronic and mass spectra. The IR spectra of the prepared complexes were suggested that the H 3Suz behaves as a bi-dentate ligand through the carboxylic and phenolic groups. The molar conductance measurements gave an idea about the non-electrolytic behavior of the H 3Suz complexes. The thermal decomposition processes for metal(II) complexes of H 3Suz viz: [M(HSuz)(H 2O) 4] (where M = Mg(II), Ca(II), Sr(II) or Ba(II)) have been accomplished on the basis of TG/DTG and DTA studies, and the formula conforms to the stoichiometry of the complexes based on elemental analysis. The kinetic analyses of the thermal decomposition were studied using the Coats–Redfern and Horowitz–Metzger equations. The antitumor and antimicrobial activities of the H 3Suz and their alkaline metal(II) complexes were evaluated.

Synthesis, characterization, magnetic and electrical properties of the novel conductive and magnetic Polyaniline/MgFe 2O 4 nanocomposite having the core–shell structure

Conductive and magnetic Polyaniline/MgFe 2O 4 nanocomposite was successfully synthesized in the form of core–shell via in situ chemical polymerization of aniline in the presence of MgFe 2O 4 nano-particles. X-ray powder diffraction of ferrites indicated that the structure of the core material is having the spinel structure, and demonstrated the formation of PAni/MgFe 2O 4 nanocomposite. XRD and TEM photographs showed that the particle's size of the MgFe 2O 4 core-material were around 30–35 nm before coating with Polyaniline, and grown up to 45 nm in the core–shell nanocomposite after coating. Although PAni has a relatively smaller electrical field coefficient than the core–shell nanocomposite, the resistivity of the core–shell material decreased, and hence its conductivity increased after a certain threshold voltage of 0.98 V equivalent to threshold electric field value equals 5.5 V cm −1. The magnetic hysteresis loops investigated with VSM indicated that coating MgFe 2O 4 with Polyaniline has an healing effect which covers the ferrite surface defects, thus decreasing the magnetic surface anisotropy of ferrite particles leading to a decrease of the saturated magnetization (Ms) from 21.33 emu/g to 5.905 emu/g and a decrease of the coercivity (Hc) from 88.66 Oe to 81.6 Oe for MgFe 2O 4 and the core–shell nanocomposite respectively due to the amount of Polyaniline added. TGA and DTA revealed improved thermal stability of the core–shell nanocomposite with respect to that of Polyaniline due to the incorporation of ferrites. Raman spectroscopy confirmed TGA, DTA and XRD studies, and revealed that pure PAni is less stable than the corresponding core–shell nanocomposite with respect to molecular changes which might occur during heating at elevated temperatures. Moreover, Raman study confirmed the interfacial interaction between the core and the shell materials, and lead to an assumption about the presence of different conjugation chain lengths and types, such as the presence of the semi-quinones aside the quinone rings in the polymer chain, which showed different response upon heating the sample.

Characterization of anion–cationic surfactants modified montmorillonite and its application for the removal of methyl orange

Anion–cationic, anionic and cationic surfactants modified montmorillonite (MMT) are prepared by incorporating cationic surfactants cetyl trimethyl ammonium bromide (CTMAB), anionic surfactants sodium stearate (SSTA) and their mixture to montmorillonite. The modified samples are characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy and Thermogravimetry–differential thermal analysis (TG–DTA). XRD result shows that both the anionic and cationic surfactants can be intercalated into the MMT, making the interlayer spaces of MMT expand. TG–DTA studies indicate the organic carbon contents of anion–cationic surfactants modified MMT are higher than the montmorillonite modified by anionic or cationic surfactants solely. The adsorption experiments indicate that CTMAB/10SSTA–MMT had the largest adsorption capacity compared with CTMAB–MMT and 10SSTA–MMT due to the formation of a highly effective partition medium by anion–cationic surfactant micelle. The adsorption kinetic of methyl orange onto the modified MMT samples can be best described by the pseudo-second-order model, and the adsorption isotherm is in good agreement with the Langmuir equation. The activation energy, change of free energy, enthalpy and entropy of anion–cationic modified MMT are also evaluated for the adsorption of methyl orange. Thermodynamic results indicate that the adsorption is a spontaneous and exothermic process.

Evaluation of Thermal Behavior of Microwave Induced Graft Copolymerization of Ethylmethacrylate onto Soy Protein Concentrate

Graft copolymerization of ethylmethacrylate (EMA) onto soy protein concentrate (SPC) was carried-out using ascorbic acid/potassium persulphate as redox initiator under microwave radiations. Different reaction parameters like reaction time, solvent amount, initiator ratio, pH and monomer concentration were optimized to get maximum graft yield (78.8%). The graft copolymer formed was characterized by FTIR, XRD, SEM, TGA, DTA and DTG techniques. Graft copolymer showed higher moisture resistance along with increased chemical and thermal stability. TGA, DTA and DTG studies could reveal the distinctive features of graft copolymerization of EMA onto S-S linkages of soy protein concentrate under the influence of microwave irradiations in addition to grafting at peptide linkages, which were further supported by FT-IR studies.

Thermal study of unaltered and altered dolomitic rock samples from ancient monuments

In this study, the decomposition behaviour of unaltered and altered dolomitic rock samples used in Cultural Heritage buildings was studied by simultaneous TG–DTA experiments at different atmospheres, X-ray diffraction in a high-temperature chamber, and evolved gas analysis. The components of dolomite rock samples and hydrated calcium oxalate formed during the alteration processes of the rocks were characterized, and the decomposition mechanisms of these components were determined. The TG–DTA experiments carried out at CO2 atmosphere were used to determine the carbonate compounds in the rock samples. The TG–DTA study characterized the presence of organic compounds formed during the biological degradation of the rock samples, possibly responsible of the hydrated calcium oxalate formation.

Production and characterization of PHA from recombinant E. coli harbouring phaC1 gene of indigenous Pseudomonas sp. LDC-5 using molasses.

Polyhydroxyalkanoates (PHA) are biodegradable and biocompatible green thermoplastics, synthesized by wide variety of bacteria as an intracellular carbon and energy storage intermediate. They are used as an alternative to nonrenewable petroleum derived plastics. The current interest in these biopolyesters is stimulated by the search for cost-effective capitalized production. This paper attempts to achieve maximized production rate from recombinant system using inexpensive substrate. Molasses from agro-industrial waste was used to produce PHA from recombinant E.coli in batch culture. PHA yield in molasses (3.06g/L ± 0.05‒75.5%) was higher than that of sucrose (2.5g/L ± 0.05 - 65.1%). Properties of the polymer produced from molasses and sucrose were analyzed by DSC, TGA, DTA, GC/MS, TLC and optical rotation studies. The findings suggested that molasses enhanced PHA production in recombinant E.coli.

Synthesis, characterization and analytical application of nano-composite cation-exchange material, poly-o-toluidine Ce(IV) phosphate: Its application in making Cd(II) ion selective membrane electrode

An organic-inorganic composite, poly-o-toluidine Ce(IV) phosphate was chemically synthesized by mixing ortho-toluidine into the gel of Ce(IV) phosphate in different mixing volume ratios. Effect of eluant concentration, elution behavior and pH-titration studies were carried out to understand the ion-exchange capabilities. The physico-chemical properties of the material were determined using AAS, CHN elemental analysis, UV–VIS spectrophotometry, FTIR, SEM/EDX, TGA–DTA, TEM (Transmission electron microscopy), XRD and SEM studies. The distribution studies revealed that the cation-exchange material is highly selective for Cd(II). Due to selective nature of the cation-exchanger, ion selective membrane electrode was fabricated for the determination of Cd(ІІ) ions in solutions. The analytical utility of this electrode was established by employing it as an indicator electrode in electrometric titrations.

Silver loss during the oxidative refining of silver–copper alloys

The high temperature oxidative refining of molten silver–copper alloys is accompanied by silver losses to the slag. Typically, borosilicate slags are utilized as a flux and air or oxygen is injected into the molten alloy. The majority of the copper can be selectively oxidized to copper oxide, but some silver is also lost to the slag. In this research, the mechanism of silver loss has been investigated. Firstly, TGA and DTA studies of molten silver–copper alloys were performed, in order to elucidate the oxidation processes occurring at the gas–metal interface in the bubble. Secondly, the silver losses to the slag in the high temperature refining tests were quantified. Thirdly, the slag was characterized using XRD and the morphology of the silver in the slag was examined. Fourthly, a pseudo-equilibrium model of the refining process was developed and this was utilized to suggest methods for minimizing the silver loss to the slag. Finally, possible methods for recovering the silver from the slag are discussed.

Growth and characterization of α and γ-glycine single crystals

Single crystals of α- and γ-glycine were grown by the slow evaporation solution growth method using deionised water as solvent. The α-glycine was transformed to γ-glycine by addition of KNO3 as additive and both the forms of glycine single crystals were grown and the characteristic properties were studied and compared. From the single crystal XRD analysis the grown α- and γ-glycine crystals are confirmed. The presence of the functional groups of α- and γ-glycine was analyzed from the recorded FT-IR spectrum. The optical transmission was ascertained from UV–vis–NIR spectrum. The lower cut-off wavelengths of α- and γ-glycine are 292 and 272nm, respectively. The second harmonic generation relative efficiency was measured by the Kurtz and Perry powder technique. Group theoretical analysis predicts 120 vibrational optical modes in α-glycine and 90 vibrational optical modes in γ-glycine. The TGA, DTA and dielectric studies were carried out to explore information about thermal and dielectric behavior, respectively, for α- and γ-glycine.

Synthesis, dielectric behavior and impedance measurement studies of Cr-substituted Zn–Mn ferrites

Graphical abstract: Variation of dielectric constant with frequency. Research highlights: {yields} Sol-gel route synthesized spherical crystalline nanoparticles of ZnMn{sub 1-x}Cr{sub x}FeO{sub 4}. {yields} XRD, DTA, FTIR, SEM, dielectric and impedance study. {yields} The ferrites show concentration dependence of ac electrical conductivity. {yields} Impedance response is dominated by grain boundary behavior. -- Abstract: Nanocrystalline ZnMn{sub 1-x}Cr{sub x}FeO{sub 4} (1.0 {>=} x {>=} 0) ferrites were synthesized by sol-gel technique. X-ray diffraction (XRD) confirmed the formation of single phasic cubic spinel lattice for all the compositions studied. Lattice parameter shows a decreasing trend with an increase in Cr content in the compositions. Formation of spherical nanoparticles was revealed by scanning electron microscopy (SEM) analysis. Infrared spectroscopic studies revealed two main absorption bands in the range 400-800 cm{sup -1} arising due to tetrahedral (A) and octahedral (B) site vibrations. Dielectric constant, dielectric loss tangent, ac conductivity and complex impedance were measured as a function of frequency in the range 20 Hz to 1 MHz. Frequency dependence of dielectric constant shows dielectric dispersion due to the Maxwell-Wagner type of interfacial polarization. The role of chromium in modifying structural and dielectric properties of these ferrites has been explained.

Synthesis, luminescence properties of a novel aromatic carboxylic acid ( L) and corresponding Eu(III) and Tb(III) compounds as well as the binding characteristics of L with bovine serum albumin (BSA)

A novel polyamino polycarboxylic pyridine derivative ligand, N, N, N 1, N 1-(2,6-bis((3-(aminoethyl)-5-methyl-1H-pyrazol-1-yl)methyl)pyridine)hexakis(acetic acid) ( L), was designed and synthesized with the motive that it is able to sensitize the emission of lanthanides. Its corresponding Eu(III) and Tb(III) complexes Na 4EuLCl 3·3H 2O and Na 4TbLCl 3·5H 2O were successfully prepared. The ligand and the complexes were characterized by elemental analysis, IR, MS, NMR and TG–DTA. The luminescence properties of the compounds in solid state were investigated; each complex had very narrow emission bands and strong luminescence intensity up to about 10,000. The TG–DTA studies showed that the initial decomposition temperature of both complexes was over 250 °C, elucidating the complexes had a high thermal stability. Meanwhile, the comparison with similar complexes suggested that the ligand with more coordination sites possessed more efficient antenna effect. To explore the potential medicinal value of L, the binding interaction of L and bovine serum albumin (BSA) was carried out by fluorescence spectrum. The studies indicated that the reaction between L and BSA was a static quenching procedure. The binding site number n and binding constant Ka were calculated according to the double logarithm regression equation. The thermodynamic parameters showed the Van der Waals and hydrogen bond interactions were the mainly impulse to the reaction.

ChemInform Abstract: High-Temperature Phase Transition in Potassium Dihydrogen Phosphate Crystals.

Abstract Single crystals of potassium dihydrogen phosphate (KDP) were grown by slow evaporation from supersaturated aqueous solution. The crystal structure of KDP was identified by X-ray diffraction analysis. Simultaneous TG, DTG and DTA thermal analysis of KDP crystals over the temperature range 25–600° C showed that the potassium orthophosphate decomposed to potassium pyrophosphate and then to metaphosphate as end product. DTA studies at the higher heating rates of 50 and 100° C min−1 showed a clear resolution of the first peak into two peaks; the first was attributed to a phase transition at 200 °C and the second was due to the decomposition of the sample. It is interesting to note that the high-temperature phase transition for KDP was also obtained at 175° C by DSC studies at 2° C min−1. The activation energies for the thermal processes of KDP occurring at 230, 265 and 310°C were calculated as 155.56, 286.56 and 81.46 kJ mol−1 by the Kissinger method, and 164.01, 294.97 and 91.34 kJ mol−1 by the Ozawa method. X-ray diffraction and infrared absorption spectra confirmed the high-temperature phase transition obtained by DTA and DSC as well as the thermal decomposition of the KDP samples.

Synthesis, spectral investigations, antimicrobial activity and DNA-binding studies of novel charge transfer complex of 1,10-phenanthroline as an electron donor with π-acceptor p-Nitrophenol

Proton or charge transfer (CT) complex of donor, 1,10-phenanthroline (Phen) with π-acceptor, p-Nitrophenol (PNP) has been studied spectrophotometrically in methanol at room temperature. The binding of the CT complex with calf thymus (ct) DNA has been investigated by fluorescence spectrum, to establish the ability of the CT complex of its interaction with DNA. Stern–Volmer quenching constant ( Ksv) has also been calculated. The formation constant ( K CT), molar extinction coefficient ( ε CT), free energy (Δ G o) and stoichiometric ratio of the CT complex have been determined by Benesi–Hildebrand equation. The stoichiometry was found to be 1:1. The CT complex was screened for its pharmacology as antibacterial and antifungal activity against various bacterial and fungal strains, showing excellent antibacterial and antifungal activity. The newly synthesized CT complex has been characterized by FTIR spectra, elemental analysis, 1H NMR, electronic absorption spectra. TGA–DTA studies were also carried out to check the stability of CT complex.

Preparation and characterization of polyethylene oxide (PEO)/gelatin blend for biomedical application: Effect of gamma radiation

Abstractpolyethylene oxide (PEO)/gelatin blend membranes of four different compositions (w/w) (5/95, 10/90, 20/80, and 30/70) were prepared by solution casting. The films were irradiated by gamma radiation at a total dose of 250 krad (dose rate of 321 krad/h). The X‐ray diffractograms demonstrate both the PEO and radiation influences on the blend thus enhancing crystallinity of gelatin. X‐ray diffractograms of irradiated blend films containing 30% PEO showed highest integrated intensity. The DTA and TGA study showed that the irradiated blend films are more thermally stable than the non‐irradiated films. TMA study showed that the incorporation of PEO into gelatin increased melting point of the blend films. The melting point for irradiated gelatin film changes from 52.9°C to 75.6°C and the glass point changes from 60.3°C to 90.6°C. The phase separation and compatibility of the PEO/gelatin blend films were studied by scanning electron microscopy (SEM). The experimental results showed that the blend films exhibit higher thermal stability and improved mechanical properties in dry state, which suggests the occurrence of interaction detected by XRD and DTA among gelatin, PEO, and water molecules in the films. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

IR, density and DTA studies the effect of replacing Pb 3O 4 by CuO in pseudo-binary Li 2B 4O 7–Pb 3O 4 glass system

Effect of replacement of Pb 3O 4 by CuO on structure and properties of pseudo-binary [75%] Li 2B 4O 7–[25 − x%] Pb 3O 4 glass system, where x = 0, 5, 10, 15, 20 and 25 mol% CuO, have been investigated. IR spectra of the prepared glasses show that CuO goes into the network and play also a role as a glass modifier. The addition of CuO decreases the formation of tetrahedral groups (BO 4) and increasing the triangle one (BO 3), led to increase the borate non-bridging oxygen (NBO). The observed increase in T g with CuO reflect increase in bond strength, also the glass-forming ability and stability decrease with increasing CuO reflects the reduction of the network rigidity and loosening of glassy structure. The density and molar volume were discussed in terms of the structural modifications that take place in glass matrix. The distance between Cu and Cu atoms and the polaron radius have been carried for all samples.