DTA Studies Research Articles

Effect of CuO Doping on the Electrical Behavior of ZrO2

AbstractElectrical conductivity has been measured at different temperatures for ZrO2 doped with various molar ratios of CuO. The conductivity increases due to migration of vacancies, created by doping. The conductivity was found to increase with increase in temperature till 220 °C and thereafter decrease due to collapse of the fluorite framework. A second rise in conductivity around 500 °C was observed due to phase transition of ZrO2. X‐ray powder diffraction, DTA and IR studies were carried out for confirming doping effect and phase transition in ZrO2.

Synthesis and characterization of iron aluminide nanoparticles by DC thermal plasma jet

Intermetallic iron aluminide alloy nanoparticles were synthesized by non-transferred DC plasma spray torch at atmospheric pressure. These powder particles were characterized by vibrating sample magnetometer (VSM), X-ray diffraction (XRD), environmental scanning electron microscopy (ESEM), laser scattering particle size distribution analyzer, energy dispersive X-ray spectra (EDX) and thermo gravimetric-differential thermal analysis (TG/DTA) studies and the results are discussed. Commercially available iron and aluminium powders in the size range between 40 and 100 μm were ball milled with suitable ratio (Fe-85% and Al-15%) by weight to form a iron–aluminium blende; this was used as feed stock to synthesize iron aluminide nanoparticles. These nanoparticles particles were spherical in shape and black in colour, with the size range between 30 and 70 nm observed by ESEM. It is seen that the powders processed at higher power levels (15.3 kW) have more number of single spherical nanoparticles than powders processed at lower power levels (9.8 kW). The formation of iron aluminide nanoparticles is confirmed by XRD analysis and an exothermic reaction by DTA studies.

Effect of Na2O/K2O substitution on thermophysical properties of PbO based phosphate glasses

PbO based phosphate glasses having composition 40P2O5·12Al2O3·6B2O3·9PbO·xNa2O·(33−x)K2O (x=0−33) [F=Na/(Na+K)] have been prepared using conventional melt quench technique. Density, morphology, thermal expansion coefficient (α) and glass transition temperature (Tg) were studied as a function of Na/(Na+K) ratio. Formation of transparent, bubble free and clear glass was observed up to x=18 mol%. Density was found to vary from 2.70 to 3.69 g cm−3. The significant changes were noticed in external morphologies at temperatures corresponding to softening, half ball and melting points under high temperature microscope for three compositions (x=0, 10 and 15 mol%). These glasses recorded the softening and half ball temperatures in the range 454–470°C and 523–576°C respectively and melting temperatures agree well with DTA studies within the experimental limits. Glass transition temperature showed a broad maxima while thermal expansion coefficient (TEC) a broad minima around Na/(Na+K)=0.54. This behaviour is explained on the basis of bond formation/phase separation.

Effect of solvent exchanging process on the preparation of the hydrophobic silica aerogels by ambient pressure drying method using sodium silicate precursor

Experimental results obtained on the preparation of hydrophobic silica aerogels by ambient pressure drying method using the sodium silicate precursor with the variation of solvent exchanging process, are reported. The silica hydrogel was prepared by passing the 1.12 specific gravity sodium silicate through the Amberlite (TM) 120 Na+ resin and addition of 1 M ammonium hydroxide to silicic acid. The gel was kept in an oven for 3 h to strengthen the gel. Solvent exchange was carried out with ethanol and hexane for 36 h each followed by 24 h silylation using 20% hexamethyldisilazane (HMDZ) in hexane. Unreacted HMDZ was washed with hexane by keeping the gel in hexane for 24 h. Solvent was decanted and the gel was dried for 24 h by keeping the gel at 50 °C for 6 h, at 150 °C for 12 h and at 200 °C for 6 h. The low density (0.06 g/cm3), highly porous (96.9%), highly hydrophobic (contact angle of 160°), low thermal conductivity (0.07 W/m K) aerogels were obtained for the process of three times exchange with ethanol and three times exchange with hexane in 36 h each, followed by silylation with 20% HMDZ in hexane and two times washing with hexane in 24 h. FTIR studies showed the increase in the intensity of the Si–H and C–H bands of the aerogels with the increase of solvent exchanging times because of increase in silylation for more times of solvent exchange processes. It was found from the TG–DTA studies that the hydrophobicity of the aerogels retained up to the temperature of 325 °C. Water absorption studies show that the aerogels were remained hydrophobic up to 4 months when the aerogels were placed over the water as well as for up to 60 h in a 90% humid atmosphere. SEMs of the aerogels reveal that the pore sizes of the silica network increased, so the percentage of optical transparency decreased with the increase in exchange times with ethanol and hexane.

Synthesis and characterization of methylammonium tetrachlorocuprate (II) dihydrate crystals

AbstractSingle crystals of methylammonium tetrachlorocuprate (II) dihydrate were obtained by slow evaporation method at room temperature. The crystals were characterized through powder XRD, thermogravimetric (TG‐DTA), low temperature DSC studies and FTIR and far IR spectra. While the powder XRD confirms the crystallinity of the compound, the TG and DTA studies confirm the formation of the compound in the stoichiometric ratio and the presence of two water molecules of crystallization. The low temperature DSC study indicates a thermal anomaly at ‐3°C. The ordering of CH3NH3 group at low temperature causes phase transitions in the compound. The IR spectra characterize the various chemical bonding and water molecules in the compound. Laser Raman spectral studies under progress would help understand the mechanism of phase transitions at low temperatures. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Synthesis of a nanosize copolymer of 3,4‐ethylenedioxythiophene with diclofenac and characterization

AbstractCopolymer of 3,4‐ethylenedioxythiophene (EDOT) and diclofenac (DCF) was synthesized by chemical oxidation using FeCl3 in neutral medium. The copolymer exhibited good solubility in many organic solvents. The UV‐vis spectrum of the copolymer revealed the presence of benzenoid and polaron or bipolaron state. Random distribution of the monomers in the copolymer was proposed based on the reactivity ratios of the monomers determined using Fineman‐Ross and Kelen‐Tudos methods. The rate of the copolymerization depended on the first power of each monomer. The FTIR spectrum showed the presence of hydrogen bonded N‐H, quinone type structure of thiophene ring and C‐Cl bond in the copolymer. Linear variation of anodic peak current at 560 mV in the cyclic voltammogram of copolymer thin film with scan rate indicated the adherence of electroactive copolymer. When the applied potential increased from −600 to 1000 mV, the color of the copolymer changed from neutral yellow to brown and to violet medium showing multicolor electrochromic behaviour. XRD results revealed crystallite copolymer with size 87 nm. SEM analysis confirmed uniform crystalline nature of the copolymer. The TGA, DTA and DSC studies suggested good thermal stability of the copolymer. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2787–2796, 2007

Thermal behaviour of some Al(III)-Mg(II) polynuclear coordination compounds with polycarboxylic acid anions as ligands, precursors of aluminates

A TG, DTG and DTA study of three polynuclear coordination compounds, containing Al(III)-Mg(II), namely (NH4)4[Al2Mg(C4O5H4)4(OH)4]⋅2H2O, (NH4)4[MgAl2(C4H4O6)4(OH)4]⋅3H2O and (NH4)2[Al2Mg(C6O7H11)5(OH)5]⋅3H2O, has been reported together with the associated thermal decomposition mechanism rationalized in terms of intermediate products. As decomposition end-product, magnesium-aluminum spinel is obtained. The values of MgAl2O4 mean crystallite size depend on the anionic ligand contained by the precursor compound, varying in the order: malate (143 A) ligand contained by the precursor compound, varying in the order: malate (143 A)

Synthesis, characterization and crystal structure of zinc dimolybdate pentahydrate [formula omitted

The method of synthesis of zinc dimolybdate pentahydrate ZnMo 2 O 7 · 5 H 2 O has been elaborated. The crystal structure has been solved by X-ray powder diffraction methods. The space group of ZnMo 2 O 7 · 5 H 2 O is P 2 1 / c (14), with lattice parameters: 6.0021(9), 18.886(3), 8.725 ( 1 ) A ˚ , β = 93.85 ( 1 ) ∘ , V = 986.8 ( 2 ) A ˚ 3 . The decomposition of ZnMo 2 O 7 · 5 H 2 O in air and nitrogen was studied in situ by X-ray diffraction. Results of crystal structure determination and refinement by the Rietveld method, as well as results of IR and TGA, DTA studies performed for ZnMo 2 O 7 · 5 H 2 O , are presented.

Preparation and characterization of heat-resistant interpenetrating polymer network (IPN)

Interpenetrating polymer network (IPN) is a novel type of polymer hybrids, which possess physicochemical properties suitable for high performance coatings. Heat-resistant IPN have been prepared from immiscible resins, epoxy and silicones using a cross-linking agent and a catalyst. The products were analyzed by GPC, FT-IR, TG, DTA and SEM studies. The heat resistance property and corrosion behaviour of the IPNs were also determined. It was different from those of the individual resins. Silicone microdomains could be seen uniformly distributed in epoxy regions. Corrosion resistance property of the IPNs was evaluated by salt spray and impedance measurements. The IPNs withstood longer durations in the salt spray chamber.

Preparation and characterization of a new organic–inorganic nano-composite poly- o-toluidine Th(IV) phosphate: Its analytical applications as cation-exchanger and in making ion-selective electrode

An organic–inorganic hybrid poly- o-toluidine Th(IV) phosphate was chemically synthesized by mixing ortho-tolidine into the gel of Th(IV) phosphate in different mixing volume ratios, concentration of inorganic reactant with a fixed mixing volume ratios of organic polymer. The physico-chemical characterization was carried out by elemental analysis, TEM, SEM, XRD, FTIR and simultaneous TGA–DTA studies. The ion-exchange capacity, chemical stability, effect of eluant concentration, elution behavior and pH titration studies were also carried out to understand the ion-exchange capabilities. The distribution studies revealed that the cation-exchange material is highly selective for Hg 2+, which is an important environmental pollutant. Due to selective nature of the cation-exchanger ion-selective membrane electrode was fabricated for the determination of Hg(II) ions in solutions. The analytical utility of this electrode was established by employing it as an indicator electrode in electrometric titrations.

Growth and characterization of 2-amino-5-chlorobenzophenone (2A-5CB) single crystals

Organic nonlinear optical single crystals of 2-amino-5-chlorobenzophenone (2A-5CB) were grown in ethanol by slow solvent evaporation technique. The grown crystals were characterized by single-crystal XRD, FTIR, FT-Raman and UV–vis–NIR techniques. The UV–vis–NIR spectrum ascertains the cut-off wavelength of the sample as 390 nm. The powder second harmonic generation (SHG) technique reveals that 2A-5CB crystal has its SHG efficiency nearly three times that of KDP. The dielectric response of the sample was studied in the frequency region of 50 Hz–1 MHz at varying temperatures. The photoconductivity studies indicate that the 2A-5CB crystal exhibits negative photoconductivity. TGA–DTA studies confirm the melting point of the sample as 101.5 °C.

Antimicrobial Study of Newly Synthesized Lanthanide(III) Complexes of 2‐[2‐hydroxy‐3‐methoxyphenyl]‐3‐[2‐hydroxy‐3‐methoxybenzylamino]‐1,2‐dihydroquinazolin‐4(3H)‐one

New lanthanide(III) complexes with 2-[2-hydroxy-3-methoxyphenyl]-3-[hydroxyl-3-methoxybenzylamino]-1,2-dihydroquin- azoline-4(3H)-one (Hmpbaq) have been synthesized and characterized by elemental analysis, conductance measurements, magnetic susceptibilities, spectroscopic (IR, NMR, UV, EPR), and thermal studies. Molar conductance studies indicate 1 : 1 electrolytic behavior for these complexes. IR spectra indicate that Hmpbaq acts as a tridentate ligand coordinating through carbonyl oxygen, benzyl amine nitrogen, and deprotonated phenolic oxygen. TG and DTA studies of La(III) and Pr(III) complexes indicate the presence of two coordinated water molecules. Based on these studies, the complexes have been formulated as [La(mpbaq)2(H2O)2]NO3, where Ln = La(III), Pr(III), Nd(III), Sm(III), Eu(III), Gd(III), Th(III), Dy(III), and Y(III). The ligand, lanthanide(III) salts, and the corresponding complexes have been simultaneously screened for their antibacterial and antifungal activities and compared with the drugs in use.

Pyridine based zirconium(IV) and tin(IV) phosphates as new and novel intercalated ion exchangers

Pyridine based zirconium(IV) phosphate (PyZrP) and tin(IV) phosphate (PySnP) have been synthesized as new and novel intercalated ion exchangers. These materials have been characterized using X-ray, IR spectra, TG, DTG and DTA studies in addition to their ion exchange capacity, elution, pH titration, concentration and distribution behaviour. The distribution studies towards several metal ions in different media/concentrations have suggested that PyZrP and PySnP are selective for Hg(II) and Pb(II), respectively. As a consequence some binary separations of metal ions involving Hg(II) and Pb(II) ions have been performed on a column of these materials, demonstrating their analytical and environmental potential.

Structural influence of aluminium, gallium and indium metal oxides by means of dielectric and spectroscopic properties of CaO–Sb 2O 3–B 2O 3 glass system

Dielectric constant ( ɛ′), loss (tan δ), ac conductivity ( σ) of CaO–Sb 2O 3–B 2O 3:M 2O 3 (Al 2O 3, Ga 2O 3 and In 2O 3) glasses with varying concentrations of M 2O 3 (0–5 mol%), were measured as a function of frequency and temperature over moderately wide ranges. The analysis of results of these studies along with IR, Raman and optical absorption spectra and also DTA studies indicated that in the concentration ranges, 0 ≤ Al 2O 3 ≤ 4, 0 ≤ Ga 2O 3 ≤ 2 and 1 ≤ In 2O 3 ≤ 5, Al 3+, Ga 3+ ions occupy tetrahedral positions whereas In 3+ ions take up octahedral substitutional positions, cross-link with the other structural units in the glass network and increase the rigidity of the glass network.

Effect of MnO2 on the electrical conductivity of ZrO2

Electrical conductivity of ZrO2 doped with MnO2 has been measured at various temperatures for different molar ratios. The conductivity increases due to hopping of oxygen into neighboring vacancies, created by doping. Increase in temperature increases the rate of hopping, which results in the rise in conductivity and after attaining a maximum the conductivity, decrease due to collapse of the fluorite framework. All compositions show phase transition in ZrO2 from monoclinic to tetragonal at 746 K. The XRD, DTA, and FT-IR studies were carried out for confirming the doping effect and transition in ZrO2.

Crystallization and characterization of nonlinear optical l‐histidinium dihydrogen orthophosphate orthophosporic acid single crystal

AbstractL‐histidinium dihydrogen orthophosphate orthophosporic acid (abbreviated as LHP) with molecular formula C6H10N3O2+·H2PO4‐·H3PO4 was successfully grown by slow evaporation technique from aqueous solution. The crystal was characterized by X‐ray diffractometry (XRD), UV‐Vis‐NIR, TGA, DTA, microhardness and solubility studies. The dielectric constant and dielectric loss of the crystal were studied as function of frequency. Photoconductivity studies were also carried out on the sample. The SHG efficiency of the crystal is studied using the Kurtz and Perry technique. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Feasibility study on Czochralski (Cz) growth of 3-methoxy 4-hydroxy benzaldehyde (MHBA) single crystals for nonlinear optical applications

Reported large nonlinear optical coefficients such as d 22 = 23.8 d 36 KDP, d 21 = 13.5d 36 KDP, d 23 = 29.1 d 36 KDP, d 25 = 12.8 d 36 KDP of 3-methoxy 4-hydroxy benzaldehyde (MHBA) attract research on its bulk crystal growth for device application. The X-ray rocking and X-ray topographic studies of Cz-grown organic monoclinic crystals invariably reveal closely aligned sub-crystals which made melt growth difficult. In this context, the single crystal growth of MHBA by Czochralski pulling technique has been successfully demonstrated for the first time in the literature. Comparison study of obtained X-ray powder diffraction data with the literature confirmed the monoclinic structure. High-resolution X-ray diffraction (HRXRD) study confirms the better crystalline perfection of the grown crystal in comparison to that of solution-grown crystals and revealed the optimization of the growth process along [211¯] direction. TG, DTA and optical transmission studies carried out on the grown crystal exhibit its thermal and optical properties for SHG application.

Preparation, physico-chemical characterization, analytical applications and electrical conductivity measurement studies of an ‘organic–inorganic’ composite cation-exchanger: Polyaniline Sn(IV) phosphate

Polyaniline Sn(IV) phosphate, an ‘organic–inorganic’ composite material, was synthesized via sol–gel mixing of an electrically conducting organic polymer polyaniline into the matrices of inorganic precipitate of Sn(IV) phosphate. This material was used as a cation-exchanger. The physico-chemical properties of the material were determined using AAS, CHN elemental analysis, ICP-MS, UV–VIS spectrophotometry, FTIR, TGA–DTA, XRD, and SEM studies. Ion-exchange capacity, chemical stability, thermal stability and distribution behavior were also carried out to understand the cation-exchange behavior of the material. On the basis of distribution studies, the material was found to be highly selective for Pb(II). Its selectivity was examined by achieving some important binary separations like Pb(II)–Mg(II), Pb(II)–Sr(II), Pb(II)–Zn(II), and Pb(II)–Fe(III) on its column. This material possessed DC electrical conductivity in the semi-conducting range, i. e. 10 −5–10 −3 S cm −1. The stability in terms of DC electrical conductivity retention was also studied in an oxidative environment by two slightly different techniques viz. isothermal and cyclic techniques. The DC electrical conductivity of composite material was found stable upto 110 °C under ambient conditions.

Growth, crystal structure and thermal properties of calcium bis(malate) dihydrate

A new coordination compound crystal of calcium with malic acid is prepared by gel aided solution growth. Single crystal X-ray diffraction studies revealed that the structural formula of the compound is Ca(C 4H 4O 5) 2·2H 2O. It crystallizes in the monoclinic system with space group C2/ c, Z = 4, with unit cell parameters a = 15.916(9) Å, b = 5.886(3) Å, c = 13.046(6) Å and β = 90.678(4)°. Data were collected by oscillation method and full-matrix least squares refinement was applied to the model converging to final R indices R 1 = 0.0416 and ωR 2 = 0.1255. Compound forms a layer-type polymeric structure, stabilized by intermolecular hydrogen bonding. Ca 2+ is eight-fold coordinated. Malate is coordinated to Ca 2+ tridendate–bidendate through two carboxylates and monodendate through oxygen atom of the hydroxyl group. Thermal behavior investigated using TG and DTA studies is in conformity with the proposed structure.

Synthesis, characterization and ion-exchange properties of a new and novel ‘organic–inorganic’ hybrid cation-exchanger: Nylon-6,6, Zr(IV) phosphate

Organic–inorganic hybrid materials enable the integration of useful organic and inorganic characteristics within a single molecular-scale composite. Unique ion-exchange properties of these types of materials have been observed, and many others can be envisioned for this promising class of materials. In this paper, we describe the ion-exchange and physico-chemical properties of one family of self-assembling organic–inorganic hybrid based on nylon-6,6, framework with Zr(IV) phosphate an inorganic ion-exchanger. The physico-chemical properties of this hybrid material were determined using atomic absorption spectrophotometry (AAS), CHN elemental analysis, ICP–MS, UV–vis spectrophotometry, FTIR, TGA–DTA and scanning electron microscope (SEM) studies. Ion-exchange capacity (IEC), thermal stability and distribution behavior, etc. were also carried out to understand the cation-exchange behavior of the material. On the basis of distribution studies, the material was found to be highly selective for Hg(II), a highly toxic environmental pollutant. Its selectivity was examined by achieving some important binary separations like Hg(II)–Mg(II), Hg(II)–Zn(II), Hg(II)–Fe(III), Hg(II)–Bi(III), etc. Thus, the relatively new field of “organic–inorganic” hybrids offers a variety of exciting technological opportunities to decrease the environmental pollution.