DTA Methods Research Articles

Iron(III) complex of a tridentate NNN type ligand: synthesis, X-ray structure, thermal analysis and voltammetric studies

A mononuclear iron(III) complex with 2,6-bis(3,4,5-trimethyl-N-pyrazolyl)pyridine (btmpp) has been synthesized, and characterized by X-ray crystallography, IR, UV–Vis and TGA–DTA methods. The Fe(III/II) couple was characterized by way of cyclic voltammetry using DMF solvent, where the complex was observed to have an irreversible behaviour.

Deposition of thin TiO 2 layers on platinum by means of cyclic voltammetry of selected complex Ti(IV) media leading to anatase

Thin layers of anatase TiO 2, up to 1 μm, were produced on the surface of a platinum electrode by means of cycling voltammetry from the aqueous solutions of the peroxo-oxalate complexes and the oxalate complexes of titanium(IV). Mechanisms of TiO 2 electrodeposition as well as different electrochemical reactions causing pH changes at the electrode were studied. The electroreduction processes of hydrogen peroxide and nitrite ion on platinum cause the highest pH changes. Values of the molar ratio of Ti(IV)/H 2O 2 should be kept closely to 0.5. In all cases studied, the electrodeposition led to the partially decomposed amorphous oxalate compounds of titanium(IV), which can be converted into crystalline anatase above 500 °C in air. The thermal behaviour of TiO 2 precursor compounds was examined by DRIFTS and TG–DTA methods. Strong effects of K + and NH 4 + ions on the electrodeposition process were found by using of the EQCM technique, Raman spectroscopy and XRD measurements. The ammonium electrolyte warrants purity of the anatase phase. Morphology of the oxide films produced in different solvents was examined by SEM.

Oxidation resistance before and after heat treatment for compacted Al2O3–SiC–C mixtures with aluminum-chromium-phosphate binder

Oxidation resistance has been examined for compacted Al2O3–SiC–C mixtures, which contain an aluminum-chromium-phosphate binder without firing (DTA method) and ones that have been previously fired and given isothermal heat treatment at 800°C (as indicated by the mass loss). To obtain oxidation-resistant materials, the content of silicon carbide should not exceed 10 wt.% and the recommended graphite content is not more than 20 wt.%.

Microwave-assisted boration of potato starch

Granular potato starch was successfully borated with boric acid and sodium tetraborate decahydrate (borax) in a microwave-assisted solid state reaction. Products of starch boration reached (dependently on the conditions of the process) the maximal value of the degree of esterification (DE) equal to 0.27 when boric acid was applied, and 0.18 when borax was used. DTA, TG, DTG and FT-IR methods revealed that boration of starch provided boron esters or borate complexes. High-pressure size exclusion chromatography (HPSEC), DSC and X-ray diffraction showed that although the boration of starch caused changes in its macrostructure, the thermal stability of borated starch was enhanced even by 20 °C when compared with native product, with larger stability exhibited by complexes than by esters. The thermal stability of the borated starch increased with an increase in DE. After modification, granularity of starch was retained, as was indicated by the scanning electron microscopy.

Spectroscopic properties of lanthanoid benzene carboxylates in the solid state: Part 1

Europium and terbium complexes of benzoic acid (HBA), 9-anthracene carboxylic acid (9-HACA), 1-naphthoic acid (1-HNA), 2-naphthoic acid (2-HNA), cinnamic acid (HCA), o-phenylbenzoic acid ( o-HPhBA), p-phenylbenzoic acid ( p-HPhBA), o-methylbenzoic acid ( o-HMeBA), m-methylbenzoic acid ( m-HMeBA), p-methylbenzoic acid ( p-HMeBA), p- tert-butylbenzoic acid ( p- tert HBuBA), phthalic acid (H 2Phth), isophthalic acid (H 2-IsoPhth) and terephthalic acid (H 2-TerePhth) were synthesised by aqueous metathesis reactions. The compositions were determined by microanalysis, DTA, and EDTA volumetric methods. Structural conclusions were drawn from powder XRD patterns and IR spectra. The optoelectronic properties were determined in the solid state, including reflectance, excitation, emission, and excitation efficiency, complemented by considering triplet state energies, which were derived from phosphorescence spectra of the corresponding gadolinium complexes. Besides the emission efficiencies, the splitting pattern of the 5D 0 → 7F J transitions of Eu 3+ were used to derive structural information and the intensities relative to the 5D 0 → 7F J were used to gain information about the mechanism, adding electronic allowed dipole character to the forbidden emissions.

XRF, XRD, and Thermal Analysis Techniques for Quantitative Determination of Portland Cement and Slag Cement Constituents

Abstract Two rapid test methods to determine and quantify sulfate forms in cement are presented—DSC and XRD. The DSC method is applicable to hydrated calcium sulfates: gypsum and bassanite. Its description includes preparation of standards, calibration curves, and calculation of hydrated sulfates in an unknown cement sample. The XRD method is used qualitatively and quantitatively for both hydrated and nonhydrated sulfate forms. The qualitative approach is used to identify the presence of sulfates in cement samples. The quantitative approach describes the Rietveld analysis applied to a cement sample containing gypsum, bassanite, anhydrite, and arcanite. The calculated total SO3 content is compared with another direct analytical technique (Sulfur Analyzer). The other two methods used to determine the amount of granulated blast furnace slag added to cement are discussed—DTA and XRD. With the DTA method, the exothermic peak that accompanies slag devitrification at high temperatures is measured and converted in slag percentages. The method’s description includes preparation of standards, calibration curve, and calculation of slag content of an unknown cement sample. The XRD method works as a qualitative tool to show the effect of amorphous slag to a cement diffractogram as well as a quantitative tool (Rietveld analysis using an internal standard). Rietveld analysis on cement containing slag samples is used with XRF oxide analysis to correct the Bogue formula calculation for C3S. Three different calculations/corrections are discussed showing reasonably good approximate results.

Methods for improving volume stability of steel slag as fine aggregate

Suitable methods for enhancing the volume stability of steel slag utilized as fine aggregate were determined. The effects of steam treatment at 100 °C and autoclave treatment under 2.0 MPa on the soundness of steel slag sand were investigated by means of powder ratio, linear expansion, compressive and flexural strength. DTA, EDX, XRD and ethylene glycol methods were employed to analyze both the treated slags and susceptible expansion grains. Experimental results indicate that powder ratio, content of free lime and rate of linear expansion can express the improvement in volume stability of different treated methods. Steam treatment process cannot ultimately prevent specimens from cracking and decrease of strength, but mortar made from autoclave treated slag keeps integration subjected to hot water of 80 °C until 28 d and its strength do not show significant decrement. The hydration of over-burn free lime and periclase phase are the main cause for the disintegration or crack of untreated and steam treated steel slag’s specimens. Autoclave treatment process is more effective than steam treatment process on enhancement of volume stability of steel slag.

New structural motifs and properties of squaric acid anions in the presence of the l-lysinium counterion

Two novel l-lysinium hydrogensquarate monohydrate ( 1) and the corresponding salt of the l-lysinium dication ( 2) are synthesized and their structure and properties elucidated in detail spectroscopically, thermally and structurally, using single crystal X-ray diffraction, linear-polarized solid-state IR-spectroscopy oriented colloid suspensions in nematic host, TGA, DSC, DTA methods, positive and negative HPLC tandem mass spectrometry (ESI-MS·MS). Quantum chemical methods are used to calculate the electronic structure, vibrational data and electronic spectra. Two novel structural motifs have been obtained, isolated [(HSq −)] and tetramolecular [(H 2Sq)(HSq) 2(Sq)] 4− anion, respectively. Preliminary second harmonic generation measurements are also performed.

Studies on glass transition of lithium-iron phosphate glasses

Abstract Amorphous analogs of lithium-iron phosphates (LFP) were prepared by standard press-quenching method and their thermal stabilities as well as structural properties were studied for the first time. Glass transition temperature T g determined by DTA method was observed at the temperature range 492–523°C, depending on the glass composition. The maxima of crystallization peaks were observed in the 555–579°C range. In products obtained after heating up to 700°C the XRD patterns have revealed the presence of: LiFePO4 (triphylite), FePO4 (heterosite), α-FePO4 (quartz like structure) and Li3Fe2(PO4)3 (Nasicon like structure) phases.

Reactivity of the oxides in the ternary V2O5-CuO-α-Sb2O4 system in air

In this work it has been established which compounds finally are formed in air in the two-component CuO-V2O5 and CuO-α-Sb2O4 systems. Unknown thermal properties of CuV2O6, Cu2V2O7 and Cu11V6O26 have been established. Reactivity of the oxides and phase relations in the ternary V2O5-CuO-α-Sb2O4 system in air have been studied by using XRD and DTA methods. The results have showed the reaction of V2O5, CuO with α-Sb2O4 does not produce any compound where all the three oxides would be involved. It has been established that the α-Sb2O4 reacts and forms binary phases independently with CuO or V2O5. On the base of these results the investigated system was divided into subsidiary subsystem in which CuSb2O6 remains at equilibrium in the solid state with other phases formed in corresponding binary systems.

The melting diagram of the Ti–Zr–Sn system below 40 at.% Sn

By the methods of DTA, X-ray diffraction, metallography and EPMA, phase equilibria in the Ti–Zr–Sn system at <40 at.% Sn were studied. The partial liquidus and solidus projections, and the melting diagram (solidus + liquidus) were constructed. The liquidus surface is characterized by the presence of primary crystallization regions of (βTi) (β), (Ti 3Sn) (α 2) and (Ti,Zr) 5Sn 3 (5/3) phases. The solidus surface is characterized by the presence of two three-phase fields, β + α 2 + 5/3 and α 2 + (Ti 2Sn)(2/1) + 5/3. The first one results from an invariant four-phase equilibrium L U + α 2 ↔ β + 5/3 taking place at 1510 ± 10 °C. The invariant point U is located at the composition ∼53Ti–30Zr–17Sn. The second three-phase region results from an equilibrium at 1515 °C with participation of L + α 2 + 5/3 + 2/1 phases. The character of the equilibrium is not determined. Two invariant three-phase equilibria were found, L e 1 ↔ α 2 + 5 / 3 at 1600–1650 °C and L e 4 ↔ β + 5 / 3 at 1423 °C.

Study of TATP: Spontaneous Transformation of TATP to DADP

AbstractTATP, prepared in the presence of catalysts methanesulfonic, perchloric, or sulfuric acid, has been found to undergo transformation to DADP. However, no transformation occurs if TATP is purified or prepared involving catalysts such as hydrochloric acid, tin(IV) chloride, and nitric acid. The transformation has been monitored by the methods of DTA and HPLC.

Investigation on synthesis and microstructure of potassium tetratitanate

Potassium tetratitanate K2Ti4O9 was synthesized from the anatase-K2CO3 starting materials by the heating calcination. DTA, TG, DTG and XRD methods were used to study the formation of intermediate compounds and the final product. The characterization of the K2Ti4O9 crystals was carried out by means of scanning electron microscope (SEM).

Growth and characterization studies of ferroelectric diglycine nitrate (DGN) single crystals

Single crystals of diglycine nitrate [(NH 2CH 2COOH) 2HNO 3] (DGN), a ferroelectric material with Curie temperature 206 K, were grown in silica gel at room temperature by the solubility reduction method at room temperature (39 °C). Bulk crystals of dimension 21 mm × 18 mm × 11 mm have been grown by optimizing the growth conditions. The grown crystals have been characterized by structural, optical and mechanical characterization studies. Fourier transform infrared (FTIR) spectral analysis reveals that the crystal consists of all functional vibrational groups. FT-Raman spectrum, which is complement to FTIR studies, has also been recorded. Surface analysis by SEM reveals that the crystal absorbs water from the moisture. The optical transparency range and the lower cut-off of UV transmission were identified from the recorded UV–vis spectrum of DGN. The UV cut-off wavelength of DGN is 286 nm. Thermal analysis of the crystalline sample was performed by TGA and DTA methods. The crystal is thermally stable up to 217 °C. The Vicker's microhardness value of DGN crystal is decreases with increase of load. The work hardening coefficient ( n) of diglycine nitrate was determined using the least squares fit method and found to be 1.5.

DTA, FTIR and impedance spectroscopy studies on lithium–iron–phosphate glasses with olivine-like local structure

Amorphous analogs of lithium–iron–phosphates (LFP) with olivine-like local order were prepared by standard press-quenching method and their thermal stabilities as well as structural and electric properties were studied for the first time. Glass transition temperature T g determined by DTA method is equal to 492–523 °C depending on the glass composition. Fourier transform infrared (FTIR) absorption spectroscopy was used to study local order. Local structure and thermal properties are almost independent on the lithium content. Electrical properties were studied by impedance spectroscopy. Impedance measurements indicated that the studied lithium–iron–phosphate glasses with olivine-like local order exhibit predominantly electronic (polaronic) conductivity. Total electrical conductivity at 450 °C for a glass of nominal composition LiFePO 4 approaches 10 − 2 S/cm. Electrical conductivity at 25 °C of Li 0.4FePO 4 glass after nanocrystallization (caused by heating up from room temperature to the beginning of crystallization temperature) increased by a factor close to 4. Nanocrystallization seems to be the way for electrical conductivity improvement of olivine-like cathode materials.

Dioxomolybdenum(VI) complexes of 2-hydroxybenzaldehyde 4-phenyl-S-methylthiosemicarbazone

Mixed ligand complexes of dioxomolybdenum(VI) with 2-hydroxybenzaldehyde 4-phenyl-S-methylthiosemicarbazone (H2L) were prepared with the formula [MoO2(L)D] (D = H2O, methyl, n-butyl, and n-undecyl alcohol, DMF, DMSO, pyridine, 4-picoline, and 3,5-lutidine). The compounds were characterized by elemental analysis, IR and 1H NMR spectroscopy. The thermal decomposition of the compounds were investigated by using TGA, DTG, and DTA methods in air, and the thermal behavior depending on the second ligand molecule was discussed. A single crystal of the DMF coordinated complex was studied by X-ray diffractometry.

Characterization and ethylene adsorption of natural and modified clinoptilolites

The ethylene adsorption of Turkey clinoptilolite-rich tuff from Gordes and Bigadic region of western of Anatolia and their exchanged forms (K +, Na + and Ca 2+) were investigated. The clinoptilolite samples were characterized using XRD, TG–DTA and nitrogen adsorption methods. Adsorption isotherms for ethylene on natural and modified forms of both adsorbents at 277 K and 293 K were obtained at pressures up to 38 kPa. Uptake of ethylene increased as Na-CLN < Ca-CLN < K-CLN < Natural CLN for Gordes zeolite at 277 K, 293 K and for Bigadic zeolite at 277 K. For Bigadic zeolites at 293 K, uptake of ethylene increased in the order Ca-CLN < Na-CLN < K-CLN < Natural CLN. It was found that ethylene adsorption capacity of Bigadic clinoptilolite samples was much greater than Gordes clinoptilolite samples except K + modified forms at both temperatures. These results show that both natural clinoptilolites have a considerable potential for the removal of ethylene.

Experimental and computational study on [2,6-bis(3,5-dimethyl- N-pyrazolyl)pyridine]-(dithiocyanato)mercury(II)

The mercury complex of 2,6-bis(3,5-dimethyl- N-pyrazolyl)pyridine (bdmpp) has been synthesized and characterized by X-ray diffraction, IR, UV–Vis and TGA–DTA methods. The structure consists of units in which the mercury atom is pentacoordinate with two sulfur and three nitrogen atoms. [Hg(bdmpp)(SCN) 2] has a distorted square pyramid geometry. Calculations using both PM3 and density functional theory (DFT) methods were also carried out on the studied complex. The optimized geometries from both methods agree with the X-ray structure well. The infrared spectrum of the title complex was studied in the 4000–400 cm −1 frequency range, experimentally and theoretically. The experimental results are in better agreement with the DFT results at the B3LYP/LanL2DZ level than semiempirical results at the PM3 level.

Synthesis, spectroscopic and theoretical study of isoquinoline alkaloid dehydrosalsolinol base and its triacetylated derivative

Dehydrosalsolinol and its triacetylated derivative i.e. are synthesized, isolated, and the spectra and structure are elucidated. Solid-state linear-dichroic infrared spectroscopy, 1H and 13C NMR, TGV and DTA methods are applied. The potential energy surface of both compounds are explored with DFT correlation functional B3LYP method and MP2, using the 6-311++G ∗∗ basis set. Single point calculations are performed at levels up to B3LYP/6-311++G ∗∗// MP2/6-311++G ∗∗ and MP2/6-311++G ∗∗. Two isomers of dehydrosalsolinol are located and the relative energies are determined. The planar quinoidal structure with strong intramolecular OH…O hydrogen bond and dipole moment of 7.392 D is more stable than the diphenolic form. Calculated vibrational frequencies are used to determine the type of molecular motions associated with each of the experimental IR-bands observed. IR-spectroscopic data show that dehydrosalsolinol exists in solid-state as the quinoide form in contrast to solution, where 1H NMR data indicate a keto-diphenolic equilibrium. Comparison between calculated and experimental IR-frequencies of triacetyl derivative shows the presence of two phenolic ester carbonyl and one-amide groups and an exocyclic double bond. The same conclusions are obtained by corresponding 1H NMR data.

Synthesis, characterization and chromotropic properties of MnII, CoII, NiII and CuII with bis(acesulfamato)bis(3-methylpyridine) complexes

The novel \([\hbox{M(acs)}_{2}(\)3-\(\hbox{pic})_{2}(\hbox{H}_{2}\hbox{O})_{2}]\) [M: MnII, CoII, and NiII] and \([\hbox{Cu(acs)}_{2}(\)3-\(\hbox{pic)}_{2}]\) complexes (acs: acesulfamate; 3-pic: 3-methylpyridine) have been synthesized and characterized using elemental analyses, magnetic moments, UV–Vis and FT-IR spectra. The thermal behaviour of the complexes was also studied by simultaneous TG, DTG and DTA methods in static air atmosphere. The chromotropic properties of all complexes have been studied using thermal and spectral analysis. While the complexes of CoII and NiII show reversible continuous thermochromism, an irreversible discontinuous thermochromism is observed in the MnII and CuII) complexes in the solid state. The observed thermochromism in the MnII, CoII and NiII complexes is due to the different ligand field strength associated with the deaquation reaction. The solvatochromic behaviour of the complexes is also studied and all \([\hbox{M(acs)}_{2}(3 \hbox{-pic})_{2}]\) anhydrous complexes (except MnII) exhibit solvatochromic properties depending on the donor number of the solvent.