DTA Data Research Articles

Use of Genetic Algorithm to Determine the Kinetic Model of Solid‐State Reactions

Solid‐state reactions take place by different rate‐controlling heterogeneous processes. To find the appropriate kinetic model for a particular solid‐state reaction, a genetic algorithm‐based simulation technique was carried out using DTA data with a fitness function, and a computer program was developed for the same. The process was applied to the decomposition reactions of limestone and magnesite samples. It was observed that both the decomposition reactions mostly followed the Avrami–Erofeev kinetics model.

Research on preservation and enrichment mechanisms of organic matter in muddy sediment and mudstone

Using multidiscipline methodologies, the differences in preservation and enrichment mechanisms of organic matter (OM) in muddy sediment and mudstone are investigated. In clay fractions, concentrations of TOC and chloroform bitumen “A” are significantly higher than those in coarser fractions. This indicates that clay minerals (CM) play an important role in enriching OM. The content of chloroform bitumen “A” increases obviously in the clay fraction, which reveals that dissolvable OM is the main composition of coalesce with clay minerals. Furthermore, TG and DTA data show that OM enrichment mechanisms and preservation forms have multiplicity. Several exothermic peaks in the DTA curves demonstrate that muddy sediment and mudstone contain a number of bioclasts and amorphous OM besides dissolvable OM. Through analyzing with XRD and DTA after mudstone samples were pretreated, the conclusions can be arrived at. Firstly, CM interlayer space of XRD curves and exothermic peaks of DTA curves both change as temperature increases. Secondly, the changes of CM interlayer space and exothermic peaks are concordant and stable around 350°C. All these are the features that OM enters CM interlayers to form stable organo-clay complexes. Therefore, the combination format of OM with CM is not only surface adsorption, partial OM enters CM interlayers to form stable organo-clay complexes. Finally, through the research on OM preservation forms and enrichment mechanisms in muddy sediment and mudstone, the hydrocarbon-generation processes and the global carbon cycle and budget can be explained.

Thermodynamic Characteristics of Chain Molecules in the Nematic State: PVT Studies of Main-Chain Liquid Crystal Comprising a Long Oxyethylene-Type Spacer

Thermodynamic characteristics of a dimer liquid crystal comprising a relatively long spacer −O(CH2CH2O)6− were investigated. The contour length of the flexible spacer (∼25 A) exceeds that of the hard segments (∼18 A). The compound exhibits a nematic mesophase (N) between the crystal (C) and the isotropic melt (I) over a sizably wide temperature range (∼80 °C). Thermodynamic quantities such as thermal expansion coefficient α, isothermal compressibility β, thermal pressure coefficient γ (=α/β), and the volume change ΔV at the CN and NI interphase were carefully determined by the PVT measurements. The transition entropies due to volume expansion were estimated by the well-known relation ΔSV = γΔV. The latent entropies (ΔStr)P for both CN and NI transitions were estimated according to the Clapeyron relation from the PVT and DTA data. The magnitude of the constant-volume entropy changes (ΔStr)V calculated was found to be about 50−60% of the corresponding values of (ΔStr)P. These results were consistent with th...

Dimethyltin(IV) complexes with zwitterionic buffers (Mes and Mops)

Equilibrium studies in aqueous solution are reported for dimethyltin(IV) complexes of the zwitterionic buffers “Good’s buffer”, such as Mes and Mops ( L). Stoichiometry and stability constants for the complexes formed were determined at different temperature and ionic strength 0.1 M NaNO 3. The results showed the best fit of the titration curves were obtained when complexes ML, MLH −1, MLH −2, and MLH −3 were expected beside the hydrolysis products of the dimethyltin(IV) cation. The thermodynamic parameters Δ H°, Δ S° and Δ G° calculated from the temperature dependence of the formation constant of the dimethyltin(IV)–Mes complex was investigated. The effect of dioxane as a solvent on the formation constants of dimethyltin(IV)–Mes complex was discussed. The concentration distribution of the various complex species was evaluated as a function of pH. The bonding sites of the dimethyltin(IV) complexes in solid state with Mes and Mops were characterized by means of elemental analyses and FTIR. The NMR ( 1H, 13C) spectra of the DMT–Mes complex exhibits the strongly distorted octahedron geometry around tin atom. Also, thermal analyses (TGA and DTA) were discussed. Thermodynamic parameters such as activation energy ( E a), pre-exponential factor ( A), entropy of activation (Δ S ∗) and free energy of activation (Δ G ∗) have been calculated for each step, employing integral method Coats and Redfern. The reaction enthalpy (Δ H) is obtained from DTA data.

Estimation of Glass Forming Ability of Amorphous Alloys Based on the Thermal Analysis Data during Cooling

Based on the analytic approach, a new parameterTrn (reduced difference of nucleation temperatures) for estimating the glass forming ability (GFA) has been suggested with simple DTA data at two different cooling rates. The new parameter described GFA of amorphous alloys very well. Besides, an equation for estimating the critical cooling rate has also been suggested using the new parameter for GFA. The results of prediction model have been in good agreement with the previous experimental results. (doi:10.2320/matertrans.MRA2007026)

Synthesis and characterization of zeolite mazzite analogue in Na2O–Al2O3–SiO2–Piperazine–H2O

Zeolite Mazzite (MAZ) analogue was synthesized directly using piperazine as a structure directing agent. The reactive gel composition used was (5.0–7.0) piperazine:(6.0–7.0) Na2O:Al2O3:20.0SiO2:400H2O. Using this composition, the reaction time was shortened greatly to 4 days and the crystallization time was reduced as well. The DTA data showed that piperazine, in as-synthesized zeolite omega decomposed easily. The decomposition of the piperazine occurred at 400–480°C. NH3-TPD analysis proved that zeolite H-omega from piperazine had strong surface acidity with ammonia desorption temperature up to 590°C.

Structure and catalytic properties of dealuminated modified zeolites Y

The effect of treatment with a zirconyl nitrate aqueous solution on the structure; the hydroxyl-layer constitution; and the adsorptive, acid, and catalytic properties of dealuminated zeolite Y was studied. The zeolite was prepared by boiling NH4Y in an ethylenediaminetetraacetic acid disodium salt solution followed by ion exchange with ammonium chloride and calcination in a 100% steam flow at 750°C. X-ray diffraction, IR spectroscopy, and DTA data show the formation of an ultrastable form of zeolite Y. The incorporation of zirconium in zeolite led to an increase in the proportion of strong acid sites, thus raising the yield of cracking products during n-hexane conversion tested on platinum-containing catalyst samples.

Self-assembly, crystal structure and photoluminescent properties of a novel organic–inorganic hybrid coordination polymer: [CdCl 3(CH 3) 3NH

A novel organic–inorganic coordination polymer [CdCl 3(CH 3) 3NH] 1 was synthesized by the reaction of CdCl 2 with trimethylamine (TMA) at 170 °C for 5 days in ethanol and structurally characterized by means of X-ray single diffraction. The title compound affords a one-dimensional chain structure. It crystallizes in hexagonal system space group P 6 ( 3 ) / m with a = 9.1401 ( 13 ) Å , b = 9.1401 ( 13 ) Å , c = 6.7313 ( 13 ) Å , γ = 120.00 ° , V = 487.00 ( 14 ) Å 3 , Z = 2 , D C = 1.895 Mg / m 3 , F ( 000 ) = 266 , M r = 277.86 , μ ( Mo K α ) = 2.99 mm −1 , the final R = 0.0420 and ω R = 0.1020 for 355 observed reflections with I > 2 σ ( I ) . The title compound consists of cation [(CH 3) 3NH] + and anion chain [ ( CdCl 3 ) ] n − , and they are combined by static attracting forces in the crystal. TG–DTA, XRD and IR data for the title compound are reported and discussed. The photoluminescent properties of the compound 1 were also investigated.

T-x diagram and transport properties of the GeSe-GeI2 solid electrolyte

The T-x diagram for the GeSe-GeI2 system was plotted based on DTA, XRD, and conductivity data. The diagram features a simple eutectic and a limited region of solid solutions with prevalent GeSe content. It was established that, in the region of solid solutions, the properties of the GeSe-GeI2 solid electrolyte are substantially dependent on the concentration of the GeI2 dopant. The highest conductivity (10−3−10−4 S/cm at 150°C), lowest activation energy of electric conduction (0.3–0.4 eV), and lowest electronic (hole) transport numbers (10−5−10−7 at 150°C) at high ionic (∼1.0) and cationic (0.9–1.0) transport numbers were observed at a GeI2 concentration of 3–6 mol %. In the two-phase region, the transport properties (conductivity and activation energy of conduction) only slightly depend on the dopant concentration.

Inclusion Properties of 11b-Substituted 2,3,5,6,11,11b-Hexahydro-3-oxo-1H-indolizino[8,7-b]indole-5-carboxylic Acid Esters. New Chiral Host Compounds Derived from l-Tryptophan

Abstract New chiral host compounds have been prepared from l-tryptophan and 3-aroylpropionic acids. These hosts show broad inclusion and sorption abilities toward solvent and racemic molecules, and are characterized by X-ray crystallographic analysis, which clarify the one-dimensional channel structures of the hosts, the helical arrangements of the guests, and the occurrence of weak interactions such as C–H···O and C–H···Cl between the hosts and the guests. The TG and DTA data show the high cohesion of the hosts, and the PXRD patterns indicate that the crystal structures of the hosts remain ordered after removal of the guest molecules. These hosts have potential usefulness in the optical resolution of racemic guest molecules such as s-butyl chloride and 4-methylcyclohexene.

Synthesis and characterization of non-noble nanocatalysts for hydrogen production in microreactors

Nanoscale Co and Ni catalysts in silica were synthesized using sol–gel method for hydrogen production from steam reforming of methanol (SRM) in silicon microreactors with 50 μm channels. Silica sol–gel support with porous structure gives specific surface area of 452.35 m 2 g −1 for Ni/SiO 2 and 337.72 m 2 g −1 for Co/SiO 2. TEM images show the particles size of Ni and Co catalysts to be <10 nm. The EDX results indicate Co and Ni loadings of 5–6 wt.% in silica which is lower than the intended loading of 12 wt.%. The DTA and XRD data suggest that 450 °C is an optimum temperature for catalyst calcination when most of the metal hydroxides are converted to metal oxides without significant particle aggregation to form larger crystallites. SRM reactions show 53% methanol conversion with 74% hydrogen selectivity at 5 μL min −1 and 200 °C for Ni/SiO 2 catalyst, which is higher than that for Co/SiO 2. The activity of the metal catalysts decrease significantly after SRM reactions over 10 h, and it is consistent with the magnetization (VSM) results indicating that ∼90% of Co and ∼85% of Ni become non-ferromagnetic after 10 h.

Thermoreactivity of Sol-Gel Precursor for ZnO-Based Thin Films

The thermoreactivity of a zinc acetate non-alkoxide solution used for the preparation of ZnO-based thin films was investigated in the temperature range 20-600°C by TG-DTA, XRD and SEM data. We found that the formation in air of ZnO crystallites from the sol-gel precursor occurs above 150°C simultaneously with the decomposition of an intermediary compound, most probably carbonate hydroxide (sclarite and/or hydrozincite). At 200 °C, the crystalline structure is well defined in terms of ZnO hexagonal lattice parameters, although residual organic compounds and water were not yet fully removed and an amorphous phase coexists. A kinetic investigation on the thermal decomposition of sol-gel precursor from DTA data using Kissinger differential equation is also presented. Apparent activation energy values of about. 100 kJ mol-1 corresponding to the nonisothermal decomposition of solid precursors in the temperature range 170-250oC have been found.

DFT modeling and spectroscopic study of metal–ligand bonding in La(III) complex of coumarin-3-carboxylic acid

The binding mode of coumarin-3-carboxylic acid (HCCA) to La(III) is elucidated at experimental and theoretical level. The complexation ability of the deprotonated ligand (CCA −) to La(III) is studied using elemental analysis, DTA and TGA data as well as FTIR, 1H NMR and 13C NMR spectra. The experimental data suggest the complex formula La(CCA) 2(NO 3)(H 2O) 2. B3LYP, BHLYP, B3P86, B3PW91, PW91P86 and MPW1PW91 functionals are tested for geometry and frequency calculations of the neutral ligand and all of them show bond length deviations bellow 1%. B3LYP/6-31G(d) level combined with large quasi-relativistic effective core potential for lanthanum is selected to describe the molecular, electronic and vibrational structures as well as the conformational behavior of HCCA, CCA − and La–CCA complex. The metal–ligand binding mode is predicted through molecular modeling and energy estimation of different La–CCA structures. The calculated atomic charges and the bonding orbital polarizations point to strong ionic metal–ligand bonding in La–CCA complex and insignificant donor acceptor interaction. Detailed vibrational analysis of HCCA, CCA − and La(CCA) 2(NO 3)(H 2O) 2 systems based on both calculated and experimental frequencies confirms the suggested metal–ligand binding mode.

Synthesis, thermal and calorimetric investigations of cobalt(ii) trihydrogen hexaoxoperiodate tetrahydrate

A new cobalt(II) trihydrogen hexaoxoperiodate tetrahydrate has been synthesized: CoH3IO6·4H2O and has been characterized by quantitative analysis, TG, DTA, DSC and IR spectroscopy. Based on DTA and DSC data, a thermal decomposition scheme has been proposed for this complex.

Experimental Investigations of Amino Acid-Layered Double Hydroxide Complexes: Glutamate−Hydrotalcite

XRD, TGA−DTA, compositional analyses, and 13C NMR data for hydrotalcite (HT) intercalated with the amino acid glutamic acid (GA) provide a detailed picture of the effects of synthesis pH, synthesis...

Thermal and mineralogical contribution to the ancient ceramics and natural clays characterization

In the present work 39 ancient ceramic sherds from the archaeological excavation of Abdera, North-Eastern Greece, dating to 7th century B.C., and 11 local raw clay bricks, fired at temperatures ranging from 500 to 1000°C, were characterized by ICP-AES, powder X-ray diffraction (PXRD) and thermal analysis (TG-DTA) techniques. It has been found that the mineralogical composition of the most studied sherds is quartz, feldspars and micas, which is in agreement with the composition of the local bricks. Chlorite is also present in a few samples, while there is one completely different sherd, which belongs to the Ca-rich clays. From the simultaneous TG/DTG and DTA data, under nitrogen atmosphere in the temperature ranges ambient to 1000°C, we comment on the possible firing temperature and distinguish between samples of different origin. The existence of muscovite or illite in most of the samples denotes that the firing temperature was lower than 950°C, while the existence of chlorite means that the firing process in these samples stopped before 700°C. A very different thermogram gave the Ca-rich ceramic sherd, due to the existence of calcite, denoting that the firing temperature was about 700°C.

The location of the second critical point of water

Based on the DTA data for homogeneous ice nucleation of emulsified liquid water at low temperatures and high pressures, the location of the second critical point (SCP) of water, which is expected to exist in addition to the normal liquid–vapor critical point, is estimated to be at 145 K < T c2 < 175 K and P c2 = ∼200 MPa ( T c2: second critical temperature, P c2: second critical pressure). It is shown that SCP is closely associated with the break point of the curve for the homogeneous ice nucleation temperature ( T H) of liquid water and with the transition between low density and high density amorphous solid water (LDA and HDA). Although the existence of SCP has become more realistic, the location seems to be less favorable to the water model of the second-critical-point interpretation.

The Liquidus Surface of the Ternary System Cu-In-Ti

The phases occurring upon lead free soldering of copper substrates using indium, which contains for improved wetting additions of Ti, belong to the ternary system Cu-In-Ti. Thus, the liquidus surface of the ternary system Cu-In-Ti is determined using DTA data. Alloys were prepared from high purity metals by arc melting under pure argon. Before measuring the heating curves, all alloys were equilibrated at appropriate temperatures and XRD phase analysis were performed. A reaction scheme linking the phase equilibria found in the annealed alloys to the liquid phase is obtained. A projection of the resulting liquidus surface, which is dominated by the primary crystallisation field of the congruently melting Heusler phase t1-Cu2TiAl, is presented. In the In-rich composition corner the liquid phase solidifies in a ternary eutectic (In) + Ti2In5 + Cu11In9 at 155°C.

Synthesis and physical properties of Ag5Pb2O6 compound

A simple method for the synthesis of the Ag5Pb2O6 compound in argon atmosphere is suggested. The optimum conditions for the synthesis of the stoichiometric Ag5Pb2O6 compound are determined on the basis of thermogravimetric and DTA data. It is shown that the introduction of strontium ions during synthesis does not considerably change the lattice parameters, crystal structure, electrophysical properties, or thermal stability of the compound.

Development and Evaluation of a TG/DTA/Raman System

Abstract Modification of a commercially available TG/DTA instrument enabled development of a working TG/DTA/Raman system. The TG/DTA was modified by replacing a portion of the furnace wall above the sample and reference holders with a double layer insulated quartz window. The quartz window provided ready access for Raman spectroscopy, enabling simultaneous collection of TGA, DTA, and Raman data during thermal analytical experiments. Insertion of the quartz glass window did not impact TGA or DTA performance as demonstrated by the comparison of baseline drift and temperature calibration for modified and unmodified furnaces.