DTA Traces Research Articles

Phase diagram of the eutectic type LiCl-PrCl3-KCl system with wedging liquidus of binary compound

Based on the published experimental data (phase diagrams of three binary systems, four isothermal sections and DTA curves of 33 alloys), a spatial (three-dimensional – 3D) computer model of the LiCl-PrCl3-KCl phase diagram has been constructed. It is shown that, in the general case, the diagram is formed by 66 surfaces and 27 phase regions; however, due to the negligible solubility of the initial chlorides and the stoichiometry of the two binary compounds in reality, it consists of 31 surfaces and 14 phase regions. The evaluation of the quality of the obtained 3D model is a comparison of model and initial isothermal sections and calculation of response functions for 33 alloys with temperature values at the boundaries of the primary crystallization regions shown on DTA traces. The geometric structure of the LiCl-PrCl3-KCl phase diagram is also considered as an illustration of the features of ternary systems of the eutectic type, depending on the nature of the formed in them binary compounds.

Enhancement of the red emission of Eu3+ by Bi3+ sensitizers in yttrium alumino bismuth borosilicate glasses

Trivalent europium ions doped yttrium alumino bismuth borosilicate glasses (YABiBS) of the composition are synthesized by the melt - quenching method. The structural, thermal and spectral properties of the prepared glasses have been investigated by XRD, EDS, FT-IR, DTA, optical absorption, photoluminescence and decay profiles. XRD indicated the amorphous nature of the samples. From the DTA traces thermal Parameters like ΔT, S and H are evaluated to verify the thermal stability of the titled glasses. FTIR spectra exhibited bands due to various fundamental vibrational units of borate and silicate groups. The optical absorption spectra exhibited the bands due to 7F0 → 5G4, 7F0 → 5L6, 7F0 → 5D2, 7F0 →7F6, and 7F1 → 7F6 transitions of Eu3+ ions. In addition the absorption spectra also exhibited a band due to 1S0 → 1P1 transition of Bi3+ ions. From the absorption spectra, the optical band gap and Urbach energies and also nephelauxetic ratios were evaluated. The emission spectra (excited at 392 nm) exhibited five luminescence bands at 577, 590, 612, 651 and 700 nm assigned to 5D0 → 7F0, 5D0 → 7F1, 5D0 → 7F2, 5D0 → 7F3, and 5D0 → 7F4 transitions of Eu3+ ions, respectively. The absorption and emission spectra were characterized using Judd-Ofelt (J-O) theory and radiative parameters viz., radiative transition probability (AR), branching ratio (βR), and luminescence quantum efficiency (η), radiative life time (τ), stimulated emission cross-section (σPE) were evaluated. The values of radiative parameters are found to be the highest for the transition 5D0→7F2 of 0.6mol% Eu3+ doped YABiBS glass (BE0.6). The co-doping of Bi3+ ions (10.0mol %) caused a substantial enhancement (nearly three times) in the intensity of this red emission. These results suggested the energy transfer between Bi3+ ions and Eu3+ ions. The energy transfer efficiency has been explained in terms of structural modifications taking place in the glass network.

Mixed polyanion NaCo1−x (VO) x PO4 glass–ceramic cathode: role of ‘Co’ on structural behaviour and electrochemical performance

Glass samples with general formula NaCo1−x (VO) x PO4 (x = 0.1, 0.3, 0.5 and 0.7) are synthesized via a simple melt quenching method followed by high-energy ball milling for 30 h to form the homogeneous nanoscaled glass powders. DTA traces of all the glass and glass–ceramic samples indicated exothermic processes confirming selective crystallization induced in the glass network. The formation of major crystalline phase [sodium cobalt pyrophosphate (Na2CoP2O7)] with an ordered layered structure was monitored by X-ray diffraction and the same was justified by SEM images. Structural illustration of major crystalline Na2CoP2O7 phase offered more intra-layer Co–Co distance (7.12 A) than inter-layer Co–Co distance (5.37 A) which facilitates two-dimensional Na-ion diffusion pathways to achieve the fast intercalation and de-intercalation phenomenon along the a and c directions. The ionic conductivity was monitored by Impedance analysis and achieved to be highest (6.41 × 10−7 S cm−1) for the glass–ceramic cathode x = 0.3, NaCo1−x (VO) x PO4. The initial discharge capacity for the highest conducting NaCo0.7(VO)0.3PO4 cathode is obtained as 93 mA h g−1 in 0.1 C and had 65% capacity retention even at high rate 10 C.

Study on thermophysical properties and phase evolution in Nd doped Li2O-Al2O3-SiO2 glass nucleated by multiple nucleating agents

Lithium aluminium silicate (LAS) glasses of compositions (wt%) (1) LASa: 59SiO2-19Al2O3-3.5Li2O-5B2O3-1.5ZnO-1MgO-2TiO2-2ZrO2-7P2O5 and (2) LASb: 58SiO2-19Al2O3-3.5Li2O-5B2O3-1.5ZnO-1MgO-2TiO2-2ZrO2-7P2O5-1Nd2O3 were prepared by melt-quench technique and converted to glass-ceramics. In glass samples, addition of Nd2O3 showed an increase in the glass transition temperature (Tg) and crystallization temperature. Thermo-mechanical analysis (TMA) showed that crystallized samples have very low thermal expansion coefficient (α) of value around 2.5×10−6/°C (30–300). The microhardness and density values of crystallized samples were found to be higher than the base glasses. XRD and SEM techniques were employed to see nature of phases and their microstructures in glass/glass ceramic samples. From XRD formation of β-spodumene (LiAlSi2O6) as major crystalline phase while Berlinite (AlPO4)and Srilankite (TiZrO4) were identified as minor crystalline phases after heat treatment at 850°C.·The microstructure of LASa and LASb samples heat treated at 675°C showed formation of nanocrystals (size <50nm) of TiZrO4 within the glass matrix, whereas samples heat treated at maximum 850°C showed formation of shell type/spherical particles structure which support the three dimensional or bulk crystallization in these samples. Micro-laser Raman spectroscopy was carried out to confirm presence of TiZrO4 phase after heat treatment at 675°C. Crystallization kinetics study was carried out by recording DTA traces at different scanning rate. Activation energy (E) and Avrami parameter (n) were calculated by using Kissinger and Marotta methods and Augis-Bennett equation. Activation energy of crystallization for LASa and LASb were found to be 263kJ/mol and 270kJ/mol, respectively whereas the Avrami parameter (n) for LASa and LASb glass was found to be greater than 2 and greater than 4, respectively. Avrami parameter greater than 2 indicates near three dimensional growth of spodumene phase, which is also confirmed by microstructural analysis and parameter greater than 4 indicated interfacial controlled growth.

Prominent spectral features of Sm3+ ion in disordered zinc tellurite glass

Trivalent rare earth doped glasses with modified spectroscopic features are essential for solid state lasers and diverse photonic applications. Glass composition optimisation may fulfil such demand. Stimulating the spectral properties of samarium (Sm3+) ions in tellurite glass host with desired enhancement is the key issue. Glasses with composition (80−x)TeO2–20ZnO–(x)Sm2O3, where 0⩽x⩽1.5mol% are prepared using melt quenching method. The role of varying Sm3+ contents to improving the absorption and emission properties of the prepared glasses are determined. XRD pattern verifies amorphous nature of synthesised glasses. FTIR spectroscopy has been used to observe the structural modification of (TeO4) trigonal bipyramid structural units. DTA traces display prominent transition peaks for glass transition, crystallisation and melting temperature. Samples are discerned to be stable with desired Hruby parameter and superior glass forming ability. The UV–Vis–NIR absorption spectra reveals nine peaks centred at 470, 548, 947, 1085, 1238, 1385, 1492, 1550 and 1589nm. These bands arise due to 6H5/2→4I11/2, 4G5/2, 6F11/2, 6F9/2, 6F7/2, 6F5/2, 6F3/2, 6H15/2 and 6F1/2 transitions, respectively. The direct, indirect band gap and Urbach energy calculated from the absorption edge of UV–Vis–NIR spectra are found to appear within (2.75–3.18)eV, (3.22–3.40)eV, and (0.20–0.31)eV, respectively. The observed increase in refractive index from 2.45 to 2.47 is ascribed to the generation of non-bridging oxygen atoms via the conversion of TeO4 into TeO3 units. Conversely the decrease in refractive index to 2.39 is attributed to the lower ionic radii (1.079Å) of Sm3+. PL spectra under the excitation of 452nm display four emission bands centred at 563, 600, 644 and 705nm corresponding to 4G5/2→6H5/2, 6H7/2, 6H9/2 and 6H11/2 transitions of samarium ions. Excellent features of the results nominate these compositions towards prospective applications.

Transport Properties and Scaling Spectra of Lithium Gallium Titanate Phosphate Glass Ceramics Materials

A B S T R A C T Lithium gallium phosphate glass samples were synthesized through melt quenching by varying lithium oxide, titanium oxide and gallium oxide concentrations. The de-polymarizability of glass ceramic samples was identified by Hurby’s parameter (Kgl) with the data of DTA traces. Impedance measurements were made on all the glass ceramic samples at different temperatures. The bulk resistance (R) for all the samples relative to each experimental temperature is deduced from the

Synthetic preparation of proton conducting polyvinyl alcohol and TiO2-doped inorganic glasses for hydrogen fuel cell applications

This paper is focused on preparation and determination of physicochemical properties of new composite glass protonic membranes (P2O5–SiO2–TiO2) with the addition of PVA which could be a crucial modification for their application as electrolytic materials in fuel cells operating in the temperature range 30–150°C. Samples were obtained through sol–gel process with post-thermal treatment of the obtained hydrogel. The process was realized under FTIR and Raman spectroscopies control of the reaction progress. XRD was used to prove the amorphisicity of the samples. Two interesting correlations were observed during a more detailed analysis of conductivity data. One of them correlates endothermic transition observed in the DTA traces with TD value for ionic lattice in the samples while the other shows that the dimensionality of the conductivity process can be correlated with the sample surface area. The preliminary tests of the samples in fuel cells operated with hydrogen showed stable values of OCV in the whole investigated temperature range. Current density and power increase with temperature.

Studies on lithium alumino phosphate glasses doped with selenium ions for hard electrolytes

Glass samples of the system (100 − x) (0.5 Li2O–0.2Al2O3–0.3P2O5) + xSeO2 (x is ranging from 0 to 12 mol%, labeled as LAPS x ) were prepared using the melt quenching technique. FTIR spectral studies indicate that selenium ions mostly occupy network modifying sites due to isolated selenite (SeO3 2−) groups up to 6 mol% of SeO2 (LAPS6) in the LAPS glass network. This has a tremendous effect on the electrical properties. Glass forming ability parameter (K gl) and the glass transition temperature (T g) of LAPS samples were characterized by DTA traces. Electrical measurements were carried out as a function of frequency and temperature over the frequency range of 10 Hz to 106 Hz and a temperature range of 303–423 K. The electric modulus formalism was applied to study the relaxation behavior using the impedance data for all the samples at 303 K and also for analyzing the relaxation behavior of the highest conducting sample (6 mol% of SeO2) at different temperatures. An attempt has been made to relate the measured properties to the structural modifications due to the modifying effect of isolated selenite (SeO3 2−) groups in the glass network.

Thermal Properties of Cu-Hf-Ti Metallic Glass Compositions

ABSTRACTThe glass transition temperature Tg, crystallization temperature Tx, solidus temperature Tm, and liquidus temperature Tl, of a number of ternary Cu-Hf-Ti glassy alloys in the composition range of 51&lt; Cu &lt;67, 5 &lt; Hf &lt; 40 and 5 &lt; Ti &lt;40 (at.%) are reported and discussed. It is found that increasing the Ti:Hf ratio results in a rapid decreasing of Tg and Tx. This behavior is related to the fact that the melting point and cohesive energy for Ti are substantially lower than for Hf. The solidus temperature Tm, remains relatively constant on a wide range of compositions. The liquidus temperatures data suggest a ternary eutectic within the compositional field encompassed by the Cu55Hf20Ti25, Cu59Hf21Ti20, Cu60Hf20Ti20 and Cu55Hf21Ti24 alloys, with a liquidus temperature, Tl, of ∼1170 K; this is supported by the DTA traces, which show a single melting peak. Based on the DTA analysis, the experimentally calculated liquidus projection for the ternary Cu-Hf-Ti alloy system is also reported.

Formation of Nanocrystalline Phases in Sol-gel Masses in the Fe-W-C(O) System and Densification up to 1100°C

Nanoparticles (50-200nm) containing W, C and Fe (with W/Fe weight ratios between 1.5 and 9) were produced from alkoxide-mixtures subjected to partial oxidation and reduction in 10%H2-Ar up to 1000°C. During heating in a dilatometer under Ar or 10%H2-Ar flow, pellets made of nanoparticles with a W/Fe=1.5 ratio exhibited an expansion at low temperatures (400-600°C) and then rapid densifications at higher temperatures. For such a material DTA traces under Ar flow showed endothermic/exothermic peaks at about 400°C and 700°C. The formation of pure Fe and FeWO4 at ca. 300°C was detected by XRD at high temperatures (and under vacuum). A clear densification between 650°C and 900°C was detected in the pellet treated in the dilatometer under a flow of 10%H2-Ar (up to about 1030°C), associated to solid state sintering stage of nanoparticles of Fe and FeWCxO1-x (Fe6W6C, Fe3W3C, W2C, WC, FeWO4) compositions. After a subsequent similar run under 10%H2-Ar the specimen only showed expansion between 500 and 900°C and continued densifying for temperatures higher than 900°C. At the end of the run the sample was completely reduced to a mixture of Fe & Fe2W (Laves phase). The consolidation increased the particle size considerably.

ROLE OF PROCESS CONTROL AGENTS ON MILLING BEHAVIOR OF Al AND TiO2 POWDER MIXTURE TO SYNTHESIZE TiAl/Al2O3 NANO COMPOSITE

In this study effect of adding various process control agents (PCAs) to powder mixtures of Al and TiO 2 which are mechanically activated so as to form TiAl - Al 2 O 3 nano-composite have been investigated. Phase constitutions and morphology of the milled powders were evaluated by XRD and SEM techniques, respectively. The mean crystallite sizes of the milled powders were calculated by Cauchy-Gaussian method. Thermal behavior of the milled powders was also studied by DTA to investigate formation of the final phases. The results showed that the mean crystallite size of the milled powders in the presence of PCAs was smaller than that of the sample milled without PCA addition. DTA traces showed that addition of PCAs retards the reduction of TiO 2 by Al . In samples milled in presence of PCA, the reductive reaction generally took place after melting of Al particles whereas the sample milled without PCA addition showed an opposite behavior. Also, in comparison with the sample milled with no PCA addition, in other samples the reductive reaction took place at relatively lower temperatures.

Effect of preparation method on the surface properties and activity of Ni 0.7Cu 0.3Fe 2O 4 nanoparticles

Ni 0.7Cu 0.3Fe 2O 4 nanoparticles were synthesized via sol–gel combustion technique, co-precipitation method and solid state milling method. Simultaneous thermogravimetric and differential thermal analysis (TG–DTA) was carried out to monitor the decomposition process of the precursors. The samples were characterized by Fourier transform infrared (FT-IR), inductively coupled plasma spectroscopy (ICPS), X-ray diffraction (XRD), BET surface area measurement, scanning electron microscopy (SEM), transmission electron microscopy (TEM), temperature programmed reduction (TPR) and X-ray photoelectron spectroscopy (XPS). TG–DTA traces of the precursors show that the crystallization temperature for spinel formation by sol–gel combustion technique is lower than those by co-precipitation method and solid state milling method. XRD analysis reveals that the powders obtained are single phase with cubic spinel structure. Mutual promotion of reduction performance between CuO and NiFe 2O 4 is observed from TPR patterns. The experimental study indicates that the copper in the octahedral sites plays a crucial role in the direct oxidation of benzene with hydrogen peroxide as oxidant to phenol.

Study of the hyperfine structure, thermal stability and electric–dielectric properties of vanadium iron phosphate glasses

In the present study the thermal analysis, hyperfine structure and electric transport properties were investigated for the (60−X) P2O5 (20+X) V2O5 20Fe2O3 [PVF] (X=10, 15, 20, 30 and 40 mol%) glasses. The glassy state of the samples was characterized using DTA and Mössbauer spectroscopy. Two glass transition temperatures Tg1 and Tg2 were detected at the DTA traces of the investigated system. The glassy sample with X=20 mol% (PVF3) is of the highest glass thermal stability where ΔT=177±2 K. Also, it has the highest value of crystallization activation energy for the first and the second crystallization peaks (305 and 316±3 kJ/mol%) among the other samples. The obtained ME spectra showed the presence of Fe3+ alone located in the tetrahedral and octahedral sites. Increasing V2O5 content, the dc conductivity increases while the activation energy decreases. The room temperature dc conductivity is typically 2.9×10−7–2.5×10−5 with an activation energy 0.60–0.37±0.011 eV. The power law exponent s was found to be temperature dependent and exhibited a minimum, for PVF3 and PVF4. The dielectric constant ε1(ω) increases with increasing V2O5 content which was attributed to the increase in the deformation of glass network.

Sol–gel synthesis of hydrous ruthenium oxide nanonetworks from 1,2-epoxides

Hydrous ruthenium oxide (RuO 2· xH 2O) xerogels were synthesized through the addition of a 1,2-epoxide, propylene oxide, to commercial hydrated ruthenium chloride, “RuCl 3· xH 2O,” in ethanol. After a blue-black monolithic gel formed in 4 h, the samples were allowed to age for 24 h and were dried in ambient conditions. The dried samples were then characterized by XPS, XRD, DTA and TGA. XPS showed the Ru(3 d 5/2) peak at a binding energy of 281.7 eV, corresponding to that of hydrous ruthenium oxide. XRD data revealed the synthesized material as amorphous. Heating the sample in inert atmospheres caused the complete reduction of the oxide to the zero-valent state, whereas heating the sample in air resulted in both crystalline anhydrous RuO 2 and zero-valent ruthenium, depending on the method of heating. DTA traces showed an endotherm ending at 150 °C, corresponding to the loss of coordinated water, as well as two higher temperature crystallization exotherms when the sample was heated in both inert and oxygen-rich atmospheres. TGA runs also confirmed the complete reduction of the hydrous oxide when heated in nitrogen below 270 °C and the formation of anhydrous ruthenium oxide when heated in air, confirming the XRD results.

Thermal behavior of poly(acrylic acid)–poly(vinyl pyrrolidone) and poly(acrylic acid)–metal–poly(vinyl pyrrolidone) complexes

AbstractThermal analysis (TGA and DTA) of samples of PAA, PVP, PAA–PVP complexes, containing different weight fractions of PAA and ternary polymer–metal–polymer complexes, were studied. The activation energy parameters for the thermal degradation were also calculated. The study of the effect of FeCl3, NiCl2, and Ni(NO3)2 on the TGA and DTA curves of the complexes showed that the decompositions are dependent on the concentrations and the nature of the metal ions. The DTA traces of PAA–PVP complex containing FeCl3, NiCl2, and Ni(NO3)2 showed that the treatment of the complex with these metal ions causes considerable changes in the thermal decomposition of PAA–PVP complex. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4049–4057, 2006

Growth and characterization of nonlinear optical single crystals of l-arginine diiodate

Growth of good optical quality single crystals of l-arginine diiodate (abbreviated as LADI), a semiorganic nonlinear optical (NLO) material is reported. Crystals of dimension up to 14 × 6.5 × 5 mm 3 were obtained from its aqueous solution by slow solvent evaporation technique. The crystals were characterized by single crystal XRD, FTIR, optical absorption spectrum, microhardness, dielectric and photoconductivity studies. The DTA and TGA traces of LADI confirm the decomposition of the sample at 145 °C.

Processing, characterisation and biocompatibility of iron-phosphate glass fibres for tissue engineering

Iron-phosphate glass fibres based on the CaO–Na 2O–Fe 2O 3–P 2O 5 system have been processed and characterised via thermal, XRPD, dissolution rates, diameter and biocompatibility studies. The compositions investigated were fixed at 50 mol% P 2O 5, and the CaO content was varied between 30, 35 and 40 mol%. The Fe 2O 3 was added in low amounts from 1–5 mol%, substituting it for the Na 2O mol%. The number of T c (crystallisation temperature) peaks detected from the thermal analysis traces only showed correlation with XRPD analysis, for five out of the 15 compositions investigated. It has been suggested that either the crystalline phases had very similar T c temperatures or that the other phase(s) were present in very small quantities. There was a good match seen with number of T m (melting temperature) peaks picked up from the DTA traces, with the number of phases identified from XRPD analysis. The main phases identified from XRPD were NaCa(PO 3) 3, CaP 2O 6 and NaFeP 2O 7. Using network connectivity (NC), predictions on Q n species present within the compositions investigated were made. The predicted species (metaphosphates) matched with phases identified from XRPD analysis. A decrease in dissolution rates for the bulk glass and glass fibres was seen with an increase in CaO mol%, along with an increase in Fe 2O 3 mol%. An increase in fibre dissolution rates was seen with a decrease in diameter size. The biocompatibility studies were conducted using a conditionally immortal muscle precursor cell line derived from the H-2Kb-tsA58 immortomouse. It was found that iron-phosphate glass fibres containing 4–5 mol% Fe 2O 3 was sufficient for cell attachment and differentiation. It was seen that myotubes formed along the axis of the fibres (which was indicative of differentiation). The biocompatibility of these compositions was attributed to the enhanced chemical durability of the glass fibres.

Synthesis and dielectric properties of A m−1 Bi 2B mO 3 m+3 ceramic ferroelectrics with m=1.5

Bismuth containing ceramic materials of molecular formula Bi 5TiWNbO 15, Bi 5Ti 1/2W 1/2Nb 2O 15, Bi 5Nb 3O 15 have been synthesised and fabricated. The materials are known as the Aurivillius phases. The Aurivillius phases are a family of oxide ferroelectrics generally formulated as A m−1 Bi 2B m O 3 m+3 . The process of preparation was investigated by X-ray diffraction method as well as the simultaneous thermal analysis, in which both thermal (DTA) and mass change effects (TG) were measured on the same sample. The synthesis of the Aurivillius phases was carried out according to the solid state reaction from the conventional mixture of oxides (Nb 2O 5, WO 3, Bi 2O 3, and TiO 2). DTA and TG traces showing the synthesis effects have been recorded. Investigations of the crystalline structure, microstructure and basic dielectric properties were performed.

RuSi 2: evidence of a new binary phase in the ruthenium–silicon system

Ru 2Si 3 single crystals have been grown by the zone melting technique with radiation heating. These crystals contain inclusions, about 500 nm in size, which consist of monocrystalline ruthenium disilicide. Endothermic peaks detected at T=962°C in the DTA traces of RuSi x are interpreted as decomposition of RuSi 2 to Ru 2Si 3 and Si. This enabled us to update the Si-rich part of the Ru–Si phase diagram.

Effects of composition on crystallization behaviour and mechanical properties of bioactive glass-ceramics in the MgO–CaO–SiO 2–P 2O 5 system

The effects of replacement of P 2O 5 by SiO 2, on the crystallization behaviour, mechanical properties and bioactivity of glass-ceramics in the MgO–CaO–SiO 2–P 2O 5 system were investigated. By decreasing P 2O 5 and increasing SiO 2, the apatite crystallization peaks disappeared from DTA traces, whereas the wollastonite peaks remained unchanged. XRD results showed that by decreasing P 2O 5 and increasing SiO 2 contents, the amount of apatite and wollastonite phases were decreased and increased, respectively. The diametral compression strength (DSC) and indentation fracture toughness (IFT) values gradually raised with increasing wollastonite content. The best results obtained for the specimens with the maximum amount of wollastonite were 36.6 and 2.74 MPa m 1/2 for DCS and IFT, respectively. The bioactivity of specimens after being soaked in a simulated body fluid for one month were examined by SEM/EDX and FT–IR. A thin apatite layer was formed even on the surface of specimens containing the minimum amount of apatite phase.