Differential Scanning Thermal Analysis Research Articles

Preparation of MoO3 powder by hydrothermal method

Abstract Based on the raw material of ammonium tetramolybdate in the experiment, molybdenum trioxide was prepared by hydrothermal synthesis, and the effects of different pH, hydrothermal reaction time, filling degree, and calcination temperature on molybdenum trioxide powder were studied. Meanwhile, the molybdenum trioxide powder was characterized through scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and thermal analysis differential scanning calorimetry analysis so as to study the morphology and phase changes during the experiment. As is evident from the research findings, MoO3 powders with uniform and suitable size, smooth and clear surface, good dispersibility, and no adhesion can be obtained at the conditions of pH = 1, 16 h hydrothermal reaction, 90% of filling degree, and 550°C of calcination temperature. In the calcination process, MoO3 crystal undergone crystal transformation and was completely transformed from h-MoO3 to α-MoO3 at the calcination temperature of 350°C.

Glass Stability and Glass Forming Ability of Ge25−xSe75Sbx (x = 12, 15, and 18) Chalcogenide Glasses Using Thermal Parameters

AbstractIn the present communication glass stability (GS) and glass forming ability (GFA) of Ge25−xSe75Sbx (x = 12, 15, and 18) chalcogenide glasses have been calculated in terms of certain thermal parameters, i.e., reduced glass transition temperature (Trg), Hruby number (H), S‐parameter (S), and ΔT. The glassy samples have been prepared by quenching of melt technique. For structure characterization, XRD technique has been used. For thermal analysis Differential Scanning Calorimetery (DSC) has been used. DSC scans have been recorded at different heating rates, i.e., 5, 10, 15, and 20 K min−1. Stability of glassy samples has also been confirmed in terms of activation energy of glass transition calculated by Kissinger relation. All these parameters indicate that GS and GFA both decrease with increase of Sb content in Ge25−xSe75Sbx (x = 12, 15, and 18) glassy series.

Preparation of chitosan-coated hollow tin dioxide nanoparticles and their application in improving the oral bioavailability of febuxostat

The aim of this study was to design a chitosan-coated hollow tin dioxide nanosphere (CS-HSn) for loading febuxostat (FEB) using an adsorption method to obtain a sustained-release system (CS-HSn-FEB) to improve the oral bioavailability of FEB. The morphological characteristics of hollow tin dioxide nanospheres (HSn) and CS-HSn were analyzed by transmission electron microscopy (TEM) and dynamic light scattering (DLS). The hemolysis test and CCK-8 test were used to assess the biosafety of HSn and CS-HSn. Powder X-ray diffraction (PXRD) and differential scanning thermal analysis (DSC) were performed on CS-HSn-FEB to analyze the drug presence status. The dissolution behavior and changes in plasma drug concentration of CS-HSn-FEB were evaluated in vitro and in vivo. Sections of intestinal tissues from SD rats were obtained to observe whether chitosan could increase the distribution of nanoparticles in the intestinal tissues. The results showed that FEB was present in CS-HSn in an amorphous state. Moreover, CS-HSn, with good biosafety, significantly improved the water solubility and oral absorption of FEB, indicating that CS-HSn has great potential to improve the intestinal absorption and oral bioavailability of insoluble drugs.

Hydrogenation of High-Density Polyethylene during Decompression of Pressurized Hydrogen at 90 MPa: A Molecular Perspective.

To investigate changes in the physical and chemical properties of high-density polyethylene (HDPE) upon the rapid release of hydrogen gas at a pressure of 90 MPa, several characterization techniques have been employed, including optical microscopy, scanning electron microscopy, X-ray diffraction, differential scanning thermal analysis, and attenuated total reflectance Fourier-transform infrared spectroscopy. The results showed that both physical and chemical changes occurred in HDPE upon a rapid release of hydrogen gas. Physically, a partial hexagonal phase was formed within the amorphous region, and the overall crystallinity of HDPE decreased. Chemically, hydrogenation occurred, leading to the addition of hydrogen atoms to the polymer chains. Oxidation also occurred, for example, the formation of ester -C=O groups. Crosslinking and an increase in -CH3 end termination were also observed. These changes suggest that structural transformation and chemical modification of HDPE occurred upon the rapid release of hydrogen gas.

Preparation and Characterization of a Eutectic Mixture of Fenofibric Acid and Nicotinic Acid and Evaluatuion of In Vivo Antihyperlipidemic Activity

Fenofibric Acid (FA) is classified under Biopharmaceutical Classification System (BCS) class II due to its poorly soluble in water and high permeability. The present study aimed to prepare the eutectic mixture of FA with nicotinic acid (NA) and characterize its solid state properties and in vitro dissolution rate, along with its in vivo antihyperlipidemic activity. Solvent drop grinding was the method chosen to prepare the eutectic mixture of FA and NA. Solid-state properties were evaluated using thermal analysis Differential Scanning Calorimetry (DSC), crystallographic analysis Powder X-Ray Diffraction (PXRD), FT-IR spectroscopic analysis, and Scanning Electron Microscopy (SEM). To examine in vivo antihyperlipidemic activity, 16 male Swiss Webster rats were injected with 1% hyperlipidemia-inducing solution, followed by the oral administration of 9.45 mg/kg FA and NA (equivalent to 9.45 mg/kg FA), after which the decrease in cholesterol levels was measured. Two-way ANOVA was used to evaluate the data, followed by Duncan’s multiple range test (95% confidence interval). The results proved that FA formed the eutectic mixture with NA at a molar ratio of 6:4. The eutectic mixture of FA-NA had a better solubility and in vitro dissolution rate compared to intact FA, which also led to notably improved antihyperlipidemic activity.

The Use of Copper Oxides as Cross-Linking Substances for Chloroprene Rubber and Study of the Vulcanizates Properties. Part I.

The purpose of this work was to verify the ability to cross-link the chloroprene rubber (CR) by using copper oxides: copper(I) oxide or copper(II) oxide. The use of copper oxides arises from the need to limit the application of ZnO as a cross-linking agent of CR. The obtained results indicate that CR compositions cross-linked with copper oxides are characterized by good mechanical properties and a high cross-linking degree. The results show that the type and the amount of copper oxides influence the cross-linking of the CR and the properties of the vulcanizates. For compositions containing copper(II) oxide, the properties are linearly dependent on the amount of CuO. Such a relationship is difficult to notice in the case of the use of copper(I) oxide—when analyzing individual parameters, the best results are obtained for different samples. Infrared spectroscopy (IR) studies confirmed the possibility of cross-linking of chloroprene rubber with copper oxides. This is evidenced by the characteristic changes in the intensity of the bands. Structural changes in the material during heating were determined by the thermal analysis—differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Regardless of the type and amount of copper oxide, all compositions exhibit similar characteristics, and there are no significant changes in the glass transition temperature of the material.

Comparing the ignition and combustion characteristics of ball-milled Al-based composites with Ti, Zr, and Mg additives

ABSTRACT The morphology/microstructure and ignition/combustion properties of ball-milled Al composite powders containing Ti, Zr, and Mg were studied and compared. The particles contained 50 at% Al or Al-8Mg alloy and 50 at% Ti or Zr, yielding four different chemistries: Al:Zr, Al-8Mg:Zr, Al:Ti, and Al-8Mg:Ti. Ignition temperatures were measured by resistively heating the powders on a nichrome wire in air. All composite particles exhibit ignition temperatures (~625-725 K) that are significantly lower than those for pure Al of similar size (~2100 K). The Ti-based composites have slightly lower ignition temperatures than the Zr-based powders. The difference is attributed to the Ti-based powders having more energetic intermetallic formation reactions as measured by differential thermal analysis (DTA). The microstructures of the as-milled composites were analyzed via powder x-ray diffraction and scanning electron microscopy and helped to explain the measured heats and ignition temperatures. The addition of Mg did not significantly affect the ignition temperatures, but it did alter the number of peaks, the peak positions and overall heat release in the DTA scans compared to the binary samples. Mg also improved refinement of both internal microstructures and the size of composite particles during milling. Spectroscopy and high-speed videography of the combusting powders revealed vapor-based emission species such as Al and AlO for the binary samples and Mg and MgO for the ternary composites. Higher average maximum combustion temperatures were measured for the Ti-based powders (3470 ± 450 K and 3300 ± 880 K) than the Zr-based powders (3340 ± 350 K and 3100 ± 400 K) with the Mg containing powders being hotter for Ti and Zr chemistries. The Ti-based composites displayed a dual-phase combustion mechanism and micro-explosions, similar to those seen for Al:Zr composites in previous studies.

Thermal, optical and electrical properties of MnO2-doped mixed sodium potassium phosphate glasses

Glasses in the system (1 − x)(0.5NaPO3–0.5KPO3)–xMnO2, with 0 ≤ x ≤ 50 mol%, have been prepared using a melt-quench route. The glasses exhibit a yellow to dark color with the increase in manganese content owing to the presence of Mn2+ and Mn3+ ions in the network. The amorphous state of the glasses is evidenced by the X-ray diffraction. In order to get an insight into the physical and structural aspects of these vitreous materials, we have determined some of their parameters such as density, molar volume and glass transition temperature. From differential thermal analysis scan on heating, we evaluated the glass transition temperature (Tg) of each glass, which corresponds to the phase transition temperature from solid to viscous liquid. The density (ρ) as a structural index is found to increase while the corresponding molar volume decreases with MnO2 content. The structural approach of the studied glasses is evaluated by infrared (IR) and electron paramagnetic resonance (EPR) spectroscopies. IR technique allowed us to identify the coexisting bond vibration modes in the glass network, and it has shown that many structural phosphates units coexist, mainly pyrophosphate and metaphosphate structural groups. EPR experiments have shown the presence of Mn2+ centers in the glasses. The UV–Visible absorption is utilized to estimate the values of the optical band gap (Eg) and Urbach energy (ΔE). The optical band gap energy is determined from both the absorption spectrum fitting (ASF) and Tauc’s methods. These optical parameters are composition dependence. The dc conductivity of the glasses is determined in the temperature range from 303 to 473 K. It decreases with increasing manganese content. It is thermally activated and followed an Arrhenius behavior. The crystallization of glasses is realized by submitting them to heat treatments, and the crystallized phases are identified by XRD analysis. The crystallization kinetic was studied under non-isothermal conditions. The activation energy (Ec) and the Avrami parameter (n) were determined.

Modeling nonisothermal crystallization in a BaO∙2SiO2 glass

AbstractThe accuracy of a differential thermal analysis (DTA) technique for predicting the temperature range of significant nucleation is examined in a BaO∙2SiO2 glass by iterative numerical calculations. The numerical model takes account of time‐dependent nucleation, finite particle size, size‐dependent crystal growth rates, and surface crystallization. The calculations were made using the classical and, for the first time, the diffuse interface theories of nucleation. The results of the calculations are in agreement with experimental measurements, demonstrating the validity of the DTA technique. They show that this is independent of the DTA scan rate used and that surface crystallization has a negligible effect for the glass particle sizes studied. A breakdown of the Stokes‐Einstein relation between viscosity and the diffusion coefficient is demonstrated for low temperatures, near the maximum nucleation rate. However, it is shown that accurate values for the diffusion coefficient can be obtained from the induction time for nucleation and the growth velocity in this temperature range.

Concentration dependence of the elastic moduli, thermal properties, and non-isothermal kinetic parameters of Yb3+ doped multicomponent tellurite glass system

The thermal properties and the kinetic parameters of TeO2–Li2O–ZnO–Nb2O5–Yb2O3 glass series have been evaluated as a function of increasing Yb2O3 content. The theoretical elastic properties and the quantitative analysis (the link between the elastic features and the changed chemical composition of the glass) have been determined by the use of bond compression and Makishima–Mackenzie models. The thermal analysis Differential Scanning Calorimetry (DSC) test was used for estimating the glass characteristics temperatures, thermal stability, and non-isothermal kinetic parameters at the heating rates (β) 10, 15, 20 and 25 K/min. The activation energies of the glass transition 〈Eg〉 and crystallization 〈Ec〉, as well as the order of the crystallization reaction (n), have been computed by different models with clear consistency and harmony between them. It was found that the characteristics temperatures of transition (Tg), softening (Ts), the onset of the crystallization (Tx) and the crystallization (Tc) increased with increasing the heating rate. Also, the results showed the higher thermal stability values (>100 K) for the understudied glass which is confirmed by KSP and ((Tc–Tg)/Tg) parameters values. Calculating of (n) showed that the crystallization started with surface nucleation and finished with bulk volume nucleation with rising Yb2O3 (mol %). The computed elastic moduli were linked with the interpretation of the thermal parameters to give a comprehensive image of the studied glass system.

Thermal analysis of the sulfur vulcanization

It is known that rubber mixes containing vegetable oils and vulcanized vegetable oils give better flow properties, plasticizing action, low temperature flexibility and ozone resistance. Now, in this investigation, the aim was to provide additional information about the effect of two vegetable oils (linseed oil and peanut oil) upon accelerated sulfur vulcanization system using thermal analysis—differential scanning calorimetry (DSC) and thermogravimetry. Several combinations of curatives (ZnO, sulfur and 2-t-butylbenzothiazole sulfenamide or TBBS) with stearic acid or vegetable oils were investigated, and DSC curves showed that vulcanization systems where linseed oil or peanut oil replaced stearic acid as activator proceeded an outline of basic steps similar to conventional mixture. However, the formation of the complex between Zn2+, sulfur and products of TBBS decomposition, main step in the vulcanization reaction, required much more energy. Exothermic ΔH values of 45.4 and 20.3 J g−1 were found for ZnO/S/TBBS/linseed oil and ZnO/S/TBBS/peanut oil, respectively, against only 5.8 J g−1 in the case of ZnO/S/TBBS/stearic acid mixture.

Effect of substrate movement speed by synchronous rolling-casting freeform manufacturing for metal on microstructure and mechanical property of ZL104 aluminum alloy slurry

Synchronous rolling-casting freeform manufacturing for Metal (SRCFMM) means that the refined liquid metal is continuously pressed out from the bottom of crucible. There is a horizontal movable plate beneath the outlet. The clearance between the outlet and the plate is about several hundred micrometers. SRCFMM, similar to additive manufacturing, implies layer by layer shaping and consolidation of feedstock to arbitrary configurations, normally using a computer controlled movable plate. The primary dendritic crystal is easily crushed by movement of substrate in the rolling-casting area. ZL104 was used as the test materials, determining the control temperature by differential scanning thermal analysis ( DSC), preparing a kind of samples by SRCFMM, then analyzing microstructures and mechanical property of the samples. Characteristics and distribution of the primary particles were assessed by optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectrum (EDS) and image analysis software. Mechanical property of the samples was assessed by vickers hardness. The results show that the samples fabricated by SRCFMM have uniform structures and good performances with the velocity of the substrate controlled about 10 cm/s and temperature at about 580 degrees C.

Structure and Crystallization Kinetics of Glassy CaO-Al2O3-SiO2-CaF2-Na2O Mold Fluxes with Varying Basicity

The structure and the crystallization kinetics of CaO-Al2O3-SiO2-CaF2-Na2O mold fluxes with varying basicities were investigated by solid-state 29Si nuclear magnetic resonance with magic angular spinning (MAS-NMR) and differential thermal analysis (DTA) technique, respectively. 29Si MAS-NMR study indicated that the increase of basicity decreased the degree of polymerization of mold fluxes. With the increasing basicity, Q 0, Q 2, and Q 3 gradually decreased, while Q 1 gradually increased, and the overall degree of polymerization was reduced. Crystallization analysis showed the cuspidine first crystallized from glass, and wollastonite crystal crystallized at elevated temperature for the samples with basicity (defined as CaO/SiO2 mass ratio) values of 0.9 and 1.0, respectively. Only cuspidine was found to crystallize from glass for the samples with basicity values of 1.1 and 1.2, indicating that the crystallization of wollastonite was suppressed with the increase of basicity. Crystallization kinetics analysis by DTA and field emission scanning electron microscopy equipped with energy dispersive spectroscopy investigation showed that growth mechanism of cuspidine is mainly of the diffusion-controlled three-dimensional growth with the increasing number of nuclei during heating. Activation energies for growth of cuspidine decreased with the increasing basicity of mold flux, which indicated that the crystallization ability was enhanced with the increase of basicity. The relationship between structure and crystallization of mold fluxes was established.

Reaction mechanism of lanthanum nitrate-doped Mo–La material during solid–liquid spray doping processing

At three critical temperatures which were obtained by thermo-gravimetry-differential thermal analysis–differential scanning calorimetry (TG/DTG/DSC) curves of lanthanum nitrate crystal, the air thermal decomposition experiments and solid–liquid spray doping simulation procedures of lanthanum nitrate crystal were carried out, and their products were analyzed by X-ray diffraction (XRD). Meanwhile, the spray doping processing of MoO2–50 wt% La(NO3)3 composite powder was undergone with lanthanum nitrate solution as the dopant, and doped MoO2 powder was analyzed by XRD. The results demonstrate that during the traditional solid–liquid spray doping processing, lanthanum nitrate, in the form of either crystal or aqueous solution, would be converted into La(NO3)3·4H2O by the dehydration reaction, rather than be decomposed to La2O3 and NO or NO2. Therefore, it is inferred that the oxynitride gas produced from the process is attributed to the decomposition of residual HNO3 in lanthanum nitrate crystal. The source of HNO3 is supported by the chemical composition of lanthanum nitrate crystal.

The Microstructure Evolution of AA7050 in the Process of Homogenization

This paper used the metallographic analysis, X-ray diffraction analysis (XRD), differential scanning thermal analysis (DSC), scanning electron microscope (SEM) and electron probe analysis (EPMA) system to research the evolution law of the microstructure and properties of AA7050 under different homogenization system. And analyzes the cause of this evolution combined with the test results put forward. The research shows that high melting point eutectic phase S (Al2CuMg) can be fully re-dissolution through two-stage homogenization, at the same time avoid the overburning of low melting eutectic phase. We optimized the AA7050 homogenization heat treatment system and the optimal homogenization scheme is 430°C/18h+467°C/12h.

Preparation, thermal characterization, and DFT study of the bacterial cellulose

Bacterial cellulose (BC)-triethanolamine (TEA) membranes have been prepared by the immersion of never dried BC membranes in BC-TEA aqueous solutions. Scanning electron microscopy showed that TEA covers BC nanofibrils, causing the aggregation of them. The thermal analysis differential scanning calorimetry (DSC) and ther- mogravimetric analysis (TG), together with the DTG curves, showed that moisture retention is improved with TEA addition, through the formation of hydrogen bonds between water molecules and hydroxyl groups of TEA and BC. Peaks related to water retention in DSC curves of BC-TEA samples were shifted to higher temperatures, around 120 C, in comparison with that observed for the same BC peak, about 52 C. TG curves of BC-TEA samples provided information regarded to mass losses in this range (from ambient up to 150 C, the mass losses are 72, 52, and 10 %, respectively, for BC-TEA 1 M, BC-TEA 0.1 M, and BC- TEA 0.01 M samples), which are gradually higher than mass loss of 5 % in this range, shown in BC curve. Through spectroscopic techniques (FT-IR spectroscopy and Raman scattering), vibration groups of BC and TEA were identified. Density functional theory studies strongly suggest BC-TEA interactions through hydrogen bonds formation.

Thermal Properties of Multiwalled Carbon Nanotubes-Alumina (MWCNT-Al<sub>2</sub>O<sub>3</sub>) Hybrid Filled Silicone Rubber Composites

A hybrid compound of multiwalled carbon nanotubes-alumina (MWCNT-Al2O3) was successfully synthesized using chemical vapour deposition (CVD) method. MWCNT-Al2O3 at three different weight percent (0.5wt.%, 1.0wt.% and 1.5wt.%) was added into Silicone rubber of Polydimethylsiloxane (PDMS) using ultrasonic sonicator. Thermal analysis Differential Scanning Calorimetry (DSC) and Thermogravimetry (TGA) was performed on each composites and their thermal stability was compared. TGA thermogram showed that 1.0wt.% and 1.5wt% of hybrid compound had more weight loss recorded at decomposition temperature of 400°C. In addition, DSC thermogram also indicated that heat of fusion increased with increasing content (wt.%) of hybrid compound MWCNT-Al2O3 in the Polydimethylsiloxane composites. It was found that the presence of MWCNT-Al2O3 hybrid compound had changed the internal energy and the mass loss of the composite.

Effect of Y2O3 on the crystallization kinetics of TiO2 nucleated LAS glass for the production of nanocrystalline transparent glass ceramics

Crystallization kinetics of metastable β-quartz solid solution as a desirable phase for the production of transparent lithium aluminosilicate (LAS) glass ceramics was investigated in the presence of Y2O3. Accordingly, differential thermal analysis scans were performed thoroughly to study the mechanism of crystallization kinetics. The aim of this investigation is to discover the complicated mechanism of crystallization process in the presence of co-additives and accordingly find a way for increasing the transparency of glass ceramics. It is shown that the bulk (3D) growth is intensively increased by the enhancement of Y2O3. Then again, reducing nucleation and increasing growth mechanisms were recognized for the LAS system in the presence of Y2O3. Results of the investigation illustrate that when co-additives are added to glasses, it is necessary to nucleate the optical component separately before the growth process.

Elongational and shear flow behavior of calcium carbonate filled low density polyethylene: Effect of filler particle size, content, and surface treatment

AbstractIn this article, calcium carbonate filled low density polyethylene (LDPE) was prepared and the influence of filler content, particle size, and surface treatment with stearic acid on the strain hardening and viscoelastic properties of the composites were investigated. Both elongational and shear rheological measurements were conducted on the different formulations and completed by microscopical observations and by differential scanning thermal analysis. The obtained results indicate that the effect of filler content and particle size are negligible on strain hardening behavior. Also the filler surface treatment has a less important effect on the nonlinear elongational tests in comparison with low frequency range measurements. However in shear rheology, we noted the absence of yield stress and network structure at different filler contents, and the presence of shear thinning behavior. Scanning electron microscopy (SEM) observations showed the enhancement of dispersion for surface treated samples, while differential scanning calorimetry (DSC) experiments have shown that the content of crystallinity of LDPE matrix is slightly affected by the presence of filler. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Low-temperature electron paramagnetic resonance studies on natural calumetite from Khetri copper mine, Rajasthan, India

We report here for the first time low-temperature (123–295 K) electron paramagnetic resonance (EPR) spectroscopic data on naturally occurring calumetite [Cu(OH,Cl2)·2H2O] from the Khetri copper complex, Jhunjhunu district, Rajasthan, India. The sample was characterized by X-ray powder diffraction (XRD), differential thermal analysis (DTA), and thermogravimetric (TG) analysis techniques. DTA scans show two endothermic reactions at about 378 and 598 K, which are attributed to dehydration of the sample. TG data indicate weight loss of up to 24 wt% in the temperature region between 600 and 700 K. The room-temperature EPR spectrum exhibits parallel and perpendicular components centered at g || = 2.26 and g ⊥ = 2.10, respectively. The evaluated spin-Hamiltonian parameters indicate that these resonance signals are characteristic of Cu2+ ions in distorted octahedral symmetry. The population difference (N) between the Zeeman levels has been evaluated and is found to increase with decreasing temperature.