DSC Investigations Research Articles

ДСК-дослідження дії фракцій екстрактів плаценти людини на термічну стабільність білкових комплексів еритроцитарних мембран

ДСК-дослідження дії фракцій екстрактів плаценти людини на термічну стабільність білкових комплексів еритроцитарних мембран

In situ DSC investigation into the kinetics and microstructure of dispersoid formation in Al-Mn-Fe-Si(-Mg) alloys

Dispersoid strengthening in Al-Mn-Fe-Si(-Mg) aluminum wrought alloys can play an important role in applications at elevated temperatures. Fine and evenly distributed dispersoids are needed to increase alloy strength, which can be achieved by conducting an adapted homogenization heat treatment. In this work for the first time, the precipitation behavior of dispersoids in direct chill casted Al-Mn-Fe-Si(-Mg) alloys was systematically investigated in situ during heating by means of differential scanning calorimetry. In situ analysis of the phase transformation kinetics during heating and homogenization was complemented by ex situ testing of the electrical conductivity and Vickers hardness, as well as micro- and nano-structural analyses by optical light and transmission electron microscopy. The influence of the heating rate on precipitation behavior was determined by calorimetric in situ experiments, covering a wide heating rate, ranging from 0.003 to 2K/s. The influence of 400 and 550°C homogenization temperatures and soaking durations on hardness and electrical conductivity was also investigated. The highest dispersoid strengthening was obtained after heat treating the as-cast Mg-containing alloy at 400°C for 3 to 10h. Furthermore, the Mg content heavily influenced the precipitation behavior by forming β-Mg2Si precursor phases, which can act as nucleation sites for dispersoid precipitation.

Effect of a cyclic heating process on the CO 2 /N 2 separation performance and structure of a ceramic nanoporous membrane supporting the ionic liquid 1-methyl-3-octylimidazolium tricyanomethanide

This work presents an investigation of the CO2 and N2 mixed-gas permeation rates through a supported ionic liquid membrane (SILM) developed on a ceramic composite nanofiltration substrate with a separation layer pore size of 10 nm. The ionic liquid 1-methyl-3-octylimidazolium tricyanomethanide was used as supported liquid phase. The hybrid membrane was subjected to a cyclic heating process including isothermal steps of 180 °C, under inert gas flow. In this context, the effect of temperature (over the range of 25–180 °C) and feed composition on the permeation properties and CO2/N2 separation performance was studied prior to and after completion of each heating cycle. For all heating cycles, the highest CO2/N2 selectivity values (up to 50.4) were provided at ambient temperature unlike to CO2 permeance that was favored by elevation of temperature, reaching to 2.48 · 10−9 mol·m−2·s−1·Pa−1 at 180 °C. Thermal analysis by means of DSC and TGA investigations allowed to determine the physical state and thermal stability of the immobilized IL phase, thereby providing a better understanding of the determined gas permeation properties. Confinement into the nanopores of the developed SILM substantially affected the thermal behaviour and assisted decomposition of the ionic liquid phase upon heat treatment. UV/Vis spectroscopy indicated formation of functionalized by-products during prolonged periods of heating at 180 °C that could form stable chemical complexes with CO2 molecules, thus drastically affecting both CO2 solubility and diffusivity, and CO2/N2 separation efficiency.

Effects of Aging Temperature on Microstructure and Thermal Properties of CuAlMn Shape Memory Alloys

The use of copper-based shape memory alloys is increasing rapidly. In this study, the aging effects of CuAlMn shape memory alloys were investigated. Three different alloys were produced during the work. These alloys were then aged for one hour at temperatures of 200 ° C, 300 ° C, 400 ° C and 500 ° C. DSC, XRD and microstructural investigations were carried out on samples which were not aged and aged at different temperatures. Experiments have shown that aging at high temperatures has an adverse effect on shape memory effect on alloys.

Optimal selection of appropriate fuels for a miniaturized motor and numerical simulations on its temperature distributions and thermal deformation

In this work, the energy characteristics of different propellants were thermodynamically calculated using the Minimum Gibbs free energy method. Based on such calculations and the previous experimental results using the DSC investigations on the thermal decomposition behavior, an optimized propellant formulation was selected. The numerical simulations on the temperature distributions for a prepared miniaturized motor with this formulation were conducted, and the resultant thermalstress and deformationof the thruster array were investigated. In particular, a physical micro model was established, and the effects of combustion parameters on the thermal performance were studied. The results showed thatthe highest temperature occurred at the boundary of the combustion chamber, where the thermal stress and deformation were the maximum. Furthermore, the thermal stress and deformation of silicon material was smaller than steel, and the thermal stress was the main reason for the destruction of micro-thruster stability. In addition, the maximum thermal deformation was small and had little effects on the thermalstability, whereas the thermal stress was the main reason for the poor thermal stability.

A Versatile Method for Nanostructuring Metals, Alloys and Metal Based Composites

A new severe plastic deformation method based on High Pressure Torsion is described. The method patented as High Speed High Pressure Torsion (HSHPT) shows a wide scope and excellent adaptability assuring large plastic deformation degree on metals, alloys even on hard to deform or brittle alloys. The paper present results obtained on aluminium, magnesium, titan, iron and coper alloys. In addition capability of HSHPT to process metallic composites is described. OM SEM, TEM, DSC, RDX and HV investigation methods were employed to confirm fine and ultrafine structure.

DSC study and thermodynamic modelling of the system paracetamol–o-acetylsalicylic acid

The study reports a DSC investigation of solid–liquid equilibria in the paracetamol–o-acetylsalicylic acid binary system revealing a simple eutectic behaviour. The eutectic temperature and temperatures of liquidus were determined. Further, assessed eutectic and liquidus temperatures together with the data for pure components were used for the evaluation of Redlich–Kister equation parameters for the excess Gibbs energy of binary melts. Finally, binary T–x phase diagram of the above mentioned system was calculated using the FactSage software.

AC-Impedance, Dynamic mechanical analysis and DSC investigations on poly(methyl methacrylate)–LiTf polymer electrolyte systems

Gel polymer electrolytes synthesized from Poly(methylmethacrylate) (PMMA) as the host, ethylene carbonate (EC)/propylene carbonate (PC) as plasticizer and LiCF3SO3 (LiTf) as a salt has been prepared using solution casting technique. X-ray characterization confirms the complete dissociation of the LiTf salt in the gel polymer. The effect of LiTf salt on ionic conductivity, ionic transference number (tion) and mechanical characteristics were investigated. The ac impedance has been studied to evaluate the ionic conductivity. It was observed that the ionic conductivity of the prepared gel reached the highest value of 6.60 x 10-5 S/cm at 10.2 wt.% (1M) of LiTf salt. The temperature dependence studies showed that the samples were ionic conductors and seemed to obey the Vogel–Tamman–Fulcher (VTF) rule. Dynamic mechanical analysis (DMA) indicates that the LiTf salt induces a remarkable increase in the storage modulus of the matrix at temperatures above the glass transition (rubbery plateau region).

Elaboration, Structural, Vibrational, DSC Investigations and Hirshfeld Surface Analysis of New Organic–Inorganic Hybrid Compound: [H2mela]Cu2Br6

The present paper accounts for the synthesis, crystal structure, differential scanning calorimetry and vibrational spectroscopy of a new compound (1,3,5-triazinidium-2,4,6-triamine) hexabromidodicuprate (II) grown at room temperature by slow evaporation of aqueous solution. From X-ray diffraction data collected at room temperature, it is concluded that it crystallizes in the monoclinic system (P21/c space group). The anion and the cation are linked by N–H···Br hydrogen bonds. Furthermore, the room temperature IR and Raman spectra of the title compound were recorded and analyzed. The differential scanning calorimetric has also been investigated. Hirshfeld surfaces were used to confirm the existence of inter-molecular interactions in the compound.

DSC investigation of phase equilibria in the Bi-Pb-Sb system

Two sections at XBi/XPb=2/3 and XPb=0.6 atomic fraction of the Bi-Pb-Sb system are analysed by Differential Scanning Calorimetry. The graphical representations of both sections are drawn in agreement with the binary side systems and the phase boundaries determined from DSC thermograms suit well above T=373.2K. A transitory peritectic reaction is observed at T=(445.2±0.5)K. Isothermal sections at 445.25K and 273.15K are proposed.

Synthesis and Characterization of Thermal Properties of Type Eu2O3-ZrO2 Sinters

Abstract The oxides with pyrochlore or defected fluorite structure are a potential alternative ceramic materials for now widely used yttria-stabilized zirconia 8YSZ in the application for the insulation layer of thermal barrier coatings systems. This paper presents a procedure of synthesis of europium zirconate of Eu2Zr2O7 type, by the method of high temperature sintering under pressure. The analysis of the effect of the powders` homogenization methods on homogeneity of final sintered material showed that the highest homogeneity can be obtained after mechanical mixing in alcohol. Moreover, the DSC investigation carried out on a mixture of powders before the sintering process and on the material after high temperature sintering under pressure, suggest the synthesis of a new phase an europium zirconate Eu2Zr2O7 with the pyrochlore structure. Obtained phase was characterized by stability over the entire range of tested temperature, i.e. to 1450°C. The resulting material based on europium zirconate has a lower coefficient of thermal diffusivity than the now widely used 8YSZ.

Thermodynamic and analytical studies of drugs binary systems of paracetamol mixed with pseudoephedrine.HCl, dextropropoxyphene.HCl and tramadol.HCl

In this paper, we report a DSC investigation of solid–liquid equilibria in three binary mixtures of paracetamol, namely with pseudoephedrine, dextropropoxyphene and tramadol, resulting in a temperature-composition phase diagrams with eutectic equilibrium. Eutectic mole fractions, temperatures and enthalpies were determined and reported for each system.The study reports also a direct exploitation of the DSC results for the quantification purpose, which were in good agreement with those obtained by a standard analytical method namely high performance thin layer chromatography (HPTLC), used in this work for comparison purpose.

TG and DSC investigation of water intercalation and protonation processes in perovskite-like layered structure of titanate K2Nd2Ti3O10

The article presents results of the complex study of hydration and protonation processes of promising photocatalysts K2Nd2Ti3O10, belonging to the family of perovskite-type layered Ruddlesden–Popper phases. K2Nd2Ti3O10 was synthesized by solid-state method and was monitored using powder X-ray diffraction. The behavior in water has been studied by means of thermogravimetric analysis, simultaneous thermal analysis and differential scanning calorimetry. The substitution of potassium cations for protons and the water intercalation into the interlayer space of the crystal structure were observed. Proton-containing layered oxides with general formula HxK2−xNd2Ti3O10·yH2O (0.07 ≤ x ≤ 1.7, 0.06 ≤ y ≤ 0.44) have been obtained.

Solid-state preformulation studies of amiodarone hydrochloride

This paper deals with the application of fast screening tools such as FTIR, thermal analysis and DSC in the evaluation of compatibility between the active pharmaceutical ingredient amiodarone hydrochloride and different pharmaceutical excipients used in tablet formulations, such as polyvinylpyrrolidone, microcrystalline cellulose, starch, talc and anhydrous lactose. Samples were investigated initially immediately after preparation by FTIR analysis and later by TG/DTG/HF technique. It was found that under ambient condition, amiodarone hydrochloride was compatible with all selected excipients. During the non-isothermal thermal treatment in oxidative atmosphere, amiodarone showed incompatibility with lactose. The final investigations consisted of maintaining the samples under moderate thermal stress (48 h at 40 °C), when DSC investigations revealed that thermal-induced interactions occurred with all selected excipients except talc.

Auricularia auricular polysaccharide-low molecular weight chitosan polyelectrolyte complex nanoparticles: Preparation and characterization

Novel polyelectrolyte complex nanoparticles (AAP/LCS NPs) were prepared in this study and these were produced by mixing negatively charged auricularia auricular polysaccharide (AAP) with positively charged low molecular weight chitosan (LCS) in an aqueous medium. The AAP was extracted and purified from auricularia auricular, and then characterized by micrOTOF-Q mass spectrometry, UV/Vis spectrophotometry, moisture analyzer and SEM. The yield, moisture, and total sugar content of the AAP were 4.5%, 6.2% and 90.12% (w/w), respectively. The AAP sample was water-soluble and exhibited white flocculence. The characteristics of AAP/LCS NPs, such as the particle size, zeta potential, morphology, FT-IR spectra, DSC were investigated. The results obtained revealed that the AAP/LCS NPs had a spherical shape with a diameter of 223 nm and a smooth surface, and the results of the FT-IR spectra and DSC investigations indicated that there was an electrostatic interaction between the two polyelectrolyte polymers. Bovine serum albumin (BSA, pI = 4.8) and bovine hemoglobin (BHb, pI = 6.8) were used as model drugs to investigate the loading and release features of the AAP/LCS NPs. The results obtained showed that the AAP/LCS NPs had a higher entrapment efficiency (92.6%) for BHb than for BSA (81.5%). The cumulative release of BSA and BHb from AAP/LCS NPs after 24 h in vitro was 95.4% and 91.9%, respectively. The in vitro release demonstrated that AAP/LCS NPs provided a sustained release matrix suitable for the delivery of protein drugs. These studies demonstrate that AAP/LCS NPs have a very promising potential as a delivery system for protein drugs.

Study of Thermal Properties of Mixed (PP/EPR)/ABS with Five Model Compatibilizers

The influences of incorporating compatibilizers E-EA-MAH, E-MA-GMA, E-AM, SEBS KRATON G, or PP-g-MAH on the thermal properties of mixed (polypropylene/ethylene propylene rubber)/acrylonitrile butadiene styrene (PP/EPR)/ABS have been investigated. DSC investigations have revealed that the incorporation of 5% of ABS in the copolymer (PP/EPR) does not fundamentally affect the thermal properties of the basic copolymer; additionally, the addition of 1.5% of each of the compatibilizers in the basic mixture does not significantly alter the crystallization temperature values and the melting of the -P- sequences. There is a variation of melting enthalpy values of the -P- sequences of 18.23% using SEBS KRATON G and of 10.38% using E-AM-GMA. When the rate of each of the compatibilizers increases to 5%, overall crystallization enthalpies of -P- sequences are almost kept unchanged, except for the case of using the compatibilizer E-AM-GMA with a variation of 8.42%. There is a minor variation of the melting enthalpy of -P- sequences with higher levels of compatibilizer. The incorporation of 5% ABS copolymer in the PP/EPR does not significantly alter the thermal properties of the basic structure of (PP/EPR)/ABS.

The synthesis, structure and properties of a new lithium-rich manganese(ii) phosphate Li5CsMn(P2O7)2: a congruently melting compound with a 'lithium hamburger' structure.

The crystals of the title compound have been grown in molten salt media. Single-crystal X-ray diffraction experiment revealed that the compound crystallizes in an orthorhombic space group Pbcn (no. 60) with cell parameters: a = 5.1023(10) Å, b = 19.717(4) Å, c = 12.557(3) Å, and Z = 4. The structure of Li5CsMn(P2O7)2 consists of one-dimensional manganese pyrophosphate chains [MnP4O14]∞ interleaved with Cs(+) and Li(+) cations. A pseudo-two-dimensional layer [CsMnP4O14]∞ parallel to the ab plane is made up of [MnP4O14]∞ chains and Cs-O polyhedra through sharing the oxygen atoms. The three crystallographically distinct Li atoms are all located in the interlayered space to form a 'lithium hamburger' structure. Magnetic studies demonstrated that the compound shows paramagnetic behavior. DSC and XRD investigations revealed that the compound melts congruently. AC impedance studies show that the conductivity is 1.3 × 10(-5) S cm(-1) at 573 K and the activation energy is 0.42 eV. In addition, Li ion diffusional pathways were obtained using the bond valence map.

DSC Investigations of the Phase Transition in the High Strength Steel S960QL

Studies of the heat capacity temperature characteristics for microalloyed high strength steel S960QL is reported. The investigations were concentrated in the region of the second order phase transition. Experiments were carried out using the Differential Scanning Calorimeter DSC 404F1 Pegasus (Netzsch). As a tested material a sample from the high strength steel S960QL was used within temperature range of 50-1100 °C. In addition to this dilatometric investigations with the same temperature range as DSC ones were carried out using Netzsch dilatometer DIL 402C. Measurements of thermal characteristic, i.e. the heat capacity cp(T) and thermal expansion α*(T) were performed several times in order to observe thermal processes taking place in microalloyed high strength steel. Previous investigations have revealed the thermal hysteresis of the linear expansion in the region of the second order magnetic phase transition in the S960QL steel.

Thermal analytical characterization of mixtures of antipsychotic drugs with various excipients for improved drug delivery

Antipsychotics are a class of psychiatric medication that is primarily effective at reducing psychosis symptoms, particularly in schizophrenia and bipolar disorders. This study aims to formulate mixtures of the antipsychotic drugs quetiapine fumarate (QUE), nortriptyline (NOR), propranolol (PROP) and haloperidol (HAL) with excipients urea, niacin (NIA) and niacinamide (NIM) to obtain an enhanced bioavailability and therapeutic effect. The mixtures were prepared by the solvent method and are characterized by various analytical techniques such as differential scanning calorimetry, wide angle X-ray diffraction, scanning electron microscopy and dissolution studies. Out of the various mixtures that have been prepared and tested, five of them showed eutectic behavior and their eutectic points are as follows: quetiapine fumarate–urea (QUE–UREA) 20–80, w/w; nortriptyline–niacin (NOR–NIA) 70–30, w/w; propranolol–niacin (PROP–NIA) 80–20, w/w; propranolol–niacinamide (PROP–NIM) 40–60, w/w; and haloperidol–niacinamide (HAL–NIM) 20–80, w/w. DSC investigation has revealed the formation of an eutectic system and the phase diagrams and Tamman’s triangle construction along with the hot-stage microscopy confirmed their melting points. PXRD study indicated no chemical interaction between either of the mixtures, while SEM study showed the size reduction in these mixtures that has been achieved. In vitro studies of the five mixtures showed an appreciable increase in the dissolution rate compared to that of the drug alone. In conclusion, five simple eutectic mixtures have been formulated by the solvent method and were found to show better dissolution rates than that of the pure form of the drugs, thus improving the bioavailability of these poorly water-soluble drugs.

Combining Flash DSC, DSC and broadband dielectric spectroscopy to determine fragility

New experimental results focused on Flash DSC, DSC and broadband dielectric spectroscopy investigations are reported in this work. The fictive temperatures and fragility indexes are estimated from Flash DSC experiments and compared to values obtained from classical DSC. The consistency of the Tool–Narayanaswamy–Moynihan model and fragility concept is then investigated over a large range of cooling rates. Indeed, the Flash DSC allows exploring thermal properties of materials over a continuous and broad range of heating and cooling rates, complementary to rates usually available with DSC. The reliability of investigations is also demonstrated by comparing results obtained from two model amorphous polymeric systems: polystyrene and poly(ethylene terephthalate)-glycol. The temperature dependence of the cooling rate obtained by Flash DSC and DSC is also compared to the temperature dependence of the relaxation times obtained from broadband dielectric spectroscopy, experiment considered as the reference concerning the fragility measurements. The comparison of these two dependencies implies a better understanding about the origin of the temperature dependence of the cooling rate.