Differential Scanning Calorimeter Method Research Articles

Interpretation of measurements results of ice content in freezing mortars using DSC method

The results of investigations of heat flows recorded at the low temperature differential scanning calorimeter (DSC) in the freezing cement mortars soaked with water are presented. Methods for extracting the thermal effects associated with the phase change of water as well as the methods for calculating the weight of ice with reference to the specific process temperature at which the phenomenon occurs are analyzed. It is found that computation assumptions and technical limitations of the calorimeter described in the technical literature can lead to significantly different results of determining the mass of formed ice.

Microstructural evolution during homogenization of Al-Cu-Li-Mn-Zr-Ti alloy

The microstructure evolution of Al-Cu-Li-Mn-Zr-Ti alloy during homogenization was investigated by optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDX), and differential scanning calorimeter (DSC) methods. The results show that severe dendritic segregation exists in the experimental alloy ingot. Numerous eutectic phases can be observed in the grain boundary, and the distribution of the main elements along the interdendritic region varies periodically. The main secondary phase is Al2Cu. The overburnt temperature of the alloy is 520 °C. The second phases are gradually dissolved into the matrix, and the grain boundaries become spare and thin during homogenization with increasing temperature or prolonging holding time. Homogenization can be described by a constitutive equation in exponential function. The suitable homogenization treatment for the alloy is (510 °C, 18 h), which agrees well with the results of homogenization kinetic analysis.

The surface oxidation behavior of Ni–45.16%Ti shape memory alloys at different temperatures

The isothermal oxidation behavior of Ni–45.16%Ti (composition in atomic percent) alloy was investigated by thermogravimetric analysis, and differential scanning calorimeter (DSC) methods. It was found that Ni-rich NiTi alloy exhibits a different oxidation behavior at temperatures above 400 °C in oxygen atmosphere. The alloy was exposed to oxygen atmosphere isothermally, i.e., between 400 and 800 °C, for 1 h. A gravimetric method was used to determine the oxidation kinetics and it was seen that the oxidation constant increases significantly with isothermal temperature. The activation energy of oxidation reaction for NiTi alloy was determined to be 65.47 kJ mol−1. According to DSC measurements, the transformation temperature of alloy (M s, M f, A s and A f) was increased and also R phase disappeared above 500 °C. The formal oxides were determined by means of SEM–EDX measurements and obtained oxides are TiO and TiO2 oxides.

Poly(N-isopropylacrylamide-co-hydroxyethylacrylamide) thermosensitive microspheres: The size of microgels dictates the pulsatile release mechanism

Poly(N-isopropylacrylamide-co-N-hydroxyethylacrylamide) (poly(NIPAAm-co-HEAAm)) was prepared as a new thermosensitive copolymer possessing a sharp phase transition around the human body temperature. The effect of the copolymer concentration on the lower critical solution temperature (LCST) was determined under physiological conditions by cloud point (CP) and differential scanning calorimetric (DSC) methods. Then, thermosensitive microspheres were prepared from preformed copolymers by chemical cross-linking of hydroxyl groups with glutaraldehyde at a temperature situated slightly below LCST of the copolymer solution. The volume phase transition temperature (VPTT) of corresponding cross-linked microspheres was determined from swelling degree-temperature curve. The microspheres were loaded with model drug indomethacin by the solvent evaporation method. The DSC analysis proved that the drug is molecularly dispersed in the polymer network. Finally, the influence of the microsphere size on drug release was investigated. It was established that microspheres with the diameter ranging between 5 and 60μm release the drug with almost the same rate below (in the swollen state) and above the VPTT (in the collapsed state). On the contrary, microspheres with the diameter ranging between 125 and 220μm release a significantly higher amount of indomethacin below than above the VPTT. This different behavior is enough to assure a pulsatile release mechanism when the temperature changes cyclically below and above the VPTT. However, both small and large microspheres release a large amount of the drug during the collapsing process.

The Synthesis and Characterization of N-Butyl Pyridine Tetrafluoroborate

The halogenated hydrocarbon and pyridine are used in the synthesis of room temperature ionic liquid intermediates chlorinated N-butyl pyridine BPC, and the nuclear magnetic resonance instrument and the intermediate infrared spectrometer are used in chemical structure characterization, so it is determined that the synthesis is the room temperature ionic intermediates BPC. We use differential scanning calorimetric method for the determination of BPC melting point and enthalpy change. We use the double decomposition reaction of BPC and NaBF4 in acetone for the synthesis of BP-BF4ionic liquids. We use infrared spectrometer for the structure characterization, it is proved that we have gotten BP-BF4room temperature ionic liquids. Solvent polarity and acid alkali both will have an influence on ultraviolet spectrum diagram displacement of room temperature ionic liquid, so in the research of ultraviolet spectrum diagram of ionic liquids and other solvent mixed solution, it is necessary to indicate which solvent is used.

Structure evolution and entropy change of temperature and magnetic field induced magneto-structural transition in Mn1.1Fe0.9P0.76Ge0.24

The compound Mn1.1Fe0.9P0.76Ge0.24 has been studied using neutron powder diffraction (NPD), differential scanning calorimeter (DSC), and magnetic measurements, in order to clarify the nature of the magnetic and structural transition and measure the associated entropy change (ΔS). The strongly first order transition occurs from a paramagnetic (PM) to a ferromagnetic (FM) phase and can be induced either by temperature or by an applied magnetic field. Our investigations indicate that the two processes exhibit identical evolutions regarding the crystal and magnetic structures, indicating they should have the same entropy change. We, therefore, conclude that the ΔSDSC obtained by the DSC method (where the transition is temperature induced) is valid also for the magnetically induced transition, thus avoiding uncertainties connected with the magnetic measurements. We have obtained the ΔSDSC = 33.8 J/kg · K for this sample upon cooling, which would increase to 42.7 J/kg · K for a impurity-free and completely homogeneous sample. For comparison, the magnetic entropy changes (ΔSM) induced by magnetic field and calculated using the Maxwell relation yields a ΔSM = 46.5J/kg · K, 38% higher than ΔSDSC. These entropy results are compared and discussed.

Synthesis of cross-linked comb-type polysiloxane for polymer electrolyte membranes

Abstract Hydrosilylation reaction of 2.4.6.8-tetrahydro-2.4.6.8-tetramethylcyclotetrasiloxane with allyl acetoacetate and vinyltriethoxysilane at 1:3:1 ratio of initial compounds in the presence of Karstedt’s catalyst (Pt2[(VinSiMe2)2O]3), platinum hydrochloric acid (0.1 M solution in THF) and platinum on the carbon have been studied and D4R,R’ type methylorganocyclotetrasiloxane has been obtained. Ring-opening co-polymerization reactions of methylorganocyclotetrasiloxane and hexamethyldisiloxane, in the presence of catalytic amount of powder-like potassium hydroxide, have been carried out and linear methylsiloxane oligomer with regular arrangement of propyl acetoacetate and triethoxysilane groups in the side chain has been obtained. The synthesized methylorganocyclotetrasiloxane and oligomers were studied by FTIR, 1H, 13C, 29Si NMR spectroscopy. Comb-type oligomers were characterized by gel-permeation chromatography, wide- angle X-ray and differential scanning calorimetric methods. Via sol-gel processes of doped with lithium trifluoromethylsulfonate (triflate) or lithium bis- (trifluoromethylsulfonyl)imide oligomer systems solid polymer electrolyte membranes have been obtained. The dependence of ionic conductivity as a function of temperature and salt concentration has been studied. The electrical conductivity of these materials at room temperature belongs to the range of 7x10-8 to 4x10-6 S cm-1 and depends on the structures of grafted anion receptors and the polymer backbones.

Properties of a Model Aryl Boronic Acid and Its Boroxine

Many boronic acid-containing molecules are currently under investigation as possible therapeutics. An increase in the knowledge of the physical and chemical properties of these compounds will lead to their improved formulation into usable dosage forms. The current study describes the formation and characterization of a boronic acid anhydride, called a boroxine. The model boronic acid, 4-methoxybenzeneboronic acid is used. The current study demonstrates the utility of thermal (differential scanning calorimetry and thermogravimetric analysis) and spectral (solid-state nuclear magnetic resonance and ultraviolet spectroscopy) methods to quantitate and characterize the boronic acid and its boroxine, validated against definitive structures solved by single-crystal X-ray diffraction. The present work also demonstrates that the hydrolysis of the boroxine in the presence of water is very rapid in a time scale relative to drug substance manufacture and product formulation.

Does Illinois bituminous coal manifest glass transition: DMA, DSC, and FTIR results

It has been argued that coal, especially deep, unmineable seams, holds the potential of sequestering carbon dioxide (CO2) while recovering fuel gases. In the recent past, it has been proposed that various ranked coals display glass transition or second order transition at 100°C⩽T⩽200°C under nitrogen environment, and this transition temperature shifts to lower temperatures when coals were pressurized with relatively low pressure (⩽3MPa) CO2. If glass transition does exist in coal, then on pressurizing the deep, unmineable coal seams, where pressures are expected to be higher than 3MPa of CO2, the presence of glass transition could potentially pose reservoir stability concerns. We undertook differential scanning calorimetric (DSC) and dynamic mechanical analysis (DMA) measurements on Murphysboro seam coal (Illinois bituminous) at 30°C⩽T⩽250°C under N2 gas environment to ascertain whether this coal even has a glass transition. These experiments were further complemented by conducting in situ diffuse reflectance infrared spectroscopic measurements (DRIFT). It is worth mentioning that the DMA technique is much more sensitive in detecting glass transition than the DSC technique, and previously reported glass transitions were ascertained by the DSC method. Though we did observe thermal events, ascribed to the evaporation of bulk and hydrogen-bonded water at 90°C⩽T⩽190°C, we did not observe any glass or second order transition for Murphysboro coal at 30°C⩽T⩽250°C. The storage modulus (E′) of the coal steadily decreased as the temperature increased from 30°C with E′ showing two minima at 158°C and 221°C. These minima could be attributed to the evaporation of CO2 from the coal produced during self oxidation rather than any thermodynamic event.

Ordering of the 7CB liquid crystal induced by nanoscale confinement and boundary lubrication

In this study, the thermodynamic properties of nanoscale-thick 4-heptyl-4′-cyanobiphenyl (7CB) liquid crystals (LCs) confined in carbon nanotubes were investigated using differential scanning calorimetric methods. Both the isotropic-nematic phase transition temperature and the enthalpy increase decrease as the nanoscale confining size decreases, indicating the ordering effect of the 7CB molecules under nanoscale confinement. An average-order parameter <S> is calculated to quantitatively identify the ordering effect of LCs by utilising a simple expression of the Landau–de Gennes (LdG) free energy. The average-ordering parameter <S> of the 7CB LC can be 0.7 within a confinement thickness of ∼25 nm and above 0.5 within a film thickness of up to 100 nm. When lubricating the 7CB LC between a steel ball and chromium-coated glass disk at low speeds, a stable boundary layer with a thickness of 10 nm is formed that is independent of the entrainment speed. At higher speeds, the thickness of the 7CB lubrication film ranges from several tens of nanometres to 100 nm, resulting in a stable velocity-independent friction coefficient of approximately 0.03. The ordered microstructure of the 7CB molecules under confinement provides the underlay mechanism of its boundary lubrication property.

Synthesis, thermal polymerization, and properties of benzoxazine resins containing fluorenyl moiety

AbstractThree difunctional fluorene‐based benzoxazine compounds were synthesized via Mannich condensation and were characterized by proton nuclear magnetic resonance spectroscopy (1H NMR), Fourier transform infrared spectroscopy (FTIR), and elementary analysis (EA). The polymerization of benzoxazine monomers were investigated with differential scanning calorimeter (DSC) method. Thermal properties of the polybenzoxazines were studied by thermogravimetric analysis (TGA) and DSC. Water absorption of the polybenzoxazines was tested. Contact angle measurement was employed to characterize the surface property of materials. The glass transition temperatures (Tgs) and thermal stability were improved significantly in comparison with bisphenol‐A‐based analogue because of the incorporation of rigid fluorenyl group. The fluorenyl‐based polybenzoxazines showed hydrophobic characteristics, which was ascribed to the low polarity of fluorenyl and pi–pi stacking interaction of fluorenyl on the surface. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers

A study on thermal behavior of a poly(VDF‐CTFE) copolymers binder for high energy materials

AbstractThis article describes a study on thermal behavior of poly(vinylidene fluoride‐chlorotrifluoroetheylene) [poly(VDF‐CTFE)] copolymers as polymeric binders of specific interest for high energy materials (HEMs) composites by thermal analytical techniques. The non‐isothermal thermogravimetry (TG) for poly (VDF‐CTFE) copolymers was recorded in air and N2 atmospheres. The results of TG thermograms show that poly(VDF‐CTFE) copolymers get degrade at lower temperature when in air than in N2 atmosphere. In the derivative curve, there was single maximum degradation peak (Tmax) indicating one‐stage degradation of poly(VDF‐CTFE) copolymers for all the samples. The other thermal properties such as glass transition temperature (Tg) and degradation temperature (Td) for poly(VDF‐CTFE) copolymers were measured by employing differential scanning calorimeter (DSC) technique. The kinetic parameters related to thermal degradation of poly(VDF‐CTFE) copolymers were investigated through non‐isothermal Kissinger kinetic method using DSC method. The activation energies for thermal degradation of poly(VDF‐CTFE) copolymers were found in a range of 218–278 kJ/mol. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Coordination between yttrium ions and amide groups of polyamide 6 and the crystalline behavior of polyamide 6/yttrium composites

Different amounts of yttrium ions were introduced into polyamide 6 (PA6) matrix by solution casting process. Structure, morphology and properties of the obtained PA6/Y3+ composite films were investigated by using FT-IR spectroscopy, Raman spectroscopy, scanning electron microscope (SEM), polarized optical microscope (POM) and differential scanning calorimeter (DSC) methods. Yttrium ions show strong coordination ability and their complexation with amide groups of PA6 can be reflected by the appearance of new bands in the amide A and amide I regions in FT-IR and Raman spectra. Furthermore, the FT-IR and Raman spectra of the PA6/Y3+ composite show that the resultant chain conformations of the amide groups in the composite films are twisted from the ideal trans conformation. The DSC results reveal that Y3+ ions cause a significant reduction of the melting point of PA6. In addition, the existence of Y3+ prevents the crystallization of molten PA6/Y3+ composite films during the cooling process. Moreover, the PA6/Y3+ composite can convert into γ phase PA6 or α phase PA6 when different solvents are used to remove Y3+ ions and induce crystallization of PA6.

Investigation on Miscibility of Sodium Alginate/Pullulan Blends

Miscibility studies of Sodium alginate (NaAlg)/Pullulan have been carried out in different percentage of blend components. The ultrasonic velocity, viscosity, density and refractive index were measured at 30 and 40 °C. Further the blend films of NaAlg and Pullulan were prepared by solution casting method and characterized by differential scanning calorimetric (DSC), fourier transition infrared spectroscopic (FTIR), and scanning electron microscopic (SEM) methods. Using the viscosity data, interaction parameters were computed to determine the miscibility. The data suggest that the blend is miscible in the entire composition range. The change in temperature had no significant effect on the miscibility of NaAlg/Pullulan blends. The miscibility is confirmed by SEM, DSC, ultrasonic velocity, density, and refractive index methods. The specific interactions of hydrogen bonding type of the blends were investigated by FTIR.

Effect of processing parameters on the microstructures and corrosion behaviour of high‐velocity oxy‐fuel (HVOF) sprayed Fe‐based amorphous metallic coatings

AbstractA FeCrMoMnWBCSi amorphous metallic coating was prepared by using high‐velocity oxy‐fuel spray. The influence of processing parameters on microstructure, porosity level, amorphous phase fraction and corrosion behaviour of the coatings was characterised by scanning electron microscopy, X‐ray diffraction, differential scanning calorimeter and electrochemical methods. The results indicated that the microstructures of the coatings were sensitive to the spray parameters considerably. Porosity and unmelted particle proportion decreased with the oxygen/fuel (O/F) ratio and increased with the powder feed rate. The trend of oxides content was opposite to the porosity and unmelted particle proportion. The coatings obtained with higher O/F ratio and lower powder feed rate exhibited higher hardness. The low coating hardness was mainly due to the high porosity especially when the porosity was higher than 1.21%. The spraying parameters strongly affected the amorphous phase fraction. There was a critical passive current density for balancing the porosity and the amorphous phase fraction. Corrosion resistance is dominant by the amorphous phase fraction when the porosity is less than 1.21%, while by porosity when it is higher than that. Open‐circuit potential, potentiodynamic polarisation and electrochemical impedance spectroscopy results showed that the coatings obtained with the O/F ratio of 4.2 and the powder feed rate of 40 g/min exhibiting the best corrosion resistance in 1 wt% sodium chloride solution.

Moisture sorption isotherms and glass transition temperature of elecampe (Inula helenium L.) and burdock (Arctium lappa L.) roots at 25°C

Sorption isotherms of elecampe (Inula helenium L.) and burdock (Arctium lappa L.) root samples were obtained at 25 °C. Elecampe exhibited hysteresis loop in the range of 0.35-0.90 a(w) , whereas burdock roots showed significant differences between adsorption and desorption isotherms from 0.65 to 0.80 a(w) . Blahovec-Yanniotis was considered to give the best fit over the whole range of a(w) tested. Various parameters describing the properties of sorbed water derived from GAB, Henderson and Blahovec-Yanniotis models have been discussed. Differential scanning calorimetric method was used to measure the glass transition temperature (T (g)) of root samples in relation to water activity. The safe moisture content was determined in 12.01 and 14.96 g/100 g d. b. for burdock and elecampe root samples at 25 °C, respectively. Combining the T (g) line with sorption isotherm in one plot, it was found that the glass transition temperature concept overestimated the temperature stability for both root samples.

Synthesis and Characterization of a Biodegradable Poly (&lt;i&gt;Glycerol-glycol-sebacate&lt;/i&gt;) Terpolymer

A biodegradable poly (glycerol-glycol-sebacate) terpolymer (PGGS) with different composition is prepared by a three-step method. The structure and properties of the PGGS terpolymers were characterized by means of attenuated total reflectance-Fourier transform infrared (ATR-FTIR), differential scanning calorimeter (DSC) and X-ray diffraction (XRD) methods. The experiment results indicate that the the composition of terpolymers have an obvious influence on the structure of PGGS terpolymers. The degradation rate increases with the increasing crosslink degree of PGGS.

A Nano-SiO&lt;sub&gt;2&lt;/sub&gt; Form-Stable Phase Change Material for Building Thermal Energy Conservation

A stable form-phase change materials (PCM), based on capric-lauric acid eutectic served as the absorption material and the support of nano-silica material to prepare by sol-gel method. The best ratio capric-lauric acid eutectic combination is determined for 60 wt. %. Capillarity because of the influence of the hydrogen bonding, fatty acid and eutectic can be fixed in the three dimensional network structure of the construction of the silicon atom bonds and O still so solid sample melting point composite heating more fatty acid eutectic. Form and chemical properties of the composite phase change the transmission electron microscope, semi and Fourier transform infrared method.- Differential scanning calorimetric hot method is used for measuring phase transition temperature and phase change of latent heat composite, value 19.57 and 71.28 J/g , respectively. At the same time, service performance and other composite material thermal stability and thermal conductivity coefficient test using thermo gravimetric analysis and transient hotline method, respectively.

Analysis of crystallization kinetics of sputtered SmCo based permanent magnetic films

Crystallization kinetics of the sputtered SmCo based permanent magnetic films was investigated by differential scanning calorimeter, x-ray diffraction, and atomic force microscope methods. The results show that the apparent activation energy for crystallization is observed as 173.7kJ/mol, and the local activation energy for crystallization decreases with increasing crystal phase transformation fraction in non-isothermal crystallization. For isothermal crystallization, the apparent activation energy for crystallization is 159.8kJ/mol. The local activation energy for crystallization exhibits non-monotonic dependence on the crystal phase transformation fraction. The crystallization mechanism is obtained from the investigation of Avrami exponent and microstructure.

Study on Effective Storage Time of Constant Viscosity Natural Rubber

The effective storage time (i.e. storage life) of constant viscosity natural rubbers prepared with hydroxylamine hydrochloride, hydroxylammonium sulphate, hydrazine hydrate, aniline and semicarbazide hydrochloride respectively were investigated with heat accelerated storage aging combined with differential scanning calorimeter(DSC) method as well as the heat aging life equation. The results show that the effective storage time of constant viscosity natural rubber prepared with hydroxylamine hydrochloride is 19.2 years at 30°C, 39.4 years at 25°C and 82.9 years at 20°C. The effective storage time of constant viscosity natural rubber prepared with hydroxylammonium sulphate is 16.3 years at 30°C, 32.6 years at 25°C and 66.5 years at 20°C. The effective storage time of constant viscosity natural rubber prepared with hydrazine hydrate is 42.5 years at 30°C, 85.9 years at 25°C and 177.9 years at 20°C. The effective storage time of constant viscosity natural rubber prepared with aniline is 30.4 years at 30°C, 66.7 years at 25°C and 150.2 years at 20°C. The effective storage time of constant viscosity natural rubber prepared with semicarbazide hydrochloride is 13.5 years at 30°C, 27.4 years at 25°C and 57.1 years at 20°C.