The Experts below are selected from a list of 273 Experts worldwide ranked by ideXlab platform

Akira Konno - One of the best experts on this subject based on the ideXlab platform.

  • Thermal measurements of curdlan in aqueous suspension during gelation
    Food Hydrocolloids, 2000
    Co-Authors: H. Zhang, L Huang, Mineo Watase, Katsuyoshi Nishinari, Akira Konno
    Abstract:

    Abstract Differential scanning calorimetry (DSC) measurements of curdlan in aqueous suspension were carried out in a temperature range of 40–200°C by using silver pans with and without heat treatment, respectively. Silver pans with heat treatment were heated at 200°C and then cooled. Heating DSC curves of curdlan in aqueous suspension showed an endothermic Peak around 60°C and were identical below 120°C, but quite different above 120°C. A large Exothermic Peak was observed at 140–190°C in a heating DSC curve when a non-heated pan was used, whereas a small endothermic Peak was observed at 140–160°C and no Exothermic Peak was observed at higher temperatures when a heated pan was used. It was suggested that the large Exothermic Peak was attributed to an interaction between the non-heated silver pan and water above 120°C. Only the endothermic Peak at 140–160°C reflected the reality of the thermal property of curdlan in aqueous suspension, which was caused by the melting of the curdlan gel formed.

  • Thermal properties of curdlan in aqueous suspension and curdlan gel
    Food Hydrocolloids, 1991
    Co-Authors: Akira Konno, Tokuya Harada
    Abstract:

    Abstract The thermal properties of curdlan in aqueous suspension and curdlan gel were studied by differential scanning calorimetry (DSC). The DSC curve of curdlan in aqueous suspension showed two sharp endothermic Peaks, at 50–64 and 140–160°C, and a broad endothermic Peak between the two Peaks. An Exothermic Peak at ~140°C was also observed. The two endothermic Peaks are caused by the swelling of curdlan and the melting of gel formed. The broad Peak may be caused by the formation of firm gel stabilized by hydrophobic interaction. The Exothermic Peak may be due to the formation of microfibrils. The swelling temperature and enthalpy of curdlan in aqueous suspension were 49.7°C and 10 J/g, respectively. The swelling temperature of curdlan in the presence of sodium chloride or urea shifted to a higher or a lower temperature range, respectively.

P. Plaindoux - One of the best experts on this subject based on the ideXlab platform.

  • Influence of benzene on the Ni3Fe nanocrystalline compound formation by wet mechanical alloying: An investigation combining DSC, X-ray diffraction, mass and IR spectrometries
    Materials Chemistry and Physics, 2011
    Co-Authors: Bogdan Neamtu, Olivier Isnard, Ionel Chicinaş, C. Vagner, N. Jumate, P. Plaindoux
    Abstract:

    Nanocrystalline Ni3Fe powders were obtained via wet mechanical alloying using benzene as surfactant. The differential scanning calorimetry (DSC) measurements showed the presence of an Exothermic Peak which does not correspond to any phase transformation or phase formation as was proved by X-ray diffraction measurements. The Exothermic Peak was observed neither for the dry milled samples nor for the wet milled and subsequently annealed powders at 350 degrees C for 4 h. The infra-red (IR) spectra registered for the wet milled samples showed a series of vibration bands corresponding to C6H6 and also to a series of fragments resulting from benzene decomposition. The results obtained by IR investigation were confirmed by thermogravimetry and mass spectrometry (TG + MS) investigations. The main fragments resulting from the benzene decomposition on the surface of the nanocrystalline Ni3Fe powders are: CO2, CO and C. The evolution of the particle size distribution versus the milling time has been determined for the wet mechanical milling process of nanocrystalline Ni3Fe powders. The DSC analysis reveals a displacement of the Exothermic Peak onset towards lower temperatures and an increase of the surface of this Peak attributed to the changes in the particles specific surface and to the quantity of benzene added in the milling experiments.

  • Influence of benzene on the Ni3Fe nanocrystalline compound formation by wet mechanical alloying: An investigation combining DSC, X-ray diffraction, mass and IR spectrometries
    Materials Chemistry and Physics, 2011
    Co-Authors: B.v. Neamţu, Olivier Isnard, Ionel Chicinaş, C. Vagner, N. Jumate, P. Plaindoux
    Abstract:

    Abstract Nanocrystalline Ni3Fe powders were obtained via wet mechanical alloying using benzene as surfactant. The differential scanning calorimetry (DSC) measurements showed the presence of an Exothermic Peak which does not correspond to any phase transformation or phase formation as was proved by X-ray diffraction measurements. The Exothermic Peak was observed neither for the dry milled samples nor for the wet milled and subsequently annealed powders at 350 °C for 4 h. The infra-red (IR) spectra registered for the wet milled samples showed a series of vibration bands corresponding to C6H6 and also to a series of fragments resulting from benzene decomposition. The results obtained by IR investigation were confirmed by thermogravimetry and mass spectrometry (TG + MS) investigations. The main fragments resulting from the benzene decomposition on the surface of the nanocrystalline Ni3Fe powders are: CO2, CO and C. The evolution of the particle size distribution versus the milling time has been determined for the wet mechanical milling process of nanocrystalline Ni3Fe powders. The DSC analysis reveals a displacement of the Exothermic Peak onset towards lower temperatures and an increase of the surface of this Peak attributed to the changes in the particles specific surface and to the quantity of benzene added in the milling experiments.

Lide Zhang - One of the best experts on this subject based on the ideXlab platform.

  • The thermal stability of nanocrystalline maghemite
    Journal of Physics D: Applied Physics, 1998
    Co-Authors: Dong-sheng Lin, Zhengkuan Jiao, Lide Zhang
    Abstract:

    Nanocrystalline maghemite O was prepared by a wet chemical method. The thermal stability of this material has been investigated by using differential thermal analysis (DTA) measurements and x-ray diffraction analyses. One Exothermic Peak without weight loss appears irreversibly on the DTA curve. It was confirmed for the first time that this Exothermic Peak corresponds completely to the maghemite-to-hematite (-to-) structural phase transition. The nanocrystalline maghemite O particles grow very slowly when the temperature is lower than the range of the Exothermic Peak; whereas, during and after the transition, the nanocrystalline hematite O particles grow rapidly with increasing temperature. Moreover, the transition temperature of nanocrystalline maghemite O is higher than that of the coarse-grained counterpart. In this paper, the authors have also suggested some preliminary physical interpretations of the experimental results.

Maria Helena Fernandes - One of the best experts on this subject based on the ideXlab platform.

  • Crystallization kinetics of a barium-zinc borosilicate glass by a non-isothermal method
    Journal of Alloys and Compounds, 2014
    Co-Authors: Andreia A. S. Lopes, Regina Da Conceição Corredeira Monteiro, Roque S. Soares, Maria Margarida Rolim Augusto Lima, Maria Helena Fernandes
    Abstract:

    The crystallization kinetics of a glass with a molar composition 40BaO–20ZnO–30B2O3–10SiO2 was investigated. The kinetic parameters, activation energy for crystallization (Ec) and Avrami exponent (n), were evaluated under non-isothermal conditions using the results obtained by differential thermal analysis (DTA) performed at different heating rates. DTA curves exhibited two overlapping Exothermic Peaks associated with the crystallization of the glass. Barium borate (BaB4O7) was the first crystalline phase to be formed and it was followed by the formation of barium zinc silicate (BaZnSiO4), as identified by XRD. For the first Exothermic Peak, when the fraction of crystallization (v) increased from 0.1 to 0.9, the local activation energy (Ec(v)) decreased from 700 to 500 kJ/mol, while for the second Exothermic Peak, Ec(v) slightly increased from 490 to 570 kJ/mol. For the range of 0.1

Miguel G. Neumann - One of the best experts on this subject based on the ideXlab platform.

  • Evaluation of postpolymerization as a function of the storage time of triethylene glycol dimethacrylate/2,2‐bis[4‐(2‐hydroxy‐3‐methacryloxy‐prop‐1‐oxy)‐phenyl]propane bisphenyl‐α‐glycidyl ether dimethacrylate copolymers used in dental resins by diffe
    Journal of Applied Polymer Science, 2009
    Co-Authors: Isabel C. Rigoli, Carla Cristina Schmitt Cavalheiro, Miguel G. Neumann
    Abstract:

    The aim of this work was to evaluate the effect of the storage time on the thermal properties of triethylene glycol dimethacrylate/2,2-bis[4-(2-hydroxy-3-methacryloxy-prop-1-oxy)-phenyl]propane bisphenyl-α-glycidyl ether dimethacrylate (TB) copolymers used in formulations of dental resins after photopolymerization. The TB copolymers were prepared by photopolymerization with an Ultrablue IS light-emitting diode, stored in the dark for 1–60 days at 37°C, and characterized with differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and Fourier transform infrared spectroscopy with attenuated total reflection. DSC curves indicated the presence of an Exothermic Peak, confirming that the reaction was not completed during the photopolymerization process. This Exothermic Peak became smaller as a function of the storage time and was shifted at higher temperatures. In DMA studies, a plot of the loss tangent versus the temperature initially showed the presence of two well-defined Peaks. The presence of both Peaks confirmed the presence of residual monomers that were not converted during the photopolymerization process. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

  • evaluation of postpolymerization as a function of the storage time of triethylene glycol dimethacrylate 2 2 bis 4 2 hydroxy 3 methacryloxy prop 1 oxy phenyl propane bisphenyl α glycidyl ether dimethacrylate copolymers used in dental resins by differe
    Journal of Applied Polymer Science, 2009
    Co-Authors: Isabel C. Rigoli, Carla Cristina Schmitt Cavalheiro, Miguel G. Neumann
    Abstract:

    The aim of this work was to evaluate the effect of the storage time on the thermal properties of triethylene glycol dimethacrylate/2,2-bis[4-(2-hydroxy-3-methacryloxy-prop-1-oxy)-phenyl]propane bisphenyl-α-glycidyl ether dimethacrylate (TB) copolymers used in formulations of dental resins after photopolymerization. The TB copolymers were prepared by photopolymerization with an Ultrablue IS light-emitting diode, stored in the dark for 1–60 days at 37°C, and characterized with differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and Fourier transform infrared spectroscopy with attenuated total reflection. DSC curves indicated the presence of an Exothermic Peak, confirming that the reaction was not completed during the photopolymerization process. This Exothermic Peak became smaller as a function of the storage time and was shifted at higher temperatures. In DMA studies, a plot of the loss tangent versus the temperature initially showed the presence of two well-defined Peaks. The presence of both Peaks confirmed the presence of residual monomers that were not converted during the photopolymerization process. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

  • Thermal behaviour of TEGMMA copolymers obtained by photopolymerization using iron complexes
    Eclética Química, 2007
    Co-Authors: Isabel C. Rigoli, Miguel G. Neumann, Carla C. Schmitt, Luiz Antônio Ramos, Éder Tadeu Gomes Cavalheiro
    Abstract:

    Copolymers of methyl methacrylate (MMA) and triethyleneglycol dimethacrylate (TEGDMA) obtained by photoinitiated polymerization using Fe(III) complexes were submitted to thermogravimetry (TGA) under dynamic air atmosphere and N 2 , and differential scanning calorimetric analysis (DSC). Thermal events were observed only between 90 - 110 °C. Glass transitions were observed at ca. 100 °C, followed by an Exothermic Peak at 170 °C. The Exothermic Peak was assigned to a thermal curing process due to the presence of unreacted vinyl groups of the monomers. DSC revealed to be a useful tool to evaluate the curing completeness in this kind of material, using small amounts of sample in relatively short time.