KMITL

Permanent URI for this communityhttps://dspace.kmitl.ac.th/handle/123456789/1

Browse

Settings

Access type: UnknownSubject: search.filters.subject.Thermal analysis

Search Results

Now showing 1 - 4 of 4
  • Loading...
    Thumbnail Image
    Some of the metrics are blocked by your 
    consent settings
    Item type:Publication,
    The apparent PTCR effect in layered alkali titanates - A correlation between temperature dependent electrical properties and thermal analyses
    (2024-12-01)
    Pulphol, Phieraya
    ;
    Chaithaweep, Kanokwan
    ;
    Vittayakorn, Naratip
    ;
    Maluangnont, Tosapol
    Adsorbed water promotes proton conduction in ceramics at ambient conditions prior to its evaporation, apparently leading to the positive temperature coefficient of resistivity (PTCR) effect. Using surface water-containing Cs<inf>2</inf>Ti<inf>6</inf>O<inf>13</inf> (1.8 mol water/mol titanate) as an example, the static conductivity (at 50 °C) of ∼10<sup>−5</sup> S cm<sup>−1</sup> is one thousand times that at 200 °C due to the enhanced proton conduction. At 50–150 °C, the conductivity decreases by 4 orders of magnitude because water evaporation decreases the number of charge carriers. At 150–400 °C, the conduction in water-free Cs<inf>2</inf>Ti<inf>6</inf>O<inf>13</inf> is thermal-activated with the apparent activation energy E<inf>a</inf> ∼58–72 kJ mol<sup>−1</sup>, depending on the formalisms. We show clearly that an endothermic DSC peak (water evaporation) in Cs<inf>2</inf>Ti<inf>6</inf>O<inf>13</inf> coincides with all eight presentations of AC properties examined. Similar correlations are obtained from the TG/DTG curves in Cs<inf>2</inf>Ti<inf>5</inf>O<inf>11</inf>·H<inf>2</inf>O containing mostly intercalated water. The correlation between thermal analyses and AC properties points out that water molecules essentially contribute to the charge transport at ambient conditions of layered alkali titanates. This scenario might be potentially extended to other humidity-sensitive ceramics.
  • Loading...
    Thumbnail Image
    Some of the metrics are blocked by your 
    consent settings
    Item type:Publication,
    Design and Thermal Analysis of a Solid Oxide Fuel Cell System Integrated with Ethanol Steam Reforming
    (2012-01-01)
    Thanomjit, Chollaphan
    ;
    Patcharavorachot, Yaneeporn
    ;
    Arpornwichanop, Amornchai
    In this study, a thermal management of the solid oxide fuel cell (SOFC) system integrated with a steam reformer was investigated. Due to its renewable and green energy sources, ethanol was chosen as a fuel for the SOFC system in which it was converted into a hydrogen rich gas via a steam reforming. Modeling of the SOFC system was performed using a process simulator. The SOFC system performance was evaluated with respect to key operating parameters such as reforming temperature, SOFC temperature and steam to ethanol ratio. It was found that the ethanol reformer and pre-heaters require high energy consumption. To improve its thermal efficiency, the SOFC system with heat integration was analyzed and the exhaust gas from an SOFC stack was considered a useful heat source. Pinch analysis was applied to design the SOFC system with the aim to minimize the requirement of external energy sources. © 2012 Elsevier B.V.
  • Loading...
    Thumbnail Image
    Some of the metrics are blocked by your 
    consent settings
    Item type:Publication,
    Soft solution synthesis, non-isothermal decomposition kinetics and characterization of manganese dihydrogen phosphate dihydrate Mn(H2PO4)2·2H2O and its thermal transformation products
    (2008-06-15)
    Boonchom, Banjong
    ;
    Danvirutai, Chanaiporn
    ;
    Maensiri, Santi
    Manganese dihydrogen phosphate dihydrate (Mn(H<inf>2</inf>PO<inf>4</inf>)<inf>2</inf>·2H<inf>2</inf>O) was synthesized by a simple, rapid and cost-effective method using Mn(c) and H<inf>3</inf>PO<inf>4</inf> in water-acetone medium at ambient temperature. The thermal stability of the Mn(H<inf>2</inf>PO<inf>4</inf>)<inf>2</inf>·2H<inf>2</inf>O was studied by means of the non-isothermal kinetic (Kissinger method). The specificity of thermal decomposition was characterized by identification of the bonds to be selectively activated due to energy absorption at vibrational level, which was assigned by comparison of the calculated wavenumbers with the observed wavenumbers in FTIR spectra. These results were used to identify the molecules or ions that were eliminated in each thermal transition step. The thermal transformation products from the synthesized Mn(H<inf>2</inf>PO<inf>4</inf>)<inf>2</inf>·2H<inf>2</inf>O according to the thermal treatments at 243, 773 and 1073 K were obtained to be Mn(H<inf>2</inf>PO<inf>4</inf>)<inf>2</inf>, Mn<inf>2</inf>P<inf>4</inf>O<inf>12</inf> and Mn<inf>2</inf>P<inf>2</inf>O<inf>7</inf>, respectively. The synthesized Mn(H<inf>2</inf>PO<inf>4</inf>)<inf>2</inf>·2H<inf>2</inf>O and its thermal transformation products were characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), and FTIR spectroscopy. The SEM micrographs of the obtained products show the different morphologies, which are important for specific applications. © 2007 Elsevier B.V. All rights reserved.
  • Loading...
    Thumbnail Image
    Some of the metrics are blocked by your 
    consent settings
    Item type:Publication,
    Nanocrystalline manganese dihydrogen phosphate dihydrate Mn(H2PO4)2·2H2O and its decomposition product (Mn2P4O12) obtained by simple precipitation route
    (2008-06-12)
    Danvirutai, Chanaiporn
    ;
    Boonchom, Banjong
    ;
    Youngme, Sujittra
    Manganese dihydrogenphosphate dihydrate (Mn(H<inf>2</inf>PO<inf>4</inf>)<inf>2</inf>·2H<inf>2</inf>O) was prepared by using MnCO<inf>3</inf>-H<inf>3</inf>PO<inf>4</inf> and Mn(c)-H<inf>3</inf>PO<inf>4</inf> systems at ambient temperature. The precipitates were investigated by thermoanalytical techniques (TG/DTG/DTA), scanning electron microscope (SEM), X-ray powder diffraction (XRD), and FTIR spectroscopy. Thermal treatment of obtained Mn(H<inf>2</inf>PO<inf>4</inf>)<inf>2</inf>·2H<inf>2</inf>O from two synthetic systems at 400 °C yielded a crystalline dehydrated manganese cyclo-tetrametaphosphate (Mn<inf>2</inf>P<inf>4</inf>O<inf>12</inf>). The XRD and FTIR results indicate that the prepared Mn(H<inf>2</inf>PO<inf>4</inf>)<inf>2</inf>·2H<inf>2</inf>O and its dehydration product Mn<inf>2</inf>P<inf>4</inf>O<inf>12</inf> from both synthetic systems have a pure monoclinic phase without the presence of any phase impurities. The lattice parameters and particles sizes analyzed from XRD spectra of Mn(H<inf>2</inf>PO<inf>4</inf>)<inf>2</inf>·2H<inf>2</inf>O and its dehydration product Mn<inf>2</inf>P<inf>4</inf>O<inf>12</inf> are different for both systems. The difference of some physical and chemical properties of Mn(H<inf>2</inf>PO<inf>4</inf>)<inf>2</inf>·2H<inf>2</inf>O and its dehydration product Mn<inf>2</inf>P<inf>4</inf>O<inf>12</inf> from both synthetic systems are discussed. Crown Copyright © 2007.