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  • Thermal evolution of the oxidation characteristics of pulverized coal with different particle sizes and heating rates
    Thermochim. Acta (IF 2.251) Pub Date : 2020-01-25
    Rongkun Pan; Tian Qiu; Jiangkun Chao; Hongyan Ma; Jian Wang; Cong Li
    更新日期:2020-01-26
  • Simultaneous thermal analysis of samples in the Bi2O3-P2O5-SiO2 system: comparison with the KEMS data
    Thermochim. Acta (IF 2.251) Pub Date : 2020-01-23
    V.L. Stolyarova; V.A. Vorozhtcov; S.I. Lopatin; V.L. Ugolkov

    This paper presents and compares the results of investigation of the samples in the Bi2O3-P2O5-SiO2 system by means of simultaneous thermal analysis, X-ray phase analysis, and Knudsen effusion mass spectrometry. The samples were synthesized by the melt quenching technique using Bi2O3, SiO2, and NH4H2PO4. By differential scanning calorimetry, characteristic temperatures and enthalpies of phase transformations in the samples were determined. Mass losses of the samples obtained by thermogravimetric analysis in dynamic air flow were compared with those found by Knudsen effusion mass spectrometry in vacuum. Using X-ray phase analysis, unknown phases were identified in several samples. These phases might consist of previously unknown compounds containing bismuth, phosphorus, and silicon together. The results of the present study should be regarded as being preliminary information concerning phase equilibria in the Bi2O3-P2O5-SiO2 system.

    更新日期:2020-01-23
  • 更新日期:2020-01-23
  • The correctness of Cp measurements by DSC, actions to do and not to do
    Thermochim. Acta (IF 2.251) Pub Date : 2020-01-22
    I. Blanco

    Considering the importance of performing heat capacity (Cp) measurements to gain information about the most important material properties, such as Energy (U), Gibbs Energy (G), Free Energy (F), Enthalpy (H) and Entropy (S) this short review aims at highlight some procedural key steps, in order to correctly carry out the Cp measurement. After a brief presentation of the state of the art's evolution, with particular regards to the Italian calorimetric field, the manuscript faces the main steps of a DSC measure, from the calibration to the choice of the weight and shape of the sample, suggesting the most suitable instrumental and operating conditions.

    更新日期:2020-01-22
  • Vaporization/sublimation enthalpies of mono- and dimethyl-esters estimated by solution calorimetry method
    Thermochim. Acta (IF 2.251) Pub Date : 2020-01-22
    Aizat A. Samatov; Ruslan N. Nagrimanov; Evgeniy A. Miroshnichenko; Boris N. Solomonov

    The additive scheme for calculating the solvation enthalpies of aliphatic compounds has been expanded to determine the solvation enthalpy of linear mono- and dimethyl-esters. Ester group contribution to the enthalpy of solvation in n-heptane was obtained. Accuracy of the proposed approach for determination of solvation enthalpies of linear mono- and dimethyl-esters was tested by comparison with experimental solvation enthalpies. In most cases, deviations do not exceed 1 kJ·mol-1. It was found that the dependence of the solution enthalpies of mono- and dimethyl-esters on the number of carbon atoms in the molecule can be fit by power function. This dependence together with a group-additivity scheme for solvation enthalpy was used to estimation the enthalpies of phase transitions of mono- and dimethyl-esters. Evaluated values of sublimation, vaporization, and fusion enthalpies at 298.15 K are in good agreement with experimental data obtained by conventional methods.

    更新日期:2020-01-22
  • 更新日期:2020-01-21
  • Thermodynamic properties of Ge0.25-yGayTe0.75-xIx glasses (y = 0.10, 0.15; x = 0 – 0.06 mole fraction) for optical applications
    Thermochim. Acta (IF 2.251) Pub Date : 2020-01-20
    А.D. Plekhovich; A.M. Kut'in; A.P. Velmuzhov; N.S. Zernova; M.F. Churbanov

    For the obtained high-purity glasses of crystallization-resistant compositions Ge0.25-yGayTe0.75-xIx (y = 0.10, 0.15, x = 0-0.06 mole fractions) by method TM-DSC heat capacity experimentally determined and glass transition characteristics studied. Based on the results of theoretical processing of calorimetric data, standard thermodynamic functions were calculated in the temperature range 0 – 530 K which are complemented by temperature dependences of density and coefficient of thermal expansion. These thermodynamic functions are necessary for determining the conditions of synthesis by minimizing the Gibbs energy of promising representatives of the glass-forming system Ge–Ga–Te–I and prediction of the properties of glasses including those with functional additives that determine their optical-sensory applications.

    更新日期:2020-01-21
  • Effect of Molecular Structure on Excess Molar Enthalpy of Amine-based Carbon Dioxide Absorbent and Water
    Thermochim. Acta (IF 2.251) Pub Date : 2020-01-18
    Zhang Rui-lei; Chen Jian; Cao Gui-rong; Gu Hong-biao; Xiao Rui-jie; Chen Kai-wen

    Amine-based carbon dioxide absorbent has the characteristics of high selective absorption rate and strong absorption capacity and occupies the leading position in the carbon dioxide absorption process. The absorption performance of amine carbon dioxide absorbents is directly related to their thermodynamic properties. Accordingly, for the selection of new absorbents, the important thermodynamic properties such as the excess molar enthalpy of the system must be determined first. In this paper, the excess molar enthalpies for amine-based carbon dioxide absorbents in water were measured with C-80 calorimeter at atmospheric pressure. With the experimental data in this work and the literature data, the relationship between the molecular structure and excess molar enthalpy of amine-based carbon dioxide absorbent was studied.

    更新日期:2020-01-21
  • Cure-kinetic parameters of nanoclay-containing unsaturated polyester resins: effect of chemical structure of resin
    Thermochim. Acta (IF 2.251) Pub Date : 2020-01-17
    Mehdi Poorabdollah; Saeid Danaei

    An unsaturated polyester resin was synthesized and filled with Cloisite 10A nanoparticles. The kinetic parameters of the synthesized and filled unsaturated polyester resins were calculated by an advanced isoconversional method and using dynamic DSC data. The influence of diethylene glycol present in the resin structure on the kinetic parameters was examined. The effect of glycol type on the miscibility of alkyd chains and styrene and the significance of this miscibility on the kinetic behavior of the resin containing nanoparticles were investigated. The results showed that change in glycol type changed the miscibility between alkyd chains and styrene, which in turn, caused to vary the kinetic parameters of curing reaction of the resin containing nanoparticles. Diffusion phenomenon was studied and the results demonstrated that by addition of nanoclay in the resin formulation the diffusion becomes a more dominant mechanism.

    更新日期:2020-01-17
  • Isobaric Heat Capacity Measurements for 1,3-diethylbenzene from 303 K to 489 K and Pressure up to 12 MPa
    Thermochim. Acta (IF 2.251) Pub Date : 2020-01-16
    Yaona Xu; Xiaoming Zhao; Xin He; Hengheng Shao

    The isobaric heat capacity of 1,3-diethylbenzene was studied in the liquid phase. A total of 68 experimental data were acquired for ten isotherms from 303.16 K to 489.81 K in the pressure range of 0.17 MPa to 12 MPa. The experimental data were correlated with an empirical equation. The isobaric heat capacity of water was measured to verify the reliability of the experimental system before this experiment.

    更新日期:2020-01-17
  • Aqueous sol-gel synthesis, thermal analysis, characterization and electrical properties of V2O5 doped Bi2O3 system
    Thermochim. Acta (IF 2.251) Pub Date : 2020-01-11
    Austėja Diktanaitė; Giedrė Gaidamavičienė; Edvardas Kazakevičius; Algimantas Kežionis; Artūras Žalga
    更新日期:2020-01-13
  • Nanocalorimetry of Explosives Prepared by Inkjet Printing
    Thermochim. Acta (IF 2.251) Pub Date : 2020-01-10
    Feng Yi; Greg Gillen; Jeffrey Lawrence; Thomas P. Forbes; Matthew Staymates; David A. LaVan

    Nanocalorimetry can generate rapid and arbitrary heating profiles for thermal and thermodynamic measurements with high sensitivity, especially for small samples, often at the nanogram mass scale. These features make nanocalorimetry a potentially useful tool for fundamental studies of the behavior of nanogram quantities of explosives during thermal desorption which is the front-end process for many analytical techniques used in screening of these materials in trace residues. Here, inkjet printing was used to reproducibly deposit nanogram quantities of explosives onto the active area of the nanocalorimeters and allowed for an estimation of sample mass based on gravimetric calibration, including cyclotrimethylenetrinitramine (RDX), pentaerythritol tetranitrate (PETN), trinitrotoluene (TNT), and potassium chlorate (PC). Nanocalorimetry results on common explosives demonstrated the measurement capability. We observed both α-RDX and the metastable β-RDX phase using nanocalorimetry, along with the competitive vaporization and decomposition of RDX. Finally, nanocalorimetry coupled mass spectrometry was demonstrated to characterize thermal desorption events during analysis of trace quantities of explosives.

    更新日期:2020-01-11
  • The Kinetics of Thermal Decomposition of 1-Alkyl-3-Methylimidazolium Chloride Ionic Liquids under Isothermal and Non-Isothermal Conditions
    Thermochim. Acta (IF 2.251) Pub Date : 2020-01-10
    Michael L. Williams; James S. Dickmann; Mary E. McCorkill; John. C. Hassler; Erdogan Kiran
    更新日期:2020-01-11
  • Development of Advanced Methods of Determining the Chemical Stability of Hydrocarbon Fuels
    Thermochim. Acta (IF 2.251) Pub Date : 2020-01-08
    A.A. Boryaev

    Experimental studies have shown that it is impossible to obtain reliable values of chemical stability indices of hydrocarbon fuels using the existing methods of fuel quality control. Techniques for the determination of such chemical stability indices of hydrocarbon fuels as the content of existent gums and oxidation degree, to the improvement of which this article is devoted, are identical both in the Russian Federation and in countries of the European Union. In order to improve the method for determining the content of existent gums in hydrocarbon fuels and create a new method for determining the oxidation degree, experimental studies were carried out, which allowed establishing correlations between the oxygen consumed for oxidation and final products of oxidation. Based on the conducted studies, an addition to the existing technique for determining the content of existent gums in hydrocarbon fuels is given, which allows for the elimination of the new formation of oxidation products in the course of measurements. The carried out experimental studies allowed for the development of a new technique for determining the oxidation degree of hydrocarbon fuels. It was experimentally established that the amount of the oxygen consumed for hydrocarbon fuel oxidation correlated well with the oxidation degree index, which made it possible to take the amount of the oxygen consumed for oxidation and the concentration of solubilized water as the basis for the new method of determining the fuel oxidation degree. A scheme of the installation for determining the concentration of solubilized water in hydrocarbon fuel and a technique of measurements are given. After the calculation of the concentration of solubilized water, the amount of the reacted oxygen referred to the hydrocarbon volume and the fuel oxidation degree are determined as per the experimental nomographic chart.

    更新日期:2020-01-09
  • Estimating errors in the determination of activation energy by advanced nonlinear isoconversional method applied for thermoanalytical measurements performed under arbitrary temperature programs
    Thermochim. Acta (IF 2.251) Pub Date : 2019-12-30
    P. Budrugeac

    In a previous paper (Thermochim. Acta 670 (2018) 1–6) it was shown that the estimation of errors (ΔE) in the determination of apparent activation energies (E) determined by a nonlinear isoconversional method applied for thermoanalytical measurements performed under constant heating rates involves the following successive steps: (1) the determination of Fisher confidence interval (ΔFE) for confidence level of 95 % by applying the procedure suggested by Vyazovkin and Wight, and (2) the application of the relation: ΔE=0.2447×ΔFE+0.00037×ΔFE2. The check of this procedure when using advanced nonlinear incremental isoconversional method (A-NL method) suggested by Vyazovkin is applied for thermoanalytical data under arbitrary temperature programs has been performed for: simulated sinusoidal modulated data, thermogravimetric (TG) data for thermal decomposition of a sort of high density polyethylene (HDPE) under quasi-isothermal conditions, and TG data corresponding to thermal decomposition of a sort of low density polyethylene under arbitrary temperature programs. It has been concluded that the suggested procedure for estimating the error in E evaluation based on above relationship is also applicable when A-NL method is used for kinetic analysis of thermoanalytical data recorded under arbitrary temperature programs.

    更新日期:2019-12-30
  • 更新日期:2019-12-30
  • Phase diagram of the low-density polyethylene – dimethyl terephthalate system: A new topology
    Thermochim. Acta (IF 2.251) Pub Date : 2019-12-30
    Andrey V. Basko; Konstantin V. Pochivalov; Alexander V. Bazanov; Georgiy A. Shandryuk; Alexander A. Ezhov; Vladimir V. Artemov; Yaroslav V. Kudryavtsev

    A new type of phase diagram semicrystalline polymer – low molecular mass substance is found for the low-density polyethylene – dimethyl terephthalate mixture. Exploiting an original optical method and differential scanning calorimetry, we demonstrate that the studied system combines the features of polymer – poor solvent and polymer – high-melting substance mixtures. Its diagram also contains a curve describing the solubility of the low molecular mass component in the polymer, which is often missing in the literature. An experimental phase diagram enables us to perform a detailed analysis of the differential scanning calorimetry, optical and scanning electron microscopy data on the cooling of homogenized mixtures of different compositions, which leads to the formation of capillary-porous polyethylene bodies via thermally induced phase separation and following removal of dimethyl terephthalate crystals.

    更新日期:2019-12-30
  • Size effects of nano-rutile TiO2 on latent heat recovered of binary eutectic hydrate salt phase change material
    Thermochim. Acta (IF 2.251) Pub Date : 2019-12-23
    Yushi Liu; Kunyang Yu; Yingzi Yang; Minjie Jia; Fuzheng Sun

    In the current work, we reported the size effects of rutile TiO2 nanoparticles on the latent heat recovered of eutectic hydrate salt (EHS) phase change material (PCM). The nanoparticles modified EHS composites were prepared with different volume loadings (0.1 %, 0.3 % and 0.5 %) of TiO2 nanoparticles with two different sizes of 25 and 100 nm. The rheological behaviour analysis was carried out to demonstrate the dispersion stability of TiO2 nanoparticles in EHS. The factorial experiment method has been developed to evaluate the size effects of TiO2 nanoparticles. Meanwhile, the characterization technique, DSC was used to investigate the thermal properties. The results showed that the nanoparticles modified EHS composites incorporated with TiO2 nanoparticles in diameter of 25 nm achieved an optimal latent heat recovered, of which the mechanism analyses were validated by SEM and FT-IR. This study will provide insights into the further improvement of thermal properties of nanoparticles modified PCM composites by means of tailoring the size of nanoparticles.

    更新日期:2019-12-23
  • Enthalpies of dilution of amino alcohols in aqueous solutions at 298.15 K
    Thermochim. Acta (IF 2.251) Pub Date : 2019-12-23
    Carmen M. Romero; Yadhi P. Cruz; Silvia Perez-Casas

    The enthalpies of dilution of aqueous solutions of the amino alcohols: 3-amino-1-propanol, (RS)-1-amino-2-propanol, (RS)-3-amino-1,2-propanediol, and 1,3-diamino-2-propanol were measured as a function of concentration at 298.15 K using a Thermal Activity Monitor (TAM). The results of the experimental measurements were treated according to the McMillan-Mayer theory, to obtain the enthalpic homogeneous interaction coefficients. The pair interaction coefficient hxx shows a clear dependence on the position and number of polar groups. The enthalpic coefficients are discussed in terms of the molecular interaction between solvated solute molecules.

    更新日期:2019-12-23
  • Enhancing thermal conductivities of hexagonal boron nitride/fluorinated polyimide composite materials using direct current electrical fields
    Thermochim. Acta (IF 2.251) Pub Date : 2019-12-23
    Masashi Haruki; Jun Tada; Ren Funaki; Hajime Onishi; Yukio Tada

    The effect of the electrical field treatment using the direct current (DC) during preparation of the composite sheets on their effective thermal conductivity (TC) and electrical insulation property for the hexagonal boron nitride (hBN)/fluorinated polyimide was studied. By the electrical field treatment, the aggregation of hBNs was obviously observed in the cross-sections of the composite sheets, and the number of hBNs lying parallel to the in-plane direction of the sheets was decreased based on XRD study. Moreover, the effective TC in the out-of-plain direction of the composite sheets treated with a one-way electrical field was increased approximately 1.5-fold that of the corresponding sheets prepared without electrical field treatment at 14.2 vol%. On the other hand, electrical insulation properties were deteriorated by the electrical field treatment, and the values for breakdown voltage against DC roughly approximated that following electrical field treatments to high content of hBNs regardless of their size.

    更新日期:2019-12-23
  • Characterization and modeling on the role of Mg2+ in seawater blended Portland cement systems
    Thermochim. Acta (IF 2.251) Pub Date : 2019-12-19
    X.S. Li; Z.H. Shui; X. Gao; Y. Huang; R. Yu; K.Z. Liu

    In this study, the effect of Mg2+ on early hydration of Portland cement is addressed. Heat flow calorimetry and ICP-OES are employed to characterize the cement hydration at early age. XRD, TG-DSC are utilized to demonstrate the changes of phase composition during early age. SEM-EDS and 27Al MAS NMR are used to reveal phase transformation of aluminum related hydration products. The results show that the induction period of cement is prolonged after Mg2+ incorporation, resulting in decreased dissolution of clinker minerals. The effect of Mg2+ on acceleration period depends on its concentration. Mg2+ hinders the formation of Ca(OH)2 and transformation from AFt to AFm and TAH.

    更新日期:2019-12-19
  • Anisotropic thermal expansion behavior of an interpenetrating metal/ceramic composite
    Thermochim. Acta (IF 2.251) Pub Date : 2019-12-18
    Siddhartha Roy; Alwin Nagel; Kay André Weidenmann

    Thermal expansion behavior of an interpenetrating metal/ceramic composite having ceramic contents in the range of 34-60 vol% is studied in this work. Four thermal cycles were carried out between room temperature and 500 °C at a constant heating/cooling rate of 5 °C/min. Both thermal strain and thermal expansion coefficient decrease with increasing ceramic content in the composite. Evolution of the thermal expansion coefficient with temperature shows anisotropic nature. At all ceramic contents, highest thermal strain and thermal expansion coefficient are obtained along the preform press direction. The extent of thermal expansion anisotropy depends upon both temperature and ceramic content in the composite. The evolution of the observed thermal expansion anisotropy has been attributed to the elastic anisotropy of the preforms and composites, considering as well the elastic-plastic flow behavior of the metallic matrix. The results have been compared with several analytical theoretical models.

    更新日期:2019-12-19
  • A highly stable hydroxylated graphene/ethylene glycol-water nanofluid with excellent extinction property at a low loading for direct absorption solar collectors
    Thermochim. Acta (IF 2.251) Pub Date : 2019-12-17
    Jiawu Huang; Zhaofeng Chen; Zhiqing Du; Xinxin Xu; Zhengguo Zhang; Xiaoming Fang

    In order to explore a graphene-containing nanofluid with good dispersion stability as the working fluid for a low-temperature direct absorption solar collector (DASC), firstly, two kinds of functionalized graphene, hydroxylated graphene (GOH) and carboxylated graphene (GCOOH), were dispersed into a mixture of ethylene glycol (EG) and water (1:1 mass ratio), at the same loadings. It is found that, although the obtained GOH nanofluid exhibits a slight lower zeta potential than the GCOOH one, its optical absorption property is obviously higher. Consequently, GOH was employed to prepare the EG-water based nanofluids at different loadings, followed by the investigations on their optical absorption and thermophysical properties, photo-thermal conversion performance, and dispersion stability. It is shown that, at a loading as low as 0.007 wt%, the transmittance of the corresponding GOH/water-EG nanofluid is reduced to zero, and its extinction coefficient is 100 times higher than that of the base fluid. Under the illumination of 1000 W/m2, the 0.007 wt% GOH/EG-water nanofluid can reach a high final temperature of 55 °C. More significantly, the zeta potential of the 0.007 wt% GOH/EG-water nanofluid increases with temperature and reaches 47.63 mV at 60 ℃, suggesting its good dispersion stability at the elevated temperatures. These good characteristics of the GOH/EG-water nanofluid make it a very promising working fluid for a low temperature DASC.

    更新日期:2019-12-18
  • Gas evolution characterization and phase transformation during thermal treatment of cathode plates from spent LiFePO4 batteries
    Thermochim. Acta (IF 2.251) Pub Date : 2019-12-12
    Yafei Jie; Shenghai Yang; Fang Hu; Yun Li; Longgang Ye; Duoqiang Zhao; Wei Jin; Cong Chang; Yanqing Lai; Yongming Chen
    更新日期:2019-12-13
  • Thermal stability and specific heats of coordinating ionic liquids
    Thermochim. Acta (IF 2.251) Pub Date : 2019-12-12
    Bernardo Monteiro; Leonor Maria; Adelaide Cruz; José M. Carretas; Joaquim Marçalo; João P. Leal
    更新日期:2019-12-13
  • Kinetics of non-isothermal crystallization in FeNiPC(Nb) Alloys
    Thermochim. Acta (IF 2.251) Pub Date : 2019-12-09
    S.S. Jiang, L. Zhu, H. Zheng, Y.G. Wang

    The effects of minor Nb addition on the crystallization mechanism for a FeNiPC(Nb) amorphous alloy were studied via investigating its non-isothermal crystallization kinetics. With minor Nb addition, the thermal stability of the alloy increases as evidenced by the enlargement of the supercooled liquid region. Meanwhile, the location activation energy of both Nb-added and without Nb-added alloys correlates positively with the crystallized volume fraction during the whole primary crystallization stages, as calculated by the isoconversional methods. However, the kinetics analysis using the modified Johnson-Mehl-Avrami-Kolmogorov equation indicates that the addition of Nb changes the crystallization mode of the alloys, that is, from the growth with a decrease nucleation rate to a constant nucleation rate in a diffusion-controlled manner. This can be further confirmed by the atomic force microscopy showing that Nb would restrain the atomic diffusivity and suppress the crystallization growth rate in this alloy.

    更新日期:2019-12-11
  • Critical review on measured phase transition enthalpies of salt hydrates in the context of solid-liquid phase change materials
    Thermochim. Acta (IF 2.251) Pub Date : 2019-12-06
    Henri Schmit, Christoph Rathgeber, Peter Hoock, Stefan Hiebler

    During the last decades, salt hydrates have become increasingly popular in research on phase change materials (PCM) due to their generally higher phase transition enthalpies and lower costs compared to organic PCM. However, in most published reviews on phase transition enthalpies of salt hydrates, the data stems from earlier data collections and the original experimental sources are often not mentioned. Therefore, a review on original experimental phase transition enthalpies of selected salt hydrates based on chlorides, hydroxides, and nitrates as well as some other materials popular in PCM literature is provided here. Additionally, information on the preparation process of the samples is contained along with the used calorimeter. This information helps to assess the experimental results especially for salt hydrates where considerable deviations for the phase transition enthalpies exist in literature. Even though salt hydrates are heterogeneous materials, the collected data shows that it is possible to obtain reliable values for their phase transition enthalpies via differential scanning calorimetry (DSC), but only under certain conditions.

    更新日期:2019-12-06
  • AN EXPERIMENTAL INVESTIGATION INTO THE OPERATION OF AN ELECTRICALLY HEATED TOBACCO SYSTEM
    Thermochim. Acta (IF 2.251) Pub Date : 2019-12-04
    V. Cozzani, F. Barontini, T. McGrath, B. Mahler, M. Nordlund, M. Smith, J.P. Schaller, G. Zuber

    An experimental investigation of the thermal processes taking place in the tobacco substrate of a recently developed multicomponent electrically heated tobacco product (EHTP) that is part of an electrically heated tobacco system (EHTS – also referred to as the Tobacco Heating System 2.2) was carried out. Temperature profiles in the tobacco substrate of the EHTP were characterized using thermocouples positioned at different distances from the heater surface. The average maximum temperature of the tobacco measured 0.2 mm from the heater’s surface was < 260 °C, well below the temperature required for the self-sustaining smoldering combustion of the tobacco substrate to occur. The chemical composition of the aerosol generated from the EHTP when the EHTS was operated under oxidative and non-oxidative atmospheres was investigated. The aerosol derived from the controlled heating of the tobacco substrate is comprised principally of water, nicotine and glycerol that are evaporated from the tobacco substrate. No significant change in aerosol composition and in the amounts of CO, NO and NOx were detected when comparing the aerosol formed under non-oxidative (where combustion processes cannot occur) and oxidative atmospheres.

    更新日期:2019-12-04
  • The vapor pressure of Se and SeO2 measurement using thermogravimetric analysis
    Thermochim. Acta (IF 2.251) Pub Date : 2019-12-03
    Wenting Xu, Qiang Song, Guochang Song, Qiang Yao

    The vapor pressure data of Se and SeO2 in low temperature range are essential for the study of emission and migration of selenium from stationary sources. The vapor pressure of SeO2 at 353.2-473.2 K was measured by thermogravimetric analysis, and the corresponding pressure was 0.026-319.2 Pa. The vapor pressure of Se at 423.2-573.2 K was measured, and the corresponding pressure was 0.007-80.9 Pa. The triple point temperature and pressure of Se determined in this experiment were 491.2 ± 1 K and 2.16 ± 0.27 Pa. The extended uncertainty of temperature measurement (k = 2) was 1.86 K, and the extended relative uncertainty of pressure measurement (k = 2) was 0.128p. The vapor pressures of Se and SeO2 were fitted to Antonie equation, respectively, and compared with the available literature data.

    更新日期:2019-12-03
  • Thermogravimetric analysis of aromatic boronic acids for potential flame retardant applications
    Thermochim. Acta (IF 2.251) Pub Date : 2019-12-02
    Benjamin Cromwell, Adelaide Levenson, Mindy Levine
    更新日期:2019-12-02
  • Thermo-Physical Properties Investigation In Relation To Deposition Orientation For SLM Deposited H13 Steel
    Thermochim. Acta (IF 2.251) Pub Date : 2019-12-02
    J. Džugan, K. Halmešová, M. Ackermann, M. Koukolíková, Z. Trojanová

    Components produced by additive manufacturing (AM) exhibit a heterogeneous microstructure, hence results in anisotropic mechanical properties. There are very limited studies available on thermo-physical properties variation in relation to the deposition orientation. Variation in these properties may result in an uneven stress distribution. In this work, thermo-physical properties of H13 tool steel fabricated by selective laser melting (SLM) process were experimentally investigated. The effect of three deposition directions (vertical, horizontal and 45° to base plane of build platform) on thermal expansion, thermal diffusivity, specific heat, thermal conductivity and simplified CCT diagram was studied. Additionally, mechanical properties and metallographic studies of the microstructure were carried out together with the porosity evaluation measurements across the specimens.

    更新日期:2019-12-02
  • Energetic characterization of uracil derivatives: orotic and isoorotic acids
    Thermochim. Acta (IF 2.251) Pub Date : 2019-12-02
    Luísa M.P.F. Amaral, Piotr Szterner, Victor M.F. Morais, Maria D.M.C. Ribeiro da Silva, Manuel A.V. Ribeiro da Silva
    更新日期:2019-12-02
  • Thermal stability of soil carbon pools: inferences on soil nature and evolution
    Thermochim. Acta (IF 2.251) Pub Date : 2019-12-02
    C. Natali, G. Bianchini, P. Carlino

    The quantification of soil carbon pools is a pressing topic both for the agriculture productivity and to evaluate the Greenhouse Gases (GHG) sequestration potential, therefore a rapid and precise analytical protocol for carbon speciation is needed.Temperature-dependent differentiation of soil carbon in compliance with the DIN (German Institute for Standardization) 19539 standard has been applied for the first time on 24 agricultural soil samples from the Po River Plain (Italy), with the aim of investigate their thermal behavior in the 50-900 °C interval. The results invariably show the existence of three soil carbon pools having different thermal stabilities, namely, thermally labile organic carbon (TOC400), residual oxidizable carbon (ROC) and total inorganic carbon (TIC900), in the intervals of 300-400 °C, 510-600 °C and 700-900 °C, respectively. Significant relationships have been observed between the above mentioned organic and inorganic carbon pools and the associated isotopic composition: 1) inverse correlation between TOC400/ROC and δ13C links thermal stability and soil organic matter (SOM) composition; 2) direct correlation between carbonate breakdown temperature and δ13C denotes the mineralogical association of the inorganic pool. The results give clues regarding the nature and evolution of soil carbon pools.

    更新日期:2019-12-02
  • 更新日期:2019-11-30
  • A dual-wavelength flash Raman method for simultaneously measuring thermal diffusivity and line thermal contact resistance of an individual supported nanowire
    Thermochim. Acta (IF 2.251) Pub Date : 2019-11-30
    Hu Yudong, Fan Aoran, Liu Jinhui, Wang Haidong, Weigang Ma, Zhang Xing

    Precise thermal characterization of supported nanowires is crucial for the thermal analysis in their applications. This paper developed a one-dimension dual-wavelength flash Raman (DFR) method to measure the thermal diffusivity and line thermal contact resistance of an individual supported nanowire. In this method, two laser pulses with different wavelengths are used for heating the sample and probing the Raman spectra, respectively. The temperature variation curves can be captured by changing the time delay between the two pulses, and the temporal resolution can reach to 100 ps. The laser absorption coefficient of the nanowire can be eliminated in the determination of thermal properties, which greatly enhance the measurement accuracy. To the consideration of accuracy and easy operation of the measurement, for different situations, the complete model considered the temperature variation of the substrate and the simplified model ignored the substrate temperature rise were both analyzed. This method has been used to measure a silicon nanowire which is supported by a sliver substrate. Experimental results of the supported silicon nanowire show that the thermal diffusivity of silicon nanowire is (7.3 ± 1.4) ×10-5 m2/s, and the line thermal contact resistance between the nanowire and the substrate is (2.6 ± 0.1) m·K/W.

    更新日期:2019-11-30
  • Comparison of Crystallization Kinetics of Polyethylene Terephthalate (PET) and Reorganized PET
    Thermochim. Acta (IF 2.251) Pub Date : 2019-11-29
    Amita A. Gaonkar, Vrishali V. Murudkar, Vineeta D. Deshpande
    更新日期:2019-11-30
  • Gasification of Real MSW-Derived Hydrochar under Various Atmosphere and Temperature
    Thermochim. Acta (IF 2.251) Pub Date : 2019-11-25
    Chuanjin Lin, Jing Zhang, Peitao Zhao, Zheng Wang, Maolin Yang, Xin Cui, Hongjing Tian, Qingjie Guo

    The hydrothermal carbonization could improve the fuel quality of municipal solid waste (MSW), in terms of water content reduction, chlorine removal, and energy densification. The chlorine content plays a significant role in determining whether the derived hydrochar is suitable as a fuel or chemical product. Many works focus on the chlorine behavior and fuel quality of hydrochar. However, few works focus on the gasification characteristics of real MSW-derived hydrochar. In this work, the hydrochar derived from real MSW employing hydrothermal treatment were gasified under various temperatures (600-1000 °C) and atmospheres (Air, CO2/O2 and steam/O2), with gas and tar analyzed by GC and GC-MS, respectively. The results showed that the hydrothermal treatment could remove 90.5% chlorine of the MSW at an HTC temperature of 220 °C for 30 mins. The syngas quality was improved whereas the tar yield was generally reduced with the reaction temperature, independent on the atmosphere. The H2, CO and CH4 yield was increased gradually, while the CO2 yields kept decreasing with the gasification temperature ranging from 600 to 900 °C. The highest H2 yield occured in the steam/O2 gasification, resulting in the highest H2/CO ratio of 4.58 at a gasification temperature of 1000 °C. The tar yield in the air gasification was the maximum, while it was the minimum in the steam/O2 gasification. The carbon conversion rate was increased with the gasification temperature. 900 ℃ was supposed to be a suitable operating window for obtaining gas with high H2 concentration and heating value. All these results indicated that the hydrothermal carbonization (HTC) coupled with gasification was an effective approach to produce hydrogen-rich gas from MSW. And these findings might be helpful for the design and further optimization MSW thermochemical conversion process.

    更新日期:2019-11-26
  • The Influence of Dopants on the Surface Enthalpy of Yttrium Aluminum Garnet (YAG)
    Thermochim. Acta (IF 2.251) Pub Date : 2019-11-25
    Geetu Sharma, Kimiko Nakajima, Dereck N.F. Muche, Ricardo H.R. Castro

    Surface enthalpy is an important parameter to predict the phase stability of crystalline materials at the nanoscale, having parametric influence in processes such as coarsening and single crystal nucleation and growth. Yttrium aluminum garnet (Y3Al5O12, YAG) is a base material for solid state laser, with limited thermodynamic information on interfacial energies available. In the present study, we experimentally determined by using microcalorimetry the surface enthalpy of YAG by using nanoparticles to enhance the respective heat effect exploiting their intrinsically high surface area, and further tracked the effect of La or Mg as dopants on the surface enthalpy of YAG. The results indicate that there is a slight reduction in the surface enthalpy of YAG nanoparticles after doping with 2 %-La or Mg. The anhydrous surface enthalpy of undoped YAG was measured as 1.28 ± 0.11 J/m2 and was reduced to 0.98 ± 0.09 and 1.11 + 0.07 J/m2 for 2%-La, and Mg doped YAG nanoparticles, respectively, confirming anhydrous surface energies of YAG can be modified by dopants. The effect of water adsorption on the energies, however, show that the differences between doped and undoped YAG surface energies become negligible at relative pressures as low as 20%, challenging surface energy control as a viable process optimization parameter when humidity is present.

    更新日期:2019-11-26
  • A new thermogravimetric application for determination of vapour pressure curve corresponding to average boiling points of oil fractions with narrow boiling ranges
    Thermochim. Acta (IF 2.251) Pub Date : 2019-11-23
    Rivo Rannaveski, Vahur Oja

    The average boiling point of oil fractions with narrow boiling ranges or pseudo-components is an important parameter in thermodynamic calculations in the fields of process design and environmental protection. The present work provides an experimental approach, involving a method based on the thermogravimetric analysis, for determination of the pressure dependence of average boiling points (or in other words for determination of "the vapour pressure curve corresponding to average boiling points") of oil fractions with narrow boiling ranges, pre-prepared by distillation. This method can be used for determination of the atmospheric average boiling points (corresponding to atmospheric pressure) of thermally unstable fractions from the pressure dependence curves, obtained from the tests conducted at lower pressures. The method uses the principle of ASTM E1782 “Standard Test Method for Determining Vapor Pressure by Thermal Analysis”, where the material is vaporised at pre-determined pressure from a hermetically sealed capsule through a pinhole using a constant heating rate experiment. The accuracy of the method was evaluated on the basis of the average boiling point values of narrow boiling ranges fractions determined by rectification both at atmospheric pressure and in vacuum (determined as the arithmetic mean of the lower and upper temperature limits of the fraction). The pressure dependence curves of the average boiling points, formed here on the basis of average boiling points obtained in the pressure range from 5 kPa to atmospheric pressure, can be reliably described by the integrated Clausius-Clapeyron equation. To increase the accuracy in determining the atmospheric average boiling points of thermally unstable fractions, obtained in extrapolation from the Clausius-Clapeyron curve of the average boiling points in the tests conducted at lower pressures, a higher number of tests, on the basis of which to conduct the extrapolation, is desirable.

    更新日期:2019-11-26
  • Experimental investigation of effect of temperature on ignition behaviour of seeded refined kerosene
    Thermochim. Acta (IF 2.251) Pub Date : 2019-11-23
    Aldin Justin Sundararaj, B.C. Pillai, K.R. Guna

    Nano additives in fluid has been of great interest for researchers in recent times due to the improvement in heat carrying capacity. The current study focuses on the effect of temperature on the ignition behaviour of nano additive with refined kerosene. The investigation is carried out for volume fractions of 0.01%, 0.05% and 0.1% of alumina-refined kerosene and aluminium-refined kerosene respectively. Two different experimental methods are used to investigate the ignition behavior of seeded refined kerosene. First method: The ignition probability was measured experimentally using hot plate. The temperature range studied for ignition probability is from 200 °C to 480 °C. Second method: Tests were carried out in shock tube to determine ignition delay of the seeded refined kerosene. The study is carried out for the temperature range of 950–1450 K in a shock tube. The driven section of the shock tube is maintained at an oxygen-rich condition. The pressure range is limited to 4 to 10 atm. The experimental investigations confirms, irrespective of alumina or aluminum nanoadditives the ignition probability increased with the increase in temperature. The ignition probability also increased with an increase in volume fraction of seeded refined kerosene. However the ignition delay did not have much significant effect on the low volume fraction of 0.01% and 0.05%. With the increase in volume fraction and temperature, the effect on ignition delay is prominent.

    更新日期:2019-11-26
  • An in-depth analysis of some methodical aspects of applying pseudo-adiabatic calorimetry
    Thermochim. Acta (IF 2.251) Pub Date : 2019-11-22
    Arcady Kossoy

    The Accelerating Rate Calorimeter (ARC) - the first representative of the family of pseudo-adiabatic calorimeters - was designed for assessing reactive hazards of chemical processes. Over time the ARC and similar instruments have found much wider applications such as testing of reactive substances, study of reaction kinetics, design of the emergency relief systems. In all these cases precise knowledge about the current state of the sample is required. There are numerous publications regarding the methodical aspects of pseudo-adiabatic calorimetry but many problems are still waiting for the solution. The aim of this paper is to consider in detail the following serious problems: non-uniformity of the system "sample + bomb"; absence of equilibrium between sample and bomb; variability of thermal inertia; uncertainty of the state of reacting system at the onset. The results presented here demonstrate that in many cases the basic assumptions used for interpretation of adiabatic data can be violated and due attention should be paid to the conditions of an experiment that allow it to remain within the applicability limits of the method.

    更新日期:2019-11-22
  • Enhancing thermal properties of polybenzoxazine by incorporation of 4-cyanophenol
    Thermochim. Acta (IF 2.251) Pub Date : 2019-11-22
    Yongfei Zhu, Junming Su, Runsheng Lin, Yuhua Jiang, Peilin Li

    In order to study the effect of strong electron-withdrawing group on thermal properties of polybenzoxazine, 4-cyanophenol-based benzoxazines were prepared and their cured samples were investigated by FTIR, TGA, TGA-FTIR, Py-GC-MS and LOI tests. FTIR results indicate that nitrile group hardly polymerized and existed in polybenzoxazine at present cured conditions. TGA results show that the introduction of nitrile group in phenol could remarkably improve the char yield at 800 °C, thermal and thermo-oxidative stability of polybenzoxazine compared with the analogous polybenzoxazines without electron-withdrawing group. Moreover, nitrile group decreased the charge density of phenolic ring and made hydroxyl be cleared more easily, the free hydroxyl not only could oxidize -CH2- of -CH2-NR-CH2- in polybenzoxaizne into CO2 but also transformed into H2O, resulting in that there was always a volatilization of CO2 and H2O during thermal degradation process. Furthermore, the incorporation of nitrile group also increased significantly the flame retardancy of polybenzoxazine.

    更新日期:2019-11-22
  • Measurements of isobaric heat capacity of R143a and R227ea at liquid phase by quasi-steady scanning
    Thermochim. Acta (IF 2.251) Pub Date : 2019-11-16
    Yi-jian He, Shu-peng Zheng, Guang-ming Chen

    A modified heat conduction calorimeter was developed and utilized in experiments using a quasi-scanning method. The isobaric heat capacities of R143a and R227ea in the liquid phase were measured at a maximum pressure over 5 MPa and temperatures of 310.15 K-365.15 K, respectively. The relatively expanded uncertainties of the measurements were estimated to be 0.030 and 0.029 for R143a and R227ea, respectively.The measurements resulted in 27 data points for R143a and 53 data points for R227ea. All experimental data were correlated with an empirical equation. The equations showed AAD% (Average Absolute Deviations (%)) of 0.32% and 0.27% between the experimental and calculated values of the correlated equations for R143a and R227ea, respectively. In addition, the MAD% (Maximum Absolute Deviations (%)) for R143a and R227eawere 1.01% and 1.14%, respectively. Heat capacity values of R143a and R227ea in the saturated liquid state were obtained by extrapolation of the correlated equations. Furthermore, comparisons were drawn between the measured values and those reported in literature.

    更新日期:2019-11-18
  • 更新日期:2019-11-14
  • Suppression of propane cup-burner flame with HFO-1336mzz(Z) and its thermal stability study
    Thermochim. Acta (IF 2.251) Pub Date : 2019-11-14
    Xingyu Wang, Rui Wu, Lu Cheng, Xiao Zhang, Xiaomeng Zhou
    更新日期:2019-11-14
  • Simultaneous encapsulation of hydrophilic and lipophilic molecules in liposomes of DSPC
    Thermochim. Acta (IF 2.251) Pub Date : 2019-11-13
    Mariana R. Romero-Arrieta, Elizabeth Uria-Canseco, Silvia Perez-Casas
    更新日期:2019-11-13
  • Thermodynamic functions of holmium orthophosphate HoPO4 in the range 9−1370 K
    Thermochim. Acta (IF 2.251) Pub Date : 2019-11-11
    A.V. Tyurin, M.A. Ryumin, A.V. Khoroshilov, V.M. Gurevich, K.S. Gavrichev
    更新日期:2019-11-11
  • 更新日期:2019-11-11
  • Hydration kinetics and properties of cement blended with mechanically activated gold mine tailings
    Thermochim. Acta (IF 2.251) Pub Date : 2019-11-08
    Xianjun Lyu, Geng Yao, Zhiming Wang, Qiang Wang, Lin Li

    In this study, the hydration kinetics and properties of cement blended with raw and mechanically activated gold mine tailings were investigated. The results showed that the activity index of the activated tailings was 82.88%, and it is feasible to prepare blend cement from mechanically activated tailings. The Krstulovic–Dabic model could well simulate the hydration process of the paste sample blended with activated tailings, but not suitable for the paste blended with raw tailings. The addition of the activated tailings in cement reduced the hydration heat, prolonged the nucleation and crystal growth stage, and shorten the interactions at phase boundaries reaction stage. The mechanically activated gold mine tailings could react with Ca(OH)2 to form hydration products due to the pozzolanic reaction. The present experimental research provided a theoretical basis for utilizing gold mine tailings in cement as pozzolan, which would be environmentally friendly and cost-effective.

    更新日期:2019-11-08
  • Verification of Solution Calorimetry Approach for Determination of Vaporization and Sublimation Enthalpies in Different Solvents: Example of Disubstituted Benzenes
    Thermochim. Acta (IF 2.251) Pub Date : 2019-11-07
    Vladimir B. Novikov, Ilnar F. Yamaleev, Mikhail A. Varfolomeev

    Vaporization/sublimation enthalpies for twenty-one disubstituted benzenes were calculated from dissolution enthalpies and solvation enthalpies in four solvents of different polarity: carbon tetrachloride, benzene, N,N-dimethylformamide, and acetonitrile. The values of solvation enthalpy were calculated using group-additivity scheme for each solvent. Dissolution enthalpies of some substances were taken from literature and fifty-six original values were measured in the present work. The calculated values of vaporization/sublimation enthalpy were compared with the literature data. It was concluded that calculated vaporization/sublimation enthalpies do not depend on the choice of solvents excluding those that interact with the solute specifically.

    更新日期:2019-11-08
  • Phase diagrams of mixtures of n-hentriacontane and saturated monoacid triacylglycerols
    Thermochim. Acta (IF 2.251) Pub Date : 2019-11-07
    C. Tapia-Ledesma, S.B. Araujo-Díaz, E. Dibildox-Alvarado, J.J. Ornelas-Paz, J.D. Pérez-Martínez
    更新日期:2019-11-08
  • 更新日期:2019-11-06
  • Synthesis, characterization, and thermoanalytical study of aceclofenac of light lanthanides in the solid state (La, Ce, Pr, and Nd)
    Thermochim. Acta (IF 2.251) Pub Date : 2019-11-06
    Adrian Santos de Souza, Bruno Ekawa, Claudio Teodoro de Carvalho, José Augusto Teixeira, Massao Ionashiro, Tiago André Denck Colman

    Lanthanide aceclofenac compounds were synthesized by the addition of lanthanide nitrate aqueous solution to aceclofenac–acetone solution. The compounds obtained in the solid state were characterized by thermal and spectroscopic studies, as well as by complementary x-ray diffraction data. The metal–ligand stoichiometric ratio was defined by simultaneous thermogravimetry and differential scanning calorimetry (TG-DSC) as [Ln(Acec)3·nH2O], where Ln represents the metal centre (La, Ce, Pr, or Nd) and Acec represents the ligand, with n = 4(La), 3(Ce), and 2.5(Pr, Nd). TG-DSC and Fourier transform infrared spectroscopy (FTIR) data also allowed for determination of the thermal behaviour and possible coordination modes between the metal and the ligand.

    更新日期:2019-11-06
  • Curing kinetic of self-promoted alicyclic-based bisphthalonitrile monomer
    Thermochim. Acta (IF 2.251) Pub Date : 2019-11-05
    Jiangbo Lv, Zhengzhou Liu, Renke Li, Yao Liu, Jianghuai Hu, Ke Zeng, Gang Yang

    Self-promoted alicyclic-based phthalonitrile possesses outstanding properties, which would be determined by the special free radical curing mechanism and curing process. Thus, the curing kinetic of alicyclic-based phthalonitrile was studied and the curing kinetic parameters were determined by DSC at various heating rates. Double fit peaks were used to analyze the reaction processes. The autocatalytic model based on Šesták–Berggren model of DAIM-PN was confirmed. Moreover, the predicated models of DAIM-PN could fit well with the experimental values.

    更新日期:2019-11-06
  • Thermal Conductivity of Nylon 46, Nylon 66 and Nylon 610 Characterized by Flash DSC Measurement
    Thermochim. Acta (IF 2.251) Pub Date : 2019-11-05
    Kefeng Xie, Yucheng He, Jun Cai, Wenbing Hu
    更新日期:2019-11-06
  • Study of the curing kinetics of melamine/phthalonitrile resin system
    Thermochim. Acta (IF 2.251) Pub Date : 2019-11-03
    Jiangbo Lv, Jinlang Hong, Bo Liang, Erjin Zhao, Ke Zeng, Menghao Chen, Jianghuai Hu, Gang Yang

    The exploration of curing process is important for the application of phthalonitrile resins in advanced materials. In this study, the curing behaviors of 1,3-bis (3,4-dicyanophenoxy) benzene (3BOCN) and melamine (MI) system was studied by differential scanning calorimetry (DSC) at different heating rates. An autocatalytic model could describe the curing reaction of 3BOCN-MI. The curing parameters including apparent activation energy, reaction orders and pre-exponential factor were calculated. The average activation energies for the three different proportions of 3BOCN-MI (8:1, 8:2, 8:3) system were 93, 98 and 96 kJ/mol, respectively. Besides, the predicted models for the reaction of 3BOCN-MI curing fitted well with the experimental data.

    更新日期:2019-11-04
  • THERMAL DIFFUSIVITY OF CAST Al-Cu ALLOYS
    Thermochim. Acta (IF 2.251) Pub Date : 2019-11-03
    A.G. Esmeralda, A.F. Rodríguez, J. Talamantes-Silva, R. Torres, N.F. Garza-Montes-de-Oca, J.R. Benavides-Treviño, R. Colás

    The regulations imposed to reduce fuel consumption by internal combustion engines and the corresponding reduction in CO2 emissions to the atmosphere has become more stringent. Industry has responded by designing smaller and lighter engines able to develop higher power outputs by increasing the temperature within their combustion chambers, although the higher temperatures may affect the mechanical and structural response of the materials, in such a way that conventional Al-Si alloys are reaching their limits. This work presents the results of studies conducted on a wide range of alloys to evaluate the dependence of their thermal diffusivity with respect to temperature, chemical composition and microstructure. The analyses show that thermal diffusivity can be enhanced by modifying their processing to achieve grain refining and precipitation coarsening. It is also found that thermal diffusivity is enhanced at higher temperatures.

    更新日期:2019-11-04
  • Observation of Dipolar-glass Transition by Adiabatic Calorimetry in C5NH6(BF4)1−x(PF6)x Solid-solution System
    Thermochim. Acta (IF 2.251) Pub Date : 2019-11-02
    Masaki Nomoto, Minoru Hanaya

    In order to elucidate a dipolar-glassy state realized in the solid-solution system of PyH(BF4)1−x(PF6)x (Py = C5NH5) at low temperatures, we investigated thermal properties of the solid solutions by adiabatic calorimetry. The solid solutions with the compositions x = 0.18, 0.51, and 0.89 exhibited enthalpy relaxations characteristic of glass transitions respectively between 30 and 90 K. The enthalpy relaxation time of 103 s at the glass transition temperature was well reproduced by the temperature dependence of dielectric relaxation times obtained by dielectimetry for each solid-solution sample. The result indicates that the calorimetrically observed glass transition is the dipolar-glass transition, and the dipolar-glassy state is revealed to be a thermodynamically non-equilibrium state where the configuration of the electric dipoles are frozen in by slowing down of the thermally activated reorientational motion of the dipoles.

    更新日期:2019-11-04
  • Vibrational heat capacity of the linear 6,4-polyurethane
    Thermochim. Acta (IF 2.251) Pub Date : 2019-11-01
    A. Czerniecka-Kubicka, W. Zielecki, W. Frącz, M. Janus-Kubiak, L. Kubisz, M. Pyda
    更新日期:2019-11-01
  • Effect of Sm on Crystallization Kinetics of Cu-Zr-Al Metallic Glasses
    Thermochim. Acta (IF 2.251) Pub Date : 2019-10-31
    F. Sıkan, G. Polat, I. Kalay, Y.E. Kalay

    The effect of Sm micro-alloying on non-isothermal and isothermal crystallization kinetics of (Zr50Cu40Al10)100-xSmx (x = 0, 2, 4 at. % Sm) alloys were investigated using differential scanning calorimetry (DSC), transmission electron microscopy (TEM), and X-ray diffraction (XRD). Crystallization activation energies for each composition were calculated in non-isothermal conditions using Kissinger and Ozawa methods and in isothermal conditions using Johnson-Mehl-Avrami model. XRD analysis showed that crystallization product Cu10Zr7 changes to Cu2Sm with Sm presence in isothermal conditions. Both isothermal and isochronal calculations yield that the energy barrier for crystallization has increased with Sm addition. On the other hand, crystallization point drops to lower temperature at the expense of an increase in the pre-exponential factor. The Avrami exponents for all compositions were found to be below 2.5, indicating that crystallization was governed by a diffusion-controlled three-dimensional growth with a decreasing nucleation rate. The apparent increase in crystallization activation energies with increasing Sm content can be one of the affecting factors for commonly held idea of increased glass forming ability for rare-earth containing Zr-based metallic glasses.

    更新日期:2019-11-01
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