NetsuSokutei   30(1), 3-8 (2003)

Thermal Stability of Materials Used in Lithium-Ion Cells

Jun-ichi Yamaki

Lithium-ion (abbreviated as Li-ion) cells are widely used as power sources for portable electric devices. Recently, the study of the utilization of the high-performance Li-ion cells as power sources of electric vehicles (EV) and other large-sized equipments has been undertaken by many corporations and laboratories. However large-sized Li-ion cells are not used practically, primarily due to safety considerations. Organic compounds are used as electrolytes of Li-ion cells, and these compounds are flammable. Therefore the generation of heat by chemical decomposition and the chemical reactions in the cells is an important factor to be considered. It is not easy to measure the thermal stability of electrolytes because of their low boiling points. Although, it would be quite interesting to evaluate the stability in a closed sample case such as a cell case, there has been no previous report of such investigations. Therefore, we used DSC to measure the thermal stability of electrolytes as well as the influence of Li metal, C6Li and cathode (Li0.49CoO2) addition on the thermal behavior of these electrolytes under air tight conditions. This report reviews recent studies on thermal stability of materials in Li-Ion cells including our study.

Institute of Advanced Material Study
 
 

NetsuSokutei   30(1), 9-13 (2003)

Thermodynamic Stability and Cathode Performance of Li-Mn-O Spinel System as a Cathode Active Material for Lithium Secondary Battery

Yasushi Idemoto

We investigated the relation between the thermodynamic stability and cathode performance of lithium manganese spinels as cathode active materials for the lithium secondary batteries. The heat of dissolution of these samples was measured by the solution calorimetry method. The standard enthalpy of formation, DfH0, the enthalpy change of reaction, DH, and the enthalpy change per mole of atoms for the formation reaction, DHR, were calculated from the heat of dissolution. The larger ィ「DHィ「 or ィ「DHRィ「 means a thermodynamically more stable sample. A more thermodynamically stable sample makes a stable crystal structure and leads to a good cycle performance.

Dept. of Pure and Applied Chemistry, Faculty of Science and Technology, Tokyo Univ. of Science
 
 

NetsuSokutei   30(1), 14-17 (2003)

Evaluation od a Negative Electrode Material for a Lithium Ion Battery Using an Immersion Heat Analysis

Jun Aragane

For the evaluation of the chemical properties of the anode active materials for the lithium ion battery, the immersion heat analysis method was studied. The immersion heat is detected when the anode active material like graphite is immersed in organic solvent. The heat value depends on the graphite structure. It was found that the anode active materials were separated in the point of immersion heat.

Energy Technology Dept., Advanced Technology R&D Center, Mitsubishi Electric Corp.
 
 

  NetsuSokutei   30(1), 18-24 (2003)

Thermal Behavior of Lithium-Ion Cells during Charge and Discharge

Yoshiyasu Saito

Calorimetry of lithium-ion cells that were commercially available was carried out to characterize the thermal behavior of the cells during charge and discharge. The generated heat was mainly caused by the entropy change of the cell reaction and the electrochemical polarization.  However, in the cell using non-graphitizable carbon material as the anode, complicated heat generation behavior was observed with hysteresis in charging and discharging voltage. Thermal behaviors due to crystal phase transition of the cathode active materials and due to variation of stage structure of graphitic carbon as the anode materials were also observed. Temperature dependency of the crystal phase transition of the cathode active materials was also discussed. Calorimetry could be one of effective methods to characterize the performance of lithium-ion cells.

Energy Electronics Institute, National Institute of Advanced Industrial Science and Technology
 
 

  NetsuSokutei   30(1), 25-30 (2003)

Development of a Microcalorimeter for Detecting the Output Energy of nW

Kenji Tsutsumi。、Yo Kobayashi, Seiichi Hagiwara, and Michihiro Miyake

The basic examination has been made for the development of a calorimeter detecting a nano-watt output voltage and an efficiency of a newly constructed calorimeter has been tested.
The representative improvements of the calorimeter are as follows; (1) improvement of the thermomodule for the exclusion of temperature noise incident to atmospheric pressure change, (2) improvement of a circuit regulating the sensibility of the thermomodule for the reduction of the base-line drift, (3) temperature stabilization of a water bath immersing the calorimeter, and (4) elimination for the electrostatic and electromagnetic coupling noise. The precision of the calorimeter was less than 0.02 mV 4 K。ン1 24 h。ン1(0.18 mW) for the base line drift in a long time and 0.016 mV (0.144 mW) for the noise-level of the base line.
The linear relation of the thermal detection to the step-wise supply of the electric energy by about 1 mW has been found in the devised calorimeter. As an efficiency test of the calorimeter, calorimetric measurement of a Zn/O2 coin-type cell at low generating power has been carried out, resulting in good effect.

Calorimetry Center, Tokyo Riko Co., Ltd.
 
 

NetsuSokutei   30(2), 54-65 (2003)

Mixing Schemes in Binary Aqueous Solutions of Non-electrolytes

Yoshikata Koga

Our thermodynamic studies on Mixing Schemes operating in aqueous solutions of non-electrolytes are reviewed. We use the data of higher order of G than hitherto utilized. Generally there are three distinctively different Mixing Schemes present over the entire composition range. Some details of each Mixing Schemes are described as much as known at this time. The findings by other techniques are also discussed where applicable.

Dept. of Chemistry, The University of British Columbia
 
 

NetsuSokutei   30(2), 66-75 (2003)

Theoretical Estimations of Thermodynamic Quantities of Solutions by using the Integral Equation Theory

Masaharu Ohba

If we want to get the deep understandings for the behavior of thermodynamic quantities of solutions in connection with its microscopic structure, we must proceed to the collaboration of experimental study with theoretical ones. In this article, the outline of the integral equation theory of solutions is described, because the integral equation theory is the representative theory to describe the structure and thermodynamic properties of solutions on the same theoretical bases. At first, the basic properties of distribution functions are discussed. Next, the relations of thermodynamic quantities with the distribution functions and the integral equations on the distribution functions are summarized. Finally, calculated results are shown in the cases of excess enthalpies and partial molar enthalpies of binary mixtures as an example of an attempt to construct the intuitive image for the behavior of solutions on the rigorous theoretical basis.

Dept. of Applied Biochemistry, Faculty of Agriculture, Meijo Univ.
 
 

NetsuSokutei   30(2), 76-84 (2003)

Excess Thermodynamic Functions of Binary Liquid Mixtures Using Rayleigh Laser Light Scattering

Gerald R. Van Hecke and Robert A. Westervelt

Rayleigh light scattering ratios obtained using a laser light source, combined with molar volume and refractive index measurements, were used to evaluate the excess Gibbs potentials of mixing in binary liquid mixtures. When these quantities are measured as functions of temperature, as well as composition, the excess enthalpy and entropy of the binary mixtures can be obtained. This contribution presents the pertinent experimental techniques and data analyses necessary to extract excess Gibbs potentials from light scattering measurements. Data is presented for one representative system consisting of toluene and propan-2-ol mixtures.

Department of Chemistry, Harvey Mudd College
 
 

NetsuSokutei   30(3), 98-105 (2003)

Phase Transition of Organic Molecular Crystal Observed by Thermal Diffusivity

Naoko Miyamoto, Junko Morikawa, and Toshimasa Hashimoto

Fourier transform temperature wave analysis (FT-TWA) is proposed as a method to observe the phase transition of organic molecular crystals. By analyzing the harmonics of temperature wave, it enables a simultaneous measurement of thermal diffusivity as a function of frequency and temperature. This technique was applied to a temperature range including the solid-solid or the solid-liquid phase transition of n-alkane, 1-alkanol, 1-alkanoic acid and its esters. Thermal diffusivity of n-alkanes showed a rapid fall-off on each phase transition and the odd-even effect of carbon number was observed. The frequency dependence of thermal diffusivity just below the melting temperature was observed only for n-alkanes and 1-alkanol, which showed a clear solid-solid phase transition with a conventional method. The effect of terminal group on thermal diffusivity was also examined.

Department of Organic and Polymeric Materials, Tokyo Institute of Technology
 
 

NetsuSokutei   30(3), 106-110 (2003)

Development of a Twin Type Conduction Calorimeter with a Vacuum Chamber for Radioactivity Measurements

Seikichi Iwamoto, Seiichi Hagiwara, and Tsuguo Genka

A twin type conduction calorimeter having a vacuum chamber was developed for high sensitive measurements of radioactivity of radionuclides with lower noise level and smaller baseline drift. The object of present experiment was to investigate the effect of low pressure (around 0.67 Pa) atmosphere on the thermal noise and baseline drift of the calorimeter output. The results showed lower thermal noise, 0.015 mV p-p, (0.09 mW), smaller baseline drift, 0.015 mV p-p, (0.135 mW), and higher sensitivity, 0.17 mV mW。ン1 in comparison with a conventional calorimeter operated in the atmospheric pressure.
Small amount of thermal power evolved from the radioactive sample of carbon-14 (Ba14Co3) sealed in a glass vial was non-destructively measured using this calorimeter.
The radioactivity of C-14 was determined from the measured thermal output of 3.56 mW。゛1.58 % (standard deviation) and its overall uncertainty was estimated by considering various factors. Consequently the result was found to be 450 MBq (12 mCi) 。゛4.9 % (in 99.7 % credibility limit). The result suggested more than 10 times improvement in sensitivity of radioactivity measurement was attained.

Tokyo Riko Co.,Ltd., / Frontier R&D Center, Tokyo Denki Univ.
 
 

NetsuSokutei   30(3), 111-115 (2003)

Thermal Properties of the Liquid Silk for Silkworms 。ン Domestic and Mutant Domestic and Wild Silkworm 。ン

Toshihisa Tanaka, Yoshiko Magoshi, and Jun Magoshi

The thermal properties of liquid silk obtained from the domesticated silkworm (Bombyx mori), the mutant domesticated silkworm (Sericin cocoon silkworm, Nd-s), and four wild silkworms (Samia cynthia ricini, Dictyoploca japonica, Antheraea pernyi and Antheraea yamamai) were investigated by differential scanning calorimetry (DSC).
The weak endothermic peak in the DSC curves for the liquid silk of the domestic silkworm corresponded to the breaking of hydrogen bonds in the a-form of fibroin. The process of crystallization of the liquid silk differed between domestic and wild silkworm. The starting temperature of transition for the liquid silk of the domestic silkworm was calculated.

Dept. of Biopolymer, National Institute of Agrobiological Sciences, and Core Research for Evolutional Science and Technology
 
 

NetsuSokutei   30(3), 116-124 (2003)

Enthalpies of Sublimation after a Century of Measurement: A View as Seen through the Eyes of a Collector

James S. Chickos

Measurements of sublimation enthalpy are reviewed from an empirical perspective. Some of the reasons responsible for the lack of agreement between measurements are discussed and some general advice is given to prospective users of the sublimation enthalpy data.

Dept. of Chemistry and Biochemistry, University of Missouri-St. Louis
 
 

NetsuSokutei   30(3), 125-130 (2003)

Solubility Parameter Prediction of Polymers by Thermal Analysis

Nobuyuki Tanaka

Solubility parameter of polymers is defined as the square root of the cohesive energy per cm3. For crystalline polymers, the cohesive energy is approximated by the sum of the heat of fusion, the heat of transition due to ordered parts in the amorphous regions, and the heat of glass transition. In this review, the methods to obtain these thermodynamic quantities by thermal analysis and as the background, the glass transition and the melting for polymers were discussed.

Department of Biological and Chemical Engineering, Gunma Univ.
 
 

NetsuSokutei   30(3), 131-136 (2003)

Changes of the Structure and Physical Properties of Polysaccharide Aqueous Solutions by Annealing

Masato Takahashi, Tokihiro Takizawa, Tatsuko Hatakeyama, and Hyoe Hatakeyama

Changes of the structure and physical properties of polysaccharide aqueous solutions by annealing are discussed based on the experimental results of viscoelastic measurements and thermal analysis. In the annealing process of polysaccharide aqueous solutions, dynamic modulus increased as functions of annealing time and temperature suggesting the change of molecular association. It was found that the solution annealed in the sol state tends to form hydrogels. Furthermore it was shown that the amount of non-freezing water in the system is closely related to the molecular association of polysaccharides and gelation characteristics. In this dtudy, the structural change of polysaccharides, such as xanthan gum and hyaluronan, in the annealing process is discussed based on the experimental results.

Faculty of Textile Science and Technology, Shinshu Univ.
 
 

NetsuSokutei   30(3), 137-145(2003)

Excess Molar Enthalpy Measurements of Multicomponent Alcohol-Ether Mixtures and

their Representation in Terms of an Association Model

Mohammad Mainul Hossain Bhuiyan, and Kazuhiro Tamura

Our recent studies on the measurement of excess molar enthalpies of alcohol-ether multicomponent solutions are reviewed in terms of a UNIQUAC associated-solution model. In this model, we have taken into account the self-association like alcohols, multicross-association of unlike alcohols and solvation between alcohols and ethers. The UNIQUAC associated-solution model, which includes association constants, solvation constants and optimally fitted binary parameters obtained solely from the pertinent binary correlation, can predict the ternary excess molar enthalpies with an excellent accuracy.

Dept. of Chemistry and Chemical Engineering, Kanazawa Univ.
 

NetsuSokutei   30(4), 154-160 (2003)

Thermal Properties of Epoxy Resins from Ester-Carboxylic Acid Derivatives of Mono- and Disaccharides

Shigeo Hirose, Tatsuko Hatakeyama, and Hyoe Hatakeyama


Mono- and disaccharides (SAC) such as glucose (Glc), fructose (Frc) and sucrose (Suc) were dissolved in ethylene glycol and each of the obtained mixture was reacted with succinic anhydride to form a mixture of ester-carboxylic acid derivatives (SAC-polyacid, SACPA). Ethylene glycol-polyacid (EGPA) was also prepared from ethylene glycol. Each of the obtained mixtures of ester carboxylic acid derivatives was reacted with ethylene glycol diglycidyl ether in the presence of a catalytic amount of dimethylbenzylamine to form ester-epoxy resins. The molar ratios of epoxy groups to carboxylic acid groups ([EPOXY]/[ACID] ratios, mol mol。ン1) were varied from 0.5 to 1.3. The contents of SACPA in the mixture of SACPA and EGPA were also varied from 0 to 100 %. Thermal properties of epoxy resins were studied by differential scanning calorimetry (DSC) and thermogravimetry (TG). Glass transition temperatures (Tg's) of epoxy resins showed a maximum value of 。ン8.1。� when [EPOXY]/[ACID] ratio was 1.0. Tg's increased with increasing SACPA contents suggesting that saccharides act as hard segments   in epoxy resin networks. Thermal decomposition temperatures (Td's) of epoxy resins slightly decreased with increasing SACPA contents, while mass residue at 500。� increased with increasing SACPA contents.

AIST
 
 

NetsuSokutei30(4), 161-166 (2003)
 

Temperature Change of Orientation Function of Polymer Crystals Evaluated by the Simultaneous DSC-XRD and DSC-FTIR Methods

Takeshi Yamada, Takafumi Watanabe, and Hirohisa Yoshida

Temperature changes of orientation functions for uniaxial drawn polypropylene (iPP) were evaluated by the simultaneous DSC-XRD and DSC-FTIR methods. In order to evaluate the orientation function with high time resolution, two-dimensional CCD detector and MCT detector were used for XRD and FTIR measurements, respectively. The crystallographic and conformational orientation functions of crystal c-axis were obtained from two-dimensional XRD profiles and polarized FTIR spectra, respectively. The uniaxial drawn polypropylene showed the melting peak with a shoulder at lower temperature side. The crystallographic orientation function of c-axis decreased and the conformational orientation function of c-axis increased at temperature below the melting. This fact suggested that the melt-recrystallization was brought into the re-organization of drawn iPP.

Tokyo Metropolitan University
 

NetsuSokutei 30(4), 167-172 (2003)
 

Analysis of Oxidation and Degradation of Polymers in Early Stage by Oxyluminescence Method

Ling Sun, Yukiko Kondo, Koji Kirisawa, Junko Morikawa, and Toshimasa Hashimoto

The oxyluminescence method was applied to fabric and subjected to a constant heating rate in air. Compared with conventional thermogravimetry, the luminescence was observed in a temperature region that is about 150。� lower than conventional standards. This temperature region corresponds to the early stage of oxidation and degradation of the selected materials. This method was used on each silk sample according to the apparent activated energy distribution, spectrum of luminescence and contrast with IR absorption spectrum. After thorough analysis, it was determined that the oxyluminescence is particularly useful in investigating the oxidation and degradation processes of polymeric materials, especially when compared with conventional method such as TGA and FT-IR.

Tokyo Institute of Technology
 

NetsuSokutei 30(4), 173-179 (2003)
 

Thermodynamic Properties of Polymer Solutions

Takahiro Sato


Various statistical thermodynamic theories have been presented so far to understand thermodynamic properties of polymer solutions. The basic model and assumptions as well as deficiency of the theories are explained. The famous Flory-Huggins theory is favorably compared with experiment only at high polymer concentrations. The cluster expansion theory for polymer systems successfully calculates the second virial coefficient in dilute polymer solutions but not the higher virial coefficients. The renormalization-group theory makes possible the calculations of the higher virial coefficients, but it is not applicable to concentrated polymer solutions. A perturbation theory extended to polymer solutions is favorably compared with experiment except for high-molecular-weight flexible polymer solutions with low concentrations.

Osaka University
 
 

NetsuSokutei 30(4), 180-188 (2003)
 

Spin State and Spin Crossover Phenomena of Perovskite-type Cobalt Oxides

Shingo Tsubouchi, Toru Kyomen, Mitsuru Itoh


It has been reported that the intermediate spin state becomes the ground state of Co ions in perovskite-type cobalt oxides and that peculiar spin-crossover phenomena occur in the oxides. The experimental facts and their interpretation on the spin state and the spin crossover phenomena of LaCoO3 and Pr0.5Ca0.5CoO3 are introduced in comparison with those in spin-crossover complexes. The spin crossover phenomena of the perovskite-type cobalt oxides are correlated with the change in electrical resistivity. It has been considered that the correlation originates from the strong Co 3d eg-O 2p hybridization connecting with the intermediate spin state. In addition, many facts imply that the roles of vibrational and magnetic energies to the spin-crossover phenomena are different between perovskite-type cobalt oxides and spin-crossover complexes.

Tokyo Institute of Technology
 
 

NetsuSokutei 30(4), 189-195 (2003)
 

Titration Calorimetry of Oil Solutions of Surface Active Substances

Ryo Murakami, Youichi Takata, and Makoto Aratono

The thermodynamic equations that take account of aggregate formation in the oil solutions were developed to analyze the enthalpy of mixing of an oil soluble substance with solvent oil measured by the isothermal titration calorimetry (ITC). They were applied to the ITC results of the oleyl alcohol-cyclohexane and -benzene mixtures. The enthalpy of aggregate formation of the alcohol molecules was obtained as -16~-20 kJ mol-1 and thus the hydrogen-bonded cyclic tetramer was supposed to be a predominant aggregate for the cyclohexane system. On the other hand, the corresponding enthalpy of the benzene systems was - kJ mol-1 and thus a hand drum-shaped aggregate or normal micelle with small aggregation number and a large quantity of solvation of the OH group was suggested.

Kyushu University

NetsuSokutei 30(4), 196-204 (2003)
 

Multiple Metastable States of Biomaterial-Water Systems Produced by Heat Treatments

Toshiharu Takizawa

Heat treatments produce the ubiquitous endothermic transitions in the differential scanning calorimetry of biological substance-water systems. The transitions appear at the temperature ranges from 20 to 60。� depending on both of the temperature and the duration of the heat treatments. The transition enthalpies per gram of water in the sample lie between 2 to 20 J g-1 for the systems containing not so much water. These ubiquitous phenomena are explained as a memory effect of various kinds of weak hydrogen bonds formed in the biological substance-water system by the heat treatments.