All issues
Volume 20 (1993)
- Issue 4 Pages 175-
- Issue 3 Pages 111-
- Issue 2 Pages 61-
- Issue 1 Pages 2-
Volume 20, Issue 4
Displaying 1-7 of 7 articles from this issue
- |<
- <
- 1
- >
- >|
-
Kazuko Kitamura, Takeshi Tsuchida, Michio Inagaki1993 Volume 20 Issue 4 Pages 175-181
Published: October 30, 1993
Released on J-STAGE: September 07, 2009
JOURNAL FREE ACCESSMonodispersed, spherical particles of hydrated alumina were prepared by hydrolyzing of aluminum sulfate solution ([Al2(SO4)3·18H2O]=0.5∼2.0×10-3mol/dm3) at 90°C in the presence of urea ([CO(NH2)2]=0.15mol/dm3). The particle size changed from about 0.2 to 1.0μm depending on the initial concentration of aluminum sulfate in the solution. These particles were amorphous, and transformed to η-Al2O3 at 900°C and then to α-Al2O3 at 1100°C. The particles of η-Al2O3 heated up to 900°C were also monodispersed spheres and had a relatively large specific surface area of about 90m2/g.View full abstractDownload PDF (1905K) -
Takeshi Tsuchida, Kazuko Kitamura, Michio Inagaki1993 Volume 20 Issue 4 Pages 182-186
Published: October 30, 1993
Released on J-STAGE: September 07, 2009
JOURNAL FREE ACCESSThe tetrahedral coordinate Al(Al(4)) and a small amount of SO42- ions were present in monodispersed, spherical particles of hydrated alumina. During the aging in mother liquid at room temperature for ∼25days, these particles crystallized in bayerite of block-like shape accompanying with the disappearance of Al(4) and SO42- ions. It was considered that the compound having Keggin structure such as monoclinic [Al13O4(OH)25(H2O)11][SO4]3·xH2O was present as a mixture in the spherical particles of hydrated alumina.View full abstractDownload PDF (1419K) -
Kiyoshi Terayama, Toshiharu Shimazaki, Takayoshi Ishiguro1993 Volume 20 Issue 4 Pages 187-192
Published: October 30, 1993
Released on J-STAGE: September 07, 2009
JOURNAL FREE ACCESSThe present study is concerned with the burnout process of the organic binders from green bodies of super hard material fabricated by the extrusion forging method. The multi-techniques of TG, DTA and TMA were used for more high precision measurements. The green was debinded during heating from room temperature to about 700K under nitrogen atmosphere.
The fundemental data is thought to be useful to design the optimum heating curve without any crack formations, and to clarify the debinding mechanism of seramics.View full abstractDownload PDF (1239K) -
Hirohisa Satoh, Matsuhide Horikawa, Naoki Kamegashira1993 Volume 20 Issue 4 Pages 193-197
Published: October 30, 1993
Released on J-STAGE: September 07, 2009
JOURNAL FREE ACCESSNew method for the measurement of heat capacity at high temperature was developed with DSC by using the special heating patterns where the temperature region in each cycle overlaps with that in the previos or next cycle, and a procedure of multiple regression analysis was used for calculation of the heat capacity. Accuracy of this method was checked by measuring heat capacities of standard α-Al2O3 and Mn2O3 from room temperature to 850K and comparing those with the corresponding values from the references. The accuracy was within ±2.5% in relative error.
Using this method, heat capacities of nonstoichiometric compound (BaSm2Mn2)1-xO7 (x=0.000 and 0.031), whose thermodynamic data are very poor, were measured, and a (λ-type) heat capacity anomaly caused by the phase transition was observed for the stoichiometric composition. The transition temperature and the enthalpy change accompanied by the phase transition were 520K and 1.65kJ·mol-1, respectively. The difference of the heat capacity between the stoichiometric and nonstoichiometric phase at 840K was about 8J·mol-1·K-1, while difference of heat capacity predicted by Dulong-Petit's law from their chemical formula is 4J·mol-1·K-1. Thus it was considered that the values of heat capacity tends to decrease slightly with increasing nonstoichiometry.View full abstractDownload PDF (652K) -
Kusuo Narita, Taketsune Miyahara, Kiyo Yamamoto, Hisayo Kitamura, Mits ...1993 Volume 20 Issue 4 Pages 198-205
Published: October 30, 1993
Released on J-STAGE: September 07, 2009
JOURNAL FREE ACCESSThermogravimetric determination of sulfate ash was studied. The equipment was improved to carry out an accurate analysis of TG: a pan stop and a tare with the same weights as the sample container was used to eliminate hysteresis in the balance, an insulator was placed at the junction between furnace and balance, and warm water was circulated to the casing, and was protected with the magnetic shield of the balance case. Thus baseline variation was reduced to less than 20μg when the sample was heated up to 800°C. For the analysis, samples that were either hygroscopic or volatile were covered with a piece of cellophane tape and affixed securely to the interior wall of the sample container, thus sealing the sample. After the weight of container was adjusted to zero, a drop of sulfuric acid was added, the sample was heated, and the ash was weighed. The method thus permits accurate measurement of ash such as aluminum oxide, which is highly hygroscopic or its sample is either hygroscopic or volatile. With this method each measurement takes about one hour to obtain. The results are accurate and precise to a maximum error of 0.3% (2σ).View full abstractDownload PDF (1034K) -
Minoru Arai1993 Volume 20 Issue 4 Pages 206-209
Published: October 30, 1993
Released on J-STAGE: September 07, 2009
JOURNAL FREE ACCESSA method for determining the SOF oxidation temperature of the actual initiation has been needed for accurate evaluation of the performance of a diesel oxidation catalyst. In this study, TG and DTA were used. A small piece of honeycomb catalyst was used to absorb the SOF extracted from the particulate sampling filter. The SOF oxidation characteristics of catalysts were evaluated using these thermal analysis methods. The order of activation of each catalyst was determined with the inflection points in TG curves and the DTA peak points indicate the catalytic characteristics. The thermal analysis methods have been found to be effective in evaluating the performance of catalysts.View full abstractDownload PDF (520K) -
Nobuyoshi Koga, Jiri Malek, Jaroslav Sestak, Haruhiko Tanaka1993 Volume 20 Issue 4 Pages 210-223
Published: October 30, 1993
Released on J-STAGE: September 07, 2009
JOURNAL FREE ACCESSKinetic models of solid-state reactions are often based on a formal description of geometrically well defined bodies treated under strictly isothermal conditions; for real processes these assumptions are evidently incorrect. The kinetic parameters are distorted by the difference of the real process from the idealized kinetic model. In this respect, it can be useful to find an empirical function containing the smallest possible number of constants, so that there is some flexibility enough to describe real process as closely as possible. In such a case the models of heterogeneous kinetics can be assumed as a distorted case of the simpler homogeneous kinetics and then mathematically treated by multiplying an “accommodation” function. The empirical function also accommodates the deviation of the non-isothermal process from the process under the isothermal condition. The mutual dependence of the Arrhenius parameters observed empirically is recognized as a simple mathematical consequence of the exponential form of the rate constant in the Arrhenius equation, resulting from both the poorly controlled measuring condition in the thermal analysis and the false kinetic treatment. The isoconversion method allows to check the invariance of the activation energy during the course of reaction, which is the fundamental assumption in the derivation of the kinetic equation. Once the characteristic activation energy is determined, it is possible to find the kinetic model function which best describes the measured set of TA data using the two special functional relationships in the kinetic equation.View full abstractDownload PDF (2059K)
- |<
- <
- 1
- >
- >|