Y-Ba-Cu oxalate powder with a presumed Y:Ba:Cu molar ratio of 1:2:4 was prepared by a modified co-precipitation method and
its solid-phase thermal decomposition was studied from 25 to 1000C, the major evolved gases being H2O and CO2. The air-dried powder contained residual moisture. It required isothermal heat treatment for elimination of the evolved gases.
The melting point of the co-precipitation Y-Ba-Cu oxalate powder, determined by DSC at a heating rate of 10C min−1 was approximately 882C in N2, 949C in air and about 979C in O2. The dependence of the sintering properties of this material upon the atmosphere and the temperature is considered.
The effect of CuO on the thermal behaviour of Zr/KClO4 primer mixtures was studied by thermoanalytical techniques, and the Bruceton method and its related calculation. It was found
that the CuO catalytically promoted the decomposition of Zr/KClO4 primer mixtures and shifted the exothermic peak of DSC curves to lower temperatures. In addition, the Zr/KClO4 primer mixture containing CuO had a significant effect on the firing characteristics of electro-explosive devices.
Authors:Jinn-Shing Lee, C.-K. Hsu, and Chin-Wang Huang
The effects of Al2O3 and SiO2 additives on the crystallization of calcium phosphate glasses were studied. When the Al2O3 content was higher than 7 mol%, surface devitrification occurred in the glasses. However, for glasses with Al2O3 contents higher than 10 mol%, bulk devitrification predominanted. For the glasses with SiO2, a surface devitrification mechanism predominanted. Non-isothermal DTA techniques were applied in order to establish the
devitrification mechanism, and the kinetic parameters of crystal growth were obtained. The parameter m depends on the mechanism
and morphology of devitrification of calcium phosphate, glass containing SiO2 as additive, the values of m being lower than 1.2. These results indicate that the devitrification is controlled by the reaction
at the glass-crystal interface, or occurs from surface nuclei.
Authors:Chung-King Hsu, Jinn-Shing Lee, and Chin-Wang Huang
The kinetics of the decomposition of Y, Ba and Cu oxalates and coprecipitanted Y-Ba-Cu oxalate was investigated under a nitrogen
atmosphere on the basis of dynamic thermogravimetric data, the average activation energies of the decomposition of Y, Ba and
Cu oxalates were obtained from the slopes of the T. Ozawa plot.
The average activation energies for the dehydration of these oxalate and coprecipitated Y-Ba-Cu oxalate were also evaluated
from the thermogravimetric curves.
Authors:Jinn-Shing Lee, Chung-King Hsu, Li-Kuo Lin, and Chin-Wang Huang
Thermal decomposition of Zr/KClO4 priming compositions containing different concentration of additives, such as graphite, Fe2O3 and Al2O3 have been studied by DSC/TG techniques. The firing characteristics of these primer mixtures have also been examined by Bruceton
test and by adiabatic calorimeter. The results of these experiments suggest that strong interaction has been occurred between
KClO4 and Fe2O3 in the solid state.
Vitreous solder glasses, such as Mansol #40 and FEG-2002, are commercialized solder glasses, which are compression sealing
glasses that can be used to solder materials with expansions between 55-68⊙10-7C-1, such as Al2O3.
In order to understand and tailor the thermal behaviour of solder glasses, cylindrical-like glasses were first carefully ground
with a stainless steel mortar and pestle. Initially, no exothermic or endothermic data were obtained from the DTA/DSC curves
except those relating to melting. However, exothermic peaks appeared after the glass samples were re-melted. In this work,
kinetic parameters such as the activation energy, and the morphology of the devitrification mechanisms for two kinds of solder
glasses were also investigated, using non-isothermal DTA techniques. The activation energies ranged from 220 to 235 kJ mol-1 and the devitrification mechanism parameters were close to 1. This indicates that the devitrification mechanisms of the two
kinds of solder glasses involve surface nuclei.