Hydroxides containing Zr and Ce were coprecipitated from Zr nitrate and Ce chloride solution by addition of NH₄OH. CeO₂ content in the samples was ranging from 0 to 21mol% CeO₂. Calcination was carried out at 1, 000°C for 3 hours. Then the powder was pressed by isostatic pressure of 4, 000kg/cm². Sintering was done at 1400°C for 1.5 hours in a SiC electric furnace and at 1, 670°C for 1.5 hours in a city gas furnace.
12mol% CeO₂ sample did not show expansion due to transformation of ZrO₂. Tetragonal ZrO₂ solid solution had 22.1kcal/mol of activation energy for electrical conduction, cubic ZrO₂, however, had 30kcal/mol. In the case of 12mol% CeO₂ mixture, electrical conductivities at 700°C, at 1, 000°C and at 1, 300°C were 1.57×10⁴ ohm-cm, 1.34×10³ ohm-cm and 3.24×10² ohm-cm respectively.
Transformation temperatures from tetragonal phase to monoclinic were identical both by method of electrical resistance and by dilatometric method. Thermal expansion of 12mol% CeO₂ showed 1.07% up to 1, 100°C. Lattice constants of solid solution were increased with increase of CeO₂ content.
Evaluation of the ZrO₂-CeO₂ mixtures sintered at 1, 400°C for 1.5 hours in the SiC furnace as oxide heating elements, was worse than mixtures in the system ZrO₂-CaO or ZrO₂-Y₂O₃, because of value of electrical resistance and activation energy of electrical conduction.

抄録全体を表示

In the manufacturing process of clay refractory or in the use, the color change occurs frequently with degradation of the clay refractory. To obtain fundamental data on these phenomena, behaviors of Fe₂O₃ in the mullite specimen containing 5% of Fe₂O₃ in solid solution and in the mixed specimen of mullite and 5% of Fe₂O₃ were examined.
Specimens of both types were heated from 800° to 1, 300°C in the atmosphere of CO, O₂ and N₂. The result by the measurement of lattice constant and color change of mullite showed that:
1. When the mullite containing Fe₂O₃ in solid solution was heated at higher temperatures in oxygen stream, lattice contraction of the mullite and color change were observed. This might be attributed to the partial reduction of solid soluted Fe₂O₃.
2. The amount of Fe₂O₃ solid soluted in mullite in the mixture of 5% of Fe₂O₃ and mullite in nitrogen stream was more than that in oxygen stream.
3. In the mullite-Fe₂O₃ system in which 5% of Fe₂O₃ was contained, the brightness of the specimen became higher as the amount of Fe₂O₃ solid soluted increased.

抄録全体を表示

Aluminum nitride (AlN) sublimates at 2, 450°C and does not possess a liquid phase under ordinary pressure. Since the sintering proceeds by solid diffusion, sintered samples do not have enough mechanical strength to be useful as a refractory. The sintering of the AlN-Al in N₂ of one atmospheric pressure was studied. The authors attempted to bind AlN particles by molten Al and then change Al matrix into AlN by nitriding reaction.
Samples with Al contents different by 5% from 0 to 20%, were formed under the pressure of 5ton/cm², and sintered at 10 different temperatures between 500°C and 1, 400°C in N₂ of one atmospheric pressure. The sintered products were tested on reaction process by X-ray diffraction, density, flexural strength, thermal shock resistance, and heat resistance in vacuum. Nitriding reaction of Al began at 500°C and completed. up to 700°C. The density of samples with the Al content of 20% was 72% of the theoretical value and the flexural strength was 3.1kg/mm². For the thermal shock test, sintered samples of AlN endured the heating and cooling between a room temperature and 1, 200°C in a minute. Weight loss by vaporization was very small up to 1, 600°C in vacuum of 10^-5mmHg.
This result was applied to manufacture the crucible for vapor deposition of Al in vacuum. High purity aluminum metal was heated in the AlN crucible in vacuum and the reaction between the crucible and molten Al was tested. The result shows that molten Al did not wet the AlN crucible up to 1, 300°C and was spherical as a drop of mercury. The result also shows that although the crucible was wetted by Al due to the falling of the viscosity of Al above 1, 300°C, the AlN crucible was not eroded by molten Al.

抄録全体を表示

Water content of BaO-P₂O₅ glasses prepared by various preparation conditions was determined by chemical analysis and the effects of the residual water on the transformation temperature and the structure of these glasses were investigated. Following conclusions were obtained.
(1) The transformation temperature of the glasses is exceedingly influenced by preparation condition.
(2) The cause of such a variation of transformation temperature is attributed to the change of water content in the glasses.
(3) Water content in the glasses is 1-3 wt% and varies according to preparation condition and composition.
(4) The cause why such a considerable amount of water is contained in the glasses is attributed to the nature of the chemical bond of PO₄ group; that is, the branching point P*O₄ group is unstable according to Van Wazer's “Antibranching Rule of PO₄ group”. Therefore, it is assumed that the residual water in the glasses exists as OH group as in the following.
-O-^O|P_|O|-*O-^O|P_|O|-*O-^+H₂O→_^←-H2O2[-O-^O|P_|OH-O-]
(5) Considering “Antibranching Rule” and high volatility of P₂O₅ component, the preparation of water free BaO-P₂O₅ glasses is impossible.
(6) Since the water in the glasses can be regarded as the network modifier in the glass structure, residual water has a great influence on the transformation temperature of the glasses.

抄録全体を表示