Showing papers in "Journal of the Ceramic Association, Japan in 1976"

Three Phases of Potassium Titanate Fibers Obtained under Hydrothermal Conditions

Abstract: Phases obtained from the glass of the system K2O-TiO2 under hydrothermal conditions depended on the presence of potassium hydroxide in water. Using aqueous solution of potassium hydroxide, potassium hexatitanate and non-crystalline potassium titanate fibers were obtained. And using water without potassium hydroxide as starting liquid, potassium hexatitanate, potassium tetratitanate and non-crystalline potassium titanate fibers were formed, even though potassium hydroxide was formed by the dissolution of glass into water during the process.

An Experimental Observation of the Tempering of Flat Glass

Abstract: Paying attention to both the thermal fractures taking place in glass tempering process and the fracture densities of tempered glass, the experiments of oil tempering of glass were performed. From these experimental data, the following results have been obtained.1) Critical thermal conditions on which the fracture takes place in tempering are depended on both the preheating temperature of glass and Biot's number. Furthermore, stress relaxation of glass surface in visco-elastic region can be determined on the basis of the conditions mentioned above.2) There exists the linear relationship between the fracture densities and the residual surface stresses determined by the procedure of extrapolation on the basis of the curve obtained by experiments.

Effects of LiF on the Formation of BaTiO3 from BaCO3 and TiO2

Abstract: 炭酸バリウムと酸化チタンからメタチタン酸バリウムを合成する反応に対する弗化リチウムの反応促進作用を研究した. 弗化リチウムを添加すると炭酸バリウムの分解反応およびメタチタン酸バジウムの生成反応が促進されるのが認められた. 炭酸バリウム, 酸化チタンおよび弗化リチウムの三成分が共存する場合の炭酸バリウムの分解反応はこれら三成分が同時に相互作用することが必要であることを示した. この三成分の同時相互作用の際, リチウムイオンはバリウムイオンより強く炭酸塩に作用し, 酸化チタンとの反応により分解するのを促進していることを認めた. また弗素イオンはこの分解反応を促進する効果があることがわかった. 三成分の同時相互作用により生成した分解反応の中間生成物であるチタン酸リチウムと弗化バリウムはさらに反応してメタチタン酸バリウムを生成することを示した. 弗化リチウムの作用下でのメタチタン酸バリウムの生成は, このメタチタン酸リチウムと弗化バリウムの反応および弗化バリウムの弗素の作用下での炭酸バリウムと酸化チタンの直接反応の同時進行によるとして説明できる.

The Products of the Hydrothermal Treatment of Mixtures Corresponding to Ca_3Al_2O_6 Composition Adding ZnO

Abstract: Mixtures of Ca(OH)2, Al2O3 and ZnO corresponding to 100-80 (3CaO+Al2O3)+0-20 (ZnO) in composition were treated hydrothermally at temperatures between 120°C and 300°C in saturated steam condition. The treated specimens were examined with an X-ray diffractometer and a polarizing or electron microscope.The results obtained were as follows.1) The mixture of 3CaO+Al2O3 gave Ca3Al2(OH)12 at temperatures between 120°C and 220°C and a mixture of Ca3Al2(OH)12+Ca4Al6O10(OH)6+Ca(OH)2 at temperatures between 230°C and 300°C.2) The mixtures of 98-80 (3CaO+Al2O3)+2-20 (ZnO) gave mixtures of Ca3Al2(OH)12+ZnO at temperatures between 120°C and 170°C, Ca3Al2(OH)12+Ca(OH)2+ZnAl2O4 at temperatures between 180°C and 220°C and Ca3Al2(OH)12+Ca4Al6O10(OH)6+Ca(OH)2+ZnAl2O4 at temperatures between 230°C and 300°C.3) The crystals of Ca3Al2(OH)12 were appeared as characteristic dodecahedrons ranging from 4μm to 10μm in diameter. ZnAl2O4 were appeared as granular crystals ranging from 1μm to 5μm in diameter.

白金点電極アルゴン雰囲気中での安定化ジルコニアの電圧-電流-時間特性

Abstract: Voltage-current-time characteristic of stabilized zirconia with point contact platinum electrode was investigated in the temperature range of 480-650°C under Ar gas ambient. The applied voltage was chosen higher than 20 volts to give rise to deep polarization across the specimen. The current-time characteristic consisted of three stages. In the first stage of the characteristic the current increased slowly. Colored part gradually developed from cathode to anode. In this stage the ionic current predominated over the electronic current. The point at which the front of the colored part reached the anode was a transition to the second stage of characteristic, in which the rate of current increase was proportional to the current itself, where the current was of electronic behavior. Electrons thus injected were of the mobility by the order of 2×10-6cm2/V⋅sec at 580°C indicating hopping mechanism. Finally the breakdown took place. The color arose from injection of electrons from cathode.

Preparation of α-Si3N4 with Low Oxygen Impurity

Abstract: Prismatic single crystals of α-Si3N4 were prepared on a graphite susceptors by vapor phase reaction from SiCl4, N2 and H2 gaseous mixture. Growth conditions were chosen as follows; SiCl4=2.7×10-4mol/min, H2=1000cc/min, N2=1000cc/min, total pressure=1atm, susceptor temperature=1600°C, duration=3-6h.1) Oxygen and water in a gaseous mixture were analysed from electromotive force of an oxygen concentration cell and dew point. The amounts of oxygen and water supplied in the reaction vessel were 8.9×10-7mol per min and 4.46×10-8mol per min at room temperature, respectively.2) Equilibrium oxygen partial pressure at elevated temperature was calculated using the data of raw gas analysis, growth condition and JANAF thermochemical data. The results calculated in the system were as follows;Po2=3.5×10-26atm at 1300°KPo2=6.7×10-20atm at 1900°KThe values were very much lower than those of equilibrium state governed by the reduction of H2 or CO which had been used in the conventional processes.3) Calculation of equilibrium oxygen partial pressure in the system indicated the following results;1. The effect of hydrogen-nitrogen mole ratio were very small.2. Oxygen as an impurity in raw gas mixture affected Po2 distinctly at low temperature.3. Water as an impurity in raw gas mixture affected Po2 distinctly at high temperature.4) Oxygen content and structural data of α-Si3N4 crystals prepared by this method under the above mentioned conditions were compared with those already reported. It contained less oxygen (0.05-0.09wt%) than any other α-Si3N4 crystals ever prepared.