The pyrochemical properties of the naturally compact pyrophyllite from Shôkô-Mountain were investigated in detail. The comparative study on ceramic properties was also made about cut-off samples and wet ball-milled samples.
The mineralogical compositions of this sample were 23% fine-grained quartz, 4% sericite, and a little kaolinite. The ground sample lost the combined water between 400° and 800°C, and the compact sample between 500° and 900°C without breakdown of the crystal lattice, but the specific surface area, which was determined by BET method, gave the maximum value with 700°C fired sample. The specific gravity decreased from 500° to 800°C rapidly. The apparent porosity and the water absorption of the fired compact sample increased from 600° to 900°C, and then decreased slowly; but with the ball-milled sample these properties decreased from 900°C and rapidly from 1100°C. The fired volume change was also different, the compact sample indicated permanent expansion from 600° to 1400°C, but the ground sample contracted from 1000°C. The bending strength of the compact sample decreased rapidly from 1300°C, but the ground sample increased from 1200°C rapidly. Samples which were fired between 900° and 1300°C gave very low thermal expansion, but samples fired above 1350°C gave marked cristobalite effect. The moisture expansion of the compact sample which was fired above 1100°C showed almost negligible value, but under the 1100°C fired sample showed some degrees of moisture expansion. On the contrary, ground sample showed marked moisture expansion above 1100°C.

抄録全体を表示

Cobalt-substituted 2MgO⋅SnO₂, xCoO⋅(2-x)MgO⋅SnO₂, reveals brilliant blue, socalled cerulean blue. On the contrary, cobalt-substituted 2ZnO⋅SnO₂, xCoO⋅(2-x)ZnO⋅SnO₂, reveals greyish green. In cobalt-substituted NiO⋅MgO⋅SnO₂, xCoO⋅(1-x)NiO⋅MgO⋅SnO₂, blue colors develope, while in cobalt-substituted NiO⋅ZnO⋅SnO₂, xCoO⋅(1-x)NiO⋅ZnO⋅SnO₂, bluish green colors.
To observe the influence of tetrahedral and octahedral preference of cations such as Mg²⁺, Zn²⁺, Co²⁺, Ni²⁺ and Sn⁴⁺ upon the formation and the color development of the tin spinels, the gradual substitution of Zn²⁺ for Mg²⁺ of the spinels in CoO-MgO-SnO₂, NiO-MgO-SnO₂ and CoO-NiO-MgO-SnO₂ systems was carried out. On samples prepared by calcining the oxide and basic carbonate mixtures at 1300°C for 1 hour, the reflectance between 400-760mμ was measured by self-recording spectrophotometer, and the X-ray analysis was also carried out to observe the spinel formation and calculate the lattice constant. The results were summarized as follows.
1. CoO-MgO-ZnO-SnO₂ system.
All samples prepared according to 0.2CoO⋅(1.8-x)MgO⋅xZnO⋅SnO₂, 0.5CoO⋅(1.5-x)MgO⋅xZnO⋅SnO₂ and CoO⋅(1-x)MgO⋅xZnO⋅SnO₂, revealed the formation of single spinel. In these systems, in the case of x=0, fresh blue developed, giving deep absorption characteristic of tetrahedral Co²⁺ ions at about 550-680mμ. But with increasing the amount of x, the absorption in this region became shallow to some extent, while the absorption at about 400-540mμ became deep. Therefore color changed from blue to greyish green in Zn²⁺ ion-rich region, showing the absorption of octahedral Co²⁺ ions owing to the strong tetrahedral preference of Zn²⁺ ions.
2. NiO-MgO-ZnO-SnO₂ system.
In nickel-substituted 2MgO⋅SnO₂, xNiO⋅(2-x)MgO⋅SnO₂, the spinel formation became difficult with increasing the amount of Ni²⁺ ions, owing to the lack of cations occupying the tetrahedral interstices. (Ni²⁺ and Sn⁴⁺ ions have octahedral preference and Mg²⁺ ion also seems to be the same because MgO is of rock salt type.) NiO⋅MgO⋅SnO₂ was identified by X-ray analysis to be composed of no single spinel, but a mixture of SnO₂, NiO-MgO solid solution and spinel. Only the diffraction peaks of NiO and SnO₂ were observed in the calcined sample of 2NiO⋅SnO₂. In this system zinc-substituted NiO⋅MgO⋅SnO₂ was prepared according to NiO⋅(1-x)MgO⋅xZnO⋅SnO₂. The spinels were obtained in the range of x≥0.5. The color became some what bluish in the case of x=0.5, owing to the absorption of tetrahedral Ni²⁺ ions, In Zn²⁺ ion-rich region however, this absorption diminished, and in NiO⋅ZnO⋅SnO₂ only the absorption of octahedral Ni²⁺ ions was observed.
3. CoO-NiO-MgO-ZnO-SnO₂ system.
Samples with the composition of 0.1CoO⋅0.9NiO⋅(1-x)MgO⋅xZnO⋅SnO₂, 0.2CoO⋅0.8NiO⋅(1-x)MgO⋅xZnO⋅SnO₂ and 0.5CoO⋅0.5NiO⋅(1-x)MgO⋅xZnO⋅SnO₂ were prepared. Cobalt-substituted NiO⋅MgO⋅SnO₂,

抄録全体を表示