For the purpose of researching the formation and the color development of titanium-tin single spinels, the gradual substitution of Sn⁴⁺ ion for Ti⁴⁺ ion in titanium spinels was carried out. Thus CoO-MgO-TiO₂-SnO₂, CoO-ZnO-TiO₂-SnO₂, NiO-MgO-TiO₂-SnO₂, NiO-ZnO-TiO₂-SnO₂, CoO-NiO-MgO-TiO₂-SnO₂ and CoO-NiO-ZnO-TiO₂-SnO₂ systems were investigated.
Each oxide mixture was calcined at 1350°C for 1 hour. The reflectance between 400-760mμ was recorded by self-recording spectrophotometer to pursue the displacement of absorption and to represent the result by C. I. E. color specification. X-ray analysis was also carried out to observe the spinel formation and to calculate the lattice constant of spinels. The results were summarized as follows.
1. Each smple was composed of single spinel and not mixture of spinels.
2. CoO-MgO-TiO₂-SnO₂ system.
In this system, samples were prepared according to 0.2CoO⋅1.8MgO⋅(1-x)TiO₂⋅xSnO₂, 0.5CoO⋅1.5MgO⋅(1-x)TiO₂⋅xSnO₂ and CoO⋅MgO⋅(1-x)TiO₂⋅xSnO₂. When x=0, brilliant hues ranging from greenish blue to green developed, giving deep absorption characteristic of tetrahedral Co²⁺ ions at about 550-680mμ. With increasing the amount of Sn⁴⁺ ions, this absorption shifted towards the violet region, owing to the contraction of tetrahedral interstices in spite of the expansion of the lattice. At the same time, the interaction between Co²⁺-Ti⁴⁺ ions being feeble, the absorption about 400-500mμ became shallow remarkably.
Therefore color changed bluish, and when x=1, clear hue so-called cerulean blue developed.
3. CoO-ZnO-TiO₂-SnO₂ system.
There was a typical difference in color between CoO-MgO-TiO₂ and CoO-ZnO-TiO₂ and between CoO-MgO-SnO₂ and CoO-ZnO-SnO₂ system. Samples of CoO-ZnO-TiO₂ system were brown, while in xCoO⋅(2-x)ZnO⋅TiO₂ dark green developed only in the range of x>1. On the other hand, samples of CoO-ZnO-SnO₂ system were greyish green. Zn²⁺ ions having gtrong tetrahedral preference, small amount, of Co²⁺ ions occupied tetrahedral interstices in these spinels. The influence of Zn²⁺ ions being more intense in titanium spinels than in tin spinels, the main absorption band of tetrahedral Co²⁺ ions appeared more distinctly in the latter. Samples of CoO-ZnO-TiO₂-SnO₂ system did not show clear hue.
4. NiO-MgO-TiO₂-SnO₂ system.
Although nickel titanate, 2NiO⋅TiO₂, and nickel stannate, 2NiO⋅SnO₂, did not exist, it was possible to substitute about 10% of the Mg²⁺ ions in 2MgO⋅TiO₂ and 2MgO⋅SnO₂ by Ni²⁺ ions at 1350°C. NiO⋅MgO⋅TiO₂ and NiO⋅MgO⋅SnO₂ did not form the single spinel owing to the lack of cations having tetrahedral preference. In this system samples were prepared acccording to 0.2NiO⋅1.8MgO⋅(1-x)TiO₂⋅xSnO₂, and light green resulting from the octahedral Ni²⁺ ions developed in all ones.
5. NiO-ZnO-TiO₂-SnO₂ system.
It was possible to substitute 50% of the Zn²⁺ ions in 2ZnO⋅TiO₂ and 2ZnO⋅SnO₂ by Ni²⁺ ions. In this system samples with the composition of NiO⋅ZnO⋅(1-x)TiO₂⋅xSnO₂ were prepared, and the

抄録全体を表示

The bursting expansion is one of the important disintegrations of the chrome bearing refractories and has been studied by synthetic spinels, chrome ores and chrome spinel grains separated from chrome ores.
The mechanism of the bursting expansion is related to formation of solid solution and is one of the phenomena of the Kirkendall effect. (a) Formation of solid solution among spinel group minerals, (b) unequal diffusion coefficients of ions in the phases, (c) movement of Pt-mark in the sample, (d) displacement of Pt-mark during heating, inversely proportional to square root of diffusion time, (e) occurrence of pores in the refractories, and (f) expansion after heat treatment and/or reaction are evidences for the fact that the bursting expansion is the Kirkendall effect. By adopting the Kirkendall effect ast he mechanism of the bursting, it is able to explain of pores and expansion after heat treatment.
The bursting expansions of synthetic spinel mixtures by a dilatometric method are divided into 3 types namely type E, type S and type L. Samples of the type E showed the bursting expansion, samples of the type S did not show the bursting expansion but showed shrinkage and samples of the type L showed a linear expansion up to 1600°C.
In the case of the chrome spinel grains, there are 2 types of E and S for the bursting. The type E of the chrome spinel grains for the bursting belongs to the type C and A of TGA curves and the type S for the bursting showed TGA curve of the type B. The type C showed the largest bursting expansion among 3 types of A, B and C and the second expansion was shown by the type A. The type B did not show the bursting.
Chrome spinel grains of No. 5 Inazumi, No. 2 Imobara, No. 12 Hinokami No. 18 Cuba and No. 19 Masinloc belonged to the type B, No. 1 and No. 6 Wakamatsu belonged to the type A and No. 3 Hatta, No. 4 Tomioto Shizunai, No. 7 Akaishi, No. 8 Philippine, No. 9 Philippine, No, 10 Hatta Main Mixture, No. 11 Tomimoto Nukahira, No. 13 Nitto, No. 14 Tsuchiya Horokanai, No. 15 Hatta Yawata, No. 16 Hatta Main, and No. 17 Nitto Washing belonged to the type C.
The bursting expansions of the 15 chrome ores by means of a bottom method were in the following order from large to small: No. 17 Nitto Washing, No. 13 Nitto, No. 10 Hatta Main Mixture, No. 9 Philippine, No. 1 Hirose, No. 6 Wakamatsu, No. 8 Philippine, No. 16 Hatta Main, No. 3 Hatta, No. 14 Tsuchiya Horokanai, No. 2 Imobara, No. 5 Inazumi, No. 7 Akaishi and the smallest No. 4 Tomimoto Shizunai.
Diffusion coefficients of ⁵⁹Fe at 1200°C and 1400°C in the system MgO⋅Cr₂O₃-iron oxide were D₁₂₀₀=2.89×10^-11cm²/sec and D₁₄₀₀=3.69×10^-10cm²/sec, respectively.
We have to consider the following points as counterplans for the bursting expansion: (a) selection of chrome spinel grains from chrome ores, (b) content of chrome spinel grains in the refractory, (c) grain size, (d) calcination of chrome ore, (e) dense structure of the refractory, (f) porous structure and (g) others.

抄録全体を表示