“マイカ”-スポジウメン系デビトロセラムの研究

Devitrified Ceramicsに関する研究

抄録

A new ceramics, including Pyroceram, Fotoceram etc. studied in Corning Glass Works, has recently been developed in many countries. The new ceramics, the crystalline materials, devitrified from glass by heat treatment named by authors as “Devitrified Ceramics” (“Devitroceram” in abbreviation).
In our laboratory, studies were made in order to produce the heat resisting devitroceram of superior quality by means of the devitrification of glass. The devitroceram has been obtained by the following two stage heat treatment of special glasses.
The glasses whose composition (Table 1) may be regarded as the mixture of mica, Li1/3Na2/3Mg₃ (Si₃Al₁₀)F₂ and spodumene, Li₂O⋅Al₂O₃⋅4SiO₂, were subjected to the heat treatments:
(1) The glass was heated in 1 hour up to the temperature slightly higher than that of exothermic peak in thermal analysis and kept constant for 2 hours.
(2) In order to stabilize sufficiently the micro-crystals separated out the specimen was heated to 950°C in 1 hour and then to 1000°C in 2 hours.
The specific gravity and expansion coefficient of glassy and crystalline specimens given in Table 3. Although M₁₀₀ (pure mica) turned out an unstable glass having inferior workability, M₇₅S₂₅ (75 Mol. % mica, 25 Mol % spodumene) gave a mass of uniform texture composed of submicroscopic crystalls from which may be expected the highest mechanical strength among this group.
The X-ray spectrometer pattern was able to separate into two groups, one belongs to β-spodumene and the other, probably, to mica. In order to study the process of crystallization the samples of M₃₀S₇₀ and M₇₅S₂₅ were drawn out from furnace at intermediate stages of the heat treatment and then subjected to X-ray analysis. It was confirmed that from M₃₀S₇₀ came out β-spodumene as primary crystal which was followed by the separation of mica, while the order was reverse with M₇₅S₂₅.
Furthermore, the glasses were heated for 24 hours at a temperature below that of the first stage of the heat treatment. The samples taken out from time to time were analyzed by X-ray. On referring to the results of both X-ray analysis it was concluded that the separation of β-spodumene proceeds more and more easily with the increasing amount of mica composition leading to the texture of uniform and compact assembly of submicroscopic crystalls which gives higher strength.