The effects of particle size distribution on the rheological, and other physical properties of wet ball-milled Amakusa pottery-stone, as well as the properties of the fired specimens prepared frmo the body each containing the particles of limitted size were studied. The mineralogical constitution, in particular, of the samples containing the particles of 7 microns and downwards obtained by elutriating of the milled products was also investigated.
The milling was carried out under different conditions to give the particles whose specific surface area covers from 10740 to 15170cm
2/g. The green bodies classified according to 7 different grain sizes were fired at 8 different temperatures to measure their physical properties. The results obtained are summarized as follows:
(1) By wet ball milling with rather large quantity of water the amount of particles larger than 10μ decreases with time along a logarithmic curve, while the amount of medium size particles (5μ-10μ) increases at first linearly and then slows down with the elaps of time. The rate of gain in amount of the particles finer than 2μ is rather slow.
(2) The concentrated slips prepared by this way show not only thixotropy but also dilatancy at the same time owing to their grain size distribution.
(3) The finer the grains the less is the thermal expansion of green body, while the firing shrinkage increases with increasing fineness.
(4) While the firing temperature is still low a larger shrinkage was observed with the specimens having larger surface area, but after reaching the maturing temperature the firing shrinkage completes during the schedule as long as the surface area exceeds a certain value. This means that the smaller grain size reduces the maturing temperature and broden the firing range.
(5) During the low firing range the porosity and absorption of fired specimens are influenced by the packing of particles, but in maturing temperatures such properties are mainly governed by specific surface area. The relation between the firing temperature and the bulk density, ultimate strength of the specimens is just reverse what it has with the porosity.
(6) The reflection and gloss of the fired specimens are also influenced by grain size. In low firing range these properties are affected by the surface area, while in maturing temperature they are mainly influenced by the degree of packing.
(7) The above justifies that for use of Amakusa pottery-stone in a porcelain body such grain size distribution as 43-46% under 5 microns, 34-37% 5-10 microns, 22-11% on 10 microns, whose surface area lies between 12000 and 13000cm
2/g, may be regarded as a standard.
抄録全体を表示