ABSTRACT
Slurry is usually not a final product but an intermediate one. Slurry as intermediate product is shaped and then dried before final use. Since in the shaping process slurry must have fluidity, measurement of viscosity is very important to characterize the slurry. After shaping, fluidity is not important because the slurry does not need to deform or flow; on the contrary, characterization of the thickening behavior of the slurry becomes important. A settling test is widely done to characterize thickening behavior, and it is reported that the morphology of spray-dried granules can be estimated from this settling test. Slurry composed of dense sediment makes hollow granules, whereas slurry composed of less dense sediment makes solid granules.1,2 The disadvantage of the settling test is that it takes a long time; for example, in the case of submicron particles it takes weeks or months under gravity, and even in a centrifuge it takes days. Consequently the settling test is hard to use for on-site optimization or control of production process in factories.
