Various hydrothermal treatments have been carried out for mesoporous silica particles. The hydrothermal treatments are classified into two categories according to the phase in which reactions progresses. In liquid phase, reactions were initiated by immesrsing silica particles in various solutions, whereas in gas phase, silica particles were exposed to water vapor under high pressure by means of autoclave. By measuring increases in immersional heat and H-bond type silanol density, progress of the rehydration of surface siloxane is quantified in both methods. Particulary in liquid phase, rehydroxylation was significantly promoted by the addition of basic substances and also at high temperature. On the other hand, in gas phase, nitrogen and water adsorptions change geometric structure of silica particles in addition to rehydroxylation. This is because dissolution of silica surface, redeposition of the solute and consequently the rehydration occurred in the process of hydrothermal treatments in gas phase. The dissolution progressed significantly with temperature higher than 160°C

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We noticed that the boundary condition on the top surface of the consolidated bed in the theoretical calculations was incorrectly imposed in ref.1) and ref.2). Revised calculations are presented in this paper. In ref.1) a new theory for the constant load consolidation was proposed together with a convenient boundary conditions on the bottom of the consolidated bed (Eq. (7) in this paper) which assumed that the void ratio suddenly jumped to the final value immediately after the loading. If strict forward consideration is assumed, the boundry condition (BC) should be varied with time according to the increases in friction and particle network stress, i. e., Eq. (8) has to be imposed in place of Eq. (7). However, the previous calculations together with Eq. (7) predicted the observed consolidation curves even until middle of the consolidation period. To overcome this contradiction is the main objective of this work. Variable load consolidation experiments are compared with theoretical calculations for both BC's. Calculations for frictionless wall on the constant load are also conducted and discussed. It is concluded from these examinations that during the constant load consolidation the stress hardening must occur after the loading to balance out the extra load until strain in the bed reaches to a normal stressstrain relation, since strain could develop only when dewatering from the bed has progressed. Modified theory including the stress hardening and recovery process predicts consolidation experiments quite well for the whole period of the consolidation. Master curves for the constant load and the variable load consolidations are also presented.

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An image analyzing technique was applied to evaluate the dispersion state of chopped aramid fibers (average diameter: 12μm and aspect ratio: 83.3) in matrix powders. In order to measure the fiber distribution in the fluffy fiber-powder mixtures just after mixing operation, the mixture samples were pre-pressed to one-fifth in volume at a constant pressure and formed into disk shape with molding epoxy resin. In the range of fiber-powder ratio at which fibers are unravelable the total number of fibers lying in the cross-section of molded test piece was proportional to the initial fiber concentration being independent of the degree of dispersion state. The experimental values agreed well with the estimated number of fibers based on a simplified arrangement model. Therefore, it has been shown that evolution of fiber dispersion state could be discussed with the coefficient of variation, Cυ. Further it ascertained that the bulk density of unraveled sample, ρ₀ of the fiber-powder mixture is one of the effective indices for expressing the degree of dispersion.

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