Bubbling behavior of a fluidized bed of fine particles caused by vibration-induced air inflow.

We demonstrate that a vibration-induced air inflow can cause vigorous bubbling in a bed of fine particles and report the mechanism by which this phenomenon occurs. When convective flow occurs in a powder bed as a result of vibrations, the upper powder layer with a high void ratio moves downward and is compressed. This process forces the air in the powder layer out, which leads to the formation of bubbles that rise and eventually burst at the top surface of the powder bed. A negative pressure is created below the rising bubbles. A narrow opening at the bottom allows the outside air to flow into the powder bed, which produces a vigorously bubbling fluidized bed that does not require the use of an external air supply system.

Anionic surfactant with hydrophobic and hydrophilic chains for nanoparticle dispersion and shape memory polymer nanocomposites.

An anionic surfactant comprising a hydrophilic poly(ethylene glycol) (PEG) chain, hydrophobic alkyl chain, and polymerizable vinyl group was synthesized as a capping agent of nanoparticles. TiO(2) nanoparticles modified by this surfactant were completely dispersible in various organic solvents with a wide range of polarities, such as nitriles, alcohols, ketones, and acetates. Furthermore, these particles were found to be dispersible in various polymers with different properties, such as thermosetting epoxy resins and radical polymerized poly(methylmethacrylate) (PMMA). A polymer composite of surface-modified TiO(2) nanoparticles in epoxy resins prepared by using the developed surfactant also possessed temperature-induced shape memory properties.

Tuning the stability of TiO2 nanoparticles in various solvents by mixed silane alkoxides.

The surface of TiO(2) nanoparticles which were well dispersed into acidic aqueous solution was successfully modified by silane alkoxides without strong aggregate formations. By adding decyltrimethoxysilane (DTMS) as silane alkoxides into the TiO(2) aqueous solution which were carefully diluted with methanol, DTMS slowly attached onto the TiO(2) surface without rapid hydrolysis and condensation reaction among DTMS. Because of the hydrophobicity of DTMS, the dispersed TiO(2) nanoparticles slowly formed flocks as DTMS reacted on TiO(2). These flocks were able to be completely redispersed into nonpolar solvents even after they were collected by centrifugation and drying under vacuum as dry powder. Furthermore the surface of TiO(2) nanoparticles have been successfully tuned by combining silane alkoxides which contains hydrophobic and hydrophilic groups such as DTMS and 3-aminopropyltrimethoxysilane (APTMS), respectively, toward their complete redispersion into various solvents. While TiO(2) nanoparticles modified by DTMS were redispersible into toluene, those modified by mixed alkoxides of 50 mol % DTMS and 50 mol % APTMS were redispersible into a mixed solution of toluene and methanol. Further when they were modified by mixed alkoxides of 25 mol % DTMS and 75 mol % APTMS, they were redispersible into polar solvents such as methanol with a little addition of acids.