Using powders prepared by a high-gravity reactive precipitation process, grain-controlled barium titanate ceramics were obtained under conventional sintering conditions. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, as well as dielectric measurements were used to characterize the samples. The powder was densified to >95% of theoretical density when sintered at 1200℃ (K1200), and the average grain size of the resulting ceramics was <0.5μm. Increasing sintering temperature increased the grain size and did not arise the exaggerated grain growth. The grain size significantly affects the permittivity of the resulting ceramics. Room temperature permittivity of the sample K1200 showed relatively lowvalues (2800) compared with those (typically 4143) for ceramics sintered at 1250℃, consisting of larger grains (≈1μm). The lower permittivity was attributed to an incomplete development of the tetragonal structure.

To study the feasibility of producing nanoparticles of organic pharmaceuticals using a novel high-gravity reactive precipitation (HGRP) technique, reactive precipitation of benzoic acid as a model compound was carried out in a rotating packed bed under high gravity. The main factors such as the rotating bed speed, concentration and volume flow rate of the reactants (sodium benzoate and HCl) affecting the particle size of the precipitate were studied. Particle size was measured by transmission electron microscopy. Benzoic acid was precipitated as nanoparticles as fine as 10nm. The particle size was decreased with increasing rotating bed speed, concentration and volume flow rate of the reactants. The formation of ultrafine particles was due to intensified micro-mixing of reactants in the rotating bed to enhance nucleation while suppressing crystal growth. The results have demonstrated the feasibility to produce nanodrugs by the principle of acid-base precipitating reaction using HGRP.

Preparation and characterization of porous hollow silica nanoparticles (PHSN) for controlled release applications were investigated. Through orthogonally designed experiments, the optimal synthesis conditions for the preparation of PHSN were obtained and the produced PHSN were characterized by BET, SEM, TEM and IR. Scanning and transmission electron microscopy images revealed their hollow shell-core structure and also demonstrated that the size and shape of PHSN are determined by the templating CaCO3 nanoparticles. The produced PHSN were applied as a carrier to study the controlled release behaviors of Brilliant Blue F (BB), which was used as a model drug. Being loaded into the inner core and on the surfaces of the nanoparticles, BB was released slowly into a bulk solution for about 1140min as compared to only 10min for the normal SiO2 nanoparticles, thus exhibited a typical sustained release pattern without any burst effect. In addition, higher BET of the carriers, lower pH value and lower temperature prolonged BB release from PHSN, while stirring speed showed little influence on the release behavior. It showed that PHSN have a promising future in controlled drug delivery applications.

The colloidal stability of nanosized barium titanate (BaTiO3) aqueous suspensions with ammonium polyacrylate (PAA-NH4) at different pH values has been investigated by means of zeta potential, adsorption isotherm, sedimentation, and rheology characterization. The isoelectric point of BaTiO3 powders is at pH 2.5 and the value of zeta potential is at its maximum near pH 10. The amount of leached barium ion decreases with increasing pH, but the change decreases with increasing initial pH. Adsorption of PAA-NH4 onto the surface of BaTiO3 decreases its zeta potential. Results show that PAA-NH4 adsorption follows Langmuir monolayer adsorption isotherms and the amount of PAA-NH4 required to stabilize nanosized BaTiO3 suspensions decreases as the pH increases. The mechanism of stabilization of BaTiO3 is shown to be electrosteric under the experimental conditions. Good agreement between zeta potential, sedimentation, and rheological tests is found, which identifies an optimum pH value of about 10 and an optimum dispersant concentration of about 2.0wt%, independent of the solids volume fraction of suspensions.

Adsorption of sodium salt of poly (acrylic) acid (PAANa) on nano-sized CaCO3 surface was studied by using potentiometric titration. The dispersion of nano-sized CaCO3 in water was also studied, and the viscosity of nano-sized CaCO3 slurry was measured. The results indicate that the adsorption of PAANa on nano-sized CaCO3 is significantly affected by the pH of the slurry, and the saturation adsorption amount decreases as pH value increases. The dispersion of nano-sized CaCO3 in water depends on the amount of added PAANa and also on slurry pH value. In the range of the pH values studied, the stronger the alkalinity of nano-sized CaCO3 slurry, the better is the dispersion of nano-sized CaCO3 modified with PAANa. Moreover, there exists an optimum amount of the added PAANa corresponding to the lowest viscosity of the dispersion. In short, PAANa is an effective dispersant to improve the dispersion of nano-sized CaCO3 particles in water.