Suspension Chemistry Research Articles

Electrophoretic deposition of ferroelectric thin films

Abstract Doped lead zirconate titanate (PZT) thin films have been deposited by electrophoresis from suspensions of commercial PZT powder in acetone with additions of nitric acid and nitrocellulose. Suspension characteristics have been examined by zeta potential measurements. It is shown that the suspension chemistry has a marked effect so that acid concentration, binder additions and suspension age all combine to change the zeta potential and therefore the quality of the deposit. The effect of deposition/firing schedule on microstructure of the final film have been studied. Films upto 10μm thick can be produced by a multiple deposition and sintering method. Measurements of dielectric constant and dielectric loss as a function of frequency have been made before and after poling. A pyroelectric coefficient of 266μCm−2K−1 has been measured and the pyroelectric figure of merit calculated to be 1.28 × 10−5Pa−½. The films have been shown to exhibit a piezoelectric response after poling.

Macrocolloidal Transport in Membrane Filters in Slow Laminar Flows: Polarization Chromatography

Particle transport in crossflow membrane filters is the result of complex interactions originating from module hydrodynamics, suspension chemistry and external forces. Experimental and theoretical investigations of particle transport in dilute suspensions were conducted in a laboratory model membrane filter to understand fundamental aspects of macrocolloidal transport. Particle residence time distributions (RTDs) were obtained experimentally under varying hydrodynamic conditions in the filter by making pulse inputs. Under conditions of laminar flow, particle transport can be divided into two regimes: convection dominated and diffusion dominated. Convective transport is described quantitatively by theories of particle mechanics as evidenced by correlations presented regarding the first passage time as well as the peak response. Diffusive transport is demonstrated by multiple peaks in the RTDs under existing experimental conditions. Understanding these transport processes can lead to a more rational design, selection and operation of membrane systems and pre-treatment options.