Controlled struvite precipitation is a promising solution for phosphorus recovery in wastewater treatment plants. Particle size distribution of recovered struvite affects its efficacy as a fertilizer, so should be considered in the design and operation of struvite recovery reactors. This contribution analyzes the effect of varying the average shear rate (between 150 s(-1) and 876 s(-1)) and saturation index (between 0.76 and 2.96) in two different experimental set-ups. Solution pH and particle number and size measurements using an electric zone sensing method are used to monitor the process. In addition, photomicrographs are used to observe the shape of the precipitated particles. Interestingly, for identical thermochemical conditions, a higher mixing intensity, associated with the shear rate, leads to shorter induction times, faster precipitation and a greater particle density. On the other hand, for similar mixing conditions, a higher saturation index is also linked with shorter induction times, faster precipitation and a greater particle density. From the experimental data it is concluded that the effect of the fluid shear rate cannot be ignored and should be further studied in the precipitation process.

Piezoelectric materials are used in several applications, including sensors and actuators. Perovskite type ferroelectrics, specially, lead zirconate titanate (PZT), due to its excellent dielectric, piezoelectric and ferroelectric properties are usually employed. In this work, a series of Spin Coated PZT thick films were deposited on alumina and stainless steel substrates. These PZT-based films were obtained using inks containing either pArtículos or a precursor that were synthesised using a chemical method. In order to consolidate the deposit as a thick film, a thermal treatment is required after deposition on a substrate. Under temperature exposure, the PZT pArtículos tend to sinter after the elimination of the organic vehicle. Moreover, the PZT precursor transforms to crystalline PZT. Films based on the PZT precursor exhibited many cracks after treatment, while those constituted by PZT pArtículos required sintering temperatures higher than 1000 degrees C which resulted in unstable PZT structures. As an alternative, slurries forming mixtures of PZT precursor and pArtículos, varying their relative proportions, were studied to improve the properties of the films. Films generated in this study were characterized by SEM and X-ray diffractometry.

Lead zirconate titanate (PZT) Pb(ZrxTi1-x)O-3 is one of the most studied perovskite type ferroelectric materials due to its excellent dielectric, piezoelectric and ferroelectric properties. PZT particles and a PZT precursor were synthesized using a chemical method. A vehicle was added to the synthesized particles and precursor for obtaining two inks with appropriate rheological properties to be printed by Inkjet Printing. The use of an 80 mu m diameter nozzle made necessary the utilization of an energetic ball milling for assuring the dispersion of small PZT particles in the ink. After ball milling nanoparticles of 150 nm diameter were obtained. These inks were deposited on alumina and steel substrates followed by sintering using a pulsed laser of 1064 nm wavelength. The work shows the effect laser sintering has on, both inks, the one containing PZT nanoparticles and that one based on the PZT precursor. Laser processing was optimized in order to generate suitable films to be subsequently poled. The effect of poling on these films was also studied and their piezoelectric properties were measured by a compression test. The microstructural characteristics of these films were obtained by SEM and X ray diffractometry.