Ankita Bose

Sonication mediated hydrothermal process – an efficient method for the rapid synthesis of DDR zeolite membranes

The formation and growth of a DDR zeolite membrane was developed on the low cost indigenous clay–alumina substrate for separation of H2 from H2–CO2 mixture by selective deposition of oriented seed crystals, followed by secondary growth method with sonication mediated hydrothermal technique. The formation of free radicals by ultrasonic irradiation in the sonochemical method enhances the rate of nucleation which ultimately reduces the DDR zeolite crystallization time. Surface seeding not only accelerates the zeolite crystallization on the support surface but also enhances the formation of an homogenous zeolite membrane layer. The DDR seeds were synthesized by a sonication mediated hydrothermal technique within a short crystallization time i.e. 2 days and used to provide nucleation for the membrane growth. Accordingly DDR zeolite membranes were synthesized on seeded substrate within 5 days. The membrane thickness was found to be ∼26 μm. The synthesized membranes along with seed crystals were characterized by XRD, FTIR, FESEM and EDAX analysis. The performance of the membrane formed was evaluated by single gas as well as mixture gas permeation measurement for H2 and CO2. The H2–CO2 separation selectivity of the membrane increased up to 3.7 at room temperature which is more than the reported values. To the best of our knowledge, there is no report on the synthesis of a DDR zeolite membrane within 7 (2 days for seed crystal and 5 days for membrane synthesis) days by a secondary growth technique.

Characterization of RF Sputter-Deposited Ultra Thin PZT Films and Its Interface With Substrate

Lead Zirconate Titanate [Pb(Zr,Ti)O3, PZT] thin films have been extensively studied due to their possible applications in ferroelectric and piezoelectric devices. This work deals with the synthesis and characterization of ultra thin PZT films of thickness ∼100 nm deposited on Si/SiO2/TiO2/Pt(111) by RF Magnetron Sputtering under optimized deposition and post-annealing conditions. Various techniques like XRD, XPS, SIMS, SEM and TEM, have been employed to characterize the film nanostructure and the interface quality in the post-annealed films. Though the XRD results showed the formation of ∼87 vol% perovskite phase with 111 orientation, the films failed to show good electrical and ferroelectric properties. In XPS study of annealed PZT films, Pb was found to exist in both oxidised and metallic states. Both SIMS depth profiling and STEM-EDX line profile results showed that there is an enrichment of Pb along the PZT/Pt interface. This suggests interdiffusion of the elements in the film during post-annealing. It is concluded that interdiffusion of the chemical species during annealing results in Pb enrichment at the film substrate interface. In addition, the presence of ∼13% non-ferroelectric pyrochlore phase as well as some amount of Pb species present in metallic state further degrades the film quality.

Preparation and Characterization of PZT Thin Films

In analogy with Piezoelectric Wafer Active Sensors (PWAS), Lead Zirconate Titanate (PZT) thin films also seem to be promising for Structural Health Monitoring (SHM) due to a number of reasons. Firstly, PZT thin films with well oriented domains show enhanced piezoelectric response. Secondly, PWAS requires comparatively large voltage leading to a demand for thin PZT films (≪ μm in thickness) for low voltage operation at ⩽10 V. This work focuses on two different aspects: (a) growing oriented PZT thin films in ferroelectric perovskite phase in the range of (80–150) nm thickness on epitaxial Si/Pt without a seed layer and (b) synthesizing perovskite phase in PZT thin films on Corning glass 1737 using a seed layer of TiOx (TiOx thickness ranging between 30 nm to 500 nm).

Pore modification of deca-dodecasil-rhombohedral zeolite membrane by carbon loading from in situ decomposition of 1-adamantanamine for improved gas separation

A simple method of pore modification coupled with the removal of surface defects of a deca-dodecasil-rhombohedral (DDR) zeolite membrane has been developed via carbon (C) deposition. Carbon deposition was achieved by controlled decomposition of the structure-directing agent (SDA), 1-adamantanamine (1-ADA), into the membrane pore surface. Membranes that were synthesized with and without pore modification were characterized by thermal analysis, X-ray diffraction analysis, infrared spectroscopy, transmission electron microscopy, and Raman spectroscopy. Finally, the performance of the membranes was evaluated by permeance studies. The non-wetting characteristics of C had imparted hydrophobicity to the membrane pores, leading to enhanced permeability of the gas mixture. Modified membranes were shown to offer a relatively high hydrogen permeance of 13.47 × 10−7 mol m−2 s−1 Pa−1. The selectivity of H2/CO2 was 4.9 based on single gas permeation and the separation factor increased to 8.5 for a H2–CO2 gas mixture at room temperature. In the light of these findings, the current technique is proposed to be useful for making a defect-free C-loaded membrane in a single step with high separation selectivity and permeability in tandem. This is the novelty that was achieved.

Diffusion patterns of gas flow through clay alumina supported DDR ZeoliteMembrane

Generation of clean hydrogen energy involves separation of H2 from CO2 mixture by a Deca Dodecasil Rhombohedral (DDR) zeolite membrane. Permeance, permeability coefficient and selectivity of such a membrane contribute to the membrane efficiency. These parameters are usually controlled by the gas transport properties of the membrane which is directly related to diffusion mechanisms of gaseous components through the membrane pores. In this study, transport phenomena namely the Viscous, Knudsen and Molecular Sieving have been evaluated to analyze the contribution of each flux to the individual H2 and CO2 and their gas mixture through the zeolite membrane. To study the flow properties of the supported membrane, a simple, two-parameter, steady state model was formulated based on the analytical solution of the dusty gas model for both H2 and CO2. Maximum percentage deviation between the experimental data and the model predictions was 6%. This reasonably low value validates the proposed model. By and large good agreement between calculated and experimental fluxes confirms the computational and theoretical premises of the study.