Continuous c-Oriented AlPO₄-5 Films by Tertiary Growth

Abstract

c-Oriented AlPO 4 -5 films were synthesized by seeded growth on silicon substrates. Secondary hydrothermal treatment of the seeded substrates under conditions that favor c-out-of-plane growth yielded non-intergrown, highly oriented columnar crystals with a length of 7 µm. Modifying the conditions so that in-plane growth is favored and executing yet another ("tertiary") growth, the crystals obtained by secondary treatment were grown in-plane, along the a-, b-directions, filling the gaps between the columnar grains and yielding well-intergrown, highly oriented, continuous AlPO 4 -5 films. The oriented films obtained by the technique presented here can be potentially useful for separations and catalysis as well as electronic and electrochemical applications.

Microstructural Engineering of Hydroxyapatite Membranes to Enhance Proton Conductivity

“…Here we report a different approach for improving the performance of ion‐conducting membranes by engineering the membrane microstructure to optimize ion transport. Our approach is analogous to the microstructural optimization of zeolite and molecular sieve membranes to improve mass transport 11, 12…”

“…As a result, calcium phosphate becomes locally supersaturated and HAP crystals nucleate and grow on the cathode surface. The crystals tend to grow with c ‐axes oriented normal to the cathode surface since the c ‐axis is the fastest growing 12, 21…”

Thin Film Nanocomposite Membranes for Water Desalination

“…Thus, carbon nanotubes and other types of nanotubes [127] may have the potential for use in high-flux desalination membranes. In particular, considering the salt and water molecular sizes, nanotubes with very small channel sizes (e.g., <1 nm) [128][129][130][131] are highly desirable for high salt rejection. Therefore, the fabrication of small-channel nanotube-polymer TFN membranes deserves more attention.…”

Oriented CoSAPO‐5 Membranes by Microwave‐Enhanced Growth on TiO2‐Coated Porous Alumina

“…Those published have exemplified challenges in the development of supported AFI-type membranes: a multi-step process for the alignment of metal-embedded AlPO 4 -5 crystals with a low ratio of crystal area to overall membrane area and hindering cost-effective scale-up, [9] crystalline misorientation limiting selective transport pathways, [10] and most recently, crystal densification and defect formation at temperatures necessary for membrane activation (removal of structure-directing agent molecules). [11] Although other methods have succeeded in the fabrication of preferentially oriented AFI-type films, [12][13][14][15][16][17][18][19] an examination of their quality through molecular separation performance has not yet been reported.…”