Porous silica coatings were prepared by acid- and base-catalyzed sol−gel method. Surface morphology studies by atomic force microscopy showed smooth surface for acid-catalyzed coatings while base catalysis resulted in coarse particle morphology. On increasing the tetraethyl orthosilicate to base molar ratio from 1:1 to 1:3, the mean particle size of the coating shifted from 30 to 100 nm while the pore size varied from 4.7 to 14 nm. Infrared spectral analysis exhibited a change in the ratio of integrated peak intensities of Si−O−Si to Si−OH in acid-and base-catalyzed silica coatings. Textural studies showed an increase in particle size and porosity with base concentration. Optical transmission and surface roughness of base-catalyzed samples were found to be higher than that of acid-catalyzed silica coatings.

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Solution precursor plasma spray (SPPS) synthesis is a simple, single-step, and rapid technique for synthesizing nano-ceramic materials from solution precursors. This innovative method uses molecularly mixed precursors as liquids, avoiding a separate processing method for the preparation of powders and enabling the synthesis of a wide range of metal oxide powders and coatings. Also, this technique is considered to be promising for the formation of nonequilibrium phases in multi-component oxide systems. This short review provides an insight into the important aspects of SPPS, the properties obtained in comparison to conventional plasma spray, and the potential applications of the SPPS process. S. Seal is a professor, K.S. Babu is a research associate, and E. Brinley is a graduate student with the Surface Engineering and Nanotechnology Facility, Advanced Materials Processing and Analysis Center, Mechanical Materials and AerospaceEngineering, Nanoscience and Technology Center, University of Central Florida, Orlando, Florida. S. Seal can be reached at sseal@mail.ucf.edu.