The directional freezing of micro-fiber suspensions is used to assemble highly porous (porosities ranging between 92 to 98%) SiC networks. These networks exhibit a unique hierarchical architecture in which thin layers with honeycomb-like structure and internal strut length in the order of 1 to 10 µm in size are aligned with an interlayer spacing ranging between 15 to 50 microns. The resulting structures exhibit strengths (up to 3 MPa) and stiffness (up to 0.3 GPa) that are higher than aerogels of similar density and comparable to other ceramic micro-lattices fabricated by vapor deposition. Furthermore, this wet processing technique allows the fabrication of large-size samples that are stable at high temperature, with acoustic impedance that can be manipulated over one order of magnitude (0.03-0.3 MRayl), electrically conductive and with very low thermal conductivity. The approach could be extended to other ceramic materials and opens new opportunities for the fabrication of ultralight structures with unique mechanical and functional properties in practical dimensions.2
ElsevierOzuna López, C.; Gomez Alvarez-Arenas, T.; Riera, E.; Carcel Carrión, JA.; García Pérez, JV. (2014). Influence of material structure on air-borne ultrasonic application in drying. Ultrasonics Sonochemistry. 21(3): 1235-1243. doi:10.1016/j.ultsonch.2013.12.015.Milk powder agglomerate growth and properties in fluidized bed agglomerationAbstract Fluidized bed agglomeration is used to produce large and porous dry agglomerates with improved instant properties. Water (or binder solution) is sprayed in the fluidized bed of particles to render their surface sticky. The agglomerate growth results from the repetition of different steps (wetting of the particle surface, particles collision and bridging, and drying) and depends on the processing conditions and product properties. In this work, skim and whole milk powders were fluidized in hot air and agglomerated by spraying water in a bench-scale batch fluidized bed. The aim was to study the impact of the sprayed water flow rate (0-5.5 g.min − 1 ), particle load (300-400 g), initial particle size (200-350 μm), and composition (skim-whole milk) on the growth mechanisms and on the properties of the agglomerates obtained. Powder samples were regularly taken in the fluidized bed during agglomeration and characterized for the size, size distribution, and water content. Whatever the conditions tested, the size increase and the evolution of the particle size distribution during agglomeration were found to mainly depend on the relative amount of water sprayed in the particle bed. Agglomeration occurred in two stages, with first the rapid association of initial particles into intermediate structures, and second, the progressive growth of porous agglomerates. In any case, agglomeration allowed improving instant properties of the milk powder.
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