A novel class of preceramic paper may serve as a preform to manufacture lightweight as well as multilayer ceramic products. In this article, we discuss the formation, microstructure, and properties of preceramic papers and their conversion into ceramic materials. Oxide as well nonoxide ceramics were processed into single‐sheet, corrugated structures, and multilayer ceramics. A high filler loading and uniform distribution of ceramic fillers involves control of colloidal surface interaction including electrostatic, electrosteric, and mechanical retention. Sintering of an oxide‐loaded preceramic paper in air results in highly porous products, with the porosity shape and distribution templated by the pulp fiber used in papermaking. In the case of carbide‐loaded paper, dense composite materials are obtained by reactive infiltration processing. Anisotropic properties of machine‐fabricated preceramic paper and bonding interfaces in multilayer stacks give rise to anisotropic mechanical properties of the resulting ceramic composites. Noncatastrophic failure was observed when tensile loading stress was applied parallel to the interfaces (in‐plane loading). Applying well‐established paper processing technologies, including laminated object manufacturing, ceramic structures of complex shape and size can easily be processed, offering a high potential for economical manufacturing.

Laminated object manufacturing, a rapid prototyping method, is applied to paper sheets containing SiC filler particles. Upon pyrolysis and melt filtration of Si, the sheets can be transformed into dense ceramic objects with complex shapes such as the 18‐layered gearwheel shown in the figure.

International audienceNitrogen-doped titanium oxides are attractive materials for the degradation of organic pollutants in water due to their photocatalytic activity in the visible light range. The evolution of the photocatalytic properties was studied on a number of TiO x N y powder samples where x varied from 2 to 0 (TiO2 to TiN) through increasing the nitrogen content (y = 0-1). X-ray diffraction and Raman spectroscopy showed that an anatase type TiO x N y was obtained at low nitrogen contents (<2 wt%). With increasing nitrogen content a structural transition from anatase to cubic TiN was observed. Electron spin resonance measurements of the TiO x N y samples confirmed the presence of unpaired electrons and defects for the TiO x N y materials with low nitrogen content (<2 wt%). The photo-induced activity of the TiO x N y materials was evaluated under VIS illumination of solutions containing methylene blue as an organic probe. The TiO x N y samples exhibited an improved photocatalytic activity under visible light illumination compared to TiO2 at nitrogen levels lower than 2 wt%. A photocatalytic activity could not be detected at nitrogen levels higher than 10 wt% and after conversion of the TiO x N y into the cubic phase. Optimum photocatalytic activity in the visible range can be achieved at nitrogen levels lower than 2 wt% for TiO x N y materials

The microstructure and properties of porous Si/silicon carbide (SiC) composites manufactured from nonwoven cellulosic fabrics have been investigated. A fibrillar reaction product with a microstructure reproducing the initial preform morphology consisting of b-SiC and unreacted Si was obtained. Improvement of strength is expected to be achieved by increase of SiC content and reduction of porosity.

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