Crystal architectures of a layered silicate on monodisperse spherical silica particles cause the topochemical expansion of the core-shell particles

Anisotropic structural changes in an expandable layered silicate (directed towards the c-axis) occurring on isotropic and monodisperse microspheres were detected by measurable increases in the grain size. The hierarchical changes were observed through pursing the sophisticated growth of expandable layered silicate crystals on monodisperse spherical silica particles with diameters of 1.0 mu m; the core-shell hybrids with a quite uniform grain size were successfully produced using a rotating Teflon-lined autoclave by reacting spherical silica particles in a colloidal suspension with lithium and magnesium ions under alkaline conditions at 373 K. The size distribution of the core-shell particles tended to be uniform when the amount of lithium ions in the initial mixture decreased. The intercalation of dioctadecyldimethylammonium ions into the small crystals through cation-exchange reactions expanded the interlayer space, topochemically increasing the grain size without any change occurring in the shapes of the core-shell particles. (C) 2015 Elsevier Inc. All rights reserved.ArticleMICROPOROUS AND MESOPOROUS MATERIALS. 215:168-174 (2015)journal articl

Consolidation by Spark Plasma Sintering of Polyimide and Polyetheretherketone

This article presents two high- temperature thermoplastic powders which were sintered by spark plasma sintering in order to get homogeneous mechanical properties. Dense polyimide (PI) and polyetheretherketone (PEEK) specimens were obtained at temperatures as low as 320 degrees C for PI and 200 degrees C for PEEK, respectively. Relative densities higher than 99% were reached for both materials. In order to characterize their properties, in situ measurements with compression and hardness tests were carried out on sintered samples. This method allowed to obtain polymeric materials with improved mechanical properties. (C) 2014 Wiley Periodicals, Inc