Ceramics based on Si(3)N(4) have been comprehensively studied and are widely used in structural applications. The development of an interlocking microstructure of elongated grains is vital to ensure that this family of ceramics have good damage tolerance. Until now this has been accomplished by heating the appropriate powder compacts to temperatures above 1,700 degrees C for extended periods. This procedure involves a necessary step of controlling the size and population of seeds added ex situ or formed in situ to ensure selective grain growth. Here we report the very fast (within minutes) in situ formation of a tough interlocking microstructure in Si(3)N(4)-based ceramics. The microstructures are obtained by a dynamic ripening mechanism, an anisotropic Ostwald ripening process that results from the rapid heating rate. The resulting microstructures are uniform and reproducible in terms of grain size distribution and mechanical properties, and are easily tailored by manipulating the kinetics. This process is very efficient and opens up new possibilities to optimize mechanical properties and cost-effectively manufacture ceramics.

200 nm templates were purchased from Whatman and 40 nm porous alumina templates were prepared in our laboratory [9].Electrodeposition of (Bi 1±x Sb x ) 2 Te 3 was performed using a standard threeelectrode cell (EG&G PAR model 273 potentiostat/galvanostat). The working electrode was prepared by attaching a copper wire to the Pt side of the porous alumina template with Ag paint (Ted Pella, Inc., colloidal silver paste), and the back and edges of the alumina were masked with clear nail enamel. The cathode assembly and anode (Pt gauze) were submerged in the solution. The reference electrode (Ag/AgCl) was in a separate cell in a 1.0 M KNO 3 solution. The two cells were connected via a 1.0 M KNO 3 /agar salt bridge. Depositions of (Bi 1±x Sb x ) 2 Te 3 were performed under potentiostatic control with potentials more negative than~±0.17 V versus Ag/AgCl.The composition and morphology of the films and nanowires arrays were analyzed using several techniques: EDS (JEOL 6300), X-ray diffraction (Siemens D5000, Cu Ka radiation), and field-emission SEM (Hitachi S-5000).

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Aerogels with the nominal composition ZrW2O8 have been prepared by pore solvent exchange with liquid CO2 followed by supercritical drying. These aerogels are amorphous and can be tailored to have extremely high surface areas. Thermal expansion is measured for the amorphous aerogel as well as the aerogel post thermal treatment. The cubic phase forms at 900 °C in less than 30 s. The cubic phase prepared this way has a large negative thermal expansion coefficient of −10.5 × 10-6 °C-1 as shown by variable temperature X-ray diffraction.

The abnormal grain growth in α–sialon ceramics was investigated. The preparations had stoichiometric compositions on the oxygen-rich phase boundary, and they were stabilized by Y, Nd, Sm, Dy, and Yb, respectively. Specimens were prepared from α–Si3N4 as precursor powder by applying conventional hot pressing and a novel rapid consolidation process, namely spark plasma sintering (SPS). Single-phase α–sialon ceramics with in situ reinforced bimodal microstructure, i.e., large elongated grains embedded in a matrix consisting of small equiaxed grains, were obtained above 1750 °C in all systems compacted by SPS and above 1800 °C in systems stabilized by Nd and Sm but not Dy, Y, or Yb by a two-step hot-pressing procedure. It was observed that the formation of abnormally grown α–sialon grains was strongly temperature-dependent, indicating that it was encouraged by the formation of a transient liquid phase that stimulated the dissolution of any remaining nitride precursors and early formed small α–sialon grains and sequentially facilitated supersaturation by the α–sialon constituents. The presence of elongated grains improves fracture resistance in the obtained materials.