Silica, carbon and boron nitride monoliths with hierarchical. porosity prepared by spark plasma sintering process

Silica SBA-15, carbon CMK-3, boron nitride (BN), the latter synthesized from the first two compounds as templates, are mesoporous materials in the form of powders. They have a high specific surface area and an important mesoporous volume. The porosity is organized with the hexagonal symmetric space group p6mm. For selected applications, it could be interesting to preserve these characteristics with materials in a well-defined shape at a macroscopic scale (few millimeters to centimeter). Spark plasma sintering (SPS) is a well-known technique which allows to prepare monoliths with relatively mild conditions. The SPS technique has been used on these mesoporous powders without charge or with a uniaxial charge and at temperatures of 600 degrees C, 800 degrees C for silica, 1100 degrees C, 1300 degrees C for carbon and 1600 degrees C, 1700 degrees C for boron nitride during 1-5 min. The nitrogen adsorption/desorption isotherms reveal that the obtained monoliths present high specific surface area (300-500 m(2)/g) and important mesoporous volume. The coexistence of interconnected mesoporosity and macroporosity (with volume's close value) was observed by SEM and TEM, while the XRD and TEM characterization show that the mesoporosity organization is partially,preserved. (C) 2007 Elsevier Inc. All rights reserved.