The viability of producing silicon nanoparticles using the HWCVD process is investigated. A system is assembled and particles are produced from silane at pressures between 0.2 and 48 mbar, with hydrogen dilutions of 0-80%, at a total flow rate of 50 seem and with a tungsten filament maintained at 1650 degrees C. The as-prepared powder varies in colour from yellowish to dark brown and is deposited on all surfaces inside the reaction chamber. The material is a highly porous agglomeration of nanoparticles of primary size in the order of 40 nm, with a narrow size distribution. The nanoparticles produced are mostly amorphous, hydrogenated and have a partially oxidised surface. (c) 2007 Elsevier B.V. All rights reserved.