Effect of APC addition on precursors properties during synthesis of B 4C nano powder by a sol–gel process

Abstract

In this study different characteristics regarding to dispersion of a suspension containing precursor particles with respect to charge, particle size and rheological measurements were investigated. Ammonium poly carboxylate (APC) was used here as a dispersing agent. From our investigations it was exhibited that point zero charge (PZC) for precursor particles is about 6.5–7. On the other hand, it was revealed that surface charge of precursor particles was changed significantly in presence of ammonium poly carboxylate agent, and also PZC amounts shifted toward lower acidic pHs in the range of 4.04–4.4. From electrokinetic data, adsorption specific free energy ( Δ G sp 0 ) between superficial sites and adsorbing poly electrolytes (APC) were measured and it was found that Δ G sp 0 has a negative amount (equivalent to −3.1181 RT) in presence of dispersant agents. In presence of APC dispersant agent particle size can be designed to the range of less than 10 nm. From rheometerical measurements performed on a sol containing precursor particles revealed that in mean pH ranges sol viscosity rises and finally particles will show less stability. FTIR analysis from gel powder sample showed existence of B–O–C bonds formed during hydrolysis and condensation reactions. XRD investigations on sintered powder at 1270 °C revealed that final product mainly was composed of B 4C phase. Raman spectroscopy was employed to support the results of B 4C formation. TEM analysis exhibited that B 4C particle size was in the range of 20–40 nm and formed particles are polycrystalline with homogenous morphology.