Reaction spark plasma sintering of niobium diboride

Effect of sintering techniques on the microstructure and mechanical properties of niobium borides

“…This shows the effectiveness of SPS technique which exhibit a local increase in the temperature at the particle contacts due to the applied high electric current through powders. This local temperature rise which significantly enhances the diffusivity of the powders accelerates the phase transformation in a very short time [40]. Additionally, the presence of different stoichiometries of the niobium boride phases (NbB, Nb 3 B 4 and Nb 5 B 6 ) confirms the colour contrasts in the BSE SEM image of the N5-SPS sample ( Fig.…”

“…Recent studies are mainly focused on the sintering of niobium borides using various techniques including high-pressure sintering and spark plasma sintering (SPS) of elemental Nb and B powder mixtures [13,25,40] and pressureless sintering using NbB 2 /B/Nb starting materials [15,16]. Sintering studies have been mostly carried out to investigate the superconducting behaviour of niobium borides, in which any microstructural or mechanical properties of bulk products have not been reported [13,15,16].…”

“…Only few studies reported the mechanical properties (e.g. microhardness, fracture toughness, elastic modulus) of the sintered niobium boride bodies [25,40]. Among them, bulk NbB 2 with a relative density of 98% was prepared by sintering at 1600 • C under a pressure of 4 GPa [25].…”

“…Among them, bulk NbB 2 with a relative density of 98% was prepared by sintering at 1600 • C under a pressure of 4 GPa [25]. Moreover, NbB 2 compact with a density of 97.7% was obtained by SPS of the NbB 2 precursors at 1900 • C for 15 min under a pressure of 70 MPa [40]. On the basis of reported studies, it should be noted that the utilized precursors are commercially available and expensive raw materials (Nb, B, NbB 2 , etc.…”

Pressureless sintering of chromium diboride using spark plasma sintering facility

“…Diboride-based ceramics can be categorized under difficult to sinter materials as it possesses high melting points and strong covalent bonding [8][9][10][11][12][13]. In recent past, SPS has been extensively used to study the densification behaviour of diboride based ceramics, due to its fast heating rates and short holding time coupled with application of high mechanical pressures [4,9,11,14]. But, this method is mainly limited to fabricate simple shaped components as load has to be applied to keep components intact in order to close the electric circuit during sintering operation.…”