The zeta potential of
ZrB2 slurries. The isoelectric point (IEP) of ZrB2 was ~4.5, which was close to
the previously reported values of ~4.7. The surface charge of ZrB2 was negative
when pH was higher than the IEP. However, the IEP of ZrB2 shifted towards a
basic region in the presence of PEI. This is due to the fact that PEI ionizes
in the acid condition, carries a positive charge, and adsorbs onto the particle
surface via electrostatic force (hydrogen bonding is proposed to be the
dominant mechanism). The dispersion of ZrB2 in the water could be attributed to
the surface oxide layer, which earlier researchers illustrated. In the current
work, not only ZrB2 but also other powders were concerned since the
co-dispersion behavior of ZrB2, SiC, B4C, and C is critical to obtain green
bodies with chemical homogeneity. The zeta potentials of ZrB2, SiC, B4C, and C
powders in the presence of PEI. The maximum absolute zeta potential values
appeared in the acidic condition (all >30 mV at pH ≈ 3), which manifested the best co-dispersion status.
It is worth noting that previous researchers have already reported the surface
chemistry and dispersion behavior of PEI onto SiC powder and that they believed
that an acid solution was the best dispersing medium. Thus the ZSBC powders can
be well co-dispersed in an acidic solution in the presence of PEI. The raw
materials, monoclinic ZrO2 (99%, Aldrich, USA), B2O3 (98%, Fluka, Germany), and
Al (99%, Aldrich, USA) powders, were used to produce zirconium diboride–alumina
composite powder. Elemental zirconium (99%, Alfa Aesar, Germany) and boron
(97%, amorphous, Aldrich, USA) were also used for studying a sub-reaction. The
starting materials were subjected to high-energy ball milling in a modified
planetary ball mill (Pulverisette7, Fritsch, Germany). The connection of the
vial to the gas cylinder during the milling experiments was maintained by a
rotating union and a flexible polyamide tube. An SMC solenoid valve (model
EVT307-5DO-01F-Q, SMC Co, Tokyo, Japan) monitored the pressure change vs. time
to record the ignition time. A sharp peak due to the pressure rise appears when
the MSR reaction occurs. The position of this peak represents the ignition
time. The system used in this work has already been shown elsewhere. If you are looking for high quality, high purity and cost-effective Zirconium
diboride, or if you require the latest price of Zirconium diboride, please feel
free to email contact mis-asia.
