Abstract
The zirconate of lithium and potassium was synthesized through a solid state
reaction. This ceramic material is new in brake applications. It has a platelet morphology
without either fibres or whiskers. For analogy, its braking performances were compared with
those of the titanate of potassium and lithium, which, among potassium titanates, exhibits the
best platelet morphology. A simplified low steel formula was used to compare the effect of
the substitution of the titanate with the zirconate on braking performances. Dynamometer full
scale tests were executed in order to compare friction performances of the two materials. A
momentum of inertia of 70.23 kgm2 was set for the dyno test. AK-Master (SAE J2522), and
VW TL110 wear tests ( both at 50 and 100 km h-1) were performed. The tribolayer formed on
the rotor surface was studied by means of scanning electron microscopy in both cases (SEM).
The elemental analysis was carried out by means of energy dispersion spectroscopy (EDS),
while an elemental depth profile was carried out by means of glow discharge spectrometry
(GDS). Thermal gravimetric analysis (TGA) and differential thermal analysis (DTA) of the
zirconate were carried out in CO2 atmosphere and in air in order to study the ability of adsorb
and desorb CO2. The dyno-results showed that the material with zirconate had a better
recovery of the coefficient of friction after the fading test. Moreover, wear tests showed that
wear of both the friction material and rotor were substantially decreased by the zirconate. The
worn thickness of the brake pads with the zirconate is ca. 50% lower than those with the
titanate in the test at 100 kmh-1. Moreover, in both cases the whole thickness wear of the rotor is ca. 60% and 50 % lower for the zirconate in the tests at 100 and 50 kmh-1, respectively. The depth penetration of zirconium and titanium in the rotor surface was around 1.5-2.0 m. However, the tribolayer formed by the zirconate was more uniform, while that formed by the titanate exhibited more detachments and grooves. It is noteworthy to point out the zirconate was able to adsorb and desorb CO2 in a reversible manner. This study should be extended to other type of formulations and with different momenta of inertia.
KEYWORDS Zirconates, titanates, thermal dissipations, friction performances, CO2
adsorption