Fatigue limit of Y-TZP reinforced with carbon nanotubes
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Dental Materials
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Purpose/aim: To compare the Cyclic Fatigue Limit (CFL)
of a control yttria-stabilized tetragonal zirconia pollycristal
(Y-TZP) with a composite produced by adding multi-walled
carbon nanotubes (CNT) into Y-TZP.
Materials and methods: CNT were coated with zirconium
oxide and yttrium oxide to form a powder (CNT/ZYO) using
a hydrothermal co-precipitation method. Powders made of
Y-TZP + (CNT/ZYO) were produced using 99 vol% of Y-TZP and
1 vol% of CNT/ZYO. CAD-CAM blocks (42.5×16.0×16.0mm)
were obtained by uniaxial pressing (67MPa/30 s) of each
powder in a steel matrix. These blocks were partially sintered
at argon atmosphere (1100 ◦C/1 h/5 ◦C/s) and then sectioned to
produce 14 bar-shaped specimens (3.0×4.0×25.0mm/edges
chamfered according to ISO6872:2008) of each material,
which were sintered also in argon atmosphere
(1.400 ◦C/4 h/5 ◦C/min). Density measured by Archimedes’
method was used to calculate the relative density (RD), based
on the theoretical values for both materials (6.06 g/cm3).
Flexural strength (FS) was measured in four-point bending
with specimens immersed in water at 37 ◦C (inner and outer
supports of 10 and 20 mm). CFL was determined in four-point
bending, using the staircase method (10,000 cycles/5 Hz). In
each cycle, the stress varied between the maximum stress
(MS) and 50% of MS. The applied stress in the first specimen
was 50% of FS. After 10,000 cycles, in case the specimen did
not fracture, 10MPa was added to the next specimen. RD and
FS were analyzed by Student’s t test (alpha = 5%). CFL was calculated
according to: CLF =X0+d(SUMini/SUMni±0.5), where
X0 is the lowest stress value tested, d is the stress added or
subtracted to each cycle and n is the number specimens that
survived or failed in each stress level. The lowest stress level
was computed as i = 0, and the next one was computed as i=1,
and so on. Fracture surfaces were fractographically analyzed.
Results: Specimens containing nanotubes showed significantly
lower RD compared to the control (p = 0.009).
Nanotube addition also caused a 50% significant decrease in
FS (p = 0.003). However, the FS coefficient of variation for the
control was higher (17%) compared to that of the composite
(10%). CFL calculated for the control was 2.5 times higher than
that of the composite. The %CFL (CFL in terms of percentage
of the FS) was also higher for the control. Fractography indicated
fracture origins associated to surface defects and porous
regions related to nanotube agglomerates.
Conclusions: The processing method used to produce the
composite Y-TZP/nanotubes needs to be improved since nanotube
addition to Y-TZP caused a significant reduction of the
relative density, strength and fatigue limit.
Como referenciar
SILVA, L.H.; LAZAR, D.R.R.; USSUI, V.; YOSHITO, W.K.; TANGO, R.N.; BELLI, R.; LOHBAUER, U.; CESAR, P.F. Fatigue limit of Y-TZP reinforced with carbon nanotubes. Dental Materials, v. 33, p. e19-e19, 2017. suppl. 1. DOI: 10.1016/j.dental.2017.08.036. Disponível em: http://repositorio.ipen.br/handle/123456789/28614. Acesso em: 30 Dec 2025.
Esta referência é gerada automaticamente de acordo com as normas do estilo IPEN/SP (ABNT NBR 6023) e recomenda-se uma verificação final e ajustes caso necessário.