Mn
x
Ga
thin films (1.64 ≤ x ≤ 2) were grown
at room temperature by molecular
beam epitaxy on the native SiO2 layer of Si(100) commercial
wafers. After growth, Mn
x
Ga films were
thermally annealed at different temperatures (200, 300, and 400 °C).
The X-ray diffraction results reveal D022-Mn2Ga as the main phase and an improvement of the crystalline quality
as a function of the annealing temperature. The samples were also
investigated using X-ray photoelectron spectroscopy, atomic force
microscopy, and vibrating sample magnetometry techniques. The magnetization
curves suggest that the magnetic behavior is strongly dependent on
the annealing time and temperature and that the saturation magnetization
decreases with an increase in the Mn concentration in the alloy. These
magnetic properties are related to the morphology and crystallinity
of the samples. The magnetic moment distributions of the films were
calculated using density functional theory, bringing a better understanding
of the origin of the observed magnetic anisotropy.
Purpose
Lithium disilicate glass-ceramics (LS2 GC) are widely used as dental prosthetics and dental restorations. Based LS2 GC have hardness and translucency similar to that of natural teeth. This study aims to investigate the tribological features of LS2 GC with crystalline volume fraction of 64% and different crystal sizes from 8 µm to 34 µm for different counterparts.
Design/methodology/approach
The tribological behavior was investigated using a pin-on-disc tribometer with alumina and tungsten carbide (WC) spheres, applied load of 5 N and sliding speed of 5 cm/s at normal conditions. The coefficient of friction was measured continuously up to 10,000 sliding cycles. The specific wear rate was calculated from tribological and profile measurements. The wear mechanism was investigated by surface morphology analysis.
Findings
The coefficient of friction during running-in varied from 0.8 to 1.0 for the alumina counterpart, because of severe wear. Afterwards, it reduced and reached a stationary regime, characterized by a mild wear regime and the formation of a tribolayer formed by the debris. For the WC counterpart, the coefficient of friction curves increased initially with sliding cycles up to a stationary regime. The samples tested against WC presented the lowest specific wear rate (k), and no variation of wear rate with crystal size was observed. For samples tested against the alumina, crystallization and crystal size increased the wear resistance.
Originality/value
This study evaluated the effect of different counterfaces on the tribological properties of the LS2 GC, an important glass-ceramic base for many dental prosthetics and dental restorations, discussing results in light of the contact mechanics. Different specific wear rates, wear regimes and dependence on the glass-ceramic microstructure were observed depending on the counterpart.
Peer review
The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-08-2019-0352/
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