Papers by Keyword: Nanoindentation

Abstract: Chemical tempered glasses were prepared using glass slides as substrate and KNO₃ as melting agent by ion-exchange during 2h, 4h, 6h at 430°C,450°C and 500°C respectively. The surface composition of the glasses was analyzed by energy dispersive spectrometer (EDS), the mechanical properties and wear resistance were characterized by nanoindentation/nanoscratch tests. The results indicate that the ion- exchange method can be a good way to increase the strength and improve wear resistance of Na-Ca-Si glass. The chemical tempering has an optimal treating temperature and time.

Abstract: To find out the penetration of PF into the wood cell wall and its effects onthe mechanical properties in the cellular level, the elastic modulus and hardness of secondary wall (S₂ layer) and compound corner middle lamella (CCML) near PF bond line region were determined by nanoindentation. Compare to the reference cell walls (unaffected by PF), PF penetration into the wood tissues showed improved elastic modulus and hardness. And the mechanical properties decreased slowly with the increasing the distance from the bond line, which are attributed to the effects of PF penetration into S₂ layer and CCML. The reduced elastic modulus variations were from18.8 to 14.4 GPa for S₂ layer, and from10.1 to 7.65 GPa for CCML. The hardness was from 0.67 to 0.52 GPa for S₂ layer, and from 0.65 to 0.52 GPa for CCML. In each test viewpoint place, the average hardness of CCML was almost as high as that of S₂ layer, but the reduced elastic modulus was about 50% less than that of S₂ layer. But the increase ratio of mechanical properties was close. All the results showed PF penetrates into the CCML. The penetration behavior and penetration depth from bond line were similar in both S₂ layer and CCML.

Abstract: Nanoindentation was used to measure the hardness and Young’s modulus of prepared-TiO2 films. The thickness and refractive index of the TiO2 films were measured using ellipsometry with a monochromator. Scanning electron microscopy was used to determine the micrography of the TiO2 films. Pure TiO2 films were prepared from sols made by 3 % (w/w) of prepared-TiO2 suspension solution coated onto silicon wafers. After the dip-coating was completed, the coatings were further treated by various procedures, natural air-drying, water-vapor exposure, and calcinations. The prepared-TiO2 films were smooth and free of macro cracking. The grain sizes of these films were uniform and in the range of 50–100 nm and the films were of rutile structure. The prepared-TiO2 coatings exhibited more favorable porosity in water-vapor exposure than those under other conditions. The T-H2SO4 coatings exhibited higher hardness and modulus than those with T-H2O and T-NH4OH coatings after high temperature calcination. The values of hardness and modulus for T-H2SO4 coatings were 11.93 GPa and 226.25 GPa, respectively. Curves of hardness and modulus as a function of depth (0–2200 nm) of the coatings under calcination conditions show a peak at shallow contact depth within 100 nm and then demonstrate being rather constant. The hardness and modulus curve obtained from T-H2SO4 coatings in water-vapor exposure are rather constant.

Abstract: The nano-indentation and friction/wear properties of a magnetron sputtered SiC (silicon carbon) films on nanostructured titanium (produced by severe plastic deformation) substrate were investigated. The results show that the films exhibited low nano-hardness (10.6 GPa), low Young's modulus (83.3 GPa) and high hardness-to-modulus ratio (0.128). As sliding against Si₃N₄ (silicon nitride) balls (2 mm in radius) under Kokubo simulation body fluid (SBF) at room temperature, the films displayed superior friction/wear properties at the considerably high normal load of 1000g, with the friction coefficient of about 0.18, the special wear rate on the order of 10⁻⁶ mm³ N^-1m^-1 without film cracking and interface delaminating. The impressive film cracking and interface delaminating resistance is in accordance with the low hardness (high ductility) of the films and the small film-substrate modulus difference that was caused by the low modulus of the films.

Abstract: Nanoindentation technique was employed to study the hardness and elastic modulus for different regions in the welded joint of high strength steel. And the variation in mechanical behavior at micro scales was analyzed combined with microstructure observation. Experimental results showed that both maximum hardness (4.11GPa) and maximum elastic modulus (210.3GPa) were obtained in the coarse grained HAZ and the corresponding microstructure was granular bainite. While the weld metal and fine grained HAZ had similar values of hardness and elastic modulus, and corresponding microstructures were acicular ferrite and polygonal ferrite respectively.

Abstract: The interface adhesion, nano-indentation and friction/wear properties of the CNx films in CNx/SiC (carbon nitride/silicon carbon) double layer films (SiC as interlayer) deposited on Mg alloy (AZ91D) substrate by using magnetron sputtering technique at room temperature were investigated. The results show that the interface between CNx film and SiC film and the interface between SiC film and Mg substrate both showed obvious and gradual element diffusions as well as high adhesion. The CNx films exhibited low nano-hardness (3.85 GPa) and Young's modulus (30.46 GPa) but high hardness-to-modulus ratio (0.126). As sliding against Si3N4 (silicon nitride) ball (4 mm in diameter) using ball-on-disc friction and wear tester under dry sliding condition at 200g load, the CNx films exhibited the friction coefficient of about 0.20 and the special wear rate in the order of magnitude of 10−6 mm3 m−1 N−1 without film cracking and interface delaminating.

Abstract: The elastic modulus (E) and hardness (H) of the cement particles that embedded in different subbases (namely epoxy resin and hardened cement pastes with different ages) were measured by nanoindentation. The results indicate that the measured values of E and H of the cement particles encased in resins are smaller than normal values, while the measured values of cement particles embedded in hardened cement pastes are closely related to the hydration degree of subbase cement pastes. As nanoindentation measurement of cement particles is significantly affected by the hardness of the subbase, the test of E and H of cement particles should be carried out based upon a rather hard substrate.

Abstract: Hardness of Calcium Silicate Hydrate (CSH) at different ages was measured by nanoindentation test. The results show obvious indentation size effect in hardness of CSH. Hardness decreases with increasing depth. Moreover, both low density CSH and high density CSH follow the same size effect law in hardness. This phenomenon further indicates that two types of CSH are of the same basic composition but different packing densities.

Abstract: Mechanical properties of (001) Mo and (001) Mo – 1.5 at.% Ir single crystals have been studied by nanoindentation. It has been found that the iridium addition to molybdenum leads to an increase in both hardness and elastic modulus. An abrupt elasto-plastic transition (pop-in) at a depth of about 20 - 40 nm caused by dislocation nucleation in previously dislocation-free volume has been observed in the initial portion of the loading curve. It has shown that the Ir addition essentially affects the dislocation nucleation. Mean shear stress required for the dislocation nucleation increased from 10.8 GPa (G/12) for a Mo single crystal to 18.2 GPa (G/8) for the Mo – 1.5 at% Ir solid solution. Thus, the Ir solution in a Mo single crystal affects not only the resistance to the motion of dislocations (hardness) but the nucleation of them as well. The latter is likely to occur as a result of an increase in the structure perfection of the Mo – 1.5 at% Ir solid solution as compared to the pure Mo single crystal.