The present study explores the physics behind the loading rate (dP/dt or [Formula: see text]) dependent nanoscale plasticity (NSP) events observed during carefully controlled nanoindentation (NI) experiments on 1, 3, and 5 wt. % Titania Densified Alumina (TDA) ceramics. Characterizations of the TDA ceramics are carried out by x-ray diffraction, field emission scanning electron microscopy (FESEM), and NI techniques. A significant enhancement (∼30%) of the nanohardness of TDA ceramics occur with an enhancement in [Formula: see text]. The results confirm that both the critical load ( Pc) at which micro-pop-in or the NSP events initiate and the corresponding critical depth ( hc) are sensitive functions of relative density, size of relatively finer grains, loading rate, and the amount of sintering aids. The experimentally observed empirical power law dependence of all the NSP related parameters on [Formula: see text] is rationalized theoretically and qualitatively. It is suggested that the shear induced homogeneous dislocation nucleation underneath the nanoindenter may be the main factor contributing to the occurrence of the NSP events at relatively lower loading rates. However, especially at the relatively higher loading rates, the FESEM based evidence and the data obtained from the related NI experiments suggest that there is a more acute interconnection between the homogeneous dislocation nucleation induced profuse occurrence of the NSP events, shear band formations, and microcrack formation in the TDA ceramics. Finally, the design implications of the present results for the development of better alumina ceramics for load and strain tolerant applications are discussed.
We demonstrate the precise variation of self-imaging distance with width of a Gaussian input, centrally fed into a symmetric dielectric slab waveguide of width ∼20λ0. The width of the Gaussian is varied from the paraxial to completely nonparaxial domain. Unlike the paraxial case, the self-imaging distance is found to depend on the beam width and change with the number of excited modes in the waveguide. These features should be useful in designing devices that exploit self-imaging for improved efficiency, especially in nanophotonic circuits.
The cost-effective hydrogen production via electrolyser depends on the availability of highly efficient, low-cost, and robust OER and HER catalysts. We fabricated NiÀ NC and NC electrocatalysts via a simple, cheap, and scalable by direct mixing route followed by carbonization at 900 °C under the N 2 atmosphere. The addition of Ni into NC substantially increases the crystallite size, particle size, and I D /I G ratio. The NiÀ NC sample exhibits excellent bifunctional OER and HER activities.The overpotentials to achieve (À ) 10 mA.cm À 2 current density for the OER were 400 mV and 263 mV for the HER in 0.1 M NaOH electrolyte. The Tafel slope analysis of the NiÀ NC sample for the OER (123 mV.dec À 1 ) revealed the hydroxyl-ion discharge is the rate-determining step. In comparison, for the HER (145 mV.dec À 1 ), the Volmer-Heyrovsky pathway is the ratedetermining step. The short-term stability test displayed the sustained current density for 10 h at 1.68 V vs. RHE.
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