Constant strain rate nanoindentation hardness measurements at high sustained strain rates cannot be made in conventional nanoindentation testing systems using the commonly employed continuous stiffness measurement technique (CSM) because of the “plasticity error” recently reported by Merle et al. [Acta Mater.134, 167 (2017)]. To circumvent this problem, here we explore an alternative testing and analysis procedure based on quasi-static loading and an independent knowledge of the Young's modulus, which is easily obtained by standard nanoindentation testing. In theory, the method applies to any indentation strain rate, but in practice, an upper limit on the rate arises from hardware limitations in the testing system. The new methodology is developed and applied to measurements made with an iMicro nanoindenter (KLA, Inc.), in which strain rates up to 100 s−1 were successfully achieved. The origins of the hardware limitations are documented and discussed.

Variation of stress across the length and thickness of a cantilever during creep allows obtaining multiple pairs of strain rates and stress under steady-state condition. This work applies digital image correlation (DIC) and conjugate analytical models to obtain several such “strain rate–stress” pairs during steady-state creep by testing a single cantilever at a constant applied load. Furthermore, these strain rate–stress pairs are used to accurately determine the stress exponent of the material (e.g., Al and Pb). In addition, an empirical observation of plotting strain rate as a function of stress at fixed strain during primary creep for estimating stress exponent is extended to bending creep, wherein strain rates of the points in the cantilever lying on an iso-strain contour were plotted against the moment at the point to determine stress exponent. This study, thereby, proves that the “bending creep–DIC” combination is a high throughput test methodology for studying steady-state creep.

The stress and hence strain fields in a cantilever deforming as per power-law creep vary across the length and thickness of the sample, which allow obtaining multiple stress–strain pairs from a single test. Here, a high-throughput method is described to quantify the primary-cum-steady-state creep response of materials by testing a single cantilever sample in bending and mapping strain fields using digital image correlation. The method is based on the existence of stress invariant points in a cantilever, where the value of stress does not change during creep. It is demonstrated that strain evolution throughout primary and steady-state stages at these points is identical to the creep response obtained under uniaxial tests. Furthermore, the gained insights were exploited to obtain various parameters of a power-law type primary-cum-steady-state creep equation by testing only one cantilever sample. The developed method allows obtaining uniaxial creep curves at multiple stresses by testing a single cantilever, thereby reducing the time and number of samples required to understand the creep behavior of a material. The method has been validated by performing bending tests on Al and comparing the results with those of corresponding uniaxial tests.

A detailed electron backscatter diffraction (EBSD) characterization was utilized to investigate abnormal grain growth behavior of nanocrystalline (NC) Au films constrained by a flexible substrate under cyclic loading. Abnormally grown grains (AGGs) in front of about 15 fatigue cracks were picked out to investigate the grain reorientation behavior during abnormal grain growth in the fatigue crack tip in the cyclically deformed thin films. It shows that the AGGs exhibited 〈001〉 orientation along the loading direction, whereas grains grown far away from fatigue cracks had no significant texture change. The cyclic cumulative shear strain was found to play a key role in grain reorientation. A lattice rotation model was proposed to elucidate the grain reorientation mechanism during abnormal grain growth. Such grain reorientation behavior of NC metals was found to provide an intrinsic resistance of the NC metals to fatigue damage.

With the ever-increasing importance of nanoscale deformation phenomena in contemporary technologies, basic understanding of material behavior at the nanoscale has become of critical importance. Especially, nanomechanical testing that provides the capability to study fundamental nanoscale deformation and phase change phenomena in real time and under controlled loading conditions is essential for nanomaterial research. In this study, acoustic emission (AE) was used in situ to characterize nanoindentation-induced deformation, microfracture, and phase transformation processes intrinsic of bulk single-crystal MgO and polycrystalline Al, thin films of polycrystalline SiC, and thick films of austenitic TiNi shape-memory alloy. Scale-dependent plastic deformation and microfracture affected by the indenter tip radius and the applied normal load are interpreted in terms of the type and intensity of AE events revealed by abrupt displacement excursions in the loading response of the indented materials. The amplitudes of AE waveforms are used to examine characteristic deformation, microfracture, and phase change mechanisms in the time domain. Fast Fourier transformation and short-time Fourier transformation analyses provide further insight into the material behavior and structural changes due to indentation loading in the frequency and time-frequency domain, respectively. The methodology developed in this study represents an effective approach for nanomechanical testing and in situ characterization of nanoscale deformation, microfracture, and phase transformation phenomena.

A systematic analysis was carried out to study the effect of shock waves on copper sulfate crystal in such a way that its optical properties and surface morphological properties were examined for different number of shock pulses (0, 1, 3, 5, and 7) with the constant Mach number 1.7. The test crystal of copper sulfate was grown by slow evaporation technique. The surface morphological and optical properties were scrutinized by optical microscope and ultraviolet–visible spectrometer, respectively. On exposing to shock waves, the optical transmission of the test crystal started increasing from the range of 35–45% with the increase of shock pulses and thereafter started decreasing to 25% for higher number of applied shocks. The optical band transition modes and optical band gap energies were calculated for pre- and post-shock wave loaded conditions. The experimentally obtained data prove that the optical constants such as absorption coefficient, extinction coefficient, skin depth, optical density, and optical conductivity are strongly altered, so also the optical transmission due to the impact of shock waves. Hence, shock wave induced high transmission test crystal can be used as an appropriate candidate for ultraviolet light filter applications.

In this work, PbS and PbS/CdS core–shell quantum dots (QDs) were synthesized by a new photochemical approach. Prepared QDs were characterized by means of x-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive x-ray analysis (EDAX), UV–Vis, and Z-scan analyses. Synthesized QDs were in a cubic phase with a spherical morphology, and the crystallite sizes are estimated using the strain–size method. A uniform shift of Bragg diffraction peaks and quenching (200) Bragg plane are interpreted as the growth of the CdS shell. Linear optical properties were investigated using Urbach analysis and Tauc formula. It was found that the density of states of QD conduction and valence bands are three dimensional. The estimated sizes of PbS QDs and PbS/CdS using exciton absorption peaks at room temperature are 1.8 and 2.7 nm, respectively, which are in good agreement with the strain–size plot analysis. The growth of the CdS shell resulted in a considerable decrease in the nonlinearity refractive index and a significant increase in the nonlinear absorption.

The present work investigates the influence of sodium doping on structural, morphological, photoluminescence, linear, nonlinear (NL), and optical limiting (OL) parameters of NaxCd1−xS thin films (where x= 0.0, 0.5, 1.0, 2.5, and 5.0 wt%) deposited on glass substrates using spray pyrolysis route. X-ray diffraction and Raman analyses confirmed the hexagonal polycrystalline nature of films. Crystallite sizes were decreased from 30 to 17 nm with doping. Scanning electron microscopy (SEM) micrographs also confirmed the nanocrystalline spherical growth. Energy dispersive X-ray spectroscopy (EDS) and SEM mapping studies revealed the presence and homogeneous distribution of individual elements. Transmission of films is found to lie between 45 and 60%. Although the low doping caused the reduction of the effective band gap, higher doping caused a blue shift in band gap, with an associated reduction in crystallite sizes. The refractive index values are found within 1–2 in visible and their maximum values (in range 2.65–3.16) are observed at 2500 nm. Photoluminescence (PL) spectra showed broad emission peak at ∼520 ± 10 nm. Dielectric and NL analyses were also carried out. OL results were promising for the systematic gradual decrease of intensity from 100 to 72%, with doping for power regulating applications.

A simple composition of TeO2–Yb2O3 binary glass was selected as the host glass matrix for discussing the structure of tellurite glass with increasing Yb2O3 content. Raman spectra were measured to investigate the structure of the binary tellurite glasses, and upconversion and downconversion fluorescence characteristics were employed for discussing the relationship between the structural units and the state of Yb3+ in the tellurite glasses. The results suggested that the decrease of TeO4/2 in the glasses would result in the formation of Yb3+ clusters and Yb3+–O2− couple in the tellurite glasses, and then results in the decrease of cooperative upconversion and downconversion fluorescence intensity.

A de novo drug delivery nanosystem based on gold nanoparticles (GNPs), decorated poly(ethylene glycol) (PEG), and folate (FA)-conjugated graphene oxide (GO) was designed and developed successfully. Initially, the graphite (G) powder was oxidized to the GO, and then functionalized with chloroacetic acid to afford a carboxylated graphene oxide (GO–COOH). The obtained GO–COOH was functionalized with an amine end-caped PEG, FA, as well as 3-amino-1-propanethiol to produce a GO–PEG–FA–SH. In another experimental section, GNPs were synthesized through a citrate-mediated reduction approach, and subsequently decorated onto/into GO–PEG–FA–SH through the formation of Au–S bond to afford a GO–PEG–FA/GNP nanosystem. The resultant nanosystem was loaded with doxorubicin hydrochloride (DOX) as a model anticancer drug, and its drug-loading capacity as well as pH-dependent drug release behavior were investigated. The anticancer activity of the developed theranostic nanomedicine was extensively evaluated using MTT assay against human breast cancer cells (MCF7). The developed GO–PEG–FA/GNPs–DOX theranostic nanomedicine exhibited an excellent cancer chemotherapy feature. In addition, this nanomedicine can be used in chemo-photothermal therapy of solid tumors because of the presence of GO and GNPs in its structure.