A novel method for the in situ thermomechanical test of micro/nanoscale samples at high temperature is presented. During the in situ test, the stage is resistively heated while the temperature is measured by a cofabricated temperature sensor. For experimental demonstration of the thermomechanical testing method, we fabricate the Micro-Electro-Mechanical Systems (MEMS) stage using silicon carbide (SiC) and carry out in situ uniaxial tests for single-crystal silicon (SCS) microsamples at temperatures from room temperature to 400 °C. We recover the known elastic modulus of SCS within 1% error in this temperature range.

Pop-ins on nanoindentation load–displacement curves of a ferritic steel were correlated with yield drops on its tensile stress–strain curves. To investigate the relationship between these two phenomena, nanoindentation and tensile tests were performed on annealed specimens, prestrained specimens, and specimens aged for various times after prestraining. Clear nanoindentation pop-ins were observed on annealed specimens, which disappeared when specimens were indented right after the prestrain, but reappeared to varying degrees after strain aging. Yield drops in tensile tests showed similar disappearance and appearance, indicating that the two phenomena, at the nano- and macro-scale, respectively, are closely related and influenced by dislocation locking by solutes (Cottrell atmospheres).

The shapes of the interfacial delamination crack and stress states during wedge indentation in a soft-film-on-hard-substrate system were investigated systematically using the three-dimensional (3D) finite element simulation and wedge indentation experiment. In the simulation, a traction–separation law was used to characterize the failure behaviors of the interface. The effects of the wedge indenter tip length and the film thickness on the onset and growth of interfacial delamination were analyzed. It was shown that a two-dimensional (2D) to 3D transition of stress states occurred depending on the ratio of indenter length to film thickness. Furthermore, the interfacial delamination process by wedge indentation was conducted experimentally, and comparisons between the computational and experimental results yielded quantitative good agreement. Finally, a straightforward criterion based on the curvature of the delamination crack front was proposed to indicate the transition of stress states during the interfacial delamination. A guideline was therefore proposed to classify the 2D and 3D stress states for extracting the interface adhesion properties.

In this study, bulk and multifoil diffusion couple experiments were conducted to examine the interdiffusion process in Ni–Pt and Co–Pt binary alloy systems. Inter-, intrinsic-, and tracer-diffusion coefficients at different temperatures, and as a function of the composition, were estimated by using the experimental data. Results show that in both the alloy systems, Pt is the slower diffusing species, and hence the interdiffusion process is controlled by either Ni or Co. The thermodynamic driving force makes the intrinsic diffusion coefficients of Co and Ni higher in the range of 30–70 at.%. The low activation energy for Co and Ni impurity diffusion in Pt compared with Pt in Ni and Co indicates that the size of the atoms plays an important role. The vacancy wind effects on the diffusion process are examined in detail, and it was demonstrated that its contribution falls within the experimental scatter and hence can be neglected.

Gold nanoparticle–coated ZnO tetrapods have been utilized as a substrate for the detection of fluorescently labeled protein tetramethylrhodamine isothiocyanate bovine serum albumin and phospholipid 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine-N-(Lissamine rhodamine B sulfonyl) down to the concentrations of 15 pM and 79 nM, respectively. Our detection scheme is based on enhanced fluorescence excitation of the biomolecular analytes by the surface plasmon polaritons of gold nanoparticles coated on the ZnO tetrapod whiskers. This enhanced excitation is confirmed using COMSOL Multiphysics, where the optical near field is shown to be dependent on the coating density of the gold nanoparticles and branching of the ZnO nanostructures.

Porous zirconium metal microspheres were synthesized successfully by a combustion technique using ZrO2 + 2Mg starting mixture. In this process, a controlled amount of KClO3 + 3Mg is mixed with ZrO2 + 2Mg to enable a self-sustaining combustion process and to promote a reduction of the ZrO2. The framework structure, morphology, and porosity of zirconium microspheres were determined using various techniques. Microscopic visualization suggested that the spherical structure has macroporous windows of diameter ∼0.5–5.0 μm and the space between the macropores has a wormhole-like mesoporous/microporous structure. The mesoporous structure had a pore diameter of ∼1.19 nm. This procedure provides an easy method for the synthesis of porous microspherical assemblies of Zr composed of submicrometer size particles.

Ba8Ga16−xGe30+x is the clathrate with the highest thermoelectric figure of merit known to date. However, no p-type material could be obtained by conventional synthesis from the melt. Here we show that the time and cost-effective melt spinning technique can produce Ba8Ga16−xGe30+x in a metastable state, where x can be varied continuously from negative to positive values, resulting in both p- and n-type materials. The quenched phases were characterized by x-ray powder diffraction and transmission electron microscopy. It was surprising that they were perfectly crystalline, with large grain sizes of the order of a micrometer. Temperature dependent measurements of the electrical resistivity, Hall effect, thermopower, and thermal conductivity are presented and discussed in terms of a two-band model.

This article reports on the role of annealing on the development of microstructure and its concomitant effects on the thermoelectric properties of polycrystalline AgPbmSbTe2+m (m = 18, lead–antimony–silver–tellurium, LAST-18) compounds. The annealing temperature was varied by applying a gradient annealing method, where a 40-mm-long sample rod was heat treated in an axial temperature gradient spanning between 200 and 600 °C for 7 days. Transmission electron microscopy investigations revealed Ag2Te nanoparticles at a size of 20–250 nm in the matrix. A remarkable reduction in the thermal conductivity to as low as 0.8 W/mK was also recorded. The low thermal conductivity coupled with a large Seebeck coefficient of ∼320 μV/K led to high ZT of about 1.05 at 425 °C for the sample annealed at 505 °C. These results also demonstrate that samples annealed above 450 °C for long term are more thermally stable than those treated at lower temperatures.

Within the framework of a new optimization strategy based on self-compatible thermoelectric elements, the ability to reach maximum performance is discussed. For the efficiency of a thermogenerator and the coefficient of performance of a Peltier cooler, the constraint z T = ko = const. turned out to provide a suitable criterion for judging maximum performance. In this paper ko is calculated as an average of the temperature dependent figure of merit z T.

This article gives a brief comparative overview of the upper critical fields Hc2(T)—the magnetic fields above which superconductivity disappears—of MgB2- and Fe-based superconductors. We discuss manifestations of multiband superconductivity, Pauli pair-breaking, and pairing symmetry in the shapes of Hc2(T) curves, and the ways of tuning Hc2(T) by doping and by impurity scattering. We show that the effective route to high Hc2 is by disordering in MgB2 and by doping-assisted tuning of the Fermi surface in Fe-based superconductors. These effects allow extremely high Hc2 values in both material classes that well exceed those found in Nb-based superconductors, opening up new opportunities for high-field applications.

Improved room temperature plasticity was achieved by microalloying Cu in a series of (Fe71Nb6B23)100−xCux (x = 0, 0.25, 0.5, 0.75, and 1) glass matrix alloys with tunable size and volume fraction of precipitates composed of α-Fe and Fe23B6 phases. When ∼10-nm-sized nano-scale precipitates are formed with a size comparable to the shear bandwidth by controlling the added content of Cu, the (Fe71Nb6B23)99.5Cu0.5 alloy exhibits a maximum plastic strain of 4.3 ± 0.8% with pronounced multiple shear banding. A further increase in the size of the precipitates up to micrometer scale results in catastrophic fracture accompanied with irregular cracks, revealing that the fracture mechanism of the different alloys is controlled by the precipitate size.