As electronic devices are indispensable in many aspects of our lives today, their integration with unconventional surfaces is increasingly essential. Electronic devices which maintain their electrical properties upon stretching are desirable for various wearable applications. Stretchable devices demonstrated are conventionally fabricated using semiconductor processing techniques. In this study, we demonstrate stretchable electrodes, which are basic components of electrical circuits, using screen printing, a large area printing method. It provides a low cost and scalable method to fabricate large area stretchable devices. Despite the larger width and thickness of the electrodes which increases the stiffness of the material, stretchability beyond 40% is demonstrated, which is suitable for certain wearable applications. The stretchable electrodes are integrated with light emitting diodes (LEDs) to demonstrate a stretchable LED matrix. The large area LED matrices exhibit variable stretchability, depending on the LED areal coverage. This technique is expected to be applicable in the fabrication of other stretchable, large area, and more complex electronic systems.

Nanoindentation is useful for evaluating the mechanical properties, such as elastic modulus, of multilayer thin film materials. A fundamental assumption in the derivation of the elastic modulus from nanoindentation is that the unloading process is purely elastic. In this work, the validity of elastic assumption as it applies to multilayer thin films is studied using the finite element method. The elastic modulus and hardness from the model system are compared to experimental results to show validity of the model. Plastic strain is shown to increase in the multilayer system during the unloading process. The indentation-derived modulus of a monolayer material shows no dependence on unloading plasticity while the modulus of the multilayer system is dependent on unloading-induced plasticity. Lastly, the cyclic behavior of the multilayer thin film is studied in relation to the influence of unloading-induced plasticity. It is found that several cycles are required to minimize unloading-induced plasticity.

Indentation deformation of glass under a sharp diamond indenter causes cracking during and after a loading–unloading cycle. To get a deeper insight into the indentation cracking in glass, it is critical to understand the elastic and inelastic deformation behavior of glass under the indenter. In this study, in situ observations during Vickers indentations are carried out for silica, soda-lime, and lead–silicate glasses. It is found that the true contact area during indentation is different from the area estimated from the contact depth and the indenter geometry, and that the ridges of a Vickers indenter affect the contact shape during indentation. The contact region of silicate glasses under a Vickers indenter is not a regular square but a concave square. This results in edge cracking during indentation. It is concluded that the contact shape and the deformation mechanism of glass under the indenter are closely related to its cracking behaviors.

This study describes the nonlinear characteristics of SrCoO3-doped ZnO varistors and multilayer ceramic varistors (MLCVs) with copper electrodes, both of which are sintered in a reducing atmosphere. Due to postannealing effects in air or N2 with low-oxygen concentration (0.02%), bulk disks can be sintered in a reducing atmosphere, with a usable V1 mA/mm (e.g., 1600 V for bulk bodies or 1200 V for Cu cofiring) and highly nonlinear indices (α10 μA = V1 mA/V10 μA < 1.3), regardless of whether cofiring with Cu electrodes on disk surfaces was conducted or not. On the basis of this procedure, Cu-MLCVs were successfully produced, without oxidation of Cu-internal electrodes or structural defects. They exhibited high stability as well as a useful nonlinearity of V1 mA = 10.4 V and α10 μA = 1.93. The resultant stability against electrostatic discharge (ESD) satisfies the highest standard of level 4 in IEC61000-4-2 (ESD stability test). This is the first report to show that MLCVs with base metals have practical properties, including stability.

A facile synthesis method was adapted to prepare Ortho-chloropolyaniline/graphite oxide (OPANI/GO) composites. The properties of these composites have been discussed based on different characterizations such as scanning electron microscopy, FTIR, and dielectric studies. The important peaks of benzenoid and quinoid rings in the spectrum confirm the formation of composites. Scanning electron microscopic studies indicate that the morphology of the prepared composites was influenced by different weight ratios of GO in OPANI and the resulting micrographs of these composites exhibited flaky and folded structures. The electrical conductivity study was carried out and found that 6 wt% of GO in PANI shows high conductivity value of 20 × 10−2 S/cm. The obtained results suggest an easy approach to prepare such novel nanocomposites with excellent dielectric properties which can be used in many technological applications.

A noncentrosymmetric aluminum borate crystal, Al5BO9, was obtained via high-temperature solution method. Considering the structure diversities of Al5BO9, the single crystal structure was cautiously redetermined before the investigation. The fundamental building blocks of the structure are BO3 triangles, AlO4 tetrahedra, and AlO6 octahedra. Since Al5BO9 only consists of strong covalent B–O and Al–O bonds, it is worth investigating the structure–optical property relationship thoroughly, especially the linear and nonlinear optical properties. To gain further insight into the origin of the nonlinear optical response of Al5BO9, the electronic structure calculations, second harmonic generation (SHG)-weighted electron density, and dipole moment of polyhedra were analyzed in detail. All evidences deduced from calculated results indicate that the SHG contribution from the Al–O polyhedra is more pronounced than that of the BO3 group in Al5BO9, which is anticipated to open a window for the search and design of new inorganic materials.

This work aims to synthesize PtPd catalytic clusters and to study the effect of the particle size, the curvature and possible alloying on the catalytic activity for oxygen reduction reaction, electrochemical stability, the mass-transfer of redox active species toward catalytic sites and the electro-kinetic of the oxygen reduction reaction (ORR) process. The curvature and the chemical composition of the catalyst surface significantly influence the electrochemically active surface area and catalytic activity toward oxygen reduction, regardless the particle size. The best catalytic activity was accomplished for 45 nm clusters due to possible alloying that enhance the O2 adsorption and dissociation. The complementary impedance studies demonstrated that 45 nm cluster has also the shortest effective diffusion length and the highest reaction rate constant among all morphologies, indicating on superior reactant transport to the catalytic sites. In addition, the 45 nm clusters showed improved electrochemical stability that is believed to be the combined effect of alloying and the compactness of the structure.

Liquid film migration (LFM) in the fiber laser welded Inconel 617 joint was investigated. The results show that the LFM occurs in HAZ of the laser welded Inconel 617 joint. The element of Mo in the migrated region is slightly richer than that in the adjacent matrix. The diffusional coherency strain due to the lattice mismatch between the element of Mo and the matrix atom is the dominant factor contributing to the occurrence of LFM in HAZ of laser welded Inconel 617. The migration of the liquid film is promoted by the thin initial liquid film and the slow cooling rate in large heat input. LFM tends to occur on the grain boundary (GB) with the fine particles and the GB-resolidified particles are formed on the GB with the large particles. Liquation cracking is reduced in the welds with the high heat input and in the solution treatment condition by LFM (1100 °C/1 h).

We investigated how coherent interfaces, between face centered cubic (fcc)/hexagonal close packed (hcp) systems, affect large strain deformation and fracture modes in hcp zircaloy aggregates with fcc hydrides. We derived 36 unique transformations related to coherent interfaces between fcc and hcp systems. We then used these orientation relations (ORs) with a dislocation-density crystalline plasticity formulation, a nonlinear finite-element, and a fracture approach that account for crack nucleation and propagation. We investigated how these ORs affect crack nucleation and propagation, dislocation density and inelastic slip evolution, stress accumulation, lattice rotation, and adiabatic heating. The predictions indicate that the physical representation of ORs affects local deformation and fracture behavior and are, therefore, essential for the accurate predictions of behavior at different physical scales in heterogeneous crystalline systems.

We investigated improvements to the mechanical properties of iron matrix composites for the case where the surfaces of the reinforcing particles are coated with copper and a hybrid mixture of different types of reinforcing ceramic particles (hybrid particles mixture) is used. Copper coating on the surfaces of SiC, TiC, and TiN particles can eliminate interfacial defects to significantly improve the composites' mechanical properties. The addition of uncoated hybrid particles mixture has little effect on the tensile strength improvement of composites compared with composites reinforced by monolithic particles, whereas copper-coated hybrid reinforcement has a significant effect. Any composite reinforced with copper-coated hybrid particles mixture will always have higher strength than that reinforced with monolithic particles. Our findings suggest that the load transfer between the matrix and reinforcing particles improved because of different elastic moduli, coefficients of thermal expansion and reaction heats of different types of reinforcing particles.

This research article investigates the effect of SiO2 flux on Nd:YAG laser welding of 5 mm thick plates of super-austenitic stainless steel, AISI 904L. Microstructure studies revealed multidirectional grain growth comprising columnar and cellular dendrites along with a prominent, fine equiaxed dendritic growth at the centerline of the fusion zone. Tensile studies showcased the fracture at the fusion zone in all the trials. The average tensile strength reported for the flux assisted laser weldments was found to be 587 MPa which was slightly lower than the parent metal. The impoverishment of tensile strength could be attributed to the formation of centerline equiaxed grains. Similarly the impact toughness of the joints was found to be 58 J. The studies demonstrated the possibility of using a 2 kW Nd:YAG laser welding machine to weld 5 mm thick plate with the use of SiO2 flux. A detailed study on the structure–property relationship of flux assisted Nd:YAG laser weldment was carried out using the combined techniques optical microscopy, scanning electron microscopy, and energy dispersive x-ray analysis.

Aluminum matrix composite with 10 wt% of MoO3 particulate reinforcement was synthesized through powder metallurgy technique. The cold upsetting studies of the composites were investigated based on Taguchi L9 orthogonal array experimental design to evaluate the significance of compaction pressure, sintering temperature, and sintering time on strength coefficient. The combination of 350 MPa pressure, 600 °C temperature, and 90 minutes sintering time was identified as the optimum blend for maximum strength coefficient using the main effect plot. From the analysis of variance, compaction pressure and sintering temperature were identified as highly contributing parameters on strength coefficient. Further, a confirmation test was also conducted with the optimum parameter for validation of the Taguchi results. X-ray diffraction and scanning electron microscopy were used to confirm the presence of MoO3 and its uniform distribution over the aluminum matrix.