Fatigue properties of Mo/W multilayers with individual layer thickness (λ) of 5, 20, 50 and 100 nm on flexible polyimide substrates were investigated. The experimental results show that the fatigue resistance increases with decreasing λ from 100 nm to 20 nm, and reaches the maximum at λ=20 nm, and then decreases when further decreasing λ. Fatigue cracks of Mo/W multilayers with different λ were found to propagate along columnar grain boundary in the out-of-plane direction and along the boundary of cluster structures. The enhanced fatigue resistance is attributed to the larger cluster inclination angles and the more tortuous in-plane cracking paths.

Fracture of crystalline silicon (c-Si) solar cells in photovoltaic modules is a big concern to the photovoltaics (PV) industry. Cell cracks cause performance degradation and warranty issues to the manufacturers. The roots of cell fractures lie in the manufacturing and integration process of the cells and modules as they go through a series of elevated temperature and pressure processes, involving bonding of dissimilar materials, causing residual stresses. Evaluation of the exact physical mechanisms leading to these thermomechanical stresses is highly essential to quantify them and optimize the PV modules to address them. We present a novel synchrotron X-ray microdiffraction based techniques to characterize the stress and fracture in the crystalline silicon PV modules. We show the detailed stress state after soldering and lamination process, using the synchrotron X-ray microdiffraction experiments. We also calculate the maximum tolerable microcrack size in the c-Si cells to sustain the residual stress after lamination. We further demonstrate the effect of these residual stresses on the cell fractures using the widely accepted fracture (4-point bending) tests. These test results show that the soldering and lamination induced localized residual stresses indeed reduce the load-carrying capacity of the c-Si cells.

Conductive composites are being considered for use in applications such as electromagnetic shielding. Prior work has shown correlation of electrical conductivity to the microstructure of corresponding composite. In the present paper, composites consisting of polyurethane acrylic and dispersed nickel nanoparticles were fabricated, and tested for their electrical conductivity. In the fabrication process, half of the suspensions were agitated by sonication and half were not. Correlations between electrical conductivity and composite microstructural details are presented. These correlations show an optimum concentration of nickel nanoparticles that result in maximum conductivity enhancement. In addition, sonicating the suspensions increased conductivity of resulting nanocomposites. Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS) images were used to estimate surface concentration and distribution of Nickel nanoparticles, and were correlated to electrical conductivity measurements. Parameters such as number of particles in contact and junction distance between the nano particles in the composites are suggested as a way of enhancing electrical conductivity.

Natural structural materials (NSMs) such as nacre, teeth, bones and crustacean exoskeleton are usually made of weak biomaterials arranged in specific structural design imparting them remarkable mechanical characteristics. Such hierarchical structural layouts found in nature encourage designing of mechanically desirable synthetic structural materials (SSMs). Among variety of natural hierarchical layouts, this paper specifically focuses on helicoidal architectural design found in the tough dactyl club of mantis shrimp. We first decode the mechanics behind helicoidal microstructural design and document the development of impact resistant macroscale helicoidal architectured synthetic structural materials (HA-SSMs). Next, near-field electrospinning technique (NFES)- both melt (polycaprolactone) and solution (polyvinylidene fluoride) type has been discussed in detail, as a novel method for developing lab scale 3D biomimetic HA-SSMs in micro-nanoscale. Further, the effect of the helical arrangement, size of substructures and surface treatment on strength and toughness of NFES fabricated HA-SSMs samples is analysed.

Soil samples were obtained from three different locations; Ijapo, Ibule and FUTA North Gate in Akure, Ondo State, Nigeria. The materials were dried, crushed and calcined by heating the samples in a muffle furnace to 850 °C, holding for three hours and and then brought out of the furnace to cool in the laboratory so that the organic and volatile matter escaped, and the oxide content increased. The calcined materials were milled with a ball mill and then sieved with 75 µm mesh size British standard sieves. The samples that passed through the sieves were collected for analysis to determine their extender characteristics through x-ray flouresence (XRF) spectroscopy, x-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), specific gravity, oil absorption, pH and refractive index measurements as well as the determination of their resistance to chemicals. XRF results showed that materials are kaolinite in nature. XRD results showed the phase compositions of each sample as materials suitable for applications as extenders in the paints industry. SEM micrographs showed the homogeneity of the samples from Ijapo and FUTA North Gate while the sample from Ibule showed segregation of the phase compositions. The specific gravity, pH, oil absorption and refractive index of each material were within the range of those of commercial extenders used in the paints industry. The calcined materials were found to be resistant to various chemical media. The characterized materials will be suitable as extenders and pigments in the paints industry.