Composition and strain relaxation of In x Ga1−x N graded core–shell nanorods

Two In x Ga1−x N nanorod samples with graded In compositions of x = 0.5–0 (Ga-rich) and x = 0.5–1 (In-rich) grown by molecular beam epitaxy were studied using transmission electron microscopy. The nanorods had a wurtzite crystal structure with growth along 0001 and core–shell structures with an In-rich core and Ga-rich shell. Energy-dispersive x-ray analysis confirmed grading over the entire compositional range and showed that the axial growth rate was primarily determined by the In flux, and the radial growth rate by the Ga flux. There was no evidence of misfit dislocations due to grading, but the strain due to the lattice mismatch between the In-rich core and Ga-rich shell was relaxed by edge dislocations at the core–shell interface with Burgers vectors a and

Cracks, microcracks and fracture in polymer structures: Formation, detection, autonomic repair

The first author would like to acknowledge the financial support from the European Union under the FP7 COFUND Marie Curie Action. N.M.P. is supported by the European Research Council (ERC StG Ideas 2011 n. 279985 BIHSNAM, ERC PoC 2015 n. 693670 SILKENE), and by the EU under the FET Graphene Flagship (WP 14 “Polymer nano-composites” n. 696656)

Mechanical Properties of Poly(vinyl alcohol) Montmorillonite Nanocomposites

The properties of polymers are greatly enhanced when they are incorporated with silicate-layered clays as they find many applications in the fields of electronics, automobile industry, packaging, and construction. In this study a thermoplastic polymer poly(vinyl alcohol) (PVA) and montmorillonite (MMT) clay were used to prepare MMT-PVA nanocomposites and their mechanical properties were investigated. In general PVA is used in paper coating and packaging where their tensile strength and tearing strength are vital. The MMT-PVA nanocomposites displayed more than 60% increase in the tensile strength and young’s modulus where as the tearing energy doubles the value of neat PVA. This is a substantial enhancement compared to that reported so far. The enhancement was achieved at low clay content probably due to its exfoliated structure. The dispersed clay layers are well embedded with PVA matrix via strong interatomic interactions leading to better material properties. </jats:p

Microstructure of In x

Transmission electron microscopy is used to examine the structure and composition of In x Ga 1− x N nanorods grown by plasma-assisted molecular beam epitaxy. The results confirm a core–shell structure with an In-rich core and In-poor shell resulting from axial and lateral growth sectors respectively. Atomic resolution mapping by energy-dispersive x-ray microanalysis and high angle annular dark field imaging show that both the core and the shell are decomposed into Ga-rich and In-rich platelets parallel to their respective growth surfaces. It is argued that platelet formation occurs at the surfaces, through the lateral expansion of surface steps. Studies of nanorods with graded composition show that decomposition ceases for x ≥ 0.8 and the ratio of growth rates, shell:core, decreases with increasing In concentration