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Optical metamaterials (OMs) at visible wavelengths have been extensively developed. OMs reported recently are all composed of periodic structure, and fabricated by top-down approaches. Here demonstrated are the colored visible light frequency metamaterials composed of double layer array disordered and geometrical variational dendritic cells as well as fabricated by a novel bottom-up approach. The experiment demonstrates that the OMs composed of random silver dendritic cells caused the appearance of multiple transmission passbands at red and yellow light frequencies. Moreover, the slab focusing experiment reveals a clear point image in the range of half-wavelength with an intensity of 5 % higher than that of the light source. The proposed OMs will create a new way to prepare the cloak and the perfect lens suitable for optical frequency. more...

A 2.0 mm thick Al–Li alloy 2198-T8 plate is welded by friction stir welding in this work. Four dog-bone type samples are designed to use and measure stress–strain curves and mechanical properties. M(T) samples with transverse weld in the center are designed. Fatigue tests under different R ratio loads are performed on the welded samples with crack growing in the welded nugget and parent material samples. Fatigue crack growth rates in these welded nuggets are obtained and compared. It is shown that there is no peculiar yielding process in the stress–strain curve of the welded nugget compared with the parent material. Yield strength and tensile strength have a “U” shape through the weld zone and a lower value in the weld zone while the elongation is in reverse. Unlike the parent material, fatigue crack growth rates in the welded nugget are not sensitive to R ratios. Based on K res , finite element models are built and the crack closure method is used to calculate the effect of residual stress. Redistributions of residual stress with crack growth are taken into account. Fracture surfaces are investigated to summarize the fracture feature of the welded nugget under fatigue load. more...

Large-scale ordered ultralong silver nanobelts, which built a beautiful chrysanthemum-like structure, are prepared on the interface between dibutyl sebacate (DBS) and silver nitrate solution by a chemical electro-deposition technique. The influences of chemical circumvent of interface, concentration of silver nitrate solution and applied voltage on the formation of silver nanobelts are investigated. It is shown that the silver nanobelts possess a perfect single crystal structure and well-defined nanobelt-like morphology with a length of 5 mm, width 80–150 nm, and thickness 20 nm, respectively. The growth mechanism of the nanobelts is discussed. Furthermore, UV–vis spectra of the silver nanobelts show similar surface plasmon resonance properties to silver nanowires. more...

Left-handed metamaterials (LHMs) composed of random dendritic cells demonstrate a multi-band resonance and negative refractive index. A nano-assembly approach is established to fabricate optical LHMs. Random nanostructures of silver dendritic cells are prepared and further fabricated into a sandwich-like structure with a dielectric medium. The dentritic nano-assembled configuration reveals a multi-band resonance and a high intensity of the pass-band at infrared frequencies, and can be facilely and cheaply prepared on a large-scale of effective area. more...