Antireflection coatings (ARC), not only reduce the reflection of the incident radiation but also protect the surface from environmental degradations. In present study, three- layer design was theoretically calculated and experimentally realized on the surface of lead chalcogenide, which had high refractive characteristics. First the theoretical designs of three- layers of different dielectric materials (i.e., ZnSe, SnO2, SiO and MgF2) were simulated using optical matrix approach. Subsequently, the developed designs were experimentally produced on lead sulfide thin films using thermal evaporation technique. The efficiency of the designs was evaluated for 1500-2400 nm spectral range and found that the design comprising ZnSe-SiO-MgF2 had 23% better performance than ZnSe-SnO2-MgF2, besides consistent coating adhesion and morphology. The difference between theoretical and experimental results was less than 10 and 16 % for ZnSe-SiO-MgF2 and ZnSe-SnO2-MgF2, respectively.

Abstract: Soldering electrical contacts to gold thin films is a matter of consideration due to high soldering temperature, restricted wetting, excessive scavenging and low strength offered by most of the common soldering alloys. Indium alloys offer certain benefits for gold soldering justifying their increased cost. In the present study, hypo-, hyper- and eutectic In-Ag solder were prepared and investigated for compositional and structural homogeneity, soldering temperature, contact angle, spreading factor, scavenging zone and scavenging phase (i.e. Auln2). It was found that addition of silver (-3.5%) ameliorated the above mentioned characteristics for better control of soldering practice with gold thin films besides lowering the soldering temperature.

Aluminum/carbon nanotube composite is a promising candidate material for aerospace applications owing to its high strength-to-weight ratio. Because of the low density of carbon nanotubes (CNTs), their dispersion is difficult in molten metal. We investigated induction melting, a fairly distinct approach to facilitate the dispersion of CNTs in molten aluminum. The nanocomposites were characterized using scanning electron microscopy, X-ray diffraction, transmission electron microscopy and mechanical testing. Refinement in crystallite size (∼320 nm) and increase in lattice strain (∼3.24 × 10−3) were observed in the composites. A simultaneous increase in yield strength (∼77%), tensile strength (∼52%), ductility (∼44%) and hardness (∼45%) was observed. Induction melting appeared to be a potential method to fabricate aluminum-CNTs composites.

During synthesis of MWCNTs using CVD, role of carbonaceous material and catalyst, besides other process parameters, has considerable influence on the structure and yield of pristine nanotubes. In present study, different flow rates (i.e. 10, 25, 40 and 55 sccm) of precursor ethanol were used for the synthesis of MWCNTs at 750 ºC in a CVD reactor, where nickel particles were supported on quartz as catalyst. Further, these nanotubes were characterized using XRD, SEM, TGA and Raman spectroscopy to investigate the effect of ethanol flow rate on the catalytic activity of nickel for optimum production of MWCNTs. It was observed that at different ethanol flow rates, variations in synthesis products (i.e. CNTs, amorphous carbon and carbon nanoparticles) were associated with catalytic activity. Maximum catalytic activity of nickel particles was attained by optimizing ethanol flow rate (at 25 sccm). At the optimum flow rate a maximum purity of MWCNTs (>83%) was attained along with other relevant structures i.e. amorphous carbon <1.5% and SWCNT <10% balancing with retained catalytic particles. Any increase from the optimum limit caused not only defects within the CNTs' structure but also increased the impurities which were correlated with the reduction in activity of the nickel particles due to the saturation of active sites.