Sun Ig Hong

Novel green synthetic strategy to prepare ZnO nanocrystals using rambutan (Nephelium lappaceum L.) peel extract and its antibacterial applications.

In the present investigation, we report a sustainable novel green synthetic strategy to synthesis zinc oxide nanocrystals. This is the first report on sustainable biosynthesis of zinc oxide nanocrystals employing Nephelium lappaceum L., peel extract as a natural ligation agent. Green synthesis of zinc oxide nanocrystals was carried out via zinc-ellagate complex formation using rambutan peel wastes. The successful formation of zinc oxide nanocrystals was confirmed employing standard characterisation studies. A possible mechanism for the formation of ZnO nanocrystals with rambutan peel extract was also proposed. The prepared ZnO nanocrystals were coated on the cotton fabric and their antibacterial activity were analyzed. ZnO nanocrystals coated cotton showed good antibacterial activity towards Escherichia coli (E. coli), gram negative bacteria and Staphylococcus aureus (S. aureus), gram positive bacteria.

Structural and toxic effect investigation of vanadium pentoxide.

A facile inorganic complex synthesis route has been developed to synthesis V2O5 nanostructures. The effects of varying incubation time on the crystallinity and morphology of the V2O5 phase has been investigated. The obtained XRD result clearly revealed the pure orthorhombic V2O5 crystalline phase. Raman antiphase bridging VO and chaining VO stretching modes peaks at 686 and 521cm(-1) attributed orthorhombic V2O5 characteristics. The V2p3/2 peak at the binding energies of 517eV and V2p1/2 peak at 524eV assigned to V(5+) oxidation state. Bioinspired V2O5 nanostructures as a biocompatible material for anticancer agents show excellent cytotoxicity at higher V2O5 concentration.

Nanocomposited and Functionally Graded ZrN/HA Coatings on cp-Ti by RF Magnetron Sputtering

Nanocomposited and Functionally graded (FG) ZrN/hydroxyapatite coatings with good mechanical strength and biocompatibility were prepared on cp-Ti substrate for biomedical applications and detailed analysis of the nanocomposite coatings for its structural, morphological, topographical and biocompatibility properties were carried out. Crystallite size of the coating for the functionally graded coatings was smaller compared to that of nanocomposite coatings. The arrangement of grains was observed to be denser in the FG coatings due to the decrease in the grain size. Hardness and modulus of FG coatings were observed to be greater than those of nanocomposite coating, which was attributed to the reduction in the crystallite size in FG coatings. Both ZrN/HA nanocomposite and functionally graded coatings was found to induce biomineralization formation, suggesting both are promising candidates for the future biomedical applications.

Interface Cracking and Fracture in As-Roll-Bonded and Heat-Treated 3-Ply Cu/Al/Cu Hybrid Plate

The interface cracking and fracture behaviors of as-roll-bonded and heat-treated 3-ply Cu/Al/Cu clad metal were investigated Interfacial intermetallic layer were observed to be formed at the Cu/Al interface upon annealing at and above 300°C. The presence of Cu9Al4, CuAl, Cu3Al2 and CuAl2 at the Cu/Al interface was confirmed by XRD. The intermetallic reaction layer has a detrimental effect on the bonding strength of the Cu/Al/Cu clad metal, inducing interface cracks. The length of the delaminated region increased with increasing heat treatment temperature. No strain incompatibility and cracks were observed across the interface in the as roll-bonded clad composite and, for annealed clad composites at 300°C, some appreciable strain incompatibiliy developed, starting to form interface microcracks. For annealed clad composites at 450°C, the interface crack opened wide up with strain because the separated Cu and Al plate deform, developing their independent necks and fracture independently.

Mechanical Reliability of Oxidized Zr-1.1Nb-0.5Cu Alloy Nuclear Cladding Tube in Compression

Ring compression tests on the oxidized Zr-1.1Nb-0.05Cu cladding tubes were performed to examine the mechanical reliability of Zr-Nb-Cu cladding tubes. In compression of the non-oxidized cladding tubes, large load drop associated with the cladding failure appeared at the total displacement of 6.3 mm. After oxidation at 600°C for 24 hrs and 700°C for 3 hrs, small drop of load resulting from small cracks in the thin oxide film was observed at the total displacement of 1.0 mm. After oxidation at 700°C for 24hrs, load was extremely low, but catastrophic fracture occurred at the total displacement of 6.2~6.5 mm. The oxide of Zr-1.1Nb-0.05Cu cladding tubes formed at high temperature apparently causes the premature failure of tubes.

Microstructure and Mechanical Propertiesof Ti/Cu-Cr/S20C and Ti/Cu-Ag/S20C Clad Composites

In this study Cu-Ag or Cu-Cr layer was sandwiched by Ti and Fe plates and the three layers of Ti/Cu-8Ag/S20C were clad by High Pressure Torsioning(HPT). The effect of post-HPT heat treatment on the interfacial reaction products and the mechanical performance in Ti/Cu-Ag/S20C and Ti/Cu-Cr/S20C clad material were studied. Cu4Ti3 and Cu4Ti Intremetallic compound layers were observed at the Ti/Cu-Ag and Ti/Cu-Cr interfaces in the clad heat-treated at 500°C where as no intermetallic compounds were observed at the Cu-Ag/S20C and Cu-Cr/S20C interfaces. The strength of as-HPTed Ti/Cu-8Ag/S20C is much higher than that of Ti/Cu-1Cr/S20C. The strengthening mechanism of Cu-Ag deformed severely is the interface and strain hardening in which dislocations are deposited at the Cu/Ag interfaces and can contribute to the strengthening of the clad composite just after HPT processing, rendering the high strength just after processing. In both clad composites, the strength and ductility increased after heat treatment at 350°C, which are likely caused by the enhanced bonding at the interfaces.

Bending Deformability and Fracture Behavior of Heat-Treated 3-ply Cu/Al/Cu Clad Plates

The effect of heat treatment on the bending deformability and fracture behavior of roll-bonded Cu/Al/Cu clad plates were investigated. As-rolled clad plate and that annealed at 200OC exhibited the initial high load maintained for a short period and then a rapid drop of the load. The rapid softening promotes the continued localized bending once bending occurs because the work hardening due to the localized bending is negligible, leading to the localized fracture. Cu/Al/Cu clad metal annealed at 300OC, up to 450OC, initial load for bending decreased remarkably due to recovery/recrystallization, but work hardening occurred for an extended period before gradual softening took place. The initial extensive work hardening in the localized bent region tends to distribute the bending deformation uniformly, leading to the rather uniform bending. For annealed clad plates at high temperatures, the periodic cracks perpendicular to the interface were observed in the intermetallic layer and the localized slip developed both in Cu and Al emanating from the open cracks in the intermetallic layer. The localized slip marking was more evident in Cu than in Al, reflecting the lower stacking fault energy in Cu.

Creep Behaviors of Stress-Relieved and Annealed Zr-1Nb-0.7Sn-0.1Fe Nuclear Cladding Tubes at Intermediate Temperatures

In order to explore the possibility of enhanced creep resistance by grain size control, creep tests of stress-relieved and annealed Zr-1Nb-0.7Sn-0.1Fe cladding tubes were carried out at intermediate temperatures. The creep rate decreased significantly with increase of grain size from ~1.2 μm to 4 μm with annealing. The stress exponent was observed to be in the range of 5.0~6.5 for both stress-relieved and annealed Zr-1Nb-0.7Sn- 0.1Fe, suggesting that the dislocation climb is the rate controlling creep mechanism. It was shown that not only the creep rate decreased but also creep life increased in the annealed Zr-1Nb-0.7Sn-0.1Fe, suggesting the grain size control may provide an effective way to enhance the creep resistance in Zr alloys for nuclear application.

Interfacial Microstructure of Diffusion-Bonded and Annealed Cu-10Fe/Al6061 Clad Material

Diffusion bonding between the Cu-10%Fe and Al6061 alloys were successfully achieved at various temperatures (450-525°C) in the argon atmosphere. The bonding interface regions were analyzed using scanning electron microscopy and energy dispersive spectrometry and XRD. The presence of Fe particles in Cu was found to have an influence on the kinetics of intermetallic compound layer formation. Cu-Fe/Al 6061 exhibited the slower growth rate of intermetallic layers than Cu/Al 6061 after diffusion bonding. The movement of Cu-Fe/Cu9Al4 interface into Cu-Fe substrate appears to be hindered by the presence of populated Fe-containing particles and filaments. In addition to Cu9Al4, CuAl and CuAl2 intermetallic layers, Al7Cu2Fe and unreacted Fe were observed to be present in the intermetallic layers. The intermetallic layers which are close to Cu such as Cu9Al4 and CuAl were observed to be harder in Cu-10%Fe/Al 6061 than in Cu/Al 6061, suggesting Fe and its intermetallics have some strengthening effect on Cu9Al4 and CuAl.

Effect of Nitrogen Flow Rate on the Structure and Properties of TiN Thin Films Deposited onto β-Type Ti-15Mo-3Nb-3Al-0.2Si Alloy Substrates by Reactive Magnetron Sputtering

Titanium Nitride (TiN) thin film was deposited on β-type Ti-15Mo-3Nb-3Al-0.2Si alloy plates by RF magnetron sputtering method. The effect of nitrogen flow rate on the structure and properties of the TiN thin films were studied. The preferred orientation of TiN thin films changed from (111) to (200) as the nitrogen flow rate increased due to the effect of the kinetic energy of the bombarding particles. The coating thickness was found to decrease with increasing nitrogen concentration, which also favors (200) orientation with increasing nitrogen flow rate. With increase of nitrogen flow, the morphology of the TiN thin films films changed from characteristic pyramidal shaped grains to columnar-shaped grains. The roughness analysis of the coating shows that the average roughness of the coating decreased with increasing nitrogen flow rate. The increase of hardness with increasing nitrogen flow rate is attributed to the decrease in grain size.