Nanolamellar Tantalum Interfaces in the Osteoblast Adhesion

The design of topographically patterned surfaces is considered to be a preferable approach for influencing cellular behavior in a controllable manner, in particular to improve the osteogenic ability of bone regeneration. In this study, we fabricated nanolamellar tantalum (Ta) surfaces with lamellar wall thicknesses of 40 and 70 nm. The cells attached to nanolamellar Ta surfaces exhibited higher protein adsorption and expression of β1 integrin, as compared to the nonstructured bulk Ta, which facilitated the initial cell attachment and spreading. We thus, as expected, observed significantly enhanced osteoblast adhesion, growth, and alkaline phosphatase activity on nanolamellar Ta surfaces. However, the beneficial effects of nanolamellar structures on osteogenesis became weaker as the lamellar wall thickness increased. The interaction between cells and Ta surfaces was examined through adhesion forces using atomic force microscopy. Our findings indicated that the Ta surface with a lamellar wall thickness of 40 nm exhibited the strongest stimulatory effect. The observed strongest adhesion force between the cell-attached tip and the Ta surface with a 40 nm thick lamellar wall encouraged the much stronger binding of cells with the surface and thus well-attached, -stretched, and -grown cells. We attributed this to the increase in the available contact area of cells with the thinner nanolamellar Ta surface. The increased contact area allowed the enhancement of the cell surface interaction strength and, thus, improved osteoblast adhesion. This study suggests that the thin nanolamellar topography shows immense potential in improving the clinical performance of dental and orthopedic implants

Effect of water and mercury quenching on microstructure and mechanical behavior of room temperature rolled Zircaloy-2

The present study investigates the effect of water and mercury quenching on the microstructural and mechanical behavior of room temperature rolled Zircaloy-2. Solution treatment of zircaloy-2 at 1073 K followed by quenching in mercury and water has been performed prior to rolling. Different reduction from 25% to 85% of the quenched alloy and further characterization has been performed by tensile testing, Electron back scattered diffraction (EBSD) and Transmission Electron Microscopy (TEM). Enhanced tensile strength (745 MPa) after 85% rolling reduction was obtained compared to 389 MPa after water quenching. Rolling reduction results an increase in the dislocation density, thereby enhancing the mechanical strength. Initial deformation has been observed by the activation of extension twinning from EBSD microstructure. Twinning results the inclination of ‘c’ axis towards the normal direction which makes near basal grains orientation along the deformation direction. Due to hard orientation i.e. ‘c’ axis aligned along the loading direction, the grain fragmentation is heterogeneous. Grain fragmentation leads to improvement in the ductility with minimal loss in strength owing to rearrangement of dislocations after annealing at 400o C for 30 minutes. By optimizing the annealing temperature (400o C for 30 minutes) bulk ultrafine grained zircaloy-2 have been produced in 85% room temperature rolled zircaloy-2

Effect of water and mercury quenching on the microstructure and mechanical behavior of room temperature rolled Zircaloy-2

432-436The present study investigates the effect of water and mercury quenching on the microstructural and mechanical behavior of room temperature rolled Zircaloy-2. Solution treatment of Zircaloy-2 at 1073 K followed by quenching in mercury and water has been performed prior to rolling. Different reduction from 25% to 85% of the quenched alloy and further characterization has been performed by tensile testing, Electron back scattered diffraction (EBSD) and Transmission Electron Microscopy (TEM). Enhanced tensile strength (745 MPa) after 85% rolling reduction was obtained compared to 389 MPa after water quenching. Rolling reduction results an increase in the dislocation density, thereby enhancing the mechanical strength. Initial deformation has been observed by the activation of extension twinning from EBSD microstructure. Twinning results the inclination of ‘c’ axis towards the normal direction which makes near basal grains orientation along the deformation direction. Due to hard orientation i.e. ‘c’ axis aligned along the loading direction, the grain fragmentation is heterogeneous. Grain fragmentation leads to improvement in the ductility with minimal loss in strength owing to rearrangement of dislocations after annealing at 400o C for 30 minutes. By optimizing the annealing temperature (400o C for 30 minutes), bulk ultrafine grained Zircaloy-2 have been produced in 85% room temperature rolled Zircaloy-2

Surface segregation of primary glassy nanoparticles of Fe90Sc10 nanoglass

Electron energy loss spectroscopy (EELS) technique has, been used to map the elemental distribution in Fe90Sc10 primary glassy nanoparticles (GNp) and in the corresponding nanoglass (NG) produced by consolidation of the GNp. Due to the effect of surface segregation, Fe has been identified to enrich at the surfaces of the primary GNp. This behavior was found to agree with the theoretical results calculated based on a monolayer model. In addition, the heterogeneous structure of Fe90Sc10 NG with Fe enriched interfaces have also been observed directly, which may be attributed to the surface segregation of the primary GNp. (C) 2016 Elsevier B.V. All rights reserved

Influence of wire rolling on Zircalloy-2: tensile behaviour and microstructural investigation

In the present work, the microstructure, tensile and texture properties of Zircalloy-2 (Zr-2) processed by the room temperature wire rolling (RTWR) have been investigated. The detail microstructural investigation was performed with the help of optical microscopy, Transmission Electron Microscopy (TEM) and Electron Back Scattered Diffraction (EBSD). Dislocation density was calculated by using X-ray diffraction (XRD) through modified Williamson Hall technique. The dislocation density increased as the true strain increased from 0.69 to 1.32, but at the same time when true strain increased from 1.32 to 2.77, dislocations density start decreasing. It was occurred due to the formation of large volume fraction of dynamic recrystallization grains (DRX) after inducing true strain of 2.77. The maximum yield strength of 750 MPa was achieved after true strain of 1.32, but as the induced true strain increased to 2.77, the yield strength decreased to 620 MPa. It was due to the formation of high volume fraction of DRX grain and grain coarsening led by the dislocations annihilation mechanism. The highest ductility was achieved after true strain of 2.77 is attributed to domination of dislocations annihilation assisted mechanism. The EBSD and tensile test investigation further confirmed the presence of Extension twinning ({101¯2}) after inducing a true strain of 1.32 and more, which signify the severe deformation through the RTWR. Further, deformation mechanism of Zr-2 alloy has been proposed through processing by RTWR with the help of experimental investigation

Nanofriction of Graphene/Ionic Liquid-Infused Block Copolymer Homoporous Membranes

We have infused graphene/ionic liquid into block copolymer homoporous membranes (HOMEs), which have highly ordered uniform cylindrical nanopores, to form compact, dense, and continuous graphene/ionic liquid (Gr/IL) lubricating layers at interfaces, enabling a reduction in the friction coefficient. Raman and XPS analyses, confirmed the parallel alignment of the cation of ILs on graphene by the π–π stacking interaction of the imidazolium ring with the graphene layer. This alignment loosens the lattice spacing of Gr in Gr/ILs, leading to a larger lattice spacing of 0.36 nm in Gr of Gr/ILs hybrids than the pristine Gr (0.33 nm). The loose graphene layers, which are caused by the coexistence of graphene and ILs, would make the sliding easier, and favor the lubrication. An increase in the friction coefficient was observed on ILs-infused block copolymer HOMEs, as compared to Gr/ILs-infused ones, due to the absence of Gr and the unstably formed ILs film. Gr/ILs-infused block copolymer HOMEs also exhibit much smaller residual indentation depth and peak indentation depth in comparison with ILs-infused ones. This indicates that the existence of stably supported Gr/ILs hybrid liquid films aids the reduction of the friction coefficient by preventing the thinning of the lubricant layer and exposure of the underlying block copolymer HOMEs