Laser surface texturing of stainless steel 316L cylindrical pins for interference fit applications

This study is focused on the development of a novel method for designing high-end interference fit fasteners. In this work, a new surface laser treatment process was utilized to enable enhanced usability and bond strength control of press-fit connections. Cylindrical 10 mm diameter pins of 316L were textured over a 10 mm length using a pulsed CO2 laser beam focused one millimeter below the surface, with the thermal energy adjusted to bring the surface to just above the melting point of the metal. The pin surface morphology and dimensions were precisely controlled by controlling the laser processing parameters specifically the laser beam power, the pulse repetition frequency, and the overlap between scan tracks. The pin was inserted into a hub hole diameter of 10.05±0.003 mm and pull out joint bond strengths were examined. The results of this study showed that surface thus altered provided improved control of the bond strength which is a particular novelty of this new interference fit joining method. Surface roughness, Ra, from 40 to 160 µm, melt pool depths from 0.4 to 1.7 mm, increases in the pin outer diameter from 0.5 to 1.1 mm, and pull out forces of up to 7.51 kN were achieved. The bond joint was found to re-grip before final failure providing a more secure joint and increased safety. This joining method allows for the possibility of joining different materials. The pulse repetition frequency was measured to be the most significant processing parameter for control of the resulting mechanical properties and the bond strength with a clear inverse relationship

Polylactic acid/nano chitosan composite fibers and their morphological, physical characterization for the removal of cadmium(II) from water

This work discusses the fabrication of polylactic acid (PLA)/nano chitosan (nCHS) composite fibers by electrospinning method for Cd2+ metal ion adsorption from water. Here nCHS was synthesized by ionic gelation method and which is used as a reinforcement for PLA. The scanning electron microscopic analysis revealed that the addition 0.1 wt% nCHS has decreased the fiber diameter as well as the secondary pore size and hence imparted unique properties to electrospun composite fibers. The positive zeta potential values for the composites indicated their higher stability, though; the inclusion of nCHS reduced the crystallinity of the neat membranes. The contact angle measurements showed that the hydrophilicity of the composite was increased up to 0.1 wt% nCHS, and hence the surface energy was increased. Inverse gas chromatography results suggested that the basic character of the composites has intensified with the increase in nCHS addition. The adsorption capacity of the neat electrospun PLA and PLA–nCHS composites for Cd2+ ions were investigated and studies revealed that adsorption capacity of the composite was two times faster (approximately 70%) in comparison with neat PLA fibers. The increase in surface area as well as presence nCHS improved the adsorption capacity of the electrospun membrane.info:eu-repo/semantics/publishedVersio

Tissue engineering scaffold material with enhanced cell adhesion and angiogenesis from soy protein isolate loaded with bio modulated micro-TiO2 prepared via prolonged sonication for wound healing applications

Tissue engineering is a technique that promotes healing by creating an ideal environment for endogenous cells to migrate and grow into the site of injury via a scaffold, improving regeneration and reducing the time required for in vitro cell culture. In this work, the effect of the addition of sonicated TiO2 in the soy protein isolate (SPI) matrix for tissue engineering applications was studied. In comparison to adding expensive nano TiO2, this method of incorporating sonicated TiO2 into the SPI matrix will aid in achieving improved properties at a lower cost. The effect of the addition of sonicated TiO2 on the morphological, UV transmittance, mechanical, thermal, surface energy, and hydrophilicity of SPI films was investigated. The result shows that the uniformly distributed TiO2 particles successfully blocked 95% of UV light. Scanning electron microscopy revealed a significant reduction in the TiO2 agglomerate size and homogeneous distribution of the same when sonication was applied instead of mechanical dispersion. A simultaneous increase of tensile strength (from 3.16 to 4.58 MPa) and elongation at break values (from 24.25% to 95.31%) with 0.5% TiO2 was observed. The addition of 0.25% TiO2 was found to significantly enhance the elongation at break value to 120.83%. Incorporation of micro-TiO2 particles could improve the surface roughness, surface energy, and wettability of SPI films. In vitro cell adhesion studies and in vivo subcutaneous implantation studies were performed to assess the cell growth and angiogenesis of the developed film membranes. An MTT assay showed that SPI-1%TiO2 film favored cell viability up to 118%, and in vivo subcutaneous implantation studies showed enhanced cell growth and angiogenesis for SPI-1% TiO2 films. This SPI-TiO2 film with enhanced surface properties can be used as an ideal candidate for tissue engineering applications.info:eu-repo/semantics/publishedVersio

Nano- and micro-structural surface reorganizations in polymer thin films : a multi-technique investigation

Surfaces of materials are dynamic regions, which readily rearrange or react, leading to properties different from the bulk. This thesis explores the surface phenomena exhibited by polymer thin films using different surface characterization techniques including ToF-SIMS, NanoSIMS, XPS, AFM, SEM and water contact angle measurements. Thin films of compositionally similar but structurally dissimilar systems like blends and di-block copolymers of polystyrene and poly(methyl methacrylate) exhibited different segregation behaviour in terms of the surface composition on annealing. A realistic portrait of the surface and interfacial behaviour of these thin films was obtained, only on combining the surface morphological and compositional information from the different characterization techniques. The effect of processing parameters like the film thickness, the time and temperature of annealing was investigated. In blends, the increase in film thickness increased the surface domain sizes from "nano" to "micro" range, with the surface composition and morphology remaining similar for the different thicknesses. Copolymer surfaces showed that the surface morphology changed with the film thickness but the surface composition remained the same. An increase in temperature was found to facilitate the phase separation process in blends while in copolymers, it aided the formation of distinct surface morphology. The effect of reactive blending on the surface segregation behaviour in blends was also examined. The studies showed that unless verified by independent techniques, the compositional information may not be able to predict accurately the film morphology and vice versa. Thus, a multi-technique investigation was found necessary for obtaining the complete picture of the surface and interfacial changes undergone by these polymeric thin films.Doctorat en sciences appliquées (FSA 3)--UCL, 200

Hyphenated analytical techniques for materials characterisation

This topical review will provide a survey of the current state of the art in 'hyphenated' techniques for characterisation of bulk materials, surface, and interfaces, whereby two or more analytical methods investigating different properties are applied simultaneously to the same sample to better characterise the sample than can be achieved by conducting separate analyses in series using different instruments. It is intended for final year undergraduates and recent graduates, who may have some background knowledge of standard analytical techniques, but are not familiar with 'hyphenated' techniques or hybrid instrumentation. The review will begin by defining 'complementary', 'hybrid' and 'hyphenated' techniques, as there is not a broad consensus among analytical scientists as to what each term means. The motivating factors driving increased development of hyphenated analytical methods will also be discussed. This introduction will conclude with a brief discussion of gas chromatography-mass spectroscopy and energy dispersive x-ray analysis in electron microscopy as two examples, in the context that combining complementary techniques for chemical analysis were among the earliest examples of hyphenated characterisation methods. The emphasis of the main review will be on techniques which are sufficiently well-established that the instrumentation is commercially available, to examine physical properties including physical, mechanical, electrical and thermal, in addition to variations in composition, rather than methods solely to identify and quantify chemical species. Therefore, the proposed topical review will address three broad categories of techniques that the reader may expect to encounter in a well-equipped materials characterisation laboratory: microscopy based techniques, scanning probe-based techniques, and thermal analysis based techniques. Examples drawn from recent literature, and a concluding case study, will be used to explain the practical issues that arise in combining different techniques. We will consider how the complementary and varied information obtained by combining these techniques may be interpreted together to better understand the sample in greater detail than that was possible before, and also how combining different techniques can simplify sample preparation and ensure reliable comparisons are made between multiple analyses on the same samples—a topic of particular importance as nanoscale technologies become more prevalent in applied and industrial research and development (R&D). The review will conclude with a brief outline of the emerging state of the art in the research laboratory, and a suggested approach to using hyphenated techniques, whether in the teaching, quality control or R&D laborator

Electrochemical, surface and electrocatalytic properties of layer-by-layer multilayer assemblies composed of silver nanoparticles and a Ni(II)-crown type polyoxometalate

Multilayer assemblies composed of the crown type polyoxometalate, Ni4[(P8W48O148)(WO2)]28 12, and silver nanoparticles, have been immobilised onto glassy carbon electrode surfaces through the layer-by-layer (LBL) technique. The resulting thin films have been characterised by electrochemical and surface based techniques with the multilayers showing electrocatalytic ability towards the reduction of chlorate in solution. The layers exhibited redox activity for both the POM and silver nanoparticle moieties with the layers showing good stability towards redox cycling and thin layer behaviour. The layers were found to be highly conductive due to the presence of the nanoparticles as shown by AC impedance and resulting charge transfer resistance values (Rct) obtained for the layers. A clear and significant catalytic ability of Ni4[(P8W48O148)(WO2)]28/AgNP's assembly towards the chlorate reduction was observed with a measured sensitivity of 32.3mAcm 122/(\u3bcM)

Multitechnique characterization of thin films of immiscible polymer systems: PS-b-PMMA diblock copolymers and PS-PMMA symmetric blends

Immiscible polymer systems are known to form various kinds of phase-separated structures capable of producing self-assembled patterns at the surface. In this study, different surface characterization methods were utilized to study the surface morphology and composition produced after annealing thin polymer films. Two different SIMS techniques - static time-of-flight secondary ion mass spectrometry (ToF-SIMS) and dynamic nano-SIMS - were used, complemented by x-ray photoelectron spectrometry (XPS) and atomic force microscopy (AFM). Thin films (spin-coated onto silicon wafers) of polystyrene (PS)-poly(methyl methacrylate) (PMMA) symmetric blends and diblock copolymers of similar molecular weight were investigated. Surface enrichment by PS was found on all as-cast samples. The samples were annealed at 160° C for different time periods, after which the blend and the copolymer films exhibited opposite behaviour as seen by ToF-SIMS and XPS. The annealed blend surface presented an increase in the PMMA concentration whereas that of copolymers showed a decrease in PMMA concentration compared with the as-cast sample. For blends, the nano-SIMS as well as AFM images revealed the formation of phase-separated domains at the surface. The composition information obtained from ToF-SIMS and XPS, as well as the surface mapping by nano-SIMS and AFM, allowed us to conclude that PS formed phase separated droplet-like domains on a thin PMMA matrix on annealing. The three-dimensional nano-SIMS images showed that the PS droplets were supported inside a rim of PMMA and that these droplets continued from the surface like columnar rods into the film until the substrate interface. In the case of annealed copolymer samples, the AFM images revealed topographical features resembling droplet-like domains on the surface but there was no phase difference between the domains and the matrix. In the case of copolymers, owing to the covalent bonding between the blocks, complete phase separation was not possible. The three-dimensional nano-SIMS images showed domain structures in the form of striations inside the film, which were not continuous until the substrate interface. Information from the different techniques was required to gain an accurate view of the surface composition and topographical changes that have occurred under the annealing conditions. Copyright © 2005 John Wiley & Sons, Ltd

End group effect on surface and interfacial segregation in PS-PMMA blend thin films

Thin films of polystyrene (PS)/poly (methyl methacrylate) (PMMA) blends with different end groups were investigated using TOF-SIMS and AFM. PS with -OH and -NH2 end groups were blended in toluene solvent with pure PMMA homopolymer, and PMMA having anhydride end group. The ToF-SIMS spectra of PS-OH/PMMA resembled that of pure PS-PMMA blends showing an increase of PMMA intensity after annealing. On the contrary, the PS-NH2 blended with PMMA showed an increase in PS intensity on the surface after annealing. The ToF-SIMS spectra were similar to that of a pure PS-PMMA di-block copolymer. These results indicate copolymer formation at the surface. The PS-NH2 with PMMA-anhydride blend spectra showed very slight changes in spectra before and after annealing and the AFM images revealed spinodal bicontinuous structures on the surface before and after annealing. The copolymer formation is found to occur in the as-cast film itself and not after thermal treatment. (c) 2006 Elsevier B.V. All rights reserved

Development of a flexible and conductive elastomeric composite based on chloroprene rubber

Flexible and conductive nanocomposites with enhanced mechanical and dielectric properties have been fabricated from reduced graphene oxide (RGO) reinforced polychloroprene rubber (CR). Composites were prepared on a two-roll mixing mill and the morphological analysis using SEM and TEM showed good dispersibility and exfoliation of RGO layers in the matrix. It imparted a critical role in the enhancement of mechanical and electrical properties of the composites. Composites with 0.9 phr of RGO showed an enhancement in tensile strength, tensile modulus and electrical conductivity as 92%, 75%, and 103 % respectively more than the pristine polychloroprene. RGO formed a good conducting percolating network in the polychloroprene matrix and it led to the formation of a dielectric composite material with enhanced electrical properties