Laser ablation has been used to grow silicon nanowires with an average diameter of 6.7 nm ± 2.7 nm surrounded by an amorphous SiOx sheath of 1–2 nm. This paper reports the imaging, chemical and structural analysis of these wires. Due to the growth temperature and the presence of calcium impurities and trace oxygen, two distinct types of wires are found. They appear to grow by two different processes. One requires a metal catalyst, the other is catalyzed by oxygen.

Joining large and complex polymer-matrix composite structures is becoming increasingly important in industries such as automobiles, aerospace, sports, wind turbines, and others. Ultrasonic welding is an ultra-fast joining process and also provides excellent joint quality as a cost-effective alternative to other joining processes. This research aims at investigating the welding characteristics of novel methyl methacrylate Elium®, a liquid thermoplastic resin. Elium® is the first of its kind of thermoplastic resin, which is curable at room temperature and is suitable for mass production processes. The welding characteristics of Elium® composites were investigated by optimizing the welding parameters with specially designed integrated energy directors (ED) and manufactured using the Resin transfer molding process. The results showed a 23% higher lap shear strength for ultrasonically welded composite joints when compared to the adhesively bonded joints. The optimized welding time for the ultrasonic welded joint was found to be 1.5 s whereas it was 10 min for the adhesively bonded joint. Fractographic analysis showed the significant plastic deformation and shear cusps formation on the fractured surface, which are typical characteristics for strong interfacial bonding.

Current research aims at investigating the fatigue strength of ultrasonically welded composite joints with novel liquid acrylic thermoplastic Elium (R). Fatigue response of the welded joints with integrated Energy Director (ED) and flat Elium (R) film was investigated and the baseline comparison was carried out with control adhesives. The results showed 10-12% higher fatigue life at 10(5) and 10(6) fatigue cycle as compared to the adhesively bonded joints. Fractographic investigation of fractured welded joints showed features such as fibre impingement and shear cusps formation which contributed to strong interfacial adhesion. (C) 2020 Elsevier B.V. All rights reserved.

The current research work presents a first attempt to investigate the welding attributes of Elium® thermoplastic resin and the fusion bonding using ultrafast ultrasonic welding technique. The integrated energy director (ED) polymer-matrix composites (PMCs) panel manufacturing was carried out using the Resin Transfer Moulding (RTM) technique and the scheme is deduced to manufacture a bubble-free panel. Integrated ED configurations and flat specimens with Elium® film of different thickness at the interface were investigated for ultrasonic welding optimization. Optimised weld time for integrated ED and flat Elium® panels with film (0.5 mm thick) configuration was found to be 1 s and 5.5 s, respectively. The ED integrated configuration showed the best welding results with a lap shear strength of 18.68 MPa. The morphological assessment has shown significant plastic deformation of Elium® resin and the shear cusps formation, which enhances the welding strength. This research has the potential to open up an excellent and automated way of joining Elium® composite parts in automotive, wind turbines, sports, and many other industrial applications.

Poly(lactide) (PLA) and poly(methyl methacrylate) (PMMA) are melt compounded with chopped glass fiber using laboratory scale twin-screw extrusion. Physical properties are examined using differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), thermogravimetric analysis (TGA), tensile testing, impact testing, X-ray computed tomography (CT) scanning, and field emission scanning electron microscopy (FE-SEM). Molecular weight is determined using gel permeation chromatography (GPC). Miscibility of the blends is implied by the presence of a single glass transition temperature and homogeneous morphology. PLA/PMMA blends tend to show positive deviations from a simple linear mixing rule in their mechanical properties (e.g., tensile toughness, modulus, and stress at break). The addition of 40 wt % glass fiber to the system dramatically increases physical properties. Across all blend compositions, the tensile modulus increases from roughly 3 GPa to roughly 10 GPa. Estimated heat distortion temperatures (HDTs) are also greatly enhanced; the pure PLA sample HDT increases from 75 degrees C to 135 degrees C. Fiber filled polymer blends represent a sustainable class of earth abundant materials which should prove useful across a range of applications. (c) 2017 Wiley Periodicals, Inc.

One of the current challenges in the widespread adoption of wind energy is the ability to make larger, more reliable wind blades without significantly increasing the weight of the blades. Increase in service life is needed for both wind blade composites and adhesives. Thermoset composites and adhesives are valued for excellent strength, chemical resistance and high temperature properties but suffer from low toughness. For wind energy applications, it is necessary to improve the fracture toughness and fatigue performance of blades and adhesives without effecting mechanical properties such as strength or modulus or processing variable such as viscosity or curing kinetics. Although many additives exist for improving the toughness of thermosets, most are difficult to incorporate into formulations or result in a "trade-off' of properties. Arkema's controlled radical polymerization technology has been used to synthesize Nanostrength block copolymers additives, which provide excellent toughening to thermosets at low loading levels without sacrificing other properties. By controlling structuration of these polymers, a wide range of mechanical properties can be achieved while controlling the viscosity of the resin.

The effect of low T-g polybutadiene (PBD) rubbery polymer as a part of polysiloxane/PBD E-glass fibers sizing on mechanical properties of a corresponding epoxy composite material has been evaluated by the punch shear test technique. The results show that the use of hydroxyl terminated PBD led to significant increase in interface shear strength, energy absorption, as well as dynamic modulus and T-g in a corresponding composite material. The sizing composition and fiber morphology were characterized by FTIR spectroscopy and AFM microscopy, respectively. Possible rational for such sizing composition! material property relationship is discussed. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 118: 841-848, 2010

SmallVolume 5, Issue 24 p. 2797-2801 Communication Polymer-Protected Sub-2-nm-Nanogap Fabrication for Biological Sensing in Near-Physiological Conditions† Huijuan Zhang, Huijuan Zhang Advanced Materials for Micro- and Nano-Systems Program Singapore–MIT Alliance 117576 (Singapore)Search for more papers by this authorRobert J. Barsotti, Robert J. Barsotti Department of Materials Science and Engineering Massachusetts Institute of Technology Cambridge, MA 02139 (USA)Search for more papers by this authorChee-Leong Wong, Chee-Leong Wong Centre for IC Failure Analysis and Reliability Department of Electrical & Computer Engineering National University of Singapore 4 Engineering Drive 3, 117576 (Singapore)Search for more papers by this authorXuejia Xue, Xuejia Xue Department of Chemistry National University of Singapore 117543 (Singapore)Search for more papers by this authorXiaogang Liu, Xiaogang Liu Department of Chemistry National University of Singapore 117543 (Singapore)Search for more papers by this authorFrancesco Stellacci, Francesco Stellacci Department of Materials Science and Engineering Massachusetts Institute of Technology Cambridge, MA 02139 (USA)Search for more papers by this authorJohn T. L. Thong, Corresponding Author John T. L. Thong [email protected] Department of Electrical and Computer Engineering National University of Singapore 117576 (Singapore)Department of Electrical and Computer Engineering National University of Singapore 117576 (Singapore).Search for more papers by this author Huijuan Zhang, Huijuan Zhang Advanced Materials for Micro- and Nano-Systems Program Singapore–MIT Alliance 117576 (Singapore)Search for more papers by this authorRobert J. Barsotti, Robert J. Barsotti Department of Materials Science and Engineering Massachusetts Institute of Technology Cambridge, MA 02139 (USA)Search for more papers by this authorChee-Leong Wong, Chee-Leong Wong Centre for IC Failure Analysis and Reliability Department of Electrical & Computer Engineering National University of Singapore 4 Engineering Drive 3, 117576 (Singapore)Search for more papers by this authorXuejia Xue, Xuejia Xue Department of Chemistry National University of Singapore 117543 (Singapore)Search for more papers by this authorXiaogang Liu, Xiaogang Liu Department of Chemistry National University of Singapore 117543 (Singapore)Search for more papers by this authorFrancesco Stellacci, Francesco Stellacci Department of Materials Science and Engineering Massachusetts Institute of Technology Cambridge, MA 02139 (USA)Search for more papers by this authorJohn T. L. Thong, Corresponding Author John T. L. Thong [email protected] Department of Electrical and Computer Engineering National University of Singapore 117576 (Singapore)Department of Electrical and Computer Engineering National University of Singapore 117576 (Singapore).Search for more papers by this author First published: 14 December 2009 https://doi.org/10.1002/smll.200900938Citations: 15 † This work is supported by the Singapore–MIT Alliance and the National University of Singapore. H. Zhang is grateful to the Singapore–MIT Alliance for support through a fellowship. Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Graphical Abstract Polymer-protected sub-2-nm nanogaps that are fabricated via a novel electrical stressing approach exhibit substantial ionic-current reduction in near-physiological conditions. These devices enable direct DNA detection in aqueous solution by utilizing assembly of oligonucleotide-modified gold nanoparticles to the nanogap (see image). Citing Literature Supporting Information Detailed facts of importance to specialist readers are published as "Supporting Information". Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Filename Description smll_200900938_sm_supplfigs.pdf376.5 KB supplfigs Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article. Volume5, Issue24December 18, 2009Pages 2797-2801 RelatedInformation

We present a predictive framework for the controlled assembly of nanoparticles onto the surface of small (15 - 150 nm) electrode gaps using the dielectrophoretic (DEP) force. By combining Brownian dynamics (BD) simulations with continuum descriptions for the spatial distributions of nanoparticles, we arrive at a concise analytic description for the number of particles assembled as a function of the applied voltage, nanoparticle properties, and geometric parameters, such as the size of the electrode gap. Our model is predictive and successfully describes the presence of a voltage threshold, below which no assembly is observed.

The directed assembly of nanoparticles and nanoscale materials onto specific locations of a surface is one of the major challenges in nanotechnology. Here we present a simple and scalable method and model for the assembly of nanoparticles in between electrical leads. Gold nanoparticles, 20 nm in diameter, were assembled inside electrical gaps ranging from 15 to 150 nm with the use of positive ac dielectrophoresis. In this method, an alternating current is used to create a gradient of electrical field that attracts particles in between the two leads used to create the potential. Assembly is achieved when dielectrophoretic forces exceed thermal and electrostatic forces; the use of anchoring molecules, present in the gap, improves the final assembly stability. We demonstrate with both experiment and theory that nanoparticle assembly inside the gap is controlled by the applied voltage and the gap size. Experimental evidence and modeling suggest that a gap-size-dependent threshold voltage must be overcome before particle assembly is realized. Assembly results as a function of frequency and time are also presented. Assembly of fewer than 10 isolated particles in a gap is demonstrated. Preliminary electrical characterization reveals that stable conductance of the assembled particles can be achieved.

Shaping up nicely…︁ Micrometer-sized gold crystals have been synthesized through a binary mixture of amine ligand molecules in the presence of a gold precursor under slow growth conditions (see picture). A wide range of morphologies in the form of triangles, octahedra, pentagonal decahedra, platelets, and nanowires with well-defined morphologies can be derived by varying the composition and ratio of the ligand mixture.