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PubMed | Brazilian Nanotechnology National Laboratory LNNano, São Paulo State University, Federal University of São Carlos and Jaume I University
Type: | Journal: Scientific reports | Year: 2016

The study of the interaction of electron irradiation with matter and the response of the material to the passage of electrons is a very challenging problem. However, the growth mechanism observed during nanostructural evolution appears to be a broad and promising scientific field in nanotechnology. We report the in situ TEM study of nanostructural evolution of electron-driven silver (Ag) nanocrystals through an additive-free synthetic procedure. Observations revealed the direct effect of the electron beam on the morphological evolution of Ag nanocrystals through different mechanisms, such as mass transport, site-selective coalescence, and an appropriate structural configuration after coalescence leading to a more stable configuration. A fundamental understanding of the growth and formation mechanisms of Ag nanocrystals, which interact with the electron beam, is essential to improve the nanocrystal shape-control mechanisms as well as the future design and study of nanomaterials.

Santos T.F.A.,Brazilian Nanotechnology National Laboratory LNNano | Santos T.F.A.,University of Campinas | Santos T.F.A.,Brazilian Center for Research and Development in Telecommunications | Idagawa H.S.,Brazilian Nanotechnology National Laboratory LNNano | And 2 more authors.
Science and Technology of Welding and Joining | Year: 2014

Consolidated UNS S32205 duplex stainless steel joints welds were performed using a friction stir welding (FSW) process. An experimental set-up was used to record the thermal history of duplex stainless steel FSW joint. For points at equal distance from the weld centreline, temperature measured near the beginning of the weld was lower than that measured in the middle of the welded joint. This was attributed to a non-stationary transfer condition. FSW thermal cycle showed shorter time spent at elevated temperature compared that presented by fusion welding, indicating less propensity to detrimental second phase precipitation. To support temperature measurements with thermocouples, a three-dimensional finite element thermal model of FSW was implemented, which provided a good agreement with experimental data. © 2014 Institute of Materials, Minerals and Mining.

PubMed | Leiden University, Imperial College London, 1 Netherlands Center for Electronic Nanoscopy, Maastricht University and 4 more.
Type: | Journal: Scientific reports | Year: 2015

Large datasets are emerging in many fields of image processing including: electron microscopy, light microscopy, medical X-ray imaging, astronomy, etc. Novel computer-controlled instrumentation facilitates the collection of very large datasets containing thousands of individual digital images. In single-particle cryogenic electron microscopy (cryo-EM), for example, large datasets are required for achieving quasi-atomic resolution structures of biological complexes. Based on the collected data alone, large datasets allow us to precisely determine the statistical properties of the imaging sensor on a pixel-by-pixel basis, independent of any a priori normalization routinely applied to the raw image data during collection (flat field correction). Our straightforward a posteriori correction yields clean linear images as can be verified by Fourier Ring Correlation (FRC), illustrating the statistical independence of the corrected images over all spatial frequencies. The image sensor characteristics can also be measured continuously and used for correcting upcoming images.

Grimm D.,Leibniz Institute for Solid State and Materials Research | Grimm D.,TU Chemnitz | Bof Bufon C.C.,Leibniz Institute for Solid State and Materials Research | Bof Bufon C.C.,Brazilian Nanotechnology National Laboratory LNNano | And 10 more authors.
Nano Letters | Year: 2013

We fabricate inorganic thin film transistors with bending radii of less than 5 μm maintaining their high electronic performance with on-off ratios of more than 105 and subthreshold swings of 160 mV/dec. The fabrication technology relies on the roll-up of highly strained semiconducting nanomembranes, which compacts planar transistors into three-dimensional tubular architectures opening intriguing potential for microfluidic applications. Our technique probes the ultimate limit for the bending radius of high performance thin film transistors. © 2012 American Chemical Society.

Escobar J.D.,National University of Colombia | Velasquez E.,National University of Colombia | Santos T.F.A.,Brazilian Nanotechnology National Laboratory LNNano | Santos T.F.A.,University of Campinas | And 3 more authors.
Wear | Year: 2013

The cavitation erosion (CE) resistance of an UNS S32205 duplex stainless steel (DSS) was improved through microstructural modification using friction stir processing (FSP). As-received material was processed using 200. rpm and 100. mm/min spindle and travel speeds, respectively. The cavitation erosion tests were performed in a vibratory apparatus according to ASTM G32 standard. The incubation period, the maximum erosion rate and the variation of surface roughness during the tests are reported and the results are compared with those obtained for the base metal samples (BMS). The worn surfaces were characterized using roughness measurements and scanning electron microscopy (SEM). After a CE testing time of 10. h, FSP samples showed a 70% diminution of the mass loss when compared to the BMS. Moreover, a 200% enhancement of incubation time and 100% reduction in the erosion rate were achieved after FPS. The improvement of CE performance is related to the recrystallized and refined microstructure, as well as to the modification of the elongated α/γ interfaces. © 2012 Elsevier B.V.

Venarusso L.B.,Federal University of Mato Grosso do Sul | Bettini J.,Brazilian Nanotechnology National Laboratory LNNano | Maia G.,Federal University of Mato Grosso do Sul
Journal of Solid State Electrochemistry | Year: 2016

Nanocrystals (NCs) of a Pt or Pd or Pt–Pd alloy shell supported on a Au core were synthesized and dripped onto a glassy carbon (GC) surface to generate thin films. Their electrocatalytic activity towards the oxygen reduction reaction (ORR) was studied employing hydrodynamic cyclic voltammetry. Of the Pt or Pt–Pd alloy electrocatalysts synthesized over a Au core (including Au cores produced from redox-transmetalation of Ni cores), Pt–Pd@Au, Pt@Au, and Pt@Au′ NCs—which contained heterogeneous NCs with spherical, triangular, squared, pentagonal, hexagonal, heptagonal, and rod-like shapes, with large (about 80 nm in several cases), well-defined crystalline structures, and evidenced a nanodendritic Pt or Pt–Pd alloy covering pattern at the NC surface—exhibited high electrocatalytic activity towards ORR and high stability (without dissolution of inner metallic nanoparticles such as Au) after 10,000 potential scans—features that suggest their utility for use in acid fuel cells. [Figure not available: see fulltext.] © 2016 Springer-Verlag Berlin Heidelberg

Santhiago M.,Brazilian Nanotechnology National Laboratory LNNano | Bettini J.,Brazilian Nanotechnology National Laboratory LNNano | Araujo S.R.,Brazilian Nanotechnology National Laboratory LNNano | Bufon C.C.B.,Brazilian Nanotechnology National Laboratory LNNano | Bufon C.C.B.,University of Campinas
ACS Applied Materials and Interfaces | Year: 2016

The fabrication of three-dimensional (3D) polypyrrole conductive tracks through the porous structure of paper is demonstrated by the first time. We combined paper microfluidics and gas-phase pyrrole monomers to chemically synthesize polypyrrole-conducting channels embedded in-between the cellulose fibers. By using this method, foldable conductive structures can be created across the whole paper structure, allowing the electrical connection between both sides of the substrate. As a proof of concept, top-channel-top (TCT) and top-channel-bottom (TCB) conductive interconnections as well as all-organic paper-based touch buttons are demonstrated. © 2016 American Chemical Society.

Torres E.A.,Brazilian Nanotechnology National Laboratory LNNano | Torres E.A.,Metropolitan Institute of Technology | Montoro F.,Brazilian Nanotechnology National Laboratory LNNano | Righetto R.D.,Brazilian Nanotechnology National Laboratory LNNano | Ramirez A.J.,Brazilian Nanotechnology National Laboratory LNNano
Journal of Microscopy | Year: 2014

Nowadays, the implementation of sophisticated in situ electron microscopy tests is providing new insights in several areas. In this work, an in situ high-temperature strain test into a scanning electron microscope was developed. This setup was used to study the grain boundary sliding mechanism and its effect on the ductility dip cracking. This methodology was applied to study the mechanical behaviour of Ni-base filler metal alloys ERNiCrFe-7 and ERNiCr-3, which were evaluated between 700°C and 1000°C. The ductility dip cracking susceptibility (threshold strain; εmin) for both alloys was quantified. The εmin of ERNiCrFe-7 and ERNiCr-3 alloys were 7.5% and 16.5%, respectively, confirming a better resistance of ERNiCr-3 to ductility dip cracking. Furthermore, two separate components of grain boundary sliding, pure sliding (Sp) and deformation sliding (Sd), were identified and quantified. A direct and quantitative link between grain boundary tortuosity, grain boundary sliding and ductility dip cracking resistance has been established for the ERNiCrFe-7 and ERNiCr-3 alloys. © 2014 Royal Microscopical Society.

Rodriguez J.,Brazilian Nanotechnology National Laboratory LNNano | Rodriguez J.,University of Campinas | Ramirez A.J.,Brazilian Nanotechnology National Laboratory LNNano | Ramirez A.J.,University of Campinas
Science and Technology of Welding and Joining | Year: 2014

Friction stir welding parameters were developed for a 6 mm thick dissimilar butt joint made of mild steel and Ni based alloy 625. A composite W-Re/polycrystalline cubic born nitride tool was used to study the effect of tool offset (between 0 and 3.13 mm away from the alloy 625 plate) and rotational speed (between 250 and 350 rev min-1) on joint consolidation. When non-optimal parameters were used, macrovoids were observed at the advancing side and faying surface near the joint interface root. Defect free joints were obtained using 300 rev min-1, 100 mm min-1, tool offset of 1.63 mm, and axial force between 25 and 30 kN, under force controlled mode. © 2014 Institute of Materials, Minerals and Mining.

PubMed | Brazilian Nanotechnology National Laboratory LNNano and University of Campinas
Type: | Journal: Biosensors & bioelectronics | Year: 2016

The combination of organic and inorganic materials to create hybrid nanostructures is an effective approach to develop label-free platforms for biosensing as well as to overcome eventual leakage current-related problems in capacitive sensors operating in liquid. In this work, we combine an ultra-thin high-k dielectric layer (Al

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