428 research outputs found
High-temperature Fiber Matrices: Electrospinning and Rare-earth Modification
We demonstrate the production of nonwoven mats of high-temperature organic and inorganic fibers by electrospinning. Specifically, glass/ceramic (tetraethylorthosilicate-SiO) and fire-blanket (polydiphenoxyphosphazene-PDPP) precursors are electrospun, and the resulting fibers are characterized by scanning electron microscopy, thermogravimetric analysis, and infrared (IR) spectroscopy. We find that the SiO fibers are smaller in diameter and more uniform than the PDPP fibers, and stable to higher temperatures. We also coat these fiber systems with several rare-earth nitrates, and find that these coatings can be used to selectively modify the near-IR spectra of the fibers. This work extends the use of electrospinning into two new classes of materials, and demonstrates that we can subsequently modify the optical properties of the electrospun fibers. (C) 2003 American Vacuum Society
Electrical, Structural, and Chemical Properties of Semiconducting Metal Oxide Nanofiber Yarns
The electrical, structural, and chemical properties of twisted yarns of metal-oxide nanofibers, fabricated using a modified electrospinning technique, are investigated in this report. In particular, synthesized zinc oxide and nickel oxide yarns having diameters in the range of 4-40 mu m and lengths up to 10 cm were characterized, whose constituent nanofibers had average diameters of 60-100 nm. These yarns have one macroscopic dimension for handling while retaining some of the properties of nanofibers. (C) 2008 American Institute of Physics
Electrospinning Route for the Fabrication of P-n Junction Using Nanofiber Yarns
Electrospinning is a simple, versatile, and cost effective method for generating nanoscale fibers, wires, and tubes. Nanowires and nanotubes could be important building blocks for nanoscale electronics, optoelectronics, and sensors as they can function as miniaturized devices as well as electrical interconnects. We report on a simple method to fabricate free standing ceramic nanofiber heterostructures, which exhibit rectifying behavior of a p-n junction
Electrical Conductivity of Electrospun Polyaniline and Polyaniline-Blend Fibers and Mats
Submicrometer fibers of polyaniline (PAni) doped with (+)-camphor-10-sulfonic acid (HCSA) and blended with poly(methyl methacrylate) (PMMA) or poly(ethylene oxide) were electrospun over a range of compositions. Continuous, pure PAni fibers doped with HCSA were also produced by coaxial electrospinning and subsequent removal of the PMMA shell polymer. The electrical conductivities of both the fibers and the mats were characterized. The electrical conductivities of the fibers were found to increase exponentially with the weight percent of doped PAni in the fibers, with values as high as 50 ± 30 S/cm for as-electrospun fibers of 100% doped PAni and as high as 130 ± 40 S/cm upon further solid state drawing. These high electrical conductivities are attributed to the enhanced molecular orientation arising from extensional deformation in the electrospinning process and afterward during solid state drawing. A model is proposed that permits the calculation of mat conductivity as a function of fiber conductivity, mat porosity, and fiber orientation distribution; the results agree quantitatively with the independently measured mat conductivities.United States. Army Research Office (Institute for Soldier Nanotechnologies, Contract ARO W911NF-07-D- 0004
BaFe12O19 single-particle-chain nanofibers : preparation, characterization, formation principle, and magnetization reversal mechanism
BaFe12O19 single-particle-chain
nanofibers have been successfully prepared by
an electrospinning method and calcination
process, and their morphology, chemistry,
and crystal structure have been characterized
at the nanoscale. It is found that individual
BaFe12O19 nanofibers consist of single nanoparticles which are found to stack along the
nanofiber axis. The chemical analysis shows that the atomic ratio of Ba/Fe is 1:12, suggesting a
BaFe12O19 composition. The crystal structure of the BaFe12O19 single-particle-chain nanofibers
is proved to be M-type hexagonal. The single crystallites on each BaFe12O19 single-particlechain
nanofibers have random orientations. A formation mechanism is proposed based on
thermogravimetry/differential thermal analysis (TG-DTA), X-ray diffraction (XRD), and transmission
electron microscopy (TEM) at six temperatures, 250, 400, 500, 600, 650, and 800 �C.
The magnetic measurement of the BaFe12O19 single-particle-chain nanofibers reveals that the
coercivity reaches a maximum of 5943 Oe and the saturated magnetization is 71.5 emu/g at
room temperature. Theoretical analysis at the micromagnetism level is adapted to describe the
magnetic behavior of the BaFe12O19 single-particle-chain nanofibers
Records of the Franciscan monastery in Našice, vol. 3 (1821-1842) (eds. Tamara Tvrtković – Milan Vrbanus) Hrvatski institut za povijest – Hrvatski institut za povijest – Podružnica za povijest Slavonije, Srijema i Baranje – Zavičajni muzej Našice – Franjevački samostan Sv. Antuna Padovanskoga u Našicama – Grad Našice, Našice – Slavonski Brod – Zagreb, 2017, pp. 520
SiO2 nanofibers have been produced by the electrospinning method by two different approaches: direct spinning of silica precursor-containing nanofibers and spinning of polymer nanofibers followed by sol–gel silica coating. After pyrolysis of the resulting materials, both methods yield silica nanofibers. We extend this work by coating the silica nanofibers with AlN films using a reactive magnetron sputtering technique. Substrate temperature, input gas composition and radio frequency (rf) power are the critical operating parameters for the formation of different crystal structures of the AlN shells. The AlN/SiO2 core-shell heterostructures demonstrate that electrospinning has the potential to produce low-mass, high-surface-area flexible nanofibers for potential space-based applications
Recent Nanofiber Technologies
This article is a perspective that includes a brief introduction to nanofiber production methods, their potential applications, and three review articles in the field of nanofibers. Although the full range of applications that best exploit these new developments are yet to be developed, the emerging innovative applications of nanofibers in biomedical, sensor, electronic, and other areas will likely be enabled or enhanced by these recent advances in several key techniques. Three review articles, distinct but interrelated, discuss technical research and development, and include possible applications for several industries in the polymer nanofiber arena
Patterning of light-emitting conjugated polymer nanofibres.
Organic materials have revolutionized optoelectronics by their processability, flexibility and low cost, with application to light-emitting devices for full-colour screens, solar cells and lasers. Some low-dimensional organic semiconductor structures exhibit properties resembling those of inorganics, such as polarized emission and enhanced electroluminescence. One-dimensional metallic, III-V and II-VI nanostructures have also been the subject of intense investigation as building blocks for nanoelectronics and photonics. Given that one-dimensional polymer nanostructures, such as polymer nanofibres, are compatible with sub-micrometre patterning capability and electromagnetic confinement within subwavelength volumes, they can offer the benefits of organic light sources to nanoscale optics. Here we report on the optical properties of fully conjugated, electrospun polymer nanofibres. We assess their waveguiding performance and emission tuneability in the whole visible range. We demonstrate the enhancement of the fibre forward emission through imprinting periodic nanostructures using room-temperature nanoimprint lithography, and investigate the angular dispersion of differently polarized emitted light
Biocompatibility and Bone Formation of Flexible, Cotton Wool-like PLGA/Calcium Phosphate Nanocomposites in Sheep
BACKGROUND: The purpose of this preliminary study was to assess the in vivo performance of synthetic, cotton wool-like nanocomposites consisting of a biodegradable poly(lactide-co-glycolide) fibrous matrix and containing either calcium phosphate nanoparticles (PLGA/CaP 60:40) or silver doped CaP nanoparticles (PLGA/Ag-CaP 60:40). Besides its extraordinary in vitro bioactivity the latter biomaterial (0.4 wt% total silver concentration) provides additional antimicrobial properties for treating bone defects exposed to microorganisms.
MATERIALS AND METHODS: Both flexible artificial bone substitutes were implanted into totally 16 epiphyseal and metaphyseal drill hole defects of long bone in sheep and followed for 8 weeks. Histological and histomorphological analyses were conducted to evaluate the biocompatibility and bone formation applying a score system. The influence of silver on the in vivo performance was further investigated.
RESULTS: Semi-quantitative evaluation of histology sections showed for both implant materials an excellent biocompatibility and bone healing with no resorption in the adjacent bone. No signs of inflammation were detectable, either macroscopically or microscopically, as was evident in 5 µm plastic sections by the minimal amount of inflammatory cells. The fibrous biomaterials enabled bone formation directly in the centre of the former defect. The area fraction of new bone formation as determined histomorphometrically after 8 weeks implantation was very similar with 20.5 ± 11.2 % and 22.5 ± 9.2 % for PLGA/CaP and PLGA/Ag-CaP, respectively.
CONCLUSIONS: The cotton wool-like bone substitute material is easily applicable, biocompatible and might be beneficial in minimal invasive surgery for treating bone defects
Organic nanofibers embedding stimuli-responsive threaded molecular components
While most of the studies on molecular machines have been performed in
solution, interfacing these supramolecular systems with solid-state
nanostructures and materials is very important in view of their utilization in
sensing components working by chemical and photonic actuation. Host polymeric
materials, and particularly polymer nanofibers, enable the manipulation of the
functional molecules constituting molecular machines, and provide a way to
induce and control the supramolecular organization. Here, we present
electrospun nanocomposites embedding a self-assembling rotaxane-type system
that is responsive to both optical (UV-visible light) and chemical (acid/base)
stimuli. The system includes a molecular axle comprised of a dibenzylammonium
recognition site and two azobenzene end groups, and a dibenzo[24]crown-8
molecular ring. The dethreading and rethreading of the molecular components in
nanofibers induced by exposure to base and acid vapors, as well as the
photoisomerization of the azobenzene end groups, occur in a similar manner to
what observed in solution. Importantly, however, the nanoscale mechanical
function following external chemical stimuli induces a measurable variation of
the macroscopic mechanical properties of nanofibers aligned in arrays, whose
Young's modulus is significantly enhanced upon dethreading of the axles from
the rings. These composite nanosystems show therefore great potential for
application in chemical sensors, photonic actuators and environmentally
responsive materials.Comment: 39 pages, 16 figure
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