Showing papers on "Fiber published in 2012"

Critical review of recent publications on use of natural composites in infrastructure

Abstract: Compared to most synthetic fibers, natural fibers are low-cost, are easier to handle, have good specific mechanical properties, and require only around 20–40% of the production energy. Using natural materials and modern construction techniques reduces construction waste and increases energy efficiency while promoting the concept of sustainability. Several drawbacks of natural composites which would be even more pronounced in their use in infrastructure include their higher moisture absorption, inferior fire resistance, lower mechanical properties and durability, variation in quality and price, and difficulty using established manufacturing practices when compared to synthetic composites. Many researchers have been working to address these issues, with particular attention paid to the surface treatment of fibers and improving the fiber/matrix interface. Because of their positive economic and environmental outlook, as well as their ability to uniquely meet human needs worldwide, natural composites are showing a good potential for use in infrastructure applications.

Fiber-based all-solid-state flexible supercapacitors for self-powered systems.

Abstract: All-solid-state flexible supercapacitors based on a carbon/MnO2 (C/M) core–shell fiber structure were fabricated with high electrochemical performance such as high rate capability with a scan rate up to 20 V s–1, high volume capacitance of 2.5 F cm–3, and an energy density of 2.2 × 10–4 Wh cm–3. By integrating with a triboelectric generator, supercapacitors could be charged and power commercial electronic devices, such as a liquid crystal display or a light-emitting-diode, demonstrating feasibility as an efficient storage component and self-powered micro/nanosystems.

Interfacial Microstructure and Properties of Carbon Fiber Composites Modified with Graphene Oxide

Abstract: The performance of carbon fiber-reinforced composites is dependent to a great extent on the properties of fiber–matrix interface. To improve the interfacial properties in carbon fiber/epoxy composites, we directly introduced graphene oxide (GO) sheets dispersed in the fiber sizing onto the surface of individual carbon fibers. The applied graphite oxide, which could be exfoliated to single-layer GO sheets, was verified by atomic force microscope (AFM). The surface topography of modified carbon fibers and the distribution of GO sheets in the interfacial region of carbon fibers were detected by scanning electron microscopy (SEM). The interfacial properties between carbon fiber and matrix were investigated by microbond test and three-point short beam shear test. The tensile properties of unidirectional (UD) composites were investigated in accordance with ASTM standards. The results of the tests reveal an improved interfacial and tensile properties in GO-modified carbon fiber composites. Furthermore, significa...

A Hybrid Piezoelectric Structure for Wearable Nanogenerators

Abstract: A hybrid-fiber nanogenerator comprising a ZnO nanowire array, PVDF polymer and two electrodes is presented. Depending on the bending or spreading action of the human arm, at an angle of ∼90°, the hybrid fiber reaches electrical outputs of ∼0.1 V and ∼10 nA cm(-2) . The unique structure of the hybrid fiber may inspire future research in wearable energy-harvesting technology.

State of the art of carbon nanotube fibers: opportunities and challenges.

Abstract: The superb mechanical and physical properties of individual carbon nanotubes (CNTs) have provided the impetus for researchers in developing high-performance continuous fibers based upon CNTs. The reported high specific strength, specific stiffness and electrical conductivity of CNT fibers demonstrate the potential of their wide application in many fields. In this review paper, we assess the state of the art advances in CNT-based continuous fibers in terms of their fabrication methods, characterization and modeling of mechanical and physical properties, and applications. The opportunities and challenges in CNT fiber research are also discussed.

Rapid determination of myosin heavy chain expression in rat, mouse, and human skeletal muscle using multicolor immunofluorescence analysis.

Abstract: Skeletal muscle is a heterogeneous tissue comprised of fibers with different morphological, functional, and metabolic properties. Different muscles contain varying proportions of fiber types; therefore, accurate identification is important. A number of histochemical methods are used to determine muscle fiber type; however, these techniques have several disadvantages. Immunofluorescence analysis is a sensitive method that allows for simultaneous evaluation of multiple MHC isoforms on a large number of fibers on a single cross-section, and offers a more precise means of identifying fiber types. In this investigation we characterized pure and hybrid fiber type distribution in 10 rat and 10 mouse skeletal muscles, as well as human vastus lateralis (VL) using multicolor immunofluorescence analysis. In addition, we determined fiber type-specific cross-sectional area (CSA), succinate dehydrogenase (SDH) activity, and α-glycerophosphate dehydrogenase (GPD) activity. Using this procedure we were able to easily identify pure and hybrid fiber populations in rat, mouse, and human muscle. Hybrid fibers were identified in all species and made up a significant portion of the total population in some rat and mouse muscles. For example, rat mixed gastrocnemius (MG) contained 12.2% hybrid fibers whereas mouse white tibialis anterior (WTA) contained 12.1% hybrid fibers. Collectively, we outline a simple and time-efficient method for determining MHC expression in skeletal muscle of multiple species. In addition, we provide a useful resource of the pure and hybrid fiber type distribution, fiber CSA, and relative fiber type-specific SDH and GPD activity in a number of rat and mouse muscles.

Supplementary Material for The Geometric Structure of the Brain Fiber Pathways

Abstract: Building the Brain Brain connectivity is often described as a network of discrete independent cables analogous to a switchboard, but how is the physical structure of the brain constructed (see the Perspective by Zilles and Amunts)? Wedeen et al. (p. 1628) used high-resolution diffusion tensor imaging in humans and four species of nonhuman primates to identify and compare the geometric structure of large fiber tracts in the brain. Fiber tracts followed a highly constrained and regular geometry, which may provide an efficient solution for pathfinding during ontogenetic development. Much of development occurs through elaboration and assembly of semiautonomous building blocks. Chen et al. (p. 1634) applied statistical analysis to the form of the human cortex in brain-imaging studies that compared more than 400 di- and mono-zygotic twins. The findings suggest that the structure of the human cortex is defined by genetics. The macroscopic pathways of human brain nerve fibers are organized according to a single, highly curved three-dimensional grid. The structure of the brain as a product of morphogenesis is difficult to reconcile with the observed complexity of cerebral connectivity. We therefore analyzed relationships of adjacency and crossing between cerebral fiber pathways in four nonhuman primate species and in humans by using diffusion magnetic resonance imaging. The cerebral fiber pathways formed a rectilinear three-dimensional grid continuous with the three principal axes of development. Cortico-cortical pathways formed parallel sheets of interwoven paths in the longitudinal and medio-lateral axes, in which major pathways were local condensations. Cross-species homology was strong and showed emergence of complex gyral connectivity by continuous elaboration of this grid structure. This architecture naturally supports functional spatio-temporal coherence, developmental path-finding, and incremental rewiring with correlated adaptation of structure and function in cerebral plasticity and evolution.

Poultry response to high levels of dietary fiber sources varying in physical and chemical characteristics

Abstract: SUMMARY The ban on the use of antibiotics in feeds as growth promoters in many countries throughout the world has increased the incidence of enteric disorders in poultry. Natural additives, inclusion of whole cereals, feeding coarse mash diets, and increasing the level of fiber in the diets have been explored as nutritional strategies to reduce the incidence of the problem. Traditionally, dietary fiber has been considered a diluent of the diet and, often, an antinutritional factor. However, moderate amounts of fiber might improve the development of organs, enzyme production, and nutrient digestibility in poultry. Some of these effects are a consequence of better gizzard function, with an increase in gastroduodenal refluxes that facilitate the contact between nutrients and digestive enzymes. These effects often result in improved growth and animal health, but the potential benefits depend to a great extent on the physicochemical characteristics of the fiber source. In conclusion, poultry require a minimal amount of fiber in the diet for proper functioning of the digestive organs. The response to fiber inclusion depends on the source and level of dietary fiber and the characteristics of the diet as well as on the physiological status and health of the bird. In particular, the inclusion in the diet of moderate amounts of coarse, insoluble fiber sources, such as oat hulls, at levels between 2 and 3% usually improves the growth performance of broilers fed low-fiber diets.

Chitin nanofibers: preparations, modifications, and applications

Abstract: Chitin nanofibers are prepared from the exoskeletons of crabs and prawns by a simple mechanical treatment after the removal of proteins and minerals. The obtained nanofibers have fine nanofiber networks with a uniform width of approximately 10–20 nm and a high aspect ratio. The method used for chitin-nanofiber isolation is also successfully applied to the cell walls of mushrooms. They form a complex with glucans on the fiber surface. A grinder, a Star Burst atomization system, and a high speed blender are all used in the mechanical treatment to convert chitin to nanofibers. Mechanical treatment under acidic conditions is the key to facilitate fibrillation. At pH 3–4, the cationization of amino groups on the fiber surface assists nano-fibrillation by electrostatic repulsive force. By applying this finding, we also prepared chitin nanofibers from dry chitin powder. Chitin nanofibers are acetylated to modify their surfaces. The acetyl DS can be controlled from 1 to 3 by changing the reaction time. An acetyl group is introduced heterogeneously from the surface to the core. Nanofiber morphology is maintained even in the case of high acetyl DS. Optically transparent chitin nanofiber composites are prepared with 11 different types of acrylic resins. Due to the nano-sized structure, all of the composites are highly transparent. Chitin nanofibers significantly increase the Young's moduli and the tensile strengths and decrease the thermal expansion of all acrylic resins due to the reinforcement effect of chitin nanofibers. Chitin nanofibers show chiral separation ability. The chitin nanofiber membrane transports the D-isomer of glutamic acid, phenylalanine, and lysine from the corresponding racemic amino acid mixtures faster than the corresponding L-isomer. The chitin nanofibers improve clinical symptoms and suppress ulcerative colitis in a DSS-induced mouse model of acute ulcerative colitis. Moreover, chitin nanofibers suppress myeloperoxidase activation in the colon and decrease serum interleukin-6 concentrations.

Natural Fiber Reinforced Composites

Abstract: In this review, insight into the use of bio-based fibers as composite reinforcement has been addressed. Specifics on the varieties of natural fibers, and the resultant properties from their constituents and hierarchal structures are described. The methods used to enhance the interface of these fibers with a variety of polymer matrices are reviewed. In addition, the influence of textile operations on creating various fiber architectures with resulting reinforcing capabilities, along with the methods in which natural fiber reinforced composites can be processed, are addressed. Finally, discussion of the correlation between structure, processing, and final composite properties are provided.

Recent Progress in Fabrication, Structure, and Properties of Carbon Fibers

Abstract: This paper reviews recent developments in carbon fibers. Intensive studies focus on relationships among processing conditions, chemical/physical structures and tensile properties of polyacrylonitrile and meso-phase pitch based carbon fibers. Carbon fibers with specific geometry, such as hollow, porous, and patterned, have been fabricated for specific applications. Additionally, carbon nanotubes (CNTs), which have excellent mechanical properties, have been processed into macroscopic continuous fibers. Incorporating CNTs in precursor fiber also improves tensile strength and modulus of the resultant carbon fiber. Although extensive studies have been conducted for improving carbon fiber tensile strength and modulus as well as for reducing their production cost, these issues remain amongst the main challenges for broadening their applications.

Effect of fiber surface treatments on mechanical and abrasive wear performance of polylactide/jute composites

Abstract: The main focus of this work is to improve the adhesion of jute fiber with polylactide (PLA). For this purpose, surface of the jute fiber was modified by alkali, permanganate, peroxide and silane treatments. The surface modified fibers were characterized by FTIR spectroscopy. Unidirectional composites were prepared with treated jute fibers and PLA matrix by hot pressing of solvent impregnated prepregs. Surface treatments resulted in enhancement of tensile and flexural properties and reduction in Izod impact strength. Dynamic mechanical analysis (DMA) results showed that, treated composites have higher storage modulus and lower tangent delta with respect to untreated composite. The degree of interfacial adhesion between the jute fiber and PLA was estimated using adhesion parameter obtained through DMA data. The results of thermogravimetric analysis (TGA) showed a higher thermal stability for silane treated composites. Experimental results on abrasive wear tests revealed that the wear resistance of composite is sensitive to fiber/matrix adhesion.

Bamboo fiber and its reinforced composites: structure and properties

Abstract: Natural plant fibers have unequivocally contributed economic prosperity and sustainability in our daily lives. Particularly, bamboo fibers have been used for industrial applications as diverse as textiles, paper, and construction. Recent renewed interest in bamboo fiber (BF) is primarily targeted for the replacement or reduction in use of glass fiber from non-renewable resources. In this review, various mechanical, chemical, and biological approaches for the preparation and separation of macro-, micro-, and nano-sized fibers from raw bamboo are summarized. The differences in the mechanical, thermal, and other properties of fibers from different materials are linked to their size, aspect ratio, surface charge and groups, and their function in nature. Biocomposites made of BF are considered to be green, environmentally responsible eco-products. Different processing parameters such as fiber extraction, surface modification, and synthesis of the composites affect the characteristics of composites. Fiber length, orientation, concentration, dispersion, aspect ratio, selection of matrix, and chemistry of the matrix must all be considered during fabrication in order to achieve desirable functionalities and performance. Because of the hydrophilic nature of BF, different methods may be adopted to improve interfacial surface adhesion. A better understanding of the fiber structure and characteristics that influence composite performance could lead to the development of additives, coatings, binders, or sizing suitable for natural fiber and a variety of polymeric matrices.

Prediction of tensile properties of hybrid-natural fiber composites

Abstract: The tensile strength and modulus of short, randomly oriented hybrid-natural fiber composite was found out experimentally and also predicted using Rule of Hybrid Mixture (RoHM). Hybrid composites were prepared using banana/sisal fibers of 40:0, 30:10, 20:20, 10:30, and 0:40 ratios, while overall fiber volume fraction was fixed as 0.4 V f . The comparison between experimental and RoHM showed that they are in good agreement.

Cotton fiber: a powerful single-cell model for cell wall and cellulose research.

Abstract: Cotton fibers are single-celled extensions of the seed epidermis. They can be isolated in pure form as they undergo staged differentiation including primary cell wall synthesis during elongation and nearly pure cellulose synthesis during secondary wall thickening. This combination of features supports clear interpretation of data about cell walls and cellulose synthesis in the context of high throughput modern experimental technologies. Prior contributions of cotton fiber to building fundamental knowledge about cell walls will be summarized and the dynamic changes in cell wall polymers throughout cotton fiber differentiation will be described. Recent successes in using stable cotton transformation to alter cotton fiber cell wall properties as well as cotton fiber quality will be discussed. Future prospects to perform experiments more rapidly through altering cotton fiber wall properties via virus induced gene silencing will be evaluated.

A review on mechanical behavior of natural fiber based hybrid composites

Abstract: Hybrid composites are manufactured by combining two or more fibers in a single matrix. Hybrid composites can be made from artificial fibers, natural fibers and with a combination of both artificial and natural fibers. Hybrid composites can help us to achieve a better combination of properties than fiber reinforced composites. The constituent fibers in a hybrid composite can be altered in a number of ways leading to variation in its properties. The importance of this review can be attributed to the significant aspects of natural fiber based hybrid composites which are found to be predominantly affected by factors which include variation in fiber volume/weight fraction, variation in stacking sequence of fiber layers, fiber treatment and environmental conditions.

Intertwined aligned carbon nanotube fiber based dye-sensitized solar cells.

Abstract: Metal wires suffer from corrosion in fiber-shaped dye-sensitized solar cells (DSSCs). We report herein that stable, ultrastrong, and highly flexible aligned carbon nanotube fibers can be used not only as catalytic counter electrodes but also as conductive materials to support dye-loaded TiO(2) nanoparticles in DSSCs. The power conversion efficiency of this fiber solar cell can achieve 2.94%. These solar power fibers, exhibiting power conversion efficiency independent of incident light angle and cell length, can be woven into textiles via a convenient weaving technology.

Design and Fabrication of Tubular Scaffolds via Direct Writing in a Melt Electrospinning Mode

Abstract: Flexible tubular structures fabricated from solution electrospun fibers are finding increasing use in tissue engineering applications. However it is difficult to control the deposition of fibers due to the chaotic nature of the solution electrospinning jet. By using non-conductive polymer melts instead of polymer solutions the path and collection of the fiber becomes predictable. In this work we demonstrate the melt electrospinning of polycaprolactone in a direct writing mode onto a rotating cylinder. This allows the design and fabrication of tubes using 20 μm diameter fibers with controllable micropatterns and mechanical properties. A key design parameter is the fiber winding angle, where it allows control over scaffold pore morphology (e.g. size, shape, number and porosity). Furthermore, the establishment of a finite element model as a predictive design tool is validated against mechanical testing results of melt electrospun tubes to show that a lesser winding angle provides improved mechanical response to uniaxial tension and compression. In addition, we show that melt electrospun tubes support the growth of three different cell types in vitro and are therefore promising scaffolds for tissue engineering applications.

1D hollow α-Fe2O3 electrospun nanofibers as high performance anode material for lithium ion batteries

Abstract: Hollow-structured α-Fe2O3 nanofibers were successfully synthesized by a simple electrospinning technique using iron acetylacetonate (Fe(acac3)) and polyvinylpyrrolidone (PVP) precursor. Fe (acac)3–PVP composite fibers were calcined at high temperature to form an interconnected 1D hollow-structure of α-Fe2O3 nanofibers. Thermogravimetric analysis (TGA), X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and Brunauer–Emmett–Teller (BET) were employed to characterize α-Fe2O3 hollow fibers. Based on the characterization results, a formation mechanism for electrospun α-Fe2O3 hollow fibers is proposed. Electrochemical measurements showed that the hollow-structure of α-Fe2O3 nanofibers played an important role in improving the electrode cycle stability and rate capability in lithium ion batteries. The α-Fe2O3 hollow fiber anodes exhibit a high reversible capacity of 1293 mA h g−1 at a current density of 60 mA g−1 (0.06 C) with excellent cycle stability and rate capability. Based on our study this high performance is attributed to the interconnected hollow-structure of large aspect ratio α-Fe2O3 nanofibers, which makes them a potential candidate for lithium ion batteries.

Investigation of physical, chemical and mechanical properties of raw and alkali treated Borassus fruit fiber

Abstract: The natural fibers nowadays play a major role as reinforcement in composites due to their important properties like lightweight, biodegradability and non-toxicity. Borassus fruit fiber is one such type possessing high cellulose which is inexpensive and available in plenty. The Borassus fruit fibers were extracted and its physical, chemical and mechanical properties such as density, diameter, cellulose, hemicellulose, lignin, wax, denier, tenacity and tensile force were experimentally determined. In this study, the Borassus fruit fibers were treated with 5%, 10% and 15% NaOH and the effect of alkali treatments on the fiber properties were explored. It is interesting to note that 5% NaOH treatment yielded significant improvement in tensile properties of the fibers than the others. The Fourier Transform Infrared Spectrometry (FT-IR) analysis was made to identify the chemical compounds of the raw and alkali treated fibers. The morphological study on raw and alkali treated fibers by Scanning Electron Microscope (SEM) revealed the existence of the impurities on the raw fiber surface and the removal of the same on the treated fibers.

Design and fabrication of tubular scaffolds via direct writing in a melt electrospinning mode

Abstract: Flexible tubular structures fabricated from solution electrospun fibers are finding increasing use in tissue engineering applications. However it is difficult to control the deposition of fibers due to the chaotic nature of the solution electrospinning jet. By using non-conductive polymer melts instead of polymer solutions the path and collection of the fiber becomes predictable. In this work we demonstrate the melt electrospinning of polycaprolactone in a direct writing mode onto a rotating cylinder. This allows the design and fabrication of tubes using 20 μm diameter fibers with controllable micropatterns and mechanical properties. A key design parameter is the fiber winding angle, where it allows control over scaffold pore morphology (e.g. size, shape, number and porosity). Furthermore, the establishment of a finite element model as a predictive design tool is validated against mechanical testing results of melt electrospun tubes to show that a lesser winding angle provides improved mechanical response to uniaxial tension and compression. In addition, we show that melt electrospun tubes support the growth of three different cell types in vitro and are therefore promising scaffolds for tissue engineering applications.