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Showing papers on "Fiber published in 2000"


Journal ArticleDOI
17 Nov 2000-Science
TL;DR: A simple method was used to assemble single-walled carbon nanotubes into indefinitely long ribbons and fibers, and the obtained elastic modulus is 10 times higher than the modulus of high-quality bucky paper.
Abstract: A simple method was used to assemble single-walled carbon nanotubes into indefinitely long ribbons and fibers. The processing consists of dispersing the nanotubes in surfactant solutions, recondensing the nanotubes in the flow of a polymer solution to form a nanotube mesh, and then collating this mesh to a nanotube fiber. Flow-induced alignment may lead to a preferential orientation of the nanotubes in the mesh that has the form of a ribbon. Unlike classical carbon fibers, the nanotube fibers can be strongly bent without breaking. Their obtained elastic modulus is 10 times higher than the modulus of high-quality bucky paper.

1,728 citations


Govind P. Agrawal1
01 Jan 2000
TL;DR: The field of nonlinear fiber optics has advanced enough that a whole book was devoted to it as discussed by the authors, which has been translated into Chinese, Japanese, and Russian languages, attesting to the worldwide activity in the field.
Abstract: Nonlinear fiber optics concerns with the nonlinear optical phenomena occurring inside optical fibers. Although the field ofnonlinear optics traces its beginning to 1961, when a ruby laser was first used to generate the second-harmonic radiation inside a crystal [1], the use ofoptical fibers as a nonlinear medium became feasible only after 1970 when fiber losses were reduced to below 20 dB/km [2]. Stimulated Raman and Brillouin scatterings in single-mode fibers were studied as early as 1972 [3] and were soon followed by the study of other nonlinear effects such as self- and crossphase modulation and four-wave mixing [4]. By 1989, the field ofnonlinear fiber optics has advanced enough that a whole book was devoted to it [5]. This book or its second edition has been translated into Chinese, Japanese, and Russian languages, attesting to the worldwide activity in the field of nonlinear fiber optics.

1,206 citations


Journal ArticleDOI
TL;DR: In this article, the tensile properties of polypropylene (PP) reinforced with short glass fibers (SGF) and short carbon fibers (SCF) were investigated with extrusion compounding and injection molding techniques.
Abstract: Composites of polypropylene (PP) reinforced with short glass fibers (SGF) and short carbon fibers (SCF) were prepared with extrusion compounding and injection molding techniques. The tensile properties of these composites were investigated. It was noted that an increase in fiber volume fraction led to a decrease in mean fiber length as observed previously. The relationship between mean fiber length and fiber volume fraction was described by a proper exponential function with an offset. The tensile strength and modulus of SGF/PP and SCF/PP composites were studied taking into account the combined effect of fiber volume fraction and mean fiber length. The results about the composite strength and modulus were interpreted using the modified rule of mixtures equations by introducing two fiber efficiency factors, respectively, for the composite strength and modulus. It was found that for both types of composites the fiber efficiency factors decreased with increasing fiber volume fraction and the more brittle fiber namely carbon fiber corresponded to the lower fiber efficiency factors than glass fiber. Meanwhile, it was noted that the fiber efficiency factor for the composite modulus was much higher than that for the composite strength. Moreover, it was observed that the tensile failure strain of the composites decreased with the increase of fiber volume fraction. An empirical but good relationship of the composite failure strain with fiber volume fraction, fiber length and fiber radius was established.

717 citations


Patent
03 Aug 2000
TL;DR: A stent structure includes a stent and one or more fibers disposed on the stent, the fiber adapted to provide a therapeutic agent as mentioned in this paper, where nuclei containing therapeutic agents that impede restenosis may be included within the fiber or within separate particles that are contained within hollow core fibers.
Abstract: A stent structure includes a stent and one or more fibers disposed on the stent, the fiber adapted to provide a therapeutic agent. Nuclei containing therapeutic agents that impede restenosis may be included within the fiber or within separate particles that are contained within hollow core fibers. The fibers and the particles may be bioerodible. A permeable, biocompatible sheath may be interposed between the stent and the fiber. A kit including a stent, a fiber, and a delivery catheter is also described.

622 citations


Journal ArticleDOI
TL;DR: In this article, a non-mechanical, electrostatic spinning (electrospinning) technique was used to produce polyaniline fiber mat for de-doping and redoping with camphorsulfonic acid (PAn).

551 citations



Journal ArticleDOI
TL;DR: In physiological ionic strength the fibers possess a dynamic structure in which the fiber locally interconverting between "open" and "closed" states because of thermal fluctuations.
Abstract: Single chicken erythrocyte chromatin fibers were stretched and released at room temperature with force-measuring laser tweezers. In low ionic strength, the stretch-release curves reveal a process of continuous deformation with little or no internucleosomal attraction. A persistence length of 30 nm and a stretch modulus of ≈5 pN is determined for the fibers. At forces of 20 pN and higher, the fibers are modified irreversibly, probably through the mechanical removal of the histone cores from native chromatin. In 40–150 mM NaCl, a distinctive condensation-decondensation transition appears between 5 and 6 pN, corresponding to an internucleosomal attraction energy of ≈2.0 kcal/mol per nucleosome. Thus, in physiological ionic strength the fibers possess a dynamic structure in which the fiber locally interconverting between “open” and “closed” states because of thermal fluctuations.

428 citations


Journal ArticleDOI
TL;DR: Detailed image analysis of nonwoven textile fabrics produced from elastin-mimetic fibers revealed that the distribution of single fiber orientation was isotropic with an associated unimodal distribution of protein fiber diameter.
Abstract: Elastin-mimetic peptide polymers have been synthesized, and the morphological properties of fabricated small diameter fibers and nonwoven fabrics have been characterized. An 81 kDa recombinant protein based upon the repeating elastomeric peptide sequence of elastin (Val-Pro-Gly-Val-Gly)4(Val-Pro-Gly-Lys-Gly) was obtained through bacterial expression of an oligomerized gene coding for tandem repeats of the monomer. The protein was processed into fibers by an electrospinning technique and morphology defined by SEM and TEM. The choice of processing parameters influenced both fiber diameter and morphology with diameters varying between 200 and 3000 nm and three morphological patterns noted: beaded fibers, thin filaments, and broad ribbonlike structures. Detailed image analysis of nonwoven textile fabrics produced from elastin-mimetic fibers revealed that the distribution of single fiber orientation was isotropic with an associated unimodal distribution of protein fiber diameter. In a dry state, the ultimate ...

384 citations


Journal ArticleDOI
TL;DR: In this paper, two types of enhancement techniques were studied: randomly oriented fibers and a fiber brush for enhancing the thermal conductivities of energy storage media, and the results showed that the fiber brush increases the effective thermal conductivity to the maximum values predicted which is theoretically.

363 citations


Journal ArticleDOI
TL;DR: In this paper, a 1.5mm-wavelength fiber laser was constructed by placing glass microsphere resonators along a fiber taper, which served the dual purpose of transporting optical pump power into the spheres and extracting the resulting laser emission.
Abstract: We demonstrate a 1.5-mm-wavelength fiber laser formed by placement of glass microsphere resonators along a fiber taper. The fiber taper serves the dual purpose of transporting optical pump power into the spheres and extracting the resulting laser emission. A highly doped erbium:ytterbium phosphate glass was used to form microsphere resonant cavities with large gain at 1.5 mm. Laser threshold pump powers of 60 mW and fiber-coupled output powers as high as 3 mW with single-mode operation were obtained. A bisphere laser system consisting of two microspheres attached to a single fiber taper is also demonstrated. © 2000 Optical Society of America

316 citations


Journal ArticleDOI
TL;DR: Chemomechanical transduction was studied in single fibers isolated from human skeletal muscle containing different myosin isoforms and the main difference between slow and fast fibers was reproduced by increasing the rate constant for the hydrolysis step, which was rate limiting at low loads.

Journal ArticleDOI
TL;DR: In this article, a review of carbon-matrix composites containing short carbon fibers is presented, which exhibit attractive tensile and flexural properties, low drying shrinkage, high specific heat, low thermal conductivity, high electrical conductivity and high corrosion resistance and weak thermoelectric behavior.
Abstract: This is a review of cement-matrix composites containing short carbon fibers. These composites exhibit attractive tensile and flexural properties, low drying shrinkage, high specific heat, low thermal conductivity, high electrical conductivity, high corrosion resistance and weak thermoelectric behavior. Moreover, they facilitate the cathodic protection of steel reinforcement in concrete, and have the ability to sense their own strain, damage and temperature. Fiber surface treatment can improve numerous properties of the composites. Conventional carbon fibers of diameter 15 μm are more effective than 0.1 μm diameter carbon filaments as a reinforcement, but are much less effective for radio wave reflection (EMI shielding). Carbon fiber composites are superior to steel fiber composites for strain sensing, but are inferior to steel fiber composites in the thermoelectric behavior.

Journal ArticleDOI
TL;DR: In this article, the authors measured polarization-dependent Raman spectra on oriented carbon nanotubes and found that all the Raman line intensities were observed to decrease in nearly equal amounts for the 647.1 nm laser excitation polarized perpendicular to the fiber axis versus that polarized parallel to the fibre axis.
Abstract: To probe the one-dimensional nature of single-wall carbon nanotubes (SWNTs) in bulk samples, we have devised a simple method for generating fibers of aligned SWNTs. We measured polarization-dependent Raman spectra on the oriented fibers. Contrary to what is expected from their theoretically assigned vibration-mode symmetries, all the Raman line intensities are observed to decrease in nearly equal amounts for the 647.1 nm laser excitation polarized perpendicular to the fiber axis versus that polarized parallel to the fiber axis. The effect is explained as a loss of resonance Raman scattering for the perpendicular polarization case.

Journal ArticleDOI
TL;DR: Almost no degradation in the bending strength was observed and the modulus of elasticity showed high values of 5-10 GPa when the fibers of 20-60 wt% were introduced, implying that HAF in the composites can share the applied load efficiently due to the formation of a bond between HAF and PLA.

Journal ArticleDOI
TL;DR: An optical fiber humidity sensor (OFHS) was fabricated using a hydrophilic gel (agarose) deposited on the thinner zone of a biconically tapered single-mode optical fiber as discussed by the authors.
Abstract: An optical fiber humidity sensor (OFHS) has been fabricated using a hydrophilic gel (agarose) deposited on the thinner zone of a biconically tapered single-mode optical fiber. A variation of up to 6.5 dB of the transmitted optical power was obtained with relative humidity (RH) changes between 30% and 80%. Furthermore, the sensor shows an invariant behavior with time. This inexpensive material showed a good reproducibility with low hysteresis and its use with tapered optical fiber makes it useful for industrial and environmental applications.

Journal ArticleDOI
TL;DR: Headspace SPME is a valid alternative for the determination of two- to five-ring PAHs and the reproducibility of the measurements between fibers was found to be very good.

Journal ArticleDOI
TL;DR: In this article, the basic principles for use of dispersion compensating fibers (DCF) are reviewed, including definition of figure of merit and condition for dispersion slope compensation, and the main design features of a triple-cladding index profile design are examined theoretically and experimentally.

Journal ArticleDOI
TL;DR: In this article, a defect-free polyimide hollow fiber membrane was formed using a dry-jet, wet quench process with spin dopes both with and without volatile solvents.

Journal ArticleDOI
TL;DR: Investigating growth- and breed-related changes of muscle fiber characteristics in cattle and their importance to meat quality found no significant differences in muscle fiber total number, muscle fiber type frequencies, or meat quality characteristics among breeds, with the exception of BBDM.
Abstract: The objective of this study was to investigate the growth- and breed-related changes of muscle fiber characteristics in cattle and their importance to meat quality Four cattle breeds with different growth impetus and muscularity were reared and slaughtered under experimental conditions German Angus as a beef type, Galloway as a hardy type, Holstein Friesian as a dairy type, and double-muscled Belgian Blue as an extreme type for muscle growth were used Between 5 and 17 bulls of each breed were slaughtered at 0, 2, 4, 6, 12, 18, and 24 mo of age Muscle fiber traits were determined and classified by computerized image analysis, and several measures of meat quality were also determined, including shear force value, meat color, and im fat content The postnatal growth of semitendinosus muscle in cattle was characterized by a nearly 10-fold increase of muscle fiber area from birth to 24 mo of age In the first few months after birth, a transformation of type IIA fibers into IIB fibers was found, whereas type I fibers were nearly unaffected by age The apparent total muscle fiber number of semitendinosus muscle did not increase during postnatal life These results confirm that the fiber number is determined in embryonic development Throughout the study, the double-muscled Belgian Blue (BBDM) bulls had almost twice the fiber number of the other breeds, emphasizing a more extensive hyperplasia of muscle fibers during embryonic development in BBDM compared with the other three breeds The apparent number of type I fibers was, however, not affected by breed, which suggests that the additional fibers found in BBDM postnatally were type IIB and IIA fibers We did not find significant differences in muscle fiber total number, muscle fiber type frequencies, or meat quality characteristics among breeds, with the exception of BBDM Having pooled the four breeds, paler meat was related to a higher frequency of type IIB fibers, a lower area of type IIA and type I fiber, and a higher total muscle fiber number These findings based on data of double muscling give us some hints for biological causes for the variation of meat quality Further investigation, in particular within each breed, is necessary to identify the superior fiber traits for bovine meat production

Journal ArticleDOI
TL;DR: In this article, a polyvinylidene fluoride (PVDF) asymmetric hollow fiber membranes were prepared by introducing small molecular additives, which include nonsolvents (water, ethanol and 1-propanol) and inorganic salt (LiCl).

Journal ArticleDOI
TL;DR: In this paper, the authors used differential scanning calorimetry to study the crystallization kinetics and the energy of polysilane-based and silane-constrained polysilicon composites.
Abstract: In this paper, oil palm fiber reinforced phenol formaldehyde (PF) treated, as well as untreated, composites have been taken for the study. The untreated sample (sample 1) contains oil palm fiber reinforced in the PF matrix, and the same fiber is treated with silane (sample 2) and with alkali (sample 3) to produce two types of treated fibers. These treated fibers were then reinforced in the matrix to produce two treated samples. Differential scanning calorimetry has been employed to study the crystallization kinetics and the energy of crystallization for all the samples. All the samples show the well-defined peaks of crystallization. In the case of silane-treated sample, double crystallization is observed. The crystallization data are analyzed in terms of a modified Kissinger’s equation to determine the activation energy. The activation energy and other crystallization parameters have also been determined using Matusita’s equation and are compared with the values obtained from other equations. It has also been found that various treatments have improved the thermal stability of the composites to different extents.

Journal ArticleDOI
TL;DR: In this article, the deformation of carbon fiber reinforced shape memory polymer matrix composites for deployable space structure applications was investigated using both satin and plain weave fiber architectures, and it was shown that the dominant local deformation mode was buckling of the carbon fibers on the inner surface of the bend.
Abstract: In this paper we present results on the deformation of carbon fiber reinforced shape memory polymer matrix composites for deployable space structure applications. The composites were processed using resin transfer molding or a pre-impregnated (pre-preg) laminate press, with both satin and plain weave fiber architectures. The polymer matrix glass transition temperature, Tg, was approximately 95°C. Composite specimens were bent to specific radii at T = 120°C, and cooled while constrained to a temperature of 25°C, which left them frozen in the bent state. Heating the specimens above Tg caused the composites to return to their original unbent shape with up to 95% recovery based on bend angle. The effect of constraint hold times up to 350 hours on the recoverability was found to be negligible. Microscopic investigations revealed that the dominant local deformation mode of the composites was buckling of the carbon fibers on the inner surface of the bend. Localized buckling out of the material plane lead to detr...

Journal ArticleDOI
TL;DR: In this article, a theory for phase transitions in materials made from natural fibers is proposed, which predicts structural phase transitions of the first order at heating, showing the universal behavior of a scaling law, which is unusual for first order phase transitions.
Abstract: We propose a theory for the phase transitions in materials made from natural fibers. At heating, the theory predicts structural phase transitions of the first order. The normalized thermodynamical characteristics show the universal behavior of a scaling law, which is unusual for first order phase transitions The scaling exponents depend only on the exponent of the energy of small-angle interaction between fiber segments. We consider here some specific fibers like collagen which ``melt'' (denaturate) at higher temperature and we found explicit expressions for the thermodynamics characteristics, which can be verified by experiment.

Journal ArticleDOI
TL;DR: In this paper, the authors demonstrate that carbon nanotubes can be used as fiber materials for metal matrix composites and demonstrate that they show a large increase in hardness and Young's modulus as compared to pure Ti.
Abstract: Carbon nanotubes, a kind of high order fullerenes, offers remarkable electronic as well as mechanical properties, e.g., an extremely high Young’s modulus of TPa order has been reported. This suggests the suitability of carbon nanotubes as novel fiber materials for metal matrix composites. The authors demonstrate that Ti/ nanotube composites show a large increase in hardness and Young’s modulus as compared to pure Ti. This makes the composite an attractive advanced material for future applications.

Journal ArticleDOI
TL;DR: In this article, the effect of the types of alkaline earth metal ions (Mg2+, Ca2+ and Ba2+) and concentration of Al2O3 and BaO on the refractive index and the effective emission linewidths of the 4I13/2−4I15/2 transition of Er3+ ions in phosphate glasses was investigated.
Abstract: The effect of the types of alkaline earth metal ions (Mg2+, Ca2+ and Ba2+) and concentration of Al2O3 and BaO on the refractive index and the effective emission linewidths of the 4I13/2−4I15/2 transition of Er3+ ions in phosphate glasses, 64P2O5 · 12Al2O3 · 3.5( Er 2 O 3 + La 2 O 3 )·20.5 MO ( M = Mg , Ca , Ba ) and 64P2O5 · 3.5(Er2O3+La2O3) · (21.5 − x)Al2O3 · (11+x) BaO (x=0,3.5,6.5 and 9.5) , were investigated. A single mode Er3+ doped phosphate glass fiber with a core diameter of 4 μm was fabricated by the rod-in-tube technique. A new Er3+ doped fiber amplifier is demonstrated pumping with a 980 nm fiber pigtailed-laser diode. A gain per unit length greater than 2 dB/cm is demonstrated, which is the largest gain per unit length for fiber amplifiers to our knowledge.

Journal ArticleDOI
TL;DR: In this paper, a combination of chemical and mechanical methods was used for the extraction of bamboo fibers and the fiber population from both the techniques were characterized, and the fibers obtained from CMT and RMT were used to make unidirectional composites of polyester.
Abstract: Few investigations have been carried out with bamboo fibers despite its high strength, biodegradability, and low cost. The overall objective of this work was to investigate fiber extraction from bamboo and the use of these bamboo fibers as reinforcement in polymeric composites. A combination of chemical and mechanical methods was used for the extraction of bamboo fibers. Conventional methods of compression molding technique (CMT) and roller mill technique (RMT) were explored for the mechanical separation. Fiber population from both the techniques were characterized. Mechanical properties of the fibers also were evaluated. Bamboo fibers obtained from CMT and RMT were used to make unidirectional composites of polyester. High values of tensile strength were observed in all the composites. The predominant mode of failure for the composite was shown to be the cracking of the fiber–matrix interface. Quantitative results from this study will be useful for further and more accurate design of bamboo reinforced composite materials. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 83–92, 2000

Journal ArticleDOI
TL;DR: In this article, a particle-level simulation technique was developed to simulate fibers as chains of rods connected by hinges to probe fiber flocculation, incorporating fiber flexibility, irregular fiber equilibrium shapes, and frictional fiber interactions.
Abstract: Non-Brownian fibers commonly flocculate in flowing suspensions at relatively low concentrations (<1% by weight) We have developed a particle-level simulation technique modeling fibers as chains of rods connected by hinges to probe fiber flocculation The model incorporates fiber flexibility, irregular fiber equilibrium shapes, and frictional fiber interactions Model fibers reproduce known orbits of isolated rigid and flexible fibers in shear flow Simulation predictions of first normal stress differences in homogeneously dispersed, dilute flexible fiber suspensions agree with experimental data Fiber features such as flexibility and irregular equilibrium shapes strongly impact single fiber and suspension behavior Fibers aggregate in simulations with interfiber friction, in the absence of attractive forces between fibers Strong flocculation is observed in suspensions of stiff fibers with irregular equilibrium shapes Flocs contain many fibers with three or more contact points, and derive cohesiveness f

Journal ArticleDOI
TL;DR: In this paper, the effect of fiber surface pretreatment on the interfacial strength and mechanical properties of wood fiber/polypropylene (WF/PP) composites is investigated. And the results demonstrate that fiber surface conditions significantly influence the fiber-matrix interfacial bond, which, in turn, determines the mechanical properties.
Abstract: The effect of fiber surface pretreatment on the interfacial strength and mechanical properties of wood fiber/polypropylene (WF/PP) composites are investigated. The results demonstrate that fiber surface conditions significantly influence the fiber–matrix interfacial bond, which, in turn, determines the mechanical properties of the composites. The WF/PP composite containing fibers pretreated with an acid–silane aqueous solution exhibits the highest tensile properties among the materials studied. This observation is a direct result of the strong interfacial bond caused by the acid/water condition used in the fiber pretreatment. Evidence from coupling chemistry, rheological and electron microscopic studies support the above conclusion. When SEBS-g-MA copolymer is used, a synergistic toughening effect between the wood fiber and the copolymer is observed. The V-notch Charpy impact strength of the WF/PP/SEBS-g-MA composite is substantially higher than that of the WF/PP composite. The synergistic toughening mechanisms are discussed with respect to the interfacial bond strength, fiber-matrix debonding, and matrix plastic deformation. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1000–1010, 2000

Journal ArticleDOI
TL;DR: In this article, mesostructural features of importance to the stiffness and strength of unidirectionally extruded materials were characterized as a function of the processing variables, including void geometry/density and the extent of bonding between contiguous fibers.
Abstract: Fused‐deposition (FD) is a robotically controlled “fiber” extrusion process that produces a new class of materials with a variety of controllable mesostructural features related to fiber layout and the presence of voids. Mesostructural features of importance to the stiffness and strength of unidirectionally extruded materials were characterized as a function of the processing variables. Samples were made using the Stratasys FDM1600 Modeler with the P400 acrylonitrile‐butadiene‐styrene plastic. Results showed that the void geometry/density and the extent of bonding between contiguous fibers depended strongly on the fiber gap and extrusion flow rate. Settings for minimum void and maximum fiber‐to‐fiber bonding were determined. Void and bond length densities in the plane transverse to the fiber extrusion direction varied from 4 to 16 per cent and 39 to 73 per cent respectively. The results quantify the important mesostructural features as a function of the FD process variables and are expected to find use with other FD materials.

Journal ArticleDOI
TL;DR: In this paper, the effect of maleic anhydride on the swelling and mechanical properties of plant fiber polymer composites has been assessed and the impact strength and Shore-D hardness have been found to be higher in maleic-anhydride-treated fiber composites than the untreated-fiber composites.