Specific Surface Area Of Fibers Research Articles

CeO2/Co heterostructure encapsulated in hollow necklace-like carbon fiber as an advanced host material for high-performance lithium-sulfur batteries

The shuttle effect of lithium polysulfides (LiPSs) and the sluggish reaction kinetics of LiPSs conversion pose serious challenges to the commercial feasibility of lithium-sulfur (Li-S) batteries. To address these obstacles, herein, we construct CeO2/Co heterostructures in hollow necklace-like carbon fibers (CeO2/Co-CNFs) as the cathode host material for Li-S batteries. The specific surface area of fibers is significantly enhanced by using a template, thereby promoting the utilization efficiency of sulfur. Meanwhile, CeO2/Co-CNFs show strong conductivity, effective adsorption to LiPSs, and robust catalytic activity for LiPSs conversion. As a result, the Li-S battery with CeO2/Co-CNFs displays 961 mAh g−1 at 0.2 C, with an 86 % capacity retention rate after 100 cycles. At 2.0 C current density, the composite cathode maintains an initial discharge capacity of 782 mAh g−1, with a mere 0.044 % capacity loss per cycle. Furthermore, in situations with limited electrolytes, high sulfur loading, and high areal mass loading, the composite cathode can provide a high areal capacity of 6.2 mg cm−2 over 100 cycles. This work provides a useful approach for investigating high-performance Li-S battery cathodes.

Growth, Spectroscopy, and Laser Performance of a 2.79 μm Er: YSGG Single Crystal Fibers.

Single crystal fibers combine the great specific surface area of fibers and the single crystal property of the bulk crystal which shows great potential for a high-power laser. For an Er-doped crystal, due to the fluorescence quenching at the 3 μm wavelength, high Er doping is necessary to increase the fluorescent up-conversion for the breaking limitation. However, a high Er doping concentration must lead to high heat accumulation, resulting in poor laser performance. Compared with an Er-doped bulk crystal, Er-doped SCF has the great potential to remove the heat in the crystal, and it is easy to obtain a high power. In this paper, Er: Y3Sc2Ga3O12 (Er: YSGG) single crystals were successfully grown using the micro-pulling-down method (μ-PD). Owing to the stably grown interface, the diameter of the crystal is 2 mm with a length up to 80 mm. Then, the measurements of Laue spots and Er3+ distribution indicated that our crystals have a high quality. Based on the as-prepared Er: YSGG SCF, the continuous-wave (CW) laser operations at 2794 nm were realized. The maximum output was 166 mW with a slope efficiency of up to 10.99%. These results show that Er: YSGG SCF is a suitable material for future high-power 3 μm laser operation.

Fabrication of one-dimensional Bi2WO6/CuBi2O4 heterojunction nanofiber and its photocatalytic degradation property

In this paper, electrospinning method was used to prepare a one-dimensional nanostructured copper bismuthate-bismuth tungstate photocatalyst. The bismuth tungstate nanosheet structure was prepared by solvothermal method, and the copper bismuthate-bismuth tungstate precursor nanofibers were prepared by electrospinning using the doping method. The one-dimensional copper bismuthate-bismuth tungstate nanofiber structure was prepared by the high-temperature decomposition. The results show that the diameter of the bismuth tungstate and copper bismuthate nanofibers is about 280 nm, with continuous and regular fiber morphology. The fibers are composed of semiconductor nano-heterojunction and show good photocatalytic degradation efficiency for tetracycline hydrochloride. After 120 min of illumination, the degradation efficiency is greater than 90%, and it can be recycled and reused. The photocatalytic mechanism analysis showed that the energy band structure of the copper bismuthate-bismuth tungstate nano-semiconductor fiber was a Z-type heterojunction, and the free radical capture experiment showed that h + and •O 2− were main groups involved in oxidation reaction. The structure of high specific surface area of the nanofibers will improve the separation of photo-generated electrons and holes, and the experiment results show it has good performance of photocatalytic. • Electrospinning was used to prepare a one-dimensional nanostructured copper bismuthate-bismuth tungstate photocatalyst. • The fibers are composed of nano-heterojunction and show good photocatalytic performance for tetracycline hydrochloride. • High specific surface area of fibers improves the separation of electrons and holes to show good photocatalytic performance.

Electrochemical analysis of conducting reduced graphene oxide/polyaniline/polyvinyl alcohol nanofibers as supercapacitor electrodes

Supercapacitor is a promising electrochemical energy-storage device, which has the advantage of good cycle stability, short charging time, and high power density, so it has broad application prospects. Electrode as a core component has an important influence on the specific capacitance and performance of the supercapacitor. In this study, a series of reduced graphene oxide/polyaniline/polyvinyl alcohol (RGO/PANI/PVA) nanofibers with different RGO concentrations were synthesized by electrospinning method and then studied as electrode materials for supercapacitors. The experimental result reveals that the PANI/PVA nanofiber shows the pseudocapacitance properties, while the RGO/PANI/PVA nanofibers exhibit the electrochemical properties of the double-layer capacitor. In addition, the RGO/PANI/PVA nanofibers have a uniform diameter distribution of 119.8 nm without beads and droplets sticking when the concentration of RGO is 0.2%. This morphology contributes to a large specific surface area of fibers and provides sufficient channels for the transport of ions. RGO/PANI/PVA nanofibers exhibit better specific capacitance of 174 F/g when compared with the PANI/PVA (105 F/g). The research indicates that RGO/PANI/PVA nanofibers with high specific capacitance can provide a promising application as supercapacitor electrodes.

The effect of specific surface area of macro fibers on energy absorption capacity of concrete

Energy absorption capacity is the salient property of concrete. Reinforcement of concrete with macro fibers is one of the techniques that has led to enhancement of this important feature of concrete. However, the effect of specific surface area of melt-spun polypropylene macro fibers has hardly been studied so far. In this work, the effect of this parameter on mechanical behavior of fiber reinforced concrete (FRC) was investigated. Diameter of macro fibers was varied by changing the melt feeding rate and fiber draw ratio. Changes in fibers diameter affect fibers specific surface area, which in turn influences the adhesion of fibers to the matrix in FRCs. In order to evaluate the FRCs behavior, bending tests were conducted and the area under load-displacement curves was studied. It was found that increase in specific surface area of fibers results in considerable increase in energy absorption capacity of the FRCs. Concrete reinforced with the larger diameter fibers exhibited 6× energy absorption capacity than the reference sample. This was found to be in line with the 14× energy absorption capacity of sample which was reinforced by smaller diameter fibers. This was attributed to the increase in total contact area between the finer fibers and the matrix as a direct consequence of the increase in number of fibers for a given fiber volume fraction.

Design and fabrication of flexible mesoporous Si-doped Al2O3 ultrafine fibers by electro-blow spinning (EBS) technique

Abstract In this paper, flexible mesoporous Si-doped Al 2 O 3 ultrafine fibers were successfully prepared by electro-blow spinning (EBS) technology followed by a calcination process. The effects of spinning parameters, including air pressure, voltage, and solution injection rate on the morphology and diameter of fibers were investigated. The results showed that the spinning parameters played a key role on determining the morphology and diameter of fibers, and the specific surface area of fibers significantly increased with the increasing content of pore forming agents (polytetrafluoroethylene, PTFE), at the same time the pore size distribution was mainly concentrated at ~5 nm. Most importantly, Si(OC 2 H 5 ) 4 was introduced to act as the flexible regulator which could inhibit the growth of alumina crystal, decrease the crystal size, and thus the flexibility of obtained mesoporous Si-doped Al 2 O 3 ultrafine fibers can be improved. Moreover, the fibers productivity by EBS method was higher than that of traditional electro-spinning. In the future, the mesoporous Si-doped Al 2 O 3 ultrafine fibers may perform desired function and spread their applications in different areas.

Fiber Characteristics and Bonding Strength of Poplar Refiner-Chemical Preconditioned Alkaline Peroxide Mechanical Pulp Fractions

In China, alkaline peroxide mechanical pulping performed with refiner-chemical preconditioning (P-RC APMP) is well known to produce fiber with high bulk, opacity, and light scattering coefficient but weak bonding and strength properties. In this study, the characteristics of different P-RC APMP fiber fractions were investigated, and their effects on bonding strength properties were determined. The results showed that there was only 5.8% R30 fiber fraction and 14.1% P100/R200 fiber fraction, and the specific surface area increased from R30 to P100/R200. The tensile index increased by 51.85% and the bonding index increased by 15.35%, when the fibers were changed from the R30 fraction to the P100/R200 fraction. The short fiber fraction (P100/R200 fraction) had smaller fiber length and coarseness but larger specific surface area and greater surface charge density than the long fiber fraction (R30 fraction). The fiber specific surface area and surface charge density made significant contributions to the bonding capacity, whereas fiber coarseness and length were negatively correlated with the tensile index.

Combined mechanical and enzymatic treatments for improving the Fock reactivity of hardwood kraft-based dissolving pulp

The cellulose reactivity is a key parameter in the viscose rayon production process. To increase the reactivity of hardwood kraft-based dissolving pulp, a combined mechanical refining and enzymatic treatment was applied based on the hypothesis that a mechanical pretreatment can enhance the subsequent enzymatic treatment efficiency. Compared with the control sample, increases in the fiber specific surface area and fines content of dissolving pulp by 66 and 10 %, respectively, were achieved because of the fiber fibrillation induced by PFI refining, which led to increased accessibility and thus enzymatic hydrolysis efficiency in the following cellulase treatment. As a result, the Fock reactivity by following the combined mechanical and enzymatic treatment was further enhanced, from 76 to 82 % compared with enzymatic treatment only. The effects of combined mechanical and enzymatic treatments on other properties of the dissolving pulp, for example, intrinsic viscosity and molecular weight, were also determined.

Revisiting hardboard properties from the fiber sorting point of view

Abstract This study investigates the effects of fiber dimensions on hardboard properties. Fiber size is determined by the amount of energy applied during refining, and fiber size affects board properties; that is, production cost and board performance are closely related. Therefore, in the present paper, the effects of fiber dimensions on hardboard performance have been investigated. To optimize the hardboard process, fiber size was varied via screening, and the screen fractions were further classified using a Bauer-McNett apparatus. Hardboards were produced with mixtures of classified fibers. Bending strength, internal bond, and thickness swelling of the final boards were evaluated according to EN 310, EN 319, and EN 317, respectively. The effects of fiber size on the investigated properties were analyzed by means of multivariate linear regression. Generally, a higher proportion of small fibers appears to improve board performance presumably due to the higher specific surface area of fibers, which facilitate interfiber bonding.

Preparation and characterization of interconnected carbon nanofibers

A strategy to prepare interconnected carbon nanofibers using an electrospinning technique is proposed. This strategy lies in the addition of poly(acrylonitrile-co-butadiene (PAN-co-PB) copolymer in a precursor solution composed of polyacrylonitrile (PAN) and N,N-dimethylformamide. During pyrolysis, PB decomposed, softening the fibers and creating the possibility of fiber–fiber connection. The fiber diameter decreased with an increase in the PAN-co-PB content. Further addition of PAN-co-PB caused the fusion of neighboring fibers, which enlarged the fiber diameter and decreased the specific surface area of fibers. The microcrystallite sizes of carbon nanofibers depended on the PAN-co-PB content; and the addition of PAN-co-PB promoted the development of ordered graphite crystallites. The interconnected carbon nanofibers exhibited an electrical conductivity four times larger than that of the nanofibers with a uniform separated fibrous structure. The purpose of this work is to prepare carbon nanofiber mats with good electrical conductivity and well-controlled morphology for further use as energy-associated devices and catalyst supports.

Influence of Heat Treatment Process on Properties of Polycrystalline Alumina Fiber

Polycrystalline alumina fibers were prepared by sol-gel method. The influence of heating rate on average tensile strength of fibers as well as the influence of calcining temperature on average tensile strength of fibers, crystal phases form, specific surface area of fibers were studied. The results show that when the heating rate (below 600°C) is 4°C/min,the average tensile strength of fibers over 1000Mpa The fibers pulverize obviously when the heating rate＞7°C/min. The average tensile strength and the specific surface area of fibers decreased with calcining temperature rising. When the calcining temperature reaches over 1300°C, the average tensile strength of fibers decreased quickly and the specific surface area of fibers decreases slowly for the crystalline growth.

Adhesion Promotion in Fibers and Textiles Using Photonic Surface Modifications

Obtaining good bonding between two dissimilar materials is critical for several aspects in textile finishing, processing and application, including the durability of common textile finishes and fabric coatings, and the performance of fiber reinforced composites. Both functional properties and long term performance are dependent on the effective adhesion between the fiber on one hand and finishing agent, coating polymer or resin on the other. It is generally accepted that good adhesion is achieved through covalent chemical bonding, acid–base interactions or hydrogen bonding, surface energies that favor complete wetting of the fibers, large specific surface area of fibers, and surface roughness that allows lock and key type mechanical bonding. In practice, various surface treatments have been applied to fibers to alter their surface characteristics and to improve their adhesion properties. For example, chemical modifications such as acid oxidation, corona or plasma pre-treatments have been commonly employed. This paper aims to provide some insight into photon-based processes which, depending on the spectral range of radiation and the characteristics of the radiation sources, can be used to bring about chemical as well as morphological changes to fiber surfaces. We have considered two major applications of surface modification; (1) textiles for improving adhesion to finishes and (2) fiber/resin adhesion enhancement in fiber reinforced composites to improve their mechanical properties. The technical approaches cover photo-chemical surface modification and micro-roughening of fiber surfaces using monochromatic UV lamps and pulsed UV excimer lasers.

Polyurethane–silver fibers prepared by infiltration and reduction of silver nitrate

Silver-incorporating polyurethane fibers were prepared by infiltration of silver nitrate on electrospun polyurethane fibers and reduction with sodium borohydride. They were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and energy-dispersive X-ray system. The Ag nanoparticles prepared by reduction of silver nitrate showed nano-sized crystals of 4–10 nm in diameter. However, larger aggregated Ag particles of 50–200 nm were also found to be dispersed in the polyurethane matrix when Ag particles were formed in electrospun fibers by the infiltration–reduction process of silver nitrate. As a result, infiltration method of silver nitrate into the electrospun fibers was significantly effective to produce silver-incorporating fibers due to a high specific surface area of fibers.

Relationships Between a Cotton Fiber's Specific Surface Area and Its Physical Properties

The physical properties of six ICCS fibers—B—26, C-36, D-5, E-4, G-17, and I-26-their percent crystallinity, and the amount of absorbed water are measured in order to establish relationships with specific surface areas measured by the absorption of methy lene blue in a liquid phase. The results show the relationships between the surface area as measured by methylene blue absorption and fineness as measured by the gravimetric method, FMT3, and AFIS. Furthermore, there is a linear relationship between the surface area and the water content of cotton fibers, as determined by thermal-balance analysis. There is no clear relationship between the surface area and the percent crystallinity of the fibers.

Physical properties of silver-containing pitch-based activated carbon fibers

Silver-containing pitch-based carbon fibers were prepared and activated in steam. SEM and TEM were used to investigate the surface morphology and the behavior of the silver particles in fibers. Physical properties such as density, tensile strength, and electrical resistivity were measured. The SEM photos of fibers containing silver (at initial concentrations of 1000 and 10 000 ppm) were similar to those of non-activated carbon fibers at high level burn-off. Silver particles accelerate the activation rate. However, the specific surface areas of silver-containing activated carbon fibers were similar to those of non-silver containing activated carbon fibers. The apparent density and the tensile strength of the 10 000 ppm silver-containing carbon fibers were 1.677g/cm3 and 24 kgf/mm2, and these decreased to 0.795 g/cm3 and 6 kgf/mm2, respectively, at 69% burn-off. The electrical resistivity of isotropic pitch-based carbon fiber was 97 μΩ m. By comparison, as the initial silver content of the fiber was increased to 1000 and 10 000 ppm, the resistivity decreased to 69 and 57 μΩ m, respectively. These resistivities depended on the total pore volume and increased exponentially with increasing specific surface area of fibers.

Measurement of external specific surface area of fibers by solution adsorption

Measurement of external specific surface area of fibers by solution adsorption

Structure analysis of graphite fiber surfaces I. Mass spectrometry and low temperature adsorption of N2 and Ar

A study was made of the surface properties of unsized vacuum heat treated “Thornel–50” graphite fibers. The techniques used were low temperature N2 and Ar adsorption by microgravimetry, and mass spectrometry. The experiments showed that graphite fiber specific surface area was low — on the order of 1 M2/g. This specific surface first decreased and then increased slightly as the fibers were heated to higher and higher temperatures, The shape of the adsorption isotherms, comparison of adsorption data for fibers heat treated to different temperatures, analysis of the mass spectra of gases evolved during heating, and the known dimensions of the graphite crystallites provided strong evidence for three kinds of adsorption site patches on the fiber. These were identified as planar faces, edges (of the basal planes), and oxidized edges of oriented graphite crystallites in the fiber surface. The fractions of the fiber surface composed of these three patch types were ca. 0.67, ca. 0.26, and ca. 0.07. Vacuum heat treatment decreased the oxidized edge and increased the unoxidized edge surface. Lack of adsorption hysteresis at high relative pressures suggested a negligible number of large pores opening to the outside of the fiber. However, presence of a relatively large number of micropores was indicated. Comparison of the BET surface area obtained with nitrogen at 77°K with a calculation based on scanning electron microscopy indicated a fiber roughness factor of 3.