Electrothermaly conditioned carbon fibre for the analysis of volatile pollutants.

This study deals with the development of an inexpensive and single-step sorbent manufacturing methodology for the analysis of air pollutants. Disposable carbon fibre sorbents were prepared in a few minutes using the electrothermal conditioning technique. The sorbent conditioning current and time were optimised to obtain the best extraction of benzene, toluene, ethylbenzene and xylenes (BTEX) from the air samples. After sorbent characterisation, analysis parameters affecting the BTEX extraction efficiency, such as sampling volume, humidity and sampling flow rate, were optimised for active BTEX sampling. Under optimum conditions, validation parameters such as the limit of detection (LOD), repeatability, reproducibility, and linear range were found to be 0.07-0.11 mg m - 3, 1.1%-1.8%, 5.6%-9.5% and 0.24-45 mg m - 3, respectively. Thereafter, the BTEX analysis was successfully conducted using the proposed method, with acceptable recovery values (96%-103%) in the real indoor environments.

Kraft lignin-based piezoresistive sensors: Effect of chemical structure on the microstructure of ultrathin carbon fibers.

In an attempt to diversify lignin applications, in this study, electrospun mats composed of ultrathin carbon fibers from Eucalyptus globulus Lignin (EKL) and sugarcane bagasse Kraft lignin (BKL) capable of detecting certain human body motions were fabricated and their chemical structures fully investigated accordingly. Results suggested that the main chemical structure of EKL was slightly linear with sinapyl alcohol and coniferyl alcohol as the basic units and pinoresinol, arylglycerol-ß-aryl ether, phenylcoumaran, with diphenylethane as the main linkages. The slightly linear EKL and cross-linked BKL tended to form amorphous carbon and graphite crystallites under the same heat treatment process respectively, thereby resulting in a large difference in the resistance of fabricated sensors. The amplitude of signals due to changes in the relative resistance (△R/R0) for EKL ultrathin carbon fiber (CF)-based sensor was approximately 9 × 104 during the finger bending process, while large (△R/R0 ~380) and small (△R/R0 < 10) relative resistance variations due to BKL-CF-based sensors were detected during the arm bending and finger pressing motions respectively.

Tuning the microstructure and electrochemical behavior of lignin-based ultrafine carbon fibers via hydrogen-bonding interaction.

Hardwood Kraft lignin (HKL)-based ultrafine carbon fibers with different pore structures and properties were prepared by controlling the intermolecular interaction between HKL and incorporated poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (PEG-PPG-PEG) triblock copolymer. The thermal properties of HKL-based ultrafine fibers together with the morphology and pore structures of HKL-based ultrafine carbon fibers were extensively investigated with DSC, TG, SEM, BET, DLS and HRTEM to provide comprehensive knowledge on the effect of added PEG-PPG-PEG on the properties of obtained fibers. Results suggested that addition of PEG-PPG-PEG increased the thermal stability of HKL and promoted the formation of graphite crystallites in HKL-based ultrafine carbon fibers via enhanced intermolecular hydrogen bonding interactions. The electrochemical behavior of HKL-based ultrafine carbon fibers with different PEG-PPG-PEG contents were also characterized to expand their potential application in electrochemical capacitors. All the HKL ultrafine carbon fibers-based electrodes showed good capacitive behavior and stability. Besides, the specific capacitance of HKL-based ultrafine carbon fibers can be significantly tuned by the addition of PEG-PPG-PEG.

Improving Interlaminar Fracture Toughness and Impact Performance of Carbon Fiber/Epoxy Laminated Composite by Using Thermoplastic Fibers.

The effects of thermoplastic polyimide (PI) and polypropylene (PP) fibers and areal density of toughened layer on interlaminar fracture toughness and impact performance of carbon fiber/epoxy (CF/EP) laminated composites were studied. Mode I interlaminar fracture toughness (GIC) was analyzed via double cantilever beam (DCB) tests. When comparing for the toughener type, PI played a positive role in enhancing the mode-I fracture toughness, while PP was not effective due to the less fiber bridge formed during composite curing. The toughening effects of areal density of PI were further investigated by end notched flexure (ENF) testing and low velocity impact testing to better understand the toughening mechanisms. The results revealed that the toughening effect reached its best effectiveness when the areal density of toughened layer was 30 g/m2. Compared with the control group, GIC and GIIC of CF/EP laminated composite were increased by 98.49% and 84.07%, and Fmax and Ee were enhanced by 92.38% and 299.08% under low velocity impact. There is no obvious delamination phenomenon on the surface of laminates after low velocity impact, indicating the improved interlaminar and impact performance of laminated composite.

Three-Dimensional CdS@Carbon Fiber Networks: Innovative Synthesis and Application as a General Platform for Photoelectrochemical Bioanalysis.

This Letter reports a novel synthetic methodology for the fabrication of three-dimensional (3D) nanostructured CdS@carbon fiber (CF) networks and the validation of its feasibility for applications as a general platform for photoelectrochemical (PEC) bioanalysis. Specifically, 3D architectures are currently attracting increasing attention in various fields due to their intriguing properties, while CdS has been most widely utilized for PEC bioanalysis applications because of its narrow band gap, proper conduction band, and stable photocurrent generation. Using CdS as a representative material, this work realized the innovative synthesis of 3D CdS@CF networks via a simple solvothermal process. Exemplified by the sandwich immunoassay of fatty-acid-binding protein (FABP), the as-fabricated 3D CdS@CF networks exhibited superior properties, and the assay demonstrated good performance in terms of sensitivity and selectivity. This work features a novel fabrication of 3D CdS@CF networks that can serve as a general platform for PEC bioanalysis. The methodology reported here is expected to inspire new interest for the fabrication of other 3D nanostructured Cd-chalcogenide (S, Se, Te)@CF networks for wide applications in biomolecular detection and beyond.

Influence of calcium chloride impregnation on the thermal and high-temperature carbonization properties of bamboo fiber.

In this study, bamboo fiber was pretreated with calcium chloride (CaCl2) solution by using an ultrasonic method, and then heat-treated at 250°C and carbonized at 1000°C. The effect of impregnation with CaCl2 on the thermal and chemical properties and morphology of bamboo fiber was determined using thermogravimetric and differential thermogravimetric analyses, in situ Fourier transform infrared spectroscopy, and scanning electron microscopy. The pore structure of the carbonized bamboo fiber was investigated. The results revealed that bamboo fiber pretreated with 5% CaCl2 (BFCa5) showed a downward shift in the temperature of the maximum rate of weight loss253°C and increase in char residue to 31.89%. BFCa5 was expected to undergo dehydration under the combined effect of oxygen-rich atmosphere and CaCl2 catalysis from 210°C, and cellulose decomposition would be remarkable at 250°C. Pretreatment with 5% CaCl2 promoted the formation of porous structure of the carbonized fiber, which exhibited a typical Type-IV isotherm, with the Brunauer-Emmett-Teller specific surface area of 331.32 m2/g and Barrett-Joyner-Halenda adsorption average pore diameter of 13.6440 nm. Thus, CaCl2 was found to be an effective catalyst for the pyrolysis of bamboo fiber, facilitating the formation of porous carbonized fiber.

Synthesis of electrospun polyacrylonitrile- derived carbon fibers and comparison of properties with bulk form.

This study deals with the fabrication of polyacrylonitrile (PAN) nanofibers via an electrospinning process followed by stabilizing and carbonization in order to remove all non-carboneous matter and ensure a pure carboneous material. The as-spun PAN fibers were stabilized in air at 270°C for one hour and then carbonized at 750, 850, and 950°C in an inert atmosphere (argon) for another one hour. Differential scanning calorimetry and Raman spectroscopy were employed to determine the thermal and chemical properties of PAN. Surface features and morphologies of PAN-derived carbon nanofibers were investigated by means of scanning electron microscopy (SEM). SEM micrograms showed that fiber diameters were reduced after carbonization due to evolution of toxic gases and dehydrogenation. The Raman spectra of carbonized fibers manifested D/G peaks. The Raman spectroscopy peaks of 1100 and 500 cm-1 manifested the formation of γ phase and another peak at 900 cm-1 manifested the formation of α-phase. The water contact angle measurement of carbonized PAN fibers indicated that the nanofibers were superhydrophobic (θ > 150o) due to the formation of bumpy and pitted surface after carbonization. In DSC experiment, the stabilized fibers showed a broad exothermic peak at 308°C due to cyclization process. The mechanical andThermal analysis was used to ascertain mechanical properties of carbonized PAN fibers. PAN-derived carbon nanofibers possess excellent physica and mechanical properties and therefore, they may be suitable for many industrial applications such as energy, biomedical, and aerospace.