Pure CF Research Articles

Co/N-codoped carbon nanoplate array coated carbon fiber cathode for solar driven uranium extraction from complex radioactive wastewater

Organics bring great challenge on uranium reduction due to the formation of stubborn complexes between uranyl ions (UO22+) and organics. Herein, we developed an effective strategy to synchronously degrade organics and extract uranium from complicated radioactive wastewater, accompanied with electricity generation, by a novel self-driven photocatalytic fuel cell (NSPFC) system, in which a three-dimensional (3D) Co/N-doped carbon nanoplate array (Co-N-C/CF) decorated carbon fiber is employed as the cathode for highly efficient UO22+ reduction. Compared to pure CF, the optimized Co-N-C/CF cathode increases the rate constants (k) by 9 and 9.1 times for UO22+ and organic elimination, respectively, and improves electricity output by 2 times (Pmax, 1180 μW/cm2). This improvement should be ascribed to the 3D morphology of Co-N-C/CF that provided plenty of surface area for U(VI) reduction, and the doping of N and Co, which effectively increased the U(VI) adsorption sites and optimized the electron behavior on the cathode, respectively. These features endow the NSPFC system with excellent adaptability in treating complex radioactive wastewater with a wide range of pollutant concentration, pH, co-existed ions, pollutant organics and natural organic matters. Fascinating activity is also achieves in treating polluted seawater or under real sunlight illumination. This work not only provides a outstanding nanostructured cathode for uranium reduction but also suggests a charming system to resourcefully treatment of radioactive wastewater or polluted water bodies.

Impedance matching optimization of hierarchical carbon fiber@MoS2@PANI nanocomposite with core‐sheath structure for achieving excellent microwave absorption

AbstractCarbon fiber (CF) has been extensively used in the research of microwave absorption owning to its excellent performance, but it also faces a series of problems such as impedance mismatch and low absorption intensity. The core‐sheath microstructure with CF as the inner core is constructed to solve the above issues by the introduction of other sheath layers. In this work, the MoS2 sheath and polyaniline (PANI) sheath are successively introduced into the CF matrix to obtain a hierarchical CF@MoS2@PANI nanocomposite with core‐sheath structure through a straightforward hydrothermal method and in‐situ polymerization. The obtained CF@MoS2@PANI nanocomposite exhibit the minimum reflection loss value of −42.23 dB at 10.11 GHz while the thickness is 2.5 mm, much higher than those of pure CF (below −10 dB) and CF@MoS2 nanocomposite (−25.60 dB). Moreover, the distinctive hierarchical core‐sheath structure contributes to providing more active sites, prolonging the transmission path of electromagnetic waves, and forming heterogeneous interfaces. Consequently, the electromagnetic wave attenuation mechanism of CF@MoS2@PANI nanocomposite is attributed to a synergistic effect of conductive loss, multiple reflection/scattering, dipole polarization, and interface polarization. This work offers an effective and promising strategy to design a three‐dimensional hierarchical core‐sheath microstructure for the development of composite absorbers.

Applying Box-Behnken Design for Formulation and Optimization of PLGA-Coffee Nanoparticles and Detecting Enhanced Antioxidant and Anticancer Activities.

In an attempt to prove biological activity enhancement upon particle size reduction to the nanoscale, coffee (Cf) was chosen to be formulated into poly(lactic-co-glycolic) acid (PLGA) nanoparticles (NPs) using the single emulsion-solvent evaporation (SE-SE) method via Box–Behnken Design (BBD) to study the impact of certain process and formulation parameters on the particle size and size homogeneity, surface stability and encapsulation efficiency (EE%). The coffee-loaded PLGA (PLGA-Cf) NPs were characterized by different methods to aid in selecting the optimum formulation conditions. The desirable physicochemical characteristics involved small particle sizes with an average of 318.60 ± 5.65 nm, uniformly distributed within a narrow range (PDI of 0.074 ± 0.015), with considerable stability (Zeta Potential of −20.50 ± 0.52 mV) and the highest EE% (85.92 ± 4.01%). The antioxidant and anticancer activities of plain PLGA NPs, pure Cf and the optimum PLGA-Cf NPs, were evaluated using 2,2-Diphenyl-1-picryl-hydrazyl (DPPH) and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays, respectively. As a result of nano-encapsulation, antioxidant activity was enhanced by 26.5%. Encapsulated Cf showed higher anticancer potency than pure Cf against different cancerous cell lines with an increase of 86.78%, 78.17%, 85.84% and 84.84% against MCF-7, A-549, HeLa and HepG-2, respectively. The in vitro release followed the Weibull release model with slow and biphasic release profile in both tested pH media, 7.4 and 5.5.

Modeling the effect of stochastic heating and surface chemistry in a pure CF4 inductively coupled plasma

The physics and chemistry of inductively coupled plasma generated in pure tetrafluoromethane are analyzed using a self-consistent two-dimensional plasma fluid model coupled with Maxwell's equations. The model also takes into account the stochastic electron heating typical for low-pressure inductive discharges. We show that this effect is important for the explanation of experimentally measured plasma parameters. We also analyze the influence of several model parameters on the plasma. These parameters include the mechanism of surface reactions, the sticking coefficient of fluorine atoms at the walls, the uncertainty in the electron impact dissociation reactions, and the background gas pressure.

Nanocomposites of multi-walled carbon nanotubes/cobalt ferrite Nanoparticles: Synthesis, structural, dielectric and impedance spectroscopy

Cobalt ferrite ‘CoFe2O4’ (CF) nanoparticles were prepared by co-precipitation method and their nano-composites with Multi-Walled Carbon Nanotubes (MWCNTs) (i.e.; CF/(MWCNTs)x; x = 0–30 wt% were synthesized using ultra-sonication route. Toluene was used as dispersive medium for uniform dispersion of MWCNTs. These nano-composites were characterized through X-ray diffraction (XRD), scanning electron microscopy (SEM), dielectric and impedance measurements. Single phase FCC structures of these nano-composites were explored by XRD and the aggregation of CF nanoparticles on MWCNTs was seen by SEM. The dielectric and impedance measurements were carried out with the help of LCR meter. The dielectric parameters i.e.; dielectric constants, dielectric loss, and loss tangent were increased with augmented MWCNTs contents in comparison to pure CF nanoparticles. While, impedance measurements showed leaning behavior with increased MWCNTs contents. These enhanced dielectric properties of CF/(MWCNTs)x nano-composites can be subjugated in various energy storage devices.

Synthesis of one-dimensional PAN-based carbon fiber/NiO composite as an anode material for structural lithium-ion batteries

The devices with high energy storage such as structural lithium-ion batteries (SLIBs) have recently attracted extensive attention, and many efforts have been made to prepare the high-performance anodes. Polyacrylonitrile (PAN)-based carbon fiber with light weight can save volume and quality, which has been recognized as a promising anode material for structural lithium-ion batteries (SLIBs). Herein, we successfully developed a one-dimensional PAN-based carbon fiber/NiO composite (CF/NiO) through an easy and convenient method. Benefiting from the combination of high theoretical specific capacity and high electrical conductivity of NiO (~ 780 mAh g−1) and strong mechanical properties of carbon fiber, the resulting CF/NiO exhibits excellent performance in lithium-ion storage. CF/NiO composite presents a coulombic efficiency of over 99% and good cyclic ability. It performs a high reversible capacity of 648 mAh g−1 after 150 cycles at a current density of 100 mA g−1, approximately 2.5 times as high as the pure CF (~ 260 mAh g−1). The excellent electrochemical performance can be attributed to the synergistic effect between the one-dimensional structural carbon fiber and NiO, making the electrochemical reaction highly reversible.

Effect of decorating cobalt ferrite spinel structures on pistachio vera shell –derived activated carbon on energy storage applications

In this work, a simple insitu chemical co-precipitation technique was adopted for the synthesis of CoFe2O4 (Cf) decorated Pistachio shell derived activated carbon (Cf@Pv-AC) composite to fabricate electrodes for supercapacitor (SC) application. Doping of Cf particles on the surface of the Pv-AC effectively enhanced the diffusion of electrolyte ions by facilitating a porous structural morphology which act as the reservoir of electrolyte ions during the electrochemical redox reactions. FT-IR spectrum of Cf@Pv-AC composite exhibited the strong absorption band at 608 cm−1, which was associated to M-O bonds (Where M=Co and Fe) in Cf structure. FE-SEM images of Cf@Pv-AC suggested that Co-ferrite particles have evenly covered the surface of porous Pv-AC rods. Further, Cyclic voltammetric analysis (CV) of Cf@Pv-AC coated Ni foil electrode proved the battery type behavior of Cf in Cf@Pv-AC sample and delivered the specific capacity of 1233 C/g in the potential range of 0–0.69 V at the scan rate of 5 mV/s. These results revealed that the specific capacity value increased two fold than that of pure Cf (434 C/g) at the same scan rate. Moreover, the obtained results were also substantiated by Galvanostatic charge-discharge (GCD) measurements. About 93% of specific capacity retention was achieved by Cf@Pv-AC electrode, even after 5000 GCD cycles at the current density of 4 A/g, which were evident for the better capacitive performance of Cf@Pv-AC electrode material.

Improving the Mechanical Properties of Cf/ PEEK Composite by Implanting Functionalized Multi-Wall Carbon Nanopaper

The multi-walled carbon nanotubes were prepared into nanopaper with three-dimensional network structure by ultrasonic dispersion technology and suction filtration, and then implanted into Cf / PEEK composite materials by mold pressing process. The microstructure, tensile strength, flexural strength and abrasion resistance of the composites were tested. The influence of the nanopaper on the properties of composites were discussed and analyzed. After implanting a well- dispersed PANI-functionalized nanopaper layer, the tensile strength and bending strength of the 0.1 mm nanopaper composite increased by 20.6% and 26.6% respectively, which meant that high load is needed to cause the composite to break. There are pores in the interface of 0.2 mm nanopaper composite after hot pressing, and the improvement of mechanical properties is not significant. Compared with the pure Cf / PEEK composite, the friction coefficient of 0.1 mm nanopaper composite is reduced by 0.05, and the wear rate is reduced by 26%. This should be ascribed to that the self-lubricating property of MWCNTs. The three-dimensional network structure of nanopaper with good thermal conductivity can disperse the heat generated in the friction process and reduce the contact area between the Si3N4 ball and the resin matrix.

Preparation of PAN-based carbon fiber/Co3O4 composite and potential application in structural lithium-ion battery anodes

Lightweight polyacrylonitrile (PAN)-based carbon fiber can give volume and mass savings, which has been considered as a promising anode material for structural lithium-ion batteries (SLIBs). However, the current issue is the limitation of low capacity. To improve the situation, a novel PAN-based carbon fiber/Co3O4 composite (CF/Co3O4) has been developed through a chemical deposition method. Since combining advantage of high theoretical specific capacity of Co3O4 and great electroconductivity as well as strong mechanical of carbon fiber, the prepared CF/Co3O4 shows excellent performances as an anode material for SLIBs. It presents a coulombic efficiency of over 99% and stable cyclic ability. Even if the number of cycles reaches to 150, a steady discharge reversible capacity up to 625 mAh g−1 can be retained, approximately 2.7 times as much as pure CF (~ 230 mAh g−1). The improved cycling stability of CF/Co3O4 can be owed to the interactions between CF and Co3O4 anchored on the CF. Furthermore, a solid polymer electrolyte was also prepared with the flexibility, which shows a steady discharge reversible capacity of 500 mAh g−1 at 100 mA g−1. The paper provides an affordable method to solve the problem of the limitation of capacity in current SLIBs when using commercial carbon fibers as anode materials.

Preparation of PAN-based carbon fiber@MnO2 composite as an anode material for structural lithium-ion batteries

Carbon fiber@MnO2 composite (CF@MnO2) has been successfully synthesized based on the redox mechanism, and the morphological and electrochemical features are also studied. As a promising anode material for structural lithium-ion batteries (SLIBs), CF@MnO2 composite presents a coulombic efficiency of over 99% and good cyclic ability. It performs a high reversible capacity of 648 mAh g−1 after 150 cycles at a current density of 100 mA g−1, approximately 2.5 times as high as the pure CF (~ 260 mAh g−1). Moreover, the images of attained composite after the cycle show the fibrous structure do not change much, which verifies it retains good cycle stability. The superior electrochemical performance of the CF@MnO2 composite can be attributed to the unique hierarchy architecture and the synergistic effect between MnO2 and CF, which can effectively alleviate the volume expansion of MnO2 during the lithium insertion/extraction.

Boltzmann analysis of electron swarm parameters in CHF 3 +CF 4 mixtures

The electron drift velocity, mean energy, ionization, attachment, effective ionization coefficient, limit electrical field, and synergism of pure CHF 3 (fluoroform), pure CF 4 (tetrafluoromethane), and CHF 3 +CF 4 gas mixtures are calculated by Boltzmann equation analysis in a wide range of density normalized electrical fields (E/N). The finite difference method is used to solve the two-term approximation of the Boltzmann equation under steady-state Townsend conditions. To our knowledge, no previous electron swarm parameters of these mixtures have been published. At constant E/N values, the electron mean energies and drift velocities increase with decreasing CHF 3 content. The addition of CF 4 into the mixture increases the attachment coefficient but reduces the ionization coefficient since CF 4 is more electronegative than CHF 3 . Furthermore, the limit electrical fields increase with increasing CF 4 concentration.

Fluorographane C2FH: Stable and wide band gap insulator with huge excitonic effect

We present structural, vibrational, electronic and optical properties of recently prepared fully fluorinated and hydrogenated graphene, called fluorographane. We consider 1:1 ratio of F and H adatoms and we carefully investigate possible structural conformers in C2FH stoichiometric material. The reported results show that all conformers are dynamically stable and homogeneous structures with F and H atoms on both sides of carbon honeycomb structure are more stable than the Janus structures with F atoms on one side and all H atoms on the other. While the main structural and vibrational features are roughly similar for various conformers, electronic and optical properties are very sensitive to local structure (namely specific combinations of F and H adatoms on the graphene surface) and differ significantly. Our highly accurate results based on many-body methods (GW and BSE) indicate that homogeneous fluorographane has unusually wide indirect electronic band gap of ∼10 eV (larger than both pure graphane CH and pure fluorographene CF) and embodies a huge excitonic effect (∼3 eV). Fluorographane C2FH is therefore a material with the widest electronic gap and a largest binding energy of exciton in the class of currently known 2D materials.

Grafting TiO2 nanoparticles onto carbon fiber via “thiol-ene” click chemistry and its photodegradation performance for methyl orange

In this article, we presented a novel and facile method for obtaining a photocatalyst of carbon fiber grafted with TiO2 (CF-TiO2) via “thiol-ene” click chemistry. The as-prepared CF-TiO2 was characterized by FT-IR, TGA, SEM, TEM and XRD. The results demonstrate the successful grafting of TiO2 onto the CF surface and the grafting content of TiO2 is about 9%. The photocatalytic activity of CF-TiO2 was evaluated by measuring the photodegradation of methyl orange (MO) under UV irradiation. The photodegradation rate of CF-TiO2 (89%) is significantly higher than that of pure CF (5.4%) and pure TiO2 (56%). In addition, the photostability test of CF-TiO2 demonstrates that it is reusable and stable due to strong covalent bonds between CF and TiO2.

Promoting dynamic adsorption of Pb2+ in a single pass flow using fibrous nano-TiO2/cellulose membranes

A variety of nano-TiO2/cellulose composite fibers (TiO2/CF) were synthesized via both in situ growing rutile TiO2 nanocrystals and electrostatic self-assembly of commercial nano rutile TiO2 particles onto cellulose fibers. These fibers were then processed into fibrous membrane beds by wet-laid technique. Dynamic adsorption of lead (Pb2+) was subsequently carried out by pumping the feed solution through the bed in a single-pass flow mode. The influence of various parameters including flow rate, bed height and bed stacking pattern on bed breakthrough behavior was investigated. It was found that the in situ-TiO2/CF bed outperformed others; its loading capacity of Pb2+ was 13 times that of pure CF bed, and 9 times that of the self-assembled TiO2/cellulose bed prior to 10% breakthrough. The dynamic adsorption behavior of the in situ-TiO2/CF bed was better predicted by Dose–Response model among other models tested. The bed was also selective for Pb2+ over Ca2+, and was readily regenerable when eluted with 0.1M HCl solution for repeated use. The outstanding performance of the in situ-TiO2/CF bed was a result of larger fiber adsorption capacity and faster adsorption kinetics compared with the other beds having similar geometric bed structure.

Near-infrared photocatalysts of BiVO4/CaF2:Er3+, Tm3+, Yb3+with enhanced upconversion properties

Upconversion photocatalysts have the potential to absorb the near-infrared (NIR) light in solar energy and improve the photocatalytic performance. A hierarchical upconversion photocatalyst of BiVO₄ (BVO)/CaF₂:Er(3+), Tm(3+), Yb(3+) (CF) combined with the narrow-band semiconductor of BVO and the luminescence agent of CF to enhance upconversion properties was synthesized via the hydrothermal method. The CF particles were deposited homogeneously on the surface of the BVO/CF composite with regular dendritic structure, which led to efficient upconversion emissions. The upconversion emission intensity of the BVO/CF composite was 8 times higher than that of pure CF, through tailoring the crystal symmetry of lanthanide ions by Bi(3+) ions. The upconverted ultraviolet (361 and 379 nm), violet (408 nm), and blue (485 nm) light was able to excite BVO for photocatalysis in BVO/CF under NIR irradiation, which improved the degradation rate of methyl orange (MO).

Design, construction, operation and performance of a Hadron Blind Detector for the PHENIX experiment

A Hadron Blind Detector (HBD) has been developed, constructed and successfully operated within the PHENIX detector at RHIC. The HBD is a Cherenkov detector operated with pure CF 4 . It has a 50 cm long radiator directly coupled in a windowless configuration to a readout element consisting of a triple GEM stack, with a CsI photocathode evaporated on the top surface of the top GEM and pad readout at the bottom of the stack. This paper gives a comprehensive account of the construction, operation and in-beam performance of the detector.

A Measurement of the Scintillation Light Yield in ${\rm CF}_{4}$ Using a Photosensitive GEM Detector

The absolute photon yield of scintillation light produced by highly ionizing particles in pure CF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> has been measured using a photosensitive Gas Electron Multiplier (GEM) detector. The detector consists of two standard GEMs and a CsI coated GEM which acts as a photocathode that is sensitive to the 160 nm scintillation light produced in CF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> . The light yield was determined in terms of the number of scintillation photons emitted into a 4π solid angle produced per MeV of energy deposited in the gas by a 5.5 MeV alpha particle and found to be 314 ±15 photons per MeV. The quantum yield was determined using a fitting method to determine the number of photoelectrons from the measured pulse height distribution, and by an independent method using the measured gain of the GEM detector. The effect of scintillation light in CF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> on the performance of Cherenkov detectors, such as the PHENIX Hadron Blind Detector (HBD) at RHIC, is also discussed.

Formation of PTFE-like films in CF 4 microwave plasmas

The study focuses on the deposition of films from pure CF 4 using low pressure microwave plasmas (MW) on polystyrene substrate with a subsequent examination of the resulting surfaces. It is generally accepted, that the F/C-ratio of the precursor molecule plays an important role for the outcome of a low pressure plasma process, or the balance between fluorocarbon deposition and material etching. Surprisingly, thin film formation could be observed using MW gas discharges in CF 4, a typical etching gas. Coatings with a thickness of at least 10 nm are formed. The films are polytetrafluoroethylene (PTFE)-like, characterized by an F/C-ratio of 1.8, and a hydrophobic surface with a water contact angle of 110°.

An optimized protocol for the multigram synthesis of 3-(trifluoromethyl)bicyclo[1.1.1]pent-1-ylglycine (CF 3-Bpg)

An optimized procedure for the multigram synthesis of 3-(trifluoromethyl)bicyclo[1.1.1]pent-1-ylglycine (CF 3-Bpg) has been developed. The overall yield of the synthesis for the optimized up-scaling was increased from 35% to 53%. Moreover, conditions for separating the key isomeric aminonitriles 7 and 8 by crystallization were found, which greatly facilitated the isolation of 8 on a multigram scale. Following this optimized protocol, 100 g of optically pure CF 3-Bpg have been synthesized.

Catalytic Asymmetric Intramolecular Hydroamination of Alkynes in the Presence of a Catalyst System Consisting of Pd(0)-Methyl Norphos (or Tolyl Renorphos)-Benzoic Acid

Enantiomerically pure methyl Norphos (A), tolyl Norphos (B), CF(3) Norphos (C), methyl Renorphos (D), and tolyl Renorphos (E) were synthesized and used as chiral bisphosphine ligands for the catalyst system, Pd(2)(dba)(3) x CHCl(3)/PhCOOH, in an intramolecular hydroamination of aminoalkynes 15. Among the Norphos series, methyl Norphos (A) was the best ligand for the hydroamination, and the corresponding five- and six-membered nitrogen heterocycles 16 were obtained in high yields with high enantioselectivities. Among the Renorphos series, tolyl Renorphos (E) gave the best result; both methyl Norphos (A) and tolyl Renorphos (E) afforded high yields and high enantioselectivities. NMR investigation using Me-Norphos revealed that this ligand was oxidized gradually in the presence of Pd(2)(dba)(3).CHCl(3) in C(6)D(6) even under the conditions using Ar atmosphere to give Me-Norphos oxide, which prevented the intramolecular hydroamination. On the other hand, Me-Norphos was rather stable in C(6)D(6) in the absence of the palladium catalyst under Ar atmosphere and was not converted to its oxide even after 3 days. The gradual oxidation of ligands (A and E) in the presence of the Pd catalyst is perhaps a reason why 20 mol % of A or E was needed to obtain high yields and high ee's of 16.