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This work is concerned with design and analysis of a renewable power generation process featured with fast speed of biomass processing, low NOx and SOx emissions and ease of carbon capture. It is based on chemical looping with oxygen uncoupling (CLOU) of hydrochar derived from hydrothermal carbonization (HTC) of biomass. An air reactor and a fuel reactor employing CuO/Cu2O redox reactions are integrated with a combined Brayton and Rankine cycle to generate power. The design simulation is conducted using Aspen Plus V11. By implementing multiple-stage intercooled compression and multiple-stage reheat expansion in the Brayton cycle and multi-pressure steam generation in the Rankine cycle, an overall thermal efficiency of 35.3% on HHV basis without carbon capture (or 32.4% with carbon capture) is obtained.

Aerogel composites are multicomponent highly porous materials with air as the major dispersed phase. There are many kinds of aerogel composites including synthetic and natural aerogel composites. Aerogel composites have found wide applications in sorption, thermal insulation, vibration damping, and noise control. This mini review focuses on the aerogel composites with oil water separation function for spilled oil cleaning. The design and fabrication of various aerogel composites for oil cleaning are emphasized. The commonly used technologies including in-situ reaction, sol–gel spinning, templating, and self-assembling are introduced. The microstructure control through directional freeze casting, bio-inspired approach, coating, etc., are discussed.

In this work, a manganese oxide electrode, containing carbon nanofiber composites (MnO2/CNF), has been made through electrospinning, oxidization, and partial carbonization high-temperature treatment. Scanning electron microscopy (SEM) was used to observe the morphology of the nanofiber and analyze the composition of the fiber. The fiber size range and element distribution were determined. The oxide nanoparticles were modeled as electrorheological suspensions in the polyacrylonitrile polymer solution during electrospinning. The dielectrophoretic behavior of the particles subjected to non-uniform electric fields were analyzed and the motion of the oxide particles under the actions from fluctuating electric fields was investigated to explain the sporadic distribution of nanoparticles within the composite nanofibers. A photoactive anode was made from the composite nanofiber and the decomposition of spilled oil was performed under sunlight illumination. It was observed that the manganese oxide containing carbon nanofiber composite electrode can generate electricity and clean the spilled oil under sunlight. Both energy conversion and environment cleaning concepts were demonstrated.

To mitigate the damage of oil spills, a filter modified with a hydrophilic and oleophobic coating is proposed for affordable and efficient oil separation and recovery from water. The sol–gel method was chosen to produce a colloidal suspension of titanium dioxide particles for its ease of production and its versatility in application for many different substrates, including paper and cloth fabric. After immersing the substrates into a titanium-containing solution, three techniques were applied to increase the production of titanium dioxide—microwave-assisted, refrigeration, and ultra-sonication. Contact angle tests were done to investigate the change in the filter’s oleophobicity. The titanium dioxide present on the surface of the filter was amorphous, but all treatment methods showed an improvement in oleophobicity. All treated filters improved oil filtration performance by up to eighty percent. The filters isolated motor oil from a mixture while allowing water to pass through. The coated filters also displayed photocatalytic activity by degrading methylene blue on its surface when exposed to sunlight, demonstrating the filter’s self-cleaning ability. For real-world applications, the filter can be supported by a stainless mesh for enhanced strength and durability. While being dragged through the water, the filter collects the surface oil, allowing water to pass through via gravity.

The first Special Issue on “Composite Carbon Fibers” is situated in the section “Fiber Composites” in the open access Journal of Composites Science (ISSN 2504-477X) [...]

This paper deals with preparing a functional composite carbon fiber with a large surface area for spilled oil cleaning. The composite fiber consisted of photosensitive oxide particles and polymer-derived carbon. It was made by co-spinning the polymer and metallic compounds. After heat treatment at high temperatures, an activated carbon fiber containing oxide particles was obtained. The particles were found distributed in the fiber and at the surface of the fiber. The composite fiber was found sensitive to sunlight. Fiber mats made of the composite fiber possessed a high surface area for oil absorption and removal. Cobalt(II) titanate particles were obtained from the reaction of titanium dioxide and cobalt oxide. The reaction happened in situ through the hydrolysis of metallic compounds in the spun fiber. The titanium dioxide and cobalt(II) titanate particle-containing fibers demonstrated the photoactivity in the visible light spectrum. It was concluded that particle-containing composite carbon fiber mats can be prepared successfully by co-electrospinning. Due to the oleophilic property and the high active surface area, the composites are suitable for spilled oil cleaning through fast absorption.

Porous metals and alloys have many important characteristics such as light weight, high surface area, good electrical conductivity, and enhanced surface plasmonics. They have found many applications in chemical and biomedical engineering fields. This review deals with various dealloying techniques for making nanoporous metals, alloys, and composite materials. Typical dealloying processes and their recent development are introduced. The dealloying techniques include chemical etching, electrochemical leaching, high temperature element removal, thermic reduction, Galvanic replacement, template approach, physical vacuum processing, magnetic field induced processing, plasma reaction etc. Although various noble porous metals such as Pt, Pd, Au, and Ru were extensively studied earlier for applications in catalysis and energy storage/conversions, other porous metallic alloys are under investigations for the removal of pollutants, energy absorbing, filtration of metal ions, organic dyes, and microbial organisms. Advances in processing nanoporous particles, nanosheets, and porous fibers will be discussed. The applications of recently developed nanoporous metals are presented as well.

This paper provides a brief review on manufacturing polymer composite materials through the nontraditional electrohydrodynamic (EHD) casting approach. First, the EHD technology will be introduced. Then, typical functional polymer composite materials including thermoelectric and photoelectric energy conversion polymers and their composites will be presented. Specifically, how to make composite materials containing functional nanoparticles will be discussed. Converting polymeric fibers into partially carbonized fiber composites will also be shown. The latest research results of polymeric composite materials with energy conversion and sensing functions will be given.

Biomass wastes are abundant around us. They are renewable and inexpensive. Product manufacturing from renewable resources has caught increasing interest recently. Activated carbon preparation from biomass resources, including various trees, leaves, plant roots, fruit peels, and grasses, is a good example. In this paper, an overview of activated carbon production from biomass resources will be given. The first part will be on the processing technologies. The second part will focus on the carbon activation methods. The third part will introduce the biomass resources. The fourth part will be on surface modification of activated carbon through the addition of various components. Finally, the development of product applications will be discussed with an emphasis on adsorption, filtration, water purification, energy conversions, and energy storage.

The objective of this article is to provide an overview on the current development of micro- and nanoporous fiber processing and manufacturing technologies. Various methods for making micro- and nanoporous fibers including co-electrospinning, melt spinning, dry jet-wet quenching spinning, vapor deposition, template assisted deposition, electrochemical oxidization, and hydrothermal oxidization are presented. Comparison is made in terms of advantages and disadvantages of different routes for porous fiber processing. Characterization of the pore size, porosity, and specific area is introduced as well. Applications of porous fibers in various fields are discussed. The emphasis is put on their uses for energy storage components and devices including rechargeable batteries and supercapacitors.

In this work, cobalt acetate was incorporated into polyacrylonitrile (PAN) polymer through electrospinning as the cobalt oxide source. After oxidization and pyrolysis, a PAN-derived composite carbon fiber containing cobalt oxide was obtained. Measuring the electrical and photonic properties of the composite fiber under visible light irradiation was performed to evaluate the photoelectric behavior of the composite fiber. The p-type semiconducting behavior of the composite fiber was confirmed by measuring the open circuit voltage of a photochemical fuel cell consisting of the photosensitive electrode made from the composite fiber. The application of the composite fiber for glucose sensing was demonstrated.

This article provides an overview on manufacturing composite carbon nanofiber-based aerogels through freeze casting technology. As known, freeze casting is a relatively new manufacturing technique for generating highly porous structures. During the process, deep cooling is used first to rapidly solidify a well-dispersed slurry. Then, vacuum drying is conducted to sublimate the solvent. This allows the creation of highly porous materials. Although the freeze casting technique was initially developed for porous ceramics processing, it has found various applications, especially for making aerogels. Aerogels are highly porous materials with extremely high volume of free spaces, which contributes to the characteristics of high porosity, ultralight, large specific surface area, huge interface area, and in addition, super low thermal conductivity. Recently, carbon nanofiber aerogels have been studied to achieve exceptional properties of high stiffness, flame-retardant and thermal-insulating. The freeze casting technology has been reported for preparing carbon nanofiber composite aerogels for energy storage, energy conversion, water purification, catalysis, fire prevention etc. This review deals with freeze casting carbon nanofiber composite materials consisting of functional nanoparticles with exceptional properties. The content of this review article is organized as follows. The first part will introduce the general freeze casting manufacturing technology of aerogels with the emphasis on how to use the technology to make nanoparticle-containing composite carbon nanofiber aerogels. Then, modeling and characterization of the freeze cast particle-containing carbon nanofibers will be presented with an emphasis on modeling the thermal conductivity and electrical conductivity of the carbon nanofiber network aerogels. After that, the applications of the carbon nanofiber aerogels will be described. Examples of energy converters, supercapacitors, secondary battery electrodes, dye absorbents, sensors, and catalysts made from composite carbon nanofiber aerogels will be shown. Finally, the perspectives to future work will be presented.

Fibers are promising materials being utilized in electronics, principally in the areas of capacitors and sensors. In this study, we examine the effect of pyrolysis temperature on the electrical conductive behavior and photosensitivity of a carbon-based fiber, which was made by electrospinning a polymer solution containing polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), and dimethylformamide (DMF). Converting the polymeric fiber into a carbon fiber was performed through the controlled pyrolysis during which oxidation, stabilization, and carbonization happened. After oxidation at an elevated temperature, the linear polymer fiber was stabilized to have a backbone structure. Then the oxidized fiber was treated in an even higher temperature range to be partially carbonized under the protection of argon gas. We utilized multiple samples of the fibers treated at various pyrolysis temperatures inside a heat furnace and examined the effects of the temperatures on the properties. The partially carbonized fiber is highly active in view of electron generation under photon energy excitation. The unique electrical and photovoltaic property are due to their semiconducting behavior. The morphology of the specimen before and after the pyrolysis was examined using scanning electron microscopy (SEM). The SEM images displayed the shrinkage of the fiber due to the pyrolysis. There are two stages of pyrolysis kinetics. Stage I is related to the oxidation of the PAN polymer. Stage II is associated with the carbonization and the activation energy of carbonization is calculated as 118 kJ/mol.

Our current study deals with the dye adsorption and electrical property of a partially carbonized composite fiber containing transition metal oxides including, iron oxide, nickel oxide, and titanium oxide. The fiber was made by electrospinning, carbonization, and hydrothermal treatment. During the electrospinning, titanium oxide particles were dispersed in polyacrylonitrile (PAN) polymer-dimethylformamide (DMF) solution. Nickel chloride and iron nitrate were added into the solution to generate nickel oxide and iron oxide in the subsequent heat treatment processes. The polymer fiber was oxidized first at an elevated temperature of 250 °C to stabilize the structure of PAN. Then, we performed higher temperature heat treatment at 500 °C in a furnace with hydrogen gas protection to partially carbonize the polymer fiber. After that, the oxide-containing fiber was coated with activated carbon in a diluted sugar solution via hydrothermal carbonization at 200 °C for 8 h. The pressure reached 1.45 MPa in the reaction chamber. The obtained product was tested in view of the dye, Rhodamine B, adsorption using a Vis-UV spectrometer. Electrical property characterization was performed using an electrochemical work station. It was found that the hydrothermally treated oxide-containing fiber demonstrated obvious dye adsorption behavior. The visible light absorption intensity of the Rhodamine B dye decreased with the increase in the soaking time of the fiber in the dye solution. The impedance of the fiber was increased due to the hydrothermal carbonization treatment. We also found that charge build-up was faster at the surface of the specimen without the hydrothermally treated carbon layer. Electricity generation under visible light excitation is more intensive at the hydrothermally treated fiber than at the one without the hydrothermal treatment. This result is consistent with that obtained from the dye adsorption/decomposition test because the charge generation is more efficient at the surface of the hydrothermally treated fiber, which allows the dye to be decomposed faster by the treated fibers with activated carbon.

Through this work, a carbon network/aluminum matrix porous composite material was analyzed for its susceptibility to material degradation in sulfuric acid and seawater corrosive media. Simple potentiodynamic electrochemical testing was implemented, and from polarization curves, the Tafel coefficients and exchange current densities were obtained for a comparative analysis. The pseudo exchange current densities for corrosion of the composite material were compared to those found for Al 1235 and 6061-T6. By relating the pseudo icorr of these materials in each environment, an understanding regarding the relative propensity to corrosion was determined. According to the recovered data, the composite had the lowest pseudo icorr in all corrosion systems and was consequently inferred the least likely to corrode. The factor that primarily contests this conclusion is the material’s relatively large exposed surface area. The existence of carbon along the grain boundaries in the C/Al composite improved its corrosion behavior. Further discussion concerning the implication of βc is offered. Electrochemical impedance spectroscopic (EIS) tests were performed in the frequency range from 0.001 Hz to 100 kHz. An immersion corrosion test was conducted to calculate the corrosion rate in different environments. Morphological observation on the corrosion surface was also carried out to evaluate the corrosion product deposition on each material.

In this paper, a titanium dioxide particle coated carbon fiber was prepared by reaction spinning. Polyacrylonitrile (PAN) was used as the precursor to generate a continuous carbon nanofiber. A solution containing 10% wt PAN polymer dissolved in dimethylformamide (DMF) was made as the core fluid. The sheath fluid contains 10% titanium (IV) isopropoxide, 85% ethanol, and 5% acetic acid. The two solutions were co-spun onto an aluminium plate covered with a layer of soft tissue paper. A titanium hydroxide layer formed at the surface of the PAN fiber through the hydrolysis of titanium isopropoxide due to the moisture absorption in the co-spinning process. The reaction spun fiber was converted to a partially carbonized nanofiber by the heat treatment in air at 250 °C for two hours, then in hydrogen at 500 °C for two hours. During the early stage of the heat treatment, the titanium hydroxide decomposed and produced titanium dioxide nanoparticles at the surface of the carbon fiber. The structure and composition of the carbonized fiber were studied by scanning electron microscopy (SEM). The photosensitivity of the particle-containing fiber was characterized by measuring the open circuit voltage under visible light excitation. The photoelectric energy conversion behavior of the fiber was confirmed by open circuit potential measurement. The potential applications of the composite fiber for photovoltaics and photonic sensing were discussed.

In this work, iron oxide nanoparticle loaded carbon fibers were prepared by electrohydrodynamic co-casting a polymer and particle mixture followed by carbonization. The precursor used to generate carbon fibers was a linear molecular chain polymer: polyacrylonitrile (PAN). A solution containing iron (II, III) oxide (Fe3O4) particles and the PAN polymer dissolved in dimethylformamide (DMF) was electrohydrodynamically co-cast into fibers. The fibers were stabilized in air and carbonized in hydrogen at elevated temperatures. The microstructure and composition of the fibers were analyzed using scanning electron microscopy (SEM). A quantitative metallographic analysis method was used to determine the fiber size. It was found that the iron (II, III) oxide particles distributed uniformly within the carbonized fibers. Photosensitivity of the particle containing fibers was characterized through measuring the open circuit potential of the fiber samples under the visible light illumination. Potential applications of the fibers for photovoltaics and photonic sensing were discussed.

The objective of this article is to provide a review of friction stir processing (FSP) technology and its application for microstructure modification of particle reinforced composite materials. The main focus of FSP was on aluminum based alloys and composites. Recently, many researchers have investigated this technology for treating other alloys and materials including stainless steels, magnesium, titanium, and copper. It is shown that FSP technology is very effective in microstructure modification of reinforced metal matrix composite materials. FSP has also been used in the processing and structure modification of polymeric composite materials. Compared with other manufacturing processes, friction stir processing has the advantage of reducing distortion and defects in materials. The layout of this paper is as follows. The friction stir processing technology will be presented first. Then, the application of this technology in manufacturing and structure modification of particle reinforced composite materials will be introduced. Future application of friction stir processing in energy field, for example, for vanadium alloy and composites will be discussed. Finally, the challenges for improving friction stir processing technology will be mentioned.

This paper deals with the effect of interface structures on the mechanical properties of fiber reinforced composite materials. First, the background of research, development and applications on hybrid composite materials is introduced. Second, metal/polymer composite bonded structures are discussed. Then, the rationale is given for nanostructuring the interface in composite materials and structures by introducing nanoscale features such as nanopores and nanofibers. The effects of modifying matrices and nano-architecturing interfaces on the mechanical properties of nanocomposite materials are examined. A nonlinear damage model for characterizing the deformation behavior of polymeric nanocomposites is presented and the application of this model to carbon nanotube-reinforced and reactive graphite nanotube-reinforced epoxy composite materials is shown.

To increase the performance of photochemical fuel cells, nonequilibrium electrodeposition has been performed on Cu and Ni to make photosensitive anodes. Processing parameters including electrolyte concentration, and electrode potential were studied using cyclic voltammetry. Scanning electron microscopy (SEM) and X-ray Spectroscopy (EDS) were performed to understand the formation of the nanostructures during the nonequilibrium deposition of copper fractals. An increase in the deposition rate was observed with the increase in electrolyte concentration (from 0.05 M to 1.0 M). Similar trend was found when the cathode potential was decreased from −0.5 V to −4.5 V. The effect of substrate material was also examined. Porous fractal structures on copper were achieved, while the deposited material showed high density of surface cracks on nickel. The fractal structures deposited on copper electrode with the increased surface area were converted into copper oxide by oxidation in air. Such oxide samples were made into anodes for photochemical fuel cell application. We demonstrated that an increase in the magnitude of open circuit output voltage is associated with the increase in the fractal surface area under the ultraviolet irradiation test conditions. However, the electrodeposited fractals on nickel showed very limited increase in the magnitude of open circuit voltage.