Nano-sized Carbon Research Articles

Hydrothermal synthesis of bentonite carbon composites for ultra-high temperature filtration control in water-based drilling fluid

In this study, bentonite hydrothermal carbon composites (BHCCs) were fabricated by green and facile hydrothermal carbonization, employing glucose as the carbon source and bentonite as the template. BHCCs were characterized by Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The effects of the BHCCs on the rheological and filtration properties of bentonite dispersions were investigated before and after thermal aging at 220 °C and 240 °C, respectively. The results demonstrated that, unlike conventional synthetic polymers, the BHCCs exhibited a minor influence on the rheology of bentonite dispersion and had extraordinary filtration control both before and after ultra-high-temperature aging. The incorporation of BHCCs helped introduce the oxygenated groups with carbon species, thereby enhancing the dispersion stability of bentonite particles. The spherical nano-sized carbon particles in BHCCs filled the gaps between large particles in the filter cake. The above factors contributed to excellent filtration control under hostile, high-temperature conditions.

Integrated Thermo-Electric Measurement of Electrospun Nanofiber for Polymer Electrolyte Fuel Cell

Polymer electrolyte fuel cell (PEFC), as an efficient hydrogen energy conversion device, has been developed for decades. Catalyst layer (CL), where the oxygen reduction reaction occurs, predominantly determines the performance of PEFC. Since 1889, the mass activity of catalyst layer has been improved for more than three orders of magnitudes, thanks to the invention of PFSA ionomer and highly dispersed catalyst on nano-sized carbon support. In recent years, introducing order into CL is bringing the CL performance to a higher level. The CLs with state-of-the-art performance feature nanofiber structures. One type of is ionomer nanofibers deposited with Pt/C catalyst on the surface, and another type is composite nanofiber containing ionomer, Pt/C catalyst, and binding polymer. Their superior performance may come from the ordered mass transport network and the size effect of nanofiber conductivity. To further improve the CL performance, the structure-property-performance relationship of ionomer nanofibers or composite nanofibers needs to be clarified.In this work, we designed a setup to measure the proton, electron and thermal conductivity as well as the performance of a single ionomer or composite nanofiber. We developed a self-bonding method to fix the nanofiber on the micro-electrode. For proton and electron conductivity measurement, four-probe method was adopted to eliminate the electrical contact resistance and interfacial effect. For thermal conductivity measurement, Raman assisted steady state method was used to directly measure the temperature profile along the nanofiber. So, the measurement error resulting from the thermal contact resistance between the sample and the temperature sensor/heat sink can be eliminated. For performance measurement, three-electrode system was adopted using the Ag/AgCl electrode as the reference electrode and the Zn/ZnCl2 electrode as the counter electrode. We prepared nanofibers with different size, polymer content, and cross-sectional component distribution by controlling the ink recipe and electrospinning parameters. The integrated thermo-electric measurement found that the proton and thermal conductivity of nanofiber are one order of magnitude higher than bulk properties and increases with decreasing fiber radius. This is attributed to the oriented ionic morphology along the nanofiber. Furthermore, a nanofiber model was developed to extract the catalytic activity and gas diffusion coefficient of nanofiber. These characterization and modelling work can provide guidance to the design and optimization of catalyst layer with electrospun ionomer or composite nanofibers.

Carbide-directed enhancement of electrochemical hydrogen evolution reaction on tungsten carbide–oxide heterostructure

Carbide–oxide heterointerfaces have been known to be responsible for electrochemical activity, however, it is rarely investigated in tungsten carbide-oxide heterostructure for the hydrogen evolution reaction (HER). Furthermore, typical carbide preparation includes carbonization of oxide under gaseous carbon sources at a high temperature, resulting in sintering and collapse of the heterostructures. In this work, nano-sized carbon dots (CDs, ∼2 nm in diameter) were adopted as carbon sources and dispersed on tungsten oxide nanorods allowing abundant nucleation sites for oxide-to-carbide conversion, resulting in high density of carbide-oxide heterointerfaces. The resulting tungsten carbide-oxide heterostructure decorated with carbon dots (WO(3−x) − WCy/CDs) exhibited superior electrocatalytic activity toward the HER with a low overpotential of 65 mV at a current density of − 10 mA cm−2 in acidic media. This performance is among the best electrocatalytic activities compared to the state-of-the-art tungsten carbide-based electrocatalysts. Importantly, the single-cell test using WO(3−x) − WCy/CDs as the cathode showed a current density of 10 mA cm−2 with a cell voltage of only 1.47 V, which is very close to that for Pt/C (1.41 V). In addition, a combined analysis of the X-ray spectroscopic and electrochemical results suggested an optimal W–C ratio in the tungsten carbide-oxide composite to guarantee the high HER activity. Theoretical calculations provided more insight into the carbide-directed enhancement of the electrocatalytic activity of WO(3−x) − WCy/CDs.

Study on the kinetics of methane hydrate formation in the carbon microtube system

The current studies focused mostly on the promotion effects of nano-sized carbon nanotubes on hydrates, while the effect of carbon microtubes on the kinetics of methane hydrate formation is rarely mentioned. Therefore, this paper added 3–15 μm multi-walled carbon microtubes (MWCMTS) to a 4L autoclave (under the conditions of 3–6 MPa, and 0–5 ℃) to investigate the influence of the micron-medium concentration on the kinetics of hydrate formation. The results demonstrated that the addition of micro-carbon nanotubes could reduce the nucleation time of methane hydrate; a higher degree of subcooling could shorten the reaction time. Furthermore, the increase in carbon nanotube concentration could lead to higher gas storage capacity. Gas storage capacity was the highest at 32.4 V/V under the condition of 13:3 gas–liquid ratio; this rate was over 3 times larger than that of the pure water system. Micro-carbon nanotube-pure water system methane hydrate formation process was prone to the “platform period” phenomenon. However, this phenomenon would have on impact the final water conversion rate under the conditions of a sufficient driving force. Therefore, this study proved that carbon microtubes had an obvious effect on the promotion of methane hydrate formation and could be used as a cost-effective promoter.

CO2-free hydrogen production by liquid-phase plasma cracking from benzene over perovskite catalysts

A method for producing hydrogen from liquid benzene without CO2 generation using plasma is proposed. A liquid plasma was emitted from the liquid reactant to crack liquid benzene to produce hydrogen. The only gaseous product was H2 and no CO2 was formed. Carbon crystals were produced as a solid product. To increase the decomposition efficiency of liquid benzene and the efficiency of hydrogen production, perovskite was applied as a catalyst. The reaction produced nano-sized carbon particles with hydrogen as the main product without impurities. The crystal size of carbon black was very small (<10 nm) and uniform. The carbon products were similar in crystal shape and size regardless of the reaction time. Liquid benzene is decomposed by active species in the liquid plasma to produce hydrogen and carbon without catalyst injection. When the perovskite catalyst was applied to the reaction using liquid plasma, the hydrogen production rate and carbon yield were significantly increased. Liquid benzene simultaneously produces hydrogen and carbon black through a decomposition reaction by liquid plasma. The LPP cracking process of liquid benzene can be evaluated as a ‘green hydrogen’ production technology that does not generate CO2.

Reactive spark plasma sintering of ZrB2-TiC composites: Role of nano-sized carbon black additive

ZrB2-TiC composites with and without nano-sized carbon black as the sintering additive were densified through spark plasma sintering at 1900 °C for 7 minutes under the applied pressure of 40 MPa. The role of carbon black in densification behavior, phase arrangement, microstructural characteristics and mechanical properties of the sintered composites were then investigated. While both of the composite samples were found to be fully sintered, the thermodynamic of the reactive sintering was also studied. Results indicated that whereas the reactive sintering process leads to complete consumption of TiC through the formation of the solid solution as the matrix in both of the composite samples, the presence of carbon black at the initial composition of the samples can result in remained carbon at the final microstructure. Besides the in-situ synthesized zirconium carbide as the major reinforcement phase, such a remained carbon can lead to significantly different mechanical behavior of the composites. Accordingly, the hardness of 21.8 and 24.3 GPa and the indentation fracture toughness of 3.3 and 4.5 MPa.m0.5 were obtained for carbon-black free and doped samples, respectively. The densification, hardening, and toughening mechanisms in both of the composite samples were finally discussed.

Polyhydroxylated Nanosized Graphite as Multifunctional Building Block for Polyurethanes.

Polyurethane nanocomposites were prepared with a nanosized high surface area graphite (HSAG) functionalized on its edges with hydroxyl groups as a building block. Edge functionalization of HSAG was obtained through reaction with KOH. The addition of OH groups was demonstrated by means of infrared (FTIR) and thermogravimetric analysis (TGA), and the Boehm titration allowed estimation of a level of about 5.0 mmolOH/gHSAG. Results from wide-angle X-ray diffraction (WAXD) and Raman spectroscopy suggested that functionalization of the graphene layers occurred on the edges. The evaluation of the Hansen solubility parameters of G-OH revealed a substantial increase of δP and δH parameters with respect to HSAG. In line with these findings, homogeneous and stable dispersions of G-OH in a polyol were obtained. PU were prepared by mixing a dispersion of G-OH in cis-1,4-butenediol with hexamethylene diisocyanate. A model reaction between catechol, 1,4-butanediol, and hexamethylene diisocyanate demonstrated the reactivity of hydroxylated aromatic rings with isocyanate groups. PU-based G-OH, characterized with WAXD and differential scanning calorimetry (DSC), revealed lower Tg, higher Tc, Tm, and crystallinity than PU without G-OH. These results could be due to the higher flexibility of the polymer chains, likely a consequence of the dilution of the urethane bonds by the carbon substrate. Hence, G-OH allowed the preparation of PU with a larger temperature range between Tg and Tm, with potential positive impact on material applications. The model reaction between butylisocyanate and 1-butanol revealed that HSAG and G-OH promote efficient formation of the urethane bond, even in the absence of a catalyst. The effect of high surface area carbon on the nucleophilic oxygen attack to the isocyanate group can be hypothesized. The results here reported lead us to comment that a reactive nanosized sp2 carbon allotrope, such as G-OH, can be used as a multifunctional building block of PU. Indeed, G-OH is a comonomer of PU, a promoter of the polymerization reaction, and can definitely act as reinforcing filler by tuning its amount in the final nanocomposite leading to highly versatile materials. The larger temperature range between Tg and Tm, together with the presence of G-OH acting as a reinforcing agent, could allow the production of piezoresistive sensing, shape-memory PU with good mechanical features.

Synergistic enhancement in electrical conductivity of polymer composites simultaneously filled with multi-walled carbon nanotube and pitch-based carbon fiber via one-step solvent-free fabrication

Recently, studies have been reported to synergistically improve the electrical conductivity of polymer composites by simultaneously incorporating hybrid fillers, but systematic studies on filler loading and ratio are still scarce. In this study, a one-step process was proposed to induce the incorporation of uniformly dispersed fillers with a high content, and synergistic improvement in the electrical conductivity of polymer composites was studied by applying two types of carbon fillers: nano-sized multi-walled carbon nanotube (MWCNT) and micro-sized pitch-based carbon fiber (PCF). Based on the proposed process, it was possible to fabricate a polymer composite in which the filler was uniformly dispersed within 40 wt%. The electrical conductivity of the composite containing up to 10 wt% MWCNT which was the percolation plateau content and 30 wt% PCF was 3940 S m−1, showing the maximum performance. This result was improved by 595% and 586%, respectively, compared to the electrical conductivity of the composite containing only 40 wt% MWCNT or PCF. These findings can contribute to expanding the application of conductive composites in the fields of antistatic or electromagnetic interference shielding by providing insight into the optimal design of hybrid filler systems to improve the electrical conductivity of composites.

Carbon-dot hydrogels as superior carbonaceous adsorbents for removing perfluorooctane sulfonate from water

Efficiently removing perfluorooctane sulfonate (PFOS) from wastewaters is a hot topic in environmental field. Herein, crosslinking the nano-sized and zero-dimensional carbon dots (CDs) with polyethylene glycol diglycidyl ether (PEG) and polypropylene glycol diglycidyl ether (PPG) resulted in CD hydrogels that were verified by TEM, SEM, FTIR and XPS. The obtained CD hydrogels could efficiently adsorb PFOS from water through their CD moieties. The kinetic curves were fitted well by the pseudo-second order model, indicating the involvement of chemisorption in the rate-limiting step. The adsorption isotherm measurements showed that the hydrogel with the highest CD content had a PFOS maximum uptake capacity of ca. 2.82 g/g (5.64 mmol/g) in the neutral water, which was much higher than the ever-reported carbonaceous materials, and also ranked the top three among the superior positively-charged adsorbents. The superior PFOS adsorption of CD hydrogels could be attributed to good dispersion of the nanoscale CDs in the PEG/PPG hydrogel matrix, leading to the substantial exposure of the binding sites of CDs towards PFOS molecules. Moreover, CD hydrogels did not show pronounced loss of adsorption capacity after experiencing five adsorption-desorption cycles. As for the real wastewaters, CD hydrogels could efficiently treat not only the high concentration of PFOS in the neutral firefighting wastewaters, but also the extremely low concentration of PFOS in the neutral environmental wastewater, where the residual PFOS concentration could be reduced less than 5 ng/L, satisfying the standard of the U.S. Environmental Protection Agency.

Nano-sized hematite-assembled carbon spheres for effectively adsorbing paracetamol in water: Important role of iron.

This study developed a new α-Fe2O3 (hematite) nanoparticles-loaded spherical biochar (H-SB) through the direct pyrolysis of glucose-derived spherical hydrochar and FeCl3. The optimal impregnation ratio (hydrochar and FeCl3) was 1/1.25 (wt/wt). H-SB was applied to remove paracetamol (PRC) from water. Results indicated that H-SB exhibited a relatively low surface area (127 m2/g) and total pore volume (0.089 cm3/g). The presence of iron particles in its surface was confirmed by scanning electron microscopy with energy dispersive spectroscopy. The dominant form of iron nanoparticles (α-Fe2O3) in its surface was confirmed by X-ray powder diffraction and Raman spectrum. The crystallite size of α-Fe2O3 in H-SB was 27.4 nm. The saturation magnetization of H-SB was 6.729 cmu/g. The analysis of Fourier-transform infrared spectroscopy demonstrated that the C-O and O-H groups were mainly responsible for loading α-Fe2O3 nanoparticles in its surface. The adsorption study indicated the amount of PRC adsorbed by H-SB slightly decreased within solution pH from 2 to 11. The adsorption reached a fast saturation after 120 min. The Langmuir maximum adsorption capacity of H-SB was 49.9 mg/g at 25 °C and pH 7.0. Ion-dipole interaction and π-π interaction played an important role in adsorption mechanisms, while hydrogen bonding and pore filling were minor. Therefore, H-SB can serve as a promising material for treating PRC-contaminated water streams.Electronic Supplementary MaterialSupplementary material is available in the online version of this article at 10.1007/s11814-021-1013-z.

Impact of particle sizes on the microwave absorption properties of nano-sized Carbon black/epoxy composites

The nano-sized carbon black (NCB) with particle sizes of 15, 25, 55 and 65 nm are added in epoxy matrix in order to investigate the impact of particle sizes on the microwave absorption properties of the nano composites. The NCB powders were characterized by X-ray diffraction and Scanning electron microscopy (SEM) for identification of impurity phases. The complex permittivity spectra were recorded for the composites in the frequency range of 8.2-12.4 GHz. The results revealed that the particle sizes had substantial impact on the electromagnetic properties. On decreasing the particle size, the complex permittivity increases first up to certain extent then decreases. Interestingly, the particle size dependent tangent loss of NCB/epoxy composites shows that 25 nm size is most suited for high loss characteristics, whereas, losses decreases with size < 25 nm, which is attributed to high surface area of the particles. In addition, NCB/epoxy composite with 25 nm particle size illustrated substantial EM absorption efficiency at a frequency of 9.5 GHz, with RL reaching −13.2 dB and reflection loss below −10 dB up to 2.5 GHz with thickness of 2.0 mm. The effect of particle sizes on the electromagnetic properties was also discussed. Copyright © 2018 VBRI Press.

Development of Novel Carbon Electrode for Electrochemical Energy Storage. Nano-sized Carbon and Classic Carbon Electrodes for Capacitors

Development of Novel Carbon Electrode for Electrochemical Energy Storage. Nano-sized Carbon and Classic Carbon Electrodes for Capacitors

Preparation and characterization of carbon fibre powder (CFP)-polyvinyl alcohol (PVA) composite films showing percolation threshold behaviour

Carbon based polymer composites are important because of their probable electronic and biomedical applications. In the present work, we have prepared a composite of nano-size carbon fibre powder (CFP) with polyvinyl alcohol (PVA), hereafter referred to as CFP-PVA composite. Thin films of CFP-PVA composites have been prepared by solution casting method with different CFP concentrations (0.0–16 wt% or volume fraction f ∼ 0.0–9.15%). X-Ray diffraction (XRD) of the composites indicated enhanced crystallinity which influenced the electrical, dielectric, mechanical and thermal properties of the composite films. CFP filler concentration dependent conductivity and dielectric permittivity of the CFP-PVA composites showed interesting anomalous behaviour around a critical CFP concentration of 4 wt% (or fc ∼ 2.36% volume fraction). The observed anomalous behaviour indicated percolation threshold behaviour. Significantly high dielectric permittivity of the composite with low dissipation factor (tanδ varying from ∼ 0.1–0.5, for different concentrations, at a fixed frequency of 1 kHz) was considered to be due to the formation of micro capacitors in the composite and charge ordering within these micro-capacitors, near the percolation threshold. Improved electrical conductivity, dielectric permittivity, mechanical and other properties indicated multifunctional behaviour of the conducting CFP-PVA composites. The probable electronic and other applications of the composites have also been discussed.

Antibacterial fluorescent nano-sized lanthanum-doped carbon quantum dot embedded polyvinyl alcohol for accelerated wound healing

Bacteria is one of the main culprits that cause human diseases and pose long-term challenges to people’s health. Rare earth elements have unique antibacterial advantages, but little research is available. In this paper, we reported an antibacterial composite film based on lanthanum-doped carbon quantum dot nanoparticles (La@N-P-CQDs) and polyvinyl alcohol (PVA) film for fluorescence of antibiotics and accelerating wound healing. PVA/La@N-P-CQDs composite film presented excellent hydrophilicity, biocompatibility, fluorescence intensity, and antibacterial effects. The antibacterial activity of La@N-P-CQDs was evaluated by employing antibacterial assay using Escherichia coli (E.coli)and Staphylococcus aureus (S.aureus) in vitro. La@N-P-CQDs showed enhanced antibacterial activity compared with N-P-CQDs. Moreover, the PVA/La@N-P-CQDs composite film with 0.5 mg/mL La@N-P-CQDs showed better antibacterial capability and wound healing performance than PVA and PVA/N-P-CQDs films in bacterial adhesion experiment. PVA/La@N-P-CQDs composite film could be used for wound dressing in vivo experiment and had no side effects on major organs in mice. The antibacterial composite film significantly promoted in vivo wound healing process because of its multifunctional properties. Therefore, it was an excellent candidate for wound dressing.

Synthesis of highly fluorescent carbon dots from spices for determination of sunset yellow in beverages

Sunset yellow is synthetic azo dye used to color food products in food industry. Sunset yellow has no toxicity if taken in permissible amounts. The daily acceptable intake of dye is 2.5 mg/Kg as per WHO health guidelines. Above the permissible limit, sunset yellow dye is dangerous posing serious threat to human health worldwide leading to multiorgan (gastric, immunological, neurological) failure related symptoms especially in children can cause DNA damage. Other symptoms include ADHD like behavior in children. This has led to Food Safety Agencies to regulate permissible limit of sunset yellow in food products. Therefore, it is necessary to develop method for the removal of dye in different foodstuffs. Nano-sized fluorescent carbon dots (CDs) have been synthesized from spices (fenugreek, cloves and cumin) under hydrothermal conditions. Characterization has been done through UV–Vis, TEM, FT-IR and XRD spectroscopy. Results reveals that CDs possess high water solubility due to surface rich hydroxyl groups, excellent photo-stability and are non-toxic. There was strong quenching of fluorescence intensity (F0/F) of CDs in the presence of sunset yellow food dye. Further, there was no effect to fluorescence intensity with the presence of interferences. The linear concentration range obtained was 0.25 µM-60.0 µM with the detection limit of 0.20 µM. The calculated relative standard deviation (RSD) for determination of sunset yellow was found to be 0.21%. The present method was applied successfully for the determination of sunset yellow dye in various food samples with recovery values of 99.8 and 103.6%.

Characteristic of low-density polyethylene reinforcement with nano/micro particles of carbon black: a comparative study

Purpose: Low density polyethylene is commonly used polymer in the industry because of its unique structure and excellent overall performance. LDPE, is relatively low mechanical properties and thermal stability can sometimes limit its application in industry. Therefore, the development of particulate reinforced polymer composites is one of the highly promising methodologies in the area of next generation engineering products. Design/methodology/approach: Nano and Micro composite from low density polyethylene LDPE reinforced with different weight fraction of carbon black particles (CB) (2, 4 and 8)% prepared by first dispersion Nano and Micro carbon black particles CB in solvent and then mixing manually with low density polyethylene LDPE pellet and blended by twin-screw extruder, the current research study the mechanical properties (tensile strength, elastic modulus,and hardness), FTIR, DSC,and thermal conductivity of prepared nano and micro composites using two methodes and the morphological properties of nano-micro composites. Findings: The tensile strength of the LDPE/CB nano and micro composites improved at 2% and 4%, respectively, and decreasing at 8%, addition of carbon black nanoparticles led to increase the tensile strength of pure low-density polyethylene from 13.536 MPa to 19.71 MPa, and then dropping to 11.03 MPa at 8% percent,while the elastic modulus of LDPE/ CB nano and miro composites shows an improvement with all percentages of CB. The results show that the mechanical properties were improved by the addition carbon black nanoparticles more than addition micro- carbon black . FTIR show that physical interaction between LDPE and carbon black. The thermal conductivity improvement from 0.33 w/m.k for pur LDPE to 0.62234 w/m.k at 2% CB microparticle content and the reduced to 0.18645 w/m.k and 0.34063 w/m.k at (4 and 8)% micro-CB respectively , The thermal conductivity of LDPE-CB nano-composites is low in general than that the LDPE-CB microcomposite. DSC result show improvement in crystallization temperature Tc, melting temperature and degree of crystallization with addition nano and micro carbon black. Morever, SEM images revealed to uniform distribution and good bonding between LDPE and CB at low percentages and the precence of some agglomeration at high CB content.Research limitations/implications: This research studied the characteristics of both nano and micro composite materials prepared by two steps: mixing CB particles with solvent and then prepared by twin extruder which can be used packaging material, but the main limitation was the uniform distribution of nano and micro CB particles within the LDPE matrix. In a further study, prepare a blend from LDPE with other materials and improve the degradation of the blend that used in packaging application. Originality/value: LDPE with nanocomposites are of great interest because of their thermal stability, increased mechanical strength, stiffness, and low gas permeability, among other properties that have made them ideal for applications in the packaging and automotive industries. LDPE reinforcements nano-sized carbon black can have better mechanical and thermal properties than micron, resulting in less material being needed for a given application at a lower cost.

Carbonized cotton textile with hierarchical structure for superhydrophobicity and efficient electromagnetic interference shielding

Endowing electromagnetic interference (EMI) shielding materials with superhydrophobicity is regarded as an effective method to guarantee their service reliability under harsh environments. However, it is still a great challenge to integrate superhydrophobicity on EMI shielding materials due to the requirement for complex structural design. Herein, an superhydrophobic EMI shielding textile was facilely fabricated by carbonizing cotton textile and regulating the surface structure with nano-sized carbon black (CB) and low-surface energy polydimethylsiloxane (PDMS). The composite textile exhibited a superior EMI shielding effectiveness (42.9 dB), a large water contact angle (157.8°), and a low sliding angle (6.9°). It also showed strong resistance to physical deformations and chemical environments. These attractive features were attributed to the joint action of highly conductive carbonized textile, CB coating with nanoscale roughness, and PDMS protective layer. This work provides novel ideas for designing superhydrophobic EMI shielding materials for applications in electronic equipment under harsh environment.

Praperation of magnetic Fe,N co-doped nano-sized graphitized carbon aerogel with hierarchical porous structure and its electrochemical and adsorption performance

<p indent=0mm>Nano-sized carbon materials have received intensive preoccupation owing to their extraordinary properties such as high specific surface area, abundant porous structure, and excellent electronic properties. Doping non-metallic element N can effectively modulate the electronic properties of graphene, and doping metallic element Fe can further improve their catalytic activity. To date, applications of Fe-N/C materials are mostly concentrated in supercapacitors, electrochemical double layer electrode materials or adsorption. In this communication, we present a novel route for fabricating Fe,N co-doped nano-sized graphitized carbon materials (FeNC aerogels) by a chelate-carbonization-activation process using chitosan-Fe³⁺ chelate and KOH as precursor and activator respectively. Chitosan-Fe³⁺ chelate aerogel was first formed via sol-gel process, and Fe³⁺ was chelated by chitosan and evenly distributed in 3D networks of aerogel. Then in a nitrogen atmosphere, Chitosan-Fe³⁺ chelate aerogel was pyrolyzed at elevated temperature, and Fe³⁺ was reduced to Fe nanoparticles under the control of chitosan molecular in this carbonization process. At the last stage of KOH activation process, most of the amorphous carbon was etched, and abundant nanoscale pores appeared. Upon mild heating at 70°C in air, core@shell Fe@Fe₃O₄ nanoparticles were formed due to the reaction of Fe nanoparticles inside the Fe-N/C aerogels with oxygen in air. The morphology, structure, and properties of the obtained FeNC aerogels were characterized using field emission scanning electron microscope (FESEM), high-resolution transmission electron microscope (HRTEM), element mapping, Raman spectra, X-ray diffraction analysis (XRD), X-ray photoelectron spectroscopy (XPS), and vibrating-sample-magnetometer (VSM). FeNC aerogels were confirmed to be Fe,N-contained carbon aerogels with 3D hierarchical porous scaffold including macropores, micropores and mesopores, displayed low density and good magnetic response. The as-prepared FeNC(1-100)-K800 showed extremely large specific surface area <sc>(3103 m²/g),</sc> low density <sc>(27 mg/cm³),</sc> and high nitrogen content (4%). The magnetic response ability of FeNC aerogels increased with the increase of Fe content, and Fe was doped as Fe@Fe₃O₄ and Fe-N. FeNC aerogels exhibited good electrocatalytic oxidation-reduction activity, which increased with the increase of Fe doping amount, graphitization degree, and specific surface area. The obtained FeNC(1-20)-K800 with the highest Fe doping amount showed the highest initial potential of <sc>0.98 V,</sc> half-wave potential of <sc>0.82 V</sc> in<sc>0.1 mol/L</sc> KOH electrolyte saturated with O₂, and the highest initial potential of <sc>0.92 V,</sc> half-wave potential of <sc>0.62 V</sc> in<sc>0.05 mol/L</sc> H₂SO₄ electrolyte, respectively. Meanwhile, FeNC aerogels showed good performance of the electric double layer capacity and good cycling stability, and the specific capacitance enhanced with the increase of specific surface area. The specific capacitance, energy density, and power density of FeNC(1-40)-K800 was <sc>253 F/g,</sc> 35.1 W h/kg, and <sc>249.7 W/kg</sc> respectively. And its specific capacitance retention rates were 92.9% and 88.6% respectively after 6000 times and 10000 times continuous charge-discharge cycles at a current density of <sc>10 A/g.</sc> Furthermore, The saturated adsorption capacities of four kinds of dyes: Methyl orange (anionic dye), Rhodamine B (neutral dye), crystal violet and malachite green (cationic dyes), on FeNC(1-20)-K800 all exceeded <sc>400 mg/g,</sc> and the saturated adsorption capacity of malachite green reached up to <sc>816 mg/g.</sc> FeNC aerogel prepared here is a new type of carbon materials with application potential in the field of new energy and environmental remediation. The novel aerogel preparation process we preposed is suitable for large-scale industrial preparation without environmental risks because complex nitrogen and iron treatment steps and expensive equipments are not needed.

Fabrication and dielectric performance of RGO-PANI reinforced PVDF/BaTiO3 composite for energy harvesting

Today’s techno savvy world demands smart devices which are light-weight, flexible, and scalable. Functional polymers and their composites are suitable candidates that can fulfill the requirements in flexible device applications. Polyvinylidene fluoride (PVDF) is one kind of functional polymers possessing a large dielectric strength as well as permanent electrical dipole. To improve the dielectric and ferroelectric performance of the PVDF polymer, it can be hybridized with an inorganic/organic inclusion phase, usually ferroelectric ceramic particles or nano-sized low dimensional carbon. In this work, reduced- graphene oxide (RGO) and RGO-PANI were chosen as the inclusion phase (filler). The present work focuses towards enhancing the dielectric and ferroelectric properties of PVDF-BaTiO3 (P/BT) nanocomposites impregnated with RGO and RGO/PANI(Polyaniline) nanofillers. In-situ polymerization method was adapted to fabricate the RGO/PANI nanocomposite and spin coating method for P/BT composites. X-ray diffractograms and FTIR corroborate the presence of ferroelectric phases in P/BT matrix. Wayne Kerr precision impedance analyzer was used in the frequency frame of 1 Hz to 1 MHz and temperature window from 30 °C to 160 °C to study the dielectric properties. The P-E hysteresis loops were obtained using Radiant Ferroelectric Tester at different voltage cycles. The dielectric constant of P/BT matrix with 0.03% RGO loading exhibited the highest dielectric constant 2 × 105. Remarkable increase in the energy density of composites with filler loading was observed. P/BT with 1 wt% loading of RGO-PANI achieved the maximum value of polarization 3.6 µC/cm2 and discharge energy density 0.76 J/cm3 (under the electric field of 170 kV/cm) with 55% efficiency. This contribution provides a potential route to design and fabricate high energy density flexible capacitor for microelectronic devices.

Oxidation of Acetaldehyde Over Cobalt Supported on Nanosized Carbon Black Catalysts.

In this study, we investigated the oxidation of acetaldehyde over Co/carbon black catalysts. All experiments were conducted in the temperature range of 200-440 °C, at an acetaldehyde concentration of 0.94 mol% in air, and using Co loading amounts in the range of 2-60 wt%. The nanosized carbon black and Co/carbon black catalysts were characterized using thermogravimetric analysis (TGA) and X-ray diffraction (XRD) analysis. The TGA data revealed that the nanosized carbon black was stable at high temperatures (600 °C), and the XRD results indicated that Co/carbon black was deteriorated and Co oxides, such as Co₃O₄, were formed. The addition of Co₃O₄ crystallites on the catalyst surface provided the greatest increase in catalytic activity. The catalytic activity of the supports used in this study for the acetaldehyde oxidation reaction increased as follows: SiO₂ < TiO₂ < carbon black < SiO₂-Al₂O₃. The experimental results and economic considerations revealed that nanosized carbon black could be effectively used as catalyst support for the oxidation of acetaldehyde. The activity of the Co/carbon black catalysts varied with the Co loading amount, and the optimum Co loading amount was 10 wt%.