A polyurethane series (PHEI-PU) was prepared via a one-shot bulk polymerization method using hexamethylene diisocyanate (HDI), polycarbonate diol (PCD), and isosorbide derivatives (ISBD) as chain ...extenders. The mechanical properties were evaluated using a universal testing machine (UTM), and the thermal properties were evaluated using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The PHEI-PU series exhibited excellent mechanical properties with an average tensile strength of 44.71 MPa and an elongation at break of 190%. To verify the applicability of different proportions of PU as an electrode binder, PU and Ag flakes were mixed (30/70 wt%) and coated on PCT substrates, the electrodes were evaluated by four-point probe before and after 50% elongation, and the dispersion was evaluated by scanning electron microscopy (SEM). The electrical resistance change rate of PHEI-PU series was less than 20%, and a coating layer with well-dispersed silver flakes was confirmed even after stretching. Therefore, it exhibited excellent physical properties, heat resistance, and electrical resistance change rate, confirming its applicability as an electrode binder for in-mold coating.
Heteroatom‐doping into graphitic networks has been utilized for opening the band gap of graphene. However, boron‐doping into the graphitic framework is extremely limited, whereas nitrogen‐doping is ...relatively feasible. Herein, boron/nitrogen co‐doped graphene (BCN‐graphene) is directly synthesized from the reaction of CCl4, BBr3, and N2 in the presence of potassium. The resultant BCN‐graphene has boron and nitrogen contents of 2.38 and 2.66 atom %, respectively, and displays good dispersion stability in N‐methyl‐2‐pyrrolidone, allowing for solution casting fabrication of a field‐effect transistor. The device displays an on/off ratio of 10.7 with an optical band gap of 3.3 eV. Considering the scalability of the production method and the benefits of solution processability, BCN‐graphene has high potential for many practical applications.
Mixing it up a bit: B/N‐doped graphene was directly synthesized from the reaction of CCl4, BBr3, and N2 in the presence of potassium. It has good dispersibility in N‐methyl‐2‐pyrrolidone, allowing solution casting for the fabrication of field‐effect transistors with an on/off ratio of 10.7 and an optical band gap of 3.3 eV. The method is scalable and solution processable, making it suitable for many applications.
We describe the oxidation mechanism of a highly crystalline graphitic carbon in a nitric acid/sulfuric acid mixture, which is the most commonly used medium for the purification and chemical ...modification of carbon-based materials. Highly ordered pyrolytic graphite (HOPG) specimens embedded in acid-proof high-density polyethylene were treated in the acid mixture at 100°C for between one to four days. The degree of HOPG damage could be seen by transmission and scanning electron microscopy, X-ray photoelectron and Raman spectroscopy, and X-ray diffraction. In addition to “interlayer-acid-penetration” (acid-intercalation), the results suggest that a new corrosion process could be “direct-acid-penetration” from the outer to inner graphitic layers with nitration and sulfonation. This observation shows that the most commonly used acid mixture is not only introducing oxygenated groups together with nitrogen- and sulfur-containing groups, but also creating structural defects in the graphitic carbon lattice.
Boron (B)-nitrogen (N)-phosphorus (P) doped GnPs (BNP-GnPs) were synthesized by Poly(anilineboronic acid, PABA), which is one of the conducting polymers and acts as a feedstock for BNP doping, was ...in-situ grafted to edge-amine functionalized GnPs (A-GnPs). After heat-treatment, the resultant BNP-GnPs demonstrated significantly improved electrocatalytic activity towards the oxygen reduction reaction, suggesting that the BNP-GnPs can be one of the best alternatives to precious Pt-based electrocatalysts.
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•Boron (B)-nitrogen (N)-phosphorus (P) doped graphene nanoplatelets (GnPs) were prepared.•BNP-GnPs were realized by edge-grafting of poly(anilineboronic acid, PABA) and subsequent annealing.•The structure of BNP-GnPs was confirmed by spectroscopic and microscopic analyses.•The BNP-GnPs demonstrated significantly improved electrocatalytic activity towards the oxygen reduction reaction.•BNP-GnPs can be one of the best alternatives to precious Pt-based electrocatalysts.
Doping with foreign atoms is a powerful technique for modifying the inherent properties of a host materials. In this work, we report a strategy for preparing multiple heteroatom-doped graphene nanoplatelets (GnPs). Poly(anilineboronic acid, PABA), which is one of the conducting polymers, was in-situ grafted to edge-amine functionalized GnPs (A-GnPs) in phosphoric acid. The isolated PABA grafted A-GnPs phosphoric acid salts (PA-GnP salts) were heat-treated at 900 °C under argon atmosphere to yield boron (B)-nitrogen (N)-phosphorus (P) doped GnPs (BNP-GnPs). The structure of the BNP-GnPs was confirmed by various techniques, including transmission electron microscopy, scanning electronic microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy and thermogravimetric analysis. The BNP-GnPs demonstrated significantly improved electrocatalytic activity towards the oxygen reduction reaction, suggesting that BNP-GnPs can be one of the best alternatives to precious Pt-based electrocatalysts.
Solid-state reaction of organic molecules holds a considerable advantage over liquid-phase processes in the manufacturing industry. However, the research progress in exploring this benefit is largely ...staggering, which leaves few liquid-phase systems to work with. Here, we show a synthetic protocol for the formation of a three-dimensional porous organic network via solid-state explosion of organic single crystals. The explosive reaction is realized by the Bergman reaction (cycloaromatization) of three enediyne groups on 2,3,6,7,14,15-hexaethynyl-9,10-dihydro-9,10-1,2benzenoanthracene. The origin of the explosion is systematically studied using single-crystal X-ray diffraction and differential scanning calorimetry, along with high-speed camera and density functional theory calculations. The results suggest that the solid-state explosion is triggered by an abrupt change in lattice energy induced by release of primer molecules in the 2,3,6,7,14,15-hexaethynyl-9,10-dihydro-9,10-1,2benzenoanthracene crystal lattice.
In the present study, the development of strength in different calcium aluminate cement (CAC) mixture mortars with granulated ground blast-furnace slag (GGBS) was investigated. The substitution of ...GGBS levels was 0, 20, 40, and 60% weight of binder, of which the CAC used in this study naturally contained C2AS clinker as a secondary phase. To activate a hydraulic nature of the phase, in addition to the mineral additive, all specimens were cured at 35 ± 2°C for the first 24 hours and then stored in a 95% humidity chamber at 25 ± 2°C. The penetration resistance of fresh mortar was measured immediately after pouring, and the mortar compressive strength was monitored for 365 days. Simultaneously, to evaluate the hydration kinetics at early ages, in terms of heat evolution, the calorimetric analysis was performed at the isothermal condition (35°C) for 24 hours. The hydration behavior in the long term was characterized by X-ray diffraction, which was supported by microscopic observation using scanning electron microscopy with energy dispersive spectroscopy. Furthermore, an examination of the pore structure was accompanied to quantify the porosity. As a result, it was found that an increase in the GGBS content in the mixture resulted in an increased setting time, as well as total heat evolved for 24 hours in normalized calorimetry curves. In addition, the strength development of mortar showed a continuous increased value up to 365 days, accounting 43.8–57.5 MPa for the mixtures, due to a formation of stratlingite, which was identified at the pastes cured for 365 days using chemical and microscopic analysis. However, GGBS replacement did not affect on the pore size distribution in the cement matrix, except for total intrusion volume.
Solid‐state reactions have been rapidly gaining popularity in organic chemistry owing to their simplicity, efficiency, and selectivity compared to liquid‐phase reactions. Herein, we describe the ...formation of superstructures through the solid‐state reaction of an organic single‐crystal. The superstructure of 5,5′,5′′‐(1,3,5‐triazine‐2,4,6‐triyl)triisophthalonitrile (TIPN) can be formed by cyclotrimerization of 1,3,5‐tricyanobenzene (TCB) single crystals. The TIPN superstructure was confirmed by single crystal X‐ray diffraction and visualized by transmission electron microscopy. The superstructure has hexagonally packed 1‐dimensional (1D) channels along the crystal axis. Furthermore, the superstructure arises from interdigitated nitrile interactions in the crystal lattice, and thus has electron‐beam tolerance and very high thermal stability.
Sturdy crystals: The formation of organic‐molecule‐based superstructures was realized by solid‐state conversion of an organic single‐crystal. The resultant porous organic framework with 1‐dimensional channels showed unusually high thermal stability tolerance to electron‐beams.
Due to its high specific surface area, good chemical stability and outstanding electrical properties, graphene, a class of two-dimensional allotrope of carbon-based materials, is one of ideal ...candidates for next generation energy conversion and storage devices. In this review, we will present an overview on electrochemical characteristics of graphene by summarizing the recent research trend on graphene for energy conversion and storage applications, such as fuel cells and supercapacitors, along with some discussions on future research directions.
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► Graphene has a high specific surface area, good chemical stability and outstanding electrical properties. ► Graphene is one of ideal candidates for next generation energy conversion and storage devices. ► This review is an overview on electrochemical characteristics of graphene. ► Particularly, graphene for fuel cells and ultracapacitor applications.
Kish graphite, a waste (called dust) from a steelmaking process, can be simultaneously purified and functionalized by mechanochemical ball‐milling in the presence of iodine. The resultant iodinated ...Kish graphite (I‐Kish‐G) contains low content of impurities and high iodine content (1.83 at%, 16.17 wt%, energy dispersive X‐ray spectroscopy) with high crystallinity. It has high specific surface area (924.3 m2 g−1), indicating that I‐Kish‐G is significantly purified, functionalized, and exfoliated into a few graphitic layers. More importantly, I‐Kish‐G displays outstanding electrocatalytic activity for oxygen reduction reaction with long‐term durability and robustness against methanol crossover and CO poisoning effects in alkaline media.
Using mechanochemical ball‐milling, waste Kish graphite (Kish‐G) is simply converted into high‐quality electrocatalyst for oxygen reduction reaction in alkaline media. Ball‐milling Kish‐G in the presence of iodine simultaneously purifies and functionalizes Kish‐G into iodinated Kish‐G (I‐Kish‐G) with low content of impurities, high iodine content, high degree of crystallinity, and high specific surface area.
Heteroatom doping into the graphitic frameworks have been intensively studied for the development of metal-free electrocatalysts. However, the choice of heteroatoms is limited to non-metallic ...elements and heteroatom-doped graphitic materials do not satisfy commercial demands in terms of cost and stability. Here we realize doping semimetal antimony (Sb) at the edges of graphene nanoplatelets (GnPs) via a simple mechanochemical reaction between pristine graphite and solid Sb. The covalent bonding of the metalloid Sb with the graphitic carbon is visualized using atomic-resolution transmission electron microscopy. The Sb-doped GnPs display zero loss of electrocatalytic activity for oxygen reduction reaction even after 100,000 cycles. Density functional theory calculations indicate that the multiple oxidation states (Sb(3+) and Sb(5+)) of Sb are responsible for the unusual electrochemical stability. Sb-doped GnPs may provide new insights and practical methods for designing stable carbon-based electrocatalysts.
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