Carbon Honeycomb Research Articles

Electrochemical conversion of CO2 into value-added carbon with desirable structures via molten carbonates electrolysis.

Direct conversion of CO2 to high value-added carbon products based on molten salt electrochemistry has been proven to be a feasible approach to solve the climate problem and achieve carbon neutrality. In this work, carbon nanotubes (CNTs), carbon spheres (CSs) and honeycomb carbon are synthesized by electrolysis of a single or multiple alkali metal carbonate electrolyte. The elemental composition, morphology and structure, crystallinity and graphitization degree of carbon products are characterized by electron dispersive spectroscopy (EDS), scanning electron microscopy (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD) and Raman microspectroscopy (RAM). The results demonstrate that a high yield of CNTs is obtained in Li2CO3 electrolyte by regulating the electrolysis temperature and current density. Compared to pure Li2CO3, Li–Na carbonate electrolyte with 1 wt% stannic oxide/cerium oxide (SnO2/GeO2) favors CS formation rather than CNT formation. Additionally, honeycomb carbon products are generated in Li–Na–K electrolyte, when the electrolysis temperature is lower than 600 °C. Overall, this work provides a novel carbon neutral strategy where high value-added carbon products are synthesized using CO2 as a carbon source.

Cпектроскопия комбинационного рассеяния наноразмерных сотовидных углеродных структур

Cпектроскопия комбинационного рассеяния наноразмерных сотовидных углеродных структур

Honey-comb carbon nanostructure derived from peach gum to yield high microwave absorption

Lightweight and highly efficient electromagnetic absorptions are crucial for microwave absorption materials due to the fast development of information technology. Bio-derived carbon materials are ideal resistance loss-type microwave absorbers with lightweight. A honey-comb carbon structure has been obtained from peach gum by facile hydrothermal and pyrolysis processes. The skeleton of the as-derived honey-comb carbon structure is composed of carbon nanoparticles with diameters around 40 nm. The honey-comb structures were further carbonized at 850 °C (NPG-850) to have a large specific surface area of 1401.7 m2 g−1 with an average pore diameter of 3.2 nm. A minimum reflection loss (RL) of − 59.4 dB was obtained by NPG-850 at a thickness of 2.0 mm with an effective absorption bandwidth (EAB, RL < − 10 dB) of 4.1 GHz (14.7–10.6 GHz). The RL value of the peach gum-derived honey-comb carbon nanostructures is much higher than the reported carbon nanostructures even with thinner thickness and less mass loading, which might due to the multi-reflection effect of the honey-comb structures and the skeleton composition.

Free vibration analysis of honeycomb doubly curved shell integrated with CNT-reinforced piezoelectric layers

The present article studies free vibration analysis of sandwich doubly curved shell composed of a honeycomb core and carbon nanotubes (CNTs) reinforced piezoelectric face-sheets. First-order shear deformation theory as well as Hamilton’s principle is employed to derive the governing equations of motion. The effective material properties of core and face-sheets are estimated using the Gibson's formula and extended rule of mixture, respectively. The governing equations of motion are solved for simply supported boundary conditions to investigate the variation of natural frequencies of sandwich doubly curved shell in terms of important parameters of core and face-sheets such as side length ratio and length to thickness ratio of honeycomb cell, volume fraction, and distribution of CNTs and overall geometric parameters of the sandwich doubly curved shell. It is concluded that the maximum and minimum values of natural frequencies are obtained for FG-VA and FG-AV, respectively.

Efficient Na‐Ion Storage in 2D TiS2 Formed by a Vapor Phase Anion‐Exchange Process

AbstractHierarchical nanocomposites that couple downsized 2D materials with carbonaceous functional supports are promising electrode materials for metal ion batteries. Herein, a honeycomb‐like Na‐ion battery (NIB) anode material, which comprises 2D downsized TiS2 nanocrystals uniformly dispersed in a 3D porous carbon honeycomb, is developed by a vapor phase anion‐exchange reaction of CS2 with a dual‐template of TiO2 sealing in hydrogen‐substituted graphdiyne (HsGDY). On the one hand, the 2D downsized TiS2 nanolayers offer much more accessible active sites for both Na+ storage and polysulfide trapping; on the other hand, the 3D porous hollow carbon nanoscale honeycomb not only provides numerous space‐confined nanorooms to reduce the stacking of the tiny 2D TiS2 nanolayers and suppress the dissolution of polysulfide, but also works as built‐in 3D conductive networks to support the electron/ion transfer and buffer the volume expansion during cycling. In light of this, such a hybrid 3D TiS2@carbon honeycomb achieves a high reversible capacity with high‐rate and long‐life performance for NIBs.

Measuring the coefficient of moisture expansion of Hysol 9396 loaded with boron nitride powder

The future ATLAS ITk strip tracker [1] will consist of 17,000 silicon strip detector modules mounted on support structures called cores. Cores are assembled from a number of components, among others carbon fibre facings, honeycomb structure and carbon foam surrounding titanium tubes used for cooling, using a two-component epoxy (Hysol 9396) loaded with boron nitride for good thermal conductivity. The adhesive constitutes about 20% of a core's weight. During operation, the detector is cooled down to -40̂C} using bi-phase carbon dioxide and flushed with dry gas to prevent condensation. The effect of this temperature change has been simulated to study the impact of Coefficient of Thermal Expansion (CTE) mismatches between different materials and investigate resulting deformations and misalignment. In addition to the shrinking of an adhesive during cooling, which can be estimated well using its known CTE, flushing the detector volume with dry gas removes the moisture contained in the adhesive, leading to an additional shrinking. In order to estimate the impact of shrinking during drying, the Coefficient of Moisture Expansion (CME) of Hysol samples with different contents of boron nitride as well as their overall moisture absorption were measured and their extent compared to the contraction associated with cooling.

Investigation and improvements of the mechanical structure of cylindrical GEMs for the BESIII experiment

Gas Electron Multipliers (GEMs) can be produced in large foils and molded in different shapes. The possibility to create cylindrical layers has opened the opportunity to use such detector as internal tracker at collider experiments. One crucial item is to have low material budget in the active area, so the supporting structure of anode and cathode must be light. KLOE2 collaboration has built the first Cylindrical GEM detector with honeycomb material with carbon fiber skins produced at high temperature. BESIII is developing an innovative CGEM detector with charge and time readout. Among several innovative features, the mechanical structure was designed to be a sandwich of Rohacell and Kapton, a PMI foam. After the transportation of a first production of the detectors from the construction site in Italy to the Institute of High Energy Physics in Beijing, some malfunctions have been observed in some of them, compatible with GEMs deformation inside the detector. We have performed a detailed study by means of an industrial CT scan available in IHEP laboratory and autopsy to the damaged detectors. In this talk, we will review the construction process, the shipment, the findings of the investigation. A new supporting structure of carbon fiber and honeycomb, assembled at room temperature, has been designed and developed. The thickness of the carbon fiber is small enough to keep the material budget of a single detector layer below 0.5% of a radiation length, while the mechanical robustness results beyond the purpose of a detector for HEP. A first detector with such a mechanical structure has been built and shipped to IHEP, preliminary results from operation (e.g. current stability, discharges, temperature and humidity correlation) of the detectors are also presented in this paper.

A 3D porous honeycomb carbon as Na-ion battery anode material with high capacity, excellent rate performance, and robust stability

Motivated by the synthesis of three-dimensional (3D) honeycomb carbon structures and the subsequent theoretical prediction of an energetically more favorable hexagonal carbon phase composed of 28 carbon atoms in the unit cell (hC28) with ordered pores, excellent mechanical properties, and metallic feature, we explore its potential for a Na-ion battery (NIB) anode material. Using density functional theory based calculations, we find that hC28 is a promising candidate whose specific capacity of 717 mAh/g is almost three times larger than that of hard carbon (∼250 mAh/g). In addition, migration barrier of Na ions along the honeycomb channel is only 0.08 eV and the volume change during the charging/discharging process is merely 2.30%, which are much less than those of other carbon-based NIB anode materials. The average voltage is also low (0.36 eV) which can provide high operating voltage when connected to the cathode. These encouraging results would pave the way towards the development of hC28 as NIB anode with high capacity, excellent rate performance, low open-circuit voltage, and long-term cycle life.

A Revisited Mechanism of the Graphite-to-Diamond Transition at High Temperature

Graphite and diamond are two well-known allotropes of carbon with distinct physical properties due to different atomic connectivity. Graphite has a layered structure in which the honeycomb carbon sheets can easily glide, while atoms in diamond are strongly bonded in all three dimensions. The transition from graphite to diamond has been a central subject in physical science. One way to turn graphite into diamond is to apply the high pressure and high temperature (HPHT) conditions. However, atomistic mechanism of this transition is still under debate. From a series of large-scale molecular dynamics (MD) simulations, we report a mechanism that the diamond nuclei originate at the graphite grain boundaries and propagate in two preferred directions. In addition to the widely accepted [001] direction, we found that the growth along [120] direction of graphite is even faster. In this scenario, cubic diamond (CD) is the kinetically favorable product, while hexagonal diamond (HD) would appear as minor amounts of twinning structures in two main directions. Following the crystallographic orientation relationship, the coherent interface t-(100)gr//(11-1)cd + [010]gr//[1-10]cd was also confirmed by high-resolution transmission electron microscopy (HR-TEM) experiment. The proposed phase transition mechanism does not only reconcile the longstanding debate regarding the role of HD in graphite-diamond transition, but also yields the atomistic insight into microstructure engineering via controlled solid phase transition.

Gas-phase infrared spectroscopy of the rubicene cation (C26H14•+)

Infrared bands at 3.3, 6.2, 7.6, 7.8, 8.6, and 11.2 μm have been attributed to polycyclic aromatic hydrocarbons (PAHs) and are observed toward a large number of galactic and extragalactic sources. Some interstellar PAHs possibly contain five-membered rings in their honeycomb carbon structure. The inclusion of such pentagon defects can occur during PAH formation, or as large PAHs are eroded by photo-dissociation to ultimately yield fullerenes. Pentagon formation is a process that is associated with the bowling of the PAH plane, that is, the ability to identify PAH pentagons in space holds the potential to directly link PAHs to cage and fullerene structures. It has been hypothesized that infrared (IR) activity around 1100 cm−1 may be a spectral marker for interstellar pentagons. We present an experimentally measured gas-phase IR absorption spectrum of the pentagon-containing rubicene cation (C26H14•+) to investigate if this band is present. The NASA Ames PAH IR Spectroscopic Database is scrutinized to see whether other rubicene-like species show IR activity in this wavelength range. We find that a specific molecular characteristic is responsible for this IR band. Namely, the vibrational motion attributed to this IR activity involves pentagon-containing harbors. An attempt to find this specific mode in Spitzer observations is undertaken and tentative detections around 9.3 μm are made toward the reflection nebula NGC 7023 and the H II-region IRAS 12063-6259. Simulated emission spectra are used to derive upper limits for the contributions of rubicene-like pentagonal PAH species to the IR band at 6.2 μm toward these sources.

Adsorption and Diffusion of Hydrogen in Carbon Honeycomb.

Carbon honeycomb has a nanoporous structure with good mechanical properties including strength. Here we investigate the adsorption and diffusion of hydrogen in carbon honeycomb via grand canonical Monte Carlo simulations and molecular dynamics simulations including strength. Based on the adsorption simulations, molecular dynamics simulations are employed to study the effect of pressure and temperature for the adsorption and diffusion of hydrogen. To study the effect of pressure, we select the 0.1, 1, 5, 10, 15, and 20 bars. Meanwhile, we have studied the hydrogen storage capacities of the carbon honeycomb at 77 K, 153 K, 193 K, 253 K and 298 K. A high hydrogen adsorption of 4.36 wt.% is achieved at 77 K and 20 bars. The excellent mechanical properties of carbon honeycomb and its unique three-dimensional honeycomb microporous structure provide a strong guarantee for its application in practical engineering fields.

Dynamic Covalent Synthesis of Crystalline Porous Graphitic Frameworks

Summary Porous graphitic framework (PGF) is a two-dimensional (2D) material that has emerging energy applications. An archetype contains stacked 2D layers, the structure of which features a fully annulated aromatic skeleton with embedded heteroatoms and periodic pores. Due to the lack of a rational approach in establishing in-plane order under mild synthetic conditions, the structural integrity of PGF has remained elusive and ultimately limited its material performance. Here, we report the discovery of the unusual dynamic character of the C=N bonds in the aromatic pyrazine ring system under basic aqueous conditions, which enables the successful synthesis of a crystalline porous nitrogenous graphitic framework with remarkable in-plane order, as evidenced by powder X-ray diffraction studies and direct visualization using high-resolution transmission electron microscopy. The crystalline framework displays superior performance as a cathode material for lithium-ion batteries, outperforming the amorphous counterparts in terms of capacity and cycle stability.

Etching of Carbon Fiber-Reinforced Plastics to Increase Their Joint Strength

An original method to increase the mechanical strength of adhesively joined carbon fiber-reinforced plastics (CFRPs) and honeycomb CFRP sandwich structures by etching is proposed, based on sulfuric acid etching of the CFRP surface. Etched composites are joined by a novel phenolic resin-based adhesive and are cured, and their cross section is observed by FESEM. Etching of CFRP was aimed to obtain a “brush”-like composite to be infiltrated by the adhesive, giving a fiber-reinforced, stronger composite joint. This method gave a 100% increase in the lap shear strength for the adhesively joined etched CFRP, compared to the non-etched ones.

The synergetic effects of a multifunctional citric acid and rice husk derived honeycomb carbon matrix on a silicon anode for high-performance lithium ion batteries

Using silicon/carbon composites is one of the most attractive strategies to improve the anode performance for lithium ion batteries.

Old Story New Tell: The Graphite to Diamond Transition Revisited

Graphite and diamond are two well-known allotropes of carbon with distinct physical properties due to different atomic connectivity. Graphite has a layered structure in which the honeycomb carbon sheets can easily glide, while atoms in diamond are strongly bonded in all three dimensions. The transition from graphite to diamond has been a central subject in physical science. One way to turn graphite into diamond is to apply the high pressure and high temperature (HPHT) conditions. However, atomistic mechanism of this transition is still under debate. From a series of large-scale molecular dynamics (MD) simulations, we report a mechanism that the diamond nuclei originate at the graphite grain boundaries and propagate in two preferred directions. In addition to the widely accepted [001] direction, we found that the growth along [120] direction of graphite is even faster. In this scenario, cubic diamond (CD) is the kinetically favorable product, while hexagonal diamond (HD) would appear as minor amounts of twinning structures in two main growth directions. Following the crystallographic orientation relationship, the coherent interface t-(100)gr//(11-1)cd + [010]gr//[1-10]cd was also confirmed by high-resolution transmission electron microscopy (HR-TEM) experiment. The proposed phase transition mechanism does not only reconcile the longstanding debate regarding the role of HD in graphite-diamond transition, but also yields the atomistic insight into microstructure engineering via controlled solid phase transition.

Bco-C24: A new 3D Dirac nodal line semi-metallic carbon honeycomb for high performance metal-ion battery anodes

Three-dimensional porous carbon materials play a significant role in gas separation and energy storage. However, their low performances in energy storage hamper their applications. Herein, we propose a new possible category of carbon honeycomb (CHC), i.e. CHCs with asymmetrical channels (denoted as asymmetrical CHCs), to increase their performance. As an example, by cross-linking graphene sheet with sp3–hybridized carbon chains, we prepare a new 3D porous asymmetrical CHC, i.e. bco-C24. It is dynamically, thermally, and mechanically stable. Our first-principles calculations and tight binding results demonstrate that it possesses a significant electronic band structure of Dirac nodal lines, which are ascribed to the px and py orbitals of α carbon atoms in the graphene ribbons that have both α and β carbon atoms. It provides high carrier mobility between 7.98 × 105 and 9.99 × 105 m/s. It has high theoretical capacities (743.8/495.9/991.8/743.8 mA h/g), low diffusion barriers (0.077/0.032/0.117/0.169 eV), low average voltages, and negligible volume changes for Na/K/Ca/Li-ion batteries. This study not only constructs a new concept of asymmetrical CHCs and provides a strategy of cross-linking graphene sheets to create its sample structures, but also suggests new carriers for ion storage in the superior next generation metal-ion battery anodes.

A 3D cross-linked graphene-based honeycomb carbon composite with excellent confinement effect of organic cathode material for lithium-ion batteries

Organic cathode materials are drawing increasing attention in lithium-ion battery for their abundance, environmental friendliness, high specific capacity, low cost, and flexibility. But their application has been hindered by poor electrochemical performance because of inherent low conductivity and high solubility in the polar organic electrolyte. Herein, an organic-inorganic composite by impregnating electrochemically active 4,8-dihydrobenzo [1,2-b:4,5-b’] dithiophene-4,8-dione (BDT) into the pores of 3D cross-linked graphene-based honeycomb carbon (3DGraphene) has been prepared, which not only offers a highly conductive framework with plenty of interconnected pores from the 3D graphene network, but also simultaneously overcomes the two typical drawbacks of organic cathode materials. The excellent confinement effect of the nanopores and the strong π-π interaction between BDT and 3DGraphene largely avoid the dissolution of BDT in the electrolyte. Therefore, the obtained BDT/3DGraphene composite shows a much improved good rate capability (more than 100 mAh g −1 at 4.0C vs less than 50 mAh g −1 for BDT) and cycling stability (about 80% capacity retention at 0.5C while only ∼14% for BDT for 200 cycles), as well as high reversible specific capacity (over 210 mAh g −1 ).

A new honeycomb carbon monolith for CO2 capture by rapid temperature swing adsorption using steam regeneration

A rapid process for CO2 capture is of key importance for the economic feasibility of the process in industry, consequently short adsorption/desorption cycles are crucial. With this aim in mind, a carbon based honeycomb monolith was evaluated for CO2 capture in a thermal swing adsorption process at short contact times. The effect of (1) regeneration time, (2) presence of water vapor during adsorption and desorption and (3) regeneration method (steam versus hot air) on CO2 adsorption was studied. The monolith was characterized in terms of porosity and CO2, N2, and H2O isotherms. Cyclic adsorption/desorption experiments were performed using different synthetic gas mixtures with concentrations of CO2 ranging between 6 and 15 vol%. The effect of water vapor in the synthetic gas mixture on adsorption capacity was limited but increases with relative humidity. Steam of 120 °C was used to heat the monolith and desorb CO2. Advantages of steam usage are the facile separation of steam and concentrated CO2 and the low (waste) heating energy cost of steam. It was demonstrated that the steam allows very fast heating and cooling of the monolith. However, the presence of residual condensation water after the cooling step reduces the cyclic adsorption capacity, requiring an additional drying step with hot or cold air.

3D Honeycomb Architecture Enables a High-Rate and Long-Life Iron (III) Fluoride-Lithium Battery.

Metal fluoride-lithium batteries with potentially high energy densities, even higher than lithium-sulfur batteries, are viewed as very promising candidates for next-generation lightweight and low-cost rechargeable batteries. However, so far, metal fluoride cathodes have suffered from poor electronic conductivity, sluggish reaction kinetics and side reactions causing high voltage hysteresis, poor rate capability, and rapid capacity degradation upon cycling. Herein, it is reported that an FeF3 @C composite having a 3D honeycomb architecture synthesized by a simple method may overcome these issues. The FeF3 nanoparticles (10-50 nm) are uniformly embedded in the 3D honeycomb carbon framework where the honeycomb walls and hexagonal-like channels provide sufficient pathways for the fast electron and Li-ion diffusion, respectively. As a result, the as-produced 3D honeycomb FeF3 @C composite cathodes even with high areal FeF3 loadings of 2.2 and 5.3 mg cm-2 offer unprecedented rate capability up to 100 C and remarkable cycle stability within 1000 cycles, displaying capacity retentions of 95%-100% within 200 cycles at various C rates, and ≈85% at 2C within 1000 cycles. The reported results demonstrate that the 3D honeycomb architecture is a powerful composite design for conversion-type metal fluorides to achieve excellent electrochemical performance in metal fluoride-lithium batteries.

Molecular Dynamics Simulation on Mechanical and Piezoelectric Properties of Boron Nitride Honeycomb Structures.

Boron nitride honeycomb structure is a new three-dimensional material similar to carbon honeycomb, which has attracted a great deal of attention due to its special structure and properties. In this paper, the tensile mechanical properties of boron nitride honeycomb structures in the zigzag, armchair and axial directions are studied at room temperature by using molecular dynamics simulations. Effects of temperature and strain rate on mechanical properties are also discussed. According to the observed tensile mechanical properties, the piezoelectric effect in the zigzag direction was analyzed for boron nitride honeycomb structures. The obtained results showed that the failure strains of boron nitride honeycomb structures under tensile loading were up to 0.83, 0.78 and 0.55 in the armchair, zigzag and axial directions, respectively, at room temperature. These findings indicated that boron nitride honeycomb structures have excellent ductility at room temperature. Moreover, temperature had a significant effect on the mechanical and tensile mechanical properties of boron nitride honeycomb structures, which can be improved by lowering the temperature within a certain range. In addition, strain rate affected the maximum tensile strength and failure strain of boron nitride honeycomb structures. Furthermore, due to the unique polarization of boron nitride honeycomb structures, they possessed an excellent piezoelectric effect. The piezoelectric coefficient e obtained from molecular dynamics was , which was lower than that of the monolayer boron nitride honeycomb structures, . Such excellent piezoelectric properties and failure strain detected in boron nitride honeycomb structures suggest a broad prospect for the application of these new materials in novel nanodevices with ultrahigh tensile mechanical properties and ultralight-weight materials.