Honeycomb Architecture Research Articles

A honeycomb-like nitrogen-doped carbon as high-performance anode for potassium-ion batteries

Potassium-ion batteries (PIBs) have caused great concern owing to their low cost and the reserve-abundance of potassium, but a critical limitation in PIBs anodes is the low capacity for efficient intercalation/de-intercalation of K ions with a larger size. Herein, we successfully synthesize a nitrogen-doped carbon with a honeycomb architecture (cellular N-C) via directed growth of metal-organic frameworks (MOFs) on the surfaces of LDHs nanosheets followed by the pyrolysis and acid-etching processes. The resulting cellular N-C material exhibits promising PIBs anode activity, which is superior to the N-doped carbon (N-C) derived directly from MOFs. Through the structure design, compared with the N-C, the cellular N-C has the characteristics of finely controlled honeycomb-like morphology with higher specific surface area, well-distributed hierarchical micro/meso/macro-pores, and expanded interlayer distance. These features can greatly facilitate the K+ diffusion kinetics and make the electrode materials accommodate more K ions. Therefore, the cellular N-C electrode can deliver outstanding rate capability up to 10 A g−1 and great cycling performance at 1 A g−1 over 2000 cycles (143 mAh g−1).

Ex vivo culture of adult CD34+ stem cells using functional highly porous polymer scaffolds to establish biomimicry of the bone marrow niche

Haematopoiesis, the process of blood production, occurs from a tiny contingent of haematopoietic stem cells (HSC) in highly specialised three-dimensional niches located within the bone marrow. When haematopoiesis is replicated using in vitro two-dimensional culture, HSCs rapidly differentiate, limiting self-renewal. Emulsion-templated highly porous polyHIPE foam scaffolds were chosen to mimic the honeycomb architecture of human bone. The unmodified polyHIPE material supports haematopoietic stem and progenitor cell (HSPC) culture, with successful culture of erythroid progenitors and neutrophils within the scaffolds. Using erythroid culture methodology, the CD34+ population was maintained for 28 days with continual release of erythroid progenitors. These cells are shown to spontaneously repopulate the scaffolds, and the accumulated egress can be expanded and grown at large scale to reticulocytes. We next show that the polyHIPE scaffolds can be successfully functionalised using activated BM(PEG)2 (1,8-bismaleimido-diethyleneglycol) and then a Jagged-1 peptide attached in an attempt to facilitate notch signalling. Although Jagged-1 peptide had no detectable effect, the BM(PEG)2 alone significantly increased cell egress when compared to controls, without depleting the scaffold population. This work highlights polyHIPE as a novel functionalisable material for mimicking the bone marrow, and also that PEG can influence HSPC behaviour within scaffolds.

Ice-templated freeze-dried cryogels from tunicate cellulose nanocrystals with high specific surface area and anisotropic morphological and mechanical properties

High aspect ratio cellulose nanocrystals (CNCs) extracted from tunicate were used to create so-called cryogels from an ice-templating directional freeze-drying process. The structure of the resulting solid foam was investigated at the micro- and nanoscales by scanning electron microscopy and nitrogen adsorption measurements were used to extract the specific surface area. The mechanical properties were probed by compression tests. To highlight the specificities of tunicate CNC-based cryogels, results were compared with the one obtained from two other types of nanocellulose, namely cellulose nanofibrils (CNFs) from wood and CNCs from cotton, which exhibit different dimensions, aspect ratio, flexibility and crystallinity. While CNF- and cotton CNC-based cryogels exhibited a classical morphology characterized by a sheet-like structure, a particular honeycomb organization with individual particles was obtained in the case of tunicate CNC cryogels. The latter cryogels presented a very high specific surface area of about 122 m2 g−1, which is unexpected for foams prepared from a water-based process and much higher than what was obtained for CNF and cotton CNC cryogels (25 and 4 m2 g−1, respectively). High mechanical resistance and stiffness were also obtained with such tunicate CNC cryogels. These results are explained by the high crystallinity, aspect ratio and rigidity of the tunicate CNCs combined with the particular honeycomb architecture of the cryogel.

Mechanics of Chiral Honeycomb Architectures With Phase Transformations

Abstract The mechanics of phase transforming cellular materials (PXCMs) with three different chiral honeycomb architectures, viz., hexachiral, tetra-anti-chiral, and tetra-chiral, are investigated under quasi-static loading/unloading. Each PXCM comprises interconnected unit cells consisting of tape springs rigidly affixed to circular nodes that can rotate and/or translate. The phase change is associated with snap-through instability due to bending of the tape springs and corresponds to sudden changes in the geometry of the unit cells from one stable configuration to another stable (or metastable) configuration during loading/unloading. When compared with similar chiral materials with flat ligaments, the chiral PXCMs exhibit a significantly higher energy dissipation in quasi-static experiments. The hexachiral PXCM was selected for detailed parametric analysis with finite element simulations including 21 models constructed to investigate the effects of PXCM geometry on phase change and energy dissipation. An analytical formalism is developed to predict the minimum compressive load required to induce phase transformation and snap-through. The formalism predictions are compared with those from finite element simulations. An Ashby plot is developed in which the energy dissipated per unit volume versus work conjugate plateau stress of the H-PXCM is compared with other energy absorbing materials.

Scalable, Large-Area Printing of Pore-Array Electrodes for Ultrahigh Power Electrochemical Energy Storage

Through-electrode thickness honeycomb architectures were layer-by-layer self-assembled directly through a scalable printing process for ultrapower hybrid lithium-ion capacitor applications. Initially, the electrochemical performance of the pore-array electrodes was investigated as a function of the active material type (graphene plates, carbon nanofibers, and activated carbon). Inactive components (conductive carbon and polymer binder) were then minimized to 5 wt %. Finally, an optimized activated carbon-based cathode was paired with a spray-printed Li4Ti5O12-based anode and a range of anode-to-cathode mass ratios in a lithium-ion capacitor arrangement were investigated. A 1:5 anode/cathode mass ratio provided an attractive energy density comparable with a Li4Ti5O12/LiFePO4 lithium-ion battery but with outstanding power capability that was an order of magnitude greater than typical for lithium-ion batteries. The pore-array electrode was reproduced over areas of 20 cm × 15 cm in a double-sided coated configuration, and the option for selectively patterning electrodes was also demonstrated.

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.

Strontium Manganese Oxide Getter for Capturing Airborne Cr and S Contaminants in High-Temperature Electrochemical Systems.

Traces (ppm to ppblevel) of airborne contaminants such as CrO2(OH)2 and SO2 irreversibly degrade the electrochemical activity of air electrodes in high-temperature electrochemical devices such as solid oxide fuel cells by retarding oxygen reduction reactions. The use of getter has been proposed as a cost-effective strategy to mitigate the electrode poisoning. However, owing to the harsh operating conditions (i.e., exposure to heat and moisture), the long-term durability of getter materials remains a considerable challenge. In this study, we report our findings on strontium manganese oxide (SMO) as a robust getter material for cocapture of airborne Cr and S contaminants. The SMO getter with a 3D honeycomb architecture, fabricated via slurry dip-coating, successfully maintains the electrochemical activity of solid oxide cells under the flow of gaseous Cr and S species, validating the getter's capability of capturing traces of Cr and S contaminants. Investigations found that both Sr and Mn cations contribute to the absorption reaction and that the reaction processes are accompanied by morphological elongation in the form of SrSO4 nanorods and SrCrO4 whiskers, which favors continued absorption and reaction of incoming S and Cr contaminants. The SMO getter also displays robust stability at high temperatures and in humid environments without phase transformation and hydrolysis. These results demonstrate the feasibility of the use of SMO getter under severeoperating conditions representative of high-temperature electrochemical systems.

Optimizing electromagnetic wave absorption performance: Design from microscopic bamboo carbon nanotubes to macroscopic patterns

Achieving ideal electromagnetic wave absorbing materials and effective artificial super structures design are increasingly attractive for their irreplaceable role in aerospace stealth structure, Over the Air (OTA) test and civil wireless communication systems. In this work, the bamboo carbon nanotubes (CNTs) were prepared by a simple thermal treatment method. The microstructure and yields of bamboo CNTs were tunable by changing the feeding amounts of polypropylene fabrics precursors. The optimal reflection losses (RL) value of as-prepared bamboo CNTs was up to −54.5 dB at 14.45 GHz with 1.85 mm, meanwhile the effective bandwidth (fe) covered from 12.31 to 17.76 GHz. With subsequent macroscopic honeycomb architecture design based on the as-fabricated bamboo CNTs, the artificial structures with variable radius, thickness and height exhibited more than 90% absorption in 8.5–18 GHz. The results suggested that combination of developing microscopic microwave absorbers and macroscopic structure design would fundamentally optimize the electromagnetic wave absorption with low matching thickness and extensive effective bandwidth.

Routing and Clustering of Sensor Nodes in the Honeycomb Architecture

Energy is the most valuable resource in wireless sensor networks; this resource is limited and much in demand during routing and communication between sensor nodes. Hierarchy structuring of the network into clusters allows reducing the energy consumption by using small distance transmissions within clusters in a multihop manner. In this article, we choose to use a hybrid routing protocol named Efficient Honeycomb Clustering Algorithm (EHCA), which is at the same time hierarchical and geographical protocol by using honeycomb clustering. This kind of clustering guarantees the balancing of the energy consumption through changing in each round the location of the cluster head, which is in a given vertex of the honeycomb cluster. The combination of geographical and hierarchical routing with the use of honeycomb clustering has proved its efficiency; the performances of our protocol outperform the existing protocols in terms of the number of nodes alive, the latency of data delivery, and the percentage of successful data delivery to the sinks. The simulations testify the superiority of our protocol against the existing geographical and hierarchical protocols.

Microwave-constructed honeycomb architectures of h-BN/rGO nano-hybrids for efficient microwave conversion

Honeycomb architectures of h-BN/rGO nano-hybrids were built from the self-assemblies of hexagonal boron nitride (h-BN) and graphene oxide (GO) through microwave heating for a few seconds. Incorporation of h-BN nanosheets into 3D reduced graphene oxide (rGO) foams was accompanied by the removal of oxygen-containing groups during the rapid “bread baking” process. TEM and SEM images revealed the layer-stacked structure of the samples. XPS, Raman and XRD spectra showed the presence of h-BN layers that were interlaced into the honeycomb architectures of rGO frameworks. The microwave absorption properties and the complex permittivity could be adjusted by varying the microstructure and the content of h-BN. For the wax composite filled with 6.25 wt% h-BN/rGO nano-hybrid with thickness of 1.8 mm, the reflection loss value reached −35.63 dB at 17.2 GHz, and the effective frequency bandwidth reached 6.96 GHz at 2.6 mm with a low surface density. The honeycomb architecture of the hybrid provided multiple electromagnetic transmission paths and consumed significant amount of microwave energy due to the multiple interfaces. Embedding h-BN in the architecture enables excellent impedance matching, and provides highly efficient dielectric material that can be used for microwave absorption. This work demonstrates that microwave treatment is a facile approach to obtaining optimal microwave absorbing properties of h-BN/rGO nano-hybrids.

Development of an innovative capsule with three-dimension honeycomb architecture via one-step titration-gel method for the removal of methylene blue.

In this study, the capsules were prepared via the one-step titration-gel method by injecting spherical droplets of polyvinyl alcohol (PVA), sodium alginate (SA) and graphene oxide (GO) gelled mixture into the bath with calcium chloride (CaCl2) and oversaturated boric acid (H3BO3) solutions. The prepared capsules were then further modified with glutaraldehyde (GA). The formation mechanism of the prepared capsules was investigated. The morphology of the prepared capsules exhibited distinct micro-porous "3D honeycomb" pattern and hierarchical pore sizes distribution. It was also observed that GA not only acted as a co-cross-linked reagent in the fabricating process to increase the specific surface area of the capsules, but also offered exceptional tolerance property to work under a wide pH range (i.e. 2-12). The PVA-SA-GO capsules performed comparatively much better than PVA-SA capsules and they improved the adsorption capacity by up to 21.94%. Their adsorptive performance well followed the Langmuir isotherm. Moreover, the pH of the MB solution was evidently declined after adsorption, demonstrating the electrostatic attraction or ion-exchange might be the governing removal mechanism of methylene blue (MB) dye by the capsules. Importantly, the prepared capsules could be regenerated by simply washing with water and reused for at least 6 consecutive treatment cycles.

Constructing honeycomb architectures from polymer carbon dot composites for luminous efficacy enhancement of LEDs

In this work, we report a facile construction of honeycomb-patterned membranes from polymer carbon dot (PCD) composites, which are demonstrated to effectively enhance the luminous efficacy of GaN-based light-emitting diodes (LEDs). A series of PCD composites were successfully achieved by a pyrolysis process from poly(methyl methacrylate-co-dimethyl diallyl ammonium chloride) copolymers, in which CDs were in situ formed and bonded with the polymer chains. Subsequently, ordered porous PCD membranes with a bifunctionality of fluorescence and hydrophobicity were generated via a “breath figure” method under humid conditions. Significantly, these honeycomb-like architectures could contribute to 41.9% improvement of the luminous efficacy for LEDs, showing great potentials for electrical, optoelectronic, and photovoltaic applications.

Compressive behaviour of 3D printed thermoplastic polyurethane honeycombs with graded densities

Fused filament fabrication of thermoplastic polyurethanes (TPUs) offers a capability to manufacture tailorable, flexible honeycomb structures which can be optimised for energy absorbing applications. This work explores the effect of a range of grading methodologies on the energy absorbing and damping behaviour of flexible TPU honeycomb structures. By applying density grading, the energy absorbing and damping profiles are significantly modified from the uniform density equivalent. A 3D-printing procedure was developed which allowed the manufacture of high-quality structures, which underwent cyclic loading to densification without failure. Graded honeycomb architectures had an average relative density of 0.375 ± 0.05. After quasi-static testing, arrays were subjected to sinusoidal compression over a range of amplitudes at 0.5 Hz. By grading the structural density in different ways, mechanical damping was modified. Cyclic compressive testing also showed how strain-softening of the TPU parent material could lead to reduced damping over the course of 50 cycles. Samples were subjected to impact loading at strain-rates of up to 51 s-1 and specific impact energies of up to 270 mJ/cm3. Lower peak loads were transferred for graded samples for the most severe impact cases. This behaviour reveals the potential of density grading of TPU structures to provide superior impact protection in extreme environmental conditions.

Facile synthesis of three dimensional porous cellular carbon as sulfur host for enhanced performance lithium sulfur batteries

Lithium sulfur battery has drawn intense interests due to its high theoretical specific capacity and high energy density. However, it remains a big challenge to achieve high capacities and sulfur loadings of cathode via a facile and scaled-up method for the practical applications of lithium sulfur batteries. Herein we designed a three dimensional porous cellular carbon framework (PCCF) as sulfur host via a simple template-activation method. The honeycomb architecture of the PCCF with high BET surface area could encapsulate high content sulfur and the 3D interconnected carbon framework could realize high sulfur loading electrode. Benefiting from the 3D porous cellular architecture, the obtained cellular PCCF/S cathode delivers a notable enhancement in the sulfur content, sulfur loading, cycling stability and rate performance. The PCCF/S cathode with high sulfur content of 84.75% exhibits an initial discharge capacity of 1264.4 mAh g−1 at 0.1C rate and shows good cycling stability with a low capacity decay rate of 0.14% per cycle after 200 cycles at 1C rate. With a high sulfur loading of 6.40 mg cm−2, the cell delivers an initial discharge capacity of 1162.3 mAh g−1 and maintains good cycling stability.

Birnessite manganese oxide nanosheets assembled on Ni foam as high-performance pseudocapacitor electrodes: Electrochemical oxidation driven porous honeycomb architecture formation

It has not been considered in the reported literatures that the current or the cyclic number of galvanostatic charge-discharge process controls the morphology growth of manganese oxide materials. Here, standing birnessite nanosheets assembled porous honeycomb architecture is in situ formed on Ni foam by electrochemical oxidation of hydrothermally synthesized Mn3O4 nanospheres electrodes via a electrochemical cycling technique. The birnessite morphology much depends on the conditions of the electrochemical cycling. By tuning the current and cycle number, Mn3O4 nanospheres are converted to birnessite with optimal morphology, while a high pseudocapacitive performance is achieved. The optimized birnessite electrodes exhibit a high level of specific capacitance (377 F g−1 at 1 A g−1), a superior rate capability (227 F g−1 at 30 A g−1) and a good cycling stability (75% retention after 4000 cycles). This work provides useful strategies for developing high-performance manganese oxide electrodes.

Fuzzy logic based multihop topology control routing protocol in wireless sensor networks

Reducing energy consumption has been a recent focus of wireless sensor network as it directly affects network lifetime. Geographical adaptive fidelity (GAF) is one of the well-known topology management multihop location-based routing protocols. Its main objective is to turn-off unnecessary sensor nodes while maintaining uninterrupted connectivity between communicating sensors. It is proved to be able to extend the lifetime of self-configuring systems by exploiting redundancy to conserve energy while maintaining application fidelity. Traditional GAF introduces unreachable corners; also the symmetric property is at stake thus providing with less network utility. In this paper, we propose a fuzzy logic based geographic routing protocol named FGAF-HEX to achieve higher energy optimization. Further, we use a GAF based Honeycomb Architecture to replace the traditional square grid with the hexagonal virtual grid. Simulation and analysis results show significant improvement in proposed work over traditional GAF in terms of various parameters, i.e., network lifetime and network connectivity. Results show that FGAF-HEX provides a substantial improvement in terms of various metrics as compared to traditional GAF.

Three Dimensional Honeycomb Patterned Fibrinogen Based Nanofibers Induce Substantial Osteogenic Response of Mesenchymal Stem Cells

Stem cells therapy offers a viable alternative for treatment of bone disorders to the conventional bone grafting. However clinical therapies are still hindered by the insufficient knowledge on the conditions that maximize stem cells differentiation. Hereby, we introduce a novel 3D honeycomb architecture scaffold that strongly support osteogenic differentiation of human adipose derived mesenchymal stem cells (ADMSCs). The scaffold is based on electrospun hybrid nanofibers consisting of poly (L-lactide ε-caprolactone) and fibrinogen (PLCL/FBG). Classical fibers orientations, random or aligned were also produced and studied for comparison. The overall morphology of ADMSC’s generally followed the nanofibers orientation and dimensionality developing regular focal adhesions and direction-dependent actin cytoskeleton bundles. However, there was an initial tendency for cells rounding on honeycomb scaffolds before ADMSCs formed a distinct bridging network. This specific cells organization appeared to have significant impact on the differentiation potential of ADMSCs towards osteogenic lineage, as indicated by the alkaline phosphatase production, calcium deposition and specific genes expression. Collectively, it was observed synergistic effect of nanofibers with honeycomb architecture on the behavior of ADMSCs entering osteogenic path of differentiation which outlines the potential benefits from insertion of such bioinspired geometrical cues within scaffolds for bone tissue engineering.

A Honeycomb-like Co@N-C Composite for Ultrahigh Sulfur Loading Li-S Batteries.

Because of the high theoretical capacity of 1675 mAh g-1 and high energy density of 2600 Wh kg-1, respectively, lithium-sulfur batteries are attracting intense interest. However, it remains an enormous challenge to realize high utilizations and loadings of sulfur in cathodes for the practical applications of Li-S batteries. Herein, we design a quasi-2D Co@N-C composite with honeycomb architecture as a multifunctional sulfur host via a simple sacrificial templates method. The cellular flake with large surface area and honeycomb architecture can encapsulate much more sulfur, leading to high sulfur content (HSC) composites, and by stacking these HSC flakes, a high sulfur loading (HSL) electrode can be realized due to their high layer bulk density. Compared to our previous work in multifunctional Co-N-C composites, the cellular Co@N-C composite displays a distinct enhancement in the sulfur content, sulfur loading, cycle stability, and rate performance. Benefiting from the cellular morphology, a composite with an HSC of 93.6 wt % and an electrode with an HSL of 7.5 mg cm-2 can be obtained simultaneously, which exhibited excellent rate performance up to 10 C (3.6 mg cm-2) and great cycling stability.

3D inkjet printing of tablets exploiting bespoke complex geometries for controlled and tuneable drug release

A hot melt 3D inkjet printing method with the potential to manufacture formulations in complex and adaptable geometries for the controlled loading and release of medicines is presented. This first use of a precisely controlled solvent free inkjet printing to produce drug loaded solid dosage forms is demonstrated using a naturally derived FDA approved material (beeswax) as the drug carrier and fenofibrate as the drug. Tablets with bespoke geometries (honeycomb architecture) were fabricated. The honeycomb architecture was modified by control of the honeycomb cell size, and hence surface area to enable control of drug release profiles without the need to alter the formulation. Analysis of the formed tablets showed the drug to be evenly distributed within the beeswax at the bulk scale with evidence of some localization at the micron scale. An analytical model utilizing a Fickian description of diffusion was developed to allow the prediction of drug release. A comparison of experimental and predicted drug release data revealed that in addition to surface area, other factors such as the cell diameter in the case of the honeycomb geometry and material wettability must be considered in practical dosage form design. This information when combined with the range of achievable geometries could allow the bespoke production of optimized personalised medicines for a variety of delivery vehicles in addition to tablets, such as medical devices for example.

Formation of g-C3N4@Ni(OH)2 Honeycomb Nanostructure and Asymmetric Supercapacitor with High Energy and Power Density.

Nickel hydroxide (Ni(OH)2) has been regarded as a potential next-generation electrode material for supercapacitor owing to its attractive high theoretical capacitance. However, practical application of Ni(OH)2 is hindered by its lower cycling life. To overcome the inherent defects, herein we demonstrate a unique interconnected honeycomb structure of g-C3N4 and Ni(OH)2 synthesized by an environmentally friendly one-step method. In this work, g-C3N4 has excellent chemical stability and supports a perpendicular charge-transporting direction in charge-discharge process, facilitating electron transportation along that direction. The as-prepared composite exhibits higher specific capacities (1768.7 F g-1 at 7 A g-1 and 2667 F g-1 at 3 mV s-1, respectively) compared to Ni(OH)2 aggregations (968.9 F g-1 at 7 A g-1) and g-C3N4 (416.5 F g-1 at 7 A g-1), as well as better cycling performance (∼84% retentions after 4000 cycles). As asymmetric supercapacitor, g-C3N4@Ni(OH)2//graphene exhibits high capacitance (51 F g-1) and long cycle life (72% retentions after 8000 cycles). Moreover, high energy density of 43.1 Wh kg-1 and power density of 9126 W kg-1 has been achieved. This attractive performance reveals that g-C3N4@Ni(OH)2 with honeycomb architecture could find potential application as an electrode material for high-performance supercapacitors.