Zhibing Fu

Excellent Electromagnetic Absorption Capability of Ni/Carbon Based Conductive and Magnetic Foams Synthesized via a Green One Pot Route

Electromagnetic microwave absorption materials have attracted a great deal of attention. Foams for the low density and tunable porosity are considered as ideal microwave absorbents, while with the requirement of improving their inherent electromagnetic properties. In this manuscript, an innovative, easy, and green method was presented to synthesize an electromagnetic functionalized Ni/carbon foam, in which the formation of Ni nanoparticles and carbon occurred simultaneously from an affordable alginate/Ni(2+) foam precursor. The resultant Ni/carbon foam had a low density (0.1 g/cm(-3)) and high Ni nanoparticles loading (42 wt %). These Ni nanoparticles with a diameter of about 50-100 nm were highly crystallized and evenly embedded in porous graphite carbon without aggregation. Also, the resultant foam had a high surface area (451 m(2) g(-1)) and porosity and showed a moderate conductivity (6 S/m) and significant magnetism. Due to these special characteristics, the Ni/carbon foam exhibited greatly enhanced microwave absorption ability. Only with 10 wt % of functional fillers being used in the test template, the Ni/carbon foam based composite could reach an effective absorption bandwidth (below -10 dB) of 4.5 GHz and the minimum reflection value of -45 dB at 13.3 GHz with a thickness of 2 mm, while the traditional carbon foam and nano-Ni powder both showed very weak microwave absorption (the minimum reflection value < -10 dB). This foam was demonstrated to be a lightweight, high performance, and low filler loading microwave absorbing material. Furthermore, the detailed absorption mechanism of the foam was investigated. The result showed that the derived strong dielectric loss, including conductivity loss, interface polarization loss, weak magnetic loss, and naoporosity, contributes a great electromagnetic absorption.

Three-Dimensional Macroassembly of Sandwich-Like, Hierarchical, Porous Carbon/Graphene Nanosheets towards Ultralight, Superhigh Surface Area, Multifunctional Aerogels.

A new, ultralight, superhigh surface area, multifunctional aerogel, which is macroassembled from sandwich-like, hierarchical, porous carbon/graphene nanosheets, is described. The multifunctional aerogel was characterized by means of XRD, SEM, TEM, Raman spectroscopy, and UV/Vis absorption spectroscopy. The multifunctional aerogel had an ultralow density of 8 mg cm(-3) and a superhigh surface area of 2650 m(2)  g(-1) . The multifunctional aerogel was thermal stability and compressible. Meanwhile, the multifunctional aerogel exhibited high capacity for the adsorption of oils and organic solvents, unexpectedly high hydrogen adsorption and good electrochemical performance.

Biomass-Based Mechanically Strong and Electrically Conductive Polymer Aerogels and Their Application for Supercapacitors

A novel biomass-based mechanically strong and electrically conductive polymer aerogel was fabricated from aniline and biodegradable pectin. The strong hydrogen bonding interactions between polyaniline (PANI) and pectin resulted in a defined structure and enhanced properties of the aerogel. All the resultant aerogels exhibited self-surppoted 3D nanoporous network structures with high surface areas (207-331m(2)/g) and hierarchical pores. The results from electrical conductivity measurements and compressive tests revealed that these aerogels also had favorable conductivities (0.002-0.1 S/m) and good compressive modulus (1.2-1.4 MPa). The aerogel further used as electrode for supercapacitors showed enhanced capacitive performance (184 F/g at 0.5 A/g). Over 74% of the initial capacitance was maintained after repeating 1000 cycles of the cylic voltammetry test, while the capacitance retention of PANI was only 57%. The improved electrochemical performance may be attributed to the combinative properties of good electrical conductivity, BET surface areas, and stable nanoporous structure of the aerogel. Thus, this aerogel shows great potential as electrode materials for supercapacitors.

A solution-phase synthesis method to prepare Pd-doped carbon aerogels for hydrogen storage

A solution-phase synthesis method was studied to prepare Pd-doped carbon aerogels (Pd/CAs) with different contents. The physical properties of the pristine CAs and Pd/CAs were systematically characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, and N2 adsorption measurements. We concluded that increasing Pd content produced an increase of the metal particle size and decrease of the surface area of the CAs. The effects of different amounts of palladium loading on the hydrogen uptake capacities of CAs have been investigated. The results show that Pd doping has a negative effect on hydrogen uptake capacity at 77 K. At 298 K, hydrogen uptake capacity depends on Pd content and particle size in the low pressure region ( 10 bar), the pore volume controls hydrogen uptake capacity.

Adsorption sensitivity of graphane decorated with B, N, S, and Al towards HCN: a first-principles study

The geometric structure, adsorption energy, electronic structure, and magnetic properties of hydrogenated graphene (graphane) with the adsorption of a HCN molecule were investigated by first-principles calculations. Compared with graphane, the adsorption of HCN on H-vacancy defected graphane (VHG) exhibited higher stability, which implied that the H-vacancy improved the sensitivity of graphane. However, the small adsorption energies and large bond distance indicated that the weak adsorption of a HCN molecule on the graphane and VHG substrates was due to physisorption. By introducing dopants (B, N, S, and Al), the activity of graphane was significantly improved. The adsorption of HCN changed to chemisorption on the graphane with dopants. Meanwhile, the opening of band gaps by HCN adsorption can be used as an electronic signal to detect HCN gas. Interestingly, the spin polarized density of states (PDOS) results suggested that the adsorption of HCN on VHG and S-doped VHG exhibited magnetic character and half-metallicity behavior. These results could provide useful information to design gas sensors for HCN or spintronic devices based on graphane.

Adsorption of H2S on graphane decorated with Fe, Co and Cu: a DFT study

Herein, density functional theory (DFT) calculations were performed to investigate the adsorption of a H2S molecule on the surface of hydrogenated graphene (graphane). In our results, we found that the appearance of an H-vacancy significantly improved the reactivity of graphane due to the unpaired electrons of the vacancy site. However, small adsorption energy and low charge transfer indicated that the interaction between the H2S molecule and the pure H-vacancy-defected graphane occurred via physisorption. By introducing transition-metal dopants (Fe, Co, and Cu), the adsorption process of the H2S molecule changed to chemisorption. Furthermore, the adsorption of H2S induced a decrease in the band gaps, which could be seen as signal for the detection of H2S gas.

Capacitive deionization of NaCl solutions with ambient pressure dried carbon aerogel microsphere electrodes

Carbon aerogel (CA) microspheres were pyrolyzed from resorcinol–formaldehyde (RF) organic aerogels, which were prepared by emulsion polymerization of resorcinol and formaldehyde using ambient drying technique. Structural and microstructural characteristics of CA microspheres were investigated by scanning electron microscopy (SEM), Raman spectroscopic techniques and nitrogen adsorption. The SEM images show that the resultant CA microspheres are all fine spherical without cracks. Results of Raman spectroscopy indicate that CA microspheres are mainly formed by amorphous carbon structure with a few graphite carbons. The surface area and porosity analysis prove that the CA microspheres have high specific surface area (910 m2 g−1), appropriate pore size distribution (PSD) (3–15 nm) and high ratio of mesoporosity (44%). The results of cyclic voltammetry indicate that the CA microspheres have ideal capacitive behavior, and the maximum specific capacitance values of 83 F g−1 was measured at a scan rate of 10 mV s−1 in 1 M NaCl. These parameters can significantly improve the desalination capacity for the carbon-based electrode materials in capacitive deionization (CDI). The performance of CDI is investigated by different solution concentrations (500–650 mg L−1) and applied voltages (0.8–1.4 V). With the optimum initial NaCl concentration of 500 mg L−1 and applied voltage of 1.2 V, the specific salt-adsorption capacity for CA microspheres was found to be 5.62 mg g−1. The electrosorption and electrodesorption procedures displayed the stability and regeneration of CA microsphere electrodes. This preliminary study demonstrated that the CA microsphere electrodes in CDI process can be considered to be an alternative candidate for desalination.

Optimized Synthesis of Carbon Aerogels via Ambient Pressure Drying Process as Electrode for Supercapacitors

Carbon aerogels were synthesized via ambient pressure drying process using resorcinolformaldehyde as precursor and P123 to strengthen their skeletons. CO2 activation technology was implemented to improve surface areas and adjust pore size distribution. The synthesis process was optimized, and the morphology, structure, adsorption properties and electrochemical behavior of different samples were characterized. The CO2-activated samples achieved a high specific capacitance of 129.2 F/g in 6 M KOH electrolytes at the current density of 1 mA/cm2 within the voltage range of 0-0.8 V. The optimized activation temperature and duration were determined to be 950 °C and 4 h, respectively.

Multi-Scale Modeling for Predicting the Stiffness and Strength of Hollow-Structured Metal Foams with Structural Hierarchy

This work was inspired by previous experiments which managed to establish an optimal template-dealloying route to prepare ultralow density metal foams. In this study, we propose a new analytical–numerical model of hollow-structured metal foams with structural hierarchy to predict its stiffness and strength. The two-level model comprises a main backbone and a secondary nanoporous structure. The main backbone is composed of hollow sphere-packing architecture, while the secondary one is constructed of a bicontinuous nanoporous network proposed to describe the nanoscale interactions in the shell. Firstly, two nanoporous models with different geometries are generated by Voronoi tessellation, then the scaling laws of the mechanical properties are determined as a function of relative density by finite volume simulation. Furthermore, the scaling laws are applied to identify the uniaxial compression behavior of metal foams. It is shown that the thickness and relative density highly influence the Young’s modulus and yield strength, and vacancy defect determines the foams being self-supported. The present study provides not only new insights into the mechanical behaviors of both nanoporous metals and metal foams, but also a practical guide for their fabrication and application.

Minimal surface designs for porous materials: from microstructures to mechanical properties

AbstractIn this work, we present four types of topological bicontinuous porous structures, namely Gyroid (G), Schwarz Diamond (D), Schwarz Primitive (P), and iWp (W), which are generated from mathematically defined triply periodic minimal surfaces. A systematic semi-theoretical investigation is performed to analyze the relations between the microstructures and the macroscopic mechanical behavior. Benefiting from the straightforward controllability on parameters, the scaling laws of the geometrical properties and mechanical properties are determined as functions of the relative density according to numerical analysis and computational simulation. An application to additive manufacturing accompanying with uniaxial compression testing is also performed, and the results show a highly agreement with the above scaling laws. Moreover, the simulation results indicate that the mechanical properties are highly dependent on topological architectures, which affect the deformation behavior of porous materials. It is shown that P topology has the highest stiffness and strength with stretching-dominated mode, while the rest exhibit a flexibly bending-dominated deformation behavior. The present study provides not only new insights into the structure–property relations of such topologies, but also a practical guide for their fabrication and application.