Hao-Bin Zhang

Tough Graphene−Polymer Microcellular Foams for Electromagnetic Interference Shielding

Functional polymethylmethacrylate (PMMA)/graphene nanocomposite microcellular foams were prepared by blending of PMMA with graphene sheets followed by foaming with subcritical CO(2) as an environmentally benign foaming agent. The addition of graphene sheets endows the insulating PMMA foams with high electrical conductivity and improved electromagnetic interference (EMI) shielding efficiency with microwave absorption as the dominant EMI shielding mechanism. Interestingly, because of the presence of the numerous microcellular cells, the graphene-PMMA foam exhibits greatly improved ductility and tensile toughness compared to its bulk counterpart. This work provides a promising methodology to fabricate tough and lightweight graphene-PMMA nanocomposite microcellular foams with superior electrical and EMI shielding properties by simultaneously combining the functionality and reinforcement of the graphene sheets and the toughening effect of the microcellular cells.

Functionalization and reduction of graphene oxide with p-phenylene diamine for electrically conductive and thermally stable polystyrene composites

A facile and efficient approach was developed to simultaneously functionalize and reduce graphene oxide (GO) with p-phenylene diamine (PPD) by simple refluxing. This was possible by the nucleophilic substitution reaction of epoxide groups of GO with amine groups of PPD aided by NH(3) solution. As a consequence, electrical conductivity of GO-PPD increased to 2.1 × 10(2) S/m, which was nearly 9 orders of magnitude higher than that of GO. Additionally, after the incorporation of GO-PPD in polystyrene (PS), the composites exhibited a sharp transition from electrically insulating to conducting behavior with a low percolation threshold of ~0.34 vol %, which was attributed to the improved dispersion and the reduction of GO-PPD. Thermal stability of the PS/GO-PPD composite was also ~8 °C higher than that of PS.

Hydrophobic, Flexible, and Lightweight MXene Foams for High‐Performance Electromagnetic‐Interference Shielding

Ultrathin, lightweight, and flexible electromagnetic-interference (EMI) shielding materials are urgently required to manage increasingly serious radiation pollution. 2D transition-metal carbides (MXenes) are considered promising alternatives to graphene for providing excellent EMI-shielding performance due to their outstanding metallic electrical conductivity. However, the hydrophilicity of MXene films may affect their stability and reliability when applied in moist or wet environments. Herein, for the first time, an efficient and facile approach is reported to fabricate freestanding, flexible, and hydrophobic MXene foam with reasonable strength by assembling MXene sheets into films followed by a hydrazine-induced foaming process. In striking contrast to well-known hydrophilic MXene materials, the MXene foams surprisingly exhibit hydrophobic surfaces and outstanding water resistance and durability. More interestingly, a much enhanced EMI-shielding effectiveness of ≈70 dB is achieved for the lightweight MXene foam as compared to its unfoamed film counterpart (53 dB) due to the highly efficient wave attenuation in the favorable porous structure. Therefore, the hydrophobic, flexible, and lightweight MXene foam with an excellent EMI-shielding performance is highly promising for applications in aerospace and portable and wearable smart electronics.

Thermally conductive and electrically insulating epoxy nanocomposites with silica-coated graphene

Graphene oxide was reduced and functionalized simultaneously by reacting with 3-aminopropyltriethoxysilane (APTES) without the use of conventional reducing agents. Silica was subsequently formed in situ on APTES functionalized graphene (A-graphene) sheets by a sol–gel approach using tetraethyl orthosilicate as the precursor of silica. The covalently bonded APTES on A-graphene enhances the compatibility between A-graphene and silica nanoparticles. The silica-coated A-graphene (S-graphene) sheets were incorporated to improve the thermal conductivity of epoxy. The presence of silica nanoparticles not only enhances the interfacial interaction between S-graphene and the epoxy matrix, but also alleviates the modulus mismatch between the fillers and the matrix and thus benefits the interfacial thermal conductance. The thermal conductivity of the epoxy nanocomposite with 8 wt% S-graphene is improved by 72% in comparison with that of neat epoxy, while the electrically insulating feature of the nanocomposite is retained.

Highly Efficient High-Pressure Homogenization Approach for Scalable Production of High-Quality Graphene Sheets and Sandwich-Structured α-Fe2O3/Graphene Hybrids for High-Performance Lithium-Ion Batteries

A highly efficient and continuous high-pressure homogenization (HPH) approach is developed for scalable production of graphene sheets and sandwich-structured α-Fe2O3/graphene hybrids by liquid-phase exfoliation of stage-1 FeCl3-based graphite intercalation compounds (GICs). The enlarged interlayer spacing of FeCl3-GICs facilitates their efficient exfoliation to produce high-quality graphene sheets. Moreover, sandwich-structured α-Fe2O3/few-layer graphene (FLG) hybrids are readily fabricated by thermally annealing the FeCl3 intercalated FLG sheets. As an anode material of Li-ion battery, α-Fe2O3/FLG hybrid shows a satisfactory long-term cycling performance with an excellent specific capacity of 1100.5 mA h g-1 after 350 cycles at 200 mA g-1. A high reversible capacity of 658.5 mA h g-1 is achieved after 200 cycles at 1 A g-1 and maintained without notable decay. The satisfactory cycling stability and the outstanding capability of α-Fe2O3/FLG hybrid are attributed to its unique sandwiched structure consisting of highly conducting FLG sheets and covalently anchored α-Fe2O3 particles. Therefore, the highly efficient and scalable preparation of high-quality graphene sheets along with the excellent electrochemical properties of α-Fe2O3/FLG hybrids makes the HPH approach promising for producing high-performance graphene-based energy storage materials.

Simultaneous functionalization and reduction of graphene oxide with polyetheramine and its electrically conductive epoxy nanocomposites

Simultaneous functionalization and reduction of graphene oxide (GO) is realized by refluxing of GO suspension with polyetheramine (D2000) followed by thermal treatment at 120 °C. Compared to GO, the D2000-treated GO (GO-D2000) becomes hydrophobic, thermally stable and highly conductive with an electrical conductivity of 11 S/m, which is almost 8 orders of magnitude higher than that of GO. Due to the high conductivity and improved dispersion of GO-D2000, its epoxy nanocomposites exhibit a sharp transition from electrically insulating to conducting with a low percolation threshold of 0.71 vol%. With 3.6 wt% GO-D2000, the glass transition temperature of the epoxy nanocomposite is 27 K higher than that of neat epoxy.

FeCl3 intercalated few-layer graphene for high lithium-ion storage performance

We report a facile and efficient approach to prepare graphene and FeCl3-intercalated few-layer graphene (FeCl3-FLG) with stage 1 FeCl3-graphite intercalation compounds (GICs) as a precursor by a non-oxidation process. The enlarged interlayer spacing by the intercalation of FeCl3 greatly weakens the interaction among graphite sheets and thus facilitates the exfoliation of FeCl3-GICs. By ultrasonic treatment, FeCl3-GICs are well exfoliated to graphene sheets (<2 nm) with a high yield of 100%, while the ultrasonication of pristine graphite is less efficient with a low yield (about 32%) of graphene sheets. By simply controlling the sonication time, FeCl3-FLG consisting of graphene sheets and sandwiched FeCl3 is also prepared, which exhibits a high capacity of 989 mA h g−1 after 50 cycles, fairly higher than that of the sonicated graphite (503 mA h g−1) and the theoretical value of graphite (372 mA h g−1). Furthermore, FeCl3-FLG still retains a reversible capacity as high as 539 mA h g−1 even at a current density of 1000 mA g−1. Therefore, the high reversible capacity, remarkable cycling stability and superior capability make FeCl3-FLG promising as anode materials for large-scale and high-capacity lithium ion batteries.

One-Pot Sintering Strategy for Efficient Fabrication of High-Performance and Multifunctional Graphene Foams

Macroscopic three-dimensional (3D) graphene foams (GFs) were fabricated efficiently by immediately sintering low-temperature exfoliated graphene powder under inert atmosphere at the temperature over 500 °C. The one-pot sintering process not only integrated two-dimensional (2D) graphene sheets into 3D GF, but also accelerated the structural integrity of graphene by inducing its deoxygenation and repairing the defects. More importantly, the whole process could be finished within hours, usually less than 12 h, and the resultant GFs with interconnected graphene framework as well as meso- and macroporous structure exhibited exceptional attenuating performance for high-frequency electromagnetic interference and adsorption capacities for organic pollutants. In comparison with conventional hydro/solvothermal, sol-gel chemistry, sol-freezing, and templating methods, our sintering strategy possesses more advantages in maneuverability, efficiency, and repeatability, benefiting for the mass production of high-performance and multifunctional GFs.

Multifunctional, Superelastic, and Lightweight MXene/Polyimide Aerogels

2D transition metal carbides and nitrides (MXenes) have gained extensive attention recently due to their versatile surface chemistry, layered structure, and intriguing properties. The assembly of MXene sheets into macroscopic architectures is an important approach to harness their extraordinary properties. However, it is difficult to construct a freestanding, mechanically flexible, and 3D framework of MXene sheets owing to their weak intersheet interactions. Herein, an interfacial enhancement strategy to construct multifunctional, superelastic, and lightweight 3D MXene architectures by bridging individual MXene sheets with polyimide macromolecules is developed. The resulting lightweight aerogel exhibits superelasticity with large reversible compressibility, excellent fatigue resistance (1000 cycles at 50% strain), 20% reversible stretchability, and high electrical conductivity of ≈4.0 S m-1 . The outstanding mechanical flexibility and electrical conductivity make the aerogel promising for damping, microwave absorption coating, and flexible strain sensor. More interestingly, an exceptional microwave absorption performance with a maximum reflection loss of -45.4 dB at 9.59 GHz and a wide effective absorption bandwidth of 5.1 GHz are achieved.

Highly Electrically Conductive Three-Dimensional Ti3C2Tx MXene/Reduced Graphene Oxide Hybrid Aerogels with Excellent Electromagnetic Interference Shielding Performances

Two-dimensional transition-metal carbides/carbonitrides (MXenes) with both superb electrical conductivity and hydrophilicity are promising for fabricating multifunctional nanomaterials and nanocomposites. However, the construction of three-dimensional (3D) and lightweight MXene macroscopic assemblies with excellent electrical conductivity and mechanical performances has not been realized due to the weak gelation capability of MXene sheets. Herein, we demonstrate an efficient approach for constructing highly conductive 3D Ti3C2T x porous architectures by graphene oxide assisted hydrothermal assembly followed by directional freezing and freeze-drying. The resultant hybrid aerogels exhibit aligned cellular microstructure, in which the graphene sheets serve as the inner skeleton, while the compactly attached Ti3C2T x sheets present as shells of the cell walls. The porous and highly conductive architecture (up to 1085 S m-1) is highly efficient in endowing epoxy nanocomposite with a high electrical conductivity of 695.9 S m-1 and an outstanding electromagnetic interference (EMI)-shielding effectiveness of more than 50 dB in the X-band at a low Ti3C2T x content of 0.74 vol %, which are the best results for polymer nanocomposites with similar loadings of MXene so far. The successful assembly methodology of 3D and porous architectures of Ti3C2T x would greatly widen the practical applications of MXenes in the fields of EMI shielding, supercapacitors, and sensors.