Xiang Zhang

Bio: Xiang Zhang is an academic researcher from Tianjin University. The author has contributed to research in topics: Graphene & Ultimate tensile strength. The author has an hindex of 15, co-authored 29 publications receiving 1204 citations. Previous affiliations of Xiang Zhang include National University of Singapore.

2D Space-Confined Synthesis of Few-Layer MoS2 Anchored on Carbon Nanosheet for Lithium-Ion Battery Anode.

Abstract: A facile and scalable 2D spatial confinement strategy is developed for in situ synthesizing highly crystalline MoS2 nanosheets with few layers (≤5 layers) anchored on 3D porous carbon nanosheet networks (3D FL-MoS2@PCNNs) as lithium-ion battery anode. During the synthesis, 3D self-assembly of cubic NaCl particles is adopted to not only serve as a template to direct the growth of 3D porous carbon nanosheet networks, but also create a 2D-confined space to achieve the construction of few-layer MoS2 nanosheets robustly lain on the surface of carbon nanosheet walls. In the resulting 3D architecture, the intimate contact between the surfaces of MoS2 and carbon nanosheets can effectively avoid the aggregation and restacking of MoS2 as well as remarkably enhance the structural integrity of the electrode, while the conductive matrix of 3D porous carbon nanosheet networks can ensure fast transport of both electrons and ions in the whole electrode. As a result, this unique 3D architecture manifests an outstanding lo...

Fabrication of in-situ grown graphene reinforced Cu matrix composites

Abstract: Graphene/Cu composites were fabricated through a graphene in-situ grown approach, which involved ball-milling of Cu powders with PMMA as solid carbon source, in-situ growth of graphene on flaky Cu powders and vacuum hot-press sintering. SEM and TEM characterization results indicated that graphene in-situ grown on Cu powders guaranteed a homogeneous dispersion and a good combination between graphene and Cu matrix, as well as the intact structure of graphene, which was beneficial to its strengthening effect. The yield strength of 244 MPa and tensile strength of 274 MPa were achieved in the composite with 0.95 wt.% graphene, which were separately 177% and 27.4% enhancement over pure Cu. Strengthening effect of in-situ grown graphene in the matrix was contributed to load transfer and dislocation strengthening.

A powder-metallurgy-based strategy toward three-dimensional graphene-like network for reinforcing copper matrix composites

Abstract: Three-dimensional graphene network is a promising structure for improving both the mechanical properties and functional capabilities of reinforced polymer and ceramic matrix composites. However, direct application in a metal matrix remains difficult due to the reason that wetting is usually unfavorable in the carbon/metal system. Here we report a powder-metallurgy based strategy to construct a three-dimensional continuous graphene network architecture in a copper matrix through thermal-stress-induced welding between graphene-like nanosheets grown on the surface of copper powders. The interpenetrating structural feature of the as-obtained composites not only promotes the interfacial shear stress to a high level and thus results in significantly enhanced load transfer strengthening and crack-bridging toughening simultaneously, but also constructs additional three-dimensional hyperchannels for electrical and thermal conductivity. Our approach offers a general way for manufacturing metal matrix composites with high overall performance. Graphene networks have been used to reinforce polymer and ceramic composites, but connecting graphene into a three dimensional network in a metal matrix is challenging. Here the authors use a powder-metallurgy-based strategy to construct a three-dimensional graphene network reinforced copper matrix composite.

Achieving high strength and high ductility in metal matrix composites reinforced with a discontinuous three-dimensional graphene-like network

Abstract: Graphene or graphene-like nanosheets have been emerging as an attractive reinforcement for composites due to their unique mechanical and electrical properties as well as their fascinating two-dimensional structure. It is a great challenge to efficiently and homogeneously disperse them within a metal matrix for achieving metal matrix composites with excellent mechanical and physical performance. In this work, we have developed an innovative in situ processing strategy for the fabrication of metal matrix composites reinforced with a discontinuous 3D graphene-like network (3D GN). The processing route involves the in situ synthesis of the encapsulation structure of 3D GN powders tightly anchored with Cu nanoparticles (NPs) (3D GN@Cu) to ensure mixing at the molecular level between graphene-like nanosheets and metal, coating of Cu on the 3D GN@Cu (3D GN@Cu@Cu), and consolidation of the 3D GN@Cu@Cu powders. This process can produce GN/Cu composites on a large scale, in which the in situ synthesized 3D GN not only maintains the perfect 3D network structure within the composites, but also has robust interfacial bonding with the metal matrix. As a consequence, the as-obtained 3D GN/Cu composites exhibit exceptionally high strength and superior ductility (the uniform and total elongation to failure of the composite are even much higher than the unreinforced Cu matrix). To the best of our knowledge, this work is the first report validating that a discontinuous 3D graphene-like network can simultaneously remarkably enhance the strength and ductility of the metal matrix.

Fast parallel algorithms for short-range molecular dynamics

Abstract: Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

Stabilizing the MXenes by Carbon Nanoplating for Developing Hierarchical Nanohybrids with Efficient Lithium Storage and Hydrogen Evolution Capability.

Abstract: The MXenes combining hydrophilic surface, metallic conductivity and rich surface chemistries represent a new family of 2D materials with widespread applications. However, their poor oxygen resistance causes a great loss of electronic properties and surface reactivity, which significantly inhibits the fabrication, the understanding of the chemical nature and full exploitation of the potential of MXene-based materials. Herein we report a facile carbon nanoplating strategy for efficiently stabilizing the MXenes against structural degradation caused by spontaneous oxidation, which provides a material platform for developing MXene-based materials with attractive structure and properties. Hierarchical MoS2 /Ti3 C2 -MXene@C nanohybrids with excellent structural stability, electrical properties and strong interfacial coupling are fabricated by assembling carbon coated few-layered MoS2 nanoplates on carbon-stabilized Ti3 C2 MXene, exhibiting exceptional performance for Li storage and hydrogen evolution reaction (HER). Remarkably, ultra-long cycle life of 3000 cycles with high capacities but extremely slow capacity loss of 0.0016% per cycle is achieved for Li storage at a very high rate of 20 A g-1 . They are also highly active HER electrocatalyst with very positive onset potential, low overpotential and long-term stability in acidic solution. Superb properties highlight the great promise of MXene-based materials in cornerstone applications of energy storage and conversion.

2D Monolayer MoS2–Carbon Interoverlapped Superstructure: Engineering Ideal Atomic Interface for Lithium Ion Storage

Abstract: A novel strategy for the controlled synthesis of 2D MoS2/C hybrid nanosheets consisting of the alternative layer-by-layer interoverlapped single-layer MoS2 and mesoporous carbon (m-C) is demonstrated. Such special hybrid nanosheets with a maximized MoS2 /m-C interface contact show very good performance for lithium-ion batteries in terms of high reversible capacity, excellent rate capability, and outstanding cycling stability.

Boosted Electrocatalytic N2 Reduction to NH3 by Defect-Rich MoS2 Nanoflower

Abstract: The industrial artificial fixation of atmospheric N-2 to NH3 is carried out using the Haber-Bosch process that is not only energy-intensive but emits large amounts of greenhouse gas. Electrochemical reduction offers an environmentally benign and sustainable alternative for NH3 synthesis. Although Mo-dependent nitrogenases and molecular complexes effectively catalyze the N-2 fixation at ambient conditions, the development of a Mo-based nanocatalyst for highly performance electrochemical N-2 fixation still remains a key challenge. Here, greatly boosted electrocatalytic N-2 reduction to NH3 with excellent selectivity by defect-rich MoS2 nanoflowers is reported. In 0.1 m Na2SO4, this catalyst attains a high Faradic efficiency of 8.34% and a high NH3 yield of 29.28 mu g h(-1) mg(cat.)(-1) at (-)0.40 V versus reversible hydrogen electrode, much larger than those of defect-free counterpart (2.18% and 13.41 mu g h(-1) mg(cat.)(-1)), with strong electrochemical stability. Density functional theory calculations show that the potential determining step has a lower energy barrier (0.60 eV) for defect-rich catalyst than that of defect-free one (0.68 eV).