Guolin Hou

“Protrusions” or “holes” in graphene: which is the better choice for sodium ion storage?

The main challenge associated with sodium-ion battery (SIB) anodes is a search for novel candidate materials with high capacity and excellent rate capability. The most commonly used and effective route for graphene-based anode design is the introduction of in-plane “hole” defects via nitrogen-doping; this creates a spacious reservoir for storing more energy. Inspired by mountains in nature, herein, we propose another way – the introduction of blistering in graphene instead of making “holes”; this facilitates adsorbing/inserting more Na+ ions. In order to properly answer the key question: ““protrusions” or “holes” in graphene, which is better for sodium ion storage?”, two types of anode materials with a similar doping level were designed: a phosphorus-doped graphene (GP, with protrusions) and a nitrogen-doped graphene (GN, with holes). As compared with GN, the GP anode perfectly satisfies all the desired criteria: it reveals an ultrahigh capacity (374 mA h g−1 after 120 cycles at 25 mA g−1) comparable to the best graphite anodes in a standard Li-ion battery (∼372 mA h g−1), and exhibits an excellent rate capability (210 mA h g−1 at 500 mA g−1). In situ transmission electron microscopy (TEM) experiments and density functional theory (DFT) calculations were utilized to uncover the origin of the enhanced electrochemical activity of “protrusions” compared to “holes” in SIBs, down to the atomic scale. The introduction of protrusions through P-doping into graphene is envisaged to be a novel effective way to enhance the capacity and rate performance of SIBs.

Dopant-Controlled Morphology Evolution of WO3 Polyhedra Synthesized by RF Thermal Plasma and Their Sensing Properties

In this paper, a simple way is developed for the synthesis of Cr-doped WO3 polyhedra controlled by tailoring intrinsic thermodynamic properties in RF thermal plasma. Scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy are used to characterize the detail structures and surface/near-surface chemical compositions of the as-prepared products. Kinetic factors showed little effects on the equilibrium morphology of Cr-doped WO3 polyhedra, while equilibrium morphologies of WO3 polyhedra can be controlled by the thermodynamic factor (Cr doping). Set crystal growth habits of pure WO3 as an initial condition, coeffects of distortions introduced by Cr into the WO3 matrix, and a chromate layer on the crystal surface could reduce the growth rates along [001], [010], and [100] directions. The morphology evolution was turning out as the following order with increasing Cr dopants: octahedron-truncated octahedron-cuboid. 2.5 at. % Cr-doped WO3 polyhedra exhibit the highest sensing response due to coeffects of exposed crystal facets, activation energy, catalytic effects of Cr, and particle size on the surface reaction and electron transport units. By simply decorating Au on Cr-doped WO3 polyhedra, the sensing responses, detection limit, and response-recovery properties were significantly improved.

Synthesis of uniform α-Si3N4 nanospheres by RF induction thermal plasma and their application in high thermal conductive nanocomposites.

In this paper, single-crystalline α-Si3N4 nanospheres with uniform size of ∼50 nm are successfully synthesized by using a radio frequency (RF) thermal plasma system in a one-step and continuous way. All Si3N4 nanoparticles present nearly perfect spherical shape with a narrow size distribution, and the diameter is well-controlled by changing the feeding rate. Compact Si3N4/PR (PR = phenolic resin) composites with high thermal conductivity, excellent temperature stability, low dielectric loss tangent, and enhanced breakdown strength are obtained by incorporating the as-synthesized Si3N4 nanospheres. These enhanced properties are the results of good compatibility and strong interfacial adhesion between compact Si3N4 nanospheres and polymer matrix, as large amount of Si3N4 nanospheres can uniformly disperse in the polymer matrix and form thermal conductive networks for diffusion of heat flow.

Thermal stability of phases in a NiCoCrAlY coating alloy

[Liang, J. J.; Wei, H.; Hou, G. C.; Zheng, Q.; Sun, X. F.; Guan, H. R.; Hu, Z. Q.] Chinese Acad Sci, Inst Met Res, Superalloys Div, Shenyang 110016, Peoples R China. [Liang, J. J.] Chinese Acad Sci, Grad Sch, Beijing 100039, Peoples R China.;Wei, H (reprint author), Chinese Acad Sci, Inst Met Res, Superalloys Div, Shenyang 110016, Peoples R China;hwei@imr.ac.cn

Well dispersed silicon nanospheres synthesized by RF thermal plasma treatment and their high thermal conductivity and dielectric constant in polymer nanocomposites

In this paper, well dispersed Si nanospheres (Si-NSs) were successfully synthesized via a simple and efficient method by using radio-frequency (RF) thermal plasma treatment. Structures and morphologies of the prepared samples were characterized by various techniques, including XRD, EDX, FESEM, HRTEM, SAED, BET and Raman spectroscopy. It is found that the obtained Si-NSs present uniform spherical shape and smooth surface. The effects of experimental parameters (including quenching gas and length of reaction path) on morphology and size distribution of Si particles were investigated. The growth mechanism of Si nanoparticles in the thermal plasma was discussed. Si-NS/phenolic resin (PR) composites were fabricated and their performances including thermal stability, thermal conductivity, and dielectric properties were measured. It indicates the composites exhibit high thermal conductivity (6.2 W m−1 K−1) and dielectric constants of 106 at 100 Hz, which implies they are applicable for energy storage-capacitors. The high thermal conductivity and dielectric constant can be attributed to their uniform spherical shape and smooth surface, which enable them to disperse uniformly in the polymer matrix.

Scalable synthesis of highly dispersed silicon nanospheres by RF thermal plasma and their use as anode materials for high-performance Li-ion batteries

Si nanospheres (SiNSs) have been synthesized via a simple, continuous and one-step way by using a radio frequency (RF) thermal plasma system on a large-scale. The synthesized SiNSs display a perfect spherical shape with a smooth surface and good dispersity. By a simple ball-milling post-processing, silicon nanosphere/porous carbon (SiNS/PC) composites with synthesized Si nanospheres uniformly dispersed in the carbon matrix have been prepared, and the composite particles have a core/shell structure (i.e., every Si nanosphere is well covered by the complete porous carbon shell). As anodes for Li-ion batteries, the prepared composite materials could maintain microstructural stability after cycles and exhibit remarkably improved electrochemical performance with large storage capacity, super cycling stability and high rate capability. These desirable electrochemical performances are attributed to the unique structure of the SiNS/PC composite, which has a high capacity Si core with a nanosphere morphology to alleviate the inner volume changes, and a porous shell acting as a conductive matrix to enhance the conductivity, accommodate the silicon volume expansion, and facilitate lithium-ion transportation during charging–discharging.

Gold–tin co-sensitized ZnO layered porous nanocrystals: enhanced responses and anti-humidity

High responses and good selectivity are key sensing properties of metal oxide (MOX) gas sensors. However, it is still a major challenge for a single MOX gas sensor to achieve both of them. Specially, the research in the field of high performance gas sensors has been hindered by negative effects of the typical interference, relative humidity (RH). In this paper, we report the successful preparation of gold–tin co-sensitized ZnO layered porous nanocrystals (Au–5Sn–ZLPCs) via a sequential solvothermal reaction and deposition-reduction method. Based on Sn dopants sensitized ZLPCs, the introduction of Au decoration can act as a secondary sensitized element on the crystal surfaces of ZnO. The special synergy between noble metals and oxides can introduce additional catalytic effects to further improve sensing properties. As a result of Au–Sn co-sensitization, sensing properties of sensors towards reducing VOC gas were significantly enhanced, while those towards oxidizing ozone gas were different to each other. Besides the typical sensing properties including responses, operating temperature, response & recovery properties, etc., Au–Sn co-sensitized samples significantly reduced negative effects of RH on responses to both reducing and oxidizing gases (good anti-humidity).