Fabrication and mechanical properties of Al2O3–TiC ceramic composites synergistically reinforced with multi-walled carbon nanotubes and graphene nanoplates

In this study, Al₂O₃–TiC composites synergistically reinforced with multi-walled carbon nanotubes (MWCNTs) and graphene nanoplates (GNPs) were prepared via spark plasma sintering (SPS). The effects of the MWCNT and GNP contents on the phase composition, mechanical properties, fracture mode, and toughening mechanism of the composites were systematically investigated. The experimental results indicated that the composite grains became more refined with the addition of MWCNTs and GNPs. The nanocomposites presented high compactness and excellent mechanical properties. The composite with 0.8 wt% MWCNTs and 0.2 wt% GNPs presented the best properties of all analysed specimens, and its relative density, hardness, and fracture toughness were 97.3%, 18.38 ± 0.6 GPa, and 9.40 ± 1.6 MPa m^1/2, respectively. The crack deflection, bridging, branching, and drawing effects of MWCNTs and GNPs were the main toughening mechanisms of Al₂O₃–TiC composites synergistically reinforced with MWCNTs and GNPs.     

Facile synthesis of ultrathin magnetic iron oxide nanoplates by Schikorr reaction

In this work, a very facile one-pot hydrothermal synthesis approach has been developed for the preparation of ultrathin magnetite nanoplates. The hydrothermal procedure was performed by aging ferrous hydroxide under anaerobic conditions, which is known as Schikorr reaction. Ethylene glycol (EG), which was introduced to the reaction as another solvent, played a critical role in the formation process of these nanoplates. Typically, hexagonal Fe₃O₄ nanoplates with a thickness of 10 to 15 nm and a side length of 150 to 200 nm have been synthesized with EG/H₂O = 1:1 in experiments. Our data suggest that the thickness of Fe₃O₄ nanoplates decreases, and the shape of the nanoplate becomes more irregular when the concentration of EG increases. The as-prepared Fe₃O₄ nanoplates were highly crystallized single crystals and exhibited large coercivity and specific absorption rate coefficient.     

Microwave-assisted green synthesis of MnO2 nanoplates with environmental catalytic activity

In this paper, MnO₂ nanoplates were synthesized in aqueous solution under the microwave irradiation, without using any templates, catalysts, and organic reagents. The as-prepared MnO₂ nanoplates were systematically characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), high-resolution TEM (HRTEM), Fourier transform infrared (FT-IR) spectroscopy, differential scanning calorimetry (DSC) and thermo-gravimetric (TG) analysis, and nitrogen sorption measurements. Microwave irradiation could produce MnO₂ with uniform size and well-defined shape as well as high crystallinity. On the basis of experimental results, a possible formation mechanism of MnO₂ nanoplates was proposed. Furthermore, the resulting MnO₂ nanoplates were found to exhibit remarkable environmental catalytic performance in degradation of Rhodamine B (RhB) in aqueous solution, indicating these MnO₂ nanoplates is very promising for wastewater treatment.     

Pd纳米盘的光热辅助合成及其对乙醇的电催化氧化

以氯化钯(Pd Cl2)为金属前驱体,乙醇为还原剂,十六烷基三甲基溴化铵(CTAB)为稳定剂和导向剂,利用普通市售白炽灯产生的光热作用,辅助合成Pd纳米盘材料。用XRD、TEM、选区电子衍射(SAED)和UV等技术对合成产物进行表征,考察了CTAB用量对纳米Pd微观形貌和尺寸的影响,并通过循环伏安法研究了纳米Pd修饰玻碳电极对乙醇的电催化氧化活性。结果表明,通过改变Pd Cl2和CTAB的摩尔比,可以调控纳米Pd的微观形貌和尺寸;当Pd Cl2与CTAB的摩尔比为1:80,可见光辐照6 h时,得到的Pd纳米盘呈多边形貌,平均粒径为46 nm,对乙醇有较好的电催化活性和抗中毒能力。     

单晶多孔ZnO制备及对室内空气污染物的气敏性能的研究

通过使用对液相法合成的前驱体进行煅烧的方法成功的制备了具有单晶多孔结构的Zn O纳米片。通过X射线衍射仪(XRD)、环境扫描电子显微镜(FESEM)、高分辨透射电子显微镜(TEM)对单晶多孔Zn O纳米片进行了结构以及形貌的表征和分析。以其为敏感膜,制作气体传感器,对室内空气污染物,包括苯和甲醛,进行检测。结果显示单晶多孔Zn O纳米片对苯和甲醛都有着良好的响应,且响应和恢复时间都非常迅速。对敏感机理以及材料的结构对响应时间的影响也进行了较深入的探讨。     

Aniline- and N,N-dimethylformamide-assisted processing route for graphite nanoplates: intercalation and exfoliation pathway

Aniline-intercalated graphite nanoplates (AGNPs) were synthesized directly from graphite via an intercalation and exfoliation pathway using aniline as the intercalating agent and N,N-dimethylformamide (DMF) as the exfoliating agent. Thus, the obtained AGNPs were dispersible in various organic solvents like ethanol, isopropanol, chloroform, and benzene. This process is convenient, readily scalable and eco-friendly. We found that π-π interactions and the charge transfer complex formation between aniline and graphite nanoplates (GNPs) are responsible for the dispersion of AGNPs in organic solvents. The formation of AGNPs was confirmed by transmission electron microscopy (TEM), high-resolution TEM (HRTEM), selected area electron diffraction (SAED), X-ray diffraction (XRD), X-ray photoelectron (XPS), Raman and UV-Visible spectroscopic measurements.     

One‐Step Hydrothermal Synthesis of 2D Hexagonal Nanoplates of α‐Fe2O3/Graphene Composites with Enhanced Photocatalytic Activity

There has been significant progress in the field of semiconductor photocatalysis, but it is still a challenge to fabricate low‐cost and high‐activity photocatalysts because of safety issues and non‐secondary pollution to the environment. Here, 2D hexagonal nanoplates of α‐Fe₂O₃/graphene composites with relatively good distribution are synthesized for the first time using a simple, one‐step, template‐free, hydrothermal method that achieves the effective reduction of the graphene oxide (GO) to graphene and intimate and large contact interfaces of the α‐Fe₂O₃ nanoplates with graphene. The α‐Fe₂O₃/graphene composites showed significantly enhancement in the photocatalytic activity compared with the pure α‐Fe₂O₃ nanoplates. At an optimal ratio of 5 wt% graphene, 98% of Rhodamine (RhB) is decomposed with 20 min of irradiation, and the rate constant of the composites is almost four times higher than that of pure α‐Fe₂O₃ nanoplates. The decisive factors in improving the photocatalytic performance are the intimate and large contact interfaces between 2D hexagonal α‐Fe₂O₃ nanoplates and graphene, in addition to the high electron withdrawing/storing ability and the highconductivity of reduced graphene oxide (RGO) formed during the hydrothermal reaction. The effective charge transfer from α‐Fe₂O₃ nanoplates to graphene sheets is demonstrated by the significant weakening of photoluminescence in α‐Fe₂O₃/graphene composites.