三维泡沫状结构生物质碳/MoS2复合材料的电化学储锂性能

以废弃油茶籽粕作为碳源,将MoS2负载于生物质碳上,再涂覆聚多巴胺盐酸盐构建复合型生物质碳/MoS2电极材料.研究不同MoS2含量复合电极材料的电化学储锂性能.SEM观察结果表明,该复合材料具有以MoS2作为夹层的三维泡沫状结构.XRD和HRTEM测试结果表明MoS2的层间距增大.XPS分析结果显示,活性材料中已形成M...     

In situ synthesis of Co3O4/graphene nanocomposite material for lithium-ion batteries and supercapacitors with high capacity and supercapacitance

Co₃O₄/graphene nanocomposite material was prepared by an in situ solution-based method under reflux conditions. In this reaction progress, Co²⁺ salts were converted to Co₃O₄ nanoparticles which were simultaneously inserted into the graphene layers, upon the reduction of graphite oxide to graphene. The prepared material consists of uniform Co₃O₄ nanoparticles (15-25 nm), which are well dispersed on the surfaces of graphene nanosheets. This has been confirmed through observations by field emission scanning electron microscopy, transmission electron microscopy and atomic force microscopy. The prepared composite material exhibits an initial reversible lithium storage capacity of 722 mAh g⁻¹ in lithium-ion cells and a specific supercapacitance of 478 F g⁻¹ in 2 M KOH electrolyte for supercapacitors, which were higher than that of the previously reported pure graphene nanosheets and Co₃O₄ nanoparticles. Co₃O₄/graphene nanocomposite material demonstrated an excellent electrochemical performance as an anode material for reversible lithium storage in lithium ion cells and as an electrode material in supercapacitors.     

微波原位制备作为锂离子电池电极材料的石墨烯/TiO2 纳米复合物

通过改造的家用微波炉,实现了原位高效制备石墨烯/TiO₂纳米复合物。结果表明：微波辅助法能够在商用锐钛矿型TiO₂纳米颗粒表面均匀制备石墨烯纳米片,通过SiO₂/Si的剧烈电晕放电,其制备时间仅需数分钟（最短3 min）。石墨烯纳米片的尺寸大约为50 nm且缺陷很少。TiO₂晶体结构仍为锐钛矿型,主要归功于极短的制备周期和较低的反应温度（600~700 ℃）。石墨烯具有优异的电导率,可以提升锂离子扩散速率、提高电子传输速率并降低接触电阻。在1 C（170 mA·g^-1）条件下石墨烯/TiO₂纳米复合物的电池放电比容量提高了2倍。与商业化锐钛矿型TiO₂纳米颗粒相比,在1 C到5 C的不同充放电倍率下,石墨烯/TiO₂纳米复合物的比容量差距显著扩大。     

Preparation of Fe2O3/graphene composite and its electrochemical performance as an anode material for lithium ion batteries

The micro-sized sphere Fe₂O₃ particles doped with graphene nanosheets were prepared by a facile hydrothermal method. The obtained Fe₂O₃/graphene composite as the anode material for lithium ion batteries showed a high discharge capacity of 660 mAh g⁻¹ during up to 100 cycles at the current density of 160 mA g⁻¹ and good rate capability. The excellent electrochemical performance of the composite can be attributed to that graphene served as dispersing medium to prevent Fe₂O₃ microparticles from agglomeration and provide an excellent electronic conduction pathway.     

Synthesis and characterization of ɛ-VOPO4 nanosheets for secondary lithium-ion battery cathode

Vanadium (III) phosphate monoclinic VPO₄·H₂O was synthesized hydrothermally. The ?-VOPO₄ nanosheets, formed by the oxidative de-intercalation of protons from monoclinic VPO₄·H₂O, can reversibly react with more than 1 mol lithium atoms in two steps. Crystal XRD analysis revealed that the structure of the ?-VOPO₄ nanosheets is monoclinic with lattice parameters of α=7.2588(4) Å, b=6.8633(2) Å and c=7.2667(4) Å. The results show that the ?-VOPO₄ nanosheets have a thickness of 200 nm and uniform crystallinity. Electrochemical characterization of the ?-VOPO₄ monoclinic nanosheets reveals that they have good electrochemical properties at high current density, and deliver high initial capacity of 230.3 mA·h/g at a current density of 0.09 mA/cm². Following the first charge cycle, reversible electrochemical lithium extraction/insertion at current density of 0.6 mA/cm² affords a capacity retention rate of 73.6% (2.0–4.3 V window) that is stable for at least 1000 cycles.     

Tensile,compressive and wear behaviour of self-lubricating sintered magnesium based composites

The graphite (Gr)/MoS₂ reinforced Mg self-lubricating composites were prepared through powder metallurgy. The composites were characterized for microstructure, physical, mechanical and wear properties. Gr/MoS₂ phase in the composites was identified by XRD analysis. Microstructural observation showed that the Gr/MoS₂ particles were homogeneously dispersed within the magnesium matrix. Micro-hardness was measured using an applied load of 5 g with a dwell time of 15 s at room temperature. Hardness of all the composites was measured to be in the range of VHN 29–34. The mechanical properties were studied using micro-hardness, tensile and compression tests. A fractographic analysis was performed using scanning electron microscope. The highest values of hardness, compressive strength and tensile strength were attained using Mg–10MoS₂ composite. A pin-on-disk tribometer was used to measure the friction coefficient and the wear loss of the sintered composites. In addition to that, the friction and wear mechanism of the composites were systematically studied by worn surface characterization and wear debris studies using SEM analysis. The reduced friction coefficient and wear loss were achieved in MoS₂ rather than Gr.     

石墨烯纳米片对AgCuTi钎料熔点与润湿性的影响

采用球磨法在AgCuTi钎料中添加不同质量分数的石墨烯纳米片(GNSs)制备出复合钎料,利用差示扫描量热仪(DSC),SEM以及XRD等方法研究了微量的石墨烯纳米片对AgCuTi钎料微观形貌、熔点以及在蓝宝石表面润湿性的影响. 结果表明,球磨法对GNSs-AgCuTi复合钎料的物相没有影响,石墨烯均匀地分散在AgCuTi颗粒周围;复合钎料熔点随着石墨烯含量的增加而降低,当石墨烯含量为0.5%,熔点降低了3.2 ℃;微量的石墨烯,改善钎料在蓝宝石表面的润湿性,0.3%GNSs-AgCuTi复合钎料的润湿角减小了4.4°,铺展面积增加了10 mm2,而过多的石墨烯也使得复合钎料的润湿性变差;石墨烯与元素Ti反应生成TiC,复合钎料与蓝宝石界面反应产物为Ti₃Cu₃O相.     

Water/oil repellency and work of adhesion of liquid droplets on graphene oxide and graphene surfaces

The study examines the water/ethylene glycol (EG) repellency of graphene and graphene oxide sheets prepared by the chemical exfoliation of natural graphite powders. The graphene nanosheets were produced by reducing graphene oxide with EG under microwave irradiation. The graphene sheets were assembled into a thin paper, and a facile fluorination was used to coat a thin fluorine layer over the graphene paper. The graphene oxide paper is generally hydrophilic, whereas without aid of any fluorination, the resulting graphene paper displays superhydrophobicity (contact angle: 150.1 ± 2.3°) and low fraction in contact with solid (12.2%). Such low solid fraction may be attributed to the air pocket trapped in (i) the interspaces between graphene powders and (ii) the flake-like voids between graphene sheets, referred to as the Cassie state. The EG repellency of graphene paper can be significantly improved by surface fluorination. Taking into account Young-Duprè's equation incorporated with the Cassie parameter, the W_ad values of the graphene papers for water repellency were found to fall in the region of 9.62-12.5 mJ/m². The low W_ad value between the droplets and the graphene surface can be ascribed to the fact that porous graphene sheets offer an air cushion to repel the drop penetration, inducing the low work required for the movement of droplets on graphene paper. On the basis of the results, this study offers fundamentals on the water and EG repellency of graphene and graphene oxide surfaces.     

ZnO hierarchical structures synthesized via hydrothermal method and their photoluminescence properties

The controlled synthesis of ZnO hierarchical structures has been successfully realized in a large scale via a simple hydrothermal method. It was demonstrated that the morphology of the final products was simply tuned by adding different amounts of soluble salt. ZnO microparticles were prepared when no soluble salt was added, whereas microspheres and nanoflowers were selectively prepared in the presence of different amounts of NaF. ZnO nanosheets were obtained when adding appropriate amount of NaCl, Na₂SO₄, or K₂SO₄. ZnO nanobelts were obtained in the presence of appropriate amount of sodium citrate (C₆H₅Na₃O₇). The photoluminescence (PL) properties of those products were researched, and the origin of the PL was discussed.     

锂离子电池用氧化亚铜/石墨烯负极材料的制备

在不添加表面活性剂的水溶液体系中,采用水合肼作为还原剂制备得到具有八面体形貌的氧化亚铜/石墨烯复合材料。透射电镜分析表明：氧化亚铜颗粒与石墨烯在复合物中呈多层次分布,而且氧化亚铜一次颗粒很好地嵌入在石墨烯层间。相比于纯氧化亚铜,氧化亚铜/石墨烯复合材料作为锂离子电池负极材料的电化学性能得到了显著的改善。在100 mA/g的电流密度下循环50次后,氧化亚铜/石墨烯复合物的可逆比容量高达348.4 mA？h/g,同时,在不同倍率下（50,100,200,400,800 mA/g）循环60次后,其可恢复容量仍达305.8 mA？h/g。     

爆炸喷涂WC-12Co/MoS_2复合涂层的摩擦磨损性能

为进一步提高爆炸喷涂WC-12Co涂层的耐磨性,在WC-12Co合金粉末中添加不同比例的MoS2粉末,利用爆炸喷涂技术在Q235钢表面制备了系列WC-12Co/MoS2复合涂层.采用金相显微镜、扫描电子显微镜、X射线衍射仪、显微硬度计及摩擦磨损试验机对WC-12Co/MoS2复合涂层的微观组织形貌、结构、显微硬度、摩擦磨损性能进行了研究.结果表明,MoS2均匀的分布于复合涂层中,当MoS2含量为2%时,复合涂层的硬度、致密度变化不大,但摩擦系数和磨损率大幅度下降,分别为WC-12Co涂层的50%和36%.随着MoS2含量的增加,复合涂层的摩擦系数和磨损率均呈上升趋势.     

花状CuO和花状CuO/石墨烯复合材料的制备及其在锂离子电池中的应用(英文)

采用水热法合成了花状CuO和花状CuO/石墨烯复合材料。采用XRD、SEM、TEM、BET、TG对材料的结构、形貌及性能进行表征和分析。花状CuO由CuO的纳米片组成,平均直径为4.2μm,比表面积为12.6m2/g。与花状CuO相比,花状CuO/石墨烯复合材料具有更高的充放电容量和更优良的循环稳定性。在0.1C、1C倍率下,其放电容量分别为603mA·h/g、382mA·h/g;在1C倍率下,经过50次循环,其容量保持率高达95.5%。     

Tribological behavior of self lubricating Cu/MoS2 composites fabricated by powder metallurgy

The effects of MoS₂ content on microstructure, density, hardness and wear resistance of pure copper were studied. Copper-based composites containing 0–10% (mass fraction) MoS₂ particles were fabricated by mechanical milling and hot pressing from pure copper and MoS₂ powders. Wear resistance was evaluated in dry sliding condition using a pin on disk configuration at a constant sliding speed of 0.2 m/s. Hardness measurements showed a critical MoS₂ content of 2.5% at which a hardness peak was attained. Regardless of the applied normal load, the lowest coefficient of friction and wear loss were attained for Cu/2.5MoS₂ composite. While coefficient of friction decreased when the applied normal load was raised from 1 to 4 N at any reinforcement content, the wear volume increased with increasing normal load. SEM micrographs from the worn surfaces and debris revealed that the wear mechanism was changed from mainly adhesion in pure copper to a combination of abrasion and delamination in Cu/MoS₂ composites.     

Effect of Ni-coated MoS2 on microstructure and tribological properties of (Cu−10Sn)-based composites

The (Cu−10Sn)−Ni−MoS₂ composites, prepared by powder metallurgy, were studied for the effects of Ni-coated MoS₂ on the microstructure, mechanical properties and lubricating properties. The mechanism of effects of Ni and MoS₂ on the properties of composites was analyzed through a comparative experiment by adding Ni and MoS₂ separately. The results show that the nickel wrapping around the MoS₂ particles decreases the reaction rate of MoS₂ with the copper matrix, and greatly improves the bonding of the matrix. The composites with 12 wt.% Ni-coated MoS₂ (C12) show the optimum performance including the mechanical properties and tribological behaviors. Under oil lubrication conditions, the friction coefficient is 0.0075 with a pressure of 8 MPa and a linear velocity of 0.25 m/s. The average dry friction coefficient, sliding against 40Cr steel disc, is measured to be 0.1769 when the linear velocity and pressure are 0.25 m/s and 4 MPa, respectively.     

Tribological properties of Cr- and Ti-doped MoS2 composite coatings under different humidity atmosphere

Solid-lubricant MoS₂ coatings have been successfully applied in high vacuum and aerospace environments. However, these coatings are very sensitive to water vapor and not suitable for applications in moist environments. In this work, Cr- and T-doped MoS₂ composite coatings were developed. The results demonstrated that these composite coatings are promising for applications in high humidity environments.MoS₂-Cr and MoS₂-Ti composite coatings with different Cr or Ti content were deposited on high speed steel substrate by unbalanced magnetron sputtering. The composition, microstructure, and mechanical properties of the as-deposited MoS₂-metal composite coatings were analyzed by energy dispersive analysis of X-ray (EDX), X-ray diffraction (XRD), and nanoindentation experiments. The tribological properties of the coatings were evaluated against an alumina ball under different relative humidity atmosphere using a ball-on-disc tribometer. The MoS₂-Cr and MoS₂-Ti coatings showed a maximum hardness of 7.5 GPa and 8.4 GPa at a dopant content of 16.6 at.% Cr or 20.2 at.% Ti, respectively. The tribological test results showed that, with a small amount of Cr and/or Ti doping, the tribological properties of MoS₂ coatings under humid atmosphere could be significantly improved. The optimum doping level was found to be around 10 at.% for both MoS₂-Cr coatings and MoS₂-Ti coatings to show the best tribological properties, with both the lowest friction coefficient and wear rate. The excellent tribological properties of the MoS₂-Cr and MoS₂-Ti coatings with an appropriate metal doping level in moist atmosphere are found due to their ability to form stable transfer layer on the surface of the counterbody, which supplies lubrication for the contact surface.     

MoS2 coated with Al2O3 for Ni-MoS2/Al2O3 composite coatings by pulse electrodeposition

The MoS₂ powders were coated with Al₂O₃ (5 wt.%) through controlling hydrolysis of Al (NO₃)₃·9H₂O. MoS₂ powder coated with Al₂O₃ was written as MoS₂/Al₂O₃ hereinafter. MoS₂/Al₂O₃ powders were put into Ni plating electrolyte bath. Cetyltrimethylammonium bromide (CTAB) — the surfactant was also put into the bath. The experiment proves that MoS₂/Al₂O₃ particles were absorbed onto the Ni plate. The amount of MoS₂/Al₂O₃ deposited on Ni plate rises with the increasing concentration of MoS₂/Al₂O₃ in the bath. The microhardness, micro-surface, phase and the tribological property of the MoS₂/Al₂O₃ multi-plating coating were measured and analyzed. The performances of microhardness and wear resistance of the Ni-MoS₂/Al₂O₃ composite are better than those of Ni-MoS₂ composite.     

Facile decoration of polypyrrole nanoparticles onto graphene nanosheets for supercapacitors

A facile approach was developed to prepare the graphene nanosheets (GNS) supported polypyrrole (PPy) nanoparticles via the in situ chemical oxidative polymerization of pyrrole onto the surfaces of the GNS modified with sodium dodecyl sulfonate (SDS) as surfactant for GNS and dopant for PPy simultaneously. The morphologies of the graphene nanosheets supported polypyrrole nanoparticles (GNS/PPy nanocomposites) with different feeding ratios were characterized with transition electron microscopy (TEM). It indicated that the PPy nanoparticles had been successfully decorated onto the GNS surfaces. The electrochemical performances of the GNS/PPy nanocomposites were investigated with cyclic voltammetry (CV), constant current charge–discharge and electrochemical impedance spectroscopy (EIS) techniques. The nanocomposite exhibited specific capacitance of 294 F g⁻¹ at the charge–discharge current density of 10 mA cm⁻² in 1.0 M NaNO₃ electrolyte. It showed that the GNS/PPy nanocomposites might be promising electrode materials for supercapacitors.     

Microstructure analysis of MoS2 deposited on diamond-like carbon films for wear improvement

A compound solid lubricating film containing a MoS₂ top layer deposited on DLC interlayer by UBM sputtering technique was investigated for its tribological applications in humid environments. TEM, Raman and XRD analysis revealed the amorphous nature of the MoS₂ film which contains only short-range order in its lattice structure. The as-deposited MoS₂ compound films showed well-bonded interfaces. The MoS₂, however, is very susceptible to humidity and oxidation, which resulted in higher friction coefficients and lower wear life. A friction coefficient of 0.05 was measured between steel balls and MoS₂ in atmosphere of 90% RH. Excessive abrasive wear was identified, as a result of the wear debris and the oxidized transfer layers between MoS₂ and its counterpart. The inclusion of a supportive DLC interlayer has effectively improved the wear behavior of MoS₂ films under various loading conditions. The overall wear mechanism of MoS₂ was complicated due to its oxidation problem which needs to be resolved for successful usage of MoS₂ in humid environments.     

Molybdenum disulfide as a lubricant and catalyst in adaptive nanocomposite coatings

Nanocomposite YSZ-Ag-Mo-MoS₂ coatings with different MoS₂ additions (0-100 at.%) were deposited with a hybrid pulsed laser/magnetron sputtering/filtered cathodic arc process. Wear testing was performed from 25 to 700 °C for each of the coatings. Electron microscopy and other characterization techniques were used to examine the surfaces and wear tracks of the coatings and to determine the mechanisms resulting in the measured tribological properties. Adaptive coatings containing 8 at.% MoS₂ demonstrated a friction coefficient of 0.2 throughout the temperature range examined here, compared to 0.4 for YSZ-Ag-Mo with no MoS₂. Characterization of the YSZ-Ag-Mo-8% MoS₂ coating revealed that MoS₂ and silver provided lubrication at temperatures ≤ 300 °C, while silver molybdate phases and MoO₃ were effective lubricants at higher temperatures. Silver molybdate was not observed in the coatings containing 0% MoS₂. The role of sulfur in the formation of silver molybdate is briefly discussed.     

Characterization and frictional behavior of nanostructured Ni–W–MoS2 composite coatings

Ni–W–MoS₂ composite coatings were obtained by pulse plating from a Ni–W electrolyte containing suspended MoS₂ particles. The coating composition, morphology, crystalline structure, microhardness and frictional behavior were studied as a function of MoS₂ concentration. The results obtained in this study indicate that co-deposited lubricant particles strongly influenced the composite Ni–W coating properties. It was found that increasing co-deposited MoS₂ diminished tungsten content in the coating and consequently increased the average grain size. Ni–W nanostructured coatings with high MoS₂ content have a porous sponge-like structure, high surface roughness and irregular frictional behavior. However, the friction coefficient of Ni–W coatings is reduced to half its value with low MoS₂ content.