Carbon nanotubes produced by fluidized bed catalytic CVD: first approach of the process

Multi-walled carbon nanotubes have been produced with high yield on an iron supported catalyst by catalytic chemical vapor deposition in a fluidized bed reactor. The choice of such a technique allows to reach high selectivity towards the desired material. A remarkable feature of this process is the huge bed expansion observed during the nanotubes growth that affects the fluidization regime due to the evolution of the apparent density of the composite powder. The catalytic powder, the composite material and the purified nanotubes have been analyzed by SEM, TEM and BET nitrogen adsorption.     

纳米LiNi0．5Mn0．5O2中锂离子扩散的尺寸效应研究

采用电势阶跃法分析了纳米LiNi0．5Mn0．5O2电极中锂离子的表观扩散系数随材料XRD粒度的变化规律,表观扩散系数随粒度的增大先增加后减小。校正尺寸几何因素后得到了LiNi0．5Mn0．5O2中锂离子的本征扩散系数随XRD粒度的变化规律,本征扩散系数随粒度的增大而增大。     

Abrasion resistance of nanostructured and conventional cemented carbides

The abrasion resistance of nanostructured WC-Co composites, synthesized by a novel spray conversion method, is determined and compared with that of conventional materials. Scratching by diamond indenter and abrasion by hard (diamond), soft (zirconia) and intermediate (SiC) abrasives was investigated. The size of the scratch formed by the diamond is simply related to the hardness of the composite. Plastic deformation, fracture and fragmentation of the WC grains increase with their size. Nanoscale composites show purely ductile scratch formation. Nanocomposites possess an abrasion resistance approximately double that of the most resistant conventional material: this is a higher gain than the increase in hardness which is at most 23%. This large gain is due to a specific grain size effect on abrasion resistance in the case of diamond and SiC abrasive and to a very rapid increase of abrasion resistance with hardness in the case of the softer (SiC and ZrO₂) abrasives. The observation of the abraded surfaces of conventional composites reproduced the known mechanisms: plastic deformation and fracture of WC grains by hard abrasives; removal of binder phase and fall-out of WC by soft abrasives. Magnetic fields from the ferromagnetic Co prevent the observation of abrasion mechanisms in the very fine-structured nanocomposites.     

In situ nanostructured (TiCr)CN coating by reactive plasma spraying

In situ nanostructured (TiCr)CN composite coating was prepared by reactive plasma spraying Ti-Cr-graphite powder under air atmosphere. The phase composition, microstructure, mechanical properties and wear performance were investigated. The results show that the coating consists of a mixture of TiN, Ti(CN), (TiCr)N, Cr, Ti₃O, and amorphous graphite and CrN phases. The grain size is about 70 nm and the grains present equiaxed and columnar crystal morphologies. Moreover, 5 nm-sized nanocrystals are embedded in an amorphous phase. The (TiCr)CN composite coating possesses high hardness (1325 ± 120 HV) and toughness (4.35 ± 0.53 MPa m^1/2). The friction coefficient and wear rate of the coating are 0.46 and 3.01 ± 0.17 × 10^?6 mm³ N^?1 m^?1, respectively. The inclusion of metallic phase Cr could improve the toughness and wear resistance of the (TiCr)CN coating.     

Controllable synthesis and magnetic properties of hydrothermally synthesized NiCo2O4 nano-spheres

In the work, we explored an efficient synthetic platform to purposefully fabricate different morphologies of NiCo₂O₄ by controlling the hydrothermal temperature. All the obtained samples were characterized by means of X-ray diffraction, scanning electron microscopy, high resolution transmission electron microscopy. With the increase of hydrothermal temperature, the morphology of obtained samples transformed from spongy nanosphere to ellipse-like, then to peanut-like structure and an effective blue shifting of Raman spectroscopy occurred. The magnetic measurements indicated that the materials transform from paramagnetic to weak ferromagnetic with the increase of hydrothermal temperature.     

Preparation of nanostructured Gd2Zr2O7-LaPO4 thermal barrier coatings and their calcium-magnesium-alumina-silicate (CMAS) resistance

Nanostructured 30 mol% LaPO₄ doped Gd₂Zr₂O₇ (Gd₂Zr₂O₇-LaPO₄) thermal barrier coatings (TBCs) were produced by air plasma spraying (APS). The coatings consist of Gd₂Zr₂O₇ and LaPO₄ phases, with desirable chemical composition and obvious nanozones embedded in the coating microstructure. Calcium-magnesium-alumina- silicate (CMAS) corrosion tests were carried out at 1250 °C for 1–8 h to study the corrosion resistance of the coatings. Results indicated that the nanostructured Gd₂Zr₂O₇-LaPO₄ TBCs reveals high resistance to penetration by the CMAS melt. During corrosion tests, an impervious crystalline reaction layer consisting of Gd-La-P apatite, anorthite, spinel and tetragonal ZrO₂ phases forms on the coating surfaces. The layer is stable at high temperatures and has significant effect on preventing further infiltration of the molten CMAS into the coatings. Furthermore, the porous nanozones could gather the penetrated molten CMAS like as an absorbent, which benefits the CMAS resistance of the coatings.     

Fabrication of ZnO nanowire arrays by cycle growth in surfactantless aqueous solution and their applications on dye-sensitized solar cells

Large-scale ZnO nanowire arrays vertically aligned on the substrates were achieved from cycle growth without surfactants. The 8 μm long ZnO nanowire arrays were prepared by 20 cycles. The aspect ratio of ZnO nanowire can be increased with increasing the growth cycle. As displayed by microstructures and photoluminescence (PL) analysis, the ZnO nanowire was good single crystal and the defects in the as-prepared ZnO nanowire arrays were controlled at a low concentration. By increasing the length and aspect ratio of ZnO nanowire, the performances of dye-sensitized solar cells based on the ZnO nanowire arrays were improved. As-prepared ZnO nanowire arrays have potential applications in fabricating next generation nanodevices.     

超音速等离子喷涂纳米防污陶瓷涂层研究

以NiCr合金为底层,含防污成分的纳米Al_2O_3-13%TiO_2为面层,采用超音速等离子喷涂方法制备纳米防污陶瓷涂层。研究了不同工艺对涂层截面形貌、孔隙率、显微硬度及结合强度的影响,探讨了涂层的防污性能,获得了较优的喷涂工艺参数:Ar流量3.6～3.8 m~3/h,H_2流量0.4 m~3/h,电流400～420A,电压150V,喷距100mm,送粉量30g/min。采用较优超音速等离子喷涂工艺制备的纳米防污陶瓷涂层孔隙率可达0.8%,HV_(0.3)≥987,结合强度≥35.15 MPa,并且抗海生物附着性能优良。     

Polymeric nanostructured materials for biomedical applications

Polymeric nanostructured materials (PNMs), which are polymeric materials in nanoscale or polymer composites containing nanomaterials, have become increasingly useful for biomedical applications. In specific, advances in polymer-related nanoscience and nanotechnology have brought a revolutionary change to produce new biomaterials with tailored properties and functionalities for targeted biomedical applications. These materials, including micelles, polymersomes, nanoparticles, nanocapsules, nanogels, nanofibers, dendrimers and nanocomposites, have been widely used in drug delivery, gene therapy, bioimage, tissue engineering and regenerative medicine. This review presents a comprehensive overview on the various types of PNMs, their fabrication methods and biomedical applications, as well as the challenges in research and development of future PNMs.