Haojie Song

Synthesis of α-Fe2O3 nanorod/graphene oxide composites and their tribological properties

The composites of graphene oxide (GO) nanosheets fabricated by α-Fe2O3 nanorods were prepared through a facile hydrolysis route. As-synthesized α-Fe2O3 nanorods incorporated into GO nanosheets in the composites were observed with diameters of 3–5 nm and lengths of 15–30 nm. The formation mechanism of anchoring α-Fe2O3 nanorods onto GO nanosheets was proposed as the intercalation and adsorption of iron ions onto the surface of GO nanosheets, followed by the nucleation and growth of α-Fe2O3 nanorods. Tribological properties of α-Fe2O3 nanorod/GO composites as lubricating oil additive were investigated by employing a ball–plate tribotester. It is shown that anti-wear and reduced frictional abilities were improved by the addition of α-Fe2O3 nanorod/GO composites into the base oil. The oil with α-Fe2O3 nanorod/GO composites showed better tribological properties than those in the oil with GO nanosheets. Good friction and wear properties of α-Fe2O3 nanorod/GO composites can be explained by the combination of rolling effects between the rubbing surface and formed thin physical tribofilms on the substrate.

Flexible morphology-controlled synthesis of monodisperse α-Fe2O3 hierarchical hollow microspheres and their gas-sensing properties

Microspheres constructed with α-FeOOH nanorods were fabricated by a sodium dodecylbenzenesulfonate (SDBS) assisted hydrolysis process in an ethanol/H2O co-solvent system, and could be transformed into hollow microspheres constructed with α-Fe2O3 nanorods by calcining in air at 600 °C for 2 h. α-Fe2O3 hierarchical hollow microspheres with size about 320 nm in diameter were constructed by the radically oriented single-crystalline nanorods with length and diameter of about 20–40 nm and 15–20 nm, respectively. The investigation on the evolution formation revealed that SDBS was critical for controlling the assembly of the freshly formed nanocrystallites, and hollowing formation was proven to be the Ostwald ripening process by tracking the structure of the products at different growth stages. Scanning electron microscopy, X-ray diffraction, transmission electron microscopy, and high-resolution transmission electron microscopy were used to characterize the structure of the synthesized products. An investigation of the gas-sensing properties showed that α-Fe2O3 hierarchical hollow spheres exhibited high gas response to ethanol at the optimum working temperature of 300 °C.

Templated-assisted one-dimensional silica nanotubes: synthesis and applications

Silica (SiO2) is one of the most frequently used inorganic materials. This review covers the research progress in the synthesis of one-dimensional silica nanotubes as well as the newest aspects of silica nanotubes in applications where their structural attributes are exploited. The synthetic methods for well-defined silica nanotubes and a variety of specific silica nanotubes including hollow silica nanotubes, mesoporous silica nanotubes, chiral or helical silica nanotubes are summarized. One-dimensional tubular silica nanomaterials display structures that differ from those of other kinds of nanostructured silica materials and provide unique features such as very uniform diameter, open at both ends. In addition, sol–gel process and silane chemistry offer the reliable and robust surface modification or functionalization of silica nanotubes. Attractively, end functionalization of silica nanotubes may be able to control drug release, resulting in their wide applications in controlled drug and gene delivery; also their distinctive inner and outer surfaces can be differentially functionalized making silica nanotubes ideal multifunctional nanostructure candidates for biomedical applications in various areas such as biosensing, bioseparation and biocatalysis.

Controllable fabrication, growth mechanism, and gas sensing properties of hollow hematite polyhedra

We report a facile and efficient fluoride ion-assisted hydrothermal route to prepare novel hollow hematite polyhedral architectures without any template or surfactant. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images reveal that the microparticles with empty interior are polyhedra. On the basis of time-dependent experiments, a multistage reaction mechanism for the formation of the hollow hematite polyhedra was proposed. This procedure brought into play the synergetic effects of the oriented attachment, recrystallization and etching. To demonstrate potential applications, we have fabricated a gas sensor from the as-synthesized hollow α-Fe2O3 polyhedra and investigated it for ethanol detection. Results show that the hollow α-Fe2O3 polyhedral sensor exhibits significantly improved gas sensitivity and selectivity performances in comparison with the compact α-Fe2O3 polyhedral structures.

Controllable synthesis of monodisperse polyhedral nickel nanocrystals

Monodisperse polyhedral nickel nanoparticles composed of small nanocrystals have been successfully synthesized by a facile poly(N-vinyl-2-pyrrolidone) (PVP) mediated solution reduction process with hydrazine hydrate as the reducing agent. The phase structure, morphology and magnetic properties of the as-prepared products were extensively characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). XRD pattern indicated that the as-synthesized products were nickel with well-crystallized face-centered cubic structure. SEM and TEM observations showed that the polyhedral nanoparticles consist of nanocrystals with size around 2 nm. The formation of these polyhedral nanoparticles is attributed to the oriented aggregation of nickel nanocrystals around a polymer-Ni2+ complex framework structure. The magnetic property investigation shows that the polyhedral nickel nanoparticles exhibit a ferromagnetic behavior and possess a higher coercive field value than that of the bulk nickel.

Controllable synthesis, characterization and growth mechanism of three-dimensional hierarchical PbWO4 microstructures

We report on the synthesis of three-dimensional (3D) hierarchical PbWO4 microstructures by an oil-in-water microemulsion-mediated route. As-prepared PbWO4 samples are characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. A possible three-step growth mechanism of PbWO4, in which initial nucleation, self-assembly (oriented aggregation), and subsequent crystal growth (Ostwald ripening) are involved, is proposed to explain the formation of PbWO4 microstructures based on observations of a time-dependent morphology evolution process. The approach is facile, environmentally friendly, and provides a new strategy in the use of microemulsion systems for material design and processing. The oil-in-water microemulsion technique presented here offers promising microstructured media for the synthesis of other inorganic materials with complex 3D architectures and unique morphologies and properties.

One-step template-free synthesis of hollow core–shell α-Fe2O3 microspheres with improved lithium storage and gas-sensing properties

Hollow core–shell α-Fe2O3 microspheres were easily prepared by a one pot hydrothermal method without employing any templates/substrates or surfactants. The as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and nitrogen adsorption–desorption isotherms. Results showed that the shell was constructed by aggregated α-Fe2O3 nanoparticles, while the core presented a novel porous structure. The morphology of the hollow core–shell α-Fe2O3 microspheres can be controlled by optimizing the experimental conditions. A possible formation mechanism was also proposed. As anodes in lithium ion cells, the hollow core–shell α-Fe2O3 microspheres show a high initial discharge capacity of 1465 mA h g−1 and still a rather high capacity of 728 mA h g−1 after 60 cycles. When applied as gas sensors, the hollow core–shell α-Fe2O3 microspheres exhibited high gas sensitivity toward NO2 gas. The intrinsic hollow core–shell nature as well as high porosity of the core contributes greatly to the improvement of their performance as anode materials for lithium ion batteries and the superior sensitivities to NO2 gas.

Preparation and tribological behaviors of poly (ether ether ketone) nanocomposite films containing graphene oxide nanosheets

The composite films of poly (ether ether ketone) (PEEK) filled with different proportions of graphene oxide (GO) nanosheets were prepared by the cast method. The tribological behaviors of the composite films under boundary lubrication (water and liquid paraffin oil lubrication) were investigated and compared with that under dry sliding on an UMT-2 friction and wear machine, by running a steel sphere against the composite films. The results were as follows: GO nanosheets as the filler greatly improve the wear resistance of PEEK under boundary lubrication, though the composites show a different dependence of wear resistance on the filler content. Scanning electron microscopy and optical microscopy performed to analyze the wear scar surfaces after friction confirmed that the outstanding lubrication performance of GO could be attributed to their small size and extremely thin laminated structure, which allow the GO to easily enter the contact area, thereby preventing the rough surfaces from coming into direct contact.

Fabrication of superoleophobic surfaces with controllable liquid adhesion from polyelectrolyte multilayer film

Superoleophobic surfaces with controllable liquid adhesion were developed on micro/nanostructured aluminum substrates through the deposition of polyelectrolyte multilayer films ion-paired with perfluorooctanoate anions. Various liquids, such as water, glycerol, rapeseed oil, and hexadecane, can be tuned from rolling state to pinned state on the superoleophobic surfaces with increasing number of polyelectrolyte bilayers. The effects of chemical heterogeneity and topographic roughness of polyelectrolyte deposited substrates on liquid adhesion properties were systematically studied. The combined effect of surface chemical defects coupled with the disappearance of nanoflakes and the interconnection of protrusions with the polyelectrolyte deposition led to the surfaces changing from sliding superoleophobicity to sticky superoleophobicity. Our results gave a useful attempt to understand the fabrication principle of preparing superoleophobic surfaces with controllable liquid adhesion. Moreover, the function of controllable liquid adhesion from polyelectrolyte multilayer film could potentially be used in important applications, such as in the selection and transportation of microdroplets.

Slippery lubricant-infused textured aluminum surfaces

To overcome instability of the lotus-inspired surfaces, slippery lubricant-infused surfaces inspired by Nepenthes pitcher plant were fabricated by the combination of fluorinated hierarchical texture and perfluoropolyether (PFPE). The hierarchical structures composed of facets, cavities, and nanoflakes were formed on the aluminum substrates by the HCl etching and the boiling water treatment. After surface fluorination, PFPE can spread over the textured aluminum surfaces via capillary effect to form continuous and homogeneous liquid films. The liquid repellency of the textured surface was demonstrated by visible experimental results and contact angle measurements. Due to the hierarchical structures that trapped enough lubricant and resisted the deformation of lubricant film, the lubricant-infused textured aluminum surface exhibited an excellent liquid repellency, low sliding angles for various liquids, and high environmental durability. Therefore, this slippery aluminum surface would be a good candidate for liquid-repellent surfaces to meet emerging needs in practical applications.