Hongxin Dang

Preparation and tribological properties of tetrafluorobenzoic acid-modified TiO2 nanoparticles as lubricant additives

Abstract A tetrafluorobenzoic acid-modified TiO 2 nanoparticles with average diameter of 40 nm were chemically synthesized. The nanoparticles were amorphous and had good thermal stability. The nanoparticles were characterized by transmission electron microscope, Fourier transformation infrared ray, X-ray Diffraction, and their thermal stability was investigated by means of TGA and differential thermal analysis. The tribological properties of the FA–TiO 2 nanoparticles as additive to liquid paraffin were evaluated with a four-ball tester. The morphologies on the worn surfaces of the lubricated GCr15 steel were studied using scanning electron microscope. The results show that the FA–TiO 2 nanoparticles exhibit good performance in wear and friction reduction. The antiwear and load capability of liquid paraffin increased and the wear scar diameter strikingly deceased after adding nanometer TiO 2 .

A novel method for preparation of silver nanoparticles

A new method to prepare silver nanoparticles was posed. Metal nanoparticles can be produced through reduction of relevant metallic salts in liquid ammonia. The method is convenient as compared with the similar method. The morphology and structure of synthesized silver nanoparticles were characterized on transmission electron microscopy (TEM), X-ray diffraction (XRD), infrared spectrum (FT-IR) and thermogravimetric analysis (TGA). The result shows that the morphology of Ag nanoparticles is spherical and the mean size is about 20 nm.

Preparation of tin nanoparticles by solution dispersion

Abstract In this paper, we report a novel solution dispersion method for preparing tin nanoparticles from bulk tin. Tin nanoparticles, with average diameter of 30–40 nm, have the same crystal structure as the bulk tin, and the particle surface has been oxidized. In addition, tin nanoparticles show excellent antiwear properties.

Fabrication of nanopatterned DNA films by Langmuir–Blodgett technique

Abstract Fractal-like nanopatterned DNA thin films have been fabricated on mica substrate by Langmuir–Blodgett (LB) technique. Structures and components of DNA nanopatterns were investigated using atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The effect of surface pressure on the transferred DNA composite films has been studied. Scanning force microscopic observations revealed that the surface structure and morphology of DNA nanopatterns can be well controlled by changing the surface pressure. The growth mechanism of the fractal-like nanopatterns is discussed in terms of the diffusion-limited aggregation (DLA) model. The formation of large-scale DNA networks provided a well-defined template for the construction of nanocomposite films. Patterns of silver metal were prepared on DNA networks by subsequent metallization process.

Synthesis of In-Sn alloy nanoparticles by a solution dispersion method

In this paper, we report a novel solution method for preparing alloy nanoparticles that involves dispersion, surface oxidation and solvent absorption. In–Sn alloy nanoparticles were prepared by dispersing melt In–Sn alloy in a suitable solvent from In–Sn alloy. Transmission electron microscopy shows that the nanoparticles appear to be close to a spherical shape and have an average diameter of 60 nm. Electron diffraction and power X-ray diffraction studies confirm that the formation of In–Sn alloy nanoparticles that have the same crystal structure with equilibrium phase In3Sn and InSn4 as the bulk alloy. Thermal analysis reveals that the samples contain at least 3 wt% organic solvent. In addition, the tribological properties of In–Sn alloy nanoparticles as an additive in lubricating oil were evaluated on a four-ball tester. The results show that the In–Sn alloy nanoparticles have excellent performance in wear, which is better than that of the corresponding monometallic particles.

Synthesis and tribological behavior of surface modified (NH4)3PMo12O40 nanoparticles

Abstract Surface modified (NH 4 ) 3 PMo 12 O 40 nanoparticles were synthesized in a mixture solution of water–ethanol with cetyltrimethyl ammonium bromide as a modifying agent. The morphology, structure and thermal properties of modified (NH 4 ) 3 PMo 12 O 40 nanoparticles were investigated by means of transmission electron microscopy, X-ray powder diffraction, Fourier transform infrared spectrum, thermogravimetric analysis, and differential scanning calorimetry. Their tribological behaviors were evaluated on a four-ball testing machine. The results show that the modified (NH 4 ) 3 PMo 12 O 40 nanoparticles as oil additives can improve the load-carrying capacity and antiwear property of the base oil. The rubbed surfaces were investigated by scanning electron microscopy and X-ray photoelectron spectroscopy. It can be inferred that a tribological reaction film was formed, which contributed to the good tribological properties of surface modified (NH 4 ) 3 PMo 12 O 40 nanoparticles.

STUDY OF THE SURFACE STATES AND ACTIVITY OF A Pt/TiO2 PHOTOCATALYST

This paper deals with the correlation of surface states and photoactivity of a Pt/TiO2 catalyst prepared by means of photoreduction of on anatase nano-TiO2 powders. Conductivity measurements of pressed powders and XPS were applied in analysis of the surface states energy levels and chemical states of Pt at the nano-TiO2 surface, respectively. The results revealed a new surface state with the energy level of 0.35 eV, lower than the conduction band edge of TiO2. According to the XPS analysis, the new surface state can be attributed to the Pt0 clusters deposited on the surface of TiO2 particles. The photoactivity of the as-prepared Pt/TiO2 catalyst was characterized by photodecoloration of brilliant red X-3B in aqueous solution. The experimental results indicated that the photoactivity of the Pt/TiO2 catalyst is much higher than that of TiO2. The surface Pt0 clusters possibly function as trapping centers of generated electrons, resulting in the promotion of photocatalytic activity.