Li Hua Dong

New Application of the “Underwater Super-Hydrophobic” Surface in the Corrosion Protection

“Underwater super-hydrophobic” surface applied in the corrosion protection was prepared by melting myristic acid (CH3(CH2)12COOH) adsorbed onto the anodized aluminum. The static contact angle for seawater on the surface was measured to be 154°. The surface structure and composition were then characterized by means of scanning electron microscopy (SEM) with energy dispersive X-ray spectrum (EDX) and atomic force microscope (AFM). The electrochemical measurements showed that the super-hydrophobic surface significantly improved the corrosion resistance of aluminum in sterile seawater.

Solution Phase Synthesis of Amorphous Carbon Nanoparticles under Ambient Atmosphere

A novel solution-phase method is developed for preparation of amorphous carbon nanoparticles with high specific surface area under ambient atmosphere by the reaction of ferrocene and ammonium chloride in polyethylene glycol 400 (PEG 400) at 200 oC. Samples are characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (SEM), transmission electron microscopy (TEM) and N2 adsorption-desorption isotherms. It is found that the nanoparticles are complete amorphous and agglomerate together due to the strong surface tension. The amorphous carbon nanoparticles with a diameter of 40-100 nm have a wide size distribution of mesopores with a Brunauer-Emmett-Teller (BET) surface area of 402.28m2•g-1. It is proposed that the dissolved reactants uniformly dispersing in the solutions could react at a molecular level to form uniform carbon nanoparticles.

Molecular Simulation of the Interfacial Properties of an Epoxy Composite Reinforced Using a Carbon Nanotube/Carbon Fiber Hybrid

Molecular simulations of the interfacial properties of (1) a composite with an epoxy(EP) matrix and a carbon nanotube(CNT)/carbon fiber(CF) multi-scale reinforcement and (2) a traditional CF/EP composite were performed employing Materials Studio 4.0 software. Results indicate that the interfacial atom concentration of material 1 is higher that that of material 2 by interfacial molecular structure analysis, and there are many benzene rings in both material 1 and material 2 which are parallel to the crystal layers of CF. The contact layer thickness of material 1 and material 2 is 0.25 and 0.10 nm, respectively. The concentration distribution calculation of EP molecules in the interface shows that the most concentrated part of EP in material 2 appears in the carry-forward area of the contact layer, while it is more close to the contact layer in material 1.

Synthesis of Uniform Barium Ferrite Powders by Co-Precipitation Method

The uniform hexagonal barium ferrite powders were synthesized by co-precipitation method using metal chloride. The effects of the amount of hexadecyltrimethyl ammonium bromide (CTAB), the water bath and calcination temperature on the phase formation, microstructure and density of barium ferrites were systematically investigated. The results showed that the formation of uniform hexagonal barium ferrite powders was significantly influenced by the amount of CTAB and the water bath could lead to the larger grain size and density. The SEM demonstrated that the BaFe12O19 powders had plate-like shape with crystallite sizes varing from 150 to 200 nm. When the amount of CTAB was 0.2g/100ml and the calcination temperature was 850 °C, the barium ferrite powders were uniform which indicated that the amount of surfactant and calcination temperature were very optimum.

Synthesis and Characterization of Si 3 N 4 Nanopowder by RF Induction Thermal Plasma

Nano-Si3N4 has been synthesized by the thermal plasma with silicon tetrachloride (SiCl4) as the Si source, liquid ammonia (NH3) as the N source, and silane (SiH4) as the catalyst. And the prepared Nano-Si3N4was heat-treated atfour different temperatures of 1350°C, 1400°C, 1450°C, 1500°C. The as-prepared samples were characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and fourier transform infrared spectroscopy (FTIR). The results showed that the particle size of the nano-Si3N4 powder was less than 100 nm and it was amorphous when the temperature below 1450°C. At 1500°C, the synthesized Si3N4 powder with the grain size of 10 nm was crystallized, and the α-phase Si3N4 reached more than 90%.

Fabrication of (TiB2, TiCx)/B4C Composites via Ti3Al IMC Added in B4C Ceramics

Ti3Al inter-metallic compounds were successfully prepared via high energy ball milling and the subsequently heat treatment. Near full dense (TiB2, TiCx)/B4C matrix composites were fabricated by the addition of Ti3Al. The maximum values of hardness, flexural strength and fracture toughness are HRA 94.1, 580.34MPa and 8.07MPa•m1/2 respectively for 20wt% Ti3Al content. Furthermore, the microstructures of the composites were analyzed by XRD, SEM and energy spectrum methods.

Dielectric and Conduction Properties of Lu3NbO7 Transparent Ceramic

The dielectric response and electrical conduction of Lu3NbO7 transparent ceramic produced by spark plasma sintering were investigated. Lu3NbO7 transparent ceramic exhibited low frequency dielectric dispersion and a peak in dielectric loss, shifting to higher frequency at high temperatures. This indicated space charge polarization and broad relaxation time, confirmed by impedance and modulus spectra. The Nyquist plot shows the dominant grain effect in the electrical conduction. The AC conductivity of Lu3NbO7 transparent ceramic is 4.18×10-2 S m-1 at 1073 K, with an activation energy of 1.30 eV.

Wear and Corrosion Behaviours of FeCrNiSi Alloy Coatings by Laser Cladding

Soft and hard FeCrNiSi alloy coatings were obtained on 30CrMo alloy steel surface by laser cladding. The phase constitution, microstructure, frictional wear behavior and corrosion resistance of the composite coating were analyzed using X-ray diffraction (XRD), scanning electron microscope (SEM), three-dimensional non-contact surface mapping, friction and wear testing machine and electrochemical workstation, separately. XRD analysis showed that the cladding layer was mainly composed of Fe-based alloy composition, accompanied by a small amount of cobalt nickel alloy. There were massive protrusions in the interface of the soft sample, and the coating was regularly dendritic. Hard sample coating lines were cluttered, and there was no bulk deposition. Under the same wear condition, the soft coating exhibited serious abrasive wear, while the hard coating had slight abrasive wear behavior. The polarization curves in 3%NaCl solution revealed that the self-corrosion potential of the soft coating was positive shifted more than that the hard coating. The soft coating has better corrosion resistance than the hard coating.

Reciprocating Wear Resistance of PTAW Deposited WC/Ni-Based Composite Overlays

Microstructure and tribological characteristics of WC/Ni-based plasma transferred arc welding (PTAW) overlays have been investigated. WC/Ni-based composite overlays were deposited under same conditions with different percent of WC particle (20-70 wt.%) in the 304L stainless steel. Reciprocating wear tests were undertaken according to the ASTM G133-05 standard. Microstructure and surface micrographs of the cross-section and worn surfaces were characterized. The results indicated that the wear rate decreased with the increasing percent of WC particle, revealing no visible decrease in wear when the percent of WC particle reached more than 50 wt.%. Coating with 50 wt.% WC particle possessed a fine abrasion resistance due to a homogeneous microstructure. Furthermore, at a low concentration (20 wt.% to 40 wt.%), the wear mechanism were adhesive wear and oxidation wear, whereas in 50wt.% WC particle, the main wear mechanism were adhesive wear and abrasive wear. In the case of high concentration of WC particle (above 50 wt.%), the predominant wear mechanism was three-body abrasive wear.

Microstructure and Corrosion Behaviour of Laser–clad Double-ceramic-layer Composite Coating

A double-layer composite coating on Q235 steel substrate was prepared using a new developed in situ technology consisting of SHS reaction, laser cladding and metal dusting techniques. A double-layer composite coating consists of the TiO2–TiC ceramic outer layer and the TiC-CNTs cermet inner layer. An excellent bonding was observed among the outer layer, the inner layer and the steel substrate. Corrosion behavior of the coating was investigated and the commercial 304SS was used for comparison. The outer layer exhibited the highest corrosion resistance and 304SS the lowest corrosion resistance, whereas the inner coating exhibited the intermediate corrosion resistance. However, the severe pitting corrosion which was observed in 304SS did not exist for the coating.