Ma Zhibin

Adhesion improvement of diamond films on cemented carbides with copper implant layer

Abstract The deposition of diamond films on cemented carbides is strongly influenced by the catalytic effect of cobalt under typical deposition conditions. Decreasing the content of Co on the surface of the cemented carbide is often used for the diamond film deposition. But the leaching of Co from the WC-Co substrate leads to a mechanical weak surface, often causing poor adhesion. In this paper we adopt a copper implant layer to improve the mechanical properties of the Co leached substrate. The copper implant layer is prepared with vaporization. The diamond films are grown by microwave plasma chemical vapor deposition from the CH4/H2 gas mixture. The morphology and the quality of the diamond films have been characterized by scanning electron microscopy and Raman spectroscopy. A Rockwell apparatus has evaluated the adhesion of the diamond on the substrate. The results indicate that the diamond films have good adhesion to the cemented carbide substrate due to the recovery of the mechanical properties of the Co depleted substrate after the copper implantation and less graphite formation between the substrate and the diamond film.

Study on Modification of Nano-Sized Anatase Titanium Dioxide by Nitrogen-Plasma

The nano-sized particles of anatase titanium oxide (TiO2) were obtained by hydrolysis of titanium ester (TNB) in basic media and dehydrated in acid media. And then the anatase titanium oxide was treated with nitrogen plasma. The effect of nitrogen plasma treating time on the activity of photo-catalytic reduction of the Cr2O72− for sample obtained was investigated. The samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Transmission Electron Microscope (TEM) and Ultraviolet (UV). A peak of 396 eV in the N 1 s XPS spectra of sample obtained with nitrogen plasma treated TiO2 showed that nitrogen-doped titanium oxide (TiO2−xNx) has been obtained. The spectra of UV showed that the light absorption of TiO2−xNx obtained by nitrogen plasma treated TiO2 for 10min. had moved to the visible region. The picture of TEM and spectra of XRD indicated that the crystallographic forms and particle dimension had no apparent change for both the modified and the unmodified TiO2. When the TiO2 sample was treated for 7 min with nitrogen plasma, it exhibited best photo-catalytic activity.

Preparation of flat adherent diamond films on thin copper substrates using a nickel interlayer

Abstract Flat adherent diamond films on copper substrates have been prepared using a nickel interlayer. The structure of the interface between the substrate and the diamond film has been investigated using X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). XRD shows that a Cu–Ni alloy is formed on the substrate surface after a hydrogen plasma annealing treatment. XPS demonstrates that some chemical bonds such as CO, CC and C-metal appear on the surface of the substrate. The adhesion of the diamond film on the copper substrate is improved due to the formation of Cu–Ni alloy and C–Ni bonds at the interface. The optimum thickness of the nickel interlayer for the adhesion improvement is 5∼10 μm. To minimize the deformation of the specimen owing to the largely thermally-induced stress, a new three-step-method has been adopted to relax this stress. In the three-step-method, the intrinsic stress of the diamond film characterized by micro-Raman spectroscopy is controlled and adjusted by the deposition conditions. By balancing the tensile intrinsic stress and compressive thermal stress, a flat diamond film/copper substrate composite is obtained when the substrate temperature falls from the deposition temperature to room temperature.

Deposition of Diamond Films on Copper Substrate

The direct deposition of diamond films on copper substrate has been suffered from adhesion problems due to the mismatch of the thermal expansion coefficients of diamond and copper. In this paper, nuclei with valuable density were directly introduced through a submicron diamond powder layer. The diamond grits partially were buried in the copper substrate leading to better adhesion. Another method with nickel intermediate layer for enhancing the adhesion was studied here in detail. It was suggested that Cu-Ni eutectic between the copper substrate and Ni interlayer might contribute to the adhesion improvement. The quality of the diamond films deposited with nickel interlayer was investigated by scanning electron microscopy and Raman spectroscopy.

Microstructure and surface state of plasma-treated high-density polyethylene elucidated by energy-tunable positron annihilation and water contact angle measurements

High-density Polyethylene Elucidated by Energy-tunable Positron Annihilation and Water Contact Angle Measurements Zhe Chen1,2,∗, Zhi Wang1,2, Qiuming Fu1,2, Zhibin Ma1,2, Pengfei Fang3, and Chunqing He3 1Hubei Key Laboratory of Plasma Chemistry and New Materials, Wuhan Institute of Technology, Wuhan, 430073, China 2School of Material Science and Engineering, Wuhan Institute of Technology, Wuhan, 430073, China 3School of Physics and Technology, Wuhan University, Wuhan, 430072, China

Synthesis of Crystalline Carbon Nitride Thin Films by Pulsed Arc Discharge at Atmospheric Pressure

The preparation of crystalline C3N4 films was investigated using pulsed arc discharge from mixed methanol and ammonia water at atmospheric pressure. The X-ray diffraction (XRD) patterns of the films prepared at a substrate temperature of 450oC suggested that the film was composed of α-C3N4 and β-C3N4 crystallites. Raman spectra exhibited distinct peaks which are in good agreement with those predicted theoretically for C3N4 crystallites.

Microwave Plasma Chemical Vapor Deposition of Diamond Films on Silicon From Ethanol and Hydrogen

Diamond films with very smooth surface and good optical quality have been deposited onto silicon substrate using microwave plasma chemical vapor deposition (MPCVD) from a gas mixture of ethanol and hydrogen at a low substrate temperature of 450°C. The effects of the substrate temperature on the diamond nucleation and the morphology of the diamond film have been investigated and observed with scanning electron microscopy (SEM). The microstructure and the phase of the film have been characterized using Raman spectroscopy and x-ray diffraction (XRD). The diamond nucleation density significantly decreases with the increasing of the substrate temperature. There are only sparse nuclei when the substrate temperature is higher than 800°C although the ethanol concentration in hydrogen is very high. That the characteristic diamond peak in the Raman spectrum of a diamond film prepared at a low substrate temperature of 450°C extends into broadband indicates that the film is of nanophase. No graphite peak appeared in the XRD pattern confirms that the film is mainly composed of SP3 carbon. The diamond peak in the XRD pattern also broadens due to the nanocrystalline of the film.

Synthesis of Carbon Nanotubes by MWPCVD at Low Temperature

Growth of carbon nanotubes (CNTs) at low temperature is very important to the applications of nanotubes. In this paper, under the catalytic effect of cobalt nanoparticles supported by SiO2, CNTs were synthesized by microwave plasma chemical vapor deposition (MWPCVD) below 500°C. It demonstrates that MWPCVD can be a very efficient process for the synthesis of CNTs at low temperature.

Effects of Implant Copper Layer on Diamond Film Deposition on Cemented Carbides

The deposition of high-quality diamond films and their adhesion on cemented carbides are strongly influenced by the catalytic effect of cobalt under typical deposition conditions. Decreasing Co content on the surface of the cemented carbide is often used for the diamond film deposition. But the leaching of Co from the WC-Co substrate leading to a mechanical weak surface often causes a poor adhesion. In this paper we adopted an implant copper layer prepared by vaporization to improve the mechanical properties of the Co-leached substrate. The diamond films were grown by microwave plasma chemical vapor deposition from CH4:H2 gas mixture. The cross section and the morphology of the diamond film were characterized by scanning electron microscopy (SEM). The non-diamond content in the film was analyzed by Raman spectroscopy. The effects of pretreatment on the concentrations of Co and Cu near the interfacial region were examined by energy dispersive spectrum (EDS) equipped with SEM. The adhesion of the diamond on the substrate was evaluated with a Rockwell-type hardness tester. The results indicate that the diamond films prepared with implant copper layer have a good adhesion to the cemented carbide substrate due to the recovery of the mechanical properties of the Co-depleted substrate after the copper implantation and the formation of less amorphous carbon between the substrate and the diamond film.

Growth of Aligned Carbon Nanotubes through Microwave Plasma Chemical Vapor Deposition

Aligned carbon nanotubes (CNTs) were synthesized on glass by microwave plasma chemical vapor deposition (MWPCVD) with a mixture of methane and hydrogen gases at the low temperature of 550 °C. The experimental results show that both the self-bias potential and the density of the catalyst particles are responsible for the alignment of CNTs. When the catalyst particle density is high enough, strong interactions among the CNTs can inhibit CNTs from growing randomly and result in parallel alignment.