Jianbing Zang

Properties and applications of Ti-coated diamond grits

Abstract Diamond grits were coated with metal Ti by the vacuum slow vapor deposition method. The surface and interface characteristics of the Ti coating were studied using SEM and grazing incidence X-ray diffraction (GIXD). The strength of the Ti-coated diamond grits was measured by the single grit method and the thermal stability was investigated by differential thermal analysis. A diamond blade was produced with Ti-coated diamond grits and an Fe-based metal bond, and a sawing experiment was carried out. The configuration of the coated diamond grits on the working face was observed by use of a stereomicroscope. The results show that diamond grit strength improves after coating, the maximum increment reaching about 20%. The coating also can protect the diamond from oxidization, the oxidation temperature of the coated diamond grits reaching as high as 1024xa0°C. In comparison with un-coated diamond grits, the pull-out ratio of the coated diamond grits in the blade decreases dramatically from 60 to 20% and the protrusion height increases greatly also. Owing to the protection of the Ti coating on the diamond during sintering, the strength of the coated diamond eroded from the metal matrix is 24–50% higher than that of un-coated diamond in sintered tools. The blade life increases by 36%. Reducing the diamond grits concentration or using fine diamond grits can reduce the manufacturing cost of diamond tools.

Synthesis of B-doped diamond using graphite intercalation compounds (GICs)

Abstract A new method has been developed to synthesize B-doped diamond with B-doped graphite intercalation compounds (GICs). H3BO3-GICs that were prepared by the electrochemical method using a graphite slice as the anode, and saturated H3BO3 solution as the electrolyte. The stage structure was controlled by the electrolysis time. X-ray diffraction results show that 1–5 mixed stages B(OH)4-GICs were obtained after 15xa0h of anodic oxidation. The covalent B–C bond was detected by infrared absorption spectra. In order to remove impurity, annealing treatment was carried out at a temperature above 486xa0°C, which latter is the decomposition temperature of GICs. B-doped diamond was obtained by high-pressure synthesis using B-doped GICs as carbon sources. The structure and properties of the synthetic diamond were investigated by infrared absorption spectra, differential thermal analysis and scanning electron microscopy. The results show the oxidation temperature of the diamond synthesized from B-doped GICs was 1045xa0°C, which is higher than that of undoped diamond. The covalent B–C bond that lies in B-doped graphite is also present in B-doped diamond. The morphology of B-doped diamond particle shows a mosaic structure of sub-grains. The conclusion drawn from this is that the doping of B atoms leads to more nucleation cites.

Microwave synthesis and properties of MnO 2 /CNTs non-precious metal catalyst for oxygen reduction reaction in alkaline solution

Nanoscale manganese dioxide particles supported onto carbon nanotubes (MnO2/CNTs) were prepared through a microwave-assisted reduction method and used as a catalyst for oxygen reduction reaction (ORR) in an alkaline environment. The MnO2 with high crystallinity and nanosized birnessite-type was obtained by microwave irradiated for 60xa0s repeating 3 times. Especially, the MnO2/CNTs exhibited a positive onset potential (−u20098xa0mV vs. Hg/HgO) of ORR, which was similar to that of 20xa0wt% Pt supported on CNTs (Pt/CNTs). It was also found that the Koutecky–Levich plots of MnO2/CNTs suggested that its ORR proceeds via a 4-electron pathway. In addition, the accelerated durability tests indicated that the MnO2/CNTs composite catalyst was more stable than Pt/CNTs in 0.1xa0M KOH solution. The enhanced electrochemical activity and stability of MnO2/CNTs composite electrocatalyst can be attributed to the high electrical conductivity of CNTs and unique microstructure between MnO2 and CNTs, making it a promising candidate as an oxygen reduction catalyst in metal–air batteries and fuel cells.Graphical Abstract

Controllable Fabrication and Characterization of Si-coated Multiwalled Carbon Nanotubes

Quasi atomic layer deposition method has been utilized to coat MWNTs with continuous Si film. This deposition technique involves the decomposition of gaseous monosilane that is pumped into the vacuumed reaction chamber and the subsequent evacuation of the resultants alternately. The thickness of the film increases by repetitively employing this deposition process. X-ray diffraction, Raman spectra and transmission electron microscopy results indicate that the structure and the morphology of the film could be easily controlled by deposition temperature.

A novel hybrid of Ni and WC on new-diamond supported Pt electrocatalyst for methanol oxidation and oxygen reduction reactions

A hybrid of nickel and tungsten carbide on new‐diamond (Ni‐WC/nD) was synthesized by a microwave‐assisted method, in which nickel(tungsten) hydroxide was deposited on carbon black and then reduced carbothermally under N2 atmosphere. Pt nanoparticles (NPs) were deposited on the hybrid to form the Pt/Ni‐WC/nD electrocatalyst. XRD and TEM were used to investigate the structure and morphology of Pt/Ni‐WC/nD, respectively. The results revealed that Ni and WC particles formed on carbon black during the reduction of nickel(tungsten) hydroxide at 1300u2009°C under N2, and the amorphous carbon was translated to new‐diamond as a result of the catalysis of Ni. The Pt NPs deposited on Ni‐WC/nD exhibited a good affinity with the support. We demonstrated that Pt/Ni‐WC/nD was an active electrocatalyst for the methanol oxidation reaction (MOR) and the oxygen reduction reaction (ORR). Pt/Ni‐WC/nD exhibited a better electrocatalytic activity and durability than Pt/C electrocatalyst for the MOR and ORR. This can be attributed to the strong interaction between the Ni‐WC/nD support and Pt and the excellent stability of the new‐diamond.