Xueni Zhao

Nitrogen-doped carbon nanotubes synthesized by pyrolysis of nitrogen-rich metal phthalocyanine derivatives for oxygen reduction

Two kinds of N-doped multiwalled carbon nanotubes (N-MWCNTs) S1 and S2 are prepared by pyrolysis of nitrogen-rich metal phthalocyanine derivatives, i.e. a mixture of metal tetrapyridinoporphyrazines (MTAPs, M = Fe2+, Ni2+) and tetrapyrazinoporphyrazines (MPTpzs) in a chemical vapour deposition furnace. The N-MWCNTs S1 and S2 have a straight structure and a high N/C atomic ratio. The ratios of N/C in S1 and S2 are 20.01% and 18.50%, respectively. The N atoms in S1 exhibit a uniform distribution, and the majority of N atoms are present in a pyridine type environment, while the N atoms in S2 are concentrated in certain areas, and are mainly in a graphite type environment. The electrocatalytic activities of the N-MWCNTs obtained are measured by the rotating disk electrode technique and cyclic voltammetry in an oxygen-saturated 0.1 M KOH solution. The results show that S1 exhibits a one-step, four-electron pathway for the reduction of oxygen (ORR), whereas S2 exhibits a two-step, two-electron process for ORR, S1 has much higher catalytic activity than S2.

Electrorheological behavior of kaolinite–polar liquid intercalation composites

In this paper, two kaolinite hybrids have been synthesized using an intercalation method and characterized by XRD and FTIR. The result shows that DMSO (dimethyl sulfoxide) intercalated the interlayer of kaolinite and the basal spacing of hybrids was swelled from 0.715 to 1.110 nm, so that the kaolinite–organic matter intercalation compounds were formed. Then the dielectric and rheological properties of the ERF (electrorheological fluid) were measured. The results show that in electric fields of 3 kV mm−1, the shear stress of DMSO/kaolinite ERFs can be 600 Pa (shear rate 5 s−1) which is 2.14 times higher than that of pure kaolinite ERFs. In the meanwhile, the sedimentation and temperature effect is excellent. The intrinsic reason for enhancement of the rheological properties is the improvement of the dielectric properties of the intercalation hybrid. The properties of glycerol/kaolinite ERFs were enhanced also, but an optimum electrorheological effect zone appeared at a glycerol content of 6%.

N-doped graphene analogue synthesized by pyrolysis of metal tetrapyridinoporphyrazine with high and stable catalytic activity for oxygen reduction

We fabricated N-doped graphene analogue by pyrolysis of metal tetrapyridinoporphyrazine (MTAP), a kind of N rich metal phthalocyanine derivative with four pyridine substituents. The combination results of elemental analysis, X-ray photoelectron spectroscopy and electron-energy-loss spectrometry mapping show that the obtained N-doped graphene analogue is nitrogen-rich and has uniform distribution of C and N atoms. The atomic ratio of N/C in the obtained graphene is about 20.5%. The majority of N atoms are present in a pyridine type environment. Theoretical analysis based on DFT calculations has been performed for a deep understanding of the role of MTAP in the synthesis of the N-doped graphene analogue. Electrochemistry results show the N-doped graphene analogue exhibits a one-step, four-electron pathway for oxygen reduction reaction, and shows almost identical voltammetric responses before and after about 100 000 cycles, indicating that it has high and stable electrocatalytic activity for oxygen reduction.

Improved Surface Wettability of Water by Applying SiC/Ti6Al4V Coatings on Carbon/Carbon Composites

SiC/Ti6Al4V coatings were applied on carbon/carbon composites to improve the surface wettability of water. SiC interlayers were preprepared by pack cementation to bond both the carbon/carbon composites and the Ti6Al4V, and then the Ti6Al4V coatings were applied by magnetron sputtering technique. The morphology and crystalline of the SiC/Ti6Al4V coatings were analyzed by scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction. The surface wettability of the coatings was tested by video-based contact angle measuring device. The results showed that SiC can serve as an interlayer between the carbon/carbon composites and Ti6Al4V. The SiC/Ti6Al4V coatings covered the carbon/carbon composites uniformly with spherical morphology. The coatings improved the surface wettability of carbon/carbon composites with the contact angle of water decreasing from 85.7 ± 4.1° to 26.5 ± 0.1°.

A SIMPLE METHOD OF APPLYING CARBON FOAM COATING FOR CARBON/CARBON COMPOSITES TO MODULATE CELL COMPATIBILITY

A simple slurry method was used to prepare carbon foam coatings on biomedical carbon/carbon composites to modulate the cell compatibility. The surface morphology and microstructure of the coatings were characterized and the effect of applying carbon foam coatings on cell morphology and cell proliferation was investigated. The results showed that the carbon foam coatings, consisting of carbon microspheres, resin carbon matrices and pores, covered the carbon/carbon composites entirely and uniformly with amorphous structures. There were large numbers of pores with a size ranging from submicron to tens of micrometers being found for the coatings. The cell culture experiments exhibited that both the cell spreading and the cell proliferation were improved after the preparation of the carbon foam coatings. It could be demonstrated that applying carbon foam coatings by a simple slurry method was an effective way to improve the cell compatibility of carbon/carbon composites.