Doping inhomogeneity and staging of ultra-thin graphite intercalation compound flakes probed by visible and near-infrared Raman spectroscopy

When ultra-thin graphite intercalation compounds（GICs） are deposited on the SiO2/Si substrate, it is found that their colors are dependent on the thickness of GIC flakes. The sample colors of ultrathin GIC flakes can no longer provide qualitative information on the stage index. Here, multi-wavelength Raman spectroscopy is thus applied to study the doping inhomogeneity and staging of ultra-thin GICs by FeCl3 intercalation. The G band intensity of stage-1 GIC flakes is strongly enhanced by 532-nm laser excitation, while that of stage-2 and stage-3 flakes exhibits strong intensity enhancement for 785-nm laser excitation. The near-infrared lasers are suggested to probe the doping inhomogeneity and staging of ultra-thin GIC flakes.

Evaluation of The Thermal Performance of Multi-Element Doped Graphite under Steady-State High Heat Flux

Multi-element doped graphite, GBST1308 has been developed as a plasma facing material (PFM) for high heat flux components of the HT-7U device. The thermal performance of the material under steady-state (SS) high heat flux was evaluated under actively cooling conditions, the specimens were mechanically joined to copper heat sink with supercarbon sheet as a compliant layer between the interfaces. The experiments have been performed in a facility of ACT (actively cooling test stand) with a 100 kW electron gun in order to test the suitability and the loading limit of such materials. The surface temperature and bulk temperature distribution of the specimens were investigated. The experimental results are very encouraging that when heat flux is not more than 6 MW/m2, the surface temperature of GBST1308 is less than 1000℃, which is the lowest, compared with IG-430U and even with CX-2002U (CFC); The primary results indicate that the mechanically-joined material system by such a proper design as thin tile, super compliant layer, GBST as a PFM and copper-alloy heat sink, can be used as divertor plates for HT-7U in the first phase.

Sodium-doped carbon nitride nanotubes for efficient visible light-driven hydrogen production

Sodium-doped carbon nitride nanotubes （Nax-CNNTs） were prepared by a green and simple two-step method and applied in photocatalytic water splitting for the first time. Transmission electron microscopy （TEM） element mapping and X-ray photoelectron spectroscopy （XPS） measurements confirm that sodium was successfully introduced in the carbon nitride nanotubes （CNNTs）, and the intrinsic structure of graphitic carbon nitride （g-C3N4） was also maintained in the products. Moreover, the porous structure of the CNNTs leads to relatively large specific surface areas. Photocatalytic tests indicate that the porous tubular structure and Na＋ doping can synergistically enhance the hydrogen evolution rate under visible light （λ 〉 420 nm） irradiation in the presence of sacrificial agents, leading to a hydrogen evolution rate as high as 143 μmol·h-1 （20 mg catalyst）. Moreover, other alkali metal-doped CNNTs, such as Lix-CNNTs and Kx-CNNTs, were tested; both materials were found to enhance the hydrogen evolution rate, but to a lower extent compared with the Nax-CNNTs. This highlights the general applicability of the present method to prepare alkali metal-doped CNNTs; a preliminary mechanism for the photocatalytic hydrogen evolution reaction in the Nax-CNNTs is also proposed.