Uncoalesced a-plane GaN epitaxial lateral overgrowth (ELO) structures have been synthesized along two mask stripe orientations on a-plane GaN template by MOCVD. The morphology of two ELO GaN structures is performed by Scanning electronic microscopy. The anisotropy of crystalline quality and stress are investigated by micro-Raman spectroscopy. According to the Raman mapping spectra, the variations on the intensity, peak shift and the full width at half maximum (FWHM) of GaN E2 (high) peak indicate that the crystalline quality improvement occurs in the window region of the GaN stripes along [0001], which is caused by the dislocations bending towards the sidewalls. Conversely, the wing regions have better quality with less stress as the dislocations propagated upwards when the GaN stripes are along []. Spatial cathodoluminescence mapping results further support the explanation for the different dislocation growth mechanisms in the ELO processes with two different mask stripe orientations.
Ferritic-martensitic steels and ODS steels are attractive candidates for structural materials in advanced nuclear-power systems due to their good swelling resistance. Four kinds of steels, F82H, 15Cr-ODS, SIMP and T91, are investigated in this study. We take 6.4 MeV Fe3+ ions and energy-degraded 1.0 MeV He+ ions in the irradiation of these materials to 5 dpa and 60 appm He/dpa, 200 appm He/dpa and 600 appm He/dpa at 300 °C and 450 °C, respectively. The bubble formation and distribution are investigated by transmission electron microscopy (TEM). Formation and distribution of the bubbles in the four investigated steels are compared. The influence of irradiation temperature and helium injection ratio on bubble formation is discussed. It is found that there appears to be homogenously distributed bubbles at 300 °C irradiation while heterogeneously distributed bubbles at 450 °C irradiation.
Aiming at solid waste resources reuse and energy saving issue, a novel flexible paraffin/carbon fiber@carbon nanotubes (Paraffin/CF@CNTs) composite PCM was prepared in this study. In the flexible composite PCM, CNTs grow surrounding with recycled CF trunk via chemical vapor deposition to construct the fiber net-structure utilized as the supporting material, and paraffin as thermal energy storage material was absorbed into spongy CF@CNTs by vacuum impregnation methods. TG results show the paraffin/CF@CNTs composite decomposes over 215.6℃ with totally 51.9% mass loss. DSC results indicate Paraffin/CF@CNTs composite melts at 40.01 ℃ with latent heat of 81.94 Jg-1 after solid-solid phase transition with 15.28 Jg-1, while the thermal conductivity of Paraffin/CF@CNTs composite (1.551 Wm-1K-1) is enhanced by 573% than that of pure paraffin. Moreover, thermal cycling measurements show the Paraffin/CF@CNTs composite PCM has adequate structure, chemical component and thermal stability even after being subjected to 300 melting/freezing cycles. In result, the novel flexible composite PCM looks promising for applications in electronic device temperature control, near-infrared stealth, smart wear and textile industry.
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