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Theories of Synthetic Aperture Radar
Published in Maged Marghany, Automatic Detection Algorithms of Oil Spill in Radar Images, 2019
In G- Band there are numerous mobile military battlefield surveillance, missile-control and ground surveillance radar sets with a short or medium range. The dimension of the antennas delivers an exceptional precision and determination, nonetheless, the relatively small-sized antennas do not perturb a fast moving one. The impact of imperfect weather circumstances is incredibly extraordinary. Thus, air-surveillance radars deplete an antenna often maintained with circular polarization. This frequency band is encoded for furthermost sorts of weather radar, which operate to locate precipitation in temperate zone such as Europe.
Graphited mesoporous carbon as polysulfide host by chemical vapor deposition for high-rate Li-S batteries
Published in Binoy K. Saikia, Advances in Applied Chemistry and Industrial Catalysis, 2022
Xiaoqiang Liang, Cai yun Chang, Yadong Chen, Jun Tian, Yituo Wang, Na Liu, Yadi Liu
The carbons powder's X-ray diffraction (XRD) patterns via the CVD method with 950°C (named CVD-C-1), 1000°C (named CVD-C-2), and CMK-3 materials, are illustrated in Figure 1 a-b. The specific angle portions of the XRD patterns (below 2θ = 5°) show (100) peak that indicates the mesostructured of the carbons, which indicates a long-range structure ordering of materials (Jun et al. 2000). However, the low-angle region of the CVD-C-2 sample does not show any peaks, which are reduced deeply at higher CVD temperatures and long holding times (Xia & Mokaya 2004). Furthermore, the specific angle portions (above 2θ = 10°) of all the samples show peaks at 2θ = 26, 43, and 54° which can be respectively attributed to (002), (101), and (004) diffraction peaks from graphitic pore walls (Kim et al. 2003). According to the Bragg equation, the corresponding crystal plane spacing can be calculated, be 0.34nm, 0.21nm, and 0.17nm, respectively. The XRD patterns indicated that the CVD-C-2 carbon holds graphitic (i.e., crystalline) rather than amorphous pore walls. The narrow peaks (002) because of graphitic ordering in the pore walls increased at higher carbonization temperatures. The results of powder XRD with the Raman spectra of different carbons shown in Figure S1 are consistent. The Raman spectra indicate two bands at ca. 1350 cm−1 (D-band) and ca. 1580 cm−1 (G-band), respectively. The intensity ratios of the D and G bands (ID/IG) value of the CVD-C-2 sample was 1.11. It can be concluded that CVD-C-2 samples have abundant defects, which are conducive to the diffusion of lithium ions. The results proved that the carbonization temperature increased, the higher level of crystalline character of carbons formed, in accordance with the XRD patterns.
Preparation of exfoliated graphite-based polyethylene composites with enhanced thermal conductivity
Published in Soft Materials, 2020
Hongwei Fang, Yixian Liu, Guohua Li, Yingchun Liu, Lianqi He, Xiongwei Qu
where is the in-plane crystallite size, is wavelength of the laser line, is a ratio of D-band to G-band intensity.
The roles of free carbon over ZnO in enhancing the photocatalytic properties for removal of Cr(VI)
Published in Journal of Dispersion Science and Technology, 2022
Quanchao Du, Jianqi Ma, Jianwei Ji, Qian Wang, Shaobo Guo, Xianzhao Shao, Guanghui Tian
In order to investigate the effect of carbon structures on the photocatalytic activity, the samples of ZnO@C 400, ZnO@C 600 (ZnO@C-2h), and ZnO@C 800 were obtained by calcining ZnO@PDA-2h at different temperatures (400/600/800 °C) in an N2 atmosphere for 2 hours. The nature of the carbon present in the ZnO@C samples with different calcination temperatures was first investigated by Raman spectroscopy and the results were recorded, as shown in Figure 5. Two characteristic peaks of amorphous carbon were observed at around 1340 and 1585 cm−1 for all the ZnO@C samples with different calcination temperatures, which were denoted as D-band and G-band, respectively. The G-band at around 1585 cm−1 could be attributed to the Raman-active E2g mode of graphitic sheets, which revealed the presence of sp2 carbon-type structures within the carbonaceous wall of all the samples. The D-band at around 1340 cm−1 was generated by the formation of defects within the hexagonal graphitic structure.[33–35] The G-band shifted to higher wavelength with the increase in calcination temperature, indicating that graphite structure became more imperfect after calcination.[36,37] The ratio of ID and IG is also an important indicator of the content of defects and disorder in the crystalline carbon structures. From Figure 5, the ID/IG ratios of the ZnO@PDA, ZnO@C 400, ZnO@C 600, and ZnO@C 800 are 0.79, 0.89 1.05, and 1.14, respectively. It demonstrated that the content of defects in the carbon coating became larger during the carbonization process at higher temperature. It should be noted that the sample turned gray-white after calcination at 800 °C, indicating that most of the carbon coating had been burned off. Thus, the defects of ZnO@C 800 did not increase, although the content of the defects increased. The formation of more defects might be an important factor for improving the photocatalytic activity of the catalyst.