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The synthesis of 3D lamellar graphene/BaFe12O19 composites was performed by oxidizing graphite and sequentially self-propagating combustion triggered process. The 3D lamellar graphene structures were formed due to the synergistic effect of the tremendous heat induced gasification as well as huge volume expansion. The 3D lamellar graphene/BaFe12O19 composites bearing 30 wt % graphene present the reflection loss peak at -27.23 dB as well as the frequency bandwidth at 2.28 GHz (< -10 dB). The 3D lamellar graphene structures could consume the incident waves through multiple reflection and scattering within the layered structures, prolonging the propagation path of electromagnetic waves in the absorbers. [ABSTRACT FROM AUTHOR]

Amorphous carbon nanotubes (ACNTs) with diameters in the range of 7–50 nm were used as absorber materials for electromagnetic waves. The electromagnetic wave absorbing composite films were prepared by a dip-coating method using a uniform mixture of rare earth lanthanum nitrate doped ACNTs and polyvinyl chloride (PVC). The microstructures of ACNTs and ACNT/PVC composites were characterized using transmission electron microscope and X-ray diffraction, and their electromagnetic wave absorbing properties were measured using a vector-network analyzer. The experimental results indicated that the electromagnetic wave absorbing properties of ACNTs are superior to multi-walled CNTs, and greatly improved by doping 6 wt% lanthanum nitrate. The reflection loss (R) value of a lanthanum nitrate doped ACNT/PVC composite was –25.02 dB at 14.44 GHz, and the frequency bandwidth corresponding to the reflector loss at –10 dB was up to 5.8 GHz within the frequency range of 2–18 GHz. [ABSTRACT FROM AUTHOR]

Single-walled carbon nanotubes (SWCNTs) were prepared by a modified arc discharging furnace using Fe-Ni-Mg powders as catalyst at 600?C. The effects of catalyst composition and content on the production rate and purity of SWCNTs are investigated in this paper. When the Fe-Ni-Mg catalyst composition is 2 : 1 : 2 wt% and the catalyst content is 5 wt%, the experimental results indicate that the production of SWCNTs is 12 grams per hour, and the purity and diameter of SWCNTs are 70% and 1.22 ~ 1.38 nm, respectively. The results indicate that the cooperative function of catalyst composition and content plays an important role in the production of SWCNTs. The aim of this work is to control the production process of SWCNTs efficiently. [ABSTRACT FROM AUTHOR]

Abstract  The effect of oxygen on the growth of single-walled carbon nanotubes was studied with Ni–Co alloy powder as catalyst under helium atmosphere of 500 Torr by electric arc discharge. The oxygen included in nickel or (and) cobalt oxides was added in catalyst. The content of oxygen in atmosphere was controlled by changing vacuum degree inside furnace before inputting buffer gas. The examinations of TEM and Raman scattering showed that oxygen in metal oxide as catalyst promotes the nucleation of SWCNT by taking effect on the metal catalyst particles. However, O2 in atmosphere has the role of oxidizing amorphous particles along with nanotubes. When its molar proportion is higher than 0.22 ppm (Parts per million), the carbon nanotubes produced are oxidized and their purity decreases. The diameter of single-walled carbon nanotube obtained under different condition has a narrow distribution around 1.28 nm. [ABSTRACT FROM AUTHOR]

Medium-temperature coal tar pitch (CPT) which is used as C/C composites matrix precursor is modified by phenolic resin (PF) in the presence of p-toluene sulfuric (PTS) acid as catalyst. Fourier transform Infrared (FT-IR) spectroscopy techniques, polarized-light microscopy and thermaogravimetric analysis (TGA) are employed to study on structure and thermal behavior of the modified CPT, respectively. Results show that the high molecular weight aromatic species in modified CPT is found and also confirmed by the results from FT-IR and TGA analysis. Otherwise, coking yield of modified CTP has improved by 13% and soft point decreased by 25 °C compared with raw CPT. Moreover, the modification contributes to an improvement in the optical textures of resultant matrix precursor materials of C/C composites. [ABSTRACT FROM AUTHOR]

The radiation-induced damage in graphene irradiated with 8-MeV Cu2+ ions at fluences varying from 1 × 1015 ions/cm2 to 1 × 1016 ions/cm2 was studied. The samples were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and Raman spectra analysis. The number of point defects was observed to increase with the ion fluence until the adjacent point defects started to merge, forming individual amorphous regions. Then a critical stage, when the metallic nature of graphene was transformed into semiconducting, was reached for the first time in an ion beam irradiated graphene. It was noticed that further increase of the ion fluence results in a total conversion of the crystalline graphene structure into the massively disordered layer with decreased optical absorption. Density function theory calculations supported obtained experimental results. • The damage effect of 8-MeV Cu2+ irradiation on graphene was investigated. • SEM, TEM, HRTEM, and Raman analyses were used to study the ion irradiated graphene. • Vacancy and interstitial defects appeared and accumulated at low ion fluences. • Highly disordered and diffused structures arose at high fluence irradiations. [ABSTRACT FROM AUTHOR]