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SiC/multi-walled carbon nanotube (MWCNT) composites are considered to be promising materials for high-temperature electromagnetic wave (EMW) absorption due to their strong thermal stability and tunable dielectric properties. However, the EMW absorption performance of these composites is limited by poor impedance matching. This study proposes a novel multiscale structure synergistic regulation approach to enhance EMW absorption performance, which involves constructing a heterointerface structure and a triple periodic minimal surface (TPMS) meta-structure. The addition of a SiO 2 shell as an impedance layer to the SiC/MWCNT core to improve the intrinsic impedance. Meanwhile, the heterointerface between the core-shell structure leads to multiple interface polarization, significantly enhancing EMW energy dissipation. Consequently, the effective absorption bandwidth (EAB) of SiO 2 –SiC/MWCNT composites increased from 0.88 to 4.56 GHz. Furthermore, a TPMS meta-structure, fabricated by three-dimensional (3D) printing and sol infiltration technology, is developed to further improve impedance matching with the equivalent electromagnetic effect. Simulation and experimental results demonstrate that the SiO 2 –SiC/MWCNT TPMS meta-structure exhibits broadband EMW absorption performance, with the EAB reaching 7.2 GHz. This improvement is attributed to the synergistic regulation of the heterointerface structure and TPMS meta-structure, which provides a good balance between the requirements of electromagnetic loss and impedance matching. Additionally, the composites exhibit excellent oxidation resistance, as their EAB remains almost unchanged after exposure to 1000 °C for 6 h. This research offers a new design paradigm for ultrabroadband design of the nonmagnetic high-temperature absorbing materials. [Display omitted] [ABSTRACT FROM AUTHOR]

Self-organized vertically aligned or entangled randomly-oriented carbon nanotubes films filled with ferromagnetic Fe-based phases have recently attracted a great attention for numerous applications as potential electrodes. However the large difference between their synthesis –i) methods, -ii) parameters or –iii) the specific hydrocarbons-requirement have posed many challenges in the growth-selection of one of these film-morphologies. Another important issue is the brittleness of the first type of films which is generally due to low intimate contacts between each carbon nanotube comprised in the vertically aligned films and limits their direct implementation into applications. We propose an advanced low-flow rate chemical vapour deposition approach which allows the selection of either a free-standing flexible film comprising vertically aligned carbon nanotubes filled with large quantities of Fe 3 C particles or a free-standing flexible buckypaper comprising entangled randomly-oriented carbon nanotubes films partially filled with Fe 3 C through the simple control of the evaporation temperature of the used precursors consisting of large quantities of ferrocene and very low concentrations of dichlorobenzene. The morphological, cross sectional and structural properties of the obtained nanostructures are investigated. [ABSTRACT FROM AUTHOR]

We report an advanced chemical vapour deposition approach which yields not previously observed carbon-based foam-like films completely filled with a single phase of α-Fe. These films are found in the region of the chemical vapour deposition reactor where the temperature is relatively low (650–770 °C) and exhibit a high saturation magnetization as high as 200–220 emu/g at room temperature when small concentrations of Cl-radicals are added to the pyrolysing CVD system by mixing 0.15 ml of dichlorobenzene to ferrocene. Instead when the only ferrocene is used a lower saturation magnetization of 140–145 emu/g is found due to an amorphous arrangement of the Fe-phase in some parts of the foam. Also we show that for much higher concentration of Cl radicals (0.65 ml of dichlorobenzene mixed to ferrocene) a dramatic decrease of the quantity of crystalline α-Fe is found together with the formation of amorphous Fe and Fe x O x phases. [ABSTRACT FROM AUTHOR]

FePd and CoPd tetragonal ferromagnetic nanoparticles have recently attracted a great attention due to their large magneto-crystalline anisotropy of ∼10 8 erg/cm 3 ideal for fabrication of magnetic-arrays with giant-coercivities. However, no studies are reported on the fabrication of these alloys inside carbon nanotubes. Here we reveal the synthesis of the FePd 3 –Fe 0.037 Pd 0.963 –Fe 3 C inside carbon nanotubes by chemical vapor deposition of large quantities of ferrocene with low quantities of dichloro-cyclooctadiene-palladium and its transformation to Fe 0.438 Pd 0.561 through annealing. Instead, planar graphitic structures with embedded FePd 3 –Fe 0.037 Pd 0.963 or CoPd/CoPd 2 particles are found when large quantities of dichloro-cyclooctadiene-palladium are pyrolyzed with low quantities ferrocene or cobaltocene. [ABSTRACT FROM AUTHOR]

Advanced hierarchical hybrid nanostructures of polar, conductive and catalytic chemical traps/carbon with rationally tailored components, structures, and chemistries are important in determining the performance of lithium-sulfur (Li–S) batteries. Herein we propose a facile strategy to prepare 3D-structured CNF@graphene-CoSe (CNF@G L -CoSe) cable/sheath heterostructure with the in-situ formed CoSe as a catalyst for graphene-like carbon growth and Se as a catalyst promoter. The architecture integrates high electrical conductivity, effective ion transport, notable polysulfide entrapment, and polysulfide redox kinetics, availing lithium/sulfur conversion when applied as an interlayer in a Li–S battery. As expected, the battery delivered a low decay of 0.053% per cycle over 700 cycles at 1 C. The capacity even remained 649.4 and 524.5 mA h g−1 at 4 and 6 C, respectively. Furthermore, an areal capacity of about 3 mA h cm−2 at 0.1 C after long-term tests can still maintain with sulfur loading of 4.5 mg cm−2. A facile effective strategy to prepare 3D-structured CNF@graphene-CoSe cable/sheath heterostructure with the in situ formed CoSe as a catalyst for graphene-like carbon growth and Se as a catalyst promoter, achieving significant enhancement in electrochemical performance of Li–S batteries. [Display omitted] • In situ constructing CNF@graphene-CoSe cable/sheath heterostructure. • CoSe catalyzes the growth of graphene sheath and Se as a catalyst promoter. • Synergism of conductivity, absorption and catalysis. • Enabling excellent performance as an interlayer. [ABSTRACT FROM AUTHOR]

Highly purified and uniformly distributed carbon nanotube (CNT) network is one of the key issues for developing advanced nanocomposites. However, the challenge for mitigation of the aggregation of CNT bundles during the CNT film fabrication still remained. In this work, debundling and reorganization of CNT bundles have been realized simultaneously by using a high-temperature thermal treatment. The debundling of large CNT bundles into small ones started after they were heat treated under 1400 °C and uniformly distributed CNT networks with small bundles were obtained after heat treated under 1800 °C. The tensile strength of the CNT film significantly increased by about 64% compared to the pristine film. Microstructural observations showed that the iron nanoparticles started to evaporate at 1400 °C and were completely removed at 1800 °C. Hollow amorphous carbon shells wrapped on the nanoparticles were left inside the CNT networks after the removal of the iron nanoparticles. Interestingly, these amorphous carbon shells act as carbon source for the deposition of a carbon layer on the CNT surface when the heat treatment temperature was up to 2000 °C, and they were completely consumed after being treated at 2800 °C. The microstructural evolution process of CNT bundles during heat treatment suggests the simple high-temperature treatment strategy could be applied for fabrication of highly purified CNT networks with well-distributed small bundles, enabling the development of advanced multifunctional nanocomposites in the near future. A high-temperature heat treatment is used to investigate the microstructure evolution and mechanical properties of CNT films. Benefiting from the high-purity and uniformly distributed CNT networks with small bundles after heat treated under 1800 °C, the tensile strength of the CNT film has significantly increased by ∼64% compared to the pristine film. When heat treated under 2800 °C, the hollow amorphous carbon shells are completely consumed and act as carbon source for deposition of carbon layer on the CNT surface. [Display omitted] • Debundling of large CNT bundles was observed after a high temperature treatment. • A regenerative carbon layer was deposited on CNT surface under high temperature. • The microstructural evolution of CNT networks under high temperature was proposed. [ABSTRACT FROM AUTHOR]

Abstract The micro-mechanical responses of an electrode dominate its electrochemical performance and lifetime. Herein, an experimental method is proposed to investigate the micro-strain/stress of graphene electrodes during galvanostatic charge/discharge cycling. The characteristic Raman peak of the graphene electrode is acquired in situ in a modified coin cell as a function of time. And two mechanical models are established, including microscale plane strain and plane stress with Li-induced-stiffening. Combining the mechanical models and the measured 2D peak, the micro-strain and micro-stress of the graphene electrode are quantitatively characterized. Furthermore, the deformation mechanism and rate-dependent characteristics are discussed. Excepting slight compressive loads by the solid–electrolyte interface film, the graphene experiences an increasing tensile strain/stress with increasing capacity. The stresses significantly depend on the charge/discharge rate, where higher stresses are induced at higher currents with a multiplicative relationship between the stress and current increments. The origins of the stress differences between macroscale and microscale involve the elongation of the intralayer C−C bonds caused by intercalated Li between the graphene layers and a microscopic concentration gradient. This work enhances the understanding of the microscopic mechano-electro-chemical mechanism of graphene electrodes and facilitates theoretical modeling of the stress with Li concentration and current. Graphical abstract Image 106365 [ABSTRACT FROM AUTHOR]

Hydropropylcellulose (HPC)-modified multi-wall carbon nanotubes (HPC-MWCNTs) were prepared by physical adsorption of HPC on the surface of MWCNTs. The modification decreased the contact angle of water on HPC-MWCNTs and increased their water dispersion ability. However, HPC-MWCNTs dispersed in water were not stable and precipitated on the bottom of the container after 2days as cylindrical bundles with a diameter of 4–8μm and a length of 25–35μm. The cylindrical bundles were formed by self-assembly of HPC-MWCNTs by hydrophilic and hydrophobic interactions. [New Carbon Materials 2013, 29(1): 26–33] [ABSTRACT FROM AUTHOR]

Abstract: Direct-current (DC) arc plasma jet has been utilized to anneal chemical vapor deposited (CVD) polycrystalline diamond produced by the same device. Intense heating pulses around several target temperatures were achieved under constant plasma state and chamber pressure (∼5kPa), which ensured this plasma low-pressure/high-temperature (LPHT) treatment succeed without diamond graphitization. The treatment significantly improves the fracture strengths of the diamond samples. The enhancement is ideally proportional to the temperature and the largest increase is up to 96.38%. Fractographic analysis has been done by scanning electron microscope (SEM), and the transgranular fracture/intergranular fracture ratio increases as the temperature increases. Raman spectra indicate that there exists huge compressive stress (>1.6GPa) at the grain boundaries after the treatment so that the boundary strength is greatly enhanced. The interacting relationship between the interface graphitization and the compressive stress might play a crucial role in preventing the interface from further graphitization. This suggests that the plasma LPHT treatment can be improved by using higher temperature or longer time. [Copyright &y& Elsevier]