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An advanced high-speed nanoindentation technique is employed to analyze the combined benefit of the particulate and continuous fiber's reinforcing effect of carbon fibers in the SiC matrix. Spray freeze granulated well-dispersed carbon nanofibers (CNF) containing precursor SiC-CNF (1 wt%) composite powder was used as a base matrix in which continuous carbon fibers were introduced in a systematic laying pattern to produce hybrid composite tubes with 10–12 mm wall thickness. Thin tubes with a wall thickness of 1–2 mm were produced with SiC, SiC-CNF composite powder. The two types of tubes with various lengths were cold isostatically pressed and pressureless sintered at 2150°C/1hour under Argon (Ar). The surface properties of the sintered tubes were further enhanced by coating with a dense SiC layer by adopting a CVD technique. The properties of the fiber-matrix interface and coating-matrix interfaces of the tube samples were evaluated using conventional processes as well as the nanoindentation techniques and compared at different length scales. Attempts have been made to correlate the structure-property relations of complex multi-phase of SiC composites employing high-speed nanoindentation mapping as well as XRD, Digital optical, SEM, and TEM analysis. [ABSTRACT FROM AUTHOR]

Coiled carbon nanofiber were selectively synthesized over Inconel metal as substrate. Effect of different heating rates and substrate surface roughness on morphology of coiled carbon nanofibers was studied using various characterization techniques. After analysis of carbon growth, best heating rate for homogenous coiled growth was identified as 5°C min−1 with surface roughness of 1.7 µm for Inconel. The coiled carbon nanofibers were used as filler materials with different wt. % in polyurethane for fabrication of nanocomposite. Properties of nanocomposites and nanofibers were studied using FESEM and XRD. Mechanical properties were also investigated by nano indentation, wear and tensile testing. There was 114% and 48% increase in elastic modulus and hardness respectively. With increase in wt. % of carbon nanofibers there was also decrease in wear and increase in tensile strength of polymer nanocomposite. [ABSTRACT FROM AUTHOR]

In this paper, the influence of carbon fillers with different structures such as carbon black (spherical), carbon nanofibers (fibrous), carbon nanotubes (tubular) and hydroxylated carbon nanotubes on the performance of acrylonitrile-butadiene rubber (NBR) composites have been investigated. The studies prove the significant role of the filler's structure, surface characteristics and filler-filler interactions for composite reinforcement. As part of this study, the cure behaviour, crosslink density, thermal stability, electrical conductivity and mechanical properties of the filled NBR compounds were measured. Furthermore, scanning electron microscopy (SEM) as well as dibutylphthalate absorption (DBPA) measurements were carried out to determine the nature of the tested materials. It has turned out that the greatest reinforcing activity was exhibited by the carbon nanotubes (CNTs). However, all the tested carbon fillers significantly affected the performance of the nitrile rubber composites, which make them attractive additives for elastomer composites. [ABSTRACT FROM AUTHOR]

The nanomaterial is very popular in recent years. In this article, a new hybrid system by nickel oxide-modified Ag NPs/CNFs has been successfully produced by combining the electrospinning technique and calcination. Different proportions of nickel nitrate were mixed into the solution and the influence on the morphological structure of Ag nanoparticles was investigated, and then composite nanofibers were investigated, which indicated that Ag nanoparticles and NiO nanoparticles were uniform in size and dispersed homogeneously in the carbon nanofibers by different characterizations. [ABSTRACT FROM AUTHOR]

Carbon nanofibers (CNFs) containing sliver nanoparticles (Ag NPs) were prepared viain situreduction, electrospinning, and high-temperature calcination technique. Tetrabutyl titanate, the precursor of titanium dioxide (TiO2), was adsorbed to the surface of Ag/CNFs by physical adsorption process. Ag–TiO2/CNFs nanocomposites were obtained by high-temperature calcination treatment. Then, Ag NPs were oxidized to sliver bromide (AgBr) using bromine (Br2) as an oxidant. The characterizations of scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, proved that AgBr and anatase TiO2NPs deposited on the surface of CNFs. The photocatalytic experiments exhibited that the as-prepared AgBr–TiO2/CNFs were easily recycled and the introduction of AgBr NPs made them possess well photocatalytic activity under visible light (λ ≥ 400 nm). [ABSTRACT FROM AUTHOR]

Carbon nanofibers (CNFs) are ozone-treated for different time durations (45 and 90 min). Changes in surface characteristics of CNFs due to ozone treatment were studied with BET surface area analyzer and Raman spectroscopy. Raman spectroscopic studies showed that ozone treatment is imparting enhanced degree of disorder for CNFs. Changes in surface functional groups of CNFs due to ozone treatment were estimated using elemental analysis and thermogravimetric analysis. The influence of ozone-treated CNFs on the mechanical properties of laminated (2D) carbon fiber-reinforced epoxy matrix (CFRP) composites has been studied. Results indicate that ozone-treated CNFs can improve the mechanical properties of CFRPs significantly as compared to untreated CNFs due to enhanced interface compatibility between the ozone-treated CNFs to the matrix. Ozone treatment of CNFs proposed in this study has the potential to overcome the limitations of the conventional methods of generating functional groups. [ABSTRACT FROM PUBLISHER]

Electrically conducting nanocomposites were prepared by melt mixing process using high density polyethylene (HDPE) with 20 wt.% of carbon black (CB) and 0–1 wt.% of multiwalled carbon nanotubes (MWNTs). The effects of MWNTs in HDPE-CB-MWNTs composites were examined using X-ray diffraction and differential scanning calorimeter. DC resistivity (ρdc), AC conductivity (σac), and some dielectric properties and electromagnetic interference (EMI) shielding effectiveness of these composites have been investigated. The results reveal thatρdcdecreases significantly whereasσac,, and EMI shielding effectiveness increase with loading of MWNT. The values of,, andσacare frequency dependent. Positive temperature coefficient effects are observed to be dominant over temperature range of 60–105 °C and the shielding effectiveness is frequency dependent over the X band (8.2–12.4 GHz). [ABSTRACT FROM PUBLISHER]

High density polyethylene (HDPE)/poly (ethylene terephthalate) (PET) (90/10 wt.%) blends and HDPE/PET/multi-walled carbon nanotubes (MWCNTs) nanocomposites were prepared by melt mixing process, and the influence of MWCNTs on the mechanical and rheological properties of the nanocomposites was investigated. MWCNTs were added up to 5 wt.% in the HDPE/PET matrix. Transmission electron microscopy images reveal that the MWCNTs were homogeneously dispersed in the HDPE/PET matrix. Improvement of mechanical properties was observed by the addition of MWCNTs compared with HDPE/PET blends. Prominent increases in the complex viscosity and storage modulus of the nanocomposites were found with increasing MWCNT content. [ABSTRACT FROM PUBLISHER]

The addition of carbon nanofibers to a polymeric matrix is known to affect its mechanical and electrical properties, although the mechanisms responsible for the changes are not sufficiently understood. Particularly, there are currently no adequate predictive methods that allow the creation of knowledge-based structures tailored for specific electrical response. We have developed a method for predicting the electric and dielectric properties of nanofiber-reinforced polymer matrices based on the application of the graph theory and circuit laws. We consider the individual properties of the polymeric matrix and the complex nanofiber network (including fiber orientation, concentration, and size), under an applied external electric field, and from the analysis we obtain information such as perlocative pathways, breakdown voltage, and impedance of the overall system. Simulations for two-phase systems consisting of a dielectric matrix and randomly oriented nanofibers have shown that the concentration and the length of the fibers affect the properties. Increased concentrations or longer fibers both result in networks for which it is easier to establish conducting paths through breakdown mechanisms. [ABSTRACT FROM AUTHOR]

Reaction of herring-bone graphitic carbon nanofibers (GCNFs) containing surface-bound acid chloride functional groups with 3-aminopropyl triethoxysilane (APTES) leads to amide condensation and formation of carbon nanofibers surface-derivatized with pendant Si—OEt and Si—OH functional groups, GCNF-[C(O)NH(CH2)3Si(OEt)(OH)2]x. Addition of these GCNFs containing covalently bound 3-amidopropylsilyl linker molecules to silica sol-gel formulations gives GCNF/silica xerogels as dry black powders. Covalent binding of the linker molecule across the GCNF/ceramic interface is indicated by intermediate formation of especially stable GCNF/silica sol dispersions and the isolation of uniformly black GCNF/silica xerogel powders. SEM micrographs reveal excellent wetting of the carbon nanofiber surface by the silica xerogel matrix, and the presence of amido-carbonyl groups is confirmed from infrared spectral data. TGA plots show mass losses consistent with dehydration of the gel matrix and thermal decomposition of linker molecules at elevated temperature. [ABSTRACT FROM AUTHOR]