CNT Particles Research Articles

The electrical and corrosion properties of carbon nanotube coated 304 stainless steel/polymer composite as PEM fuel cell bipolar plates

In this study, the contact resistance and corrosion resistance of three different types of plates used as PEM fuel cell bipolar plates are investigated, viz. (1) 304 stainless steel without carbon nanotube treatment that was then sandwiched between polymer composites, (2) CNT particles placed on the surface of the 304 stainless steel that was then sandwiched between polymer composites, and (3) direct CNTs coated 304 stainless steel that was then sandwiched between polymer composites. Both treated and untreated 304 stainless steel covered with the polymer composites exhibited good corrosion resistance. The results showed that the highest improvement of the contact resistance was accomplished by the direct deposition of CNTs on the 304 stainless steel insert. The results of the potentiodynamic and potentiostatic measurements also showed that direct CNTs deposition on the 304 stainless steel insert did not degrade the corrosion performance under PEM fuel cell operating conditions.

Electrodeposition and properties of Zn–Ni–CNT composite coatings

Zn–Ni–CNT composite coatings were prepared by electrodeposition from a sulphate bath. The effect of CNTs on the corrosion behavior, wear resistance and hardness of the composite coatings was investigated. Their corrosion properties were evaluated by polarization, impedance, weight loss and salt spray tests. The CNT particles inclusion improved the corrosion resistance, hardness and wear resistance of the coating. The grain size of the composite coating was smaller than that of a pure Zn–Ni coating with the same Zn/Ni ratio. Scanning electron microscope images and X-ray diffraction patterns of coating revealed its fine-grain nature.

Effects of filler geometry on internal structure and physical properties of polycarbonate composites prepared with various carbon fillers

AbstractBACKGROUND: The effects of filler geometry are important for understanding the internal structure and physical properties of polymer composites. To investigate the effects of filler geometry on electrical conductivity as well as morphological and rheological properties, three types of polycarbonate (PC) composites were prepared by melt compounding with a twin‐screw extruder.RESULTS: The electrical conductivity of PC/carbon black (CB) and PC/graphite (carbon) nanofibre (CNF) composites did not show a percolation threshold through the entire filler loading ranges. However, PC‐blend‐carbon nanotube (CNT) composites showed a percolation electrical threshold for a filler loading of 1.0 to 3.0 wt% and their maximum electrical conductivity approached 10−3 S m−1. PC‐blend‐CB and PC‐blend‐CNF composites showed Newtonian behaviour like pure PC matrix, but PC‐blend‐CNT composites showed yield stress as well as increased storage modulus and strong shear thinning behaviour at low angular frequency and shear rate due to strong interactions generated between CNT–CNT particles as well as PC molecules and CNT particles on the nanometre scale.CONCLUSIONS: The electrical conductivity of the PC composites with different carbon constituents was well explained by the continuous network structure formed between filler particles. The network structure was confirmed by the good dispersion of fillers as well as by the yield stress and solid‐like behaviour observed in steady and dynamic shear flows. Copyright © 2009 Society of Chemical Industry

Novel upgraded method of recycling spent SiC abrasive powders to CNT particles

To encourage the recycling of spent SiC abrasive powders, we investigated the synthesis of CNTs from several types of powders. The surface decomposition method was applied to as-received powders, and graphite was observed on the SiC surface but CNTs were not. This could be caused by the turbulence of the crystal structure and Fe contaminants on the SiC surface. On the other hand, from TEM observations we found that particle covered of CNTs could be synthesized by applying the surface decomposition method to powders pretreated by acid and heat, because the turbulence of the crystal structure on the surface could be improved and Fe contaminants could be removed. Consequently, the spent SiC abrasive powders pretreated by acid and heat could be used as a resource for synthesizing CNT particles.

Preparation and Properties of Poly(N-vinylcarbazole) and MWCNT Nanocomposites

N-vinylcarbazole (NVC) was polymerized in bulk through the interaction of multi-walled carbon nanotube (MWCNT) without any extraneous catalyst. A PNVC-MWCNT composite was isolated by MeOH precipitation of a polymerization system containing NVC and MWCNT at melting temperature of the monomer. The inclusion of PNVC in the composite was endorsed by the FTIR study. TG analysis revealed the thermal stability trend as MWCNT > PNVC-MWCNT composite > PNVC. DTA showed two exothermic peaks at 427 degrees C and 607 degrees C in the PNVC-MWCNT composite. Transmission electron microscopic analyses of MWCNT revealed presence of tubular MWCNT particles with diameters in nm range while the corresponding analysis for the composite showed the formation of spherical dark polymer particles encapsulating cylindrical MWCNT moieties with some ends of uncoated MWCNT tubes (light shades) protruding out of the dark spherical particles. Scanning electron microscopic analysis revealed presence of tubular CNT particles entangled with the composite particles of irregular shapes and sizes. XRD analysis revealed no additional crystalline peaks for PNVC in the composite. In contrast to PNVC homopolymer (10(-12)-10(-16) S/cm), the dc conductivity values of the composite varied form 1.3 to 33 S/cm depending upon the weight ratio of MWCNT and PNVC in the composite. Current-voltage characteristics of the composite showed a linear variation and conductivity-temperature studies revealed an increase in conductivity by 35% in the temperature range 150-220 degrees C.

Complex activity of clay and CNT particles in flame retarded EVA copolymer

AbstractInterface modifications optimized for fire retardancy require detailed research. Confocal Raman microscopy was used to analyze the degradation locally in the area of the nanotube and clay additives. The double‐walled carbon nanotube (DWCNT), containing Co catalyst residue, accelerates the deacetylation process of poly(ethylene‐co‐vinylacetate) (EVA) considerably, while the montmorillonite (MMT) has no significant influence under static circumstances. The compounding process influences the effect of MMT, which causes partial crosslinking in EVA during the compounding. This mechanochemical reaction is catalyzed by uncovered MMT particles, while organophillized MMT promotes the charring process. Inorganic surface modification with various metal ions has also some stabilizing effect. Spray drying of MMT results in microparticles of increased surface area and improved thermal stability of the EVA system. The lowest rate of flame spreading was achieved using uncoated MMT, while coating with cationic surfactant was most efficient for hindering dripping. The rate of heat release (RHR) of the organically modified and the spray dried MMT was approximately the same. The combined organic‐inorganic modified clay moderates both the dripping and the flame spreading in the EVA. Copyright © 2006 John Wiley & Sons, Ltd.