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3 Open Chemistry

3 2014

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Low pressure RF plasma modification of the surface of three different nano-carbon materials

100%

Bertóti I. , Mohai M. , Balázsi C. , László K. , Szépvölgyi J.

tom 13

nr 1

Well-ordered nano-carbon materials, like multi-wall carbon nanotubes, graphene oxide, graphene due to their unique physical and chemical properties, are candidates for promising applications. In this work thin multilayered graphene, single layer graphene oxide layers and highly oriented pyrolytic graphite (HOPG) surface were treated by RF activated N2 gas plasma at nominally room temperature. Negative bias in the 0–200 V range and treatment time of 10 min was applied. Surface chemical alterations were followed by X-ray photoelectron spectroscopy (XPS). The applied treatments resulted in a significant build-up of nitrogen in the surface of these nano-carbon materials. The amount of nitrogen varied between 4 and 10 atomic %, depending on type of carbon and on biasing conditions. Evaluating the high-resolution N1s XP spectral region, typically three different chemical bonding states of the nitrogen were delineated. Peak component at 398.3 eV is assigned to C=N–C type, at 399.7 eV to sp2 N in melamine-type ring structure and at 400.9 eV to N substituting carbon in a graphite-like environment. Identical chemical bonding of the nitrogen was detected on the surface of HOPG treated in the same way for comparison.

Optical emission spectra analysis of thermal plasma treatment of poly(vinyl chloride)

86%

Fazekas P. , Keszler A. M. , Bódis E. , Drotár E. , Klébert S. , Károly Z. , Szépvölgyi J.

tom 13

nr 1

Decomposition of poly(vinyl chloride) (PVC) was investigated in radiofrequency thermal plasma in neutral, oxidative and reductive conditions. Optical emission spectroscopy (OES) was applied for the characterization of the plasma column. OES was used to identify active plasma components such as excited atoms, ions, radicals and molecules. The spectra were dominated by molecular C2, CN, OH, and CH bands, and atomic H, Ar, C, Cl and O lines. Emission intensities of main species were monitored versus various experimental parameters. The rotational-vibrational temperatures determined from different bimolecular species were considered in the range of 2000–6400 K. Solid soot samples were collected and purified to investigate the possibility of graphene formation as a by-product of the decomposition process.

Spark plasma sintering of Si3N4/multilayer graphene composites

72%

Bódis E. , Tapasztó O. , Károly Z. , Fazekas P. , Klébert S. , Keszler A. M. , Balázsi K. , Szépvölgyi J.

tom 13

nr 1

Mulitlayer graphene reinforced silicon nitride composites were prepared by spark plasma sintering to investigate the effect of the graphene addition on mechanical properties. The composites contained multilayer graphene (MLG) in various (0, 1, 3 and 5 wt%) content. Significantly higher fracture toughness of 8.0 MPa m1/2 was obtained at 1% MLG content, however, on further increasing the graphene content the toughness did not increase, but dropped to the value of the monolithic silicon nitride. The maximum hardness of 18.8 MPa was also obtained at 1% MLG, while at higher MLG contents it gradually decreased.