ICMCTF2009 Session DP: Symposium D Poster Session

Great interest has been focused on Ag-Carbon material systems due to the possibility of obtaining Ag nanoparticles encapsulated by crystalline or amorphous carbon. Silver exhibits excellent thermal and electrical conductivity and has been extensively used in catalysis, electronics, photonics, photography, biological labeling, and surface-enhanced Raman scattering. Composite nanostructures using nanoscale silver as the core have been prepared by many research groups. For example, Ag/C nanocables and Ag/C nanoparticles have been synthesized in the presence of PVP; silver/cross-linked poly (vinyl alcohol) coaxial nanocables have also been prepared. In this work we have used a High-Current Pulsed electric arc in Argon between 3.3mm graphite and 1.5mm silver electrodes to produce silver-carbon nanoparticles at different gas pressures. These nanoparticles were analyzed by TEM, SEM, Optical absorption and XRD. Firstly, we measured the relation between the deposition rate and pressure and found that the deposition rate increased when the pressure decrease. The XRD analysis showed that the silver is crystalline; to confirm this the nanoparticles were analyzed by TEM. The Electron Diffraction again showed that the silver part of the nanoparticle is crystalline. Furthermore, it was established that the particles consisted of a crystalline silver nucleus coated with amorphous carbon. The size of the particles varied from ~150nm to less than 5nm depending on the gas pressure (800-100 Torr). Additionally, small quantities of cristalline graphite and amorphous carbon were found in the produced deposits. By EDS we studied the composition and structure of the deposits as a function of the gas pressure, as well as, the duration of the arc.

Finally, the analysis of the optical absorption spectra showed that the nanoparticles are not spheres but rather spheroids (an ellipsoid with two equal axes). Both, the aspect ratios ε (the ratio of the largest to the smallest axes) and the equivalent radii r_V(radius of a sphere having the same volume) are dependant on the gas pressure. This is interesting since by changing the aspect ratios, it is possible to tune the frequency of the surface plasmon resonance (SPR). This SPR tunability makes these nanoparticles potentially interesting for many optical and optoelectronic applications.

The electric vehicle (EV) is believed to be one of the most important industries in this century, and the lithium ion polymer battery should be the main choice because of its performance. Since high rate charging of lithium-ion battery is the major problem of this electric device. Recently, graphite material has popularly taken the place of commercial meso-carbon micro-beads (MCMB) in the anode material of the lithium-ion polymer batteries. The study utilized the spray dry technique to manufacture the porous graphite/carbon and by controlling the vaporizing of solvent in different rates to synthesize varied structures of the porous graphite/carbon composites for lithium-ion polymer batteries with high rate charging. The composite graphite performs significantly batter than MCMB in surface area e.g., the MCMB is ~4 BET (m²/g) and that of the porous graphite/carbon composite is ~40 BET (m²/g). SEM shows the morphology of porous graphite/carbon composites a nd that some other tests are done for checking the electrochemical properties of those graphite/carbon materials. The porous structure of the graphite material contributes to the diffusion of the lithium-ion while charging and discharging in a battery. By increasing the efficiency of high rate charging and discharging, the porous graphite/carbon material is popularly used in lithium ion polymer batteries for the electric vehicle or high power electric devices.

¹J.Li,X.Wang, Q.Huang, S.Gamboa, P.J.Sebastian, J.Power Source 158(2006)784

²C.Lin, B.N.Popov, H.J.Ploehn, J.Electrochem, Soc, 149(2002)167.

Solid surface wettability could be controlled by a chemical treatment of the material surfaces or modification of the surface topology. The chemical treatment of material surfaces causes to change the surface energy, affecting the wetting behavior like contact angle between a water droplet and material surfaces. Furthermore the increase of the surface roughness due to the presence of the micro- or nano-texture amplifies the hydrophobicity or even hydrophilicity of the materials. Here we investigated the effect of dual roughness and chemical composition on both extreme wettabilities of superhydrophobic and superhydrophilic natures. We used the dual rough structures, imitated from the morphologies of lotus leaves by combining the micro- and nano-sacle structures¹ chosen hydrophobic DLC films (HMDSO - hexamethlydisiloxane) and hydrophilic oxygen treatment for extreme wettabilities. On the superhydrophobic surfaces, we observed the high static contact angle and l ow contact angle hysteresis. We then performed the systematic experiment that a water droplet on the surfaces was evaporated slowly and we have monitored the variation in contact angle of the droplet and the transition from Cassie-Baxter state to Wenzel state in high pressure. On the other hand, we observed the static contact angle and spreading velocity of a water droplet on superhydrophilic surfaces. Finally, switchable behaviors of wettabilities between superhydrophobic and superhydrophilic natures were demonstrated with repeat of HMDSO coatings and O2 plasma treatment and various wetting pattern applications were valid by using reversible wetting characteristics.

¹K. Bewilogua, K. H. Oh, K.-R. Lee, Chem. Phys. Lett. 436 (2007) 199.

Galvanic nickel coatings have been in use for decades and have many desirable properties including wear and corrosion resistance and relative ease of application. Recently, work has been performed to enhance the tribological properties of nickel-based coatings by incorporation of diamond nanoparticles as a wear-resistant component of this functional coating.¹ In this previous study, detonation nanodiamonds (DNDs) with primary particle size 5nm produced by detonation of carbon-containing explosives were used. The polydispersed DNDs with average aggregate size ~150nm were then employed as a hard filler in nickel electroplated films giving Ni-DND composite coatings. It was found that the presence of the DNDs significantly affected the properties of the coatings in an intriguing fashion. Toward that end, Ni-DND coatings exhibited improved microhardness and wear resistance when compared to Ni-only control coatings but the latter showed better erosion resistance.¹ In another series of experiments² it was revealed that the type of the steel substrate, its roughness and conditions of electroplating (current density, substrate purification, Ni adhesion layer formation) significantly influence the microhardness and tribological properties of the galvanic coatings. These observations warrant a better understanding of the structure of the Ni-DND coatings and the effect on various mechanical properties. The work presented in this paper relates to an investigation of the structure/tribological properties of Ni-DND composite coatings. Characterization data to be discussed includes wear rates, hardness profiles and composite structure as measured by pin-on-disk, nanoindentation and high resolution SEM test methods.

super 1@I. Petrov, P. Detkov, A. Drovosekov, M.S. Ivanov, T. Tyler, O. Shenderova, N.P. Voznecova, Y.P. Toporova, D. Schulz, Diamond & Related Materials 15 (2006) 2035–2038.

²R.A. Sailer, O.Shenderova, D.L. Schulz, W.Mecoach, G.McGuire, in preparation

Composites of Amorphous carbon films and silver were deposited by co-sputtering, where the target (10 cm diameter) was of pure graphite with small inclusion of pure silver (less than 1 cm²). The films were deposited under different power, from 40 to 250 W, and different target-substrate distances. The substrate was earthed and rotating in order to obtain an uniform distribution of the silver content (less than 10 at%). The addition of the Ag piece into the target increased the deposition rate of the carbon films, which could be related to the higher sputter yield of the silver, but there seem to be also a contribution from a larger emission of secondary electrons from the Ag that enhances the plasma and therefore the sputtering process becomes more efficient.

Scanning electron micrographs acquired using backscattered electrons showed that the silver was segregated from the carbon matrix, forming nanoparticles or larger clusters as the power was in-creased. The X-ray diffraction pattern showed that silver was crystalline and the carbon matrix remains amorphous, although for certain conditions a peak attributed to fullerene-like structures was obtained. Ellipsometric spectroscopy was used to determine the variation in the optical properties as the silver con-tent and distribution was changed; at low power conditions, the Plasmon resonance of the Ag nanoparti-cles dominates the spectra. Finally, we used Raman spectroscopy to understand the bonding characteristics of the carbon-silver composites, finding that there are variations in the D/G ratio, which can be correlated to the observed structure and X-ray diffraction results.

T-shape filtered arc deposition system (T-FAD) is powerful tool as a physical vapor deposition (PVD) system for preparing various kinds of diamond-like carbon (DLC) films with high quality, especially hydrogen-free hard DLC, named tetrahedral amorphous carbon (ta-C). Most of macro-particles (droplets) emitted from the graphite cathode are removed from the cathodic arc plasma when the plasma beam passes thorough the T corner of the filter duct. However, further droplet reduction is required.

In the present study, in order to increase the deposition rate and decrease the number of droplets on the film, the electric field was applied in the T-shape droplet-filter duct. The ion current in front of the substrate, deposition rate, and number of droplets on prepared DLC film were measured as a function of the electric field strength. As a result, the ion current had a maximum at the electric field generated by applying the same voltage as the filtered carbon-arc-pl asma potential. The deposition rate increased by approximately 10%, and thus the number of droplets was reduced by same level. Similar experiment was carried out for carbon-argon mixture plasma.

The results of TEM investigation for formation of 50-80 nm single crystals with decahedral and icosahedral faceting produced under high pressure (4-7 GPa) and temperature (1600-2000°С) in the system of 1-7 nm diamond particles of detonation synthesis are discussed. The appearance of such crystals occurs in the absence of diffusion mass transfer and is determined by the self-arrangement process, that is, by the oriented association of the initial diamond nanoparticles. A mechanism of the self-arrangement is proposed, which includes several successive elementary stages such as i) the formation of contacts between particles along morphologically flat facet surfaces; ii) selection of contacting particles and contact planes formed due to the realization of recognition mechanism (this determines the oriented growing together and/or homoepitaxy of independent particles and so the formation of single crystals of regular habitus. The oriented interaction of diamond part icles containing surface layers of non-diamond carbon¹ seems to be possible as it is known that transfer of structural information of a substance can proceed through layers of foreign substances); iii) transformation of non-diamond carbon into diamond. The mechanism of the transformation under the action of one-dimensional periodic potential arising due to the altering of layers of substances with different forbidden energy gaps is possible². A diamond particle with a surface 5-10 Å thick layer of non-diamond carbon is, in fact, a fragment of the superlattice whose constituents differ in the forbidden gap value: it is equal to 3.5 eV for diamond (particle core) and to zero for carbon with sp²- hybridization.

¹Aleksenskiy A.Ye., Baidakova M.V., Vul A.Ya., et al. FTT. 2000. T 42. N 8. S.1531-1534.

²Zavaritskaja T. N., Karavanskij V. A., Melnik N. N., Pudonin F. A. Pisma v JETF. 2004. T. 79. N 6.S.340-343.

A new thermal-oxidative gas-cycle (fire) production method for nanosized porous globules of high-purity carbon (GNC Globular Nanocarbon) by means of combustion of methane in special conditions using chlorine as an oxidizing agent has been developed.

A distinctive feature of this method is the combustion process organization in such a way as to almost all thermal energy of oxidation is consumed to the target process of chemical synthesis of complex carbon structures without effluent of carbonic acid gas and nonutilizable heat to the environment. The method allows to solve a problem of obtaining of uniform structural nanosized carbon particles using controlled high-speed chain chemical reactions proceeding in conditions wide of the equilibrium. General foundations being a basis of the method are guided by a theory of formation of permolecular structures in nonequilibrium systems developed by Professor Aleskovsky V.B. (St.Petersburg, Russia). The method is a way of obtaining of nanosized metal – carbon compounds.

A primary nanomaterial obtained by means of plasma synthesis represents an aggregate of uniform carbon microporous globules with the size of 20-30 nm coated with surface chlorine atoms chemically combined with carbon (nanocarbochloride - GNC-Cl). This material is a progenitor of a new class of nanocarbon products composed of a nanosized porous structural carbon core and a purposefully-formed shell containing functional groups combined with carbon atoms. Joint name of this class of products is GNC–globular nanocarbon.

After reductive and oxidative thermal treatment with hydrogen, methane, water or other special reagents one can obtain high-active forms of high-pure nanocarbon materials (GNC-A) with the characterization specific surface >1000 m2/g, the carbon content >99,5% and practically zero-ash content. GNC-A is characterized by an uniformity of primary nanoglobules of pure carbon and unique combination of high dispersivity of particles with their microporous structure.

The zero-ash content, high carbon basis purity, easiness of modification of surface structure make this new material very promising for all traditional directions of application of carbon nanoproducts. As for potential fields of application of GNC, these are analogous to the well-known ordered carbon structures such as fullerenes, nanotubes, ultradispersed diamonds. But, in comparison with them there is an advantage: after creation of industrial production GNC can be cheaper by a factor of 10 or 100 than above–listed analogues.

At present a modern industrial production of detonation synthesis nanodiamonds (DND) is created on the bases of FSUP «Special engineering and design bureau.

The detonation synthesis is based on the technique of explosion of TNT-RDX charge in aqueaous solution of a strong reducing agent. That allowed to redouble the yield of diamond-containing blend (DB) and DND, to decrease the content of incombustible impurities in the DB 2-3 times, to transform a main part of the incombustible impurities into a soluble form of complex salts.

The DB obtained in the form of an aqueous suspension is filtrated from coarse and fine impurities, subjected to magnetic separation and centrifugated to give a dense and readily-removed sediment. Further the moist DB is directed to the chemical purification stage where the DB is added to ~ 60% HNO3, subjected to strong dispersion, filtrated from difficult-to-remove impurities and pumped up to the system of continuous complex contour plug-flow titanium reactors. The process temperature is ~230-240°C, pressure is 8 to 10 Mpa, a stay period of reaction mass in the high temperature zone is 30-40 minutes. In this conditions the DB is purified from non-diamond carbon and incombustible impurities being as complex salt kind. As a result, a number of residuary incombustible impurities in the DND is ~0,07-0,10 wt.%. Such product can be used in any technologies of application. After chemical purification the obtained nitric-acid suspension of DND is released from nitric oxides and washed out from waste HNO₃. Then the weak-acidic suspension of DND is treated with ammonia and again added to the zone of high temperature and pressure to desorb nitric oxides and HNO₃ from internal pores of DND-agglomerates. The formed ammonium salts are decomposed at the high temperature. The obtained re-purified DND are washed out from an excess of ammonia and directed to a thickening stage to give 8-12 % aqueous suspension of pure DND (1st commodity form of DND as an aqueous suspension). In order to obtain a dry ultrafine granular product (2nd commodity form) the DND-suspension is directed to a spray-type drying stage.

Abstract Diamond-like carbon (DLC) films are a form of amorphous carbon containing a significant fraction of sp3 bonding, which are well known for their superior physical and chemical properties of high hardness, chemical inertness, optical transparency, thermal conductivity and biocompatibility.^1,2 Recently, metal-doped DLC films have stimulated great interests and been widely investigated owing to their extraordinary microstructure of nanocrystalline metal carbide precipitated in the amorphous carbon matrix.^3,4 In this study, titanium-doped diamond-like carbon (Ti-doped DLC) thin films with Ti compositions of 1.1 at. % were synthesized on a Si substrate by a process combining filtered cathodic vacuum arc (FCVA) and metal vacuum arc (MeVVA) system. This study discusses on the effect of annealing temperature on the microstructure, surface roughness, hardness and electrical resistivity of the resulting films. The Raman spectra reveal that the degree of graphizatio n of Ti-doped DLC thin films increases with increasing annealing temperature from 100 to 600°C. Because the degree of graphization of the thin films increases, the hardness of the thin films improved, and the electrical resistivity of the Ti-doped DLC thin films decreases from 0.038 to 0.006 Ω cm.

¹A. Grill, Diamond Relat. Mater. 8 (1999) 428.

²S. Sattel, J. Robertson, H. Ehrhardt. J. Appl. Phys. 82 (1997) 4566.

³K.W. Weng, Y.C. Chen, T.N. Lin, D.Y. Wang, Thin Solid Films 515 (2006) 1053.

⁴W.Y. Wu, J.M. Ting, Carbon 44 (2006) 1210.

⁵K. Baba, R. Hatada, Surf. Coat. Technol.169 (2003) 287.