Zinc-rich paint coatings containing either ionic surfactant-modified or functionalized multi-walled carbon nanotube-supported polypyrrole utilized to protect cold-rolled steel against corrosion

The intense anodic action of sacrificial zinc pigments ensured viable galvanic function of the highly porous liquid zinc-rich paints (ZRPs) result in deteriorated long-term corrosion resistance often accompanied by cathodic delamination phenomena. In our approach, such a efficacy problem related to the corrosion preventive function of ZRPs is addressed by the application of intimately structured anodic inhibitor particles composed of nano-size alumina and either polyelectrolyte-modified or chemically functionalized multi-walled carbon nanotubes (MWCNT) supported polypyrrole (PPy) in one specific zinc-rich hybrid paint formulation providing balanced active–passive protective functionality. High dispersity of the nanotube-free PPy-deposited inhibitor particles (PDIPs) with uneven polymer distribution on the alumina carrier was confirmed by transmission electron microscopy (TEM) observations. Furthermore, the MWCNT-embedded PDIPs indicated almost complete surface coverage of the alumina-nanotube carriers by PPy with decreased microstructure dispersity which is attributed to the effect of double-flocculants type co-deposition of the oppositely charged polymers causing coalescence of the modified particles. Depending on the amount of the nanotubes and their proportion to the quantities of the deposited PPy and polyelectrolyte as well as the concentration of the surfactant, varied micron-scale association of the PDIPs in the suspensions of dissolved alkyd matrix was disclosed by rheology characterization carried out at particular solid contents similar to hybrid paint formulation. The evenly distributed but less densely packed nano-structure of PPy was evidenced on the polyelectrolyte-modified nanotubes by Fourier-transform infrared (FTIR) spectroscopy whereas more compact polymer film formation was confirmed on the surface of functionalized nanotubes. According to the greater electrical conductivity, enhanced electroactivity and reversibility of the nanotube-embedded PDIPs were indicated over the nanotube-free particles by cyclic voltammetry, depending on the type and the amount of the nanotubes and their modification. Protection function of the hybrid paint coatings (formulated with spherical zinc pigment at 70 wt.%) was investigated by immersion and salt-spray chamber tests over 254 and 142 day periods, respectively. Firm barrier nature of the nanotube-embedded PDIP contained hybrids was proved by electrochemical impedance spectroscopy (EIS) and radio-frequency glow-discharge optical-emission-spectroscopy (RF-GD-OES). Furthermore, due to the increased conductivity of the nanotube-embedded PDIPs cemented in epoxy primers optimally at 0.4 and 0.6 wt.%, altered corrosion preventive behaviour of the hybrid coatings was indicated by the positively polarized open-circuit potentials (OCPs) and the X-ray photoelectron spectroscopy (XPS) detected lower relative quantities of the interfacially accumulated zinc corrosion products, moderate oxidative degradation of the epoxy vehicle. Decreasing oxidative conversion of iron at the surface was indicated by XPS found to correlate with the increasing intensity of zinc corrosion and decreasing oxidative degradation of the epoxy binder, according to the higher nanotube contents of hybrid coatings. In addition, inhibited zinc corrosion caused low rate of oxidative degradation of epoxy, allowing increased durability of coating adhesion and cohesion thereby ensuring reliable protection by zinc-rich compositions. As a conclusion, modified or functionalized MWCNTs acting as unexchangeable doping agents promote enhanced reversibility and increased conductivity of PPy, forming nano-size inhibitor particles with advanced features. Thus, such inhibitor nano-particles in zinc-rich hybrid compositions afford improved barrier and high efficiency galvanic–cathodic corrosion preventive function, exceeding long-term protection capability of the conventional ZRPs

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

Abstract 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.</jats:p

SURFACE CHARACTERIZATION OF RAPIDLY SOLIDIFIED AI ALLOYS

Rapidly solidified aluminium alloys with Mn, Fe and Mg were studied by depth profiling XPS and SIMS. Most of the Mn and Fe were found in deeper layers in metallic form while the Mg on the surface in oxide and carbonate state

XPS INVESTIGATIONS ON SOLID SURFACES: RESULTS OBTAINED BY A RECENTLY INSTALLED COMMERCIAL INSTRUMENT

The applicability of the ESCA method and the capability of the recently installed KRATOS XSAM 800 instrument is demonstrated in various fields, e.g. in gas-solid reactions, catalysts and catalysis, layer structures, glass and mineral surfaces and also in the investigation of polymers and coals

Palladium Nanoparticle–Graphene Catalysts for Asymmetric Hydrogenation

We report for the first time the application of palladium nanoparticle-graphene (Pd/Gn) catalysts in the asymmetric hydrogenation of aliphatic a,b-unsaturated carboxylic acids using cinchonidine as chiral modifier. Pd/ Gns were prepared by deposition–precipitation from the aqueous phase over graphite oxide and subsequent simultaneous reduction of both the support and the metal precursor with NaBH4. The materials obtained were characterized by ICP optical emission spectroscopy, X-ray diffraction spectroscopy, Raman spectroscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. We demonstrate that the Pd/Gns modified by cinchonidine can act as efficient catalysts in the asymmetric hydrogenation of a,b-unsaturated carboxylic acids for producing optically enriched saturated carboxylic acids

Szén alapú nano-kompozitok előállítása és komplex szerkezeti jellemzése = Preparation and complex characterisation of carbon based nano-composites

A gyorsuló műszaki-technológiai fejlődés növekvő igényeket támaszt az új, különleges tulajdonságú anyagok iránt. Ezek között kitüntetett helyet foglalnak el a szénalapú rendszerek, és különösen azok vékonyrétegei. A szén kémiai kötésviszonyaitól függően igen változatos szerkezetű, mely a gyémánt, és gyémántszerű (DLC), grafit és fullerén-szerű módosulatokig terjedhet, melyek kialakulása befolyásolható az előállítás körülményeivel és adalékanyagokkal. Az elvégzett kutatások eredményként megvalósítottuk a szén-alapú nanokompozitok vékonyrétegeinek plazmás-ionsugaras aktivációval, magnetronos porlasztással és plazmaimmerziós ionimplantációval való előállítását. Feltártuk a rétegnövesztés egyes paramétereinek hatását a rétegek összetételére, kémiai kötés- és elektronszerkezetére. Modellrendszereken kimutattuk, hogy a DLC rétegek különböző kémiai kötésszerkezetű nanométeres klaszterekből épülnek fel és így szerkezeti nanokompozitoknak tekinthetők. A különböző prekurzorokból előállított Si adalékot tartalmazó DLC rétegek amorf szerkezetűek. A szilícium befolyásolja a szénklaszterek kötésszerkezetét, a Si eloszlása atomi szinten nem egyenletes, ugyanakkor nem képez többatomos elemi Si-Si és Si-C klasztereket. A rétegek alkalmazási szempontból előnyös nanomechanikai tulajdonságokkal rendelkeznek. Az átmeneti fém (W, Cr, Ni) tartalmú szénrétegek közül a Si tartalmúak 1-5 nm-es klasszterekből álló amorf, míg a csak Ni tartalmúak részben kristályos szerkezetűek. | Novel materials with exceptional properties are required by the accelerating technical development. In this project carbon based systems, especially their thin layers, have outstanding importance. The chemical bonding structure of the carbon may have a great variety, ranging from the diamond and diamond like systems to the graphitic and fullerene like systems, development of which can be influenced by the preparation conditions and additives. The preparation facilities and conditions for deposition of carbon based thin layers were developed by plasma and ion beam activation, by magnetron sputtering, and also by plasma immersion ion implantation. It was established that the DLC layers are built of nanometre size clusters of different chemical bonding environments. The Si containing DLC layers prepared from various precursors are amorphous. The Si additive influences the chemical bond structure of the carbon clusters; the distribution of Si is not homogeneous, however, it does not form multi-atomic Si-Si or SiC clusters. The layers posses beneficial nanomechanical properties. The carbon layers doped with transition metals (W, Cr, Ni) are also amorphous with 1-5 nm sized clusters, while the Ni containing layers are partially crystalline

Structure, Mechanical and Electrochemical Properties of Thermally Reduced Graphene Oxide-poly (Vinyl Alcohol) Foams

Graphene oxide foams with a wide range of poly (vinyl alcohol) contents were synthesized by freeze casting, and then thermally reduced at 300ºC in argon atmosphere. Their thermal stability, microstructure, composition and chemical states of constituents, mechanical and electrical properties were investigated by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, thermogravimetry, compressive testing and electrochemical analysis. The results indicated that the PVA content highly influenced the crystallinity and microstructure, resulting in different mechanical properties. After thermal reduction, not only graphene oxide was reduced to graphene, but also PVA was subjected to partial pyrolysis. With the increase of the PVA content, the intensity of the sp2 C-C bond decreased while the sp3 C-C bond increased. Although the mechanical properties decreased after thermal reduction, the composite foams still showed high cyclic structure stability up to 18 % compression strain. Meanwhile, the reduced foams exhibited high electrical conductivity. Applying as anodes in lithium ion battery, the initial discharge capacity for the foams can reach 1822 mA h g-1 and it remained more than 330 mA h g-1 after 50 cycles