Katalin Papp

Dispersibility of Carbon Nanotubes

Availability of a stable carbon nanotube suspension is a prerequisite for production of polymer composites with carbon nanotube as additives. In this work nanotube suspensions, which have been prepared from various nanotubes in different dispersion agents, were compared. Dispersibility of the samples was investigated by scanning electon microscopy and atomic force microscopy. Solution of a non-ionic surfactant was also used successfully as a new dispersion agent. Geometrical parameters of the carbon nanotubes were determined by using atomic force microscopy. Correlation was found between the dispersibility and the parameters of the nanotubes and relative permittivity of the different solvents.

AFM and SEM: Competing or Complementary Techniques?

The expression, scanning microscopy has been used for scanning ele ctron microscope techniques over 20 years. With the invention of the scanning tunneling mic roscope, a development leading to the construction of a range of scanning (probe) microscopes s tarted. In this growing group the most popular of these is the atomic force microscope which b ecame competitive to the SEM method during the last decade. The different features, advanta ges and drawbacks of these two popular scanning techniques are analysed in the paper.

The investigation of thin protecting layers on roughened galvanized steel surfaces produced by different coating methods

Protective, chromate substitute thin layers on roughened galvanized surfaces produced at OCAS (Arcelor, Belgium) were characterized and compared using Scanning Electron Microscopy (SEM+EDS), Atomic Force Microscopy (AFM), Nanoindentation and X-ray Photoemission Spectroscopy (XPS). EDX maps, line scans and point analyses obtained at various places of the surfaces have shown differences between the CVD and silane nanolayers in the matter of thickness distribution and composition. At cross-section specimens the thickness of the layers could be shown. The hardness differences caused by layer thickness variations are hard to follow by nanoindentation as the penetration depth of the indenter is much larger than the thickness of the coatings. XPS measurements can distinguish between the chemical states of silicon in CVD and silane coatings.

Characterization and Comparison of Rapidly Solidified Al Particles Mechanically Milled Nanostructures and their Consolidated Structures Made by High Energy Rate Forming (HERF) Technique

The aim of the present work is to produce new types of solid nanomaterials for different purposes (coatings, fillers, foams, bulk pieces, etc.). Technologies such as RS Al flake production, high energy mechanical milling and high energy rate forming technology (HERF) for compacting are used. The products are analyzed mainly by XRD, SEM and TEM methods. It was shown that the new-type of RS Al “flake” material is suitable not only for pigments but also for powder metallurgical purposes, i.e. Al based nanocomposites. By choosing suitable parameters for mechanical alloying with the Fritsch Planetary mill 4, very fine, alloyed and composited nanostructures can be produced (Al-4.5w%Cu- 10w%Al2O3, Al-15w%Pb) Dynamic compaction (HERF) using explosive techniques seems to offer a good way for the compaction of Al (metal) matrix nanostructured composites.

Nano-Micro Pigment Composites for High Performance Paints

In this work, novel types of colored, organic and water based paints have been developed. These paints can be produced less expensively and have equivalent or better properties compared to existing paints in the market. These new paints use organic nanocrystalline dyes (about 10 nm in size), which produce the various colors by absorption. The results are achieved with pigment composites containing nano-Cu-phthalocyanine (CuPC) pigment crystallites and finely precipitated and ground micro Al(OH)3 distance-holder (“spacer”) disks.

The influence of high-energy ball milling parameters on the traditional W-type Ba-hexaferrite properties

The main task of our work was to study the influence of high energy ball milling on the process of W-type hexaferrite material production and to compare the structural, morphological and magnetic features of the different manufacturing ways. The products are analyzed mainly by XRD, SEM and TEM methods. It was shown that high energy ball milling can be used to enhance the synthesis of W-type Ba-hexaferrite due to the much smaller crystallite sizes and their larger surfaces that are produced by the milling process and due to the activation of these surfaces.

Solid-State Transformation Produced by Laser Treatment and Mechanical Alloying of Fe-Ni-Cu(P) Powders

The comparison of the phase transformations going on due to high energy ball milling (HEBM) and produced by pressure-less Direct Metal Laser Sintering (DMLS developed by EOS company) was carried out, by using an α-Fe, Ni and Cu3P powder mixture. It could be shown by X-ray diffractograms (XRD) of the two type of products, that by mechanical alloying a similar phase transformation occurs due to solid state reactions between the metal partners as in the case of laser sintering, in a given range of laser scanning speed in a laboratory laser equipment. According to the XRD evaluation the same metastable, γ-steel like phases were formed.