Papers by Author: István E. Sajó

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: New chemical synthesis procedure for the preparation of nickel zinc doped W-type hexagonal barium ferrite and aluminium doped yttrium-iron garnet nanoparticles has been developed, using the nitrate-citrate sol-gel auto-combustion method (NCSAM). The crystalline phase attributes, microstructure, morphology, specific surface area, Curie temperature (TC), permeability, thermal behavior of the as-burnt phase and the heat treated powders were characterized using XRD, SEM, FT-IR, BET, TG-DTA and AC magnetic permeability with frequency shift. In the case of the hexaferrite, the pure W-type ferrite phase is formed during 4 hour annealing at a temperature of 1200 °C, the garnet phase is formed at a lower temperature i.e. 1000 °C. Furthermore it has been confirmed, that the AC magnetic permeabilities of the garnet materials are strongly depending on the chemical composition.

Abstract: In this study we describe a two-step synthesis method for the preparation of gold nanoparticles supported on tin modified silica. The key step of the preparation procedure is the formation of surface grafted organotin complexes. The reduction of these surface species in a hydrogen atmosphere resulted in both metallic (Sno) and ionic (Sn2+) forms of tin. These forms of tin are capable to reduce gold from chloroauric acid solution forming gold nanoparticles with high dispersion on the surface of silica. It has been found that the particle size of gold strongly depends on the pH value of the gold solution and the presence or absence of ammonia.

Abstract: 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.

Abstract: In the heart of Budapest, an ensemble of nearly 40 large size bronze statues and reliefs were restored in the years of 1995 – 2002. In this paper it is shown, how the achievments of materials science were used to restore the original look and ensure long term integrity of the monument.