Hajnalka Hargitai

Investigation of Noble Metal Nanoparticles (Ag, Au, Pd, Pt) Produced by Chemical Reduction

This work describes atomic-scale, crystalline structure and size distribution for noble metal nanoparticles produced by water-based, environmental friendly technologies. The process was developed and implemented to produce noble metal nanoparticles to be used in water filters, sensors and cosmetics. The particles were investigated by TEM methods and particle size analysis. Growth process of the crystallites in sols made by chemical reduction in aqueous solutions is discussed. Comparison with growth models for vacuum deposited thin films is also identified.

Development of PA6/HDPE Nanocomposite Blends

In our experiments polyamide 6/high density polyethylene blends (25/75 wt%) were produced and maleic anhydride grafted polyethylene was used as chemical coupling agent. To get finer microstructure and enhance the mechanical properties the blends were compounded by different nanostructured reinforcements. Two kinds of nanosilicate, the layered structure montmorillonite and the needle like sepiolite were applied in different concentrations and their effect on the mechanical and melting properties were examined.

Enhanced Injection Molding Simulation of Advanced Injection Molds

The most time-consuming phase of the injection molding cycle is cooling. Cooling efficiency can be enhanced with the application of conformal cooling systems or high thermal conductivity copper molds. The conformal cooling channels are placed along the geometry of the injection-molded product, and thus they can extract more heat and heat removal is more uniform than in the case of conventional cooling systems. In the case of copper mold inserts, cooling channels are made by drilling and heat removal is facilitated by the high thermal conductivity coefficient of copper, which is several times that of steel. Designing optimal cooling systems is a complex process; a proper design requires injection molding simulations, but the accuracy of calculations depends on how precise the input parameters and boundary conditions are. In this study, three cooling circuit designs and three mold materials (Ampcoloy 940, 1.2311 (P20) steel, and MS1 steel) were used and compared using numerical methods. The effect of different mold designs and materials on cooling efficiency were examined using calculated and measured results. The simulation model was adjusted to the measurement results by considering the joint gap between the mold inserts.

Influence of Cryogenic Attrition Ball Milling on the Particle Size of Microcrystalline Cellulose at Different Moisture Contents

In this study the effect of attrition ball milling on cellulose particle size distribution was studied. The effect of moisture content of cellulose and grinding time were examined and grinding was carried out at room temperature and under cryogenic conditions, as well. The grinds obtained were studied with electron microscope, and the characteristic dimensions of ground particles were determined using image processing software. Results revealed that effective size decrease of cellulose particles was achieved at low moisture content at room temperature, while under cryogenic conditions high moisture content was necessary, i.e. frozen moisture enhances grinding efficiency in the latter case.

Characterization of Internal Stresses in Hybrid Steel Structures Produced by Direct Metal Laser Sintering

In this study hybrid structure were produced by direct metal laser sintering of maraging steel (MS1) powder onto the surface of commercial mold steels. The over-sintering method should be analyzed to find the optimum pre-and post-heat treatment to minimize the internal stresses. The internal stress is directly proportional to the deformation if the solid thick part is reduced to thin plate like parts. Based on this recognition the deformation of the plates over-sintered with MS1 could be analyzed in order to explore the internal stresses and the effect of different pre-and post-heat treatments were examined.

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.