This paper presents determination of flow curve of steel by using multi regression analysis based on only few experimental points of torsion test. It is necessary to know the flow curve of the formed metal and the best way to obtain one are different experiments such as tensile, upsetting or torsion tests. In the paper torsion test was used for obtaining the flow curve. In torsion test a cylindrical specimen is twisted by torque acting around its axis. Experimental data of torsion test were processed by determination of statistical characteristic of experimental results.
B.03 Paper at an international scientific conference
COBISS.SI-ID: 17513750This study provides the newest information regarding the synthesis of gold nanoparticles via the ultrasonic spray pyrolysis method and reduction in aqueous solution. Ultrasonic spray pyrolysis (USP) is the mostly used method for the synthesis of particles with controlled and uniform particle size because of easy powder morphology control and the availability of cheap precursor solutions. In the USP process a metal-containing solution is cold atomized forming an aerosol. Special attention is given in this paper to the formation of Gold nanoparticles from gold auric acid solution using sodium citrate as the reducing agent in an aqueous solution under atmospheric and high pressure.
B.04 Guest lecture
COBISS.SI-ID: 16906774This paper deals with the synthesis of gold nanoparticles, which was carried out by a process called Ultrasonic Spray Pyrolysis (USP). This is a chemical reduction method with a relatively easy particle morphology control and availability of cheap precursors. In order to obtain gold nanoparticles with this method, a decomposition of HAuCl4, followed by a hydrogen reduction of Au2Cl6 takes place. The experiments were conducted with an atomization of a diluted solution of tetrachloroauric acid with an ultrasonic frequency of 0.8 MHz and 2.5 MHz. The temperatures for thermal decomposition of the solution were between 260 °C and 500 °C. This technology allowed us to prepare different fractions of gold nanoparticles with spherical, cylindrical, triangular, round and irregular shapes, with sizes ranging from 10 to 260 nm. The research revealed the role of precursor concentration and selection of proper ultrasonic frequency which influenced finally the size and shape of the produced gold nanoparticles. For the purpose of characterization, we used SEM and TEM with EDS analysis.
B.03 Paper at an international scientific conference
COBISS.SI-ID: 16891670Our research work deals with the problem of producing a complex metal-ceramic nanostructural composite using the processes of internal oxidation and severe plastic deformation. For this purpose, Cu-Al alloy with 0.4 wt.% of Al was used.The internal oxidation (IO) of the sample serves in the first step of the processing as a means for attaining a fine dispersion of nano-sized oxide particles in the metal matrix. The production technology continues with repeated application of severe plastic deformation (SPD) of the resulting metal-matrix composite to produce the bulk nano-scaled structural material. SPD was carried out with equal channel angular pressing (ECAP), which allowed that the material could be subjected to an intense plastic strain through simple shear. The microstructural evolution of one phase and multiphase material was studied on internally oxidized Cu-0.4%wt. Al sample composed of one phase copper-aluminum solid solution in the core and fine dispersed oxide particles in the same matrix in the mantle region. Our purpose is to identify the microstructural features resulting in the microstructure after the ECAP process. In this manner X-ray diffraction was used. The results reflect structural changes completely. Local structures in plastically deformed samples registered with X-ray diffraction reflect the presence of Cu, Cu2O, Cu4O3 or Al2O3 structural characteristics, depending on the type of sample.
B.03 Paper at an international scientific conference
COBISS.SI-ID: 16907798In commercially available orthodontic wire we measured the transformation temperatures and we performed tensile tests where we determined the stress at both the start and end of solid state transformation. Our experimental methods for instigation of stress-induced martensite in different stress state included measurements of electrical resistance and determination of the hardness. To achieve different stress states on orthodontic wire we used devices to simulate uniaxial and multi-axial stresses. With these devices we deformed orthodontic wire so that we created different stresses on the wire, such as tension, bending, torsion and combinations of these. The results of our investigation can be used to provide better understanding of the functional behaviour of NiTi wire in the oral environment.
B.03 Paper at an international scientific conference
COBISS.SI-ID: 16907286