Mikrostrukturní změny v tenkých kovových fóliích

Katedra fyziky materiálůDepartment of Physics of MaterialsFaculty of Mathematics and PhysicsMatematicko-fyzikální fakult

Gas-Free Amino- and Alkoxycarbonylation of Aryl Iodides in a Bioinspired Deep Eutectic Solvent with Mo(CO)6 as a Safe CO Source

The Pd-catalyzed amino- and alkoxycarbonylation of aryl iodides has been exploited, for the first time, in a bioinspired Deep Eutectic Solvent and under gas-free conditions, by using Mo(CO)6 as the CO source. The method allows for the preparation of carboxylic amides and esters in high yields (up to 99%), short reaction time (2 h) and under mild reaction conditions (80 °C), with a low catalyst loading (2.5 mol%). Noteworthy, in the case of N-hexylbenzamide, it has been demonstrated that both the catalyst and DES can be used for four consecutive runs, with a moderate decrease of catalytic efficiency. The methodology has been also applied to the preparation of an Active Pharmaceutical Ingredient used for the treatment of human scabies and lice

AFM a TEM studium elementárních dislokačních mechanizmů v nanometrickém měřítku

Single crystals of iron with 20, 28 and 40 at. % aluminium were deformed in compression at room temperature. The later two alloys were deformed also at temperatures in the range of yield stress anomaly. Room temperature deformation was carried under the atomic force microscope (AFM) and the evolution of surface was recorded in-situ. Samples deformed at elevated temperatures were investigated by AFM after the deformation. Dislocation structures in deformed samples were then investigated in transmission electron microscope (TEM). Observations of surface (AFM) and bulk (TEM) are compared. Results of both techniques mutually agree and support the interpretation of observed phenomena. Several original analysis methods were developed. Most notably the stereographic reconstruction, which was applied to dislocation structures and carbide particles present in investigated alloys. Model explaining the distribution of carbide particle axes is presented. Powered by TCPDF (www.tcpdf.org)Monokrystaly železa s 20, 28 a 40 at. % hliníku byly deformovány v tlaku při pokojové teplotě. Dvě posledně zmíněné slitiny byly také deformovány při teplotách v oblasti anomálie meze kluzu. Deformace za pokojové teploty probíhaly v mikroskopu atomárních sil (AFM) a vývoj povrchu byl průběžně zaznamenáván. Povrch vzorků deformovaných při zvýšené teplotě byl v AFM prozkoumán po deformaci. Dislokace v deformovaných vzorcích byly dále pozorovány v transmisním elektronovém mikroskopu (TEM). Pozorování povrchu (AFM) a vnitřku (TEM) materiálů byla porovnána. Výsledky získané oběma technikami vzájemně souhlasí a podporují interpretaci pozorovaných jevů. Bylo vyvinuto několik originálních analytických metod. Zajímavá je stereografická rekonstrukce. Byla použita na popis dislokačních struktur a orientací částic karbidu. Byl také vytvořen model popisující distribuci orientací těchto částic. Powered by TCPDF (www.tcpdf.org)Katedra fyziky materiálůDepartment of Physics of MaterialsFaculty of Mathematics and PhysicsMatematicko-fyzikální fakult

Dispersoids in aluminium alloys

As a preparation for the study of dispersed particles in the aluminium alloys the ALCHEMI method was tested on a simple model material. This method combines the X-ray spectrum analysis and the dynamic diffraction to provide the information on site occupancies. The site preference of Cr in the Fe3Al and FeAl materials was studied. Measured variation of the X-ray yields with the orientation near the Bragg position was fitted by the calculated curves. We found that 70 resp. 80 % of Cr occupy the Al sublattice.Department of Physics of MaterialsKatedra fyziky materiálůFaculty of Mathematics and PhysicsMatematicko-fyzikální fakult

Dispersoids in aluminium alloys

As a preparation for the study of dispersed particles in the aluminium alloys the ALCHEMI method was tested on a simple model material. This method combines the X-ray spectrum analysis and the dynamic diffraction to provide the information on site occupancies. The site preference of Cr in the Fe3Al and FeAl materials was studied. Measured variation of the X-ray yields with the orientation near the Bragg position was fitted by the calculated curves. We found that 70 resp. 80 % of Cr occupy the Al sublattice

Nanoscale AFM and TEM observations of elementary dislocation mechanisms

Single crystals of iron with 20, 28 and 40 at. % aluminium were deformed in compression at room temperature. The later two alloys were deformed also at temperatures in the range of yield stress anomaly. Room temperature deformation was carried under the atomic force microscope (AFM) and the evolution of surface was recorded in-situ. Samples deformed at elevated temperatures were investigated by AFM after the deformation. Dislocation structures in deformed samples were then investigated in transmission electron microscope (TEM). Observations of surface (AFM) and bulk (TEM) are compared. Results of both techniques mutually agree and support the interpretation of observed phenomena. Several original analysis methods were developed. Most notably the stereographic reconstruction, which was applied to dislocation structures and carbide particles present in investigated alloys. Model explaining the distribution of carbide particle axes is presented. Powered by TCPDF (www.tcpdf.org

The Effect of Carbon Additions on the Creep Resistance of Fe-25Al-5Zr Alloy

Creep experiments were conducted on Fe-25 at. pct Al-5 at. pct Zr alloy with carbon additions at the temperatures of 973 K and 1173 K (700 °C and 900 °C). The alloys were tested in two different states: (i) cast and (ii) annealed at 1273 K (1000 °C) for 50 hours. Stress exponents and activation energies were estimated. The values of the stress exponent n could be explained by the dislocation motion controlled by climb. The increased values of n in the high-carbon alloy at the temperature of 1173 K (900 °C) can be described by means of the threshold stress concept. The creep resistance at 973 K (700 °C) decreased with the increasing content of carbon. This result is discussed in terms of the ratio of zirconium to carbon in the alloy. An increase of the creep resistance with increasing ratio Zr:C is in agreement with the behavior observed previously in alloys with substantially lower concentrations of zirconium. © 2016, The Minerals, Metals & Materials Society and ASM International

Optimization principle of operating parameters of heat exchanger by using CFD simulation

Design of effective heat transfer devices and minimizing costs are desired sections in industry and they are important for both engineers and users due to the wide-scale use of heat exchangers. Traditional approach to design is based on iterative process in which is gradually changed design parameters, until a satisfactory solution is achieved. The design process of the heat exchanger is very dependent on the experience of the engineer, thereby the use of computational software is a major advantage in view of time. Determination of operating parameters of the heat exchanger and the subsequent estimation of operating costs have a major impact on the expected profitability of the device. There are on the one hand the material and production costs, which are immediately reflected in the cost of device. But on the other hand, there are somewhat hidden costs in view of economic operation of the heat exchanger. The economic balance of operation significantly affects the technical solution and accompanies the design of the heat exchanger since its inception. Therefore, there is important not underestimate the choice of operating parameters. The article describes an optimization procedure for choice of cost-effective operational parameters for a simple double pipe heat exchanger by using CFD software and the subsequent proposal to modify its design for more economical operation