Academic literature on the topic 'Mikrovlnná syntéza'

Synthesis and bulk analysis of composite ceramic oxide materials and materials with perovskite-defect structure is presented within this work. Syntheses of these advanced ceramics materials were carroed out by using of nonconventional techniques (microwave-assisted hydrothermal synthesis and polycondensation techniques) and by conventional mechanochemical activation followed by high temperature solid state reaction. X-Ray difraction (XRD), Rietveld analysis, scaning microscopy (SEM), microalysis EDS-SEM, thermal analysis (TG), infrared spectroscopy (IR), determination of particles size and specific surface area were used for description of synthesized products. In case of perovskite system based on La-Sr-Fe-Ti-O electrochemical properties were studied. Part of work was focused on chemical analysis of synthesized composite oxide materials and decomposition hard structured products by using of nonconventional fields.

The aim of this thesis is introduce readers to the basics of digital frequency synthesis and design of direct digital synthesizer with circuit AD9951 by Analog Devices. The device will be controlled from a PC via RS232. The device will work with internal oscillator, with the ability to connect an external frequency standard.

The thesis deals with microwave resonators synthesis in Matlab environment. Due to the multi-objective optimization, the shape of the resonátor is subsequently changed to fit requested frequency properties. Particle swarm optimization and frequency domain finite element method are used. Accuracy of the different number of elements was tested. Values of several optimization parameters were balanced to reach the maximal efficiency of the optimization.

1. Abstract Chemistry of 5-substituted tetrazoles has been the subject of intense investigation during last ten years. 5-substituted tetrazoles have found widespread use in many branches of industry, especially in pharmacy. In many cases, 5-substituted tetrazole present an optimal isosteric analogue of carboxylic group due to similar physico-chemical properties. The advantage of 5-substituted tetrazoles is their low metabolic degradability. One of the most important uses of 5-substituted tetrazoles are antihypertensives, antagonists of angiotensin II receptors, so called "sartans". Advance in synthesis of 5-substituted tetrazoles has occurred since the publication of W. G. Finnegan in 1958. In the following years numerous new methods have been published, originating from this work. The latest trend in chemistry of tetrazoles is microwave activation instead of conventional heating. In our work we focused on efficiency of microwave activation compared to conventional heating in several methods of the preparation of 5-substituted tetrazoles. We selected a preparation of 5-phenyl-1H-tetrazole from an easily available benzonitrile as the model reaction. Surprisingly, microwave irradiation did not result in a significant decrease in the reaction time or a higher yield. Furthermore, we aimed at preparation of...

Synthesis of Xanthone Derivatives by Microwave-assisted Methods Petr Vrbata This diploma thesis deals with preparation of xanthone derivatives as inhibitors of growth of human cancer cell lines. A new methodology for synthesis of dihydropyranoxanthones 1 and 2, based on the usage of heterogeneous catalysis combined with microwave irradiation, was optimized. This allowed decreasing significantly the reaction time and improving yields. Along with this the Grover, Shah and Shah method (J. Chem. Soc. 1955, 3982) for synthesis of xanthone derivatives was improved due to usage of microwave heating. Using this method a new xanthone derivate 5,8,10-trihydroxy-7H-benzo[c]xanthen-7-on (3) was prepared. Its structure was verified by IR, 1 H NMR and 13 C NMR spectra. O O O OH O O O OH O OH OHO OH 1 2 3