|
|
Low temperature scanning tunneling microscopy
Sojka, Antonín ; Havlíček,, Marek (referee) ; Pavera, Michal (advisor)
The diploma thesis is divided into two main parts. The first part describes the production of chrome and cobalt tips for SP-STM with subsequent testing of chrome tips on the Fe-Ir system (111). Furthermore, the first results from the growth studies of niobium on iridium(111) are presented. In the second part is described in detail the experimental LT-STM microscope of the Faculty of Physical Engineering. The chapter deals with the development of the microscope and its testing on a HOPG sample under atmospheric and vacuum conditions. The chapter describes the biggest problems which were solved when the microscope was puting into operation state. The second part also introduces the design of a new vacuum transport system, which consists of a tip and sample transport pallet. At the end of the second part is described the testing of cooling systems for LT-STM and the design of their modifications.
|
|
|
Electrophoretic Determination of Tantalum in Recycled Coolants
Gogulin, Semen ; Křížek, Tomáš (advisor) ; Coufal, Pavel (referee)
This master thesis deals with the development of electrophoretic methods for determination of tantalum in recycled coolants used in the production of tantalum capacitors, as well as the separation of tantalum from chemically similar niobium. Developed methods are based on the formation of negatively charged complexes of tantalum and niobium with a number of ligands added to the separation electrolyte, especially tartaric and citric acid and 4-(2-pyridylazo)resorcinol. The separations were performed in a fused silica capillary of the inner diameter of 50 µm and the effective length of 36.5 cm, a negative voltage of -25 kV was applied to the capillary. Using a separation electrolyte containing 0.1 mol·l-1 of tartaric and citric acid at pH = 2, separation of niobium and tantalum was achieved in less than 3 minutes; the absorption spectrometric detection was carried out in the ultraviolet region at a wavelength of 200 nm, the detection limit was 2.8 ppm of tantalum, and the quantification limit was 9.2 ppm of tantalum. Addition of 4-(2-pyridylazo)resorcinol reduced the detection limit to 0.8 ppm of tantalum and the quantification limit to 2.6 ppm of tantalum; the electrolyte contained 0.1 mmol·l-1 of 4-(2-pyridylazo)resorcinol, 10 mmol·l-1 of tartaric acid, 10 mmol·l-1 of citric acid, and 25 mmol·l-1...
|
|
|
ADHESION OF BIOCOMPATIBLE TiNb COATING
Kolegar, T. ; Matoušek, M. ; Vilémová, Monika ; Starý, V.
Preparation of a coating with a high quality requires good adhesion of the film to the substrate. The paper deals with the adhesion of biocompatible TiNb coating with different base materials. Several materials such as titanium CP grade 2, titanium alloys Ti6Al4V and stainless steel AISI 316L were measured. Testing samples were made in the shape of small discs. Those samples were coated with a TiNb layer by using the PVD method (magnetron sputtering). Onto the measured layer of TiNb an assistant cylinder was stuck using a high strength epoxy adhesive E1100S. The sample with the assistant cylinder was fixed into a special fixture and the whole assembly underwent pull-off testing for adhesion. The main result of this experiment was determining the strength needed to peel the layer and morphology and size of the breakaway. As a result, we will be able to determine the best base material and conditions where the coating will be remain intact with the base material.
|
|
|
Low temperature scanning tunneling microscopy
Sojka, Antonín ; Havlíček,, Marek (referee) ; Pavera, Michal (advisor)
The diploma thesis is divided into two main parts. The first part describes the production of chrome and cobalt tips for SP-STM with subsequent testing of chrome tips on the Fe-Ir system (111). Furthermore, the first results from the growth studies of niobium on iridium(111) are presented. In the second part is described in detail the experimental LT-STM microscope of the Faculty of Physical Engineering. The chapter deals with the development of the microscope and its testing on a HOPG sample under atmospheric and vacuum conditions. The chapter describes the biggest problems which were solved when the microscope was puting into operation state. The second part also introduces the design of a new vacuum transport system, which consists of a tip and sample transport pallet. At the end of the second part is described the testing of cooling systems for LT-STM and the design of their modifications.
|
|
|
Photocatalytic niobium and tantallum doped monodispersed nanoparticles of titania for visible-ligt applications
Štengl, Václav ; Houšková, Vendula ; Bakardjieva, Snejana ; Murafa, Nataliya
Niobium or tantalum doped anatase were prepared by thermal hydrolysis of peroxotitanium complex aqueous solutions dissolving niobium or tantalum peroxo-comples at 100 degrees C for 3 days The synthesized samples were characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), High Resolution Transmission Electron Microscopy (HRTEM), surface area (BET) and porosity determination (BJH) The photocatalytic activity of doped titania samples was determined by decomposition of salicylic acid during irradiation at 365 nm and 400 nm Niobium-doping caused the increase of unit cell constants of anatase and the shape change of anatase crystallites from spindle-like to cubic-like structure. The niobium and tantalum doping increases the stability of anatase to above 1000 degrees C by inhibiting the growth of Mania crystallites.
|
guest ::
