|
| |
|
|
Photocatalytic layers of tungsten trioxide fabricated by material printing
Saňák, Tomáš ; Krystyník,, Pavel (referee) ; Dzik, Petr (advisor)
This diploma thesis deals with milling of dispersed particles of WO3 using low-cost wet ball milling. Thin layers of WO3 were formed from them. These layers were characterized by profilometry, turbidity measurements, XRD and SEM. The photocatalytic activity was studied by the electrocatalytic properties of these layers. Profilometric measurements showed declining trends with milling time. XRD measurements confirmed the milling process and revealed a change in the crystalline phase during this process. Electrophotocatalytic measurements confirmed the photocatalytic activity of these layers and revealed its trends.
|
|
|
Thin layer WO3 for electrochromic devices
Jakubis, Ivan ; Macalík, Michal (referee) ; Sedlaříková, Marie (advisor)
This work deals with issues of electrochromism and coating method electrodeposition. Electrochromic thin-films of tungsten oxide (WO3) have been electrodeposited on glass substrates covered with transparent conductive thin-film SnO2:F (FTO). Elektrochromic characteristics of these substrates that were electrodeposited for different times have been studied. Than there have been studied the impact of various annealing temperatures on electrochromic characteristics. In this work also have been compared electrolytes LiClO4 and NaClO4.
|
|
|
Functional Tungsten-based thin films and their characterization
Košelová, Zuzana ; Horáková, L. ; Sobola, Dinara ; Burda, Daniel ; Knápek, Alexandr ; Fohlerová, Z.
Anodizing is a technique by which thin oxide layers can be formed on a surface. Thin oxide layers have been found to be useful in a variety of applications, including emitters of electrons. Tungsten is still a common choice for cold field emitters in commercial microscopy applications. Its suitable quality can be further improved by thin film deposition. Not only the emission characteristic can be improved, but also the emitter operating time can be extended. Tungsten oxide is known for its excellent resistance to corrosion and chemical attack due to its stable crystal structure and strong chemical bonds between tungsten and oxygen atoms. Many techniques with different advantages and disadvantages have been used for this purpose. Anodization was chosen for this work because of the controllable uniform coverage of the material and its easy availability without the need for expensive complex equipment. The anodizing process involves applying an electrical potential to tungsten while it is immersed in an electrolyte solution. This creates a thin layer of tungsten oxide on the surface of the metal. The thickness and properties of the resulting oxide layer can be controlled by adjusting the anodization conditions, such as the electrolyte solution, voltage, and the duration of the process. In this work, H3PO4 was used as the electrolyte to test whether these tungsten oxide layers would be useful for electron emitters, for use in electron guns and other devices that require high-quality electron emitters. The properties were evaluated using appropriate techniques. In general, anodization of tungsten to form thin layers of tungsten oxide layers is a promising technique for producing high quality electron emitters.
|
|
|
Study of physical and chemical properties of surface-modified tungsten oxide
Polášek, Jan ; Mašek, Karel (advisor)
Title: Study of physical and chemical properties of surface-modified tungsten oxide Author: Jan Polášek Department: Department of Surface and Plasma Science Supervisor: Doc. RNDr. Karel Mašek, Dr., Department of Surface and Plasma Science Abstract: This work can be divided into two parts. In the first part, we examine possibilities of preparation of monocrystalline tungsten and tungsten oxide na- noclusters by means of magnetron sputtering with gas aggregation. Clusters are prepared in the non-reactive (Ar) and reactive (Ar + O2) atmosphere and heated after the deposition or during the flight by IR radiation. Influence of oxygen in the aggregation process was described and possibilities of generating crystalline tungsten and tungsten oxide clusters were found. In the second part, we study reactivity of tungsten oxide layers, pure and doped with rare metals (Pt, Au), deposited on the silicon wafer and etched carbon, towards partial methanol oxi- dation. Influence of carbon substrate and metal doppants on reactivity was found and described, along with mofrological and chemical changes that occurs in the sample during the proces. Keywords: catalysis, tungsten oxide, clusters, partial oxidation of methanol, etched carbon 1
|
|
|
Photocatalytic layers of tungsten trioxide fabricated by material printing
Saňák, Tomáš ; Krystyník,, Pavel (referee) ; Dzik, Petr (advisor)
This diploma thesis deals with milling of dispersed particles of WO3 using low-cost wet ball milling. Thin layers of WO3 were formed from them. These layers were characterized by profilometry, turbidity measurements, XRD and SEM. The photocatalytic activity was studied by the electrocatalytic properties of these layers. Profilometric measurements showed declining trends with milling time. XRD measurements confirmed the milling process and revealed a change in the crystalline phase during this process. Electrophotocatalytic measurements confirmed the photocatalytic activity of these layers and revealed its trends.
|
|
| |
|
|
Gas sensing properties of tungsten oxide thin films
Vojík, Jiří ; Mašek, Karel (advisor) ; Haviar, Stanislav (referee)
The purpose of this thesis is a study of sensing properties of pure, platinum-doped and gold-doped tungsten oxide thin films. Required films were prepared by magnetron sputtering on glass and passivated silicon. Their chemical composition was investigated by XPS. The morphology of the films was measured using AFM and SEM. Sensing response of these films to hydrogen was investigated in the range from 1,000 to 10,000 ppm and temperatures between 100 and 350 řC. It was found that platinum oxides PtO2 and PtO were partially reduced during the sensing tests. The possible encapsulation of the platinum by the tungsten oxide was discovered. The sensitivity of the metal doped films was much higher than the sensitivity of the pure films. In the case of platinum-doped films the sensitivity decreased with increasing temperature in contrast to the gold-doped films where the sensitivity increased. The gold was present in two metallic and oxidized states. The gold was reduced during the reactions with hydrogen. After the sensing tests, the size of crystalline grains increased and the platinum-doped films became coarser.
|
|
|
Studium fyzikálně-chemických vlastností povrchově modifikovaného oxidu wolframu
Polášek, Jan ; Mašek, Karel (advisor) ; Novák, Stanislav (referee) ; Plšek, Jan (referee)
This work can be divided into two parts. In the first part, we examine possibilities of preparation of monocrystalline tungsten and tungsten oxide nanoclusters by means of magnetron sputtering with gas aggregation. Clusters are prepared in the non-reactive (Ar) and reactive (Ar + O2) atmosphere and heated after the deposition or during the flight by IR radiation. Influence of oxygen in the aggre- gation process was described and possibilities of generating crystalline tungsten and tungsten oxide clusters were found. In the second part, we study reactivity of tungsten oxide layers, pure and doped with rare metals (Pt, Au), deposited on the silicon wafer and etched carbon, towards partial methanol oxidation. Influence of carbon substrate and metal doppants on reactivity was found and described, along with mofrological and chemical changes that occurs in the sample during the proces. 1
|
|
|
Study of physical and chemical properties of surface-modified tungsten oxide
Polášek, Jan ; Mašek, Karel (advisor)
Title: Study of physical and chemical properties of surface-modified tungsten oxide Author: Jan Polášek Department: Department of Surface and Plasma Science Supervisor: Doc. RNDr. Karel Mašek, Dr., Department of Surface and Plasma Science Abstract: This work can be divided into two parts. In the first part, we examine possibilities of preparation of monocrystalline tungsten and tungsten oxide na- noclusters by means of magnetron sputtering with gas aggregation. Clusters are prepared in the non-reactive (Ar) and reactive (Ar + O2) atmosphere and heated after the deposition or during the flight by IR radiation. Influence of oxygen in the aggregation process was described and possibilities of generating crystalline tungsten and tungsten oxide clusters were found. In the second part, we study reactivity of tungsten oxide layers, pure and doped with rare metals (Pt, Au), deposited on the silicon wafer and etched carbon, towards partial methanol oxi- dation. Influence of carbon substrate and metal doppants on reactivity was found and described, along with mofrological and chemical changes that occurs in the sample during the proces. Keywords: catalysis, tungsten oxide, clusters, partial oxidation of methanol, etched carbon 1
|
guest ::
