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Semiconductive gas sensors for detection of organic gases and vapours
Šedivý, Matúš ; Gablech, Evelína (referee) ; Gablech, Imrich (advisor)
This bachelor thesis is focused on gas sensors. Basic characteristics of sensors are discussed in the first part. Next part contains an overview of the most used types of gas sensors based on different physical principles. The main aim of thesis outlines last chapter where process of making gas sensors with different semiconductive metal oxides active layers is described. This thesis also describes measuring of their characteristics and characteristics of commercial gas sensor TGS 822 made by Figaro. Measured data are processed in graphs and tables and then were used for comparison with created sensors. In conclusion, there are discussed possibilities of improving selectivity of gas detection by using sensors with different active layer.
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Report on survey of salinity of masonries under 3rd courtyard at Prague Castle
Slížková, Zuzana ; Náhunková, Pavla
In 2022, the characterization of the chemical composition and amount of salt efflorescence on archaeological constructions under Prague Castle was supplemented by two new locations (at the site of the foundations of the Chapel of St. Bartholomew and near the northern wall of zone III). In the results, carbonate minerals were not detected as in previous years (except for calcite in small quantities). Sodium sulfate was again the majority component in the efflorescences. Using thermal analysis, the presence of sodium sulfate in the form of mirabilite was confirmed in the samples taken in February. The high contamination of marlstone with nitrates and chlorides in today's crown of the chapel's masonry of St. Bartholomew and increased sulfate contamination in the plinth section was detected. Conversely, no risk values of water-soluble ions were detected in the mortar or the black bricks of the perimeter wall.
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Elemental analysis of dendrochronological Norway spruce sample
Zámečník, Karel ; Hraníček, Jakub (advisor) ; Kozlík, Petr (referee)
The subject of this bachelor's thesis is the determination of lithium, sodium, magnesium, potassium, calcium, manganese, iron, zinc, selenium, rubidium, strontium, cadmium, antimony, cesium, barium, and thallium in dendrochronological samples of Norway spruce using inductively coupled plasma mass spectrometry. The samples of the Norway spruce were collected in the autumn of 2018 on the southern slope of hill Melechov in the Vysočina region. The stem sample was first divided into pieces according to the distance from the bark and labelled A1a to A1g. The ash sample was obtained by burning a cross-section of the stem and separating the bark, from which the A3b sample was created. The remaining two samples were made up of needles and twigs and labelled as samples E and F. For elemental analysis, the samples needed to be converted into a solution, which was achieved by dissolving them in a mixture of hydrochloric, nitric, and hydrofluoric acid, using a microwave digestion device. After dissolution, a solution of boric acid was added to each sample solution to complex any unreacted hydrofluoric acid, which could damage the internal components of the ICP-MS. Calibration solutions were then created with concentrations of 0,0016; 0,008; 0,04; 0,2 and 1,0 mg/l from stock solutions containing the analysed...
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Sputtering of nitride layers using Kaufman ion-beam source for bioelectronics applications
Jarušek, Jaromír ; Chmela, Ondřej (referee) ; Gablech, Imrich (advisor)
In this work, nitride layers, their applications in bioelectronics, and methods of chemical vapour deposition and physical vapour deposition are presented. The focus of this work is the preparation of titanium nitride thin films by reactive sputtering using Kaufman ion-beam sources. Thin films were deposited on silicon wafers and microslides. Deposited titanium nitride thin films are characterized by X-ray diffraction, four-point probe sheet resistance measurement and profilometry to determine residual stress.
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Preparation and Characterization of Biochar - the Effect of Pyrolysis Conditions and the Source of Used Biomass
Novotný, Maximilián ; Pořízka, Jaromír (referee) ; Kalina, Michal (advisor)
This diploma thesis is focused on preparation of biochar samples, which were characterized to reveal influence of preparation conditions on biochar properties physical-chemical properties. Preparation conditions covered temperature range of 400 °C to 700 °C and 2 different residence times were used. Biochars from each source biomass has its own characteristics, however the similiarities between biochars from different sources were found. Biochar yields were specified and the minimum yield was at least 24 %. Analysis on content revealed, that oat brans, mixed wood and corn residue contain a lot of organic matter, relatively, and also contains a lot of organic carbon. Results of structural analysis confirmed individual structural properties, porosity and content of function groups in particular. Influence of higher pyrolysis temperature results in slightly lower yields, however it provides products with higher content of organic carbon and higher surface area, in majority of cases. Subsequently, it was found out that short residence time of 10 minutes does not have to be enough for all used biomasses. On the basis of gained data, the preparation or production can be optimalized in effort to make usage of residue biomass more effective in different application, not only in agronomy sector.
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Analysis of selected elements in dendrological sample of spruce trunk
Pastrňáková, Aneta ; Hraníček, Jakub (advisor) ; Šíma, Jan (referee)
The aim of this bachelor thesis was to determine selected elements, specifically iron, manganese, sodium, potassium, calcium, magnesium, barium, copper, zinc, strontium and aluminium in the sample of a spruce wood, taken from a dry tree from an area of South Bohemia. As a suitable and sufficiently sensitive method an atomic absorption spectrometry with flame atomization was used in this bachelor thesis. Before the analysis optimal conditions for the determination of these elements were experimentally found. The beam height above the burner edge and the acetylene flow rate were optimized depending on the type of oxidant used. Under the optimal conditions, the basic characteristics of the determination of individual elements were determined. These characteristics include mainly the limit of detection and quantification, sensitivity and repeatability. Optimized methods for determination of the selected elements were further applied for the analysis of real spruce wood samples. These samples were prepared by decomposition of the wood in a microwave device in the presence of nitric acid. In order to suppress interference, the suitable reagents were added to the analyzed samples to determine the selected elements (sodium, potassium, magnesium, calcium, barium). In total, 22 samples of wood of different...
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Chromatograhic characterization of chiral and achiral separation systems
Kučerová, Gabriela ; Tesařová, Eva (advisor) ; Čabala, Radomír (referee) ; Ševčík, Juraj (referee)
Dissertation thesis is a 5-publications' collection concerning characterization and application potential of cyclodextrins, polysaccharides and macrocyclic antibiotics based chiral stationary phases. The effects of stationary phase and mobile phase are studied. This approach ensures the complex insight into separation systems studied. Systems with different nature of chiral selector were studied by HPLC. Namely, macrocyclic antibiotics and derivatized polysaccharides were used for experiments. Former ones provided better results for enantioseparation of non-coded amino acids than latter ones. Dynamic coating procedure was used for preparation of a new chiral stationary phase. Characterization of new cationic cyclodextrin based chiral stationary phase was performed. Linear free energy relationship method was used for characterization of two different separation systems, i.e. newly prepared stationary phase and commercially available stationary phase. Based on results obtained, newly prepared stationary phase showed better results for separation of different achiral groups of analysts. New stationary phase prepared by dynamic coating was compared with chromatographic system, in which the chiral selector was used as a mobile phase additive. The chiral selector used for the two different approaches was...
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Pvdf —AN Ideal Candidate For Use In Nanogenerators
Pisarenko, Tatiana
In this work, the PVDF composite, also known as polyvinylidene fluoride in the formof thin nanofibres, was created. Subsequently, a single-fibre characterization was performed, whichproves its piezoelectric properties and describes its structure. Electron microscopy, atomic forcemicroscopy and X-ray photoelectron spectroscopy were chosen as characterization methods. Thediscussion in this paper deals with the ability of these fibres to use PVDF as a nanogenerator.
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Characterization Of Pvdf Nanofibers Created By The Electrospinning Method
Pisarenko, Tatiana
The work investigates structure and properties of composite fibers created by the electrospinning method for piezoapplications. Polyvinylidene fluoride (PVDF) was used as a precursor. As an electrospining parameter, the collector speed of 300 and 2000 rpm was selected, which significantly affects the properties of nanofibers. The structure of fibers was investigated by scanning electron microscopy (SEM) using focused ion beam (FIB). Morphology and piezoelectric domains was observed using piezoresponse force microscopy (PFM). Phase composition was identified using Raman spectroscopy and by Fourier-transform infrared spectroscopy (FTIR). Found results are essential for the design and construction of piezoelectric based structures.
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