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Gas sensors, their construction and testing
Zbožínek, Štěpán ; Prášek, Jan (referee) ; Pytlíček, Zdeněk (advisor)
The presented bachelor´s thesis deals with gas sensors, their construction and methods of testing. First part shortly describes the problems of gas detection. There are introduced common principles, constructions, examples of possible applications and requirements, which should be complied with gas sensors. In more detail, there are described conductivity gas sensors. Main purpose of the work is draft software equipment determined for compiled mixing station. For check correct function of the program was also done several measurements with gas sensors containing active layer SnO2 created for oxygen detection. In conclusion, there is on the base of collected theoretical pieces of knowledge and measured information discussed accuracy of measurement, and limits of usability station.
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Tin dioxide based semiconducting gas sensors
Gablech, Imrich ; Pytlíček, Zdeněk (referee) ; Prášek, Jan (advisor)
This project is aimed at semiconductive gas sensors based on tin dioxide. In the first part, gas sensors are divided depending on their principal of functionality. Next part is about functionality of tin dioxide gas sensors and the possibilities of active layer modification. Experimental describes gas sensor from its drawing until construction, testing and characterization. Several microelectronic technologies such as thin-film, thick-film, LTCC, spray-coating or wire-bonding were used for constructing the sensor. In the last part properties of gas sensors and differences in functionality between modified and unmodified gas sensor are summarized.
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Electrochemical analytical devices for thick-film sensors measurement
Pytlíček, Zdeněk ; Adámek, Martin (referee) ; Prášek, Jan (advisor)
This work covers an area of electrochemical analytical systems for trace determination of dissolved species in water solutions with use of thick-film sensors. Several types of common electrochemical devices including special ones used for sensors are described and compared in this work. The main goal of this work is to find the suitable electrochemical arrangement with the best, reliable and reproducible current response of the thick film sensors. A new electrochemical arrangement, which should eliminate disadvantages of common devices and unite their advantages with optimization for thick film sensors, is designed here. For better current response of the sensor, suitable improvements and optimization of the new electrochemical arrangement prototype were done in this work. All measurements were done on standard electrochemical couple of potassium ferro-ferricyanide using the cyclic voltammetry. In the end of this work, all the devices are compared in term of their features and presumptions for the best detection limit of the thick film sensors.
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Gas sensors, their construction and testing
Pytlíček, Zdeněk ; Boušek, Jaroslav (referee) ; Prášek, Jan (advisor)
This work deals with branch of gas sensors, their construction and methodology of testing. The general aim is a design and implementation of a station for simple testing of conduction gas sensors. The whole station is conceived as virtual measuring apparatus, operated by PC in LabView environment. The station enables mixing of any two gases at concentration demanded and measuring of the basic conduction characteristics of the thick-film and thin-film gas sensors. The central communication interface and modular conception enable easy expansion of possibilities of the whole apparatus in the future. It is possible to measure up to eight gas sensors split into two TO-12 packages simultaneously.
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Nanostructured layers of semiconducting metal oxides in gas sensors
Bartoš, Dušan ; Pytlíček, Zdeněk (referee) ; Bendová, Mária (advisor)
This diploma thesis discusses the gas sensor preparation via anodic oxidation. It names sensor types, deals with the sensing principle of electrochemical sensors in detail and submits sensor parameters. It describes preparation technology and characterization technology methods. In the experimental part, it focuses on both the measurement methodology and the electrochemical oxygen sensor covered with titanium dioxide nanocolumns fabrication. Not the least it discusses acquired research results.
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Gas Microsensors Based on Self-Organized 3D Metal-Oxide Nanofilms
Pytlíček, Zdeněk ; Husák, Miroslav (referee) ; Kolařík, Vladimír (referee) ; Prášek, Jan (advisor)
This dissertation concerns the development, fabrication and integration in a gas sensing microdevice of a novel 3-dimensional (3D) nanostructured metal-oxide semiconducting film that effectively merges the benefits of inorganic nanomaterials with the simplicity offered by non-lithographic electrochemistry-based preparation techniques. The film is synthesized via the porous-anodic-alumina-assisted anodizing of an Al/Nb metal bilayer sputter-deposited on a SiO2/Si substrate and is basically composed of a 200 nm thick NbO2 layer holding an array of upright-standing spatially separated Nb2O5 nanocolumns, being 50 nm wide, up to 900 nm long and of 8109 cm2 population density. The nanocolumns work as semiconducting nano-channels, whose resistivity is greatly impacted by the surface and interface reactions. Either Pt or Au patterned electrodes are prepared on the top of the nanocolumn array using an innovative sensor design realized by means of microfabrication technology or via a direct original point electrodeposition technique, followed by selective dissolution of the alumina overlayer. For gas-sensing tests the film is mounted on a standard TO-8 package using the wire-bonding technique. Electrical characterization of the 3D niobium-oxide nanofilm reveals asymmetric electron transport properties due to a Schottky barrier that forms at the Au/Nb2O5 or Pt/Nb2O5 interface. Effects of the active film morphology, structure and composition on the electrical and gas-sensing performance focusing on sensitivity, selectivity, detection limits and response/recovery rates are explored in experimental detection of hydrogen gas and ammonia. The fast and intensive response to H2 confirms the potential of the 3D niobium-oxide nanofilm as highly appropriate active layer for sensing application. A computer-aided microfluidics simulation of gas diffusion in the 3D nanofilm predicts a possibility to substantially improve the gas-sensing performance through the formation of a perforated top electrode, optimizing the film morphology, altering the crystal structure and by introducing certain innovations in the electrode design. Preliminary experiments show that a 3D nanofilm synthesized from an alternative Al/W metal bilayer is another promising candidate for advanced sensor applications. The techniques and materials employed in this work are advantageous for developing technically simple, cost-effective and environmentally friendly solutions for practical micro- and nanodevices, where the well-defined nano-channels for charge carriers and surface reactions may bring unprecedented benefits.
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Oxygen detection using gas sensor
Jelínek, Tomáš ; Pytlíček, Zdeněk (referee) ; Prášek, Jan (advisor)
In this master´s thesis various types of gas sensors, their characteristics, principle, active layer and structure are described. This work is focused on semiconductor gas sensors. In the experimental part gas test station is used to measure the main characteristic of commercial sensor Figaro TGS 822 and own SnO2 gas sensors and reaction to oxygen. Both sensors and measurement results are compared with each other.
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Chemorezistive gas sensor
Venkrbec, Lukáš ; Pytlíček, Zdeněk (referee) ; Prášek, Jan (advisor)
This thesis deals with the detection of gases. Based on the research, the theoretical part is devoted to the principles and construction of chemical gas sensors, especially the chemoresistive gas sensors, mainly with the active layer consisting of metal oxides and carbon nanotubes. In the second half of the theoretical part the carbon nanostructures, their properties and the methodology of preparation are reviewed. The experimental part deals with the type of support structure, preparation of the active layer and the method of its deposition and he principle of detection. In the results and discussion, the thesis focuses on the detailed processing of the results and the evaluation of the response ammonia, the impact of the modifications and procedures. In the end, the results obtained are compared, both with each other and with the relevant literature.
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Gas sensor based on carbon nanoparticles
Morávek, Petr ; Pytlíček, Zdeněk (referee) ; Prášek, Jan (advisor)
This thesis deals with characterization of gas sensors based on carbon nanomaterials. In the theoretical chapter, the basic terms connected with the gas detection field, properties of different carbon nanoparticles and methods of their preparation are described. Practical experiments include the evaluation of samples` responses to ammonia, influence of annealing on their response and comparison of pure samples and their modifications.
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Design of measuring circuitry of gas sensor for very low limit detection measurement
Zwiener, Jan ; Pytlíček, Zdeněk (referee) ; Hubálek, Jaromír (advisor)
This thesis deals with various types of noise that affect measurement. With a special device called a lock-in amplifier, these interfering signals can be cancelled out so that the desired signal is well below the noise level. This device is described in the thesis and explains the principle of its operation. The thesis also deals with the application of this device to the device allowing the measurement of very small changes in resistance. The device is described in several functional blocks, each block is described in detail, to understand its function in the overall circuit. Part of the thesis is the creation of the proposed device and its practical verification, which is realized by measuring the device.
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