|
|
Development of dual technology for the treatment of winter rape and spring barley seeds
OLŠAN, Pavel
The dissertation thesis deals with the use of low-temperature plasma and biological treatment of winter rape seed and spring barley as an alternative to chemical dressing in relation to the Decree on Integrated Pest Management 205/2012 Coll. The seed treatment technology is conceived as a two-phase process, where a lowtemperature plasma discharge of the Gliding Arc type ignited in the air at atmospheric pressure is used in the first step and a biological preparation containing spores of Trichoderma virens is applied to the treated seed as the second step. The plasma discharge treatment allows to increase the wettability of the seed surface, which improves the adhesion of the biological preparation in the second treatment step. Plasma also enables to activate selected processes taking place in seeds, which support their germination and subsequent growth. The content of the dissertation is divided into four sub-units which are mutually related: 1. determination of plasma discharge parameters for subsequent applications in the proposed technology, 2. carrying out laboratory experiments to assess the effect of plasma on seed, 3. carrying out field experiments to compare crop yields for different seed treatment options, 4. proposal for a regulation for seed treatment in a continuous mode by plasma discharge followed by application of the preparation and production of a functional sample. The work is markedly interdisciplinary and intervenes in the field of plasma physics, chemistry, plant production and construction of technical equipment. From the results achieved we can give a short summary: 1. Plasma discharge treatment of winter rape and barley seeds results in increased surface wettability. 2. No difference in the absorption of plasma treated and untreated seeds was observed during the experiments. 3. Developed dual seed treatment technology has the potential to increase yield. The dissertation thesis was realized within the project TA04021252 ? "Development of equipment for physical treatment of seeds and malt using low-temperature plasma."
|
|
|
Plasma treatment of fabrics
STEHLÍK, Radim
The thesis deals with the surface modification of cotton fabric by low-pressure micro-wave plasma discharge. The main materials used for this experiment are cotton fabrics and hexamethyldisiloxane. The experiment itself is focused on the modification of cotton fabric to improve hydrophobic atributes. An argon process gas was used in the surface modification. The individual treated samples were operated with changes in process gas flow and the time during which the above-mentioned modifications was performed. Two methods were used to analyze the results of the experiment. The first one was aimed at determining changes in hydrophobic atributes in the form of wetta-bility in an unmodified sample compared to other modificated samples using the drop-let method. An electron microscope was used for the subsequent study of possible changes in surface topography. From the point of view of the examined results, the difference in hydrophobic properties was observed when using the droplet method to-gether with the change in the topography of the surface obtained on the electron mi-croscope in the cotton samples examined. The actual evaluation of individual methods points to the desirable changes in modified cotton compared to unmodified cotton. Further information regarding the results of the experiment, depending on the changes in individual parameters in the cotton treatment process using low pressure microwave plasma discharge, are presented in thesis.
|
|
|
The Analysis of Solder Preforms in Surface Mount Assembly
Novotný, Václav ; Vala, Radek
This article is focused on the sphere of solder joints reliability in technology of surface mount assembly and the issue of manufactory of solder joints with solder preforms is introduced closer. It also describes types of solder preforms, their application and different methods of using in surface mount assembly. Text further comprises comparison of the solder joint which is manufactured by printing of solder paste through the cooper stencil and solder joint manufactured by applying of solder preform. The results of these basic processes are compared with method of solder fortification. In conclusion, there are evaluated outputs from experimental manufactory of solder joints with solder preforms and complemented by outputs which are achieved by x-ray machine.
|
|
|
Quality of PCB Surface Finishes and Test Coupon Optimization
Minář, Jan ; Přikryl, Tomáš (referee) ; Starý, Jiří (advisor)
This master’s thesis deals with measuring and evaluation of wetting for samples of different surface finishes, using a test coupon developed in cooperation with firm Gatema. It deals with surface finishes ENIG and immersion tin. For these samples deals with quality monitoring and periodic testing of these surface finishes. The solder using for tests is SAC305. Test methods are used for simulation of reflow soldering and wave soldering.
|
|
|
Wettability enhancement of polymeric and glass micro fiber reinforcement by plasma treatment
Trejbal, J. ; Šmilauer, V. ; Kromka, Alexander ; Potocký, Štěpán ; Kopecký, L.
Plasma treatments were used to modify surface properties of polyethylene terephthalate (PET) and glass micro fibers, to improve their wettability. PET fibers, having diameter of 400 μm, and glass fibers (14 μm) were exposed to low pressure oxygen plasma. A direct horizontal optical method was used for contact angle measurements on fiber surfaces submerged into distilled water. Surface morphology changes before and after treatment were characterized by scanning electron microscopy. Finally, cement paste specimens reinforced with PET and lime-based mortars reinforced with glass fibers were made and after 28 days of mixture curing tested by four-point bending tests. After oxygen plasma treatment contact angles decreased by 60 % on PET fibers and by 25 % on glass fibers in comparison with untreated fibers. Next, SEM images revealed the significant surface damages of PET fibers and minor damages of glass fibers. Both four-point tested samples reinforced with treated fibers exhibited the maximum bending strength loss about to 10 to 20 percent compared to samples with untreated reinforcement.
|
|
|
Dynamics of drying of sessile droplets in dependence on the surface wettability
Štefaníková, Radka ; Kylián, Ondřej (advisor) ; Shukurov, Andrey (referee)
Wettability is one of the key parameters that govern interaction between solid objects and their surrounding environment. In this work wettability of two kinds of materials was investigated - untreated and plasma treated polyether ether ketone and nanostructured C:F thin films deposited either onto a smooth substrate or on substrates seeded with nanoparticles. In the first case the main focus was given to the evaluation of dependence of wettability and water droplet drying dynamics on the plasma treated PEEK on storage time. It was found that plasma treatment induces changes in surface morphology and in chemical composition that in turn results in dramatic increase of surface wettability as well as in alteration in drying dynamics. It was shown that whereas chemical composition and wettability gradually approach properties observed on untreated PEEK, the drying dynamics, namely disappearance of the constant contact angle phase, is temporally stable. In the second case the main emphasis was given to the investigation of the effect of surface nanoroughness and its character on wettability of produced samples. It was found that when the base layer was composed from nanoparticles of the same kind, the surfaces exhibited higher values of water contact angles as compared to C:F films deposited onto smooth...
|
|
|
Nanoclusters coatings for biomedical applications
Divín, Radek ; Kylián, Ondřej (advisor) ; Hanuš, Jan (referee)
Title: Nanoclusters coatings for biomedical applications Author: Radek Divín Department: Department of Macromolecular Physics (110. 32-KMF) Supervisor: RNDr. Ondřej Kylián, Ph.D. Abstract: The copper nanocluster films were prepared with the aid of the gas cluster aggregation source based on the principle of material sputtering from the magnetron target to the relatively high pressure of the working gas (Ar). The nanocluster films prepared in this way were subsequently overlapped with the layer of plasma polymer deposited by RF magnetron sputtering from the nylon polymer target in the atmosphere of the working gas (Ar, 2 Pa). A repetition of this procedure enabled to prepare nanocomposite layers having a multilayer character. These layers were subsequently investigated with regard to their morphology, chemical composition, surface wettability and optical properties. The chemical composition of the surface layer formed by nanocomposite films was determined by the X-ray photoelectron spectroscopy (XPS). It turned out that the chemical surface composition of prepared nanocomposites was not markedly influenced by the presence of the Cu nanoclusters. The morphology of prepared films was studied by the scanning electron microscopy (SEM) and the atomic force microscopy (AFM), which showed that the resulting...
|
|
|
Wetting and Spreading of Solder on PCB Surface
Wiesner, Lukáš ; Špinka, Jiří (referee) ; Starý, Jiří (advisor)
This work deals with the metal surface wetting problems of molten lead-free solder and monitoring of ongoing processes at the inter-phase interface. This work also deals with flushing monitoring of spreading velocity on solder finishes Ni/Au and Immersion Sn deposited on copper plated base material FR4 using digital cameras. Measurement is performed at the improved workplace. After the reflow process is measured by length of spreading solder. It evaluates and compares the time dependence of velocity of spreading solder for Ni/Au and Immersion Sn finishes.
|
|
|
Wettability of PCB Surface Finishes and Comparison of Methods
Vídeňský, Ondřej ; Přikryl, Tomáš (referee) ; Starý, Jiří (advisor)
This bachelor´s thesis deals with testing methods for surface finishe´s wettability PCB. For this tests has been designed and created testing board which contains testing coupons for testing methods. Boards have been created and covered by surface finishes by Gatema Boskovice. In this thesis electroless nickel with immersion gold (ENIG) and immersion tin have been tested. For simulation of reflow soldering have been used test methods solder indicator, solder spread test and dewetting test. Wetting balance test method has been used as simulation of wave soldering.
|
|
|
Joining alumina ceramics by thin metallic layers
Poloprudský, Jakub ; Krajňáková, Petra (referee) ; Jan, Vít (advisor)
This bachelor thesis is about the problematics of structural bonds between ceramics and metals with special focus on brazed bonds. First theoretical part describes thoroughly the majority of currently used methods for ceramics joining. Special attention is given to the explanation of phenomenon of bad wettability of ceramics by molten metals and how to solve it. In practical part the work focuses on an analysis of representatives of active and non-active brazing alloys with some added elements. For analysis of microstructures it was necessary to master the basics of preparation of ceramic-metal composite specimens. Important part of the practical section of the work is dedicated to an effort of making a test with comparable results that could be used for ceramic-metal brazed composites evaluation.
|
guest ::
