|
|
THE APPLICATION OF NANOMATERIALS FOR LEAD FREE SOLDERS DEVELOPMENT
Pešina, Zbyněk ; Pinkas, Jiří (referee) ; Spousta, Jiří (referee) ; Sopoušek, Jiří (advisor)
The present dissertation is motivated by the search for alternatives of lead-free soldering by nanoparticles of metals and their alloys. The research focuses on the possibility of replacing lead-free solders by nanoparticles. This issue is currently being addressed by the use of lead-free solders but their properties are not entirely equivalent to properties of lead-tin based alloys. The theoretical part of the dissertation first summarizes up-to date knowledge on the development of lead-free alloys currently used for soldering in the electronics. The work compares these lead-free solder candidates with previously used Pb-Sn alloys. The second section of the theoretical part is devoted to nanotechnology that offers possible solutions of problems associated with the use of lead-free solders. The text contains a description of the properties of nanocrystalline materials in comparison with those of compact alloys having the same chemical composition. The possibility of preparation of nanoparticles and potential problems associated with small particle sizes are also presented. Introduction of the experimental part focuses on the preparation of nanoparticles of pure metals and alloys by chemical and physical ways as well as on an instrumentation for characterisation and analysis. Attention is focused on the silver in nanoparticle form that exhibits the low temperature sintering effect, which is thermally activated by decomposition of oxide envelope covering the Ag nanoparticles. This factor is critical for low-temperature sintering and thus also for possible future applications. The thermal effects of the low sintering process were studied by methods of thermal analysis. The preparation of the Cu / Ag nano / Cu joints was carried out in-situ in inert atmosphere and under the action of atmospheric oxygen. In both cases varying conditions of thermal treatment were used. The cross sections of the prepared joints were then used for the metallographic analysis of the local mechanical properties of the resulting silver layer, for the chemical composition evaluation of the resulting layers of the joint, and for the microstructure study. Strength characteristics are represented by testing shear strength of individual joints.
|
|
|
Enhancement of laser-induced plasma signal using nanoparticles
Salajková, Zita ; Galbács, Gábor (referee) ; Hidalgo, Montserrat (referee) ; Kaiser, Jozef (advisor)
Analytické metody LIBS a LA-IPC-MS založené na Laserové Ablaci (LA) nabízejí možnost rychlé chemické analýzy přímo z povrchu vzorku. Nedávno bylo ukázáno, že interakce světla s nanočásticemi může být využita pro zlepšení analytických schopností těchto metod. Při interakci nanočástic s laserovým paprskem dochází k zesílení elektromagnetického pole v jejich blízkém okolí. Pokud jsou nanočástice přítomny na povrchu vzorku analyzovaném některou z metod založenou na LA, zesílené pole vytvořené interakcí laseru s částicemi může pozměnit průběh LA, a tak ovlivnit vlastnosti laserem indukovaného plazmatu. Bylo zjištěno, že použití nanočástic může snížit práh ablace, zesílit signál a změnit vlastnosti aerosolu. Nanočásticemi zesílená LIBS (NELIBS) našla své využití tam, kde použití konvenční LIBS je problematické, a to například při analýze vzorků, kdy je jejich poškození nežádoucí nebo u analýzy roztoků mikrolitrových objemů s limity detekce nižšími než ppm. Tato dizertační práce předkládá podrobný popis jevů doprovázejících nanočásticemi zesílenou LA, založený na rozsáhlé experimentální práci a fyzikální teorii. Na základě pochopení základních principů byly vyvinuty dvě nové aplikace. Nejprve, byla NELIBS použita pro detekci kovových iontů v řetězcích amyloidů, pokročilého bio-materiálu určeného pro čištění vody. Dále byla NELIBS využita jako nová metoda pro monitorování proteinové korony vytvořené kolem nanočástic, čímž tato aplikace rozšířila klasické použití NELIBS za hranice prvkové analýzy.
|
|
|
Development of a device and methodology for Laser-Induced Breakdown Spectroscopy (LIBS)
Képeš, Erik ; Ferus,, Martin (referee) ; Lohninger, Hans (referee) ; Kaiser, Jozef (advisor)
Táto práca sa zaoberá prenosom analytických modelov medzi rôznymi systémami spektroskopie laserom indukovanej plazmy (LIBS) a porovnaním LIBS výsledkov získaných na rôznych systémoch. Instrumentácia LIBS aj spracovanie LIBS spektier sú vysoko flexibilné. Bohužiaľ, kvôli týmto flexibilitám sú výsledky získané na jednom LIBS systéme zriedka priamo porovnateľné s výsledkami získanými na inom systéme. Toto je ďalej komplikované rôznymi, často neznámymi, účinkami algoritmov spracovania LIBS spektier. V dôsledku toho sú modely analýzy spravidla špecifické pre systém (a parametre). Prenos analytických modelov medzi rôznými systémami by viedol k významnému zlepšeniu analytických schopností metódy LIBS a k miernemu zníženiu nákladov v priemyselných aplikáciách LIBS. Práca skúma vplyv rôznych stratégií merania metódou LIBS. Naďalej, práca skúma transformáciu získaných LIBS spektier prostredníctvom spracovávania údajov. Práca sa napokon zaoberá prenosom analytických modelov medzi rôznymi LIBS systémami.
|
|
|
Impact of the atmosphere on laser ablation of matters
Černá, Svatava ; Hrdlička, Aleš (referee) ; Pořízka, Pavel (advisor)
This thesis deals with a general overview of laser-induced breakdown spectroscopy - ablation of material and plasma formation when a change of the surrounding environment occurs. The aim is to establish ideal conditions for improving detection, which is difficult for some elements when the measurement takes place in the ambient atmosphere. This is the reason why we change the ambient conditions, the gas (air, helium, argon) and its pressure. Buffer gases (helium, argon) influence the development of the material ablation and quality of generated plasma. That is why we inspect the changes in the signal according to particular atmospheres (signal change in buffer gases compared to the ambient atmosphere). The first part of the thesis presents the principle and physical nature of laser ablation with a brief search of experiments performed so far for similar purposes. Based on this search we determine conclusions about the influence of buffer gasses and pressure on the detection used gasses. In the second part of the work, the controlled experiment is presented, which consisted of the detection of spectral lines of fluorine and potassium, see chapter 5.6 and molecular transitions of calcium fluoride, see chapter 5.10. In a controlled experiment, we established two assumptions. The first assumption is the influence of the inert gas atmosphere, which should significantly improve the detection of fluorine and potassium compared to the air atmosphere. We confirmed this finding only for the argon atmosphere. In contrast, in the helium atmosphere, the detection of none of the elements improved. The second assumption is the effect of reducing the ambient pressure, which in combination with an inert gas should allow the detection of fluorine even at low concentrations in the sample. We consider the measured glass disk in chapter 5.7 to be such a sample. This assumption is not confirmed, as the increased intensity of the fluorine spectral line does not manifest itself in any way when the pressure in the vacuum chamber decreases. Finally, in chapter 7 from the results of individual parts of the experiment, the most suitable conditions for the future detection of the measured substances were proposed: fluorine, potassium and calcium fluoride molecules.
|
|
| |
|
|
Study of bioapatite geochemistry using Laser Ablation ICP-MS
Kroupa, Vojtěch ; Doležalová Weissmannová, Helena (referee) ; Vašinová Galiová, Michaela (advisor)
This diploma thesis deals with topic of investigating bioapatite from conodont samples using laser ablation ICP-MS. The aim is to evaluate effect of diagenesis on the chemical composition and content of rare earth elements (REE) in the structure of conodonts. During diagenesis, bioapatite was transformed into mineral francolite and as part of this process, adsorbed REE into its crystalline structure. The degree of adsorption of REE was influenced by presence of seawater, presence of siliciclastics in surrounding REE-enriched rocks, redox conditions and also the effects of elements such as Mn and Fe present in the pore water. It was found that a group of conodont samples from the Col des Tribes (France) underwent a major diagenetic transformation, late recrystallization with REE desorption, and also due to the increased presence of Mn ions and influence of the original suboxic conditions contains rarer positive Ce anomalies. While groups of conodont samples from the Mramorový lom near Křtiny (Czech Republic) have undergone a minor diagenetic change, they contain a larger amount of REE elements.
|
|
|
Study of bioapatite geochemistry using Laser Ablation ICP-MS
Kroupa, Vojtěch ; Doležalová Weissmannová, Helena (referee) ; Vašinová Galiová, Michaela (advisor)
This diploma thesis deals with topic of investigating bioapatite from conodont samples using laser ablation ICP-MS. The aim is to evaluate effect of diagenesis on the chemical composition and content of rare earth elements (REE) in the structure of conodonts. During diagenesis, bioapatite was transformed into mineral francolite and as part of this process, adsorbed REE into its crystalline structure. The degree of adsorption of REE was influenced by presence of seawater, presence of siliciclastics in surrounding REE-enriched rocks, redox conditions and also the effects of elements such as Mn and Fe present in the pore water. It was found that a group of conodont samples from the Col des Tribes (France) underwent a major diagenetic transformation, late recrystallization with REE desorption, and also due to the increased presence of Mn ions and influence of the original suboxic conditions contains rarer positive Ce anomalies. While groups of conodont samples from the Mramorový lom near Křtiny (Czech Republic) have undergone a minor diagenetic change, they contain a larger amount of REE elements.
|
|
| |
|
|
Preparation of plasmonic nanoparticles in non-aqueous environments and in water using chemical way and by laser ablation and their testing
Hochmann, Lukáš ; Šmejkal, Petr (advisor) ; Procházka, Marek (referee)
Příprava nanočástic (N) se stala význačnou oblastí chemie díky unikátním vlastnostem, které tyto částice mají a které vedou k širokému okruhu možných aplikací. N se běžně používají v katalýze, elektronice, fotonice a nachází se i v mnoha předmětech běžné denní potřeby. Navíc, vzhledem ke svým plasmonickým vlastnostem, se N ušlechtilých kov· hojně používají ve spektroskopii, kupříkladu při povrchově zesíleném Ramanově rozptylu (SERS). V závislosti na plánovaném použití N lze k jejich přípravě použít více cest. V pří- padě přípravy N v kapalinách (koloid·) lze použít r·zné metody chemické redukce. Tyto metody jsou dobře zavedené postupy, obzvláště ve vodném prostředí. Pro určité aplikace by však byly příhodnější koloidy v jiných rozpouštědlech. Proto je hlavním cílem této práce zhodnotit možnosti přípravy koloid· chemickou redukcí a laserovou ablací ve vodě a organick- ých rozpouštědlech. Dalším cílem je charakterizace připravených částic a zhodnocení jejich potenciálu pro SERS. Zlaté koloidy ve vodě a alkoholech byly připraveny redukcí kyseliny tetracholoro zlatité tetrahydridoboritanem sodným. K přípravě stabilních sol· v alkoholech byl dále nutný pří- davek polyvinylpyrrolidonu (PVP) jako stabilizátoru, protože přímá příprava koloid· chemickou redukcí v alkoholech vedla k jejich kolapsu. Dále...
|
|
|
Use and limitations of laser ablation ICP-MS in geoscience applications
Míková, Jitka ; Košler, Jan (advisor) ; Kanický, Viktor (referee) ; Anczkiewicz, Robert (referee)
This dissertation contributes to applications of laser ablation plasma source mass spectrometry (LA ICP-MS) in Earth sciences. The primary goal of the thesis is to address some of the fundamental processes related to laser ablation of solid samples that result in decoupling of elements during laser ablation ICP-MS analysis. Better understanding of mechanisms that cause the elemental fractionation and matrix effects is necessary before the accuracy and precision of laser ablation ICP-MS analyses can be improved. The chemical and phase compositions of particles produced by laser ablation (266 nm Nd:YAG) of silicate NIST glasses and zircon were studied by SIMS and HR-TEM techniques with a particular focus on Pb/U fractionation. This is of great importance in geology as the Pb/U elemental fractionation hampered the precision and accuracy of the measured accessory mineral ages. The data suggest that chemical composition and mineralogy of particles produced at the ablation site during laser ablation differs from the original sample and varies with their size. This can result in elemental fractionation (non-stochiometric sampling) in material delivered to the ICP-MS for quantitative analysis. Evidence of the element fractionation is preserved in chemically zoned ejecta deposited around the ablation pit....
|
guest ::
