The Master’s thesis deals with the technology of surface hardening by laser. High power diode laser is used for this purpose. Surface hardening is performed on cast iron BS 1452-77, at different speeds laser head and laser power. In introduction, the theoretical part deals with possible ways of hardening focusing on the benefits of laser hardening. There are mentioned basic parts of laser, type industrial lasers and their application in industry. The final part is mentions the using of material and methods used to evaluate samples. The practical part describes the using devices and carries out evaluation macrostructure and microstructure and evaluation of hardness depending on the distance from the surface.

Dizertační práce se zabývala syntézou a studiem kompozitních materiálů pro potenciální lékařské využití. Teoretická část je zaměřena na biomateriály, zejména na kompozity složené z polyvinylalkoholu a hydroxyapatitu(PVA/HA). Byly připraveny kompozitní membrány složené z polyvinylalkoholu s různým hmotnostním zastoupením hydroxyapatitu - 0%, 10%, 20%, 30%, 40% a 50%. Hydroxyapatit (HA) byl připraven srážecí metodou z hydrogenfosforečnanu amonného a tetrahydrátu dusičnanu vápenatého ve vodném alkalickém prostředí. Vzniklá suspenze se smísila s roztokem polyvinylalkoholu, který byl připraven rozpuštěním ve vodě o teplotě 85° C. Jednotlivé směsi byly odlity do formy a sušeny po dobu 7 dní při teplotě 30 ° C, vzniklé 0,5 mm tenké membrány byly analyzovány ATR-FTIR spektroskopií k identifikaci funkčních skupin v kompozitu, dále byla provedena XRD analýza. Zkouška tahem a TGA měření byly realizovány k určení vlivu HA na mechanické vlastnosti, respektive změnu tepelné odolnosti kompozitů ve srovnání s čistým PVA. Byla provedena zkouška bioaktivity v simulovaném krevním roztoku (SBF) po dobu 2h, 7 a 28 dnů. SEM byla použita k charakterizaci povrchové mikrostruktury biocompositních membrán před a po ponoření do SBF. Na povrchu testovaných membrán vznikla vrstva apatitu, která je charakteristická pro bioaktivní materiály. Bylo zjištěno, že s rostoucím množstvím HA částic docházelo ke vzniku aglomerátů v kompozitu, které vznikly mimo jiné jako důsledek růstu krystalů HA během sušení membrán. Bioaktivita rostla s delším působením SBF na vzorky.

This diploma thesis deals with crystallization additives used to modify cement composites. Describes their principle of operation, application methods and also mentions the different manufacturers with their products. In this work were made test samples with Xypex Admix crystallization additive which were tested for mechanical and physical properties depending on the amount of crystallization additives, aggressive environment and the duration of exposure in this environment. Selected samples were analyzed with RTG, DTA, SEM and porosimetry for detailed examination of the microstructure.

This study deals with phase transformations in metastable β titanium alloys, focusing on the investigation of evolution of nanoparticles of thermodynamically metastable ω phase. For the purpose of this research, single crystals of two metastable β titanium alloys - LCB (Ti-6.8Mo-4.5Fe-1.5Al) and Ti-15Mo (in wt. %) - were grown in an optical floating zone furnace. It was established by differential scanning calorimetry that the phase transformations occurring in the material did not change significantly as a result of the single crystal growth process. Using single crystal X-ray diffraction, the shape and the size of ω particles were determined in a series of aged samples. The lattice parameters of ω particles and the β matrix, as well as the misfit between the two structures were calculated. The β phase was found to be locally deformed in compression around ω particles. Small-angle X-ray scattering (SAXS) experiments revealed a spatial ordering of ω particles in the β matrix in a disordered cubic array with the basis vectors along 100 β directions. The SAXS data also allowed the evaluation of the mean ω particle sizes and distances and confirmed that the ω particle growth obeys the t1/3 law following from the Lifshitz-Slyozov-Wagner theory. In situ SAXS performed during isothermal ageing at selected...

Title: Magnesium alloys designed for medical applications Author: Mária Zemková Abstract: This Master thesis is focused on the influence of hot extrusion and equal channel angular pressing (ECAP) on the microstructure, mechanical and corrosion properties of magnesium alloys. Investigated materials include three magnesium alloys with the addition of neodymium and/or yttrium elements - N3, W3 and WN43, as a potential material for medical applications. Moreover, the influence of alloying elements in solid solution state was studied. Microstructure development was characterized by scanning electron microscopy together with transmission electron microscopy and X-ray diffraction. Mechanical properties was studied by compression deformation tests in two perpendicular directions and by microhardness tests. The linear polarization method was used to study corrosion resistance. The processing though ECAP resulted in grain refinement in all three alloys. Ultra-fine grained microstructure was achieved in W3 and WN43 alloy. The high degree of recrystallization during ECAP caused the formation of high-angle grain boundaries in all three alloys. Weak texture evolution was maintained during both processings. A different initial fraction of intermetallic phases before extrusion led to significant changes of microstructure...

In this work phase transformations in metastable β (primarily Ti-15Mo) alloys were studied utilizing electrical resistance, dilatometry, transmission electron microscopy and X-ray and neutron diffraction. The materials Ti-15Mo, Ti-6.8Mo-4.5Fe-1.5Al (LCB), Ti-5Al-5V-5Mo-3Cr (Ti-5553), Ti-29Nb-1Fe-0.5Si (TNFS), Ti-15Mo-3Nb-3Al-0.2Si (Timetal 21S) and Ti-13Cr-1Fe-3Al (TCFA) (in wt. %) - were subjected to a solution treatment at a temperature above β transus and quenched into water. In this condition, the microstructure of the investigated materials consists of β matrix and ω particles. Samples quenched from important temperatures determined from in-situ electrical resistance and dilatometry measurements were studied by post-mortem TEM. In-situ X-ray and neutron diffraction provided direct observations of microstructure of Ti-15Mo alloy during linear heating and confirmed statements based on results of indirect methods, such as: the decrease of volume fraction of ω phase during heating at low temperatures (up to 250 ◦ C), complete dissolution of ω phase at 560 ◦ C and precipitation of α phase without ω particles serving as its direct precursors. X-ray diffraction experiment allowed to determine relative evolution of the size of ω particles while phase fraction evolution was derived from neutron diffraction. The...

Mechanical properties of widely applicable thin nanocrystalline films have been a sub- ject of interest for some time due to deviation of their properties from the properties of bulk and micro sized grain materials. The deformation mechanisms in these materials are altered by restricted size of the material and high ratio of surface and grain boundary areas. Recent advances in transmission electron microscopy (TEM) allow direct obser- vations of the deformation mechanisms during nanoindentation or tensile deformation of the specimen. Thin Al films prepared by DC magnetron sputtering were deformed in situ in TEM and bright field TEM. High resolution TEM and automated crystallographic orientation mapping (ASTAR) were implemented to observe the ongoing deformation mechanisms. Molecular dynamic simulation designed to approach the conditions of per- formed experiment were used to visualize the deformation mechanisms on atomic scale and the reliability of both methods was discussed. 1

The master thesis discusses the alkali-activation of aluminosilicate material (metakaolin), specifies the main components of geopolymer mixture, evaluates the influence of geopolymer mixture composition and the influence of other factors on final properties of geopolymer. Results of the mechanical properties and microstructure of the geopolymer pastes made out of metakaolin activated by various amounts (50–110 % by weight of metakaolin) of liquid water glass (with varying modulus from 0,5 to 3,0) or NaOH as well as KOH solution are presented in the experimental part.

The influence of various pressure-less heating schedules (CRH - Constant Rate of Heating, TSS - Two Step Sintering, RCS – Rate Controlled Sintering) on the final microstructure of cubic zirconia ceramics was studied in this master´s thesis. There were used nanopowders ZrO2 (stabilized with 8 mol.% Y2O3) with initial particle size 80 nm (TZ-8Y) and 140 nm (TZ-8YSB). Powders were cold isostatically pressed and pressure-less sintered in air by different heating regimes. It was found that for both studied materials the modification of conventional sintering (CRH) using lower sintering temperatures and longer sintering dwell times can result in samples with finer microstructure. For example, the sintering of TZ-8YSB ceramics at a relatively low temperature (1270 °C) but for very long time (60 h) led to ceramics with the same final density (99,25 % of theoretical density) and almost identical grains (1,31 m vs. 1,27 m) in compare with TSS (1440 °C/ 1290 °C/ 15 h). On the other hand, RCS method showed no positive effect on the microstructure of both materials in comparison with CRH method. The obtained results indicate that the microstructure of c-ZrO2 ceramics can be influenced rather in its third sintering stage (by CRH and TSS methods) than in the second sintering stage (by RCS method).

The topic of the thesis is preparation of ferroelectric and dielectric composite materials, particularly the work deals with the preparation of barium strontium titanate. In the theoretical part the possibilities of BST synthesis and its processing are described. The experimental part deals with precipitation synthesis of barium strontium titanate. Prepared powders were characterized in terms of morphology and phase composition. Further, pressureless sintering and hot isostatic pressing (HIP) were used for preparation of dense ceramics. Pure BST powders, that were formed and sintered, were prepared by sol-gel precipitation synthesis. The highest density was reached by slow sintering cycle (slow increase of temperature and delay during sintering) and sintering by HIP.