Title: Microstructure, swelling and deformation behavior of methacrylate hydrogels with interpenetrating network structure Author: Zhansaya Sadakbayeva Department: Department of Macromolecular Physics, Faculty of Mathematics and Physics, Charles University in Prague Supervisor: Ing. Miroslava Dušková-Smrčková, Dr., Institute of Macromolecular Chemistry, Czech Academy of Sciences Consultant: Prof. Ing. Karel Dušek, DrSc., Institute of Macromolecular Chemistry, Czech Academy of Sciences Abstract: This work is devoted to interpenetrating polymer network (IPN) hydrogels prepared by sequential processes of redox-initiated radical polymerization of the first network prepared from 2-hydroxyethyl methacrylate (HEMA), and UV- initiated radical polymerization of the second network prepared from 2-hydroxyethyl methacrylate (HEMA) or glycerol methacrylate (GMA). Microstructure, swelling and deformation responses of the IPN hydrogels and their constituent network hydrogels were tested by various techniques. The microstructure of the first poly(HEMA) network was found sensitive to polymerization conditions. A novel route for one-step synthesis of double-porous poly(HEMA) cryogel was proposed. The formation of the second poly(GMA) network in the environment of non-porous and macroporous poly(HEMA) parent networks was...

Oxygen strengthened biomedical beta titanium alloys Beta titanium alloy Ti-35Nb-6Ta-7Zr-0.7O (wt. %) exhibits a low Young's modulus and high strength thanks to interstitial strengthening effect of oxygen. These mechanical properties are promising for implant production. In this thesis, the aforementioned alloy is thoroughly studied in conditions prepared by various thermomechanical treatments, namely: material after casting, hot compression testing, die-forging, hot rolling and finally, cold-swaged and annealed condition. Mechanical properties and microstructure of prepared conditions are studied with special interest of enhancing the fatigue performance that is poor after casting due to porosity and large grains. The hot rolling was shown to improve the fatigue performance significantly, mainly through grain refinement. It is shown that by combining the effects of cold-swaging and recrystallization annealing, extensive refinement of grain structure can be achieved. Industrial aspects of implant production by the studied methods were discussed. In the second part of the thesis, the possibility of lowering the Young's modulus by reducing the beta phase stability (by reducing of Nb and Ta content), while retaining high strength caused by high interstitial oxyen content is explored. Several alloys were...

The topic of the Ph.D. thesis was focused on the process of sintering alumina and zirconia ceramic materials with the aim to compare kinetics of sintering sub-micro and nanoparticle systems. Zirconia ceramic powders stabilized by different amount of yttria addition in the concentration range of 0 – 8 mol% were used. The different crystal structure (secured by yttria stabilization) of zirconia, as found, did not play statistically proven role in the process of zirconia sintering. The possible influence was covered by other major factors as particle size and green body structure, which does affect sintering in general. According to the Herrings law, the formula predicting sintering temperature of materials with different particle size was defined. The predicted sintering temperatures were in good correlation with the experimental data for zirconia ceramic materials prepared from both, coarser submicrometer, and also nanometer powders. In case of alumina ceramics the predicted and experimentally observed sintering temperature values did not match very well. Mainly the nanoparticle alumina materials real sintering temperature values were markedly higher than predicted. The reason was, as shown in the work, strong agglomeration of the powders and strong irregularities of particle shape. The major role of green body microstructure in the sintering process was confirmed. The final density of ceramic materials was growing in spite of sintering temperature, which was decreasing together with pore - particle size ratio (materials with similar particle size were compared). Sintering temperature was increasing together with growing size of pores trapped in the green body structure. Clear message received from the above mentioned results was the importance of elimination of stable pores with high coordination number out off the green body microstructure during shaping ceramic green parts. Same sintering kinetics model was successfully applied on the sintering process of submicro- and also nanometer zirconia ceramics. Activation energy of nanometer zirconia was notably lower in comparison to submicrometer material. For the sintering of nanoparticle zirconia was typical so called “zero stage” of sintering, clearly visible on kinetic curves. It was found out, that processes running in zirconia “green” material during zero stage of sintering are heat activated and their activation energy was determined. Pores of submicrometer zirconia were growing in an open porosity stage of sintering just a slightly (1.3 times) compared to the nanoparticle zirconia, where the growth was much higher (5.5 times of the initial pore diameter). This difference was most probably caused by preferential sintering of agglomerates within the green bodies and by particle rearrangement processes which appears in the zero stage of sintering of nanoparticular ceramics. The technology of preparation of bulk dense ytria stabilized zirconia nanomaterial with high relative density of 99.6 % t.d. and average grain size 65nm was developed within the thesis research.

<p>U disertaciji je izvršena karakterizacija mikrostrukture i mehaničkih osobina<br />nelegiranog austemperovanogi nodularnog liva (ADI materijala), kao i uticaja<br />mikrostrukture na prelaznu temperaturu u intervalu od -196 do +100&deg;C.<br />Utvrđeno je da mehaničke osobine ADI-ja zavise od morfologije ausferitne<br />mikrostrukture i količine zadržanog austenita, tj. parametara austemperovanja.<br />Na osnovu mehaničkih osobina utvrđen je i opseg procesiranja u skladu sa<br />standardima ASTM, ISO i EN. Zaključeno je da prelazna temperatura ADI<br />materijala zavisi od količine i stabilnosti zadržanog austenita. U višem<br />temperaturnom opsegu (iznad cca. -25&deg;C) dominantna je količina zadržanog<br />austenita, dok na nižim temperaturama, stabilnost. Visoka obogaćenost<br />ugljenikom, stabilnog zadržanog austenita sprečava stvaranje martenzita na<br />niskim temperaturama, a time i pojavu krtosti kod ADI-ja.</p> / <p>The object of this thesis was to characterize microstructure and mechanical properties<br />of the unalloyed ADI material (Austempered Ductile Iron). In addition, the influence of<br />microstructure on the ductile to brittle transition temperature (DBTT) by Charpy impact<br />test in temperature interval from 196 to +100&deg;C has been studied. The all properties<br />obtained depend on the morphology of microstructure and the amount of retained<br />austenite, i.e. on the austempering parameters. According to the mechanical properties<br />and standard requirements (ASTM, ISO and EN) the processing window has been<br />proposed, also. It was found that DBTT is influenced by amount and stability of retained<br />austenite. In upper temperature range (above cca. 25&deg;C) the most influence factor on<br />DBTT is amount of retained austenite, while at the lower temperatures the stability is<br />more prominent. Stability of high carbon retained austenite at lower temperatures<br />prevents transformation to martensite and thus the embrittlement of ADI.</p>

<p>Razvijene su TiAlN/TiSiN i CrAlN/TiSiN nanoslojne prevlake u kojima je napravljen spoj nanoslojnog i nanokompozitnog dizajna. Akcenat je stavljen na proizvodnju prevlaka visoke tvrdoće i visoke otpornosti na lom. Proučavane su i jednoslojne TiAlN, nanokompozitne TiSiN i višeslojne TiAlN/TiSiN prevlake kako bi se utvrdilo kako dizajn utiče na osobine prevlaka. Sve prevlake pripremane su sa jednim, dva i tri stepena rotacije. Pokazano je da dizajn i vid rotacije značajno utiču na mikrostrukturu i teksturu prevlaka, a time na njihove mehaničke osobine, otpornost na lom, adheziju između prevlake i podloge, topografiju površine i tribološko ponašanje. Nanoslojne i nanokompozitne prevlake odlikuju se kompaktnom nanokristalnom mikrostrukturom, dok jednoslojne TiAlN prevlake imaju stubastu strukturu sa kristalnim zrnima veće veličine. Pri prelasku sa jednog na više stepeni rotacije mikrostruktura prevlaka postaje kompaktnija sa kristalnim zrnima manje veličine i manjom poroznošću. U skladu sa tim, najmanju hrapavost, najveću tvrdoću, najveću otpornost na lom i najveću otpornost na habanje imaju nanoslojne i nanokompozitne prevlake pripremane sa dva i tri stepena rotacije.</p> / <p>With the aim to develop hard coatings characterized by both, high hardness<br />and high resistance to cracking, synergy between nanolayered and<br />nanocomposite design was made and nanolayered TiAlN/TiSiN and<br />CrAlN/TiSiN coatings were produced. Monolayer TiAlN, nanocomposite<br />TiSiN and multilayer TiAlN/TiSiN were also studied in order to find the<br />relation between the coating design and their properties. All coatings were<br />deposited with 1-fold, 2-fold and 3-fold rotation. It is shown that coating<br />design and type of rotation have great influence on coating microstructure<br />and texture, and in this way on their mechanical properties, resistance to<br />cracking, adhesion between coating and substrate, surface topography and<br />tribological behavior. Nanolayered and nanocomposite coatings are<br />characterized by compact nanocrystalline microstructure, while monolayer<br />TiAlN coatings have columnar structure with larger crystalline grains. By<br />increasing the number of rotational degrees from 1-fold to 3-fold size of<br />crystalline grains decreases and microstructure becomes more dense.<br />Therefore, nanolayered and nanocomposite coatings deposited with 2-fold<br />and 3-fold rotation are characterized by the highest hardness, highest<br />resistance to cracking, highest wear resistance and the smoothest surface<br />topography.</p>

This diploma thesis researchs the collocability of the german adjectives and gives some suggestions for the presentation of the collocability in the microstructure of the adjectival entries in the German-Czech translatory dictionary. The diploma thesis is a secondary product of the project of The Large German-Czech Academic Dictionary which has been realized in the Institute for German studies of the Phaculty of Arts of Charles University in Prague since 2000. The lexicographs use the methods of the corpus linguistics, especially a combination of the concepts corpus-based and corpus-driven. Analogous methods were used in this diploma thesis. By means of the Cooccurrence Data Bank (CCDB) of the Institute for the German language in Mannheim the most frequent cooccurrence partners of an adjectiv were found, concrete dictionary examples were found out in the corpus DeReKo of the IDS Mannheim using COSMAS II or on the Internet using the search engine Google. The dates were saved in a special numerical chart of a data bank which is structured on the basis of word classes. The diploma thesis comes to the conclusion that each adjectival entry can be carried out in more ways depending on the preferred criterion which can be frequency based, syntactical, semantical or didactical. In the practical part of the...