Ceramic dental restoration milling from stock based on ZrO2

V tejto bakalárskej práci je urobená rešerš na tému obrábania polotovarov z oxidu zirkoničitého pre dentálne aplikácie. V experimentálnej časti boli na spečených vzorkách vyhodnocované testy pevnosti v biaxiálnom ohybe, stanovená drsnosť a veľkosť zŕn a bolo určené lineárne zmršťovanie vzoriek. Tieto testy boli uskutočnené pre laboratórne polotovary pripravené metódou gélového odlievania z keramického prášku na báze oxidu zirkoničitého a pre dva typy komerčných polotovarov pripravených izostatickým lisovaním za studena, rovnako z oxidu zirkoničitého. Bola ukázaná závislosť pevnosti na veľkosti zŕn. Vzorky z polotovarov pripravených gélovým odlievaním mali štatisticky významne vyššie pevnosti, než vzorky z komerčných polotvaru. Finálnym krokom bolo obrobenie zubnej korunky podľa reálneho modelu zubu a to z polotovaru materiálu pozorovaného v tejto práci.In this bachelor thesis, the theoretical overview about the milling of the dental zirconia blanks was performed. The tests of biaxial flexural strength were evaluated in the experimental part, as well as the roughness and the grain size in sintered state and the linear shrinkage was determined. These tests were done for gel cast blanks from zirconia dioxide prepared in laboratories and also for two types of commercially available zirconia oxide blanks fabricated by cold isostatic pressing. The relationship between strength and grain size was shown. The samples prepared from gel cast blanks had statistically significantly higher strength than samples from commercial blanks. At the end of the thesis, the milling of dental crown was carried out based on real tooth model from gel cast zirconia blank studied in this thesis.

Transparent LiOH-doped magnesium aluminate spinel produced by spark plasma sintering: Effects of heating rate and dopant concentration

The effects of LiOH doping of magnesium aluminate spinel powders and various Spark Plasma Sintering (SPS) schedules on densification behavior and final transparency of polycrystalline magnesium aluminate spinel were studied. Two commercial magnesium aluminate spinel powders, with different specific surface areas, were doped with up to 0.6 wt% of LiOH and consolidated using SPS with slow (2.75 °C/min) and fast (100 °C/min) heating rates. The slow heating rate was optimal for undoped magnesium aluminate spinel (LiOH-free) with the best real in-line transmittance (RIT) of 84.8% (measured at 633 nm on a disc 0.8 mm thick). For the magnesium aluminate spinel doped with 0.3 wt% of LiOH, the fast heating rate was beneficial, and an RIT of 76.5% was achieved. μ-Raman analysis confirmed that the addition of LiOH suppressed carbon contamination

A brief introduction and current state of polyvinylidene fluoride as an energy harvester

This review summarizes the current trends and developments in the field of polyvinylidene fluoride (PVDF) for use mainly as a nanogenerator. The text covers PVDF from the first steps of solution mixing, through production, to material utilization, demonstration of results, and future perspective. Specific solvents and ratios must be selected when choosing and mixing the solution. It is necessary to set exact parameters during the fabrication and define whether the material will be flexible nanofibers or a solid layer. Based on these selections, the subsequent use of PVDF and its piezoelectric properties are determined. The most common degradation phenomena and how PVDF behaves are described in the paper. This review is therefore intended to provide a basic overview not only for those who plan to start producing PVDF as energy nanogenerators, active filters, or sensors but also for those who are already knowledgeable in the production of this material and want to expand their existing expertise and current overview of the subject

Milling of pre-sintered ceramics using CAD / CAM

Diploma thesis is focused on determination of proper pre-sintering temperatures of zirconia ceramic blanks intended for CAD-CAM milling. Functional properties of milled and sintered samples are also discussed. Experimental part is aimed on determination of properties of blanks which affect directly the CAD-CAM process. Another solved issue is definition of mechanical and physical properties of sintered bodies. Final properties are compared with properties of ceramic blanks made from standard ceramic powder. Dental crown, dental three-unit bridge and partial knee joint were prepared successfully. The tests of geometric accuracy were performed on dental crown as well as on partial knee joint replacement with using 3D scanner

Comprehensive characterization of PVDF nanofibers at macro- and nanolevel

This study is focused on the characterization and investigation of polyvinylidene fluoride (PVDF) nanofibers from the point of view of macro- and nanometer level. The fibers were produced using electrostatic spinning process in air. Two types of fibers were produced since the collector speed (300 rpm and 2000 rpm) differed as the only one processing parameter. Differences in fiber’s properties were studied by scanning electron microscopy (SEM) with cross-sections observation utilizing focused ion beam (FIB). The phase composition was determined by Fourier-transform infrared spectroscopy (FTIR) and Raman spectroscopy. The crystallinity was determined by differential scanning calorimetry (DSC), and chemical analysis of fiber’s surfaces and bonding states were studied using X-ray photoelectron spectroscopy (XPS). Other methods, such as atomic force microscopy (AFM) and piezoelectric force microscopy (PFM), were employed to describe morphology and piezoelectric response of single fiber, respectively. Moreover, the wetting behavior (hydrophobicity or hydrophilicity) was also studied. It was found that collector speed significantly affects fibers alignment and wettability (directionally ordered fibers produced at 2000 rpm almost super-hydrophobic in comparison with disordered fibers spun at 300 rpm with hydrophilic behavior) as properties at macrolevel. However, it was confirmed that these differences at the macrolevel are closely connected and originate from nanolevel attributes. The study of single individual fibers revealed some protrusions on the fiber’s surface, and fibers spun at 300 rpm had a core-shell design, while fibers spun at 2000 rpm were hollow