Processing of reinforced alumina ceramics

Byla provedena literární rešerše přípravy objemové Al2O3 keramiky a jejího zhouževnaťování. Na základě provedených experimentů byly vytvořeny technologické postupy přípravy zhouževnatělé Al2O3 keramiky pomocí jejího sycení oxidem nikelnatým a oxidem zirkoničitým. Výsledky byly diskutovány z hlediska dosažené tvrdosti, pevnosti, mikrostruktury a fázového složení.Literature review of processing and toughening of bulk Al2O3 ceramics was performed. Based on performed experiments, optimal technological conditions of infiltration of alumina ceramics by nickel oxide and zirconia dioxide were found. These approaches were used for preparation of toughened alumina. The properties of sintered alumina matrix composites were discussed from the point of view of their hardness, bending strength, microstructure and phase composition.

Processing of Electroceramics from Nanopowders

Byla provedena literární rešerše přípravy objemové EuTiO3 keramiky. Na základě provedených experimentů byly stanoveny experimentální podmínky reakce v tuhém stavu práškových materiálů Eu2O3 s Ti2O3, resp. TiO2 vedoucí k fázově čisté EuTiO3 keramice. Pomocí izostatického lisování a slinování v redukční atmosféře se podařilo připravit objemovou keramiku vhodnou pro měření elektromagnetických vlastností.Literature review of processing of bulk EuTiO3 ceramics was performed. Based on experiments performed the experimental conditions of solid-state reaction of Eu2O3 with Ti2O3, resp. TiO2 leading to single phase EuTiO3 were established. Balk EuTiO3 ceramics were prepared by means of cold isostatic pressing and sintering in reduction atmosphere. This ceramics is suitable for further evaluation of electromagnetic properties.

Processing of Electroceramic Materials for Advanced Applications

Disertační práce se zabývá přípravou pokročilých keramických materiálů se zajímavými fyzikálními vlastnostmi. Materiály, připravené v rámci této práce, byly vyrobeny tuho-fázovými popř. hydrotermálními syntézami. První ze zkoumaných materiálů je elektrokeramika EuTiO3 s perovskitovou mřížkou. Absence termodynamických dat tohoto systému vedla k rozsáhlému experimentálnímu výzkumu vhodných podmínek jeho přípravy. Tři směsi práškových prekurzorů (Eu2O3 s Ti2O3 nebo TiO2 – rutil či anatas) byly homogenizovány mletím v planetovém mlýnu a formovány izostatickým tlakem 300 MPa. Vzniklé keramické polotovary diskového tvaru byly slinovány konvenčními metodami v redukčních atmosférách (Ar + 7 % H2 nebo pouze čistý H2) popř. pokročilou slinovací metodou Spark Plasma Sintering (SPS). Následně byl studován vliv slinovací metody, teploty, složení atmosféry a prodlevy na finální hustotu a fázovou čistotu vzorků. Tento výzkum vyústil v úspěšnou přípravu jednofázové EuTiO3 objemové keramiky s relativní hustotou vyšší než 95 % teoretické hustoty (%TH). S ohledem na dostupnou literaturu jsou tyto materiály jedinými publikovanými vzorky fázově čisté EuTiO3 keramiky s tak nízkou porozitou. Důležitost těchto výsledků je podložena čtyřmi publikacemi v impaktovaných časopisech, kde byly vlastnosti měřené na těchto vzorcích prezentovány. Spektra infračervené odrazivosti byla porovnána s výsledky v literatuře. Byla tak demonstrována nezbytnost fázově čistých vzorků s minimálním porozitou pro měření jejich reálných (neovlivněných) fyzikálních vlastností. Další výzkum byl zaměřen na hydrotermální syntézu (HTS) keramického prášku Eu0,5Na0,5TiO3. Prezentované HTS byly uskutečněny ve vysoce zásaditém prostředí vodných roztoků NaOH nebo KOH při teplotách 220 – 250 °C. Experimenty s různými koncentracemi prekurzorů (EuCl3 a TiCl4) a redukčních činidel vedly k přípravě jednofázového práškového perovskitu Eu0,5Na0,5TiO3 s krychlovými částicemi s rozměry pod 1 m. Jiný titaničitan - MgTiO3 – byl syntetizován tuho-fázovou reakcí směsi práškových prekurzorů MgO a TiO2. Směsi byly mechanicky aktivovány v kulovém mlýnu po dobu 0, 10, 40, 80 nebo 160 min. Keramická tělesa byla slinována pomocí dvou různých přístupů a to buď metodou Two-step Sintering (TSS) na teplotách 1300 °C (30 min) a následně 1200 °C (20 h) nebo nejprve konvenčním slinováním při 1300 °C popř. 1400 °C po dobu 30 min a poté ještě pomocí metody Hot Isostatic Press (HIP) na 1200 °C popř. 1280 °C. V případě HIP-ovaných vzorků při 1280 °C po 3 hodiny v inertní Ar atmosféře o tlaku 200 MPa byly získány fázově čisté keramické vzorky MgTiO3 s relativní hustotou nad 93 %TH. Poslední z prezentovaných materiálů je Ba(Ca)Ti(Zr)O3 bezolovnatá piezokeramika, která byla připravena tuho-fázovou reakcí práškových směsí mletých v planetovém kulovém mlýnu za rozdílných podmínek. Keramická tělesa lisovaná izostatickým tlakem (300 MPa) byla dále zhutněna beztlakým slinováním na teplotách 1200, 1300, 1400 popř. 1500 °C po dobu 1 h na vzduchu. Byly studovány potřebné podmínky pro přípravu jednofázové perovskitové Ba0,85Ca0,15Ti0,9Zr0,1O3 keramiky s požadovanou mikrostrukturou. Úspěšně tak byly připraveny vzorky fázově čisté Ba(Ca)Ti(Zr)O3 keramiky o relativní hustotě až 96 %TH. Prezentované výsledky potvrzují význam volby vhodné metody výroby a potřebných parametrů k získání pokročilých elektrokeramických materiálů s požadovanou mikrostrukturou i fázovým složením a tudíž i pro správné stanovení jejich fyzikálních vlastností.The doctoral thesis is focused on processing of advanced ceramic materials with interesting physical properties. The materials were prepared by solid-state resp. hydrothermal syntheses. The first investigated material described in this work is EuTiO3 perovskite ceramics. Absence of thermodynamic data of this system led to extensive experimental research of proper processing conditions. Three mixtures of different powder precursors (Eu2O3 with Ti2O3 resp. TiO2 – rutile or anatase) were homogenized by planetary ball mill and formed by isostatic pressure of 300 MPa. These cylindrical green bodies were sintered conventionally in reducing atmospheres (Ar + 7 % H2 resp. pure H2) or by Spark Plasma Sintering (SPS). The influence of the sintering technique, temperature, atmosphere composition and dwell time on final density and phase purity was discussed. The investigation resulted in successful processing of phase pure EuTiO3 ceramic with relative density higher than 95 % of theoretical density (%TD). According author’s best knowledge, it is up to now the best bulk EuTiO3 ceramic sample. The importance of this achievement is also declared by four publications in respected journals where the properties of these samples were presented. The infra-red reflectivity spectra of prepared materials were compared with data from literature. It was proven that only single phase samples with low content of porosity are suitable for establishing their real (undistorted) physical properties. The next research was aimed on processing of Eu0.5Na0.5TiO3 ceramics by hydrothermal syntheses (HTS). The HTS were performed in highly alkaline environment of NaOH resp. KOH solution at temperature range 220 – 250 °C. The experiments with varied precursors (EuCl3 and TiCl4) and reductant agent concentrations led to processing of pure Eu0.5Na0.5TiO3 perovskite ceramic powder with submicron cubic particles. Another titanate - MgTiO3 - was synthetized by solid-state reaction from MgO and TiO2 powder mixtures. The mixtures were mechanically activated in ball mill for 0, 10, 40, 80 resp. 160 min. The green bodies were formed by isostatic pressure of 300 MPa and sintered by two different approaches. The first batch of samples was sintered by two-step sintering technique at 1300 °C (30 min) and 1200 °C (20 h). The second set was sintered conventionally at 1300 °C resp. 1400 °C for 30 min and post-sintered by Hot Isostatic Press (HIP) at 1200 °C resp. 1280 °C. The phase pure MgTiO3 samples with relative density higher than 93 %TD were reached after post-sintering by HIP at 1280 °C for 3 hours in Ar atmosphere and pressure of 200 MPa. The last studied material was Ba(Ca)Ti(Zr)O3 lead-free piezoceramics, which was prepared by solid-state reaction from powder mixtures milled by planetary ball mill at different conditions. The pressure-less sintering of isostatically pressed bodies (300 MPa) at 1200, 1300, 1400 resp. 1500 °C for 1 h in air was performed. The processing condition needed for single phase perovskite Ba0.85Ca0.15Ti0.9Zr0.1O3 ceramics with required microstructure were studied. The single phase Ba(Ca)Ti(Zr)O3 sample with relative density 96 %TD was successfully prepared. Our results proved the importance of careful choice of the processing techniques and their variables for reaching of desired microstructure and phase composition of advanced electroceramics and therefore for proper evaluation of their physical properties.

Thermal annealing effects in polycrystalline EuTiO3 and Eu2Ti2O7

Using time-differential perturbed angular correlation of gamma rays, we investigated the electric-field gradient of polycrystalline EuTiO3 and Eu2Ti2O7, with Hf-181(Ta-181) as a probe, following different thermal treatments. The measurements were performed at ISOLDE-CERN following 80 keV implantation at the Bonn Radioisotope Separator. The experimental results indicated successful induction of different phases in the implantation recovery process at 1273 and 1373 K. These observations were combined with ab initio calculations and X-ray diffraction measurements. A comparison of ab initio calculated electric-field gradients with the measured values discriminates between different structures and defects and rules out many possible cases. The Ta probe at the Ti site in the Eu2Ti2O7 phase is found to be the most probable case of site occupation after annealing at 1373 K, while annealing at 1273 K keeps EuTiO3 in the vicinity of the Ta probe. A discussion of the hyperfine interactions that promote variation in the interaction strength at the Ta-181 site is presented

Life in Health 2019: Research and Practice

This proceedings contains a selection of papers from the internacional interdisciplinary conference Life in Health 2019, which took place from 5 to 6 September 2019 in the Czech Republic at the Faculty of Education, Masaryk University. The papers focus on general as well as specific approaches to public health protection and promotion. The findings presented are based on research data and are applicable in health education and general education of children and the whole population

Přehled anatomických odchylek a vrozených vad děložních trubic a jejich vliv na plodnost

Anatomické variace a vrozené anomálie děložních trubic (UTAVsCAs) jsou vzácné stavy, které jsou často nediagnostikovány nebo náhodně diagnostikovány při zobrazovacích vyšetřeních, laparotomii, laparoskopii pro nesouvisející stav nebo při císařském řezu. UTAVsCA jsou často asymptomatické, ale jejich klinický význam spočívá v jejich možném nepříznivém vlivu na plodnost. Vzhledem k jejich vzácnému výskytu jsou obvykle publikovány jako kazuistiky. Nejtypičtěji jsou popisovány: ageneze děložních tub (UT), akcesorní UT (duplikace UT), akcesorní ostium UT a paratubální cysty (např. Morgagniho hydatidová cysta). UTAVsCA jsou zařazeny do zastřešující kategorie anomálií mülleriánských vývodů (MDA), která zahrnuje anomální vývoj všech orgánů vyvíjejících se z paramesonefrických (mülleriánských) vývodů, tedy UT, dělohy a horní části pochvy. Je zajímavé, že většina klasifikačních systémů MDA pojednává výhradně o děložních a vaginálních anomáliích, zatímco UT jsou často zcela opomíjeny. To pravděpodobně pramení ze skutečnosti, že UT přestávají být pro mnoho kliniků zajímavé, protože UT považují za nadbytečné orgány, jejichž funkci lze snadno nahradit v laboratoři pro oplodnění in vitro (IVF). Moderní reprodukční medicína skutečně velmi pomáhá při početí neplodných párů. V mnoha případech se skutečně podaří UT obejít a narodí se dítě "ze zkumavky". Nicméně UT jsou stále naprosto unikátní v tom, že poskytují vhodné prostředí pro oplodnění a raný vývoj embrya - procesy, které dosud nebyly zcela pochopeny. Tato skutečnost by mohla částečně vysvětlit, proč se úspěšnost IVF pohybuje "pouze" kolem 30-50 % v závislosti na věku. Výzkum UTAVsCA má proto v kontextu reprodukční medicíny stále klinický význam a neměl by být z výzkumného úsilí vynechán.Anatomical variations and congenital anomalies of the uterine tubes (UTAVsCAs) are rare conditions, which are often undiagnosed, or accidentally diagnosed upon imaging, laparotomy, laparoscopy for unrelated condition, or during the Cesarean section. UTAVsCAs are often asymptomatic, but their clinical relevance lies in their possibly adverse impact on fertility. Since their rare occurrence, they are usually published as case reports. The most typically described are: agenesis of the uterine tubes (UTs), accessory UT (UT duplication), accessory UT ostium, and paratubal cysts (e.g. the hydatid cyst of Morgagni). UTAVsCAs are classified into an umbrella category of Müllerian duct anomalies (MDAs) which comprises anomalous development of all the organs developing from the paramesonephric (Müllerian) ducts, i.e., UTs, uterus and upper portion of the vagina. Interestingly, most of the classification systems of MDAs discuss solely the uterine and vaginal anomalies, while the UTs are often utterly ignored. This probably originates from the fact that UTs are no longer interesting for many clinicians as they think of UTs as superfluous organs whose function can be easily replaced in the in vitro fertilization (IVF) laboratory. Indeed, the modern reproductive medicine has been helping enormously with the conception of infertile couples. In many instances, the UTs are in fact successfully bypassed and a “test-tube” baby is born. Nevertheless, the UTs are still absolutely unique in providing suitable environment for fertilization and early embryo development - processes that has not been still completely understood. This fact could partially explain why the success rate of IVF is “only” around 30-50 % depending on age. Therefore, the research of the UTAVsCAs is still clinically relevant in the context of reproductive medicine and should not be omitted from research endeavors

In search of the Rheic suture: detrital zircon geochronology of Neoproterozoic to Lower Paleozoic metasedimentary units in the Balkan fold-and-thrust belt in Bulgaria

The Rheic Ocean opened between Avalonia and Gondwana in the late Cambrian to early Ordovician, triggering break-up of other terranes from the former Avalonian–Cadomian belt. In turn, the Gondwana-derived terranes recorded contrasting drift histories and were variably reworked within the younger orogens, tracing the Rheic suture thus remains challenging. In this paper, we attempt to locate the enigmatic easterly trace of the suture along the boundary of the Avalonian-type Moesia microplate attached to the southeastern margin of Baltica and the Balkan fold-and-thrust belt in Bulgaria, which contains Neoproterozoic to Early Paleozoic basement slivers of unknown provenance. We present new U–Pb detrital zircon ages from several pre-Darriwillian low-grade units (Lakavitsa, Berkovitsa, Bilo, Diabase–Phyllitoid Complex) but also from the overlying Darriwillian Grohoten and Famennian–Frasnian Katina formations. The age spectra and the maximum depositional ages of the pre-Darriwillian units suggest deposition in an accretionary wedge/forearc basin setting, or in an incipient rift superposed on the Cadomian forearc/arc region, from the latest Ediacaran to late Cambrian. The basins were sourced from a magmatic arc with a limited input of cratonic detritus, presumably adjacent to the Trans-Saharan belt or Saharan metacraton. In contrast, samples from the overlying formations indicate a sustained delivery of the cratonic detritus, perhaps first into passive-margin basins of the ‘Gondwana super-fan’ system and then into a Variscan foreland basin. Our statistical analysis shows that the sampled units exhibit age spectra compatible with the Cadomian terranes and that they differ significantly from those reported from Moesia. The detrital zircon ages thus possibly define the Rheic suture and also suggest that the easterly Cadomian terranes may have remained attached to Gondwana during the Early Paleozoic. It cannot be excluded, however, that the Rheic suture even did not reach that far east and terminated at an intraoceanic transform plate boundary

Recently Discovered Interstitial Cell Population of Telocytes: Distinguishing Facts from Fiction Regarding Their Role in the Pathogenesis of Diverse Diseases Called “Telocytopathies”

In recent years, the interstitial cells telocytes, formerly known as interstitial Cajal-like cells, have been described in almost all organs of the human body. Although telocytes were previously thought to be localized predominantly in the organs of the digestive system, as of 2018 they have also been described in the lymphoid tissue, skin, respiratory system, urinary system, meninges and the organs of the male and female genital tracts. Since the time of eminent German pathologist Rudolf Virchow, we have known that many pathological processes originate directly from cellular changes. Even though telocytes are not widely accepted by all scientists as an individual and morphologically and functionally distinct cell population, several articles regarding telocytes have already been published in such prestigious journals as Nature and Annals of the New York Academy of Sciences. The telocyte diversity extends beyond their morphology and functions, as they have a potential role in the etiopathogenesis of different diseases. The most commonly described telocyte-associated diseases (which may be best termed “telocytopathies„ in the future) are summarized in this critical review. It is difficult to imagine that a single cell population could be involved in the pathogenesis of such a wide spectrum of pathological conditions as extragastrointestinal stromal tumors (“telocytomas„), liver fibrosis, preeclampsia during pregnancy, tubal infertility, heart failure and psoriasis. In any case, future functional studies of telocytes in vivo will help to understand the mechanism by which telocytes contribute to tissue homeostasis in health and disease

Synthesis of centrifugally spun polyacrylonitrile-carbon fibers

This work demonstrates the carbonization of centrifugally spun polyacrylonitrile (PAN) fibers. Initially, the optimal centrifugal spinning conditions for producing homogeneous PAN fibers were identified. Second, the process continued by stabilization and carbonization of PAN to ensure a pure carbonaceous fiber material by eliminating all non-carbonaceous matter. The spun PAN fibers were stabilized at 240 °C in air at a heating rate of 1 °C/min, then carbonized between 600 and 1200 °C in argon at 5 °C/min. After carbonization, the fibers were characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and Raman spectroscopy (RS). The SEM results showed that by increasing the carbonization temperature, the prolonged elimination of other functional groups resulted in the formation of thinner carbon fibers. FTIR spectra of PAN fibers revealed that the peaks associated with C≡N bonds were substantially reduced and C–H bonds were eliminated in the fibers during the stabilization. These reductions are attributed to the cyclization of nitrile groups and the stabilizing process, and increasing carbonization temperatures resulted in flatter FTIR curves, supporting the findings. According to XRD, the structure of PAN was disturbed, as desired, and carbonization led to the formation of broad bumps resulting from amorphous carbon. Raman investigations found that increasing the carbonization temperature from 600 to 1200 °C resulted in no significant R values, suggesting that all fibers had no structural ordering. The study results could be used in many other areas, such as the fabrication of electrodes, supporting catalytic reactions, filter media, and energy