Technologie hmot a dílců AdMaS


Recent Submissions

Now showing 1 - 5 of 13
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    Design of tailored biodegradable implants: The effect of voltageon electrodeposited calcium phosphate Coatings on puremagnesium
    (The American Ceramic Society, 2019-01-01) Horynová, Miroslava; Remešová, Michaela; Klakurková, Lenka; Dvořák, Karel; Ročňáková, Ivana; Yan, Shaokun; Čelko, Ladislav; Song, Guang-Ling
    Magnesium, as a biodegradable metal, offers great potential for use as a tempo-rary implant material, which dissolves in the course of bone tissue healing. It cansufficiently support the bone and promote the bone healing process. However, thecorrosion resistance of magnesium implants must be enhanced before its applica-tion in clinical practice. A promising approach of enhancing the corrosion resis-tance is deposition of bioactive coating, which can reduce the corrosion rate ofthe implants and promote bone healing. Therefore, a welldesigned substratecoat-ing system allowing a good control of the degradation behavior is highly desir -able for tailored implants for specific groups of patients with particular needs. Inthis con tribution, the influence of coating formation conditions on the charact eris-tics of potentiostatically elect rodeposited CaP coatings on magnesium substratewas evaluated. Results showed that potential variation led to formation of coat-ings with the same chemical composition, but very different morphologies.Parameters that mostly influence the coating performance, such as the thickness,uniformity, deposits size, and orientation, varied from produced coating to coat-ing. These characteristics of CaP coatings on magnesium were controlled by coat-ing formation potential, and it was demonstrated that the electrodeposition couldbe a promising coating technique for production of tailored magnesium CaPimplants.
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    Synthetic preparation of thaumasite – several possible routes for thaumasite formation
    (Elsevier, 2016-08-04) Rybová, Alexandra; Fridrichová, Marcela; Dvořák, Karel
    Presented work is a part of an experiment where limestone is partially replaced by fluidized fly ash during cement manufacturing. Hydration of this type of cement is connected to formation of AFt phases – thaumasite and ettringite that cause serious damage to cement stone. Thaumasite (CaSiO3·CaCO3·CaSO4·15H2O) is less known and less common. It forms especially at lower temperatures. During its growth C-S-H phases are built into thaumasite unite cell, therefore, cement stone decomposes. To preclude thaumasite formation, further research of this mineral is necessary; therefore, its synthetic preparation in sufficient quality is important. The aim of this work was to verify several routes for thaumasite synthetic preparation. In the beginning, burning of mixtures prepared on stoichiometric proportions of compounds in thaumasite was done then two methods used in literature were tried and in the end a new method based on main calcium silicate phases was realized.
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    Study of Possibilities of Using Special Types of Building and Demolition Waste in Civil Engineering
    (Budapest University of Technology and Economics, 2020-01-15) Drochytka, Rostislav; Dufek, Zdeněk; Michalčíková, Magdaléna; Hodul, Jakub
    Construction and demolition waste makes up a substantial part of all waste produced in Europe. Its impact on the environment may be relatively small, but it exists in large amounts and holds many options of re-use. This is why it remains a frequently discussed topic of European policy. As part of circular economy, the European Commission has already proposed new goals and strategies for existing types of waste. However, they are not entirely clear on the usage of new kinds of building and demolition waste, as they are yet to be specified by existing legislation. This paper discusses new kinds of building and demolition waste and the basic principles (new technology) of their use. The possibilities of utilizing new kinds of waste are based on a multicriteria optimization calculation, specifying each material and proposing ways of its further use. Recent findings can expand the choice of new uses of construction and demolition waste and reduce their impact on the environment (less waste, better properties and more effective processing, reducing transportation needs, maximizing re-use and recycling).
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    Heat treatment induced phase transformations in zirconia and yttriastabilized zirconia monolithic aerogels
    (Elsevier, 2019-07-01) Torres Rodríguez, Jorge Alberto; Kalmár, József; Menelaou, Melita; Čelko, Ladislav; Dvořák, Karel; Cihlář, Jaroslav; Cihlář, Jaroslav; Kaiser, Jozef; Győri, Enikő; Veres, Péter; Fábián, István; Lázár, István
    Monolithic, structurally stable zirconia (ZrO2) aerogels can be used in high temperature applications and as medical implants. The macroscopic properties of these solids can be fine-tuned by the appropriate thermal treatment of the amorphous aerogels. Herein, we investigate the thermally induced phase transitions of ZrO2 and yttria-stabilized zirconia (YSZ) monolithic aerogels. All aerogels were produced by an acid-catalyzed sol-gel technique and subsequent supercritical drying (SCD). A complete reaction mechanism is proposed for the formation of the wet gel network. Also, the phase transformations taking place during calcination were followed as function of temperature by in-situ X-ray diffraction measurements. Composition and size of the forming crystallites were calculated from the XRD data. Phase transition is controlled by the temperature-dependent growth of crystallite size during calcination up to 1200 °C. Both tetragonal and monoclinic zirconia form in pure ZrO2 aerogels, and a single tetragonal phase forms in YSZ aerogels.
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    The role of different high energy ball milling conditions of molybdenum powder on the resulting particles size and morphology
    (Tanger Ltd., 2019-05-24) Dyčková, Lucie; Casas Luna, Mariano; Torres Rodríguez, Jorge Alberto; Dyčka, Martin; Jech, David; Dvořák, Karel; Deák, Andréa; Čelko, Ladislav
    High energy ball milling is a powder processing method in which the powder particle size can be decreased to micrometer size in a relatively short period of time. This method is based on the friction and the high energy kinetic collisions between the balls and the trapped powder particles. The milling process is influenced by many process variables such as mainly the rotational speed, ball to powder weight ratio and processing time. In the present study, high energy ball milling process was performed for molybdenum powder using a high energy ball mill under different milling conditions varying the: (i) rotational speed from 600 to 800 rpm, (ii) ball to powder weight ratio of 100:3 and 100:6, (iii) milling time in the range of 10 to 60 minutes, (iv) process control agent using polyethylene glycol, and (v) milling atmosphere under air or nitrogen. The used initial molybdenum powder was of globular morphology and 100 µm in particle size. The powders after milling were characterized by a scanning electron microscope (SEM) and a laser diffraction size analysis. The particle size of milled powders was decreased down to 1.1 µm. As the most effective ball to powder weight ratio was found 100:6 with the milling speed of 800 rpm. The milling time played a crucial role for the refinement of particles up to 45 min, where the further milling had negligible effect on the overall trend of particle size evolution.