prof. RNDr. Karel Maca, Dr.

E-mail:   maca@fme.vutbr.cz  Dept.:   Institute of Materials Science and Engineering Position:   Institute Secretary for R&D Activities Room:   A2/205 Dept.:   Institute of Materials Science and Engineering Dept. of Ceramics and Polymers Position:   Head of Department Room:   A2/205 Dept.:   Institute of Materials Science and Engineering Dept. of Ceramics and Polymers Position:   Professor Room:   A2/205

Supervised courses:

• Chemical Thermodynamics and Kinetics (WCT)
• High temperature process in inorganics materials (DS214A)
• High temperature process in inorganics materials (DS214A)
• High temperature processes in inorganics materials (DS214)
• High temperature processes in inorganics materials (DS214)
• Nonmetallic Materials (WNE)
• Sintering of Ceramics Materials (9SKE)
• Topics in advaced ceramic materials (DS215)
• Topics in advaced ceramic materials (DS215)
• Topics in Advaced Ceramic Materials (DS215A)
• Topics in Advaced Ceramic Materials (DS215A)

Publications:

• DRDLÍKOVÁ, K.; KLEMENT, R.; DRDLÍK, D.; SPUSTA, T.; GALUSEK, D.; MACA, K.:
  Luminescent Er3+doped transparent alumina ceramics, Elsevier
  journal article in Web of Science
• SALAMON, D.; KALOUSEK, R.; ZLÁMAL, J.; MACA, K.:
  Role of conduction and convection heat transfer during rapid crack-free sintering of bulk ceramic with low thermal conductivity
  journal article in Web of Science
• POUCHLÝ, V.; MACA, K.:
  Sintering kinetic window for yttria-stabilized cubic zirconia
  journal article in Web of Science
• SPUSTA, T.; SVOBODA, J.; MACA, K.:
  Study of pore closure during pressure-less sintering of advanced oxide ceramics
  journal article in Web of Science
• SALAMON, D.; KALOUSEK, R.; MACA, K.; SHEN, Z.:
  Rapid Grain Growth in 3Y-TZP Nanoceramics by Pressure-Assisted and Pressure-Less SPS
  journal article in Web of Science
• MACA, K.; POUCHLÝ, V.; BODIŠOVÁ, K.; ŠVANCÁREK, P.; GALUSEK, D.:
  Densification of fine-grained alumina ceramics doped by magnesia, yttria and zirconia evaluated by two different sintering models
  journal article in Web of Science
• XIONG, Y.; FU, Z.; POUCHLÝ, V.; MACA, K.; SHEN, Z.:
  Preparation of Transparent 3Y-TZP Nanoceramics with No Low-Temperature Degradation
  journal article in Web of Science
• POUCHLÝ, V.; MACA, K.; SHEN, Z.:
  Two-stage master sintering curve applied to two-step sintering of oxide ceramics,
  Journal of the European Ceramic Society, Vol.33, (2013), No.12, pp.2275-2283, ISSN 0955-2219
  journal article - other

List of publications at Portal BUT

Abstracts of most important papers:

• POUCHLÝ, V.; MACA, K.; SHEN, Z.:
  Two-stage master sintering curve applied to two-step sintering of oxide ceramics,
  Journal of the European Ceramic Society, Vol.33, (2013), No.12, pp.2275-2283, ISSN 0955-2219
  journal article - other
  Tetragonal (3 mol% Y2O3) and two cubic zirconia (8 mol% Y2O3) as well as alumina green bodies were used for the construction of the Master Sintering Curve (MSC) created from sets of constant-rate-of-heating (CRH) sintering experiments. The activation energies calculated according to the MSC theory were 770 kJ/mol for Al2O3, 1270 kJ/mol for t-ZrO2, 620 kJ/mol and 750 kJ/mol for c-ZrO2. These values were verified by an alternative approach based on an analysis of the densification rate in the intermediate sintering stage. The MSCs established from the Two-Step Sintering (TSS) experiments showed at high densities a significant deflection from those constructed from the CRH experiments. This deflection was explained by lower sintering activation energy in the closed porosity stage. A new two-stage MSC model was developed to reflect the change in sintering activation energy and to describe TSS. The efficiency of TSS of four materials under investigation was correlated with their activation energies during the final sintering stage.
• KACHLÍK, M.; MACA, K.; GOIAN, V.; KAMBA, S.:
  Processing of phase pure and dense bulk EuTiO3 ceramics and their infrared reflectivity spectra, ELSEVIER
  journal article in Web of Science
  The aim of this work was to prepare phase pure and dense EuTiO3 ceramics and to establish their infrared reflectivities. Two kinds of stoichiometric powder mixture (Eu2O3+Ti2O3 and Eu2O3+TiO2) were used as precursors for shaping green bodies by cold isostatic pressing. Dense bulk samples were prepared by pressure-less sintering in reducing (Ar+7%H2, 100%H2) conditions in a temperature range of 1300–1650 C. The sample prepared from Eu2O3+TiO2 powder mixture sintered in pure hydrogen at a temperature of 1400 C for 2 hours exhibited a relative density higher than 95%TD and 100% phase purity, which resulted in its high infrared reflectivity affected by neither low density nor phase impurities
• MACA, K.; POUCHLÝ, V.; ŽALUD, P.:
  Two-Step Sintering of Oxide Ceramics with Various Crystal Structures, Elsevier
  journal article in Web of Science
  The influence of Two-Step Sintering (TSS) process on the final microstructure of oxide ceramic materials with three different crystal structures was studied. Two kinds of alumina (particle size 100nm resp. 240nm) as well as tetragonal zirconia (stabilized with 3mol%Y2O3, particle size 60nm) and cubic zirconia (8mol%Y2O3, 140nm) powders were cold isostatically pressed and pressureless sintered with different heating schedules. The microstructures achieved with TSS method were compared with microstructures achieved with conventional Single-Step Sintering schedule (SSS). The results showed that the efficiency of the TSS of these oxide ceramics was more dependent on their crystal structure than on their particle size and green body microstructure. The method of TSS brought only negligible improvement of the microstructure of tetragonal zirconia and hexagonal alumina ceramics. On the other hand, TSS was successful in the sintering of cubic zirconia ceramics; it led to a decrease in grain size by a factor of 2.
• MACA, K.; CIHLÁŘ, J.; ČÁSTKOVÁ, K.; ZMEŠKAL, O.; HADRABA, H.:
  Sintering of gadolinia-doped ceria prepared by mechanochemical synthesis, Elsevier Science
  journal article in Web of Science
  Gadolinia-doped ceria (GDC) ceramics were prepared by mechanochemical synthesis of ceria and gadolinia (10mol.%) powders with subsequent uniaxial pressing and pressureless sintering. The mechanochemical synthesis was conducted in an attritor with different dispersion media: neutral (distilled water), basic (aqueous solution of ammonia), acidic (aqueous solution of propionic acid), and non-polar medium (xylene with stearic acid). The effect of suspension composition and attritor milling time on the sintering behaviour and ionic conductivity of GDC was studied. An attritor milling time of 3 to 6 hours was evaluated as the optimum milling time from the viewpoint of further sintering behaviour. Longer milling times resulted in nanometre-sized powders, whose sintering behaviour deteriorated due to powder agglomeration. The appearance of agglomerates in the non-polar medium was reduced. The ionic conductivity of the samples was evaluated by impedance spectroscopy and correlated with their microstructure.
• TRUNEC, M.; MACA, K.:
  Compaction and Pressureless Sintering of Zirconia Nanoparticles,
  Journal of the American Ceramic Society, Vol.90, (2007), No.9, pp.2735-2740, ISSN 0002-7820, Blackwell Publishing
  journal article - other
  Four nanometer-sized zirconia powders stabilized by 3 mol% Y2O3 were used for the preparation of dense bulk ceramics. Ceramic green bodies were prepared by cold isostatic pressing at pressures of 300-1000 MPa. The size of pores in ceramic green bodies and their evolution during sintering were correlated with the characteristics of individual nanopowders and with the sintering behavior of powder compacts. Only homogeneous green bodies with pores of less than 10 nm could be sintered into dense bodies (>99% t.d.) at sufficiently low temperature to keep the grain sizes in a range <100 nm. Powder with uniform particles of 10 nm in size yielded green bodies of required microstructure. These nanoparticle compacts were sintered without pressure to give bodies (diameter 20 mm, thickness 4 mm) with a relative density higher than 99% and a grain size of about 85 nm (as determined by linear intercept method).