Papers by Author: Magdalena Szutkowska

Abstract: The present study reports some preliminary results obtained by reinforcing Al2O3-10 wt% ZrO2 (partially stabilized with Y2O3 -Y5 and monoclinic phase m-ZrO2) composite with TiC phase in amount of 5 wt %. Ceramic composites were prepared on the basis submicro and nano scale trade powders. Apparent density, porosity, Vicker’s hardness, Young’s modulus and fracture toughness (KIC) were determined. Wear resistance (Vn) very important property for tool ceramics was specified by the speed of mass lost. Scanning electron microscopy (SEM) to observation of the fracture surface microstructure was used. The titanium carbide reinforced composite tool ceramics based on alumina exhibit high hardness, fracture toughness (critical stress intensity factor KIC increase up to 5,2 MPa m1/2), high elastic moduli and higher wear resistance in related to pure alumina. Cutting tests confirm the high performance of these ceramic composites.

Abstract: The relationship of KR versus crack length c (R curve) for Al2O3-30wt.% Ti(C,N).and for comparison alumina ceramics has been examined. The R-curve has been evaluated using pronounced long-crack formed during the three point bending (3PB) of the double edge notched beam. A combination of in situ microscopic crack growth observation and mechanical testing enabled measurement of crack growth resistance curves. The special device consisting of light microscope coupled with CCD camera, was fitted to Zwick 1446 testing machine. These observations reveal the existence of flat R-curve for Al2O3-30wt.% Ti(CN) and increasing R-curve for pure alumina. A study of slow-crack-growth (SCG) in tested materials was carried. The load-relaxation technique was used for observation at slow-crack-growth. The crack length was evaluated by linear-elastic analysis from the compliance of single-edge-notched specimen in three-point bending test. Parameters of stable crack growth n and logA, work-of fracture (WOF), stress intensity factor at the moment of crack initiation KI0 and maximum values of stress intensity factor KImax were determined. Mechanism of grain bridging responsible for occurrence of R-curve was observed by SEM and TEM.

Abstract: In this study the hydroxyapatite powder was sintered together with magnetite nanopowder, which due to its low reactivity is commonly used in medicine, eg. in magnetic resonance. Two types of sintered materials, containing equal content 6 mol% of biogenic hydroxyapatite (BGHAp), reinforced with 50 wt% of different glass phases, were tested. The same technological conditions comprising two-stage sintering with T1 (1100°C) and T2 (780°C) were used for both types of materials. For selected specimens 2 wt% of 9 nm powder of Fe3O4 was added. The microhardness of the specimens varies within quite wide range from 150 to 508 HV0.025. Compressive splitting strength of the specimens (measured along the sample diameter) is within a range of 3.61 – 4.99 MPa. Young’s modulus, modulus of rigidity and Poisson’s ratio are in the ranges of: 20.81 – 24.86 GPa, 7.89 – 9.71 GPa and 0.252 – 0.307, respectively. Indentation fracture toughness KIC is within a range of 0.6-1.0 MPa m1/2. The hysteresis loops were determined in order to asses the possibility of application of this material as affecting the drug delivery carriers. The specimens exhibit magnetization of the order of 1.5 emu/g.

Abstract: The R-curve (KR versus crack length c) behavior has been examined in alumina-10 wt% zirconia ceramics with 3 mol% yttria stabilized zirconia, alumina-10 wt% zirconia ceramics with 12 mol% nano ceria stabilized zirconia and Al2O3-30 wt% Ti(C,N) ceramics. An observation of in situ microscopic long-through thickness crack growth during three point bending (3PB) of a single edge notched beam (SENB) enabled measurement of the R-curve. It was found that both aluminazirconia ceramics with yttria or ceria stabilized zirconia exhibit a rising R-curve while for Al2O3-30 wt% Ti(C,N) ceramics such relationship was not observed. Moreover the slow crack growth parameters (n, logA) were determined by means of load-relaxation technique for tested alumina matrix ceramics.