Anna Pyda

Implantation of natural hydroxyapatite from porcine bone into soft tissues in mice.

The natural origin of hydroxyapatite (HA) derived from pig bones (Polish patent No.P-359 960 pending from 5th May 2003) was histologically examined for its biocompatibility following implantation into mouse muscles. The implanted ceramic was encapsulated by well vascularized connective tissue and very slowly resorbed by multinucleated cells. This material did not elicit an immune reaction and adjacent bones were unaffected. This ceramic could be safely used as a filling material alone, or as a composite graft.

Preceramic polysiloxane networks obtained by hydrosilylation of 1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane.

Precreamic polysiloxane networks were prepared by hydrosilylation of 1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane (D(4)(Vi)) with a series of linear hydrogensiloxanes as well as with a cyclic hydrogensiloxane, namely 2,4,6,8-tetramethylcyclotetrasiloxane (D(4)(H)) at various hydrogensiloxane/D(4)(Vi) molar ratios in the starting reaction mixture. FTIR spectroscopic measurements conducted during the processes as well as for the reaction products allowed to reveal that the rate of D(4)(Vi) hydrosilylation as well as its efficiency are influenced by the type of hydrogensiloxane used and by the reactants molar ratio. Ceramic yields determined at 1000°C by thermogravimetric analyses were higher for D(4)(Vi)-D(4)(H) than for D(4)(Vi) - linear hydrogensiloxane networks (86-89% vs 65-76%, respectively). Preceramic polysiloxanes prepared as well as the products of their pyrolysis obtained after thermal investigations were monolithic, pore-less materials.

TiO2-Doped Ca-TZP/WC Particulate Composites

A method of physical mixing was used to prepare composite mixtures, which contained 10 vol% WC micropowder and 90 vol% zirconia stabilised with 7 mol% CaO nanopowder. The latter, prepared by co-precipitation and subsequent hydrothermal treatment, was doped with up to 1.5 mol% TiO2. The homogeneous mixtures were hot-pressed for 1 hr at the temperatures ranging from 1200 to 1350 o C under 25 MPa, in argon. Density, phase composition, Vickers hardness, fracture toughness, bending strength and wear resistance of the composites were studied in function of TiO2 content and sintering temperature. It has been found that the applied TiO2 additives enable manufacturing composites with improved properties. For illustration, bending strength of a 7Ca-TZP/WC particulate composite doped with 0.5 mol% TiO2 was as high as 1.3±0.1 GPa. Introduction Zirconia matrix composites reinforced with SiC whiskers [1] or platelets [2], Al2O3 platelets [3], TiC [4,5] or WC [6] particulates are generally made from zirconia powders stabilised with yttrium or cerium oxide. A TZP matrix stabilised with calcium oxide has never been used so far. However, in a recent study on hot-pressing of CaO-ZrO2 nanopowders doped with TiO2, it has been shown that Ca-TZP materials with a nearly theoretical density, bending strength of 1.0 GPa and fracture toughness of 13.0 MPa·m 0.5 can be successfully produced [7]. This enables manufacturing of CaTZP matrix composites. The aim of the present work was to produce Ca-TZP/WC particulate composites using CaO-ZrO2 nanopowders doped with TiO2 and to characterise their properties. Experimental The zirconia nanopowders with a constant CaO:ZrO2 molar ratio of 7:93 and a TiO2 content of 0, 0.5, 1.0 or 1.5 mol% were prepared by co-precipitation and subsequent hydrothermal crystallisation. Aqueous solutions of appropriate chlorides and NaOH were used to co-precipitate zirconia hydrogels at a pH value of 9.8. The hydrogels were hydrothermally treated for 4 hrs at 240±5°C under the pressure of saturated water vapour in the mother liquor. The crystalline powders were washed with water, dried and attrition milled for 1 hr in isopropyl alcohol. The powders were composed of nanometric crystallites, 8.0±0.2 nm in size. The values of specific surface area and monoclinic phase content ranged from 126.0 to 128.8 m 2 /g and from 0 to 3 vol%, respectively. The predominant phase was tetragonal. Commercial WC powder was milled in a rotary-vibratory mill with zirconia grinding media for 40 hrs in distilled water before being used in the experiments. A median particle size of 0.52 μm was measured by the sedimentation method. Physical powder mixtures, which contained 90 vol% calciazirconia powder and 10 vol% WC, were prepared by means of attrition milling with zirconia grinding media for 1 hr in isopropyl alcohol. The homogeneous mixtures were hot pressed for 1 hr at 1200-1350°C under 25 MPa, in argon. Heating rate was 15°C/min. Key Engineering Materials Online: 2004-05-15 ISSN: 1662-9795, Vols. 264-268, pp 833-836 doi:10.4028/www.scientific.net/KEM.264-268.833

Transformation of Bone Origin Hydroxyapatite at Elevated Temperatures and in Selected Atmospheres

In the present work the behaviour of HAp extracted from pig bones at elevated temperatures up to 1000oC in O2 and CO2 atmospheres has been studied. It has been found that CO2 atmosphere arrests HAp decomposition. Chemical analysis and infrared spectroscopy reveal that no free CaO appears and no decrease of CO3 -2 concentration groups occurs in the material calcined in CO2 atmosphere. In the O2 atmosphere at elevated temperatures CaO and CO2 are emitted from the samples, although the remaining material retains the HAp structure as indicated by the X-ray diffraction.