Liana Ivanchenko

Preparation and Properties of Hydroxyapatite Strengthened with a Glass Phase

A method is described for preparing hydroxyapatite strengthened with a glass phase. The properties of the composites obtained containing both biological and synthetic hydroxyapatite are studied. Characteristics of the test materials such as pycnometric density, volumetric porosity, biological solubility, and mechanical strength are determined.

Microstructure and Properties of Biogenic Hydroxyapatite Doped with Magnetite

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.

Composite Coatings from Bioactive Calcium Phosphate Ceramics on Metal Substrates

Porous bioactive membrane-type calcium phosphate coatings on metal substrates are produced. Their microstructure and physicochemical properties are studied. Titanium (including porous) and medical stainless steel are used as metal substrates. The bioactive coatings are based on biogenic hydroxyapatite or synthetic calcium phosphates (calcium phosphate content was between 68 and 85 %) and sodium borosilicate glass. To add bacteriostatic properties to the coatings, some compositions were additionally doped with cerium dioxide (5 %). The surface microstructure, some mechanical properties, and in vitro behavior of the coatings in physiological solution are examined.

Sintering of different hydroxyapatite powders and low-melting sodium borosilicate glass

The paper analyzes the sintering of three types of calcium phosphate powders and S–B–Na glass powder under the same conditions. It is concluded that a liquid phase, represented by the glass melt, shows up when the glass is sintered with biogenic or synthetic hydroxyapatite or a mixture of synthetic phosphates. The substantial pore formation in the sintering process is mainly due to the removal of carbon oxides and water vapors resulting from glass charge decomposition and glass boiling. Parameters of grain and porous microstructures of the ceramics are shown before and after the primary and secondary sintering. The mechanical strength and biosolubility of the ceramic samples are reported as well.