Alicja Rapacz-Kmita

Hot pressed hydroxyapatite–carbon fibre composites

Abstract Composite samples were obtained from hydroxyapatite powder and carbon fibres by hot pressing at 1100°C and 25 MPa for 15 min in argon atmosphere. Two types of cut carbon fibres produced in a carbonisation process of polyacrylonitrile (PAN) precursor were used both in non-coated or coated form. The coatings of calcium phosphate were applied by sol–gel technique. The highly sintered composite with the best strength properties was obtained from coated carbon fibres with basic character of the surface. The existence of hydroxyl groups on fibre surface makes possible formation of bonds with the calcium phosphate layer formed as a result of polycondensation following the sol–gel procedure.

Instrumental characterization of the smectite clay–gentamicin hybrids

This paper focusses on the intercalation of clay mineral with gentamicin (an aminoglycoside antibiotic). The smectite clay–gentamicin hybrids were prepared by a solution intercalation at 60∘C and the process was carried out on unmodified smectite clay and on smectite after Na+ ionic activation. The resulting structural/microstructural properties and the potential for introducing gentamicin between smectite clay layers were investigated by means of X-ray diffraction, Fourier transform infrared spectroscopic techniques and transmission electron microscopy and scanning electron microscopy with energy-dispersive spectroscopy X-ray analysis. The results confirm the successful intercalation of gentamicin into the interlayer space of smectite clay, demonstrating that the material thus obtained could potentially be used as a drug carrier.

CaZrO3-based powders suitable for manufacturing electrochemical oxygen probes

AbstractCalcium zirconate powders doped with a small amount of CaO were synthesised using the Pechini method. X-ray analysis revealed that solid solution was formed in the concentration up to 51.5% mol CaO. For synthesis of stoichiometric CaZrO3, the highest temperature was required (1150°C), but introduction of excess CaO from 50.5 to 51.5% mol enabled us to lower the synthesis temperature to 800°C. The sintering behaviour of such samples under non-isothermal conditions was studied by dilatometric methods. Deviations were found in stoichiometry; by increasing the CaO concentration in CaZrO3 sinterability improved in comparison to CaZrO3 with stoichiometric composition. The presence of CaO as second phase caused deterioration of the sinterability of the CaZrO3-based samples. Pellets sintered at 1500°C for 2 h reached 96–98% of theoretical density. SEM and TEM observations were used to characterise the microstructure of the prepared samples. The electrical properties of CaZrO3-based samples were investigated by the AC-impedance spectroscopy method. It was found that introduction of excess CaO into the CaZrO3 structure caused an increase in ionic conductivity up to the solubility limit. The possibility of using CaZrO3-based samples for constructing prototype electrochemical oxygen probes to determine activity of oxygen dissolved in molten copper is also demonstrated.

Some observations on the synthesis and electrolytic properties of (Ba1-xCax) (M0.9Y0.1)O3, M = Ce, Zr-based samples modified with calcium

Abstract In this paper, the impact of partial substitution of calcium for barium in (Ba1-xCax) (M0.9Y0.1) O3, M = Ce, Zr on physicochemical properties of the powders and sintered samples was investigated. The powders, with various contents of calcium (x = 0, 0.02, 0.05, 0.1), were prepared by means of thermal decomposition of organometallic precursors containing EDTA. All of the BaCeO3-based powders synthesised at 1100 °C were monophasic with a rhombohedral structure, however, completely cubic BaZrO3-based solid solutions were obtained at 1200 °C. A study of the sinterability of BaZr0.9Y0.1O3 and BaCe0.9Y0.1O3-based pellets was performed under non-isothermal conditions within a temperature range of 25 to 1200 °C. The partial substitution of barium for calcium in the (Ba1-xCax) (M0.9Y0.1) O3, M = Ce, Zr solid solution improved the sinterability of the samples in comparison to the initial BaCe0.9Y0.1O3 or BaZr0.9Y0.1O3. The relative density of calcium-modified BaCe0.9Y0.1O3-based samples reached approximately 95 to 97 % after sintering at 1500 °C for 2 h in air. The same level of relative density was achieved after sintering calcium-modified BaZr0.9Y0.1O3 at 1600 °C for 2 h. Analysis of the electrical conductivity from both series of investigated materials showed that the highest ionic conductivity, in air and wet 5 % H2 in Ar, was attained for the compositions of x = 0.02 to 0.05 (Ba1-xCax)(M0.9Y0.1)O3, M = Zr, Ce. The oxygen reduction reaction on the interface Pt│BaM0.9Y0.1O3, M = Ce, Zr was investigated using Pt microelectrodes. Selected samples of (Ba1-xCax) (M0.9Y0.1)O3, M = Zr, Ce were tested as ceramic electrolytes in hydrogen-oxygen solid oxide fuel cells operating at temperatures of 700 to 850 °C.

Potential of Superhydrophobic Layer on the Implant Surface

The aim of the work was the deposition of polymer fibres of submicrometric and nanometric diameter. A layer of the fibres was produced from biocompatible polymer, i.e. poli (ε) caprolactane (PCL). The polymer was dissolved in a mixture of DMF:DCM solvents. In order to enhance the hydrophobic effect, silica particles (5–10 nm) were introduced into the polymer solution. PCL fibres were produced using electric field of 25 kV. Wettability of the produced layer was determined using the method of sitting drop (DSA T500). Its microstructure was observed using scanning an electron microscope (Nova NanoSEM) and an atomic force microscope (MULTIMODE 8 AFM, Bruker). It was revealed that only coatings made of the pure polymer fibres showed superhydrophobicity (PCL fibres, wetting angle of 151o), while the nanocomposite fibres made of PCL and 3 wt.% SiO2 formed a layer with a wetting angle of 113o, which was more hydrophobic than a conventional polymer layer made by casting (wetting angle of PCL foil is 90o).

Mechanical properties and microstructure of fast – fired clinker tiles based on Wierzbka I raw material

Abstract The article presents results of research on microstructural and mechanical properties of floor tiles clinker manufactured on the basis of Wierzbka I raw material, which is part of the deposit Wierzbka, near Suchedniów. Wierzbka I clay was added in various volume fractions to the standard tile compositions used in industrial practice. The samples were pressed in a range of from 21 MPa to 42 MPa and fired in the laboratory furnace at 1130°C to 1190°C. Selected compositions were pressed at 28 MPa and fired in a standard industrial environment. The process of firing was conducted in an industrial kiln at temperature of 1160°C for 38 minutes, with holding for 4 minutes at maximum operating temperature. The samples, which were prepared in the laboratory and industrial conditions were evaluated for the effect of addition of the Wierzbka I clay on their microstructural and mechanical properties based on the measurement results of linear shrinkage, bulk density, open porosity, water absorption and flexural strength (Ϭ) of the tiles. Microstructural changes were observed with a scanning electron microscope (SEM). The results revealed that the tested tiles were characterized by a high degree of sintering, an apparent density of 2.5 g/cm3, an open porosity and water absorption below 0.5%. The measurement results of mechanical bending strength showed that the tested samples had a high strength of 50 MPa.