In this article new rapid biomimetic method for the deposition of octacalcium phosphate coatings on zirconia ceramics (Y-TZP) is described. Such coatings are bioactive and enable the growth of bone tissue on the sruface of bone implants. The method described is fast, simple and very reproducible. After the thermal treatment the coatings exhibit good mechanical properties and excellen adhesion to the substrate.
COBISS.SI-ID: 25607207
The evolution of aluminum hydroxides in diluted aqueous aluminum nitride (AlN) powder suspensions in the temperature range 22–90 °C was studied in order to set up a general mechanistic model over a broad temperature range, uniting previously observed hydrolysis reactions at room temperature and at elevated temperatures into a single scheme. It is shown that dispersing the AlN powder in the water results in the temperature-dependent formation of various aluminum hydroxides in the following sequence: amorphous aluminum hydroxide gel, aluminum monohydroxide (boehmite), and aluminum trihydroxides (bayerite, nordstrandite, and gibbsite). The unique interdependency between the temperature and the pH of the hydrolyzing AlN powder suspension, governed by the ammonia’s solubility and the exothermic hydrolysis reactions producing Al(OH)4– species, is the driving force for several evolution paths of these aluminum hydroxides exhibiting numerous morphologies.
COBISS.SI-ID: 25586727
The mechanical properties of partially wick-debinded, Al2O3-based ceramic parts, prepared by low-pressure injection molding have been investigated. These properties depend on the residual paraffin wax binder content and on the chemical nature of the binder, which changes drastically if the wick-debinding takes place in air at a temperature above 190°C. Under these conditions, the paraffin binder undergoes a transformation, as a result of complex exothermic chemical reactions with oxygen. Part of it forms volatile products, while the remaining part cures into a nonvolatile, brown-colored, solid substance, which resides in the wick-debinded part and bonds the powder particles firmly together. The curing can be beneficial, as strong wick-debinded parts with bending strengths up to 14 MPa, containing less than 2% of the residual binder, can be obtained without flaws. The strength of the partially debinded parts increases with the dwelling time at 200°C, whereas the binder content reaches a minimum value of about 1.6% and then remains constant with the dwell time. Strong debinded parts can be easily manipulated and can be rapidly sintered due to the low amount of the residual organic phase.
COBISS.SI-ID: 25320487
The research presented in this paper is focused on formation, structure and chemical composition of friction layer on sintered metal–matrix brake linings sliding surface at early stage of braking against SiC ceramic. The character of the friction layer formed at sliding temperatures 200, 300 and 400 °C was investigated using scanning electron spectroscopy (SEM), Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS). In this starting stage of braking we confirmed the two-layer oxide structure of the friction layer composed from CuO on the top and Fe2O3 below. There is practically no change between structure, thickness and composition of the friction layer formed on sliding surface of the sample with only metallic matrix and the sample with the addition of graphite.
COBISS.SI-ID: 26178087
Nanostructured, γ-Al2O3/TiO2 composite powder was fabricated via an in situ, sol–gel reaction of titanium iso-propoxide in a self-assembled, polyelectrolyte multilayer (PEM) formed on the surface of high-specific-area, polycrystalline, γ-Al2O3 lamellas. The infiltration of the titanium precursor into the PEM, followed by the hydrolysis and condensation reactions with the water absorbed in the PEM after annealing, resulted in the formation of a nanostructured TiO2 layer on the surface of the γ-Al2O3 lamellas. The as-formed, nanostructured, γ-Al2O3/TiO2 composite powder exhibited a 2.7-times-higher photo-activity in the near-UV region compared to commercially available TiO2 (Degusa P25), as monitored by the photo-decomposition of a methylene blue (MB) dye.
COBISS.SI-ID: 25268519