Some experiments were conducted in connection with gold nanoparticle production in an effort to produce a more accurate model for determining gold nanoparticle synthesis with a modified Ultrasonic Spray Pyrolysis (USP). As previous experiments with gold nanoparticles have yielded nanoparticles of various shapes (spherical, triangular, cylindrical…), a focus on synthesizing only spherical nanoparticles is underway, as a mixture of different shapes is difficult to characterize and utilize. One of the factors for particle formation is droplet evaporation. In an attempt to produce optimal conditions for droplet evaporation with solvent diffusion and precipitation, a separate furnace and separate reaction gas inlets were used. This modification separates the evaporation stage from the reaction stage, compared to a standard USP setup. A longer evaporation time gives better conditions for diffusion of solvent into the center of the droplet and a higher probability of formation of a spherical particle.
COBISS.SI-ID: 18972438
Hydroxyapatite (HA) coatings were deposited on high purity titanium substrate by atmospheric plasma spraying (APS) with high electric energy input. Previously, the surface of the titanium was prepared by alkali etching with NaOH and subsequent diverse thermal treatments. The phase composition, structure and morphology of the nano-structured HA coatings were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Auger electron spectroscopy (AES). The XRD pattern showed that the coatings deposited by APS consisted mainly of HA with crystallite sizes between 15.5 and 31 nm and small quantities of the amorphous HA phase. The SEM observation showed that the as-deposited coatings had very different morphology with typical features of micro-structural patterns, which are desirable for improving the biological performances of HA coatings. AES analysis of various spots of the titanium substrate-coating interface showed the presence of an oxide layer with implanted Ca ions owing to the high kinetic energy of the plasma jet. This layer caused a significant increase in the measured adhesive strength, showing values in the range of 51.8-62.5 MPa. The sintering mechanism was studied using several approaches that show that the dominant sintering mechanism was volume diffusion.
COBISS.SI-ID: 18312214
In this work, an Al–Mn–Be–Cu alloy was studied containing a primary and eutectic icosahedral quasicrystalline phase in the as-cast microstructure. Special attention was given to a transmission electron microscopy investigation of precipitates formed within the aluminium solid solution (Alss) at different temperatures. At 200 °C, only binary Al–Cu precipitates (θ′) were formed. At 300 °C, icosahedral quasicrystalline (IQC) precipitates prevailed with a crystallographic orientation relationship with the Alss. The rods of the T-phase (Al20Mn3Cu2) which were precipitated above 400 °C, also had a specific orientation relationship with the Alss. The primary and eutectic IQC microstructural constituent started to transform rapidly to the T-phase and Be4Al(Mn,Cu) at 500 °C.
COBISS.SI-ID: 18717462
The manuscript focuses on manufacturing of new in situ foam-filled tubes (in situ FFTs) of Al-alloys including the foaming stage and studying their mechanical behaviour under quasi-static and dynamic bending loadings. The composite structures were manufactured by the powder compact foaming technique. These structures are fabricated by heating foamable precursor material pieces above their solid temperature inside thin-walled tubes. Different manufacturing parameters were appropriately adjusted based on preliminary experiments. The mechanical crushing behaviour and failure mechanisms were assessed by three-point bending experiments supported by infrared thermography. The bending performance of in situ FFTs and ex situ foam-filled heat treated tubes (ex situ FFTTs) were compared with that of empty tubes subjected to heat treatment. The observed results have been explained in terms of the structural changes in the thermally treated tubes, the surface roughness derived from oxidation, and the dimensions of the interface gap between the two components in the composite structures. The in situ FFTs composite structures confirmed stable and controllable deformation and a promising energy absorption capability.
COBISS.SI-ID: 18290198
The observations of microstructure before and after explosive compaction revealed that explosive loading resulted in intensive fragmentation of grains that are enriched with sub-grain layered structure. The analysis of the results has shown that grain size refinement made the main contribution to the strengthening of explosive treated copper.
COBISS.SI-ID: 18561558