Search

Still unsolved is the problem of monitoring the tissue regeneration with the use of implants (substrates) in in vivo conditions. The multitude of implant materials combined with their specific immanent often limit standard diagnostic methods, i.e. X-rey or computer tomography (CT). This is particularly difficult in therapies using polymeric high-resistance substrates for tissue engineering. The aim of this study was to fabricate a non-woven carbon fiber composed of carbon fibers (CF) which were then subjected to a surface modification by magnetron sputtering. A layer of iron (Fe) was applied under inert conditions (argon) for different time periods (2-10 min). It was shown that already after 2-4 minutes of iron sputtering, the voxel surface (CF_Fe2', CF_Fe4') was covered with a heterogeneous iron layer observed by scanning electron microscope (SEM) with energy dispersive X-ray analysis (EDS). The longer the modification time, the more uniform the layer on the fiber surface becomes. This can be seen by the change in the wettability of the nonwoven surface which decreases from 131° for CF_Fe2 to 120° for CF_Fe10. The fibers do not change their geometry or dimensions (~11.5 um). The determination of pore size distribution by adsorption and desorption techniques (BJH) and specific surface area by nitrogen adsorption method (BET) have shown that the high specific surface area for the CF_Fe2' fibers decreases by 10% with the increasing iron sputtering time. All the studied CF_Fe fibers show good biocompatibility with osteoblastlike cells MG-63 cells after both 3 and 7 days of culture. Osteoblasts adhere to the fiber surface and show correct morphology. [ABSTRACT FROM AUTHOR]

The main objective of the work was to create a layer of carbon nanofibre on the surface of the NiTi shape memory alloy. The coating process was carried out in three stages. First, polyacrylonitrile was deposited by electrospinning. Then it was stabilized at temperatures up to 250°C. The last stage was the carbonization performed below 1000°C. The microstructure of the obtained coatings was observed using a scanning electron microscope. The X-ray diffraction techniques were applied to analyze the coating structure. After the polyacrylonitrile deposition, the fibers had an average diameter of about 280 nm, and the final fibers were almost twice as tiny. The applied steps also changed the phase and crystalline state of the fibers, finally leading to the formation of amorphous-nanocrystalline graphite. [ABSTRACT FROM AUTHOR]

The spectroscopic measurements of Eu-doped Lu(sub 2)O(sub 3) nanocrystalline powders and the comparison of the results obtained for micronmeter-sized polycrystalline sintered specimens fabricated from nanoparticulate powder are presented. The excitation spectra reveals that the host material is able to transfer acquired energy to the Eu(sub 3+) ions and excite them, which indicates that the Lu(sub 2)O(sub 3)/Eu composition are noteworthy for high-energy ionizing radiation detection.

The paper reports on the course of decomposition of hydrated lutetium nitrate and lutetium chloride to Lu2O3 in the eutectic mixture of NaNO2 and KNO2. It was shown that a crystallographically pure phase of the cubic Lu2O3 is formed at temperature as low as 250 °C. IR spectra revealed that the recovered powder contains some OH-contamination, however. The powders are characterized by crystallites sizes in the range of 18–30 nm in average. Emission and excitation spectra of Eu-doped powders show characteristic features for Eu3+ ion in an oxide host, which indicates that the procedure is appropriate for making activated nanoparticulate oxide phosphors. Most profound emission appears around 611 nm and the luminescence from the powder made starting with Lu(NO3)3 was noticeably higher compared to the product obtained from LuCl3. The excitation spectrum of Eu3+ emission at 611 nm contains a band related to the fundamental absorption of the lutetia host lattice, which indicates an existence of the host-to-activator energy transfer. [Copyright &y& Elsevier]

Two series of Lu2O3:Eu nanocrystalline phosphors were prepared using either combustion procedure with urea fuel or the Pechini procedure. The dopant concentration varied in both series from 0.2 to 13% with respect to Lu. Despite full crystallization and very similar microstructure of materials of both series, we found profound variations in their spectroscopic properties. The combustion-made phosphors were much less efficient emitters and their emission was strongly concentration-quenched above 3% of the dopant content. For the Pechini-derived materials, the concentration quenching was not observed below 10% of the dopant content and even for the dopant concentrations equal to 10 and 13% the quenching was insignificant. In EPR spectra for Gd3+-doped materials, a significant broadening of lines was found for the combustion-made powders. All these observations imply a strong agglomeration of the dopant ions in the specimens made by applying urea fuel in the combustion process. A semi-two-phase composition was suggested in the combustion-prepared powders. In the Pechini-derived nanocrystalline powders, the dopant ions are uniformly, statistically distributed in the host lattice. [Copyright &y& Elsevier]

Efforts to obtain translucent pellets of BAM for Martian UV-dosimeter were undertaken. Sinterability of both commercial BAM powder and a Pechini-derived one was examined. The commercial phosphor sinters with difficulty only, while the one made with Pechini procedure sinters easily and translucent pellets could be obtained in such a way. Vacuum sintering at 1750 °C for 15 h was also enough to fully convert Eu3+ into Eu2+ in the sintered pellets without the necessity of using hydrogen-containing gas. The spectroscopy of the sintered BAM differs noticeably from its commercial powdered counterpart. The excitation is much more flat in the entire UV and especially strong enhancement of the excitation efficiency is observed in the near-Vis part of the UV region. Decay kinetics is exactly the same for commercial powder and sintered ceramic, which proves the lack of luminescence quenching in the latter. The sintered pellets of BAM made in our laboratory show mechanical and spectral characteristics, which make the material suitable for Martian UV-dosimeter. [Copyright &y& Elsevier]

The size effect of nanoparticles on optical properties of Lu2O3:Eu3+ was investigated. No pronounced effect was observed for structure of emission spectra. It was found that effect is mainly manifested in the decay profiles of Eu3+ emission. We have noticed that the decay times were almost the same for low concentrations of Eu3+ ions. It is concluded that the size effect is associated with agglomeration of Eu3+ in nanorange particles. [Copyright &y& Elsevier]

Nanoparticulate powders of Eu-doped Lu2O3 were prepared using combustion process and glycine as a fuel. Such powders could be relatively easily sintered to translucent bodies at 1700 °C. Excitation and emission spectra were recorded for both types of the materials. The excitation spectra revealed the existence of much more efficient energy transfer from the host to the dopant in the sintered ceramics. Strong variations in the relative intensities of the excitation transitions are seen when comparing the powder and its sintered analog. This was explained assuming preferential occupation of the C3i site in the glycine-derived powder in comparison with the pellets. Most profound emission under X-ray excitation was found for the sintered ceramic doped with 5% of Eu. [Copyright &y& Elsevier]

Using combustion synthesis and urea as a fuel, Lu2O3 powders were prepared and their morphology defined with HRTEM measurements. The powders were sintered at 1700 °C for 5 h and the microstructure of the obtained ceramics was characterized. It turned out that the as-made powders were strongly agglomerated compositions with a mean particle size of 15–25 nm. High-temperature sintering caused some increase in the size of the crystallites, diameter increased to an average of 25–35 nm. However, domains of about 200–300 nm diameter were formed. These were separated by relatively broad transient regions. The inter-domain regions of rather ample thickness are blamed for relatively high scattering of the sintered ceramic specimens. The formation of the domains is correlated to the existence of agglomerates in the urea-derived nanoparticulate powders. [Copyright &y& Elsevier]

Lu2O3 doped with Eu of varying concentrations was prepared using a convenient combustion technique. Emissions from two different crystallographic sites, C2 and S6, were found and analyzed. Using various spectroscopic techniques, luminescence of Eu3+ exclusively from site C2 or site S6 could be detected. Kinetics of both emissions was characterized and time constants of 1.5 and 4.3 ms were found, respectively. Energy transfer from Eu3+ in site S6 to Eu3+ in site C2 was proved to take place when the dopant content reaches about 1% or higher. For rising activator concentration the transfer becomes more efficient and for heavily doped samples the emission from S6 site lasts in a vestige form only. The only emission transitions detected from Eu in centrosymmetric site S6 were the 5D0–7F1 three-line band. [Copyright &y& Elsevier]