National Institute Of Materials Physics - Romania

An alternative and simple coprecipitation method was developed to obtain carbon nanotube-hydroxyapatite (CNTs:HAp) based nanocomposites. The incorporation of CNTs (in a concentration of 5% and 10% of total weight of the nanocomposite) and their impact on both structural and biological properties were studied by using a set of standard complementary biological, microscopic, and spectroscopic techniques. The characteristic peaks of carbon structure in CNTs were not observed in the CNTs-HAp composites by X-ray diffraction analysis. Moreover, FTIR and Raman spectroscopies confirmed the presence of HAp as the main phase of the synthesized CNTs: HAp nanocomposites. The addition of CNTs considerably affected the nanocomposite morphology by increasing the average crystallite size from 18.7 nm (for raw HAp) to 28.6 nm (for CNTs:HAp-10), confirming their proper incorporation. The biocompatibility evaluation of CNTs:HAp-5 and CNTs:HAp-10 nanocomposites included the assessment of several parameters, such as cell viability, antioxidant response, and lipid peroxidation, on human G-292 osteoblast cell line. Our findings revealed good biocompatibility properties for CNTs: HAp nanocomposites prepared by the coprecipitation method supporting their potential uses in orthopedics and prosthetics.

The present work reports a simple adapted co-precipitation method for the synthesis of stable Ce-substituted Ca hydroxyapatite (HAp) nanoparticles. The structural and morphological properties of the Ce-doped hydroxyapatite (Ce:HAp) were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX). The optical properties of the Ce-doped hydroxyapatite were also investigated using Fourier transform infrared (FTIR) spectroscopy, Fourier transform Raman spectroscopy and photoluminescence analysis. The results of the XRD studies revealed the progressive increase in the a-and c-axes with increasing Ce concentration. In the FTIR studies of Ce: HAp powders, a structure similar to that of hydroxyapatite was observed. The IR and Raman wavenumbers and the peak strengths of the bands associated with the P-O and O-H bonds decreased progressively with increasing Ce concentration. All the emission maxima could be attributed to 5d-4f transitions of the Ce ions. The displacements of the maximum emission bands with increasing Cerium in the samples were in agreement with the results obtained by XRD studies. The Ce: HAp samples with x(Ce) = 0.03 and 0.05 exhibited significant antibacterial activity against Staphylococcus aureus and Escherichia coli bacterial strains compared to Ce: HAp samples with xCe = 0 (pure HAp) and 0.01.

The study of various types of nanoparticles with different biomedical applications is of high interest in the last decades. For this purpose, among other techniques, ultrasounds have been used to characterize the aqueous solutions. A non-invasive method is preferable for the characterization of these materials, due to the fact that they are designed to be used for targeted delivery of a chemotherapeutic solution to the tumor site. The present research is focused on ultrasound characterization of solutions based on maghemite and 5-fluorouracil.

Aluminum Nitride (AlN) films were deposited at 450 degrees C in nitrogen ambient at a pressure of 0.1 Pa and at a laser incident fluence of similar to 3 J/cm(2) and pulse repetition rate of 40 Hz. Grazing Incidence X-ray Diffraction patterns evidenced the presence of nanocrystallites in the amorphous AlN matrix. In the FTIR spectra the characteristic Reststrahlen band of AlN crystal with a hexagonal lattice is observed but it is quite broadened (950-550 cm(-1)). The angular dependence of the reflectance spectra in p-polarised incidence radiation demonstrates the sensitivity of the A(1)LO phonon mode of the AlN nanocrystallites to their orientation toward the normal to the substrate surface. With decrease of the incidence beam angle the intensity of the A(1)LO phonon mode diminishes and softening of the resonance frequency occurs.

The aim of this study was to evaluate the adhesion of different bioceramic coatings deposited by radio frequency magnetron sputtering on the biodegradable implant-type magnesium-calcium (MgCa) alloys. Hydroxyapatite (HA) and bioactive glass (BG) were chosen as coating materials, due to their remarkable biological potential. The morphology, composition, structure and adhesion of the deposited thin coatings was characterized by scanning electron microscopy, atomic force microscopy, energy dispersive X-ray spectroscopy, grazing incidence X-ray diffraction, Fourier transform infrared spectroscopy and pull-out adherence measurements. A variation of the coating-to-substrate adhesion has been recorded and correlated with the physico-chemical results. The bonding strength values of the coatings were promising (being superior to the ISO13779-2:2008 fabrication standard for load-bearing biomedical coatings), and thus, encourage us to further proceed with the biological evaluation of the HA or BG coatings-MgCa substrate couples.

The influence of the heat treatments on the martensitic transformation, magnetic properties and thermo- and magnetic induced strain on Ni50Fe20Ga27Cu3 ferromagnetic shape memory alloy prepared as ribbons by melt spinning technique are investigated. The degree of atomic order as effect of different thermal treatments produces important changes in the magneto-crystalline anisotropy of the martensite phase. The anomalies evidenced in the thermo-and magnetic-strain curves are discussed and correlated with the thermo-magnetic data. The transformation-induced strains with and without magnetic field have been measured, the results setting out the influence of the pre-martensitic transformation. Copyright (C) 2016 The Authors. Published by Elsevier B.V.

In this paper, the design of aperture-couplet rectangular dielectric resonator antennas arrays is illustrated. The effect of slot feed on the dielectric resonator antenna (DRA) and the effect of the spacing between array elements is observed. This paperwork can be useful for WLAN applications with the operating frequency 5.8 GHz.

A two dimensional photonic crystal with hexagonal symmetry is investigated by finite-difference time-domain and finite difference frequency-domain theoretical calculations. The system consist in a germanium substrate patterned with holes of different radii, varying from 0.1 alpha to 0.45 alpha, The photonic band gaps (PBGs) and the reflectance spectra allow a complete characterization of the structure. It was shown the presence of PBGs at telecommunication wavelengths which makes the present systems suitable for optoelectronic applications, representing a potential alternative to Si-based technology

The direct detection of dark matter candidates, for which semiconductor materials are used, is based on the detection of low energy selfrecoils. We show that the corrections to the energy partition curves due to the energy exchange during the transient processes modify the predictions of the standard Lindhard theory. These effects, calculated in the frame of a new model developed by the authors, depend on the initial temperature at which the detector operates, and on the energy of the recoil. Most of the available experimental data accumulated during more than fifty years. support these results.

The experimental demonstration of fundamental direct bandgap, group IV GeSn alloys has constituted an important step towards realization of the last missing ingredient for electronic-photonic integrated circuits, i.e. the efficient group IV laser source. In this contribution, we present electroluminescence studies of reduced-pressure CVD grown, direct bandgap GeSn light emitting diodes (LEDs) with Sn contents up to 11 at.%. Besides homojunction GeSn LEDs, complex heterojunction structures, such as GeSn/Ge multi quantum wells (MQWs) have been studied. Structural and compositional investigations confirm high crystalline quality, abrupt interfaces and tailored strain of the grown structures. While also being suitable for light absorption applications, all devices show light emission in a narrow short-wave infrared (SWIR) range. Temperature dependent electroluminescence (EL) clearly indicates a fundamentally direct bandgap in the 11 at.% Sn sample, with room temperature emission at around 0.55 eV (2.25 mu m). We have, however, identified some limitations of the GeSn/Ge MQW approach regarding emission efficiency, which can be overcome by introducing SiGeSn ternary alloys as quantum confinement barriers.