In this paper we propose the study of nanocomposites for white light emission in a semiconductor device, by incorporating the yttrium aluminum garnet doped with cerium ions (YAG:Ce3+), into a polymeric matrix of poly methyl methacrylate. The co-precipitation method was used for the synthesis of YAG:Ce yellow phosphor. The transition from the amorphous state to the crystalline was observed at a temperature of 1200°C. In order to obtain a better dispersion of the nanoparticles in the polymeric matrix has been chosen a capping agent. The structural analysis of the nanocomposite and the phosphor were studied by Fourier transform infrared spectroscopy and x-ray diffraction, morphological properties were investigated by scanning electron microscope, and photoluminescence spectrometry has highlighted the applicability of phosphors and, implicitly, of the nanocomposite for application in emitting optoelectronics.
Due to the honeycomb arrangement of carbon atoms, graphene exhibits unique properties, such as superior thermal conductivity, exceptionally large surface area and zero bandgap, and has become one of the fastest growing domains of scientific research. Many processes have been developed to obtain single layer graphene by chemical vapour deposition, but the main drawback of using graphene in large area industrial manufacturing processes is the transfer procedure from the transition metal to the target substrate. In the present paper we study the possibility to obtain single layer graphene by chemical vapour deposition (CVD) on copper catalyst and transfer it to different substrates. The quality of CVD graphene on copper catalyst and on substrate target after transfer was evaluated from the structural (by Raman spectroscopy), morphological (by SEM) and optical properties (UV-VIS) point of view. The transfer process proposed in this paper enable the use of this type of material in applications such as pressure sensors and field effect transistors, when proper control of the graphene/substrate interface is very important.
In this paper we aim to perform a cross section morphological characterization of an acrylic polymer used for dental prostheses subjected to microwave disinfection. The method was largely investigated and the microbiological effectiveness is well established, but there are some issues regarding the in-depth alteration of the material. In our research, the surface roughness is insignificant and the samples were not polished or refined by any means. Two groups of 7 acrylic discs (20 mm diameter, 2 mm thickness) were prepared from a heat-cured powder. Half of the samples embedded a stainless steel reinforcement, in order to observe the changes at the interfaces between the polymer and metallic wire. After the gradual wet microwave treatment, the specimens - including the controls - were frozen in liquid nitrogen and broken into pieces. Fragments were selected for gold metallization to ensure a good contrast for SEM imaging. We examined the samples in cross section employing a high resolution SEM. We have observed the alterations occurred at the surface of the acrylic sample and at the interface with the metallic wire along with the increase of the power and exposure time. The bond configuration of acrylate samples was analysed by FTIR spectrometry.
The purpose of this research was to model, design and fabricate a biodynamic analysis microsystem required for the
determination of various molecular transport properties of the non-Newtonian biological fluids. In order to achieve this, a
lab-on-a-chip device is studied. The microsystem consists of a microchannels system and gear wheels for the rotator
pump and for the detection system. The microchannel system developed satisfies the objectives for the study of
microcirculation and characterization of cell rheological properties, functions and behavior. The microchannel types are:
straight, bifurcated, stenosed and endothelial profiled. Some simulations were made in order to provide an idea about
blood flow through blood vessels and microchannels. The gear wheel was fabricated using the silicon surface
micromachining technology, combining the undercut and refill technique with pin-joint bearing permitting the
fabrication of bushings. A giant magnetoresistive sensor with a non-contacting transduction mechanism, in full
Wheatstone bridge configurations with four active resistors in the middle of the sensitive structure and four shielded
reference resistors, very attractive for detection of low magnetic fields in lab-on-a-chip applications, is used to transform
the rotor rotation rate into an electrical signal.
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