Adrian Manea

Electrodeposition of Co and CoMo alloys coatings using choline chloride based ionic liquids - evaluation of corrosion behaviour

This study deals with the electrodeposition of Co and CoMo alloys from various ionic liquids based on choline chloride (ChCl) – urea and ChCl – ethylene glycol eutectic mixtures. The Co and Co–Mo (with 1–8 wt-% Mo content) deposits obtained were adherent, compact and uniform onto copper substrates. A decrease of the Mo content in the alloy has been shown as the applied current density increased in the range of 7–25 mA cm−2, at 90–100°C. Some peaks assigned to MoO3 or Co3Mo phases have been identified in the XRD patterns. The average size of crystallites has been estimated to be in the range of 7–9.2 nm (nanocrystalline deposits). Atomic Force Microscopy analysis gave evidence that Co deposits were formed by multiple compact almost rounded crystallites, while Co–Mo alloy ones consisted of multiple relatively compact grains with cylindrical shape. The coatings’ corrosion performance has been also measured by continuous immersion testing in 0.5M NaCl solution, and potentiodynamic polarisation and electrochemical impedance spectra.

Ni–Mo alloy nanostructures as cathodic materials for hydrogen evolution reaction during seawater electrolysis

In the case of hydrogen production involving seawater electrolysis, one of the main targets is to develop more active cathodic materials, to optimize the efficiency of hydrogen evolution reaction (HER) and, by doing so, enhance the overall energy efficiency of electrolysis. Thus, to develop suitable HER electrocatalysts either an increase of the electrode active surface area or a design of a material having high intrinsic catalytic activity should be taken into consideration, both of them decreasing the HER overpotential. In the present work, various Ni–Mo alloy nanostructures (10–40 wt% Mo) have been prepared involving electrochemical deposition from aqueous and deep eutectic solvent (DES)-based electrolytes as potential cathodic materials suitable for hydrogen evolution reaction during water electrolysis. The electrocatalytic activity of the obtained layers has been investigated using real seawater electrolyte. The determined Tafel slopes suggested that the electrodeposited Ni–Mo alloy coatings follow an HER mechanism controlled by the Volmer reaction step. The EIS results indicated that the use of choline chloride-based ionic liquids as electrolytes facilitated Ni–Mo alloy coatings showing a significant increase in surface roughness. Studies of the intrinsic activity showed that the main contribution towards the apparent activity comes from the increase of the real surface area, although a slight increase of the intrinsic electrocatalytic activity in the case of Ni–Mo alloy coatings electrodeposited on Ni foam was also noticed. These results showed that Ni–Mo alloy coatings electrodeposited from the novel electrolytes based on choline chloride–urea–citric acid ternary mixtures associated with a porous substrate may represent a promising technological approach to build cathodic materials suitable for seawater electrolysis.

Optical measurements for excitation of CdTe quantum dots

The paper presents the experimental results obtained using a laboratory setup installation for fluorescence excitation of CdTe QDs used as biomarkers for clinical diagnostics. Quantum Dots (QDs) made of Cadmium Telluride (CdTe), are highly fluorescent and they are used as robust biomarkers. Generally, QDs are referred to as the zero-dimensional colloidal crystals that possess strong size dependence and multi-colored luminescence properties. Along with its intrinsic features, such as sharp and symmetric emission, photo-stability and high quantum yields, QDs play a vital role in various applications, namely the identification of the chemical moieties, clinical diagnostics, optoelectronics, bio-imaging and bio-sensing1.

Development of optoelectronics in Politehnica University of Bucharest

Optoelectronics is facing with an ever dynamic increasing in our lives. We feel a growing demand for specialists in design and operation of optoelectronic systems. In accord with this demand Politehnica University of Bucharest (PUB) has introduced optoelectronics curricula since 1992 year. The theoretical courses are covered by laboratory activities, to provide the students with actual experience of optoelectronic systems. Some experiments are presented in this paper. To get a good efficiency of experiments, the student should study Laboratory guide manual, before entering the laboratory. PUB in collaboration with SPIE organization is intending to develop an integrated optoelectronics laboratory for education ofoptoelectronics specialization students with the following principles: define the educational goals and experimental laboratory courses to fulfill the objectives, design the instrumentation and systems to enable practical, experimental investigation and measurements; elaboration of experimental algorithms and laboratory guide for students, which include exercises and problems with responses connected with real world of optoelectronics specialists demand. This paper focuses on the presentation of laboratory courses that would be developed a meaningful understanding of optoelectronic devices, and systems.

Integration of optoelectronics and SAW technology

The number of radio frequency surface acoustic wave (SAW) filters produced presently exceeds 3 billion per year. The demand for high-frequency SAW filters for telecommunications and remote sensing, has led to extensive research, focusing on new SAW microdevices. SAW devices have shown compact structures, small size, low cost, high sensitivity and fast response. The need of miniaturized systems, with high sensitivity and low energy has motivated the need to integrate on the same substrate all the structure of SAW device and connecting electronic circuits. As a consequence, many types of methods of both constructive and operating characterization of SAW devices have been developed. This paper provides a short introduction regarding the developed level of SAW microdevices and describes the results of literature investigation research of optoelectronic techniques for constructive characterization of SAW microdevices. Further research will be done into the determination of SAW parameters such as the amplitude of surface wave, the velocity of wave propagation on the surface of the piezoelectric substrate. Substrates of quartz, lithium tantalite (LiTaO3) and lithium niobate (LiNbO3), are piezoelectric materials commonly used in manufacturing of SAW devices, but these materials are not compatible with the integrated circuit (IC) technology. Three optoelectronic measurement techniques are known for detection of surface acoustic waves: diffraction grating technique, the knife-edge technique, and the detection of ultrasonic vibrations using optical interferometry. The research work given in this paper concentrates on describing of optoelectronic techniques used for constructive characterization of SAW microdevices. Finally, we try to draw some conclusion where: optoelectronic techniques are predicted to be one of the fundamental measurement methods for measurement of future SAW microdevices.

Front Matter: Volume 7297

This PDF file contains the front matter associated with SPIE Proceedings Volume 7297, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

Laser Characterization of the Periodic Line-Space Micro/Nano Structures

Recent advances in micro/nanotechnology devices have demonstrated periodic line-space structure with dimensions of order less than ten nm. Laser scatterometry is a noncontact measurement method for collecting and analyzing of scattered light from the structures. Methods using laser scatterometry can characterize periodic line-space structures. The objective of this paper is three-fold: (1) characterization of laser beam quality which is used for optical metrology; (2) optical characterization of periodic line-space structures; (3) some conclusions regarding experimental results are presented.

Modeling fiber taper shape

The taper (i.e. thin fiber with transitions from large to small diameter) is created during pulling of the molten fiber. Its shape depends on many parameters of the pulling process, such as pulling speed, pulling temperature, pulling stages step, etc. This paper attempts to describe the taper shape as a function of pulling parameters and provide comparison for different heating methods.

Antenna for passive RFID tags

Minuscule devices, called RFID tags are attached to objects and persons and emit information which positioned readers may capture wirelessly. Many methods of identification have been used, but that of most common is to use a unique serial number for identification of person or object. RFID tags can be characterized as either active or passive [1,2]. Traditional passive tags are typically in “sleep” state until awakened by the reader’s emitted field. In passive tags, the reader’s field acts to charge the capacitor that powers the badge and this can be a combination of antenna and barcodes obtained with SAW( Surface Acoustic Wave) devices [1,2,3] . The antenna in an RFID tag is a conductive element that permits the tag to exchange data with the reader. The paper contribution are targeted to antenna for passive RFID tags. The electromagnetic field generated by the reader is somehow oriented by the reader antenna and power is induced in the tag only if the orientation of the tag antenna is appropriate. A tag placed orthogonal to the reader yield field will not be read. This is the reason that guided manufacturers to build circular polarized antenna capable of propagating a field that is alternatively polarized on all planes passing on the diffusion axis. Passive RFID tags are operated at the UHF frequencies of 868MHz (Europe) and 915MHz (USA) and at the microwave frequencies of 2,45 GHz and 5,8 GHz . Because the tags are small dimensions, in paper, we present the possibility to use circular polarization microstrip antenna with fractal edge [2].

Characterization of SAW filters based on GaPO4

The results of research into Surface Acoustic Wave – SAW – filters have been recognized for their efficiency and versatility in the electrical signals processing 1,3. Gallium Orthophosphate (GaPO4) is a relative new material, which has a long term high stability and, moreover, has an excellent behavior with temperature variation 2,3. The characterization of SAW filters based on GaPO4 is uses the comparative analysis of simulated results of parameters, with different software programs, which were developed for designing of these filters. Simulation covers the determination and analysis of the characteristics of this filter, namely, mechanical parameters (constructive) and operational parameters in comparison with the design data. In order to obtain the parameters of SAW filters we have used the algorithms and software for modelling, simulation. The paper presents several versions of software programs, in Matlab and Microsoft Visual C#, for the design of GaPO4 SAW filters and their interpretation. These modeling, simulations were performed successively by each program, until we set the parameters of SAW filter. By the comparison of the data obtained with each program, we have improved the constructive dimensions of fingers, we obtained the desired parameters. With this data, we realised SAW filters based on GaPO4, and with the help of the Network Analyzer we measured parameters of the filter, which are presented in the paper2,10.