Stage 2 - P4
Phase no. 7
Responsible: Dr. V. CRACIUN
Title: "Synthesis of new ceramic compounds for radioactive nuclear waste encapsulation"
Abstract: The main activity of this stage was the deposition of advanced ceramic materials in the form of thin films, in order to study the radiation effects on the properties, structure and stoichiometry. Based on these results we will develop new ceramic compounds with resistance to radiation effects, which can be used for the encapsulation of the radioactive waste.
Among the obtained results we will mention the most important ones, in the list below:
- synthesis of thin ceramic films by pulsed laser ablation technique using excimer lasers (KrF-248 nm- and ArF-193 nm), with morphological characteristics of the surface compatible to the experimental investigation techniques for structure and properties, with a depth resolution on the order of nanometers;
- the use of the XRR technique (specular X-ray reflectometry) to determine any film's density variations due to irradiation with energetic ions or gamma radiation;
- investigation of irradiation effects induced by Ar ions of 800 keV on the nanocrystalline grain sizes;
- investigation of irradiation effects induced by Ar ions of 800 keV on the chemical composition of ceramic materials;
- deposition of HfO2 amorphous films with good electrical and structural properties using the PLD technique with an ArF laser (l=193 nm);
- investigation of the gamma radiation effects on the structure and optical properties of HfO2 amorphous films.
The objectives of this phase were completely fulfilled. We have fulfilled all the necessary conditions for the successful continuation of the researches and accomplishment of the next proposed objectives.
Phase no. 8
Responsible: Dr. I. TISEANU
Title: "Development and application of nondestructive techniques for the quality assurance monitorization of laser, plasma and radiation processing methods"
Abstract: X-ray tomography (XCT) was developed as a method for industrial metrology and quality assurance that allows simultaneously defectoscopic and very precise geometric information for complex 3D structures produced by laser, plasma or radiation processing. This topic provides the context for developing procedures for a systematic application of existing non destructive techniques (NDT) as methods of ensuring in INFLPR the quality of synthesis and processing techniques.
The following activities were realized during this reporting period:
- Micro tomography analysis of aluminium laser welds made with a continuous wave laser TruDisk3001 with a focal spot of 600 µm connected to a robotic system with six degrees of freedom.
- An inspection procedure for composite samples based on natural rubber or sawdust that shows the improved adhesion degree of natural rubber matrix and the volumetric distribution of the components concentration. Dimensional evaluation of the internal structures of polymer networks based on hydrogels was performed with Volume Graphics metrology module.
- XRF analysis have enabled 2D mapping composition and to determine the thickness uniformity on layers of W, Ni, Fe alloys with carbon substrate, depositions of interest in the nuclear fusion technology field.
- The micro tomography analysis method was certified with the CertRom MS ISO 9001 Quality and Environment IDO-14001 standards.
The main objectives of the phase were reached by demonstrating the applicability of existing non destructive techniques (NDT) in INFLPR as service methods for monitoring and quality assurance by applying laser, plasma or radiation processing.
Phase no. 9
Responsible: Dr. M. ZAMFIRESCU
Title: "Diffractive Optical Elements as security elements obtained through ablation using picosecond laser pulses"
Abstract: Diffractive Optical Elements (DOE) are a class of passive optical devices generally used for obtaining arbitrary intensity distributions. A special category of DOE is comprised of those elements which modulate incident light according to a computer generated hologram calculated beforehand. Such devices are applied in security marking, optical manipulation, communications and other related domains.
Over the period of this activity, the following results were obtained:
- An integrated and partially automated installation has been produced for the fabrication of DOE, based on 2D laser direct writing methods. The main elements of the installation are represented by the industrial microprocessing laser system, which offers picosecond pulses with 3 central wavelengths (1064nm, 532nm, 355nm), and a high precision XY translation stage (Aerotech). The system can be used for any 2D microprocessing, in the accepted parameters.
- A software application has been developed, under “CC Attribution 4.0” license, for designing arbitrary image holograms using two numerical methods based on the scalar model of diffraction, and holograms for two-dimensional Airy beams. The software can also transform 8bit computer generated holograms into binary detour-phase holograms.
- All hologram types mentioned above have been fabricated, using direct laser writing on a thin Cr film, deposited on a glass substrate.
Obtained results can further the development of DOE fabrication, as well as other complex microprocessing methods based on 2D direct laser writing. The system can be extended for 3D processing, both for direct writing methods and other types of processing (cutting, piercing, welding). Experimental results are to be published in an ISI scientific journal.
Phase no. 10
Responsible: Dr. A. SCARISOREANU
Title: "Sinteza si caracterizarea fizico-chimica a mixturilor; hidrogel superabsorbant cu grafena, obtinute in faza solida, prin iradiere cu radiatii ionizante"
Phase no. 11
Responsible: Dr. A. ROTARU
Title: "Thermal stability of heterobimetallic coordination complexes of Zn(II)/Ni(II) and Ln (III) with derivatives of o-vanillin and 2.2- dimethyl- propylenediamine"
Abstract: The main purpose of this phase comprised the determination of thermal stability and thermophysical properties of heterobimetallic coordination complexes of Zn(II)/Ni(II) and Ln (III) with derivatives of o-vanilline and derivatives of propilendiamine, which are inorganic-complex luminescent materials, some of these being materials that behave as micro-antennas with respect to the accumulations of energy that correspond to more excitation wavelengths. In this phase, it was determined the proposed target, namely: thermal stability of compounds from the class of heterobimetallic coordination complexes from above (ligands: L1=Valpn and L2=Valdmpn), in conditions of inert atmosphere of Ar and respectively of synthetic air atmosphere, and also the validation for choosing those that will be used as photoluminescent materials, as solid powder and as thin films. There were determined the temperature domains corresponding to the thermal stability; tough, it was conferred the possibility and assured the use of defined temperatures during the laser processing of proposed thin films. Also, in the coordination environment of Zn(II)/Ni(II) it may be found a fragment of H2O, while in the coordination environment of Ln(III) there are 3 anions (NO3)- which compensate in the same time also the positive charges of lanthanide cations, and this entire complex is sometimes crystallized with H2O molecules; simultaneously with checking the thermal stability and behaviour, by thermal analysis one may determine or confirm the number and type of coordination or crystallization fragments present in each investigated molecule. In general, these compounds have more or less the same stability in argon and in air, the only difference appearing when the pyrolysis vs. burning of the organic ligand happens. It was evidenced a slightly higher thermal stability of the compounds bearing ligand L1 with respect to those bearing ligand L2, but certainly by overlapping the thermoanalytical curves there are clues indicating that the decomposition reactions of the analogues with L1 are kinetically favoured. It is not possible to assign a different thermal stability corresponding to these compounds, the maximum of the process rate for the elimination of NO2 being in all these 3 cases at 300 °C. In the case of Ni(II) compounds, the thermoanalytical curves are similar, but the thermal stability is usually weaker compared to that of the analogues containing Zn(II) and respectively the corresponding ligands.
Phase no. 12
Responsible: Dr. S. AMARANDEI
Title: "Investigation of structured beams propagation through particulate media"
Abstract: Structured beams have been generated experimentally using a phase-only liquid crystal spatial light modulator and their characteristics have been measured. The effect of propagation of structured beams through solutions of polystyrene microspheres in water has been studied for different volume concentration levels ranging from 0 to 2.5%. Measurements show that elements of the structured beams profile are preserved after the scattering in aqueous solutions of polystyrene microspheres.
Phase no. 13
Responsible: Dr. N. PAVEL
Title: "Advanced diode-pumped solid-state laser configurations for ignition of fuel in internal combustion engines"
Abstract: The laser ignition of fuel mixtures is an alternative technique to the classical ignition with a spark plug, presenting particular interest in internal combustion engines. Among the advantages of this method it is worthwhile to mention: (i) the absence of "quenching" of the flame front due to the absence electrode, which leads to shorter burning time (ii) the possibility of realizing ignition at an optimal position in the combustion chamber; (iii) decreases in fuel consumption and exhaust gas emissions, or (iv) the ability to ignite lean air-fuel mixtures and thus to reduce the engine emissions and its influence on the environment.
In this contract we are presented results on two diode-pumped solid-state laser configurations that could have applications in the ignition of flammable combustible mixtures.
The first configuration consists of an Nd:YAG/Cr4+: YAG composite medium that is pumped longitudinally with diodes laser so as to emit four laser beams. Each laser beam has the energy and pulse duration suitable for inducing the air-breakdown phenomenon. Different focusing arrangements were presented to obtain ignition in a variable volume.
The second laser configuration was an Nd:YAG/YAG medium that was shaped as an “active lens”. The Nd:YAG/YAG was a thin-disk composite medium that has a cylindrical central part of Nd: YAG surrounded by a undoped YAG area. One side of this medium is flat whereas the other one is concave. The pump was made laterally from three directions with fiber-coupled diode lasers.
Dissemination: an article published in a ISI Web of Science journal, two poster presentations at international conferences, a project proposal; a manuscript in preparation.
Phase no. 14
Responsible: Dr. T. CRACIUNESCU
Title: "Assessment of the efficiency of instabilities control by mean of the analysis of time series synchronization"
Abstract: ELMs are instabilities that almost invariantly affect H mode plasmas, causing a reduction of the energy confinement through deterioration of the edge transport barrier. This sudden degradation of the confinement at the edge induces an expulsion of energy and matter from the plasma on a sub millisecond time scale, which can result in unacceptable erosion of the plasma facing components in the divertor. Various forms of ELM pacing have been tried in the past to influence their behaviour using external perturbations. One of the main issues of these synchronization experiments resides in the fact that ELMs are quasi periodic in nature and therefore, after any pulsed perturbation, if enough time is allowed to elapse, an ELM always occurs. To evaluate the effectiveness of ELM pacing techniques, it is therefore essential to determine an appropriate interval over which they can really have a triggering capability. We have developed a method that exploits the properties of Joint Recurrence Plots and is based on the analyses of the recurrence properties of dynamical systems. The obtained results indicate that the proposed technique provide much better estimates than the traditional heuristic criteria reported in the literature. It allows also improving the time resolution of the assessment and determining the efficiency of the pellet triggering in different phases of the same discharge. The method can be used to provide a quantitative and statistically sound estimate of the triggering efficiency of ELM pacing in realistic experimental conditions.
Phase no. 15
Responsible: Dr. G. SOCOL
Title: "Development of an experimental setup and protocols for the detection of trace gases"
Abstract: In the project, we designed and assembled an experimental setup for gas sensors testing based on electrical resistivity measurement of the sensing media. It is worth mentioning that the setup can be adapted to test sensors working on the variation of other physical parameters (ex. SAW gas sensors). The system is able to assess gas sensitive structures like thin films as well as pellets, crystals, membranes, etc. Moreover, the system can provide a wide range of gas mixtures starting from pure or premixed gases. For experiments, there are available several pure or premixed gases as NH3, CO, CO2, ethylene, CH4. A comprehensive gas testing protocol that highlights the performance of gas sensors that work on this detection principle was developed. The system is controlled by means of a software that provides all calculations necessary to generate the concentration for the chosen gas mixture.
Phase no. 16
Responsible: Dr. D. MIU
Title: "Production by laser ablation in liquid and characterization of SnO2 nanoparticles and cells for sensors and photovoltaic cells"
Abstract: For the production of SnO2 nanoparticles, the target was ablatet in liquid environment with laser pulses with duration of 8 ps, with wavelength of 1064 nm, and 355 nm respectively. The laser beam was focused and moved on the target surface using a galvanometric scanner with a constant speed of 2000 mm/s. In all experiments, the target ablation area was located at 3 mm below the liquid surface. Nanoparticle products were analyzed by FTIR spectroscopy, XRD diffractometer and TEM.
Samples for FTIR and XRD were prepared by settling the colloid, followed by precipitation by centrifugation at 15000 rpm for 2 minutes. FTIR spectroscopy and X-ray diffractometry confirmed the presence of SnO2, dominant crystalline phase being SnO2 - cassiterite. Estimated average crystallite size using Scherrer formula is between 45 and 52 nm.
TEM microscopy were used colloid without any special preparation. TEM images show that most nanoparticles have dimensions below 10 nm. The average particle size was evaluated by fractal analysis of images from electron microscopy TEM, the average size being 17 nm maximum and the minimum 7 nm.
Phase no. 17
Responsible: Dr. F. SPINEANU
Title: "Analysis of the efficiency of the methods for the study of the cosmic ray transport in stochastic magnetic fields and identification of the transport regimes"
Abstract: The aim of this research (included in the OG3 topics) is the identification of the transport regimes of the cosmic rays in the conditions of the solar wind and of the solar corona. These results are essential for the estimation of the fast particle flux in the atmosphere. The objectives of the present stage are: the analysis and extension of the theoretical methods for the study of the complex nonlinear processes scheduled for the next stages and the development of numerical codes. We have compared the results of the decorrelation trajectory method (DTM), of the Corrsin (C) approximation and of the improved-Corrsin (i-C) method, which was developed in this project. We have analyzed the nonlinear processes in the drift and gyro-kinetic approximation of the motion in the frame of 2- and 3-dimensional models of the stochastic transport. We have developed five numerical codes cods for the calculation of the diffusion coefficients. The main conclusions are:
- In the case of the 2d and 3d stochastic velocity fields with statistically independent components, the three methods (C, i-C and DTM) lead to similar results. The transport process is Gaussian and the nonlinear effects are weak.
- In the case of 2d velocity fields with zero-divergence (incompressible), large differences between the three methods can appear. They correspond to the conditions that lead to processes of transitory trajectory trapping. The transport is non-Gaussian and the transport coefficients are anomalous (they have completely different dependences on the parameters of the stochastic velocity compared to those of the Gaussian case). DTM leads to results that are compatible to the numerical simulations, while C and i-C are not adequate to the study of the strongly nonlinear processes.
These results are included in two ISI articles (one in the evaluation phase and one accepted for publication). Both journals are in the red zone of the ANCSI ordering.
Phase no. 18
Responsible: Dr. B. MITU/ Dr. V. SATULU
Title: "Plasma synthesis of planar structures with alternation of properties; evaluation of morphology and chemical structure"
Abstract: During the phase 18 of the project, we have synthesized bicomponent layers of Si/a-C:H/PTFE si Si/PTFE/a-C:H by alternating magnetron sputtering and plasma assisted chemical vapor deposition processes (PVD/PECVD), with the aim of identifying the influenec of the layer deposition order on the properties of bi-component structures. The morphological and compositional properties of the structures upon the applied RF power on the plasma sources during deposition process, while selecting the deposition times such as the two layers would have the same thickness, as well as upon the temporal sequences which conduct to various thicknesses of the structures, have been investigated. Also, we have synthesized multilayered structures with extremely low thicknesses (10 nm/layer) and we have demonstrated that the component layers can be detected when intermediate Au films are deposited. This fact underlines once more the high uniformity of the deposition processes and the reproducibility of the hybrid PVD/PECVD system.