Shema de realizare a proiectului 19 15 01 01 - Anul 2020 - Etapa I
Phase no. 37
Responsible: Dr. M. Zamfirescu
Title: "Caracterizarea fasciculelor de electroni accelerați la interactia pulsurilor ultraintense cu ținte gazose"
Abstract: The main result of this stage of the project is the demonstration for the first time in Romania of the accelerated electron beams at energies over 100 MeV. The team from CETAL-PW laboratory from INFLPR designed and built the experimental setup for electron acceleration in gas-jet targets. The acceleration parameters studied are electron energy, divergence, angular stability. These have been optimized by variating the energy and duration of the laser pulse, the focal plane relative to the target and the parameters of the target gas, respectively the gas pressure. The accelerated electrons are detected on a scintillator screen (LANEX) placed at the exit of the extension of the interaction chamber. The luminescence emitted by the LANEX screen is monitored with an optical system and a video camera. From the spatial stability studies of the electron beams an angular variation was determined from pulse to pulse of approximately 25 mrad. To accurately measure electron spectra, an electron spectrometer was designed and built based on a permanent dipole magnet with high intensity magnetic field (0.86 T). High energy electrons, up to hundreds of MeV, are deflected by such electron beams spectrometer. Electrons with distributions with a peak intensity at 370 MeV energy were measured. All the parameters of the experiment are sufficiently well controlled, so that obtaining electron beams accelerated over 200 MeV was reproducible for all the experiments campaigns.
Phase no. 38
Responsible: Dr. C. Ristoscu
Title: "Straturi subtiri de apatita biomimetica - chitosan obtinute prin tehnici laser cu aplicatii antimicrobiene"
Abstract: Chitosan/biomimetic apatite thin films were grown in mild conditions of temperature and pressure by Combinatorial Matrix-Assisted Pulsed Laser Evaporation (C-MAPLE) on Ti, Si or glass substrates. Compositional gradients were obtained by simultaneous laser vaporization of the two distinct material targets. A KrF* excimer (λ=248 nm, τFWHM=25 ns) laser source was used in all experiments. The nature and surface composition of deposited materials and the spatial distribution of constituents were studied by SEM, EDS, AFM, GIXRD, FTIR, micro-Raman, and XPS. The antimicrobial efficiency of the chitosan/biomimetic apatite layers against Staphylococcus aureus and Escherichia coli strains was interrogated by viable cell count assay.
Combinatorial thin films were found amorphous and showed a morphology characteristic to laser deposited structures composed of nanometric round grains. The surface roughness has progressively increased with chitosan concentration. FTIR, EDS and XPS analyses indicated that the composition of the BmAp-CHT C-MAPLE composite films gradually modified from pure apatite to chitosan.
The bioevaluation tests indicated that S. aureus biofilm is more susceptible to the action of CHT - rich areas of the films, whilst the E. coli biofilm proved more sensible to areas containing less CHT.
The best compromise should therefore go, in our opinion, to zones with intermediate-to-high chitosan concentration which can assure a large spectrum of antimicrobial protection concomitantly with a significant enhancement of osseointegration, favored by the presence of biomimetic hydroxyapatite.
Phase no. 39
Responsible: Dr. L. Gheorghe
Title: "Dezvoltarea de cristale optic neliniare Nd:LGSB pentru generarea de radiatie laser in domeniul spectral verde prin procese de autodublare de frecventa"
Abstract: Nd:LGSB-type single crystals, with optimized compositions for the generation of laser radiation in the green spectral range by self-frequency doubling (SFD) processes, were grown for the first time internationally by the Czochralski method. The nonlinear optical (NLO) and spectroscopic properties of the La0.721Nd0.046Gd0.452Sc2.781(BO3)4 (4.6 at.% Nd:LGSB) grown crystal were investigated, and the laser emission experiments in the 1 µm range permitted to be obtained laser emission at λem= 1061.97 nm with a slope efficiency of 73%. Laser emission in green at ~ 531 nm was obtained for various configurations of the laser resonator, and the obtained results demonstrate that the 2.5 at.% Nd:LGSB single crystal constitutes an experimental and functional model of green laser source based on SFD processes. Future research will focus on the investigation of 4.6 at.% Nd:LGSB crystal as a self-frequency doubling laser active medium with efficient emission in the green spectral domain (~ 531 nm).
Phase no. 40
Responsible: Dr. E. Grigore
Title: "Obtinerea straturilor de WN utilizand metoda de depunere HiPIMS"
Abstract: Increasing the lifetime and the performance of industrial components by using hard coatings represent key objectives for the aplication field known as Surface Engineering. From this perspective, for a long time, the transitional metals nitrides are considered potential candidates for a wide field of aplications.
The research investigations performed with the present project were devoted to the synthesis of tungsten nitride coatings obtained by HiPIMS (High Power Impulse Magnetron Sputtering) deposition and to evaluation of their properties. The study was focused on finding the correlation between the chemical composition and the mechanical properties of the coatings.
The chemical and structural properties of the coatings were investigated by using GDOES (Glow Discharge Optical Emission Spectrometry), XRD (X-ray Diffraction) and SEM (Scanning Electron Microscopy). Subsequently, a series of mechnical characteristics such as microhardness, friction coefficient and wear resistance were determined whereas the influence of the nitrogen mass flow rate on these properties was quantified.
The measurements of friction coefficient and coatings wear rate were performed by using the pin on disk test, while the thermal stability of the coatings was analyzed by using TDS (Thermal Desorption Spectroscopy).
The synthetized coatings had a nitrogen content in the range 2.0-5.3 at.%. The XRD investigations did not reveal the formation of W-N compounds, with nitrogen dissolving in the W matrix. It was noticed that the microhardness increases with the nitrogen content within the coatings up to 2711 HV0.05 for a nitrogen content of 5.3 at.%. It was observed that the coating with a N content of 2.0 at.% possess the lowest friction coefficient (0.474) and wear rate (2.33x10-6 mm3/Nm).
Phase no. 41
Responsible: Dr. G. Socol
Title: "Investigarea diverselor materiale plasmonice pentru îmbunătățirea performanței senzorului cu fibră optică bazat pe rezonanță plasmonică de suprafață (FO-SPR)"
Abstract: Surface plasmons (SP) are electromagnetic waves that form along the interface between a continuous metallic thin film (typically gold – Au) and a dielectric medium, representing the analysing environment (typically a liquid). Surface Plasmon Resonance (SPR) devices are well-established optical tools used in various fields of life sciences, agro-food sector and medical diagnostics due to their ability to provide real-time information about biological interactions and chemical reactions. Fiber Optic (FO) - SPR sensors are offering advantages such as low-cost production, small size, remote sensing capability and the safety for in vivo measurement. The FO coated with a thin metallic film is used to guide the light towards the plasmonic interface. Any event occuring at this interface (e.g., the interaction between a receptor and the target molecule) will trigger a change in the SPR signal, which can be further processed in a graph. Such a FO-SPR detection platform was also developed within INFLPR. While the potential of FO-SPR tehnology is undeniable, increasing its sensitivity remains an important objective in order to translate this potential into various applications. In this context, in this work, various plasmonic materials were investigated, such as gold (Au), silver (Ag), palladium (Pd) and platinum (Pt), in order to improve the FO-SPR sensor performance. The protocols for the plasmonic materials deposition on the FO substrates were optimized and the performance indicators (sensitivity and figure of merit) were determined separately for each FO-SPR sensor. As a general conclusion of this study, each tested plasmonic material comes with its own advantages and disadvantages, the choice of using it is depending entirely on the desired application.
Phase no. 42
Responsible: Dr. A. Staicu
Title: "Studiul proprietăților de udare a suprafețelor de către picături de medicamente expuse la radiație laser în condiții de hipergravitație"
Abstract: In this stage, under hypergravity conditions generated by the Large Diameter Centrifuge (European Space Agency, European Space Research and Technology Centre, Noordwijk, The Netherlands) at 1, 2, 5, 10 and 20 g, the wetting properties of medicine solutions were evaluated on Parafilm M, aluminium, and cotton surfaces by determining the contact angles. The studied solutions were unirradiated chlorpromazine and chlorpromazine irradiated for 4 hours by a laser emitting at 266 nm (the forth harmonic of the fundamental beam of the Nd:YAG laser system). Similarly, the wetting properties of ultrapure water were also investigated. The interaction was studied by generating pendant droplets and measuring the contact angles of sessile drops formed by the liquid-solid-air interface.
In order to determine the contact angles, the pictures obtained during the hypergravity experiment have been analysed using the ADVANCE (KRÜSS) software.
Data analysis showed that as the level of gravity increased, the values of the contact angles decreased. In most of the cases, the laser irradiated drug solution possesses the best wetting properties amongst the three studied solutions. The results also indicated that reducing the volume of the drop leads to a decrease in the amplitude of the oscillations. Moreover, as the level of gravity gets higher, there is a linear increase in the oscillation frequency.
Phase no. 43
Responsible: Dr. G. Craciun
Title: "Obtinerea de materiale polimerice liniare pe baza de acrilamida si alginat de sodiu prin iradiere cu electroni accelerati, destinate epurarii apelor"
Abstract: The main phase objectives were as follows: (1) the synthesis and characterization of a polyelectrolyte based on acrylamide and sodium alginate (alginate-g-acrylamide) by grafting, using a 5.5 MeV electron beam; (2) determining the flocculation efficacy and heavy metal removal capacity from aqueous solutions of known concentrations. The sodium alginate concentrations in monomers solutions were of 1 and 2%, respectively, and the irradiation dose used for grafting was varied between 0.5 and 2 kGy. In these conditions two types of polyelectrolites were obtained and characterized by physical, chemical and structural investigations. Flocculation efficacy was evaluated under stirring conditions on kaolin suspensions of 0.5, 0.1 and 0.2%. The heavy metal removal capacity was investigated on aqueous solutions containing Cu2+ and Cr6+ ions. The sodium alginate concentration in the monomer solution and irradiation dose generate different acrylamide grafting ratios on sodium alginate backbone: 2000% for samples containing 1% sodium alginate and up to 500% for samples containing 2% sodium alginate. Transmittances between 98 and 100% were obtained using polyelectrolytes containing 2% sodium alginate in concentrations of 0.5 and 1 ppm on kaolin suspension of 0.1 wt %. The polymer concentration was found critical for kaolin suspension of 0.05 and 0.1 wt %, respectively. Polymers containing 1% sodium alginate were efficient in Cr6+ ion removal, while those containing 2% in Cu2+ ion removal.
Phase no. 44
Responsible: Dr. M. Magureanu
Title: "Caracterizarea descarcarii electrice utilizate pentru functionalizarea materialelor"
Abstract: In this project phase a glow discharge in hydrogen was investigated in various operating regimes: at low pressure (0.2 mbar), where the negative light (NL) region occupies the whole plasma reactor, and for higher pressure (2-4 mbar), where the positive column (PC) is visible on the entire length of the tube. The discharge power was varied in the range 0.4-1.4 W. It was found that the dissociation degree of molecular hydrogen is smaller in the positive column as compared to the negative light. The electron excitation temperature was determined in the NL region, with values in the range 8600-9060 K. The rotational temperature (which is in this case a good measure of the gas temperature) was also evaluated, having values in the range 350-500 K.
Phase no. 45
Responsible: Dr. M. Filipescu
Title: "Depunere si caracterizare de heterostructuri dielectrice"
Abstract: In the last decade, in Romania, the development of facilities based on high power lasers such as ELI-NP having high power laser systems with ultra-short pulses (> 10 PW) and CETAL within INFLPR having with a 1 PW laser, involves the use of optical components with special properties.
This report established the final configuration of AR coatings as single-layers of silicates (HfSixOy or AlSixOy), presenting the investigations of the physical properties of these coatings. The AR layers were obtained by pulsed laser deposition (PLD) and pulsed laser deposition assisted by radio frequency discharge (RF-PLD), looking for the optimal experimental parameters (wavelength, reactive gas pressure, laser fluence, number of laser pulses) to obtain layers with anti-reflection properties capable to resist to interaction with high energy laser radiation. Thus, the single-layers based on HfSixOy or AlSixOy are obtained from the combination of the binary compounds HfO2 and SiO2 /or Al2O3, in equal percentages.
From the investigations performed and taking into account the necessary specifications for a layer to be used as anti-reflex coating, the best single-layer structures are those of hafnium silicate and those of silicate of aluminum obtained by PLD (λ = 193 nm, Ts = 600˚C).
It was proved that the presence of RF discharge in the PLD deposition process is not beneficial for obtaining AR layers, this leading to a nanostructuring of the films and implicitly a higher roughness.
Phase no. 46
Responsible: Dr. C. Fleaca
Title: "Producerea de nanostructuri carbonice preponderent uni sau bidimensionale prin tehnici asistate cu laser CO2 in unda continua"
Abstract: In this phase we managed to obtain a series of carbon nanostructures with potential applications in energy generation/storage. Thus, a first research direction aimed at the synthesis of carbon nanoparticles doped/containing various halogens (F, Cl or I) by laser pyrolysis and their characterization (by XRD, EDS, Raman, FTIR, TEM techniques). Thus, two gaseous hydrocarbons were used as precursors - acetylene and ethylene - which also act as a laser energy transfer agent, as well as halogenated compounds such as sulfur hexafluoride, tin tetrachloride, trichlorethylene, molecular iodine and methyl iodide. The structure of these nanoparticles is generally turbostratic type, in some cases we obtained halogenated aromatic hydrocarbons such as C6Cl6, but also fullerene C60. Another development direction was the coupling of laser pyrolysis with the thermal deposition from vapor phase (CVD) in a furnace to generate in the presence of acetylene nitrogen-doped carbon nanotubes/nanofibers catalyzed by iron-based nanoparticles from pentacarbonyl iron and ammonia precursors surrounded/diluted of argon. In some experiments, the formation of submicron carbon particles with very close dimensions was also observed. The third direction focused on obtaining and characterizing of graphenes with porous structure and large specific surface area (called laser-induced graphene LIG) using the interaction in the environmental air of an infrared CO2 laser emitting at 10.6 μm with aromatic polyimide films that were in turn obtained by imidation of the corresponding polyamic acid, which has the advantage of solubility in certain polar solvents and thus can be deposed in desired shapes and thickness. The morphology of the nanostructures resulting from laser pyrolysis + CVD as well as that of the foam-type graphene structures generated during the pyrolysis of polyimides was observed in detail by the SEM scanning microscopy technique.
Phase no. 47
Responsible: Dr. A. Popescu
Title: "Imprimare 3D de obiecte metalice cu geometrie complexa"
Abstract: In this Nucleus Project phase we produced 3D objects by LMD 3D printing. The main goal was to establish the limitations of the method in producing small and large size metallic objects. We achieved remarkable progress in increasing the 3D printing method's resolution and produced fixture devices for orthopedic implants. The scanning strategy and the laser parameters optimization played an essential role in the success of these experiments. On the other hand for large size objects two main issues had to be solved: i. non-linear growth of the deposited material which can cause a lack of precision in the 3D printing of an object which will not respect the dimensions of the technical drawing; ii. the CAM software can become too large in case of complex shapes for the limited memory of the 3D printing system. The first issue was solved by conducting a study on the distance between the layers that form the 3D object. After numerous tests, we obtained a linear increase of the deposited material which allowed for 3D printing of shapes with correct dimensions. The second problem was solved by manufacturing the object from multiple programs. There is however a small inconvenient because on the object`s surface will be some clear delimitations between the sections produced by program sequences.
Phase no. 48
Responsible: Dr. C. Achim
Title: "Evaluarea produsilor stresului oxidativ utilizand testele de respiratie"
Abstract: Scuba diving could increase free radicals production which acts as signaling molecules to induce adaptation against oxidative attack.
The aim of the new research was to study the impact of scuba diving effects on multiple gas composition responses from the exhaled breath of professional divers. Ethylene, ammonia, and carbon dioxide concentrations from diver’s respiration were measured before and after the immersion to 8 m depth in the Black Sea. The ethylene gas (for oxidative stress condition), the ammonia gas (for proteins degradation) and the carbon dioxide gas from the respiration of the six divers, were evaluated by mean of the breath test using infrared laser absorption spectroscopy. The experimental results for each breath test of scuba divers will be presented and discussed.
Phase no. 49
Responsible: Dr. C. Gheorghe
Title: "Cercetări privind soluții avansate pentru realizarea de surse coerente de fotoni bazate pe ionii Pr3+ si Pr3+-Yb3+ cu emisie in vizibil. Procese de conversie superioara in fosfori de tip perovskit dopati cu Er3+ si Yb3+"
Abstract: I. Spectroscopic investigations of Pr3+ and Pr3+-Yb3+ ions in Ca3(Nb,Ga)5O12 (CNGG) as monocrystals and ceramics were performed for evaluation as laser and phosphorus materials for visible emissions. Pr: CNGG and Pr-Yb: CNGG monocrystals were grown by the Czochralski method and the ceramic samples were obtained by the solid-state reaction method. All samples were characterized by X-ray diffraction and optical spectroscopy. For CNGG crystal: Pr (1.8 at%) were calculated the emission cross-sectictions for various transitions in the visible field and the largest value was 1.9×10-19 cm2 at 656 nm corresponding to the 3P0 → 3F2 transition, which recommends this material as a potential laser materials in the red domain; Energy transfer processes in CNGG ceramic samples co-doped with Pr, Yb ions were also investigated. CIE chromaticy diagrams of the emission spectra corresponding to Pr3+ ions obtained from different excitation wavelengths were made. It has been observed that depending on the excitation wavelength and the concentration of Yb3+ ions, the CIE coordinates move in red, blue and green region. These changes in color coordinates demonstrates that CNGG: Pr -Yb systems can be adjusted by controlling the concentration of Yb3+ ions as well as the pumping source.
II. Perovskite type LaAlO3 and SrTiO3 ceramics co-doped with Er3+-Yb3+ ions were investigated for evaluation as phosphors in the visible range. LaAlO3 and SrTiO3 ceramics co-doped with Er:Yb ions with different ions concentrations were obtained by two synthesis methods: solid state reaction and sol-gel. The obtained materials were investigated by X-ray diffraction. The diffractograms showed that the LaAlO3: Er: Yb and SrTiO3: Er: Yb phosphors, sintered by both methods, are well crystallized indicating the LaAlO3 and SrTiO3 phases, respectively. The LaAlO3: Er: Yb and SrTiO3: Er: Yb phosphors were characterized by optical spectroscopy (diffuse reflectance and luminescence). Thus, by up-conversion proccesses under 973 nm excitation, visible luminescence in red (660 nm, 4F9/2 → 4I15/2), green (550 nm, (2H11/2,4S3/2) → 4I15/2), violet (408 nm, 2H9/2→4I15/2) and ultraviolet (380 nm, 4G11/2→4I15/2) were observed. The most efficient luminescence was in green domain. Experiments have shown that the phosphors obtained by the sol-gel method are more efficient than phosphors obtained by solid state reaction and LaAlO3 phosphor doped with Er3+(1%) and Yb3+(3%) is more efficient than SrTiO3 doped with Er3+(1%) and Yb3+(3%). The obtained results recommends LaAlO3:Er3+:Yb3+ as efficient phosphors by upconversion processes for visible applications.
Phase no. 50
Responsible: Dr. C. Porosnicu
Title: "Caracterizarea retentiei de He in filmele de W, Fe respectiv Cr co-depuse prin tehnologia HiPIMSS"
Abstract: A key factor for the development of thermonuclear fusion reactors are the materials that compose the components exposed to plasma. These components have the role of protecting the structure of the reaction chamber and other sub-components (as coils) from the negative effects of the plasma-wall interaction. EUROFER (9Cr-1W) is the reference structural material for future DEMO reactors and the ITER test module.
The objective of this phase was to study the optimal conditions for the deposition of thin films with tungsten, chromium and iron content and helium as gas inclusions. Thin layers of these materials were obtained by depositions using the HiPIMS (High Power Impuse Magnetron Sputtering) method. All films were studied from a morphological, structural, compositional point of view, as well as from the perspective of characterizing the helium retention mechanism in these materials as a model for nuclear fuel retention during the operation of the fusion reactor.
The Cr-W, W-Fe and Cr-Fe films obtained by using the HiPIMS method in the Ar-He atmosphere were morphologically analyzed by scanning electron microscopy and compositionally by X-ray fluorescence. This study was mainly focused on investigating the He-release behavior of the obtained structures. thermal desoprtoion spectroscopy measurements were then performed to determine the deuterium inventory in the samples. The Cr-Fe structures co-deposited in the Ar + He atmosphere showed a high uniformity of the resulting films while for thin films with W content, surface structures with hemisphere fetures of 280 nm average size were highlighted. He desorption from the analyzed structures has characteristics similar to the release of noble metal gases over wide temperature ranges. He desorption at low temperature was attributed to the release from low energy traps.
Phase no. 51
Responsible: Dr. A. Petris
Title: "Răspunsul neliniar de ordinul trei al unor probe semiconductoare structurate sub-lungimea de undă"
Abstract: The semiconductor materials with high transparency in different spectral domains, which present significant modifications of the optical properties induced by laser radiation are used in photonic functionalities of waveguiding, switching, limiting, data storage, generation, optical sensing with applications in optical communications, energy saving, security, space science, etc.
The micro- and nano-structuring of photonic materials allow, under certain conditions, the control of light - structured material interaction by the modification of their linear optical properties, the confinement of electromagnetic field, the selective spatial and spectral propagation that can lead to an enhancement of the nonlinear optical response with many applications in photonics. The study of ultrafast nonlinear processes generated by ultrashort laser pulses in subwavelength structured materials is important from the fundamental point of view and also for applications in photonic functionalities.
Silicon (Si), the dominant material in microelectronics industry, has become in the last decade, the most important technological platform for photonic circuits. The succes of the Si platform is particularly based on silicon-to-insulator (SOI) technology and on the implementation of SOI wafers for integrated photonic circuits and for integration of electronics with photonics, taking the advantage of the high investments in the electronics industry.
We developed a theoretical analysis and an experimental study regarding the influence of the subwavelength structuring on the efficiency of the ultrafast nonlinear response, of electronic origin, specific to the third harmonic generation in SOI and in periodically structured, at a subwavelength scale, SOI samples. The third harmonic generation is obtained using ultrashort laser pulses (~120fs) at 1550nm wavelength, important to photonic functionalities with applications to optical communications.
The theoretical analysis addressed particularly the effective refractive index of the investigated subwavelenght structures, considered as homogenous composite media, and its influence on the efficiency of the generation of the third harmonic as well as, on a qualitative level, on the possible confinement of the electromagnetic field in the elements of the investigated subwavelength structures.
The experiments on the third harmonic generation have proved the enhancement of the nonlinear optical response (the efficiency of third harmonic generation) in SOI and, especially in nano-structured SOI, face to bulk Si, and have allowed the determination of some parameters that describe the nonlinearity of the ultrafast optical response of the studied subwavelength structured semiconductor materials, at a laser wavelength important in optical communications.
Phase no. 52
Responsible: Dr. S. Irimiciuc
Title: "Evaluarea produsilor stresului oxidativ utilizand testele de respiratie"
Abstract: In the framework of the project we build upon our aim to develop new research directions based on plasma diagnostics in the INFLPR. Specifically, we focused on the implementation of a plasma investigations and monitorization technique through optical non-invasive technique. We started by investigating the dynamics of transient plasmas generated by nanosecond lasers on metallic targets in expansion geometries similar to those used in pulsed laser deposition (PLD). The implementation of such a technique it is absolutely necessary, especially in the view of transitioning the PLD from an experimental technique to an industrial one. The monitoring of the PLD processes has a dual role: one is to investigate the fundamental aspect of transient plasmas and their chemistry during the deposition process and another is to tailor the deposition and offer feedback during the overall process. The ICCD fast camera imaging technique was implemented in various deposition geometries, by changing he target-substrate distance, and various pressure conditions in order to influence the energy of the ejected particles. The performed analysis revealed the presence of two or three plasma structure, depending on the experimental conditions, which are induced by the nature of the ejection mechanism (electrostatic or thermal). By changing the deposition geometry, we could induce significant changes in plasma structure and overall shape of the plasma which is a result of the confinement in the axial expansion direction and it can lead to a plasma reflection at the substrate. These phenomena can strongly affect the quality and structure of the deposited film and it can be of great importance in the tailoring of new emerging technologies based on PLD. The position of the substrate can also influence the kinetics of the plasma. We observe that if we increase the target-substrate distance, the values of the expansion velocities for each of the observed structures, regardless of the background pressure, are asymptotically reaching the “free expansion” velocity. The implementation of such non-invasive techniques can bring multiple benefits and offer fast feedback during the deposition process, however it is the first step in controlling the deposition process as in order to understand some of the phenomena involved we need to look in spectra resolved measurements and a more in-depth analysis of the chemistry inside de plasma volume.
Phase no. 53
Responsible: Dr. V. Dinca
Title: "Dezvoltarea de bio-platforme specific/localizat functionalizate pentru studiul asupra celulelor mamaliene -obtinerea si analiza morfologica si structurala de substraturi structurate prin MAPLE si/sau prin transfer indus cu laserul –LIFT"
Abstract: The use of synthetic biodegradable polymers as versatile materials with well-defined physico-chemical, biological, biomechanical and degradability characteristics is of interest in the fields of medicine and beyond. For example, for medical implants, the surface is often covered / functionalized with coatings to which biomolecules or cells can adhere better, or which may include and release active substances with specific functionalities (antimicrobial, antitumor, osteogenesis stimulants, etc.). Among the methods used to obtain thin films and or localized structures for advanced applications in various fields, such as medicine, pharmacy, electronics, optics, mechanics, sensors, etc., laser methods have proven to be useful tools in surface processing for obtaining bio-interfaces with controlled properties, from topographic models of natural and synthetic polymeric surfaces to simple or complex coatings for studies related to the interaction between cell and substrate. For example, the use of MAPLE and LIFT techniques for obtaining both multifunctional coatings and for the transfer with localized and high spatial resolution of many types of functional organic and inorganic, biological or synthetic materials on substrates has proven to be an effective method in various fields (electronics, sensors, surface biofunction). In this phase, the PLCL-PEG-PLCL multiblock copolymer was used both to obtain coatings with optimized characteristics (by MAPLE technique) and to obtain localized polymer pixels (by LIFT technique). Their morphological characteristics and roughness were modified by varying the concentration of the target material, the number of pulses and the laser fluence and the properties of the coatings were characterized in relation to the deposition parameters and the preliminary behavior of osteoblastic cells on the optimized coatings.
Phase no. 54a
Responsible: Dr. F. Sima
Title: "Dispozitiv lab-on-a-chip cu dimensiuni nanometrice fabricat in sticla prin tehnologii laser substractive (partea I)"
Abstract: Micro- and nano-scale emerging technologies for biomaterial processing offer multiple possibilities to manufacture microfluidic devices with increased spatial resolution that allow testing biochemical reactions in nanoliter volumes. Herein we present the fast 3D fabrication in glass by picosecond (ps) laser assisted etching (PLAE) of a compact, large area, microfluidic systems with scale up-scale-down characteristics. These are consisting of open microreservoirs connected through embedded channels. The process consists of laser irradiation (Nd:YVO4, λ=532 nm, τ<10ps) followed by thermal treatment and wet chemical etching of photosensitive glasses and allows fabricating 3D embedded micro-channels, with high precision, down to micrometric sizes. A second thermal treatment is herein proposed for downsizing channel dimensions as well as for the improvement of optical and morphological quality of glass surface processed by PLAE. By tailoring the temperature and treatment time interval, very smooth, defect free, with roughness down to few nanometers were achieved for glass processed surfaces.
Phase no. 55
Responsible: Dr. O. Toma
Title: "Transferul de energie in materiale oxidice cu fononi de energie mica pentru fosfori in domeniul vizibil. Ceramici sesquioxidice codopate cu ioni de pamanturi rare pentru emisie laser in domeniul vizibil"
Abstract: Transparent ceramic Y2O3 samples doped with lanthanide trivalent ion pairs (Yb3+,Er3+) and (Nd3+,Er3+) were synthesized by solid-state reaction. The obtained samples are characterized by a very good optical quality, adequate for laser emission. The energy transfer between the co-doping lanthanide ions was put into evidence as the main up-conversion excitation mechanism for the Er3+ luminescence emission in visible.
Phase no. 56
Responsible: Dr. C. Surdu-Bob
Title: "Explorarea posibilitatii de utilizare a filmelor cu continut de nitrura de carbon precum si optimizarea acestora pentru noi senzori optici, dispozitive fotocatalitice sau LED-uri"
Abstract: This work targeted research on the prospective application of thin films with carbon nitride content (deposited using the C-HVAP plasma source) for optical properties and applications in senzor or other electronic components. The research focused on humidity, methane and carbon oxide sensing.
The sensing capacity of the materials were tested using in-house built equipment.
Two types of senzors were developed: on organic and also on anorganic substrates.
The experimental results showed that our thin films with carbon nitride content have sensing capacity for humidity and methane gase, respectively, at room temperature. It is worth mentioning that the curve of humidity sensor had a fast response. The response curve of the methane gas sensor had also been fast, with an instantaneous response. The sensitivity of the sensor is extremely high, the sensor being able to sense methane gas concentartions as low as 10 ppm.
Future research could envisage further development of humidity and methane sensors, respectively, with the aim of testing specificity and the optimal ambiental conditions for smooth functioning and accurate detection.
Phase no. 57
Responsible: Dr. T. Craciunescu
Title: "Metode de segmentare de tip semantic a imaginilor provenite din reconstructii tomografice (retele neuronale convolutionale, retele cu codare-decodare)"
Abstract: TNondestructive X‐ray computed tomography (CT) is able to produce high‐resolution, three‐dimensional representations of pore structure within porous materials. In order to use of this information for various theoretical and practical applications to fluids, at the pore scale, image segmentation is a crucial step. Various thresholding and locally adaptive segmentation techniques have been proposed in industrial and synchrotron X‐ray CT images of natural and artificial porous media. Recently deep convolutional neural networks have emerged as an efficient solution for this problem. In the present work a Un-net network is used the segmentation of samples related to oil industry. The samples have been measured using the X-ray micro-tomography facility at INFLPR (tomography.inflpr.ro) which comprises an Microfocus X-ray source, a flat panel Varex PerkinElmer (2048x2048 pixeli) and a sample micrometric manipulator. The structure of the samples has been numerically simulated in order to generate the training set for the network, avoiding in this way time and costly measurements for establishing a comprehensive training set for the ‘U-net’ network. It is shown that this novel strategy is able to provide very good segmentation.
Phase no. 58
Responsible: Dr. M. Nemtanu
Title: "Impactul sinergetic de tratamente fizice combinate asupra comportamentului reologic al amidonului"
Abstract: The aim of the work was to evaluate the possibility of combining the electron beam irradiation EBI with plasma treatment PT (corona electrical discharges - CED or radio-frequency plasma - RF) for modification of native starch, highlighting a synergistic effect of these combined treatments on the rheological behavior of starch. At the same time, the analysis and mathematical modeling of the “dose-effect” evolution were performed from the perspective of the apparent viscosity of the starch modified by studied treatments.
The joint action of EBI and PT caused changes in the native starch properties for the same irradiation dose compared to the single EBI. Thus, the study focused on investigating and evaluating of starch rheological behavior, especially the apparent viscosity, and synergistic effect of the combined treatments applied to modify the native starch compared to EBI.
The apparent viscosity was affected after EBI as well as after the application of combined treatments, but following different exponential decrease patterns. Thus, the corresponding mathematical models for the evolution of the apparent viscosity with the irradiation dose for each investigated treatment were developed. Based on these models, several parameters were estimated: the specific EBI dose of the native starch (DEBI), the specific irradiation dose for the fraction (f) affected by plasma (D) in the case of PT/EBI, the characteristic response dose of the irradiated starch, from the fraction (f) affected by plasma (DEBI) in the case of EBI/PT, and the fraction (f) of the starch granule affected by plasma.
All doses obtained for combined treatments showed significantly lower values compared to the characteristic average dose of native starch irradiated with electron beam. The different values obtained for the characteristic irradiation dose and fraction (f) affected by plasma, in the case of combined treatments, suggest that RF plasma causes a higher sensitization of starch to EBI than CED. Once irradiated native starch responds relatively similarly to plasma exposure, regardless of its type.
The synergistic ratio SR for each EBI dose in conjunction with PT, regardless of their sequence of application, showed that combined treatments resulted in a synergistic effect. Plasma pretreatment of starch exposed then to EBI has also been shown to be more effective in decreasing the apparent viscosity of maize starch than EBI and combined EBI/PT, using a lower irradiation dose than in the irradiation cases with electron beam or even EBI/PT, to obtain the same effect on the apparent viscosity.
Phase no. 59
Responsible: Dr. B. Mitu
Title: "Realizarea prin tehnici cu plasma a unor structuri periodice relevante pentru aplicații în microaccelerare și caracterizarea acestora"
Abstract: The present stage of the project highlights the processing capabilities of low pressure reactive plasmas for obtaining periodic structures with relevance for electron microacceleration. Silica spheres of approximately 522 nm diameter were synthesized by Stober method, and, for comparison, commercially available polystyrene beads of 400 nm diameter were purchased. They were subsequently self-assembled by spin coating in monolayer structures with controlled periodicity. The obtained results highlight the possibility of controlled etching of the spheres, if the proper reactive plasma atmosphere is used, thus generating masks based on colloidal lithography. Moreover, by further etching of the substrate, under specific conditions, pillars can be obtained in the substrate, maintaining the desired dimensionality and their ordering, induced by the processed mask. Mathematical processing techniques for Fourier transforming of the images resulted upon Scanning Electron Microscopy and Atomic Force Microscopy investigations complement those of experimental investigation of structures and support the obtained results. In addition, we also proved the possibility of obtaining ordered honeycomb structures by covering the mask with metallic layers followed by the removal of masks used for processing.