Soda-silica and soda-lime-silica glasses have been irradiated with protons of energy 600 keV at different fluences and total charges. The Na concentration profiles have been obtained by using a specific nuclear reaction, before and after... more
Soda-silica and soda-lime-silica glasses have been irradiated with protons of energy 600 keV at different fluences and total charges. The Na concentration profiles have been obtained by using a specific nuclear reaction, before and after the proton irradiations. The experimental results have been explained on the basis of a field-assisted migration process. A quantitative analysis has been accomplished by numerical
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Research Interests: Materials Engineering, Condensed Matter Physics, Materials Science, FTIR spectroscopy, Raman Spectroscopy, and 9 morePulsed Laser Deposition, Diamond Like Carbon, Nitrogen, Structure Analysis, Surface and Coatings Technology, Raman Spectra, Fourier transform infrared, Mechanical Property, and pulsed laser ablation
High dose implanted Cu and Pb profiles show considerable rearrangement after Q-switched ruby laser pulse irradiation, when observed using 1.6 MeV He Rutherford backscattering.Cu rearranged profiles may be interpreted as due to a Cu atom... more
High dose implanted Cu and Pb profiles show considerable rearrangement after Q-switched ruby laser pulse irradiation, when observed using 1.6 MeV He Rutherford backscattering.Cu rearranged profiles may be interpreted as due to a Cu atom diffusion into a liquid Aluminum phase (under a condition of constant concentration at the side of the implanted profile toward the bulk of the sample).
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ABSTRACT In this work we have implanted at various fluences silicon carbide (SiC) thin films deposited on AISI 316L stainless steel and oxygen-free high conductivity copper. It was observed that the improvements in the mechanical... more
ABSTRACT In this work we have implanted at various fluences silicon carbide (SiC) thin films deposited on AISI 316L stainless steel and oxygen-free high conductivity copper. It was observed that the improvements in the mechanical properties depend strongly on the ion fluence as well as on the ion species (Ar+, N+). High Ar+ fluence leads, by ion beam mixing, to the formation of a brittle Fe-Si interlayer which is deleterious with regard to the mechanical properties, as determined by scratch resistance tests. However, N+ implantation of SiC films can result in the formation of silicon carbonitrides and in particular the interface zone can be converted to iron-chromium nitrides. These composite multilayer structures on steel are suitable for obtaining surfaces with the optimum adhesion, friction and wear resistance properties.
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Soda-lime glasses have been irradiated with protons of 600 keV energy at different fluences. The surface temperature increments have been measured as a function of irradiation time by analysing the emission of infrared radiation. The... more
Soda-lime glasses have been irradiated with protons of 600 keV energy at different fluences. The surface temperature increments have been measured as a function of irradiation time by analysing the emission of infrared radiation. The experimental results have been compared with a theoretical model. The alkali migration processes in glasses during irradiation with low-mass particles, reported in previous papers, have been revised to take into consideration an enhanced diffusion coefficient.
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This work reports on Ar+-implantation effects on structure, compositional and mechanical properties of the WC/Ti-6Al-4V system interface. The WC films were deposited by r.f. magnetron sputtering on Ti-6Al-4V substrates and then implanted... more
This work reports on Ar+-implantation effects on structure, compositional and mechanical properties of the WC/Ti-6Al-4V system interface. The WC films were deposited by r.f. magnetron sputtering on Ti-6Al-4V substrates and then implanted at the film-substrate interface with Ar+ ions at 160 keV. Two parameters have been varied in the implantations: the ion dose, Φ (Φ varying in the 1 ×
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Research Interests: Geochemistry, Materials Science, Chemistry, Diffusion, Alkali Metals, and 13 moreIon Implantation, Temperature Dependence, Silicate Glass, Elastic Scattering, Radiation Effect, Ion, Irradiation, Interdisciplinary Engineering, Silicate, Liquid Nitrogen, PHENOMENOLOGICAL MODEL, Charged Particles, and Heavy Ions
We report on a study of the electronic, chemical and lattice structure of carbon films and of the microstructural modifications induced by 0953-8984/9/8/007/img10 implantation. Correlations were made with the new mechanical properties of... more
We report on a study of the electronic, chemical and lattice structure of carbon films and of the microstructural modifications induced by 0953-8984/9/8/007/img10 implantation. Correlations were made with the new mechanical properties of the implanted films. The C films were r.f. magnetron sputtered from a graphite target with Ar discharge. 0953-8984/9/8/007/img10 implantations were performed with energies ranging from 30 to
Research Interests: Materials Engineering, Condensed Matter Physics, Materials Science, Microstructure, Nanotechnology, and 10 moreMagnetron Sputtering, Ion Implantation, Microstructures, Chemical Properties, Raman Scattering, X Ray Photoelectron Spectroscopy, Hard Anodizing Coating, Biochemistry and cell biology, Ion Irradiation, and Mechanical Property
Coupled continuity equations for silver-atom and vacancy fluxes are solved to obtain theoretical fits to the Ag Auger profiles in Ag-Ni layered systems, measured at different temperatures. It is observed that silver atoms are trapped by... more
Coupled continuity equations for silver-atom and vacancy fluxes are solved to obtain theoretical fits to the Ag Auger profiles in Ag-Ni layered systems, measured at different temperatures. It is observed that silver atoms are trapped by vacancies at higher temperatures. This phenomenon sharpens the Ag profile measured at 603 K. It is argued that this sharpening of Ag profile at
Research Interests: Materials Engineering, Condensed Matter Physics, Materials Science, Chemistry, Nanotechnology, and 13 moreIon beam irradiation for material modification, Diffusion, Theoretical Condensed Matter Physics, Activation Energy, Nickel, Ion Implantation, Crystal Defects, Vacancy Defect, Sharpening, Continuity Equation, transport process, radiation induced segregation, and Radiation enhanced diffusion
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Abstract The ionic conductivity in single-alkali aluminosilicate glasses has been analyzed on the basis of a previously published empirical relation derived for binary alkali silicate glasses. Moreover ionic conductivity in mixed-alkali... more
Abstract The ionic conductivity in single-alkali aluminosilicate glasses has been analyzed on the basis of a previously published empirical relation derived for binary alkali silicate glasses. Moreover ionic conductivity in mixed-alkali aluminosilicate glasses has been analyzed on the basis of a previously published phenomenological model derived from the thermodynamics of irreversible processes. Some features of the microscopic structure of aluminosilicate glasses and their connection to transport phenomena have been emphasized. Some aspects of the mixed-alkali effect for ionic conductivity have been revised for low alkali concentration silicate glasses.
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Previously reported experimental results on time evolution of Si/Pt profiles during Ar ion implantation have been analyzed on the basis of a theoretical model which accounts for the preferential sputtering and enhanced diffusion of Si... more
Previously reported experimental results on time evolution of Si/Pt profiles during Ar ion implantation have been analyzed on the basis of a theoretical model which accounts for the preferential sputtering and enhanced diffusion of Si atoms. Si sputtering yield reflects the energy dependence of the Ar nuclear stopping power at the SiPt mobile surface. Comparison with experimental results on metallic and dielectric systems has been performed in order to clarify the mechanism which induces the enhanced diffusion process.
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We present tables of the differential, total, and transport cross sections for the elastic scattering of 500–4000 eV positrons by neutral atoms in the atomic number rangeZ= 1–92. The cross sections were computed by numerically solving the... more
We present tables of the differential, total, and transport cross sections for the elastic scattering of 500–4000 eV positrons by neutral atoms in the atomic number rangeZ= 1–92. The cross sections were computed by numerically solving the Dirac equation for a central electrostatic field up to a large radius where the atomic potential becomes negligible. The atomic potential used was Hartree–Fock forZ= 1–18 and Dirac–Hartree–Fock–Slater forZ= 19–92.
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Research Interests: Materials Science, Hydrogen, Multidisciplinary, Graphite, Nitrogen, and 11 moreSputtering, Room Temperature, Electrical Properties, Microstructures, Elastic Properties, X Ray Photoelectron Spectroscopy, Rf-Magnetron Sputtering, Sputter Deposition, Reactive Sputtering, Electric Conductivity, and Dynamic Behaviour
ABSTRACT Carbon-supported palladium thin films were synthesized at room temperature by KrF excimer pulsed laser deposition by using oriented pyrolytic graphite and Pd target. By changing the experimental conditions, a range of structures,... more
ABSTRACT Carbon-supported palladium thin films were synthesized at room temperature by KrF excimer pulsed laser deposition by using oriented pyrolytic graphite and Pd target. By changing the experimental conditions, a range of structures, from smooth to porous cluster-assembled carbon films were obtained prior to deposition of the Pd films. High amount of sp 2 coordinated graphitic carbon embedded with large degree of disorder is observed in these carbon films. Surface morphology was studied by using scanning electron microscopy, while compositional analysis was performed by using energy dispersive spectroscopy. Structural analysis was performed using Raman spectroscopy and Fourier transform infrared spectroscopy. The importance of morphology and chemical structure of carbon films on their catalytic activity was investigated by using the hydrolysis of aqueous NaBH 4 as a reference process. Pd/C film produced by pulsed laser deposition are here demonstrated to be a better catalyst than Pd/C powder because of the high content of sp 2 bonding carbon atoms arranged into the porous and irregular surface of the carbon film. # 2007 Elsevier B.V. All rights reserved.
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Mg films with mixed Fe and Zr metallic additives were prepared by rf magnetron sputtering keeping the total metal content constant, about 7 at. %, and changing the [Fe]/[Zr] ratio. Isothermal hydrogen desorption curves showed that the... more
Mg films with mixed Fe and Zr metallic additives were prepared by rf magnetron sputtering keeping the total metal content constant, about 7 at. %, and changing the [Fe]/[Zr] ratio. Isothermal hydrogen desorption curves showed that the kinetics depends on [Fe]/[Zr] ratio and is fastest when the [Fe]/[Zr] ratio is ∼1.8. X-ray diffraction analysis revealed formation of Fe nanoclusters and Mg grain refinement. The improvement of the hydrogen desorption kinetics can be explained by the presence of atomically dispersed Zr and Fe nanoclusters acting as nucleation centers, as well as Mg grain refinement.
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Amorphous a-SiC films were deposited by rf magnetron sputtering on stainless steel and N+ implantations were performed at room temperature over a fluence range of 1×1016–1×1017 ions/cm2 at 30 and 160 keV. Chemical characterization of the... more
Amorphous a-SiC films were deposited by rf magnetron sputtering on stainless steel and N+ implantations were performed at room temperature over a fluence range of 1×1016–1×1017 ions/cm2 at 30 and 160 keV. Chemical characterization of the a-SiC/steel interface and compositional depth profiles were obtained by Auger electron spectroscopy. Adhesion properties of the films were examined using a scratch tester in conjunction with scanning electron microscopy. A strong adhesion enhancement (about a factor of eight) along with an improvement of the fracture toughness were observed in the implanted a-SiC/steel specimens. The key mechanisms envisaged to explain the enhanced adhesion is mainly related to the new chemical bondings, involving C and N in Si—(N,C)—Cr complexes formation at the a-SiC/steel interface.
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Various studies on ion-beam mixing suggest that the extent of mixing is sensitive to the sign and magnitude of the heat of mixing, ΔHm. This implies a role, not only for random motion, but also for chemical driving forces of the type... more
Various studies on ion-beam mixing suggest that the extent of mixing is sensitive to the sign and magnitude of the heat of mixing, ΔHm. This implies a role, not only for random motion, but also for chemical driving forces of the type where the total diffusion flux is modified by the factor [1−αi(1−αi) 2hmp/RT(1+p)]. Here α1 is the atomic fraction of component i, αi(1−αi)hm is the heat of mixing of a regular solution, and p is the ratio of the diffusivities for chemically guided defect motion to those for random motion of all types. The parameter p has never been evaluated for any system and we wish to evaluate it first by analyzing the profiling experiments of Marton, Fine, and Chambers on multilayers of Ni-Ag. We then obtain further values of p from ion-beam mixing experiments on bilayers and multilayers. It is shown that it is possible to understand a variety of experimental results relating to profiling and to ion-beam mixing in terms of chemical driving forces and, moreover, to ...
Research Interests: Engineering, Physics, Chemistry, Physical sciences, Thermal, and 3 moreIon, Ion Beam, and Ion beam mixing
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With this wide spread of applications, earth-abundant photocatalysts are attracting extensive interest, especially based on anatase TiO2 due to its abundance, 6–8 and low toxicity.5,9 Due to its wide bandgap at 3.2 eV, however, it is not... more
With this wide spread of applications, earth-abundant photocatalysts are attracting extensive interest, especially based on anatase TiO2 due to its abundance, 6–8 and low toxicity.5,9 Due to its wide bandgap at 3.2 eV, however, it is not a good absorber in the visible range. Viable routes to extend its absorption include doping with transition metals to induce defect states in the lattice and tune the bandgap towards the visible.
Previously reported experimental results on Na depletion in the surface region of 50 keV Ar-implanted soda-lime silica glass have been interpreted on the basis of preferential sputtering of Na. A phenomenological model which accounts for... more
Previously reported experimental results on Na depletion in the surface region of 50 keV Ar-implanted soda-lime silica glass have been interpreted on the basis of preferential sputtering of Na. A phenomenological model which accounts for the preferential ejection of Na atoms from the surface, and for the enhanced diffusion over the range of Ar, explains the experimental data very well. The model is also consistent with experimental results obtained in other laboratories.
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ABSTRACTThis work presents the first results of a study aimed at better understanding the elastic behaviour of hard coatings produced by various techniques. This is important also in view of the need to be able to control the level of... more
ABSTRACTThis work presents the first results of a study aimed at better understanding the elastic behaviour of hard coatings produced by various techniques. This is important also in view of the need to be able to control the level of internal stresses, particularly in PVD coatings. It is well known that in extreme cases excessive internal stress can lead to complete film destruction. We devote this paper to reactively magnetron sputtered TiN, one of the most widely used compounds. Thin TiN films of different compositions were deposited on Si substrates and characterized by SEM, AES, XRD and Brillouin light scattering.
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A general description of the thermal noise in a SQUID, without limits in the choice of the physical parameters is presented. The central point of the numerical integration of Fokker-Planck equation in the theoretical analysis of the... more
A general description of the thermal noise in a SQUID, without limits in the choice of the physical parameters is presented. The central point of the numerical integration of Fokker-Planck equation in the theoretical analysis of the thermal noise is performed in this work. Indicative numerical solutions are presented.
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ABSTRACT Pulsed laser deposition (PLD) is a versatile technique to synthesize films of a given material with strongly different properties. In this chapter we discuss the microstructure and structure of carbon films ranging from... more
ABSTRACT Pulsed laser deposition (PLD) is a versatile technique to synthesize films of a given material with strongly different properties. In this chapter we discuss the microstructure and structure of carbon films ranging from diamond-like carbon to tetrahedral amorphous carbon, to nanometer-sized cluster assembled films, depending on PLD process parameters. All films are hydrogen-free, as shown by FTIR spectroscopy, and result invariably structurally disordered. Carbon local hybridisation was checked by Raman spectroscopy, both visible and UV. Vacuum deposited films undergo a transition from mainly disordered graphitic to up to 80% tetrahedral amorphous carbon above a threshold laser energy density. The microstructure and morphology of the deposited films were studied in a complementary way by SEM and AFM. All vacuum deposited films appear featureless. Cluster assembled glass-like films display different growth modes, mainly depending on the deposited energy per laser pulse and nature-pressure of the ambient gas. Film morphology is correlated with the ballistic mechanisms that occur when plasma plume constituents interact with ambient gas atoms. Cluster formation in the plume is modelled, and we estimate the average number of atoms per cluster. Model predictions agree with cluster sizes deduced by Raman spectroscopy and observed by TEM imaging. ch:OssiMiotello Ossi-begin
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The characteristic times and lengths involved in the problem of heat flow through a semiinfinite Al sample irradiated with nanosecond laser pulses are discussed with reference both to the underlying physics and to the numerical solution... more
The characteristic times and lengths involved in the problem of heat flow through a semiinfinite Al sample irradiated with nanosecond laser pulses are discussed with reference both to the underlying physics and to the numerical solution of heat diffusion equation. Laser pulse energies allow sample melting, but no vaporization. The numerical solution proceeds via subdividing the sample into layers of
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The use of polymeric materials is often limited by low hardness, poor wear resistance and wettability considerations. The area of mechanical changes caused by ion beam treatments has been explored only to a limited extent for polymers... more
The use of polymeric materials is often limited by low hardness, poor wear resistance and wettability considerations. The area of mechanical changes caused by ion beam treatments has been explored only to a limited extent for polymers despite their growing usage in automotive, biomedical and aerospace applications, in which traditionally metals have been used.Polycarbonate (PC) specimens were subjected to medium–high
Research Interests: Materials Engineering, Condensed Matter Physics, Materials Science, Polymer, Surface modification, and 15 moreNitrogen, Composite Material, Ion Implantation, Surface and Coatings Technology, Ion, Irradiation, Surface Properties, Three Dimensional, Elastic Modulus, Ion Beam, Wear resistance, Ion Beam Assisted Deposition, High energy, Ion Irradiation, and ion bombardment
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ABSTRACT Carbon films have been synthesized on (100) Si substrates at room temperature by KrF Excimer Pulsed Laser Deposition (PLD) of highly oriented pyrolitic graphite. Changing laser power density (from 0.5 to 19 MW mm−2) and ambient... more
ABSTRACT Carbon films have been synthesized on (100) Si substrates at room temperature by KrF Excimer Pulsed Laser Deposition (PLD) of highly oriented pyrolitic graphite. Changing laser power density (from 0.5 to 19 MW mm−2) and ambient conditions (vacuum; molecular nitrogen at 1 Pa; helium, from 0.6 Pa to 2 kPa), a range of structures and microstructures, from DLC to nanosized cluster assembled (CA) films were obtained. The microstructure and morphology of the films were studied by Scanning Electron Microscopy. The surface of all films deposited in vacuum and in nitrogen appears uniform, flat, featureless. In CA films, the nature-pressure of ambient gas and the energy deposited by each laser pulse determine threshold fluences of increasing value. These correspond to the sequence of dense columns, followed by nodule-like morphology and by an open dendritic structure. Atomic Force Microscopy on several CA films allowed to estimate the size distribution and relative abundancies of aggregates of carbon clusters. Film morphology is correlated with the ballistic mechanisms that occur when the plasma plume constituents interact with ambient gas atoms. For all films, local carbon coordination was studied by visible Raman spectroscopy. UV Raman spectra were collected for vacuum- and nitrogen-deposited films. The films are hydrogen-free, as shown by Fourier Transform Infra-Red spectroscopy, and result invariably structurally disordered. Vacuum-deposited films undergo a transition from mainly disordered graphitic to up to 80% tetrahedral amorphous carbon (ta-C) above a threshold power density. Transmission Electron Energy Loss spectra on selected samples confirmed ta-C formation. The same transition is absent in films deposited in N2 atmosphere. All CA films are structurally disordered, sp2 coordinated, and belong to the family of carbon nanoglasses. The mechanisms underlying the graphite to ta-C transition are discussed with reference to the different atmospheres.
Research Interests: Engineering, Materials Science, Chemistry, Microstructure, Carbon, and 15 moreMorphology, Atomic Force Microscopy, Clusters, Pulsed Laser Deposition, Physical sciences, Nanostructures, Nitrogen deposition, Nanostructure, Nitrogen, Cluster, Microstructures, Amorphous carbon, Carbon Fibers, C, and Power Density
Research Interests: Materials Engineering, Condensed Matter Physics, Materials Science, Microstructure, Metallurgy, and 11 moreScanning Electron Microscopy, Sputtering, Magnetron Sputtering, Energy Dispersive X-Ray Analysis, Surface and Coatings Technology, X ray diffraction, Microstructures, Permeation, Sputter Deposition, Carbon Steel, and High Power Impulse Magnetron Sputtering
The effect of nitrogen implantation into pure aluminium has been extensively explored, taking into account the variation of several physical and technological properties of the implanted layer. In particular, the formation of aluminium... more
The effect of nitrogen implantation into pure aluminium has been extensively explored, taking into account the variation of several physical and technological properties of the implanted layer. In particular, the formation of aluminium nitride, which occurs under specific choices of the implantation parameters, is associated with an increase in hardness. In this work, we consider two Al alloys (Al-7075 and
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One of the most important features regarding ion-beam mixing of metals-on-oxides is that discussed recently by McHargue et al. They showed that for metals on Al2O3, ZrO2, YPO4, and Si3N4 the tendency was that mixing would not be expected... more
One of the most important features regarding ion-beam mixing of metals-on-oxides is that discussed recently by McHargue et al. They showed that for metals on Al2O3, ZrO2, YPO4, and Si3N4 the tendency was that mixing would not be expected in most instances using the enthalpy rule and that experimentally one normally observes either no detectable mixing, or what is termed segregation or agglomeration, or only ballistic mixing (the latter, of course, is independent of thermodynamic considerations). A notable exception was metals on SiO2 and SiC. There is thus a fundamental difference from the mixing of metals-on-metals, where there are only very few examples of systems which do not mix, and where the small but universal ballistic component is commonly supplemented by a much larger component due to bombardment-induced residual defects (‘defect-enhanced motion’). By referring to the extensive defect calculations of Catlow, Mackrodt and coauthors it emerges that the motion of the basic defects is significantly different. With all metals the interstitial is mobile at 300 K, while the vacancy is sometimes mobile or, at worst, becomes mobile with only a moderate increase in temperature. Furthermore, such changes as occur at higher temperatures invariably occur in the sense expected. With oxides, however, both cation and anion vacancies typically show motional temperatures exceeding ~600 K. The notable exception is the anion vacancy of LaAlO3, UO2 and cubic-ZrO2. The situation with interstitials is less straightforward. Nevertheless, one of the several conclusions to be reached is that the failure to observe extensive mixing with appropriate metals-on-oxides is due to the lack of a contribution from defect-enhanced motion, this being in turn due to the target temperature being too low. The existence of an activation energy may also be involved with metals-on-oxides, but we are unable to comment on this possibility.
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... of TIN-TIC bilayers deposited on martensitic stainless steel R. Checchetto a, M. Bonelli a, LM Gratton a, A. Miotello a, A. Sabbioni a, L. Guzman b, Y ... iI131 C. Shari, A. Wu, Y. Li, Z. Zhao, Q. Chen, Q. Huang and S. Shi, J. Nucl.... more
... of TIN-TIC bilayers deposited on martensitic stainless steel R. Checchetto a, M. Bonelli a, LM Gratton a, A. Miotello a, A. Sabbioni a, L. Guzman b, Y ... iI131 C. Shari, A. Wu, Y. Li, Z. Zhao, Q. Chen, Q. Huang and S. Shi, J. Nucl. ... Cl51 RW Lee, RC Frank and DE Swets, J. Qertt. ...
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ABSTRACT
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In this paper, we describe the apparatus for pulsed laser deposition of thin solid films that we have developed in our laboratories of Trento University. Our apparatus is original for many of its adopted technical solutions: (i) the... more
In this paper, we describe the apparatus for pulsed laser deposition of thin solid films that we have developed in our laboratories of Trento University. Our apparatus is original for many of its adopted technical solutions: (i) the substrate-manipulator mechanism possesses four degrees of freedom, x, y and z translation and a rotation, which permits one to treat samples with non-planar geometry; (ii) an independent target-handling mechanism moves a circular target with calculated speed profiles which permits a uniform ablation of the target surface to be obtained (normally, laser ablation deposition apparatus uses a beam-bending mechanism and a simple target translation at constant velocity); and (iii) the maximum substrate dimensions can be relatively large, about 85 mm × 85 mm, and, in the case of samples with approximately cylindrical symmetry, by exploiting the rotation, 85 mm × 85 mm × 85 mm.
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... and user-friendly experimental apparatus for the study of the hydrogen storage in metal compounds based on the volumetric technique (Sievert-type apparatus): the ... SC, sample chamber; RC, reservoir chamber; AC, admission chamber;... more
... and user-friendly experimental apparatus for the study of the hydrogen storage in metal compounds based on the volumetric technique (Sievert-type apparatus): the ... SC, sample chamber; RC, reservoir chamber; AC, admission chamber; TC, K-type thermocouple; VLV ...