Pure and mixed films preparation using thermionic vacuum arc method (original contribution) II 1. TVA principle 3. Hard antireflexive diamond like carbon coatings OUTLINE 2. Fusion Energy; Be coatings on Inconel and marker tiles 4. Preparation of Giant Magnetoresistive (GMR) films 6. Tribological coatings 5. High temperature corrosion resistant coatings Substrate TVA – thermionic vacuum arc - principle ~ Hot Cathode Whenelt Cylinder HV Anode Vacuum 10-6 Torr No buffer gas + - Rb Ignition of the TVA plasma cupru 001_0001 cupru 001_0002 cupru 001_0003 cupru 001_0004 cupru 001_0005 cupru 001_0006 cupru 001_0007 cupru 001_0008 cupru 001_0009 cupru 001_0010 cupru 001_0011 cupru 001_0012 Typical arrangement used for the first Be depositions The viewing angle for uniform depositions 20 and 50 degree from the horizontal line. Viewing angle unghi Circular TVA Substrate Cathode Rb + HV - ˜ Anode material IMG_1319 IV-Ag 14 I-V characteristics of the TVA plasma running in Ag vapors for different heating currents THE ADVANTAGES OF THE TVA TECHNOLOGY •the high purity of the layers (high vacuum conditions); •no gas consumption; •the films are growing from the plasma created in the pure vapors of the evaporating material •the formed films are continuously bombarded by the genuine ions and the advantages are: •no gas inclusions •good adherence •the ions energy can be controlled by cathode external heating and anode voltage •the deposition rates = 1 to 10 nm/sec. Fusion Energy: - Climate friendly and yields similar energy production as fission, between 1 and 1.5 gigawatt per plant. - Do not produce highly radioactive waste or potential nuclear weapon material. - Its supplies are nearly unlimited. (Main fuel: H3) 2. Fusion Energy; ITER project ModelA_first_drawing Machine view ITER DEMO PHYSICS PROGRAMME POWER PLANT TECHNOLOGY PROGRAMME Nuclear fusion development JET EFDA-JET homepage: www.efda.org. iter JETSRP-Be-W JET ITER-like wall experiment ITER 100m2 Tungsten • Low erosion • high melting T • Negligible T retention Optimise lifetime & T- retention But high Z & melting 700m2 Beryllium first wall • low Z • Oxygen getter Optimise plasma performance But large erosion & melting 50 m2 Graphite CFC •Lowish Z •No melting in transients •Superior heat shock behaviour Optimise heat flux resistance But large erosion & T retention W CFC JET Image taken from EFDA-JET homepage: www.efda.org. ITER-like wall installed at JET Licensed laboratory to work with beryllium and beryllium containing composites Vacuum deposition system: - stainless steel chamber, - glass, quartz and - germanium windows; - volume; 250 l, - base pressure; 6*10-7 torr - mechanical pump (60 m3/h), - buster pump (200 m3/h), - diffusion pump (3000 l/s) IMG_2414 IMG_2127 Tun TVA cu sageti Be plasma BERILLYUM TVA evaporator and plasma running in pure Be vapors 23_11_2009_Be_SS3_VB430V_50000x Be/St Steel Bias: +430V 21_11_2009_Be_SS1_Ground0_50000x Be/St Steel Bias: 0 V 18_11_2009_Be_inox_VB-285V_50000x 24_11_2009_Be_SS3_VB-750V_50000x Be/St Steel Bias: -285 V Be/St Steel Bias: -750 V 23_11_2009_Be_SS3_VB430V_50000x 21_11_2009_Be_SS1_Ground0_50000x 18_11_2009_Be_inox_VB-285V_50000x 24_11_2009_Be_SS3_VB-750V_50000x Bias: +430 V 0 V -285V -750 V Rotation of Re-exposure of T2_10000x_001 Re-exposure of 24_11_2009_Be_001 Be Marker coated tiles for ILW 30 mm 26 mm Be block for High Heat Flux (HHF) testing with a hole for thermocouple Face to be coated 30 mm 26 mm 20 mm Be coating (7-9 microns) 2-3 microns Ni Tun TVA cu sageti 011020092195 Be plasma IMG_0865 Be plasma Ni plasma IMG_3606 DSCN0510 Ni and Be evaporators Cross-section of Be blocks ModuleAssyStdAXploded IMG_3610 IMG_3643 IMG_3662 IMG_3602 IMG_4155 IMG_4185 PRODUCTION-Run 5/13.05.2010 IMG_4155 (Before Ni+Be deposition) PRODUCTION-Run 5/13.05.2010 IMG_4185 (After Ni+Be deposition) Thermal evaporation in vacuum of Be (Manufacturing of Be / inconel tiles) (in cooperation with NUCLEAR FUEL PLANT (NFP) Mioveni-Pitesti, Romania DSC00007 Schematic arrangement for thermal evaporation in vacuum Photograph of the substrate holder 1000x 5000x Inconel substrate (THERMAL) Stainless steel substrate (TVA) 1000X1 5000X1 Scanning Electron Microscopy, Microscope XL 30 ESEM PHILIPS (1000 x and 5000 x) 1000 5000 5µm 5µm 20µm 20µm SEM images: microstructure of the Be/Inconel coating from TOP surface • Consists of platelets, occasionally hexagonal morphology, which originated from crystallographic structure • Size of platelet ~5 µm SEM image obtained at FZJ Juelich 2 high heat flux (HHF) test schemes: ü(i) screening tests, ü(ii) cyclic heat load tests ü JET requirements: 0.5 MW/m2 for 20 s (10 MJ/m2) (i) Screening tests Aim: determine the allowable energy density limit of the Be coating Tests: energy density of 4 MJ/m2 to 20 MJ/m2, (0.4 MW/m2 to 1.8 MW/m2 for 10 s ; 2.6 MW/m2 for 6.2 s) (ii) Cyclic heat load tests Aim: study the degradation of the Be coatings by thermal fatigue Tests: 50 cycles of 1 MW/m2 in 10 s corresponding to 10 MJ/m2. ü Observation during the high heat flux testing • Surface temperature was monitored with a 10 Hz infra-red (IR) camera • Surface temperature was measured at a black-coloured surface with an emissivity of 0.85. Ø Surface morphology of Be/Inconel (Inconel_2) after 50 thermal cyclic loads at 1 MW/m2, 10 s (10 MJ/m2). After test Before Ø Cross section of Be/Inconel (Inconel_2) after 50 thermal cyclic loads at 1 MW/m2, 10 s (10 MJ/m2). Eutectic alloy formation DSC00398 DSC00368 DSC00110 DSC00378 PRODUCTION OF BERYLLIUM COATED INCONEL TILES •Thermionic vacuum arc (TVA) method developed at the National Institute for Laser, Plasma and Radiation, Bucharest, Romania, was used for: •Optimization of deposition of pure films: 2-3 µm Ni, 7-9 µm Be •Preparation of marker tiles: test samples, test coupons, qualification of the deposition method, pre-production run, production runs •Thermal evaporation in vacuum method developed at Nuclear fuel Plant, Mioveni-Pitesti, was used for: •Production of Be coatings 7-9 µm on inconel tiles: test samples, qualification of the deposition method, pre-production run, production runs Summary Carbon circular TVA vu2mb Hard antireflexive diamond like carbon coatings prepared by TVA method C/Si 200nm ID/IG=2.46 Micro-Raman-LABRAM HR 800 –Horiba Jobin Yvon on surfaces observed through the optical microscope . •Raman characterisation of the samples Laser sources: λ=633 nm, 514nm, 488nm Power on sample: 2.5-13.2 mW Range: 150-4000cm-1 CNT on Si 226 306 368 The most important feature in the Raman spectrum of CNT’s is the Radial Breathing Mode (RBM), which is often observed between 100 and 500 cm-1. The frequency of the RBM in cm-1 is directly linked to the reciprocal of the nanotube diameter (dt) Non isolated SWNT’s are subject to inter-tube interactions which increase the frequency of the RBM C/Si 100nm CNT bunch in the low frequency region •The characteristic D and G bands (C-C stretching in the graphite plane) modes of carbon were found in all samples, with the ratios of the integral intensities varying slightly with: i)deposition parameters; ii) thickness; iii) substrate material. •In addition to the sp2 and sp3 modes, a feeble Raman feature was observed in the low frequency range of the spectra of C/Si deposited at ion energies below 800 eV. This feature is specific to CNT-like structures and its characteristic frequency is related to the nano-dimension of the crystallites embedded in the disordered carbon phase. •RBM (Radial Breathing Mode) frequency is subject of resonance effects DSC05978 CONCLUSIONS •The carbon-metal films were identified as a nanocrystals complex (5 nm average diameter) surrounded by amorphous structures with a strong graphitization tendency. •The Raman spectra showed typically D and G-bands of the amorphous carbon. By XPS were identified C-C (sp3 bonds) and C=C (sp2 bonds) depending on process parameters and carbon-tungsten relative concentrations. •The coefficients of friction of the prepared films were in the range of 0.15-0.25, for C-Ag, 0.15-0.25 for C-Ni and 0.4 –0.45 in the stable phase for C-W, three to five times lower than the uncoated substrates. GMR •Giant Magnet-Resistive films • •GMR factor: (RH-R0)/R0 • •Or: ΔR/R The GMR effect, discovered in 1986-1988, means the very large change in resistance (due to the spin-dependent scattering of electrons) in a magnetic ultra-thin multilayer film. Very small thickness of the layer (nm range) - change of the magnetic moment - surface or interface anisotropy - low-dimensional effects Multilayer effects - interlayer coupling - exchange interaction Magnetic sensors - high sensitivity for low fields Magnetic read heads - high linear voltage versus field Physical properties of the magnetic super lattices Technological applications: The GMR is a spin determined electrical phenomenon: Consider two electron collision in metals. There are two cases: A.Parallel spin case= symmetric spin function → anti-symmetric scatter amplitude: f(θ,φ)s-a = C[f(θ,φ)- f(π-θ,φ+ π)] →collision cross section: σa = | f(θ) - f(π-θ)|2 (1) B. Anti-parallel spin case → symmetric scatter amplitude: f(θ,φ)s-a = C[f(θ,φ)+ f(π-θ,φ+ π)] → collision cross section σs = | f(θ) + f(π-θ)|2 (2) Conclusion: σs > σa (3) fig1 GRANULAR STRUCTURES Granular structure The magnetic domains are introduced into a conducting (or insulator) material network. Granular distances Critical parameters: • the cluster dimensions • the distance between the clusters • • the magneto-resistance effect is lower as in the multi-layer case •the initial domain orientation can no be made purely anti parallel –at least it is randomly oriented. • when the domains are of the same dimensions the GMR dependence against the external magnetic field is expected to be square-like. Giant and tunneling magnetoresistive (GMR, TMR) films IMG_3109.JPG Multi elements deposition system Glass/ Silicon Ta Co + Cu + MgO Ta Composite and multilayer coatings GRANULAR, MAGNETOREZISITIVE FILMS •Two (three) independents TVA guns •Every gun: independent filament and dc supply •A metallic screen separates TVA discharges. Co Cu φ1 φ2 Catode 1 Catode 2 Screen Substrate Trei desc 2 -two (or three) independent generated plasmas : for Co, (Fe, Ni) and Cu (Ag etc) DSCN0458 Plasma appearance in Fe-Mn vapors Fe-Cu Lungu Fig Fe concentration in Cu matrix Fe-Cu Lungu Fig •A to E: Face centered cubic (fcc) Cu phase and the body centered cubic (bcc) α-Fe phase. High Fe content (A) => lattice defects or fine particles. •The main peak 111 of the fcc-Cu phase only appears as a weak shoulder of the Fe-110 peak at high Fe concentration (A) •Increasing the relative copper content (C and E), the fcc-Cu phase become more evident. XRD of Fe-Cu films Fe-Cu Lungu Fig 57Fe Mössbauer spectra were collected at room temperature in transmission geometry, by using a constant acceleration spectrometer and a 57Co(Rh) matrix. Fe-Cu Lungu Fig The spectra of samples A and B give evidence for the presence of two magnetic nonequivalent Fe positions (bulk and interfacial) of the α-Fe phase. A third paramagnetic component (a central singlet), with an isomer shift close to zero, was assigned to superparamagnetic bcc-Fe clusters. The Mössbauer spectrum of sample C (with a lower amount of Fe) at RT reveals only superparamagnetic bcc-Fe clusters. Clearly, samples A to E present different magnetic interactions Mössbauer analysis Fe-Cu Lungu Fig m7 lungu 10 m 3d Magnetic domain distribution in a Fe-Cu film (B) m7 lungu 10 t 3d Topographic AFM image of a Fe-Cu film (B) MFM microscopy of Fe-Cu films m7 lungu 2,5 t 3d Topographic MFM image 100 nm m7 lungu 2,5 m 3d Magnetic domains distribution of a Fe-Cu film Fe-Cu Lungu Fig • Positive MR-effects of about 38% at saturating fields close to 0.8 T are definitely observed for sample B. • Lower Fe content decreases significantly the observed effect, down to about 20% in sample D. • However, for sample A, with the maximum Fe content, an effect of only 3% was observed and is most probably due to the lack of RT superparamagnetic bcc-Fe clusters in this film. GMR of Fe-Cu films GMR in Fe-Cu thermally treated and as deposited= high abrupt variation=uniform dimensional distribution of formed domains GMR in Ni-Cu composite layer COCU4012 COCU4013 FECUL012 AFM images of the Co-Cu films FECUL013 AFM images of the Fe-Cu films M8A28P GMR in Co-Cu layers – high step variation GMR in Cu-permalloy layers; no high steps present •-co-deposited gadolinium or holmium in combination with fullerene (C60) •-gadolinium or holmium were deposited from their plasma using the following conditions: • -filament heating current – 40 A • -current discharge – 300 mA (Gd) and 400 mA (Ho) •-the fullerene was evaporated from ceramic oven using 9A electrical current flowing through the surrounding copper conductor • •-the Gd – C60 combination can furnish interesting magneto-electrical behavior, gadolinium being a rare earth magnetic element •-the Ho – C60 combination can furnish interesting conductor/semiconductor behavior •-the deposition geometry was similar with the one used for two metals co-deposition •-probes with different metal – fullerene relative concentrations were obtained CONCLUSIONS (GMR section) •Composite thin films were prepared by TVA technology •One of the fim consisting of a-Fe nanoparticles embedded in the Cu matrix. •The size of the Fe nanoparticles and their dispersion, to the purity of the Cu matrix, were analyzed starting from the Mössbauer spectra and finally correlated with the magnetoresistance effects, AFM and XRD measurements. •The greatest GMR effect appear in the case of Co-Cu structure and for Fe-Cu and Ni-Cu cases, very special kind (quadratic) of GMR dependence appear. •This could suggest a very narrow distribution of the cluster dimensions within the copper structure that can be explained by the special conditions of deposition in TVA technology. High temperature oxidation resistant composites: Re, Re-Ni-Cr, Ni-Al multilayers •Plasma ignition in pure Re vapours: thoriated tungsten filament heated by a 90-100 A a.c. current. •The emitted electrons: were focused on the Re anode by a Mo Whenelt cylinder. •The anode: Re rod of 8-10 mm in diameter and supported by a Mo flange. • The distance between the thermoemissive filament and the Re anode: 3-4 mm •The angle between the electron beam and the vertical line: 600. 3 tunuri TVA - Ni bara cu text ENGLEZA Experimental set-up used for simultaneously depositions of Re, Ni and Cr > NILPRP I-V charateristics of Re plasma as function of the filament current Re30Cr10Ni Fig Mixed layer formation –low friction composites Crucible Material to be evaporated φ1 φ2 Cathode 1 Cathode 2 Screen Substrate Images of the structure of the upper layer: tubular features with about 10 nm width and 50-100 nm length appear together with small grains with a lateral size of about 5 nm. The mentioned features are surrounded by a brighter carbon matrix. 200407_4k_1 200407_HR_50k_1 HRTEM of Ni-C layer 2 nm Coefficient of friction of C-Ni composite Plain bearings for automotive applications Using TVA method were obtained nanostructured films with applications in: Electronics (magnetoresistive films0 Mechanics (solid lubricants) Nuclear technology (compact films for First Wall coatings) CONCLUSIONS codepuneri Be-W composite preparation Deposition set-up Distance between anodes: 20cm Sample holder-anodes dist.: 25 cm. IMG_2755 IMG_1590 W anode Concentration variation •The relative concentration for each of the material of a certain sample depends on the incident particle flux and on the incident angle: • • • •d is the distance from the source (anode) to the sample and θ is the particle incident angle of the substrates • Theoretical estimation of the relative concentration • Relative concentration based on EDS measurements P9_20000x P1_090408_20000x P13_20000x Be+W on graphite at R.T. Be - 52.36 % O - 38.81 % W - 8.83 % Be - 60.55 % O - 36.21 % W - 3.25 % Be+W on Si at R.T. P3_090410_20000x Be+W on Si at 350oC Be+W on Si at 500oC Be- 12.52 % O - 22.98 % W – 64.48 % Be- 11.83 % O – 18.09 % W – 70.06 % Rough surface morphology of the RT prepared samples. Smooth surfaces on the heated substrates samples:> higher atom’s mobility RBS experimental and SIMNRA code simulated spectra of the Be-W film deposited on graphite substrate at room temperature and 500oC RBS tartat 500 grade RBS la RT Be-W film prepared at RT Be-W film prepared at 500oC The depth profile of the Be-W film deposited on graphite substrate at RT. The depth profile of the Be-W film deposited on graphite substrate at 500oC At RTsubstrates the Be-W film was oxidized only at the surface and at the interface For the heated substrates the oxygen was present at the surface, and diffuses into the material, oxidizing the beryllium and the tungsten in the whole film. Oxygen present at the interface begins to migrate into the substrate as the temperature increased. XPS survey spectra at the interface of Be-W film XPS core spectra Be1s peak of the Be-W film W4f pattern Discharge parameters (Be deposition on graphite) Ifil= 50 A Idischarge= 1.5 A Udischarge= 600 V poza_301 Be-C formation Be film depositions on graphite substrate U:\img\dllungu\bea16p.tif Be-Si_6mic7_5kx BeSi3_002 Be fim morphology and structure Polycrystalline Be Si substrate Graphite substrate Be-Si_6mic7_5kx 1_B07 SEM images Before (left side) and after (right side) annealing Be film on graphite at 750 ºC • re-crystallization • surface cracks/holes • the film remains stable After annealing at 750 ºC: As deposited (Be on graphite) samples: • oxidized surface (due to air exposure after deposition) • oxygen present at the interface (porous graphite surface/residual oxygen in the deposition chamber) Annealed samples: • oxidized surface • oxygen from the interface migrates into the film • mixed material formation occurs at the interface TT 350oC Thermal treatment at 750 ºC of the Be film coated on graphite Heating the sample to 750 ºC it was observed from the RBS spectra that the carbon from the substrate diffused into the beryllium film forming a mixed layer. Also, the oxygen present at the Be – C interface diffused to the surface. RT 750oC RBS Measurements C1s peak at the interface C1s peak in depth Be2C formation: Be reactivity; Ion bombardment XPS measurements XPS measurements before (left side) and after (right side) thermal treatment are in good agreement with the results obtained by RBS • Be2C alloy is present in the whole film •strong oxidation of the film •less than 20 % of the beryllium remains in pure metallic form •the film remains stable XPS measurements Be-C-W films preparation Be - C: TVA evaporation anode W: TVA evaporation anode W rod Morphology of Be-C-W films 2%20-%202%2001 2%20-%203%2002 2%20-%204%2003 2%20-%204%2004 Be-CW22 Be-CW24 Be-CW25 Be-CW23 Be – 19.70 at% C – 29.20 at% W – 27.65 at% O – 23.42 at% 23.02.2010 Be+C+W on Si; Sample nr. 2 Be - 22.00 at% C – 30.44 at% W – 25.27 at% O – 22.29 at% 22.02.2010 Be+C+W on Si; Sample nr. 5 Be - 25.34at% C – 27.21at% W – 23.31at% O – 23.64 at% 22.02.2010 Be+C+W on Si substrate Sample nr. 2 Concentration (at%) EDS SEM 50.000 X SEM 10.000 X Cod probă SEM and EDS characterization of the Be-C-W films Probele au fost analizate SEM si EDS iar rezultatele acestor analize au evidentiat prezenta celor 3 materiale in film. bewsia17a TEM image of the Be-C-W film Elemental mapping (EDS analysis) and concentration compositions of Be-C-W films deposited on silicon wafers Be-C-W depth profile film analysis by XPS Be-C-W depth profile film analysis by SIMS Concentratii Be-C-W Concentratii Be-C-W RBS XPS depth profile RBS depth profile T1 T6 TVA gun E-Beam irradiation/annealing After annealing Before annealing CONCLUSIONS •Thermionic Vacuum Arc method (TVA), was used for preparation of composite films for fusion programme. •RBS and XPS analysis proved the formation of binary/ternary mixtures at interfaces and as prepared and annealed films. •At RT the films were oxidized only at the surface and at the interface, while for the heated substrates the oxygen was present at the surface, and diffuses into the material, oxidizing the beryllium and the tungsten in the whole film. In addition, the oxygen present at interfaces begins to migrate into the substrate as the temperature increased. •In the case of 350 ºC annealing of Be/graphite, Be2C compound occurs only at the interface but the thickness of the mixed layer increases with the duration of the thermal treatment. • Annealing Be/graphite samples at 750 ºC, Be2C was formed in the whole film • Oxygen from the interface migrates into the film forming BeO • The films were stable after annealing • PULSED LASER BEAM INTERACTION WITH CARBON, TUNGSTEN AND BERYLLIUM COATINGS The the behavior of the 0.5 - 10 µm thickness carbon, tungsten and beryllium layers in interaction with single or multiple terawatt laser beam pulses in vacuum was studied. Terawatt laser system (Tewalas), a modern facility of the National Institute for Laser, Plasma and Radiation Physics (NILPRP) is a high power, 20-360 x 10– 15 s pulse duration, 100-450 mJ pulse energy, 10 Hz repetition rate. The 1012 - 1014 W/cm2 density power laser beam was focalized, in vacuum, on the W, C, Be coatings prepared using the orginal technology of thermionic vacuum arc (TVA) developed at NILPRP. The laser pulses were programmed to have durations of pico or femtoseconds, in order to obtain duration and power densities compared to the fusion plasma instabilities. The spectroscopy of plasmas produced by laser breakdown using pico and femtosecond laser pulses reveal features not observed with longer (nanosecond) laser pulses. Were studied the effects of the laser produced plasmas with pure C, W and Be films. The coatings characterizations before and after exposures were performed using modern techniques as: atomic force microscopy (AFM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. IMG_1416 IMG_1407 3 Scanning electron microscopy (SEM) images taken with a SUPRA VP 40 microscope (ZEISS) on the laser irradiated zones (craters) are shown The sp3 content is estimated from the area corresponding to diamond and the sum of the areas of the overlapping peaks of graphite and CO phases. An estimation of sp3 content results in 39.4% at the raw surface on the inside crater of the irradiated zone 6, compared to 30.8% of the non-radiated zone Conclusions: Carbon films with the thickness of about 2500 nm were coated on top of 200 nm tungsten films deposited on fine grain graphite substrates and were irradiated using ultra-short laser pulses of as The craters produced by the laser irradiation contain ordered structures as observed in the SEM images, which correspond to rhombohedral structures with lattice parameters a =0.25221 nm, c = 4.3245nm (diamond) as identified by SAED analysis. The micro-Raman scattering measurements performed on the craters in comparison with the spectrum of a diamond tip show the 1330 cm‑1 wide enough to allow a discontinuous diamond structure interpretation. SEM images associated with EDS analysis prove the existence of W particles in the diamond-graphite structure of the irradiated zones. The ratio of sp3/sp2 bonds estimated using XPS was found larger than 60%. The Raman characterization leads to the conclusion that the films are built of NCD and NC graphite as a result of hysteresis. .