The surface of Ni-Cr-Fe (Inconel-600) alloy was modified by implanting 500 keV nitrogen ions at room temperature using pelletron accelerator to dose of 1.87 × 10
14
ions/cm
2
. X-ray diffraction ...analysis of the ions implanted samples indicated the formation of Cr
2
N phase. Electrochemical testing of Inconel-600 alloy before and after the ions implantation was conducted using potentiodynamic tafel scan, potentiodynamic anodic polarization and electrochemical impedance spectroscopy techniques in an acidic saline solution. The higher anodic polarization slope (β
a
), low cathodic polarization slope (β
c
) and decrease in corrosion current density after ions implantation were attributed to the modification of passive film by the nitrogen ions. The scanning electron microscopy and electrochemical analyses of the ions implanted samples revealed an improvement in the pitting resistance of the alloy.
Laser induced plasma plume imaging and surface morphology of silicon Khaleeq-ur-Rahman, M.; Siraj, K.; Rafique, M.S. ...
Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms,
04/2009, Letnik:
267, Številka:
7
Journal Article
Recenzirano
Shot-to-shot variation in the characteristics of laser produced plasma plume and surface profile of N-type silicon (1
1
1) are investigated. In order to produce plasma, a Q-switched Nd: YAG laser ...(1064
nm, 10
mJ, 9–14
ns) is tightly focused on silicon target in air at room temperature. Target was exposed in such a way that number of laser shots was increased from point to point in ascending order starting from single shot at first point. Target was moved 2
mm after each exposure. In order to investigate shot-to-shot variation in the time integrated emission intensity regions within the plasma plume, a computer controlled CCD based image capture system was employed. Various intensity regimes were found depending strongly on the number of incident laser pulses. Plasma plume length was also found to vary with the number of pulses. The topographic analysis of the irradiated Si was performed by Scanning Electron Microscope (SEM) which shows the primary mechanisms like thermal or non-thermal ablation depend on the number of shots. Surface morphological changes were also studied in terms of ripple formation, ejection, debris and re-deposition of material caused by laser beam at sample surface. The micrographs show ripples spacing versus wavelength dependence rule
Λ
≈
λ/(1
−
sin
θ). Intensity variations with number of shots are correlated with the surface morphology of the irradiated sample.
Investigations are performed on thermal, optical and electrical response of UV laser-irradiated platinum (Pt). 4N pure, annealed and fine polished samples are exposed to the KrF Excimer laser ...(248 nm, 20 ns, 50 mJ) under vacuum ∼10
−6
torr at different laser fluences (0.5-2.5 J/cm
2
). Space-resolved plasma plume dynamics is studied by analyzing the captured plume images with the help of a computer controlled image-grabbing system. The irradiated targets are characterized for surface morphology, structural, optical and electrical investigations using the diagnostics; scanning electron microscopy, X-ray diffraction, rotating compensator auto-aligned ellipsometer and four-point probe, respectively. The value of maximum intensity emitted by Pt plasma plume is 250 grey scales. Surfaces of the target metals are modified by craters, moltens and redeposited material. Laser-induced periodic surface structures are produced at low laser fluence. Irradiation of Pt causes changes in diffracted X-rays intensity and grain sizes, dislocation in line densities and strain in the target materials. Considerable changes occur in optical parameters as well. A decrease in electrical conductivity of the irradiated targets also takes place in an exponential way with the change in laser fluence.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, GIS, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Yttrium ions of energy 0.5MeV were implanted to modify the surface of Inconel 600 by using a Pelletron Accelerator. Microstructural and XRD studies reveal austenitic nickel solid solution (γ) and ...intergranular carbides. The surfaces were electrochemically investigated by potentiodynamic polarization, Electrochemical impedance spectroscopy and Mott–Schottky techniques in acidic saline solution. The results indicate that the yttrium ions implantation significantly reduces the intragranular pitting as compared to the intergranular pitting tendency of the alloy. The low passive current density, minor pseudo-capacitive behavior and high flat band potential with p-type nature of passive film limit the electrochemical dissolution of the yttrium implanted Inconel.
► The surface of Inconel 600 was modified by 0.5MeV yttrium ions at room temperature. ► Electrochemical testing of the material was conducted before and after irradiation. ► Potentiodynamic polarization, EIS and Mott–Schottky techniques were used. ► Ion implantation greatly improves the intragranular pitting resistance of the alloy.
► Co-DLC multilayer thin films have been deposited by PLD. ► Co-particles of different sizes are embedded in DLC matrix. ► Raman spectra contain characteristics D- and G-bands of DLC films. ► VSM ...analysis reveals Co–C multilayer films show ferromagnetic behaviour. ► Optical band gaps of DLC films can be tuned by varying Co-content.
Cobalt-DLC multilayer films were deposited with increasing content of cobalt, keeping carbon content constant by pulsed laser deposition technique. A cobalt free carbon film was also deposited for comparison. Excimer laser was employed to ablate the materials onto silicon substrate, kept at 250
°C, while post-deposition annealing at 400
°C was also performed in situ. The formation of cobalt grains within the carbon matrix in Co-DLC films can be seen through scanning electron and atomic force micrographs while no grains on the surface of the cobalt-free DLC film were observed. Raman spectra of all the films show D- and G-bands, which is a confirmation that the films are DLC in nature. According to Vibrating sample magnetometer (VSM) measurements, the DLC films with cobalt revealed ferromagnetic behaviour whereas the cobalt free DLC film exhibited diamagnetic behaviour. The pure DLC film also shows ferromagnetic nature when diamagnetic background is subtracted. Spectroscopic Ellipsometry (SE) analysis showed that the optical band gaps, refractive indices and extinction coefficients of Co-DLC films can be effectively tuned with increasing content of cobalt.
Localized behavior of laser induced metallic plasmas has been investigated using Langmuir probe as an electrostatic diagnostic tool. A Q-switched Nd:YAG pulsed laser (1064
nm, 12
ns, 1.1
MW) is ...tightly focused on metal targets (Cu, Zn, Cd, Ag, Pt and Au) having dimensions 2
×
2
×
0.2
cm
3 under vacuum ∼10
−3
torr. The varying biasing voltages are applied to Langmuir probe. The electric signals are recorded on two channel 200
MHz digital storage oscilloscope (UNI T – UTT 2202). A comparison shows strong dependence of electron parameters (temperature, density, Debye length, plasma frequency and number of particles in Debye sphere) in plasmas on target materials' properties (atomic number, surface binding energy etc.). The maximum values for electron density (8.08502
×
10
17
m
−3), Debye length (8.07066
×
10
−4
m), plasma frequency (5.19627
×
10
10
Hz) are found for silver and copper metals, respectively, where as the electron temperature shows variation in this trend i.e. maximum value (1.36581
×
10
6
K) for cadmium and minimum value is for gold (1.0008
×
10
5
K). the maximum value of number of particles in Debye length at +15
V (1.47
×
10
26) for Pt and that minimum for Ag (2.1355
×
10
7).
Silver was irradiated both in air at normal atmospheric pressure as well as in vacuum (∼10
−6
Torr) with a Q-switched Nd:YAG laser of wavelength 1.064
μm, pulse energy 10
mJ and pulse duration 9–14
...ns. The silver plasma plume dynamics was investigated using CCD camera. Harmonic generation of Nd:YAG laser and Bremsstrahlung radiations from silver plasma were studied. The surface morphology of the irradiated specimens was examined using metallurgical microscope. The damages produced on the target surface due to interaction of laser pulses were in the form of sputtering, ejection of particles, craters and ripple formation. It was observed that in air collisional sputtering, crater formation, ripples and bubble formation were dominant, while in vacuum hydrodynamic sputtering and exfoliational sputtering were playing their role.
The microstructural morphological changes in laser irradiated targets are investigated. Nd:YAG laser (1064nm, ∼12ns nominal, 1.1MW) is used to irradiate 4N pure (99.99%) fine polished and annealed ...silver samples in ambient air and under vacuum ∼10−6Torr. The laser spot size and power density at tight focus are 12μm and 3×1011W/cm2, respectively. SEM micrographs and X-ray diffractograms of the exposed and unexposed targets reveal the surface texture and structural changes, respectively. Amongst the ablation mechanisms involved, exfoliation and hydrodynamic sputtering are found to be dominant. Surface modifications appear in the form of craters and ripples formation. Heat is conducted non-uniformly through narrow channels at the surface. Thermal stresses induced by the laser do not disturb inter planar distance of the target. On the other hand irradiation causes significant variations in grain size and diffracted X-rays intensities.
We report for the first time a facile synthesis of niobium (Nb) doped (1-D) ZnO nanopillars and nanowires by aerosol assisted chemical vapour deposition with improved structural and optical ...properties. The micro structural, vibrational and optical properties of Nb-doped ZnO were investigated by X-ray diffraction (XRD), Raman spectroscopy, Scanning electron microscopy (SEM)/Energy dispersive spectroscopy (EDS) and UV–Vis spectroscopy (UV/VIS). The results presented show that Nb doping and solvent choice can effectively control the growth of ZnO nanostructures as well as their reproducibility. The XRD results revealed that the highest estimated crystallite size of Nb doped ZnO was found to be 4.7 nm from depositions conducted in methanol and 5.4 nm from depositions conducted in toluene for 0.2 M% Nb doping. It is further explored that with an increase of Nb content, ZnO films show poor crystallinity with preferential orientation along the 0 0 2 plane. The change in morphology and local structure of ZnO also led to variations in the vibrational properties of the materials. Upon Nb doping, the A1 (LO) mode of ZnO was found to red shift and broaden, whereas a blue shift was found for the 2A1 (LO), 2E1 (LO) and 2LO vibrational modes. The UV–Visible spectroscopy of Nb doped ZnO revealed that excellent visible transmittance (∼89%) was achievable and witnessed an increase in band gap from 3.3 eV to 3.5 eV with increased Nb doping.
We report nanostructured tungsten oxide (WO) cauliflowers for the first time that are fabricated onto silica glass substrate at 400 °C by aerosol assisted chemical vapor deposition using tungsten ...hexacarbonyl and multiwalled CNTs in toluene. The deposited films are characterized by Scanning electron microscopy, Energy dispersive x-ray spectroscopy, X-ray diffractometry, Fourier transform infrared and UV–VIS spectroscopy and four-point probe for microstructural, optical and electrical properties. Surface morphology exhibits the growth of nanocauliflowers followed by the aggregation of spherical nanoparticles with high angle grain boundaries. Structural information reveals the transformation of triclinic to tetragonal phase with preferential switching from (0 2 0) to (0 0 1) plane having signatures of W-O-W symmetric vibration between (700cm-1 and 900 cm−1, somewhat perturbed by the addition of doping. In additions, films show inconsistent variation in electrical resistivity (15–109) Ω-cm due to agglomeration of MWCNTs at grain boundaries and appearance of “nanocracks” due to ionic radii mismatch of tungsten and CNTs at higher doping ratios. Black color films present decrease in optical transmittance for range of 300–400 nm attributed to trapping sites and defects generated due to incorporation of multiwalled CNTs. The splitting of Fermi level as a result of incorporation of MWCNTs caused the increase of band gap energy in range of 3.18 eV, useful in tungsten oxide based new material system which can act as the light harvesting material and energy storage simultaneously.
