Browsing by Author "Cisternas, M."

Now showing 1 - 5 of 5
  • No Thumbnail Available
    Item
    Effect of RF acetylene plasma on the composition and dynamics of a titanium plasma plume in a plasma enhanced pulsed laser deposition system
    (2025) Bhuyan, H.; Escalona, M.; Villegas, R.; Mal, E.; Cisternas, M.; Saikia, P.; Bora, B.; Kausik, S. S.; Wyndham, E.; Favre, M.
    We report the effect of radio frequency (RF) acetylene plasma on the dynamics and composition of titanium (Ti) plasma plume in a plasma-enhanced pulsed laser deposition (PEPLD) system. The titanium target, mounted inside a capacitively coupled RF discharge, was ablated by using a nanosecond Nd:YAG pulsed laser at 1064 nm with a power density of 2.65 GW/cm(2). The experiments were performed at different operating pressures of acetylene. Fast imaging and optical emission spectroscopy were employed to study the physics behind the pulsed laser deposition in both (PLD) and PEPLD systems. A nonlinear dependence of the plasma plume evolution was observed over a range of pressure. Different expansion regimes correspond to the pressure of the experiments. The plume expansion velocity ranges between 6 x 10(3) m/s and 30 x 10(3) m/s. Emission spectra reveal the presence of C II and Ti II lines depending on the experimental conditions. The presence of background RF plasma leads to substantial enhancement of the emission intensity of the C II spectral lines. In addition, with increasing RF power and background pressure, the intensities of the C II spectral lines increase; whereas the intensities of the Ti II spectral lines decrease with the increase in RF power. Plasma temperature was estimated from the Ti II lines using the Boltzmann plot method, whereas the electron density was estimated from the Stark-broadened Ti II line at 454.9 nm. The calculated densities and temperatures lie between 10(17)-10(18 )cm(-3) and 0.8-2.0 eV, respectively. These results show the effects of the different backgrounds (either neutral or RF plasma) on the propagation of the laser-produced plasma (LPP), which we propose to be useful in the thin film deposition process using PLD.
  • No Thumbnail Available
    Item
    Enfermedad de Erdheim-Chester. Una causa rara de derrame pericárdico. Caso clínico
    (2011) Vega, J.; Cisternas, M.; Bergoeing Reid, Michel Paul; Espinosa, R.; Zapico, A.; Chadid, P.; Santamarina, M.
  • Thumbnail Image
    Item
    Low mycorrhizal diversity in the endangered and rare orchids Bipinnula volckmannii and B. apinnula of Central Chile
    (2020) Claro, A.; Mujica Pérez de Castro, María Isabel; Cisternas, M.; Armesto, Juan J.; Pérez, F.
  • Thumbnail Image
    Item
    NITRIDING OF SUPER-FERRITIC STAINLESS STEEL BY PLASMA IMMERSION ION IMPLANTATION IN RADIO FREQUENCY AND ECR-MICROWAVE PLASMA SYSTEM
    (IEEE, 2015) Bhuyan, H.; Favre, Mario; Cisternas, M.; Henriquez, A.; Wyndham, E.; Mandl, S.; Manova, D.; Walczak, M.
    Stainless steel 470 Li-24 Cr and 460Li-21 Cr are two new generation super-ferritic nickel free grades, contains titanium (Ti), niobium (Nb) and very small percentage of carbon (C) and nitrogen (N). The Ti and Nb enhance the corrosion resistance while the low interstitial content of C and N leads to finer precipitates and greater ductility. These grades are economic alternative to 316L and 304 with corrosion resistance comparable or superior. However, as 316L and 304 can be nitrided efficiently to improve the mechanical surface properties like hardness and wear; it has to be asked whether these new generation super-ferritic grade stainless steels can be improved further by plasma nitriding too. Two sets of experiments have been carried out, one with capacitively coupled radio frequency Plasma at PUC Chile and the other is microwave plasma at IOM Leipzig, to investigate further improvements in the mechanical properties of 470 Li-24 Cr and 460Li-21 Cr steel. Nitrided and unnitrided substrates are further investigated using different surface characterization techniques including secondary ion mass spectroscopy, scanning electron microscopy, energy dispersive x-ray analysis, Vickers hardness, wear resistance, corrosion test etc. In most of the characterizations the nitrided 470 Li-24 Cr and 460Li-21 Cr shows similar results. Increase of surface roughness for higher treatment temperature is observed in both the experiments, independent of the steel types. The formation of chromium nitride compound takes place at treatment temperature around 400 o C-450 o C, and it increases with further increase in temperature. But at higher temperature corrosion property deteriorate. The characterization results show up to 25% of nitrogen, 4-5 times increased in hardness and diffusion of nitrogen layer up to 4-6 micron for different experimental conditions. The samples implanted with temperature higher than 400°C presented wear resistance values around two orders of magnitude higher than the others.
  • Thumbnail Image
    Item
    Nutrients and fungal identity affect the outcome of symbiotic germination in Bipinnula fimbriata (Orchidaceae)
    (2020) Mujica Pérez de Castro, María Isabel; Cisternas, M.; Claro, A.; Simunovic, M.; Pérez Trautmann, María Fernanda