491 research outputs found
Ultra-Short Pulsed Laser Deposition of Oxides, Borides and Carbides of Transition Elements
No full textOxides, borides and carbides of the transition elements are materials of great interest from a technologic point of view. Many of these materials are used in the form of thin films, so several techniques are commonly used to deposit them. Among these techniques, Pulsed Laser Deposition (PLD) performed using ultra-short pulse lasers, mainly fs lasers, presents unique characteristics in respect to PLD performed using conventional short pulse lasers. Indeed, the films deposited using fs PLD are often nanostructured, and this technique often allows the target stoichiometry to be transferred to the films. In this work, we will review the use of ultra-short PLD in the production of films obtained from transition metal oxides, borides and carbides, evidencing the advantages offered by this technique, together with the problems arising with some of the studied systems. We conclude that even if ultra-short PLD is surely one of the most important and useful deposition techniques, it also presents limits that cannot be ignored
Substituted hydroxyapatite, glass, and glass-ceramic thin films deposited by nanosecond pulsed laser deposition (Pld) for biomedical applications: A systematic review
No full textThe deposition of thin films of bioactive materials is the most common approach to improve the bone bonding ability of an implant surface. With this purpose, several wet and plasma assisted deposition methods were proposed in the scientific literature. In this review, we considered films obtained by nanosecond Pulsed Laser Deposition (PLD). Since hydroxyapatite (HA) has composition and structure similar to that of the mineral component of the bone, the initial studies focused on the selection of experimental conditions that would allow the deposition of films that retain HA stoichiometry and crystallinity. However, biological apatite was found to be a poorly crystalline and multi-substituted mineral; consequently, the attention of researchers was oriented towards the deposition of substituted HA, glass (BG), and glass-ceramic (BGC) bioactive materials to exploit the biological relevance of foreign ions and crystallinity. In this work, after a description of the nanosecond ablation and film growth of ceramic materials, we reported studies on the mechanism of HA ablation and deposition, evidencing the peculiarities of PLD. The literature concerning the PLD of ion substituted HA, BG, and BGC was then reviewed and the performances of the coatings were discussed. We concluded by describing the advantages, limitations, and perspectives of PLD for biomedical applications
Development of a vegetation damage severity index based on hyperspectral sensor data
No full textThe SAP4PRISMA (Development of algorithms and products for supporting the PRISMA mission) project is one of the five research projects funded by ASI (Italian Space Agency) with the objective to develop applications capable of suitably exploiting the data acquired by the satellite hyperspectral sensor PRISMA. PRISMA (PRecursore IperSpettrale della Missione Applicativa) is an earth observation system combining a hyperspectral sensor with a panchromatic medium-resolution camera. The mission, fully supported by the Italian Space Agency (ASI), is de-voted to Earth Observation and Remote Sensing Research to answer to the users increasing de-mand of accurate quantitative information about the Earth system. SAP4PRISMA project is focus-ing its research activities only on those geophysical parameters/applications/products that are suit-able for the characteristics of the mission and in perspective for further international hyperspectral missions (EnMAP, HyspIRI, etc.). The project is structured in interconnected research activities aimed at consolidating the methodological issues for retrieving geophysical and agro-environmental parameters to be used as inputs for the development of innovative complex prod-ucts (e.g., nitrate leaching, land degradation and fuel maps, etc.). The products proposed in the frame work of the SAP4PRISMA project regard: (a) land degradation and vegetation status, (b) products development for agricultural areas, (c) management and monitoring of natural and in-duced hazards. Regarding the application of PRISMA for the management and monitoring of natu-ral and anthropogenic hazards, we focus on the assessment of the damage severity and mainly on the effects of fire in vegetated areas interested by a fire. Moreover, project goal is to develop an index that, in the presence of an area where the vegetation shows a sharp decline, is able to under-stand the causes, that may not necessarily be linked to the occurrence of a fire (e.g., oil spills, floods, etc.). This paper aims at showing the results reached up-to-now in the process of develop-ing such an index called DSI (Damage Severity Index)
Em perspectiva, a crítica de Roberto Schwarz a uma entrevista dos signatários do Manifesto Música Nova
No full textAinda que não tenham se constituído como um grupo de compositores e intérpretes com uma unidade consistente, tanto no que diz respeito à continuidade da produção quanto a seu alinhamento estético, os signatários do Manifesto Música Nova (publicado em 1963 na Revista Invenção) foram responsáveis pela divulgação no Brasil da música de vanguarda europeia das décadas de 1950 e 1960 e das discussões e questionamentos suscitados em seu entorno. Abriram com essa iniciativa um amplo horizonte de novas influências, materiais e procedimentos composicionais, em oposição às tendências até então hegemônicas. Tanto em suas posições pessoais quanto em seu programa de ação musical, esses compositores e intérpretes reivindicam um alinhamento entre o estado da arte das últimas experiências artísticas e seu significado progressista ou até revolucionário, vendo a composição e a crítica musical um campo de relevo no combate às forças reacionárias na sociedade. Essa prerrogativa, exposta de forma provocativa e bastante irônica em uma entrevista de membros do grupo na grande mídia (Música não-música antimúsica, publicada n’O Estado de S. Paulo em 1967), é questionada no ano seguinte por Roberto Schwarz, em seu texto Nota sobre vanguarda e conformismo. Por um lado, a entrevista ao Estado, realizada por Júlio Medaglia com os compositores Damiano Cozzella, Rogério Duprat, Willy Corrêa de Oliveira e Gilberto Mendes, pode hoje ser avaliada tanto em relação ao Manifesto Música Nova (e ao Plano Piloto para a Poesia Concreta, do qual é diretamente reminiscente) quanto às trajetórias ulteriores, marcadamente contrastantes, de seus protagonistas. Ao mesmo tempo, uma vez colocada em perspectiva a crítica de Schwarz, é possível verificar sua pertinência em relação aos posicionamentos políticos posteriores e à evolução do pensamento musical de cada um desses compositores. Se as contradições no tom geral de seu discurso nessa entrevista são bem apontadas por Schwarz, que inclusive faz uso do mesmo teor irônico daqueles que critica, faz-se necessário precisar uma diferenciação ausente em sua crítica, entre o pensamento, os posicionamentos e as contradições de cada um dos compositores entrevistados, o que é possível de se propor com mais clareza observando sua trajetória em retrospecto.Versão final do editorUniversidade Estadual Paulista (UNESP
Ultra-short Pulsed Laser Deposition of Gallium Arsenide: a Comprehensive Study
No full textA Gallium Arsenide target has been ablated by using a frequency-doubled Nd:glass laser with a pulse duration of 250 fs and thin films have been deposited in vacuum. The plasma produced by the ablation process and the deposited films have been studied by several different techniques, including optical emission spectroscopy, ICCD fast imaging and electron microscopies, X-ray diffraction, Raman spectroscopy, respectively. The data evidence that the films, which composition shows an excess of Ga, are formed by the coalescence of a large number of nanoparticles. These results, even if the plasma does not evidence the presence of nanoparticles, seem to indicate that the ablation-deposition mechanism is the same found for the majority of the other systems deposited by ultra-short pulse lasers
Diamond-like carbon thin films produced by femtosecond pulsed laser deposition of fullerite
No full textDiamond-like carbon films have been deposited from a fullerite target by ultra-short pulsed laser deposition technique. The results indicate that the films morphology and structure, determined by scanning electron microscopy, atomic force microscopy and energy dispersive X-ray diffraction, depend strongly on the substrate temperature. X-ray photoelectron. X-ray Auger electron, Raman and surface enhanced Raman scattering spectra indicate that the fs-DLC films composition involves a mixed sp, sp(2) and sp(3) carbon network consisting of aromatic rings and sp(3) diamond-like structures linked by chains of different lengths and composition. The films deposited at room temperature, presenting the higher content of sp(3) carbon (48%), also contain C(60) crystalline phase and show a very high hardness of 49 GPa
Laser ablation of GaAs in liquid: the role of laser pulse duration
No full textThe synthesis of gallium arsenide (GaAs) nanoparticles has attracted wide scientific and technological interest due to the possibility of tuning the GaAs NP (nanoparticle) band gap across the visible spectrum and their consequent use in optoelectronic devices. In recent years, laser ablation in liquid (LAL) has been widely used for the preparation of colloidal solutions of semiconducting and metallic nanoparticles, thanks to its flexibility. With the aim of highlighting the key role played by laser pulse duration on the ablation mechanism and on the properties of the obtained materials, laser ablation of a gallium arsenide target in acetone was performed using laser sources operating in two different temporal regimes: Nd:glass laser (l = 527 nm, pulse duration of 250 fs and frequency repetition rate of 10 Hz) and Nd:YAG laser (l = 532 nm, pulse duration of 7 ns and frequency repetition rate of 10 Hz). The ablation process was studied following the dynamics of the laser induced shock waves (SWs) and cavitation bubbles (CBs) by fast shadowgraphy, showing that CB dimension and lifetime is related to the laser pulse length. A characterization of the obtained materials by TEM (transmission electron microscopy) and microRaman spectroscopy have shown that quite spherical gallium oxide/GaAs nanoparticles can be obtained by nanosecond laser ablation.
On the other hand, pure polycrystalline GaAs nanoparticles can be produced by using an ultrashort laser source
Andrea Paolini, Amanda Bianchi, Paolo Crisi, Maria Veronica Giordano, Massimo Vignoli, Francesco Collivignarelli, Claudia Ristori, Sara Canal, Francesca Del Signore, Andrea De Bonis, Martina Rosto, Roberto Tamburro
No full textUltrashort Pulsed Laser Ablation of Magnesium Diboride: Plasma Characterization and Thin Films Deposition
No full textA MgB2 target has been ablated by Nd:glass laser with a pulse duration of 250 fs. The plasma produced by the laser-target interaction, showing two temporal separated emissions, has been characterized by time and space resolved optical emission spectroscopy and ICCD fast imaging. The films, deposited on silicon substrates and formed by the coalescence of particles with nanometric size, have been analyzed by scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, micro-Raman spectroscopy, and X-ray diffraction. The first steps of the films growth have been studied by Transmission Electron Microscopy. The films deposition has been studied by varying the substrate temperature from 25 to 500°C and the best results have been obtained at room temperature
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