| 1. |
- Maurizio, C., et al.
(författare)
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Thermal evolution of cobalt nanocrystals embedded in silica
- 2007
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Ingår i: Materials science & engineering. C, biomimetic materials, sensors and systems. - : Elsevier BV. - 0928-4931 .- 1873-0191. ; 27:1, s. 193-196
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Tidskriftsartikel (refereegranskat)abstract
- The structural evolution of cobalt nanoclusters synthesized in silica glass by ion implantation has been investigated upon thermal annealing. The samples were characterized by in-situ grazing incidence X-ray diffraction, exploiting a synchrotron radiation beam and following their evolution during thermal treatments in vacuo up to T = 800 °C. Before heating, the system is composed of hcp Co nanocrystals; we have not detected the transition from hcp to fcc structure that in the bulk phase occurs around 420 °C; nevertheless, the differences in the diffraction pattern recorded at T = 800 °C with respect to the corresponding one at room temperature suggest the presence of a second crystalline phase. © 2006 Elsevier B.V. All rights reserved.
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| 2. |
- De Julián Fernández, C., et al.
(författare)
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Study of the gas optical sensing properties of Au-polyimide nanocomposite films prepared by ion implantation
- 2005
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Ingår i: Sensors and actuators. B, Chemical. - : Elsevier BV. - 0925-4005 .- 1873-3077. ; 111-112:SUPPL., s. 225-229
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Tidskriftsartikel (refereegranskat)abstract
- Au-polyimide nanocomposites have been synthesized by implanting Au + ions in pyromellitic dianhydride-4,4′ oxydianiline polyimide films prepared by glow discharge vapor deposition polymerisation (GDVDP). A structural and optical characterization shows that Au clusters grow only implanting 5 × 1016 Au+/cm2. This sample class shows interesting dynamic optical absorption sensing responses towards methanol and ethanol vapors in the spectral range corresponding to the surface plasmon resonance (SPR) peak of the gold nanoparticles. Traditional surface plasmon resonance measurements performed onto virgin polyimide thin films in controlled atmosphere show a sensing activity due to a variation of the film thickness and of the real part of refractive index. The comparison of the results obtained onto virgin films and implanted ones suggests that the sensing mechanisms can be attributed both to the modification of polymer optical properties and to the chemical activity of gold nanoparticles. © 2005 Elsevier B.V. All rights reserved.
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| 3. |
- Carturan, S., et al.
(författare)
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Formation of silver nanoclusters in transparent polyimides by Ag-K ion-exchange process
- 2007
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Ingår i: European Physical Journal D. - : Springer Science and Business Media LLC. - 1434-6060 .- 1434-6079. ; 42:2, s. 243-251
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Tidskriftsartikel (refereegranskat)abstract
- Silver nanoclusters embedded in two transparent fluorinated polyimides, 4,4'-hexafluoroisopropylidene diphthalic anhydride - 2,3,5,6-tetramethyl paraphenylene diamine (6FDA-DAD) and 3,3',4,4' - biphenyltetracarboxylic acid dianhydride - 1,1-bis(4-aminophenyl)-1-phenyl-2,2,2-trifluoroethane (BPDA-3F), have been produced by surface modification with KOH aqueous solution followed by K-assisted Ag doping and thermal reduction in hydrogen atmosphere. The reaction rate of the nucleophilic hydrolysis in KOH, studied by Fourier transform infrared spectroscopy (FT-IR) and Rutherford backscattering spectrometry (RBS), depends on the polyimide chemical structure. After ion-exchange in AgNO 3 solution and subsequent annealing, the polyimide structure recovery was monitored by FT-IR whereas the characteristic surface plasmon absorption band of silver nanoparticles was evidenced by optical absorption measurements. The structure of silver nanoclusters as related to size and size distribution in the different polyimide matrices was thoroughly investigated by Transmission electron microscopy (TEM) and X-ray diffraction (XRD). The collected data evidenced a uniform distribution of Ag clusters of nanometric size after thermal treatment at 300 °C in both polyimides. For the same ion-exchange treatment parameters and annealing temperature, XRD analyses evidenced the presence of crystallites with similar sizes. © EDP Sciences/Società Italiana di Fisica/Springer-Verlag 2007.
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| 4. |
- Fernandez, R.C., et al.
(författare)
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Electric propulsion applications for lunar cargo missions
- 2006
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Konferensbidrag (refereegranskat)abstract
- Different nations are currently developing a number of plans to put man back on the moon by 2020. The natural extension of returning humankind to the Moon is to create a permanent presence there. This implies that large amount of cargo must be transported on a regular basis to the Moon, so there is a need to develop new techniques to create an economical way of achieving this goal. The success of the SMART - 1 mission demonstrates Electric Propulsion as a valid propulsion method that can be employed to reduce the amount of propellant needed for the mission. This paper will study the use of Electric Propulsion in order to transport cargo to the moon, and the requirements that such systems will have to fulfill. The main advantage of using Electric Propulsion over traditional liquid/solid propellants is the reduction in the weight budget, due mainly to the reduction in the amount of propellant needed and the use of solar energy as the main power source. Electric Propulsion gives an 1sp higher than liquid or solid propellant rocket engines, with a lower thrust, with a consequent increase in the duration of the mission
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