21 research outputs found
Synthesis of iron-doped TiO2 nanoparticles by ball-milling process : the influence of process parameters on the structural, optical, magnetic, and photocatalytic properties
Titanium dioxide (TiO2) absorbs only a small
fraction of incoming sunlight in the visible region thus
limiting its photocatalytic efficiency and concomitant
photocatalytic ability. The large-scale application of TiO2
nanoparticles has been limited due to the need of using an
ultraviolet excitation source to achieve high photocatalytic
activity. The inclusion of foreign chemical elements in the
TiO2 lattice can tune its band gap resulting in an absorption
edge red-shifted to lower energies enhancing the photocatalytic
performance in the visible region of the electromagnetic
spectrum. In this research work, TiO2
nanoparticles were doped with iron powder in a planetary
ball-milling system using stainless steel balls. The
correlation between milling rotation speeds with structural
and morphologic characteristics, optical and magnetic
properties, and photocatalytic abilities of bare and Fedoped
TiO2 powders was studied and discussed.This work was partially financed by FCT-Fundacao para a Ciencia e Tecnologia-under the project PTDC/FIS/120412/2010: "Nanobased concepts for Innovative & Eco-sustainable constructive material's surfaces.
Simultaneous onset of steroid resistant nephrotic syndrome and IDDM in two young children
Fabrication Method of Carbon-based Materials in CH4/N2 Plasma by RF-PECVD and Annealing Treatment for Laser Diodes
The present research addresses the synthesis of carbon materials thin films by RF-PECVD in N2/CH4 gas mixture. Carbon materials film was formed at 40/48 sccm of CH4/N2 of the total gas flow rate ratio CH4/CH4+N2 = 0.45 and 200/100 W HF/LF power at a deposition temperature of 350 oC and 1000 mTorr pressure. Then, post-annealing of carbon materials film took place at 400 oC by means of RTA under N2 flow. The formation of carbon nanostructures was investigated by scanning electron microscopy, energy dispersive X-ray, Raman spectroscopy, and atomic force microscopy, respectively. AFM shows that the films consisted of nanocrystalline grains. The surface morphology and structural characteristics of materials were studied as a gas flow function and substrate temperature. EDX results indicated the carbon presence, and Raman spectroscopy analysis revealed two broad bands: D-band 1381.64 cm−1 and G-band 1589.42 cm−1. The temperature-dependent post-annealing of carbon materials plays a key role in the graphite crystallites growth at high substrate temperatures. Our results indicate carbon materials incorporation for laser diode applications
Fabrication Method of Carbon-based Materials in CH4/N2 Plasma by RF-PECVD and Annealing Treatment for Laser Diodes
The present research addresses the synthesis of carbon materials thin films by RF-PECVD in N2/CH4 gas mixture. Carbon materials film was formed at 40/48 sccm of CH4/N2 of the total gas flow rate ratio CH4/CH4+N2 = 0.45 and 200/100 W HF/LF power at a deposition temperature of 350 oC and 1000 mTorr pressure. Then, post-annealing of carbon materials film took place at 400 oC by means of RTA under N2 flow. The formation of carbon nanostructures was investigated by scanning electron microscopy, energy dispersive X-ray, Raman spectroscopy, and atomic force microscopy, respectively. AFM shows that the films consisted of nanocrystalline grains. The surface morphology and structural characteristics of materials were studied as a gas flow function and substrate temperature. EDX results indicated the carbon presence, and Raman spectroscopy analysis revealed two broad bands: D-band 1381.64 cm−1 and G-band 1589.42 cm−1. The temperature-dependent post-annealing of carbon materials plays a key role in the graphite crystallites growth at high substrate temperatures. Our results indicate carbon materials incorporation for laser diode applications
Fabrication Method of Carbon-based Materials in CH4/N2 Plasma by RF-PECVD and Annealing Treatment for Laser Diodes
The present research addresses the synthesis of carbon materials thin films by RF-PECVD in N2/CH4 gas mixture. Carbon materials film was formed at 40/48 sccm of CH4/N2 of the total gas flow rate ratio CH4/CH4+N2 = 0.45 and 200/100 W HF/LF power at a deposition temperature of 350 oC and 1000 mTorr pressure. Then, post-annealing of carbon materials film took place at 400 oC by means of RTA under N2 flow. The formation of carbon nanostructures was investigated by scanning electron microscopy, energy dispersive X-ray, Raman spectroscopy, and atomic force microscopy, respectively. AFM shows that the films consisted of nanocrystalline grains. The surface morphology and structural characteristics of materials were studied as a gas flow function and substrate temperature. EDX results indicated the carbon presence, and Raman spectroscopy analysis revealed two broad bands: D-band 1381.64 cm−1 and G-band 1589.42 cm−1. The temperature-dependent post-annealing of carbon materials plays a key role in the graphite crystallites growth at high substrate temperatures. Our results indicate carbon materials incorporation for laser diode applications
Monodispersed NiO Nanoparticles into SBA-15: An Efficient Nanocatalyst to Produce Ketone-Alcohol (KA) Oil by the Oxidation of Cyclohexane in Mild Conditions
A simple and efficient approach to preparing highly efficient and reusable NiO@SBA-15 nanocatalysts for the oxidation of cyclohexane to produce ketone-alcohol (KA) oil was reported. These nanocatalysts were prepared by the dispersion of NiO NPs into SBA-15 using a coordination-assisted grafting method. In this approach, four commercially available nickel salts were immobilized into amino-functionalized SBA-15. After washing and calcination, four new nanocatalysts were obtained. The high dispersion of NiO NPs into SBA-15 was confirmed by HR-TEM and XRD. Different oxidants such as O2, H2O2, t-butyl hydrogen peroxide (TBHP), and meta-Chloroperoxybenzoic acid (m-CPBA) were evaluated. However, m-CPBA exhibited the highest catalytic activity. Compared to different catalysts reported in the literature, for the first time, 75–99% of cyclohexane was converted to KA oil over NiO@SBA-15. In addition, the cyclohexane conversion and K/A ratio were affected by the reaction time, catalyst dose, Ni content, and NiO dispersion. Moreover, NiO@SBA-15 maintained a high catalytic activity during five successive cycles