C. Morant

Electrodeposition of hydroxyapatite coatings in basic conditions

Hydroxyapatite films have been grown in this work by an electrodeposition method involving both physical and chemical processes and presenting several differences with respect to other reported works. Description of the coating formation is based on the evolution of current through the sample placed as positive electrode in the basic electrolyte. The characterisation of hydroxyapatite films is of special importance since the bioactive properties related to HAP have been directly identified with its specific composition (Ca/P ratio) and crystalline structure. This characterisation has been traditionally fulfilled by the use of XRD, FTIR and SEM. Results of a further characterisation of the coatings by TEM and SFM, additional to the analysis by XRD, FTIR and SEM, are presented. Interpretation and comparison of our results with those obtained by other electrodeposition methods lead to arguments in favour of a deposition produced directly from ionic species.

Low Temperature Preparation of High Refractive Index and Mechanically Resistant Sol-gel TiO2 Films for Multilayer Antireflective Coating Applications

TiO2 sol-gel thin films have attracted a large attention for applications which require high refractive index transparent layers. In this work, sol-gel TiO2 layers were prepared by Aerosol-gel deposition followed by a thermal treatment procedure in air. Depending on the experimental conditions, abrasion resistant and high refractive index layers could be obtained after post-treatment at only 110°C. In this paper, the experimental parameters which allow the preparation of functional TiO2 sol-gel layers at such low temperature are discussed. It is concluded that the preparation of high refractive index and mechanically resistant TiO2 layers can be interpreted in terms of competition between polycondensation and densification mechanisms. This result allows to envisage the sol-gel processing at low temperature of multilayer antireflective coatings.

The melting behavior of passivated nanocrystalline aluminum

Abstract A nanocomposite Al 2 O 3 Al material has been prepared by consolidation of nanocrystalline aluminum particles which have been passivated with an alumina overlayer prior to the compaction step. Nanostructured Al has been prepared by the gas phase condensation method. The material has been characterized by XPS (X-ray photoelectron spectroscopy). DSC (differential scanning calorimetry), TEM (transmission electron microscopy) and AFM (atomic force microscopy). This study allowed us to demonstrate that the consolidated Al 2 O 3 Al material, although showing a metallic shine and an ohmic electrical resistivity, presents a microstructure constituted by Al grains interconnected by a very thin alumina network, which prevents the material from falling apart when heated at temperatures above the melting point of aluminum.

The Electronic-Structure of Zro2 - Band-Structure Calculations Compared to Electron and X-Ray-Spectra

Abstract We present and discuss band-structure calculations of ZrO2 in the cubic phase calculated by means of the Localized-Spherical-Waves (LSW) method with an extended basis set. The results obtained are in agreement with previous calculations and confirm a large covalent contribution to the bonding in ZrO2. The results are also compared to x-ray and electron spectra showing an overall good agreement between theory and experiment. In particular, the calculations reproduce well the distribution of the spectral weight and the magnitude of the band gap and the crystal-field splitting.

Preparation of hollow magnetite microspheres and their applications as drugs carriers

AbstractHollow magnetite microspheres have been synthesized by a simple process through a template-free hydrothermal approach. Hollow microspheres were surface modified by coating with a silica nanolayer. Pristine and modified hollow microparticles were characterized by field-emission electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, FT-IR and Raman spectroscopy, and VSM magnetometry. The potential application of the modified hollow magnetite microspheres as a drug carrier was evaluated by using Rhodamine B and methotrexate as model drugs. The loading and release kinetics of both molecules showed a clear pH and temperature dependent profile.Graphical abstractHollow magnetite microspheres have been synthesized. Load-release experiments with Rhodamine-B as a model drug and with Methotrexate (chemotherapy drug used in treating certain types of cancer) demonstrated the potential applications of these nanostructures in biomedical applications.

Bonding and morphology study of carbon nitride films obtained by dual ion beam sputtering

Thin carbon–nitrogen films (i.e., CNx) have been obtained by dual ion beam sputtering. The chemical composition and the type of bonding of the CNx material have been examined, as a function of the deposition parameters, by Fourier transform infrared spectroscopy, x-ray photoelectron spectroscopy (XPS), and electron energy loss spectroscopy (EELS). The high concentration of C≡N bonds present in some of the samples, as stated by FT-IR, allowed us to correlate this type of bonding with some of the features observed in the corresponding XPS and EELS spectra. Nitrogen concentrations of up to 45 at. %, depending on the deposition conditions, have been estimated by XPS and EELS. The films deposited at low energy were rather homogeneous, as demonstrated by Auger electron spectroscopy depth profiling, and show the highest C–N simple bonds concentration. On the contrary, the use of high energy assisting nitrogen ions leads to the formation of carbonitrile groups (i.e., C≡N), as well as resputtering effects that significantly reduce the thickness of the films and even hinder the growth of a film. The topography and morphology of the different films, as determined by atomic force microscopy, were also observed to depend on the conditions of assistance.Thin carbon–nitrogen films (i.e., CNx) have been obtained by dual ion beam sputtering. The chemical composition and the type of bonding of the CNx material have been examined, as a function of the deposition parameters, by Fourier transform infrared spectroscopy, x-ray photoelectron spectroscopy (XPS), and electron energy loss spectroscopy (EELS). The high concentration of C≡N bonds present in some of the samples, as stated by FT-IR, allowed us to correlate this type of bonding with some of the features observed in the corresponding XPS and EELS spectra. Nitrogen concentrations of up to 45 at. %, depending on the deposition conditions, have been estimated by XPS and EELS. The films deposited at low energy were rather homogeneous, as demonstrated by Auger electron spectroscopy depth profiling, and show the highest C–N simple bonds concentration. On the contrary, the use of high energy assisting nitrogen ions leads to the formation of carbonitrile groups (i.e., C≡N), as well as resputtering effects that sig...

PhotocatalyticDegradation of Rhodamine -B Under UV-Visible Light IrradiationUsing Different Nanostructured Catalysts

Aims: The goal of this research is to determine the efficiency of different catalysts for the degradation of organic compounds as possible alternative for wastewater treatments. To reach this goal, many objectives should be previously satisfied including the synthesis of different catalysts and the catalytic tests for the different processes. Study Design:A multifactorial design was used for the experimental study.

Electronic structure and chemical characterization of ultrathin insulating films

Abstract We report on the use of photoemission to probe the electronic structure of ultrathin films. The electronic structure of Zr 3 N 4 grown by low energy N 2 + implantation in polycrystalline zirconium has been investigated. The insulating characteristics of Zr 3 N 4 as well as the metal–insulator phase transition in ZrN x , when x approaches 1.33, can be nicely observed by photoemission during the implantation process. Other examples correspond to the understanding of oxide/oxide interfaces by in situ characterization of the growth of an oxide film on a dissimilar oxide. We have studied the electronic properties of the TiO 2 /SiO 2 interface by examining the O 2p valence band and the O 2s and Ti 3p core levels during growth of ultrathin films of TiO 2 on SiO 2 . We report evidence for the formation of cross linking oxygen ions to form Si O Ti bonds at the interface. In addition we use the high sensitivity of the Ni 2p XPS core level lineshape to the local co-ordination of the nickel atoms to study the interface NiO/MgO(100) by in situ characterization of the growth of ultrathin NiO films on MgO(100).

X-ray photoelectron spectroscopic study of the oxidation of polycrystalline rhenium by exposure to O2 and low energy O2+ ions

Abstract X-ray photoelectron spectroscopy has been used to study the interaction of O 2 and low energy O 2 + ions with polycrystalline rhenium. The results indicate that rhenium oxides cannot be obtained at temperatures below 630 K even for very high O 2 exposures at low pressures or by low energy O 2 + implantation. It has been observed that upon exposure to oxygen the oxygen atoms incorporate into the near surface region of the metal up to 17 atom% (i.e., ReO 0.2 ) by a non-thermally activated process, at least for temperatures below 630 K. At higher exposures and more markedly at high temperatures a suboxide labelled as ReO forms at the surface up to coverages of ≈0.7 monolayers (ML). Bombardment with low energy O 2 + ions caused a higher incorporation of oxygen atoms up to 30 atom% (ReO 0.45 ), but in no case an oxidation state higher than Re 2+ was detected. In addition it is shown that the full width at half maximum (FWHM) of the Re 4f peak can be used to determine the oxygen incorporated into the Re (i.e., ReO x ) during the initial steps of the oxidation process, where no appreciable chemical shifts are observed.

An alternative route for the synthesis of silicon nanowires via porous anodic alumina masks

Amorphous Si nanowires have been directly synthesized by a thermal processing of Si substrates. This method involves the deposition of an anodic aluminum oxide mask on a crystalline Si (100) substrate. Fe, Au, and Pt thin films with thicknesses of ca. 30 nm deposited on the anodic aluminum oxide-Si substrates have been used as catalysts. During the thermal treatment of the samples, thin films of the metal catalysts are transformed in small nanoparticles incorporated within the pore structure of the anodic aluminum oxide mask, directly in contact with the Si substrate. These homogeneously distributed metal nanoparticles are responsible for the growth of Si nanowires with regular diameter by a simple heating process at 800°C in an Ar-H2 atmosphere and without an additional Si source. The synthesized Si nanowires have been characterized by field emission scanning electron microscopy, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and Raman.