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A one-step, annealing-free, and rapid aerosol assisted CVD method was used for the growth of composite BiFeO3 coatings. Through this method, an area of approximately 19 cm2 was coated in 7.5 min. Microstructural characterization by X-ray diffraction, Raman spectroscopy, and electron microscopy proved that BiFeO3 can be deposited onto amorphous and crystalline substrates. According to X-ray diffraction and Raman spectroscopy, small amounts of binary oxides of Bi and Fe were found in the samples; however, a more homogeneous BiFeO3 single phase was achieved using TiO2 coated borosilicate glass substrates. The samples exhibited a composite microstructure, which consisted of a thin layer of BiFeO3 (around 70 nm thick) covered by truncated and porous spherical particles of BiFeO3, Bi2O3, and Fe2O3 of several hundreds of nanometers of diameter. Findings suggested a rapid transformation of the precursor solution aerosols while traveling towards the substrate, which due to differences in size and volume, provoked variations in the composition and the development of irregular morphologies. Although the samples exhibited rough surfaces, the porous coatings offer the possibility of having materials with high-surface areas supported on inert substrates, which are attractive for applications involving surface reactions, such as photocatalysis or ambient remediation. The direct band gap of the samples exhibited values of 2.1 and 2.45 eV, reinforcing the feasible use of these materials in applications that could be triggered upon absorption of visible light.

The optimal synthesis conditions for the growth of delafossite CuFeO2 thin films via aerosol assisted CVD were studied. An iterative synthesis process was followed until the average atomic ratio of Cu/Fe in the synthesized thin films was close to 1. TiO2 coated borosilicate was initially used as substrate. Complete characterization of selected samples revealed the formation of polycrystalline CuFeO2 in a rhombohedral phase. Small amounts of tenorite (CuO) were also observed. Further investigation of the growth of CuFeO2 was achieved using ZnO coated borosilicate substrates. The synthesized thin films were in all cases homogeneous and had an average thickness of 45 ± 3 nm and 41 ± 3 nm when grown onto TiO2 or ZnO, respectively. Outcomes indicated an almost negligible influence of the buffer layer on the microstructure and optical properties of CuFeO2. Therefore, the direct synthesis via AACVD technique of this bimetal and visible light absorbing oxide was verified.

The discoloration of methylene blue in aqueous solution was studied under illumination by a fluorescent lamp, LEDs of red, green, and blue light, and a UV-A black light bulb. Overall results showed that methylene blue was discolored with and without the presence of any photoactive semiconductor. Outcomes depended on the combination substrate-light source employed. Photosensitization was assumed as the discoloration mechanism followed upon visible light irradiation. Fluorescence spectroscopy and high-performance liquid chromatography were used to investigate the possible intermediates formed in the irradiated solutions. The detailed nature of formed species was not stablished, but it was proved that the dye molecule photo-bleached and partially defragmented in several intermediates including leuco dyes, demethylated phenothiazine dyes, and probably humic substances. Since the fluorescence intermediates found were similar for most of the irradiated solutions, it was assumed that comparable reactive species were responsible for the discoloration of the molecule in solution. Results proved the misconception of discoloration experiments found in the literature when employing visible light near the absorption region of the dye.

This paper describes the ability of composite Fe-Ti oxides nanoparticles to simultaneously adsorb As5+, As3+, Cd2+, Cu2+, Pb2+ and F− ions from water. The nanoparticles were comprised of tightly bounded Fe3O4, Fe2TiO5 and amorphous FexTixOx crystallites having a mean size of 9 ± 3 nm and a surface area of 208 m2 g−1. Despite the concentration of essayed pollutants in water was higher than that in the guidelines used as reference, outcomes revealed that the nanoparticles enabled the complete removal of As5+, As3+ and Cd2+ after only 1 min. This behavior was maintained for up to 25 min. Moreover, the maxima removal efficiencies for Cu2+ and F−, were 85% and 45% respectively after 15 min. For the case of Pb2+, the percentage of removal was of 94% after 25 min. The observed effectiveness of the adsorbent was attributed to the high surface area and to the presence of multiple oxides in the synthesized material. The study of the thermodynamic equilibrium of the adsorption process was also carried out along with the determination of the capacity of adsorption for each ion. The adsorption free energy indicated that the interactions among the adsorbate and the adsorbent were of the physical type, i.e. physisorption process. The chemical composition analyses performed by XPS and EDXS to recovered nanoparticles confirmed the presence of the studied pollutants at the surface. Overall outcomes confirmed that the composite Fe-Ti oxides nanoparticles could be promising materials for water treatment.

The synthesis of composite Fe-Ti oxides nanoparticles was achieved through the modification of a precursor solution containing different Ti loadings. The nanostructured materials were produced via aerosol assisted chemical vapor deposition method using the conditions reported elsewhere for the synthesis of pure magnetite nanoparticles. The microstructure, morphology, saturation magnetization and surface area of the produced materials were studied using grazing incidence x-ray diffraction and scanning and transmission electron microscopy, Raman spectroscopy, magnetic sample magnetometry and Brunauer-Emmet-Teller method by multi point surface area analysis. Outcomes showed that single crystalline Fe and Ti oxides as well as composite Fe-Ti materials were formed when Ti was added to the precursor solution. Raman spectroscopy confirmed the coexistence of multiple oxides in the samples. Moreover, as the amount of Ti increased, the development of an amorphous phase was seen. An evident modification of the surface morphology of the particles occurred with the change of Fe:Ti ratio, shifting from uniform and smooth, to rough surfaces. Transmission electron microscopy confirmed these observations and revealed that solid-like spherical particles gradually formed as more and more Ti was incorporated. The saturation magnetization values ranged from 30 emu g−1 to about 0.56 emu g−1, less than that of pure Fe3O4 of 45 emu g−1. Surface areas ranging from 107 m2 g−1 to 204 m2.g−1 were obtained. Yet, Batch experiments are needed in order to evaluate how the surface area and heterogeneous composition affect the adsorption capacity of the prepared materials.

In this work, we report the synthesis and characterization of antimony doped tin oxide thin films for their possible application as transparent conducting oxides. Thin films of antimony doped tin oxide were deposited by aerosol assisted chemical vapor deposition. Surface morphology and microstructure were studied by field emission scanning electron microscopy. X-ray diffraction results indicate the presence of two tin oxide phases in some samples (from thickness of 30–120 nm) and only the cassiterite phase in samples with thicknesses greater than of 140 nm. Optical properties of the samples were analyzed by total transmittance spectra. Resistivity of the films was obtained by the sheet resistance method. Electrical properties and conductivity type of samples were determined by Hall effect method. The results show low resistivity in antimony doped tin oxide materials decreasing up to six orders of magnitude compared to pure tin oxide, and obtaining resistivity in the order of magnitude of 10− 4 Ω·cm. Thermal treatment was performed on some materials and stability was observed because it did not decrease its resistivity and in addition the thermal treatment improved Hall mobility.

We report the synthesis and characterization of Al-doped magnetite hollow spheres synthesized by aerosol assisted chemical vapor deposition. The microstructure of the nanoparticles was characterized by grazing incidence X-ray diffraction and transmission electron microscopy. Surface area determination was measured with Brunauer, Emmett y Teller method. Batch removal efficiency tests of As and F − ions were realized at three different contact times of 1, 10 and 15 min by contact with Al-doped magnetite nanoparticles with the As:F − solutions. After the exposure time elapsed, the solutions were immediately centrifuged to separate the nanoparticles. Subsequently, the decanted solution was analyzed by atomic absorption spectroscopy to determine the presence of As and Fe, and by the fluoride selective electrode technique to determine the F − ion. A high and fast As and F − adsorption efficiency was obtained. The adsorption capacity of the nanoparticles was determined and adsorption isotherms were calculated to determine the adsorption mechanism. The collected nanoparticles were analyzed by high resolution transmission electron microscopy to observe the presence of As:F − ions adsorbed on the surface. In addition, the presence of the species of As +3 and As +5 in the nanoparticles were analyzed by μ-X-ray fluorescence and μ-X-ray absorption near edge structure of As K-edge at the Stanford Synchrotron Radiation Lightsource.

Core-shell nanostructures were synthesized by aerosol assisted chemical vapor deposition method. A ZnO nanorod (ZNR) was the core material, while the shell coating was individually film of Ti, Cu-Zn or Fe oxide. The crystalline phases of the synthesized materials were identified as oxides in the form of wurtzite (ZnO), anatase (TiO2), tenorite (CuO) and hematite (Fe2O3). Only for samples prepared using single Ti and Fe sources, amorphous shells were detected. The photocatalytic performance of all samples was tested by the discoloration of methylene blue. Findings confirmed that bare ZnO nanorods and commercial photocatalyst (Degussa P25) are comparable photocatalysts since 99% of dye discoloration was achieved in 60 min. Additionally, discoloration tests performed with the core-shell nanostructures revealed that the ZNR/TiOx and ZNR/CuO-ZnO samples exhibited more than 93% of discoloration in 60 min. Nevertheless, with samples involving ZNR/Fe2O3 and ZNR/FeOx/TiO2/Fe2O3, a maximum of 33% of dye discoloration was measured. Microstructural changes of the samples before and after the photocatalysis essays were examined. Results showed that the bare ZnO and CuO-ZnO coated nanorods dissolved in the aqueous medium. Conversely, the integrity of the ZnO core was evidenced through the morphological and structural analysis, when single TiOx and multiple FeOx and Fe2O3 layers, were employed. Furthermore, quantitative measurement of Zn solubility was performed in selected samples to confirm dissolution inhibition. Noteworthy, outcomes suggest that the functionality of ZnO when applied in aqueous systems could be assured solely with the developed ZNR/TiOx material.

Synthesis of TiO2 nanoparticles in anatase, and anatase-brookite phase mixture, deposited over multilwalled carbon nanotubes (MWCNT) is reported. The materials were obtained from an amorphous titania and MWCNT initial composite, using the sol-gel method at low temperature. To achieve the different crystalline phases, the initial composites were treated at different conditions: i) for the anatase phase, a thermal treatment at 400 °C was carried out, and ii) for the anatase-brookite mixture, the composite was placed in a reflux system at 80 °C during 5 h. The nominal weight percentage of MWCNT added to composites was 5%. The influence of MWCTN on the physical-chemical parameters of TiO2 was studied using diverse characterization techniques such as thermogravimetric analysis, X-ray diffraction, transmission electron microscopy, Raman and UV spectroscopies, and surface area analysis. Results indicate that the TiO2 crystal sizes of the different phases was not affected for the addition of MWCNT. Although, there was an effect on the surface area, vibrations of molecular bonds and on the band gap energy, indicating an interaction between the TiO2 nanoparticles and the carbonaceous support. Prime novelty statement The novelty of the presented research work is the finding of a facile methodology using mild conditions (400 °C) to obtain TiO2 nanoparticles in anatase and anatase-brookite phases in a composite material with carbon nanotubes. The effect of the synthesis conditions as well as the addition of multiwalled carbon nanotubes to TiO2 particles was studied. The most significant achievement was to increase the surface area of the materials while reducing the bandgap. In addition it was possible to obtain small particle size and a well distribution of phases.

In the present work, cupric oxide and cobalt oxide thin films were synthesized as selective absorbent coatings by aerosol-assisted chemical vapor deposition, a simple, relatively inexpensive technique, it can represent an attractive development alternative for the industrial sector. Here it is reported, the synthesis and microstructural characterization of thin films of a single layer or multilayer onto different substrates, the microstructural, optical and morphological properties are presented using X-ray diffraction, UV–Vis-Infrared spectrophotometry and field emission scanning electron microscopy. To complete the work, thermal emittance measurements at different temperatures were acquired from the materials obtained. As a complement, the Tauc method and variations of the Kubelka-Munk method were employed to estimate the band gap of each material. Finally, the influence of the metal oxides synthesized in single layer or multilayers, the thickness obtained from them, their morphological structure and the substrate composition in the spectral selectivity are discussed. The optical properties of the selective materials obtained in the present work clearly indicated the dependence of the thickness and the morphology generated. In general, optimal selectivity values were acquired in the materials obtained. Maximum solar absorptance of 92% and thermal emittance of 0.08 were determined.

Silicon doped multiwalled carbon nanotubes (Si-CNT) were synthesized by a modified chemical vapor deposition method, using toluene as carbon source, ferrocene as metal catalyst and triphenylsilane to provide the dopant atoms. The effect of synthesis temperature and concentration of Si-containing precursor on the microstructural properties were studied by high-resolution scanning electron microscopy (HR-SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and Thermogravimetric analysis. The microscopy results showed that the Si-CNT were structurally modified with various forms of roughness, distortions and defects not only in the inner walls but also on outer walls. The elevated synthesis temperature had the most significant effect in the graphitic carbon network. XPS elemental surface composition analysis showed that the maximum silicon content was 1.3 ± 0.2 at.%. It was found that the increment in the silicon content, inhibited the growth of Si-CNT. According to Raman results, the Si-CNT presented greater structural disorder due to the integration of silicon atoms in the carbon, which increased the disorder in the hexagonal network due to the higher ionic radius of Si. TGA confirmed that silicon was introduced into the Si-CNT and that they are also thermally stable. Based on the results, the nanotube growth mechanism was proposed, which showed that silicon has high mobility and diffusion on the carbon network as the temperature rises. Prime novelty statement The originality reported in the manuscript is the novel and facile method to obtain carbon nanotubes doped with silicon and the effect of synthesis temperature on the physical-chemical properties. Also the growth mechanism of the Si-CNT is proposed.

This chapter presents a brief description of basic concepts of nanostructured materials, with a focus on metal oxides, including its synthesis, microstructure, properties, and applications. Nanostructured metal oxides represent one of the most important and studied class of materials, because they offer a broad range of unique properties, which differ to a great extent to those observed in their bulk analogues. As examples of nanostructured metal oxides, case studies are included: Fe3O4 hollow nanospheres, ZnO and CuO nanorods, and CuFeO2 thin films. Their synthesis conditions via aerosol-assisted chemical vapor deposition (CVD), their characterization and applications for water remediation and H2 generation are also depicted.

The synthesis of anatase TiO 2 nanoparticles by an acid-assisted sol–gel method at 25 and 80 °C is described. Specifically, acetic acid (AA) was used and the evolution of the anatase phase with the amount of AA was observed. The results of X-ray diffraction (XRD) and transmission electron microscopy (TEM) both showed that a pure anatase phase was obtained with particle size smaller than 5 nm. Structural refinements and quantitative determination of phase composition was achieved by using the Rietveld method. The particle size distribution became slightly narrower as the amount of AA was increased. Raman spectroscopy showed that when the amount of AA was increased a small amount of brookite was present at the contamination level. The anatase phase was studied by differential thermal analysis (DTA), providing phase stability up to 600 °C. These and other results were discussed in terms of particle size and structure. Likewise, the formation of the anatase phase under these synthesis conditions was explained.

Copper oxide is a particularly interesting material because it presents photovoltaic, electrochemical and catalytic properties. Its unique properties are very important in the area of nanotechnology and may be an advantage because these nanomaterials can be applied in the design and manufacture of nanosensors, photocatalysis area, nanolasers switches and transistors. Nowadays one-dimensional nanostructures as nanorods, nanowires, etc., have generated a great importance and have received considerable attention and study due to their unique physical and chemical properties. In this work we report the synthesis, microstructural characterization and optical properties of CuO nanorods and nanowires grown by aerosol assisted chemical vapor deposition onto a CuO, ZnO and TiO 2 thin film covered and bare borosilicate glass substrate. Concentration of the precursor solution and carrier gas flux were previously optimized and fixed at 0.1 mol dm −3 and 5 L min −1 , respectively. Other deposition parameters such as substrate temperature, as well the carrier gas velocity and deposition time were varied from 623 to 973 K, 0.88 to 1.77 m s −1 and 11 to 16 min, respectively. Their influence on the morphology, microstructure and optical properties of the nanorods and nanowires were analyzed. The crystalline structure of the materials was characterized by grazing incidence X-ray diffraction; results indicate the presence of the tenorite phase. Surface morphology and microstructure were studied by field emission scanning electron microscopy, and high resolution transmission electron microscopy. Optical properties in the UV–visible–NIR interval were analyzed from reflectance and transmittance spectra.

The development and optimization of methodologies to generate magnetite nanoparticles is currently an innovation topic. For a desired application such as arsenic removal from waste water, the generation of these nanostructures with specific microstructural properties is determinant. Therefore, it is necessary to understand the phenomenon during the nanoparticles formation process. Thus, in this work it is reported the influence of synthesis parameters of AACVD technique on the formation of magnetite nanoparticles. Parameters were according to: (1) synthesis temperature, (2) tubular reactor diameter, (3) concentration of the precursor solution and type of solvent, (4) carrier gas flow and (5) solvent type in the collection process. The effect of these synthesis parameters on the morphology, size and microstructure are discussed in detail and related with the mechanism of formation of the particles. Theoretical simulations were performed on two of these parameters (1 and 4). The microstructure and surface morphology of the different nanostructures obtained were characterized by field emission scanning electron and transmission electron microscopy. Subsequently two materials, were selected for further microstructural analysis. Finally, to determine the removal efficiency in the two materials the arsenic adsorption was evaluated. A major contribution of this work was the calculation of the number of spherical particles formed from a single drop of precursor solution. This calculation matched with the value found experimentally.

Core–shell nanorod structures were prepared by a sequential synthesis using an aerosol assisted chemical vapor deposition technique. Several samples consisting of ZnO nanorods were initially grown over TiO 2 film-coated borosilicate glass substrates, following the synthesis conditions reported elsewhere. Later on, a uniform layer consisting of individual Al, Ni, Ti or Fe oxides was grown onto ZnO nanorod samples forming the so-called single MO x /ZnO nanorod core–shell structures, where MO x was the metal oxide shell. Additionally, a three-layer core–shell sample was developed by growing Fe, Ti and Fe oxides alternately, onto the ZnO nanorods. The microstructure of the core–shell materials was characterized by grazing incidence X-ray diffraction, scanning and transmission electron microscopy. Energy dispersive X-ray spectroscopy was employed to corroborate the formation of different metal oxides. X-ray diffraction outcomes for single core–shell structures showed solely the presence of ZnO as wurtzite and TiO 2 as anatase. For the multi-layered shell sample, the existence of Fe 2 O 3 as hematite was also detected. Morphological observations suggested the existence of an outer material grown onto the nanorods and further microstructural analysis by HR-STEM confirmed the development of core–shell structures in all cases. These studies also showed that the individual Al, Fe, Ni and Ti oxide layers are amorphous; an observation that matched with X-ray diffraction analysis where no apparent extra oxides were detected. For the multi-layered sample, the development of a shell consisting of three different oxide layers onto the nanorods was found. Overall results showed that no alteration in the primary ZnO core was produced during the growth of the shells, indicating that the deposition technique used herein was and it is suitable for the synthesis of homogeneous and complex nanomaterials high in quality and purity. In addition, materials absorptance determined from the total transmittance and reflectance spectra revealed a broader absorption interval including visible light, indicating potential uses of these nanostructures on solar energy appliances.

In this work, it is presented the synthesis, microstructural characterization and photocatalytic properties of bilayered CuO–ZnO/ZnO thin films onto borosilicate glass and fused silica substrates. The films were deposited by aerosol assisted chemical vapor deposition, using an experimental setup reported elsewhere. Deposition conditions were optimized to get high quality films; i.e. they were structurally uniform, highly transparent, non-light scattering, homogeneous, and well adhered to the substrate. Different Cu/Zn atomic ratios were tried for the upper layer. The microstructure of the films was characterized by grazing incidence X-ray diffraction (GIXRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy. GIXRD results indicate the presence of ZnO Wurzite and Cu oxide phases. Results of SEM and HRTEM analysis of the cross sectional microstructure showed that the films were composed of compact and dense layers with no visible evidence of an interfacial boundary or porosity. Optical absorbance of the bilayered films showed a clear shift of the absorption toward the visible range. Optical band gap was determined roughly at 3.2 and 2 eV for ZnO and Cu oxide, respectively. Photocatalytic activity of the samples, for the degradation of a 10 − 5 mol dm − 3 solution of methylene blue (MB), was determined after 120 and 240 min of irradiation with an UV-A source. Around 90% of MB degradation was reached by bilayered films with roughly 50 at.% of Cu in the upper Zn–Cu oxide layer deposited onto a ZnO buffer film.

Nowadays, mesoporous magnetite nanoparticles are an important class of new nanomaterials which occupy a valuable position in materials science. Owing to their several advantages over bulk magnetite and particularly with respect to higher adsorption capacity, there is a growing interest towards the use of these materials for the adsorptive removal of a variety of contaminants, including organic dyes from wastewater. Through aerosol assisted chemical vapor deposition (AACVD) technique is possible to synthesize spherical hollow nanoparticles with external diameter from 50 to 500 nm, composed of a shell of crystallites smaller than 30 nm. In the AACVD method, the structural morphology of resultant nanoparticles strongly depends on the starting precursors and operating conditions. Some advantages of this technique are the high production rate, continuous operation, use of relatively simple equipment, easy doping and the possibility to scale the process industrially. Therefore, in order to understand the formation of magnetite nanoparticles by AACVD, theoretical simulations were performed on two important steps of the synthesis: (i) temperature and carrier gas flow distribution inside of tubular reactor, and (ii) the distribution of molar concentration of the precursor in the synthesis process. Reaction kinetics of the precursor was studied to determine Arrhenius parameters. Activation energy and pre-exponential factor were calculated experimentally from thermal analysis, these values were used in the calculation of reactants and product concentration distribution inside of the tubular reactor. Results from the simulation were compared with those obtained from the experiments.

ZnO nanorods were synthesized by aerosol assisted chemical vapor deposition onto TiO2 covered borosilicate glass substrates. Deposition parameters were optimized and kept constant. Solely the effect of different nozzle velocities on the growth of ZnO nanorods was evaluated in order to develop a dense and uniform structure. The crystalline structure was characterized by conventional X-ray diffraction in grazing incidence and Bragg–Brentano configurations. In addition, two-dimensional grazing incidence synchrotron radiation diffraction was employed to determine the preferred growth direction of the nanorods. Morphology and growth characteristics analyzed by electron microscopy were correlated with diffraction outcomes. Chemical composition was established by X-ray photoelectron spectroscopy. X-ray diffraction results and X-ray photoelectron spectroscopy showed the presence of wurtzite ZnO and anatase TiO2 phases. Morphological changes noticed when the deposition velocity was lowered to the minimum, indicated the formation of relatively vertically oriented nanorods evenly distributed onto the TiO2 buffer film. By coupling two-dimensional X-ray diffraction and computational modeling with ANAELU it was proved that a successful texture determination was achieved and confirmed by scanning electron microscopy analysis. Texture analysis led to the conclusion of a preferred growth direction in [001] having a distribution width Ω = 20° ± 2°.

This work reports the synthesis, micro-structural characterization and optical properties of lithium niobate (LiNbO3) thin films deposited by aerosol assisted chemical vapor deposition (AACVD) on silicon substrates. The films deposited were polycrystalline, uniform, dense, non-light scattering and firmly adhered to the substrate. This was deduced from high resolution electron microscopy studies and spectral reflectance measurements. The films were not epitax­ial; however, they are considered smooth enough to be employed in optical waveguide applica­tions, since their roughness is very low compared to the wavelength of the utilizable radiation.

This paper presents the effect of Ni in PtRu electrocatalysts over multiwalled carbon nanotubes (MWCNT) utilized for the electro-oxidation of methanol with the purpose of increasing reaction activity and tolerance to carbon monoxide. Two kinds of MWCNT were prepared using the same technique but different catalytic agents, ferrocene, and nickelocene. MWCNT obtained from ferrocene were treated after the synthesis to eliminate amorphous carbon and Fe excess, while MWCNT from nickelocene were used as synthesized to leave the nickel nanoparticles formed during the synthesis. PtRu particles were deposited over the surface of both types of MWCNT in order to study the effect of the Ni presence. The structure of the electrocatalysts was analyzed by transmission electron microscopy (TEM) and X-ray diffraction (XRD). Chemical elemental microanalysis was carried out by X-ray energy dispersive spectroscopy (EDS). The synthesized MWCNT had an average diameter in the order of 60 nm and an average length of about 30 microns. Metallic nanoparticles deposited had a particle size in the order of 10 nm each. The electrochemical surface area (ESA) was measured using CO stripping curves and the activity toward the methanol oxidation reaction was evaluated. The ESA was improved with the presence of Ni, achieving an activity and onset potential similar to a commercial electrocatalyst (20 wt% PtRu/C, ETEK) with a lower PtRu loading (10 wt% PtRu).

New nanotechnology alternatives and methodologies have been developed in order to overcome the limitations of conventional techniques for metal ions removal from water. Currently, the removal of heavy metals requires multiple steps which include the separation and post-treatment of the generated sludge. Usually, this sludge is composed of dangerous environmental pollutants mixed with the material used for removing the metal ion. Thus, the removal of these metals becomes a challenging task. Herein we report the synthesis of magnetite nanoparticles with high specific area by the aerosol assisted chemical vapour deposition method. Deposition temperature were fixed at 450 °C and a mixture of Ar–air were used as a carrier gas, a flow of 1.0 and 0.015 L min−1 were used for Ar and air, respectively. The precursor solution was a dilution of Fe (II) chloride in methanol, with different concentration 0.01, 0.05 and 0.1 mol dm−3. The crystalline structure of the nanoparticles was characterized by grazing incidence X-ray diffraction. Morphology and microstructure were analyzed by field emission scanning electron microscopy, scanning probe microscopy and transmission electron microscopy. Magnetic properties were evaluated with a vibrating sample magnetometer and specific area was measured by the Brunauer–Emmett–Teller method. To determine the removal efficiency of arsenic ion from water, several tests were carried out at six exposition times 1, 3, 5, 10, 20 and 30 min. Results showed high removal efficiency, more than 99%, in less than 1 min.

ZnO thin films were deposited inside of fused silica tubing by aerosol assisted chemical vapor deposition technique. The films were transparent, uniform, highly adherent and non-light scattering. Photocatalytic activity of internally ZnO coated tubing was evaluated by discoloration of a methyl orange aqueous solution in a batch reactor. Tubing was externally irradiated with UV-A at room temperature. A one dimensional model was proposed to calculate the spatial distribution of the carrier density and the films’ surface charge carrier concentration. This model can explain the influence of the films thickness on the photocatalytic activity. Results showed that the photocatalytic activity largely depends on the film thickness. For external irradiation of the films the optimum thickness was around 60–70 nm, for which the photocatalytic activity was maximum. The photonic efficiency of internally ZnO coated tubular reactors was evaluated as a function of initial colorant concentration, irradiation time and intensity. Furthermore, due to the high activity of the ZnO films, the films were repeatedly exposed to UV-A irradiation cycles, followed by activity measurement.

Globally, water pollution is mainly caused by the presence of heavy metals and metalloids such as arsenic. The majority of the techniques employed in the removal are of low efficiency and high cost. Therefore, in this work it is presented the adsorption processes of arsenic (As III and V) ions employing magnetite nanoparticles (MNPs) synthesized by the aerosol assisted chemical vapor deposition (AACVD) process. The adsorption efficiency was determined at different times and concentrations. The remaining As concentration in the solutions was analyzed by atomic absorption spectroscopy. The adsorbed As ions on the surface of the NMPs was analyzed by high resolution transmission electron microscopy. The results showed an overall removal efficiency of 87% for As+3 and 98% for As+5, in a contact time of 15 minutes. Results suggested the use of NMPs as a promising alternative in the removal of As ions in water.

Lead titanate PbTiO3 films were deposited onto Pt(111)/Ti/SiO2/Si(100) substrates by the aerosol assisted chemical vapor deposition (AA-CVD) process followed by thermal annealing at 550 °C for 12 h. Piezoresponse force microscopic observations revealed a nano laminar domain structure in the PbTiO3 grains, and we attribute the lamellar domains to 180 and 90° ferroelectric domains. The polarization-switching mechanism of the domains in the representative PbTiO3 film under an external electric fields has also been studied, and it was revealed that a large-area polarization switching is usually accompanied by the appearance of a new direction of 90° domains in order to reduce the stress in the grains. Finally, nanomechanical properties such as the elastic modulus and hardness were evaluated by nanoindentation using the continuous stiffness measurement technique.

This work presents the synthesis, characterization and electrochemical evaluation of electrocatalysts for PEM fuel cells base on Pt and Pt–Ni nanoparticles over multi-walled carbon nanotubes (MWCNT). The MWCNT were synthesized by spray pyrolysis of toluene, using ferrocene and nickelocene as catalytic agents. The Pt nanoparticles were deposited using the ultrasound assisted aqueous deposition method, followed by either thermal or chemical reduction. The materials were characterized by scanning and transmission electron microscopy, as well as X-ray diffraction. The MWCNT exhibit lengths of 200 μm (using ferrocene) and 30 μm (using nickelocene) and diameters around 50–70 nm. Pt nanoparticles showed sizes between 4 and 8 nm. The electrochemical active area toward the hydrogen oxidation reaction was evaluated by cyclic voltammetry (CV) in a standard three electrodes cell. In addition to corroborate the electrochemical active area, CO stripping tests were done. From both, the CV and CO stripping analyses, it was found that the synthesized electrocatalysts exhibited an electrochemical activity higher (140–230 m2gr−1) than 10%Pt/Vulcan (Etek).

Water extractable arabinoxylan (WEAX) aerogels were prepared by extracting the solvent from the alcogels (WEAX hydrogels with an alcohol as the solvent) with carbon dioxide under supercritical conditions. WEAX aerogels were characterized using scanning electron microscopy and adsorption and desorption nitrogen isotherms. The micrographs indicate a heterogeneous porous network structure in WEAX aerogel. Adsorption/desorption nitrogen isotherms of this material were type IV, which confirm that this material possess a mesoporous structure. WEAX aerogels rehydration capability was evaluated and the water absorption mechanism was determined. The WEAX aerogels water absorption mechanism was non-Fickian (n = 0.54).

Thin films of PbTiO3 were deposited onto (001) silicon single-crystal substrates by aerosol assisted chemical vapor deposition method at different temperatures, using organometallic precursors. With the objective of stabilizing and homogenizing the perovskite phase, the films were annealed at 800 °C, in a Pb-rich atmosphere, for 4 and 6 h. The evolution of compositions and microstructure of the films was characterized before and after annealing, by grazing incidence X-ray diffraction, two-dimensional detection of grazing incidence diffraction with synchrotron radiation, scanning electron microscopy and high resolution transmission electron microscopy. X-ray diffraction results showed that the crystalline structure of optimized PbTiO3 films corresponded to a tetragonal perovskite-type, with lattice parameters a = 0.387(4) nm and c = 0.406(4) nm. In addition, the inverse pole figure of the fiber texture representation, had a Gaussian (1, 1, 0) component and distribution width Ω = 15°.

Carbon nanotube/2024 aluminum alloy (CNT/Al2024) composites were fabricated with a combination of mechanical alloying (MA) and powder metallurgy routes. Composites were microstructurally and mechanically evaluated at sintering condition. A homogeneous dispersion of CNTs in the Al matrix was observed by a field emission scanning electron microscopy. High-resolution transmission electron microscopy confirmed not only the presence of well dispersed CNTs but also needle-like shape aluminum carbide (Al4C3) crystals in the Al matrix. The formation of Al4C3 was suggested as the interaction between the outer shells of CNTs and the Al matrix during MA process in which crystallization took place after the sintering process. The mechanical behavior of composites was evaluated by Vickers microhardness measurements indicating a significant improvement in hardness as function of the CNT content. This improvement was associated to a homogeneous dispersion of CNTs and the presence of Al4C3 in the aluminum alloy matrix.

Thin films of yttria-stabilized zirconia (YSZ) exhibit exceptional properties, such as high thermal, chemical and mechanical stability. Here, we report the synthesis of YSZ thin films by aerosol assisted chemical vapour deposition onto borosilicate glass and fused silica substrates. Optimum deposition temperature was 673 ± 5 K. In addition, different Y content was tried to analyse its influence in the microstructure and properties of the films. The films were uniform, transparent and non-light scattering. Surface morphology and cross sectional microstructure were studied by field emission scanning electron microscopy. The microstructure of the films was characterized by grazing incidence X-ray diffraction. Crystallite size and lattice parameter were obtained. Optical properties were analysed from reflectance and transmittance spectra; from these measurements, optical constants and band gap were obtained. Quantum confinement effect, due to the small grain size of the films, was evident in the high band gap energy obtained. Nanoindentation tests were realized at room temperature employing the continuous stiffness measurement method, to determine the hardness and elastic modulus as a function of Y content.

The 2024 aluminum alloy produced from elemental powders and reinforced by the addition of carbon nanotubes were microstructural and mechanically characterized. Composites were synthesized through milling process followed by cold consolidation, sintering and hot extrusion. The effect of the nanotubes on the microstructure and mechanical properties were analyzed in the composites after T6 thermal treatment. Al 4 C 3 formation was due to the reaction of carbon nanotubes and Al matrix. Precipitated Al–Cu phase coexists and presents interaction with crystallized carbide and dispersed nanotubes. There is a direct relationship of carbon nanotubes content and hardness answer.

A feasible method to synthesize CuO covered ZnO nanorods was realized. Firstly, ZnO nanorods were grown by wet-chemical route at 90 °C onto borosilicate glass substrates. Subsequently, the CuO covered ZnO matrix was obtained by Aerosol-Assisted Chemical Vapor Deposition at different temperatures (300, 400, 500 and 600 °C). The CuO–ZnO nanocrystals were microstructurally characterized by electron microscopy and Rietveld refinement. Results showed a CuO formed nanocrystals but also an amorphous fraction of CuO which increases with the synthesis temperature. Additionally, it was evident the presence of secondary copper-oxide phase (paramelaconite), which also has grown over the ZnO nanorod surface.

The wear behavior of the 2024 aluminum alloy and its composites was evaluated through a pin-on-disk system. For this purpose the aluminum alloy was reinforced by carbon nanotubes dispersion produced by milling process. The nanotubes dispersion was carried out using a high energy mill for a fixed milling time. Milled powders were cold consolidated, sintered and then microstructurally and mechanically evaluated. The wear behavior of the alloy and its composites was evaluated considering the different nanotube contents under several abrasive conditions. The composites with higher nanotube concentration (5.0 wt%) displayed an improved wear resistance in all cases evaluated in this work.

Nanostructured composites of 7075 aluminum alloy and carbon coated silver nanoparticles were produced by mechanical milling and indirect hot extrusion. The milling products were obtained in a high energy SPEX ball mill, and then were compacted by uniaxial load and pressure-less sintered under argon atmosphere. Finally, the sintered product was hot extruded. Carbon coated silver nanoparticles were well distributed in the matrix of the extruded material. Tensile tests were carried out to corroborate the hypothesis that second phase particles, well dispersed in the matrix, improve the strength of the material. High resolution transmission electron microscopy was employed to locate and make sure that the silver nanoparticles were homogeneously and finely dispersed.

In the present work, the 2024 aluminum alloy (Al2024) alloy has been produced by mechanical alloying (MA). The alloy was then strengthened by dispersion of carbon nanotubes (CNTs) during different times. Thus, the effect of CNTs concentration and milling time on the microstructure of the Al2024-CNTs composites was studied. The results show a homogeneous dispersion of CNTs into the Al-matrix phase by mechanical milling (MM). It was observed that the increment in the milling time, for a fixed amount of CNTs, causes a reduction of the particle size of powders resulting from MA. The finest particle size was obtained at 20 h of milling. These observations were confirmed by scanning and transmission electron microscopy. After 10 h of milling, Cu, Mg and other alloying elements constituting the Al2024 alloy, form a solid solution and only some remnant Mn particles were observed but not detected by X-ray diffraction.

Al-based composites were fabricated by solid-state route and were characterized by optic and scanning electron microscopy in order to follow their microstructural evolution. Composites were prepared using powder metallurgy techniques in order to obtain samples to carry out mechanical tests on hot extruded and machined samples. Microstructural characterization reveals that, by milling, a homogeneous dispersion of insoluble particles into Al matrix is obtained; this produced an important improvement on hardness and strength compared with the reference. Milling intensity and particle concentration have an important effect on the mechanical properties of composites.

Many semiconductor oxides (ZnO, TiO 2 , SnO 2 ) when doped with a low percentage of non-magnetic (V, Sc) or magnetic 3d (Co, Mn, Ni, Fe) cation behave ferromagnetically. They have attracted a great deal of interest due to the integration of semiconducting and magnetic properties in a material. ZnO is one of the most promising materials to carry out these tasks in view of the fact that it is optically transparent and has n or p type conductivity. Here, we report the synthesis, microstructural characterization and optical properties of undoped, V and Sc doped zinc oxide thin films. ZnO based thin films with additions of V and Sc were deposited by the Aerosol Assisted Chemical Vapour Deposition method. V and Sc were incorporated separately in the precursor solution. The films were uniform, transparent and non-light scattering. The microstructure of the films was characterized by Grazing Incidence X-ray Diffraction, Scanning Electron Microscopy, and Scanning Probe Microscopy. Average grain size and surface rms roughness were estimated by the measurement of Atomic Force Microscopy. The microstructure of doped ZnO thin films depended on the type and amount of dopant material incorporated. The optical properties were determined from specular reflectance and transmittance spectra. Results were analyzed to determine the optical constant and band gap of the films. An increase in the optical band gap with the content of Sc dopant was obtained.

Elemental powders and carbon nanotubes (CNTs) were mixed and milled in a high energy shaker mill (SPEX-8000M), to produce 2024 aluminum (Al2024) matrix composites reinforced with CNTs. Milled products were consolidated by uniaxial load pressing followed by pressure-less sintering under argon atmosphere for 2 h at 773 K. The effect of CNTs concentration and milling time on Vickers microhardness (µHV) was studied. Scanning electron microscopy (SEM) micrographs show that by milling process it is possible to obtain a homogeneous dispersion of CNTs into the aluminum matrix. The mechanical properties of the composites show an important improvement with respect to reference samples. The possible strengthening mechanisms are discussed in the present work.

Composites of 7075 aluminum alloy (Al7075) with carbon-coated silver nanoparticles (Ag-C NP) were prepared by the mechanical milling process. It had been found that Ag-C NP have an effect in refining the powder and in the crystal size. MgZn2 phase presents in annealed samples was dissolved by milling process. The Vickers microhardness (HVN) values are higher at higher Ag-C NP contents. It has been found that a saturation point exists where microhardness does not present variation.