Transparent magnetic oxide thin films of Fe3O4 on glass

Transparent magnetic oxide (TMO) thin films of magnetite (Fe₃O₄) were grown on top of a (Zn,Al)O transparent conducting oxide on a glass substrate. The polycrystalline magnetite thin films show the typical Raman spectrum of Fe₃O₄, a sharp Verwey transition at 120 K and hysteretic behavior. The highest achieved average transmittance in the visible range (400-800 nm) for the entire multilayer was slightly below 80%. TMOs permit the inclusion of magnetic functionalities into transparent electronics. Our results show that TMOs can be successfully used to add magnetic functionalities to transparent conducting oxides.     

Magnetic/SiO2 nanocomposite thin films prepared by sol-gel dip coating modified method

Nanocomposite thin films of Spinel Iron-Oxide and SiO₂ have been prepared with sol-gel dip-coating technique involving the synthesis of a ferrofluid, which has been stabilized in absence of organic media and led to the formation of magnetic nanoparticles. Structural and morphological characteristics of the synthesized ferrofluid and the relevant derived nanocomposite films are reported, as determined from X-ray diffraction (XRD), Raman, Fourier-transform infrared, Mössbauer and Ultraviolet-visible experimental techniques. Scanning electron microscopy, atomic force and magnetic force microscopy results are also reported. The synthesized ferrofluid, composed of magnetic nanoparticles of an XRD estimated average size of 18 nm, exhibit Raman spectra characteristic of a maghemite phase. These ferromagnetic nanoparticles retained their nanostructure after being inserted into the as prepared films. After heat treatment under Ar atmosphere, the maghemite nanoparticles were transformed to non-stoichiometric magnetite, providing the final composite material with useful potential application characteristics. The calcined films reported here exhibit crack-free morphology, consisting of aggregated silica/magnetic nanoparticles, with a final average size of c.a. 100 nm, while the film roughness shows a maximum peak to peak of c.a. 10 nm.     

Mechanical properties of a-C:H and a-C:H/SiOx nanocomposite thin films prepared by ion-assisted plasma-enhanced chemical vapor deposition

a-C:H and a-C:H/SiO_x nanocomposite thin films were deposited on silicon, aluminum and polyimide substrates at 25 °C in an asymmetric 13.56 MHz r.f.-driven plasma reactor under heavy ion bombardment. Fourier transform infrared spectra of the films indicate that the nanocomposite filmsappears to consist of an atomic scale random network of a-C:H and SiO_x. Raman spectroscopy revealed that the sp² carbon fraction in the nanocomposite film was reduced compared with the a-C:H film. The intrinsic stress of both films increased with increasing negative bias voltage (−V_dc) at the substrate. However, the nanocomposite films exhibited lower intrinsic stress compared w with a-C:H-only films. Especially, a thin SiO_x-rich interlayer was very effective in reducing the film stress and enhancing the bonding strength at the interface. The interlayer allowed deposition of thick films of up to 5 μm. Also, the nanocomposite films were stable in 0.1 M NaOH solution and showed good microhardness.     

Compositional optimization of magnetite thin films prepared by rf sputtering from a composite target of wüstite and Ge

This study investigated the compositional optimization of magnetite (Fe₃O₄) thin films containing a small amount of Ge to enhance magnetization. No substrate bias was applied during deposition. In a pure Ar atmosphere, the film structure changed from the phase mixture of magnetite and wüstite (Fe_1 − xO) to the weak appearance of wüstite with increasing Ge content. The antiferromagnetic wüstite thus obtained was employed as a starting material to prepare single-phase magnetite, and a gas mixture of Ar and O₂ was then applied. Single-phase magnetite thin films exhibit ferrimagnetic behavior with maximum magnetization of 0.42 T at 1196 kA m⁻¹(15 kOe), which exceeds that of a composite target of ceramic magnetite with Ge chips. Simultaneously adding Ge to the iron-excess wüstite target therefore effectively enhanced magnetization.     

Nanoparticulate magnetite thin films as electrode materials for the fabrication of electrochemical capacitors

Magnetite nanoparticles in stable colloidal suspension were prepared by the co-precipitation method. Nanoparticulate magnetite thin films on supporting stainless steel plates were prepared by drop-coating followed by heat treatment under controlled conditions. The effects of calcination temperature and atmosphere on the microstructure and electrochemical properties of nanoparticulate magnetite thin films were investigated. Nanoparticulate magnetite thin films prepared under optimized conditions exhibited a specific capacitance value of 82 F/g in mild aqueous 1.0 M Na₂SO₄ solution. Due to their high charge capacity, good cycling reversibility, and stability in a mild aqueous electrolyte, nanoparticulate magnetite thin films appear to be promising electrode materials for the fabrication of electrochemical capacitors.     

Synthesis and characterization of carbon nanotube-reinforced epoxy: Correlation between viscosity and elastic modulus

We report the synthesis and characterization of nanocomposite thin films consisting of single-walled carbon nanotubes with different functionalization schemes dispersed in an epoxy matrix. The thermal, rheological, and mechanical properties of nanocomposite thin films were experimentally characterized to establish a relationship between processing and performance. The results from the rheological analysis confirmed that the nanotube type and functionalization strongly affect the resin viscosity during cure. A correlation between the rheological behaviour and the measured elastic properties was established. Nanotubes produced by plasma and functionalized with carboxyl group had the lowest influence on viscosity and led to the highest improvement in elastic properties. The measured increase in elastic modulus was consistent with predictions based on Mori–Tanaka micromechanics.     

Preparation and characterization of self-assembled organic–inorganic nacre-like nanocomposite thin films

The SiO₂/Poly(DMCB) nanocomposite thin films were prepared by supermolerculer self-assembly method on glass substrate. In the nanocomposite thin films, the surfactant DMCB was used as both structure-directing agents and poly monomers. The structures of the films were characterized using FT-IR, XRD and TEM. The results indicated that the films were composed of organic and inorganic layers with orderly interlaced arrangement and the distance between organic layer and inorganic layer was 3.48 nm before polymerization and 2.84 nm after polymerization, respectively.     

Study of Sago starch-CdS nanocomposite films: fabrication, structure, optical and thermal properties

A synthetic procedure for the preparation of nanocomposite films of sago starch and CdS nanoparticles was introduced. The films were characterized using optical, structural, and thermal techniques. The formation of nanostructured CdS in the starch matrix was confirmed by a blue shift in the onset of absorption in the UV-VIS spectra of the nanocomposites. The average size of the nanoparticles varied from 3.6 to 5 nm, depending on the initial concentration of cadmium acetate during the nanocomposite preparation. Fluorescence measurements of the sago-CdS nanocomposite film showed broad emission in the orange-red part of the spectrum. DSC and TGA analyses revealed significant effects of CdS nanoparticles on the thermal properties of the starch matrix.     

Adsorption of polymer coated magnetite composite particles onto carbon nanotubes and their magnetorheology

Polymer coated nano-sized magnetite (Fe₃O₄) particles with multiwalled carbon nanotube (MWNT) nanohybrid were prepared by four step procedures in this study. Initially, magnetic particles were synthesized by a co-precipitation method with ammonium hydroxide and oleic acid, and then the produced particles were coated with polyacrylamide (PAAm). Finally PAAm coated magnetite particles (Mag-PAAm) were physically adsorbed onto multiwalled carbon nanotubes (MWNT) under ultrasonication. Transmission electron microscopy (TEM) was used to investigate the formation of Mag-PAAm-MW nanohybrids nanostructure, confirming that prepared Mag-PAAM particles were well adsorbed onto the surfaces of MWNT. In addition, MR characteristics of PAAm coated magnetite particles with MWNT (Mag-PAAm-MW) nanohybrids were investigated under six different external magnetic field strengths via a rotational rheometer, exhibiting typical MR behavior of yield stress and shear stress.     

Microstructure and hardness of SiC-TiC nanocomposite thin films prepared by radiofrequency magnetron sputtering

Silicon carbide-titanium carbide (SiC-TiC) nanocomposite thin films were prepared by radiofrequency magnetron sputtering using SiC-TiC composite targets fabricated by spark plasma sintering. The SiC thin films were amorphous at substrate temperatures below 573 K and crystallized in the cubic crystal system (3C) at substrate temperatures greater than 773 K. Cubic SiC-TiC nanocomposite thin films, which contain a mixture of 3C-SiC and B1-TiC phases, were obtained at a TiC content of greater than 20 mol%. The amorphous films possessed a dense cross-section and a smooth surface. The morphology of the SiC-TiC nanocomposite thin films changed from granular to columnar with increasing substrate temperature. The SiC-TiC nanocomposite thin films prepared at TiC content of 70-80 mol% and substrate temperature of 573 K showed the highest hardness of 35 GPa.     

Solar absorption and thermal emission properties of multiwall carbon nanotube/nickel oxide nanocomposite thin films synthesized by sol–gel process

Multiwall carbon nanotubes (MWCNTs)/nickel oxide (NiO) nanocomposites were successfully prepared by a sol–gel process and coated on an aluminium substrate. The MWCNTs were chemically functionalized and then added into NiO alcogels, and magnetic stirred for homogeneous dispersion into the NiO matrix solution. The morphology of the resulting nanocomposite thin films showed that the MWCNTs were embedded in the NiO nano-particle matrix, while HRTEM confirmed that the MWCNTs were surrounded by the NiO nano-particles. Raman spectra for functionalized MWCNTs displayed a red shift from the pristine MWCNTs suggesting successful purification/functionalization. The spectrum for the MWCNTs/NiO nanocomposite indicated the presence of both the TO and LO phonons of NiO, and the D and G bands of the MWCNTs. Red and blue shifts of the NiO phonons and the MWCNT phonons suggested that the vibrational properties of both materials were changed to form new nanocomposite vibrational properties. Despite unoptimized layer thickness and composition, the solar absorptance of the functionalized MWCNTs/NiO nanocomposite films was 0.84 (for a single layer). The thermal emittance at 100 °C was approximately 0.2. These results suggest that MWCNTs/NiO nanocomposite materials are suitable for solar thermal applications.     

Evaporation-induced self-assembly of organic–inorganic ordered nanocomposite thin films that mimic nacre

The present study attempts to incorporate acrylate-based polymers into ordered lamellar organic–inorganic nanocomposite thin films composed of alternating Poly(TPGDA)/ITO layers. The films were prepared by dip-coating from a homogeneous solution containing the soluble inorganic metal salts (InCl₃·4H2O and SnCl₂·2H₂O), surfactant, cross-linkers, organic monomers, and initiators, thus leading to composite lamellar nanocomposite materials through evaporation-induced self-assembly method. The final polymer/ITO nanocomposite thin film was obtained by a separate free-radical polymerization step, initiated by UV exposure. Structures and composition of the films were characterized using FTIR, XRD, UV–Vis spectrophotometer and TEM. The results indicated that the films were composed of organic and inorganic layers with orderly interlaced arrangement.     

Dielectric engineering of Ge nanocrystal/SiO2 nanocomposite thin films with Ge ion implantation: Modeling and measurement

Ge nanocrystal (nc-Ge) embedded SiO₂ nanocomposite thin films have been synthesized with the ion implantation technique. The distribution profile of nc-Ge in the SiO₂ matrix can be tailored by varying the implantation energy and dose in the Ge ion implantation process; thus the effective dielectric constant of the nc-Ge/SiO₂ nanocomposite thin films can be engineered. The effective metal–oxide-semiconductor (MOS) capacitance of the nanocomposite thin films has been calculated using the sub-layer model and the Maxwell–Garnett effective medium approximation, taking the reduced dielectric constant corresponding to the nanometer size of nc-Ge into account. On the other hand, capacitance–voltage measurements on the MOS structures based on the nc-Ge/SiO₂ thin films have been conducted to extract the capacitance experimentally. The modeling and measurement results have shown good agreement, suggesting that the nanocomposite dielectric engineering can be easily realized through the energy- and dose-controlled Ge⁺ implantation technique.     

Magnetite thin films

A low temperature process for converting hematite (α-Fe2O3) thin films into magnetite (Fe3O4is described. The films produced are unambiguously identified as magnetite by several complementary methods of analysis. These include α-backscattering spectrography, X-ray powder diffractometry, and observations of electrical, magnetic, and optical properties.     

Thermochromic nanocrystalline Au-VO2 composite thin films prepared by radiofrequency inverted cylindrical magnetron sputtering

Highly crystalline Au-VO₂ nanocomposite thin films were prepared on Corning glass substrates by reactive radiofrequency inverted cylindrical magnetron sputtering (ICMS). It is a low cost potential coating technology for the production of large area uniform nanocomposite thin films exhibiting plasmonic properties. This paper reports the synthesis and feasibility of reliably reproduced high quality of Au-VO₂ by ICMS. Structural, morphological, interfacial analysis and optical properties of synthesized Au-VO₂ nanocomposite thin films are reported.     

Transparent high refractive index nanocomposite thin films

This work reports the preparation of acetic acid-modified TiO₂ nanoparticles by sol–gel synthesis method. The nanoparticles can be incorporated directly into the polymer matrix to form transparent high refractive index nanocomposite thin films. The result shows that increasing the titania content in the hybrid nanocomposite thin films can significantly increase the refractive index. Hybrid nanocomposite thin film with refractive index value of 2.38 had been prepared. All prepared films also exhibit excellent optical transparency in the visible region.     

Copper and iron based thin film nanocomposites prepared by radio frequency sputtering. Part I: elaboration and characterization of metal/oxide thin film nanocomposites using controlled in situ reduction process

Copper and iron based thin films were prepared on glass substrate by radio-frequency sputtering technique from a delafossite CuFeO₂ target. After deposition, the structure and microstructure of the films were examined using grazing incidence X-ray diffraction, Raman spectroscopy, electron probe micro-analysis and transmission electron microscopy coupled with EDS mapping. Target to substrate distance and sputtering gas pressure were varied to obtain films having different amount and distribution of copper nanoparticles and different composition of oxide matrix. The overall reaction process, which starts from CuFeO₂ target and ends with the formation of films having different proportion of copper, copper oxide and iron oxide, was described by a combination of balanced chemical reactions. A direct relationship between the composition of the metal/oxide nanocomposite thin film and the sputtering parameters was established. This empirical relationship can further be used to control the composition of the metal/oxide nanocomposite thin films, i.e. the in situ reduction of copper ions in the target.     

Gold-titania nanocomposite films with a periodic 3D nanostructure

In this study, we synthesized gold-titania nanocomposite thin films by using mesoporous titania thin films formed on indium tin oxide substrates as templates. The pore structure of our mesoporous titania thin films can be described as a periodic 3D pore network by interconnecting 7 nm sized cages. Electrochemical deposition of gold into the pores led to gold-titania nanocomposite films. Both gold and titania form continuous 3D network structures with internal periodicity. Because of the low conductivity of indium tin oxide substrate, the deposited gold formed isotropic islands. The absorption spectrum of the resultant gold-titania nanocomposite thin films showed two peaks, one at 640 nm and the other over a broad range of wavelengths longer than 1500 nm. These peaks grow with the increase of the deposition time but do not change the positions. The optical properties were explained in terms of the unique nanostructure of our gold-titania nanocomposite film.     

Synthesis and characterisation of starch/agar nanocomposite films for food packaging application

In the present work cassava starch/agar Ag and ZnO nanocomposite films were prepared by the solution casting method. The structural, physical and antimicrobial properties of the nanocomposite films were studied as a function of the concentration of Ag and ZnO nanoparticles. The results of the thermogravimetric analysis showed 8–15% degradation of both the nanocomposite films at 150°C endorsing the thermal stability of the films. Scanning electron microscopic analysis reveals the uniform blending of Ag and ZnO nanoparticles with a starch/agar matrix with tiny waves like appearance on the surface. The incorporation of Ag and ZnO nanoparticles in the film was found to reduce the moisture content, water solubility and water vapour permeability with increase in the concentration of Ag and ZnO nanoparticles. The growth kinetics study of Pseudomonas aeruginosa and Staphylococcus aureus in the presence of Ag and ZnO blended nanocomposite films showed promising results especially against Gram‐negative P. aeruginosa. Thus, the film synthesised in the present study bears the potential to be used as active packaging material to prevent food from bacterial contamination and spoilage.Inspec keywords: casting, microorganisms, scanning electron microscopy, nanoparticles, food preservation, solubility, thermal analysis, zinc compounds, food processing industry, food products, thermal stability, permeability, antibacterial activity, food packaging, contaminationOther keywords: water vapour permeability, food packaging, solution casting method, structural properties, physical properties, antimicrobial properties, water solubility, agar nanocomposite film, starch nanocomposite film, Pseudomonas aeruginosa, Staphylococcus aureus, bacterial contamination prevention, spoilage prevention, scanning electron microscopic analysis, thermogravimetric analysis, temperature 150.0 degC, Ag, ZnO     

An efficient method for decoration of the multiwalled carbon nanotubes with nearly monodispersed magnetite nanoparticles

A one-pot method has been developed to prepare magnetite nanoparticles decorated carbon nanotubes (CNTs) by thermal decomposition of iron chloride on CNTs templates in diethylene glycol. The morphological and structural characterizations indicate that magnetite nanoparticles are coated on the surfaces of the CNTs to form CNT-based nanocomposites. The density of magnetite nanoparticles on CNTs could be easily tuned by adjusting the weight ratio of iron chloride to CNTs. Magnetic measurements showed that the nanocomposites are superparamagnetic at room temperature and the magnetic properties of the samples can also be tuned by adjusting preparing conditions. The nanocomposites can be readily dispersed in water to form a stable solution and can be manipulated using an external magnetic field. As-synthesized nanocomposites may have potential applications in target–drug delivery, detection and separations, and in clinical diagnosis.