Nanocomposite SiO2 Research Articles

Hydrophobic and antibacterial properties of textiles using nanocomposite chitosan and SiO2 from rice husk ash as-coating

This research aims to develop hydrophobic and antibacterial properties of textiles using chitosan and silica oxide (SiO2) nanocomposite coating. SiO2 was extracted from rice husk ash and chitosan from crustacean shells. SiO2 and chitosan powder were pulverized using High Energy Milling (HEM). The nanocomposite was synthesized using the sol-gel method with concentration variations of 0.2 %:0.4 %, 0.4 %:0.6 %, 0.6 %:0.8 %, and 0.8 %:1 %. Textile coating was carried out by dip coating method with variations of 1x, 2x, 3x, and 4x dyeing. The crystal structure and size of the nanocomposites were obtained using X-ray Diffraction (XRD). Surface morphology and particle size were obtained using a Scanning Electron Microscope (SEM). The contact angle was measured using the sessile drop method. The bacterial activity tests were conducted by measuring the surface temperature of textiles with a thermal camera after being irradiated with UV-C. The ability of textiles to inhibit bacterial growth was tested using Staphylococcus aureus bacteria. The results showed that the smallest crystal size obtained was 30.21 nm. The amount of particle size and contact angle are significantly influenced by the quality of Citosan-SiO2 and coloring changes. The smallest particle size obtained is 32 nm. The highest value of contact angle obtained was 161° The average surface temperature of the textile after being irradiated with UV-C reached 40.7 °C. The highest zone of inhibition obtained was 17 mm and is in the strong category. This research shows that textiles coated with chitosan-SiO2 can inhibit bacterial growth and have potential applications in the clothing industry.

Erbium activating effect on the photoluminescence, morphology, and structure studies of nano-composite Phospho-silicate SiO2–P2O5

Smart nano-composites Phospho-silicate (SiO2–P2O5) prepared in monolith form containing 16 mol% P2O5, and doped with different mol% of Er3+ ions between 0.5 and 5 mol%; the composite has been synthesized by Sol-Gel technique, and subsequently annealed at 850 °C.X-ray diffraction patterns show the structural properties of the mentioned prepared samples, giving rise to the crystallite sizes to increase in a range between 18, and 20.8 nm as the molar percent of the Er3+ ion increase from 0% to 5%. The morphology, and surface morphology of the prepared samples were characterized using TEM, and FESEM, respectively. The Raman analyses show that the active Raman bands are corresponding to silicate, and phosphate. These bands were enveloped by the strong asymmetric vibrations of Er2O3 at 420, and 840 cm−1, their Bose-Einstein corrected intensities increased gradually by increasing the Er3+ ions concentration in the regions from 3400 up to 3450 cm−1, and 3550 up to 3700 cm−1. The optical studies show that the refractive index increased by increasing Er3+ ions concentration, from 1.7 up to 1.8 for as the concentration of Er3+ ions increase. The photoluminescence are exhibiting an emission with splitting at 1545, and 1555 nm, which is related to the intra 4F transition. It has been found that the optimal doping content of Er is 1 mol% then, after quenching caused by OH groups in Er3+ ions doped Phospho-silicate at higher concentrations. It is obviously that 1 mol% of Erbium ions is a suitable candidate for photonic applications such as Laser waveguide, and optical amplifier.

Preparation of eco-friendly natural rosin-based SiO2–NH2@GO hybrid sealant and study on corrosion resistance of Fe-based amorphous coating for steel substrate

Sealing treatment is an effective method to prolong the service life of Fe-based amorphous coatings for steel substrates. Common sealants always have the disadvantages of releasing amounts of volatile organic compounds (VOC) and are expensive, prompting researchers to develop an eco-friendly, low cost and high-performance sealant. However, their simultaneous improvement is restricted by some inevitable contradictions among them. Herein, natural rosin was introduced as a sealing material and an eco-friendly natural rosin-based SiO2–NH2@GO hybrid sealant was successfully prepared by the sol-gel method. In addition, the functional nanocomposite SiO2–NH2@GO was added to the hybrid sealant system to achieve the purpose of extending the service life of the sealant. The filling efficiency, adhesion, thermal stability and long-term corrosion resistance of hybrid sealants were investigated. The study showed that the adhesion of the hybrid sealant to the Fe-based amorphous coating was improved by 10.59% after adding the nanocomposite. The hybrid sealant reaches maximum thermal decomposition at 414.3 °C. The corrosion current density (icorr) of the sample NSG-0.5‰ still decreased by about two orders of magnitude after immersion for 672 h (0#, icorr = 1.39 × 10−4 A/cm2; NSG-0.5‰, icorr = 1.51 × 10−6 A/cm2). Full immersion experiments explore the failure process of hybrid sealants, where corrosion always tends to propagate with unmelted particles. The hybrid sealant prepared has the advantages of being eco-friendly and low cost, and provides a specific preparation process, which provides a new direction for the development of the sealant.

Fabrication of a novel nanocomposite SiO2–H3BO3–V2O5–Al2O3 via melt-quenching technique: structural and surface morphological characteristics for carbon dioxide gas sensing applications

Fabrication of a novel nanocomposite SiO2–H3BO3–V2O5–Al2O3 via melt-quenching technique: structural and surface morphological characteristics for carbon dioxide gas sensing applications

Evaluation of the Mechanical Characteristics of Hybrid Nanocomposite Materials (TiO2-SiO2- ZrO2)

Hybrid nanocomposite materials have opened the way for more promising applications in the areas of optics, electronics, Ionics, mechanics, energy, environment, biology and medicine. In this work hybrid nanocomposite materials were synthesized, by mechanical stirring method, using SiO2+ZrO2+TiO2 nanoparticles with different percentages (4 wt.% to 10 wt.%), as a reinforcement material. The effect of the added nanoparticles on the mechanical properties was evaluated in terms of tensile strength, impact strength and hardness. The results revealed that the hybrid nanocomposite with 4 wt.% SiO2+ZrO2+TiO2 showed maximum tensile strength, hardness, and impact resistance. Further, the best development in the mechanical properties achieved in the literature, due to the addition of different Nano fillers (TiO2, SiO2, and SiO2 +ZrO2) with different percentages (4 wt.% to 10 wt.%), were compared with the achieved results in the present work. The results showed that the addition of hybrid nanocomposite SiO2+ZrO2+TiO2 provides significant mechanical properties development compared to the other materials addition.

SiO2 NPs-PQ/PMMA Photopolymer Material Doped with a High-Concentration Photosensitizer for Holographic Storage.

Dispersing nanoparticles and increasing the photosensitizer concentration have been regarded as effective approaches for improving the performance of a holographic storage material. In this paper, SiO2 nanoparticle (NP)-dispersed PQ/PMMA nanocomposite material (SiO2 NP-PQ/PMMA) with a high PQ doping concentration was prepared. By introducing the co-monomer methyl isobutyl ketone (MIBK) that comes from an SiO2 NP colloidal solution, the concentration of PQ in the system increased to 1.2 wt %. We investigated the performance of polarization holographic recordings in both traditional PQ/PMMA and nanocomposite material SiO2 NP-PQ/PMMA with the orthogonally polarized signal and reference waves. With the dispersion of the SiO2 NPs colloidal solution and the increase in the PQ concentration, diffraction efficiency and photoinduced birefringence were multiplied. In addition, high-quality holographic image reconstruction was achieved by our homemade material.

Molecular Dynamics Simulations on Polymeric Nanocomposite Membranes Designed to Deliver Pipobromane Anticancer Drug

Three chitosan (CS), polyethylene glycol (PEG) and polylactic acid (PLA) nanocomposite systems containing SiO2 nanoparticles and water molecules were designed by molecular dynamics (MD) simulations to deliver pipobromane (PIP) anticancer drug in order to discover the most appropriate drug delivery system (DDS) in aqueous medium which was analogous to the human body. The density for the CS matrix was 1.25 g/cm3 but it was decreased to 1.16 g/cm3 in PLA and 1.02 g/cm3 in PEG. The potential energies of the CS, PLA and PEG DDSs were near 195000, 3700 and –4600 kcal/mol while their related non-bond energies were around 14000, –150 and –6150 kcal/mol, respectively, indicating the PEG composite had the most negative energies whereas the most positive values belonged to the CS system. The CS system revealed the greatest fractional free volume (FFV) of 77.232% but PLA offered the smallest FFV (65.804%). The radial distribution function (RDF) data displayed that the PIP molecules had strongest H-bond interactions with the CS chains which reflected the drug molecules would diffuse the slowest inside the CS nanocomposite. The diffusion coefficients for the PLA, PEG and CS systems were equal to 0.0183×10–4, 0.0163×10–4 and 0.0154×10–4 cm2/s, respectively approving the slowest drug diffusion was happened in the CS cell which certified the most controlled and sustained drug delivery.

Peculiarities of electron transport in SiOx films obtained by ion-plasma sputtering

The electrical conductivity of SiOx and nanocomposite SiO2(Si) films obtained by ion-plasma sputtering with subsequent high-temperature annealing has been investigated. On the basis of the detailed analysis of the current characteristics some electric parameters have been calculated and mechanisms of the electrical conductivity of the SiOx and SiO2(Si) films have been determined. The electrical conductivity of the films is based on the mechanism of hopping conductivity with variable-range hopping through the traps near the Fermi level (Mott’s mechanism). The minimum of current in current–voltage characteristics has been revealed in the temperature range 78–225 K. The qualitative model for explanation of the features of electron transport in SiOx and SiO2(Si) films has been proposed.

Resonant tunneling at electron field emission from Si tips coated with SiO2(Si) films

The electron field emission from Si tips coated with ultrathin nanocomposite SiO2(Si) films containing Si nanocrystals embedded into silicon dioxide matrix of varying thickness have been investigated. The peaks in emission current–voltage characteristics have been observed in case of some definite thicknesses of the films. The observed experimental results have been explained on base of resonance tunneling through multilayer structure containing SiO2 sublayer from one (inner) side and SiO2 sublayer + vacuum from outer side as the barriers and Si nanocrystals as the quantum well. The fitting of theoretical modeling to experimental results allowed to clarify some details of the nanostructure.

Electron transport through nanocomposite SiO2(Si) films containing Si nanocrystals

Electron transport through nanocomposite SiO2(Si) films containing Si nanocrystals

Electron Transport through Thin SiO<sub>2</sub> Films Containing Si Nanoclusters

The electron transport mechanisms through nanocomposite SiO2(Si) films containing Si nanoclusters into dielectric SiO2 matrix have been investigated. SiO2(Si) films were obtained by oxide assisted growth. At the first stage the SiOx films with different content of excess Si were deposited by LP CVD method. Second stage includes high temperature (T=1100 C) annealing of SiOx films that promotes formation of Si nanocrystals. Current transport through SiO2(Si) films were studied in temperature range 100-350 K. As it was observed the dominant mechanism of electron transport depends as on voltage and temperature. The Mott’s conductivity caused by traps near Fermi level was revealed in low-voltage range for all temperatures. At increasing the voltage the SCLC conductivity is observed for films with higher content of excess silicon while in case low content of Si the Pool-Frenkel mechanism dominates. The further increase in voltage results in a double carrier injection.

Transformation of SiOx films into nanocomposite SiO2(Si) films under thermal and laser annealing

Transformation of SiOx films into nanocomposite SiO2(Si) films under thermal and laser annealing

Nanocomposite films prepared from stabilized aqueous SiO2 sols

Using sol-gel method, the films containing appropriate nanoparticles have a wide range of application as protective, dielectric and superhydrophobic layers. The system “stabilized aqueous SiO2 sol–acetic acid–isopropyl alcohol” was used to study the possibilities of preparation of nanocomposite SiO2 films and their properties. The properties of surface of prepared films, such as morphology, topography and adhesion forces, were studied using atomic force microscopy (AFM). The contact angle of water and diiodomethane was measured to specify the polar and disperse components of surface tension. The changes in observed properties, mainly the difference of samples X4, X5 and X6, are explained on the basis of changes in stabilization process of sols used for films preparation. For the given observed properties, the determining process is the change from electrostatic to steric stabilization of studied sols.

Electrical Properties of Composite Films with Silicon Nanocrystals in the Insulating Matrix

The electrical properties of nanocomposite SiO2(Si) films containing Si nanoclusters have been investigated. The films were formed by oxide assisted growth that included ion plasma sputtering (IPS) of Si target and following high temperature annealing. It was determined that electrical conductivity of the films correspond to the mechanism of hopping conductivity with variable hopping length through the traps near the Fermi level (Mott mechanism) due to the large number of silicon dangling bonds in the dielectric matrix. The peculiarities of charge capture in nanocomposite SiO2(Si) films for their application as the medium for charge storage in memory cells have been investigated by C-V method. The good charge storage possibility of SiO2(Si) films formed by IPS deposition with followed temperature annealing has been observed. The negative differential capacitance has been revealed in conditions of semiconductor surface accumulation. The physical model for explanation of the negative differential capacitance of MIS structures with nanocomposite SiO2(Si) films as the dielectric has been proposed. The model is based on the parallel conjunction of the oxide capacitance and nanocrystals capacitance.

FORMATION OF SILICIM MICRO- AND NANOSTRUCTURES FOR ELECTRON FIELD EMISSION

In this work resonance-tunnel structure based on nano-composite films SiO2 (Si),which contain Si nanocrystals in a dielectric matrix have been formed by method of chemical deposition at low pressure (LP CVD — low pressure chemical vapor deposition) and ion plasma sputtering (IPS).Silicon nanosize structures were formed as on a flat surface and on the silicon tip. The formation of silicon nanoislands from silicon enriched SiOx films were performed during annealing at temperatures of 10000C, 1100°C and 10500C. AFM topography image of the original SiOx and annealing films, deposited by ion-plasma sputtering have been obtained. The influence of annealing for samples with different concentration of silicon in the initial film have been investeng on nanoclastersize. The effect of nonmonotonic electron field emission (EFE) from the surface film SiO2 (Si) formed by LP CVD method has been revealed.

Effects of Dispersoids on Wear Behavior of Cu-Based Nanocomposite Containing SiO2 Nanoparticles

Solid particles in discontinuous reinforcement metal matrix composites (DRMMCs) drastically improve their strength. Since the strength of DRMMCs is improved by the Orowan mechanism, smaller particles, such as nanoparticles, are effective as dispersoids. In this study, the effects of nanoparticles on the sliding wear behavior of DRMMCs are investigated using Cu-based composites containing 0.6, 1.2, and 1.7 vol % SiO2 particles. Wear resistance of the Cu–SiO2 composite is improved by increasing the volume fraction of SiO2 particles. Moreover, the amount of wear for the Cu–SiO2 composites increases with increasing sliding distance and then becomes saturated beyond about 1000 m. Vickers hardness for all specimens becomes the same regardless of the volume fraction of SiO2 particles as the sliding distance increases. This behavior can be explained by the work-hardening rate of the Cu matrix and the critical hardness for adhesion with a counter-material. It is found that nanoparticles in DRMMCs improve wear resistance by increasing the work-hardening rate of the metal matrix.

Structural properties of nanocomposite SiO2 (Si) films obtained by ion-plasma sputtering and thermal annealing

The nanocomposite SiO2(Si) films containing Si nanoclusters inside insulating SiO2 matrix are promising for many nanoelectronics applications. The ion-plasma sputtering of Si in O2 containing gas mixture and following thermal annealing have been used to form nanocomposite SiO2(Si) films. The structural properties of the obtained films have been studied using several methods. Among them, there were ellipsometry, IR spectroscopy, Raman spectroscopy, and AFM. Transition of SiOx matrix into insulating SiO2 matrix has been revealed by IR spectroscopy. The shift of the transmittance spectra toward high frequency region and the increase in their intensity have been observed. The existence of amorphous and nanocrystalline phases into SiO2(Si) films have been confirmed using Raman spectroscopy. Two material phases on the film surface, namely SiO2 and Si, and surface density of silicon nanoclusters have been determined using AFM. It was shown that the size of silicon nanoclusters and their surface density depend on the level of enrichment with silicon of the initial SiOx film after ion-plasma sputtering and the temperature of subsequent annealing.

Resonant tunnelling through individual Au nanoclusters embedded in ultrathin SiO2 films studied by Tunnelling AFM

The observation of the resonant electron tunnelling through the individual Au nano-clusters (NCs) embedded in the ultrathin (4−5 nm thick) SiO2 films on n-Si(001) substrates by Tunnelling Atomic Force Microscopy (TUNA) at 300K is reported. The nanocomposite SiO2:NC-Au structures with Au NCs 3–7 nm in lateral size and 1–2 nm in thickness were formed by Pulsed Laser Deposition (PLD). The spots of increased probe current (or the current channels) on the sample surface 3–10 nm in diameter attributed to the electron tunnelling through the individual Au NCs have been observed. The I–V curves of the probe-to-sample contact measured in the current channels having larger (5–10 nm) size exhibited Coulomb staircase while those measured in the smaller channels exhibited the peaks attributed to the resonant tunnelling through the Au NCs less than 1 nm in thickness. In order to explain the experimental results we had employed a double barrier Pt/SiO2/Au/SiO2/Si structure model, which has provided a satisfactory description of the obtained experimental data.

Electrical characterization of SiO2(Si) films as a medium for charge storage

AbstractAt present, the nonvolatile memory devices based on different kinds of nanocrystals are intensively developed. The important problem for further progress is connected with the optimization of gate multilayer structure. The aim of this work is the investigation of the electrical properties of thin nanocomposite SiO2(Si) films as a medium for the charge storage. The silicon enriched SiOx films were deposited by plasma enhanced chemical vapor deposition (PE CVD) method. The film composition was controlled changing the ratio of the flows of reactive gases SiH4 and N2O in a vacuum chamber. Subsequent thermal annealing led to the phase separation in SiOx films with a formation of nanocomposite SiO2(Si) structure of Si nanocrystals in dielectric matrix. Capacity‐voltage and current‐voltage measurements of MIS structures with gate nanocomposite SiO2(Si) films allowed to optimize the technological conditions of the formation of MIS structures with good charge storage properties. The value and the sign of stored charge were determined from the shift of C‐V characteristics. Analysis of the C‐V characteristics of MIS structures with nanocomposite SiO2(Si) films used equivalent circuit with the capacity of nanocrystals connected in parallel to the capacity of dielectric. The decrease of capacity in the accumulation region caused by nanocrystals was observed. The mechanism of current transport through the SiO2(Si) films was analyzed. It is determined to occur by tunneling through the SiO2 layers between the Si nanocrystals. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Nanocomposite SiO2(Si) films as a medium for non-volatile memory

Nanocomposite SiO2(Si) films containing Si nanocrystals (NCs) in a SiO2 dielectric matrix obtained through (i) plasma enhanced chemical vapor deposition (PE CVD) or (ii) pulse laser deposition (PLD) have been investigated as a medium for charge storage. The C–V method was used to characterize charging effects in the MIS structure (capacitor) with a nanocomposite SiO2(Si) film as an insulator. The obtained results indicate (i) the capture of small negative charge at the positive gate voltage in the nanocomposite SiO2(Si) film, (ii) significant capture of positive charge at the negative gate voltage, and that (iii) the difference between the positive and negative charge captured in both cases cannot be explained by dropping a part of the positive gate voltage in the semiconductor’s depletion region. A model of charge transport and capture in nanocrystals of nanocomposite SiO2(Si) film is proposed to explain the experimental results.