Hybrid Sol Gel Method Research Articles

Hybrid manufacturing process for the synthesis of doped TiO2 nanoparticles and optimization to determine an efficient photocatalyst

The hybrid sol-gel method was used to synthesize the transition metals (Cu and Ag) doped TiO2 nanoparticles for achieving enhanced visible light response photocatalysts. Different characterization techniques such as UV–Visible, FESEM, EDS, and TEM were carried out to characterize prepared nanocomposites. The synthesized Cu/TiO2 and Ag/TiO2 photocatalysts exhibit redshifts with improved light absorption capacity compared with pure TiO2. Scanning electron microscopic images show almost spherical morphology with relatively uniform sizes. Photocatalytic degradation of Methylene Blue (MB) and hydrogen production were carried out to estimate the photocatalytic efficiency of synthesized photocatalysts. As a result of increased charge separation efficiency and higher visible light absorption for photoexcitation, the photocatalytic response of the modified photocatalyst was elevated. In this study, the significant factors like initial pH, nitrate concentration, and dopant were identified. These factors were investigated in terms of hydrogen generation as a response to the successful optimization for the determination of the most efficient photocatalyst. In addition, in this work, density functional theory was used to simulate metals (Cu/Ag) doped TiO2 to learn more about the impact of doping on the structural, electrical, and photocatalytic properties of TiO2. Ag/TiO2 nanocomposite prepared via nitrate precursor concentration of 0.9 M and operated at an initial pH value of 4 exhibits maximum hydrogen generation capacity.

Fabrication and function examination of PZT-based MEMS accelerometers

In this study, a hybrid sol-gel method was used to fabricate Pb(Zr0.52Ti0.48)0.98Nb0.02O3 (PNZT) piezoelectric thick films. By preparing Pb(Zr0.52Ti0.48)0.98Nb0·02O3 sol-gel solutions and mixing them with PZT-5A piezoelectric powders, therefore, the thickness of single layer coating can be increased and reduce the risk of film cracks. The proposed PNZT films have the dielectric constant of 1750, dielectric loss of 0.063, remnant polarization of 58 μC/cm2, and d33 of 133 p.m./V. Piezoelectric cantilever beam MEMS accelerometers were then designed, simulated and fabricated via photolithography methods on Si substrates. The sensitivity and natural frequency of the cantilever beam accelerometer are 16.8 mV/g and 200Hz, respectively. Finally, a cantilever beam accelerometer is successfully applied for the server hard-drive fault detection.

Effects of Nb Doping on Crystalline Orientation, Microstructure and Electrical Properties of Non-Stoichiometric PZT Thick Films via Hybrid Sol-Gel Method

In this research, a hybrid sol-gel method was used to fabricate Pb(Zr0.52Ti0.48)1−xNbxO3 PZT-based piezoelectric thick films. By preparing sol-gel solutions with different Nb concentrations (x = 0%–4%) and mixing them with PZT-5A piezoelectric powders, the microstructure and electrical properties were improved. The X-ray diffraction (XRD) and scanning electron microscope (SEM) results showed that PZT films with 2% Nb doping exhibited high crystallinity and dense surfaces. The maximum dielectric constant, piezoelectric coefficient d33 of 133(pm V−1), and remnant polarization value of 58(μC cm−2) were obtained in a 2% Nb-dopant. These data were much better than the published results. Roughness and dielectric loss were also improved significantly with 2% Nb dopants.

The studies of a new ceramic composite — (Zr0.92Y0.08)O1.96 dispersed lanthanum titanium aluminium oxide

A new ceramic composite (Zr0.92Y0.08)O1.96 dispersed in LaTi2Al9O19 as a thermal barrier material was synthesized by the hybrid sol–gel method. The composite ceramic has good thermochemical stability up to 1500°C. The thermal conductivity of composite ceramic is circa. 1.0W/m·K at ambient temperature and the coefficients of thermal expansion are very stable and comparable to (Zr0.92Y0.08)O1.96 about 10.7×10−6K−1 at 1223K. The sintering resistance and mechanical properties become better after being dispersed. Therefore, the new ceramic composite synthesized by hybrid sol–gel method can be a promising candidate as a thermal barrier material on Ni-based superalloy.

The Influence of Different Carbon Sources on Li3V2(PO4)3/C Synthesized by a Hybrid Sol–Gel Method as Cathode for Lithium‐Ion Batteries

AbstractUsing cetyltrimethyl ammonium bromide (CTAB) as the surfactant, here we present the synthesis of lithium vanadium phosphate (LVP) Li3V2(PO4)/C by using a hybrid sol–gel method. Glucose, phenolic resin, and polyvinylidene fluoride (PVDF) are respectively used as the carbon sources for the three final products, LVP@GC, LVP@PR, LVP@PF. In addition, pure Li3V2(PO4), which is marked as LVP@0, was synthesized under the same conditions for comparison. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) results indicate that LVP@PR and LVP@PF have particle sizes less than 0.5 μm. Li‐cycling studies are preformed in half‐cell over the potential range of 3.0–3.4 V. All four samples exhibited outstanding cycle performance, but the rate performances of LVP@0 and LVP@GC are worse than the other two. LVP@0 only delivers a discharge capacity of 40 mAh g−1 and LVP@GC delivers 70 mAh g−1 at 15 C [Li3V2(PO4) theoretical capacity=132 mAh g−1 over 3.0–3.4 V). LVP@PR and LVP@PF showed impressive electrochemical performance. LVP@PF delivered a near‐theoretical capacity at ≤2 C rate. At rates of 10 C and 15 C, the capacities of LVP@PR and LVP@PF are both above 90 mAh g−1 and LVP@PF is slightly higher than LVP@PR.

ChemInform Abstract: Synthesis of Li3V2(PO4)3/C for Use as the Cathode Material in Lithium Ion Batteries Using Polyvinylidene Fluoride as the Source of Carbon.

AbstractThe cathode material of title is prepared by a hybrid sol—gel method from an aqueous 1:3:1.5:3:0.1 mixture of V2O5, Li2CO3, NH4H2PO4, H2C2O4, and cetyltrimethyl ammonium bromide using polyvinylidene fluoride as the carbon source (sintering at 700 °C for 10 h under Ar).

Development of durable self-cleaning coatings using organic–inorganic hybrid sol–gel method

Self-cleaning coatings with excellent water-repellence and good mechanical properties are in high demand. However, producing such coatings with resistance to mechanical abrasion and environmental weathering remains a key challenge. Mechanically robust coatings based on tetraethylorthosilicate (TEOS) and glycidoxypropyltriethoxysilane (Glymo) have been prepared using a sol–gel method. Emphasis is given to the addition of Glymo, an epoxy silane which creates an organic matrix that blends with the inorganic SiOSi matrix formed from the TEOS. The combination of the blended matrix produced coatings with good adhesion to substrates and improved mechanical properties. Fluoroalkylsilane (FAS) and silica fillers were introduced to increase the hydrophobicity of the coating. It was found that the water contact angle (CA) of these coatings increases from 115° to 164° upon decreasing filler size from 1–5μm to 10–20nm. The sliding angle (SA) for coatings with 15wt.% loading of 10–20nm silica is around 2°. UV weathering does not show significant effect on the properties of the coatings. Mechanical properties and performances including hardness, Young's modulus, coating adhesion and abrasion resistance were systematically analyzed. In the current work, a simple self-cleaning test, which measures the extent of dirt accumulation and subsequent removal by water spray, was performed. The coatings with 15wt.% loading of 10–20nm silica particles show the best self-cleaning performance both before and after mechanical abrasion. The developed coating process is simple and can be easily scaled-up for large surfaces that require self-cleaning function.

Synthesis and electrical properties of Pb(Zr0.52Ti0.48)O3 thick films embedded with ZnO nanoneedles prepared by the hybrid sol–gel method

Pb(Zr0.52Ti0.48)O3 thick films embedded with ZnO nanoneedles (PZT–ZnOn) were successfully prepared on Pt/Cr/SiO2/Si substrates by the hybrid sol–gel method via spin-coating ZnOn suspension and lead zirconate titanate (PZT) sol. To control the orientation of the films, a PbTiO3 (PT) layer was first deposited as a seed layer. Effects of annealing method and ZnOn contents on the corresponding orientation and crystallization of PZT–ZnOn films were investigated by XRD and SEM. The results show that all the PZT–ZnOn composite thick films have pure perovskite structure and high-quality film surface. The dielectric and ferroelectric properties of the PZT–ZnOn films are close to the PZT films, and have a little decrease with the increasing of the ZnOn contents.

A novel hybrid sol–gel method for the synthesis of highly porous silica employing hyperbranched poly(ethyleneimine) as a reactive template

A novel hybrid sol–gel templating route employing hyperbranched polymers for the production of nanostructured silica with tailored porosity and high specific surface area values is proposed based on the use of hyperbranched poly(ethyleneimine) both as a reactive template and as a macromolecular “porogen”. The procedure developed involves dissolution of hyperbranched poly(ethyleneimine), PEI, of two different molecular weights (5,000 and 25,000), in N,N-dimethylformamide or chloroform serving as solvents of different polarity and addition of 3-(triethoxysilyl)propyl isocyanate as a silica precursor which is also reactive towards PEI’s amino groups. The obtained triethoxysilyl functionalized macromolecules after hydrolysis and subsequent polycondensation reactions lead to the formation of a novel silica network architecture. By firing this hybrid material a silica powder of nanoporous structure and advanced textural properties is obtained. Synthetic reactions are monitored by FTIR spectroscopy, while the silica network formed after firing is characterized by TGA, low and wide-angle XRD, TEM and N2 adsorption techniques. The influence of several parameters, i.e., molecular weight of PEI, PEI/silica precursor molar ratio and solvent polarity on silica’s porosity is studied. Depending on the synthesis conditions, this novel templating route proved effective for the successful imprinting of mesoporous cavities into silica structure. In this way, nanostructures with tailor-made properties were obtained exhibiting specific surface area values varying from ∼600 to 1100m2/g and pore diameters up to around 5nm.

Investigations on B-doped SiO 2 thermal protective coatings by hybrid sol–gel method

This study first prepared B-doped SiO 2 coating by hybrid sol–gel method. SiO 2 coatings had been successfully used for thermal protection, but its toughness, oxidation resistance and cost are weak points. Hybrid sol–gel method could prepare ultra thin and low cost SiO 2 coatings on nickel alloys. And doping B could improve the coatings’ toughness and oxidation resistance. Thermogravimetry, differential thermal analysis and Fourier transform infrared spectroscopy were used to investigate the additives’ effect on coatings’ formations at different temperatures. X-ray photoelectron spectroscopy and X-ray diffraction were used to investigate the coatings’ element distribution and phase. The results showed that B-doped SiO 2 thermal protective coatings could withstand 1050 °C, and Si–O–B bond was generated to improve the coatings’ toughness. A crystal mullite phase formed on the coatings’ surface at high temperature by thermal diffusion of Al, which significantly improved B-doped SiO 2 thermal protective coatings’ oxidation resistance.

Improved photoluminescence properties of sol-gel derived Er3+ doped silica films

Silica films (amorphous and crystalline) doped with erbium were fabricated on silica glass substrate and characterized. The inorganic-organic hybrid sol-gel method was used to prepare the films and the Na codoping induced the crystallization of silica film. Photoluminescence (PL) measurements revealed that the Er3+ ions can be excited from the ground state through an energy transfer process mediated by active defective sites in SiO2 film matrix. The annealing temperature and atmospheres have large effects on the local environment of Er3+ and the 1.54 μm PL intensity can be improved significantly by suitable heating treatments. We could correlate Er3+ sensitization effect due to the presence of carbon related species in the films. The PL intensity at nonresonant (476.5 nm) condition can be made as intense as the resonant (488 nm) one, for particular annealing conditions. Noticeable changes in PL emission intensities have not been observed whether the matrix silica film is amorphous or crystalline in nature; however, the defect-related luminescence is almost vanished in case of crystalline silica films.

High-Surface-Area Alumina-Silica Nanocatalysts Prepared by a Hybrid Sol-Gel Route Using a Boehmite Precursor

High-surface-area alumina–silica mixed oxide (Al2O3:SiO2) nanocatalysts have been prepared by a hybrid sol–gel method using boehmite (synthesized from aluminum nitrate) as the source of alumina and tetraethyl orthosilicate as the source of silica. The gels, after calcination at 400°C, result in mixed oxides with specific surface areas of 287 m2/g (Al2O3:SiO2=3:1) and 262 m2/g (Al2O3:SiO2=3:4). Further heating to 600°C produces materials with specific surface areas of 237 and 205 m2/g, respectively. The larger specific surface areas characteristic of the 3Al2O3:SiO2 samples are attributed, via transmission electron micrograph investigations, to the presence of ∼10 nm size, needle-like particles having an aspect ratio of 1:50. Further addition of silica leads to the formation of larger needles of 20–75 nm size. Calcination at 600°C induced an approximately 5% decrease in the total pore volume for the 3Al2O3:SiO2 sample. In contrast, the material with Al2O3:SiO2=3:4 showed an approximately 12% increase in pore volume when heated at 600°C. The pore-size distribution was in the range 1–3.5 nm with rmax at ∼2 and ∼2.5 nm at 600° and 800°C, respectively. Adsorption isotherms and pore-size distribution analyses are discussed in some detail for the aluminosilicates at different calcination temperatures. This discussion is supported by structural information determined from FTIR and 27Al MAS NMR studies. Relatively high acidity values (0.234 mmol/g for Al2O3: SiO2=3:4) are observed for silica-rich compositions consistent with their application as efficient acid catalysts.

Effects of the addition of inorganic nanoparticles on the adhesive strength of a hybrid sol–gel epoxy system

A combination of inorganic nanoparticles was added as reinforcement to a diglycidyl ether of bisphenol-A (DGEBA)-based epoxy resin modified by a hybrid sol–gel method. Different epoxy/sol–gel systems were prepared to evaluate their adhesive strength. The mechanical performance of different formulations was characterised by shear and tensile tests to define the influence of nano-fillers on adhesive strength performance of the modified epoxy/hybrid sol–gel. The results obtained indicate that the incorporation of a selected ratio of inorganic nanoparticles in the epoxy/sol–gel adhesive improves the adhesion performance between substrate surfaces. A significant increase in adhesive lap shear strength of the sol–gel modified epoxy, compared with that of the neat epoxy, was observed. Butt joint strengths of the modified epoxy/sol–gel were also recorded, showing good adhesion behaviour to mild steel surfaces. Tensile strength of joints up to 28.5 MPa for 16 h/150 °C cure time/temperature was observed. The modified system exhibited a high yield point and large extension compared with that of the unmodified epoxy. The study further showed that doping with small amounts of one type of nanoparticle to the system increases adhesive cross-linking. Epoxy/sol–gel adhesive strength was also evaluated as a function of cure temperature for mild steel and Al2024-T3 substrates. Results showed adhesive strength decreased with increased cure temperature on the Al substrate, while lap joint strength of the mild steel exhibited no significant changes at three different cure temperatures. This may be attributed to good interfacial bonding of the sol–gel adhesive to the mild steel over the designated temperature range.

Preparation and electrical properties of Pb(Zr0.52Ti0.48)O3 thick films embedded with ZnO nanowhiskers by a hybrid sol–gel route

Pb(Zr 0.52 Ti 0.48 )O 3 thick films embedded with ZnO nanowhiskers (ZnO w –PZT) were successfully prepared on Pt/Cr/SiO 2 /Si substrates by a hybrid sol–gel method via spin-coating ZnO w suspension and PZT sol. Effects of annealing time and thickness on the corresponding orientation and crystallization of ZnO w –PZT films are investigated. XRD and SEM results show that ZnO w –PZT composite thick films have perovskite structure and high-quality film surface. The composite thick films also exhibit good ferroelectric and dielectric properties, which are close to those of PZT thick films. The remanent polarization, coercive field, dielectric constant and dielectric loss of ZnO w –PZT thick film with thickness of 2 μm are 24 μC/cm 2 , 177 kV/cm, 223 and 0.06, respectively. Moreover, the longitudinal piezoelectric coefficient is calculated to be 35 pm/V, which is comparable to that of PZT thick film.

Preparation and studies of photocatalytic silver-loaded TiO2 films by hybrid sol–gel method

Abstract Ag/TiO 2 photocatalytic films were produced by hybrid sol–gel method. The photocatalytic degradation of methyl orange (MO) in aqueous solution under both UV and visible light irradiation on TiO 2 and Ag/TiO 2 thin films was investigated. The state and amount of Ag species within the film and the enhancement mechanism of photocatalytic activity of Ag/TiO 2 were discussed. The maximum catalytic efficiency was observed under both UV and visible light irradiation. The molar ratio of Ag/Ti corresponding to the best catalytic activity depends on the wavelength of the radiation employed.

Studies on photocatalytic activity of Ag/TiO2 films

Ag/TiO2 photocatalytic films were produced by hybrid sol-gel method. The photocatalytic degradation of methyl orange (MO) in aqueous solution under 365 nm irradiation on TiO2 and Ag/TiO2 thin films was investigated. The state and amount of Ag species within the film and the enhancement mechanism of photocatalytic activity of Ag/TiO2 were discussed. With a loading molar ratio of Ag/Ti = 0.135 in TiO2 film, the maximum catalytic efficiency was observed.

Electrical properties of lead zirconate titanate thick films prepared by hybrid sol–gel method with multiple infiltration steps

High-quality ferroelectric thick films are required for various piezoelectric applications including high-frequency transducers and microelectromechanical systems. In this work, we report the fabrication of dense crack-free lead zirconate titanate (PZT) thick films on Pt-coated Si substrates using commercial PZT powder dispersed in a sol–gel precursor solution without viscous additives. Preannealed films were infiltrated with the same solution and heat treated at 500 °C. Dielectric and ferroelectric properties of the films are found to be strongly dependent on the number of infiltration steps reaching sufficiently high values: dielectric constant ∼2270 and remanent polarization ∼35 μC cm −2. Moderate coercive field of 60 kV cm −1 and low dielectric loss ∼0.04 are observed in these films. Effective longitudinal piezoelectric coefficient d 33 also depends on the number of infiltrations demonstrating remanent value of ∼80 pm V −1 for eight infiltration steps. The results show the suitability of hybrid sol–gel method for the fabrication of PZT thick films for dielectric and piezoelectric applications.

Synthesis of Titania coated Alumina Particles by a Hybrid Sol-gel Method

ABSTRACTModifying their surface with a coating of another ceramic material can dramatically alter the properties of ceramic particles. In the present work we have demonstrated that the Al2O3 particles can be successfully coated by TiO2 using a novel sol-gel technique. The nature of these coatings was predicted on the basis of scanning electron microscopy imaging in conjunction with the micro-Raman scattering measurements. The surface morphology of these particles shows that either individual or group of sub-micron alumina particles are coated with the nano-crystalline titania particles. The thickness of the titania coating could be varied by changing the precursor sol concentration. Amorphous titania was converted to anatase phase at 400°C and upon further heating it started transforming to rutile phase, and both these phases coexisted in the coated particles that were heat treated up to 800°C. The mechanical strength of the titania coating was measured qualitatively by ultrasonicating the coated powders for longer duration to observe that titania coatings are strongly adhered with the alumina particles.

Effect of cerium zirconate (Ce2Zr2O7) on microstructure and mechanical properties of Ce-ZTA

Powders for ZrO2 toughened Al2O3 (ZTA) composites containing 8, 11, 13.8 and 16.5 vol% ZrO2 (stabilized with 11.5 mol% CeO2) are prepared by a hybrid sol-gel method using Al2O3 powders and a sol formed from Zr-alkoxide and cerium nitrate. Besides ZrO2, a small amount of a Ce-zirconate phase (Ce2Zr2O7) forms when the powders are calcined in air. The zirconate phase persists in the sintered specimens and its amount increases from surface to centre of the specimen. Presence of higher amount of Ce2Zr2O7 promotes exaggerated grain growth of Al2O3. Particles of Zr rich phases are found to be trapped inside the Al2O3 grains. Composites exhibit higher fracture toughness despite lower transformability of t-ZrO2 during fracture when they contain high amount of zirconate. Crack bridging is shown to be an important mechanism contributing to enhancement in fracture toughness in these composites.

Strengthening of alumina by cerium-zirconate (Ce2Zr2O7)

Composite powders of Al2O3 and 0 to 30 vol% Ce2Zr2O7 are prepared by a hybrid sol-gel method using Al2O3 powders and a sol formed from Zr-alkoxide and cerium nitrate. All the Zr from the sol goes to form the cerium zirconate phase when the powders are calcined in N2. Pressureless sintering in air at 1500°C yields composites with high density (∼98%). Maximum values of fracture toughness and strength, 6.5 MPa \(\sqrt {\text{m}}\) and 620 MPa respectively, (e.g. 3.5 MPa \(\sqrt {\text{m}}\) and 350 MPa for pure Al2O3) are obtained in 10 vol% Ce2Zr2O7 composite sintered in air. The dominant mechanism for enhancement in KIC is believed to be crack bridging. Crack bridging activity in the 10 vol% composite is found to be maximum and extends upto ∼190 μm from the crack tip.