Increasing TiO2 Content Research Articles

Nanostructured perovskite CdTiO3 films for methane sensing

Cadmium titanate (CdTiO3) thin films with different concentrations of titanium dioxide (TiO2) were synthesized by magnetron co-sputtering method on to glass substrates. X-ray diffraction (XRD) patterns confirmed the formation of perovskite orthorhombic crystal structure at relatively low deposition temperature. The crystallinity of the films decreased with increase in TiO2 concentration due to structural deformation caused by differences in the ionic radii of the Cd2+ and Ti4+ atoms. The grain size value was found to decrease from 80 to 30nm and a blue shift of the optical band edge was observed. The CdTiO3 films with lower concentrations of TiO2 exhibited better methane (CH4) sensing properties (100ppm) at an operating temperature of 250°C with fast response and recovery time.

The Nanocrystalline SnO2–TiO2 System—Part I: Structural Features

The phases present and their crystal structure and microstructure in the nanocrystalline SnO2–TiO2 system were studied in the compositional range Sn1−xTixO2 (0.0 ≤ x ≤ 0.9). There is an apparent increase in the solubility limits in the solid solution compared to bulk crystalline SnO2–TiO2. No two phase region was observed with increasing TiO2 content. Electron energy loss spectroscopy, infrared spectroscopy (FTIR), and X‐ray diffraction (XRD) of the nanopowders showed that the apparent increase in solubility is related to the systematic Ti4+ segregation on the particle surface (surface excess) at the SnO2‐rich side, avoiding the nucleation of a second phase even at high Ti4+ contents. Is this finding in accord with Raman spectra, which suggest localized Ti‐rich sites in the absence of a second crystalline phase. Ti4+ surface excess is also lead to a modification of the surface hydroxyls and a decrease in the crystallite size of the nanoparticles (with a concomitant increase in surface area), with expected implications to catalytic and sensorial properties of these nanoparticles.

Effect of TiO2 content on the microstructure and antibacterial activity of TiO2 -loaded activated carbon fibers derived from liquefied wood

In this study, activated carbon fibers derived from liquefied wood (WACF) were as a carrier to support TiO2. The weight of TiO2 coating on TiO2-loaded WACF (TiO2/WACF) was designed as a variable to explore their effect on the microstructure and antibacterial activity of TiO2/WACF. The results showed that the crystal structure, surface chemical structure, pore structure, and antibacterial activity of TiO2/WACF had a high affinity for the TiO2 content. The increasing TiO2 content (from 0.40 to 3.50 g/g) enlarged the average crystal size of TiO2/WACF, whereas their O―H group quantity, specific surface area, and pore volume had a reverse trend. The TiO2/WACF with 0.85 g/g TiO2 showed the strongest antibacterial activity because of their synergies between photocatalytic activity and adsorption capacity. This study on TiO2/WACF could improve their antibacterial activity and extend the application fields of WACF. Copyright © 2015 John Wiley & Sons, Ltd.

Surface modification of TiO2nanoparticles and preparation of TiO2/PDMS hybrid membrane materials

TiO2 nanoparticles were surface-modified by a convenient and mild sol–gel method. A novel hybrid membrane material was prepared by crosslinking reaction based on poly(dimethylsiloxane) (PDMS) as organic matrix and TiO2 nanoparticles as inorganic filler as well as a crosslinking agent. The chemical structure, mechanical and thermal properties, swelling performance and morphology of the hybrid membranes were characterized and investigated by FTIR, SEM, TG, and so on. The results showed that the surface modification method could make the compatibility between organic component and inorganic component good. The ultrathin PDMS hybrid membrane could easily be prepared by crosslinking reaction at room temperature and the conventional solution casting method. The preparation technology enhanced forming-membrane ability of the hybrid membrane, shortened reaction time, and decreased some by-products. In addition, the stress at break and the elongation at break of the hybrid membranes increased significantly with increasing TiO2 contents. The enhanced mechanical properties of the hybrid membranes will develop potential application of PDMS membranes. POLYM. COMPOS., 38:1541–1548, 2017. © 2015 Society of Plastics Engineers

Studies on structural and electrical properties of ZnO/TiO2 composite materials

The synthesis of the ZnO/TiO2 composites prepared by conventional solid–state reaction has been reported. The structural properties of the pellets have been investigated by X-ray diffraction and their dielectric spectra were measured in the frequency range from 0.1 Hz to 10 MHz and temperature range from 0 °C to 200 °C. XRD patterns have revealed the presence of three crystalline phases of the ZnO, Zn2TiO4 (cubic) and ZnTiO3 (hexagonal) compounds. Grain sizes were obtained in the range of 73–87 nm. It also exhibits a decrease of grain sizes and an increase of residual stress with the increase of TiO2 content from 1 wt% to 7 wt%. When the temperature is increased, the dc conductivity and the activation energies were found to be in the range of 10−9 – 10−5 S/cm and 0.13–1.19 eV, respectively. The alternating current (ac) conductivity was well represented by the power law Aωs. The electric conduction was dominant by the correlated barrier hopping (CBH) model. The electron barrier height, WM, varies greatly on the content of TiO2 where their values were found to be temperature- and frequency-dependent for all ZnO/TiO2 composites.

Kinetic and structural analyses for the formation of anatase nanocrystals in barium titanoborate glasses

Transparent barium titanoborate glass-ceramics bearing TiO2 (anantase) nanocrystals were prepared by the conventional melt-quenching and subsequent heat treatment of 35BaO–xTiO2–110B2O3 (in mol) (x = 20, 25, and 30) glasses. X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) results clearly reveal the formation of highly-crystalline anatase nanocrystals in glass matrices. The average crystal size ranges from ∼10 to 20 nm according to TiO2 contents. Non-isothermal kinetic analyses were performed to understand the crystallization behavior of each glass using differential scanning calorimetry (DSC) scan curves. With the increase of TiO2 contents in the glass, the crystallization peak temperature of TiO2 decreases, while the activation energy for crystallization increases. We propose a possible mechanism for the formation of TiO2 nanocrystals based upon kinetic analysis results and structural changes in barium titanoborate glass matrices according to TiO2 contents. The nanocrystalline glass-ceramics show ∼60–75% visible light transmittance and sharp UV-light absorption edges at ∼387 nm, corresponding to the energy band gap of anatase (3.2 eV). They show apparent photocatalytic properties and ∼70% of methylene blue solution was decomposed within 180 min.

Morphology and kinetic mechanism of facile one-step preparing TiO2/polyacrylate/TiO2 multilayer core–shell hybrid emulsion via miniemulsion polymerization

In this paper, we report a facile method for the preparation of TiO2/polyacrylate/TiO2 multilayer core–shell hybrid emulsion through polymerization. The chemical compositions of the copolymer were studied with Fourier transform infrared. TEM images reveal that nanocomposites show different core–shell structures with different TiO2 contents. As the weight percentage of TiO2 is 2 wt% (based on monomer, same below), there are no TiO2 cores in some nanocomposites. When TiO2 increases to 3 wt%, the TiO2/polymer/TiO2 multilayer core–shell composite particles are prepared. But the TiO2 shells disappeared when the TiO2 content kept increasing. TGA shows that the TiO2 dispersed in latex films uniformly and the thermal stabilization improved with increasing TiO2 contents. The effect of operating variables such as polymerization temperature and the concentrations of polymerizable emulsifier, initiator, extremely hydrophilic monomer, modified TiO2 and HD on the kinetic behaviors was investigated. The formation mechanism of TiO2/polymer/TiO2 multilayer core–shell structure was inferred.

Composition dependent interfacial thermal stability, band alignment and electrical properties of Hf1−xTixO2/Si gate stacks

The optical properties, interface chemistry and band alignment of Hf1−xTixO2 (x=0.03, 0.08, 0.12 and 0.20) high-k gate dielectric thin films, deposited by RF sputtering on Si substrate, have been systematically investigated. The effect of TiO2 incorporation on the interfacial chemical structure and energy-band discontinuities has been investigated by using X-ray photoelectron spectroscopy (XPS) and ultraviolet-visible spectroscopy (UV–vis). It has been found that the band gap and band offsets of the Hf1−xTixO2 thin film decrease with the increase of TiO2 concentration. Meanwhile, the obtained band offsets are all over 1eV. Thin film capacitors fabricated with the MOS configuration of Al/Hf1−xTixO2/n-Si/Al exhibits excellent electrical properties with low interface state density, hysteresis voltage and low leakage current density. The suitable band gap, symmetrical band offsets relative to Si and prominent electrical properties render sputtering-derived Hf1−xTixO2 with 9% TiO2 films as promising candidates for high-k gate dielectrics.

Spray deposited CeO2–TiO2 counter electrode for electrochromic devices

Optically passive thin films of CeO2–TiO2 mixed oxides with molar ratio of Ce/Ti of 0.05 were deposited by the spray pyrolysis technique (SPT) on a glass and fluorine-doped tin oxide (FTO)-coated glass substrates. Precursor solution containing cerium nitrate hexahydrate (Ce(NO3)2⋅6H2O) and titanium tetraiso-propoxide (Ti(OiPr)4) having different volumetric proportions (0–5 vol% of Ti) in methanol were used. These films were characterized for structural, morphological, molecular, optical, electrochromic and colourimetric analysis. CeO2–TiO2 films deposited at 400 ∘ C were found to be polycrystalline with cubic fluorite crystal structure. Transformation from polycrystalline to amorphous phase was observed with increasing TiO2 content. The band centred at 539 cm−1 is assigned to Ce–O stretching vibration and the two medium intensity bands assigned to (Ti–O) and (Ti–O–Ti) stretching modes at 798 and 451 cm−1, which confirms the mixed CeO2 and TiO2 phases. The band gap energy decreases (E g) from 3.45 eV for pristine CeO2 to 2.98–3.09 eV for CeO2–TiO2 films. The ion storage capacity (ISC) of CeO2–TiO2 thin film with 3 vol% Ti (Ce–Ti3 sample) was found to be 26 mC cm−2 and electrochemical stability up to 30,000 cycles in 0.5 M LiClO4-PC electrolyte. The optically passive behaviour of CeO2–TiO2 thin film is confirmed by its negligible transmission modulation (Δ T ∼ 2.5%) upon Li+ ion insertion/extraction, irrespective of the extent of Li+ ion intercalation. The optical modulation of sputter deposited electrochromic WO 3 thin film was found to be enhanced from 56 to 61% with rapid increase in colouration efficiency (CE) from 42 to 231 cm2 C−1 when CeO2–TiO2 is coupled as a counter electrode with WO3 in an electrochromic device (ECD). On reduction of WO3 thin film with CeO2–TiO2 as counter electrode, the CIELAB 1931 2 ∘ colour space coordinates show the transition from colourless to the deep blue state (L ∗ = 88.07, a ∗ = −2.37, b ∗ = 24.59 and L ∗ = 40.32, a ∗ = −1.16, b ∗ = −5.65) with steady decrease in relative lightness. Yxy and L ∗ a ∗ b ∗ coordinates signify CeO2–TiO2 films and it also exhibits the application as counter electrode in electrochromic smart windows in which they are able to retain their transparency under charge insertion/extraction.

Fabrication and characterization of poly(phenylene ether-ether sulfone) based nanofiltration membranes modified by titanium dioxide nanoparticles for water desalination

Asymmetric poly(1,4-phenylene ether–ether-sulfone) (PPEES)-blend-poly ethylene glycol nanocomposite nanofiltration membranes were prepared using phase inversion technique with N-methyl pyrrolidone as solvent and titanium dioxide (TiO2) nanoparticles as inorganic filler additive. The effect of additive concentration in casting solution on membrane physico-chemical properties was studied. Morphological study was carried out employing scanning electron microscopy. To characterize the prepared membranes, water flux and salt rejection were used as criteria. The effect of TiO2 content in casting solution on membrane mechanical property (tensile strength) and its water content and contact angle were also studied. Results showed that adding the TiO2 nanoparticles in the membrane matrix caused a sharp increase of water flux (WF) from 15.72 to 133.85L/m2·h. Results revealed that salt rejection was declined initially by the increase of TiO2 nanoparticle content up to 0.05wt.% in the membrane matrix but with more additive loading, it began rising. The membrane's tensile strength was improved by the increase of TiO2 concentration in casting solution. The water content and contact angle experiments showed that the membrane hydrophilicity generally was improved by the addition of TiO2. The increase of feed pH value was associated with the salt rejection enhancement.

Nano-TiO2 reinforced PEEK/PEI blends as biomaterials for load-bearing implant applications.

Biocompatible ternary nanocomposites based on poly(ether ether ketone) (PEEK)/poly(ether imide) (PEI) blends reinforced with bioactive titanium dioxide (TiO2) nanoparticles were fabricated via ultrasonication followed by melt-blending. The developed biomaterials were characterized using FT-IR, SEM, XRD, DSC, TGA, and DMA. Further, their water-absorption, tensile, tribological, dielectric, and antibacterial properties were evaluated. PEI acts as a coupling agent, since it can interact both with PEEK via π-π stacking and polar interactions as well as with the nanoparticles through hydrogen bonding, as corroborated by the FT-IR spectra, which resulted in a homogeneous titania dispersion within the biopolymer blend without applying any particle surface treatment or polymer functionalization. A change from promotion to retardation in the crystallization rate of the matrix was found with increasing TiO2 concentration, while its crystalline structure remained unaltered. The nanoparticles stiffened, strengthened, and toughened the matrix simultaneously, and the optimal properties were achieved at 4.0 wt % TiO2. More interesting, the tensile properties were retained after steam sterilization in an autoclave or exposure to a simulated body fluid (SBF). The nanocomposites also displayed reduced water absorption though higher thermal stability, storage modulus, glass transition temperature, dielectric constant, and dielectric loss compared to the control blend. Further, remarkable enhancements in the tribological properties under both SBF and dry environments were attained. The nanoparticles conferred antibacterial action versus Gram-positive and Gram-negative bacteria in the presence and the absence of UV light, and the highest inhibition was attained at 4.0 wt % nanoparticle concentration. These nanocomposites are expected to be used in long-term load-bearing implant applications.

Influence of SiO2 on M/TiO2 (M = Cu, Mn, and Ce) Formulations for Low-Temperature Selective Catalytic Reduction of NOx with NH3: Surface Properties and Key Components in Relation to the Activity of NOx Reduction

A series of M/TiO2 and M/TiO2–SiO2 (with M = Mn, Cu, and Ce) catalysts were prepared by adopting a wet–impregnation method and investigated for the selective catalytic reduction (SCR) of NOx in the temperature range of 100–500 °C with excess (10 vol %) oxygen in the feed at industrially relevant conditions. Our X-ray diffraction (XRD) results suggest that the growth of the crystalline TiO2 phase is strongly inhibited because of SiO2 migration into the TiO2 lattice. The increase of SiO2 molar content in the TiO2–SiO2 support led to the decrease in the anatase phase of the titania peak intensity of the XRD spectrum and also exhibited a lower crystallinity of TiO2 with no phase transition of anatase to rutile. Our X-ray photoelectron spectroscopy (XPS) depth profile analysis illustrated that the surface atomic ratio of Cu1+/ Cu2+ wasgreatly enhanced with an increase in TiO2 content in the TiO2–SiO2 support, and these results are consistent with the H2-TPR results in which the additional reduction peak evolve...

Effect of TiO2 nanoparticles on structure and properties of high density polyethylene membranes prepared by thermally induced phase separation method

Polyethylene/TiO2 membranes were fabricated via thermally induced phase separation (TIPS) method. A set of characterization tests including FE‐SEM, EDX, XRD, DSC, TGA, DMA, mechanical test and relative pure water flux for characterization of membranes were carried out to investigate the effect of TiO2 nanoparticles on membrane properties. The results of EDX, XRD and TGA analyses confirmed the presence of TiO2 nanoparticles in the polymer matrix. The results of DSC analysis revealed that the melting point as well as the crystallinity of the membranes increased slightly with increasing TiO2 content. However, the glass transition temperature of the membranes was not affected by the presence of particles. Addition of nanoparticles also increased storage modulus, loss modulus and tensile strength at break of the membranes due to the stiffness improvement effect of inorganic TiO2. Finally, it was observed that incorporation of the nanoparticles improved pure water flux of the membranes. Copyright © 2015 John Wiley & Sons, Ltd.

Effect of TiO2 on crystallization of the glass ceramics prepared from granite tailings

The effect of TiO2 on the crystallization behaviors of the glass ceramics prepared from granite tailings was investigated by differential scanning calorimetry (DSC), X-ray diffraction (XRD), and field emission scanning electron microscopy (FESEM). The results showed that the crystallization peak temperature decreased firstly, and then increased with the increase of TiO2 content. The optimum addition amount of TiO2 was 8 wt%. With a single-step heat treatment at 924 °C for 1 h, augite precipitated as the only crystalline phase both on the surface and in the interior. The avrami parameter of the sample was 3.25, suggesting a two-dimensional crystallization mechanism. The activation energies for phase separation and crystallization of augite were 321.75 and 698.83 kJ/mol, respectively.

Fabrication of a New Polyimide/Titania (TiO2) Nanocomposite Thin Film by the Sol-Gel Route

Polyimide/titania nanocomposite (PI/TiO2 NC) was successfully fabricated through the in situ formation of TiO2 within a PI matrix by the sol-gel process. FT-IR and XRD results confirmed the formations of the TiO2 in the PI matrix. Transmission electron microscopy of the NC10% showed that the TiO2 phase was well dispersed in the polymer matrix. The mechanical properties of the NC films were increased and elongation at break decreased with increasing TiO2 content. Thermogravimetric analysis results revealed that the decomposition temperature of hybrid materials was increased with an increase in the content of TiO2 nanoparticles within the NC films.

Crystallization Kinetics of CaO-SiO<sub>2</sub>(CaO/SiO<sub>2</sub>=1)-TiO<sub>2</sub>-10 mass%B<sub>2</sub>O<sub>3</sub> Glassy Slag by Differential Thermal Analysis

Crystallization characteristics of the CaO-SiO2-TiO2-10%B2O3 glassy slag at w(CaO)/w(SiO2)=1 have been studied by Differential Thermal Analysis (DTA) and Matusita-Sakka method. Crystallization products have been distinguished by employing X-ray diffraction (XRD) and Scanning Electron Microscopy equipped with Energy Dispersive Spectroscopy (SEM-EDS). As the TiO2 content is within 10-18%, the crystal phase precipitated is mainly CaSiO3, and the effective activation energies for crystal growth increase with the increase of TiO2 content. Crystallization mechanism for CaSiO3 shifted from surface crystallization to one-dimensional growth with increase of TiO2. As the TiO2 content in slag further increases to 22% and 26%, CaTiSiO5 becomes the predominant crystal phase precipitated, and the effective activation energies for crystal growth decrease with the increase of TiO2 content. Crystallization mechanism for CaTiSiO5 is mainly surface crystallization. Therefore, with the increase of TiO2 content, the crystallization ability of the CaO-SiO2-TiO2-10%B2O3 glass system decreases initially and then increases.

Removal of Crystal Violet and Hexavalent Chromium using TiO2-Bentonite under Sunlight: Effect of TiO2 Content

The main objective of this study was to investigate the correlation between TiO2 content in photoactive bentonite (B-TiO2) and the pathway by which crystal violet (CV) and hexavalent chromium (Cr (VI)) are removed from water under sunlight. B-TiO2 samples were prepared by impregnation with TiCl4 with different weight ratios (g/g) (namely, 5, 10, 20 and 30%). Materials were characterized using different techniques, among which: SEM, FT-IR, XRD, HRTEM, EDX and Zeta potential measurements. Results show that, only the anatase TiO2 polymorph was formed in the bentonite and the porosity of materials decreases with the increase of TiO2 content. Furthermore, zeta potential measurements indicate that, when TiO2 content increases, the negative charge of materials decreases. On the other hand, experimental results show that these materials combine both adsorption and photocatalytic reactions to remove CV molecules from water. As the TiO2 content increases, the adsorption capacity decreases, while the photocatalytic activity is more important. In the case of Cr (VI) species, all samples show a few adsorption because of the repulsion effect between these species and the negative charge of the bentonite. Therefore, under sunlight, the Cr (VI) removal occurred mainly by the photoreduction reaction that is more efficient when the TiO2 content increases.

Preparation and investigation of the gas separation properties of polyurethane-TiO2 nanocomposite membranes

The effect of TiO2 nanoparticles on the gas separation properties of polyurethane has been investigated. Polyurethane was synthesized using hexamethylene diisocyanate (HDI) and 1,4-butanediol (BDO) as hard segment and poly(tetramethylene glycol) (PTMG, 2,000 g/mol) as soft segment. The synthesized polymer was in a 1: 2: 1 molar ratio of polyol:diisocyanate:chain extender through bulk two-step polymerization. PU membranes were prepared by thermal phase inversion method. Scanning electron microscopy (SEM), X-ray diffraction and Fourier Transform Infrared (FTIR) analyses characterized the prepared membranes. FTIR and SEM results indicate the good interaction between particles and polymer matrix and also the nanoscale dispersion of TiO2 particles in polymer matrix. Gas permeation properties of PU-TiO2 nanocomposite membranes with TiO2 contents up to 30 wt% were studied for N2, O2, CH4 and CO2 gases at 10 bar and 25 °C. Results suggest a decrease in permeability of studied gases and increase in gas selectivities as TiO2 content increases.

Novel sol–gel preparation of (P2O5)0.4–(CaO)0.25–(Na2O)X–(TiO2)(0.35−X) bioresorbable glasses (X = 0.05, 0.1, and 0.15)

Quaternary phosphate-based glasses in the P2O5–CaO–Na2O–TiO2 system with a fixed P2O5 and CaO content of 40 and 25 mol% respectively have been successfully synthesised via sol–gel method and bulk, transparent samples were obtained. The structure, elemental proportion, and thermal properties of stabilised sol–gel glasses have been characterised using X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), 31P nuclear magnetic resonance (31P NMR), titanium K-edge X-ray absorption near-edge structure (XANES), fourier transform infrared (FTIR) spectroscopy, and differential thermal analysis (DTA). The XRD results confirmed the amorphous nature for all stabilized sol–gel derived glasses. The EDX result shows the relatively low loss of phosphorus during the sol–gel process and Ti K-edge XANES confirmed titanium in the glass structure is in mainly six-fold coordination environment. The 31P NMR and FTIR results revealed that the glass structure consist of mainly Q1 and Q2 phosphate units and the Ti4+ cation was acting as a cross-linking between phosphate units. In addition DTA results confirmed a decrease in the glass transition and crystallisation temperature with increasing Na2O content. Ion release studies also demonstrated a decrease in degradation rates with increasing TiO2 content therefore supporting the use of these glasses for biomedical applications that require a degree of control over glass degradation. These sol–gel glasses also offer the potential to incorporate proactive molecules for drug delivery application due to the low synthesis temperature employed.

Synthesis of TiO2 nanowire/reduced graphene oxide nanocomposites and their photocatalytic performances

TiO2 nanowire/reduced graphene oxide (TiO2/RGO) nanocomposites were synthesized through a modified hydrothermal method with cetyl trimethyl ammonium bromide (CTAB) as a surfactant. The characterization of phase structure and morphology of TiO2/RGO nanocomposites revealed that most of graphene oxides (GO) were reduced to form RGO during the hydrothermal treatment, and TiO2 nanowires were grown in situ on the surfaces of the RGO layers in the presence of CTAB. Compared with TiO2/RGO prepared without CTAB, RGO in TiO2/RGO-C nanocomposites were layered with smooth surface. TiO2 nanowires in the nanocomposites were much longer than the TiO2 nanorods synthesized with the same method. Furthermore, with the increase of TiO2 content, TiO2 nanowires tended to be several micrometers in length. Compared with the obtained RGO and TiO2 nanorods, the TiO2/RGO nanocomposites exhibited a higher photocatalytic activity as a result of the synergistic effect between TiO2 and RGO. The TiO2/RGO nanocomposite with the optimized mass ratio of TiO2: GO of 0.6 showed a significant enhancement in photocatalytic activity. Furthermore, a deeper insight into the photocatalytic mechanism of TiO2/RGO nanocomposites was put forward.