Introduction Of TiO2 Research Articles

The effect of TiO2 addition on microstructure and electrical properties of SnO2 varistors prepared from nanomaterials

The effects of various amounts of TiO2 in the composition of SnO2-based varistors made from nano-sized materials on microstructure and electrical properties have been investigated. Titanium oxide acts as both a densifier and grain growth enhancer resulting in relative densities in the range of 96–99%. The addition of TiO2 from 0 to 3mol% has changed the average grain size from 1.8 to 5μm. The introduction of TiO2 causes precipitation of Ta2O2.2 phase on the sample surfaces. The lowest breakdown field, 2kV/cm, has been observed for the sample containing 0.75mol% of TiO2, and the best surge-withstand parameters (residual voltage ratio, 2.4, withstanding surge current density, 5kA/cm2) have been observed for the sample with 0.25mol% TiO2. Larger amounts of TiO2 have had an adverse effect on the surge-withstand capability due to the loss of homogeneity in the samples caused by tantalum transpiration.

Dual phase Li4Ti5O12–TiO2 nanowire arrays as integrated anodes for high-rate lithium-ion batteries

Lithium titanate (Li4Ti5O12) is well known as a zero strain material inherently, which provides excellent long cycle stability as a negative electrode for lithium ion batteries. However, the low specific capacity (175mAhg−1) limits it to power batteries although the low electrical conductivity is another intrinsic issue need to be solved. In this work, we developed a facile hydrothermal and ion-exchange route to synthesize the self-supported dual-phase Li4Ti5O12–TiO2 nanowire arrays to further improve its capacity as well as rate capability. The ratio of Li4Ti5O12 to TiO2 in the dual phase Li4Ti5O12–TiO2 nanowire is around 2:1. The introduction of TiO2 into Li4Ti5O12 increases the specific capacity. More importantly, by interface design, it creates a dual-phase nanostructure with high grain boundary density that facilitates both electron and Li ion transport. Compared with phase-pure nanowire Li4Ti5O12 and TiO2 nanaowire arrays, the dual-phase nanowire electrode yielded superior rate capability (135.5 at 5C, 129.4 at 10C, 120.2 at 20C and 115.5mAhg−1 at 30C). In-situ transmission electron microscope clearly shows the near zero deformation of the dual phase structure, which explains its excellent cycle stability.

Preparation of TiO<sub>2</sub>-Al<sub>2</sub>O<sub>3</sub> Support and Hydrodenitrogenation over Ni<sub>2</sub>P/TiO<sub>2</sub>-Al<sub>2</sub>O<sub>3 </sub>Catalyst

A series of TiO2-Al2O3 composite supports were prepared by co-precipitation of titanium sulfate and aluminium nitrate , and the nickel phosphide catalysts were prepared by incipient wetness impregnation and in situ H2 reduction method. The catalysts were characterized by XRD, N2 adsorption, TPR, TEM and XPS techniques. Their hydrodenitrogenation (HDN) performances were evaluated by using quinoline as model molecules . The results show that TiO2 was evenly dispersed on massive γ-Al2O3 surface. The introduction of TiO2 weakened the strong interaction between Al2O3 and phosphate, and improved the reducibility of the precursors , facilitating to the formation of Ni2P active phase. TiO2 acted as an electronic promoter for the Ni-P catalyst and enhanced both the hydrogenation and C-N bond cleavage activities. Different Ti / Al molar ratio had great influence on HDN activity of the catalyst. The Ni2P /TiO2-Al2O3 with Ti/Al ratio of 1/8, exhibited the highest activity for quinoline HDN.

Microstructure and optical limiting properties of multicomponent inorganic gel-glasses: A focus on SiO2, TiO2 and PbO gel-glasses

Two kinds of multicomponent inorganic gel-glasses, namely, SiO2–TiO2 binary and SiO2–TiO2–PbO ternary gel-glasses, were obtained via the hydrolysis and co-condensation of tetraethyloxysilane (Si(OC2H5)4, TEOS), titanium tetraisopropoxide (Ti(C4H9O)4, TTIP), and lead (II) acetate trihydrate (Pb(Ac)2). X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, and pore structure measurements were performed to investigate the morphology, structure, and texture properties of the gel-glasses. The samples were mainly composed of amorphous phase without any detected phase separation. The introduced Ti4+ and Pb2+ were partially involved in the hydrolysis and condensation processes. Furthermore, the composition had a significant influence on the pore structure of silica-based gel-glasses, and the introduction of TiO2 in the gel-glasses caused the formation of bimodal-distributed pore shapes and dimensions in multicomponent inorganic gel-glasses. The optical limiting (OL) properties were measured at 532nm by using the open aperture Z-scan technique. The SiO2–TiO2 binary and SiO2–TiO2–PbO ternary gel-glasses exhibited greatly enhanced OL behaviors than the SiO2 unitary gel-glass. The observed OL phenomenon in the SiO2–TiO2 binary gel-glass originated from two-photon absorption (TPA), whereas TPA followed by nonlinear scattering (NLS) contributed to the increased OL performance of the SiO2–TiO2–PbO ternary gel-glass. SiO2–TiO2 binary and SiO2–TiO2–PbO ternary gel-glasses are potential materials for practical applications in the fields of optics, all-optical switching, and related optical devices.

Study on the properties of nano‐TiO2/polybutylene succinate composites prepared by vane extruder

Different proportions of nanoscale TiO2 (nano‐TiO2)‐filled polybutylene succinate (PBS) composites were prepared by vane extruder. The crystalline, thermal, dynamic viscoelastic, mechanical, and UV‐resistance properties of the composites were studied, and X‐ray diffraction, differential scanning calorimetry, and thermogravimetric analysis were conducted. Results show that the crystalline structure of the PBS composites did not change with TiO2 addition. TiO2 almost has no effect on the crystallization and melting behavior of PBS. Nevertheless, the introduction of TiO2 has improved the thermal stability, tensile modulus, flexural modulus, and flexural strength of the PBS composites. The UV resistance of the composites has also been significantly enhanced with TiO2 addition. POLYM. COMPOS., 35:53–59, 2014. © 2013 Society of Plastics Engineers

Improved hydrogen storage performance of Ca(BH4)2: a synergetic effect of porous morphology and in situ formed TiO2

A porous Ca(BH4)2-based hydride, CaB2H7, with nano-TiO2 introduced in situ, was successfully synthesized via mixing Ca(BH4)2 with Ti(OEt)4 followed by heat treatment. The effects of the porous structure and introduction of TiO2 on both the non-isothermal and isothermal hydrogen desorption–absorption properties of the porous system were systematically investigated. The results show significant improvements on both the kinetics and thermodynamics of hydrogen desorption–absorption of the porous CaB2H7–0.1TiO2 system, compared with the dense Ca(BH4)2. The desorption peak temperature is reduced by more than 50 °C and sorption capacity of ca. 5 wt% H2 is rapidly achieved below 300 °C. The porous structure was retained in the dehydrogenated products, and rapid hydrogen absorption, approximately 80% of the desorption capacity, is obtained upon heating the product, post-dehydrogenated at 300 °C for 1 h, to 350 °C at 90 bar H2. External addition of nano-TiO2 also enhances the hydrogen storage properties of Ca(BH4)2, but to a lesser extent, compared with the synergetic effect of the porous structure and the in situ formed nano-TiO2. In addition, desorption–absorption mechanisms of the porous CaB2H7–0.1TiO2 system are also proposed.

Investigation of photocatalytic activities over ZnO–TiO2–reduced graphene oxide composites synthesized via microwave-assisted reaction

ZnO–TiO2–reduced graphene oxide (RGO) composites were successfully synthesized by microwave-assisted reduction of graphite oxide in ZnO precursor solution with TiO2 suspension using a microwave synthesis system. Their morphology, structure, and photocatalytic performance in the reduction of Cr(VI) were characterized by scanning electron microscopy, X-ray diffraction spectroscopy, and UV–vis absorption spectrophotometer. The results show that ZnO–TiO2–RGO composites exhibit an enhanced photocatalytic performance in reduction of Cr(VI) with a maximum removal rate of 99.4% under UV light irradiation as compared with pure ZnO (58%) and ZnO–RGO (98%) composites due to the increased light absorption intensity and the reduction of electron–hole pair recombination in ZnO with the introduction of TiO2.

Effect of substituting SiO2 with TiO2 on viscosity and crystallisation of mould flux for casting titanium stabilised stainless steel

During casting of titanium stabilised stainless steel, a gradual increase in TiO2 content in the molten mould slag from absorption of TiO2 inclusions causes changes in properties of the mould flux, such as viscosity, solidification temperature and crystallisation behaviour. To simulate this effect mould fluxes were prepared with SiO2 being substituted with 5 and 10%TiO2 and viscosity and crystallisation behaviour studied. Experimental results indicate that the substitution of SiO2 with TiO2 leads to suppression of crystallisation of cuspidine and formation of perovskite in glass quenched from mould fluxes. The crystallisation tendency is reduced by the introduction of TiO2. The high temperature viscosity of mould fluxes shows a decrease with increasing TiO2. At lower temperature, the viscosity of mould fluxes with 10%TiO2 is greater than that of TiO2 free slag, which could be attributed to precipitation of solid particles.

Preparation of Polymer/TiO2Hybrid Nanofibers Microporous Membranes and Its Application in Dye-Sensitized Solar Cells

The electrospinning technique provides a simple, cost-effective approach for producing polymeric and inorganic nanofibers with structures that vary with the processing parameters. In this paper, the polymer/TiO2 hybrid nanofibers micro- porous membranes were prepared from a polymer solution containing titanium (IV) butoxide (TBT) by electrospinning tech- nique. The as-spun nanofibers microporous membranes were placed in air for 5 h to allow complete hydrolysis. The mor- phology of the microporous membranes was observed using electron scanning microscopy (SEM) under vacuum condition. The uptake and porosity of microporous membranes were investigated by weighting method before and after soaking elec- trolyte. The ionic conductivity of the microporous membranes was measured using the complex impedance technique. The blocking cell of stainless steel/microporous membranes/stainless steel was used at 1—10 5 Hz frequency range at 25 ℃. The AC amplitude was 5 mV. The TiO2 electrode was obtained by spreading titania paste (P25) on the conducting glass substrate using a doctor blade technique. The dye-sensitized solar cells (DSSCs) devices were fabricated based on the microporous membrane electrolyte by sandwiching a slice of the polymer/TiO2 hybrid nanofibers microporous membrane between a dye-sensitized TiO2 electrode and a Pt counter electrode. The edges of the cell were sealed with narrow strips of Surlyn hot melt. The morphology and three-dimensional structure of polymer/TiO2 hybrid nanofibers microporous membranes did not markedly change after absorbing liquid electrolyte, which indicated that the introduction of TiO2 into polymer nanofibers could improve the mechanical properties of the nanofibers. These also made the polymer/TiO2 hybrid nanofibers microporous membranes possess high uptake and porosity. The TiO2 content in hybrid nanofibers was about 50 wt% according to the TG results. The wetting and diffusion properties of hybrid nanofibers microporous membranes to liquid electrolyte were im- proved due to the incorporation of TiO2. The ionic conductivities of PVP/TiO2, PAN/TiO2 hybrid nanofibers microporous membranes quasi-solid electrolyte could reach 2.81 mScm -1 and 2.62 mScm -1 , respectively, which were close to those of liquid electrolytes. The overall conversion efficiencies of quasi-solid DSSCs with N719 dye based on PVP/TiO2, PAN/TiO2 hybrid nanofibers microporous membranes quasi-solid electrolyte reached 7.79% and 7.97%, respectively, which exceeded over 90% of the liquid electrolyte. Meanwhile, the fabricated DSSCs showed good long-term stability. Keywords dye sensitized solar cells; electrospinning; nanofiber; microporous membrane; conductivity

Effect of TiO2 on the hydrodesulfurization performance of bulk Ni2P

The bulk Ni2P and TiO2-doped bulk Ni2P (Ti–Ni2P(x), x represents the Ti/Ni atomic ratio) were prepared by a co-precipitation method followed by an in-situ H2 temperature-programmed reduction procedure. The passivated catalysts were characterized by N2 adsorption–desorption method and X-ray absorption spectroscopy (XAS). Their hydrodesulfurization (HDS) performances were studied using dibenzothiophene (DBT) as the model molecule. The XAS results indicated that Ti–Ni2P(0.01) and Ti–Ni2P(0.03) were more oxidized than the other samples during passivation. The EXAFS analysis showed that Ni was formed in the presence of TiO2. The coordination number of NiNi shell of Ni in Ti–Ni2P(x) reached its maximum at a Ti/Ni atomic ratio=0.05. The HDS activity of Ni2P was substantially improved by the introduction of TiO2. TiO2 had different promoting effects on the direct desulfurization pathway and the hydrogenation pathway activities of Ni2P. The promoting effect of TiO2 is discussed by considering the electronic interactions between surface TiO2 and Ni2P species and the variations in the active site distributions.

Surface Photochemistry: on the Search of Efficient Photodegradation Methods for Indigo Dyes Through Advanced Oxidative Processes

PP-29-115 Background/Aims: Immobilization of TiO2 layers on glass and Modified Fenton test of the effect of advance oxidative processes on photocatalytic degradation of indigo blue. Particularly TiO2 photocatalysis and Fenton are known for being nonselective processes able to mineralize recalcitrant chemicals. Methods: A TiO2 emulsion was prepared, mixing 12 g TiO2, 4 mL H2O and 0.4 mL acethylketone for 10 minutes. Then, 25 mL H2O and 0.2 mL Triton X-100 were added. After proving that TiO2 deposited on glass effectively enhances the photodegradation of adsorbed indigo, we test various continuous flow and batch reactors, with and without TiO2 adsorbed on internal reactor wall, using different irradiation sources. Modified Fenton approaches are also being tested. Results: TiO2-coated glass enhances photodegradation of adsorbed indigo and dye absorption totally disappears after 6 hours irradiation with 125 watts Hg lamp; approximately 40% of color disappears in the first 1 hour. We tested continuous flow and batch reactors also on treatment of dye liquid streams (with or without TiO2 on internal reactor wall) using lamps. In TiO2 absence, there is no indigo degradation. Irrespective reactor or irradiation source used, very low % of degradations (<10%) with TiO2 introduction in the system. Fenton-based processes gave more promising results, with more than 50% color removed in about 0.5 hour. The problem of iron residue removal remains to be solved. Conclusion: To date, only Fenton-based methodologies seem to be able to remove the indigo blue color from those model waters.

Influence of Support Preparation Methods on Structure and Catalytic Activity of Co/TiO2-SiO2 for Fischer–Tropsch Synthesis

TiO2-SiO2 supports were prepared by various methods including precipitation, impregnation, hydrolysis-reflux and sol–gel, and then cobalt was impregnated on those supports. The properties of various catalysts were characterized by N2 physisorption, XRD, XPS and TPR. The introduction of TiO2 led to stronger Co-support interaction, accompanying with the variation of dispersion and reduction degree of cobalt. The catalytic test for F-T synthesis revealed that the addition of TiO2 improved the performance of catalysts prepared by precipitation, impregnation and hydrolysis-reflux, but had a negative effect with sol–gel method.

Promoting Effect of TiO2on the Hydrodenitrogenation Performance of Nickel Phosphide

TiO2-containing bulk Ni2P catalysts (Tix-Ni2P) were prepared by coprecipitation and in situ H2 temperature-programmed reduction (TPR), and characterized by XRD, CO chemisorption, TEM, XPS, TPR, and NH3-TPD. Their hydrodenitrogenation performances were studied by using quinoline and decahydroquinoline (DHQ) as the model molecules. Both the hydrogenation and C−N bond cleavage activities of Ni2P were improved by the introduction of TiO2. The TiO2 species were mainly located separately on the surface of the catalysts and had strong interactions with surface Ni and P species. The reducibility of the precursors as well as the surface electronic properties of Ni2P catalysts were affected by the addition of TiO2. Tix-Ni2P showed higher CO uptake but less acid sites than Ni2P. The promoting effect of TiO2 was discussed by considering the electronic interactions between surface Ti and Ni2P species and changes in the adsorption geometries of quinoline, DHQ, as well as the partially hydrogenated intermediates over Ti...

Crystallisation behaviour and in vitro characterisation of TiO2 doped spodumene glass ceramics

Crystallisation behaviour of Li2O–Al2O3–SiO2 system (LAS) glass ceramics containing TiO2 doping and non-doping is investigated by differential thermal analysis (DTA), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The introduction of TiO2 decreases the crystallising peak temperature Tp and the crystallising activation energy E and improves the crystallisation stage to obtain fine crystal with a size of ∼100 nm. A controlled surface reaction of the ceramic is an important factor governing the bioinert and biodegradation nature of the implanted ceramic. The addition of TiO2 improves the chemical durability of the glass ceramic, by reducing the number of non-bridging oxygens, suppressing the tendency for amorphous phase separation and provides a more dense and stable structure. This results in a decrease in the release rate of Li+, Al3+ and Si4+ ions in a simulated body fluid.

Preparation, structures and photoluminescent enhancement of CdWO4–TiO2 composite nanofilms

For the first time, Cadmium tungstate (CdWO4)–TiO2 composite nanofilms on a glass substrate were prepared by means of the dip-coating technique, in which collodion was used as a dispersant and film-forming agent. The films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), thermo gravimetric and thermal analyses (TG/DTA), FTIR and photoluminescence (PL) methods, respectively. SEM and XRD characterization of these films indicated that CdWO4 particles crystallized in a monoclinic wolframite-type structure whereas TiO2 particles were Anatase phase; and both of them were well distributed in the nanofilms. FTIR spectra proved the presence of CdWO4 on the nanofilms. Photoluminescent results showed that the emitting peak of CdWO4 films blue shifted slightly relative to that of CdWO4 crystal. Moreover, the PL intensity of CdWO4–TiO2 composite nanofilm was much higher than that of CdWO4 nanofilm. We ascribed that the introduction of TiO2 should be responsible for the PL enhancement.

Preparation and characterization of linear low‐density polyethylene/low‐density polyethylene/TiO2 membranes

AbstractBecause of their special functions, the application of nanoscale powders has recently attracted both industrial and theoretical interest. In this study, nanoscale TiO2, which exhibited a special UV absorption and consequent antibacterial function, was added to a low‐density polyethylene/linear low‐density polyethylene hybrid by melt compounding to yield functional composite membranes. TiO2 exhibited an apparent induced nucleation effect on the crystallization of polyethylene, and the size of the crystallites decreased while the number increaed with the introduction of TiO2; however, the crystallinity of polyethylene changed little. Also, TiO2 exhibited an ideal dispersion in the membrane with an average size less than 100 nm, and this excellent dispersion provided the membranes extra UV absorption; moreover, the transparency of the membranes was maintained to satisfy common requirements. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 216–221, 2005

Sharkskin mechanism of high‐impact polystyrene (HIPS) and rheological behavior of HIPS/TiO2 composites

AbstractThe rheological behaviors of high‐impact polystyrene (HIPS) and HIPS/TiO2 composites were investigated by use of a rheometer in the present article. HIPS exhibited a constant critical stress of the sharkskin in various temperatures, and the analysis indicated that the mechanism of sharkskin of HIPS was wall–slip and its special temperature dependency was determined by weak wall–melt adsorption. The experimental results also showed that the introduction of TiO2 into HIPS only slightly influenced the apparent viscosity (ηa) of the composites. Moreover, TiO2 exhibited an unusual effect on the non‐Newtonian index of the composites at high shear rate. Both phenomena indicated the increase of inner free volume induced by TiO2 in molecularly rigid HIPS. Moreover, it was noteworthy that a featured stress could be used to label the dispersion of TiO2 in the HIPS matrix, and the numeric affinity of this featured stress and the critical stress of sharkskin revealed that both processes were relevant to the same molecular relaxation. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 802–807, 2005

Investigations into the effect of LDV seed particles on the operating characteristics of a spark ignition engine

LDV measurements are commonly made in spark ignition engines to investigate the interaction between the flow field and the combustion process. To achieve high LDV data rates relatively large quantities of seed particles must be introduced into the engine intake flow. Based on the measurement of the characteristic engine operating parameters, it was determined that the introduction of TiO2 seed particles into an optical L-head research engine fuelled by natural gas at stoichiometric and lean conditions did not significantly influence the combustion process.

Substrate dependence in the growth of epitaxial Pb1−xLaxTiO3 thin films

The metalorganic chemical vapor deposition (MOCVD) technique has been applied to the growth of epitaxial Pb1−xLaxTiO3 (PLT) thin films with x=0.28. By first introducing an initial TiO2 layer, three-dimensional epitaxial PLT films were grown on the (100) surface of MgO substrate. For both KTaO3 (100) and Al2O3 (0001) substrates, heteroepitaxy was achieved without the introduction of TiO2 as the initial, intervening layer between the PLT film and the substrate. On Al2O3 substrates, PLT films with a [111] preferred orientation were grown with a good epitaxial in-plane relationship.

Tensile properties of TiO2‐filled poly(vinyl acetate) in the transition region

AbstractThe stress–strain properties of TiO2‐filled poly(vinyl acetate) have been studied at filler percentages of 0, 10, 20, 30, and 40% TiO2 over a strain‐rate range of 100–5000%/ min at 24°C. Tensile strength, Young's modulus, and offset yield strengths all were found to increase with higher strain rates and higher TiO2 contents. Ultimate elongations decreased with greater TiO2 content and higher strain rates. Shift factors for volume fraction of filler were estimated for tensile properties as function of test rate. Stress relaxation studies have shown a reduction in relaxation times with increasing TiO2 content. Calculations of the out‐of‐phase Young's modulus were made as a function of filler content employing a box‐type of distribution of relaxation times. A possible explanation for the stress–strain behavior observed is that introduction of TiO2 changes the internal viscosity of the system, similar to the effect of temperature. This would also mean that the ultimate properties would be dependent on filler content and strain rate because viscous resistance to chain deformation would be altered. The effect of filler on stress relaxation could be thought of being due to an increase in short‐range chain motion.