Increasing TiO2 Content Research Articles

Influence of TiO2 content on phase evolution, microstructure and properties of fluorcanasite glass-ceramics prepared through sintering procedure for dental restoration applications

This study aims to highlight the role of TiO2 (titanium dioxide) on concurrent densification-crystallization behavior, microstructure as well as mechanical and chemical properties of fluorcanasite glass-ceramics. According to the obtained results, the addition of TiO2 to the base composition (stoichiometric fluorcanasite) and an increase of its content, decreased crystallinity of the relevant glass-ceramics; but improved their sinterability. Fully densified glass-ceramics were obtained from TiO2 containing compositions after sintering at 900–950 °C. Calcium fluoride and fluorcanasite crystallized in all fabricated glass-ceramics during sintering; while goetzenite crystallized as the dominant crystalline phase in those glass-ceramics contained more than 6 weight ratios of TiO2. On the basis of microstructural observation, the interlocking status between the precipitated crystals was remarkably diminished by an increase of TiO2 content. Measurement of mechanical properties confirmed the rise of Vickers micro-hardness and simultaneous decrease of flexural strength and fracture toughness by enhancing of TiO2 content in the examined glass-ceramics.

Synthesis, thermal, structural and linear optical properties of new glasses within the TeO2-TiO2-WO3 system

The glass-forming domain and physical properties, namely, the density, thermal, structural and linear optical properties of new glasses within the TeO2-TiO2-WO3 system have been investigated. By means of micro-Raman spectroscopy, the structure of these glasses was examined based on a full-scale spectral decomposition. The optical transmission and refractive index dispersion were measured by UV–Vis-NIR spectroscopy and spectroscopic ellipsometry respectively. Consistent correlations were established between the structural and linear optical properties. Only minor structural modifications of the original TeO2-rich network are taking place upon adding TiO2 or WO3, suggesting the absence of Te–O–Te bond network depolymerization. Our results also suggest that, upon increasing TiO2 content, a phase separation occurs between amorphous TeO2-rich and amorphous TiO2-rich regions. We also argue that the structural trends upon adding WO3 evolve from uniformly dispersed WO6 octahedra (at low WO3 content) to amorphous WO3-like regions (at higher WO3 content) before the crystallization of γ-WO3 at 30 mol% of WO3. The compositional dependence of the refractive index and several optical constants (Urbach EU and dispersion Ed energies, oxide ion polarizabilities) is highlighted. These glasses collectively exhibit high refractive indices in the order of ~2.2.

Corrosion resistance behavior of PVA/TiO2 composite in 3.5% NaCl

Marine structures come into contact with the seawater. Corrosion occurs on the walls of these structures and can quickly lead from surface damage to aesthetics impairment. The main cause of the corrosiveness are chloride ions which facilitate initiation and propagation of pits. Stainless steels provide a wide range of applications in seawater environments. They are used for the construction of heat exchangers, tanks and capacitors for electrical systems, refrigeration systems for power plants, tidal power, wind turbines localized at sea. Mild steel find its role in almost every product created from metal due to its low cost and easy availability. The polymeric materials are having multiple adsorption sites for bonding with metal surface and provides higher inhibition efficiency than the corresponding monomers. In the present work, the corrosion inhibition of mild steel in 3.5% NaCl by polyvinyl alcohol/TiO2 composites were studied. The composite samples were characterized by using XRD, FTIR and SEM. Potentiodynamic polarization and electrochemical impedance spectroscopic techniques were used to explore the enhanced corrosion inhibition of composites. The corrosion inhibition efficiency of PVTi composites were found to increase with increase in concentration of TiO2.

The Effect of Graphene/TIO<sub>2</sub> Nanomaterials on Photocatalytic Performance for Industrial Wastewater Treatment

The aim of the present work is to combine TiO2/Graphene to increase photo-catalytic activity and obtain efficient removal of direct red 23 azo dye without difficult synthesis. Many operating variables which affect the process and some design aspects were studied. Reactor geometry is the main design parameter where slurry rectangular reactor and bubble column were compared with respect to hydrodynamic regimes, overall degradation efficiency and applicability in industrial scale. The removal rate was found to increase with increase in TiO2 concentration, approaching a limiting value at catalyst loads of 3g/L. For rectangular reactor only 0.005g/L of rGO able to enhance the activity of photo-catalysis. However, the optimum concentration of rGO is decreased in the bubble column reactor to be 0.001g/L. In both reactor systems, photocatalytic activity increase significantly by decreasing wavelength of the irradiated lamp from 365 nm to 254 nm. Also, results show the ability of bubble column reactor to treat high concentrations of dye up to 200 ppm. That makes it suitable to be integrated with biological system to convert non-biodegradable contaminates into biodegradable organics. That reduces the operating cost of the process and makes it more applicable in industrial scale. Rectangular reactor has the ability to be modified to use sunlight instead of artificial lamps because of high surface exposed to sunlight. In general the performance of bubble column reactor was better than rectangular reactor because it has excellent mass transfer characteristics, which enhance the efficiency of the process.

Judd−Ofelt Parameters via Bayesian Inference

Bayesian inference was used as a new approach to calculate of rare earth (RE) ion spectroscopic parameters within the Judd−Ofelt theory using the Li2O-B2O3-Al2O3 glass system doped with Nd2O3 and TiO2. This system was synthesized by the fusion method, and the physical properties of the as-synthesized material were investigated. Optical absorption, photoluminescence, micro-Raman, mass density, refractive index, and radiative lifetime calcuations were performed. We investigated the effects of crystal field changes on Nd3+-ions caused due to co-doping with increasing TiO2 content. We observed that co-doping with TiO2 altered the radiative transition rates A(J,J′), favored symmetry enhancement around the Nd3+-ions, and promoted the onset of vibrational modes, contributed to the attenuation of O-H bonds, and substantially increased the spectroscopic quality, χ.

Low Temperature Selective Catalytic Reduction Using Molding Catalysts Mn-Ce/FA and Mn-Ce/FA-30%TiO2

Mn-Ce/FA (M) and Mn-Ce/FA-TiO2 (M), using fly ash (FA) with and without TiO2 as the carriers, were prepared by an integral molding technique. With the increase of TiO2 content, the rates of NO conversion and denitration of Mn-Ce/FA-TiO2 (M) increased, and the NO2 and N2O formation rates decreased. It is found that TiO2 could effectively inhibit the excessive oxidation of NO and the generation of N2O. The effects of space velocity, oxygen concentration and ammonia nitrogen ratio on three types of nitrogen oxides (NO, NO2, N2O) and denitration rates of the Mn-Ce/FA (M) and Mn-Ce/FA-30%TiO2 (M) were further investigated. In addition, it is demonstrated that Mn-Ce/FA (M) and Mn-Ce/FA-30%TiO2 (M) were more suitable to be used in the environment of low sulfur and less water.

Measurement of mass stopping power of chitosan polymer loaded with TiO2 for relativistic electron interaction

The Mass Stopping Power (MSP) of relativistic electrons in chitosan loaded with TiO2 of different proportions has been measured by recording the spectrum of internal conversion electrons. The internal conversion electrons of energies 614keV from Cs137, 942keV and 1016keV from Bi207 source are allowed to pass through chitosan-TiO2 alloy and transmitted electrons are detected with a Si (Li) detector coupled to an 8K multichannel analyzer. By knowing the energies of incident electrons and transmitted electrons, the energy loss and the MSP are determined. Thus measured MSP values of the alloys are compared with the values calculated using Braggs additivity rule. The disagreement between theory and experiment is found to increases with increasing TiO2 concentration in chitosan, indicating the influence of chemical environment in the properties of such polymeric membrane.

Free-standing TiO2–SiO2/PANI composite nanofibers for ammonia sensors

Free-standing TiO2–SiO2/polyaniline (TS/PANI) composite nanofibers were prepared by electrospinning, in situ polymerization and calcination method. The effect of tetra-n-butyl titanate (TBT) in the electrospinning solution on the morphology and the ammonia sensing properties of TS/PANI composite nanofibers were investigated. The obtained nanofibers were characterized by scanning electron microscope, Fourier transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy, thermo-gravimetric analysis and gas sensor test system. It is proved that too much TBT in the solution would make the fibrous morphology and ammonia sensing properties worse. Gas sensing tests showed that the TS/PANI composite nanofibers ammonia sensor can work at room temperature and possess ideal response values, selectivity and repeatability. With the increase in TiO2 content in the TS nanofibers, the ammonia sensing properties were improved because of the increase in P–N heterojunctions formed between TiO2 and PANI in the sensors.

Hydroxyapatite-enhanced structural, photocatalytic and antibacterial properties of photoreactive TiO2/HAp/polyacrylate hybrid thin films

IntroductionSurfaces with attached semiconductor photocatalyst content can kill numerous microorganisms because of their photocatalytic properties. There are various techniques to develop antimicrobial surfaces, but only a few optimize the structure and the chemical properties. ObjectivesBoth the TiO2/HAp composites and the TiO2/polymer hybrid materials are separately well known in the literature, however, here we presented that the incorporation of bacterial adhesive HAp lamellae in the TiO2/polyacrylate hybrid thin films improved the photocatalytic and antibacterial properties of the composite layers. MethodsThe structure of the synthetized TiO2/HAp composites and the TiO2/HAp/polyacrylate hybrid layers were investigated with XRD, SAXS, IR, EDX and BET measurements. The optical and morphological properties of the hybrid layers were measured with UV–Vis spectrophotometer and SEM, respectively. Finally, the photooxidation and antibacterial effect of the synthesized nanohybrid films were also determined. ResultsThe TiO2/HAp samples possess measurably higher specific surface areas (~120m2g−1) with increasing TiO2 content (TiO2/HAp 40/60, 60/40 and 80/20) compared to the pure components (HAp: 116m2g−1 and TiO2: 53m2g−1). SEM, EDX and SAXS measurements also prove the homogeneous distribution of TiO2 particles on the surface of HAp lamellae. This enhanced photoreactive surface and higher TiO2 accessibility were also proved by the photocatalytic and antibacterial measurements. ConclusionThe presence of biocompatible HAp microlamellae in the TiO2/polymer hybrid layers results in an incompact structure of the thin films with enhanced photocatalytic surface accessibility. Due to this structure-opening effect of the HAp lamellae the hybrid film consists of 36/24/40wt% TiO2/HAp/polyacrylate showed the same antibacterial activity as the film with 60/40wt% TiO2/polyacrylate composition. Moreover, the presence of inert HAp lamellae in the TiO2/polyacrylate matrix was significantly decreased the undesired photodegradation of the polymer binder.

Application of CaCO3, CaF2, SiO2, and TiO2 particles to silicone lens for enhancing angular color uniformity of white LED lamp

In this study, we present an insightful investigation on optimal selection of scattering enhancement particles (SEP) to satisfy each specific optical property of white LEDs (WLEDs). The interested contenders include CaCO3, CaF2, SiO2, and TiO2, each of them is added with YAG:Ce phosphor compounding. The quality improvement on each considered property is demonstrated convincingly by applying Mie-scattering theory together with Monte Carlo simulation on a particular WLEDs which has the color temperature of 8500K. It is observed by simulation results that TiO2 particles provide the highest color uniformity among the SEP, as increasing TiO2 concentration. These results of this work can serve as a practical guideline for manufacturing high-quality WLEDs.

Crystal structure, mixture behavior, and microwave dielectric properties of novel temperature stable (1 − x)MgMoO4 − xTiO2 composite ceramics

Novel temperature stable MgMoO4–TiO2 microwave dielectric ceramics were prepared by a solid state reaction process at low temperature (950°C). As TiO2 content increases, the relative permittivity increases while the Q×f value decreases, and the variation mechanisms are proposed, respectively. The temperature coefficient of resonant frequency (τf) shifts to the positive direction as TiO2 is added. The mixture mechanisms of τf value for two-phase composite materials are supposed. A near-zero τf value (3.2ppm/°C) is obtained when x=0.3, with εr=9.13±0.03 and Q×f=11,990GHz. The 0.7MgMoO4–0.3TiO2 composites are considered to be appropriate as a low temperature co-fired ceramic material for microwave wireless communication applications.

Thermal and calorimetric investigations of titania–silica composites

The paper presents the studies of effects of TiO2 amount differentiation on the structural and thermal properties of titania–silica complex oxides prepared by chemical vapor deposition of TiCL4 onto the Si-40, Si-60, and Si-100 silica gels. The mesoporous materials, characterized by a varied pore structure with highly developed surface and large pore volume, were obtained. The porous structure of materials under investigations was characterized by the low-temperature nitrogen adsorption–desorption method as well as by power spectral density calculated from the calorimetric investigations of water confined in the pores. Moreover, the thermodesorption of water using the quasi-isothermal thermogravimetry was used to characterize their thermal and surface properties. The adsorbed water layers and the concentration of weakly and strongly bound water as well as the surface free energy on the adsorbent–water interfaces were calculated. It was stated that the increase of titania content causes a gradual decrease of specific surface area and has a significant effect on the porous structure formation. The water thermodesorption from the surface proceeds in few stages because of the porosity created by TiO2. The decrease in the total surface free energy (Δ GΣ) can be observed with the increasing TiO2 content. The largest Δ GΣ value at the adsorbent/strongly bound water interface is exhibited by the adsorbents of Si-100 series. The lowering of the freezing/melting points of water contained in the pores of the studied materials is strongly connected with their porous structure.

Effects of titanium dioxide (TiO2) nanoparticles on the photodissolution of particulate organic matter: Insights from fluorescence spectroscopy and environmental implications

Widely used titanium dioxide (TiO2) nanoparticles are likely to accumulate ultimately in sediments and potentially pose a risk to water ecosystems. This study evaluated the effect of TiO2 nanoparticles on the photodissolution of particulate organic matter (POM) through fluorescence spectroscopy. Excitation-emission matrices and parallel factor analyses revealed that the fluorescent characteristics of produced dissolved organic matter (DOM) during photodissolution of suspended sediment and synthetic particulate organic matter (SPOM) were primarily humic-like. SPOM particles appeared to simulate well the photodissolution of suspended sediment. Quasi-complete increases in fluorescence intensity and chromophoric DOM (CDOM) abundance were reached after 90, 60, and 50 min irradiation for TiO2 concentrations of 0, 2, and 5 mg L−1, respectively. The faster increment of fluorescence intensity and CDOM abundance indicated the photocatalytic dissolution of SPOM, as opposite charges between TiO2 and SPOM at pH = 4 favored the adsorption of TiO2 onto SPOM. For sediments, the CDOM abundance and fluorescence intensity decreased with increasing TiO2 concentration, resulting from the photocatalytic degradation of photoproduced DOM from sediments. These results demonstrated that pH plays an important role in the photocatalytic dissolution of POM by TiO2. Therefore, appropriate pH controls should be implemented when TiO2 are used to treat sediments contaminated with organic pollutants. Finally, with increasing use of TiO2, its accumulation in sediments may affect the fate of carbon, nutrients, and heavy metals in shallow-water ecosystems.

Effect of TiO 2 on phase composition and microwave dielectric properties of Zn 1.01 Nb 2 O 6 ceramics

Nonstoichiometry has been playing an important role in the microwave dielectric performance of columbites A2+Nb2O6 (A2+ = Ca, Mg, or a transition metal). Herein, with an excess of 0.01 mol Zn, the Q×f values of ZnNb2O6 ceramics could be effectively improved from 121 000 GHz to 138 000 GHz. On the basis of high-Q Zn1.01Nb2O6 ceramics, TiO2 was chosen to further tune the τf values for the matrix materials prepared by the conventional solid-state reaction method. The results showed that, with the increase of TiO2 content, the ZnNb2O6-based ceramics underwent four phase regions: columbite (ZnNb2O6) solid solution, ixiolite (ZnTiNb2O8) solid solution, mixture of ZnTiNb2O8 and rutile (Zn1/3Nb2/3)0.5Ti0.5O2, and (Zn1/3Nb2/3)0.5Ti0.5O2 solid solution. Such changes in phase formation had an important influence on the microwave dielectric behavior of (1-x)Zn1.01Nb2O6-xTiO2 ceramics. Importantly, τf could be tuned from −15.3 ppm/°C to +13.9 ppm/°C along with x increased from 0.58 to 0.6. Accompanied with er ≈ 44.64 ~ 47.43 and Q×f ≥ 12 300 GHz, these materials are promising candidates for applications in microwave components and devices.

Effect of TiO2 addition on the microstructures, mechanical and dielectric properties of porous Si3N4-based ceramics

ABSTRACTPorous Si3N4-based ceramics with different TiO2 contents were prepared by gas pressure sintering method. The effects of TiO2 addition ranging from 0 to 25 wt-% on the phase compositions, microstructures, mechanical performance and dielectric properties were investigated. The addition of TiO2 significantly promoted the density which increased from 1.64 to about 2.3 g cm−3. The mechanical properties of porous Si3N4-based ceramics with TiO2 addition decreased first and then increased with the increase of TiO2 content, and the flexural strength and elastic modulus are more than 167.4 MPa and 72.8 GPa, respectively, which were higher than that of the Si3N4 ceramic without TiO2 addition. With the increase of TiO2 content, both the dielectric constant and dielectric loss increased, and the dielectric constant enhanced obviously. These results suggested that the TiO2 was beneficial for the improvement of mechanical properties and dielectric constant of porous Si3N4-based ceramics.

Effect of gelatin/agar bilayer film incorporated with TiO2 nanoparticles as a UV absorbent on fish oil photooxidation

AbstractThis research evaluated the effect of gelatin/agar bilayer film and nanocomposites containing different concentrations of TiO2 nanoparticles (0.5%, 1% and 2%) as ultraviolet (UV) and oxygen barriers on the oxidative stability of fish oil. Samples of fish oil covered with the bilayer films were stored under UV light or in darkness and with or without lids at 18 °C for 12 days. Oil quality in terms of peroxide values (PV), thiobarbituric acid (TBA), conjugated diene (CD), fatty acids profile and colour change (∆E) was monitored during storage. Fish oil photooxidation was hindered by increasing TiO2 concentration, so that nanocomposite containing 2% of the nanoparticles could control photooxidation, similar to the samples stored in darkness. Furthermore, upon studying both photooxidation and autoxidation, the highest amounts of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), as well as the lowest amount of changes in PV, TBA, CD and ∆E, were observed in oils covered with the nanocomposites.

Physical characteristics of PbO−ZrO2−SiO2:TiO2 glass ceramics embedded with Pb2Ti2O6 cubic pyrochlore crystal phase: Part-I electrical properties

This study is mainly focused on electrical characteristics of PbO−ZrO2−SiO2: TiO2 glass ceramics embedded with Pb2Ti2O6 cubic pyrochlore crystal phases. The samples were synthesized by usual melt quenching technique and subsequent heat treating at crystallization temperature for prolonged times. The samples were characterized by XRD, SEM and DSC, IR, EPR and optical absorption spectroscopy techniques. Later, dielectric properties viz., dielectric constant, loss tangent, electric moduli, electrical impedance and a.c. conductivity over wide ranges of frequency and temperature, have been measured as a function of TiO2 content. The results of characterization techniques viz., XRD, SEM and DSC, indicated that the samples are embedded with multiple crystal grains (with sizes varying from 0.1 to 1 μm) cemented with residual glass phase. The volume fraction of the crystal grains is found to increase with increase of TiO2 content. The XRD studies on PbO−ZrO2−SiO2:TiO2 glass ceramics revealed that Pb2Ti2O6 cubic pyrochlore crystal phase is the principal phase present in the bulk samples. The studies have also confirmed that a small part of Pb(Zr 0.5Ti0.5)O3 and Ti2O3 crystal grains are also present in the titled glass ceramics. The results of IR spectral studies have indicated that there is an increasing degree of polymerization of glass network with increasing TiO2 content up to 0.6 mol%. This is attributed to the presence of Ti ions predominantly in Ti4+ state (in this concentration range of TiO2) that take part in the network forming positions with TiO4 and also substitutionally positioned octahedral sites. The results of optical absorption and EPR spectral studies have pointed out that a part of the Ti ions were reduced to Ti3+ state and such ions were predicted to act as modifiers. These studies have also indicated that the concentration of Ti3+ ions is higher in the samples crystallized with 0.8 and 1.0 mol%. The values of dielectric parameters are decreased with increasing of crystallizing agent. The decrease is attributed to the participation of Ti ions in the formation of Pb2Ti2O6 cubic pyrochlore crystalline phases with TiO4 structural units. Quantitative analysis of the dielectric properties of PbO−ZrO2−SiO2:TiO2 glass ceramics together with the results of spectroscopic studies indicated that the electrical insulating strength is the highest for the glass crystallized with 0.6 mol% of TiO2.

Viscosity measurement of FeO–SiO2–V2O3–TiO2 slags in the temperature range of 1644–1791 K and modelling by using ion-oxygen parameter

ABSTRACTThe viscosity of the FeO–SiO2–TiO2–V2O3 system with TiO2 between 5 and 15-mass %, V2O3 between 5 and 15-mass% and FeO/SiO2 mass ratio between 1.4 and 2.2 was measured at temperature 1644–1791 K. It was found that the viscosity of slag increased with increasing V2O3 level, decreased with increasing temperature and FeO/SiO2 ratio, and decreased with increasing TiO2 content. The viscosity values of FeO–SiO2–V2O3–TiO2 system were calculated by employing various viscosity models. The mean deviations are about 54.04, 84.13, 18.96, and 4.48% for the values by Mill, modified Riboud, and , respectively. Thus, a model based on the ion-oxygen parameter, which can describe the influence of components and temperature, provided the best fit to the viscosity data. There were three kinds of crystalline phases, Fe2SiO4, Fe2TiO4, and FeV2O4 in all samples. The SiO2 crystal appeared in Al, Al3, and B3 samples.

Structural units distribution, phase separation and properties of PbO–TiO2–B2O3 glasses

Glasses of the formula 50PbO·xTiO2·(50−x)B2O3·0.5CuO (0≤x≤30mol%) have been investigated by XRD, FTIR, SEM. Phase separation is observed in as-prepared glasses, but there are no crystalline species. Crystalline PbTiO3 and PbB2O7 phases are formed in 50PbO·30TiO2·20B2O3·0.5CuO glass samples after thermal treatment at 530°C for 8h. The IR spectra do not show peaks related to structural units of TiO2. The fraction of BO4 units decreases slightly with increasing TiO2 content. This change is assumed due to formation of TiO6 units at the expense of TiO4 units. Both the density and molar volume do not change with composition. Calculations based on the concentration and volume of the structural units indicate that the molar volume has mostly the same value between 0 and 30mol% TiO2.

Cytocompatibility studies of titania-doped calcium borosilicate bioactive glasses in-vitro

The present study aims to elucidate the applications of Titania (TiO2) doped calcium borosilicate glass as a biocompatible material in regenerative orthopedic applications. In this context, we have examined the bioactivity of various concentrations of TiO2 doped glasses with the help of simulated body fluid (SBF). Cytocompatibility, cell proliferation, and protein expression studies revealed the potential candidature of TiO2 doped glasses on osteoblast cell lines (MG-63). We hypothesized that TiO2 doped calcium borosilicate glasses are most cytocompatible material for bone implants. Glasses with composition 31B2O3-20SiO2-24.5Na2O-(24.5−x) CaO- x TiO2 (x=0,0.5,1,2) have been prepared by the conventional melt-quenching technique. After immersion of glasses in the SBF, formation of hydroxyapatite layer on the surface was confirmed by X-ray Diffractometer (XRD), Fourier Transform Infrared Spectroscopy (FT-IR) and Scanning Electron Microscopy-Energy Dispersive Spectroscopy (SEM-EDS) analysis. Significant change in the pH of the body fluid was observed with the addition of titania. Degradation test was performed as per the ISO 10993. The results showed that partial substitution of TiO2 with CaO negatively influenced bioactivity; it decreased with increase in concentration of TiO2. Vickers hardness tester was used to measure the microhardness values of the prepared glasses. With the increasing of TiO2 content, the microhardness of the glass samples was increased from 545Hv to 576Hv. Cytocompatibility has been evaluated with MG-63 cells by using MTT assay. Further, we observed that there was no change in expressions of cyclin levels even after the incorporation of titania. The antibacterial properties were examined against E. coli and S. aureus. Strong antibacterial efficacy was observed for 2% TiO2 in the system. Hence it can be concluded that titania-doped borosilicate glasses may be used as potential materials in bone tissue engineering.