Effect Of TiO2 Doping Research Articles

Influence of TiO2dopingand spraying power on the microstructure, mechanical properties and cavitation erosion resistance of YSZ coatings

Yttria-stabilized zirconia (YSZ) and TiO2- doped YSZ (TiYSZ) coatings were prepared using Atmospheric Plasma Spraying (APS) at different power levels to protect of flow passage components from cavitation erosion. We analyzed, the effects of TiO2 doping and spraying power on the coatings' phase structure, microstructure and mechanical properties using XRD, Raman spectroscopy, SEM, Vickers hardness and nano-indentation. We tested the cavitation erosion behavior of TiYSZ coatings and YSZ coatings (as a reference) in a laboratory setting employing vibration-induced cavitation in accordance with ASTM standard G32-16. The results showed that the YSZ coating contained 50% c-phase and 50% t-phase, while the TiYSZ coating contained approximately 78 % c-phase. Spraying power hadlittle effect on the phase structure of either coating. However, higher spraying power increased the density of the coating, leading to greater microhardness. TiYSZ coatings were denser than YSZ at any power level and did not exhibit a distinct microcolumnar grain structure, unlike YSZ. Additionally, TiYSZ coatings displayed better mechanical properties, including higher hardness, elastic modulus, toughness, and fracture strength compared to YSZ. As a result, the cavitation resistance of TiYSZ coatings improved by about 50% compared to YSZ. Furhermore, we found that chemical degradation of YSZ-based ceramics under cavitation erosion conditions plays a role in cavitation erosion. We also observed that cavitation-induced amorphization is a key mechanism contributing to this degradation.

Sol-gel derived silicate-phosphate glass SiO2–P2O5–CaO–TiO2: The effect of titanium isopropoxide on porosity and thermomechanical stability

Despite of several decades lasting extensive research of bioactive and bioresorbable glasses the systematic parametrization and determination of the key factors affecting porosity and thermomechanical characteristics still remains challenging. Here, we present silica-phosphate glasses, with the composition 70SiO2–20P2O5–(10-x)CaO–xTiO2 (mol%; x = 0, 2.5, 5, and 7.5), prepared by sol-gel method and reinforced by titanium dioxide via titanium isopropoxide (TTIP) incorporation which demonstrated tunable variation of porosity from micro-to macro-region and superb mechanical integrity during the calcination process. The presence of 7.5 mol% TiO2 promotes dimensional stability up to 1000 °C as investigated by thermomechanical analysis. The XRD showed the dominant presence of silicon phosphate [Si(P2O7)], titanium phosphate [Ti(P2O7)] and calcium phosphates [β-Ca(P2O6) and γ- Ca2(P2O7)]. The effect of TiO2 doping on the multiscale morphology and porosity was investigated by means of SEM, MIP, μCT, N2 adsorption and USAXS/SAXS. Increasing TiO2 content leads to the formation of open porosity up to 70 vol% and drives the formation of a refined interconnected macroporosity of 2–30 μm. In contrast, mesoporosity with a dominance of 3–6 nm pores decreases in all samples with increasing TiO2 content. USAXS/SAXS revealed an increase in primary particle size with increasing TiO2 content which is in good agreement with the nitrogen physisorption analysis showing that microporosity decreases with increasing TiO2 content.

Low-temperature firing, temperature-independent, and microwave dielectric performances of ZnNb1.8V0.1O5.75 systems for LTCC applications

The effects of TiO2 doping on the phase transition and microwave dielectric performances of ZnNb1.8V0.1O5.75@xTiO2 (0.05 ≤ x ≤ 0.60) ceramics prepared by conventional mixing methods were investigated. In this study, we report for the first time the phase transition of ZnNb2O6 with columbite structure at low temperature (950 °C) where the τf value is adjusted to near zero. With the increase of TiO2 doping, the following phase transitions are experienced in the ceramics: columbite + monoclinic → columbite + monoclinic + ixiolite → monoclinic + ixiolite → monoclinic + ixiolite + rutile. The microscopic morphology of ceramics is greatly influenced by TiO2 doping. The grain size of ceramics continues to grow as TiO2 doping increases. The microwave dielectric performances of ceramics are intimately connected to the phase transition process, which occurs when the Q×f value constantly declines while the τf value steadily increases and is adjusted to near zero at x = 0.50. After sintering at 950 °C for 6 h, the most optimal microwave dielectric performances were obtained for x = 0.50 with a dielectric constant of 41.18, a Q×f value of 6852 GHz, and a τf value of +6.83 ppm/°C, providing a new option with great potential for microwave devices requiring medium dielectric ceramics.

Effect of TiO2 on the properties of microwave-sintered ceramics derived from coal fly ash for Nd-contaminated soil immobilization

ABSTRACT Coal fly ash (hereinafter CFA) was employed to rapidly immobilise Nd-contaminated soil with the addition of TiO2 via microwave sintering technology. The effect of TiO2 doping on the phase composition, microstructure, elemental distribution, density, and chemical durability of the solidified samples was systemically investigated. The results indicated that the Nd element can be incorporated in the matrix with oxyapatite and pyrochlore as TiO2 content increased at 1200°C. Moreover, the sintered sample with the high bulk density and low open porosity was fabricated at a TiO2-doping amount of 7 wt.%. Meanwhile, the as-prepared samples doping with TiO2 exhibited excellent chemical durability. Especially, the sintered sample doping with 3 wt.% TiO2 had the lowest leaching rate (7.97×10−6 g·m−2·d−1 at 28 d). Our investigation reflects that CFA is suitable for Nd-contaminated soil immobilisation via microwave sintering technology and the introduction of TiO2 is conducive to the improvement of densification and chemical durability.

Effect of TiO2 doping on the sintering behavior of Zr-based ceramic for use as TBC

Effect of TiO2 doping on the sintering behavior of Zr-based ceramic for use as TBC

Effect of TiO2 doping on structural and electrical properties of melt-quench V2−xTixO5−δ, 0.15 ≤ x ≤ 0.30 systems

Effect of TiO2 doping on structural and electrical properties of melt-quench V2−xTixO5−δ, 0.15 ≤ x ≤ 0.30 systems

Effect of TiO2 doping on degradation rate, microstructure and strength of borate bioactive glass scaffolds.

A titanium-containing borate glass series based on the system (52-X) B2O3-12CaO-6P2O5-14Na2O-16ZnO-XTiO2 with X varying from 0, 5 and 15 mol% of TiO2 incorporated, identified as BRT0, BRT1 and BRT3, respectively, were used in this study. Scaffolds (pore sizes, 165-230 μm and porosity, 53.51-69.51%) were prepared using a polymer foam replication technique. BRT3 scaffolds exhibited higher compressive strength (7.16 ± 0.22 MPa) when compared to BRT0 (6.02 ± 0.47 MPa) and BRT1 (5.65 ± 0.28 MPa) scaffolds with lower, or no, TiO2 content. The solubility of the scaffolds decreased as the TiO2 content increased up to 15 mol% when samples of each scaffold were immersed in DI water and the pH of all these extracts went up from 7.0 to 8.5 in 30 days. The cumulative ion release from the scaffolds showed significant difference with respect to TiO2 content; addition of 5 mol% TiO2 at the expense of borate (B2O3) decreased the ion release remarkably. Furthermore, it was found that for all three scaffolds, cumulative ion release increased with incubation time. The results indicate that the degradation rates and compressive strengths of borate bioactive glass scaffolds could be controlled by varying the amount of TiO2 incorporated, confirming their potential as scaffolds in TKA and rTKA.

Structural and Morphological Properties of Fe2O3 and TiO2:Fe2O3 Thin Films Prepared by Spray Pyrolysis Technique

Various doping percentage (1, 3 and 5 %) of titanium dioxide TiO2 were successfully introduced into the iron oxide Fe2O3 thin films obtained by spray pyrolysis technique (SPT) on a glass substrate. The effect of TiO2 doping on structural and morphological properties of deposited thin films was studied by X-ray diffraction analysis and atomic forces microscope (AFM) respectively. XRD result showed that all samples are polycrystalline and the crystallite size decreases with the increasing percentage of (TiO2). All films have peaks appears at (110), (211), (101), (222), (210), (202), (312), (332), (310) and (432) planes with preferred orientation along (211). The (AFM) results show that the grain size, roughness rate, and the root mean square decreases with increasing dopant ratios.

Effects of TiO2 doping on microstructure and properties of directed laser deposition alumina/aluminum titanate composites

ABSTRACT Al2O3-based composite ceramics have excellent high temperature performance and are ideal materials for preparing hot end components. However, poor fracture toughness and thermal shock resistance limit its applications. Based on the excellent low thermal expansion characteristics and thermal shock resistance of Al2TiO5 ceramic, different composition ratios of Al2O3/Al2TiO5 composite ceramics were prepared by directed laser deposition (DLD) technology. Effects of TiO2 doping amount on microstructure and properties of the composite ceramics were investigated. Results show that α-Al2O3 phase is discretely distributed in the continuous aluminum titanate matrix when TiO2 doping amount between 2 and 30 mol%. With the increase of TiO2 doping amount, content of Al2O3 gradually decreases and its morphology changes from cellular to dendritic. When TiO2 doping amount reaches 43.9 mol%, the microstructure transforms into fine Al2TiO5/Al6Ti2O13 eutectic structure. Property test results show that Al2O3/Al2TiO5 composite ceramics have good comprehensive mechanical properties when TiO2 doping amount between 2 and 6 mol%.

Effect of TiO2 doping on crystallization, microstructure and dielectric properties of CBS glass-ceramics

In this study, calcium borosilicate (CaO-B2O3-SiO2, CBS) glass-ceramics were fabricated using chemically pure CaO, SiO2, and B2O3 as raw materials. Differential scanning calorimetry, X-ray diffraction, scanning electron microscopy, and electrical measurements were conducted to explore the effect of titanium dioxide (TiO2) doping on crystallization, microstructure, and dielectric properties of CBS glass-ceramics. Furthermore, the influence of sintering temperature and sintering schemes on crystalline phases of CBS glass-ceramics was systematically investigated. Results showed that the increase of TiO2 content led to the reduction in sintering temperature of CBS glass-ceramics and promoted the precipitation of wollastonite crystal phase. For instance, with the increase of content of TiO2 from 0 to 3 wt%, transition temperature and crystallization temperature were reduced by 12.9 and 27.6 °C, respectively. However, excessive TiO2 affected the precipitation of wollastonite crystal phase, destroyed crystal structure, and damaged close arrangement of crystal grains. Moreover, higher TiO2 content was found to weaken dielectric properties of CBS glass-ceramics. In this study, the best molar ratio of ingredients, meeting that of ideal target material, is n(Ca): n(Si): n(B) = 1:1:0.6, with doping mass fraction of 2 wt% of TiO2. After optimal sintering procedure, dielectric constant of the best sample was found to be 1.4 (1 MHz), 1.3 (10 MHz), and dielectric loss was 3.9 × 10−3 (1 MHz) and 3.8 × 10−3 (10 MHz).

Effect of TiO2 doping on densification and mechanical properties of hydroxyapatite by microwave sintering

Abstract Hydroxyapatite (HAP) possesses excellent bioactivity/osteointegration properties. Nevertheless, its inferior flexural strength and fracture toughness limit its use in human weight-bearing parts. We investigated a microwave sintering technology which can be effectively used to develop titanium dioxide-hydroxyapatite (TiO2-HAP) ceramics with different amounts of TiO2 (0.8,1.6,2.4,3.2,4.0,4.8,5.6 and 6.4 wt%), which contribute to extremely high flexural strength (90–130 MPa) along with a good combination of elastic modulus and fracture toughness. The results of the Rietveld refinement show that multiphase bioceramics (HAP, β-TCP) can be achieved by doping nano-TiO2 under microwave sintering. Despite the fact that the main phases of the sintered TiO2-HAP ceramics are HAP and β-TCP, X-ray diffraction confirms the formation of the CaTiO3 and CaTi2O4(OH)2 phases. Furthermore, the sintering reactions to form these phases are discussed and the results show that an appropriate amount of nano-TiO2 can not only effectively inhibit the growth of grain, but also change the fracture mode and increase the relative density. Finally, it is found that doping nano-TiO2 by microwave heating is an effective technique for producing HAP/β-TCP composite load-bearing implants in clinical applications without coarsening the size of grain.

Effects of TiO2 doping on Li+-stabilized Na-β″-alumina for energy storage applications

Sodium-ion conductive Li+-stabilized Na-β″-alumina was synthesized by calcinating a mixture of AlO(OH), Na2CO3 and Li2CO3. For additional improvement of the characteristics the ceramic powder was doped with various amounts of TiO2 and sintered at 1400, 1500 and 1600 °C. The effects of doping and sintering temperature were evaluated by measuring fracture strength, ionic conductivity, density, morphology and phase composition. The conductivity was raised from 0.2 to 0.3 S cm−1 at 300 °C by adding 1.5 wt.-% TiO2 to the Na-β″-alumina. By adding 1 wt.-% of TiO2 to the electrolyte material, the characteristic fracture strength σ0 was increased from 188 to 277 MPa. Aside from that, changes in the microstructure, due to doping were observed. The altered properties of the ceramic were mainly assigned to changes in the microstructure.

Effect of TiO<sub>2</sub> Doping on Microdefects and Electrical Properties of ZnO-Based Varistors

Positron lifetime spectrum and electrical property measurements were performed on ZnO-based ceramics doped with different contents of TiO2. For ZnO-based ceramics with TiO2 content less than 1.8 mol%, the mean positron lifetime of the ZnO-based ceramic decreases with increasing in TiO2 content, and reaches a minimum value at 1.8 mol% TiO2. As the TiO2 content higher than 1.8 mol%, the mean positron lifetime increases with TiO2 content. The ZnO-based varistor with 1.8 mol% TiO2 exhibites an optimized varistor property; it has a relatively low leakage current IL, a relatively low breakdown voltage VB, and a relatively high nonlinear coefficient α. The effects of TiO2 doping on microdefects and electrical properties of ZnO-based varistors were discussed.

Electrochromic response of WO3 and WO3-TiO2 thin films prepared from water-soluble precursors and a block copolymer template

Electrochromic tungsten trioxide (WO3) thin films are attracting renewed attention as transmittance-controllable windows for use in automobile, aircraft, and building applications. In order to achieve high electrochromic performance, high cycle stability, and high reliability, the microstructure and compositional homogeneity of WO3 thin films have to be optimized. In this study, non-doped WO3 and TiO2-doped WO3 thin films were fabricated from water-soluble precursors of tungsten and titanium, and their electrochromic response was investigated. Amorphous WO3 and TiO2-doped WO3 thin films were fabricated by calcining the spin-coated films at 573 K. The use of a PEO-PPO-PEO block copolymer as a porogen facilitated the redox reactions occurring on the thin film/electrolyte interface. Although the effect of TiO2-doping on the cycle stability of WO3 thin films has not been fully elucidated, this study demonstrated that TiO2 doping up to 15 mol% effectively enhanced the cycle stability.

TiO2 nanoparticles doped SiO2 films with ordered mesopore channels: a catalytic nanoreactor

Titanium dioxide (TiO2) incorporated ordered 2D hexagonal mesoporous silica (SiO2) films on a glass substrate were fabricated for use as a catalytic nanoreactor. Films were prepared using a tetraethyl orthosilicate (TEOS) derived SiO2 sol and a commercially available dispersion of TiO2 nanoparticles (NPs) in the presence of pluronic P123 as the structure directing agent. The effect of TiO2 doping (4-10 mol% with respect to the equivalent SiO2) into the ordered mesoporous SiO2 matrix was thoroughly investigated. The undoped SiO2 film showed a mesostructural transformation after heat-treatment at 350 °C whereas incorporation of TiO2 restricted such a transformation. Among all the TiO2 incorporated films, TEM showed that the 7 equivalent mol% TiO2 doped SiO2 film (ST-7) had an optimal composition which could retain the more organized 2D hexagonal (space group p6mm)-like mesostructures after heat-treatment. The catalytic activities of the TiO2 doped (4-10 mol%) films were investigated for the reduction of toxic KMnO4 in an aqueous medium. ST-7 film showed the maximum catalytic activity, as well as reusability. A TEM study on the resultant solution after KMnO4 reduction revealed the formation of MnO2 nanowires. It was understood that the embedded TiO2 NPs bonded SiO2 matrix increased the surface hydroxyl groups of the composite films resulting in the generation of acidic sites. The catalytic process can be explained by this enhanced surface acidity. The mesoporous channel of the ST-7 films with TiO2 doping can be used as a nanoreactor to form extremely thin MnO2 nanowires.

Effect of TiO2 doping and gamma ray irradiation on the properties of SrO–B2O3 glasses

Glasses from the binary strontium borate system of the basic composition 45%SrO–55%B2O3 together with samples containing different concentrations of TiO2 (2–10%) replacing equivalent SrO were prepared. The prepared samples were characterized by means of combined Fourier transform infrared absorption (FTIR) and UV-visible optical absorption spectroscopic measurements before and after subjecting the glasses to gamma irradiation with doses up to 8Mrad. XRD diffraction patterns have indicated the amorphous nature of the prepared glasses over the entire compositional range. Binary undoped strontium borate glass exhibits strong UV absorption bands which are attributed to the presence of unavoidable trace iron impurities (mainly Fe3+ ions) while the TiO2 containing glasses reveal an additional UV band which can be related to the presence of titanium ions mostly as tetravalent Ti4+ ions in this host strontium borate glass.FTIR spectra of the prepared glasses show the appearance of both triangular and tetrahedral borate units in their specific wavenumbers with the first groups in higher ratio. Minor changes have been identified in the intensity or position of the borate IR vibrational bands upon the increase of TiO2 within the glass content. The resolution of a distinct IR peak at 420cm−1 can be related to the presence of B―O or Ti―O―Ti bonding upon the increase of TiO2 content.

The effect of TiO2 doping on catalytic performances of Ru/CeO2 catalysts during catalytic combustion of chlorobenzene

The lower temperature catalytic combustion of chlorinated hydrocarbons (CHCs), including chlorobenzene (CB), 1,2-dichloroethane (DCE) and trichloroethylene (TCE), over RuO2 supported on Ti-doped CeO2 catalysts (Ru/Ti–CeO2) was investigated, and the effects of preparation methods, Ti content, Ru content, inlet CB concentration and space velocity, oxygen concentration and water were studied detailedly. Moreover, the doping of other different metals (Mn, Co, Sn and Mg) and the supporting of different precious metals (Pt, Pd, Rh, Au and Ag) also were briefly explored. The results show that the doping of Ti can improve obviously the catalytic activity and stability of CeO2 based catalysts. The better catalytic activity of Ru/Ti–CeO2 is ascribed to the expose of more oxygen vacancies and high energy lattice plane CeO2 (110) and (100), and the Cl dissociatively adsorbed at active sites of CeO2 can be oxidized into Cl2 catalyzed by RuO2 supported Ti–CeO2 at lower temperature (such as 200̊C) which be responsible to the excellent stability of Ru/Ti–CeO2 catalysts.

Ferromagnetic insulating and spin glass properties of La0.7Sr0.3MnO3–TiO2 composites

In this study, the effect of TiO2 doping on the electro-magnetic properties of (1−x)La0.7Sr0.3MnO3+xTiO2 (with 0%≤x≤6%, in wt%) composites has been investigated. X-ray diffraction observations show the evidence of reaction between the La0.7Sr0.3MnO3 and TiO2 grains. Also the results show that by increasing TiO2 doping levels, the metal insulator transition temperatures decrease and the system becomes an insulator. Furthermore, the paramagnetic–ferromagnetic transition temperature also decreases as TiO2 content increases. The spin glass state exists in the composites with x=5% and 6%. The dynamic properties of the magnetic properties are investigated by temperature dependence of dc magnetization and frequency dependence of ac susceptibilities. A dynamic scaling analysis of ac susceptibility data using conventional critical slowing down indicates that a finite spin-glass phase-transition temperature (Tg) and a dynamic exponent (zv) change from 103K and 9.30 correspondingly for 0.95La0.7Sr0.3MnO3/0.05TiO2 to 133K and 9.10, for 0.94La0.7Sr0.3MnO3/0.06TiO2. In addition, MR in low temperature of these samples decline simultaneously with occur spin-glass behavior. These results are interpreted as the dilution of Mn3+/Mn4+ interactions by the random Ti substitution on the Mn site considerably reduces the ferromagnetic double exchange interaction within the manganese lattice.

The effect of TiO2 doping on the catalytic properties of nano-Pd/SnO2 catalysts during the reduction of nitrate

The monometallic catalysts Pd/TiO2–SnO2 and Pd/SnO2 prepared by impregnation method were investigated for their ability to catalyze the reduction of nitrate with formic acid as the reducing agent and were characterized by X-ray diffraction (XRD), BET surface area, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Pd and TiO2 were in high dispersion on the surface of the SnO2 support when the mol fraction of TiO2 was less than 15%. The SnO2 crystal lattice was partially replaced by titanium ions, causing SnO2 lattice distortion and resulting in the increase of oxygen vacancies as catalytic active sites. The best catalytic properties of the formic acid–Pd/TiO2–SnO2 system were achieved at a mol fraction of 10% TiO2. Compared with the Pd/SnO2 catalyst, the catalytic activity of Pd/TiO2–SnO2 increased by 48% from 2.08mg/(mingcata) to 4.00mg/(mingcata), while the NH4+ concentration decreased from 13.0mg/L to 5.2mg/L. The catalytic activity, selectivity and stability of the Pd/TiO2–SnO2 catalyst were superior to those of Pd/SnO2 with the same Pd loading and formic acid concentration. The results of the XPS analysis indicated that the catalysts Pd/SnO2 and Pd/TiO2–SnO2 were of high oxygen vacancy. Pd/TiO2–SnO2 has better catalytic properties than Pd/SnO2 may attribute to the increased amount of oxygen vacancy after TiO2 doping.

Structural, thermal and electrical properties of Ti4+ substituted Bi2O3 solid systems

In the present study, the effect of TiO2 doping on (1−x) Bi2O3 (x)TiO2 (x=0.05, 0.10, 0.15, 0.20) materials is investigated using X-ray diffraction (XRD), differential thermal analysis (DTA), ac conductivity, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). XRD results show the formation of single phase Bi12TiO20 at x≥0.15 concentration of TiO2. It is observed that, the lower concentration of TiO2 leads to the formation of mixed phase. The x=0.15 and x=0.20 samples exhibit regular and uniform distribution of the grains as compared to x=0.10 sample. The highest conductivity is observed for x=0.15 specimen, e.g., 9×10−7Scm−1.