Effect Of Titania Addition Research Articles

Porous alumina‐based ceramics with very low thermal conductivity prepared by the starch consolidation route

AbstractAlumina‐based porous ceramics were fabricated via the starch consolidation casting route, using titanium oxide as a sintering additive. Alumina‐titania‐starch slurries with starch contents of 2.5, 5, 7.5, and 10 wt% relative to the alumina‐titania system were prepared. Titania was added to the slurries in proportions of 0, 1, 3, and 5 wt%, relative to alumina. The effects of starch and titania contents in the green bodies on the linear and volumetric shrinkage, as well as the total and open porosities of the sintered alumina product, were investigated. The effect of titania addition on mechanical, electrical, and thermal properties of the obtained porous alumina ceramics was studied. Microstructure and pores morphology were characterized by SEM. The alumina‐based ceramics obtained had external porosities that varied between 54 and 76 vol%. Thermal conductivities as low as 0.06–0.1 W/m.K were achieved and the volume electrical resistivity ranged from 3.6 to 600 GΩ·m, while compressive strengths up to 2.8 MPa for a titania ratio of 1 wt% were attained.

Effect of titania addition and sintering temperature on the microstructure, optical, mechanical and biological properties of the Y-TZP/TiO2 composite

ObjectiveThe aims of this study were: 1) to evaluate the effect of sintering temperature on microstructure, density and flexural strength of a 3Y-TZP/TiO2 composite containing 12.5 wt% of TiO2 compared to 3Y-TZP specimens (control); 2) to compare 3Y-TZP with the experimental 3Y-TZP/TiO2 composite, both sintered at 1400 °C, with respect to the following parameters: optical properties, characteristic strength, Weibull modulus, fatigue behavior, induction of osteoblasts proliferation and differentiation (mineralization nodules formation). MethodsThe 3Y-TZP and 3Y-TZP/TiO2 powders were uniaxially pressed and sintered at 1200 °C, 1300 °C, 1400 °C or 1500 °C for one hour in a furnace. The microstructural analysis consisted of X-ray diffraction and scanning electron microscopy. The density was measured by the Archimedes' principle and the flexural strength was obtained by the biaxial flexure test. The optical properties were measured using a spectrophotometer operating in the visible light wavelength range. The step-stress accelerated life testing was performed by the pneumatic mechanical cycler and the biological behavior achieved by using osteoblast-like cells (Osteo-1 cell line). ResultsTetragonal zirconia was identified in all groups and cubic zirconia was identified only at 3Y-TZP group. The addition of TiO2 decreased the values of density and flexural strength of the composite 3Y-TZP/TiO2 in relation to 3Y-TZP regardless of the sintering temperature. The color difference between the two materials was not significant regarding L*a*b* parameters. The composite showed higher probability of failure, and induced higher proliferation and differentiation than control. SignificanceThe composite developed have good aesthetic and biologics properties. However, its microstructure and mechanical properties need to be improved for future dental implant applications.

Effect of titania addition on adhesion of silver colloids to glass substrate

ABSTRACTThe purpose of this study was to investigate the effects of titania addition on adhesion strength of silver colloids to glass substrate. Our results indicated that when the pH was adjusted to 10, the mixed slurry of titania and silver colloids was stable with no sign of settling at approximately 4 hr. After film deposition by doctor blade method and subsequent sintering treatment, the adhesion strength between silver film and glass substrate was measured by both ASTM D3359 and D4541 standards. The results showed positive correlation of adhesion strength to both the titania concentration and sintering temperature. The adhesion strength reached 7.0 MPa when we added 8 wt% titania (based on silver) and sintered the film at 320°C for 20 min. X-ray photoelectron spectroscopy data revealed that interdiffusion of Ti into both glass substrate and silver colloid might be responsible for adhesion enhancement. On the other hand, the electrical resistivity of films increased with titania addition. This fact implied that we need to compromise between these two properties when titania addition was used to improve adhesion between silver colloid and glass substrate. An empirical model was subsequently proposed to simulate the compromise between adhesion strength and electrical resistivity.

Effect of titania addition on the properties of freeze-cast alumina samples

This work investigated the behavior of TiO2-containing α-Al2O3 samples prepared by the freeze-casting technique. Camphene and liquid nitrogen were used as the solvent and cooling fluid, respectively. Camphene resulted in the formation of dendritic pores, in the direction of the freeze-casting cold front during sample preparation. The formation of β-Al2TiO5 phase occurred at 1300°C, and became more evident as the sintering temperatures reached 1500°C. The TiO2 loading did not affect the sample porosity at a given temperature, but it was detrimental in the case of mechanical properties under certain conditions. For instance, the flexural strength slightly improved with increasing the TiO2 loading and sintering temperature from 1100 to 1300°C. This effect was attributed to the occurrence of a more effective sintering of alumina. However, as the heat treatment temperature was raised from 1300 to 1500°C, the flexural strength did not increase as a function of the TiO2 loading, even though the densification occurred with loss of porosity. The loss of mechanical strength was found to be associated with the formation of microcracks which stemmed from the formation of β-Al2TiO5 phase for TiO2 loadings in excess of 4wt% at these high sintering temperatures.

Effect of Titania Addition on the Mechanical Properties of Y-TZP

Effect of Titania Addition on the Mechanical Properties of Y-TZP

Effect of Titania Addition on the Performance of CoMo/Al2O3 Sour Water Gas Shift Catalysts under Lean Steam to Gas Ratio Conditions

CoMo/Al2O3 sour water gas shift catalysts with and without TiO2 modification have been tested in parallel industrial reactors under lean steam/gas conditions for two years, and part of catalyst samples was taken out each year during the maintenance period. The catalyst samples have been characterized using temperature programmed sulfurization (TPS), X-ray diffraction (XRD), and laser Raman and BET surface area measurements. The results have shown that adding TiO2 to the catalyst makes the active components, e.g., Mo and Co, easier to be sulfurized with higher sulfur capacity in the catalyst itself. This may be the main reason why the TiO2 modified CoMo catalyst to be active even at low H2S gas stream. The results from industrial operation showed that adding TiO2 to the shift catalyst increases the catalyst activity and stability, presents the higher shift activity in a broader range of H2S content, depresses the aggregating of the molybdenum oxide, and reduces carbon deposition. In addition, the TiO2 addi...

Effect of titania addition on hot hardness of UO 2

Large grain UO 2 is a potential fuel for LWR’s for achieving extended burn up. Large grains are obtained by addition of dopants like Nb 2O 5, TiO 2, Cr 2O 3, V 2O 5 etc. However, presence of such dopants might affect the thermophysical and thermomechanical properties of the fuel. In the present investigation the effect of TiO 2 addition on the hot hardness ( H) of sintered UO 2 fuel has been studied from ambient to 1573 K in vacuum. TiO 2 content was varied from 0.01 to 0.15 w/o resulting in a grain size ( G) variation of 9 to 94 μm. With increase in grain size (or TiO 2 content) H first decreases, attains a minima and then increases further. The increase is more prominent at lower temperature (<773 K) than that at higher temperatures. H vs. G −1/2 plots indicates the same type of variation like other oxide ceramics with H minima at an intermediate grain size at low temperature. The intrinsic hardness and softening coefficient of UO 2 indicate cubic dependence on TiO 2 content.

Effect of titania addition on yttria-stabilised tetragonal zirconia ceramics sintered at high temperatures

In order to combine the mechanical properties of yttria-stabilised zirconia (ZrO 2–3 mol% Y 2O 3; code Y–ZrO 2) with the bioactivity of titania (TiO 2), Y–ZrO 2–TiO 2 green compacts with 0–40 vol.% TiO 2 were sintered at 1300, 1400, and 1500 °C for 4 h, respectively. The microstructural features such as grains, pores, and phases were examined using scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy dispersive spectroscopy (EDX). The mechanical properties such as hardness and toughness were also determined using the methods of Vickers indentation and Knoop indentation. All the composites showed the major tetragonal Y–ZrO 2 phase regardless of the content of the added TiO 2. However, rutile TiO 2 phase was obtained at 1300 °C, whereas zirconium titanate (ZrTiO 4) phase was found at 1400 and 1500 °C. The Y–ZrO 2–ZrTiO 4 composites sintered at 1500 °C showed relatively high hardness (860–1000 kg/mm 2) and toughness (4.0–4.5 MPa m 0.5), whereas the Y–ZrO 2–TiO 2 composites sintered at 1300 °C had slightly lower hardness (720–950 kg/mm 2) and fracture toughness (3.1–3.3 MPa m 0.5).

Effect of titania addition on crystallization process and some properties of calcium mica–apatite glass-ceramics

In order to obtain calcium mica–apatite glass-ceramics having high water resistance and excellent machinability, TiO 2 was added to the starting materials of glass-ceramics with chemical composition of 3:7 weight ratio of fluoroapatite to calcium–mica. A large number of fine spherical particles in which mica and apatite should be included were generated uniformly. The mica and apatite were crystallized at lower temperatures and at narrower temperature ranges than those in the undoped specimen. However, the crystallization quantity ratio of apatite to mica was smaller, compared with that of apatite to mica for the undoped specimen. These results suggest that TiO 2 acted as a nucleation agent of mica but impeded the crystallization of apatite. Mica in the fine spherical particles became plate-like when TiO 2 was separated at ⩾900 °C. The plate-like mica with size of 0.5–2 μm was surrounded by apatite, TiO 2 and residual glass, and formed the interlocking microstructure at 1000 °C. Such a microstructure resulted in high water resistance and excellent machinability. Particularly, a large number of fine TiO 2 particles surrounded the mica uniformly, which was very effective in the deterrence of disintegration.

Effect of Titania Addition on the Sintering of Alumina

The sintering behaviour of Bayer grade alumina in the temperature range 1400°—1800°C in a partially reducing atmosphere is reported. A 1 wt% addition of titania is found to improve the sinterability of alumina appreciably. The pellet density after two hours of sintering was the highest at 1475°C. The microstructure of the sintered pellets showed enhanced but uneven grain growth compared to that of similar alumina pellets without the titania addition. They also showed that the titania addition did not form any eutectic phase with the impurities in the Bayer alumina during the sintering.