TiO2 Foams Research Articles

Grain boundary corrosion of highly porous ceramic TiO2 foams is reduced by annealing and quenching

Porous bioceramics, such as scaffolds, can be used for bone regeneration. Bioceramics are instantly attacked by body fluids, macrophages and osteoclasts during stages of bone repair. Acidic microenvironments generated by these cells may amplify the well-known effect of grain boundary dissolution. Grain boundary corrosion in such porous scaffolds can have significant impact on the mechanical strength due to the high surface area of the scaffold. Corrosive media were found to significantly affect the mechanical strength of highly porous TiO2 scaffolds. Compressive strength decreased significantly after 12h in an aqueous acidic solution with a reduction to 35±10% after 8 weeks immersion time. Following post-sintering heat treatments by combining air quenching and annealing, the strength was maintained throughout a corrosion period of 8 weeks in acidic environment. Impurity segregation to the grain boundaries and thus, susceptibility to grain boundary corrosion was reduced by the synergistic effect of both heat treatments.

Immobilization of TiO2 into Self‐Supporting Photocatalytic Foam: Influence of Calcination Temperature

Immobilization of photocatalytic powder is crucial to obtain industrially relevant purification processes. To achieve this goal, self‐supporting TiO2 foams were manufactured by a polyacrylamide gel process. These gels were calcined at different temperatures to study the effect of the calcination temperature on foam characteristics (rigidity, crystallinity, and porosity) and its influence on photocatalytic activity. The results show that an optimal degradation is achieved for those foams calcined between 700 and 800°C. Calcination at higher temperatures results in a steep decrease in activity, explained by stability issues of the material due to formation of Na2SO4 phases and a larger rutile fraction.

Macroporous TiO2 foam with mesoporous walls

We demonstrate a simple route for the preparation of new three-dimensionally interconnected hierarchically porous anatase TiO2 foams via a dual-templating approach. The macropores in TiO2 foams are induced through a process of sintering the polyurethane foams template, while a surfactant templating agent promotes the formation of mesopores in the walls of a macroporous monolith of TiO2 foam. The macropore sizes of interconnected networks can be tuned by varying the pores per linear inch of polyurethane foams. This single step method of synthesis from cheap commercially available chemicals is suitable for mass production of three-dimensionally interconnected macro/mesoporous TiO2 foams.

동결 주조법으로 제조된 티타늄 옥사이드 폼의 구조 연구

The TiO₂ foam synthesized using freeze-casting is a promising photocatalyst and photovoltaic electrode for a variety of energy applications, because the freeze-casting technique is easy to use, cheap, and suitable for mass-production. Despite its several advantages, little scientific information is available on the processing and morphology of the TiO₂ foams processed by freeze-casting. In particular, no systematic study has been performed on the microstructural evolution and morphological change of the rutile-phase TiO2 foams during sintering. Therefore, in the present study, several TiO2 foam samples were produced using the freeze-casting technique, which were then sintered at a relatively high temperature of 1200℃ for 1, 2, and 4 h to compare the morphological changes in the microstructure and to understand the effects of processing parameters of the rutile-phase TiO2 foams. The foam ligament size increased near linearly with increasing sintering time whereas the average pore size decreased only slightly with increasing sintering time, with changes in particle morphology from sphere to rod and complete phase transformation from anatase to rutile.

TiO<sub>2</sub> Foam: Characterization and Cell Adhesion

In recent years, it has been proposed that the new era of implants design should be focused on the use of the new generation of biocompatible materials or reengineers the currently available materials. The objective of this research was to study cell-metal interactions using highly porous TiO2 foam. To obtain the porous TiO2 foam, polymeric foam replication methods might be one of the most effective methods. Surface chemical composition, morphology and phase are investigated by field emission scanning electron microscope (FESEM) and X-Ray Diffraction (XRD). In vitro cellular response of cells has been studied on TiO2 foam. In the investigations of the cellular responses of cells, two aspects were considered: the number of growing cells and their morphological features. It was clear that rough surface morphology was important factor for better cell-metal interaction. Surface topography can affect the cell migratory significantly and adhesion behavior on implant surfaces.

Photocatalytic inactivation and removal of algae with TiO2-coated materials

The capabilities of TiO2-coated materials for the inactivation and removal of algae were investigated. As supports for TiO2, non-woven fabric and Ni foam were chosen. To evaluate the ability of noble metal cocatalyst additions to facilitate the photocatalytic algal inhibition of TiO2-coated materials, Pd nanoparticles were deposited on non-woven fabric-supported TiO2 by photoelectrochemical deposition. The fabric-supported Pd/TiO2 showed higher inhibition activity for algal growth compared to the fabric-supported TiO2 without Pd. In addition, Ni foam-supported TiO2 also showed high inhibition activity, both in laboratory-scale tests and open-air tests. Therefore, TiO2-coated materials with suitable coating methods such as the use of cocatalysts or large surface area can substantially inhibit algal growth. The ability of the TiO2-coated materials to inhibit algae correlated well with their activity for the photocatalytic decolorization of methylene blue, suggesting a nonspecific mechanism in the breakdown of cellular structures.

Hierarchical Porous, Self‐Supporting La‐ and F‐Codoped TiO2 with High Durability for Continuous‐Flow Visible Light Photocatalysis

Hierarchical porous, self‐supporting La‐ and F‐codoped TiO2 with high durability was prepared using a simple polymer template gel. The TiO2 foams were in the anatase phase, with a specific surface area of up to 88 m2/g, and showed a network‐like structure containing meso‐/macropores. The macropores had a diameter of ca. 300 nm and a wall thickness of 100–300 nm, while the mesopores were narrowly distributed with a mean diameter of around 5.4 nm. The UV‐vis diffuse reflection spectra of the sample showed that the presence of intraband gap states was likely responsible for its absorption of visible light. X‐ray photoelectron spectroscopy revealed that La2O3 and O–Ti–F bonds were formed. The sample showed an excellent visible light photocatalytic activity and a high durability of photocatalytic activity for the degradation of methylene blue solution.

TiO2 foams with poly-(d,l-lactic acid) (PDLLA) and PDLLA/Bioglass® coatings for bone tissue engineering scaffolds

TiO2 foam-like scaffolds with pore size ~300 μm and >95% porosity were fabricated by the foam replication method. A new approach to improve the structural integrity of the as-sintered foams, which exhibit extremely low compression strength, was explored by coating them with poly-(d,l-lactic acid) (PDLLA) or PDLLA/Bioglass® layers. The PDLLA coating was shown to improve the mechanical properties of the scaffold: the compressive strength was increased by a factor of ~7. The composite coating involving Bioglass® particles was shown to impart the rutile TiO2 scaffold with the necessary bioactivity for the intended applications in bone tissue engineering. A dense hydroxyapatite layer formed on the surface of the foams upon immersion in simulated body fluid for 1 week.

Photocatalytic activity of TiO2 foams

Photocatalytic activity of TiO2 foams