Xinyan Yue

Toughening mechanisms in iron-containing hydroxyapatite/titanium composites.

Pure hydroxyapatite (HA) is brittle and it cannot be directly used for the load-bearing biomedical applications. The purpose of this investigation was to develop a new iron-containing HA/titanium composite via pressureless sintering at a relatively low temperature with particular emphasis on identifying the underlying toughening mechanisms. The addition of iron to HA/titanium composites led to a unique and favorable core/shell microstructure of Ti-Fe particles that consisted of outer titanium and inner iron, and good interfacial bonding with HA matrix. While the relative density, hardness and Youngs modulus reduced, the flexural strength, fracture toughness, fatigue resistance, and the related fracture surface roughness increased significantly with increasing amount of Ti-Fe particles. Different toughening mechanisms including crack bridging, branching and deflection were observed in the composites, thus effectively increasing the crack propagation resistance and resulting in a substantial improvement in the mechanical properties of the composites.

Partitioned cooperative self-assembly process: taking the mesopore swelling strategy one step further for the preparation of mesocellular foams

This work demonstrates that the combination of recently developed partitioned cooperative self-assembly (PCSA) process with the conventional mesopore swelling strategy can take the preparation of mesocellular foams (MCFs) one step further based on cheap sodium silicate precursor. Compared with conventional method derived MCFs, such synthesized MCFs show more uniform cell size distributions without using commonly employed additives, i.e., NH4F. Furthermore, when prepared with aging at 120 °C via the PCSA process, MCFs with large uniform cells (38.3 nm) and enlarged windows up to 7.9 nm can be obtained, resembling the conventional MCFs based on TEOS/P123/NH4F system. Moreover, a simple adjustment in the order of addition of trimethylbenzene in the PCSA process produces unique bimodal meso-mesoporous MCFs with ordered normal SBA-15 regions dispersed in the matrix.

An in-vitro investigation of iron-containing hydroxyapatite/titanium composites

The in-vitro biological behavior of a newly-developed iron-containing hydroxyapatite/titanium (HA/Ti) composite was investigated by immersing the composites in the simulated body fluid (SBF) for up to 5 weeks. The addition of iron was observed to have a significant influence on the in-vitro biological behavior of the composites. The obtained results revealed that the stability of the composites in the physiological solution was markedly improved. The solubility decreased in the order of pure HA, HA/5%(Ti-33%Fe), and HA/15%(Ti-33%Fe). Precipitation occurred on the surface of HA/5%(Ti-33%Fe) composite, showing a good combination of physiostability with bioactivity, while HA/15%(Ti-33%Fe) composite exhibited superior physiostability since there was no obvious change on the surface of HA/15%(Ti-33%Fe).

High temperature and water-based evaporation-induced self-assembly approach for facile and rapid synthesis of nanocrystalline mesoporous TiO2

Various appealing applications of mesoporous TiO2 continuously spur research on related mesostructural design as well as innovations in preparation. This paper reports a novel high temperature and water-based evaporation-induced self-assembly (HW-EISA) approach based on a simple ternary templating system (peroxotitanic acid/P123/H2O), enabling the facile and rapid synthesis of nanocrystalline mesoporous TiO2 with unusual structures: high surface areas (140–240 m2 g−1), ultra-large mesopores (20–30 nm)/pore volumes (0.7–1.0 cm3 g−1) and tunable bicrystallinity (anatase plus rutile). The unusual templating and subsequent decomposition behaviors of P123 were newly unveiled to play crucial and multiple roles in inducing self-assembly between peroxotitanic acid and P123 for final meso-TiO2 with ultra-large mesopores/pore volumes during the HW-EISA and helping preserve the integrity of mesostructures during calcination and rendering bicrystallinity in the titania frameworks as well. Other PEO-based nonionic surfactants were also demonstrated to be applicable in producing similar mesostructures. The photocatalytic testing results showed that both high surface areas and the synergistic effects of bicrystallinity of anatase plus rutile are of great significance in enhancing the photocatalytic properties of meso-TiO2.

Improvement in strength of SiC reticulated porous ceramics

Silicon carbide reticulated porous ceramics (SiC RPCs) were fabricated via polymer sponge technique. In order to obtain SiC RPCs with optimised mechanical performance, influence of sintering holding time, silica fume content and particle size distribution has been investigated in details. It was found that sintering holding time and content of silica fume have influence on the physical and mechanical properties of SiC RPCs, and the optimal value were 2 h and 17 mass-% respectively. At the same time, to thicken the struts, the recoating technique has been applied, through which mechanical strength has been improved significantly.