Materials Science Forum Vols. 654-656

Abstract: The microstructure and optical properties are investigated for MgO-doped alumina fabricated by spark plasma sintering at temperatures between 1100 and 1550 °C. The MgO doping renders the microstructure less sensitive to the sintering temperature by suppressing grain growth, whereas it has no significant effect on the densification of alumina and resultantly no effect in enhancing the total forward transmission. The value of the total forward transmission can be used as an indirect measure of the slight change in density.

Abstract: The energy storage density of (1-x) BaTiO3 – x Ba(Mg1/3Nb2/3)O3 (x = 0, 0.1, 0.2, 0.3) ceramics was investigated. The microstructure of samples was characterized by scanning electron microscopy (SEM). The energy storage density was calculated from the P-E hysteresis loops measured at room temperature. Experimental results show that the energy storage density of 0.9 BaTiO3 – 0.1 Ba(Mg1/3Nb2/3)O3 ceramics is highest among all compositions. At 15.8kV/mm electric field, the energy storage density of the sample can reach up to 1.07J/cm3, which is about 1.5 times higher than pure BaTiO3. The improvement of the energy density can be due to two factors: one is the improved breakdown strength caused by the optimized microstructure, the other is the decreased remnant polarization. This result indicates that bulk 0.9 BaTiO3 – 0.1 Ba(Mg1/3Nb2/3)O3 ceramic has advantages compared with pure BaTiO3 ceramic for energy storage applications, and with further improvements in microstructure and reduction of sintering temperature, could be a good candidate for energy storage capacitors.

Abstract: A series of new sub-micro-layered Ti3C2/(Cu-Al) cermets were prepared by in-situ hot-extruding a mixture of Ti3AlC2 and Cu powders, and some properties of these materials were tested. These cermets have quite high fracture strength and electric conductivity, due to the strong combination between Ti3C2 and (Cu-Al), and a special network microstructure formed by the (Cu-Al) phase surrounding the sub-micro-sheet layered Ti3C2 phase. The in-situ hot-extruding after pressless sintering can effectively eliminate pores contained in (Cu-Al) phase, and accelerate the diffusing of Cu towards the interlayer between Ti3C2 layers, so the fracture strength and electric conductivity are increased. With increasing the content of the ceramic phase, the strength of the cermets can be further increased while the ductility is reduced.

Abstract: Nanostructured implant materials are considered as promising future biomaterials. Specifically, titanium based nanomaterial is the mostly used implant materials in orthopedic, dental and vascular surgeries. Due to the advantage of nanoscale features, treatment with nano porous and nano bump surface features have shown enhanced biocompatibilities, such as adhesion, proliferation and differentiation for bone and vascular cells. In addition, nanotoxicity issue with immune cells (macrophages) is currently paramount interest for determining subsequent tissue cellular response on implanted biomaterials. In this review, we demonstrated altered cellular interaction of bone, vascular cells on nanostructured titanium based alloys/materials through systematic controlling of nanoscale surface features, such as porosity and nanobumps. All this knowledge will be beneficial for both understanding and designing nanostructured biomaterials for increasing biocompatibility, thus, all these endeavors will lead increment of functionality of biomaterials and will eventually prolong the life time of implanted biomaterials.

Abstract: Titanium and its alloys have been widely used for medical and aerospace applications because of their excellent attributes of light metal, high strength, high corrosion resistance and high biocompatibility. Especially, Ti-6Al-7Nb alloy has been developed as a more suitable biomaterial to replace Ti-6Al-4V alloy, because vanadium is toxic element to the biological body. However, it is not easy to fabricate the complex shaped and precise parts by the conventional methods due to their poor castability and machinability. In this study, laser forming technique has been applied to solve the above problems. The precise structure was obtained by optimizing the laser forming parameters. Using this technique, a honeycomb structure was fabricated　effective to grow the neighboring tissue and also encourage osseointegration. Finally, mouse osteoblasts were cultured on the formed structures, resulted in the effectiveness of the honeycomb structure for biocompatibility.

Abstract: Micropore and nanotube formation on the Ti oxide are important to improve the cell adhesion and proliferation in clinical use. In this study, nanotube and micropore of Ti alloy for biocompatibility have been investigated using FE-SEM and XRD. Ternary alloys were prepared by using high purity sponge Ti Ta, Zr and Nb sphere (99.95% wt.%). Two-step anodizing was used for surface modification of the titanium alloys. Micropore formation was first performed using a potentiostat in 1 M H3PO4 electrolyte and nanotube formation was performed in 1M H3PO4 + 0.8wt% NaF solution by using a potentiostat. The two-step anodizing process is an efficient method for forming micropores and nanotubes on the surfaces of ternary titanium alloys, and the morphology of micropore and nanotube is dependent on the alloying element and composition of ternary alloy.

Abstract: Calcium phosphate ceramics such as hydroxy apatite (HA), β-tricalcium phosphate (β-TCP) and bicalcium phosphate (BCP) have been used as a bone graft biomaterial because of their good biocompatibility and similarity of chemical composition to natural bones. To increase the mechanical and osteoconductive properties, the granules and spongy type porous bone graft substitutes were prepared by fibrous monolithic process and polyurethane foam replica methods, respectively. The pore sizes obtained using these approaches ranged between 100-600 µm. The cytotoxicity, cellular proliferation, differentiation and ECM deposition on the bone graft substitutes were observed by SEM and confocal microscopy. Moreover, the scaffolds were implanted in the rabbit femur. New bone formation and biodegradation of bone graft were observed through follow-up X-ray, micro-CT analysis and histological findings. After several months (2, 3, 6, 12 and 24 months) of implantation, new bone formation and ingrowths were observed in defect sites of the animal by CaP ceramics and 2 to 3 times higher bone ingrowths were confirmed than that of the normal trabecular bones in terms of total bone volume (BV).

Abstract: The biodegradable polymers are widely used in therapeutic surgery and pharmaceutics, in which the degradation process has drawn significant attention in recent years. In this paper, we propose a mathematical model to predict the polymer degradation in tissue engineering applications. A stochastic model is introduced to characterize the hydrolysis reaction in an elemental basis and the mass transport is also performed to investigate the diffusive transport of polymer erosion. Two representative polymeric films in different configurations are studied. It is found that for biodegradable systems, mass transport plays an important role in controlling the erosion pathway, in which the matrix configuration could be one of the key factors that determine the characteristics of erosion and drug release rates. The proposed model makes a useful benefit to the design optimization of the matrix architectures for biodegradable devices.