Dielectric Properties and Spectral Characteristics of Photocatalytic Constant of TiO2 Nanoparticles Doped with Cobalt.

Dielectric properties and spectral dependence of the photocatalytic constant of Co doped P25 Degussa powder were studied. Doping of TiO2 matrix with cobalt was achieved by precipitation method using of Tris(diethylditiocarbamate)Co(III) precursor (CoDtc-Co[(C2H5)2NCS2]3). Five different Co contents with nominal Co/Ti atomic ratios of 0.005, 0.01, 0.02, 0.05 and 0.10 were chosen. Along with TiO2:Co samples, a few samples of nanopowders prepared by Sol-Gel method were also studied. As it follows from XPS and NMR studies, there is a concentration limit (TiO2:0.1Co) where cobalt atoms can be uniformly distributed across the TiO2 matrix before metallic clusters start to form. It was also shown that CoTiO3 phases are formed during annealing at high temperatures. From the temperature dependence of the dielectric constant it can be concluded that the relaxation processes still take place even at temperatures below 400 °C and that oxygen defect Ti-O octahedron reorientation take place at higher temperatures. The spectral dependency of the photocatalytic constant reveals the presence of some electronic states inside the energy gap of TiO2 for all nanopowdered samples.

Tunable Pseudo-Piezoelectric Effect in Doped Calcium Titanate for Bone Tissue Engineering.

CaTiO3 is a promising candidate as a pseudo-piezoelectric scaffold material for bone implantation. In this study, pure and magnesium/iron doped CaTiO3 are synthesized by sol-gel method and spark plasma sintering. Energy dispersive X-ray mapping confirm the homogenous distribution of doping elements in sintered samples. High-energy X-ray diffraction investigations reveal that doping of nanostructured CaTiO3 increased the strain and defects in the structure of CaTiO3 compared to the pure one. This led to a stronger pseudo-piezoelectric effect in the doped samples. The charge produced in magnesium doped CaTiO3 due to the direct piezoelectric effect is (2.9 ± 0.1) pC which was larger than the one produced in pure CaTiO3 (2.1 ± 0.3) pC, whereas the maximum charge was generated by iron doped CaTiO3 with (3.6 ± 0.2) pC. Therefore, the pseudo-piezoelectric behavior can be tuned by doping. This tuning of pseudo-piezoelectric response provides the possibility to systematically study the bone response using different piezoelectric strengths and possibly adjust for bone tissue engineering.

Structural properties of iron-phosphate glasses: spectroscopic studies and ab initio simulations.

Vitrification is the most effective method for the immobilization of hazardous waste by incorporating toxic elements into a glass structure. Iron phosphate glasses are presently being considered as matrices for the storage of radioactive waste, even of those which cannot be vitrified using conventional borosilicate waste glass. In this study, a structural model of 60P2O5-40Fe2O3 glass is proposed. The model is based on the crystal structure of FePO4 which is composed of [FeO4][PO4] tetrahedral rings. The rings are optimized using the DFT method and the obtained theoretical FTIR and Raman spectra are being compared with their experimental counterparts. Moreover, the proposed model is in very good agreement with X-ray absorption fine structure spectroscopy (XANES/EXAFS) and Mössbauer spectroscopy measurements. According to the calculations the Fe(3+) is in tetrahedral and five-fold coordination. The maximal predicted load of waste constituents into the glass without rebuilding of the structure is 30 mol%. Below this content, waste constituents balance the charge of [FeO4](-) tetrahedra which leads to their strong bonding to the glass resulting in an increase of the chemical durability, transformation and melting temperatures and density.

Preparation, microstructures, mechanical properties, and cytocompatibility of TiMn alloys for biomedical applications.

The titanium-manganese (TiMn) alloys have been extensively used in aerospace and hydrogen storage. In this study, the TiMn alloys with various manganese contents ranging from 2 to 12 wt % were prepared by using mechanical alloying and spark plasma sintering (SPS) techniques. The microstructures, mechanical properties including hardness, elastic modulus and ductility, cytotoxicity and cell proliferation properties of the TiMn alloys were investigated to explore their biomedical applications. The addition of manganese to the titanium reduced the alpha to beta transformation temperature and was confirmed as a beta stabilizer element. The manganese increased the relative density of the alloy and thus high density TiMn alloys with alpha+beta structure were prepared by using SPS at 700 degrees C. The hardness increased significantly ranging from 2.4 GPa (Ti2Mn) to 5.28 GPa (Ti12Mn) and the elastic modulus ranging from 83.3 GPa (Ti2Mn) to 122 GPa (Ti12Mn), the ductility decreased ranging from 21.3% (Ti2Mn) to 11.7% (Ti12Mn) with increasing manganese content in the Ti. Concentrations of Mn below 8 wt % in titanium reveal negligible effects on the metabolic activity and the cell proliferation of human osteoblasts. The Mn could be used in lower concentrations as an alloying element for biomedical titanium. The Ti2Mn, Ti5Mn, and Ti8Mn alloys with supervisor mechanical properties and acceptable cytocompatibility have a potential for use as bone substitutes and dental implants.