Member of the Research Training Group, 1.12.2009 - 30.11.2011

Titanium alloys and composites with superficial structure gradients for implants

Despite the number of available bio-ceramics today (hydroxylapatite, tricalciumphosphate basis) there is still demand for the development of new materials with improved biocompatibility, higher mechanical strength and bone-like dielectric properties. In Project A-2 "Titanium alloys and composites with superficial structure gradients for implants" new composite materials with optimized wear and mechanical properties as well as higher biocompatibility in comparison to common titanium implants and coatings.
The emphasis of this project lies on nanocrystalline calcium titanate (CaTiO3) powder produced by the wet-chemical sol-gel-synthesis and its application as porous specimens formed by conventional sintering and  pore-forming agents, as high-densed implants realized by spark plasma sintering (SPS) and as coating material by electromagnetic sputtering for modified Ti(-Al-V) implants. Calcium titanate is known to improve the bonding between titanium and hydroxyapatite [1,2], to have better mechanical properties [3] and a 4.5 times higher osteoblast adhesion rate than hydroxylapatite [4].

1. Synthesis of pure and modified calcium titanate
2. Characterization
   
   • thermal: differential scanning calorimetry, thermogravimetric analysis
   • structural: X-ray powder diffraction (in-house and high energy at DESY/HASYLAB)
   • mechanical: micro/nano indentation
   • morphological: scanning and tunneling electron microscopy, atomic force microscopy (with kelvin probe), micro-computed tomography
   • surface area and porosimetry analysis (by physisorption)

First studies of sintered pellets show a direct relationship between their porosity and their specific impedance being in the range of human bone material which is expected to improve the acceptance by the surrounding tissue.
Furthermore doping of the studied calcium titanate is in the focus of this project because it can change its mechanical and dielectrical properties to achieve tailor-made properties convenient to the tissue at the region of implantation.

Conferences:

• ZHANG, F., OTTERSTEIN, E., ROTT, G.A., BECK, U., WEISS, D.G., BURKEL, E., 2010. Preparation and surface modification of TiMn foams for bone implants, 55 (1), ISSN (Online) 1862-278X, ISSN (Print) 0013-5585, DOI: 10.1515/BMT.2010.244.
• ROTT, G.A., ZHANG, F., HABA, Y. and BURKEL, E., 2010. Dielectric properties of porous calcium titanate. Biomedical Engineering, 55 (1), ISSN (Online) 1862-278X, ISSN (Print) 0013-5585, DOI: 10.1515/BMT.2010.546.
• ROTT, G.A., ZHANG, F., HABA, Y., KRÖGER, W. and BURKEL, E., 2010. Dielectric Spectroscopy and Microstructure of Sintered Calcium Titanate (CaTiO3) Samples With Different Porosities. Material Science and Engineering 2010 (Darmstadt).
• VAN RIENEN, U., APPALI, R., BADER, R., BAUMANN, W., BECK, U., BEHREND, D., BENECKE, R., BIALA, K., BIRKHOLZ, H., BURKEL, E., ENGEL, G., GIMSA, J., GIMSA, U., GONGADZE, E., GRÜNBAUM, A., HABA, Y., LIESE, F., LIU, B., LÜDER, M., MATSCHEGEWSKI, C. and MITTELMEIER, W., MIX, E., NEBE, J.B., NOWAK, K.A., PAHNKE, J., PAU, H.W., PAULEWEIT, S., PETERSEN, S., POLNICK, S., REIMER, T., ROTT, G., SALOMON, R., VINTER, E., WEIHE, T., and WOLKENHAUER, O., 2010. Analysis and Simulation of Electrical Interactions of Implants with Biosystems, Biomedical Engineering, 55 (1), pp. 167–170, 2010, ISSN (Online) 1862 -278X, ISSN (Print) 0013-5585, DOI: 10.1515/BMT.2010.543.
• ROTT, G.A., ZHANG, F., HABA, Y., KRÖGER, W. and BURKEL, E., 2011. Dielectric Properties of Porous Calcium Titanate (CaTiO3). The American Ceramic Society's Ceramic Transactions proceedings (From the MS&T'10 meeting). Biomaterials Science -- Processing, Properties, and Applications: Ceramic Transactions, Volume 228.

In addition to the entire graduate school, my supervisors are:

• Prof. Dr. Eberhard Burkel