Zwei-Strahl-Gerät (Feldemissions-SEM und Focused Ion Beam)

• Subject Area: Materials Science
• Term: Funded in 2009
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 142952340

• Final Report Year: 2013

Final Report Abstract

Silica-doped hydroxyapatite (HA) is a promising material concerning biocompatibility to natural bone, bioactivity and osteoconductive characteristics. To avoid cracks during sintering, the exact knowledge of the phase transition temperatures is necessary. The phase transformations in the system HA–SiO2 were analyzed by using differential scanning calorimetry followed by quantitative phase analysis by X-ray diffraction with the Riedveld method. In laser surface sintered (LSS) samples, amorphous SiO2, HA, and Si-α-TCP (or α-TCP) were detected. By comparison, only crystalline phases, such as cristobalite, HA, β- TCP, and Si-α-TCP (or α-TCP), were determined after furnace sintering. Scanning electron microscopy micrographs of furnace sintered and LSS samples show the differences in the resulting microstructures. iocompatibility was determined by measuring cell activity of osteoblasts cultivated on laser-sintered materials in the HA–SiO2 system in comparison to normal cell culture plastic. Transparent microspheres with the eutectic composition 65 Al2O3-16 Y2O3-19 ZrO2 (mol%) have been produced by laser fusing with a CO2 laser. The influence of the starting material as well as the laser power on the resulting microspheres was investigated. After fabrication, the microspheres were analyzed by means of XRD to quantify the amorphous content of the spheres as well as to identify the residual crystalline phases, with a laser granulometer to measure the particle sizes of the starting material and the resulting microspheres, with DSC to characterize the glass transition temperature and crystallization behavior, and with SEM to investigate the microstructure of the microspheres. The laser-treated materials consist of transparent and opaque beads as well as sintered particles. Based on these results transparent beads were collected and annealed over a range of temperatures to analyze the crystallization behavior. Resistance to plastic deformation on surfaces of excavated glass fragments of late Byzantinic provenance and from early modern manufacturing was studied using Vickers indentation. Each glass surface consisted of a silica-rich alteration layer of consecutive multiple bands, as a result of a dissolution-reprecipitation mechanism of corrosion under long-time acidic conditions. A sharp drop in decrease of hardness and Young's modulus (> 90%) was evident at the pristine glass/alteration layer interface. Stiffness and indent sizes across the alteration bands revealed a corresponding pattern of increasing hardness and Young's modulus towards the outer parts, which indicated clogging of the porous corrosion products. Micromechanical properties of the banded alteration obeyed Gibson–Ashby equation for porous materials of complex microstructure.

Publications

• Laser-Fused Transparent Microspheres with the Eutectic Composition Al2O3-Y2O3-ZrO2 (AYZ). Journal of Ceramic Science and Technology, Vol. 2. 2011, No. 2, pp. 103 - 110.
  C. Oelgardt, J. Günster, J. G. Heinrich
  
• Anwendung bekannter und weiterführender Untersuchungsmethoden zur Charakterisierung des Lias Epsilon (Posidonienschiefer) aus Süd-Deutschland. Erdöl Erdgas Kohle, 128. Jg. 2012. Heft 10, S. 379 - 384.
  S. Schatzmann, F. Werunsky, C. D. Sattler, R. Görke, J. Wegner, L. Ganzer
  
• Compatibility of antireflective coatings on glass for solar applications with photocatalytic properties. Solar Energy, Vol. 86. 2012, Issue 3, pp. 831-836.
  G. Helsch, J. Deubener
  
• Nanocomposites based on technical polymers and sterically functionalized soft magnetic nanoparticles – synthesis, processing and characterization. Journal of Nanomaterials, Vol. 2012 (2012), Article ID 670531, 8 pages.
  S. Kirchberg, M. Rudolph, G. Ziegmann,U. A. Peuker
  
• Influence of processing parameters on microstructure and biocompatibility of surface laser sintered hydroxyapatite–SiO2 composites. Journal of Biomedical Materials Research Part B: Applied Biomaterials, Vol. 101B. 2013, Issue 4, pp. 568–575.
  E. Kivitz, R. Görke, A. F. Schilling, J. Zhang, J. G. Heinrich
  
• Polyurethane Coatings Reinforced by Halloysite Nanotubes. Coatings, Vol. 3. 2013, Issue 1, pp. 16 - 25.
  X. Li, I. Nikiforow, K. Pohl, J. Adams, D. Johannsmann
  
• Preparation of transparent microspheres in the system K0.5Na0.5NbO3 by laser fusing. Journal of Ceramic Science and Technology, Vol. 4. 2013, No. 1, Pages 41-48.
  F. Hmood, C. Oelgardt, R. Görke, J. G. Heinrich
  
• Selective Laser Densification of Lithium Alumosilicate Gass Ceramic Tapes. Applied Surface Science, Vol. 265. 2013, pp. 610-614.
  A. Zocca, P. Colombo J. Günster, T. Mühler, J. G. Heinrich
  
• Submicrometer silica spheres generated generated by Laser Fuming. Journal of Ceramic Science and Technology, Vol. 4. 2013, No. 1, pp. 11-18.
  C. M. Gomes, R. Müller, J. Günster, T. Mühler, R. Görke, J. G. Heinrich
  
• Slurry-based additive manufacturing of ceramics. International Journal of Applied Ceramic Technology, Vol. 12.2015, Issue 1, pp. 18–25.
  T. Mühler, J. G. Heinrich, C. M. Gomes, Jens Günster