Browsing by Author "Hartmann, Peter"
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- ItemEffect of composition changes on the structure and properties of phosphate glasses in the pyrophosphate region(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1997) Vogel, Jürgen; Wange, Peter; Hartmann, PeterThe structures of phosphate glasses in the ultra- and polyphosphate region are well-investigated. Discontinuous changes of the properties in the composition ränge around 50 mol% P₂O₅ (transition from network to chain-like structures) are known. The present work is concerned with the structural transition of chain-like phosphate glasses to pyrophosphate glasses. ³¹P MAS N M R in vestigations were used for the quantitative structural analyses of pyrophosphate and mixed pyrophosphate/orthophosphate glasses. Several chemical and physical properties of these glasses were determined in dependence on composition and structure. The in vestigated phosphate invert glasses are very sensitive to additives. Therefore, some important properties of phosphate invert glasses and glass-ceramics can be controlled by addition of relatively small and highly charged cations.
- ItemPhosphate glasses and glass-ceramics for medical applications(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1997) Vogel, Jürgen; Wange, Peter; Hartmann, PeterModified calcium phosphate glass Systems meet the requirements for the development of different biomaterials. Bioactive, longterm stable phosphate glass-ceramics and resorbable phosphate glasses were prepared in the Systems P₂O₅ - CaO - Al₂O₃ - Na₂O and P₂O₅ - CaO - MgO - Na₂O . Due to their high thermal expansion coefficients the bioactive phosphate glass-ceramics are excellently suited for coating metals. Using a salt-sintering process, porous resorbable glasses can be obtained. The properties of glassceramic coatings on cobalt/chromium alloys and the production of porous resorbable phosphate invert glasses are described.
- Itemstructural investigations of SiO₂-containing phosphate glasses(Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1998) Vogel, Jürgen; Jana, Carsten; Hartmann, PeterThe incorporation of SiO₂ into phosphate glasses is interesting in view of the development of phosphatic biomaterials. The present investigation is concerned with the incorporation of SiO₂ into phosphate base glasses possessing different phosphate structures. Due to their structural characteristics, they can be classified into three groups: glasses with long phosphate chains or rings formed by Q² phosphate structural groups, glasses with shorter phosphate chains formed by Q² and Q¹ groups and glasses with phosphate invert glass structure, possessing ortho(Q°)- and pyrophosphate groups (two Q¹ groups) exclusively. The structures of these glasses in dependence on the incorporated silica were investigated by transmission electron microscopy and by ³¹P MAS NMR. The principles of incorporation are discussed.