Browsing by Author "Karlsson, Kaj H."

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    Chemical approach to medium range order in glass
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1990) Karlsson, Kaj H.; Fröberg, Kaj; Skrifvars, Bengt
    The question on medium range order in glass is approached from three different angles. Voltammetric determinations indicate that below 30 mol% alkali oxide, binary lithium silicate melts contain silica clusters, while sodium and potassium silicate melts form discrete ions about 2 nm in size. Regardless of the alkali ion, silica forms complexes with acidic cations. By applying the Lux-Flood acid-base concept, it can be shown that the lithium silicate as well as the acidic sodium silicate melts contain bidentate ligands, while potassium as well as alkaline sodium silicate melts contain monodentate ligands. The complexation of acidic cations is in accordance with expectations from basic concepts of chemical bonding.
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    Covalent oxocomplexes and electrovalent coordination in glass
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1989) Karlsson, Kaj H.
    The differenee in electronegativity between an oxide ion bonded to silicon and a metal ion gives a hint whether an oxoeomplex is expected or not. This has an implication for formulating correct stoichiometric reactions for transition metal ions in glass melts.
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    Estimation of liquidus temperatures in silicate glasses
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 2001) Karlsson, Kaj H.; Backman, Rainer; Cable, Michael; Peelen, Jan; Hermans, Jan
    Two models for estimating liquidus temperature from composition are presented and compared with thermodynamically calculated temperature as well as primary phase. A simple polynomial model is given for high silica glasses, while a model covering a wide composition range and several primary phase fields is more complex. Thermodynamic calculations generally give too high liquidus temperatures in the devitrite field and too low in the primary field for Na2O · 2 CaO · 3 SiO2. In the wollastonite field the values are scattered, but in general too high.
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    Models for physical properties and bioactivity of phosphate opal glasses
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1988) Andersson, Örjan H.; Karlsson, Kaj H.; Kangasniemi, Kari; Yli-Urpo, Antti
    Bioactive glasses are glasses to which bone can attach through a tight chemical bond after implantation. Glasses are, however, brittle and therefore they are preferably used in combination with other ceramic materials or metals. In this work potentially bioactive phosphate opal glasses have been studied. Phenomenological equations describing the influence of glass composition on transition temperature, thermal expansion, chemical durability and bone bonding are developed. The equations may be used for development of various implant materials based on bioactive glass, for example enamels for metal protheses. The corrosion behaviour in body fluid is also discussed and compared with the bone bonding. The role of alumina is briefly considered.
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    Property-composition relationships for potentially bioactive glasses
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1998) Karlsson, Kaj H.; Rönnlöf, Minna
    The compositional dependence of thermal expansion, A (in 10¯⁶ K¯¹), transformation temperature, Tg (in °C), dilatometric softening point. Mg (in °C), and viscosity, η (in dPa s), was determined for low-silica glasses in the S y s t e m Na₂O - K₂O - MgO - CaO - -Β₂O₃-Ρ₂O₅-SiO₂. The following phenomenological equations were established: A = 3.625 + 0.345p_Na₂O + 0.266p_K₂O + 0.098p_CaO + 0.064p_P₂O₅ , Tg = 635.9 - 5.26p_Na₂O + 3.18p_K₂O- 3.16p_MgO - 0.47p_Na₂O*p_K₂O - 0.12p_K₂O * p_CaO , Mg = 790.6 - 17.83p_Na₂O - 5.79p_K₂O + 0.28p²_Na₂O - 0.39p²_MgO where p_ is oxide content in wt%. The viscosity was modelled to f i t an Arrhenius-type equation, lgη = A + B/T. Giving η in dPa s, the compositional dependence of A and Β were found as A = - 55.707 + 0.597p_Na₂O + 0.591p_K₂O + 0.604p_MgO + 0.516p_CaO + 0.429p_P₂O₅ + 0.387p_SiO₂, Β = - 9 1 . 4 6 3p_Na₂O + 162.861p_CaO + 485.020p_Β₂O₃ + 249.200p_P₂O₅ + 285.212p_SiO₂·