ABSTRACT
Additives and/or impurities in NiCr alloys would be expected to affect the oxidation and adherence of dental glasses. Oxidation characteristics and bonding of several glasses to a commercial impure 80Ni20Cr alloy and laboratory-prepared purer alloys were thus studied at 1000 degrees C. The commercial alloy formed a porous and buckled single-layer oxide scale with lenticular voids at the interface. The scale was penetrated by glass which formed a chemical bond at the alloy/glass interface, resulting in excellent adherence with fracture in the glassy phase. The purer alloy formed a complex multilayer oxide scale to which the glass bonded but did not penetrate; the assembly was not satisfactory, since fracture occurred in the oxide scale.
Subject(s)
Chromium Alloys , Dental Bonding , Dental Porcelain , Adhesiveness , Chemical Phenomena , Chemistry, Physical , Oxidation-Reduction , Surface PropertiesSubject(s)
Dental Alloys , Dental Bonding , Glass , Adhesiveness , Chemical Phenomena , Chemistry, Physical , Oxidation-Reduction , Surface Properties , WaterABSTRACT
Diffusion couples, consisting of sapphire and fused silica, which were annealed in the temperature range from 1678 degrees to 2003 degrees C and analyzed by electron beam microprobe, have provided data on the stable phase equilibrium of the silica-alumina system. Under stable equilibrium conditions, the intermediate compound of this system, mullite (3Al(2)O(3) . 2SiO(2)), melts incongruently at 1828 degrees +/- 10 degrees C and its solid solution field extends from 70.5 to 74.0 percent (by weight) alumina. The stable phase diagram is a composite of the two binary eutectic diagrams: silica-mullite in the absence of alumina and silica-alumina in the absence of mullite. Under metastable conditions, mullite melts congruently at approximately 1890 degrees +/- 10 degrees C and its solid solution field extends to approximately 83.2 percent (by weight) alumina.
