Layer characteristics in strength-gradient multilayered yttria-stabilized zirconia.

Objectives: To investigate crystallography, translucency, phase content, microstructure and flexural strength of two commercial strength-gradient multilayered dental zirconia grades.

Methods: Two zirconia grades, i.e.

Nano-micrometer-architectural acidic silica prepared from iron oxide of Leptothrix ochracea origin.

We prepared nano-micrometer-architectural acidic silica from a natural amorphous iron oxide with structural silicon which is a product of the iron-oxidizing bacterium Leptothrix ochracea. The starting material was heat-treated at 500 °C in a H2 gas flow leading to segregation of α-Fe crystalline particles and then dissolved in 1 M hydrochloric acid to remove the α-Fe particles, giving a gray-colored precipitate. It was determined to be amorphous silica containing some amount of iron (Si/Fe = ~60).