• Homepage
• Research

  • Research Group
  • Photo Gallery
  • Projects
  • Thesis
  • Scientific Meetings
  • Publications
• Facilities
  • Electron Microscope Investigations
  • X-Ray Fluorescence and Diffractometer Analysis
  • Molecular Bond Characterization
  • Powder and Bulk Materials Characterizations
  • Thermal Analysis
  • Colour Measurements
  • Refractometer
  • Microscopes
  • Microdardness Test
• Courses

  • Materials Science I
  • Biomaterials
  • Bioceramics
• Contact
• Photo Gallery

EFFECTS OF NUCLEATING AGENT (TiO2) ADDITION ON CRYSTALLIZATION BEHAVIOR AND ELECTRICAL PROPERTIES OF MACHINABLE GLASS CERAMICS CONTAINING POTASSIUM MICA AND CORDIERITE

Machinable glass ceramics are materials produced by the similar production methods of melting and casting that all glass ceramics undergo with controlled nucleation and crystallization. The property that makes machinable glass ceramics different and special is that they obtain proper microstructure and microhardness value that allows machinability after a heat treatment is applied. Machinable glass ceramics have good electrical and mechanical properties besides mechanical forming.

In the first stage of the study, 5 glass composition with a potassium mica to cordierite ratio of 6:4 have been prepared, mixed and cast at proper temperatures. One of the compositions didn’t contain any TiO2, others contained various amount ranging from 0.5% to 2% TiO2. 4% CeO2 as a stabilizer and 2% CaO as melting agent were added to glass compositions. The glasses produced after casting is milled and sieved for differantial thermal analysis (DTA). According to DTA results, exothermic and endothermic heat effects are determined. In order to figure out which heat effect belongs to which phase, XRD analysis was applied to the powder specimens.

In the second stage of the experimental studies, disc and cylindrical shaped glass samples were cast. After heat treatment, microstructure and mechanical properties were determined in terms of micro hardness (Hv) and machinability. Machinability test was applied by drilling. After machinability tests, chemical resistances of produced materials were determined.

As a result of experimental studies, it was determined that TiO2 addition promotes cordierite formation. In these glass compositions curved mica that provides machinability precipitated in glass base matrix and cordierite phase that provides hardness and chemical resistance precipitated in boundaries between mica crystals. It was observed that TiO2 addition of 1% and above reduces porosity, thus increasing both hardness and chemical resistance. Addition of 1% or more TiO2 also resulted in very high dielectric constant values.