2013, Vol.23, No.2

Journal of the Korean Crystal Growth and Crystal Technology 2023 KCI Impact Factor : 0.19

pISSN : 1225-1429 / eISSN : 2234-5078
https://journal.kci.go.kr/jkcgct

Sapphire crystals are used in a substrate of the LED devices. Both Kyropoulos (Ky) and Czochralski (CZ)growth process are widely applied techniques for growing high quality sapphire single crystal. A successful growth of the sapphire crystals requires the control of heat and mass transport phenomena. In this study, the growth processes of the sapphire crystal using the resistivity-heated Ky method and the inductively-heated CZ method have been analyzed numerically using finite element method. Based on the simulation results, the melt-crystal interface of the crystal changed from the concave to the flat shape as the Ky process progressed. In case of the CZ method, the high temperature positions moved from the crucible surface to inside the melt and the interface changed to the flat shape when the RPM was increased. Also the interface shape of the grown crystal has been influenced by the formed shoulder shape at the initial stage.

In order to improve osseo-integration of a dental implant with bone crystal we studied an implant with holes inside its body to deliver bioactive materials based on a proposed patent. After bioactive material is absorbed, bone crystal can grow into holes to increase implant bonding in addition to surface integration. The larger cross section area of outlet holes showed the less values of the maximum stress, and the stress concentrations near the uppermost outlet holes were also reduced with an increasing number of outlet holes. The conclusion, that the uppermost outlet design improvement was most effective to reduce the stress concentration and improve the growth rate of bone crystal, could be drawn. After the design optimizations, Type 6-C had provided the best results in this study. The overall shape optimization studies on the shape, location, number, and so on, of the outlet holes, should be carried out further.

For further improvement of osseo-integration of bone crystal with a dental implant, a design optimization study is carried out for various holes inside its body to deliver bioactive materials and the effect of bioactive material injection on the bone crystal growing. When bioactive material is absorbed, the bone crystal can grow into holes, which would increase the strength of implant bonding as well as a surface integration. The stress concentrations near the uppermost outlet holes were reduced with increasing the number of outlet holes. A design improvement in the uppermost outlet was shown to be effective in reducing the stress concentration. For design parameters under consideration in this study, total area of outlet of 6.38 mm2 and maximum stress of 1.114 MPa, which corresponds to type 6-C. It is due to the minimization of maximum stress and total area of outlet. The design of the outlet facing down was more effective in reducing the maximum stress value compared with a horizontal symmetry.