생체친화성 세라믹의 합성과 수종 임플란트 금속재료에의 코팅에 관한 실험적 연구 = STUDIES ON SYNTHESIS OF BIOACTIVE CERAMICS AND ITS COATING ONTO SEVERAL MTALLIC IMPLANT MATERIALS

다국어 초록 (Multilingual Abstract)

Although metal substrates can be adversely affected by the sintering of the hydroxyapatite(HAP) coating when using electrophoresis-sintering coating technique, investigation of this aspect is rare. And the studies for the application of glass-ceramic as a HAP-coating binder, and for the related problems on the preparation of the metal-HAP composite material are insufficient for the practical use of the electrophoresis-sintering method. The purpose of this study is to investigate these points.
I synthesized HAP by the co-precipitation mehtod, and coated it uniformly on the pure titanium(Ti), Ti-6Al-4V, SUS316L, and Co-Cr alloy by electrophoretic method and sintered it in the 10^-8 torr vacuum furnace.
I investigated the coating thickness by the function of electrophoretic condition, requirements of HAP powder for coating, effects of coating thickness, and coefficients of substrate metals and compacted HAP as preconditions for ideal HAP coating. And I manufactured crystallizable glass which has been studied for usage as a binder, and inspected the crystallographic and mechanical changes by the heat treatment during the sintering of the HAP coating. Moreover, I investigated the metallographic and mechanical property changes during sintering heat treatment.
The results are as follow;
1. By the coprecipitation reaction of calcium nitrate and diammonium hydrogen phosphate solution at pH 11, Ca/P ratio 1.75, 37℃ for 48 hours, white precipitate was yielded and it was identified to be pure HAP.
2. Glass-ceramic binder at the composition of 4.6MgO-44.9CaO-34.2SiO_2-16.3P_2O_5(-0.5CaF_2) was manufactured. By the heat treatment apatite crystals were formed from 820℃, apatite and acicular wollastonite crystals were formed at 930℃. With the temperature increase, wollastonite crystal grew gradually, and at 1200℃ whitlockite appeared in addition to apatite and wollastonite crystals. Up to 1150℃, the diametral tensile strength increased gradually, but at 1200℃ it partially melted and the strength decreased significantly.
3. HAP powder suspended in isopropanol electrolytic solution was uniformly coated on cathode metallic substrate. The coating thickness increased linearly with the increase of voltage, and relatively large particles were adhered on the surface at the electrophoretic condition of 90V-60sec, 60V-120sec.
4. If the coating was thick, cracks developed by the cohesive contraction during the sintering of HAP coating and the cracks developed mainly around the large particles.
5. The tensile strength of Ti heat-treated at 900℃ slightly decreased with the coarsening of equiaxed crystal size.
At heat treatments higher than 1000℃, the metallurgic microstructure was changed to piled thick needle-like crystals with orientation and the strength increased as the heat treatment temperature increaed. The percent strain at maximum tensile strength decreased suddenly from 900℃ heat treatment.
Under the 1000℃ heat treatment, Ti-6Al-4V showed coarsening of α-phase crystal accompanying decrease of the tensile strength as the treatment temperature increased. From 1100℃ treatment, the microstructure changed to Widmansta¨tten structure with the increase of strength. The percent strain at maximum tensile strength was lower than Ti and SUS316L.
SUS316L showed decrease of tensile strength with the coarsening of the grain size by the increase of the heat-treatment temperature. The percent strain at maximum tensile strength was markedly lower than that of Ti or Ti-6Al-4V. At 1200℃ heat treatment, the elastic modulus increased significantly.
Co-Cr alloy showed increase of tensile strength with the homogeneous distribution of small carbides by the increase of the heat treatment temperature till 1100℃ treatment, but at 1200℃ the carbide formation was excessive, resulting in significant strength decrease and showing lowest tensile strength among the four types of metals.
6. The compacted HAP pellet shrunk significantly by sintering from 700℃, and it shrunk about 22.5% by heating from room temperature to 1200℃. Ti and Ti-6Al-4V showed lower thermal expansion coefficients than those of SUS316L and Co-Cr alloy up to 900℃. Ti showed abrupt shrinkage followed by an increase of the thermal expansion coefficient at phase transition temperature 882℃, and Ti-6Al-4V showed abrupt expansion around phase transition temperature 990℃.

목차 (Table of Contents)

• Ⅰ. 서 론
• Ⅱ. 실험재료 및 방법
• Ⅲ. 실험성적
• Ⅳ. 총괄 및 고찰
• Ⅴ. 결 론
• 참고문헌
• 영문초록
• 사진부도 설명
• 사진부도