Investigation of Growth and Decomposition of Ca-Deficient - PowerPoint PPT Presentation

Investigation of Growth and Decomposition of Ca-Deficient Hydroxyapatite Koji NISHIO, Masato TAMAI, Mitsuhiro NAKAMURA and Toshiyuki ISSHIKI Nano-Structural Science Laboratory, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto 606-8585, Japan

Contents • Introduction of hydroxyapatite (HAp) • Growth of calcium-deficient hydroxyapatite (Ca-def HAp) T. Isshiki et al. , In: Proc. ICEM15, 2002, Durban, 1 , 1047 • High-temperature behavior of Ca-def HAp M. Tamai et al. , J. Mater. Sci. in Med. 14 (2003) in print M. Tamai et al. , In: Proc. ICEM15, 2002, Durban, 1 , 1057 Nano-Structural Science Laboratory, Kyoto Institute of Technology

Hydroxyapatite a Hydroxyapatite ( Ca 10 ( PO 4 ) 6 ( OH ) 2 : HAp) • Crystal structure: Similar to a bone Hexagonal ( a = 0 . 943 nm , c = 0 . 688 nm ) ⇓ b widely noticed and expected [00¯ 1] • As an alternative material for bone c • Application to a biosensor making good use of biocompatibility b [100] Nano-Structural Science Laboratory, Kyoto Institute of Technology

Synthesis of Hydroxyapatite Dry process ⇒ Stoichiometric HAp (s-HAp) 6CaHPO 4 + 4CaCO 3 → s - HAp + 2H 2 O + 4CO 2 Wet process ⇒ Non-stoichiometric HAp • Sol-gel method • Hydrolysis method A. Nakahira et al. , J. Am. Ceram. Soc. 82 (1999) 2029-2032 Nano-Structural Science Laboratory, Kyoto Institute of Technology

Hydrolysis Method before hydrolysis before hydrolysis before hydrolysis before hydrolysis before hydrolysis α -tricalcium phosphate ( α - Ca 3 ( PO 4 ) 2 : α -TCP) ⇓ Hydrolysis in a mixture of water and alcohol α -TCP particle α -TCP particle α -TCP particle α -TCP particle α -TCP particle Calcium-deficient HAp ( Ca 10 − Z ( HPO 4 ) Z ( PO 4 ) 6 − Z ( OH ) 2 − Z ⋅ n H 2 O ( Z = 0 - 1 ) : 1 µ m 1 µ m 1 µ m 1 µ m 1 µ m ⇓ ⇓ ⇓ ⇓ ⇓ Ca-def HAp) after after after after after Advantage of this method: • Easy to synthesis within several hours under mild conditions • Easy to control of crystal morphology Ca-def HAp Ca-def HAp Ca-def HAp Ca-def HAp Ca-def HAp whiskers whiskers whiskers whiskers whiskers plate-, blade-, whisker-like shape, etc. 500 nm 500 nm 500 nm 500 nm 500 nm Nano-Structural Science Laboratory, Kyoto Institute of Technology

Ca-Deficient Hydroxyapatite 770 ° C 770 ° C 770 ° C 770 ° C 770 ° C Ca-def HAp → s-HAp + β -TCP Important reaction to develop 900 ° C 900 ° C 900 ° C 900 ° C 900 ° C new biomaterials Whisker-like shape is favorable 980 ° C 980 ° C 980 ° C 980 ° C 980 ° C as a source to produce porous biomaterials 1040 ° C 1040 ° C 1040 ° C 1040 ° C 1040 ° C ⇒ In-situ high-temperature SEM observation of sintering process 1 µ m 1 µ m 1 µ m 1 µ m 1 µ m of Ca-def HAp whiskers Nano-Structural Science Laboratory, Kyoto Institute of Technology

Growth of Ca-def HAp • Introduction of HAp α -TCP • Growth of Ca-def HAp ↓ Hydrolysis HRTEM observation of Ca-def HAp ♦ initial stage of hydrolysis ↓ ♦ growth of HAp whiskers Annealing s-HAp + β -TCP • High-temperature behavior of Ca-def HAp Nano-Structural Science Laboratory, Kyoto Institute of Technology

Experimental Procedure Specimen preparation Compressing Thinning Specimen I and sintering Hydrolysis Thin α -TCP for HRTEM α -TCP observation powder Specimen II Hydrolysis α -TCP powder Dropping on a TEM grid for mass production Nano-Structural Science Laboratory, Kyoto Institute of Technology

Hydrolysis Hydrolysis in a water solvent suspending 1-octanol α -TCP Mixture : water : 1-octanol 0.01 mol : 60 ml : 100 ml Initial pH 11 (adjusted with NH 4 OH) 70 ° C Temperature Time 0 - 48 hours Instruments TEM JEOL, JEM-2010/SP JEOL, JEM-2000EX XRD Rigaku, RINT 2000 Nano-Structural Science Laboratory, Kyoto Institute of Technology

Initial stage of hydrolysis Specimen I hydrolyzed for 2 h hydrolyzed for 2 h hydrolyzed for 2 h hydrolyzed for 2 h hydrolyzed for 2 h amorphous layer amorphous layer (Thinned α -TCP) amorphous layer amorphous layer amorphous layer ↓ ↓ ↓ ↓ ↓ before hydrolysis before hydrolysis before hydrolysis before hydrolysis before hydrolysis α -TCP α -TCP α -TCP α -TCP α -TCP 300 nm 300 nm 300 nm 300 nm 300 nm α -TCP α -TCP α -TCP α -TCP α -TCP 20 nm 20 nm 20 nm 20 nm 20 nm Nano-Structural Science Laboratory, Kyoto Institute of Technology

Dendritic structure on the amorphous layer amorphous layer amorphous layer amorphous layer amorphous layer amorphous layer hydrolyzed hydrolyzed hydrolyzed hydrolyzed hydrolyzed 30 nm 30 nm 100 nm 100 nm 30 nm 4 h 100 nm 30 nm 30 nm 100 nm 100 nm for 2 h for 2 h for 2 h 4 h for 2 h for 2 h 4 h 4 h 4 h Dendrites composed of Nuclei • twigs with a few nm Embryo of • not on the α -TCP ⇒ ⇒ Ca-def in width • but on the surface of • trunks with several HAp the amorphous layer tens nm in width Nano-Structural Science Laboratory, Kyoto Institute of Technology

Growth of Ca-def HAp whiskers 100 Specimen II Conversion rate [%] HAp ( α -TCP powder) Intensity [a.u.] 80 3 h 60 2 h 40 1 h α -TCP α -TCP 20 α -TCP α -TCP α -TCP 0 h 0 20 25 30 35 40 0 60 120 180 before hydrolysis before hydrolysis before hydrolysis Diffraction angle 2 θ [degree] before hydrolysis before hydrolysis Hydrolyzed time [min] α -TCP α -TCP α -TCP α -TCP α -TCP 500 nm 500 nm 500 nm 500 nm 500 nm hydrolyzed for 1 h hydrolyzed for 1 h hydrolyzed for 1 h hydrolyzed for 1 h hydrolyzed for 1 h 2 h 2 h 3 h 3 h 2 h 3 h 3 h 3 h 2 h 2 h Nano-Structural Science Laboratory, Kyoto Institute of Technology

Summary (Growth of Ca-def HAp) ⇒ ⇒ ⇒ ⇒ ⇒ ⇒ ⇒ ⇒ ⇒ ⇒ α -TCP Amorphous layer on Nucleation of HAp on the surface of α -TCP ⇓ ⇓ ⇓ ⇓ ⇓ the amorphous layer Dendritic structures Ca-def HAp whiskers Needle-like HAp crystals on the nuclei ⇐ ⇐ ⇐ ⇐ ⇐ ⇐ ⇐ ⇐ ⇐ ⇐ Nano-Structural Science Laboratory, Kyoto Institute of Technology

H. T. Behavior of Ca-def HAp • Introduction of HAp α -TCP • Growth of Ca-def HAp ↓ Hydrolysis High-temperature behavior Ca-def HAp • of Ca-def HAp ↓ Annealing s-HAp + β -TCP HRTEM observation of the Ca-def HAp whiskers annealed at various conditions Nano-Structural Science Laboratory, Kyoto Institute of Technology

Experimental Procedure Specimen Source: Whisker-like shape, Ca-def HAp synthesized by hydrolysis method (Ca/P molar ratio = 1.58) Annealed at 200-1100 ° C in air Heat (heating rate: 5 ° C/min, keep time: 2-6 hours) treatment: Instruments JEM-2010F ∗ TEM JEOL, JEM-2010/SP JEOL, JED-2300T ∗ (EDS) Noran, Vantage JEOL, XRD Rigaku, RINT 2000 FT-IR JEOL, IR-WINSPEC100 ∗ Acknowledgements: Dr. E. Okunishi, Application & Research Center, JEOL Ltd. Nano-Structural Science Laboratory, Kyoto Institute of Technology

TEM images of samples before & after annealing annealed at 600 ° C annealed at 600 ° C annealed at 600 ° C annealed at 600 ° C annealed at 600 ° C before annealing before annealing before annealing before annealing before annealing Ca-def HAp whiskers 2 ∼ 5 µ m Length ( c axis): ∼ 0.1 µ m Width: Ca/P molar ratio: 1.58 5 ° C/min Heating rate: Keep time: 2 hours 700 ° C 700 ° C 800 ° C 800 ° C 900 ° C 900 ° C 700 ° C 700 ° C 700 ° C 800 ° C 800 ° C 800 ° C 900 ° C 900 ° C 900 ° C 500 nm 500 nm 500 nm 500 nm 500 nm Nano-Structural Science Laboratory, Kyoto Institute of Technology

Analysis of XRD patterns 900 ° C 900 ° C 900 ° C 900 ° C 900 ° C 1100 ° C 800 ° C 800 ° C 800 ° C 800 ° C 800 ° C 1000 ° C 900 ° C → Intensity [a.u.] β -TCP 800 ° C → HAp 600 ° C → 600 ° C 600 ° C 600 ° C 600 ° C 600 ° C 400 ° C before annealing before annealing before annealing before annealing before annealing 200 ° C before annealing → 25 30 35 40 45 500 nm 500 nm 500 nm 500 nm 500 nm Diffraction angle 2 θ [degree] Nano-Structural Science Laboratory, Kyoto Institute of Technology

Ca-def HAp whisker annealed at 800 ° C 50 nm 50 nm 50 nm 50 nm 50 nm HAp HAp HAp HAp HAp 100 100 → → ← ← 100 → ← 100 100 → → ← ← 002 002 002 002 002 HAp HAp HAp HAp HAp → → → → → [010] [010] HAp HAp [010] HAp [010] [010] HAp HAp Planar defect / Layered precipitate • traversing in the whisker • parallel to (100) plane (100) (100) (100) 3 nm 3 nm (100) (100) 3 nm 3 nm 3 nm Nano-Structural Science Laboratory, Kyoto Institute of Technology

Planar defect and layered phase 600 ° C 600 ° C 700 ° C 700 ° C 800 ° C 800 ° C 600 ° C 700 ° C 800 ° C 600 ° C 600 ° C 700 ° C 700 ° C 800 ° C 800 ° C 20 nm 20 nm 20 nm 20 nm 20 nm ↑ ↑ ↑ ↑ ↑ 1.43 nm 1.43 nm 1.43 nm 1.43 nm 1.43 nm ↓ ↓ ↓ ↓ ↓ planar defect planar defect planar defect planar defect planar defect ↑ ↑ ↑ ↑ ↑ (100) (100) (100) (100) (100) (100) (100) (100) (100) (100) 5 nm 5 nm (001) (001) 5 nm 5 nm 5 nm (001) [021] [021] [010] [010] (001) (001) [010] [010] [021] [010] [010] [021] [021] [010] [010] [010] [010] Nano-Structural Science Laboratory, Kyoto Institute of Technology