Unveiling morphology phase transition mechanism of calcium phosphate system from crystal growth record

2021 Fiscal Year Final Research Report

• Project/Area Number: 18K05282
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 36010:Inorganic compounds and inorganic materials chemistry-related
• Research Institution: National Institute of Technology, Toyama College
• Principal Investigator: TOSHIMA TAKESHI 富山高等専門学校, その他部局等, 准教授 (60447076)
• Project Period (FY): 2018-04-01 – 2022-03-31
• Keywords: 結晶成長 / リン酸カルシウム / モルフォロジー

Outline of Final Research Achievements

The morphology of dicalcium phosphate dihydrate change over time was traced in detail by controlling the starting solution mixing rate by nano-misting the solution with an ultrasonic nebulizer.
A new crystal growth environment that yields needle-like morphology has been identified. The environment in which anisotropic growth is realized is limited to the initial process when the concentration of calcium ions is low enough to affect the spatial distribution of calcium ion on the crystal surface. Needle-like particles are obtained when cations are attracted to negatively charged crystal faces and become highly concentrated, resulting in a higher growth rate on those crystal faces than on other faces.
Based on the obtained results, experiments were conducted in the presence of citrate ions, that dissolve the particles anisotropically, the researcher succeeded in creating long plate-shaped particles and sharpened corolla-like particles.

Free Research Field

結晶成長

Academic Significance and Societal Importance of the Research Achievements

第二リン酸カルシウムの溶液合成では反応に水素イオンの放出を伴う．反応時の濃度変化にpH変化も伴うため結晶の溶解度が変化する．そのため溶液混和の精密制御が重要であり、ナノミスト噴霧による溶液混和抑制法の成果は、溶液の混合合成で得られる他の結晶系にも波及効果が期待される．また、合成初期過程における形状変化観察の重要性について改めて発信されることも意義があると言える．
粒子形状変化は表面状態の変化に伴う化学的特性だけではなく、粉体の操作性という物理的特性にも影響を及ぼし、材料を変更せずに性能を向上させうる．同じ化学物質であれば操作性も同一と思われる先入観を変え、材料科学の重要性を改めて宣伝できた．