title: Expansion of nanosized pores in low-crystallinity nanoparticle-assembled plates via a thermally induced increase in solid-state density.
abstract: We investigated thermally induced changes in a low-crystallinity hydroxyapatite (HAp)-nanoparticle-assembled plate containing nanosized pores. We first prepared an aqueous dispersion of low-crystallinity HAp nanoparticles (particle size, 48 nm) via a wet chemical process and then prepared the nanoparticle-assembled plate by drying the dispersion on an oil substrate to prevent crack formation. Before the plates were subjected to heat treatments, they contained 7.9-nm-sized pores because of the gap between the nanoparticles, and their porosity was 60%. After the heat treatments (600-1100 °C) were performed for 1 h, the solid-state density determined using helium pycnometry increased from 2.85 to 3.21 g/cm(3), and the pore size increased from 7.9 to 250 nm. These results indicate that the pore size expanded because of increases in crystallinity and density, despite the large decrease in the total volume because of thermally induced sintering of the nanoparticles.
authors.affiliation: Department of Biomaterials, Osaka Dental University, 8-1 Kuzuha-Hanazono, Hirakata, Osaka 573-1121, Japan. okada-m@cc.osaka-dent.ac.jp
authors.forename: Masahiro
authors.initials: M
authors.lastname: Okada
authors.forename: Keiko
authors.initials: K
authors.lastname: Fujiwara
authors.forename: Mayo
authors.initials: M
authors.lastname: Uehira
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Matsumoto
authors.forename: Shoji
authors.initials: S
authors.lastname: Takeda
mesh_terms: D002516:Ceramics / Q000737:chemistry; D003460:Crystallization; D017886:Durapatite / Q000737:chemistry; D006371:Helium / Q000737:chemistry; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D008823:Micelles; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D053758:Nanoparticles / Q000737:chemistry*; D036103:Nanotechnology; D016062:Porosity; D013499:Surface Properties; D013696:Temperature; D013997:Time Factors; D014961:X-Ray Diffraction
chemical_list: D008823:Micelles; D006371:Helium; D017886:Durapatite