Hydrothermal preparation of tailored hydroxyapatite

Hydroxyapatite (HA) particles synthesized by hydrothermal treatment of octacalcium phosphate (OCP) particles were characterized in detail and the reaction mechanism was discussed. The calcium-deficient HA particles were firstly formed and their compositions gradually closed to the stoichiometric composition with reaction progress. While their compositions closed to the stoichiometric composition, split of plate-shaped HA particles into smaller strips and subsequent crystal growth of HA particles were observed. The [001] direction of synthesized HA was parallel to the [001] direction of starting material of OCP. The hydrothermal treatment of OCP particles is useful for synthesis of plate-shaped HA particles with different morphologies and compositions.

Section: Discussionmentioning

confidence: 77%

Section: Introductionmentioning

confidence: 89%

Section: Introductionmentioning

confidence: 99%

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Hydrothermal synthesis and characterization of hydroxyapatite from octacalcium phosphate

Ito

Kamitakahara

Murakami

et al. 2010

“…18) Whiskers of HAp between 20 and 30¯m in length were formed through hydrothermal treatment of beta-tricalcium phosphate [¢-TCP; Ca 3 (PO 4 ) 2 ] with the addition of citric acid. 19) The formation of needle-shaped HAp crystals 0.4¯m in length was also reported after hydrothermal treatment of monocalcium phosphate monohydrate [MCPM; Ca(H 2 PO 4 ) 2 21) In addition, a mixture of DCPD and ¢-TCP was used for hydrothermal synthesis of needle-shaped HAp crystals with a maximum length of 60¯m.…”

Section: )17)mentioning

confidence: 99%

Comparative study of hydroxyapatite formation from α- and β-tricalcium phosphates under hydrothermal conditions

Goto

Kim

Kikuta

et al. 2012

We investigated the crystal growth of hydroxyapatite (HAp) from ¡-phase (¡-TCP) and ¢-phase (¢-TCP) tricalcium phosphates showing different solubility, under hydrothermal conditions. Samples of ¡-TCP and ¢-TCP were treated up to 72 h under hydrothermal conditions at 120°C. The ¡-TCP sample was completely transformed into HAp crystals within 1 h after the powder was exposed to hydrothermal conditions. In contrast, the ¢-TCP sample required more than 72 h to achieve complete transformation into HAp crystals. This difference in transformation behavior affected the morphology of the formed HAp crystals, which were observed to form plate-and rod-shaped crystals from ¡-and ¢-TCP, respectively. The high dissolution rate of ¡-TCP led to fine, plate-shaped crystals whose morphology was maintained up to 72 h once they formed. In comparison, the low dissolution rate of ¢-TCP allowed production of large, well-crystallized HAp crystals through the hydrothermal treatment conditions, even though the chemical composition of the reactant samples were the same. The morphology of the HAp crystals formed as a result of the hydrothermal conditions was controlled by selecting starting materials whose solubility affects an increase in the degree of supersaturation in the solution.

“…18), 19) In addition, Ioku et al has reported that Ca/P atomic ratios were very similar to values determined by chemical analysis with inductively coupled plasma spectroscopy of rod-shaped HA. 10) Mechanical strength was estimated by measuring the compressive strength of specimens at a loading rate of 2 mm·min ¹1 with a mechanical testing machine (TG-5kN, Minebea Co., Ltd., Japan). Compressive strength was determined by the mean values of 3 samples from each specimen at a maximum load per unit surface area before specimens failed.…”

Section: ¹3mentioning

confidence: 99%

Fabrication of porous blocks of calcium phosphate through hydrothermal processing under glycine coexistence

Kawachi

Misumi

Fujimori

et al. 2010

Porous hydroxyapatite (HA) and beta-tricalcium phosphate (¢-TCP) blocks are well known biomaterials employed as bone substitutes. Control of the porosity and morphology of these ceramics are important in governing their biological properties upon implantation. One synthetic method, hydrothermal processing, produces porous ceramics with distinct morphologies. In the present study, porous calcium phosphate blocks with unique structures were produced from compacted powder mixtures of alpha-tricalcium phosphate (¡-TCP) and glycine (Gly) treated by exposure to water vapor at 120, 160, and 200°C for 5 h. Hydrothermal treatment at 200°C for 5 h of mixtures of Gly/¡-TCP with mass ratios of 50/50 and 67/33 could give the porous materials of single phase HA. The obtained porous HA blocks had micrometer-sized pores due to the entanglement of rod-shaped particles, and large-sized pores of over 100 µm in diameter derived from Gly. After the heating at 900°C for 3 h in air, HA was converted to ¢-TCP with almost same microstructure in comparison with that of pre-heating one. The present methods provided insight into the production of porous blocks composed of rod-shaped calcium phosphate particles with both submicron-sized pores and large-sized pores of about 100 µm in size.