• Journal of the Korean Crystal Growth and Crystal Technology
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• v.32 no.3
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• pp.96-102
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• 2022

Hydroxyapatite (HAp) was synthesized from calcium hydroxide (Ca(OH)₂) reacting with phosphoric acid (H₃PO₄) in aqueous solution. HAp powders were synthesized from extremely high concentration of precursor solutions over 3 M of Ca(OH)₂ aqueous suspension using modified process parameters such as phosphoric acid (H₃PO₄) pouring rate, aging time and post ball milling process. Regardless of phosphoric acid pouring rate, the DCPD (dicalcium phosphate dihydrate) was formed at room temperature and when heated above 700℃, β-TCP (tricalcium phosphate) was synthesized and the amount reached its maximum at 900℃. When the synthesized powder was sintered at 1150℃, β-TCP, a high temperature impurity phase, remained. The single HAp phase without DCPD was obtained from post ball-milled precipitates followed by 3 day aging. For the ball-milled precipitates even without the aging process, the desired single HAp phase without β-TCP could be obtained by heat treatment above 500℃. The post ball milling process provided a convenient route for HAp synthesis.

• Journal of Environmental Science International
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• v.10 no.6
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• pp.387-391
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• 2001

The hydroxyapatite(HAp) as a carrier the for ion exchange agent of $Ag^+$ions was prepared in semiconductor fabrication, The Ca/P molar ratio of the HAp was 1.65. The HAp is molded in shape of the antimcrobial ball and then sintered at 100$0^{\circ}C$ Ag-containing HAp(HAp-Ag) was prepared by incorporating $Ag^+$/ions in HAp crystals through an ion-exchange reaction in solutions containing 0.01M $AgNO_3$. The antimicrobial effect of HAp-Ag for bacteria such as Escherichial coli and Staphylococcus aureus has been Investigated. The concentrations of silver in the antimicrobial ball was determined by inductively coupled plasma and the amount of $Ag^+$ions was 9.0$\mu\textrm{g}$/g. The HAp-Ag exhibited excellent antimicrobial effect for bacteria such as E. coli and S. aureus. The bactericidal activity was considered to be caused by direct contact of bacteria with $Ag^+$ions in the HAp crystals. The HAp would likely to be possible as a carrier of antimicrobial metal ions such as Ag, Cu, and Zn by recycling of waste sludge in the semiconductor fabrication process.

• Journal of the Korean Ceramic Society
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• v.50 no.4
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• pp.245-250
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• 2013

A hydroxyapatite air filter was made with hydroxyapatite powder, water and chitosan solution. The structures of the sintered HAp samples were determined by MP-XRD. Hydroxyapatite has antibacteria properties against Staphylococcus aureus, Klebsiella pneumoniae and Escherichia coli. The bacteria removal rate was 99.9%. In the case of Pseudomonas aeruginosa, Colon bacterium and Listeria monocytogenes, the hydroxyapatite air filters had a clear zone which confirmed antibacteria properties. Using the microscopy, we observed that the HAp powder absorbed E. coli bacteria.

• Bulletin of the Korean Chemical Society
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• v.33 no.12
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• pp.3950-3956
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• 2012

In order to improve the bioactivity and mechanical properties of hydroxyapatite (HAp), chitosan (Chi) was in situ combined into HAp to fabricate a composite scaffold by a sublimation-assisted compression method. A highly porous film with sufficient mechanical strength was prepared and the bioactivity was investigated by examining the apatite formed on the scaffolds incubated in simulated body fluid. In addition, the cytotoxicity of the HAp/Chi composite was studied by evaluating the viability of murine fibroblasts (L-929 cells) exposed to diluted extracts of the composite films. The apatite layer was assessed using scanning electronic microscopy, inductively coupled plasma-optical emission spectrometry and weight measurement. Composite analysis showed that a layer of micro-sized, needle-like crystals was formed on the surface of the composite film. Additionally, the WST-8 assay after L-929 cells were exposed to diluted extracts of the composite indicated that the HAp/Chi scaffold has good in vitro cytocompatibility. The results indicated that HAp/Chi composites with porous structure are promising scaffolding materials for bone-patch engineering because their porous morphology can provide an environment conductive to attachment and growth of osteoblasts and osteogenic cells.

• Journal of the Korean Ceramic Society
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• v.38 no.11
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• pp.1030-1036
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• 2001

Hydroxyapatite[COL] nanocomposite was prepared through coprecipitation process. The chemical bond formation between HAP and COL was confirmed by diffusive reflectance FT-IR and TEM observation. Higher concentration of COL in the preparation induced tiny nanocrystalline composite particles, but lower concentration of COL contributed to form the well developed HAP particles. From TEM observation and ED(Electron Diffraction) pattern the embedded HAP nanoparticles were oriented along the c-axis of COL fiber. In an aqueous system of constant [Ca$\^$2+/] and [PO$_4$$\^$3-/], quantity of soluble COL matrix was doing an important role of controlling the heterogeneous nucleation site for the formation of HAP nanocrystals. Higher concentration of COL will provide more nucleation sites for Ca$\^$2+/ and so the concentration of calcium ions for the total number of active nucleation sites will be getting relatively dilute.

• Applied Chemistry
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• v.9 no.2
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• pp.25-28
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• 2005

To evaluate the dental restorative application of polymer composites filled with hydroxyapatite (HAP) which is an inorganic component of human bone material, dental properties of the polymer composites were investigated. A visible light system was utilized to activate the acrylate resin matrix of the composites. Maximum loading percentage of HAP in composite was 65 wt% and the depth of cure was 6.0 mm which can be applicable for dental restoration. With increasing the HAP content, degree of conversion of polymer composites was slightly decreased, however, polymerization shrinkage value was not varied. Diametral tensile strength value was enhanced with an increase of HAP content, however, there was no strict trend between flexural strength and HAP concentration. Anyhow, polymer composites prepared herein have superior mechanical properties sufficient specifications applicable to dental materials.

• Journal of the Korean GEO-environmental Society
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• v.12 no.11
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• pp.31-37
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• 2011

This study investigated on the adsorption and photocatalysis of Reactive Black 5(RB5) by the hydroxyapatite(HAP)/Titanium dioxide($TiO_{2}$) media. The adsorption of RB5 on $TiO_{2}$, HAP and $TiO_{2}$/HAP was investigated during a series of batch adsorption experiments. The amounts adsorbed at equilibrium were measured. Langmuir and Freundlich isotherm models were tested for their applicability. The result of equilibrium studies of $TiO_{2}$, HAP and $TiO_{2}$/HAP adsorbent were found to follow Langmuir isotherm model. The adsorbed amounts(Qmax) were found to be 5.28mg/g on single $TiO_{2}$, 12.45mg/g on single HAP and 9.03mg/g on $TiO_{2}$/HAP, respectively. The experimental data were analysed using the pseudo-first-order adsorption and photocatalysis kinetic models. According to these models, RB5 degradation by $TiO_{2}$/HAP was affected by interaction effect of photocatalysis and adsorption.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.360.1-360.1
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• 2016

Hydroxyapatite (Ca10(PO4)6(OH)2, HAP) particles have attracted a great deal of attention in biomedical fields due to their good biocompatibility, bioactivity and fairly broad applications as drug delivery, dental implant, bone cement, and etc. Thus, many researchers have made an effort to add new functionalities such as luminescence, drug delivery, and bone regeneration properties up to HAP powders by controlling their nanostructure as well as composition. In this research, the mesoporous strontium substituted HAP (Sr-HAP) microspheres were synthesized using a hydrothermal method. In this synthesis, aspartic acid monomers were utilized to form microsphere by controlling surface energy of HAP particles and Sr ions were substituted into Ca ion sites, which induced luminescence property in HAP powders. Moreover, the change in the amount of Sr substitution was found to influence the particle size, morphology, and concurrently surface area, which led to changing drug loading as well as drug release property. The amount of Sr influences the morphology, luminescent properties, particle size, surface area cell viability and drug loading property, which are investigated by SEM, TEM, XRD, FTIR, BET, XPS and in vitro test such as MTT assay and drug release test. In particular, the multifunctional Sr-HAP with molar ratios of 0.25 (Sr/(Ca+Sr)) possessed the strongest luminescent property as well as the superior drug loading and sustained release properties that were correspondent with large surface area and pore size. Our study indicates that the fabricated multifunctional Sr-HAP microspheres are quite useful for bone regeneration and drug delivery.

• The Journal of Natural Sciences
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• v.8 no.1
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• pp.47-51
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• 1995

Several intermediate glasses are investigated to bond the alumina and the hydroxyapatite (HAp). The chemical compositions of the intermediate glasses are chosen as $CaO-Al_2O_3$. The mole ratio of CaO/$Al_2O_3$ is changed from 0.5 to 3.0. The lowest melting is observed at $1355^{\circ}C$ in the specimen of CaO/$Al_2O_3$ at the mole ratio of 2. With increasing contents of $Al_2O_3$, the melting temperatures gradually increase and a number of pores are observed. The sectional microstructure shows that the good wetability is observed in higher contents of CaO specimens. This implies that the good wetability is obtained in the mole ratio range of CaO/$Al_2O_3geq2$. The phase transformations are observed after treatment but the major peaks of HAp still exist.

• Korean Journal of Materials Research
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• v.23 no.3
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• pp.168-176
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• 2013

In this study, hydroxyapatite (HAp) was incorporated into toothpaste and its effect on the remineralization and restoration of dental enamel was evaluated. Different sets of toothpaste were incorporated with HAp levels of 0%, 5%, 10 %, and 15 %. The filler particles of the resulting toothpaste samples were observed via SEM and XRD and compared with compositions of several commercially available toothpastes, showing that the HAp was successfully incorporated into the toothpaste samples. Different sets of human enamel were inflicted with lesions and then treated with the different fabricated toothpaste samples for five minutes three times a day for seven days. During the treatment, the teeth were subjected to demineralization and remineralization cycles to simulate the effect of natural saliva. The surface of the enamel samples were observed using SEM before and after one week of treatment, showing the formation of HAp layers on the surfaces of the enamel samples. The effect of the toothpaste on the lesions was observed using an inverted light microscope and the lesion depth was found to decrease as the concentration of HAp in the toothpaste used increased. HAp was successfully incorporated in the toothpaste and its presence was found to lessen lesion depths and improve tooth remineralization.