• Corrosion Science and Technology
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• v.4 no.1
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• pp.15-18
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• 2005

Hydroxyapatite(HAp) was synthesized using the waste sludge from semiconductor process and used as an anticorrosive pigment. The water absorption of coating pigmented with anticorrosive pigment and the corrosion at interface between coating and substrate were monitored using AC impedance techniques. The anticorrosive performance of HAp was compared with those of red lead(RL) and zinc potassium chromate(ZPC), which have been known as representative anticorrosive pigments. The amount of absorbed water in ZPC- and HAp- pigmented coatings was much higher compared to that in RL-pigmented and unpigmented film. However, it seems that the water absorbed into HAp- or ZPC-pigmented film is beneficial to anticorrosive function. The anticorrosive performance of HAp is superior or at least comparable to those of ZPC and RL. The excellent anticorrosive properties of HAp can be explained by its passivating ability, caused by the reaction of the soluble component of HAp with Fe to form iron phosphate in the presence of water.

• Applied Chemistry for Engineering
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• v.30 no.5
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• pp.639-642
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• 2019

Hydroxyapatite (HAP) containing hexadecyltrimethylammonium chloride (CTAC) as a cationic surfactant was prepared by a precipitation method. X-ray diffraction (XRD), transmission electron microscopy (TEM) and micropore physisorption analyzer were used for characterizing the crystal phase, morphology and specific surface area of HAP and CTAC-HAP. After thermal treatment, the specific surface area of both pure HAP and CTAC-HAP were reduced. The sharp rod morphology of CTAC-HAP was changed into a round shape with a smaller aspect ratio after the heat treatment. The morphological change by thermal treatment was also observed in pure HAP. Therefore, the morphological change and decrease of the specific surface area suggested that pores from the removal of CTAC during thermal treatment were not retained.

• Journal of the Korean Ceramic Society
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• v.40 no.6
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• pp.566-571
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• 2003

Hydroxyapatite (HAp)/Polyacrylic Acid(PAA) homogeneous composites of four different composition ratio were preparation by co-precipitation process with synthetic HAp and PAA as a binder. HAP/PAA composites were molding by cold isostatic pressing and were sintering by various condition in air. Crystallinity and structure of sintered HAp/PAA composites were investigated by XRD and FT-IR. Also, the compressive strength and the fracture surface of sintered specimens were measured by UTM and SEM. HAp/PAA composites were showed phase transformation of partially ${\alpha}$, ${\beta}$-tricalcium phosphate at sintering condition of 1200$^{\circ}C$ and 3 h. The pore size and porosity of sintered body were showed the range of 0.2∼3.0 $\mu\textrm{m}$ and 0.49∼13.43%, respectively. The compressive strength of sintered specimens were appeared the range of 36.6∼58.2 MPa. From these results, the sintered HAp/PAA comosites can be accounted for the microporous HAp having a good compressive strength due to homogeneous pore morphology.

• Bulletin of the Korean Chemical Society
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• v.30 no.4
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• pp.887-890
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• 2009

Hydroxyapatite (HAp)-based materials have attracted considerable attention on account of their excellent stability and recrystallization. Nanoscale HAp powders with a mean particle size of 200 nm were used to regenerate the enamel layers of damaged teeth. An artificially scratched tooth was immersed in a nanoscale HAp powder suspension in d.i. water (HAp of 70 wt%) at 37 ${^{\circ}C}$ for a period of 1~3 months. SEM and AFM showed that the scratched surface was ultimately inlaid with HAp after three months and the roughness increased from 2.80 to 5.51. Moreover, the hardness of the neo-generated HAp layer on the crown was similar to that of the innate layer. $Ca^{2+}$ and ${PO_4}^{3-}$ ions from the HAp powders dissolved in d.i. water were precipitated on the tooth to produce cemented pasteson the enamel surface due to its high recrystallizing characteristics, resulting in a hard neo-regenerated HAp layer on the enamel layer. This nanoscale HAp powder solution might be used to heal decayed teeth as well as to develop tooth whitening appliances.

• Proceedings of the Korean Fiber Society Conference
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• 2002.04a
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• pp.21-24
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• 2002

Hydroxyapatite(HAp, Ca$\sub$10/(PO$_4$)$\sub$6/(OH)$_2$, is a compound with structural and chemical resemblance bone mineral and of particular importance in the field of biomaterials. In addition to the non-toxicity and high compatibility with hard and soft tissue, HAp exhibits strong affinity to host hard tissues and protein molecules. However, HAP is difficult to shape in the specific forms due to its hardness and brittleness. (omitted)

• Korean Journal of Materials Research
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• v.15 no.10
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• pp.652-656
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• 2005

The samples were prepared with hydroxyapatite(HAp) powder and Polycaboxylate (P.C/HAp=10, 15, 20, 25, 30, 35 $wt\%$). The hydroxyapatite green body with Polycaboxylate were obtained by compaction and drying at room temperature for 3hrs. The higher mechanical properties were observed in HAp sample with $35 wt\%$ Polycaboxylate. The average compressive ana bending strength in HAp with $35 wt\%$ Polycaboxylate are $302 kgf/cm^2$ and $213 kgf/cm^2$ respectively. This strength is higher compare to that of the cortical bone.

• Journal of the Korean Ceramic Society
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• v.41 no.9
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• pp.715-721
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• 2004

Hydroxyapatite (HAp)/Gelatin (GEL) homogeneous composites of four different composition ratio were prepared by the co-precipitation process with synthetic HAp and GEL as a binder, HAP/GEL composites were molding by cold isostatic pressing and were sintering by various condition in air. Crystallinity and structure of sintered HAp/GEL composites were investigated by XRD and FTIR. Also, the compressive strength and the fracture surface of sintered specimens were measured by UTM and SEM. HAp/GEL composites showed a phase transformation to partially ${\alpha}$, ${\beta}$-tricalcium phosphate at the sintered condition of 1200$^{\circ}C$ for 3 h. The porosity of sintered body was in the range of 1.2-30.2％. The compressive strength of the sintered specimens was in the range of 16.2-60.1㎫, and its strength of sintered HAp/GEL comosites was higher than expected when the porosity was considered.

• Journal of the Korean Ceramic Society
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• v.30 no.3
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• pp.215-221
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• 1993

The Hydroxyapatite powders were prepared by Wet-direct and Hydrothermal synthesis using Ca(NO3)2.4H2O and (NH4)2.HPO4.Stoichiometric and good cristalline HAp powders were obtained 9$0^{\circ}C$ by wet-direct process. The aspect ratio of HAp powders prepared by hydrothermal synthesis was increased with increasing synthetic temperature. The HAp particles obtained at 20$0^{\circ}C$ for 10hr were needle shaped ultra fine crystals, about 100nm in size. Small amount of TCP was obtained above 80$0^{\circ}C$ after heat-treatment of hydrothermally synthesized HAp but good crystalline HAp phase was maintained up to 120$0^{\circ}C$ as the primary phase.

• Korean Journal of Materials Research
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• v.16 no.4
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• pp.272-275
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• 2006

In order to evaluate the possibility of Polymethyl methacrylate (PMMA) as a binder on hydroxyapatite (HAp) which has good biocompatibility, the properties of HAp compacts with PMMA were examined. When adding 50 wt% of PMMA on HAp and pressed, the compression strength and the hardness of the compacting body were 168MPa and 55 Hv, respectively, and the strength of compacts was higher than that of cortical bone and the hardness was similar to the value of molar. We demonstrated that HAp ceramics can be obtained without additional heat treatment and machining of the ceramic was feasible. Therefore, the HAp compacts have potential to apply to implant or artificial bone after the clinical trials guarantees biocompatibility of it.

• Journal of the Korean Ceramic Society
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• v.42 no.11 s.282
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• pp.770-776
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• 2005

Hardening and hydroxyapatite(HAp) formation behavior of the bioactive cements in the system of $CaO-SiO_{2}-P_{2}O_{5}$ glasses and the corresponding glass-ceramics were studied. DCPD (Dicalcium Phosphate Dihydrate: $CaHPO_4{\cdot}2H_2O$) and DCPA (Dicalcium Phosphate Anhydrous: $CaHPO_4$) were developed when the prepared glass and glass-ceramic powders were mixed with three different solutions. The DCPD and DCPA transformed to HAp when the cement was soaked in Simulated Body Fluid (SBF), and this HAp formation strongly depended on the releasing capacity of $Ca^{2+}$ ions from the cements. The glass-ceramic containing apatite showed fast setting, but no HAp formation was observed because no $Ca^{2+}$ ions were released from this glass-ceramics. The compressive strength of the cements increased with reaction time in SBF until all DCPD and DCPA transformed to HAp.