• Journal of the Korea Institute of Building Construction
• /
• v.14 no.1
• /
• pp.68-75
• /
• 2014

In order to increase the integrity of the wellbore which is used to prevent the leakage of supercritical $CO_2$, it is necessary to develop a concrete that is strongly resistant to carbonation. In an environment where the concentration of $CO_2$ is exceptionally high, $Ca^{2+}$ ion concentration in pore solution of Portland cement concrete will drop significantly due to the rapid consumption of calcium hydroxide, which decreases the stability of the calcium silicate hydrate. In this research, calcium phosphates were used to modify Portland cement system in order to produce hydroxyapatite, a hydration product that is strongly resistant to carbonation under such an environment. According to the experimental results, calcium phosphates reacted with Portland cement to form hydroxyapatite. The formation of hydroxyapatite was verified using X-ray diffraction analyses with selective extraction techniques. When using dicalcium phosphate dihydrate and tricalcium phosphate, the 28-day compressive strength was lower than that of plain cement paste. However, the specimen with monocalcium phosphate monohydrate showed equivalent strength to that of plain cement paste.

• Korean Journal of Soil Science and Fertilizer
• /
• v.46 no.5
• /
• pp.308-312
• /
• 2013

The monitoring of chemical dynamic changes in controlled horticultural lands is very important for agricultural sustainability. Field monitoring was performed to evaluate the soil chemical properties of 200 controlled horticultural soil samples in Gyeongnam province every 4 years from 2000 to 2012. Soil chemical properties such as pH, amount of organic matter, available phosphate, nitrate nitrogen, and exchangeable potassium, calcium, magnesium, and sodium were analyzed. The amount of exchangeable calcium and soil pH were significantly higher in 2012 than in 2000. In 2012, the frequency distribution for values of pH, organic matter, available phosphate, and exchangeable potassium, calcium, and magnesium that were within the optimum range was 16.0%, 22.5%, 11.5%, 3.5%, 2.5%, and 5.0%, respectively. Especially, available phosphate and exchangeable calcium were excess level with portions of 76.0% and 96.5%, respectively. These results indicated that a balanced management of soil chemical properties can reduce the amount of fertilizer applied for sustainable agriculture in controlled horticultural lands.

• Journal of the Korean Ceramic Society
• /
• v.47 no.3
• /
• pp.244-248
• /
• 2010

Porous calcium phosphates were successfully fabricated by using a cuttlefish bone. The cuttlefish bone, which is composed of $CaCO_3$, showed a special porous microstructure containing uniform-sized voids. In this study, the pre-forms infiltrated distilled phosphoric acid were sintered at $1200^{\circ}C$ in an air atmosphere. The porous microstructure of the pre-forms was kept their original pattern after sintering with a synthesis of calcium phosphate. The obtained porous calcium phosphate, sintered at $1200^{\circ}C$ for 3 h at 17% concentration of phosphoric acid, showed uniform open pores of 150 ${\mu}m$ in size and $\beta$-TCP phase in the XRD patterns. Above 16% concentration, CaO phase, derived from the decomposition of $CaCO_3$, decreased gradually in the sintered samples, and the measured Ca/P ratios of the samples prepared from 16% and 18% concentration were 1.67 and 1.43, which are close to stoichiometric HA (1.66) and $\beta$-TCP (1.50).

• Korean Journal of Materials Research
• /
• v.13 no.4
• /
• pp.246-250
• /
• 2003

Calcium phosphate was prepared by chemical reaction formula using Oyster shells and $H_3$$PO_4$solutions. After added to 0.1 M∼0.9$ M H_3$$PO_4$ solution for oyster shell, prepared powders were investigated for heating properties and formation phase with heat treatment temperatures. As the results of XRD analysis of heated powders at $500^{\circ}C$∼$1200^{\circ}C$,$ CaCO_3$ phases were observed at the temperature of below 900 TEX>$^{\circ}C$ and in the condition of 0.1 M∼0.9 M $H_3$$PO_4$ solutions. However, $CaCO_3$, $CaPO_3$(OH) and $Ca_3$($PO_4$)$_2$ phases were appeared at the temperature range between $500∼900^{\circ}C$ and in the solution of 0.7 M to 0.9 M $H_3$$PO_4$. $Ca_{ 5}$($PO_4$)$_3$(OH) and CaO phases due to the decarbonation of oyster shells($CaCO_3$) were appeared at above $1000^{\circ}C$ and in the solution of below 0.5 M $H_3$X$PO_4$. However in the case of above 0.7 M $H_3$$H_4$ solutions, $Ca_{5}$ ($PO_4$)$_3$(OH) was decomposed into $Ca_3$($PO_4$)$_2$ at more higher 100$0^{\circ}C$. Thus $Ca_3$(X$Ca_4$)$_2$ phases were appeared at higher than 100$0^{\circ}C$.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.22 no.2
• /
• pp.99-104
• /
• 2012

The co-precipitation technique has been applied to synthesize biphasic calcium phosphate (BCP). $Ca(NO_3)_2{\cdot}4H_2O$ and $(NH_4)_2HPO_4$ as the starting materials was used. X-ray diffraction (XRD) and Fourier transformed infrared (FT-IR) spectroscopy were used to characterize the structure of as-synthesized and calcined BCP powders. After immersion in Hanks' Balanced Salt Solution (HBSS), for 1 week a precipitation started to be formed with individual small granules on the specimen surface. An MTT assay indicated that BCP powders have no cytotoxic effects on MG-63 cells, and that they have good biocompatibility.

• Korean Journal of Agricultural Science
• /
• v.3 no.2
• /
• pp.139-144
• /
• 1976

To deter-mine the most reasonable method for improving of newly reclaimed soil, seven kinds of improving methods were tested and the soybean was cultivated as test crop. The results obtained are summarized as follow: The newly reclaimed soil where this experiment was carried out showed low acidity and was deficient in the humus, the phosphate, the calcium and the magnesium. Both the fused phosphate as well as the calcium was much effective to the correction of the soil acidity. The compost was the most effective source to increase the content of the humus in the soil, and also the calcium application showed a significant effect to increase the amount of humus. Not only compost but also fused phosphate were much effective to increase the content of calcium in the soil. Each factor as the calcium, the fused phosphate, the compost and the deep plowing has an effect to increase the amount of magnesium in soil significantly. The compost increased the potassium in soil. The amount of magnesium in soybean plant was significantly increased by the application of the calcium, the fused phosphate or the compost. And the calcium and the fused phosphate had an effect to increase the grain yield of soybean. The highest grain yield of soybean was taken at the treatment of N.P.K.+Compost+Calcium+Deep-plowing. The grain yield of soybean was significantly correlated with the soil acidity, the amount of the humus and the magnesium in soil and the amount of the magnesium in soybean plant.

• Journal of Life Science
• /
• v.14 no.1
• /
• pp.174-179
• /
• 2004

To develop high effiency biofertilizer, a bacterium having ability to solubilize inorganic phosphate was isolated from cultivated soils, using a sucrose minimal agar-hydroxyapatite medium. The strain was identified as Klebsiella sp. DA7l-1, based on the physiological and biochemical properties. The activity of solubilizing inorganic phosphate of Klebsiella sp. DA7l-1 against three types of insoluble phosphate such as tri-calcium phosphate, aluminium phosphate, hydroxyapatite were quantitatively determined. The results indicated that the strain solubilized hydroxyapatite. The MPS (mineral phosphate solubilizing) conditions of Klebsiella sp. DA7l-1, were measured to determine the optimal conditions. The optimal temperature and initial pH to solubilize insoluble phosphate in sucrose minimal medium were $30^{\circ}C$ and pH 6.0, respectively.

• YAKHAK HOEJI
• /
• v.36 no.6
• /
• pp.513-517
• /
• 1992

The effect of solubility and hygroscopicity of some tablet diluents on the disintegration of enzyme tablets was investigated. Tablets were prepared by direct compression method using sodium starch glycolate, crospovidone, croscarmellose sodium and low-substituted hydroxypropyl cellulose as super disintegrants. Lactose, dextrose, sucrose, sorbitol and calcium phosphate dibasic were selected as typical diluents in this study. They were different in solubility (sucrose, sorbitol>dextrose>dextrose>lactose>calcium phosphate dibasic) and hygroscopicity (sorbitol>sucrose>dextrose>caicium phosphate dibasic, lactose). The disintegrants accelerated differently the disintegration of the tablets prepared with different diluents in the decreasing order of calcium phosphate dibasic>lactose>dextrose>sucrose and sorbitol. These results indicate highly soluble and/or hygroscopic diluents decrease the efficiencies of super disintegrants in the enzyme tablets.

• Korean Journal of Agricultural Science
• /
• v.38 no.3
• /
• pp.459-464
• /
• 2011

A simplified model for the colloidal calcium phosphate (CCP) nanocluster was developed from an active role of phosphate in the precipitation of casein (CN)/Ca mixtures and the composition of casein micelles (CM). The possible shape of the CCP nanocluster was selected as a tetrahedron, and we estimated that 4 CN molecules were involved in crosslinking a single CCP nanocluster. Similar values were obtained for the number of CN molecules involved in stabilizing the nanocluster when the number of CNs attached onto each nanocluster surface was deduced from the composition of CM. If one phosphoserine cluster consisted of 3 phosphoserine residues, the theoretical molecular weight and volume for the nanocluster were estimated to be 4,898 g/mol and 2.88 $nm^3$, respectively. It was also shown that the position of Ca present in our model were reasonably located to accommodate the serine phosphate in CN molecule.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2012.10a
• /
• pp.161-162
• /
• 2012