• Journal of the Korean Vacuum Society
• /
• v.7 no.s1
• /
• pp.30-36
• /
• 1998

The plasma-spray technique is currently the most frequently used method to produce calcium phosphate coatings. Hydroxyapatite(HAp), one form of calcium phosphate, is preferred by its ability to form a direct bond with living bone, resulting in improvements of implant fixation and faster bone healing. Recently, concerns have been raised regarding the viable use and long-term stability of plasma-spray HAp coatings due to its nature of comparatively thick, porous, and poor bonding strength to metal implants. Thin layers (maximum of few microns) of calcium phosphate were formed by an e-beam evaporation with and without ion bombardments. The Ca/P ration of film was controlled by either using the evaporants having the different ration of Ca/P with addition of CaO, or adjusting the ion beam assist current. The Ca/P ration had great effects on the structure formation after heat treatment and the dissolution bahavior. The calcium phosphate films produced by IBAD exhibited high adhesion strength.

• Korean Journal of Materials Research
• /
• v.28 no.5
• /
• pp.308-314
• /
• 2018

Among the fuel cell electrolyte candidates in the intermediate temperature range, glass materials show stable physical properties and are also expected to have higher ion conductivity than crystalline materials. In particular, phosphate glass has a high mobility of protons since such a structure maintains a hydrogen bond network that leads to high proton conductivity. Recently, defects like volatilization of phosphorus and destruction of the bonding structure have remarkably improved with introduction of cations, such as Zr4+ and Nb5+, into phosphate. In particular, niobium has proton conductivity on the surface because of higher surface acidity. It can also retain phosphorus content during heat treatment and improve chemical stability by bonding with phosphorus. In this study, we fabricate niobium phosphate glass thin films through sol-gel processing, and we report the chemical stability and electrical properties. The existence of the hydroxyl group in the phosphate is confirmed and found to be preserved at the intermediate temperature region of $150-450^{\circ}C$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.20 no.9
• /
• pp.756-760
• /
• 2007

Flame retardant(FR) properties were investigated with tricredyl phosphate(TCP) and tris(pentafluorophenyl)phosphine(TFPP) as additives for lithium-ion batteries. Thermal stability was improved with additives in $Li/LiNi\frac{1}{3}Mn\frac{1}{3}Co\frac{1}{3}O_2$ cells comparing to non-additive electrolytes. Oxygen evolution reaction of the cathode material was delayed to up $55^{\circ}C$, from $275^{\circ}C\;to\;330^{\circ}C$. Electrolytes with the 1 wt.% additives provided good FR properties while the resonable battery performance is maintained.

• Journal of the Korea Institute of Building Construction
• /
• v.17 no.4
• /
• pp.341-348
• /
• 2017

The performance degradation of concrete pavement by winter deicer is very serious in Korea, and its maintenance and rehabilitation brings a high expense. Therefore, a suitable method for rehabilitation of such concrete pavement and repair material of proper performance are required. In this study, the properties of compressive strength, ability to resist chloride ion penetration, and properties of dry shrinkage of magnesium phosphate ceramics were assessed to evaluate its applicability as a repair material for concrete pavement in Korea. As a result, the mortar flow showed a normal level of 190 mm, but the viscosity was high and the self-flow ability was poor. The setting time was 12 minutes, leading very rapid-hardening, and thus a prompt work was required. The compressive strength of mortar was 38.4MPa in 2 hours, 73.8MPa in 24 hours, and 111.0MPa in 28 days, showing a significant level. As a result of the test to chloride ion penetration resistance, mortar showed 143 Coulombs, and concrete showed 172.6 Coulombs, which fell under very low level. The drying shrinkage of MPC concrete in 40 days was below $60{\times}10-6$, and comparing with normal cement concrete, it showed the level below 1/10 of other concrete to secure an excellent volume stability. As above, magnesium phosphate ceramics has excellent strength performance, chloride ion penetration resistance, and volume stability, and this in the future shall be used in construction under the consideration of working time or workability, requiring further improvement for such performance.

• Journal of Electrochemical Science and Technology
• /
• v.12 no.1
• /
• pp.67-73
• /
• 2021

Nickel-rich lithium nickel-cobalt-manganese oxides (NCM) are viewed as promising cathode materials for lithium-ion batteries (LIBs); however, their poor cycling performance at high temperature is a critical hurdle preventing expansion of their applications. We propose the use of a functional electrolyte additive, triphenyl phosphate (TPPa), which can form an effective cathode-electrolyte interphase (CEI) layer on the surface of Ni-rich NCM cathode material by electrochemical reactions. Linear sweep voltammetry confirms that the TPPa additive is electrochemically oxidized at around 4.83 V (vs. Li/Li+) and it participates in the formation of a CEI layer on the surface of NCM811 cathode material. During high temperature cycling, TPPa greatly improves the cycling performance of NCM811 cathode material, as a cell cycled with TPPa-containing electrolyte exhibits a retention (133.7 mA h g-1) of 63.5%, while a cell cycled with standard electrolyte shows poor cycling retention (51.3%, 108.3 mA h g-1). Further systematic analyses on recovered NCM811 cathodes demonstrate the effectiveness of the TPPa-based CEI layer in the cell, as electrolyte decomposition is suppressed in the cell cycled with TPPa-containing electrolyte. This confirms that TPPa is effective at increasing the surface stability of NCM811 cathode material because the TPPa-initiated POx-based CEI layer prevents electrolyte decomposition in the cell even at high temperatures.

• Korean Journal of Metals and Materials
• /
• v.47 no.3
• /
• pp.188-194
• /
• 2009

Recently, new extraction technology for manganese nodule has been developed as alternative noble metallic resources. It is important to understand thermodynamic behaviors of phosphorus in low basic slag system from the viewpoint of the refining processing optimization. Thermodynamic behaviors of phosphorus in the $FeO-MnO-CaO-SiO_2-MgO_{satd.}$ slag system were investigated at 1723 K with various oxygen potential and slag composition of low basicity. The experimental results for dependence of phosphorus on oxygen potential and slag basicity indicated that the dissolution mechanism of phosphorus into slag of low basicity could be derived as follows; $[P]+5/4O_2+(O^{2-})=({PO_{3.5}}^{2-})$ Present experimental results implied that stability of phosphorus in slag would be depended on both of $O^{2-}$ (basicity) and content of $Ca^{2+}$ in molten slag. The thermodynamic effect of FeO, MnO and $Na_2O$ on low basicity on phosphate capacity was discussed.

• Journal of Electrochemical Science and Technology
• /
• v.8 no.2
• /
• pp.162-168
• /
• 2017

$LiNi_xCo_yMn_zO_2$ cathode materials have been the focus of much attention because of their high specific capacity. However, because of the poor interfacial stability between cathodes and electrolytes, the cycling performance of these materials fades rapidly, especially at high temperatures. In the present paper, we propose the use of tris(trimethylsilyl) phosphate (TMSPO), which contains phosphate and silyl functional groups, as a functional additive in electrolytes. The addition of TMSPO resulted in the formation of cathode electrolyte interphase (CEI) layers on the surfaces of the cathodes and effectively suppressed electrolyte decomposition reactions, even at high temperatures. As a result, cells cycled with TMSPO exhibited remarkable capacity, which remained after 50 cycles (82.0%), compared to cells cycled without TMSPO (64.6%).

• Journal of the Mineralogical Society of Korea
• /
• v.15 no.4
• /
• pp.315-327
• /
• 2002

Al-pillared clay was synthesized by constructing pillars of aluminum oxides at the interlayer of montmorillonite in bentonite. XRD, DTA and chemical analyses of Al-pillared clay were performed to examine mineralogical properties. Batch adsorption experiments were also conducted to determine the adsorption properties of this synthesized clay for phosphate ions. XRD analyses showed that the interlayer space of Al-pillared clay expanded to 18.03 $\AA$ at room temperature and shifted to $17 \AA$ after heating to $550^{\circ}C$. A small change in interlayer space after heating indicates high thermal stability. The interlayer expansion by glycerol was also very small. From DTA analyses, pillared clay showed the characteristic endothermic peaks at 270 and $420^{\circ}C$ , which might be caused by dehydration in framework of pillars between interlayers. Adsorption experiment revealed that Al-pillared clay had an excellent adsorption capacity to the phosphate ions, whereas montmorillonite had very low adsorption capacity to phosphate ions. In phosphate solution concentration up to 300 mg/L, 2 g of pillared clay could uptake almost 100% of phosphate ions from 20 mL of solution. After heat treatment of the phosphate adsorbed pillared clay at 50$0^{\circ}C$ to remove phosphate, the calcined pillared clay could adsorb phosphate ions with a little decreased adsorption efficiency. This fact indicates that Al-pillared clay can be recycled for the adsorption of phosphate ions.

• 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.

• Journal of Periodontal and Implant Science
• /
• v.43 no.1
• /
• pp.18-23
• /
• 2013

Purpose: The purpose of this study was to evaluate the osseointegration of calcium phosphate (CaP)-coated implants by ion beam assisted deposition with a lack of primary stability. Methods: A total of 20 CaP-coated implants were bilaterally placed in the mandible of five dogs. In the rotational implant group, the implants were inserted in oversized drilled sockets without mechanical engagement, while the conventional surgical protocol was followed in the control group. Each group was allowed to heal for 4 and 8 weeks. The bone-to-implant contact (BIC, %) was measured by a histometric analysis. Results: All of the implants were well-maintained and healing was uneventful. In the histologic observation, all of the implants tested were successfully osseointegrated with a high level of BIC at both observation intervals. There was no significant difference in BIC among any of the groups. Conclusions: Within the limitation of this study, successful osseointegration of CaP-coated implants could be achieved in unfavorable conditions without primary stability.