• Transactions of the Korean hydrogen and new energy society
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• v.13 no.1
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• pp.13-23
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• 2002

Hydrogenation properties of Mg-Ni and Mg-Ti-Ni alloys were investigated by Pressure-Composition Isotherm (PCI) test. Those alloys were fabricated by a new alloying method, Rotation-Cylinder Method (RCM). The as-cast microstructure of Mg-10 mass% Ni alloy consists of an island-like hydride forming $\alpha$-Mg phase and the eutectic structure. After 350 cyclic tests, Mg-lO mass % Ni alloy was pulverized into fine particles of 100 nm. The fine particles, which have a large specific surface area, are highly reactive with hydrogen. However, extreme pulvehzation can separate Mg from $Mg_2Ni$ in the eutectic structure, so $Mg_2Ni$ of the eutectic structure cannot behave as a dissociated hydrogen supplier.

• Journal of the Korean Vacuum Society
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• v.6 no.S1
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• pp.141-153
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• 1997

The paraelectric cubic-to-ferroelectric tetragonal phase transition of the thin Pb(Zr, Ti)$O_3$ (PZT) films grown on MgO(001) substrate was investigated in a series of synchrotron x-ray scattering experiments. As the thickness of the film decreases the transition temperature and the amount of the tetragonal distortion were decreased continuously Different from only the c-domains were existent in the thinnest 25nm thick film. Based on this we propose a model for the domain structure of the tetragonal PZT/MgO(100) film that is very different from the ones suggested in literature. We attribute the suppression of the transition to the substrate field that prefers the c-type domains near the interface and suppresses the tetragonal distortion to minimize the film-substrate lattice mismatch.

• Electrical & Electronic Materials
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• v.6 no.5
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• pp.470-475
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• 1993

1150, 1450, 1600.deg.C에서 MgO-SiO$_{2}$-Al$_{2}$O$_{3}$계를 유리성분으로 하는 mullite-glass질 회로기판재료의 소결거동에 미치는 MgO첨가량과 소성시간에 따른 영향을 조사하였으며 주로 소성시간이 밀도, 기공분포, 미세구조 및 생성상에 미치는 영향을 조사하였다. 1150.deg.C에서는 MgO의 첨가량에 관계없이 소결이 진행되지 않았으며 1450.deg.C에서는 MgO첨가량에 따라 소결속도가 증가하였다. 1600.deg.C에서는 각조성의 시료 모두가 빨리 과소성단계에 도달하였다. 1450.deg.C에서는 MgO 0.85% 첨가했을때 소성시간에 따라 기공량은 감소하는 반면 기공경은 일정하게 증가하였다. 먼저 .alpha.-SiO$_{2}$가 cristobalite로 전이한 후에 MgO와 반응하여 유리상으로 된다.

• Journal of Radiation Protection and Research
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• v.34 no.4
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• pp.155-164
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• 2009

In this paper, we used computerized glow curve deconvolution (CGCD) software with several models for the simulation of a TL glow curve which was used for analysis. By using the general approximation plus model, parameters values of the glow curve were analyzed and compared with the other models parameters (general approximation, mixed order kinetics, general order kinetics). The LiF:Mg,Cu,Si and the LiF:Mg,Cu,P material were used for the glow curve analysis. And we based on figure of merits (FOM) which was the goodness of the fitting that was monitored through the value between analysis model and TLD materials. The ideal value of FOM is 0 which represents a perfect fit. The main glow peak makes the most effect of radiation dose assessment of TLD materials. The main peak of the LiF:Mg,Cu,Si materials has a intensity rate 80.76% of the whole TL glow intensity, and that of LiF:Mg,Cu,P materials has a intensity rate 68.07% of the whole TL glow intensity. The activation energy of LiF:Mg,Cu,Si was analyzed as 2.39 eV by result of the general approximation plus(GAP) model. In the case of mixed order kinetics (MOK), the activation energy was analyzed as 2.29 eV. The activation energy was analyzed as 2.38 eV by the general order kinetics (GOK) model. In the case of LiF:Mg,Cu,P TLD, the activation energy was analyzed as 2.39 eV by result of the GAP model. In the case of MOK, the activation energy was analyzed as 2.55 eV. The activation energy was analyzed as 2.51 eV by the GOK model. The R value means different ratio of retrapping-recombination. The R value of LiF:Mg,Cu,Si TLD main peak analyzed as $1.12\times10^{-6}$ and $\alpha$ value analyzed as $1.0\times10^{-3}$. The R of LiF:Mg,Cu,P TLD analyzed as $7.91\times10^{-4}$, the $\alpha$ value means different ratio of initial thermally trapped electron density-initial trapped electron density (include thermally disconnected trap electrons density). The $\alpha$ value was analyzed as $9.17\times10^{-1}$ which was the difference from LiF:Mg,Cu,Si TLD. The deep trap electron density of LiF:Mg,Cu,Si was higher than the deep trap electron density of LiF:Mg,Cu,P.

• Journal of the Korean Ceramic Society
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• v.37 no.6
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• pp.537-544
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• 2000

Thin-film humidity sensor which TiO2, ZrO2, or CeO2 was added to MgCr2O4-based materials, respectively, were fabricated on the alumina substrate by using a resistant-heating evaporator. Thin films were approximately 2${\mu}{\textrm}{m}$ in grain size and shwoed porous microstructures. The resistance of the sensor decreased with increasing the relative humidity and the MgCr2O4-TiO2 sensor had the best humidity-sensing characteristics (linearity in relative humidity versus resistance).

• Korean Journal of Materials Research
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• v.22 no.3
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• pp.111-117
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• 2012

The effect of Al addition on the precipitation behavior of a binary Mg-Zn alloy was investigated based on the changes in the morphology, distribution and element concentration of precipitates formed during aging treatment. The as-cast Mg-6.0 mass%Zn (Mg-6Zn) and Mg-6.0 mass%Zn-3.0 mass%Al (Al-added) were homogenized at 613 K for 48 h and at 673 K for 12 h; they were then solid solution treated at 673 K for 0.5 h and 1 h, respectively. The Mg-6Zn and Al-added alloys were aged at 403 K and 433 K. The peak hardness of the Al-added alloy was higher than that of the Mg-6Zn alloy at each aging temperature. Rod-like, plate-like, blocky, and lath-like precipitates were observed in the Al-added alloy aged at 433 K for 230.4 ks, although the rod-like and plate-like precipitates were observed in the TEM microstructure of the Mg-6Zn alloy aged at 433 K for 360 ks. Moreover, the precipitates in the Al-added alloy were refined and densely distributed compared with those in the Mg-6Zn alloy. The Cliff-Lorimer plots obtained by the EDS analysis of the rod-like ${\beta}_1^'$ and plate-like ${\beta}_2^'$ phases in the Al-added alloy peak aged at 433 K for 230.4 ks were examined. It was confirmed that the ${\beta}_2^'$ phases had higher concentration of solute Al atom than was present in the ${\beta}_1^'$ phases, indicating that the properties of precipitates can be changed by Al addition.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.198-198
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• 2016

An ideal orthopedic implant should provide an excellent bone-implant connection, less implant loosening and minimum adverse reactions. Commercial pure titanium (CP-Ti) and Ti alloys have been widely utilized for biomedical applications such as orthopedic and dental implants. However, being bioinert, the integration of such implant in bone was not in good condition to achieve improved osseointegraiton, there have been many efforts to modify the composition and topography of implant surface. These processes are generally classified as physical, chemical, and electrochemical methods. Plasma electrolytic oxidation (PEO) as an electrochemical route has been recently utilized to produce this kind of composite coatings. Mg ion plays a key role in bone metabolism, since it influences osteoblast and osteoclast activity. From previous studies, it has been found that Mg ions improve the bone formation on Ti alloys. PEO is a promising technology to produce porous and firmly adherent inorganic Mg containing $TiO_2$($Mg-TiO_2$ ) coatings on Ti surface, and the amount of Mg introduced into the coatings can be optimized by altering the electrolyte composition. In this study, a series of $Mg-TiO_2$ coatings are produced on Ti-6Al-4V ELI dental implant using PEO, with the substitution degree, respectively, at 0, 5, 10 and 20%. Based on the preliminary analysis of the coating structure, composition and morphology, a bone like apatite formation model is used to evaluate the in vitro biological responses at the bone-implant interface. The enhancement of the bone like apatite forming ability arises from $Mg-TiO_2$ surface, which has formed the reduction of the Mg ions. The promising results successfully demonstrate the immense potential of $Mg-TiO_2$ coatings in dental and biomaterials applications.

• Journal of the Korean Ceramic Society
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• v.53 no.3
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• pp.282-287
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• 2016

This study involves enhancing the performance of the $Na(Li,Ti)O_2$ system as an Na-ion battery anode with the addition of Mg, which partially replaces Li ions. We perform both computational and experimental approaches to achieve a higher reversible capacity and a faster transport of Na ions for the devised system. Computational results indicate that the $Na(Li,Mg,Ti)O_2$ system can provide a lower-barrier path for Na-ion diffusion than can a system without the addition of Mg. Experimentally, we synthesize various $Na_z(Li_y,Mg_x,Ti)O_2$ systems and evaluate their electrochemical characteristics. In agreement with the theoretical study, Mg addition to such systems improves general cell performance. For example, the prepared $Na_{0.646}(Li_{0.207}Mg_{0.013}Ti_{0.78})O_2$ system displays an increase in reversible capacity of 8.5% and in rate performance of 13.5%, compared to those characteristics of a system without the addition of Mg. Computational results indicate that these improvements can be attributed to the slight widening of the Na-$O_6$ layer in the presence of Mg in the $(Li,Ti)O_6$ layer.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.23 no.2
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• pp.152-156
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• 2014

Lightweight materials such as aluminum and magnesium have recently received much attention in the automotive industries because of environmental and fuel-efficiency concerns. Using the powder metallurgy (PM) process for these materials creates significant opportunities for the cost-effective manufacture of lightweight automotive parts. In the present study, an Al-Cu-Mg alloy was fabricated using conventional PM processes. Primarily, the effects of the alloying elements on the sintering characteristics and mechanical behavior after heat treatment were investigated. A microstructural analysis was performed using an optical microscope and a scanning electron microscope to investigate the behavior of liquid phase sintering, including the formation of precipitates. The dependence of the mechanical behavior on the alloying elements was evaluated based on the transverse rupture strength.

• Journal of the Korean Ceramic Society
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• v.41 no.12 s.271
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• pp.929-932
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• 2004

It is known that small amount of MgO in excess is often added to develop pure perovskite single phase of PMN-based composite, however, extra MgO precipitates in grains and inhibits densification of PMN. In this study PMN-PT-BT (PBT) powder was prepared by a conventional mixed oxide method using $(MgCO_3)_4{\cdot}Mg(OH)_2{\cdot}5H_{2}O$ instead of MgO. The precursor was heated at $500^{\circ}C/1h$ and its surface was modified with MgO sol. This effect was investigated in the aspects of sintering and dielectric properties. Small amount of added MgO sol ($0.5{\sim}1.0wt\%$) enhanced sintering substantially below $1000^{\circ}C$. The PBT with $0.5wt\%$ MgO sol sintered at $900^{\circ}C/2h$ had density of $7.62\;g/cm^3$, room temperature dielectric constant of 14800, loss of dielectric constant of $1.1\%$, which were comparable to those of the PBT sintered at $1000^{\circ}C/2h$. It was noticeable that the extra MgO precipitated mostly on triple points and grain boundaries and resulted in inhibition of grain growth.