• The Korean Journal of Ceramics
• /
• 제4권3호
• /
• pp.231-234
• /
• 1998

LaNiO3 thin films were fabricated on various substrates by spin-coating technique using metal naphthenates as starting materials. Highly-oriented LaNiO3 films with smooth and crack-free surfaces were grown on SrTiO3 (100) and LaAlO3(100) substrates, while films on MgO(100) and Si(100) substrates showed random orientation. In this study, we concluded that lattice-mismatches between LaNiO3 films and substrates used affect film's properties.

• 한국초전도ㆍ저온공학회논문지
• /
• 제9권4호
• /
• pp.16-18
• /
• 2007

We report the results of MOD-processed YBCO coated conductors on the IBAD-MgO template. The precursor solution was coated on the $CeO_2-buffered$ IBAD-MgO template using a slot-die coating method, calcined at a temperature of $550^{\circ}C$, and fired at high temperatures for 2.5 h in a reduced oxygen atmosphere. The $J_C$ value of YBCO coated conductors was found to be very sensitive to the microstructure, and thus higher $J_C$ value could be achieved when the in-plane texture was higher and the difference in $T_{C,zero}$. was negligible. Optimally processed YBCO coated conductor exhibited $J_C$ value of $0.75MA/cm^2$ at 77 K in self-field, which might be due to somewhat depressed $T_{C,zero}$ of 87.3 K caused by possible $Sm^{3+}$ substitution on the $Ba^{2+}$ site.

• 한국재료학회지
• /
• 제25권10호
• /
• pp.509-515
• /
• 2015

MAO ceramic coatings were prepared on AZ61 magnesium alloy for various processing times ranging from 5 to 60 min, in an electrolyte solution based on silicate-fluoride. The mechanical, electrochemical and, microstructural properties and the phase compositions of the coating layers were investigated. In this work, unlike previous studies, coatings with high amounts of the $Mag_2SiO_4$ phase were formed which contained small amounts of MgO and $MgF_2$ at a processing condition of 30 min. A microstructural analysis revealed that the porosity of the coatings was reduced considerably with an increase in the processing time, together with a change in the pore geometry from an irregular to a spherical shape. Potentiodynamic polarization and mechanical testing results showed that the coatings acquired after a processing time of 30 min were superior to all of the others.

• 한국분말야금학회:학술대회논문집
• /
• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
• /
• pp.1110-1111
• /
• 2006

[ $Ti_3SiC_2$ ] was coated with $Al_2O_3$, MgO and $SiO_2$ respectively by sol-gel method and cured at 900 and $1200^{\circ}C$. The coated oxides did not react with $Ti_3SiC_2$ at $900^{\circ}C$ but reacted with it to form $TiC_x$ at $1200^{\circ}C$. The specimen coated with $SiO_2$ at $900^{\circ}C$ formed a dense protecting layer and showed the best oxidation resistance at $800^{\circ}C$ in air. However, the dense protecting layers did not form in $Al_2O_3$ and MgO coated specimens cured even at $900^{\circ}C$. MgO coated specimen showed the worst improvement in the oxidation resistance because the reactivity of MgO with $Ti_3SiC_2$ was highest. On the other hand, the electrical conductivities were measured in MgO and $Al_2O_3$ coated specimens to have TiCx but could not be measured in the $SiO_2$ coated ones because of the nonconductive dense protected layers.

• Corrosion Science and Technology
• /
• 제17권3호
• /
• pp.101-108
• /
• 2018

AA7010 is an Al-Zn-Mg-Cu alloy containing Zr, developed as an alternate to traditional AA7075 alloy owing to their high strength combined with better fracture toughness. It is necessary to improve the corrosion resistance and surface properties of the alloy by incorporating plasma electrolytic oxidation (PEO) method. AA7010-T7452 aluminum alloy has been processed through the forging route with multi-stage working operations, and was coated with $10{\mu}m$ thick $Al_2O_3$ ceramic aluminina coating using the plasma electrolytic oxidation (PEO) method. The corrosion, stress corrosion cracking (SCC) and nano-mechanical behaviours were examined by means of potentiodynamic polarization, slow strain rate test (SSRT) and nano-indentation tests. The results indicated that the additional thermomechanical treatment during the forging process caused a fully recrystallized microstructure, which lead to the poor environmental cracking resistance of the alloy in 3.5% NaCl solution, despite the overaging treatment. Although the fabricated PEO coating improved general corrosion resistance, the brittle nature of the coating did not provide any improvement in SCC resistance of the alloy. However, the hardness and elastic modulus of the coating were significantly higher than the base alloy.

• 한국전기전자재료학회논문지
• /
• 제33권3호
• /
• pp.214-218
• /
• 2020

In this study, Mg_xZn_1-xO thin films, which can be applied not only to active layers of light-emitting devices (LEDs), such as UV-LEDs, but also to solar cells, high mobility field-effect transistors, and power semiconductor devices, are fabricated using the sol-gel method. ZnO and Mg_0.3Zn_0.7O solution synthesized by the sol-gel method and the thin film were grown by spin coating on a Si (100) substrate and sapphire substrate. The solutions are synthesized by dissolving precursor materials in 2-methoxyethanol (2-ME) solvent, and then monoethanolamine (MEA) was added to the mixed solution as a sol stabilizer. Zinc acetate dihydrate is used as a ZnO precursor, while Mg nitrate hexahydrate and Mg acetate tetrahydrate are used as an MgO precursor. Then, the optical and structural characteristics of the fabricated thin films are compared. The molar concentration of the Zn precursor in the solvent is fixed at 0.3 M, and the amount of the Mg precursor is 30% of Mg²⁺/Zn²⁺. The optical characteristics are measured using an UV-vis spectrophotometer, and the transmittance of each wavelength is measured. Structural characteristics are measured using X-ray diffraction (XRD) and transmission electron microscopy (TEM). Composition analyses are performed using energy dispersive X-ray spectroscopy (EDS). The Mg_0.3Zn_0.7O thin film was well formed at the ratio of the Mg precursor added regardless of the type of Mg precursor, and the c-axis of the thin film was decreased, while the band gap was increased to 3.56 eV.

• 한국표면공학회:학술대회논문집
• /
• 한국표면공학회 2016년도 추계학술대회 논문집
• /
• pp.198-198
• /
• 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.

• 한국세라믹학회지
• /
• 제35권9호
• /
• pp.969-973
• /
• 1998

Pb(Zr, Ti)O3 (PZT) (Zr:Ti= 52: 48) thin films were prepared on MgO(100) substrates by dipping-py-rolysis process using metal naphthenates as starting materials. Thin films were fabricated by spin coating technique and the precursor films were prefired at 20$0^{\circ}C$ in air for 0.5, 1, 2, 3, and 24 h followed by final heat treatment at 75$0^{\circ}C$ for 30min. Film prefired for 24 h lost orientational properties and pole figure analysis showed the lost of the epitaxial relationship between the films and substrate while highly a/c-axis oriented thin films were obtained for the samples prefired for 1, 2, and 3h.

• 대한전기학회논문지:전기물성ㆍ응용부문C
• /
• 제55권7호
• /
• pp.359-363
• /
• 2006

Single-walled carbon nanotubes (SWCNTs) with few defects and very small amount of amorphous carbon coating have been synthesized by catalytic decomposition of methane in $H_2$ over well-dispersed metal particles supported on MgO. The yield of SWCNTs was estimated to be 88.5% and the purities of SWCNTs thus obtained were more than 90%. Peak of the radial breathing mode in the Raman spectrum demonstrated that the diameters of synthesized CNTs are in the range 0.4-2.0 nm. Our results also indicated that MgO support materials are useful to a large-scale synthesis of high-quality SWCNTs. Increasing temperature could remarkably increase the yield and also improve the quality of SWCNTs from catalytic decomposition of methane. The morphologies and microstructures of the synthesized carbon materials were characterized by scanning electron microscopy (SEM), Thermogravimetric analysis (TGA), Raman spectroscopy, and X-ray diffraction (XRD).

• Transactions on Electrical and Electronic Materials
• /
• 제13권2호
• /
• pp.64-68
• /
• 2012

We have successfully demonstrated a bandgap alteration of transparent zinc oxide (ZnO) thin film with Mg dopant by using sol-gel spin coating technique. By increasing the dopant from 0 to 30 atomic percent (at.%), a decrement value in the cutoff is observed, where the absorption edge shifts continuously to the shorter wavelength side, towards 300 nm. This resulted in a significant bandgap increment from 3.28 to 3.57 eV. However, the transmittance of the thin film at 350-800 nm gradually downgraded, from 93 to 80 % which is most probably due to the grain size that becomes bigger, and it also affected the electrical properties. The decrement from 45 to 0.05 mA at +10 V was observed in the I-V characteristics, concluding the significant relationship; where higher optical bandgap materials will exhibit lower conductivity. These findings may be useful in optoelectronics devices.