• Applied Chemistry for Engineering
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• v.24 no.5
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• pp.507-512
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• 2013

Perovskite-type oxides were successfully prepared using microwave-assisted process, and by XRD, XPS, BET, and $H_2-TPR$. Their catalytic activities for the combustion of benzene were also examined. Most of catalysts studied showed the perovskite crystalline phase with the particle size of 21~35 nm. The $LaMnO_3$ catalyst showed the highest activity and the conversion reached almost 100% at $250^{\circ}C$. The catalysts prepared by microwave-assisted process showed higher activity compared to those prepared sol-gel method. In addition, the catalytic activity was increased with an increase of calcination temperature of $LaMnO_3$-type catalyst. The TPR results on the measurement of redox property showed a good correlation with the order of catalytic activity on the benzene combustion reaction.

• Advances in nano research
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• v.14 no.1
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• pp.103-115
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• 2023

Recent developments in the synthesis of nanomagnesia of controlled sizes and shapes that are suitable for various applications are reviewed. Two main methods, based on liquid-phase synthesis, i.e., chemical methods and bio-based methods, are used to synthesize nanomagnesia. Conventionally, nanomagnesia was synthesized by chemical methods such as coprecipitation, sol-gel, combustion method, and so on using different chemical agents and stabilizers which later on become responsible for several biological risks because of the toxicity of used chemicals. Bio-based protocols are growing as another environmental friend method for the synthesis of various nanostructures especially nanomagnesia using biomass, plant extracts, alga, and fungi as a source of precursor material. The ideal method should offer better control of textural properties of nanostructures and decrease the necessity for purification of the synthesized nanoproducts, which sequentially removes the use of large amounts of chemicals and organic solvents and manipulation of products that are unsafe to the environment. Finally, the broad applicability of nanomagnesia in diverse areas is presented. Employment of nanomagnesia reported in several laboratory and industrial fields are valued from the standpoint of the significance of these issues for technological requests, as described in the literature. Nanomagnesia has various applications such as antimicrobial performance, removing pollutants, batteries application, and catalysis.

• Bulletin of the Korean Chemical Society
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• v.30 no.1
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• pp.219-223
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• 2009

$TiO_2$ doped with $Er^{3+\;and\;Yb^{3+}$ was used for fabricating a scattering layer and a nano-crystalline $TiO_2$ electrode layer to be used in dye-sensitized solar cells. The material was prepared using a new sol-gel combustion hybrid method with acetylene black as fuel. The $Er^{3+}$-$Yb^{3+}$ co-doped titanium oxide powder synthesized at 700oC had embossed structure morphology with a size between 27 to 54 nm that agglomerated to produce micron size particles, as observed by the scanning electron micrographs. The XRD patterns showed that the $Er^{3+}$-$Yb^{3+}$ co-doped titanium oxide had an amorphous structure, while using the same method without doping $Er^{3+}\;or\;Yb^{3+},\;TiO_2$ was obtained in the crystallite form with thea dominance of rutile phase. Fabricating a bilayer structure consisting of nano-crystalline $TiO_2$ and the synthesized $Er^{3+}$-$Yb^{3+}$ co-doped titanium oxide showed better scattering property, with an overall increase of 15.6% in efficiency of the solar cell with respect to a single nano-crystalline $TiO_2$ layer.

• Journal of the Microelectronics and Packaging Society
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• v.22 no.3
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• pp.45-50
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• 2015

The goal of this research is the create novel magnets with no rare-earth contents, with larger energy product by comparison with currently used ferrites. For this purpose we developed nano-sized hard-type/soft-type composite ferrite in which high remanent magnetization (Mr) and high coercivity (Hc). Nano-sized Ba-ferrite, Ni-Zn ferrite and $BaFe_{12}O_{19}/Ni_{0.5}Zn_{0.5}Fe_2O_4$ composite ferrites were prepared by sol-gel combustion method by use of glicine-nitrate and citric acid. Nanocomposite ferrites were calcined at temperature range $700-900^{\circ}C$ for 1h. According to the X-ray diffraction patterns and FT-IR spectra, single phase of NiZn-ferrite and Ba-ferrite were detected and hard/soft nanocomposite ferrite was indicated to the coexistence of the magnetoplumbite-structural $BaFe_{12}O_{19}$ and spinel-structural $Ni_{0.5}Zn_{0.5}Fe_2O_4$ that agreed with the standard JCPDS 10-0325 data. The particle size of nanocomposite turn out to be less than 120 nm. The nanocomposite ferrite shows a single-phase magnetization behavior, implying that the hard magnetic phase and soft magnetic phase were well exchange-coupled. The specific saturation magnetization ($M_s$) of the nanocomposite ferrite is located between hard ($BaFe_{12}O_{19}$) and soft ferrite($Ni_{0.5}Zn_{0.5}Fe_2O_4$). The remanence (Mr) of nanocomposite ferrite is much higher than that of the individual $BaFe_{12}O_{19}$ and $Ni_{0.5}Zn_{0.5}Fe_2O_4$ ferrite, and $(BH)_{max}$ is increased slightly.

• Journal of the Korean Magnetics Society
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• v.24 no.3
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• pp.81-85
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• 2014

Nano-sized Ba-ferrite, Ni-Zn ferrite and $BaFe_{12}O_{19}/Ni_{0.5}Zn_{0.5}Fe_2O_4$ nanocomposite ferrite were prepared by sol-gel combustion method. Nanocomposite was calcined at temperature range of $600{\sim}900^{\circ}C$ for 1 h. According to the diffraction patterns, hard/soft nanocomposite was indicated to the coexistence of the magnetoplumbite structural $BaFe_{12}O_{19}$ and spinel $Ni_{0.5}Zn_{0.5}Fe_2O_4$ and agree with the standard data (JCPDS 10-0325). The particle size of nanocomposite turn out to be less than 90 nm. The nanocomposite ferrite shows a single-phase magnetization behavior, implying that the hard magnetic phase and soft magnetic phase were well exchange-coupled. The specific saturation magnetization ($M_s$) of the nanocomposite is located between hard ($BaFe_{12}O_{19}$) and soft ferrite ($Ni_{0.5}Zn_{0.5}Fe_2O_4$). The remanence (Mr) of nanocomposite ferrite is much higher than that for the individual $BaFe_{12}O_{19}$ and $Ni_{0.5}Zn_{0.5}Fe_2O_4$ ferrite. $(BH)_{max}$ is increased, generally.