• Journal of Powder Materials
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• v.25 no.5
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• pp.426-434
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• 2018

In this study, $MgO-CaO-Al_2O_3-SiO_2$ (MCAS) nanocomposite glass powder having a mean particle size of 50 nm and a specific surface area of $40m^2/g$ is used as a sintering additive for AlN ceramics. Densification behaviors and thermal properties of AlN with 5 wt% MCAS nano-glass additive are investigated. Dilatometric analysis and isothermal sintering of AlN-5wt% MCAS compact demonstrates that the shrinkage of the AlN specimen increases significantly above $1,300^{\circ}C$ via liquid phase sintering of MCAS additive, and complete densification could be achieved after sintering at $1,600^{\circ}C$, which is a reduction in sintering temperature by $200^{\circ}C$ compared to conventional $AlN-Y_2O_3$ systems. The MCAS glass phase is satisfactorily distributed between AlN particles after sintering at $1,600^{\circ}C$, existing as an amorphous secondary phase. The AlN specimen attained a thermal conductivity of $82.6W/m{\cdot}K$ at $1,600^{\circ}C$.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.25 no.6
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• pp.245-251
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• 2015

We have applied mechanical alloying (MA) to produce soft magnetic composite material using a mixture of elemental $Fe_2O_3$-Mg powders. An optimal milling and heat treatment conditions to obtain soft magnetic ${\alpha}$-Fe/MgO composite with fine microstructure were investigated by X-ray diffraction, differential scanning calorimetry (DSC) and vibrating sample magnetometer (VSM) measurement. It is found that ${\alpha}$-Fe/MgO composite powders in which MgO is dispersed in ${\alpha}$-Fe matrix are obtained by MA of $Fe_2O_3$ with Mg for 30 min. The saturation magnetization of ball-milled powders increases with increasing milling time and reaches to a maximum value of 69.5 emu/g after 5 h MA. The magnetic hardening due to the reduction of the ${\alpha}$-Fe grain size by MA was also observed. Densification of the MA powders was performed in a spark plasma sintering (SPS) machine at $800{\sim}1000^{\circ}C$ under 60 MPa. X-ray diffraction result shows that the average grain size of ${\alpha}$-Fe in ${\alpha}$-Fe/MgO nanocomposite sintered at $800^{\circ}C$ is in the range of 110 nm.

• Journal of the Korean Ceramic Society
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• v.56 no.3
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• pp.256-268
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• 2019

In this research, some mechanical properties of Al₂O₃-based composites containing nanoSiC and nanoMgO additives, including elasticity modulus, hardness, and fracture toughness, have been evaluated. Micron-sized Al₂O₃ powders containing 0.08 wt.% nanoMgO particles have been mixed with different volume fractions of nanoSiC particles (2.5 to 15 vol.%). Untreated samples have been sintered by using hot-press technique at temperatures of 1600 to 1750℃. The results show significant increases in the mechanical characteristics with increases in the sintering temperature and amount of nanoSiC particles, with the result that the elasticity modulus, hardness, and fracture toughness were obtained as 426 GPa, 21 GPa, and 4.5 MPa.m^1/2, respectively.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1363-1364
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• 2007

The composites such as Sn-CNTs, $SnSb_{0.5}$-CNTs and $CoSb_3$-CNTs have attracted much attention in the past years owing to their good overall properties. In these samples, intermetallic compounds show high specific capacities. Recently, interest in metal oxides such as $Al_{2}O_{3}$, MgO and $TiO_2$ has been largely stimulated by the realization that they can improve the cycling stability of the Li-ion battery electrodes. The reversible capacity of the $TiO_2$/CNTs composite reaches 168 mAh $g^{-1}$ at the first cycle and remains almost constant during long-term cycling. In this study, a nanocomposite of $TiO_2$/CNTs was prepared by sol-gel method and its electrochemical properties as anode materials for Li-ion batteries were studied by galvanostatic cycling, cyclic voltammograms (CV) and electrochemical impedance spectroscopy (EIS).

• Carbon letters
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• v.26
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• pp.43-50
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• 2018

In this research, a novel and efficient quinoline thioacetamide functionalized magnetic graphene oxide composite ($GO@Fe_3O_4@QTA$) was synthesized and utilized for dispersive magnetic solid phase preconcentration of Cd(II) and Ni(II) ions in urine and various food samples. A number of diverse methods were employed for characterization of the new nanosorbent. The design of experiments approach and response surface methodology were applied to monitor and find the parameters that affect the extraction performance. After sorption and elution steps, the concentrations of target analytes were measured by employing FAAS. The highest extraction performance was achieved under the following experimental conditions: pH, 5.8; sorption time, 6.0 min; $GO@Fe_3O_4@QTA$ amount, 17 mg; 2.4 mL $1.1mol\;L^{-l}$ $HNO_3$ solution as the eluent and elution time, 13.0 min. The detection limit is 0.02 and $0.2ng\;mL^{-1}$ for Cd(II), and Ni(II) ions, respectively. The accuracy of the new method was investigated by analyzing two certified reference materials (sea food mix, Seronorm LOT NO 2525 urine powder). The interfering study revealed that there are no interferences from commonly occurring ions on the extractability of target ions. Finally, the new method was satisfactorily employed for rapid extraction and determination of target ions in urine and various food samples.