• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.343-344
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• 2008

A surface micromachined uncooled microbolometer based on the amorphous silicon was designed, fabricated, and characterized. We designed the microbolometer with a pixel size of $44\times44{\mu}m^2$ and a fill factor of about 50 % ~ 70% by considering such important factors as the thermal conductance, thermal time constant, the temperature coefficient of resistance, and device resistance. Also, we successfully fabricated the microbolometer by using surface MEMS technology. Finally, we investigated responsivity and detectivity properties depends on the active area size.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.32A no.1
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• pp.129-137
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• 1995

AlGaAs/GaAs HBTs have been fabricated using SABM (Self-Aligned Base Metal) process technique. The mesa type HBTs were fabricated through following steps: isolation implant, wet etching, metal lift-off, and airbridge interconnection process. The fabricated HBTs with 2umx10um size emitter showed a common emitter current gain of 10 at a collector current density of Jk=100kA/cm$^{2}$, a breakdown volgate BVCEO of 8V, and the ideality factors of base and collector junctions of 1.6 and 1.1, respectively. On-wafer S-Parameter measurement at 0.5~18GHz has been made for the characterization of the common emitter HBTx with a 2umx10um size emitter. The extrapolated current gain cut-off frequency of ft=30GHz and maximum oscillation frequency of fmax=23 GHz were obtained at a collector current density of Jc=70kA/cm$^{2}$. Small signal HBT equivalent circuit was extracted from the S-Parameter data.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.3 s.234
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• pp.425-431
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• 2005

The efficiency of complex slurry preparation route for developing the high performance SiC matrix of $RS-SiC_{f}/SiC$ composites has been investigated. The green bodies for RS-SiC materials prior to the infiltration of molten silicon were prepared with various C/SiC complex slurries, which associated with both the sizes of starting SiC particles and the blending conditions of starting SiC and C particles. The characterization of Rs-SiC materials was examined by means of SEM, EDS and three point bending test. Based on the mechanical property-microstructure correlation, the process optimization is also discussed. The flexural strength of Rs-SiC materials greatly depended on the content of residual Si. The decrease of starting SiC particle size in the C/SiC complex slurry was effective for improving the flexural strength of RS-SiC materials.

• YAKHAK HOEJI
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• v.44 no.3
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• pp.251-256
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• 2000

Sterically stabilized liposomes (SSL) composed of distearoylphosphatidylcholine, cholesterol, dicetylphosphate and distearoylphosphatiodylethanolamine-N-poly(ethyleneglycol) 2000 (DSPE-PEG 2000) were made by reverse phase evaporation method to prolong biological half-life and decrease toxic side effect of drug. Streptozocin (572), a water-soluble antitumor agent with short half-life, was selected as a model drug. The size of SSL was controlled by polycarbonate extrusion to 100 nm which is adequate size for long circulation in plasma. The release rate of drugs from SSL in PBS was evaluated. And the stability of STZ-containing liposomes against drug leakage into rat plasma was evaluated in order to investigate the interaction of liposome and plasma protein. Incorporation of DSPE-PEG 2000 into conventional liposomes significantly decreased the drug leakage into rat plasma.

• Journal of the Korean Ceramic Society
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• v.27 no.2
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• pp.265-273
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• 1990

Fine Si-Al-OH-C coprecipitate powders were prepared from Si(OC2H5)4, Al(i-OC3H7)3, and carbon black by a hydrolysis method before fabrication of Sialon-SiC composite powder by carbothermal reduction at 1350$^{\circ}C$ for 10h under N2/H2 mixed atmosphere. The characterization of the synthesized Sialon-SiC composite powders was performed using XRD, BET, SEM, TEM and particle size analysis methods. The average particle size and specific surface area of the synthesized Sialon-SiC composite powder were 0.13$\mu\textrm{m}$ and 20.1㎡/g, respectively when Z=1 and N2 : H2=50 : 50.

• Journal of the Korean Ceramic Society
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• v.27 no.2
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• pp.274-282
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• 1990

SnO2 powder was prepared by hydroxide method and oxalate method. In hydroxide method, the pH dependence of powder characteristics was investigated by using buffer solution. As increasing the pH of solution, SnO2 powder size was decreased because nucleation rate was inctreased by more supersaturation of solution. Also, we found that the powder by our method has larger specific surface area in comaprison with other method. And the degree of agglomeration of precipitate with the change of precipitation temperature was investigated in oxalate method. The SnC2O4 was angular shape precipitate, and the size of the SnC2O4 was increased with the increase of precipitation temperature in methanol solvent.

• Journal of the Korean Ceramic Society
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• v.47 no.4
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• pp.338-342
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• 2010

Co, $Fe_3O_4$ and Co/$Fe_3O_4$ nanoparticles were synthesized by a polyol process in order to develop their new applications and improve chemical, magnetic properties. The synthesis involved a polyol process using Fe, Co acetylacetonate as precursors and 1-2 hexadecanediol as the polyol. The synthesized $Fe_3O_4$ and Co/$Fe_3O_4$ nanocomposite particles were monodispersed and self arrayed ranging in size of 8~10 and 10~25 nm, respectively. The Co nanoparticle has a crystallite size of 10~40 nm. The synthesized nanoparticles were characterized by their structural, morphological, compositional and magnetic properties using TEM-EDS, XRD, and PPMS techniques.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.684-689
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• 2008

In this study, homogenization method combined with the effective interface model for the characterization of properties of the nanoparticulate composites is developed. In order to characterize particle size effect of nanocomposites, effective interface model has been developed. The application range of analytical micromechanics approach is limited because a simple analytical approach is valid only for simple and uniform geometry of fiber particles. Therefore this study focuses on the analysis of mechanical properties of the effect interface through the continuum homogenization method instead of using analytical micromechanics approach. Using the homogenization method, elastic stiffness properties of the effective interface are numerically evaluated and compared with the analytically obtained micromechanics solutions. The suggested homogenization method is expected to be applied to optimization problems for nanocomposite design.

• Korean Journal of Materials Research
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• v.15 no.6
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• pp.370-374
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• 2005

Doppler broadening spectrometer for positron annihilation experiment(DBPAS) has been used to characterize nano size defect structures in materials. DBPAS measures the concentration, spatial distribution, and size of open volume defects in the rare-earth intensifying screen materials. The screens were exposed by X-ray varying the exposed doses from 3, 6, 9, and 12 Gy with 6 W and 15 MV respectively and also irradiated by 37 MeV proton beams ranging from 0 to $10^{12}ptls$. The S parameter values increased as the exposed time and the energies increased, which indicated the defects were generated more. The S parameters of the samples with X-rays varied from 0.5098 to 0.5108, on the other hand, as proton beams varied from 0.4804 to 0.4821.

• Proceedings of the Korean Geotechical Society Conference
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• 1992.10a
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• pp.65-68
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• 1992

In characterizing a suspension, heterogenety is included onto the previous characterization using solids concentrations and flocculent characteristics, because of its importance in hydrodynamics. The mechanism of interface formation during the sedimentation of concentrated suspension (thickening) is investigated from a microcosm consisting of four particles in a same plane and a smaller particle below. The critical distances after shich interface forms are calculated as a function of particle size ratio when the small particle is located in the middle of the squre datermined by the large particles. The results shows that the critical separation distance increase as the size ratio approaches to one (homogeneous suspension). This conforms to the trend of existing observations that homogeneous suspensions create the solid-liquid interface at much lower concentration (at al larger separation distance) that the heterogeneous suspensions.