• Journal of the Korean institute of surface engineering
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• v.50 no.2
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• pp.72-84
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• 2017

In this work, electrophoretic paint (E-paint) was deposited on AZ31 Mg alloy after four different surface pretreatments: knife abrading, SiC paper abrading, deionized (DI) water immersion and NaOH immersion. The deposition process of E-paint was studied by analyses of voltage-time and current-time curves, amount of deposited paint, current efficiency and surface oxide film resistance and the adhesion of E-paint was examined by tape test before and after immersion in DI water for 500 h at $40$^{\circ}C$. It was found that the induction time for the deposition, the amount of deposited paint and the current efficiency are inversely proportional to the resistances of surface films prepared by different surface pretreatment methods. The electrophoretic painting showed longer inductance time, larger amount of deposited paint and higher current efficiency on the highly conducting surfaces, such as knife-abraded and SiC-abraded surfaces than on the less conducting surfaces, such as DI water-immersed and NaOH-immersed samples. Excellent adhesion was observed on the E-paintings deposited onto knife-abraded and SiC-abraded AZ31 Mg alloy samplesSiC-abraded AZ31 Mg alloy samples.

• Nuclear Engineering and Technology
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• v.55 no.8
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• pp.2879-2888
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• 2023

In fusion environments, large scales of helium (He) atoms are produced by a radical transformation along with structural damage in structural materials, resulting in material swelling and degradation of physical properties. To understand its irradiation effects, this paper investigates the stability, electronic structure, energetics, charge density distribution, PDOS and TDOS, and diffusion processes of He impurities in 6HSiC materials. The formation energy indicates that a stable, favorable position for interstitial He is the HR site with the lowest energy of 2.40 eV. In terms of vacancy, the He atom initially prefers to substitute at pre-existing Si vacancy than C vacancy due to lower substitution energy. The minimum energy paths (MEPs) with migration energy barriers are also calculated for He impurity by interstitial and vacancy-mediated diffusion. Based on its calculated energy barriers, the most possible diffusion path includes the exchange of interstitial and vacancy sites with effective migration energies ranging from 0.101 eV to 1.0 eV. Our calculation provides a better understanding of the stabilization and diffusion behaviors of He impurities in 6H-SiC materials.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.2
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• pp.101-106
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• 2009

In this paper, Thin films of $HfO_2$/Hf were deposited on p-type wafer by Atomic Layer Deposition (ALD). We studied the electrical and material characteristics of $HfO_2$/Hf/Si MOS capacitor depending on thickness of Hf metal layer. $HfO_2$ films were deposited using TEMAH and $O_3$ at $350^{\circ}C$. Samples were then annealed using furnace heating to $500^{\circ}C$. Round-type MOS capacitors have been fabricated on Si substrates with $2000\;{\AA}$-thick Pt top electrodes. The composition rate of the dielectric material was analyzed using TEM (Transmission Electron Microscopy), XRD (X-ray Diffraction) and XPS (X-ray Photoelectron Spectroscopy). Also the capacitance-voltage (C-V), conductance-voltage (G-V), and current-voltage (I-V) characteristics were measured. We calculated the density of oxide trap charges and interface trap charges in our MOS device. At the interface between $HfO_2$ and Si, both Hf-Si and Hf-Si-O bonds were observed, instead of Si-O bond. The sandwiched Hf metal layer suppressed the growing of $SiO_x$ layer so that $HfSi_xO_y$ layer was achieved. And finally, the generation of both oxide trap charge and interface trap charge in $HfO_2$ film was reduced effectively by using Hf metal layer.

• Journal of the Korean Ceramic Society
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• v.39 no.5
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• pp.452-459
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• 2002

This paper addresses the hydrothermal reactivity of blast furnace slag and fly ash with lime, respectively. The test conditions were CaO-to-$SiO_2$ ratio (C/S), autoclaving temperature ($140{\circ}C$ and $180{\circ}C$) and time (20 to 60h). The study was carried out in terms of the hydrothermal reactivity between $SiO_2$ contained in each hydraulic material and (pure) lime and the compressive strength of autoclaved specimens. Porosity measurement and the XRD analysis were also made in order to ascertain the hydraulicity of the siliceous materials. Compressive strength of the specimens was interpreted in terms of porosity and the reactivity of CaO and $SiO_2$. And the XRD analysis showed the C/S change of the hydrates in the course of autoclaving process. $SiO_2$ in the blast furnace slag was more reactive with CaO than that in the fly ash and consequently the blast furnace slag specimens resulted in much higher compressive strength. A maximum compressive strength of $807kg/cm^2$ was obtained for the blast furnace slag at the autoclaving condition of $180{\circ}C$ and 40 h, while only $397kg/cm^2$ was maximally to achieve with fly ash.

• Journal of the Korean Ceramic Society
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• v.23 no.1
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• pp.51-59
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• 1986

It was the first time the MgO-C brick was developed for the lining materials in the hot spots in electric are furnace in 1972. MgO-C brick is high registant to thermal and structural spalling. Futhermore for the reason that carbon is hard to react with slag and MgO is high fireproof MgO-C brick shows a high corrosion registance to slag attack compared with conventional basic refractories. Owing to their excellent properties the use of MgO-C refractories are being developed widely in the field of shaped refractories and even in that of monolithic refractories. In this paper the oxidation of carbon the infiltration of slag into the brick texture and effects of additions were investigated. The results obtained were as follows : 1) The use of fused MgO-clinker and high purity carbon as raw materials increased the corosion registance and hot modulus of rupture of MgO-C brick. 2) As the oxidation reaction of the carbon proceeded the slag infiltrated into the brick texture. And then the slag components reacted with the MgO grains and formed low melting point compounds particulary CaO.MgO.$SiO_2$ and 3CaO.MgO.$2SiO_2$ that resulted in the wear of the brick. 3) It is recongnized the Al, Si, $B_3C$ effects on the oxidation registant properties of MgO-C brick by contribu-ting to the decrease of permeability according to the formation of $Al_4C_3$, SiC, $B_2O_3$ and the decrease of open pores relating to the formation of MgO.Al2O3, $SiO_2$, 3MgO.$B_2O_3$ at the decarbonized layer.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07a
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• pp.160-163
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• 2003

This paper describes on anodic bonding characteristics of MLCA(Multi Layer Ceramic Actuator) to Si-wafer using evaporated Pyrex #7740 glass thin-films for MEMS applications. Pyrex #7740 glass thin-films with same properties were deposited on MLCA under optimum RF magneto conditions(Ar 100 %, input power $1\;/cm^2$). After annealing in $450^{\circ}C$ for 1 hr, the anodic bonding of MLCA to Si-wafer was successfully performed at 600 V, $400^{\circ}C$ in - 760 mmHg. Then, the MLCA/Si bonded interface and fabricated Si diaphragm deflection characteristics were analyzed through the actuation test. It is possible to control with accurate deflection of Si diaphragm according to its geometries and its maximum non-linearity is 0.05-008 %FS. Moreover, any damages or separation of MICA/Si bonded interfaces do not occur during actuation test. Therefore, it is expected that anodic bonding technology of MICA/Si wafers could be usefully applied for the fabrication process of high-performance piezoelectric MEMS devices.

• Journal of Sensor Science and Technology
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• v.15 no.1
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• pp.53-57
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• 2006

This paper describes a novel processing technique for fabrication of polymer-derived SiCN (silicone carbonitride) microstructures for super-temperature MEMS applications. PDMS (polydimethylsiloxane) mold is fabricated on SU-8 photoresist using standard UV photolithographic process. Liquid precursor is injected into the PDMS mold. Finally, solid polymer structure is cross-linked using HIP (hot isostatic pressure) at $400^{\circ}C$, 205 bar. Optimum pyrolysis and annealing conditions are determined to form a ceramic microstructure capable of withstanding over $1400^{\circ}C$. The fabricated SiCN ceramic microstructure has excellent characteristics, such as shear strength (15.2 N), insulation resistance ($2.163{\times}10^{14}{\Omega}$) and BDV (min. 1.2 kV) under optimum process condition. These fabricated SiCN ceramic microstructures have greater electric and physical characteristics than bulk Si wafer. The fabricated SiCN microstructures would be applied for supertemperature MEMS applications such as heat exchanger and combustion chamber.

• Journal of the Korean Vacuum Society
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• v.19 no.3
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• pp.230-235
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• 2010

In this paper, we controlled the deposition rate and reflective index with process conditions that are TCP power, gas flow ratio and bias for optical properties of $SiO_2$ thin film using TCP-CVD equipment. We obtained a excellent $SiO_2$ thin film which has a excellent uniformity (<1 [%]), deposition rate (0.28 [${\mu}m$/ min]) and reflective index (1.4610-1.4621) within 4" wafer with process conditions ($SiH_4:O_2$=50 : 100 [sccm], TCP power 1 [kW], bias 200 [W]) at [$300^{\circ}C$].

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.53 no.2
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• pp.103-108
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• 2004

This paper shows the simulation of electric field distribution and removal characteristics of Escherichia coli for water discharge tube with globular $SiO_2$. At the experiments of the removing Escherichia coli used the discharge tube with globular dielectric($SiO_2$), because the electric field is increased when applied voltage is increased, the removed ratio of Escherichia coli was related with increasing of applied voltage. When a passing number of test water in water discharge tube is increased, the removed ratio of Escherichia coli is increased because passing number of territory with electric field is increased. When diameter of globular dielectric($SiO_2$) is increased, the removed time of Escherichia coli was decreased because electric field for dielectric polarization of globular dielectric($SiO_2$) was increased. Also, the removed ratio of Escherichia coli of the water discharge tube with globular dielectric($SiO_2$) was measured higher than the removal ratio of the discharge tube without globular dielectric($SiO_2$)

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.187-187
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• 2007

This paper presents the electrical properties of SiGe HBTs designed with bottom collector and single metal layer structure for RF power amplifier. Base layer was formed with graded-SiGe/Si structures and the collector place to the bottom of the device. Bottom collector and single metal layer structures could significantly simplify the fabrication process. We studied about the influence of SiGe base thickness, number of emitter fingers and temperature dependence (< $200^{\circ}C$) on electrical properties. The feasible application in 1~2GHz frequency from measured data $BV_{CEO}$ ~10V, $f_r$~14 GHz, ${\beta\simeq}110$, NF~1 dB using packaged SiGe HBTs. We will discuss the temperature dependent current flow through the e-b, b-c junctions to understand stability and performance of the device.