PVA 용액법을 통한 나노 Cu 분말합성 및 소결체의 열적 특성

오복현,마충일,이상진,Oh, Bok-Hyun,Ma, Chung-Il,Lee, Sang-Jin 한국재료학회 2020 한국재료학회지 Vol.30 No.2

Effective control of the heat generated from electronics and semiconductor devices requires a high thermal conductivity and a low thermal expansion coefficient appropriate for devices or modules. A method of reducing the thermal expansion coefficient of Cu has been suggested wherein a ceramic filler having a low thermal expansion coefficient is applied to Cu, which has high thermal conductivity. In this study, using pressureless sintering rather than costly pressure sintering, a polymer solution synthesis method was used to make nano-sized Cu powder for application to Cu matrix with an AlN filler. Due to the low sinterability, the sintered Cu prepared from commercial Cu powder included large pores inside the sintered bodies. A sintered Cu body with Zn, as a liquid phase sintering agent, was prepared by the polymer solution synthesis method for exclusion of pores, which affect thermal conductivity and thermal expansion. The pressureless sintered Cu bodies including Zn showed higher thermal conductivity (180 W/m·K) and lower thermal expansion coefficient (15.8×10^-6/℃) than did the monolithic synthesized Cu sintered body.

Control of particle morphology and size of yttria powder prepared by hydro(solvo)thermal synthesis

오복현,이상진 한국세라믹학회 2022 한국세라믹학회지 Vol.59 No.4

Yttria (Y 2 O 3 ) is a representative material having excellent plasma resistance, and yttria powder, applied to semiconductor components and thermal spray coating, requires excellent sinterability and fl owability, for which particle shape and size are important factors. In the present study, to synthesize yttria powder having various shape applicable to many industrial areas, the morphology of yttria particles was controlled through hydro(solvo)thermal synthesis. The yttria powder was synthesized using deionized water, ethylene glycol and glycerol as solvents. The precursor concentrations and the synthesis conditions such as synthesis temperature and time were examined. The particle shape and size of the yttria powder were adjusted to plate-type, rod-type and spherical-type depending on the applied solvent, precipitant and synthesis temperature. The thermal treatment following the hydro(solvo)thermal synthesis did not have a signifi cant eff ect on the shape of the yttria particles. Cubic single-phase yttria was observed at a calcination temperature of 450 °C or higher, and the crystal phase further devel- oped as the thermal treatment temperature increased. In the powder synthesized using deionized water, the crystal phase developed mostly on the [222] direction depending on the temperature during oriented attachment. On the other hand, in the powder synthesized using ethylene glycol and glycerol as a solvent, the crystal phase developed homogeneously in all crystalline directions.

Co₂O₃ 첨가가 알루미나의 액상소결 및 기계적 물성에 미치는 영향

오복현,윤태규,공헌,김남일,이상진 한국결정성장학회 2020 한국결정성장학회지 Vol.30 No.4

Alumina (Al₂O₃) is mainly used as a structural ceramic material and to have good mechanical properties requires a dense microstructure. In commercial fabrication, the liquid phase sintering process is adjusted to reduce the sintering temperature of alumina. In this study, the effect of added amounts of cobalt oxide as a coloring agent on the microstructureand mechanical properties was investigated in the CaO-SiO₂-MgO-system liquid phase sintering of 92 % alumina at various sintering temperatures. When 11 wt% Co₂O₃ was added, a rearrangement of alumina particles, which is the main densification step in liquid phase sintering, occurred from a sintering temperature of 1200°C. Solution re-precipitation and coalescence steps followed from 1300°C with the grain growth of alumina particles. The addition of excess Co₂O₃ and sintering temperatures above 1400°C resulted in a decrease in sintered density and Vickers hardness, because of the low viscosity of the liquid phase. In 92 % alumina with the addition of 11 wt% Co₂O₃, a sintered density and Vickers hardness of 3.86 g/cm³ and 12.32 GPa, respectively, were obtained at a sintering temperature of 1350°C. 구조용 세라믹재료로 주로 사용되는 알루미나(Al₂O₃)는 우수한 기계적 특성을 위해 치밀한 미세구조를 요구하며, 소결온도를 낮추기 위해 상업적으로 액상소결(liquid phase sintering)이 적용된다. 본 연구에서는 SiO₂, MgO, CaO를 액상소결 조제로 사용하는 92 % 상업용 알루미나의 액상소결 시, 착색제(coloring agent)로 주로 사용되는 산화코발트(Co₂O₃)의 첨가량과 다양한 소결온도가 알루미나의 미세구조 및 기계적 특성에 미치는 영향을 고찰하였다. 약 11 wt% 산화코발트첨가에 따라 1200°C부터 고상입자 재배열에 의한 수축이 시작되었고 1300°C 이상의 온도에서 용해 재석출 및 합체(coalescence)에 의한 알루미나의 결정립 성장이 관찰되었다. 1400°C 이상의 열처리 온도 혹은 과량의 Co₂O₃ 첨가는 액상의점도를 낮추어 소결밀도를 감소시켰고, 이와 함께 경도값도 감소하였다. 산화코발트를 11 wt% 첨가하여 1350°C에서 소결할경우, 3.86 g/cm³의 밀도와 12.32 GPa의 경도를 갖는 치밀한 소결체 제조가 가능하였다.

Thermal Properties of Copper Matrix-Ceramic Filler Composite Prepared by Polymer Solution Method

오복현,마충일,공헌,곽지연,이상진 대한금속·재료학회 2022 대한금속·재료학회지 Vol.60 No.1

A copper (Cu) metal-ceramic filler composite with high thermal conductivity and a suitable thermal expansion coefficient was designed for application as a high-performance heat dissipation material. The purpose of the designed material was to utilize the high thermal conductivity of Cu while lowering its high coefficient of thermal expansion by using a ceramic filler. In this study, a Cu-sol containing a certain amount of AlN or SiC ceramic filler was prepared using a non-aqueous solvent. A complex was produced by applying a PVB polymer to prepare a homogeneous precursor. The composite sintered without pressure in a reducing atmosphere showed low thermal conductivity due to residual pores, but the hot press sintered composite exhibited improved thermal conductivity. The Cu composite with 30 wt% AlN filler added exhibited a thermal conductivity of 290 W/m·K and a thermal expansion coefficient of 9.2 × 10-6/oC. Due to the pores in the composite, the thermal conductivity showed some difference from the theoretical value calculated from the rule of mixture. However, the thermal expansion coefficient did not show any significant difference.

적외선 렌즈용 BaO-GeO2-La2O3-ZnO-Sb2O3계 중금속 산화물 유리의 특성

박상진,오복현,이상진 한국재료학회 2023 한국재료학회지 Vol.33 No.10

Infrared radiation (IR) refers to the region of the electromagnetic radiation spectrum where wavelengths range from about 700 nm to 1 mm. Any object with a temperature above absolute zero (0 K) radiates in the infrared region, and a material that transmits radiant energy in the range of 0.74 to 1.4 um is referred to as a near-infrared optical material. Germanatebased glass is attracting attention as a glass material for infrared optical lenses because of its simple manufacturing process. With the recent development of the glass molding press (GMP) process, thermal imaging cameras using oxide-based infrared lenses can be easily mass-produced, expanding their uses. To improve the mechanical and optical properties of commercial materials consisting of ternary systems, germanate-based heavy metal oxide glasses were prepared using a melt-cooling method. The fabricated samples were evaluated for thermal, structural, and optical properties using DSC, XRD, and XRF, respectively. To derive a composition with high glass stability for lens applications, ZnO and Sb2O3 were substituted at 0, 1, 2, 3, and 4 mol%. The glass with 1 mol% added Sb2O3 was confirmed to have the optimal conditions, with an optical transmittance of 80 % or more, a glass transition temperature of 660 °C, a refractive index of 1.810, and a Vickers hardness of 558. The possibility of its application as an alternative infrared lens material to existing commercial materials capable of GMP processing was confirmed.

구형 단분산 실리카 분말을 이용한 SiOx 음극활물질 제조 및 형상조절 기술

권주찬,오복현,이상진 한국재료학회 2023 한국재료학회지 Vol.33 No.12

The theoretical capacity of silicon-based anode materials is more than 10 times higher than the capacity of graphite, so silicon can be used as an alternative to graphite anode materials. However, silicon has a much higher contraction and expansion rate due to lithiation of the anode material during the charge and discharge processes, compared to graphite anode materials, resulting in the pulverization of silicon particles during repeated charge and discharge. To compensate for the above issues, there is a growing interest in SiOx materials with a silica or carbon coating to minimize the expansion of the silicon. In this study, spherical silica (SiO2) was synthesized using TEOS as a starting material for the fabrication of such SiOx through heating in a reduction atmosphere. SiOx powder was produced by adding PVA as a carbon source and inducing the reduction of silica by the carbothermal reduction method. The ratio of TEOS to distilled water, the stirring time, and the amount of PVA added were adjusted to induce size and morphology, resulting in uniform nanosized spherical silica particles. For the reduction of the spherical monodisperse silica particles, a nitrogen gas atmosphere mixed with 5 % hydrogen was applied, and oxygen atoms in the silica were selectively removed by the carbothermal reduction method. The produced SiOx powder was characterized by FE-SEM to examine the morphology and size changes of the particles, and XPS and FT-IR were used to examine the x value (O/Si ratio) of the synthesized SiOx.

우리나라 化粧品産業의 마케팅經路戰略에 관한 硏究

朴允在,吳福炫 숭실대학교 1994 中小企業論文集 Vol.5 No.1

캠핑 가스버너 및 부탄 캔 사고원인 규명

이장우,김문택,오복현,조완수,김훈배,김대현 한국화재조사학회 2012 한국화재조사학회 학술대회 Vol.2012 No.1

가스보일러 PCB에 의한 CO중독 패턴 해석

이장우,김문택,오복현,조완수,김훈배,김대현 한국화재조사학회 2012 한국화재조사학회 학술대회 Vol.2012 No.1

접합용기의 파열로 인한 피해영향 분석에 관한 연구

이장우,김문택,오복현,여창훈,최충석 한국화재조사학회 2012 한국화재조사학회 학술대회 Vol.2012 No.1