• Journal of the Korean Ceramic Society
• /
• v.38 no.5
• /
• pp.461-465
• /
• 2001

La$_{0.7}$Ca$_{0.3}$MnO$_3$분말은 공기중에서 하소온도와 시간의 변화에 따라 각각 용액연소법과 고상반응법을 이용하여 제조되었다. 조성 및 구조 특성을 XRD와 SEM으로부터 조사하였으며 소결성은 dilatometer에 의해 조사되었다. 또한 분말 특성은 BET에 의해 조사되었고 분말의 하소온도는 TG 분석으로부터 결정되었다. 하소온도 및 시간이 증가함에 따라 La$_{0.7}$Ca$_{0.3}$MnO$_3$상의 XRD peak가 증가하였는데, 고상반응법을 이용한 경우 100$0^{\circ}C$에서 24시간 동안 하소해서야 겨우 La$_{0.7}$Ca$_{0.3}$MnO$_3$의 단상을 얻을 수 있었으나 용액연소법을 이용한 경우, $650^{\circ}C$에서 30분 동안 하소함으로써 submicron 입자크기를 갖는 단상이면서 초미세한 La$_{0.7}$Ca$_{0.3}$MnO$_3$분말을 쉽게 얻을 수 있었다. 또한 용액연소법에 의해 제조된 다결정인 La$_{0.7}$Ca$_{0.3}$MnO$_3$분말은 49.44$m^2$/g 정도의 매우 큰 비표면적을 얻을 수 있었다. 이 값은 고상반응법에 의해 제조된 분말의 비표면적 보다 매우 컸으며 이와 같으 사실로 인해 용액연소법에 의해 제조된 분말의 소결온도를 낮출 수 있었다. 분말의 소결온도를 낮출 수 있었다.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.8 no.3
• /
• pp.508-512
• /
• 1998

The NTC thermistors were sintered by using microwave hybrid heating method at $1100^{\circ}C$~$1300^{\circ}C$ and those electrical properties were investigated. The obtained $B_{25^{\circ}C/85^{\circ}C}$ values from temperature dependence of electrical resisitivity were around 3100~3200 K which were almost the same values as conventionally sintered ones. Compared with conventional sintering process, this process could complete whole sintering process within 20 minutes. This the processing time and energy consumption could be reduced through this rapid heating by using microwave hybrid heating.t there were showed only two peaks, glycolide melting peak and lower molecular weight melting peak without lauryl alcohol. Conversion increased slowly with the reaction time up to 50 minutes, and then gave a sudden increase above that. The reaction time to disappear in glycolide melting peak during polymerization was shortened with the increase of lauryl alcohol content. Zero-shear viscosity of polyglycolic acid decreased with the increase of free acid content in glycolide.ssional energy and bending hysteresis increased. \circled3 Surface characteristics such as friction coefficient and thickness variation of highly shrinkage fabrics became relatively roughened state. \circled4 Since stiffened and roughened characteristics of highly shrinkage fabrics, drapabilities of them were significantly lowered. Additionally thermal insulation property of high shrinkage fabric was higher than that of low shrinkage fabric due to bulky and thickened feature. From the results, it is considered that the silk fabrics with high filling shrinkage have the good bulkiness and heat keeping properties and thus they have the suitable characteristics for high quality men's and women's formal garments.

• Journal of the Korean Ceramic Society
• /
• v.39 no.7
• /
• pp.669-674
• /
• 2002

Ni-Zn ferrite was sintered by microwave hybrid sintering method using microwave energy of 2.45 GHz, 700 W in the temperature range of 900$^{\circ}C$ ∼ 1070$^{\circ}C$. A high density (98%TD) Ni-Zn ferrite, added Bi$_2$O$_3$ and CuO, with a single phase was obtained by microwave sintering at 970$^{\circ}C$ for 15 min. All the sintered samples showed sintered density over 90% of TD. These results indicate that the processing time and energy consumption can be reduced significantly by microwave hybrid sintering method.

• Proceedings of the Korean Nuclear Society Conference
• /
• 1997.05b
• /
• pp.92-97
• /
• 1997

경수로용 전산코드인 ERAPCON2를 CANDU 핵연료의 거동에 사용하기 위하여 소결체-피복관틈새 열전도 모형과 소결체내 중성자속 분포 모형을 개조하였다. 기존의 CANDU핵연료 전산코드와 비교한 결과 CANDU핵연료의 열적거동 분석에 있어 거의 동일한 결과를 얻었다. 이를 사용하여 DUPIC 핵연료의 열적 거동특성을 알아보았다. 고용성 핵분열생성물에 의해 감소된 DUPIC 핵연료의 열전도도에 의하여 핵연료 중심부 온도가 증가됨을 알 수 있었다. 선출력 500W/cm에서 중심온도가 230-320K 정도 증가하였다. 따라서, DUPIC핵연료 설계에서 중심온도 증가에 대한 세밀한 분석이 요구된다.

• Korean Journal of Materials Research
• /
• v.8 no.1
• /
• pp.58-63
• /
• 1998

5-64.3mol% AI$_{2}$O$_{3}$를 함유하는 AIN(1wt% $Y_{2}$O$_{3}$)의 1650-190$0^{\circ}C$ 상압소결에 따른 치밀화 거동, 미세구조, 열전도도가 검토 되었다. XRD 분석결과, AION(5NIN \ulcorner9 AI$_{2}$O$_{3}$ ), 27R AIN다형, AIN이 소결체의 주상으로서 동정되었다. AI$_{2}$O$_{3}$ 의 함량이 증가할수록 소결체의 부피밀도는 증가 하였다. AION을 기지상으로 하는 물질($\geq$ 30mol% AI$_{2}$O$_{3}$ )인 경우는 175$0^{\circ}C$ 소결에서 최대의 부피밀도를 나타내었으며, AIN을 기지상으로 하는 경우(5mol% AI$_{2}$O$_{3}$ ) 는 소결온도가 증가할수록 밀도가 감소하였다. $Y_{2}$O$_{3}$의 존재하에서 주로 185$0^{\circ}C$이상에서 AI$_{2}$O$_{3}$ 와 AIN의 반응에 으해서 액상이 생성되었다. AION을 기지로 하는 물질의 치밀화는 주로 액상의생성 및 AION의 입성장에 의해서 지배되었으나, AIN을 기지로 하는 물질에 있어서는 1$650^{\circ}C$에서 액상이 생성되었고, 소결온도가 190$0^{\circ}C$까지 상승할 동안 AIN의 입성장은 크게 일어나지 않았다. AI$_{2}$O$_{3}$ 함량이 증가할수록 낮은 열도도를 갖는 다량의 AION 및 액상의 생성으로 인하여 소결체의열전도도는 감소 하였다. 5mol% AI$_{2}$O$_{3}$ 를 함유한 190$0^{\circ}C$ 소결체가 최대의 열전도도(77.9W/(m\ulcornerk))를 나타내었다.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.17 no.2
• /
• pp.75-81
• /
• 2007

Densification and grain growth have been investigated in 5 wt% $U_3O_8$ seeded $UO_2$ and compared with those of the common $UO_2$ pellet. $UO_2$ compacts and $U_3O_8$ seeded $UO_2$ compacts were sintered at $1300{\sim}1700^{\circ}C$ for 0 h to 4 h. Density and grain size of the sintered pellets were measured by the water immersion method and the image analyzer, respectively. The seeded pellet has a slightly lower density during the intermediate sintering stage. However, the difference of density between two pellets decreases to about 0.5%TD with increasing the sintering temperature. The grain size of the two pellets is similar until $1600^{\circ}C$ but that of the seeded pellet rapidly increases with increasing the sintering temperature.

• Applied Chemistry for Engineering
• /
• v.8 no.6
• /
• pp.1000-1005
• /
• 1997

The properties of ceramics by solid-state reaction with hydroxyapatite[$Ca_{10}(PO_4)_6(OH)_2$], which was isolated from tuna bone by wet milling process were investigated. The bulk density $2.93g/cm^3$ at $1350^{\circ}C$ was close to the calculated density $3.21g/cm^3$. On X-ray measurements, the major phases were identified as hydroxyapatite at below $1300^{\circ}C$, but the whitlockite [$Ca_3(PO_4)_2$] phases were appeared due to a decomposition of hydroxyapatite with temperature. The microstructures of sintering specimens were shown as small closed pores between grain boundaries. The mean bending strength of the sintered hydroxyapatite by solid-state reaction is about 58 MPa and this value is higher than that of the articular cartilage maximum strength, 40MPa.

• Membrane Journal
• /
• v.15 no.4
• /
• pp.349-354
• /
• 2005

YSZ (yttria-stabilized zirconia) determined with an electrolyte that analyzed thermal stability along sintering condition and an electric characteristic. As sintering temperature increases by SEM, grain grows and it showed that pore decreases relatively. and confirmed effect by grain size. It evaluated that particle internal resistance and electric performance by resistance in an electrolyte and electricity conductivity measurement through ac impedance measurement in temperature of $800\~1000^{\circ}C$ in 2-probe method In order to recognize an electric characteristic. In dry process and wet process, density was each 6.13, 6.25 $g/cm^3$ and the relative density was each 98, 99$\%$ when sintering condition is $1400^{\circ}C$.

• Journal of the Microelectronics and Packaging Society
• /
• v.9 no.4
• /
• pp.47-53
• /
• 2002

In this study, two different (NiCuZn)-ferrite which were fabricated by using ultra-fine powders synthesized by the wet processing and conventionally commercialized powder, were investigated and compared each other in terms of the low temperature sintering and electromagnetic properties. Composition of x and w in $(Ni_{0.4-x}Cu_xZn_{0.6})_{1+w}(Fe_2O_4)_{1-w}$ were controlled as 0.2 and 0.03, respectively. The sintering temperature were $900^{\circ}C$ for ultra-fine powders by way of initial heat treatment and $1150^{\circ}C$ for commercialized powders. The (NiCuZn)-ferrite by ultra-fine powders showed love. sintering temperature than that of commercialized powders by over $200^{\circ}C$, and excellent electromagnetic properties such as the quality factor which is a important factor in the multi-layered chip inductor. In addition, characteristics of B-H hysteresis, crystallinity, microstructure and powder morphology were analyzed by a vibrating sample method(VSM), x-ray diffractometer(XRD), transmission electron microscope (TEM) and scanning electron microscope(SEM).

• Proceedings of the Korean Ceranic Society Conference
• /
• 2000.04a
• /
• pp.42.2-42.2
• /
• 2000