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침전법에 의한 알루미나 분말제조 IV.ZrO₂의 분산에 의한 Al₂O₃/ZrO₂ 복합체의 제조 및 기계적 특성
홍기곤,이홍림,이형직,이호순 연세대학교 산업기술연구소 1992 논문집 Vol.24 No.2
In this study, a precipitation method, one of the most effective liquid phase reaction, was adopted in order to prepare high-tech Al₂O₃/ZrO₂ composite ceramics. Al₂(SO₄)₃·18H₂O, ZrOCl₂·8H₂O and YCl₃·6H₂O were used as starting materials and NH₄OH as a precipitation agent. Fine powders were prepared at optimum calcination condition. Sinterability of each fine powder and the effects of ZrO₂ on the grain size and mechanical properties of Al₂O₃ were investigated. The composition of Al₂O₃/ZrO₂ composites was fixed as Al₂O₃-15v/o ZrO₂(+3m/o Y₂O₃). The effect of MgO on the grain size of Al₂O₃ZrO₂ ceramics was also investigated.
반응소결 Sialon 및 Sialon 세라믹스의 제조와 재소결 특성
이홍림,이형직,이은복 연세대학교 산업기술연구소 1991 논문집 Vol.23 No.2
Sialon and Sialon-SiC ceramics were prepared by reaction sintering and post-sintering of powder mixture of Si, Al₂O₃, AIN, SiC, Y₂O₃. The powders were mixed to have the composition of Z=2. After nitridation, the specimens were post-sintered with powder bed. In the nitridation process Si was nitrided effectively by decreasing the amount of N2 below 1.0cc/sec. In the case of using passive powder bed, weight loss and β-Sialon were observed. On the contrary, when active powder beds were used, weight gain, β-Sialon and J-Sialon were observed. In active powder bed, higher strength and lower shrinkage were observed. Composition D, post-sintered in the SNSOC powder bed, has the largist strength of 332 MPa and the shrinkage of 6.2%.
Si₃N₄/SiC 복합체의 기계적 성질에 미치는 Y₂O₃-Al₂O₃계 소결조제의 영향
이홍림,서유석,이형직 연세대학교 산업기술연구소 1992 논문집 Vol.24 No.2
Si₃N₄/SiC composites were prepared by mixing Si₃N₄powder with SiC powders of 0, 10, 20, 30 vol%. To these composites were added the powders of Y₂O₃-Al₂O₃system as sintering aids. These samples were hot-pressed at 1850℃ for 60min under a pressure of 30 MPa in N₂. Some of the samples were annealed at 1400℃ for 4 hr under N₂ before the measurement of mechanical properties. β-Si₃N₄ phase is starting powder was all transformed to β-Sic phase remained unchanged. The fracture toughness of the composites increased more or less with the increase of SiC content. The room temperature strength decrease was observed around 10-30 vol% of SiC content. For the sample in which grain boundary crystallization occurred after annealing, fracture toughness increased while roon-temperature strength decreased.
이형직,송두규,권혁병,정해경,윤상옥,이형복,이홍림 국립7개대학공동논문집간행위원회 2003 공업기술연구 Vol.3 No.-
소결첨가제나 바인더를 넣지않고 만든 무첨가 PZT 분말 성형체를 플라즈마 소결-로 열처리 후의 미세조직의 변화, PbO의 거동 그리고 이에 따른 유전특성을 로소결한 경우와 비교하여 다음과 같은 결과를 얻었다. 플라즈마 소결-로 열처리로 만든 PZT 시편이 로 소결 시편과 비교하여 입성장이 크게 일어나지 않은 미세조직을 나타내었으며, 또한 균일한 Pb, Zr, Ti 성분분포를 보였다. 유전특성에 있어서는 1kHz에서 20%정도의 유전율의 향상을 얻을 수 있었으며 유전소실 또한 40%정도 낮출 수 있었다. 상기의 결과는 DC 플라즈마 소결법의 특징인 소결초기의 급속가열 효과와 PbO의 증발 억제 효과에 의한 것으로 고려된다. PZT powder compacts without additives and binder were processed by plasma sintering-furnace annealing. Microstructures, PbO behaviour and dielectric properties were investigated, and compared to the specimen obtained by furnace sintering. The specimen prepared by plasma sintering-furnace annealing showed more not only fine microstructures but also homogeneous pb, Zr, Ti composition distribution, and revealed 20% higher dielectric constant as well as 40% lower dielectric loss (measured at 1kHz). Above results might be considered to be caused by rapid heating effects, high temperature sintering effects and preventing effects of PbO evaporation characterized by dc plasma sintering.
전홍준,노승직 朝鮮大學校 附設 醫學硏究所 1983 The Medical Journal of Chosun University Vol.8 No.1
Because of this many types of retroperitoneal tumors and their rarity, information concerning the diagnosis, and treatment of a large series of these are of importance. This study is based on the clinical analysis of 12 patients with the retroperitoneal tumors experienced at Kwang-ju Christian Hospital during the period from 1975 to 1980 and review of literatures. The results were as follows ; 1. 58% of the retroperitoneal tumors are benign and 42%. of the tumors are malignant with a ratio of 1.4 benign to 1 malignant. 2. The age incidence of the retroperitoneal tumor revealed prevalence under the age of 10(58%) and beyond the age of 50(25%). The male to female ratio was 1:1. 3. In the majority of cases(75%), symptoms had been present for 1 year or less. The chief complaints in order of frequency were abdominal mass(84%), systemic manefestations(40%), and genitourinary symptoms (8%). 4. The positive physical findings were palpable abdominal mass(91%), abdominal distention(25%) and abdominal tenderness (9%). 5. Roentgenography, especially I.V.P. and upper G-I series was useful diagnostic procedures in retroperitoneal tumors. 6. Thc histilogical diagnosis of this series in order of frequency were teratoma, cyst, liposarcoma and neuroblastoma. 7. 66% of patients were treated wih curative resection, others were treated with biopsy or palliative resection with irradiation.
Mg 其他 複合材料의 强化材 量 및 分布에 따른 機械的性質特性
안선규,하홍수,김영직,임병수 成均館大學校 科學技術硏究所 1997 論文集 Vol.48 No.1
The effect of different SiC particle size and weight fraction in Mg/SiC particle MMC on the mechanical properties has been investigated. In this study, different particle sizes of 7㎛, 20㎛ and 50㎛ were prepared with various weight fraction of 10wt.%, 20wt.% and 30wt.% for sample preparation. By tension tests, the properties of ultimate tensile stress, yield stress and % elongation were observed and by tension-tension fatigue tests, whose procedures are standardized in ASTM standard 647E-93, the ΔK vs, da/dN curves were also obtained. Finally, the crack propagation paths were observed by optical microscope.
이형복,이홍림,이형직,임헌진 연세대학교 산업기술연구소 1985 논문집 Vol.17 No.2
Nitridation behavior of Hadong Pink Kaolin was studied over the temperature range of 1250-1350℃ in N₂-H₂atmosphere. Carbon was used as a reducing agent. Mullite, α-quartz, Si₂N₂O, X-phase, 15R-AIN, SiC and cristobalite were formed as intermediate products during reaction. But the final product was almost β-Sialon phase, when the reaction proceeded longer than 10hr at the C/H.K.(SiO₂) ratio larger than 3.
침전법에 의한 알루미나 분말제조 Ⅲ. 소결체의 열적·기계적 특성
임헌진,이홍림,이형직,홍기곤 연세대학교 산업기술연구소 1992 논문집 Vol.24 No.1
A precipitation method was adopted in order to prepare high-tech Al₂O₃ceramics. Al₂(SO₄)₃·18H₂O was used as a starting materials and alumimum hydroxides were obtained by single precipitation method at the pH condition 7 and 11, using NH₄OH as a precipitation agent. Fine Al₂O₃powders were prepared at optimum calcination condition and were sintered at 1650℃ for 4 h in air. Microstructures and mechhanical properties of Al₂O₃ceramics were investigated. Doped MgO limited the grain growth of Al₂O₃and increased grain size homogeneity of Al₂O₃Flexural stregth values were 340∼430 MPa. Critical temperature difference?? was 175 K showing rapid strength degradation by thermal shock.