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건식코팅장치를 이용하여 제조한 NH2-HNT를 충진재로 응용한 에폭시 복합체의 기계적 물성 향상
김문일 한국산업융합학회 2024 한국산업융합학회 논문집 Vol.27 No.2
Epoxy resins are widely used in various fields due to their high adhesion, mechanical strength, and solvent resistance. However, as the volume decreases during the hardening process and the cooling process after hardening, stress is generated and when an external force is applied, the brittle material exhibits destruction behavior. To complement this, research has been conducted using inorganic nanofillers such as halloysite nanotube(HNT). HNT has a nanotube structure with the chemical formula of Al2Si2O5(OH)4· nH2O and is a natural sediment of aluminosilicate. It has been used as additive to improve the mechanical properties of epoxy composites with exchange of amine group as a terminal functional group. In order to simplify complicated procedures of common wet method, a dry coating machine was designed and used for amine group exchange in previous research. In this study, they were applied as filler in epoxy composites, and mechanical properties such as tensile strength and flexural strength of composites were examined.
CeO2 안정화 정방정 Zirconia 다결정체(Ce-TZP)에 관한 연구(I) : CeO2 함량에 따른 Ce-TZP의 기계적 성질과 파괴거동의 변화
김문일,박정현,강대석,문성환 한국세라믹학회 1989 한국세라믹학회지 Vol.26 No.5
By using commercial zirconia powder CeO2-ZrO2 ceramics containing 8~16mol% CeO2 was made by heat treatment at 1350~155$0^{\circ}C$ for 1~10hr. The minimum amount of CeO2 for obtaining complete tetragonal phase was 12mol%, and in the tetragonal phase region fracture toughness of Ce-TZP was decreased with increasing CeO2 content and the maximum value was obtained when 12mol% CeO2 was added. The bending strength goes through maximum at 14mol% CeO2. Fracture mode of Ce-TZP transformed from intergranular to transgranular fracture with increasing CeO2 content, so the morphology of fracture surface of 16mol% Ce-TZP was wholly transgranular and this tendency was independent on grain size. The crystal structure of the 12mol% Ce-TZP was monoclinic with fringes along the grain boundaries which are lying in the particular plane from the TEM observation. The chemical composition of the sintered body was homogeneous as a whole and some amorphism or air pocket was observed at the triple junction.
CeO2 안정화 정방정 Zirconia 다결정체(Ce-TZP)에 관한 연구(IV) : 12 Ce-TZP 세라믹스에 미치는 MgO 첨가 영향
김문일,박정현,강대석,이현권,문성환 한국세라믹학회 1990 한국세라믹학회지 Vol.27 No.2
For theinvestigation of MgO addition effect on 12Ce-TZP ceramics, MgO-CeO2-ZrO2 ceramics was fabricated using commercial powders under sintering condition of 130$0^{\circ}C$-1$600^{\circ}C$ for 2hr. Fully tetragonal phase could be obtained by proper heat treatment and MgO addition amount. Minor cubic phase was appeared in relatively high MgO content composition at each sintering temperature. As alloying amount of MgO increased, tetragonal stability increased and grain size decreased. Grain size dependence on MgO content was verified by SEM observation of fractured surface. Surface bloating was observed from the 2 m/o to 6m/o in the temperature range of 150$0^{\circ}C$ to 1$600^{\circ}C$. In spite of very porous microstructure owing to surface bloating, 100% TZP could be maintained in 2.0m/o MgO composition by heat treatment of 150$0^{\circ}C$. This result indicated that MgO was more powerful stabilizer than CeO2. Mechanical proprties of MgO-CeO2-ZrO2 ceramics were consistent with the stability observation of tetragonal phase very well.
김문일,Kim Moon Il 대한화학회 1969 대한화학회지 Vol.13 No.2
The crystal structure of rubidium hydrogen carbonate has been determined by single crystal X-ray diffraction method. the crystals are monoclinic with a = 15.05 $\AA$, b = 5.83 $\AA$, c = 4.02 $\AA$, and $\beta$ = $107^{\circ}.$ There are four chemical units per unit cell and the space-group was fixed as $C2-C^3_2$. Patterson and trial-and-error methods gave the approximate structure and its refinements were made by two-dimentional Fourier summation. The Co3 group is planar with tshhe C-O distances of 1.32 $\AA$, 1.32 $\AA$, and 1.33 $\AA$ within experimental error and the two $CO_3$ groups are linked together to form a complex anion [$H_2C_2O_6$] with the O-H${\cdot}{\cdot}{\cdot}$O distance, 2.53 $\AA.$ Two molecules of $RbHCO_3$ make the dimer structure with two hydrogen bonds. The values of reliability factor for $F_{(hol)}$, $F_{(hko)}$and $F_{(okl)}$are 0.15, 0.15 and 0.17 respectively. Each rubidium ion has eight oxygen neighbours with the Rb-O distances of 2.84~3.11 $\AA.$.
김문일,유소민,김나희,이원아,함보영,송철호,이우균 한국환경생물학회 2017 환경생물 : 환경생물학회지 Vol.35 No.3
This manuscript describes the relationship between climate change and forest growth, forest species, carbon stocks, and tree mortality. 1) In the aspect of forest growth, the growth of major coniferous species, including Pinus densiflora, had a negative correlation with temperature. On the other hand, major deciduous oak species, including Quercus variabilis and Quercus mongolica, had a positive correlation with temperature. 2) When considered in the aspect of the forest species distribution, various models commonly showed a decrease in the distribution of coniferous species and an increase in oak species due to climate change in the medium to long term. 3) From the carbon stock perspective, there was a difference in the estimation according to the status of forest management. Most of Korean forests will mature to become over-matured forest after year 2030 and are estimated to produce approximately 410 million ton forest biomass until 2090 with the current cutting regulations for sustainable forest management announced by the Korean Forest Service. 4) In the forest mortality, the mortality rate of the major coniferous species showed a clear tendency to increase higher temperatures while it decreased for the oak species with no verification of statistical significance. Moreover, the mortality of the subalpine coniferous species was projected to progress rapidly. considering the overall impacts described above, there should be a management strategy for coniferous species that are relatively vulnerable to climate change. Moreover, a sustainable forest plan in the aspect of ecosystem services, carbon sequestration and storage, which is linked to global issues such as Sustainable Development Goals, ecosystem services and negative emission.
저합금강(STD61)의 2차경화 현상에 의한 초음파 특성
김문일,이인선 연세대학교 대학원 1985 延世論叢 Vol.21 No.4
This experimental study has been carried out in order to investigate the effect of the secondary hardening for the longitudinal ultrasonic attenuation in STD 61 steel. The measurement of ultrasonic attenuation and hardness testing were performed to the specimens which had been subjected to solution treatment and tempering. According to the results in this experiment, the attenuation in the longitudinal ultrasonic waves was decreased with temperature and its rate of change has maximum value for the temperature range of secondary hardening in those tempered microstructures. These experimental results were inferred that ultrasonic attenuation was affected by the strain due to coherent precipitate fine alloy carbides as well as elastic anisotropy in the tempered martensite