• 대한전기학회논문지:전기물성ㆍ응용부문C
• /
• 제53권4호
• /
• pp.192-199
• /
• 2004

Elastic-factor of elastic epoxy were investigated by TMA (Thermomechanical Analysis), DMTA (Dynamic Mechanical Thermal Analysis), TGA (Thermogravimetric Analysis) and FESEM (Field Emission Scanning Electron Microscope) for structure-images analysis as toughness-investigation to improve brittleness of existing epoxy resin. A range of measurement temperature of the TMA and DMTA was changed from -20($^{\circ}C$) to $200^{\circ}(C)$, and TGA was changed from $0^{\circ}(C)$ to $600^{\circ}(C)$. Glass transition temperature (Tg) of elastic epoxy was measured through thermal analysis devices with the content of 0(phr), 20(phr) and 35(phr). Also, thermal expansion coefficient (a), high temperature, modulus and loss factor were investigated through TMA, TGA, and DMTA. In addition, the structure of specimens was analyzed through FESEM, and then elastic-factor of elastic epoxy was visually showed by FESEM. As thermal analysis results, 20(phr) was more excellent than 30(phr) thermally and mechanically. Specially, thermal expansion coefficient, high temperature, modulus, and damping properties were excellent. By structure-images analysis through FESEM, we found elastic-factor of elastic epoxy that is not existing epoxy, and proved high impact.

• Bulletin of the Korean Chemical Society
• /
• 제18권6호
• /
• pp.628-631
• /
• 1997

The preparation and characterization of $Co(dmppz)_2(3,6-dbq)_2$ (dmppz=1,4-dimethylpiperazine; 3,6-dbq=3,6-di-tert-butyl-1,2-quinone) are established. Temperature-dependent magnetic moments (100-400 K), variable-temperature IR, and electronic spectra are presented to show that the title complex exhibits an equilibrium via a catechol to cobalt intramolecular electron transfer. At temperatures below 350 K, the charge distribution of the complex is $Co^Ⅲ(dmppz)_2(3,6-dbsq)(3,6-dbcat)$ (3,6-dbsq=3,6-di-tert-butyl-1,2-semiquinonato; 3,6-dbcat=3,6-di-tert-butylcatecholato) whereas at the temperature beyond 390 K, the complex is predominantly Co^Ⅱ(dmppz)_2(3,6-dbsq)_2$ form in the solid state. At the temperature range of 350-390 K a mixture of Co(Ⅲ) and Co(Ⅱ) redox isomers exist at equilibrium. The transition temperature (Tc) of Co(Ⅲ)/Co(Ⅱ) in solution is approximately 50° lower than that in the solid state. In particular, thermal analysis on solid sample of the complex discloses that the transition for the Co(Ⅲ)/Co(Ⅱ) is accompanied by the change in heat content of 12.30 kcal/mol.

• Bulletin of the Korean Chemical Society
• /
• 제17권3호
• /
• pp.285-288
• /
• 1996

The electrical conductivity of some phthalimide derivatives and their complexes with Co(II), Ni(II), Cu(II), or Zn(II) has been measured in the temperature range 290-435 K. Both the structure of phthalimide molecule and its complexes played an effective role in the conduction process. Conductometric titration and IR spectra were used to characterize the structure of studied samples.

• 한국주조공학회지
• /
• 제22권5호
• /
• pp.252-256
• /
• 2002

Ni-Nb-Ti-Zr amorphous alloys were manufactured using melt-spinning methods. Amorphous formability, the supercooled liquid region before crystallization and mechanical properties were examined. The value of the reduced glass transition temperature and the supercooled liquid region of $Ni_{62}Nb_{10}Ti_{13}Zr_{15}$ alloy were relatively high and were 0.612 and 76 K respectively. However, amorphous bulk alloy rod was not formed using the Cu-mold die casting. The mechanical properties were in the range of $800{\sim}900DPN$ of hardness and $2.5{\sim}2.8$ GPa of tensile strength in the whole composition range.

• Environmental Analysis Health and Toxicology
• /
• 제22권2호통권57호
• /
• pp.177-184
• /
• 2007

Gaseous organochlorine pesticides (OCPs : heptachlor epoxide, p, p'-DDE, ${\gamma}-HCH,\;{\alpha}-chlordane,\;{\gamma}-chlordane$ and trans-nonachlor) concentration was measured using PUF high volume sampler from June, 2000 to June, 2002 in the semi-rural atmosphere. The OCPs concentration in atmosphere, which is estimated by the slope (m) of Clausius-Clapeyron equation and phase-transition energy $({\Delta}H)$, was influenced by revolatilization from environmental matrix (soil, water and tree leaves) and a long range transportation of air mass. But the former affected OCPs concentration more than the latter. The degradation rate constants (k) of OCPs calculated using multiple regression analysis and revised standard temperature method were in good agreement each other. The value of k of ${\gamma}-HCH$ was very low as -0.0007, but the range of k of other components were $-0.00l8{\sim}-0.0038$. The half-life $({\tau})$ which was calculated by k of ${\gamma}-HCH$ was 2.6 years-the longest one, but that of heptachlor epoxide was in 0.5 year-the shortest one. $({\tau})\;of\;{\alpha}-chlordane,\;{\gamma}-chlordane$ and trans-nonachlor in technical chlordane was 1.0, 1.1 and 0.7 year respectively.

• 한국주조공학회지
• /
• 제25권6호
• /
• pp.254-258
• /
• 2005

Semisolid process is possible in any material system possessing a freezing range where the microstructure should consist of the nondendritic globular solid phase separated and enclosed by the liquid phase, referred to as semisolid slurry. There are two primary semisolid processing routes, thixocasting and rheocasting. Especially, rheocasting process has become a new focus in the field of semisolid process because of its many advantages such as no special billet required and possibility of in-house scrap recycling, compared with the thixocasting process. In-Ladle direct thermal control (DTC) rheocasting has been developed, based on the fact that there is slurry and mush transition in every molten metal and the transition, which normally occurs in the range of liquid traction of 0.1 to 0.6, could be controlled by controlling solid shape and relative solid-liquid interfacial energy. In this study, A356 Al alloy was investigated to verify In-Ladle DTC rheocasting for obtaining semisolid slurry. Modeling of heat transfer was carried out to investigate the effect of pouring temperature and ladle material, geometry and temperature and the simulation results were compared with the actual experiments.

• 한국세라믹학회지
• /
• 제27권7호
• /
• pp.841-850
• /
• 1990

The electrical conductivity of SrTiO3 thick films, which has been prepared by screen printing and sintering on polycrystalline Al2O3 substrates, was determined as a function of oxygen partial pressure and temperature. The data showed that electrical conductivity was proportional to the -1/4th power of the oxygen partial pressure for the oxygen partial pressure range from 10-4-10-8 to 10-20 atm and proportional to Po2+1/4 for the oxygen partial pressure range from 10-6-10-4 to 1atm. And then n-p transition region of electrical conductivity moved to lower oxygen partial pressure region as the sintering temperature of thick film specimens increased under about 140$0^{\circ}C$. These data were consistent with the presence of small amounts of acceptor impurities in SrTiO3 thick film which have been diffused from Al2O3 substrate in the range of solid solubility limit.

• 소성∙가공
• /
• 제13권3호
• /
• pp.290-295
• /
• 2004

Mircolens and microlens V-groove are realized using a novel fabrication technology based on the exposure of a resist, usually PMMA, to deep X-rays and subsequent thermal treatment and inclined deep X-ray lithography, respectively. The fabrication technology is very simple and produces microlenses and microlens V-groove with good surface roughness of several nm. The molecular weight and glass transition temperature of PMMA is reduced when it is irradiated with deep X-rays. The microlenses were produced through the effects of volume change, surface tension, and reflow during thermal treatment of irradiated PMMA. Microlenses were produced with diameters ranging from 30 to $1500\mu\textrm{m}$. The surface X-ray mask is also fabricated to realize microlens arrays on PMMA sheet with a large area. The size of the micro V-groove is fabricated in the range of 12~$60\mu\textrm{m}$.

• 한국조명전기설비학회:학술대회논문집
• /
• 한국조명전기설비학회 1991년도 추계학술발표회논문집
• /
• pp.18-22
• /
• 1991

Far Infrared radiators should have functionality to convert thermal energy into electron wave. In order to apply the Far Infrared to the substance, the absorption characteristics of the substance should be considered. In this paper, interrelation of emissivity with emission energy according to temperature in the range of 2.5$\mu$m to 25$\mu$m after the transition element oxides (MnO2, Fe2O3, CuO, Co3O4) of first grade reagent were molded in press, then they were calcinated in 1050˚C, and they were used as samples.

• 한국조명전기설비학회지:조명전기설비
• /
• 제9권6호
• /
• pp.32-40
• /
• 1995

Far Infrared radiators should have functionality to convert thermal energy into an electromagnetic wave. In order to apply the Far Infrared to the substance, the absorption characteristics of the substance should be considered. In this paper, interrelation of emissivity with emission energy according to temperature in the range of [$2.5\mu\textrm{m}$] to 25[$\mu\textrm{m}$] after the transition element oxides (MnO2, Fe2O3, CuO, Co3O4) of first grade reagent were molded in press, then they were sintered in [$1050^{\circ}C$], and they were used as samples.