• 한국농림기상학회:학술대회논문집
• /
• 한국농림기상학회 2018년도 하계 학술발표초록집
• /
• pp.79-79
• /
• 2018

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2006년도 춘계 학술발표회 논문집(II)
• /
• pp.433-436
• /
• 2006

This study is basic experiment for estimating influence of strength by curing temperature of concrete's heat of hydration and estimate relationship of compressive strength development by initial curing temperature factor, and then asume temperature factor which influence compressive strength development and for showing basic document of quality control. According to the result of managerial test pieces by the curing temperature factor high-curing temperature shows high strength on 3 day compare with low curing-temperature, shows higher strength than the piece of high curing temperature.

• 열처리공학회지
• /
• 제23권5호
• /
• pp.233-238
• /
• 2010

The phase transformations and the shape memory effect in In-rich Pb alloys and In rich-Sn alloys have been studied by means of X-ray diffractometry supplemented by metallographic observations. The alloys containing 12~15 at.%Pb transform from the ${\alpha}_2$ (fct) phase to the ${\alpha}_1$ (fct) phase by way of an intermediate phase (m phase) on cooling. The results of X-ray diffraction show that the metastable intermediate phase is observed both on cooling and heating, and has a face-centered orthorhombic (fco) structure. It is concluded that the ${\alpha}_1{\rightleftarrows}{\alpha}_2$ transformation is expressed by the ${\alpha}_1{\rightleftarrows}m{\rightleftarrows}{\alpha}_2$ transformation both on usual cooling and heating with the rate more than $8{\times}10^{-3}$ K/s. The $m{\rightleftarrows}{\alpha}_2$ transformation takes place with a mechanism involving macroscopic shear and are of diffusionless (martensitic) type. The temperature hysteresis in the two transformations is 10~13 K between the heating and cooling transformations. The alloys containing 0~11 at.%Sn are -phase solid solutions with a face centered tetragonal structure (c/a > 1) at room temperature, the axial ratio increasing continuously with tin content. The In-(11~15) at.%Sn alloys are mixtures of ${\alpha}$ and ${\beta}$ phases, the ${\beta}$ phase having a f. c. tetragonal structure (c/a < 1). The alloys containing more than 15 at.%Sn are ${\beta}$-phase solid solutions. The In-(12.9~15.0) at.%Sn alloys show a shape memory effect only when quenched to the temperature of liquid nitrogen, although their effect becomes weak and finally disappears after keeping at room temperature for a long time. The ${\beta}{\rightarrow}{\alpha}^{\prime}$ phase transformation is of the diffusionless (martensitic) type, and takes place between 330 K at 12.9 at.%Sn and 150 K at 14.5 at.%Sn. The hysteresis of transformation temperatures on heating and cooling is considerably large (29~40 K), depending on the composition. Both In-Pb and In-Sn alloys showed distinct the shape memory effects.

• 한국자기학회:학술대회 개요집
• /
• 한국자기학회 2004년도 동계학술연구발표회 논문개요집
• /
• pp.219-220
• /
• 2004

Superparamagnetic regions and magnetic anisotropic properties in randomly orientated Co nano dots(NDs) were investigated as a function of dot diameter, spacing, and density. The Co NDs were fabricated by intentionally exposing a laser source on ultra thin film. Various dot sizes are ultimately realized by changing laser power, scan condition, and intial film thickness. Magnetic hysteresis loops, angle-dependent magnetization, and temperature dependence magnetization of the Co NDs were measured with a superconducting quantum interference device. The analysis of magnetization and hysteresis loops was effectively used to determine superparamagnetic regions of the Co NDs. Up to now, the experimentally observed results repeal that room temperature superparamagnetic limit of our Co NDs was about 30 nm in diameter, with the confirmation of high resolution transmission electron microscope.

• 한국전기전자재료학회논문지
• /
• 제14권6호
• /
• pp.470-474
• /
• 2001

This paper describes the fabrication and characteristics of CrN thin-film type pressure sensors, in which the sensing elements were deposited on SuS. 630 diaphragm by DC reactive magnetron sputtering in an argon-nitride atmosphere(Ar-(10%)N$_2$). The optimized condition of CrN thin-film sensing elements was thickness range of 3500$\AA$ and annealing condition(300$\^{C}$, 3 hr) in Ar-10%N$_2$ deposition atmosphere. Under optimum conditions, the CrN thin-films for strain gauges is obtained a high resistivity, ρ=1147.65 $\mu$Ωcm, a low temperature coefficient of resistance, TCR=186ppm/$\^{C}$ and a high temporal stability with a good longitudinal, 11.17. The output sensitivity of fabricated CrN thin-film type pressure sensors is 2.36 mV/V, 4∼20nA and the maximum non-linearity is 0.4%FS and hysteresis is less than 0.2%FS.

• 한국주조공학회지
• /
• 제28권1호
• /
• pp.31-36
• /
• 2008

Ti-Ni-Cu alloys are very attractive shape memory alloys for applications as actuators because of a large transformation elongation and a small transformation hysteresis. Rapidly solidified Ti-Ni alloy ribbons have been known to have the shape memory effect and superelasticity superior to the alloy ingots fabricated by conventional casting. In this study, solidification structures and shape memory characteristics of $Ti-Ni_{30}-Cu_{20}$ alloy ribbons prepared by melt spinning were investigated by means of DSC and XRD. Operating parameters to fabricate the amorphous ribbons were the wheel velocity of 55 m/s and the melt spinning temperature of $1500^{\circ}C$. The crystallization temperature was measured to be $440^{\circ}C$. The crystallized ribbons exhibited very fine microstructure after annealing at $440^{\circ}C$ for 10 minutes and $460^{\circ}C$ for 5 minutes and was deformed up to about 6.8% and 6.23% in ductile manner, respectively. Stress-strain curve of the ribbon exhibited a flat stress-plateau at 64 MPa and this is associated with the stress-induced a B2-B19 martensitic transformation. During cycle deformation with the applied stress of 220 MPa, transformation hysteresis and elongation associated with the B2-B19 transformation were observed to be $4.3^{\circ}C$ and 3.6%.

• 한국세라믹학회지
• /
• 제52권3호
• /
• pp.209-214
• /
• 2015

Silicon nitride films were deposited at $100^{\circ}C$ by using the catalytic chemical vapor deposition technique. The source gas mixing ratio, $R_N=[NH_3]/[SiH_4]$, was varied from 10 to 30, and the hydrogen dilution ratio, $R_H=[H_2]/[SiH_4]$, was varied from 20 to 100. The breakdown field strength reached a maximum value at $R_N=20$ and $R_H=20$, whereas the resistivity decreased in the same sample. The relative permittivity had a positive correlation with the breakdown field strength. The capacitance-voltage threshold curve showed an asymmetric hysteresis loop, which became more squared as $R_H$ increased. The width of the hysteresis window showed a negative correlation with the slope of the transition region, implying that the combined effect of $R_N$ and $R_H$ overides the interface defects while creating charge storage sites in the bulk region.

• 한국세라믹학회지
• /
• 제35권10호
• /
• pp.1061-1069
• /
• 1998

The thermal instability of Al2TiO5 Ceramics was contrlled by solid solution with MgO SiO2 and ZrO2 through electrofusion in an arc furnace. The thermal expansion properties of Al2TiO5 composites show the hysteresis due to the strong anisotropy of The crystal axes of these material. These phenomena are ex-plained by the opening and closing of microcracks. The difference in microcracking temperatures e.g 587.6(ATG2), 405.9(ATG3) and 519.7$^{\circ}C$(ATG4) is caused by the difference in grain size and stabilizer type. The thermal shock behaviour under cyclic conditions between 750-1400-75$0^{\circ}C$ show no change in mi-crostructure and phase assemblage for all three stabilized specimens. After the thermal loading test at 110$0^{\circ}C$ for 100hrs. ATG1 and ATG2 materials decomposes completely to its components corundum and ru-tile in both cases. However with approximatelly 20% retention of the Al2TiO5 Thus in order to prevent decomposition of the stabilized material in the critical temperature range 800-130$0^{\circ}C$ it must be traversed within a short period of time.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 1999년도 추계학술대회 논문집
• /
• pp.136-139
• /
• 1999

The post-annealing treatments on RF (Radio Frequency) magnetron sputtered PZI(Pb$\_$1.05/(Zr$\_$0.52/, Ti$\_$0.48/)O$_3$thin films(4000${\AA}$) have been investigated. for a structure of PZT/Pt/Ti/SiO$_2$/Si Crystallization pproperties of PZT films were strongly dependent on RTA(Rapid Thermal Annealing) annealing temperature. We were able to obtain a perovskite structure of PZT at a low temperature of 600$^{\circ}C$. P-E curves of Pd/PZT/Pt capacitor annealed at 700$^{\circ}C$ demonstrate typical hysteresis loops. The measured values of P$\_$r/, E$\_$c/, by post annealed at 700$^{\circ}C$ were 12.1 ${\mu}$C/$\textrm{cm}^2$, 120KV/cm respectively.

• Bulletin of the Korean Chemical Society
• /
• 제16권10호
• /
• pp.934-938
• /
• 1995

A series of solid solutions in the Ca2AlxFe2-xO5 (x=0.00, 0.50, 0.66, 1.00 and 1.34) system with brownmillerite structure has been synthesized at 1100 ℃ under an atmospheric air pressure. The solid solutions are analysed by powder x-ray diffraction analysis, Mohr salt titration, thermal analysis, and Mossbauer spectroscopic analysis. The x-ray diffraction analysis assigns the compositions of x=0.00 and 0.50 to the space group Pcmn and those of x=0.66, 1.00, and 1.34 to the Ibm2. Mo&ssbauer spectra have shown the coordination state and disordering of Al3+ and Fe3+ ions. The substituting preference of Al3+ ions for the tetrahedral site decreases with increasing x value. Magnetic susceptibility of the system has been measured in the temperature range of 5 K to 900 K. The solid solutions of the compositions of x=0.00, 0.50 and 0.66 have shown a thermal hysteresis and the thermoremanent magnetization gap decreases with increasing x value in the above systems. However the compositions of x=1.00 and 1.34 do not show the hysteresis. The exchange integral is calculated from Fe3+ ion occupancy ratio. The integral decreases with x value and thus the magnetic transition temperature decreases with the increasing x value.