The effect of Cu content on hydrogen reduction behavior of ball-milled -CuO nanocomposite powders was investigated. Hydrogen reduction behavior and reduction percent() of nanopowders were characterized by thermogravimetry (TG) and hygrometry measurements. Activation energy for hydrogen reduction of nanopowders with different Cu content was calculated at each heating rate and reduction percent(). The activation energy for reduction of obtained in this study existed in the ranging from 129 to 139 kJ/mol, which was in accordance with the activation energy for powder reduction of conventional micron-sized

We manufactured the metal hydrides of using a very easy and cheap way that Ti-12%Mg blending powder was mechanically milled with liquid milling media such as isopropyl alcohol (, containing oxygen) and hexane (, no oxygen) as hydrogen source. The synthesized in isopropyl alcohol contained the high oxygen of 11.2%, while one in hexane had the low oxygen content of 0.7%. Such a difference of oxygen content affected the dehydriding behavior, phase transformation, and microstructural evolution at high temperature, which was investigated through X-ray diffraction and DSC measurements, and electron microscope observations

Ultrasonic-milling of metal oxide nanopowders for the preparation of tungsten heavy alloys was investigated. Milling time was selected as a process variable. XRD results of metal oxide nanopowders ultrasonic-milled for 50 and 100h showed that mean crystallite size reduced with increasing milling time and there was no evidence of contamination or change of composition by impurities. It was found that nanocomposite powders reduced at in atmosphere had a composition of 93.1W-4.9Ni-2.0Fe by EDX analysis. Hardness of sintered samples of 50 and 100h was 390 and 463 Hv, respectively, which corresponds to the hardness of commercial products.

Magnetic properties of nanostructured materials are affected by the microstructures such as grain size (or particle size), internal strain and crystal structure. Thus, it is necessary to study the synthesis of nanostructured materials to make significant improvements in their magnetic properties. In this study, nanostructured Fe-20at.%Co and Fe-50at.%Co alloy powders were prepared by hydrogen reduction from the two oxide powder mixtures, and . Furthermore, the effect of microstructure on the magnetic properties of hydrogen reduced Fe-Co alloy powders was examined using XRD, SEM, TEM, and VSM.

This studies were carried out in summer season to increase high temperature tolerance using hydrogen peroxide treatments on cucumber in greenhouse. The water stress of cucumber in greenhouse by the hydrogen peroxide treatments showed as control〉250 mM〉500 mM treatments in order. The photosynthesis rate of cucumber at 30℃ did not show difference with each hydrogen peroxide treatment in temperature controlled greenhouse. However, the photosynthesis rate of cucumber in the control and hydrogen peroxide treatments at 40℃ was significantly different. The photosynthesis rate of cucumber in combined treatment with 1,000 mg·L-1 CO2 supply and hydrogen peroxide was also higher than control, however, there was no different of photosynthesis in 250 mM and 500 mM treatment. The value of Fv/Fm and Fm/Fo of chlorophyll fluorescent in 500 mM hydrogen peroxide treatment at 40℃ was highest. Also the activity of POD, the antioxidant enzyme, was higher with high hydrogen peroxide concentration than the other treatments. The high temperature limits for growth were 43℃ in the control, 44℃ in the 250 mM and 46℃ in the 500 mM according to analyze chlorophyll fluorescent Fo. The high temperature tolerance in cucumber increased approximately 3℃ by the hydrogen peroxide treatments under this experiment conditions.

We have calculated 2448 interstellar cloud models to investigate the formation and destruction of high rotational level H2 according to the combinations of five physical conditions: the input UV intensity, the H2 column density, cloud temperature, total density, and the H2 formation rate efficiency. The models include the populations of all the accessible states of H2 with the rotational quantum number J < 16 as a function of depth through the model clouds, and assume that the abundance of H2 is in a steady state governed primarily by the rate of formation on the grain surfaces and the rates of destruction by spontaneous fluorescent dissociation following absorption in the Lyman and Werner band systems. The high rotational levels J = 4 and J = 5 are both populated by direct formation into these levels of newly created molecules, and by pumping from J = 0 and J = 1, respectively The model results show that the high rotational level ratio N(4)/N(0) is proportional to the incident UV intensity, and is inversely proportional to the H2 molecular fraction, as predicted in theory.

We present measurements of interstellar H2 absorption lines in the continuum spectra of 54 early-type stars in the Galactic disk and halo and 3 stars in the Magellanic Clouds. The data were obtained with the Berkeley Extreme and Far-Ultraviolet Spectrometer (BEFS), part of the ORFEUS telescope, which flew on the ORFEUS-SPAS I and II space-shuttle missions in 1993 and 1996, respectively. The spectra extend from the interstellar cutoff at 912＼AA to about 1200＼AA with a spectral resolution of ∼3000 and statistical signal-to-noise ratios between 10 and 65. Assuming a velocity profile derived from optical observations (when available), we model the column densities N(J) of the rotational levels J = 0 through 5 for each line of sight. Our data reproduce the relationships among molecular and total hydrogen column density, fractional molecular abundance, and reddening first seen in Copernicusobservations of nearby stars (Savage et al. 1977). The results show that most of these molecular clouds have H2 total column densities between 1015cm−2 and 1021cm−2, and kinetic temperatures from 21 K to 232 K, with average of 89 K, consistent with the result of Copernicus (Savage et al. 1977).

Carbonization products C1, C2, C3, C4 and C5 were prepared by the carbonization of date pit in limited air, at 500, 600, 700, 800 and 1000℃, respectively. C1-V-600, C3-V-600, C1-V-1000 and C3-V-1000 were prepared by thermal treatment of C1 and C3 under vacuum at 600 and 1000℃. The textural properties were determined from nitrogen adsorption at 77 K and from carbon dioxide adsorption at 298 K. The surface pH, the FTIR spectra and the acid and base neutralization capacities of some carbons were investigated. The amounts of surface oxygen were determined by out-gassing the carbon-oxygen groups on the surface as CO2 and CO. The adsorption of water vapor at 308 K on C1, C2, C3 and C4 was measured and the decomposition of H2O2 at 308 K was also investigated on C1, C2, C3, C4 and C5. The surface area and the total pore volume decreased with the rise of the carbonization temperature from 500 to 1000℃. The adsorption of water vapor is independent on the textural properties, while it is related to the amount of acidic carbon-oxygen groups on the surface. The catalytic activity of H2O2 decomposition does not depend on the textural properties, but directly related to the amount of basic carbon-oxygen complexes out-gassed as CO, at high temperatures.

이트리아 안정화 지르코니아(yttria stabilized zirconia, YSZ)를 전해질로 선정하여 소결조건에 따른 열적 안정성과 전기적인 특성을 분석하였다. SEM사진으로 소결온도가 증가할수록 입자가 커지므로 상대적으로 기공은 줄어드는 것을 보였고 입자크기에 따른 영향을 확인하였다. 전기적 특성을 알아보고자 2단자법(2-probe method)으로 800~1000℃의 오도에서 교류 임피던스 측정을 통하여 전해질 내의 저항과 전기전도도 측정으로 입자 내부 저항 및 전기적 성능을 평가하였다. 소결온도가 1400℃일 때 건식법과 습식법에서 밀도는 각각 6.13, 6.25 g/cm3이며, 상대밀도는 각각 98, 99%였다. 소결온도가 올라갈수록 저항은 낮아지고, 전도도는 커지는 것을 확인할 수 있으며, 건식 및 습식법으로 제작한 전해질의 전기전도도는 10000℃에서 각각 8.8×10-2,;11×10-2 S/cm이었다.

The hydrogen sorption speed of nanocrystalline and amorphous alloys was evaluated at room temperature. Nanocrystalline alloys of were prepared by planetary ball milling. The hydrogen sorption speed of nanocrystalline alloys was higher than that of the amorphous alloy. The enhanced sorption speed of nanocrystalline alloys was explained in terms of surface oxygen stability which has been known to retard the activation of amorphous alloys. The retardation can be reduced by formation of nanocrystals, which results in the observed increase in sorption properties