• Bulletin of the Korean Chemical Society
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• v.24 no.12
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• pp.1785-1792
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• 2003

Zirconia modified with $MoO_3$ was prepared by impregnation of powdered $Zr(OH)_4$ with ammonium heptamolybdate aqueous solution followed by calcining in air at high temperature. Spectroscopic studies on prepared catalysts were performed by using FTIR, Raman, XRD, and DSC and by measuring surface area. Upon the addition of molybdenum oxide to zirconia up to 15 wt%, the specific surface area increased in proportion to the molybdate oxide content, while acidity measured by irreversible chemisorption of ammonia exhibited a maximum value at 3 wt% of $MoO_3$. Since the $ZrO_2$ stabilizes the molybdenum oxide species, for the samples equal to or less than 30 wt%, molybdenum oxide was well dispersed on the surface of zirconia and no phase of crystalline $MoO_3$ was observed at any calcination temperature above $400^{\circ}C$. The catalytic activities for cumene dealkylation were roughly correlated with the acidity of catalysts measured by ammonia chemisorption method, while the catalytic activities for 2-propanol dehydration were not correlated with the acidity because weak acid sites are necessary for the reaction.

• Korean Journal of Microbiology
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• v.6 no.1
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• pp.22-28
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• 1968

Chlorella ellipsoidea cells were cultured in an iron, copper, zinc, manganese, molybdenum or boron-free medium. Biosynthetic activities of nucleic acids, protein and phospholipid in chlorella cells, which were growing in a microelement deficient medium were compared with those of the normal cells by measuring the contents of phosphate, amino acids or UV-absorbing substances in the various cell fractions. When the algae were grown in a molybdenum-free medium, the amounts of phosphate in the acid-soluble fraction of the cells increased, whereas the amounts of alkali-stable protein and RNA decreased compared with the normal cells showing that the synthesis of protein and RNA from the early products of photosynthesis was inhibited. When the algae were grown in a boron-free medium, amounts of alkali-labile protein and phospholipid of the cells decreased, while the amount of phosphate in acid-soluble fraction increased compared with the normal cells showing that the biosynthesis of protein and phospholipid from the early products of photosynthesis was retarded. In general, amounts of protein and RNA in the microelement deficient cells significantly decreased compared with those of the normal cells. Phosphate content in the acid-soluble fraction of the algal cell grown in an zinc, copper, molybdenum, or boron-free medium increased considerably, whereas that of the algal cell grown in an iron or manganese-free medium decreased remarkably compared with that of the control. It is considered, therefore, that molybdenum, zinc, copper and boron etc. play an important role in the biosyntbesis of macromolecule from acid-soluble phosphate compounds, in contrast to the principal action of iron and manganese on the photosynthetic process itself.

• Particle and aerosol research
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• v.9 no.1
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• pp.31-36
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• 2013

In this study, Mo metal powder was prepared by hydrogen reduction of Mo trioxides with different purity of 2N and 3N grades. We have obtained Mo metal powder with oxygen content of 1450 ppm by hydrogen reduction and subsequent heat treatment for degassing. Using the Mo metal powder, a low-oxygen Mo ingot was prepared by repetitive vacuum arc melting. The oxygen content of the obtained Mo ingot was less than 70 ppm after vacuum arc melting for 30 min. The purity of the Mo metal powder and the ingot was evaluated using glow discharge mass spectrometry. The purity of the respective Mo ingots was increased to 3N and 4N grades from the Mo powder of 2N and 3N grades after the repetitive vacuum arc melting. The low oxygen Mo ingot thus can be used as a raw material for sputtering targets.

• Journal of the Korean Ceramic Society
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• v.22 no.6
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• pp.58-70
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• 1985

The bond strength of metal to ceramic sealing in Mo-Mn metallizing was investigated by examining the effects of flux composition in alumina ceramics particle size of molybdenum metal powder wet hydrogen atmosphere and temperature in metallizing. The maximum bond strength was obtained when the glass phase filled almost all the microstructural cavities around the interfacial area with few micropores. Such a favorable microstrcutre waas formed and maximum bond strength was observed between 130$0^{\circ}C$. Also the metal to ceramic bond strength was increased using finer molybdenum metal powder than coarse powder. When content of $SiO_2$ in the flux of alumina ceramics was constant metal to ceramic bond strength was improved with increasing the ratio of CaO to MgO in the flux.

• Journal of Korea Foundry Society
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• v.27 no.4
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• pp.159-166
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• 2007

Effects of alloying elements on the mechanical properties of 3.60wt%C-2.50wt%Si ductile cast iron with annealing and normalizing were investigated. Yield and tensile strengths were increased from 278 and 415 MPa to 316 and 440 MPa respectively as manganese content was increased upto 0.45wt% while elongation was decreased from 24.2 to 5.0%. The formers were increased and the latter was decreased with the increased amount of copper, molybdenum or nickel added. Meanwhile the tensile strength of annealed specimen was increased with the amount of alloying elements added, it was decreased by annealing. It was increased greatly by normalizing and the amount of alloying elements added except molybdenum.

• Korean Chemical Engineering Research
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• v.57 no.6
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• pp.891-897
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• 2019

In this study, heteropoly acid PVMo catalysts were supported on activated carbon with various composition of phosphoric acid ($H_3PO_4$), vanadium (V) pentoxide ($V_2O_5$) and molybdenum (VI) trioxide ($MoO_3$). Catalytic performance was examined at $140^{\circ}C$ for 1hour in vapor formaldehyde. XRD and BET analyses were carried with the catalysts before and after the reaction. Formaldehyde conversion was increased with decreasing Mo and $H_3PO_4$ content and increasing $V_2O_5$ content. Acidity of the catalysts was investigated with $NH_3-TPD$. Crystallinity of the catalysts was relatively low, and surface area was decreased after the reaction. In $NH_3-TPD$ result, the ratio of strong acid site corresponding to $NH_3$ desorption between $400^{\circ}C$ and $500^{\circ}C$ was increased by decreasing $MoO_3$ and $H_3PO_4$ content and increasing $V_2O_5$ content. Therefore, it was found that the strong acid site could affect the catalytic reactivity in vapor formaldehyde conversion.

• Korean Journal of Veterinary Research
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• v.39 no.3
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• pp.501-512
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• 1999

We analyzed the contents of 12 types of minerals such as calcium in muscle from various species. Thereafter we observed changes of the concentrations according to age, part and sex in major domestic animals. The concentrations of calcium, iron, sodium, potassium, magnesium and zinc were high respectively whilst the content of cobalt, chromium, copper, manganese, molybdenum and nickel were low respectively in the muscle. The concentration of calcium was high in duck and dog but low in pig and horse. Also high level of sodium content was detected in dog and the content of potassium, iron showed high level in horse compared with the content in other animals. In 6 types of microminerals as cobalt, the level of muscle were no more than 1 ppm showing very low content in all animal, but $2.99{\pm}0.85$ppm of copper in duck was an exceptional case. According to the age some species showed small range of variation centering on macrominerals and there was no remarkable change in microminerals. Distribution of minerals was different according to the part and the variation was very diverse compared with other factors such as age and sex. Additionally, the content of minerals in muscle was higher in female than in male chicken and duck. In conclusion, the difference of the content of minerals according to the species was mainly focused on macrominerals.

• Asian-Australasian Journal of Animal Sciences
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• v.12 no.3
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• pp.422-428
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• 1999

The mineral status of native goats and forage species, namely; Cynodon plectostachyus, Pennisetum purpureum. Eleusine indica, Cynodon dactylon, Calopogonium muconoides, Centrosema pubescens, Leucaena leococephala, and Mimosa pudica in lahar affected areas of Concepcion, Tarlac, Philippines were determined. Forage and blood samples were collected six times in 1996-97, and analyzed for calcium, phosphorus, magnesium, sulfur, copper, iron, molybdenum, selenium, and zinc. Forage calcium and sulfur are non-limiting. Most species had low phosphorus, copper and selenium, while some had magnesium and zinc levels lower than the critical limit because of low mineral content and high percolation rate of lahar deposits. Iron and molybdenum were in excess. The effect of seasonal variation was observed only in copper, sulfur and iron. Average blood mineral concentration of the animals was above critical limit, but there were no significant differences between seasons. All the animals had plasma phosphorus and magnesium above critical level; but 20 % had low copper, zinc and selenium especially in dry season possibly due to insufficient amount of these elements and excessive molybdenum and iron in most forage. Conversely, calcium in forage was high; but 40 % of the animals had low plasma calcium concentration. Although no clinical signs of mineral deficiencies were observed, supplemental feeding would be important since the condition of the pasture in lahar-laden areas is not expected to improve in the next five years. Intensified use of L. leucocephala with better mineral profile would be ideal.

• Journal of Electrical Engineering and Technology
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• v.12 no.6
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• pp.2348-2352
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• 2017

The electrical contact characteristics including temperature rise, contact resistance and arc erosion rate of the $Ag-SnO_2$ materials with increased $SnO_2$ content were investigated during the repeated make-and-break operations. The thickness of arcing melting layer reduces by half and the arc erosion rate decreases more than 70% under 10000 times operations at AC 10 A with the $SnO_2$ content increasing from 15 wt.% to 45 wt.%, on one hand, temperature rise and contact resistance increase obviously but could be reduced to the same order of conventional $Ag-SnO_2$ materials by increasing the contact force. The microstructure evolution and the effect of $SnO_2$ on the arc erosion, contact resistance were analyzed.

• Journal of Korea Foundry Society
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• v.18 no.5
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• pp.467-473
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• 1998

For enhancing the mechanical properties of LTE (low thermal expansion) cast steel, systematic researches have been carried out. The effects of alloying elements such as vanadium, molybdenum and carbon on the hardness and linear thermal expansion coefficient were investigated. In the range of $0.5{\sim}2.3\;wt%$ carbon, addition of 1.73 wt% carbon caused hardness increase due to the formation of eutectic carbide having high hardness but over the range of 1.73 wt% carbon, hardness was decreased. Thermal expansion coefficient increases with carbon contents. In the LTE cast steel containing 0.6 wt% carbon, hardness increased up to 1.96 wt% vanadium addition. But over the range of 1.96 wt% vanadium hardness was decreased by coarse eutectic carbide. Thermal expansion coefficient of LTE cast steel containing 0.6 wt%carbon moderately increased with increasing vanadium contents. There was no significant variation of hardness and thermal expansion coefficient according to molybdenum content in LTE cast steel.