• Journal of Nutrition and Health
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• 제37권8호
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• pp.645-654
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• 2004

This study examined the effect of excess calcium (Ca) on the iron (Fe) bioavailability and bone growth of marginally Fe deficient animals. Two groups of weanling female SD rats were fed either normal Fe (35 ppm) or Fe deficient diet (8 ppm) for 3 weeks. Then each group of animals were assigned randomly to one of three groups and were fed one of six experimental diets additionally for 4 weeks, containing normal (35 ppm) or low (15 ppm) Fe and one of three levels of Ca as normal (0.5%), high (1.0%), or excess (1.5%). Feces and urine were collected during the last 3 days of treatment. After sacrifice blood, organs, and femur bone were collected for analysis. Final body weight and average food intake were not affected by either the levels of dietary Ca or Fe. Low Fe diet significantly reduced the level of serum ferritin, however, for Hb, Hct, and TIBC no difference was shown than those in the normal Fe group. TIBC increased slightly by high and excess Ca intake in low Fe groups. For both normal and low Fe groups, high and excess Ca intakes reduced the apparent absorption of Fe and Fe contents of liver significantly (p < 0.05). Calcium contents in kidney and Femur of rats that were fed high and excess levels of Ca were significantly greater than those of normal Ca groups. However, weight, length, and breaking force of the bone were not affected by increased Ca intakes. Both in control and low Fe groups, high and excess intakes of Ca decreased the apparent absorption of Ca. These results indicate that the excess intakes of calcium than the normal needs would be undesirable for Fe bioavailability and that the adverse effects be more serious in marginally iron deficient growing animals. In addition bone growth and strength would not be favorably affected by high Ca intakes, though, the long term effect of increased Ca contents in bone requires further examination.

• 한국자기학회지
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• 제19권1호
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• pp.12-16
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• 2009

Z-Type 바리움 페라이트($Ba_{3}Co_{0.8}Zn_{1.2}Fe_{24}O_{41}$)를 공침법으로 제조하고 결정구조와 자기적 성질을 조사하였다. $Ba_{3+{\delta}}Co_{0.8}Zn_{1.2}Fe_{24}O_{41}$(${\delta}$ = 3, 5, 7, 13 wt%)와 $Ba_{3}Co_{0.8}Zn_{1.2}Fe_{{24}+{\delta}}O_{41}$(${\delta}$ = 5, 7, 10 wt%)의 조성을 가진 분말의 ${\delta}$ 값에 따른 자기적 성질의 변화를 조사하였다. 제조된 모든 바리움 페라이트에는 Z-type으로 상전이 하지 않은 M-type이 상당량 잔류하고 있었다. 포화자화는 Ba와 Fe의 과잉 첨가량 ${\delta}$가 각각 7 wt%와 5 wt% 일 때 최대로 나타났고 보자력은 조사된 모든 분말에서 다소 높게 나타났다. 높은 보자력은 M-type이 잔류하기 때문이다. 과잉의 Ba와 Fe 첨가에 따른 결정구조의 변화는 없었다. Z-type 바리움 페라이트의 연자성 특성을 향상시키기 위해서는 M-type이 Z-type 형성온도에서 상전이가 일어나도록 해야 함을 알았다.

• 한국세라믹학회지
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• 제34권11호
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• pp.1159-1164
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• 1997

Magnetite(Fe3O4) powders were synthesized through glycothermal reaction by using crystalline $\alpha$-FeOOH as precursor and ethyleanne glycol as solvent. The phase, morphology and particle size of synthesized powders were characterized by XRD and an SEM. When only ethylene glycol was used as solvent, the phase was transformed from $\alpha$-FeOOH to $\alpha$-Fe2O3 and finally Fe3O4 at 27$0^{\circ}C$ for 6hr without morphological change. But by addition of water, Fe3O4 powders were synthesized at 23$0^{\circ}C$ for 3hr through solution-recrystalization process. As the content of water addition increased, the particle shape changed from sphere to octahedron and the partcle size increased. When the excess amount of water added, residual $\alpha$-FeOOH or $\alpha$-Fe2O3 was recrystalized.

• Journal of Magnetics
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• 제14권1호
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• pp.7-10
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• 2009

In this work, we studied the effects of Sn addition on the ordering temperature of FePt thin film. The coercivity of FePtSn film was about 1000 Oe greater than the coercivity of FePt film for an annealing temperature of $600^{\circ}C$. Therefore, Sn addition was effective in promoting the $L1_0$ ordering and in reducing the ordering temperature of the FePt film. From our X-ray diffraction results, we found that in the as-deposited film, the addition of Sn induced a lattice expansion in disordered FePt thin films. After the annealing process, the excess Sn diffuses out from the ordered FePt thin film because of the difference in the solid solubility of Sn between the disordered and ordered phases. The existence of precipitates of Sn from the FePt lattice was deduced by Curie temperature measurements of the FePt and FePtSn films. Therefore, the key role played by the addition of Sn to the FePt film can be explained by a reduction in the activation energy for the $L1_0$ order-disorder transformation of FePt which originates from the high internal stress in the disordered phase induced by the supersaturated Sn atoms.

• Journal of Korean Society for Atmospheric Environment
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• 제15권E호
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• pp.9-16
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• 1999

This study has been focused on NO conversion for metal-incorporated silicates(Fe-silicate, Mn-silicate, and Fe-Mn-bimetallosilicate) with a similar MFI type. Used metallosilicates were prepared by the rapid crystallization method. Their catalytic performance for the conversion of NO under excess O2(10%) condition with the addition of hydrocarbon of low concentration(1,100ppm n-C8H18) were investigated. As a result, the NO conversion on the Fe-Mn-bimetallosilicate was enhanced compared with on the Fe- or Mn-silicates. Furthermore, the performances for NO concentration on Fe-Mn-bimetallosilicate more increased with an increased in n-C8H18 concentration, a decrease in NO concentration, and an increase in O2 concentration.

• 한국환경과학회지
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• 제9권1호
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• pp.43-47
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• 2000

A study on the remediation of heavily for ion contaminated soils from abandoned iron mine was carried out, using ex-situ extraction process. Also, oxalic acid as a complex agent was evaluated as a function of concentration, reaction time and mixing ratio of washing agent in order to evaluate Fe removability of the soil contaminated from the abandoned iron mine. Oxalic acid showed a better extraction performance than 0.1N-HCl, i.e., the concentrations of Fe ion extracted from the abandoned mine for the former at uncontrolled pH and the latter were 1,750 ppm and 1,079 ppm, respectively. The optimum washing condition of oxalic acid was in the ratio of 1:5 and 1:10 between soil and acid solution during l hr reaction. The total concentrations of Fe ion by oxalic acid and EDTA at three repeated extraction, were 4,554 ppm and 864 ppm, respectively. The recovery of Fe ions from washing solution was achieved, forming hydroxide precipitation and metal sulfide under excess of calcium hydroxide and sodium sulfide. In addition, the amounted of sodium sulfide and calcium hydroxide for the optimal revovery of Fe were 15g/$\ell$ and 5g/$\ell$ from the oxalic acid complexes, respectively.

• 한국대기환경학회지
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• 제14권1호
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• pp.25-33
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• 1998

We have studied the reduction of NO by propane over perovskite-type oxides prepared by malic acid method. The catalysts were modified to enhance the activity by substitution by substitution of metal into A or B site of perovskite oxides. In addition, the reaction conditions, such as temperature, $O_2$ concentration, space velocity have been studed. In the $LaCoO_3$ type catalyst, the partial substitution of Ba, Sr into A site enhanced the catalytic activity in the reduction of NO. In the $La_{0.6}Sr_{0.4}Co_{1-x}Fe_xO_3(x=0 \sim 1.9)$ catalyst, the partial substitution of Fe into B site enhanced the conversion of NO, but excess amount of Fe decreased the conversion of NO. The surface area and catalytic activity of perovskite catalysts prepared by malic acid method showed higher values than those of solid reaction method. In the $La_{0.6}Sr_{0.4}Co_{1-x}Fe_xO_3$ catalyst, the conversion of NO increased with increasing $O_2$ concentration and contact time. The introduction of water into reactant feed decreased the catalytic activity.

• 한국재료학회지
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• 제10권1호
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• pp.34-40
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• 2000

디지털형 압전/전왜 액츄에이터 응용을 위하여 상경계(반강유전상/강유전상) 조성인 $Pb_{0.94}Y_{0.04}[(Zr_0.6Sn_0.4)_{0.915}Ti_0.085]O_3$ (PYZST) 계를 택하여 과잉 PbO의 첨가량 및 소결 조건 변화에 따른 상전이 특성, 유전 특성 및 전기장 유기변형 특성을 연구하였다. 사방정 구조를 갖는 PYZST 세라믹스에서 과잉 PbO 첨가에 따른 결정구조의 변화는 거의 확인되지 않았으나, 소결 후 입자가 약간 작아지며 둥근 형태로 변화하였고 첨가량 증가에 따라 적정 소결온도는 감소하였다. 과잉 PbO의 첨가량이 증가함에 따라, 분극측정시 반강유전상이 보다 안정되는 경향을 보였고, 전계유도변형 측정시 인가전기장 제거상태에서의 변형의 형상기억성이 감소하고 디지털형 변형곡선 특성이 강화되었다. 또한 최대 유전상수와 전계 유기변형량은 감소하였으나 반면 상전이(반강유전상$\leftrightarrow$강유전상) 전기장 및 비저항은 증가하는 경향을 나타냈다. 이러한 결과는 과잉으로 첨가된 PbO에 의한 격자 결함반응 및 분역벽 이동 거동 가능성과 연관시켜 설명하였다.

• 한국세라믹학회지
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• 제53권2호
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• pp.162-166
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• 2016

0.75BF-0.25BT ceramics were prepared by sintering at $980-1040^{\circ}C$ in air or under atmosphere powder. A sample with 1 mole %-excess $Bi_2O_3$ was also prepared to compensate for $Bi_2O_3$-evaporation. Physical and piezoelectric properties of these three samples were compared. When the sintering temperature increased from $980^{\circ}C$ to $1040^{\circ}C$, the density of the sample sintered in air decreased continuously due to Bi-evaporation. Due to the suppression of Bi-evaporation, the sample sintered under atmosphere powder had a higher density at sintering temperatures above $1000^{\circ}C$ than did the sample sintered in air. The addition of 1 mole %-excess $Bi_2O_3$ successfully compensated for Bi-evaporation and kept the density at the higher value until $1020^{\circ}C$. Grain size increased continuously when the sintering temperature increased from 980 to $1040^{\circ}C$, irrespective of the sintering atmosphere. When the sintering temperature increased, the piezoelectric constant ($d_{33}$) and the electromechanical coupling factor ($k_p$) increased for all samples. The sample with 1 mole % excess-$Bi_2O_3$ showed the highest density and the best piezoelectric properties at sintering temperature of $1020^{\circ}C$.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• 제4권2호
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• pp.95-102
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• 2000

Methane combustion over perovskite-type oxides prepared using the malic acid method was investigated. To enhance the catalytic activity, the perovskite oxides were modified by the substitution of metal into their A or B site. In addition, the reaction conditions, such as the temperature, space velocity, and partial pressure of the methane were varied to understand their effect on the catalytic performance. With the LaCoO3-type catalyst, the partial substitution of Sr or Ba into site A enhanced the catalytic activity in the methane combustion. With the LaBO3(B=Co, Fe, Mn, Cu)-type catalyst, the catalytic activities were exhibited in the order of Co>Fe Mn>Cu. Futhermore, the partial substitution of Co into site B enhanced the catalytic activity, whereas an excess amount of Co decreased the activity. The surface area and catalytic activity of the perovskite catalysts prepared using the malic acid method showed higher values than those prepared using the solid reaction method. The catalytic activity was enhanced with decreased methane concentration and with a decrease in the space velocity.