• 한국세라믹학회지
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• 제35권2호
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• pp.107-114
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• 1998

ZnO powder as phosphor was prepared by precipitation method with zinc acetate and ammonia solution and the size and shapes of precipitates were examined with variation of pH and concentration of solution. Its cathodoluminesence properties was evaluated with various heat tratment condition. Optimum con-dition for uniform precipitates was 11.8 of pH and 0.4M of concentration. ZnO:Zn phosphor was obtained by heat treatment of precipitates in reduction atmosphere using ZnS powder. With addition of 20wt% ZnS and 1 hour firing at 1000$^{\circ}C$ the highest cathodoluminescence was obtained.

• 자원리싸이클링
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• 제30권6호
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• pp.36-42
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• 2021

폐리튬이온배터리에 함유된 유가금속을 회수하기 위해 고온에서 용융환원처리한다. 용융환원된 금속상을 염산용액으로 침출한 다음 용매추출과 침전으로 유가금속을 분리한 여과액에는 니켈(II)과 미량의 규소(IV)가 함유되어 있다. 여액으로부터 고순도 니켈화합물을 회수하기 위해 흡착법에 의한 규소(IV)의 분리와 니켈(II)의 선택적 침전에 대해 조사했다. Polyacrylamide는 규소(IV)를 선택적으로 흡착했으나 용액의 점도 역시 증가하여 여과가 어렵다. 침전제로 탄산나트륨을 첨가하면 니켈(II)과 미량의 규소(IV)가 공침되었다. 반면 옥살산나트륨은 상온에서 니켈(II)만을 선택적으로 침전시켜 순도 99.99% 이상의 니켈옥살산염 결정상을 회수할 수 있었다.

• 자원리싸이클링
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• 제1권1호
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• pp.58-68
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• 1992

아연을 함유하고 있는 산업폐기물로부터 첨단산업의 소재원료인 미립의 고순도 ZnO 분말을 아연제련의 용매추출 공정에서 직접 합성할 수 있는 방법을 개발하고자 하였다. 아연 함량이 55%인 선재산업의 폐기물을 황산으로 침출하여 아연을 추출하였다. 함아연 용액에서 철분을 침전시켜 제거한 후 D2EHPA를 추출제로 사용하는 용매추출에 의해 아연이온을 유기상으로 추출하여 정제한 뒤 oxalic acid와 같은 침전제를 사용하여 유기상의 아연 이온을 precipitation stripping 법으로 탈거, 침전시켜 $ZnC_2O_4$ 분말을 합성하였으며 이를 해소하여 99.9% 이상의 ZnO 분말을 제조하였다. 황산농도, 침출시간, 황액농도가 아연의 침출율에 미치는 영향과 용매추출시 용액의 산도에 따른 아연과 불순물의 추출거동을 조사하여 최적정제조건을 얻었다. 또한 oxalic acid의 농도, 온도, 계면활성제의첨가, 침전시간 등이 생성된 $ZnC_2O_4$ 분말의 형상과 입자크기 및 분포에 미치는 영향에 대해 조사하였다.

• 한국표면공학회지
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• 제4권1호
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• pp.5-15
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• 1971

"Rapid Determination of Boric Acid in Nickel Plating Solution" by the addition of Na$_2$C$_2$O$_4$ and thus preventing the precipitation of i(OH)$_2$ during titiration , has previously been reported. In this paper, the exact amount of glycerine and the complexing possibility of oxalate with nickel has been determined by measn of conductivity titrations. This experimental work has been supported by the mathematical application of the Debye-Huckel and mass action equitions as well as statistical analysis. The results were ; (1) Fro determining boric acid in nickel plating solution, 20 ml of 400ml/ι glycerine was sufficient, since 97% of the H$_3$BO$_3$ was dissoicated by this addition. (2) In the absence of Na$_2$C$_2$O$_4$ the continious precipitation of Ni(OH)$_2$ during titration with NaOH even past end -point for boric acid determination resulted in considerable anlaytical error. (3) In the presence of Na$_2$C$_2$O$_4$ during titration , Ni++ combined with C$_2$O$_4$-to form NiC$_2$O$_4$. The solution with this precititate of very fine, colloidal , trantsparent particles, remained quite clear for approximately 2 hours. Therefore it was shown that the presence of Na$_2$C$_2$O$_4$ prevents the formation of gross Ni(OH)$_2$ precititation by forming NiC$_2$O$_4$ instead of a complex salt with Ni++ , which did not interfere with the visible determination of the end point for boric acid with NaOH titation. This observous may be interpreted in the light of the previously published solubility ratio for NiC$_2$O$_4$ and Ni(OH)$_2$, 0.3mg/100g H$_2$O(25$^{\circ}C$), respectively. Precipitation of the less soluble , albeit transparent salt, NiC$_2$O$_4$ precluded therefore the precipitation of the Ni(OH)$_2$ salt.

• 한국재료학회지
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• 제30권9호
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• pp.474-479
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• 2020

The effect of precipitation and dissolution of Si on the thermal diffusivity in the Al-Si alloy system is reported in this study and solution heat treatment followed by aging treatment is carried out to determine the effects of heat treatment on the thermal characteristics. The solution treatment is performed at 535 ℃ for 4 and 10 h and then the specimens are cooled by rapid quenching. The samples are aged at 300 ℃ for 4 h to precipitate Si solute. The addition of 9 wt% silicon contents makes the thermal diffusivity decrease from 78 to 74 mm/s² in the cases of solid solution treated and quenched samples. After quenching and aging, the Si solute precipitates on the Al matrix and increases the thermal diffusivity compared with that after the quenched state. In particular, the increase of the thermal diffusivity is equal to 10 mm/s² without relation to the Si contents in the Al-Si alloy, which seems to corresponded to solute amount of Si 1 wt% in the Al matrix.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1998년도 추계학술대회
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• pp.231-232
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• 1998

The purpose of this study was to examine whether the precipitation of calcium phosphate on titanium surface was affected by surface modification. To improve the bone conductivity, of titanium, samples were devided into 4 groups. Group 1 was immersed in 5M-NaOH solution at $60^{\circ}C$ for 24 hours. Group 2 was immersed in 5M-NaOH solution at $60^{\circ}C $ for 24 hours and heat-treated at $600^{\circ}C$ for 1 hour. Group 3 was anodized in Hanks' solution at 1V, $25^{\circ}C$ for 1 hour. Group 4 was anodized in Hanks' solution at 5V, $80^{\circ}C$ for 5 minutes. And then, all specimens were immersed in the MEM Eagle's medium whose composition was similar to that of extracellular fluid for 30 days. The precipitation of the calcium phosphate on implant surface was increased by the immersion in the NaOH solution, and more highly accelerated by heat treatment at $600^{\circ}C$. The precipitation of the calcium phosphate on titanium implant was increased with the treatment of the anodic oxidation in Hanks' solution at 5V, $80^{\circ}C$.

• 한국세라믹학회지
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• 제35권6호
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• pp.559-568
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• 1998

Studies of preparation condition and characteristics of AUC(ammonium uranyl carbonate) were carried out to optimize AUC process with different reactor sizes and precipitation methos. As results four types of precipitates with different chemical compositions and morphologies were obtained from the reaction of {{{{ {(NH }_{4 }) { }_{2 } {CO }_{3 } }} with {{{{ {UO }_{2 }( {NO }_{3 }) { }_{2 } }} solution. A phase diagram has been made and crystal structure and chemical composition of each phase have been characterized by using SEM X-ray IR and thermal analysis. It was found that ammonium uranyl carbonate {{{{ {(NH }_{4 }) { }_{4 } {UO }_{2 } {(CO }_{3 }) { }_{3 } }} with monoclinic crystal morphology could be syn-thesized when the mole ratio of in {{{{ {(NH }_{4 }) { }_{2 } {CO }_{3 }/ {UO }_{2 } {(NO }_{3 }) { }_{2 } }} in the solution was higher than 5 Also a mechanism and a precipitating condition on rounding of the AUC particle were examined in the course of the AUC pre-cipitation. The rounding of the AUC particle was possible only by external circulation using pump not by internal circulation using agitator.

• 한국식품과학회지
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• 제26권6호
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• pp.683-689
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• 1994

With a view to utilizing effectively fish skin wastes from marine manufactory, a gelatin solution extracted from yellowfin sole skin was fractionated by precipitation with ethanol, and then the functional and physico-chemical properties for the fractionated gelatin were determined. Ethanol was added up to 50% of ethanol content to a gelatin solution extracted from yellowfin sole skin, then the mixture was left to stand at $0^{\circ}C$ for 12 hours. Finally, the precipitates were dried by hot-air ($40^{\circ}C$). The gel strength and melting point of a 10% gel of gelatin prepared from yellowfin sole skin by precipitation with ethanol has 322.4g and $23.3^{\circ}C$, respectively. The physico-chemical properties of the ethanol treated fish skin gelatin were superior to those of fish skin gelatin prepared without ethanol treatment. Besides, the functional properties of the ethanol treated gelatin were lower in solubility and higher in water holding capacity, oil binding capacity, emulsifying activity, emulsifying stability, foam expansion and foam stability than those of pork skin gelatin sold on market as well as gelatin prepared without ethanol treatment. It may be concluded, from these results, that the fish skin gelatin prepared by precipitation with ethanol can be effectively utilized as a human food by improving the functional properties.

• Geomechanics and Engineering
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• 제7권6호
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• pp.649-663
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• 2014

In past few years, the use of bacterial calcium carbonate precipitation (biocementation) has become popular as a ground improvement technique for sandy soil. However, this technique was not applied to organic soil. This study focused on bacterial calcium carbonate precipitation and its effect on permeability in organic soil. A special injection system was prepared for inducing bacterial solution to the samples. The bacterial solution supplied to the samples by gravity for 4 days in specific molds designed for this work. Calcite precipitation was observed by monitoring pH value and measuring amount of calcium carbonate. Change in the permeability was measured before and after biocementation. The test results showed that the pH values indicates that the treatment medium is appropriate for calcite precipitation, and amount of precipitated calcium carbonate in organic soil increased about 20% from untreated one. It was also found that the biocementation can be considered as an effective method for reducing permeability of organic soil. The results were supported by Scanning electron microscopy (SEM) analysis and energy-dispersive x-ray (EDX) analysis.

• 한국세라믹학회지
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• 제35권5호
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• pp.451-457
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• 1998

$Li_2$$ZrO_3$ powder which is one of the candidates of breeding materials for the fusion reactor was syn-thesized by a precipitation-combustion process. Although precipitates from the reaction between zirconium nitrate and citric acid were existed in a precursor solution. $Li_2$$ZrO_3$ could easily be obtained by using the mixed fuel of urea and citric acid in stoichiometric composition. The phases of as-synthesized powder con-sisted of $Li_2$$ZrO_3$ and small amounts of $Li_6$$Zr_2O_3$ and $Li_2$$ZrO_3$ The latter phases disappeared after the cal-cination at $1100^{\circ}C$ for 2 h. The primary particle size and the specific surface area of as-synthesized powders were smaller than 20nm and 10-14 $M^2$/g, respectively. The primary particle size of the precipitation-combustion synthesized powders was affected by the size of precipitates present in a precursor solution.