• 아시안잔디학회지
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• 제6권1호
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• pp.23-28
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• 1992

Urea, the major N source of world agriculture involves a serious urea-N loss through NH$_3$volatilization. Approaches to decrease N loss include using urease inhibitors in view of the environmental protection and the increase of urea-N efficiency. The purpose of laboratory researches was toassess the potential value of urease inhibitors to increase urea-N efficiency in soil and Kentucky blue-grass(Poa Pratensis L.) turf. The activity of urease inhibitors Phenyiphosphorodiamjdate(ppD) and N-(n-butyl) thiophosphoric triamjde(NBPT) measured to break-down ammonia volatilization. The soil and turf used in this project were from the fairway in one of the Korean gof course. The researches were carried out for two weeks to measure the urease activities on urea hydrolysis under four temperatures (10~ 40$^{\circ}C$) and for one week on turfgrass using forced-draft system. Results indicated that Urea-N involves considerable loss through gaseous NH$_3$ by urease activities in plant-soil systems. Urease inhibitors PPD and NBPT have potential value for increasing N use efficiency by reduing NH$_3$ volatilization. NBPT deserves futher evaluation as fertilizer amendment than PPD use of urea in turf industries.

• 한국결정성장학회지
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• 제14권6호
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• pp.267-271
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• 2004

우레아 가수분해법을 이용하여 리튬이차전지용 $LiCoO_2$ 양극 분말을 합성하였다. Li/Co 몰비가 다르고 가수분해에 의해 얻어진 전구체는 다양한 온도에서 열처리되었다. 저온상 $LiCoO_2(LT-LiCoO_2)$와 고온상 $LiCoO_2(HT-LiCoO_2)$는 $500^{\circ}C$에서 2시간 열처리 후 합성되었고, 저온상에서 고온상으로 상전이는 $700^{\circ}C$ 이상에서 완전히 일어났다. 열처리 온도가 증가함에 따라 $LiCoO_2$의 층상구조가 잘 발달하였다. 충방전 실험결과 Li/Co의 몰비가 1.2이고 $800^{\circ}C$에서 열처리한 $LiCoO_2$의 초기용량이 152 mAh/g으로 높았으며, 40회 충.방전 후에는 9.2%의 용량감소를 나타내는 상대적으로 안정한 충방전 특성을 나타내었다.

• Applied Biological Chemistry
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• 제39권1호
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• pp.70-76
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• 1996

일련의 pyridylsulfonyl urea들을 합성하고 25%(v/v) 디옥산 수용액의 넓은 pH범위에서 가수분해 반응속도 상수를 측정하였다. pH-효과, 용매 효과($m{\ll}1,\;n{\ll}3$ 및 ${\mid}m{\mid}{\ll}{\mid}{\ell}{\mid}$), 일반 염기-효과, 산-해리상수(pKa, 3: 4.9 및 5: lit.4.6), 열역학적 활성화 파라미터(${\Delta}H^{\neq}=0.025\;Kcal.mol.^{-1}$ 및 ${\Delta}S^{\neq}=0.54{\sim}\;-2.19\;e.u.$) 및 생성물 분석 결과로부터 반응속도식을 유도하고 가수분해 반응 메카니즘을 제안하였다. 즉, 비(H)치환체, 1-(4,6-dimethoxypyrimidine-2-yl)-3-(2-pyridylsulfonyl) urea, 3은 산성용액에서 A-2형(또는 $A_{AC}2$)반응 그리고 염기성 용액 에서는 $(E_1)_{anion}$ 메카니즘으로 가수분해 반응이 일어난다. 반면에 trifluoromethyl-치환체, 1-(4,6-dimethoxypyrimidine-2-yl)-3-(3-trifluorornethyl-2-pyridylsulfonyl) urea, 5(Flazasulfuron)는 산성 용액중에서 $A-S_N2Ar$형의 반응으로 생성된 conjugate acid($5H^+$), 그리고 pH 9.0 이상에서는 $(E_1)_{anion}$ 및 $(E_1CB)_R$ 반응으로 생성된 conjugate base(CB)를 거쳐 산성 및 염기성 용액중에서 모두 5원자 고리 중간체를 경유하는 Smile 자리옮김 반응으로 산성에서는 3-trifluoromethyl-2-pyridylpyrimidinyl urea(PPU) 그리고 염기성에서는 3-trifluoromethyl-2-pyridyl-4,6-dimethoxy-pyrimidinyl amine(PPA)을 생성하는 가수분해 반응이 일어남을 알았으며 5는 3보다 약 3.5배 빠른 반응속도를 나타내었다.

• 한국토양비료학회지
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• 제31권4호
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• pp.392-399
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• 1998

본 연구에서는 합성 요소억제제나 질산화억제제와는 달리 쑥(Artemisia asiatica)과 같은 천연물에 의한 토양중 요소분해와 질산화작용에 대한 저해효과를 검토하고저 하였다. 이를 위 위하여 쑥의 열수추출액과 유기용매 분획추출물을 준비하여 밭토양에 처리하였고 2일, 5일 동안 배양후에 요소태질소와 암모늄태질소, 질산태 질소를 측정하고 요소분해균과 urease 효소활성에 대한 각 추출액과 분획추출물의 영향도 검토하였다. 이번 실험을 통하여 얻은 결과를 요약하면 다음과 같다. 쑥잎의 열수추출액은 요소분해를 미약한 수준으로 촉진하였으나 반면 질산화작용은 억제하였고, 쑥잎 열수추출액을 0.5ml, 3.0 ml를 가하였을 때 질산태 질소함량은 무처리구에 비하여 각각 65.2%, 68.8% 줄어들었다. 쑥잎의 유기용매 분획추출물 중, chloroform분획을 제외한 모든 분획물이 요소분해에 대해 저해효과를 나타내었고 chloroform/methanol 분획을 2.0 ml 가했을 때, 잔존한 요소태질소 함량은 무처리구의 5.8배로 요소분해억제효과가 가장 좋았다. 한편 유기용매 분획추출물들의 질산화작용 억제효과 유무는 불명확 하였다. urease activity의 경우, 요소분해율이 무처리구와 비교시 97.5%에서 99.50%로 높게 나타났기 때문에 분획물이 urease의 활성을 저해하지 않는 것으로 생각되었다. 요소분해 bacteria 수는, 쑥의 chloroform 분획을 처리한 경우를 제외하고 모든 처리에 의해 감소하였다 (적요 2의 결과와 일치). 이로서 요소분해 저해효과는 urease의 활성을 저해하기 보다는 요소분해균을 저해하기 때문에 나타나는 것으로 생각되었다. 각 추출물 성분에 대한 예비시험과 박층 chromatogram을 통해, 그 조성이 복잡하고 다양한 화합물들이 요소분해와 질산화작용 억제과정에 관여할 것으로 추측되며 이를 분획 또는 단일활성 물질을 추적하여 그 효과를 확인할 일이다.

• 공업화학
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• 제18권1호
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• pp.10-16
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• 2007

본 연구에서는 인체의 해로운 요소를 분해하고 분해 생성물인 암모니아($NH_3$)의 제거를 위한 우레아제 고정막 제조와 가수분해 특성에 관하여 검토되었다. 우레아제 고정막은 방사선 그라프트 중합법에 의해 다공성 중공사막에 음이온 교환기로서 DEA를 도입한 후 요소의 가수분해를 위해 우레아제를 고정시켜 제조하였다. 음이온 교환기가 도입된 막에 우레아제가 고정된 경우 그라프트율이 증가할수록 고정량이 증가하였다. 이것은 그라프트율이 증가할수록 그라프트 체인이 신장하여 단백질이 다층으로 고정되기 때문이다. 한편, 가교제의 첨가는 우레아제 고정막의 세척 과정에서 발생하는 탈리 현상을 억제할뿐 아니라 막의 반복사용도 가능하게 하였다. 5 h의 가교 반응을 통하여 탈리현상이 발생되지 않는 우레아제 고정막을 제조하였으며, 이때 제조된 우레아제 고정막은 1 mol과 4 mol의 요소 용액에서 각각 98%와 50% 이상의 가수분해 성능을 나타내었다.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2002년도 International Meeting on Information Display
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• pp.792-794
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• 2002

Uniform cylinder-shaped precursors for (Y,Gd)$BO_3$:Eu phosphors were prepared by urea hydrolysis reaction. After heating the precursors at lower temperature than general synthetic methods, the phosphor powders were well dispersed and held their original shapes. Their emissions under vacuum-ultraviolet (VUV) excitation appeared with the peaks at 593nm due to magnetic dipole transition from $^5D_0$ to $^7F_1$, 612nm and 627nm due to electric dipole transition from $^5D_0$ to $^7F_2$

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2005년도 하계학술대회 논문집 Vol.6
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• pp.361-362
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• 2005

Antimony doped tin oxide(ATO) nano powders have been synthesized by homogeneous precipitation method using $SnCl_4\cdot5H_2O$ for precursor, $SbCl_3$ as doped material and urea. The hydrolysis of urea and conductive mechanism and Heat treatment was performed at the temperature from $500^{\circ}C$ to $700^{\circ}C$ in air. The ATO nano powders are characterized by means of Thermogravimetry differential thermal analyzer (TG-DTA), X-ray diffraction (XRD), Brunauer, Emmett, and Teller adsorption (BET), Scanning electron microscopy (SEM) ATO nano powders with an average size of nm and the highest surface area 129 $m^2g^{-1}$ are obtained.

• Asian-Australasian Journal of Animal Sciences
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• 제18권7호
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• pp.957-965
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• 2005

The effect of ammoniation with urea and with soybean meal (SBM) as a source of urease on the nutritive value of wheat straw was evaluated in sheep. Twenty-four male Najdi lambs were used in a 3${\times}$2 factorial design, in which the animals were allocated to three straw treatments: 0% urea-treated (NT), 6% urea-treated (UT) and 2.2% urea-supplemented (US) straws. Each straw treatment was either supplemented or non-supplemented with 70 g SBM $kg^{-1}$ straw during the treatment time with urea, giving a total of six straw treatments. Each of these treatments was individually fed ad libitum to 4 lambs, together with 300 g of barley grain/head/day. Total N content of UT and US straws increased significantly (p<0.001) as compared to NT straw. The degree of urea hydrolysis, either with or without SBM addition, was nearly similar. Lambs fed either UT or US straw based diets had significantly (p<0.01) and numerically (p>0.05) higher straw DM intake (g $d^{-1}$ $kg^{-1}$ $BW^{0.75}$), compared to those fed NT straw based diet. Apparent DM or OM digestibilities increased significantly (p = 0.014) in lambs fed UT diet, and numerically (p>0.05) in lambs fed US diet as compared to those fed NT diet. Fiber (CF, NDF, ADF, cellulose and hemicellulose) digestibility increased to a similar magnitude, averaging 20.2 (p<0.001) and 7.8% (p<0.07); this corresponds to 35 (p<0.001) and 51% (p<0.001) in N digestibility and approximately 78 (p<0.017) and 105% (p<0.002) in N retention, for UT and US diets, respectively, as compared to NT diet. However, the UT diet had higher (p<0.01) fiber digestibility over the US diet. Addition of SBM tended to improve (p = 0.09) straw DM and digestible OM intakes, while significantly increasing (p<0.001) total and digestible CP intakes across all diets. Lambs fed on US diet had higher ruminal ammonia N than those fed on UT (p<0.05) or NT (p<0.001) diets. However, ruminal pH and molar proportion of the volatile fatty acids did not differ (p>0.05) among the treatment diets. This study suggests that US and UT treatments, particularly the latter, improved straw intake, digestibility and N utilization by lambs compared to NT treatment. On the other hand, addition of SBM as a source of urease had a negligible effect on urea hydrolysis.

• 한국환경농학회지
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• 제28권3호
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• pp.233-237
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• 2009

It has widely been observed that the effect of elevating atmospheric $CO_2$ concentrations on rice productivity depends largely on soil N availabilities. However, the responses of ammonia volatilization from flooded paddy soil that is an important pathway of N loss and thus affecting fertilizer N availability to concomitant increases in atmospheric $CO_2$ and temperature has rarely been studied. In this paper, we first report the interactive effect of elevated $CO_2$ and temperature on ammonia volatilization from rice paddy soils applied with urea. Urea labeled with $^{15}N$ was used to quantitatively estimate the contribution of applied urea-N to total ammonia volatilization. This study was conducted using Temperature Gradient Chambers (TGCs) with two $CO_2$ levels [ambient $CO_2$ (AC), 383 ppmv and elevated $CO_2$ (EC), 645 ppmv] as whole-plot treatment (main treatment) and two temperature levels [ambient temperature (AT), $25.7^{\circ}C$ and elevated temperature (ET), $27.8^{\circ}C$] as split-plot treatments (sub-treatment) with triplicates. Elevated temperature increased ammonia volatilization probably due to a shift of chemical equilibrium toward $NH_3$ production via enhanced hydrolysis of urea to $NH_3$ of which rate is dependent on temperature. Meanwhile, elevated $CO_2$ decreased ammonia volatilization and that could be attributed to increased rhizosphere biomass that assimilates $NH_4^+$ otherwise being lost via volatilization. Such opposite effects of elevated temperature and $CO_2$ resulted in the accumulated amount of ammonia volatilization in the order of ACET>ACAT>ECET>ECAT. The pattern of ammonia volatilization from applied urea-$^{15}N$ as affected by treatments was very similar to that of total ammonia volatilization. Our results suggest that elevated $CO_2$ has the potential to decrease ammonia volatilization from paddy soils applied with urea, but the effect could partially be offset when air temperature rises concomitantly.

• 한국대기환경학회지
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• 제32권5호
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• pp.526-535
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• 2016

Recently, fine dust in atmosphere have been considerably issued as a harmful element for human. Nitrogen oxide ($NO_x$) exhausted from diesel engines and power plants has been disclosed as a main source of secondary production of fine dust. In order to prevent exhausting these nitrogenous compounds into atmosphere, a treatment system with selective catalytic reduction (SCR) catalyst with ammonia as a reductant has been used in various industries. Urea solution has been widely studied to supply ammonia into a SCR catalytic reactor, safely. However, the conversion of urea solution to ammonia has several challenges, especially on a slow conversion velocity. In the present study, a fast urea conversion system including a plasma burner was suggested and designed to evaluate the performances of urea conversion and initial operation time. A designed lab-scale facility has a plasma burner, urea nozzle, mixer, and SCR catalyst which is for hydrolysis of isocyane. Flow rate of methane that is a fuel of the plasma burner was varied to control temperatures in the urea conversion facility. From experimental results, it is found that urea can be converted into ammonia using high temperature condition of above $400^{\circ}C$. In the designed test facility, it is found that ammonia can be produced within 1 min from urea injection and the result shows prospect commercialization of proposed technology in the SCR facilities.