• 한국세라믹학회지
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• 제23권3호
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• pp.53-61
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• 1986

A gas sensor which has been made by wet process had fabricated by coating each of the mixture on alumina tube and firing at 85$0^{\circ}C$ for 3hrs. A gas concentration such $H_2$, CO, $C_3H_8$, $C_2H_2$ and $CH_4$ vs its detection voltage characteristics has been in-vestigated on $SnO_2-In_2O_3-MgO$ system doped with PdO, $La_2O_3$, $ThO_2$, NiO and $Nb_2O_5$ The optimum sensitivity composition for various gases were 90w/o $SnO_2$-9w/o $In_2O_3$-1w/o MgO for $H_2$, $C_2H_2$ CO and $C_3H_8$ and 95w/o $SnO_2$-4w/o $In_2O_3$-1w/o MgO for $CH_4$. The sample which has been made by wet process than dry process had predominated sensitivity for each gases and particle size of the sample coprecipitated with PH=9 was 0.1${\mu}{\textrm}{m}$ The $SnO_2$-In2_O_3-MgO$ system doped with 2w/o $Nb_2O_5$ and NiO was the most sensitive for $H_2$ and $C_2H_2$ gas. In $SnO_2$-In2_O_3-MgO$ system doped with $ThO_2$ the sensitivity of $H_2$ gas was decreased but CO gas was in-creased when dopant con was increased.

• 한국세라믹학회지
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• 제31권10호
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• pp.1231-1239
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• 1994

In this study, gel powder which had relatively high hydration reactivity in CaO and P2O5 rich composition of CaO-P2O5-SiO2-H2O system was prepared by sol-gel process and its hydrated specimen was manufactured. The it was investigated to appropriate calcination temperature in sol-gel process which hydrated specimen of gel powder have proven to strength and the effect of factors influenced strength in hydration process. The major product of before and after hydration reaction was hydroxyapatite, and crystalline phase of C-S-H was already formed during gelation process. After hydration reaction of pressed specimen, crystalline phase of C-S-P-H was formed. It was hydrated product of silicocarnotite (5CaO.P2O5.SiO2). Gel phases of C-S-H and C-S-P-H occured as a result of partial substitution of amorphous silica by P2O5 was formed. The strength of hydrated hardened body is developed by strong bonding and bridging between the gel phases of C-S-H or C-S-P-H and the crystalline products such as hydroxyapatite, Ca(OH)2 C-S-H and C-S-P-H. In addition, the ultrafine gel powder have an great effect on increase of hydration reaction.

• 대한환경공학회지
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• 제22권2호
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• pp.241-249
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• 2000

난분해성 폐수인 사진현상폐수의 $UV/H_2O_2$ 및 $H_2O_2$의 고급산화에 의한 오염물질의 제거 실험을 실시하였다. $UV/H_2O_2$ 산화에서 $H_2O_2$의 분해로 $OH^-$ 라디칼이 발생되는데 파장 190~300 nm의 UV가 반응의 촉매 역할을 한다. $OH^-$ 라디칼은 수명은 짧으나 강력한 산화력을 갖고 있는데, 이 산화력은 폐수처리에서 폐수나 액상 폐기물의 유기물질을 제거하는데 이용된다. 본 연구에서 기존의 tube형 반응조의 단점을 보완한 UV-자유반사 반응조를 제작하여 사용하였으며 UV원으로는 수은 고압램프가 이용되었다. 본 실험에서는 반응시간과 $H_2O_2$ 주입량 및 pH 변화에 따른 오염물의 처리효율의 변화를 조사하였는데 $H_2O_2$의 주입량이 증가할수록 처리효율이 높았으나 그 차이는 미미하였으며, pH 8에서 보다는 3에서 처리효율이 약간 높았으나 그 차이 역시 크지 않았다. 본 연구에서 사진현상폐수 처리의 적정 운전조건은 pH 8, $H_2O_2$ 주입량은 유입수의 COD를 기준으로 한 1.3배 화학량론적 주입으로 나타났는데, 5시간의 처리에서 $COD_{Cr}$, TOC 및 색도의 제거효율은 각각 약 47.5%, 75.0% 및 91.5%로 나타났다. 반응 후 생분해성의 지표인 BOD/COD 비는 초기 0.04에서 0.21로 약 5.3배 증가하였다.

• 공업화학
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• 제18권6호
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• pp.552-556
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• 2007

연구에서는 $TiO_2$ 담체에 귀금속(Pd, Ru, Ir)을 담지시켜 촉매를 제조하였다. 금속분산의 향상을 위해 $H_2O-H_2$ 전처리 기술이 이용되었고, 반응물로서 xylene, toluene 그리고 MEK를 사용하였다. 단일금속과 합금금속의 촉매들은 함침법에 의해 준비하였고, XRD, XPS 분석을 통하여 특성 분석하였다. Pd-Ru, Pd-Ir 촉매는 다양한 활성점을 나타내었고, 그것은 Pd의 metal 영역를 강화시켰다. 합금금속으로 이루어진 촉매가 단일 금속으로 이루어진 촉매에 비해 VOCs 전환율이 더 높았다. $H_2O-H_2$ 전처리 기술은 Pd 입자를 고르게 분산시켰다. 이는 촉매의 효율을 증진시키는 효과를 보여주었다. 본 연구에서 Pd에 소량의 Ru, Ir 첨가는 VOCs의 산화반응을 증진시켰고, $TiO_2$ 담체상에서 $H_2O-H_2$ 전처리는 VOCs의 제거효율을 증진시켰다.

• 대한화학회지
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• 제50권1호
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• pp.60-64
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• 2006

구조의 유기-무기 혼성화합물 Cu2(OH)3(CH3COO)·H2O를 선구물질로 사용하여 Cu2O를 합성하였다. 75oC의 수용액에서 Cu2(OH)3(CH3COO)·H2O를 글루코오스로 환원시켜서 정육면체 Cu2O를 합성하였다. 선구물질과 글루코오스의 효과를 조사하였다. Cu2(OH)3(CH3COO)·H2O의 구조는 균일한 크기의 Cu2O를 만드는데 중요한 역할을 한다.

• 대한화학회지
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• 제67권5호
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• pp.333-338
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• 2023

In this study, the H₂O reaction with SiO clusters was investigated using ab initio Monte Carlo simulations and density functional theory calculations. Three chemistry models, PBE1/DGDZVP (Model 1), PBE1/DGDZVP (Si atom), and aug-cc-pVDZ (O and H atoms), (Model 2) and PBE1/aug-cc-pVDZ (Model 3), were used. The average bond lengths, as well as the relative and reaction energies, were calculated using Models 1, 2, and 3. The average bond lengths of Si-O and O-H are 1.67-1.75 Å and 0.96-0.97 Å, respectively, using Models 1, 2, and 3. The most stable structures were formed by the H transfer from an H₂O molecule except for Si₃O₃-H₂O-1 cluster. The Si₃O₃ cluster with H₂O exhibited the lowest reaction energy. In addition, the Bader charge distributions of the Si_nO_n and (SiO)_n-H₂O clusters with n = 1-7 were calculated using Model 1. We determined that the reaction sites between H₂O and the SiO clusters possessed the highest fraction of electrons.

• 한국세라믹학회지
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• 제32권7호
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• pp.853-857
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• 1995

ZrSiO4 powders were prepared from partially hydrolyzed solution of Si(OC2H5)4 and ZrOCl2.8H2O solution by the sol-gel method and formation rate of ZrSiO4 on the reaction parameter was investigated. In order to prepare homogeneous ZrSiO4 precursor gels, the H2O/Si(OC2H5)4 molar ratio of about 2, the pH of the ZrOCl2.8H2O solution fo about 4 and stirring time of the mixed solutions of about 2 hrs were appropriate. Formation of temperature of ZrSiO4 reduced about 15$0^{\circ}C$ by milling and formation of ZrSiO4 at 1300~135$0^{\circ}C$ showed an accelerative increase through the hedvall effect by silica.

• 한국재료학회지
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• 제23권11호
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• pp.631-637
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• 2013

Synthesis of sub-micron $2SnO{\cdot}(H_2O)$ powders by chemical reduction process was performed at room temperature as function of viscosity of methanol solution and molecular weight of PVP (polyvinylpyrrolidone). Tin(II) 2-ethylhexanoate and sodium borohydride were used as the tin precursor and the reducing agent, respectively. Simultaneous calcination and sintering processes were additionally performed by heating the $2SnO{\cdot}(H_2O)$ powders. In the synthesis of the $2SnO{\cdot}(H_2O)$ powders, it was possible to control the powder size using different combinations of the methanol solution viscosity and the PVP molecular weight. The molecular weight of PVP particularly influenced the size of the synthesized $2SnO{\cdot}(H_2O)$ powders. A holding time of 1 hr in air at $500^{\circ}C$ sufficiently transformed the $2SnO{\cdot}(H_2O)$ into $SnO_2$ phase; however, most of the PVP (molecular weight: 1,300,000) surface-capped powders decomposed and was removed after heating for 1 h at $700^{\circ}C$. Hence, heating for 1 h at $500^{\circ}C$ made a porous $SnO_2$ film containing residual PVP, whereas dense $SnO_2$ films with no significant amount of PVP formed after heating for 1 h at $700^{\circ}C$.

• 대한환경공학회지
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• 제28권4호
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• pp.429-437
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• 2006

화학세정폐수에 함유되어 있는 citric acid의 효율적인 처리방안을 수립하기 위해 $UV/H_2O_2,\;UV/TiO_2/H_2O_2$, Photo-Fenton 산화방법을 이용하여 각각 citric acid의 제거효율 및 그에 따른 전력소비량을 평가하였다. 그 결과 조사된 최적 처리조건에서 $UV/H_2O_2,\;UV/TiO_2/H_2O_2$, Photo-Fenton 산화방법을 이용한 citric acid 농도에 근거한 TOC 제거효율은 각각 95.5%, 92.3%, 91.5%로 조사되었으며, 그에 따른 전력소비량은 $11.26kWh/m^3,\;3.85kWh/m^3,\;0.799kWh/m^3$으로 조사되었다. 이 결과에 의하면 세가지 광화학적 산화방법 모두 유기물질이 90% 이상 제거되어 citric acid의 분해에 효과적인 것으로 판단되었다. 그러나 Photo-Fenton 산화방법이 다른 방법에 비해 처리에 소요되는 반응시간이 짧은 것으로 나타났다. 또한 광화학적 산화방법의 운영비를 결정짓는데 중요한 요소인 전력소모량 측면에서도 Photo-Fenton 산화방법이 다른 방법에 비해 우수한 것으로 조사되어 본 연구에서 비교하는 세가지 방법 중 citric acid 처리에는 Photo-Fenton 방법이 효율적인면과 경제성면에서 가장 적합한 처리기술로 결론지을 수 있었다.

• Environmental Engineering Research
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• 제16권3호
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• pp.131-136
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• 2011

The degradation of 30 pharmaceuticals and personal care products (PPCPs) subjected to $O_3$, $O_3$/UV, and $O_3/H_2O_2$ treatments were investigated using semi-batch tests and evaluated by their pseudo-first-order rate constants. The additional application of UV or $H_2O_2$ during $O_3$ treatment significantly improved the degradation rate of most of the PPCPs. At the same $O_3$ feed rate, $O_3$/UV treatment exhibited much higher PPCP degradation efficiency than that of $O_3$ treatment. This was probably due to degradation of the PPCPs by $O_3$, direct UV photodegradation, and OH radicals that formed from the photodegradation of $O_3$ during $O_3$/UV treatment. PPCP degradation by $O_3$ was also promoted by adding $H_2O_2$ during the $O_3$ treatment. However, when the initial $H_2O_2$ concentration was high during $O_3$ treatment, OH radicals were likely to be scavenged by excess $H_2O_2$, leading to low PPCP degradation. Therefore, it is important to determine the appropriate $H_2O_2$ dosage during $O_3$ treatment to improve PPCP degradation when adding $H_2O_2$ during $O_3$ treatment.