• Title, Summary, Keyword: Hydrazine

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Hydrazine Cross-linking in PAN Films in a Reaction Medium of Aqueous DMF Solution (DMF 수용액 매개체에서 PAN 필름의 히드라진 가교 반응)

  • Park, Heung Su;Mun, Seon Yeong;Kim, Young Ho
    • Textile Science and Engineering
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    • v.54 no.2
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    • pp.100-108
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    • 2017
  • The introduction of cross-linking into polyacrylonitrile (PAN) films with hydrazine solutions in a reaction medium of various concentrations of aqueous N,N'-dimethylformamide (DMF) solution was studied. The effect of the DMF concentration in the reaction medium, hydrazine concentration, reaction temperature, and time on the hydrazine addon and the degree of DMF swelling was investigated. The swelling in the DMF decreased with an increase in the hydrazine add-on, indicating that the modified PAN films became insoluble and swollen in the DMF. Although all the reaction conditions affected the hydrazine add-on, a high temperature of $110^{\circ}C$ in a 60 % (v/v) aqueous DMF solution with a 6 % (w/v) hydrazine solution resulted in more effective cross-linking at the same hydrazine add-on values. Analysis of the FTIR and UV-Visible spectra confirmed the introduction of the hydrazine cross-linking. The crystallinity of the modified PAN film reduced with increasing hydrazine cross-linking.

Use of Hydrazine for Pitting Corrosion Inhibition of Copper Sprinkler Tubes: Reaction of Hydrazine with Corrosion By-Products

  • Suh, Sang Hee;Kim, Sohee;Suh, Youngjoon
    • Corrosion Science and Technology
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    • v.16 no.5
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    • pp.247-256
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    • 2017
  • The feasibility of using hydrazine for inhibiting pitting corrosion in copper sprinkler tubes was investigated by examining microscopical and structural evolution of corrosion by-products with SEM, EDS, and XRD. Hydrazine removed dissolved oxygen and reduced CuO and $Cu_2O$ as well. The stable phase was changed from CuO to $Cu_2O$ or Cu depending on hydrazine concentration. Hydrazine concentration of 500 ppm could convert all CuO corrosion by-products to $Cu_2O$. In a tightly sealed acryl tube filled with aqueous solution of 500 ppm hydrazine, octahedral $Cu_2O$ particles were formed while plate-like structures with high concentration of Cu, O, N and C were formed near a corrosion pit. The inside structure of a corrosion pit was not altered by hydrazine aqueous solution. Uniform corrosion of copper was almost completely stopped in aqueous solution of 500 ppm hydrazine. Corrosion potential of a copper plate was linearly dependent on log (hydrazine concentration). The concept of stopping pitting corrosion reaction by suppressing oxygen reduction reaction could be verified by applying this method to a reasonable number of real sprinkler systems before full-scale application.

Preparation of SnO and SnO, SnO2 fine powder by hydrazine method (Hydrazine법에 의한 SnO, SnO2 미분말의 합성)

  • Kim, Kang-Min;Kim, Ki-Won;Cho, Pyeong-Seok;Lee, Jong-Heun
    • Journal of Sensor Science and Technology
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    • v.14 no.5
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    • pp.297-301
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    • 2005
  • Nanocrystalline SnO and $SnO_{2}$ powder have been prepared by hydrazine method. Sn-Hydrazine complex was formed by the reduction between aqueous $SnCl_{2}$ solution and hydrazine monohydrate. $SnO_{2}$ nano powder was prepared by the decomposition of Sn-Hydrazine complex at $450^{\circ}C$. When NaOH was added to Sn-hydrazine complex, SnO powder with nano-sheet morphology could be prepared. This can be attributed to the role of $OH^{-}$ ion as a reducing agent.

Preparation of Copper Fine Particles from Waste Copper by Chemical Reduction Method (폐동분으로부터 화학환원법에 의한 Cu 미립자 제조)

  • Kim, Yoon-Do;Song, Ki Chang;Song, Jong-Hyeok
    • Korean Chemical Engineering Research
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    • v.45 no.6
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    • pp.560-565
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    • 2007
  • Copper fine particles, ranging from $0.11{\mu}m$ to $0.64{\mu}m$ in average size, were prepared by a chemical reduction method using hydrazine ($N_2H_4$) as a reduction agent in waste copper solutions. The effect of the amount of hydrazine addition was investigated on the properties of the obtained powders. Also, the effect of the addition of dispersing agents [Polyvinyl alcohol (PVA), polyvinyl pyrrolidone (PVP)] during particle synthesis was studied. The powders, obtained from 1 M waste copper solutions, showed the mixtures of Cu and $Cu_2O$ crystals at low hydrazine addition amounts of 0.8 mol and 1.0 mol, while those exhibited pure Cu crystals at adequate hydrazine addition amount of 0.12 mol. The average size of the Cu powders decreased with increasing the concentrations of hydrazine and dispersing agents. The addition of PVA to the solutions as a dispersing agent was more effective than that of PVP in preventing the aggregation of particles.

Indirect Spectrophotometric Determination of Trace Quantities of Hydrazine

  • Haji Shabani, A.M.;Dadfarnia, S.;Dehghan, K.
    • Bulletin of the Korean Chemical Society
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    • v.25 no.2
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    • pp.213-215
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    • 2004
  • An indirect, sensitive and accurate method for the determination of trace amounts of hydrazine is described. The method is based on the oxidation of hydrazine by a known excess of iodate in the presence of hydrochloric acid. The unreacted iodate is used in the oxidation of hydroxylamine to nitrite. Sulfanilic acid is diazotized by the nitrite formed. The resulting diazonium ion is coupled with N-(1-naphthyl)ethylenediamine to form a stable azo dye, which shows an absorption maximum at 540 nm. Hydrazine can be determined in the range of 20-400 ng $mL^{-1}$ with a detection limit of 3.1 ng $mL^{-1}$. The relative standard deviation for 50, 200 and 400 ng $mL^{-1}$ of hydrazine is 2, 1.5 and 1.3%, respectively (n = 10). The method was applied to the determination of hydrazine in water samples.

Technology trend & its future for the space application of hydrazine (우주분야에서의 Hydrazine 적용현황 및 발전방향)

  • Kim In-Tae;Lee Jae-Won;Jang Ki-Won;Yu Myoung-Jong
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • pp.17-22
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    • 2006
  • Anhydrous hydrazine and its methyl derivatives MMH and UDMH have been safety used as monopropellant and bipropellant fuels in thousands of satellites and expendable launch vehicles. Since KOMPSAT program, We have been developing skills on the hydrazine propulsion system for several years. This paper presents an overview of the hydrazine for the space application - propellant overview, material compatibility, handling cautions and the future of hydrazine systems.

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Effects of the Swelling of Polyacrylonitrile Films in Various Aqueous Solutions on Their Reaction with Hydrazine (여러 가지 수용액에서의 폴리아크릴로니트릴 필름의 팽윤이 히드라진과의 반응에 미치는 영향)

  • Park, Heung Su;Kim, Young Ho
    • Textile Science and Engineering
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    • v.51 no.4
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    • pp.159-167
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    • 2014
  • Swelling behaviors of polyacrylonitrile (PAN) films in various aqueous solutions, such as N,N'-dimethylformamide (DMF)/water, N,N'-dimethylacetamide (DMAc)/water, dimethylsulfoxide (DMSO)/water, NaSCN or KSCN solution, the effects of the concentrations of these solutions, and the effects of swelling temperature and time on the degree of swelling of PAN films were analyzed. Among the various aqueous solutions, DMF and NaSCN solution were found to be effective for high swelling of PAN films. High swelling of PAN films in the hydrazine solutions wherein aqueous, organic solvents or salt solutions were used as solvents for hydrazine, resulted in higher absorption of hydrazine and a high degree of cross-linking. Analysis of the bands of FT-IR spectra and the cyclization peaks of DSC curves for various hydrazine-treated PAN films showed that the effective cross-linking of PAN films at the same hydrazine concentration was obtained by using DMF/water or NaSCN/water solutions as solvents for hydrazine and treating medium for PAN films.

The α-Effect in SNAr Reaction of 1-Fluoro-2,4-dinitrobenzene with Hydrazine: Ground-State Destabilization versus Transition-State Stabilization

  • Cho, Hyo-Jin;Um, Ik-Hwan
    • Bulletin of the Korean Chemical Society
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    • v.35 no.8
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    • pp.2371-2374
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    • 2014
  • A kinetic study is reported on SNAr reaction of 1-fluoro-2,4-dinitrobenzene with a series of primary amines including hydrazine in $H_2O$ at $25.0^{\circ}C$. The plots of $k_{obsd}$ vs. [amine] are linear and pass through the origin, indicating that general-base catalysis by a second amine molecule is absent. The Br${\o}$nsted-type plot exhibits an excellent linear correlation with ${\beta}_{nuc}$ = 0.46 when hydrazine is excluded from the correlation. The reaction has been suggested to proceed through a stepwise mechanism, in which expulsion of the leaving group occurs after the rate-determining step (RDS). Hydrazine is ca. 10 times more reactive than similarly basic glycylglycine (i.e., the ${\alpha}$-effect). A five-membered cyclic intermediate has been suggested for the reaction with hydrazine, in which intramolecular H-bonding interactions would facilitate expulsion of the leaving group. However, the enhanced leaving-group ability is not responsible for the ${\alpha}$-effect shown by hydrazine because expulsion of the leaving group occurs after RDS. Destabilization of the ground-state of hydrazine through the electronic repulsion between the nonbonding electron pairs is responsible for the ${\alpha}$-effect found in the current $S_NAr$ reaction.

A Consideration of Hydrazine Syntheses (Hydrazine 合成의 一考察)

  • Lee, Hac-Ki
    • Journal of the Korean Chemical Society
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    • v.5 no.1
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    • pp.1-6
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    • 1961
  • It is important to study hydrazine because of the development of new uses for its derivatives. The Rasching method is the only satisfactory one for synthesizing hydrazine; it involves the oxidation of ammonia by sodium hypochlorite in the presence of some such catalyst as gelatin. Calcium hypochlorite was substituted for the sodium hypochlorite particularly in this work, applying agar-agar as catalyst. The results of the experiments are as follow: 1. The yield is proportional to the mole-ratio of ammonia to available chlorine in calcium hypochlorite and about 60% is obtained when the ratio is 20. 2. Agar-agar can be used as a catalyst and its proper concentration in the solution is 0.005%. 3. Proper concentration of available chlorine in the reaction solution is 0.23 mole/l. 4. The most effective condition for the reaction is a temperature of $60{\sim}65^{\circ}C.$ maintained for $20{\sim}25min$. 5. The reaction takes place equally well in either an open or closed container. 6. When calcium hypochlorite is applied in place of sodium hypochlorite, the yield of hydrazine is increased as much as 17%. 7. The yield of hydrazine is decreased by eliminating the suspension of $Ca(OH)_2$ which results from the use of calcium hypochlorite. 8. When $Ca(OH)_2$ is added to Rasching process, the yield of hydrazine is raised normally. 9. The fact that some metal ions, such as $Cu^{++},$ inhibit the formation of hydrazine was proved. 10. The suspension of $Ca(OH)_2$ acted as a remarkable adsorbent for $Cu^{++}$ like gelatin. The suspension of $Ca(OH)_2$ which results from the use of calcium hypochlorite acts as a catalyst, absorbing metal ions, to increase the yield of hydrazine. So I think that calcium hypochlorite is a more efficient oxidant than sodium hypochlorite in hydrazine syntheses.

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Effect of Hydrazine as a Complex Agent on the Growth of ZnS Thin Film by Using Chemical Bath Deposition (CBD) (CBD법에 의한 ZnS 박막 성장의 하이드라진 효과)

  • Lee, Cha Ran;Kim, Jeha
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.31 no.3
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    • pp.177-181
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    • 2018
  • We prepared ZnS thin films via chemical bath deposition (CBD) in an aqueous solution of ammonia ($NH_3$) and hydrazine ($N_2H_4$). The composition ratio of hydrazine used was 0%, 17%, 22%, 29%, or 50%. We investigated the effects of hydrazine and ammonia on the growth, and the structural and optical properties of ZnS in terms of surface uniformity, voids, and grain size. We found that during the growth of ZnS films, hydrazine was very effective for improving the surface morphology and layer uniformity with fast layer formation, while it had no effect on the bandgap energy, $E_g$.