Hydrazine In Solution Research Articles

Electrochemical Etching of Silicon by Hydrazine

The anodic dissolution and passivation of n‐ and p‐type Si in different concentrations of hydrazine solution and etching temperatures were studied. During etching, performed at 70 and 90°C, it was observed that the current‐potential characteristics for both n‐ and p‐type Si snowed a current reduction after reaching a peak value. A linear I‐V relation was observed for the room temperature etching. A mechanism, which accounts for the semiconductor energy level change in solution as under different biasing conditions, is proposed to give a qualitative explanation of the different I‐V behaviors for n‐ and p‐type semiconductors.

Corrosion products on steel 20 in aerated hydrazine solutions: Mössbauer study

Composition of corrosion layers on steel 20 in aerated solutions with hydrazine concentrations less than 11 ppm was studied at 50, 60, and 80°C in dynamic conditions by transmission Mossbauer spectroscopy and X-ray diffraction as supplementary technique. Corrosion rates were determined by gravimetric method. A comparison with corrosion in water at 80°C was made. The observed layers have not any protective character. For 0.1 m/s linear velocity, they are composed by nonstoichiometric magnetite, (Fe3−xO4,x=0.02–0.04) with lepidocrocite (γ-FeOOH) as secondary phase at 50°C. Haematite (α-Fe2O3) is observed at 60 and 80°C with a 19 nm particle size. It becomes smaller for higher velocity (0.7 m/s).

A study by pulse radiolysis of the radiation-chemical transformation of aqueous solutions of hydrazine in the presence of oxygen

It is shown by pulse radiolysis that in aqueous solutions of hydrazine containing oxygen the radical N2H3 reduces oxygen to O2− at pH > 7 (k ≥3·109 dm3· mole−1·sec−1), while this reaction does not occur for the protonated form N2H4+ at pH < 7 (k≤, 5·106 dm3·mole−1·sec−1). The rate constants for the disappearance of O2− have been determined in the pH range from 4 to 12. Rate constants have been calculated for the reaction of O− with N2H4 [k=(1.6 ±0.2)·109 dm3·mole−1·sec−1] and of O3with N2H4 [k=(1.2 ±0.2)·106 dm3· mole−1·sec−1].

Glass of the past: The degradation and deterioration of medieval glass artifacts

Medieval artifacts made of glass are at a serious disadvantage concerning the chemical stability compared with ancient or common modern glasses. The total amount of silica and other network formers such as alumina is very low and potassium instead of sodium was introduced into the silicate structure by using local raw material. By means of scanning electron microscopy (SEM), secondary ion mass spectrometry (SIMS) and nuclear reaction analysis (NRA) a weathering mechanism governed by an ion exchange process could be determined for medieval glass paintings exposed to the ambient air for centuries. Additionally, the leached glass surface of medieval hollow glass artifacts found in a well and exposed to moist earth show a brown discoloring due to the oxidation of Mn(II) to Mn(IV) oxide. That process can be converted by a treatment of the glass objects in an aqueous hydrazine solution.

Anodic Dissolution and Passivation of Silicon in Hydrazine

Anodic dissolution and passivation of silicon in aqueous hydrazine has been studied. The current‐voltage characteristics of anodic‐biased silicon wafers, (100) oriented n‐ and p‐type with various doping concentrations, in hydrazine were examined. It is found that there is a critical current density for anodic biased silicon to be passivated in hydrazine solution. A mechanism of p‐n junction etch‐stop is proposed in which p‐n junction leakage current and critical passivation current density (CPI) are two determining parameters. For n‐type silicon, the CPI is found to be about 60 μA/mm2, independent of its resistivity; whereas for p‐type silicon the CPI depends on silicon resistivity. The different behavior of anodic biased n‐ and p‐type silicon wafers in hydrazine is attributed to the existence of surface states and their effects on the surface potential as well as the availability of holes at surface.

Exposure to Hydrazine and its Control in Power Plants

Abstract The use of hydrazine in power plants was surveyed with a postal inquiry to detect differences in exposure when alternative technical procedures were used in the handling of hydrazine. The exposure level of employees in eight plants was estimated based on the concentration of hydrazine in the air and the potential absorption through the skin. The questionnaire was sent to 288 power plants and 264 were returned, 100 of which used hydrazine. About 500 employees dosed and diluted strong (15% or 35%) hydrazine solution. The dosing was usually done with a pump or an ejector in bigger plants and with a measure in small plants. The airborne hydrazine concentrations in the rooms where hydrazine was handled were: < 0.01–0.06 ppm (mean < 0.02 ppm) for dosing with measure; < 0.01–0.37 ppm (mean 0.12 ppm) for dosing with pump; < 0.01–0.33 ppm (mean 0.09 ppm) for dosing with ejector, tank not closed; and < 0.01–0.04 ppm (mean 0.02 ppm) for dosing with ejector, tank closed and equipped with exhaust. The time-we...

Compensating corner undercutting in anisotropic etching of (100) silicon

Convex corner undercutting in anisotropic etching of (100) silicon is studied. The main beveling planes at undercut corners are all {212} planes, whether KOH, hydrazine, or EPW solutions are used as etchant. A novel mask pattern for compensating corner undercutting is presented, which fits all three anisotropic etchants. A simple, efficient method for calculating this design is presented with which satisfactory compensation is obtained.

Structural analysis of electrochemically synthesized polyanilines by X-ray Photoelectron Spectroscopy.

Polyaniline was synthesized electrochemically from an aqueous solution of aniline containing perchloric acid. The obtained polymer films were treated with an aqueous solution of hydrazine or sodium hydroxide. Otherwise, anodic or cathodic potential were applied to the polyaniline films in an aqueous solution of perchloric acid. X-ray photoelectron spectroscopy (XPS) was utilized to investigate the differences in these various kinds of polyaniline films. A peak which changed its intensity according to the conductivity of the films and the amount of perchlorate ion contained was found at a higher binding energy position than that of the nitrogen photoelectron peak. The scheme of conductive polyaniline proposed by Bredas et al. give a reasonale explanation to these results.

ChemInform Abstract: Anisotropic Etching of Silicon in Hydrazine

Abstract This paper contains a detailed discussion of the practical issues related to the anisotropic etching of single crystal silicon using a 5050 hydrazinewater solution. Characteristics of the etchant, etching reactor design, etch procedures, safety precautions, etch rate data for typical samples and appropriate etch-masks are among the topic discussed. The etching process is carried out in a atmospheric reflux reactor, continuously purged with nitrogen. The etch rate of (100) silicon at 115°C in this hydrazine solution is nearly 3 μm/min, which is much higher than that of ethylenediaminepyrocatecholwater (EDP) solutions. Silicon dioxide, silicon nitride and most metallic thin films, except aluminium, can be used to mask the etching process. The etch rate is reduced significantly in highly-boron-doped silicon; a boron concentration of 1.5 × 10 20 cm −3 practically stops the etch. The use of the hydrazine solution for micromachining thin silicon diaphragms, cantilevers and fibers is demonstrated.

Anisotropic etching of silicon in hydrazine

This paper contains a detailed discussion of the practical issues related to the anisotropic etching of single crystal silicon using a 5050 hydrazinewater solution. Characteristics of the etchant, etching reactor design, etch procedures, safety precautions, etch rate data for typical samples and appropriate etch-masks are among the topic discussed. The etching process is carried out in a atmospheric reflux reactor, continuously purged with nitrogen. The etch rate of (100) silicon at 115°C in this hydrazine solution is nearly 3 μm/min, which is much higher than that of ethylenediaminepyrocatecholwater (EDP) solutions. Silicon dioxide, silicon nitride and most metallic thin films, except aluminium, can be used to mask the etching process. The etch rate is reduced significantly in highly-boron-doped silicon; a boron concentration of 1.5 × 10 20 cm −3 practically stops the etch. The use of the hydrazine solution for micromachining thin silicon diaphragms, cantilevers and fibers is demonstrated.

I — kinetics of reduction of manganese dioxide by ascorbic acid and hydrazine solutions

The reduction rates of 7 commercial (4 γ-MnO 2 and 3 ε-MnO 2) and 5 prepared MnO 2 samples by ascorbic acid solution at 25 °C have been

N-pyridoxylidenehydrazine-N',N'-diacetic acid. III. Formation of metal chelates in solution.

Metal chelate formation of N-pyridoxylidenehydrazine-N ', N '-diacetic acid (1) and related hydrazines in solution was studied by means of absorption spectroscopy. Compound 1 and N-pyridoxylidene-N'-methylhydrazine (2) in methanol formed Cu (II) chelates of the same spectral character, which indicated the chelation of the phenolate oxygen and the hydrazine nitrogen atoms to Cu (II). The compositions of the chelates were 1 : 1 for 1 and 1 : 2 for 2, indicating that 1 acts as a tri- or tetradentate ligand. N- (3-Hydroxy-4-pyridylmethylene) hydrazine-N', N'-diacetic acid formed a Cu (II) chelate similar to that of 1 but N-pyridoxylidene-N', N'-dimethylhydrazine and N-pyridoxylidene-N', N'-diphenylhydrazine did not form chelates under similar conditions. Addition of an equimolar or excess amount of Co (II), Ni (II), Zn (II), Cd (II) or La (III) salt to 1 in methanol gave rise to absorption assignable to the chelate of 1, whereas 2 did not form metal chelates under the same conditions. It was concluded that the iminodiacetic acid moiety of 1 coordinated to the metal ions and enhanced the stability constant of the metal chelates.

Conformational analysis of N-[3,4-dihydro-4-oxoquinazolin-3-yl]aziridines

The X-ray crystal structure of the aziridine (7a) shows that the preferred orientation around the N–N bond has the lone pairs of electrons on adjacent nitrogens eclipsed; the rotamer equilibria around the N–N bonds in the two stereoisomers (7a) and (7b) suggest that this is also the preferred conformation for these substituted hydrazines in solution.

Some titrimetric applications of manganese(III) salt solutions: analysis of higher valent complexes of manganese and nickel

Mn2(SO4)3, prepared by oxidising 0.1 M MnSO4 solution in 6 M H2SO4 with 0.02 M KMnO4, was used for titrating solutions of hydrazine or ascorbic acid. The kinetics of dissolution of manganese dioxide in ascorbic acid solution were followed by titration against Mn2(SO4)3 solution. MnIII, NiIII or MnIII+ MnIV were determined in prepared solids by adding a known excess of ascorbic acid solution, which reduces the metal to the divalent state, and back-titrating with Mn2(SO4)3 solution. Although the latter solution can be successfully used for titrating H2O2 or FeII, even in the presence of high concentrations of chlorides, it is not recommended for titrating nitrites or lower vanadium compounds.

Preparation and physico-chemical properties of bis(salicylaldehyde hydrazonato)-iron(III), manganese(III) and chromium(III) iodides

Bis(salicytaldehyde hydrazonato)iron(llI) iodide has been prepared by reduction of tris(salicylaldehyde hydrazonato)iron(III) with hydrazine in dimethylformamide solution followed by reaction with methyl iodide. This reaction has been shown to involve an iron(I) chelate intermediate. Reaction of bis(salicylaldehyde hydrazonato)iron(II) with iodine in dimethylformamide solution also leads to formation of bis(salicylaldehyde hydrazonato)iron(III) iodide. The reaction of methyl iodide with a dimethylformamide solution of bis(salicylaldehyde hydrazonato)manganese(II) and hydrazine leads to the formation of bis(salicylaldehyde hydrazonato)- manganese(III) iodide which can also be obtained by reaction of the manganese(II) chelate with iodine. The reduction pathway has been shown to involve the formation of a manganese(O) hydrazine chelate while the use of hydroxylamine, sodium borohydride and sodium dithionite for the reduction of the manganese(II) chelate lead to the formation of a manganese(i) intermediate. Bis(salicylaldehyde hydrazonato)chromium(III) nitrate forms as a result of the reaction of hydrated chromium(III) nitrate with salicylaldehyde hydrazone in dimethylformamide and has been used to prepare the corresponding iodide, chloride, bromide, thiocyanate and cyanide by anion exchange reactions in dimethylformamide. Each product has been characterized by the observation of well resolved ESR spectra.

ChemInform Abstract: Reaction of Hopeite with Hydrazine.

AbstractThe title compound (I), on reaction with hydrazine, yields the complexes (II), (III) or (IV), depending on the concentration of the hydrazine solution.

Ｃａ添加Ｂｉ置換鉄ガーネット膜の光吸収損失に及ぼす還元効果

Reducing treatment effects on magneto-optical properties were studied for Ca-doped Bisubstituted iron garnet (BiGdCa)3(FeAlGa)5O12 films grown by the LPE technique. The films were reduced by using a hydrazine solution at 100∼110°C. Faraday rotation and absorption loss of as-grown and reduced films were measured at wavelength λ between 0.5 and 2.0 μm. By reducing treatment, the Faraday rotation remained unchanged, however, the absorption loss decreased for both Ca-free and Ca-doped films. The reduced Ca-doped films had lower absorption loss compared with that of the reduced Ca-free films. The minimum absorption loss reached 220 dB/cm at λ=0.79 μm and 1∼2 dB/cm at λ=1.15 μm. The saturation field was below 200 Oe for all the films.An optical isolator for the 0.8 μm region was constructed by using a reduced thick film. The forward loss of the isolator was 3 dB and the backward loss 27 dB at 0.79 μm.

Spectroscopic studies of chemically liberated "free" hydroxyl groups in aqueous hydrazine, ammonia, and methylamine solutions

The spectroscopic character of free -OH groups produced by chemical means at constant temperature is compared with that of the putative free -OH produced in pure water alcohols, etc. by temperature increases. Free, or at least very weakly bonded, -OH groups have been produced quasi-stoichiometrically at room temperature by displacing bound -OH groups from OH O bonds previously free with previously free -NH groups, the competitive status of which has been abruptly increased by protonation of the amine group. The sharp overtone bands of the unbonded -NH groups necessarily present in amine + H/sub 2/O solutions (due to the excess of protons over lone pairs) disappear stoichiometrically on protonation using HClO/sub 4/, and an equivalent number of weakly bonding -OH groups are produced. The spectroscopic signature of the chemically liberated -OH group is almost indistinguishable from that of the group liberated thermally, and a well-defined isosbestic point at 1442 nm (close to the approximate isosbestic point at 1440-1450 nm in the heated water spectra) implies that the same mechanism of exciting across the centroid (a (strong bond) in equilibrium (weak bond) exchange within a continuum model) is involved in each case. 13 references, 7 figures.

13C nuclear magnetic resonance studies of the products of reaction of acetaldehyde and of simple ketones in liquid ammonia, in hydrazine hydrate, and in some substituted hydrazine solutions

13 C N.m.r. shows that acetaldehyde rapidly forms the classical ‘aldehyde–ammonia’ in liquid ammonia, together with 2,4,6-trimethylhexahydro-1,3,5-triazine. For the first time, the formation of gem-aminohydroxy products corresponding to aldehyde–ammonia adducts by a range of ketones under the same conditions has been observed directly. In parallel studies, the products formed by acetaldehyde and by various ketones in hydrazine hydrate and in some simply substituted hydrazines have also been determined. It has been possible not only to detect hydrazones, azines, and a hexahydrotetrazine with the appropriate reagents, but also to identify the formation of gem-hydrazino-hydroxy adducts corresponding to aldehyde–ammonia adducts.

Acute toxicity of hydrazine hydrate to the fathead minnow (Pimephales promelas) and daphnid (Daphnia pulex).

Utilities that depend on steam generation for the production of electricity have benefitted greatly from the use of hydrazine (H/sub 2/NNH/sub 2/). The chemical is a strong antioxidant that reacts with oxygen in water to form water and nitrogen gas. Deoxygenated boiler water helps reduce oxidation inside boilers and steam systems, thereby increasing their efficiency and longevity. Idle boilers are protected with layup solutions of hydrazine in concentrations as high as 200 mg/L. Hydrazine may enter the aquatic environment as controlled industrial discharge or as a result of an accidental spill. Data on the aquatic toxicity of hydrazine hydrate, however, are lacking. This paper addresses the acute toxicity of hydrazine hydrate to a freshwater fish (fathead minnow, Pimephalas promelas) and invertebrate (daphnid, Daphnia pulex).