NaOH Solution Treatment Research Articles

Enhancement of crystallinity in YBa 2Cu 3O 7− x ceramic by water or NaOH solution attack

The attack of water or NaOH solution on YBa 2Cu 3O 7− x powder prior to the sintering process forms large crystallites in the sintered ceramic product. This enhancement of crystallinity leads to higher density and larger critical current. The water or NaOH solution treatment of the YBa 2Cu 3O 7− x powder leads to the formation of a BaO-CuO flux during the high-temperature sintering process. Water exposure, though destructive to YBa 2Cu 3O 7− x in general, can be used in an advantageous way for preparation of sintered YBCO ceramic material.

Prevention of Pyrite Dissolution in Acidic Media

Abstract Three samples of pyrites (n- and p-type semiconductors) were investigated for their corrosion behavior in 1 M H2SO4 using a potentiodynamic polarization technique. The corrosion behavior as influenced by the surface treatment of pyrite by acetyl acetone, methoxy triacetoxy silane (MTS), glycidoxy propyl trimethoxy silane (GPTS), phenyl triacetoxy silane (PTS), humic acid, lignin—NaOH solution, oxalic acid, and benzene was investigated. It was found that the corrosion rate of pyrite in sulfuric acid can be decreased significantly (up to 98%) by acetyl acetone and humic acid treatment. Pyrite is also passivated by PTS, lignin—NaOH solution, benzene, GPTS, and oxalic acid treatment. A mechanism is proposed to explain pyrite passivation due to surface treatment by chemicals used in this study.

Synthesis of zeolites from mechanically activated kaolin clays

The hydrothermal treatment in NaOH solution of clays activated by grinding leads to the formation of different zeolites, whose nature depends on the amorphization of the clay obtained by applying a periodic stress by means of an oscillating mill. In this way, hydroxysodalite, mixtures of hydroxysodalite and NaA zeolite, or NaA pure zeolite can be obtained. In the present paper, it is shown that the product varies in composition, and is enriched in NaA zeolite as the crystalline structure of the clay is destroyed by grinding. It is proved that the activation by impact grinding is an alternative method to the classical calcination for the synthesis of the NaA zeolite.

ChemInform Abstract: Activation of the Iron Surface to Hydrogen Absorption Resulting from a Long Cathodic Treatment in NaOH Solution.

AbstractHydrogen permeation measurements, together with ellipsometric and optical observations of the electrode surface, are performed on pure iron cathodically polarized in 0.1 M NaOH.

Activation of the Iron Surface to Hydrogen Absorption Resulting from a Long Cathodic Treatment in NaOH Solution

Electrochemical measurements of the permeation rate of hydrogen through pure iron cathodically polarized in , together with ellipsometric and optical observations of the electrode surface, were performed. A long, uninterrupted charging caused disintegration of a subsurface metal layer and, as a result, the metal surface became more prone to both hydrogen absorption and corrosion. The permeation rate through activated iron membranes was controlled by the cathodic current density. An addition of EDTA into increased the activity of the iron surface by removing from it some oxidized products of the chemical reaction of iron with water. Therefore, at the same charging current density, the hydrogen permeation rate through iron membranes was much greater in the presence than in the absence EDTA. On the contrary, a layer of palladium on the input surface impeded the entry of hydrogen.

Herty法による高窒素鋼中酸素の定量について

It was experimented to see whether the AlN affected the results and to finl a method of eliminating its effect, when the oxygen in high-nitrogen steel was determined. By this research, the following facts were found:(1) It was observed that when the oxygen was analysed in the sample of steel, whose N2 content was high (N2 content over 0.010%), by the ordinary Herty's method, a certain quantity of AlN remained together with Al2O3, due to its difficulty of being solved in acid; and that accordingly, it made the resultant figures higher and also induced a fluctuation of the results.(2) The counter-measure for it was found better to eliminate the effect of AlN only by treating the Al2O3+AlN residue with the solution of NaOH (3%). By this method the authors obtained the true value. Consequently, it became clear that NaOH solution treatment was absolutely necessary for such sample, and thus the procedure of the Herty's method of high-N2steel was established too.