Corrosion of 99.999% Al in
1M normalNaCl
at pH 11 was studied at naturally occurring as well as artificial pits. Electrolytic solution extracted from within natural pits was found to have a pH between 3 and 4. Solution extracted from within artificial pits and complexed with ferron exhibited a UV spectrum that indicated that 84% of the dissolved Al was present as monomeric species, and the remainder as polymeric species. The 27Al NMR spectrum of solution extracted from artificial pits was found to be similar to that of synthetic solutions of
normalAlfalse(OH)2normalCl
and
normalAlfalse(OHfalse)Cl2
. The saturation concentration of the monomeric salts was found to be about 3M, and the pH at 90% of saturation was about 3. Implantation of Fe ions into the surface of pure Al through a 5 μm diam mask was discovered to create a site which, upon immersion at −0.5V SCE, corroded preferentially and thus acted as a nucleation site for pit growth. The current density at such single corrosion pits was determined directly by electrochemical measurement of current and by optical measurement of surface area, and was found to decrease during pit growth with the square root of time. The current density was in quantitative agreement with theoretical predictions based on the hypothesis that the corrosion rate was mass transport controlled by the dissolution of an aluminum oxychloride salt film formed by precipitation of dissolution products.
Femtosecond laser-induced ultrafast crystallization in 80 nm as-deposited Ge 2 Sb 2 Te 5 films has been investigated by timeresolved microscopy. With an average fluence of approximately 10 mJ/cm 2 , a transient nonequilibrium state of the excited material was formed within 2 ps. The results can be interpreted as an electronically induced nonthermal phase transition.
AbstracL A theoretical investigation of the photostimulated thermomagnetic effect by electrons in a semiconduclor superlallice (SL) in the lowest miniband is presenfed. The possibilily of controlling the thermopwer 01, rhe eleclron thermal conductivity x and lhe electmconductivily LT of lhe SL with the help of laser radiation is indicated. The parameters 01, x and were found to oscillate. The H a l l constanl, the Righi-Leduc and lhe Maggie-Righi-Leduc effectS were calculated. The prospect of using the SL as a good-quality and highly efficienl thermoelement is also proposed.
025ChemInform Abstract The local chemical environment in naturally occurring and artificial corrosion pits on pure Al in 1 M NaCl at pH 11 is studied. The solution within the natural pits is found to have a pH of 3-4, which is explained by hydrolysis of Al3+. 84% of the dissolved Al is present as monomeric species. The 27Al NMR spectrum of the solution extracted from artificial pits is similar to that of synthetic solutions of Al(OH)2Cl and Al(OH)Cl2. Implantation of iron ions is found to create sites which are corroded preferentially. Measurements of the time-dependent variation of the current density are in quantitative agreement with theoretical predictions based on the hypothesis that the corrosion rate is mass transport controlled by the dissolution of an aluminum oxychloride salt film formed by precipitation of dissolution products.
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