Polyaniline was electrodeposited on platinum and semiconducting (Cd‐chalcogenides, Si, normalGaAs , normalGaP ) electrodes from aqueous solution false(pH=1false) containing aniline. The electrochemical behavior of such films was examined in aqueous and nonaqueous solutions by cyclic voltammetry. Results show that the polyaniline film is conducting in both cathodic and anodic regions at pH<3 as evidenced by the electrochemical redox reactions of various redox couples on polyanilinecoated electrodes. In general, all polyaniline‐coated semiconductor electrodes examined in this work exhibited enhanced stability of the photocurrent when compared to that of the naked electrodes.

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High-quality specimens of sufficient thickness for reliable testing are needed if the enhanced properties observed for ultrastructured multilayered metals are to be understood and exploited. In the present paper, factors affecting the quality of multilayers electrodeposited from a single electrolyte, via concerted modulation of the electrode potential and electrolyte mass transport, are discussed. The importance of precise control of the potential during deposition of the more noble metal is emphasized. Results obtained by a pulse technique show that Ni passivation does not occur under the conditions used to electrodeposit Ni-Cu multilayers. Attainable deposit quality is illustrated by tensile test data for a series of 90%Ni-10%Cu specimens that are twice as strong as Ni and for which the standard deviations for the ultimate tensile strength and modulus are only 1.5 and 3.9%, respectively.

As the layer thicknesses in 90% Ni-10% Cu multilayered alloys electrodeposited from a sulfamate bath are decreased, the ultimate tensile strength peaks at 1100 MPa for 6-7 nm Cu layers, and then decreases to about 1000 MPa as the Cu layer thickness reaches 1 nm. This decrease in deposit strength is associated with a reduction in the deposit (100) texture caused by the influence of Cu, which has a (110) preferred orientation in the sulfamate system. The results suggest that highly coherent nanostructured multilayers can only be deposited from a single electrolyte if the preferred orientation for the two metals is the same.In spite of the considerable interest in multilayered metal structures generated by the report of greatly enhanced mechanical properties for materials with ultrathin layers (1), the origin of the observed effects is still not clearly understood (2). One difficulty has been that the vacuum-deposited materials generally used are of insufficient quality and are too thin, 1-2 ~m, for reliable measurements (3). Work in our laboratory has resulted in a method for electrodeposition of multilayered metals (4), which has recently been refined so that thick specimens, 50 i~m, with extremely reproducible properties can be prepared (5).In the present paper, the effect of layer thickness on the tensile properties of 90% Ni-10% Cu multilayer materials electrodeposited from a sulfamate electrolyte is discussed in terms of the deposit structure as investigated by x-ray diffraction. Such materials have been shown previously (4, 5) to exhibit an approximately twofold enhancement in tensile strength for sufficiently thin layers. This enhancement may result from grain refinement associated with the layered structure in accordance with the Hall-Petch relationship (6-8), or be attributable to restricted dislocation movement across alternating layers of materials with high and low elastic constants, as proposed by Koehler (9). ExperimentalDetails concerning the specimen preparation and tensile test procedures are given in previous publications (4, 5). Specimens were electrodeposited at 45~ via concerted modulation of the cathode potential and rotation rate from a commercial nickel sulfamate bath (Barret SN) containing 5 mM copper sulfate. The cathode was a 25 mm diam x 13 mm long stainless steel mandrel, sandwiched between chlorofluorocarbon end pieces, to which a 2 ~m thick Cu basal layer was applied from a standard additive-free pyrophosphate bath at 45~ Pure Cu layers were plated at -0.14 V vs. saturated calomel electrode (SCE) with cathode rotation at 750 rpm, and Ni layers containing 0.8% Cu were plated at -105 mA/cm 2 from the stagnant bath. The nominal compositions reported, usually 90% Ni-10% Cu, do not take into account the 0.8% Cu codeposited during Ni deposition.Plated foils were nominally 50 ~m thick and were fashioned into dogbone specimens having a reduced section width of 6.3 mm and a gage length of 2.8 cm. Tensile testing was performed at room temperature at a cross head speed of 0.1 mm/min, and strain ...