Sampling electrodeposition

EC-AFM is a particular working mode of AFM in which contact-mode AFM imaging is performed in situ in an electrolytic solution so as to allow the sample to be placed under electrochemical control. When applied to conducting polymers, EC-AFM is thus used in an electrochemical cell especially dedicated to AFM studies, in which the back of the cell supports the conducting polymer sample electrodeposited at the top of the working electrode (see Figure 3.9). For electrochemical conditioning of the sample, reference and counter-electrodes are added to the ceU. 

Fig. 7.43 The thickness of the individual phases, dniP) and dniy), and the intermediate layer, dn, obtained by the analysis of the results presented in Fig. 7.42. (a) Samples electrodeposited from the solution 2 M NiS04 + 0.2 M Na3C6H507 + 0.002 M CdS04 (b) Samples electrodeposited from the solution 2 M Ni(NH2S03)2+ 0.5 M H3BO3 + 0.002 M CdS04 (Reprinted from Ref. [5] with kind permission from Springer)...

It is noteworthy that with the increase of the h.c.p. a-Co (100) phase in the powder electrodeposit and the decrease of the f.c.c. -Ni (111) phase, the shape of dendrite agglomerates changes from typical 2D fem-like dendrites to 3D dendrites. This is in accordance with the statement [1] that in the presence of the (111) orientation (f.c.c. -Ni (111) phase) 2D dendrite growth prevails (the highest intensity for f.c.c. -Ni (111) phase is detected in sample electrodeposited at Ni /Co + ions ratio 1.00). Such dendrites are denoted in the literature [1] as 2D 100 60°, with the angle of 60° between the main tree of the dendrite and the branches. In order to explain the influence of other orientations (h.c.p. a-Co (100) etc.) on the growth of dendrites in the investigated powder and appearance of 3D dendrites in the powder deposit, additimial experiments and more detailed analysis are needed. 

X-ray diffraction pattern for Co powder samples electrodeposited either with 7pd(l) or 7pd(2), from sulfate or chloride electrolytes, is shown in Fig. 2.26. As can be seen the powder consists only of the hexagonal close-packed a-cobalt phase with the lattice parameters of a = 2.5007 A and c = 4.0563 A. No hydroxide or oxide impurities were detected [99]. 

The phase composition of all alloy powder samples was determined by the X-ray technique. The X-ray diffraction patterns of all four samples electrodeposited from ammonium hydroxide containing solutions are shown in Fig. 5.8. 

As can be seen, XRD patterns contain the characteristic peaks for Ni-based solid solution (Ni-rich phase, j -Ni phase) ( ) with face-centered cubic lattice (f.c.c., space group Fm3m) and h.c.p. a-Co phase (V). It is seen in Fig. 5.8 that with the decrease of Ni VCo ions ratio peaks for j -Ni phase ( ) become smaller and some of them disappear, while the peaks for h.c.p. a-Co phase (V) become more pronounced. For samples electrodeposited from the solutions containing higher concentration of Ni ions than Co " ions (Ni VCo = 4.00 and 1.50) only the presence of -Ni phase ( ) was detected, while at... 

Table 5.3 Results of the EDS analysis of powder samples electrodeposited from different electrolytes, obtained at different positions (spectra) at powder agglomerates presented in Fig. 5.37...

Two powder samples, electrodeposited from the solutions with Ni/Mo = 1/1 (sample 2) and Ni/Mo = 1/3 (sample 3), were analyzed by DSC and TGA to determine recrystallization temperature (Fig. 5.50) [121]. For both samples a multistep process with the sharp exothermic maximum on the DSC curves indicates that the recrystallization occurs at 543°C and should be performed at this or higher temperature. It should be noted that on the DSC curve for sample 2 additional small exothermic maximum, appearing at lower temperature of about 420° C, could be ascribed to the recrystallization of another phase present in the powder. At the same time, the TGA analysis revealed the weight loss of the samples of about 15%, corresponding most probably to the evaporation of electrolyte left in the pores of as-deposited powders. 

Hardness of the aimealed metals covers a wide range. Rhodium (up to 40%), iridium (up to 30%), and mthenium (up to 10%) are often used to harden platinum and palladium whose intrinsic hardness and tensile strength are too low for many intended appHcations. Many of the properties of rhodium and indium. Group 9 metals, are intermediate between those of Group 8 and Group 10. The mechanical and many other properties of the PGMs depend on the physical form, history, and purity of a particular metal sample. For example, electrodeposited platinum is much harder than wrought metal. 

Adhesion of copper films to PMDA/ODA polyimide was determined by peel tests conducted on samples that were prepared by vapor-depositing a thin layer of copper onto the polyimide and then building the thickness of the metal layer to about 18 p,m by electrodeposition of copper. Results of the adhesion measurements correlated well with substrate pretreatment. When the substrate... 

If the electrolysis parameters (precursor concentrations, pH, temperature, cur-rent/potential, substrate) be defined in a precise manner, a self-regulated growth of the compound can be established, and highly (111 )-oriented zinc blende (ZB) deposits up to several p,m thickness are obtained at potentials lying at the anodic limit of the diffusion range (Fig. 3.3) [60]. Currently, the typical method of cathodic electrodeposition has been developed to yield quite compact and coherent, polycrystalline, ZB n-CdSe films of well-defined stoichiometry. The intensity of the preferred ZB(f 11) orientation obtained with as-deposited CdSe/Ni samples has been quite high [61]. 

Mishra et al. [198] discussed in an exemplary way the dark and photocorrosion behavior of their SnS-electrodeposited polycrystalline films on the basis of Pourbaix diagrams, by performing photoelectrochemical studies in aqueous electrolytes with various redox couples. Polarization curves for the SnS samples in a Fe(CN) redox electrolyte revealed partial rectification for cathodic current flow in the dark, establishing the SnS as p-type. The incomplete rectification was... 

Early measurements of " Th were on seawater samples and Th was co-precipitated from 20-30 L of seawater with iron hydroxide (Bhat et al. 1969). This procedure may not recover all of the " Th in the sample, and an alpha emitting Th isotope (e g., °Th or Th) is added as a yield monitor. Following chemical purification of the Th fraction by ion exchange chromatography, the Th is electrodeposited onto platinum or stainless steel planchets. The planchets are then counted in a low background gas-flow beta detector to measure the beta activity and subsequently with a silicon surface barrier detector to determine the alpha activity of the yield monitor. The " Th activity is thus determined as ... 

Measurements of " Th in sediment samples (Aller and Cochran 1976 Cochran and Aller 1979) used much the same approach as outlined above. In this case, the dried sediment sample ( 10 g) was leached with strong mineral acid (HCl) in the presence of a yield monitor (generally Th, an artificial Th isotope resulting from the decay of Th that is produced by neutron capture on Th). Thorium was separated from U and purified by ion exchange chromatography, and electrodeposited onto stainless steel planchets. Counting and determination of " Th activity followed the procedure outlined above. 

Urine Spiked sample clean-up by co-precipitation, purified by TRU-spec column and electrodeposition a -Spectrometry 0.016 pCi/800 cm3 95% at 0.1-100 pCi/sample Goldstein et al. 1991... 

Soft tissue Sample wet ashed, spiked with 243Am, purified by anion exchange, solvent extraction, and electrodeposition a -Spectrometry No data 98% Mclnroy et al. 1985... 

Soft tissue Spiked sample wet ashed, treated with HN03/H202, purified by A-CU column, anion exchange, TRU-spec column, and electrodeposition a -Spectrometry No data 53% Qu et al. 1998... 

Air Cellulose filter dry ashed, dissolved in HNO3/HF, H202/HCI04, purified with anion exchange, TRU-spec columns followed by electrodeposition. a -Spectroscopy 0.023 pCi/sample 102% Goldstein et al. 1997... 

Sediments Sample leached with HNO3/HF, filtered, purified by KL-HDEHP resin columns, solvent extracted, and electrodeposition a -Spectroscopy No data 95-99% Guogang et al. 1998... 

The high stability of the metal clusters allows one to hold the sample potential slightly positive of the Nernst potential, typically at +10 mV versus Cu/Cu2 + in the case of copper. Thus, normal electrodeposition onto the sample directly from solution is prevented, whereas the tip-generated Cu clusters remain on the surface [96]. 

Air (particulate lead) Collection of sample onto filter addition of206Pb to filter dissolution of filter in NaOH acidification separation of lead by electrodeposition dissolution in acid IDMS 0.1 ng/m3 No data Volkening et al. 1988... 

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