Composition-modulated films

Electrodeposition of composition-modulated films was first performed by Brenner in 1939 (1) by employing two separate baths for the two components and a periodic immersion of the deposit in the two baths. This is too cumbersome a method to be adopted in practice. Deposition from a single bath with the presence of salts of the two components of the multilayer is what is desired, but there was a serious problem with the deposition of two metals from one bath. Specifically, whereas a layer of the more noble member can be deposited by choosing the potential to be between the reduction potentials of the two metals, one can expect that when the potential is set to a value appropriate for reduction of the less noble member, both will be deposited, resulting in an alloy layer rather than a pure metal. Thus, to nobody s surprise, even as recently as 1983, Cohen et al. (2), were able to deposit only a layered structure of alloys rather than pure metals. In addition they cast doubt on the possibility that a modulation cycle (the thickness of the basic layers, the periodic repetition of which... 

Electrodeposition of composition-modulated films was first performed by Brenner in 1939 (1) by employing two separate baths for the two components and a periodic immersion of the deposit in the two baths. This is too cumbersome a method to be adopted in practice. Deposition from a single bath with the presence of salts of the two components of the multilayer is what is desired. 

Fig. 2. Schematic examples of various types of multiiiQreis or compositionally modulated films (CMF).

Krishnan V, Ham D, Mishra KK, Rajeshwar K J (1992) Electrosynthesis of thin films of CdZnSe Composition modulation and bandgap engineering in the ternary system. J Electrochem Soc 139 23-27... 

The use of UPD layers can in principle generate deposits with composition modulated on the atomic scale, and Pauling et al. have produced what they call hetero-structured ultra-thin films containing Ag, Pd and T1 by this method [158], Stickney and coworkers have assembled multilayered deposits of CdTe and GaAs by addition of one atomic layer of the individual components at a time, a process they call electrochemical atomic-layer epitaxy [159 162], The essential controlling feature in the UPD mechanism is that the deposited layers are allowed to reach equilibrium. Hence, the process represents an extreme of local, reversible control. 

Different authors have shown that compositionally modulated 3D metallic alloys can be electrochemically deposited using cyclic polarization conditions and multicomponent electrolytes [6.108, 6.109, 6.113, 6.114]. Alloy formation takes place alternately by diffusion and charge transfer control of the deposition reactions of different metal components. Similar conditions have been used for the deposition of ultrathin metal films and heterostructures (cf. Section 6.4). 

Sato, K. Kida, H. (1988). Calculations of magneto-optical spectra in compositionally-modulated multilayered films. Journal de Physique, Colloque C8, C8-1779-80. 

We develop the potential-programmed electropolymerization method for modulating the composition of conducting polymer composite thin films to the depth direction. In this study, nm-order compositional control of composite thin films of conducing polymer, the... 

Oberle RR, Cammarata RC (1995) Dependence of hardness rat modulation amplitude in electrodeposited Cu-Ni compositionally modulated thin films. Scr Metall Et Mater 32 583-588... 

Zr—Fe/TbFe)n amorphous multilayers. Katayama et al. (1987) have studied the variation of saturation magnetization as a function of the composition modulation period. As the multilayers becomes thinner, increases. This is explained by the fact that magnetization of Fe within the ZrFe film is induced by the TbFe film. 

Cu/Y) . R.W. Johnson et al. (1989a,b) have shown that compositionally modulated (Cu/Y) films form an amorphous C%Yphase at 293 K. The amorphization reaction occurs both at the original Cu/Y interface and within the Y grain boundaries (fig. 26). The authors refer to the Yhep—>Yfcc transition in the case of the thiimer... 

In a multilayer structure built by successive depositions, it can happen that the structures at the top and bottom interfaces of each layer have different chemical profiles. In other words, the compositional modulation may have a unidirectional profile with respect to the film growth direction. Mossbauer spectroscopy is a unique method to clarify the difference of interface chemical profile in two interfaces top and bottom. In general, if a Mossbauer probe is located at the interface of magnetic layer, observed hyperfine field distribution is useftd information for the estimation of degree of intermixing at the interface. 

Hollow-fiber designs are being displaced by spiral-wound modules, which are inherently more fouling resistant, and require less feed pretreatment. Also, thin-film interfacial composite membranes, the best reverse osmosis membranes available, have not been fabricated in the form of hoUow-fine fibers. 

The membrane material is a thin-film composite in a 20-cm module. 

The schematic diagram of the experimental setup is shown in Fig. 2 and the experimental conditions are shown in Table 2. Each gas was controlled its flow rate by a mass flow controller and supplied to the module at a pressure sli tly higher than the atmospheric pressure. Absorbent solution was suppUed to the module by a circulation pump. A small amount of absorbent solution, which did not permeate the membrane, overflowed and then it was introduced to the upper part of the permeate side. Permeation and returning liquid fell down to the reservoir and it was recycled to the feed side. The dry gas through condenser was discharged from the vacuum pump, and its flow rate was measured by a digital soap-film flow meter. The gas composition was determined by a gas chromatograph (Yanaco, GC-2800, column Porapak Q for CO2 and (N2+O2) analysis, and molecular sieve 5A for N2 and O2 analysis). The performance of the module was calculated by the same procedure reported in our previous paper [1]. 

The geometries for asymmetric mixed-matrix membranes include flat sheets, hollow fibers and thin-fihn composites. The flat sheet asymmetric mixed-matrix membranes are formed into spirally wound modules and the hollow fiber asymmetric mixed-matrix membranes are formed into hollow fiber modules. The thin-film composite mixed-matrix membranes can be fabricated into either spirally wound or hollow fiber modules. The thin-film composite geometry of mixed-matrix membranes enables selection of different membrane materials for the support layer and low-cost production of asymmetric mixed-matrix membranes utilizing a relatively high-cost zeolite/polymer separating layer on the support layer. 

The design and manufacture is described in detail of a dashboard module from polypropylene. The lightweight monomaterial dashboard comprises an outer material of a TPO film, foam backed with an EPP foam. This decorative element, together with a highly integrated composite fibre hybrid cross beam, forms the core element of the lightweight dashboard module. The prototype consists of four individual components, and is designed in such a way that it can be built into and tested in the Mercedes A class car. 3 refs. 

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