Duplex layer model

As explained previously, electrodissolution in ionic liquids is a simple and efficient process, particularly in chloride-based eutectics. Type III eutectics based on hydrogen bond donors are particularly suitable for this purpose. However, it has been noted that the polishing process only occurs in very specific liquids and even structurally related compounds are often not effective. It has been shown that 316 series stainless steels can be electropolished in choline chloride ethylene glycol eutectics [19] and extensive electrochemical studies have been carried out. The dissolution process in aqueous solutions has been described by two main models the duplex salt model, which describes a compact and porous layer at the iron surface [20], and an adsorbate-acceptor mechanism, which looks at the role of adsorbed metallic species and the transport of the acceptor which solubilises... 

Several qualitative models have been proposed to explain porous Si formation but none of them allow full explanation of the rich variety of morphology exhibited by porous Si and, in particular, the formation of the duplex layers (nano -I- macroporous). In addition, they possess very little predictive power. A majority of the models focussed on the pore propagation, whereas the mechanism of pore initiation received very little attention. A comprehensive review of the various models proposed to explain pore formation is found in excellent review articles by Smith and Collins [5], Parkhutik [12], and Chazalviel and coworkers [13]. Two main categories of models have been proposed. The first one is basically electrostatic in nature, based on the consideration that physical effects associated with the SCR play a major role in the pore-formation mechanism. The second category is based on computer simulations. 

Yin K. M. (1996), Duplex diffirsion layer model for pulse with reverse plating . Surf. Coat. TechnoL, 88,162, doi 10.1016/80257-8972(96)02904-0. 

The analysis of the XPS measurements of the passive layers and their interpretation require a model for their structure. This will be discussed for the formation of passive layers on Fe in 1 M NaOH. Similar procedures have been applied for several other systems, as will be discussed in detail in the following sections of this paper. Passive layers are generally not homogeneous and at least a duplex structure has to be accepted. Angular-dependent XPS measurements suggest this situation, as has been shown already for the case of Fe in alkaline solution (Fig. 17). Quantitative XPS allows the determination of the intensity ratio of the Fe species of different valency. The intensity ratios according to Eqs. (20) and (21) provide a possibility to calculate the thickness of the inner d and outer d-> part. Eq. (19) permits the conclusion about which species is located at the inner and which at the outer side. 

Fig. 45. Band structure model for passive layers on Cu for increasing potential explaining quantitatively the formation of the duplex film and the transpassive behavior [86],...

Therefore, the model of mass transport in a MREF waveform can be illustrated using a simple model of duplex diffusion layer , which was developed by Ibl 111121 for pulse plating. As shown in Figure 2, the diffusion layer may be divided into two parts, a pulsating diffusion layer of thickness 8p and a stationary diffusion layer. At the end of a pulse, the pulsating diffusion layer thickness 8p (under low duty cycle) is given by ... 

Moreover, gradients of stoichiometry limit the accuracy of thickness determinations that often only refer to parts of the passive film. Many oxide films show an increase of oxidation state from metal to the electrolyte, for example, on Cu [13]. In case of passive iron, many traditional techniques only evaluate the thickness of the outer Fe203-film, but not that of the inner Fc3 04-layer. While Vetter [28] described the film by a duplex model, Wagner [14] presented a model with continuous change of stoichiometry. 

In experiments covering a larger potential region, from the oxidized state until the complete neutral state, a new resonance circuit was found not described by the transmission line model. A new model was suggested by Pickup et al., which was used and modified later by Rammelt and Plieth et This model is corroborated by the duplex film structure (Figure 11.9). A compact layer on the metal/polymer interface with neutral state properties in the neutral state and double-layer properties in the oxidized state describes the compact polymer film the transmission fine model represents the porous part (Figure 11.17). 

When using the creep model for duplex microstructure, as developed by French et al. [98], it is possible to fabricate a composite with a defined creep resistance that will control the grain size, the width of the layers, and the compression axis. In the case of isostrain, where the strain and strain rate are the same for each phase, and assuming the creep equation in a compact form as, e = Ajo the stress for this configuration, o, is given as ... 

There are seven layers in the OSI model, starting with the physical layer handling the raw data transmission over a physical medium. The most common transmission media are twisted pair (copper wires), coaxial cable, and fiber optics. The data link layer, usually implemented in the network adaptors, is above the physical layer and is concerned with the organization of data into frames and the reliable transportation of these frames over a direct link. The specific problems of multi-access links such as channel allocation and collision detection are handled by the data link sub-layer called medium access control (MAC). Reliable frame delivery, frame ordering, and frame retransmission are provided in the layer by sliding window protocols. This is a set of protocols for full-duplex data frame transmission, in which the sender and the receiver both keep windows of frame acknowledgements and send frames only if a certain number of already sent frames were acknowledged by the receiver. The data link layer also includes some error detection and correction functions such as parity bit code and cyclic redundancy code (CRC). 

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