Built-up films

Blodgett KB, Langmuir I (1937) Built-up films of barium stearate and optical properties. Phys Rev 51 964-982... 

To prepare ultrathin polymer films on the surface of wafers, especially those of large diameter (6 or 8 inch), uniformity and defect density become important factors in determining the resist quality. The conventional spin coating method has been reported to introduce interference striations (11) and high defect densities (2.31 when used to prepare ultrathin polymer films. As an alternative approach, the LB technique has been proposed as being suited to the preparation of more uniform ultrathin polymer films (2). Using this technique monolayer polymer films can be transferred layer by layer to the surface of a solid substrate from the water surface. An important feature of the LB technique is that the accumulation of monolayer films allows the thickness of the built-up film to be controlled in a precise manner. Consequently, extremely uniform and ultrathin polymer films can be prepared. 

Built-up films have been obtained by the vertical lifting method at room temperature with a 105 type LB trough. The IR spectra were recorded on a Nicolet FI-IR spectrometer, the UV-Vis spectra were measured using a Perkin-EImer 330 spectrometer whereas the SAXD measurements were performed on a D/Max-rA X-ray diffractometer (CuKa radiation with A = 0.15405nm). The AFM images were obtained on an SAP 400 (Seiko Instrument Inc.) microscope. 

RDE and RRDE are very convenient voltammetric methods for studying the mechanism and kinetics of ORR and are by far the most widely used methods. However, it is important to bear in mind that the underlying mathematical formulations of these methods are theorized for smooth electrode surfaces under laminar flow hydrodynamics. There are many examples in recent literature where RDE and RRDE have been used to study catalyst films for which turbulent flow hydrodynamics is quite obvious. The collection efficiency of RRDE for microscopically disordered films, for example, very porous materials and irregularly built-up films (as may be the case for catalysts modified with nanocarbons such as carbon nanotubes and graphenes), is likely to be determined erroneously due to sporadic hydrodynamics. Therefore, the quality of a given catalyst film has a great influence on the correctness of results obtained from RDE and RRDE. It is generally recommended that catalyst films for RDE and RRDE studies should be as thin as... 

Note that this relationship is in conPadiction to the well known equation for the calculation of the thickness resolving power given by Halmshaw in 111. The relationship in 111 requires explicit knowledge about built-up factors for scatter correction and the film contrast factory (depending on D) and is only valid for very small wall thickness changes compared to the nominal wall thickness. 

Volumes in mm (liquid) radii and film thicknesses in A area in m g . The remainder of the standard columns ([1] to [9]) may be built up from Tabic 3.2A an alternative table, based on regular intervals of r, may be built up from Table 3.2B. 

The right-reading positive image resides on the receptor film after lamination, exposure through a positive, and wash-out of the unexposed areas with a solvent or aqueous developer. The four-color proof is built up by the sequential lamination, exposure, and development steps. 

Hydrodynamic whirl N > 2Nt Nf =, 5N Nf <, 5N built-up parts Fluid film bearings... 

Modem apparatus are equipped with a rotating table to accommodate the TLC plate above the base of the reaction chamber This means that microwaves can penetrate the TLC plate from below through the glass plate or plastic film Aluminium foil backings are not suitable They reflect the radiation and high potentials are built up between the aluminium foil and the wall of the reaction chamber, these result in electrical discharges... 

Any real sample of a colloidal suspension has boundaries. These may stem from the walls of the container holding the suspension or from a free interface towards the surroundings. One is faced with surface effects that are small compared to volume effects. But there are also situations where surface effects are comparable to bulk effects because of strong confinement of the suspension. Examples are cylindrical pores (Fig. 8), porous media filled with suspension (Fig. 9), and thin colloidal films squeezed between parallel plates (Fig. 10). Confined systems show physical effects absent in the bulk behavior of the system and absent in the limit of extreme confinement, e.g., a onedimensional system is built up by shrinking the size of a cylindrical pore to the particle diameter. 

Tin when made anodic shows passive behaviour as surface films are built up but slow dissolution of tin may persist in some solutions and transpassive dissolution may occur in strongly alkaline solutions. Some details have been published for phosphoric acid with readily obtained passivity, and sulphuric acid " for which activity is more persistent, but most interest has been shown in the effects in alkaline solutions. For galvanostatic polarisation in sodium borate and in sodium carbonate solutions at 1 x 10" -50 X 10" A/cm, simultaneous dissolution of tin as stannite ions and formation of a layer of SnO occurs until a critical potential is reached, at which a different oxide or hydroxide (possibly SnOj) is formed and dissolution ceases. Finally oxygen is evolved from the passive metal. The nature of the surface films formed in KOH solutions up to 7 m and other alkaline solutions has also been examined. 

Comparative study of LB films of cytochrome P450 wild type and recombinant revealed similar surface-active properties of the samples. CD spectra have shown that the secondary structure of these proteins is practically identical. Improved thermal stability is also similar for LB films built up from these proteins. Marked differences for LB films of wild type and recombinant protein were observed in surface density and the thickness of the deposited layer. These differences can be explained by improved purity of the recombinant sample. In fact, impurity can disturb layer formation, preventing closest packing and diminishing the surface density and the average monolayer thickness. Decreased purity of... 

Multilayer assemblies of -0.5 pm thickness were built up on quartz plates and the films were characterized in detail using spectroscopic (vis. IR) and electron microscopic techniques. 

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