Evaporation speed

In this way, the liquid can be transferred at a speed corresponding to the evaporation speed. The fraction to be analysed is contained in a loop (see Eigure 2.5), connected to a switching valve. By opening the valve, the sample in the loop is driven by the carrier gas into the GC unit (8), instead of the LC pump. An early vapour exit is usually placed after a few metres of the deactivated precolumn (9) and a short piece (3-4 m) of the main column (retaining precolumn). This valve is opened during solvent evaporation in order to reduce the amount of solvent that would reach the detector, and at the same time, to increase the solvent evaporation rate (6). 

LB films of cadmium octadecanoate and other amphiphiles were transferred on a quartz-crystal microbalance (QCM, 9 MHz, AT-cut) as a substrate with a vertical dipping method. Frequencies of the QCM substrate were followed with time in air, after the QCM was raised from the interface. From the time courses of these frequency changes at each dipping cycle, the transfer amount of dry LB films (W ), the incorporated amount of water (W2), and its evaporation speed (v) could be obtained in nanogram level. 

The gradual frequency increase from points B to C is explained by the mass decrease due to the evaporation of water deposited between layers from the subphase. The amount of incorporated water (W2 / ng) and its evaporation speed (v / ng min- ) were calculated from the frequency change and the initial slope of the time course between points B and C, respectively. The cadmium octadecanoate LB films were observed to incorporate W2 = 209 5 ng of water with 4 layers of LB films (W, = 232 3 ng) at the first dipping cycle cadmium octadecanoate were transferred on a substrate with the water of almost the same mass of LB films. 

Figure 4 Effect of number of layers on the amount of incorporated water (W2) and the evaporation speed of the water (v) in the transfer of cadmium octadecanoate LB films. The hydrophilic (O) and hydrophobic ( )...

The W2 and v values at the 5th dipping cycle were obtained at various surface pressures, and the results are shown in Figure 5. Both W 2 and v values increased with decreasing the surface pressure. At the low surface pressures below 20 mN m-i, the LB films having many defects were transferred with a low transfer ratio below 1.0, and the large amount of water was incorporated in these defects and its evaporation speed was fast through the disordered film. 

W 2 and v values at the 5th transfer cycle of cadmium octadecanoate at 20 mN m-i as a function of dipping speed of the QCM substrate are summarized in Table 1. The transfer ratio of LB films (W,) was 0.95 0.05 at the dipping speeds of 40 - 100 mm min. When the dipping speed was decreased, the evaporation speed (v) was decreased the well-oriented LB films could be obtained at the low dipping speed. This is consistent with the report by Pitt, et. al. that the lower transfer speed was favorable to obtain the higher quality LB films in the first 10 layers [31]. 

The W2 and v values for LB films prepared from various aliphatic acid cadmium salts having different alkyl-chain lengths (C)6 - C22) were also obtained and the results are shown in Figure 6. All LB films could be transferred with the transfer ratio of 1.0 0.1 in these conditions. The W2 value was constant and independent of the chain length, but the v value decreased with decreasing the chain length. This indicates that the chain length of lipids mainly affects the evaporation speed of water in LB interlayer and has no effect on the amount of the incorporated water. 

Thus, the incorporated water seems to exist near the hydrophilic head groups, so that the W2 value depended on their hydrophilicity, but not on the alkyl chain length. On the contrary, the evaporation speed v... 

The evaporation speed is expressed in the following equation according to Fick s low, where the water evaporation is supposed to occurs only from the outer layer, but not from the side part of LB films [32] ... 

LB films of various lipids were transferred on a QCM as a substrate under various conditions. The mass of the transferred film (W, the transfer ratio), the amount of incorporated water (W 2), and the evaporation speed (v) were evaluated from the frequency changes of the QCM during transfer processes in situ. We could estimate the deposition state and structures of LB films from these values. When the LB films deposited at the lower surface pressure and at the higher dipping speed on the more hydrophilic surface, the smaller transfer ratio and the larger amount of incorporated water, and the larger evaporation speed of the water were observed, which indicates the deposition of the disordered LB films. On the contrary, when the well-packed LB films are obtained, the good transfer ratio (W ), the small W2... 

Fig. 9.23 Evaporation speed of water from a green product.

When shrinking the ehannel length of the transistor deviee, the ehannel resis-tanee is redueed. Beneath a eertain threshold, contaet properties beeome visible in the present materials. To obtain optimal eharaeteristies for the sub-mierometer transistors, the ehoiee of the electrode material is erueial. Figure 22.7 shows mobility values ju(L) obtained from three series of OFETs with different eleetrode materials and DH4T as semiconduetor. The thiekness of the semieonduetor was 10 nm ( 4 monolayers), deposited at an evaporation speed of 2 pm/s. The eleetrode materials were Ti/Au (thiekness 5/20 nm), Ti/Pt (5/20 nm), and Pd (25 nm). Samples were produced by optieal lithography and... 

Evaporation without contamination has today been solved by modem means such as new types of non-reactive boat material and inserts or electron beam guns for refractory metals most difficult to evaporate because of high evaporation temperatures. Condensation, problematic in a few cases, such as Zn, Cd, Ga, Sn, Sb, can be influenced by nucleation and the selection of evaporation speed (generally high) and substrate temperature (generally low). Reactions with the residual gas during condensation which cause undefined film products, difficult to reproduce, can be reduced by decreasing the residual gas pressure and the unwanted gas components, and by correct choice of substrate temperature and evaporation speed [292, 293]. 

From the above analysis of volatile explosives, it is concluded that the mass speed of combustion equals the evaporation speed of liquids (Eq. 2.6). 

The simplest way to prepare a plasmonic nanostructure is thermal and electron beam deposition in vacuum on a flat substrate that is either hydrophilic or hydrophobic. Even though the roughness of the structure depends on the contact angle between the metal and substrate, which is less controllable, the method can be well applied to some metals. DUV plasmonic nanostructures were readily formed by thermal deposition of indium onto a glass substrate. The size of indium nanostructures can be controlled from 15 to 50 nm by the evaporation speed, pressure, and the deposited thickness. The resulting extinction peaks due to the dipole resonance were tuned to between 260 and 600 nm, which were used for surface enhancement of Raman spectroscopy by DUV excitation [7]. Self-assembled arrays of hemispherical gallium nanoparticles were deposited by molecular beam epitaxy on a sapphire support as a substrate for UV plasmonics. The mean NanoParticle radii of 23, 26, and 70 nm were fabricated at LSPR frequencies... 

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