Immersion

The quantity ( xsl- tsv) is called the work of immersion Wi because it defines the surface energy change when a S/V surface of unit area is replaced by a S/L interface of equal area by immersion of a solid in a liquid. In both the immersion and capillary rise processes, S/V and S/L areas change but the total L/V surface remains constant. Using the Young equation (1.16), Wf and ze can be written  

Chernov, A. A. (1984) Modern Crystallography III Crystal Growth, ed. M. Cardona, P. Fulde and H. J. Queisser, Springer-Verlag, Berlin 

Collins, R. E. and Cooke, C. E. (1959) Trans. Faraday Soc., 55,1602 Defay, R., Prigogine, I., Bellemans, A. and Everett, D. H. (1966) Surface Tension and Adsorption, Longmans, London de Gennes, P. G. (1985) Reviews of Modern Physics, 57, 827 

(1869) Theorie Mecanique de la Chaleur, Chapter IX, Actions moleculaires (suite), published by Gauthier-Villars, Paris 

Laplace (Marquis), P. S. (1805) Traite de Mecanique Celeste, fourth volume, first section (theorie de Taction capillaire) of the supplement to Book 10 (sur divers points relatifs au systeme du monde), published by Chez Courier, Paris Marmur, A. (1996) Langmuir, 12, 5704 Marmur, A. (1997) 7. Colloid and Interface Science, 186, 462 McNutt, J. E. and Andes, G. M. (1959)7. Chem. Phys., 30,1300 Merlin, V. (1992) Ph.D. Thesis, INP Grenoble, France Mullins, W. W. (1957)7. Appl. Phys., 28, 33 Mullins, W. W. (1960) Trans. Met. Soc. AIME, 218, 354 Mullins, W. W. (1963) Metal Surfaces Structure, Energetics and Kinetics, ASM 

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It has been used as a bird repellant and is the parent compound of the anthraquinone vat dyes in which the dyeing is carried out by immersion in the reduced vat solution followed by air oxidation to the original insoluble compound. 

In case hardening C and N are introduced into the iron by heating in a Nj —NH3 atmosphere or by immersing the steel in molten NaCN/Na2C03 at about 900"C. 

In the standard method, the metal enclosure (called the air chamber) used to hold the hydrocarbon vapors is immersed in water before the test, then drained but not dried. This mode of operation, often designated as the wet bomb" is stipulated for all materials that are exclusively petroleum. But if the fuels contain alcohols or other organic products soluble in water, the apparatus must be dried in order that the vapors are not absorbed by the water on the walls. This technique is called the dry bomb" it results in RVP values higher by about 100 mbar for some oxygenated motor fuels. When examining the numerical results, it is thus important to know the technique employed. In any case, the dry bomb method is preferred. 

Finally, other tests to control jet fuel corrosivity towards certain metals (copper and silver) are used in aviation. The corrosion test known as the copper strip (NF M 07-015) is conducted by immersion in a thermostatic bath at 100°C, under 7 bar pressure for two hours. The coloration should not exceed level 1 (light yellow) on a scale of reference. There is also the silver strip corrosion test (IP 227) required by British specifications (e.g., Rolls Royce) in conjunction with the use of special materials. The value obtained should be less than 1 after immersion at 50°C for four hours. 

Copper strip corrosion NFM 07-015 ISO 2160 ASTM D 130 Appearance of a copper blade after immersion... 

Corrosive sulfur NFT 60-131 ISO 5662 ASTM D 1275 Observation of copper strip after immersion for 19 h at HOT... 

In service inspections of French nuclear Pressure Water Reactor (PWR) vessels are carried out automatically in complete immersion from the inside by means of ultrasonic focused probes working in the pulse echo mode. Concern has been expressed about the capabilities of performing non destructive evaluation of the Outer Surface Defects (OSD), i.e. defects located in the vicinity of the outer surface of the inspected components. OSD are insonified by both a "direct" field that passes through the inner surface (water/steel) of the component containing the defect and a "secondary" field reflected from the outer surface. Consequently, the Bscan images, containing the signatures of such defects, are complicated and their interpretation is a difficult task. 

Let us consider one more physical phenomenon, which can influence upon PT sensitivity and efficiency. There is a process of liquid s penetration inside a capillary, physical nature of that is not obvious up to present time. Let us consider one-side-closed conical capillary immersed in a liquid. If a liquid wets capillary wall, it flows towards cannel s top due to capillary pressure pc. This process is very fast and capillary imbibition stage is going on until the liquid fills the channel up to the depth l , which corresponds the equality pcm = (Pc + Pa), where pa - atmospheric pressure and pcm - the pressure of compressed air blocked in the channel. 

The properties of the piezocomposite material mentioned above offer special benefits when the transducer is coupled to a material of low acoustic impedance. This especially applies to probes having plastic delay lines or wedges and to immersion and medical probes. These probes with piezocomposite elements can be designed to have not only a high sensitivity but also at the same time an excellent resolution and, in addition, the effort required for the probe s mechanical damping can be reduced. 

For immersion probes we also get similar improvements using piezocomposite transducers as demonstrated by the third example. In Fig. 8 we compare pulse form and frequency spectrum for a 2 MHz probe Z2K with 10 mm transducer diameter. The echo of the composite probe has 11 dB more amplitude and is clearly shorter than for the old design, also indicated by the increase in bandwidth from 45 to 76 %. 

Fig. 8 Pulse shape (top) and spectrum (bottom) for a 2 MHz immersion probe with PZT (left) and composite transducer (right)...

The Champ-Sons model is a most effieient tool allowing quantitative predictions of the field radiated by arbitrary transducers and possibly complex interfaces. It allows one to easily define the complete set of transducer characteristics (shape of the piezoelectric element, planar or focused lens, contact or immersion, single or multi-element), the excitation pulse (possibly an experimentally measured signal), to define the characteristics of the testing configuration (geometry of the piece, transducer position relatively to the piece, characteristics of both the coupling medium and the piece), and finally to define the calculation to run (field-points position, acoustical quantity considered). 

The method is now applied to an object "o" consisting of an aluminum rod immersed in a tank and fixed at the supposed center of the bench the section of the rod being smaller than the central wavelength the size of the square section of the rod is 4 mm and the wavelength is 6 mm (the central frequency of the transducer is 250 kHz). Figure la gives the time-sinogram of the object without correction ... 

Figure 1 Examples of anay transducers, a/ Dual anay probe for plate inspection b/ Immersion 45° SW focused anay probe for inner tube inspection, c/ Immersion encircling probe for tube inspection...

Figure 4 Acoustic beam characterization set-up for the immersion SW array probe a/ Angle beam characterization principle b/ General view of the automatic bench...

The HILL-SCAN 30XX boards can be used in different PCs. Desktop- and tower-PCs as well suited for laboratory uses. For in-field inspections rugged notebooks and portable PCs are advantageous. A typical portable system is shown in Fig. 2 (USPC 3010), used in MUSE (Mobile Ultrasonic Equipment). This portable PC not only contains the boards for ultrasonic testing but also a controller with power supply for stepper motors, so that a manipulator can be connected directly. The MUSE system is enlarged with a water circulation system which enables a local immersion technique" for in-field inspections. A typical result is shown in Fig. 3, which presents a D-scan of a CFRP- component in RTM-techniques. The defect area caused by an impact is clearly indicated. The manipulator is described in [3]. 

The use of the surface ultrasonic waves seems to be convenient for these purposes. However, this method has not found wide practical application. Peculiarities of excitation, propagation and registration of surface waves created before these time great difficulties for their application in automatic systems of duality testing. It is connected with the fact that the surface waves are weakened by soil on the surface itself In addition, the methods of testing by the surface waves do not yield to automation due to the difficulties of creation of the acoustic contact. In particular, a flow of contact liquid out of the zone of an acoustic line, presence of immersion liquid, availability of chink interval leads to the adsorption and reflection of waves on tlie front meniscus of a contact layer. The liquid for the acoustic contact must be located only in the places of contact, otherwise the influence on the amplitude will be uncontrolled. This phenomenon distorts the results of testing procedure. 

Fig.5. Appearance of installation for the testing of pistons of diesel engines. 1- ultrasonic flow detector 2- electronic blocks 3- electromechanical drives 4- immersion bath 5-controllable detail.

An immersion technique would be preferred to overcome to couple the signal from the... 

For the prototype equipment normal immersion inspection in water was selected instead of the delay line solution. 

Through the use of lab tests implemented by the pulp and paper companies in the United States and Canada it was determined that all but one manual technique were both unrepeatable and inaccurate. During some years ago the operators of black liquor recovery boilers have been able to take advantage of the latest teehnology to inspect the wall thickness of the near drum generator tubes. The technology utilises immersion ultrasound and automated computer... 

A modification of the foregoing procedure is to suspend the plate so that it is partly immersed and to determine from the dry and immersed weights the meniscus weight. The procedure is especially useful in the study of surface adsorption or of monolayers, where a change in surface tension is to be measured. This application is discussed in some detail by Gaines [57]. Equation 11-28 also applies to a wire or fiber [58]. 

The Wilhelmy slide has been operated in dynamic immersion studies to measure advancing and receding contact angles [59] (see Chapter X). It can also... 

According to the simple formula, the maximum bubble pressure is given by f max = 27/r where r is the radius of the circular cross-section tube, and P has been corrected for the hydrostatic head due to the depth of immersion of the tube. Using the appropriate table, show what maximum radius tube may be used if 7 computed by the simple formula is not to be more than 5% in error. Assume a liquid of 7 = 25 dyn/cm and density 0.98 g/cm. ... 

In the Wilhelmy slide method, it seems best to partly immerse the slide and determine the change in height with constant upward pull or the change in pull at constant position of the slide. If the latter procedure is used, then... 

Fig. V-5. The repulsive force between crossed cylinders of radius R (1 cm) covered with mica and immersed in propylene carbonate solutions of tetraethylammonium bromide at the indicated concentrations. The dotted lines are from double-layer theory (From Ref. 51).

While evidence for hydration forces date back to early work on clays [1], the understanding of these solvent-induced forces was revolutionized by Horn and Israelachvili using the modem surface force apparatus. Here, for the first time, one had a direct measurement of the oscillatory forces between crossed mica cylinders immersed in a solvent, octamethylcyclotetrasiloxane (OMCTS) [67]. 

Calculate A/Aq of Eq. VI-38 assuming that the mica cylinders are immersed in a dilute aqueous solution at 25°C and taking the parameters to have the indicated typical values. 

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