Parallel-plate technique

In Table 5.1, it can be seen that 48 out of 103 data sets of thermal conductivity of aqueous solutions at high temperatures, were derived with the parallel-plate technique. This technique for the measurement of the thermal conductivity has been in use for almost a century (Todd, 1909), and it has in feet been considerably improved over the years (Sengers, 1962 Michels et al, 1962, 1963 Sirota et al, 1974 Amirkhanov and Adamov, 1963 Amirkhanov et al, 1974 Guseynov, 1987, 1989 Moster et al, 1989 and 

Solute First author Reference Code for Appendix Concentration Temperature (K) Pressure (MPa) Method Uncertainty (%) 

C2H4O2 (acetic acid) Bleazard, Sun and Teja, 1996 25-100 mass % 298-412 1 CF 2.0 

Cal2 Abdulagatov Magomedov, 2000a tc-Cal2-l.l 2.5-25 mass % 293/473 0.1/2-100 PP 1.6 

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Fig. 1 Setup for electrospinning aligned nanofibers using the (a) rotating mandrel, and the (b) parallel plate techniques, (c) Calculated electric field strength vectors and (d) electrostatic force (F) analysis associated with the parallel plate techniques [62]...

A major limitation of the parallel plate technique is limited fiber density and mat thickness, as explained in Sect. 3.2.1. This problem can be overcome by utilizing other forces that are able to overcome the electrostatic repulsive force between nanofibers. Thick aligned nanofiber mats were fabricated across parallel plates when a magnetic field was used to attract fibers to a mesh across parallel plates [97]. Another technique utilized mechanical forces to assemble low density aligned fiber arrays into thicker constructs [98]. This technique used automated tracks to provide continuous mechanical assembly of fiber arrays, and allows theoretically infinite mat thicknesses. 

The parallel-plate technique is schematically represented in Fig. 5e. It is an important method because it covers the intermediate viscosity range, 8 < logr/ < 4 (Pas). The equation which relates the viscosity to the deformation is... 

There are two electrode sensor geometries that are common in dielectric analysis. As noted previously, the traditional electrode is a parallel-plate capacitor (Fig. 47). However, this geometry is not well suited for thermoset cure monitoring. In order to obtain high signal levels with the classical parallel-plate technique, thin specimens with large areas are required, and the dielectric properties are an average of the bulk. In addition, low frequency measurements, which can reveal... 

According to the parallel-plate technique, the fluid under investigation is confined between two horizontal plates, heated from above, so that the upper plate is at a higher temperature than the lower one. Provided the two plates are maintained at constant uniform temperatures T and T2 respectively, the steady-state solution of Equation (5.1) is... 

Fig. 4.15 a Set-up for electrospinning aligned nanofibres using the parallel plate technique, b Dark field optical micrograph of PVP nanofibres collected across a void gap formed between two silicon strips. Reproduced from Ref. [190]... 

Plasmas can be used in CVD reactors to activate and partially decompose the precursor species and perhaps form new chemical species. This allows deposition at a temperature lower than thermal CVD. The process is called plasma-enhanced CVD (PECVD) (12). The plasmas are generated by direct-current, radio-frequency (r-f), or electron-cyclotron-resonance (ECR) techniques. Eigure 15 shows a parallel-plate CVD reactor that uses r-f power to generate the plasma. This type of PECVD reactor is in common use in the semiconductor industry to deposit siUcon nitride, Si N and glass (PSG) encapsulating layers a few micrometers-thick at deposition rates of 5—100 nm /min. 

Capacitive Sensors. This device usually consists of a capacitor which is formed either from two concentric cylinders or from a pair of parallel plates. The solid sample to be analyzed for moisture content is passed between these plates. Since w has a large dielectric constant, the w content of the sample causes a significant change in the dielectric constant of the solid, which is measured using bridge or frequency techniques. 

Our experimental techniques have been described extensively in earlier papers (2, 13). The gamma ray irradiations were carried out in a 50,000-curie source located at the bottom of a pool. The photoionization experiments were carried out by krypton and argon resonance lamps of high purity. The krypton resonance lamp was provided with a CaF2 window which transmits only the 1236 A. (10 e.v.) line while the radiation from the argon resonance lamp passed through a thin ( 0.3 mm.) LiF window. In the latter case, the resonance lines at 1067 and 1048 A. are transmitted. The intensity of 1048-A. line was about 75% of that of the 1067-A. line. The number of ions produced in both the radiolysis and photoionization experiments was determined by measuring the saturation current across two electrodes. In the radiolysis, the outer wall of a cylindrical stainless steel reaction vessel served as a cathode while a centrally located rod was used as anode. The photoionization apparatus was provided with two parallel plate nickel electrodes which were located at equal distances from the window of the resonance lamp. 

In the laser flash method, a melt of interest is placed between two parallel plates. The upper plate is heated stepwise and the thermal diffusiv-ity is measured from the rise in temperature. The specific design for molten materials and especially slags employed by Ohta et al. is based on the differential three-layer technique utihzing a special cell that can be accommodated in the system. A schematic diagram of the principle of the measurement section is shown in Fig. 31. A laser pulse irradiates the upper (platinum) crucible and the temperature response of the surface of the lower platinum crucible is observed, a liquid specimen being sandwiched between the two. 

Three different dry etch techniques were investigated isotropic O2 plasma etching in a Tegal 200 reactor, R.I.E. in a parallel-plate in-house modified Tegal AOO reactor and R.I.M. in a Veeco, Model RG-830. The conditions of operation for each system were as follows where time is the time to etch 1.2 p of fully cured polyimide. 

Chapter H2 describes the measurement of textural properties of solid-like foods. The first unit in that chapter, unit H2.i, describes a general procedure commonly used to evaluate the texture of solid foods. This method involves the compression of the food material between two parallel plates. There are a number of empirical textural parameters which can be evaluated with this technique. Simple compressive measurements do not provide a complete textural picture of some foods untthi.i presents variations to the parallel plate compression method with the use of special fixtures. For example the use of a puncture probe or a wire cutting device provide data that may relate more directly to the consumer s evaluation of texture for products like apples and cheese, unit m.3 describes a general protocol for the evaluation of a number of sensory texture parameters. This protocol is... 

The use of a rotating vane has become very popular as a simple to use technique that allows slip to be overcome (33,34). Alderman et al (35) used the vane method to determine the yield stress, yield strain and shear modulus of bentonite gels. In the latter work it is interesting to note that a typical toique/time plot exhibits a maximum torque (related to yield stress of the sample) after which the torque is observed to decrease with time. The fall in torque beyond the maximum point was described loosely as being a transition from a gel-like to a fluid-like behavior. However, it may also be caused by the development of a slip surface within the bulk material. Indeed, by the use of the marker line technique, Plucinski et al (15) found that in parallel plate fixtures and in slow steady shear motion, the onset of slip in mayonnaises coincided with the onset of decrease in torque (Fig. 8). These authors found slip to be present for... 

Applications of optical methods to study dilute colloidal dispersions subject to flow were pioneered by Mason and coworkers. These authors used simple turbidity measurements to follow the orientation dynamics of ellipsoidal particles during transient shear flow experiments [175,176], In addition, the superposition of shear and electric fields were studied. The goal of this work was to verify the predictions of theories predicting the orientation distributions of prolate and oblate particles, such as that discussed in section 7.2.I.2. This simple technique clearly demonstrated the phenomena of particle rotations within Jeffery orbits, as well as the effects of Brownian motion and particle size distributions. The method employed a parallel plate flow cell with the light sent down the velocity gradient axis. 

Silicon nitride films produced by this technique proved to be comparable to those created in parallel-plate reactors in terms of stoichiometry and hydrogen content, as evidenced by the data presented in Figures 17 and 18. 

Experimental techniques such as those used to measure specific values of viscosity (e.g. softening point) are still in common use, but are not as powerful as those in which a range of viscosities can be measured. Hence, only the Margules (1 to 106 Pa-s), parallel plate (103 to 108), and beam bending viscometers (107 to 1014 Pa-s) will be discussed here. These devices are manufactured and marketed by Theta Industries. 

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