Thermal electrical measurement

An alternative approach by Zhu et al. (1990) yielded a similar activation energy (for P), while providing new information on the donor-hydrogen dissociation reaction. With electrical measurements they studied the electric-field induced migration of hydrogen that is thermally released from PH... 

The analysis can be made in situ using an optical, thermal, electrical or other method. The average time, during which the reaction proceeds before an element of volume and reaches a distance d along the reaction tube, is d/v, where v is the linear velocity. From the measurements made at various... 

Tests are usually classified by the parameters to be measured -mechanical, thermal, electrical etc. These can be sub-divided to list the actual properties so that under mechanical, for example, there are strength, stiffness, creep etc. This form of classification will be used in this book because of its convenience. However, in terms of the purposes of testing discussed above and considering what is required of the results from a particular method, this classification is not particularly useful. A more generalised way of classifying tests is to consider -... 

Ammonia is readily detectable in air in the range of a few parts per million by its characteristic odor and alkaline reaction. Specific indicators, such as Nessler s reagent (Hgk in KOH), can detect ammonia in a concentration of 1 ppm. For the quantitative determination of ammonia in air, synthesis gas and aqueous solutions, these methods can be used74 Acidimetry and Volumetric Analysis By Absorption, Gas Chromatography, Infrared Absorption, Thermal Conductivity Measurement, Electrical Conductivity Measurement, Measurement of Heat of Neutralization, and Density Measurement (for aqueous ammonia). 

Thermal emission measurements are generally based on electrical transport and in most cases involve the effects of a trapped space charge, Q. The two main ways of extracting information about the density of states distribution are from the release time of the charge from the traps... 

Plutonium. Gardner et al. (26) have made a careful high temperature x-ray diflFraction study of the plutonium-oxygen system in the range from room temperature to 900°C. observing diffraction from oxide samples contained in silica capillaries. They review briefly previous work apropos of phase transformations (i.e., thermal and electrical measurements) and construct a phase diagram as shown in Figure 5. 

Certain features of the study were emphasized such as the fact that although the PuOi.ei phase was assumed b.c.c., the powder patterns were not good enough to show the superstructure lines. Also the eutectoid in the proposed diagram of Chikalla et al. (22) was not observed in the x-ray studies. No satisfactory explanation of electrical resistivity and thermal expansion measurements which led to this earlier construction has emerged. Gardner et al. (26) also looked for but did not see any indication of ordered intermediate phases at low temperatures such as were described above for the rare earth oxides nor did they observe a failure of the miscibility gap to close as would have occurred if the end members, PuOi.oi and PuOi.gg, had different symmetries. They could... 

A 3-mm-diameter and 5-m-long electric wire is tightly x rapped with a 2-mm-1 thick plastic cover whose thermal conductivity is Ar = 0.15 W/m "C. Electrical measurements indicate that a current of 10 A passes through the wire and there is a voltage drop of 8 V along the wire. If the insulated wire is exposed to a medium at = 30°C v/ith a heat transfer coefficient of /i = 12 W/m °C, determine the temperature at the interface of the wire and the plastic cover in steady operation. Also determine whether doubling the thickness of the plastic cover will increase or decrease this interface temperature. 

Table 4. Best CFI parameters for RA12 compounds obtained from magnetic, thermal and electrical measurements (45,54, 61,64, 65, 68, 69).

Reviews of the application of electrical measurements in solid state decompositions have been given by Kabanov [52]. Electrical conductivity measurements, both a.c. and d.c. studies, have been used to characterize the species that participate in the thermal decomposition of ammonium perchlorate [53,54] (this reaction is discussed in Chapter 15). Other studies have been concerned with the mechanisms of oxide decompositions [55,56]. Torkar et al. [56] conclude from electrical conductivity evidence that the decompositions of alkali oxides are more complicated than exciton formation processes. 

Figure 24-4 Emission or chemiluminescence processes. In (a), the sample is excited by the application of thermal, electrical, or chemical energy. These processes do not involve radiant energy and are hence called nonradia-tive processes. In the energy-level diagram (b), the dashed lines with upward-pointing arrows symbolize these nonradiative excitation processes, while the solid lines with downward pointing arrows indicate that the analyte loses its energy by emission of a photon. In (c), the resulting spectrum is shown as a measurement of the radiant power emitted Pg as a function of wavelength, A.

The phase composition of the resulted specimens was identified by X-ray diffraction (XRD). Rod-like pieces (3x3xl5mm) and disk-shaped pieces (2mm thickness and 10mm diameter) were cut out for the electrical conductivity measurement and the thermal conductivity measurement, respectively. Microstmcture and phase distribution were observed by a scanning electron microscopy equipped with EPMA (JEOL JXA-8621MX). Electrical conductivity was measured using a D.C. four-probe method. Thermal conductivity was measured using a laser-flash technique. All the measurements were performed in the temperature range of 300 to 1200 K. 

In this work, an attempt was made to prepare IrSbs by liquid-solid phase sintering (LSPS) and hot pressing of pulverized LSPS powders. The LSPS powder were characterized by using an X-ray diffractometer. These procedures were also applied to form an IrSbs-CoSba solid solution. The electrical conduction parameters of these materials were examined on the electrical measurement. The thermal stability of the hot-pressed IrSbs was also investigated. 

The resistivity, that could be also regarded as an apparent quantity, was also calculated in the manner that the electrical resistance (V/1) was multiplied by the cross-sectional area and divided by the length of the current pass. Such a method as the above mentioned may not be always verified right for thermoelectric measurements, but would be a simpler and easier manner to make a preliminary evaluation of FGM samples to be placed in large temperature gradients. As for the thermal conductivities, however, no data were obtained because of difficulty originated in our equipment of thermal conductivity measurement (the Laser Flash... 

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