Insulating samples measurement

The ratio Db/Da is a so-called relative sensitivity factor D. This ratio is mostly determined by one element, e. g. the element for insulating samples, silicon, which is one of the main components of glasses. By use of the equation that the sum of the concentrations of all elements is equal to unity, the bulk concentrations can be determined directly from the measured intensities and the known D-factors, if all components of the sample are known. The linearity of the detected intensity and the flux of the sputtered neutrals in IBSCA and SNMS has been demonstrated for silicate glasses [4.253]. For SNMS the lower matrix dependence has been shown for a variety of samples [4.263]. Comparison of normalized SNMS and IBSCA signals for Na and Pb as prominent components of optical glasses shows that a fairly good linear dependence exists (Fig. 4.49). 

In the absence of space charges, but where an electric field is applied across the insulating sample, the current transient reflects the induced charges at the electrode/insulator interface. Since these charges occupy a negligible depth, the profile of the current peaks reflects the profile of the pressure pulse itself. This enables a calibration of the measurement system to be made. 

Another method for measuring thermal diffusivity is the flash method developed by Parker et al. [48] and successfully used for the thermal diffusivity measurement of solid materials [49]. A high intensity short duration heat pulse is absorbed in the front surface of a thermally insulated sample of a few millimeters thick. The sample is coated with absorbing black paint if the sample is transparent to the heat pulse. The resulting temperature of the rear surface is measured by a thermocouple or infrared detector, as a function of time and is recorded either by an oscilloscope or a computer having a data acquisition system. The thermal diffusivity is calculated from this time-temperature curve and the thickness of the sample. This method is commercialized now, and there are ready made apparatus with sample holders for fluids. There is only one publication on nanofluids with this method. Shaikh et al. [50] measured thermal conductivity of carbon nanoparticle doped PAO oil. 

Figure 11.24. Apparatus used by Chiu (102) for parallel TG—DTG-DTA and ETA measurements. A. balance housing B, balance beam sheath C, beam stop D, quartz beam E, sample container F. thermocouple block G, sample measuring thermocouple H. ceramic tubing I, platinum jacket J. reference quartz tube K. sample quartz tube L, outer platinum electrode M, center platinum electrode N, cold beam member O. P. platinum lead wires Q, sample thermocouple junction R, reference thermocouple junction S. spacer T, ceramic insulation U, V. sample thermocouple wires W. platinum grounding wire.

Laser ablation-AAS is also useful for insulating samples, where AA analysis is performed directly in the laser plume. Due to the production of various particles in the measurement zone (solid particles, molecules, radicals) and the resulting background emission, appropriate techniques for the correction of spectral interferences must be used. 

A schematic diagram of this calorimeter and its supporting apparatus is shown in Fig. 1, and a photograph of the calorimeter is shown in Fig. 2. The rate of heat transfer through an insulation sample is determined by measuring the mass rate of flow of saturated vapor leaving the inner measuring vessel Temperatures of the inner and outer wall surface are determined in the usual manner from the pressure measurements and the thermodynamic properties of the liquid gas used to fill the inner and outer containers, respectively. 

Example 7.1. The thermal conductivity of a 30 cm by 30 cm insulation insulator is measured in a guarded hot plate. The uncertainty of a differential thermocouple measuring the temperature is 0.3 K. The power applied to the sample is 5 kW 1 % and the temperature differential is 55 K across the 2.0 mm thick sample. What is the thermal conductivity of the insulation and what is the measurement uncertainty ... 

A small Curie term has been observed in all metallic conducting polymers at very low temperatures (T < 20 K) [18]. This indicates the presence of localised spins due to impurities, defects, etc. The x T) of PANI-CSA samples near the M-I transition show this behaviour [50]. The density of states at the Fermi level for metallic PANI-CSA and PPy-PFg samples are one states per eV per two rings and three states per eV per four rings, respectively [51]. These values are rather similar to that obtained from the thermoelectric power measurements. The Curie term at low temperatures is lower for metallic samples than for insulating samples. The magnetic properties and spin dynamics in doped conducting polymers are described in recent review articles [51]. 

There are few reports of thermal property measurements (e.g., thermal conductivity, specific heat, etc.) [52, 53]. The linear term in specific heat at low temperatures is evidence of the continuous density of states with a well-defined Fermi energy for any metallic system. The low temperature specific heat, C, for a metallic PPy-PFg sample and for an insulating PPy-p-toluenesulfonate (TSO) sample is shown in Figure 2.13 [54]. The data for both samples fit to the equation C/T = y+ jS P, where yand P are the electronic and lattice contributions, respectively. From the values of P and y, the calculated density of states for metallic and insulating samples are 3.6 0.12 and 1.2 0.04 states per eV per unit, and the corresponding Debye temperatures are 210 7 and 191 6.3 K, respectively. These values are comparable to those obtained from the spin susceptibility data. 

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