Muhammad Anis-ur-, Rehman (2004) PREPARATION AND THERMOPHYSICAL CHARACTERIZATION OF BI(PB) SR(BA)2223 SUPERCONDUCTORS AND INSULATORS. Doctoral thesis, Quaid-i-Azam University, Islamabad.

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The foremost attempt in this thesis is aimed to added progression of the Transient Plane Source (TPS) technique, to measure thermal properties of solids. The modified TPS technique referred to as Advantageous Transient Plane Source (ATPS) technique, offers the possibility to measure thermal properties which are directly related to heat conduction such as thermal conductivity, thermal diffusivity and heat capacity per unit volume, with more simplicity and enhanced precision. The newly designed system accomplished the -major objectives like, to acquire data with high speed and accuracy; interactively process/analyze measured data for an immediate use or store it for future post-processing; in addition, this system allows for an easy adjustment and enhancement of instruments by revision of software programs. Also specimen size variation is incorporated very well by using the TPS sensors of different sizes. Small sized sensors and specimen could be used without any significant loss of accuracy. It is also possible to get the information about Cp by very simple experiment. To check the validity of the ATPS technique, it was calibrated by using fused quartz, carbon steel and silver chloride crystals. Materials selected for calibration are representative of insulators, conductors and crystalline materials. All measurements were done form room down to liquid nitrogen temperature. Thermal data for AgC1 crystals is an addition to the existing literature. For measurements at elevated temperatures modified sensors were designed and calibrated. Two sets of insulating materials. namely, ceramics fibres and synthetic insulating foams were studied. Ceramic fibres include VK.-60, ABK and Nextel/VK-80 fibres. The investigation of thermal properties of three different types of ceramic fibers showed that all materials have good thermal insulation properties and that fibers produced by the steam blowing technique Le. VK-60, can be used as a substitute for more costly analogous materials obtained from the nozzle dissemination technique. Insulating foams consist of fibre glass, closed cell foam and foam samples. The samples which are studied in the present. work, are used as insulators for the temperature control of air-conditioned space and thus for saving energy. From this point of view, the closed cell foam insulation is a better choice. So these materials are suitable for insulation purposes and may be very vital in saving energy. Various Bi-based superconducting compositions were prepared and analyzed but the detail of the most reproducible composition is given. High-Tc superconducting samples with nominal composition Bi1.6 Pb0.4Sr1.6 Ba0.4 Ca2Cu3Oy were prepared by solid state reaction method. Samples were characterized by dc electrical resistivity, ac susceptibility, X-ray diffraction and thermal analysis. All the tests showed that the samples were with almost single phase. Thermal diffusivity data are an addition to literature as previously one can hardly find any data for superconducting samples. Simultaneous measurement of thermal conductivity and thermal diffusivity makes it possible to estimate specific heat and the Debye temperature (H)D, as well as to separate the electron and phonon contributions to thermal conductivity and diffusivity. The simultaneous measurement also provides a useful check on the reliability and the consistency of the analyses. All the above measurements show that Advantageous Transient Plane Source technique is working very well under extreme environmental conditions. Thermoelectrical power (TEP) measurements were .done by a newly designed and calibrated .apparatus. Simplicity, ease of use and precision are the major plus of the designed TEP system. Electrothermal conductivity and figure of merit are also calculated showing that the sample composition could be a potential candidate for thermoelectric devices.

Item Type: Thesis (Doctoral)
Uncontrolled Keywords: superconductors, insulators, transient plane source technique, tps, advantageous transient plane source technique, atps, ceramics fibres, synthetic insulating foams, fibre glass, thermoelectrical power, synthetic porous solids, fibrous insulating solids, ceramic fibrous solids
Subjects: Q Science > QC Physics
Depositing User: Muhammad Khan Khan
Date Deposited: 07 Sep 2016 09:40
Last Modified: 07 Sep 2016 09:40

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