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-state conditions before measurements can be taken, but such long time leads to evaporation of the moisture within and thus significantly alters the material properties. Also most established methods are developed for measuring the thermal conductivity only, and
The heat capacityC p of a sample can be considered as a frequency dependent quantity; its behaviour can reflect the dynamics of enthalpy fluctuations. In order to take into account the dynamic nature of the measured quantity, calorimetry can mimic experimental methods as those of dielectrometry, performing experiments in time domain or in frequency domain.
Abstract
For the simultaneous measurements of thermophysical properties a cylindrical sample is heated up in radial direction in a quasi-steady way. After a short settling time, the radial temperature profile will have established in the sample, which does not change with time anymore if the thermophysical and geometrical parameters of the sample remain constant. By this, one gets three properties (λ, a, c p) directly without knowledge of the density, with only one sample, in only one measuring course, at temperatures up to 2000 K. However, two preconditions must be fulfilled for the simultaneous measurement of the three properties: firstly the heating mechanism of the sample to be measured has to be adiabatic and secondly the temperature difference within the sample must be high enough (for the measurement of the specific heat alone the second precondition is not nesessary). A respective instrument has been designed and tested with molybdenum, titanium and alumina.
Abstract
In order to optimize the infrared extinction of a SiC-powder in a silica powder matrix, Mie scattering calculations for spherical SiC-particles have been performed. A single oscillator-model was applied to calculate the optical constants of SiC. Taking into account the particle size distribution of a commercially available SiC-powder, its wavelength dependent extinction coefficient was calculated. The result is in very good agreement with the extinction spectrum of the powder derived by infrared optically measurements. Mie scattering theory also was used to find the optimum mean SiC-particle diameter of a mixture of 20% SiC-powder and 80% silica powder.
high temperatures include measuring thermal conductivity and specific heat during decomposition. Difficulties arise when the endothermic and/or exothermic reaction enthalpies confound the thermophysical property measurement. Significant volume changes
temperature, and κ is the thermal conductivity. The quantity S 2 σ is commonly considered as “power factor.” Increment in power factor and decrement in thermal conductivity are essential requirements for the enhancement of ZT value. Reducing the
that can be generated by viscous dissipation, thermal conductivity or other physical properties [ 3 ]. Whatever the medium in which instability arises, the motion of the fluid particles caused by buoyancy effects is always driven either by the
Renewable agricultural fibers as reinforcing fillers in plastics
Prediction of thermal properties
Abstract
Thermal properties such as melting and crystallization are important aspects in understanding the morphology and its contribution to the physical properties of semicrystalline polymers, such as polypropylene. The inclusion of fillers, which are small particles dispersed in the continuous polymer phase, often complicates the predictability of these properties by acting as nucleating agents or defect origins. This paper discusses the creation and use of empirical models based on experimental data for predicting and optimizing the thermal properties of agricultural filler-polypropylene (AgFiller-PP) composites, including peak melting temperature (T m), peak crystallization temperature (T c) and percent of crystallinity (X c). Experiments were performed using differential scanning calorimetry (DSC) to gather data necessary for building appropriate prediction models. Finally, additional experiments were carried out to test the prediction results generated by the models.
Thermal conductivity In addition to the specific heat capacity, thermomechanical coupled material models also contain the thermal conductivity as a material parameter. Within this study the thermal conductivity of fully cured bone cement was
