Thermal Diffusivity Of Sample Research Articles

An Investigation on Optical, Mechanical and Thermophysical Properties of Sodium Sulfanilate Dihydrate Single Crystal for Optical Window And Microelectronics Applications

AbstractA nonlinear optical single crystal of sodium sulfanilate dihydrate (SSDH) is formed using the slow evaporation solution approach. Using X‐ray diffraction, the properties of the unit cell are extracted from a single crystal. Using UV‐Vis‐NIR spectroscopy, the optical transmittance of crystals is determined. Mechanical toughness is evaluated using a Vickers micro hardness test. Sodium sulfanilate dihydrate is synthesized as a single crystal and etched for analysis. Photoacoustic spectroscopy is used to examine the sample's thermal diffusivity. The crystal's thermophysical properties are vital for every element of heat transfer incidences, in addition to being employed in many other applications, including as Nd:YAG lasers, Nd:YLF lasers, acousto‐optics, and microelectronics industry applications.

Influence of stabilizing ions and sintering process on the thermal conductivity of α‐SiAlON ceramics

Abstractα‐SiAlON ceramics with different stabilizing ions of Yb, Dy, Nd, Y, Ca, and binary stabilizing ions of (Yb + Ca) and (Yb + Nd) were prepared by spark plasma sintering at 1600°C and gas pressure sintering at 1800 and 1900°C, and their thermal conductivity was investigated. It was found that α‐SiAlON ceramics with larger and heavier stabilizing ions had lower thermal conductivity and the thermal conductivity could be further reduced by using binary stabilizing ions, which can be explained by phonon scattering from point defects. At the same time, the samples prepared at lower sintering temperatures showed smaller grain sizes and lower thermal conductivity. The relationship between the thermal diffusivity of samples and temperature was studied, where the dependence of inverse thermal diffusivity on temperature was better fitted by a quadratic fitting function than the usual linear one over a wide temperature range from 25 to 800°C.

Thermal diffusivity measurement of boron nitride by photoacoustic spectroscopy

A photoacoustic spectrometer (PAS) is a very common method to measure non-radiative decay. When modulated electromagnetic light interacts with any solid powder sample, their thermal energy production is due to non-radiative decay. Then acoustic noise is produced due to temperature difference which is formed by the periodic heat transfer from the optical source. In this work, we have fabricated a PA cell and a pre-amplifier circuit and optimized them by parametric studies to get the desired signal. For the optimum signal, the volume of the cell cavity is found to be 5.30 × 10-6 m3. We have successfully synthesized Boron nitride (BN) by simple hydrothermal method with NH4Cl (Sample I) and without NH4Cl (Sample II). The XRD and FESEM data confirm the crystal phase and morphological structure of the synthesized material. The thermal diffusivity of sample I is obtained (7.22–8.31) × 10-6 m2/s. Similarly, for sample II, the thermal diffusivity is found to be (7.38–8.72) × 10-6 m2/s.

Differential Equations Applied to Photopyroelectric Detection

The present research aimed to study the technique of photopyroelectric detection, it is specifically setting SPPE. Besides performing graphics simulations analytical amplitude and phase of the thermal signal due to the modulation frequency generated to obtain ownership for a sample thermal diffusivity of vegetable oil.

Simultaneous thermal and optical characterization of semiconductor materials exhibiting high optical absorption by photopyroelectric spectroscopy

This work presents the results of the investigations on the thermal and optical properties of materials exhibiting high optical absorption. As test samples, some II-VI binary semiconductors were grown by using the Bridgman-Stockbarger method. The photopyroelectric (PPE) method, in two configurations (calorimetric and spectroscopic), was applied for both thermal and optical characterization of the specimens. The thermal diffusivity was obtained in the back detection configuration (BPPE) with an intensity-modulated laser as an excitation source. The same detection configuration, but with a tunable light source, provided information about the energy gap, the absorption coefficient, and the investigated sample's thermal diffusivity. The results obtained with these two methods were also compared with the data collected by conventional transmission and luminescence spectroscopies (absorption coefficient, energy gap). The main conclusion is the photopyroelectric spectroscopy (PPES) can provide in one measurement good quality information about the thermal and optical properties of the specimen.

Non-contact photopyroelectric approach for complete thermal characterization of porous building materials

The suitability of two photopyroelectric (PPE) methods for measuring the thermal diffusivity and effusivity of porous solids is described. The main characteristic of both methods, associated with the possibility of investigating porous solids, is the absence of coupling fluid between the pyroelectric sensor and sample. The first method (proposed initially by Salazar et al., Measurement 121, 96 (2018) [1]) relies on the front detection configuration with opaque pyroelectric sensor and thermally thick sample. Based on the phase frequency scan of the PPE signal, this method leads to the direct measurement of the sample’s thermal effusivity. The second method (proposed initially by Zammit et al., J. Appl. Phys. 117, 105,104 (2015) [2]) is based on two successive measurements (frequency scans), one in back and one in front PPE configuration, followed by a self-normalization of the phase vs. modulation frequency dependence. This method uses transparent pyroelectric sensor and backing material, allowing the direct measurement of the sample thermal diffusivity. In the paper, both methods were adapted and improved for investigating some porous building materials of interest: old bricks with unknown values of thermal parameters.

Study of effect of moisture and temperature on thermal and physical properties of limestone using a transient plane source technique

This study investigated the thermophysical properties of limestone in its dry and moist states. A thermal constant analyser, based on Transient Plane Source (TPS) technique, was used to study the thermophysical properties. Temperature dependence of thermophysical properties of limestone was investigated by elevating the temperature up to 433 K. The chemical and mineral composition of samples were studied using SEM-EDS and XRD analysis. The thermal conductivity of dry and moist limestone showed that in situ measurements are necessary for the precise determination of thermal properties. The variations in thermal properties of limestones as a function of temperature were described by mineral composition and heat transfer mechanism. The thermal conductivity of limestone was measured in the range of 2.586 to 3.054 Wm−1K−1. The thermal diffusivity of samples was ranged from 1.390 to 1.601 mm2s−1 while specific heat capacity of limestone was in the range of 1.847 to 2.066 MJm−3K−1. A noticeable change in thermal properties of moist limestone was observed as compared to the dry limestone.

Effects of Pore on Thermal Diffusivity and Thermal Radiation Properties of C/SiC Composites at High Temperatures

The effects of pore in C/SiC composites on thermal diffusivity and thermal radiation properties were investigated systematically. Pores were introduced into C/SiC by oxidizing carbon phase at 700 °C and damaged the thermal properties of C/SiC composites. Because of little changes in the pore shape and the pore orientation in C/SiC, thermal diffusivity of samples increased linearly with porosity. The pores within C/SiC absorbed and reflected the radiated heat, decreasing spectral emissivity. However, the temperature dependence of spectral emissivity didn’t change by the pore. With measurement temperature increasing, the pores weakened the thermal radiation property of samples gradually. A linear relation was suggested to quantify the negative effect of pores on the total emissivity.

Extraordinary air water harvesting performance with three phase sorption

Water scarcity is a current concern and a future problem. Air-water harvesting (AWH) is a novel proposed solution to provide enough water for human-being's needs especially in remote areas. However, the sorbent material is one of the challenging components of these systems. Generally, a proper sorbent must have a high water uptake capacity, a low regeneration temperature and an easy replacement structure, suitable to deploy in the bed. Here we synthesized three active carbon felt composites with a layer structure and analyzed their potential for being used in AWH systems. The performance of these ACFs composites concerning three different salts was investigated. Experimental results showed that the highest capacity is 2.9 g water per g sorbent at 70% of RH without any leakage. Also, pore parameters, non-equilibrium and equilibrium adsorption, regeneration temperature, recyclability and thermal diffusivity of samples were tested. The thermodynamic cycle of the system is studied, and a three-phase sorption cycle is proposed in this study. The detailed analysis reveals that the presence of the combined use of adsorption-absorption process can improve the sorption capacity extensively. The experimental and theoretical studies proved that these composites are very promising materials for water harvesting applications. To demonstrate these materials capability, a prototype is proposed which adopts these materials as its desiccant. This small prototype automatically could harvest 1.51 g of fresh water per cycle per g of sorbent at RH of 70%, without any human involvement.

Microstructural, thermal and mechanical characterization of TiB2–SiC composites doped with short carbon fibers

Spark plasma sintering method, at the temperature of 1800 °C under the pressure of 40 MPa for 7 min, was employed for fabrication of TiB2–SiC-based composites. The influences of short carbon fiber (Cf) addition (2 wt%) on microstructural, mechanical and thermal properties of TiB2–SiC ceramics were studied. Carbon fiber addition increased the relative density of sintered composite which observed to have direct effect on mechanical and thermal properties. The mechanical properties of composites were measured by nanoindentation method. Hardness and elastic modulus of TiB2/SiC interfaces in carbon fiber doped composite were measured 27.1 GPa and 445 GPa, respectively, while these values were obtained 24.2 GPa and 422 GPa for carbon-free sample. The thermal diffusivity of samples was measured by laser flash technique (LFT). It was found that TiB2–SiC–Cf composite has a higher thermal conductivity (55 w/m.K) compared to TiB2–SiC ceramic with a value of 54.8 w/m.K.

Thermal diffusivity measurement in thin metallic filaments using the mirage method with multiple probe beams and a digital camera.

Photothermal beam deflection is a well-established technique for measuring thermal diffusivity. In this technique, a pump laser beam generates temperature variations on the surface of the sample to be studied. These variations transfer heat to the surrounding medium, which may be air or any other fluid. The medium in turn experiences a change in the refractive index, which will be proportional to the temperature field on the sample surface when the distance to this surface is small. A probe laser beam will suffer a deflection due to the refractive index periodical changes, which is usually monitored by means of a quadrant photodetector or a similar device aided by lock-in amplification. A linear relationship that arises in this technique is that given by the phase lag of the thermal wave as a function of the distance to a punctual heat source when unidimensional heat diffusion can be guaranteed. This relationship is useful in the calculation of the sample's thermal diffusivity, which can be obtained straightforwardly by the so-called slope method, if the pump beam modulation frequency is well-known. The measurement procedure requires the experimenter to displace the probe beam at a given distance from the heat source, measure the phase lag at that offset, and repeat this for as many points as desired. This process can be quite lengthy in dependence of the number points. In this paper, we propose a detection scheme, which overcomes this limitation and simplifies the experimental setup using a digital camera that substitutes all detection hardware utilizing motion detection techniques and software digital signal lock-in post-processing. In this work, the method is demonstrated using thin metallic filaments as samples.

تاثیر دما و میزان ماده جامد محلول بر خصوصیات فیزیکی– حرارتی عصاره مالت

تعیین خواص حرارتی- فیزیکی عصاره مالت جهت تخمین سرعت انتقال حرارت، تولید، حمل ونقل و نگهداری همچنین ارزیابی و مدل سازی فرایند هایی از قبیل خشک کردن و تغلیظ ضروری است. در این پژوهش خواص حرارتی– فیزیکی عصاره مالت شامل گرمای ویژه، ضریب هدایت حرارتی، ضریب انتشار حرارتی و جرم حجمی در سه سطح ماده جامد محلول 60،70 و 80 درصد و در محدوده دمایی 25 تا 90 درجه سانتی گراد بررسی و تعیین گردید. نتایج حاصل از تحلیل داده‌ها نشان می‌دهد که هم درصد ماده جامد وهم دما بر خواص حرارتی– فیزیکی عصاره مالت تاثیر معنی داری دارند. با افزایش درصد ماده جامد گرمای ویژه،ضریب هدایت حرارتی و ضریب انتشار حرارتی کاهش یافته ولی جرم حجمی افزایش می-یابد. همچنین با افزایش دما گرمای ویژه، ضریب هدایت حرارتی و ضریب انتشار حرارتی افزایش یافته ولی دانسیته کاهش می یابد. از سوی دیگر با تجزیه و تحلیل رگرسیون چند گانه، مدل های پیش بینی کننده خواص حرارتی– فیزیکی عصاره مالت بر مبنای متغیر های کاری تعیین گردید.

Thermal diffusivity measurement by lock-in photothermal shadowgraph method

Here, we present a novel application of the shadowgraph technique for obtaining the thermal diffusivity of an opaque solid sample, inspired by the orthogonal skimming photothermal beam deflection technique. This new variant utilizes the shadow projected by the sample when put against a collimated light source. The sample is then heated periodically by another light beam, giving rise to thermal waves, which propagate across it and through its surroundings. Changes in the refractive index of the surrounding media due to the heating distort the shadow. This phenomenon is recorded and lock-in amplified in order to determine the sample's thermal diffusivity.

Synthesis and Optimization of Electric Conductivity and Thermal Diffusivity of Zinc-Aluminum Hydroxide (Zn–Al–NO3–LDH) Prepared at Different pH Values

Zn–Al–NO3–LDH was synthesized using the co-precipitation method at different pH values of 6, 7, 8, 9 and 10 with Zn2+/Al3+ = 4. The structural, textural and morphological properties of samples were studied. All prepared samples were mesoporous materials. The dielectric response of Zn–Al–NO3–LDH samples can be described by anomalous low frequency dispersion (ALFD). Thermal diffusivity of samples has been measured as a function in in situ temperature at range 27 – 210°C. The optimized electrical conductivity and thermal diffusivity has been found with the synthesized Zn–Al–NO3–LDH sample at pH 8.

THERMAL DIFFUSIVITY STUDIES OF ZnO-CuO AT HIGH TEMPERATURES

An n-type semiconducting oxide such as Zinc Oxide (ZnO) has been exploited for their well-known gas sensing properties. Previous studies on these applications have mainly focused on electrical properties. Only limited reports were available on thermophysical properties of ZnO-based ceramics gas sensor. Therefore in this work, we report on the thermal diffusivity of Zinc Oxide-Copper Oxide (ZnO-CuO) ceramic composites by solid-state method using a laser flash technique. Thermal diffusivity of samples was measured at temperatures between 27 °C to 400 °C. The role of CuO was observed to enhance the thermal diffusivity of ZnO system with respect to the temperatures. ZnO-CuO samples played a significant role in improvement of thermal diffusivity value at temperature of 200 °C and above. Subsequently, sample of higher thermal diffusivity will exhibit lower initialization time for gas sensor to activate. Hence, the enhanced thermal diffusivity suggested that ZnO-CuO composite samples hold a promising possibility in gas sensor application.

Peak Diffusing Measurement Method for Estimating Thermal Diffusivity of Thin Films

A novel peak diffusing measurement method is reported. In this method, a pulsed Gaussian heat source is focused on the material’s surface, and a thermal camera is utilized for detecting the temperature evolution. Specially, the peak temperature timetmaxat different distance from the heat source center is extracted using the Singular Spectrum Analysis (SSA). Thermal diffusivity is then calculated by fitting multiple sets of extractedtmaxinto the derived regression equation. The advantage of this method is that it does not require the high precision time synchronization between the excitation source and detector. Also, the calculation process is very simple, which achieves an efficient in situ measurement of the thermal diffusivity. The measured radial thermal diffusivity of samples prepared from Ti and Ni is in good agreement with the reference data with a 1.8% and a 3.9% error bound.

Investigation of Thermal Properties of SiC Ceramics Containing Carbon Nanostructures by Photothermal Measurements

This work presents an analysis of the influence of graphene reinforcement on properties of silicon carbide composites. Samples were prepared by a spark plasma sintering method. The density and hardness were obtained in the preliminary experiments. The thermal diffusivity was determined by the continuous wave photothermal technique with detection based on infrared radiometry. The thermal diffusivity is in the range of (0.48 to 0.57) cm\(^{2} \,\,{\cdot }\,\, \)s\(^{-1}\) for samples prepared from granulated SiC and in the range of (0.56 to 0.71) cm\(^{2} \,\,{\cdot }\,\, \)s\(^{-1}\) for samples prepared from SiC powder. Thermal properties are correlated with the density of SiC ceramics. The thermal diffusivity of samples with a higher density is lower in comparison to samples with a lower density.

Thermal diffusivity and mechanical properties of polymer matrix composites

Polypropylene–iron-silicon (FeSi) composites with spherical particles and filler content from 0 vol. % to 70 vol. % are prepared by kneading and injection molding. Modulus, crystallinity, and thermal diffusivity of samples are characterized with dynamic mechanical analyzer, differential scanning calorimeter, and laser flash method. Modulus as well as thermal diffusivity of the composites increase with filler fraction while crystallinity is not significantly affected. Measurement values of thermal diffusivity are close to the lower bound of the theoretical Hashin-Shtrikman model. A model interconnectivity shows a poor conductive network of particles. From measurement values of thermal diffusivity, the mean free path length of phonons in the amorphous and crystalline structure of the polymer and in the FeSi particles is estimated to be 0.155 nm, 0.450 nm, and 0.120 nm, respectively. Additionally, the free mean path length of the temperature conduction connected with the electrons in the FeSi particles together with the mean free path in the particle-polymer interface was estimated. The free mean path is approximately 5.5 nm and decreases to 2.5 nm with increasing filler fraction, which is a result of the increasing area of polymer-particle interfaces. A linear dependence of thermal diffusivity with the square root of the modulus independent on the measurement temperature in the range from 300 K to 415 K was found.

Behavior of the thermal diffusivity of native and oxidized human low-density lipoprotein solutions studied by the Z-scan technique

Modifications in low-density lipoprotein (LDL) have emerged as a major pathogenic factor of atherosclerosis, which is the main cause of morbidity and mortality in the western world. Measurements of the heat diffusivity of human LDL solutions in their native and in vitro oxidized states are presented by using the Z-Scan (ZS) technique. Other complementary techniques were used to obtain the physical parameters necessary to interpret the optical results, e.g., pycnometry, refractometry, calorimetry, and spectrophotometry, and to understand the oxidation phase of LDL particles. To determine the sample's thermal diffusivity using the thermal lens model, an iterative one-parameter fitting method is proposed which takes into account several characteristic ZS time-dependent and the position-dependent transmittance measurements. Results show that the thermal diffusivity increases as a function of the LDL oxidation degree, which can be explained by the increase of the hydroperoxides production due to the oxidation process. The oxidation products go from one LDL to another, disseminating the oxidation process and caring the heat across the sample. This phenomenon leads to a quick thermal homogenization of the sample, avoiding the formation of the thermal lens in highly oxidized LDL solutions.

The thermal diffusivity of a colloidal solution of nanosilver as a function of the pressure at room temperature

The results of an experimental measurement of the thermal diffusivity of colloidal nanosilver as a function of the pressure at room temperature using the laser flash method are presented. By processing the experimental data, an empirical equation was obtained, by means of which one can calculate the thermal diffusivity of samples without carrying out investigations.