Specific Heat Capacity Measurements Research Articles

Measurement of Thermal Conductivity and Specific Heat Capacity of Three Major Geomorphological Units in Akwa Ibom State, Nigeria

Measurement of Thermal Conductivity and Specific Heat Capacity of Three Major Geomorphological Units in Akwa Ibom State, Nigeria

Coincidence of collective relaxation anomaly and specific heat peak in a bulk metallic glass-forming liquid

The study of relaxational behavior of multicomponent metallic liquids still holds the key to understanding and improving the glass-forming abilities of bulk metallic glasses. Herein, we report measurements of the collective relaxation times in a melted bulk metallic glass $(\mathrm{LM}601{\mathrm{Zr}}_{51}{\mathrm{Cu}}_{36}{\mathrm{Ni}}_{4}{\mathrm{Al}}_{9})$ in the kinetic regime $(Q$: $1.5--4.0{\AA{}}^{\ensuremath{-}1})$ using quasielastic neutron scattering. The results reveal an unusual slope change in the Angell plots of the collective relaxation time of this metallic liquid around $950{\phantom{\rule{0.16em}{0ex}}}^{\ensuremath{\circ}}\mathrm{C}$, beyond the melting point of the material. Specific heat capacity measurement also reveals the presence of a peak around the same temperature. The coincidence is rationalized using Adams-Gibbs theory, and motivates more careful experimental and computational studies of the metallic liquids in the future.

Specific heat of metal oxide nanofluids at high concentrations for heat transfer

In this work isobaric specific heat capacity measurements were performed for five different nanofluid sets designed as dispersions up to 15% mass concentrations of MgO, ZnO and ZrO2 in pure ethylene glycol as well as ZnO and ZrO2 in an ethylene glycol+water mixture at 50:50% in volume. Isobaric specific heat capacities for the three dry metallic oxide nanopowders and the two base fluids were also studied with the aim of contributing to elucidate on the heat capacity behavior of nanofluids for heat transfer applications. Measurements were carried out by using a quasi-isothermal Temperature-Modulated Differential Scanning Calorimetry (TMDSC) method in the temperature range from 243.15 to 473.15K. Base fluid results were compared with literature data to validate the measurement procedure. The specific heats for nano-sized materials here presented were also compared with literature data for bulk-sized of the same metallic oxides. In addition, the experimental values were used to evaluate the goodness of different models existing in literature to predict or correlate the specific heat capacities. A new fitting equation was also proposed to correlate specific heats of nanofluids as a function of the base fluid, nanoparticles as well as nanoparticle concentration.

Thermal properties measurement of binary carbonate salt mixtures for concentrating solar power plants

Specific heat capacity of an alkali molten salt mixture which is composed of lithium carbonate and potassium carbonate was measured using a differential scanning calorimeter (DSC). The specific heat capacity measurement was performed for 14 different composition ratios of the molten salt mixture to examine the effect of composition ratios on the specific heat capacity. The measured specific heat capacity values were compared with theoretically predicted values by the thermal equilibrium model. Additionally, changes in both melting point and latent heat of fusion were also investigated with change in the composition of two salts. In results, according to the heat flow curves in liquid phase obtained from DSC, the carbonate molten salt mixture could be categorized to three distinct groups: (1) gradually increased specific heat capacity, (2) dramatic decrease in the specific heat capacity, and (3) uniform specific heat capacity. Moreover, the specific heat capacity of the carbonate salt mixtures was strongly dependent upon the mole fraction of lithium carbonate. The specific heat capacity of the salt mixtures was drastically increased up to that of pure lithium carbonate in liquid phase, and decreased down to that of pure potassium carbonate in solid phase. In comparison with theoretical prediction, while the predictions were linearly increased with mole fraction of lithium carbonate, however, the measured data showed no linearity in the change of the specific heat capacity. The effect of the composition was also shown in the melting temperature and latent heat of fusion.

Structural, thermal and optical properties of KTi0.92La0.08OPO4 and KTi0.94Nd0.06OPO4

KTi0.92La0.08OPO4 (KTP:La) and KTi0.94Nd0.06OPO4 (KTP:Nd) single crystals are grown using high temperature top seeded flux growth technique. The strain derived from doping is calculated from Williamson–Hall relation. The packing structure and lattice parameter of the grown crystals are analyzed using single crystal X-ray diffraction. The bonding, distortion and change in inter-atomic distances by strain effects of doping are assessed by Raman spectroscopy. Thermal stabilities of grown crystals are evaluated by specific heat capacity measurement. Pronounced high specific heat capacity is recorded as 1.16J/gK at 498K for KTP:Nd. Second harmonic generation intensities are measured for KTP:Nd and KTP:La single crystal.

Thermophysical properties of solid phase ruthenium measured by the pulse calorimetry technique over a wide temperature range

Abstract This paper presents experimental results on four thermophysical properties of pure polycrystalline ruthenium samples over a wide temperature range. Specific heat capacity and specific electrical resistivity were measured from 250 to 2 500 K, while hemispherical total emissivity and normal spectral emissivity at 900 nm were measured from 1 300 to 2 500 K. All the properties were obtained by using the pulse calorimetry technique. The 200 mm long specimens were in the form of a thin rod, of about 3 mm in diameter. For necessary corrections, literature data on thermal linear expansion were applied. The results are compared with available literature data and discussed. The specific heat capacity and specific electrical resistivity measurements did not indicate any allotropic transformation of the samples over the entire temperature range.

Coefficient of Thermal Diffusivity of Insulation Brick Developed from Sawdust and Clays

This paper presents an experimental result on the effect of particle size of a mixture of ball clay, kaolin, and sawdust on thermal diffusivity of ceramic bricks. A mixture of dry powders of ball clay, kaolin of the same particle size, and sawdust of different particle sizes was mixed in different proportions and then compacted to high pressures before being fired to 950°C. The thermal diffusivity was then determined by an indirect method involving measurement of thermal conductivity, density, and specific heat capacity. The study reveals that coefficient of thermal diffusivity increases with decrease in particle size of kaolin and ball clay but decreases with increase in particle size of sawdust.

Enhanced ferromagnetic properties and high temperature dielectric anomalies in Bi0.9Ca0.05Sm0.05FeO3 prepared by hydrothermal method

Enhanced ferromagnetic properties and high temperature dielectric anomalies in the temperature range of 300–873K in Bi0.9Ca0.05Sm0.05FeO3 (BCSFO) prepared by hydrothermal method are reported. BiFeO3 is seen to crystallize in rhombohedrally distorted perovskite structure without any impurity phase. Substitution of small amount of Ca and Sm (Bi0.9Ca0.05Sm0.05FeO3) leads to increase in the lattice constant values and formation of small amount of secondary phase. Magnetization curve of pure BFO indicates very weak ferromagnetism combined with antiferromagnetic nature of the samples. Whereas, BCSFO sample shows very clear and enhanced ferromagnetic nature. Saturation magnetization and Neel’s temperature values are found to be 4.36emu/g and 664K, respectively. X-ray photoelectron spectroscopy indicates the creation of oxygen vacancies upon Ca substitution in Bi site. Dielectric anomalies at 420 and 540K were observed for Bi0.9Ca0.05Sm0.05FeO3 from the temperature variation of dielectric constant and specific heat capacity measurements. Observation of dielectric anomalies in pure BiFeO3 sample reveals that the origin of dielectric peaks is purely from the primary phase. Raman spectroscopy study indicates a clear shift and broadening of A modes (between 100 and 200cm−1) at the dielectric anomaly temperatures supporting the observed dielectric anomalies.

Specific Heat Capacity Measurements of Intermetallic Phases in the Ternary Al-Ti-Cr System

Specific heat capacities of the γ-TiAl and τ phases in the Al-Ti-Cr system were determined in the temperature range between 298 and 773/873 K based on one binary (51.2Al-48.8Ti) and three ternary alloys (53Al-44Ti-3Cr, 64.6Al-30.2Ti-5.2Cr, 65.3Al-26.7Ti-8Cr). The specific heat capacity measurements in this system were performed for the first time. The measurements were carried out using heat-flux DSC devices employing the classical three step method. The measured heat capacities were lower than the approximation using the Neumann-Kopp rule. These differences in the heat capacity data arise probably due to the variation of the chemical bonding state between the intermetallic phases and the pure elements which are not taken into account by Neumann-Kopp’s rule. In order to check the reliability of the obtained results, the enthalpy increment was measured by using drop calorimetry. The heat increments determined using the drop calorimetry was in an excellent agreement with the enthalpy increments calculated using the analytic description of the heat capacities from DSC.

Enhanced specific heat capacity of molten salt-based nanomaterials: Effects of nanoparticle dispersion and solvent material

This study investigated the effect of nanoparticle dispersion on the specific heat capacity for carbonate salt mixtures doped with graphite nanoparticles. The effect of the solvent material was also examined. Binary carbonate salt mixtures consisting of lithium carbonate and potassium carbonate were used as the base material for the graphite nanomaterial. The different dispersion uniformity of the nanoparticles was created by employing two distinct synthesis protocols for the nanomaterial. Different scanning calorimetry was employed to measure the specific heat capacity in both solid and liquid phases. The results showed that doping the molten salt mixture with the graphite nanoparticles significantly raised the specific heat capacity, even in minute concentrations of graphite nanoparticles. Moreover, greater enhancement in the specific heat capacity was observed from the nanomaterial samples with more homogeneous dispersion of the nanoparticles. A molecular dynamics simulation was also performed for the nanomaterials used in the specific heat capacity measurements to explain the possible mechanisms for the enhanced specific heat capacity, including the compressed layering and the species concentration of liquid solvent molecules.

Specific heat of nanofluids synthesized by dispersing alumina nanoparticles in alkali salt eutectic

In this study, we report large enhancement in specific heat capacity of a eutectic salt mixture on dispersing alumina nanoparticles at 1% mass concentration. Eutectic of lithium carbonate and potassium carbonate (62:38 by molar ratio) was dissolved in distilled water with alumina nanoparticles at 1.0% mass concentration and with a nominal diameter of ∼10nm. The specific heat capacity measurement was performed using a differential scanning calorimeter (DSC). An alternate model involving in situ phase transformation was proposed which was found to be in good agreement with the variations observed in the experimental data for the different types of nanomaterial samples used in this study. These salt nanofluids can lead to the development of efficient thermal energy storage systems which in turn can enable significant reduction in the cost of solar power.

Thermal conductivity and specific heat capacity measurements of CuO nanofluids

A study of thermal properties of CuO dispersed in water and ethylene glycol as a function of the particle volume fraction and at temperatures between 298 and 338 K has been performed. Thermal conductivities have been studied by the steady-state coaxial cylinders method, using a C80D microcalorimeter (Setaram, France) equipped with special calorimetric vessels. Heat capacities have been measured with a Micro DSC II microcalorimeter (Setaram, France) with batch cells designed in our laboratory and the “scanning or continuous method.” Results for thermal conductivities can be well justified using a classical model (Hamilton–Crosser), and experimental measurements of heat capacities can be justified with a model of particles in thermal equilibrium with the base fluid.

Development and Processing of Novel Aluminum Powder Metallurgy Materials for Heat Sink Applications

The objective of this research was to design aluminum powder metallurgy (PM) alloys and processing strategies that yielded sintered products with thermal properties that rivaled those of the cast and wrought aluminum alloys traditionally employed in heat sink manufacturing. Research has emphasized PM alloys within the Al-Mg-Sn system. In one sub-theme of research, the general processing response of each PM alloy was investigated through a combination of sintering trials, sintered density measurements, and microstructural assessments. In the second, the thermal properties of sintered products were studied in detail. Thermal conductivity was first determined using a calculated approach through discrete measurements of specific heat capacity, thermal diffusivity, and density and subsequently verified using a transient plane source technique on larger specimens. Experimental PM alloys achieved >99 pct theoretical density and exhibited thermal conductivity that ranged from 179 to 225 W/m K. Thermal performance was largely dominated by the amount of magnesium present within the aluminum grains and, in turn, bulk alloy chemistry. Data confirmed that the novel PM alloys were highly competitive with even the most advanced heat sink materials such as wrought 6063 and 6061.

Optical and thermal properties of spinel with revised (increased) absorption at 4 to 5 μm wavelengths and comparison with sapphire

Infrared absorption of high-quality, commercial, polycrystalline MgAl 2 O 4 spinel is ∼40% greater in the range of 3.8 to 5.0 μm than the value predicted by the computer code OPTIMATR®, which has been used for window and dome design for more than 20 years. As a result, spinel and a -plane sapphire windows designed to support the same external pressure with the same probability of survival have approximately the same infrared absorptance in the range 3.8 to 5.0 μm. c -Plane sapphire has greater absorptance than spinel in the range 3.8 to 5.0 μm. Spinel has two weak absorption bands near 1.8 and 3.0 μm. At 1.064 μm, the laser calorimetric absorption coefficient of spinel is 10 to 50 times greater than that of sapphire. New measurements of specific heat capacity, thermal expansion, thermal conductivity, elastic constants, and refractive index (including dn/dT ) of spinel are reported.

Enhanced Specific Heat Capacity of Nanomaterials Synthesized by Dispersing Silica Nanoparticles in Eutectic Mixtures

Anomalous enhancements in the specific heat capacity values of nanomaterials were measured in this study. Silica nanoparticles (∼2–20 nm) were dispersed into eutectic of lithium carbonate and potassium carbonate (62:38 by molar ratio) at 1.5% mass concentration. The specific heat capacity measurements were performed using a differential scanning calorimeter (DSC). The specific heat capacity of the silica nanocomposite (solid phase) was enhanced by 38–54% and the specific heat of the silica nanofluid (liquid phase) was enhanced by 118–124% over that of the pure eutectic. Electron microscopy of the samples shows that the nanoparticles induce phase change (forms a higher density “compressed phase”) within the solvent material. Hence, a new model is proposed to account for the contribution of the compressed phase to the total specific heat capacity of the nanomaterials. The proposed model is found to be in good agreement with the experimental data. These results have wide ranging implications, such as for the development of efficient thermal storage systems that can enable significant reduction in the cost of solar thermal power.

HFO-1234ze(E)+HFC-32 混合冷媒の密度および定圧比熱の測定

HFO-1234ze(E)+HFC-32 混合冷媒の密度および定圧比熱の測定

Nanoscale specific heat capacity measurements using optoelectronic bilayer microcantilevers

We describe a technique for optically and electrically detecting and heating bilayer microcantilevers (BMCs) to high temperatures at fast heating rates for nanoscale specific heat capacity measurements. The platinum and silicon nitride (Pt−SiNx) BMCs act simultaneously as a heater, temperature sensor, and mass sensor (24 pg resolution). The calibration of the system was validated for a mass of 12.6 ng by melting point and specific heat capacity measurements of deposited aluminum nanoparticles.

A method for heat capacity measurement by photoacoustics

In this paper a photoacoustic method is proposed for specific heat capacity measurements in solids using a heat transmission configuration, where illumination takes place at the reference–sample interface. The method involves the use of a liquid reference sample so that it becomes free of instrumental function influence due to effects dependent on the detection cell, the frequency dependence of the microphone response and of the involved electronics. The method is validated with measurements performed in test samples of different materials.

Thermal conductivity and specific heat capacity measurements of Al2O3 nanofluids

Thermal conductivity and specific heat capacity measurements of Al2O3 nanofluids

Evidence fors±-wave pairing symmetry in LiFeAs from its low-temperature specific heat

We report specific heat capacity measurements on a LiFeAs single crystal at temperatures down to 400 mK and magnetic fields up to 9 T. A small specific heat jump at ${T}_{c}$ and finite residual density of states at $T=0$ K in the superconducting (SC) state indicate that there are strong unitary scatterers that lead to states within the SC gap. A sublinear magnetic field dependence of the Sommerfeld coefficient $\ensuremath{\gamma}(H)$ at $T=0$ K is equally well fitted by both a nodal d-wave gap as well as a sign changing multiband ${s}_{\ifmmode\pm\else\textpm\fi{}}$-wave gap. When impurity effects are taken into account, however, the linear temperature dependence of the electronic specific heat ${C}_{\text{el}}/T$ at low temperatures argues against a nodal d-wave superconducting gap. We conclude that the SC state of LiFeAs is most compatible with the multiband ${s}_{\ifmmode\pm\else\textpm\fi{}}$-wave SC state with the gap values ${\ensuremath{\Delta}}_{\text{small}}=0.46{\ensuremath{\Delta}}_{\text{large}}$.