Specific Heat Capacity Measurements Research Articles

Isobaric Specific Heat Capacity Measurement in the Trans-Critical Temperature Regions for Kerosene RP-3 under Pressures of 6–8 MPa

Isobaric Specific Heat Capacity Measurement in the Trans-Critical Temperature Regions for Kerosene RP-3 under Pressures of 6–8 MPa

Type-II superconductivity at 9K in Pb–Bi alloy

In the present work, we report the synthesis of Pb–Bi alloy with enhanced Tc of up to 9K, which is higher than that of Pb. The alloy is synthesized via a solid-state reaction route in the vacuum-encapsulated quartz tube at 700°C in an automated furnace. The synthesized sample is characterized by X-ray Diffraction(XRD) and Energy dispersive X-ray analysis(EDAX) for its phase purity and elemental composition. Rietveld refinement of XRD reveals that the end product is a majority hexagonal Pb7Bi3, with minor rhombohedral Bi. The electronic transport measurement shows metallic behavior with the Debye temperature of 108K and a superconductivity transition temperature (Tc) below 9K, which is the maximum to date for any reported Pb–Bi alloy, Pb or Bi at ambient pressure. Partial substitution of Bi at the Pb site may modify the free density of electronic states within the BCS model to attain the optimum Tc, which is higher by around 2K from the reported Tc of Pb. The superconductor phase diagram derived from magneto-transport measurements reveals that the synthesized alloy is a conventional superconductor with an upper critical field (Hc2) of 3.9 T, which lies well within the Pauli paramagnetic limit. The magnetization measurements carried out following ZFC(Zero Field Cool) protocols infer that the synthesized alloy is a bulk superconductor below 9K. The isothermal M-H(Magnetization vs. Field) measurements performed below Tc establish it as a type-II superconductor. The specific heat capacity measurements show that the Pb–Bi alloy is a strongly coupled bulk superconductor below around 9K with possibly two superconducting gaps.

Investigation on specific heat and Raman spectroscopy of YbFe2As2

We hereby present a comprehensive study of polycrystalline YbFe2As2 which includes detailed investigation on the specific heat capacity and Raman spectroscopy measurements at high magnetic fields (up to 16 T) and low temperatures. Low temperature x-ray diffraction investigations at 30 K on YbFe2As2 reveal an orthorhombic unit cell structure, which indicates structural transitions from monoclinic to orthorhombic as temperature decreases. In specific heat capacity measurements, a slope change is observed around 70 K. It may be a signature of spin density wave (SDW) phase transition. The specific heat data has been fitted in the temperature ranging from 20 to 90 K. It has been found that linear coefficient of specific heat (γ) is quite enhanced suggesting the existence of quasi particles with heavy effective mass. Its value changes slowly with magnetic field below 70 K. Raman spectra have been studied in the temperature range of 4 to 300 K. It is observed that there is a trend of shifting the B1G peak position in Raman spectra on the higher side as the temperature decreases. A change of slope in shift of B1G versus temperature plot is noticed around 70 K suggesting phase transition which is consistent with specific heat and previous resistivity measurements. Overall, our results provide new insights into the physical properties and phase transitions of YbFe2As2.

Investigation of both thermal parameters and applications of closed-cell plastic thermal insulation foams with building energetic aspects

Nowadays, if one wants to renovate or build a building, the question of thermal insulation is an essential construction process. Polyurethane is a key thermal insulation material that belongs to plastic foams. It can be applied as a spread or board heat-insulating material. Its thermal insulation properties are superior compared to polystyrene, but still a bit neglected. In this article, we would like to perform thermal investigations executed on a new type of polymeric foam such as polyisocyanurate. We will present acceptably low thermal conductivity (~ 0.022 W m-1 k-1), raised specific heat capacity (~ 1400 J kg-1 K-1) and calorimetric (bomb and differential) measurement results completed with optical microscopic images. Moreover, scanning electron microscopic analysis and X-ray diffractometry will be also presented. The results will be used for cost calculations applied by buildings and will show justified reasons for its application based on structural measurements too. The results are extremely encouraging.

Experimental measurement and modeling of lattice thermal expansion and specific heat capacity of C15-Cr2Nb Laves phase intermetallic compound

In order to determine the lattice thermal expansion and specific heat capacity (Cp) of the C15-Cr2Nb Laves phase, an experimental investigation and modeling were carried out in the present paper by employing high-temperature X-ray diffraction (HTXRD) and differential scanning calorimetry (DSC). A thorough analytical model was utilized to predict the temperature-dependent variations of enthalpy and specific heat, and the predicted findings were compared to the experimentally measured data. Arc melting was employed to synthesize Cr2Nb samples with distinct hexagonal (C14/C36) and cubic (C15) Laves phase structures, which were then subjected to the appropriate heat treatment. Room temperature XRD patterns, SEM, and EDAX experiments on homogenized samples at 1273 K for 72 h validated the homogeneity and C15 (Fd-3 m) crystal structure of Cr2Nb. Rietveld refinement was used to determine the lattice parameters and relative phase fractions of the constituent phases. The average thermal expansion coefficient was determined to be αai = 0.659 × 10−5 and αVi = 1.977 × 10−5 K−1 respectively. The Cp of the C15-Cr2Nb Laves phase intermetallic compound was measured employing heat flux DSC, utilizing conventional “three-step” procedures, and being reported for the first time. The measured Cp and enthalpy increment data (HT – H298.15) with varying temperatures reported in the present investigation are being correlated utilizing the theoretical model applying the quasi-harmonic Debye Grüneisen model in the temperature range 0–860 K and illustrated different contributions to the total heat capacity i.e., vibrational, anharmonic, and electronic.

Robust Spin Liquidity in 2D Metal-Organic Framework Cu3 (HHTP)2 with S=1 /2 Kagome Lattice.

On one hand electron or hole doping of quantum spin liquid (QSL) may unlock high-temperature superconductivity and on the other hand it can disrupt the spin liquidity, giving rise to a magnetically ordered ground state. Recently, a 2D MOF, Cu3 (HHTP)2 (HHTP - 2,3,6,7,10,11-hexahydroxytriphenylene), containing Cu(II) S= frustrated spins in the Kagome lattice is emerging as a promising QSL candidate. Herein, we present an elegant in situ redox-chemistry strategy of anchoring Cu3 (HHTP)2 crystallites onto diamagnetic reduced graphene oxide (rGO) sheets, resulting in the formation of electron-doped Cu3 (HHTP)2 -rGO composite which exhibited a characteristic semiconducting behavior (5 K to 300 K) with high electrical conductivity of 70 S ⋅ m-1 and a carrier density of ~1.1×1018 cm-3 at 300 K. Remarkably, no magnetic transition in the Cu3 (HHTP)2 -rGO composite was observed down to 1.5 K endorsing the robust spin liquidity of the 2D MOF Cu3 (HHTP)2 . Specific heat capacity measurements led to the estimation of the residual entropy values of 28 % and 34 % of the theoretically expected value for the pristine Cu3 (HHTP)2 and Cu3 (HHTP)2 -rGO composite, establishing the presence of strong quantum fluctuations down to 1.5 K (two times smaller than the value of the exchange interaction J).

Low-Temperature Specific Heat Capacity of Water-Ammonia Mixtures Down to the Eutectic.

Robust thermodynamic data are essential for the development of geodynamic and geochemical models of ocean worlds. The water-ammonia system is of interest in the study of ocean worlds due to its purported abundance in the outer solar system, geological implications, and potential importance for origins of life. In support of developing new equations of state, we conducted 1 bar specific heat capacity measurements (Cp) using a differential scanning calorimeter (DSC) at low temperatures (184-314 K) and low mass fractions of ammonia (5.2-26.9 wt %) to provide novel data in the parameter space most relevant for planetary studies. This is the first known set of data with sufficient fidelity to investigate the trend of specific heat capacity with respect to temperature. The obtained Cp in the liquid phase domain above the liquidus generally increases with temperature. Deviations of our data from the currently adopted equation of state by Tillner-Roth and Friend[Tillner-Roth R.; Friend D. G.J. Phys. Chem. Ref. Data1998, 27, 63-96]. are generally negative (ranging from +1 to -10%) and larger at lower temperatures. This result suggests that suppression of the critical behavior of supercooled water (rapid increase in specific heat with decreasing temperature) by ammonia starts at a smaller concentration than that set by Tillner-Roth and Friend.[Tillner-Roth R.; Friend D. G.J. Phys. Chem. Ref. Data1998, 27, 63-96]. Cp measurements of the liquid were also obtained in the partial melting domain between the eutectic and liquidus. This novel data set will be useful in future investigations of conditions where such partial melt may exist, such as the ice shell-ocean boundary or the interiors of ocean worlds that may contain relatively large proportions of dissolved ammonia.

Thermodynamic properties of cis-1-chloro-2,3,3,3-tetrafluoro-1-propene [R-1224yd(Z)]: Experimental measurements of the density and speed of sound and modeling with the Patel–Teja equation of state

Measurements of compressed liquid density and speed of sound have been performed in cis-1-chloro-2,3,3,3-tetrafluoro-1-propene, also known as R-1224yd(Z). Density has been measured in the temperature range from 273.15 K to 353.15 K and for pressure up to 35 MPa. The relative expanded uncertainty (k=2) for the obtained results has been estimated to be better than 0.05%. Speed of sound has been measured in the temperature range from 263 K to 353 K and for pressure up to 35 MPa. The expanded relative uncertainty (k=2) for these measurements has been estimated to be better than 0.06%. Using the properties measured in this work and including measurements of vapor pressure and ideal gas specific heat capacity published in scientific literature, a Patel-Teja equation of state has been implemented for describing the properties of the refrigerant both in liquid and in vapor phase. An independent model for predicting the speed of sound has been proposed to allow to calculate the adiabatic compressibility of the fluid with an accuracy higher than that accessible from Patel-Teja formulation.

Solid solutions of lithium niobate and lithium tantalate: crystal growth and the ferroelectric transition

Specific heat capacity measurements by differential scanning calorimetry (DSC) of single crystals of solid solutions of LiNbO3 and LiTaO3 are reported and compared with corresponding ab initio calculations, with the aim to investigate the variation of the ferroelectric Curie temperature as a function of composition. For this purpose, single crystals of these solid solutions were grown with Czochralski pulling along the c-axis. Elemental composition of Nb and Ta was investigated using XRF analysis, and small samples with homogeneous and well known composition were used for the DSC measurements. We observed that the ferroelectric Curie temperature decreases linearly with increasing Ta concentration in the LiNb 1 − x Ta x O3 solid solution crystals. Furthermore, the ferroelectric transition width of a mixed crystal appears to be smaller, as compared to pure LiTaO3.

Identification of invisible fatigue damage of thermosetting epoxy resin by non-destructive thermal measurement using entropy generation

To quantify carbon fiber-reinforced plastic (CFRP) fatigue, herein, we investigate the relationship between fatigue and an epoxy resin used in CFRPs. Generally, fatigue is related to the entropy, which comprises the mechanical entropy, calculated from the dissipated energy and temperature, and thermal entropy, calculated from the relationship between specific heat capacity and temperature. According to previous studies, mechanical entropy generation and thermal entropy generation are equal. Herein, 100 cyclic loading tests are conducted on epoxy resin specimens consisting of 4,4’-DDS and bisphenol a diglycidyl ether. The dissipated energy is determined based on stress – strain curves, and mechanical entropy generation is quantified. An equation for the relationship between the specific heat capacity and temperature is developed based on the Debye model, and the increase in specific heat capacity is calculated for equal mechanical and thermal entropy generations. Generally, differential scanning calorimetry is used for specific heat capacity measurements; however, because these measurements are performed by cutting the specimen, a nondestructive measurement method is required. In this study, the specific heat capacity is measured using lock-in thermography (LIT), and the measured and estimated values are comparable. Thus, fatigue can be estimated by quantifying the thermophysical properties, and the lock-in thermography method is a suitable thermophysical property measurement method for this application.

Exchange bias effect and inhomogeneous magnetism in 6H Ba3CoFeRuO9: Role of structural site disorder

Structural, magnetic, electrical and thermal investigations on ternary barium ruthenate Ba3CoFeRuO9 (BCFRO) reveal the role of the two different octahedral B-site in creating locally varying competing antiferromagnetic and ferromagnetic interactions. BCFRO forms in 6H hexagonal structure in the P63/mmc space group. Neutron diffraction and specific heat capacity measurements affirmed the absence of any long-range ordering and structural transition in the compound. DC thermomagnetic studies evidences spin glass magnetism with Tg ∼ 50 K. A large exchange bias (EB) field of 3.48 kOe is obtained at 3 K under a cooling field of 50 kOe. Careful analysis indicates, EB in our system stems from inhomogeneous magnetism owing to spatially varying chemical composition. Competing ferromagnetic and antiferromagnetic phases giving rise to spin glass behaviour is the manifestation of site disorder induced by mixed valences of magnetic ions. The exchange bias training effect in our system follows spin relaxation model of rotatable and frozen spins which are exchange coupled at the interface. Strong electron localisation occurs by virtue of the specific 6H structure with corner shared octahedral 2a site and face shared octahedral 4f site. The electrical and thermal transport in BCFRO follows Efros-Shklovskii variable range hopping (ES VRH) model below 150 K. The high resistivity of BCFRO at low temperatures is also reflected in the low thermal conductivity and huge Seebeck coefficient.

Strong Antibonding I (p)-Cu (d) States Lead to Intrinsically Low Thermal Conductivity in CuBiI4.

Chemical bonding present in crystalline solids has a significant impact on how heat moves through a lattice, and with the right chemical tuning, one can achieve extremely low thermal conductivity. The desire for intrinsically low lattice thermal conductivity (κlat) has gained widespread attention in thermoelectrics, in refractories, and nowadays in photovoltaics and optoelectronics. Here we have synthesized a high-quality crystalline ingot of cubic metal halide CuBiI4 and explored its chemical bonding and thermal transport properties. It exhibits an intrinsically ultralow κlat of ∼0.34-0.28 W m-1 K-1 in the temperature range 4-423 K with an Umklapp crystalline peak of 1.82 W m-1 K-1 at 20 K, which is surprisingly lower than other copper-based halide or chalcogenide materials. The crystal orbital Hamilton population analysis shows that antibonding states generated just below the Fermi level (Ef), which arise from robust copper 3d and iodine 5p interactions, cause copper-iodide bond weakening, which leads to reduction of the elastic moduli and softens the lattice, finally to produce extremely low κlat in CuBiI4. The chemical bonding hierarchy with mixed covalent and ionic interactions present in the complex crystal structure generates significant lattice anharmonicity and a low participation ratio in low-lying optical phonon modes originating mostly from localized copper-iodide bond vibrations. We have obtained experimental evidence of these low-lying modes by low-temperature specific heat capacity measurement as well as Raman spectroscopy. The presence of strong p-d antibonding interactions between copper and iodine leads to anharmonic soft crystal lattice which gives rise to low-energy localized optical phonon bands, suppressing the heat-carrying acoustic phonons to steer intrinsically ultralow κlat in CuBiI4.

Experimental investigation on rock thermal properties under the influence of temperature

The rock thermal parameters is of basic interest in geophysical, underground and engineering applications. The most relevant properties are thermal conductivity, specific heat capacity and thermal diffusivity. The present paper focuses on thermal properties of several rock types and minerals under the influence of temperature. On one hand, we provide a detailed review of rock thermal parameters and available correlations, and on the other hand, a series of laboratory measurements are presented and data are analyzed. For specific heat capacity measurements at atmospheric pressure and over a temperature range from 20 to 600 °C, the Differential Scanning Calorimetry (DSC) method is used and an indirect method is proposed. The results demonstrated an increase of specific heat capacity with a second order polynomial regression. The thermal conductivity and thermal diffusivity were investigated between 20 and 180 °C using the Hot Disk method. A logarithmic decrease with temperature was observed. In addition, a simple and inexpensive apparatus for measuring thermal conductivity at room temperature (20.0 ± 0.2 °C) is described and the results are compared with the commercial device. The results showed good performance with the estimated errors below 10%. To improve the applicability of the obtained results, empirical equations are developed to predict the thermal properties as a function of temperature and other physical properties. It was observed that the empirical relationships and the predicted values by the proposed equations are in agreement with the experimental data and with literature. Research results in this paper can be used as a support for rock engineering and a solution of a range of scientific and applied problems.

Thermal insulation capability of nanostructured insulations and their combination as hybrid insulation systems

The applications of insulation materials in buildings and vehicles are more important than ever. Therefore, the application of thermal insulation materials having high-performance heat-blocking properties such as nano-structured insulations like aerogels and graphite polystyrene is essential. In this paper a comprehensive thermal characterization will be presented, executed on two types of fibrous aerogels (slentex, pyrogel) as well as on graphite-expanded polystyrene, to compare their thermal insulation capability. Moreover, their possible sandwich-structured application as hybrid insulation systems was tested, too. The surface analysis of the samples is going to be presented through microscopic and wetting experiments. Thermal conductivity as well as specific heat capacity measurement results of both individual and sandwich structures will be shown. Slentex aerogel has the lowest thermal conductivity and performed best of all. The results of the hybrid structures are promising. The moisture uptake of the pyrogel aerogel is the highest. Based on the measured values theoretical models will be applied for validation, moreover, a face-to-face analysis will also be presented. Furthermore, calculations regarding thermal properties will also be highlighted. Results of both infrared absorption tests and differentiated scanning calorimetry would help the decision makers and it proves the high infrared absorption of graphite polystyrene.

A new approach for measurement of the low-temperature specific heat capacity

The manuscript presented the application of simultaneous thermal analyzer (STA449F3) at low-temperature Differential Scanning Calorimetry (DSC) and specific heat capacity tests. Moreover, some problems were found during the specific heat capacity measurement. The STA449F3 instrument can provide accurate characteristic temperature and enthalpy values calculation. However, the specific heat capacity deviation increased gradually when temperature increased above room-temperature. The liquid nitrogen cooling way led to nonlinear change of temperature with time during increasing, decreasing and holding temperature process, and larger deviation of low-temperature specific heat capacity. Three ways were adopted to measure the specific heat capacity from below zero to above room-temperature. The error between the studied and reference values was greatly reduced via creating a non-liquid nitrogen cooling environment.

Ground states and thermodynamics of the spin–electron model with mixed spins: Application to rare-earth tetraborides

A simple, but very realistic, spin–electron model is used to study the influence of mixed spins (from electron and spin subsystems) on a formation of fractional magnetization plateaus in rare-earth tetraborides. The spin subsystem is described by the ordinary Ising model and the electron subsystem by the ordinary Hubbard model. Moreover, both subsystems are coupled by the anisotropic spin-dependent interaction of the Ising type. To model the most realistically situation in rare-earth compounds we study the following combination of mixed spins: S = 1 , 3 / 2 and 2 in the spin subsystem and s d = 1 / 2 in the electron subsystem. It is shown that the mixed spins, in a combination with the Coulomb interaction U , have the significant impact on the formation and stabilization of different magnetization plateaus. In particular, we have found that the Coulomb interaction for S = 1 and S = 3 / 2 stabilizes the 1/2 plateau and strongly suppresses the 1/3 plateau which is in perfect agreement with the experimental measurements in TmB 4 and ErB 4 compounds. At nonzero temperatures our numerical results predict one high-temperature peak (of the Ising type) in the temperature dependence of the specific heat capacity, which accords with specific heat capacity measurements in TmB 4 and ErB 4 , and one low-temperature electron peak, which is not, however, seen in experiments. The reason is probably the fact that the electron peak appears at a several times lower temperature than the spin peak and thus the experiments, made only to 2 K, did not catch it. • A new spin–electron model with mixed spins is proposed. • Mixed spins in a combination with the Coulomb interaction stabilize 1/2 plateau. • Specific heat curves exhibit single- and double-peaked structure. • Predictions of our model are in a very good agreement with experiments in TmB 4 and ErB 4 .

Anisotropic thermal behavior of extrusion‐based large scale additively manufactured carbon‐fiber reinforced thermoplastic structures

AbstractLarge format additive manufacturing (AM) enables rapid manufacturing of large parts and structures with minimum waste in material and energy. Extrusion‐based AM deposition processes provide parts with highly anisotropic thermal properties, which are not typically reflected in textbook values for these materials. In order to develop accurate models that describe the directionally dependent thermal behavior of these materials in processing and service, accurate measurements of specific heat capacity and thermal conductivity are required. This work characterizes, documents, and analyzes the effect of the anisotropic nature of the extrusion‐based deposition process on the specific heat capacity and thermal conductivity of the resulting AM products. All measurements were made over a temperature range of 20–180°C using the transient plane source technique, also referred to as the hot disk technique. Three of the most commonly used large format AM feedstock materials that utilize carbon fiber reinforcement were examined in this work: acrylonitrile butadiene styrene, polyphenylene sulfide and polyphenylsulfone. These findings can serve as a thermal design/process guideline for future large format AM applications.

Specific Heat Capacity and Thermal Conductivity Measurements of PLA-Based 3D-Printed Parts with Milled Carbon Fiber Reinforcement.

This research focuses on the thermal characterization of 3D-printed parts obtained via fused filament fabrication (FFF) technology, which uses a poly(lactic acid) (PLA)-based filament filled with milled carbon fibers (MCF) from pyrolysis at different percentages by weight (10, 20, 30 wt%). Differential scanning calorimetry (DSC) and thermal conductivity measurements were used to evaluate the thermal characteristics, morphological features, and heat transport behavior of the printed specimens. The experimental results showed that the addition of MCF to the PLA matrix improved the conductive properties. Scanning electron microscopy (SEM) micrographs were used to obtain further information about the porosity of the systems.

Multiscale Thermal Investigations of Graphite Doped Polystyrene Thermal Insulation.

Nowadays, to improve quality of life, to have a more comfortable life, in internal spaces we try to maintain conditions that are free from external environmental influences. Thus, existing as well as newly built houses have adequate interiors maintaining their temperature, warming, or cooling due to the environment compensation. One way to create this is to reduce the heat loss in buildings. An option to achieve this is the application of thermal insulations. Nowadays, the use of super insulation materials such as aerogel and vacuum insulation panels and other nano-structured insulations, such as graphite doped expanded polystyrene, is becoming increasingly justified. These are relatively new materials, and we know only a little about them. This paper presents research results based on temperature-induced investigations of nanostructured graphite expanded polystyrene, to reveal its thermal stability after long-term and short-term thermal annealing, simulating the ageing of the material. Firstly, with a differential scanning calorimeter, we will explore the thermal stability profile of the specimens. After this, the paper will present temperature-induced changes in both the thermal properties and the structure of the samples. We will also present changes in the thermal conductivity, modifications in the surface, and compressive property variation induced by thermal annealing. The samples were thermal annealed at 70 °C for 6 weeks, at 100 and 110 °C for 1 h. Besides the thermal conductivity measurements with Netzsch 446 heat flow meter equipment, we will present specific heat capacity measurement results executed with the same equipment. Moreover, sorption isotherms of the as-received and annealed samples were registered and completed with hydrophobic experiments, too. Furthermore, from the measurements, we showed that temperature should affect a significant change in the thermal conductivity of materials. Moreover, the changes in the graphite expanded polystyrene before and after thermal annealing were investigated by Scanning Electron Microscopy, as well as optical microscopy. The structural changes were further followed by an X-ray diffractometer and the IR absorption capability was tested, too.

The effect of the sample pan position on the determination of the specific heat capacity for lipid materials using heat flux DSC

Accurate measurements of specific heat capacity for lipids as a function of temperature, Cp (T), are needed for modeling their crystallization behavior. Differential Scanning Calorimetry, DSC, has been the main technique to determine Cp (T) for numerous materials, including lipids. Key experimental conditions (heating/cooling ramps, sample size, purge gas, and temperature modulation) that affect the measured heat flow, from which Cp (T) is calculated, have been extensively discussed in the literature. Usually, DSC manufacturers provide procedures of what they consider to be the best experimental conditions to measure accurate Cp (T) values with the least uncertainties. The successive nature of these procedures requires the user to perform each step separately, which means that the user needs to take out the empty pan from the DSC furnace to load either the standard material (usually sapphire) or the sample and place it back again into the furnace. Following this method will result in a different pan placement on the sensor each time the DSC furnace is opened, which consequently will influence the heat flow signals. Utilizing the Guide to the Expression of Uncertainty in Measurements (GUM),this paper is intended to quantitatively evaluate the uncertainties in Cp (T) measurements due to the pan position on a heat-flux DSC sensor. Due to this effect, relative expanded uncertainty U values were ∼1.5%, and at least 15–25% as a result of pan placement. The sapphire uncertainty values were much smaller than those from the trimyristin (MMM) sample. With the assistance of FEM simulation, the effect of the different thermal diffusivity of MMM and sapphire on the Cp (T) measurements is elucidated.