The nano heat effect of replacing macro-particles by nano-particles in drop calorimetry: the case of core/shell metal/oxide nano-particles (original) (raw)
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Experimental Mechanics, 2014
This paper proposes a non-contact original method to estimate local thermophysical properties (heat capacity and thermal conductivity) and heats of transition from plane thin specimens. This method is based on measurement of temperature fields with an infrared camera during a drop calorimetric experiment. A studied specimen and a reference specimen, with similar geometries, are simultaneously tested. Firstly, the method is validated by estimating heat capacity and thermal conductivity of Vanadium specimens and by comparing the determined values with those obtained by Differential Scanning Calorimetry and by a laser flash method, respectively. Secondly, the method is used to determine latent heats of martensitic transformations. These heats of transition are determined during homogeneous and heterogeneous drop calorimetric experiments of NiTi shape memory alloys specimens.
Physics Reports, 2019
Nanomaterials possess superior optical, electrical, magnetic, mechanical, and thermal properties, which have made them suitable for a multitude of applications. The present review paper deals with recent advances in the measurement and modeling of thermophysical properties at the nanoscale (from the solid state to colloids). For this purpose, first, various techniques for the measurement of the solid state properties, including thermal conductivity, thermal diffusivity, and specific heat capacity, are introduced. The main factors that affect the solid state properties are grain size, grain boundaries, surface interactions, doping, and temperature, which are discussed in detail. After that, methods for the measurement and modeling of thermophysical properties of colloids (nanofluids), including thermal conductivity, dynamic viscosity, specific heat capacity, and density, are presented. The main parameters affecting these properties, such as size, shape, and concentration of nanoparticles, aggregation, and sonication time are studied. Furthermore, the properties of not only simple nanofluids but also hybrid nanofluids (which are composed of more than one type of nanoparticles) are investigated. Finally, the main research gaps and challenges are listed.
The Determination of Surface Thermodynamic Properties of Nanoparticles by Thermal Analysis
Journal of Modern Physics, 2013
The effect of dispersivity on thermodynamic and kinetic parameters of chemical reactions in nanodispersed systems is theoretically investigated. On the basis of the established theoretical dependences the new method of determination of surface thermodynamic properties of nanoparticles (surface enthalpy, surface entropy and surface energy) by thermal analysis (DTA or DSC) was developed. Three examples of calculation of surface properties of nanoparticles were presented to prove the feasibility of this method.
Features of heat transfer during the evaporation of a drop of nanofluid
Journal of Physics: Conference Series, 2019
In the present work, experimental studies of factors affecting heat and mass transfer during the evaporation of droplets of nanofluids with SiO 2 nanoparticles (base liquid-water) were carried out in a wide range of mass concentrations and initial environmental parameters (temperature and flow rate). According to the results of the study, it was found that the effect of nanoparticles under forced convection depends on the initial environmental conditions.
A sensitive calorimetric technique to study energy (heat) exchange at the nano-scale
Nanoscale, 2018
Every time a chemical reaction occurs, an energy exchange between reactants and environment exists, which is defined as the enthalpy of the reaction. In the last decades, research has resulted in an increasing number of devices at the micro-or nano-scale. Sensors, catalyzers, and energy storage systems are more and more developed as nano-devices which represent the building blocks for commercial "macroscopic" objects. A general method for the direct evaluation of the energy balance of such systems is not available at present. Calorimetry is a powerful tool to investigate energy exchange, but it usually needs macroscopic sample quantities. Here we report on the development of an original experimental setup able to detect temperature variations as low as 10 mK in a sample of ∼ 10 ng using a thermometer device having physical dimensions of 5 × 5 mm 2. The technique has been utilized to measure the enthalpy release during the adsorption process of H2 on a titanium decorated monolayer graphene. The sensitivity of these thermometers is high enough to detect a hydrogen uptake of ∼ 10 −10 moles, corresponding to ∼ 0.2 ng, with an enthalpy release of about 23 µJ. The experimental setup allows, in perspective, the scalability to even smaller sizes.
The shape and size dependent melting thermodynamics of metallic nanoparticles are predicted by application of bond theory model, free of any adjustable parameter. Thermodynamic properties like Debye frequency, Curie temperature, melting entropy and enthalpy of Al, Sn, In, Cu, β-Fe and Fe 3 O 4 for spherical and non spherical shapes nanoparticles with different size have been studied. In this model, the effects of relaxation factor for the low dimension solids are considered. The depression in Debye frequency, Curie temperature, melting entropy and enthalpy is predicted. The model predictions are supported by the available experimental and simulation results.
Theoretical analysis of thermophysical properties of nanomaterials
Materials Today: Proceedings, 2021
In the present study, a theoretical comparative work is done to calculate the variation of melting temperature in nanomaterials by using two quantum models i.e. Lu model and Jiang model and the expression of melting temperature calculated with the help of best model is extended to calculate the variation of Debye temperature and thermal expansion coefficient with size and shape of nanomaterials. The melting temperature and Debye temperature are observed to increase as the diameter of nanomaterials is increased and thermal expansion coefficient decrease with increase in the diameter of nanosolid. The results obtained from the given models are compared with the experimental values to judge the bestsuited model for the study of the thermodynamic properties of nanosolids. The available experimental results are found very close to the results from the Jiang model and then Debye temperature and thermal expansion coefficient are calculated with the help of Jiang model.
An Experimental Investigation into the Thermal Properties of Nano Fluid
Nano fluid came into picture in the field of heat transfer in systems since it was introduced by Choi [1]. The heat transfer coefficient of a fluid depends on thermal properties like conductivity, viscosity and specific heat. So far the effect of particle size, volume fraction and temperature was studied by many researchers but the effect of sonication and settling time on Nano fluid is studied by few researchers . Calvin investigated effect of volume fraction and temperature on the CuO and Al 2 O 3 nanoparticles based water Nano fluid and the results showed an increase of 52% in the thermal conductivity of DI water, when CuO nanoparticles were dispersed at a volume fraction of 6% . Also, an increase of 30% in the conductivity of Al 2 O 3 based Nano fluid was reported at volume fraction 10% in a temperature range of 27.5 to 34.7°C. Jang investigated the effect of temperature and volume fraction on the viscosity Al 2 O 3 nanoparticles dispersed in water, the results reported an increase of 2.9% in the viscosity of base fluid at a volume fraction of 0.3% and with the increase in temperature the viscosity of Nano fluid decreases continuously . The results of Zhou showed that the specific heat of water decreases by 50%, when Al 2 O 3 nanoparticles were dispersed in a volume fraction range of 0 to 21.7% . In this paper, the effect of volume fraction, sonication time, settling time, diameter of particles and temperature on the thermal properties of zinc oxide and single walled carbon nanotube based Nano fluid s is presented.
Oriental Journal of Chemistry
The shape and size dependent melting thermodynamics of metallic nanoparticles are predicted by application of bond theory model, free of any adjustable parameter. Thermodynamic properties like Debye frequency, Curie temperature, melting entropy and enthalpy of Al, Sn, In, Cu, β-Fe and Fe3O4 for spherical and non spherical shapes nanoparticles with different size have been studied. In this model, the effects of relaxation factor for the low dimension solids are considered. The depression in Debye frequency, Curie temperature, melting entropy and enthalpy is predicted. The model predictions are supported by the available experimental and simulation results.
Size-Dependent Melting Properties of Small Tin Particles: Nanocalorimetric Measurements
Physical Review Letters, 1996
For the first time, the latent heat of fusion DH m for Sn particles formed by evaporation on inert substrate with radii ranging from 5 to 50 nm has been measured directly using a novel scanning nanocalorimeter. A particle-size-dependent reduction of DH m has been observed. An "excluded volume" is introduced to describe the latent heat of fusion from the enhanced surface melting of small particles. Melting point depression has also been found by our nanocalorimetric technique. [S0031-9007(96) PACS numbers: 61.46.+w, 64.70.Dv, 65.40.+g The unusual properties of nanometer-sized materials have generated tremendous interest in both scientific and technological communities [1]. One particular phenomenon-particle-size-dependent melting point depression-occurs when the particle size is of the order of nanometers, as first demonstrated by Takagi [2] by means of transmission electron microscope (TEM) observation. At these reduced dimensions, the surface-tovolume ratio is high and the surface energy substantially effects the interior "bulk" properties of the material. For example, the melting point T m of nanometer-sized Au particles can be 300 K lower than the bulk value .