Study of heat capacity enhancement in some nanostructured materials

Tan, Zhi‐Cheng; Wang, Lan; Shi, Quan

doi:10.1351/pac-con-08-09-15

Cited by 28 publications

(15 citation statements)

References 63 publications

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“… Higher Cp of nanoparticles compared to their bulk counterpart. Reported by Tan et al ( 2009 ), the increased exposure of surface atoms is showed to increase the Cp value measured in various tested nanoparticles (Tan et al 2009 ). This mode is unlikely to play a major role in enhancement but might contribute to it.…”

Section: Resultsmentioning

confidence: 84%

In situ production of titanium dioxide nanoparticles in molten salt phase for thermal energy storage and heat-transfer fluid applications

2016

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In this study, TiO2 nanoparticles (average particle size 16 nm) were successfully produced in molten salt phase and were showed to significantly enhance the specific heat capacity of a binary eutectic mixture of sodium and potassium nitrate (60/40) by 5.4 % at 390 °C and 7.5 % at 445 °C for 3.0 wt% of precursors used. The objective of this research was to develop a cost-effective alternate method of production which is potentially scalable, as current techniques utilized are not economically viable for large quantities. Enhancing the specific heat capacity of molten salt would promote more competitive pricing for electricity production by concentrating solar power plant. Here, a simple precursor (TiOSO4) was added to a binary eutectic mixture of potassium and sodium nitrate, heated to 450 °C, and cooled to witness the production of nanoparticles.

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Section: Resultsmentioning

confidence: 84%

In situ production of titanium dioxide nanoparticles in molten salt phase for thermal energy storage and heat-transfer fluid applications

2016

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“…The specific heat of smaller particles (Al 2 O 3 nanoparticle) size is more susceptible to temperature than that of larger particles (coarse-grained Al 2 O 3 ). The specific heat of small particles is higher for five main reasons: (1) smaller particle size means larger specific surface area (SSA), so the temperature affects the thermal expansion in the cluster of particle, (2) heat capacity is also larger because smaller particles are with larger porosity in the particle cluster at the same weight, (3) the smaller the particle size, the higher the number of particles; the interface layer between particles and particles or gas will also affect the specific heat, (4) the energy structure of nanostructured Al 2 O 3 is higher than that in a coarse-grained state [36], (5) the heat capacity of a grain boundary increases with an increment of the grain boundary's excess volume [37,38]: The excess specific heat depends on grain size [39]. For a particle size of 20 nm ( -Al 2 O 3 ) and a temperature of 25 -65 C, the specific heat ratio increases by 16.37% in the current experimental results.…”

Section: Resultsmentioning

confidence: 99%

Estimation and experimental study of the density and specific heat for alumina nanofluid

Teng

Hung

2012

Journal of Experimental Nanoscience

121

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This study analyses the density and specific heat of alumina (Al 2 O 3 )/water nanofluid to determine the feasibility of relative calculations. The Al 2 O 3 /water nanofluid was produced by the directsynthesis method with cationic chitosan dispersant served as the experimental sample, and was dispersed into three concentrations of 0.5, 1.0 and 1.5 wt.%. This experiment measures the density and specific heat of nanofluid with weight fractions and sample temperatures with a liquid density meter and a differential scanning calorimeter (DSC). To assess the availability of these equations, it then compares the experimental data with the calculated results according to the concepts of mixing theory and statistical mechanism. Comparing the calculated results of density and specific heat with the experimental data, the deviation of density fell within the range of À1.50% to 0.06% and 0.25% to 2.53%, whereas the deviation of specific heat fell within the range of À0.07% to 5.88% and À0.35% to 4.94%, respectively. Calculated results of density and specific heat show a trend of greater deviation with an increased concentration of nanofluid. However, two kinds of density and specific heat of the calculated results fall within an acceptable deviation range in this study.

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“…The density q was measured exploiting the Archimedes' principle. The specific heat c p was taken from the literature [45], neglecting possible contributions from doping and nanocrystallinity [46,47]. The synthesis-method itself should not have an impact on the specific heat [48].…”

Section: Characterizationmentioning

confidence: 99%

Thermoelectric transport properties of boron-doped nanocrystalline diamond foils

Engenhorst

Fecher

Notthoff

et al. 2015

Carbon

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A B S T R A C TNatural diamond is known for its outstanding thermal conductivity and electrical insulation. However, synthetic production allows for doping and tailoring microstructural and transport properties. Despite some motivation in the literature and the ongoing search for abundant and non-toxic thermoelectric materials, the first experimental study on a set of eight substrate-free boron-doped nanocrystalline diamond foils is presented herein.All transport coefficients were determined in the same direction within the same foils over a broad temperature range up to 900°C. It is found that nanostructuring reduces the thermal conductivity by two orders of magnitude, but the mobility decreases significantly to around 1 cm 2 V À1 s À1 , too. Although degenerate transport can be concluded from the temperature dependence of the Seebeck coefficient, charge carriers notably scatter at grain boundaries where sp 2 -carbon modifications and amorphous boron-rich phases form during synthesis. A detailed analysis of doping efficiency yields an acceptor fraction of only 8-18 at%, meaning that during synthesis excess boron thermodynamically prefers electrically inactive sites. Decent power factors above 10 À4 W m À1 K À2 at 900°C are found despite the low mobility, and a Jonker-type analysis grants a deeper insight into this issue.Together with the high thermal conductivity, the thermoelectric figure of merit zT does not exceed 0.01 at 900°C.

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Study of heat capacity enhancement in some nanostructured materials

Cited by 28 publications

References 63 publications

In situ production of titanium dioxide nanoparticles in molten salt phase for thermal energy storage and heat-transfer fluid applications

In situ production of titanium dioxide nanoparticles in molten salt phase for thermal energy storage and heat-transfer fluid applications

Estimation and experimental study of the density and specific heat for alumina nanofluid

Thermoelectric transport properties of boron-doped nanocrystalline diamond foils

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