Thermal transport and grain boundary conductance in ultrananocrystalline diamond thin films

Angadi, Maki A.; Watanabe, Taku; Bodapati, Arun; Xiao, Xingcheng; Auciello, Orlando; Carlisle, John A.; Eastman, J. A.; Keblinski, Pawel; Schelling, Patrick K.; Phillpot, Simon R.

doi:10.1063/1.2199974

Cited by 148 publications

(87 citation statements)

References 109 publications

(103 reference statements)

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“…43. For MgO, l k~3 0 nm at 300 K which decreases to ~3 nm at 1473 K. The effect is less dramatic in NDZ, with l k decreasing from 4 nm at 300 K to 1.75 nm at 1473 K. These decreases are consistent with the trends seen previously for UO 2 133 and diamond 134 , in both of which, the temperature dependence of l k decreased with temperature for both materials.…”

Section: Grain Size Dependence Of Mgo and Ndz Polycrystal Thermal Consupporting

confidence: 80%

Neri Final Technical Report, De-Fc07-O5id14647, Optimization of Oxide Compounds for Advanced Inert Matrix Materials

Nino¹

2009

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The following is a technical report summarizing all the procedures, experiments, simulations and technical findings of this NERI project. For additional information, details or technical questions regarding this project, please contact jnino@mse.ufl.edu MgO and NDZ......................................................................69 8.4. Grain Size Dependence of MgO and NDZ Polycrystal Thermal Conductivity75 8.5 2009 Composite Processing and Characterization IntroductionIn order to reduce the current excesses of plutonium (both weapon grade and reactor grade) and other transuranium elements, a concept of inert matrix fuel (IMF) has been proposed for an uranium free transmutation of fissile actinides which excludes continuous uranium-plutonium conversion in thermal reactors and advanced systems. 1,2 Magnesium oxide (MgO) is a promising candidate for inert matrix (IM) materials due to its high melting point (2827 °C) 2 , high thermal conductivity (13 W/K·m at 1000 °C) 2 , good neutronic properties, and irradiation stability 3,4 However, MgO reacts with water and hydrates easily, which prevents it from being used in light water reactors (LWRs) as an IM. To improve the hydration resistance of MgO-based inert matrix materials, Medvedev 5 and coworkers have recently investigated the introduction of a secondary phase that acts as a hydration barrier. An MgO-ZrO 2 composite was specifically studied and the results showed that the composite exhibited improved hydration resistance than pure MgO. However, ZrO 2 is insoluble in most acids except HF, which is undesirable for fuel reprocessing. Moreover, the thermal conductivity of ZrO 2 is low and typically less than 3 W·m at 1000 °C. 6 In search for an alternative composite strategy, Nd 2 Zr 2 O 7 , an oxide compound with pyrochlore structure, has been proposed recently as a corrosion resistant phase, and MgO-Nd 2 Zr 2 O 7 composites have been investigated as potential IM materials. at 1000 °C for the MgO-Nd 2 Zr 2 O 7 composite with 90 vol% MgO was recently calculated and reported. 8,9 Other simulations proposed that the MgO-pyrochlore composites could exhibit higher radiation stability than previously reported. 10 Final optimization of the composite microstructure was performed on the 70 vol% MgONd 2 Zr 2 O 7 composite that burnup calculations had shown to have the closest profile to that of MOX fuel. Theoretical calculations also indicated that a homogeneous 70 vol% MgO composite could achieve the desired microstructure that would result in satisfying the dual requirements of good thermal properties. Experimental Procedures Composite Synthesis Solid State Synthesis of Nd 2 Zr 2 O 7Stoichiometric ratios of Nd 2 O 3 (Alfa Aesar 99.9%) and ZrO 2 (99.7%) were added to spherical 3 mm and 10 mm yttria stabilized zirconia (YSZ) milling media in a PTFE (polytetrafluoroethylene) ball mill jar with 100 ml of deionized water and 3 ml of ammonium polyacrylate dispersant (20 vol% Darvan 821A in deionized water). The slurry was milled for 24 hours on the ball mill at 85 rpm ...

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Section: Grain Size Dependence Of Mgo and Ndz Polycrystal Thermal Consupporting

confidence: 80%

Neri Final Technical Report, De-Fc07-O5id14647, Optimization of Oxide Compounds for Advanced Inert Matrix Materials

Nino¹

2009

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“…This variation mimics the behaviour of highly sp 3 carbons which have been extensively studied [4,5,28]. As shown by Angadi et al [28] nanometre-sized sp 3 grains lead to small thermal conductivities (around tens of Wm −1 K −1 ), while larger grains lead to an exponentially increasing thermal conductivity which approaches the diamond limit (2000 Wm −1 K −1 ). Combining our present studies of sp 2 ordering with previous works on sp 3 ordering provides a unified picture showing how the thermal conductivity is determined by the microstructure.…”

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confidence: 79%

“…Increasing the grain size will lead to even higher thermal conductivities, tending towards the theoretical limit for graphite of circa 4000 Wm −1 K −1 in the basal plane [26]. This variation mimics the behaviour of highly sp 3 carbons which have been extensively studied [4,5,28]. As shown by Angadi et al [28] nanometre-sized sp 3 grains lead to small thermal conductivities (around tens of Wm −1 K −1 ), while larger grains lead to an exponentially increasing thermal conductivity which approaches the diamond limit (2000 Wm −1 K −1 ).…”

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confidence: 99%

Effect of microstructure on the thermal conductivity of disordered carbon

Suarez-Martinez

Marks

2011

Applied Physics Letters

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Computational methods are used to control the degree of structural order in a variety of carbon materials containing primarily sp 2 bonding. Room-temperature thermal conductivities are computed using non-equilibrium molecular dynamics. Our results reproduce experimental data for amorphous and glassy carbons and confirm previously proposed structural models for vitreous carbons. An atomistic model is developed for highly oriented thin films seen experimentally, with a maximum computed thermal conductivity of 35 Wm −1 K −1 . This value is much higher than that of the amorphous and glassy structures, demonstrating that the microstructure influences the thermal conductivity more strongly than the density.

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“…15 However, it is known that the abundance of grain boundaries, and therefore, the grain size, can reduce dramatically its thermal conductivity. [16][17][18] The average distance phonons travel between scattering events (MFP) in the bulk diamond lattice is very large, being $80% of the heat carried by phonons with MFPs greater than 200 nm at room temperature, 19 making the role of the grain boundaries especially critical near the nucleation region. Here, the lateral dimensions of the grains, which typically develop in a columnar shape, are not greater than a few hundreds of nanometers.…”

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confidence: 99%

Thermal conductivity of ultrathin nano-crystalline diamond films determined by Raman thermography assisted by silicon nanowires

Anaya

Rossi

Alomari

et al. 2015

Applied Physics Letters

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The thermal transport in polycrystalline diamond films near its nucleation region is still not well understood. Here, a steady-state technique to determine the thermal transport within the nano-crystalline diamond present at their nucleation site has been demonstrated. Taking advantage of silicon nanowires as surface temperature nano-sensors, and using Raman Thermography, the in-plane and cross-plane components of the thermal conductivity of ultra-thin diamond layers and their thermal barrier to the Si substrate were determined. Both components of the thermal conductivity of the nano-crystalline diamond were found to be well below the values of polycrystalline bulk diamond, with a cross-plane thermal conductivity larger than the in-plane thermal conductivity. Also a depth dependence of the lateral thermal conductivity through the diamond layer was determined. The results impact the design and integration of diamond for thermal management of AlGaN/GaN high power transistors and also show the usefulness of the nanowires as accurate nano-thermometers.

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Thermal transport and grain boundary conductance in ultrananocrystalline diamond thin films

Abstract: X-ray photoelectron spectroscopic investigation of surface chemistry of ternary AsS -Se chalcogenide glasses

Cited by 148 publications

References 109 publications

Neri Final Technical Report, De-Fc07-O5id14647, Optimization of Oxide Compounds for Advanced Inert Matrix Materials

Neri Final Technical Report, De-Fc07-O5id14647, Optimization of Oxide Compounds for Advanced Inert Matrix Materials

Effect of microstructure on the thermal conductivity of disordered carbon

Thermal conductivity of ultrathin nano-crystalline diamond films determined by Raman thermography assisted by silicon nanowires

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