Thermal conductivity of κ-Al2O3 and α-Al2O3 wear-resistant coatings

Cahill, David G.; Lee, S.-M.; Selinder, T. I.

doi:10.1063/1.367500

Cited by 124 publications

(47 citation statements)

References 23 publications

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“…The volume thermal conductivity of CSH does not alter with the Ca∶Si ratio and it is close to that of 11-Å tobermorite (see Table II). The above K v values for CSH are close to those of amorphous silica measured experimentally [89][90][91][92][93] and calculated numerically [94] and theoretically [95,96]. Since the variation of the Ca∶Si ratio is merely achieved by removing SiO 2 groups from 11-Å tobermorite, it can be viewed as a parameter that is inversely proportional to the defect content.…”

Section: Nanoscale Heat-conductivity Calculationssupporting

confidence: 53%

Physical Origins of Thermal Properties of Cement Paste

2015

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Despite the ever-increasing interest in multiscale porous materials, the chemophysical origin of their thermal properties at the nanoscale and its connection to the macroscale properties still remain rather obscure. In this paper, we link the atomic-and macroscopic-level thermal properties by combining tools of statistical physics and mean-field homogenization theory. We begin with analyzing the vibrational density of states of several calcium-silicate materials in the cement paste. Unlike crystalline phases, we indicate that calcium silicate hydrates (CSH) exhibit extra vibrational states at low frequencies (< 2 THz) compared to the vibrational states predicted by the Debye model. This anomaly is commonly referred to as the boson peak in glass physics. In addition, the specific-heat capacity of CSH in both dry and saturated states scales linearly with the calcium-to-silicon ratio. We show that the nanoscale-confining environment of CSH decreases the apparent heat capacity of water by a factor of 4. Furthermore, full thermal conductivity tensors for all phases are calculated via the Green-Kubo formalism. We estimate the mean free path of phonons in calcium silicates to be on the order of interatomic bonds. This satisfies the scale separability condition and justifies the use of mean-field homogenization theories for upscaling purposes. Upscaling schemes yield a good estimate of the macroscopic specific-heat capacity and thermal conductivity of cement paste during the hydration process, independent of fitting parameters.

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Section: Nanoscale Heat-conductivity Calculationssupporting

confidence: 53%

Physical Origins of Thermal Properties of Cement Paste

2015

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“…Compared to BeO and AlN, single crystal Al 2 O 3 (sapphire) exhibits a low thermal conductivity of only 34 W/mK, 317,318 but comparable to the value of ∼14 W/mK for single crystal SiO 2 (quartz). 319 The reported thermal conductivities for poly-crystalline 254,320 and amorphous [57][58][59]321 Al 2 O 3 of 16-33 and 0.7-2.6 W/mK, respectively, are also comparable to the previously discussed lower range reported for AlN and amorphous SiO 2 (see Table VIII Regarding HfO 2 , we are unaware of any reports of thermal conductivity for single-crystal hafnia.…”

Section: 283mentioning

confidence: 99%

Review—Investigation and Review of the Thermal, Mechanical, Electrical, Optical, and Structural Properties of Atomic Layer Deposited High-kDielectrics: Beryllium Oxide, Aluminum Oxide, Hafnium Oxide, and Aluminum Nitride

Gaskins

Hopkins

Merrill

et al. 2017

ECS J. Solid State Sci. Technol.

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Atomic layer deposited (ALD) high-dielectric-constant (high-k) materials have found extensive applications in a variety of electronic, optical, optoelectronic, and photovoltaic devices. While electrical, optical, and interfacial properties have been the primary consideration for such devices, thermal and mechanical properties are becoming an additional key consideration for many new and emerging applications of ALD high-k materials in electromechanical, energy storage, and organic light emitting diode devices. Unfortunately, a clear correspondence between thermal/mechanical and electrical/optical properties in ALD high-k materials has yet to be established, and a detailed comparison to conventional silicon-based dielectrics to facilitate optimal material selection is also lacking. In this regard, we have conducted a comprehensive investigation and review of the thermal, mechanical, electrical, optical, and structural properties for a series of prevalent and emerging ALD high-k materials including aluminum oxide (Al 2 O 3 ), aluminum nitride (AlN), hafnium oxide (HfO 2 ), and beryllium oxide (BeO). For comparison, more established silicon-based dielectrics were also examined, including thermally grown silicon dioxide (SiO 2 ) and plasma-enhanced chemically vapor deposited hydrogenated silicon nitride (SiN:H). We find that in addition to exhibiting high values of dielectric permittivity and electrical resistance that exceed those of SiO 2 and SiN:H, the ALD high-k materials exhibit equally exceptional thermal and mechanical properties with coefficients of thermal expansion ≤ 6 × 10 -6 / • C, thermal conductivites (κ) of 3-15 W/m K, and Young's modulus and hardness values exceeding 200 and 25 GPa, respectively. In many cases, the observed extreme thermal/mechanical properties correlate with the presence of crystallinity in the ALD high-k films. In contrast, some of the electrical and optical properties correlate more strongly with the percentage of ionic vs. covalent bonds present in the high-k film. Overall, the ALD high-k dielectrics investigated concurrently exhibit compelling thermal/mechanical and electrical/optical properties. The drive to reduce gate leakage currents in highly scaled complementary metal-oxide-semiconductor (CMOS) transistors has led to the exploration and development of a wide variety of high-dielectricconstant (high-k) materials to replace silicon dioxide (SiO 2 ) as the insulating gate dielectric material.1-8 Many of these same high-k materials have found additional applications in future non-CMOS logic and memory storage products such as solid-state electrolytes in resistive switching devices, 9,10 tunnel barriers in spin-transport devices, 11 and as a ferroelectric in magnetoelectric devices. While electrical, physical, and thermodynamic properties have clearly been a key consideration in all of the above applications, thermal properties have become an additional important consideration for higk-k dielectrics as aggressive dimensional scaling of devices has created the need to dissipate ...

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“…Finally, the phonon calculations in the BTE employ a 15x15x15 k-mesh in the first Brillouin zone, with the additional refinement of a factor of 10 along the z-axis to ensure that the energy -function is well obeyed. Bose-Einstein statistics are used to allow direct comparison with the experimental data by Cahill and coworkers 63 and previous DFT/LDA data of Tang and Dong 61 in Figure 3. One can see that the DFT results are slightly higher than the experimental data points, but somewhat lower than previously reported DFT results.…”

Section: Example Of First Principles Calculationsmentioning

confidence: 99%