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Thermal conductivity enhancement in thermal grease containing different CuO structures.

Yu W, Zhao J, Wang M, Hu Y, Chen L, Xie H - Nanoscale Res Lett (2015)

Bottom Line: The morphologies and crystal structures of these CuO structures are characterized by field-emission scanning electron microscope and X-ray diffractometer, respectively.Compared with pure silicone base, the thermal conductivities of thermal greases with CuO microdisks, CuO nanoblocks, and CuO microspheres are 0.283, 0256, and 0.239 W/mK, respectively, at filler loading of 9 vol.%, which increases 139%, 116%, and 99%, respectively.These experimental data are compared with Nan's model prediction, indicating that the shape factor has a great influence on thermal conductivity improvement of thermal greases with different CuO structures.

View Article: PubMed Central - PubMed

Affiliation: College of Engineering, Shanghai Second Polytechnic University, 2360 Jin Hai Road, Pudong District,, Shanghai, 201209 China.

ABSTRACT
Different cupric oxide (CuO) structures have attracted intensive interest because of their promising applications in various fields. In this study, three kinds of CuO structures, namely, CuO microdisks, CuO nanoblocks, and CuO microspheres, are synthesized by solution-based synthetic methods. The morphologies and crystal structures of these CuO structures are characterized by field-emission scanning electron microscope and X-ray diffractometer, respectively. They are used as thermal conductive fillers to prepare silicone-based thermal greases, giving rise to great enhancement in thermal conductivity. Compared with pure silicone base, the thermal conductivities of thermal greases with CuO microdisks, CuO nanoblocks, and CuO microspheres are 0.283, 0256, and 0.239 W/mK, respectively, at filler loading of 9 vol.%, which increases 139%, 116%, and 99%, respectively. These thermal greases present a slight descendent tendency in thermal conductivity at elevated temperatures. These experimental data are compared with Nan's model prediction, indicating that the shape factor has a great influence on thermal conductivity improvement of thermal greases with different CuO structures. Meanwhile, due to large aspect ratio of CuO microdisks, they can form thermal networks more effectively than the other two structures, resulting in higher thermal conductivity enhancement.

No MeSH data available.


Comparison of theoretical predictive model with experimental data.
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Fig5: Comparison of theoretical predictive model with experimental data.

Mentions: Figure 5 shows the comparison of theoretical predictive model with experimental data, where theoretical predictive values of thermal conductivity are presented. For Equation 1, p is the aspect ratio of CuO microdisks, and the average value is 20 obtained by analyzing SEM images of CuO microdisks. d is the thickness of CuO microdisks (90 nm). kf is the thermal conductivity of CuO microdisks (33 W/mK [34,35]). After trial and error analyses, Rk is set to 1.2 × 10−7 Km2/W. It can be seen that the experimental thermal conductivity data of thermal grease with CuO microdisks are in reasonable agreement with the predicted results of Equation 1. For Equation 3, p (1), d (1 μm), and kf (33 W/mK) are aspect ratio, diameter, and thermal conductivity of CuO microspheres, respectively. Its predictive curve is also in reasonable agreement with the experimental thermal conductivity of thermal grease with CuO microspheres. However, for CuO nanoblocks, p, d, and kf are, respectively, equal to 3, 130 nm, and 33 W/mK, and the predicted results of Equation 2 deviate from the experimental values. It is postulated that the nanosized CuO blocks could form many clusters in the silicone base, which could increase the actual size of CuO particles. Therefore, the aspect ratio of CuO nanoblocks will increase. At the same time, the clusters are favorable for thermal conductivity enhancement of thermal grease [30]. Add it all up and the shape factor has a great influence on thermal conductivity improvement of thermal greases with different CuO structures. The larger the shape factor is, the stronger the ability to thermal conductivity augment is. Interpreting this increased thermal conductivity as a high aspect ratio, it is reasonable to increase the particle-to-particle contact and the corresponding geometric parameter [26,27,36]. This structures some effective thermal conductive networks, in turn facilitating phonon transfer and resulting in high enhancement in thermal conductivity.Figure 5


Thermal conductivity enhancement in thermal grease containing different CuO structures.

Yu W, Zhao J, Wang M, Hu Y, Chen L, Xie H - Nanoscale Res Lett (2015)

Comparison of theoretical predictive model with experimental data.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4385151&req=5

Fig5: Comparison of theoretical predictive model with experimental data.
Mentions: Figure 5 shows the comparison of theoretical predictive model with experimental data, where theoretical predictive values of thermal conductivity are presented. For Equation 1, p is the aspect ratio of CuO microdisks, and the average value is 20 obtained by analyzing SEM images of CuO microdisks. d is the thickness of CuO microdisks (90 nm). kf is the thermal conductivity of CuO microdisks (33 W/mK [34,35]). After trial and error analyses, Rk is set to 1.2 × 10−7 Km2/W. It can be seen that the experimental thermal conductivity data of thermal grease with CuO microdisks are in reasonable agreement with the predicted results of Equation 1. For Equation 3, p (1), d (1 μm), and kf (33 W/mK) are aspect ratio, diameter, and thermal conductivity of CuO microspheres, respectively. Its predictive curve is also in reasonable agreement with the experimental thermal conductivity of thermal grease with CuO microspheres. However, for CuO nanoblocks, p, d, and kf are, respectively, equal to 3, 130 nm, and 33 W/mK, and the predicted results of Equation 2 deviate from the experimental values. It is postulated that the nanosized CuO blocks could form many clusters in the silicone base, which could increase the actual size of CuO particles. Therefore, the aspect ratio of CuO nanoblocks will increase. At the same time, the clusters are favorable for thermal conductivity enhancement of thermal grease [30]. Add it all up and the shape factor has a great influence on thermal conductivity improvement of thermal greases with different CuO structures. The larger the shape factor is, the stronger the ability to thermal conductivity augment is. Interpreting this increased thermal conductivity as a high aspect ratio, it is reasonable to increase the particle-to-particle contact and the corresponding geometric parameter [26,27,36]. This structures some effective thermal conductive networks, in turn facilitating phonon transfer and resulting in high enhancement in thermal conductivity.Figure 5

Bottom Line: The morphologies and crystal structures of these CuO structures are characterized by field-emission scanning electron microscope and X-ray diffractometer, respectively.Compared with pure silicone base, the thermal conductivities of thermal greases with CuO microdisks, CuO nanoblocks, and CuO microspheres are 0.283, 0256, and 0.239 W/mK, respectively, at filler loading of 9 vol.%, which increases 139%, 116%, and 99%, respectively.These experimental data are compared with Nan's model prediction, indicating that the shape factor has a great influence on thermal conductivity improvement of thermal greases with different CuO structures.

View Article: PubMed Central - PubMed

Affiliation: College of Engineering, Shanghai Second Polytechnic University, 2360 Jin Hai Road, Pudong District,, Shanghai, 201209 China.

ABSTRACT
Different cupric oxide (CuO) structures have attracted intensive interest because of their promising applications in various fields. In this study, three kinds of CuO structures, namely, CuO microdisks, CuO nanoblocks, and CuO microspheres, are synthesized by solution-based synthetic methods. The morphologies and crystal structures of these CuO structures are characterized by field-emission scanning electron microscope and X-ray diffractometer, respectively. They are used as thermal conductive fillers to prepare silicone-based thermal greases, giving rise to great enhancement in thermal conductivity. Compared with pure silicone base, the thermal conductivities of thermal greases with CuO microdisks, CuO nanoblocks, and CuO microspheres are 0.283, 0256, and 0.239 W/mK, respectively, at filler loading of 9 vol.%, which increases 139%, 116%, and 99%, respectively. These thermal greases present a slight descendent tendency in thermal conductivity at elevated temperatures. These experimental data are compared with Nan's model prediction, indicating that the shape factor has a great influence on thermal conductivity improvement of thermal greases with different CuO structures. Meanwhile, due to large aspect ratio of CuO microdisks, they can form thermal networks more effectively than the other two structures, resulting in higher thermal conductivity enhancement.

No MeSH data available.