Abstract:Nanoscale solely amorphous layer is achieved in silicon (Si) wafers, using a developed diamond wheel with ceria, which is confirmed by high resolution transmission electron microscopy (HRTEM). This is different from previous reports of ultraprecision grinding, nanoindentation and nanoscratch, in which an amorphous layer at the top, followed by a crystalline damaged layer beneath. The thicknesses of amorphous layer are 43 and 48 nm at infeed rates of 8 and 15 μm/min, respectively, which is verified using HRTEM.… Show more
“…5b and c. It could be main reasons as following: (a) the well-bridged and efficient thermal conduction network between nanowires and nanowires; (b) SiC NWs with larger aspect ratio than SiC MPs and (c) a better interaction between SiC NWs with the epoxy matrix 27 .Figure 5( a ) Thermal diffusivity and ( b ) thermal conductivity as a function of SiC NWs or SiC MPs content; ( c ) Thermal conductivity enhancement (TCE) of epoxy composites with 3 wt% filler compared to neat epoxy; ( d ) The model of heat flow for the epoxy composites.
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In this study, we report a facile approach to fabricate epoxy composite incorporated with silicon carbide nanowires (SiC NWs). The thermal conductivity of epoxy/SiC NWs composites was thoroughly investigated. The thermal conductivity of epoxy/SiC NWs composites with 3.0 wt% filler reached 0.449 Wm−1 K−1, approximately a 106% enhancement as compared to neat epoxy. In contrast, the same mass fraction of silicon carbide micron particles (SiC MPs) incorporated into epoxy matrix showed less improvement on thermal conduction properties. This is attributed to the formation of effective heat conduction pathways among SiC NWs as well as a strong interaction between the nanowires and epoxy matrix. In addition, the thermal properties of epoxy/SiC NWs composites were also improved. These results demonstrate that we developed a novel approach to enhance the thermal conductivity of the polymer composites which meet the requirement for the rapid development of the electronic devices.
“…5b and c. It could be main reasons as following: (a) the well-bridged and efficient thermal conduction network between nanowires and nanowires; (b) SiC NWs with larger aspect ratio than SiC MPs and (c) a better interaction between SiC NWs with the epoxy matrix 27 .Figure 5( a ) Thermal diffusivity and ( b ) thermal conductivity as a function of SiC NWs or SiC MPs content; ( c ) Thermal conductivity enhancement (TCE) of epoxy composites with 3 wt% filler compared to neat epoxy; ( d ) The model of heat flow for the epoxy composites.
…”
In this study, we report a facile approach to fabricate epoxy composite incorporated with silicon carbide nanowires (SiC NWs). The thermal conductivity of epoxy/SiC NWs composites was thoroughly investigated. The thermal conductivity of epoxy/SiC NWs composites with 3.0 wt% filler reached 0.449 Wm−1 K−1, approximately a 106% enhancement as compared to neat epoxy. In contrast, the same mass fraction of silicon carbide micron particles (SiC MPs) incorporated into epoxy matrix showed less improvement on thermal conduction properties. This is attributed to the formation of effective heat conduction pathways among SiC NWs as well as a strong interaction between the nanowires and epoxy matrix. In addition, the thermal properties of epoxy/SiC NWs composites were also improved. These results demonstrate that we developed a novel approach to enhance the thermal conductivity of the polymer composites which meet the requirement for the rapid development of the electronic devices.
“…This single-mode mechanical deformation at small load has been proven by a recent experiment 2 . A defect free region is necessary for engineering applications, for example, defect free CMP (the chemical mechanical polishing) and the ultraprecision grinding of silicon have been developed based on this principle 34 .…”
Section: Discussionmentioning
confidence: 99%
“…On scratching and grinding process, the α-Si on the topmost of the scratched surface and the damaged crystalline Si with high densities of dislocations underneath the α-Si feature the deformation region 30 – 33 , and an alternative phase transformation route is suggested: Si-I → α-Si → Si-III/Si-XII in α-Si, which is quite different from that in the case of nanoindentation (i.e., Si-I → Si-II → Si-III/Si-XII or α-Si). Recently, nanoscale solely amorphous layer, followed by pristine crystalline lattice, is obtained under ultraprecision grinding using the newly developed diamond wheel with ceria 34 .…”
Silicon has such versatile characteristics that the mechanical behavior and deformation mechanism under contact load are still unclear and hence are interesting and challenging issues. Based on combined study using molecular dynamics simulations and experiments of nanoindentation on Si(100), the versatile deformation modes, including high pressure phase transformation (HPPT), dislocation, median crack and surface crack, were found, and occurrence of multiple pop-in events in the load-indentation strain curves was reported. HPPTs are regard as the dominant deformation mode and even becomes the single deformation mode at a small indentation strain (0.107 in simulations), suggesting the presence of a defect-free region. Moreover, the one-to-one relationship between the pop-in events and the deformation modes is established. Three distinct mechanisms are identified to be responsible for the occurrence of multiple pop-in events in sequence. In the first mechanism, HPPTs from Si-I to Si-II and Si-I to bct5 induce the first pop-in event. The formation and extrusion of α-Si outside the indentation cavity are responsible for the subsequent pop-in event. And the major cracks on the surface induces the pop-in event at extreme high load. The observed dislocation burst and median crack beneath the transformation region produce no detectable pop-in events.
“…Moreover, traditional heat dissipating materials like copper and aluminium show CTE mismatch to silicon and insulating ceramics and cannot be used for direct device attachment without stress compensating interlayers [27,28]. Silicon carbide (SiC) is on account of its particular crystal structure, usually used in new fixed abrasive lapping slurry [29], development of novel ceramic bond diamond wheels for grinding soft brittle [30][31][32], hard brittle crystals [33], and truing of new resin bond diamond wheels [34]. Not only the hardness property but also the high intrinsic thermal conductivity of SiC possess.…”
Electronic packaging materials and thermal interface materials (TIMs) are widely used in thermal management. In this study, the epoxy composites with core-shell structure SiC@SiO 2 nanowires (SiC@SiO 2 NWs) as fillers could effectively enhance the thermal conductivity of epoxy composites. The unique structure of fillers results in a high thermal conductivity of epoxy composites, which is attributed to good interfacial compatibility epoxy matrix and bridging connections of SiC@SiO 2 NWs. From neat epoxy to 2.5 wt% loading of SiC@SiO 2 NWs, the thermal conductivity is significantly increased from 0.218 to 0.391 W m −1 K −1 , increased by 79.4%. In addition, the composite with 2.5 wt% filler possess lower coefficient of thermal expansion and better thermal stability than that of neat epoxy. All these outstanding properties imply that epoxy/SiC@SiO 2 NWs composites could be the ideal candidate for TIM. 2 Materials SiC NWs were produced by Changsha Sinet Advanced Materials Co., Ltd. China. Anhydrous ethanol was produced by Sinopharm Chemical Reagent Co., Ltd. Using as latent catalyst of neodymium (III) acetylacetonatetrihydrate (Nd(III)acac) was purchased from Aldrich Chemicals. Cycloaliphatic epoxy resin (6105, DOW Chemicals) along with hardener of methyl-hexahydrophthalic anhydride (Shanghai Liyi Science & Technology Development, China) is used in the present study. High-frequency induction heating furnace (XJH-15A) was produced by Chien Wah Induction Co., Ltd.
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