Simple Fabrication and Characterization of Discontinuous Carbon Fiber Reinforced Aluminum Matrix Composite for Lightweight Heat Sink Applications

The constant increase in power and heat flux densities encountered in electronic devices fuels a rising demand for lightweight heat sink materials with suitable thermal properties.In this study,discontinuous pitch-based carbon fiber reinforced aluminum matrix（Al-CF） composites with aluminum–silicon alloy（Al–Si） were fabricated through hot pressing.The small amount of Al–Si contributed to enhance the sintering process in order to achieve fully dense Al–CF composites.A thermal conductivity and CTE of 258 W/（m K） and 7.0 9 10-6/K in the in-plane direction of the carbon fibers were obtained for a（Al95 vol%＋ Al–Si5 vol%）-CF50 vol%composite.Carbon fiber provides the reducing of CTE while the conservation of thermal conductivity and weight of Al.The achieved CTEs satisfy the standard requirements for a heat sink material,which furthermore possess a specific thermal conductivity of 109 W cm3/（m K g）.This simple process allows the low-cost fabrication of Al–CF composite,which is applicable for a lightweight heat sink material.

Effect of CF and RPP on the Mechanical and Electrical Properties of Smart Aggregate

By using redispersible polymer powder（RPP） and carbon fiber（CF） to adjust the flexibility and electrical properties of the smart aggregate, a new kind of smart aggregate with Z type structure was proposed. The study shows that Z type aggregate is more sensitive to the feedback of external force than the prism aggregate in the same loading environment, and it indicates that Z type aggregate is more suitable for the research and application of concrete health monitoring. Although the incorporation of RPP would cause the compressive strength of the aggregates and the elastic modulus of hardened cement mortar to reduce slightly within the dosage of RPP by 2.25% because of the polymer film formed in the internal system, this would improve the deformability of the aggregates. In the early loading stage（in the first 60 seconds）, the intelligent concrete specimens implanted with Z type smart aggregate do not show higher sensitivity as expected, although the resistance change rate changes a little bit more, the overall of it is still in balance. Adding RPP could improve the flexibility of smart aggregates exactly, and it plays an active role in prolonging the life of the smart aggregates. By implanting Z type aggregates the damage and failure of the concrete structure could be predicted accurately in this study. The results of this paper will help to promote further research and application of intelligent concrete.

Preparation and Performance of Corona-proof Conductive Composite Coatings

Because of its merits,acrylic resin was chosen to improve the mechanical,conductive and hydrophobic properties.Carbon fiber powders (CF),carbon nanotubes (MWCNT),and nano-TiO_(2) were incorporated into the acrylic resin to prepare the corona-proof conductive composite coatings.The incorporation of CF and MWCNT may improve the conductivity and mechanical strength of the coatings.However,the addition of nano-TiO_(2) may increase the hydrophobicity of the coatings.Thus,the effects of different additives on the mechanical properties,conductivity,hydrophobicity and heat resistance of the conductive film were studied.The experimental results show that the incorporation of carbon fiber powders and multi walled carbon nanotubes can significantly improve both the conductivity and mechanical properties of the conductive coatings,and the addition of nano titanium dioxide can improve the hydrophobicity of the conductive film.