| 其他摘要 | Study on the Influence of Carbon Fiber Coatings on Carbon Fiber Reinforce Magnesium-Based Composites Interface
Huang Yuanfei (Material Processing and Engineering)
Supervised by Pro. Liu Yue
Carbon fiber reinforced magnesium (Cf/Mg) composites have good application in the area of aviation, aerospace, and automobile industries, as well as sport equipments, due to their extraordinary low density and coefficient of thermal expansion (CTE), high tensile strength, mould and damping capacity.
In this paper Cf/Mg composites were fabricated by vacuum pressing method with three kinds of carbon fibers without coating and coated with Ni and SiO2, respectively. Ni and SiO2 coatings were fabricated on the surface of carbon fibers by electroless and Sol-Gel plating, respectively.
Organic adhesives on the surface of carbon fiber were cleaned up in vacuum furnace at 400°C for 30 min. The uniform and compact Ni coating 0.5-0.8μm in thickness was fabricated on carbon fiber surface in a plating solution with a PH value of 4.5-4.9, a temperature of 85 °C, and a coating time of 10min.
Uniform SiO2 coating was fabricated by Sol-Gel method with a sol solution viscosity of 1.8mPa•s, a pulling rate of 1.6mm/s. The heating rate was 1°C/min and 2°C/min, respectively, for the sintering temperature of 30-210°C and 210-500°C, and the sintering time was 30min at both 210°C and 500°C.
Cf/Mg composites were fabricated by vacuum pressing method with three kinds of carbon fibers without coating and coated with Ni and SiO2, respectively. The preparative procedure of Cf/Mg composites was: vacuum pumping and heating the furnace, filling argon of 0.1 MPa press into the furnace when the temperature was heated to 670°C and maintained for 20min. Mg was infiltrated into carbon fibers after the temperature was maintained at 710°C for 20min. Cf/Mg composites were cooled down in the furnace after infiltration was completely finished. Both Ni and SiO2 coatings on carbon fiber surface enhanced the wettability between carbon fiber and Mg matrix, which made Mg completely infiltrate into the fibers gaps, and the interface be compact, carbon fiber distributed uniformly in Cf/Mg composites. The staggered arrangement and asymmetrical distribution of carbon fibers lowered the mechanical properties of Cf/Mg composites. There were some cracks in the Cf/Mg composite if it cooled very fast due to different CTEs between carbon fiber and Mg.
The interface was very clean without any chemical reaction in non-coated carbon fiber reinforced Mg matrix composite. Ni coating on the surface of carbon fiber reacted with Mg to form Mg2Ni, which formed an eutectic structure with Mg. SiO2 coating on the surface of carbon fiber reacted with Mg to form a small amount of MgO. The tensile strength of the Mg matrix composites was 325MPa, 240MPa, and 190MPa, respectively, for SiO2-coating, non-coating, and Ni-coating, and the elongation 2.2%, 1.9%, and 1.3% for three composites. In the fracture process of Cf/Mg composites, non-coated fibers pulled out from the matrix with a large length, and the pull-out length of the SiO2-coated carbon fibers was smaller. By comparison, Ni-coated carbon fibers did not pull out and the composite exhibited a brittle fracture.
Kew words: Carbon Fiber; Magnesium; Coatings; Composites; Interface |
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