Effects of Heat Treatment Atmosphere and Temperature on the Properties of Carbon Fibers

Abstract

In this study, carbon fibers were heat-treated in a nitrogen and oxygen atmosphere according to temperature to elucidate the mechanism of chemical state changes and oxygen functional group changes on the carbon fiber surface by analyzing the mechanical and chemical properties of carbon fibers. Carbon fibers before and after heat treatment were analyzed using FE-SEM (Field Emission Scanning), UTM (Universal Tensile Testers), XPS (X-ray Photoelectron Spectroscopy), and surface-free energy. In the nitrogen atmosphere, which is an inert gas, the tensile strength was equivalent to that of the virgin up to 500 °C but decreased to 71% with respect to the virgin at 1000 °C. Furthermore, as the temperature increased from room temperature to 1000 °C, the oxygen functional group and the polar free energy gradually decreased compared with the virgin. On the other hand, in the oxygen atmosphere, which is an active gas, the tensile properties were not significantly different from those of the virgin up to 300 °C but gradually decreased at 500 °C. Above 600 °C, the carbon fibers deteriorated, and measurement was impossible. The oxygen functional group decreased at 300 °C, but above 300 °C, among the oxygen functional groups, the hydroxyl group and the carbonyl group increased. Furthermore, the lactone group formed and rapidly increased compared with the virgin, and the polar free energy increased as the temperature increased.

Oxidation Behavior of Carbon Fibers in Ceramizable Phenolic Resin Matrix Composites at Elevated Temperatures

“…However, it is easily oxidized under a high-temperature aerobic environment, which greatly weakens its comprehensive mechanical properties, and the stability of the composites declines sharply [ 23 , 24 ]. Gyungha Kim et al [ 25 ] explored the mechanical properties of carbon fibers after heat treatment in nitrogen and oxygen atmospheres. They found that the tensile strength at 500 °C was equivalent to that of the virgin carbon fibers in the nitrogen atmosphere, decreasing to 71% at 1000 °C.…”

“…Carbon fiber can still maintain good mechanical properties in an inert atmosphere above 2000 • C. However, it is easily oxidized under a high-temperature aerobic environment, which greatly weakens its comprehensive mechanical properties, and the stability of the composites declines sharply [23,24]. Gyungha Kim et al [25] explored the mechanical properties of carbon fibers after heat treatment in nitrogen and oxygen atmospheres. They found that the tensile strength at 500 • C was equivalent to that of the virgin carbon fibers in the nitrogen atmosphere, decreasing to 71% at 1000 • C. In the oxygen atmosphere, the tensile properties gradually decreased at 500 • C and the carbon fibers deteriorated above 600 • C, at which point the tensile properties were unable to be measured.…”

Effect of the Chemical Properties of Silane Coupling Agents on Interfacial Bonding Strength with Thermoplastics in the Resizing of Recycled Carbon Fibers

“…The optimum value of 0.51 at 10 s was about twice that of the APS. Other studies have reported that the surface activity of carbon fibers is enhanced when the O/C is higher than 0.26 [11]. As shown in Table . 2, the O/C of commercial carbon fibers is 0.28; thus, the recycled carbon fibers in this study are considered to have sufficiently introduced oxygen functional groups.…”

“…Carbon fibers are lightweight materials with low density, high specific strength, heat resistance, and excellent thermal and electrical conductivity, and their applications are expected to expand not only in the aerospace industry but also in all industries in the future [1][2][3][4][5][6][7][8][9]. However, due to the high price of carbon fiber and the expensive manufacturing process, it is only used for expensive parts, such as aerospace, shipbuilding, and sporting goods, and it is difficult to expand its application to fields such as general commercial vehicles due to its high price [10,11]. In addition, carbon composites currently in use are made of thermosetting resins, which are difficult to recycle, and most are disposed of by landfill and incineration, causing environmental pollution [12].…”

Investigating the Effects of Nitric Acid Treatments on the Properties of Recycled Carbon Fiber

“…In general, surface treatment includes wetting methods (liquid oxidation) such as sulfuric acid and nitric acid [ 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 ], dry methods (dry gaseous oxidation) [ 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 ] such as high-temperature treatment in an atmosphere of oxidizing gas or inert gas, electric oxidation methods [ 3 , 30 , 31 , 32 ], the plasma method [ 33 , 34 , 35 , 36 , 37 , 38 , 39 ] of surface treatment using ionized gas, and exposure to strong energy such as ozone and ultraviolet rays (energetic ions oxidation) [ 40 , 41 , 42 ].…”