Rapid Densification of Carbon/Carbon Composites Plate by Pressure‐Gradient Chemical Vapor Infiltration

Abstract

Carbon/carbon (C/C) composites plate is prepared in the temperature range 1 223-1 373 K by improved pressure-gradient chemical vapor infiltration (CVI). The bulk densities and pore distributions of C/C composites after different infiltration period are measured and the densification kinetics is investigated. The results show that C/C composites plate with 300 Â 300 Â 15 mm is able to be densified to 1.52 g cm À3 within 60 h by pressure-gradient CVI. The porosity of pores with a size larger than 60 mm reduces markedly and the large pores are able to be filled more effectively by pressure-gradient CVI. The densification kinetics depends on the temperature and competition between reaction and convection mass transport. The activation energy is about 366 kJ mol -1 at 1 223-1 313 K and 43.2 kJ mol À1 above 1 313 K.

Carbon Nanotube Reinforced Strong Carbon Matrix Composites

“…Under high temperatures (600–1000 °C), the gaseous carbon source is pyrolyzed and converted into the pyrolytic carbon (PyC) that is deposited on the surface of the CNT preform as a coating. To achieve a better infiltration into the inside and obtain a continuous carbon matrix phase throughout the CNT preform, some critical processing parameters are to be adjusted and changed accordingly, including (1) the deposition temperature and time, ,,, (2) the flow rate of gaseous carbon sources, , and (3) the deposition pressure within the furnace . A typical SEM image in Figure b displays the surface of an aligned CNT/C composite film after an 18 h CVI process at 700 °C, which was sufficiently covered with the PyC .…”

“…To achieve a better infiltration into the inside and obtain a continuous carbon matrix phase throughout the CNT preform, some critical processing parameters are to be adjusted and changed accordingly, including (1) the deposition temperature and time, 48,49,51,101 (2) the flow rate of gaseous carbon sources, 102,103 and (3) the deposition pressure within the furnace. 104 A typical SEM image in Figure 2b displays the surface of an aligned CNT/C composite film after an 18 h CVI process at 700 °C, which was sufficiently covered with the PyC. 51 Generally, as the PyC grows, the thickness of the PyC coating increases.…”

Improving the Bonding Strength of Nb–C/C Composite Brazed Structures by Preoxidation

“…[1] Carbon-carbon (C/C), as a typical carbon fiber-reinforced composite, has great application potential in the thermal protection of a hypersonic vehicle due to its advantages of low density, high thermal conductivity, low coefficient of thermal expansion (CTE), and great ablation resistance. [2][3][4] C/C composite components with a large size or a complex shape are difficult and expensive to manufacture based on the existing process conditions. Therefore, C/C is usually combined with metals that possess great processability in practical engineering applications.…”

“…Critical hot‐end components, such as the nose cone of a hypersonic vehicle and the combustion chamber of a scramjet engine, typically withstand extremely high temperatures greater than 1800 °C during service . Carbon–carbon (C/C), as a typical carbon fiber‐reinforced composite, has great application potential in the thermal protection of a hypersonic vehicle due to its advantages of low density, high thermal conductivity, low coefficient of thermal expansion (CTE), and great ablation resistance . C/C composite components with a large size or a complex shape are difficult and expensive to manufacture based on the existing process conditions.…”