Common types of carbon fiber Hot Zone materials
Carbon fiber graphite felt is primarily divided into rayon-based graphite felt, polyacrylonitrile-based graphite felt (PAN-based graphite felt), and pitch-based graphite felt. Rayon-based graphite felt is produced through processes such as weaving, needling, impregnation and drying, low-temperature carbonization, and high-temperature graphitization; while PAN-based graphite felt is produced through processes such as weaving, needling, pre-oxidation, low-temperature carbonization, and high-temperature graphitization.
Graphite rigid felt is a material produced by adding carbon cloth, resin, reinforcing agents, and other auxiliary materials to a soft felt base, followed by bonding, curing and shaping, carbonization, graphitization, machining, and surface treatment processes.
Carbon/carbon composite materials are made from carbon fiber filaments, which are processed through weaving or open-mesh forming, needle-punching, shaping, multi-layer needle-punching, and secondary shaping to form a preform. The preform is then subjected to deposition, graphitization, machining, and surface treatment to produce the final material.
Combined Application of Carbon Fiber Materials in Hot Zone
Due to their low thermal conductivity, excellent thermal insulation properties, and resistance to ablation, carbon fiber graphite soft felt, hard felt, and carbon-carbon composite materials can all be used as hot zone materials in fields such as solar photovoltaics, semiconductors, and powder metallurgy. Typically, different materials are combined based on specific thermal field requirements to leverage their respective advantages. For example, in a single-crystal furnace for solar photovoltaic applications, carbon fiber flow guide soft felt, insulation cylinder soft felt, insulation cylinder hard felt cover, furnace bottom hard felt, carbon/carbon composite insulation cylinder, and crucible can be used. This ensures hot zone functionality while controlling production costs.
| Product Category | Application |
| Carbon Fiber Graphite Soft Felt | Flow Guide Soft Felt, Insulation Cylinder Soft Felt, Furnace Bottom Soft Felt |
| Graphite Hard Felt | Insulation cylinder hard felt cover felt, flow cylinder hard felt, furnace bottom hard felt, furnace bottom protective plate |
| Carbon-carbon composite materials | Insulation cylinder, flow cylinder, crucible, sheet material |
Comparison of the Advantages of the Three Major Hot Zone Materials
Carbon fiber graphite soft felt can be produced in large widths and rolls, meeting the demand for larger silicon wafers—as silicon furnace dimensions increase, hot zone insulation materials must also cover larger areas. Additionally, graphite soft felt can be produced with low or no phosphorus content, meeting the increasingly stringent requirements for low ash content in silicon wafers in the photovoltaic and semiconductor industries, particularly the trend toward P-type to N-type silicon wafers in solar applications.
Compared to soft felt, graphite hard felt has higher bulk density and strength, making it suitable for a wide range of applications. It can be used not only in single-crystal furnaces and multi-crystal furnaces in the photovoltaic and semiconductor industries but also in powder metallurgy industrial furnaces and vacuum sintering furnaces. On the other hand, the service life of hard composite felt is longer than that of soft felt. Generally, hard felt in photovoltaic thermal field single-crystal furnaces can be used for about one year.
Carbon/carbon composite materials have high specific modulus and stable performance, making them suitable for critical structural components in thermal fields, such as crucibles, flow guides, and insulation cylinders in single-crystal furnaces. Additionally, due to their high dimensional stability at high temperatures, carbon/carbon composite materials can be used as fasteners for various high-temperature equipment.