Research Note: The Acheson Process & Silicon Carbide (SiC)
The Acheson process, patented by Edward Goodrich Acheson in 1896, is the primary method for synthesizing silicon carbide (SiC) and graphite. It involves heating a mixture of silicon dioxide (usually as silica or quartz sand) and carbon (as powdered coke) to temperatures between 1700-2500°C in an electric furnace. This high-temperature carbothermic reaction produces layers of silicon carbide, primarily in alpha and beta phases, around a graphite core. The process is highly endothermic and results in the emission of carbon monoxide. Originally developed in an attempt to synthesize diamonds, Acheson instead created blue crystals of silicon carbide, which he named carborundum. This discovery led to the development of an efficient electric furnace design that remains the basis for most silicon carbide manufacturing today. The Acheson process allowed for large-scale commercial production of silicon carbide, with the first plant built in Niagara Falls, New York, taking advantage of cheap hydroelectric power for the energy-intensive process.
The Acheson process is important for several key reasons
The Acheson process for producing silicon carbide (SiC) and graphite utilizes specialized electric furnaces. Here's a detailed description of these furnaces based on the information provided and my knowledge of the process:
Basic Design: The Acheson furnace is essentially a large, resistive heating furnace. It consists of an elongated structure, typically rectangular or oval in cross-section.
Core Element: At the center of the furnace is a graphite rod or core, which serves as both a heating element and a nucleation site for SiC crystal growth.
Reaction Mixture: Surrounding the graphite core is a mixture of silica (SiO2) in the form of sand or quartz, and carbon, usually as petroleum coke. This mixture may also include sawdust (in older designs) and other additives to control purity and reaction conditions.
Electrical Connections: Large carbon electrodes are connected to the ends of the graphite core. These electrodes carry the electric current that heats the furnace.
Insulation: The reaction mixture itself acts as thermal insulation. The outer layers of the mixture remain relatively cool compared to the core.
Temperature Gradient: As the core heats up, a temperature gradient forms in the mixture. The highest temperatures (1700-2500°C) are reached near the core, where SiC formation occurs.
Size and Capacity: Industrial Acheson furnaces can be quite large. Some designs mention dimensions of about 9 meters in length, 35 cm in width, and 45 cm in depth.
Power Supply: The furnaces operate on high electrical power. A typical setup might start at 200V and 300A (60 kW), with current increasing as the resistance drops during heating.
Operation Time: A full cycle in an Acheson furnace can take several days. The heating phase might last about 20 hours, followed by a cool-down period that can take weeks.
Variations: There are variations of the Acheson furnace design, such as the Castner lengthwise graphitization furnace. This design places the items to be graphitized end-to-end between the electrodes, with the surrounding coke acting primarily as insulation.
Emission Control: Modern Acheson furnaces often incorporate emission control systems to manage the carbon monoxide produced during the reaction.
Batch Operation: These furnaces typically operate in batch mode, with each cycle producing a large amount of material that is then harvested and processed further.
Black Silicon Carbide (SiC) Vendors
Saint-Gobain
Washington Mills
Ningxia Jinjing
Lanzhou Heqiao
Ningxia Tianjing
Tianzhu Yutong
Foshan RISING Technology
Futong Industry
Cumi Murugappa
Elsid
Erdos
Ningxia Shenzhou
Zaporozhsky Abrasivny Combinat
Yakushima Denko
Elmet
Snam Abrasives
Navarro
ESK-SIC
ESD-SIC
Ningxia Jiyuan
Green Silicon Carbide (SiC) Vendors
Cree (Wolfspeed)
II-VI Advanced Materials
Rohm
Infineon
STMicroelectronics
ON Semiconductor
Fuji Electric
Mitsubishi Electric
Hitachi Power Semiconductor Device
GeneSiC Semiconductor
Ascatron
Norstel
SICC
TankeBlue
SiCrystal
GTAT Technologies
Dow
Ningbo Huitai New Materials Technology
Hebei Synlight Crystal
SiC Substrate and Wafer Vendors
Cree (Wolfspeed)
II-VI Advanced Materials
SiCrystal
SK Siltron
GTAT Technologies
Norstel
SICC
TankeBlue
Xiamen Powerway Advanced Material
Showa Denko
TISICS