Commercially, the stabilization process uses a variety of equipment and techniques. In some processes, the fibers are drawn through a series of heated chambers. In others, the fibers pass over hot rollers and through beds of loose materials held in suspension by a flow of hot air.
Some processes use heated air mixed with certain gases that chemically accelerate the stabilization. The lack of oxygen prevents the fibers from burning in the very high temperatures. The gas pressure inside the furnace is kept higher than the outside air pressure and the points where the fibers enter and exit the furnace are sealed to keep oxygen from entering. As the fibers are heated, they begin to lose their non-carbon atoms, plus a few carbon atoms, in the form of various gases including water vapor, ammonia, carbon monoxide, carbon dioxide, hydrogen, nitrogen, and others.
As the non-carbon atoms are expelled, the remaining carbon atoms form tightly bonded carbon crystals that are aligned more or less parallel to the long axis of the fiber. In some processes, two furnaces operating at two different temperatures are used to better control the rate of heating during carbonization. After carbonizing, the fibers have a surface that does not bond well with the epoxies and other materials used in composite materials. To give the fibers better bonding properties, their surface is slightly oxidized.
The addition of oxygen atoms to the surface provides better chemical bonding properties and also etches and roughens the surface for better mechanical bonding properties.
Oxidation can be achieved by immersing the fibers in various gases such as air, carbon dioxide, or ozone; or in various liquids such as sodium hypochlorite or nitric acid.
The fibers can also be coated electrolytically by making the fibers the positive terminal in a bath filled with various electrically conductive materials. The surface treatment process must be carefully controlled to avoid forming tiny surface defects, such as pits, which could cause fiber failure.
Carbon fiber is made from organic polymers, which consist of long strings of molecules held together by carbon atoms. Gases, liquids, and other materials used in the manufacturing process create specific effects, qualities, and grades of carbon fiber. Carbon fiber manufacturers use proprietary formulas and combinations of raw materials for the materials they produce and in general, they treat these specific formulations as trade secrets.
The highest grade carbon fiber with the most efficient modulus a constant or coefficient used to expresses a numerical degree to which a substance possesses a particular property, such as elasticity properties are used in demanding applications such as aerospace.
Creating carbon fiber involves both chemical and mechanical processes. Raw materials, known as precursors, are drawn into long strands and then heated to high temperatures in an anaerobic oxygen-free environment. Rather than burning, the extreme heat causes the fiber atoms to vibrate so violently that almost all non-carbon atoms are expelled. After the carbonization process is complete, the remaining fiber is made up of long, tightly interlocked carbon atom chains with few or no non-carbon atoms remaining.
These fibers are subsequently woven into fabric or combined with other materials that are then filament wound or molded into the desired shapes and sizes. The following five segments are typical in the PAN process for the manufacture of carbon fiber:.
Carbon nanotubes are manufactured via a different process than standard carbon fibers. Estimated to be 20 times stronger than their precursors, nanotubes are forged in furnaces that employ lasers to vaporize carbon particles.
The manufacture of carbon fibers carries a number of challenges, including:. As carbon fiber technology continues to evolve, the possibilities for carbon fiber will only diversify and increase. At Massachusetts Institute of Technology, several studies focusing on carbon fiber are already showing a great deal of promise for creating new manufacturing technology and design to meet emerging industry demand.
MIT Associate Professor of Mechanical Engineering John Hart, a nanotube pioneer, has been working with his students to transform the technology for manufacturing, including looking at new materials to be used in conjunction with commercial-grade 3D printers.
The results were prototype machines that printed molten glass, soft-serve ice cream—and carbon fiber composites. Additionally, Hart worked with MIT Associate Professor of Chemistry Mircea Dinca on a recently concluded three-year collaboration with Automobili Lamborghini to investigate the possibilities of new carbon fiber and composite materials that might one day not only "enable the complete body of the car to be used as a battery system," but lead to "lighter, stronger bodies, more-efficient catalytic converters, thinner paint, and improved power-train heat transfer [overall].
Actively scan device characteristics for identification. In chemistry terms, a precursor refers to any chemical that transforms into another substance. Manufacturers draw the carbon precursor into long fibers, then heat these to an incredibly high temperature. During this time, the fibers must not come into contact with oxygen.
This lack of oxygen prevents the material from burning. Instead, the fiber vibrates at a rapid speed until it removes most of the non-carbon atoms. Before the fibers carbonize, carbon fiber makers must chemically alter the fiber to a more thermally stable ladder bonding. Manufacturers do this by heating the fibers to about degrees Fahrenheit for approximately minutes. When the fibers reach this temperature, they collect oxygen molecules and rearrange their atomic pattern.
Carbon fiber manufacturing companies accomplish this through several differing means. Regardless, each process produces similar results. Once the fibers have stabilized, manufacturers heat them to a temperature ranging from 1, to more than 5, for several minutes.
They heat the carbon in a furnace filled with a non-oxygenic gas mixture. This mixture preserves the fibers from catching fire. This process further expels non-carbon atoms from the fibers, along with a few carbon atoms.
0コメント