Coulomb explosion
Encyclopedia
A Coulomb explosion is a mechanism for coupling electronic excitation energy from intense electromagnetic fields into atomic motion. The atomic motion can break the bonds that hold solids together. When done with a narrow laser beam, a small amount of solid explodes into a plasma
of charged atomic particles.
With their low mass, outer valence electrons responsible for chemical bond
ing are easily stripped from atoms, leaving them positively charged. Given a mutually repulsive state between atoms whose chemical bonds are broken, the material explodes into a small plasma cloud of energetic ions with higher velocities than seen in thermal emission.
A Coulomb explosion is one particular mechanism that permits laser-based machining.
Coulomb explosions for industrial machining are made with brief (picosecond or high femtoseconds) laser pulses. The enormous beam intensities required (10 to 400
thresholds, depending on material) are only practical to generate, shape and deliver for very brief instants of time.
A Coulomb explosion is a "cold" alternative to the dominant laser etching technique of thermal ablation
, which depends on local heating, melting, and vaporization of molecules and atoms using less-intense beams. Pulse brevity down only to the nanosecond regime is sufficient to localize thermal ablation – before the heat is conducted far, the energy input (pulse) has ended. Nevertheless, thermally ablated materials may seal pores important in catalysis or battery operation, and recrystallize or even burn the substrate, thus changing the physical and chemical properties at the etch site. In contrast, even light foams remain unsealed after ablation by Coulomb explosion.
Coulomb explosion etching can be used in any material to bore holes, remove surface layers, and texture and microstructure surfaces; e.g., to control ink loading in printing presses.
Plasma (physics)
In physics and chemistry, plasma is a state of matter similar to gas in which a certain portion of the particles are ionized. Heating a gas may ionize its molecules or atoms , thus turning it into a plasma, which contains charged particles: positive ions and negative electrons or ions...
of charged atomic particles.
With their low mass, outer valence electrons responsible for chemical bond
Chemical bond
A chemical bond is an attraction between atoms that allows the formation of chemical substances that contain two or more atoms. The bond is caused by the electromagnetic force attraction between opposite charges, either between electrons and nuclei, or as the result of a dipole attraction...
ing are easily stripped from atoms, leaving them positively charged. Given a mutually repulsive state between atoms whose chemical bonds are broken, the material explodes into a small plasma cloud of energetic ions with higher velocities than seen in thermal emission.
A Coulomb explosion is one particular mechanism that permits laser-based machining.
Coulomb explosions for industrial machining are made with brief (picosecond or high femtoseconds) laser pulses. The enormous beam intensities required (10 to 400
thresholds, depending on material) are only practical to generate, shape and deliver for very brief instants of time.A Coulomb explosion is a "cold" alternative to the dominant laser etching technique of thermal ablation
Ablation
Ablation is removal of material from the surface of an object by vaporization, chipping, or other erosive processes. This occurs in spaceflight during ascent and atmospheric reentry, glaciology, medicine, and passive fire protection.-Spaceflight:...
, which depends on local heating, melting, and vaporization of molecules and atoms using less-intense beams. Pulse brevity down only to the nanosecond regime is sufficient to localize thermal ablation – before the heat is conducted far, the energy input (pulse) has ended. Nevertheless, thermally ablated materials may seal pores important in catalysis or battery operation, and recrystallize or even burn the substrate, thus changing the physical and chemical properties at the etch site. In contrast, even light foams remain unsealed after ablation by Coulomb explosion.
Coulomb explosion etching can be used in any material to bore holes, remove surface layers, and texture and microstructure surfaces; e.g., to control ink loading in printing presses.