Low-temperature plasma treatment is a non condensed state system produced by ionizing gas under specific conditions, which can be understood as an excited gas. It contains stripped electrons, ions with opposite charges, and excited atoms, and still exhibits neutrality as a whole. There are complex elastic or inelastic collisions (ionization) between various particles in plasma. High temperature and low temperature are one of the main distinguishing features of plasma, which means that it has dual temperature high temperature (thermal equilibrium). The temperature of various particles inside the plasma reaches a very high temperature range (106-108K), and controlled nuclear fusion is one of the ways it is generated. The difference between low-temperature (non-equilibrium) plasma and other low-temperature particles (300-500K) is that the electron temperature is much higher, reaching 104K, so its ionization degree is usually lower.

The generation of low-temperature plasma treatment depends on the external driving force (electric field). The energy applied by the external environment is transferred to electrons or ions, which break down molecules into atoms and free radicals through collisions. Some ions are heavy and therefore driven at lower speeds, resulting in less intense collisions, while electrons collide and contact at high speeds, leading to the system being in a non-equilibrium state and forming low-temperature plasmas. The energy provided by low-temperature plasma allows the system to easily overcome reaction limitations, enabling many chemical reactions that typically cannot occur or require extreme conditions to occur in the plasma.

The effect of low-temperature plasma treatment on materials

Plasma surface modification material technology is one of the earliest techniques for preparing materials using plasma. It is a plasma treatment of the shallowest surface of the material. Due to the higher energy of plasma compared to chemical bonds (20ev>10ev), it can cause etching, cross-linking, chemical modification, and other effects on the surface of the material. Etching is similar to leaving scratches on the surface of a material with a blade, making the material surface rough and changing its physical and chemical properties; Crosslinking refers to the possibility of adjacent polymers being connected to each other due to the presence of free radicals; Chemical modification refers to the hydrogen dissociation or formation of double bonds on the micro surface of materials, or the formation of new functional groups through the reaction of plasma gas on the surface.

Advantages of low-temperature plasma treatment materialsPlasma has the advantages of high efficiency, convenience, cleanliness, and no pollution, and is widely used in modified materials. There are many advantages to low-temperature plasma treatment of materials, mainly including the following five points: (1) Low temperature plasma can maintain the modification process at a lower temperature during the material treatment process, avoiding damage to the material caused by excessive temperature; (2) Plasma acts on the surface and near surface of the substrate, avoiding changes to the overall structure of the processed material and maintaining the properties of the substrate as a whole; (3) A large variety of active particles, such as ions, electrons, excited molecules, atoms, and free radicals, can act on the surface of materials and undergo surface reactions. Previous reports have revealed that reactive gases such as O2, CO/CO2, NH3/N2 can introduce - OH, - COOH, - NH2 groups on the surface of the substrate; (4) Different active or inert gases can be used as needed, and even combinations of various gases can be used for plasma reactions to provide abundant active substances. (5) Plasma is environmentally friendly and produces almost no toxic substances. Therefore, the use of plasma technology can easily achieve material modification, which is much more convenient than traditional chemical modification methods.