1. Standard environmental conditions: Temperature 20℃, relative humidity 65%, atmospheric pressure 101325 Pa.
2. Standard state of the gas: Temperature 0℃, pressure 101325 Pa.
3. Pressure (intensity): The rate of change of momentum of gas molecules passing through an imaginary plane along the positive normal direction of that plane, divided by the area of that plane; or the normal component of the force exerted by gas molecules on the surface of its container, divided by the surface area.
4. Pascal (symbol: Pa): The SI unit of pressure, 1 Pa = 1 N/m².
5. Partial pressure: The pressure of a specific component in a gas mixture.
6. Total Pressure: The sum of the pressures of all components in a gas mixture.
7. Vacuum: A gaseous state below one atmosphere of pressure within a specified space.
8. Degree of Vacuum: The rarefaction of a gas under vacuum conditions, usually expressed as a pressure value.
9. Gas: A substance that is not bound by intermolecular forces and can freely occupy any space. (Note: In vacuum technology, the term "gas" is not strictly applied to non-condensable gases and vapors.)
10. Non-condensable Gas: A gas above its critical temperature, i.e., a gas that cannot be liquefied simply by increasing pressure.
11. Steam: A gas below its critical temperature, meaning a gas that can be liquefied simply by increasing its pressure.
12. Saturated vapor pressure: The vapor pressure of a substance at a given temperature when its vapor and condensed phase are in phase equilibrium.
13. Degree of saturation: The ratio of vapor pressure to its saturated vapor pressure.
14. Saturated steam: Steam at a given temperature whose pressure equals its saturated vapor pressure.
15. Unsaturated steam: Steam at a given temperature whose pressure is less than its saturated vapor pressure.
16. Molecular Number Density (unit: m⁻³): The number of molecules in the volume surrounding a point in a gas at a given instant, divided by the product.
17. Mean Free Path: The distance a molecule travels in two consecutive collisions with other gas molecules is called the free path. The average of a considerable number of different free paths is called the mean free path.
18. Collision Rate: The average number of collisions a molecule (or other defined particle) experiences relative to other gas molecules (or other defined particles) within a given time interval, divided by that time. This average number of collisions should be obtained with a sufficiently large number of molecules and a sufficiently long time interval.
19. Volumetric Collision Rate: The average number of collisions between gas molecules within a spatial range around a specified point within a given time interval, divided by that time and the volume of that spatial range. The time interval and volume should not be too small.
20. Gas Quantity: The product of the volume occupied by an ideal gas in equilibrium and its pressure. This value must specify the gas temperature or be converted to a value at 20°C. (Note: The amount of gas refers to 2/3 of the intrinsic energy (or potential energy) of the gas in the volume occupied by that amount of gas.)
21. Gas diffusion: The movement of a gas in another medium due to a concentration gradient. The medium can be another gas (in which case diffusion is called interdiffusion) or a condensable substance.
22. Diffusion system: The ratio of the absolute value of the mass flow rate per unit area to the normal concentration gradient per unit area.
23. Viscous flow: A flow state where the mean free path of gas molecules is much smaller than the minimum cross-sectional size of the duct. Therefore, the flow depends on the viscosity of the gas; viscous flow can be laminar or laminar.
24. Viscosity coefficient: The ratio of the tangential force per unit area in the direction of the gas velocity gradient to the velocity gradient.
25. Poisson's flow: Laminar-viscosity flow through a long duct with a circular cross-section.
26. Intermediate flow: Gas flow through a conduit in a state between laminar and molecular flow.
27. Molecular flow: Flow where the mean free path of gas molecules is much larger than the maximum cross-sectional area of the conduit.
28. Knuth number: The ratio of the mean free path of gas molecules to the diameter of the conduit.
29. Molecular spillway: Flow when gas flows through a thin-walled orifice, where the mean free path of its molecules is much larger than the orifice size.
30. Escape: Gas flow through a porous material caused by a pressure difference.
31. Thermal Escape: In molecular flow, gas flow occurs between two connected containers due to temperature differences. When gas transport reaches equilibrium, a pressure gradient forms between the two containers.
32. Molecular Flow Rate: The difference between the number of molecules passing through a surface in a given direction and the number passing through the surface in the opposite direction within a given time interval, divided by the time.
33. Molecular Flow Rate Density: Molecular flow rate divided by the surface area.
34. Mass Flow Rate: The mass of gas passing through a cross-section within a given time interval, divided by the time.
35. Flow Rate: The amount of gas passing through a cross-section within a given time interval, divided by the time.
36. Volumetric Flow Rate: The volume of gas passing through a cross-section under given temperature, pressure, and time interval conditions, divided by that time.
37. The number of moles of gas passing through a given cross-section within a given time interval, divided by that time.
38. Maxwell Velocity Distribution: A velocity distribution determined by the Maxwell-Boltzmann velocity distribution function. That is, the velocity distribution of gas molecules in equilibrium at a given temperature and when the distance to the container wall is greater than the mean free path of the molecules.
39. Transport Probability: The probability that molecules that randomly enter the inlet of a conduit will exit through the outlet.
40. Molecular Conductivity: The molecular conductivity of gas flowing through two specified cross-sections or orifices of a pipe, expressed as the ratio of its molecular flow rate to the average molecular number density difference between the two cross-sections or orifices of the pipe.
41. Conductivity: Under isothermal conditions, the ratio of the flow rate of a gas through a conduit or orifice to the average pressure difference across two specified cross sections of the conduit or orifice.
42. Intrinsic Conductivity: Under conditions where the Maxwell velocity distribution dominates in a container, the conductivity of a conduit (or orifice) connecting two such containers. Under molecular flow conditions, it is equal to the product of the inlet conductivity and the transport probability.
43. Flow Resistance: The reciprocal of conductivity.
44. Adsorption: The capture of gas or vapor (adsorbate) by a solid or liquid (adsorbent).
45. Surface Adsorption: The adsorption of gas or vapor (adsorbate) onto the surface of a solid or liquid (adsorbent).
46. Physicoadsorption: Adsorption due to physical processes.
47. Chemiadsorption: Adsorption due to chemical processes.
48. Absorption: The diffusion of gas or vapor (adsorbate) into the interior of a solid or liquid (adsorbent).
49. Fit coefficient: The ratio of the average energy actually exchanged between a particle incident on a surface and the surface to the average energy that the particle should exchange to reach complete thermal equilibrium on the surface.
50. Incident rate: The number of molecules incident on a surface within a given time interval, divided by that time and the surface area.50. Incident rate: The number of molecules incident on a surface within a given time interval, divided by that time and the surface area.
51. Condensation Rate: The number of molecules (or mass of matter) condensed on a given surface area within a given time interval, divided by that time and that surface area.
52. Adhesion Rate: The number of molecules adsorbed on a surface within a given time interval, divided by that time and that surface area.
53. Adhesion Probability: The ratio of adhesion rate to incident rate.
54. Residence Time: The average time a molecule is confined in an adsorbed state on a surface.
55. Migration: The movement of molecules on a surface.
56. Desorption: The release of gas or vapor adsorbed by a material. Release can be natural or accelerated by physical methods.
57. Degassing: The artificial desorption of gas from a material.
58. Degassing: The natural desorption of gas from a material.
59. Desorption, degassing, or gas removal rate: The flow rate (or molecular flow rate) of gas desorbed (or degassed) from the material within a given time interval, divided by that time and that surface area.
60. Evaporation rate: The number of molecules (or mass of matter) evaporated from the surface within a given time interval, divided by that time and that surface area.
61. Permeation: The phenomenon of gas passing through a solid barrier layer. This phenomenon includes gas diffusion through a solid, and may also include other surface phenomena.
62. Permeability: Under steady flow conditions, the flow rate of gas through a barrier layer (such as a vessel wall) divided by a function of the pressures on both sides of the barrier layer. The form of this function depends on the physical processes involved in the actual permeation.
63. Permeability Coefficient: The product of permeability and barrier layer thickness, divided by the permeable surface area.
The above is a summary of common vacuum coating equipment industry terms. We hope this information is helpful, as mastering these terms is essential for entering the vacuum industry.
