吸气剂的分类
①蒸散型吸气剂,也称为扩散型或闪烧型：
需要对吸气金属加热后蒸散出来形成吸气薄膜。以钡、锶、镁、钙为主体材料，典型蒸散型吸气剂常用的有钡铝镍吸气剂和掺氮吸气剂。钡铝镍吸气剂广泛用于各类功率发射管、振荡管、摄像管、显像管、太阳能集热管等器件中。一些显像管中使用的是渗氮的钡铝吸气剂，它在蒸散放热反应中放出大量的氮气，在大量钡蒸散时由于与氮分子的碰撞，使吸气剂钡膜不致附着在屏面或荫罩上面而是集聚在管颈周围，不但吸气性能好，还提高了屏的亮度。
②非蒸散型吸气剂：
不需要把吸气金属蒸散出来，通过对吸气金属表面激活使其具有吸气能力而是。目前常以锆为主体。是体积型的吸气剂（涂层型），它分为单质体积型、合金体积型、大比表面积型三种。它们适于应用在不能使用膜吸气的场合。例如：器件体积很小，无合适的蒸散沉膜表面，怕漏电和怕引入寄生电容的器件以及工作温度高的器件等均不能用蒸散型吸气剂。一般把它制成片状或带状,广泛用于功率管、磁控管、真空继电器、气体激光器、吸气泵、真空保温容器、X光管、图象转换器、摄像管、磁控管、静电悬浮陀螺仪、心脏起搏器等装置中。典型非蒸散型吸气剂常用的有：锆铝16、锆钒铁和锆石墨等。
③复合型吸气剂：由蒸散型与非蒸散型吸气剂混合在一起的。如释放汞的吸气剂，它既能释放出汞金属，又能吸气的，这种吸气剂就称为复合型吸气剂。典型复合型吸气剂还有碱金属释放剂（碱源）。
吸气剂的吸气机理
蒸散型吸气剂吸气过程有三个主要作用因素：蒸散吸气、表面吸附和内部扩散,三者之间的关系：首先是蒸散吸气，表面吸附孕育着扩散因素，内部扩散必须以表面吸附为前提。非散型吸气剂的吸所过程：表面吸附，内部扩散。
①蒸散吸气：
在受热蒸散时，飞溅出来的钡原子与管内空间的气体分子相碰撞，在碰撞过程中有的钡原子仅仅改变其蒸散方向，有的则与气体分子起化学作用，产生相应的化合物，并且沉积在管壳内表面上。结果管内空间的气体浓度减少了，残余气体大部分被吸收了。
②表面吸附：
当气体分子碰撞固体表面时，它可能被弹回，也可能被吸附，被吸附的分子可能被吸附得很牢，也可能只被很微弱的力所束缚。
(1)范德华力：物理吸附
(2)剩余价力：化学吸收
③内部扩散：
表面吸附的气体，具有较大的表面迁移率，它可以迅速地在整个表面上扩散开来。随着表面扩散的进行，在一定的条件下，表面吸附的气体将进一步向吸气金属内部进行体扩散。体扩散的形式有：
(1)深入金属表面凹陷或损伤部位;
(2)浸入晶界之间;
(3)扩散到结晶本身的缺陷之中;
(4)和金属化合成金属间化合物;
(5)和金属形成固溶体。
Classification getter
① evaporable getter, also known as diffusion or the flash type:
The need for heating after getter metal getter film is formed out of evapotranspiration. Barium, strontium, magnesium, calcium as the main material, typically evaporable getter commonly used aluminum, nickel and barium getter and a nitrogen-doped getter. Aluminum, nickel and barium getter widely used in various power transmitting tubes, oscillating tube, camera tube, tube, tube solar collectors and other devices. Some CRT is used in nitriding of aluminum, barium getter, which emit large amounts of nitrogen in evapotranspiration exothermic reaction, a large number of barium evapotranspiration due to the collision with the nitrogen molecule, barium getter film without adhering screen or mask above but gather around the neck, only good suction performance, but also increases the brightness of the screen.
② non-evaporable getter:
It does not require the getter metal evapotranspiration out by activation of the getter metal surface so as to have the ability to inhale it. Now often zirconium as the main body. Is the volume-type getter (coating type), it is divided into elemental volume type, the volume of alloy type, large specific surface area of the three. They are suitable for use in the film can not be used suction occasions. For example: the device are small, no suitable membrane surface evapotranspiration Shen, fear and fear the introduction of the leakage device parasitic capacitance and high working temperature of the device can not be used etc. NEG. Usually it into a sheet or strip, widely used in power tubes, magnetrons, vacuum relay, gas lasers, suction pump, vacuum thermos flasks, X-ray tubes, image converters, camera tube, magnetron electrostatic suspended gyroscope, pacemakers and other devices. Typical non-evaporable getter commonly used are: aluminum zirconium 16, zirconium, vanadium, zirconium and iron and graphite.
③ composite getter: from evaporable mixed with non-evaporable getter. As mercury releasing getter, which both mercury releasing metal getter can, which is called a getter composite getter. Typical composite getter release agents as well as alkali metal (alkaline source).
Suction mechanism getter
NEG getter process has three main contributing factor: ET breathing, internal surface adsorption and diffusion, the relationship between the three: First, the suction evapotranspiration, surface adsorption breeds diffusion factors, internal diffusion must be adsorbed to the surface as a precondition. The absorption of non-bulk type getter process: surface adsorption, internal diffusion.
① ET inspiration:
When heated evapotranspiration, splashing out of the gas molecules and atoms of barium tube space collide on a collision course some barium atoms only change its direction evapotranspiration, some chemical reaction with gas molecules to produce the corresponding compound, and the deposition on the envelope surface. Results pipe gas concentration within the space is reduced, most of the residual gas is absorbed.
② Adsorption:
When gas molecules collide solid surface, it may be bounced back, may also be adsorbed, the adsorbed molecules can be adsorbed very firmly, it can only be bound by a very weak force.
(A) van der Waals forces: physical adsorption
(2) the remaining valence forces: chemical absorption
③ Internal diffusion:
Gas adsorbed on the surface, has a large surface mobility, it can quickly spread to the entire surface. As the surface diffusion, under certain conditions, the gas adsorbed on the surface will be further getter metal inside diffusion. Diffusion of the form:
(1) metal surface of the deep depression or lesion;
Between (2) was immersed in the grain boundary;
(3) into the crystalline defects among themselves;
(4) Synthesis of metal and intermetallic compounds;
(5) and the metal form a solid solution. |
