Ti-Mo吸气材料的表面改性及其选择性吸气性能研究

Surface Modification and Selective Gettering Performance of Ti-Mo Getter Material

为了实现真空器件内微量气体的选择性控制,提升吸气剂在复杂气氛环境下的适用性,采用化学镀方法将Ni沉积在Ti-Mo粉体表面制备出Ni/Ti-Mo粉体,并通过粉末冶金压制和热处理烧结工艺制备了对H2和O_(2)具有选择性吸收性能的Ni/Ti-Mo吸气材料。采用扫描电子显微镜(SEM)、能谱(EDS)、感耦合等离子体原子发射光谱(ICP)对Ni/Ti-Mo粉体的表面形貌及成分进行表征,结果表明:化学施镀45 min后的Ni/Ti-Mo粉体,颗粒表面Ni层与Ti-Mo基体间贴合良好,Ni对Ti-Mo的包覆效果较好,且游离非包覆态Ni含量较少。进一步对经过不同温度热处理后Ni/Ti-Mo压制样品进行XRD和SEM表征,结果表明:当热处理温度超过400℃时,Ni原子将向Ti颗粒内部扩散,当热处理温度达到970℃时,Ni原子将扩散到Ti颗粒芯部,材料主相由Ti, Ni相逐渐转变为Ti2Ni相。对不同温度热处理后样品进行吸气性能测试,结果表明:Ni的引入能有效提高Ti-Mo材料的吸氢阻氧能力,870℃热处理10 min后Ni/Ti-Mo样品与无镀Ti-Mo样品相比,10 min对H2的吸收速率提升了34%,对O_(2)的吸收速率下降了54%,具有良好的吸氢阻氧性能。

With the development of vacuum device technology,some residual gases play a very important role in the specific working.In the laser gyroscope,there are two kinds of residual gases H2 and O2.H2 is one of the most harmful residual gases to the laser gyro⁃scope which will decrease output power of the laser device.And a small amount of O2,which can reduce the loss of optical compo⁃nents,prolong the service life of devices.In summary,it’s helpful that achieving residual gas selective control in the device which can improve the performance of the device.Getter material is a kind of functional material used in electronic vacuum devices,which has a strong adsorption effect on the active gas in the device,so it can ensure the vacuum environment in the device,reduce the loss of the device and improve the service life.There are two types of getters:evapotranspiration getter and non evapotranspiration getter(NEG).NEG technology has been developed in the 1970′s,it is a commonly used passive long-term maintenance method of vacuum.NEG is usually a kind of alloy with metal Ti or Zr as matrix and C,V,Fe,Mo as additive elements.After heating at a certain temperature for a certain time,NEG reaches the active state,removes the passivation film on the surface,and the getter starts to absorb the active gas inside the device.It can remove the residual gas such as H2,O2 and CO by chemical adsorption to maintain the atmosphere environ⁃ment in vacuum devices.There are three kinds of NEG:Zr-based NEG,Ti-based NEG and TiZr-based NEG.From these three kinds of getters,ZrAl16,ZrVFe,Zr-C,TiZrV and Ti-Mo are developed.Among all kinds of NEG,Ti-Mo getter has been widely used because of its high mechanical strength and large absorption of various active gases.However,the single hydrogen absorption performance as a measure of getter performance has gradually been unable to meet the requirements of vacuum devices.Enhancing the selective absorp⁃tion performance of the getter in a complex trace gas atmosphere plays a crucial role in some vacuum devices.Ti-Mo getter,which will remove all residual gas including H2 and O2 can not selective remove H2 and selective retain a small amount of O2.It’s necessary to have a modified Ti-Mo getter to achieve selective absorption of H2 and O2.Ni can be used as an anti-oxidation coating,which has a strong barrier to O2.At the same time,Ni film can catalyze the dissociation of H2 and penetrate H that is advantageous to improving H2 absorption ability.It is obvious that Ni can be an effective modifying element to the Ti-Mo getter.As a technology that can effectively change the surface properties of devices,surface modification can meet the requirements of new materials for special use conditions and functions.Electroless plating is a widely used surface modification technology.As a plating method that combines substrate with thin film,it has the advantages of simple equipment and high plating efficiency.It is widely used in machinery,electronics,aerospace and other industrial sectors.The coating that can be applied has expanded from metal coating such as Cu,Co,Pb and Au to alloy coat⁃ing such as Fe-W-B.According to the different uses,electroless plating has a variety of process options,the electroless plating of pow⁃der is one of them.In order to achieve the selective absorption of hydrogen and obtain the excellent hydrogen absorption and oxygen re⁃sistance materials,a modified Ni/Ti-Mo getter material was prepared by combining the methods of powder surface electroless plating and vacuum heat treatment,which showed a better hydrogen absorption and oxygen resistance performance.The morphology and com⁃position characterization tests of the modified Ni/Ti-Mo powders showed that Ni/Ti-Mo powders prepared with 45 min chemical plating exhibit a good interfacial bonding between Ni layer and Ti-Mo matrix.X-ray diffraction(XRD)and scanning electron microscope(SEM)results of Ni/Ti-Mo samples sintered at different temperatures showed that Ni atoms diffuse into Ti particles rapidly when the sintering temperature exceeded 400℃.When the temperature reached to 970℃,Ni atoms diffused into the core area of Ti particles,and the main phase of the material gradually changed from Ni and Ti phases to Ti2Ni phases.The gettering performance of the sample showed that the modification effect of Ni atoms improved the hydrogen absorption and oxygen resistance of Ti-Mo materials effectively.Compared with Ti-Mo samples without powder surface electroless plating treatment,the modified Ni/Ti-Mo samples sintered at 870℃for 10 min showed the absorption rate of H2 increased by 34%and the absorption rate of O2 decreased by 54%.