Low-Temperature Activation Performance of Ti-Based Non-Evaporable Getter
With the development of vacuum technology,non-evaporable getters have been widely used in sealed-off devices.In many of these devices,the getter is required to work or activate under relatively low temperature conditions,to reduce risk of damaging heat sensitive components surrounding the getter,and to reduce outgassing from the components or walls nearby the getter.For these devic-es,Zr56V37Fe7 nonevaporable getters can be activated at 450 ℃ for 10 min or at 300 ℃ for 90 min,the degree of this activation is suit-able for applications that do not need high gettering rate.On the other hand,Zr56V37Fe7 getter have been developed by the European Nu-clear Center(CERN)for the project of the Large Hadron Collider(LHC).These kinds of Ti-based getters have high hydrogen adhe-sion coefficient and low activation temperature,which can be fully activated at only 180 ℃ for 24 h,and are often used in vacuum en-velopes with space and shape restrictions.Although this kind of getter has outstanding advantages,the shortcomings of its small sorp-tion quantity and high production cost restrict its application in many directions.This study is expected to provide valuable information for the better development of Ti-based bulk getters,and Ti40Zr22V24Cr8Mn6 pill-shaped getter was prepared.X-ray diffraction analysis(XRD),microscope analysis,scanning electron microscope(SEM)and energy dispersive analysis(EDS)were used to characterize the phase structure,surface morphology and surface composition of the alloy.From XRD pattern,it was clear that two distinct crystal-lographic phases coexisted in the alloy,namely Ti-based solid solution phase with body-centered cubic(bcc)structure and C15 Laves phase with AB,type cubic structure.Using Rietveld analysis,the weight fraction of bcc and C15 phases were determined to be 55.1％and 44.9％,respectively.SEM image showed that there were three different parts in the alloy,namely black colonies(A),gray matrix(B)and white precipitates(C).In this alloy,micron-sized white precipitates were scattered throughout the matrix,and black colonies presented a broken fishbone structure,forming three-dimensional(3D)framework.It was reported that the microstructure of"Laves phase related bcc solid solution"displayed as a kind of dendritic phase distributed in an interpenetrating matrix.Furthermore,it was pointed out that 3-D interpenetrating Laves phase worked as a catalyst for bcc phase which had a high absorption hydrogen capacity.In-situ X-ray photoelectron spectroscopy(in-situ XPS)was used to investigate the temperature dependence of Ti40Zr22V24Cr8Mn6 non-evap-orable getter material,and the results showed that the reduction of Ti,V,Cr,Mn could be completed,while Zr still contained a small amount of oxidation state at 350 ℃,which meant that the reduction rate of Zr in this temperature range as relatively slow.After activa-tion at 450 ℃,a small amount of zirconia still existed on the surface.Therefore,to complete the activation of the getter,methods of appropriately extending the holding time or slightly increasing the activation temperature could be used.Dynamic sorption method was used to test the H2 sorption performance of the getter,and the room temperature hydrogen absorption performance of Ti40Zr22V24Cr8Mn6 getter was compared with Zr56V37Fe7 getter under the same preparation process and test conditions.The results showed that the hydro-gen pumping speed of the former was about 1.4 times that of the latter under the condition of baking activation(250 ℃,3 h).Further reactivated the getter at 400 ℃ for 30 min,the hydrogen pumping speed of the former was about 1.2 times that of the latter,which could be seen that Ti40Zr22V24Cr8Mn6 getter had excellent low-temperature activation characteristics.This breakthrough in Ti-based get-ter material system provided effective information for the development of a new generation of low-temperature activation materials.
NETL
NSTL
万方数据
