不同喷涂工艺对Cr3+掺杂Al2O3陶瓷涂层相结构及发光性能影响研究

通过火焰喷涂工艺和等离子喷涂工艺制备了Cr^3+掺杂Al2O3陶瓷涂层。采用扫描电镜、X射线衍射、荧光光谱仪等方法表征了涂层的微观形貌、孔隙率、相结构及发光性能等。对比两种不同工艺制备的Cr^3+掺杂Al2O3陶瓷涂层性能结果表明:等离子喷涂制备的涂层形貌、颗粒熔化状态、厚度均一性均优于火焰喷涂涂层,但火焰喷涂工艺涂层的发光性能远优于等离子工艺涂层,其原因是火焰喷涂制备的涂层中Al2O3粒子的熔融状态更差,保留了更多的α-Al2O3相,未熔粒子部分将以喷涂原粉中稳定的α-Al2O3结构存在涂层中进而影响其光学性能。

High throughput construction for the deformation mechanism diagram and dynamic recrystallization of a bimodal-sized particle-reinforced Ti-2.5Zr-2Al-1(Si,C)titanium alloy

An in situ autogenous particle-reinforced Ti-2.5Zr-2Al-1(Si,C)titanium alloy is prepared by vacuum induction melting.The wide range of an effective strain between 0.2 and 1.2 and the corresponding microstructure are obtained by the double-cone high-throughput compression test and finite element simulation.The deformation mechanism diagram with strains of 0.2-1.2 and strain rates of 0.7-1.5 s^(-1)at 900℃ is constructed.When the strain rate is 1.3 s^(-1),dynamic recovery occurs in the small strain range(<0.377),dynamic recrystallization(DRX)occurs in the medium strain range(0.377-1.182),and deformation instability occurs in the large strain range(>1.182),resulting in the deformation bands.High-angle annular dark field and high-resolution transmission electron microscopy are used to determine the existence of bimodal particle distribution,namely micron-scale TiC particles and nano-scale Ti5Si3 and(Zr,Si)particles.The average radius of the(Zr,Si)nanoparticles measured by small angle neutron scattering is 19.3 nm,and the volume fraction is 0.35%.DRX grains with an average size of 0.49μm are obtained at 900°C,strain rate of 1.3 s^(-1),and strain of about 0.6.Micron-scale particles stimulated DRX nucleation,while nanoscale particles hindered the growth of new grains,resulting in grain refinement.

Design of imaging system for CSNS near-target beam diagnostics

Introduction China Spallation Neutron Source(CSNS)is an accelerator-based pulsed neutron source which produces neutron with spallation reaction induced by proton bombarding tungsten target.With increasing beam powers and influences on target,near-target monitoring becomes extreme necessary.In this situation,an optical imaging system for proton beam diagnostics and monitoring near the target is being developed at CSNS,which can provide real-time images of the beam on target and beam distribution information.Target imaging system design and development In the design of CSNS target imaging system,coating of Cr^(3+):Al_(2)O_(3) is used to convert particle radiation into emission light.According to the geometry limits of CSNS target station,a special optical system was designed and fabricated to collect the emission light.When the proton beams strike on the target,the coating on the target will be excited,emitting luminescence at the same time.The mirrors and lenses of the optical system image the distribution of emission light into a radiation-hard imaging fiber,which transmits the images to the GigE camera located at low-dose area outside of the target station.Software was written on the LabView platform to control the camera and analyze the images on line.Mock-up of the imaging system was manufactured to test and evaluate the performances of the system.Some important characteristics of the system were obtained and studied.Conclusion Tests on the mock-up of the system present reliably expectation for beam diagnostics.The imaging system has been installed at CSNS recently.More work will be continued to improve the properties of the system.

Measurements and characteristics of Al_(2)O_(3):Cr^(3+) coating for the proton beam imaging system

Introduction To set up an online proton beam diagnostic system near the neutron production target of China Spallation Neutron Source(CSNS),a luminescence coating sprayed on the target windowand a corresponding optic system were fabricated.In the work,the fabrication of Al_(2)O_(3):Cr^(3+) coating was explored.Measurements on the sprayed samples were performed to analyze the characteristics of the Al_(2)O_(3):Cr^(3+) coating.Fabrication and tests of coating samples Three kinds of powders with different Cr concentrations were used to fabricate the luminescence coating samples.The flame spraying,plasma spraying and D-gun spraying processes were explored.Photoluminescence(PL),X-ray diffraction(XRD),scanned electron mirror(SEM)and radioluminescence experiment by 300 MeV deuterium beam were carried out to analyze and characterize the samples.Results The emission spectrum excited by 532-nm laser has two obvious peaks at 692.9 nm and 694.3 nm.The samples by flame spraying process with the powders obtained from melting method show higher luminescence intensity than the samples by plasma spraying process.It is observed that the luminescence intensity has some relationships with the alpha phase in the samples,which is deduced from the XRD and photoluminescence tests results.A lower temperature during the flame spraying process will help to keep more alpha phase in the material.The selected four samples show successful fluoresced results in the radioluminescence experiment.Conclusions The luminescence intensity of the coating is improved greatly by the studies on the fabrication process and the characteristics of the samples.The luminescence coating used in beam diagnostics will be fabricated by the confirmed technical process.More works will be continued to improve the characteristics of the luminescence light by controlling Cr concentration and annealing in 1200∼2000℃ environment in the future.