To further explore the material early-warning application of the luminescent coating, we demonstrated a new method by preparing a mixture layer of metallic erbium and oxidized zirconium （Er-ZrO2 layer） using the double glow plasma surface alloying technology with Zr and Er co-sputtering under oxygen plasma exposure. The microstructure, composition and luminescence proper-ties of the layers were characterized by scanning electron microscopy, X-ray diffraction, Raman and photoluminescence spectra. The dependence of the luminescence on the gradual concentration was studied. Results indicated that the contents of Zr, Er and O in the layer decreased gradually along the depth direction. The luminescence properties were concentration-dependent. X-ray dif-fraction analysis showed that the crystalline structure of ZrO2 layer transferred from a mixture phase of tetragonal and monoclinic to pure monoclinic phase with the Zr-Er co-sputtering. The Raman bands of the layers depended on its local ZrO2crystal struc-tures. Photoluminescence characteristics of Er-ZrO2layer revealed that the main emission bands were assigned to2H11/2→4I15/2and 4S3/2→4I15/2transition under the excitation at 325 nm. The fact suggested that the plasma surface alloying is an effective method to obtain luminescent layer.
AI coatings with different microstructures were prepared on the surface of Gd using the magnetron sputtering technique to improve its corrosion resistance. The corrosion behaviors for the pure Gd and Gd with Al coating in distilled water were studied using the mass loss and electrochemical performance. As a result, pure Gd without coating shows a certain amount of surface cracks under water flow conditions, whereas the polygonal Al coating decreases the path of the corrosive medium to body due to the existence of eroding pits structure. Compared with the polygonal structure Al coating and pure Gd, the lamellar structure of Al coating exhibits a higher electrochemical protection performance （e.g., a lower corrosion current and higher self-corrosion potential） and no occurrence of pitting corrosion. Due to an effective physical shield, the formation of the lamellar structure protected the inner Gd part from being corroded, and prolonged the duration of cathodic protection.
Based on a simple classical model specifying that the primary electrons interact with the electrons of a lattice through the Coulomb force and a conclusion that the lattice scattering can be ignored, the formula for the average energy required to produce a secondary electron （ε） is obtained. On the basis of the energy band of an insulator and the formula for e, the formula for the average energy required to produce a secondary electron in an insulator （εi） is deduced as a function of the width of the forbidden band （Eg） and electron affinity X. Experimental values and the εi values calculated with the formula are compared, and the results validate the theory that explains the relationships among Eg, X, and ei and suggest that the formula for εi is universal on the condition that the primary electrons at any energy hit the insulator.
