Effects of substrate bias and argon partial pressure on microstructure and interfacial characteristic of aluminum coating on uranium surface

Aluminum was coated by ion magnetron sputtering process on depleted uranium surface under different substrate bias and argon partial pressures. Surface and interfacial morphologies of aluminum coating were observed with SEM, and the elemental profile of interface between coating and substrate was analyzed with Auger electron spectrometer with the microstructure of coating analyzed by TEM. The results indicated that the aluminum coating at pulsed bias is more compact than at DC bias, and the compactness of coating is better if the pulsed bias is in the range from -500V to -1000V. It was found that the coating adheres to substrate tightly with "pseudo -diffusion layer"existing in interfacial zone between coating and substrate. With increasing pulsed bias, the "pseudo-diffusion layer"broadens. The coating is of columnar structure and, with decreasing argon partial pressure, grain refining in the coating is available so as to improve its compactness.