Investigation on Solar Absorption and Thermal Emittance of Al Films Deposited by Magnetron Sputtering

A metal layer with high reflectance is widely used as the bottom mirror of smart radiation devices. Reduced solar absorption and enhanced emittance tunability are required for smart radiation devices applied in aerospace. Thus, reducing the absorption in the metal is also necessary. Here, Al films have been prepared by direct current magnetron sputtering on the fused silica substrate. The structure, morphology, and optical properties of the films have been analyzed at various deposition temperatures and deposition times. The spectrum absorption tends to increase with the increase of surface roughness due to the agglomeration and size increase of Al particles, which has been further demonstrated by the simulated results. The optimized Al film exhibits small solar absorption of 0.14 and low emittance of 0.02, which benefits the application for smart radiation devices and solar reflectors.

Structure, phase evolution, and properties of Ta films deposited using hybrid high-power pulsed and dc magnetron co-sputtering

Crystalline phase and microstructure control are critical for obtaining desired properties of Ta films deposited by magnetron sputtering. Structure, phase evolution, and properties of Ta films deposited by using hybrid high power impulse magnetron sputtering (HiPIMS) and direct current magnetron sputtering (DCMS) under different fractions of DCMS power where Ta ion to Ta neutral ratios of the deposition flux were changed are investigated. The results revealed that the number of Ta ions arriving on the substrate/growing film play an important role in structure and phase evolution of Ta films. It can effectively avoid the unstable arc discharge under low pressure and show a higher deposition rate by hybrid high power impulse magnetron sputtering (HiPIMS) and direct current magnetron sputtering (DCMS) compared with only high power impulse magnetron sputtering (HiPIMS). Meanwhile, the high hardness α-Ta films can be directly deposited by hybrid co-sputtering compared to those prepared by direct current magnetron sputtering (DCMS). In the co-sputtering technology, pure α-Ta phase film with extremely fine, dense and uniform crystal grains were obtained, which shows smooth surface roughness (3.22 nm), low resistivity (38.98 μΩ·cm) and abnormal high hardness (17.64 GPa).

Nanomechanical and Nanotribological Properties of Nanostructured Coatings of Tantalum and Its Compounds on Steel Substrates

The present paper addresses the problem of identification of microstructural, nanomechanical, and tribological properties of thin films of tantalum (Ta) and its compounds deposited on stainless steel substrates by direct current magnetron sputtering. The compositions of the obtained nanostructured films were determined by energy dispersive spectroscopy. Surface morphology was investigated using atomic force microscopy (AFM). The coatings were found to be homogeneous and have low roughness values (<10 nm). The values of microhardness and elastic modulus were obtained by means of nanoindentation. Elastic modulus values for all the coatings remained unchanged with different atomic percentage of tantalum in the films. The values of microhardness of the tantalum films were increased after incorporation of the oxygen and nitrogen atoms into the crystal lattice of the coatings. The coefficient of friction, CoF, was determined by the AFM method in the “sliding” and “plowing” modes. Deposition of the coatings on the substrates led to a decrease of CoF for the coating-substrate system compared to the substrates; thus, the final product utilizing such a coating will presumably have a longer service life. The tantalum nitride films were characterized by the smallest values of CoF and specific volumetric wear.