Ultra-fine grain structure

Key words chromium, molybdenum, coatings, ultra-fine grain structure, nanohardness. 

It is shown, that chromium and molybdenum coatings have ultra-fine grain structure (Fig. 1). So, the grains size in 80 and 400 nm thickness chromium and molybdenum coatings are equal to 40 -50 nm and 20 nm accordingly. The diffraction pattern shows that only lines corresponding to lines body-centered cubic lattices chromium and molybdenum are precisely fixed, additional lines are not revealed. 

The nanohardness of 400 nm thickness chromium coatings with ultra-fine grain (nanocrystalline) structure is equal to 21.61 GPa (Table 1), which is 8-9 times higher than that of cast chromium. At the same time the nanohardness of molybdenum coatings, which characterized even more fine-grain structure, is equivalent to 9.98 GPa. It is necessary to note, that in a massive state hardness of polycrystalline chromium is lower than hardness of polycrystalline molybdenum (2 GPa and 1.3 GPa for poly crystalline molybdenum and chromium accordingly [7]). 

S. Lefebvre, B. Devincre, T. Hoc, Simulation of the Hall-Petch effect in ultra-fine grained copper. Mater. Sci. Eng. 400, 150-153 (2005). Structural Materials Properties Microstructure and Processing... 

DuPont has developed materials with excellent photospeed across the visible spectrum, extending from the UV at about 350 nm out to far red at about 700 nm. Typical sensitivities range in the few to tens of mJ/cm, which is competitive with most other photopolymer systems and even approaches the photospeed of the ultra-fine grained silver halide materials [12] that are employed to record similar structures. 

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