Vanadium dioxide films have been prepared with different thicknesses using radio-frequency magnetron sputtering technique followed by postdeposition annealing in oxygen ambient. Films with a thickness of 300nm show a switching efficiency of ∼74% and most importantly with a near-zero infrared transmission in the switched state. As the film thickness decreases, the inherent transmission in the switched state increases along with reduced switching efficiencies.
We demonstrate the image conversion from mid-IR to near-IR (NIR) exploiting high-contrast optical switching in vanadium oxide thin-film layers. The intensity distribution of a mid-IR beam is converted to NIR wavelengths exploiting the strong reflectivity changes induced by optical pumping in the mid-IR. We show an experimental setup in which the radiation of a Tm-doped fiber laser at 1940 microm and a carbon dioxide at 10.6 microm has been converted to both 850 nm and 1064 nm. The resolution was 35 microm and was reached by using an inexpensive CCD camera. The sensitivity of the device increases linearly with sample temperature. We measured a threshold of 144 mW/cm(2), with a sample temperature of 62 degrees C.
Chromium thin films are technologically important as underlayers for the deposition of cobalt-based magnetic films because of their good lattice match and adhesion. The structural orientation and morphology of the chromium under layers control the magnetic properties of the cobalt-based films deposited on them. Hence, optimization of the structure and properties of chromium under layers is essential for realizing magnetic thin films with desired properties. In this paper, we report the structural variation observed in chromium thin films deposited on silicon(1 0 0) substrates deposited using Ion Beam Sputter Deposition (IBSD) technique. The influence of process parameters, such as ion beam current density, substrate temperature and the angle of incidence of the condensing species, on the structural transformation from (1 1 0) orientation to (2 0 0) orientation has been presented. The structural variation and morphological variations observed have been discussed based on the growth models and the energetics involved in the process.
Several tests were conducted on 316 stainless steel, and 17-4 PH stainless steel to understand the effect of additive manufacturing on their mechanical properties in general. The samples were produced via a custom-built laser wire metal deposition, with variable laser power of 3600W for 316 stainless, and 4000W for 17-4 PH, but all other printing parameters were kept same. Four different tests, Tensile, Rockwell hardness, Charpy impact, and optical microscopy were carried out to establish the material properties and surface characterization. Through our assessment, it was found that the properties of the laser-printed samples can be greatly varied by printing in an inert atmosphere, while the printing orientation and post-print heat treatment process also play a dominant role in determining the properties. This research showed that the properties of additively manufactured 316 stainless, and 17-4 PH have fared well when compared to ASTM standard values for annealed metals. Details of the results are presented.
Inspecting the 316 stainless, the metal strength and hardness were high while being printed in x orientation, while the metal was much more ductile when printed in y orientation. The 316 stainless micro-structure contained no porosity or no anomalies from the samples tested. The results of 17-4 stainless samples matched the ASTM standard values for strength and hardness. But with Charpy impact tests, the results seemed slightly ductile as the values were slightly lower than the threshold. That brittle nature could have been a result of porosity that was visible under microscope. But the porosity levels decreased tremendously when the sample was once again printed in an inert environment. The results of this research have helped us understand the intricate nature of 316 and 17-4 PH stainless steels while being additively printed. The beneficial research experience of participating undergraduate students in collaboration with industry is a special feature of this project.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.