Water environment

About: Water environment is a research topic. Over the lifetime, 13384 publications have been published within this topic receiving 125138 citations.

Structural analysis of (Cr1−xSix)N coatings and tribological property in water environment

Abstract: A series of (Cr 1− x Si x )N coatings were deposited by a multicathode unbalanced magnetron sputtering system (UBMS) using Cr and Si targets under Ar/N 2 atmosphere on stainless steel (AISI630). Si content x was varied from 0 to approximately 0.8 by changing the input power to Si target. X-ray diffraction (XRD) analysis revealed that the coating underwent a continuous structural change from crystalline (NaCl structure) to amorphous structure as x was increased. Average grain size, which was derived from the XRD measurements using the Scherrer's equation, decreased from 17 to 2 nm by increasing the Si amount x from 0 to 0.45. Hardness of (Cr 1− x Si x )N coating increased slightly from 15 to 17 GPa by increasing the Si content x from 0 to 0.3. Tribological evaluations using a ball-on-disk tribometer of (Cr,Si)N-coated substrates were conducted in distilled water against the (Cr,Si)N coating itself. The friction coefficient decreased drastically nearly down to zero as x was increased more than ca. 0.6. The specific wear rate was also decreased by a factor of 10 from 4×10 −7 to 5×10 −8 mm 3 N −1 m −1 . A thin (approximately 10 nm) amorphous Si–Cr oxide layer was formed on the surface of worn section that was estimated to be formed by the tribochemical reaction during the tribological test. It was concluded that this tribochemically formed amorphous oxide layer was responsible for the ultralow friction behavior.

Noncovalent Interaction of Methylene Blue with Carbon Nanotubes: Theoretical and Mass Spectrometry Characterization

Abstract: Noncovalent interaction of methylene blue dye cation (MB+) with single walled carbon nanotubes (CNT) is characterized by molecular dynamics (MD) simulation, quantum chemical calculations, and laser desorption/ionization (LDI) mass spectrometry. The MD simulation of the (MB+)n–CNT (n = 1–10) complexes in water demonstrates that the MB+ cations are adsorbed on the nanotube surface in the monomeric form. MD reveals both parallel and perpendicular orientations of the MB+ tricyclic plane in relation to the long axis of CNT when placed in the water environment. The interaction energy between the components of the complex in the perpendicular conformation, as determined by quantum chemical calculations at the DFT/M05-2X/6-31++G(d,p) level of theory, explains why the bending of the MB+ cation at the sulfur atom weakens the π-system of bonds and allows for the perpendicular orientation to occur. It is also found that the adsorbed MB+ induces positive electrostatic potential around the adjacent semicylindrical segm...