Mechanochemical reactions of GaN-Al2O3 interface at the nanoasperity contact: Roles of crystallographic polarity and ambient humidity

Abstract

Mechanochemical reactions of the GaN-Al2O3 interface offer a novel principle for scientific and technological merits in the micro-/nano-scale ultra-precision surface machining. In this work, the mechanochemical reactions on Ga- and N-faced GaN surfaces rubbed by the Al2O3 nanoasperity as a function of the environmental humidity were investigated. Experimental results indicate that the N-face exhibits much stronger mechanochemical removal over the relative humidity range of 20%–80% than the Ga-face. Increasing water molecules in environmental conditions significantly promotes the interfacial mechanochemical reactions and hence accelerates the atomic attrition on N-face. The hypothesized mechanism of the selective water-involved mechanochemical removal is associated with the dangling bond configuration, which affects the mechanically-stimulated chemical reactions via altering the activation energy barrier to form the bonding bridge across the sliding interface. These findings can enrich the understanding of the underlying mechanism of mechanochemical reactions at GaN-Al2O3 interface and a broad cognition for regulating the mechanochemical reactions widely existing in scientific and engineering applications.

Investigation of nanosized alumina‐binder feedstock rheology for ceramics injection molding (CIM) and survey spark plasma sintering of output green body to obtain transparent alumina

“…reported an alumina wear rate with the grain size of 450 nm, 750 nm, and 4 μm as 1.0 × 10 −7 , 4–4.5 × 10 −7 , and 6–6.5 × 10 −7 mm 3 /N m, respectively. Thus, the amount of wear for the grain size of the alumina sintered in the present research (1–4 μm) seems to be logical 32–43 …”

“…Thus, the amount of wear for the grain size of the alumina sintered in the present research (1-4 μm) seems to be logical. [32][33][34][35][36][37][38][39][40][41][42][43]…”

Effect of Native Oxide Layer on Mechanochemical Reaction at the GaN–Al2O3 Interface

“…The above results showed that by combining chemically active counter-surface and external mechanical stress, material removal can occur on GaN surface due to the mechanochemical reactions in humid air under purely elastic contact situation, where the material removal does not introduce the lattice damage into the subsurface (Guo et al, 2021a). Since the strong oxygen signal of the oxide layer on the GaN-AR surface will cover the signal of wear debris completely, the chemical states of wear debris on GaN-HF substrate were characterized using SAXPS to further confirm the mechanism of material-removal caused by Al 2 O 3 counter-surface.…”

“…Based on the Derjaguin-Muller-Toporov (DMT) contact theory, 4 µN normal load in the reciprocating wear process provides a maximum contact pressure of ∼1.6 GPa, which is far below the yield strength of crystal GaN material (∼20 GPa) (Schwarz, 2003). In this case, the material removal of GaN-HF substrate is not caused by the mechanical action of the Al 2 O 3 counter-surface, but by the water-participated interfacial mechanochemical reaction that is highly humidity-dependent (Guo et al, 2021a).…”

Design, preparation, and characterization of CS/PVA/SA hydrogels modified with mesoporous Ag2O/SiO2 and curcumin nanoparticles for green, biocompatible, and antibacterial biopolymer film

“…All hydrogels are water-insoluble 3D polymer networks that can absorb body uids in a biological environment. [1][2][3][4][5] Various polymers of natural and synthetic origin are used to make hydrogels. [6][7][8][9][10] Physical hydrogels are formed through weak secondary forces and chemical hydrogels are created by covalent forces.…”