Sung-Hwan Lim

Oxidation and corrosion behavior of nanolaminated MAX-phase Ti 2 AlC film synthesized by high-power impulse magnetron sputtering and annealing

Nanolaminated MAX-phase Ti2AlC thin films were synthesized by high-power impulse magnetron sputtering (HiPIMS) from a MAX-phase Ti2AlC target. The amorphous matrix Ti-Al-C films were deposited at room temperature, while the MAX-phase Ti2AlC films were obtained through annealing process of the as-deposited amorphous matrix films. The microstructure, oxidation resistance, and corrosion behavior of these two films were comparatively investigated. The results indicated that the MAX-phase Ti2AlC films had superior antioxidation and anticorrosion properties than the amorphous matrix Ti-Al-C films, which is attributed to the rapid formation of dense Al2O3 layer on the top of MAX-phase Ti2AlC films because of the rapid diffusion of Al atoms in the typical nanolaminated structure of MAX phase.

The Effect of Polyethylene Glycol on the Trivalent Chromium Electroplating

The effect of organic additives, polyethylene glycol (PEG), on the trivalent chromium electroplating was analysed in the view point of current efficiency, solution stability and metallurgical structure. It was measured that PEG-containing trivalent chromium solution had about 10% higher current efficiency than pure solution and controlled the micro-crack density of electrodeposits. PEG exhibited profound effect on the solution stability by reducing the consumption rate of formic acid which acts as a complexant to lower the activation energy required for electrochemical reduction of trivalent chromium ions. It was also revealed that the formation of chromium carbide layer was facilitated in the presence of polyethylene glycol, which meant easier electrochemical codeposition of chromium and carbon, not single chromium deposition. Trivalent chromium layer formed from PEG-containing solution was amorphous with local nano-crystalline particles, which were prominently developed on the entire surface after non-oxidative heat treatment.