Synthesis and optimization of methyl 5-acetyl-1,4-dihydro-2,6-dimethyl-4-(substituent benzylidene)pyridine-3-carboxylate

Two 1,4-dihydro-Hantzsch pyridine derivatives were synthesized by three steps. In the condensation step, the reaction time can be shortened to 1.5 h through using H2SO4-acetic anhydride system as a catalyst rather than the acetic acid-piperidine systemin the cyclization step, the reaction time was shortened from 20 h in ethanol to 15 h in polar aprotic solvent, and the yield of two products also was increased from 43.3% and 39.7% in traditional solvent to 93.2% and 90.1% in polar aprotic solvent

Ceramic Conversion Treatment of Commercial Pure Titanium with a Pre-Deposited Vanadium Layer

Titanium is characterized by poor wear resistance which restricts its application. Ceramic conversion treatment (CCT) is used to modify the surface; however, it is a time-consuming process. In this work, a thin vanadium layer was pre-deposited on the commercial pure titanium (CPTi) samples’ surface, and it increased the oxygen absorption significantly and assisted in obtaining a much thicker oxide layer than those samples without a V layer at the treatment temperatures of 620 °C and 660 °C. The oxidation of the samples pre-deposited with the V layer had a much higher oxidation rate, and V was evenly distributed in the oxide layer. After CCT, all samples had a low wear volume and stable coefficient of friction in comparison to the untreated CPTi sample. A slightly higher wear area in the wear track was observed on the V pre-deposited samples than those samples without vanadium, especially those with a thicker oxide layer (>4 µm). This might be associated with defects in a thicker oxide layer and insufficient support from a shallower oxygen diffusion zone or hard debris created at the initial stage. Vanadium in the oxide layer reduced the contact angles of the surface and increased the wettability significantly