1,2,3-triazoles as X-factor in gold(I) activation of challenging C-C triple bond transformations

The \u27click chemistry\u27 which provides 1,4-disubstituted 1,2,3-triazoles has been reported in 2001. New method for highly funtionalized 1,2,3-triazole synthesis becomes very desirable along with the discovery of unique properties of this heterocyclic structure. Our group focused on the synthesis of functional 1,2,3-triazole for several years and new methodologies have been developed such as arylation, vinylation, propargylation and allenation. Besides the new methods are benefiting the field related to triazole functionalization, new reactivity of ligand-metal complexes was revealed.;A series of 1,2,3-triazole gold complexes were synthesized/characterized. This dissertation presents the results of research effort to explore the unique chemoselectivity and improved thermal stability that arises when triazole is introduced as a X-factor or secondary ligand. This effort successfully led to the efficient synthesis of traditionally challenging compounds. The benzotriazole modified gold(I) complex showed high reactivity toward propargyl ester/vinyl ether. Through a simple 3,3-rearrangement, allene derivatives, which were usually considered as intermediate in the gold(I) chemistry, were isolated as a major product. The treatment of allene derivatives with triazole gold complex showed no apparent decomposition of allene and confirmed the triazole-gold complex could selectively perform the pi-acidity toward C-C triple bond over allene. With this triazole modification, the thermal stability of the corresponding gold(I) complexes is significantly improved. Triazole-gold(I) facilitated alkyne hydroboration was accomplished at 80 °C, which is a temperature leads to serious complex decomposition of previous cationic gold(I) species. Moreover, 31P NMR proved the stability of triazole-gold complex toward the highly reductive reaction precursor (such as boronhydride). This new strategy enabled an efficient method for amine borane heterocyclic structures synthesis, which has been considerable investigated recently as a potential hydrogen storage material

Influence of jarosite precipitation on iron balance in heap bioleaching at Monywa copper mine

Ferric iron is an important oxidant in sulfide ore bioleaching. However, recirculating leach liquors leads to excess iron accumulation, which interferes with leaching kinetics and downstream metal recovery. We developed a method for controlling iron precipitation as jarosite to reduce excess iron in heap bioleaching at Monywa copper mine. Jarosite precipitation was first simulated and then confirmed using batch column tests. From the simulations, the minimum pH values for precipitation of potassium jarosite, hydronium jarosite, and natrojarosite at 25 °C are 1.4, 1.6, and 2.7, respectively; the minimum concentrations of potassium, sulfate, ferric, and sodium ions are 1 mM, 0.54, 1.1, and 3.2 M, respectively, at 25 °C and pH 1.23. Column tests indicate that potassium jarosite precipitation is preferential over natrojarosite. Moreover, decreased acidity (from 12 to 8 g/L), increased temperature (from 30 to 60 °C), and increased potassium ion concentration (from 0 to 5 g/L) increase jarosite precipitation efficiency by 10, 5, and 6 times, respectively. Jarosite precipitation is optimized by increasing the irrigating solution pH to 1.6. This approach is expected to reduce the operating cost of heap bioleaching by minimizing the chemicals needed for neutralization, avoiding the need for tailing pond construction, and increasing copper recovery

Multi-factor coupling system characteristic of the dynamic roll gap in the high-speed rolling mill during the unsteady lubrication process

In the present work, a multi-factor coupling dynamic model of a rolling mill system for a dynamic roll gap during an unsteady lubrication process was developed on the basis of the rolling theory, lubrication and the friction theory, and the mechanical vibration theory. The multi-factor coupling model of interfacial film binding was coupled with the rolling force model, dynamic roll gap interface friction model and work roll movement model. The corresponding distributions of friction and pressure at varying surface roughness and times were systematically analyzed during the unsteady mixed lubrication process. The effects of the main processing parameters on the critical speed and amplitude for self-excited vertical vibration were investigated

Numerical and experimental studies on wrinkling control methods of sheet metal part with high curvature and large flange in rubber forming

Wrinkling is one of the main failure modes in sheet metal forming process and may lead to assembly problems of the parts. Control of wrinkling is difficult due to the complex deformation behavior of the sheet metal. A finite element model for side blankholder method to control wrinkling was established and used for the simulation. Trials and simulations were conducted to analyze the parameters of wrinkling characteristics. Results show that with the increase in the angle of the side blankholder, the resistance force of the side blankholder decreases. The blank length on the side blankholder should be small enough. The fillet radius of the side blankholder should be large enough to reduce the deformation. The bottom gap between the die and the side blankholder cannot be too large because the support of the blank will decrease in the forming process. In order to verify the simulation results, three blank lengths (20, 15, and 5 mm) over the side blankholder were used in the experiment. The results of the comparison tests testify the reliability of the simulation. The optimal parameter of the blank length is 5 mm. A new clamp method was designed for wrinkling control to overcome the shortcomings of the side blankholder method. The precision of the part met the requirement using soft rubber and two layers of rubber plates