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Liu, Yidong,Liu, Song,Li, Dongmei,Zhang, Nan,Peng, Lei,Ao, Jun,Song, Choong Eui,Lan, Yu,Yan, Hailong American Chemical Society 2019 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.141 No.2
<P>The development and characterization of enantioselective catalytic kinetic resolution of allylic alcohols through asymmetric isomerization with chiral BINOL derivatives-based alkoxides as bifunctional Brønsted base catalysts were described in the study. A number of chiral BINOL derivatives-based alkoxides were synthesized, and their structure-enantioselectivity correlation study in asymmetric isomerization identified a promising chiral Brønsted base catalyst, which afforded various chiral secondary allylic alcohols (ee up to 99%, <I>S</I> factor up to >200). In the mechanistic study, alkoxide species were identified as active species and the phenol group of BINOL largely affected the high reactivity and enantioselectivity via hydrogen bonding between the chiral Brønsted base catalyst and substrates. The strategy is the first successful synthesis strategy of various chiral secondary allylic alcohols through enantioselective transition-metal-free base-catalyzed isomerization. The applicability of the strategy had been demonstrated by the synthesis of the bioactive natural product (+)-veraguensin.</P> [FIG OMISSION]</BR>
Liu, Yang,Li, Fushan,Qiu, Lichun,Yang, Kaiyu,Li, Qianqian,Zheng, Xin,Hu, Hailong,Guo, Tailiang,Wu, Chaoxing,Kim, Tae Whan American Chemical Society 2019 ACS NANO Vol.13 No.2
<P>Perovskite materials have exhibited promising potential for universal applications including backlighting, color conversion, and anticounterfeiting labels fabricated using solution processes. However, owing to the tendency of those materials to have uncontrollable morphologies and to form large crystals, they cannot be utilized in discontinuous microminiaturization, which is crucial for practical optoelectronic applications. In this research, combining the effects of adding polyvinylpyrrolidone (PVP), precisely controlling the inkjet printing technique, and using a postprocessing procedure, we were able to fabricate <I>in situ</I> crystallized perovskite-PVP nanocomposite microarrays with perfect morphologies. The viscosity of the perovskite precursor increased with the addition of PVP, eliminating the outward capillary flow that induces the coffee-ring effect. In addition, because of the presence of metallic bonds with the C═O groups in PVP and the spatial confinement of such a polymer, we were able to fabricate regulated CsPbBr<SUB>3</SUB> nanocrystals capped with PVP and with a uniform size distribution. The as-printed patterns showed excellent homogeneity on a macroscale and high reproducibility on a microscale; furthermore, those patterns were invisible in the ambient environment, compatible with flexible substrates, and cost-efficient to produce, indicating that this technique holds promising potential for applications such as anticounterfeiting labels.</P> [FIG OMISSION]</BR>
Effects of Nano-Silica Particle Size on Fresh State Properties of Cement Paste
Hailong Sun,Xiuzhi Zhang,Peng Zhao,Di Liu 대한토목학회 2021 KSCE JOURNAL OF CIVIL ENGINEERING Vol.25 No.7
The rheometer was used to test the rheology of cement paste with and without nano-silica, and the fluidity and free water content were tested, the isothermal calorimetry of cement and C3S was tested and hydration products were monitored using Raman spectroscopy. A modified Bingham model was used to describe the rheological properties of the paste, and the effects of nano-silica with different particle sizes on rheological parameters including yield stress, plastic viscosity and thixotropy were derived. The results show that the fresh state properties of the cement paste vary with the particle size of nano-silica at the same dosage. The decrease in the particle size of nano-silica reduces the fluidity and free water content, but increases the yield stress and plastic viscosity. The flocculation and surface water absorption of nano-silica reduce the free water content at 5 minutes, which results in a decrease in flow diameter and an increase in yield stress. During the time evolution, the heat of hydration and Raman spectroscopy show that nano-silica with smaller particle size has higher nucleation and pozzolanic effect, that is, with the same dosage, nano-silica with small particle size provides more nucleation sites to form calcium silicate hydrate (C-S-H) seeds and to promote the hydration of C3S and the formation of C-S-H.
Oxalate formation during hydrogen peroxide-reinforced oxygen delignification
Yingying Liu,Shujuan Ge,Youming Li,Bingyun Li,Hailong Li 한국공업화학회 2018 Journal of Industrial and Engineering Chemistry Vol.58 No.-
The effects of different process parameters (alkali dosage, hydrogen peroxide dosage, temperature, reaction time, and oxygen pressure) on oxalate formation during hydrogen peroxide-reinforced oxygen delignification (OP) of Eucalyptus kraft pulp were investigated in the present study. The relationships between oxalate formation and the dosages of both alkali and peroxide were found to be almost linear. Oxalate formation could be divided into “fast” and “slow” periods, depending on the reaction time. The best selectivity for the OP process was achieved using an alkali dosage of 2.0%, a hydrogen peroxide dosage of 2.0%, a temperature of 100 °C, an oxygen pressure of 0.6 MPa and a reaction time of 60 min. Oxalate formation was also, to some extent, reduced under these conditions. These results will be very helpful in optimizing the OP process, controlling oxalate formation and improving product quality.
Performance Analysis of Wide Magnesium Alloy Foil Rolled by Multi-Pass Electric Plastic Rolling
Lipo Yang,Hailong Zhang,Gengliang Liu 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.10
Wide magnesium alloy foil is usually difficult to roll due to severe anisotropy or texture. It has become the biggest obstacle to the traditional rolling process, although it can be realized through some special methods. Low efficiency and high cost limit its application. Aimed at this problem, a multi-pass electric plastic rolling process was designed to successfully roll the magnesium alloy foil from 1.0 to 0.13 mm. According to actual test results, the anisotropy and properties of magnesium alloy foil were analyzed when the pulse current densities were adjusted. Under the same temperature as the isothermal rolling process, the pure electric effect could contribute to remarkably improving the plasticity and rollability of magnesium alloy foil. Thus, it could minimize the action of Joule heat as much as possible to avoid surface oxidation and grain growth. In addition, the size effect of magnesium alloy foil should be considered for the electric plastic rolling. Practical measured data verified that varied pulse current densities played important roles in the performances of wide magnesium alloy foil when the grain size and anisotropy were online adjusted by the synergy of electric plastic effect and reduction rate.
Paladhi, Sushovan,Liu, Yidong,Kumar, B. Senthil,Jung, Min-Jung,Park, Sang Yeon,Yan, Hailong,Song, Choong Eui THE AMERICAN CHEMICAL SOCIETY 2017 ORGANIC LETTERS Vol.19 No.12
<P>The potential of Song's chiral oligoethylene glycol's (oligoEGs) as catalysts was explored in the enantioselective protonation of trimethylsilyl enol ethers in combination with alkali metal fluoride (KF and CsF) and in the presence of a proton source Highly enantioselective protonatigns of various silyl enol ethers of alpha-substituted tetralohes were achieved, producing chiral alpha-substituted-Jetralones in full conversion and with up to 99% ee. The established protocol was successfully exiended to the synthesis of biologically relevant chiral alpha-substituted chromanone and thiothromarione derivatives.</P>
Anisotropy evolution of wide magnesium alloy foils during continuous electroplastic rolling
Lipo Yang,Hailong Zhang,Gengliang Liu 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.4
Anisotropy or brittleness poses an obstacle to the rolling of wide magnesium alloy foils, particularly those with a thickness of 1.0 mm. To address this problem, a special electroplastic rolling (EPR) process was developed to provide a better method than traditional isothermal heat treatment. Actual measured results showed that the pulse current with high energy could rapidly adjust high brittleness and severe anisotropy. This condition was helpful in the plasticity and rollability of wide magnesium alloy foils during continuous EPR process. Finally, a 0.13 mm-thick magnesium alloy foil was successfully rolled through continuous EPR processes without any intermediate annealing or reheating in the furnace. Evidently, the developed method contributed to the best matching conditions between the pulse current and deformation parameters along different directions. Therefore, EPR is a promising technology for changing the anisotropy or brittleness of wide magnesium alloy foils online.
Duan, Mengying,Liu, Yidong,Ao, Jun,Xue, Lu,Luo, Shilong,Tan, Yu,Qin, Wenling,Song, Choong Eui,Yan, Hailong American Chemical Society 2017 ORGANIC LETTERS Vol.19 No.9
<P>A chiral, fluoride-catalyzed asymmetric cascade sulfaMichael/aldol condensation reaction of 1,4-dithiane-2,5-diol and a series of alpha,beta-unsaturated ketones is described to access chiral trisubstituted tetrahydrothiophene derivatives. The target products, including the spiro tetrahydrothiophene derivatives bearing a five-, six-, and seven-membered ring, were highly functionalized and showed high ee value. This established protocol realized a highly enantioselective reaction with a catalytic amount of KF and Song's chiral oligoEG via in situ generated chiral fluoride to construct useful heterocyclic skeletons with great complexity.</P>