Modulation of the thermal transport of micro-structured materials from 3D printing

It is desirable to fabricate materials with adjustable physical properties that can be used in different industrial applications.Since the property of a material is highly dependent on its inner structure,the understanding of structure–property correlation is critical to the design of engineering materials.3D printing appears as a mature method to effectively produce micro-structured materials.In this work,we created different stainless-steel microstructures by adjusting the speed of 3D printing and studied the relationship between thermal property and printing speed.Our microstructure study demonstrates that highly porous structures appear at higher speeds,and there is a nearly linear relationship between porosity and printing speed.The thermal conductivity of samples fabricated by different printing speeds is characterized.Then,the correlation between porosity,thermal conductivity,and scanning speed is established.Based on this correlation,the thermal conductivity of a sample can be predicted from its printing speed.We fabricated a new sample at a different speed,and the thermal conductivity measurement agrees well with the value predicted from the correlation.To explore thermal transport physics,the effects of pore structure and temperature on the thermal performance of the printed block are also studied.Our work demonstrates that the combination of the 3D printing technique and the printing speed control can regulate the thermophysical properties of materials.

Enantioselective epoxidation of olefins with hydrogen peroxide catalyzed by bioinspired aminopyridine manganese complexes derived from L-proline

Three chiral aminopyridine ligands derived from L-proline were prepared. Careful evaluation of the corresponding aminopyridine manganese complexes in asymmetric epoxidation of olefins revealed a broad substrate scope in the presence of 0.2 mol% manganese complex and 0.5 equiv. 2,2-dimethylbutyric acid, with aqueous hydrogen peroxide as an oxidant. A variety of olefins including styrenes, chromenes, and cinnamamides were transformed successfully into the target epoxides with moderate to excellent enantioselectivity（yield up to 95%, ee up to 99%）.

Effects of Mouse Thatched on Soil Temperature, Yield and Quality in Apple Orchard

[Objectives]This study was conducted to study the effect of mouse thatched on soil temperature,yield and quality in orchards.[Methods]The response of orchard soil,yield and quality to sod culture was studied by comparisons of grassing for two years,three years and clean cultivation.[Results]In April,the soil temperature in mouse thatched area was higher than that in clean cultivation area,and the temperature in the three years of sward was the highest.From May to July,the temperature in mouse thatched area was lower than that in clean cultivation area,and the temperature was lowest in the three years of sward.At the same time,the fruit yield and quality were improved.Averaged the two years,the yield of apple increased by 12%,and the contents of sugar,soluble solids and vitamin C and the firmness of the fruit were increased,and the total acid content was decreased by planting mouse thatched.[Conclusions]Adjusting soil temperature in orchards by planting grass achieved the effects of promoting the activity of microorganisms,facilitating the growth of root system,increasing the yield and improving the quality.

手性Mn(Ⅲ)-Salen配合物催化的2-芳基环烷醇的高对映选择性氧化动力学拆分

本文发展了一种通过氧化动力学拆分获得光学活性2-芳基环烷醇的方法:该体系以N-溴代丁二酰亚胺为氧化剂,简单易得的手性Mn(Ⅲ)-salen配合物(0.5 mol%)为催化剂.该方法底物适用性广、具有高度的立体控制且易于进行克级规模的反应,为光学活性2-芳基环烷醇类化合物的合成提供了一种高效、实用的方法.

Influence of conformational change of chain unit on the intrinsic negative thermal expansion of polymers

Negative thermal expansion(NTE) behavior has roused wide interest for the control of thermomechanical properties of functional materials.Although NTE behaviors have been found in kinds of compounds,it remains challenging for polymers to achieve intrinsic NTE property.In this work,we systematically studied the conformational change of dibenzocyclooctadiene(DBCOD) derivatives between chair(C) and twist-boat(TB) forms based on density-functional theo ry(DFT) calculations,and found clear evidence of the relationship between the structure of DBCOD units and the thermal contraction behavior of the related polymers.In order to obtain the polymer with NTE property,two conditions should be met for the thermal contracting DBCOD related units as follows:(i) the TB conformation can turn into C conformation as the temperature increases,and(ii) the volume of C conformation is smaller than that of TB conformation.This rule should offer a guidance to exploration of the new intrinsic NTE polymers in the future.