A Non‐Fullerene Acceptor with Chlorinated Thienyl Conjugated Side Chains for High‐Performance Polymer Solar Cells via Toluene Processing

Small molecular acceptors (SMAs) BTC‐2F and BTH‐2F, based on heptacyclic benzodi(cyclopentadithiophene) electron‐donating core (CBT) with chlorinated‐thienyl conjugated and thienyl conjugated side chains, respectively, are designed and synthesized. Compared with non‐chlorine acceptor BTH‐2F, BTC‐2F exhibits slightly blue‐shifted absorption spectra, similar the lowest unoccupied molecular orbital (LUMO) (–3.91 eV), deeper highest occupied molecular orbital (HOMO) energy level and higher electron mobility than that of BTH‐2F. PM6, a wide bandgap polymer, is selected as the donor material to construct bulk heterojunction polymer solar cells processed with nonhalogenated solvent toluene. The optimized PM6:BTC‐2F‐based device presents a 12.9% power conversion efficiency (PCE), while the PCE of PM6:BTH‐2F‐based device is only 11.3%. The results suggest that it is an effective strategy to optimize the photoelectric properties of SMAs by incorporating chlorine atom into the conjugated side chains.     

1.5GHz铌腔RF超导的实验研究

北京大学重离子所自1988年开始“超导腔”课题的研究工作,经过三年不懈努力获得了重大进展,受到国内外同行与专家的好评。本文详述了此课题的实验准备工作及低温超导物理实验过程,总结了RF(射频)超导实验技术、微波及锁相测量技术、腔体的后处理技术、计算机模拟设计及计算机控制、数据获取与处理等有关工作的进展和成果。目前,1.5GHz铌腔在CW模式的低温超导实验中获得了8.6MV/m(Q_o=6.5×10~8)的加速梯度,并在2K温度时,测得Q_o=8×10~9,这些实验结果达到了当前国际上的先进水平。     

Microstructure Manipulation of Covalent Organic Frameworks (COFs)-based Membrane for Efficient Separations

Covalent organic framework(COF) membranes have exhibited great potential to become the next-generation membranes for efficient separations due to the diverse structures, ordered framework pores, tunable functionality and excellent stability. This review presents the microstructure manipulation strategies for separation performance enhancement of COF membranes in recent years. Based on the three mechanisms of molecular sieving, surface diffusion, and facilitated transport, the structural modulation methods to enhance the selectivity of COF membranes are analyzed in detail. Next, strategies of realizing ultrashort mass transfer pathways and ultralow mass transfer resistance for the permeability enhancement are elaborated. Furthermore, the framework stability in COFs, interlayer stability between COF nanosheets and interfacial stability between COF layer and substrate are discussed. Finally, we discuss the existing challenges and perspectives on the future development of COF membranes, targeting at identifying the most promising strategies and directions for the engineering of COF membranes.     

ZnO纳米管的光学性质及其对甲基橙降解的光催化活性

以十二烷基硫酸钠为模板剂采用水热法合成了ZnO纳米管,以尿素和ZnSO4为原料制备了ZnO纳米颗粒,并应用透射电镜、x射线衍射、光致发射光谱、拉曼光谱、比表面积测定、傅里叶红外光谱和紫外-可见漫反射光谱等技术对样品进行了表征.结果表明,ZnO纳米管的比表面积较大,在λ≈650nm的可见光波段ZnO纳米管开始出现吸收峰,而ZnO纳米颗粒在可见光波段几乎没有吸收.ZnO纳米管和纳米颗粒在紫外光照射下均对甲基橙有降解作用,其中ZnO纳米管的光催化活性较高.随着催化剂用量的增加和光照时间的延长,甲基橙降解率逐渐提高;甲基橙浓度的增大使甲基橙降解率降低.     

Surface cavity effect on C2H4 formation from electrochemical reduction of CO2 as studied using Cu2O cubes

Journal of Solid State Electrochemistry - Surface morphology of Cu-based catalysts is considered as an important factor affecting both activity and product selectivity of electrochemical reduction...     

The finite volume scheme preserving extremum principle for diffusion equations on polygonal meshes

We construct a new nonlinear finite volume scheme for diffusion equation on polygonal meshes and prove that the scheme satisfies the discrete extremum principle. Our scheme is locally conservative and has only cell-centered unknowns. Numerical results are presented to show how our scheme works for preserving discrete extremum principle and positivity on various distorted meshes.     

钇、钕和钐负载的MCM-41介孔材料的合成和表征

以十六烷基三甲基溴化铵(CTMAB)为模板剂,以正硅酸乙酯(TEOS)为硅源,采用水热晶化法成功合成了Y,Nd,Sm骨架负载的MCM-41介孔材料,通过XRD,N2吸附脱附、SEM,IR,TG-DTA等测试手段对其孔结构、微形貌和Y,Nd,Sm的存在状态进行了表征。XRD结果表明,合成样品具有典型的六方有序排列的MCM-41结构,Y,Nd,Sm离子可以进入介孔材料骨架。N2吸附脱附等温线表明样品具有明显的介孔特征。SEM图片表明各负载样品呈较规则的球形颗粒分布,直径约在0.10~0.15μm。样品的IR图谱在960~985cm-1区间分别出现了Si-O-Ln(Ln=Y,Sm,Nd)的特征吸收峰,证明Y,Nd,Sm存在于介孔材料的骨架中。TG-DTA结果表明,YMCM-41,NdMCM-41和SmMCM-41介孔材料中存在着两种不同的模板剂键合位,进一步证明了Y,Nd,Sm进入了介孔材料骨架。     

Effects of pyrolysis upgrading temperature on semi-coke explosibility for blast furnace injection

Journal of Thermal Analysis and Calorimetry - The purpose of this work is to understand the semi-coke explosion issues and to improve the safety in semi-coke injection. It shows that the higher...     

Experimental study on high-pressure rheology of water/crude oil emulsion in the presence of methane

The crude oil is in most cases accompanied with water and natural gas. For this reason, it is important to understand the rheology of the oil emulsion. There are already many works relating to rheology of the oil/water emulsion. However, studies on high-pressure rheology of water/crude oil emulsion in the presence of CH₄ are rare. In this work, light crude oil with characteristics of high wax content, which is typical in Northwest China, was studied. The rheology of water/crude oil emulsion in the presence of CH₄ under various conditions were fully studied. The results show that the crude oil emulsion showed obvious characteristics of non-Newtonian fluid at a lower temperature. Before water fraction reached a certain limit, the viscosity increases with the increase of water fraction, when water fraction reaches and exceeds the limit the emulsion viscosity drops with the increase of water fraction. The shear stress–shear rate curves become similar as the increase of temperature, indicating the decreasing effect of temperature on the relation between shear stress and shear rate. When the pressure reaches 8 MPa, the shear stress measured with CH₄ in the system surpasses that measured without CH₄. At higher pressure, CH₄ shows obvious influence on the rheology.     

加氢处理催化剂的制备和表征Ⅰ. MoNiP/Al2O3催化剂的制备及助剂的作用

采用专利方法制备出一种新型的γ-Al