轧制速度对AZ31镁合金管材冷轧成形的影响

轧制速度是三辊式冷轧成形过程中关键的工艺参数，决定其力学特征及温升情况。基于此，本文以冷轧AZ31镁合金管材为研究对象，通过全流程数值仿真计算，对比分析不同轧制速度在各特征变形段对等效应力、等效塑性应变及节点温度的影响规律。结果表明，等效应力、等效塑性应变及节点温度均随轧制速度的增大而增大。通过元胞自动机模型及实验等手段，探明了晶粒在轧制过程中产生连续再结晶并细化的初步组织演变规律；对比分析实验与模拟结果并结合多方面因素，得到800mm/s的轧制速度可以更好的满足工艺要求的结果，为冷轧镁合金管材轧制速度的选择提供依据。     

Study on wax precipitation characteristics of wax deposit in pipes

Wax deposit properties are a significant concern in pipeline pigging during waxy crude oil transportation. In the present work, the impacts of flow conditions and oil properties on the wax precipitation characteristics of wax deposits are investigated. A flow loop apparatus was developed to conduct wax deposition experiments using four crude oils collected from different field pipes. The differential scanning calorimetry (DSC) technique was employed to observe the wax precipitation characteristics of crude oil and wax deposit. The results show that the wax content and the wax appearance temperature (WAT) of the deposits increase with shear stress and radial temperature gradient, and decrease with radial wax molecule concentration gradient near the pipe wall. The DSC tests on the wax deposits revealed that the deposit wax content is strongly correlated to the oil wax content. Furthermore, an empirical correlation was developed to predict the wax content and the WAT of the wax deposit. Verification of the empirical correlation using the different oils indicated that the average relative error of the wax content prediction and average absolute error of WAT prediction were 13.2% and 3.6°C, respectively.     

某低品位铜铅锌多金属硫化矿选矿工艺研究

某低品位铜铅锌多金属硫化矿的原矿品位分别为Cu 0.47%、Pb 1.236%和Zn 0.891%。矿石中铜铅锌有用矿物的嵌布粒度较细且共生关系较复杂。试验着重探讨了磨矿细度、浮选捕收剂和调整剂的优化,在解决矿物有效解离的前提下,提高铜铅锌浮选分离的选择性。当原矿磨矿细度为-0.074mm占80%时,采用乙硫氮作捕收剂,石灰、硫酸锌和亚硫酸钠作调整剂,粗选获得的铜铅混合粗精矿再磨至-0.043mm占81.31%后,经两次精选获得铜铅混合精矿。铜铅混合精矿采用活性炭脱药,亚硫酸钠和CMC组合抑铅,Z200浮选铜,实现了铜铅分离。铜铅混合浮选尾矿,采用硫酸铜活化,丁基黄药作捕收剂,浮选获得锌精矿。最终浮选指标为:铜精矿的铜品位27.26%,铜回收率80.62%;铅精矿的铅品位59.35%,铅回收率85.20%;锌精矿的锌品位41.14%,锌回收率为82.74%。为该低品位铜铅锌多金属硫化矿资源的开发利用提供了可行的技术方案。     

Single copper sites dispersed on hierarchically porous carbon for improving oxygen reduction reaction towards zinc-air battery

The demand for high-performance non-precious-metal electrocatalysts to replace the noble metal-based catalysts for oxygen reduction reaction(ORR)is intensively increasing.Herein,single-atomic copper sites supported on N-doped three-dimensional hierarchically porous carbon catalyst(Cu₁/NC)was prepared by coordination pyrolysis strategy.Remarkably,the Cu₁/NC-900 catalyst not only exhibits excellent ORR performance with a half-wave potential of 0.894 V(vs.RHE)in alkaline media,outperforming those of commercial Pt/C(0.851 V)and Cu nanoparticles anchored on N-doped porous carbon(CuNPs/NC-900),but also demonstrates high stability and methanol tolerance.Moreover,the Cu₁/NC-900 based Zn-air battery exhibits higher power density,rechargeability and cyclic stability than the one based on Pt/C.Both experimental and theoretical investigations demonstrated that the excellent performance of the as-obtained Cu₁/NC-900 could be attributed to the synergistic effect between copper coordinated by three N atoms active sites and the neighbouring carbon defect,resulting in elevated Cu d-band centers of Cu atoms and facilitating intermediate desorption for ORR process.This study may lead towards the development of highly efficient non-noble metal catalysts for applications in electrochemical energy conversion.     

General Decay Synchronization and H ∞ Synchronization of Multi-weighted Coupled Reaction-diffusion Neural Networks

This paper investigates the general decay synchronization and general decay H∞ synchronization problems of multi-weighted coupled reaction-diffusion     

冷轧预变形对新型铝锂合金的时效析出与力学性能影响

采用大气熔炼铸造及热变形方法制备了Al-4.5Cu-1Li-0.7Mg-1Zn-0.3Ag-0.3Mn-0.2Zr新型铝锂合金板材。通过维氏硬度、拉伸性能、扫描电镜、透射电镜等方法，研究了固溶后不同冷轧预变形量对显微组织和力学性能影响。结果表明，时效前的冷轧预变形量有效促进了新型铝锂基体合金中T1(Al2CuLi)相的析出与均匀分布，减少了θ′(Al2Cu)相的体积分数。冷轧预变形量的增加，缩短了峰时效时间，晶界析出相由连续析出变为非连续析出，无沉淀析出区宽度变小。当冷轧预变形量为15%时，时效态合金的屈服强度与抗拉强度分别达到了668 MPa、690 MPa，延伸率保持在7.9%。     

Visible light-activated degradation of microcystin-LR by ultrathin g-C3N4 nanosheets-based heterojunction photocatalyst

Microcystins (MCs) is a harmful toxin generated by blue-green algae in water, which has seriously threatened the ecological safety of water and human body. It is urgent to develop new catalysts and techniques for the degradation of MCs. A feasible electrostatic self-assembly method was carried out to synthesize BiVO₄/g-C₃N₄ heterojunction photocatalyst with highly efficient photocatalytic ability, where BiVO₄ nanoplates with exposed {010} facets anchored to the g-C₃N₄ ultrathin nanosheets. The morphology and microstructure of the heterojunction photocatalysts were identified by XRD, SEM, TEM, XPS, and BET. The g-C₃N₄ nanosheets have huge surface area over 200 m²/g and abundant mesoporous ranging from 2-20 nm, which provides tremendous contact area for BiVO₄ nanoplates. Meanwhile, the introduction of BiVO₄ led to red-shift of the absorption spectrum of photocatalyst, which was characterized by UV-vis diffuse reflection spectroscopy (DRS). Compared with pure BiVO₄ and g-C₃N₄, the BiVO₄/g-C₃N₄ heterojunction shows a drastically enhanced photocatalytic activity in degradation of microcystin-LR (MC-LR) in water. The MC-LR could be removed within 15 minutes under the optimal ratio of BiVO₄/g-C₃N₄. The outstanding performance of the photocatalyst is attributed to synergetic effect of interface Z-scheme heterojunction and high active facets {010} of BiVO₄ nanoplates, which provides an efficient transfer pathway to separate photoinduced carriers meanwhile endows the photocatalysts with strong redox ability.     

超疏水表面在金属防护中应用的研究进展

超疏水表面由于具有独特的微纳米粗糙结构和低表面能性质,能形成空气垫物理屏障层,减小材料表面与水或其他腐蚀介质之间的接触面积,因此被广泛应用于金属的腐蚀防护。首先简单介绍了超疏水表面的相关理论,主要包括Young氏方程、Wenzel模型和Cassie-Baxter模型。然后,归纳总结了三种制备超疏水表面的有效途径:在低表面能物质上构建微纳米级粗糙结构;先构建出具有微纳米级的粗糙结构,再对表面进行低表面能修饰;一步法完成低表面能修饰和微纳米级粗糙结构的构建。在此基础上,详细地综述了常见的超疏水表面(薄膜或涂层)在金属防护中的应用。进一步介绍了通过在超疏水体系中引入缓蚀剂的方式,构建具有主动防护功能的超疏水表面,并介绍了此种超疏水表面在金属防护中的应用。最后指出了目前的超疏水表面在制备工艺以及耐久性等方面存在的问题,并对其在金属防护领域的应用前景和发展方向作出了展望。