Chlorine-free emission disposal of spent acid etchant in a three-compartment ceramic membrane reactor

Electrochemical technologies for the on-site treatment of spent acid etchant have received great attention due their ease of operation and economic benefits. On the other hand, a large amount of Cl₂ is generated during the electrolysis process, which leads to potential environmental risks. In the present work, a novel threecompartment ceramic membrane flow reactor, including a cathode chamber, an anode chamber, and a gas absorption chamber was developed. The three chambers were divided by an Al₂O₃ ceramic membrane and a breathable hydrophobic anode diffusion electrode (ADE). The Cl₂ evolution onset potential of the ADE was increased to 1.19 V from 1.05 V of the graphite felt, effectively inhibiting the chlorine evolution reaction (CER). The anode-generated Cl₂ diffused into the gas absorption chamber through the ADE and was eventually consumed by the H₂O₂ adsorbent. Cu could be recovered without emitting chlorine due to the special structure of reactor. The current efficiency of copper precipitation and cathode reduction from Cu²⁺ to Cu⁺ reached 97.7% at a working current of 150 mA. These results indicated that the novel membrane reactor had high potential for application in the copper recovery industry.     

高熵合金AlCrTaTiZrRu/(AlCrTaTiZrRu)N0.7扩散阻挡层的制备与性能研究

目的 验证15 nm厚度AlCrTaTiZrRu/(AlCrTaTiZrRu)N0.7的势垒层热稳定性和扩散阻挡性能。方法 采用直流磁控溅射技术在n型Si(111)基片上真空溅射沉积15 nm的AlCrTaTiZrRu(3 nm)/(AlCrTaTiZrRu)N0.7 (12 nm)双层阻挡层，随后在双层AlCrTaTiZrRu/(AlCrTaTiZrRu)N0.7薄膜的顶部沉积50 nm厚的Cu膜，最终制得Cu/AlCrTaTiZrRu/(AlCrTaTiZrRu)N0.7/Si复合薄膜试样。将样品在真空退火炉中分别进行600~900 ℃高温退火30 min，以模拟最恶劣的应用环境。用场发射扫描电镜(FE-SEM)、X射线衍射仪(XRD)、能谱分析仪(EDS)、四探针电阻测试仪(FPP)以及原子力显微镜(AFM)对试样的表面形貌、物相组成、化学成分、方块电阻和粗糙度进行表征分析。结果 沉积态AlCrTaTiZrRu/(AlCrTaTiZrRu)N0.7薄膜呈现非晶结构，与Cu膜和Si衬底的结合良好。在800 ℃退火后，Cu/AlCrTaTiZrRu/(AlCrTaTiZrRu)N0.7/Si薄膜系统结构完整，膜层结构界面之间未出现分层现象，表面Cu颗粒团聚现象加剧，Si衬底和Cu膜表面未发现Cu-Si化合物生成，薄膜方阻保持在较低的0.070 ?/sq;900 ℃退火后，薄膜系统未出现层间分离和空洞现象，Cu膜表面形成孤立的大颗粒Cu-Si化合物，薄膜电阻率大幅上升。结论AlCrTaTiZrRu/(AlCrTaTiZrRu)N0.7双层结构在800 ℃退火后仍能有效抑制Cu与Si相互扩散，其非晶结构增强了Cu/HEA/HEAN0.7/Si体系的热稳定性和扩散阻挡性。     

Characterization of the structure and diffusion behavior of calcium alginate gel beads

A simple and novel method using gel shrinkage to indirectly characterize the structure of calcium alginate gel (CAG) beads during the calcium alginate gelation process was presented in this study. The effect of preparation process parameters (gelling cations, bead diameter, and alginate M _w and concentration) on the structure of the CAG bead formation process was thoroughly investigated. It was found that (a) the concentration of the Na⁺ and Ca²⁺ ion in gel bath was found to be the determining factor in the gel structure formation process by regulating the dissociation of alginate and the complexation of the calcium; (b) Na⁺ acts as a competitor with calcium and a screen in the electrostatic repulsion; (c) the effect of beads size below 700 μm on the structure of CAG beads can be neglected; and (d) the sodium alginate concentration has no significant effect on the gel formation process. Furthermore, the diffusion of bovine serum albumin (BSA) was controlled by the density of CAG bead. Consequently, a faster diffusion rate of BSA within the looser structure of beads can be observed. These results are keys to understanding the behavior and performance of beads in their utilization medium. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48923.     

方腔内耦合传热传质非对称流动数值模拟

对带有质热源的方腔内流体传热传质进行数值研究。针对不同Ra、Nc、Sr和Df，探究对称方腔内流体传热传质的分岔特性。结果表明：存在临界Ra_c使流体流动形态发生转变，当Ra<Ra_c时，流体流线、温度场和浓度场对称分布；当Ra>Ra_c时，流体发生偏斜。增大浮升力，流体更易发生分岔现象。增强Soret和Dufour效应可增强传热对称性并增大流体发生分岔的临界Rayleigh数。     

中锰Q&P钢连续退火过程碳元素分配行为

采用扫描电镜、X射线衍射等研究了连续退火工艺中退火、淬火和配分等关键过程参数对中锰Q&P钢碳元素分配行为的影响,并分析了相应工艺条件下残留奥氏体量与碳含量的关系。结果表明:两相区退火温度的提高会导致奥氏体中的碳含量下降,微观组织表现为奥氏体含量增加,渗碳体量减少;退火时间10~60 s时,随着退火时间的延长,奥氏体含量和碳含量急剧增加,60 s后基本保持稳定;试验条件下淬火温度对残留奥氏体及碳含量的影响不显著;配分温度350~500℃时,随着配分温度的提高,奥氏体含量和碳含量呈现先增加后减小的趋势,配分温度450℃时均达到最大值;延长配分时间,残留奥氏体含量呈现先减少后增大再减少的趋势,残留奥氏体中的碳含量先减小后增加。     

Content and diffusion of water and gases in MgAl2O4 spinel crystals synthesized to produce ceramics

Content, evolution and diffusion characteristics of water and gases in fine-crystalline spinel MgAl₂O₄ were studied by kinetic thermodesoption mass spectrometry. Water is the main volatile component by quantity in the spinel structure. From the spinel crystals with an average size of 0.52 μm, water is released in vacuum in three temperature ranges: at 100–200 °C due to desorption from micropores, at 300–600 °C due to near-surface dehydroxylation and at 500–800 °C due to diffusion of water from the crystal bulk. The content of structural water, diffusively released from the crystals, is about 3000 ppm. The coefficients and activation energy of diffusion of water from spinel crystals in the range 500–700 °C were calculated. This allows us to estimate at any temperature the degassing time of the spinel with a certain degree of dispersion and ceramics made of it, and thereby promote the production of high-quality ceramics.     

Boundary control and estimation of reaction–diffusion equations on the sphere under revolution symmetry conditions

ABSTRACT

Recently, the problem of designing boundary controllers and observers for unstable linear constant-coefficient reaction–diffusion equation on N-balls has been solved by means of the backstepping method. However, the extension of these results to spatially varying coefficients is far from trivial. This work deals with radially varying reaction coefficients under revolution symmetry conditions on a sphere (the three-dimensional case). Under these conditions, the equations become singular in the radius. When applying the backstepping method, a similar type of singularity appears in the backstepping control and observer kernel equations. However, with a simple scaling transformation, we are able to reduce the singular equation to a regular equation, which turns out to be the same kernel equations appearing when using the one-dimensional backstepping method. In addition, the scaling transformation allows us to prove stability in the H ¹ space.     

A novel constitutive stress-strain law for compressive deformation of the gas diffusion layer

Substantial compressive deformation occurs in the gas diffusion layer (GDL) under the pressure applied during the fuel cell assembly. The GDL deformation has a direct impact on the efficiency and performance of the fuel cell since it leads to the alteration of the GDL microstructure and porosity. This makes the accurate characterization of the GDL compressive behavior crucial for analyzing the fuel cell performance and its optimal design. In this paper, analytical, experimental, and numerical methods have been employed to comprehensively study the constitutive law of the GDL under compression. Starting from the recently developed stress-density relations, the constitutive stress-strain equations are derived for the GDL and the relation between the stress-density and stress-strain laws are revealed. Experimental compression tests have been performed on GDL samples and the capability of the proposed constitutive law in capturing the real behavior of the material has been proved. It has been observed that the simplifying assumption of constant zero Poisson's ratio in the through-plane direction made in many previous studies cannot accurately represent the GDL material behavior and a modification is proposed. The developed constitutive law has been successfully implemented in a finite element model of the GDL-bipolar plate assembly in the fuel cell structure and the variations of the GDL porosity, density, and through-plane Young's modulus and Poisson's ratio have been investigated for different vertical displacements of the bipolar plate.     

扩散时间对W在TiAl合金中扩散行为的影响

通过光学显微镜、扫描电镜和硬度测试等分析手段研究了在1250 ℃下扩散保温不同时间对W元素在TiAl合金中扩散行为的影响。结果表明:试样在1250 ℃下进行扩散不同时间后,渗层界面处连接良好,可观察到明显的冶金结合。扩散层厚度随扩散时间的延长而增加,扩散4 h后可得到约15 μm厚的渗层,扩散24 h后可得到约45 μm厚的渗层,此外较长的扩散时间(24 h)可显著改善界面处的裂纹和气孔等缺陷。W在TiAl合金中的扩散机制主要为置换和空位扩散,且W和Ti的原子半径和热膨胀系数等存在差异,使得晶格畸变的出现并进一步阻碍了W元素的扩散。显微硬度试验结果表明W在TiAl合金中进行扩散,可以增强TiAl合金的硬度,且硬度值随W含量的增大而增大。     

工艺参数对6061-T6铝合金真空扩散焊接接头形貌和性能的影响

在不同工艺参数下对化学清洗去除表面氧化膜的6061-T6铝合金进行真空扩散焊接,研究了焊接温度(500~560℃)、焊接压力(1.0~5.0MPa)和保温时间(0.5~3h)对焊接接头界面形貌和剪切强度的影响,得到了优化工艺参数。结果表明:随着焊接温度的升高、焊接压力的增大和保温时间的延长,接头焊缝变窄并最终消失,剪切强度和焊合率增大;但当保温时间延长到3h时,焊缝附近晶粒发生粗化,导致剪切强度降低,且接头发生较大变形;不同工艺参数下接头的剪切断裂形式均为脆性断裂;较优的真空扩散焊接工艺参数为焊接温度540℃、保温时间2h、焊接压力4.0MPa。