Design and optimization of ceramic membrane structure: From the perspective of flux matching between support and membrane

The support flux was first investigated as a separate influencing factor for its effect on performances of ceramic filtration membranes. Three pre-membranes were prepared by tape-casting and then transfer-coated to supports to form dual-layer ceramic membranes after sintering. Experiments demonstrated that membrane layers with almost the same properties were obtained despite the huge difference in support flux. When the support flux increases from 3.120 to 97.53 m³m^?2h^?1, the flux of these three membrane series have increased by 75%, 186% and 228%, respectively. Experimental rules can provide structural design and evaluation from the perspective of permeability. The limit membrane flux of a certain system was derived according to the resistance distribution law of internal membrane structure and the Darcy's theorem. On this basis, a method for designing support flux was proposed. Furthermore, we present a criterion to quickly and easily evaluate the match between the support and the top layer, which is the ratio of membrane resistance to total resistance. Finally, the filtration resistance of penetration caused by suction of membrane particles into the support was measured for the first time, taking the advantage of the transfer-coating method that inherently free of penetration. Our works are expected to deepen the understanding of the ceramic membrane structure and provided guidance for its rational design and optimization.     

Synthesis of CuTi-LDH supported on g-C3N4 for electrochemical and photoelectrochemical oxygen evolution reactions

A nanocomposite CuTi layered double hydroxide (LDH) supported on g-C₃N₄ (15 wt% of g-C₃N₄) is facilely synthesized by hydrothermal method. There are electrostatic interactions between positive layers of CuTi-LDH and negatively charged inner g-C₃N₄ sheets. The nanocomposite and its precursors are characterized through various analytical techniques, which affirmed the presence of both g-C₃N₄ and CuTi-LDH characteristic features. The pore-enriched hybrid geometry of CuTi-LDH@g-C₃N₄ with high specific surface area (146 m²/g), and suitable band gap of 2.46 eV enables the nanocomposite to act as both an electrocatalyst and photoelectrocatalyst for oxygen evolution reaction (OER). Both the electrochemical and photoelectrochemical studies are done using 1 M KOH (pH = 13.6) with applied potential of ?0.2 V to 1.5 V vs. Ag/AgCl. The onset potential of CuTi-LDH@g-C₃N₄ for OER appears at η = 0.36 V in dark and η = 0.32 V under visible light illumination of 30 min. Also, Mott-Schottky analysis shows n-type semiconductor behaviour for CuTi-LDH@g-C₃N₄ and its precursors. The photoelectrochemical water oxidation proceeds by charge transfer across a Type II heterojunction formed between the CuTi-LDH and g-C₃N₄ materials.     

Layered Birnessite Cathode with a Displacement/Intercalation Mechanism for High-Performance Aqueous Zinc-Ion Batteries

Mn-based rechargeable aqueous zinc-ion batteries(ZIBs)are highly promising because of their high operating voltages,attractive energy densities,and eco-friendliness.However,the electrochemical performances of Mn-based cathodes usually suffer from their serious structure transformation upon charge/discharge cycling.Herein,we report a layered sodium-ion/crystal water co-intercalated Birnessite cathode with the formula of Na0.55Mn2O4·0.57H2O(NMOH)for high-performance aqueous ZIBs.A displacement/intercalation electrochemical mechanism was confirmed in the Mn-based cathode for the first time.Na+and crystal water enlarge the interlayer distance to enhance the insertion of Zn^2+,and some sodium ions are replaced with Zn^2+ in the first cycle to further stabilize the layered structure for subsequent reversible Zn^2+/H^+ insertion/extraction,resulting in exceptional specific capacities and satisfactory structural stabilities.Additionally,a pseudo-capacitance derived from the surface-adsorbed Na^+ also contributes to the electrochemical performances.The NMOH cathode not only delivers high reversible capacities of 389.8 and 87.1 mA h g^−1 at current densities of 200 and 1500 mA g^−1,respectively,but also maintains a good long-cycling performance of 201.6 mA h g^−1 at a high current density of 500 mA g^−1 after 400 cycles,which makes the NMOH cathode competitive for practical applications.     

热稳定处理时间对TNM合金糊状区组织的影响

利用真空非自耗电弧炉制备了TNM(Ti-44Al-4Nb-1Mo-0.1B at.%)合金锭,研究其铸态组织形貌,并利用Bridgeman定向凝固装置对TNM合金进行热稳定处理实验,分析热稳定处理时间对合金定向凝固糊状区的影响。实验结果显示,其铸态组织是以(α₂+γ)片层团为主体,网络状B2相、细小的γ相及硼化物分布于片层团间的近片层组织。热稳定处理时,热稳定时间越长、TNM合金固/液界面越平整,界面前沿温度场和溶质场趋向均匀,但从减少坩埚对熔体的污染的角度考虑,热稳定处理时间不宜过长,30~60 min的热稳定时间即可提供平整的定向凝固启动界面。 热稳定处理影响着TNM合金固/液界面附近固液两相中Al元素的分布,进而影响硼化物的分布。     

壳牌气化炉激冷口盘管损坏原因分析及改进

简要介绍壳牌气化炉结构及工艺流程、激冷口结构及存在问题;分析激冷口盘管损坏原因及如何避免;检修优化及取得的效果。     

Solubility parameters and solvent affinities for polycaprolactone: A comparison of methods

Intrinsic viscosity measurements were used in combination with the functional solubility parameter (FSP) and Hansen solubility parameter (HSP) fitting methods to determine the solubility parameters (SPs) of polycaprolactone (PCL). Despite using only eight solvents, a simple similarity criteria approach showed that the HSPs and FSPs were good predictors of the relative solvent-PCL affinity compared to HSPs available in the literature and SPs calculated using additive group contribution methods. Three complementary computational methodologies—Conductor-like Screening MOdel for Real Solvents (COSMO-RS), partial solvation parameters (PSPs), and a thermodynamic quantitative structure–property relationship (QSPR) approach—were used to substantiate the relative solvent–PCL affinities revealed by the intrinsic viscosity measurements. The solvent affinities predicted by all three techniques were in good agreement with the trend observed in the experimental intrinsic viscosity data, but the COSMO-RS activity coefficients, ln(γ_PCL), were slightly superior to the PSP and thermodynamic QSPR methods, particularly when incorporating the Elbro free-volume combinatorial correction in the COSMO-RS calculations. As part of this study, the FSP fitting algorithm was modified to obtain the PSPs for PCL in terms of the intrinsic viscosity data, thereby, presenting a promising new way to calculate the PSPs of polymers from empirical solubility and solvent affinity data. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48908.     

模具流道环流协同LDPE/HDPE吹塑薄膜结构性能研究

通过新型的旋转芯棒薄膜吹塑设备制备了低密度聚乙烯(LDPE)/高密度聚乙烯(HDPE)复合薄膜,并研究了该设备模具流道环流协同作用对吹塑聚乙烯薄膜结构和性能的影响。结果表明,制备的聚乙烯薄膜呈现一种互锁片晶结构;芯棒转速的提高对聚乙烯薄膜样品的结晶度、片晶厚度也有一定增益作用,使得结晶更完善;聚乙烯薄膜的拉伸性能和撕裂性能随芯棒转速提高都有所提升,尤其是横向力学性能,横向拉伸性能最大提升幅度为25.75%,横向撕裂性能最大提升幅度为27.64%;同时,该技术实现了在不影响聚乙烯薄膜的纵向热收缩率的情况下,大幅提高其横向热收缩率,提升幅度可达128.41%。     

线上线下混合模式的实验课程改革——以数据结构课程为例

该文以数据结构课程为例,从课程性质和内容进行介绍,利用线上线下混合式教学,对实验实施改革。以数据分析作为基础进行方法总结,对实验课程内容进行全方位的改革和实施。     

Influence of interfaces roughness on elastic properties of layered media

We present a numerical study of the effect of the interfaces’ roughness on layered media’s upscaled elastic parameters. First, we consider a layered model with two types of elastic materials, assuming that the interfaces are not flat but rough, and apply the numerical upscaling technique to estimate the effective elastic properties of such models. After that, we apply a downscaling technique to reconstruct a layered media with flat interfaces but with uncertainties in elastic moduli of the layers. Next, we compute the covariance of the elements of the reconstructed stiffness matrix and prove that the logarithm of this matrix is linearly related to the logarithms of the standard deviation and the correlation length of the interfaces of the original problem. Finally, we use generated dataset to estimate covariance matrices of the stiffness matrix for arbitrary interface roughnesses.     

Effect of formic-acid-to-acetic-acid ratio on the structure and spinnability of aqueous aluminium sol of alumina fibre

The structure and spinnability of sol are essential for obtaining high-performance continuous alumina-based fibres. Herein, the surface electrostatic potential analysis and conventional experimental methods (X-ray diffraction, Fourier-transform infrared spectroscopy, ²⁷Al nuclear magnetic resonance solution spectra and rheological methods) were combined to investigate and discuss the relationship between the structure and spinnability of aluminium carboxylate sols with different formic-acid-to-acetic-acid molar ratios. The results showed that the aluminium carboxylate sol structure changed with the formic-acid-to-acetic-acid molar ratio and greatly affected the sol's spinnability. The tetramer (AlO6 oligomer) products comprising two effective active carboxylate groups in the sol increased with the formic acid content, which helped form linear long-chain polymers. However, excess formic acid content led to a large increase of AlO6 monomer products that were unable to form linear long-chain polymers, which decreased the sol's spinnability. When the formic-acid-to-acetic-acid molar ratio was 1.15:0.85, the sol containing more AlO6 oligomer products had the best spinnability. Furthermore, α-Al₂O₃ ceramic fibres with good morphology, small grains and uniform diameter distribution were obtained after calcination at 1200 °C.