多壁碳纳米管-炭复合泡沫材料的制备和吸附性能

通过在聚氨酯泡沫模板中沉积多壁碳纳米管，用炭的预制体酚醛树酯将碳纳米管粘接固定在一起，经过高温碳化过程制备了碳纳米管-炭复合泡沫材料。红外光谱结果表明利用浓硫酸和浓硝酸的混合溶液处理可以使复合泡沫表面活化形成羧基和羟基，从而使复合泡沫具备较强的分子吸附能力。扫描电镜和氮吸附实验表明这种复合泡沫同时具备大孔和介孔，大孔能够满足流体自由流动的通畅性，介孔可以满足中分子的吸附需要。对标定物维生素B12的吸附实验证明这种复合泡沫对中分子量的生化分子具有有效的吸附能力。这种宏观尺寸的泡沫材料与传统的颗粒状活性炭相比具有简化工艺，提高吸附效率的应用潜力。     

Time‐resolved in situ tomography for the analysis of evolving metal‐foam granulates

An experimental setup has been developed that allows for capturing up to 25 tomograms s^?1 using the white X‐ray beam at the experimental station EDDI of BESSY II, Berlin, Germany. The key points are the use of a newly developed, precise and fast rotation stage, a very efficient scintillator and a fast CMOS camera. As a first application, the foaming of aluminium alloy granules at 923 K was investigated in situ. Formation and growth of bubbles in the liquid material were observed and found to be influenced by the limited thermal conductivity in the bulk granules. Changes that took place between two tomographic frames separated in time by 39 ms could be detected and analysed quantitatively.     

Coconut coir dust extract: a novel eco-friendly corrosion inhibitor for Al in HCl solutions

Abstract

Corrosion inhibition of aluminium in 1 M HCl by coconut coir dust extract (CCDE) was studied using weight loss and hydrogen evolution techniques at 30 and 60°C. It was found that the studied extract exhibits a very good performance as inhibitor for aluminium corrosion in 1 M HCl. Results show that the inhibition efficiency increases with increasing temperature and concentration of the extract. Inhibitive effect was afforded by adsorption of the extracts' components which was found to accord with Langmuir adsorption isotherm. Inhibition mechanism is deduced from the temperature dependence of the inhibition efficiency and was further corroborated by the values of activation parameters obtained from the experimental data.     

Stereodivergent Carbamate Synthesis by Selective in Situ Trapping of Organic Carbonate Intermediates

Trans carbamates have been prepared in a diastereoselective approach by a judicious one‐pot combination of organic carbonates, prepared in situ, and suitable amine reagents under appropriate reaction conditions. This unprecedented approach allows for stereodivergence from a single oxirane substrate with easy access to both cis and trans carbamate isomers with high stereoselectivity (>19:1 d.r.). Key to the control of the diastereoselective nature of the conversions that lead to the trans carbamates is the in situ formation of trans‐configured oligo/polycarbonates through Al catalysis, which provides the targeted products after aminolysis. The present results demonstrate the valorization of a renewable carbon‐based reagent (CO₂) into new valuable scaffolds and an unusual stereocontrol exerted through carbonate intermediates. A series of control experiments support the proposed mechanistic rationale towards the trans carbamate products, which is based on the trapping of an in situ formed trans‐configured oligo/polycarbonate.     

A Novel Reactivity of Phosphanylalumane (>P−Al<): Reversible Addition of a Saturated Interelement Bond to Olefins

The reversible addition of olefins to a phosphanylalumane, P−Al single-bond species, was investigated. The P−Al bond added to ethylene and relatively small terminal alkenes (propylene and hex-1-ene) at room temperature to give the corresponding alkene adducts. Heating the terminal alkene adducts released the corresponding alkenes and regenerated the P−Al bond, but no release of ethylene was observed even under vacuum conditions. The reactivity of ethylene adduct as a new saturated C₂ vicinal P/Al-based FLP was also investigated. The ethylene adduct was found to undergo complexation with nitriles to give the corresponding nitrile adducts to the Al center, which retained the ethylene tether as in the case of the corresponding P/B-based FLP. However, the reactivity of ethylene toward CO₂ and benzaldehyde differed from that of the P/B system giving the corresponding adducts.     

A HF Loaded Lewis-Acidic Aluminium Chlorofluoride for Hydrofluorination Reactions

The very strong Lewis acid aluminium chlorofluoride (ACF) was loaded with anhydrous HF. The interaction between the surface of the catalyst and HF was investigated using a variety of characterization methods, which revealed the formation of polyfluorides. Moreover, the reactivity of the HF-loaded ACF towards the hydrofluorination of alkynes was studied.     

镓铟锡液滴撞击泡沫金属表面的运动学特性研究

常温下为液态的镓铟锡合金以其优异的导热性能在具有特殊要求的传热领域有着重要的应用价值,与传统流动介质相比较大的表面张力使得其产生的流动现象必有所区别.本文研究镓铟锡所形成的液滴撞击泡沫金属表面后所产生的铺展、回缩及回弹现象.采用高速相机拍摄液滴投影轮廓随液滴运动的变化过程,并通过图像处理获得不同撞击速度、底板表面孔径下的液滴铺展系数、中心位置轮廓高度以及液滴回弹后在空中的振动特性.研究结果表明:具有较高表面张力的镓铟锡液滴的铺展系数随无量纲时间的变化在铺展初始阶段仍满足常规流体的1/2次幂关系,只在铺展后期与底板的无量纲孔径有关系;液滴的最大铺展系数在较小无量纲孔径底板大于在光滑镍板,且随底板无量纲孔径增大而逐渐减小;在回弹过程,由于底板孔隙结构的存在使得液滴回弹后在空中的振动呈现3种形态:规则的横向和纵向振动、带旋转的横向和纵向振动以及旋转振动;最后,通过对振动频率的拟合和分析,进一步拓展了传统振动频率理论公式在非规则振动过程预测中的应用.      

Disordered kalsilite KAlSiO4

The X‐ray powder diffraction pattern that corresponds to the disordered state of kalsilite (potassium aluminium orthosilicate), KAlSiO₄, is investigated. The directionality of (Al,Si)O₄ tetrahedra within single six‐membered tetrahedral ring building units (S6R) could not be defined. With equal probability for the directionality of each tetrahedra within one S6R [free apex pointing up (U) or down (D)], an undefined sequence of U and D directionalities is needed to describe the S6R building units. The extinction conditions of disordered kalsilite are also different compared to ordered kalsilite within the space group P6₃. In disordered kalsilite, h0l and hhl reflections with l = 2n + 1 are systematically absent.