Toward optimization of a robust low-cost sulfonated-polyethersulfone containing layered double hydroxide for PEM fuel cells

Polyethersulphone (PES) is an aromatic thermoplastic, at low environmental impact, evaluated in this work as a promising candidate for new polymer electrolytes in the PEMFCs technology. A sulfonation procedure has been tuned in order to graft sulfonic acid groups on the polymer chains (sPES) and to make it hydrophilic. Homogeneous membranes with different polymer's sulfonation degrees (SD%) have demonstrated excellent mechanical properties and very low permeability toward methanol (important in the DMFCs), even if low proton conductivity. Nanocomposite sPES membranes were prepared by dispersion of highly hydrophilic lamellar particles such as layered double hydroxide (LDH) in the polymer. Deep investigations performed by a combination of PFG-NMR, EIS, XRD, DMA, and scanning electron microscopy have evidenced the exfoliation of the lamellae in polymer matrix. However, a certain anisotropy was evidenced both in the morphology and molecular diffusion, favored in the longitudinal direction (parallel to surface), while completely inhibited in the cross-section. This finding is most likely induced by the polymer structure, therefore particular attention must be paid to the choice of the filler and preparation of the composites. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47884.     

Dispersion characterization in layered double hydroxide/Nylon 66 nanocomposites using FIB imaging

Layered double hydroxides (LDHs), a newly emerging 2D host material, consist of cationic brucite-like layers and exchangeable interlayer anions. In this work, the morphology and dispersion of LDH particles in LDH/Nylon 66 (salt) nanocomposites has been investigated using focused ion beam (FIB) techniques, transmission electron microscopy (TEM) and X-ray diffraction (XRD). The FIB images show that LDHs are present in the polymer phase dispersed to different degrees, with partial intercalation, exfoliation, and aggregation all being observed. The most even dispersion was achieved in nanocomposites with the lowest loading (0.5 wt % LDH). Residual tactoids and agglomerates were most common in the samples made with the highest concentration of LDHs studied here (5 wt %). The dispersion observed using FIB was consistent with TEM and XRD analysis, yet this technique had significant benefits in terms of time and simplicity over these “conventional” technologies. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Preparation and flame resistance properties of revolutionary self-extinguishing epoxy nanocomposites based on layered double hydroxides

Layered double hydroxides/epoxy (LDHs/EP) nanocomposites were prepared from organo-modified LDHs, a diglycidyl ether of bisphenol A monomer (DGEBA) and amine curing agents. The organo-modified LDHs were obtained by ionic exchange of a magnesium-aluminum carbonate LDH in an acid medium. X-ray diffraction and transmission electron microscopy showed a dispersion of the layers at a nanometer scale, indicating the formation of LDH/EP nanocomposites. The thermal degradation and flame resistance properties of LDH/EP nanocomposites, montmorillonite-epoxy (MMT/EP) nanocomposites, LDH/EP microcomposites and aluminum hydroxide-epoxy microcomposites were compared by thermogravimetrical analyses, simultaneous thermal analyses, UL94 and cone calorimeter tests. Only LDH/EP nanocomposites showed self-extinguishing behavior in the horizontal UL94 test; LDH/EP microcomposites and MMT/EP nanocomposites samples burned completely showing that the unique flame resistance of LDH/EP nanocomposites is related to both the level of dispersion and the intrinsic properties of LDH clay. Furthermore, cone calorimeter revealed intumescent behavior for LDH/EP nanocomposites and a higher reduction in the peak heat release rate compared to MMT/EP nanocomposites.     

尼龙6/水滑石纳米复合材料的制备与表征

利用熔融插层复合法制备了插层型尼龙6／水滑石纳米复合材料。Ⅺ砌分析了水滑石的结构，确认成功制备出了具有典型层状结构的水滑石。利用透射电子显微镜（TEM）观察水滑石在尼龙6基体中的分散，确认制备出了插层型的纳米复合材料。对纳米复合材料的力学性能测试结果表明：加入水滑石之后，材料的屈服强度、定伸强度及拉伸模量都有明显提高，而且冲击强度基本不变。其中2号水滑石与尼龙6复合后拉伸模量与尼龙相比提高了26．8％。DSC和TGA测试结果显示，由于水滑石的存在对纳米复合材料的结晶性能和热稳定性略有影响。     

提高层状双金属氢氧化物水中吸附性能研究进展

介绍了LDH这类绿色环保、结构独特、理化性能优异的高效吸附剂,归纳了国内外科研工作者对于LDH材料在水处理方面的研究成果,分析了LDH吸附性能的影响因素并解释了污染物的吸附机理。认为吸附剂的吸附能力与自身结构和特性有关,可以通过增大比表面积和改变表面化学性质来提高吸附剂吸附性能。表面改性使LDH具有吸附专向性,提高了对特定污染物的吸附效率;改变形貌结构增大了吸附剂的比表面积和孔隙率,为LDH提供更多的吸附位点,为离子转输提供了有利条件。     

A study of tailored blank welding between mild steel sheet and zn-coated steel sheet by CO2 laser beam

Research was conducted on tailored blank welding between mild steel sheet and Zn-coated steel sheet using CO₂ laser beam. The materials used in this study were low carbon steel sheets with a thickness of 1.2 mm and Zn-coated steel sheet with the same thickness and 6.3 μm Zn coating. Experiments were conducted by applying the Taguchi method to obtain optimum conditions for the application of this tailored blank laser welding method in practical manufacturing processes. Optical microscopy, XRD, SEM and TEM analysis were performed to observe the microstructures and to determine the structures of welded zone. In addition, mechanical properties were measured by the microhardness test, tensile test and Erichsen test to evaluate the formability of the welded specimen. There was no trapped Zn in the fusion zone, and the phases of this region consisted of polygonal ferrite, quasi-polygonal ferrite, banitic ferrite and martensite. The elongation value of welded specimen was more than 80% of the value in substrate metal, and the LDH value was more than 90% of the value in substrate metal.     

聚合物/层状双羟基氧化物纳米复合材料的研究进展

层状双羟基氧化物具有独特的结构优势、尺寸优势、性能优势,与高分子材料组装可得到聚合物/LDH纳米复合材料。重点阐述了聚合物/LDH纳米复合材料制备的最新研究进展,指出了聚合物/LDH纳米复合材料发展趋势。开发高性能的,具有特殊结构和性能的聚合物/LDH纳米复合材料,是今后的研究方向。     

有机层状双氢氧化物对水体中腐殖酸的吸附及其影响因素

采用共沉淀法合成了十二烷基苯磺酸钠插层的有机镁铝层状双氢氧化物(LDH-SDBS).对合成的有机LDH-SDBS进行超声震荡,使其比表面积增大,以提高吸附能力.研究了LDH-SDBS对水中腐殖酸的去除效果.结果表明,LDH-SDBS可以有效地去除水中腐殖酸.吸附过程受LDH-SDBS的投加量、竞争性阴离子、温度、吸附时间和溶液的pH值等因素的影响.     

Amorphous FeOOH decorated hierarchy capillary-liked CoAl LDH catalysts for efficient oxygen evolution reaction

Electrocatalytic water splitting is a promising route for the generation of clean hydrogen. However, the anodic oxygen evolution reaction (OER) suffers greatly from low reaction kinetics and thereby hampers the energy efficiency of alkaline water electrolysers. In recent years, tremendous efforts have been dedicated to the pursuit of highly efficient, low cost and stable electrocatalysts for oxygen evolution reaction. Herein, an amorphous FeOOH roughened capillary-liked CoAl layered double hydroxide (LDH) catalyst grown on nickel foam (denoted as FeOOH–CoAl LDH/NF) was reported for OER electrolysis. The developed FeOOH–CoAl LDH/NF electrode shows excellent OER activity with overpotentials of 228 mV and 250 mV to deliver a current density of 50 mA cm^?2 and 100 mA cm^?2 in 1.0 M KOH solution, respectively, ranking it one of the most promising OER catalysts based on transition-metal-based LDH. This is owed to the formed capillary-liked hierarchy structure with high-porosity as well as the strong electronic interaction between FeOOH and CoAl LDH. The developed morphological engineering approach to build hierarchal porous structures together with facile amorphous FeOOH modification may be extended to other layered double hydroxide catalyst for enhanced OER activities.     

Toxicity and Metabolism of Layered Double Hydroxide Intercalated with Levodopa in a Parkinson’s Disease Model

Layered hydroxide nanoparticles are generally biocompatible, and less toxic than most inorganic nanoparticles, making them an acceptable alternative drug delivery system. Due to growing concern over animal welfare and the expense of in vivo experiments both the public and the government are interested to find alternatives to animal testing. The toxicity potential of zinc aluminum layered hydroxide (ZAL) nanocomposite containing anti-Parkinsonian agent may be determined using a PC 12 cell model. ZAL nanocomposite demonstrated a decreased cytotoxic effect when compared to levodopa on PC12 cells with more than 80% cell viability at 100 μg/mL compared to less than 20% cell viability in a direct levodopa exposure. Neither levodopa-loaded nanocomposite nor the un-intercalated nanocomposite disturbed the cytoskeletal structure of the neurogenic cells at their IC₅₀ concentration. Levodopa metabolite (HVA) released from the nanocomposite demonstrated the slow sustained and controlled release character of layered hydroxide nanoparticles unlike the burst uptake and release system shown with pure levodopa treatment.