热复合土工膜拉伸、抗渗性能的影响因素分析

非织造复合土工膜的主要性能指标为拉伸力学性能指标和抗静水压力指标 ,其影响因素复杂。从材料的拉伸破坏和水渗透破坏机理入手 ,对这些影响因素进行分析和研究 ,并对有关问题提出解决的办法和建议。     

Influence of doping level in Yttria-Stabilised-Zirconia (YSZ) based-fillers as degradation inhibitors for proton exchange membranes fuel cells (PEMFCs) in drastic conditions

Yttria-Stabilized-Zirconia fillers with different Y₂O₃ loadings are used to prepare composite Nafion membranes for PEMFCs. XRD and BET demonstrate the formation of a c-ZrO₂ mesoporous structure. SEM reveals a size reduction of the agglomerates increasing the ZrO₂ doping level. A good mechanical resistance, no variation into the water retention, swelling restraint and an increased Ion Exchange Capacity (IEC) of the membranes are found respect to reference membrane, above all for highly doped membranes, indicating an acidic properties enhancement. Proton conductivity (PC) at 100%RH (80–100 °C) is unchanged for composite membranes compared to reference. At 75%RH, PC is positively affected by the highest YSZ loadings. Fenton's test on membranes evidences a higher oxidative chemical stability for composite membranes. This improved stability is confirmed by accelerated stress test in drastic conditions: composite highly doped membranes work for more than 110 cycles with a good performance and lower H₂-crossover against 95 cycles and higher H₂-crossover than reference membrane.     

Review: Enhancement of composite anode materials for low-temperature solid oxide fuels

Solid oxide fuel cell (SOFC) technology is attractive for its high-energy efficiency and expanded fuel flexibility. It is also more environmentally benign than conventional power generation systems. Recently, increasing attention has been paid to intermediate-to-low-temperature solid oxide fuel cells, which operating at 400–800 °C. Reducing its operating temperature can render SOFC more competitive with other types of fuel cells and portable energy storage system (EES) over a range of applications (eg: transportation, portable, stationary) and more conducive for commercialization. The high-performance composite anode requirements for low operating temperature (400–600 °C) demand microstructural and chemical stability, high electronic conductivity, and good electrochemical performance. The current high-temperature anode, Ni-YSZ (nickel-yttria stabilized zirconia) is generally reported with high interfacial resistance at reduced temperatures. This review highlights several potential composite anode materials (Ni-based and Ni-free) that have been developed for low-temperature SOFCs within the past 10 years. This literature survey shows that most of these anodes still exhibit relatively high polarization resistance. Focus is also given on reducing polarization resistance to maintain the cell power density. In literature, common approaches that have been adopted to enhance the performance of anodes are (i) selecting high-performance electrolyte, (ii) exploiting nanopowder properties, and (iii) adding noble metals as electrocatalysts.     

Application of a deep eutectic solvent to prepare nanocrystalline Ni and Ni/TiO2 coatings as electrocatalysts for the hydrogen evolution reaction

The paper reports the electrochemical deposition of nanocrystalline nickel and composite nickel-titania films as effective electrocatalysts for the hydrogen evolution reaction. To produce the composite Ni/TiO₂ electrodeposits, a plating bath based on a deep eutectic solvent, a novel kind of ionic liquids, was used for the first time. The electrolyte contained ethaline (a eutectic mixture of choline chloride and ethylene glycol), 1 M NiCl₂⋅6H₂O and the addition of extra water (3, 6, 9 mol dm⁻³). Titania dispersed phase was introduced into the electrolyte as nanopowder Degussa P 25 (0–10 g dm⁻³). It was shown that the introduction of extra water to the plating bath allowed appreciably increasing the content of TiO₂ phase in the coating (from ca. 2 to 10 wt%). The effects of electrolysis conditions on the TiO₂ content in the coatings, surface morphology and microstructure were determined. The results of voltammetry measurements showed that the Ni and composite Ni/TiO₂ coatings electrodeposited from the plating electrolyte based on a deep eutectic solvent exhibit improved electrocatalytic properties towards the hydrogen evolution reaction as compared with deposits obtained from commonly used aqueous electrolytes. The mechanism of the hydrogen evolution reaction on the Ni and composite Ni/TiO₂ coatings is a combination of Volmer-Heyrovsky reactions. The introduction of TiO₂ particles into the nickel matrix results in the acceleration of the hydrogen evolution reaction. An improved catalytic activity of Ni/TiO₂ composites towards the hydrogen evolution reaction can be associated with the presence of titanium-containing redox couples on the surface.     

Quality characteristics of biscuits prepared from finger millet seed coat based composite flour

Finger millet seed coat is an edible material and contains good proportion of dietary fibre, minerals and phytochemicals. The seed coat matter (SCM) forms a by-product of millet milling, malting and decortication industries and can be utilised as composite flour in biscuit preparation. The SCM from native, malted and hydrothermally treated millet contained 9.5–12% protein, 2.6–3.7% fat and 40–48% dietary fibre, besides 3–5% polyphenols and 700–860 mg/100 g of calcium. The biscuits prepared using the composite flour were of crisp texture and exhibited breaking strength of 1480–1690 g compared to control biscuits (1560 g). The biscuits were of mild grey colour (ΔE = 40–50) and exhibited higher protein, dietary fibre and calcium contents. The sensory evaluation of the biscuits indicated that 10% of SCM from native and hydrothermally processed millet and 20% from malted millet could be used in composite biscuit flour.     

Novel composite membrane based on zirconium phosphate-ionic liquids for high temperature PEM fuel cells

Composite membranes composed of zirconium phosphate (ZrP) and imidazolium-based ionic liquids (IL), supported on polytetrafluoroethylene (PTFE) were prepared and evaluated for their application in proton exchange membrane fuel cells (PEM) operating at 200 °C. The experimental results reported here demonstrate that the synthesized membrane has a high proton conductivity of 0.07 S cm^?1, i.e, 70% of that reported for Nafion. Furthermore, the composite membranes possess a very high proton conductivity of 0.06 S cm^?1 when processed at 200 °C under completely anhydrous conditions. Scanning electron microscopy (SEM) images indicate the formation of very small particles, with diameters in the range of 100–300 nm, within the confined pores of PTFE. Thermogravimetric analysis (TGA) reveals a maximum of 20% weight loss up to 500 °C for the synthesized membrane. The increase in proton conductivity is attributed to the creation of multiple proton conducting paths within the membrane matrix. The IL component is acting as a proton bridge. Therefore, these membranes have potential for use in PEM fuel cells operating at temperatures around 200 °C.     

Controllable electrodeposition synthesis of Pd/TMxOy-rGO/CFP composite electrode for highly efficient methanol electro-oxidation

A novel and high-efficiency Pd/TM_xO_y-rGO/CFP (TM_xO_y = Co₃O₄, Mn₃O₄, Ni(OH)₂) electrocatalyst for directly integrated membrane electrode was synthesized by controllable cyclic voltammetry electrodeposition combined with hydrothermal process. The results showed excellent performance towards methanol oxidation reduction. The Pd/Co₃O₄-rGO/CFP as-prepared catalyst has the best electrocatalytic activity, and mass activity is 5181 mA·mg⁻¹_Pd, which is about 40 times and 4.3 times that of the commercial Pd/C and Pt/C catalyst (JM). It can be attributed that the small size of Pd nanoparticle, uniformity of distribution, and the synergistic interaction between transition metal oxide on the support surface and Pd nanoparticles. The prepared Pd/TM_xO_y-rGO/CFP composite electrode is a promising catalyst for integrated membrane electrode assembly of proton exchange membrane fuel cells in the future.     

Novel multilayer Nafion/SPI/Nafion composite membrane for PEMFCs

A novel multilayer membrane for the proton exchange membrane fuel cell (PEMFC) was developed. Nafion was dispersed uniformly onto both sides of the sulfonated polyimide (SPI) membrane. The Nafion/SPI/Nafion composite membrane was prepared by immersing the SPI into the Nafion-containing casting solution. Through immersing both membranes into the Fenton solution at 80 °C for 0.5 h for an accelerated ex situ test, chromatographic analysis of the water evacuated from the cathode and the anode of the cells and a durability test of a single proton exchange membrane fuel cells, it was proved that the stability of the composite membrane has been greatly improved by adding the Nafion layer compared with the SPI membrane. The fuel cell performance with the SPI and Nafion/SPI/Nafion membranes was similar to the performance with the commercial product Nafion^® NRE-212 membrane at 80 °C.     

位置尺寸合成误差的计算

阐述了在机械设计和计算中对不是互相平行的,而是互成一定角度,分布在一个或几个平面内的位置尺寸,如何由位置尺寸各组成环的公差计算其合成误差,或由限定的合成误差来确定各组成环的公差,计算采用极大极小法求解方法。     

Investigation of Ce0.9Gd0.1O2-δ dispersed Sm1.5Sr0.5NiO4+δ: Cathode for intermediate temperature solid oxide fuel cell applications

Dispersion of nanocrystalline (94–350 nm) Ce_0.9Gd_0.1O_2-δ in superfine (260–312 nm) Sm_1.5Sr_0.5NiO_4+δ using modified precipitation technique is established using X-ray powder diffraction, scanning electron microscopy and transmission electron microscopy. Presence of Ce_0.9Gd_0.1O_2-δ grains inhibits grain growth of Sm_1.5Sr_0.5NiO_4+δ, which provides morphological stability (up to 1100 °C). Ce_0.9Gd_0.1O_2-δ concentration dependent behaviours of ionic conductivity, surface exchange rate and electrode polarization resistance (R_p) of composites (determined using electrochemical impedance spectroscopy) are comprehended using percolation model. Three oxygen reduction reaction mechanisms are considered to understand electrochemical performance. Minimum R_p (0.81 Ω cm² at 700 °C) for 70Sm_1.5Sr_0.5NiO_4+δ:30Ce_0.9Gd_0.1O_2-δ is correlated to percolation threshold (optimum (i) electrochemically active sites (ii) oxygen reduction reaction kinetics, (iii) O^2- conductivity and (iv) charge transfer rate). Nano crystallite size of Ce_0.9Gd_0.1O_2-δ is crucial for enhancement in electrochemical performance. Oxygen partial pressure dependent electrochemical impedance spectroscopy studies reveal dominance of coexisting non-charge transfer oxygen adsorption/desorption and bulk O^2- diffusion.