脉冲激光沉积制备的HfO2薄膜的结构与电学性能

采用脉冲激光沉积（PLD）方法在Si（100）基底上制备了有效氧化层厚度为8．6nm，介电常数为29．3的HfO2薄膜．借助C射线衍射（XRD）、原子力显微镜（AFM）、高分辨透射电镜（HRTEM）分析了样品的微观结构，对电容的C-V与I-V电学特性进行了测试。实验结果表明，该方法制得的HfO2薄膜表面光滑，N2500℃下退火30mm后样品表面粗糙度由0．203nm变为0．498nm，薄膜由非晶转变为简单正交结构，界面层得到有效控制，该栅介质电容具有良好的C-V特性，较低的漏电流密度（4．3×10^-7A/cm^2，@-1V），是SiO2栅介质的理想替代物．     

Kinetics and crystal structure of isothermal crystallization of poly(lactic acid) plasticized with triphenyl phosphate

In this article, the spherulitic growth rate of neat and plasticized poly(lactic acid) (PLA) with triphenyl phosphate (TPP) was measured and analyzed in the temperature range of 104–142°C by polarizing optical microscopy. Neat PLA had the maximum value of 0.28 μm/s at 132°C, whereas plasticized PLA had higher value than that of neat PLA, but the temperature corresponding to the maximum value was shifted toward lower one with increasing TPP content. The isothermal crystallization kinetics of neat and plasticized PLA was also analyzed by differential scanning calorimetry and described by the Avrami equation. The results showed for neat PLA and its blends with various TPP contents, the average value of Avrami exponents n were close to around 2.5 at two crystallization temperatures of 113 and 128°C, the crystallization rate constant k was decreased, and the half‐life crystallization time t_1/2 was increased with TPP content. For neat PLA and its blend with 15 wt % TPP content, the average value of n was 2.0 and 2.3, respectively, the value of k was decreased, and the value of t_1/2 was increased with crystallization temperature (T_c). Further investigation into crystallization activation energy ΔE_a of neat PLA and its blend with 15 wt % TPP showed that ΔE_a of plasticized PLA was increased compared to neat PLA. It was verified by wide‐angle X‐ray diffraction that neat PLA and its blends containing various TPP contents crystallized isothermally in the temperature range of 113–128°C all form the α‐form crystal. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Processing of high-performance Co doped Y2O3 as a single-phase electrolyte for low temperature solid oxide fuel cell (LT-SOFC)

The high-performance single-phase semiconductor materials with higher ionic conductivity have drawn substantial attention in fuel cell applications. Semiconductor materials play a key role to enhance ionic conductivity subsequently promoting low temperature solid oxide fuel cell (LT-SOFC) research. Herein, we proposed a semiconductor Co doped Y₂O₃ (YCO) samples with different molar ratios, which may easily access the high ionic conductivity and electrochemical performances at low operating temperatures. The resulting fabricated fuel cell 10% Co doped Y₂O₃ (YCO-10) device exhibits high ionic conductivity of ∼0.16 S cm⁻¹ and a feasible peak power density of 856 mW cm⁻² along with 1.09 OCV at 530 °C under H₂/air conditions. The electrochemical impedance spectroscopy (EIS) reveals that YCO-10 electrolyte based SOFC device delivers the least ohmic resistance of 0.11–0.16 Ω cm² at 530-450 °C. Electrode polarization resistance of the constructed fuel cell device noticed from 0.59 Ω cm² to 0.28 Ω cm² in H₂/air environment at different elevated temperatures (450 °C to 530 °C). This work suggests that YCO-10 can be a promising alternative electrolyte, owing to its high fuel cell performance and enhanced ionic conductivity for LT-SOFC.     

Asymmetric alumina-based ultrathin composite ceramic membranes with interfacial modification of black talc nanosheets

In this work, ultrathin planar alumina-based ceramic membranes with asymmetric structure and thickness less than 0.85 mm were successfully prepared by one-step molding phase transformation/sintering method using low-cost black talc (BT) nanosheets for the first time. The microstructure, pore structure, mechanical strength and permeability of novel ceramic membranes were systematically investigated with different BT amount and sintering temperatures. The doping of BT nanosheets effectively modulated the interfacial bonding area and strength between the grains, achieving significant increase in flexural strength through the evolution of the dense layer structure. The asymmetric structural features formed by the phase transformation/sintering process in combination with polymer substrate significantly reduced the thickness of effective separation layer, thus weakening the loss of flux caused by the densification of the film layer due to the interfacial modification process. Moreover, the organic carbon layers between BT layers were oxidized during the sintering process, forming fine pores and increasing the porosity, which showed to be unique characteristic different from other clay mineral materials. The prepared composite membrane had the pure water flux up to 16335 L m⁻² h⁻¹/bar at 1350 °C sintering, which achieved stable permeation of ∼5200 L m⁻² h⁻¹/bar and high retention over 90% for O/W emulsions.     

Platinum-nickel bimetallic catalyst doped with rare earth for enhancing methanol electrocatalytic oxidation reaction

Platinum (Pt) is often used as anodic catalyst for direct methanol fuel cell (DMFC). However, platinum is difficult to achieve large-scale application because of its low stability and high cost. In this work, the electrocatalytic activity and stability of the Pt-based catalyst for methanol oxidation (MOR) are significantly improved by adding Ce and Ni to the catalyst. Additionally, the rare earth element-Pr (Dy) is also chosen to be added into the catalysts for comparison. A series of PtMNi (M = Ce, Pr, Dy) catalysts are prepared by impregnation and galvanic replacement reaction methods using carbon black as support. The electrocatalytic mass activity of PtCeNi/C, PtDyNi/C, PtPrNi/C and Pt/C is 3.92, 1.86, 1.69 and 0.8 A mg_Pt⁻¹, respectively. The mass activity of these the above four catalysts after stability measurement is 3.14, 1.49, 1.27 and 0.72 A mg_Pt⁻¹. Among them, PtCeNi/C has the highest catalytic activity. These as-prepared catalysts are also characterized by various analyzing techniques, such as TEM, HRTEM, XRD, XPS, ICP-OES, STEM, STEM-EDS elemental mapping and line-scanning etc. It shows that PtCeNi/C exhibits best catalytic activity (3.92 A mg_Pt⁻¹) among the as-obtained catalysts, 4.9 times higher than that of commercial Pt/C (0.8 A mg_Pt⁻¹). PtCeNi/C is also with excellent anti-CO poisoning ability. The outstanding catalytic performance of PtCeNi/C for the MOR is mainly attributable to uniform-sized PtCeNi nanoparticles, uniform Ni, Ce and Pt element distribution, and electron interaction among Pt-, Ni- and Ce-related species (electron transferring from Pt to CeO₂).     

Au3Pd1 intermetallic compound as single atom catalyst for formic acid decomposition with highly hydrogen selectivity

Developing efficient catalysts for formic acid decomposition has been studied extensively. Herein, the Au₃Pd₁ intermetallic compound is designed as a single atom catalyst for the dehydrogenation of formic acid. By using density functional theory calculations, the thermodynamic stability, electronic structure, and reaction mechanism for the Au₃Pd₁ catalyst are systematically investigated, and the surface charge polarization and atom-ordered arrangement were confirmed to play an important role in the efficient formic acid dehydrogenation. The special positively charged Pd single atom on the Au₃Pd₁ surface becomes the adsorption site of HCOO⁻ and the reaction site for formic acid decomposition. The nearby Au sites suppress the C–O bond cleavage due to their weak interaction with CO1 and OH1. As a result, the HCOO⁻ dehydrogenation pathway is predominant on the Pd single atomic sites and the CO formation is well inhibited. This intermetallic-based catalyst can be extended to other systems and provided general guidance for efficient catalyst design.     

A multi-objective model for optimizing hydrogen injected-high pressure natural gas pipeline networks

The paper develops a statistical model for optimizing the Hydrogen-injected Natural gas (H-NG) high-pressure pipeline network. Gas hydrodynamic principles are utilized to construct the pipeline and compressor station model. The model developed is implemented on a pipeline grid that is supposed to carry Hydrogen as an energy carrier in a natural gas-carrying pipeline. The paper aims to optimize different objectives using ant colony optimization (ACO). The first objective includes a single objective optimization problem that evaluates the maximum permissible hydrogen amounts blended with natural gas (NG) for a set of pipeline constraints. We also evaluated the variations in operational variables on injecting Hydrogen into the natural gas pipeline networks at varying fractions. The study further develops a multi-objective optimization model that includes bi-objective and tri-objective problems and is optimized using ACO. Traditional studies have focused on single-objective optimization with minimal bi-objective issues. In addition, none of the earlier research has shown the effect of introducing Hydrogen to the NG network using tri-objective function evaluations. The bi-objective and tri-objective functions help evaluate the effect of injecting Hydrogen on different operational parameters. The study further attempts to fill the gap by detailing the modelling equations implemented through a bi-objective and tri-objective function for the H-NG pipeline network and optimized through ACO. Pareto fronts that show the tradeoff between the different objectives for the multi-objective problem have been generated. The primary objective of the bi-objective and tri-objective optimization problems is maximizing hydrogen mole percent in natural gas. The other objective chosen is minimizing compressor fuel consumption and maximizing delivery pressure, throughput, and power delivered at the delivery station. The findings will serve as a roadmap for pipeline operators interested in repurposing natural gas pipeline networks to transport hydrogen and natural gas blend (H-NG) and seeking to reduce carbon intensity per unit of energy-delivered fuel.     

Oxygen depletion properties of glucose-grafted polyethylene resins filled with sodium ascorbate/modified iron compounds

Oxygen scavenging plastic can react with oxygen that was trapped in the packaging materials or permeated into the packages, and then, extend the shelf life of food contained in packages. Sodium ascorbate (SA) and modified iron (MFe) compounds were chosen as the main components of oxygen scavengers to prepare the oxygen scavenging LDPE plastics. However, the widely used hydrophobic LDPE packaging material will slow down the oxygen depletion rate of these oxygen scavenger compounds. So glucose was used to modify the hydrophobic property of LDPE to improve the oxygen depletion properties of LDPE oxygen scavenging plastic. The oxygen depletion efficiency of L₉₅[SA_x(MFe)_y]₅ series samples improved initially as the weight ratios of SA/MFe increase, and reached the best as the weight ratios of SA/MFe approach 7/3. After modifying LDPE with glucoses, the oxygen depletion efficiency of each ML₉₅[SA_x(MFe)_y]₅ specimen improved even better than that of the corresponding L₉₅[SA_x(MFe)_y]₅ specimen with the same loading of oxygen scavenger compound, wherein the oxygen depletion efficiency of ML₉₅[SA_x(MFe)_y]₅ series specimens reached the best as the weight ratios of SA/MFe approach 1/9. In consistent with the oxygen depletion properties found in the previous section, the peroxide values of modeled food samples tested in the airtight flask with L₉₅[SA_x(MFe)_y]₅ and ML₉₅[SA_x(MFe)_y]₅ series samples reduce consistently as their oxygen depletion properties improve. In order to understand the interesting oxygen depletion properties of L₉₅[SA_x(MFe)_y]₅ and ML₉₅[SA_x(MFe)_y]₅ series samples, Fourier transform infrared spectroscopy, scanning electron microscope and energy dispersive X-rays analysis of these samples were performed.     

Effect of fiber loading on the properties of treated cellulose fiber-reinforced phenolic composites

The effect of fiber loading on the properties of treated cellulose fiber-reinforced phenolic composites was evaluated. Alkali treatment of the fibers and reaction with organosilanes as coupling agents were applied to improve fiber–matrix adhesion. Fiber loadings of 1, 3, 5, and 7 wt% were incorporated to the phenolic matrix and tensile, flexural, morphological and thermal properties of the resulting composites were studied. In general, mechanical properties of the composites showed a maximum at 3% of fiber loading and a uniform distribution of the fibers in such composites was observed. Silane treatment of the fibers provided derived composites with the best thermal and mechanical properties. Meanwhile, NaOH treatment improved thermal and flexural properties, but reduced tensile properties of the materials. Therefore, the phenolic composite containing 3% of silane treated cellulose fiber was selected as the material with optimal properties.