Low-temperature densification by plasma activated sintering of Mg2Si-added Si3N4

In this study, highly dense Si₃N₄ ceramics with excellent mechanical properties were fabricated using Mg₂Si as a sintering additive by plasma-activated sintering at 1400–1500 °C. The effects of the sintering temperature and content of Mg₂Si on the densification, microstructures, and mechanical properties of the Si₃N₄ ceramics were investigated. The mechanism responsible for the effect of Mg₂Si in the promotion of the sinterability of Si₃N₄ is discussed. The results showed that the addition of Mg₂Si could effectively remove the oxide layers on the Si₃N₄ particles and form a liquid phase during the sintering, promoting the densification and phase transition of the Si₃N₄ ceramics. The Si₃N₄ ceramic sintered at 1450 °C with 6.0 wt% of Mg₂Si exhibited the maximum strength of 1050 MPa.     

Synthesis and X-ray characterization of the quindecanuclear nickel/sulfur paramagnetic cluster [Ni15(μ3-S)6(μ4-S)9(PEt3)6]+

The quindecanuclear nickel/sulfur cluster [Ni₁₅(μ₃-S)₆(μ₄-S)₉(PEt₃)₆]⁺ has been isolated by reaction of Ni(ClO₄)₂·6H₂O with H₂S and PEt₃ in ethanol\dichloromethane solution and has been characterized by X-ray diffraction studies.     

Poly(vinyl alcohol) nanocomposites reinforced with cellulose fibrils isolated by high intensity ultrasonication

Cellulose fibrils in micro and nanoscales generated from biomass are relative new reinforcing materials for polymer composites, which have potential lightweight and high strength and are biodegradable. The objective of this study was to reinforce biodegradable polymers by cellulose fibrils generated from several cellulose sources by ultrasonic treatment in order to utilize biomass to fabricate high-value products. The geometrical characteristics of the fibrils were investigated by polarized light microscopy (PLM) and atomic force microscopy (AFM). The degree of fibrillation of the fibers evaluated by water retention value was significantly increased after treatment. The treated cellulose and separated fibrils were used to reinforce poly(vinyl alcohol) (PVA) to make biodegradable nanocomposites by film casting. The mechanical properties of PVA were significantly improved by most of the small fibrils. The morphological characteristics of the nanocomposites were investigated with PLM, scanning electron microscopy, and AFM.     

Evaluation of the effects of fat replacers on the quality of wheat bread

The performance of different fat replacers at various levels (Inulin powder, Inulin gel and Simplesse) in wheat bread and dough compared to a control containing block fat was examined. Empirical and fundamental rheological tests were carried out on the doughs. Volume yield, crumb texture, crust colour and crumb image characteristics were measured for the baked loaves. The addition of inulin gel was found to increase water absorption. Dough complex modulus for doughs containing fat was significantly lower (P<0.01) than the doughs containing the replacers. The addition of simplesse and inulin increased the complex modulus (P<0.01). Loaves containing the control fat and inulin gel had similar volume yields, significantly higher (P<0.01) than loaves containing simplesse or inulin powder. Inulin powder and simplesse had adverse effects on crumb hardness, producing slices significantly harder (P<0.01) than slices with the control fat or inulin gel. Overall it was found that breads containing the inulin gel were similar in quality characteristics to the control breads containing fat.     

重烷基苯磺酸盐溶液中混合无机碱对大庆原油界面流变性质的影响

为阐明碱对化学驱体系界面性质的影响规律,利用振荡滴方法系统研究了重烷基苯磺酸盐与大庆原油间的界面扩张流变性质,考察了无机碱对重烷基苯磺酸盐 大庆原油界面性质的影响。研究发现,重烷基苯磺酸盐分子与大庆原油中活性组分混合吸附,形成具有一定强度的界面膜,界面扩张模量和相角随重烷基苯磺酸盐质量分数的增加变化较小。无机碱与大庆原油中的石油酸作用,随碱质量分数增大和碱性增强,界面膜强度不断增大。NaOH与重烷基苯磺酸盐之间存在协同效应,明显增大界面扩张模量,有利于原油乳化;而Na2CO3和NaHCO3破坏重烷基苯磺酸盐界面膜的结构,造成界面扩张模量降低。     

Preparation of hollow mesoporous silica spheres by a sol–gel/emulsion approach

Hollow mesoporous silica spheres were synthesized by a sol–gel/emulsion (oil-in-water/ethanol) approach, in which cetyltrimethylammonium bromide (CTAB) surfactant was employed to stabilize and direct the hydrolysis of oil droplets of tetraethoxysilane (TEOS). The diameters of the hollow spheres can be tuned in the range from 210 to 720 nm by varying the ratio of ethanol-to-water and their shell thickness can be mediated by changing the concentration of CTAB used in the system. BET surface areas of the hollow silica spheres are determined to be in the range of 924–1766 m² g^?1 and their pore sizes are around 3.10 nm as determined by BJH method.     

ZnO/C nanocomposite microspheres with capsule structure for anode materials of lithium ion batteries

Well-designed nanostructures are very critical to the lithium-storage performance of electrode materials. To enhance the electrochemical performance of zinc oxide anode materials, a capsule structure, composed of carbon shell and its encapsulating ZnO microsphere, is designed. This capsule structured ZnO/C nanocomposite microspheres are prepared by a sol-gel method combined with two calcination processes. The carbon capsule shows great advantages of enhancing the structural stability of active material, reducing the formation of solid electrolyte interface (SEI) layer, and improving the conductivity of electrode. These factors are quite beneficial to the improvement of cycling stability, initial coulombic efficiency and rate capability. Consequently, capsule structured ZnO/C nanocomposite microspheres deliver an initial charge capacity of 790 mA h g⁻¹, an initial coulombic efficiency of 71%, and a reversible capacity retention of 63% after 100 cycles, all of which are higher than those of pure ZnO microspheres. These results suggest that the design of carbon encapsulated ZnO microsphere is quite effective for enhancing the lithium-storage properties and can also show general significance for developing high-performance electrode materials.     

考虑时变风险的成品油二次配送路径优化

成品油属于易燃易爆炸危险品,其配送过程一旦发生事故后果严重。考虑到配送过程人群聚集程度、载重和车速的动态变化,本文建立时变风险度量模型,运用BP神经网络预测车速,预测了城市高速路段和主干路路段的车速。在此基础上,构建了同时考虑配送成本与时变风险的成品油二次配送双目标路径优化模型,并提出改进的多目标列队竞争算法进行求解。本文还采用改进的多目标列队竞争算法求解文献报道的实例,求得非支配解完全支配文献报道中的非支配解,验证了算法的有效性。某武汉石化企业实例研究表明,预测的车速具有较高的准确度,所提出的方法能同步考虑配送过程的时变风险和配送成本,求得的Pareto最优配送路径集可以为企业决策者提供多样化的选择方案,具有较好的应用价值。     

The behaviour of polyvinyl alcohol at the planar Cd/Cd(OH)2 electrode interface

The anodic oxidation of Cd in alkaline solution was investigated using potentiostatic pulse and a.c. impedance techniques. In the active dissolution region, the slope of the η—log i curve was close to the “Nernstian” Tafel slope of 30 mV/decade. Addition of an organic additive, polyvinyl alcohol (PVA), to the electrolyte caused a marked change in the Tafel slope corresponding to a 2e consecutive electron transfer reaction. Impedance measurement indicated a decrease in the charge transfer resistance in the presence of PVA. The results indicate that expanders such as PVA modify the anodic oxidation mechanism of Cd in alkaline solution.