The current detour effect observed on materials with random microstucture: experimental evidence from Li3xLa2/3−xTiO3 studied by impedance spectroscopy

Impedance spectroscopy (IS) has been used to study the influence on the low frequency part of the impedance diagrams of the microstructure of a fast ionic conductor, Li_3xLa_2/3−xTiO₃ with x = 0.10 (named hereafter LLTO). This oxide has been synthesised by sol–gel method. After synthesis, the powder of LLTO displays a large distribution of grain size and agglomerates. The grain size distribution and the porosity of the ceramic have been changed by heat-treatment from 600 °C to 1200 °C in air. The impedance spectra of these ceramics, recorded at different temperatures from room temperature (RT) to 400 °C, show a low-frequency depressed arc, which is characteristic of the grain boundary response of the ceramic. Its shape depends strongly on the heat-treatment of the ceramic, and therefore, on its microstructure. It is a simple arc when the pellet is well sintered but becomes very complex for non-sintered ceramics with high resistive grain boundary and pores. The observed “fish” shape indicates the presence of current “detours effect” in the material. This effect means that current detours around blocking grain boundary and/or pores occur to lower the impedance. Consequently, the brick layer model (BLM), which assumes an ideal microstructure, and then no current “detours effect”, can not be used to analyse these impedance data.     

硫酸酯化魔芋葡甘聚糖的制备及其应用研究

目的制备硫酸酯化魔芋葡甘聚糖(sulfated konjac glucomannan,SKGM)并研究其与大分子黄原胶的复配作用机制。方法用市售魔芋精粉为原料,采用创新的乙醇-超滤沉淀法获得高纯度的魔芋葡甘聚糖(konjac glucomannan,KGM),在氯磺酸的作用下制备出硫酸酯化魔芋葡甘聚糖,以粘度为指标,分析讨论SKGM与大分子黄原胶(xanthan gum,XG)的作用机制。结果制备的魔芋葡甘聚糖冻干粉纯度为98.61%,此时粘均分子量179万,粘度870 mpa/s;合成硫酸酯化魔芋葡甘聚糖最佳反应条件是时间3 h,温度为70℃,氯磺酸6 m L,通过计算得知取代度为1.053。硫酸酯化魔芋葡甘聚糖和黄原胶复配物因为氢键作用使得粘度显著增加。结论该研究获得一种精制高粘度魔芋葡甘聚糖及其酯化产物的方法,并得到其酯化产物SKGM和XG的复配机制。     

A kinetic study of gaseous alkali capture by kaolin in the fixed bed reactor equipped with an alkali detector

In this study, the interaction between gas phase potassium species and kaolin was investigated in a fixed bed reactor equipped with a surface ionization detector, which is capable of detecting alkali metals in gas phase at ppb level. The effects of mass transport, space time, sorbent temperature and concentration of KCl on the rate of potassium adsorption on kaolin were studied in air. Kaolin, mainly composed of kaolinite—Al₂Si₂O₅(OH)₄, was found to be very efficient in removing gaseous alkali species from hot flue gases at fluidized bed combustion temperatures. The removal efficiency increased as temperature was decreased or KCl concentration was increased. The capture of potassium by kaolin was irreversible with formation of both water-soluble and water-insoluble products. Kaolin captured KOH almost as effectively as KCl, but K₂SO₄ was captured much less effectively than KCl.     

反应精馏技术的研究现状及应用进展

反应精馏是化学反应和精馏过程耦合为一体的单元操作,已成为当今的重要研究领域。本文对反应精馏技术的研究现状及其应用进行了综述,介绍了反应精馏塔及催化剂,对催化剂床中传质及流体力学特征,数学模型和反应精馏塔设计方程进行了总结;同时介绍了反应精馏技术的应用现状及其可能的应用领域．     

污水处理工艺方法的研究现状与进展

首先对传统污水处理工艺方法进行了简要介绍,之后对高级氧化技术中几种典型而且近年来研究比较热门的工艺方法进行了详细论述。     

Copper(II) 8-hydroxyquinolinate 3D network film with corrosion inhibitor embedded for self-healing corrosion protection

This work presents a self-healing protective coating for copper. The complex coating is composed of copper(II) 8-hydroxyquinolinate (Cu(8HQ)₂) 3D network film storing corrosion inhibitor as base layer and epoxy as top layer covering on the base layer. The results of EIS and polarization curves reveal the self-healing effect of Cu(8HQ)₂ 3D network film with corrosion inhibitor embedded. After being scratched with a knife-edge, the complex coating rapidly releases inhibitor embedded in 3D network structure to suppress the corrosion process. The scratch on the coating is covered with inhibitor adsorption film and the anodic activity is restrained.     

Crystal defect modulation in cathode materials for non-lithium ion batteries: Progress and challenges

Non-lithium ion (Na/K/Mg/Ca/Zn/Al-ion) batteries (NLIBs) have stepped into the spotlight as alternatives or supplements to lithium-ion batteries in large-scale energy storage systems with the aid of vast advantages in resource and production cost. In the past years, a lot of efforts have been taken to develop high-performance cathode materials for various NLIBs by exploiting new cathode materials or optimizing the existing categories. As an efficient optimizing strategy to break the bottleneck of intrinsic lattice, crystal defect modulation attracts much attention and has been applied in many cathode materials. Suitable crystal defects in cathode materials could enhance the electrochemical reactivity, electronic conductivity, ionic diffusivity, and structural stability, then improving the capacity, rate performance and cycling stability of batteries. In this review, the investigations of crystal defect modulation in cathode materials for NLIBs are systematically summarized by highlighting some typical and recent progresses. The positive effects and improvement mechanism of intentionally introduced defects, including substitutional impurity, interstitial impurity, vacancy defect, cation disorder and amorphization, are discussed. Besides, the challenges and the perspectives about future directions of crystal defect modulation on the cathode materials for NLIBs are presented.     

Limit of absolute stability for crystal growth into undercooled alloy melts

The limit of absolute stability for crystal growth of binary alloys into an undercooled melt is discussed in respect of a positive temperature gradient in the solid and different thermal properties of liquid and solid. It is shown that the positive temperature gradient and the better heat conductivity and diffusivity of the solid phase reduce the velocity corresponding to the limit of absolute stability. Thus although the solid grows into an undercooled melt a planar interface may be stable with a quite lower growth rate than the absolute thermal velocity.     

魔芋葡甘聚糖的研究现状

魔芋葡甘聚糖是由D-葡萄糖和D-甘露糖以β-1,4糖苷键结合而成一种天然的高分子多糖,主要存在于魔芋块茎中。我国是魔芋生产大国,深度开发魔芋葡甘聚糖的应用途径,将会推动国民经济的发展。魔芋葡甘聚糖具有良好的吸水性、成膜性、胶凝性、保湿性以及降血压、降血脂等特殊的生理功效,在食品、医疗和化工等领域受到广泛应用。本文综述了魔芋葡甘聚糖应用现状和提纯方法,并分别从接枝共聚、氧化、交联、酯化等方面对魔芋葡甘聚糖化学修饰研究进行了阐述,以期为魔芋葡甘聚糖的进一步开发提供理论依据。     

桑黄风味酸奶发酵工艺优化

该试验以桑黄发酵液、脱脂奶粉为主要原料,将保加利亚乳杆菌、嗜热链球菌、乳双歧杆菌1∶1∶1混合作为发酵菌剂,生产桑黄酸奶。通过单因素试验和正交试验分别考察桑黄发酵液添加量、奶粉添加量、白砂糖添加量、发酵菌剂接种量、发酵时间和发酵温度对桑黄风味酸奶品质的影响。结果表明,桑黄风味酸奶的最佳发酵工艺条件为桑黄发酵液添加量15 mL/100 mL、奶粉添加量17 g/100 mL、白砂糖添加量7 g/100 mL、发酵菌剂（8.4×108 CFU/mL）接种量5 mL/100 mL、发酵时间5 h、发酵温度42 ℃。在此优化条件下,制备的桑黄风味酸奶感官评分为92.2分,蛋白质和脂肪含量分别为1.86 g/100 g、0.6 g/100 g、1,1-二苯基-2-三硝基苯肼（DPPH）自由基清除率为46%。