任意多边形上非定常扩散方程的单元中心型有限体积格式

针对二维非定常扩散方程,构造适用于任意多边形网格的单元中心型有限体积格式。采用向后欧拉格式进行时间离散,空间上在离散扩散算子时,利用网格顶点作为辅助插值点,通过求解一个欠定方程组将辅助插值点信息替换成网格单元中心点信息,最终得到只含单元中心未知量的离散格式。该格式既满足局部守恒条件,又满足线性精确准则。在几类多边形网格上进行数值实验,分别考虑扩散系数是连续和间断的情况,发现新格式均可达到二阶收敛。其数值表现显著优于算数平均加权和逆距离加权的九点格式,与双线性插值的加权方式结果相近,并且克服了双线性插值加权方式不适用于三角形网格的弊端。数值算例表明新格式求解非线性扩散方程仍然可以达到二阶收敛。     

Electrochemical reduction of nickel ions from diluteartificial solutions in a GBC reactor

The electrochemical reduction of nickel ions from a dilute solution has been carried out in a gas diffusion electrode packed bed electrode cell (GBC). Particle size and electrode configuration have been found to have a significant influence on the reduction process. Electrodes with a high porosity and large pores have been found to be the best for nickel deposition. The nickel current efficiency, Ni, is reported to be dependent on the current density, volumetric flow rate, nickel and boric acid concentration, and the pH. The fall in the nickel current efficiency is caused by an increase in electrode surface pH above a certain level, caused by either high bulk solution pH or high current density, leading to possibly formation of Ni(OH)2. It has been found that under conditions of exclusively metallic nickel deposition Ni/(1–Ni) is proportional to i0.69,Q10.52,CNi0.67,CBA–0.19 and pH1.0.     

硫黄在NR硫化胶中的溶解及扩散

根据分配定律,测定了４０℃时硫黄在ＮＲ硫化胶中的溶解度为１０４,硫黄在胶料与硫化胶之间的分配因子Ｋ为０８４,由此计算出４０℃时硫黄在胶料中的溶解度为１２４。根据硫黄实验扩散曲线计算硫黄在硫化胶中的平均扩散系数Ｄ为３２×１０－５ｍｍ２·ｓ－１,由此推算出４０℃下任意贮存时间内硫黄从胶料向硫化胶迁移的理论扩散曲线。     

CO_2/PS等静压微孔发泡研究

对CO_2与PS在高压设备中进行等静压处理的微孔发泡进行了研究。结果表明,改变CO_2的压力可以控制发泡的泡孔密度和泡孔大小。增加等静压的压力和PS中CO_2的浓度,可以提高泡孔的密度、减小泡孔的直径。结合CO_2的扩散及释压发泡,获得了CO_2在PS中扩散过程的数据,采用剩余界面法得出了CO_2在PS中的扩散厚度与扩散时间的关系。根据CO_2在PS中解吸附的特征,对泡沫不发泡皮层的厚度控制也进行了研究。     

Water Sorption and Diffusion in (Reduced) Graphene Oxide‐Alginate Biopolymer Nanocomposites

The water sorption and diffusion in (reduced) graphene oxide‐alginate composites of various compositions is analyzed. Water sorption of sodium alginate can be significantly reduced by the inclusion of graphene oxide sheets due to the formation of an extensive hydrogen bonding network between oxygenated groups. Crosslinking alginate with divalent metal ions and the presence of reduced graphene oxide can further improve the swelling resistance due to the strong interactions between metal ions, alginate, and filler sheets. Depending on conditions and composition, the overall water barrier properties of alginate composites improve upon (reduced) graphene oxide filling, making them attractive for moisture barrier coating applications. Water sorption kinetics in all alginate composites indicate a non‐Fickian diffusion process that can be accurately described by the Variable Surface Concentration model. In addition, the water barrier properties of sodium alginate‐graphene oxide composites can be adequately predicted using a simple model that takes the orientational order of filler sheets and their effective aspect ratio into account.

     

催化剂颗粒形状对甲烷水蒸气重整反应的影响及工业反应器模拟

甲烷水蒸气重整工艺是现阶段最主要的工业制氢技术,催化剂颗粒形状和反应器操作条件是影响重整反应器性能和产物组成的重要因素。首先从颗粒尺度研究催化剂形状对甲烷水蒸气重整反应的影响,在不同的反应温度和压力下,计算并比较了球形、柱形和环形催化剂的效率因子,其大小顺序为:柱形 < 球形 < 环形。其次,将反应器床层的质量、热量和动量传递与环形催化剂颗粒的扩散-反应方程相结合,建立了用于描述甲烷水蒸气重整工业反应器的一维轴向数学模型。计算并分析了反应器进口温度和压力对反应器床层的温度和压力分布、催化剂效率因子以及甲烷转化率和各组分浓度分布的影响,确定了适宜的工业反应器进口温度和压力,分别为773 K和3 MPa。     

零长柱技术用于分子筛晶内扩散的研究进展

分子筛晶内扩散系数对吸附分离和择形催化具有重要的指导作用。概述了重量法、核磁共振法和分子模拟等分子筛晶内扩散研究方法,并对零长柱技术用于分子筛晶内扩散的原理和应用等方面研究进行了详细阐述,包括两种进样方式（气相进样和液相进样）的单组分气相扩散、二元体系气相扩散和互扩散、液相扩散以及吸附扩散数学模型修正和拓展,还探讨了当前存在的一些问题,最后对零长柱法用于烃类分子在多孔材料中的扩散研究进行了展望。     

PS-Cy和PS-Acyl-Cy树脂的制备及其吸附对硝基酚

用1,4,7,10-四氮杂环十二烷(Cyclen)分别修饰氯甲基化的聚苯乙烯微球及氯乙酰化的聚苯乙烯微球,合成Cyclen型聚苯乙烯(PS-Cy)树脂及Cyclen型氯乙酰化的聚苯乙烯(PS-Acyl-Cy)树脂。测定了两种树脂的增重率及全交换容量并研究了其吸附动力学。结果表明:PS-Cy树脂的全交换容量达1.59 mmol/m L,对对硝基酚(PNP)的最大吸附量达118.93 mg/m L,吸附过程符合Langmuir模型;而PS-Acyl-Cy树脂的全交换容量为1.45 mmol/m L,对PNP的最大吸附量为90.87 mg/m L,吸附过程符合Freundlich模型。两种树脂的吸附过程都符合准二级动力学方程并且液膜扩散为主要控制步骤。     

铝合金压铸用8407模具钢的表面改性

8407钢是常用的铝合金压铸用模具钢.为改善模具的抗热疲劳和抗熔损性能,对冷喷涂A1后的8407钢试样在500,550℃下进行扩散处理,渗铝后的试样在纯O2气氛,570℃的条件下进行氧化,渗层表面形成了Fe-A1-O的混合氧化物.考察了扩散温度和扩散时间对渗层质量的影响,研究了在纯O2气氛下Fe-A1合金表面的氧化情况.结果表明,8407钢经过冷喷涂铝后再进行低温扩散处理能够实现低温渗铝.渗铝后,在580℃以下,纯O2气氛条件下氧化,Fe-A1合金表面生成了FeO和.A12O3的混合氧化物.该氧化膜与铝液不润湿,可防止粘膜并改善模具的抗热疲劳和抗熔损性能.     

Effect of particle size on flow and mixing in a bladed granular mixer

A number of studies have modeled flow and mixing of granular materials using the discrete element method (DEM). In an attempt to reduce computational costs, many of these DEM studies model particles larger than the actual particle size without investigating the implications of this assumption. Using DEM, the influence of the modeled particle size on flow and mixing in a bladed granular mixer is studied. The predicted flow microdynamics, including mixing rates, are strongly dependent on the particle diameter. The effect of particle size on macroscopic advective flow also is significant, particularly for dilute flow regions. These results suggest that the influence of particle size needs to be taken into consideration when using larger particles in DEM mixing simulations. To guide scale‐up efforts, particle‐size‐based scaling relationships for several key flow measurements are presented. © 2014 American Institute of Chemical Engineers AIChE J, 61: 46–57, 2015