A level set based immersed boundary method for simulation of non-isothermal viscoelastic melt filling process

In this work, the polymer melt filling process is simulated by using a coupled finite volume and level-set based immersed boundary (LS-IB) method. Firstly, based on a shape level set (LS) function to represent the mold boundary, a LS-IB method is developed to model the complex mold walls. Then the non-isothermal melt filling process is simulated based on non-Newtonian viscoelastic equations with differ-ent Reynolds numbers in a circular cavity with a solid core, and the effects of Reynolds number on the flow patterns of polymer melt are presented and compared with each other. And then for a true polymer melt with a small Reynolds number that varies with melt viscosity, the moving interface, the temperature distributions and the molecular deformation are shown and analyzed in detail. At last, as a commonly used application case, a socket cavity with seven inserts is investigated. The corresponding physical quantities, such as the melt velocity, molecular deformation, normal stresses, first normal stress differ-ence, temperature distributions and frozen layer are analyzed and discussed. The results could provide some predictions and guidance for the polymer processing industry.     

Water vapor volatilization and oxidation induced surface cracking of environmental barrier coating systems: A numerical approach

A numerical model is developed for surface crack propagation in brittle ceramic coatings, aiming at the intrinsic failure of rare-earth silicate environmental barrier coating systems (EBCs) under combustion conditions in advanced gas turbines. The main features of progressive degradation of EBCs in such conditions are captured, including selective silica vaporization in the top coat due to exposure to water vapor, diffusion path-dependent bond coat oxidation, as well as crack propagation during cyclic thermal loading. In light of these features, user-defined subroutines are implemented in finite element analysis, where surface crack growth is simulated by node separation. Numerical results are validated by existing experimental data, in terms of monosilicate layer thickening, thermal oxide growth, and fracture behaviors. The experimentally observed quasi-linear oxidation in the early stage is also elucidated. Furthermore, it is suggested that surface crack undergoes rapid propagation in the late stage of extended thermal cycling in water vapor and leads to catastrophic failure, driven by both thermal mismatch and oxide growth stresses. The latter is identified as the dominant mechanism of penetration. Based on detailed analyses of failure mechanisms, the optimization strategy of EBCs composition is proposed, balancing the trade-off between mechanical compliance and erosion resistance.     

关于固体废物资源化利用方向课程设置的思考

随着工业的发展、环境的恶化,固体废物资源化利用越来越受到国家的重视。固体废物资源化利用作为环境工程专业的重要方向之一,如何合理高效开设相关课程,对培养合格的环境工程人才十分重要。文章以吉首大学环境工程专业为例,从课程教学内容和教学方法等方面提出了几点固体废物资源化利用方向课程设置的思考。     

Predictions of structural,electronic, mechanical,and thermodynamic properties of TMBCs (TM = Ti,Zr, and Hf) ceramics

In the present work, we have investigated the structural, electronic, elastic, and thermodynamic properties of transition-metal boron-carbon compounds (TMBCs) (TM = Ti, Zr, Hf) using the first-principles calculations. The results showed that TMBCs are energetically and thermodynamically stable, and the sequence of phase stability is HfBC > ZrBC > TiBC. B-C bonds can be formed in TMBCs ceramics due to the strong hybridization between B-2p and C-2p states. The elastic anisotropies of TMBCs were illustrated by elastic anisotropy indexes, 3D surface constructions, and 2D projections, and the results indicated that the sequence of elastic anisotropy is ZrBC > TiBC > HfBC. Finally, the calculated minimum thermal conductivities, based on the Clarke's and Cahill's models, of all TMBCs are anisotropic with the sequence of ZrBC > TiBC > HfBC.     

Microwave Sintering of Ti3Si(Al)C2 Ceramic

In this work, microwave sintering (MWS) method was successfully applied for fabrication of dense layered ternary Ti₃Si(Al)C₂ ceramic. Compared to conventional pressureless approaches, MWS could significantly decrease preparation temperature from 1600°C to 1400°C. The activation energy of the MWS process was estimated as 233 ± 18 kJ/mol, which was much lower than those in previous sintering techniques. The low sintering temperature likely originates from the low activation energy during MWS process. Such low temperature do not only make the as‐received Ti₃Si(Al)C₂ ceramic much smaller grain size and better mechanical properties, but also indicate higher energy converting efficiency during the sintering processes. Wide application of MWS techniques in MAX phases is expected to promote the practical applications of these materials and contribute to the energy saving during sintering process.     

超声辅助碱浸铜冶炼烟灰中铜砷分离

采用超声辅助Na₂S-NaOH浸取体系对铜冶炼烟灰进行研究,在NaOH、Na₂S与烟灰质量比0.4：1,液固比20：1,反应温度75℃,反应时间5 min,超声功率80 W,搅拌速率400 r·min^-1条件下,As浸出率为88.81%,Cu浸出率为0.025%,实现了Cu和As的有效分离。采用该方法处理后,与单独碱浸相比,As浸出率提高9.21%,烟灰中As含量由0.85%降至0.58%,Cu含量由2.21%增至2.30%,且As浸出毒性浓度由12.66 mg·L^-1降至2.84 mg·L^-1,为烟灰的资源化利用创造了条件。超声辅助碱浸除砷动力学满足收缩核混合反应控制模型,表观活化能0.114 kJ·mol^-1。XRD、XPS和重金属形态分析结果表明,超声空化作用可使As（Ⅲ）氧化为As（Ⅴ）,有利于As浸出,故超声过程强化有利于Cu和As在碱浸体系中的选择性分离。     

5-乙酰乙酰氨基苯并咪唑酮合成工艺研究

以5-硝基苯并咪唑酮为原料,采用水合肼还原制备5-氨基苯并咪唑酮(BI),反应条件温和,安全,环境友好。研究了溶剂对BI合成5-乙酰乙酰氨基苯并咪唑酮(AABI)的影响:在乙酸乙酯中,BI与双乙烯酮反应合成AABI,收率可达89.3%。     

低毒磷酸三甲苯酯的研制

为解决传统的磷酸三甲苯酯的毒性问题，开展研究和试验工作，开发出新型低毒产品。经检验，产品达到化工部部标一级品，ＬＤ５９０试验为低毒性，其阻燃性和增塑性相当于或好于国内同类产品。     

利用立体图分析马蹄焰窑蓄热室内流场分布

介绍了一种能直观、形象地反映蓄热室流场分布的新方法－把离散的实验数据绘制成透视立体图。对蓄热室流场的改善结果利用立体图进行了分析，认为流场分布立体图为流场改善程度的判断提供了一个有力的依据。     

提高产品合格粒级产率的试验研究

扼要介绍了某选厂碎磨试验研究的情况．并根据研究结论，提出了该厂技术改造应当采用的流程与设备方案，以提高产品合格粒级产率。