Fire‐resistant effect of nanoclay on intumescent nanocomposite coatings

The aim of the study is the development of an intumescent nanocomposite coating to provide fire protection for the metallic substrate. Acrylic nanocomposites containing nanoclay and relative intumescent nanocoatings are prepared. The effect of nanoclay on the thermal degradation of an intumescent nanocomposite coating is analyzed by using differential thermal analysis, thermogravimetry, and X‐ray diffraction. The influence of the added content of nanoclay on fire performance is studied by a fire protection test and measurements of the limiting oxygen index and effective thermal conductivity. The distribution of nanoparticles in the acrylic nanocomposite is characterized by transmission electron microscopy. The flame‐retardant efficiency of the intumescent nanocomposite coating is improved by 1.5% well‐distributed nanoclay particles. However, 3% nanoclay produces a negative effect on the fire performance of the coating. Fire protection tests and scanning electron microscopy observations reveal that the fire‐retardant property of a conventional intumescent coating is destroyed by aging, whereas the nanocomposite coating modified with 1.5% nanoclay demonstrates good aging and fire resistance. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1681–1689, 2007     

Moving horizon approach of integrating scheduling and control for sequential batch processes

Online integration of scheduling and control is crucial to cope with process uncertainties. We propose a new online integrated method for sequential batch processes, where the integrated problem is solved to determine controller references rather than process inputs. Under a two‐level feedback loop structure, the integrated problem is solved in a frequency lower than that of the control loops. To achieve the goal of computational efficiency and rescheduling stability, a moving horizon approach is developed. A reduced integrated problem in a resolving horizon is formulated, which can be solved efficiently online. Solving the reduced problem only changes a small part of the initial solution, guaranteeing rescheduling stability. The integrated method is demonstrated in a simulated case study. Under uncertainties of the control system disruption and the processing unit breakdown, the integrated method prevents a large loss in the production profit compared with the simple shifted rescheduling solution. © 2014 American Institute of Chemical Engineers AIChE J, 60: 1654–1671, 2014     

电磁分离高硅铝硅合金制备低硅铝硅合金

在不考虑杂质元素的情况下研究了含铝45wt%的铝硅合金熔体电磁分离过程中电流频率、下拉速度、保温温度及坩埚材质对初晶硅相分离效果的影响. 结果表明,在电流频率3 kHz、保温温度1000℃、下拉速度10 ?m/s的条件下,以石墨坩埚为容器,可使合金的硅铝质量比降至0.0939. 保温温度对合金中硅的去除影响最大,相同条件下1500℃时合金硅铝质量比为0.11439;低频交变电流能强化电磁搅拌从而加强传质,降低下拉速度对降低合金中硅含量有一定作用,且可使分离界面更平坦.     

承压设备热处理探讨

本文概述了我国承压设备热处理环节的技术标准以及与ASME规范的差异,实际操作中存在的问题,以及新标准实施后如何改进热处理工艺的质量控制。     

锂/钠离子电池过渡金属氟磷酸盐正极材料研究进展

便携式电子产品、电动汽车和储能领域的快速发展对电池能量密度的要求越来越高,正极材料是限制电池能量密度的主要因素。过渡金属氟磷酸盐（A₂MPO₄F,A=Li、Na,M=Mn、Fe、Co、Ni）是一类高比容量（~300 mA·h/g）和高能量密度（>1 000 W·h/kg）的新型正极材料。主要介绍了A₂MPO₄F的结构、合成方法与改性方面的最新进展。讨论了A₂MPO₄F所面临的主要挑战,特别是实现两电子反应所面临的困难。展望了它们的应用前景。     

Formation of Sr2Si5N8:Eu2+ and Its Transformation to SrSi6N8:Eu2+ Controlled by Temperature and Gas Pressure

Firing temperature and gas pressure effect of synthesizing Sr₂Si₅N₈:Eu²⁺ were investigated. The emission intensity is positively correlated with the firing temperature under 0.1 and 0.5 MPa gas pressure. The Sr₂Si₅N₈:Eu²⁺ with the highest emission intensity was found at 1700°C and 1980°C under 0.1 and 0.5 MPa gas pressure, respectively. Although the maximum emission intensity of Sr₂Si₅N₈:Eu²⁺ obtained under 0.5 MPa gas pressure condition is higher than that under 0.1 MPa. The Sr₂Si₅N₈:Eu²⁺ synthesized under 0.5 MPa gas pressure in the temperature range from 1600°C to 1800°C have lower emission intensities than that synthesized under 0.1 MPa indicating that the melting of Sr₃N₂ is an important step for the formation of Sr₂Si₅N₈:Eu²⁺. Moreover, the Sr₂Si₅N₈:Eu²⁺ undergoes phase transition into SrSi₆N₈:Eu²⁺ completely after elongating the heating duration to 6 h at 1980°C under 0.5 MPa gas pressure. The same feature was observed under 0.1 MPa gas pressure after firing 8 h at 1750°C. Different heating durations led to different degrees of phase transition.     

Mechanical properties of refractory castables bonded with hydratable magnesium carboxylate-boric acid

Hydratable magnesium carboxylate (HMC), which is similar to the properties of cement, can be used as a potential binder for refractory castables. However, its decomposition may lead to poor mechanical properties at medium temperatures (300 °C–1100 °C). This work investigated the effects of boric acid on the mechanical properties and microstructural evolution of castables bonded with hydratable magnesium carboxylate. The mechanical strength, bulk density, apparent porosity, thermal shock resistance, and sintering properties of the castables were evaluated. The results showed that the mechanical properties of HMC-bonded castables (HMCC) at various temperatures can be improved by adding boric acid. Boric acid reacts with HMC to form magnesium carboxylate borate ester (MCBE), which improves the bonding strength between HMC molecules. Thus, the cold modulus of rupture of HMCC containing boric acid dried at 110 °C are higher than that of calcium aluminate cement-bonded refractory castables (CACC). The decomposition temperature of MCBE is 77 °C higher than that of HMC, so MCBE can endow castables with better mechanical properties at 110 °C–500 °C. The B₄C obtained by MCBE pyrolysis could form a boron-rich liquid phase, which can accelerate the structural densification of castables via transient liquid phase sintering, thus improving the mechanical properties of castables at 500 °C–1100 °C. Moreover, boric acid can improve the thermal shock resistance of HMCC. The residual strength rate first increases and then decreases with an increasing boric acid, and reaches a maximum value of 29.7% (1 wt% boric acid is added), which is 2.3 times that of the CACC. The nanoindentation test showed that the microcracks in the matrix of 1 wt% boric acid castables are easy to initiate but difficult to propagate, so the microcracks are many and wavy.     

页岩中黏土矿物吸附特性分子模拟

页岩的吸附解吸特性对页岩气资源开发具有重要意义。为深入了解页岩中黏土矿物微观吸附机理, 利用Material Studio 分子模拟软件构建了伊利石、蒙脱石和高岭石3种黏土矿物分子模型, 采用巨正则Monte Carlo(GCMC)方法对3种模型的等温吸附量和吸附热进行了模拟计算。研究表明, 在相同温度和压力条件下3种黏土矿物对CH₄分子的吸附量大小顺序是伊利石>蒙脱石>高岭石;随压力增大3种黏土矿物对CH₄分子的吸附量均有所增加, 而且伊利石和蒙脱石对CH₄分子的吸附量对压力变化更为敏感;3种黏土矿物的等量吸附热均小于42 kJ·mol^-1, 对CH₄的吸附为物理吸附;随着温度的升高, CH₄分子的吸附热和吸附量均减小。     

民用建筑防排烟系统设计要点探讨

文章结合《高层民用建筑防火规范》和《建筑设计防火规范》等规范条文,对民用建筑防排烟系统的设计要点进行了一些探讨。     

改进硫脲法浸出含硫铁矿炼锌渣中银的工艺

采用硫脲为络合剂、双氧水为氧化剂,研究了在硝酸介质中浸出含硫铁矿炼锌渣中银的工艺。考察了搅拌速率、反应时间、反应温度、硝酸初始浓度、双氧水浓度、硫脲浓度等因素对银浸出率的影响。结果表明,银的浸出率随着搅拌速率的增大和反应时间的延长先增大然后保持不变,随反应温度、硫脲浓度、双氧水浓度和硝酸初始浓度的增加先增大后减小。当搅拌速率为200 r/min、硝酸浓度为4.11 mol/L、双氧水浓度为0.82 mol/L、硫脲浓度为3.25 mol/L、反应温度为50 ℃、反应时间为1 h时,银浸出率可达82.0%。