焙烧还原条件下硬脂酸钠改性水滑石的制备及应用

以镁铝碳酸根型水滑石MgAl-CO₃-LDHs(LDHs)为前驱体,硬脂酸钠(NaSt)为改性剂,通过焙烧还原法在硬脂酸钠的溶液中制备硬脂酸钠改性水滑石LDHs-NaSt,采用X射线衍射仪(XRD)、傅里叶转变红外光谱仪(FTIR)和扫描电镜(SEM)对结构进行表征,并研究不同改性剂加入量条件下得到的改性水滑石对聚氯乙烯(PVC)热稳定性能的影响。结果表明,在氮气保护下,焙烧后的水滑石可以成功复原,硬脂酸钠对LDHs的改性为表面改性,但影响复原水滑石的结晶度。改性水滑石可以改善PVC的初期着色性和长期热稳定性,随着改性剂浓度的增大,当NaSt与LDHs质量比为1∶4时,静态热老化时间可以达到370 min,比未改性水滑石热稳定性能提升了61%。     

电位滴定法测定啤酒中氯离子含量

本文讨论了用银电极电位滴定法测定啤酒中氯离子含量。在20ml啤酒样品,0.5ml 6mol/LHNO_3和2.0ml 0.1g/mlKNO_3组成的体系中,测得滴定终点电位值为270±2mv。三种不同标准添加量的方法回收率都大于98.6％。方法精密度:同一样品连续测定12次,标准偏差为0.74,变异系数0.65％。同时测得三种国产啤酒中氯离子含量为114～152mg/L。     

Experimental investigation and numerical modeling of chloride penetration and calcium dissolution in saturated concrete

Chloride penetration and calcium dissolution have been investigated for a saturated concrete after exposure to a 0.5 mol/L NaCl solution for a period of up to 3150 days. Simultaneous ion transport model (SiTraM) that allows the transport of chloride and calcium ions to be simultaneously simulated in a hydrated cement system has been used to verify the experimental results.Self-compacting concrete (SCC) with a water to cement ratio of 0.3 resulted in a limited chloride penetration depth while the calcium dissolution was also reduced within the near surface zone. Increased unit water content for normal concrete resulted in higher chloride penetration depth and larger dissolution front of Ca(OH)₂ regardless of having the same water to cement ratio.It was revealed that the SiTraM can predict the profiles of chloride and calcium for self-compacting concrete. It was also found that the primary factor to control chloride penetration front and the dissolution front of Ca(OH)₂ was the pore structure characteristic of concrete.     

Antioxidant activities of aqueous extracts of selected plants

The antioxidant properties of 25 edible tropical plants, expressed as Trolox equivalent antioxidant capacity (TEAC), were studied using DPPH (1,1-diphenyl-2-picrylhydrazyl free radical) scavenging and reducing ferric ion antioxidant potential (FRAP) assays. Their cupric ion chelating activities (CCA) and total polyphenol contents (TPC) were also determined. A strong correlation between TEAC values obtained for the DPPH assay (TEAC_DPPH) and those for the FRAP assay (TEAC_FRAP) implied that compounds in the extracts were capable of scavenging the DPPH free radical and reducing ferric ions. A satisfactory correlation of TPC with TEAC_DPPH and TEAC_FRAP suggested that polyphenols in the extracts were partly responsible for the antioxidant activities while its correlation with CCA was poor, indicating that polyphenols might not be the main cupric ion chelators. Principal component analysis (PCA) indicated that TEAC_DPPH, TEAC_FRAP and TPC contributed to the total variation in the antioxidant activities of the plants.     

AM／AMPS／DMDAAC／AMC16S共聚物的合成与性能

采用氧化还原引发体系合成了丙烯酰胺（ＡＭ）／２丙烯酰胺基－２－甲基丙磺酸（ＡＭＰＳ）／二甲基二烯丙然氯化铵（ＤＭＤＡＡＣ）／２－丙烯酰胺基十六烷磺酸（ＡＭＣ１６Ｓ）四元共聚物,借助红外光谱和差热分析研究了聚合物的结构和热稳定性,初步评价了共聚物的溶液性能,结果表明,ＡＭ／ＡＭＰＳ／ＤＭＤＡＡＣ／ＡＭＣ１６Ｓ共聚物具有较好的热稳定性和耐温抗盐能力。     

氯乙烯-醋酸乙烯酯共聚物的后功能化研究

通过将氯乙烯－醋酸乙烯酯－丙烯酸羟乙醋共聚物（VAGF）与马来酸酐酯化接枝，制得带羟基的氯醋三元共聚物。探索了原料配比、催化剂用量、反应时间及反应温度对酯化接枝反应的影响，并用红外光谱进行表征。得到酯化反应的最佳条件为：催化剂用量为VAGF质量的0．8％，VAGF质量分数为15％，温度100℃，时间9h。氯乙烯－醋酸乙烯酯－丙烯酸羟乙酯三元共聚物的马来酸酐酯化活性高于氯乙烯－醋酸乙烯酯－乙烯醇三元共聚物。     

氯乙烯悬浮聚合釜搅拌工程的研究

以冷模方法对目前我国广泛采用的氯乙烯悬浮聚合ＬＦ３０－Ⅱ型３０ｍ￣３，７０ｍ￣３及１３０ｍ￣３聚合釜搅拌工程进行了研究。剖析了搅拌桨叶、挡板的设置；并对这几种聚合釜的搅拌功率准数、搅拌功率消耗、循环特性和湍流强度等特性进行了具体的比较。其结果为氯乙烯悬浮聚合釜的搅拌设计与工业釜的改造提供了技术数据。     

Irreversible dilation of NaCl contaminated lime-cement mortar due to crystallization cycles

The mechanism of damage occurring in NaCl contaminated materials has not been clarified yet. Apart from crystallization pressure, other hypotheses have been proposed to explain the cause of decay. Irreversible dilation has been observed in a few cases but has never been studied in a more systematic way. The aim of the research is to contribute to the modeling of this phenomenon.In the present paper the effect of NaCl on the hydric and hygric behavior of a lime-cement mortar is extensively studied. The results indicate that NaCl influences the hydric and hygric dilation behavior of the material. The material contaminated with NaCl shrinks during dissolution and dilates during crystallization of the salt. This dilation is irreversible and sufficient to damage the material after few dissolution/crystallization cycles. This behavior is not restricted to NaCl, but is observed in the presence of other salts as well (NaNO₃ and KCl). Outcomes of electron microscopy studies suggest that salts causing irreversible dilation tend to crystallize as layers on the pore wall.     

Evaluation of chloride penetration in high performance concrete using neural network algorithm and micro pore structure

Chloride attack is one of the major causes of deterioration of reinforced concrete structures. In order to evaluate the chloride behavior in concrete, a reasonable prediction for the diffusion coefficient of chloride ion, which governs mechanism of chloride diffusion inside concrete, is basically required. However, it is difficult to obtain chloride diffusion coefficients from experiments due to time and cost limitations.In this study, a numerical technique for chloride diffusion in high performance concrete (HPC) using a neural network algorithm is proposed. In order to collect comparative data on diffusion coefficients in concrete with various mineral admixtures such as ground granulated blast-furnace slag (GGBFS), fly ash (FA), and silica fume (SF), a series of electrically driven chloride penetration tests was performed. Seven material components in various mix designs and duration time are selected as neurons in a back-propagation algorithm, and associated learning of the neural network is carried out. An evaluation technique for chloride behavior in HPC using the obtained diffusion coefficients from the neural network algorithm is developed based on, so-called, Multi-Component Hydration Heat Model (MCHHM) and Micro Pore Structure Formation Model (MPSFM). The applicability of the developed technique is verified by comparing the analytical simulation results and the experimental results obtained in this study. Furthermore, this proposed technique using the neural network algorithm and micro modeling is applied to available experimental data for verification of its applicability.     

Enhanced performance of direct peroxide/peroxide fuel cell by using ultrafine Nickel Ferric Ferrocyanide nanoparticles as the cathode catalyst

Direct peroxide-peroxide fuel cell (DPPFC) employing with H₂O₂ both as the fuel and oxidant is an attractive fuel cell due to its no intermediates, easy handling, low toxicity and expense. However, the major gap of DPPFC is the cathode performance as a result of the slow reaction kinetics of H₂O₂ electro-reduction and thus the target issue is to design cathode catalysts with high performance and low cost. Herein, different with using noble metal of state-of-the-art, we have successfully synthesized ultra-fine NiFe ferrocyanide (NiFeHCF) nanoparticles (the mean particles size is 2.5 nm) through a co-precipitation method, which is used as the cathode catalyst towards H₂O₂ reduction in acidic medium. The current density of H₂O₂ reduction on the resultant NiFeHCF electrode after the 1800 s test period at ?0.1, 0 and 0.1 V are 121, 93 and 76 mA cm², respectively. Meanwhile, a single two-compartment DPPFC cell with NiFeHCF nanoparticles as the cathode and Ni/Ni foam as the anode is assembled and displayed a stable OCP of 1.09 V and a peak power density of 36 mW cm^?2 at 20 °C, which is much higher than that of a DPPFC employed with Pd nano-catalyst as cathode.