Influence of the composition of the binder and the carbonation on the zeta potential values of hardened cementitious materials

Electroosmotic experiments have been carried out on eight different mixes of hardened cementitious matrixes including concrete, mortar and pastes, different types of binders, carbonated and non-carbonated specimens and different test conditions. From these trials, the zeta potential values have been determined and the optimum experimental parameters and devices have been established. In addition, the influence of the composition of the binder on the zeta potential has been quantified indicating that higher amounts of Al₂O₃ in the binder lead to higher positive values of zeta potential, while the SiO₂ acts just on the opposite side. This has been explained in terms of the different i.e.p. (isoelectric point) for both oxides. Concerning the influence of carbonation, it increases the absolute value of the zeta potential toward more negative values; this behaviour has been attributed to the influence of the specifically adsorbed Ca²⁺ in the negative sites of the surface in the non-carbonated samples.     

Effect of solution properties on nanofibrous structure of electrospun poly(lactic‐co‐glycolic acid)

Electrospinning of poly(lactic‐co‐glycolic acid) (PLGA) in chloroform or 1,1,1,3,3,3‐hexafluoro‐2‐propanol (HFIP) was investigated, focusing on its solution parameters, to develop nonwoven biodegradable nanofibrous structures for tissue engineering. PLGA nanofibers were obtained by electrospinning of 15 wt % PLGA solution and the resulting average fiber diameters were varied with the range of 270–760 nm, depending on solution property. When small amounts of benzyl triethylammonium chloride (BTEAC) was added to the PLGA/chloroform solution, the average diameter was decreased from 760 to 450 nm and the fibers were densely amounted in a straight shape. In addition, the average fiber diameter (270 nm) of nanofibers electrospun from polar HFIP solvent was much smaller than that (760 nm) of nanofibers electrospun from nonpolar chloroform solvent. Therefore, it could be concluded that conductivity or dielectric constant of the PLGA solution was a major parameter affecting the morphology and diameter of the electrospun PLGA fibers. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1214–1221, 2006     

Electrical double layer characteristics of nanoporous carbon derived from titanium carbide

Electrochemical parameters of the nanoporous carbide-derived carbon|organic electrolyte have been studied by cyclic voltammetry and electrochemical impedance spectroscopy. The gas adsorption measurements have been used for evaluating the specific surface area, pore size distribution and porosity as the essential parameters influencing the double layer performance of carbon. The region of ideal polarizability, values of series and parallel resistance, capacitance and other important electrical double layer parameters were established. It was shown that specific capacitance of typical nanoporous carbon derived from titanium carbide is in the range of 70-90 F cm⁻³ or 100-130 F g⁻¹ and it depends on the synthesis conditions. The influence of the electrolyte solvent to the capacitance was insignificant, although acetonitrile was advantageous with respect of smaller viscosity.     

Structure, thermal-stability and reducibility of Si-doped Ce–Zr–O solid solution

The Si-doped Ce–Zr–O solid solutions have been prepared by the reverse microemulsion method. The effects of Si and its content on the structure characters, thermal-stability and reducibility of the Ce–Zr–O solid solution have been studied by N₂ adsorption, XRD, laser Raman (LR), TPR, FT-IR, NMR and XPS methods. The results indicate that, there are the bonds of Si–O–M (Ce or Zr) in the Ce–Zr–Si–O solid solutions, and the presence of Si can increase obviously the surface area, thermal-stability, crystal lattice distortion rate, and reducibility of the solid solution. The surface area of the sample with 20 wt.% Si reaches 153 m² g⁻¹ after being calcined at 900 °C for 6 h. The Ce–Zr–O solid solution with 5.2–10 wt.% Si shows excellent thermal-stability and reducibility.     

非水电解质浓溶液的热力学研究(Ⅰ)——用缔合模型关联、推算298.15K时HCL甲醇浓溶液的活度系数

利用HCl在甲醇中稀溶液的活度系数,通过Pitzer的缔合模型,关联出298.15K HCl在甲醇中的缔合常数Kx=1.7×10~2,然后利用HCl在甲醇中浓溶液的活度系数关联出近程作用单参数,进而推算溶剂甲醇的活度系数及溶液总压,均得到满意的结果,说明HCl甲醇浓溶液的热力学关联必须考虑HCl的部分离解效应。     

苯乙酸溶解度测定及提取工艺研究

为了提取6-氨基青霉烷酸(6-APA)、7-ADCA生产过程中产生的副产物苯乙酸,采用物理法测定了苯乙酸在水、水-乙醇、水-丙酮中的溶解度及其在水中的溶解速率,由此确定了水法多次提取的工艺方案。结果表明,在提取温度(60±2)℃,时间10~15 m in,水用量1 500 mL,提取次数3~4次时,苯乙酸收率为90.8%,纯度为99.3%。该法污染少、成本低,所得PAA产品质量好。     

Thermodynamic assessment of MCl–YCl3 (M=Na,K, Rb,Cs) systems

Thermodynamic properties and phase diagrams of the MCl–YCl₃ (M=Na, K, Rb, Cs) systems were reassessed by using the CALPHAD method with the latest phase diagram data. A two-sublattice ionic solution model (M⁺)_P(Cl⁻, ${\mathrm{YCL}}_6^{3-}$, YCl₃)_Q reflecting the ionic behavior of the components was adopted to describe the liquid phase in the systems. A new set of optimized model parameters was found, and the calculated phase diagrams and enthalpies of mixing have good agreement with experimental data. The calculated liquidus near to YCl₃ side agrees much better with experimental data compared with previous work. In consideration of high and low temperature modifications as well as stability of intermediate compounds, Gibbs energies of formation of these compounds evaluated in the present work are more reasonable.     

间歇反应器中料液脱溶时间的估算

介绍以对间歇反应器的一些基本合理的假设为基础,利用溶剂和传热介质的热力学和物性参数,推导出分别用水蒸汽和传热流体(THF)作为反应器夹套加热介质时,估算将反应器内料液进行脱溶浓缩所需时间的数学表达式,并用示例加以说明。     

TiO2加入量对富铝尖晶石烧结性能的影响

以α-Al2O3、分析纯的MgO及分析纯的TiO2为原料,研究了在1400℃、1500℃、1600℃保温3 h下,TiO2加入量(分别为0、1%、2%、4%)对Al2O3与MgO物质的量比为21的富铝尖晶石烧结性能的影响,并利用XRD进行物相组成分析,利用SEM和EDAX进行显微结构分析.结果表明由于TiO2与MgAl2O4的固溶作用,加入TiO2可显著改善富铝尖晶石的烧结性能;随着TiO2加入量的增加,试样的体积密度增加,显气孔率降低,特别是在1600℃烧结后的试样尤为显著.