Effects of surfactant/silica and silica/cerium ratios on the characteristics of mesoporous Ce-MCM-41

Using the surfactant CTMABr (cetyltrimethyl ammonium bromide) and cerium(IV) sulfate, mesoporous Ce-MCM-41 molecular sieves were produced under a hydrothermal condition with various surfactant/silica (surfactant/Si) and silica/cerium (Si/Ce) ratios. Changes to the structural traits caused by changing the molar ratios of both surfactant/Si and Si/Ce were investigated. XRD (X-ray diffraction), FT-IR (fourier transform infrared spectroscopy), and SEM (scanning electro microscopy) were used for the characterization of prepared mesoporous samples. Among the tested molar ratios, surfactant/Si ratio of 0.5 and 0.2 showed highest values of d_1 0 0 and intensity, respectively, for the Si-MCM-41. XRD analysis also identified a quintessential hexagonal structure of Ce-MCM-41 for the Si/Ce molar ratio higher than 40 (maintaining the surfactant/Si ratio at 0.2). When cerium content was increased to have the Si/Ce molar ratio of 20, the hexagonal structure of Ce-MCM-41 was collapsed due to the structural stress of substituted cerium. FT-IR results confirmed calcination of Ce-MCM-41 and the incorporation of Ce⁴⁺ ions of cerium sulfate into the silica surface with proper removal of the surfactant. Rod-like shape with rounded edges of the prepared Ce-MCM-41 samples was identified by SEM. These results suggest surfactant/Si ratio of 0.2 and Si/Ce ratio of 40 for the production of Ce-MCM-41 with the highest level of crystallinity.     

低渗透油田合理注采井距的确定--以纯41块沙4段低渗透油田为例

以纯41块沙4段低渗透油田为例，从低渗透油田渗流机理出发，分析了造成低渗透油田开发效果差的主要原因。在计算注水井最大井底流压、油井最小井底流压、油水井之间可建立的最大注采压差的基础上，结合室内试验确定的最小启动压力梯度公式计算油田技术极限注采井距，并结合经济合理井距计算结果，确定了油田合理注采井距，并提出了下二步调整方案，实施后取得了显著的效果。该方法为低渗透油田合理井距的确定、提高低渗透油田的开发效果提供了理论依据。     

高可靠镀Ni／Au工艺及其在微波PTFE电路上的应用

介绍了高可靠电镀Ｎｉ／Ａｕ工艺在ＰＴＦＥ微波印制电路上的应用，并分析了氨基磺酸盐镀软镍和亚硫酸盐镀软金工艺的影响因素及提高Ｎｉ／Ａｕ镀层之间附着力的措施。通过实验及应用证明了与直接镀金工艺相比，在软基材ＰＴＦＥ敷铜箔板上镀Ｎｉ／Ａｕ工艺能大大提高微波电路的可焊性，高温稳定性和长期可靠性，并且用其所制作的微波器件的高频性能也优于直接镀金工业。     

官能团化MCM-41在分离低碳醇-水混合物中的应用

采用一步法水热合成了介孔材料氯丙基官能团化的MCM-41(Cl(CH2)3-MCM-41)、氨丙基官能团化MCM-41(NH2(CH2)3-MCM-41)、甲基官能团化MCM-41(CH3-MCM-41)和氯丙基官能团化硅胶,并考察了它们作为气相色谱固定相分离低碳醇-水混合物的情况。实验结果表明,Cl(CH2)3-MCM-41能够分离低碳醇-水混合物中的各组分,随水、甲醇、乙醇、异丙醇、正丁醇极性的减小,各分子与Cl(CH2)3-MCM-41的作用力增强,保留时间延长。氯丙基官能团化硅胶、NH2(CH2)3-MCM-41)和CH3-MCM-41均不能分离低碳醇-水混合物,表明介孔材料规则的孔道结构、表面嫁接基团等对低碳醇-水混合物的分离有重要影响。同时考察了Cl(CH2)3-MCM-41的氯丙基负载量对低碳醇-水混合物分离效果的影响,结果表明,当氯丙基的摩尔分数为15%时,分离效果最佳。     

In Situ Formation of a Novel Nanocomposite Structure Based on MCM-41 and Polyethylene

M41S materials are prepared by in situ assembly of inorganic precursors and organic template and can be viewed as nanocomposites of the siliceous phase and organic surfactant. Calcination of these precursors gives the M41S materials that have been used to prepare novel nanocomposite structures, in which the organic phase inside the nano-sized pores is isolated by the nano-sized inorganic pore walls. The nanocomposite structures can be formed by in situ polymerization of monomers inside the channels. Polymerization of ethylene takes place inside the nano-sized pores, producing the desired nanocomposite structure. The resulting polyethylene was found to be a mixture of crystalline and amorphous phases.     

碱对AlMCM-41介孔分子筛合成的影响

分别用NaOH和TEAOH合成了AlMCM 4 1介孔分子筛 ,用XRD、2 7AlMASNMR、SEM、TEM、IR、N2 低温吸附和TG DTA对样品进行了表征和比较。结果表明 ,TEAOH和NaOH对AlMCM 4 1有序结构的影响不同。当硅铝原子比为 2 5或 5 0时 ,用NaOH合成的样品有序性较高 ;而当硅铝比为 15时 ,用TEAOH合成的样品有序性较高。交换成氢型AlMCM 4 1后 ,当硅铝比为 2 5或 15时 ,用TEAOH合成的样品抗水解性能优于用NaOH合成的样品 ,其酸量也较大。用TEAOH合成的样品粒度小 ,比表面积、孔径和孔体积都大于用NaOH合成的样品     

Congestion pricing of multi-modal transportation systems

This paper deals with the pricing and investment decision problem of multi-modal transportation systems in which the congestion is a significant factor in the assessment of system costs. This study approaches this congestion pricing problem with a number of social welfare maximization problems, all of which have the identical structure except financial constraints. One welfare maximization problem examined in this study yields the pricing and investment decision, which can attain the first-best social optimality for multi-modal transportation systems. Other welfare maximization problems show he second-best optimal solutions that can address two policy questions in transportation economics, namely, the cross-subsidy between competing modes and peak-period congestion charges on a single highway link. Received: February 2001/Accepted: December 2001 This work was supported in part by funds from BK21 Research Division of Seoul National University for Social Infrastructure and Construction Technology.     

冷41-平14"L"型水平井轨迹优化与控制技术

冷41-平14井受地面条件的限制,靶前位移小,为保证中间套管和完井管柱的顺利下入,剖面设计为“反向造斜-稳斜-降斜-正向造斜-水平段”的“L”型。简要介绍了冷41-平14“L”型水平井的设计概况,详细介绍了该井井眼轨道优化设计原则和设计结果,以及实钻井眼轨迹连续控制技术。该井精确命中A、B靶,两靶处的井斜角、方位角和垂深等达到了设计要求,在A靶实现了软着陆。该井井眼轨道优化设计和井眼轨迹控制技术为类似水平井的井眼轨道设计和轨迹控制提供了有益的借鉴。     

Kinetics of AuSn4 migration in lead-free solders

The relatively fast diffusion of Au atoms in eutectic PbSn matrix is considered one of the contributing factors to the Au embrittlement problem. In this study, we further investigated the Au embrittlement problem in high-Sn solders. Experimentally, Sn3.5Ag (wt.%) spheres with 500-μm diameter were soldered over the Au/Ni soldering pads. It was found that some of the AuSn₄ needles that formed after reflow inside the solder migrated back to the solder/pad interface during thermal aging. However, the migration kinetics in high-Sn solders was slower compared to that in eutectic PbSn. The difference in migration kinetics of AuSn₄ in eutectic PbSn and SnAg was ascribed to the difference in the magnitudes of the Au flux and the Ni flux. In eutectic PbSn, the Au flux was much greater than that of the Ni flux, and the Au and Ni flux were in the same order of magnitude in eutectic SnAg. The relative magnitude of the Au and Ni flux changed in eutectic PbSn and SnAg because the homologous temperatures of PbSn and SnAg were different.     

SFG and DFG investigation of Au(111), Au(210), polycrystalline Au,Au–Cu and Au–Ag–Cu electrodes in contact with aqueous solutions containing KCN and 4-cyanopyridine

We report on potential-dependent in situ SFG and DFG spectroscopy carried out at Au(111), Au(210), polycrystalline Au, Au–Cu and Au–Ag–Cu electrodes in contact with aqueous solutions containing CN⁻ and 4-cyanopyridine (4CP). Spectroelectrochemical work was complemented by cyclic voltammetry. The chief stress has been placed on systematising and quantifying the interaction between 4CP and CN⁻ and the attending effects on the vibrational and electronic structures of the interface. The voltammetric behaviour of the investigated electrodes, modified by the addition of 4CP to the CN⁻ electrolyte, denote changes in the CN⁻ adsorption characteristics and effects of the adsorbed CN⁻ layer on the electrodic reactivity of 4CP. The differences among the investigated electrodes can be explained in terms of their respective degrees of atomic packing or with alloying effects on the stability of adsorbed CN⁻. The potential-dependent spectra have been analysed quantitatively with a model for the second order non linear susceptibility accounting for vibrational and electronic effects. The spectral changes induced by addition of 4CP denote interaction of the aromatic with the electrode through the CN⁻ monolayer. The non-resonant contribution yields information on the effects of 4CP on the fine structure of the bound electron density of states.