聚丙烯与SBS嵌段共聚物共混时的结晶行为

用偏光显微镜,小角光散射,动态力学测量和DSC等方法研究了聚丙烯和SBS共混物的结晶行为。结果表明,SBS的混入可以降低聚丙烯的结晶程度和阻碍球晶的形成,因而有利于提高聚丙烯塑料的抗冲击性能。从DSC实验也看到共混物中的聚丙烯具有较高的结晶速率。     

Laser ablation in analytical chemistry-a review

Laser ablation is becoming a dominant technology for direct solid sampling in analytical chemistry. Laser ablation refers to the process in which an intense burst of energy delivered by a short laser pulse is used to sample (remove a portion of) a material. The advantages of laser ablation chemical analysis include direct characterization of solids, no chemical procedures for dissolution, reduced risk of contamination or sample loss, analysis of very small samples not separable for solution analysis, and determination of spatial distributions of elemental composition. This review describes recent research to understand and utilize laser ablation for direct solid sampling, with emphasis on sample introduction to an inductively coupled plasma (ICP). Current research related to contemporary experimental systems, calibration and optimization, and fractionation is discussed, with a summary of applications in several areas.     

Molecular films of water-miscible ionic liquids formed on glassy carbon electrodes: characterization and electrochemical applications

This letter describes the formation and possible electrochemical applications of molecular films of water-miscible imidazolium-based ionic liquids (ILs) on glassy carbon (GC) electrodes. X-ray photoelectron spectroscopy (XPS) and electrochemical results indicate that the water-miscible ILs used in this study can interact with the GC electrode and form molecular films on the electrode surface. The formed molecular films are found to possess striking electrochemical properties such as electrocatalysis toward ascorbic acid (AA) and the capability to facilitate direct electron transfer of horseradish peroxidase (HRP). This demonstration would pave the way for new electrochemical applications of water-miscible ILs and is envisaged to be useful for the investigation of the electrochemical properties of water-miscible ILs in aqueous media provided the same counteranion is used as the supporting electrolyte.     

The effect of B2O3 addition on the crystallization of amorphous TiO2-ZrO2 mixed oxide

The effect of B₂O₃ addition on the crystallization of amorphous TiO₂-ZrO₂ mixed oxide was investigated by X-ray diffraction (XRD), thermogravimetric and differential thermal analysis (TG/DTA). TiO₂-ZrO₂ mixed oxide was prepared by co-precipitation method with aqueous ammonia as the precipitation reagent. Boric acid was used as a source of boria, and boria contents varied from 2 to 20 wt%. The results indicate that the addition of small amount of boria (<8 wt%) hinders the crystallization of amorphous TiO₂-ZrO₂ into a crystalline ZrTiO₄ compound, while a larger amount of boria (?8 wt%) promotes the crystallization process. FT-IR spectroscopy and ¹¹B MAS NMR results show that tetrahedral borate species predominate at low boria loading, and trigonal borate species increase with increasing boria loading. Thus it is concluded that highly dispersed tetrahedral BO₄ units delay, while a build-up of trigonal BO₃ promote, the crystallization of amorphous TiO₂-ZrO₂ to form ZrTiO₄ crystals.     

An in situ STM study on the long-range surface restructuring of Au(1 1 1) in a non-chloroaluminumated ionic liquid

We report an in situ STM study of a potential-dependent long-range surface restructuring of Au(1 1 1) electrode in neat 1-butyl-3-methylimidazolium tetrafluoroborates (BMIBF₄) ionic liquid. Au(1 1 1) undergoes a significant long-range surface restructuring upon cathodic excursion to −1.0 V vs. Pt quasi-reference. The restructuring involves the formation of tiny pits, which then develops into a stable worm-like network with an average width of the network grids 2 nm. Electrochemical annealing occurs at the cathodic limit with the presence of a reduction product of cation BMI⁺. A smooth surface is recovered with the appearance of the typical (√3 × 22) reconstruction of Au(1 1 1). The surface restructuring is reestablished upon anodic excursion to −1.3 V after the adsorbed reduction product is oxidized. The long-range surface restructuring phenomenon is tentatively explained as a result of partial charge transfer to the weakly adsorbed BMI⁺, which reduces the metal–metal cohesive energy. In addition, the synergetic effect of the counter anion BF₄⁻ may also be involved. The results provide a knowledge of Au(1 1 1) electrode behavior in the neat ionic liquid and are beneficial to understanding in situ STM results involving surface morphological changes in such a media.     

CO在Pd／ZrO2—Al2O3催化剂上表面反应性能的研究

用流动反应法和ＴＰＳＲＭＳ等技术研究了ＣＯ在Ｐｄ／γＡｌ２Ｏ３和含有ＺｒＯ２的催化剂上的吸脱附行为、表面反应及催化氧化活性，同时用ＸＲＤ技术测定了催化剂的物相结构。结果表明，在Ｐｄ／γＡｌ２Ｏ３催化剂中用浸渍法添加ＺｒＯ２或掺杂超细ＺｒＯ２后，催化剂的氧化活性均有明显提高；ＣＯＴＰＳＲ的实验结果表明，ＣＯ在氧化态Ｐｄ催化剂上程序升温脱附过程中主要与表面氧发生氧化反应，而在还原态Ｐｄ催化剂上发生歧化反应，并发现ＣＯ２的脱附量及脱附峰温次序与对ＣＯ的氧化活性有一致的对应关系。     

ZrO2对Mn—O／γ—Al2O3催化剂中表面氧性能的影响

用ＴＰＤ－ＭＳ和ＴＰＲ技术研究了Ｍｎ－Ｏ／γ－Ａｌ２Ｏ３和Ｍｎ－Ｏ／ＺｒＯ＋γ－Ａｌ２Ｏ３催化剂中表面氧的脱附、还原性能和再生氧化恢复性能，并用ＸＲＤ对催化剂的固相结构进行了表征。结果表明，Ｍｎ－Ｏ／γ－Ａｌ２Ｏ３或Ｍｎ－Ｏ／ＺｒＯ２＋γ－Ａｌ２Ｏ３催化剂上存在ＭｎＯ２、Ｍｎ２Ｏ３和少量Ｍｎ３Ｏ４物种。ＺｒＯ２的存在不影响Ｍｎ－Ｏ／γ－Ａｌ２Ｏ３的ＴＰＲ的ＴＰＤ的特征峰，但使ＭｎＯ２的量明显增加，     

Capillary electrochromatographic separation of enantiomers under aqueous mobile phases on a covalently bonded cellulose derivative chiral stationary phase

A chemically bonded cellulose tris(3,5-dimethylphenylcarbamate) chiral stationary phase (CSP) was prepared by a radical polymerization reaction. The prepared CSP was packed into fused-silica capillaries with inner diameter of 75 microm to perform enantiomer separations in CEC. The electrochromatographic behavior of the CSP was investigated. On the prepared CSP, high EOF could be generated under acidic mobile phases, which represented an advantage for the separation of acidic enantiomers. Several neutral, acidic, and basic enantiomers were resolved on the prepared CSP under aqueous mobile phases. The column efficiencies were between 20,000 and 100,000 plates/m, which were much higher than those of HPLC. In addition, it was observed that the separation of some enantiomers benefited from the adoption of THF as mobile phase modifier.     

Ferromagnetic anomaly associated with the antiferromagnetic transitions in (donor)[Ni(mnt)2]-type charge-transfer salts

Three newly prepared [Ni(mnt)2] complexes, (HMTTF)[Ni(mnt)2], (ChSTF)[Ni(mnt)2], and (DBTTF)2[Ni(mnt)2], are reported (DBTTF = dibenzotetrathiafulvalene, ChSTF = 2,3-cyclohexylenedithio-1,4-dithia-5,8-diselanafulvalene, HMTTF = bis(trimethylene)-tetrathiafulvalene, and mnt = maleonitrile dithiolate). The former two compounds have usual DA-type (D = donor, A = acceptor) mixed stacks, whereas the DBTTF complex has DDDDAA-type 6-fold columns. These compounds are electrical insulators, but the HMTTF and ChSTF complexes exhibit chiT minima at 16 and 55 K, respectively, followed by chiT peaks at 8 and 16 K. Below these temperatures the ESR signal disappears, indicating antiferromagnetic transitions. The origin of the ferromagnetic interaction is explained either from the difference of the g values between the donor and the anion or from the intrinsic ferromagnetic interaction of the [Ni(mnt)2] anions.     

Template-free, polymerase-free DNA polymerization

A combination of a DNA ligase and a restriction endonuclease provides a DNA polymerase activity, which might suggest a novel strategy for polymer synthesis.