Mechanical Strength and Tribological Properties of Diglycidyl Ether of Bisphenol-A Cured by Poly(Amide-Amidic Acid) and 4,4’-Diaminodiphenylsulfone

Diglycidyl ether of bisphenol-A (DGEBA) was cured by poly(amide-amidic acid) (PAA) and a commonly used curing agent, 4,4’-diaminodiphenylsulfone (DDS), in different molar ratios. It was found that the flexural strength, tensile strength, tribological properties, and thermal stability strongly depended on the molar ratios of PAA and DDS in the mixed curing agents. The highest flexural strength was obtained when DGEBA was cured with PAA individually. The tensile strength increased with the increase of PAA content in the mixed curing agents. The DGEBA cured with PAA containing curing agents possessed lower friction coefficient than that cured with DDS individually. The wear rate greatly decreased with the PAA content increasing in the mixed curing agent. Tribological behaviors and wear mechanisms were discussed by observing the morphology of wear debris and worn surfaces of the tested samples using scanning electron microscopy (SEM).     

The practical application and electron transfer mechanism of SR-Fenton activation by FeOCl

Research on Chemical Intermediates - An efficient FeOCl for persulfate (PS) and peroxymonosulfate (PMS) catalysis was synthesized by one-step method, followed by the exploration of structure and...     

Enhanced multiple exciton dissociation from CdSe quantum rods: the effect of nanocrystal shape

A unique ability of semiconductor nanocrystals (NCs) is the generation and accommodation of multiple excitons through either optical or electric current pumping. The development and improvement of NC-based optoelectronic devices that utilize multiple excitons requires the understanding of multiple exciton dynamics and their efficient conversion to emitted photons or external charges prior to exciton-exciton annihilation. Here, we demonstrate that significantly enhanced multiexciton dissociation efficiency can be achieved in CdSe quantum rods (QRs) compared to CdSe quantum dots (QDs). Using transient absorption spectroscopy, we reveal the formation of bound one-dimensional exciton states in CdSe QRs and that multiple exciton Auger recombination occurs primarily via exciton-exciton collision. Furthermore, quantum confinement in the QR radial direction facilitates ultrafast exciton dissociation by interfacial electron transfer to adsorbed acceptors. Under high excitation intensity, more than 21 electrons can be transferred from one CdSe QR to adsorbed methylviologen molecules, greatly exceeding the multiexciton dissociation efficiency of CdSe QDs.     

仲烷基卤化锌与6-氯嘌呤类化合物的Negishi偶联反应

在室温条件下,以邻菲罗啉作为配体,无水氯化镍催化的Negishi偶联反应合成了一系列6位链状仲烷基取代的嘌呤化合物.该方法反应条件温和、原料易得、产物收率高.     

A scanning laser induced fluorescence detection system for capillary electrophoresis microchip based on optical fiber

In this paper, a scanning laser induced fluorescence detection system for capillary electrophoresis microchip based on single-mode optical fiber has been established using a green diode pumped solid-state laser as excitation source. It includes laser induced fluorescence detection subsystem, capillary electrophoresis microchip, mechanical scanning platform, channel identification unit and fluorescent signal processing subsystem. Two V-shaped detecting probes composed of optical fiber for transmitting the excitation light and detecting the induced fluorescence were constructed. Parallel four-channel signal analysis of capillary electrophoresis was performed by this system using Rhodamine B sample solution. Furthermore, the separation and distinction of different concentrations of Rhodamine B sample were achieved with the constructed detection system. The lowest detected concentration is 1.0 × 10⁻⁵ mol/L for Rhodamine B sample. The results show that the constructed detection system possesses some advantages of compact structure, low cost, and better stability which could be used as reference to the design and optimization of laser induced fluorescence detection system for capillary electrophoresis microchip.     

自动校准型pH计电计输入阻抗引起的示值误差检定方法的探讨

由于一些自动校准型pH计设置的校准点与计量检定规程要求的pH 7(或电计等电位值)无法对应,探讨了用pH 6.86点代替pH 7点,解决了电计输入阻抗引起的示值误差无法按照计量检定规程要求进行检定的问题。通过实验验证了该方法的可行性。     

用于萤石化学分析的标准样品的研制

萤石又称氟石,主要成分为氟化钙。萤石因产地不同常含有二氧化硅、磷、硫、氧化铝、硫酸钡和三氧化二铁等杂质,同时还含有砷、铅和汞等微量元素[1-3]。通过萤石矿浮选工艺制备氟化钙含量大于97%的萤石精粉,萤石精粉是化学工业中制备氢氟酸等含氟化合物的主要原料[4],其原料成分的纯度直接影响产品质量.     

Catalytic Dealkylation of Ethers to Alcohols on Metal Surfaces

On‐surface synthesis has prompted much interest in recent years because it provides an alternative strategy for controlling chemical reactions and allows for the direct observation of reaction pathways. Herein, we combined scanning tunneling microscopy and density functional theory to provide extensive evidence for the conversion of alkoxybenzene‐containing ethers into alcohols by means of surface synthesis. The reported dealkylation reactions are finely controlled by the annealing parameters, which govern the onset of successive alkyl chains dissociations. Moreover, density functional theory calculations elucidate the details of the reaction pathways, showing that dealkylation reactions are surface‐assisted and very different from their homogeneous analogues in solution.     

Rheology Properties and Plugging Performance of Fluorescent Polyacrylamide Microspheres in Fractures

Polyacrylamide microspheres have recently drawn great attention in conformance control due to their advantages over traditional gel treatments. One important question that has been raised is whether the tiny particles can be produced from production wells. However, current products are difficult to use for detecting fluids generated by production wells. In this paper, the fluorescent polyacrylamide microspheres were successfully synthesized; they can emit blue fluorescence under ultraviolet irradiation. Their swelling property, fluorescence characteristics, rheology property, creep-recovery property, and plugging performance were evaluated in the laboratory. The results indicated that the microspheres could emit blue fluorescence under ultraviolet irradiation after passing through a fracture model. Their creep-recovery ability after deformation was very high, and their elastic recovery rate extended to 94.1%, which suggests that the microspheres almost recover to their original shape and size after deformation. The transparent fracture model plugging test shows that the microspheres can migrate and plug a fracture with a width of 0.3 mm, which is much smaller than the diameter of the microspheres.