Structure and Pyrolysis Characteristics of Lignin Derived from Wood Powder Hydrolysis Residues

Physicochemical characteristics of wood powder acid hydrolysis residue (WAHR) were studied firstly in this study, and WAHL (lignin derived from WAHR) was separated successfully from WAHR based on an improved isolating method. The content of functional group such as phenolic hydroxyl group of guaiacyl, syringyl, and hydroxyl?Cphenyl units in WAHL were identified by ³¹P-NMR and DFRC (derivatization followed by reductive cleavage) method. Thermal degradation experiments were carried out on a thermogravimetric (TG) analyzer to show pyrolysis characteristics of WAHL. The compositions of pyrolysis products of WAHL were also studied throughout a pyrolysis?Cgas chromatography?Cmass spectrometry (Py?CGC?CMS) analyzer. It was shown that the pyrolysis of WAHL took place in a wide temperature range and there were two obvious peaks in the differential thermogravimetric diagram. Results of Py?CGC?CMS analysis indicated that pyrolysis products were mainly formed through cleavage of the ??-O-4 connection and multiple pyrolysis.     

铜激光倍频光亚微米投影光刻系统的设计和实验研究

为了研究波长在２５５．３ｎｍ的铜蒸气激光倍频在亚微米光刻中的可行性，设计了带宽为１ｎｍ的１：１折反射式投影光刻物镜和一个带散射板的光管式均匀照相系统，获得了０．６μｍ的光刻分辨率。此结果表明，铜激光倍频光可作为亚微米光刻的照明光源。     

Synthesis of self-assembly BaTiO3 nanowire by sol–gel and microwave method

Self-assembly ferroelectric BaTiO₃ nanowires were fabricated using sol–gel and microwave method. The X-ray diffraction patterns show that BaTiO₃ nanowires belong to the tetragonal perovskite structure. An increase in the intensity of (1 1 0) peak was observed as the annealing time increased. The shape of BaTiO₃ nanowires microwave-annealed for different minutes was investigated using atomic force microscopy. It is found that nanowires of BaTiO₃ annealed for 2.5 min are very clear-cut, orderly and almost uninterrupted. The height of nanowire is near to the film thickness. However, nanowires of BaTiO₃ annealed for 5 min are lesser, shorter and lower, and the distances among these nanowires are wider and well-proportioned. The origin of the distinct differences due to the remotion of atoms obtained enough energy was discussed.     

Transition‐Metal‐Free Defluorosilylation of Fluoroalkenes with Silylboronates

Silylated fluoroalkenes are important synthetic intermediates with complementary reactivity, which play a key role in the construction of natural products, pharmaceuticals, and manmade materials. Converting the normally highly stable fluoroalkenes into silylated fluoroalkenes by selective defluorosilylation is a challenging task. Herein, we report a simple, inexpensive and robust defluorosilylation of a variety of fluoroalkenes with silylboronates in the presence of alkoxy base to directly synthesize various silylated fluoroalkenes. The protocol features mild and safe reaction conditions that avoid a catalyst, a transition metal, a ligand, and high reaction temperature and tolerates a wide scope of fluoroalkene substrates without compromising the efficiency. Density functional theory calculations show that transient silyl anion complex undergoes an S_N2’ or S_N^V substitution, which is responsible for this base‐mediated defluorosilylation.     

涂层厚度与粘接质量的电磁声谐振无损检测

为了解决电磁超声(EMAT)涂层质量检测中接收信号信噪比较低的问题,将电磁声谐振技术(EMAR)应用于涂层质量检测,有效提高了超声接收信号的信噪比.在EMAR仿真中,通过变步长离散仿真得出了谐振与非谐振状态下的时域波形和频谱图,验证了利用电磁声谐振进行涂层质量检测的可行性.以电磁超声谐振驻波作为检测信号,实验中谐振信号...