Experimental evidence of structural evolution for TiB2 microcrystal under externally high stresses

The morphology evolution and defect structure of TiB₂ microcrystals treated under high stresses were analyzed using scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). The results show that hexagonal TiB₂ with large particle size gradually evolved to flowerlike TiB₂ with small particle size under high stresses. The evolution process is mainly determined by the preferential cleavage of TiB₂ microcrystal, and the presence of multiple lamellar nanotwin and edge dislocation directly provides some evidence of plastic deformation and structural evolution. For clarity, a possible model is suggested based on the HTREM observation and the natural properties of TiB₂ materials to explain the process mechanism.     

研究生创新能力平台的构建与实施

通过建立研究生联合培养基地,整合企业与高校的教育资源,构建研究生创新能力平台,可提高研究生的实践与创新能力。本文详细探讨了构建研究生创新能力平台的具体实施方案。     

三聚氰胺衍生物在高温油田采出水中的缓蚀作用及其机制

以三聚氰胺为基体,通过2步反应制备了三聚氰胺衍生物——三聚氰胺缩甲醛丁二酸钠(MFSS)。采用质量损失法、极化曲线法、交流阻抗法和量子化学计算考察了MFSS在高温模拟油田采出水中对X80钢的缓蚀性能及其缓蚀机制。质量损失分析表明,当MFSS缓蚀剂质量浓度为180 mg/L时,在60 ℃和80 ℃下X80钢的缓蚀率分别可达91.9%和93.7%,说明MFSS可有效地抑制X80钢在油田采出水中的腐蚀;电化学分析表明,MFSS缓蚀剂对X80钢腐蚀的阴、阳极反应过程均有抑制作用,但其抑制阳极反应更为显著,属于以抑制阳极反应为主的混合型缓蚀剂;量子化学计算表明,MFSS分子的HOMO轨道主要集中在胺基基团以及—C=N基团上,三嗪环通过π电子与Fe的螯合作用而平行吸附于Fe(001)面上,缩甲醛丁二酸酯取代基则在Fe(001)面的竖直方向。     

Activation behaviors of isotropic pitch-based carbon fibers from electrospinning and meltspinning

Pitch fibers were prepared from identical petroleum-derived isotropic pitch precursors (IPPs) by both meltspinning and electrospinning. The fibers obtained were stabilized, carbonized, and then finally activated by steam at various conditions. The specific surface area of the noble electrospun (E-spun) fibers was calculated to be 6.4 times larger than that of meltspun (M-spun) fibers due to their finer diameter. The activation was considered as first-order reaction with frequency factor 6.55 × 10⁻⁴ s⁻¹ and the activation energy of 162.3 kJ/mol for E-spun fibers, and for the M-spun fibers with respective values of 4.45 × 10⁻⁴ s⁻¹ and 183.5 kJ/mol. The activation rates of the E-spun fibers were calculated to be 13–20 times faster than those of M-spun fibers in the activation temperatures. The higher activation rates for the E-spun fibers were rationalized on the basis of the higher frequency factors and the lower activation energy due to their finer diameters and less ordered structure than those of M-spun fibers.     

Interfacially reinforced methylphenylsilicone resin composites by chemically grafting multiwall carbon nanotubes onto carbon fibers

Both silane and multiwall carbon nanotubes (CNTs) were grafted successfully onto carbon fibers (CFs) to enhance the interfacial strength of CFs reinforced methylphenylsilicone resin (MPSR) composites. The microstructure, interfacial properties, impact toughness and heat resistance of CFs before and after modification were investigated. Experimental results revealed that CNTs were grafted uniformly onto CFs using 3-aminopropyltriethoxysilane (APS) as the bridging agent. The wettability and surface energy of the obtained hybrid fiber (CF-APS-CNT) were increased obviously in comparison with those of the untreated-CF. The CF-APS-CNT composites showed simultaneously remarkable enhancement in interlaminar shear strength (ILSS) and impact toughness. Moreover, the interfacial reinforcing and toughening mechanisms were also discussed. In addition, Thermogravimetric analysis and thermal oxygen aging experiments indicated a remarkable improvement in the thermal stability and heat oxidation resistance of composites by the introduction of APS and CNTs. We believe the facile and effective method may provide a novel interface design strategy for developing multifunctional fibers.     

Ni1−xCoxSe2?C/ZnIn2S4 Hybrid Nanocages with Strong 2D/2D Hetero-Interface Interaction Enable Efficient H2-Releasing Photocatalysis

Designing a semiconductor-based heterostructure photocatalyst for achieving the efficient separation of photogenerated electron-hole pairs is highly important for enhancing H₂ releasing photocatalysis. Here, a new class of Ni_1−xCo_xSe₂–C/ZnIn₂S₄ hierarchical nanocages with abundant and compact ZnIn₂S₄ nanosheets/Ni_1−xCo_xSe₂^ C nanosheets 2D/2D hetero–interfaces, is designed and synthesized. The constructed heterostructure photocatalyst exposes rich hetero-junctions, supplying the broad and short transfer paths for charge carriers. The close contacts of these two kinds of nanosheets induce a strong interaction between ZnIn₂S₄ and Ni_1−xCo_xSe₂ C, improving the separation and transfer of photo-generated electron-hole pairs. As a consequence, the distinctive Ni_1−xCo_xSe₂ C/ZnIn₂S₄ hierarchical nanocages without using additional noble-metal cocatalysts, display remarkable H₂-relaesing photocatalytic activity with a rate of 5.10 mmol g⁻¹ h⁻¹ under visible light irradiation, which is 6.2 and 30 times higher than those of fresh ZnIn₂S₄ nanosheets and bare Ni_1−xCo_xSe₂ C nanocages, respectively. Spectroscopic characterizations and theory calculations reveal that the strong interaction between ZnIn₂S₄ and Ni_1−xCo_xSe₂ C 2D/2D hetero-interfaces can powerfully promote the separation of photo-generated charge carriers and the electrons transfer from ZnIn₂S₄ to Ni_1−xCo_xSe₂ C.     

2-苯基喹唑啉-4-酮的Vilsmeier反应研究

以邻氨基苯甲酸、苯甲酸酐和乙酸为原料,经过绿色合成方法合成了2-苯基喹唑啉-4-酮,然后对2-苯基喹唑啉-4-酮进行了Vilsmeier反应研究。用IR对其结构进行了表征。考察了反应时间、反应温度和投料配比对Vilsmeier反应的影响。结果表明,反应时间为4 h,反应温度为80~90℃,原料POCl3与2-苯基喹唑啉-4-酮的摩尔比为1.5：1为最佳的反应条件,收率可达67.8%。     

室温离子液体1-丁基-3-甲基咪唑磷酸二丁酯的电导率研究

利用磷酸三丁酯与N-甲基咪唑在恒温150℃下一步合成了离子液体1-丁基-3-甲基咪唑磷酸二丁酯,考察了其在丙酮,水,DMF,乙酸溶剂中的电导率及摩尔电导率。实验发现该离子液体在不同溶剂中的电导率(κ)相差很大,其顺序为κa(水)>κb(DMF)>κc(丙酮)>κd(乙酸)。在相同温度下,电导率及摩尔电导率随浓度的增大而增大;在相同浓度下,电导率及摩尔电导率随温度的升高而增大。