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1.
Haijie Li Yuting Shang Wenrui Huang Bingfeng Xue Xiaomeng Zhang Zhe Cui Peng Fu Xinchang Pang Qingxiang Zhao Minying Liu 《应用聚合物科学杂志》2021,138(39):51017
Succinic acid is an important synthetic monomer but it is difficult to use it as a precursor for synthesizing high molecular weight polyamide, due to its tendency to perform intra-cyclization reaction at high temperature. In order to solve this problem, in this paper, the direct solid-state polymerization (DSSP) method with the initial reactant, nylon salt which was composed of 1, 5-diaminopentane, succinic acid, and terephthalic acid, was applied to synthesize the bio-based copolyamide PA 5T/54. In comparison with the conventional melting polymerization method, the DSSP method can prevent the cyclization reaction of succinic acid effectively due to the lower reacting temperature as well as the restriction effect of the nylon salt. As a result, the product fabricated by DSSP method has higher molecular weight and much lighter color from red to white. Therefore, the DSSP method is advantageous for the synthesis of the polymers or copolymers composed of the succinic acid as the monomer. Furthermore, the polymerization mechanism proposed in this work can serve as a guidance for the design of the molecular structure and control of the polymerization process. 相似文献
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Yunyan Liu Ning Jiang Yao Liu Dawei Cui Chang-Feng Yu Huiqiang Liu Zhao Li 《Ceramics International》2021,47(16):22416-22423
Pulsed laser deposition (PLD) was used to prepare tungsten trioxide (WO3) films on ITO substrates with a varying laser power density of 4.0–5.5 W/cm2. XPS indicated that when the laser power density decreased, the peak positions of the W 4f and O 1s orbits shifted slightly to low energy due to the difference in oxygen vacancies. As the laser power density decreased, W6+ gradually replaced the lattice position of O2?, increasing oxygen vacancies in the lattice. The transmittance modulated values (ΔT) were over 44% at 830 nm, indicating strong absorption by the WO3 thin films in the near-infrared ray. The switching time of the WO3 thin films between bleached states and coloured states decreased as the laser power density increased due to the amorphous structure, morphology, and lower oxygen deficiency at a high power density. The high ΔT and very fast switching time of tb (1.09 s) and tc (6.01 s) demonstrated the excellent electrochromic (EC) properties of the WO3 films prepared by PLD. 相似文献
5.
Xuye Wang Guopu Shi Qinggang Li Junyan Wu Hao Wu Liu Zhang Zhi Wang 《Ceramics International》2021,47(2):2280-2287
Owing to the good physicochemical compatibility and complementary mechanical properties of Ti3SiC2 and Al2O3, Ti3SiC2/Al2O3 composites are considered as ideal structural materials. However, TiC and TiSi2 typically coexist during the synthesis of Ti3SiC2/Al2O3 composites through an in-situ reaction, which adversely affects the mechanical properties of the resulting composites. In this study, Ti3SiC2/Al2O3 composites were prepared via in-situ hot pressing sintering at 1450 °C. Ge, which was used as a sintering aid, improved the purity and mechanical properties of the Ti3SiC2/Al2O3 composites. This is because Ge replaced some of the Si atoms to compensate the evaporation loss of Si to form Ti3(Si1-xGex)C2, which showed a crystal structure similar to that of Ti3SiC2. Furthermore, the molten Ge accelerated the diffusion reaction of the raw materials, increasing the overall density of the Ti3SiC2/Al2O3 composites. The optimum Ge amount for improving the mechanical properties of the composites was found to be 0.3 mol. The flexural strength, fracture toughness, and microhardness of the composite with the optimum Ge amount were 640.2 MPa, 6.57 MPa m1/2, and 16.21 GPa, respectively. The formation of Ti3(Si1-xGex)C2 was confirmed by carrying out X-ray diffraction, energy dispersive spectroscopy, and transmission electron microscopy analyses. A model crystal structure of Ti3(Si1-xGex)C2 doped with 0.3 mol Ge was established by calculating the solid solubility of Ge. 相似文献
6.
Gui-Jia Gao Mei-Qi Zeng En-Liang Zhang Rong-Chang Zeng Lan-Yue Cui Dao-kui Xu Feng-Qin Wang M.Bobby Kannan 《材料科学技术学报》2021,83(24):161-178
The microstructure and chemical compositions of the solid solution-treated Mg-3Nd-1Li-0.2Zn alloy were characterized using optical microscope,scanning electron microscope(SEM),transmission electron microscope(TEM),electron probe micro-analyzer(EPMA)and X-ray photoelectron spectroscopy(XPS).The corrosion behaviour of the alloy was investigated via electrochemical polarization,electrochemical impedance spectroscopy(EIS),hydrogen evolution test and scanning Kelvin probe(SKP).The results showed that the microstructure of the as-extruded Mg-3Nd-1Li-0.2Zn alloy contained α-Mg matrix and nanometric second phase Mg41 Nd5.The grain size of the alloy increased significantly with the increase in the heat-treatment duration,whereas the volume fraction of the second phase decreased after the solid solution treatment.The surface film was composed of oxides(Nd2O3,MgO,Li2O and ZnO)and carbonates(MgCO3 and Li2CO3),in addition to Nd.The as-extruded alloy exhibited the best corrosion resistance after an initial soaking of 10 min,whereas the alloy with 4h-solution-treatment possessed the lowest corrosion rate after a longer immersion(1 h).This can be attributed to the formation of Nd-containing oxide film on the alloys and a dense corrosion product layer.The dealloying corrosion of the second phase was related to the anodic Mg41Nd5 with a more negative Volta potential relative to α-Mg phase.The preferential corrosion of Mg41Nd5 is proven by in-situ observation and SEM.The solid solution treatment of Mg-3Nd-1Li-0.2Zn alloy led to a shift in corrosion type from pitting corrosion to uniform corrosion under long-term exposure. 相似文献
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随着对环保及自用水率的要求日益严格,水厂生产废水的减排已成为发展趋势.但既有水厂用地紧张和生产废水的处理工艺占地多存在矛盾,制约了水厂新增生产废水处理工艺的可行性.文中引入斜管沉淀提升沉淀效率、取消浓缩池、使用叠螺脱水机代替离心脱水机的优化设计方案,相较原设计的传统分离式生产废水处理工艺,生产废水停留时间减少75%,占地面积减少约48%.实践证明,该优化设计方案能够有效解决水厂生产废水处理工艺设计过程中遇到的用地不足问题,并有效地降低建设投资. 相似文献
8.
采用有限元模拟和实验研究了挤压钛合金弯曲管件。通过实验验证了工件的形状和尺寸精度,并通过有限元模拟分析了工艺参数对挤出过程中变形体的平均压应力分布情况和挤出弯管件的曲率半径的影响规律。结果表明:有限元模拟中,弯管件的曲率半径误差为6.03%,弯管直径误差为3.82%;在靠近定径带处,平均压应力呈非均匀分布;在焊合腔内,靠近细分流孔区域的平均压应力小于靠近粗分流孔区域的平均压应力,平均压应力的大小顺序在通过粗、细分流孔前后相反;在模具结构固定不变时,弯管件的曲率半径随挤压速度的减小而增大,不随挤压温度的变化而变化。 相似文献
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Nowadays, oil pollution has become more serious, which causes great threats both to the ecological environment and human life. In this study, a novel type of multifunctional deacetylated cellulose acetate/polyurethane (d-MCA:MTPU) composite nanofiber membranes for oil/water separation are successfully fabricated by electrospinning, which show super-amphiphilicity in air, super-hydrophilicity in oil, and oleophobicity in water. All the d-MCA:MTPU composite nanofiber membranes with different mass ratios can be used as water-removing, oil-removing, and emulsion separation substance only by gravity driving force. The highest separation flux for water and oil reaches up to 37 000 and 74 000 L m−2 h−1, respectively, and all the separation efficiencies are more than 99%. They have outstanding comprehensive mechanics performance, which can be controlled by simply adjusting the mass ratios. They show excellent antifouling and self-cleaning ability, endowing powerful cyclic stability and reusability. Those results show that d-MCA:MTPU composite nanofiber membranes have great application prospects in oil/water separation. 相似文献