Synthesis of highly crystalline spinel LiMn2O4 by a soft chemical route and its electrochemical performance

Highly crystalline spinel LiMn₂O₄ was successfully synthesized by annealing lithiated MnO₂ at a relative low temperature of 600 °C, in which the lithiated MnO₂ was prepared by chemical lithiation of the electrolytic manganese dioxide (EMD) and LiI. The LiI/MnO₂ ratio and the annealing temperature were optimized to obtain the pure phase LiMn₂O₄. With the LiI/MnO₂ molar ratio of 0.75, and annealing temperature of 600 °C, the resulting compounds showed a high initial discharge capacity of 127 mAh g⁻¹ at a current rate of 40 mAh g⁻¹. Moreover, it exhibited excellent cycling and high rate capability, maintaining 90% of its initial capacity after 100 charge-discharge cycles, at a discharge rate of 5 C, it kept more than 85% of the reversible capacity compared with that of 0.1 C.     

Studies on the synthesis and properties of poly(amide-azomethine)

Homopolymer and copolymer of poly(amide-azomethine) were synthesized from the corresponding diamines and dialdehydes. The polymerization was proceeded in the mixed solvent of o-chlorophenol and m-cresol (1: I by volume) at 0 °C for I S h. The inherent viscosities of the new aromatic poly(amide-azomethine)s are in the range of 0.51 to 2.31 dl/g. These polymers were soluble in sulfuric and formic acid. The TGA results show that no weight loss up to 400 °C under nitrogen atmosphere, which suggests the relatively good thermal stabilities.     

预应力片材加固负载RC梁受弯承载力分析

分析有初始弯矩作用时,预张纤维片材粘贴加固混凝土梁中加固材料相对该处混凝土滞后应变或超前应变的计算方法和纤维片材中有效预应力的取值;对预应力FRP粘贴加固梁构成的复合截面,分析各种可能应变组合下的受弯极限状态,给出两大弯曲破坏类型(分别由片材拉断和混凝土压碎引发)的界限判别条件和极限承载力计算表达式.试验分析表明,极限承载力试验值与计算值比值的均值为0.99,变异系数为0.047.     

CFRP加固钢筋混凝土梁滞后应变计算方法

为了系统研究从零负载状态到满负载状态各个阶段CFRP片材加固梁滞后应变的计算方法,在充分考虑加固梁不同负载状态及受压区混凝土非线性本构关系的基础上,分别建立了不同负载贴片加固梁考虑混凝土抗拉作用时的滞后应变计算公式及不考虑混凝土抗拉作用时的简化计算公式.试验数据和对比分析结果表明:"考虑混凝土抗拉作用"公式的计算结果与试验数据吻合良好,计算误差<8%,明显优于现有文献的计算方法;"不考虑受拉区混凝土抗拉作用"公式的计算结果在混凝土开裂前和试验值相差较大,但对已裂加固梁的计算误差与"考虑混凝土抗拉作用"公式的计算误差接近.为简化计算,对未裂和已裂混凝土梁贴片加固时的滞后应变可分别采用"换算截面"公式和"不考虑混凝土抗拉作用"公式进行计算,两种简化方法的误差均不会超过10%.     

精制棉电催化氧化技术及工艺研究

利用电催化氧化技术使棉短绒发生快速断裂反应,同时使木质素、果胶等带色基团退色,减少污水处理难度。生产的精制棉纤维素一致性率、a-纤维素含量达到98%以上,聚合度降低到700DP,反应时间由原来的2.5h缩短到20min,色度减少80%。通过实践,实现了生产精制棉节能降耗的目的,且明显减轻了对环境的污染。     

景观桥钢箱梁加固方案的设计计算及比较分析

对某景观桥进行了检测评定,提出了3种加固方案,并采用大型通用有限元软件ANSYS建立了桥梁上部结构模型以及3种加固方案的模型,其中加固方案模型建立于根据静载试验数据修正后的模型之上;利用该模型进行了设计荷载工况下的静力分析和模态分析,并根据计算结果比较了3种加固方案以及参数变化对桥梁挠度、支座区最大等效应力、极限承栽力以及动力特性的影响。结果表明：综合采用加固方案1和加固方案3是比较合理的。     

砖混墙门洞口扩宽、加固施工方案

使用型钢加固的组合柱、梁及碳纤维材料用于混凝土加固修补等技术在一些砖混结构房屋的承重墙上开洞,或者去掉某些承重墙扩大空间的改造加固工程中,发挥着非常重要的作用.     

PLLA-PEG-PLLA三嵌段共聚物的合成及性能

以萘钾和聚乙二醇形成大分子引发剂,在超声波震荡下引发L-丙交酯开环共聚,合成出不同EO/LA物质的量比的PLLA-PEG-PLLA三嵌段共聚物。利用FT-IR和1HNMR表征了三嵌段共聚物的结构。通过接触角和吸水率测试表明共聚物的亲水性是随着EO含量的增大而增强。采用DSC和POM研究共聚物的热性能和结晶形貌表明,共聚物各段熔点比各自均聚物低且有一个Tg,由于共聚物中EO/LA物质的量比的不同,表现出某段的单独结晶或两段都不结晶。因此,可通过改变嵌段含量,制备不同性能的材料,扩大聚乳酸的应用范围。     

Relationship between processing,microstructure, and mechanical properties of injection molded thermotropic LCP

A commercial thermotropic liquid crystalline polymer (LCP), Vectra A950, was injection molded into rectangular sheets of thickness ranging from 1 to 4 mm. By changing the thickness of the mold, the shear rate experienced by the TLCP melt in the mold could be varied. The 1‐mm test sample was highly anisotropic while that with larger thickness (4 mm) was less anisotropic. X‐ray diffraction profile at various depths for each of the test sample corresponded to the degree in the fiber orientation present in the test samples. The anisotropy can be described macroscopically by measuring the tensile strength and modulus in the longitudinal and transverse direction. The ratio between the longitudinal and transverse property decreases proportionally to the thickness of the test sample. This reduction corresponded to the reduction in the shear field as the thickness of the mold was increased. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1713–1718, 2003     

Synthesis and characterization of side‐chain liquid‐crystalline ionomers containing quaternary ammonium salt groups

A series of thermotropic side‐chain liquid‐crystalline ionomers (LCIs) containing 4‐(4‐alkoxybenzyloxy)‐4′‐allyloxybiphenyl (M) as mesogenic units and allyl triethylammonium bromide (ATAB) as nonmesogenic units were synthesized by graft copolymerization upon polymethylhydrosiloxane. The chemical structures of the polymers were confirmed by IR spectroscopy. DSC was used to measure the thermal properties of these polymers. The mesogenic properties were characterized by polarizing optical microscopy, DSC, and X‐ray diffraction. Homopolymers without ionic groups exhibit smectic and nematic mesophases. The nematic mesophases of the ionomers disappear and the mesomorphic temperature ranges decrease with increasing concentration of ionic units. The influence of the alkoxy chain length on clearing temperature (T_c) values of ionomers clearly shows an odd‐even effect, similar to that of other side‐chain liquid‐crystalline polymers. The mesomorphic temperature ranges increase with increasing alkoxy chain length when the number of alkoxy carbon is over 3. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2879–2886, 2003