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921.
Chuan Li Jiawei Luo Manping Ma Junkun Tang Qiaolong Yuan Farong Huang 《Journal of polymer science. Part A, Polymer chemistry》2019,57(23):2324-2332
Poly(silylene arylacetylene) (PSA) is a kind of poly(arylacetylene) silicon‐containing resins with excellent heat resistance and good mechanical performances. In this article, the sulfur atom is introduced into the main chain of the PSA molecule to obtain a sulfur‐containing poly(silylene arylacetylene), named S‐PSA. By Williamson and Sonogashira reactions, bis(4‐ethynylphenyl)sulfide and bis(4‐ethynylphenyl)sulfone were synthesized. Thereafter, through Grignard reagent way, the poly(silylene ethynylene phenylene sulfide phenylene ethynylene) (PSESE) and poly(silylene ethynylene phenylene sulfone phenylene ethynylene) (PSESO2E) were synthesized from bis(4‐ethynylphenyl)sulfide, bis(4‐ethynylphenyl)sulfone, and methylphenyl dichlorosilane. Poly(silylene ethynylene phenylene sulfoxide phenylene ethynylene) (PSESOE) was synthesized by the oxidation of PSESE. The structures and properties of these resins were characterized and the mechanical properties of the T300 reinforced composites were tested. The results show that the novel S‐PSA resins have excellent heat resistance and good mechanical properties, and could be used as resin matrices for high‐performance composites in high‐tech fields. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 2324–2332 相似文献
922.
Hsiang‐Ning Luk Hsin‐Yuan Peng Yan‐Wei Han Che‐Kuan Lin Wang‐De Lin Ren‐Jang Wu 《中国化学会会志》2019,66(1):75-80
A novel sensing material, MnFe2O4/polyaniline (PANI), was fabricated by doping PANI to MnFe2O4 on a modified glassy carbon electrode (GCE). This sensing material was characterized using X‐ray diffraction (XRD), scanning electron microscopy (SEM), and high‐resolution transmission electron microscopy (HR‐TEM). Using a cyclic voltammetry electrochemical‐sensing method, we tested MnFe2O4/PANI, and an acetaminophen concentration of 0.0625–5 mM was recorded. Furthermore, the sensor responses were 2.05–22.44. The detection limit was 2.23 × 10?7 M. Strong selectivity was observed for MnFe2O4/PANI, which is a possible sensing mechanism. 相似文献
923.
Yuan Yu Zhiquan Chen Qingwu Zhang Mengwei Jiang Zhihao Zhong Tingting Chen Juncheng Jiang 《先进技术聚合物》2019,30(4):998-1009
Modified montmorillonite‐containing phytic acid (PA‐MMT) has been prepared by acid treatment and then introduced into unsaturated polyester resin (UPR) with an intumescent flame retardant (IFRs). The flame retardancy and thermal degradation of UPR/IFRs/PA‐MMT were evaluated by a limiting oxygen index (LOI) test, a vertical burning test (UL‐94), a thermogravimetric analysis (TGA), and a cone calorimeter test (CCT). Besides, the mechanical properties were studied by a universal testing machine. The LOI value of UPR/IFRs/PA‐MMT composites was increased to 29.2%. The CCT results indicated that the incorporation of PA‐MMT and IFRs significantly improved the combustion behavior of UPR. The results of the mechanical properties indicated that 1.5 wt% loading of PA‐MMT in UPR/IFRs showed the highest improvement in flexural strength and tensile strength. The flame‐retardant mechanism of PA‐MMT/IFRs was examined and discussed based on the results of combustion behavior and char analysis. 相似文献
924.
Zhongwei Chen Tingting Chen Yuan Yu Qingwu Zhang Zhiquan Chen Juncheng Jiang 《先进技术聚合物》2019,30(9):2458-2467
Metal‐organic framework MIL‐53 (Fe)@C/graphite carbon nitride hybrid (MFeCN), a novel flame retardant, was synthesized by hydrothermal reaction and subsequently added into unsaturated polyester resin (UPR). The structure, morphology, and thermal stability of MFeCN were characterized by Fourier transform infrared spectroscopy (FTIR), X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy‐dispersive X‐ray spectroscopy (EDS), and thermogravimetric analysis (TG). The thermal stability and flammability of the UPR composites were characterized by TG and cone calorimeter tests (CCT). The results of CCT demonstrated that the peak heat release rate (pHRR), total heat release (THR), peak smoke production rate (pSPR), and total smoke production (TSP) of UPR/MFeCN‐4 were reduced by 39.8%, 10.2%, 33.3%, and 14.5%, respectively, comparing with UPR. The results of TG and CCT indicated that MFeCN could improve the thermal stability, flame retardancy, and smoke suppression properties of the UPR composites. The residues after CCT were then characterized by laser Raman spectroscopy (LRS), XPS, and SEM. Finally, based on the above experimental results and analysis, the flame retardancy mechanism of MFeCN was proposed. 相似文献
925.
本文对多层螺旋CT(MSCT)诊断甲状腺癌中的辐射和对比剂剂量选择进行了分析。选取2016年12月~2018年12月本院行MSCT检查的甲状腺癌、甲状腺良性结节患者各200例,依据随机数字表分为A组、B组、C组、D组,每组50例,A组参数为对比剂1.2 mL/kg、120 kV、180 mA,B组为对比剂1.0 mL/kg、120 kV、180 mA,C组为对比剂1.2 mL/kg、100 kV、100 mA,D组为对比剂1.0 mL/kg、100 kV、100 mA。结果显示,A组和B组CT容积剂量指数(CTDIvol)、剂量长度乘积(DLP)、有效辐射剂量(ED)明显低于C组和D组,A组和B组甲状腺CT值、背景信号、背景噪声明显高于C组和D组,差异有统计学意义(P<0.05),A组、B组、C组、D组信噪比(SNR)、对比信噪比(CNR)、图像质量评分比较,差异无统计学意义(P>0.05);A组、B组、C组、D组诊断甲状腺癌的敏感度、特异度、准确度比较,差异无统计学意义(P>0.05)。本文证实,对于MSCT诊断甲状腺癌中的辐射和对比剂剂量,选择1.0 mL/kg、100 kV、100 mA可在不严重影响图像质量及检查结果下有效减少患者的CT辐射,值得临床推广。 相似文献
926.
Hongming He Qian‐Qian Zhu Chuanqi Zhang Ying Yan Jing Yuan Jing Chen Cheng‐Peng Li Miao Du 《化学:亚洲杂志》2019,14(7):917-917
927.
Lin Jia Hui Yang Jun Deng Junmei Chen Yuan Zhou Pan Ding Leigang Li Na Han Yanguang Li 《中国化学》2019,37(5):497-500
Electrocatalytic carbon dioxide reduction holds great promise for reducing the atmospheric CO2 level and alleviating the energy crisis. High‐performance electrocatalysts are often required in order to lower the high overpotential and expedite the sluggish reaction kinetics of CO2 electroreduction. Copper is a promising candidate metal. However, it usually suffers from the issues of poor stability and low product selectivity. In this work, bimetallic Cu‐Bi is obtained by reducing the microspherical copper bismuthate (CuBi2O4) for selectively catalyzing the CO2 reduction to formate (HCOO–). The bimetallic Cu‐Bi electrocatalyst exhibits high activity and selectivity with the Faradic efficiency over 90% in a wide potential window. A maximum Faradaic efficiency of ~95% is obtained at –0.93 V versus reversible hydrogen electrode. Furthermore, the catalyst shows high stability over 6 h with Faradaic efficiency of ~95%. This study provides an important clue in designing new functional materials for CO2 electroreduction with high activity and selectivity. 相似文献
928.
Lu Yuan Ming Kang Guanjun Chang Xiangmeng Lv Simin Shen Rong Sun 《无机化学与普通化学杂志》2019,645(21):1240-1246
Due to the unique size effects, nanomaterials in infrared absorption have attracted much attention for their strong absorption in the infrared region. To achieve the infrared multi‐band absorption, we propose to synthesize a core‐shell structure nanomaterial consisting of NaYF4:Yb3+, Er3+ core and a layer of SiO2 as shell. A series of NaYF4:Yb3+, Er3+ nanocrystals were synthesized through hydrothermal method by adjusting the ratio of citric acid(CA)‐to‐NaOH, and the effects of CA concentration, and NaOH concentration were studied in detail. NaYF4:Yb3+, Er3+@SiO2 nanoparticles were synthesized by sol‐gel method using TEOS as silica source. The results show that the core‐shell NaYF4:Yb3+, Er3+@SiO2 nanoparticles were successfully synthesized. Up‐conversion spectra of these nanoparticles were recorded with 980 nm laser excitation under room temperature. There are no changes of the emission centers of nanoparticles before or after silica coating, but the emission intensities of nanoparticles after silica coating are weakened. Furthermore, the property of infrared multi‐band absorption was tested through ultraviolet‐visible‐near infrared spectrophotometer and infrared absorption spectra. The results illustrate that the multi‐band infrared absorption nanomaterial was successfully synthesized. 相似文献
929.
Zhengluo Wang Zhiwei Zhao Yanru Zhang Dr. Xiaopeng Yang Xuan Sun Dr. Jinyang Zhang Prof. Linrui Hou Prof. Changzhou Yuan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(3):863-873
The exploration of anode materials with a high degree of electrochemical utilization for Li-ion batteries (LIBs) still remains a huge challenge despite pioneering breakthroughs. Rational engineering of electrode structures/components by facile strategies would offer infinite possibilities for the development of LIBs. In this study, one-dimensional ultralong nanohybrids of ultrafine NiCoO2 nanoparticles dispersed in situ in and/or on the surface of amorphous N-doped carbon nanofibers (NCO@ANCNFs) were fabricated by a bottom-up electrospinning protocol. By virtue of synergistic structural/component features, the obtained ultralong NCO@ANCNFs with low NCO loading (≈33.6 wt %) show highly efficient Li+ storage performance with high reversible capacity, high rate capability, and long cycle life. The unusual reversible crystalline transformation during cycling was analyzed. Quantitative analysis revealed that the pseudocapacitive contribution mainly accounts for the superior lithium storage of the NCO@ANCNFs. Besides, the ability of the hybrid anode to deliver competitive Li-storage properties even without conductive carbon greatly enhances its commercial applicability. An NCO@ANCNFs//LiNi0.8Co0.15Al0.05O2 full battery was assembled and exhibited striking electrochemical properties. This contribution offers a scalable methodology to fabricate highly efficient hybrid anodes for advanced next-generation LIBs. 相似文献
930.
Ling-Yang Hsu Qiumin Liang Zhiheng Wang Hsin-Hung Kuo Wun-Shan Tai Shi-Jian Su Xiuwen Zhou Yi Yuan Yun Chi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(67):15375-15386
Iridium complexes bearing chelating cyclometalates are popular choices as dopant emitters in the fabrication of organic light-emitting diodes (OLEDs). In this contribution, we report a series of blue-emitting, bis-tridentate IrIII complexes bearing chelates with two fused five-six-membered metallacycles, which are in sharp contrast to the traditional designs of tridentate chelates that form the alternative, fused five-five metallacycles. Five IrIII complexes, Px-21 – 23 , Cz-4 , and Cz-5 , have been synthesized that contain a coordinated dicarbene pincer chelate incorporating a methylene spacer and a dianionic chromophoric chelate possessing either a phenoxy or carbazolyl appendage to tune the coordination arrangement. All these tridentate chelates afford peripheral ligand–metal–ligand bite angles of 166–170°, which are larger than the typical bite angle of 153–155° observed for their five-five-coordinated tridentate counterparts, thereby leading to reduced geometrical distortion in the octahedral frameworks. Photophysical measurements and TD-DFT studies verified the inherent transition characteristics that give rise to high emission efficiency, and photodegradation experiments confirmed the improved stability in comparison with the benchmark fac-[Ir(ppy)3] in degassed toluene at room temperature. Phosphorescent OLED devices were also fabricated, among which the carbazolyl-functionalized emitter Cz-5 exhibited the best performance among all the studied bis-tridentate phosphors, showing a maximum external quantum efficiency (EQEmax) of 18.7 % and CIEx,y coordinates of (0.145, 0.218), with a slightly reduced EQE of 13.7 % at 100 cd m−2 due to efficiency roll-off. 相似文献