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1.
采用熔融共混及模压的方法制备了碳纳米管(CNT)-高密度聚乙烯(HDPE)复合材料,并用介电谱仪研究了逾渗值附近的导电填料对复合材料体系在不同温度、频率条件下的介电常数、介电损耗、交流电阻率的变化规律。结果表明:复合材料的介电常数、介电损耗均随CNT质量分数增加而逐渐增大;在频率为103~106 Hz,温度为40~130℃时,HDPE基体的介电常数随频率和温度的变化较小,而添加CNT填料的复合材料的介电常数随频率和温度的增加而略微降低。当w(CNT)0.5%时,复合材料的交流电阻率表现出对频率的强烈依赖性;而当w(CNT)0.5%时,在低频处表现出直流特性,在高频处显示出交流电阻率的降低。 相似文献
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通过金属点蚀技术制备了表面多孔形貌的羰基铁粉(PCIP),并采用共沉淀及原位聚合方法,将CoFe2O4与聚苯胺(PANI)负载于多孔羰基铁表面,得到具有电磁吸收性能的PCIP/CoFe2O4/PANI复合材料.通过扫描电子显微镜(SEM)、X射线衍射仪(XRD)、傅里叶变换红外光谱仪(FTIR)、热重分析仪(TGA)及矢量网络分析仪(VNA)等对复合材料的形貌、成分和吸波性能进行了研究.结果表明,CoFe2O4/PANI团聚于PCIP表面,显著提升了复合材料电损耗能力,促进了低频电磁波的1/4波长干涉相消.当苯胺添加量为0.5 mL,复合材料在频率为5.7 GHz时,反射损耗达到-22.9 dB,低频吸波性能得到大幅提升.利用1/4波长干涉相消理论及电磁波界面反射模型对复合材料低频吸波性能提升的内在原因进行了分析. 相似文献
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用一种硅炔杂化树脂聚(甲基硅烷-二乙炔基苯)(PSP)改性有机硅树脂(HS),通过FT—IR和TGA研究了树脂体系的固化反应及耐热性,并对制备的复合材料进行力学性能、耐热性能和介电性能研究。结果表明:当HS与PSP的质量比为5:5时综合性能最优,树脂体系在氮气氛围下质量损失5%时的温度(T幽)为691℃,1000℃时质量保留率为88%;HS—PSP树脂短切玻纤复合材料冲击强度为21kJ/m^2,弯曲强度为65MPa,200℃时的弯曲强度高温保留率为78%,介电常数为4.6,介电损耗因数为7.9×10,体积电阻为6.7×10^13Ω。改性后的复合材料具有优异的力学、耐热和介电性能。 相似文献
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以双酚A二缩水甘油醚(DGEBA)环氧树脂(Epoxy Resin,EP)为基体、甲基六氢苯酐(MHHPA)为固化剂、以多壁碳纳米管(MWCNTs)为添加剂制备了环氧树脂/碳纳米管纳米复合材料。通过对微观结构、玻璃化转变温度(Tg)、热失重、热导率和锥形量热测试结果分析,研究了质量分数少于1.5%的MWCNTs对环氧树脂的导热和阻燃性能影响,结果表明,MWCNTs质量分数为1.5%时,复合材料发生团聚;纳米复合材料随着MWCNTs质量分数的增加Tg值先增加后降低;失重5%时,对应的温度先增加后降低,残炭量增加;样品的热导率呈现先升高后降低的趋势,当MWCNTs质量分数为1%时,复合材料的热导率最大;MWCNTs加入后环氧树脂的总释热量减少,释烟量增加,阻燃性得到一定程度的提高。 相似文献
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PI/PANI复合材料的制备与表征 总被引:1,自引:0,他引:1
以纳米聚苯胺为电磁波的吸收剂,高强度、耐高温的聚酰亚胺为基体设计与制备了高强度、耐热、质轻、薄和吸收宽的新型纳米复合吸波材料.利用微乳液法,以十二烷基苯磺酸(DBSA)为乳化剂和掺杂剂,以过硫酸铵(APS)为氧化剂合成了纳米级聚苯胺(PANI).在此基础上,以PANI的NMP溶液为均苯四甲酸二酐(PMDA)与4,4′-二氨基二苯醚(ODA)的聚合场所,室温下,原位聚合出PANI/聚酰胺酸(PAA)复合材料,再经过亚胺化制备出了PANI/PI复合材料.利用XRD表征了聚合物的结晶形态.红外光谱表征了中间体和聚合物.利用场发射扫描电镜发现PANI/PI复合材料呈现海岛结构,PANI像岛屿一样分散在PI的连续相中,两种材料复合并没有破坏各自的结晶形态.利用数字电桥和自制电极表征了不同含量复合材料的损耗性能,当聚苯胺加到3.4%以上时,复合材料的损耗因数提高了,并且随着频率的增大损耗因数直线增大. 相似文献
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生物质气催化合成甲醇的研究 总被引:17,自引:6,他引:11
在高压微型反应装置上进行了生物质气合成甲醇的研究。利用组成为H2/CO/CO2
/N2(体积比)=52.5/21.5/22.8/3.2 的富CO2原料气考察了不同温度、压力和空速条件时甲醇的时空产率和质量分数。结果表明,在所考察的范围内,甲醇的产率和质量分数在260 ℃达到最大。产率和质量分数随反应压力升高而增大,空速增加使产率增大,甲醇的质量分数降低。当p=4 MPa,t=260 ℃,WHSV=5 280 h-1时, 甲醇的时空产率为0.79 g·(mL·h)-1,质量分数为96.2%,与工业合成气相比,分别下降25.8%和1.64%。 相似文献
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Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction
Laurent Gavara Thomas Boisse Jean-Pierre Hénichart Adam Daïch Philippe Gautret 《Tetrahedron》2010,66(38):7544-5571
In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments. 相似文献
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KMnO4-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields. 相似文献
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N. A. Nedolya 《Chemistry of Heterocyclic Compounds》2008,44(10):1165-1219
The review contains a concise historical account and information on the most significant researches undertaken by the staff
at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry
of Heterocyclic Compounds.
Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee.
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008. 相似文献
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Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields. 相似文献
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Uroš Grošelj Mojca Žorž Amalija Golobič Branko Stanovnik Jurij Svete 《Tetrahedron》2013,69(52):11092-11108
A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives. 相似文献
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The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp3)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp2)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp2)?H and aliphatic 1,5- and 1,6-C(sp3)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp3)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp2)?H insertion. 相似文献
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Rebecca J. Burton Mandy L. CrowtherNeal J. Fazakerley Shaun M. FilleryBarry M. Hayter Jason G. KettleCaroline A. McMillan Paula PerkinsPeter Robins Peter M. SmithEmma J. Williams Gail L. Wrigley 《Tetrahedron letters》2013
The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines. 相似文献
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An efficient approach to the synthesis of highly congested di, penta and hexacyclic pyrazoles as well as imidazole fragment containing novel heterocyclic molecule has been developed through a carbanion induced transformation of suitably functionalized 2H-pyran-2-ones, benzo[h]chromene and thiochromeno[4,3-b]pyrans. Due to the presence of fluorescence, we report their prime application metal sensor as off/on switching in ferric ions. 相似文献
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N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%). 相似文献