共查询到19条相似文献,搜索用时 46 毫秒
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三元脂肪酸/膨胀石墨复合相变材料的制备、包覆定形及热性能 总被引:1,自引:0,他引:1
采用癸酸、 月桂酸和棕榈酸的三元共晶混合物作为相变材料, 以膨胀石墨为基体, 通过膨胀石墨多孔结构的毛细吸附和复合涂饰剂的包覆定形, 将多元相变材料固定在膨胀石墨的孔道结构中, 制备出结构稳定、 密封性能优异、 热稳定性好和高导热的新型三元脂肪酸/膨胀石墨复合定形相变材料. 膨胀石墨具有膨胀疏松的多孔结构和良好的吸附性能; 其熔融潜热为95.6 J/g, 结晶焓为82.8 J/g, 说明其具有很好的相变蓄热特性和热循环稳定性; 材料的导热性能可增加至0.738 W/(m·K), 与脂肪酸相比得到大幅度提高. 相似文献
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探讨气体节流膨胀过程中的熵(S)的变化,指出任何气体的节流膨胀都是熵增过程,并且是不可逆的。在此基础上,讨论和总结了节流膨胀过程的全部热力学特征。 相似文献
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以平均粒径为19.71μm的天然微细鳞片石墨为原料,通过化学氧化法制备了具有不同氧化程度的可膨胀石墨,采用XRD、FTIR、Raman、SEM等对可膨胀石墨的结构与膨胀性进行了表征。结果表明:当氧化程度较低时制得的微细鳞片可膨胀石墨由石墨、石墨层间化合物和氧化石墨三相组成;随着氧化程度的增加,氧化石墨相含量与可膨胀石墨结构无序程度逐渐增高,石墨层间化合物相含量先增加后减少,石墨相含量则逐渐降低;氧化促使HSO4-或SO42-插入石墨层间,插入层间的HSO4-或SO42-量是决定可膨胀石墨膨胀容积的关键因素,制备的微细鳞片膨胀石墨的膨胀容积可达65.9mL·g-1。 相似文献
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Craig M. Davis Megan F. Klein Kenneth T. Nicholson 《Phosphorus, sulfur, and silicon and the related elements》2013,188(3):659-664
Attempts were made to synthesize dinuclear Group 6 metal complexes of the arachno -octahydrotriborate anion. Specifically, the dimer [CpW(CO) 3 ] 2 (Cp = m 5 -C 5 H 5 ) was employed as the metal reagent. However, the formation of dinuclear metallaborane complexes did not ensue. Rather, clean, rapid, systematic borane-cage expansion was observed. The [B 3 H 8 ] m cluster was quantitatively converted to B 5 H 9 ,[B 9 H 14 ] m , or [B 11 H 14 ] m , or both, depending on reaction conditions. Refluxing a 1:1 mixture of [B 3 H 8 ] m and [CpW(CO) 3 ] 2 in toluene or dioxane lead to the rapid, quantitative conversion of [B 3 H 8 ] m to B 5 H 9 . However, refluxing a 2:1 mixture of [B 3 H 8 ] m and [CpW(CO) 3 ] 2 in the same solvents yielded [B 9 H 14 ] m and [B 11 H 14 ] m as the primary products; when glyme was the solvent, only [B 9 H 14 ] m was observed, even after prolonged heating. 相似文献
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采用联苯二酐与3种含酰胺结构二胺制备了具有不同取代基团的聚酰胺-酰亚胺薄膜,考察了酰胺结构对薄膜力学、耐热及尺寸稳定性的影响,研究了聚集态结构与薄膜热膨胀行为的关系和规律.该系列薄膜具有超高强度和优异的耐热性能,拉伸强度高达280. 5 MPa,玻璃化转变温度在389~409℃,并在30~300℃温度范围内表现出超低负膨胀,热膨胀系数(CTE,ppm/℃,即106cm·cm-1·℃-1)在-3. 05~-1. 74ppm/℃之间.聚集态分析结果表明,酰胺结构使分子链间形成了强氢键相互作用,分子链在薄膜面内方向高度有序取向,并在膜厚方向堆积更为紧密,使薄膜表现出热收缩现象.通过不同体积大小的取代基团进一步调控分子链间相互作用及排列堆积,可实现薄膜在高温下近乎零尺寸形变,为设计制备超低膨胀聚合物基板材料提供了新思路. 相似文献
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Ria Thielhorn Isabelle Heing-Becker Nadja Hümpfer Jakob Rentsch Rainer Haag Kai Licha Helge Ewers 《Angewandte Chemie (International ed. in English)》2023,62(28):e202302318
Expansion microscopy (ExM) is a recently developed technique that allows for the resolution of structures below the diffraction limit by physically enlarging a hydrogel-embedded facsimile of the biological sample. The target structure is labeled and this label must be retained in a relative position true to the original, smaller state before expansion by linking it into the gel. However, gel formation and digestion lead to a significant loss in target-delivered label, resulting in weak signal. To overcome this problem, we have here developed an agent combining targeting, fluorescent labeling and gel linkage in a single small molecule. Similar approaches in the past have still suffered from significant loss of label. Here we show that this loss is due to insufficient surface grafting of fluorophores into the hydrogel and develop a solution by increasing the amount of target-bound monomers. Overall, we obtain a significant improvement in fluorescence signal retention and our new dye allows the resolution of nuclear pores as ring-like structures, similar to STED microscopy. We furthermore provide mechanistic insight into dye retention in ExM. 相似文献
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The expansion coefficient of a flexible polyelectrolyte molecule is evaluated as a function of the concentration of simple salt added to the solution. It is shown that the coefficient has a term which is inversely proportional to the square root of the concentration of added salt. 相似文献
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A. Cuccuru 《Thermochimica Acta》1975,12(2):135-140
An analysis of the behaviour of five fluoroelastomers in the temperature range ?120 to +150°C has been carried out by thermomechanical analysis; the linear expansion coefficient of crude and of gamma-irradiated fluoroelastomers has been evaluated. Finally the influence of the thermal history of the sample has been examined. 相似文献
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Javier Luis-Barrera Víctor Laina-Martín Thomas Rigotti Dr. Francesca Peccati Prof. Dr. Xavier Solans-Monfort Prof. Dr. Mariona Sodupe Prof. Dr. Rubén Mas-Ballesté Dr. Marta Liras Prof. Dr. José Alemán 《Angewandte Chemie (International ed. in English)》2017,56(27):7826-7830
Described herein is a new visible-light photocatalytic strategy for the synthesis of enantioenriched dihydrofurans and cyclopentenes by an intramolecular nitro cyclopropane ring expansion reaction. Mechanistic studies and DFT calculations are used to elucidate the key factors in this new ring expansion reaction, and the need for the nitro group on the cyclopropane. 相似文献
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William J. Bailey 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(5):849-865
It is demonstrated that polymerization of bicyclic monomers in which two rings are opened for every new dbond formed in the polymer chain will produce either very small changes in volume or significant expansion. 相似文献