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991.
以正硅酸乙酯作为硅源,采用沉淀法将四氧化三铁颗粒包覆在二氧化硅中,制备了Fe3O4@SiO2磁性催化剂载体材料。考察了氨水浓度、正硅酸乙酯浓度和四氧化三铁加入量对样品包覆率的影响,并对样品的物相和显微结构做了表征。结果表明:正硅酸乙酯可作为制备Fe3O4@SiO2磁性催化剂载体的硅源;在氨水浓度为0.4 mol/L、正硅酸乙酯浓度为0.02 mol/L、Fe3O4加入量为0.04 g的适宜反应条件下,样品包覆率为99%;二氧化硅有效包覆了四氧化三铁颗粒,但团聚较严重。 相似文献
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Di Zhou Wen‐Bo Li Li‐Xia Pang Jing Guo Ze‐Ming Qi Tao Shao Zhen‐Xing Yue Xi Yao 《Journal of the American Ceramic Society》2014,97(11):3597-3601
Ag2MoO4 ceramic was prepared by using the solid‐state reaction method, which could be sintered at 450°C for 2 h, having a relative permittivity of 8.08, a Qf value of 17 000 GHz, and a temperature coefficient of resonance frequency about ?133 ppm/°C. Ag2MoO4 ceramic was chemically compatible with silver but reacted seriously with aluminum to form (Ag0.5Al0.5)MoO4 during the sintering. The fitting of infrared spectra and the Shannon's additive rule were employed to study intrinsic dielectric behaviors of the ceramics at microwave region. Ionic displacive polarization and the electronic polarization contributed almost equally to the dielectric permittivity of the ceramic at microwave region. The Ag2MoO4 ceramics could be a good candidate for ultra‐low temperature co‐fired microwave devices. 相似文献
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Smell and taste are among the basic senses with which we perceive the world around us. In addition to enabling recognition of chemical moieties that provide social or nutritional clues, taste and smell receptors are expressed in many extraoral tissues, including the gastrointestinal, respiratory, and reproductive systems. It is, therefore, likely that taste and smell receptors have additional physiological roles, which are currently under intensive study. Most of the taste modalities, as well as olfaction, are mediated by G-protein coupled receptors (GPCRs). Recent breakthroughs in crystallography and signaling studies of GPCRs (celebrated by the 2012 Nobel Prize in Chemistry to Robert Lefkowitz and Brian Kobilka) provide excellent opportunities for applying this information towards furthering our understanding of taste and smell signaling. No crystal structures of odorant or taste receptors are currently available. However, computational techniques, many of which stem from the pioneering contributions of the 2013 Nobel Prize in Chemistry laureates, Martin Karplus, Michael Levitt, and Arieh Warshel, can shed light on the function of taste and olfactory GPCRs. In this review, we highlight examples of iterative combinations of simulation and experiment that were successfully applied toward delineating binding modes of tastants and odorants and toward predicting additional ligands. Further studies are required in order to answer remaining questions regarding receptor promiscuity versus selectivity, the details of receptor coupling to G-proteins, and the roles of oligomerization and of allosteric modulation in taste and smell transduction. 相似文献
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Isothermal and non‐isothermal crystallization of poly(L‐lactic acid)/poly(butylene terephthalate) blends 下载免费PDF全文
Isothermal and non‐isothermal crystallization kinetics of poly(l ‐lactic acid)/poly(butylene terephthalate) (PLLA/PBT) blends containing PLLA as major component is detailed in this contribution. PLLA and PBT are not miscible, but compatibility of the polymer pair is ensured by interactions between the functional groups of the two polyesters, established upon melt mixing. Crystal polymorphism of the two polyesters is not influenced by blending, as probed by wide‐angle X‐ray analysis. The addition of PLLA does not affect the temperature range of crystallization kinetics of PBT, nor the crystallinity level attained when the blends are cooled from the melt at constant rate. Conversely, PBT favors crystallization of the biodegradable polyester. The addition of PBT results in an anticipated onset of crystallization of PLLA during cooling at a fixed rate, with a sizeable enhancement of the crystal fraction. Isothermal crystallization analysis confirmed the faster crystallization rate of PLLA in the presence of PBT. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40372. 相似文献
995.
A weather resistant super‐hydrophobic coating that can offer good substrate adhesion and yet to be easily processed at large scale can be of practical use in emerging fields of self‐cleaning and anti‐icing paint, combing all these properties together remains challenging task. Here we describe a composite coating composed of a fluorinated epoxy resin emulsion with embedded in situ surface‐modified dual‐scale nano‐silica, which displayed durable super‐hydrophobicity and excellent adhesive strength. The as‐prepared coating possesses water contact angle of 158.6 ± 1°, sliding angle around 3.8 ± 0.2° which remain stable even under acidic/alkaline, heat/cool, and accelerated aging treatment. The results demonstrate that surface roughness had a micron‐ and nanometer scale distribution with increased particle loading beyond 40 wt %. Through quantitative comparison of surface Attenuated Total Reflection (ATR) with bulk FT‐IR transmission spectra, a gradient coating with surface enrichment of hydrophobic groups was determined. The air‐side fluorinated polysiloxane‐rich layer endows coating with weather‐resistance and ultra‐hydrophobicity while bottom epoxy resin layer enhances substrate adhesion. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40955. 相似文献
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采用二氯甲烷对3家公司的5种电子烟油样品进行萃取,并用气-质联用(GC-MS)法鉴定。通过对NIST 11谱库的检索,对5种样品中挥发性成分进行了比较分析。结果表明5种样品中的挥发性成分差别较大,共鉴定出40种挥发性成分,依据作用或来源分为雾化剂、烟叶提取物和薄荷提取物三类。其中相对含量水平较高且在5种样品中都检出的成分是丙二醇、烟碱和甘油。3家公司的5种烟草味电子烟油在抽吸品质上有所差异,C公司样品在抽吸感官感受上相较其他两家公司样品具有明显优势,其中样品C1又略好于C2。比较发现,C公司电子烟油的挥发性成分中含特有的8种多甘醇类化合物,可能是这些物质的协同作用而改善了抽吸品质。 相似文献