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71.
Allan L. Smith Rose B. Mulligan Hamid M. Shirazi 《Journal of Polymer Science.Polymer Physics》2004,42(21):3893-3906
The quartz crystal microbalance/heat conduction calorimeter (QCM/HCC) is a versatile instrument coupling both gravimetric and calorimetric techniques. The QCM/HCC is used to probe vapor sorption in thin films. Three parameters are measured simultaneously as a thin film undergoes vapor sorption, namely: mass changes in the film (±10 ng), corresponding thermal effects upon vapor sorption (±100 nW), and motional resistance (±0.5Ω) changes within the film. A range of film thicknesses (0.75 to 8.5 μm) of the polymer, Tecoflex? are cast on QCMs and the interaction of each film with ethanol and water is determined. From the direct calorimetric measurements, sorption enthalpies (ΔsorptionH kJ/mol) are determined for the film–vapor interactions. Sorption isotherms are then analyzed for each film. The isotherms shown here generally display a linear Henry's Law dissolution relationship between the vapor pressure and the amount of vapor sorbed into the film. Motional resistance data provides a window to view viscoelastic effects of the polymer films upon vapor sorption. Motional resistance data are compared for ethanol sorption in a relatively thin (0.75 μm) and thicker (8.5 μm) Tecoflex? film. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3893–3906, 2004 相似文献
72.
Kaveh Parvanak Boroujeni Elham Rezazadeh Shirazi Mohammad Mahdi Doroodmand 《Phosphorus, sulfur, and silicon and the related elements》2016,191(5):683-688
A supported acidic catalyst was easily prepared via anchoring imidazolium salt-based ionic liquid onto multiwalled carbon nanotube by covalent bonds. This novel immobilized acidic ionic liquid effectively catalyzed the one-pot synthesis of α-aminophosphonates from the reaction of amines and aldehydes with diethyl phosphite. The catalyst can be easily recovered and reused without appreciable change in its efficiency. 相似文献
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Ohne Zusammenfassung
Contribution to the calculation of the weight and number mean and the molecular weight heterogeneity of synthetic polymers相似文献
75.
A sensitive new measurement technology is described which combines calorimetry, gravimetry, and rheology applied to chemical reactions in thin films: quartz crystal microbalance/heat conduction calorimetry (QCM/HCC). The quartz crystal microbalance/heat conduction calorimeters constructed so far simultaneously measure heat generation, mass uptake or release, and viscoelastic property changes in the same, sub-milligram solid film sample when gases interact with the film in an isothermal surrounding. It is possible to measure the energetics of formation of a single layer of adsorbed molecules on a gold surface with this technique. The principles of operation of both the mass and the heat flow sensor are described, and one implementation of the combined sensor and apparatus and its electronics is presented. Methods for calibration and the preparation of thin sample films are summarized. As an illustrative example, the determination of the sorption enthalpy of hydrogen in a 25 °C palladium film of 140 nm thickness is discussed in detail. Other examples of the operation of the QCM/HCC are tabulated. 相似文献
76.
Quartz Microbalance Microcalorimetry: A new method for studying polymer-solvent thermodynamics 总被引:1,自引:0,他引:1
We have developed a sensitive method of determining enthalpy changes for gas-surface interactions: quartz microbalance microcalorimetry. We mount in an isoperibol environment both sample and reference combinations of a quartz crystal microbalance (QCM) in intimate thermal contact with a heat flow sensor. We coat the sample QCM with a thin (1 µm) polymer film. By exposing the film to ethanol vapor, we measure simultaneously the change in mass per unit area (to ±0.25 ng cm–2) and the resulting heat flows (to ±50 nW) when the polymer adsorbs or desorbs ethanol. The molar enthalpies of sorption of ethanol vapor in Tecoflex, an aliphatic polyurethane elastomer, are adsorptionH= –53±8 kJ mol–1 and desorptionH=52±3 kJ mol–1.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
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Morteza Maghrebi Abbas Ali Khodadadi Yadollah Mortazavi Ali Sane Mohsen Rahimi Yaser Shirazi Zviad Tsakadze Subodh Mhaisalkar 《Applied Physics A: Materials Science & Processing》2009,97(2):417-424
The mm-long carbon nanotube (CNT) arrays were grown in a floating catalyst reactor, using xylene-ferrocene and a small amount
of acetic acid as the feed. The CNT arrays deposited on a quartz substrate at several positions along the reactor were extensively
characterized using Raman spectroscopy, scanning electron microscopy, X-ray diffraction, high-resolution transmission electron
microscopy, and optical microscopy. Various characterization methods consistently reveal that the acetic acid additive to
the feed alleviates deposition of amorphous carbon layer, which gradually thickens CNTs along the reactor. The acetic acid
also resulted in a higher growth rate along the so-called growth window, where CNT arrays are deposited on the quartz substrate.
High-performance liquid chromatography of extracted byproducts (PAHs) confirmed the presence of some polycyclic aromatic hydrocarbons.
The solid weight of PAHs decreased upon addition of ferrocene as the catalyst precursor, as well as of acetic acid to xylene
feed. The results suggest that primary light products of xylene pyrolysis can be competitive reactants for both catalytic
and subsequent pyrolytic reactions. They may also be more efficient feeds for CNT growth than xylene itself. 相似文献