In-Situ Oxygen-Atom Erosion Study of a Polyhedral Oligomeric Silsesquioxane (POSS)-Siloxane Copolymer Using a Novel Hyperthermal Oxygen Atom Source and Analysis by X-Ray Photoelectron Spectroscopy

1999 ◽  
Author(s):  
Rene I. Gonzalez ◽  
Shawn H. Phillips ◽  
Gar B. Hoflund
Keyword(s):  
Oxygen Atom ◽  
Photoelectron Spectroscopy ◽  
Polyhedral Oligomeric Silsesquioxane ◽  
X Ray ◽  
Atom Source ◽  
Oligomeric Silsesquioxane

scholarly journals Structural Analysis of Polyhedral Oligomeric Silsesquioxane Coated SiC Nanoparticles and Their Applications in Thermoset Polymers

2015 ◽  
Vol 2015 ◽  
pp. 1-13 ◽  
Author(s):  
Md. Reza-E-Rabby ◽  
Shaik Jeelani ◽  
Vijaya K. Rangari
Keyword(s):  
Photoelectron Spectroscopy ◽  
Polyhedral Oligomeric Silsesquioxane ◽  
Mechanical And Thermal Properties ◽  
Tem Analysis ◽  
Sic Nanoparticles ◽  
X Ray ◽  
Thermoset Resin ◽  
Transmission Electron ◽  
Xrd Techniques ◽  
Oligomeric Silsesquioxane

The SiC nanoparticles (NPs) were sonochemically coated with OctaIsobutyl (OI) polyhedral oligomeric silsesquioxane (POSS) to create a compatible interface between particle and thermoset polymer. X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) techniques were used to analyze the structure of OI-POSS coated SiC nanoparticles. These results revealed the formation of a covalent bonding between SiC and OI-POSS. The transmission electron microscopy (TEM) analysis of OI-POSS coated SiC nanoparticles has also shown the indication of attachment between these two nanoparticles. The OI-POSS coated SiC nanoparticles were further reinforced into a thermoset resin system in order to evaluate mechanical and thermal properties of nanocomposites. The flexural strength, modulus, and glass transition temperature were found to be enhanced while SiC and OI-POSS coated SiC were infused into epoxy system compared to those properties of neat epoxy resin.

scholarly journals A novel polyhedral oligomeric silsesquioxane-modified layered double hydroxide: preparation, characterization and properties

2018 ◽  
Vol 9 ◽  
pp. 3053-3068 ◽  
Author(s):  
Xianwei Zhang ◽  
Zhongzhu Ma ◽  
Hong Fan ◽  
Carla Bittencourt ◽  
Jintao Wan ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Heat Release ◽  
Layered Double Hydroxide ◽  
Photoelectron Spectroscopy ◽  
Degradation Kinetics ◽  
Polyhedral Oligomeric Silsesquioxane ◽  
Step Method ◽  
X Ray ◽  
Double Hydroxide ◽  
Oligomeric Silsesquioxane

A novel layered double hydroxide modified by octa-substituted carboxy-terminated polyhedral oligomeric silsesquioxane was prepared via a one-step method and characterized by Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, transmission electron microscopy, scanning electron microscopy, elemental analysis, thermogravimetric analysis, and microscale combustion calorimetry (MCC). Results showed that the silsesquioxane modified-LDH (OLDH) revealed an increase in the interlayer distance, nanoscale plate-like morphology of primary particles, and improved thermal stability. A synergistic effect between the siloxane moiety and Mg–Al hydroxide was found during thermal degradation, and confirmed by the study of degradation kinetics together with the analysis of the surface morphologies and elemental components of char residues. Moreover, in contrast to conventional organic modified LDH (e.g., dodecylbenzenesulfonate-LDH), the MCC results showed a significant decrease in the heat release rate and total heat release, indicating the low flammability of OLDH.

Effect of Atomic Oxygen Exposure on Polyhedral Oligomeric Silsesquioxane/Polyimide Hybrid Materials in Low Earth Orbit Environment

2011 ◽  
Vol 492 ◽  
pp. 521-524 ◽  
Author(s):  
Shu Wang Duo ◽  
Mi Mi Song ◽  
Ting Zhi Liu ◽  
Chang Yuan Hu ◽  
Mei Shuan Li
Keyword(s):  
Photoelectron Spectroscopy ◽  
Atomic Oxygen ◽  
Polyhedral Oligomeric Silsesquioxane ◽  
Surface Region ◽  
Low Earth Orbit ◽  
Hybrid Films ◽  
Sem Images ◽  
Near Surface ◽  
X Ray ◽  
Oligomeric Silsesquioxane

A novel polyimide (PI) hybrid nanocomposite containing polyhedral oligomeric silsesquioxane (POSS) had been prepared by copolymerization of octa(aminophenyl)silsesquioxane (OAP-POSS), 4,4’ -oxydianiline (ODA), and pyromellitic dianhydride (PMDA). The AO resistance of these POSS/PI hybrid films was tested in the ground-based AO simulation facility. Exposed and unexposed surfaces have been characterized by X-ray photoelectron spectroscopy and FTIR. The XPS data indicate that the carbon content of the near-surface region is decreased from 63.6 to 19.3 at% after AO exposure. The oxygen and silicon concentrations in the near-surface region increase after AO exposure. The data reveal the formation of a passive inorganic SiO2 layer on the POSS/PI hybrid films during the AO exposure, which serves as a protective barrier preventing further degradation of the underlying polymer with increased exposure to the AO flux. SEM images showed that the surface of the 10 wt% POSS/PI became much less rough than that of the pristine polyimide. The AO resistance of the POSS/PI hybrid films is up to several tenfold than that of the pristine polyimide.

scholarly journals In situ monitoring of the influence of water on DNA radiation damage by near-ambient pressure X-ray photoelectron spectroscopy

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Marc Benjamin Hahn ◽  
Paul M. Dietrich ◽  
Jörg Radnik
Keyword(s):  
Dna Damage ◽  
Radiation Damage ◽  
Photoelectron Spectroscopy ◽  
Ambient Pressure ◽  
In Situ Monitoring ◽  
Strong Increase ◽  
Oh Radicals ◽  
Strand Breaks ◽  
X Ray

AbstractIonizing radiation damage to DNA plays a fundamental role in cancer therapy. X-ray photoelectron-spectroscopy (XPS) allows simultaneous irradiation and damage monitoring. Although water radiolysis is essential for radiation damage, all previous XPS studies were performed in vacuum. Here we present near-ambient-pressure XPS experiments to directly measure DNA damage under water atmosphere. They permit in-situ monitoring of the effects of radicals on fully hydrated double-stranded DNA. The results allow us to distinguish direct damage, by photons and secondary low-energy electrons (LEE), from damage by hydroxyl radicals or hydration induced modifications of damage pathways. The exposure of dry DNA to x-rays leads to strand-breaks at the sugar-phosphate backbone, while deoxyribose and nucleobases are less affected. In contrast, a strong increase of DNA damage is observed in water, where OH-radicals are produced. In consequence, base damage and base release become predominant, even though the number of strand-breaks increases further.

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