Structure And Properties Of Binary Rodlike/Flexible Polyimide mixtures.

1991 ◽  
Vol 227 ◽  
Author(s):  
S. Rojstaczer ◽  
M. Ree ◽  
D Y. Yoon ◽  
W. Volksen
Keyword(s):  
Photoelectron Spectroscopy ◽  
Surface Segregation ◽  
Amic Acid ◽  
Structure And Properties ◽  
Matrix Component ◽  
X Ray ◽  
Solution Blending ◽  
Thermal Imidization ◽  
Rodlike Polymers ◽  
Strong Surface

Abbstract:Binary mixtures of a rodlike poly(p-phenylene pyromellitimide) (PMDA-PDA) and a flexible 6F-BDAF polyimide synthesized from hexafluoroisopropylidene diphthalic anhydride and 2,2-bis(4-aminophenoxy-p-phenylene) hexafluoropropane were prepared by solution-blending of the meta-PMDA-PDA poly(amic ethyl ester) and 6F-BDAF poly(amic acid) precursors, followed by solvent evaporation and thermal imidization. The size scale of the phase separation, as measured by light scattering, is ca. I μm or smaller in most cases. Dynamical mechanical thermal analysis measurements indicate that the glass transition temperature of 6F-BDAF is unaffected in all of the mixtures studied, indicating complete demixing of rodlike and flexible polyimides in agreement with theory. X-ray photoelectron spectroscopy results show a strong surface segregation of 6F-BDAF in mixtures containing as low as 10% by weight of the 6F-BDAF component in the bulk. The mixtures with PMDA-PDA as the major matrix component therefore maintain excellent bulk properties of rodlike polymers, i.e., high modulus to 500°C, and low coefficients of thermal expansion (< ca. 10 ppm/°C). On the other hand, the surface properties of the mixtures are dominated by the flexible 6F-BDAF, resulting in excellent polymer/polymer self-adhesion (lamination) properties between fully imidized films.

Surface segregation of boron in BxGa1−xAs/GaAs epilayers studied by x-ray photoelectron spectroscopy and atomic force microscopy

2003 ◽  
Vol 82 (12) ◽  
pp. 1830-1832 ◽  
Author(s):  
H. Dumont ◽  
D. Rutzinger ◽  
C. Vincent ◽  
J. Dazord ◽  
Y. Monteil ◽  
...  
Keyword(s):  
Atomic Force Microscopy ◽  
Photoelectron Spectroscopy ◽  
Surface Segregation ◽  
X Ray ◽  
Force Microscopy ◽  
Atomic Force

scholarly journals Montecarlo Simulation and HAXPES Analysis of Organosilane Segregation in Titania Xerogel Films; Towards a Generic Surface Chemofunctionalization Process

Surfaces ◽  
2020 ◽  
Vol 3 (3) ◽  
pp. 352-365
Author(s):  
Javier Mateo Moreno ◽  
Rodrigo Calvo Membibre ◽  
Sergio Pinilla Yanguas ◽  
Juan Rubio Zuazo ◽  
Miguel Manso Siván
Keyword(s):  
Photoelectron Spectroscopy ◽  
Surface Segregation ◽  
Titanium Isopropoxide ◽  
Condensation Process ◽  
X Ray ◽  
Depth Profiles ◽  
Partial Charges ◽  
Xerogel Films ◽  
Non Destructive

The formation of xerogels implies a sequence of hydrolysis and condensation reactions, which are intricate to analyze in heteromolecular sols. We analyze by probabilistic Montecarlo methods the development of hybrid organosilane–titania xerogels and illustrate how partial charges of the reacting molecules can help estimating relative probabilities for the condensation of the molecules. Since the condensation rate of Ti alkoxides is much higher than the corresponding rate of Si alkoxides (especially if bearing a non-hydrolizable group), by imposing a fast condensation process in agreement with low pH kinetics, the process leads to a surface segregation of the organosilane. The simulation results are compared with results of characterization of thin condensates of two different organosilanes within a titanium–isopropoxide matrix. Non-destructive in-depth profiles were obtained by hard x-ray photoelectron spectroscopy, which can resolve through estimation of Si and specific moieties of the organosilane molecules the progress of the condensation. These results are relevant for the generalization of chemo-functionalization processes by kinetic demixing of organosilanes, which have myriad applications in biomedicine and biotechnology.

Surface Segregation of Sulfur and Its Effect on Surface-Energy-Induced Selective Grain Growth in Magnetostrictive Fe-Ga-B Alloy

2008 ◽  
Author(s):  
Suok-Min Na ◽  
Alison B. Flatau
Keyword(s):  
Surface Energy ◽  
Grain Growth ◽  
Photoelectron Spectroscopy ◽  
Electron Spectroscopy ◽  
Surface Segregation ◽  
Iron Sulfide ◽  
Rolling Direction ◽  
X Ray ◽  
Sulfur Atmosphere ◽  
Xrd Patterns

The surface-energy-induced selective grain growth with a specific plane can be governed in polycrystalline Fe-Ga-B alloys doped with sulfur. The segregated sulfur during texture annealing played an important role in controlling the surface energy to induce the selective growth of {100} or {110} grains, corresponding to maximum magnetostrictive performance, along <001> orientation with respect to rolling direction. The results show that sulfur diffuses (adsorbs) from bulk interior (sulfur atmosphere) then segregates on the surface. The amount of segregated sulfur increases with an increase of annealing time at the temperature of 1200°C. Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) data on the surface as well as selective development of {100}<001> and {110}<001> preferred textures are presented in this work. The XPS fitted peaks of S 2p3/2 at binding energy of 161.2 and 163.2 eV for annealed Fe-Ga-B doped with sulfur represent the presence of stoichiometric FeS and FeSn (polysulfide), respectively. For all of the sulfur-free Fe-Ga-B sheets annealed in the ampoule with sulfur element, XPS indicated contributions centered at approximately 161.7 (S 2p) that has been assigned to iron sulfide as well. The presence of FeS was clearly confirmed by XRD patterns and XPS fitted peak positions at 161.5 eV (S 2p3/2) and 710.2 eV (Fe 2p3/2). The segregation of sulfur and boron during annealing were also confirmed by AES depth profile results, which exhibited peak concentrations of 10 at.%S and 20 at.%B at the surface, respectively. The peak magnetostriction of 201 ppm was obtained at annealed (Fe81.3Ga18.7)99B1 alloy with near {100}<001> orientation under sulfur atmosphere containing the amounts of 6.4 mg S. On the other hand, the texture of sulfur-free Fe-Ga-B alloy was close to {110}<001> after annealing at 1200°C for 6h under flowing argon, corresponding to the magnetostriction of 160 ppm.

An X-Ray Photoelectron Spectroscopic Study of the Free Surface Segregation of Impurities in Platinum and Palladium

1987 ◽  
Vol 41 (3) ◽  
pp. 516-522
Author(s):  
Alan J. Paul ◽  
Peter M. A. Sherwood
Keyword(s):  
Free Surface ◽  
Spectroscopic Study ◽  
Photoelectron Spectroscopy ◽  
Surface Segregation ◽  
Pure Metal ◽  
Binding Energies ◽  
X Ray ◽  
The Core ◽  
Segregation Of Impurities ◽  
Elemental Form

X-ray photoelectron spectroscopy has been used to observe the free surface segregation of impurities in samples of platinum and palladium. Heating in vacuo to 600°C promoted the surface segregation of silver, gold, and carbon in platinum and the surface segregation of silver and sulfur in palladium. All species segregated in their elemental form. The core level binding energies of the silver and gold segregants were lower than those measured for the corresponding pure metal states.

Properties of SiO2CuOx Films for Nitrogen Dioxide Detection

2013 ◽  
Vol 834-836 ◽  
pp. 112-116 ◽  
Author(s):  
Tatiana Myasoedova ◽  
G.E. Yalovega ◽  
V.V. Petrov ◽  
O.V. Zabluda ◽  
V.A. Shmatko ◽  
...  
Keyword(s):  
Thin Films ◽  
Nitrogen Dioxide ◽  
Photoelectron Spectroscopy ◽  
Sol Gel ◽  
Structure And Properties ◽  
X Ray Diffraction ◽  
X Ray ◽  
Gel Technique ◽  
Operating Temperatures

SiOxCuOythin films were prepared by the deposition on to the Si/SiO2substrates from the alcoholic solutions employing the sol-gel technique. The various analytic techniques were applied to characterize structure and properties of the films under study . The both X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) studies showed the presence CuO as well as CuO2phases and formation of a dual-oxide CuSiO3with the average crystallites sizes of 35-50 nm. The conductance of the films was rather sensitive to the presence of 1-20 ppm NO2concentration at the operating temperatures in the range of 20–200◦C.

Molecular Composites of Rodlike/Flexible Polyimides

1989 ◽  
Vol 171 ◽  
Author(s):  
S. R. Rojstaczer ◽  
D.Y. Yoon ◽  
W. Volksen ◽  
B.A. Smith
Keyword(s):  
Molecular Weight ◽  
Phase Separation ◽  
Light Scattering ◽  
Film Thickness ◽  
Domain Size ◽  
Amic Acid ◽  
Solution Blending ◽  
Thermal Imidization ◽  
Precursor Polymers ◽  
Molecular Composites

ABSTRACTMixtures of a rodlike and a flexible polyimide were prepared by solution-blending of the respective poly(amic alkyl ester) and poly(amic acid), followed by solvent evaporation and thermal imidization. The size scale of the phase separation, as measured by light scattering, is primarily set during the demixing of the precursor polymers, with no significant coarsening observed due to the imidization performed at 400°C. The observed variation of the domain size with parameters such as composition, molecular weight and film thickness is discussed in terms of the miscibility of the precursor polymers as well as the thermal history to which these were exposed.

Surface Characterization of Clean Gd5Ge4(010)

2012 ◽  
Vol 1517 ◽  
Author(s):  
Chad D. Yuen ◽  
Gordon J. Miller ◽  
Patricia A. Thiel
Keyword(s):  
Scanning Tunneling Microscopy ◽  
Photoelectron Spectroscopy ◽  
Surface Characterization ◽  
Surface Segregation ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
X Ray ◽  
Show Evidence ◽  
Bulk Structure

AbstractBased on X-ray photoelectron spectroscopy, Gd5Ge4(010) does not show evidence of surface segregation. Scanning tunneling microscopy reveals two types of terraces which alternate laterally on the surface. From the step heights, these two surface terminations are assigned as dense, Gd-pure layers in the bulk structure. There is evidence of reconstruction on one type of terrace.

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