scholarly journals Synthesis, structure, and mechanical properties of silica nanocomposite polyrotaxane gels

2015 ◽  
Vol 11 ◽  
pp. 2194-2201 ◽  
Author(s):  
Kazuaki Kato ◽  
Daisuke Matsui ◽  
Koichi Mayumi ◽  
Kohzo Ito
Keyword(s):  
Silica Nanoparticles ◽  
Young’S Modulus ◽  
Network Structure ◽  
Young's Modulus ◽  
Silica Content ◽  
Homogeneous Distribution ◽  
Chain Polymer ◽  
Nanocomposite Gels ◽  
Compression Strain ◽  
Infinite Network

A significantly soft and tough nanocomposite gel was realized by a novel network formed using cyclodextrin-based polyrotaxanes. Covalent bond formation between the cyclic components of polyrotaxanes and the surface of silica nanoparticles (15 nm diameter) resulted in an infinite network structure without direct bonds between the main chain polymer and the silica. Small-angle X-ray scattering revealed that the homogeneous distribution of silica nanoparticles in solution was maintained in the gel state. Such homogeneous nanocomposite gels were obtained with at least 30 wt % silica content, and the Young’s modulus increased with silica content. Gelation did not occur without silica. This suggests that the silica nanoparticles behave as cross-linkers. Viscoelastic measurements of the nanocomposite gels showed no stress relaxation regardless of the silica content for <20% compression strain, indicating an infinite stable network without physical cross-links that have finite lifetime. On the other hand, the infinite network exhibited an abnormally low Young’s modulus, ~1 kPa, which is not explainable by traditional rubber theory. In addition, the composite gels were tough enough to completely maintain the network structure under 80% compression strain. These toughness and softness properties are attributable to both the characteristic sliding of polymer chains through the immobilized cyclodextrins on the silica nanoparticle and the entropic contribution of the cyclic components to the elasticity of the gels.

The Effects of Silica Content and Thermal Cycles on Young’s Modulus and Residual Stresses in Yttria Stabilized Zirconia Thermal Barrier Coatings

1997 ◽  
Author(s):  
R.T.R. McGrann ◽  
E.F. Rybicki ◽  
J.R. Shadley ◽  
R.E. Sanchez ◽  
W.J. Brindley
Keyword(s):  
Residual Stresses ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Silica Content ◽  
Yttria Stabilized Zirconia ◽  
Ceramic Layer ◽  
Thermal Barrier ◽  
Stabilized Zirconia ◽  
Thermal Cycles ◽  
Plasma Sprayed

Abstract The Young's modulus of the ceramic top coat of a plasma sprayed thermal barrier coating (TBC) has been reported to vary by as much as a factor of three with changes in processing parameters and by as much as a factor of four due to prolonged thermal exposure. Since the residual stress is expected to vary directly with the modulus of the ceramic layer, it follows that a change in modulus will change the residual stresses in the ceramic layer. The objective of this study was to evaluate the modulus of plasma sprayed coatings as a function of thermal cycle exposure and silica content of the ceramic. The study employed the Cantilever Beam Bending Method to examine Young's modulus for an yttria stabilized zirconia TBC applied by plasma spraying, for zero and ten thermal cycles and for silica contents of 0.1% and 1.0%. Results are discussed in terms of mechanisms that may affect modulus and the effect of modulus variations on residual stresses.

Preparation and Characterization of Poly(Acrylamide)/Silica Nanocomposite Gels

2011 ◽  
Vol 306-307 ◽  
pp. 1252-1256
Author(s):  
Li Li Wu ◽  
Ling Zi Zeng ◽  
Hai Bo Chen ◽  
Chao Can Zhang
Keyword(s):  
Silica Nanoparticles ◽  
Ph Value ◽  
Silica Content ◽  
Polymer Particle ◽  
Silica Sol ◽  
Organic Polymer ◽  
Nanocomposite Gels ◽  
Silica Nanocomposite ◽  
Afm Micrographs ◽  
High Degree

A series of PAM/silica nanocomposite (NC) gels using silica sol as the inorganic component were prepared by in situ free-radical polymerization. The addition of silica sol was first used to bring silica nanoparticles to form organic (polymer)/inorganic system. Results from the swelling experiment indicated that the effect of silica particle was nevertheless rather complex as polymer/particle binding. Additionally, it revealed that the swelling ratio of the NC gels with a certain silica content increased with the increasing pH value. Moreover, it exhibited absorption of the polymer onto silica because the chemical cross-linked PAM has changed to the organic/inorganic system. The spectroscopic results showed that the silica nanoparticles formed by silica sol promoted high degree of attachment to the polymer chain. The AFM micrographs displayed that silica particles were of nano degree and in the monodisperse. Both evidences proved that the organic/inorganic system was effectively formed through the addition of silica sol.

Effect of Addition of Nano Silica on Modulus of an Acrylic/Melamine Automotive Topcoat

2012 ◽  
Vol 488-489 ◽  
pp. 915-918
Author(s):  
Nargess Tahmassebi
Keyword(s):  
Young’S Modulus ◽  
Ball Bearing ◽  
Young's Modulus ◽  
Silica Content ◽  
Nano Particles ◽  
Indentation Modulus ◽  
Nano Silica ◽  
Nano Indentation

In the present study, the influence of addition of various loads of hydrophobic nano silica on modulus of an acrylic melamine automotive topcoat was investigated. The results indicated that addition of hydrophobic nano silica to acrylic melamine decreased its Young’s modulus. The same behavior was observed for nano indentation modulus just at low nano silica content. This property was increased at high nano silica content. Poor interaction between nano particles / acrylic melamine and ball bearing effects of nano particles were used to explain decrease in modulus. Increase in nano indentation modulus was attributed to particle flocculation.

scholarly journals Effect of Mesoporous Silica Nanoparticles on The Physicochemical Properties of Pectin Packaging Material for Strawberry Wrapping

Nanomaterials ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 52 ◽  
Author(s):  
Asmaa Al-Asmar ◽  
C. Valeria L. Giosafatto ◽  
Mohammed Sabbah ◽  
Alfredo Sanchez ◽  
Reynaldo Villalonga Santana ◽  
...  
Keyword(s):  
Tensile Strength ◽  
Mesoporous Silica ◽  
Physicochemical Properties ◽  
Silica Nanoparticles ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Mesoporous Silica Nanoparticles ◽  
Barrier Properties ◽  
Citrus Peel ◽  
Seal Strength

Citrus peel pectin was used to prepare films (cast with or without glycerol) containing mesoporous silica nanoparticles. Nanoparticles reduced significantly the particle size, and had no effect on the Zeta potential of pectin solutions. Mechanical characterization demonstrates that pectin+nanoparticles containing films slightly increased tensile strength and significantly decreased the Young’s modulus in comparison to films made only of pectin. However, elongation at the break increased in the pectin+nanoparticles films cast in the presence of glycerol, while both Young’s modulus and tensile strength were reduced. Moreover, nanoparticles were able to reduce the barrier properties of pectin films prepared with or without glycerol, whereas positively affected the thermal stability of pectin films and the seal strength. The 0.6% pectin films reinforced or not with 3% nanoparticles in the presence of 30% glycerol were used to wrap strawberries in order to extend the fruit’s shelf-life, over a period of eighty days, by improving their physicochemical properties.

Mechanical properties of FeAlSi powders prepared by mechanical alloying from different initial feedstock materials

2019 ◽  
Vol 107 (2) ◽  
pp. 207 ◽  
Author(s):  
Jaroslav Čech ◽  
Petr Haušild ◽  
Miroslav Karlík ◽  
Veronika Kadlecová ◽  
Jiří Čapek ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Mechanical Alloying ◽  
Young’S Modulus ◽  
Milling Time ◽  
Young's Modulus ◽  
Element Model ◽  
X Ray Diffraction ◽  
X Ray ◽  
Powder Particles ◽  
Complete Homogenization

FeAl20Si20 (wt.%) powders prepared by mechanical alloying from different initial feedstock materials (Fe, Al, Si, FeAl27) were investigated in this study. Scanning electron microscopy, X-ray diffraction and nanoindentation techniques were used to analyze microstructure, phase composition and mechanical properties (hardness and Young’s modulus). Finite element model was developed to account for the decrease in measured values of mechanical properties of powder particles with increasing penetration depth caused by surrounding soft resin used for embedding powder particles. Progressive homogenization of the powders’ microstructure and an increase of hardness and Young’s modulus with milling time were observed and the time for complete homogenization was estimated.

Degradation of Rocks, Through Cracking Caused by Differential Thermal Expansion, in Relation to Nuclear Waste Repositories

1981 ◽  
Vol 6 ◽  
Author(s):  
J.R. Mclaren ◽  
R.W. Davidge ◽  
I. Titchell ◽  
K. Sincock ◽  
A. Bromley
Keyword(s):  
Thermal Expansion ◽  
Grain Boundary ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Crack Density ◽  
Granitic Rocks ◽  
Multiphase Materials ◽  
Thermal Expansion Behaviour ◽  
Waste Repositories ◽  
Expansion Behaviour

ABSTRACTHeating to temperatures up to 500°C, gives a reduction in Young's modulus and increase in permeability of granitic rocks and it is likely that a major reason is grain boundary cracking. The cracking of grain boundary facets in polycrystalline multiphase materials showing anisotropic thermal expansion behaviour is controlled by several microstructural factors in addition to the intrinsic thermal and elastic properties. Of specific interest are the relative orientations of the two grains meeting at the facet, and the size of the facet; these factors thus introduce two statistical aspects to the problem and these are introduced to give quantitative data on crack density versus temperature. The theory is compared with experimental measurements of Young's modulus and permeability for various rocks as a function of temperature. There is good qualitative agreement, and the additional (mainly microstructural) data required for a quantitative comparison are defined.

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