The Use of Mechanical Property Measurements to Characterize Gels and Gelation Processes

1991 ◽  
Vol 248 ◽  
Author(s):  
Y. Yang ◽  
N. Ichise ◽  
Z. Li ◽  
Q. Yuan ◽  
J. E. Mark ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Phenol Formaldehyde ◽  
Structural Characteristics ◽  
Sol Gel ◽  
Ceramic Materials ◽  
Organic Polymer ◽  
High Tech ◽  
Aging Effects ◽  
Cross Links ◽  
Induction Times

AbstractThere are a variety of gels (highly swollen solids) that are of considerable interest to polymer scientists, materials scientists, and ceramists. One type consists of typical organic polymers such as polyethylene or polystyrene, in networks which are formed by means of physical cross links, such as crystallites or physical aggregates. Such gels are thermoreversible in that liquefaction occurs upon heating. Another type consists of chain-like structures permanently bonded into covalent networks. These permanently branched and cross-linked chains can be either organic (phenol-formaldehyde resins, epoxies, etc.), or inorganic [silica (SiO2), titania (TiO2), zirconia (ZrO2), etc.] Both the organic and inorganic covalent types have been used to prepare aerogels, and the inorganic ones are now much used to prepare high-tech ceramics by the new sol-gel route.In the case of the thermoreversible, organic polymer gels, moduli can be measured as a function of concentration, temperature, and structural characteristics of the polymer (molecular weight, molecular weight distribution, and nature and degree of any chain branching). Such equilibrium results give information on the nature of the gels, including the influence of morphology, and the presence of dangling-chain irregularities. Measurements carried out as a function of time, for example, on polyethylene homopolymers and copolymers, can give information about their gelation kinetics.In the case of the ceramic materials, the evolution of the shear modulus with time is very useful in establishing induction times, rates of gelation, and aging effects. Correlation of such information with results of scattering studies can give much insight into the nature of the sol-gel process.

Templating Nanopores Into Poly(MethylSilsesquioxane): New Lowdielectric Coatings Suitable for MicroElectronic Applications

1998 ◽  
Vol 511 ◽  
Author(s):  
Julius F. Remenar ◽  
Craig J. Hawker ◽  
James L. Hedrick ◽  
Sung Mog Kim ◽  
Robert D. Miller ◽  
...  
Keyword(s):  
Experimental Data ◽  
Thin Films ◽  
Molecular Weight ◽  
Thermal Decomposition ◽  
Dielectric Constants ◽  
Organic Polymer ◽  
Low Molecular Weight ◽  
Polymer Templates ◽  
Cross Links ◽  
Poly Caprolactone

ABSTRACTThin films of nanoporous poly(methylsilsesquioxane) have been prepared from organic/inorganic polymer hybrids. Low molecular weight 6-arm star poly(caprolactone)s are incorporated into partially pre-condensed methylsilsesquioxane resin. Upon heating, the glass resin cross-links around the organic polymer templates. Thermal decomposition of the orgainc polymer produces nanoporous thin films which show tunable dielectric constants as low as 1.9 and exhibit properties suitable for use in interconnect devices. Experimental data including porosity, morphology, and dielectric constants are presented.

Sol-gel and SPS combined synthesis of highly porous wollastonite ceramic materials with immobilized Au-NPs

2017 ◽  
Vol 43 (11) ◽  
pp. 8509-8516 ◽  
Author(s):  
E.K. Papynov ◽  
O.O. Shichalin ◽  
V.Yu. Mayorov ◽  
E.B. Modin ◽  
A.S. Portnyagin ◽  
...  
Keyword(s):  
Sol Gel ◽  
Ceramic Materials ◽  
Au Nps ◽  
Highly Porous

scholarly journals Hard Coating Materials Based on Photo-Reactive Silsesquioxane for Flexible Application: Improvement of Flexible and Hardness Properties by High Molecular Weight

Polymers ◽  
2021 ◽  
Vol 13 (10) ◽  
pp. 1564
Author(s):  
Jong Tae Leem ◽  
Woong Cheol Seok ◽  
Ji Beom Yoo ◽  
Sangkug Lee ◽  
Ho Jun Song
Keyword(s):  
Molecular Weight ◽  
Surface Morphology ◽  
High Molecular Weight ◽  
Sol Gel ◽  
Xrd Analysis ◽  
Polyhedral Oligomeric Silsesquioxanes ◽  
Coating Materials ◽  
Pencil Hardness ◽  
Coated Film ◽  
Flexible Application

EPOSS of polyhedral oligomeric silsesquioxanes (POSS) mixture structure and LPSQ of ladder-like polysilsesquioxane (LPSQ) structure were synthesized via sol–gel reaction. EPSQ had a high molecular weight due to polycondensation by potassium carbonate. The EPSQ film showed uniform surface morphology due to regular double-stranded structure. In contrast, the EPOSS-coated film showed nonuniform surface morphology due to strong aggregation. Due to the aggregation, the EPOSS film had shorter d-spacing (d1) than the EPSQ film in XRD analysis. In pencil hardness and nanoindentation analysis, EPSQ film showed higher hardness than the EPOSS film due to regular double-stranded structure. In addition, in the in-folding (r = 0.5 mm) and out-folding (r = 5 mm) tests, the EPSQ film did not crack unlike the EPOSS coated film.

scholarly journals Sol-Gel Synthesis of the Double Perovskite Sr2FeMoO6 by Microwave Technique

Materials ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 3876
Author(s):  
Jesús Valdés ◽  
Daniel Reséndiz ◽  
Ángeles Cuán ◽  
Rufino Nava ◽  
Bertha Aguilar ◽  
...  
Keyword(s):  
Particle Size ◽  
Hydrothermal Synthesis ◽  
Microwave Radiation ◽  
Structural Characteristics ◽  
Sol Gel ◽  
Synthesis Method ◽  
Double Perovskite ◽  
Synthesis Methods ◽  
X Ray ◽  
Sol Gel Synthesis

The effect of microwave radiation on the hydrothermal synthesis of the double perovskite Sr2FeMoO6 has been studied based on a comparison of the particle size and structural characteristics of products from both methods. A temperature, pressure, and pH condition screening was performed, and the most representative results of these are herein presented and discussed. Radiation of microwaves in the hydrothermal synthesis method led to a decrease in crystallite size, which is an effect from the reaction temperature. The particle size ranged from 378 to 318 nm when pH was 4.5 and pressure was kept under 40 bars. According to X-ray diffraction (XRD) results coupled with the size-strain plot method, the product obtained by both synthesis methods (with and without microwave radiation) have similar crystal purity. The Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS) techniques showed that the morphology and the distribution of metal ions are uniform. The Curie temperature obtained by thermogravimetric analysis indicates that, in the presence of microwaves, the value was higher with respect to traditional synthesis from 335 K to 342.5 K. Consequently, microwave radiation enhances the diffusion and nucleation process of ionic precursors during the synthesis, which promotes a uniform heating in the reaction mixture leading to a reduction in the particle size, but keeping good crystallinity of the double perovskite. Precursor phases and the final purity of the Sr2FeMoO6 powder can be controlled via hydrothermal microwave heating on the first stages of the Sol-Gel method.

Nanostructured TiO2-Based Composites for Light Absorption

2014 ◽  
Vol 975 ◽  
pp. 207-212
Author(s):  
Dayse I. dos Santos ◽  
Olayr Modesto Jr. ◽  
Luis Vicente A. Scalvi ◽  
Americo S. Tabata
Keyword(s):  
Metal Oxide ◽  
Light Absorption ◽  
Structural Characteristics ◽  
Sol Gel ◽  
Second Phase ◽  
X Ray Diffraction ◽  
Two Phase ◽  
X Ray ◽  
Oxide Powders

Metal oxide nanocomposites were prepared by two different routes: polyol and sol-gel. Characterization by X ray diffraction showed that the first process produces directly a two-phase material, while the sol-gel powder never showed second phase below 600°C. Light spectroscopy of the treated powders indicated similarities for the processed materials. Although the overall material compositions are about the same, different structural characteristics are found for each processing. With the exception of Ti-Zn materials, all the double metal oxide powders showed higher absorbance than either TiO2 powder.

Synthesis of Novel Vanadium Oxide Nanotubes and Nanofibers

2002 ◽  
Vol 740 ◽  
Author(s):  
Samuel T. Lutta ◽  
Hong Dong ◽  
Peter Y. Zavalij ◽  
M. Stanley Whittingham
Keyword(s):  
Thermal Analysis ◽  
Vanadium Oxide ◽  
Electrochemical Behavior ◽  
Redox Reactions ◽  
Sol Gel ◽  
Vanadium Oxides ◽  
Organic Polymer ◽  
Fibrous Morphology ◽  
Surfactant Templates ◽  
Vanadium Oxide Nanotubes

ABSTRACTWe are exploring the synthesis and properties of structured vanadium oxides mainly nanotubes and nanorods. Nanotubes initially formed with surfactant templates have been readily exchanged with simple cations without change of the basal-plane structure. These compounds contain d-like vanadium oxide layers with the vanadium in VO6 octahedra. This structure is particularly suitable for redox reactions. In this paper we report on synthesis of vanadium oxide, (NH4)xV2O5-d·nH2O rods using organic polymer as template. This compound has been synthesized by sol-gel reaction and subsequent hydrothermal treatment. TGA, SEM, XRD and FTIR were used to characterize this compound. Thermal analysis of this compound shows that the fibrous morphology is maintained when it is heated in nitrogen and oxygen above 300 °C. However, in both cases the size of the fibers decreases. Performance of this compound as cathode material in secondary electrolyte has been investigated using LiPF6 as electrolyte. A capacity of 140 mAh/g was obtained which remained fairly constant with up to at least 10 cycles. We also investigated electrochemical behavior of thermal products.

Synthesis and structural characteristics of high surface area TiO2 aerogels by ultrasonic-assisted sol–gel method

2018 ◽  
Vol 29 (7) ◽  
pp. 075702 ◽  
Author(s):  
Feng Qingge ◽  
Cai Huidong ◽  
Lin Haiying ◽  
Qin Siying ◽  
Liu Zheng ◽  
...  
Keyword(s):  
Surface Area ◽  
Structural Characteristics ◽  
High Surface ◽  
Sol Gel ◽  
High Surface Area ◽  
Gel Method ◽  
Sol Gel Method ◽  
Ultrasonic Assisted

EXPERIMENTAL VALIDATION OF THE CHARLESBY AND HORIKX MODELS APPLIED TO DE-VULCANIZATION OF SULFUR AND PEROXIDE VULCANIZATES OF NR AND EPDM

2016 ◽  
Vol 89 (4) ◽  
pp. 671-688 ◽  
Author(s):  
M. A. L. Verbruggen ◽  
L. van der Does ◽  
W. K. Dierkes ◽  
J. W. M. Noordermeer
Keyword(s):  
Experimental Validation ◽  
Main Chain ◽  
Sol Gel ◽  
Chain Scission ◽  
Cross Linking ◽  
Cross Link ◽  
Practical Reality ◽  
Cross Links ◽  
The Cross ◽  
Theoretical Considerations

ABSTRACT The theoretical model developed by Charlesby to quantify the balance between cross-links creation of polymers and chain scission during radiation cross-linking and further modifications by Horikx to describe network breakdown from aging were merged to characterize the balance of both types of scission on the development of the sol content during de-vulcanization of rubber networks. There are, however, disturbing factors in these theoretical considerations vis-à-vis practical reality. Sulfur- and peroxide-cured NR and EPDM vulcanizates were de-vulcanized under conditions of selective cross-link and random main-chain scissions. Cross-link scission was obtained using thiol-amine reagents for selective cleavage of sulfur cross-links. Random main-chain scission was achieved by heating peroxide vulcanizates of NR with diphenyldisulfide, a method commonly employed for NR reclaiming. An important factor in the analyses of these experiments is the cross-linking index. Its value must be calculated using the sol fraction of the cross-linked network before de-vulcanization to obtain reliable results. The values for the cross-linking index calculated with sol-gel data before de-vulcanization appear to fit the experimentally determined modes of network scission during de-vulcanization very well. This study confirms that the treatment of de-vulcanization data with the merged Charlesby and Horikx models can be used satisfactorily to characterize the de-vulcanization of NR and EPDM vulcanizates.

Control of Hierarchically Ordered Positive and Negative Replicas of Wood Cellular Structures by Surfactant-Directed Sol-Gel Mineralization

2002 ◽  
Vol 726 ◽  
Author(s):  
Yongsoon Shin ◽  
Jun Liu ◽  
Li-Qiong Wang ◽  
Jeong Ho Chang ◽  
William D. Samuels ◽  
...  
Keyword(s):  
Silicic Acid ◽  
Cell Walls ◽  
Cellular Structure ◽  
Sol Gel ◽  
Ceramic Materials ◽  
Silica Particles ◽  
Low Ph ◽  
Cellular Structures ◽  
Inner Surface

AbstractWe here report the synthesis of ordered ceramic materials with hierarchy produced by an in-situ mineralization of ordered wood cellular structures with surfactant-templated sol-gel at different pH. At low pH, a silicic acid is coated onto inner surface of wood cellular structure and it penetrates into pores left, where degraded lignin and hemicellulose are leached out, to form a positive replica, while at high pH the precipitating silica particles due to fast condensation clog the cells and pit structures to form a negative replica of wood. The calcined monoliths produced in different pHs contain ordered wood cellular structures, multi-layered cell walls, pits, vessels well-preserved with positive or negative contrasts, respectively. The surfactant-templated mineralization produces ordered hexagonal nanopores with 20Å in the cell walls after calcination.

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