A Comparison of Structures and Crystallization Behavior of Gels, Gel-Derived Classes and Conventional Glasses

1986 ◽  
Vol 73 ◽  
Author(s):  
Shyama P. Mukherjee
Keyword(s):  
Kinetic Parameters ◽  
Crystallization Behavior ◽  
Water Concentration ◽  
Processing Parameters ◽  
Activation Energies ◽  
Crystallization Behaviors ◽  
Gel Processing

ABSTRACTStudies on the structures and crystallization behavior of gels in TiO2, GeO2, SiO2-GeO2 and PbO-GeO2 systems are presented to analyze the differences in structures and crystallization behavior of gel-derived glasses and conventional glasses. The kinetic parameters for crystallization such as activation energies and frequency factors of gels, gel-derived glasses and conventional glasses in the GeO2-PbO system are presented to elucidate their difference in nucleation and crystallization behaviors. The influence of gel processing parameters such as pH and water concentration on the crystallization behavior of gels are discussed.

Diamond Machinable Sol-Gel Silica Based Hybrid Coatings for High Precision Optical Molds

2010 ◽  
Vol 438 ◽  
pp. 65-72 ◽  
Author(s):  
Andreas Mehner ◽  
Ju An Dong ◽  
Timo Hoja ◽  
Torsten Prenzel ◽  
Yildirim Mutlugünes ◽  
...  
Keyword(s):  
Injection Molding ◽  
High Precision ◽  
Sol Gel ◽  
Processing Parameters ◽  
Hybrid Coatings ◽  
Optical Elements ◽  
Optical Components ◽  
New Approach ◽  
Free Silica ◽  
Gel Processing

The demand for high precision optical elements as micro lens arrays for displays increases continually. Economic mass production of such optical elements is done by replication with high precision optical molds. A new approach for manufacturing such molds was realized by diamond machinable and wear resistant sol-gel coatings. Crack free silica based hybrid coatings from base catalyzed sols from tetraethylorthosilicate (TEOS: Si(OC2H5)4) and methyltriethoxysilane (MTES: Si(CH3)(OC2H5)3) precursors were deposited onto pre-machined steel molds by spin coating process followed by a heat treatment at temperatures up to 800°C. Crack-free multilayer coatings with a total thickness of up to 18 µm were achieved. Micro-machining of these coatings was accomplished by high precision fly cutting with diamond tools. Molds with micro-structured coatings were successfully tested for injection molding of PMMA optical components. The wear resistance of the coatings was successfully tested by injection molding of 1000 PMMA lenses. Hardness and elastic modulus of the coatings were measured by nano indentation. The chemical composition was measured by X-ray photo electron spectroscopy (XPS) as a function of the sol-gel processing parameters.

Injection-molded PP composites reinforced with talc and nanoclay for automotive applications

2019 ◽  
Vol 33 (11) ◽  
pp. 1478-1498 ◽  
Author(s):  
Mohammadreza Nofar ◽  
Elif Ozgen ◽  
Burcu Girginer
Keyword(s):  
Automotive Industry ◽  
Crystallization Behavior ◽  
Charpy Impact ◽  
Processing Parameters ◽  
Mechanical And Thermal Properties ◽  
Automotive Applications ◽  
X Ray Diffraction ◽  
X Ray ◽  
Injection Molded ◽  
Two Alternatives

In this study, a commercially available polypropylene (PP) copolymer with 30-wt% talc was used as a reference material. Two different PP copolymers with 30- and 20-wt% talc were also taken as alternatives. Despite the reference PP compound, the other two alternatives are still under development and never used for the production of any exterior trim part in automotive industry. These three PP compounds were injection molded with fixed mold and barrel temperatures. Then, the samples were molded at different mold and barrel temperatures to investigate the effects of processing parameters on the mechanical and thermal properties of the final product. Finally, the effect of addition of 1-, 3- and 5-wt% nanoclay on the final properties of the PP with 20-wt% talc was explored. Differential scanning calorimeter was used to analyze the crystallization behavior of the samples. Tensile, bending, and Izod and Charpy impact tests were performed on these samples. Heat deflection temperatures and Vicat softening points were also measured. The X-ray diffraction analysis was performed to see the dispersion of the nanoclay in the PP matrix.

Crystallization Behavior of Polypropylene/Syndiotactic1,2-Polybutadiene Blends

2012 ◽  
Vol 531-532 ◽  
pp. 182-185
Author(s):  
Xiao Feng He ◽  
Shuai Wang ◽  
Tie Jun Ge ◽  
Xue Quan Zhang ◽  
Chun Yu Zhang
Keyword(s):  
High Temperature ◽  
Melting Temperature ◽  
Crystallization Temperature ◽  
Crystallization Behavior ◽  
Strong Impact ◽  
Crystallization Behaviors ◽  
Supercooling Temperature ◽  
Melting And Crystallization

The melting and crystallization behaviors of Polypropylene/Syndiotactic1,2-polybutadiene (PP/s-PB) blends and neat PP were studied by using DSC, the results showed that the presence of s-PB in PP would have a strong impact on the crystallization capacity of PP. The presence of s-PB in PP could increase the crystallization temperature(Tc) of PP, and the s-PB could obviously lower supercooling temperature(Tm-Tc) of PP, but the s-PB in PP have a Slightly influence on the melting temperature(Tm) of PP. The proposed reason for those are that the crosslinking s-PB in high temperature is a nucleator for PP’s crystallization and increases PP’s crystalline rate. However, the s-PB lowers PP’s crystallinity. At the same time, the presence of PP in blends lowers s-PB’s crystallinity, but the PP in blends have a Slightly influence on the melting temperature(Tm) and crystallization temperature(Tc) of s-PB.

Crystallization Behavior in Precursor-Modified Sol-Gel Lead

1992 ◽  
Vol 284 ◽  
Author(s):  
Titanate Powders ◽  
Wei-Heng Shie ◽  
Qing Lu ◽  
Wan Y. Shih
Keyword(s):  
Crystallite Size ◽  
Crystallization Behavior ◽  
Sol Gel ◽  
Weight Percent ◽  
Titanium Isopropoxide ◽  
Structural Units ◽  
X Ray ◽  
Nucleation Sites ◽  
Gel Processing ◽  
Gel Network

ABSTRACTThe molecular structure of precursors in sol-gel processing of PbTiO3 is modified via β-diketone substitution for the isopropyl groups of titanium isopropoxide. Crystallite size and crystallization behavior are studied using x-ray diffractometry and differential thermal analysis. The crystallite size decreases with increasing amount of β-diketone substitution. Whereas the weight percent of crystalline phase first decreases and then increases with increasing β-diketone substitution. Our results indicate that the β-diketone substitution reduces the size of the structural units in the gel network resulting in smaller crystallite size and more nucleation sites in the powders produced.

Effect of sol-gel processing parameters on thermal properties of silica aerogels

1997 ◽  
Vol 49 (2) ◽  
pp. 129-134 ◽  
Author(s):  
D. Haranath ◽  
G.M. Pajonk ◽  
P.B. Wagh ◽  
A. Venkateswara Rao
Keyword(s):  
Thermal Properties ◽  
Sol Gel ◽  
Processing Parameters ◽  
Silica Aerogels ◽  
Gel Processing

Effect of Sn on Glass Formation Ability and Crystallization Behaviors of Cu-Based Bulk Metallic Glass Alloy

2010 ◽  
Vol 139-141 ◽  
pp. 102-106 ◽  
Author(s):  
Deng Wei Zhang ◽  
Xin Ying Teng ◽  
Bo Li ◽  
Wen Jie Zhang
Keyword(s):  
Metallic Glasses ◽  
Volume Fraction ◽  
Bulk Metallic Glasses ◽  
Activation Energies ◽  
Continuous Heating ◽  
Heating Rates ◽  
Crystallization Behaviors ◽  
Characteristic Temperatures ◽  
Mold Casting ◽  
Crystallization Volume

Cu-based bulk metallic glasses (BMGs) with 5 mm in diameter were synthesized by copper mold casting. The effects of tin (Sn) addition on glass-forming ability (GFA), thermal stability of BMGs were investigated. It was found the addition of 4 at. % Sn is effective for an increase in GFA. The crystallization behaviors of Cu-based bulk metallic glasses during continuous heating are investigated mainly by differential scanning calorimeter(DSC).The results show that the characteristic temperatures(Tg,Tx and Tp) shifted to high temperature region with increasing of heating rates. The activation energies Eg, Ex and Ep, corresponding to characteristic temperatures Tg, Tx, and Tp, respectively, were obtained from Kissinger and Ozawa equations. The calculated activation energies agree well with Kissinger or Ozawa equations due to the almost invariability of the crystallization volume fraction at the characteristic temperatures for different heating rates.

scholarly journals Effect of sol-gel processing parameters on structure of zirconia

Cerâmica ◽  
2019 ◽  
Vol 65 (suppl 1) ◽  
pp. 17-21 ◽  
Author(s):  
D. G. da Silva ◽  
W. L. Vasconcelos
Keyword(s):  
Sol Gel ◽  
Processing Parameters ◽  
Gel Processing
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