The Nature of the Paramagnetic States in SiO2-GeO2-Sol-Gel Glasses

1985 ◽  
Vol 61 ◽  
Author(s):  
George Kordas ◽  
S. P. Mukherjee
Keyword(s):  
Gamma Ray ◽  
Sol Gel ◽  
Esr Spectra ◽  
Minor Importance ◽  
Esr Spectrum ◽  
Heat Treated ◽  
Gel Glasses

ABSTRACTThe 9.5 GHz ESR-spectra of gamma-ray irradiated 94 SiO2 6 GeO2 (mol%) aero gels heat treated at 462°C were recorded at 300 K. The ESR-spectrum of this gel consisted of an asymmetric line (g1 = 2.001, g2 = 1.995, and g3 = 1.994) attributed to the Ge(3)-center and other components which have not yet been identified. The 94 SiO2 6 GeO2 gel was treated at 1000 and 1280°C and then exposed to gamma-ray radiation. The Ge(1)- and Ge(3)-centers were identified in the 94 SiO2 6 GeO2 gel with TH = 1000°C. At TH = 1280°C the signal of the Ge(1)-center dominated the spectrum of this sample. The spectra of the 58 SiO2 42 GeO2 gels with TH = 1200 and 1400°C can be described by the Ge(3)-center. The Ge(1)-center was of minor importance in these samples.

The Structure of SiO2-Sol-Gel Glasses Produced from Gels with Various Mole-Water per Mole-TEOS Ratios

1985 ◽  
Vol 61 ◽  
Author(s):  
George Kordas
Keyword(s):  
Gamma Ray ◽  
Sol Gel ◽  
Heat Treating ◽  
Paramagnetic Centers ◽  
Paramagnetic Defect ◽  
Defect Centers ◽  
Gamma Ray Irradiation ◽  
Gel Glasses

ABSTRACTSiO2-gels produced with 4,8, and 16 mol water per mol TEOS were densified up to 1000°C and then exposed to gamma-ray irradiation in order to produce paramagnetic defect centers. Various paramagnetic states were detected during densification of these gels, the formation of which depends on the mol water per mol TEOS ratio. In the gels O−2 ions were detected. The paramagnetic centers detected in the n = 16 gel with TH = 900°C were attributed to a non-bridging oxygen and an E'1-center. Three different O−2 ions, probably in interstitial positions, were detected in the n = 16-gel with TH = 1000°C. The CO−2 center was observed in the n = 8 gel with TH = 900°C. A variety of new components occur at TH = 1000°C in the n = 8 gel, the origin of which remains unresolved at present. The CH3, CO−2, and E1′-centers were detected in the n = 4 gel with TH = 700°C. The CO−2 and E′1 centers were preserved after heat treating the n = 4 gel at TH = 1000°C.

TEM visualization of surface replicated acid and base catalyzed sol-gel glasses

1986 ◽  
Vol 44 ◽  
pp. 448-449
Author(s):  
George C. Ruben ◽  
Merrill W. Shafer
Keyword(s):  
Elevated Temperatures ◽  
Sol Gel ◽  
Basic Medium ◽  
Glass Transition Point ◽  
Structural Space ◽  
Acid And Base ◽  
Organometallic Precursors ◽  
New Processing ◽  
Gel Glasses ◽  
Physical Phenomena

Traditionally ceramics have been shaped from powders and densified at temperatures close to their liquid point. New processing methods using various types of sols, gels, and organometallic precursors at low temperature which enable densificatlon at elevated temperatures well below their liquidus, hold the promise of producing ceramics and glasses of controlled and reproducible properties that are highly reliable for electronic, structural, space or medical applications. Ultrastructure processing of silicon alkoxides in acid medium and mixtures of Ludox HS-40 (120Å spheres from DuPont) and Kasil (38% K2O &62% SiO2) in basic medium have been aimed at producing materials with a range of well defined pore sizes (∼20-400Å) to study physical phenomena and materials behavior in well characterized confined geometries. We have studied Pt/C surface replicas of some of these porous sol-gels prepared at temperatures below their glass transition point.

scholarly journals Nanostructured LiFe5O8 by a Biogenic Method for Applications from Electronics to Medicine

Nanomaterials ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 193
Author(s):  
Silvia Soreto Teixeira ◽  
Manuel P. F. Graça ◽  
José Lucas ◽  
Manuel Almeida Valente ◽  
Paula I. P. Soares ◽  
...  
Keyword(s):  
Spinel Ferrite ◽  
Sol Gel ◽  
Reaction Medium ◽  
Magnetic Hyperthermia ◽  
Magnetic Characteristics ◽  
Secondary Phases ◽  
Heat Treated ◽  
Structure Morphology ◽  
Sol Gel Process ◽  
Crystallite Sizes

The physical properties of the cubic and ferrimagnetic spinel ferrite LiFe5O8 has made it an attractive material for electronic and medical applications. In this work, LiFe5O8 nanosized crystallites were synthesized by a novel and eco-friendly sol-gel process, by using powder coconut water as a mediated reaction medium. The dried powders were heat-treated (HT) at temperatures between 400 and 1000 °C, and their structure, morphology, electrical and magnetic characteristics, cytotoxicity, and magnetic hyperthermia assays were performed. The heat treatment of the LiFe5O8 powder tunes the crystallite sizes between 50 nm and 200 nm. When increasing the temperature of the HT, secondary phases start to form. The dielectric analysis revealed, at 300 K and 10 kHz, an increase of ε′ (≈10 up to ≈14) with a tanδ almost constant (≈0.3) with the increase of the HT temperature. The cytotoxicity results reveal, for concentrations below 2.5 mg/mL, that all samples have a non-cytotoxicity property. The sample heat-treated at 1000 °C, which revealed hysteresis and magnetic saturation of 73 emu g−1 at 300 K, showed a heating profile adequate for magnetic hyperthermia applications, showing the potential for biomedical applications.

Photopatterning of hybrid sol–gel glasses: generation of volume phase gratings under visible light

2004 ◽  
Vol 398 (1-3) ◽  
pp. 151-156 ◽  
Author(s):  
M. Feuillade ◽  
C. Croutxé-Barghorn ◽  
L. Mager ◽  
C. Carré ◽  
A. Fort
Keyword(s):  
Visible Light ◽  
Sol Gel ◽  
Volume Phase ◽  
Gel Glasses

Bioencapsulation in Sol-Gel Glasses

1998 ◽  
Vol 519 ◽  
Author(s):  
L. Bergogne ◽  
S. Fennouh ◽  
J. Livage ◽  
C. Roux
Keyword(s):  
Sol Gel ◽  
Porous Silica ◽  
Silica Matrix ◽  
Whole Cells ◽  
The Past ◽  
Wide Range ◽  
Activity Of Enzymes ◽  
Gel Glasses ◽  
Micro Organisms

AbstractBioencapsulation in sol-gel materials has been widely studied during the past decade. Trapped species appear to retain their bioactivity in the porous silica matrix. Small analytes can diffuse through the pores allowing bioreactions to be performed in-situ, inside the sol-gel glass. A wide range of biomolecules and micro-organisms have been encapsulated. The catalytic activity of enzymes is used for the realization of biosensors or bioreactors. Antibody-antigen recognition has been shown to be feasible within sol-gel matrices. Trapped antibodies bind specifically the corresponding haptens and can be used for the detection of traces of chemicals. Even whole cells are now encapsulated without any alteration of their cellular organization. They can be used for the production of chemicals or as antigens for immunoassays.

Structural Stability of Azurin Encapsulated in Sol-Gel Glasses: A Fluorometric Study

2004 ◽  
Vol 30 (3) ◽  
pp. 205-214 ◽  
Author(s):  
Massimo Bottini ◽  
Almerinda Di Venere ◽  
Lutz Tautz ◽  
Alessandro Desideri ◽  
Paolo Lugli ◽  
...  
Keyword(s):  
Structural Stability ◽  
Sol Gel ◽  
Gel Glasses ◽  
Fluorometric Study

Synthesis of WO3 Electrochromic Sensor by Sol-Gel Method and Characterization of Its Electrochemical and Optical Properties

2006 ◽  
Vol 317-318 ◽  
pp. 807-810 ◽  
Author(s):  
Chang Yeoul Kim ◽  
Jin Wook Choi ◽  
Tae Yeoung Lim ◽  
Duck Kyun Choi
Keyword(s):  
Thin Film ◽  
Sol Gel ◽  
Dip Coating ◽  
Xrd Pattern ◽  
Starting Solution ◽  
Oxide Crystal ◽  
Heat Treated ◽  
Coating Method ◽  
Dip Coating Method

Electrochromic WO3 thin film was prepared by using tungsten metal solution in hydrogen peroxide as a starting solution and by sol-gel dip coating method. XRD pattern showed that tungsten oxide crystal phase formed at 400. In the view of electrochemical property, WO3 thin film which was heat-treated at 300 and was amorphous had better than that of the crystalline phase.

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