Activation Energy for Strength Degradation of Fused Silica Optical Fibers

1998 ◽  
Vol 531 ◽  
Author(s):  
Yunn-Shin Shiue ◽  
M. John Matthewson
Keyword(s):  
Activation Energy ◽  
Optical Fibers ◽  
Pure Water ◽  
Strength Degradation ◽  
Fused Silica ◽  
Static Fatigue ◽  
Buffer Solution ◽  
Silica Fibers ◽  
Apparent Activation Energies ◽  
Stress Dependent

AbstractThe strength degradation behavior of fused silica optical fiber is well known to be sensitive to the temperature and an apparent activation energy can be determined. In addition, it has been observed that the activation energy also depends on the applied stress and the nature of the environment. However, no consistent model for this behavior has emerged. We propose a chemical kinetics model which accounts for the temperature dependence of the dissociation of water which predicts that degradation should be faster in pH 7 buffer than in pure water. Static fatigue of fused silica fibers in both water and pH 7 buffer solution has been carefully studied as a function of temperature to test the model. The apparent activation energies are stress dependent, and, while the dependency is not clear, different environments give different dependencies. These observations support the proposed model.

Strength-Flaw Relationship of Corroded Pristine Silica Studied by Atomic Force Microscopy

1994 ◽  
Vol 332 ◽  
Author(s):  
Qian Zhong ◽  
Daryl Inniss ◽  
Charles R. Kurkjian
Keyword(s):  
Optical Fibers ◽  
Strength Degradation ◽  
Force Microscopy ◽  
Silica Glasses ◽  
Spatially Resolved ◽  
Atomic Force ◽  
Silica Fibers ◽  
Surface Flaws ◽  
Relationship Of ◽  
Microscopic Surface

ABSTRACTGlass strength is controlled by microscopic surface flaws. Attempts to quantify the strengthflaw relationship for corroded silica fibers have been unfruitful, principally because of the difficulty in identifying the nanometer-sized, strength-controlling flaws on a uniformly corroded surface. In this paper, studies on corrosion of pristine silica optical fibers by HF vapor are presented. The HF-treated fibers exhibit strength degradation and contain well-defined, spatially-resolved surface flaws, which are characterized with an atomic force microscope. Excellent strength agreement is obtained for all chemically corroded fibers when the flaws are modeled as partially embedded hemispheres (i.e., blunt flaws). The implication of these results to the corrosion and fatigue process of silica glasses is discussed, since all previous analyses have assumed the strength-controlling flaws to be sharp.

Acid stripping of fused silica optical fibers without strength degradation

1997 ◽  
Vol 15 (3) ◽  
pp. 490-497 ◽  
Author(s):  
M.J. Matthewson ◽  
C.R. Kurkjian ◽  
J.R. Hamblin
Keyword(s):  
Optical Fibers ◽  
Strength Degradation ◽  
Fused Silica

Deposition of Hermetic Carbon Coatings on Silica Fibers

1989 ◽  
Vol 172 ◽  
Author(s):  
R. G. Huff ◽  
F. V. DiMarcello ◽  
A. C. Hart ◽  
K. L. Walker
Keyword(s):  
Optical Fibers ◽  
Carbon Coating ◽  
Fiber Surface ◽  
Static Fatigue ◽  
Degradation Mechanisms ◽  
Forming Process ◽  
Deposition Rates ◽  
Carbon Coatings ◽  
Silica Fibers ◽  
Carbon Coated

AbstractCarbon coated optical fibers have recently been shown to have excellent resistance to both static fatigue and hydrogen induced losses. The deposition technique used to form the carbon coating strongly affects the coating's ability to resist these degradation mechanisms. The system developed by AT&T utilizes an atmospheric CVD chamber in which a hydrocarbon has is pyrolyzed on the fiber surface. The heat retained in the fiber from the fiber forming process is used to drive the reaction, and high draw speeds are typically used to attain the ˜900°C temperature required to deposit the hermetic form of the carbon coating. Deposition rates of ˜1μm/sec are required to produce the ˜500 Å coating.

The Application of Chemically Modified Fused Silica Fibers in the Extraction of Organics from Water Matrix Samples and their Rapid Transfer to Capillary Columns

1989 ◽  
Vol 24 (1) ◽  
pp. 179-191 ◽  
Author(s):  
Robert P. Belardi ◽  
Janusz B. Pawliszyn
Keyword(s):  
Optical Fibers ◽  
Limit Of Detection ◽  
Solid Phase ◽  
Fused Silica ◽  
Chemically Modified ◽  
Water Matrix ◽  
Silica Fibers ◽  
Response Range ◽  
Initial Results ◽  
Rapid Transfer

Abstract A technique for water sample analysis is presented which uses chemically modified fused silica optical fibers as micro solid phase extractors. The small size of the fibers (100 µm o. d. ) allows for direct introduction into the on column injector port of a high resolution gas chromatograph (GC), where the analytes are thermally desorbed. This eliminates the need for solvents and syringes which are used in liquid-liquid or solid phase extraction techniques. Thus, this method lowers cost and analysis time per sample, as well as eliminates possible sources of error. Results show that the efficiency and selectivity of this technique are dependent upon the thickness and polarity of the stationary phase. Initial results indicate that the limit of detection for 2-naphthol and FID detection is approximately 5 ng/g with a linear response range of 5 orders of magnitude.

scholarly journals Effect of CaO on catalytic combustion of semi-coke

2021 ◽  
Vol 10 (1) ◽  
pp. 011-020
Author(s):  
Luyao Kou ◽  
Junjing Tang ◽  
Tu Hu ◽  
Baocheng Zhou ◽  
Li Yang
Keyword(s):  
Activation Energy ◽  
Apparent Activation Energy ◽  
Combustion Rate ◽  
Activation Energies ◽  
Combustion Reaction ◽  
Tg Analysis ◽  
Conversion Rates ◽  
Apparent Activation Energies ◽  
Ozawa Integral Method ◽  
Addition Amount

Abstract Generally, adding a certain amount of an additive to pulverized coal can promote its combustion performance. In this paper, the effect of CaO on the combustion characteristics and kinetic behavior of semi-coke was studied by thermogravimetric (TG) analysis. The results show that adding proper amount of CaO can reduce the ignition temperature of semi-coke and increase the combustion rate of semi-coke; with the increase in CaO content, the combustion rate of semi-coke increases first and then decreases, and the results of TG analysis showed that optimal addition amount of CaO is 2 wt%. The apparent activation energy of CaO with different addition amounts of CaO was calculated by Coats–Redfern integration method. The apparent activation energy of semi-coke in the combustion reaction increases first and then decreases with the increase in CaO addition. The apparent activation energies of different samples at different conversion rates were calculated by Flynn–Wall–Ozawa integral method. It was found that the apparent activation energies of semi-coke during combustion reaction decreased with the increase in conversion.

Microfabricated Fiber Probe by Combination of Electric Arc Discharge and Chemical Etching Techniques

2012 ◽  
Vol 462 ◽  
pp. 38-41 ◽  
Author(s):  
Wan Maisarah Mukhtar ◽  
P. Susthitha Menon ◽  
Sahbudin Shaari
Keyword(s):  
Optical Fibers ◽  
Chemical Etching ◽  
Arc Discharge ◽  
Etching Rate ◽  
Electric Arc ◽  
Buffer Solution ◽  
Fiber Probe ◽  
Optical Fiber Probes ◽  
Electric Arc Discharge ◽  
Fiber Probes

In this study, optical fiber probes were fabricated by combination of electric arc discharge and chemical etching techniques. Size of tips diameters fabricated using different etching solutions were observed. When the optical fibers were pulled and heated by the electric arc discharge using a fusion splicer, fiber tips with few microns in diameter were obtained. To minimize the tips diameter, the pulled fiber probes were etched vertically for 10 minutes using two different etching solutions namely 49% HF and HF buffer solution (49% HF and 40% NH4F) with ratio of 2:1. A thick overlayer was added on top of the HF solution to prevent dangerous vapors escape to the environment. When the tapered part of the pulled fiber (FP1) was dipped into 49% HF solution, the diameter of tip was slightly decreased from 4.41μm to 1.31μm with etching rate of 5.17x10-3 μms-1. When the pulled fiber (FP2) was etched into HF buffer solution, the etching rate was increased up to 52.35% with the etching rate of 10.85x10-3μms-1. The tip diameter was reduced from 7.01μm to 468.9 nm in diameter. Combination of “heat and pull” technique with chemical etching by using HF buffer solution produced fiber probe with small tip diameter.

Mechanical Properties of SiO2 vs. SiO2-TiO2 Bulk Glasses and Fibers

1991 ◽  
Vol 244 ◽  
Author(s):  
Suresh T. Gulati
Keyword(s):  
Mechanical Properties ◽  
Optical Fibers ◽  
Mechanical Performance ◽  
Fatigue Behavior ◽  
Deformation Mode ◽  
Strength Distribution ◽  
Fused Silica ◽  
Space Applications ◽  
Silica Glasses ◽  
Silica And Titania

ABSTRACTThe mechanical properties of silica and titania-doped silica glasses, in bulk and fiber forms, are presented. These include the elastic properties (E and ν), strength distribution (in tension and bending), fatigue behavior (dynamic and static loading) and fracture toughness. Following a brief review of above properties for fused silica and ULE™ glasses (Coming Codes 7940 and 7971), used primarily for space applications, the mechanical properties data for silica and titania-doped silica-clad optical fibers are presented. The enhancement of mechanical performance of titania-doped silica clad fiber is also discussed.The effect of titania doping on fundamental properties like stress-free activation energy, crack tip pH, and deformation mode of Si-O-Si bond is discussed. In addition, the crack velocity data obtained from DCDC specimens of homogeneous silica and titania-doped silica glasses are compared in an attempt to understand the role titania plays in improving the fatigue resistance of optical fibers.

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