Charles R. Kurkjian

Mössbauer spectroscopy in inorganic glasses

Abstract Recoil-free emission and resonant absorption of nuclear gamma rays (i.e., the Mossbauer effect) has proven to be an effective tool in the study of certain physical and chemical properties of crystalline systems. The theory of the effect, as well as certain practical details, are presented. On this basis the experimental work on inorganic glasses is discussed and the usefulness of the tool in such systems assessed.

Mechanical and Structural Properties of Phosphate Glasses

Abstract Mechanical and structural properties of sodium (NAFP) and zinc (ZAFP) iron–aluminum–phosphate bulk glass and fibers have been investigated. Youngs modulus of the fibers was measured by a three-point bending method while the strength was measured by a two-point bending method. In general, the tensile strength of the ZAFP fibers (4.2–7.2 GPa) was higher than the tensile strength of the NAFP fibers (2.8–4.2 GPa). After exposing the fibers to air for 10 days, the strength decreased by 15–34%. The structure of bulk glass as well as fibers, studied by Mossbauer and IR spectroscopy, was very similar for all the compositions studied.

The intrinsic strength and fatigue of oxide glasses

Recent studies on the strength of glass fibers suggest that the time is ripe for new, fundamental studies in this area which may significantly advance our understanding of the intrinsic strength of glasses. In order to set the stage, in this paper we define various terms (intrinsic and extrinsic strength and inert and environmental fatigue) and analyze techniques for their measurement. We illustrate and evaluate these parameters by means of literature data on silica and E-glass. In addition we present some preliminary new data on E-glass fibers using 2-point bending. These new data report higher strength than previously reported and some possible reasons for this are given. While these comments deal primarily with the science of strength, a better understanding of these issues may lead to improvements in glass technology and glass products.

Mechanical properties of phosphate glasses

The strengths of fibers drawn from three metaphosphate glasses [NaPO3, Zn(PO3)2 and a Schott laser glass, LG 770, with the approximate molar composition 20K2O‐10MgO‐10Al2O3‐60P2O5] and a pyrophosphate (P2O7) glass of nominal composition 40FeO3‐60P2O5 have been measured in 2-point bending at room temperature and at 77 K. While the three metaphosphate glasses have relatively smaller strengths at low temperature (3 GPa), the iron phosphate glass has a strength at this temperature (6 GPa), 1/2 that of silica (13 a 2 GPa). No correlation was found with either the square root of Young’s modulus (E) 1=2 or fracture toughness (KIC), but an understanding of the results was obtained by considering the overall integrity of the individual glass networks. ” 2000 Elsevier Science B.V. All rights reserved.

Nanoscale roughness of oxide glass surfaces

A comparative atomic force microscopy (AFM) study of melt-formed and fracture surfaces of silica and E-glass is reported. It is proposed that the minimum observed nanoscale roughness of a pristine melt-formed surface is controlled by the surface tension of the melt at the glass transition temperature and that the minimum observed nanoscale roughness observed in the mirror region of a fracture surface reflects the intrinsic inhomogeneities in the structure of the glass.

Structure and phonon spectra of SiO2, B2O3 and mixed SiO2B2O3 glasses

Abstract We present and interpret computed infrared and Raman spectra for SiO2, B2O3 and mixed SiO2B2O3 glasses. The calculations reproduce the main observed spectral bands in all three types of glass - very fully in the case of SiO2, and with a reasonable degree of success for B2O3 and SiO2B2O3. An analysis based on a network of B3O6 boroxol rings gives a satisfactory account of the optical spectra of glasses containing B2O3, whereas calculations based on a network of simple BO3 triangles do not.

The fatigue of high-strength fused silica optical fibers in low humidity ☆

Abstract The strength and dynamic fatigue of UV-acrylate coated silica optical fibers were measured as a function of relative humidity in the range ∼0.025–13% at 25 °C. The degradation kinetics of silica in low humidities was investigated and it was found that the reaction order was approximately first-order with respect to humidity. In our previous work, a second-order reaction was found in the humidity range 20–95% RH at 25 °C and the process for obtaining this reaction order was found to be independent of the mathematical form of the kinetic models used. The change in reaction order observed here verifies some earlier results based on the power law which implied a change in the reaction order from ∼2 (15–100% RH) to ∼1 at low humidity (

Understanding mechanical properties of lightguides: a commentary

While great progress has been made recently in the development of mechanically satisfactory lightguide fibers, detailed fundamental understanding in a number of areas seems lacking. Although in some cases this understanding may seem practically unimportant, in others it is critical to our ability to improve our product as well as to predict its reliability confidently.

Strength of silica optical fibers with micron size flaws

Abstract Silica fibers have been indented with a diamond having a cube-corner tip. The tensile strengths of fibers indented with loads from 0.2 to 10 g were 465–130 MPa, respectively, with Weibull m -values ∼30–70. Radial cracks (0.5–6.5 μm) were produced in all cases, with no transition to sub-threshold behavior at the lowest load (0.2 g) employed.

Influence of solubility on the reliability of optical fiber

Recent advances in the understanding of reliability of silica optical fiber indicate that the chemical durability of the fiber can control the long duration lifetime both under stress- induced fatigue and zero-stress aging conditions. In particular, dissolution of surface material produces strength degrading surface roughness. These mechanisms are discussed and strategies for improving reliability by inhibiting dissolution are examined. As an example, a modified polymer coating formulation is described that is shown to increase the lifetime of the fiber by up to a factor of thirty-fold. Strategies for improving the strength and durability of non-oxide fibers using a similar approach are also discussed.