Grain Growth and Tensile Strength of 3M Nextel 720™ After Thermal Exposure

Hay, Randall S.; Boakye, Emmanuel E.; Petry, M. D.; Berta, Yolande; Lehmden, K. Von; Welch, John R.

doi:10.1002/9780470294567.ch19

Cited by 28 publications

(30 citation statements)

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“…11, Table III). 35 With the exceptions noted above, the coated-fiber strength was lower than that measured in the control experiments (Table I). For the coating control experiments, fibers were moved through the coater furnace without coating deposition, but with contact with liquids and environments encountered for typical precursors.…”

Section: December 2001contrasting

confidence: 44%

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Monazite Coatings on Fibers: I, Effect of Temperature and Alumina Doping on Coated‐Fiber Tensile Strength

Hay

Boakye

2001

Journal of the American Ceramic Society

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Monazite was continuously coated onto Nextel 720 fibers, using an aqueous precursor and in-line heat treatment at 900°-1300°C. Some experiments were repeated with alumina-doped precursors. Coated fibers were heat-treated for 100 h at 1200°C. Coatings were characterized by optical microscopy, scanning electron microscopy, and analytical transmission electron microscopy. Coated-fiber tensile strengths were measured by singlefilament tensile tests. The precursors were characterized by X-ray diffractometry, differential thermal analysis/thermogravimetric analysis, and mass spectrometry. Coated-fiber tensile strength was lower for fibers coated at higher deposition temperatures. Heat treatment for 100 h at 1200°C decreased tensile strength further. The coatings were slightly phosphate-rich and enhanced alumina grain growth at the fiber surface, but phosphorus was not detected along the alumina grain boundaries. Fibers with alumina-doped coatings had higher tensile strengths than those with undoped coatings after heat treatment for 100 h at 1200°C. Alumina added as ␣-alumina particles gave higher strengths than alumina added as colloidal boehmite. Alumina doping slowed monazite grain growth and formed rough fiber-coating interfaces after 100 h of heat treatment at 1200°C. Possible relationships among precursor characteristics, coating and fiber microstructure development, and strength-degradation mechanisms are discussed in this paper.

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Section: December 2001contrasting

confidence: 44%

“…Alumina grain-size distributions at the Nextel 720 fiber surface (plate, long dimension) after 100 h at 1200°C for undoped, AKP-53 alumina-doped, Condea alumina-doped, and uncoated fiber (this study); fibers coated with ethanolic monazite precursor after 100 h at 1200°C 15 ; and as-received fiber 35. …”

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confidence: 99%

Monazite Coatings on Fibers: I, Effect of Temperature and Alumina Doping on Coated‐Fiber Tensile Strength

Hay

Boakye

2001

Journal of the American Ceramic Society

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“…14). 24 A slight growth of alumina grains occurred at the fiber surface after heat treatment for 100 h at 1200°C. The grain size (long dimension), determined from 75 measurements, was log normal, with a log-average of 2.04 (nm), a standard deviation of 0.16, a skewness of 0.07, and a kurtosis of Ϫ0.…”

Section: (3) Coated-fiber Strengthmentioning

confidence: 99%

Monazite Coatings on Fibers: II, Coating without Strength Degradation

Boakye

Hay

Mogilevsky

et al. 2001

Journal of the American Ceramic Society

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Washed and unwashed rhabdophane (LaPO 4 ⅐xH 2 O) sols were used to apply monazite coatings to 3M Nextel 720 and 610 fibers. This precursor was designed to minimize stress corrosion from gaseous decomposition products at high temperature. The coatings were heat-treated in-line at 900°-1300°C, in air, using a continuous vertical coater with immiscible liquid displacement. Coatings were characterized by optical microscopy, scanning electron microscopy, and transmission electron microscopy. The sol was characterized with light-scattering and zeta-potential measurements. Precursor phase evolution was studied with differential thermal analysis/thermogravimetric analysis and X-ray diffractometry. The washed sol had a higher pH and lower weight loss than the unwashed sol. The as-coated fibers were tensile tested, along with coated fibers heattreated in air at 1200°C for 100 h. The precursor was slightly phosphate-rich, and this excess phosphate reacted with alumina in the fiber to occasionally make very small (<10 nm) pockets of AlPO 4 at the coating-fiber interface after 100 h at 1200°C. Both washed and unwashed sols made coated fibers with higher tensile strengths than those of coated fibers made from other precursors, and the washed sol may actually have slightly increased fiber strength when in-line heat treatments at <1200°C were used. A small amount of AlPO 4 may also have helped seal preexisting flaws. Degradation mechanisms during fiber coating are discussed in this paper.

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“…[22][23][24][25]43 Fiber strengths were not high, but considering the large grain sizes (> 1 µm), they were impressive; strengths of alumina and alumina/mullite fibers with similar grain sizes would be so low that they would be difficult to test. 50 This lack of grain-size sensitivity for strength is evidence for the lack of intergranular residual stress in cubic YAG, and has not been widely appreciated.…”

Section: Polycrystalline Optical Quality Yagmentioning

confidence: 98%

Towards optical quality yttrium aluminum garnet (YAG) fibers: recent efforts at AFRL/RX

et al. 2010

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Traditional silica fibers currently are unlikely to be able to sustain the powers needed for future Air Force applications. The low thermal conductivity of silica makes it difficult to control thermal gradients within the fibers resulting in failure or degradation in beam quality. While some of these problems can be ameliorated by using longer fibers, this results in problems with nonlinear effects such as stimulated Raman and Brillouin scattering (SRS and SBS). Yttrium aluminum garnet (Y 3 Al 5 O 12 , YAG) has the potential for overcoming these problems due to 1) higher thermal conductivity, 2) reduced thermal lensing, and 3) higher SBS threshold. Polycrystalline YAG has been demonstrated to be a highly efficient and economical laser host material in slab form. Polycrystalline YAG can be doped more uniformly and at higher levels than single-crystals with no dopant loss by zone refinement, has higher fracture toughness than single-crystals, and supports higher power densities. Despite the anticipated advantages, polycrystalline YAG has never been demonstrated in high-power fiber lasers. The development and characterization of YAG fibers for high energy laser applications is the primary goal of our research. Recent results in the processing of optical quality polycrystalline YAG fibers will be presented and discussed.

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Grain Growth and Tensile Strength of 3M Nextel 720™ After Thermal Exposure

Cited by 28 publications

References 0 publications

Monazite Coatings on Fibers: I, Effect of Temperature and Alumina Doping on Coated‐Fiber Tensile Strength

Monazite Coatings on Fibers: I, Effect of Temperature and Alumina Doping on Coated‐Fiber Tensile Strength

Monazite Coatings on Fibers: II, Coating without Strength Degradation

Towards optical quality yttrium aluminum garnet (YAG) fibers: recent efforts at AFRL/RX

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