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- Al2O3-inclusions (1)
- Damage threshold (1)
- Glasmatrix-Komposit (1)
- Glaspulver (1)
- Glass matrix composites (1)
- Kristallisation (1)
- LTCC (1)
- Multimode fiber (1)
- Nanosecond laser (1)
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Eingeladener Vortrag
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The sintering of Low Temperature Co-fired Ceramics prepared from alumoborosilicate
glass- and Al2O3 powders of similar small particle size was studied by dilatometry, heating microscopy,
microstructure analysis, glass- and effective viscosity measurements. The steric effect of
Al3O3 inclusions was studied using a gnon-reactiveh model composite. With increasing Al3O3 volume
fraction (Φ ≤ 0.45), sintering decelerates and its final stage shifts to higher temperature. The
attainable shrinkage is reduced as Al2O3 particle clusters bearing residual pores become more frequent.
The kinetics of sintering could be described formally superposing the weighed contributions
of differentially sized and randomly composed glass-crystal particle clusters and assuming a sintering
rate controlled by the effective matrix viscosity, which increases with Φ and with progressive
wetting of Al2O3 particles during densification. The "reactive" model composite shows significant
dissolution of Al2O3 into the glass, which has two opposed effects on sintering: reducing Φ and increasing
glass viscosity. For the present case (Φ = 0.25), the latter effect dominates and sintering is
retarded by Al2O3 dissolution. Crystallization of wollastonite starts after full densification. Dissolution
of Al2O3 was found to promote the subsequent growth of anorthite.
High-power optical multimode fibers are essential components for materials processing
and surgery and can limit the reliability of expensive systems due to breakdown at the end faces.
The breakdown threshold of fibers is determined by intrinsic materials properties and parameters of
the technology applied. The aim of this paper is the identification of technological parameters that
are crucial for the fiber quality.
Fibers were drawn from preforms of Heraeus SWU with core material F300 and a low amount of
OH-. Both, the cladding (fluorine doped SiO2) to core diameter ratio (CCDR) and the drawing speed
were varied. CCDR values between 1.05 and 1.4 were used. Afterwards, the laser-induced damage
thresholds (LIDT) of the fibers were determined. For comparison, also samples from preforms,
which underwent different thermal treatments above the transition temperature, were tested with
respect to their damage resistivity. Single and multi pulse LIDT measurements were done in
accordance with the relevant ISO standards. Nd:YAG laser pulses with durations of 15 ns (1064 nm
wavelength) and 8.5 ns (532 nm) at a repetition rate of 10 Hz were utilized. For the fibers, LIDT
values (1-on-1, 1064 nm and 532 nm) increased with growing CCDR and with decreasing drawing
velocities.