FT-IR Optical Fiber Remote Detection of Aluminum Hydroxide by Evanescent Wave Absorption Spectroscopy

Abstract

Remote detection of very small amounts of aluminum hydroxide has been achieved with the use of evanescent wave absorption spectroscopy. Aluminum hydroxide is a principal corrosion product of aluminum. Five absorption bands have been recorded in the spectral range from 3350 to 3650 cm−1. The recorded positions, transition strengths, and widths of the absorption bands are in qualitative agreement with reference spectral data. A four-wavenumber-resolution Michelson interferometer and decoated 200-μm-core-diameter multimode chalcogenide optical fibers were combined to make the evanescent wave absorption measurements. One-to four-meter lengths of fiber were used with 15 to 25 cm of the fibers decoated. The technique is very sensitive and can detect a very small amount of aluminum hydroxide in contact with the decoated fiber core. This study is a valuable step in the development of a technique for monitoring industrial corrosion of aluminum alloys.

Synthesis and Characterization of A Novel Layered Aluminophosphate of Kanemite-like Structure

“…Little informa- tion can be drawn from the spectra due to the strong quadrupolar interaction between 27 Al nuclei of I ) 5 / 2 , except confirming that the Al atoms remain in tetrahedral coordination. In contrast, there is an obvious shift from -3.6 to -26.4 ppm and broadening of the peak in the 31 P NMR spectra after AlPO-ntu was heated at temperatures above 300 °C. Since the 31 P NMR signals of aluminophosphate of three-dimensional framework usually appear at -19 to -30 ppm, 26 these results indicate that the layered structure of AlPO-ntu is destroyed and the compound transforms to a threedimensional network after interlayer amine species have been removed through heating.…”

“…Solid-state 27 Al MAS NMR spectra were taken with a Bruker MSL-500 spectrometer at a frequency of 130.32 MHz, rotation speed of 5 kHz, pulse length of 3.0 ms, recycling delay time of 1 s, and a 1 M AlCl3 solution was used as external reference. Solid-state 31 P MAS NMR spectra were taken with a DMX-300 spectrometer at a frequency of 121.49 MHz, rotation speed of 5 kHz, pulse length of 7.0 ms, recycling delay time of 30 s, and a 85% H3PO4 solution was used as external reference.…”

“…Figure2. Solid-state (A)27 Al and (B)31 P MAS NMR spectra of as-synthesized AlPO-ntu with (a) n-butylamine, (b) nhexylamine, and (c) octylamine as template. The peaks with asterisks are spin sidebands.…”

“…Figure10. Solid-state (A)27 Al and (B)31 P MAS NMR spectra of Na + -exchanged AlPO-ntu (a) at room temperature, and after calcination at (b) 200, (c) 400, and (d) 600 °C. The peaks with asterisks are spin sidebands.…”

Synthesis and Structural Characterization of a CHA-type AlPO4 Molecular Sieve with Penta-Coordinated Framework Aluminum Atoms

“…It is interesting to note here that the sum of theoretical weight losses associated with the dehydroxylation (3.5%) and OSDA removal (20.0%), calculated from the refined unit cell composition, is in excellent agreement with the total weight loss between 300 and 600 °C (23.4 wt %) in the TGA/DTA profiles (Figure ). The variable-temperature IR spectra in Figure S3 show that a band around 3540 cm –1 , assignable to the stretching vibration of Al–OH–Al linkages, , remains intact at temperatures up to 300 °C. It is worth noting that the refined unit cell volume (736.93 Å 3 ) of AlPO 4 -34­( t ) V is smaller by at least 2.5% than the values (755.45–781.28 Å 3 ) of any of the previously reported triclinic AlPO 4 -34 materials. − , This is true even when compared with the unit cell volume (757.13 Å 3 ) of as-made SIZ-10c, a triclinic AlPO 4 -34 containing 13DMI, the same organic as that used in the synthesis of AlPO 4 -34­( t ) V .…”