Jay H. Hendricks

In Situ Raman Spectroscopic Investigation of Aqueous Iron Corrosion at Elevated Temperatures and Pressures

In situ Raman spectroscopy was employed to investigate iron corrosion in air saturated water at a pressure of 25.1 MPa and temperatures from 21 to 537°C. Upon heating, various combinations of Fe 3 O 4 . α-Fe 2 O 3 , γ-FeOOH, and γ-Fe 2 O 3 were observed depending on the location on or temperature of the iron coupon. In some cases, different species were observed at the same temperature at different locations on the surface. This was attributed to oxygen concentration gradients in the solution caused by recirculation zones in the cell. The surface of the corrosion coupon changed little after it was heated to 537°C. This was attributed to the formation of a relatively thick, protective oxide scale after exposure to supercritical water. The ex situ Raman spectra were very similar to the in situ spectra obtained during cooling but different from those obtained during heating. This indicates that the corrosion layer present during cooling is similar to that observed ex situ but different from that observed during heating. Ex situ characterization of the coupon identified a two layered structure: an inner corrosion layer consisting of Fe 3 O 4 and α-Fe 2 O 3 and an outer layer consisting of γ-Fe 2 O 3 and α-Fe 2 O 3 .

In Situ Raman Spectroscopic Investigation of Stainless Steel Hydrothermal Corrosion

Abstract In situ Raman spectroscopy was used to investigate corrosion of Type 304L stainless steel ([SS] UNS S30403) in airsaturated water at a pressure of 25.2 MPa and temperatures up to 496°C in an optically accessible flow cell. The exposed Type 304L SS coupon also was characterized ex situ with Raman spectroscopy and scanning electron microscopy. After exposure, nickel(II) iron(III) oxide (NiFe2O4) and alpha chromium(III) oxide hydroxide (α-CrOOH) phases were detected on the coupon surface. The NiFe2O4 phase was first identified after the coupon was heated to 247°C and was observed under all subsequent conditions. Upon heating from 247°C to 326°C, the crystallinity and possibly the thickness of the NiFe2O4 phase increased. The α-CrOOH phase was first identified after the coupon was heated to 326°C and was observed under all subsequent conditions. At least a portion of the α-CrOOH phase probably originated as a corrosion product released from the optical cell and/or flow system. In situ Raman spectra i...

In situ Raman spectroscopic investigation of zirconium-niobium alloy corrosion under hydrothermal conditions

Abstract In situ Raman spectroscopy was employed to investigate corrosion of a zirconium–niobium alloy in air-saturated water at a pressure of 15.5 MPa and temperatures ranging from 22 to 407 °C in an optically accessible flow cell. Monoclinic ZrO 2 (m-ZrO 2 ) was identified under all conditions after the coupon was heated to 255 °C for 19 h. Cubic ZrO 2 (c-ZrO 2 ) was tentatively identified in situ during heating at temperatures between 306 and 407 °C, but was not observed under any other conditions. Species tentatively identified as α-CrOOH and a Cr VI and/or Cr III /Cr VI compound were observed in situ during heating at temperatures between 255 and 407 °C, but were not observed under any other conditions. The chromium compounds were identified as corrosion products released from the optical cell and/or flow system.

In Situ Raman Spectroscopic Investigation of Nickel Hydrothermal Corrosion

Abstract A nickel coupon was exposed to air-saturated water at a pressure of 25.4 MPa and temperatures ranging from 21°C to 460°C in an optically accessible flow cell. In situ Raman spectra were collected at a number of temperatures as the coupon was heated and then cooled. The coupon also was characterized ex situ with Raman spectroscopy, scanning electron microscopy, energy dispersive x-ray spectrometry, and x-ray diffraction. Corrosion species were observed in situ at temperatures >249°C during heating and under all conditions during cooling. The species were identified as nickel monoxide (NiO) and alpha chromium (III) oxide hydroxide (α-CrOOH). The α-CrOOH originated as a corrosion product released from the optical cell and/or flow system. The NiO Raman features were more intense during cooling than at the corresponding temperatures during heating, indicating that NiO was present in greater amounts and/or was more crystalline during cooling.

Performance of a dual Fabry–Perot cavity refractometer

We have built and characterized a refractometer that utilizes two Fabry-Perot cavities formed on a dimensionally stable spacer. In the typical mode of operation, one cavity is held at vacuum, and the other cavity is filled with nitrogen gas. The differential change in length between the cavities is measured as the difference in frequency between two helium-neon lasers, one locked to the resonance of each cavity. This differential change in optical length is a measure of the gas refractivity. Using the known values for the molar refractivity and virial coefficients of nitrogen, and accounting for cavity length distortions, the device can be used as a high-resolution, multi-decade pressure sensor. We define a reference value for nitrogen refractivity as n-1=(26485.28±0.3)×10(-8) at p=100.0000  kPa, T=302.9190  K, and λ(vac)=632.9908  nm. We compare pressure determinations via the refractometer and the reference value to a mercury manometer.

Alloy 600 Aqueous Corrosion at Elevated Temperatures and Pressures: An In Situ Raman Spectroscopic Investigation

Two alloy 600 coupons with different surface treatments were exposed in an optically accessible flow cell to air-saturated, high-purity water: one coupon at temperatures up to 543°C at a pressure of 25.4 MPa and one coupon at temperatures up to 392°C at 15.65 MPa. In situ Raman spectra were collected at various temperatures as each coupon was heated and then cooled. Each coupon was also characterized ex situ with Raman spectroscopy, scanning electron microscopy, and energy dispersive X-ray spectrometry. A NiFe 2 O 4 phase was identified on both coupon surfaces while Cr III -containing phases, including α-CrOOH and α-Cr 2 Ο 3 , were identified only on the coupon exposed at higher temperatures, at a higher pressure, and with a rougher surface finish. In addition, the results from the alloy 600 coupon exposed at higher temperatures and a 304L stainless steel coupon exposed under nominally identical conditions were compared. Both NiFe 2 Ο 4 and α-CrOOH phases were observed on the 304L stainless steel coupon. In general, in situ Raman spectroscopy was found to be sensitive to differences in alloy 600 corrosion processes attributed to different surface treatments and differences in alloy 600 and 304L stainless steel corrosion processes attributed to the different oxidation resistance of each alloy.

Comparison measurements of low-pressure between a laser refractometer and ultrasonic manometer

We have developed a new low-pressure sensor which is based on the measurement of (nitrogen) gas refractivity inside a Fabry-Perot cavity. We compare pressure determinations via this laser refractometer to that of well-established ultrasonic manometers throughout the range 100 Pa to 180 000 Pa. The refractometer demonstrates 10(-6) ⋅ p reproducibility for p > 100 Pa, and this precision outperforms a manometer. We also claim the refractometer has an expanded uncertainty of U(pFP) = [(2.0 mPa)(2) + (8.8 × 10(-6) ⋅ p)(2)](1/2), as realized through the properties of nitrogen gas; we argue that a transfer of the pascal to p < 1 kPa using a laser refractometer is more accurate than the current primary realization.

A Low Differential-Pressure Primary Standard for the Range 1 Pa to 13 kPa

The National Institute of Standards and Technology (NIST) has completed the development of a low differential-pressure primary standard covering a range from 1 Pa to 13 kPa for operation with line pressures up to 200 kPa. The standard is based on an ultrasonic interferometer manometer (UIM) primary pressure standard and includes a test-instrument manifold with pressure control systems. The standard was found to be equivalent to low differential-pressure primary standards at three other national metrology institutes (NMIs) in a recent international key comparison. Initial performance of the standard was limited in large part by pressure instabilities. This problem has been addressed with the development of two types of active pressure control, one for calibrating pressure-measuring instruments such as capacitance diaphragm gauges, resonant silicon gauges and Bell-type micromanometers and the other for characterizing pressure-generating instruments such as conical-piston, ball and force-balanced piston gauges. The UIM is characterized by a standard (k = 1) uncertainty due to systematic effects of [(3 × 10−3 Pa)2 + (3.2 × 10−6P)2]1/2 where P is the pressure in pascal. Random uncertainties are dominated by pressure instabilities which can be controlled to a level that varies from standard deviations of 3 mPa at lowest differential pressures to about 60 mPa at full range. The NIST primary standard is described, along with results of comparisons with primary standards developed at other NMIs.

Development of a new high-stability transfer standard based on resonant silicon gauges for the range 100 Pa to 130 kPa

The National Institute of Standards and Technology (NIST) has developed a new transfer standard capable of absolute-mode and differential-mode operation in the range 100 Pa to 130 kPa. This newly built transfer standard relies on resonant silicon gauges (RSGs) of the same type used to provide superior long-term calibration stability in NIST piloted international key comparisons CCM.P-K4 and CCM.P-K5, which covered absolute and differential pressure standards pressures up to 1 kPa (Miiller et al 2002 Metrologia 39 Tech. Suppl. 07001 and 07002). The new transfer standard package differs from the previous packages in that it fully covers the atmospheric pressure range (100 Pa to 130 kPa). This was made possible by the addition of a pair of 130 kPa RSGs to complement a pair of 10 kPa RSGs. The RSG transfer standard package has demonstrated good short-term zero stability and pressure resolution, and has demonstrated long-term instability of only a few ppm at 130 kPa, increasing to 0.01% at 100 Pa. The long-term instability is nominally commensurate with that associated with piston gauge standards, which are limited to pressures of nominally 10 kPa and higher. The main advantage of the new package is that it operates easily at lower pressures than piston gauges while still covering the atmospheric pressure range 100 Pa to 130 kPa.

Final report on the key comparison CCM.P-K4.2012 in absolute pressure from 1 Pa to 10 kPa

The report summarizes the Consultative Committee for Mass (CCM) key comparison CCM.P-K4.2012 for absolute pressure spanning the range of 1 Pa to 10 000 Pa. The comparison was carried out at six National Metrology Institutes (NMIs), including National Institute of Standards and Technology (NIST), Physikalisch-Technische Bundesanstalt (PTB), Czech Metrology Institute (CMI), National Metrology Institute of Japan (NMIJ), Centro Nacional de Metrología (CENAM), and DI Mendeleyev Institute for Metrology (VNIIM). The comparison was made via a calibrated transfer standard measured at each of the NMIs facilities using their laboratory standard during the period May 2012 to September 2013. The transfer package constructed for this comparison preformed as designed and provided a stable artifact to compare laboratory standards. Overall the participants were found to be statistically equivalent to the key comparison reference value.