A Predictive Instrument for Sensitive and Expedited Measurement of Ultra-Barrier Permeation

The reliable operation of flexible display devices poses a significant engineering challenge regarding the metrology of high barriers against water vapor. No reliable results have been reported in the range of 10^–6 g∙(m²∙d)⁻¹, and there is no standard ultra-barrier for calibration. To detect trace amount of water vapor permeation through an ultra-barrier with extremely high sensitivity and a greatly reduced test period, a predictive instrument was developed by integrating permeation models into high-sensitivity mass spectrometry measurement based on dynamic accumulation, detection, and evacuation of the permeant. Detection reliability was ensured by means of calibration using a standard polymer sample. After calibration, the lower detection limit for water vapor permeation is in the range of 10^–7 g∙(m²∙d)⁻¹, which satisfies the ultra-barrier requirement. Predictive permeation models were developed and evaluated using experimental data so that the steady-state permeation rate can be forecasted from non-steady-state results, thus enabling effective measurement of ultra-barrier permeation within a significantly shorter test period.     

Repeatability and Reproducibility Standard Deviations in the Measurement of Trace Moisture Generated Using Permeation Tubes

Permeation-tube moisture generators are used in industry as calibrated sources of water vapor and carrier gas mixtures. Measurements were made using three permeation-tube moisture generators of the type used in the semiconductor industry. This paper describes repeatability and reproducibility standard deviations in measurement of moisture concentration from such generators. Repeatability refers to measurements within a system and reproducibility refers to measurements between systems. Two independent methods were used to measure the realized concentration of water vapor. The first measurement, the calculated value, was determined using calibrated permeation rate of permeation-tube and flow rate of dry carrier gas. This is the industrial method of evaluating moisture concentration. The second measurement, the measured value, was determined using the low frost-point generator at the National Institute of Standards and Technology (NIST) and a quartz-crystal-micro-balance. Four pairs of independent measurements for each generator and for six nominal levels in the range from10 nL/L to 100 nL/L were made. The characteristic used to quantify repeatability and reproducibility standard deviations in industrial measurements is the calculated value minus the measured value. Repeatability standard deviation ranges from 1 nL/L to 2 nL/L, approximately. Reproducibility standard deviation ranges from 2 nL/L to 8 nL/L, approximately. The documentary ASTM standard E691-99 was used for both data validation and quantification of the repeatability and reproducibility standard deviations.     

The NIST Primary Radon-222 Measurement System

Within the United States, the national standard for radon measurements is embodied in a primary radon measurement system that has been maintained for over 50 years to accurately measure radon (²²²Rn) against international and national radium (²²⁶Ra) standards. In turn, all of the radon measurements made at the National Institute of Standards and Technology (NIST) and the radon transfer calibration standards and calibration services provided by NIST are directly related to this national radon standard. This primary radon measurement system consists of pulse ionization chambers and ancillary gas handling and gas purification equipment. The system is currently undergoing a significant upgrading and expansion which will replace the extant outdated system.     

Using thermogravimetry for weight loss monitoring of permeation tubes used for generation of trace concentration gas standards.

Permeation tubes are convenient analyte sources for generating standard gas mixtures (containing, in particular, volatile organic compounds) used in the calibration of analytical instruments. For small permeation rates, corresponding to trace levels of analytes, the calibration of permeation tubes is time-consuming. The use of thermogravimetry as a means to measure rapidly the weight loss at constant temperature was investigated. An attempt to apply this technique to calibrating a permeation tube filled with benzene is described. In the 20 ng/min range of permeation rate, day-to-day variations of <5% were observed. The continuous weight loss monitoring of permeation tubes by thermogravimetry allows their rapid characterization.     

Characterization of the silicon oxide thin films deposited on polyethylene terephthalate substrates by radio frequency reactive magnetron sputtering

Transparent silicon oxide films were deposited on polyethylene terephthalate substrates by means of reactive magnetron sputtering with a mixture of argon and oxygen gases. The influences of process parameters, including the oxygen flow ratio, work pressure, radio frequency (RF) power density and deposition time, on the film properties, such as: deposition rate, morphology, surface roughness, water vapor/oxygen transmission rate and flexibility, were investigated. The experimental results show that the SiO_x films deposited at RF power density of 4.9 W/cm², work pressure of 0.27 Pa and oxygen flow ratio of 40% have better performance in preventing the permeation of water vapor and oxygen. Cracks are produced in the SiO_x films after the flexion of more than 100 cycles. The minimum transmission rates of water vapor and oxygen were found to be 2.6 g/m² day atm and 15.4 cc/m² day atm, respectively.     

Comparative Study of Humidity Analyzers in Nitrogen Below 1?μ mol/mol

A precision trace humidity calibration system using permeation tubes has been implemented, and measurements have been performed in the range between 100?nmol/mol (100 ppb_v) and 245?nmol/mol (245 ppb_v) with flow rates between ${1\,{\rm L}{\cdot}{\min}^{-1}}$ and ${5\, {\rm L}{\cdot} {min}^{-1}}$ . The preliminary results of the commissioning of the permeation tube generator and its use in the comparison of humidity analyzers based on different measurement principles are presented and discussed. The work reported comprises the first stage in establishing the detailed design and operational characteristics of the future standard moisture generation to extend the range currently covered by Spanish national humidity standards. A precision optical dew-point hygrometer, a quartz crystal microbalance moisture analyzer, and a cavity ringdown spectrometer have been compared, and the response times and repeatability have been investigated. The design criteria and the characterization of the system as well as the estimation of measurement uncertainty in each case are presented.     

Studies of Excess Heat and Convection in a Water Calorimeter

To explain a difference of 0.5 % between the absorbed-dose standards of the National Institute of Standards and Technology (NIST) and the National Research Council of Canada (NRCC), Seuntjens et al. suggest the fault lies with the NIST water calorimeter being operated at 22 °C and the method with which the measurements were made. Their calculations show that this difference is due to overprediction of temperature rises of six consecutive ⁶⁰Co radiation runs at NIST. However, the consecutive runs they refer to were merely preliminary measurements to determine the procedure for the NIST beam calibration. The beam calibration was determined from only two consecutive runs followed by water circulation to re-establish temperature equilibrium. This procedure was used for measurements on 77 days, with 32 runs per day. Convection external to the glass cylindrical detector assembly performed a beneficial role. It aided (along with conduction) in increasing the rate of excess heat transported away from the thin cylindrical wall. This decreased the rate of heat conducted toward the axially located thermistors. The other sources of excess heat are the: (1) non-water materials in the temperature probe, and (2) exothermic effect of the once-distilled water external to the cylinder. Finite-element calculations were made to determine the separate and combined effects of the excess heat sources for the afterdrift. From this analysis, extrapolation of the measured afterdrifts of two consecutive runs to mid radiation leads to an estimated over-prediction of no more than about 0.1 %. Experimental measurements contradict the calculated results of Seuntjens et al. that convective motion (a plume) originates from the thermistors operated with an electrical power dissipation as low as 0.6 μW, well below the measured threshold of 50 μW. The method used for detecting a plume was sensitive enough to measure a convective plume (if it had started) down to about the 10 μW power level. Measurements also contradict the NRCC calculations in predicting the behavior of the NIST afterdrifts.     

Effects of water vapor on corrosion behaviors of C/SiC in oxidizing atmosphere containing Na2SO4 vapor

Corrosion of a C/SiC composite has been investigated in the atmosphere containing oxygen, water vapor and sodium sulfate vapor at the temperatures range from 1000 to 1500 °C. The effect of water vapor on the corrosion mechanism of C/SiC were discussed based on the weight change, the residual strength change, the microstructure and calculated results from FactSage. The corrosion of C/SiC is attributed to (i) the permeation of gas through the SiO₂ film below 1300 °C, (ii) the diffusion of oxidant through pores caused by bubbles broken in the SiO₂ film above 1300 °C. The water vapor does not change the corrosion mechanism of C/SiC composite but the temperature range in which the corrosion mechanism works by accelerating the oxidation of SiC and the corrosion of SiO₂.     

Effects of water vapor on corrosion behaviors of C/SiC in oxidizing atmosphere containing Na2SO4 vapor

Corrosion of a C/SiC composite has been investigated in the atmosphere containing oxygen, water vapor and sodium sulfate vapor at the temperatures range from 1000 to 1500 °C. The effect of water vapor on the corrosion mechanism of C/SiC were discussed based on the weight change, the residual strength change, the microstructure and calculated results from FactSage. The corrosion of C/SiC is attributed to (i) the permeation of gas through the SiO₂ film below 1300 °C, (ii) the diffusion of oxidant through pores caused by bubbles broken in the SiO₂ film above 1300 °C. The water vapor does not change the corrosion mechanism of C/SiC composite but the temperature range in which the corrosion mechanism works by accelerating the oxidation of SiC and the corrosion of SiO₂.     

Electrical conduction in La<Subscript>0.9</Subscript>Ba<Subscript>0.1</Subscript>Er<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Mg<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>O<Subscript>3−α</Subscript> ceramics

Doubly doped LaErO₃ ceramics, La_0.9Ba_0.1Er_1−x Mg _x O_3−α (x = 0.05, 0.10, 0.15, 0.20), were synthesized by solid-state reaction method and characterized by X-ray diffraction (XRD). The samples have a single orthorhombic perovskite-type structure. The conduction behavior was investigated using various electrochemical methods including AC impedance spectroscopy, gas concentration cell, isotope effect of hydrogen, and hydrogen electrochemical permeation (pumping) in the temperature range of 500–1000 °C. The results indicated that specimens were pure ionic conductors under low oxygen partial pressure (about 10⁻⁷–10⁻²⁰ atm) and mixed conductors of proton, oxide ion, and electron hole under high oxygen partial pressure (about 10⁻⁵–1 atm). The pure ion conduction of the ceramics in hydrogen atmosphere was confirmed by electromotive force method of hydrogen concentration cell, and the observed emf values coincided well with the theoretical ones. The conductivity in H₂O–Ar atmosphere was higher than that in D₂O–Ar atmosphere, exhibiting an obvious isotope effect and proton conduction in water vapor containing atmosphere. It has been confirmed by electrochemical hydrogen permeation (hydrogen pumping) experiment that the ceramics were mainly proton conductors in hydrogen containing atmosphere. Whereas in dry oxygen-containing atmosphere, observed emf values of the oxygen concentration cell were far lower than the theoretical ones, indicating that the ceramics were mixed conductors of electron hole and oxide ion.     

Preparation of accurate, low-concentration gas cylinder standards by cryogenic trapping of a permeation tube gas stream

National and international measurements are underpinned by accurate, low concentration standards. These standards are typically produced gravimetrically, or volumetrically, by a series of dilutions of the pure material by the balance gas. This blend technique is time-consuming and may involve the handling of pure, hazardous material. These problems have been overcome by developing a novel blend technique whereby the process gas stream, from an appropriate permeation tube, was cryogenically trapped in an aluminum cylinder. The permeation rate of the component is monitored by real time mass determinations using a magnetic suspension balance system. With the combination of the real-time calculated permeation rate, plus the use of a dilution system, a one step production of a very low concentration of the minor component in nitrogen gas can be achieved. This method was used to prepare low μmol/mol standards of propane, a known stable compound. Analysis of a conventional gravimetrically prepared 10 μmol/mol propane standard and a cryogenically prepared standard via a permeation gas stream resulted in agreement between the two of <0.1% at 10 μmol/mol, confirming the accuracy of the permeation method. After confirmation of the validity of the permeation/cryogenic trapping system, the propane permeation tube was replaced with a methyl mercaptan tube (a toxic, reactive compound) in balance nitrogen. After cryogenically trapping the methyl mercaptan output stream from the permeation system into a cylinder, the output stream and the cylinder gas mixture were analyzed. The results showed agreement of <0.6% for methyl mercaptan at 5, 10, 15, and 20 μmol/mol to the expected blend concentration, thereby demonstrating the validity of the method.     

NIST–NRC Comparison of Total Immersion Liquid-in-Glass Thermometers

The use of liquid-in-glass (LIG) thermometers is described in many documentary standards in the fields of environmental testing, material testing, and material transfer. Many national metrology institutes, including the National Institute of Standards and Technology (NIST) and the National Research Council of Canada (NRC), list calibration services for these thermometers among the Calibration Measurement Capabilities of Appendix C of the BIPM Key Comparison Database. NIST and NRC arranged a bilateral comparison of a set of total-immersion ASTM-type LIG thermometers to validate their uncertainty claims. Two each of ASTM thermometer types 62C through 69C were calibrated at NIST and at NRC at four temperatures distributed over the range appropriate to each thermometer, in addition to the ice point. Collectively, the thermometers span a temperature range of  − 38 °C to 305 °C. In total, 160 measurements (80 pairs) comprise the comparison data set. Pair-wise differences (T _NIST–T _NRC) were formed for each thermometer at each temperature. For 8 of the 80 pairs (10 %), the differences exceed the k = 2 combined uncertainties. These results support the claimed capabilities of NIST and NRC for the calibration of LIG thermometers. Disclaimer Certain commercial equipment, instruments, or materials are identified in this article in order to adequately specify the experimental procedure. Such identification does not imply any recommendation or endorsement by the NIST.     

A Humidity Generator for Temperatures up to 200?°C and Pressures up to 1.6?MPa

A new humidity generator that produces gas streams of known moisture content at temperatures from 85?°C to 200?°C, absolute pressures from 0.2?MPa to 1.6?MPa, and relative humidities from 10 % to 90 % has been developed. The generator produces a moist gas stream by injecting fixed-rate streams of dry gas and liquid water into a vaporizer, where the water evaporates into the gas. The gas stream passes into a re-entrant radio-frequency (RF) cavity, which serves as our reference hygrometer, and then a test chamber. The present standard uncertainty of the RF hygrometer is 0.6 %, limited by the uncertainty of literature values for the polarizability of water. Dry nitrogen gas purging the pressure transducer line also combines with the moist gas stream downstream of the test chamber and flows through one of a set of capillaries. Modulation of gas flow through the fixed flow impedance of the capillary gives a simple method for controlling pressure. Individual insulated, temperature-controlled aluminum ovens enclose each major component. A larger oven encloses these ovens and their connecting tubing. To minimize corrosion, critical components are constructed of high-nickel alloys. The small total volume (<1?L) and small flow rate (<0.5 L·min^?1) reduce operational hazards from steam scalding or from gas explosion.     

Study of water vapor pressure equilibration in a vacuum system

We have studied the approach to equilibrium pressure distribution after a sudden introduction of a given quantity of water vapor into a vacuum chamber. The time delay of a pressure reading of a spinning rotor gauge at the end of a 0.50 m and 0.935 m long stainless steel tube with inside diameter of 16 mm was measured. This time delay increased with decreasing pressure approximately as P^−0.55. With a 0.5 m tube the time delay was approximately 5 times shorter than with a 0.935 m tube. At 1 × 10⁻⁴ mbar the times to reach a 99.7% level of equilibrium at the end of 0.50 m and 0.935 m tubes were 60 s and 330 s, respectively.     

Pressure effect on the release of supercooled water with dissolved air

It is proposed that vapor has been elucidated to having relation to the release of supercooled water.In this study, considering that the vapor has a relation to dissolved air, a supercooling experiment is performed to test tubes of pure water with three patterns of initial dissolved oxygen (DO_i = 4.1, 7.5, and 12.6 mg L⁻¹), i.e. dissolved air. The initial DO in each test tube is kept to the value as constant as possible during supercooling. And the pressure effect on supercooling release of pure water is observed by measuring supercooling degree and by visualizing bubbles enclosed to the ice after full crystallization of the pure water.From this study, it appeared that the factors such as cooling rate, initial DO and pressure of pure water are related to the release of supercooling (supercooling degree and supercooling time). Moreover, the initial DO was confirmed to the confined bubble in fully frozen ice of pure water.     

Two-phase split of refrigerants at a T-junction

The present study experimentally investigated the two-phase flow split of refrigerants at a T-junction. As geometric parameters, the direction of the inlet or branch tube and the tube diameter ratio of branch to inlet tube were chosen. As inlet flow parameters, the inlet mass flux and quality were varied from 100 to 700 kg m⁻² s⁻¹ and from 0.1 to 0.9, respectively, for the condition of distribution header of a multi-pass evaporator in the general refrigeration system. All experiments were performed for R-22, R-134a, and R-410A. The measured data were compared with the values predicted by the models developed for air–water or steam–water mixture in the literature. We propose a modified model for application to the reduced T-junction and vertical orientation of tubes. Among the geometric parameters, the branch tube direction showed the largest sensitivity to the mass flow rate ratio for the gas phase, while the inlet quality showed the largest sensitivity to the mass flow rate ratio among the inlet flow parameters.     

气态元素汞校准的一致性光学评定检测实验研究

利用低压汞灯作为光源,结合单色仪,对汞渗透管法和汞饱和蒸气法气态元素汞校准进行一致性光学评定检测研究。在汞渗透管实验中,吸收度面积值与理论浓度的皮尔逊相关系数为0.996 8,拟合优度为0.993 6,说明两组数据相关性较好且符合郎伯比尔定律。取实验的吸收截面作为标准参考吸收截面,对相同浓度汞蒸气横向对比及不同浓度汞蒸气纵向对比,浓度误差最大为7.45%,表明渗透管法的稳定性较好且精度较高,验证了渗透管法作为汞标气法的可行性。在渗透管实验中加入SO₂,气态汞浓度测量误差最大为12.82%,说明SO₂对汞吸收度测量产生一定程度的干扰。汞饱和蒸气法实验中,以渗透管为基准测得的最大误差在标准允许误差之内,表明2种校准方法具有一致性。但汞饱和蒸气法与渗透管法相比,其重复性及精度仍有不足,待提升空间较大。     

Water permeation through organic-inorganic multilayer thin films

We prepared organic (self-assembled monolayer (SAM))-inorganic (TiO₂) multilayer barrier films on polyethylene terephthalate substrate using atomic layer deposition and molecular layer deposition methods in the same deposition chamber. The water permeation was mainly blocked by the inorganic TiO₂ layer. While the lag time was proportional to the thickness of the TiO₂ layer, the steady-state permeation rate was relatively independent of the thickness. The multilayer approach was effective in extending the lag time due to both the tortuous path effect and the internal desiccant effect. Water permeation occurred sequentially in the organic-inorganic multilayer barriers by water accumulation in the organic SAM layers. The water vapor transmission rate was 7.0 × 10^− 4 g/m²·day during the lag time of 155 h at 60 °C and a relative humidity of 85% with 5-dyad barrier film.     

SiO2 thin film deposition on the inner surface of a poly(tetra-fluoroethylene) narrow tube by atmospheric-pressure glow microplasma

SiO₂ thin films were deposited on the inner surfaces of a commercial poly(tetrafluoroethylene) narrow tube with an inner diameter of 0.5 mm using tetraethoxysilane/O₂ feedstock gases and He carrier gas by atmospheric-pressure microplasma-enhanced chemical vapor deposition. A glow microplasma was generated inside the tube by radio frequency (RF) capacitively coupled discharge. X-ray photoelectron spectroscopy spectra showed that the tube inner surface was covered by a SiO₂ thin film. Transparent SiO₂ thin films were obtained with a deposition rate of 230 nm/min at an RF power of 6 W and substrate temperature of 100 °C. The wettability of the SiO₂-coated tube was about 3 times as large as that of an untreated sample tube.     

Estimation of moisture barrier ability of thin SiNx single layer on polymer substrates prepared by Cat-CVD method

The SiNx films with the thickness of 50 nm were prepared by Cat-CVD method on the cyclic olefin copolymer (COC) and the polyethylene terephthalate (PET) substrates, and their moisture barrier abilities were evaluated. MOCON measurement method and Ca degradation test showed the moisture permeation results of 0.02 g/(m² day) for PET substrate and 0.006 g/(m² day) for COC substrate after SiNx deposition. Applying the simple model of gas barrier property, it was estimated that the Cat-CVD method achieves the high coverage ratio of over 99% for SiNx film on these substrates, and the moisture permeation rate of single SiNx film with the thickness of 50 nm was estimated to be 0.0045 g/(m² day).