Trace Moisture Research Articles

Trace Moisture Drives Lithium Volatility during Cathode Synthesis

Trace Moisture Drives Lithium Volatility during Cathode Synthesis

Corrosion-life prediction model for 316L stainless steel under electronic special gases containing trace moisture employed in semiconductor manufacturing industry

Special gases with trace moisture cause the formation of dynamic acidic microdroplets (DMD), which results in corrosion of semiconductor manufacturing devices. In this study, a predictive model for corrosion damage in 316L stainless steel (SS) was developed by combining the DMD process and the pitting initiation model. The DMD process was modeled using the BET model to describe the moisture-to-solution conversion. The pitting initiation model was reconstructed by incorporating the Sridhar model, temporal corrosion model, and Macdonald model. Finally, the predicted results were validated by various experimental data, indicating that the prediction model was accurate and highly reliable.

Origin identification and accuracy control of electrode interface-related asymmetrical hysteresis in light-controlled resistive switching of single CH3NH3PbI3 micro/nanowire

Remarkable photoresponse and resistive switching (RS) performance of CH3NH3PbI3 has garnered significant attention. However, precise control over the emergence and polarity of hysteresis loops in bipolar RS remains challenging. Herein, we constructed an individual CH3NH3PbI3 micro/nanowire device configured with two symmetrical Ag electrodes and asymmetrically modulated their electrode interface states by encapsulating only one electrode. We propose an electrode interface-related RS mechanism to modulate the hysteresis features and achieve different types of high-performance light-controlled RS. In an unpacked electrode interface, large potential induces oxidation of Ag to AgI with high resistivity under light and trace moisture, resulting in a high-resistance state. On the other hand, in a packed electrode interface, large potential triggers hole injection into interface traps with the assistance of light, resulting in a low-resistance state. Additionally, reversible Ag/AgI oxidation/reduction-related negative RS and hole injection/ejection-associated positive RS lead to bipolar RS, accompanied by clockwise and counterclockwise hysteresis loops in two directions. Furthermore, performance is entirely determined by illumination intensity and bias amplitude, achieving photomemory. This work unveils the influence of moisture and illumination on electrode interface and the actual origin of hysteresis, while also precisely controlling photomemory performance. Therefore, it provides a specific strategy for designing high-performance light-controlled RS with nonvolatile photomemory.

FTIR determination of the degree of molar substitution for hydroxypropyl chitosan

We developed and validated a novel Fourier transform infrared (FTIR) method to determine the degree of molar substitution (MS) for hydroxypropyl chitosan (HPCS) using nuclear magnetic resonance (1H NMR) as a reference, and investigated the factors influencing the MS assay. Through extensive screening of integration methods for candidate bands in the FTIR spectrum of HPCS using 20 HPCS samples with degrees of acetylation (DA) ranging from 0.003 to 0.139, we found that when using band area at 2970 cm−1 as a probe integral, the MS values obtained via the 1H NMR method exhibited linear correlations (R2 > 0.98) with at least 16 integral ratios derived from their FTIR spectra. The optimal reference bands with high reliability are located at 3440 cm−1 and 1415 cm−1, with R2 exceeding 0.99 and a MS range of 0.17–1.92. The band at 2875 cm−1 is less affected by the trace moisture present in HPCS samples than the others. The results of the method validation demonstrated a mean recovery of 98.9 ± 2.8 % and an RSD below 10 %, suggesting a simple, robust, and highly accurate and precise method. This method could be extendable for the determination of the MS of insoluble HPCS derivatives and other hydroxypropylated polysaccharides.

Effect of moisture on the phase transition of β-PbSnF4 at ambient temperature as the fast fluoride ion conductor

The solid-state electrolyte β-PbSnF4 has been reported to have the highest fluorine-ion conductivity at room temperature among four different structures of the monoclinic (α), orthorhombic (o), cubic (γ), and tetragonal (β) at steady state. Therefore, finding an effective way to prepare β-PbSnF4 or to transform β-PbSnF4 from other phases is a research hotspot in FIBs. In particular, the transition mechanisms between γ-PbSnF4 and β-PbSnF4 are still unclear in the reported literature because the influence of trace moisture is ignored in previous research, which always leads to controversial conclusions about the phase transition mechanism. Previous articles have reported that γ-PbSnF4 can only be transformed into β-PbSnF4 by aging at a high temperature above 100 °C. However, this work shows that the transition from γ-PbSnF4 to β-PbSnF4 can occur at room temperature. Moisture is the critical factor in inducing the phase transition from γ to β-PbSnF4. The resulting β-PbSnF4 has a high fluoride-ion conductivity of 8.1 × 10−4 S cm−1, while the solid electrolyte for an all-solid-state FIB with BiF3 as the cathode and Sn as the anode has a maximum discharge capacity of 55.8 mAh g−1 at 120 °C.

A low-cost, swift response, highly sensitive MOF-based dual sensing device enables detection of ultralow humidity levels and solvent polarity changes

A Eu-MOF-based sensing device has been developed for monitoring trace moisture levels and solvent polarity changes. The sensor exhibits a remarkably low detection limit of 0.84 ppm with excellent atmospheric stability.

Mechanisms behind the environmental sensitivity of carbon fiber reinforced polytetrafluoroethylene (PTFE)

AbstractCarbon fiber reinforced polytetrafluoroethylene (CF/PTFE) composites are known for their exceptional tribological performance when sliding against steel or cast iron in inert gas environments. Compared to experiments in humid air, about an order of magnitude lower wear rate and several times lower coefficient of friction have been reported for tests conducted in dry nitrogen and hydrogen. Moreover, trace moisture has been shown to affect the friction and wear significantly of this tribosystem, although a possible effect of oxygen cannot be ruled out due to uncertainties regarding the oxygen concentrations. While several studies have pointed out the environmental sensitivity of CF/PTFE, the understanding of the underlying mechanisms are very limited. The objective of this research is to investigate the individual and combined effect of oxygen and moisture on the tribological behavior of CF/PTFE sliding against steel. Additionally, this study aims to elucidate the underlying mechanisms that govern the environmental sensitivity of the system. Climate-controlled three-pin-on-disc experiments were conducted in nitrogen atmospheres at various concentrations of oxygen and moisture. The tribological results clearly demonstrate that both moisture and oxygen contribute to increased friction and wear. However, the adverse effect was much more pronounced for oxygen than moisture. A qualitative method was developed to estimate the tribofilm coverage on the CF/PTFE surface. Results showed strong correlation between high coverage of strongly adhered tribofilm and low wear rate. Moreover, a loosely adhered tribofilm was observed on top of the CF/PTFE surface in presence of moisture. FTIR analysis indicated that the loosely adhered tribofilm found in the moisture-enriched environment contained a significant amount of adsorbed water, which may explain the lower coefficient of friction in presence of moisture compared to oxygen. The adsorbed water in the loosely adhered tribofilm could be an indication of moisture-driven lubrication by the non-graphitic carbon in the tribofilm.

Accurate determination of line intensity of H[formula omitted]O near 7181 cm−1 : SI-traceable measurement using primary trace-moisture standard in N[formula omitted] gas

The absorption spectra of trace water vapor in N2 gas with a mole fraction of 500 nmol/mol in the pressure range of 20 kPa to 140 kPa were obtained near 7181 cm−1 using wavelength-meter-controlled cavity ring-down spectroscopy (WMC-CRDS). The reference gas (water vapor in N2 gas) was produced using a generation system of primary measurement standards for trace moisture in gases, where the amount of water vapor was measured using a gravimetric method. The obtained spectra of H2O were analyzed using a multispectrum fitting technique with a speed-dependent asymmetric Voigt profile (SDAVP). The values of the line intensity were determined with traceability to the International System of Units (SI). We could achieve the expanded uncertainty below 2 % for the line intensities of the strong lines.

Effects of trace moisture content on tribofilm formation, friction and wear of CF-filled PTFE in hydrogen

This study investigated the effects of trace moisture in hydrogen gas on the tribological behavior of carbon fiber (CF)-filled polytetrafluoroethylene (PTFE) composites by examining 20 wt% polyacrylonitrile-based CF-reinforced PTFE composites against stainless-steel disks in gaseous hydrogen environments, where moisture content was controlled at 1, 10, 20, and 40 ppm. The results revealed tribological characteristics of the sliding couples were significantly affected by the moisture content. Wear rates of pin specimens tended to increase gradually with moisture content. Similarly, average coefficient of friction increased as moisture content increased from 1 to 20 ppm. However, it decreased upon further increasing the water content. Moreover, surface analyses of the formed tribofilms at varying moisture contents revealed significant variations in terms of the amount and structure.

Insights of the Ultralow Wear and Low Friction of Carbon Fiber Reinforced PTFE in Inert Trace Moisture Environment

Ultralow wear rates and low friction have been observed for carbon fiber reinforced PTFE (CF/PTFE) when sliding against steel or cast iron in dry gas environments. Although the strong environmental sensitivity of this tribosystem is well known, the origin of the outstanding tribological performance in dry gas remains unanswered. Some researchers attribute the low friction and wear to the formation of carbon-rich surfaces in the absence of oxygen and moisture in the environment. However, low friction between carbon surfaces is generally dependent on moisture. In this paper, extensive analyzes are conducted on the tribofilms formed on the CF/PTFE surface and the steel counterface after sliding in a high-purity nitrogen environment. TEM analysis of a cross-section of the tribofilm on the steel surface reveals that the sliding surface consists mainly of iron (II) fluoride and not carbon, even though a significant amount of carbon was observed near the surface. XPS and TEM analysis further revealed that the tribofilm formed on the worn composite surface consisted of nanoparticle agglomerates, anchored to the PTFE matrix and to each other by carbon with turbostratic structure. Turbostratic carbon also formed an ultrathin and surface-oriented superficial layer on top of the agglomerates. Governing mechanisms of the low friction and wear of the CF/PTFE—steel tribosystem were investigated by complementary tribotests with pure graphite samples and MD simulations of the identified surfaces. These indicated that the low friction between the carbon and iron fluoride in the tribofilms is due to poor adhesion between the distinctly different surfaces.Graphical

Primary measurement standards for trace moisture in multiple gases: extension of gas species to He and O2

The National Metrology Institute of Japan developed a multi-gas trace-moisture generator which was designed for generating trace water vapor (trace moisture) in multiple gases. Using this system, we previously developed primary measurement standards for trace moisture in N2 (10 nmol mol−1–5 μmol mol−1) and Ar (10 nmol mol−1–1 μmol mol−1). In this study, we have extended the target gas species; trace-moisture standards in He and O2 in the rage of 10 nmol mol−1 − 1 μmol mol−1 were developed. The relative expanded uncertainty (k = 2) of the trace-moisture standard in He was 0.74 %–5.7 %, and that in O2 was 0.78 %–8.9 %. In addition, we have improved stability of the flow rate of the diluent gas by controlling the temperature around the flow measurement/control systems and re-evaluated the uncertainty of the trace-moisture standards in N2 and Ar. The updated relative expanded uncertainty (k = 2) of the trace-moisture standard in N2 and Ar is 0.41 %–2.6 % and 0.73 %–2.6 %, respectively. The uncertainty budgets of the standards in these four gases are presented. The trace-moisture standard in N2 developed using the multi-gas trace-moisture generator was confirmed to be consistent with the standards realized by other generators, whose international comparability were already ensured. A commercial moisture analyzer (MA) based on the cavity ring-down spectroscopy (CRDS) was connected to the multi-gas trace-moisture generator as a device under test, and its performance was evaluated by comparing the readings with the standard values. The MA showed lower accuracy and stability in the measurement of moisture in He when it was used in the default setting, whereas it performed well in N2. This performance difference is related to the pressure-broadening coefficient of water, which depends on the gas species. We estimated the pressure-broadening coefficients of water by N2, Ar, He and O2 and discuss the gas-type dependence of the performance of CRDS-based MAs.

Study on the trace moisture influence on the adhesion phenomenon in Cd-based crystal growth

The chemical reactions between trace moisture and raw Cd materials and their effect on the adhesion phenomenon during Cd-based crystal growth were investigated.

Controllably modulated asymmetrical photoresponse with a nonvolatile memory effect in a single CH3NH3PbI3 micro/nanowire for photorectifiers and photomemory.

Nanostructured hybrid organic-inorganic perovskites exhibit remarkable photodetection performance due to their abundant surface states and high responsivity to visible light. However, in traditional photodetectors with a symmetrical configuration of two-terminal electrodes, the photoresponse is independent of bias polarity. Moreover, for self-powered photodetectors, an asymmetric structure of the chemical composition, such as p-n and Schottky junctions, and two different electrodes are necessary. Herein, we demonstrate a modulable asymmetrical photoresponse by packing only one electrode end in a single CH3NH3PbI3 micro/nanowire with two symmetrical Ag electrodes. This not only enables the high performance of light- and bias-modulated multifunctional photorectifiers and self-powered photodetectors, but also allows controllable implementation of nonvolatile photomemory with a tunable spectral responsivity and range. At an unpacked electrode interface, trace moisture in the environment promotes a good bonding of Ag+ and I-, substantially decreasing the interface barrier. Conversely, at a packed electrode interface, abundant surface states can be well preserved, leading to a high interface barrier. Notably, under a large voltage and strong light, the redox of Ag/AgI at the unpacked electrode interface and the injection and ejection of holes at the packed electrode interface can be reversibly conducted by inverting the voltage polarity, enabling a controllable nonvolatile modulation. Therefore, by clarifying the actual origin of the photoelectrical response of CH3NH3PbI3 micro/nanowires at electrode interfaces, high-performance multifunctional photorectifiers and self-powered photodetectors based on asymmetrical interface photovoltaic effects with two symmetrical electrodes can be controllably realized. Furthermore, by precise cooperative modulation of two electrode interface states with a large voltage and strong illumination, nonvolatile photomemory with a tunable spectral responsivity and range can be implemented.

Fluorometric detection of trace moisture in methanol, ethanol and n-propanol using N, P-codoped carbon dots

Trace moisture was firstly measured in methanol, ethanol and n-propanol at room temperature. The N, P-codoped carbon dots (CDs) were prepared by one pot solvothermal method, which displayed solvent-dependent fluorescence. The N, P-codoped CDs exhibited green fluorescence, with the quantum yields (QY) of 27.9%, 37.4%, 26.2% and 2.3% in methanol, ethanol, n-propanol and water, respectively. Based on the hydrogen bond interactions between the protic solvents and the N, P-codoped CDs, with the water content increased, the fluorescence intensity of N, P-codoped CDs gradually decreased in methanol, ethanol and n-propanol. The decrement in the fluorescence intensity is linearly related to the water content within the content range of 2% to 8%, 0.04% to 5% and 0.04% to 1.0%, with a limit of detection of 0.22%, 0.009% and 0.021% in methanol, ethanol and n-propanol, respectively. Therefore, the present system has a prospective value for the application in the determination of trace water in the relevant fields.

Ionic Liquid-Type Additive for Lithium Metal Batteries Operated in LiPF6 Based-Electrolyte Containing 2500 ppm H2O.

The presence of trace amounts of moisture in the electrolyte can cause hydrolysis of LiPF6 and deteriorate the stability of lithium metal batteries. Herein, we propose a multifunctional ionic liquid-type additive constituting a 1-methyl-1-butyl pyrrolidium cation (Py14+) and an acetate anion (CH3COO-) (denoted as IL-AC in this study), which can effectively adsorb the trace moisture and thus prevent the hydrolysis of LiPF6 via intermolecular interactions. The prepared IL-AC can also remove HF to suppress the dissolution of transition metal ions from cathode materials through the reaction CH3COO- + HF → CH3COOH + F-. Compared with the baseline electrolyte, the contents of HF and transition metal ions are significantly lower in the electrolyte with 0.5% IL-AC. Upon the addition of 0.5% IL-AC additive and 2500 ppm H2O, the Li||NCM811 battery shows a capacity of 153.7 mAh g-1 after 300 cycles, while the Li||LNMO battery possesses stable capacity retention of 93.22% after 500 cycles at 1C and a Coulombic efficiency greater than 99%. Thus, this work provides a convenient and effective method to absorb trace amounts of water and remove HF in the electrolyte and provides a new path for the expensive and tedious process of water removal from the electrolyte in industry.

Aggregation induced bathochromic shift of emission for detection of moisture in organic solvents and food stuffs

Accomplishing significant spectral shift with trace moisture is intriguing as well as challenging. Though, numerous small organic molecules discriminate moisture by change in intensity while probes which distinguish by spectral shift are scarce and the commonly employed strategy of small molecules effectuating spectral shift for moisture detection is solvatochromism. Here in this work, an astounding behaviour of simple chalcone in polar protic solvents and its facilitation to determine moisture in organic solvents and food stuffs were demonstrated. Unlike conventional solvatochromism, an unprecedented mechanism for striking bathochromic shift was corroborated as hydrogen bonding governed aggregation with suitable vindications. This new perspective would enable researcher to formulate a sensorial system in an exceptional aspect for detection of target.

Pillared-layer ultramicroporous material for highly selective SO2 capture from CO2 mixtures

Removal of low concentration sulfur dioxide (SO2) from gas mixture is of great significance in gas purification, but the selective recognition of SO2 from carbon dioxide (CO2) still remains a great challenge with low separation selectivity. Herein, we reported a highly-stable pillared-layer ultramicroporous material CPL-1-NH2 for efficient separation of SO2 and CO2 with benchmark IAST selectivity (485) in metal organic frameworks (MOFs). The high separation selectivity is attributed to the narrow channel with lined amino groups, which exhibits significantly higher affinity to SO2 than CO2. Even in the presence of CO2 and trace moisture, the dynamic SO2 capture performance is hardly affected, demonstrating its great promise for SO2 capture. Simulation studies were conducted to gain the deep insight into the microscopic adsorption behaviors of SO2 and CO2.

Effect of roughness on the running-in behavior and tribofilm formation of carbon fiber reinforced PTFE composite in trace moisture environment

Counterface roughness is known to affect the tribological behavior of carbon fiber reinforced PTFE. However, the effect of roughness in trace moisture environments has not yet been extensively investigated. In this study, the tribological behavior and tribofilm formation were evaluated for a carbon fiber reinforced PTFE composite sliding in a trace moisture environment against 34CrNiMo6 steel counterfaces with different roughness. Tribotests were conducted with a three-pin-on-disc tribometer at a sliding velocity of 2.2 m/s and in a nitrogen environment with moisture content controlled to 11 ppm. Generally, smoother counterfaces gave lower wear, both during running-in and steady-state. Contrarily, the coefficient of friction was only affected by roughness during running-in. Surface analysis from different stages of running-in were done to elucidate the formation of tribofilms and their different characteristics. For the rough countersurface, a loosely adhered transfer film is transitionally formed at the beginning of sliding to enable the formation of a persistent transfer film. Contrarily, for the case of a smooth countersurface, the formation of a persistent transfer film is initiated from the start. Similarly for the rough and smooth countersurface, a micrometer thick tribofilm with excellent low friction properties is observed on the PTFE composite after running-in.

3J1-2 Fundamental study of nondestructive testing of inner surface of stainless-steel tubings by ball SAW trace moisture sensor

3J1-2 Fundamental study of nondestructive testing of inner surface of stainless-steel tubings by ball SAW trace moisture sensor

Spectral analysis of H2O near 7180 cm–1 to accurately measure trace moisture in N2 gas: evaluation of line shape profiles using Akaike Information Criterion

The absorption spectra of H2O in N2 gas were measured at atmospheric pressure and room temperature near 7180 cm–1 in the moisture range of 9.7–148.7 nmol mol−1 in mole fraction using cavity ring-down spectroscopy. The line shape profiles used for the spectral analysis for the trace moisture measurement were evaluated based on the Akaike Information Criterion as well as the fitting residuals. The optimal line shape profile in this study was the speed-dependent asymmetric Voigt profile (SDAVP). From the comparison of the fitting results calculated using the Lorentzian profile (LP) with those calculated using the SDAVP, the relative difference in the integrated line area between the two line shape profiles was found to be systematic and constant. The measurement error due to the use of the LP could be corrected using a correction factor of 1.00479 ± 0.00077.