Residual Water Vapor Research Articles

Constant rate thermal analysis of cobaltoblödite and cupper–kröhnkite at low water vapor pressure 5 hPa

Thermal decomposition mechanisms for cobaltoblodite Na2Co(SO4)2·4H2O and cupper–krohnkite Na2Cu(SO4)2·2H2O have been developed using constant rate thermal analysis technique under controlled residual water vapor pressure above the sample $$ P_{{{\text{H}}_{2} {\text{O}}}} = \, 5\;{\text{hPa}} $$ . The apparent activation energy of each dehydration process was measured by means of two CRTA curves without any presumption to the kinetic low. Correlation between structure and thermal behavior was highlighted. It has shown that dehydration of cobaltoblodite mineral occurs in two steps with formation of Na2Co(SO4)2·1.5H2O and Na2Co(SO4)2 as intermediate and final phases, respectively. The activation energies of both dehydration steps are 167 kJ mol−1 and 107 kJ mol−1, respectively. For cupper–krohnkite mineral, its dehydration occurs in one step leading to Na2Cu(SO4)2. The corresponding activation energy was found equal to 71 kJ mol−1.

Monitoring System Heartrat and Respiration Based on Microcontroller

Abstract - The heart is a vital organ in the body whose role is very important in the survival of someone other than the brain, because the heart is responsible for circulating blood throughout the body. And the blood carries oxygen in hemoglobin to meet the oxygen needs in the body. The oxygen demand in the body can be fulfilled through the process of respiration. Oxygen is needed by every cell in the human body. in the process of biochemical reactions (biological oxidation) that function produces ATP (Adenosin Tri Phosphat) energy. The results of substances that occur in the form of residual carbon dioxide and water vapor then exhaled. So the breathing process is needed by humans to get ATP which is useful for doing various activities. Heart rate and respiration measurements can provide important information about the condition or work system of vital organs such as the heart and lungs. Although there are several ways to measure heart rate and respiration rate, the most efficient method of measurement is needed without having to involve manual measurements that can interfere with patient comfort. The Photoplethysmography (PPG) technique is one method of measuring heart rate that can be applied because it is non-invasive so it does not interfere with patient comfort while monitoring heart rate. Whereas to measure the level of respiration can be done by using a temperature sensor that is placed on the air outlet, namely in the mouth. This project aims to create a stand-alone pulse rate and respiration monitoring device that monitors the data can be seen via LCD.Keyword : heart, respiration, photoplethysmography, adenosina trifosfat, oxygen

Selective Growth of Interface Layers from Reactions of Sc(MeCp)2(Me2pz) with Oxide Substrates.

The transformation of an oxide substrate by its reaction with a chemical precursor during atomic layer deposition (ALD) has not attracted much attention, as films are typically deposited on top of the oxide substrate. However, any modification to the substrate surface can impact the electrical and optical properties of the device. We demonstrate herein the ability of a precursor to react deep within an oxide substrate to form an interfacial layer that is distinct from both the substrate and deposited film. This phenomenon is studied using a scandium precursor, Sc(MeCp)2(Me2pz) (1, MeCp = methylcyclopentadienyl, Me2pz = 3,5-dimethylpyrazolate), and five oxide substrates (SiO2, ZnO, Al2O3, TiO2, and HfO2). In situ Fourier transform infrared (FTIR) spectroscopy shows that at moderate temperatures (∼150 °C) the pyrazolate group of 1 reacts with the surface hydroxyl groups of OH-terminated SiO2 substrates. However, at slightly higher temperatures (≥225 °C) typically used for the ALD of Sc2O3, there is a direct reaction between 1 and the SiO2 layer, in addition to chemisorption at the surface hydroxyl groups. This reaction is sustained by sequential exposures of 1 until an ∼2 nm thick passivating interface layer is formed, indicating that 1 reacts with oxygen derived from SiO2. A shift of the Si 2p core level position, measured by ex situ X-ray photoelectron spectroscopy, is consistent with the formation of a ScSi xO y layer. Similar observations are made following the exposure of a ZnO substrate to 1 at 275 °C. In contrast, Al2O3, TiO2, and HfO2 substrates remain resistant to reaction with 1 under similar conditions, except for a surface reaction occurring in the case of TiO2. These striking observations are attributed to the differences in the electrochemical potentials of the elements comprising the oxide substrates to that of scandium. Precursor 1 can react with SiO2 or ZnO substrates, since the constituent elements of these oxides have less-negative electrochemical potentials than do aluminum, titanium, and hafnium. Additionally, Sc2O3 and surface carbonates are deposited on all substrates by gas-phase reactions between 1 and residual water vapor in the reactor. The extent of gas-phase reactions contributing to film growth is governed by the relative pressure of water vapor in the presence of 1. These results suggest caution when using very reactive, oxophilic precursors such as 1 to avoid misinterpreting unconventional film deposition as that resulting from a standard ALD process.

How the sputtering process influence structural, optical, and electrical properties of Zn3N2 films?

Abstract

Degradation and Its Control of Ultraviolet Avalanche Photodiodes Using PEDOT:PSS/ZnSSe Organic–Inorganic Hybrid Structure

We investigated device degradation in PEDOT:PSS/ZnSSe organic–inorganic hybrid ultraviolet avalanche photodiodes (UV-APDs). ZnSSe/n-GaAs wafers were grown by molecular beam epitaxy, and PEDOT:PSS window layers were formed by inkjet technique. We observed rapid degradation with APD-mode stress (~ 30 V) in the N2 (4 N) atmosphere, while we observed no marked change in forward bias current stress and photocurrent stress. In the case of a vacuum condition, we observed no detectable degradation in the dark avalanche current with APD-mode stress. Therefore, the degradation in the PEDOT:PSS/ZnSSe interface under the APD-mode stress was caused by the residual water vapor or oxygen in the N2 atmosphere and could be controlled by vacuum packaging.

Study on Thermal Behaviour of AP/LiBH4 Energetic System

AbstractAmmonium perchlorate(AP) and LiBH4 can form an oxidation‐fuel energetic system, which provides a new development direction in designing novel mixed explosive formula. The microcalorimetry and self‐designed slow cook‐off setup were used to study thermal performance of AP/LiBH4 energetic powders and grains respectively. Experimental results show that heat release in microcalorimetry method for the mixed system at low temperature was due to the reaction between LiBH4 and residual water vapour. The oxidant gases from AP decomposition participate in the oxidation of LiBH4 at high temperature. The ignition temperature for the AP/LiBH4 grain was 270 °C and the explosion reactions were violent in slow cook‐off test.

Polymeric Systems Under External Thermal Stress Studied by FTIR Technique

Background: Temperature behavior of a class of PolyEthylene Oxide and Ethylene Glycol (EG) by means of InfraRed spectroscopy as a function of temperature and concentration. Methods: EG and PEO with Mw of 1000 were purchased from Aldrich-Chemie; To collect the FTIR spectra in the 39°C-80°C temperature range by means of a FTIR Vertex 70V spectrometer by Bruker Optics. Spectra were obtained using an average of 36 scans with a resolution of 4 cm-1 in a window range of 400 ÷ 4000 cm-1. Each measure was performed under vacuum in order to minimize spectral contributions due to residual water vapor and finally the data were processed through the OPUS/Mentor software interface, Mathematica and Matlab. Results: The addition of EG to PEO increases the thermal restraint of the polymeric matrix due an increase of the H-bond connectivity. Conclusion: The analysis highlights an increased H-bonded connectivity in the polymeric mixture, which determines a higher resistance to temperature changes of the mixture. Keywords: Ethylene glycol, PolyEthylene oxide, FTIR spectroscopy, hypsochromic frequency shift, polymeric mixture, H-bonded.

Emission spectral diagnosis of argon-helium plasma produced by radio frequency capacitive discharge

Optically pumped metastable rare-gas laser (OPRGL) have been proposed to overcome the shortcomings of diode-pumped alkali-vapor laser in the recent years. The OPRGL promises to realize high-scale output. But how to achieve enough particle density of metastable atoms is still an open problem. Usually, plasma produced by discharge serves as a gain medium of the OPRGL. Here in this paper, we are to reveal the effects of different discharge parameters on the plasma properties, such as particle density of metastable argon atoms. Gas discharge at a radio frequency of 13.56 MHz is adopted to excite argon atoms. Emission spectrum is employed to study argon and helium radio frequency discharge of optically pumped argon laser at high pressure, different powers of discharge and various content of argon. Gas temperature is obtained by analyzing rotational spectrum (A2∑+ → X2Π) of OH radical generated by residual water vapor and comparing simulated spectrum with the measured spectrum. The electronic excitation temperature relating to electron temperature is obtained by the method of Boltzmann's plot. Stark broadening of the spectrum is used to determine the electron density. The results show that gas temperature rises slightly with the increase of pressure and varies little with content and discharge power changing. The electronic excitation temperature increases with the decrease of pressure evidently and decreases slightly with the increase of content. The electron density is on the order of 1015 cm-3 under various conditions controlled by us. Long time discharge test reveals that residual water vapor can lead to the decrease of electron temperature, and thus reducing the yield of argon metastable state. In conclusion, considering that the higher gas temperature can improve the collision relaxation rate of helium and argon, and the higher electron temperature can improve the rate of production of argon metastable state. Thus a proposal is put forward that appropriately heating gas and reducing gas pressure can obtain higher particle density of metastable argon. Furthermore, It can be found from these results that heating and cleaning the gas during discharge may be candidate methods to obtain and sustain the higher particle density in the plasma.

Effects of vacuum annealing on carrier transport properties of band gap-tunable semiconducting amorphous Cd–Ga–O thin films

The effect of vacuum annealing on the amorphous oxide semiconductor Cd–Ga–O system with a tunable band gap was examined. While the amorphous halo peak in XRD patterns of the films with Cd concentration of ~70% started sharpening after annealing at a temperature ≥200°C. In contrast, the films with Cd content of ~50% and ~20% were not crystallized for annealing temperatures up to 700°C. Carrier concentrations and Hall mobilities of ~70% and ~50% films were maximized by annealing at 400°C and 500°C, respectively, regardless of the properties of the as-deposited films, which were varied because of the unintended variation of deposition conditions such as the residual water vapor pressure in the deposition chamber. The initial electrical conductivity of ~20% films widely varied from <10−8 to 11S·cm−1, and annealing at 500°C was required for obtaining conductive films from the insulating as-deposited films. The maximum Hall mobility for films with Cd content of ~70% and ~50% films was ≥10cm2V−1s−1 and that for the film with ~20% Cd content was ≥3cm2V−1s−1.

Fatigue propagation of short and long cracks in gaseous hydrogen environment in 3.5NiCrMoV steel

Abstract Turbo generators for nuclear plants are mostly equipped with hydrogen cooling systems. Current practice of characterizing the growth of fatigue cracks on the basis of fracture mechanics primarily relies on fatigue tests for long cracks which are typically of several millimeters in length. However, in view of extended life for the plants, the damage tolerance evaluation of such fatigue-critical engineering components requires understanding of the propagation of cracks of significantly smaller dimensions. Then the near threshold of short cracks is investigated and compared to the behavior of long crack by experiments under 4 bar hydrogen atmosphere. The short crack fatigue propagation in hydrogen atmosphere is shown similar to that in air, growing faster than the long crack and at ΔK ranging below the long crack threshold; this effect is related to a reduced crack closure shielding. The propagation behavior of long crack under hydrogen atmosphere is shown similar to that obtained in air in the low rate range, i.e. when the maximum of the stress intensity factor K max is lower than a critical level of about 16 MPa m 1/ 2 with higher crack growth rate than in high vacuum. This environment effect is related to the presence of residual water vapor in both gases. For higher K max , much faster growth rates under hydrogen atmosphere in comparison to air and vacuum are observed and related to hydrogen assisted intergranular propagation combining fatigue and sustained loading damage. The results are discussed on the basis of micrographic observations supporting the involved mechanisms.

Synthesis and thermal behaviour of Na2SO4·MgSO4·4H2O

The thermal behaviour of astrakanite was investigated by conventional thermal analysis techniques in air and by constant rate thermal analysis (CRTA) under residual water vapour pressure above the sample $$ P_{{{\text{H}}_{ 2} {\text{O}}}} = 5 $$ hPa. It has been shown that the pathway of the thermal dehydration depends strongly on the nature of atmosphere above the sample. A correlation between structure evolution and thermal behaviour was developed. The apparent activation energies corresponding to the two dehydration steps of Na2Mg(SO4)2·4H2O were also measured experimentally by means of two CRTA curves and were found equal to 83 ± 7 and 111 ± 8 kJ mol−1, respectively.

Fatigue Crack Propagation in Gaseous Hydrogen Environment in Low Alloy Steel

Fatigue crack propagation in low alloyed steel (3.5Ni-1.5Cr-0.5Mo-V) used for turbine generator of nuclear plant is studied under 4bar hydrogen atmosphere in comparison to ambient air and high vacuum. Tests are conducted on CT specimens and the variation of the fatigue crack growth rate da/dN with respect to the amplitude of the applied stress intensity factor ΔK is explored in a wide range and especially in the near threshold domain. The propagation behaviour under hydrogen atmosphere is shown similar to that obtained in air in the low rate range, i.e. when the maximum of the stress intensity factor Kmax is lower than a critical level of 16 MPam1/2 with higher crack growth rate than in high vacuum. This environment effect is related to the presence of residual water vapour in both gases. For Kmax higher than 16 MPam1/2, much faster growth rates under hydrogen atmosphere in comparison to air and vacuum are observed and related to hydrogen assisted intergranular propagation combining fatigue and sustained loading damage. The results are discussed on the basis of micrographic observations supporting the involved mechanisms.

Membrane gas absorption for CO2 capture from flue gas containing fine particles and gaseous contaminants

Membrane gas absorption contactor has been an effective alternative for CO2 capture, and usually installed at the outlet of wet flue gas desulfurization (WFGD) system. However, there are also residual SO2, fine particles and water vapor in desulfurized flue gas, which possibly has significant impact on the stable operation of CO2 absorption using membrane. In order to obtain a better understanding on the influence of these components, the capture process of CO2 using polypropylene (PP) hollow fiber membrane from flue gas containing fine particles and gaseous contaminants were investigated in this work. At first, simulated flue gas was used to study the effects of SO2, water vapor and fine particles on the CO2 capture respectively. Then the separation of CO2 using PP membrane was operated under the condition of actual coal-fired desulphurized flue gas. The results revealed that the absorption performance of membrane was slightly deteriorated at the individual presence of SO2 or water vapor while the effects fine particles was significant. Following the fine particles exposure, a bulk decrease of the CO2 removal efficiency was observed due to the deposition and adsorption of fine particles on the membrane surface and pores. In addition, water vapor could accelerate the deposition of fine particles.

Fatigue Crack Propagation in Hydrogen Gas in Low Alloyed Steel

This paper deals with fatigue crack propagation under 4 bar hydrogen atmosphere in low alloyed steel (3.5Ni-1.5Cr-0.5Mo-V) used for turbine generator of nuclear plant. The tests are conducted in the same way in ambient air and high vacuum on CT specimens and the fatigue crack growth rate specially investigated in the near threshold range is plotted with respect to the applied stress intensity factor. It is shown that the propagation under hydrogen atmosphere is similar to that obtained in air up to a Kmax value of 16,5 MPam1/2 with increased growth rate compared to that in high vacuum leading to a threshold value lower that in vacuum, this effect being related to residual water vapor. For Kmax higher than 16,5 MPam1/2, much faster growth rates under hydrogen atmosphere becomes are associated to an intergranular propagation mechanism induced by an hydrogen effect. The results are discussed on the basis of available models.

Performance and lifetime of vacuum deposited organic light-emitting diodes: Influence of residual gases present during device fabrication

Understanding the influence of residual gases present during vacuum deposition of organic light-emitting diodes (OLEDs) and their effect on the device lifetime and the electrical characteristics of OLEDs is crucial for advancing industrial fabrication. In order to gain a more in-depth understanding, the influence of residual nitrogen, oxygen, and water vapor on lifetime and electrical characteristics is investigated. This is achieved by introducing the residual gases into the evaporation chamber through a needle valve while monitoring the partial pressures with the help of a mass spectrometer. We find that water vapor introduces a series resistance to the OLED while the other gases do not influence the electric characteristics. The presence of oxygen or nitrogen impacts the lifetime of the OLEDs by the same amount. Water vapor introduces an additional, even faster degradation process within the first hours of OLED operation. The electrically stressed OLEDs are analyzed by laser desorption/ionization time-of-flight mass spectroscopy. We identify the dimerisation of BPhen as well as the complexation reaction of α-NPD with an Ir(piq)2 fragment as sources of device degradation.

Residual impurities in a process chamber on the characteristics of a-Si:H solar cells

Hydrogenated amorphous silicon (a-Si:H) p-i-n solar cells were grown in a single, non-load-locked chamber by using 13.56MHz plasma. Residual air impurities were controlled with high vacuum pumping, or not controlled, and the concentrations were measured at the onset, before p-layer deposition. The low pressures (approximately 10−7–10−8Torr) of N2 and O2 near the lowest vacuum pressure of the chamber, incorporated base contamination levels of nitrogen and oxygen (approximately 1018–1019atoms/cm3). High pressures of H2O (10−5–10−6Torr) resulted in extremely high oxygen contamination levels (approximately 1021atoms/cm3), which was the dominant residual impurity. High concentration un-stabilized H2O showed a rapidly decreasing rate which induced non-uniform oxygen doping and resulted in a non-uniform distribution of the internal electric field in the i-layer. The net loss (ΔQE(0,V)) of quantum efficiency (QE) of the cells between zero and a forward bias showed the increase of QE loss in the long-wavelength region for increasing forward bias resulted in poor performance of the low fill factor and energy conversion efficiency, and a high series resistance of the cells. The removal of residual water vapor from the chamber is a key factor in improving the performance of a-Si:H solar cells.

Synthesis and Aggregation of In2O3 Nanoparticles: Impact of Process Parameters on Stoichiometry Changes and Optical Properties

Metal-organic chemical vapor synthesis provides agglomerated In2O3 nanoparticles with a low abundance of particle-particle interfaces. Via exposure to bulk water and subsequent dehydration treatment these powders can be transformed into networks of aggregated nanoparticles. Two major effects arise from the associated emergence of particle-particle interfaces: an enhanced susceptibility to annealing induced n-type doping and a significant red-shift of the optical absorption threshold by 0.2 eV. On the basis of control experiments with pure water, we further explored the impact of the environmental gas atmosphere during annealing on the integral ensemble properties. We found that residual water vapor promotes the mutual attraction of particles, facilitates their condensation, and generates particle-particle interfaces. This work may prove to be of great value for the reproducible production and formulation of percolating metal oxide nanoparticle networks with high control over particle aggregation state, on the one hand, and n-type conductivity as well as optical properties, on the other.

STUDY ON THE CORROSION MECHANISM OF T2 COPPER CONDENSER TUBE UNDER THE HUMID ENVIRONMENT

During the maintenance of two years, T2 copper tube in a heat exchanger has leaked, it can be deduced that the residual water and volatile water vapor would play an important role in leakage. By SEM, OM, stereo microscope observation, it was found that serious corrosion happened on the surface of copper in the gaps constituted by copper tube and stainless steel baffle holes, and perforation occurred in a few locations. Wetting experiments show that the gap formed between the T2 copper tube and the baffle hole wall is small enough that it could produce siphon liquid film, which could connect the copper tube surface and baffle hole. Therefore there is a difference of oxygen supply between the copper tube outer surface and the copper tube in the gap site, the outer surface of copper tube becomes oxygen–rich zone and the copper tube in the gap site oxygen–poor zone. Potential monitoring results show that the potential of the external surface of copper tube with an oxide is higher than that of copper in the gap site leading to a galvanic cell formed between them. The surface of copper in the gap site is anode region and the external copper tube surface is cathode region. The differences of oxygen supply combined the effect of the galvanic cell leads to the severe localized corrosion of copper tube in the gap site.

Anti-contamination device for cryogenic soft X-ray diffraction microscopy

Cryogenic microscopy allows one to view frozen hydrated biological and soft matter specimens with good structural preservation and a high degree of stability against radiation damage. We describe a liquid nitrogen-cooled anti-contamination device for cryogenic X-ray diffraction microscopy. The anti-contaminator greatly reduces the buildup of ice layers on the specimen due to condensation of residual water vapor in the experimental vacuum chamber. We show by coherent X-ray diffraction measurements that this leads to fivefold reduction of background scattering, which is important for far-field X-ray diffraction microscopy of biological specimens.

铝、镍和铪金属膜表面的最初氧化动力学研究

High precision, single-wavelength optical monitoring of reflectance was shown to be useful in the study of initial oxidation of very thin metal films by low pressure oxygen at room temperature. Thin films of Al, Ni, and Hf metal were sputter-deposited on silicon substrates and their subsequent oxidations were observed at low oxygen partial pressure using a temperature-stabilised laser diode reflectometer. Based on the derived properties of the appropriate metal and oxide films, optical monitoring data were fitted as a multilayer stack comprised of oxide/metal/SiO2/Si. The fitting results show that the exposure to oxygen at a partial pressure of 0.04 Pa forms a certain finite thickness of oxide film on the metal surface. A range of kinetic models such as Deal-Grove, Massoud, and Cabrera-Mott are commonly used to describe the surface oxidation process. However, these models cannot be applied to the initial stage of oxidation, which occurs when a pure metal surface is exposed to oxygen as measured here. Instead, simple chemical reaction kinetics is used to model the time-dependent experimental results of the early stages of oxidation, thus we obtain the equation d(t) = do[1iexp(it/τ )] and d(t) = do[1i1/(1+t/τ )] for the gas environments of this investigation. OCIS codes: 240.0240, 240.0310, 240.6648. doi: 10.3788/COL201008S1.0087. An oxide layer forms rapidly when a fresh metal surface is exposed to an oxygen-including atmosphere. At atmospheric pressure and room temperature, the layer is usually self-limiting, resulting in a so-called native-oxide layer with a thickness of a few nanometers. For example, in Banerjee’s report [1] , a silicon wafer had a native oxide layer of around 2 nm, while according to the investigation in Ref. [2] on the initial oxidation of Fe-nanoparticles, the typical thickness of the native oxide layer was said to be 2i3 nm. The thickness of oxide formed on thin metal films is of interest for a number of applications. This is particularly so for metallisation layers used in the manufacture of backplanes for plastic electronics where two or more very thin layers of metal may be necessary to provide both adhesion to the polymer substrate and sufficiently low sheet resistance (e.g., Ti/Au, Ni/Au, Cr/Au, etc.). Even when no oxygen is deliberately introduced into the vacuum chamber, low levels may still be available to the metal films due to residual water vapour outgassing from the polymer substrate or the chamber walls. The degree and rate of oxidation of the less noble, adhesion-promoting layers at the typical oxygen pressures encountered in vacuum chambers are of great importance in determining the performance and lifetime of devices and are not easily measured after deposition is complete. In the course of researching alternative metallisation layers, we investigated the first stage of oxidation of several metals at low oxygen partial pressures and presented some initial results. Precise in-situ measurements of reflectance during the deposition and oxidation of thin metal films of Al, Ni, and Hf on silicon substrates were used to measure reliably extremely thin oxide films formed in very low oxygen partial pressures.