Changes In Oxygen Concentration Research Articles

ИССЛЕДОВАНИЕ ВЛИЯНИЯ УСЛОВИЙ ИЗГОТОВЛЕНИЯ НА ФОТОПРОВОДИМОСТЬ ГРАНИЦЫ РАЗДЕЛА ДВУХ ПОЛИМЕРНЫХ ПЛЕНОК

The study of optical properties in organic materials requires taking into account a wide range of features of these materials in connection with their sensitivity to external influences and aggressive environment. In this work, we studied the features of the photoconductivity of the interface between two dielectrics (polydiphenylene phthalide (PDP)) manufactured under different conditions. Drying was carried out in air and in vacuum. This study is necessary to determine the features of the manufacturing process and its effect on the photoconductive properties of the interface. Currently, the structure of the polymer / polymer interface has been fairly well studied by various methods, in particular, atomic force microscopy. However, there is a certain difficulty in obtaining repeatable results due to the presence of dilution of the lower PDP film when the upper polymer layer is applied. In this work, the photoconductive properties were studied on the basis of the measurements of the current-voltage characteristics (CVC) and the curves of the growth and relaxation of the photocurrent. Based on the results obtained within the framework of this work, it is possible to draw conclusions about the contribution of the drying method of experimental structures to the photoconductivity of the interface. It is known that oxygen makes a significant contribution to the electrical conductivity of thin PDP films. Earlier, it was shown on this polymer material that the presence of oxygen leads to a decrease in the conductivity of PDP films due to the formation of charge carrier traps. Moreover, when oxygen interacts with fragments of a polymer molecule, a chemical bond does not arise, which leads to a reversible change in electrical conductivity with a change in oxygen concentration. Due to this, the PDP films demonstrate a high stability of the electrophysical characteristics for several years when repeated measurements are carried out in an open atmosphere and at room temperature. It can be argued that the effect on the response of photoconductivity in organic materials, as well as on the relaxation time, can be associated with the presence of oxygen traps in the PDP films, increasing the relaxation time. This result is extremely important from the point of view of the practical application of these structures.

Fixing skeletal muscle PO2 eliminates hyperinsulinemic microvascular blood flow response.

To determine if insulin-mediated hyperemia is partially dependent on local muscle oxygen concentration. Sprague-Dawley rats were anesthetized, and the extensor digitorum longus (EDL) was reflected onto an inverted microscope. Intravital video microscopy sequences were recorded during baseline and hyperinsulinemic euglycemia. The muscle was reflected over a glass stage insert (Experiment 1a and 1b), or over a gas exchange chamber (Experiment 2), and microvascular capillary blood flow was recorded during sequential changes (7%-12%-2%-7%) of oxygen (O2 ) concentration. Blood flow was measured by the red blood cell supply rate (SR) in number of cells per second. All animal protocols were approved by Memorial University's Institutional Animal Care Committee. In Experiment 1a, SR increased from 8.0 to 14.0 cells/s at baseline to euglycemia (p=.01), while no significant SR variation was detected after performing a sham hyperinsulinemic euglycemic clamp (Experiment 1b). In Experiment 2, SR decreased at 12% O2 and increased at 2% O2 , compared to 7% O2 , under both experimental conditions. Magnitude of SR responses to oxygen oscillations during euglycemia were not different to those at baseline at each O2 concentration (p > .9). Our results suggest that increased blood flow observed in response to insulin is eliminated if tissue oxygen microenvironment is fixed at a given oxygen concentration.

Optimization of Parylene C and Parylene N thin films for use in cellular co-culture and tissue barrier models

Parylene has been used widely used as a coating on medical devices. It has also been used to fabricate thin films and porous membranes upon which to grow cells. Porous membranes are integral components of in vitro tissue barrier and co-culture models, and their interaction with cells and tissues affects the performance and physiological relevance of these model systems. Parylene C and Parylene N are two biocompatible Parylene variants with potential for use in these models, but their effect on cellular behavior is not as well understood as more commonly used cell culture substrates, such as tissue culture treated polystyrene and glass. Here, we use a simple approach for benchtop oxygen plasma treatment and investigate the changes in cell spreading and extracellular matrix deposition as well as the physical and chemical changes in material surface properties. Our results support and build on previous findings of positive effects of plasma treatment on Parylene biocompatibility while showing a more pronounced improvement for Parylene C compared to Parylene N. We measured relatively minor changes in surface roughness following plasma treatments, but significant changes in oxygen concentration at the surface persisted for 7 days and was likely the dominant factor in improving cellular behavior. Overall, this study offers facile and relatively low-cost plasma treatment protocols that provide persistent improvements in cell-substrate interactions on Parylene that match and exceed tissue culture polystyrene.

Ethanol fermentation- and ethylene physiology-related gene expression profiles in Red Delicious apples stored under variable hypoxic conditions and protocols

Dynamic Controlled Atmosphere (DCA) is beneficial in maintaining specific quality parameters but, due to the extreme oxygen levels applied, can cause adverse effects on the fruit by inducing excessive anaerobic metabolism and the production of off-flavors. The metabolic adaptation and responses of apples (Malus domestica Borkh.) cv. Red Delicious to static or dynamic oxygen concentrations (0.3 and 0.8%, with sequential shifts) during cold storage for 7 months were studied by monitoring quality parameters and the expression of genes involved in sugar, fermentative metabolism, and ethylene physiology. Ethanol content reached the highest levels (around 400 mg/kg FW) under 0.3% oxygen concentration and fruit firmness appeared to be reduced in samples accumulating the highest levels of ethanol. Oxygen switch was effective in reducing the ethanol concentrations with timing-dependent variable effects. The expression of fermentative (alcohol dehydrogenase, lactate dehydrogenase, pyruvate decarboxylase) and sugar metabolism (β-amylase; phosphofructokinase; sucrose synthase) genes resulted to be differently affected by the hypoxic conditions imposed, in particular during the early stages of storage. Sucrose synthase expression appeared to be highly sensitive to changes in low oxygen concentration. Ethylene biosynthesis (ACC synthase and oxidase) genes showed marked differences in their expression in relation to the static and dynamic protocols and the hypoxic conditions, as well as six Ethylene Responsive Factors (ERF) genes, some of them possibly involved in the oxygen sensing mechanism operating in fruit tissues.

Comparison of Oropharyngeal Oxygen Pooling and Suctioning During Intubated and Nonintubated Dental Office-Based Anesthesia.

The risk of a spontaneous surgical fire increases as oxygen concentrations surrounding the surgical site rise above the normal atmospheric level of 21%. Previously published in vitro findings imply this phenomenon (termed oxygen pooling) occurs during dental procedures under sedation and general anesthesia; however, it has not been clinically documented. Thirty-one children classified as American Society of Anesthesiologists I and II between 2 and 6 years of age undergoing office-based general anesthesia for complete dental rehabilitation were monitored for intraoral ambient oxygen concentration, end-tidal CO2, and respiratory rate changes immediately following nasotracheal intubation or insertion of nasopharyngeal airways, followed by high-speed suctioning of the oral cavity during simulated dental treatment. Mean ambient intraoral oxygen concentrations ranging from 46.9% to 72.1%, levels consistent with oxygen pooling, occurred in the nasopharyngeal airway group prior to the introduction of high-speed oral suctioning. However, 1 minute of suctioning reversed the oxygen pooling to 31.2%. Oropharyngeal ambient oxygen concentrations in patients with uncuffed endotracheal tubes ranged from 24.1% to 26.6% prior to high-speed suctioning, which reversed the pooling to 21.1% after 1 minute. This study demonstrated significant oxygen pooling with nasopharyngeal airway use before and after high-speed suctioning. Uncuffed endotracheal intubation showed minimal pooling, which was reversed to room air ambient oxygen concentrations after 1 minute of suctioning.

Water Formation Kinetics on Co(0001) at Low and Near-Ambient Hydrogen Pressures in the Context of Fischer–Tropsch Synthesis

Understanding the kinetics of oxygen removal from catalytically active metal surfaces by hydrogen is important for several catalytic reactions such as Fischer–Tropsch synthesis, methanation of CO or CO2, and the reverse-water–gas-shift reaction. Motivated by FTS, a Co(0001) single crystal model catalyst was used to study the kinetics of oxygen removal through reaction with hydrogen. Kinetic studies in the 10–7–10–4 mbar H2 pressure regime show that water formation is first order in the surface hydrogen concentration while the order in oxygen concentration changes from one at low oxygen coverage to zero at high oxygen coverage. In situ XPS shows that the hydrogen surface concentration saturates around 10–1 mbar and on this basis the typical temperature of 450 K needed for water formation in this pressure regime can be considered as typical for high pressures as well. The absence of OH buildup during the reaction points to O + H as the rate-limiting step, with a barrier of ∼120 kJ mol–1. Such a high barrier shows that slow removal of adsorbed oxygen from the surface of reactive metal catalysts such as cobalt may be rate-limiting for the overall reaction.

Investigation of VxOy thin films using Raman Spectroscopy: Role of oxygen vacancies and structural phase transformation on thermochromic properties

Vanadium Oxide is a well-known transition metal oxide showing metal–insulator transition and is important for thermochromic and smart window applications. We have grown amorphous vanadium oxide thin films on barium borosilicate 7059 glass using cathodic arc- deposition methods. Especially, here we present a detailed investigation of these films using Raman spectroscopy performed at different temperatures and laser powers and correlate these results with XRD measurements. We demonstrate the static and dynamic structural phase transformations induced by laser and explain these results due to oxygen content changes.

Numerical investigations to identify environmental factors for field-scale reactive transport of pathogens at riverbank filtration sites

While induced bank filtration is a proven method for facilitating sustainable drinking water production, it is at risk from surface water contaminations (e.g., pathogens). Induced bank filtration and pathogen transport in groundwater have been studied extensively. However, long-term studies that consider real-world conditions are missing. These conditions include seasonal changes to environmental conditions and waterworks operations. Therefore, to analyze the effect of seasonal changes on the transport of human pathogenic viruses and their indicators in induced bank filtration, concentrations of adenoviruses and pathogen indicators were monitored over 16 months at an active bank filtration plant at the Rhine River, in Düsseldorf (Germany). Based on this data, a 2D groundwater model was created in PFLOTRAN that simulated flow, heat transport, conservative transport of chloride and the resulting electrical conductivity, reactive transport of oxygen and nitrate, and colloid-based transport of coliforms, somatic coliphages, and adenoviruses. The results show that reduced travel time was the key factor determining periods with a low removal of coliforms and somatic coliphages in the aquifer. Travel time was controlled by river level variations during rainy seasons, and the waterworks extraction rates during dry seasons. For adenovirus transport, travel distance in the subsurface appeared to be the key factor, while travel time had no significant impact. Coliform removal increased when the colmation layer permeability decreased, while coliphage and adenovirus removal was unaffected by the colmation layer permeability. Seasonal changes in temperature and oxygen content did not significantly impact the removal of coliphages and adenoviruses in groundwater. Denitrifying conditions correlated with a lowered coliform removal, but the modelling could not establish a connection between denitrifying conditions and coliform removal. Our study showed that removal of pathogens and pathogen indicators at induced bank filtration plants varies greatly in time and space (e.g., for coliforms from 1 to 4 log-levels at 20 m travel distance), and that adenovirus transport differs considerably from transport of coliforms and somatic coliphages

Accelerated methane emission from permafrost regions since the 20th century

Carbon dioxide has been increasing in the atmosphere since the industrialization, resulting in global warming, which in turn enhanced methane emissions from permafrost regions. However, methane emitted into the atmosphere is quickly oxidized, such that the intensity and threat of methane emission in the past are severely underestimated. Here we show that the ratio between annual changes in atmospheric oxygen and carbon dioxide concentrations (ΔO2/ΔCO2 index) dropped dramatically between 1945 and 1958. There are no such abrupt changes in the fossil fuel combustion curve. Considering that atmospheric methane has the residence time less than ∼9 years through biological and chemical processes, this crisis is attributed to the World War II, which had disturbed gas hydrates underneath ocean floors and permafrost regions. Consistently, the land-ocean temperature index fluctuated more severely in permafrost regions than the global average during the WWII, indicating stronger greenhouse effects induced by methane emission. This is supported by the changes in the ΔO2/ΔCO2 index, coupled with higher atmospheric methane concentrations and lower δ13CO2 in permafrost regions in the last three decades, suggesting accelerated methane emission. The anthropogenic carbon dioxide emission has been pushing the accelerated thawing of permafrost, which promotes methane emission that further intensifies permafrost thawing and global warming. Such a positive feedback at an inflection point of Earth climate may break the glacial-interglacial cycle and initiate a long-lasting greenhouse period.

Study on the Relationship between Indoor Vertical Greening and Oxygen Content in High-Rise Buildings

This article clarifies the quantitative relationship between vertical greening, indoor ventilation, and the oxygen content in high-rise buildings, with the aim of determining values for a high-oxygen-content threshold to assess the ventilation and greening of high-rise buildings. The quantitative index could be provided to architects to assist in the sustainable design of vertical greening in high-rise buildings. The quantitative index offers an effective, convenient, and environmentally friendly oxygen-content-testing method for interior spaces, while avoiding the air pollution caused by the current red phosphorus combustion method. Firstly, a floor of a high-rise building in Harbin was selected for on-site and fixed-point experiments. Secondly, through the design of a candle-burning experiment in a gas bottle, we measured the change in candle-burning time before and after installing vertical greening, as well as under different ventilation states. Finally, the changes in relative oxygen content in each functional space before and after vertical greening and under different ventilation states were statistically analyzed. The results showed that there was a potential correlation between indoor oxygen content and vertical greening placement in high-rise buildings; this correlation was found to be directly related to room orientation, the degree of the plants’ photosynthesis, and indoor airflow. In general, vertical greening should be placed in south-facing rooms. For daily ventilation, two or more windows should be opened to ensure convection in rooms, which can increase their oxygen content.

Do Ultrafine Bubbles Work as Oxygen Carriers?

Fine bubbles (FBs) are bubbles with sizes less than 100 μm and are divided into ultrafine bubbles (UFBs, < 1 μm) and microbubbles (MBs, 1-100 μm) depending on their size. Although FB aeration is known as a more efficient way than macrobubble aeration to increase the oxygen level in unoxygenated water, few reports have demonstrated whether dispersed UFBs work as oxygen carriers or not. Furthermore, oxygen supersaturation is one of the attractive characteristics of FB dispersion, but the reason is yet to be revealed. In this study, we evaluated the relationship between the FBs, especially UFB concentration, and oxygen content in several situations to reveal the two questions. The FB concentration and oxygen content were examined using particle analyzers and our developed oxygen measurement method, which can measure the oxygen content in FB dispersion, respectively. First, in the evaluations of the oxygen dispersion from UFBs with respect to the surrounding oxygen level, UFBs did become neither small nor diminish even in degassed water. Second, the changes in UFBs and oxygen content upon storage temperature and the existence of a lid during storage were evaluated, and there was no correlation between them. It means UFBs contribute little to the oxygen content in UFB dispersion. Furthermore, the oxygen content in the UFB dispersion decreased over time identically as that of the oxygen-supersaturated water with little UFBs. Third, we evaluated the relationship between FB concentration and oxygen content during FB generation by measuring them simultaneously. The results showed that dispersed MB and UFB concentrations did not account for the supersaturation of the FB dispersion. From the result, it was revealed that 100-200 nm of UFBs themselves did not work as oxygen carriers, and the oxygen supersaturation in FB dispersions was due to the supersaturated state of dissolved oxygen that was prepared during the FB generation process.

Assessment of Bioenergetics in BAT Mitochondria.

High-resolution respirometry is commonly used to quantify mitochondrial respiratory rates. In the respirometry chamber, a change in oxygen concentration is measured by a polarographic electrode to derive the rate of oxygen consumption (JO2). Here, we describe our adapted protocol to bioenergetically phenotype mitochondria from mouse brown adipose tissue (BAT). Given the presence of uncoupling protein 1 (UCP1), mitochondria from BAT provide unique challenges and opportunities in applying high-resolution respirometry to understand energy transduction through oxidative phosphorylation (OXPHOS).

Effect of Antioxidant on Sperm Freezing

A major cause of male infertility, which includes 50 causes of infertility, is oxidative stress. Aerobic respiration in the sperm cell is associated with the production of reactive oxygen species (ROS). Some reactions, such as sperm capacitation and acrosome reactions require moderate levels of ROS. However, when the amount of ROS production surpasses the natural antioxidant defense of the cell, it causes a harmful effect called oxidative stress. This results in the oxidation of lipids, proteins, carbohydrates, and nucleotides. The production of ROS is increased by various factors, including the presence of leukocytes, sperms with abnormal and immature morphology, centrifugation of samples, and changes in oxygen concentration, pH, and temperature. Sperm freezing is a method widely used in assisted reproductive technology (ART) as well as infertility treatment. The process of freezing also contributes to increased oxidative stress because it alters the fluidity of the mitochondrial membrane, leading to increased production and release of ROS. Sperm have defense mechanisms against oxidative stress caused by increased ROS production, which includes the presence of enzymatic and non-enzymatic antioxidants in semen. The utilization of supplementary antioxidants in the freezing environment is a strategy to combat oxidative stress. This review aims to summarize the current evidence on the effect of antioxidants on sperm freezing.

Comparative Analysis of Peak Air Pressure and Oxygen Flow between Conventional and Modified Endotracheal Tube for Retromolar Intubation (PUNTUBE)- An In Vitro Study.

In conventional practice for retromolar intubation, endotracheal tube (ET) is bent. This leads to compression of the inner diameter of the tube which in turn reduces airflow. Furthermore, conventionally ETs are stabilised in position using inflated tracheal cuff. Elastic sticky tapes around the exit pose hindrance for surgical procedures on the face. Surgical manipulation and maxillomandibular fixation may lead to compression, damage or accidental extubation of ET. We have developed a modified ET dedicated to retromolar intubation with innovative means for tube stabilisation to solve these problems. To study the efficacy of the tube, a comparative in vitro study was done on mannequins. Null hypothesis of no change in air pressure and oxygen concentration in bent conventional ET versus modified ET was formulated. Comparison was done on the basis of the peak air pressure (PEP) and oxygen concentration, which was checked using air-gas monitor. The mean PEP was found to be 24.29 psi with standard deviation (SD) of 9.54 in sequentially bent conventional tube. This was found to be only 10.35 psi with SD of 3.22 in modified ET. Oxygen delivery was found to be 3.96 L/min in bent conventional tube, which was 5.22 L/min in modified tube. Both the findings were statistically significant. Modified retromolar tube (PUNTUBE) has been found to be efficient in maintaining low PEP while delivering more oxygen as compared to bent conventional tube. Novel mode of tube stabilisation in the form of PUNSTAB is an easy and effective way of tube stabilisation.

A Wearable Functional Near-Infrared Spectroscopy (fNIRS) System for Obstructive Sleep Apnea Assessment.

Obstructive sleep apnea (OSA), one of the most common sleep-related breathing disorders, contributes as a potentially life-threatening disease. In this paper, a wearable functional near-infrared spectroscopy (fNIRS) system for OSA monitoring is proposed. As a non-invasive system that can monitor oxygenation and cerebral hemodynamics, the proposed system is dedicated to mapping the pathogenic characteristics of OSA to dynamic changes in blood oxygen concentration and to constructing an automatic approach for assessing OSA. An algorithm including feature extraction, feature selection, and classification is proposed to signals. Permutation entropy(PE), for quantitative measuring the complexity of time series, is firstly involved to characterize the features of the physiological signals. Subsequently, the principal component analysis (PCA) for feature dimensionality reduction and support vector machine (SVM) algorithm for OSA classification are applied. The proposed method has been validated on a dataset that collected by the wearable system. It includes 40 subjects and composes of normal, and various severity cessation of breathing (e.g., mild, moderate, and severe). Experimental results exhibit that the proposed system can effectively distinguish OSA and non-OSA subjects, with an accuracy of 91.89%. The proposed system is expected to pave the novel perspective for OSA assessment in terms of cerebral hemodynamics.

Body size dictates physiological and behavioural responses to hypoxia and elevated water temperatures in Murray cod (Maccullochella peelii).

Increasing drought frequency and duration pose a significant threat to fish species in dryland river systems. As ectotherms, fish thermal and hypoxia tolerances directly determine the capacity of species to persist in these environments during low flow periods when water temperatures are high and waterbodies become highly stratified. Chronic thermal stress can compound the impacts of acute hypoxic events on fish resulting in significant fish mortality; however, it is not known if all size classes are equally susceptible, or if the allometric scaling of physiological processes means some size classes are disproportionately affected. We investigated the physiological responses of Murray cod (Maccullochella peelii) over a four-fold body size range (0.2-3000g) to acute changes in water temperature and oxygen concentration following 4 weeks of acclimation to representative spring (20°C) and summer (28°C) water temperatures. We recorded maximum thermal tolerance (CT max), oxygen limited thermal tolerance (PCTmax ), lowest tolerable oxygen level (as the oxygen level at which lose equilibrium; O2,LOE), gill ventilation rates and aerial surface respiration threshold, blood oxygen transport capacity and lactate accumulation. Acclimation to elevated water temperatures improved thermal and hypoxia tolerance metrics across all size classes. However, body size significantly affected thermal and hypoxia responses. Small M. peelii were significantly less hypoxia tolerant than larger individuals, while larger fish were significantly less thermal tolerant than smaller fish. Hypoxia constrained thermal tolerance in M. peelii, with both small and large fish disproportionally compromised relative to mid-sized fish. Our findings indicate that both very small/young (larvae, fry, fingerlings) and very large/older M. peelii in dryland rivers are at significant risk from the combined impacts of a warming and drying climate and water extraction. These data will inform policy decisions that serve to balance competing demands on precious freshwater resources.

Examination of effects of indoor fires on building structures and people

The scientific study of the harmful effects of indoor fires on building structures and on the environment is a top issue today. Indoor fires frequently occur all over the world. The goal of our research is to examine the effects of an average room fire on the survival possibility of a trapped person and on the building structure, taking into account features of the Eastern European architecture. First, a computational fluid dynamics (CFD) simulation was performed to examine the change of temperature, oxygen, and carbon monoxide concentration in a selected room in a vacant building used for military training. Based on the results, a 1:1 scale fire experiment was carried out with the parameters used in the simulation. The experiment was repeated once with the same settings. It was observed that without the intervention of firefighters, the temperature in the experiment could have rapidly reached 400 °C, as suggested by the simulation, which could have caused structural damage to the building. Furthermore, after 3 min the carbon monoxide concentration reached 400 ppm in both experiments and the simulation, which is a harmful level to people trapped inside the room. Also, in the experiment there was sufficient oxygen at the ground level with what people can survive 3 min.

Competitive sensitization effect towards Luminescence-tuned Lanthanide-doped TiO2/SiO2 Core-shell nanoparticles for enhanced responsivity oxygen detection

The luminescence of TiO2 doped with Sm3+ can be excited through TiO2 band-to-band absorption, which exhibits oxygen sensitivity. However, its carrier behaviors and oxygen sensing mechanism have not yet been clarified, which inhibits the further improvement of sensitivity. In this study, using Eu3+ ions as an “energy level probe,” we demonstrated a novel strategy using a C@SiO2:2%Sm3+@TiO2 hollow double-shell nanostructure containing surface oxygen vacancies, designated a competitive sensitization effect for the first time. Density-functional theory combined with the experimental results revealed the carrier behaviors and oxygen sensing mechanism. Further, we demonstrated that the charge state of oxygen vacancies is controlled by the adsorption and desorption of dioxygen molecules, which affects electron relaxation and indirectly affects the luminescent behaviors. The effective exploitation of the competitive sensitization effect and revelation of the oxygen sensing mechanism ensured that the excitation of Sm3+ in C@SiO2:2%Sm3+@TiO2 can be controlled by the ambient oxygen concentration. Therefore, compared to the widely reported Sm3+-doped TiO2, C@SiO2:2%Sm3+@TiO2 demonstrated increased oxygen sensitivity (by over three folds) with a detection minimum of sub-100 ppm. Moreover, as ambient oxygen concentration changes, the luminescence color of the films prepared by using C@SiO2:2%Sm3+@TiO2 and commercial blue phosphors changes significantly (from pink to blue).

Microstructure and Formation Mechanisms of Nanowires and Nanoplates ZrO&lt;sub&gt;2&lt;/sub&gt; during the ZrB&lt;sub&gt;2&lt;/sub&gt; Deposition Process

Preparation of boride by chemical vapor deposition (CVD) is sensitive to oxygen, subtle changes in oxygen concentration during the deposition of ZrB2 can induce the formation of Zirconium dioxide (ZrO2) with a novel nanoplate-stacked structure and nanowire structure. The ZrO2 nanostructure changed with - oxygen concentration. Nanowires with uniform size of 50-100 nm in diameter and over 100 μm in length were obtained at high oxygen concentration, while highly-ordered nanoplate arrays were obtained at low oxygen concentration. Both of these nanostructures were grown in situ on the surface of ZrB2-coating. In this paper, the preparation method of novelty ZrO2 nano-structures grown in situ was provided, the morphologies and compositions of the nano-structural ZrO2 were characterized and the formation mechanism was proposed, which also provides experimental basis for the industrial morphology control of ZrB2 deposited by CVD method.

High temperature thermographic phosphors YAG:Tm;Li and YAG:Dy in reduced oxygen environments

Phosphor thermometry for surface temperature measurements has become an established remote thermometry technique. However, measuring at temperatures above 1700 K is still challenging because of the weak phosphorescence and intense background from black-body radiation, leading to low signal-to-noise ratios. Therefore, lifetime-based phosphor thermometry with YAG:Tm;Li and YAG:Dy for high-temperature applications were investigated in this study with the aim of improving the precision of high-temperature measurements. The phosphors were coated on an alumina-oxide disc, which was placed in a temperature-controlled oven that exposed the phosphors to temperatures of up to 1930 K. The emission spectra and temporal decay of the luminescence were recorded for the investigated phosphors including their sensitivity to oxygen concentration in the gas environment. Knowledge of oxygen environment sensitivities for measurements of reduced oxygen concentrations at high temperatures, such as in combustion, is of great importance to increase confidence in the measurement. The results suggest that performing a mono-exponential decay time fit in a region of the decay curve that is dominated by a single lifetime component reduces the sensitivity to changes in the gas oxygen concentration for YAG:Tm;Li. Moreover, YAG:Tm;Li performs better than YAG:Dy in terms of signal-to-noise ratio (SNR), with a peak signal value and SNR almost an order of magnitude higher. With an appropriate decay curve fitting procedure, the effects of oxygen quenching can be minimized, such that the measurement error due to oxygen quenching is within the measurement precision for both phosphors.