Effect of Water-Vapor Content on Reaction Rate of Hexagonal BN Powder at 1273 K

2013 ◽  
Vol 32 (3) ◽  
pp. 275-280 ◽  
Author(s):  
Ziyou Yu ◽  
Xinmei Hou ◽  
Zhiyuan Chen ◽  
Kuo-Chih Chou
Keyword(s):  
Weight Loss ◽  
Water Vapor ◽  
Reaction Rate ◽  
Average Particle Size ◽  
Water Vapor Content ◽  
Main Reaction ◽  
Average Particle ◽  
Volatile Product ◽  
Two Stages

AbstractHexagonal BN powder with average particle size of 1.2 µm was exposed at 1273 K in H2O/air gas mixture with the range of mass ratio from 0:100 to 6.5:100 at a total pressure of 1 atm. Thermalgravimetry (TG) method was used to measure the reaction behavior of BN powder in water vapor. XRD and SEM were employed to analyze the phases and morphological revolution during reaction. The TG curves showed that the overall reaction process could be divided into two stages. In first stage, weight gained rapidly and the main reaction was the oxidation of BN. The weight gain turning point of the curves with different water-vapor contents varied, indicating that water-vapor had an impact on oxidation rate to some degree. In second stage, weight loss due to B2O3 reacting with H2O to form volatile product. The rate of weight loss increased with increasing the water vapor content. The reaction rate was described by a linear rate law, i.e., α = −klt. The relationship between kl and partial pressure of water vapor p was described by a function of kl = 0.4p. The determination of the activation energy was complicated due to variations in the reaction mechanism.

A New Method for Direct Determination of the Recoilless Fraction with Application to Magnetic Nanoparticles

2002 ◽  
Vol 721 ◽  
Author(s):  
Monica Sorescu
Keyword(s):  
Room Temperature ◽  
Average Particle Size ◽  
Direct Determination ◽  
Average Particle ◽  
Lattice Method ◽  
Recoilless Fraction ◽  
Single Room ◽  
Magnetite Particles ◽  
Physical Mixtures

AbstractWe propose a two-lattice method for direct determination of the recoilless fraction using a single room-temperature transmission Mössbauer measurement. The method is first demonstrated for the case of iron and metallic glass two-foil system and is next generalized for the case of physical mixtures of two powders. We further apply this method to determine the recoilless fraction of hematite and magnetite particles. Finally, we provide direct measurement of the recoilless fraction in nanohematite and nanomagnetite with an average particle size of 19 nm.

Synthesis and Electromagnetic Properties of Hollow Ceramic Microspheres

2011 ◽  
Vol 492 ◽  
pp. 260-263 ◽  
Author(s):  
Bao Cai Xu ◽  
Jian Jiang Wang ◽  
Rong Xia Duan ◽  
Xing Jian Huo
Keyword(s):  
Reflection Loss ◽  
Structural Characteristics ◽  
Average Particle Size ◽  
Coaxial Line ◽  
Electromagnetic Properties ◽  
Flame Spraying ◽  
Average Particle ◽  
Composite Powders ◽  
Composite Microspheres

The hollow ceramic microspheres were prepared by Self-reactive flame spraying method. The structural characteristics and morphology properties of the composite powders were obtained by XRD and SEM. The results show that the obtained particles are hollow ceramic microspheres. The average particle size is about 30μm. An analytical method for the determination of electromagnetic parameters (ε, μ) of materials under test is presented by the analysis of normalized general matrix of equivalent network of coaxial line filled with samples. The analysis of vector network analyzer show that reflectance of hollow composite microspheres could well absorb microwaves in 2-18 GHz. The reflection loss is less than -l0dB in the range of 12.4 to15.2GHz while the minimum reflection loss is -18.5dB at 13.6GHz.

scholarly journals Analysis of the application of the optical method to the measurements of the water vapor content in the atmosphere – Part 1: Basic concepts – the measurements of the water vapor content in the atmosphere with the optical method

2010 ◽  
Vol 3 (6) ◽  
pp. 5705-5741
Author(s):  
V. D. Galkin ◽  
F. Immler ◽  
G. A. Alekseeva ◽  
F.-H. Berger ◽  
U. Leiterer ◽  
...  
Keyword(s):  
Water Vapor ◽  
Optical Method ◽  
Measurement Errors ◽  
Total Content ◽  
Water Vapor Content ◽  
Optical Photometry ◽  
Power Approximation ◽  
Meteorological Observatory ◽  
Total Column

Abstract. We retrieved the total content of the atmospheric water vapor from extensive sets of photometric data obtained since 1995 at Lindenberg Meteorological Observatory with star and sun photometers. Different methods of determination of the empirical parameters that are necessary for the retrieval are discussed. The instruments were independently calibrated using laboratory measurements made at Pulkovo Observatory with the VKM-100 multi-pass vacuum cell. The empirical parameters were also calculated by the simulation of the atmospheric absorption by water vapor, using the MODRAN-4 program package for different model atmospheres. The results are compared to those presented in the literature, obtained with different instruments and methods of the retrieval. The accuracy of the empirical parameters used for the power approximation that links the water vapor content with the observed absorption is analyzed. Currently, the calibration and measurement errors yield the uncertainty of about 10% in the total column water vapor. We discuss the possibilities for improving the accuracy of calibration to ~1%, which will make it possible to use data obtained by optical photometry as an independent reference for other methods (GPS, lidar, etc).

scholarly journals Electrochemical Biosensor Based on Furosemide-Gold Nanoparticles for The Determination of Dopamine for Practical Applications

2021 ◽  
Vol 5 (1) ◽  
Keyword(s):  
Gold Nanoparticles ◽  
Average Particle Size ◽  
Average Particle ◽  
Limit Of Quantification ◽  
Strong Absorption Band ◽  
Amperometric Determination ◽  
Practical Applications ◽  
Vis Spectroscopy ◽  
The One

In this study, by taking the advantage of the facile & controlled synthesis of furosemide derived gold nanoparticles (Fr-AuNps) for rapid and sensitive amperometric determination of dopamine (DP). The one-step synthesis of FrAuNps was carried out at room temperature without the use of strong reducing agents. The synthesized Fr-AuNps were studied by UV-Vis spectroscopy, and a strong absorption band for gold nanoparticles was observed at 520 nm. Transmission electron micrographs (TEM) revealed the average particle size below 100 nm. HRTEM showed excellent crystalline features as prepared gold nanoparticles. The electrochemical behavior of gold nanoparticles was examined by cyclic voltammetry (CV) which demonstrated the enhanced electrocatalytic kinetics activity towards the oxidation of dopamine. The presented dopamine biosensor exhibited a linear response for the dopamine in the range of 0.25 to 7 µM. The calculated the detection limit found to be 18.3 nM and limit of quantification 61.5 nM respectively. The proposed dopamine biosensor was successfully employed for the quantification of trace amount of dopamine from human serum and the obtained results are very satisfactory.

scholarly journals Adsorption-Semiconductor Sensor Based on Nanosized SnO2 for Early Warning of Indoor Fires

2021 ◽  
Author(s):  
Nelli Maksymovych ◽  
Ludmila Oleksenko ◽  
George Fedorenko
Keyword(s):  
Tin Dioxide ◽  
Early Stage ◽  
Dynamic Properties ◽  
Sol Gel ◽  
Average Particle Size ◽  
High Sensitivity ◽  
Average Particle ◽  
Semiconductor Sensor ◽  
Wide Range

The paper is devoted for a solution of indoors fires prevention at early stage by determination of H2 (fire precursor gas) in air using a semiconductor sensor. A material based on Pt-containing nanosized tin dioxide with an average particle size of 10–11 nm obtained via a sol–gel method was created for a gas sensitive layer of the sensor. The developed sensor has high sensitivity to H2 micro concentration, a wide range of its detectable content in air, selectivity of H2 measuring in the presence of СО and СН4, good dynamic properties. The combination of these properties is very important for prevention of inflammations on their early stages before the open fires appearance. Economic benefit of the proposed sensor is due to a lower cost and higher reliability of the fire situation detection.

The determination of the total atmospheric water vapor content over the oceans using the MTVZA-GY microwave radiometer measurements

2020 ◽  
pp. 83-98
Author(s):  
Анжелика Андреевна Косторная ◽  
Алексей Николаевич Рублев ◽  
Владимир Викторович Голомолзин
Keyword(s):  
Water Vapor ◽  
Approximation Error ◽  
Water Vapor Content ◽  
Atmospheric Water Vapor ◽  
Microwave Range ◽  
Adaptive Search ◽  
Atmospheric Water ◽  
Water Vapor Absorption ◽  
Optimal Set

Представлена методика определения интегрального влагосодержания в безоблачной атмосфере над океанскими и морскими акваториями по измерениям микроволнового радиометра МТВЗА-ГЯ, устанавливаемого на российских гидрометеорологических спутниках серии “Метеор-М”. Определение влагосодержания осуществляется с помощью регрессий, предикторами которых являются измеренные интенсивности излучения в выбранных каналах радиометра. В их число могут входить каналы с рабочими спектральными диапазонами внутри и вне полос поглощения водяного пара. Адаптивный поиск оптимального набора каналов для различных районов земного шара проводится в зависимости от типа поверхности и климатической зоны. Критерием выбора каналов и вида регрессии является минимальная среднеквадратичная невязка получаемых оценок влагосодержания атмосферы с контрольными значениями, рассчитанными по данным реанализа Национального центра экологического прогнозирования (NCEP) и специальных атмосферных моделей, разработанных в Европейском центре среднесрочных прогнозов погоды (ECMWF) The determination of the total atmospheric water vapor content over the cloudless ocean using the MTVZA-GY measurements in microwave range is described. The microwave scanning radiometer MTVZA-GY is located on the Russian meteorological satellites “Meteor-M” and outgoing radiation of the surface-atmosphere system is measured in 29 channels. To calculate the integrated water vapor, the adaptive searching of the optimal set of channels using regression analysis was proposed. Frequencies that are not related to water-vapor absorption lines are used as predictors. The minimum of total approximation error was obtained for selected channels and corresponding regression coefficients values. The quality control of retrieval integrated water vapor (kg/m) was conducted with the help of the set of atmospheric profiles obtained by M. Matricardi and NCEP/NCAR Reanalysis as a priori data using the proposed method. Standard deviations (RMS) obtained by determined adaptive search for the predictors are about 3 kg/m2. Application of the method for cloudless water areas allowed finding a set of 6 channels MTVZA GY (18.7H, 23.8V, 23.8H, 57+0.32+0.025H, 57+0.32+0.01H и 183+1.4V) for which the RMS values are minimal - 4.4 kg/m. The use of all channels of the device in the search allows reducing the error in determining the integrated water vapor content. The proposed method for recovering the content of water vapor from measurements in the channels of the MTVZA-GYa device allows an adaptive search for an optimal set of channels for different regions of the globe and find the best combinations for various climatic zones and surface types

Determination of the atmospheric-water-vapor content in the 940-nm absorption band by use of moderate spectral-resolution measurements of direct solar irradiance

1998 ◽  
Vol 37 (21) ◽  
pp. 4678 ◽  
Author(s):  
Victoria E. Cachorro ◽  
Pilar Utrillas ◽  
Ricardo Vergaz ◽  
Plinio Durán ◽  
Angel M. de Frutos ◽  
...  
Keyword(s):  
Water Vapor ◽  
Absorption Band ◽  
Spectral Resolution ◽  
Solar Irradiance ◽  
Water Vapor Content ◽  
Atmospheric Water Vapor ◽  
Atmospheric Water

Determination of Latex Particle Size Distributions by Fractional Creaming with Sodium Alginate

1961 ◽  
Vol 34 (2) ◽  
pp. 433-445 ◽  
Author(s):  
E. Schmidt ◽  
P. H. Biddison
Keyword(s):  
Particle Size ◽  
Electron Microscope ◽  
Sodium Alginate ◽  
Mass Distribution ◽  
Average Particle Size ◽  
Average Particle ◽  
Particle Sizes ◽  
Size Distributions ◽  
Particle Size Distributions

Abstract Knowledge of mass distribution of particle sizes in latex is very important to the latex technologist. Therefore, it is desirable to have available a simple method for the determination of mass distribution of particle sizes. This paper presents a method, based on fractional creaming of latex with sodium alginate, which can be used in any laboratory without special equipment. The method is particularly advantageous for analyzing latexes of very wide particle size distributions. When analyzed with an electron microscope, these latexes require counting a very large number of particles. McGavack found that partial creaming of normal hevea latex with ammonium alginate gives concentrates of larger average particle size than the original latex. He found that the average particle size in the cream approaches that of the original latex as the amount of creaming agent is increased. In a previous paper from this laboratory, Schmidt and Kelsey demonstrated that the phenomenon of fractionation according to particle size with increasing amounts of creaming agent is applicable in a wide variety of anionic latex systems and in colloidal silica. Their results indicated also the existence of a quantitative relationship, independent of the nature of the dispersed particles, between the concentration of creaming agent and size of creamed particles. Maron confirmed fractionation with respect to particle size as a consequence of partial creaming with alginate. He showed that the mass average particle sizes of fractions, determined optically, cumulate to that of the original latex. Although the previous paper by Schmidt and Kelsey implied the basic concept of a method of determining particle size distribution by fractional creaming, it was not exploited at that time. In order to adapt the fractional creaming phenomenon to a quantitative method for particle size determination, we required a more precise knowledge of the relation between creaming agent concentration and size of particles creamed. It was proposed to establish this relationship with the aid of the electron microscope. Various factors influencing the creaming of latex, such as polymer concentration, electrolyte, soap content, and variability of the creaming agent, had to be considered in standardizing the creaming procedure.

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