Showing papers on "Vapours published in 2014"

Conducting polymer–carbon black nanocomposite sensor for volatile organic compounds and correlating sensor response by molecular dynamics

Abstract: Volatile organic compounds (VOCs) are present in our every day used products such as plastics, cosmetics, air fresheners, paint, etc. The determination of amount of VOC present in atmosphere can be carried out via various sensors. In this work a nanocomposite of a novel thiophene based conducting polymer and carbon black is used as a volatile organic compound sensor. The fabricated 2 lead chemiresistor sensor was tested for vapours of toluene, acetone, cylcohexane, and carbon tetrachloride. The sensor responds to all the vapours, however, exhibit maximum response to toluene vapours. The sensor was evaluated for various concentrations of toluene. The lower limit of detection of the sensor is 15 +/- 10 ppm. The study of the effect of humidity on senor response to toluene showed that the response decreases at higher humidity conditions. The surface morphology of the nanocomposite was characterized by scanning electron microscopy. Diffuse reflectance spectroscopy was used to investigate the absorption of vapours by the nanocomposite film. Contact angle measurements were used to present the effect of water vapour on the toluene response of nanocomposite film. Solubility parameter of the conducting polymer is predicted by molecular dynamics. The sensing behaviour of the conducting polymer is correlated with solubility parameter of the polymer. Dispersion interaction of conducting polymer with toluene is believed to be the reason for the selective response towards toluene. (C) 2014 Elsevier B.V. All rights reserved.

Acetone and ethanol sensing characteristics of magnesium zinc ferrite nano-particulate chemi-resistive sensor

Abstract: In the present work, acetone and ethanol sensing characteristics of wet chemically prepared magnesium zinc ferrite (MZFO) nano-particles have been investigated. X-ray diffraction and electron microscopy studies are carried out to know the phase formation behaviour and microstructure evolution of the synthesized particles. The gas sensing characteristics (response %, response time, recovery time, etc.) are estimated by varying the operating temperature of the sensor and concentrations of the test vapours. It is observed that the nanocrystalline MZFO-based sensor is more sensitive to acetone than ethanol. In addition, the sensor can detect even 10 ppm of acetone and ethanol vapours. The excellent repeatability of the sensing performances is verified by switching the sensor back and forth between air and test vapours.

SOSAA – A new model to simulate the concentrations of organic vapours, sulphuric acid and aerosols inside the ABL – Part 2

Abstract: Natural and anthropogenic aerosols may have a great impact on climate as they directly interact with solar radiation and indirectly affect the Earth’s radiation balance and precipitation by modifying clouds. In order to quantify the direct and indirect effects, it is essential to understand the complex processes that connect aerosol particles to cloud droplets. Modern measurement techniques are able to detect particle sizes down to 1 nm in diameter, from ground to the stratosphere. However, the data are not sufficient in order to fully understand the processes. Here we demonstrate how the newly developed one-dimensional column model SOSAA was used to investigate the complex processes of aerosols at a boreal forest site for a six-month period during the spring and summer of 2010. Two nucleation mechanisms (kinetic and organic) were tested in this study, and both mechanisms produced a good prediction of the particle number concentrations in spring. However, overestimation of the particle number concentration in summer by the organic mechanism suggests that the OH oxidation products from monoterpenes may not be the essential compounds in atmospheric nucleation. In general, SOSAA was correct in predicting new particle formation events for 35% of the time and partly correct for 45% of the time.

Development of ITO thin film sensor for the detection of formaldehyde at room temperature

Abstract: Thin films of indium tin oxide were grown by the direct evaporation technique. The sensors fabricated under the optimized deposition conditions were exposed at room temperature (303 K) to different concentrations of formaldehyde vapours and the relative change in resistance was measured. The effect of the film thickness on the response to test vapours was studied. In order to enhance the sensitivity, sensors with thin promoting layers of different metals and oxide like Cu, Ag and MgO deposited on the top of the film were fabricated and tested. The sensors with improved sensitivity were studied for the elaborate response to formaldehyde vapours at room temperature.

Aliphatic amines vapours detection by quartz crystal microbalance sensor

Abstract: Polymerized castor oil based quartz crystal microbalance (QCM) sensors are fabricated for the detection of aliphatic amines vapours. The sensors are fabricated by solution dip-dry method followed by heating at 100 °C under argon atmosphere to get cross linked film on QCM surface. A series of sensors with various weight percentages of benzoyl peroxide added to the solution are fabricated for the optimization of the sensitivities of the polymeric films. It is found that the sensor fabricated with a solution having 1.40% (w/v) of benzoyl peroxide has high sensitivity for vapours of organic compounds and are very effective for aliphatic amines vapours. The adsorption of the vapours to the surface of the QCM sensor is determined by the frequency shift of QCM. The frequency shift linearly increases with the gas vapour concentrations from 5 to 250 ppm at room temperature. The sensitivity-values of methylamine, ethylamine, tert-butylamine, diethylamine, triethylamine and ammonia vapours are 0.917, 0.657, 0.655, 0.543, 0.407 and 0.397 Hz/ppm respectively. The structure of the polymeric film is studied by FTIR spectra. The surface morphologies of the QCM sensor before and after gas adsorption are characterized by AFM, which indicates mild swelling of the surface after adsorption and it is reversible.

Oxidation of volatile organic compound vapours by potassium permanganate in a horizontal permeable reactive barrier under unsaturated conditions: experiments and modeling

Abstract: In this research we evaluated the potential of using solid potassium permanganate to create a horizontal permeable reactive barrier (HPRB) for oxidizing VOC vapours in the unsaturated zone. We have performed batch experiments, short column, and long column experiments, and have fully analyzed the data. In the batch experiments, we investigated the ability of potassium permanganate to fully oxidize three selected target compounds, namely, trichloroethylene (TCE), toluene, and ethanol. We also determined kinetic parameters for their oxidation reactions in both gas and water phases. Results for both phases showed that oxidation rate decrease in the order TCE>ethanol>toluene. In addition, the determined reaction rate constants for target compounds in the vapour phase were found to be much smaller than for aqueous phase. In short column experiments, VOC vapours arising from a liquid pool of a target compound were allowed to diffuse through a one-centimeter thick layer of mixed sand and potassium permanganate, representing a horizontal permeable reactive barrier (HPRB) and become accumulated in the headspace above the layer. Through analyzing the headspace concentration, we determined the capability of the layer to oxidize VOC vapours. We observed a high removal efficiency and reactivity of the HPRB for all target compounds at the highest water saturation (Sw=0.6). The change in pH was found to be a main reason for the reduction in the oxidation rate VOC in the HPRB.Results showed that adding carbonate minerals into initial HPRB increases the longevity of potassium permanganate during the oxidation of TCE vapour by buffering the pH. Furthermore, we found that the negative effect of low pH on the reactivity of the HPRB was mitigated by adding water during the TCE experiment.A developed model for reactive vapour transport, which included pH-dependent oxidation rates, was able to simulate the experimental data for TCE, toluene, and ethanol. With increasing water contents, an increasing discrepancy between the simulation results and experimental data was found for ethanol. The total oxidized mass of ethanol vapour was found to be higher than TCE and toluene for identical water saturations, despite a larger oxidation rate constant for TCE than for ethanol and toluene. To test the effectiveness of the HPRB under situations similar to field conditions, we performed larger column experiments. In this setup, we investigated the effects of the thickness of HPRB and the elevation of the HPRB layer above the groundwater table on the reactivity of HPRB. Results suggest that the thickness of the HPRB was a very important factor in oxidizing VOC vapours. We further found that the location of the HPRB relative to the water table, and consequently its background water saturation, had a strong effect on the removal capacity of the HPRB. A rough estimate of the longevity shows that HPRB could be a viable option for preventing VOC vapours to reach indoor spaces.

Możliwości zdalnego wykrywania par alkoholu w kabinie pojazdu

Abstract: Investigations of the developed model of the device for stand-off detection of alcohol vapours were carried out To simulate the car cabins special glass tubes were used Concentrations of the examined vapours in the tubes corresponded to the concentrations exhaled by a person under the influence of alcohol To simulate appropriate concentration of the alcohol vapours a special device was built (Possibilities of stand-off detection of alcohol in car cabins)

Breakdown voltage of zinc and magnesium vapours

Abstract: In this paper the findings of a study into the electrical breakdown of zinc and magnesium metal vapours are reported. The interest in the breakdown of these vapours lies in the fact that there is a growing interest in producing zinc?magnesium coated articles using physical vapour deposition. For commercial scale operations which require a high power input, a disturbance by electrical breakdown of the metal vapour is unacceptable. Hence, knowledge of the breakdown voltage and pressure relation of these elements is essential in the engineering of a set-up.To determine the breakdown of these metal vapours, a Knudsen effusion cell is built. It is proven that the flow through the Knudsen cell does not change the minimum breakdown voltage or location of this minimum, and is a reliable apparatus for determining the zinc and magnesium vapour data. The outcome of the experiments show that the minimum breakdown for zinc is in agreement with the reported data in the literature, around 350?V. Magnesium has a much lower minimum breakdown voltage than that found for zinc, around 110?V. Furthermore, the locations of the minimum breakdown voltages of both zinc and magnesium are found at around 4?7?Pa?m and 1.5?Pa?m respectively.

Electric sensor for hydrazine vapours

Abstract: FIELD: chemistry.SUBSTANCE: electric sensor for hydrazine vapours contains a dielectric substrate, on which placed are: electrodes and a sensitive layer, which changes photoconductivity as a result of hydrazine vapour adsorption; the sensitive layer consists of the following structure - graphene-semiconductor quantum dots, whose photoconductivity decreases when hydrazine molecules are adsorbed on the surface of quantum dots proportionally to the concentration of hydrazine vapour in a sample. If hydrazine vapours are present in the air sample, hydrazine molecules are adsorbed on the surface of quantum dots, decreasing intensity of quantum dot luminescence, which results in decrease of graphene conductivity proportionally to the concentration of hydrazine vapours in the analysed sample.EFFECT: increase of sensitivity, decrease of determination sluggishness and simplification of the sensor manufacturing.1 ex, 7 dwg

Study the Sensitivity of Quartz Crystal Microbalance (QCM) Sensor Coated with Different Thickness of Polyaniline for Determination Vapors of Ether, Chloroform, Carbon tetrachloride and Ethyl acetate

Abstract: A quartz crystal microbalance (QCM) sensor coated with a thin film of polyaniline was used as a sensitive method for the determination of a number of following vapours: Ether, Chloroform, Carbon tetrachloride and Ethyl acetate. The detection was based on the absorption of the vapours of these organic compounds into the film by using gas cell chamber. The detection of these vapours can be obtained in part per million (ppm). The work includes the use of polyaniline films with different thickness (55, 82, 102 and 153) nm where thickness of the PANI films was controlled by the spin coating process. Results show that increasing of sensitivity with increase of the concentration of injected analyte when the PANI-film-coated QCM was exposed to the vapours of ethanol, propanol hexane and benzene. Best sensitivity to ethanol and hexane were obtained with film thicknesses 93nm while in the case of propanol best results were obtained with thickness of 118 and 93 nm. Thickness of 93 and 176 nm gave good sensitivity to benzene. Keywords: QCM, Polyaniline, Vapors, Sensor, Thickness .

Production of silicon with the use of aluminium subchloride

Abstract: FIELD: metallurgy.SUBSTANCE: proposed method comprises reduction of silicon from vapours of silicon compounds with chlorine or silicon with chlorine and hydrogen at mixing of said vapours with vapours of lower aluminium chlorides at 1000-1250°C in transfer gas flow. Said gas represents the mix of hydrogen with argon or the mix of hydrogen with helium containing 2-20 molar parts of hydrogen per one part of silicon compounds vapours. Note here that aluminium lower chlorides of required purity are produced from aluminium metal of 99.0-99.8% purity and gaseous aluminium trichloride or hydrogen chloride or chlorine by multiple reiteration of sublimation and decomposition of formed lower aluminium chlorides. Note also that precipitated silicon crystals are subjected to heat treatment at above 577°C and less than 1400°C, processed by hydrochloric acid and subjected to refining remelting.EFFECT: higher purity of silicon, lower production costs.2 dwg, 4 ex

Method for obtaining gas-sensitive material based on zinc oxide to acetone vapours

Abstract: FIELD: nanotechnologies.SUBSTANCE: according to the invention, a method for obtaining material based on zinc oxide, which is sensitive to acetone vapours, consists in preparation of sol by dilution of non-organic zinc salt in alcohol, in addition of tetraethoxy silane, distribution of sol along a substrate surface, annealing and processing of the obtained material by action on it of a flow of electrons accelerated up to energy of 540-900 keV at absorbed dose of 25-200 kGy.EFFECT: invention allows increasing sensitivity of material to acetone vapours.2 ex, 2 tbl

Portable Sensing of Organic Vapours based on a Single Semiconductor Sensor

Abstract: A notable need for lightweight, simple-to-use portable gas analysers with facilities aimed at wide range of applications is observed in the market of measuring instruments today. In this work, a concept of portable sensing of organic vapours is presented. As the most reliable, the semiconductor gas sensor technology was chosen. However, due to high power consumption of this kind of sensors only a single sensor option is currently feasible for the portable device. In view of partial selectivity of the metal oxide based gas sensors, the unsatisfactory analytical abilities of the device could be anticipated. But, we showed that a single semiconductor gas sensor may be used for identification and quantification of the organic compounds vapours. In our solution, this goal is accomplished by applying active gas sampling. It was demonstrated that variable exposure conditions of a sensor, which are induced by the gas flow, allow for obtaining the sensor signal that has high information content. It is sufficient to characterize the test gases qualitatively and quantitatively. The achieved accuracy is very good for a screening device.

System and method for treatment of flash vapours sent to a crude distillation column

Abstract: A system and method for treatment of crude hydrocarbon vapours generated from a pre-flash drum, prior to sending these vapours to a distillation column, is disclosed. The crude hydrocarbon vapours are cooled and condensed in a condenser unit, and the immiscible phases are separated in a separator unit into an aqueous phase, a liquid hydrocarbon phase, and a light hydrocarbon containing vapour phase. The light hydrocarbon containing vapour phase and the immiscible liquid hydrocarbon phase are conveyed to the distillation column, whereas the immiscible phase may be further treated to remove dispersed water droplets. Water and salts are removed from the vapours which reduces the water dew point as well as NH 4 C1 de-sublimation temperature at the column overheads. The system and method thereof reduce corrosion problem in the distillation column and simultaneously provide favorable product slate from the given crude blend.

Method of methanol recovery from gas-vapour mixture at its storage and transshipment

Abstract: FIELD: oil and gas industry.SUBSTANCE: invention is related to the method of methanol recovery from gas-vapour mixture at its storage and transhipment and may be used in chemical industry, petrochemical industry, oil and gas producing and processing industries. The method includes extraction of vapours from the gas-vapour mixture in the plant vessel, cooling of the gas-vapour mixture and condensation of vapours in the vapour-condensing unit, condensate return to the vessel and emptying of the vessel. At that cooling of the gas-vapour mixture in the vapour-condensing unit consisting of a vessel for cooled methanol and a packed column installed on it is made to counter-flow interaction of the gas-vapour mixture containing vapours of methanol cooled up to the temperature within the range of minus 25 up to minus 36°C at pressure close to atmosphere pressure when condensed methanol is returned to the vessel for cooled methanol.EFFECT: method allows increasing quality of storage due to recovery and return of methanol vapours to the vessel.1 dwg, 1 tbl