Search results for "Gravimetric analysis"
showing 10 items of 264 documents
Diffusion technique for the generation of gaseous halogen standards
2009
Abstract Halogens are known to play an important role in the tropospheric ozone-depletion chemistry and are of special interest because of their influence on the atmospheric oxidation capacity. In this paper, we investigate the application of a capillary diffusion technique for the generation of gaseous halogen standards like Br 2 , IBr, ICl and I 2 . The influence of capillary dimension (i.e. length and inner diameter), ambient pressure and headspace volume of the diffusion vessel on the test gas output has been evaluated. The experimental output rates are determined from the mass loss of the analyte vessel on a regular schedule and compared with their respective theoretical predictions. W…
Direct gravimetric sensing of GBL by a molecular recognition process in organic cage compounds.
2013
Organic cages were identified as highly potent affinity materials for the tracing of γ-butyrolactone. The selectivity over ethanol and water is based on the interior functional groups which allow preferential hydrogen bonding to the target analyte.
Study of phase composition, photocatalytic activity, and photoluminescence of TiO2 with Eu additive produced by the extraction-pyrolytic method
2021
The Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART2. The work was also partially supported by the LZP grant 2020/2-0074. R. Burve has been supported by the project “Synthesis of nanostructured materials based on titanium dioxide and tin dioxide and investigation of their physicochemical properties” Nr. MP-2019/7, for strengthening scientific personnel capacity 2019/2020 at the Riga Technical University. Authors are grateful to Dr. K. Šmits for the microscopic measurements and SEM images.
Sol-gel derived anatase TiO2: morphology and photoactivity
1994
Abstract High-surface area TiO 2 (anatase) was prepared by the sol-gel method and characterized by various instrumental and analytical methods, including X-ray diffraction, thermogravimetric analysis, infrared spectroscopy, porosimetry, specific surface area measurements, scanning electron microscopy, and titration of surface hydroxyl groups. The specimen was tested for photodegradation of phenol and nitrophenols carried out in aqueous suspension at pH = 3; photoactivity was compared with that of commercially available anatase TiO 2 . Results are discussed in terms of porosity, surface area, and availability and population of surface OH groups, consequent upon the particular method used for…
Sorption of argon and nitrogen on network types of zeolites and aluminophosphates
1991
Abstract Synthetic zeolites and aluminophosphates comprising 10- and 12- membered ring openings, unidimensional and network type of pore systems (MFI, MEL, ERI, LTA, AEL, AFI and FAU) were used as model adsorbents to examine the impact of micropore structure on the sorption properties. Argon and nitrogen were employed as adsorptives. Adsorption measurements were carried out on gravimetric and volumetric sorption devices and also monitored by microcalorimetry. From the low coverage regime of the isotherm Henry's constants and isosteric heats of adsorption were derived. Both quantities allowed the discrimination between 10- and 12- membered ring systems. Unidimensional 10- and 12- membered ri…
Influence of soil water content on the thermal infrared emissivity of bare soils. Implication for land surface temperature determination.
2007
[1] The influence of soil water content in thermal infrared emissivity is a known fact but has been poorly studied in the past. A laboratory study for quantifying the dependence of emissivity on soil moisture was carried out. Six samples of surface horizons of different soil types were selected for the experiment. The gravimetric method was chosen for determining the soil moisture, whereas the emissivity was measured at different soil water contents using the two-lid variant of the box method. As a result, the study showed that emissivity increases from 1.7% to 16% when water content becomes higher, especially in sandy soils in the 8.2–9.2 μm range. Accordingly, a set of equations was deriv…
Estimation of volume fraction and gravimetric moisture of winter wheat based on microwave attenuation: a field scale study
2019
A considerable amount of water can be stored in vegetation, especially in regions experiencing large quantities of precipitation (mid-latitudes). In this context, an accurate estimate of the actual water status of the vegetation could lead to an improved understanding of the effect of plant water on the water budget. In this study, we developed and validated a novel approach to retrieve the vegetation volume fraction (δ) (i.e., volume percentage of solid plant material of a canopy in air) and the gravimetric vegetation water content (m g ) (i.e., amount of water per wet biomass) for winter wheat. The estimation was based on the attenuation of L-band microwave measurements through vegetation…
Sensor Properties of Pristine and Functionalized Carbon Nanohorns
2016
Nanodispersions of pristine single-wall carbon nanohorns (i.e., p-SWCNHs) and oxidized-SWCNHs (i.e.; o-SWCNHs) were used to modify screen printed electrode (SPE). p-SWCNHs and o-SWCNHs were fully characterized by using several analytical techniques, as: HR-TEM (High Resolution-Transmission Electron Microscopy), FE-SEM/EDX (Field Emission-Scanning Electron Microscopy/Energy Dispersive X-ray Analysis), Raman spectroscopy, thermogravimetric analysis, differential thermal analysis (DTA), and the Brunauer-Emmett-Teller (BET) method. The chemically modified SPEs were also characterized with Cyclic Voltammetry (CV), using several different electro-active targets. In all cases, p-SWCNHs showed bett…
Investigation of characterizing methods for the microstructure of cement
2002
Volumetric, gravimetric, calorimetric, flow methods, mercury porosimetry and laser granulometry were used to investigate the surface structure and the sorption behavior of industrial cements and hydrated cement paste. The suitability of the measuring methods is assessed.
Thermal analyses of commercial magnesium stearate pseudopolymorphs
2005
Abstract Two commercial magnesium stearate powders in two well-characterised structural states are investigated using DSC and coupled TGA–DTA under dry nitrogen flow. They consist of either a mixture of crystalline hydrates or a poorly crystallised so-called anhydrate. Following the degassing of unbound water, 1 or 3 weight-loss peaks are observed below about 100 °C, each associated with one heat loss peak at the same temperature. The present results and a review of graphical data from literature show that the so-called anhydrate always contains a significant amount of water. At the beginning of the dehydration process, the heat loss is the same as the standard heat of vaporisation of water…