On the morphological properties of tungsta-titania de-NOxing catalysts

1993 ◽  
Vol 8 (8) ◽  
pp. 2019-2025 ◽  
Author(s):  
C. Cristiani ◽  
M. Bellotto ◽  
P. Forzatti ◽  
F. Bregani
Keyword(s):  
Surface Area ◽  
Mercury Porosimetry ◽  
Microstructural Analysis ◽  
Laser Raman Spectroscopy ◽  
Morphological Properties ◽  
X Ray Diffraction ◽  
Laser Raman ◽  
Surface Hydroxyls ◽  
Different Temperatures ◽  
Adsorption Of Water

Tungsta-titania samples with different W loadings up to 15 wt.% and calcined at different temperatures have been prepared and characterized by surface area measurements, mercury porosimetry, x-ray diffraction, microstructural analysis, and laser Raman spectroscopy. It has been found that W inhibits the initial sintering of TiO2 (anatase) and the anatase → rutile transformation. The morphological and structural properties of the samples (surface area, porosity, and phase composition) have been related to the microscopic properties of the materials such as crystallite dimensions and defects concentration. A model for the sintering of TiO2 is discussed. This model is based on the diffusion of surface hydroxyls, formed upon adsorption of water on surface oxygen vacancies. A role for W is proposed in terms of stabilization of both material defects and surface hydroxyls.

scholarly journals Influence of thermal treatment and combustible additives on properties of Latvian clay ceramics pellets

2013 ◽  
Vol 7 (4) ◽  
pp. 175-180 ◽  
Author(s):  
Liga Dabare ◽  
Ruta Svinka
Keyword(s):  
Surface Area ◽  
Ph Value ◽  
Water Solution ◽  
Porous Ceramic ◽  
Mercury Porosimetry ◽  
Environmental Application ◽  
Wide Range ◽  
Different Temperatures ◽  
Ph Level ◽  
Clay Ceramics

Porous ceramic pellets for possible environmental application were produced from different Latvian clays by sintering at different temperatures. Their characteristics and influence of additives were analysed using X-ray diffraction, mercury porosimetry and BET tests. The obtained ceramic pellets from calcareous clays after immersion in distilled water change its pH value, which affects their capability to adsorb ions or molecules on the surface. The sorption capabilities are dependent on the pH level of water solution, composition of clays, and used adsorbate. Porosity of the produced pellets is mostly within range from 15 to 25 % throughout all sintering temperatures with a slight decrease at 1050 ?C. The specific surface area has a wide range up to 30 m2/g. The highest surface area has pellets sintered at lower temperatures. The adsorption capability of pellets was evaluated using water solutions with different ions. The most promising results were obtained with iodine sorption. For most pellets the sorption capacity was 12.7 mg/g, although for the pellets sintered at 1050 ?C it was lower.

scholarly journals Effect of Graphene Oxide Concentration in Electrolyte on Corrosion Behavior of Electrodeposited Zn–Electrochemical Reduction Graphene Composite Coatings

Coatings ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 758 ◽  
Author(s):  
Yang ◽  
Zhang ◽  
Wang ◽  
Wang ◽  
Chen ◽  
...  
Keyword(s):  
Corrosion Behavior ◽  
Electrochemical Impedance ◽  
Composite Coatings ◽  
Laser Raman Spectroscopy ◽  
304 Stainless Steel ◽  
Sulfate Electrolyte ◽  
X Ray Diffraction ◽  
X Ray ◽  
Tafel Polarization ◽  
Laser Raman

Pure Zn and Zn–ERGO composite coatings were prepared by direct current electrodeposition on 304 stainless steel. Samples were characterized by X-ray diffraction (XRD), scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM/EDS), and laser Raman spectroscopy (Raman). Results obtained have shown that the concentration of GO sheets in zinc sulfate electrolyte has an important effect on the preferred crystal orientation and the surface morphology of Zn–ERGO composite coatings. A study of the corrosion behavior of the coatings by Tafel polarization and electrochemical impedance spectroscopic (EIS) methods leads to the conclusion that the Zn-1.0 g/L ERGO composite coating possesses the best corrosion resistance compared to the pure Zn coating and other composite coatings in this study.

The determination of the surface area of silica by laser Raman spectroscopy

1976 ◽  
Vol 29 (3) ◽  
pp. 507 ◽  
Author(s):  
RP Cooney ◽  
NT Tam
Keyword(s):  
Raman Spectroscopy ◽  
Raman Spectrum ◽  
Surface Area ◽  
Surface Coverage ◽  
Silica Surface ◽  
Quantitative Agreement ◽  
Laser Raman Spectroscopy ◽  
Laser Raman ◽  
Bet Method

Changes in the Raman spectrum of pyridine on a silica surface with increasing surface coverage may be used to determine the monolayer capacity. The method, which is independent of the BET method, produces a result which is in quantitative agreement with the BET result.

X-ray diffraction Warren–Averbach mullite analysis in whiteware porcelains: influence of kaolin raw material

Clay Minerals ◽  
2018 ◽  
Vol 53 (3) ◽  
pp. 471-485 ◽  
Author(s):  
Angel Sanz ◽  
Joaquín Bastida ◽  
Angel Caballero ◽  
Marek Kojdecki
Keyword(s):  
Crystallite Size ◽  
Firing Temperature ◽  
Microstructural Analysis ◽  
Stoichiometric Composition ◽  
Raw Material ◽  
Size Distributions ◽  
X Ray Diffraction ◽  
X Ray ◽  
Different Temperatures ◽  
Crystallite Sizes

ABSTRACTCompositional and microstructural analysis of mullites in porcelain whitewares obtained by the firing of two blends of identical triaxial composition using a kaolin B consisting of ‘higher-crystallinity’ kaolinite or a finer halloysitic kaolin M of lower crystal order was performed. No significant changes in the average Al2O3 contents (near the stoichiometric composition 3:2) of the mullites were observed. Fast and slow firing at the same temperature using B or M kaolin yielded different mullite contents. The Warren–Averbach method showed increase of the D110 mullite crystallite size and crystallite size distributions with small shifts to greater values with increasing firing temperature for the same type of firing (slow or fast) using the same kaolin, as well as significant differences between fast and slow firing of the same blend at different temperatures for each kaolin. The higher maximum frequency distribution of crystallite size observed at the same firing temperature using blends with M kaolin suggests a clearer crystallite growth of mullite in this blend. The agreement between thickening perpendicular to prism faces and mean crystallite sizes <D110> of mullite were not always observed because the direction perpendicular to 110 planes is not preferred for growth.

The Effect of Ru on Unsupported Pt-Ru Alloys for Methanol Electro-Oxidation at Different Temperatures

1995 ◽  
Vol 393 ◽  
Author(s):  
Deryn Chu ◽  
Charles Walker ◽  
Sol Gilman
Keyword(s):  
Cyclic Voltammetry ◽  
Sulfuric Acid ◽  
Surface Area ◽  
Hydrogen Adsorption ◽  
X Ray Diffraction ◽  
X Ray ◽  
Different Temperatures ◽  
Adsorption Surface ◽  
Electro Oxidation ◽  
Bulk Alloys

ABSTRACTUnsupported different atomic ratios of platinum-ruthenium bulk alloys were prepared. The alloys were characterized by cyclic voltammetry, X-ray diffraction and energy dispersive X-ray spectroscopy. These alloys were also tested as anodes for methanol electro-oxidation in sulfuric acid over a range of temperatures. Ruthenium is inactive for methanol electro-oxidation at 25 °C, but becomes active at higher temperatures. When a comparison is made on the basis of “true” (hydrogen adsorption) surface area, a 30 atomic percent Ru electrocatalyst provides the highest activity for methanol electro-oxidation as measured at either 0.4 or 0.5V vs. RHE at both 25 and 60 °C.

Synthesis of CeO2/e-HTiNbO5 Nanocomposite and Its Application for Photocatalytic Oxidation Desulfurization

NANO ◽  
2016 ◽  
Vol 11 (02) ◽  
pp. 1650018 ◽  
Author(s):  
Yuanjiao Zhang ◽  
Ningning Wang ◽  
Jie He ◽  
Liangguo Da ◽  
Zhong Li
Keyword(s):  
Photocatalytic Activity ◽  
Photocatalytic Oxidation ◽  
Diffuse Reflectance Spectroscopy ◽  
Proton Exchange ◽  
Light Irradiation ◽  
Laser Raman Spectroscopy ◽  
Natural Light ◽  
X Ray Diffraction ◽  
Laser Raman ◽  
Transmission Electron

Nanoscaled CeO2/e-HTiNbO5 composite was assembled by a facile process using colloidal TiNbO[Formula: see text] (e-HTiNbO5) nanosheet and CeO2 colloid as precursors at room temperature. The nanosheet e-HTiNbO5 was obtained through proton-exchange and exfoliation process from its parent KTiNbO5. The microstructures and properties of the as-prepared samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Laser Raman spectroscopy (LRS), and UV-vis diffuse reflectance spectroscopy (UV-vis DRS), etc. The photocatalytic activity of the obtained nanocomposite is evaluated by the adsorption and photocatalytic oxidation of ethyl mercaptan (EM) under natural light irradiation. The results show that CeO2 nanoparticles are dispersed uniformly on the surface of e-HTiNbO5 and the layered structure of e-HTiNbO5 nanosheet maintains integrity. The interaction between dispersed CeO2 particles and e-HTiNbO5 results in lower bandgap compared to its precursors, and the photocatalytic activity of CeO2/e-HTiNbO5 are enhanced under natural light irradiation.

Synthesis and Characterization of Rodlike Ammonium Tetrathiomolybdate and its Thermal Decomposition Mechanism

2011 ◽  
Vol 287-290 ◽  
pp. 2049-2052 ◽  
Author(s):  
Jun Zhang ◽  
Su Ping Hu ◽  
Yu Li Feng ◽  
Bo Xu ◽  
Yan Hui Guo
Keyword(s):  
Thermal Decomposition ◽  
Raw Materials ◽  
Decomposition Mechanism ◽  
Laser Raman Spectroscopy ◽  
Thermal Decomposition Mechanism ◽  
X Ray Diffraction ◽  
Laser Raman ◽  
Ammonium Sulfide ◽  
Ammonium Tetrathiomolybdate ◽  
Ammonium Dimolybdate

Rodlike ammonium tetrathiomolybdate has been synthesized via ultrasonic assistance using monocrystal ammonium dimolybdate and ammonium sulfide as raw materials. The phase compositions, purity of as-synthesized products were characterized by x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), laser Raman spectroscopy(LRS). The thermal decomposition mechanism of ammonium tetrathiomolybdate was deduced by thermoanalysis. It is shown that brownish-red rhombic ammonium tetrathiomolybdate crystal with high purity could be obtained at 60°C for 1h under relatively mild conditions.

Assessment of the Hydrophilic-Hydrophobic Balance of Alumina Oxidized at Different Temperatures via H2O and C4H10 Vapor Adsorption

2019 ◽  
Vol 397 ◽  
pp. 161-168 ◽  
Author(s):  
Naouel Hezil ◽  
Mamoun Fellah ◽  
Ridha Djellabi ◽  
Mohamed Zine Touhami ◽  
Alex Montagne ◽  
...  
Keyword(s):  
Surface Area ◽  
Hydrophobic Surface ◽  
Treatment Temperature ◽  
Area Measurement ◽  
Bet Surface Area ◽  
Alumina Powder ◽  
Surface Samples ◽  
Surface Area Measurement ◽  
Different Temperatures ◽  
Adsorption Of Water

The hydrophilic-hydrophobic surface area of alumina powder (Al2O3) oxidized at different temperatures was determined on the base of adsorption of water and butane vapor at 25°C. In the order to study the influence of thermal oxidation upon hydrophilic/hydrophobic character of the surface, samples of Al2O3 were characterized using granulometry, SEM and BET surface area measurement. SEM results showed that the thermal treatment does not affect the morphology of the Alunima. However, the increase of treatment temperature from 250 to 900°C results in changing of the hydrophilic-hydrophobic balance of Al2O3 surface.

scholarly journals Nano-silica added to Portland cement

2021 ◽  
Vol 43 ◽  
pp. e51699
Author(s):  
Thiago Melanda Mendes ◽  
Wellington Longuini Repette
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Gas Adsorption ◽  
Mechanical Performance ◽  
Raw Materials ◽  
Microstructural Analysis ◽  
Silica Content ◽  
X Ray Diffraction ◽  
Nano Silica

For a controlled particle size distribution, nano-silica was added to three different cements. The chemical and mineralogical compositions of the cements were characterized by fluorescence and X-ray diffraction. The granulometric distributions of cements and nano-silicas were obtained by laser granulometry and dynamic lightning scattering. The specific surface area of the raw materials was determined by gas adsorption. The effect of nano-silica and type of cement on rheological behavior was evaluated by rotational rheometry. The mechanical performance was investigated through the compression strength. The microstructural analysis was performed by scanning electron microscopy. The water demand and the consumption of dispersant increases according to the nano-silica content. The reduction in the inter-particle separation, and the agglomeration of nano-silica led to an increase in the viscosity of the suspension. The mechanical performance was directly affected by the specific surface area of the cements. Microstructural analysis showed that nano-silica changed from a layered adsorbed structure, to a porous or agglomerated structure.

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