Systematic characterization of polycrystalline silica–carbonate helices

2016 ◽  
Vol 18 (33) ◽  
pp. 23044-23052 ◽  
Author(s):  
Elias Nakouzi ◽  
Pamela Knoll ◽  
Kenzie B. Hendrix ◽  
Oliver Steinbock
Keyword(s):  
Amorphous Silica ◽  
Barium Carbonate ◽  
Alkaline Media

Biomorphs are complex, life-like structures that emerge from the precipitation of barium carbonate and amorphous silica in alkaline media.

Mn-Mo-O Catalysts for Methanol Oxidation. I. Preparation and Characterization of the Catalysts

1992 ◽  
Vol 57 (12) ◽  
pp. 2529-2538 ◽  
Author(s):  
Krasimir Ivanov ◽  
Penka Litcheva ◽  
Dimitar Klissurski
Keyword(s):  
Methanol Oxidation ◽  
Solution Concentration ◽  
Alkaline Media ◽  
Acidic Media ◽  
Chemical Methods ◽  
X Ray ◽  
Ph Values ◽  
Precipitate Composition

Mn-Mo-O catalysts with a different Mo/Mn ratio have been prepared by precipitation. The precipitate composition as a function of solution concentration and pH was studied by X-ray, IR, thermal and chemical methods. Formation of manganese molybdates with MnMoO4.1.5H2O, Mn3Mo3O12.2.5H2O, and Mn3Mo4O15.4H2O composition has been supposed. It is concluded that pure MnMoO4 may be obtained in both acid and alkaline media, the pH values depending on the concentration of the initial solutions. The maximum Mo/Mn ratio in the precipitates is 1.33. The formation of pure Mn3Mo4O15.4H2O is possible in weakly acidic media. This process is favoured by increasing the concentration of initial solutions.

Acidity Characterization of Amorphous Silica–Alumina

2012 ◽  
Vol 116 (40) ◽  
pp. 21416-21429 ◽  
Author(s):  
Emiel J.M. Hensen ◽  
Dilip G. Poduval ◽  
Volkan Degirmenci ◽  
D.A J. Michel Ligthart ◽  
Wenbin Chen ◽  
...  
Keyword(s):  
Amorphous Silica ◽  
Silica Alumina

scholarly journals Optimization of nanostructured/nano sized rice husk ash preparation

2020 ◽  
Vol 17 (3(Suppl.)) ◽  
pp. 0953
Author(s):  
Medhat Mostafa ◽  
Hamdy Salah ◽  
Amro B. Saddek ◽  
Nabila Shehata
Keyword(s):  
Particle Size ◽  
Rice Husk ◽  
Amorphous Silica ◽  
Particle Shape ◽  
Rice Husk Ash ◽  
Loss On Ignition ◽  
Shape Distribution ◽  
Disk Mill ◽  
Grinding Time

The objective of the study is developing a procedure for production and characterization of rice husk ash (RHA). The effects of rice husk (RH) amount, burning/cooling conditions combined with stirring on producing of RHA with amorphous silica, highest SiO2, lowest loss on ignition (LOI), uniform particle shape distribution and nano structured size have been studied. It is concluded that the best amount is 20 g RH in 125 ml evaporating dish Porcelain with burning for 2 h at temperature 700 °C combined with cooling three times during burning to produce RHA with amorphous silica, SiO2 90.78% and LOI 1.73%. On the other hand, cooling and stirring times affect the variation of nano structured size and particle shape distribution. However, no crystalline phases were found in RHA in all cases. Results proved that the Attritor ball mill was more suitable than vibration disk mill for pulverizing nano structured RHA with 50% of particle size (D50) lower than 45 mm and 99 % of particle size (D99) lower than 144 mm to nanosized RHA with D50 lower than 36 nm and D99 lower than 57 nm by grinding time 8.16 min to every 1 g RHA without changes in morphousity of silica.

scholarly journals Synthesis and characterization of novel metal complexes of (pentulose-?-lactone-2,3-enedibenzoate barbituric acid) with some metal ions

2013 ◽  
Vol 10 (3) ◽  
pp. 597-606
Author(s):  
Baghdad Science Journal
Keyword(s):  
Atomic Absorption ◽  
Magnetic Moment ◽  
Sodium Methoxide ◽  
Barbituric Acid ◽  
Molar Conductivity ◽  
Alkaline Media ◽  
Synthesis And Characterization ◽  
Conductivity Measurements ◽  
Vis Spectroscopy

New (pentulose-?-lactone-2,3-enedibenzoate barbituric acid) (L) have been synthesized by reaction of (5-C-dimethyl malonyl-pentulose-?-lactone-2,3-enedibenzoate) with urea in alkaline media (sodium methoxide). (Ca+2, Co+2, Ni+2, Cu+2, Zn+2, Cd+2 and Hg+2) complexes of (pentulose-?-lactone-2,3-enedibenzoate barbituric acid) (L) have been prepared and characterized by (1H and 13CNMR), FTIR, (U.V-Vis) spectroscopy, Atomic absorption spectrophotometer (A.A.S), Molar conductivity measurements and Magnetic moment measurements, and the following general formula has been given for the prepared complexes [MLCl2(H2O)].XH2O, where M = (Ca+2, Co+2, Ni+2, Cu+2, Zn+2, Cd+2, Hg+2), X = five molecules with (Cd+2) complex, L = (pentulose-?-lactone-2,3-enedibenzoate barbituric acid).

Characterization of Microstructure and Crystallographic Texture of Silicate and Phyllosilicate Ceramics

2010 ◽  
Vol 68 ◽  
pp. 13-22 ◽  
Author(s):  
Daniel Chateigner ◽  
Philippe Blanchart ◽  
Sarah Deniel ◽  
Luca Lutterotti ◽  
Hans Rudolf Wenk
Keyword(s):  
Amorphous Silica ◽  
Crystallographic Texture ◽  
The Other ◽  
Uniaxial Pressure ◽  
Composite Ceramics ◽  
Combined Analysis ◽  
X Ray ◽  
Cell Parameters ◽  
Fibre Texture

We illustrate the x-ray Combined Analysis approach capabilities in characterizing silicates and phyllosilicates for samples exhibiting crystallographic textures. Two mullite composite ceramics, one elaborated under uniaxial pressure the other under centrifugation, and one uniaxially pressed montmorillonite aggregate, are studied in terms of texture, cell parameters and phase contents. Several weak texture components are present in the mullite samples, combinations of planar- and fibre-like textures. The methodology is able to take account of the amorphous silica-like matrix of the composite, and cell parameters and structure of mullite correspond to the commonly modelled used for this phase. The montmorillonite turbostratic phase is correctly reproduced with its fibre texture, eventhough minor phases are also present and modelled in the aggregate.

Characterization and genesis of horizontal banding in Brazilian agate: an X-ray diffraction, thermogravimetric and electron microprobe study

2013 ◽  
Vol 77 (3) ◽  
pp. 227-248 ◽  
Author(s):  
T. Moxon ◽  
C. M. Petrone ◽  
S. J. B. Reed
Keyword(s):  
Amorphous Silica ◽  
Electron Microprobe ◽  
X Ray Diffraction ◽  
X Ray ◽  
Wall Lining ◽  
Defect Site ◽  
Site Water ◽  
Stage Process ◽  
Upper Chamber

AbstractCharacterization of Brazilian agates containing a lower horizontally banded section and an upper chamber with bands parallel to the walls shows that these agates formed much later than the 135 Ma Paraná basalt host rock. Age differentiation between the two types of banding shows that the horizontal bands formed between 43 to 63 Ma ago with a final infill of wall-lining bands between 7 and 27 Ma later. The horizontal bands have a higher Al3+ concentration and a greater crystallite size than the wall-lining layers; they have a lower mogánite content and defect-site water content. The formation of these agates appears to be the result of a three-stage process. After the separate formation of horizontally banded and wall-lining agate, a silica infill seals the gap between the agate and the cavity wall. The detection of cristobalite in some specimens indicates that genesis of both the horizontally banded and wall-lining deposits in the Brazilian samples proceeds along an amorphous silica → opal-CT → opal-C → chalcedony pathway.

Synthesis and Characterisation of Slag Based Geopolymers

2010 ◽  
Vol 636-637 ◽  
pp. 155-160 ◽  
Author(s):  
C. Panagiotopoulou ◽  
Glykeria Kakali ◽  
Sotiris Tsivilis ◽  
T. Perraki ◽  
Maria Perraki
Keyword(s):  
Compressive Strength ◽  
Blast Furnace ◽  
Blast Furnace Slag ◽  
Starting Material ◽  
Alkaline Media ◽  
High Compressive Strength ◽  
Geopolymer Matrix ◽  
Furnace Slag ◽  
Alkali Ion

In the present work the geopolymerisation of blast furnace slag (GGBS) under varying conditions is being investigated. The experimental comprises the following parts: i) dissolution of slag in alkaline media and the investigation of the effect of the alkali ion (K or Na) on the dissolution of Al+3 and Si4+, ii) synthesis of slag based geopolymers and the investigation of the effect of the Si/Al ratio and the kind of alkaline ion on the development of the compressive strength and iii) characterization of geopolymers by means of XRD, FTIR and SEM/EDS measurements. As it is concluded, blast furnace slag geopolymers exhibit high compressive strength, with the maximum being 112.7±2 MPa. The Si/Al ratio of the starting material is found to affect strongly the development of the geopolymer compressive strength. The microstructure of slag–based geopolymers and the incorporation of Ca in the geopolymer matrix are also discussed.

scholarly journals NMR Spectroscopic Characterization of Flame‐Made Amorphous Silica‐Alumina for Cyclohexanol and Glyceraldehyde Conversion

ChemCatChem ◽  
2019 ◽  
Vol 12 (1) ◽  
pp. 287-293 ◽  
Author(s):  
Zichun Wang ◽  
Yijiao Jiang ◽  
Catherine Stampfl ◽  
Alfons Baiker ◽  
Michael Hunger ◽  
...  
Keyword(s):  
Amorphous Silica ◽  
Spectroscopic Characterization ◽  
Silica Alumina
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