Rietveld refinement of amorphous SiO2 prepared via sol–gel method

Samples of Mn-doped amorphous SiO 2 matrix with manganese concentration 0.7 and 3 at.% have been prepared by a sol-gel method. Transmission electron microscopy analysis has shown that the samples contain agglomerates of amorphous silica particles 10 -20 nm in size. Two types of Mn-rich particles are dispersed in silica matrix, smaller nanoparticles with dimensions between 3 and 10 nm, and larger crystalline areas consisting of aggregates of the smaller nanoparticles. High-temperature magnetic susceptibility reveals that dominant magnetic phase at higher temperatures is λ-MnO 2 . At temperatures below T C = 43 K strong ferrimagnetism originating from the minor Mn 3 O 4 phase masks the relatively weak magnetism of λ-MnO 2 . Magnetic field dependence of the maximum in the zero-field-cooled magnetization for both the samples in the vicinity of 40 K, and a frequency shift of the real component of the AC magnetic susceptibility in the sample with 3 at.% Mn suggest that the magnetic moments of the smaller Mn 3 O 4 nanoparticles with dimensions below 10 nm are subject to thermally activated blocking process just below the Curie temperature T C . The low-temperature maximum in the zero-field-cooled magnetization observed for both the samples below 10 K indicates possible spin glass freezing of the magnetic moments in the geometrically frustrated Mn sublattice of the λ-MnO 2 crystal structure.

show abstract

“…The shape of the diffractogram and position of the wide band correspond to amorphous silica [8]. No separated narrow XRD lines were observed.…”

Section: Resultsmentioning

confidence: 90%

Magnetic Properties of Mn-Doped Amorphous SiO₂Matrix

et al. 2011

View full text Add to dashboard Cite

show abstract

“…Broad peaks observed in the powder XRD pattern of the particles clearly indicate their amorphous SiO 2 nature (Fig. 3a) [42]. The average size of the MARIMO SiO 2 particles obtained at 400 °C is 1316 ± 305 nm (dynamic light scattering (DLS) measurements; The one-pot, one-step supercritical alcohol method was then applied to the synthesis (Fig.…”

Section: Resultsmentioning

confidence: 99%

Versatility of one-pot, single-step synthetic approach for spherical porous (metal) oxide nanoparticles using supercritical alcohols

Wang

Ueno

Takigawa

et al. 2013

The Journal of Supercritical Fluids

View full text Add to dashboard Cite

We developed a rapid, one-pot, single-step synthetic method for preparing spherical porous (metal) oxides, titanium dioxide, silica, zirconium dioxide, cerium dioxide, and zinc oxide with large surface areas in a supercritical alcohol containing formic acid or phthalic acid as organic additive in a very short reaction time (10 min). A new type of hollow TiO 2 nanoparticle was obtained by slowly heating the reaction mixtures. The shell thickness of hollow TiO 2 nanoparticles was controlled by adjusting the heating rate.The method proved highly versatile for synthesizing solid and hollow spherical meso/microporous nanoparticles. The spherical mesoporous TiO 2 nanoparticles photocatalytically degraded methylene blue in water under UV irradiation, and successfully transported DNA under biolistic bombardment.

show abstract

“…• C [33]. It is known that the coesite phase can be obtained from quartz phase under high pressures.…”

Section: Resultsmentioning

confidence: 99%

Coesite Formation at Ambient Pressure and Low Temperatures

Martı́nez

Vázquez-Durán

Martínez-Castañón

et al. 2008

Advances in Materials Science and Engineering

Self Cite

View full text Add to dashboard Cite

Partial crystallization of silica xerogel in the form of coesite has been obtained at low-pressure conditions and temperatures of ∼565• C, in samples containing chlorophyll aggregates dispersed in amorphous silica. Silica xerogel samples were prepared by the sol-gel method using an ethanol:H 2 O:TEOS molar ratio of 4:11.6:1 and loaded with extracts from frozen spinach leaves. The silica xerogel microstructure of the powders was studied as a function of annealing temperature. It was found that partial crystallization of the glass matrix in the form of coestite was obtained at lower pressure than those specified by the phase diagram. Chlorophyll aggregates were added to the starting solutions which, upon thermal treatments, form small colloidal particles in the glass matrix. The presence of coesite is corroborated by the Rietveld refinement method.

show abstract

Rietveld refinement of amorphous SiO2 prepared via sol–gel method

Cited by 159 publications

References 21 publications

Magnetic Properties of Mn-Doped Amorphous SiO₂Matrix

Magnetic Properties of Mn-Doped Amorphous SiO₂Matrix

Versatility of one-pot, single-step synthetic approach for spherical porous (metal) oxide nanoparticles using supercritical alcohols

Coesite Formation at Ambient Pressure and Low Temperatures

Contact Info

Product

Resources

About

Rietveld refinement of amorphous SiO2 prepared via sol–gel method

Cited by 159 publications

References 21 publications

Magnetic Properties of Mn-Doped Amorphous SiO2Matrix

Magnetic Properties of Mn-Doped Amorphous SiO2Matrix

Versatility of one-pot, single-step synthetic approach for spherical porous (metal) oxide nanoparticles using supercritical alcohols

Coesite Formation at Ambient Pressure and Low Temperatures

Contact Info

Product

Resources

About

Magnetic Properties of Mn-Doped Amorphous SiO₂Matrix

Magnetic Properties of Mn-Doped Amorphous SiO₂Matrix