Determination of Percent Crystallinity of Partly Devitrified Glass by X‐Ray Diffraction

“…The degree of amorphization achieved by the SrCO 3 contained in the precursor mixtures as a function of milling time was estimated using a method developed by Ohlberg and Strickler (16,17), which is based on Equation 1: (1) where A denotes the degree of amorphization, U and I denote the background and the integrated intensities, respectively, of the diffraction lines of the reference (i) or the mechanically activated (x) samples in the corresponding XRD patterns.…”

Section: Characterization Of Precursor Mixturesmentioning

confidence: 99%

Influence of mechanical activation on the synthesis of Sr-Celsian employing a precursor mixture containing coal fly ash

Lopez‐Badillo¹,

López-Cuevas²,

Rodríguez-Galicia³

et al. 2013

Bol. Soc. Esp. Ceram. Vidr.

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Strontium aluminosilicate, SrAl₂Si₂O₈ (SAS), was synthesized by a solid state reaction using coal fly ash (CFA) as main raw material. A precursor mixture of SrCO₃, CFA and Al₂O₃ was mechanically-activated for times of up to 12 h using an attrition mill, and subsequently sintered at temperatures of 900-1300 °C. The CFA and the mechanical activation were employed with the aim to promote the transformation from the hexagonal (Sr-Hexacelsian) into the monoclinic (Sr-Celsian) polymorphic form of SAS, since the latter phase is associated with better physical and mechanical properties but the former tends to be the first one to appear. The mean particle size, the crystallite size and the temperature at the end of the curve of weight loss (T_f) decreased, while the specific surface area and the degree of amorphization increased, with increasing milling time. Samples milled for at least 4 h and then sintered at 1100 °C achieved full transformation into Sr-Celsian. The same result was obtained for sintering temperatures higher than 1100 °C, independently of milling time. An increment in both the milling time and the sintering temperature allowed us to improve the densification and the mechanical properties of the synthesized materials.

Aluminosilicato de estroncio, SrAl₂Si₂O₈ (SAS), fue sintetizado por reacción en el estado sólido empleando ceniza volante (CFA) como materia prima principal. Una mezcla precursora de SrCO₃, CFA y Al₂O₃ fue activada mecánicamente por tiempos de hasta 12 h en un molino de atrición, y después sinterizada a temperaturas de 900-1300 °C. El empleo de la CFA y la activación mecánica tuvieron el propósito de promover la transformación polimórfica de la fase hexagonal (Hexacelsiana de Sr) a la monoclínica (Celsiana de Sr) del SAS, ya que esta última se asocia con mejores propiedades físicas y mecánicas pero la primera tiende a aparecer primero. El tamaño promedio de partícula y de cristalita, así como la temperatura al final de la curva de pérdida en peso (T_f), disminuyeron, mientras que el área superficial y el grado de amorfización aumentaron, al incrementar el tiempo de molienda. Las muestras molidas por al menos 4 h y sinterizadas a 1100 °C se transformaron completamente a Celsiana de Sr. Sucedió lo mismo a temperaturas de sinterización mayores a 1100 °C, independientemente del tiempo de molienda. El incremento tanto en el tiempo de molienda como en la temperatura de sinterización permitió mejorar la densificación y las propiedades mecánicas de los materiales sintetizados

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“…The degree of magnetite amorphization was calculated by method published in [14,15]. The samples were left uncovered from any conductive material in order to keep their original properties.…”

Section: P Baláž Et Almentioning

confidence: 99%

Magnetic Properties and Sorption Activity of Mechanically Activated Magnetite Fe₃O₄

et al. 2010

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It is known that the action of mechanical forces on solids (mechanical activation and/or mechanochemistry) leads to changes of their properties and reactivity. We have studied the physico-chemical and sorption properties of magnetite Fe3O4 (Kiruna, Sweden) mechanically activated in a planetary mill. Several methods such as X-ray diffractometry, Mössbauer spectroscopy, magnetometry, specific surface area measurement as well as arsenic sorption tests have been applied. By X-ray diffractometry strong amorphisation of magnetite has been evidenced. In parallel, specific surface area increased from 0.1 m 2 /g for the reference (non-milled) sample to the values 0.5-6.1 m 2 /g for milled samples. The Mössbauer spectrum of the reference sample is well fitted with two subspectra corresponding to tetrahedrally (A) and octahedrally (B) coordinated iron cations in the spinel structure of Fe 3 O 4 . In mechanically activated samples (B)-site subspectrum becomes asymmetric, while (A)-site spectrum remains more or less unchanged. The more covalent character of the Fe(A)-O bond compared to the Fe(B)-O bond can explain qualitatively why the spin-density transfer from (A) to (B) in the spinel structure is more effective than vice versa. The value of the saturation magnetization at room temperature was 67.4 ≈ 43.6 emu/g which is significantly lower than that of the bulk particles 92 emu/g. This reduction may be attributed to the surface disorder or spin canting at the particle surface. During the milling process the coercivity value increases from 150 Oe up to 460 Oe with milling time. This increase can be related to the fact that magnetic anisotropy may increase when particle size decreases. The sorption activity of Fe 3 O 4 was enhanced as a consequence of its disordering: 88% of As 3+ was captured for the mechanically activated sample in comparison with 0% for the non-milled one.

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Determination of Percent Crystallinity of Partly Devitrified Glass by X‐Ray Diffraction

Cited by 152 publications

References 3 publications

Effects of mechanical activation on the structural changes and microstructural characteristics of the components of ferruginous quartzite beneficiation tailings

Effects of mechanical activation on the structural changes and microstructural characteristics of the components of ferruginous quartzite beneficiation tailings

Influence of mechanical activation on the synthesis of Sr-Celsian employing a precursor mixture containing coal fly ash

Magnetic Properties and Sorption Activity of Mechanically Activated Magnetite Fe₃O₄

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Determination of Percent Crystallinity of Partly Devitrified Glass by X‐Ray Diffraction

Cited by 152 publications

References 3 publications

Effects of mechanical activation on the structural changes and microstructural characteristics of the components of ferruginous quartzite beneficiation tailings

Effects of mechanical activation on the structural changes and microstructural characteristics of the components of ferruginous quartzite beneficiation tailings

Influence of mechanical activation on the synthesis of Sr-Celsian employing a precursor mixture containing coal fly ash

Magnetic Properties and Sorption Activity of Mechanically Activated Magnetite Fe3O4

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Magnetic Properties and Sorption Activity of Mechanically Activated Magnetite Fe₃O₄