Synthesis and characterization of ceramic composites of the binary system Ba0.75Sr0.25AlSi2O8 - Al2O3

2012 ◽  
Vol 1485 ◽  
pp. 107-112
Author(s):  
Jorge López-Cuevas ◽  
Magaly V. Ramos-Ramírez ◽  
José L. Rodríguez-Galicia
Keyword(s):  
Mechanical Activation ◽  
Milling Time ◽  
Relative Proportion ◽  
Ceramic Composites ◽  
Synthesis Conditions ◽  
Surface Nucleation ◽  
Attrition Milling ◽  
C 50

ABSTRACTBa0.75Sr0.25AlSi2O8 (SBAS) - Al2O3 composites, with SBAS/Al2O3 weight ratios of: (a) 90/10, (b) 70/30, and (c) 50/50, are in situ synthesized by reactive sintering at 900-1500°C/5h. The effect of mechanical activation of the precursor mixtures for 0, 4 or 8h in an attrition milling device on the microstructure and phase composition of the composites is studied. Only SBAS and Al2O3 phases are obtained at 1300-1500°C, independently of milling time. In general, the relative proportion of the desirable monoclinic SBAS (Celsian) phase increases in the materials with increasing milling time and sintering temperature, which is enhanced by their SrO content. The promotion of surface nucleation of the undesirable hexagonal SBAS (Hexacelsian) phase by mechanical activation results in a maximum Hexacelsian to Celsian conversion fraction of only 81.4%, obtained for composition 2 milled for 8h and sintered at 1500°C/5h. Under these synthesis conditions, an increment in the amount and size of the Al2O3 particles in the composites is detrimental for the Hexacelsian to Celsian conversion.

scholarly journals Characterization of the Physical, Chemical, and Adsorption Properties of Coal-Fly-Ash–Hydroxyapatite Composites

Minerals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 774
Author(s):  
Eleonora Sočo ◽  
Dorota Papciak ◽  
Magdalena M. Michel ◽  
Dariusz Pająk ◽  
Andżelika Domoń ◽  
...  
Keyword(s):  
Fly Ash ◽  
Coal Fly Ash ◽  
Thermal Power ◽  
Synthesis Conditions ◽  
High Calcium ◽  
Ft Ir ◽  
Ir Analysis ◽  
Wet Synthesis

(1) Hydroxyapatite (Hap), which can be obtained by several methods, is known to be a good adsorbent. Coal fly ash (CFA) is a commonly reused byproduct also used in environmental applications as an adsorbent. We sought to answer the following question: Can CFA be included in the method of Hap wet synthesis to produce a composite capable of adsorbing both heavy metals and dyes? (2) High calcium lignite CFA from the thermal power plant in Bełchatów (Poland) was used as the base to prepare CFA–Hap composites. Four types designated CFA–Hap1–4 were synthesized via the wet method of in situ precipitation. The synthesis conditions differed in terms of the calcium reactants used, pH, and temperature. We also investigated the equilibrium adsorption of Cu(II) and rhodamine B (RB) on CFA–Hap1–4. The data were fitted using the Langmuir, Freundlich, and Redlich–Peterson models and validated using R2 and χ2/DoF. Surface changes in CFA–Hap2 following Cu(II) and RB adsorption were assessed using SEM, SE, and FT-IR analysis. (3) The obtained composites contained hydroxyapatite (Ca/P 1.67) and aluminosilicates. The mode of Cu(II) and RB adsorption could be explained by the Redlich–Peterson model. The CFA–Hap2 obtained using CFA, Ca(NO3)2, and (NH4)2HPO4 at RT and pH 11 exhibited the highest maximal adsorption capacity: 73.6 mg Cu/g and 87.0 mg RB/g. (4) The clear advantage of chemisorption over physisorption was indicated by the Cu(II)–CFA–Hap system. The RB molecules present in the form of uncharged lactone were favorably adsorbed even on strongly deprotonated CFA–Hap surfaces.

In Situ Synthesis of Rod-Like Tielite / Alumina Ceramic Composites via Mechanical Activation

2007 ◽  
Vol 352 ◽  
pp. 111-114
Author(s):  
Xiao Hu Chen ◽  
Xiao Min Chen ◽  
Huang Zhao ◽  
Ji Huai Wu
Keyword(s):  
Composite Materials ◽  
Mechanical Activation ◽  
Ceramic Composite ◽  
Ceramic Composites ◽  
Al2o3 Ceramic ◽  
Longitudinal Length ◽  
In Situ Formation ◽  
Ceramic Composite Materials ◽  
Α Al2o3

The purpose of this paper is to investigate the possibility of rod-like Al2TiO5 / α-Al2O3 composites in situ formation via a mechanical activation process. A QM-ISP-4 Planetary Mill was employed to activate mechanically the mixtures of anatase and corundum in air at room temperature for different times. The milled powder mixtures were pressed into platelets and then sintered in air at 1300°C for 3 h. The XRD results showed that only Al2TiO5 and α-Al2O3 phases could be detected in the sintered samples when the activated time reached 30 hours. The SEM observations illustrated the unusual microstructure of Al2TiO5 / α-Al2O3 ceramic composite materials. Abnormal grains with longitudinal length ~10 μm23 transversal length ~1 μm and equiaxed matrix grains of ~3 μm on an average were observed. EDXA proved that the rod-like grains and the fine equiaxed matrix grains were composed of Al2TiO5 and α-Al2O3, separately. The roles of anisotropic grain growth caused by mechanical activation are discussed for the in situ formation of rod-like Al2TiO5 / α-Al2O3 ceramic composite materials.

scholarly journals Advanced Synthesis and Characterization of Vanadia/Titania Catalysts through a Molecular Approach

Catalysts ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 322
Author(s):  
Eleni Tella ◽  
Antonios Trimpalis ◽  
Athanasios Tsevis ◽  
Christos Kordulis ◽  
Alexis Lycourghiotis ◽  
...  
Keyword(s):  
Raman Spectroscopy ◽  
Temperature Dependent ◽  
In Situ Raman Spectroscopy ◽  
Monomeric Species ◽  
Synthesis Conditions ◽  
In Situ Raman ◽  
Titania Surface ◽  
Inner Sphere

Vanadia/titania catalysts were synthesized by the equilibrium deposition filtration (EDF) method, which is a synthesis route that follows a molecular-level approach. The type of interfacial deposition as well as the interfacial speciation of the deposited oxo-V(V) species were determined by means of a model that takes into account experimental “proton-ion” curves and “adsorption edges”. It is shown that at pH ≥ 9.5, the deposition proceeds exclusively through the formation of mono-substituted inner sphere monomeric species in an “umbrella”-like Ti–OV(OH)2O configuration, whilst with lowering of the pH, a second species, namely the disubstituted inner sphere quadrameric species in a (Ti-O)2V4O10 configuration possessing two mono-oxo V=O and two di-oxo V(=O)2 terminations gradually prevails, which is in co-existence with the monomeric species. Raman spectroscopy is used for verifying the solution speciation, which is different compared to the interfacial speciation of the deposited oxo-V(V) species. Furthermore, in situ Raman spectroscopy was used to verify the model-predicted interfacial speciation of the deposited oxo-V(V) species and to monitor the temperature-dependent evolution up to 430 °C. Hence, a controlled formation of a specific vanadia species on a titania surface is enabled, which, depending on the synthesis conditions, can result in specific catalyst characteristics and thus possibly different catalytic behavior for a specific reaction.

scholarly journals Examination of milled h-BN addition on sintered Si3N4/h-BN ceramic composites

2018 ◽  
Vol 12 (4) ◽  
pp. 357-365 ◽  
Author(s):  
Katalin Balázsi ◽  
Mónika Furko ◽  
Zsolt Fogarassy ◽  
Csaba Balázsi
Keyword(s):  
Milling Time ◽  
Hexagonal Boron Nitride ◽  
Hot Isostatic Pressing ◽  
Ceramic Matrix ◽  
Ceramic Composites ◽  
Milling Parameters ◽  
Attrition Milling ◽  
Transmission Electron ◽  
Hardness Values ◽  
Si3n4 Ceramics

Silicon nitride (Si3N4) ceramics containing 1 and 5 wt.% of hexagonal boron nitride (h-BN) were prepared by attrition milling and hot-isostatic pressing. Thorough morphological characterizations have been carried out to reveal the influence of the milling parameters on the size of the h-BN additives. The results confirmed significant decrease in h-BN particle size by increasing milling time. The transmission electron microscopy observations revealed that the h-BN particles were incorporated into the ceramic matrix. The results showed that the increase of the h-BN content decreased significantly the hardness of materials. Moreover, the hardness values were higher when the size of h-BN was larger. The same tendency was observed in the case of Young?s modulus.

The Use of Advanced Analytical Techniques for Characterization of the Chemical, Physical, and Crystallographic Nature of a Surface

1973 ◽  
Vol 31 ◽  
pp. 132-133 ◽  
Author(s):  
R. E. Herfert
Keyword(s):  
Surface Characterization ◽  
Analytical Techniques ◽  
X Ray Diffraction ◽  
Depth Of Penetration ◽  
X Ray ◽  
The Past ◽  
Transmission Electron ◽  
Scanning Electron

Studies of the nature of a surface, either metallic or nonmetallic, in the past, have been limited to the instrumentation available for these measurements. In the past, optical microscopy, replica transmission electron microscopy, electron or X-ray diffraction and optical or X-ray spectroscopy have provided the means of surface characterization. Actually, some of these techniques are not purely surface; the depth of penetration may be a few thousands of an inch. Within the last five years, instrumentation has been made available which now makes it practical for use to study the outer few 100A of layers and characterize it completely from a chemical, physical, and crystallographic standpoint. The scanning electron microscope (SEM) provides a means of viewing the surface of a material in situ to magnifications as high as 250,000X.

A very rapid in situ Kikuchi technique to determine relative crystal misorientation

1988 ◽  
Vol 46 ◽  
pp. 830-831
Author(s):  
J. I. Bennetch
Keyword(s):  
Electron Beam ◽  
Analytical Techniques ◽  
Superplastic Forming ◽  
The Other ◽  
Kikuchi Pattern ◽  
Kikuchi Line ◽  
Line Analysis

In a recent study of the superplastic forming (SPF) behavior of certain Al-Li-X alloys, the relative misorientation between adjacent (sub)grains proved to be an important parameter. It is well established that the most accurate way to determine misorientation across boundaries is by Kikuchi line analysis. However, the SPF study required the characterization of a large number of (sub)grains in each sample to be statistically meaningful, a very time-consuming task even for comparatively rapid Kikuchi analytical techniques.In order to circumvent this problem, an alternate, even more rapid in-situ Kikuchi technique was devised, eliminating the need for the developing of negatives and any subsequent measurements on photographic plates. All that is required is a double tilt low backlash goniometer capable of tilting ± 45° in one axis and ± 30° in the other axis. The procedure is as follows. While viewing the microscope screen, one merely tilts the specimen until a standard recognizable reference Kikuchi pattern is centered, making sure, at the same time, that the focused electron beam remains on the (sub)grain in question.

Coherent electron nanodiffraction from clean silver nano particles in a UHV STEM

1993 ◽  
Vol 51 ◽  
pp. 1058-1059
Author(s):  
J. Liu ◽  
M. Pan ◽  
G. E. Spinnler
Keyword(s):  
Supported Catalysts ◽  
Imaging Techniques ◽  
Nano Particles ◽  
Metal Particles ◽  
Shape Structure ◽  
Dynamical Simulations ◽  
Small Metal Particles ◽  
Extract Information

Small metal particles have peculiar chemical and physical properties as compared to bulk materials. They are especially important in catalysis since metal particles are common constituents of supported catalysts. The structural characterization of small particles is of primary importance for the understanding of structure-catalytic activity relationships. The shape and size of metal particles larger than approximately 5 nm in diameter can be determined by several imaging techniques. It is difficult, however, to deduce the shape of smaller metal particles. Coherent electron nanodiffraction (CEND) patterns from nano particles contain information about the particle size, shape, structure and defects etc. As part of an on-going program of STEM characterization of supported catalysts we report some preliminary results of CEND study of Ag nano particles, deposited in situ in a UHV STEM instrument, and compare the experimental results with full dynamical simulations in order to extract information about the shape of Ag nano particles.

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