scholarly journals Firing transformations of an argentinean calcareous commercial clay

Cerâmica ◽  
2013 ◽  
Vol 59 (350) ◽  
pp. 254-261 ◽  
Author(s):  
M. F. Serra ◽  
M.S. Conconi ◽  
G. Suarez ◽  
E. F. Agietti ◽  
N. M. Rendtorff
Keyword(s):  
Internal Standard ◽  
Ceramic Materials ◽  
Thermal Treatments ◽  
Quartz Content ◽  
Spinel Type ◽  
Porosity Evolution ◽  
Phase Quantification ◽  
Alumino Silicate ◽  
Diffraction Patterns ◽  
Sintering Characteristics

Mineralogical transformations caused by firing are usually studied by XRD methods only semi-quantitatively. In this work the original mineral disappearance and the neo-mineralization were evaluated quantitatively. Furthermore an indirect non crystalline phase quantification was performed under 1100 ºC was also carried out using the quartz content as internal standard. This study specifically discusses the behavior of an Argentinean white calcareous earthenware commercial when subjected to traditional ceramic firing, besides the technological importance of this particular material, it acts as a model for other clay based ceramic materials. Materials were subjected to thermal treatments between 700 ºC and 1100 ºC. A preliminary sintering characterization was carried out by contraction and porosity evolution. Simultaneous thermogravimetric and differential thermal analysis (TG-DTA) was carried out to elucidate the actual temperature at which the chemical changes occur. Finally, a quantitative analysis based on the Rietveld refinement of the X-ray diffraction patterns was performed to characterize the crystalline phases present in both the clay and in the materials obtained after different thermal treatments. The actual chemical reactions are proposed. The phases identified after firing at traditional working temperature (1040 ºC) are quartz, plagioclase, and the Spinel type alumino-silicate, accompanied by the non-diffracting un-reacted metakaolin and some amount of amorphous glassy phase. At intermediate temperatures (900 ºC) the presence of gehlenite was also detected. The carbonates (calcite and dolomite) presence and decomposition were also evaluated and demonstrated to determine the sintering characteristics of this material.

scholarly journals Quantitative firing transformations of a triaxial ceramic by X-ray diffraction methods

Cerâmica ◽  
2014 ◽  
Vol 60 (356) ◽  
pp. 524-531 ◽  
Author(s):  
M. S. Conconi ◽  
M. R. Gauna ◽  
M. F. Serra ◽  
G. Suarez ◽  
E. F. Aglietti ◽  
...  
Keyword(s):  
Glassy Phase ◽  
Internal Standard ◽  
Rietveld Analysis ◽  
Internal Standard Method ◽  
X Ray Diffraction ◽  
Spinel Type ◽  
X Ray ◽  
Porosity Evolution ◽  
Diffraction Patterns ◽  
Low Crystalline

The firing transformations of traditional (clay based) ceramics are of technological and archeological interest, and are usually reported qualitatively or semiquantitatively. These kinds of systems present an important complexity, especially for X-ray diffraction techniques, due to the presence of fully crystalline, low crystalline and amorphous phases. In this article we present the results of a qualitative and quantitative X-ray diffraction Rietveld analysis of the fully crystalline (kaolinite, quartz, cristobalite, feldspars and/or mullite), the low crystalline (metakaolinite and/or spinel type pre-mullite) and glassy phases evolution of a triaxial (clay-quartz-feldspar) ceramic fired in a wide temperature range between 900 and 1300 ºC. The employed methodology to determine low crystalline and glassy phase abundances is based in a combination of the internal standard method and the use of a nanocrystalline model where the long-range order is lost, respectively. A preliminary sintering characterization was carried out by contraction, density and porosity evolution with the firing temperature. Simultaneous thermo-gravimetric and differential thermal analysis was carried out to elucidate the actual temperature at which the chemical changes occur. Finally, the quantitative analysis based on the Rietveld refinement of the X-ray diffraction patterns was performed. The kaolinite decomposition into metakaolinite was determined quantitatively; the intermediate (980 ºC) spinel type alumino-silicate formation was also quantified; the incongruent fusion of the potash feldspar was observed and quantified together with the final mullitization and the amorphous (glassy) phase formation.The methodology used to analyze the X-ray diffraction patterns proved to be suitable to evaluate quantitatively the thermal transformations that occur in a complex system like the triaxial ceramics. The evaluated phases can be easily correlated with the processing variables and materials properties. These correlations can be employed for materials characterization, design and processing control.

scholarly journals Validation of XRD phase quantification using semi-synthetic data

2020 ◽  
Vol 35 (4) ◽  
pp. 262-275
Author(s):  
Nicola Döbelin
Keyword(s):  
Reference Materials ◽  
Certified Reference Materials ◽  
Synthetic Data ◽  
Statistical Validation ◽  
Validation Parameters ◽  
Phase Quantification ◽  
Characteristic Features ◽  
Diffraction Patterns ◽  
Synthetic Datasets ◽  
Multi Phase

Validating phase quantification procedures of powder X-ray diffraction (XRD) data for an implementation in an ISO/IEC 17025 accredited environment has been challenging due to a general lack of suitable certified reference materials. The preparation of highly pure and crystalline reference materials and mixtures thereof may exceed the costs for a profitable and justifiable implementation. This study presents a method for the validation of XRD phase quantifications based on semi-synthetic datasets that reduces the effort for a full method validation drastically. Datasets of nearly pure reference substances are stripped of impurity signals and rescaled to 100% crystallinity, thus eliminating the need for the preparation of ultra-pure and -crystalline materials. The processed datasets are then combined numerically while preserving all sample- and instrument-characteristic features of the peak profile, thereby creating multi-phase diffraction patterns of precisely known composition. The number of compositions and repetitions is only limited by computational power and storage capacity. These datasets can be used as input files for the phase quantification procedure, in which statistical validation parameters such as precision, accuracy, linearity, and limits of detection and quantification can be determined from a statistically sound number of datasets and compositions.

X-ray diffraction measurement of the quartz content of clay and silt fractions in soils

Clay Minerals ◽  
1992 ◽  
Vol 27 (1) ◽  
pp. 47-55 ◽  
Author(s):  
M. Hardy
Keyword(s):  
Particle Size ◽  
Size Fraction ◽  
Internal Standard ◽  
Diffraction Measurement ◽  
Particle Sizes ◽  
Quartz Content ◽  
Size Fractions ◽  
Particle Size Fractions ◽  
Calibration Curves ◽  
Fine Quartz

AbstractAn XRD method for measurement of quartz content using ZnO as the internal standard was tested on different particle sizes between 0 and 20 µm. Calibration curves showed a good correlation coefficient for particle-size fractions up to 20 µm; the slope increased for the fractions from 0·7 to 5 µm and was relatively constant for coarser particle sizes. Fine quartz fractions were etched with hydrofluoric acid to remove the surface layer damaged during dry grinding. The use of such etched quartz increased the slopes of the calibration curves for small particle-size fractions and approximated the natural fine quartz fraction much better than the original dry-ground material. The mean of six measurements gave good accuracy provided that the slope of the calibration curve was adjusted for the particular particle-size fraction. This method was used on 0–2 µm, 0–0·2µm and 0·2–2 µm fractions of French silty soils and the results are in agreement with the data from chemical analysis and with the mineralogical interpretation.

Sedimentology, Mineral Facies, and Petrofabric of the Meaford–Dundas Formation (Upper Ordovician) in Southern Ontario

1973 ◽  
Vol 10 (12) ◽  
pp. 1790-1804 ◽  
Author(s):  
K. Czurda ◽  
C. G. Winder ◽  
R. M. Quigley
Keyword(s):  
Clay Minerals ◽  
Heavy Minerals ◽  
Carbonate Content ◽  
The South ◽  
Upper Ordovician ◽  
Quartz Content ◽  
Southern Ontario ◽  
The North ◽  
Bedding Planes ◽  
Diffraction Patterns

The Meaford–Dundas Formation in southern Ontario is a medium gray shale with good fissility and resistant interbeds of gray fossiliferous limestones and siltstones. The hard layers are up to 20 cm in thickness and comprise 10 to 20% of the formation. The shale layers vary in thickness from 50 cm to 2 m.The clay minerals are principally illite, iron-chlorite, and small amounts of vermiculite and mixed-layer types. The carbonate content seems constant across the area at about 4 to 5% of the formation, except for the southwestern area where the carbonate increases to 20 or 25%. This increase is chiefly in dolomite content, a feature which reflects such factors as original conditions of deposition and possibly diagenesis subsequent to burial. The quartz content in the shale beds, and especially in the hard interbeds, increases towards the north to an average of 35 to 40% compared with 10 to 15% in the south. Framboids (aggregates of pyrite grains in spheroidal clusters) are a striking feature of the shale beds of the Meaford–Dundas Formation in the Meaford area.Fabric studies by means of X-ray diffraction patterns and scanning electron photomicrographs reveal, in most cases, high parallelism of clay platelets in the bedding planes, resulting in the good fissility of the shale.The principal source rock areas are the Appalachian orogen in the east (Taconic Mountains), which probably supplied most of the clay minerals and some quartz, and the Canadian Shield in the north, which provided the basin of sedimentation in the south with heavy minerals and additional quartz.

Processing and characterization of lead magnesium tantalate ceramics

1997 ◽  
Vol 12 (10) ◽  
pp. 2617-2622 ◽  
Author(s):  
Mehmet A. Akbas ◽  
Peter K. Davies
Keyword(s):  
Relaxor Ferroelectrics ◽  
Dark Field ◽  
Processing Route ◽  
Chemical Ordering ◽  
Lead Magnesium ◽  
Resolution Imaging ◽  
Diffraction Patterns ◽  
Sintering Characteristics ◽  
Polar Clusters

Using a processing route that employed platinum crucibles, single phase ceramics of Pb(Mg1/3Ta2/3)O3 (PMT) relaxor ferroelectrics were prepared with densities greater than 95% of their theoretical value. The improvements in the sintering characteristics of this system that result from this route were reflected by the dielectric properties, at 182 K, which are similar to those reported for single crystal PMT. Contrast originating from nanosized polar clusters was evident in dark-field TEM images collected from the PMT ceramics at room temperature and showed little change upon cooling through the permittivity maximum. The electron diffraction patterns contained weak superlattice reflections at (h ± 1/2, k ± 1/2, l ± 1/2) that originate from a 1: 1 ordering of the B-site cations. High resolution imaging indicated that the length scale of the chemical ordering in PMT is essentially identical to niobate relaxors such as PMN, with the 1–2 nm ordered domains being surrounded by a disordered matrix.

Felsite in Ceramic Materials Production

2021 ◽  
Vol 410 ◽  
pp. 704-708
Author(s):  
Valeriya M. Razgulyaeva ◽  
Irina A. Pavlova ◽  
Elena P. Farafontova
Keyword(s):  
Glass Phase ◽  
Glassy Phase ◽  
Chemical Resistance ◽  
Ceramic Materials ◽  
Ceramic Tiles ◽  
Quartz Content ◽  
High Acid ◽  
Light Color ◽  
Fine Ceramics

This project is devoted to the study of the felsite properties for the purpose of its application in the production of various types of fine ceramics: ceramic tiles, acid-resistant tiles, aluminosilicate proppants, etc. Felsite is a mixture of quartz (about 40%) and feldspars. In the compositions of ceramic masses, felsite can play the role of both nonplastic due to the quartz content, and flux due to the content of feldspars, that reduces the amount of mixture components. When felsite is fired, the melt appears at a temperature above 950°C. The felsite has a sintering effect when fired at a temperature of 1000°C. Glass phase enriched with SiO2 ensures the absence of material deformation after firing. Also, glassy phase provides high-acid and chemical resistance of materials based on it. In addition, after firing above 1150°C, felsite has a light color, which is a great advantage in comparing it as a melt with other iron-alkali-containing materials. Ceramics based on felsite does not require the use of opacified glazes.

Advanced Process Model for Polymer Derived Ceramic Processing

2006 ◽  
Author(s):  
Xiaolin Wang ◽  
Suraj C. Zunjarrao ◽  
Hui Zhang ◽  
Raman P. Singh
Keyword(s):  
Chemical Reactions ◽  
Process Model ◽  
Transport Phenomena ◽  
Chemical Properties ◽  
Ceramic Materials ◽  
Source Material ◽  
Porosity Evolution ◽  
Polymer Precursors ◽  
Polymer Pyrolysis ◽  
Lower Temperature

Pyrolysis of preceramic polymers allows a new type of ceramic materials to be processed at a relatively low temperature. The ceramics via polymer pyrolysis display a number of exceptional mechanical, thermal and chemical properties, including high thermal stability, high oxidation/creep resistance, etc. Moreover, they offer better geometrical accuracy compared to conventional ceramics. In addition, thermal induced pyrolysis of organometallic polymer precursors offers the possibility of net shape manufacturing at a lower temperature compared to traditional powder sintering process. The pyrolysis of polymer precursors involves curing of polymer precursors in which the polymer undergoes cross-linking to form a green body, followed by a pyrolysis stage that involves the formation of amorphous SiC and crystallization of SiC at a higher temperature. The source material changes phase and composition continuously during polymer pyrolysis based ceramic process. Chemical reactions and transport phenomena vary accordingly. To obtain ceramics with high uniformity of microstructure and species without crack, transport phenomena in material processing needs to be better understood and a process model needs to be developed to optimize the fabrication process. In this paper, a numerical model is developed, including heat and mass transfer, polymer pyrolysis, species transport, chemical reactions and crystallization. The model is capable of accurately predicting the polymer pyrolysis and chemical reactions of the source material. Pyrolysis of a sample with certain geometry is simulated. The effects of heating rate, particle size and initial porosity on porosity evolution, mass loss and reaction rate are investigated. Optimal conditions for the manufacturing are also proposed.

A method for quantitative mineralogical analysis by X-Ray powder diffraction

1960 ◽  
Vol 32 (249) ◽  
pp. 492-499 ◽  
Author(s):  
W. A. Mitchell
Keyword(s):  
Quantitative Analysis ◽  
Powder Diffraction ◽  
Internal Standard ◽  
Published Data ◽  
Intensity Scale ◽  
Mineralogical Analysis ◽  
X Ray ◽  
Diffraction Patterns

SummaryA method of quantitative analysis by photometry of X-ray powder diffraction patterns is described. Co-Kα radiation is used and absorption difficulties are overcome by using thin diluted specimens containing an internal standard. An arbitrary universal intensity scale has been established and the values for the stronger lines of a number of minerals are given. Within individual patterns these are consistent with published data obtained by counter diffractometry.

scholarly journals Preparation, Characterization, and Evaluation of Humidity-Dependent Electrical Properties of Undoped and Niobium Oxide-Doped TiO2 : WO3 Mixed Powders

2017 ◽  
Vol 2017 ◽  
pp. 1-9 ◽  
Author(s):  
Pedro M. Faia ◽  
Juliano Libardi ◽  
Itamar Barbosa ◽  
Evando S. Araújo ◽  
Helinando P. de Oliveira
Keyword(s):  
Electrical Properties ◽  
Electrical Characterization ◽  
Ternary Systems ◽  
Ceramic Materials ◽  
Bet Surface Area ◽  
X Ray Diffraction ◽  
Order Of Magnitude ◽  
Diffraction Patterns ◽  
Pellet Form

The study of selective metal oxide-based binary/ternary systems has received increasing interest in recent years due to the possibility of producing efficient new ceramic materials for relative humidity (RH) detection, given the superior properties of the mixed compounds in comparison with pristine ones. The aim of this work was focused on preparation and characterization of non-doped and Nb2O5-doped TiO2 : WO3 pair (in the pellet form) and evaluation of corresponding humidity-dependent electrical properties. The microstructure of the samples was analyzed from scanning electron microscopy, X-ray diffraction patterns, Raman spectra, BET surface area analysis, and porosimetry. The electrical characterization was obtained from impedance spectroscopy (100 Hz to 40 MHz) in the 10–100% RH range. The results showed that adequate doping levels of Nb2O5 introduce important advantages due to the atomic substitution of Ti by Nb atoms in highly doped structures with different levels of porosity and grain sizes. These aspects introduced a key role in the excursion (one order of magnitude) in the bulk resistance and grain boundary resistance, which characterizes these composite ceramics as a promising platform for RH identification.

Study of the anatase-rutile transformation in TiO2 powders obtained by laser-induced synthesis

1993 ◽  
Vol 8 (10) ◽  
pp. 2709-2715 ◽  
Author(s):  
Laura E. Depero ◽  
Paolo Bonzi ◽  
Marcello Zocchi ◽  
Cristina Casale ◽  
Gennaro De Michele
Keyword(s):  
Anatase Phase ◽  
Rutile Phase ◽  
Thermal Treatments ◽  
Crystallite Growth ◽  
Titanium Alkoxides ◽  
Wet Impregnation ◽  
Anatase Structure ◽  
Microstructural Parameters ◽  
Powder Samples ◽  
Diffraction Patterns

Powder samples of pure anatase were produced using laser-induced pyrolysis of titanium alkoxides, and the catalysts were prepared using conventional wet impregnation methods. The diffraction patterns were interpreted in microstructural terms by Fourier analysis of their peak profiles. The transition temperature for the anatase-rutile transition in these catalysts was found between 500° and 550 °C. For the reflections of the anatase phase, a decrease of their Bragg (2θ) positions was observed up to 550 °C when the presence of the rutile phase becomes important. The response of the anatase structure to the thermal treatment is anisotropic with the c-axis showing the highest sensitivity to the observed expansion of the lattice. The rutile Bragg reflections are sharper than those of the anatase phase. The corresponding microstructural parameters indicate that, in all cases, the transformation is accompanied by an increase of the crystallites and/or of the lattice perfection. The evolution of these parameters is influenced by the presence of vanadium. The V-treated surface layer must be particularly distorted and apparently act as a restraint to perfecting by thermal treatments. Only the transition to rutile is capable of overcoming that restraint by allowing crystallite growth at the expense of the smaller and distorted anatase crystallites.

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