Quantitative X-Ray Diffraction Analysis

Copeland, L. E.; Bragg, Robert H.

doi:10.1021/ac60134a011

Cited by 111 publications

(44 citation statements)

References 16 publications

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“…Nevertheless, Rietveld refinement of x-ray diffraction patterns on hydrating cement pastes has been established in the literature over the past 50 y. [30][31][32] In fact, the empirical kinetic model of Parrott and Killoh that is adopted in this paper used QXRD to establish values of the degree of hydration coefficients for each of the clinker phases. 8 The analysis of hydrated cement utilizes diffraction traces from crystal structure models of each phase in the material system, from which the x-ray diffraction pattern can be calculated for any given set of volume fractions of those phases.…”

Section: Tracking Hydration and Microstructure Developmentmentioning

confidence: 99%

Coupling thermodynamics and digital image models to simulate hydration and microstructure development of portland cement pastes

et al. 2011

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Equilibrium thermodynamic calculations, coupled to a kinetic model for the dissolution rates of clinker phases, have been used in recent years to predict time-dependent phase assemblages in hydrating cement pastes. We couple this approach to a 3D microstructure model to simulate microstructure development during the hydration of ordinary portland cement pastes. The combined simulation tool uses a collection of growth/dissolution rules to approximate a range of growth modes at material interfaces, including growth by weighted mean curvature and growth by random aggregation. The growth rules are formulated for each type of material interface to capture the kinds of cement paste microstructure changes that are typically observed. We make quantitative comparisons between simulated and observed microstructures for two ordinary portland cements, including bulk phase analyses and two-point correlation functions for various phases. The method is also shown to provide accurate predictions of the heats of hydration and 28 day mortar cube compressive strengths. The method is an attractive alternative to the cement hydration and microstructure model CEMHYD3D because it has a better thermodynamic and kinetic basis and because it is transferable to other cementitious material systems.

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Section: Tracking Hydration and Microstructure Developmentmentioning

confidence: 99%

Coupling thermodynamics and digital image models to simulate hydration and microstructure development of portland cement pastes

et al. 2011

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“…Copeland & Bragg [5] suggested that the system can be doped with known amounts of the phase, say A, the fraction of which is to be determined. The system already contains another phase, say B, which is considered as the reference phase.…”

Section: (I) Determination Of the Fraction Of A Phase Using Repeated mentioning

confidence: 99%

Quantitative phase analysis by X-ray diffraction – Simple routes

Popović

2015

Maced. J. Chem. Chem. Eng.

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The elemental composition of a multiphase material can be obtained by means of chemical and spectroscopic techniques. However, these techniques face a great difficulty in distinguishing the chemical identity of the phases present in the material and in derivation of the fractions of particular phases. X-ray powder diffraction seems to be an ideal technique for the analysis of a multiphase material. Each crystalline phase of the material gives its characteristic diffraction pattern independently of the other phases; this fact makes it possible to identify the phase of interest and to determine its fraction. The intensities of diffraction lines of a given phase are proportional to its fraction and an appropriate quantitative analysis can be performed after the application of the correction for the absorption of X-rays in the material.The principles of quantitative X-ray diffraction phase analysis of a multiphase material are presented, with a special attention paid to the doping methods. The following methods are described: (i) determination of the fraction of a phase using repeated dopings, (ii) determination of the fraction of a phase using a single doping, (iii) simultaneous determination of the fractions of several phases using a single doping; (iv) determination of the fraction of the dominant phase. The applicability of the doping methods is stated and the optimum conditions to minimize systematic errors are discussed. Recent approaches in quantitative X-ray diffraction phase analysis are also mentioned in short.Keywords: X-ray powder diffraction; quantitative phase analysis; doping methods КВАНТИТАТИВНА ФАЗНА АНАЛИЗА СО ПОМОШ НА РЕНДГЕНСКА ДИФРАКЦИЈА -ЕДНОСТАВНИ ПАТИШТАХемискиот состав на мултифазен материјал може да се определи со помош на хемиски и спектроскопски техники. Меѓутоа, при користење на овие техники се појавуваат големи тешкотии на патот на дефинирање на хемискиот идентитет на присутните фази во материјалот, како и при определувањето на фракциите на одредените фази. Рендгенската дифракција на спрашени обрасци е една од идеалните техники за анализа на мултифазни материјали. Секоја од кристалните фази во материјалот дава нејзини карактеристични дифракциони максимуми, независно од другите фази. Тоа овозможува да се определат присутните фази, како и нивните фракции. Интензитетите на дифракционите линии на определена фаза се пропорционални со нејзината фракција, што овозможува да се направи квантитативна анализа по примена на корекција на апсорпцијата на рендгенските зраци во материјалот.Презентирани се принципите на квантитативната фазна анализа на мултифазен материјал со помош на рендгенска дифракција, при што посебно внимание е обрнато на методот на додатоци. Опишани се следните методи: (i) определување на фазна фракција користејќи повторени додавања, (ii) определување на фазна фракција користејќи едно додавање, (iii) симултано определување на фазни фракции користејќи едно додавање и (iv) определување на фракција на доминантната фаза. Наведена е применливоста на методот на додатоци и дискутирани ...

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“…El contenido de las distintas fases de Si 3 N 4 se han calculado de acuerdo con el metodo propuesto por Gazzara y Messier [7] y el contenido de silicio no reaccionado se ha cuantificado utilizando el método de adiciones sucesivas [8] . Las velocidades del frente de reacción han sido evaluadas mediante la colocación en el interior de la mezcla inicial de termopares (W/5% Re-W/ 20% Re) a distancias conocidas.…”

Section: Parte Experimentalunclassified

Obtención de Si<sub>3</sub>N<sub>4</sub> mediante SHS

Cano¹,

Rodrı́guez²

2003

Bol. Soc. Esp. Ceram. Vidr.

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En el presente trabajo se presentan los resultados obtenidos en el estudio de las reacciones de Síntesis Autopropagada a Alta Temperatura (Self-propagating High-temperature Synthesis, SHS) de Nitruro de Silicio. La síntesis autopropagada a alta temperatura consiste básicamente en la generación de reacciones altamente exotérmicas capaces de automantenerse. Se puede considerar como principal ventaja del método el ahorro energético que supone. La síntesis se realiza sobre una mezcla inicial de silicio metálico sobre la cual se realizan adiciones de diluyente y otros aditivos (sales amónicas) que afectan al desarrollo de la reacción. Se ha estudiado la influencia que en este sistema pueden tener las proporciones de las distintas incorporaciones en la mezcla, tanto en el material resultante como en las condiciones de reacción. Igualmente se ha estudiado la posibilidad de utilización de nuevos aditivos que puedan minimizar el impacto medio ambiental. Se presentan los estudios microestructurales del material obtenido, la identificación cristalográfica de las fases presentes así como los comportamientos de los parámetros que definen la propia reacción. Con la información obtenida se propone el mecanismo predominante de la síntesis del Nitruro de Silicio mediante SHS. Palabras clave: Síntesis, Nitruro de Silicio, SHS Synthesis of Si 3 N 4In the present paper results obtained during synthesis of Silicon Nitride by Self-propagating High-temperature Synthesis (SHS) are shown. Self-propagating High-temperature Synthesis is based on the high enthalpy of certain reactions able to be self-sustained. One of the most important advantages of the method is its very low energy consumption. The synthesis is carried out with a mixture of silicon powder with some additions of diluents and other synthesis aids (ammonium salts). The influence of the mixture composition on reaction parameters and characteristics of the obtained products has been studied. The use of new synthesis aids has been also studied in order to decrease the environmental impact of the process. Microstructural study, XRD and reaction parameters are shown. Finally a mechanism of Silicon Nitride synthesis is proposed.Key words: Synthesis, Silicon Nitride, SHS INTRODUCCIÓNLa síntesis autopropagada a alta temperatura (conocida como SHS) [1 , 2] consiste básicamente en la generación de reacciones altamente exotérmicas capaces de propagarse a traves de la mezcla inicial, tranformandola en los compuestos deseados, sin aporte externo de energía. Se puede considerar como principal ventaja del método el ahorro energético que supone, principalmente si se compara con los métodos utilizados convencionalmente.Como es bien conocido la síntesis de nitruro de silicio (Si 3 N 4 ) se puede realizar por distintas vías, una de las cuales es a través de la reacción de silicio metálico en atmósfera de nitrógeno la cual bajo las condiciones adecuadas, es una reacción autopropagada [3 , 4] . La primera restricción que se ha observado en esta reacción SHS es debida a que la tempera...

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Quantitative X-Ray Diffraction Analysis

Cited by 111 publications

References 16 publications

Coupling thermodynamics and digital image models to simulate hydration and microstructure development of portland cement pastes

Coupling thermodynamics and digital image models to simulate hydration and microstructure development of portland cement pastes

Quantitative phase analysis by X-ray diffraction – Simple routes

Obtención de Si<sub>3</sub>N<sub>4</sub> mediante SHS

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