Quantitative X-ray Powder Diffraction Research Articles

Insight into Solvent-Dependent Conformational Polymorph Selectivity: The Case of Undecanedioic Acid

Here we report the polymorph nucleation of undecanedioic acid (UDA) having high solvent-dependent selectivity. Solvents with high hydrogen bond donating (HBD) ability preferred to produce form II, while form I was obtained from solvents with no HBD ability. Cooling experiments in a series of binary solvents with an HBD ability value from 0 to 86 were designed to affirm the strong correlation between solute–solvent interactions and polymorph formation verified by solution Fourier transform infrared (FTIR) spectroscopy and quantitative powder X-ray diffraction. Two crystal structures, evaluated as conformational dimorphs assisted by FTIR, solid-state NMR, and quantum chemistry calculations, were reported. Furthermore, the crystal structures suggest that UDA molecules from various solutions went through different conformation rearrangements resulting in two forms during nucleation. Meanwhile, we reveal that there is no direct connection between the solution chemistry of UDA in solvents with various HBD stren...

Prediction and Measurement of the Kinetics of Isothermal Crystallization and Devitrification of Mold Powder Slags

The rate and extent of formation of crystalline phases in the slag film that develops between the mold and the strand in steel continuous casting determine heat transfer and lubrication between them and therefore play crucial roles in shell integrity. In this work, a commercial mold powder for casting medium carbon (MC) thin steel slabs is selected for carrying out detailed comparisons between predicted and experimental results of the rates of isothermal crystallization and devitrification of liquid and glassy slag, respectively. Predictions are obtained with a kinetic model that combines the induction period (of Simon and Kolman) and the Kissinger methods to evaluate time–temperature–transformation (TTT) diagrams for the devitrification and crystallization reactions associated with the peaks appearing in non-isothermal thermo-analysis traces. To obtain experimental validation of the diagram, a high-temperature confocal laser scanning microscope (HT-CLSM) is used to rapidly heat or cool a sample, ~ 140 mg, of glassy powder or liquid slag, respectively, to selected isothermal conditions, where it is held for a prescribed length of time before quenching. Identification and quantification of the phases present in the quenched samples are done by a quantitative X-ray powder diffraction analysis (QXRPDA) method that uses a PONKCS (partial or not known crystal structure) procedure based on Le Bail and Rietveld strategies for refinement of diffraction patterns. The many experimental results indicate that the predicted TTT diagrams for devitrification and crystallization of the mold slag give a good estimation of the rate of the transformations that take place at different temperatures and reveal the differences in the reactions that occur along both paths.

Quantitative X-Ray Powder Diffraction and the Illite Polytype Analysis Method for Direct Fault Rock Dating: A Comparison of Analytical Techniques

AbstractIllite polytypes are used to elucidate the geological record of formations, such as the timing and provenance of deformations in geological structures and fluids, so the ability to characterize and identify them quantitatively is key. The purpose of the present study was to compare three X-ray powder diffraction (Q-XRPD) methods for illite polytype quantification for practical application to directly date clay-rich fault rocks and constrain the provenance of deformation-related fluids in clay-rich brittle rocks of the upper crust. The methods compared were WILDFIRE© (WF) modeling, End-member Standards Matching (STD), and Rietveld whole-pattern matching (BGMN®). Each technique was applied to a suite of synthetic mixtures of known composition as well as to a sample of natural clay gouge (i.e. the soft material between a vein wall and the solid vein). The analytical uncertainties achieved for these synthetic samples using WF modeling, STD, and Rietveld methods were ±4–5%, ±1%, and ±6%, respectively, with the caveat that the end-member clay mineral used for matching was the same mineral sample used in the test mixture. Various particle size fractions of the gouge were additionally investigated using transmission electron microscopy (TEM) to determine polytypes and laser particle size analysis to determine grain size distributions. The three analytical techniques produced similar 40Ar/39Ar authigenesis ages after unmixing, which indicated that any of the methods can be used to directly date the formation of fault-related authigenic illite. Descriptions were included for pre-calculated WF illite polytype diffractogram libraries, model endmembers were fitted to experimental data using a least-squares algorithm, and mixing spreadsheet programs were used to match end-member natural reference samples.

Near-surface clay authigenesis in exhumed fault rock of the Alpine Fault Zone (New Zealand); O-H-Ar isotopic, XRD and chemical analysis of illite and chlorite

Exhumed fault rock of the central Alpine Fault Zone (South Island, New Zealand) shows extensive clay mineralization, and it has been the focus of recent research that aims to describe the evolution and frictional behavior of the fault. Using Quantitative X-ray powder diffraction, 40Ar/39Ar geochronology, hydrogen isotope (δD) geochemistry, and electron microbeam analysis, we constrain the thermal and fluid conditions of deformation that produced two predominant clay phases ubiquitous to the exposed fault damage zone, illite and chlorite. Illite polytype analysis indicates that most end-member illite and chlorite material formed in equilibrium with meteoric fluid (δD = −55 to −75‰), but two locations preserve a metamorphic origin of chlorite (δD = −36 to −45‰). Chlorite chemical geothermometry constrains crystal growth to T = 210–296 °C. Isotopic analysis also constrains illite growth to T < 100 °C, consistent with the mineralogy, with Ar ages <0.5 Ma. High geothermal gradients in the study area promoted widespread, near-surface mineralization, and limited the window of clay authigenesis in the Alpine Fault Zone to <5 km for chlorite and <2 km for illite. This implies a significant contrast between fault rock exposed at the surface and that at depth, and informs discussions about fault strength, clays and frictional behavior.

Active sulfate-rich belite sulfoaluminate cement

This work focuses on the activation of belite to improve the strength development of sulfate-rich belite sulfoaluminate cements. Borax was used to act as an activator to promote stabilisation of high-temperature belite polymorphs. The phase compositions of clinkers were analysed by using quantitative X-ray powder diffraction. The transformation of β-belite (C2S) to α′-C2S mainly depends on the dosage of borax, and the change in polymorphs is almost complete when the dosage of borax reaches 5%. The formation of α′-C2S can significantly increase the compressive strength and the concentration of borax has a great effect on the strength development of the activated cements. The hydration products of activated cements were also investigated. The results show that the activation of belite can promote the formation of ettringite. Moreover, the crystallisation of ettringite is also affected by the polymorphs of belite, and a fine microstructure of ettringite is found in the activated cement paste.

Sintering characteristics of BCSAF cement clinker with added wastes from production of manganese and magnesium metals

The production of belite-calcium sulfoaluminate-ferrite (BCSAF) cement with the addition of industrial wastes as feedstock has been studied for many years. The preparation of clinkers is essential in cement production, in which all raw materials react with each other to generate key phases in cement under some specified conditions. The objective of this study was to investigate the sintering characteristics of BCSAF cement clinkers. Four BCSAF clinkers with different compositions were examined. High-temperature microscopy, quantitative x-ray powder diffraction analysis and scanning electron microscopy were used to analyse sintering features and phase composition. The results show that the use of wastes from the production of manganese and magnesium metals, which were added to the raw materials to make clinker pellets, can significantly reduce the firing temperature of BCSAF clinker. The firing temperatures of clinkers with added wastes were below 1300°C, much lower than the temperature used for convention...

Kinetics of Formation and Crystal Structure Determination of Sr4Al6O12SO4

The sulphoaluminate of strontium, Sr4Al6O12SO4, was synthesized by solid state reaction from mixture of SrCO3, Al2O3 and SrSO4 (3:3:1 molar ratio) as pellets. The kinetics of formation has been studied in the range of temperature between 850oC and 1100oC using quantitative X-ray powder diffraction data (XRD) analysis. Likewise, at room temperature, the crystal structure was determined from conventional X-ray powder diffraction data using direct methods and it was refined by the Rietveld method. The kinetics mechanisms that showed the best fit, were identified as geometrical contraction at grain boundary (R1.1) and nucleation and growing by energy law (P1.1). The activation energy values obtained were 145.47KJmol-1 (R1.1) and 151.35KJmol-1 (P1.1), respectively. The resulting crystal structure was orthorhombic type (a: 13.32802A, b: 13.34430A and c: 9.38704A). The observed adjustment parameters were RB: 0.0985, Rwp: 0.137, Rp: 0.0925 and Chi2: 1.94.

Phase Analysis of Portland Cement by Combined Quantitative X-Ray Powder Diffraction and Scanning Electron Microscopy.

X-ray powder diffraction (XRD) has been used for several decades to identify and measure the mass fractions of various crystalline phases in portland cement. More recently, a combination of scanning electron microscopy with X-ray microanalysis (SEM/XMA) and image processing has been shown to enable the quantitative characterization of microstructural features in these materials. Each technique can furnish some information that is not accessible from the other. For example, SEM/XMA can identify the microstructural location and morphology of calcium sulfate minerals, while only XRD can determine the relative abundance of the different forms of calcium sulfate, such as gypsum (CaSO4 · 2H2O), bassanite , and anhydrite (CaSO4). This document describes how XRD and SEM/XMA can be used together to establish and validate the portland cement phase composition and microstructure. Particular emphasis is laid on step-by-step procedures and best practices for XRD specimen preparation, data collection, and intepretation. Similar detail has been given recently for SEM/XMA [Stutzman et al., NIST Tech Note 1877, U.S. Department of Commerce, April 2015]. The methods are demonstrated for three portland cement powders, through which apparent discrepancies between the results of the two methods are identified and procedures are described for resolving the discrepancies and quantifying uncertainty.

Amorphous iron phases in medium temperature leach residues and associated metal loss

Leach residues, produced during pilot and demonstration scale medium temperature (150°C) hydrometallurgical processing of sulfide ores contain amorphous/poorly crystalline and metastable nano-scale iron oxides/oxyhydroxide phases. These phases control the properties of the residue and contain a relatively high loading of the valuable (Cu, Ni) metals. Residue samples from CESL and Vale pilot and demonstration plant medium temperature processes were characterized using different techniques. Poor agreement between total iron analysis by inductively coupled plasma mass spectroscopy (ICP-MS) and quantitative X-ray powder diffraction QXRPD indicated the presence of amorphous/poorly crystalline iron oxide phases. QXRPD coupled with sequential extraction was used for quantification of the amorphous iron phases. Amorphous iron oxides/oxyhydroxides were found to be a major source of copper and nickel losses to the residue. The distribution of copper and nickel into the amorphous and crystalline iron oxide phases was determined by a two-stage sequential extraction process. Association of copper and nickel to the amorphous phases was found to be approximately 2–4 times higher than with the crystalline iron oxide phases.

Thermo-kinetic analysis of Ni–Al intermetallic phase formation in powder system

Thermo-kinetic analysis was carried out to determine the kinetics of Ni–Al intermetallic phase formation from powder mixture of Ni and Al. The kinetic data were generated using dynamic temperature program at 5, 10, 15, 20 K min−1 in a differential scanning calorimeter. The phase formation was studied with the help of both qualitative and quantitative powder X-ray diffraction using Rietveld refinement. The activation energy for the reaction was calculated from model-free isoconversional technique employing both differential (Friedman’s method) and integral (Flynn–Wall–Ozawa and Kissinger–Akahira–Sunose method) methods. The result shows that formation of NiAl from elemental powders is multi-step in nature involving $$\hbox {Ni}_2\hbox {Al}_3$$ as a major intermediate. The appropriate kinetic model for the reaction was evaluated by means of Malek’s method (model selection technique). Sestak Breggren (auto-catalytic model) was found to be in good agreement with the experimental data. The corresponding kinetic parameters and rate expression were determined for the reaction system involving solid–solid reaction between Ni and Al in the powder form.

Synthesis of belite sulfoaluminate-ternesite cements with phosphogypsum

Phosphogypsum (PG) is an industrial byproduct from phosphoric acid production. In order to facilitate the use of PG, belite sulfoaluminate-ternesite cements were produced with high amounts of PG. This work regards the laboratory production of belite sulfoaluminate-ternesite cements by using a new synthesis method. Using a secondary heat treatment step, the method achieves the coexistence of ye'elimite and ternesite. Quantitative X-ray powder diffraction and electron microscopy were used to analyze the phase composition of clinkers. The secondary heat treatment between 1100 and 1200 °C can significantly facilitate the formation of ternesite in the clinkers. The presence of large amount of ternesite results in a decrease in early strength, but the hydration of ternesite at later ages can increase the strength after 56 days of hardening. The hydration products of pure ternesite and the clinker containing ternesite were also investigated. The results show that pure ternesite can hydrate at a slow rate, and the addition of ye'elimite promotes the hydration of ternesite and the formation of ettringite. The ettringite formation for the clinker containing ternesite mainly depends on the dissolution of gypsum originating from the hydration of ternesite.

Special Aspects of Hydration Process of Microfine Cement

The aim of the present research was to determine special features of hydration process of two commercial microfine cements compared to CEM I 42.5N cement with similar mineralogical composition. The influence of cement fineness and composition on the hydration process was investigated by isothermal calorimetry of cement pastes and quantitative X-ray powder diffraction of hydration products at 1, 3, 7, 14 and 28 days.

The Orvieto-Bagnoregio Ignimbrite: pyroxene crystal-chemistry and bulk phase composition of pyroclastic deposits, a tool to identify syn- and post-depositional processes

This study aims to characterize the crystallization conditions of the ignimbritic flux, the spatial and temporal evolution as well as the post-depositional processes of the Orvieto-Bagnoregio pyroclastic deposits from Bolsena Complex (Roman Magmatic Province, Italy) from a mineralogical and a geochemical point of view. Single-crystal X-ray diffraction together with electron-microprobe analysis (EMPA) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) data were used to determine the crystal-chemistry of ten clinopyroxene samples from three outcrops of the Bolsena Complex: Orvieto, Bagnoregio and Porano. In addition, quantitative X-ray powder diffraction analyses of amorphous and crystalline phases by the Rietveld method were performed both on the bulk rock and on the juvenile products (mainly pumices and scoriae). The chemical composition and lattice parameters of the Orvieto and Bagnoregio clinopyroxenes indicate diopsides with a common mineralogical and petrogenetic affinity, but slightly different crystallization conditions from the samples of the Porano deposit. Cell volume and M1 polyhedral volume indicate a very low pressure of crystallization in comparison to those calculated for other eruptive centres of the Roman Magmatic Province (Sabatini, Vico and Alban Hills). Notwithstanding a common very high REE content in clinopyroxenes, the decrease of the REE content from the bottom to the top of the stratigraphic sequence of Orvieto is interpreted as an indication of the chemical zoning of the magmatic chamber. The bulk mineralogical composition is characterized by the presence of clinopyroxene, biotite, anorthite, leucite, analcime and zeolite, in particular phillipsite and chabazite. The Orvieto sequence is affected by strong differences in the amorphous content ranging from 1.3 to 82.0 wt%, as well as in the sanidine/zeolite ratio: sanidine content changes from 15.5 to 55.9 wt% and chabazite from 3.4 to 68.4 wt%. The large amount of zeolites along the pyroclastic sequence testifies that the Orvieto-Bagnoregio Ignimbrite was emplaced by hydromagmatic eruption at quite high temperatures with diffuse zeolitization that indicates strong variations in the chemical-physical composition of the pyroclastic flows which in turn have influenced the post-depositional processes and the cohesion of the rock.

X-ray powder diffraction: A powerful tool for industrial protein production

X-ray powder diffraction (XRPD) offers a method of characterizing a crystalline protein suspension [1], and data can be collected within 30 minutes, which is appealing for industrial applications. In industry, enzymes are produced and handled in high concentrations, which can in turn cause problems for the processes due to protein precipitation in the production pipeline. XRPD is useful for identification of the crystal forms present, by fitting calculated patterns of known single crystal forms to the observed XRPD pattern. For this purpose we have developed a streamlined program for calculation of diffraction patterns from pdb-files taking into account bulk-solvent, peak asymmetry and background [2]. XRPD was applied to a suspension from a large-scale industrial production of the widely used Bacillus lentus subtilisin. A dominant crystal form was identified by XRPD, but two other different crystal forms were found by a complementary single crystal micro-diffraction analysis of the larger single crystals present in the sample [3]. The study serves as a reminder that when a crystal is picked out from a batch crystallization for single crystal analysis, it might not be representative of the bulk microcrystalline material in the sample. To estimate the fraction of the different crystal forms in production samples with significant polymorphism, a further XRPD study was performed on binary mixtures of different lysozyme and subtilisin crystal forms. Quantitative XRPD generally requires careful sample preparation, and working with protein slurries leads to further challenges in terms of varying crystal density. After careful optimisation of suspension medium, the relative composition of crystal forms can be determined within 10%. This work demonstrates the value of in-house XRPD as an analysis tool in industrial enzyme production, and its potential to help troubleshooting the production process and to provide information for further refining the manufacturing of enzymes.

Structural characteristics of cordierite/steatite ceramics sintered from mixtures containing pore-forming organovermiculite

The preceramic mixtures appropriate to the composition of cordierite are composed of talc, kaolinite and vermiculite (Ver), and/or organovermiculite (Ver-org) as a pore-forming agent. The preceramic mixtures for sintering at 1300°C were prepared in two different ways, loosely in crucibles and compressed into pellets. Structural characterization of cordierite/steatite ceramic was performed using X-ray powder diffraction (XRD), FTIR spectroscopy, scanning electron microscopy analysis and porosity measurement. The ceramic samples showed (1) bimodal meso-macropore size distribution and unimodal macropore size distribution, when the preceramic mixtures included Ver and Ver-org, respectively, and (2) higher porosity when sintering mixtures occurred in crucibles in comparison with pellets. The XRD patterns and quantitative XRD phase analysis revealed cordierite/steatite ceramics in the composition of indialite (IND) and two orthorhombic forms of enstatite: protoenstatite (PEN) and orthoenstatite (OREN). All cordierite/steatite samples contained a greater amount of PEN than OREN and a slightly higher quantity of IND when sintered in crucibles compare to pellets. The ceramic samples prepared from the preceramic mixtures with twice the amount of Ver-org contained a high quantity of IND (91vol%), PEN (about 9vol%) and no OREN. The unit cell parameter c in comparison with the pure IND was about 0.001–0.003nm shorter at all INDs. The pore-forming Ver-org supports structural substitution of cations during crystallization of IND with the substitution Ca0.50Mg1.50–Ca0.25Mg1.75. The IR spectra in the 400–1600cm−1 region confirmed the presence of cordierite and steatite.

Quantitative X-Ray Powder Diffraction Analysis of Portland Cements: Proficiency Testing for Laboratory Assessment

Abstract Quantitative X-ray powder diffraction analysis (QXRD) is being used within the cement industry for phase characterization of hydraulic cement. The current ASTM standard test method for powder diffraction analysis of cements provides guidance, but not an explicit method, for quantifying phase concentrations. The standard utilizes qualification criteria, where an analysis of a set of certified reference materials must fall within stated precision and bias limits. Validation of X-ray powder diffraction analyses by the Rietveld method is particularly important because the normalization inherent in the mass fraction calculations can obscure accuracy problems. Currently, the only certified reference materials for phase abundance are a set of NIST SRM clinkers, which lack the calcium sulfate and carbonate phases found in portland cements. A set of portland cements was distributed to 29 laboratories for analysis according to each lab’s individual protocols. The objective was to provide each lab with quantitative feedback on its precision and accuracy performance. The results from all the labs are presented graphically with Youden plots that incorporate ranking to illustrate relative lab precision and accuracy based upon a consensus mean for each phase and ASTM C1365 performance qualification criteria. Labs that fall outside of the compliance limits are provided with information via the Youden plots to assess their systematic and random error. Proficiency testing of this sort provides participating laboratories with a quantitative assessment of their performance relative to peers using a wider range of materials encompassing the broad spectrum of modern hydraulic cement production. These newer materials may include, for example, the calcium sulfate phases and the limestone additions that have become commonplace in today’s cements. Such a quantitative assessment could be used to qualify laboratories and may be stipulated in a specification.

Thermoelectric performance of multiphase XNiSn (X = Ti, Zr, Hf) half-Heusler alloys

Quantitative X-ray powder diffraction analysis demonstrates that mixing Ti, Zr and Hf on the ionic site in the half-Heusler structure, which is a common strategy to lower the lattice thermal conductivity in this important class of thermoelectric materials, leads to multiphase behaviour. For example, nominal Ti0.5Zr0.5NiSn has a distribution of Ti1−xZrxNiSn compositions between 0.24 ≤ x ≤ 0.70. Similar variations are observed for Zr0.50Hf0.5NiSn and Ti0.5Hf0.5NiSn. Electron microscopy and elemental mapping demonstrate that the main compositional variations occur over micrometre length scales. The thermoelectric power factors of the mixed phase samples are improved compared to the single phase end-members (e.g. S2/ρ = 1.8 mW m−1 K−2 for Ti0.5Zr0.5NiSn, compared to S2/ρ = 1.5 mW m−1 K−2 for TiNiSn), demonstrating that the multiphase behaviour is not detrimental to electronic transport. Thermal conductivity measurements for Ti0.5Zr0.5NiSn0.95 suggest that the dominant reduction comes from Ti/Zr mass and size difference phonon scattering with the multiphase behaviour a secondary effect.

Rietveld quantification of γ-C2S conversion rate supported by synchrotron X-ray diffraction images

The pure γ-Ca2SiO4 (γ-C2S) phase was prepared at 1623 K of calcining temperature, 10 h of holding time and furnace cooling. The β-C2S phase was obtained through γ-C2S conversion with the following calcination system which was adopted at 1473 K of calcining temperature, 1 h of holding time and then water-cooling. The conversion rate of γ-C2S was studied by the Rietveld quantitative laboratory X-ray powder diffraction supported by synchrotron X-ray diffraction images. The refinement results show that the final conversion rate of γ-C2S is higher than 92%. The absolute error of the γ-C2S conversion rate between two Rietveld refinements (sample with or without α-Al2O3) is 3.6%, which shows that the Rietveld quantitative X-ray diffraction analysis is an appropriate and accurate method to quantify the γ-C2S conversion rate.

Alite-ye'elimite cement: Synthesis and mineralogical analysis

Alite-ye'elimite cement is an alternative cement that combines desirable characteristics of calcium sulfoaluminate cements and Portland cement in that it shows improved strength development at early age while retaining high portlandite contents. The key problem in the clinkering process is to produce the alite-ye'elimite phase assemblage so that both phases can co-exist. In this study, a new synthesis method is proposed to achieve the coexistence of alite and ye'elimite consisting of a secondary heat treatment step at 1250°C after regular Portland clinker firing at 1450°C. Quantitative X-ray powder diffraction and electron microscopy were used to analyze the phase composition of clinker before and after the secondary heat treatment. The results show that ye'elimite develops during secondary heat treatment of calcium sulphate enriched clinker by reaction of C3A and sulphate phases. Additional ferrite is formed as result of rejection of Fe originally in solid solution with C3A during ye'elimite formation.

Hydrated phases and pore solution composition in cementsolidified saltstone waste forms

The mineral phases and pore solution composition of hydrated cement- solidified synthetic saltstone waste forms are quantified using thermogravimetric analysis, quantitative X-ray powder diffraction, and inductively coupled plasma atomic emission spectroscopy. Although the synthetic waste contained additional sulfate, the overall chemistry of the system suppressed the formation of sulfate-bearing mineral phases. This was corroborated by the pore solution analysis that indicated very high sulfur concentrations. After one year of hydration, the mineral phases present and the composition of the pore solution are stable, and are generally consistent with expectations based on the hydration of high volume portland cement replacement mixtures.