Quantitative X-ray Diffraction Analysis Research Articles

Detoxification and immobilization of chromite ore processing residue in spinel-based glass-ceramic

A promising strategy for the detoxification and immobilization of chromite ore processing residue (COPR) in a spinel-based glass-ceramic matrix is reported in this study. In the search for a more chemically durable matrix for COPR, the most critical crystalline phase for Cr immobilization was found to be a spinel solid solution with a chemical composition of MgCr1.32Fe0.19Al0.49O4. Using Rietveld quantitative X-ray diffraction analysis, we identified this final product is with the phases of spinel (3.5wt.%), diopside (5.2wt.%), and some amorphous contents (91.2wt.%). The partitioning ratio of Cr reveals that about 77% of the Cr was incorporated into the more chemically durable spinel phase. The results of Cr K-edge X-ray absorption near-edge spectroscopy show that no Cr(VI) was observed after conversion of COPR into a glass-ceramic, which indicates successful detoxification of Cr(VI) into Cr(III) in the COPR-incorporated glass-ceramic. The leaching performances of Cr2O3 and COPR-incorporated glass-ceramic were compared with a prolonged acid-leaching test, and the results demonstrate the superiority of the COPR-incorporated glass-ceramic matrix in the immobilization of Cr. The overall results suggest that the use of affordable additives has potential in more reliably immobilizing COPR with a spinel-based glass-ceramic for safer disposal of this hazardous waste.

Unified Theory for Decoding the Signals from X-Ray Florescence and X-Ray Diffraction of Mixtures.

For research and development or for solving technical problems, we often need to know the chemical composition of an unknown mixture, which is coded and stored in the signals of its X-ray fluorescence (XRF) and X-ray diffraction (XRD). X-ray fluorescence gives chemical elements, whereas XRD gives chemical compounds. The major problem in XRF and XRD analyses is the complex matrix effect. The conventional technique to deal with the matrix effect is to construct empirical calibration lines with standards for each element or compound sought, which is tedious and time-consuming. A unified theory of quantitative XRF analysis is presented here. The idea is to cancel the matrix effect mathematically. It turns out that the decoding equation for quantitative XRF analysis is identical to that for quantitative XRD analysis although the physics of XRD and XRF are fundamentally different. The XRD work has been published and practiced worldwide. The unified theory derives a new intensity-concentration equation of XRF, which is free from the matrix effect and valid for a wide range of concentrations. The linear decoding equation establishes a constant slope for each element sought, hence eliminating the work on calibration lines. The simple linear decoding equation has been verified by 18 experiments.

High temperature oxidation behavior of an equimolar refractory metal-based alloy 20Nb[sbnd]20Mo[sbnd]20Cr[sbnd]20Ti[sbnd]20Al with and without Si addition

The high temperature oxidation behavior of a refractory high-entropy alloy (HEA) 20Nb20Mo20Cr20Ti20Al at 900 °C, 1000 °C and 1100 °C was investigated. The oxidation kinetics of the alloy was found to be linear at all temperatures. Oxide scales formed are largely inhomogeneous showing regions with thick and porous layers as well areas with quite thin oxide scales due to formation of discontinuous chromium-rich oxide scales. However, the oxidation resistance can be moderately improved by the addition of 1 at.% Si. The thermogravimetric data obtained during oxidation of the Si-containing alloy at 1000 °C and 1100 °C reveal pronounced periods of parabolic oxidation that, however, change towards linear oxidation after prolonged exposure times. Microstructural investigations using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) document that the Si addition gives rise to a nearly continuous alumina-rich layer which seems to be responsible for the good protection against further oxidation. Pronounced zones of internal corrosion attacks consisting of different oxides and nitrides were observed in both alloys. In order to determine the chemical composition of the corrosion products and their mass fraction, quantitative X-ray diffraction (XRD) analysis was performed on powdered oxide scales that formed on the alloys after different oxidation times. Rutile was identified as the major phase in the oxide scales rationalizing the relatively high mass gain during oxidation.

Quantitative Estimation of Mullite in Alumina Based Porcelain Insulators Samples

Although porcelain insulators in power lines have been in use for decades, several undergo catastrophic failures while early in service. A study addressing the materials aspects has been conducted on alumina based porcelain insulators. Apart from their electro mechanical stability characteristics, material aspects like composition, phase and microstructure play a very important role in their performance. The qualitative phase analyses on the insulator samples give an idea about the different major and minor phases present. Attempts have already been made to estimate α alumina and α quartz content in porcelain body. Mullite is another important phase present in the porcelain body, which gets formed during firing of raw materials during insulator manufacture and which has not been estimated quantitatively. An attempt has been made here to assess the mullite content in the alumina based insulator samples by X-Ray diffraction quantitative analysis. Internal standard method of quantification has been adopted successfully for the analysis. This article describes the quantification of mullite phase by the internal standard method based on X-Ray diffraction principle.

Characterization of Precipitates in a Microalloyed Steel Using Quantitative X-ray Diffraction

Quantitative X-ray diffraction (QXRD) (also known as the Rietveld method) was used to analyze the precipitates present in Grade 100 microalloyed steel. The precipitates were extracted from the steel using electrolytic dissolution and the residue from the dissolution was analyzed using XRD. The XRD pattern exhibited three (3) distinct diffraction peaks, and significant broadening of a fourth peak corresponding to the <10 nm size precipitates. QXRD analysis was applied to the XRD pattern to obtain precipitate size, composition, and weight fraction data for each of the four diffraction peaks observed. The predicted mean precipitate diameter and average atomic composition of the nano-size (<10 nm) precipitates was 4.7 nm and (Nb0.50Ti0.32Mo0.18)(C0.59N0.41), respectively. The predicted precipitate size correlates well with the average size of precipitates measured in previous work by the authors using both transmission electron microscopy (TEM) and small angle neutron scattering (SANS). The average atomic composition correlates well with the composition measured in this work using energy dispersive X-ray (EDX) analysis of individual nano-sized precipitates. The calculated weight fraction of the nano-size precipitates in the extracted residue was 42.2 wt. %. The calculated atomic compositions of the other three diffraction peaks were TiN, (Ti0.87Nb0.13)N, and (Nb0.82Ti0.18)(C0.87N0.13) with weight fraction values of 12.9 wt. %, 31.7 wt. %, and 13.1 wt. %, respectively. The sizes of both the (Ti0.87Nb0.13)N and the (Nb0.82Ti0.18)(C0.87N0.13) groups of precipitates were directly measured and were observed to range from 150 nm to 570 nm and from 90 nm to 475 nm, respectively. QXRD was unable to determine a reasonable mean precipitate size for either of these two groups of precipitates. The wide compositional range (i.e., varying levels of Nb and Ti) of these precipitates (as measured by EDX) resulted in XRD peak broadening that was erroneously interpreted as a size broadening effect.

An Improved Approach to Characterize Potash-Bearing Evaporite Deposits, Evidenced in North Yorkshire, United Kingdom

Traditionally, potash mineral deposits have been characterized using downhole geophysical logging in tandem with geochemical analysis of core samples to establish the critical potassium (% K2O) content. These techniques have been employed in a recent exploration study of the Permian evaporite succession of North Yorkshire, United Kingdom, but the characterization of these complex deposits has been led by mineralogical analysis, using quantitative X-ray diffraction (QXRD). The novel QXRD approach provides data on K content with the level of confidence needed for reliable reporting of resources and also identifies and quantifies more precisely the nature of the K-bearing minerals. Errors have also been identified when employing traditional geochemical approaches for this deposit, which would have resulted in underestimated potash grades. QXRD analysis has consistently identified polyhalite (K2Ca2Mg(SO4)4·2(H2O) in the Fordon (Evaporite) Formation and sylvite (KCl) in the Boulby Potash and Sneaton Potash members as the principal K-bearing host minerals in North Yorkshire. However, other K hosts, including kalistrontite (K2Sr(SO4)2) a first recorded occurrence in the UK, and a range of boron-bearing minerals have also been detected. Application of the QXRD-led characterization program across the evaporitic basin has helped to produce a descriptive, empirical model for the deposits, including the polyhalite-bearing Shelf and Basin seams and two, newly discovered sylvite-bearing bittern salt horizons, the Pasture Beck and Gough seams. The characterization program has enabled a polyhalite mineral inventory in excess of 2.5 billion metric tons (Bt) to be identified, suggesting that this region possesses the world’s largest known resource of polyhalite. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution and reproduction in any medium provided that the original work is properly attributed.

Effects of calcium and ferric ions on struvite precipitation: A new assessment based on quantitative X-ray diffraction analysis

The precipitation of struvite (MgNH4PO4·6H2O) from waste streams has attracted considerable attention due to its potential for recovering phosphorus for fertilization. As struvite is primarily acquired by means of precipitation and crystallization from aqueous solutions, it is important to evaluate the roles of common metal ions, particularly those that are commonly found in wastewater, in the struvite crystallization process. This study was performed to quantitatively evaluate the effects of calcium and ferric ions on struvite crystallization using the Rietveld refinement method, which is based on the analysis of X-ray diffraction data. The results indicate that both calcium and ferric ions significantly inhibit the formation of struvite crystals, and the effects vary under different pH conditions. There was a negative linear correlation between the struvite weight content in the precipitates and the Ca/Mg molar ratio in the initial solution. However, ferric ions were confirmed to be a more efficient inhibitor of struvite crystallization. Ca2+ and Fe3+ further modified the needle-like struvite into irregular shapes. An unambiguous and quantitative understanding of the effects of foreign ions on struvite crystallization will help to reliably improve the quality of struvite products recovered from wastewater and the control of struvite deposits in water and sludge piping systems.

Facile synthesis, characterization, and electrochemical performance of multi-scale AgVO3 particles

Multi-scale AgVO3 particles were successfully synthesized from different organic acids using a facile sol–gel method; a series of techniques were then used to characterize the particles. The X-ray Diffraction (XRD) patterns showed that a main characteristic peak of element Ag is at around 38°. The X-ray photoelectron spectroscopy (XPS) spectra demonstrated the binding energies of Ag0 3d (5/2) and Ag0 3d (3/2), which further confirmed the existence of element Ag. In addition, the composition of the samples, including the amorphous phase, was determined with a quantitative X-ray diffraction (QXRD) analysis. With a heating rate of 10 °C/min, the products synthesized with citric acid at 450 °C had a larger amorphous phase (26.4% in wt.%) than the samples synthesized with citric acid at 500 °C. To obtain lesser amorphous phase, the precursors were treated at 500 °C with a slower heating rate of 5 °C/min. The electrochemical performance of these three samples, particularly their suitability as cathode materials for lithium ion batteries, were investigated. The products with minimum amorphous phase (9.4%) showed higher specific discharge capacity than other two samples at the first 40 cycles. However, with the increasing fading rate, only 27% of the initial capacity was retained after 100 cycles. Amorphous phase can stabilize the material and avoid the structural collapse during the cycles. Therefore, under the synergistic effect of amorphous content and particle size, the products obtained at 500 °C with quicker heating rate exhibited the optimal capacity and cycling stability. This electrode showed a high initial capacity of 243 mA h/g and retained 41% of the initial capacity after 100 cycles.

Kinetic investigation of sulfidizing annealing of scorodite in processing of refractory oxidized gold-containing ores

The results of kinetic studies on the removal of arsenic from scorodite using sulfidizing annealing are presented. The reaction order with respect to the reactant and the activation energy are established from the experimental data. The rate-determining step of the sulfidizing annealing process is determined. The main reactions that occur during the sulfidizing of arsenic in scorodite are proposed on the basis of the obtained results and confirmed by thermodynamic calculations and chemical analyses. The major results of testing this technology, as applied to the refractory oxidized ores in which arsenic is mainly concentrated in scorodite, are presented. Arsenic removal from this ore is confirmed by chemical and quantitative X-ray diffraction analyses and by qualitative phase analysis. Industrial use of this technology provides safe and efficient processing of refractory gold-containing ores, where arsenic is mainly concentrated in scorodite.

Quantitative x-ray diffraction analysis of bimodal damage distributions in Tm implanted Al0.15Ga0.85N

In this work radial symmetric x-ray diffraction scans of Al0.15Ga0.85N thin films implanted with Tm ions were measured to determine the lattice deformation and crystal quality as functions of depth. The alloys were implanted with 300 keV Tm with 10° off-set to the sample normal to avoid channelling, with fluences varying between 1013 Tm cm−2 and 5 × 1015 Tm cm−2. Simulations of the radial 2θ–ω scans were performed under the frame of the dynamical theory of x-ray diffraction assuming Gaussian distributions of the lattice strain induced by implantation defects. The structure factor of the individual layers is multiplied by a static Debye–Waller factor in order to take into account the effect of lattice disorder due to implantation. For higher fluences two asymmetric Gaussians are required to describe well the experimental diffractograms, although a single asymmetric Gaussian profile for the deformation is found in the sample implanted with 1013 Tm cm−2. After thermal treatment at 1200 °C, the crystal quality partially recovers as seen in a reduction of the amplitude of the deformation maximum as well as the total thickness of the deformed layer. Furthermore, no evidence of changes with respect to the virgin crystal mosaicity is found after implantation and annealing.

Quantitative XRD Analysis of Binary Blends of Siliceous Fly Ash and Hydrated Cement

AbstractQuantitative analysis of the amorphous phase in binary blends of siliceous fly ash and hydrated cement is presented using the Partial Or No Known Crystal Structure (PONKCS) method. In binary blends, the total amorphous phase contains contributions from the glassy phase in fly ash and amorphous components of hydrated cement. A single pseudo-Voigt function is found to adequately fit the broad hump in the X-ray diffraction pattern resulting from diffuse scattering produced by the glassy phase in siliceous fly ash. The weight fractions of the amorphous component of hydrated cement and the glassy phase of siliceous fly ash in a binary blend are determined using the fitted profiles for the X-ray diffraction (XRD) patterns. For low lime content of less than 5%, the peak characteristics of the fitted function for the broad hump in the XRD pattern of fly ash are nominally identical for different oxide compositions of the glassy phase. The PONKCS method is shown to provide good accuracy in determining silic...

Whole-Rock Geochemistry and Mineralogy of Triassic Montney Formation, Northeastern British Columbia, Western Canada Sedimentary Basin

Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) was used to analyze chemical elements—major, trace and rare earth elements (REE) concentrations, augmented with quantitative X-ray diffraction (XRD) analysis and thin-section petrography for mineralogical characterization of the Triassic Montney Formation in northeastern British Columbia, Western Canada Sedimentary Basin (WCSB). Results from this study indicate that integration of chemical elements with mineralogy shows affinity to the host lithologies. Evidently, chemical elements are the building blocks for minerals, thus, their significances in the interpretation of geological systems are unambiguous. Herein, major elements concentration such as Al, Fe, K, Mg, Ca, Mn in the samples analyzed from the Montney Formation are interpreted as: 1) indication of dolomitization and diagenesis; 2) trace elements—Rb, Th, U, and Cs are related to the organic matter—kerogen in the clay component of the Montney Formation source rock; and 3) transition metals—Sc, V, Co, Cr, Zn show strong affinity with diagenesis in the study interval.

INFLUENCE OF CALCINED NANOCLAY ON FRACTURE TOUGHNESS OF NAOH-TREATED HEMP FABRIC REINFORCED CEMENT NANOCOMPOSITES

influence of calcined nanoclay (CNC) on the porosity and fracture toughness of treated hemp fabric-reinforced cement nanocomposites is presented in this paper. Characterisation of microstructure is investigated using Quantitative X-ray Diffraction Analysis (QXDA) and High Resolution Transmission Electron Microscopy (HRTEM). An optimum replacement of ordinary Portland cement with 1 wt% CNC is observed through reduced porosity and increased fracture toughness of treated hemp fabric-reinforced nanocomposite. The microstructural analysis indicates that the CNC affect not only as a filler to improve the microstructure, but also as the activator to support the pozzolanic reaction and thus improved the adhesion between the treated hemp fabric and the matrix. Cost-benefit analysis indicates the benefit of such cement eco-nanocomposites to develop new environmentally friendly nanomaterials and it can be used for various construction applications such as, ceilings and roofs.

Chalcopyrite Bioleaching at High Sulfate Concentrations

The efficiency of chalcopyrite bioleaching in a high sulfate background was evaluated using acidophilic microorganisms adapted to sulfate. The concentration of magnesium sulfate added to mesophilic, moderately thermophilic and thermophilic bioleaching tests was equivalent to 100, 40 and 80 g L-1SO42-, respectively. Biological copper extraction was highest at 45 °C (67 %), followed by 60 °C (54 %) and 30 °C (16 %). Quantitative x-ray diffraction (QXRD) analysis of the ROM ore and bioleached residues revealed the complete disappearance of pyrrhotite and a significant reduction of pyrite at all temperatures. Significant chalcopyrite was leached at 45 and 60 °C; however, no chalcopyrite was leached at 30 °C. As the bioleach did not plateau after 31 days, it is possible that higher copper yields may have been achieved with prolonged leaching.

Solid-State Synthesis of Calcium Carbide by Using 2.45 GHz Microwave Reactor

A simple solid-state method has been described for the synthesis of CaC2 from CaO and graphite powders by using a 2.45 GHz microwave reactor. The reaction mechanism of CaC2 formation in the microwave environment is explained and compared with that of the conventional method. The whole microwave process completed within 180 min because of efficient coupling of microwaves with graphite powder. X-ray diffraction quantitative analysis results revealed 71.8% CaC2 formation at 1700 °C for 30 min of microwave exposure, whereas conventional heat treatment at 1700 °C for 30 min showed 14.1% CaC2 and 1750 °C for 60 min showed 62.8% CaC2. The X-ray photoelectron spectroscopy quantitative chemical state analysis based on C 1s spectra indicated 54.02% CaC2 in microwave heat-treated samples and 30.75% CaC2 in conventional heat-treated samples. The preliminary experimental results suggest that synthesis of CaC2 by microwave reactor is fast because of rapid volumetric heating.

Quantitative phase separation in multiferroic Bi0.88Sm0.12FeO3 ceramics via piezoresponse force microscopy

BiFeO3 (BFO) is a classical multiferroic material with both ferroelectric and magnetic ordering at room temperature. Doping of this material with rare-earth oxides was found to be an efficient way to enhance the otherwise low piezoelectric response of unmodified BFO ceramics. In this work, we studied two types of bulk Sm-modified BFO ceramics with compositions close to the morphotropic phase boundary (MPB) prepared by different solid-state processing methods. In both samples, coexistence of polar R3c and antipolar Pbam phases was detected by conventional X-ray diffraction (XRD); the non-polar Pnma or Pbnm phase also has potential to be present due to the compositional proximity to the polar-to-non-polar phase boundary. Two approaches to separate the phases based on the piezoresponse force microscopy measurements have been proposed. The obtained fractions of the polar and non-polar/anti-polar phases were close to those determined by quantitative XRD analysis. The results thus reveal a useful method for quantitative determination of the phase composition in multi-phase ceramic systems, including the technologically most important MPB systems.

Quantitative XRD Analysis of the Structural Changes of Ba-Exchanged Montmorillonite: Effect of an in Situ Hydrous Perturbation

The structural changes along the c axis, of the Ba-exchanged montmorillonite (Swy-2-Ba), under variable relative humidity (% RH), is investigated. In this regard, the arrangement, amount and position of both exchangeable cation and the water molecules in the interlamellar space (IS), are evaluated. This aim is achieved using the X-ray diffraction (XRD) profile modeling approach that consists of comparing experimental and theoretical patterns calculated from structural models. The contributions of the hydration states and the interlayer water amounts, as a function of the % RH, are registered by quantitative XRD investigation. The validated structural models are heterogeneous, suggesting various proportions of layer types at different RH ranges, which means the coexistence of different mixed layer structure MLS packages, exhibiting different proportions of layers with contrasting hydration states. This result is attributed to the orientation of the applied hydration sequence. Indeed, the interlayer water molecule amounts, which led to the appearance of a logic hydration hysteresis, are strongly affected by hydrous perturbation.

Effects of acetic acid on early hydration of Portland cement

Partially hydrolysed polyvinyl alcohols (PVAs) are used commonly in polymer-modified mortars to manipulate their properties. These PVAs undergo hydrolysis in wet cement which results in the release of acetate groups into the pore water. To evaluate their contribution to cement hydration, the present work investigates the impact of acetic acid on the early hydration of off-white Portland cement using glacial acetic acid concentrations of up to 0.20 mass% (cement basis). To this end, the heat flow of the hydration of unmodified and acetic acid-modified cement pastes was monitored over the first 24 h following mixing using isothermal calorimetry, and the mineralogical compositions of these cement pastes were determined using quantitative X-ray diffraction analysis. Acetic acid addition showed a mixed effect. The slow reaction period was extended; in the acceleration period, the hydration of C3S to form calcium silicate hydrate (C-S-H) and Ca(OH)2 (CH) and the hydration reaction of C3A and gypsum to form ettringite were retarded; in the deceleration period, the exsolution of CaSO4 and renewed formation of ettringite were delayed, while the formation of monosulphate was accelerated. These effects were enhanced with increasing acetic acid concentration up to a surface adsorption acetate saturation level that could be identified from the curves of heat flow.

Study of thermal and CH4 adsorption properties

In this study, the adsorption of methane (CH4) on zeolite from Sivas-Yavu region of Turkey and on forms treated with 1 M heavy metal nitrate solutions (AgYZ, Cu YZ and FeYZ) and 1, 3 and 5 M HCl solutions (HYZ, 3HYZ and 5HYZ) was investigated. Adsorption isotherms of methane by zeolite minerals were obtained using volumetric apparatus at 0 and 25 °C up to 100 kPa. Natural and modified samples were characterized by X-ray fluorescence, X-ray diffraction (XRD), thermogravimetric/differential thermal analysis and nitrogen adsorption methods. Quantitative XRD analysis showed that the major components of the natural zeolite were clinoptilolite and mordenite, together with minor amounts of quartz, feldspar and clay mineral. Among all the modified forms, Fe-form of zeolite sample exhibited the highest adsorption capacity for CH4 at both temperatures. The adsorption capacity of CH4 on FeYZ increased from 0.597 to 0.796 mmol g−1 as the temperature decreased from 25 to 0 °C. In addition, uptake of CH4 on the adsorbents decreased with increasing acid concentrations.

Characterization and understanding of residual stresses in a NiCoCrAlY bond coat for thermal barrier coating application

The residual stresses in a NiCoCrAlY bond coat deposited on a Ni-base superalloy substrate after oxidation at 1150°C were studied by X-ray diffraction using the sin2Ψ technique. The stresses were found to be tensile; they first increased and then decreased with oxidation time. High temperature stress measurement indicated that the stress developed and built up upon cooling, predominantly within the temperature range from 1150°C to 600°C. Microstructural examination suggested that, due to the limited penetration depth into the bond coat, the X-ray only probed the stress in a thin surface layer consisting of the single γ-phase formed through Al depletion during oxidation. Quantitative high temperature X-ray diffraction analysis revealed that, above 600°C, the volume fraction of the β-phase in the bond coat increased with decreasing temperature. The mechanisms of stress generation in the bond coat were examined and are discussed based on the experiments designed to isolate the contribution of possible stress generation factors. It was found that the measured bond coat stresses were mainly induced by the volume change of the bond coat associated with the precipitation of the β-phase upon cooling.