Quantitative Phase Analysis Research Articles

Spectroscopic Investigation of the Interaction of Silicate Ions with Lead Carbonates Under Drinking Water Conditions.

The presence of lead has been identified as a critical health risk in drinking water systems serviced by Pb-bearing plumbing. Among several corrosion control strategies, the use of sodium silicates has attracted interest due to the advantages it offers compared to other approaches, such as phosphate dosage. However, the interaction of silicate ions with lead corrosion scales and other ubiquitous dissolved species such as Al ions in drinking water is not well understood. In this work, surface and bulk spectroscopic analysis of the solid scale is combined with quantitative analysis of the aqueous phase. A detailed spectroscopic probing of the transformations taking place on the solid phase enables us to develop a mechanistic framework for reports published in the last four years in the open literature, suggesting that silicates may not be an adequate corrosion control option in drinking water systems rich in solid lead carbonates. The spectroscopic data obtained demonstrate that in the presence of chlorine residual, silicates inhibit Pb(II) carbonates from oxidizing into less soluble Pb(IV) oxides thus, negatively impacting water quality. Furthermore, aluminum ions interact with silicates resulting in the formation of solid allophane phase over the lead scale surface, extending into the bulk. However, the formation of this new solid allophane phase does not protect against lead dissolution.

Evaluation of the Mechanical Properties and Fatigue Resistance of the ZrO2CeYAl2O3 Composite

This work aimed to evaluate the fatigue limit of the zirconia ceramic composite stabilized with yttria and ceria reinforced with alumina platelets (ZrO2CeYAl2O3) and characterize the mechanical properties of sintered specimens. Bar-shaped specimens were compacted by uniaxial pressing in a rigid die and sintered at 1500 °C-2 h. Subsequent characterizations included quantitative phase analysis by X-ray diffractometry, determination of density, modulus of elasticity, microhardness, fracture toughness, four-point flexural strength, and fatigue limit. Observations of fracture mechanisms were carried out using confocal and scanning electron microscopy (SEM). The sintered samples presented values above 98% of relative density. Complex microstructures with equiaxed, homogeneously distributed submicrometer grains and planar alumina platelets were observed by SEM. The composite samples showed high values of fracture toughness due to the transformation, during the test, from the tetragonal to monoclinic phase, causing an increase in volume and creating compression zones around the crack, making it difficult to propagate. The average flexural strength reached 445.55 MPa, with a Weibull modulus (m = 16.8), revealing low flexural rupture stress data dispersion. In the composite evaluated in this work, the occurrence of the tetragonal → monoclinic transformation that occurs in the Ce-TZP present at the triple points and grain boundaries during cyclic loading produces “crack tip shielding”, that is, a restricted elastic zone (zone shielding) that surrounds the crack tip. This phenomenon leads to a reduction in the stress intensity factor at the tip of the crack and slows down its growth, generating an increase in the fatigue resistance of the composite.

The effect of reference material crystallinity on absolute quantitative phase analysis using the internal standard method

Equations are given which allow an analyst to obtain a correct absolute quantitative phase analysis via the internal standard method when a reference material with a known crystallinity of less than 100% is used. Comparisons are made with previous equations, and a numerical example is given.

Label-free quantitative phase imaging and analysis of airborne pollen

Abstract Pollen morphology, involving the physical characteristics of pollen grains from seed plants during reproduction, plays an important role in plant biology, ecology, and evolution. High pollen concentrations in the air can degrade air quality and exacerbate respiratory conditions such as asthma. Understanding pollen morphology and its implications for air quality is significant for mitigating respiratory health risks. Conventionally, fluorescence microscopy is used for pollen imaging, but photobleaching, quenching, and phototoxicity affect the surface morphology and do not provide quantitative data on the pollen grains. For this study, we used bright field (BF) imaging and quantitative phase imaging (QPI), a label-free interferometric microscopy method, to look at differences in the shape of pollen. BF imaging provides information about the shape and size of the different pollens but has a limitation of low contrast. To obtain high-contrast images and quantitative data on the pollen grains without any exogenous agents, we employed QPI and BF imaging in the present study. QPI enables the extraction of detailed information regarding the cell wall, aperture, and thickness of pollen while also maintaining their natural state without the need for chemical treatments. In the present work, we sampled the ambient air from May 2023 to January 2024 on the IIT Delhi campus. Subsequently, QPI and BF imaging have been done for pollen identification and phase analysis of arboreal and non-arboreal pollen. Further, by utilizing the information obtained from BF microscopy and QPI, different species of pollen have been identified, and a pollen calendar has been prepared for exhibiting pollen season throughout the year. To the best of the authors’ knowledge, they have conducted the QPI of airborne pollen grains for the first time; this technique holds great potential for characterizing airborne pollens without the need for staining or sample preparation.

Speciation of the Oxide Phase of Molybdenum‐Based HDS Catalysts Enhanced with Organic Additives Using an EXAFS/Raman Coupling Methodology

AbstractThe ability to gain access to the speciation of hydrodesulfurization (HDS) catalysts used for removing sulfur and nitrogen from transportation fuels is becoming a key feature in the understanding and improvement of their catalytic activity with the aim of reducing greenhouse gas emissions of fossil fuels. A novel coupling methodology between Raman spectroscopy and X‐ray absorption spectroscopy (XAS) was developed, which allows for precise qualitative and quantitative analysis of the oxide phase of Mo‐based catalysts. This enabled the detailed study of various impregnation parameters and the characterization of HDS catalysts before sulfidation. To illustrate this methodology, the effects of two additives (triethylene glycol and citric acid) were studied. The results demonstrated that organic additives exert a profound influence on the speciation of oxide precursors of molybdenum‐based catalysts. The presence of these additives enhances the dispersion of Keggin or Dawson heteropolyanions (HPAs) on the support by maintaining a high phosphorus‐to‐molybdenum ratio in solution. This is achieved by two strategies: triethylene glycol (TEG) exhibits a pronounced affinity for alumina hydroxyls, while citric acid compensates for phosphate adsorption through the formation of a stable Mo‐citrate complex.

Quantitative phase analysis of transparent phase objects in a radial shearing interferometer incorporating a wire-grid polarizer

Quantitative phase analysis of transparent phase objects in a radial shearing interferometer incorporating a wire-grid polarizer

Rice Husk as Raw Material in Synthesis of NaA (LTA) Zeolite.

The present work deals with the hydrothermal synthesis of a Na-A (LTA) zeolite using rice husk as a starting material. The focus was on defining the most favorable conditions for the synthesis of zeolite Na-A from rice husk in order to economize on both energy (i.e., synthesis temperatures) and reaction time and to enlarge the field of the pure and isolated synthesized phase. Four sets of experiments were carried out at environmental pressure temperatures varying from 40 °C to 85 °C with a SiO2/Al2O3 ratio from 1.75 to 3.5. Optimal conditions for crystallization of the Na-A zeolite from rice husk were reached at 60 °C with a SiO2/Al2O3 ratio of 1.75. Sixty degrees Celsius represents the minimum known temperature used for the synthesis of NaA zeolite from rice husk. The products of synthesis were characterized by X-ray diffraction, scanning electron microscopy, infrared and Raman spectroscopy. The purity of the synthesized zeolite is verified here for the first time through quantitative phase analysis using the combined Rietveld and reference intensity ratio methods.

3D X-ray Tomography Analysis of Mg–Si–Zn Alloys for Biomedical Applications: Elucidating the Morphology of the MgZn Phase

Temporary metal implants, made from materials like titanium (Ti) or stainless steel, can cause metabolic issues, raise toxicity levels within the body, and negatively impact the patient’s long-term health. This necessitates a subsequent operation to extract these implants once the healing process is complete or when they are outgrown by the patient. In contrast, medical devices fabricated from absorbable alloys have the advantage of being biodegradable, allowing them to be naturally absorbed by the body once they have fulfilled their role in facilitating tissue healing. Among the various absorbable alloy systems studied, magnesium (Mg) alloys stand out due to their biocompatibility, mechanical properties, and corrosion behavior. The existing literature on absorbable Mg alloys highlights the effectiveness of silicon (Si) and zinc (Zn) additions in improving mechanical properties and controlling corrosion susceptibility; however, there is a lack of comprehensive quantitative morphological analysis of the intermetallic phases within these alloy systems. The quantification of the complex morphology of intermetallic particles is a challenging task and has significant implications for the micromechanical properties of the alloys. This study, therefore, aims to introduce a robust set of morphometric parameters for evaluating the morphology of intermetallic phases within two as-cast Mg alloys with Si and Zn additions. X-ray Computed Tomography (XCT) was used to capture the 3D tomographic data of the alloys, and a novel pair of morphological parameters (ratio of convex hull to particle volume and convex hull sphericity) was applied to the 3D tomographic data to assess the MgZn phase formed in the two alloys. In addition to the impact of composition, the effect of solidification rate on the morphological parameters was also studied. Furthermore, Scanning Electron Microscopy (SEM) and Energy-Dispersive Spectroscopy (EDS) were employed to gather detailed 2D microstructural and compositional information on the intermetallics. The comprehensive characterization reveals that the morphological complexity and size distribution of the MgZn phase are influenced by both compositional changes and the solidification rate. However, the change in MgZn intermetallic particle morphology with size was found to follow a predictable trend, which was relatively agnostic of the chosen casting conditions.

A Quantitative Phase Analysis by Neutron Diffraction of Conventional and Advanced Aluminum Alloys Thermally Conditioned for Elevated-Temperature Applications.

As the issue of climate change becomes more prevalent, engineers have focused on developing lightweight Al alloys capable of increasing the power density of powertrains. The characterization of these alloys has been focused on mechanical properties and less on the fundamental response of microstructures to achieve these properties. Therefore, this study assesses the quality of the microstructure of two high-temperature Al alloys (A356 + 3.5RE and Al-8Ce-10Mg), comparing them to T6 A356. These alloys underwent thermal conditioning at 250 and 300 °C for 200 h. Time-of-flight neutron diffraction experiments were performed before and after conditioning. The phase evolution was quantified using Rietveld refinement. It was found that the Si phase grows significantly (13-24%) in T6 A356, A356 + 3.5RE, and T6 A356 + 3.5RE alloys, which is typically correlated with a reduction in mechanical properties. Subjecting the A356 3.5RE alloy to a T6 heat treatment stabilizes the orthorhombic Al4Ce3Si6 and monoclinic β-Al5FeSi phases, making them resistant to thermal conditioning. These two phases are known for enhancing mechanical properties. Additionally, the T6 treatment reduced the vol.% of the cubic Al20CeTi2 and hexagonal ᴨ-Al9FeSi3Mg5 phases by 13% and 23%, respectively. These phases have detrimental mechanical properties. The Al-8Ce-10Mg alloy cubic β-Al3Mg2 phase showed significant growth (82-101%) in response to conditioning, while the orthorhombic Al11Ce3 phase remained stable. The growth of the beta phase is known to decrease the mechanical properties of this alloy. These efforts give valuable insight into how these alloys will perform and evolve in demanding high-temperature environments.

A study integrating in-process thermal signatures, microstructure, and corrosion behaviour of AISI 316L coatings on low carbon steel substrate deposited by laser-directed energy deposition (L-DED)

Surface coating through Laser Directed Energy Deposition (L-DED) of AISI 316L on low-carbon steel was carried out by varying laser fluence. The resulting melt pool characteristics, obtained through IR pyrometer, played a significant role in evolution of the microstructure. A higher heat input resulted in an equiaxed grain structure with finer grain sizes and improved deposition quality. The quantitative phase analysis revealed the presence of a dominant austenite phase and a secondary ferrite phase, along with traces of molybdenum carbide. Corrosion analysis reveals improved resistance at a higher laser fluence, attributed to increased content of corrosion-resistant alloying elements (Mo, Cr) and predominance of the austenite phase. Electrochemical Impedance Spectroscopy (EIS) confirms a higher corrosion resistance at a higher laser fluence, supported by a significantly higher polarization resistance and presence of a duplex-structured passive film. Results indicate that moderate laser fluence levels, ranging from 5 to 7.5 kJ/cm2, accompanied by medium to high thermal signatures and moderate cooling rates, yield coatings with refined microstructures, enhanced mechanical strength, and corrosion resistance. For superior corrosion resistance, a laser fluence of 10 kJ/cm2 is recommended, although careful consideration of its potential impact on mechanical properties is advised.

Hybrid kidney stones physicochemical and morphological characterization: A spectroscopic study analysis

This study was designed to scrutinize the practical health index of uroliths for investigating composition, structural characterization, phase quantification and shape of kidney stone patients with respect to socioeconomically status in territory of Bahawalpur, southern Punjab, Pakistan. Morphology of the kidney stones were determined using SEM. The Ultra violet spectra of kidney stones in narrow range of 220–280 nm. Quantitative phase analysis of stones indicates as oxalate, calcium oxalate monohydrate, calcium oxalate dehydrates, calcium phosphate, cysteine and uric acid with 40.51 %, 26.24 %, 14.24 %, 36.45 %,13.18 % and 9.86 % respectively. A survey analysis also supports the vitro data showing patient age with 30–40 years with more predominance in males than females. Metabolic abnormalities were detected in 75 % patients with stone recurrence 15 % complained of having digestive disease. The overall concludes from qualitative and quantitative results suggested the community for preventive measures in reducing the risk of pervasiveness and relapse of urolithiasis.

Physical and mechanical properties of ceramics based on ZrN-ZrO2 obtained by spark plasma sintering method

Relevance. Increasing the service life of mining tools is an important task in the development of geology associated with the investigation of new ceramic materials for functional purposes. The ability to reduce wear and thermal and chemical effects of rocks on the working elements of mining equipment determines the vector of development of the use of super-hard, high-strength and refractory ceramics. At the same time, the task is set to increase the fracture toughness of the materials used to solve the problem of maintaining the operability of equipment under conditions of critical deformations. To accomplish this task, it is necessary to study the patterns of consolidation of ceramic materials and search for the optimal combination of consolidation parameters to achieve improved physical and mechanical properties. Aim. To develop a method for producing high-density durable ceramics based on commercially available zirconium nitride powders using spark plasma sintering under vacuum conditions, to study the phase composition and physical and mechanical properties of the resulting samples. Methods. X-ray phase analysis of the studied samples, nanoindentation, microscopic analysis. Results and conclusion. The authors have studied the physical and mechanical properties of zirconium nitride consolidated by spark plasma sintering at 2000℃, a pressure of 30–60 MPa and a holding time at a given temperature of 5–10 minutes. Qualitative and quantitative X-ray phase analysis was carried out, within which the content of the main phase of zirconium nitride and zirconium dioxide phase was determined. It was found that an increase in the pressure applied during consolidation and holding time contributes to better compaction and a decrease in the porosity of the samples from 8.52 to 2.72%. It was found that with a decrease in porosity, the elastic modulus increased in the range from 320 to 378 GPa, and the hardness from 7.3 to 10.4 GPa. At the same time, by extrapolating the data, it was established that non-porous zirconium nitride samples will have an elastic modulus of 394 GPa and a Martens hardness of 11.56 GPa. For the samples under study, critical stress intensity factors were determined. It was established that at a porosity of less than 5%, the critical stress intensity factor of zirconium nitride consolidated by spark plasma sintering has values of at least 4 MPa m1/2.

Electrochemical Activation of LiGaO2: Implications for Ga-Doped Garnet Solid Electrolytes in Li-Metal Batteries.

Ga-doped Li7La3Zr2O12 garnet solid electrolytes exhibit the highest Li-ion conductivities among the oxide-type garnet-structured solid electrolytes, but instabilities toward Li metal hamper their practical application. The instabilities have been assigned to direct chemical reactions between LiGaO2 coexisting phases and Li metal by several groups previously. Yet, the understanding of the role of LiGaO2 in the electrochemical cell and its electrochemical properties is still lacking. Here, we are investigating the electrochemical properties of LiGaO2 through electrochemical tests in galvanostatic cells versus Li metal and complementary ex situ studies via confocal Raman microscopy, quantitative phase analysis based on powder X-ray diffraction, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and electron energy loss spectroscopy. The results demonstrate considerable and surprising electrochemical activity, with high reversibility. A three-stage reaction mechanism is derived, including reversible electrochemical reactions that lead to the formation of highly electronically conducting products. The results have considerable implications for the use of Ga-doped Li7La3Zr2O12 electrolytes in all-solid-state Li-metal battery applications and raise the need for advanced materials engineering to realize Ga-doped Li7La3Zr2O12for practical use.

Determination of the degree of crystallinity of polyphenylene sulfide composited with crystalline and non-crystalline fillers by applying the direct derivation method

A new procedure for determining the degree of crystallinity (DOC) has been recently proposed, and it has been verified using experimental and computer-generated powder diffractometry data [Toraya (2023). J. Appl. Cryst. 56, 1751–1763]. As an application to real materials like engineering plastics, this procedure is here applied to the DOC determination of plate-like polyphenylene sulfide (PPS) samples, composited with crystalline and non-crystalline fillers. The coexistence of partially crystallized polymer with non-crystalline fillers in target materials makes it difficult to separate the non-crystalline part of the partially crystallized polymer. This problem is here solved by the inverse application of the direct derivation (DD) method for quantitative phase analysis (QPA). The intensity–composition (IC) formula used in the DD method can derive the weight fractions of the individual components from just the total sums of observed intensities and the chemical composition data for these components [Toraya (2016). J. Appl. Cryst. 49, 1508–1516]. For the present purpose, the IC formula has been inversely applied to calculate the relative intensity ratios of individual components under the assumption that the chemical compositions and weight fractions of the respective components are known. The total halo intensity could then be separated into the non-crystalline part of the polymer and the non-crystalline filler. Analyzed results of PPS composites in four different DOCs are reported.

Mechanical properties of blended cements affected by impurities in thermally activated clays

Abstract With the scarcity of raw materials, energy intensiveness and environmental burden connected with producing Portland cement, there is a growing need to find substitute binders. Thermally activated clay also appears to be a suitable material for partial cement replacement. However, not all clays are the same. It depends very much on the place of collection, its chemical and phase composition, and the activation temperature. This study compared six different types of clays fired at 600 °C in terms of quantitative phase analysis and mechanical strength results. In addition to the fineness of grinding and firing temperature, the clay composition had an immense impact on mechanical properties. Content of illite up to 20% was found to be beneficial, as this clay reached the highest mechanical strengths. Regarding the quartz, its presence did not harm the overall performance of thermally activated clays and the presence of calcite could cause the improvement of the mechanical strengths. However, the clay with the most miscellaneous composition caused the deterioration of compressive strength but reached much higher bending strength compared to pure cement.

Laser powder bed fusion of NdFeB and influence of powder bed heating on density and magnetic properties

Laser powder bed fusion (L-PBF) is an additive manufacturing technique that provides an opportunity to create complex NdFeB magnets, potentially enhancing their performance. L-PBF possesses its own processing challenges, such as porosity/cracks and thermal stresses due to rapid cooling. This study focused on optimizing the parameters and the use of elevated temperature (300–550 °C) powder bed heating to reduce defect generation. This paper includes a detailed process parameter investigation, which revealed samples with a maximum energy product, (BH)max, of 81 kJ/m3 (remanence, Br 0.72 T; coercivity, Hci 891 kA/m) without post/pretreatment, which are the highest (BH)max and Br for L-PBF-processed NdFeB commercial powder. It was observed that all the high-magnetism samples possessed high density, but not all the high-density samples possessed high magnetism. The SEM images and discussions are academically valuable since they clearly illustrate grain formation and morphology in the melt pool, areas where the literature provides limited discussion. Furthermore, this paper incorporates quantitative phase analyses, revealing that the magnetic properties increase with increasing volume fraction of the strong magnetic phase Nd2Fe14B. Another significant contribution of this paper is that it is the first study to investigate the effect of heated bed on L-PBF-NdFeB alloys. The density of the samples and Br can be improved with the use of elevated powder bed heating, while the Hc decreases. The (BH)max can also be improved from 55 to 84 kJ/m3 through elevated powder bed heating. The maximum magnetic properties obtained with the heated bed (400 °C) were as follows: Br, 0.76 T; Hci, 750 kA/m; and (BH)max, 84 kJ/m3.

Exploring the preparation of YbBa2Cu3O7-y superconductor in flowing oxygen atmosphere.

REBCO has been used extensively as coated conductors applied to superconducting magnets due to its exceptional superconducting properties. As a REBCO superconductor, YbBa2Cu3O7-y (Yb123) has a low melting temperature, making it suitable for use as an intermediate medium connector while preparing the superconducting joint. However, there is still uncertainty about the formation mechanism of Yb123 and the synthesis of this superconductor has not been fully understood. Therefore, this study systematically investigated the phase transformation process of Yb123 during heat treatment in flowing oxygen. The results indicated that Yb123 sample with the highest phase purity could be obtained by annealing at 927°C or 937°C but not in between, respectively. Furthermore, a quantitative phase analysis revealed that the sample annealed at 937°C had a phase purity greater than 80 wt%. Additionally, a strong c-axis texture was observed in the bulk Yb123 superconductor prepared at 937°C. Meanwhile, the superconducting results revealed that the bulk sample's Tc was 89.9 K, and its self-field critical current densities at 4.2 K and 77 K were 1.3 × 105 A/cm2 and 5.0 × 103 A/cm2, respectively. Based on the results mentioned above, the phase transformation process and formation mechanism of Yb123 in flowing oxygen were elaborated.

PDF-5+: a comprehensive powder diffraction file™ for materials characterization

For more than 80 years, the scientific community has extensively used International Centre for Diffraction Data's (ICDD®) Powder Diffraction File (PDF®) for material characterization, including powder X-ray diffraction analysis. Historically, PDF was made available for two major material types: one for inorganic analysis and the other for organic analysis. In the early years of the PDF, this two-material approach was implemented due to limited computer capabilities. With Release 2024, ICDD provides a comprehensive database consisting of the entire PDF in one database called PDF-5+, comprised of more than one million entries (1,061,898). The PDF-5+ with a relational database (RDB) construct houses extensive chemical, physical, bibliographic, and crystallographic data, including atomic coordinates and raw data, enabling qualitative and quantitative phase analysis. This wealth of information in one database is advantageous for phase identification, materials characterization, and several data mining applications in materials science. A database of this size needs rigorous data curation and structural and chemical classifications to optimize pattern search/match and characterization methods. Each entry in the PDF has an editorially assigned quality mark. An editorial comment will describe the reason if an entry does not meet the top-quality mark. The editorial processes of ICDD's quality management system are unique in that they are ISO 9001:2015 certified. Among several classifications implemented in PDF-5+, subfiles (such as Bioactive, Pharmaceuticals, Minerals, etc.) directly impact the search/match in minimizing false positives. Scientists with specific field expertise continuously review these subfiles to maintain their quality. This paper describes the features of PDF with an emphasis on the newly released PDF-5+.

Clinkering and hydration of alite-belite-ye'elimite cement with increasing ye'elimite percentage

Alite-belite-ye'elimite (ABY) cement is considered to be eco-cements with adequate mechanical properties and fewer CO2 emissions. The phase assemblage and ye’elimite content of ABY cement play a very important role in cement properties. In this study, ABY clinkers with increasing ye'elimite percentage (0.3 wt%-36.4 wt%) were prepared at 1300 °C and the phase composition was characterized by Rietveld Quantitative Phase Analysis combined with energy dispersive X-ray spectrometry. The ye'elimite formed with a calculated composition of Ca3.92Mg0.02Al2.81Fe0.05Si0.04S1.16, incorporating additional sulfur compared to the theoretical value. In addition, the hydration properties of heat evolution, hydration products and compressive strength of ABY cement are studied. The result shows that the increase of ye'elimite content leads to a more intense initial heat release and a higher cumulative heat release. The presence of ye'elimite inhibits the hydration of alite at early ages. ABY mortars with increasing ye'elimite (15.8 wt%) exhibited a higher strength (29.6 MPa) at 3 days by the contribution of ye'elimite hydration, and an increase (47.4 MPa) at 28 days. An adequate proportion of ye'elimite (<15 wt%) is favorable to the performance of ABY cement, and releases 12% less CO2.

Substantial composition and technological treatment of potassium rocks of the Upper Pechora salt basin

The material composition of potassium and potassium-magnesium salts of the Upper Pechora salt-bearing basin was studied, their lithological variability was established over the area of productive strata, depending on the tectonic features of the foundation. The main mining and geological conditions that complicate the possibility of their extraction and the environmental conditions for organizing mining and processing production of mineral salts were established. The basic physical and technological properties of sylvinite and carnallite rocks mined by the mine method were studied for their enrichment by halurgical and flotation methods. The objectives of the work were: determining the material composition, studying textural and structural features and assessing the technological processing of potassium rocks in the Upper Pechora salt-bearing basin. When solving the problems, the following methods were used: a study of the textural and structural features of sylvinites using the petrographic method; the chemical composition of samples and solutions was analyzed by AES spectrometry; the mineral composition of the water-insoluble residue is determined by X-ray quantitative phase analysis.