Quantitative X-ray Powder Diffraction Research Articles

Sintering kinetics and microstructure development of synthetic lunar highlands and mare regolith

Kinetics and microstructure development during pressureless sintering of two Lunar regolith simulants are reported and discussed. Dry-pressed cylindrical specimens of either a Highlands simulant or a Mare simulant were heated at 80 K min−1 to a prescribed sintering temperature and held for ten hours while dimensional changes were tracked in situ by optical dilatometry. The axial and volumetric strains and densification rates were calculated as a function of time and temperature. Possible phase transformations were evaluated by quantitative X-ray powder diffraction. The relative density increased with the logarithm of time at any temperature, and densification rates decreased continuously and sharply with increasing density. Sintered microstructures and compositional characteristics were observed by scanning electron microscopy and X-ray microprobe analysis of polished surfaces. The microstructures of both materials show evidence of heterogeneous densification, with large but isolated high-density domains surrounded by lower-density regions with interconnected porosity. No significant compositional differences were detected between the higher- and lower-density regions, meaning that the heterogeneous local densities are caused by gradients in particle size or packing that induce locally varying thermodynamic driving forces for densification. The apparent activation enthalpy for densification was measured as 445 kJ mol−1 and 440 kJ mol−1 for the Highlands and Mare simulants, respectively, values that were observed to be independent of temperature and sintered density to within the measurement uncertainty.

Material and mechanical properties of young basalt in drill cores from the oceanic island of Surtsey, Iceland

Characterization of 2017 drill core samples from Surtsey, an oceanic island produced by 1963−1967 eruptions in the offshore extension of Iceland’s east rift zone, reveals highly heterogeneous microstructural, physical, and mechanical properties in subaerial, submarine, and subseafloor basaltic deposits. The connected porosity varies from 42% in weakly consolidated lapilli tuff in a submarine inflow zone to 21% in strongly lithified lapilli tuff in upper subseafloor deposits near the explosively excavated conduit. Permeability, however, varies over six orders of magnitude, from 10−18 m2 to 10−13 m2. Uniaxial compressive strength, P-wave velocity, and thermal conductivity are also highly variable: 10−70 MPa, 1.48−3.74 km·s−1, and 0.472−0.862 W·m−1·K−1, respectively. Synchrotron X-ray microdiffraction analyses integrated with major-element geochemistry and quantitative X-ray powder diffraction analyses describe the initial alteration of fresh glass, incipient consolidation of a fine-ash matrix, and partial closure of pores with mineral cements. Permeability, micromechanical, and thermal property modeling highlight how porosity and pore size in eruptive fabrics—modified through diverse cementing microstructures—influence the physical properties of the pyroclastic deposits. Borehole temperatures, 25−141 °C (measured from 1980 to 2018), do not directly correlate with rock strength properties; rather, the abundance and consolidation of a binding fine-ash matrix appears to be a primary factor. Analytical results integrated with archival data from 1979 drill core samples provide reference parameters for geophysical and heat transfer studies, the physical characteristics of pyroclastic deposits that lithify on a decadal scale, and the stability and survival of oceanic islands over time.

Reduce the cost and embodied carbon of ultrahigh performance concrete using waste clay

Recent research has recognized limestone calcined clay cement (LC3) a promising sustainable cementitious material. While LC3 could be used in a wide range of applications, it is important to explore its feasibility in developing (ultra-)high performance concrete. In this paper we attempt to produce ultrahigh performance LC3 concrete (UHP-LC3). With 20%, 30%, and 40% OPC replaced by coal gangue waste calcined clay and limestone (LC2), the mechanical, hydration, and microstructural properties were extensively studied. The mechanical properties were investigated by compressive and flexural tensile tests. The hydration behavior of UHP-LC3 was evaluated by thermogravimetric analysis (TGA), quantitative X-ray powder diffraction (QXRD) analysis, 29Si nuclear magnetic resonance (NMR) spectroscopy, and scanning electron microscope (SEM). Finally, the microstructure of UHP-LC3 was studied by mercury intrusion porosimetry (MIP). Results show that the substitution of LC2 improve the early strength by quickly pozzolanic reaction to form denser hydration products as well as the synergistic interaction between silica fume and limestone/calcined clay in the system. However, the long-term strength would drop as LC3 caused insufficient hydration reaction due to the high water-demand of calcined clay that reduced the amount of free water. Also, there are abundant unreacted calcined clay particles in the hydrated system. Meanwhile, LC3 substitution of OPC seems to improve the polymerization of C-A-S-H gel and densify the pore structure, thus display excellent carbonation resistance. This paper explores new options to prepare more sustainable and cost-effective UHPC.

Old Polymorph, New Technique: Assessing Ritonavir Crystallinity Using Low-Frequency Raman Spectroscopy.

Two decades ago, postmarket discovery of a second crystal form of ritonavir with lower solubility had major implications for drug manufacturers and patients. Since then, ritonavir has been reformulated via the hot-melt-extrusion process in an amorphous form. Here, quantitative low- and mid-frequency Raman spectroscopy methods were developed to characterize polymorphs, form I and form II, in commercial ritonavir 100 mg oral tablets as an alternate analysis approach compared to X-ray powder diffraction (XRPD). Crystallization in three lots of ritonavir products obtained from four separate manufacturers was assessed after storage under accelerated conditions at 40 °C and 75% relative humidity (RH). Results were compared with quantitative XRPD methods developed and validated according to ICH Q2 (R1) guidelines. In a four-week open-dish study, form I crystallization occurred in two of the four products and form II crystallization was detected in another ritonavir product. The limits of detection for XRPD, low-frequency Raman (LFR), and mid-frequency Raman (MFR) were determined to be 0.7, 0.8, and 0.5% for form I and 0.6, 0.6, and 1% for form II, respectively. Root-mean-squared-error of predictions were 0.6-1.0 and 0.6-2.5% for LFR- and MFR-based partial least-squares models. Further, ritonavir polymorphs could also be identified and detected directly from ritonavir tablets using transmission LFR. In summary, LFR was applied for the assessment of polymorphism in real-world samples. While providing analytical performance similar to conventional techniques, LFR reduced the single measurement time from 66 min (XRPD) to 10 s (LFR) without the need for tedious sample preparation procedures.

Mechanism of Be-Thermodiffusion in Rutile Inclusions of Fancy Sapphires

The solid-state chemistry of inclusions in Al2O3 is of high relevance in several applications, spanning from photonics to materials engineering and gemology. Be-thermodiffusion is a common treatment of corundum crystals to improve their optical properties. The chemistry of such a high-temperature process is still unclear. Particularly, the interconversion between corundum host and guest inclusion species involves many chemical species and several steps, whose knowledge would guide the tuning of corundum chemical preparation. Herein, 43 thermodiffusion-treated sapphires are investigated, with a focus on 14 samples endowed with blue halos, via optical microscopy, scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDS) quantitative chemical analyses, Raman microspectroscopy, and X-ray powder diffraction. This study searches for the snapshots of the chemical path and then recomposes them to propose a novel chemical mechanism in which Be reduces TiO2 inclusion, which is then converted, mediated by iron ions, to several titanates. The chemical mechanism is discussed in terms of applications not limited to only gemology but to any derivative corundum crystal preparation.

Quantitative phase analysis of anhydrous clinker Portland using Rietveld method

Abstract Modern cements are complex materials with well-defined compositions that reach to high and consistent results. Automated techniques such as Rietveld analysis lead to provide an understanding of the composition and polymorphism of cement phases that could lead to control of the clinkering conditions to optimize characteristics and consequently quality product. For the characterization of cements used in the construction sector, Rietveld method has significant benefits over other analytical techniques. The precise information about phase assemblage and polymorphism lets monitoring the hydration behavior of binder materials. The objective of this paper is to report the quantitative Rietveld phase analyzes for three industrial clinkers, to review the most recent quantitative X-ray powder diffraction studies on anhydrous cement and to discuss the influence of the different parameters elaborated in the Rietveld method.

Characterisation of Tailings from Itakpe Iron Ore Mine, Itakpe, Nigeria

Knowledge of tailings characteristics is required for utilisation and management purposes in the mining and construction industry. Tailings from the mine waste dumps at Itakpe iron ore mine were collected and analysed in the laboratory to determine their chemical and physical characteristics and these include; permeability, porosity, specific gravity, particle size distribution, chemical composition and bioavailability factor of element. Geochemical speciation with quantitative X-ray powder diffraction was used to evaluate the chemical and mineral composition of Itakpe iron ore tailings. The aim is to offer base line data necessary to assess metal mobility and bioavailability. The distribution of heavy metals such as Cu, Ni, Cd, Cr, Zn and Fe was determined using multi- step sequential extraction. The results obtained indicate that the permeability is 6.24 x 10-3 cm/sec; porosity is 35%; and specific gravity is 3.58. The tailings is well graded and is sand gravel. Nickel and Zinc was found to be considerably high in exchangeable and bound to carbonates fraction which are mobile region and is bound to Fe – Mn oxides which is slightly mobile region but the higher concentration of Ni found in residual fraction. The implication of this result is that Nickel and Zinc partially enter into the food chain. Chromium and Cadmium concentration result indicated that these metals can easily enter into the food chain because of their presence in the mobile region and their higher mobility percentage.

Metamorphic graphite from Szendr\u0151l\xe1d (Szendr\u0151 Mts., NE-Hungary) detected by simultaneous DTA-TG

Graphite, one of the polymorphic forms of carbon, has become a versatile industrial material of nowadays due to its particular attributes. It is used mainly in the automobile industry, metal extractive industry and in the high-tech industry. Moreover, it is also included in the list of critical raw materials for the EU. Our aim was to prove the presence of graphite by thermal analysis beyond X-ray powder diffraction (XRD) and Raman spectroscopy. Thermogravimetry yields comparable results with quantitative XRD. The formation conditions are described by Raman spectrometry and microscopy examinations of drill core samples from Szendrőlád (Szendrő Mts, NE-Hungary; (Szendrőlád Limestone Formation, middle-late Devonian, shelf-basin facies). Polished rock slabs were made for optical microscopy, scanning electron microscopy with energy dispersive spectrometry (SEM–EDS) and Raman spectroscopy. X-ray powder diffraction (XRD) and thermal analysis (DTA-TG) measurements were made on powders. Based on our results, the graphite is epigenetic; its quantity varies between 1.5–3 mass% in the samples. It was developed in 20–50 μm sized flakes, which are often arranged in > 300 μm sized aggregates. Graphite was formed during regional metamorphism from the organic matter-rich shales. The average formation temperature, calculated from the results of Raman spectroscopy, is around 410 °C (± 30 °C). The Raman measurements also indicated the presence of a partially graphitized (disordered graphite) material beside graphite.

PowdR: An R package for quantitative mineralogy using full pattern summation of X-ray powder diffraction data

X-ray powder diffraction (XRPD) is consistently found to be the most accurate analytical technique for qualitative and quantitative mineralogy. For environmental samples such as rocks, sediments and soils that can contain a range of crystalline, disordered and amorphous components, quantitative XRPD methods implemented in Excel-based programmes such as FULLPAT and RockJock have proved particularly appropriate. Such programmes quantify phase concentrations in complex mixtures by treating the diffractogram of a given mixture as the sum of contributions from individual components. Thus, using this full pattern summation (FPS) approach, an observed diffractogram of a sample can be modelled by scaling the contributions of the diffractograms for all pure phases within it and then phase concentrations computed using reference intensity ratios.Here the principles implemented in FULLPAT, RockJock and an in-house application for FPS have together been used to create the powdR package for R. The powdR package advances on previous implementations of FPS in terms of functionality, speed (parallel computation) and adaptability (via use of bespoke R code), and includes a Shiny web application for user-friendly analysis. powdR can be used to quantify samples prepared either with or without an internal standard, and includes the public domain RockJock library of 169 pure diffractograms that cover a wide range of phases that may be encountered in soil and rock samples. Furthermore, powdR contains functionality for automated phase quantification, which can select appropriate phases from a comprehensive reference library (e.g., RockJock). Here the FPS functions implemented in powdR and their use are described in detail.

Coupled reduction of bicarbonate to methane and generation/ sequestration of carbon dioxide in natural basaltic- and clay- matrices at 25 °C ≤ T ≤ 100 °C

In nature, methane (CH4) is produced via both biotic and abiotic processes, yet little is known on the abiotic mechanism(s) on the hydrogenation of abiotic carbon (C) to produce CH4 at low temperatures. This study reports on the abiotic generation of CH4via Fischer-Tropsch type reactions at room temperature. Natural sources of mineral Fe2+ were reacted with aqueous bicarbonate under sterile and non-sterile conditions. The selected sources of mineral Fe2+ were well-characterized Ediacaran basalts and green clay veins in basalts from the Volyn-Brest continental flood basalt province and hectorite SHCa-1 from Hector, California. Quantitative X-ray powder diffraction results and the Mössbauer characteristics of these materials from the literature were supplemented with specific surface area values determined by N2 physisorption, high-resolution transmission electron microscopy and nanodiffraction analysis. The headspace concentration of the gases in the dispersions was related to the presence of bicarbonate and the mineral composition. Evidence presented herein confirmed that wüstite occurs naturally in SHCa-1, which is unprecedented. Of all mineral dispersions those containing wüstite (basalt MIB and SHCa-1) showed the highest concentration of CH4 and CO2, ranging from 1457 to 6329 μmol CH4 g solid−1 and from 2100 to 8771 μmol CO2 g solid−1, respectively. The production of CO2 was also registered in dispersions containing the sources of mineral Fe(II) chlorite and saponite, which ranged from 375 to 8180 μmol CO2 g solid−1 and from 480 to 1230 μmol CO2 g solid−1, respectively. Registered mineral transformations i) wüstite → hematite and ii) chlorite or saponite → hematite, and iii) wüstite → pyrite → jarosite were explained because bicarbonate and wüstite (chlorite or saponite) reduction and oxidation to CH4 and hematite; and wustite dissolution releasing Fe2+ that reacted with sulfide ions.

Reactivity of Metakaolin in Alkaline Environment: Correlation of Results from Dissolution Experiments with XRD Quantifications.

Systematic investigation of filtrates and filter residues resulting from a 24 h treatment of metakaolin in different alkaline solutions were performed. On filtered metakaolin particles, inductively coupled plasma-optical emission spectrometry (ICP-OES) measurements reveal an enrichment of iron and titanium, which suggests an inhomogeneous distribution of these cations. Since the SiO2/Al2O3 ratio remains constant in all filter residues examined, the dissolution of the Si and Al monomers is congruent. Structural differences, identified by attenuated total reflection–Fourier transform infrared spectroscopy (ATR-FTIR) as a consequence of alkali uptake, influence the X-ray scattering contribution of metakaolin, and thus quantifications with the partial or no known crystal structure (PONKCS) method. This leads to deviations between the degree of reaction calculated from Si and Al solubility from filtrate and that quantified by quantitative powder X-ray diffraction (QPXRD) using the filter residue. Nevertheless, the described changes do not cause a shift in the X-ray amorphous hump in case of congruent dissolution, and thus allow the quantification of the metakaolin before and after dissolution with the same hkl-phase model.

A comparable study on the deterioration of limestone powder blended cement under sodium sulfate and magnesium sulfate attack at a low temperature

The deterioration mechanisms and corrosion products of Portland cement blended with limestone powder (PLC) exposed to external sulfate solutions at 5 ± 1 °C were investigated in the present study. The damage degree of paste specimens was evaluated by the evolution of appearance, strength and volume. Furthermore, to identify and quantitatively analyse the compositions of corrosion products during sulfate attack, Fourier transform infrared spectroscopy, quantitative X-ray powder diffraction and electron microprobe analysis were applied in this study. The results showed that the PLC were seriously damaged after immersion for 360 days due to the expansion of volume and the loss of strength. Moreover, the type of sulfate solution had great influence on the compositions of corrosion products from PLC immersed in sulfate solutions at low temperatures. The corrosion products of PLC immersed in sodium sulfate solution were mainly composed of thaumasite and ettringite. However, in scenario of magnesium sulfate solution, the corrosion products were basically gypsum coupled with thaumasite. The analysis results indicated that the low pH value of pore solution and decalcification effect due to magnesium sulfate attack was probably beneficial for thaumasite formation by transformation of ettringite (woodfordite route), while the sodium sulfate seemed to favour the formation of thaumasite via direct route.

Effects of fly ash on Portland limestone cement under sulfate attack at low temperature

The effects of type-F fly ash (FA) on the performance of Portland limestone cement (PLC) under sodium sulfate or magnesium sulfate attack at 5°C were evaluated. The degree of damage to the ternary blended cement exposed to 5 wt% sulfate solutions was assessed based on the evolution of the blended cement's appearance, compressive strength and volume. The sulfate product compositions from the blended cement under sulfate attack were analysed by Fourier transform infrared spectroscopy and quantitative X-ray powder diffraction. The results indicated that the PLC containing 40 wt% type-F FA was more resistant to sulfate attack than the control specimen without FA with similar mechanical properties, which was tested at a low temperature. The PLC containing 20 wt% type-F FA showed few effects in terms of improved resistance to sulfate attack. Analysis suggested that active aluminium in the FA glassy phase weakened the blended cement's resistance to sulfate attack because more ettringite was easily formed during the attack, which might accelerate thaumasite formation by means of the woodfordite route at low temperature. Therefore, the effects of type-F FA containing high contents of aluminium phase on the sulfate attack of PLC at low temperature need to be carefully evaluated and studied.

Analysis of the Kinetics of Devitrification and Crystallization of a Melilite Mold Powder Slag for Medium Carbon Steel Billet Casting

High-speed continuous casting of steel billets entails considerable turbulence in the liquid core, which results in significant slag entrapment unless high viscosity slags are used. It has been suggested that such slags remain glassy or crystallize slightly under the prevailing mold cooling, temperature and residence time conditions. Slags whose composition lead to formation of melilite minerals (i.e., to formation of calcium sodium magnesium aluminum iron disilicates), as the main crystalline phase, possess viscosities > 0.5 Pa/s at 1573 K (1300 °C), are low or do not contain F, and incorporate transition metal oxides (e.g., FeO, MnO and TiO) to absorb infrared radiation and soften steel shell-to-mold heat transfer. In this work, a commercial melilite mold powder, for casting medium carbon steels round billets, is selected to carry out detailed analysis of the kinetics of precipitation of crystalline phases from glassy—devitrification—and super-cooled liquid slags—crystallization—under non-isothermal and isothermal conditions. High-temperature confocal laser scanning microscopy is used in both cases and differential scanning calorimetry just in non-isothermal ones. Assessment of amorphous and crystalline phases in treated samples is done by quantitative X-ray powder diffraction analysis. It is found that even after prolonged treatment (» 36,000 seconds) at 1248 K (975 °C) approximately 13 wt pct of the slag remains amorphous. Additionally, the results indicate that nucleation of crystalline phases in super-cooled liquid and glassy slags occurs on the surface. Thus, it is found that crystallization kinetics is strongly influenced by the topography of the surface with which the super-cooled liquid is in contact, as well as, by shearing actions imposed on the liquid slag surface, which contribute by developing nucleation sites. Devitrification tends to be stronger on surfaces contacting foreign walls and over cracks. Moreover, it is found that predictions of the kinetic model, developed for estimating time–temperature–transformation diagrams from non-isothermal differential scanning calorimetry data, portray reasonably well experimental results of crystallization, as well as devitrification of consolidated samples.

Optimized biological tools: ultrastructure of rodent and bat teeth compared to human teeth

Enamel, the outer layer of the teeth of vertebrates, is the hardest tissue in their body. In general, enamel is highly mineralized and has a special ultrastructure that directs the mechanical properties of teeth and thereby their biological functions. However, there are differences between the enamel ultrastructures of different species. The authors compare the teeth of the Eurasian beaver Castor fiber, the African mole rat Fukomys kafuensis and the common pipistrelle bat Pipistrellus pipistrellus by high-resolution analytical methods, including scanning electron microscopy, quantitative wavelength-dispersive X-ray spectroscopy and X-ray powder diffraction. The enamel of all animals consists of long, thin and differently oriented calcium phosphate crystallites (length > 1 µm; thickness about 50 nm). On the outer surface of the beaver tooth, a thin layer of brown iron oxide was found. The diameter of the dentin tubuli was between 1 and 3 µm for all species – that is, comparable to that for human teeth.

Rheological properties of belite-rich cement doped with sulfur

Reactive belite cement based on clinker doped with sulfur is a new type of low-energy cement that is still in the laboratory testing phase. In terms of application, one of the desired properties of new cement is its well-defined rheological behavior in fresh state. The chemical composition of the belite cement was determined by wet chemistry analysis, the phase composition of the belite cement clinker by quantitative X-ray powder diffraction analysis and microscopic point counting and specific surface by Blaine method. Rheological properties were determined by rotational rheometer in flow and oscillation regime. Shear and time dependent rheological parameters were calculated from flow curves. Stability of belite cement paste was judged based on the critical strain determination in amplitude sweep test. Setting was evaluated by Tussenbrock needle penetration test and oscillation time test on rheometer. The properties of the laboratory belite cement were correlated to industrial cement CEM I, CEM II/A-LL and CEM III/A. Reactive belite cement pastes show good flow properties both due to small amount of alite and larger amount of rounded belite grains and clusters. Belite rich cement show decent stability comparable to CEM III and very good dispersing efficiency of PCE based HRWR.

X-ray powder diffraction analysis of a tungsten carbide-based ceramic

The results of the qualitative and quantitative X-ray powder diffraction analysis of the W–C system samples are presented. Powder samples were nanopowders of α-WC/W2C obtained by plasma chemical synthesis. High-density fine-grained structure of ceramics was formed using the method of electro pulse plasma sintering (spark plasma sintering) from the initial powder of the α-WC. The optimal experimental conditions for the X-ray diffraction proceeding of the tungsten carbide based ceramic samples were chosen according to the preliminary experiments. Reference intensity ratio method for quantitative phase analysis was used in this study.

Mineralogical clustering of the structural mortars from the Sarno Baths, Pompeii: A tool to interpret construction techniques and relative chronologies

Abstract Structural mortars constitute one of the most diffuse geomaterials, with stones and bricks, in ancient monuments and architectural complexes, especially related to the Roman civilization, which pushed the binder technology to technical levels unsurpassed until post-industrial revolution times. The archaeometric study of mortars is an essential tool to extrapolate great amounts of information concerning supply of raw materials, technological skills of the ancient civilizations and, finally, relative and absolute chronologies of diachronic construction phases, both related to ancient and modern architectural modifications of the buildings. In this contribution, a novel approach for the quantitative mineralogical analysis of ancient mortars is proposed. The analytical process is based on the integrated application of quantitative phase analysis (QPA) of mineral components by means of the Rietveld method applied to X-ray powder diffraction (XRPD) data and multivariate statistical treatment of the obtained results by means of the principal component analysis. The methodology has been applied on a wide set of binding materials sampled from different structural elements of the Sarno Baths, a five-storey building located in the Pompeii archaeological site. The building is characterized by a marked complexity both in terms of structural layout and constructive techniques, being the result of several modifications in ancient times from the Late Republican age up to the Vesuvius eruption in 79 AD. Furthermore, several poorly documented restorations have been performed between the 19th century and the first half of the 20th century AD. In this perspective, a quantitative characterization of the employed mortars resulted useful not only to define ancient constructive technologies and relative chronologies, but also to discriminate between the original and restored parts of the building for the execution of adequate restoration procedures. The statistical clustering of the quantitative XRPD data clearly defined two ancient constructive phases and allowed a precise definition of the structural elements rebuilt in recent times. Furthermore, the obtained results have been cross-checked with additional analyses, namely XRD analyses on the separated binder fractions, petrographic analyses and scanning electron microscopy-energy-dispersive microanalyses. Such multi-analytical approach allowed the detailed characterization of the employed raw materials, of the pozzolanic reactions between binder and aggregate and of the textural and microstructural characteristics of the mortars. The data interpretation yielded interesting insights both on the advanced optimization of mix designs of binding materials in Roman times, to improve the structural properties of the architectural elements according to their functions, and on the formulation of the restoration products during the historic excavations in Pompeii.

Bone incineration: An experimental study on mineral structure, colour and crystalline state

Unheated and heat-treated bovine bone material with differing heating times and heat-treated in increments from 100 °C to 1000 °C were analysed to study the crystallographic change of fresh biological bone mineral occuring during incineration. We combine several complementary analytical methods applied to the same unheated and heat treated material to ensure data consistency in order to establish a comprehensive study on heat-induced changes in bone. We applied quantitative powder X-ray diffraction, Fourier Transform Infrared Spectroscopy (FTIR), and Infrared-coupled Thermogravimetric Analysis (TGA-FTIR), and we correlated the analytical results with empirical indicators such as crystallinity indices (CI and IRSF) and bone colour changes after burning. At temperatures from 700 °C onwards after 30 min of heating, a considerable recrystallization reaction from bioapatite to hydroxyapatite occurred. FTIR revealed that there are no or only minor amounts of hydroxyl-ions in original bone mineral which in consequence should be referred to “carbonate-hydro-apatite” rather than hydroxyapatite. Thermal treatment induced a pronounced increase of crystallite size and an increase of hydroxyl groups in the apatite lattice accompanied by a depletion of water and reduction of carbonate contents during incineration. Thus, the heat treatment at temperatures ≥700 °C leads to the recrystallization of bioapatite to hydroxyapatite. Above 800 °C buchwaldite is formed from the Na component within the bone mineral. Moreover, we found that the transformation reaction involving crystallite growth mainly sets in after organic matrix compounds and their residues have been combusted and the apatite grains get into direct contact. The information in this work, obtained by a combination of analytical methods which are typically applied and approved to determine bone cremation temperatures, can help to better understand changes in complex biomaterials during heating. In particular, the knowledge from this study can be applied to assess the cremation conditions of archaeological bone finds. As changes in the bone mineral state are not only dependent on temperature but also on time, care must be taken to deduce a defined temperature which cremated bone finds were exposed to.

In-depth mineralogical quantification of MSWI bottom ash phases and their association with potentially toxic elements

Municipal solid waste incineration bottom ash fractions ≤4 mm are the most contaminated ones in terms of potentially toxic elements (PTEs). In order to estimate potential environmental impacts, it is important to understand the association of the PTEs with the mineral phases. Large area phase mapping (SEM/EDX) using “PhAse Recognition and Characterization - PARC” software in combination with quantitative X-ray powder diffraction has been used to characterize amorphous and crystalline BA phases for the first time. The results show that one of the main incineration products was melilite and an amorphous phase with a melilitic composition. The ratio of crystalline to amorphous melilite was 1:2. They formed an inhomogeneous layer around BA particles and contained a high percentage of the PTEs, i.e., Cu, Zn, Ni and Cr. Other major sources of PTEs (especially Ni and Cu) were iron oxides produced during incineration and the weathering products, such as calcite and ettringite (Cu and Zn). After extensive characterization of BA, a sequential extraction procedure (SEP) was performed, which exposed bottom ash to different chemical environments designed to dissolve specific phases and release their PTEs into solution. The extracted solutions and solid residues generated from the extraction procedure were analyzed to identify the association between PTEs and dissolved phases of BA. By combining SEP results with information obtained via large area phase mapping it is shown that SEP can be used for studying the association of PTEs with the phase that cannot be investigated with XRD/EDX, such as organic matter and Fe-Mn-hydrous oxides. Furthermore, according to SEP results a high percentage (40–80 wt%) of each investigated PTE can be considered immobile and not susceptible to leaching in the environment.