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In the conventional heat treatment process (CHT), a significant amount of compressive stressoccurs in the material as a result of the quenching process. After the tempering process, it is seen that thematerials lose those compressive stress. This loss can be explained by the formation of carbide structures andthe loss of tetragonality of the supersaturated martensite structure. The cryogenic treatment is a complementaryprocess that it has been given to a miscellany of materials to improve their mechanical and physical attributes. Itwas first commercially recognized as an effective method in achieving complete martensitic transformation inthe alloyed steels. In this study, microstructural investigations were carried out in order to relate themicrostructural properties to the mechanical properties following the cryogenic treatment. For this purpose, theconventional heat treatment (CHT) and the deep cryogenic treatment (DCT: -196°C) procedures were applied tovarious medium carbon spring steels. The martensite lattice parameters and the amount of retained austenitewere measured by using high-resolution X-ray diffractometer. Rietveld analysis was used to deconvolute theoverlapping peaks of martensites.

This paper deals with the ab initio structure determination of La1.26N0.24Na2.5O2.54Zr0.25triclinic structure having triclinic crystal system via powder X-ray data using the Rietveld refinement method, and with physical properties characterization of a related solid solution at the room temperature structure of three compounds belonging to the Aurivillius family La1.26N0.24Na2.5O2.54Zr0.25has been analyzed. La1.26N0.24Na2.5O2.54Zr0.25crystallizes in a triclinic crystal system with P-1 space group. The starting material was Na2CO3,Zr(NO3)4La2O3for the Zr,La and Na analogues was derived from ab initio methods and refined using the Rietveld refinement method using JANA software package and visualization by Diamond computer program. The cations Na and La are disordered over the Zr sites while the La cation is found exclusively in the layers. The cell parameters are a=4.1040 Å b=9.9102 Å c=17.6117 Å α=98.4299° β=93.4378° γ=92.2041°.The morphology and electrical properties are carried out of cited oxide.

Calcium barium sulfoaluminate (abbr. C4-xBxA₃$), one of the special cementitious minerals originated from ye'elimite (abbr.C₄A₃$), has superior hydration and hardening performance. In this paper, a series of C4-xBxA₃$ with different Ba-doping concentrations (x=0, 0.5, 1, 1.5 and 2) were prepared, and the effect of the Ba-doping concentration on the formation was systematically investigated by the Rietveld/XRD quantitative phase analysis. The results show that BaSO₄ is the essential intermediate phase for the formation of the Ba-doped ye'elimite. The solid-state reaction process of C4-xBxA₃$ is separately expressed as two main forms, corresponding to the cases in which the Ba-doping concentration (x) is larger than and less than "1", respectively. The Jander diffusion model shows the optimal fitting for C4-xBxA₃$ and it clearly proves that the C4-xBxA₃$ formation becomes increasingly difficult as the Ba-doping concentration increases. The correlation between the apparent activation energy (Ea) and the Ba-doping concentration is positively well related, which can be expressed as 'Ea) =71.9x+304' (kJ/mol).

X-ray diffraction (XRD) analysis, as one of the most powerful methods, has been widely used to identify and quantify minerals in earth science. How to improve the precision of mineral quantitative analysis is still a hot topic. To date, several quantitative methods have been proposed for different purposes and accompanied by diverse software. In this study, three quantitative mineral analysis methods, including the reference intensity ratio (RIR), Rietveld, and full pattern summation (FPS) methods, are compared and evaluated to systematically investigate their accuracy and applicability. The results show that the analytical accuracy of these methods is basically consistent for mixtures free from clay minerals. However, there are significant differences in accuracy for clay-mineral-containing samples. In comparison, it seems that the FPS method has wide applicability, which is more appropriate for sediments. The Rietveld method has been shown to be capable of quantifying complicated non-clay samples with a high analytical accuracy; nevertheless, most conventional Rietveld software fails to accurately quantify phases with a disordered or unknown structure. The RIR method represents a handy approach but with lower analytical accuracy. Overall, the present results are expected to provide a potentially important reference for the quantitative analysis of minerals in sediments.

Crystallographic textures are pervasive in ferroelectrics and underpin the functional properties of devices utilizing these materials because many macroscopic properties (e.g., piezoelectricity) require a non-random distribution of dipoles. Inducing a preferred grain texture has become a viable route to improve these functional properties. X-ray and neutron diffraction have become valuable tools to probe crystallographic textures. This paper presents an overview of qualitative and quantitative methods for assessing crystallographic textures in electroceramics (domain and grain textures) and discusses their strengths and weaknesses.

This work aims to synthesize and characterize a material that can be used as an effective catalyst for photocatalytic application to remove both organic and inorganic compounds from wastewater. In this context, sillenite Bi12ZnO20 (BZO) in a pure phase was synthesized using the sol–gel method. Before calcination, differential scanning calorimetry (DSC) analysis was done to determine the temperature of the formation of the sillenite phase, which was found to be 800 °C. After calcination, the phase was identified by X-ray diffraction (XRD) and then refined using the Rietveld refinement technique. The results prove that BZO crystals have a cubic symmetry with the space group I23 (N°197); the lattice parameters of the structure were also determined. From the crystalline size, the surface area was estimated using the Brunauer-Emmett-Teller (BET) method, which was found to be 11.22 m2/g. The formation of sillenite was also checked using the Raman technique. The morphology of the crystals was visualized using electron scanning microscope (SEM) analysis. After that, the optical properties of BZO were investigated by diffuse reflectance spectroscopy (DRS) and photoluminescence (PL); an optical gap of 2.9 eV was found. In the final step, the photocatalytic activity of the BZO crystals was evaluated for the removal of inorganic and organic pollutants, namely hexavalent chromium Cr(VI) and Cefixime (CFX). An efficient removal rate was achieved for both contaminants within only 3 h, with a 94.34% degradation rate for CFX and a 77.19% reduction rate for Cr(VI). Additionally, a kinetic study was carried out using a first-order model, and the results showed that the kinetic properties are compatible with this model. According to these findings, we can conclude that the sillenite BZO can be used as an efficient photocatalyst for wastewater treatment by eliminating both organic and inorganic compounds.

Supplementary Materials: The following supporting information can be downloaded at: https://www. mdpi.com/article/10.3390/min12101261/s1, Figure S1: Sample E70, Figure S2: Sample E 80, Figure S3: Sample E90. Figure S4: Assembly electric vibrator, Figure S5: Gravimetry fractions, Figure S6: Optical microscopy of celestine crystals replacing carbonate, sample E69., Figure S7: Scanning electron microscopy (a) and compositional SEM map of E69 sample (b).,Figure S8: Granulometry results, % massr and fi to each diameter (mm) in E60, E69, E92 samples, Figure S9: X-ray fluorescence (representative XRF spectra of one of the samples (E69), Figure S10: Correlation Al2O3/SiO2 obtained in XRF.,Figure S11: Rietveld refinement of X-ray diffraction data used for quantitative mineral analysis, Figure S12: Linear regression model between % Sr(SO4)Ba obtained by XRF and DRX, Figure S13: Linear regression model between % CaCO3 obtained by XRF and DRX, Figure S14: % CaCO3 by TGA vs. % CaCO3 by XRF or DRX; Table S1: Granulometry results, % massr and fi to each diameter (mm) in E60, E69, E92 samples, Table S2: Comparative % CaCO3 by DXR, XRF and TGA methods., Funding: This research was funded by Programa Doctorado Industrial PP19.01, UCE PP 2016.05 (Universidad de Granada), and RNM-938 (Junta de Andalucia)., The Montevive celestine mineral deposit, set in the Granada Basin in a marine evaporitic uppermost Tortonian–lowermost Messinian sequence, is the largest reserve in Europe of this economically important strontium ore. Currently, the mine has a large amount of tailings resulting from the rejection of a manual dry screening of high-grade celestine mineral. This visual and density screening was carried out in the early days of mining (1954–1973). Concentrating the celestine mineral and increasing the ore recovery rate would reduce mine operation costs and the generation of new tailings, reducing the impact on the environment. In order to define more adequate concentration methods, we have used complementary analytical techniques such as optical (OM) and scanning and transmission electron microscopy (SEM and TEM), energy-dispersive X-rays (EDXs), X-ray fluorescence (XRF), and X-ray diffraction (XRD) to fully characterize the morphology, microstructure, chemistry, and mineralogy of the celestine mineral. The low-grade mineral is made of prismatic celestine crystals that are replacing a matrix of micro sparry calcite. Other minority minerals are strontianite, dolomite, quartz, and clays (kaolinite, paragonite, and illite). There is also a certain amount of iron oxides and hydroxides (mainly magnetite) associated with clays. We showed that the concentration of low-grade celestine mineral can be achieved through a low-cost and eco-friendly method based on grinding and size separation. The coarser fractions (>5 mm) have more celestine (up to 12 percent units higher than the starting unprocessed mineral) due to the selective loss of calcite and minority minerals (quartz, clays, and iron oxides) that are mainly found in the finer fraction (, Programa Doctorado Industrial PP19.01, UCE PP 2016.05 (Universidad de Granada), RNM-938 (Junta de Andalucia)

The crystal structures of anhydrous psilocybin Forms A and B have been solved using laboratory powder X-ray diffraction data, refined using synchrotron and laboratory data, and optimized by applying density functional techniques. The crystal structures, along with that of the previously determined trihydrate, permit the qu­anti­tative analysis of a variety of historical samples of psilocybin., Psilocybin {systematic name: 3-[2-(di­methyl­amino)­eth­yl]-1H-indol-4-yl di­hydro­gen phosphate} is a zwitterionic tryptamine natural product found in numerous species of fungi known for their psychoactive properties. Following its structural elucidation and chemical synthesis in 1959, purified synthetic psilocybin has been evaluated in clinical trials and has shown promise in the treatment of various mental health disorders. In a recent process-scale crystallization investigation, three crystalline forms of psilocybin were repeatedly observed: Hydrate A, Polymorph A, and Polymorph B. The crystal structure for Hydrate A was solved previously by single-crystal X-ray dif­fraction. This article presents new crystal structure solutions for the two anhydrates, Polymorphs A and B, based on Rietveld refinement using laboratory and synchrotron X-ray dif­fraction data, and density functional theory (DFT) calculations. Utilizing the three solved structures, an investigation was conducted via Rietveld method (RM) based qu­anti­tative phase analysis (QPA) to estimate the contribution of the three different forms in powder X-ray diffraction (PXRD) patterns provided by different sources of bulk psilocybin produced between 1963 and 2021. Over the last 57 years, each of these samples qu­anti­tatively reflect one or more of the hydrate and anhydrate polymorphs. In addition to qu­anti­tatively evaluating the com­position of each sample, this article evaluates correlations between the crystal forms present, corresponding process methods, sample age, and storage conditions. Furthermore, revision is recommended on characterizations in recently granted patents that include descriptions of crystalline psilocybin inappropriately reported as a single-phase ‘isostructural variant.’ Rietveld refinement demonstrated that the claimed material was com­posed of approximately 81% Polymorph A and 19% Polymorph B, both of which have been identified in historical samples. In this article, we show conclusively that all published data can be explained in terms of three well-defined forms of psilocybin and that no additional forms are needed to explain the diffraction patterns.

Cadmium exchange on clinoptilolite is performed and structurally studied for different durations of the ion exchange process (2 h, 24 h, 72 h, 168 h, 12 days, 22 days) at room temperature and 90 °C. The distribution of Cd2+ ions in all samples is elucidated after exchange on clinoptilolite using powder XRD data processed by Rietveld structural software. Clinoptilolite is not selective for cadmium cations, but at 90 °C the exchange is ~2.5 cations per unit cell. At RT it reaches ~1.25 cations per unit cell being twice as low. The obtained maximum exchanged sample for 22 days 90 °C was structurally refined in order to find the cadmium positions in the clinoptilolite voids. The structural refinements of the occupations of the incoming and outgoing cations give an idea of how the intracrystalline diffusion is processed. A good correlation between results obtained by structural refinement of the Cd-exchanged samples and the data of the EDS measurements was achieved.

Understanding the microstructure in heterostructured nanoparticles is crucial to harnessing their properties. Although microscopy is ideal for this purpose, it allows for the analysis of only a few nanoparticles. Thus, there is a need for structural methods that take the whole sample into account. Here, a novel bulk‐approach based on the combined analysis of synchrotron X‐ray powder diffraction with whole powder pattern modeling, Rietveld and pair distribution function is presented. The microstructural temporal evolution of FeO/Fe3O4 core/shell nanocubes is studied at different time intervals. The results indicate that a two‐phase approach (FeO and Fe3O4) is not sufficient to successfully fit the data and two additional interface phases (FeO and Fe3O4) are needed to obtain satisfactory fits, i.e., an onion‐type structure. The analysis shows that the Fe3O4 phases grow to some extent (≈1 nm) at the expense of the FeO core. Moreover, the FeO core progressively changes its stoichiometry to accommodate more oxygen. The temporal evolution of the parameters indicates that the structure of the FeO/Fe3O4 nanocubes is rather stable, although the exact interface structure slightly evolves with time. This approach paves the way for average studies of interfaces in different kinds of heterostructured nanoparticles, particularly in cases where spectroscopic methods have some limitations., R.U.I. acknowledges CAPES and CNPq (No. 206983/2014‐0) Brazilian agencies. A.G.R. and J.N. thanks the support of the Generalitat de Catalunya through the 2017‐SGR‐292 project and the Beatriu de Pinos Program (2011 BPB 00209) and the Spanish Ministerio de Economía y Competitividad (MINECO) through the MAT2016‐77391‐R project. I.P. was supported by the National Research Fund of Luxembourg (Grant No. FNR‐Inter2015/LRSF). A.L.‐O. acknowledges the MINECO through the Juan de la Cierva Program (IJCI‐2014‐21530). X.T. would like to acknowledge the financial support from the MINECO projects MAT2015‐67593‐P and BIA2014‐57658‐C2‐1‐R. The ALBA Synchrotron is acknowledged for the provision of beamtime and the MSPD beamline staff is for their help during the XRD measurements. Dr. Luis G. Martinez from IPEN/CNEN is acknowledged for useful discussions about XRD techniques. Dr. Paolo Scardi from Università degli Studi di Trento is acknowledged for the helpful discussions about WPPM and for providing PM2K v.3 software. ICN2 is funded by the CERCA Programme/Generalitat de Catalunya. ICN2 also acknowledges support from the Severo Ochoa Program (MINECO, Grant No. SEV‐2013‐0295).

Bahan paduan oksida Nd1(Fe)0,4Ba1,6Cu3O7-δ yang dilakukan dengan menggunakan metode reaksi padatan dengan total lama pemanasan 18 jam. Penelitian ini dilakukan dengan tujuan untuk mengetahui struktur kristal bahan paduan oksida Nd1(Fe)0,4Ba1,6Cu3O7-δ dengan karakterisasi XRD dan mengetahui morfologi serta perbandingan jumlah atom dengan karakterisasi SEM-EDAX. Bahan paduan oksida yang disintesis adalah Nd1(Fe)0,4Ba1,6Cu3O7-δ dengan menggunakan bahan dasar Nd2O3 99.99%; BaCO3 99.98%; CuO 99.99% dan Fe 99.99%, bahan dasar tersebut dicampur dan digerus selama 3 jam kemudian dikalsinasi selama 6 jam. Hasil kalsinasi digerus ulang selama 3 jam kemudian disintering selama 6 jam dan dilanjutkan dengan annealing selama 6 jam. Hasil karakterisasi XRD menunjukkan terbentuknya fasa Nd1(Fe)0,4Ba1,6Cu3O7-δ, selanjutnya hasil analisis rietveld dengan menggunakan aplikasi Rietika diperoleh niai Gof 1,497% dan hasil refinement menunjukkan struktur kristal dari fasa Nd1(Fe)0,4Ba1,6Cu3O7-δ adalah ortorombik dengan ukuran kristal dan FWHM yang diperoleh sebesar 6,2 Å dan 0,21 serta diperoleh konstanta kisi fasa Nd1(Fe)0,4Ba1,6Cu3O7-δ yaitu a = 3.9031Å, b = 3.9072Å dan c = 11.6790Å. Hasil SEM-EDAX menunjukkan bahan paduan oksida Nd1(Fe)0,4Ba1,6Cu3O7-δ berbentuk klaster-klaster dan perbandingan jumlah atom setelah sintesis yaitu Nd: Fe:Ba:Cu = 1: 0,22 : 1,51 : 2,88.

The sintering process is a thermal agglomeration process, and it is accompanied by chemical reactions. In this process, a mixture of iron ore fines, flux, and coal particles is heated to about 1300 °C–1480 °C in a sinter bed. The strength and reducibility properties of iron ore sinter are obtained by liquid phase sintering. The silico-ferrite of calcium and aluminum (SFCA) is the main bonding phase found in modern iron ore sinters. Since the physicochemical and crystallographic properties of the SFCA are affected by the chemical composition and mineral phases of iron ores, a crystallographic understanding of iron ores and sintered ore is important to enhance the quality of iron ore sinter. Scrap and by-products from steel mills are expected to be used in the iron ore sintering process as recyclable resources, and in such a case, the crystallographic properties of iron ore sinter will be affected using these materials. The objective of this paper is to present a short review on research related to mineral phases and structural properties of iron ore and sintered ore.

Nickel laterite ore is used to produce nickel metal, predominantly to manufacture stainless steel as well as nickel sulfate, a key ingredient in the batteries that drive electric vehicles. Nickel laterite production is on the rise and surpassing conventional sulfide deposits. The efficiency of mining and processing nickel laterites is defined by their mineralogical composition. Typical profiles of nickel laterites are divided into a saprolite and a laterite horizon. Nickel is mainly concentrated and hosted in a variety of secondary oxides, hydrous Mg silicates and clay minerals like smectite or lizardite in the saprolite horizon, whereas the laterite horizon can host cobalt that could be extracted as a side product. For this case study, 40 samples from both saprolite and laterite horizons were investigated using X-ray diffraction (XRD) in combination with statistical methods such as cluster analysis. Besides the identification of the different mineral phases, the quantitative composition of the samples was also determined with the Rietveld method. Data clustering of the samples was tested and allows a fast and easy separation of the different lithologies and ore grades. Mineralogy also plays a key role during further processing of nickel laterites to nickel metal. XRD was used to monitor the mineralogy of calcine, matte and slag. The value of mineralogical monitoring for grade definition, ore sorting, and processing is explained in the paper.

Quantitative X-Ray analysis was used to quantify the phase content generated by the High Velocity Oxygen Fuel (HVOF) process following the decarburisation of WC–Co coatings. Rietveld analysis was used to quantify the different phases present. Particular attention has been made to identifying the sequence of formation of the different species, namely: during flight of the powders towards the substrate and/or during the solidification and cooling step on the substrate. The results show that decarburisation is influenced by the thermal history of the particles in flight. In particular, more W2C and W are generated with increasing spray distance indicating an increase WC decarburisation. During the coating building-up, new nanosized compounds (W3Co3C and W6Co6C) were generated. These compounds, at the reverse of W2C and W phases, decrease with the stand-off distance. Correlations are established between the mechanical properties (microhardness and crack propagation resistance) and the content of the phases determined from the Rietveld analysis.

Manuscrito revisado de los autores, aceptado y finalmente publicado en: Construction and Building Materials 264 (2020) 120258), con DOI: https://doi.org/10.1016/j.conbuildmat.2020.120258 Than stoichiometric one. However, the hydration mechanism is not well understood, in particular for the effect of Ba/Ca ratio on hydration behavior. To shed light on this issue, high purity C4-xBxA3$ samples with designed element compositions (C4A3$, C3.5B0.5A3$, and C3BA3$) were prepared and their hydration processes were investigated. The results reveal that Ba-doped ye’elimite reacts faster than the stoichiometric ye’elimite. With the increase of Ba/Ca ratio, it can gradually increase the intensity of the initial peak, shorten the dormant period and reduce the total hydration heat. The phase composition evolution based on Rietveld/XRD method demonstrates that the dissolution rate of the C3.5B0.5A3$ and C3BA3$ are about 19% and 28% higher than that of C4A3$ in 6h. Moreover, the hydration sequences and main products varied significantly. The AFt is absent for the system with barium incorporation and AFm tends to be less with the increase of Ba/Ca ratio. This paper also proposes a new acceleration mechanism of Ba-doped ye’elimite. It is summarized as a higher rate of dissolution-precipitation reaction stemmed from higher ion precipitation of BaSO4 and a combination of extra surface for the nucleation sites provided by BaSO4. This work is supported by the National Key Research and Development Plan of China (No. 2018YFD1101003 and No. 2016YFB0303505), National Natural Science Foundation of China (No. U1806222, 51602126, and 51761145023), Key Laboratory of Advanced Civil Engineering Materials (Tongji University), Ministry of Education (202001), the Taishan Scholars Program, Case-by-Case Project for Top Outstanding Talents of Jinan, Youth Innovation Support Program of Shandong Colleges and Universities (2019KJA017), State Key Laboratory of Silicate Materials for Architectures (Wuhan University of Technology) (No. SYSJJ2018-12).

Three defect pyrochlores KNbWO6&middot, xH2O, KNbTeO6 and KSbWO6 were synthesized by solid state reaction at 750 &deg, C, from stoichiometric mixtures of K2C2O4, Sb2O3, Nb2O5, WO3 and 20% excess TeO2. A neutron powder diffraction (NPD) data analysis allowed unveiling some structural features. They are all defined in the cubic F d 3 &macr, m space group symmetry, with &alpha, = 10.5068(1) &Aring, 10.2466(1) &Aring, and 10.2377(1) &Aring, respectively. Difference Fourier synthesis for KNbWO6&middot, xH2O clearly showed the presence of crystallization water, with extra O&rsquo, oxygen and H+ atoms that were located from NPD data. These O&rsquo, oxygen atoms are placed at 32e Wyckoff sites, conforming a K2O&rsquo, sublattice interpenetrated with the covalent framework constituted by (Nb,W)O6 octahedra. The H+ ions coordinate the O&rsquo, atoms at partially occupied 96g Wyckoff sites while K+ ions shift also along 32e sites, but closer to the 16c special site (0,0,0). By contrast, extra H2O molecules are absent in the other two pyrochlores: in KNbTeO6 and KSbWO6 K+ ions are shifted along 32e (x,x,x) sites further away from the origin than for the previous material, and the higher covalency of the octahedral network determines more compact structures, with shorter B&ndash, O distances and narrower B&ndash, O&ndash, B angles in the proposed AB2O6 defect pyrochlore structure.

For the first time, this work reports concentration maps of asbestos minerals in contaminated mine tailings drawn using the results of Rietveld quantitative phase analysis (QPA). The investigated sites are located in the Valle d’Aosta region (Italy): Cretaz, the most important Italian magnetite mine, active until 1979 and Emarese, one the most important chrysotile asbestos mines in Italy, active until 1968. The results of the study permit to draw the spatial distribution of the asbestos (chrysotile and tremolite in this specific case) concentration, useful to plan reclamation of the sites, with priority given to the areas with the highest asbestos concentration. Because of the complexity of the mineral assemblage, which includes, among the others, antigorite, chlorite, talc, and tremolite, the concentration of chrysotile was cross-checked using different experimental techniques such as X-ray powder diffraction (XRPD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), polarized light optical microscopy (PCOM), and differential thermal analysis (DTA). The accuracy of the results was validated by analyzing standard samples with known concentrations of chrysotile and tremolite. The comparison allowed to point out the advantages and disadvantages of each experimental method. At Cretaz, chrysotile ranges from 4.4 to 22.8 wt% and tremolite from 1.0 to 10.3 wt%, whereas at Emarese the concentration of chrysotile varies from 3.3 to 39.5 wt% and tremolite from 5.9 to 12.4 wt%. Antigorite and chlorite are the major accompanying phases with variable amounts of other accessory minerals including magnetite, carbonates, talc, olivine, pyroxene, talc, and brucite. The results of our study are of key importance for the local environmental policies as the knowledge of the spatial distribution of the asbestos concentration allows to plan a detailed reclamation agenda of the contaminated sites. The spots with the highest surface contamination of both chrysotile and tremolite were identified and classified as priority areas in the reclamation plan.

For the first time, this work inspects the accuracy of quantitative phase analysis of both crystalline and amorphous components of stoneware tiles and bricks. A number of variables were considered: the nature of the internal standard, experimental conditions and counting statistics. The so-calledG-factor method has also been applied. The results of the X-ray powder diffraction analysis have been compared with the results obtained with optical microscopy and image analysis. Only the mixtures spiked with corundum and silicon yielded accurate weight estimates of the amorphous fraction, whereas the use of highly X-ray absorbing internal standards (such as fluorite, rutile and zincite) resulted in gross underestimations. In fact, microabsorption effects are found to drastically reduce the accuracy of the results when standards with linear X-ray absorption coefficients higher than 100 cm−1are employed. It was found that very low counting statistics reduced the calculated amorphous fractions in both bricks and stoneware tiles owing to partial masking of the major peak of the internal standard, namely corundum. The application of theG-factor method to the systems investigated was also evaluated. The results are poorer than those obtained using the internal standard.

High-purity (SupT) and reagent-grade (ST), stoichiometric and silicate-containing α-tricalcium phosphate (α-TCP: ST0/SupT0 and Si-TCP x=0.10: ST10/SupT10) were prepared by solid-state reaction based on the substitution mechanism Ca3(PO4)(2-x)(SiO4)x. Samples were determined to be phase pure by X-ray diffraction (XRD), and Rietveld analysis performed on the XRD data confirmed inclusion of Si in the α-TCP structure as determined by increases in unit cell parameters; particularly marked increases in the b-axis and β-angle were observed. X-ray fluorescence (XRF) confirmed the presence of expected levels of Si in Si-TCP compositions as well as significant levels of impurities (Mg, Al and Fe) present in all ST samples; SupT samples showed both expected levels of Si and a high degree of purity. Phosphorus ((31)P) magic-angle-spinning solid-state nuclear magnetic resonance (MAS NMR) measurements revealed that the high-purity reagents used in the synthesis of SupT0 can resolve the 12 expected peaks in the (31)P spectrum of α-TCP compared to the low-purity ST0 that showed significant spectral line broadening; line broadening was also observed with the inclusion of Si which is indicative of induced structural disorder. Silicon ((29)Si) MAS NMR was also performed on both Si-TCP samples which revealed Q(0) species of Si with additional Si Q(1)/Q(2) species that may indicate a potential charge-balancing mechanism involving the inclusion of disilicate groups; additional Q(4) Si species were also observed, but only for ST10. Heating and cooling rates were briefly investigated by (31)P MAS NMR which showed no significant line broadening other than that associated with the emergence of β-TCP which was only realised with the reagent-grade sample ST0. This study provides an insight into the structural effects of Si-substitution in α-TCP and could provide a basis for understanding how substitution affects the physicochemical properties of the material.

With the increasing demand for nanomaterials, it is essential that they are produced, where possible, by sustainable or \"green\" synthesis methods, avoiding environmentally harmful processes and solvents, with the aim of reducing the production of hazardous byproducts and wastes and minimizing environmental impact. In this work, Ag-modified titania nanoparticles (NPs) were synthesized via a green aqueous sol gel method. The products of the synthesis were thermally treated at 450 and 600 degrees C, and their photocatalytic (in liquid solid and gas solid phases) and antibacterial properties were assessed using both UV- and visible-light exposure. The microstructure and phase composition of the prepared samples were also characterized using advanced X-ray powder diffraction methods (whole powder pattern modeling). Results showed that both the amount of Ag and the thermal treatment greatly influenced not only the phase composition and microstructure but also the functional properties of the TiO2. The increasing levels of Ag retarded the anatase-to-rutile phase transition to a greater extent, and 2 mol % was the optimum amount of Ag for methylene blue photodegradation with both UV- and visible-light irradiation. When using a UV-light source, samples showed a much greater antibacterial activity toward Escherichia coli (E. coli; Gram-negative) than methicillin-resistant Staphylococcus aureous (Gram-positive). It was observed that UV light caused a change in the oxidation state of silver, from ionic silver to metallic (Ag+ -> Ag-0 NPs), this being detrimental for the antibacterial activity. However, under artificial white light irradiation this did not occur and the material kept its excellent antibacterial properties (higher activity than commercial P25); because of this, it could be suitable for use in health care, helping to greatly reduce the spread of Gram-negative type bacteria such as E. coli.

Mechanical Alloying (MA) has the ability to extend the solubility limits of immiscible alloys in a solid state. In this work, a Cu-10 wt% Mo alloy was synthesized by mechanical alloying, using a high-energy mill type SPEX. The X-ray diffraction and Rietveld results show a crystallite size of 24 and 22 nm of Cu and Mo, respectively, with an occupation value of Mo inside the Cu structure of 27%, which was identificated by Energy Dispersive X-Ray Spectroscopy and High-Resolution Transmission Electron Microscopy analysis. After that, the alloy was sinterized in an oven, heating the alloy to 1000 &deg, C&mdash, close to the melting point of Cu (1085 &deg, C). Electrochemical tests were carried out under a saline environment of synthetic seawater. The results show that the polarization curve of the alloy showed a pitting corrosion at about 134.83 mV, as well as a repasivation phenomenon (Erp = 241.47 mV) in the cathodic branch. Finally, three time constants were observed in the Nyquist diagrams: formation of a corrosion product film, load transfer, and diffusion, indicating that the corrosion properties in this alloy were improved compared with other Cu&ndash, alloys.

La 0.7 Sr 0.3 Cr 0.4 Mn 0.6 O 3-δ perovskite nanoparticles have been synthetized using an ethylene glycol modified sol-gel method and impregnated by Cu 0.75 Ni 0.25 nanoparticles. The phase transitions and nucleation kinetics were studied by time resolved x-ray diffraction, Rietveld, Raman spectroscopy and high resolution transmission electron microscopy. Findings have shown that, an atomic disorder dominates from room temperature to 400 °C. Nanoparticles with crystal size 0.7 Sr 0.3 Cr 0.4 Mn 0.6 O 3-δ and SrCrO 4 solid solutions with Pm 3 ¯ m cubic and P 2 1 /n monoclinic symmetry respectively in the range of 600–650 °C. Symmetry reduction from the Pm 3 ¯ m ⟶ R 3 ¯ c space group had been obtained at a lower temperature (750 °C) than those reported in the literature in oxygen atmosphere and it was confirmed by an octahedral distortion, which takes place in the crystallographic direction [ 2 2 1 ] / ( 1 2 2 ) . The Johnson-Mehl-Avrami model had described the whole process, where the existence of two phases was shown before it reached its complete D 3 d 6 point group symmetry.

The Rietveld-internal standard method for Bragg-Brentano reflection geometry (q/2q) X-ray diffraction (XRD) patterns is implemented to determine the amorphous phase content. The effect of some minor phases on quantitative accuracy is assessed. The numerical simulation analysis of errors and the related corrections are discussed. The results reveal that high purity of crystalline phases in the standard must be strictly ensured. The minor amorphous or non-quantified crystalline phases exert significant effect on the quantitative accuracy, even with less than 2 wt% if ignored. The error levels are evaluated by numerical simulation analysis and the corresponding error-accepted zone is suggested. To eliminate such error, a corrected equation is proposed. When the adding standard happens to be present in sample, it should be also carefully dealt with even in low amounts. Based on that ignorance, the absolute and relative error equations (DAE, DRE) are derived, as proposed. The conditions for high quantitative accuracy of original equation is strictly satisfied with a lower amount of standard phase present in sample, less than 2 wt%, and a higher dosage of internal standard, larger than 20 wt%. The corrected equation to eliminate such quantitative error is suggested. MINECO BIA2014-57658-C2-2-R

Nesse trabalho, apresentamos a caracterização estrutural de regiões soldadas em aço austenítico AISI-304, que foram submetidas a processo de nitretação a plasma (20%N2 + 80%H2). Posteriormente as amostras foram hidrogenadas catodicamente. As temperaturas de nitretação foram de 400, 500 e 550°C. As regiões da solda e fora da solda hidrogenadas após a nitretação foram comparadas por DRX, microscopia ótica e microscopia eletrônica de varredura (MEV). As fases austenita-γ, martensita-α', martensita-ε, ferrita-α e os nitretos CrN, γ'-Fe4N e e-Fe2+xN foram identificados. As microestruturas de ambas as regiões e da zona termicamente ativada (ZTA) foram similares. Para 400°C, a estequiometria das fases formadas foi diferente das observadas em 500°C e 550°C. Os efeitos provocados pela hidrogenação foram mais acentuados em 550°C, com o arrancamento da camada nitretada. Structural characterization of weld and outside weld regions of AISI-304 nitrided (20%N + 80%H) and cathodically hydrogenated is presented. Nitriding temperatures were 400, 500 e 550°C. The weld and outside weld regions were compared by XRD, optical microscopy and SEM. The phases γ-austenite, α'-martensite, ε-martensita and α-ferrite and the nitrides: CrN, γ'-Fe4N e e-Fe2+xN were identified. Microstructures of both regions and the thermal active zone were similar. For 400°C the stoichiometry of the formed phases was different from that formed at 500°C and 550°C. Hydrogen effects were more intense for 550°C, due to chipping occurrence.

RESUMEN: En este proyecto hemos realizado un estudio del desorden laminar en minerales de la arcilla, incluyendo tanto desorden total, o turbostrático, como parcial. Para ello se ha empleado la técnica de difracción de rayos X aplicada a arcillas del grupo de las esmectitas. Para su interpretación se han usado diferentes programas disponibles para la simulación y el ajuste de los difractogramas de estructuras desordenadas, empleando diferentes modelos y aproximaciones. ABSTRACT: In this project we have made a study of the laminar disorder in clay minerals, including total disorder (turbostratic) and partial disorder. With this objective, we have employed the X-Ray diffraction applied to clays of the smectite group. For its interpretation, we have used different available programs for the simulation and fitting of diffractograms using different models and approaches. Grado en Física

A working procedure was developed for determining the degree of reaction of fly ash subjected to alkali activation (with 8 M NaOH) at mild temperatures. Since the reaction products dissolve in HCl, the residue left after this acid attack contains only the fraction of the original ash that failed to react with the basic solution. This residue was analysed with Rietveld XRPD quantification and NMR and the findings were compared to the results of the analyses run on the activated ash to obtain a very precise quantification of all of the (crystalline, vitreous and amorphous) phases present in the systems studied.

In this paper we investigated the structural and magnetic properties of the Gd 2− x M x Ru 2 O 7 (M=Ho and Y, x =0.0, 0.1, 0.2, 1.0 and 2.0) pyrochlores. The samples were prepared by solid state reaction method, characterized structurally by X-ray diffraction with Rietveld refinement and magnetically by measuring the temperature dependence of the magnetization. X-ray diffractograms of all samples studied presented a cubic pyrochlore type crystal structure with lattice parameters varying linearly in accordance with Vegards law. It is shown that by substituting Gd by Ho one can tune the magnetic order of this system moving from antiferromagnetic (in the absence of Ho) to ferromagnetic (in the absence of Gd). On the other hand by replacing Gd for Y the antiferromagnetic order is decreased. © 2010 Elsevier Science. All rights reserved

El objetivo de la Tesis es estudiar la síntesis y caracterización de alúminas a partir de un precursor no convencional, un residuo peligroso de la industria del aluminio. El trabajo se ha desarrollado en cinco etapas: caracterización del residuo de aluminio; síntesis y caracterización del precursor de alúminas, boehmita; obtención y caracterización de las alúminas de transición; obtención y caracterización de la fase estable de alúmina, corindón y caracterización microestructural y cuantificación de fases de alúminas mediante ajuste de los patrones de difracción por el método Rietveld. El residuo de aluminio utilizado como material de partida es un material pulverulento heterogéneo, de granulometría muy fina, con una composición compleja. Se destacan sus contenidos en aluminio metálico y nitruro de aluminio, que son dos de los parámetros más importantes relacionados con su peligrosidad ya que generan en contacto con la humedad gases tóxicos como hidrógeno y amoniaco. El tratamiento hidrotermal del residuo, permite recuperar el 90% del aluminio, que es transformado mediante un procedimiento sol-gel, en el precursor de las alúminas. Este precursor está constituido por agregados de pequeñas partículas de carácter amorfo o nanocristalino, baja porosidad y baja superficie específica. Mediante su tratamiento térmico en distintas condiciones experimentales de obtienen diferentes fases de alúminas metaestables y estable. La fase metaestable γ-Al2O3 se forma, como fase única, a 500ºC por transformación topotáctica de boehmita. Esta fase, se muestra como aglomerados de partículas delgadas de baja cristalinidad, elevada superficie específica y tamaño cristalino nanométrico, que se mantiene como fase única hasta 600ºC. A 1000ºC, coexisten cuatro fases γ, δ, θ y α-Al2O3, atribuyéndose la gran estabilidad de la fase γ-Al2O3 a la presencia de ciertas impurezas procedentes del residuo inicial, entre otros factores. La transformación de las alúminas metaestables a corindón tiene lugar de forma gradual, y con diferencias en la evolución de los diferentes granos, dependiendo de su tamaño inicial, de la fase metaestable de la que provengan (γ, θ, δ) y de las primeras partículas de α-Al2O3, formadas a baja temperatura. Se estudia la influencia de temperatura, tiempo de calcinación y atmósfera en la formación de corindón. La formación de corindón como fase cristalina única a partir del residuo de aluminio, requiere temperaturas ≥1400ºC debido a la elevada estabilidad de las alúminas de transición. A 1500ºC se obtiene corindón con una microestructura uniforme de aglomerados bien cohesionados, formados por placas hexagonales características, con un tamaño de grano entre 8 y 20μm y un tamaño de cristalito ≥150nm. Se ha realizado la caracterización microestructural del precursor y de las alúminas, determinándose los parámetros cristalográficos y el tamaño de cristalito mediante el estudio de los perfiles de difracción de rayos X por el método de Rietveld. Este método ha permitido, también, realizar la cuantificación de fases (cristalinas y amorfas) en función de las condiciones de tiempo y temperatura de tratamiento y de la atmósfera empleada. Las alúminas obtenidas a partir del residuo de aluminio presentan unas características similares a las obtenidas a partir de precursores convencionales y/o comerciales. De esta forma, se demuestra que se puede revalorizar un residuo peligroso, cuyo destino habitual es un vertedero de seguridad, (con un coste extra de tratamiento), como materia prima, es decir se contribuye al ahorro de recursos naturales mediante el aprovechamiento de materiales secundarios, que podrían ser catalogados como “End of Waste” de acuerdo con las últimas directivas europeas.

En: Constelaciones. ISSN. 2340-177X. n. 2, 2014, pp 251-264 Los jardines del museo Kröller-Müller de Otterlo alojan las reconstrucciones de los pabellones que Rietveld y Van Eyck construyeron en 1955 y 1966, para la Exposición Internacional de Escultura del parque Sonsbeek de Arnhem. Esta comunicación relata el proceso de formación del museo y la reciente historia de reconstrucción de los pabellones integrados en él. The Kröller-Müller Museum gardens in Otterlo host the reconstructions of the pavilions built by Rietveld and Van Eyck in 1955 and 1966 for the International Exhibition of Sculpture in Sonsbeek Park, Arnhem. This paper describes the museum formation process and the recent history of reconstruction of the pavilions integrated on it.

Nineteen samples of medieval transparent-glazed pottery and archaic majolica from Orvieto (central Italy) were studied. they were classified by archaeological criterion as follows: five transparent-glazed fragments with green and brown decorations (first half of the 13th century), eight green transparent-glazed fragments (13th century). SEM-EDX, XRD (the Rietveld method) and XRF were used to characterise the chemical and mineralogical compositions both of the bodies and the coatings. In all of the samples, the paste is Ca-rich with CaO contents as high as 13-20 wt%. The mineralogical composition is compatible with a firing temperature about 950°C, which is the typical temperature reached in a wood kiln. No difference was observed between the bodies of transparent-and tin-glazed pottery. In the case of transparent glazes, the burial conditions lead to heavy weathering of the samples. However, on the basis of the analyses carried out innon-weathered areas, the typical composiztion is PbO 55-65 wt%, SiO2 31-35 wt%. In tin glazes, the tin is scattered on the mass of the glaze as SnO2 crystals with a concentration of 7-14 wt%. Concerning the decorations, it is established that the green colour is due to the presence of copper; while the manganese is responsible for the brown colour. These pigments, which repersent the typical colours of "archaic majolica", are spread through the glaze homogeneously, apart from one case in which there is clear evidence of manganese oxide crystals.

The applicability, reliability, and repeatability of Si-29 MAS NMR for determination of the quantities of alite (Ca3SiO5) and belite (Ca2SiO4) in anhydrous Portland cement was investigated in detail for 11 commercial Portland cements and the results compared with phase quantifications based on powder X-ray diffraction combined with Rietveld analysis and with Taylor-Bogue calculations. The effects from paramagnetic ions (Fe3+) on the spinning sideband intensities, originating from dipolar couplings between Si-29 and the spins of the paramagnetic electrons, were considered and analyzed in spectra recorded at four magnetic fields (4.7-14.1 T) and this has led to an improved quantification of alite and belite from Si-29 MAS NMR spectra recorded at "high" spinning speeds of v(R) = 12.0-13.0 kHz using 4 or 5 mm rotors. Furthermore, the impact of Fe3+ ions on the spin-lattice relaxation was studied by inversion-recovery experiments and it was found that the relaxation is overwhelmingly dominated by the Fe3+ ions incorporated as guest-ions in alite and belite rather than the Fe3+ sites present in the intimately mixed ferrite phase (Ca2AlxFe2-xO5). (C) 2009 Elsevier Inc. All rights reserved.

The work of architect Gerrit Th. Rietveld (1888 – 1964) is appreciated throughout the world. Many of the well-known buildings he designed have survived to the present. Some have been restored or refurbished, depending on the condition of the building, current needs of the building users, etc. Rietveld himself had a very clear vision about lifestyle, simplicity, restraint and use of space and building materials. His architecture reflects his vision beautifully. Some of Rietveld's buildings are likely to be affected by developments in the near future. Here, I will discuss his Amsterdam College of Art, which has been restored, and his Arnhem College of Art, which has been refurbished. The restoration and refurbishment approaches with Rietveld's philosophy of a sustainable way of life, sustainability considerations at the time of the restoration or refurbishment, and the current view will be compared in this paper. The approaches used to deal with these two are colleges were quite different and illustrate changing attitudes and may act as a pointer for future projects. These aspects fit in the conference theme’s of Building for Transformation. The De Ploeg factory in Bergeijk will be transformed in the near future and presents us with an opportunity to consider what options there are, bearing in mind Rietveld's philosophy. To what extent can we change a building like this and still consider it as a Rietveld design?