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This study compares thirteen natural and industrial samples of supplementary or emerging supplementary cementitious materials (SCMs): slag, fly ashes, pozzolan, obsidian, silica fume, and recycled glass. These materials are used or are under consideration for decarbonization in cement plants. XRF, XRD and Raman microspectroscopy were used in order to achieve a deeper understanding of the structural characterization of SCMs. The changes in position and shape of the XRD diffuse halos were compared. Raman spectroscopy was used to study the glass part of the SCM families, to better understand their structure in terms of depolymerization degree, angle, ring size and incorporations into the glass. The chemical composition of each glassy part was also estimated using reverse Bogue calculations. The hump position is correlated with the Raman shift, and with the XRF bulk or with the calculated glass chemical composition of SCMs, in terms of CaO/(SiO 2 + Al 2 O 3) or network modifiers to formers ratios. • Natural and industrial Supplementary Cementitious Materials • Characterization of the amorphous part by XRF, XRD and Raman spectroscopy • Depolymerization degree of glass network • Correlation between XRD hump position and Raman shift • Correlations between XRD hump position and bulk chemical XRF or glass composition [ABSTRACT FROM AUTHOR]

• Amorphous based mix design framework had been developed for blended geopolymers. • The varying composition of slag and fly ash in blended geopolymer is investigated. • The optimal amorphous Si/Al ratio of blended geopolymer is 2.3. • New amorphous ratio, (Na + 2Ca)/Al, is proposed with optimal ratio 3.2. A new amorphous phase mix design framework had been successfully developed in consideration of calcium content through the combination of ground-granular blast-furnace slag (GGBFS) in fly ash (FA) blended geopolymers. The new framework has been developed considering the amorphous silicon, aluminium, sodium and calcium containing phases of the aluminosilicate sources to increase geopolymerisation reactivity and compressive strength. By utilising this new framework, this study found that the optimal amorphous Si/Al ratio of FA- and GGBFS-blended geopolymers are between 2.3 and 3.1. At 40–50% of FA replacement with GGBFS, it had been observed that blended geopolymers are able to achieve the majority of its 28 days compressive strength at 7 days. To account for the effect of calcium content, a new amorphous ratio, (Na + 2Ca)/Al, is proposed, with an optimal ratio of between 3.2 and 3.4. [ABSTRACT FROM AUTHOR]

The carbonation of ultramafic rocks, including tailings from ultramafic-hosted ore deposits, can be used to remove CO2 from the atmosphere and store it safely within minerals over geologic timescales. Quantitative X-ray diffraction (XRD) using Rietveld refinements can be employed to estimate the amount of carbon sequestered by carbonate minerals that form as a result of weathering of ultramafic rocks. However, the presence of structurally disordered phases such as serpentine minerals, which are common in ultramafic ore bodies such as at the Woodsreef chrysotile mine (New South Wales, Australia), results in samples that cannot be analyzed using typical Rietveld refinement strategies. Previous investigations of carbon sequestration at Woodsreef and other ultramafic mine sites typically used modified Rietveld refinement methods that apply structureless pattern fitting for disordered phases; however, no detailed comparison of the accuracy (or precision) of these methods for carbon accounting has yet been attempted, making it difficult to determine the most appropriate analysis method. Such an analysis would need to test whether some methods more accurately quantify the abundances of certain minerals, such as pyroaurite [Mg6 F e 2 3 + $\begin{array}{} \rm Fe^{3+}_{2} \end{array}$ (CO3)(OH)16·4H2O] and other hydrotalcite group minerals, which suffer from severe preferred orientation and may play an important role in carbon sequestration at some mines. Here, we assess and compare the accuracy, and to a lesser extent the precision, of three different non-traditional Rietveld refinement methods for carbon accounting: (1) the PONKCS method, (2) the combined use of a Pawley fit for serpentine minerals and an internal standard (Pawley/internal standard method), and (3) the combined use of PONKCS and Pawley/internal standard methods. We examine which of these approaches represents the most accurate way to quantify the abundances of serpentine, pyroaurite, and other carbonate-bearing phases in a given sample. We demonstrate that by combining the PONKCS and Pawley/internal standard methods it is possible to quantify the abundances of disordered phases in a sample and to obtain an estimate of the amorphous content and any unaccounted intensity in an XRD pattern. Eight artificial tailings samples with known mineralogical compositions were prepared to reflect the natural variation found within the tailings at the Woodsreef chrysotile mine. Rietveld refinement results for the three methods were compared with the known compositions of each sample to calculate absolute and relative error values and to evaluate the accuracy of the three methods, including whether they produce systematic under- or overestimates of mineral abundance. Estimated standard deviations were also calculated during refinements; these values, which are a measure of precision, were not strongly affected by the choice of refinement method. The abundance of serpentine minerals is, however, systematically overestimated when using the PONKCS and Pawley/internal standard methods, and the abundances of minor phases (<10 wt%) are systematically underestimated using all three methods. Refined abundances for pyroaurite were found to be increasingly susceptible to error with increasing abundance, with an underestimation of 6.6 wt% absolute (60.6% relative) for a sample containing 10.9 wt% pyroaurite. These significant errors are due to difficulties in mitigating preferred orientation of hydrotalcite minerals during sample preparation as well as modeling its effects on XRD patterns. The abundances of hydromagnesite [Mg5(CO3)4(OH)2·4H2O], another important host for atmospheric CO2 during weathering of ultramafic rocks, was consistently underestimated by all three methods, with the highest underestimation being 3.7 wt% absolute (or 25.0% relative) for a sample containing 15.0 wt% hydromagnesite. Overall, the Pawley/internal standard method produced more accurate results than the PONKCS method, with an average bias per refinement of 6.7 wt%, compared with 10.3 wt% using PONKCS and 12.9 wt% for the combined PONKCS-Pawley/internal standard method. Furthermore, the values for the refined abundance of hydromagnesite obtained from refinements using the Pawley/internal standard method were significantly more accurate than those for refinements done with the PONKCS method, with relative errors typically <25% for hydromagnesite abundances between 5 and 15 wt%. The simpler and faster sample preparation makes the PONKCS method well-suited for rapid carbon accounting, for instance in the field using a portable XRD; however, the superior accuracy gained when using an internal standard make the Pawley/internal standard method the preferable means of undertaking a detailed laboratory-based study. As all three methods displayed an underestimation of carbonate phases, applying these methods to natural samples will likely produce an underestimate of hydromagnesite and hydrotalcite group mineral abundances. As such, crystallographic accounting strategies that use modified Rietveld refinement methods produce a conservative estimate of the carbon sequestered in minerals. [ABSTRACT FROM AUTHOR]

We perform a comparative study of empirical potentials for atomistic simulations of amorphous silicon nitride (a-Si 3 N 4 ). We choose 5 different parameterizations of the Tersoff potential, the Marian-Gastreich two-body (MG2) and three-body (MG3) potential, the Vashishta (V) potential, and the Garofalini (SG) potential. Amorphous models of Si 3 N 4 , comprising of 448 atoms, are generated by each empirical potential using a melt-and-quench procedure. Subsequently, models are optimized using Density Functional Theory calculations, and structures resulting from these DFT optimizations are compared. We emphasize local coordination of atoms and the enthalpies of formation (ΔH f ) relative to crystalline β-Si 3 N 4 . The SG and MG2 potentials prove to be best options for modeling of a-Si 3 N 4 . Models generated with these potentials are close to their DFT local minimum, exhibit the smallest number of defects, and have realistic enthalpies of formation. [ABSTRACT FROM AUTHOR]

In this work, Fe 3 O 4 nanoparticles and amorphous silica coated Fe 3 O 4 @SiO 2 nanocomposites synthesized using solvothermal method and modified Stöber method are reported. Powder XRD analysis, FTIR spectroscopic technique and X-ray photoelectron spectroscopy analyzeswere employed to confirm the structure and formation of Fe 3 O 4 nanoparticles and Fe 3 O 4 @SiO 2 core shell structured nanocomposites. The structural details elucidated from TEM images and SAED patterns are very much in agreement with the XRD results and confirm the formation of Fe 3 O 4 @SiO 2 core shell structured nanocomposites. VSM analysis confirms super paramagnetic features having soft magnetic property in Fe 3 O 4 @SiO 2 albeit with reduction in saturation magnetization. The dielectric behavior was studied at different temperatures in the frequency range between 1 Hz and 1 MHz in the temperature range 373 K to 723 K in steps of 50 K. The modulus spectrum formalism reveals temperature dependent hopping type of mechanism for charge transport and the impedance spectra reveals the contribution of grain effect on the electrical properties. Further, the analysis of dielectric data indicates that the Fe 3 O 4 @SiO 2 displays positive temperature coefficient of resistance type behavior and the frequency dependent ac conductivity obeys the well-known Jonscher's power law. • Fe 3 O 4 @SiO 2 core shell nanocomposites are prepared using modified Stober process. • The value of magnetic saturation is high for Fe 3 O 4 and low for Fe 3 O 4 @SiO 2 core shell structured nanocomposites. • FTIR, XPS and TEM measurements substantiate the formation of Fe 3 O 4 @SiO 2 core shell structured nanocomposites. • When the temperature is high the dielectric constant is high and the dielectric loss is low at lower frequency region. • The cole-cole plot reveals that the material follows non-Debye type of relaxation. [ABSTRACT FROM AUTHOR]

In an effort to limit the environmental impact of concrete materials, there is increasing interest in the development and use of a wider range of minerals as acceptable supplementary cementitious materials (SCMs). This study investigated calcined blended clays of kaolinite and bentonite, with impurities, to assess their feasibility as SCMs. The combined use of Rietveld quantitative x-ray diffraction (RQXRD) and thermogravimetric analysis (TGA) techniques proved useful in initially gauging amorphous content post-calcination, lending insight into the relationship between calcination temperature and pozzolanic reactivity. The results demonstrated that for the calcined blended clays, as the amorphous content increased, the SCM consumed more portlandite and the compressive strength of cement-SCM mortars increased. Blends of kaolinite–bentonite clays, containing initially 35 wt.% crystalline kaolinite prior to calcination, achieved roughly 10% increase in compressive strength over samples containing 100 wt.% cement, at 90 days. Blended kaolinite SCMs may offer significant advantages as a low-cost alternative binder or cement replacement material, with the ability to maintain or enhance mechanical strength. [ABSTRACT FROM AUTHOR]

Abstract: The present work reports structural and optical behaviour of the Er3+/Yb3+ co-doped boro-tellurite glasses 50TeO2 +15H3BO3 +(5− x − y)La2O3 +15MgCO3 +15SrCO3 + xEr2O3 + yYb2O3 (where x =1, y =0, 0.5, 1 and 2 in wt%) studied through Fourier transform infrared (FTIR), Raman, absorption, luminescence, upconversion luminescence and lifetime measurements for green laser applications. The Teh name="sbnd" />Te, O3Bh name="sbnd" />BO3 bond bending vibrations and the fundamental stretching vibration of OH groups are confirmed through FTIR and Raman spectra. Through the absorption spectra, bonding parameters, oscillator strengths and Judd–Ofelt (JO) parameters were calculated and reported. From the luminescence spectra, radiative parameters have been calculated for the and excited state transitions. Upconversion luminescence spectra of the prepared glasses have been recorded and the excited state absorption (ESA) and Energy transfer (ET) processes are discussed. The luminescence decay curves for the transition of the title glasses under 980 excitation wavelength have also been studied and reported. [Copyright &y& Elsevier]

Abstract: The crystallization behavior and thermal stability of amorphous phases of Al65Cu20Ti15 alloy obtained by mechanical alloying were investigated by using in-situ X-ray diffraction and differential scanning calorimetry (DSC) under non isothermal and isothermal conditions. The result of a Kissinger analysis shows that the activation energy for crystallization is 1131kJ/mol. The higher stability against crystallization of Al65Cu20Ti15 amorphous alloy is attributed to the stronger interaction of atoms in the Al-Cu–Ti system and formed of complicated compound like Al5CuTi2 and Al4Cu9 as primary phases. The isothermal crystallization was modeled by using the Johnson–Mehl–Avrami (JMA) equation. The Avarami exponents suggest that the isothermal crystallization is governed by a three-dimensional diffusion-controlled growth. [Copyright &y& Elsevier]

Abstract: Thermal stability and crystallization of the Fe81B12Si4C2 alloy were investigated in the temperature range 25–700°C by the XRD and Mössbauer analysis. It was shown that on heating the as-prepared amorphous Fe81B12Si4C2 alloy undergoes thermal stabilization through a series of structural transformations involving the process of stress-relieving (temperature range 200–400°C), followed by a loss of ferromagnetic properties (Curie temperature at 420°C) and finally crystallization (temperature range 450–530°C). The process of crystallization begins by formation of two crystal phases: Fe3B and subsequently Fe2B, as well as a solid solution α-Fe(Si). With increase in annealing temperature, the completely crystallized alloy involved only two phases, Fe2B and solid solution α-Fe(Si). XRD patterns established a difference in phase composition and size of the formed crystallites during crystallization depending on the side (fishy or shiny) of the ribbon. The first nuclei of the phase α-Fe3Si were found on the shiny side by XRD after heat treatment even at 200°C but the same phase on the fishy side of ribbon was noticed after heat treatment at 450°C. The largest difference between the contact and free surface was found for the Fe2B phase crystallized by heating at 700°C, showing the largest size of crystallites of about 130nm at 700°C on the free (shiny) surface. [ABSTRACT FROM AUTHOR]

Abstract: Two simple models were developed in order to determine the chemical composition of both nanocrystals and intergranular amorphous phases in nanocrystallized Fe73.5Si13.5B9Nb3Cu1 containing Ge using data from X-ray diffraction and Mössbauer spectroscopy techniques. Saturation magnetization of the amorphous intergranular matrix (M s am ) was calculated considering the contribution of the α-Fe(Si,Ge) nanocrystals and saturation magnetization of the alloys. The behavior of M s am with the iron content of the matrix was obtained and discussed. The exchange stiffness constant for the nanograins and for the amorphous phases was determined. The increment in the coercive field (H c ) with increasing Ge content was evaluated using two theoretical models for the random magnetocrystalline anisotropy constant (〈K 1〉). Results show that the magnetic hardening observed could not be attributed to an increase in 〈K 1〉 but mainly to an important increment of the magnetostriction constant of the α-Fe(Si,Ge) nanocrystals (λ s cr ). Values for λ s cr are proposed. [Copyright &y& Elsevier]

Abstract: In this paper, a systematic investigation about the effect of Al substitution on properties of Fe–Cr–Mo–Er–C–B amorphous material, including glass-forming ability (GFA), thermal properties, and mechanical properties was presented. It was found out by X-ray diffraction (XRD) that the glass-forming ability decreased with the increase of Al, when Al reached 7at%, fully amorphous specimen was not obtained. With regard to thermal parameters, such as glass transition temperature T g, crystallization temperature T x, supercooled liquid region ΔT x, and reduced glass temperature T rg were checked by differential scanning calorimeter. A rather wide supercooled liquid region more than 40K was found. During compression test, results showed Al substitution slightly improved the fracture strength from 3.4 to 3.7GPa. The fracture morphology was observed by scanning electron microscopy. Micrographs showed the same cleavage-like fracture in spite of different Al substitution. [Copyright &y& Elsevier]

Abstract: X-ray diffraction and infrared data have been collected from a sample of ettringite from ambient pressure to 6.4 GPa. The sample was found to reversibly transform to an amorphous phase at 3 GPa. The isothermal bulk modulus of ettringite was found to be 27(7) GPa and the incompressibilities of the lattice parameters were found to be 71(30) GPa along a and 108(36) GPa along c. [Copyright &y& Elsevier]

Abstract: A combined selective dissolution/quantitative X-ray diffraction (QXRD) approach is proposed for the quantitative mineralogical phase analysis of hydraulic limes. The proposed methodology is validated by the analysis of two model mixtures. Afterwards two commercial hydraulic binders and one self-burned hydraulic quicklime were analysed. Chemical, thermal and microprobe analyses were performed to check the results. It is shown that the proposed selective dissolution/QXRD approach yields reliable quantitative mineralogical information for hydraulic limes in spite of their complex phase composition and the presence of amorphous material. [Copyright &y& Elsevier]

Abstract: In examining and analyzing over three decades of research on the transformations involved in Pu–Ga alloys, it is clear that many incongruities and contradictions exist. New analysis shows that under certain processing conditions large amounts of a non-diffracting disordered state exists in Pu–Ga alloys, which I call the amorphous state. The amorphous state is certainly not an equilibrium state, but it can be formed under certain pressure conditions, and more surprisingly once formed can persist for extended times and temperatures. It is believed that the emergence of the amorphous state is closely linked to the 5f-electrons going into a bonding mode. Being a physical state, the amorphous state has distinct physical properties, meta-stabilities, and sensitivities to Ga content. The existence of an amorphous state requires innovative new tools for identification and analysis. The density and compressibility data presented in this paper is one such tool for analyzing the amorphous state, but it requires other knowledge of the materials for proper analysis. Many studies point to radiation damage producing amorphous regions. New computer modeling studies show the existence of amorphous regions and Pu-rich interstitial defects in Pu–Ga alloys. [Copyright &y& Elsevier]

Abstract: Metallic glass alloys of Al84Ni12Zr4−x Pr x (x =0–3) were prepared by melt-spinning technique. Thermal stability and amorphous nature were investigated in Al84Ni12Zr4−x Pr x (x =0–4) alloys with X-ray diffraction (XRD) and differential scanning calorimetry (DSC). Results show that appropriate Pr addition promotes the GFA of this alloy system while declines the thermal stability. It also can be seen from the results that the total area of exothermic peaks shows good correlation with GFA. The less total area of exothermic peaks is, the better GFA of Al84Ni12Zr(4−x)Pr x (x =0–3) system is. [Copyright &y& Elsevier]

Abstract: Amorphous Pd43Ni10Cu27P20 foam is produced at 38%, 49%, and 70% porosity by isothermally expanding a 25%-porosity amorphous precursor in the supercooled liquid state for varying durations. The foam morphologies exhibit good spatial homogeneity as well as good size uniformity of bubbles, which is a consequence of the high viscosity of the supercooled liquid state which inhibits floatation and dampens the growth kinetics. The expansion capability of amorphous metals into high-porosity foam demonstrated in this study is attributed to the plastic deformability of the supercooled liquid state, which enables large plastic membrane elongations during foaming. [Copyright &y& Elsevier]

Abstract: Quantitative phase analyses of three commercial samples of hydraulic limes have been performed using the Rietveld method. Although the Rietveld method has been already applied to cement analysis, we report here the first application to different classes of hydraulic binders, such as hydraulic limes (HL) and natural hydraulic limes (NHL). Unlike HL, that are simple diluted cement, NHL are specific product of great interest for its application in building restoration and conservation. Samples were also characterized by laser granulometry and chemical analysis. Thermogravimetric analysis/Differential Scanning Calorimetry (TG/DSC) and calcimetric analyses were conducted to compare the results of such well-established techniques with those obtained with the Rietveld method. Taking advantage of the Rietveld method with the addition of an internal standard, the phase fraction of all the crystalline phases as well as the amorphous component, have been accurately determined. This technique offers a valid support for the characterization of hydraulic limes in the light of the EN classification of such industrial products. [Copyright &y& Elsevier]

The TeO2–Nb2O5–Bi2O3 system was investigated by differential scanning calorimetry and temperature programmed X-ray diffraction. A large glass-forming domain was evidenced and the complex structural evolution with temperature of these glasses was followed. The glass transition and crystallisation temperatures and the nature of crystalline phases formed were determined. Moreover, this study confirmed the existence of the metastable γ-TeO2 polymorph and of a new crystalline compound, BiNbTe2O8. [Copyright &y& Elsevier]

Abstract: In this paper the microstructure, magnetic properties and mechanical studies results for Fe61Co10Zr2+x Hf3−x W2Y2B20 (for x =1, 2 or 3) alloys are presented. The samples used in the investigations were obtained by a suction-casting method. The samples were produced in the forms of rods with diameter of 1mm and length of about 20mm and plates with thickness of 0.5mm and surface area of about 100mm2. The results show that the best soft magnetic properties were achieved by Fe61Co10Zr3Hf2W2Y2B20 amorphous alloy in the form of a plate. This sample has the highest value of saturation magnetization (1.09T) and the smallest values of coercivity (H C =1.5A/m) and core losses. All investigated samples of amorphous alloys were characterized by substantially greater values of microhardness and, unfortunately, slightly lower values of wear resistance compared with their crystalline counterparts. [Copyright &y& Elsevier]

Abstract: Wei et al. recently reported about the thermal stability of Al70Ni10Ti10Zr5Ta5 amorphous alloy powder fabricated by mechanical alloying. The phrase ‘amorphous alloy powder’ is claimed from the XRD and TEM results. However, the XRD pattern of 120h milled powder shows a small crystalline peak at 2θ ∼38°, which has not been addressed. This unaddressed peak belongs to the intermetallic Al3Ni phase which is still present after 120h of mechanical alloying. Also the TEM results support the presence of crystalline/nano-crystalline phase(s), which the authors have not addressed. Hence the powder is nearly amorphous and not completely amorphous as interpreted by Wei et al. [ABSTRACT FROM AUTHOR]