Melt crystallization of zinc alkali phosphate glasses

The investigation of new glass compositions is crucial to expand the possible applications of glass, from the typical applications for building engineering, in the form of cast blocks or floated glass, to more advanced technologies, such as 3D-printed glass or glass to metal connections. Despite the intense research activity and new glass compositions being investigated every day, there has been little innovation or evolution in the composition of architectural glass. This is partially explained by the fact that a substantial part of glass research is not relevant to practical large-scale applications. This thesis is more concerned about the development of compositions with optimized properties than the studies of the short- and intermediate-range structure of a theoretical glass that would hardly find a practical application. Thus, these compositions are inexpensive and appropriate to mass production, utilizing conventional melting techniques. Since the high melting temperatures and the brittleness are two important drawbacks of glass, this work aims to improve both properties. The modification of the properties is achieved via changes in the composition of the glass, using compounds such as phosphorus pentoxide, aluminium oxide and boron oxide. Then, the choice of different glass formers and modifiers contributes to the development of compositions with lower melting and glass transition temperatures. The reduction of the melting temperature allows a saving of energy during the manufacturing and recycling processes. The structures of the glasses differ from the standard soda-lime and borosilicate glasses, leading to a different mechanical behaviour. For instance, an anisotropic structure, which could exhibit a better mechanical performance than standard glasses. Furthermore, these new compositions incorporate up to 35% of slag and fly ash in their formulas. The valorization of these by-products that would otherwise have been previously discarded reduces costs and gas emission. The developed compositions have high water resistance, amorphous structure proved by x-ray diffraction and indentation toughness comparable to a standard soda-lime glass. The coloration of the samples varies depending on the composition and, for the samples containing slag, depending on the melting temperature. In this case, melting at higher temperatures allows the production of colorless glass. The color of the glasses is mainly influenced by the presence of sulfur and iron oxide. In conclusion, this thesis describes the development of new glass compositions containing fly ash and slag. The focus of the work is on the improvement of the properties and a comparison of performance of these new compositions with the glasses currently used in building engineering. The promising results point to the possibility of expansion of the current applications of glass.

In-situ single-crystal and powder X-ray diffraction (XRD) experiments were performed on diaspore at high temperatures. The powder XRD experiments showed that the dehydration reaction from diaspore to corundum occurs between 703 and 733 K. The in-situ single-crystal XRD measurements of diaspore could successfully determine the cell parameters, fractional atomic coordinates and anisotropic displacement parameters at high temperatures, i.e., from 295 to 698 K. Temperature variations in the cell parameters indicate that thermal expansion of the a-axis is a little higher than those of the b-axis and the c-axis. However, the axial thermal expansivity is not as anisotropic as was previously suggested. The results of structure refinements indicate that such lattice expansion behavior is the result of thermal expansion of the tunnels through O2–H···O1 hydrogen-bond separation in the diaspore structure. To the best of our knowledge, this is the first time that the thermal expansion of diaspore has been investigated at an atomic level by in-situ single-crystal XRD experiments at high temperatures.

Amorphous alloys are formed when the liquid atoms are frozen into a non-crystalline arrangement. In general, rapid quenching from the melt at cooling rates about 106 K/s is required to obtain glass formation in conventional metallic alloys. However, recent development have shown that glasses can be produced at cooling rates as low as about 102 K/s in some multicomponent systems [1–6], the so-called bulk glassy alloys. The low critical cooling rates for the bulk glassy alloys indicate that they have a very high glass forming ability (GFA). The reason for the high GFA of bulk glassy alloys has been discussed, and has resulted in the three empirical rules [7]: (1) multicomponent systems consisting of no less than three elements, (2) significant difference in atomic size ratios above about 12% among the main three constituent elements, and (3) large negative heats of mixing among the main three constituent elements. It is known that there exist short-range order in liquid alloys, and the short-range order play an important role in forming a glassy phase. So, the liquid state will determine the size of the short-ranged orders in the glassy phase. A liquid structure is inherited from the mother ingot. Hence, it is assumed that there exists a relation between the mother ingot microstructure and the GFA of an alloy. This work attempts to uncover this relation. The original ingots with nominal composition Zr60Al15Ni25 were prepared by arc melting a mixture of pure Zr (99.9 wt%), A1 (99.99 wt%) and Ni (99.9 wt%) metals in a water-cooled copper crucible under titanium-gettered argon atmosphere. To prevent segregation, the original ingots were melted 4 times at 1300 K, and were marked A0. Then, two A0 ingots were repeatedly melted 12 times at 1300 K and 1580 K, respectively, and marked AL12 and AH12. The time of one melting operation was 60 s. The melting temperatures were measured by thermocouple (type B). The solidification structures of the ingots were observed using optical microscopy. Samples with a cross section of 1 × 10 mm2 were produced by suction casting in a cop∗Author to whom all correspondence should be addressed. per mold. The amorphous nature of the as-cast samples and the phases in the ingot microstructures were identified by X-ray diffraction (XRD) using Cu Kα radiation (Rigaku Dmax-rc). Thermal analysis was performed in a differential scanning calorimeter (Netzch DSC 404) at a heating rate 10 K/min. The XRD patterns of the ingots A0, AL12 and AH12 are shown in Fig. 1. The phases in the ingots remain unchanged after repeated melting. All the ingots contain Al2Zr3, Ni42Zr58 and AlNi4Zr5 phases. Fig. 2 shows the ingot microstructures. After the repeated melting of the ingots, the microstructure becomes finer, and AH12 is finer than AL12. Fig. 3 shows the XRD patterns of the as-cast samples of A0, AL12 and AH12. All the suction cast samples are verified to be single glassy phase. The DSC curves of Zr60Al15Ni25 glasses are shown in Fig. 4. All the samples show an endothermic event, which is characteristic of glass transition, followed by an exothermic event corresponding to crystallization process. The detailed resuls of DSC are summarized in Table I. After the repeated melting of the ingots at 1300 K and 1580 K, the glass transition temperature Tg increases from 686.4 K to 694.1 and 697.7 K and the onset temperature of crystallization Tx from 758.0 K to 760.2 and 763.7 K. Meanwhile, the fusion enthalpy of the alloy decreases from 110.9 J/g to 82.55 and 80.35 J/g. The results show that the repeated melting of the mother ingot, especially the repeated melting at higher temperature, can improve the GFA of Zr60Al15Ni25 glassy alloy. The critical cooling rates Rc, above which a liquid can be frozen into glass, have a strong correlation with reduced glass transition temperatures Trg [8]. The higher the Trg, the lower the Rc is. In this work, the experimental results show that the Trg increases from 0.571 to 0.577 and 0.580 after the repeated melting 12 times at 1300 K and 1580 K, indicating that the repeated melting of an ingot improves the GFA of the alloy. The heat of mixing of Zr Al, Zr Ni and Al Ni atomic pairs is −44, −49 and −22 kJ/mol respectively [9]. Thus, the atoms in this system show a strong

Temperature dependent X-ray and neutron diffraction study of the liquid–solid and solid–solid equilibria in the Al 29.2Ga 27Zn 43.8 ternary alloy

Two kinds of materials, sprayed-on crocidolite and sprayed-on amosite, containing crocidolite and amosite respectively, were treated with aqueous acetic acid solution, the pH of which was adjusted with an ammonium acetate buffer at 5, in order to remove soluble components of cement. The liquids were filtrated with a membrane filter, and the residue collected as crocidolite samples and amosite samples, respectively. The Crocidolite and amosite thus obtained were heated up to 600-1300°C for 1h. Then, power X-ray diffraction (XRD) experiment, scanning electron microscopic (SEM) observation, and thermal analysis (TG/DTA) were carried out for these burned specimens in order to observe the change of the burned materials and melting behaviors together with their thermal properties. In addition, CaCO3 and CaCl2 were mixed with the respective sprayed-on asbestos and sprayed-on crocidolite, and a TG/DTA measurement was conducted on these mixtures. Based on the SEM observation and XRD experiment on the specimens used in the TG/DTA measurements, we tried to decompose the crocidolite and amosite, applying the method of low-temperature decomposition, the applicability of which was previously confirmed in the study on the case of chrysolite. The temperature of the TG/DTA measurement could be raised up to 1000°C, and it became evident that in the cases of specimens where CaCl2 was added, all the asbestos fibers had decomposed, but not in any other specimen. The crocidolite specimen became rounded in shape when it was heated up to 1000°C, and it looked as if it was densified due to burning. CaCO3 and CaCl2 were added to this burned crocidolite, and decomposition of the material after burning was examined. In a DTA thermogram, an endothermic peak was recognized, which corresponds to the formation of a melt of CaCO3-CaO-CaCl2 as summarized in the previous report. Thus it is experimentally verified that burned crocidolite decomposes at high temperatures.

We have investigated pressure-induced structural transitions in NaBH4 through density-functional theory calculations combined with X-ray and neutron diffraction experiments. Our calculations confirm that the cubic phase is stable up to 5.4 GPa and an orthorhombic phase occurs above 8.9 GPa, as observed in X-ray diffraction experiments. Both the calculations and X-ray diffraction measurements identify an intermediate tetragonal phase that appears between 6 and 8 GPa; that is, between the cubic and orthorhombic phases. This result is also confirmed by high-pressure neutron diffraction experiments performed on NaBD4. Our calculations and X-ray diffraction measurements show that the space group of the orthorhombic phase above 8.9 GPa is Pnma and the orthorhombic phase remains stable up to 30 GPa. The calculated equations of state are in excellent agreement with experiments.

The amount of data collected during synchrotron X-ray diffraction (XRD) experiments is constantly increasing. Most of the time, the data are collected with image detectors, which necessitates the use of image reduction/integration routines to extract structural information from measured XRD patterns. This step turns out to be a bottleneck in the data processing procedure due to a lack of suitable software packages. In particular, fast-running synchrotron experiments require online data reduction and analysis in real time so that experimental parameters can be adjusted interactively. Dioptas is a Python-based program for on-the-fly data processing and exploration of two-dimensional X-ray diffraction area detector data, specifically designed for the large amount of data collected at XRD beamlines at synchrotrons. Its fast data reduction algorithm and graphical data exploration capabilities make it ideal for online data processing during XRD experiments and batch post-processing of large numbers of images.

Multi-scale mechanisms of twinning-detwinning in magnesium alloy AZ31B simulated by crystal plasticity modeling and validated via in situ synchrotron XRD and in situ SEM-EBSD

In most studies related to milled powders, the grain size1 is analyzed via X-ray diffraction (XRD) experiments, and a transmission electron microscopy (TEM) image with high magnification, if provided, is used primarily to confirm the results obtained by XRD experiments. This widely used approach is reasonable in light of the difficulties associated with TEM sample preparation. The present study, however, addresses the hypothesis that such an approach may not be valid when there is an inhomogeneous distribution of grains present. TEM examination, carried out in carefully prepared Al-7.5 wt% Mg samples, in which a global region is observable by TEM, provided the opportunity for quantitative analysis of grain size in cryomilled powders having an inhomogeneous distribution of grain sizes. The cryomilled Al-7.5 wt% Mg had a bimodal grain microstructure of 77% (area fraction) fine grains in the range of 10 to 60 nm and 23% coarse grains of approximately 1 μm. The results show that the XRD analysis yields a grain size that is close to that present in the fine-grained regions (i.e., 10–60 nm). The present study also systematically investigated the influence of the nine possible combinations of the Cauchy (C) and the Gaussian (G) approximations on the calculated grain size value, and the results show that the CC-CC approximation resulted in the largest calculated grain size, the GG-GG generated the smallest one, and the CG-CG, the approximation recommended by Klug and Alexander [1], led to a calculated grain size that is approximately equal to the average one from the CC-CC and GG-GG approximations. The maximum possible fluctuation of grain size values stemming from the various approximations is 38%.

Upcycling Polytetrahydrofuran to Polyester

Raman spectroscopy and X-ray diffraction experiments were performed in the liquid, undercooled liquid, and glassy states of n-butanol. Clear correlated signatures are obtained below the melting temperature, from both temperature dependences of the low-wavenumber vibrational excitations and the intermediate-range order characterized by a prepeak detected in the different amorphous states. It was found that these features are related to molecular associations via strong hydrogen bonds, which preferentially develop at low temperature, and which are not compatible with the long-range order of the crystal. This study provides information on structural heterogeneities developing in hydrogen-bonded liquids, associated to the undercooled regime and the inherent glass transition. The analysis of the isothermal abortive crystallization, 2 K above the glass transition temperature, has given the opportunity to analyze the early stages of the crystallization and to describe the origin of the frustration responsible for an uncompleted crystallization.

NASICON solid electrolytes Part II - X-ray diffraction experiments on sodium-zirconium-phosphate single crystals at 295K and at 993K

Quantum mechanical (QM)/molecular mechanics (MM) calculations by the use of a large-scale QM model (QM Model V) have been performed to elucidate hydrogen-bonding networks and proton wires for proton release pathways (PRP) of water oxidation reaction in the oxygen evolving complex (OEC) of photosystem II (PSII). Full geometry optimisations of PRP by the QM/MM model have been carried out starting from the geometry of heavy atoms determined by the recent high-resolution X-ray diffraction (XRD) experiment of PSII refined to 1.9 Å resolution. Computational results by the QM/MM calculations have elucidated the hydrogen-bonding O···O(N) and O···H distances and O(N)–H···O angles in PRP, together with the Cl–O(N) and Cl···H distances and O(N)–H···Cl angles for chloride anions. The optimised hydrogen-bonding networks are well consistent with the XRD results and available experiments such as extended X-ray absorption fine structure, showing the reliability of channel structures of OEC of PSII revealed by the XRD experiment. The QM/MM computations have elucidated possible roles of chloride anions in the OEC of PSII. The QM/MM computational results have provided useful information for understanding and explanation of accumulated mutation experiments of key amino acid residues in the OEC of PSII. Implications of the present results are discussed in relation to three steps for theoretical modelling of water oxidation in the OEC of PSII and bio-inspired working hypotheses for developments of artificial water oxidation systems by use of 3d transition-metal complexes.

The structure of a mechanically alloyed Ti-45at%Al powder and its decomposition behavior during sintering have been investigated by X-ray diffraction (XRD) and analytical transmission electron microscopy (TEM). By the XRD experiments, the powder after 200 hr mechanical alloying is shown to be consisted of two phases, Ti3A1 and TiAI. The volume fraction of Ti3Al is estimated to be larger than that of TiAI, while for the sintered compact of the powder this tendency was reversed. The mechanically alloyed powder is composed of strain free fine grains (grain size ranging from 10 to 20 nm in diameter). The average composition of the grains are approximately Ti-45at%Al. Therefore, the powder may be assumed to be composed mainly of Al supersaturated Ti3Al. The results of XRD and analytical TEM experiments suggest that the decomposition of the supersaturated Ti3AI to equilibrium Ti3Al and TiAI took place during sintering.

The phase diagram of zinc (Zn) has been explored up to 140 GPa and 6000 K, by combining optical observations, x-ray diffraction, and ab initio calculations. In the pressure range covered by this study, Zn is found to retain a hexagonal close-packed (hcp) crystal symmetry up to the melting temperature. The known decrease of the axial ratio (c/a) of the hcp phase of Zn under compression is observed in x-ray diffraction experiments from 300 K up to the melting temperature. The pressure at which c/a reaches (≈10 GPa) is slightly affected by temperature. When this axial ratio is reached, we observed that single crystals of Zn, formed at high temperature, break into multiple poly-crystals. In addition, a noticeable change in the pressure dependence of c/a takes place at the same pressure. Both phenomena could be caused by an isomorphic second-order phase transition induced by pressure in Zn. The reported melt curve extends previous results from 24 to 135 GPa. The pressure dependence obtained for the melting temperature is accurately described up to 135 GPa by using a Simon–Glatzel equation: , where P is the pressure in GPa. The determined melt curve agrees with previous low-pressure studies and with shock-wave experiments, with a melting temperature of 5060(30) K at 135 GPa. Finally, a thermal equation of state is reported, which at room-temperature agrees with the literature.