Wt Ppm Research Articles

Effect of trace grain boundary segregation element bismuth on stress relaxation behavior of copper

The stress relaxation resistance of copper-based materials determines the reliability of contact and stable transmission of connector plugs. This study investigates the effect of trace bismuth (110 wt ppm) on the stress relaxation resistance of pure copper at temperatures of 25 °C, 100 °C, and 200 °C. The relationship between microstructure and stress relaxation resistance was analyzed using SEM, EBSD, and HAADF-STEM. The results demonstrate that trace bismuth significantly enhances the stress relaxation resistance of pure copper, especially at higher temperatures of 100 °C and 200 °C, where the stress relaxation rates of Cu-0.011Bi samples after 48 h decreased by 21.36 % and 18.06 %, respectively, compared to Cu samples. Trace bismuth elements exist in copper mainly in the form of double atomic layers segregated at grain boundaries, which pin the grain boundaries, inhibit grain growth, and hinder dislocation slip. At room temperature (25 °C), bismuth mainly improves stress relaxation resistance by refining grains. At higher temperatures of 100 °C and 200 °C, the significant enhancement in stress relaxation resistance is primarily related to bismuth's inhibition of the reduction in dislocation density and recrystallization during the stress relaxation process.

Study on the effect of phosphorus on anti-softening performance of oxygen-free copper

This study investigates the preparation of oxygen-free copper with varying phosphorus (P) content through vacuum melting and examines the influence of P on the mechanical properties, softening resistance, and microstructure of the material. The results indicate that as the P content increases (≤1400 wt ppm), the grain size of the oxygen-free copper becomes progressively finer, resulting in significant improvements in microhardness and softening temperature. Notably, when the P content reaches 1400 wt ppm, the microhardness and softening temperature (121.4 HV, 341.35 °C) are markedly superior compared to those with a P content of 0.01 wt ppm (101.89 HV, 210.31 °C). Electron backscatter diffraction (EBSD) was used to analyze the samples before and after softening annealing, and it was found that the P element inhibited the recrystallization behavior of oxygen-free copper by hindering dislocation movement, thereby achieving the effect of increasing the softening temperature. Transmission electron microscopy (TEM) results further demonstrate that annealing softening in P-containing oxygen-free copper (1400 wt ppm) predominantly occurs through discontinuous dynamic recrystallization (DDRX) and twinning dynamic recrystallization (TDRX), thereby altering the recrystallization mechanism of the copper.

Effect of Trace Bismuth on Deformation Behavior of Ultrahigh-Purity Copper during Hot Compression

The effect of trace Bi impurities on the flow stress, microstructure evolution, and dynamic recrystallization (DRX) of the ultrahigh-purity copper was systematically investigated by a hot compression test at 600 °C. The results show that the peak stress of the ultrahigh-purity copper gradually decreases with increasing Bi content. Trace Bi impurities can refine the microstructure of ultrahigh-purity copper. However, the refinement effect of 50 wt ppm Bi is much more significant than that of 140 wt ppm Bi during the hot deformation. This effect is ascribed to the higher concentration of Bi at GBs, which induces severe GB cracks that reduces the driving force for the nucleation of DRX grains. In addition, the introduction of Bi inhibits the DRX of the ultrahigh-purity copper and transforms its DRX process from the discontinuous dynamic recrystallization (DDRX) to the coexistence of DDRX and continuous dynamic recrystallization (CDRX) mechanisms.

Karakteristik Pembakaran Droplet Campuran Metil Oleat – Etanol dengan Penambahan Multi -Walled Carbon Nanotubes

This research intended to investigate the combustion characteristics of methyl oleic – ethanol blend with OH functionalized multi-walled carbon nanotubes (MWCNT-OH) addition. Methyl oleic is an unsaturated fatty acid methyl ester, which is a constituent of various biodiesels. The observed fuel was a mixture of Methyl oleic with 20% vol of ethanol. MWCNT-OH content was varied by 100 ppm, 200 ppm, 300 ppm, 400 ppm, and 500 ppm (wt based). The presence of ethanol in the droplets is intended to promote the microexplosion phenomenon, generating smaller droplets and a shorter burning time. The experimental results show that the MWCNT-OH addition on the droplet of Methyl oleic – ethanol blend decreased the ignition delay and droplet burning time, while the constant burning rate and droplet temperature (and flame temperature) were increased. Reducing ignition delay time due to the higher thermal conductivity of nanofluid droplets results in more effective heat absorption from the environment and better heat transport inside the droplet. Hence, droplet vaporization, flammable mixture formation and ignition occur in a shorter time. Furthermore, this condition encourages a higher burning rate and a lower droplet burning time. The higher droplet and flame temperatures are related to the higher heating value of the methyl oleic – ethanol – MWCNT-OH mixture and higher droplet burning rate, which results in a higher heat release rate.

Microstructures, hydrogen concentrations, and seismic properties of a tectonically exhumed sliver of oceanic mantle lithosphere, Moa Island, Timor-Tanimbar outer-arc, eastern Indonesia

We characterize and quantify the microstructure, hydrogen concentrations, and seismic properties of a tectonically exhumed sliver of oceanic lithospheric mantle outcropping in the Moa Island (Leti archipelago, Timor-Tanimbar outer-arc). The 18 spinel peridotites (lherzolites and harzburgites) have coarse-porphyroclastic microstructures and olivine crystal-preferred orientations (CPO) with axial-[010] (also known as AG-type) or [100](010) (A-type) patterns, similar to those observed in peridotitic xenoliths from oceanic mantle lithosphere. These coarse-porphyroclastic microstructures are variably overprinted by growth of strain-free olivine neoblasts and crystallization of secondary pyroxenes. Recrystallized fractions vary from 6.9 up to 31.3%. The interstitial (cuspate) shapes and CPOs of clinopyroxene, uncorrelated with the olivine CPOs, indicate that refertilization by a reactive melt percolation post-dated deformation. Seismic properties are calculated based on the modal compositions and CPOs of all samples. Increase in the recrystallized olivine fraction decreased the seismic anisotropy, since static recrystallization produced some dispersion of the CPO, but did not change drastically the texture acquired during deformation. Mean seismic velocities (mean Vp = 7.9 km.s−1; mean Vs = 4.5 km.s−1) and anisotropy (mean maximum S wave polarization anisotropy = 4.5%), estimated by considering coherent orientation of the foliation and lineation of all samples, are within the range of typical values for the uppermost mantle. The nominally anhydrous minerals contain small amounts of hydrogen (olivine: 13–18 ppm H2O by weight; orthopyroxene: 58–175 wt ppm H2O and clinopyroxenes: 244–288 wt ppm H2O). A bulk water content of 50 wt ppm H2O is estimated based on nomminally anhydrous minerals for the Moa peridotites, in agreement with previous estimates for the oceanic mantle lithosphere based on peridotitic xenoliths. This is the first direct measurement of hydrogen concentrations in peridotites from an oceanic mantle lithosphere which experienced melt extraction.

On the crystal-chemistry of inderite, Mg[B3O3(OH)5](H2O)4·H2O

The crystal chemistry of inderite, a hydrous borate with known ideal formula MgB3O3(OH)5·5H2O from the Kramer deposit, was re-investigated by electron probe micro-analysis in wavelength dispersive mode, laser ablation-(multi collector-)inductively coupled plasma-mass spectrometry and single-crystal neutron diffraction. The chemical data prove that the real composition of the investigated inderite is substantially identical to the ideal one, with insignificant content of potential isomorphic substituents, so that, excluding B, inderite does not contain any other industrially-relevant element (e.g., Li concentration is lower than 2.5 wt ppm, Be or REE lower than 0.1 wt ppm). The average δ11BNIST951 value of ca. − 7 ‰ lies within the range of values in which the source of boron is ascribable to terrestrial reservoirs (e.g., hydrothermal brines), rather than to marine ones. Neutron structure refinements, at both 280 and 10 K, confirm that the building units of the structure of inderite consist of: two BO2(OH)2 tetrahedra (B-ion in sp3 electronic configuration) and one BO2(OH) triangle (B-ion in sp2 electronic configuration), linked by corner-sharing to form a (soroborate) B3O3(OH)5 ring, and a Mg-octahedron Mg(OH)2(OH2)4. The B3O3(OH)5 ring and the Mg-octahedron are connected, by corner-sharing, to form an isolated Mg(H2O)4B3O3(OH)5 (molecular) cluster. The tri-dimensional edifice of inderite is therefore built by heteropolyhedral Mg(H2O)4B3O3(OH)5 clusters mutually connected by H-bonds, mediated by the zeolitic (“interstitial”) H2O molecules lying between the clusters, so that the correct form of the chemical formula of inderite is Mg[B3O3(OH)5](H2O)4·H2O, rather than MgB3O3(OH)5·5H2O. All the thirteen independent oxygen sites of the structure are involved in H-bonding, as donors or as acceptors. This confirms the pervasive nature and the important role played by the H-bonding network on the structural stability of inderite. The differences between the crystal structure of the two dimorphs inderite and kurnakovite are discussed.

Plastic deformation of dry fine-grained olivine aggregates under high pressures

Abstract This study investigates the effect of pressure on diffusion creep of dry San Carlos and synthetic (prepared by sol-gel method) olivine. We prepared dry (water content < 9 ppm wt) fine-grained (< 1 μm grain-size) olivine and deformed the samples (both San Carlos and solgel olivine in the same assembly) in the same sample assembly under high-pressure (P = 2.9–8.8 GPa) and modest temperatures (T = 980–1250 K) at a fixed strain-rate. Evolution of strength was studied using the radial X-ray diffraction from various diffraction planes. We found that San Carlos and sol-gel olivine show similar rheological behaviour (when normalized to the same grain-size). Stress estimated by the radial X-ray diffraction increases with time and initially shows similar values for all diffraction planes. In many cases, stress values start to depend on the diffraction planes in the later stage and time dependence becomes minor. The micro-structural observations show that grain-size increases during an experiment. The results are interpreted using a theory of radial X-ray diffraction and the theoretical models of diffusion and dislocation creep. We conclude that the initial stage of deformation is by diffusion creep, but deformation in the later stage is by dislocation creep. For dislocation creep, our results are in reasonable agreement with previous low temperature dislocation creep results after a correction of temperature effect. For diffusion creep, we obtain an activation volume of 7.0 ± 2.4 cm3/mol that is substantially smaller than the values reported on dislocation creep but agrees well with the results on grain-growth. By comparing the present results on dry olivine with the previous results on wet (water-saturated) olivine, we found that water enhances diffusion creep but only modestly in comparison to dislocation creep. The difference in the pressure and water content dependence between diffusion and dislocation creep has an important influence on the dominant deformation mechanisms of olivine in the upper mantle.

The effect of BaTiO3 on the magnetic behavior of MnZn ferrites at frequencies > 5 MHz

In this article an extensive study is presented on the effect of BaTiO3 on the high frequency performance of MnZn ferrite having a nominal composition Mn0.9Zn0.1Fe2.45O4. It is shown that BaTiO3 at an optimum concentration of 200 ppm wt. is a bulk dopant that dissolves in the spinel lattice leading to microstructures with smaller grain sizes, lower grain boundary resistivities and higher resonance frequencies. Despite an observed increase on the hysteresis losses, the main impact on the magnetic performance is the significant reduction of the high frequency resonance losses. In addition, no dependency has been observed on the particle size of BaTiO3 since nanoparticles produce the same effects as microparticles. Through exploitation of the beneficial effects of BaTiO3, MnZn ferrites with power losses of 195 kW m−3 (5 MHz, 10 mT, 100 °C) or 1125 kW m−3 (10 MHz, 10 mT 100 °C) and a relative initial permeability of 200 could be synthesized. These results belong to the best reported in literature and indicate that the application region of MnZn ferrites can be extended up to application frequencies traditionally dominated by other ferrite material families.

Raman spectroscopy of zirconium hydride

The characterization of zirconium hydride is important in the nuclear industry because of the hydrogen-induced embrittlement of Zircaloy cladding and its use as a neutron moderator. This paper introduces the use of Raman spectroscopy for the characterization of zirconium hydride. First-principles density functional theory (DFT) calculations were used to predict the Raman spectra of ζ-ZrH0.5, γ-ZrH, δ-ZrH1.5, δ-ZrH1.66, and ε-ZrH2 with all their predicted symmetries; ζ-ZrH0.5 (P3m1, R3¯m, C2/m, Cm, Cmmm, and Pn3¯m); γ-ZrH (P222, Ccce, and P42/mmc); δ-ZrH1.5 (P4¯m2, P42/mcm, Fmmm, Pn3¯m, Ibam, P2/c, PI, and P42/nnm); δ-ZrH1.66 (Fm3¯m); and ε-ZrH2 (Fm3¯m, R3¯m, and I4/mmm). Two samples of Zircaloy-4 containing 133 wt ppm and 360 wt ppm hydrogen were characterized by Raman spectroscopy, showing two signal lines at 215 cm−1 and 1,187 cm−1, which were assigned to the presence of δ-ZrH1.66. These signals had a good spatial correlation with visible hydride precipitates in Raman spectroscopy images. This work provides the basis for the characterization of all possible zirconium hydride compositions and structures using Raman spectroscopy.

Hydrogen in magnetite from asteroid Ryugu

AbstractIn order to gain insights on the conditions of aqueous alteration on asteroid Ryugu and the origin of water in the outer solar system, we developed the measurement of water content in magnetite at the micrometer scale by secondary ion mass spectrometry (NanoSIMS) and determined the H and Si content of coarse‐grained euhedral magnetite grains (polyhedral magnetite) and coarse‐grained fibrous (spherulitic) magnetite from the Ryugu polished section A0058‐C1001. The hydrogen content in magnetite ranges between ~900 and ~3300 wt ppm equivalent water and is correlated with the Si content. Polyhedral magnetite has low and homogenous silicon and water content, whereas fibrous magnetite shows correlated Si and water excesses. These excesses can be explained by the presence of hydrous Si‐rich amorphous nanoinclusions trapped during the precipitation of fibrous magnetite away from equilibrium and testify that fibrous magnetite formed from a hydrous gel with possibly more than 20 wt% water. An attempt to determine the water content in sub‐μm framboids indicates that additional calibration and contamination issues must be addressed before a safe conclusion can be drawn, but hints at elevated water content as well. The high water content in fibrous magnetite, expected to be among the first minerals to crystallize at low water–rock ratio, points to the control of water content by local conditions of magnetite precipitation rather than large‐scale alteration conditions. Systematic lithological variations associated with water‐rich and water‐poor magnetite suggest that the global context of alteration may be better understood if local water concentrations are compared with millimeter‐scale distribution of the various morphologies of magnetite. Finally, the high water content in the magnetite precursor gel indicates that the initial O isotopic composition in alteration water must not have been very different from that of the earliest magnetite crystals.

Influence of aluminium doping on high purity quartz glass properties.

High purity natural quartz is used as raw material for the manufacture of quartz glass crucibles for solar-grade silicon ingots production. One key challenge for cost-effective ingot pulling is to maximise the ability of the crucible to withstand the process conditions (i.e., silicon load and temperature about 1500 °C) without deformation. In order to improve this glass property, aluminium was coated into the raw quartz materials. Our results showed that an addition of up to 1000 wt ppm Al substantially reduces deformation of glass and improves viscosity at high temperatures. This is likely due to the reduction of stability of OH groups in the quartz glass as well as a trapping effect of aluminium on oxygen vacancies. This hypothesis is also supported by atomistic models. In the presence of Al, formation energies of silanol groups (Si-O-H) were much higher than without. Furthermore, the presence of Al in the structure significantly reduces mobility of the oxygen vacancies. It was also found that formation of oxygen vacancies hinders cristobalite crystallisation, on the other hand, Al atoms themselves induce local weakening of the Si-O bond which accelerates the kinetics of the reconstructive phase transition from glassy state to crystalline phase. This was also confirmed experimentally in our study.

Some Considerations on Austenite Grain Growth Kinetics from High‐Temperature Laser Scanning Confocal Microscopy Observations

For more than 20 years, high‐temperature laser scanning confocal microscopy (HT‐LSCM) has become worldwide a proven technique for observing various metallurgical phenomena in situ. HT‐LSCM turns out to be a reliable and effective method for the observation of quantification austenite grain growth kinetics in steel, being highly relevant in casting and steel processing. In the present article, the measurement technique is briefly introduced followed by some basics on austenite grain growth. Finally, selected examples of recent research activities are discussed, including investigations into pure iron and the systems Fe–P, Fe–C, Fe–Al–N, and Fe–C–Nb–N. The influence of P on the grain growth kinetics is remarkable. At 1350 °C, the final grain size decreases from 255 μm in pure iron to 145 μm by adding 0.044 wt% P. In contrast, C enhances the grain growth in specific alloying ranges (0–0.30 wt%C), particularly at elevated temperatures. For a Al content of 0.025 wt% and only 50 wt ppm N, AlN loses the pinning effect above 1150 °C. In case of Nb(C,N), an elevated Nb content (0.085 wt%) provides stabilization of Nb(C,N) at 1150 °C, but at 1250 °C, no pinning of Nb(C,N) is visible anymore.

The water-poor and reduced mantle beneath the Neo-Tethys Ocean: Tectonic setting of the western Yarlung-Tsangpo ophiolites

Water contents and deformation behaviors of minerals in mantle peridotites are diagnostic features to distinguish the physical conditions between mid-ocean ridges and subduction zones, which could serve as effective indicators for discriminating the tectonic setting of ophiolites. In this study, we report a systematic dataset of petrology, geochemistry, water contents and deformation behaviors for the mantle peridotites from the Cuobuzha ophiolite in the western Yarlung-Tsangpo suture zone (YTSZ), southern Tibet, to provide new insights into the long-standing debate for the tectonic setting of ophiolites therein. Geochemical data revealed that the Cuobuzha mantle peridotites experienced low to moderate degrees of partial melting (∼10–15%), although some harzburgites have been intensively modified by late-stage melt-rock interactions. The Cuobuzha peridotites, on the other hand, are characterized by low orthopyroxene water contents (46–95 wt ppm in average), clear olivine crystallographic preferred orientations of A- and E-types, and low oxygen fugacity (logfO2, QFM −2.55 to −0.81, where QFM means quartz-magnetite-fayalite buffer), thus indicative of the occurrence of high-temperature, water-depleted, and reduced mantle in this ophiolite. The features above of the Cuobuzha mantle peridotites are quite similar to those of abyssal peridotites at modern mid-ocean ridges and systematically different from the relatively refractory, water-rich, and oxidized characteristics typical of forearc peridotites in suprasubduction zones. Based on the data from this study and a compiled dataset for other ophiolites from the western YTSZ, we revealed that mantle peridotites with a water-poor and reduced nature are common in these ophiolites, thus providing strong evidence supporting for their origination from a mid-ocean ridge of a mature ocean basin. From the perspective of mantle peridotites, the ophiolites in the western YTSZ now geographically distributed in two branches (i.e., the northern and southern sub-belts) might have formed in a single ocean basin of the Neo-Tethys and were dismembered by late-stage tectonic events to their current locations.

INFLUENCE OF As<sub>2</sub>S<sub>3</sub> STOICHIOMETRY ON THE OPTICAL TRANSMISSION OF GLASS IN THE SPECTRAL RANGE 5–8 µm

Glassy chalcogenides AVBVI obtained by solidification of high-temperature melts inherit the polymolecular nature of the melt. The influence of this circumstance on the optical properties of glasses is important in connection with the use of optical fibers for fabrication and has not been adequately studied. Bulk samples of high-pure glasses As40 – xS60 + x (0 x 5) with the content of metal and silicon impurities less than 0.1‒0.2 ppm wt., carbon, oxygen, hydrogen compounds – no more than 0.5–1 ppm wt. and optical fibers from them were obtained. The IR spectra of bulk samples 12 cm long and optical fibers up to 15 m long were recorded in the spectral range 1000–2000 cm–1. Absorption bands with maxima near 1950, 1805, 1460, and 1320 cm–1, due to the content of superstoichiometric sulfur in glass, were found in the spectra of bulk samples and fibers, and the corresponding values of the extinction coefficients were determined. The results of the study allow us to consider the As2S3 stoichiometry as a factor that significantly affects the optical characteristics of glass.

Nitrogen storage capacity of phengitic muscovite and K-cymrite under the conditions of hot subduction and ultra high pressure metamorphism

Nitrogen storage capacity and partitioning between main N hosts have been investigated in N-bearing Al-rich natural pelite at 3.0–7.8 GPa, 825–1070 °C and oxygen fugacity (fO2) from NNO (Ni-NiO buffer)+0.3 to NNO-4.1 log units. Under the conditions of hot subduction, pelite converts into a phase assemblage typical of ultrahigh-pressure (UHP) eclogites. Phengitic muscovite in this assemblage is in equilibrium with a volatile-rich granite-like melt at 3.0 GPa and with supercritical fluid at 5.5–7.8 GPa, and contains, respectively, 115–135 and 759–962 wt ppm NH4+ at fO2 values close to NNO. Both melt and supercritical fluid have H2O and CO2 as predominant volatiles and the NH3/(NH3 + N2) ratio from 0.04 to 0.12. The pattern of nitrogen partitioning between its main hosts in pelite (DNH4Ms-Melt = 0.41–0.58 and DNH4Ms-Fluid = 0.63–2.4) proves that the ammonium exhibits moderately incompatible to compatible behavior within a hot oxidized slab in the pressure range from 3.0 GPa to 7.8 GPa. Therefore, even relatively oxidized sediments containing phengitic muscovite can efficiently transport nitrogen to the mantle at sub-arc depths under the hot subduction conditions. At the same time, the changeover of the N host from biotite to muscovite at the arc depths in combination with subsequent pelite melting and an abrupt decrease in phengitic muscovite abundance in pelite may lead to an avalanche-like N outgassing of the slab. The incorporation of an additional nitrogen source of (NH3 + N2) into pelite reduces fO2 to NNO-3.1 – NNO-4.1 log units and increases both the NH3/(NH3 + N2) ratio in the fluid (up to 0.44–0.86) and the NH4+ concentration in phengitic muscovite (up to 3750–3820 wt ppm). K-cymrite was produced in pelite at P ≥ 6.3 GPa and the bulk nitrogen content 3.2–5.9 wt%. K-cymrite possesses exceptional nitrogen storage capacity: it hosts 1.4–1.6 wt% NH4+, up to 0.5 wt% NH3, and 4–6 wt% N2. The DN-NH4Cym-Ms coefficient is as high as 20. Being stable in sediments subducted to mantle depths, K-cymrite, with its extremely high storage capacity, can act as a huge hidden redox-insensitive nitrogen reservoir in the mantle and thus can be involved in the deep nitrogen cycle.

Water release and homogenization by dynamic recrystallization of quartz

Abstract. To evaluate changes in water distribution generated by dynamic recrystallization of quartz, we performed infrared (IR) spectroscopy mapping of quartz in deformed granite from the Wariyama uplift zone in NE Japan. We analyzed three granite samples with different degrees of deformation: almost undeformed, weakly deformed, and strongly deformed. Dynamically recrystallized quartz grains with a grain size of ∼10 µm are found in these three samples, but the percentages of recrystallized grains and the recrystallization processes are different. Quartz in the almost-undeformed sample shows wavy grain boundaries, with a few bulged quartz grains. In the weakly deformed sample, bulging of quartz, which consumed adjacent host quartz grains, forms regions of a few hundred micrometers. In the strongly deformed sample, almost all quartz grains are recrystallized by subgrain rotation. IR spectra of quartz in the three samples commonly show a broad water band owing to H2O fluid at 2800–3750 cm−1, with no structural OH bands. Water contents in host quartz grains in the almost-undeformed sample are in the range of 40–1750 wt ppm, with a mean of 500±280 wt ppm H2O. On the other hand, water contents in regions of recrystallized grains, regardless of the recrystallization processes involved, are in the range of 100–510 wt ppm, with a mean of 220±70 wt ppm; these values are low and homogeneous compared with the contents in host quartz grains. These low water contents in recrystallized regions also contrast with those of up to 1540 wt ppm in adjacent host grains in the weakly deformed sample. Water contents in regions of subgrains are intermediate between those in host and recrystallized grains. These results for water distribution in quartz imply that water was released by dynamic recrystallization.

Role of grain boundary character on Bi segregation-induced embrittlement in ultrahigh-purity copper

Bismuth (Bi), as an impurity element in copper and copper-based alloys, usually has a strong tendency of grain boundary (GB) segregation, which depends on the GB characters. However, the influence of such a segregation on the properties of ultrahigh-purity copper has been rarely reported and the exact structural arrangements of Bi atoms at different GBs remain largely unclear. In this study, we investigated the influence of trace amounts of Bi (50-300 wt ppm) on the ductility of an ultrahigh-purity copper (99.99999%) in the range of room temperature to 900 °C. The tensile results show that the addition of Bi seriously damages the ductility of the ultrahigh-purity copper at temperatures of 450–900 °C, which is due to the GB segregation of Bi. On this basis, such a segregation behavior at different types of GBs, including high and low angle GBs (HAGBs/LAGBs), and twin boundaries (TBs), via the scanning electron microscope-electron backscattered diffraction (SEM-EBSD) and aberration-corrected scanning transmission electron microscope (AC-STEM) investigations, combined with the first-principles calculations were systematically studied. The atomistic characterizations demonstrate an anisotropic Bi segregation, where severe enrichment of Bi atoms typically occurs at the HAGBs, while the absence of Bi adsorption prevails at LAGBs or TBs. In particular, the segregated Bi at random HAGBs exhibited the directional bilayer adsorption, while the special symmetrical Σ7 HAGB presented a unique Bi-rich cluster superstructure. Our findings provide a comprehensive experimental and computational understanding on the atomic-scale segregation of impurities in metallic materials.

Redox‐Independent Low Water Solubility in Quartz and Implications for Water Storage in the Crust

AbstractQuartz is an important mineral constituent of the continental crust, which commonly contains trace amounts of water as hydroxyl in the lattice. Despite considerable efforts to document the roles of pressure, temperature, and chemistry on water storage in quartz, the effect of redox state, a key thermodynamic factor in Earth sciences, has not been well established. We assessed the redox effect on water solubility in quartz at 2 and 10 kbar and 800°C, by equilibrating two natural gem‐quality crystals with water over a range of redox conditions. Recovered samples show infrared absorption bands at 3,100–3,600 cm−1. Dehydration experiments at 1200°C (room pressure) suggest that the two bands at ∼3,197 and 3,293 cm−1 are linked to Si‐O overtones, with the other bands to hydroxyl. The water solubility, ∼3.7–32.2 ppm wt. H2O, is redox‐independent, differing from other minerals such as feldspar, pyroxenes, garnet, rutile, and olivine in which the water solubility is significantly redox‐dependent. This provides evidence that the water incorporation in quartz is not controlled by polyvalent elements and/or other redox‐linked mechanisms. Considering the roles of Al, Li, and B in incorporating water and its low solubility over remarkable variations in the abundances of those elements in most natural samples, quartz is not a major water carrier compared to other nominally anhydrous minerals (NAMs) in the crust. The partitioning of water between quartz and other crustal NAMs such as feldspar, pyroxenes, rutile, and garnet is redox‐influenced, and is unlikely to be constant in the crust.

Water solubility in coesite at realistic temperatures of subduction zones

To constrain the water solubility of coesite (Coe) at typical temperatures of subduction zones, a series of Coe coexisting with an aqueous fluid was synthesized at 3–6 GPa and at 600–800 °C. Most experiments were performed in the system SiO2-H2O, and some were performed with small amounts of boron addition. With very long heating durations (120–336 h), all these experiments successfully produced Coe crystals of large grain size, ranging from ∼100 to 1300 μm. For every experimental product, multiple unpolarized FTIR spectra were collected on randomly-selected Coe crystals. We have found that type-I hydrogarnet substitution (Si4+(Si2) + 4O2− = [4]□(Si2) + 4OH−) is the major water-incorporation mechanism whereas B-related defect (H+ + B3+ ↔ Si4+) makes no much contribution. The water solubility of Coe, ranging from 3(1) to 47(12) wt ppm, positively correlates with both P and T. It can be well described by the empirical equation cH2O = −49(17) + 6.0(21) × P + 0.06(2) × T (cH2O representing water content in wt ppm, P pressure in GPa and T temperature in °C) and by the thermodynamic expression cOH=exp∆S1barRfH2O2exp−∆H1bar−∆VsolidPRT (cOH representing water content in H/106 Si, fH2O water fugacity in GPa, R the gas constant, P pressure in GPa, T temperature in K, ∆S1 bar reaction entropy as 18.5(509) J/mol/K, ∆H1 bar reaction enthalpy as −10.7(516) kJ/mol, and ∆Vsolid the volume change of Coe during hydroxylation as 23.6(42) cm3/mol). Consequently, the water solubility of Coe in subduction zones should be ∼0–123 wt ppm. When Coe with deep origin becomes metastable (i.e., approaching the P-T locus of the Coe-quartz (Qz) reaction), its water content is likely less than ∼10 wt ppm. This trace water may be quickly lost along with further exhumation process, and metastable Coe becomes completely dry, as observed in the Coe discovered in all exhumed ultrahigh-pressure (UHP) metamorphic rocks. Since structurally-bonded water substantially speeds up the Coe-to-Qz phase transition, zero water in metastable Coe may be the key to the preservation of Coe in the UHP metamorphic rocks.

Method for preparing high-purity REE-doped chalcogenide glasses for bulk and fiber lasers operating at ∼ 5μm region

A method for preparing high purity rare earth elements (REEs) doped chalcogenide glasses, in which all components of the charge (Ge, Sb, Ga, Se) and REEs are loaded and subjected to additional purification by combining reactive distillation of germanium and antimony selenides and chemical vapor transport (CVT) of gallium and REE iodides under high vacuum conditions, is proposed. The technique is tested in the preparation of Ga5Ge20Sb10Se65 glass doped with (1–20)·1019 at·cm−3 Ce, Pr, Nd, Tb, Dy. In the best glass samples, the content of impurities was as following: metals – 0.03–4 ppm(wt), hydrogen – 0.01 ppm(wt), heterogeneous micron sized inclusions < 102 cm–3. The novel high purity level of Ce3+ and Tb3+ doped glasses made it possible to achieve reproducible practically significant characteristics of laser generation power in the 4.5–5.9 μm range in bulk samples and optical fibers in pulsed and continuous modes at room temperature.