Mechanochemically Synthesised Dicyanamide Hybrid Organic-Inorganic Perovskites and their Melt-Quenched Glasses

Here we present efficient and scalable mechanochemical formation of hybrid organic-inorganic perovskites of the form [TPrA][M(dca)₃] (M = Mn²⁺, Co²⁺) and the subsequent formation of their bulk melt-quenched glass samples. The thermal, chemical and adsorptive properties of the materials are also investigated.

Experimental constraints on dacite magma storage beneath Volcán Quizapu, Chile

Volcán Quizapu, Chile, is an under-monitored volcano that was the site of two historical eruptions: an effusive eruption in 1846-1847 and a Plinian eruption in 1932, both of which discharged ∼5 km3 (DRE) of lava and/or tephra. The majority of material erupted in both cases is trachydacite, nearly identical for each event. We present H2O-saturated, phase equilibrium experiments on this end-member dacite magma, using a pumice sample from the 1932 eruption as the main starting material. At an oxygen fugacity (fO2) of ∼NNO+0.2, the phase assemblage of An25-30 plagioclase + amphibole + orthopyroxene, without biotite, is stable at 865±10 °C and 110±20 MPa H2O pressure (PH2O), corresponding to ∼4 km depth. At these conditions, experiments also reproduce the quenched glass composition of the starting pumice. At slightly higher PH2O and below 860 °C, biotite joins the equilibrium assemblage. Because biotite is not part of the observed Quizapu phase assemblage, its presence places an upper limit on PH2O. At the determined storage PH2O of ∼110 MPa, H2O undersaturation of the magma with XH20fluid==0.87 would align Ptotal to mineral-based geobarometry estimates of ∼130 MPa. However, XH20fluid=1< 1 is not required to reproduce the Quizapu dacite phase assemblage and compositions. A second suite of experiments at lower fO2 shows that the stability fields of the hydrous silicates (amphibole and biotite) are significantly restricted at NNO-2 relative to NNO+0.2. Additional observations of Quizapu lava and pumice samples support the existing hypothesis that rapid pre-eruptive heating drove the effusive 1846-1847 eruption, with important refinements. We demonstrate that microlites in the end-member dacite lavas are consistent with in situ crystallization (during ascent), rather than transfer from an andesite. In one end-member dacite lava, newly identified reverse zoning in orthopyroxene and incipient destabilization of amphibole are consistent with small degrees of heating. Our work articulates a clear direction for future Quizapu studies, which are warranted given the active nature of the Cerro Azul-Descabezado Grande volcanic axis.

Metal-organic framework and inorganic glass composites

Metal-organic framework (MOF) glasses have become a subject of interest as a distinct category of melt quenched glass, and have potential applications in areas such as ion transport and sensing. In this paper we show how MOF glasses can be combined with inorganic glasses in order to fabricate a new family of materials composed of both MOF and inorganic glass domains. We use an array of experimental techniques to propose the bonding between inorganic and MOF domains, and show that the composites produced are more mechanically pliant than the inorganic glass itself.

Metal-Organic Framework and Inorganic Glass Composites

<p>Metal-organic framework (MOF) glasses have become a subject of study due to their novelty as an entirely new category of melt quenched glass and their potential applications in areas such as ion transport and sensing. In this paper we show how MOF glasses can be combined with inorganic glasses, in order to fabricate a new family of optically transparent materials, composed of both MOF and inorganic glass domains. Here, we present the design rules for this family of materials, use an array of experimental techniques to propose the bonding between inorganic and MOF domains, and show that the composites produced are more mechanically pliant than the inorganic glass itself.</p>

Metal-Organic Framework and Inorganic Glass Composites

<p>Metal-organic framework (MOF) glasses have become a subject of study due to their novelty as an entirely new category of melt quenched glass and their potential applications in areas such as ion transport and sensing. In this paper we show how MOF glasses can be combined with inorganic glasses, in order to fabricate a new family of optically transparent materials, composed of both MOF and inorganic glass domains. Here, we present the design rules for this family of materials, use an array of experimental techniques to propose the bonding between inorganic and MOF domains, and show that the composites produced are more mechanically pliant than the inorganic glass itself.</p>

The importance of crystalline phases in ice nucleation by volcanic ash

Volcanic ash is known to nucleate ice when immersed in supercooled water droplets. This process may impact the properties and dynamics of the eruption plume and cloud as well as those of meteorological clouds once the ash is dispersed in the atmosphere. However, knowledge of what controls the ice-nucleating activity (INA) of ash remains limited, although it has been suggested that crystalline components in ash may play an important role. Here we adopted a novel approach using nine pairs of tephra and their remelted and quenched glass equivalents to investigate the influence of chemical composition, crystallinity, and mineralogy on ash INA in the immersion mode. For all nine pairs studied, the crystal-bearing tephra nucleated ice at warmer temperatures than the corresponding crystal-free glass, indicating that crystalline phases are key to ash INA. Similar to findings for desert dust from arid and semi-arid regions, the presence of feldspar minerals characterizes the four most ice-active tephra samples, although a high INA is observed even in the absence of alkali feldspar in samples bearing plagioclase feldspar and orthopyroxene. There is evidence of a potential indirect relationship between chemical composition and ash INA, whereby a magma of felsic to intermediate composition may generate ash containing ice-active feldspar or pyroxene minerals. This complex interplay between chemical composition, crystallinity, and mineralogy could help to explain the variability in volcanic ash INA reported in the literature. Overall, by demonstrating the importance of crystalline phases in the INA of ash, our study contributes insights essential for better appraising the role of airborne ash in ice formation. Among these is the inference that glass-dominated ash emitted by the largest explosive volcanic eruptions might be less effective at impacting ice-nucleating particle populations than crystalline ash generated by smaller, more frequent eruptions.

The importance of crystalline phases in ice nucleation by volcanic ash

Volcanic ash is known to nucleate ice when immersed in supercooled water droplets. This process may impact the properties and dynamics of the eruption plume and cloud, as well as those of meteorological clouds once the ash is dispersed in the atmosphere. However, knowledge of what controls the ice-nucleating effectiveness (INE) of ash remains limited, although it has been suggested that crystalline components in ash may play an important role. Here we adopted a novel approach using nine pairs of tephra and their remelted and quenched glass equivalents to investigate the influence of chemical composition, crystallinity and mineralogy on ash INE in the immersion mode. For all nine pairs studied, the crystal-bearing tephra nucleated ice at higher temperatures than the corresponding crystal-free glass, demonstrating that crystalline phases are key to ash INE. Similar to findings for desert dust from arid and semi-arid regions, the presence of feldspar minerals characterises the four most ice-active tephra samples, although a high INE is observed even in the absence of alkali feldspar in samples bearing plagioclase feldspar and orthopyroxene. There is evidence of a potential indirect relationship between chemical composition and ash INE, whereby a magma of felsic to intermediate composition may generate ash containing ice-active feldspar minerals. This complex interplay between chemical composition, crystallinity, and mineralogy could help partly to explain the variability in volcanic ash INE reported in the literature. Overall, by categorically demonstrating the importance of crystalline phases in the INE of volcanic ash, our study contributes insights essential for better appraising the role of airborne ash in ice formation. Among these is the inference that glass-dominated ash emitted by the largest explosive eruptions may be less effective at impacting ice-nucleating particle populations than crystalline ash generated by smaller, more frequent eruptions.

Effect of Nd3+ on the Properties of Lithium Niobium Borate Crystal and Glass

1 mol% of neodymium-doped lithium niobium borate (NdLNB) glass and crystal have been produced by using melt-quenching and Czochralski technique, respectively. The synthesis, growth and characterizations of the samples were reported. X-ray diffraction (XRD), Differential thermal analyzer (DTA), Ultraviolet-Visible-Near-Infrared (UV-Vis-NIR) and Photoluminescence (PL) spectroscopic characterizations were made to examine the influence of Nd3+ on the physical, structural and optical properties of the samples. Various physical properties such as density, molar volume, ion concentration, polaron radius, inter-nuclear distance and field strength were calculated. The as-quenched glass was amorphous whereas crystal was crystalline as established via XRD studies. UV-Vis-NIR spectra exhibited eight prominent bands centered at 353, 475, 524, 583, 681, 745, 803, 875 nm corresponding to the transitions from the ground state to 4D3/2, 2G9/2, 4G7/2, 4G5/2, 4F9/2, 4F7/2, 4F5/2, 4F3/2 excited states, respectively. Moreover, the emission spectra at 355 nm excitation displayed several peaks that contributed to the transition of(4F3/2→4I9/2) and (4F3/2→4I11/2), respectively. Fluorescence lifetime was recorded at 53.69 µs for the glass whereas the crystal was recorded at 43.62 µs. It was found that Nd3+ ions affected the physical, structural and optical properties of the glass and crystal samples.

X-ray powder diffraction analysis of two new magnesium selenate hydrates, MgSeO4·9H2O and MgSeO4·11H2O

Several hitherto unknown hydrates of magnesium selenate have been formed by quenching aqueous solutions of MgSeO4 in liquid nitrogen. MgSeO4·11H2O is apparently isostructural with the mineral meridianiite (MgSO4·11H2O), being triclinic, $P{\rm \bar 1}$, Z = 2, with unit-cell parameters a = 6.779 00(8) Å, b = 6.965 16(9) Å, c = 17.4934(2) Å, α = 87.713(1)°, β = 89.222(1)°, γ = 63.121(1)°, and V = 736.15(1) Å3 at −25 °C. MgSeO4·9H2O represents a new hydration state in the MgSeO4–H2O system; it is monoclinic, space-group P21/c, Z = 4, with unit-cell parameters a = 7.270 24(6) Å, b = 10.510 94(9) Å, c = 17.4030(2) Å, β = 109.447(1)°, and V = 1254.02(1) Å3 at −22 °C. The heavy-atom structure of MgSeO4·9H2O has been determined by direct-space methods from X-ray powder diffraction data and consists of isolated Mg(H2O)62+ octahedra and SeO42− tetrahedra linked by hydrogen bonds. The remaining three water molecules occupy the space between the polyhedral ions, contributing to the H-bonded network, which comprises 4-, 5-, and 6-membered rings. A third phase has been observed to crystallise prior to the 11-hydrate upon warming of liquid-nitrogen-quenched glass, but this transforms rapidly to the meridianiite-structured 11-hydrate and the identity of this phase is unclear.