Early Stages Of Crystallization Research Articles

Radiolysis-Induced Crystallization of Sodium Chloride in Acetone by Electron Beam Irradiation.

In situ liquid cell transmission electron microscopy (LC-TEM) is an innovative method for studying the processes involved in the formation of crystals in liquids. However, it is difficult to capture early stages of crystallization because of the small field of view and the unfavorable changes in sample composition resulting from electron-beam radiolysis. Nevertheless, if the radiolysis required to induce the crystallization of a sample could be controlled in LC-TEM, this would be advantageous for observing the crystallization process. Here, we examined this possibility by using a mixture of sodium chlorate (NaClO3) and acetone in the LC-TEM. The electron beam induced the formation of dendritic crystals in a saturated acetone solution of NaClO3; moreover, these crystals consisted of sodium chloride (NaCl), rather than NaClO3, suggesting that chloride ions (Cl−), which were not present in the initial solution, were generated by radiolysis of chlorate ions ${\rm \lpar ClO}_3^- \rpar$. As a result, the solution then supersaturated with NaCl because its solubility in acetone is much lower than that of NaClO3. The combination of radiolysis and a solvent in which a solute is much less soluble is potentially useful for establishing crystallization conditions for materials that are difficult to crystallize directly in LC-TEM experiments.

Crystals at a Carrefour on the Way through the Phase Space: A Middle Path

Multiple supramolecular functionalities of cyclic α-alkoxy tellurium-trihalides (including Te---O, Te---X (X = Br, I) and Te---π(C=C) supramolecular synthons) afford rich crystal packing possibilities, which consequently results in polymorphism or Z’ > 1 crystal structures. Example of three crystal forms of cyclohexyl-ethoxy-tellurium-trihalides, one of which combines the packing of two others, affords a unique model to observe the supramolecular synthon evolution at the early stages of crystallization, when crystals on the way find themself at a carrefour between the evolutionally close routes, but fail to choose between two energetically close packing patterns, so taking the “middle path”, which incorporates both of them (and results in two crystallographically independent molecules). In general, this allows a better understanding of the existing structures, and an instrument to search for the new polymorphic forms.

Geochronology, geochemistry and mineral chemistry of Malayer–Boroujerd–Shazand pegmatite dikes, Sanandaj–Sirjan zone, NW Iran

Pegmatite dikes in the Malayer–Boroujerd–Shazand magmatic complex, located in the Sanandaj-Sirjan zone of the Zagros orogen, are hosted in both granitoid rocks and their contact and regional metamorphic aureoles. In this study, we report the geochronology, geochemistry and mineral chemistry of these pegmatite dikes. The granitoid rocks in the Malayer–Boroujerd–Shazand magmatic suites are mainly monzogranite, quartz diorite, granodiorite and quartz monzonite characterized by metaluminous to peraluminous I-type compositions of the calc-alkaline series and display the geochemical characteristics of volcanic arc granites related to an active continental margin. The pegmatite dikes mainly consist of quartz, feldspar (albite and orthoclase), tourmaline, muscovite and less common biotite and garnet. The tourmaline content in the igneous-hosted pegmatite dikes is higher than those of metamorphic rocks, whereas the muscovite content is lower in the igneous-hosted pegmatite dikes. The K/Rb ratio and the Rb content of pegmatite dikes and their minerals (K-feldspar and muscovite) indicate that they are less evolved. Pegmatite dikes display a typical calc-alkaline affinity of I-type granites and are classified as peraluminous Lithium-Caesium-Tantalum (LCT) family (barren sub-type) to muscovite class. The tourmaline is a schorl-foitite type, which is common in the early crystallization stage of less evolved pegmatites. U–Pb zircon dating of the Boroujerd and Shazand pegmatite dikes yield weighted mean 206Pb/238U ages of 160.2 ± 1.8 and 121.8 ± 1.5 Ma, respectively. In contrast, U–Pb zircon dating of the Malayer pegmatite dike gives a mean 206Pb/238U age of 43.2 ± 1.5 Ma. Our new geochronological data indicate that the first group of pegmatite dikes (older pegmatite dikes) in the Boroujerd district (160.2 ± 1.8 Ma) shows an overlap with the main and first magmatic episode in the Sanandaj–Sirjan zone during Jurassic times, simultaneous with the Middle Cimmerian Orogenic phase, and formed during the subduction initiation. The second group of pegmatite dikes in the Shazand district (121.8 ± 1.5 Ma) formed in the Early Cretaceous and shows a temporal overlap with previously reported ages (ca. 130–114 Ma) during the early Alpine tectonic movements (Late Cimmerian Orogenic phase). Finally, the younger group of pegmatite dikes in the Malayer district (43.2 ± 1.5 Ma) formed in the Eocene overlapping with previously reported ages (ca. 34–52 Ma) which is equivalent to the Laramian phase. These data reveal that the magmatism in the Malayer–Boroujerd–Shazand magmatic complex started in the Early-Middle Jurassic resembling adjacent areas in the Sanandaj–Sirjan zone (e.g., Hamedan region) by melting of crustal protoliths in a subduction tectonic setting. The second and third groups of pegmatite dikes formed during the late subduction to syn-collisional process, respectively. These pegmatite generation marked the subduction initiation to syn-collisional span in the region. The zircon geochemistry (negative Ce anomalies and positive Eu anomalies) is indicative of the relatively oxidized conditions of the parent magma and shows characteristics of continental crust zircon.

Origin of large diamonds in kimberlite

The evidence of the existence and fractionation of the global magmatic ocean on the Earth allows us to distinguish two stages of the formation of diamonds of increased size. The largest giant diamonds arose at an early stage of crystallization and fractionation of the peridotite layer of the magmatic ocean, since its bottom layer at that time was blocked by still hot upper ones and therefore cooled and crystallized very slowly and long. The mafic composition of this layer and the low viscosity of its magmas caused mainly octahedral cutting of the formed giant diamonds. Later crystallized mainly rhombododecahedral diamonds have increased coarseness due to the formation mainly by the growth of early octahedral crystals.

High-performance methylammonium-free ideal-band-gap perovskite solar cells

Summary The development of mixed tin-lead (Sn-Pb)-based perovskite solar cells (PSCs) with low band gap (1.2–1.4 eV) has become critical not only for pushing single-junction devices toward the maximum efficiency given by the Shockley-Queisser limit, but also for enabling all-perovskite tandem devices beyond this limit. However, achieving high power-conversion efficiency (PCE) and long-term device operation stability simultaneously remains a significant challenge for Sn-Pb-based PSCs. Here, we demonstrate near ideal-band-gap (∼1.34 eV) methylammonium-free Sn-Pb-based PSCs with high efficiency (∼20%) and promising operational stability of maintaining >80% of initial PCE over 750 h under maximum-power-point tracking. The key to this success is the use of a SnCl2⋅3FACl complex additive that improves the microstructure and reduces the development of residual stress in the Sn-Pb perovskite thin films, which in turn enhances the efficiency and stability of the Sn-Pb-based ideal-band-gap PSCs.

Reversible disorder-order transitions in atomic crystal nucleation.

Nucleation in atomic crystallization remains poorly understood, despite advances in classical nucleation theory. The nucleation process has been described to involve a nonclassical mechanism that includes a spontaneous transition from disordered to crystalline states, but a detailed understanding of dynamics requires further investigation. In situ electron microscopy of heterogeneous nucleation of individual gold nanocrystals with millisecond temporal resolution shows that the early stage of atomic crystallization proceeds through dynamic structural fluctuations between disordered and crystalline states, rather than through a single irreversible transition. Our experimental and theoretical analyses support the idea that structural fluctuations originate from size-dependent thermodynamic stability of the two states in atomic clusters. These findings, based on dynamics in a real atomic system, reshape and improve our understanding of nucleation mechanisms in atomic crystallization.

The Effect of Polyglycerol Esters of Fatty Acids on the Crystallization of Palm Olein.

This research investigated the effect of polyglycerol ester of fatty acids (PGE) on the crystallization of palm olein (POL). Three PGEs were studied: two solid-state PGEs (PGE1105 and PGE1117) and one liquid-state PGE (PGE1155). The addition of 0.5-5% wt. PGEs influenced the crystallization kinetics of POL and this depended on the type and concentration of the emulsifiers. During cooling down with a cooling rate of 5℃/min, the samples containing PGE1105 and PGE1117 started to crystallize at higher temperatures when compared with POL but the crystallization began at lower temperatures for the samples containing PGE1155. All samples with added PGEs exhibited lower solid fat content than that of POL after 12 h of crystallization time. The number of crystals decreased with an increase in the crystal size with PGE addition but there was no effect on polymorphism. Overall, the results suggested that PGE1105 and PGE1117 enhanced the early stages of POL crystallization possibly via the template effects but suppressed the later stages, whereas PGE1155 delayed the whole process of POL crystallization. The application of POL is often limited by its tendency to get cloudy at low temperatures during long-term storage. Based on the results, 1-5% wt. PGE1155 could be used to delay or prevent the crystallization of POL at low temperatures.

Observation of early ZIF-8 crystallization stages with X-ray absorption spectroscopy

The present study investigates early stages of ZIF-8 crystallization up to 5 minutes post mixing of precursor solutions. Dispersive X-ray Absorption Spectroscopy (DXAS) provides a refined understanding of the evolution of the coordination environment during ZIF-8 crystallization. Linear Combination Analysis (LCA) suggests tetrakis(1-methylimidazole)zinc2+ to be a suitable and stable mononuclear structure analogue for some early stage ZIF-8 intermediates. Our results pave the way for more detailed studies on physico-chemical aspects of ZIF-8 crystallization to better control tailoring ZIF-8 materials for specific applications.

Crystallization behavior of poly(lactic acid) and its blends

Poly(lactic acid) (PLA) is one of the most interesting bio-based biodegradable alternatives, with great promise to replace petroleum-based plastics. However, the intrinsic slow crystallization ability of PLA restricts its extensive applications. In this perspective, we highlight some recent advances in PLA crystallization, including nucleation by self-assembly nucleating agents, self-nucleation (or memory effect), conformational ordering in the very early stage of crystallization, crystal nucleation investigated by fast scanning calorimetry (Flash DSC), crystallization under flow, and pressure fields, and crystallization of enantiomeric blends. Finally, major challenges and future perspectives are proposed.

One-step self-assembly of lamellar MWW crystals through intergrowth driven by centrifugal force to form hollownest structure Zeolite

From the considering of simple synthesis step, low cost, and energy saving, one-step synthesis of hierarchical zeolite without involving additional template has obvious advantages compared with post-synthetic modification or one-step templating methods, by which Ti-containing hollownest structure zeolite (Ti-HSZ) has been successfully synthesized. Herein, the origin of Ti-HSZʼs hollownest structure has been investigated by systematical comparison study between the rotating hydrothermal (RH) and static hydrothermal (SH) synthesis routes. It is found that different synthesis routes not only influence the crystallization but also determine the chemical and physical properties of zeolites. Compared with the catalyst prepared by flower-like precursor with larger size obtained by SH route in 12 days, Ti-HSZ catalyst with smaller size formed by RH route in 3.5 days shows higher catalytic activity for the epoxidation of bulky alkenes with H2O2. On one hand, the rapid and efficient transports of various reaction species in RH environment has accelerated the crystallization rate greatly; on the other hand, the one-step self-assembly of lamellar MWW crystals has happened to facilitate the formation of hollownest structure with hierarchical pores through intergrowth driven by centrifugal force. The different evolution processes of the Si chemical environments during the early stages of crystallization reflected by the percentage of intrinsic defects origin from the different hydrothermal environments. Highly mixed and dispersed reaction species under RH condition accelerate the uniform of gel concentration, and the condensation of smaller clusters with different orientation direction through frequent contacting under dynamic condition is easy to happen to form bigger clusters, which is the basis for the further crystal intergrowth. In contrast, the relatively inhomogeneous gel environments under SH condition has led to the increase of intrinsic defects in the solid phases, and bigger clusters tend to be formed by the condensation of smaller ones with the same orientation direction. This work will be instructive not only for the understanding of zeolites’ crystallization mechanism, but also for the design and synthesis of zeolite materials with unique morphology characteristics.

Overprinting porphyry‐type veinlets on the intrusive rocks and phreatomagmatic breccias in the Southwest prospect, southwestern Sto. Tomas II (Philex), Baguio District, Philippines

AbstractThe Southwest prospect is located at the southwestern periphery of the Sto. Tomas II porphyry copper–gold deposit in the Baguio District, northwestern Luzon, Philippines. The Southwest prospect hosts a copper‐gold mineralization related to a complex of porphyry intrusions, breccia facies, and overlapping porphyry‐type veinlets emplaced within the basement Pugo metavolcanics rocks and conglomerates of the Zigzag Formation. The occurrences of porphyry‐type veinlets and potassic alteration hosted in the complex are thought to be indications of the presence of blind porphyry deposits within the Sto. Tomas II vicinity. The complex is composed of at least four broadly mineralogically similar dioritic intrusive rocks that vary in texture and alteration type and intensity. These intrusions were accompanied with at least five breccia facies that were formed by the explosive brecciation, induced by the magmatic–hydrothermal processes and phreatomagmatic activities during the emplacement of the various intrusions. Hydrothermal alteration assemblages consisting of potassic, chlorite–magnetite, propylitic and sericite–chlorite alteration, and contemporaneous veinlet types were developed on the host rocks. Elevated copper and gold grades correspond to (a) chalcopyrite–bornite assemblage in the potassic alteration in the syn‐mineralization early‐mineralization diorite (EMD) and contemporaneous veinlets and (b) chalcopyrite‐rich mineralization associated with the chalcopyrite–magnetite–chlorite–actinolite±sericite veinlets contemporaneous with the chlorite–magnetite alteration. Erratic remarkable concentrations of gold were also present in the late‐mineralization Late Diorite (LD). High XMg of calcic amphiboles (>0.60) in the intrusive rocks indicate that the magmas have been oxidizing since the early stages of crystallization, while a gap in the composition of Al between the rim and the cores of the calcic amphiboles in the EMD and LD indicate decompression at some point during the crystallization of these intrusive rocks. Fluid inclusion microthermometry suggests the trapping of immiscible fluids that formed the potassic alteration, associated ore mineralization, and sheeted quartz veinlets. The corresponding formation conditions of the shallower and deeper quartz veinlets were estimated at pressures of 50 and 30 MPa and temperatures of 554 and 436°C at depths of 1.9 and 1.1 km. Temperature data from the chlorite indicate that the chalcopyrite‐rich mineralization associated with the chlorite–magnetite alteration was formed at a much lower temperature (ca. 290°C) than the potassic alteration. Evidence from the vein offsetting matrix suggests multiple intrusions within the EMD, despite the K‐Ar ages of the potassic alteration in EMD and hornblende in the LD of about the same age at 3.5 ± 0.3 Ma. The K‐Ar age of the potassic alteration was likely to be thermally reset as a result of the overprinting hydrothermal alteration. The constrained K‐Ar ages also indicate earlier formed intrusive rocks in the Southwest prospect, possibly coeval to the earliest “dark diorite” intrusion in the Sto. Tomas II deposit. In addition, the range of δ34S of sulfide minerals from +1.8‰ to +5.1‰ in the Southwest prospect closely overlaps with the rest of the porphyry copper and epithermal deposits in the Sto. Tomas II deposit and its vicinity. This indicates that the sulfides may have formed from a homogeneous source of the porphyry copper deposits and epithermal deposits in the Sto. Tomas II orebody and its vicinity. The evidence presented in this work proves that the porphyry copper‐type veinlets and the adjacent potassic alteration in the Southwest prospect are formed earlier and at a shallower level in contrast with the other porphyry deposits in the Baguio District.

In situ TEM study of crystallization and chemical changes in an oxidized uncapped Ge2Sb2Te5 film

Ge2Sb2Te5 (GST-225) has been the most used active material in nonvolatile phase-change memory devices. Understanding the kinetics and dynamics involved in crystallization is critical for the optimization of materials and devices. A GST-225 thin film of 20 nm thickness was prepared by sputtering directly onto a Protochip and left uncapped and exposed to atmosphere for approximately 1 year. Early stages of crystallization and growth of the film have been studied inside the TEM from room temperature to 140 °C. The morphological and structural transformations have been studied by a Cs-corrected environmental TEM, and images have been recorded using a high-speed low electron dose camera (Gatan K3 IS). The amorphous to crystalline transformation has been observed at ∼35 °C. From the large field, high-resolution images obtained using the Gatan K3 IS camera early crystallization can be detected and nucleation rates and growth velocities can be obtained.

Pathway of orientational symmetry breaking in crystallization of short n-alkane droplets: A molecular dynamics study.

We carry out molecular dynamics simulations by using an all-atom model to study the nucleation and crystallization of n-alkane droplets under three-dimensional and quasi-two-dimensional conditions. We focus on the development of orientational order of chains from a random state to a neatly ordered one. Two new methods, the map of symmetry breaking and the information entropy of chain orientations, are introduced to characterize the emerge and remelting phenomena of a primary nucleus at the early stage of crystallization. Stepwise nucleation, as well as the surface induced nucleation, of large droplets is observed. We elucidate the kinetic process of the formation of a primary nucleus and the rearrangement of every single molecule involved in a primary nucleus. We found that density fluctuation and orientational preordering are coupled together and occur simultaneously in nucleation. Our results show the pathway of orientational symmetry breaking in the crystallization of n-alkane droplets that are heuristic for the deeper understanding of the crystallization in more complex molecules such as polymers.

Crystal growth by ordered coalescence of lattice arrays in ZrO2-based nanocomposites at the early stage of crystallization

Amorphous ZrO2-based nanocomposite powder synthesized by sol-gel method is often used as the raw material for preparing advanced ZrO2-based ceramics. The crystal growth process of the amorphous ZrO2-based nanocomposite powder during heat treatment has a crucial influence on the final microstructure and thus the achieved performance of ZrO2-based ceramics. However, the crystal growth process of ZrO2 nanocrystals (NCs), especially at the early stage, was ambiguous due to the lack of detailed investigation. To illustrate this issue, ZrO2-based nanocomposite powder was prepared by sol-gel method, followed by annealing at elevated temperatures. Transmission electron microscopy (TEM) was used to observe the growth process of ZrO2 NCs. Results showed that tiny ZrO2 lattice arrays without definite morphology were formed after the completion of nucleation. Nucleation might follow the classic nucleation mechanism of epitaxial growth by utilizing atoms as building blocks. Then, the randomly-oriented ZrO2 lattice arrays adopt an ordered coalescence mechanism to grow to large ZrO2 NCs. ZrO2 lattice arrays acted as building blocks and they grew rapidly by unifying their crystallography orientations. Self-perfecting, including elimination of dislocations and adjustment of lattice spacing, occurred during the growth process. Ordered coalescence of ZrO2 lattice arrays contributed to the rapid growth of ZrO2 NCs. This study deepens our fundamental understanding of the growth mechanism of amorphous ZrO2-based nanocomposite powder during heat treatment and may offer guidelines for tailoring the final microstructure and performance of ZrO2-based ceramics.

Multifunctional Self-Combustion Additives Strategy to Fabricate Highly Responsive Hybrid Perovskite Photodetectors.

To resolve the inherent trade-off issue between responsivity and detectivity in FA0.9Cs0.1PbI3 perovskite photodetectors, this paper proposes a novel strategy using multifunctional self-combustion additives (urea and ammonium nitrate). During the early stages of crystallization, urea allows for the formation of a strong Lewis complex-derived low-dimensional intermediate phase; this suppresses the formation of perovskite nuclei, while ammonium ions assist the preferred grain growth along the [110] direction. During the high-temperature annealing steps, a self-combusting exothermic reaction occurs between urea as a fuel and NH4NO3 as an oxidizer, through which a locally supplied heat facilitates the removal of residual urea and byproducts. These multifunctional roles of self-combustible additives facilitate the production of high-quality, enlarged grain-structured perovskite films with improved optoelectronic properties, as confirmed by various analyses, including impedance spectroscopy and intensity-modulated photocurrent spectroscopy. The resulting FA0.9Cs0.1PbI3-based photodiode-type photodetectors exhibit outstanding performance, such as a high responsivity (0.762 A W-1) and specific detectivity (over 5.08 × 1013 Jones) at a very low external reverse bias (-0.5 V). Our findings clearly suggest that the multifunctional self-combustion additives strategy could help realize the full potential of FA1-xCsxPbI3 as a photodiode-type photodetector.

Petrogeochemical features of the Neogene collision volcanism of the Lesser Caucasus (Azerbaijan)

The article is devoted to the petrogeochemical features of Neogene collision volcanism in the central part of the Lesser Caucasus within Azerbaijan. The main goal of the study is to determine the thermodynamic conditions for the formation of Neogene volcanism in the central part of the Lesser Caucasus using the available petrogeochemical material. Using factor analysis, as well as the “IGPET”, “MINPET”, “Petrolog-3” programs, material balance calculations were performed that simulate the phenocryst fractionation process, the crystallization temperature, pressure, and figurative nature of the rock-forming minerals of the formation rocks were calculated. It was determined that at the early and middle stages of crystallization of the rocks of the andesite-dacite-rhyolite formation, the fractionation of amphibole played an important role in the formation of subsequent differentiates. Based on computer simulation, it was revealed that rocks of the andesite-dacite-rhyolite formation were formed by fractional crystallization of the initial high-alumina basaltic magma of high alkalinity in the intermediate magma foci. The calculations of the balance of the substance, simulating the process of fractionation of phenocrysts, as well as magnetite, confirmed the possibility of obtaining rock compositions from andesites to rhyolites as a result of this process. In this case, the process of crystallization differentiation was accompanied by processes of contamination, hybridism and mixing. Based on the geochemical features of rare and rare-earth elements, changes in their ratios, the nature of the mantle source and the type of fractionation process are determined. It was revealed that the enrichment of formation rocks by light rare earths, as well as by many incoherent elements, is associated with the evolution of enriched mantle material. Under high water pressure, as a result of the fractionation of olivine and pyroxene, high-alumina basalts are formed from primary high-magnesian magma, which can be considered parental magma. It was established that, in contrast to the elevated Transcaucasian zone in the more lowered East Caucasus, under conditions of increased fluid pressure and reduced temperature, the melt underwent fractional crystallization in the intermediate centers, being enriched with alkaline, large-ion lithophilic elements, light REEs, etc. This is evidenced by the presence of large crystals of feldspars, the contamination of these minerals by numerous crystals of biotite, magnetite, several generations of these minerals, zonality, as well as the presence of related “water” inclusions, such as hornblendites, hornblende gabbro, etc. The physicochemical conditions for the formation of Neogene volcanic rocks of the Lesser Caucasus are determined.

Petrogenesis of Eocene to early Oligocene granitic rocks in Phan Si Pan uplift area, northwestern Vietnam: Geochemical implications for the Cenozoic crustal evolution of the South China Block

The Phan Si Pan uplift area of NW Vietnam is a part of the Archean to Paleoproterozoic Yangtze Block (SW China) that was displaced along the Ailaoshan-Red River Fault shear zone and adjacent structures (i.e., Song Da zone). The region is of interest as it is at the forefront of the debate regarding the extrusion of SE Asia during the Early Paleogene. Two Cenozoic silicic plutonic complexes of contrasting composition intruded the basement rocks of the Phan Si Pan uplift area. The Ban Xeo granite is ferroan (A-type), alkalic and yielded a zircon weighted-mean 206Pb/238U age of 49 ± 0.9 Ma. The major and trace element compositions of the Ban Xeo granite are similar to the spatially associated Late Permian Muong Hum granites. The εNd(t) values (−2.5 to −1.4), 87Sr/86Sr initial ratios (0.70793, 0.70989, and 0.75341), and zircon εHf(t) values (−1.1 to +3.0) indicate that the Ban Xeo granite is likely derived by differentiation of a mafic parental magma that had EMII-like mantle source characteristics. The younger Ye Yen Sun (YYS) granite is magnesian, alkali-calcic to calc-alkalic, and yielded zircon U–Pb weighted-mean ages of 35.3 ± 0.5 to 34.1 ± 0.4 Ma. The YYS granites have 87Sr/86Sr initial ratios of 0.70636 to 0.70860, εNd(t) values from −8.7 to −2.6, and zircons εHf(t) values from −9.3 to +0.6 which indicate a crustal origin. The YYS dioritic rocks range from syeno-diorite to granodiorite, and have similar Sr (87Sr/86Sr = 0.70627) and εNd(t) (−3.8) values as the YYS granites. However, the zircon Hf isotopes (εHf(t) = +0.3 to +3.2) of the syeno-diorite are slightly more chondritic than the granites and indicates that the parental magma was likely derived from a mantle source. Rhyolite–MELTS modeling results show that the YYS granites were likely generated by fractionation of a parental magma similar in composition to the granodiorite. Furthermore, the YYS syeno-diorites may be representative of a cumulate rock that developed during the early stages of emplacement or crystallization. The parental magma of YYS igneous rocks likely formed by partial melting of mafic Mesoproterozoic juvenile rocks (lower crust/uppermost mantle) by heat from the upwelling lithospheric mantle during a period of crustal relaxation. The formation of the Ban Xeo granites and Ye Yen Sun igneous rocks are likely related to lateral melt migration along the eastern edge of the India-Asia collision zone. It is possible that repeated episodes of Cenozoic magmatism was pivotal in the development and initiation of fault movement of the Ailaoshan-Red River shear zone.

Tough, strong, hard, and chemically durable enstatite‐zirconia glass‐ceramic

AbstractStrong glass‐ceramics (GCs) have been envisaged and widely researched for various applications, including large architectural panels, ballistic impact protection, bioactive medical implants, and odontological prostheses. Here, we report on the development and characterization of a novel hard, strong and tough enstatite‐zirconia (MgSiO3‐ZrO2) glass‐ceramic derived from a 51SiO2–35MgO–6Na2O–4ZrO2–4TiO2 (mol%) glass. The best GC was developed by treating glass samples for nucleation at 700°C for 12 hours, followed by crystal growth at 1090°C for 3 minutes. It was characterized by X‐ray fluorescence (XRF), differential scanning calorimetry (DSC), X‐ray diffraction (XRD), scanning electron microscopy (SEM), and high‐resolution transmission electron microscopy (HR‐TEM), and contained plate‐like enstatite, zirconia, and Ti‐containing crystals. We investigated the nucleating ability of ZrO2 and TiO2 in inducing internal nucleation. In the early stage of crystallization, enstatite spherulites were observed, which were precipitated by heterogeneous nucleation on previously nucleated ZrO2 nano‐crystals. At more advanced stages, at high temperatures, they transformed into plate‐like crystals. The ball‐on‐three‐balls strength, elastic modulus, and Vickers micro‐hardness of the GC are 323 ± 26 MPa, 146 ± 13 GPa, and 6.9 ± 0.1 GPa (load = 5N), respectively. The indentation (KC), single‐edge notched beam bending (KIC), and crack tip (Ktip) fracture toughness are 2.8 ± 0.6 MP.m0.5, 2.2 ± 0.3 MP.m0.5, 1.9 ± 0.3 MP.m0.5, respectively. The crack propagation profile after a controlled Vickers indentation was quite intricate. The enstatite and zirconia crystals enhanced crack deflection, bridging and branching, hindering crack propagation. According to the ISO 6872 for dental materials, the chemical solubility of our GC is 80 ± 5 μg/cm2. Due to this positive combination of high strength, toughness, hardness, and chemical durability, this new glass‐ceramic is envisioned as a candidate for several applications and could be further developed for memory disc substrates, architectural cladding and tiles, ceramic glazes, and dental materials.

Liquid-mediated crystallization of amorphous GeSn under electron beam irradiation

Crystallization processes of amorphous germanium–tin (GeSn) under low-energy electron-beam irradiation were examined using transmission electron microscopy (TEM). Freestanding amorphous GeSn thin films were irradiated with a 100 keV electron beam at room temperature. The amorphous GeSn was athermally crystallized by electron-beam irradiation, when the electron flux exceeded the critical value. Heterogeneous structures consisting of nano- and micro-crystallites were formed after crystallization of amorphous GeSn with ∼24 at. % Sn in the as-sputtered amorphous state. In situ TEM observations of structural changes under electron-beam irradiation revealed that random nucleation and growth of nanocrystallites occur at the early stage of crystallization, followed by rapid formation of micro-grains surrounding the nanocrystals. It has been suggested that the growth of micro-grains progresses via supercooled liquid Sn at the amorphous/crystalline interface. The resultant GeSn grains with a size of a few micrometers contained ∼15 at. % Sn, much larger than the solubility limit of Sn in Ge (∼1 at. % Sn).

A new crystallization pattern of nested tetrahedral lamellar structure for the face-centered cubic metals with low stacking fault energy

It's well known that the lamellar (LAM) and five-fold-twinning (FFT) structures are two primary patterns during the early crystallization stage of FCC (face-centered cubic) metals. In this letter, we add a new third one, i.e. a nested tetrahedral lamellar (NTL) structure. In common with LAM and FFT, NTL is also a mixture of FCC and HCP (hexagonal close-packed). Differently, NTL has four tetrahedral growth orientations corresponding to four cellular bulges and a central core of tetrahedral shells nested one-by-one. This NTL acts also as the precursor of FFT and it has great differences in growth morphology and kinetics with LAM.