Dendritic Aggregates Research Articles

Nanoscale precision welding-enabled quasi-3D conductive carbon blacks for fast-charging and long-lasting secondary batteries

Robust three-dimensional (3D) conductive networks are vital for enhancing the utilization, rate capability, and lifespan of battery electrode materials, which largely relies on the selection and synergy of various conductive additives. As the spatial dimension expands from granular to tubular or lamellar, the conductivity of conductive additives continues to increase, but the cost and dispersion difficulty will sharply rise. This determines that zero-dimensional carbon black (CB) spherical nanoparticles remain the dominant component of current composite conductive additives. Herein, we disclosed a transient high-temperature welding technique that can precisely regulate the “rearrangement-fusion” behavior of carbon atoms at specific temperatures, accurately splicing the CB nanospheres into quasi-3D dendritic aggregates with appropriate spatial extension. This not only enhances the powder conductivity of CBs by 205.1 %, but also improves the processability through reducing the specific surface area. The quasi-3D CBs upgrade their contact mode with active materials from point-to-point to line-to-point, while significantly enhancing the inter-particle connection of active materials. More encouragingly, the modified CBs greatly boost the reaction kinetics, rate and cycling performance of LiFePO4 cathode and SiO@C anode, and derives fast-charging and long-lasting SiO@C//LiFePO4 full battery. Our work provides innovative solutions for upgrading the spatial conductive network within future secondary batteries.

Unraveling the nanostructures and self-assembly behavior of perfluorosulfonic acid in water/ethanol solvent: Effect of EW and side-chain chemistry

The perfluorosulfonic acid (PFSA) ionomers are key materials for proton exchange membranes (PEMs) and catalyst layers (CLs). Their morphology is profoundly influenced by the chain assembly behavior of PFSA in dispersions. Hence, we combine the characterization techniques of dynamic light scattering (DLS), small-angle X-ray scattering (SAXS), and cryo-transmission electron microscopy (Cryo-TEM) to study the nanostructures of PFSA dispersions, and provide a structure model for diverse PFSA ionomers in water/ethanol solvent. It is seen that PFSA ionomers self-assembly into a rod-like particle in dilute dispersion. As the concentration increases, the primary rod aggregates gradually assemble into a swollen- or Gaussian-network structure. Beyond this feature, we see that different PFSA ionomers show different nanostructures in dispersion. For the long-side-chain (LSC) PFSA ionomers, the 800-LSC PFSA tends to form monodisperse rod-like aggregates that is in a highly ordered arrangement with a rod diameter of 3.16 nm and a length of 28.72 nm. As the equivalent weight (EW) increases to 960, the poor solubility of the main chains in water/ethanol solvents leads to the “end-to-end” assemblies of the primary rod particles and dendritic secondary aggregates. The short-side-chain (SSC) PFSA ionomer that shares the same backbone with 960-LSC PFSA exhibit remarkable mono-dispersity and ordered arrangement of rod-like aggregates in water/ethanol solvents due to the strong electrostatic repulsion.

ANALYSIS OF EXISTING METHODS FOR IMPROVING THE PHYSICAL AND CHEMICAL CONDITIONS OF THE ION EXCHANGE PROCESS IN WATER TREATMENT

The article deals with the issues of existing processes for improving the physical and chemical conditions of the ion exchange process in water treatment. Patents and publications on the use of the ion exchange method in water treatment have been analysed. The expediency and scientific significance are determined by the possibility of further improving the efficiency of the ion exchange process in water treatment on the basis of the obtained results. Existing methods, such as thermal and cryogenic treatment, membrane plants, distillation and reverse osmosis, have a number of disadvantages, such as high energy consumption of the process and the inability to be used on an industrial scale. A promising method to improve the efficiency of modified ion exchange resins is to use the effect of a magnetic field on the feed water with constant stirring. The article analyses ion exchange resins and their problems, existing research aimed at modernising the ion exchange process, considers ways to optimise the selectivity of ion exchange resins, their modification with dendritic aggregates, and the use of mixed cationic and anionic ion exchange resins. Regeneration of ion-exchange resins using ammonium bicarbonate technology, reagent-free regeneration methods, such as electrodialysis, electrodionization systems, in order to reduce process waste, possible schemes of using ion-exchange plants in combination with other methods of water treatment. The analysis shows the relevance of using the ion exchange process in water treatment and the prospect of further research on ways to intensify the process to reduce energy and economic resources. The obtained results demonstrate the most advanced ways to improve the method of ion exchange for water treatment, such as reagentless regeneration of ionites using electrodialysis, modification of resins by introducing the necessary functional groups.

Cellular Interactions within Clonal Dendritic Cell Aggregates Drive Immune Tolerance in Chronic Myelomonocytic Leukemia Bone Marrow Microenvironment

Introduction: Clonal dendritic cell (DC) aggregates in chronic myelomonocytic leukemia (CMML) are seen in approximately 20-30% patients at diagnosis. Previously, these were thought to be comprised of CD123+ plasmacytoid DCs but our data has suggested that these are heterogenous and comprise of myeloid DCs, monocytes, and myeloid-derived suppressor cells. Furthermore, these aggregates uniformly express immune checkpoints such as indoleamine 2,3-dioxygenase-1 (IDO), associate with an IDO-specific systemic impact (increased trytophan catabolism), and expanded regulatory T cell population in CMML, suggesting a role in inducing immune tolerance. DC aggregates are also associated with increased risk of acute myeloid leukemia (AML) transformation and resistance to hypomethylating agents, highlighting that they are important for disease progression in CMML (Mangaonkar A et al. Blood Adv 2020). We performed this study to decipher the architecture of a CMML DC aggregate to understand the complex inter-cellular interactions, and assess their impact on the adaptive immune system. Methods: In this study, we used archival fresh-frozen paraffin-embedded (FFPE) bone marrow biopsy specimens obtained from CMML patients, and isolated monocytes (CD14+ magnetic bead sorting) and lymphocytes (CD14-ve fraction) from untreated CMML and age-matched normal control (NC) peripheral blood mononuclear cells (PBMCs). DCs were cultured from monocytes using a commercial protocol. Spatial architecture of the CMML BM microenvironment was interrogated through multiplex imaging of FFPE samples by co-detection by indexing (CODEX) using 30 markers (CCR6, CD107a, CD11c, CD20, CD21, CD31, CD3e, CD4, CD44, CD45, CD45RO CD56, CD68, CD8, E-Cadherin, FoxP3, HLA-DR, CD14, CD16, CD11b, CD33, CD15, CD66b, CD123, CD303, CD34, CD163 and IDO). Single-cell transcriptomic signatures were analyzed using the 10X single cell Fixed RNA profiling platform, and validated using bulk RNA seq (Illumina stranded mRNA prep) from isolated and cultured cells. Impact of DCs on lymphocytes was assessed via autologous mixed DC-T culture experiments. Results: BM FFPE samples from 5 CMML cases (3 with DC aggregates) were included for multiplex imaging via CODEX. Results confirm the significant interactions of CD8+ and CD4+ T cells with CD123+/HLA-DR+ DCs within a CMML DC aggregate (Fig. 1A). Upon quantitative assessment of cell-cell interactions, IDO+/CD8+T ( P=0.006), IDO+/MDSC ( P=0.005), and IDO+/macrophage ( P=0.001) interactions were significantly increased in CMML samples with versus without DC aggregates . Specific findings were validated using single-stain immunohistochemistry and multiplex immunoflourescence staining. Next, in order to assess transcriptomic signatures within BM at the single-cell level, we chose two cases; CMML (BM aspirate blast% 1, WBC 49.6 x 10 9/L, ASXL1/GATA2/SETBP1/SRSF2 mutations) and AML transformed from CMML (BM aspirate blast% 81, WBC 152 x 10 9/L, NPM1/DNMT3A/TET2 mutations). Approximately, 10,000 cells were obtained and analyzed with cell type annotation through human PBMC reference (Azimuth). Results show an expanded regulatory T cell population in AML compared to CMML (UMAP plot, Fig. 1B), suggestive of immune tolerance. In order to validate findings and perform functional experiments, we used sorted monocytes and cutured DCs from CMML and NC. DC phenotype was confirmed both through visual inspection and flow cytometry, and clonality was confirmed through Sanger sequencing (for previously identified mutations). Differential gene expression analysis through bulk RNAseq showed significant differences between CMML and NC lymphocytes with immunoinhibitory receptor, LILRB2 (log2fold change=7.05, adjusted P=0.0002) being one of the top five significantly upregulated genes, further confirming immune tolerance. Finally, mixed autologous DC-lymphocyte reaction (1:4 ratio) experiments demonstrated that DCs induce T cell tolerance in CMML (expansion of exhausted PD1/TIM3/LAG3+ CD8 T cells) when compared to NC. Conclusion: Clonal dendritic cell aggregates within the CMML bone marrow microenviroment interact with T cells and induce immune tolerance. This represents a novel mechanism of disease progression in CMML with potential therapeutic targets (IDO, LILRB2, and/or CD123).

Size, surface charge and flexibility of vinegar-baked Radix Bupleuri polysaccharide affecting the immune response

Remarkably, nanomaterials can interact with the cells of immune system and either enhance or inhibit its function in many ways. Unfortunately, such valuable information has been overlooked in studies of polysaccharide immune activity. This study isolated a nano-polysaccharide from vinegar-baked Radix Bupleuri by membrane separation system, DEAE-52 and Sephadex-G200. The physicochemical characterization and immunoregulatory activity were studied through DLS, Congo red, Scanning Electron Microscope, UV–Vis, HPGPC, FT-IR, Methylation, NMR, MTT, neutral red and enzyme linked immunosorbent assay. Results showed that VBCP2.5 was an acidic polysaccharide with a molecular weight of 674 kDa. Its monosaccharides composed of mannose, rhamnose, galacturonic acid, glucose, galactose and arabinose at a molar ratio of 1.72: 9.59: 57.63: 5.37: 6.71: 18.99. VBCP2.5 possessed micelle forming ability at 52.574 µg/mL and flexible chain conformation, as well as with a small size distribution ∼ 84.99 nm and positive charge in stimulated blood fluid and different from that in deionized water. The microtopography was characterized by irregular lamellar, dendritic, cylindrical or spherical aggregates, with folds and cracks on the surface. Structure analyses showed that VBCP2.5 characterized by high proportion of 1,4 linked-α-D-GalpA and a small fraction of RG-I, some other glycosidic linkages included 1,5 linked-α-L-Araf, 1,3,5 linked-α-L-Araf, 1,3,4 linked-Galp, 1,4,6 linked-Manp, t-α-L-Araf, t-β-D-Glcp and t-α-D-Galp were also comprised. VBCP2.5 exhibited immunomodulatory potential which included the promotion of phagocytosis, the release of NO and the secretion of TNF-α and IL-6 of RAW264.7 cells. The possible activation of macrophages by VBCP2.5 may be mediated through endocytosis pathway. Small size, positive charge, shape and flexible conformation may accelerate this process. The information gathered here could lead to new platform for comprehensive understand included primary structure, properties of nanoscale, and correlation with immunoregulation of polysaccharides.

Single Crystals Self‐Assembled to Sector‐Face Dendritic Aggregates by Synchrotron Microbeam X‐Ray Analysis on Poly(ethylene succinate)

Poly(ethylene succinate) (PESu), upon crystallization with a morphology-modulating diluent and at low degree of supercooling, forms peculiarly novel sector-face dendritic aggregates. Delicate dissection by various microscopic techniques is used to confirm the unique differences of these two faces in the PESu dendrites. Powerful synchrotron-source generated X-ray microbeam analysis is performed to prove without doubt the nature of the single crystals that self-assemble into these two sectors, respectively. Both microscopy results and 1D/2D wide-angle X-ray patterns collectively confirm that one sector-face of the PESu dendrites is composed all fully flat-on with the single-crystal's basal face contacting the substrate and branching growth with mutual perpendicular ≈90° angle intersections; the second face is composed fully edge-on with the prism face contacting the substrate and growth with mutual oblique 5–30° angle intersections. The growth intersection angles are also proved by the azimuthal angles in 1D and 2D X-ray patterns.

Morpho-structural characterization and electrophoretic deposition of xonotlite obtained by a hydrothermal method

In this research, xonotlite was synthesized by a hydrothermal method in the Si-Ca-Na-H2O system. Detailed structural characterization by using XRD technique revealed that obtained material contains a small quantity of wollastonite (up to 3 %) as impurity. Calcination of the obtained sample at 900 ˚C has resulted in complete transformation of xonotlite to wollastonite which was detected as only crystal phase. Crystallite size and lattice strain of all crystal phases were calculated using Scherrer and Williamson-Hall method. SEM observation of xonotlite morphology revealed tiny needle-like crystals joined together forming dendritic or globular aggregates. Optimal conditions for electrophoretic deposition of xonotlite on 304 type stainless steel have been achieved by appropriate selection of electric field strengths, dispersing medium and dispersants. Stable suspension of material was obtained using isopropanol containing 1 % water as dispersing medium and Ca-nitrate as charging additive. Native layers of xonotlite have a very smooth morphology, while after calcination, the appearance of small cracks in the coating can be observed but the adhesion strength of the coatings to the substrate is improved.

Towards a morphology diagram for terrestrial carbonates: Evaluating the impact of carbonate supersaturation and alginic acid in calcite precipitate morphology

Ancient and recent terrestrial carbonate-precipitating systems are characterised by a heterogeneous array of deposits volumetrically dominated by calcite. In these environments, calcite precipitates display an extraordinary morphological diversity, from single crystal rhombohedral prisms, to blocky crystalline encrustations, or spherulitic to dendritic aggregates. Despite many decades of thorough descriptive and interpretative work on these fabrics, relating calcite micro-morphology with sedimentary hydrogeochemical conditions remains a challenge. Environmental interpretations have been hampered by the fact that calcite morphogenesis results from the complex interaction between different physico-chemical parameters which often act simultaneously (e.g., carbonate mineral supersaturation, Mg/Ca ratio of the parental fluid, organic and inorganic additives). To try to experimentally address the sedimentological causes of calcite morphogenesis, an experimental approach yielding a first attempt at a calcite growth-form phase diagram is presented here. The initial aim was to account for the carbonate products experimentally nucleated in alkaline, saline lake settings. These are the result of at least two competing calcite precipitation ‘driving forces’ that affect morphogenesis: the calcite supersaturation level of the parental fluid, and the concentration of microbial-derived organic molecules (alginic acid). A key finding of this study is that common naturally-occurring calcite products such as calcite floating rafts, rhombohedral prismatic forms, di-pyramid calcite crystals, spherulitic calcite grains, or vertically stacked spheroidal calcite aggregates, can be related to specific hydrogeochemical contexts, and their physical transitions pinpointed in a phase diagram. By exploring binary or ternary responses to forcing in morphological phase-space, links between calcite growth forms and (palaeo)environmental conditions can be determined. This provides a truly process-oriented means of navigating questions around carbonate precipitate morphogenesis for the future.

Мінералогічні особливості відновлених окатишів Північного гірничозбагачувального комбінату (Криворізький басейн)

The advantages of reduced iron ore pellets over oxidized ones have been considered. The chemical and physical parameters of the primary material have been given: iron ore (magnetite) concentrate (iron content is 67.30 mass %; particle size distribution is 97.0 % of 0.056 mm fraction), bentonite (montmorilonit content is 70.43 mass %; particle size distribution is 94.5% of 0.056 mm fraction), ground coke. The course of experiments has been described. The zonal structure of the obtained pellets has been characterized: the central zone is composed of hematite with relics of magnetite; intermediate one contains magnetite particles with inclusions of hematite; peripheral zone includes subidiomorphic crystals of magnetite and their dendritic aggregates. The bentonite component in the central and intermediate zones retained a crypto-crystalline structure, in the peripheral one it had been transformed into a crystalline aggregate of garnet and pyroxene. Emphasis is placed on the need to verify the impact of various indicators of temperature, firing time, quantitative ratios of charge components, mineral and chemical composition of the cementing material on mineralogical transformations.

In situ visualizing the interplay between the separator and potassium dendrite growth by synchrotron X-ray tomography

Abstract Rechargeable potassium (K) batteries are a promising next-generation technology for low-cost grid scale energy storage applications. Nevertheless, the undesirable interfacial instabilities originating from the interplay between the employed separators and electrodes largely compromise the battery’s performance, and the underlying mechanism of which remains elusive. Herein, the interfacial stability between three types of commercial separators (Celgard 2325, Celgard 2400 and GF/D) and the K electrodeposits is investigated in K|K symmetric cells via in-situ Synchrotron X-ray tomography technique. It is demonstrated that the cell built with a Celgard 2400 separator can achieve a stable cycling performance due to its high mechanical strength and integrity along the thickness direction, thus alleviating the K dendrites growth. In contrast, a GF/D membrane of low mechanical cohesion and excessive porosity is found to be easily deformed and filled with deciduous potassium dendritic aggregates during battery cycling. Similarly, the tri-layer Celgard 2325 separators, which are weakly bonded by interlaminar forces, are found to be severely delaminated by the overgrowth of K dendrites. Furthermore, it is revealed that the delamination failure behaviors of Celgard 2325 is driven by the local stress induced by the spatially and heterogeneously formed dead K dendrites. Our work provides direct visualization of morphological evolvement of the separators in presence of potassium dendrites in K|K symmetric cells and highlights the significance of mechanical cohesion, porosity distribution and mechanical integrity of separators in dictating the battery’s performance under realistic battery operation conditions. As a result, these discoveries provide an in-depth understanding that is needed to design next-generation high performance separators to mitigate the formation of potassium dendrite in KMBs.

Fracto-eutectogels: SDS fractal dendrites via counterion condensation in a deep eutectic solvent.

Glyceline, a deep eutectic solvent comprising glycerol and choline chloride, is a green nonaqueous solvent with potential industrial applications. Molecular mechanisms of surfactant self-assembly in deep eutectic solvents are expected to differ from those in their constituent polar components and are not well understood. Here we report the observation of self-assembled SDS fractal dendrites with dimensions up to ∼mm in glyceline at SDS concentrations as low as cSDS ∼ 0.1 wt%. The prevalence of these dendritic fractal aggregates led to the formation of a gel phase at SDS concentrations above ≥1.9 wt% (the critical gelation concentration cCGC). The gel microscopic structure was visualised using polarised light microscopy (PLM); rheology measurements confirmed the formation of a colloidal gel, where the first normal stress difference was negative and the elastic modulus was dominant. Detailed nano-structural characterisation by small-angle neutron scattering (SANS) further confirmed the presence of fractal aggregates. Such SDS aggregation or gelation has not been observed in water at such low surfactant concentrations, whereas SDS has been reported to form lamellar aggregates in glycerol (a component of glyceline). We attribute the formation of the SDS fractal dendrites to the condensation of counterions (i.e. the choline ions) around the SDS aggregates - a diffusion-controlled process, leading to the aggregate morphology observed. These unprecedented results shed light on the molecular mechanisms of surfactant self-assembly in deep eutectic solvents, important to their application in industrial formulation.

Bone marrow dendritic cell aggregates associate with systemic immune dysregulation in chronic myelomonocytic leukemia

Key Points Systemic immune microenvironment signatures in CMML indicate an altered T- and natural killer cell balance. CMML bone marrow dendritic cell aggregates associate with disease progression and systemic regulatory T-cell phenotypic switch.

Synchrotron XAS study of Mn and Fe in Chinese blue-and-white Ming porcelains from the second half of the 15th century

The XAS analysis of a blue-and-white Ming porcelain's decorations has been used to elucidate the porcelain's production technology. The porcelain exhibits the typical blue decorations with dark spots that are constituted by dendritic aggregates enriched in Mn and Fe. The XAS revealed that during firing Mn2+ and Fe2+ ions diffused into the glaze and started to crystallize at 900 °C as rhodonite and hausmannite-jacobsite intermediate compounds. The study of the Fe XAS pre-edges provided to be a powerful tool to assess the redox record from the porcelain. The natural basalt calibration determined the Fe3+/ƩFe × 100 in the glaze and confirmed the oxidizing conditions during its production. Hence, the obtained XAS helped to elucidate the temperatures at which the wares were produced by identifying the porcelain's pigments and the redox conditions during their production. This novel approach can also be applied on a broad range of modern and archaeological ceramics to elucidate their production technology.

Alternative Splicing and the Intracellular Domain Mediate TM-agrin’s Ability to Differentially Regulate the Density of Excitatory and Inhibitory Synapse-like Specializations in Developing CNS Neurons

Agrin is a multi-domain protein best known for its essential function during formation of the neuromuscular junction. Alternative mRNA splicing at sites named y and z in the C-terminal part of agrin regulates its interaction with a receptor complex consisting of the agrin-binding low-density lipoprotein receptor-related protein 4 (Lrp4) and the muscle-specific kinase (MuSK). Isoforms with inserts at both splice sites bind to Lrp4, activate MuSK and are synaptogenic at the neuromuscular junction. Agrin is also expressed as a transmembrane protein in the central nervous system (CNS) but its function during interneuronal synapse formation is unclear. Recently we demonstrated that transfection of a full-length cDNA coding for transmembrane agrin (TM-agrin) in cultured embryonic cortical neurons induced an Lrp4-dependent but MuSK-independent increase in dendritic glutamatergic synapses and an Lrp4- and MuSK-independent reduction of inhibitory synapses. Here we show that presynaptic specializations were similarly affected by TM-agrin overexpression. In addition, we mapped the regions within TM-agrin responsible for TM-agrin’s effects on dendritic aggregates of synapse-associated proteins. We show that the presence of a four amino acid insert at splice site y is essential for the increase in the density of puncta containing the postsynaptic density protein 95 kDa. This effect was independent of splice site z. The reduction of the gephyrin puncta density was independent of the entire extracellular part of TM-agrin but required a highly conserved serine residue in the intracellular domain of TM-agrin. These results provide further evidence for a function of TM-agrin during CNS synaptogenesis and demonstrate that different domains and alternative splicing of TM-agrin differentially affect excitatory and inhibitory synapse formation in cultured embryonic CNS neurons.

Dissolution Behavior of Isolated and Aggregated Hematite Particles Revealed by in Situ Liquid Cell Transmission Electron Microscopy.

Dissolution behavior of isolated and aggregated hematite particles in 10, 36, and 103 nm, respectively, was investigated using in situ liquid cell transmission microscopy (LCTEM). The high spatial and temporal resolution of LCTEM enables us to differentiate the respective effects of primary particle size, crystal defects, and aggregation state on particle dissolution. At similar electron-beam irradiation parameters, the initial surface-area normalized dissolution rates ( RSA,Int) of isolated 10, 36, and 103 nm particles are 4.64 ± 3.60, 0.91 ± 0.44, and 0.24 ± 0.04 mg m-2 s-1, respectively. Interface free energy, calculated from the measured RSA,Int, decreases with the decreasing primary particle size. No preferential etching occurs on 10 nm, defect-free nanoparticles, whereas dissolution preferentially originates from crystal defects on 103 nm particles. In dissolution of aggregated particles, dissolution occurs more rapidly on the particles that are more accessible to bulk solution than the others inside the aggregate. As dissolution proceeds, dendritic aggregates break into several smaller aggregates that respectively shrink into even smaller and more compact aggregates, followed by reaggregation together. This study directly shows microscopic dissolution behavior of isolated and aggregated particles in different primary particle sizes, which is important to understand bioavailability, transport, and fate of nanoparticles in aquatic systems.

Chemical and boron isotopic composition of tourmaline from the Conadong leucogranite-pegmatite system in South Tibet

Tourmalines occur widely within leucogranites and pegmatites that intrude the leucogranites in the south Tibetan plateau. Morphological and geochemical (elemental and boron-isotopic) studies on these tourmalines are very limited. Furthermore, the tourmaline genetic correlation between the leucogranite and the pegmatite is also unknown. In this contribution, two types of tourmaline occurrences have been identified in the Conadong area, south Tibet, including randomly disseminated tourmaline in leucogranite (GT type) and radial, dendritic or massive tourmaline aggregates in pegmatite dikes that intrude the leucogranite (PT type). We performed major element and boron isotopic analyses of tourmaline using electron microprobe (EMPA) and laser ablation multi-collector inductively coupled plasma mass spectrometry, respectively. The two types of tourmalines are enriched in Fe, Na and Al but relatively depleted in Ca and Mg elements, with compositions close to alkali group tourmaline and schorl. All the tourmalines are likely the products of equilibrium crystallization and their dominance of Na was controlled by the magmatic compositions of their host rocks. The GT type tourmalines show a narrow range of δ11B values between −9.78 ± 0.81‰ and − 8.53 ± 0.68‰ (with a mean of −8.91 ± 0.18‰); whereas the PT type tourmalines have significantly lower δ11B values than the GT type, ranging from −14.02 ± 0.85‰ to −11.83 ± 0.57‰ (with a mean of −13.31 ± 0.49‰). These data together with their morphology and petrography indicate that the Conadong granitic tourmalines were derived by the melts at the early magmatic stage, whereas the pegmatitic tourmalines precipitated from magmatic–hydrothermal fluids at the late magmatic stage. The variation in boron isotopic compositions (Δ11B = 4.4‰) between the PT and the GT type tourmalines is most likely correlated with their different melt/fluid source regions that had distinct Sr-Nd-B isotopic compositions.

Multi-scale patterns formed by sodium sulphate in a drying droplet of gelatin: experiment and simulation in 2-dimensions

We present a study of patterns, formed in drying drops of aqueous gelatin solution containing sodium sulphate. The patterns are highly complex, consisting of a hierarchical sequence of rings which form concentric bands as well as dendritic crystalline aggregates. We try to explain the origin of the rings and the dendritic growth from them, from a simple physical approach using the advection diffusion equations. We implement a finite difference scheme in 2-dimensions to simulate the experimental results. The effect on pattern formation using different solutions are examined by variation of contact angle and diffusivity. Our model can explain the growth dynamics of a complex pattern that covers several length scales, from the nano scale of single crystals, to the micro scale of dendrites and finally rings that are of the scale of centimeters.

Understanding Uptake of Pt Precursors During Strong Electrostatic Adsorption on Single-Crystal Carbon Surfaces

The formation of Pt clusters deposited by strong electrostatic adsorption (SEA) has been studied on highly oriented pyrolytic graphite (HOPG) as well as on higher surface area graphene nanoplatelets (GNPs), which have well-defined surface structures. Both surfaces can be hydroxylated by treatment with hydrochloric acid, and in the case of HOPG, the surface functional groups are exclusively hydroxyls. When SEA is carried out with the anionic precursor PtCl6 2− under acidic conditions, the dominant cationic sites for electrostatic adsorption are protonated aromatic rings rather than protonated hydroxyl groups, and therefore the unfunctionalized surfaces exhibit high uptake compared to the HCl-treated surfaces. In contrast, for SEA with the cationic precursor Pt(NH3)4 2+ under basic conditions, surface hydroxylation leads to higher Pt uptake since deprotonated hydroxyl groups act as negatively charged adsorption sites for the cations. After reduction of the adsorbed ionic precursors by heating in H2, the metallic Pt clusters on HOPG produced from PtCl6 2− SEA form dendritic aggregates associated with high Pt diffusion rates and irreversible Pt–Pt bonding. For Pt(NH3)4 2+ SEA on HOPG, subsequent reduction resulted in clusters preferentially located at step edges on the untreated surface, whereas smaller clusters more uniformly distributed across the terraces were observed on the hydroxylated surface. Similar trends in particle sizes and densities were observed on the GNP surfaces, demonstrating that understanding of nucleation and growth on single-crystal HOPG surfaces can be extended to the high surface area GNPs. Oxidative adsorption to Pt4+ was observed for SEA of Pt2+ precursors on both HOPG and GNP surfaces.

Toward Subtle Manipulation of Fine Dendritic β-Nucleating Agent in Polypropylene.

Dendritic β-nucleating agent (β-NA) can readily manipulate the formation of dendritic β-crystal with a unique toughening effect on polypropylene (PP) to drastically enhance the ductility. However, by the current method, the geometric size is too large to fully perform the nucleating efficiency. In this study, by comparatively investigating the effect of molecular weight of PP and diffusion of β-NAs in a PP melt, we proposed a novel carrier strategy that selective enrichment of β-NAs in a PP carrier was followed by directed migration into polymer matrix. Accordingly, the growth of NAs was controlled by the release from the PP carrier, which decreased the available amount of β-NAs during the growth stage. In this case, the viscosity difference between PP carrier and matrix determined the interfacial movement of β-NAs. When the PP carrier and matrix had same molecular weight, the diffusion and release became favorable to facilitate the formation of the dense and fine dendritic aggregates. As a result, the relative content of β-crystals reached 92%, with a drastic increase of ∼82% in the optimal condition compared to the directed compounded PP/β-NAs sample. This study can open a new avenue to tailor the topologies of β-NAs and the ensuing β-crystals for high-performance PP products.

Uncovering Structural Organization of a Solid Electrolyte Interphase Using Thin Window Si Membrane Negative Electrodes

Silicon has emerged as one of the most promising anode materials for high-performance Li-ion batteries because of its exceptional theoretical specific capacity of 4200 mAh g-1, which is more than 10 times the theoretical capacity of graphite (372 mAh/g).1 However, there are critical challenges to using Si as a negative electrode caused by a high volume expansion of up to 400 % on full lithium insertion, pulverization of the material, and growth of a solid electrolyte interphase (SEI) 1. Physico-chemical stability of the SEI at the interface between Si and the liquid electrolyte has become a crucial factor in achieving a long cycle life. In this work, we focus on phase structural transformations during the SEI formation on electron transparent c-Si anodes, which allow correlation of electrochemical properties with the structure on the same electrode feature. We have chosen for this study p-doped thin window <100>-oriented single crystalline planar c-Si membranes as model electrodes suitable for monitoring lithiation processes and characterization by high-resolution analytical scanning/transmission electron microscopy (S/TEM).2 A LiClO4solution in a 1:1 mixture by volume of ethylene carbonate (EC) : diethyl carbonate (DEC) was employed as a nonaqeuous electrolyte due to its low viscosity and anodic stability. Electrochemical measurements were carried out in a three-electrode custom-designed PTFE cell. The working electrode was a 3 mm diameter c-Si membrane that had nine 35 nm-thick windows. The Si membranes were connected to the current collector by a Cu lead. The counter and reference electrodes were made from a lithium metal foil. Cyclic voltammetry of the Si membranes in a 1M electrolyte was carried out from open circuit voltage (OCV) and between 0.01 V and 2.0 V vs. Li/Li+. The sweep rate was 0.1 mV sec-1. Lithiated membranes were held 17 h at 0.15 V. After electrochemical lithiation, the samples were transferred for studies in a TEM. A glove bag purged with an UHP Ar was used to prevent the samples from being exposed to an ambient environment during the transfer. Low-dose bright-field and dark-field TEM, STEM, high-resolution TEM, selected area electron diffraction (SAED), electron energy-loss and energy-dispersive X-ray spectroscopies were applied to characterize the morphology and compositions of the passivation films formed during lithiation/delithiation of the membrane anodes. Soaking of a control Si membrane into the electrolyte for 24 hours without electrochemical processing did not produced the SEI. The positions of the reduction peaks at 1.5 V, 1.3 V and 0.6 V in a cyclic voltammogram (Fig. 1) are in good agreement with the positions of the reduction peaks obtained for a 1 M LiClO4 / EC: dimethyl carbonate (DMC, 1:1 by vol.) with a Pt electrode 3 and can be attributed to decomposition of the electrolyte. It is considered that the SEI consists of an inner “inorganic” layer composed of Li2O, Li2CO3, LiOH, as well as LixSiOy formed from a native oxide and an outer preferentially “organic” layer comprising mostly alkyl carbonates 3-5. Si lithiation with the formation of a Li1.7Si phase occurs at 0.33 V 6 and an increase of the current intensity below 0.3 V can be attributed to lithiation of the Si matrix. The oxidation peaks at 0.7 V and 1.5 V can be attributed to delithiation of Si and SiOx, respectively 7. For the 2nd cycle, the reduction peak at 1.5 V is not as prominent as for the 1st cycle. However, reduction current is still detected suggesting that the SEI continues to grow during the 2nd cycle. TEM studies indicate that dynamically evolving SEI growth profoundly dominates over c-Si lithiation. Observed SEI features include various morphological shapes, such as dendritic sponge aggregates impregnated with a liquid electrolyte (Fig. 2a). By soaking a lithiated Si membrane in DMC, web-like multilayer structures grown on the c-Si surface with random agglomerates of LiClO4nanocrystallites (Fig. 2b) were found. An island-like growth of such loose nonuniform SEI films can cause a rise of the interfacial impedance and low Coulombic efficiency, thus essentially hampering the potential of Si anodes to be practically realized. [1] D. Ma, et al., Nano-Micro Lett. 6, (2014) 347 [2] V.P. Oleshko, et al., Microsc. Microanal. 22(Suppl.3), (2016) 1556 [3] R. Marom, et al., J. Electrochem. Soc., 157(2010) A972 [4] B. Philippe, et al., Chem. Mater. 23(2012) 1107 [5] M. Nie, et al, J. Phys. Chem. C, 117(2013) 13403 [6] J. Wen, R. A. Huggins, J. Solid State Chem., 37(1981) 271 [7] Q. Sun, et al., Appl. Surf. Science, 254 (2008) 3774 Figure 1