Growth of calcium aluminum germanate garnets in molten bismuth germanate glasses

Selected calcium (and calcium/lead) bismuth germanate melts can partially crystallize, even upon rapid cooling, to small (up to 0.35 mm, but longer in completely crystalline samples) hexagonal needles that appear to be CaBi₂Ge₂O₈. This tendency to crystallize upon cooling can be suppressed by adding small amounts of Al₂O₃. The addition of larger amounts of Al₂O₃ yields a considerable number of well formed garnets that range up to 0.15 mm in size. These crystals can be separated from the adhering glass by appropriate dissolution techniques. The density, refraction, and infrared spectrum of the garnets suggest the formula Ca₃Al₂Ge₃O₁₂. The amorphous garnet-like arrangement of the atoms in these melts appears to be an important factor in their formation.     

Growth of zinc aluminate & gallate spinels in molten bismuth germanate glasses

Small, well-formed octahedral crystals of cubic ZnAl₂O₄ (up to 0.025 mm) and ZnGa₂O₄ (up to 0.05 mm) spinels can be precipitated at 1250° C from molten ZnO/Bi₂O₃/2 GeO₂ mixtures that contain either Al₂O₃ or Ga₂O₃. After quenching, the crystals can be separated from the adhering glass by appropriate dissolution techniques. These crystals can also be doped with Cr⁺³ by adding small amounts of Cr₂O₃ to the original batches. The ZnAl₂O₄ octahedra may be highly ordered. Density, refraction, and infrared results confirm these findings.     

Anisotropic nanowire growth via a self-confined amorphous template process: A reconsideration on the role of amorphous calcium carbonate

Calcium carbonate crystals with various morphologies have been found in a variety of biospecimens and artificially synthesized structures. Usually, the diversity in morphology can be attributed to different types of interactions between the specific crystal faces and the environment or the templates used for the growth of CaCO₃ crystals. On the other hand, isotropic amorphous calcium carbonate (ACC) has been recognized as the precursor of other crystalline calcium carbonate forms for both in vivo and in vitro systems. However, here we propose a self-confined amorphous template process leading to the anisotropic growth of single-crystalline calcite nanowires. Initiated by the assembly of precipitated nanoparticles, the calcite nanowires grew via the continuous precipitation of partly crystallized ACC nanodroplets onto their tips. Then, the crystalline domains in the tip, which were generated from the partly crystallized nanodroplets, coalesced in the interior of the nanowire to form a single-crystalline core. The ACC domains were left outside and spontaneously formed a protective shell to retard the precipitation of CaCO₃ onto the side surface of the nanowire and thus guided the highly anisotropic growth of nanowires as a template.

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Cu materials—From crystal chemistry to magnetic model compounds

Based on electronic structure calculations within the density functional theory, we report a systematic approach for the modelling of low-dimensional Cu^II materials. Combining concepts of crystal chemistry with ab initio-based magnetic models, we present a systematic study of recently discovered compounds. Our calculation results are in good agreement with thermodynamic and magnetic measurements, suggesting the presented approach as a well-directed route to explore the magnetic phase diagram of low-dimensional Cu^II systems.     

Growth of BaAl2O4, SrAl12O19 & Mg2Ga4GeO10 crystals in molten bismuth germanate glasses

Small, well-formed BaAl₂O₄ blades (up to 0.5 mm), SrAl₁₂O₁₉ platelets (up to 0.01 mm), and Mg₂GeO₁₀ plates (up to 0.25 mm) can be precipitated at 1370, 1230, and 1300°C respectively from molten MO/Bi₂O₃/2 GeO₂ mixtures that contain either Al₂O₃ or Ga₂O₃. Similar experiments with PbO and CdO containing melts yielded only Al₂O₃ crystals. After quenching, all of these crystals can be separated from the adhering glass by appropriate dissolution techniques. Density, refraction, and infrared results confirm these findings.     

Ligands in Lead Halide Perovskite Nanocrystals: From Synthesis to Optoelectronic Applications

Ligands are indispensable for perovskite nanocrystals (NCs) throughout the whole lifetime, as they not only play key roles in the controllable synthesis of NCs with different sizes and shapes, but also act as capping shell that affects optical properties and electrical coupling of NCs. Establishing a systematic understanding of the relationship between ligands and perovskite NCs is significant to enable many potential applications of NCs. This review mainly focuses on the influence of ligands on perovskite NCs. First of all, the ligands-dominated size and shape control of NCs is discussed. Whereafter, the surface defects of NCs and the bonding between ligands and perovskite NCs are classified, and corresponding post-treatment of surface defects via ligands is also summarized. Furthermore, advances in engineering the ligands towards the high performance of optoelectronic devices based on perovskite NCs, including photodetector, solar cell, light emitting diode (LED), and laser, and finally to potential challenges are also discussed.     

From waste to raw material—the route from biomass to wood ash for cadmium and other heavy metals

Energetic utilization of biomass is considered an environmentally safe way of providing energy, especially for process heat and district- heating purposes. The main advantage of energy from biomass is the CO₂-neutrality of this energy-production process. However, this process produces a solid by-products, namely ash, that has to be considered. This ash contains nutrients like calcium, potassium and phosphorus that should be recycled to forest or agricultural soils, thus closing not only the carbon cycle but also the fluxes of mineral materials caused by these technologies. The problem is, however, that besides nutrients, the ash also contains heavy metals. Cadmium poses a special risk to the use of wood ash in agriculture. It pollutes a large fraction of the ash generated in a biomass combustion plant, namely the cyclone fly-ash and, to an even higher degree, the filter fly-ash or (where flue gas condensation is installed) the condensation sludge. A medium-term solution to the recycling of solid residues from biomass combustion is blending cyclone fly-ash and bottom ash and using the mixture in agriculture. Although a large part of nutrients might be recycled in this manner, care has to be taken of the relatively high amount of cadmium in this material. A new technology currently under development takes advantage of the different temperatures in a biomass combustion plant. This technology enables concentration of cadmium (and other volatile heavy metals) in a very small portion of the whole ash flux from a plant and the concentrations of environmentally relevant substances in the remainder of the ash is kept low. In this manner, wood ash from the process industry or district heating systems might be transformed from waste to raw material for agricultural use.     

从超振荡透镜到超临界透镜：超越衍射极限的光场调制

以超振荡透镜和超临界透镜为典型代表的平面超透镜是一种利用光场调控方式实现远场超衍射极限聚焦和成像的光学元件。通过精密调控各衍射结构单元之间的干涉效应,可以在焦平面上局部区域内获得高于系统最高空间频率的电场振荡,从而实现对衍射焦斑横向和轴向尺寸的可控调节。与传统的光学透镜相比,平面超透镜具有聚焦能力强,结构紧凑,设计自由度大,利于集成等优点。因其远场超衍射极限的光场调控能力,受到衍射光学和纳米光子学领域人员的广泛关注和研究。本文介绍了平面超衍射极限透镜光场调控的原理和设计方法。对超振荡透镜和超临界透镜的研究现状及其在远场光学超分辨成像领域的应用进行了分析和讨论,最后对该领域面临的问题及其拓展方向作了展望。

     

New unified laws in fatigue: From the Wöhler’s to the Paris’ regime

Generalizations and unification of the celebrated Paris’ and Wöhler’s laws for fatigue crack propagation are derived by applying the recently developed quantized (or finite) fracture mechanics. In particular, three generalized Paris’, Wöhler’s or unified laws are proposed and compared, demonstrating their applicability for predicting the life time of structures containing from small (the Wöhler’s regime) to large (the Paris’ regime) propagating fatigue cracks.     

From the organized nanoparticles of copper and vanadium containing LDHs to the small nanoparticles of mixtures of mixed oxides: A simple route

Well-dispersed nanoparticles of homogeneous mixtures of mixed oxides with an average size of 2.7 nm are obtained by using as precursors copper and vanadium containing layered double hydroxides (LDHs) possessing new self-organized morphology characteristics. The tailored organized pattern of the large nanoparticles of LDHs and the formation of the small nanoparticles of the mixed oxides are followed by the TEM analysis; the evolution from the clay structure to the mixtures of copper and vanadium mixed oxides is confirmed by the XRD analysis.     

Self-assembly: a minimalist route to the fabrication of nanomaterials

Self-assembly of molecular or nonmolecular components by non-covalent interactions offers an invaluable tool for the preparation of discrete nanostructures and extended 2D and 3D materials, which are often not accessible by any other fabrication process. In this article we summarize the most recent advances in the generation of nanomaterials such as self-assembled monolayers (SAMs) and structures formed from amphiphilic molecules, colloids, peptides, and polymers by nontemplated self-assembly either at the solid state or in solution. The current status of templated self-assembly and the use of self-assembled structures as template and for patterning other materials is also covered. A special emphasis is placed on strategies presenting either original and somehow exploratory approaches, eventually combining bottom-up and top-down methods, or that concern methods for the production of materials with potential application, e.g., in photonics, as sensors, for drug delivery and electric and magnetic devices. In all the sections, we outline self-organization and applications enabled with self-separated block copolymers.     

A novel route to photoluminescent, water-soluble Mn-doped ZnS quantum dots via photopolymerization initiated by the quantum dots

We design a photopolymerization, in which Mn-doped ZnS quantum dots (ZnS:Mn(2+)) initiate the polymerization of acrylic acid, to convert the non-cytotoxic quantum dots to water-soluble ones for biological chromophores The prepared quantum dots are nearly monodispersed in water and the resulting solution shows long-term stability for months. The water-soluble ZnS:Mn(2+) quantum dots exhibit high quantum efficiency of fluorescence. The polymerization of acrylic acid is ruled by a free-radical mechanism and results in a polymer with a random configuration. Raman scattering shows that, in the water-soluble quantum dots, the vibration modes of surface optical phonons, transverse optical phonons and longitudinal optical phonons are changed in frequencies. Results of model calculations correlate these changes to the polymerization occurring at the surface of QDs.     

From research to cost effective directional solidification and single crystal production—An integrated approach Part B - materials development

Central to the development of the DS and SC processes has been the need to develop the ceramics for the shell mould because of the significantly greater time and temperature exposure inherent in the process and the need to develop ceramic filtration technology for high temperature alloys to improve cleanliness. For Directional Solidifications (DS) it has not been necessary to develop new alloys; certain of the equiaxed superalloys may be directionally solidified successfully without modification. However to exploit the advantages of single crystal technology new alloys have had to be developed.     

Superhydrophilicity of anodic aluminum oxide films: From “honeycomb” to “bird's nest”

An electrochemical method has been used to prepare different kinds of surfaces including “honeycomb”-like and “bird's nest”-like surfaces on anodic aluminum oxide (AAO) films. The relationship between the morphology and wettability of the AAO films was investigated by scanning electron microscopy and the measurement of water contact angles. The results show that the “bird's nest”-like structure is necessary for superhydrophilic property, which provide direct experimental evidences for the 3D capillary theory concerning superhydrophilicity. It is expected that this investigation will be devoted to guiding the fabrication of superhydrophilic and superhydrophobic surfaces.     

From One‐ to Three‐Dimensional Organic Semiconductors: In Search of the Organic Silicon?

Organic semiconductors based on π‐conjugated systems are the focus of considerable interest in the emerging area of soft or flexible photonics and electronics. Whereas in recent years the performances of devices such as organic light‐emitting diodes (OLEDs), organic field‐effect transistors (OFETs), or solar cells have undergone considerable progress, a number of technical and fundamental problems related to the low dimensionality of organic semiconductors based on linear π‐conjugated systems remain unsatisfactorily resolved. This low dimensionality results in an anisotropy of the optical and charge‐transport properties, which in turn implies a control of the material organization/molecular orientation during or after device fabrication. Such a constraint evidently represents a problem when device fabrication by solution‐based processes, such as printing techniques, is envisioned. The aim of this short Review is to illustrate possible alternative strategies based on the development of organic semiconductors with higher dimensionality, capable to exhibit isotropic electronic properties.     

“Cubism” on the Nanoscale: From Squaric Acid to Porous Carbon Cubes

3D cube‐shaped composites and carbon microparticles with hierarchically porous structure are prepared by a facile template‐free synthesis route. Via the coordination of zinc acetate dihydrate and squaric acid, porous 3D cubic crystalline particles of zinc squarate can be obtained. These are easily transformed into the respective zinc oxide carbon composites under preservation of the macromorphology by heat treatment. Washing of the composite materials results in hierarchically porous carbons with high surface areas (1295 m² g^–1) and large pore volumes (1.5 cm³ g^?1) under full retention of the cube‐like architecture of the initial crystals. The materials are shown to be promising electrode materials for supercapacitor applications with a specific capacitance of 133 F g^?1 in H₂SO₄ at a scan rate of 5 mV s^?1, while 67% of this specific capacitance is retained, when increasing the scan rate to 200 mV s^?1.     

Biomimetic Solid‐State Nanochannels: From Fundamental Research to Practical Applications

In recent years, solid‐state smart nanopores/nanochannels for intelligent control of the transportation of ions and molecules as organisms have been extensively studied, because they hold great potential applications in molecular sieves, nanofluidics, energy conversion, and biosensors. To keep up with the fast development of this field, it is necessary to summarize the construction, characterization, and application of biomimetic smart nanopores/nanochannels. These can be classified into four sections: the fabrication of solid‐state nanopores/nanochannels, the functionalization methods and materials, the mechanism explanation about the ion rectification, and the practical applications. A brief conclusion and outlook for the biomimetic nanochannels is provided, highlighting those that could be developed and integrated into devices for use in tackling current and the future problems including resources, energy, environment, and health.     

Protected Lithium‐Metal Anodes in Batteries: From Liquid to Solid

High‐energy lithium‐metal batteries are among the most promising candidates for next‐generation energy storage systems. With a high specific capacity and a low reduction potential, the Li‐metal anode has attracted extensive interest for decades. Dendritic Li formation, uncontrolled interfacial reactions, and huge volume effect are major hurdles to the commercial application of Li‐metal anodes. Recent studies have shown that the performance and safety of Li‐metal anodes can be significantly improved via organic electrolyte modification, Li‐metal interface protection, Li‐electrode framework design, separator coating, and so on. Superior to the liquid electrolytes, solid‐state electrolytes are considered able to inhibit problematic Li dendrites and build safe solid Li‐metal batteries. Inspired by the bright prospects of solid Li‐metal batteries, increasing efforts have been devoted to overcoming the obstacles of solid Li‐metal batteries, such as low ionic conductivity of the electrolyte and Li–electrolyte interfacial problems. Here, the approaches to protect Li‐metal anodes from liquid batteries to solid‐state batteries are outlined and analyzed in detail. Perspectives regarding the strategies for developing Li‐metal anodes are discussed to facilitate the practical application of Li‐metal batteries.     

Carbon‐Based Microbial‐Fuel‐Cell Electrodes: From Conductive Supports to Active Catalysts

Microbial fuel cells (MFCs) have attracted considerable interest due to their potential in renewable electrical power generation using the broad diversity of biomass and organic substrates. However, the difficulties in achieving high power densities and commercially affordable electrode materials have limited their industrial applications to date. Carbon materials, which can exhibit a wide range of different morphologies and structures, usually possess physiological activity to interact with microorganisms and are therefore fast‐emerging electrode materials. As the anode, carbon materials can significantly promote interfacial microbial colonization and accelerate the formation of extracellular biofilms, which eventually promotes the electrical power density by providing a conductive microenvironment for extracellular electron transfer. As the cathode, carbon‐based materials can function as catalysts for the oxygen‐reduction reaction, showing satisfying activities and efficiencies nowadays even reaching the performance of Pt catalysts. Here, first, recent advancements on the design of carbon materials for anodes in MFCs are summarized, and the influence of structure and surface functionalization of different types of carbon materials on microorganism immobilization and electrochemical performance is elucidated. Then, synthetic strategies and structures of typical carbon‐based cathodes in MFCs are briefly presented. Furthermore, future applications of carbon‐electrode‐based MFC devices in the energy, environmental, and biological fields are discussed, and the emerging challenges in transferring them from laboratory to industrial scale are described.