Osteoconductive and Osteoinductive Properties of Zeolite MFI Coatings on Titanium Alloys

The use of zeolite MFI‐coated titanium alloy for bone cell growth and new bone formation in vitro is investigated. The corrosion‐resistant MFI coating is shown to be osteoconductive and to promote proliferation of human fetal osteoblasts (hFOBs) as compared to bare titanium alloy, Ti6Al4V. The zeolite crystal microstructure appears to facilitate osteoblast adhesion and induces osteointegration, as evaluated with microscopy. In addition, the zeolite promotes the differentiation of hFOBs into mature osteoblasts, as well as the production of a mineralized matrix at earlier times in culture compared to Ti6Al4V, indicating higher osteoinductive properties of the MFI coating than titanium alone. A significant increase in the expression of the bone morphogenetic protein (BMP‐2) gene is measured in hFOBs cultured on zeolite coatings compared to bare Ti6Al4V. This is the first report on highly corrosion‐resistant zeolite MFI coatings on Ti6A14V alloys with the potential to be used as a material of improved osteointegration appropriate for bone tissue regeneration.     

Core–Shell Zeolite Microcomposites

Core–shell zeolite composites possessing a core and a shell of different zeolite structure types have been synthesized. A characteristic feature of the obtained composites is the relatively large single‐crystal core and the very thin polycrystalline shell. The incompatibility between the core crystals and the zeolite precursor mixture yielding the shell layer has been circumvented by the adsorption of nanoseeds on the core surface, which induced the crystallization of the shell. The pretreated core crystals are subsequently subjected to a continuous growth in a zeolite precursor mixture. The feasibility of this synthetic approach has been exemplified by the preparation of core–shell β‐zeolite–silicalite‐1 composites. The synthesized composites have been characterized using X‐ray diffraction, high‐resolution transmission electron microscopy, and scanning electron microscopy. The integrity of the shell layer has been tested via N₂‐adsorption measurements on materials comprising a calcined core (β‐zeolite) and a non‐calcined tetrapropylammonium (TPA)‐containing shell, the latter being non‐permeable for the N₂ molecules. These measurements have shown that 86 % of the β‐zeolite crystals are covered with a defect‐free TPA–silicalite‐1 shell after a single hydrothermal treatment, while after three consecutive crystallization steps this value reaches 99 %. The shell integrity of the calcined composite has been studied by the adsorption of butane, toluene, and 1,3,5‐trimethylbenzene, which confirmed the superior performance of the triple‐shell composites.     

Magnetic Multi‐Functional Nano Composites for Environmental Applications

A novel concept is proposed to synthesize a new class of composites featuring magnetic, molecular sieve and metallic nanoparticle properties. These multi‐functional materials have potential applications as recyclable catalysts, disinfectants and sorbents. The magnetic property enables effective separation of the spent composites from complex multiphase systems for regeneration and recycle, safe disposal of the waste and/or recovery of loaded valuable species. The zeolite molecular sieve provides a matrix which supports a remarkably new, simple, efficient and economical method to make stable, supported silver nanoparticles by silver ion exchange and controlled thermal reduction. The silver nanoparticles generated in this way have excellent properties such as high reactivity and good thermal stability without aggregation, which act as nano reactors for desired functionality in a wide range of applications. Magnetic component (Fe₃O₄), molecular sieve matrix (zeolite) and silver nanoparticles generated by ion exchange followed by controlled reduction, together form this unique novel composite with designed functions. It represents a practically operational, economical, sustainable and environmentally friendly new advanced functional material. This paper focuses on the novel synthesis and characterization of the composite, with an example of applications as sorbents for the removal of vapor‐phase mercury from the flue gas of coal‐fired power plants.     

Versatile Nanocomposite Coatings with Tunable Cell Adhesion and Bactericidity

TiO₂‐Ag nanocomposites are known for their bactericidal effect during exposure to appropriate UV radiation. While involving hazardous radiation, and limited to accessible areas, the bactericidity of these coatings is not persistent in the absence of UV light, which impedes their commercial application. Herein it is shown that TiO₂‐Ag nanocomposites can be made highly bactericidal without the need of irradiation. Beyond this, bactericidity can even be mitigated in the presence of pre‐irradiated coatings. Biocompatibility and cell adhesion are also negligibly small for the as‐processed, non‐irradiated coatings, and become fairly high when the coatings are irradiated prior to testing. This opens the possibility to pattern the coatings into areas with high and low cell adhesion properties. Indeed by irradiating the coating through a mechanical mask it is shown that fibroblast cell adherence is sharply confined to the irradiated area. These properties are achieved using TiO₂‐Ag thin films with high silver loadings of 50 wt%. The films are processed on stainless steel substrates using solution deposition. Microstructural characterization by means of X‐ray diffraction, Raman, and X‐ray photoelectron spectroscopy, high‐resolution scanning electron microscopy, and atomic force microscopy show a highly amorphous TiO₂‐Ag_xO nanocomposite matrix with scattered silver nanoparticles. UV irradiation of the films results in the precipitation of a high density of silver nanoparticles at the film surface. Bactericidal properties of the films are tested on α‐haemolyzing streptococci and in‐vitro biocompatibility is assessed on primary human fibroblast cultures. The results mentioned above as to the tunable bactericidity and biocompatibility of the TiO₂‐Ag coatings developed herein, are amenable to silver ion release, to catalytic effects of silver nanoparticles, and to specific wettabilities of the surfaces.     

Recent Developments and Practical Feasibility of Polymer‐Based Antifouling Coatings

While nature has optimized its antifouling strategies over millions of years, synthetic antifouling coatings have not yet reached technological maturity. For an antifouling coating to become technically feasible, it should fulfill many requirements: high effectiveness, long‐term stability, durability, ecofriendliness, large‐scale applicability, and more. It is therefore not surprising that the search for the perfect antifouling coating has been going on for decades. With the discovery of metal‐based antifouling paints in the 1970s, fouling was thought to be a problem of the past, yet its untargeted toxicity led to serious ecological concern, and its use became prohibited. As a response, research shifted focus toward a biocompatible alternative: polymer‐based antifouling coatings. This has resulted in numerous advanced and innovative antifouling strategies, including fouling‐resistant, fouling‐release, and fouling‐degrading coatings. Here, these novel and exciting discoveries are highlighted while simultaneously assessing their antifouling performance and practical feasibility.     

High‐Temperature Performance of Alumina–Zirconia Composite Coatings Containing Amorphous Phases

Amorphous phases are commonly found in nanostructured plasma‐sprayed coatings. Nonetheless, the role of these phases in the resulting coatings’ properties has remained uninvestigated until now. In the present work, pseudo‐eutectic coatings—based on alumina and 8 wt% yttria‐stabilized zirconia (YSZ)—containing amorphous phases are produced using a suspension‐plasma‐spray process. These composite materials are a potential choice for thermal‐barrier coating applications. The role of the amorphous phase on the performance of the coatings is investigated before and after heat treatment. Results show that, although the amorphous phases in untreated coatings reduce the thermal conductivity, they impair the mechanical properties. However, treatment above the crystallization temperature leads to better mechanical properties as well as enhanced high‐temperature stability of the resulting nanostructure. Moreover, the role of alumina as a stabilizer of high‐temperature YSZ phases (tetragonal and cubic) is confirmed and the high‐temperature phase stability of the alumina–YSZ composite is demonstrated. The amorphous phases are found to crystallize into their corresponding high‐temperature stable phases; i. e., α‐alumina and tetragonal zirconia.     

Beyond Creation of Mesoporosity: The Advantages of Polymer‐Based Dual‐Function Templates for Fabricating Hierarchical Zeolites

Direct synthesis of hierarchical zeolites currently relies on the use of surfactant‐based templates to produce mesoporosity by the random stacking of 2D zeolite sheets or the agglomeration of tiny zeolite grains. The benefits of using nonsurfactant polymers as dual‐function templates in the fabrication of hierarchical zeolites are demonstrated. First, the minimal intermolecular interactions of nonsurfactant polymers impose little interference on the crystallization of zeolites, favoring the formation of 3D continuous zeolite frameworks with a long‐range order. Second, the mutual interpenetration of the polymer and the zeolite networks renders disordered but highly interconnected mesopores in zeolite crystals. These two factors allow for the synthesis of single‐crystalline, mesoporous zeolites of varied compositions and framework types. A representative example, hierarchial aluminosilicate (meso‐ZSM‐5), has been carefully characterized. It has a unique branched fibrous structure, and far outperforms bulk aluminosilicate (ZSM‐5) as a catalyst in two model reactions: conversion of methanol to aromatics and catalytic cracking of canola oil. Third, extra functional groups in the polymer template can be utilized to incorporate desired functionalities into hierarchical zeolites. Last and most importantly, polymer‐based templates permit heterogeneous nucleation and growth of mesoporous zeolites on existing surfaces, forming a continuous zeolitic layer. In a proof‐of‐concept experiment, unprecedented core–shell‐structured hierarchical zeolites are synthesized by coating mesoporous zeolites on the surfaces of bulk zeolites.     

Photoresponsive Sponge‐Like Coating for On‐Demand Liquid Release

Many publications report on stimuli responsive coatings, but only a few on the controlled release of species in order to change the coating surface properties. A sponge‐like coating that is able to release and absorb a liquid upon exposure to light has been developed. The morphology of the porous coating is controlled by the smectic liquid crystal properties of the monomer mixture prior to its polymerization, and homeotropic order is found to give the largest contraction. The fast release of the liquid can be induced by a macroscopic contraction of the coating caused by a trans to cis conversion of a copolymerized azobenzene moiety. The liquid secretion can be localized by local light exposure or by creating a surface relief. The uptake of liquid proceeds by stimulating the back reaction of the azo compound by exposure at higher wavelength or by thermal relaxation. The surface forces of the sponge‐like coating in contact with an opposing surface can be controlled by light‐induced capillary bridging revealing that the controlled release of liquid gives access to tunable adhesion.     

Fire‐Resistant Structural Material Enabled by an Anisotropic Thermally Conductive Hexagonal Boron Nitride Coating

Fire retardant coatings have been proven effective at reducing the heat release rate (HRR) of structural materials during burning; yet effective methods for increasing the ignition temperature and delay time prior to burning are rarely reported. Herein, a strong, fire‐resistant wood structural material is developed by combining a densification treatment with an anisotropic thermally conductive flame‐retardant coating of hexagonal boron nitride (h‐BN) nanosheets to produce BN‐densified wood. The thermal management properties created by the BN coating provide fast, in‐plane thermal diffusion, slowing the conduction of heat through the densified wood, which improves the material's ignition properties. Compared with densified wood without the BN coating, a 41 °C enhancement in ignition temperature (T_ig), a twofold increase in ignition delay time (t_ig), and a 25% decrease in the maximum HRR of BN‐densified wood can be achieved. As a proof of concept for scalability, the pieces of the BN‐densified wood are fabricated with a length larger than 25 cm, width greater than 15 cm, and thickness more than 7 mm. The improved thermal management, fire resistance, mechanical strength, and scalable production of BN‐densified wood position it as a promising structural material for safe and energy‐efficient buildings.     

Interface Design and Development of Coating Materials in Lithium–Sulfur Batteries

High‐energy Li‐S batteries have received extensive attention and are considered to be the most promising next‐generation electric energy storage devices beyond Li‐ion batteries. Interface design is an important direction to address challenges in the development of Li–S batteries. This review summarizes recently developed coatings and interlayer materials at various interfaces of Li–S batteries. In particular, advanced nanostructures and novel fabrication methods of coating and interlayer materials applied to Li–S batteries are highlighted. Furthermore, underlying mechanisms at the interfaces and electrochemical performance of the developed Li–S batteries are also discussed. Finally, existing challenges and the future development of interface design in high‐energy Li–S batteries are summarized and prospected.     

Stable White Light‐Emitting Biocomposite Films

The demonstration of reliable and stable white light‐emitting diodes (LEDs) is one of the main technological challenges of the LED industry. This is usually accomplished by incorporation of light‐emitting rare‐earth elements (REEs) compounds within an external polymeric coating of a blue LED allowing the generation of white light. However, due to both environmental and cost issues, the development of low‐cost REE‐free coatings, which exhibit competitive performance compared to conventional white LED is of great importance. In this work, the formation of an REE‐free white LED coating is demonstrated. This biocomposite material, composed of biological (crystalline nanocellulose and porcine gastric mucin) and organic (light‐emitting dyes) compounds, exhibits excellent optical and mechanical properties as well as resistance to heat, humidity, and UV radiation. The coating is further used to demonstrate a working white LED by incorporating it within a commercial blue LED.     

Satellite communications for manned spacecraft

Future manned spaceflight programs may require continuous real-time communications between the spacecraft and the mission control center. This paper examines the feasibility of relay satellite (RS) systems to meet these requirements. Anticipated requirements range from voice and low-speed data for the Skylab and Space Shuttle to television for the Space Station. Frequencies in S, C, X, and K bands (2, 5, 8, and GHz bands, respectively) are considered. Terrestrial radio-relay links may cause interference in the mission spacecraft (MS) and RS and vice versa. Possible remedies include better control of antenna sidelobes and judicious choice of channel frequencies. It is found that INTELSAT IV offers a technically feasible means of providing voice and data communications but not TV. A new dedicated satellite system can meet the requirements with two geostationary satellites both of which are visible to a single earth station (ES) in the United States. A shared satellite system, catering to other potential users as well as to manned spacecraft, offers the possibility of reduced cost to individual users. Satellite configurations for both dedicated and shared systems are presented. The satellites can be launched by boosters of the Thor-Delta class if the links between satellite and spacecraft operate in K band.     

高能激光器中晶体薄膜的研究与特性分析

介绍了用于大功率YAG激光器以及中红外激光器中晶体光学薄膜的用途、特性和制备方法。利用计算机膜系优化软件对膜系进行设计后,得到了损耗小、利于制备、重复性好的膜系结构。为了详细说明,以YAG板条晶体和ZnGeP2晶体为例,讨论了晶体不同工作表面薄膜在研究与镀制过程中的潮解、吸收以及污染等主要技术问题。通过特性测试和激光损伤试验对比,验证了以APS离子源辅助沉积的膜层损伤阈值增加,附着力增强,机械强度和环境稳定性得到了明显改善。目前相关的晶体薄膜应用在两种高能激光器中分别达到了16 kW/cm2和5 kHz下     

Facile Two‐Step Synthesis of All‐Inorganic Perovskite CsPbX3 (X = Cl,Br, and I) Zeolite‐Y Composite Phosphors for Potential Backlight Display Application

Recently developed CsPbX₃ (X = Cl, Br, and I) perovskite quantum dots (QDs) hold great potential for various applications owing to their superior optical properties, such as tunable emissions, high quantum efficiency, and narrow linewidths. However, poor stability under ambient conditions and spontaneous ion exchange among QDs hinder their application, for example, as phosphors in white‐light‐emitting diodes (WLEDs). Here, a facile two‐step synthesis procedure is reported for luminescent and color‐tunable CsPbX₃–zeolite‐Y composite phosphors, where perovskite QDs are encapsulated in the porous zeolite matrix. First zeolite‐Y is infused with Cs⁺ ions by ion exchange from an aqueous solution and then forms CsPbX₃ QDs by diffusion and reaction with an organic solution of PbX₂. The zeolite encapsulation reduces degradation and improves the stability of the QDs under strong illumination. A WLED is fabricated using the resulting microscale composites, with Commission Internationale de I'Eclairage (CIE) color coordinates (0.38, 0.37) and achieving 114% of National Television Standards Committee (NTSC) and 85% of the ITU‐R Recommendation BT.2020 (Rec.2020) coverage.     

A Shape‐Adaptive,Antibacterial‐Coating of Immobilized Quaternary‐Ammonium Compounds Tethered on Hyperbranched Polyurea and its Mechanism of Action

Quaternary‐ammonium‐compounds are potent cationic antimicrobials used in everyday consumer products. Surface‐immobilized, quaternary‐ammonium‐compounds create an antimicrobial contact‐killing coating. We describe the preparation of a shape‐adaptive, contact‐killing coating by tethering quaternary‐ammonium‐compounds onto hyperbranched polyurea coatings, able to kill adhering bacteria by partially enveloping them. Even after extensive washing, coatings caused high contact‐killing of Staphylococcus epidermidis, both in culture‐based assays and through confocal‐laser‐scanning‐microscopic examination of the membrane‐damage of adhering bacteria. In culture‐based assays, at a challenge of 1600 CFU/cm², contact‐killing was >99.99%. The working‐mechanism of dissolved quaternary‐ammonium‐compounds is based on their interdigitation in bacterial membranes, but it is difficult to envisage how immobilized quaternary‐ammonium‐molecules can exert such a mechanism of action. Staphylococcal adhesion forces to hyperbranched quaternary‐ammonium coatings were extremely high, indicating that quaternary‐ammonium‐molecules on hyperbranched polyurea partially envelope adhering bacteria upon contact. These lethally strong adhesion forces upon adhering bacteria then cause removal of membrane lipids and eventually lead to bacterial death.     

Polydopamine‐Graphene Oxide Flame Retardant Nanocoatings Applied via an Aqueous Liquid Crystalline Scaffold

A highly effective flame retardant (FR) nanocoating was developed by conducting oxidative polymerization of dopamine monomer within an aqueous liquid crystalline (LC) graphene oxide (GO) scaffold coating. Due to its high water content, the LC scaffold coating approach facilitated fast transport and polymerization of dopamine precursors into polydopamine (PDA) within the water swollen interlayer galleries. Uniform and periodically stacked (14.5 Å d‐spacing) PDA/GO nanocoatings could be universally applied on different surfaces, including macroporous flexible polyurethane (PU) foam and flat substrates such as silicon wafers. Remarkably, PDA/GO coated PU foam exhibited highly efficient flame retardant performance reflected by a 65% reduction in peak heat release rate at 5 wt% PDA/GO loading in an 80 nm thick coating. While many physically mixed flame retardants are usually detrimental to the mechanical properties of the foam, the PDA/GO coating did not affect mechanical properties substantially. In addition, the PDA/GO coatings were stable in water due to the intrinsic adhesion capability of PDA and the transformation of GO to the more hydrophobic reduced GO form. Given that PDA is produced from dopamine, a molecule prevalent in nature, these findings suggest that significant opportunities exist for new polymeric FRs derived from other natural catechols.     

Photoswitchable Nanomaterials Based on Hierarchically Organized Siloxane Oligomers

Materials with highly ordered molecular arrangements have the capacity to display unique properties derived from their nanoscale structure. Here, the synthesis and characterization of azobenzene (AZO)‐functionalized siloxane oligomers of discrete length that form photoswitchable supramolecular materials are described. Specifically, synergy between phase segregation and azobenzene crystallization leads to the self‐assembly of an exfoliated 2D crystal that becomes isotropic upon photoisomerization with UV light. Consequently, the material undergoes a rapid athermal solid‐to‐liquid transition which can be reversed using blue light due to the unexpectedly fast 2D crystallization that is facilitated by phase segregation. In contrast, enabling telechelic supramolecular polymerization through hydrogen bonding inhibits azobenzene crystallization, and nanostructured pastes with well‐ordered morphologies are obtained based on phase segregation alone, thus demonstrating block copolymer‐like behavior. Therefore, by tailoring the balance of self‐assembly forces in the azobenzene‐functionalized siloxane oligomers, fast and reversible phase‐changing materials can be engineered with various mechanical properties for applications in photolithography or switchable adhesion to lubricant properties.     

Synthesis of Thin,Oriented Zeolite A Membranes on a Macroporous Support

Continuous, thin, oriented zeolite A membranes are produced by a two‐step synthesis on macroporous α‐Al₂O₃ supports. In the first step, zeolite A nano‐cubes with ～350‐nm edges are prepared as a native impurity phase in zeolite Y synthesis dispersions, the support surface is pre‐modified with a cationic polymer having a selective affinity for zeolite A. The thus‐treated support is contacted with a colloidally stable dispersion of zeolite A and Y mixture in water, which results in selective, dense‐packed deposition of the zeolite A cubes with one face aligned to the average support surface. In a second step of hydrothermal epitaxial growth, the seed layer grows epitaxially into a continuous, meso‐defect free, ～1 µm thick zeolite A layer, already after 1 h of treatment. This microstructure of the membrane compares very favorably to what is commonly obtained. The pH value of the zeolite mixture suspension is found to have a major influence on seed layer morphology, and thereby, on the quality and orientation of zeolite A membrane after short synthesis times. The final zeolite A membrane thickness and morphology is controlled by varying secondary growth synthesis time. The approach presented is thought to be of generic use for the preparation of oriented zeolite membranes.     

Reconfigurable Anisotropic Coatings via Magnetic Field‐Directed Assembly and Translocation of Locking Magnetic Chains

A method for the generation of remotely reconfigurable anisotropic coatings is developed. To form these coatings, locking magnetic nanoparticles (LMNPs) made of a superparamagnetic core and a two‐component polymer shell are employed. Two different polymers form phase‐separated coaxial shells. The outer shell provides repulsive interactions between the LMNPs while the inner shell exerts attractive forces between the particles. Applying a non‐uniform magnetic field, one gathers the particles together, pushing them to come in contact when the internal shells could effectively hold the particles together. When the magnetic field is turned off, the particles remain locked due to these strong interactions between internal shells. The shells are thus made stimuli‐responsive, so this locking can be made reversible and the chains can be disintegrated on demand. In a non‐uniform magnetic field, the assembled chains translocate, bind to the solid substrate and form anisotropic coatings with a “locked” anisotropic structure. The coatings can be constructed, aligned, realigned, degraded, and generated again on demand by changing the magnetic field and particle environment. The mechanism of the coating formation is explained using experimental observations and a theoretical model.