Multi-Directional Growth of Aligned Carbon Nanotubes Over Catalyst Film Prepared by Atomic Layer Deposition

The structure of vertically aligned carbon nanotubes (CNTs) severely depends on the properties of pre-prepared catalyst films. Aiming for the preparation of precisely controlled catalyst film, atomic layer deposition (ALD) was employed to deposit uniform Fe₂O₃ film for the growth of CNT arrays on planar substrate surfaces as well as the curved ones. Iron acetylacetonate and ozone were introduced into the reactor alternately as precursors to realize the formation of catalyst films. By varying the deposition cycles, uniform and smooth Fe₂O₃ catalyst films with different thicknesses were obtained on Si/SiO₂ substrate, which supported the growth of highly oriented few-walled CNT arrays. Utilizing the advantage of ALD process in coating non-planar surfaces, uniform catalyst films can also be successfully deposited onto quartz fibers. Aligned few-walled CNTs can be grafted on the quartz fibers, and they self-organized into a leaf-shaped structure due to the curved surface morphology. The growth of aligned CNTs on non-planar surfaces holds promise in constructing hierarchical CNT architectures in future.     

Growth of GaN Thin Films Using Plasma Enhanced Atomic Layer Deposition: Effect of Ammonia-Containing Plasma Power on Residual Oxygen Capture

In recent years, the application of (In, Al, Ga)N materials in photovoltaic devices has attracted much attention. Like InGaN, it is a direct band gap material with high absorption at the band edge, suitable for high efficiency photovoltaic devices. Nonetheless, it is important to deposit high-quality GaN material as a foundation. Plasma-enhanced atomic layer deposition (PEALD) combines the advantages of the ALD process with the use of plasma and is often used to deposit thin films with different needs. However, residual oxygen during growth has always been an unavoidable issue affecting the quality of the resulting film, especially in growing gallium nitride (GaN) films. In this study, the NH₃-containing plasma was used to capture the oxygen absorbed on the growing surface to improve the quality of GaN films. By diagnosing the plasma, NH₂, NH, and H radicals controlled by the plasma power has a strong influence not only on the oxygen content in growing GaN films but also on the growth rate, crystallinity, and surface roughness. The NH and NH₂ radicals contribute to the growth of GaN films while the H radicals selectively dissociate Ga-OH bonds on the film surface and etch the grown films. At high plasma power, the GaN film with the lowest Ga-O bond ratio has a saturated growth rate, a better crystallinity, a rougher surface, and a lower bandgap. In addition, the deposition mechanism of GaN thin films prepared with a trimethylgallium metal source and NH₃/Ar plasma PEALD involving oxygen participation or not is also discussed in the study.     

Atomic layer deposition of polyimide on microporous polyethersulfone membranes for enhanced and tunable performances

Atomic layer deposition (ALD) of polyimide (PI) is explored to tune the separation properties of microporous polyethersulfone (PES) membranes and also to improve their mechanic and thermal stability. Conformal and uniform thin layers of PI are deposited along the pore wall throughout the entire PES membrane instead of forming a top layer merely on the membrane surface. With increasing ALD cycles, the pore size of the PES membrane is progressively reduced, leading to increased retention. The permeation is correspondingly decreased but its drop is less pronounced than the increase of retention. For example, the retention to 23‐nm silica nanospheres is significantly increased from nearly zero to 60% after 3000 ALD cycles, whereas the water flux is moderately decreased by 54%. Moreover, ALD of PI evidently enhances the mechanical strength and thermal resistance of the PES membrane as PI tightly wraps the skeleton of the membrane. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3614–3622, 2014     

医疗用非织造布纺黏层用聚丙烯的性能及应用

对目前国内医疗用非织造布市场用户认可度较高的国内外纺黏层用聚丙烯树脂进行了基础物性、分子结构、热性能的分析表征。同时,进一步用国内外专用聚丙烯树脂试生产52 g/m2的医疗用纺黏-熔喷-纺黏(SMS)非织造布,并对SMS非织造布的主要使用性能进行了测试对比,认为生产医疗用SMS非织造布时对纺黏层用聚丙烯树脂的指标要求为:熔体流动速率大于3.5 g/min,相对分子质量分布小于4.0,灰分含量小于0.015%。     

Dye adsorption on zinc oxide nanoparticulates atomic‐layer‐deposited on polytetrafluoroethylene membranes

In this work, zinc oxide (ZnO) is deposited onto porous polytetrafluoroethylene (PTFE) membranes via atomic layer deposition (ALD) and thus produced ZnO‐deposited PTFE membranes are used as adsorbents for the removal of dyes from aqueous solutions. We first examine the evolution of morphology, wettability, and crystallization of PTFE membranes with ZnO ALD. The presence of ZnO nanoparticulates significantly promotes the diffusion and contact of the aqueous solutions within the membrane on one hand, and endows the membrane a strong capability to adsorb dyes from the solutions on the other. Kinetic studies reveal that the adsorption of rhodamine B and acid orange 7 by the ZnO‐deposited PTFE membranes can be described by the pseudo‐second‐order and pseudo‐first‐order model, respectively, and the adsorption of both dyes follows the Langmuir isotherm. The used membranes can be easily regenerated by rinsing with ethanol and reused for multiple times without loss of removal efficiency. © 2016 American Institute of Chemical Engineers AIChE J, 62: 3982–3991, 2016     

Thin Films Bearing Conjugated Polymer Nanoparticles Fabricated by Microliter‐Scale Layer‐by‐Layer Deposition

A conjugated polymer, poly(9,9‐bis(6‐bromohexyl)‐9H‐fluorene‐alt‐1,4‐phenylene), is synthesized, converted to nanoparticles via a nanoprecipitation process, and utilized to fabricate thin films including conjugated polymer nanoparticles. The nanoparticles with surface bromides can be conjugated with an amine‐functionalized dendrimer via a nucleophilic coupling reaction. Thus, when microliter solutions of the particulates are dragged at a constant velocity on substrates alternately in a layer‐by‐layer manner, thin films composed of the nanoparticles and dendrimers can be successfully built up on the substrates. Our results suggest a methodology to control the deposition of thin films bearing conjugated polymer nanoparticles while minimizing processing time and decreasing material consumption.

     

Atomic layer deposition of Al2O3 on porous polypropylene hollow fibers for enhanced membrane performances

Porous polypropylene hollow fiber (PPHF) membranes are widely used in liquid purification.However,the hydrophobicity of polypropylene (PP) has limited its applications in water treatment.Herein,we demonstrate that,for the first time,atomic layer deposition (ALD) is an effective strategy to conveniently upgrade the filtration performances of PPHF membranes.The chemical and morphological changes of the deposited PPHF membranes are characterized by spectral,compositional,microscopic characterizations and protein adsorption measurements.Al2O3 is distributed along the cross section of the PP hollow fibers,with decreasing concentration from the outer surface to the inner surface.The pore size of the outer surface can be easily turned by altering the ALD cycles.Interestingly,the hollow fibers become much more ductile after deposition as their elongation at break is increased more than six times after deposition with 100 cycles.The deposited membranes show simultaneously enhanced water permeance and retention after deposition with moderate ALD cycle numbers.For instance,after 50 ALD cycles a 17％ increase in water permeance and one-fold increase in BSA rejection are observed.Moreover,the PP membranes exhibit improved fouling-resistance after ALD deposition.     

Atomic layer deposition of TiO2 on carbon-nanotubes membrane for capacitive deionization removal of chromium from water

Chromium (Cr) is a common heavy metal that has severe impacts on the ecosystem and human health. Capacitive deionization (CDI) is an environment-friendly and energy-efficient electrochemical purification technology to remove Cr from polluted water. The performance of CDI systems relies primarily on the properties of electrodes. Carbon-nanotubes (CNTs) membranes are promising candidates in creating advanced CDI electrodes and processes. However, the low electrosorption capacity and high hydrophobicity of CNTs greatly impede their applications in water systems. In this study, we employ atomic layer deposition (ALD) to deposit TiO₂ nanoparticulates on CNTs membranes for preparing electrodes with hydrophilicity. The TiO₂-deposited CNTs membranes display preferable electrosorption performance and reusability in CDI processes after only 20 ALD cycles deposition. The total Cr and Cr(VI) removal efficiencies are significantly improved to 92.1% and 93.3%, respectively. This work demonstrates that ALD is a highly controllable and simple method to produce advanced CDI electrodes, and broadens the application of metal oxide/carbon composites in the electrochemical processes.     

大尺寸陶瓷膜原子层沉积过程的CFD模拟

陶瓷膜具有耐高温、耐酸碱、强度高等优点,在液体分离领域得到了广泛应用。对陶瓷膜进行表面改性,可进一步提升其性能,但基于表面化学反应的改性方法工艺过程复杂,难于控制。原子层沉积（atomic layer deposition,ALD）是基于表面自限制化学反应过程的气固相薄膜沉积技术,可以在纳米尺度精确调控孔道结构,特别适用于多孔分离膜的改性和功能化。目前尚无适用于大尺寸陶瓷膜的ALD设备,需要对ALD过程进行专门的优化设计。通过CFD模型对1 m长的单通道陶瓷膜的ALD过程进行了研究,在数学模型中考虑了两种气体源交替进入腔体中所引发不同的表面反应,并考虑了脉冲边界的影响。模拟计算结果与实验比较平均相对误差为1.69%。在数值模拟的基础上,提出了双向交替旋转脉冲的ALD模式,为陶瓷膜的ALD沉积改性的装备设计和过程优化提供了理论依据。     

High‐Speed Preparation of Highly (100)‐Oriented CeO2 Film by Laser Chemical Vapor Deposition

CeO₂ films were prepared at deposition temperature ranged from 947 to 1096 K (corresponding laser power was from 52 to 185 W) on (100) LaAlO₃ single crystal substrate by laser chemical vapor deposition. At deposition temperature of 1027–1096 K (laser power was from 115 to 185 W), highly (100)‐oriented CeO₂ films with wedge‐caped columnar grains were prepared, whose epitaxial growth relationship was CeO₂ [100]//LAO [100] (CeO₂ [010]//LAO [011]). Their full width at half maximum of the ω‐scan on the (200) reflection and that of the ?‐scan on the (220) reflection were 0.8°–1.8° and 0.7°–1.2°, respectively. The highest deposition rate at which CeO₂ film with pure (100) preferred orientation could be obtained was 30 μm h^?1.     

Atomic layer deposition of GDC cathodic functional thin films for oxide ion incorporation enhancement

In this paper, we report successful fabrication of a gadolinia-doped ceria (GDC) thin film using atomic layer deposition (ALD) for improving the performance of solid oxide fuel cells (SOFCs). By varying the deposition conditions and adjusting the configuration of the ALD supercycle, the doping ratio of ALD GDC was controlled. The morphology, crystallinity, and chemical composition of ALD GDC thin films were analyzed. ALD GDC showed different surface chemistry, including oxidation states, at different doping ratios. The application of ALD GDC in a SOFC led to an output power density enhancement greater than 2.5 times. With an anodic aluminum oxide (AAO) porous support structure, an ALD GDC thin film SOFC (TF-SOFC) showed a high power density of 288.24 mW/cm² at an operating temperature of 450°C.     

Nano‐engineered nickel catalysts supported on 4‐channel α‐Al2O3 hollow fibers for dry reforming of methane

A nickel (Ni) nanoparticle catalyst, supported on 4‐channel α‐Al₂O₃ hollow fibers, was synthesized by atomic layer deposition (ALD). Highly dispersed Ni nanoparticles were successfully deposited on the outside surfaces and the inside porous structures of hollow fibers. The catalyst was employed to catalyze the dry reforming of methane (DRM) reaction and showed a methane reforming rate of 2040 Lh^?1gNi^?1 at 800°C. NiAl₂O₄ spinel was formed when Ni nanoparticles were deposited on alpha‐alumina substrates by ALD, which enhanced the Ni‐support interaction. Different cycles (two, five, and ten) of Al₂O₃ ALD films were applied on the Ni/hollow fiber catalysts to further improve the interaction between the Ni nanoparticles and the hollow fiber support. Both the catalyst activity and stability were improved with the deposition of Al₂O₃ ALD films. Among the Al₂O₃ ALD coated catalysts, the catalyst with five cycles of Al₂O₃ ALD showed the best performance. © 2018 American Institute of Chemical Engineers AIChE J, 64: 2625–2631, 2018     

A New Method for Identifying Osmotically Limited and Gel Layer Controlled Pressure Independent Flux in Ultrafiltration

An unequivocal determination of whether pressure independent flux regime is osmotically controlled or gel layer dominated, is still open for discussion in the membrane literature. The present work reports a method that could be used to address this issue. It is shown that analysis of post steady state transient filtration data leads to clear demarcation of osmotically limited and gel layer controlled filtration. The method proposed in this work can also be used to estimate the additional filtration resistance offered by the polarization layer to the permeate flow in macromolecular ultrafiltration and has been verified experimentally. It has also been shown that the polarization layer thickness is not sensitive to the feed pressure but varies as a function of the bulk solute concentration; higher the bulk concentration, thicker is the polarization layer.     

A Review of the Design Strategies for Tailored Cathode Catalyst Materials in Rechargeable Li-O2 Batteries

For the purpose of reducing not only the consumption of natural resources, but also the environmental pollution from internal combustion engines, much effort has been dedicated to developing new energy storage systems (ESSs) and electric vehicles (EVs) powered by batteries. There are several stringent requirements, such as high power/energy density, good safety, and high reliability against external environmental abuse. For next-generation batteries to meet these requirements, the development of a new energy conversion system is crucial. Therefore, lithium-oxygen (lithium-O₂) batteries have attracted intensive attention, due to their high theoretical energy density, compared with those of gasoline engines. However, present lithium-O₂ batteries exhibit low round-trip efficiency and cyclic degradation, thus preventing their commercialization as next-generation power sources. This drawback may be attributed to the high thermodynamic stability of discharge products and their intrinsic insulating character, leading to the surge of polarization in oxygen reduction reactions/oxygen evolution reactions (ORRs/OERs). To alleviate cyclic degradation and improve round-trip efficiency, it has been reported that the polarization can be reduced by adopting adequate cathode catalysts, based on their surface structures regulating oxygen adsorption. Here we provide and discuss several design strategies for tailoring catalytic materials from a structural and morphological viewpoint, as well as their effect on discharge products.     

Electrospun Nanofibers for Sensing and Biosensing Applications—A Review

Sensors and biosensors have found applications in many areas, e.g., in medicine and clinical diagnostics, or in environmental monitoring. To expand this field, nanotechnology has been employed in the construction of sensing platforms. Because of their properties, such as high surface area to volume ratio, nanofibers (NFs) have been studied and used to develop sensors with higher loading capacity, better sensitivity, and faster response time. They also allow to miniaturize designed platforms. One of the most commonly used techniques of the fabrication of NFs is electrospinning. Electrospun NFs can be used in different types of sensors and biosensors. This review presents recent studies concerning electrospun nanofiber-based electrochemical and optical sensing platforms for the detection of various medically and environmentally relevant compounds, including glucose, drugs, microorganisms, and toxic metal ions.     

Semi‐Crystalline Polymer Blends for Material Extrusion Additive Manufacturing Printability: A Case Study with Poly(ethylene terephthalate) and Polypropylene

Semi‐crystalline polymers are an important class of materials for engineering applications due to their high modulus and barrier properties. Traditional manufacturing methods process semi‐crystalline polymers via rigid molds and well‐controlled temperature and pressure environments to handle the significant change in specific volume occurring during crystallization; however, material extrusion additive manufacturing does not use these features. This often leads to warpage‐induced build failure in fused filament fabrication (FFF). To enable FFF of semi‐crystalline polymers, this work investigates characteristics of immiscible polymer blends (e.g., disparate crystallization behavior and phase separation) to mitigate warping failure during printing. A series of poly(ethylene terephthalate)/polypropylene/polypropylene–graft–maleic anhydride blends are explored and the effect of thermal and morphological characteristics on printability is analyzed. It is shown that these blends can be extruded into filament and printed into a 3D structure. Extrapolations indicate that phase‐separated blends with increased total crystallization half‐time are beneficial for FFF printing.     

Cinnamamide Derivatives for Central and Peripheral Nervous System Disorders—A Review of Structure–Activity Relationships

The cinnamamide scaffold has been incorporated in to the structure of numerous organic compounds with therapeutic potential. The scaffold enables multiple interactions, such as hydrophobic, dipolar, and hydrogen bonding, with important molecular targets. Additionally, the scaffold has multiple substitution options providing the opportunity to optimize and modify the pharmacological activity of the derivatives. In particular, cinnamamide derivatives have exhibited therapeutic potential in animal models of both central and peripheral nervous system disorders. Some have undergone clinical trials and were introduced on to the pharmaceutical market. The diverse activities observed in the nervous system included anticonvulsant, antidepressant, neuroprotective, analgesic, anti‐inflammatory, muscle relaxant, and sedative properties. Over the last decade, research has focused on the molecular mechanisms of action of these derivatives, and the data reported in the literature include targeting the γ‐aminobutyric acid type A (GABA_A) receptors, N‐methyl‐D ‐aspartate (NMDA) receptors, transient receptor potential (TRP) cation channels, voltage‐gated potassium channels, histone deacetylases (HDACs), prostanoid receptors, opioid receptors, and histamine H₃ receptors. Here, the literature data from reports evaluating cinnamic acid amide derivatives for activity in target‐based or phenotypic assays, both in vivo and in vitro, relevant to disorders of the central and peripheral nervous systems are analyzed and structure–activity relationships discussed.     

Polymeric pH-sensitive membranes—A review

Significant progress has been achieved in recent years in the field of pH-sensitive membranes. In many cases, pH-sensitive membranes are systems for which the flux, membrane pore size, and solute rejection ratio may be manipulated by changing the pH. This review summarizes recent developments covering the preparation, pH-responsive properties, and applications in various disciplines. The pH-sensitive groups and the evaluation parameters for pH-sensitive membranes are reviewed and discussed. A variety of preparation methodologies, including blending, pore-filling, surface-grafting, and surface-coating techniques are described, and some of their salient features are highlighted. The flat-sheet form and hollow-fiber form pH-sensitive membranes are reviewed. Membrane pore size change and electroviscous effect are discussed. Furthermore, future perspectives of pH-sensitive membranes are discussed.     

Organic-inorganic nanocomposite polymer electrolyte membranes for fuel cell applications

Organic-inorganic nanocomposite polymer electrolyte membrane (PEM) contains nano-sized inorganic building blocks in organic polymer by molecular level of hybridization. This architecture has opened the possibility to combine in a single solid both the attractive properties of a mechanically and thermally stable inorganic backbone and the specific chemical reactivity, dielectric, ductility, flexibility, and processability of the organic polymer. The state-of-the-art of polymer electrolyte membrane fuel cell technology is based on perfluoro sulfonic acid membranes, which have some key issues and shortcomings such as: water management, CO poisoning, hydrogen reformate and fuel crossover. Organic-inorganic nanocomposite PEM show excellent potential for solving these problems and have attracted a lot of attention during the last ten years. Disparate characteristics (e.g., solubility and thermal stability) of the two components, provide potential barriers towards convenient membrane preparation strategies, but recent research demonstrates relatively simple processes for developing highly efficient nanocomposite PEMs. Objectives for the development of organic-inorganic nanocomposite PEM reported in the literature include several modifications: (1) improving the self-humidification of the membrane; (2) reducing the electro-osmotic drag and fuel crossover; (3) improving the mechanical and thermal strengths without deteriorating proton conductivity; (4) enhancing the proton conductivity by introducing solid inorganic proton conductors; and (5) achieving slow drying PEMs with high water retention capability. Research carried out during the last decade on this topic can be divided into four categories: (i) doping inorganic proton conductors in PEMs; (ii) nanocomposites by sol-gel method; (iii) covalently bonded inorganic segments with organic polymer chains; and (iv) acid-base PEM nanocomposites. The purpose here is to summarize the state-of-the-art in the development of organic-inorganic nanocomposite PEMs for fuel cell applications.