Ashutosh Tiwari
Abstract
International Association of Advanced Materials (IAAM, www.iaamonline.org) names the researcher of the year who had the greatest contribution in the field of Advanced Materials. The advanced materials community would like to take this opportunity to pay rich tributes to Professor T. Venkatesan for his ...
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International Association of Advanced Materials (IAAM, www.iaamonline.org) names the researcher of the year who had the greatest contribution in the field of Advanced Materials. The advanced materials community would like to take this opportunity to pay rich tributes to Professor T. Venkatesan for his pioneering research and notable contributions to nanoscience and nanotechnology. Advanced Materials Letters have been selected his photo for the cover of this special year-end issue.
Ryo Yoshida
Abstract
In living systems, there are many autonomous and oscillatory phenomena to sustain life such as heart beating. We developed “self-oscillating” polymer gels that undergo spontaneous cyclic swelling–deswelling changes without any on–off switching of external stimuli, as with heart ...
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In living systems, there are many autonomous and oscillatory phenomena to sustain life such as heart beating. We developed “self-oscillating” polymer gels that undergo spontaneous cyclic swelling–deswelling changes without any on–off switching of external stimuli, as with heart muscle.The self-oscillating gels were designed by utilizing the Belousov-Zhabotinsky (BZ) reaction, an oscillating reaction, as a chemical model of the TCA cycle. We have systematically studied these self-oscillating polymer gels since they were first reported in 1996. Potential applications of the self-oscillating polymers and gels include several kinds of functional material systems such as biomimetic actuators, mass transport systems and functional fluids. In this review, our recent progress on the self-oscillating polymer gels is summarized.
Muchun Liu; Cintia Juliana Castilho; Robert H. Hurt
Abstract
Over the last decade, graphene research has developed into a large and multi-faceted field concerned with the synthesis, structure, properties, and applications of various ultrathin sheet-like carbon forms. This article presents a historical perspective on ultrathin carbons, and on the traditional role ...
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Over the last decade, graphene research has developed into a large and multi-faceted field concerned with the synthesis, structure, properties, and applications of various ultrathin sheet-like carbon forms. This article presents a historical perspective on ultrathin carbons, and on the traditional role of the “graphene layer” as a conceptual model for describing crystalline polymorphs in sp < sup > 2 -based carbon materials. Bulk carbons can often be usefully modelled as physical assemblies of distinct graphene layers whose length, curvature, packing, and orientation determine carbon properties and their observed anisotropy. The article then gives a brief perspective on the emerging subfield of graphene research that uses nanosheets as physical building blocks to assemble new material architectures. In analogy with macroscopic sheets of paper or fabric, graphene nanosheets can be manipulated by stacking, wrapping, folding, wrinkling, or crumpling, to make novel carbons not accessible through traditional routes based on molecular or solid-state precursors. These include aerogels, crumpled particles, encapsulation sacks, and a variety of engineered films structures that can be planar or microtextured. While much work has been done in this graphene subfield, important research opportunities remain. Among these are the creation of hybrid structures involving graphene nanosheets systematically combined with other substances to form graphene-molecular hybrids, graphene-nanoparticle hybrids (2D-0D), graphene-nanofiber hybrids (2D-1D), and nanosheet heterostructures (2D-2D).
Dan Xu; Winston Duo Wu
Abstract
Hydrogen is one of the most promising clean energy because it has a much higher energy density than gasoline and emits no carbon dioxide after burning. For the application of hydrogen, hydrogen storage is considered as a key technology. Design and synthesis of porous material with high hydrogen storage ...
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Hydrogen is one of the most promising clean energy because it has a much higher energy density than gasoline and emits no carbon dioxide after burning. For the application of hydrogen, hydrogen storage is considered as a key technology. Design and synthesis of porous material with high hydrogen storage capacity should be fully developed at first. However, none of the candidate materials developed so far has meet the DOE target yet. This review aimed to describe the presently major accomplishments and the challenges in the area of hydrogen storage.
Philippe Knauth; Maria Luisa Di Vona
Abstract
Electrochemical synthesis is a powerful tool for the preparation of conformal, thin solid electrolytes directly on the electrodes, particularly with complex shapes, such as nanostructured electrodes. Such separators should present the highest possible single ion conductivity, negligible electronic conductivity ...
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Electrochemical synthesis is a powerful tool for the preparation of conformal, thin solid electrolytes directly on the electrodes, particularly with complex shapes, such as nanostructured electrodes. Such separators should present the highest possible single ion conductivity, negligible electronic conductivity combined with high chemical and mechanical stability. These requirements drive our development work: we synthesize polymers with excellent mechanical properties, which are decisive for a high durability of the separators. The single-ion conductivity is assured by anchoring the counter-ions on the polymer backbone. The solid polymer electrolytes contain no flammable solvent guaranteeing high safety. For cation-conducting membranes, we synthesized polymers with sulfonate groups grafted on the macromolecular chain. These ionomers, including poly(styrene sulfonate) (PSS) can be used for proton exchange membrane fuel cells and Li batteries. Anion-conducting membranes contain quaternary ammonium as fixed cationic groups; they can be applied for example in hydroxide exchange membrane fuel cells. The paper presents the electrochemical synthesis procedures and the relevant structural, microstructural and electrical properties of cation- and anion-conducting polymers, including relevant data of applications, such as Li microbattery cycling.
D. H. Turkenburg; H. R. Fischer
Abstract
Internal microscopic damage is ubiquitous in composites, whether this was caused or introduced during the manufacturing process (i.e. via thermal stresses), from machining (i.e. drilling holes for bolted joints), during component assembly or ultimately from in-service loading. Incorporating an in-situ ...
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Internal microscopic damage is ubiquitous in composites, whether this was caused or introduced during the manufacturing process (i.e. via thermal stresses), from machining (i.e. drilling holes for bolted joints), during component assembly or ultimately from in-service loading. Incorporating an in-situ repair solution that can be activated after each of these individual processes could have a significant impact on reducing composite component scrappage rates, post-manufacture and other repairs and increase the time-period for non-destructive testing (NDT) inspection. By utilizing specific self-healing chemistries (i.e. via epoxy-amine polymers containing Diels-Alder based thermo-reversible bonds and/or epoxy resin healing agents) that can achieve multiple repair/healing cycles, damage generated throughout a components life cycle can be repaired and service life extended as well as complete recycling of fibers and resins can be possible. Materials of optimized composition form densely crosslinked networks at room temperature while repeatedly regaining the ability to flow at elevated temperature. Mechanical testing of bulk epoxy and reinforced polymer composite films demonstrated that the thermo-reversible effect is strong enough to achieve repetitive full self-healing of a severely cracked and delaminated test specimens without significantly affecting the mechanics of the resin. The resin has been integrated in prepreg based test specimen and the self-healing efficiency remained around 40% with 5 subsequent healing cycles. The embedded self-healing agents are thermally activated post-damage to repair the internal structure, akin to the healing functionality in animals and plants. This approach represents a truly positive benefit to industry to aid in the optimization of composite manufacture, by reducing post-manufacture inspection time and material wastage costs, and also to maximize the longevity of composite components in service as well as to introduce a true recycling possibility by recovery of the binder material system and of the reinforcing fibers.
E. Kutelia; L. Rukhadze; T. Dzigrashvili; O. Tsurtsumia; D. Gventsadze
Abstract
The present work deals with the special experiments on SEM-EDX study of morphology, chemical composition and topological transformations of the initial ground surface of the bulk iron plate-substrate after its interaction with the ethanol vapor pyrolysis products at high temperatures in the closed-loop ...
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The present work deals with the special experiments on SEM-EDX study of morphology, chemical composition and topological transformations of the initial ground surface of the bulk iron plate-substrate after its interaction with the ethanol vapor pyrolysis products at high temperatures in the closed-loop and open cycle reactors. Our experiments have shown that the mechanism of formation of Fe clusters-doped CNFs on plate-substrate surfaces may be represented as a process, the first stage of which is a protonation of the substrate subsurface layers caused by diffusion of hydrogen atoms facilitating the formation of 3D nano-groups of Fe atoms assembled in the characteristic clusters with magic numbers of atoms, depending on the thermodynamics of the metal. The spontaneous coalescence of these clusters into giant Fe-clusters at comparatively low temperatures and formation of iron nano-droplets at comparatively high temperatures results in the formation of a nanopatterned surface with the uniformly distributed catalytic centers of CNFs nucleation. The second stage of the process is a nanoparticle-guided growth through the VLS or VS (at low temperatures) growth mechanisms in which the one cluster provides nucleation of only one CNF particle so that the sizes of the nucleation centers determine the basic size of the CNF nanoparticles.
Naoya Tsugawa; Panitha Phulkerd; Ayumi Kiyama; Masayuki Yamaguchi
Abstract
We evaluated the effect of adding a small amount of poly(N-isopropylacrylamide) (PNIPAM), which is a temperature-sensitive polymer, on the glass transition temperature (Tg) of poly(vinyl acetate) (PVAc). The Tg of a blend comprising 5wt.% PNIPAM was affected by the ambient temperature; the Tg was low ...
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We evaluated the effect of adding a small amount of poly(N-isopropylacrylamide) (PNIPAM), which is a temperature-sensitive polymer, on the glass transition temperature (Tg) of poly(vinyl acetate) (PVAc). The Tg of a blend comprising 5wt.% PNIPAM was affected by the ambient temperature; the Tg was low when the blend was stored at low temperatures and high when it was stored at high temperatures. This phenomenon can be attributed to the hydrophilic–hydrophobic transition of the PNIPAM. At low temperatures, the moisture content of the blend increased, resulting in a low Tg because of the plasticizing effect of water molecules on the PVAc. Because the material becomes soft at low temperatures, this unique property can be exploited in the design of smart materials.
Gion A. Barandun; Donat Sch
Abstract
Fibre reinforced composite materials offer superior specific mechanical properties in reference to their weight. In the past years, composite materials such as carbon or glass reinforced plastics (CFRP or GFRP) are used increasingly in all sectors of transportation and for industrial or leisure products. ...
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Fibre reinforced composite materials offer superior specific mechanical properties in reference to their weight. In the past years, composite materials such as carbon or glass reinforced plastics (CFRP or GFRP) are used increasingly in all sectors of transportation and for industrial or leisure products. The composite consists of a load bearing fibre architecture, usually in the form of a continuous fabric architecture, and an embedding matrix, usually a thermoset such as epoxy. With regard to the energy efficiency and carbon footprint, due to their lightweight nature, these composite materials in general offer interesting properties, if applied in long-term operations. However, the raw materials used for the production of both typical fibre materials and thermoset resins are still based on crude oil, and the refining and processing up to the semi-finished good consume a significant amount of embodied energy. In this study, composites made of glass or flax fibres and resin systems based on condensed tannin and furfuryl alcohol, both extracted or derived from plant tissues, were manufactured using vacuum infusion (VI) and resin transfer moulding (RTM) processes. The results show that mechanical properties close to common fiber/resin combinations like glass fiber and epoxy or phenolic resins can be reached by these materials.
Qian Yang; Zhibin Wu; Zhijian Wang; Wei Liu; Jianwen Liu; Chuanqi Feng; Wei Sun; Haimin Zhao; Zaiping Guo
Abstract
Single-phase bi-metal oxides and sulfides have attracted considerable research interest recently for battery application because of their outstanding electrochemical properties, but there are few reports on single-phase bi-metal hydroxides in battery research. Herein, we pioneer the electrochemical study ...
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Single-phase bi-metal oxides and sulfides have attracted considerable research interest recently for battery application because of their outstanding electrochemical properties, but there are few reports on single-phase bi-metal hydroxides in battery research. Herein, we pioneer the electrochemical study of ZnSn(OH)6 nanocubes for lithium-ion battery application. The ZnSn(OH)6 nanocubes, synthesized by a facile hydrothermal method, can deliver a favorable specific discharge capacity of 599.3 mA h g -1 at 500 mA g -1 after 200 cycles and maintain good rate capability even at 2 A g -1 . The excellent electrochemical performance of these ZnSn(OH)6 nanocubes can be attributed to the synergetic Li storage capability of Zn and Sn elements with diverse electrochemical reactions, the small uniform nanocubes (30−50 nm) that alleviate the pulverization and cracking of the electrode and shorten electron/ion transport paths, and the good mechanical properties of ZnSn(OH)6, which facilitate maintenance of the structural integrity of the electrode during the Li + extraction/insertion process. Therefore, with these outstanding advantages, the ZnSn(OH)6 nanocubes could be one of the most promising anodes for advanced lithium-ion batteries.
Masatoshi Shioya; Takashi Kajikawa; Kuniaki Takahashi; Yoshiki Sugimoto
Abstract
Development of carbon fibers from alternative precursory materials through new production processes is a recent topic of active research. In such a research, the maximum available tensile strength, i. e. the tensile strength which will be achieved after elaboration to suppress defect formation during ...
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Development of carbon fibers from alternative precursory materials through new production processes is a recent topic of active research. In such a research, the maximum available tensile strength, i. e. the tensile strength which will be achieved after elaboration to suppress defect formation during production process, is the matter of great concern. We have developed a method for determining this strength through the tensile test on a single fiber after introducing an artificial notch. In the present paper, this method has been refined. By using the refined method, the distribution of the maximum available tensile strength at various radial positions has been measured for a polyacrylonitrile-based carbon fiber. The difference between the maximum available tensile strength and the strength predicted using other methods such as those based on the fracture toughness and the fiber-length dependence of the tensile strength has also been discussed.
Min Zhang; Yulan Zhou; Qin Xue; Jihong Li
Abstract
A dendritic growth model is established by combining the physical properties of dendritic growth with the characteristics of the cellular automaton (CA) method. The heat process and the molten pool model of the arc-shaped in the process of welding solidification are coupled by using the interpolation ...
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A dendritic growth model is established by combining the physical properties of dendritic growth with the characteristics of the cellular automaton (CA) method. The heat process and the molten pool model of the arc-shaped in the process of welding solidification are coupled by using the interpolation method. On the basis of that, the growth of dendrites in the molten pool for Ti-6%Al and Ti-45%Al alloys is simulated and the influence of aluminium content on the morphology of dendrites in the welding solidification process is analysed. And also the microstructural evolution of the molten pool during the solidification process is implemented under the condition of the non-uniform temperature field. The results indicate that the temperature presents the gradual distribution in the non-uniform temperature field and the microstructure grows competitively at the center of the molten pool. During the progress of solidification, the solute atoms are enriched in between dendrite arms with the segregation of solute. Simultaneously, with the change of temperature field, the morphology of dendrites has asymmetry. In addition, the columnar crystals are largely converted to equiaxed crystals for Ti-6%Al alloy while the result is the opposite for Ti-45%Al alloy resulting from the change of the aluminium content. The simulated results are in good agreement with the experimental ones.
Giordano T. Paganoto; Josimar Ribeiro
Abstract
Ni and Ga elements are inexpensive compared to the Pt. Ni and NiOx have been recognized to have potential applications in ethanol electrooxidation. For these reasons and based on previous results obtained with Ga addition on Pt-based electrocatalysts we have investigated the PtSn/C electrocatalysts modified ...
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Ni and Ga elements are inexpensive compared to the Pt. Ni and NiOx have been recognized to have potential applications in ethanol electrooxidation. For these reasons and based on previous results obtained with Ga addition on Pt-based electrocatalysts we have investigated the PtSn/C electrocatalysts modified with Ni and Ga. The PtSnNiGa/C electrocatalysts were characterized in acidic medium by electrochemical techniques and by physicochemical techniques such as: X-ray diffraction; Energy dispersive X-ray spectroscopy; Transmission electron microscopy. Based on the TEM analyses, the PtSnNiGa/C electrocatalysts show average particle sizes range between 3.6 – 5.5 nm, which is consistent with XRD data. The ethanol oxidation on the PtSnNiGa/C electrocatalysts occurs at lower potentials as compared to the Pt/C. The higher current normalized by Pt mass (2.62 Ag-1Pt), lower susceptibility to poisoning anodic and charge transfer resistance (245 Ω) were obtained for the Pt45Sn22Ni21Ga12/C electrocatalyst.The current normalized by Pt mass: Pt50Sn26Ni12Ga12/C (2.8 Ag -1 Pt); Pt45Sn22Ni21Ga12/C (2.62 Ag -1 Pt); Pt52Sn21Ni18Ga9/C (1.63 Ag -1 Pt) and Pt43Sn23Ni11Ga22/C (1.27 Ag -1 Pt) electrocatalysts are higher compared to binary catalysts with high Pt content. The promotion effect of PtSnNiGa/C to ethanol electrooxidation can be explained by the modification structural of Pt by incorporation of Sn, Ni and/or Ga to the face-centered cubic crystalline of Pt.
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