Li ion battery materials with core-shell nanostructures

Nanomaterials have some disadvantages in application as Li ion battery materials, such as low density, poor electronic conductivity and high risk of surface side reactions. In recent years, materials with core-shell nanostructures, which was initially a common concept in semiconductors, have been introduced to the field of Li ion batteries in order to overcome the disadvantages of nanomaterials, and increase their general performances in Li ion batteries. Many efforts have been made to exploit core-shell Li ion battery materials, including cathode materials, such as lithium transition metal oxides with varied core and shell compositions, and lithium transition metal phosphates with carbon shells; and anode materials, such as metals, alloys, Si and transition metal oxides with carbon shells. More recently, graphene has also been proposed as a shell material. All these core-shell nanostructured materials presented enhanced electrochemical capacity and cyclic stability. In this review, we summarize the preparation, electrochemical performances, and structural stability of core-shell nanostructured materials for lithium ion batteries, and we also discuss the problems and prospects of this kind of materials.     

多铁性氧化物基磁电材料的制备及性能

多铁性材料由于其不但具有单一的铁性(如铁电性、铁磁性和铁弹性),而且由于铁性的耦合协同作用,会产生一些新的效应,使其可广泛应用于换能器、传感器、敏感器、多态存储等高技术领域。而氧化物基单相/复相陶瓷及其薄膜材料(如BiFeO_3,铁氧体/锆钛酸铅等),由于其良好的铁磁、铁电性能,正成为磁电材料的研究热点。本文综合介绍了几种单相、复合磁电陶瓷、薄膜材料的制备,论述了材料的显微结构与磁电性能之间的关联,并指出了该类材料存在的问题和今后的发展方向。单相磁电材料至今还没能应用到实际中,主要是因为大部分单相材料的Neel或Curie温度较低,在很低的温度下才有磁电效应,磁也转换系数随着温度升高到室温而趋于零。具有低漏导的BiFeO_3薄膜(具有高的Curie温度)将具有铁电应用,但作为多铁性应用,还需解决弱的磁电耦合性。虽然复合磁电材料性能比单相材料性能好,但是仍然存在一些问题。磁电多铁性材料具有潜在的巨大的商业应用前景,已使其成为新的研究热点。     

Multi-scale theoretical investigation of hydrogen storage in covalent organic frameworks

The quest for efficient hydrogen storage materials has been the limiting step towards the commercialization of hydrogen as an energy carrier and has attracted a lot of attention from the scientific community. Sophisticated multi-scale theoretical techniques have been considered as a valuable tool for the prediction of materials storage properties. Such techniques have also been used for the investigation of hydrogen storage in a novel category of porous materials known as Covalent Organic Frameworks (COFs). These framework materials are consisted of light elements and are characterized by exceptional physicochemical properties such as large surface areas and pore volumes. Combinations of ab initio, Molecular Dynamics (MD) and Grand Canonical Monte-Carlo (GCMC) calculations have been performed to investigate the hydrogen adsorption in these ultra-light materials. The purpose of the present review is to summarize the theoretical hydrogen storage studies that have been published after the discovery of COFs. Experimental and theoretical studies have proven that COFs have comparable or better hydrogen storage abilities than other competitive materials such as MOF. The key factors that can lead to the improvement of the hydrogen storage properties of COFs are highlighted, accompanied with some recently presented theoretical multi-scale studies concerning these factors.     

Versatility of photoalignment techniques: From nematics to a wide range of functional materials

Alignment methods of nematic liquid crystals (LCs) by surface photoreactions on substrate surfaces were initially proposed around 1990, and the photoalignment technology of nematic LCs has recently been integrated into the LC device fabrication industry due to its profitable features. Accumulated efforts in this field have revealed that applications of photoalignment processes are not limited to conventional nematic LCs but that a variety of functional materials can also be manipulated according to this principle. Target materials have now been extended to thermotropic smectic LCs, discotic LCs, LC polymers, block copolymers, gel networks, conjugated polymers, and organic semiconductors and lyotropic systems including chromonic LCs and inorganic–organic mesostructured hybrids. Through these photochemical approaches, many types of photopatterning for both topographical and orientational modulations have become feasible. This article reviews photoalignment processes applied to a wide range of materials, surveying relatively recent work. Some important related alignment and patterning processes are also introduced to clarify the significance of these photoalignment techniques.     

Elastic Modulus-Porosity Relation in Polycrystalline Rare-Earth Oxides

Many equations have been previously proposed to describe the elastic modulus-porosity relation of brittle solids. The equations arc not applicable to all materials over a wide range of porosity. A new equation representing elastic modulus-porosity relation of brittle solids has been proposed. It has been shown that the proposed equation describes best the Young's modulus-porosity data of six rare-earth oxides over a wide range of porosity reported by previous investigators. The equation suggests that there was some kind of ordered packing in all the oxides.     

Electric Fatigue of Lead‐Free Piezoelectric Materials

A considerable body of knowledge now exists from studies involving the development of lead‐free piezoelectric ceramics and a number of high potential alternatives to current lead‐based materials have been identified. Stability under cyclic electric fields is an important property of piezoelectric materials. Here, we review the research to date which shows that fatigue under cyclic electrical loading is prevalent in many lead‐free piezoelectric ceramic compositions. However, the variety of compositions and mechanisms for piezoelectric behavior in these materials corresponds to significant variances in the nature of fatigue degradation and the likely mechanisms thereof, which do not directly parallel those of well‐studied lead‐based materials. In particular, the use of field‐induced phase changes as an actuation mechanism provides distinctive fatigue behaviors. Particular attention is given to fatigue of ferroelectric and relaxor (ergodic and nonergodic) structures and their dependence upon temperature and electric field and the potential design of materials with high fatigue resistance.     

Mechanochemical remodeling of synthetic polymers

In the past five years, the field of covalent polymer mechanochemistry has experienced a renaissance. Once limited to the simple scission of polymer chains, mechanical force can now be used to produce a wide array of productive chemistry. These outcomes have both challenged and supported classically held views of chemical reactivity. The impact of these findings has relevance in both synthetic chemistry and material science. Here, we review our efforts to exploit mechanochemical coupling to produce constructive and stress-responsive covalent chemistry in polymer materials.     

不同形貌金属氧化物的制备及其在工业催化反应中的应用

金属氧化物作为一类重要工业催化剂,广泛应用于合成氨工业、能源化工、精细化工等重要的工业生产过程。金属氧化物的形貌对其性能有重要的影响,具有特定形貌的金属氧化物催化剂因其结构上的优势,使其在许多方面表现出不同于常规块体材料的独特性能,成为当前材料科学领域的研究热点。本文总结了不同形貌的金属氧化物的制备方法、生长机制及其结构特性,聚焦于金属氧化物在氧化反应、加氢反应以及蒸汽重整反应中的最新研究进展。最后,进一步讨论了金属氧化物催化剂未来的发展趋势以及面临的挑战,并提出了解决这些问题的有效方案。     

静电纺丝纳米纤维在吸波材料中的应用

随着电子设备的迅速普及，电磁干扰和电磁污染问题随之而来，因此，高性能电磁波吸收材料的设计迫在眉睫。静电纺丝纳米纤维复合材料具有质量轻、柔性大、易加工、兼容性强等优势，有望实现吸波材料“薄、轻、宽、强”的技术要求。该文首先介绍了电磁波吸收材料的吸波原理，之后综述了静电纺丝技术在吸波材料中的研究进展，包括静电纺丝纳米纤维与金属及其氧化物、碳纳米材料与导电聚合物、过渡金属碳化物的复合以及在多层吸波材料中的应用，总结了不同种类复合材料的优缺点。最后，展望了静电纺丝纳米纤维在吸波领域的发展趋势以及应该关注的问题。     

From Zr-Rich to Ce-Rich: Thermal Stability of OSC Materials on the Whole Range of Composition

Car manufacturers use close coupled three way catalysts to reduce cold start emissions. These close coupled catalysts must show long term durability and thermal stability at temperatures higher than 1000 °C. Thus, during the past 10 years, a significant amount of attention has been paid to the design of CeO₂-ZrO₂ OSC materials with improved surface area, phase and OSC stability. Solid solutions of Ce/Zr mixed oxides are now commonly available on industrial scale. Recent studies have demonstrated that the introduction of rare earth oxides promoters such as La, Pr, Nd, Y, Sm [ENGELHARD WO patent o2 30546; OMG-DMC² EP Patent 1 181 970; DAIHATSU EP Patent 1 174 174; DELPHI US Patent 6 387 338; ENGELHARD WO Patent 02 22242] or aluminium oxide [TOYOTA EP Patent 1 172 139; Kanzawa et al. SAE Technical Paper 2003-01-0811] in the Ce/Zr matrix is a very good way to improve the thermal stability and the redox properties of these materials. Positive interactions between PGM and these 'promoters' are also claimed. Nevertheless, not only the composition but the optimization of the manufacturing processes is a key factor to obtain both high thermal stability (expressed as surface area and XRD phase purity) and OSC. To meet the increasingly stringent emission limits, Rhodia has developed a new generation of CeZr based mixed oxides. These materials show phase stability and thermal stability at temperatures higher than 1100 °C in a wide composition range: from Zr-rich to Ce-rich mixed oxides. These characteristics have been obtained with a new manufacturing process which leads to highly porous materials. The controlled morphology at microscopic and macroscopic scale prevents particle sintering under severe ageing conditions. Such materials are preferred PGM supports for cost effective catalysts with low PGM loading     

高熵氧化物的制备及应用研究进展

高熵氧化物作为近几年发展起来的新型氧化物体系,打破了传统掺杂氧化物的设计理念,由五种及以上氧化物以等摩尔或近等摩尔构成,因其具有简单的结构和优异的性能等受到国内外研究人员的广泛关注。高熵氧化物由于多主元且主元之间混乱排列,易形成岩盐型、氟化钙型、尖晶石型或钙钛矿等固溶体结构,从而表现出优异的性能,尤其在能源存储材料和磁性材料方面有十分广阔的应用前景,但目前对高熵氧化物应用研究较少。本工作介绍了国内外高熵氧化物的制备方法,主要包括固相法、热解法、共沉淀法、水热合成法和液相燃烧合成法等,比较了各方法的优缺点和发展前景;归纳了高熵氧化物作为锂离子电极材料、巨介电材料、磁性材料和催化材料等方面的应用;指出了高熵氧化物目前研究存在的问题,讨论了解决措施,展望了高熵氧化物未来的发展趋势。     

Deformation kinetics of pH‐sensitive hydrogels

Polymeric gels can undergo large deformation when subjected to external solutions of varying pH. It is imperative to understand the deformation process of pH‐sensitive hydrogels for the effective application of these attractive materials in the biomedical and microfluidic fields. In the modeling of these multi‐phase materials, finite element (FE) modeling is a useful tool for the development of future applications, and it allows developers to test a wide variety of material responses in a cost‐effective and efficient manner, reducing the need to conduct extensive laboratory experiments. Although a FE user‐defined material model is available for the equilibrium state, the transient response of pH‐sensitive gels has not been effectively modeled. Based on our recent work using the heat transfer analogy to tap into the readily available coupled temperature–displacement elements available in the commercial FE software ABAQUS for simulation of the transient swelling process of neutral hydrogels, the transient swelling process of a pH‐sensitive hydrogel is studied and a FE model is further developed to simulate the transient phenomena. Some benchmark examples are investigated to demonstrate the model's capabilities in the simulation of nonlinear deformation kinetics relevant to several applications of pH‐sensitive hydrogels. © 2013 Society of Chemical Industry     

Multimaterial Fibers

Recent progress in combining multiple materials with disparate optical, electronic, and thermomechanical properties monolithically in the same fiber drawn from a preform is paving the way to a new generation of multimaterial fibers endowed with unique functionalities delivered at optical fiber length scales and costs. A wide range of unique devices have been developed to date in fiber form-factor using this strategy, such as transversely emitting fiber lasers, fibers that detect light, heat, or sound impinging on their external surfaces, and fibers containing crystalline semiconductor cores. Incorporating such fibers in future fabrics will lead to textiles with sophisticated functionality. Additionally, long-standing issues in traditional applications of optical fibers have been addressed by multimaterial fibers, such as photonic bandgap guidance in hollow-core all-solid-cladding fibers and imparting mechanical robustness to soft-glass mid-infrared fibers. We review recent progress in this nascent but rapidly growing field and highlight areas where growth is anticipated. Furthermore, the insights emerging from this research are pointing to new ways that the fiber drawing process itself may be leveraged as a fabrication methodology. In particular, we describe recent efforts directed at appropriating multimaterial-fiber drawing for chemical synthesis and the fabrication of nanostructures such as nanowire arrays and structured nanoparticles.     

$$\pi$$-Conjugated Heterocyclic fused Bithiophene Materials

This article covers the developments on the synthesis and properties of heterocyclic fused π-conjugated bithiophene materials that are potentially applicable in molecular electronics and optoelectronics. This fairly young strategy to efficiently tuning the electronic properties generates materials with very narrow band gaps. The nature of the central bridging heteroatom has a significant impact on the electronic and luminescence properties of these materials leading to intriguing species that can be employed in organic light emitting diodes (OLEDs) or organic field effect transistors (OFETs). So far a variety of heteroelements of group 13–16 (B, Si, Ge, Sn, N, P, S) have been investigated and incorporated into molecular as well as polymeric systems. A significant number of these materials can potentially act as organic emitters, electron or hole transport materials in organic devices but further studies are needed to optimize the necessary properties for the utility of this young class of compound in molecular electronics.     

Ceramic microspheres to improve anticorrosive performance of phosphate paints

Zinc phosphate and related compounds have been proposed as “green” replacements for traditional anticorrosive pigments such as zinc chromate and lead oxides. However, environmental concerns have risen in the last years because the disposal of these materials in the environment increased phosphate levels in water and produce eutrophication of water bodies. The present paper deals with the possible incorporation of ceramic microspheres in alkyd paints in order to diminish phosphate content. The results suggested that paints with low phosphate content can be successfully formulated with a suitable selection of the amount and type of microspheres.     

Past and Future Solid-State NMR Spectroscopy Studies at the Convergence Point between Biology and Materials Research

Many cellular events involve attachment of proteins to the surfaces of rigid or semi-rigid solid materials, such as the inorganic materials in the extracellular matrix of hard tissue, and the macromolecular scaffolds made of actin and tubulin filaments in the cytoskeleton. Understanding these processes on a fundamental level will have far-reaching repercussions for the design of biomaterials, biomedical research, and biomineralization. Numerous studies have reported structural changes experienced by proteins as they adhere to surfaces, yet there are only a few examples in which detailed views of protein conformation and alignment on surfaces were measured. Modern multidimensional solid-state NMR spectroscopy is timely situated to unveil molecular details of these processes and shed light on many fundamental questions related to recognition of surfaces by biomolecules. Targeting these questions is currently at the focal point of many research fields and can lead to insights and breakthroughs in biotechnology and in biomimetic material design.     

Energy efficiency optimization strategies for greenhouse-based crop cultivation: A review

Worldwide, food scarcity is becoming a debatable concern among the scientific fraternity due to the increased populace, leading to decreased arable land. This has compelled us to explore various innovative and technological solutions, for example, large-scale greenhouse farming, to meet the surging demand for field production. In this context, research efforts have been continually made by various scientists and researchers to explore more control strategies/algorithms for keeping the indoor climate comfortable and enhancing the greenhouse's energy effectiveness. Considering this, an initiative was made to summarize the documented research findings in the last decade focusing on energy-efficient greenhouse-based crop cultivation. The findings of some studies considering selective parametric conditions have been presented in graphs/tables for reader clarity and discussion. Initially, the studies on existing energy efficient strategies, parameters, monitoring systems, sensing networks, and control algorithms have been discussed. A state of the art review found that control strategies are essential in low-energy greenhouses since they influence crop yield and cost. It was observed that advanced control algorithms and energy conservation in greenhouses received more attention due to wide spread application, high compatibility, low-cost, and user-friendly operations. In terms of future perspectives, it is anticipated that the development of machine learning, big data, and artificial intelligence, combining these technologies with traditional and advanced control strategies would lead to a revolution in the management of greenhouse energy.     

Advances in Inorganic and Hybrid Ion Exchangers

Ion-exchange materials have been used in industrial applications for well over one hundred years. Since the introduction of polymer based ion exchangers more than seventy years ago, the use of these materials has grown and has dominated the commercial market for more than half a century. Inorganic and hybrid inorganic/organic materials continue to garner attention due to their chemical and radiation stability and effectiveness over wide range of conditions. Driving these research efforts is the desire to improve the selectivity and increase the capacity of the ion-exchanger for a particular application. This article presents a review of the literature detailing the syntheses, characterization, and ion-exchange performance of inorganic and hybrid ion-exchange materials.     

Antiferroelectrics: History,fundamentals, crystal chemistry,crystal structures,size effects,and applications

Antiferroelectric (AFE) materials are of great interest owing to their scientific richness and their utility in high-energy density capacitors. Here, the history of AFEs is reviewed, and the characteristics of antiferroelectricity and the phase transition of an AFE material are described. AFEs are energetically close to ferroelectric (FE) phases, and thus both the electric field strength and applied stress (pressure) influence the nature of the transition. With the comparable energetics between the AFE and FE phases, there can be a competition and frustration of these phases, and either incommensurate and/or a glassy (relaxor) structures may be observed. The phase transition in AFEs can also be influenced by the crystal/grain size, particularly at nanometric dimensions, and may be tuned through the formation of solid solutions. There have been extensive studies on the perovskite family of AFE materials, but many other crystal structures host AFE behavior, such as CuBiP₂Se₆. AFE applications include DC-link capacitors for power electronics, defibrillator capacitors, pulse power devices, and electromechanical actuators. The paper concludes with a perspective on the future needs and opportunities with respect to discovery, science, and applications of AFE.     

Copper and silver nanocrystals in lustre lead glazes: Development and optical properties

In the early 9th century AD ancient potters of Iraq discovered that after firing some copper oxides and silver salts with clay, iron oxides and some sulphur compounds applied on a ceramic glaze produced a beautiful layer with a wide range of colours, from reddish to yellowish or even greenish, and some with a characteristic metallic copper or purplish shine. Modern studies of these layers showed that they are formed by nanocrystals of copper and silver embedded in a glass matrix. Some attempts have been performed to understand ancient lustre coloration and characteristic gloss but have failed to give a clear correlation between chemical composition and colour, and generally make some assumptions on the shape and the size of the nanoparticles and the lustre nanostructure. The aim of this paper is to establish a basis for understanding lustre nanostructure linked to its optical properties from a sequence of lustre reproductions on traditional lead glazed tiles. These modern lustre decorations have been studied by means of optical microscopy, transmission electron microscopy and electron energy loss spectroscopy, UV–vis spectroscopy, low irradiation angle X-ray diffraction, synchrotron radiation X-ray diffraction and electron microprobe analysis. These results show that changes in the lustre nanostructure affect the glaze colour and shine during the lustre formation process. Lustre nanostructure showed crystal size range as a function of depth, that subsequently disappeared followed by an increase of nanoparticles mean diameter and reduction of the interparticle distances. Consequently, the dipole plasmon coupling between copper nanoparticles appeared, and seems to be responsible for the metallic shine and copper metal like coloration of the copper lustre. However, colour from the glaze surface differs when calculated for diffuse or reflected light. Diffuse coloration appears strongly affected by the copper nanocrystals, while specular coloration is not only affected by copper but also by the presence of an inhomogeneous distribution of silver nanocrystals which gives the lustre a characteristic purplish shine.