Photorefractive properties of nanostructured organic materials doped with fullerenes and carbon nanotubes

The phenomenon of a significant increase in the photoinduced changes in refractive index, non-linear refraction, and nonlinear third-order optical susceptibility in organic materials based on polyimides, pyridines, and prolinols upon the introduction of fullerenes and carbon nanotubes (CNTs) into the organic matrix is briefly considered (with emphasis on the dominating effect of CNTs). It is established that the values of these photorefractive parameters determined in said fullerene- and CNT-doped materials using a four-wave-mixing scheme are close to the analogous values in bulk silicon-based materials. The results can be useful in developing thin-film nonlinear filters, thin diffraction gratings for passive data recording, and optically-addressed light modulators, in medical applications, and in display technology (e.g., for creating a three-dimensional medium prototype).     

One dimensional nanostructured materials

The quest for materials with molecular scale properties that can satisfy the demands of the 21st century has led to the development of one dimensional nanostructures, ODNS. Nearly, every class of traditional material has an ODNS counterpart. ODNS has a profound impact in nanoelectronics, nanodevices and systems, nanocomposite materials, alternative energy resources and national security. The interface of nanoscience and technology with biological and therapeutic sciences is expected to radically improve the ability to provide efficient treatments in otherwise impossible situations. Ironically, the huge investment in the past few years across the globe is yet to bring the real benefit of nanotechnology in day to day life. While scientists and engineers are working towards this goal, concerns about the possible harmful effects of the high aspect ratio materials are increasing every day. Following is an effort to assimilate most of the aforementioned aspects including the entire gamut of ODNS, i.e., elements, ceramics, polymers and composites, with a brief discussion on CNT and toxicology. The focus of this article is mainly on the science behind the synthesis and properties of the ODNS rather than the device fabrication. However, a few challenges in the field of device fabrication are mentioned in appropriate contexts. Possible mechanisms of the ODNS evolution from various methods, such as vapor liquid solid (VLS), template based and electrochemically induced growth, have been discussed in detail. Electron microscopy analysis has received special focus in determining the unique structural features. The article concludes by discussing current research related to environment and toxicology effects and current challenges in this rapidly evolving field.     

One-dimensional plastic materials with work-hardening

Summary Acceleration waves in one-dimensional plastic materials are investigated by the theory of singular points. The unloading wave propagates with a constant velocity, while the propagation velocity of the loading wave is less than that of the unloading wave and the velocity depends upon the stress and the work-hardening. The growth and decay of the amplitude of the waves are also analyzed. The unloading wave propagates with a constant amplitude. The amplitude of the loading wave may grow or decay and the choice between the two depends upon the stress, the work-hardening and whether the wave is compressive or expansive. In the case of growth the amplitude tends to infinity in finite time, that is, the blow time, and the acceleration wave coalesces into a shock wave. In the case of decay the amplitude tends to zero as the time tends to infinity. The propagation velocity, the blow time and the blow distance are calculated and plotted against the strain.     

Chemical routes to nanostructured materials

Abstract

Chemical synthesis has been used to fabricate polymerisable nanoparticles. Agglomerate free, well crystallised particles have been obtained by hydrothermal treatment and by using surface modifiers. Polymerisable liquids are used as modifiers to obtain polymerisable particles. Suspensions of these particles were used to carry out dip and spin on coating processes, either for optical applications or for superhard coatings. For optical purposes, a wet coating antireflection technology has been developed. The superhard coatings have been developed for polycarbonate plastic glazing for automobiles. These coatings are employed on top of nanocomposite (Nanomer) hard coatings and are cured by UV polymerisation. They show abrasion resistance of 1.5 haze after 1000 taber abrador cycles, a value which is similar to glass.     

Dissipative properties of nanostructured materials

Results of studies of the effect of the size of micro-and substructure elements (grains, twin domains, etc) on the dissipative properties of materials have been generalized. It has been shown that when the size of the microstructure elements of materials decreases to nanoscale, their dissipative properties change qualitatively. This is due to a change in mechanical energy dissipation mechanism on the transition of material to nanostructured state. The possibility of creating a new class of highly damping hard coatings based on nanostructured materials is discussed. __________ Translated from Problemy Prochnosti, No. 5, pp. 96–104, September–October, 2008.     

Review Stability of nanostructured materials

The different aspects of nanostructured material (NM) stability such as thermal and chemical stability as well as NM behavior under deformation and radiation are characterized and analyzed in detail. Grain growth, phase transitions (including spinodal decomposition), homogenization diffusion processes, relaxation of residual stresses, and behavior of grain boundary and triple junction segregations are discussed in context of the change of nanostructure and properties. Special interest is given to the availability of NMs with ultra-fine grain size and their behavior during annealing as soon as to the possibility of development of nanostructures with high thermal stability. Some unsolved problems are emphasized.     

One-dimensional van der Waals quantum materials

The advent of graphene and other two-dimensional van der Waals materials, with their unique electrical, optical, and thermal properties has resulted in tremendous progress for fundamental science. Recent developments suggest that taking one more step down in dimensionality — from mono-layer atomic sheets to individual atomic chains — can bring exciting prospects in fundamental science and practical applications. The atomic chain is the ultimate limit in material downscaling, a frontier for establishing an entirely new field of one-dimensional quantum materials. Here, we review this emerging area of one-dimensional van der Waals quantum materials and anticipate its future directions. We focus on quantum effects associated with the charge-density-wave condensate, strongly-correlated phenomena, topological phases, and other unique physical characteristics, which are attainable specifically in van der Waals materials of lower dimensionality. Possibilities for engineering the properties of quasi-one-dimensional materials via compositional changes, vacancies, and defects, as well as their potential applications in composites are also discussed.     

Synthesis and processing of nanostructured WC-Co materials

In this study a novel approach, termed the integrated mechanical and thermal activation (IMTA) process, was used to synthesize nanostructured WC-Co powder. As a result of the integration of mechanical and thermal activation, nanostructured WC-Co powder was synthesized below 1000°C, starting from WO₃, CoO and graphite powder mixtures. Furthermore, consolidation of the nanostructured WC-Co powder via high velocity oxy-fuel (HVOF) thermal spraying and solid state sintering was investigated. The results demonstrated the feasibility of converting the nanostructured WC-Co powder to coatings and bulk components, the properties of which are either comparable to or better than that of the conventional coarse-grained counterparts.     

微乳液及其制备纳米材料的研究

本文综述了目前存在的微乳液的制备方法、微观结构模型和形成理论 ,以及它在制备纳米粒子及纳米粒子 -聚合物复合材料方面的研究进展。对微乳液制备纳米材料的实施方法、影响因素及控制机理进行了归纳总结。     

Magneto-optical stokes polarimetry and nanostructured magnetic materials

Stokes parameters fully characterize the polarization state of light in an experimentally accessible manner. Photoelastic modulator (PEM) based Stokes polarimetry offers a very high sensitivity which is particularly suitable for the investigation of the magneto-optical properties of nanostructured magnetic materials. In this paper, we shall describe a robust methodology recently developed by us that utilizes a dual PEM setup. As an example of its application, we report on the magneto-optical characteristics of focused Ga ion beam patterned Fe films. We have investigated Ga ion irradiation of single-layer polycrystalline Fe films deposited on Si3N4 substrates, which allows us to study the effects of ion implantation with minimum added complications. Complemented by structural and other characterization techniques, the absolute measurement of magneto-optical effects through the determination of Stokes parameters has enabled us to effectively separate the various contributions from film thinning due to sputtering, structural modifications and compositional changes caused by Ga incorporation. A comparison is also made between the magneto-optical behavior of patterned thin films and that of anodic aluminum oxide embedded magnetic nanowire arrays.     

Computational materials: Multi-scale modeling and simulation of nanostructured materials

The paper provides details on the current approach to multi-scale modeling and simulation of advanced materials for structural applications. Examples are given that illustrate the suggested approaches to predicting the behavior and influencing the design of nanostructured materials such as high-performance polymers, composites, and nanotube-reinforced polymers. Primary simulation and measurement methods applicable to multi-scale modeling are outlined. Key challenges including verification and validation are highlighted and discussed.     

One-dimensional optical materials of microfibers by electrospinning

Optical microfibers of PMMA were fabricated by electrospinning. The fibers with the diameter ranging from 300 nm to 1000 nm were obtained by electrospinning the solutions such as PMMA/DMF, PMMA/DMF/formic acid and PMMA/formic acid. The morphology and the diameter of the fibers were analyzed by scanning electron microscopy (SEM). Results showed that the sidewalls of the fibers were smooth and the diameters were uniform. The light with the wavelength of 488 nm, 532 nm and 650 nm could be launched into the fibers and guide along them. The simulation and experimental results showed that the fibers exhibited excellent optical properties. This method provided an effective and convenient way to fabricate highly uniform micro/nano scale optical waveguide neither using expensive equipments nor involving complex procedures.     

Review: nanoparticles and nanostructured materials in papermaking

The introduction of nanoparticles (NPs) and nanostructured materials (NSMs) in papermaking originally emerged from the perspective of improving processing operations and reducing material consumption. However, a very broad range of nanomaterials (NMs) can be incorporated into the paper structure and allows creating paper products with novel properties. This review is of interdisciplinary nature, addressing the emerging area of nanotechnology in papermaking focusing on resources, chemical synthesis and processing, colloidal properties, and deposition methods. An overview of different NMs used in papermaking together with their intrinsic properties and a link to possible applications is presented from a chemical point of view. After a brief introduction on NMs classification and papermaking, their role as additives or pigments in the paper structure is described. The different compositions and morphologies of NMs and NSMs are included, based on wood components, inorganic, organic, carbon-based, and composite NPs. In a first approach, nanopaper substrates are made from fibrillary NPs, including cellulose-based or carbon-based NMs. In a second approach, the NPs can be added to a regular wood pulp as nanofillers or used in coating compositions as nanopigments. The most important processing steps for NMs in papermaking are illustrated including the internal filling of fiber lumen, LbL deposition or fiber wall modification, with important advances in the field on the in situ deposition of NPs on the paper fibers. Usually, the manufacture of products with advanced functionality is associated with complex processes and hazardous materials. A key to success is in understanding how the NMs, cellulose matrix, functional additives, and processes all interact to provide the intended paper functionality while reducing materials waste and keeping the processes simple and energy efficient.     

Thermal properties of graphene and nanostructured carbon materials

Recent years have seen a rapid growth of interest by the scientific and engineering communities in the thermal properties of materials. Heat removal has become a crucial issue for continuing progress in the electronic industry, and thermal conduction in low-dimensional structures has revealed truly intriguing features. Carbon allotropes and their derivatives occupy a unique place in terms of their ability to conduct heat. The room-temperature thermal conductivity of carbon materials span an extraordinary large range--of over five orders of magnitude--from the lowest in amorphous carbons to the highest in graphene and carbon nanotubes. Here, I review the thermal properties of carbon materials focusing on recent results for graphene, carbon nanotubes and nanostructured carbon materials with different degrees of disorder. Special attention is given to the unusual size dependence of heat conduction in two-dimensional crystals and, specifically, in graphene. I also describe the prospects of applications of graphene and carbon materials for thermal management of electronics.     

Combustion synthesis: mechanically induced nanostructured materials

Combustion synthesis (CS) is a specific approach for fabrication of a variety of advanced materials through use of self-sustaining chemical reactions. Controlling over the microstructure of the material is a key factor in defining the maturity of a technology. In this work, we demonstrate that under specific conditions, morphology and microstructure of the initial reaction media do not change during the CS process. Thus, one may control the microstructure of CS materials by preparing the desired structure of the initial reaction media. Specifically, using examples from several systems, which include intermetallics (NiAl), ceramics (SiC) and refractory carbides (TiC), we demonstrate that combination of short-term high-energy ball milling and CS allows precise control over the morphology and phase composition of product powders.     

新型纳米结构炭材料的储氢研究

氢能是一种清洁的可再生能源。由于传统的储氢材料和储氢技术达不到氢燃料电池电动车的实用要求,储氢问题已成为氢能应用中最急需解决的关键问题。近年来,各种新型纳米结构炭材料的储氢已成为国际上的一个研究热点,引起了人们的广泛关注。但在这一研究领域中一直存在着许多争议和很大的分歧。通过综述国内外近几年来各种新型纳米结构炭材料如单壁碳纳米管、多壁碳纳米管、石墨纳米纤维以及炭纳米纤维等的储氢研究进展,指出了这一领域中需要解决的问题如储氢测试方法的标准化、纳米结构炭材料的评价以及储氢机制和吸附位的研究等。     

Modification of nanostructured materials for biomedical applications

Adaptation (or incorporation) of nanostructured materials into biomedical devices and systems has been of great interest in recent years. Through the modification of existing nanostructured materials one can control and tailor the properties of such materials in a predictable manner, and impart them with biological properties and functionalities to better suit their integration with biomedical systems. These modified nanostructured materials can bring new and unique capabilities to a variety of biomedical applications ranging from implant engineering and modulated drug delivery, to clinical biosensors and diagnostics. This review describes recent advances of nanostructured materials for biomedical applications. The methods and technologies used to modify nanostructured materials are summarized briefly, while several current interests in biomedical applications for modified and functionalized nanostructured materials are emphasized.     

Nanotopography: cellular responses to nanostructured materials

Several in vitro and in vivo experiments have shown that nanostructured materials, which mimic the nanometer topography of the native tissues, improve biocompatible responses, and result in better tissue integration in medical implants. Understanding various aspects of nanotopography is extremely important for better designs of these devices. In this review paper, recent progress in the fabrication, characterization, biological responses, and application of nanostructured materials are discussed. Specifically, materials such as ceramics and polymers used to manufacture nanostructured surfaces are briefly introduced. Techniques for fabrication and characterization of nanostructured materials are also explored. Cellular responses such as morphology, alignment, adhesion, proliferation, and profiles of gene expression of various cell types after their exposure to nanofeatured materials are particularly reviewed. Finally, the paper briefly discusses some application of nanostructured materials including those in biosensor and tissue engineering fields.     

Volatile organic compound detection using nanostructured copolymers

Regioregular polythiophene-based conductive copolymers with highly crystalline nanostructures are shown to hold considerable promise as the active layer in volatile organic compound (VOC) chemresistor sensors. While the regioregular polythiophene polymer chain provides a charge conduction path, its chemical sensing selectivity and sensitivity can be altered either by incorporating a second polymer to form a block copolymer or by making a random copolymer of polythiophene with different alkyl side chains. The copolymers were exposed to a variety of VOC vapors, and the electrical conductivity of these copolymers increased or decreased depending upon the polymer composition and the specific analytes. Measurements were made at room temperature, and the responses were found to be fast and appeared to be completely reversible. Using various copolymers of polythiophene in a sensor array can provide much better discrimination to various analytes than existing solid state sensors. Our data strongly indicate that several sensing mechanisms are at play simultaneously, and we briefly discuss some of them.