Glass/carbon fibre hybrid composite laminates for structural applications in automotive vehicles

Light-weight structure is one of the keys to improve the fuel efficiency and reduce the environmental buden of transport vehicles (automotive and rail). While fibreglass composites have been increasingly used to replace steel in automotive industry, the adoption rate for carbon fibre composites which are much lighter, stronger and stiffere than glass fibre composites, remains low. The main reason is the high cost of carbon fibres. To further reduce vehicle weight without excessive cost increase, one technique is to incorporate carbon fibre reinforcement into glass fibre composites and innovative design by selectively reinforcing along the main load path. Glass/carbon woven fabrics with epoxy resin matrix were utilised for preparing hybrid composite laminates. The in-plane mechanical properties such as tensile and three-point-bending flexural properties were investigated for laminates with different carbon fibre volume and lay-up scheme. It is shown that hybrid composite laminates with 50% carbon fibre reinforcement provide the best flexural properties when the carbon layers are at the exterior, while the alternating carbon/glass lay-up provides the highest compressive strength.

Nanostructured hybrid films containing nanophosphor: Fabrication and electronic spectral properties

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Montmorillonite (MMT) effect on the structure of poly(oxyethylene) (PEO)-MMT nanocomposites and silica-PEO-MMT hybrid materials

In this work we report the effects of incorporation of variable amounts (0.5-25%w/w) of montmorillonite in poly(oxyethylene) based materials in order to decrease the polymer crystallinity. Two different classes of materials were studied: silica-poly(oxyethylene)-montmorillonite hybrids prepared by the sol-gel route and poly(oxyethylene)-montmorillonite nanocomposites prepared by mixing the dry clay or the clay aqueous suspension into the melt poly(oxyethylene). The effects of monternorillonite loading on the poly(oxyethylene) crystallization control and on the nanostructural features were investigated by X-ray powder diffraction, small-angle X-ray scattering and differential scanning calorimetry. Experimental results show that free montmorillonite layers coexist with open aggregates and tactoids in the poly(oxyethylene)-montmorillonite nanocomposites, with different features depending on the filler proportion and preparation route. The intercalation of polymer chains in montmorillonite galleries markedly hinders the crystallization of the poly(oxyethylene) matrix. For hybrids materials the silica phase favors the exfoliation of montmorillonite tactoids, so that samples are predominantly constituted by dispersed platelets. (c) 2006 Elsevier B.V. All rights reserved.

Hybrid reflections in InGaP/GaAs(001) by synchrotron radiation multiple diffraction

Hybrid reflections (HRs) involving substrate and layer planes (SL type) [Morelhao et al., Appl. Phys. Len. 73 (15), 2194 (1998)] observed in Chemical Beam Epitaxy (CBE) grown InGaP/GaAs(001) structures were used as a three-dimensional probe to analyze structural properties of epitaxial layers. A set of (002) rocking curves (omega-scan) measured for each 15 degrees in the azimuthal plane was arranged in a pole diagram in phi for two samples with different layer thicknesses (#A -58 nm and #B - 370 nm) and this allowed us to infer the azimuthal epilayer homogeneity in both samples. Also, it was shown the occurrence of (1 (1) over bar3) HR detected even in the thinner layer sample. Mappings of the HR diffraction condition (omega:phi) allowed to observe the crystal truncation rod through the elongation of HR shape along the substrate secondary reflection streak which can indicate in-plane match of layer/substrate lattice parameters. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

A review on the development and properties of continuous fiber/epoxy/aluminum hybrid composites for aircraft structures

Weight reduction and improved damage tolerance characteristics were the prime drivers to develop new family of materials for the aerospace/ aeronautical industry. Aiming this objective, a new lightweight Fiber/ Metal Laminate (FML) has been developed. The combination of metal and polymer composite laminates can create a synergistic effect on many properties. The mechanical properties of FML shows improvements over the properties of both aluminum alloys and composite materials individually. Due to their excellent properties, FML are being used as fuselage skin structures of the next generation commercial aircrafts. One of the advantages of FML when compared with conventional carbon fiber/epoxy composites is the low moisture absorption. The moisture absorption in FML composites is slower when compared with polymer composites, even under the relatively harsh conditions, due to the barrier of the aluminum outer layers. Due to this favorable atmosphere, recently big companies such as EMBRAER, Aerospatiale, Boing, Airbus, and so one, starting to work with this kind of materials as an alternative to save money and to guarantee the security of their aircrafts.

Analysis of curaua/glass hybrid interlayer laminates

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Hybrid Materials Based on Smectite Clays and Nutraceutical Anthocyanins from the Acai Fruit

Hybrid materials were prepared by combining clay mineral (montmorillonite SWy-2 and saponite SapCa-1) and dyes extracted from the acai (Euterpe oleracea Mart.) fruit, which contains mainly anthocyanins from the 3-glucoside class, to increase the stability of the dye and facilitate its handling and storage. Clay minerals are common ingredients in therapeutic and pharmaceutical products and acai phytochemicals show disease prevention properties. The extract of the acai fruit was mixed with water suspensions of layered silicates in different proportions. The dyeclay hybrids presented incorporated organic material in amounts up to 24 wt.-%. X ray diffractometry and vibrational (FTIR and Raman) and electronic spectroscopic data showed that flavylium cations were successfully intercalated between the inorganic layers. Mass-coupled thermogravimetric analysis (TGA-MS) data showed a significant gain in the thermostability of the organic species in relation to anthocyanins in the extract. MS curves related to CO2 release (m/z = 44) are ascendant above 200 degrees C when the dye cations are confined to the inorganic structure. The radical scavenging activity of the hybrid materials was monitored by electron paramagnetic resonance (EPR) toward the stable radical DPPH (1,1-diphenyl-2-picrylhydrazyl) and compared to the activity of the acai extract. In addition to the fact that interaction with clay minerals improves the stability of the acai dyes against heat, their properties as radical scavengers are preserved after intercalation. The improvement in the properties of the nutraceutical species by intercalation by using biocompatible inorganic structures can be valuable for human therapy.

Liquid crystal polymer brushes and their application as alignment layers in liquid crystal cells

Liquid Crystal Polymer Brushes and their Application as Alignment Layers in Liquid Crystal Cells Polymer brushes with liquid crystalline (LC) side chains were synthesized on planar glass substrates and their nematic textures were investigated. The LC polymers consist of an acrylate or a methacrylate main chain and a phenyl benzoate group as the mesogenic unit which is connected to the main chain via a flexible alkyl spacer composed of six CH2 units. The preparation of the LC polymer brushes was carried out according to the “grafting from” technique: polymerization is carried out from azo-initiators that have been previously self-assembled on the substrate. LC polymer brushes with a thickness from a few nm to 230 nm were synthesized by varying the monomer concentration and the polymerization time. The LC polymer brushes were thick enough to allow for direct observation of the nematic textures with a polarizing microscope. The LC polymer brushes grown on untreated glass substrates exhibited irregular textures (“polydomains”). The domain size is in the range of some micrometers and depends only weakly on the brush thickness. The investigations on the texture-temperature relationship of the LC brushes revealed that the brushes exhibit a surface memory effect, that is, the identical texture reappears after the LC brush sample has experienced a thermal isotropization or a solvent treatment, at which the nematic LC state has been completely destroyed. The surface memory effect is attributed to a strong anchoring of the orientation of the mesogenic units to heterogeneities at the substrate surface. The exact nature of the surface heterogeneities is unknown. The effect was observed for the LC brushes swollen with low molecular weight nematic molecules, as well. Rubbing the glass substrate with a piece of velvet cloth prior to the surface modification with the initiator and the brush growth gives rise to the formation of homogenous alignment of the mesogenic units in the LC polymer side chains. Monodomain textures were obtained for these LC brushes. The mechanism for the homogeneous alignment is based on the transfer of Nylon fibers during the rubbing process. A surfactant was mixed with the azo-initiator in modifying rubbed substrates for subsequent brush generation. Such brushes exhibited biaxial optical properties. Hybrid LC cells made from a substrate modified with biaxial brushes and a rubbed glass substrate show an orientation with a tilt angle of a = –15.6 . This work shows that LC brushes grown on rubbed surfaces fulfill the important criteria for alignment layers: the formation of macroscopic monodomains. First results indicate that by diluting the brush with molecules which are also covalently bound to the surface but induce a different orientation, a system is obtained in which the two conflicting alignment mechanisms can be used to generate a tilted alignment. In order to allow for an application of the alignment layers into a potential product, subsequent work should focus on the questions how easy and in which range the tilt angle can be controlled.

Inorganic-organic hybrid polymers: Solution-processible coating materials for defined surface functionalization

A new class of inorganic-organic hybrid polymers could successfully been prepared by the combination of different polymerization techniques. The access to a broad range of organic polymers incorporated into the hybrid polymer was realized using two independent approaches.rnIn the first approach a functional poly(silsesquioxane) (PSSQ) network was pre-formed, which was capable to initiate a controlled radical polymerization to graft organic vinyl-type monomers from the PSSQ precursor. As controlled radical polymerization techniques atom transfer radical polymerization (ATRP), as well as reversible addition fragmentation chain transfer (RAFT) polymerization could be used after defined tuning of the PSSQ precursor either toward a PSSQ macro-initiator or to a PSSQ macro-chain-transfer-agent. The polymerization pathway, consisting of polycondensation of trialkoxy-silanes followed by grafting-from polymerization of different monomers, allowed synthesis of various functional hybrid polymers. A controlled synthesis of the PSSQ precursors could successfully be performed using a microreactor setup; the molecular weight could be adjusted easily while the polydispersity index could be decreased well below 2.rnThe second approach aimed to incorporate differently derived organic polymers. As examples, polycarbonate and poly(ethylene glycol) were end-group-modified using trialkoxysilanes. After end-group-functionalization these organic polymers could be incorporated into a PSSQ network.rnThese different hybrid polymers showed extraordinary coating abilities. All polymers could be processed from solution by spin-coating or dip-coating. The high amount of reactive silanol moieties in the PSSQ part could be cross-linked after application by annealing at 130° for 1h. Not only cross-linking of the whole film was achieved, which resulted in mechanical interlocking with the substrate, also chemical bonds to metal or metal oxide surfaces were formed. All coating materials showed high stability and adhesion onto various underlying materials, reaching from metals (like steel or gold) and metal oxides (like glass) to plastics (like polycarbonate or polytetrafluoroethylene).rnAs the material and the synthetic pathway were very tolerant toward different functionalities, various functional monomers could be incorporated in the final coating material. The incorporation of N-isopropylacrylamide yielded in temperature-responsive surface coatings, whereas the incorporation of redox-active monomers allowed the preparation of semi-conductive coatings, capable to produce smooth hole-injection layers on transparent conductive electrodes used in optoelectronic devices.rnThe range of possible applications could be increased tremendously by incorporation of reactive monomers, capable to undergo fast and quantitative conversions by polymer-analogous reactions. For example, grafting active esters from a PSSQ precursor yielded a reactive surface coating after application onto numerous substrates. Just by dipping the coated substrate into a solution of a functionalized amine, the desired function could be immobilized at the interface as well as throughout the whole film. The obtained reactive surface coatings could be used as basis for different functional coatings for various applications. The conversion with specifically tuned amines yielded in surfaces with adjustable wetting behaviors, switchable wetting behaviors or as recognition element for surface-oriented bio-analytical devices. The combination of hybrid materials with orthogonal reactivities allowed for the first time the preparation of multi-reactive surfaces which could be functionalized sequentially with defined fractions of different groups at the interface. rnThe introduced concept to synthesis functional hybrid polymers unifies the main requirements on an ideal coating material. Strong adhesion on a wide range of underlying materials was achieved by secondary condensation of the PSSQ part, whereas the organic part allowed incorporation of various functionalities. Thus, a flexible platform to create functional and reactive surface coatings was achieved, which could be applied to different substrates. rn

Quantum dot-dye hybrid systems for energy transfer applications

In this thesis, we focus on the preparation of energy transfer-based quantum dot (QD)-dye hybrid systems. Two kinds of QD-dye hybrid systems have been successfully synthesized: QD-silica-dye and QD-dye hybrid systems.rn rnIn the QD-silica-dye hybrid system, multishell CdSe/CdS/ZnS QDs were adsorbed onto monodisperse Stöber silica particles with an outer silica shell of thickness 2 - 24 nm containing organic dye molecules (Texas Red). The thickness of this dye layer has a strong effect on the total sensitized acceptor emission, which is explained by the increase in the number of dye molecules homogeneously distributed within the silica shell, in combination with an enhanced surface adsorption of QDs with increasing dye amount. Our conclusions were underlined by comparison of the experimental results with Monte-Carlo simulations, and by control experiments confirming attractive interactions between QDs and Texas Red freely dissolved in solution. rnrnNew QD-dye hybrid system consisting of multishell QDs and organic perylene dyes have been synthesized. We developed a versatile approach to assemble extraordinarily stable QD-dye hybrids, which uses dicarboxylate anchors to bind rylene dyes to QD. This system yields a good basis to study the energy transfer between QD and dye because of its simple and compact design: there is no third kind of molecule linking QD and dye; no spacer; and the affinity of the functional group to the QD surface is strong. The FRET signal was measured for these complexes as a function of both dye to QD ratio and center-to-center distance between QD and dye by controlling number of covered ZnS layers. Data showed that fluorescence resonance energy transfer (FRET) was the dominant mechanism of the energy transfer in our QD-dye hybrid system. FRET efficiency can be controlled by not only adjusting the number of dyes on the QD surface or the QD to dye distance, but also properly choosing different dye and QD components. Due to the strong stability, our QD-dye complexes can also be easily transferred into water. Our approach can apply to not only dye molecules but also other organic molecules. As an example, the QDs have been complexed with calixarene molecules and the QD-calixarene complexes also have potential for QD-based energy transfer study. rn

Aggregation of hybrid molecules and film formation of colloidal monolayers

A unique characteristic of soft matter is its ability to self-assemble into larger structures. Characterizing these structures is crucial for their applications. In the first part of this work, I investigated DNA-organic hybrid material by means of Fluorescence Correlation Spectroscopy (FCS) and Fluorescence Cross-Correlation Spectroscopy (FCCS). DNA-organic hybrid materials, a novel class of hybrid materials composed of synthetic macromolecules and oligodeoxynucleotide segmenta, are mostly amphiphilic and can self-assemble into supramolecular structures in aqueous solution. A hybrid material of a fluorophore, perylenediimide (PDI), and a DNA segment (DNA-PDI) has been developed in Prof. A. Hermann’s group (University of Groningen). This novel material has the ability to form aggregates through pi-pi stacking between planar PDIs and can be traced in solution due to the fluorescence of PDI. I have determined the diffusion coefficient of DNA-PDI conjugates in aqueous solution by means of FCS. In addition, I investigated whether such DNA-PDIs form aggregates with certain structure, for instance dimers. rnOnce the DNA hybrid material self-assemble into supermolecular structures for instance into micelles, the single molecules do not necessarily stay in one specific micelle. Actually, a single molecule may enter and leave micelles constantly. The average residence time of a single molecule in a certain micelle depends on the nature of the molecule. I have chosen DNA-b-polypropylene oxide (PPO) as model molecules and investigated the residence time of DNA-b-PPO molecules in their according micelles by means of FCCS.rnBesides the DNA hybrid materials, polymeric colloids can also form ordered structures once they are brought to an air/water interface. Here, hexagonally densely packed monolayers can be generated. These monolayers can be deposited onto different surfaces as coating layers. In the second part of this work, I investigated the mechanical properties of such colloidal monolayers using micromechanical cantilevers. When a coating layer is deposited on a cantilever, it can modify the elasticity of the cantilever. This variation can be reflected either by a deflection or by a resonance frequency shift of the cantilever. In turn, detecting these changes provides information about the mechanical properties of the coating layer. rnIn the second part of this work, polymeric colloidal monolayers were coated on a cantilever and homogenous polymer films of a few hundred nanometers in thickness were generated from these colloidal monolayers by thermal annealing or organic vapor annealing. Both the film formation process and the mechanical properties of these resulting homogenous films were investigated by means of cantilever. rnElastic property changes of the coating film, for example upon absorption of organic vapors, induce a deflection of the cantilever. This effect enables a cantilever to detect target molecules, when the cantilever is coated with an active layer with specific affinity to target molecules. In the last part of this thesis, I investigated the applicability of suitably functionalized micromechanical cantilevers as sensors. In particular, glucose sensitive polymer brushes were grafted on a cantilever and the deflection of this cantilever was measured during exposure to glucose solution. rn

The hybrid PAX3-FKHR fusion protein of alveolar rhabdomyosarcoma transforms fibroblasts in culture.

Pediatric alveolar rhabdomyosarcoma is characterized by a chromosomal translocation that fuses parts of the PAX3 and FKHR genes. PAX3 codes for a transcriptional regulator that controls developmental programs, and FKHR codes for a forkhead-winged helix protein, also a likely transcription factor. The PAX3-FKHR fusion product retains the DNA binding domains of the PAX3 protein and the putative activator domain of the FKHR protein. The PAX3-FKHR protein has been shown to function as a transcriptional activator. Using the RCAS retroviral vector, we have introduced the PAX3-FKHR gene into chicken embryo fibroblasts. Expression of the PAX3-FKHR protein in these cells leads to transformation: the cells become enlarged, grow tightly packed and in multiple layers, and acquire the ability for anchorage-independent growth. This cellular transformation in vitro will facilitate studies on the mechanism of PAX3-FKHR-induced oncogenesis.

Synthesis of novel and stable g-C3N4/N-doped SrTiO3 hybrid nanocomposites with improved photocurrent and photocatalytic activity under visible light irradiation

Hybrid nanocomposites based on N-doped SrTiO3 nanoparticles wrapped in g-C3N4 nanosheets were successfully prepared by a facile and reproducible polymeric citrate and thermal exfoliation method. The results clearly indicated that the N-doped SrTiO3 nanoparticles are successfully wrapped in layers of the g-C3N4 nanosheets. The g-C3N4/N-doped SrTiO3 nanocomposites showed absorption edges at longer wavelengths compared with the pure g-C3N4 as well as N-doped SrTiO3. The hybrid nanocomposites exhibit an improved photocurrent response and photocatalytic activity under visible light irradiation. Interestingly, the hybrid nanocomposite possesses high photostability and reusability. Based on experimental results, the possible mechanism for prolonged lifetime of the photoinduced charge carrier was also discussed. The high performance of the g-C3N4/N-doped SrTiO3 photocatalysts is due to the synergic effect at the interface of g-C3N4 and N-doped SrTiO3 hetero/nanojunction including the high separation efficiency of the charge carrier, band energy matching and the suppressed recombination rate. Therefore, the hybrid photocatalyst could be of potential interest for water splitting and environmental remediation under natural sunlight.

Interdigitating organic bilayers direct the short interlayer spacing in hybrid organic–inorganic layered vanadium oxide nanostructures

Layered metal oxides provide a single-step route to sheathed superlattices of atomic layers of a variety of inorganic materials, where the interlayer spacing and overall layered structure forms the most critical feature in the nanomaterials’ growth and application in electronics, health, and energy storage. We use a combination of computer simulations and experiments to describe the atomic-scale structure, dynamics and energetics of alkanethiol-intercalated layered vanadium oxide-based nanostructures. Molecular dynamics (MD) simulations identify the unusual substrate-constrained packing of the alkanethiol surfactant chains along each V2O5 (010) face that combines with extensive interdigitation between chains on opposing faces to maximize three-dimensional packing in the interlayer regions. The findings are supported by high resolution electron microscopy analyses of synthesized alkanethiol-intercalated vanadium oxide nanostructures, and the preference for this new interdigitated model is clarified using a large set of MD simulations. This dependency stresses the importance of organic–inorganic interactions in layered material systems, the control of which is central to technological applications of flexible hybrid nanomaterials.

Low‑cost origami fabrication of 3D self‑aligned hybrid microfluidic structures

[EN] 3D microfluidic device fabrication methods are normally quite expensive and tedious. In this paper, we present an easy and cheap alternative wherein thin cyclic olefin polymer (COP) sheets and pressure sensitive adhesive(PSA) were used to fabricate hybrid 3D microfluidic structures, by the Origami technique, which enables the fabrication of microfluidic devices without the need of any alignment tool. The COP and PSA layers were both cut simultaneously using a portable, low-cost plotter allowing for rapid prototyping of a large variety of designs in a single production step. The devices were then manually assembled using the Origami technique by simply combining COP and PSA layers and mild pressure. This fast fabrication method was applied, as proof of concept, to the generation of a micromixer with a 3D-stepped serpentine design made of ten layers in less than 8 min. Moreover, the micromixer was characterized as a function of its pressure failure, achieving pressures of up to 1000 mbar. This fabrication method is readily accessible across a large range of potential end users, such as educational agencies (schools,universities), low-income/developing world research and industry or any laboratory without access to clean room facilities, enabling the fabrication of robust, reproducible microfluidic devices.