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Materials, Volume 4, Issue 11 (November 2011), Pages 1906-2060

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Research

Jump to: Review, Other

Open AccessArticle Hysteretic Tricolor Electrochromic Systems Based on the Dynamic Redox Properties of Unsymmetrically Substituted Dihydrophenanthrenes and Biphenyl-2,2'-Diyl Dications: Efficient Precursor Synthesis by a Flow Microreactor Method
Materials 2011, 4(11), 1906-1926; doi:10.3390/ma4111906
Received: 13 September 2011 / Revised: 6 October 2011 / Accepted: 10 October 2011 / Published: 26 October 2011
Cited by 8 | PDF Full-text (1781 KB) | HTML Full-text | XML Full-text
Abstract
A series of biphenyl-2,2'-diylbis(diarylmethanol)s 3, which have two kinds of aryl groups at the bay region, were efficiently obtained by integrated flow microreactor synthesis. The diols 3NO/NX are the precursors of unsymmetric biphenylic dications 2NO/NX2+, which are [...] Read more.
A series of biphenyl-2,2'-diylbis(diarylmethanol)s 3, which have two kinds of aryl groups at the bay region, were efficiently obtained by integrated flow microreactor synthesis. The diols 3NO/NX are the precursors of unsymmetric biphenylic dications 2NO/NX2+, which are transformed into the corresponding dihydrophenanthrenes 1NO/NX via 2NO/NX+• upon reduction, when they exhibit two-stage color changes. On the other hand, the steady-state concentration of the intermediate 2NO/NX+• is negligible during the oxidation of 1NO/NX to 2NO/NX2+, which reflects unique tricolor electrochromicity with a hysteretic pattern of color change [color 1→color 2→color 3→color 1]. Full article
(This article belongs to the Special Issue Electrochromic Materials and Devices)
Figures

Open AccessArticle Polyamide 6 Nanocomposites with Inorganic Particles Modified with Three Quaternary Ammonium Salts
Materials 2011, 4(11), 1956-1966; doi:10.3390/ma4111956
Received: 8 September 2011 / Accepted: 26 September 2011 / Published: 2 November 2011
Cited by 5 | PDF Full-text (1888 KB) | HTML Full-text | XML Full-text
Abstract
The purpose of this study was to obtain polyamide 6 nanocomposites with national organically modified clay with three quaternary ammonium salts. The obtained results confirm the intercalation of molecules of salt in the clay layers, and a good interaction with the polymer, [...] Read more.
The purpose of this study was to obtain polyamide 6 nanocomposites with national organically modified clay with three quaternary ammonium salts. The obtained results confirm the intercalation of molecules of salt in the clay layers, and a good interaction with the polymer, showing the formation of intercalated and/or partially exfoliated structures. The nanocomposites showed similar thermal stability compared to pure polymer, and the mechanical properties presented interesting and promising results. Full article
(This article belongs to the Special Issue Nanocomposites of Polymers and Inorganic Particles)
Open AccessArticle Toughening of a Carbon-Fibre Composite Using Electrospun Poly(Hydroxyether of Bisphenol A) Nanofibrous Membranes Through Inverse Phase Separation and Inter-Domain Etherification
Materials 2011, 4(11), 1967-1984; doi:10.3390/ma4111967
Received: 1 September 2011 / Revised: 12 October 2011 / Accepted: 27 October 2011 / Published: 2 November 2011
Cited by 22 | PDF Full-text (8946 KB) | HTML Full-text | XML Full-text
Abstract
The interlaminar toughening of a carbon fibre reinforced composite by interleaving a thin layer (~20 microns) of poly(hydroxyether of bisphenol A) (phenoxy) nanofibres was explored in this work. Nanofibres, free of defect and averaging several hundred nanometres, were produced by electrospinning directly [...] Read more.
The interlaminar toughening of a carbon fibre reinforced composite by interleaving a thin layer (~20 microns) of poly(hydroxyether of bisphenol A) (phenoxy) nanofibres was explored in this work. Nanofibres, free of defect and averaging several hundred nanometres, were produced by electrospinning directly onto a pre-impregnated carbon fibre material (Toray G83C) at various concentrations between 0.5 wt % and 2 wt %. During curing at 150 °C, phenoxy diffuses through the epoxy resin to form a semi interpenetrating network with an inverse phase type of morphology where the epoxy became the co-continuous phase with a nodular morphology. This type of morphology improved the fracture toughness in mode I (opening failure) and mode II (in-plane shear failure) by up to 150% and 30%, respectively. Interlaminar shear stress test results showed that the interleaving did not negatively affect the effective in-plane strength of the composites. Furthermore, there was some evidence from DMTA and FT-IR analysis to suggest that inter-domain etherification between the residual epoxide groups with the pendant hydroxyl groups of the phenoxy occurred, also leading to an increase in glass transition temperature (~7.5 °C). Full article
(This article belongs to the Special Issue Fibre-Reinforced Composites)
Open AccessArticle Cellulose Isolation Methodology for NMR Analysis of Cellulose Ultrastructure
Materials 2011, 4(11), 1985-2002; doi:10.3390/ma4111985
Received: 26 September 2011 / Accepted: 17 October 2011 / Published: 7 November 2011
Cited by 17 | PDF Full-text (333 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
In order to obtain accurate information about the ultrastructure of cellulose from native biomass by 13C cross polarization magic angle spinning (CP/MAS) NMR spectroscopy the cellulose component must be isolated due to overlapping resonances from both lignin and hemicellulose. Typically, cellulose [...] Read more.
In order to obtain accurate information about the ultrastructure of cellulose from native biomass by 13C cross polarization magic angle spinning (CP/MAS) NMR spectroscopy the cellulose component must be isolated due to overlapping resonances from both lignin and hemicellulose. Typically, cellulose isolation has been achieved via holocellulose pulping to remove lignin followed by an acid hydrolysis procedure to remove the hemicellulose components. Using 13C CP/MAS NMR and non-linear line-fitting of the cellulose C4 region, it was observed that the standard acid hydrolysis procedure caused an apparent increase in crystallinity of ~10% or less on the cellulose isolated from Populus holocellulose. We have examined the effect of the cellulose isolation method, particularly the acid treatment time for hemicellulose removal, on cellulose ultrastructural characteristics by studying these effects on cotton, microcrystalline cellulose (MCC) and holocellulose pulped Populus. 13C CP/MAS NMR of MCC indicated that holocellulose pulping and acid hydrolysis has little effect on the crystalline ultrastructural components of cellulose. Although any chemical method to isolate cellulose from native biomass will invariably alter substrate characteristics, especially those related to regions accessible to solvents, we found those changes to be minimal and consistent in samples of typical crystallinity and lignin/hemicellulose content. Based on the rate of the hemicellulose removal, as determined by HPLC-carbohydrate analysis and magnitude of cellulose ultrastructural alteration, the most suitable cellulose isolation methodology utilizes a treatment of 2.5 M HCl at 100 °C for a standard residence time between 1.5 and 4 h. However, for the most accurate crystallinity results this residence time should be determined empirically for a particular sample. Full article
(This article belongs to the Special Issue Carbohydrate Polymers)
Open AccessArticle The Rolling Transition in a Granular Flow along a Rotating Wall
Materials 2011, 4(11), 2003-2016; doi:10.3390/ma4112003
Received: 19 September 2011 / Revised: 30 September 2011 / Accepted: 13 October 2011 / Published: 11 November 2011
PDF Full-text (895 KB) | HTML Full-text | XML Full-text
Abstract
The flow of a dry granular material composed of spherical particles along a rotating boundary has been studied by the discrete element method (DEM). This type of flow is used, among others, as a process to spread particles. The flow consists of [...] Read more.
The flow of a dry granular material composed of spherical particles along a rotating boundary has been studied by the discrete element method (DEM). This type of flow is used, among others, as a process to spread particles. The flow consists of several phases. A compression phase along the rotating wall is followed by an elongation of the flow along the same boundary. Eventually, the particles slide or roll independently along the boundary. We show that the main motion of the flow can be characterized by a complex deformation rate of traction/compression and shear. We define numerically an effective friction coefficient of the flow on the scale of the continuum and show a strong decrease of this effective friction beyond a certain critical friction coefficient μ*. We correlate this phenomenon with the apparition of a new transition from a sliding regime to a rolling without sliding regime that we called the rolling transition; this dynamic transition is controlled by the value of the friction coefficient between the particle and the wall. We show that the spherical shape for the particles may represent an optimum for the flow in terms of energetic. Full article
(This article belongs to the Special Issue Advances in the Dynamics of Granular Materials)
Open AccessArticle Nanorod Self-Assembly in High Jc YBa2Cu3O7−x Films with Ru-Based Double Perovskites
Materials 2011, 4(11), 2042-2056; doi:10.3390/ma4112042
Received: 7 September 2011 / Revised: 24 October 2011 / Accepted: 9 November 2011 / Published: 17 November 2011
Cited by 2 | PDF Full-text (2975 KB) | HTML Full-text | XML Full-text
Abstract
Many second phase additions to YBa2Cu3O7−x (YBCO) films, in particular those that self-assemble into aligned nanorod and nanoparticle structures, enhance performance in self and applied fields. Of particular interest for additions are Ba-containing perovskites that are compatible [...] Read more.
Many second phase additions to YBa2Cu3O7−x (YBCO) films, in particular those that self-assemble into aligned nanorod and nanoparticle structures, enhance performance in self and applied fields. Of particular interest for additions are Ba-containing perovskites that are compatible with YBCO. In this report, we discuss the addition of Ba2YRuO6 to bulk and thick-film YBCO. Sub-micron, randomly oriented particles of this phase were found to form around grain boundaries and within YBCO grains in bulk sintered pellets. Within the limits of EDS, no Ru substitution into the YBCO was observed. Thick YBCO films were grown by pulsed laser deposition from a target consisting of YBa2Cu3Oy with 5 and 2.5 mole percent additions of Ba2YRuO6 and Y2O3, respectively. Films with enhanced in-field performance contained aligned, self-assembled Ba2YRuO6 nanorods and strained Y2O3 nanoparticle layers. A 0.9 µm thick film was found to have a self-field critical current density (Jc) of 5.1 MA/cm2 with minimum Jc(Q, H=1T) of 0.75 MA/cm2. Conversely, Jc characteristics were similar to YBCO films without additions when these secondary phases formed as large, disordered phases within the film. A 2.3 µm thick film with such a distribution of secondary phases was found to have reduced self-field Jc values of 3.4 MA/cm2 at 75.5 K and Jc(min, Q, 1T) of 0.4 MA/cm2. Full article
(This article belongs to the Special Issue New High Tc Superconductor)

Review

Jump to: Research, Other

Open AccessReview Drug-Eluting Intraocular Lenses
Materials 2011, 4(11), 1927-1940; doi:10.3390/ma4111927
Received: 6 October 2011 / Revised: 20 October 2011 / Accepted: 25 October 2011 / Published: 1 November 2011
Cited by 12 | PDF Full-text (288 KB) | HTML Full-text | XML Full-text
Abstract
Notable advances in materials science and in surgical techniques make the management of cataract by replacement of the opaque crystalline with an intraocular lens (IOL), one of the most cost-effective interventions in current healthcare. The usefulness and safety of IOLs can be [...] Read more.
Notable advances in materials science and in surgical techniques make the management of cataract by replacement of the opaque crystalline with an intraocular lens (IOL), one of the most cost-effective interventions in current healthcare. The usefulness and safety of IOLs can be enhanced if they are endowed with the ability to load and to sustain drug release in the implantation site. Drug-eluting IOLs can prevent infections and untoward reactions of eye tissues (which lead to opacification) and also can act as drug depots for treatment of several other ocular pathologies. Such a myriad of therapeutic possibilities has prompted the design of drug-IOL combination products. Several approaches are under study, namely combination of the IOL with an insert in a single device, soaking in drug solutions, impregnation using supercritical fluids, coating with drug/polymer layers, and covalent grafting of the drug. The advantages/limitations of each technique are discussed in the present review on selected examples. Although more in vivo data are required, the information already available proves the interest of some approaches in ocular therapeutics. Full article
(This article belongs to the Special Issue Materials for Ophthalmic Drug Delivery)
Figures

Open AccessReview Advances in High-Field BOLD fMRI
Materials 2011, 4(11), 1941-1955; doi:10.3390/ma4111941
Received: 16 August 2011 / Revised: 7 October 2011 / Accepted: 19 October 2011 / Published: 2 November 2011
Cited by 7 | PDF Full-text (840 KB) | HTML Full-text | XML Full-text
Abstract
This review article examines the current state of BOLD fMRI at a high magnetic field strength of 7 Tesla. The following aspects are covered: a short description of the BOLD contrast, spatial and temporal resolution, BOLD sensitivity, localization and spatial specificity, technical [...] Read more.
This review article examines the current state of BOLD fMRI at a high magnetic field strength of 7 Tesla. The following aspects are covered: a short description of the BOLD contrast, spatial and temporal resolution, BOLD sensitivity, localization and spatial specificity, technical challenges as well as an outlook on future developments are given. It is shown that the main technical challenges of performing BOLD fMRI at high magnetic field strengths—namely development of array coils, imaging sequences and parallel imaging reconstruction—have been solved successfully. The combination of these developments has lead to the availability of high-resolution BOLD fMRI protocols that are able to cover the whole brain with a repetition time (TR) shorter than 3 s. The structural information available from these high-resolution fMRI images itself is already very detailed, which helps to co-localize structure and function. Potential future applications include whole-brain connectivity analysis on a laminar resolution and single subject examinations. Full article
(This article belongs to the Special Issue High Field Magnetic Resonance Methods and Materials)
Open AccessReview Dense CO2 as a Solute, Co-Solute or Co-Solvent in Particle Formation Processes: A Review
Materials 2011, 4(11), 2017-2041; doi:10.3390/ma4112017
Received: 13 September 2011 / Revised: 13 October 2011 / Accepted: 19 October 2011 / Published: 16 November 2011
Cited by 16 | PDF Full-text (180 KB) | HTML Full-text | XML Full-text | Correction | Supplementary Files
Abstract
The application of dense gases in particle formation processes has attracted great attention due to documented advantages over conventional technologies. In particular, the use of dense CO2 in the process has been subject of many works and explored in a variety [...] Read more.
The application of dense gases in particle formation processes has attracted great attention due to documented advantages over conventional technologies. In particular, the use of dense CO2 in the process has been subject of many works and explored in a variety of different techniques. This article presents a review of the current available techniques in use in particle formation processes, focusing exclusively on those employing dense CO2 as a solute, co-solute or co-solvent during the process, such as PGSS (Particles from gas-saturated solutions®), CPF (Concentrated Powder Form®), CPCSP (Continuous Powder Coating Spraying Process), CAN-BD (Carbon dioxide Assisted Nebulization with a Bubble Dryer®), SEA (Supercritical Enhanced Atomization), SAA (Supercritical Fluid-Assisted Atomization), PGSS-Drying and DELOS (Depressurization of an Expanded Liquid Organic Solution). Special emphasis is given to modifications introduced in the different techniques, as well as the limitations that have been overcome. Full article

Other

Jump to: Research, Review

Open AccessCorrection Correction: Koush, Y.; Elliott, M.A. and Mathiak, K. Single Voxel Proton Spectroscopy for Neurofeedback at 7 Tesla. Materials 2011, 4, 1548–1563
Materials 2011, 4(11), 2057-2060; doi:10.3390/ma4112057
Received: 17 November 2011 / Accepted: 24 November 2011 / Published: 24 November 2011
Cited by 1 | PDF Full-text (167 KB) | HTML Full-text | XML Full-text
Abstract
In the published manuscript “Koush, Y.; Elliott, M.A. and Mathiak, K. Single Voxel Proton Spectroscopy for Neurofeedback at 7 Tesla. Materials 2011, 4, 1548-1563”, all estimates of T2* from the single voxel spectroscopy data were overestimated by a factor of [...] Read more.
In the published manuscript “Koush, Y.; Elliott, M.A. and Mathiak, K. Single Voxel Proton Spectroscopy for Neurofeedback at 7 Tesla. Materials 2011, 4, 1548-1563”, all estimates of T2* from the single voxel spectroscopy data were overestimated by a factor of 4. This was due to an incorrectly assumed four-fold lower sampling rate. The focus of the manuscript is on the relative changes in T2* with BOLD activation, and not on the absolute values. Therefore, none of the central claims are affected, but the scaling in most of the figures needs to be adjusted. The authors would like to make the following corrections to their published paper. [...] Full article
(This article belongs to the Special Issue High Field Magnetic Resonance Methods and Materials)

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