Next Issue
Previous Issue

E-Mail Alert

Add your e-mail address to receive forthcoming issues of this journal:

Journal Browser

Journal Browser

Table of Contents

Materials, Volume 4, Issue 9 (September 2011), Pages 1519-1631

  • Issues are regarded as officially published after their release is announced to the table of contents alert mailing list.
  • You may sign up for e-mail alerts to receive table of contents of newly released issues.
  • PDF is the official format for papers published in both, html and pdf forms. To view the papers in pdf format, click on the "PDF Full-text" link, and use the free Adobe Readerexternal link to open them.
View options order results:
result details:
Displaying articles 1-7
Export citation of selected articles as:

Research

Jump to: Review, Other

Open AccessArticle Spinning Carbon Nanotube Nanothread under a Scanning Electron Microscope
Materials 2011, 4(9), 1519-1527; doi:10.3390/ma4091519
Received: 22 June 2011 / Revised: 1 August 2011 / Accepted: 18 August 2011 / Published: 29 August 2011
Cited by 15 | PDF Full-text (401 KB) | HTML Full-text | XML Full-text
Abstract
Nanothread with a diameter as small as one hundred nanometers was manufactured under a scanning electron microscope. Made directly from carbon nanotubes, and inheriting their superior electrical and mechanical properties, nanothread may be the world’s smallest man-made fiber. The smallest thread that [...] Read more.
Nanothread with a diameter as small as one hundred nanometers was manufactured under a scanning electron microscope. Made directly from carbon nanotubes, and inheriting their superior electrical and mechanical properties, nanothread may be the world’s smallest man-made fiber. The smallest thread that can be spun using a bench-top spinning machine is about 5 microns in diameter. Nanothread is a new material building block that can be used at the nanoscale or plied to form yarn for applications at the micro and macro scales. Preliminary electrical and mechanical properties of nanothread were measured. The resistivity of nanothread is less than 10−5 Ω∙m. The strength of nanothread is greater than 0.5 GPa. This strength was obtained from measurements using special glue that cures in an electron microscope. The glue weakened the thread, thus further work is needed to obtain more accurate measurements. Nanothread will have broad applications in enabling electrical components, circuits, sensors, and tiny machines. Yarn can be used for various macroscale applications including lightweight antennas, composites, and cables. Full article
(This article belongs to the Special Issue Carbon Nanotubes: Synthesis, Characterization and Applications)
Open AccessArticle Sorption of Aromatic Compounds with Copolymer Sorbent Materials Containing β-Cyclodextrin
Materials 2011, 4(9), 1528-1542; doi:10.3390/ma4091528
Received: 1 July 2011 / Revised: 5 August 2011 / Accepted: 17 August 2011 / Published: 29 August 2011
Cited by 14 | PDF Full-text (349 KB) | HTML Full-text | XML Full-text
Abstract
Urethane copolymer sorbent materials that incorporate β-cyclodextrin (CD) have been prepared and their sorption properties with chlorinated aromatic compounds (i.e., pentachlorophenol, 2,4-dichlorophenol and 2,4-dichlorophenoxy acetic acid) have been evaluated. The sorption properties of granular activated carbon (GAC) were similarly compared in aqueous solution at variable pH conditions. The sorbents displayed variable BET surface areas as follows: MDI-X copolymers (< 101 m2/g), CDI-X copolymers (< 101 m2/g), and granular activated carbon (GAC ~103 m2/g). The sorption capacities for the copolymers sorbents are listed in descending order, as follows: GAC > CDI-3 copolymer ≈ MDI-3 copolymer. The sorption capacity for the aromatic adsorbates with each sorbent are listed in descending order, as follows: 2,4-dichlorophenol > 2,4-dichlorophenoxy acetic acid > pentachlorophenol. In general, the differences in the sorption properties of the copolymer sorbents with the chlorinated organics were related to the following factors: (i) surface area of the sorbent; (ii) CD content and accessibility; and (iii) and the chemical nature of the sorbent material. Full article
(This article belongs to the Special Issue Carbohydrate Polymers)
Figures

Open AccessArticle Single Voxel Proton Spectroscopy for Neurofeedback at 7 Tesla
Materials 2011, 4(9), 1548-1563; doi:10.3390/ma4091548
Received: 21 June 2011 / Revised: 23 August 2011 / Accepted: 5 September 2011 / Published: 15 September 2011
Cited by 4 | PDF Full-text (369 KB) | HTML Full-text | XML Full-text | Correction | Supplementary Files
Abstract
Echo-planar imaging (EPI) in fMRI is regularly used to reveal BOLD activation in presubscribed regions of interest (ROI). The response is mediated by relative changes in T2* which appear as changes in the image pixel intensities. We have proposed an application of [...] Read more.
Echo-planar imaging (EPI) in fMRI is regularly used to reveal BOLD activation in presubscribed regions of interest (ROI). The response is mediated by relative changes in T2* which appear as changes in the image pixel intensities. We have proposed an application of functional single-voxel proton spectroscopy (fSVPS) for real-time studies at ultra-high MR field which can be comparable to the EPI BOLD fMRI technique. A spin-echo SVPS protocol without water suppression was acquired with 310 repetitions on a 7T Siemens MR scanner (TE/TR = 20/1000 ms, flip angle α = 90°, voxel size 10 × 10 × 10 mm3). Transmitter reference voltage was optimized for the voxel location. Spectral processing of the water signal free induction decay (FID) using log-linear regression was used to estimate the T2* change between rest and activation of a functional task. The FID spectrum was filtered with a Gaussian window around the water peak, and log-linear regression was optimized for the particular ROI by adoption of the linearization length. The spectroscopic voxel was positioned on an ROI defined from a real-time fMRI EPI BOLD localizer. Additional online signal processing algorithms performed signal drift removal (exponential moving average), despiking and low-pass filtering (modified Kalman filter) and, finally, the dynamic feedback signal normalization. Two functional tasks were used to estimate the sensitivity of the SVPS method compared to BOLD signal changes, namely the primary motor cortex (PMC, left hand finger tapping) and visual cortex (VC, blinking checkerboard). Four healthy volunteers performed these tasks and an additional session using real-time signal feedback modulating their activation level of the PMC. Results show that single voxel spectroscopy is able to provide a good and reliable estimation of the BOLD signal changes. Small data size and FID signal processing instead of processing entire brain volumes as well as more information revealed from the acquired total water spectrum, i.e., direct estimation of the T2* values and B0 changes, make SVPS proton spectroscopy suitable and advantageous for real-time neurofeedback studies. Particular challenges of ultra-high field spectroscopy due to the non-linearity in the spectral information, e.g., poor main magnetic field homogeneity and the absence of motion correction for the SVPS sequence may lead to the special artifacts in the control signal which still need to be addressed. The contrast to noise ratio (CNR), experimental statistic (t-values) and percent signal change were used as quality parameters to estimate the method performance. The potential and challenges of the spectroscopic approach for fMRI studies needs to be further investigated. Full article
(This article belongs to the Special Issue High Field Magnetic Resonance Methods and Materials)
Open AccessArticle Coating of Carbon Fiber with Polyhedral Oligomeric Silsesquioxane (POSS) to Enhance Mechanical Properties and Durability of Carbon/Vinyl Ester Composites
Materials 2011, 4(9), 1619-1631; doi:10.3390/ma4091619
Received: 27 July 2011 / Revised: 24 August 2011 / Accepted: 6 September 2011 / Published: 21 September 2011
Cited by 9 | PDF Full-text (792 KB) | HTML Full-text | XML Full-text
Abstract
Our continuing quest to improve the performance of polymer composites under moist and saltwater environments has gained momentum in recent years with the reinforcement of inorganic nanoparticles into the polymer. The key to mitigate degradation of composites under such environments is to [...] Read more.
Our continuing quest to improve the performance of polymer composites under moist and saltwater environments has gained momentum in recent years with the reinforcement of inorganic nanoparticles into the polymer. The key to mitigate degradation of composites under such environments is to maintain the integrity of the fiber/matrix (F/M) interface. In this study, the F/M interface of carbon/vinyl ester composites has been modified by coating the carbon fiber with polyhedral oligomeric silsesquioxane (POSS). POSS is a nanostructured inorganic-organic hybrid particle with a cubic structure having silicon atoms at the core and linked to oxygen atoms. The advantage of using POSS is that the silicon atoms can be linked to a substituent that can be almost any chemical group known in organic chemistry. Cubic silica cores are ‘hard particles’ and are about 0.53 nm in diameter. The peripheral organic unit is a sphere of about 1–3 nm in diameter. Further, cubic structure of POSS remains intact during the polymerization process and therefore with appropriate functional groups, if installed on the fiber surface, would provide a stable and strong F/M interface. Two POSS systems with two different functional groups; namely, octaisobutyl and trisilanolphenyl have been investigated. A set of chemical and mechanical procedures has been developed to coat carbon fibers with POSS, and to fabricate layered composites with vinyl ester resin. Interlaminar shear and low velocity impact tests have indicated around 17–38% improvement in mechanical properties with respect to control samples made without the POSS coating. Saltwater and hygrothermal tests at various environmental conditions have revealed that coating with POSS reduces water absorption by 20–30% and retains the composite properties. Full article
(This article belongs to the Special Issue Nanocomposites of Polymers and Inorganic Particles)

Review

Jump to: Research, Other

Open AccessReview On Structure and Properties of Amorphous Materials
Materials 2011, 4(9), 1564-1598; doi:10.3390/ma4091564
Received: 15 July 2011 / Revised: 20 August 2011 / Accepted: 6 September 2011 / Published: 15 September 2011
Cited by 19 | PDF Full-text (3626 KB) | HTML Full-text | XML Full-text
Abstract
Mechanical, optical, magnetic and electronic properties of amorphous materials hold great promise towards current and emergent technologies. We distinguish at least four categories of amorphous (glassy) materials: (i) metallic; (ii) thin films; (iii) organic and inorganic thermoplastics; and (iv) amorphous permanent networks. [...] Read more.
Mechanical, optical, magnetic and electronic properties of amorphous materials hold great promise towards current and emergent technologies. We distinguish at least four categories of amorphous (glassy) materials: (i) metallic; (ii) thin films; (iii) organic and inorganic thermoplastics; and (iv) amorphous permanent networks. Some fundamental questions about the atomic arrangements remain unresolved. This paper focuses on the models of atomic arrangements in amorphous materials. The earliest ideas of Bernal on the structure of liquids were followed by experiments and computer models for the packing of spheres. Modern approach is to carry out computer simulations with prediction that can be tested by experiments. A geometrical concept of an ideal amorphous solid is presented as a novel contribution to the understanding of atomic arrangements in amorphous solids. Full article
(This article belongs to the Special Issue Amorphous Alloys)
Open AccessReview Phase Stability and Elasticity of TiAlN
Materials 2011, 4(9), 1599-1618; doi:10.3390/ma4091599
Received: 11 July 2011 / Revised: 29 August 2011 / Accepted: 31 August 2011 / Published: 15 September 2011
Cited by 23 | PDF Full-text (777 KB) | HTML Full-text | XML Full-text
Abstract
We review results of recent combined theoretical and experimental studies of Ti1−xAlxN, an archetypical alloy system material for hard-coating applications. Theoretical simulations of lattice parameters, mixing enthalpies, and elastic properties are presented. Calculated phase diagrams at ambient [...] Read more.
We review results of recent combined theoretical and experimental studies of Ti1−xAlxN, an archetypical alloy system material for hard-coating applications. Theoretical simulations of lattice parameters, mixing enthalpies, and elastic properties are presented. Calculated phase diagrams at ambient pressure, as well as at pressure of 10 GPa, show a wide miscibility gap and broad region of compositions and temperatures where the spinodal decomposition takes place. The strong dependence of the elastic properties and sound wave anisotropy on the Al-content offers detailed understanding of the spinodal decomposition and age hardening in Ti1−xAlxN alloy films and multilayers. TiAlN/TiN multilayers can further improve the hardness and thermal stability compared to TiAlN since they offer means to influence the kinetics of the favorable spinodal decomposition and suppress the detrimental transformation to w-AlN. Here, we show that a 100 degree improvement in terms of w-AlN suppression can be achieved, which is of importance when the coating is used as a protective coating on metal cutting inserts. Full article
(This article belongs to the Special Issue Hard Materials: Advances in Synthesis and Understanding)

Other

Jump to: Research, Review

Open AccessShort Note Two Types of Inulin Fructotransferases
Materials 2011, 4(9), 1543-1547; doi:10.3390/ma4091543
Received: 28 June 2011 / Revised: 25 August 2011 / Accepted: 31 August 2011 / Published: 7 September 2011
Cited by 4 | PDF Full-text (273 KB) | HTML Full-text | XML Full-text
Abstract
Inulin is a polysaccharide contained in chicory, dahlia, and other plants. An oligosaccharide DFA III is produced from inulin using a microbial enzyme, inulin fructotransferase (DFA III producing) [EC 2.4.1.93]. The oligosaccharide DFAIII has a unique functionality that accelerates the assimilation of [...] Read more.
Inulin is a polysaccharide contained in chicory, dahlia, and other plants. An oligosaccharide DFA III is produced from inulin using a microbial enzyme, inulin fructotransferase (DFA III producing) [EC 2.4.1.93]. The oligosaccharide DFAIII has a unique functionality that accelerates the assimilation of minerals (Ca, Fe, and so on) from intestines. Therefore, it has a potential for the improvement of osteoporosis and iron deficiency anemia. The production of DFA III was industrialized in 2004 in Japan. Another oligosaccharide DFA I is produced from inulin by another enzyme, inulin fructotransferase (DFA I producing) [EC 2.4.1.200]. The oligosaccharide DFA I has half the sweetness of sucrose. The genes of the two enzymes were cloned and the nucleotide sequences were determined. The deduced amino acid sequences of two enzyme genes had a homology of 49.8%. Full article
(This article belongs to the Special Issue Carbohydrate Polymers)

Journal Contact

MDPI AG
Materials Editorial Office
St. Alban-Anlage 66, 4052 Basel, Switzerland
materials@mdpi.com
Tel. +41 61 683 77 34
Fax: +41 61 302 89 18
Editorial Board
Contact Details Submit to Materials
Back to Top