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Materials, Volume 4, Issue 4 (April 2011), Pages 601-824

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Research

Jump to: Review

Open AccessArticle Synthesis and Characterization of Self-Assembled Nanogels Made of Pullulan
Materials 2011, 4(4), 601-620; doi:10.3390/ma4040601
Received: 4 March 2011 / Accepted: 17 March 2011 / Published: 25 March 2011
Cited by 6 | PDF Full-text (947 KB) | HTML Full-text | XML Full-text
Abstract
Self-assembled nanogels made of hydrophobized pullulan were obtained using a versatile, simple, reproducible and low-cost method. In a first reaction pullulan was modified with hydroxyethyl methacrylate or vinyl methacrylate, further modified in the second step with hydrophobic 1-hexadecanethiol, resulting as an amphiphilic [...] Read more.
Self-assembled nanogels made of hydrophobized pullulan were obtained using a versatile, simple, reproducible and low-cost method. In a first reaction pullulan was modified with hydroxyethyl methacrylate or vinyl methacrylate, further modified in the second step with hydrophobic 1-hexadecanethiol, resulting as an amphiphilic material, which self-assembles in water via the hydrophobic interaction among alkyl chains. Structural features, size, shape, surface charge and stability of the nanogels were studied using hydrogen nuclear magnetic resonance, fluorescence spectroscopy, cryo-field emission scanning electron microscopy and dynamic light scattering. Above the critical aggregation concentration spherical polydisperse macromolecular micelles revealed long-term colloidal stability in aqueous medium, with a nearly neutral negative surface charge and mean hydrodynamic diameter in the range 100–400 nm, depending on the polymer degree of substitution. Good size stability was observed when nanogels were exposed to potential destabilizing pH conditions. While the size stability of the nanogel made of pullulan with vinyl methacrylate and more hydrophobic chains grafted was affected by the ionic strength and urea, nanogel made of pullulan with hydroxyethyl methacrylate and fewer hydrophobic chains grafted remained stable. Full article
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Open AccessArticle Enhancing Crystallinity and Orientation by Hot-Stretching to Improve the Mechanical Properties of Electrospun Partially Aligned Polyacrylonitrile (PAN) Nanocomposites
Materials 2011, 4(4), 621-632; doi:10.3390/ma4040621
Received: 18 February 2011 / Revised: 10 March 2011 / Accepted: 30 March 2011 / Published: 6 April 2011
Cited by 16 | PDF Full-text (395 KB) | HTML Full-text | XML Full-text
Abstract
Partially aligned polyacrylonitrile (PAN)-based nanofibers were electrospun from PAN and PAN/single-walled carbon nanotubes (SWNTs) in a solution of dimethylformamide (DMF) to make the nanofiber composites. The as-spun nanofibers were then hot-stretched in the oven to enhance its orientation and crystallinity. With the [...] Read more.
Partially aligned polyacrylonitrile (PAN)-based nanofibers were electrospun from PAN and PAN/single-walled carbon nanotubes (SWNTs) in a solution of dimethylformamide (DMF) to make the nanofiber composites. The as-spun nanofibers were then hot-stretched in the oven to enhance its orientation and crystallinity. With the introduction of SWNTs and by the hot-stretched process, the mechanical properties will be enhanced correspondingly. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray scattering (XRD), differential scanning calorimetry (DSC), and the tensile test were used to characterize the microstructure and performances of the nanofibers. The orientation and crystallinity of the as-spun and hot-stretched nanofibers confirmed by X-ray have increased. Differential scanning calorimetry showed that the glass transition temperature of PAN increased about 3 °C by an addition of 0.75 wt% SWNTs indicating a strong interfacial interaction between PAN and SWNTs. The tensile strength and the modulus of the nanofibers increased revealing significant load transfer across the nanotube-matrix interface. For PAN nanofibers, the improved fiber alignment, orientation and crystallinity resulted in enhanced mechanical properties, such as the tensile strength and modulus of the nanofibers. It was concluded that the hot-stretched nanofiber and the PAN/SWNTs nanofibers can be used as a potential precursor to produce high-performance nanocomposites. Full article
(This article belongs to the Special Issue Nanocomposites of Polymers and Inorganic Particles 2011)
Open AccessArticle Prior Surface Integrity Assessment of Coated and Uncoated Carbide Inserts Using Atomic Force Microscopy
Materials 2011, 4(4), 633-650; doi:10.3390/ma4040633
Received: 21 February 2011 / Revised: 29 March 2011 / Accepted: 2 April 2011 / Published: 6 April 2011
PDF Full-text (1439 KB) | HTML Full-text | XML Full-text
Abstract
Coated carbide inserts are considered vital components in machining processes and advanced functional surface integrity of inserts and their coating are decisive factors for tool life. Atomic Force Microscopy (AFM) implementation has gained acceptance over a wide spectrum of research and science [...] Read more.
Coated carbide inserts are considered vital components in machining processes and advanced functional surface integrity of inserts and their coating are decisive factors for tool life. Atomic Force Microscopy (AFM) implementation has gained acceptance over a wide spectrum of research and science applications. When used in a proper systematic manner, the AFM features can be a valuable tool for assessment of tool surface integrity. The aim of this paper is to assess the integrity of coated and uncoated carbide inserts using AFM analytical parameters. Surface morphology of as-received coated and uncoated carbide inserts is examined, analyzed, and characterized through the determination of the appropriate scanning setting, the suitable data type imaging techniques and the most representative data analysis parameters using the MultiMode AFM microscope in contact mode. The results indicate that it is preferable to start with a wider scan size in order to get more accurate interpretation of surface topography. Results are found credible to support the idea that AFM can be used efficiently in detecting flaws and defects of coated and uncoated carbide inserts using specific features such as “Roughness” and “Section” parameters. A recommended strategy is provided for surface examination procedures of cutting inserts using various AFM controlling parameters. Full article
Open AccessArticle Efficacy and Durability in Direct Labeling of Mesenchymal Stem Cells Using Ultrasmall Superparamagnetic Iron Oxide Nanoparticles with Organosilica, Dextran, and PEG Coatings
Materials 2011, 4(4), 703-715; doi:10.3390/ma4040703
Received: 7 March 2011 / Revised: 29 March 2011 / Accepted: 2 April 2011 / Published: 7 April 2011
Cited by 13 | PDF Full-text (437 KB) | HTML Full-text | XML Full-text
Abstract
We herein report a comparative study of mesenchymal stem cell (MSC) labeling using spherical superparamagnetic iron oxide (SPIO) nanoparticles containing different coatings, namely, organosilica, dextran, and poly(ethylene glycol) (PEG). These nanomaterials possess a similar SPIO core size of 6–7 nm. Together with [...] Read more.
We herein report a comparative study of mesenchymal stem cell (MSC) labeling using spherical superparamagnetic iron oxide (SPIO) nanoparticles containing different coatings, namely, organosilica, dextran, and poly(ethylene glycol) (PEG). These nanomaterials possess a similar SPIO core size of 6–7 nm. Together with their coatings, the overall sizes are 10–15 nm for all SPIO@SiO2, SPIO@dextran, and SPIO@PEG nanoparticles. These nanoparticles were investigated for their efficacies to be uptaken by rabbit bone marrow-derived MSCs without any transfecting agent. Experimentally, both SPIO@SiO2 and SPIO@PEG nanoparticles could be successfully uptaken by MSCs while the SPIO@dextran nanoparticles demonstrated limited labeling efficiency. The labeling durability of SPIO@SiO2 and SPIO@PEG nanoparticles in MSCs after three weeks of culture were compared by Prussian blue staining tests. SPIO@SiO2 nanoparticles demonstrated more blue staining than SPIO@PEG nanoparticles, rendering them better materials for MSCs labeling by direct uptake when durable intracellullar retention of SPIO is desired. Full article
(This article belongs to the Special Issue Surface Modification and Assembly of Magnetic Nanoparticle Materials)
Open AccessArticle Open-Cellular Co-Base and Ni-Base Superalloys Fabricated by Electron Beam Melting
Materials 2011, 4(4), 782-790; doi:10.3390/ma4040782
Received: 17 March 2011 / Revised: 30 March 2011 / Accepted: 6 April 2011 / Published: 14 April 2011
Cited by 7 | PDF Full-text (763 KB) | HTML Full-text | XML Full-text
Abstract
Reticulated mesh samples of Co-29Cr-6Mo alloy and Ni-21Cr-9Mo-4Nb alloy (625) and stochastic foam samples of Co-29Cr-6Mo alloy fabricated by electron beam melting were characterized by optical metallography, and the dynamic stiffness (Young’s modulus) was measured by resonant frequency analysis. The relative stiffness [...] Read more.
Reticulated mesh samples of Co-29Cr-6Mo alloy and Ni-21Cr-9Mo-4Nb alloy (625) and stochastic foam samples of Co-29Cr-6Mo alloy fabricated by electron beam melting were characterized by optical metallography, and the dynamic stiffness (Young’s modulus) was measured by resonant frequency analysis. The relative stiffness (E/Es) versus relative density (ρ/ρs) plotted on a log-log basis resulted in a fitted straight line with a slope n ≅ 2, consistent with that for ideal open cellular materials. Full article
(This article belongs to the Special Issue Aerospace Materials)
Open AccessArticle Gold Nanostructures for Surface-Enhanced Raman Spectroscopy, Prepared by Electrodeposition in Porous Silicon
Materials 2011, 4(4), 791-800; doi:10.3390/ma4040791
Received: 18 March 2011 / Revised: 4 April 2011 / Accepted: 11 April 2011 / Published: 14 April 2011
Cited by 14 | PDF Full-text (414 KB) | HTML Full-text | XML Full-text
Abstract
Electrodeposition of gold into porous silicon was investigated. In the present study, porous silicon with ~100 nm in pore diameter, so-called medium-sized pores, was used as template electrode for gold electrodeposition. The growth behavior of gold deposits was studied by scanning electron [...] Read more.
Electrodeposition of gold into porous silicon was investigated. In the present study, porous silicon with ~100 nm in pore diameter, so-called medium-sized pores, was used as template electrode for gold electrodeposition. The growth behavior of gold deposits was studied by scanning electron microscope observation of the gold deposited porous silicon. Gold nanorod arrays with different rod lengths were prepared, and their surface-enhanced Raman scattering properties were investigated. We found that the absorption peak due to the surface plasmon resonance can be tuned by changing the length of the nanorods. The optimum length of the gold nanorods was ~600 nm for surface-enhanced Raman spectroscopy using a He-Ne laser. The reason why the optimum length of the gold nanorods was 600 nm was discussed by considering the relationship between the absorption peak of surface plasmon resonance and the wavelength of the incident laser for Raman scattering. Full article
(This article belongs to the Special Issue Porous Materials 2011)
Open AccessArticle Structural Consideration in Designing Organotin Polyethers to Arrest the Growth of Breast Cancer Cells In Vitro
Materials 2011, 4(4), 801-815; doi:10.3390/ma4040801
Received: 11 February 2011 / Revised: 4 April 2011 / Accepted: 8 April 2011 / Published: 15 April 2011
Cited by 19 | PDF Full-text (232 KB) | HTML Full-text | XML Full-text
Abstract
The ability to inhibit cancer is inherent in organotin materials yet the structural relationships that regulate/direct this activity remains unknown. We measured antitumor activity using a matched pair of cell lines MDA-MB-231 cells that are estrogen-independent, estrogen receptor negative and MCF-7 cells, [...] Read more.
The ability to inhibit cancer is inherent in organotin materials yet the structural relationships that regulate/direct this activity remains unknown. We measured antitumor activity using a matched pair of cell lines MDA-MB-231 cells that are estrogen-independent, estrogen receptor negative and MCF-7 cells, a cell line that is estrogen receptor (ER) positive. Those polyethers that contained a O-phenyl unit were able to significantly inhibit the non-estrogen sensitive cell line but were much less effective against the estrogen sensitive cell line; that is, the human breast cancer cell line MDA-MB-231 showed better test results for polymers derived from diols containing the O-phenyl moiety than the breast cancer cell line MCF-7, a well-characterized estrogen receptor positive control cell line. Those polyethers that did not contain the O-phenyl unit inhibited both cell lines approximately the same. The differential activity of the O-phenyl-containing polyethers is likely due to the estrogen-sensitive cells combining with some of the organotin polyethers minimizing their ability to inhibit cell growth. Full article
(This article belongs to the Special Issue Metal-Containing Polymers)

Review

Jump to: Research

Open AccessReview Magnetoelectric Interactions in Lead-Based and Lead-Free Composites
Materials 2011, 4(4), 651-702; doi:10.3390/ma4040651
Received: 10 February 2011 / Revised: 15 March 2011 / Accepted: 23 March 2011 / Published: 6 April 2011
Cited by 15 | PDF Full-text (1940 KB) | HTML Full-text | XML Full-text
Abstract
Magnetoelectric (ME) composites that simultaneously exhibit ferroelectricity and ferromagnetism have recently gained significant attention as evident by the increasing number of publications. These research activities are direct results of the fact that multiferroic magnetoelectrics offer significant technological promise for multiple devices. Appropriate [...] Read more.
Magnetoelectric (ME) composites that simultaneously exhibit ferroelectricity and ferromagnetism have recently gained significant attention as evident by the increasing number of publications. These research activities are direct results of the fact that multiferroic magnetoelectrics offer significant technological promise for multiple devices. Appropriate choice of phases with co-firing capability, magnetostriction and piezoelectric coefficient, such as Ni-PZT and NZFO-PZT, has resulted in fabrication of prototype components that promise transition. In this manuscript, we report the properties of Ni-PZT and NZFO-PZT composites in terms of ME voltage coefficients as a function of frequency and magnetic DC bias. In order to overcome the problem of toxicity of lead, we have conducted experiments with Pb-free piezoelectric compositions. Results are presented on the magnetoelectric performance of Ni-NKN, Ni-NBTBT and NZFO-NKN, NZFO-NBTBT systems illustrating their importance as an environmentally friendly alternative. Full article
(This article belongs to the Special Issue Advances in Ferroelectric & Piezoelectric Materials)
Open AccessReview New Approaches to the Computer Simulation of Amorphous Alloys: A Review
Materials 2011, 4(4), 716-781; doi:10.3390/ma4040716
Received: 12 March 2011 / Accepted: 2 April 2011 / Published: 13 April 2011
Cited by 7 | PDF Full-text (3012 KB) | HTML Full-text | XML Full-text
Abstract
In this work we review our new methods to computer generate amorphous atomic topologies of several binary alloys: SiH, SiN, CN; binary systems based on group IV elements like SiC; the GeSe2 chalcogenide; aluminum-based systems: AlN and AlSi, and the CuZr [...] Read more.
In this work we review our new methods to computer generate amorphous atomic topologies of several binary alloys: SiH, SiN, CN; binary systems based on group IV elements like SiC; the GeSe2 chalcogenide; aluminum-based systems: AlN and AlSi, and the CuZr amorphous alloy. We use an ab initio approach based on density functionals and computationally thermally-randomized periodically-continued cells with at least 108 atoms. The computational thermal process to generate the amorphous alloys is the undermelt-quench approach, or one of its variants, that consists in linearly heating the samples to just below their melting (or liquidus) temperatures, and then linearly cooling them afterwards. These processes are carried out from initial crystalline conditions using short and long time steps. We find that a step four-times the default time step is adequate for most of the simulations. Radial distribution functions (partial and total) are calculated and compared whenever possible with experimental results, and the agreement is very good. For some materials we report studies of the effect of the topological disorder on their electronic and vibrational densities of states and on their optical properties. Full article
(This article belongs to the Special Issue Amorphous Alloys)
Open AccessReview Progress of Application Researches of Porous Fiber Metals
Materials 2011, 4(4), 816-824; doi:10.3390/ma4040816
Received: 1 March 2011 / Revised: 1 April 2011 / Accepted: 12 April 2011 / Published: 19 April 2011
Cited by 17 | PDF Full-text (351 KB) | HTML Full-text | XML Full-text
Abstract
Metal fiber porous materials with intrinsic properties of metal and functional properties of porous materials have received a great deal of attention in the fundamental research and industry applications. With developments of the preparation technologies and industrial requirements, porous fiber metals with [...] Read more.
Metal fiber porous materials with intrinsic properties of metal and functional properties of porous materials have received a great deal of attention in the fundamental research and industry applications. With developments of the preparation technologies and industrial requirements, porous fiber metals with excellent properties are developed and applied in many industry areas, e.g., sound absorption, heat transfer, energy absorption and lightweight structures. The applied research progress of the metal fiber porous materials in such application areas based on the recent work in our group was reviewed in this paper. Full article
(This article belongs to the Special Issue Porous Materials 2011)
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