Nano Features Research Articles

Evidence for core–shell nanoclusters in oxygen dispersion strengthened steels measured using X-ray absorption spectroscopy

Nanostructured ferritic alloys (NFA) dispersion strengthened by an ultra high density of Y–Ti–O enriched nano-features (NF) exhibit superior creep strength and the potential for high resistance to radiation damage. However, the detailed character of the NF, that precipitate from solid solution during hot consolidation of metallic powders mechanically alloyed with Y2O3, are not well understood. In order to clarify the nature of the NF, X-ray absorption spectroscopy (XAS) technique, including X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) were used to characterize the local structure of the Ti and Y atoms in both NFA powders and consolidated alloys. The powders were characterized in the as-received, as-milled and after annealing milled powders at 850, 1000 and 1150°C. The consolidated alloys included powders hot isostatic pressed (HIPed) at 1150°C and commercial vendor alloys, MA957 and J12YWT. The NFA XAS data were compared various Ti and Y-oxide standards. The XANES and EXAFS spectra for the annealed and HIPed powders are similar and show high temperature heat treatments shift the Y and Ti to more oxidized states that are consistent with combinations of Y2Ti2O7 and, especially, TiO. However, the MA957 and J12YWT and annealed–consolidated powder data differ. The commercial vendor alloys results more closely resemble the as-milled powder data and all show that a significant fraction of substitutional Ti remains dissolved in the (BCC) ferrite matrix.

Особенности использования нано- и ультрадисперсных порошков окислителя в пиротехнических составах

Особенности использования нано- и ультрадисперсных порошков окислителя в пиротехнических составах

Deep sub-wavelength imaging lithography by a reflective plasmonic slab

By utilizing a reflective plasmonic slab, it is demonstrated numerically and experimentally in this paper deep sub-wavelength imaging lithography for nano characters with about 50 nm line width and dense lines with 32 nm half pitch resolution (about 1/12 wavelength). Compared with the control experiment without reflective plasmonic slab, resolution and fidelity of imaged resist patterns are remarkably improved especially for isolated nano features. Further numerical simulations show that near field optical proximity corrections help to improve imaging fidelity of two dimensional nano patterns.

Fabricated Micro‐Nano Devices for In vivo and In vitro Biomedical Applications

In recent years, the innovative use of microelectromechanical systems (MEMSs) and nanoelectromechanical systems (NEMSs) in biomedical applications has opened wide opportunities for precise and accurate human diagnostics and therapeutics. The introduction of nanotechnology in biomedical applications has facilitated the exact control and regulation of biological environments. This ability is derived from the small size of the devices and their multifunctional capabilities to operate at specific sites for selected durations of time. Researchers have developed wide varieties of unique and multifunctional MEMS/NEMS devices with micro and nano features for biomedical applications (BioMEMS/NEMS) using the state of the art microfabrication techniques and biocompatible materials. However, the integration of devices with the biological milieu is still a fundamental issue to be addressed. Devices often fail to operate due to loss of functionality, or generate adverse toxic effects inside the body. The in vitro and in vivo performance of implantable BioMEMS such as biosensors, smart stents, drug delivery systems, and actuation systems are researched extensively to understand the interaction of the BioMEMS devices with physiological environments. BioMEMS developed for drug delivery applications include microneedles, microreservoirs, and micropumps to achieve targeted drug delivery. The biocompatibility of BioMEMS is further enhanced through the application of tissue and smart surface engineering. This involves the application of nanotechnology, which includes the modification of surfaces with polymers or the self-assembly of monolayers of molecules. Thereby, the adverse effects of biofouling can be reduced and the performance of devices can be improved in in vivo and in vitro conditions.

Protonation of Epigallocatechin-3-gallate (EGCG) Results in Massive Aggregation and Reduced Oral Bioavailability of EGCG-Dispersed Selenium Nanoparticles

The current results show that epigallocatechin-3-gallate (EGCG), in the form of phenolic anions at pH 8.0, can effectively disperse selenium nanoparticles. However, at gastric juice pH (1.0), the EGCG-dispersed selenium nanoparticles (referred to as E-Se) extensively aggregated, so that nano features largely disappeared. This demonstrates that deprotonated phenolic anions of EGCG play an important role in maintaining E-Se stability and suggests that E-Se would suffer from reduced oral bioavailability. To validate this conjecture, size-equivalent E-Se and bovine serum albumin (BSA)-dispersed selenium nanoparticles (B-Se), whose physicochemical properties were not altered at pH 1.0, were orally administered to selenium-deficient mice. In comparison to B-Se, the bioavailabilities of E-Se as indicated with hepatic and renal glutathione peroxidase activity and hepatic selenium levels were significantly (p < 0.01) reduced by 39, 32, and 31%, respectively. Therefore, the present study reveals that size-equivalent selenium nanoparticles prepared by different dispersers do not necessarily guarantee equivalent oral bioavailability.

Fabrication and Characterization of Naturally Selected Epitaxial Fe-{111} Y2Ti2O7 Mesoscopic Interfaces: Some Potential Implications to Nano-Oxide Dispersion-Strengthened Steels

The smallest features of ≈2 to 3 nm in nanostructured ferritic alloys (NFA), a variant of oxide dispersion-strengthened steels, include the Y2Ti2O7 complex oxide cubic pyrochlore phase. The interface between the bcc Fe-Cr ferrite matrix and the fcc nanometer-scale Y2Ti2O7 plays a critical role in the stability, strength, and damage tolerance of NFA. To complement other characterization studies of the actual nanofeatures (NF) themselves, mesoscopic interfaces were created by electron beam deposition of a thin Fe layer on a 5 deg miscut {111} Y2Ti2O7 bulk single crystal surface. While the mesoscopic interfaces may differ from those of the embedded NF, the former facilitate characterization of controlled interfaces, such as interactions with point defects and helium. The Fe-Y2Ti2O7 interfaces were studied using scanning electron microscopy, including electron backscatter diffraction, atomic force microscopy, X-ray diffraction, and transmission electron microscopy (TEM). The polycrystalline Fe layer has two general orientation relationships (OR) that are close to (a) the Nishiyama–Wasserman (NW) OR \( \left\{ {110} \right\}_{\text{Fe}} ||\left\{ {111} \right\}_{{{\text{Y}}_{2} {\text{Ti}}_{2} {\text{O}}_{7} }} \) and \( \left\langle {100} \right\rangle_{\text{Fe}} ||\left\langle {110} \right\rangle_{{{\text{Y}}_{2} {\text{Ti}}_{2} {\text{O}}_{7} }} \) and (b) \( \left\{ {100} \right\}_{\text{Fe}} ||\left\{ {111} \right\}_{{{\text{Y}}_{2} {\text{Ti}}_{2} {\text{O}}_{7} }} \) and \( \left\langle {100} \right\rangle_{\text{Fe}} ||\left\langle {110} \right\rangle_{{{\text{Y}}_{2} {\text{Ti}}_{2} {\text{O}}_{7} }} \). High-resolution TEM shows that the NW interface is near-atomically flat, while the {100}Fe grains are an artifact associated with a thin oxide layer. However, the fact that there is still a Fe-Y2Ti2O7 OR is significant. No OR is observed in the presence of a thicker oxide layer.

Insight into the Compositional and Structural Nano Features of AlN/GaN DBRs by EELS-HAADF

III-V nitride (AlGa)N distributed Bragg reflector devices are characterized by combined high-angle annular dark-field (HAADF) and electron energy loss spectroscopy (EELS) in the scanning transmission electron microscope. Besides the complete structural characterization of the AlN and GaN layers, the formation of AlGaN transient layers is revealed using Vegard law on profiles of the position of the bulk plasmon peak maximum. This result is confirmed by comparison of experimental and simulated HAADF intensities. In addition, we present an advantageous method for the characterization of nano-feature structures using low-loss EELS spectrum image (EEL-SI) analysis. Information from the materials in the sample is extracted from these EEL-SI at high spatial resolution.The log-ratio formula is used to calculate the relative thickness, related to the electron inelastic mean free path. Fitting of the bulk plasmon is performed using a damped plasmon model (DPM) equation. The maximum of this peak is related to the chemical composition variation using the previous Vegard law analysis. In addition, within the context of the DPM, information regarding the structural properties of the material can be obtained from the lifetime of the oscillation. Three anomalous segregation regions are characterized, revealing formation of metallic Al islands.

Nanosilicon dioxide/o-phenylenediamine hybrid composite as a modifier for steel paints

Different amounts of the hybrid composite nano SiO2/o-phenylenediamine were added to a typical paint being used for protecting steel against corrosion to increase its protection efficiency. The nano features of the composite were confirmed by different electron microscopic investigations. It was found that the protection efficiency of the paint increased significantly as well as its adhesion to the steel surface increased. These conclusions had been inferred from both potentiodynamic polarization and electrochemical impedance spectroscopy techniques. To confirm the previous concept salt spray test and adhesion force measurements were carried out. The results were interpreted in terms of the filling properties of nano SiO2 and adsorption/hardening power of o-phenylenediamine.

Influence of back contact roughness on light trapping and plasmonic losses of randomly textured amorphous silicon thin film solar cells

The influence of nanotextured metallic back contacts on light trapping and plasmonic losses of amorphous silicon solar cells was investigated. The optical losses of the back contact are determined by the texture of the metallic back contact and the dielectric constant of the interlayer between the solar cell and the metal back contact. The investigations show that the optical losses are highest if nano features are present at the back contact, while the texture of the front contact which propagates through the layer stack exhibits only a minor effect on the optical losses.

Review of Electrochemical and Electrodischarge Machining

Electrochemical and electro-discharge machining processes are the two major electro-machining processes with unique capabilities. Electrical Discharge Machining (EDM) and Electrochemical Machining (ECM) offer a better alternative or sometimes the only alternative in generating accurate 3-D complex shaped macro, micro and nano features and components of difficult–to-machine materials. Technological advances reported in electrochemical and electro discharge machining processes, which reflect the state of the art in academic and industrial research and applications, are briefly reviewed in this paper.

Alumina/Iron Oxide Nano Composite for Cadmium Ions Removal from Aqueous Solutions

Magnetic alumina nano composite (MANC) was prepared for combination of the adsorption features of nano activated alumina with the magnetic properties of iron oxides to produce a nano magnetic adsorbent, which can be separated from the medium by a simple magnetic process after adsorption. MANC was characterized using XRD, SEM, TEM, EDX and surface area (BET). Quantum design SQUID magnetometer was used to study the magnetic measurement. The present study was conducted to evaluate the feasibility of MANC for the removal of cadmium ions from aqueous solutions through batch adsorption technique. The effects of pH, adsorbent dose, temperature, contact time and initial Cd2+ concentration on cadmium ions adsorption were studied. Equilibrium data were fitted to Langmuir, Freundlich and Temkin isotherms. The equilibrium data were best represented by the Langmuir isotherm. The kinetic data were fitted to pseudo-first-order, pseudo-second-order, Elovich and intraparticle diffusion models, and it was found to follow closely the pseudo-second-order model. Thermodynamic parameters were calculated for the Cd2+ ion-MANC system and the positive value of ΔH° showed that the adsorption was endothermic in nature. Furthermore, a single-stage batch adsorber was designed for the removal of Cd2+ ions by MANC based on the equilibrium data obtained.

Characterization of Pearlite Morphology and Associated Micro-Cracks in EN9 Grade Carbon Steel by Atomic Force Microscopy

Micro and Nano Features of Microstructural Properties along with Micro-Cracks and Voids, which Severely Affect the Strength and Toughness of the Material, Were Studied in Commercial EN9 Steel Round Product by Using Atomic Force Microscopy (AFM). this Has Overcome the Limitations of Optical and Scanning Microscopy. the Aim of the Present Work Is to Characterize the Pearlite Matrix Properties for Nanoscale Results as Pearlitic Morphology and Lamellae Play a Significant Role in Influencing the Mechanical Properties. it Is Also Shown that the Atomic Force Microscope Is a 3D Characterizing Tool which Can Facilitate Visualizing the Adjacent Corners in Alternate Layers of Ferrite-Cementite Lamellae. it Is Also Noted that the Micro-Sized Cracks Exist at the Weak Interfaces between the Ferrite and Cementite Lamellae, which Would Limit the Work Hardening Property of Pearlite and Thus Reduce the Ultimate Tensile Strength Significantly. in Addition, Phase Transformation from γ-Phase to Pearlite Was Schematically Predicted and Discussed as Evident from Microstructural Characterization.

Ti-doped hematite nanostructures for solar water splitting with high efficiency

Ti-doped hematite nanostructures have been synthesized for efficient solar water splitting by adding TiCN as the Ti precursor in a hydrothermal method. Ti-doped hematite nanostructures show an urchin-like morphology with nano feature size, which increases the effective surface area compared to undoped nanostructures. A remarkable plateau photocurrent density value of 3.76 mA/cm2 has been observed for Ti-doped nanostructures under standard illumination conditions in 1 M NaOH electrolyte, which is 2.5 times higher than that for undoped nanostructures (1.48 mA/cm2). The photocurrent at 1.23 V vs. RHE (1.91 mA/cm2) is also enhanced to be over 2 times higher than that for undoped nanostructures (0.87 mA/cm2). X-ray photoelectron spectroscopy and x-ray absorption spectroscopy have been used to investigate the electronic structure of Ti-doped hematite, which suggest the increased donor density of hematite by Ti doping. The remarkable plateau current density in Ti-doped hematite nanostructures can be attributed to both the favorable urchin-like morphology and the Ti doping.

Bulk Metallic Glass Multiscale Tooling for Molding of Polymers with Micro to Nano Features: A Review

There is a growing demand for single-use disposable polymer devices with features at submicron scales. This requires resilient tooling which can be patterned to scales of the order of hundreds of nanometers. The requisite topology can be imparted to silicon, but it is too brittle to be of use in a die to mold thousands of plastic parts. The polycrystalline nature of tool steel means that it cannot be patterned with submicron detail. Some bulk amorphous alloys have the requisite mechanical properties to be viable as materials for such dies, and can be patterned—e.g., via embossing as a supercooled liquid into MEMS silicon or using focused ion beam (FIB)—with submicron features which may persevere over many thousands of molding cycles. The composition of the amorphous alloy must be carefully selected to suit the particular molding application (polymer/process). The state-of-the-art methodology is presented, along with results of our recent experimental investigations.

On the structure and chemistry of complex oxide nanofeatures in nanostructured ferritic alloy U14YWT

The remarkable radiation damage resistance of nanostructured ferritic alloys (NFAs) is attributed to the large numbers of matrix nanofeatures (NFs) of various types, which can enhance the recombination of displacement defects and trap transmutant helium in fine scale bubbles. Characterizing the chemistry, crystallographic structure and orientation relationships of the NFs is critical to understanding how they enhance the radiation damage resistance of NFAs. Conventional and high-resolution transmission electron microscopy and energy-dispersive spectroscopy were used to characterize the various types of NF and larger oxide phases in a model 14Cr–3 W–0.4Ti–0.25Y2O3 NFA (14YWT) hot isostatic pressed (HIP-ed) at 1150°C. Large CrTiO3 precipitates (50–300 nm) and small diffracting NFs (<5 nm) were found in this alloy. One major new result is the observation of an additional type of nanofeature (10–50 nm), orthorhombic in structure, with a square center cross-section, which constitutes a new kind of Y–Ti-oxide phase with lattice parameters different from those of known Y and Ti complex oxides. The interfaces of these particles seem to be semicoherent, while manifesting a possible orientation relationship with the BCC matrix. The ratio of Y to Ti varies between <1 and 2 for these larger NFs.

Role of subnano-, nano- and submicron-surface features on osteoblast differentiation of bone marrow mesenchymal stem cells

Subnano, nano and sub-micron surface features can selectively activate integrin receptors and induce osteoblast differentiation of bone marrow mesenchymal stem cells. Although it is widely accepted that nanoscale titanium surface roughness may promote differentiation of various osteoblast lineages, there has been no clear report on the threshold dimension of surface features and the optimized dimensions of surface features for triggering integrin activation and stem cell differentiation. This study systematically controlled titanium surface features from the sub-nano to sub-micron scales and investigated the corresponding effects on stem cell responses, such as integrin activation, cyclins, key transcriptional genes of osteoblast differentiation and osteoblastic phenotype genes. Surface features with sub-nano surface dimensions were insufficient to increase integrin activation compared to pure nanoscale titanium surface features. Although both pure nanoscale and nano-submicron hybrid scales of titanium surface features were sufficient for activating integrin-ligand proteins interactions through the α integrin subunits, only nano-submicron hybrid titanium surface features significantly accelerated subsequent osteoblast differentiation of primary mouse bone marrow stromal cells after 2 weeks. In addition, live cell analysis of human bone marrow mesenchymal stem cells on transparent titanium demonstrated rapid cytoskeletal re-organization on the nanoscale surface features, which ultimately induced higher expression of osteoblast phenotype genes after 3 weeks.

Stabilization of Amorphous Calcium Carbonate with Nanofibrillar Biopolymers

AbstractCalcium carbonate is the most abundant biomineral that is biogenically formed with a vast array of nano and microscale features. Among the less stable polymorphs present in mineralized organisms, the most soluble, amorphous calcium carbonate (ACC), formed in chitin exoskeletons of some crustacea, is of particular interest since aqueous stability of isolated ACC is limited to a few hours in the absence of polyanions or magnesium. Here the influence of a selection of biopolymer gels on the mineralization of calcium carbonate is investigated. Mineralization is achieved in all biopolymers tested, but is particularly abundant in collagen hydrogels, in which a significant proportion of the calcium carbonate (≈18%) is found to be amorphous. In dense collagen gels, this amorphous fraction does not crystallize for up to six weeks in deionized water at room temperature. The reason why collagen in particular should stabilize this phase remains obscure, although the results suggest that the fiber diameter, fiber spacing, and the amphoteric nature of collagen fibers are important. Upon immersion in phosphate containing solutions, the calcium carbonate present within the collagen hydrogels is readily converted to carbonated hydroxyapatite, enabling the formation of a stiff bone‐like composite containing 78 wt% mineral, essentially equivalent to cortical bone.

Micro/nano-patterned metal transfer using UV-curable polymers

This study was aimed at developing a metal-transfer technique to fabricate micro/nano metal patterns by using the adhesion force between metal layers and polymer surfaces. The force was generated by partial curing on a UV-curable polymer surface. This polymer contained glycido methacrylate, polyurethane diacrylate (PU-2) and O2-sensitive initiators, and was polymerized by covering it with an O2-permeable film under UV irradiation. Another UV-curable polymer, containing isobonyl acrylate, hexa-acrylated PU (PU-6) and O2-insensitive initiators, was utilized as the master mold. A layer of gold, pre-coated on the mold, was adhered to the partially cured intermediate layer, transferring gold patterns onto the intermediate layer. A scanning electron microscope, an optical microscope and atomic force microscopy were used to inspect the transferred yield and morphology of the gold patterns. A force–distance evaluation was also carried out to explore the adhesion force of the surfaces. The results show that the partially cured polymer can maintain the morphology of the pattern after a short period of irradiation and still displays its adhesive property on its surfaces. Instead of using the traditional photolithography and the lift-off process, the technique was performed to fabricate some complex patterns having micro and nano features, and interdigital electrodes, giving the potential for direct printing of microelectrodes and flexible circuits.

Thermal imprint techniques for preparation of superhydrophobic polymer coatings

The self-cleaning property of superhydrophobic surfaces has raised considerable interest among scientists. Many preparation methods require complex and expensive fabrication techniques that cannot be used to directly modify substrates. We designed an imprint process using a micro/nano-structured mold to emboss several polymer coatings in order to introduce superhydrophobicity and still maintain their transparent/translucent properties. Polydimethylsiloxane (PDMS) elastic molds with various micro and nano features were fabricated using different grades of sandpaper as master molds, increasing the water contact angles (WCAs) on the PDMS surfaces from 120° (plain) to more than 170°. The PDMS molds were then applied to replicate some commercial polymer coatings at an elevated temperature of about 140°C to transfer the mold pattern to the coatings. The hydrophobic property of those polymer coatings was then enhanced to a WCA of greater than 150°. After fluoroalkylsilane deposition on the surfaces, the surfaces displayed an improved lipophobic property (hexadecane contact angle (HCA) went from 90° to 110°). The arbitrarily-rough surfaces displayed ‘sticky superhydrophobicity’ due to the water drops being adsorbed and not rolling off from the surfaces. Atomic force microscopy (AFM) was employed to measure the morphologies of imprinted coatings and also estimate the roughness, occupying polymer ratios, and critical CA to evaluate the wetting of sample surfaces. From the evaluation of surface properties, all the samples using sandpaper as templates exhibited stable Cassie or metastable wetting. The rougher surfaces provided some large protrusions to contact with and be immersed into water droplets, leading to high water penetration depth and thus stickiness. Additionally, the rougher the mold was, the greater the WCA was, but the transparency of the coating was reduced. However, the imprinted polymer surfaces could still maintain sufficient transparency for use in applications requiring preservation of the appearance of the underlying surface.

Structural optimization of contact electrodes in microbial fuel cells for current density enhancements

More than 200% current density enhancement in miniaturized microbial fuel cells (MFCs) has been successfully demonstrated by optimizing the contact electrode structure using micro and nano features. Two fundamental issues are addressed in this work: (1) a methodology to enhance current/power density of MFCs by changing micro and nano structural configurations of contact electrodes and (2) a study on the effectiveness of charge transfer between living cells with organic nanowire-pili and micro/nano interfacial electrodes. This paper details the fabrication and characterization processes of miniaturized MFCs with experimental results, and discusses the prospective power density of MFCs using micro/nano processes. Moreover, a hypothesis for the direct electron transport mechanism from living cells to electrodes is experimentally corroborated. As such, this work represents a step toward higher energy conversion efficiency as well as practical applications of MFCs.