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Aluminum monoxide (AlO) and a nonstoichiometric alumina (n-alumina) with its chemical composition similar to that of AlO were proposed theoretically for a promising low-loss plasmonic material. However, they were rarely studied due to the high thermodynamic instability. Recently, n-aluminas with their O/Al atomic ratios close to 1 were found to form on Al nanospheres synthesized by electrical explosion. Although a new bulk plasmon resonance was observed below the excitonic transition energy from the n-aluminas, no investigation into surface plasmon resonance – the key component for plasmonics - was conducted yet. Here I report on surface plasmons of the n-aluminas discovered by spatially-resolved electron energy loss spectroscopy. Energy loss spectra collected from local spots of the n-aluminas are analyzed to reveal that there are two types of n-aluminas; one with two surface plasmons (n-alumina A) and the other with one surface plasmon (n-alumina B). Remarkably, the oscillator strengths of the novel surface plasmons are as high as that of surface plasmon of Al. The electronic band structure proposed for the n-alumina A shows a lossless energy zone. Consequently, current study demonstrates that the n-aluminas have the potential as a new low-loss plasmonic material.

It has recently been suggested that the extraordinary strain hardening rate in Fe-16Mn-10Al-0.86C-5Ni high specific strength steel [1] is due to the high back stresses arising from the strain incompatibility between austenite matrix and B2-ordered intermetallic second phase [2]. I argue here that the alloy matrix chemistry, particularly short-range ordering of constituent atoms, could be the intrinsic factor that affects the deformation and strain hardening, rather than the stress-strain partitioning caused by the microstructural heterogeneity.

Research is conducted to understand relatively unknown electronic behavior of a nanoscale Al/alumina system. This is acquired by a two-step process where characterization by electron microscopy is first performed for crystallography, followed by electron energy loss spectroscopy for electronic response from spatially inequivalent spots of Al nanoparticles with a protective surface oxide. A novel and unique plasmon from the surface oxide is found in the energy loss spectra between 5 and 6 eV other than the previously reported transitions for individual Al and Al2O3. In the current study, various properties of the new transition are sought by evaluating its dependence on crystal structure and particle size along with related physical functions. The results indicate that the novel transition has collective properties, preceded by a single-electron excitation at a slightly lower energy. Application of the Bethe f-sum rule shows that the concentration of charge carriers reaches around the Mott density by the t...

Although steel has been the workhorse of the automotive industry since the 1920s, the share by weight of steel and iron in an average light vehicle is now gradually decreasing, from 68.1 per cent in 1995 to 60.1 per cent in 2011 (refs 1, 2). This has been driven by the low strength-to-weight ratio (specific strength) of iron and steel, and the desire to improve such mechanical properties with other materials. Recently, high-aluminium low-density steels have been actively studied as a means of increasing the specific strength of an alloy by reducing its density. But with increasing aluminium content a problem is encountered: brittle intermetallic compounds can form in the resulting alloys, leading to poor ductility. Here we show that an FeAl-type brittle but hard intermetallic compound (B2) can be effectively used as a strengthening second phase in high-aluminium low-density steel, while alleviating its harmful effect on ductility by controlling its morphology and dispersion. The specific tensile strength and ductility of the developed steel improve on those of the lightest and strongest metallic materials known, titanium alloys. We found that alloying of nickel catalyses the precipitation of nanometre-sized B2 particles in the face-centred cubic matrix of high-aluminium low-density steel during heat treatment of cold-rolled sheet steel. Our results demonstrate how intermetallic compounds can be harnessed in the alloy design of lightweight steels for structural applications and others.

In this study an ionomer, an ion-containing polymer, was investigated at various degrees of neutralization and irradiated by fast electrons to see the effects on its properties by an electron-microscope-electron-spectroscopy system. It was found that electronic and chemical structures of the polymer can be changed dramatically by neutralization and irradiation. The modifications by neutralization may be attributed to reversible cross-linking and resultant vulnerability due to residual strain while those by irradiation to irreversible cross-linking and scission. The combination of neutralization and irradiation can change the chemistry of the polymer rapidly but in a controllable manner. It can also manipulate the size of the band gap and the type of interband transition along with the degree of the modifications. Since the modifications can be induced in a nanoscale area by convergent electrons the results of the current study may lead to utilizing an ionomer for nanotechnology.

Nanometer-size iron-rich particles in carbon nanotubes have been studied by transmission electron microscopy with and without in situ and ex situ heating. Several remarkable results were found; a high temperature phase (γ-Fe) of iron stable at low temperatures and preferential presence of iron and iron carbide in carbon nanotubes. Based upon these experimental results, thermodynamics of the Fe–C phase diagram and its kinetics were used to explain the non-uniform distribution of iron and iron carbide, which also yielded a deeper insight into the formation of carbon nanotubes. Some of the results also allowed describing the role of the graphitic structure in retaining the high temperature phase (γ-Fe) of iron at low temperatures. Furthermore, methods have been demonstrated with which γ-Fe can be produced in carbon nanotubes intentionally or in a large quantity. Selected area electron diffraction patterns of iron inside nanotubes demonstrated the crystallographic relationship of the iron to the nanotube axis along with phase changes of the iron. This paper summarizes the findings and draws further conclusions on the particle shape inside multiwalled carbon nanotubes.

Crystallographic structures and orientations of nanoscale iron particles encapsulated in carbon nanotubes (CNTs) were studied with or without heat treatments at various temperatures. It was found from this study that γ-Fe with a face-centered-cubic crystal structure (known to be stable in the temperature range of 912–1394 °C for bulk iron) retains its stability in a large quantity at room temperature inside the cavities of CNTs. The relative number of γ-Fe particles was found to increase with temperature, especially with heat treatment at 1400 °C or higher. It was also found that iron particles in CNTs are oriented in specific crystallographic directions of their crystal structures along the axis of the nanotubes.

The effects of the dispersion and concentration of single walled carbon nanotube (SWNT) on the flammability of polymer/SWNT nanocomposites were investigated. The polymer matrix was poly (methyl methacrylate) (PMMA) and the SWNT were dispersed using a phase separation (‘coagulation’) method. Dispersion of SWNTs in these nanocomposites was characterized by optical microscopy on a micrometer scale. Flammability properties were measured with a cone calorimeter in air and a gasification device in a nitrogen atmosphere. In the case where the nanotubes were relatively well-dispersed, a nanotube containing network structured layer was formed without any major cracks or openings during the burning tests and covered the entire sample surface of the nanocomposite. However, nanocomposites having a poor nanotube dispersion or a low concentration of the nanotubes (0.2% by mass or less) formed numerous black discrete islands with vigorous bubbling occurring between these islands. Importantly, the peak heat release rate of the nanocomposite that formed the network layer is about a half of those, which formed the discrete islands. It is proposed that the formation of the discrete islands is due to localized accumulation of the nanotubes as a result of fluid convection accompanying bubble formation and rise of the bubbles to the surface through the molten sample layer and bursting of the bubbles at the surface. The network layer acts as a heat shield to slow the thermal degradation of PMMA.

In this study, oxidized iron particles on an amorphous carbon film were irradiated by an intensive and convergent electron beam in situ inside a transmission electron microscope. It was found that some iron particles could be fractured into several particles and also could form a graphitic film on the outer surface in a very short time by the electron beam. By the electron beam the iron particles were found to be reduced to α-Fe, γ-Fe, or Fe3C. The high temperature phase of iron (γ-Fe) was observed to be stable only when it was tightly encapsulated in a graphitic film formed during the beam irradiation. This result indicates that the high elastic modulus of graphite on the surface holds the γ-Fe phase from expanding and transforming to α-Fe (the stable phase of iron at room temperature).

Selective encapsulation of different materials or phases of a material inside a carbon nanotube leads to controlling local properties of the nanotube. We report a method of synthesizing stable γ-Fe selectively inside a carbon nanotube by transforming α-Fe through electron irradiation in situ inside a transmission electron microscope. Therefore, this method enables a single nanotube to encase both high (γ-Fe) and low (α-Fe) temperature phases of iron simultaneously. γ-Fe produced by this method may be used as a novel catalyst, and its presence inside a carbon nanotube may affect the physical properties of the nanotube, which therefore can be used to modify the nanotube.

In this paper, we report on the synthesis and structure of hierarchical zinc oxide nanotubes. Hierarchical nanotubes grown by physical vaporization of zinc in the presence of a catalyst were decorated with many secondary zinc oxide nanorods on the outer surface. The axis of these nanotubes with an average diameter of 65 nm was aligned along the c axis of wurtzite zinc oxide. The hierarchical zinc oxide nanotubes, many of which were single crystals, were transparent or opaque, depending on whether they had a zinc layer inside. The opaque nanotubes showed an abrupt change in electronic transmittance during investigation with transmission electron microscopy. The unique structure of the hierarchical ZnO nanotubes and the quantum effect resulting from the reduced dimension will modify the original properties of ZnO, leading to novel applications.

In this study, the morphology of zinc sulfide (ZnS) produced on carbon nanotubes (CNTs) by heat treatment was investigated. It was found that ZnS nanocrystals were formed on the outermost shells of CNTs in the shapes of ultrathin films, quantum dots, and nanorods. X-ray diffraction patterns show synthesized ZnS has the wurtzite structure. Hexagonal cross sections of some ZnS nanorods prove that they were grown along the 〈0 0 0 1〉 direction on the surface of CNTs. ZnS nanorods were synthesized without using any catalyst differently from the previous reports. Heterojunctions between CNTs by these ZnS nanocrystals were also found, which can be applied for nanosized optic and optoelectronic devices.

The crystallographic structure and orientation of iron nanoparticles present in carbon nanotubes (CNTs) was studied when iron was used as a catalyst. It was found that while most of the nanoparticles encapsulated inside the CNTs had the expected α–Fe (body-centered-cubic) phase, a significant number of them formed and retained the γ–Fe (face-centered-cubic) phase that is not the normal bulk phase at room temperature (nor even expected to form at the growth temperature used). It was also found iron particles at the tips of the nanotubes were either α–Fe or cementite (Fe3C). On the basis of these observations and thermodynamics, a mechanism for the formation of these particles and insights into CNT growth is proposed.

Multiwalled carbon nanotubes (MWCNTs) with outermost diameters of ~5 to more than 100 nm are modified and investigated for structural and optical properties. MWCNTs are sonicated for a long time (100 min) to intentionally introduce defects and functional groups as well as annealed at a high temperature (2,000 °C) for further graphitization. They are examined for absorption and emission behavior and compared to the initial material. The MWCNTs are found to show plenty of highly-resolvable emission bands. Since they are observed from all the samples, the bands are considered to be intrinsic to MWCNTs. The mechanisms previously suggested for the emission of MWCNTs are compared using the structural features and the optical data. It was deduced that defects or functional groups are not involved in the luminescence. Rather, the emission bands imply interband transitions between van Hove singularities in the electronic band structure. These results not only help to understand inherent properties of MWCNTs but may also give insight into the luminescence phenomena of other carbon nanotube family such as double-walled carbon nanotubes and functionalized MWCNTs.

Adding a large amount of light elements such as aluminum to steels is not a new concept recalling that several Fe–Al–Mn–C alloys were patented in 1950s for replacement of nickel or chromium in corrosion resistance steels. However, the so-called lightweight steels or low-density steels were revisited recently, which is driven by demands from the industry where steel has served as a major structural material. Strengthening without loss of ductility has been a triumph in steel research, but lowering the density of steel by mixing with light elements will be another prospect that may support the competitiveness against emerging alternatives such as magnesium alloys. In this paper, we review recent studies on lightweight steels, emphasizing the concept of alloy design for microstructures and mechanical properties. The influence of alloying elements on the phase constituents, mechanical properties and the change of density is critically reviewed. Deformation mechanisms of various lightweight steels are discussed as well. This paper provides a reason why the success of lightweight steels is strongly dependent on scientific achievements even though alloy development is closely related to industrial applications. Finally, we summarize some of the main directions for future investigations necessary for vitalizing this field of interest.

The technology of increasing Internal Vcc without using memory tester is used to enhance the photon emission and the failure range is defined in detail by nano probing. With these methods, we found out that the leakage current was caused by dislocations of STI arranged in a row.

Drastic change: A nanoscale spot of polyethylene (PE) can change its electrical properties dramatically after exposure to fast electrons-from a representative insulator, via a semiconductor, to a hopping conductor (see picture). These modifications of the chemical and energy-band structures of PE are extremely localized, thus opening a new way to use this conventional polymer in nanotechnology. Herein, a nanoscale area on a polyethylene film is investigated by an electron-microscope-electron-spectroscopy system after exposure to various doses of fast electrons. Therefore, modifications in its physical and chemical properties and the spatial size of a beam-affected area are measured. The results show that the modifications of PE by electrons are significant enough to rebuild the chemical and energy-band structures. Hydrogen is removed through scission while pi bonds are formed by cross-linking between main chains. These changes cause the energy band of PE to show dramatic variation from a wide to a narrow (down to approximately 0.8 eV) band-gap. At the highest dose (10(10) C m(-2)) used herein, an illuminated area of PE becomes quite similar in properties to graphitic amorphous carbon. On the other hand, the size of the beam-affected area is as small as roughly 50 nm in diameter. Since the extent of the modifications can be tailored in a controllable way by the dose, these findings may be fundamental for the utilization of a conventional polymer in nanotechnology.

In this study the effect of electron irradiation on properties of a nanosized area of polystyrene was investigated at various doses by an electron-microscope-electron-spectroscopy system. Therefore, changes in electronic and chemical properties by the exposure were monitored from local areas of the conventional polymer using electron energy loss spectroscopy. Also, their spatial extension was measured by a high angle annular dark field detector. From the study it was found that a nanoscale region of polystyrene can modify its electronic and chemical structures dramatically by the irradiation, and the degree of modifications can be tailored by the electron dose. These results may suggest a way of utilizing conventional polymers in nanotechnology.

Various types of zinc oxide (ZnO) nanocrystais were synthesized by physical vaporization of zinc powders without the presence of catalysts and a subsequent exposure to air at a high temperature. These crystals were found to be composed of ZnO nanowires, sheets, and tetrapods. They were observed to crystallize as wurtzite ZnO single crystals. The nanowires are about 120 nm in diameter on average and up to a few dozens of micrometers in length, making aspect ratios higher than 10. The growth direction of the nanowires was identified to be the [001] direction of wurtzite ZnO structure. It was found from microscopic analyses that these ZnO nanowires can be highly flexible. The values for the thickness of ZnO sheets are scattered, averaging 100 nm. The tetrapods may have a different number of projections radiating from one central node.

There is growing interest in the potential of electrically conducting metal-loaded polymer adhesives for solder replacement in electrical lead attachment. Eight commercial electrically conductive adhesive (ECA) pastes were selected for study, including both thermosetting and thermoplastic examples. All were silver based, except for one nickel-polymer composite. >

The influence of the high surface-to-volume ratio of ZnO nanomaterials, whose sizes are large enough to exclude the quantum effect, on electronic properties was investigated by spatially resolved valence electron energy loss spectroscopy. ZnO nanowires, nanoplates, and nanotubes with different sizes were fabricated and characterized. Both the reduced volume and the increased surface area of the large ZnO nanomaterials were found to be able to modify electronic properties significantly. Hence, a nanoplate and a nanotube with very small volumes show unique energy loss functions and dielectric functions different from those of bulk ZnO at all the probe points. On the other hand, a nanowire with a relatively large diameter (70 nm) has electronic properties similar to those of bulk ZnO at the center. However, they are dissimilar at the edge of the nanowire due to the component of surface parallel to the electron path and the reduced interaction volume. Moreover, some interband transitions shift positions and bulk plasmons change oscillator strength depending upon the size of the volume and the geometry of the surface. These empirical results demonstrate that semiconducting nanomaterials larger than the exciton Bohr radius can still behave differently from bulk materials due to the high ratio between surface area and volume.

A system composed of a metal core and a phosphor shell—a hierarchical Zn/ZnO concentric nanotube—was investigated in this study for optical properties. The system was found to show a great enhancement in the emission efficiency of ZnO in a wide—but especially in the ultraviolet (UV)—spectral region. This enhancement is attributed to efficient coupling between photons from the ZnO phosphor and surface plasmons (SPs) from the very thin Zn tubule. Its decoupling is facilitated by the unique structure and morphology of the system. Remarkably, Zn—known as a lossy metal—still can successfully multiply the luminescence yield of a phosphor, comparable to noble metals. The SP resonance energy of Zn in the system matches even better for the excitonic emission of ZnO. The nanotubes are synthesized by a simple and low-cost vaporization method. Moreover, they require no additional coating with precious metals for the high yield in luminescence while the Zn tubule is quite stable encapsulated by ZnO. Our results demonstrate that an effective conductor-dielectric geometry makes it possible not only to tune the SP resonance energy but also to increase the degree of coupling.

Wire- and belt-like single-crystalline titanium dioxide nanostructures were synthesized by using a simple thermal annealing method, which has often been avoided for the synthesis of metal oxide nanostructures from high melting point metals such as Ti. The synthesis method requires neither high reaction temperature nor complicated reaction processes, and can be used for producing dense nanomaterials with relatively short reaction time at temperatures much lower than the melting point of titanium and titanium dioxide. Key synthesis factors including the choice of eutectic catalyst, growth temperature, and annealing time were systematically investigated. The synthesis reaction was promoted by a copper eutectic catalyst, producing long nanostructures with short reaction times. For example, it was observed that only 30 min of annealing time at 850 degrees C was enough to produce densely grown approximately 10 microm long nanowires with diameters of approximately 100 nm, and longer reaction time brought about morphology changes from wires to belts as well as producing longer nanostructures up to approximately 30 microm. The nanostructures have the crystalline rutile structure along the [Formula: see text] growth direction. Finally, our simple and effective method for the synthesis of TiO2 nanostructures could be utilized for growing other metal oxide nanowires from high melting temperature metals.