Indium tin oxide (ITO) films coated on float glass slides were exposed to 5 eV hyperthermal atomic oxygen at room temperature with increasing fluences: 2×1019, 6×1019 and 2×1020 O-atoms/cm2. We characterized the structure of the ITO films after room temperature atomic oxygen exposure with scanning electron microscope (SEM) and atomic force microscope (AFM), synchrotron X-ray diffraction (XRD), and cross-sectional transmission electron microscope (X-TEM). The unexposed ITO films were found to possess a nano-crystalline surface, and clean and abrupt ITO/SiO2 interfaces without interfacial phase. Surface roughness of the exposed ITO films increased with the increasing AO influences. The interface- sensitive peaks in XRD measurements with grazing incidence revealed that the crystallinity of the ITO was modified near the interface. Cross-sectional TEM confirmed that many ITO particles with diameters ranging from 2-10 nm formed in the SiO2 substrate near the interface after AO exposure. These findings suggest that O atoms can travel through the ITO films, where the boundaries of columnar-grown grains may supply the pathway.

Auger electron spectra (AES) and Auger electron photo-ion coincidence (AEPICO) spectra of poly(vinlylidene fluoride) (PVDF) were observed to study the mechanism of effective fluorine ion (F+) desorption by irradiation of photons corresponding to the transition from F 1s to s(C-F). In the AES at photon energy (hυ) = 690.3 eV (from F1s to |σ|(C-F)), the spectator-Auger shift is about 3 eV. At hn = 690.3 eV the contribution of spectator Auger electron to the observed Auger spectrum is large. In the F+ AEPICO spectra at hυ = 690.3 eV an intense peak appears. The peak positions of the F+ AEPICO spectra are in agreement with those of the Auger spectra. These results indicate that the mechanism for effective F+ ion desorption induced by the transition from F1s to σ(C-F) occurs through the spectator-Auger processes. The efficiency of ion desorption depends on the electronic structure of the spectator-Auger final state.

UV- and vacuum UV-assisted photo-oxidation of single-walled carbon nanotube (SWNT) paper occurred with: (1) atmospheric oxygen pressure using low-pressure Hg lamps (λ = 253.7 and 184.9 nm), (2) low oxygen pressure employing emission downstream from an Ar microwave plasma (λ = 106.7 and 104.8 nm), and (3) high pressures of He in a rotating d.c. arc that was designed to produce a spectral continuum from He excimers (λ = 58 - 110 nm). The photo-oxidized materials were characterized by x-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and Raman spectroscopy. UV photo-oxidation was demonstrated to be a controlled dry procedure for introducing oxygenated functional groups (C-O-C, C=O, O-C=O and O=C-O-C=O) on SWNTs.

Information loss due to thermal activation is a major concern in ultrahigh-density magnetic recording media. The usually considered mechanism is thermally activated magnetization reversal over micromagnetic energy barriers. However, micromagnetic approaches ignore local anisotropy fluctuations, which translate into a time-dependent reduction of the remanent magnetization. The effect is negligibly small in macroscopic magnets but becomes important on a scale of a few nanometers.

ESR investigations on milled multiwalled carbon nanotubes are reported. The ESR spectra of pristine and milled nanotubes consists of two resonances, a wide line located at g>3.0 assigned to magnetic particles (catalysts residues) and a broad line with a peak to peak linewidth of about 10−2 T located at g=2.05 and assigned to the interaction between the conducting electrons delocalized over carbon nanotubes and magnetic ions. It was observed that this line depends on the milling time. For short milling times (up to 125 minutes) both the resonance linewidth and the g-factor increase as the milling time is increased. Longer milling times resulted in a decrease of both the g-factor and resonance linewidth as the milling time was increased. This behavior was assigned to the removal of the magnetic nanoparticles from nanotubes. No resonance line due to the destruction of carbon nanotubes was observed.

Bioceramics based on hydroxyapatite (HAp) is known to be a prospective material for biomedical applications. However, sintering of HAp is still understudied in sense of reasonable selection of controlling parameters. In particular, the role of impurities and co-products of powder fabrication is still questionable. The data concerning the role of ammonium nitrate coming to precipitated HAp from the mother liquor, its effect on powder compaction and subsequent sintering, are not available.

Nanosized powders of HAp were fabricated via conventional wet-precipitation technique by dropwise adding of Ca(NO3)2 solution (0.25 -1.67 M) to the stock solution of (NH4)2HPO4 (0.15-1.00 M) with pre-adjusted pH at 60°C in presence of polyvinyl alcohol (PVA). PVA was added to the stock solution in order (i) to block crystal growth during synthesis , (ii) to improve stability of Hap suspension to sedimentation, (iii) to regulate an aggregation of HA nanoparticles during synthesis and in the stage of drying.

NH4NO3 – a by-product of the precipitation reaction, presented in as-precipitated powder in amount of 30%, was evaluated as an additive affecting a compaction of the powder and the initial stage of a sintering. The powder samples were tested by XRD, FTIR, light-scattering , TEM and SEM/EDX to get particle sizes, morphology and chemical composition, dilatometry. Ceramics were sintered at 700-1250°C and evaluated with SEM/EDX and density measurements.

Addition of PVA to the stock solution in the course of HAp precipitation is a promising technique to control an aggregation of HAp nanoparticles in the stages of drying and sintering. PVA acting as a surfactant in the solution and as a binder in dry powder can keep highly reactive small HAp particles within large agglomerates providing better molding of the powder and controllable densification of ceramics. The effect of PVA on microstructure of the HAp powder and their sintering behaviour is discussed in terms of self-organisation concept and synergetics.

The condition of degradation of electrical properties of samples prepared from powder of nanoamorphous semiconductive oxide in the course of time is discovered and studied when investigating electro-physical properties of the given materials for the first time synthesized at Scientific Production Enterprise “ATOM”. It has been shown that degradation phenomenon is also present in amorphous materials, which relies on the configuration of the pores of the sample.

The resistance of sample in the open air changes over a period of several months. However, it decreases and is comparatively fast stabilized when placed in vacuum. The absorption and de-absorption of different gases have diffusion nature and highly depend on environment temperature. Water steam in atmosphere has been determined to be the main cause of degradation.

We have been developing a variety of nanomaterials for their use in power devices. An example of this is our use of both single wall carbon nanotubes and several varieties of semiconducting quantum dots (e.g., CuInS2, CdSe, InAs) for use in space solar cells. The ability of these materials to withstand the rigors of the space radiation environment will be essential for this intended application. In addition, we have also been developing both nanostructure III-V devices and radioluminescent quantum dots for use in radioisotope batteries. In this application these nanomaterials are subjected to an extremely high radiation level. Their degradation rate will be the key to determining the ultimate lifetime of these power supplies, which in principle can have an energy density that is orders of magnitude higher than any conventional battery chemistry. The nanomaterials included in this study were subjected to alpha particles fluences and the degradation in various properties were monitored using different analytical techniques. Specifically, the radioluminescence of the quantum dot intended for use in the radioisotope batteries was monitored as a function of fluence. In the case of the III-V quantum dots, their photoluminescent degradation as a function of fluence was measured in comparison to the bulk substrate on which the quantum dots were grown. Finally for the carbon nanotubes, relative intensities of the Raman peaks associated with their inherent vibrational modes was used to monitor the effects of the alpha radiation damage. Results on the radiation tolerance of these nanomaterials and its implication with regard to their ultimately utility in power devices are presented.

The synthesis of nanoscale superconductors with controlled geometries is extremely challenging. In this paper we present results on synthesis and characterization of one-dimensional (1D) NbSe2 superconducting nanowires/nanoribbons. Our synthesis approach includes the synthesis of 1D NbSe3 nanostructure precursors followed by nondestructive and controlled adjustment of the Se composition to formulate NbSe2. The morphology, composition and crystallinity of the synthesized 1D NbSe2 nanostructures were analyzed with scanning electron microscopy, x-ray diffraction and transmission electron microscopy. Transport measurements were carried out to explore the electronic properties of these confined superconducting nanostructures.

Whisker formation in pure Sn coatings on Cu conductors is a serious impediment to the development of Pb-free electronics manufacturing. Understanding whisker formation is complicated by the fact that it is the result of multiple materials kinetic processes including interdiffusion, intermetallic formation and stress generation We report preliminary studies of whisker growth kinetics and stress evolution aimed at developing a fundamental understanding of the whisker growth process. A proposed model of point defect mediated stress generation provides a simple picture of how the different processes are connected.

Copper / silver alloy thin films form with a fine, polycrystalline, metastable crystal structure. The expected effects of annealing include grain growth, transformation into the two stable phases, coarsening of the phases, texture formation, and the formation and growth of pinholes or voids. Copper/silver alloy films were deposited on single crystal sodium chloride substrates, via pulsed laser deposition ablation of an alloy target, of the eutectic composition. Free-standing films of 20-30 nm thickness were studied as-deposited and after annealing on copper TEM grids at 100°C for various times. Although several of the expected degradation processes involve short-range diffusion – essentially single atomic jumps – these were not observed, while other, longer-range diffusion effects were clearly identifiable. In particular, void shrinkage was observed in the films at short times, and void growth occurred at longer times.

We investigated the effect of organically modified clay on the thermal and flammability behavior of nylon 6 nanocomposites. We also used zinc borate along with layered silicate with an aim of achieving synergistic effect in flame retardancy. It is found that addition of 10 wt% clay reduced the onset decomposition (5% wt loss) temperature of nylon 6 by 20°C, while addition of 5 wt% zinc borate and 5 wt% clay in combination reduced it by around 10°C. Differential thermogravimetric analysis indicated that the peak decomposition temperature was not affected by the addition of clay, but the rate of weight loss decreased with increasing clay concentration. The horizontal burning behavior of the nanocomposite films of approximately 0.5mm thickness changed with additive concentration. The nanocomposites with 2.5 wt% and 5 wt% clay burned for almost the same duration as neat nylon 6 but dripping was reduced. The 10 wt% clay nanocomposite sample burned without any dripping and the flame spread rate was reduced by 25-30%. The burn rate of 5 wt % zinc borate/5 wt% clay nanocomposite sample was about 20% higher than that of 10 wt% clay nanocomposite sample, which could be attributed to varying char morphology. Scanning electron microscopy images of the 10wt% clay nanocomposite char surface and cross- section revealed an integrated layer of clay platelets with increasing density gradient from the center to the surface, while the 5 wt% zinc borate/5 wt% clay nanocomposite char appeared foamy and porous. The 5 wt% zinc borate and 5 wt% clay sample developed into a very good intumescent system in cone calorimeter test, swelling about 10-13mm height prior to ignition forming a cellular char structure. This was as effective as the 10wt% clay nanocomposite sample in reducing the heat release and mass loss rate of nylon 6 by around 65%. Fourier transform infrared spectroscopy of the 10 wt% clay nanocomposite char showed the presence of amides, indicating possible residual polymer within the shielded char.

Electron spin resonance investigations on the angular dependence of carbon nanotubes are reported. It is proved that the resonance line is a convolution of three lines one due to electron delocalized over carbon nanotubes, the second assigned either to amorphous carbon or to conducting electrons in interaction with metallic impurities, and the last one originating from catalyst residues.

Thermally activated magnetization reversal is of great importance in areas such as permanent magnetism and magnetic recording. In spite of many decades of scientific research, the phenomenon of slow magnetization dynamics has remained partially controversial. It is now well-established that the main mechanism is thermally activated magnetization reversal, as contrasted to eddy currents and structural aging, but the identification of the involved energy barriers remains a challenge for many systems. Thermally activated slow magnetization processes proceed over energy barriers whose structure is determined by the micromagnetic free energy. This restricts the range of physically meaningful energy barriers. An analysis of the underlying micromagnetic free energy yields power-law dependences with exponents of 3/2 or 2 for physically reasonable models, in contrast to arbitrary exponents m and to 1/H-type laws.

In this paper we present a study on the formation of gold colloids by laser ablation of a gold metal target in alkanes and thiol-alkane solutions. The results show a decrease of the gold particles' size up to 2 nm when thiol molecules are present in the liquid environment. In summary, we observed that laser ablation of gold targets in thiol-alkane solutions leads to the formation of stable gold clusters with size smaller than those obtained in the corresponding pure alkane. This result is a consequence of the competition between the aggregation of gold species in the plume (which allows a gold embryo to be formed and to grow) and the tendency of the dispersed thiol molecules to bond at each embryo surface stopping their growth.

The deformation kinematics for radiation damage response of bulk materials is presently semi-empirical and phenomenological based on a continuum mechanics supposition: there exists a function space of continuous functions to describe material displacement, strain, strain-rate metrics by using the mathematics of differential calculus. Existing data being assembled from tests on nano-length-scale(NLS) samples provide objective evidence that the continuum mechanics supposition is not an adequate generic mathematical description for radiation damage response in surface-dominated material structures at NLS. An alternative approach will be described that uses concepts and methods from classical statistical mechanics and describe deformation kinematics as a stochastic accumulation of discrete damage events at atomic lattice nano-length-scales. Although radiation damage deformation at a lattice length-scale in solids is mechanistically different from velocity scattering developed by Boltzmann for a kinetic theory of gases, the two problem areas are technically similar and in some simply cases there are useful mathematical analogs. The technical similarities and mathematical analogs will be used to define probability density functions (number per unit volume functions) for undamaged and damaged “size and size change” lattice species (similarity to a probability density function for atomic velocities in gas theory). In general, equations for undamaged and damaged lattice density function evolution are Boltzmann-type equations, which can be approximated and solved for simple cases of radiation induced material damage. Using a path integral approach and the two probability density functions, a stochastic functional will be derived for the relative deformation between any two arbitrary spatial points in a radiation damaged material. Given the relative deformation as an explicit functional of the undamaged and damaged lattice density functions, the kinematics metrics of relative velocity, strain, strain rate, etc., will also be functionals. In the case of radiation damage and annealing, the two lattice density functions are analog expressions to those commonly used to model “birth and death” population evolution.

Nanostructured materials are not immune from surface segregation, as can be shown for solid samples made from nanosized BaFe12−2xCoxTixO19 barium ferrite particles and a variety of free clusters. Both theory and experiment provide ample demonstration that very limited dimensions of very small clusters does not necessarily impart stability against surface and grain boundary segregation. In fact, with the larger surface to volume ratio in small clusters and lower average atomic coordination, we anticipate that compositional instabilities in small clusters will readily occur.

Although particle coarsening has been studied for over a century, it remains an active area of materials science research. The current work presents a theoretical analysis of the degradation of regular arrays of spherical particles through diffusional interaction. In order to understand the onset of coarsening, a linear stability analysis is performed on a simple square lattice of particles. It is predicted that particles will dissolve in a spatially ordered manner. The active transport mechanism plays a strong role in the selection of the coherent growth modes.

Nanostructured amorphous carbon thin films deposited by a Low Energy Carbon Cluster Beam Deposition technique have been characterized by Raman spectroscopy and Electron Spin Resonance (ESR). This study focuses on the correlation between carbon cluster structure and sp2 related defects. The ESR spectrum of as prepared and thermally annealed carbon clusters is a single line located near the free electron g-factor. Resonance lines were accurately fitted by a single line symmetric and narrow Lorentzian line. The resonance line parameters (line position, line amplitude, and line width) were found to be extremely sensitive to the thermal treatment of the as deposited samples. The paramagnetic centres are randomly distributed and correlated with the nanosized nature of the investigated system. The absence of the resonance line asymmetry, typical for the ESR spectra of conducting carbaceneous materials, confirms the small size of carbon nanoclusters and indicates poor electrical contacts between them. The resonance line parameters (position, intensity, and width) are not affected by the orientation of the carbon cluster film relative to the direction of the external magnetic field. The evolution of the ESR signal upon thermal treatments is sensitive to the increase of the sp2 average domain size as revealed by Raman spectroscopy. The Raman spectrum of as obtained and thermally annealed carbon clusters, in the domain 1000 cm−1 to 2000 cm−1 shows two Lorentzian lines located at 1300 cm−1 and 1550 cm−1 representing the D and G bands. The position and amplitude of these lines were found to be affected by thermal annealing.

The properties of carbon nanotubes (CNTs) are closely dependent on their structures, and therefore may be tailored by controllably introducing defects in the nanotube systems. In this work, we have investigated the effects of energetic ions (H+ and He+) on the thermal stability of single wall nanotubes (SWNTs) against oxidation in air. SWNTs were irradiated with MeV ions to various doses in the range 1013-1016 cm−2. Thermogravimetric analysis (TGA) was used to determine the loss of CNT masses as a result of oxidation processes. As opposed to the case of pristine SWNTs for which the temperature (Tmax) corresponding to maximum oxidation rate was found to be ∼ 495 °C, ion beam processing significantly enhanced the thermal stability of nanotubes, e.g., Tmax increased by about 30 °C after H+ implantation (dosage: 1015 cm−2) and 17 °C after He+ implantation (dosage: 1013 cm−2). The activation energies for thermal oxidation under various conditions were also extracted from TGA data, with values ranging from 1.13 eV (for pristine SWNTs) to 1.37 eV, depending on ion doses and species. Raman spectroscopy was used to determine the characteristics of the G band (C-C stretching mode) and D band (disorder induced mode) in CNTs. The work suggests that the SWNTs modifies to more stable structure (may be cross-linked SWNTs) at small doses. Once the number of defects exceeds some critical value (depending on the type and dosage of bombarding ion) the bonding energy in CNTs weakens, leading to the reduced thermal stability of CNTs against oxidation.