Measurements of the magnetization M as a function of temperature (5K - 300K) and applied magnetic field H (up to 50 kOe) in 30 Å particles of FeOOH are reported. M increases with decreasing T, peaking at TB = 65 K below which the ZFC (zero-field-cooled) and the FC (field-cooled) data separate. Hysteresis loop measured at 10 K for ZFC shows an open loop up to 40 kOe with coercivity = 2 kOe. For the FC case, the loop shifts and the loop-shift increases with the cooling field ItL, approaching saturation above Hc = 20 kOe. From the variation of M vs H above TB, a magnetic moment/particle μp = 300 μB is determined. These results suggest that the FeOOH nanoparticles have an antiferromagnetically ordered core with uncompensated surface spins yielding μp and the surface spins order in a spin-glass-like state below TB, possibly due to interparticle interactions.

Nanocrystalline Ni-P alloys produced by electrodeposition have been characterised by three-dimensional atom probe (3DAP) analysis. In the as-deposited materials, there are indications of some variation in P concentration between grains and segregation to grain boundaries. After heat treatment however, strong grain boundary segregation and the formation of Ni3P precipitates have been observed.

The body implant interaction is strongly affected by the implant surface structure and chemistry [1,2]. Thus by applying a nanoporous coating to metallic implants the implant surface can be adjusted to different needs. Compared to biological molecules the size of the pores is so small (between 5 nm and 250 nm) that the cellular response to this surface modification is not affected by the structure itself. Nevertheless by loading the pores with bioactive molecules it is possible to achieve a new kind of active implants surfaces for soft and hard tissue implants. With this coating it is possible to irreversibly bind radioactive isotopes like 99mTc, 186/188Re, 103Pd, and many more for local radiotherapy onto soft tissue implants like stents or seeds.

Relaxor ferroelectrics are one of the important classes of self-assembled nanostructure composite materials. Interesting features associated with the nanoregions give rise to the most interesting device related characteristics and unusual properties in these materials. Besides, they possess the largest property coefficients by themselves or when modified with lead titanate (PT). In this report, a detailed temperature dependent study has been carried out on (1-x)PZN-xPT relaxors with compositions x = 0.05 and 0.085 using polarized Raman scattering under optical and E-field variables and inferred the structure-property relations in order to obtain information to characterize the material for matching the application criteria. In addition, phase transitions associated with the relaxors have also been investigated to understand the polarization mechanism(s) for the unpoled and poled specimens.

Two kinds of different nickel nanoparticles with distinct morphological properties, Ni(C) and Ni(O), are studied. Magnetization measurements for the assembly of two kinds of Ni nanoparticles show, a larger coercivity and remanence as well as the deviation between the zero field cooling (ZFC) and the field cooling (FC) magnetization have been observed in the Ni(O) particles. This deviation may be explained as a typical cluster glass-like behavior due to ferromagnetic interaction among the assembly of Ni(O) particles. However, Ni(C) particles exhibit superparamagnetism at room temperature. The average blocking temperature (TB) is determined to around 115K. We also observe gradual decrease in saturation magnetization, which is attributed to the nanocrystalline nature of the encapsulated particles.

Nanocrystalline thin Au films with grain size 10 - 76 nm have been analyzed regarding the temperature dependence of the electrical resistivity. A sudden change in the power function, ρ α Tn, was found at ∼10 K, where n = 1.7 in the range 5 - 10 K and n = 3.3 in the range 10 - 15 K. This effect disappears after annealing at 773 K for 0.5 h in air at atmospheric pressure. After the annealing the grain size was ∼ 100 nm. This is an indication of interference between electron-phonon scattering and electron-grain boundary scattering in nanocrystalline materials at low temperatures.

The temperature coefficient of resistivity, TCR, increased with increasing grain size at any temperature and the position of the maximum TCR was shifted towards lower temperatures with increasing grain size.

This paper concentrates on the densification of sol gel derived thin nano-ceramic coatings by laser radiation and by furnace treatment. Deposition of the film is done by means of spin coating of Zirconia. The sintering of the layer is observed using a number of different measuring techniques. Especially, attention is paid to the densification behavior and the grain growth in the layer, investigated by scanning electron microscopy and ellipsometry. Also the different crystal phases observed are addressed. During sintering at a constant temperature a change in the sintering behavior with time is observed. This change is observed for most temperatures. Both the initial fast sintering of the process (for all sintering temperatures), and the final slow sintering (only at the higher sintering temperatures) are explained.

Alumina layers were deposited by spin coating and dip coating on different substrates (Pt, Si, Al2O3) from the water suspension of nanosize boehmite particles. It was shown, that addition of the butoxyethanol in the suspension improves wetting and the quality of the film. No separation from the substrate or cracking of the film took place up to 1000°C on all types of the substrates for the film thickness up to 10μm. Because of the minimal shrinkage, the coating can be used to smooth rough substrates as well as provide interfacial layers for either single layer or multilayer structures.

The surface chemical reactions at the origin of the CO detection by SnO2-based sensors are investigated by Fourier transform infrared spectrometry for two different SnO2 particle sizes. Knowing that the variations of the infrared energy transmitted by the sample versus surrounding gases are related to the variations of the electrical conductivity, correlation of surface chemical reactions with the sensor response is established and discussed.

Nanocrystalline silicon (nc-Si) films were deposited on fused quartz and single (100) crystal Si substrates by plasma-enhanced chemical vapor deposition from a SiH4-H2 mixture at various deposition temperatures, Tδ. The effects of plasma-assisted hydrogenation at 300°C on the optical and structural properties were examined for the nc-Si films. The film deposited at Tδ = 730°C exhibits photoluminescence (PL) in its as-deposited state, but the intensity of PL decreases after hydrogenation. We find that a correlation between the PL intensity and infrared absorption bands at around 850 and 1000 cm−1.

The electrical resistance of Ni-Al alloy thin films prepared by dc magnetron sputtering process was found to be abnormally high at room temperature. However, when heated at elevated temperatures, the resistance dropped significantly, exhibiting a remarkable negative temperature coefficient of resistance (TCR). The phenomenon was found to be substrate-independent. Cross-sectional transmission electron microscopy revealed that the films were essentially nanocrystalline and porous in nature. Analysis of the current density-electric field characteristics yielded a satisfactory agreement with either the space charge limited or the Poole-Frenkel models for electrical conduction. The negative TCR effect diminishes and the usual metallic resistance is restored in thicker films, probably due to reduction in particle separation and further coalescence of neighbouring crystallites.

Some oxide eutectic materials, such as sapphire/YAG, display an intricate “Chinese script” microstructure which strongly influences properties such as mechanical strength. We used the micro pulling-down technique to grow fibers of a series of such materials at rates over 20 mm/min, giving a uniform microstructure with a characteristic size as low as 150 nm. Bulk and surface characteristics of this microstructure were investigated by electron and atomic force microscopy. Smaller microstructure size gave higher tensile strength at 1500°C. Annealing of the fibers produced some coarsening of the microstructure, but increased the strength at lower temperatures.

Nanostructured bulks and films of TiB2, TiN, AIN, Ti(B,N), and (Ti,Al)N prepared by high pressure sintering and nonreactive magnetron sputtering accordingly. Fracture surfaces and structure of grain boundaries have been investigated by high-resolution scanning and transmission electron microscopy as well as by atomic force microscopy. The revealing of transgranular fracture, homogeneous and inhomogeneous deformation, and the availability of dislocations and amorphous phases in structure are discussed.

The Bi2Te3-Sb2Te3 compounds with the composition of useful thermoelectric cooling materials were prepared by mechanical alloying-pulse discharge sintering process. Effects of the process on the Seebeck coefficient, electrical resistivity and thermal conductivity were investigated. Temperature dependence of the Hall coefficient was also observed in the temperature range 80 - 325 K.

The figure of merit, Z, was found to be about 4.0 × 10−1K−1 at room temperature in the 25%Bi2Te3-75%Sb2Te3 composition sintered at 618K using grain refined mechanically alloyed powders which had the size of under 32 μm. The value of Z was remarkably improved with a decrease of the thermal conductivity shown in the fine grain compacts fabricated by mechanical alloying-pulse discharge sintering process.

Ge nanocrystals (nc-Ge) embedded in silicon oxide films were synthesized using RF magnetron sputtering and post-annealing procedure. To minimize the stress effect and inhomogeneity, we intentionally lower the cooling rates and reduce the temperature gradient during annealing. Significant Raman shifts ranging from 2.0 to 5.8 cm−1 have been observed from samples annealed at different temperatures. The size-dependent shift and broadening is found to be in good agreement with the phonon confinement mode together with the Gaussian weighting function, and the isotropic T02 phonon dispersion relation introduced by Sasaki et al. The Raman spectra can also be well-fitted using peaks calculated from the phonon confinement model. The inhomogeneous Raman peak broadening from our samples annealed at lower temperatures are attributed to the non-Gaussian size distribution of Ge nanocrystals.

This manuscript discusses the morphological instability observed when multilayered samples with alternating layers of Γ-Ni(Al)/γ-Ni3Al are exposed to 800C for approximately 100 hours. Samples with 20nm/20nm or 120nm/120nm layer thickness and <001> or <Ill> crystal orientation to the interface normal were tested. Pinching off of layers is strongly affected by crystal orientation and layer thickness. Corresponding modeling suggests that the stability of this system is sensitive to fluctuations in the volume fraction of the two phases, the aspect ratio of columnar grains in the layers, and whether coherent or semi-coherent interfaces are present.

Co-Cu multilayer granular films deposited onto Si substrates have been submitted to thermal treatments in scanning mode. Their magnetisation and resistance have been studied after applying two different heating rates. The comparison between the experimental data measured before and after the treatment points out that the effect of the annealings depends strongly on the heating rate used. We also present XPS data collected as a function of depth to show how the different heating rate modify the composition and chemical environment produced by thermal treatments.

We have synthesized two sets of nanometal composites of different metal concentrations via electrodeposition of gold into porous aluminum oxide membranes Within each set, both centrosymmetric and non-centrosymmetric particles were produced whose linear and nonlinear optical effects were investigated.

Because our method of template synthesis allows for the close examination of our composite materials in terms of shape, size. and symmetry, we can interpret the SHG response in terms of differences in local field enhancements of magnetic dipole and quadrupole modes.

This paper develops a method to deduce the dielectric function of nanostructures smaller than the chosen wavelength of light. It modifies the Maxwell - Garnett Effective Medium Theory equations to calculate the dielectric function of a metal embedded inside a dielectric. Specifically, reflection and transmission measurements of an array of bismuth nanowires in an anodized porous alumina template are used to calculate the frequency - dependent di-electric function of the nanowires. The spectra are taken using Fourier transform infrared spectroscopy covering the 500 to 4000 cm−1 frequency range. These data are used to determine the real and imaginary parts of the dielectric function of the composite materials. Next, the percentage of the total volume occupied by either Bi or air in the porous alumina (the “filling factor”) was found by scanning electron microscopy. The modified Maxwell-Garnett (M-G) equations specify how to use the filling factor and the dielectric function of the composite material to calculate the dielectric function of the alumina. Finally, the modified M-G equations are used a second time to calculate the dielectric function of Bi nanowires using the dielectric function of alumina, the dielectric function of the filled template, and the filling factor. The resulting dielectric function of Bi nanowires is then compared to theoretical predictions.

A theory of bound magnetic polaron (BMP) hopping, driven by thermodynamic fluctuations of the local magnetization, has been developed. It is based on a two-site model of BMP's. The BMP hopping probability rate was calculated in the framework of the “Golden Rule” approach by using the Ginzburg-Landau effective Hamiltonian method. The theory explains the main features of hopping resistivity observed in a variety of experiments in dilute magnetic semiconductors and magnetic nanocomposites, namely: (a) negative giant magnetoresistance, the scale of which is governed by a magnetic polaron localization volume, and (b) low magnetic field positive magnetoresistance, which usually preceeds negative magnetoresistance.