An innovative and cost-effective processing technique has been developed at Ceramatec Inc for the microfabrication of ceramic components requiring very high dimensional tolerance. The materials system is a proprietary nanophase composition called CERCANAM (CERamatec CAstable NAno Material). Scanning electron microscopy revealed that CERCANAM components can be fabricated with dimensional tolerance as high as ± 2 [.proportional]m for surface features on the die that have dimensions about 1 mm. The process can also be modified to fabricate nanoporous ceramic components with very high surface areas. Components with retained surface areas as high as 67-82% of the starting powder were fabricated. The fabrication process does not involve a high-temperature sintering step, which eliminates the loss of surface area from high temperature sintering. It is anticipated that microcomponents fabricated with specific microstructures and properties will have applications in the optical fiber industry as interconnects, in the electronic packaging industry and the chemical industry.

A novel preparation method of CdS nanoparticles in the core or corona of micelles is presented. Poly(styrene-block-2-vinylpyridine) (PS-b-P2VP) and cadmium ions form aggregates of single micelles, called compound micelles, upon addition of the cadmium acetate salt into a solution of the block copolymer in tetrahydrofuran. The growth of CdS nanoparticles is confined to the core of single micelles after introduction of hydrogen sulfide gas into the solution. UV-visible spectroscopy, fluorescence spectroscopy, and transmission electron microscopy were employed to characterize the prepared core-embedded CdS nanoparticles. Corona-embedded CdS nanoparticles were prepared by dropping the core-embedded CdS nanoparticles into water with a low pH value. The location change of the CdS nanoparticles was accompanied by a structural change of the micelles, a change from compound micelles to single micelles. In a single micelle, CdS nanoparticles distribute randomly in the corona. The size of the nanoparticles increases slightly after the transition.

Fe-29.6at%Pd ferromagnetic shape memory alloy (FSMA) ribbon formed by rapidly solidified, melt-spinning methods is expected to be useful as a new type of material which shows giant magnetostriction as well as quick response. The giant magnetostriction in the rolling direction depends strongly on applied magnetic-field direction and has a maximum value of 8×10-4 when the field is normal to the surface. This phenomenon is caused by the rearrangements of activated martensitic twin variants. The inverse phase transformation temperatures (As) obtained from Laser micrographs and magnetization vs. temperature curve are ∼307 K and 400∼440 K, respectively. We analyze magnetostriction, magnetic property and crystal structure of Fe-29.6at%Pd bulk sample before rapid solidification and the ribbon sample. From these results, it can be concluded that remarkable anisotropy of giant magnetostriction of ribbon sample is caused by the fine structure formed by the melt-spinning method. It may be possible to apply this method successfully to other FSMA and Ni2MnGa, which is difficult to manufacture owing to its brittleness.

In an effort to explore new highly resistive soft magnetic materials, Fe/SiO2 nanocomposite materials have been synthesized using a wet chemical reaction approach in which the precursor complex was annealed at various temperatures. The crystallographic structure, nanostructure, morphology, and magnetic properties of the synthetic Fe/SiO2 particles were studied by x-ray diffraction, transmission electron microscopy, and magnetic measurements. The experimental results show that for this approach, the [.alpha]-Fe particles are coated with amorphous silica. The progress of the reaction, the purity of Fe/SiO2 in the synthetic powder, and the Fe particle size are highly dependent on the annealing temperature. By adjusting the annealing temperature, the particle size can be controlled from approximately 20 nm to 70 nm. For the synthetic nanopowder obtained by H2 reduction at 400 °C, there exists a superparamagnetic behavior below room temperature; while for the nanopowders obtained by reduction at higher temperatures, the ferromagnetic behavior is dominant. Based on these studies, optimum synthesis conditions for Fe/SiO2 nanocomposites is determined.

In many cases, coated nanoparticles behave like isolated ones. Using the microwave plasma process, it is possible to produce oxide nanoparticles with ceramic or polymer coating. Coating the particles has the additional advantage that by proper selection of the coating it is possible to suspend the particles in distilled water without using any colloid stabilizer. From quantum dots made of sulfides or selenides, it is well known from literature that fluorescence depends strongly on the coating of the kernels. In the case of CdSe, the kernels are coated with CdS. Within this study, similar phenomena are found with coated oxide nanoparticles having sizes of ca. 6 nm exhibiting a very narrow particle size distribution. The coating consists of a second ceramic phase or a polymer one, each one influencing fluorescence differently. Obviously, the type of coating is a tool to modify fluorescence. This behavior is demonstrated on kernels made of Al2O3, ZrO2, HfO2, ZnO etc. PMMA, PTFE, or Al2O3 were used as coating material. In most cases, the fluorescence spectra showed broad bands. In some cases, such as ZnO, additionally, a sharp emission line in the UV appears. It is interesting to note that coatings made of fluorine containing polymer materials did not lead to fluorescence intensities comparable with PMMA coatings. The observed spectra are equivalent whether the powder is in aqueous suspensions or dry on a quartz glass carrier. The experimental results in this study indicate that the combination of non-fluorescent oxide core with a non-fluorescent polymer coating may lead to a nanocomposite with strong fluorescence. This is a phenomenon not described in literature until now.

Nanocomposites composed of unsaturated polyester matrix and organically modified clay filler were prepared. After the synthesis, XRD patterns showed that the interlayer spacing expanded from 1.25 nm to 4.5 nm. The mechanical properties of the nanocomposites were determined and it was found that adding only 3 w/w % organically modified clay improved the flexural modulus of unsaturated polyester by 35%. From DSC diagrams, it was found that Tgvalues of the nanocomposites also increased with the clay content. It is concluded that partially exfoliated / intercalated nanocomposites were formed at relatively low clay contents.

Parallel molecular dynamics simulations are performed to investigate dynamic fracture in bulk and nanostructured silica glasses at room temperature and 1000 K. In bulk silica the crack front develops multiple branches and nanoscale pores open up ahead of the crack tip. Pores coalesce and then they merge with the advancing crack-front to cause cleavage fracture. The calculated fracture toughness is in good agreement with experiments. In nanostrucutred silica the crack-front meanders along intercluster boundaries, merging with nanoscale pores in these regions to cause intergranular fracture. The failure strain in nanostructured silica is significantly larger than in the bulk systems.

Starting from two equilibrium solid solutions in the Au-Ni system, we analyze the change in composition due to a 400 eV/Å fast ion track simulated by molecular dynamics in the Embedded Atom approximation. We aim at determining the influence of the thermodynamic forces derived from the large thermal gradients and the rapid solidification across the solidus and liquidus on the motion of solute atoms. One dimensional gradients as well as analytic models are used to quantitatively determine the domains of influence of these forces. Evidence shows that the liquidus and solidus equilibrium solidification predicted by the phase diagram is not reached during the track. The solute concentration is mainly determined by the combined diffusion and thermomigration mechanisms in the liquid stage.

Nanocomposites are a relatively new class of materials obtained by dispersing montmorillonite clay in a polymer matrix. Evidences from literature suggest that clay platelet dispersion during nanocomposite preparation and clay-matrix adhesion are major technical issues that need to be addressed in order to achieve the desired property enhancements in polymer-clay hybrid nanocomposites. We have studied the interaction of the organically functionalized clay with the epoxy resin by including along the chain structure functional groups that will facilitate interaction with the resin. Through conventional routes, functional molecules have been synthesized and deposited on to the clay surface. Both the functionalized and nonfunctionalized clay has been analyzed using thermal gravimetric analysis (TGA), and Fourier transform infrared spectroscopy (FTIR). The exfoliation of nanoclay platelets in amine cured epoxy system has been studied using X-ray diffraction (XRD) and transmission electron microscopy (TEM).

Nanocrystalline Li-Ti-O spinel samples were prepared by solvothermal reaction of TiO2 with lithium hydroxide in water and ethanol. The hydrothermal reaction proceeds at temperature higher than 130 °C. The reaction proceeds via dissolution-precipitation mechanism and its course is not sensitive to titanium dioxide polymorph used in the reaction. Product of the reaction in water has cubic rock salt type structure. It converts, however, to spinel if annealed to temperatures exceeding 250 °C. The re-crystallization is accompanied with water removal from the structure. Solvothermal reaction in ethanol leads directly to a product with spinel structure without need for annealing. Both products are active for Li insertion; theelectrochemical activity. The specific capacity ranges between 100 and 160 mAh/g depending on the annealing temperature.

Multiple silicon nanowires were synthesized using large gallium pools and microwave plasma. Results showed that nanowires growing out of different sized large gallium drops show little variation in diameters, suggesting that our non-traditional technique can be used to synthesize bulk amounts of monodispersed nanowires out of thin films of molten gallium.

We present herein recent findings of an investigation of catalyst assembly and activation using metallic nanoparticles encapsulated with organic monolayers. Gold nanocrystals (2∼5 nm) encapsulated with thiolate monolayers assembled on electrode surfaces, were found to be catalytically active towards electrooxidation of CO and MeOH upon activation. The activation involved partial removal of the encapsulating thiolates and the formation of surface oxygenated species. A polymeric film was also used as a substrate for the assembly of the nanoparticle catalysts. When the polymer matrix was doped with small amounts of Pt, a remarkable catalytic activity was observed. These catalysts were characterized utilizing cyclic voltammetry and atomic force microscopy.

NiFe2O4 is an important high frequency soft magnetic material due to its ultra high resistivity; however, its initial permeability is rather low. Conventional magnetic ferrites are manufactured through ceramic processing. In an effort to explore innovative approaches for fabricating ferrite materials with improved performance, a study of fabricating nanostructured NiFe2O4 using wet chemical approaches has been carried out. The synthetic NiFe2O4 precursor was synthesized by a citrate reaction method followed by calcinating at various temperatures. Systematic studies concerning the crystallographic structure, the nanostructure and morphology of the particle, the phase homogeneity, the conditions for chemical reaction completion, and the magnetic properties have been carried out using x-ray diffraction, transmission electron microscopy, and magnetic measurements. The results show that by using a citrate reaction approach, pure phase and stoichiometric NiFe2O4 can be fabricated easily, and the particle size can be controlled on a nanometer scale, even at high calcination temperatures. In addition, a comparative study of the NiFe2O4 fabricated by conventional ceramic processing and this new citrate processing will be presented.

Highly-oriented ZnO nanorods were grown on the fused silica substrates by a thermal CVD technique using Zinc acetylacetonate (Zn(C5H7O2)2). The substrate was heated to 500°C and the vaporization temperature of Zn(C5H7O2)2 was keep at around 135°C. X-ray diffraction and TEM analyses reveal that the nanorods are preferentially oriented toward the c-axis direction. Photoluminescence (PL) and absorption measurements show a strong emission at around 380nm which corresponds to the near band-edge emission of the bulk ZnO. Moreover, the negligible green emission band in PL spectrum and the absence of E1(LO) mode of the ZnO crystal in Raman spectrum indicate a low concentration of oxygen vacancy in the highly-oriented ZnO nanorods.

Mesostructured semiconducting non-oxidic materials were prepared by linking [Ge4Q10]4-(Q=S, Se) clusters with the square planar noble metal cations of Pd2+ and Pt 2+ in the presence of cetylpyridinium surfactant molecules. The use of Pt2+ afforded materials with exceptionally high hexagonal pore order similar to those of high quality silica MCM-41. These materials are semiconductors with energy band gap in the range 1.8<Eg<2.5 eV.

Effect of a crystalline-amorphous interface on heat conduction has been studied using atom-istic simulations of a silicon system. System with amorphous silicon was created using the bond-switching Monte Carlo simulation method and heat conduction near room temperature was studied by molecular dynamics simulations of this system.

A combination of XRD and TEM techniques have been used to characterize the response of room temperature magnetron sputtered Fe-Pd thin films on Si-susbtrates to post-deposition order-annealing at temperatures between 400-500°C. Deposition produced the disordered Fe-Pd phase with (111)-twinned grains approximately 18nm in size. Ordering occurred for annealing at 450°C and 500°C after 1.8ks, accompanied by grain growth (40-70nm). The ordered FePd grains contained (111)-twins rather than {101}-twins typical of bulk ordered FePd. The metallic overlayers and underlayers selected here produced detrimental dissolution (Pt into Fe-Pd phases) and precipitation reactions between Pd and the Si substrate.

V2O5 nanofibers showed the rectifying current-voltage characteristics under an asymmetric contact configuration at room temperature, indicating the formation of a Schottky diode. The ideality factors as a Schottky diode were estimated to be 6.1 at the forward bias and 1.4 at the reverse bias. The larger current at the reverse bias defined by the negative voltage at the metal electrode may originate from the contribution of the tunneling via field emission or thermionic field emission. The ultimate geometric size of nanofibers enhances the influence of the tunneling mechanism and modifies the nano-scale Schottky diode, requiring more understanding in designing the nano-scale electronic devices with the metal contacts.

Nanocomposite coatings were made by incorporating nano-sized and micron-sized alumina into aqueous and non-aqueous polymer systems. At approximately 50wt% nano-sized alumina a synergistic effect was observed in coating hardness with no degradation in optical properties.

Carbon single-wall nanotubes (SWNTs) have been successfully synthesized by means of KrF laser vaporization of a Co-Ni-doped graphite pellet in a flowing argon atmosphere. The effects of two key processing parameters, namely the furnace temperature (in the 25-1150 °C range) and the laser intensity (in the 0.8-4.4 x 108 W/cm2 range), on the yield and the structural characteristics of the carbon SWNTs were investigated. By characterizing the obtained deposits by means of transmission electron microscopy and micro-Raman spectroscopy techniques, we were able to identify a threshold temperature as low as ∼550 °C, below which no carbon SWNTs can be grown. The increase of the furnace temperature from 550 to 1150 °C was found to lead not only to a significant increase in the SWNTs yield but also to the formation of larger SWNTs bundles. Raman analysis have also revealed that the diameter distribution peak shifts from ∼1.05 to ∼1.22 nm as the temperature is raised from 550 to 1150 °C. At the highest furnace temperature of 1150 °C, we also found that a minimum laser intensity of about 1.6 x 108 W/cm2 is required to grow carbon SWNTs by means of the KrF laser. Higher laser intensities have resulted in a higher yield of SWNTs with relatively thicker bundles. Moreover, the increase of the laser intensity was found to promote the growth of 1.22 nm-diameter nanotubes to the detriment of thinner carbon nanotubes (1.05 and 1.13 nm-diameters).