Nanoparticles are increasingly being heralded as the next-generation building blocks for modern materials design. Coating of semiconductor, metal, or metal oxide nanoparticles with a thin layer of a compatible material makes possible the control of interparticle and particle-matrix interactions, thereby further improving functional properties of devices and expanding the range of potential applications . The core-shell geometry has previously allowed for the enhancement of luminescence of semiconductor nanoparticles, charging of metal cores, chemical and colloidal stability, and optimization of magnetic properties of nanoparticles.

The work reported here uses new approaches to synthesize metal-coated nanoparticles characterized with high-resolution electron microscopy (HRTEM), micro-diffraction, and electron energy dispersive X-ray (EDX). Colloidal uniform composite nanoparticles of SiO2/TiO2 were synthesized using the sol-gel process. Fig. l-(a) shows a TEM micrograph of a group of particles coated with an outer layer.

One objective of the present work is to study the processes of assembly/self assembly of diamond clusters into nanostructures such as dots, wires,and filmsunder the influence of high electric fields. Diamond nanoparticles (∼2-5 nm in size) in a suspension of ethyl alcohol were deposited by pulsed electrophoresis onto sharp metal needles, such as those employed for field electron emission applications [1,2]. A custom designed sample holder has been constructed for a JEOL 2010 F, which allows for the convenient transfer of the sharp metal wires for analysis at high resolution, and then for removal (e.g. for re-deposition). These procedures allow us to precisely control the deposition thickness and morphology. They are capable of building a variety of deposition structures, even an isolated nanodiamond particle. The geometry of the deposits depends upon the applied voltage, the concentration of the suspension, the pulse duration, and the local electric field (which in turn depends on tip geometry, e.g. see Fig. 1).

Microindentation using a hard indentor is a very useful tool to probe the local mechanical properties (plastic flow, fracture, toughness, creep, etc.) of hard solids. We have used a depth sensitive indentation (DSI) version of this technique to study the shell of the conch Strombus gigas.In particular, we prepared polished sections in which the third order lamellae, the basic building block of the structure, could be indented along the three orthogonal directions; the indentation behavior along these three directions is quite different. Besides the normal information such as the hardness H from some typical dimension (typically the diameter of a pyramid-shaped indentation produced by a so-called Vickers diamond indenter) after indenting with a given load, the DSI technique also provides much additional information available from the loading and unloading curves. As can be seen from Fig. 1, the loading and unloading curves for the three orientations are quite different, as is the depth of the residual impression.

New analytical methods have been implemented with novel instrumentation designed to extend, to explore and to exploit an expanded performance envelop for high resolution imaging, EDX chemical microanalysis and chemical imaging with robust and representative bulk samples in a scanning electron microscope (SEM). A key contribution is the integrated and innovative design of the in-lens electron optics, sample holders, detectors including for EDX, specimen chamber and vacuum system. Each component has been improved individually over previous practice and they have been made to work together much better, especially with respect to combining advanced electron imaging at low voltages with efficient x-ray analysis and mapping.

Compared to a conventional out-of-lens/semi-in-lens FESEM the secondary electron image (SEI) resolution at the widely used low voltage of 1 kV is improved by a factor of almost 2x to <1.5nm and this facilitates low voltage imaging at primary magnifications of 250,000x (Fig.1) or more.

The preparation of frozen amorphous nano-meter thin films of solutions containing particles, and imaging with cryo- TEM, opens for the first time the possibility to study cluster assembles interacting with liquids. The method is here used to show evidence for assembly of ordered 3-dimensional aggregates of ligand stabilized 5-nm gold clusters in a long chain alcohol solution. The use of the plunge-freezing method allows freezing of solutions at a cooling rate that does not allow re-organization of the clusters. The stability of the amorphous solid solutions under the electron beam make it possible to record several pictures of the same aggregate at different angles and clearly identify the super-structure.

The sample preparation uses a modified controlled-environment vitrification system built in glass. Solidification of the liquid phase was achieved by plunging the solution, suspended in the holes of a lacy carbon on a copper grid, into liquid ethane (-174 °C) or in some cases liquid nitrogen.

Carbon nanotubes have many unique properties, including a tensile strength greater than that of steel and current-carrying capacity greater than any known metal or superconductor. Many applications have been identified, including field-emission displays and ultra-small transistors. At present, the main barrier to such applications is the ability to synthesize the nanotubes in a large scale with controlled properties'.

The work reported here is an effort for growing carbon nanotubes on porous silicon with a designed pattern. Experimental procedures include (1) a liquid catalyst was prepared by mixing AlCl3.6H2O, SiCl4, FeCl3.6H2O, MoO2Cl2,P-123 chemical components; (2) a flat piece of polydimethylsiloxane (PDMS) elastomer stamp containing a designed pattern was etched in the oxygen plasma, followed by spin coating the catalyst on the patterned stamp;(3) the inked stamp was printed onto a porous silicon substrate. This substrate was then heated in air at 70°C for 10 minutes to stabilize the catalytic pattern on the surface of porous silicon.

Yttria-stabilized zirconia (YSZ) has been the subject of many experimental and theoretical studies, due to the commercial applications of zirconia-based ceramics in solid state oxide fuel cells. Since the grain boundaries usually dominate the overall macroscopic performance of the bulk material, it is essential to develop a fundamental understanding of their structure-property relationships. Previous research has been performed on the atomic structure of grain boundaries in YSZ, but no precise atomic scale compositional and chemistry characterization has been carried out. Here we report a detailed analytical study of an [001] symmetric 24° bicrystal tilt grain boundary in YSZ prepared with ∼10 mol % Y2O3 by Shinkosha Co., Ltd by the combination of Z-contrast imaging and electron energy loss spectroscopy (EELS).

The experimental analysis of the YSZ sample was carried out on a 200kV Schottky field emission JEOL 201 OF STEM/TEM4.

The crystal structures of high temperature superconducting cuprates consist of alternative stacking of charge-reservoir (CR) block and conduction block. in case of YBa2Cu3Oy, (YBCO), CR block contains one-dimensional Cu(I)-O chain and BaO layers, and conduction block contains two-dimensional Cu(II)O2 planes and Y layers. YSr2Cu3Oy (YSCO), where Ba-sites of the YBCO are replaced by Sr completely can be obtained only by high-pressure synthesis. However, by replacing Cu(I) partly by Cr, YSr2Cu3-xCrxOy can be obtained even under ambientpressure conditions. The compound YSr2Cu2.8Cr0.2Oy (x=0.2) is non-superconductive, but, superconductivity is induced by partial replacement of Sr-sites with Ba; the compounds with YSr2-xBaxCu2.8Cr0.2Oy (x≤0.5) is non-superconductive, but the compound with x≥1.0 is superconductive. in order to obtain the structural information about the transition to superconducting phases, the effect of the Ba substitution is investigated by transmission electron microscopy (TEM).In the present study, the compounds with YSr2-xBaxCu2.8Cr0.2Oy (x=0-1.5) are examined by high resolution TEM (HRTEM) and electron energy-loss spectroscopy (EELS) to elucidate structural and electrical modification induced by Ba-substitution.

Since the superior properties of multi-wall carbon nanotubes (MWCNT) could improve numerous devices such as electronics and sensors, many efforts have been made in investigating the growth mechanism of MWCNT to synthesize high quality MWCNT. Chemical vapor deposition (CVD) is widely used for MWCNT synthesis, and scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS) are useful methods for analyzing the structure, morphology and composition of MWCNT.

Temperature and pressure are two important growth parameters for fabricating carbon nanotubes. in MWCNT growth by CVD, the plasma assisted method is normally used for low temperature growth. However, a high temperature environment is required for thermal CVD. A systematic study of temperature and pressure-dependence is very helpful to understanding MWCNT growth. Transition metal particles are commonly used as catalysts in carbon nanotube growth. It is also interesting to know the how temperature and pressure affect the interface of carbon species and catalyst particles.

Yttria stabilized zirconia (YSZ) is an important oxygen ion conducting solid electrolyte. YSZ is used in oxygen sensors, oxygen pumps, and fuel cells. Perovskite-type oxides of general formula ABO3 are also of fundamental significance due to their electrical and electro-optical properties. SrZrO3 is a promising material- for application as protonic conductor. in this paper, we present electron microscopy analysis of the formation of SrZrO3 nano-particles in the top surface of YSZ single crystal after ion implantation. These results demonstrate a unique process for obtaining mixed-conducting oxides in the surface layer of YSZ. in addition, it is important to study the behavior of strontium in YSZ because of the potential application of YSZ as an inert fuel matrix for “burning“ excess plutonium in nuclear reactors.

400 keV strontium ions have been implanted into YSZ at room temperature to a fluence of lxl021 ions/m2.

The ion irradiation-induced crystalline-to-amorphous transformation has been studied in many complex ceramics. Direct impact amorphization has been considered to be one of the fundamental amorphization mechanisms for complex ceramics under heavy ion irradiation . Based on the directimpact model, a highly energetic incident ion transfers its kinetic energy to the target as a thermal spike within 10“13 sec creating a “molten-like” displacement cascade, typically nanometer-scaled in diameter (as indicated by the result of a computer simulation in Fig. 1). This “molten” zone quickly quenches to a small amorphous domain within a few pico-seconds. Epitaxial recrystallization occurs around the amorphous/crystalline interface, so that the size of amorphous domains decrease with time. The accumulation and overlap of small amorphous domains eventually leads to complete amorphization of the irradiated material. Although the in-situTEM technique with the setup shown in Fig. 2 has been extensively applied to the study of the amorphization process in complex ceramics, most of the previous studies relied on in-situobservation of the electron diffraction pattern, and there has been a lack of solid evidence of direct impact amorphization due to the small nature of the cascades and the rapid kinetics of its evolution.

In colossal magnetoresistive (CMR) materials, large changes in physical properties stem from the interplay between charge ordering (CO) coupled with orbital and magnetic orderings. Thus detailed microstructural studies are important in understanding these changes in physical properties. In-situTEM observation is a very useful approach to study CO transitions in these CMR compounds. We have recently studied the CO behavior of the three-dimensional perovskite Nd1/2Sr1+2xMnO3. in this work, we report the CO of two-dimensional naturally layered compounds La2-2xSr1+2xMn2O7 (327 phase), where x is the hole doping level and varies from 0.5 to 0.6 in this work.

Thin foil TEM specimens were prepared from polycrystalline bulk samples by conventional thinning and ion milling method at liquid N2 temperature. The in-situ TEM work was carried out in the Electron Microscopy Center at Argonne National Laboratory using a Philips CM30 with a liquid N2 cold stage, and a Hitachi H-9000 with liquid He cold stage.

The traditional application of titanium dioxide was as a white pigment; later, it was discovered their photocatalytic properties as an anode for the photo-oxidation of water. Furthermore, titanium dioxide films are now widely used in catalysis and photocatalysis because of low cost and other advantageous properties. For example, they have been used for decomposition of organic contaminants in air and water. Moreover, recent studies have reported bactericidal and detoxification effects of TiO2 thin films . It has been shown that TiO2- coated materials possess deodorizing, antibacterial, and self-cleaning functions under weak ultraviolet light. Titanium dioxide films can be prepared by many deposition techniques. One of them is the spray pyrolysis (SP) technique which is a low cost, simple to manipulate, and applicable to large-scale areas (final). Photocatalytic TiO2-covered tubing can be used to decompose organic contaminants and/or to sterilize microbial cells in air or water flows , using solar panel reactors or indoor panels irradiated with UV radiation.

In conventional sintering, high heating rates are often used to enhance densification and reduce grain growth. The essence of this concept is to use fast heating rates to favor densification instead of grain growth, if the activation energy for densification is greater than that for grain growth. At low temperatures, surface diffusion is the most effective sintering mechanism but is associated with grain coarsening. Therefore, a high heating rate may take the system for densification at high temperatures before surface diffusion causes grain growth and decreases the sintering driving force. Field activated sintering technique (FAST) is a newly developed sintering method, which applies an external electrical field to enhance densification. The method applies pulsed and continuous current to powders subject to a modest pressure (< 100 MPa). Electrical current application enables fast heating rates. The sintering cycles are very short, typically less than 10 minutes for full densification.

The utility of a surface to serve as a substrate depends upon its surface structure. The presence of steps on the surface affects the quality of the deposited material. The basal surface of alumina is one of the most widely used substrate materials and hence considerable effort has been directed towards the study of this surface. The mechanism of formation of a stepped structure on the basal surface of alumina has been investigated using atomic force microscopy. The evolution of steps on the basal surface as a function of temperature has been reported. Flux growth is an attractive route for producing alumina because of the low temperatures required for processing and the extremely low dislocation densities that can be obtained. in the present study, the structure of steps on flux-grown alumina has been investigated. Formation of low-index macrofacets as a result of crystal growth has been observed.

Nanowires have potential applications in future generations of nanoscale electronics. Our motivation of studying Bi nanowires is based on the unique properties of bulk Bi. These include very small effective masses, a long mean-free path and the low melting point (271°C). Calculations of the transport properties predict that the Bi nanowires have a very high thermoelectric efficiency. The effects of quantum confinement are pronounced in Bi because of its small effective masses. The resulting change in the band structure of bulk Bi is shown in Fig. 1. The broken curves depict the band structure in which the T-point valence band overlaps with the L-point conduction band by 38mev making bulk Bi a semimetal. Due to quantum effects, the band edges split into subbands shown by solid curves. As the wire diameter decreases, eventually the lowest conduction subband and the highest valence subband no longer overlap and the material becomes an indirect-gap semiconductor (at ∼50nm diameter).

Many attempts have been made to improve the fracture toughness of brittle materials such as ceramics. Most of the methods developed so far make use of metallurgical processes, for example, phase transformation, refining of grains, formation of composite materials. However, these methods can not be applied universally to brittle materials which do not have such a useful metallurgical processes.

Moon and Saka (1) recently showed that the fracture toughness Klc of a YAG single crystal the sub-surface of which is damaged by micro-Vickers indentation at room temperature, followed by annealing at high temperatures is improved by a factor 2 from 1.13 to 2.26MPam1/2. The fracture toughness Klc was evaluated by measuring the length of cracks which initiate at the corner of Vickers indentation(2). Transmission electron microscopy of the subsurface reveals the healing of cracks introduced by room-temperature indentation and formation of dislocation cells. The thin foil specimens were prepared using a focused ion beam (FIB) technique(3).

SiC, as one of the most promising candidate ceramics for high temperature structural applications, offers many intrinsic advantages, including high melting temperatures, low density, and high elastic modulus. However, the use of SiC to date has been severely limited by its poor fracture toughness (∽ 2-3 MPa√m for commercially available materials) and crack-growth resistance. Our study focuses on the development of silicon carbide as a potentially tough, high-temperature, and damage-tolerant material. The approaches include identifying roles of sintering additives in modifying grain morphology, effects of post-annealing on grain boundary phases, and possibility in introducing nanoscale precipitates in SiC grains. Central in these efforts is structural characterization using state-of-the-art electron microscopy.

The first success was in situtoughening the SiC, by hot pressing in the presence of A1, B and C additions. Elongated and interlocked grains were developed surrounded by an Al-containing amorphous grain boundary film.

Recently, considerable efforts have been made in growing bi-axially aligned thick Yba2cu3O7 (YBCO) films on a flexible, textured metallic substrate for electrical power applications. The BaF2 post-deposition annealing process is one of the most promising methods. to understand the nucleation and growth mechanism of YBCO in this process, extended transmission electron microscopy analysis has been made. Here, we report on the evolution of Ba-Y oxy-fluoride which is pertinent to the epitaxial YBCO nucleation process on SrTiO3 (STO) substrate.

The stoichiometric ratio of Y, Cu and BaF2 was evaporated on (00l)-cut STO substrate Subsequently, these films were annealed at 735°C in an O2-H2O-N2 gas atmosphere and quenched after 10, 20, or 40 minutes. The morphology and phase composition of the precursor changed drastically with the annealing times, e.g. after 10 minutes heat treatment, the precursor consisted of fine grained CU2O and Ba-Y(Cu) oxy-fluoride (cubic, a=0.618nm) as shown in fig.la.

Mullite (3Al2O3•2SiO2) exists in a solid solution field (∼57-63 mol% Al2O3) as the only stable compound in the Al2O3•SiO2 phase diagram at ambient pressures. Equilibrium 3:2 mullite has an orthorhombic structure with b>a (o-mullite). However, when initially crystallized from molecularly mixed, 3:2 precursors at temperatures < 1200°C, the first phase that forms has lattice parameters with a ≈b. This structure is often termed pseudotetragonal mullite (pt-mullite), since even when the ‘a’ and ‘b’ lattice parameters are identical, they are symmetrically independent. Pseudotetragonal mullite has been shown to contain approx. 70 mol% Al2O3. with increasing time and temperature, the structure gradually assimilates the residual SiO2, and the lattice parameters change, such that by 1400°C, the material has attained its equilibrium structure and composition.

TEM was used to determine the spatial relationship between the crystalline phase and the residual, amorphous, SiO2-rich phase in pt-mullite. The starting materials were quenched, 3:2 mullite beads and fibers (made by containerless processing).