Transmission electron microscopy (TEM) has traditionally served as an important tool for understanding the physical properties of many materials. Recent improvements in “ex-situ” techniques have further strengthened the role of TEM as a unique characterization method.

The use of ExxonMobilfs dedicated reactor system for studying metal oxidation at moderate temperatures has been reported. However, high temperature oxidation studies have been limited by the use of holey carbon support films, which oxidize and disintegrate during these experiments. Consequently, a new method was developed to replace the holey carbon support film with a holey metal oxide support film that both maintains its structural integrity during high temperature oxidation and remains electron transparent.

The new support film was prepared using a commercially available, holey carbon coated TEM grid as a template (Figure 1). An Al metal film (∼10nm thick) was deposited onto the holey carbon coated side of the TEM grid using a magnetron sputtering system.

Small particles such as clay minerals, because of its large surface area to volume ratio and their high chemical activity on the particle surface, when added to composites affects (and often enhances) the physical, chemical and mechanical properties of materials immensely. As a result, there is a need to develop a method of characterizing these particles individually. However, physical dispersion of these particles can be very difficult, since they tend to agglomerate to reduce the high surface energy. Disperants of various sorts could be used to disperse/stabilize the system, but they could compromise/damage the integrity of the inherent state of these small particles. This paper presents a comparison study of preparing/dispersing small clay particles for electron microscopy research, and also represents the first report of cryo-microscopy of clay minerals.

Two types of smectites, namely a montmorillonite with cation exchange capacity (CEC= 140) and a saponite (CEC=42) were used for this study.

Interplanetary dust particles (IDPs) collected from the stratosphere are grains of cosmic dust delivered from asteroids and comets. IDPs are composed of complex mixtures of carbon, silicate glass and submicron to nanometer-sized minerals including Fe-Mg silicates, Fe-Ni sulfides, oxides and metal. Bulk SEM and detailed TEM investigations of stratospheric IDPs in the size range of 5 - 15 μm have shown that many IDPs have remarkably high concentrations of carbon - essentially the highest carbon abundances of any known extraterrestrial materials - and often this carbon is intermixed at the nanometer scale with other constituent phases. in order to investigate the properties, occurrence and spatial distribution of carbon in IDPs, we have developed a unique aciddissolution technique using standard microtomed thin-sections to remove the silicate and oxide fractions, thereby leaving a residue primarily of carbon and Fe-Ni sulfides. This technique causes no damage to the delicate microtomed sections or TEM grid and dramatically minimizes the quantity of acids required for etching.

Tin dioxide (SnO2) has been extensively studied and used as gas sensors to detect toxic gases such as CO, NOxand flammable gases like H2.[l] Recently, considerable researches have focused on thin film sensors due to their high performance as well as their integration compatibility with semiconductor technology for making microsensors and sensor arrays. [2] The performance of thin film sensors is remarkably influenced by the way they were fabricated.[3] Among various deposition techniques, pulsed laser deposition (PLD) has shown great prominence in the deposition of a wide variety of oxide thin film materials such as high Tc superconductors, semiconductors and dielectrics. in this work we present our experimental results on tin dioxide films deposited using pulsed laser ablation on sapphire (α -Al2O3) substrates with different surface orientations.

Tin oxide films with a thickness of 100 nm were deposited on the (1012) and (0001) sapphire by pulsed laser ablation of ceramic SnO2 targets.

Besides perfect dislocations, partial dislocations were proposed as effective means for misfit relaxation in the heretostructure system [1]. The microstructure of SrRuO3 films on SrTiO3 and LaA1O3 substrates have been studied. While misfit dislocations could be hardly found at the SrTiO3/SrRuO3 interface [2], high density of defects was observed in the SrRuO3/LaA1O3 interfaces [3]. in this paper, we report the high-resolution electron microscopy study of the SrTiO3/SrRuO3 bilayer films on (100) LaA1O3 substrates. The emphasis is focused on the means of misfit relaxation at the two interfaces.

Figure 1(a) is a low magnification cross-sectional image of a two-layer SrTiO3/SrRuO3 film on LaA1O3 taken along the [110] direction of the substrate. A high density of defects were observed along the SrRuO3/LaA1O3 interface. Figure 1(b) is a quarter of a superposed electron diffraction pattern (EDP) from the SrTiO3/SrRuO3 interface area, while fig. 1(c) is from the SrRuO3/LaA1O3 interface area.

Zinc oxide based coatings are of much interest in science and technology due to their interesting applications, such as in gas sensor devices, transparent electrodes, piezoelectric devices, varistor ,surface acoustic-wave devices ,etc. Thin films of ZnO also have some advantages over indium tin oxide (ITO) and tin oxide, which are usually used as transparent conductors, the former are chemically stable to a hydrogen plasma such as that used in the elaboration of solar cells. Many techniques have been employed to produce zinc oxide based coatings e.g. radio frequency magnetron, spray pyrolysis, sputtering, chemical vapor deposition, sol gel, pulsed laser deposition, etc. Among these techniques, the spray pyrolysis has proved to be a simple, reproducible, and inexpensive method, particularly useful for large area applications.

The main features of the spray pyrolytic system are fully described elsewhere. We have used a spray system attached onto mobile stage that provides a sweeping movement to the spray nozzle.

Mesoscopic silica is synthesized by using a self-assembling organic species to direct the structure of an inorganic matrix. It has attracted much interest because of its potential for use in a wide variety of catalysis, separations and nanotechnology applications. The commercial success of this material depends on the ability to simultaneously tailor the channel size and organization. A more complete understanding of the mechanism by which the material forms should lead to improved control over the structure. Small angle X-ray diffraction studies have shown that there is an “induction period” which precedes the observation of well-packed channels in films grown at the air-water interface. However, scattering data alone are unable to establish how the development of order might occur. Direct observation of the evolution is necessary to determine the mechanism by which well-packed, nanometer-sized channels form.

Continuous mesoporous silica thin films were grown at the air-water interface.

Thin films of amorphous silicon oxide and silicon nitride are routinely used as gate dielectrics in silicon-based microelectronic devices. It is valuable to be able to image them and measure their thicknesses quickly and accurately. This brief note describes conditions that can be used to obtain accurate and reproducible TEM images of oxide-nitride-oxide (ONO) thin films.

Obtaining adequate contrast differences between oxide and nitride is not trivial because they have the same average atomic number, and both phases are amorphous. As stoichiometric compounds, both SiO2 and Si3N4 would have average atomic numbers equal to 10. For SiO2, (14+2(8))/3=10, and for Si3N4, (3(14)+4(7))/7=10. Thus, the atomic number contrast between these two is weak or nonexistent. Similarly, the amorphous character prevents the use of conventional diffraction contrast techniques.

However, the density of Si3N4 (3.2 g/cm3) is considerably greater than the density of SiO2 (2.6 g/cm3), reflecting the higher average coordination of N compared with O.

Diamond-like carbon (DLC) has been used as thin films to protect the surface of magnetic disks in hard disk drives. Recently, in order to improve the recording density of the hard disks, DLC films need to be thinner than 10 nm in thickness. Therefore, it is necessary to develop the accurate thickness measurement technique for thin DLC films. in this study, to establish the thickness measurement technique for DLC films using electron energy-loss spectroscopy (EELS) and electron holography, we estimate the mean free path for inelastic scattering (ƛp) and the mean inner potential (U0). Through the evaluation of ƛp and U0, we compare the accuracy of EELS and electron holography on thickness measurement of DLC films.

The DLC films in this study are deposited on silicon wafers by chemical vapor deposition (CVD), sputtering and ion beam deposition (IBD) methods.

Microstructurally engineered oxide coatings have good potential as lubricants for aerospace applications over a wide range of environmental conditions1. Using composite microstructures, wear rates and friction coefficients may be reduced compared to monolithic coatings. Here, we report the characterization of ZrO2-Au composite coatings as new candidate lubricants. Au is added to ZrO2 to reduce friction and improve toughness. The composite films were grown on steel and silicon disks at room temperature (RT) by pulsed laser ablation of a ZrO2/5 wt. % Y2O3 target, with simultaneous operation of a magnetron source to add Au. The laser beam was operated at 250mJ, 40 Hz, and the magnetron was operated at 1.5-3.5 W cm-2 in 2.7 Pa argon. Varying the magnetron power produced coatings with different concentrations of Au. The coatings were prepared for transmission electron microscope (TEM) analysis by tripod polishing and ion milling on a cold stage.

Over the years, the study of the oxidation of nanoparticles of iron by transmission electron microscopy (TEM), Mossbauer spectroscopy and X-ray diffraction has established that nanoparticles of iron have a core-shell morphology in which the iron core is enclosed by shell of polycrystalline shell of ultrasmall γ-Fe2O3 and Fe3O4 crystallites. Recently, passivated nanoparticles of iron prepared by gas condensation of plasma evaporated vapor in Tianjin University exhibit remarkable resistance to further oxidation and corrosion in air and water. We have showed by TEM that these nanoparticles of iron are protected by a 4 nm epitaxial shell of γ-Fe2O3. The epitaxial orientation relationship, established by convergent beam electron diffraction from a nanoparticle, is as follows:

The [001] diffraction pattern of the oxide is rotated by 45° about a cubic axis relative to that of iron.

Cerium oxide is widely used for chemomechanical polishing (CMP) of silicate glasses. Uses include finishing of optical elements and planarizing dielectrics in the semiconductor industry. This study is designed to investigate the fundamentals of the cerium oxide/silica CMP process by measuring the interaction force between silicate glasses and cerium oxide. Surface forces involved in the polishing of glass by a cerium oxide abrasive can be studied in a controlled manner by measuring sample-tip interactions between a glass substrate and a cerium oxide tip in an atomic force microscope (AFM). Commercially available AFM tips have been coated with thin, uniform films of cerium oxide. By using a square pyramid tip as a template for the shape of the cerium oxide film, challenges related to irregular or blunt tip shape can be overcome. However, complete characterization of structure, shape and chemical composition is required before useful information can be obtained using the AFM.

The carbides and nitrides of transition metals, are excellent candidates for hard coatings for tribological applications. Recently a novel pulsed laser deposition (PLD) technique has been developed for the room temperature growth of particulate free titanium carbide (TiC) coatings on bearing steels. On a completely different scale from ball bearing applications, moving microelectricalmechanical systems (MEMS) face issues of limited lifetime as a result of rapid wear of the silicon components. The integration of hard tribological coatings into moving MEMS structures should greatly increase the functional lifetime of these devices. The same PLD technique has been used to deposit TiC thin film onto MEMS test structures consisting of multilayer coatings on Si substrates, and patterned 3-D Si substrates. This procedure for growing TiC appears to be compatible with conventional MEMS fabrication procedures.

Optical fibers have been extensively employed in a variety of fields. However, the need of high strength, excellent resistance to moisture permeation and tolerance to heat becomes apparent when such optical fibers are used in nuclear power plants and chemical plants in particular. Plastic coatings as conventional made of optical fibers cables would be replaced by the optical fiber coated with layers of metals.

The adhesion of coating to substrate is a critical property of any coating system for mechanical integrity and environmental protection of the substrate. For example, the corrosion protection of the metal coated optical fibers is highly depend on the adhesion of the coatings, if adhesion is poor, the extent of deterioration of the substrate by environmental factors (humidity, corrosive gases, etc.) is greatly accelerated. The durability and longevity of a coating required that its adhesion is to be maintained [1].

Magnetic domain structures in a Ni-5at%P alloy have been examined using Lorentz microscopy in Fresnel mode in a JEOL 2010TEM. with electron diffraction and high resolution electron imaging, the Ni-P alloy material is seen to be of FCC structure and composed of nanometer-sized grains (< 4nm in diameter), which is about 2 orders less in size than that of a single magnetic domain.

The TEM specimen was prepared using jet polishing method. Before introducing the specimen into the microscope, the objective lens was turned off in a free lens control mode to ensure that the domain structures in the specimen remain unaffected. The objective mini-lens was used to perform Lorentz imaging with out-focus method.

Stripe domains were observed. The width of these stripes is about 0.2 micron. But the length of these domains varies, sometime up to several microns. The stripe domains are grouped, which are near parallel one to the other.

In-situ composites based on (Nb) and Nb silicides, such as Nb5Si3 (tI32 crystal structure) and Nb3Si (tP32 crystal structure), are being investigated for revolutionary high-temperature structural applications [1,2]. The use of Hf and Ti alloying additions to these silicides has also been examined; in these systems Nb5Si3 has also been observed with the hP16 structure. The present paper describes EBSD analyses of a directionally solidified (DS) Nb-silicide based composite that experienced a eutectoid transformation. The composites were directionally solidified using the Czochralski method as described previously [1]. The composites were creep tested at 1200°C for 24 hours. Microstructure and microtexture characterization were performed using scanning electron microscopy, and electron backscatter diffraction pattern analysis (EBSD).

The microstructure of a composite directionally solidified from a Nb-12.5Hf-33Ti-16Si alloy is shown in Figure 1. in the as-DS condition the microstructure consisted of primary (Nb)3Si dendrites and coarse (Nb)3Si-(Nb) two-phase cells.

An important aspect in the consideration of V-4%Ti-4%Cr alloys as structural materials for proposed fusion reactors, especially for weldments, is the sensitivity of mechanical behavior to oxygen content. Following a 1-h anneal at 1200°C, sheet specimens were subjected to extended (16h to 43h) anneals at 500°C in 5 to 8 x 10-6 torr oxygen, followed by an homogenization vacuum anneal of 100 h at 600°C. Weight gains indicated ∼200 to >1400 wppm oxygen doping. Specimens were also subjected to an additional vacuum anneal for 4 h at 950°C. Specimens were prepared by standard double-jet electropolishing for TEM characterization with a Philips CM30 (LaB6) equipped with a Gatan Imaging Filter (GIF), and with a Philips CM200FEG equipped with Oxford EDS, GIF, and Emispec Vision integrated acquisition system.

Following oxygen doping and homogenization, high concentrations of nanoscale G.P.-zone-like clusters on ﹛001﹜ were observed in the matrix, with a ∼200-nm-wide precipitate free zone (PFZ) at grain boundaries.

Many aerospace components that operate in aggressive environments make use of coating techniques for protection. One of the alloy systems used in these coatings is Al-Cr-Ru, with typical alloy compositions between 20-35 at.% Al and 20-35 at.% Ru. Alloys with a higher Al content may provide protection through an aluminium oxide (AI2O3) scale which is resistant to high-temperature oxidation and corrosion. However, Al-rich alloys in the Al-Cr-Ru system have not been thoroughly investigated. Previously, the phase boundaries of the binary phases, except AI9Cr4, into the ternary were established. The two ternary phases (Ternary 1 and Ternary 2) were identified, although their phase boundaries were unclear. Thus more alloys have been studied to enable the liquidus surface, the solid phase projection and the 600°C isothermal projection to be drawn.

As-cast alloys were examined metallographically in the scanning electron microscope. The phases present were confirmed by X-ray diffraction, and the compositions obtained by energy dispersive Xray spectroscopy.

Cast 319 aluminum is an important automotive alloy used for engine blocks and cylinder heads. in order to “optimize” the as-cast microstructure and physical properties, a detailed understanding of its solidification behavior is required. One aspect of the solidification behavior which is not well understood is the mechanism by which aluminum and silicon in the eutectic regions nucleate. Figure 1 is an optical micrograph which identifies the aluminum dendrites, the Al-Si eutectic region, iron intermetallics, and Al2Cu particles. Dahle, Hjelen & Arnberg have utilized electron backscattered diffraction (EBSD) patterns, obtained with an SEM, on several Al-Si alloys to examine the orientation relationship between the aluminum in the eutectic to that of the surrounding aluminum dendrites. in this investigation transmission electron microscopy (TEM) is used to provide a more detailed examination of this eutectic structure while selected area diffraction (SAD) provide similar data to EBSD on the orientation relation between regions of primary and eutectic aluminum.

In the ternary Cu-Zn-Al alloys the bcc β phase is stable at high temperatures at electron concentrations (e/a) in the range from about 1.4 to 1.6 electrons per atom. Cu, Zn and Al atoms contribute with 1, 2 and 3 electrons, respectively. This region of stability is bounded by a β + γ twophase region at the high electron concentration border. If the P phase is retained at room temperature (RT) it transforms martensitically to a close packed structure. This transformation occurs without diffusion and provides information on the relative phase stability of the bcc and close packed structures. A detailed characterization of the microstructure of the parent bcc β phase and the martensite is thus essential for an adequate study of the transformation.

To retain the β phase at RT Cu-Zn-Al alloys must usually be quenched.