It is widely appreciated that the study of (man-made) nanomaterials is a new frontier in materials science, but it is not well appreciated that (natural) nanomaterials represent a new frontier in meteoritics and planetary science [1]. During the next decade the nanogram to microgram quantities of extraterrestrial materials will be returned to Earth from a variety of solar system bodies including comets [2]. Studies of cometary interplanetary dust particles (IDPs) collected in the stratosphere, as well as mass spectrometry data from grains analyzed in-situ at comet Halley, suggest that the returned comet samples will be heterogeneous on a scale of nanometers [3, 4]. (A single 5-10μm diameter IDP may contain >106 individual grains and many different minerals (metal, carbonaceous phases, silicates, sulfides, etc.)). More recent observations of dust around stars, in interplanetary space, and at comet Hale-Bopp indicate that the predominant astronomical grain size is in the nanometer to submicrometer size range [5,6].

In the UK, ambient levels of PM10 are approximately 20-30 micrograms/m3 but may increase 10-fold during pollution episodes. There have been concerns expressed about the possible detrimental health effects of breathing particulates generated by opencast coal mining in the United Kingdom (e.g. Glyneath in Wales, 1997). However these fears have not been confirmed due to lack of adequate monitoring, characterisation, and source apportionment of PM10. We have collected airborne particulates from several sites within ‘Park Slip West’ coal opencast pit, which is situated in the south of Wales, UK. This collection constitutes the first half of a project to collect and characterise particles, followed by an assessment of their bioreactivity. The characterisation includes Field Emission SEM, SEM-EDAX, TEM-EPXMA, ICPMS and Image Analysis.

Particles were collected using high-volume air samplers operating at pre-calibrated flow rates of 30L/minute, attached to PM10 selective-inlet heads.

Halloysite has long been regarded as being highly-disordered or even turbostratic structurally. TEM study of halloysite in the past showed little detail in the basal fringes due to rapid beam damage. Most TEM images of halloysite with various morphologies reported in recent literature are at low-magnification. In this study, tubular halloysites from six localities in Australia and New Zealand were intensely examined with HRTEM and electron diffraction using a JEOL 200CX. The results are presented in this paper.

Tubular halloysite (Fig. la) HRTEM images recorded show a 7-Å fringe spacing (Fig. lb), which suggests that halloysite has lost its all interlayer water and has collapsed under the high-vacuum conditions in the TEM. The 7-A lattice fringes revealed on the walls of halloysite tubes are similar to those of kaolinite stacks, and exhibit relatively straight layers with fewer defects compared with smectite fringes.

Chemical analysis in a TEM has usually been done as a manual point analysis by forming a probe of an appropriate size for the area of interest. This type of local analysis may provide enough information from the selected area, but these days when materials properties are found to be deeply dependent on chemical distribution, one needs to do a higher dimensional analysis using a systematic line scan or mapping.

Since the advent of the Field Emission Gun (FEG), chemical mapping using X-rays (EDS mapping) or inelastic scattered electrons (Energy Filtering mapping) has become more and more commonly used due to the extremely high resolution information available in the chemical map. Compared to the energy filtered mapping, EDS maps take longer to acquire due to the use of the scanned probe over the area but EDS mapping allows a wider choice of elements to map due to the wider energy range it covers.

Expectations arised that unique microstructures could be attained by micro- or milli-wave processing of ceramics. To determine possible effects of milli-wave radiation on the microstructure evolution of silicon nitride, a detailed study has been carried out for silicon nitride sintered under conventional resistance heating and under milli-wave radiation (28 GHz). Densification of silicon nitride is achieved by liquid-phase sintering process. The additives such as yttria (Y2O3) and alumina (A12O3) are utilized to form a liquid phase during sintering. Considering the low microwave absorption factor of silicon nitride, heating in a microwave field is associated with the preferential microwave absorption of the additives. Differences in the nature and/or in the absorption factor of the additive will influence the sintering process and hence the final microstructure.

Aluminum nitride (AIN) with high thermal conductivity has been considered as a potential substrate material for microelectronics. However, the thermal conductivity of polycrystalline AIN ceramics, prepared by liquid-phase sintering, is significantly lower than that of AIN single crystal. It has been shown that the thermal conductivity of AIN is inversely proportional to the oxygen content dissolved in the AIN lattice. Furthermore, the microstructure of AIN can also influence the thermal conductivity considerably. In the present study, we investigated the effect of grain boundaries and secondary phase distributions on thermal conductivity of two selected high density samples which contained similar oxygen content but showed different thermal conductivities.

Experimental details and selected properties of Samples A and B are shown in Table 1. Sample A with 0.8 wt% Y2O3 additive was embedded in an AIN powder bed in a BN crucible covered by a BN lid (not gas tight) during sintering, while Sample B with 3.9 wt% Y2O3 was embedded in an AIN powder bed in an open graphite crucible.

Molybdenum di-silicides (MoSi2) based materials have a strong potential for high temperature structural applications due to high melting point of 2030°C, outstanding elevated temperature oxidation resistance and limited ductility above a temperature range of 1100-1300°C. The major shortcomings of MoSi2 for structural applications are its poor room temperature fracture toughness and low high temperature strength. Sustained efforts including reinforcing MoSi2 with ceramic reinforcements, alloying and in-situ processing, have been made to improve these properties. The purity of grain boundaries and interfaces, which in turn depends on the processing method plays a significant role in the high temperature properties and this paper aims to show that.

Intimately mixed Mo and Si powders (Mo:Si = 63:37 by weight fraction) were reaction hot pressed (“RHP“) in vacuum at 1500°C for 1 h, using a pressure of 26 MPa. During the hot pressing process, Mo and Si reacted to form MoSi2.

ABSTRACT: Coal gasifiers are required to operate at very high temperatures, >1600°C, for long periods of time, > 13 months (10,000 hours) Fig.1. Under these conditions the refractory lining of choice is high chrome refractory. During operation coal contaminants form a liquid slag that run down the chamber walls which can react with the refractory walls. Albany Research Center has designed a series of experiments to understand the slag-refractory interactions, with the intent of eventually being able to reduce or minimize the problem and thereby extending the gasifier operation time before relining. To understand the slag-refractory interaction, elemental components of the slag have been allowed to react with the refractory under simulated gasifying conditions. The interactions have been characterized using X-ray diffraction, electron microscopy, elemental x-ray mapping, and quantitative microanalysis.

Oxides of iron, titanium, and iron & titanium occur as accessory mineral components of most igneous rocks and generally comprise 1-2% of the total rock volume. In the fine-grained rocks the crystals are usually equidimensional and less than 1 mm across. Because most of them are opaque they cannot be examined using polarized transmitted light in the standard petrographic microscope and must be identified by reflected light (1). We have chosen to study these minerals in the SEM using BSE imaging and EDS microanalysis of carbon-coated polished sections of the rocks which contain them. Alhough this does not permit precise identification of the minerals the technique does reveal textural details which cannot be seen with light microscopy and also allows chemical analysis of the grains or parts of the grains. Furthermore, all these the oxide minerals are very easy to see in the BSE images because they are a higher atomic number (Z) than the silicates that form the bulk of the rock.

The human eye is very sensitive to fuzziness and can hardly bear seeing blurred images. This situation is still worse for X-ray microanalysis as a defect in focussing the electron beam can induce errors in intensities (in reference 1, a focus deviation of 10 micrometers causes an error of about 5% due to the modification of the Bragg angle). While a human operator can easily modify the Z stage position depending on the optical image seen on the monitor, several hours-long acquisition sessions require an automated way of reproducing the operator behavior.

The basic principle is to use the optical signal delivered by the camera installed on the probe at different Z values, extracting for each step a simple characteristic in the image. The characteristic chosen is the standard deviation of the grey levels, which is easily computed from the histogram moments of order 1 and 2, and should be at its peak value (lowest value on Transmission Electron Microprobes) on the focussed image.

Hydrogen-free amorphous diamond-like carbon films have stimulated great interest because of their useful properties, such as high hardness, chemical inertness, thermal stability, wide optical gap, and negative electron affinity[l]. Consequently, they may have various potential applications in mechanical and optical coatings, MEMS systems, chemical sensors and electronic devices. Amorphous diamond-like carbon films often contains significant amounts of four-fold or sp3 bonded carbon, in contrast to amorphous carbon films prepared by evaporation or sputtering which consist mostly of three-fold or sp2 bonded carbon. The ratio and the structure configurations of these three-fold and four-fold carbon atoms certainly decide the properties of these amorphous diamond-carbon films. Although the ratio of three-fold and four-fold carbon has been studied with Raman spectroscopy and electron-loss-energy spectroscopy, very little has been understood regarding key questions such as how the three-fold and the four-fold carbon atoms are integrated in the film, and what structures those three-fold carbon atoms take.

The development of YBa2Cu3O7 (YBCO) thick films on a flexible, textured, metallic substrate has recently attracted considerable scientific and technical interest. It is well known that the interfacial microstructure plays an important role on the formation and alignment of the YBCO films. Thus, understanding the evolution of the phases near the substrate interface will help us to improve the quality of the films. In this study, BaF2, Cu, and Y were deposited on the (001) CeO2/LaAlO3 substrates without external heating in vacuum. Subsequently, a series of these films were annealed at 735°C for preselected time periods and then quenched. Similar to YBCO films on SrTiO3 substrates, (Ba, Y, Cu)(F,O)2 (precursor) and Cu2O phases were formed after annealing for 10 minutes. After 12 hours annealing, the formation of YBCO film was completed.

Epitaxial platinum films are used as seed layers in a number of magnetic and ferroelectric devices. It is hence very important to understand the microstructure of the seed layer to control the subsequent multilayer growth. Previous studies of epitaxial Pt films have focused on AFM, XRD and RHEED measurements. However, there has been no detailed analysis of the microstructure as of yet. In this paper, we present results of a systematic study of the microstructure of epitaxial Pt films using conventional and high resolution transmission electron microscopy.

Platinum films were grown by sputtering in an UHV chamber at 500°C on (0001) sapphire. Figure 1 shows a plan view bright field image of a Pt film with the inset showing the <111> diffraction pattern. The spot pattern confirms the epitaxial nature of the film.

The mechanical behavior of metallic thin films on silicon plays a crucial role in the performance and reliability of microelectronic devices. A substantial body of research has focused on experimental methods for determining the mechanical properties of these systems as well as their response to thermomechanical stimuli. Of particular interest is a fundamental understanding of the how these films respond to the thermal expansion stresses that develop during typical microelectronic device fabrication steps.

In this work, we present a series of real time in-situ transmission electron microscopy observations of the thermomechanical response of a model metal film on silicon system. Physical vapor deposition of approximately 50 nm of aluminum onto a clean Si substrate held at 280 °C results in the creation of an epitaxial bicrystalline film with two variants of Al (110) oriented grains. In order to observe a large, uniform area during in-situ TEM thermal cycling, the Si substrate used was a SIMOX structure composed of 300 nm of Si (001) over 370 nm of buried SiO2).

Application of an appropriate ceramic surface coating to mechanical components such as bearings and gears can provide longer life and increased performance reliability. Metal-containing hydrocarbon (Me-C:H) coatings possess high hardness, together with low friction and low wear rate. They have also been suggested to adhere better to metallic substrates. This combination of attractive mechanical/tribological properties makes Me-C:H coatings potentially useful for surface modification of a wide range of mechanical components.

Using the technique of inductively coupled plasma (ICP) assisted vapor deposition[1], we have synthesized Ti-containing hydrocarbon (Ti-C:H) coatings with a wide range of Ti compositions[2]. Coating mechanical properties such as modulus and hardness have been measured by the technique of nanoindentation and correlated to Ti and hydrogen compositions[2,3].

We have performed detailed microstructural examination of Ti-C:H coatings by transmission electron microscopy (TEM), Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy, and X-ray Absorption Near Edge Structure (XANES) spectroscopy.

Thin films of tin oxide (SnO2) with the rutile structure are the subject of many investigations due to their potential applications, such as gas sensing devices, lithium batteries cathodes and solar cells. There is a growing interest in the development of gas sensors using SnO2 thin films due to their high surface to volume ratio. Previous studies have shown that the gas sensing properties of SnO2 are very dependent on the microstructure and that doping elements can greatly influence their electrical properties. In this paper we present transmission electron microscopy (TEM) studies of the microstructure and crystal defects of SnO2 thin films.

Tin oxide films 5 nm in thickness were deposited on the surface of sapphire (A12O3) by pulsed laser ablation of ceramic SnO2 targets. The film microstructure was studied using X ray diffraction, atomic force microscopy and transmission electron microscopy. Defects were studied using high resolution transmission electron microscopy (HRTEM).

Continuous increase in recording densities of the Co-based longitudinal media requires a drastic scaling down of the grain size in order to keep the required signal to noise ratio. However, this approach to increase the areal density will collapse when the grain size reaches the superparamagnetic limit. As an alternative, based on the analysis of the demagnetization mechanisms, Iwasaki and Takemura suggested the possibility of perpendicular magnetic recording (PMR), and computer simulation, predict areal densities of more than 300Gbit/in for this configuration. The c-axis oriented Co-based hep alloys with the magnetocrystaline anisotropy larger than the demagnetizing energy, are good candidates for the PMR media. However, before this type of materials can be realized, the magnetic domain structure must be well characterized. In this paper detailed analyses of the characteristics and shape of the magnetic domains present in the c-axis oriented CoCr films with thickness relevant for the recording industry are discussed.

Hard drives in portable computers require media deposited on glass substrates and employ NiAl as the first seed layer to optimize magnetic performance. From observations of a 112 XRD peak [1], a <112> texture has been reported to develop as sputtered films of NiAl thicken; however, synchrotron analysis observes additional cubic peaks [2]. The electron diffraction in this study detects no dominant <112> orientation in NiAl, but rather that the NiAl films (and subsequent cubic underlayers) are closer to 3-D isotropic. Furthermore, the +/-20° range of ﹛1100﹜ orientations observed [3] in the Co media grains grown on NiAl/Cr occurs not because of one (or two) special zone axis relationship(s), nor due to substrate surface finish, but rather as a consequence of multiplicity relationships between the cubic and hexagonal crystals. Although an “increase” in variants is often accepted for an upper film (e.g. bicrystals of [1120] Co on [200] Cr),

Austenitic stainless steels plasma-nitrided at low temperature can have a tremendously improved surface hardness without affecting their excellent corrosion resistance. The surface layer of these nitrided materials was considered to be composed of an uncharacterized, so called “S-phase”. During the past decade, several research groups have studied “S” phase using X-ray diffraction and transmission electron microscopy (TEM), but its microstructure is not yet well understood and is still a topic of debate. In this paper, we characterize the microstructure of 316 stainless steel nitrided by intensified plasma-assisted processing (IPAP) using cross-sectional TEM.

Samples of 316 austenitic stainless steel were nitrided for 1 hour by IPAP at a temperature of ∼ 400 °C. Plasma-nitrided samples were cross-sectioned and glued face-to-face by joining the nitrided surface. Crosssectional specimens for TEM observations were prepared by mechanical grinding, polishing and dimpling followed by Ar+ milling. TEM studies were carried out in a newly installed JEOL JEM 2010 electron microscope in the Materials Characterization Facility at the Louisiana State University.

The Crystallization of amorphous silicon (α-Si:H) at lower temperatures is a challenging area of research these days because it will open up the possibilities of fabricating semiconductor devices like thin film transistors (TFT's), solar cells, active matrix liquid crystal display (AMLCD) devices at considearbly lower cost. Various metals e.g. Ni, Cu, Au, Ag and Al have been used to bring down the crystallization temperature of α-Si. We have found that aluminum assisted crystallization can bring down the temperatures of crystallization to as low as 200 °C. The crystallization behavior of α- Si:H has been studied by scanning electron microscopy, Raman spectroscopy, XPS spectroscopy and X-Ray diffraction but very little work has been carried out on microstructural investigation of the material using transmission electron microscopy. We have prepared specimen for die TEM study of α-Si:H and that of crystallized Si obtained by aluminum assisted crystallization. A detailed investigation of the crystallization behavior of α-Si:H using TEM have been carried out.