Jeffrey K. Farrer

Active Thermitic Material Discovered in Dust from the 9/11 World Trade Center Catastrophe

We have discovered distinctive red/gray chips in all the samples we have studied of the dust produced by the destruction of the World Trade Center. Examination of four of these samples, collected from separate sites, is reported in this paper. These red/gray chips show marked similarities in all four samples. One sample was collected by a Manhattan resident about ten minutes after the collapse of the second WTC Tower, two the next day, and a fourth about a week later. The properties of these chips were analyzed using optical microscopy, scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (XEDS), and differential scanning calorimetry (DSC). The red material contains grains approximately 100 nm across which are largely iron oxide, while aluminum is contained in tiny plate-like structures. Separation of components using methyl ethyl ketone demonstrated that elemental aluminum is present. The iron oxide and aluminum are intimately mixed in the red material. When ignited in a DSC device the chips exhibit large but narrow exotherms occurring at approximately 430 °C, far below the normal ignition temperature for conventional thermite. Numerous iron-rich spheres are clearly observed in the residue following the ignition of these peculiar red/gray chips. The red portion of these chips is found to be an unreacted thermitic material and highly energetic. SafetyLit Note: The editor-in-chief of this journal resigned upon the publication of this article even though she had rejected the manuscript (see: http://videnskab.dk/teknologi/chefredaktor-skrider-efter-kontroversiel-artikel-om-911 ). This article is the basis for some of the conspiracy theories concerning the New York World Trade Center attack.

EBSD of Ceramic Materials

The term “ceramics” covers a very broad range of materials. By definition, ceramics include all nonmetallic inorganic solids, containing both nonmetallic and metallic constituents; the interatomic bonds thus usually have both ionic and covalent character. The usefulness of ceramics in a wide variety of applications stems from properties such as hardness and resistance to heat, corrosion, and electricity. Ceramics are sometimes divided into two groups known as “traditional ceramics” and “new ceramics” (Kingery et al., 1976). The traditional ceramics include those primarily in the silicate industries (e.g., whitewares) and refractories. The new ceramics include electro-optic ceramics, magnetic ceramics, single crystals used for thin-film substrates, those used in the nuclear industry, and pure oxide ceramics to name a few (Kingery et al., 1976). The study of ceramics using electron backscatter diffraction (EBSD) has not yet extended into all of these areas of ceramics. However, EBSD research of certain ceramics has received considerable attention, and this will be the focus of this review.

Ferritin iron mineralization proceeds by different mechanisms in MOPS and imidazole buffers

The buffer used during horse spleen ferritin iron loading significantly influences the mineralization process and the quantity of iron deposited in ferritin. Ferritin iron loading in imidazole shows a rapid hyperbolic curve in contrast to iron loading in 3-(N-morpholino)propanesulfonic acid (MOPS), which displays a slower sigmoidal curve. Ferritin iron loading in an equimolar mixture of imidazole and MOPS produces an iron-loading curve that is intermediate between the imidazole and MOPS curves indicating that one buffer does not dominate the reaction mechanism. The UV-visible spectrum of the ferritin mineral has a higher absorbance from 250 to 450 nm when prepared in imidazole buffer than in MOPS buffer. These results suggest that different mineral phases form in ferritin by different loading mechanisms in imidazole and MOPS buffered reactions. Samples of 1500 Fe/ferritin were prepared in MOPS or imidazole buffer and were analyzed for crystallinity and using the electron diffraction capabilities of the electron microscope. The sample prepared in imidazole was significantly more crystalline than the sample prepared in MOPS. X-ray powder diffraction studies showed that small cores (~500 Fe/ferritin) prepared in MOPS or imidazole possess a 2-line ferrihydrite spectrum. As the core size increases the mineral phase begins to change from 2-line to 6-line ferrihydrite with the imidazole sample favoring the 6-line ferrihydrite phase. Taken together, these results suggest that the iron deposition mechanism in ferritin can be controlled by properties of the buffer with samples prepared in imidazole forming a larger, more ordered crystalline mineral than samples prepared in MOPS.

Annealing-induced change in quantum dot chain formation mechanism

Self-assembled InGaAs quantum dot chains were grown using a modified Stranski-Krastanov method in which the InGaAs layer is deposited under a low growth temperature and high arsenic overpressure, which suppresses the formation of dots until a later annealing process. The dots are capped with a 100 nm GaAs layer. Three samples, having three different annealing temperatures of 460°C, 480°C, and 500°C, were studied by transmission electron microscopy. Results indicate two distinct types of dot formation processes: dots in the 460°C and 480°C samples form from platelet precursors in a one-to-one ratio whereas the dots in the sample annealed at 500°C form through the strain-driven self-assembly process, and then grow larger via an additional Ostwald ripening process whereby dots grow into larger dots at the expense of smaller seed islands. There are consequently significant morphological differences between the two types of dots, which explain many of the previously-reported differences in optical properties. Moreover, we also report evidence of indium segregation within the dots, with little or no indium intermixing between the dots and the surrounding GaAs barrier.

Studying Trapped Grains in Alumina using SEM and EBSD

Despite development of high-resolution [1] and in situ [2] microscopies, grain boundaries remain something of an enigma, especially in ceramic materials where second-phase glass is often found to be present as films or precipitates in the interfacial regions. The glass is an unavoidable product in the liquid-phase sintering (LPS) process and incorporates intentional additives and accidental impurities. [3-4] Abnormal grain growth (AGG) has been associated with second-phase dissolution rather than defect or pore coalescence. [5-6] The number of crystal defects inside the polycrystalline material may dictate which of the grains will grow and which will be consumed. [5] Crystal anisotropy will promote orientation-dependent lattice diffusion of solutes, which may result in an induced strain energy within the crystal. [7] The solutes will lower the strain energy by sitting at the spacious boundaries rather than in the grain matrix.

Studying alumina boundary migration using combined microscopy techniques

Thermal grooving and migration of grain boundaries in alumina have been investigated using a variety of microscopy techniques. Using two different methods, polycrystalline alumina was used to investigate wet, (implying the presence of a glassy phase), and dry grain boundaries. In the first, single-crystal Al2O3 was hot-pressed via liquid phase sintering (LPS) to polycrystalline alumina with an anorthite glass film at the interface. Pulsed laser deposition was used to deposit approximately 100-nm thick glass films. Specimens were annealed in air at 1650°C for 20 h to induce boundary migration. Boundary characterization was carried out using visible light (VLM) and scanning electron (SEM) microscopies. Effects on migration due to surface orientation of grains were investigated using electron backscatter diffraction (EBSD). The second method dealt with heat treating dry boundaries in polycrystalline alumina to monitor boundary migration behavior via remnant thermal grooves. Heat treatments were conducted at 1650°C for 30 min. The same region of the sample was mapped using VLM and atomic force microscopy (AFM) and followed over a series of 30 min heat treatments. Boundary migration through a pore trapped inside the grain matrix was of particular interest.

Design and Construction of an Underground TEM Lab at Brigham Young University

The environment in which a TEM is installed is critical to the performance of the instrument. Among many concerns is the interference that can be caused by existing mechanical or acoustical vibrations, electro-magnetic interference (EMI) and thermal fluctuations[1]. Studies have shown various techniques that can be employed to reduce or eliminate the external interference[2]. In 2003 Brigham Young University completed the construction of a TEM facility. The installation of the microscopes (FEI, models Tecnai F30 & Tecnai F20 EFTEM) was completed in July of 2004. The facility was designed to meet or exceed the specifications from the microscope and other equipment manufacturers. This work will report on the design and construction of the facility and include a discussion of the measured effectiveness of both the well-known and the not-so-well-known procedures for eliminating the ambient disturbances.

Boundary Migration in Rutile

TiO{sub 2} is a vital material in several technologies including, photocatalysis, gas sensing, biomaterials and optical coatings. Among the several crystal structures of this oxide, rutile has the highest density and microhardness, the highest index of refraction and the highest temperature stability. The processing of dense polycrystalline materials often includes the addition of a liquid-forming phase at higher temperatures. This technique is known as liquid-phase sintering and has been studied extensively. Rutile boundaries containing an amorphous phase have been used to study boundary migration and grain-boundary grooving. Visible-light (VLM), scanning electron (SEM) and transmission electron microscopy (TEM) in addition to electron-backscatter diffraction (EBSD) and a focused-ion beam (FIB) tool were used to characterize boundary migration in rutile. EBSD analysis was carried out on a Philips XL30 FEG SEM equipped with a DigiView 1612 high-resolution, high-speed CCD camera. A 2.5 cm sample-to-camera distance was used and {approx}70{sup o} sample tilt. A Philips CM30 operated at 300 kV was used for TEM characterization and an FEI DB235 was used for FIB work. Pulsed-laser deposition (PLD) has been used to deposit thin films ({approx}100 nm thick) of silica glass on single-crystals of rutile. The film/substrate assembly is then fabricated into bicrystals of known boundary-plane orientation by hot pressing. Bicrystals were fabricated with boundary planes of nominal surface orientation of (001) and (110). After diffusion bonding a surface perpendicular to the interface is cut and polished. Bicrystals are then heat treated in air at 1650 C for varying lengths of time. Figure 1 is a VLM image of a rutile bicrystal which as been heat treated for 4 hours. During this heat treatment migration of the boundary initiates at parallel grooves contained in the crystal on the right-hand side. EBSD analysis shows that this parallel set of grooves is due to the presence of 3{sup o} boundaries within this crystal. While the boundary migrates from the left to the right with respect to the image, the 3{sup o} boundaries propagate into the reprecipitated rutile. The (001) boundary plane and (110) free surface grow at the expense of the (110) boundary plane and (001) free surface (free surface determined by EBSD). A FIB was used to prepare a cross-section TEM specimen at the migrated boundary. The FIB section was taken from an area in which the migrated boundary was 40 {micro}m from the groove remnant. A wide and shallow groove is formed at this migrated boundary and is illustrated in the bright-field (BF) TEM image in Figure 2. Of particular interest in this image is the nearly 120{sup o} groove at the free surface (see schematic in Figure 3) and the location of the grain boundary. Often in EBSD analysis and grain-boundary grooving work, grain boundaries are assumed to have a perpendicular intersection to the free surface. This FIB-prepared specimen shows in this particular case, this assumption does not hold true. Due to the grooving at the free surface and therefore a reduction in energy at the free surface, the speed of migration is faster away from the surface. Figure 3 is a schematic of this migrated boundary. The original boundary consisted of (110) and (001) planes. The side with the (001) initial boundary plane migrates into the other crystal. A benefit of using a site-specific specimen preparation technique such as FIB allows for the grain-boundary profile to accurately be determined. A variety of microscopy techniques has been used to study boundary migration in rutile. Migration in this case has originated at low-angle boundaries. The groove formed at the free surface slows the rate of migration at the surface. FIB allows the profile of the groove to be determined accurately.

Thickness-fringe Contrast Analysis of Defects in GaN

The analysis of thickness-fringe contrast in weak-beam transmission electron microscope (TEM) images has been shown to be a reliable method for the complete determination of the character, as well as the magnitude, of a dislocation Burgers vector. By selecting multiple diffraction conditions and, for each condition, determining the number of terminating thickness fringes at the exit of a dislocation from a wedge-shaped sample, the Burgers vector can be unambiguously determined. Defect analysis of GaN pyramids grown on (111)Si by the lateral epitactic overgrowth (LEO) technique reveals a core region which contains a relatively high density of dislocations and a lateral-growth region where the defect density is decreased. The thickness-fringe contrast technique was used in the lateral growth regions of the pyramids to analyze the dislocation Burgers vectors.

Exudation of Silicate Liquid from Polycrystalline Alumina

The presence of a liquid film at grain boundaries affects the mechanical properties of the material. One of the ways to eliminate the liquid film is to exude it from the grain boundaries to the free surface of the material. The present paper presents results on the exudation of a liquid silicate from grain boundaries in polycrystalline alumina. The results are compared to exudation behavior from bicrystals of alumina. This approach is very useful in understanding the mechanism of the exudation process.