Post-deposition ion implantation of boron nitride (BN) films is to be considered as a powerful method for improvement of adhesion between films and substrates and reduction of compressive stresses, which usually accompany the growth of cubic BN.

The goal of this investigation is microcharacterization of as-deposited and ion-implanted BN films to better understand effect of ion implantation on microstructure of the films and film/substrate interface. High Resolution TEM (HF-2000 with field emission gun) has been utilized because of nanocrystalline dimensions of both cubic (c-) and hexagonal (h-) BN phases.

BN films have been deposited on (100) oriented Si substrates by magnetically enhanced activated reactive evaporation2. Plasma source ion implantation has been performed to make surface modifications and to improve the adhesion of the films. X/S specimens for TEM and HRTEM have been prepared in a routine manner, using G-1 epoxy for coupling the specimens, Dimpler VCR D500I, and Gatan Precision Ion Polishing System for final thinning.

Recently, considerable efforts have been made in developing a fabrication procedure for YBa2 Cu3O7-δ superconducting films on a metallic substrate tape for electrical power applications. The central issue is to develop a method, which can produce the tape in sufficiently long lengths at a commercially viable cost. One possible approach is the so-called BaF2 post-deposition annealing process, which involves deposition of an unreacted mixture of a BaF2 -Y-Cu-O layer on a substrate by electron beam evaporation method, followed by heat-treatment of the layer in a mixed-gas atmosphere of a low partial pressure O2, saturated H2 O, and N2 . To fabricate thick and long films, it is important to understand the effects of the heat-treatment parameters on the. structure and the properties. Here, we report our structural analysis of the films annealed at different temperatures.

The films annealed at 725°C, 750°C and 800°C have a similar phase assemblage which are composed ofYBa2 Cu3O7-δ and Y2O3, CuO and Ba-Ti-Sr-O precipitates, as shown in fig. la.

Nanocrystalline bulk Ni processed by inert gas condensation of powders followed by compaction has shown impressive mechanical properties with strength values as high as 50% of the theoretical shear strength. However, the process of warm compaction required for densification often leads to grain growth, and flaws in the microstructure. In this study, thin films of nanocrystalline Ni were processed by magnetron sputtering to bypass the compaction process and achieve a microstructure with very narrow grain size distribution. This paper presents the grain size distribution and other microstructural features of nanocrystalline Ni films.

Ni films were grown on Si and NaCl substrates, using argon plasma generated with the help of a plasma d.c. magnetron source equipped with a Ni target of 99.99% purity. The target power used was 200 W and the argon pressure was maintained at around 6 millitorr during deposition. A pulsed dc negative bias of 0 or 100 V was applied on the Si substrate.

There has been a significant interest in the development of dispersion-hardened aluminum for many years for high specific strength and modulus. Such materials are usually processed by powder or ingot metallurgy routes. In this study, Al3 Ti dispersion hardened Al was obtained by annealing Al-Ti multilayers. Al-Ti multilayered films have been characterized in the past by observing the structure of the layers, as well as tensile properties and hardness. This paper reports the structure of Al-Ti multilayers and the evolution of matrix and dispersoid microstructure on annealing.

The Al-Ti multilayered structures were prepared by magnetron sputtering using Al and Ti as targets and either Si (100) or NaCl as substrates. The bi-layer thickness was maintained around 16 nm with Ti constituting 12% of the total. The substrate was alternately moved below the Al and Ti targets for the purpose of deposition. The as-deposited film on the substrate and NaCl salts were annealed at 400°C for periods between 1 and 24 h in a vacuum (10−5 torr) furnace.

Thermal spray of carbide coatings with high hardness and corrosion resistance onto steel substrates has technological importance. The adhesive strength is greatly effected by the interfacial impurities. Low porous and good quality 200 μm thick 86WC10Co4Cr coatings on 4140 steel are obtained by thermal spray methods using SC-HVOF gun at Cooper Oil Tools, Houston, TX. A Carl Zeiss DSM942 SEM with 3.5 nm resolution at 30 keV and Kevex LPX1 Super Dry Quantum Si(Li) Detector with < 145 eV resolution for Energy Dispersive X-ray Spectroscopy (EDXS) were used to study the elemental distribution across the interface. Fig. 1 shows the SEM micrographs of the interface between 86WC10Co4Cr thermal spray coating and 4140 steel substrate. The anchor patterns seen at the interface are believed to improve the adhesive qualities between the coating and the substrate.

ITO films on PET in combination with ITO films on glass substrates are extensively used in Touch Panel Displays fabrication. Main properties of interest for these systems are high optical transmittance ∽95%, low resistivity ∽10−3 Ωcm, coupled with uniform and stable sheet resistivity demanded for long term use.

The goal of this investigation is to understand relationship between microstructure and electrical/optical properties of ITO films on PET and glass substrates as a function of pre- and postdeposition annealing parameters.

ITO films of ∽60 nm thick have been deposited by radiofrequency magnetron sputtering. This method can be applied over a wide range of substrate temperatures. This is essential for plastic substrates such as PET. Regions of good and poor conductivity have been identified for TEM analysis and Analytical Electron Microscope (Philips 400 EM), equipped with light element Noran Instrument Energy Dispersive X-ray Spectrometer (EDXS) have been utilized.

Vanadium dioxide (VO2 ) exhibits a reversible semiconductor-to-metal phase transition around 341 K. The low temperature monoclinic P21 /c structure transforms into the tetragonal P42 /mnm rutile structure. The associated sharp changes in optical and electrical properties are used in various thin film switching devices. The present paper describes a study on the optical and structural changes during the synthesis of VO2 thin films using Infra-Red (IR) reflectance spectroscopy and Transmission Electron Microscopy (TEM).

The synthesis was derived from a sol-gel process by Guzman et al. Solutions of vanadyl isopropoxide (VO(OC3 H7)3 ) in n-propanol were spin-coated on a Si wafer provided with 300 nm thermal oxide. Subsequently, the wafer was transferred to an oven and heated to 773 K in a reducing H2/N2 atmosphere using a heating rate of 5 K/min. After a variable time (Δt) at 773 K, the samples were cooled down to room temperature.

Figure 1 shows the IR reflectance of thin (∽50 nm) VOx films on oxidised Si at λ,=3 μm and an angle of incidence ϕ of 30°.

In an earlier report we have shown that the infrared photoluminescence (PL) from nanocrystalline Si films shifts to lower energies with increasing deposition temperature (in the range of 180-340 °C) and with thermal annealing. These films were deposited on Corning 1737 glass substrates using a Plasma-Therm SLR 770 ECR-PECVD system to a thickness of 4500 Å. The redshift of PL correlates well with the narrowing of (111) XRD peak, the redshift of the optical absoiption profile, the increasing conductivity and the decreasing activation energy for conductivity. Therefore, the energy shift of the PL has been considered as the result of variations in bandgap due to variations in crystallite size; i.e., variations in the quantum confinement. For the samples investigated, the PL band peak was found within the extrema of 0.99 to 0.81 eV (at 77 K). These extreme values correspond to the film deposited at 180 °C (0.99 eV PL) and the same film annealed at 600 °C for 72 hours (0.81 eV PL).

Al thin films, used as interconnects in integrated circuit devices, are subject to voiding failures due to electromigration and stress. Electromigration is a diffusion process and voids are known to form at points of flux divergence such as triple junctions. Void formation in Al-Cu films has also been associated with 9θ-phase (Al2 Cu) precipitates [1], which form preferentially at grain boundaries and triple junctions. Some triple junctions are favored as nucleation sites [2], presumably due to energetic differences arising from the crystallographic nature of the junctions. Their character can be calculated from the crystallographic orientations of the surrounding grains and the associated grain boundary dislocation networks [3]. Bollmann's method of analysis results in two categories of triple lines: I-lines - the special case where the grain boundary dislocations balance; and U-lines - the general case where the dislocation arrays do not balance. U-lines should have higher energies than I-lines and should therefore behave differently [3, 4]. This paper investigates the relationship between triple-line character and the location of Al2 Cu precipitates at certain triple junctions in Al-lCu thin films.

Stainless steel-zirconium (SS-Zr) alloys have been developed as waste forms to immobilize and retain fission products generated during the electrometallurgical treatment of spent nuclear fuel. The baseline waste form is a stainless steel-15 wt.% zirconium (SS-15Zr) alloy, which is prepared by melting appropriate amount of Type 316 stainless steel (SS316) and high purity zirconium. As zirconium has very low solubility in iron, the addition of zirconium to SS316 results in the formation of ZrFe2 -type Laves intermetallic phases. The corrosion behavior of stainless steel has been widely studied; however, the corrosion behavior of the Zr-based-intermetallic has not been previously investigated. In this paper, we present a microstructural characterization of the corrosion layer formed on the Zr-intermetallic phase using energy-filtering transmission electron microscopy (TEM) and energy dispersive x-ray spectroscopy (EDS).

Specimens of SS-15Zr alloy, crushed to 75 to 150 μm sizes, were immersed in 90°C deionized water for a period of two years.

In the processing of sheet steel, slabs are normally heated in a reheat furnace in the temperature range of 1200° -1300° C, extracted, hot rolled on a hot strip mill (HSM) and further processed. Because of the high operating temperature and the availability of oxygen, the steel surface is usually severely oxidized. The furnace scale could be a few millimeters thick. Abnormally thick scale may not be easily removed by high-pressure water sprays at the HSM. Rolled-in scale can contribute to underpickling and potentially result in the generation of steel surface defects.

Furnace scale typically consists of three oxide layers, Fe2O3 (hematite) on the outside surface, Fe3O4 (magnetite) in the middle and FeO1+x (wustite) next to the steel substrate. An example is shown in Figure 1. The three oxide layers are identified by H (hematite), M (magnetite) and W (wustite). Furnace scale samples of low carbon steel have been analyzed via x-ray diffraction (XRD) and optical metallography in order to characterize the scale.

Laves phase (Cr2X) strengthened Cr solid solution [Cr(X)]-based alloys are under development for a variety of high-temperature structural applications. Among the most promising alloys are castings based on the Cr(Ta)-Cr2Ta eutectic, which exhibit room-temperature fracture toughness in the 10-12 MPa√m range and creep rupture lives in excess of 1000 h at 1000° (138 MPa) in air. These alloys exhibit superior high-temperature oxidation resistance to previously developed Cr(Nb)-Cr2 Nb based alloys despite the general similarities of Ta and Nb. In order to optimize high-temperature oxidation resistance an understanding of why the Cr(Ta)-Cr2Ta alloys are more oxidation resistant is needed. Detailed EPMA characterization of the oxidized scaleswas initiated as a first steptowards gaining this understanding.

Fig. 1 shows a backscattered electron image of cast and heat treated and heat treated Cr-10Nb at.% after a 6 cycle, 120 h exposure at 1100°C in humid air. Most of the coupon was converted to a complex mixture of Cr-, Nb-, and Cr+ Nb- oxides.

Thermal barrier coatings (TBCs) insulate gas turbine hot section components from the hot (∽1200 - 1450°C) combustion gas exhaust stream. An airline company can save millions of dollars per year by using TBCs to protect vital engine components and to improve fuel efficiency. TBCs typically consist of an 8 wt.% yttria-partially-stabilized zirconia (YPSZ) ceramic topcoat deposited on a platinum-nickel-aluminide (Pt-Ni-Al) bondcoat covering a nickel-based superalloy substrate. Thermal exposure during YPSZ electron beam-physical vapor deposition (EB-PVD) and engine operation promotes the formation of a thermally grown oxide (TGO) between the Pt-Ni-Al and the YPSZ layers. Stresses can develop at the Pt-Ni-Al/TGO and TGO/YPSZ interfaces due to TGO growth and thermal expansion coefficient mismatch. These stresses eventually cause spallation of the YPSZ, leaving the metallic substrate vulnerable to high temperature degradation since exhaust temperatures are often higher than the melting temperature of most nickel-based superalloys (∽1200 - 1450°C).

Deformation substructures, especially dislocations, play an important role in the fabrication of the Caribbean steel drum and experimental evidence also suggests dislocations play a crucial role in the harmonic tuning and related musical qualities as well. In this study, we have examined and compared the dislocation substructures in high-quality, low-carbon (0.04-0.06 weight percent carbon) steel drum heads as manufactured, and sections cut from variously deformed (10% to 50% reduction) drum head sections, including those patterned with musical notes and heat treated; utilizing TEM.

We have recently shown that the requisite heating of a steel drum over a narrow temperature range (200 to 500°C) prior to tuning actually involves strain aging. Fundamentally, strain aging in steels has been explained by dislocation theory, but as far as we know, no experimental proof exists. This study also attempts to examine the more fundamental issues in strain aging, especially as it applies in the development of a high-quality, musical steel drum instrument.

Long term aging of martensitic Fe-12Cr steels at elevated temperatures can result in a significant decrease in toughness. The mechanism responsible for this has been generally attributed to either impurity segregation and/or precipitation of second phases. The aging embrittlement of higher Cr-containing ferritic steels has long been attributed to the precipitation of bcc Cr-rich alpha prime phase[l]. Alpha prime has also been shown to embrittle certain Ni base alloys [2]. The current work has shown that alpha prime forms in Fe-12Cr steels which have been aged at 450°C for up to 32khrs. Coincident with the precipitation of alpha prime is a marked decrease in toughness.

Historically, extraction replicas and to a limited extent thin-foil TEM microscopy have been used to identify alpha prime. However, both are not without problems in these magnetic, corrosion-resistant steels, due to the fact that the alpha prime is small (<20nm) and coherent with the matrix. Volume fraction studies have been essentially impossible.

Much work has been devoted to TEM studies of nanoscale precipitates consisting of non-soluble elements in Al, as the Al matrix acts as a unique crucible enabling the study of melting/ solidification and crystal phase transformations at a nanometer scale. Recently, this work has been extended to include the ternary system of Al-Pb-Cd. This system is of particular interest, as both Pb and Cd display a large liquid miscibility gap with Al, but together they form a eutectic system. Bimetallic inclusions consist of an fcc Pb and an hcp Cd segment, joined along an internal interface parallel to the {111}Al planes. In this work, the microstructure and composition of off-eutectic Pb-Cd inclusions are studied. Polycrystalline Al samples were implanted with 1 x 1020 ions/m2 (∼3 at.%) with a Cd:Pb ratio of either 8:2 or 2:8, at temperatures to form inclusions in the 10 nm size range.

Ni-Cr-Fe alloys such as Alloy 600 and Alloy 690 are single phase fee alloys with excellent resistance to corrosion. Alloy 600 is generally used in a thermally-treated condition which is characterized by the intergranular precipitation of Cr-rich M7C3 and, depending upon the aging temperature, Cr-rich M23C6. These alloys are usually cast and processed by rolling or forging. These alloys can exhibit microstructures in which there are nonuniform distributions of intragranular carbides that appear as bands aligned parallel to the working direction (i.e. longitudinal) of the material. It is also possible for these materials to exhibit duplex grain sizes which can be associated with the banded carbide structure. Banded microstructures can become more prominent after further anneals. The resistance of the carbide bands to dissolution during solution annealing at temperatures up to 1150°C has prompted the further evaluation of banding in Alloy 600, specifically in terms of identifying those elements associated with the carbide bands.

In a study of the precipitation and aging of Invar particles in Cu, we observed that the particles evolved from spherical to cuboidal as they grew in size. This behavior has been observed in other systems, and predicted by Voorhees et al. ; they showed that the precise shape of the particle is a balance between elastic anisotropy and surface energy. The correlation between our results and their predictions are very good. It is the purpose of this note to point out that simultaneous measurements of size, shape, and mismatch of a coherent particle can be used to estimate the interfacial energy under favorable conditions.

Ternary alloys consisting of Cu - 12.8 wt% Ni -7.2 wt% Fe were arc-melted, held at 1030°C to develop extended regions of the Cu-rich solid solution, quenched, then aged at various times and temperatures to develop FCC precipitates near the Invar composition in the FCC Cu matrix.

Studies aimed at improvements in the properties of titanium aluminides continue and efforts on optimizing the microstuctural parameters and a variety of processing techniques have attracted significant attention. In particular alloy compositions containing Ti-44to48at%Al and Nb as the major ternary addition (often with other minor alloying element additions) have been found quite promising. A fine fully lamellar structure in these TiAl-based intermetallic alloys has been reported to possess a combination of improved room temperature ductility, excellent fracture toughness, good oxidation resistance and creep properties. One of the serious problems associated with the TiAl-based alloys is the large grain size that develops in these alloys especially upon casting. A recent approach is to use directional solidification techniques in producing the TiAlbased alloys and it has been shown that desired orientations can indeed be produced by choice of suitable processing parameters.

In this study, we have examined the microstructural features associated with chill-cast as well as directionally solidified Ti-44at%Al-l lat%Nb alloy.

The copper alloys commonly referred to as nickel aluminum bronzes (NAB) are widely used in marine applications due to their excellent seawater corrosion resistance and good mechanical properties. Unfortunately, these alloys are susceptible to a variety of surface sensitive degradation processes such as cavitation and wear which significantly reduce service life. Laser surface melting and cladding techniques have recently demonstrated a potential to substantially enhance the performance of NAB components. This is associated with the occurrence of a martensitic or Widmanstätten transformation from the high temperature bcc β phase accompanied by precipitation of ordered intermetallic particles collectively referred to as κ. Optimization of these techniques requires an improved understanding of the evolution of microstructure in the NAB system under conditions of rapid solidification, however little data is currently available. In this paper, transmission electron microscopy is used to examine the microstructures of a series of laser surface melted NAB alloys containing from 8 to 12 wt. % Al, 3.8 to 6.5 wt. % Ni, 3.8 to 6.5 wt. % Fe, ∽1 wt. % Mn and, in some cases, lesser amounts of Ti or Zr.