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.

The high temperature equilibrium β phase in Cu-based alloys has a disordexed bcc structure. Its stability at high temperatures is due to the large amplitude ﹛0 ζ ζ)﹜ <0 ζ ζ> soft mode which provides a large vibrational entropy. This stability decreases with temperature as the entropy term in the Gibbs free energy becomes smaller. However, by quenching it is possible to retain the β phase avoiding decomposition by diffusion controlled transformations. in ternary β phase Cu-Zn- Al alloys, ion irradiation at room temperature has been reported to induce a phase transformation to a close packed structure or to produce γ phase precipitates. in order to further study the tendency of the β phase to decompose into other phases at room temperature, ion irradiation experiments in binary Cu-Zn single crystals were carried out using a beam of 30 keV Ar ions. The changes in the microstructure were examined using transmission electron microscopy.

Previous studies on aluminum-potassium-silicon (AKS) doped tungsten wire have shown that the dispersion which provides the interlocking grain structure in recrystallized tungsten wire is bubbles of elemental potassium. However, there is little previous work on the K-containing dispersion in doped Mo. This paper will describe analyses of doped Mo.

The creation of dopant inclusions in Mo powder and generation of K bubbles in doped Mo wire both prior to and following various heat treatments has been studied. The effect of doping Mo with K, Al and Si is to increase the recrystallization temperature of the Mo and to produce a microstructure of coarse, interlocking grains after recrystallization.

Mo wire is produced in a similar manner to AKS doped tungsten, however lower processing temperatures are typically used in the production of Mo wire. The dopants are added to Mo oxide powder as potassium silicate and aluminum chloride.

It is well known that rare-gas Xe atoms embedded in a crystalline Al matrix form precipitates having cuboctahedral shapes bounded by ﹛100﹜ and ﹛111﹜ surfaces1. Below a certain critical size, Xe precipitates are observed to be solid, even at room temperature. This is a result of the Laplace pressure, which is inversely proportional to the radius of the precipitate. Donnelly et al. reported that the critical size of Xe solidification was expected at 4nm in radius at room temperature.

Using high-resolution transmission electron microscopy, it is possible to observe these particles directly. It has been demonstrated that under off-Bragg conditions, the Al lattice fringes are minimized whereas the Xe lattice fringes are maximized. From such observations, it was confirmed experimentally that the average critical size of Xe precipitates is around 4 to 5nm in radius. However, much larger Xe precipitates are sometime observed to remain solid.

Atomic structure on the 1-2 nm scale, often referred to as “medium-range order” (MRO), is of great importance for understanding the properties of disordered materials. It is, however, difficult to adequately characterize medium-range order. Fluctuation microscopy is a newly developed TEM technique that has successfully been employed to characterize MRO in amorphous semiconductors. The predominance of highly directional covalent bonds leads naturally to the presence of MRO in amorphous semiconductors. For metallic glasses, however, the bonding is primarily metallic and nondirectional. Thus, it is not readily apparent whether MRO would exist, or whether fluctuation microscopy is a useful tool for studying the structure of metallic glasses. in this work we report the use of fluctuation microscopy to identify differing degrees of MRO in Zr-based bulk metallic glasses; the MRO depends on the alloy content and the method of TEM specimen preparation.

In recent years there has been a significant increase in magnesium use as a structural material. Applications include aerospace and automotive industries as well as appliances and sporting goods. The most attractive feature about magnesium alloys is related to their low density. However, their mechanical properties require improvement to surpass the specific strength of the high strength aluminum alloys. The purpose of the present paper is to report the crystal structure determination of the precipitates found in the alloy Mg- 1.5%wtCa-6%wtZn produced by melt spinning.

The as solidified alloy was analyzed by means of Transmission Electron Microscopy(TEM), Scanning Transmission Electron Microscopy (STEM) and Energy Dispersive X-ray Spectroscopy (EDS). The crystal structure of the new precipitate observed was determined by means of comparison of experimental and simulated selected area electron diffraction patterns (SADP) and High Resolution Electron Microscopy (HREM) images. The simulations were obtained using the software EMS.

Much attention has been devoted to develop the new generation of microalloyed steels in recent years to meet the needs of high performance and low cost for the 21st century. The new type of steels is characterized by reduced carbon content, improved cleanness and refined grain size through the phase transformations.11'21 Precipitation of the carbonitrides in the steels is also one of the keypoints for controlling mechanical properties of the steels.

In the present work ultra-low carbon clean microalloyed steels, which contain 0.029∽0.047(wt)%C, 1.48∽1.54(wt)% Mn, 0.044∽0.052(wt)%Nb, 0.025∽0.044Ti(wt)%, 0.0015∽0.0020(wt)%B and 0.0045∽0.0070(wt)%N, were prepared in a vacuum induction furnace in laboratory. The contents of S and P of the steels are 0.0005(wt)% and 0.0010∽0.0024(wt)% respectively. Total amount of the impurity elements O, S, P and H in the steels is 0.0061∽0.0077%. Dominant component of the structure in both casting and as-forged samples is acicular ferrite or bainite.

Boundary properties between two adjacent grains with different crystallographic orientation relation are important factors in deciding the mechanical properties of materials. in our previous reports, we introduced the geometric compatibility equation as a factor determining the brittle crack propagation condition into the adjacent grain in banitic low alloy steel as follows:

M = cos α · cos θ

where α is the angle between crack normal in the cracked grain-I and normal to (001) plane in the adjacent grain-II and θ is the angle between normal to (001) plane in the grain II and loading axis.(see FIG. 1) Higher M gives greater possibility to the crack propagation. The geometric compatibility factor (M) could be easily calculated from the crystallographic data obtained from Electron Backscatter Diffraction (EBSD) analysis, and successfully predicted actual crack propagation plane. We also found that there was a critical M value to arrest the brittle crack propagation at the boundaries.

The insertion of hydrogen in metals promotes severe modifications of physical and mechanical properties. in the case of nickel, hydrogen induces intergranular cracking [1] and decrease of ferromagnetism [2]. Hydrogen occupies the octahedral interstices of the fee structure promoting cell expansion. Large amounts of the fcc (β hydride may be produced by high pressure hydrogenation [3] or electrolytic charging [4]. The H/Ni relation (x) in the P hydride range from 0.6 to 1.0, depending on the method and conditions of hydrogenation. The β hydride is known to be metaestable at room temperature and normal pressure [5].

In this work, a thin foil (0.02mm thick) of high purity nickel was hydrogenated by electrolytic charging in a 1N H2SO4 solution with 20 mA/cm2 by 24 hours. AS2O3 was used as catalyst in a concentration of 5xl0−5mol/l. The hydrogenated samples were analysed by X-ray diffraction and SEM immediately after and 4 hours after the charging (room temperature aging).

The mechanical alloying (MA) process has been probed to be an effective method to conveniently develop materials with novel structures. The products of MA can be processed by conventional powder metallurgy routes for further consolidation. However, the novel features conferred to the powders, such as fine crystal size and chemical homogeneity can be lost during sintering operations, due to the high chemical activity of some of the synthesized phases. The Spark Plasma Sintering (SPS) process is an alternative route to obtain highly dense MA′ed products while retaining these novel microstructures, including a metastable state. Advantages of the SPS process over conventional sintering processes are the fast heating and cooling rates, and the high pressure applied. Combining these two material processing techniques (MA and SPS) it is possible to obtain materials with interesting (far from equilibrium) microstructures. Co-Ti alloys were obtained by MA and SPS, as described in related publications.

Although amorphous phases produced by mechanical alloying (MA) in the Ni-Mo system have been reported before. It has not been presented the influence of using different milling devices and atmospheres. This work is focused to the characterization of amorphous structures thus obtained in a Mo-47 at. % Ni alloy. Selected composition corresponds to the equiatomic NiMo intermetallic. The characterization was carried-out by XRD, SEM-EDS, DSC and TEM. High resolution XRD reveals that the MA′ed products undergo partial amorphization, as shows Figure 1. The main difference in the patterns is a region that corresponds to typical Nickel reflections. Nickel preferential amorphization after milling was evident. Apparently, a major grade of amorphization was attained when using the Simoloyer mill. A rough crystallite size was calculated using Scherrer equation, which reveals that this parameter reached its minimum value with the Simoloyer mill. During DTA analysis, it was observed the presence of an exothermic peak in all samples.

In the study of metal oxidation, there is a wide gap between information provided by surface science methods and that provided by bulk oxidation studies. The former have mostly examined the adsorption of up to ∽1 monolayer (ML) of oxygen on the metal surface, where as both low and high temperature bulk oxidation studies have mainly focused on the growth of an oxide layer at the later stages of oxidation. Hence, we are visualizing the initial oxidation stages of a model metal system by in situ ultra-high vacuum (UHV) transmission electron microscopy (TEM), where the surfaces are atomically clean, in order to gain new understanding of these ambiguous stages of oxidation. We have previously studied the growth of Cu2O islands during initial oxidation of Cu(100) film. We are presently investigating the initial stages of Cu(110) oxidation, from 10−4 Torr O2 to atmospheric pressures and temperature range from room temperature to 700 °C.