The effects of high strain-rate deformation on the phase stability and interdiffusion were investigated for Al-Zn welds produced by ultrasonic welding at 513 K. The welds exhibited three distinct regions: a featureless region indicative of local melting on the zinc side, a solidified mushy layer and a layer of fcc grains enriched with zinc. Al-Zn phase diagrams calculated from vacancy-modified Gibbs free energy curves indicate that local melting at the weld interface may result even at 513 K if the vacancy concentrations in the fcc and hcp solutions approach 0.07 as a result of high strain-rate deformation. EDS analysis of the weld interface yielded an interdiffusivity of 1.9 μm2/s, which is five orders of magnitude larger than the normal diffusivity of zinc in aluminum at 513 K. Application of the mono-vacancy diffusion mechanism to the diffusion data also yields a vacancy concentration of 0.07, indicating that such a high vacancy concentration may indeed resulted during the ultrasonic welding at 513 K.

As the dimensions of materials are reduced to the nanometer scale, the stabilization of pseudomorphic crystal structures that differ from their bulk equilibrium phases can occur. The pseudomorphic growth could provide a substantially larger bulk modulus and greater hardness than the average of the constituent materials in nanolayered and nanocomposite thin films. To evaluate this effect in Ti1-xAlxN system, a series of nanostructured films with × up to 0.7 were deposited onto WC-Co substrates using arc PVD, and characterised in terms of structure-property relations. Chemical composition by RBS together with HRTEM and XRD analysis showed that for the Al content below × = 0.4 a solid solution single-phase film is formed, while for × values beyond 0.5 mixed structures made of fcc-TiN and hcp-AlN, or nanocomposite films made of fcc-TiN, hcp-AlN, and fcc-AlN appeared depending on deposition conditions. Hardness of solid solution films was found to increase almost linearly with the Al content, while two opposite behaviours were distinguished for composite structures. Hardness rapidly decreased according to the rule of mixture as soon as solid solution phase began to separate into TiN and AlN growing in their natural structures with misfit dislocation at the interface. In contrast, further hardness enhancement was measured when nanocomposites with coherent interfaces were formed due to pseudomorphic stabilization of fcc-AlN on fcc-TiN crystallites.

Graphitic carbon nanofibers were used to reinforce epoxy resin to form nanocomposite adhesive bonding. GCNFs having a herringbone atomic structure are surface-derivatized with bifunctional hexanediamine linker molecules capable of covalent binding to an epoxy matrix during thermal curing and are cut to smaller dimension using ultrasonication. Good dispersion and polymer wetting of the GCNF component is evident on the nanoscale. Tensile and shear joint strength measurements were conducted for metal-metal and polymer-polymer joints using pure epoxy and nanocomposite bonding. Very little bonding strength increase, or some bonding strength decrease, was measured.

Although it has been confirmed by diamond anvil cell experiments that germanium transforms under hydrostatic pressure from the normal diamond cubic phase (Ge-I) to the metallic β-tin phase (Ge-II) and re-transforms to Ge-III (ST12 structure) or Ge-IV (BC8 structure) during release of the pressure, there are still controversies about whether the same transformations occur during nanoindentation. Here, we present new evidence of indentation-induced phase transformations in germanium. Nanoindentation experiments were performed on a (100) Ge single crystal using two triangular pyramidal indenters with different tip angles - the common Berkovich and the sharper cube-corner. Although the indentation load-displacement curves do not show any of the characteristics of phase transformation that are well-known for silicon, micro-Raman spectroscopy in conjunction with scanning electron microscopy reveals that phase transformations to amorphous and metastable crystalline phases do indeed occur. However, the transformations are observed reproducibly only for the cube-corner indenter.

Substrate materials for flexible devices are multi-layer composite structures. On top of a base polymer functional inorganic layers such as permeation barriers and conductive layers are applied. Due to the thermal mismatch between polymer and inorganic layer, the layer is compressive loaded at ambient conditions. A characteristic failure mode, occurring with compressive loaded thin layers, is buckling failure. The interface between adjacent layers fails locally, and the thin top layer bends outwards. The buckles have a characteristic width and height. These sizes are used to analyse the compressive strain, present in the layer before failure, and the adhesion quality of the failed interface. A buckle map is introduced to guide this analysis.

A fully coupled thermo-mechanical finite element model was used to study the buildup of stresses during splat solidification, and to understand the effect of deposition conditions on crack formation during plasma spray deposition. Through the simulation, the locations and magnitudes of maximum stresses were identified, where crack formation would presumably initiate. The model showed that the stresses scaled with the temperature difference between the superheated splat and the substrate. The simulation further showed that the stresses scale with the three geometric parameters, and two independent geometric ratios were defined; ζ (defined as t/λ) and ψ (defined as A/λ). 2D maps of maximum S11 and S22 under different combinations of ζ and ψ were constructed. The mappings showed that only roughness features on the scale of splat thickness were important in providing locations of maximum stress concentration.

Originated from the tooling industry, PVD (Physical Vapor Deposition) coating development focused on increasing the wear resistance. Nowadays, a steadily increasing market is evolving by coating machine parts. The requirements that have to be met due to the needs of this new market segment focus on tribological behavior. This means, that the focus of wear resistance is shifted towards properties like coefficient of friction, wetting behavior and the response of coatings towards dynamic loads. For many tribological applications, coatings are exposed to severe alternating loads, which are usually left out in common test methods. The approach of common coating test methods are based on the static behavior of deposited coatings. The impact tester is a testing device with a novel approach to dynamic load behavior of both bulk and coated materials. In this paper, the effect of the coatings' microstructure and Young's modulus on the impact toughness was investigated. A change in microstructure was provoked by changing deposition parameters like aluminum content. In a second stage these coatings were then tested with respect to their response to high alternating loads. For this purpose both load and number of impacts were varied.

A transparent, low refractive index SiO 2 film was photo-chemically laminated on a glass slab laser head by the Xe2* excimer lamp in the atmosphere of NF3 and O2 mixed gas at room temperature; which made it possible to inhibit the decrease in the laser output power caused by the evanescent wave leakage.

The transparent SiO2 film of 260nm thickness was laminated on the non-heated substrate by the lamp irradiation for one hour. The hardness of the film before annealing was 3 by Mohs’ Scale of Hardness, and its hardness improved to 5 after annealing at 250 degrees centigrade for one hour. The refractive index of the film was 1.42, being lower than the index of silica glass that is 1.46. Furthermore, the transmittance in the visible region increased by 2% with it s antireflection coating.

Amorphous carbon was irradiated with a nitrogen ion beam and changes in composition and tribological properties after surface nitridation have been studied. The nitrogen ion beam energy was varied from 0.1 to 2.0 keV under the constant ion current density. Composition and chemical bonding states near the surface were analyzed by X-ray photoelectron spectroscopy (XPS). Tribological properties were studied by a pin-on-disk type tribotester. XPS studies show that the nitrogen concentration near the surface increases after nitrogen ion irradiation. The depth profiles of nitrogen in the irradiated specimens display that the nitrogen concentration near the surface is maximized after 0.2 to 0.7 keV ion irradiation. From the pin-on-disk testing, it is found that the friction coefficient of amorphous carbon increases after irradiation by 1.5 keV nitrogen ions, while the friction coefficient does not change drastically after irradiation by 0.2 keV ions.

Commercial alloy AA8006 (nominal composition in wt%1.5Fe, 0.4Mn, 0.2Si) exhibits electrochemical activation in chloride media as a result of annealing at temperatures above 350°C. Activation is manifested by a significant negative shift in the corrosion potential and a significant increase in the anodic current when polarized above the corrosion potential in aqueous chloride solution. This phenomenon was correlated with the enrichment of trace element Pb at the oxide-metal interface. For fixed annealing time, maximum activation and Pb-enrichment are obtained at an annealing temperature of 450 °C independent of the original surface condition. Reduced activation with increasing temperature is attributed to increasing density of the spinel crystalline phase to cause the passivity of the surface.

The deformation behavior of both ion-implanted and deposited amorphous Si (a-Si) films has been studied using spherical nanoindentation, followed by analysis using Raman spectroscopy and cross-sectional transmission electron microscopy (XTEM). Indentation was carried out on both unannealed a-Si films (the so-called unrelaxed state) and in ion implanted films that were annealed to 450°C to fully relax the amorphous film. The dominant mode of deformation in unrelaxed films was via plastic flow of the amorphous phase rather than phase transformation, with measured hardness being typically 75–85% of that of crystalline Si. In contrast, deformation via phase transformation was clearly observed in the relaxed state of ion implanted a-Si, with the load-unload curves displaying characteristic discontinuities and Raman and XTEM indicating the presence of high-pressure crystalline phases Si-III and Si-XII following pressure release. In such cases the measured hardness was within 5% of that of the crystalline phase.

Diamond films were implanted with C+, Si+ or Sn+ ions at multiple energies in order to generate a uniform region of implantation-induced disorder. Analysis of the C+ implanted surfaces by micro-Raman spectroscopy has shown only minor increase in the proportion of nondiamond or sp2-bonded carbon at doses of 5 × 1013 - 5 × 1015 ions/cm2. In comparison, an amorphization of the structure was evident after implantation with either Si+ ions at a dose of 5 × 1015 ions/cm2 or with Sn+ ions at >5 × 1014 ions/cm2. At a given implantation dose, the etch rate of the diamond film in a CF4/O2 plasma increased with the mass of the implanted species in the order of C+, Si+ and Sn+. For a given implant species, the etch rate was directly proportional to vacancy concentration as controlled by the dose or the implantation-induced disorder.

The tribological performance of MoS2-Cr films in a pin-on-disk test sliding against an aluminum ball has been examined in this study. The MoS2-Cr films were deposited by pulsed laser deposition (MoS2) and simultaneous sputter deposition of Cr, giving a Cr content in the film of 10 mol. %. The results were also compared with films of MoS2 alone. The frictional behavior of MoS2-Cr films was not improved compared to the MoS2 alone, so SEM/EDS studies of the ball and flat were conducted to determine the nature of the transfer films and examine any interface reactions that occurred during the pin-on-disk (POD) test. In the early stages of the POD test (500 cycles) on the MoS2-Cr film, Al-oxide particles formed and caused cratering and scratching of the wear track, and the coefficient of friction neared 0.7. At later stages (9000 cycles), a thick oxide-based transfer film formed on the ball, but on the flat the track composition was closer to that of the original coating. For the films without Cr, after 104 cycles a smooth wear track was observed, and a thin transfer film of MoS2 was found within grooves on the ball wear scar along with Al oxide, which resulted in superior tribological performance.

Cluster ion beam processes can produce high rate sputtering with low damage in comparison with monomer ion beam processes. Especially, it is expected that extreme high rate sputtering can be obtained using reactive cluster ion beams. Reactive cluster ion beams, such as SF6, CF4, CHF3, and CH2F2, were generated and their cluster size distributions were measured using Time-of-Flight (TOF) method. Si substrates were irradiated with the reactive cluster ions at the acceleration energy of 5–65 keV. Each sputtering yield was increased with acceleration energy and was about 1000 times higher than that of Ar monomer ions. The sputtering yield of SF6 cluster ions was about 4600 atoms/ion at 65 keV. With this beam, 12 inches wafers can be etched 0.5 μm per minute at 1 mA of beam current. The TOF measurement showed that the size of SF6 cluster was about 550 molecules and the number of fluorine atoms in a SF6 cluster was about 3300. If the sputtered product was SiF, the yield has to be less than 3300 atoms/ion. These results indicate that the reactive cluster ions etch targets not only chemically, but also physically. This high-speed processing with reactive cluster ion beam can be applied to fabricate nano-devices.

Copper nuclei have been photo-chemically patterned on the fluorocarbon film surface in copper sulfate atmosphere via the reticle with just one shot of the ArF laser. Previously, we have reported that it required more than 3, 000 shots of the ArF laser to substitute the Cu atoms on the fluorocarbon surface.

Fluorocarbon is regarded as promising as a printed wiring board material in the high- frequency band. However, the fluorocarbon is chemically stable making it difficult to bond to copper foil. Generally, a copper foil is formed on the fluorocarbon surface by electroless plating with a catalyst core. In this method, however, the surface is made rough in pretreatment, which impairs its characteristics. Using the catalysts also causes differences in the dielectric constant, generating a high frequency noise. Thus, we demonstrated the direct formation of copper nuclei on the fluorocarbon surface photo-chemically by using the Xe2 excimer lamp and the ArF excimer laser.

The sample surface was first irradiated by Xe2 excimer lamplight to ma ke it hydrophilic. The surface was then irradiated with circuit patterned ArF laser light in the presence of copper-sulfate (CuSO4) aqueous solution to substitute the Cu atom. The modified sample was immersed in the electroless plating solution at 60 degrees Celsius for 15 minutes, and the copper foil was locally formed on the areas exposed to light.

Oblique irradiation using a gas cluster ion beam (GCIB) has been studied in order to achieve low-damage smoothing of magnetic materials. We investigated how the surface morphology and surface roughness depended on the angle of incidence. Quite smooth surfaces could be obtained using both normal and grazing-incidence irradiation. At incident angles larger than 45?, periodic ripples were formed. The orientation of the ripples changed from perpendicular to parallel with respect to the GCIB when the incident angle exceeded a critical value. Surface roughening resulting from the formation of ripples was observed at incident angles between 45° and 65°. Fluctuations in the Ni/Fe component ratio and the intermixing of oxygen from the native oxide were evaluated. As the angle of incidence increased, both the thickness of the layer in which the component ratio was fluctuating and the depth of oxygen intermixing decreased. As a result, it was determined that low-damage smoothing of magnetic materials could be performed by using grazing-incidence irradiation from a GCIB.

The shot peening process is known to produce a hard layer, known as the white layer” on the surface of coil springs. However, little is known about the fatigue properties of this white-layer.

In this study, coil springs with a white-layer were manufactured. The surface of these springs was then examined using micro Vickers hardness, FE-SEM etc. to test fatigue strength of the springs.

From the results obtained, a microstructure of the white-layer with grain size of 50–100 nm was observed, with a Vickers hardness rating of 8–10 GPa.

Tow category springs were manufactured utilizing a double-peening process. These springs had the same residual stress destruction and surface roughness. Only one difference was observed: one spring had a nanocrystalline layer on the surface, while the other did not. The results of the fatigue test realized an increase in the fatigue life of the nanocrystalline surface layer by 9%.

Arrays of closely spaced quasi-static indentation were made on specimens of polycrystalline α-Al2O3, mean grain size G=1.2, 3.8 and 14.1 μm. The critical indentation spacing to produce crack coalescence between indentations, and thus significant loss of material from the surface, was determined. These data are compared to results for low-impact-velocity wet erosive wear on the same materials; a good correspondence is found. The indentation data can be used to produce “wear maps”, which provide a guideline for predicting the low-impact-velocity erosive wear resistance of brittle materials.

In order to study the surface reaction process under cluster ion impact, molecular dynamics simulations of sequential cluster impacts of fluorine and neon clusters were performed. (F2)300 and Ne600 clusters were accelerated with totally 6keV and irradiated on bare Si(100) target. By iterating impact simulation sequentially, change of surface morphology and composition of desorbed materials were studied. In the case of fluorine cluster impact, the rough surface structure was made compared with neon cluster impact because fluorine atoms adsorb on the target, which work to keep pillar structure on the surface, whereas Ne atoms evaporate immediately leaving spherical mound structure on the surface. From the study of desorption process, it was observed that large number of Si atoms are desorbed in the form of silicon fluorides. The major sputtered material was SiF2, but various types of silicon-fluorides, including the molecules consists of several tens to hundreds silicon and fluorine atoms, were observed. The distribution of clusters in desorbed materials obeyed the classical model of cluster emission from quasi-liquid phase excited with ion bombardment. From these results, the irradiation effects of reactive cluster ions were discussed.

The effects of the glass-forming coatings on the fatigue behavior of 316L stainless steel were investigated. Films consisting of 47%Zr, 31%Cu, 13%Al and 9%Ni (atomic percent) were deposited onto the stainless steel by magnetron sputtering. The influences of the substrate condition, the surface roughness, the adhesion, and the compressive residual stresses on the fatigue behavior were studied. The applications of the glass-forming coating gave rise to significant improvements in both the fatigue life and the fatigue limit, in comparison with the uncoated steel. Depending on the maximum stress applied to the steel, the fatigue life can be increased by at least 30 times, and the fatigue limit can be elevated by 30%.