Surface modification of poly(methylmethacrylate) (PMMA) substrates has been demonstrated using an excimer lamp radiating vacuum ultraviolet (VUV) light of 172 nm in wavelength. In this study, we have particularly focused on the effects of atmospheric pressure during VUV irradiation. Each of the substrates was photoirradiated with VUV light under a pressure of 10, 103 or 105 Pa. Changes in nanomechanical properties of the VUV-irradiated sample surfaces were studied based on a scratching test using a nanoindenter. The wear-depth of the PMMA sample treated at 105 Pa was about 137.0 nm, which was much larger than the wear-depth of an untreated PMMA substrate (63.3 nm). On the contrary, when samples were prepared with VUV irradiation conducted at 10 and 103 Pa, their wear-depths markedly decreased down to about 2.2 and 12.5 nm, respectively. The sample treated at 10 Pa was particularly wear-resistant. This high wear-resistance was attributable to the formation of new carbon-carbon bonds such as C=C bonds on the PMMA surfaces.

In this work, the open-air thermal stability of nanocrystalline diamond films grown on mirror-polished titanium alloy substrates by the Microwave Plasma Chemical Vapor Deposition (MPCVD) technique was studied. The results of this investigation show that nanocrystalline diamond films are highly stable in air up to 600°C with no significant change in mechanical properties. Samples annealed between 600°C and 650°C, however, exhibit values of hardness lower by as much as 40% compared to as-grown samples. Above 650°C serious delamination effects were observed in the coatings.

First, we studied the relation between the sp3 bond ratio and the hardness of 100-nm-thick tetrahedral amorphous carbon (ta-C) films deposited by a Filtered Cathodic Arc (FCA) system at different substrate bias voltages. For comparison, sputtered amorphous carbon (a-C) films and Highly Oriented Pyrolytic Graphite (HOPG) were also analyzed. According to the results, ta-C film deposited at a -70 volt substrate bias voltage had high hardness and high sp3 bond ratio of up to 88 GPa and 85%, respectively, whereas those of sputtered a-C were 29 GPa and 28%. Furthermore, we found that the hardness of carbon films, including sputtered a-C and HOPG, increased with increasing sp3 bond ratio. Based on this relation, the chemical bond structures of carbon films are considered to be closely related to their mechanical properties. Secondly, we investigated the relation between sp3 bond ratio and ta-C film thickness, over the range from 1 to 10 nm. The measurements showed that a 2-nm-thick initial layer grown on the surface of CoCrPt magnetic film had low sp3 bond ratios. It is suggested that this reduction in sp3 bond ratio in the initially grown layer seriously degrades the film's performance as a hard disk media overcoat. Further efforts to improve ta-C film processing will be required to improve its mechanical properties.

TiAlN sputtered coatings have been used with success in high-speed cutting tools in the last few years. However, the adhesive failures of the coatings refrain its application in more severe wear conditions like as high-speed machining. The assumptions for the present research were based on the hypothesis that thin metal interlayers will behave as shear stress sinkers, which could decrease the delamination of the thin films. In the present work, coatings of TiAlN with thin ductile metallic interlayers (Al, Ti, Cu and Ag) were deposited by reactive d.c. magnetron sputtering. Multilayer coatings with aluminum, titanium and silver interlayers achieve higher adhesion values (70N) than TiAlN monolithic coating (40N). Three and five metal ductile layers contribute to an increase of hardness and Young's modulus without change the residual stresses of the monolithic coating. Contrarily, the introduction of copper layers reduces all the studied mechanical properties of the TiAlN monolithic coatings, which are related to the different deformation mechanisms of the ductile interlayers.

Adhesion layers are well-known to significantly improve the lifetime of MoS2-based solid lubricants. Typically, adhesion layers are “optimized” based on a phenomenological tests and then their deposition parameters are held fixed while the functional coating is studied. Here we examine the adhesion layer itself, while holding an MoS2 layer constant. In particular, the critical interfaces between the adhesion layer and the substrate, and between the adhesion layer and functional coating are regarded. MoS2-metal solid lubricant is chosen as the functional layer because it is a relatively brittle material whose performance is significantly affected by the quality and type of adhesion treatments. Substrate surface sputter cleaning was done by cathodic arc evaporation with different arc energies and substrate bias voltages. In addition to sputter etching of any surface oxides or other contaminants, some level of shallow implantation might be expected. The more usual surface preparation technique of argon plasma sputter etching was also used for comparison. Chromium and titanium were tested as adhesion layer materials. The adhesion layer thickness and deposition pressure were varied. Rutherford backscattering spectroscopy (RBS) and transmission electron microscopy (TEM) were used to analyze the adhesion layers and their interfaces with the substrates and with the MoS2-metal coatings. Ballon-disk tribometer sliding wear tests were made to assess changes in solid lubricant performance coming from variations in the adhesion layer. Scratch test characterizations were made to further evaluate adhesion layer performance.

Faceting is the transformation of a planar surface into two or more surfaces of lower energy. Metal, semiconductor and ceramic surfaces can all undergo faceting. The evolution of facets formed on the m-plane (1010) of alumina has been monitored using atomic-force microscopy (AFM). When heat-treated, the (1010) surface reconstructs into a hill-and-valley morphology. The present study investigates the manner in which facets originally form and grow to cover a surface. A gravity-loaded indenter (load of 25 grams) was used to mark a 25 μm × 25 μm square area on as-received, polished alumina specimens. An initial heat-treatment of 1400°C for 10 minutes is carried out to initiate faceting. With the indents as guides the same area can be identified and imaged after each subsequent heat-treatment. The morphology of the facets can be described as being comprised of a “simple” and “complex” surface. The simple surface corresponds to the (1102) plane which is stable over the course of heat treatments, whereas the complex surface gradually transforms to a lower energy surface after several heat treatments and acts as a nucleation site for new facet growth.

This paper examines the effects of stacking fault energy on the micro- and nano-indentation behavior of face-centered-cubic thin films. These include: LIGA nickel MEMS structures, alpha brass, copper and high purity aluminum. The measured hardness are then fitted to a strain gradient plasticity model based on the Taylor dislocation hardening model. Hardness is shown to exhibit a size dependence with different characteristic slopes in the micron and nano-scale regimes. Deep indents are shown to exhibit classical linear behavior. However, shallow indents exhibit an abrupt decrease in slope (almost by a factor of 10), giving rise to a bi-linear behavior. Furthermore, as the gradients become less sharp, the trends in the nano-hardness data become similar to those of the microhardness data predicted by the strain gradient plasticity model. Finally, the effects of stacking fault energy are then discussed within the context of cross-slip and hardening associated with Shockly partials.

A transparent low refractive index SiO2 film laminated on a glass substrate at room temperature by photochemical reactions with the Xe2* excimer lamp (172nm). This SiO2 film grown on the fused silica glass was proved to avoid reflection of light.

A refractive index of the SiO2 film was 1.36. After annealing the film for one hour at 200 degrees centigrade, the refractive index increased to 1.42. The refractive index increased as the F atom density in the SiO 2 film decreased.

In this paper, we present a preliminary study of texture development during copper thin film deposition. Using direct current (DC) magnetron sputtering technique, we deposit copper films on a SiO2/Si(111) substrate. A thin layer of copper of <111> texture first develops, and another thin layer of <110> ensues. As deposition continues, a third layer of copper of <111> texture forms on the top, leading to a copper thin film of alternating <111> and <110> textures. The multiple layers of copper thin films of alternating textures form during continuous deposition without changing deposition conditions. The film morphology is characterized with scanning electron microscopy (SEM) and atomic force microscopy (AFM), and the texture with X-ray diffraction (XRD). Based on anisotropic elastic analyses and molecular dynamics simulations, we propose a model of texture evolution during the formation of multilayers, attributing the texture evolution to the competition of surface and strain energies.

The effects of metal doping on the surface properties of sputtered silicon dioxide (SiO2) thin films were investigated. The aluminum (Al), titanium (Ti) or zirconium (Zr) doped SiO2 thin films were deposited onto glass by RF magnetron sputtering. The optical transmission spectra of the films were almost same as that of undoping film when the doping concentration was lower than ∼3 at %. The contact angle of water droplets was measured for the films as a function of elapsed time. The hydrophobicity, resulting from the adsorption of organic substances in the atmosphere, was significantly altered by the metal doping. The surface reactivity of the film with a fluoroalkyl isocyanate silane was also changed. These alternations were due to the difference in surface OH group density of the film, which was induced by the metal doping. These results suggest that the surface properties can be modified by controlling the surface OH group density of the films.

High power Nd-YAG laser was used to fuse coatings containing a mixture of FeAl and Al, with 4340 steel. It was observed that good quality coatings could be obtained using this process. Detailed microstructural studies show that Fe aluminides and/or a solid solution of Al in Fe can form within the coating, depending on the processing conditions. Wear measurements show that the best wear properties are obtained in the presence of an aluminide in the coating and that the wear properties significantly degrade when the coating consists primarily of a solid solution of Al in Fe.

Monitoring with an Acoustic Emission (AE) sensor integrated into an indenter tip was utilized for the evaluation of the earliest stages of indentation-induced plasticity in sapphire single crystal. The evaluated surfaces included basal (C), rhombohedral (R) and two different prismatic orientations (A and M). The differences between the mechanisms of the initial stages of plasticity for the various crystallographic orientations were reflected in the following aspects of AE activity: detection of a specific type of AE waveform that correlated to the presence of linear surface features near the indentation impressions; AE signal associated with the yield point, consisting either of one or two distinct waveforms; and presence or absence of AE signals after the yield point. Moreover, analysis of AE activity revealed loading rate effects on the yield point mechanism for the M plane. The possibility of plasticity onset mechanisms involving both slip and twinning is discussed.

Nanostructured WCx thin films were reactively sputtered in argon-methane plasma. A DC planar magnetron with a pure tungsten target was used. Films were deposited on glass, quartz, silicon and sapphire substrates at temperatures up to 700 °C. The carbon content in the film was varied by changing the partial pressure of methane. The carbon content in the films was analyzed by using X-ray Photon Spectroscopy (XPS) and Rutherford Backscattering Spectroscopy (RBS).

The effect of temperature on the grain size was studied using Transmission Electron Microscopy (TEM). The target poisoning behavior was studied by measuring the target current. The critical methane concentration at which the metal – poison mode transition occurs was measured to be around 42% of CH4 in Ar. This transition is characterized by a sharp fall in the target current. The hysteresis in the target current can also be attributed to target poisoning. In this paper we describe the effects of film growth parameters on the film composition. We also discuss an alternate sputtering technique, hollow cathode sputtering, and the advantages of this technique over the conventional planar magnetron technique.

Visible-light microscopy (VLM) and atomic-force microscopy (AFM) were used to study the progression of grain-boundary grooving and migration in high-purity alumina (Lucalox™). Groove profiles from the same grain boundaries were revisited using AFM following successive heat-treatments. The grooves measured from migrating grain boundaries were found to have asymmetric partial-angles compared to those measured from boundaries that did not migrate during the experiment. For a moving boundary, the grain with the larger partial-angle was consistently found to grow into the grain with the smaller partial-angle. Migrating boundaries were observed to leave behind remnant thermal grooves. The observations indicate that the boundary may be bowing out during the migration process.

Entrapment of proteins in biodegradable nanospheres has been widely investigated as a technique to produce sustained release formulations for protein or anti-cancer drugs administration. Amphiphilic PLLA-mPEG diblock copolymer was prepared by ring opening polymerization (ROP) to form polymeric nanoparticles with a core-shell structure. The main encapsulation technique done is a water-in-oil-in-water (w/o/w) solvent evaporation technique. Here, protein was encapsulated using a newly developed water-in-oil emulsion-solvent diffusion technique. This technique leads to the formation of an emulsion combined with the immediate precipitation of the PLLA-mPEG. This phenomenon is caused by the diffusion of the polymer solvent to an external organic phase.

A new approach using an experimental hole drilling technique has been developed to determine the hardness profile of superficially heat-treated steels. This method was based on the proportionality between the hardness of the material tested and the cutting thrust measured during the drilling test. Although it was observed that, overall, the increase in the cutting thrust was linear with hardness, locally the variation of thrust was not necessarily regular and linear in particular for iron-carbon alloys. In fact, other parameters related to the material, other than hardness, can modify the cutting thrust level. We report here on the influence of parameters, such as the type of microstructure and the ductility or the work hardening of material, on drilling thrust. The cutting thrust obtained for various brittle or ductile materials will be discussed using results obtained from hardness tests, micrographic observations and microhardness of the chips obtained by drilling test.

Nickel aluminide coatings were produced on steel substrates by reactive thermal processing of pre-plated precursor layers of nickel and aluminum using plasma arc as the heat source. Controlled rapid heating melted the outer aluminum layer, which then dissolved nickel to facilitate the nucleation and growth of a nickel aluminide. The resultant coating microstructures varied from a duplex or triplex structure, consisting of either NiAl3 and a eutectic; Ni2Al3, NiAl3 and a eutectic; to a fully monolithic Ni2Al3 structure, with the latter resulting at high heat input rates and/or low heat-source traverse rates. The temperature of the reaction layer was simulated for the experimental conditions by a numerical model based on Green's function analysis. The nickel concentration at the liquid-solid interface just before any nickel aluminide nucleation was calculated by assuming local equilibrium interface conditions between the liquid layer and the fcc nickel-rich solution. The depth of nickel dissolution, which consequently determines the extent of nickel aluminide growth, was also predicted by the model. Numerical results of the nickel dissolution compared well with experimental observations.

Electron induced carbon deposition and etching was investigated by Auger electron spectroscopy in a custom designed vacuum system. The Auger electron spectrometer was used to provide a high flux electron beam to induce reactions and to monitor surface composition. During the e-beam induced deposition or etching, the gas phase pressure was 10-4 to 10-5 Torr. Several carbon precursors: benzene, cyclohexane and propane were used for deposition. The deposition rate depended on the precursor sticking coefficient and bonding structure. Among the three precursors tested, the deposition rate of carbon was cyclohexane > benzene > propane. The e-beam induced etching of carbon films was carried out in 1 × 10-4 torr oxygen ambient and the carbon film was prepared by reactive physical vapor deposition. The etching process can be divided into three stages: bulk film, interface, and substrate. For the bulk carbon film, the decrease of film thickness varies linearly with the e-beam flux, while at the interface, the film thickness shows an exponential decay with the electron flux. For the C in the Si substrate, a very slow etching rate was observed. The etching rate for bulk carbon film was ∼ 0.1 nm/min under the experimental conditions, which is equivalent tp 2.4 × 10-27 cm3/electron. At the interfacial region, the cross section of carbon removal by electrons was ∼ 4.6 × 10-21 cm2. Based on the change of the carbon line shape at the interface, we concluded that the etching rate is related to the chemical nature of the carbon species.

Electrophoretic deposition (EPD) technique has been used to fabricate green YSZ/Al composite coatings with controlled thickness and morphology. Such green coating was transformed into the YSZ/Al2O3 composite coating during following thermal treatment in air at temperatures up to 1200°C. Suspension for EPD was prepared by attrition-milling a mixture of yttria -stabilised zirconia (YSZ) and aluminium (Al) in acetyl-acetone (ACAC). The attrition milling reduced the particle size of the powder mixture. A mechanical alloying behaviour is believed to control the agglomeration and the breaking of large Al particles. Attrition milling also reduced the YSZ crystallite size, which can be attributed to the chemical reaction between YSZ/Al particles and ACAC. Thermal analyses and dilatometry measurements of the green compact indicate the temperature range for oxidation of Al and its effect on sintering of the coating. The coating obtained from EPD in the suspension after a longer milling time was found to have more uniform in microstructure.

In the present study we focus on the interaction of C60 with sp2 boron nitride (BN), a surface that is isoelectronic to graphite. The nanocrystalline BN substrate was deposited by mass selected ion beam and consists of an sp2 surface layer, which covers a cubic-BN film. The interaction and electronic properties of the C60-BN system are observed by photoelectron spectroscopy in the x-ray (XPS) and ultraviolet regime (UPS). The experiment is initiated by sequential deposition of C60 and the overlayer growth proceeds via island formation. In a second step the sample is annealed at a rate of 5–10 K/minute while simultaneously recording the UPS spectra. The majority of C60 desorbs from the sp2 BN surface at 493 K. The remaining C60 (initially about 0.6 ML) is gradually removed with increasing temperature (up to 813 K) but never completely desorbed and presumably attached at surface imperfections or grain boundaries of the nanocrystalline material. No carbide formation, preferential interaction of C60 with either element or a charge transfer are observed. The presence of C60 induces an upward band bending and related peak shifts in the sp2 BN surface layer and to a lesser extent in the underlying c-BN bulk. An upward band bending is likewise observed in the C60 overlayer, and the Fermi level has therefore to be pinned by defects in the interface region. The layered structure of the BN film allows to probe the extension of the space charge layer in the BN film.