Smoothening Effect Research Articles

Bright nickel film deposited by supercritical carbon dioxide emulsion using additive-free Watts bath

This paper is aimed on studying film smoothening effect of supercritical carbon dioxide emulsion (Sc-CO2-E) on nickel film electroplated using an additive-free Watts bath. Morphology of nickel film electroplated with Sc-CO2-E was found to be similar to that of nickel film prepared from electroless plating. Surface roughness (Ra) of nickel film electroplated with Sc-CO2-E was lower than that of nickel film electroplated through conventional method. A minimum Ra was found for nickel film electroplated through conventional method and Sc-CO2-E when increasing current density from 0.010 to 0.150 A/cm2. The minimum Ra was 69.8 nm at 0.020 A/cm2 and 14.0 nm at 0.030 A/cm2, respectively for conventional and Sc-CO2-E case. After the minimum point, increasing rate of Ra increased was lower for Sc-CO2-E case; this was because of higher hydrogen solubility in Sc-CO2. Grain size of nickel film electroplated with Sc-CO2-E was found to be finer than that of conventional case.

A Quasi-Static Mechanics Analysis of Three-Dimensional Nanoscale Surface Polishing

A quasi-static mechanics analysis of nanoscale surface polishing that provides insight into the surface topography evolution and the removal of material at the asperity level is presented. The analysis is based on a three-dimensional stochastic model that accounts for multiscale (fractal) surface roughness and elastic, elastic-plastic, and fully plastic asperity deformation by hard abrasive nanoparticles embedded in the soft surface layer of a rigid polishing plate. Numerical results of the steady-state roughness of the polished surface, material removal rate, and wear coefficient are presented in terms of the apparent contact pressure, polishing speed, original topography and mechanical properties of the polished surface, average size and density of nanoparticles, and surface roughness of the polishing plate. Simulation trends are associated with elastic-plastic and fully plastic asperity contacts, responsible for irreversible topography changes (roughening effect) and material removal (smoothening effect), respectively. Analytical trends and predictions of the steady-state roughness of the polished surface and material removal rate are shown to be in good agreement with experimental results of nanoscale surface polishing (lapping) of magnetic recording ceramic heads.

On finishing of pressing die surfaces using machine hammer peening

Machine hammer peening (MHP) is a new method for finishing of surfaces. With this method, the workpiece surface is hammered with a spherical carbide tool. The main objective of the study was to evaluate whether the MHP method could become a plausible substitute for manual polishing in pressing die manufacturing where nodular cast iron is a common workpiece material. To do this, sample nodular cast iron surfaces were hammered and evaluated. Changes to the surfaces were evaluated using surface roughness measurements, hardness measurements and optical images. First of all, the workpiece surface was smoothened. Secondly, the surface hardness was increased significantly. Thirdly, the nodules on the workpiece surface were affected. They appeared to be smaller and not as visible. This effect would likely create a die surface less prone to galling since the cavities would not be filled with sheet metal to the same extent in a forming operation. In addition, with MHP, the amount of polishing needed to manufacture a die surface can be reduced because of the smoothening effect.

UHV-EC Characterization of Ultrathin Films Electrodeposited on Well-Defined Noble Metals. I: Pd on Pt(111)

A combination of conventional electrochemistry (cyclic voltammetry and coulometry) and ultrahigh vacuum electron spectroscopies (Auger electron spectroscopy and low-energy electron diffraction) was used to characterize the interfacial chemistry of ultrathin Pd films in the presence of adsorbed and aqueous bromide. Potential-controlled adsorption-desorption cycles of aqueous bromide exerted surface smoothening effects on ultrathin Pd films with defect sites (steps); this procedure, dubbed as electrochemical (EC) annealing, constituted a nonthermal analog to conventional annealing. EC-annealed ultrathin Pd films exhibited long-range surface order and remained free of oxygen adspecies. Pd adatoms occupying step sites were selectively dissolved and/or rearranged to assume equilibrium positions in a well-ordered (1 × 1) film.

Effect of diamond smoothening on the structure and properties of the deposited metal in the laser-affected zone

Results of a study of the effect of diamond smoothening on the microhardness of deposited high-speed steel in the laser-affected zone and on the quality of surface after gas laser cutting are presented.

Antimony surfactant for epitaxial growth of SiGe buffer layers at high deposition temperatures

The effect of Sb on the growth behavior and the layer quality of graded SiGe buffer layers was studied at high-temperature CVD conditions. Sb was provided as SbCl 5 additive to the GeCl 4 precursor. Overall growth kinetics of SiGe did not change in the presence of Sb. By adding Sb the cross-hatch morphology was suppressed and smoother films could be grown. The smoothening effect and the incorporation of Sb into the SiGe layer were studied as a function of growth temperature and Sb concentration. The effect is attributed to the change in surface coverage with Sb adatoms.

Foreign Institutional Investment and Stock Market Returns in India: Evidence from ARDL Bounds Testing Approach

The paper uses Autoregressive Distributed Lag (ARDL) bounds testing approach to examine the dynamic behaviour of net foreign institutional investment flows on stock market returns in India for the daily data series from 1 st July, 1999 to 28 th February, 2009. By and large, the analysis reveals that there is an evidence of positive and negative feedback trading hypothesis in the short-run and long-run respectively. This implies that foreign institutional investment acts as destabilising forces in the short-run and has a smoothening effect in the long-run.

Overcoming the order barrier in the numerical approximation of stochastic partial differential equations with additive space–time noise

We consider the numerical approximation of parabolic stochastic partial differential equations driven by additive space–time white noise. We introduce a new numerical scheme for the time discretization of the finite-dimensional Galerkin stochastic differential equations, which we call the exponential Euler scheme, and show that it converges (in the strong sense) faster than the classical numerical schemes, such as the linear-implicit Euler scheme or the Crank–Nicholson scheme, for this equation with the general noise. In particular, we prove that our scheme applied to a semilinear stochastic heat equation converges with an overall computational order 1/3 which exceeds the barrier order 1/6 for numerical schemes using only basic increments of the noise process reported previously. By contrast, our scheme takes advantage of the smoothening effect of the Laplace operator and of a linear functional of the noise and, therefore overcomes this order barrier.

R402 – Profilometry and Skin Histology with Anti-wrinkle Agents

Problem To investigate whether topical anti-aging compounds can reduce wrinkle depth as seen by replica profilometry with comparable changes in histological parameters in murine skin. Methods Female hairless mice were exposed to topical application of a retinoic acid cream, a peptide lotion, and a soy cream on the dorsal skin areas for 4 weeks. Silicone negative replicas of treated and untreated skin surface were photographed using Optimus V6.5 image processing system (CuDerm Corporation, Texas), and evaluated for traditional surface roughness parameters (Rz, Ra, FSpace, and DL). Skin samples were also processed for histomorphometry, and immunohistochemistry of proliferating cell antigen (PCNA). Quantitative light microscopic data were acquired from tissue sections for estimating DNA replication in epidermal keratinocytes (PCNA index), epidermal thickness, depth of dermal collagen bundles. Results All quantitative data were analyzed for comparing means with one-way analysis of variance (ANOVA) using SPSS 14.0 statistical software, and significant changes in all the parameters were noted. Augmented keratinocyte proliferation and thickening of viable epidermis was observed with all three compounds although a greater effect was seen in the retinoic acid and peptide treatment groups. A similar trend was noted in respect of widening of dermal collagen layer. Epidermal surface roughness manifested maximum smoothening effect following treatment with the peptide compound. Conclusion Retinoic acid effects have been reported in literature but reports of comparison with soy and peptide preparation in this laboratory model are lacking. The pronounced effects seen with all the compounds indicate topical agents other than retinoic acid may have beneficial regenerating effects on photo aged skin without irritating effects reported for retinoic acid. Significance These results may be helpful in defining clinical strategies for topical non-invasive improvement of aging facial skin. Support This study was supported by the 2007 Leslie Bernstein Grant from the AAFPRS Foundation.

Structural Details of Cellulose Nanocrystals/Polyelectrolytes Multilayers Probed by Neutron Reflectivity and AFM

Neutron reflectivity measurements and AFM observations were used as complementary techniques to investigate multilayered films consisting of alternating sheets of rigid cellulose nanocrystals and flexible poly(allylamine hydrochloride) (PAH) prepared by the layer-by-layer assembly technique. Both techniques showed that smooth films with a high load of cellulose could be obtained. After deposition, the cellulose component occurred as a double layer with different densities: 50% and 25% for the lower and upper layer, respectively. A linear growth of the multilayer and the presence of a Bragg peak on neutron reflectivity curves indicated the formation of a well-ordered structure resulting from entropy-driven assembly and smoothening effect of the flexible PAH macromolecules. The possible alignment of the nanocrystals when anisotropic suspensions were used is also shown and opens the route to an improved control of the architecture of these multilayers.

Interaction of cleavage ridges with grain boundaries in polysilicon films

The morphology of cleavage surfaces across grain boundaries in free-standing silicon thin films was investigated. Three ridge–boundary interaction modes were identified. If the cleavage ridge was relatively deep, it could directly bypass a grain boundary. If it was relatively shallow, it would act as a stress concentrator promoting cleavage front transmission. It was also observed that due to the smoothening effect, the surface could become effectively less rough across a grain boundary.

Expression of cell adhesion receptors in human osteoblasts cultured on biofunctionalized poly-( ε-caprolactone) surfaces

This study was aimed to investigate whether the activation of poly-( ε-caprolactone) (PCL) surface by low-energy irradiation and/or the biofunctionalization by absorption of arginine–glycine–aspartic sequences (RGD), can modify the expression of integrins closely related to the osteoblast activity. For this purpose, we analysed the physicochemical changes induced by irradiation and RGD immobilization, the consequences on cell adhesion and spreading, and the effects on integrin expression. PCL irradiated with 5×10 15He +/cm 2 (10 keV energy) (irr-PCL) showed an altered surface layer with a partial loss of carboxyl species and the formation of carbonyl groups. Moreover, irr-PCL showed a small smoothening effect and a less polar character in comparison to the pristine ones. The RGD immobilization was observed only on irr-PCL (surface coverage: 7.0 pmol/cm 2). Human osteoblasts (hOB) were cultured on untreated PCL (ut-PCL), ut-PCL+RGD, irr-PCL, and irr-PCL+RGD. After 24 h, ut-PCL hindered the cell adhesion, while a discrete layer of hOB with a good cytoskeleton organization was detected on irr-PCL and irr-PCL+RGD. Before seeding, the single hOB suspension expressed α1, α2, α3, α5, β1, and αVβ3; after 24 h, cells cultured on tissue-plastic expressed high levels of β1 and αVβ3, while α1 showed a low intensity and α2, α3, and α5 were negative. β1 and αV β3 were selected to evaluate the interaction between cells and PCL samples. The β1 expression was higher in hOB cultured on irr-PCL than on the other samples. A significant increase in αVβ3 expression was observed only in irr-PCL+RGD, and confirmed by the gene expression analysis. In conclusion, ion irradiation and RGD adsorption on PCL surfaces modulate the expression of integrin involved in hOB growth and function, indicating the effectiveness of biomimetic surfaces in promoting cell adhesion. Ultimately, the study of integrin expression may suggest proper changes to the surface structure in order to improve the osteoconductivity of selected materials.

The effect of morphological smoothening by reconstruction on the extraction of peaks and pits from digital elevation models

In this paper, the effect of morphological smoothening by reconstruction on the extraction of peaks and pits from digital elevation models (DEMs) is studied. First, a mathematical morphological based algorithm to extract peaks and pits from DEMs is developed. Morphological smoothening by reconstruction is then implemented on the DEM of Great Basin using kernels of different sizes. The number of peaks and pits extracted from the resultant DEMs is computed using connected component labeling and the results are compared. This work is aimed at studying the capabilities of morphological smoothening by reconstruction in the modeling of objects and processes operating within an environment.

Enhanced visualization of microbial biofilms by staining and environmental scanning electron microscopy

Bacterial biofilms, i.e. surface-associated cells covered in hydrated extracellular polymeric substances (EPS), are often studied with high-resolution electron microscopy (EM). However, conventional desiccation and high vacuum EM protocols collapse EPS matrices which, in turn, deform biofilm appearances. Alternatively, wet-mode environmental scanning electron microscopy (ESEM) is performed under a moderate vacuum and without biofilm drying. If completely untreated, however, EPS is not electron dense and thus is not resolved well in ESEM. Therefore, this study was towards adapting several conventional SEM staining protocols for improved resolution of biofilms and EPS using ESEM. Three different biofilm types were used: 1) Pseudomonas aeruginosa unsaturated biofilms cultured on membranes, 2) P. aeruginosa cultured in moist sand, and 3) mixed community biofilms cultured on substrates in an estuary. Working with the first specimen type, a staining protocol using ruthenium red, glutaraldehyde, osmium tetroxide and lysine was optimized for best topographic resolution. A quantitative image analysis tool that maps relief, newly adopted here for studying biofilms, was used to compare micrographs. When the optimized staining and ESEM protocols were applied to moist sand cultures and aquatic biofilms, the smoothening effect that bacterial biofilms have on rough sand, and the roughening that aquatic biofilms impart on initially smooth coupons, were each quantifiable. This study thus provides transferable staining and ESEM imaging protocols suitable for a wide range of biofilms, plus a novel tool for quantifying biofilm image data.

Modeling of smoothening effect on morphologies of annealed submicron nickel particles used for electrically conductive adhesives

Microelectronic packaging has been accelerating towards adoption of solutions that offer lower cost, higher electrical performance, and better reliability. Flip chip technology lends itself excellently to these goals. The development of anisotropic and isotropic conductive adhesives (ACA and ICA, respectively) as an alternative to solder bumps has received extensive attention in flip chip packaging as it offers an array of advantages such as finer pitch interconnects, green processes, low cost, and low temperature processing. Nickel, with its lower cost than that of silver and better thermal stability than that of copper, appears to be a viable candidate material for ICA and ACA applications. In the present study, a spiky surface morphology of nickel particles synthesized by means of a hydrothermal reduction method was clearly observed. The spiky morphology may have a detrimental effect on the conductivity of the ICA and ACA flip chip interconnect due to its smaller contact surface and propensity towards oxidation. The morphology of the nickel surface can be changed by annealing the particles between 270 and 360°C for 4–12h. A smoothening effect leading to more or less smooth spherical particles along with an increase in conductivity was observed after annealing at 360°C for up to 12h. An analytical model considering surface diffusion is established here to describe the temperature activated and energy minimization driven smoothening of the Ni particles.

Surface analytical chemical imaging and morphology of Cu–Cr alloy

Cu–Cr alloys are very interesting materials to study non-equilibrium phase transformations in binary systems containing immiscible metals as well as for practical applications as high-thermal conductivity and contact materials. We studied by high resolution secondary ion mass spectrometry and atomic force microscopy the chemical element distributions and surface morphology of Cu–Cr alloys irradiated with a low energy, high current electron beam. The irradiation conditions were: energy density 4 ÷ 6 J cm − 2, pulse duration 2.8 ÷ 3.6 μs, number of shots 16. Cu–Cr alloys were prepared by powder metallurgy and contain 30 wt.% Cr. While in samples irradiated at low energy density maps of surface elements reveal the presence of well separated micrometer-sized domains of Cr and Cu, after irradiation at high energy density sub-micron spots of coexisting Cu and Cr appear. This is a clear indication of CuCr compound formation, as also supported by local mass spectrometry. Irradiated samples have reduced roughness, especially in Cr domains, with respect to the pre-treated sample. However, microcracks and microcraters appear as beam energy density and number of shots increase, thus compromising the smoothening effect and the surface integrity.

Interface engineering of short-period Ni/V multilayer X-ray mirrors

Low-energy ion-assisted magnetron sputter deposition has been used for the synthesis of highly reflective Ni/V multilayer soft X-ray mirrors. A low ion energy and a high ion-to-metal flux ratio were employed in order to stimulate the adatom mobility while minimizing ion-induced intermixing at the interfaces. An analytic model, based on the binary collision approximation, was used in order to gain insight into low-energy ion–surface interactions as a function of ion energy and ion-to-metal flux ratio. The model predicted a favorable region in the ion energy-flux parameter space where only surface atomic displacements are stimulated during growth of Ni and V for multilayers. For a series of Ni/V multilayer mirrors with multilayer periods about Λ = 1.2 nm, grown with a continuous ion assistance using energies in the range 7–36 eV and with ion-to-metal flux ratios Φ Ni = 4.7 and Φ V=20.9, specular and diffuse X-ray scattering analyses revealed that ion energies of ∼27–31 eV produced the best trade-off between reduced interfacial roughness and intermixing. However, it was also concluded that an interface mixing of about ± 1 atomic distance is unavoidable when a continuous flux of assisting ions is used. To overcome this limitation, a sophisticated interface engineering technique was employed, where the first 0.3 nm of each layer was grown with a high-flux low-energy ion assistance and the remaining part was grown with a slightly higher ion energy. This method was demonstrated to largely eliminate the intermixing while maintaining the smoothening effect of ion assistance. Two Ni/V multilayer soft X-ray mirror structures, one with 500 periods designed for near-normal incidence and one 150 periods reflecting polarizer at the Brewster angle, were grown utilizing the interface engineering concept. Both the near-normal incidence reflectivity as well as polarizability were improved by a factor of 2 as compared to previously reported data for an X-ray energy of E = 511 eV.

Improvement of the Spin Transfer Induced Switching Effect by Copper and Ruthenium Buffer Layer

The spin transfer induced magnetization switching has been reported to occur in magnetic multilayer structures whose scope usually consists of one stack of ferromagnetic / non-ferromagnetic / ferromagnetic (F / N / F) materials. In this work, it is shown that: 1) Copper used as a buffer layer between the free Co and the Au cap-layer can clearly increase the probability to get the spin transfer induced magnetization switching in a simple spin valve Co 11 / Cu 6/ Co 2 (nm); 2) Furthermore, when Ruthenium is simultaneously applied as a buffer layer on the Si-substrate, the critical switching currents can be reduced by <TEX>$30\%$</TEX>, and the absolute resistance change delta R <TEX>$[{\Delta}R]$</TEX> of that stack can be enlarged by <TEX>$35\%$</TEX>. The enhancement of the spin transfer induced magnetization switching can be ascribed to a lower local stress in the thin Co layer caused by a better lattice match between Co and Cu and the smoothening effect of Ru on the thick Co layer.

Sn-mediated Ge∕Ge(001) growth by low-temperature molecular-beam epitaxy: Surface smoothening and enhanced epitaxial thickness

Fully strained single-crystal metastable Ge1−xSnx layers were grown on Ge(001) in order to probe the role of Sn dopant and alloy concentrations (CSn=1×1018cm−3to6.1at.%) on surface roughening pathways leading to epitaxial breakdown during low-temperature (155°C) molecular-beam epitaxy of compressively strained films. The addition of Sn was found to mediate Ge(001) surface morphological evolution through two competing pathways. At very low Sn concentrations (x≲0.02), the dominant effect is a Sn-induced enhancement in both the Ge surface diffusivity and the probability of interlayer mass transport. This, in turn, results in more efficient filling of interisland trenches, and thus delays epitaxial breakdown. In fact, breakdown is not observed at all for Sn concentrations in the doping regime, 1×1018⩽CSn&amp;lt;4.4×1020cm−3 (2.3×10−5⩽x&amp;lt;0.010)! At higher concentrations, there is a change in Ge1−xSnx(001) growth kinetics due to a rapid increase in the amount of compressive strain. This leads to a gradual reduction in the film thickness h1(x) corresponding to the onset of breakdown as strain-induced roughening overcomes the surface smoothening effects, and results in an increase in the overall roughening rate. We show that by varying the Sn concentration through the dopant to dilute alloy concentration range during low-temperature Ge(001) growth, we can controllably manipulate the surface roughening pathway, and hence the epitaxial thickness, over a very wide range.

Research on pulse electrochemical finishing using a moving cathode

To improve the surface quality of parts with frictional pair, a finishing method – Pulse Electrochemical Finishing (PECF) using a Moving Cathode is studied in this paper. By experimentation we find: machining with an interelectrode gap as small as possible could smoothen the anode surface quickly; with an invariable gap size, the current density and the machining time are two key parameters influencing the smoothening effect; there is a critical current density above which a bright surface could be obtained, and this process could finish a large surface area over the critical current with a low power supply, which is helpful to get a lustrous surface. As an example, the inner surface of a part is finished. The result shows that the surface roughness value (Ra) reduces from 0.5 to 0.065 µm and a mirror-like surface is obtained.